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Sample records for group velocity tomography

  1. Eurasian surface wave tomography: Group velocities

    NASA Astrophysics Data System (ADS)

    Ritzwoller, Michael H.; Levshin, Anatoli L.

    1998-03-01

    This paper presents the results of a study of the dispersion characteristics of broadband fundamental surface waves propagating across Eurasia. The study is broader band, displays denser and more uniform data coverage, and demonstrates higher resolution than previous studies of Eurasia performed on this scale. In addition, the estimated group velocity maps reveal the signatures of geological and tectonic features never before displayed in similar surface wave studies. We present group velocity maps from 20 s to 200 s period for Rayleigh waves and from 20 s to 125 s for Love waves. Broadband waveform data from about 600 events from 1988 through 1995 recorded at 83 individual stations across Eurasia have produced about 9000 paths for which individual dispersion curves have been estimated. Dispersion curves from similar paths are clustered to reduce redundancy, to identify outliers for rejection, and to assign uncertainty estimates. On average, measurement uncertainty is about 0.030-0.040 km/s and is not a strong function of frequency. Resolution is estimated from "checker-board" tests, and we show that average resolutions across Eurasia range from 5° to 7.5° but degrade at periods above about 100 s and near the periphery of the maps. The estimated maps produce a variance reduction relative to the Preliminary Reference Earth Model (PREM) of more than 90% for Rayleigh waves below 60 s period but reduce to about 70% between 80 and 200 s period. For Love waves, variance reductions are similar, being above 90% for most periods below 100 s and falling to 70% at 150 s. Synthetic experiments are presented to estimate the biases that theoretical approximations should impart to the group velocity maps, in particular source group time shifts, azimuthal anisotropy, and systematic event mislocations near subducting slabs. The most significant problems are probably caused by azimuthal anisotropy, but above 100 s the effect of source group time shifts may also be appreciable

  2. Rayleigh Wave Group Velocity Distributions for East Asia from Ambient Seismic Noise Tomography

    NASA Astrophysics Data System (ADS)

    Witek, M.; van der Lee, S.; Kang, T. S.; Chang, S. J.; Ning, S.; Ning, J.

    2014-12-01

    We have collected continuous vertical-component broadband data from 1109 seismic stations in regional networks across China, Korea, and Japan for the year 2011 to perform the largest surface wave tomography study in the region. Using this data set, we have measured over half a million Rayleigh wave group velocity dispersion curves from 1-year stacks of station-pair ambient seismic noise cross-correlations. Quality control is performed by measuring the coherency of the positive and negative lag time sides of the cross-correlations. If the coherency is below an empirically determined threshold, the dispersion curve is measured on the side of the highest SNR. Otherwise, the positive and negative sides of the cross-correlation are averaged before dispersion curve measurement. Group velocity measurements for which the SNR was less than 10 are discarded. The Rayleigh wave group velocity dispersion curves are regionalized on a tessellated spherical shell grid in the period range 10 to 50 s to produce maps of Rayleigh wave group velocity distributions. Preliminary maps at 10 seconds period match well with geologic features at the surface. In particular, we observe low group velocities in the Songliao, Bohai Bay, Sichuan, Ordos, Tarim, and Junggar Basins in China, and the Ulleung and Yamato Basins in the East Sea (Sea of Japan). Higher group velocities are observed in regions with less sediment cover. At periods around 30 s, we observe group velocity decreases going from east to west in China, representing an overall trend of crustal thickening due to the collision between the Indian and Eurasian plates. The Ordos and Sichuan blocks show higher group velocities relative to the eastern margin of the Tibetan Plateau, possibly reflecting low temperatures in these cratons.

  3. Noise directivity and group velocity tomography in a region with small velocity contrasts: the northern Baltic shield

    NASA Astrophysics Data System (ADS)

    Poli, P.; Pedersen, H. A.; Campillo; , M.; Polenet/Lapnet Working Group

    2013-01-01

    Ambient noise tomography (ANT) is widely used to image strong velocity variations within the upper crust. Using careful processing, we obtained a 3-D model of shear velocities in the upper crust beneath northern Finland, where the lateral velocity variations are less than 3 per cent. As part of the tomography, the noise field is analysed. It is strongly heterogeneous but the signal-to-noise ratio is sufficient to obtain stable dispersion curves for all profile azimuths. Our results show that the directions of dominant noise sources of Rayleigh and Love waves are the same, but the amplitude distribution with azimuth is different for the two types of waves. More intriguingly, the high frequency Love waves are dominated by a mixture of higher modes rather than the fundamental mode. The reconstructed 3-D model shows the Lapland Granulite Belt as a high velocity body with a limit at surface in excellent agreement with geological observations at surface. Following this interface at depth, our results are compatible with previous studies suggesting an Archean north oriented subduction.

  4. Group Velocity Tomography for Eastern Mexico and Crustal Structure for Tehuantepec Isthmus

    NASA Astrophysics Data System (ADS)

    Córdoba Montiel, F.; Iglesias, A.; Melgar, D.; Singh, S.; Perez-Campos, X.

    2013-05-01

    We use seismic noise records from the broadband network of the Mexican National Seismological Service (Servicio Sismológico Nacional) and from MASE and VEOX stations (two temporal seismic experiments) to compute the vertical-vertical component of noise cross correlations for station pairs. MASE (Mesoamerican Seismic Experiment) consisted of one hundred stations deployed along a profile perpendicular to the trench and starting in Acapulco,Gro. Mex. This experiment ran from December 2004 until May, 2007. Fifty of these stations were relocated in a N-S profile crossing the Tehuantepec Isthmus from the Gulf of Mexico to the Pacific coast. These stations were operated from July 2007 until February 2009 and this stage of the experiment was called VEOX (Veracruz-Oaxaca). From the cross correlation for each pair of stations, Rayleigh wave dispersion curves were computed which represents the average group velocity between stations pairs. Furthermore, regional earthquakes recorded by the stations, were used to compute Rayleigh wave dispersion curves, which represent the average group velocity between epicenter and station. This mixed set of group velocity measurements was inverted to obtain tomographic images in discrete periods (5-50 s). Resolution tests show that the better-covered regions are surrounding both temporal experiments. Good coverage is also achieved in the large area between both experiments. In order to find details of crustal structure in the Tehuantepec Isthmus we use a set of previously computed receiver functions (Melgar and Pérez-Campos, 2011), to perform a joint inversion together with local dispersion curves reconstructed from the tomographic images. Results show good agreement with previous results by Melgar and Pérez-Campos (2011).

  5. Rayleigh-Wave, Group-Velocity Tomography of the Borborema Province, NE Brazil, from Ambient Seismic Noise

    NASA Astrophysics Data System (ADS)

    Dias, Rafaela Carreiro; Julià, Jordi; Schimmel, Martin

    2015-06-01

    Ambient seismic noise has traditionally been regarded as an unwanted perturbation that "contaminates" earthquake data. Over the last decade, however, it has been shown that consistent information about subsurface structure can be extracted from ambient seismic noise. By cross-correlation of noise simultaneously recorded at two seismic stations, the empirical Green's function for the propagating medium between them can be reconstructed. Moreover, for periods less than 30 s the seismic spectrum of ambient noise is dominated by microseismic energy and, because microseismic energy travels mostly as surface-waves, the reconstruction of the empirical Green's function is usually proportional to the surface-wave portion of the seismic wavefield. In this paper, we present 333 empirical Green's functions obtained from stacked cross-correlations of one month of vertical component ambient seismic noise for different pairs of seismic stations in the Borborema Province of NE Brazil. The empirical Green's functions show that the signal obtained is dominated by Rayleigh waves and that dispersion velocities can be measured reliably for periods between 5 and 20 s. The study includes permanent stations from a monitoring seismic network and temporary stations from past passive experiments in the region, resulting in a combined network of 34 stations separated by distances between approximately 40 and 1,287 km. Fundamental-mode group velocities were obtained for all station pairs and then tomographically inverted to produce maps of group velocity variation. For short periods (5-10 s) the tomographic maps correlate well with surface geology, with slow velocities delineating the main rift basins (Potiguar, Tucano, and Recôncavo) and fast velocities delineating the location of the Precambrian São Francisco craton and the Rio Grande do Norte domain. For longer periods (15-20 s) most of the velocity anomalies fade away, and only those associated with the deep Tucano basin and the S

  6. THE VELOCITY FIELD AROUND GROUPS OF GALAXIES

    SciTech Connect

    Hartwick, F. D. A.

    2011-06-15

    A statistical method is presented for determining the velocity field in the immediate vicinity of groups of galaxies using only positional and redshift information with the goal of studying the perturbation of the Hubble flow around groups more distant than the Local Group. The velocities are assumed to obey a Hubble-like expansion law, i.e., V = H{sub exp} R, where the expansion rate H{sub exp} is to be determined. The method is applied to a large, representative group catalog and evidence is found for a sub-Hubble expansion rate within two well-defined radii beyond the virial radii of the groups. This result is consistent with that of Teerikorpi et al. who found a similar expansion law around three nearby groups and extends it to a more representative volume of space.

  7. Chandra Observations of Low Velocity Dispersion Groups

    NASA Astrophysics Data System (ADS)

    Helsdon, Stephen F.; Ponman, Trevor J.; Mulchaey, J. S.

    2005-01-01

    Deviations of galaxy groups from cluster scaling relations can be understood in terms of an excess of entropy in groups. The main effect of this excess is to reduce the density and thus the luminosity of the intragroup gas. Given this, groups should also show a steep relationship between X-ray luminosity and velocity dispersion. However, previous work suggests that this is not the case, with many measuring slopes flatter than the cluster relation. Examining the group LX-σ relation shows that much of the flattening is caused by a small subset of groups that show very high X-ray luminosities for their velocity dispersions (or vice versa). Detailed Chandra study of two such groups shows that earlier ROSAT results were subject to significant (~30%-40%) point-source contamination but confirm that a significant hot intergalactic medium is present in these groups, although these are two of the coolest systems in which intergalactic X-ray emission has been detected. Their X-ray properties are shown to be broadly consistent with those of other galaxy groups, although the gas entropy in NGC 1587 is unusually low, and its X-ray luminosity is correspondingly high for its temperature when compared with most groups. This leads us to suggest that the velocity dispersion in these systems has been reduced in some way, and we consider how this might have come about.

  8. Raman solitons with group velocity dispersion

    NASA Astrophysics Data System (ADS)

    Skryabin, D. V.; Yulin, A. V.

    2006-10-01

    We consider the coupled propagation of the pump and Stokes waves in a Raman active medium accounting for the group velocity walk off and group velocity dispersion. Interplay of the Raman coherence and the dispersion can lead to the formation of a complete band gap in the spectrum of linear waves consisting of the two consecutive subgaps located at different frequencies. Using an approximate analytic technique, we find exponentially localized solitons residing in the complete gap, and find algebraic solitons when the gap is closed. Feasibility of observation of these structures in hollow fibers is discussed.

  9. Reconstruction of velocity fields in electromagnetic flow tomography.

    PubMed

    Lehtikangas, Ossi; Karhunen, Kimmo; Vauhkonen, Marko

    2016-06-28

    Electromagnetic flow meters (EMFMs) are the gold standard in measuring flow velocity in process industry. The flow meters can measure the mean flow velocity of conductive liquids and slurries. A drawback of this approach is that the velocity field cannot be determined. Asymmetric axial flows, often encountered in multiphase flows, pipe elbows and T-junctions, are problematic and can lead to serious systematic errors. Recently, electromagnetic flow tomography (EMFT) has been proposed for measuring velocity fields using several coils and a set of electrodes attached to the surface of the pipe. In this work, a velocity field reconstruction method for EMFT is proposed. The method uses a previously developed finite-element-based computational forward model for computing boundary voltages and a Bayesian framework for inverse problems. In the approach, the vz-component of the velocity field along the longitudinal axis of the pipe is estimated on the pipe cross section. Different asymmetric velocity fields encountered near pipe elbows, solids-in-water flows in inclined pipes and in stratified or multiphase flows are tested. The results suggest that the proposed reconstruction method could be used to estimate velocity fields in complicated pipe flows in which the conventional EMFMs have limited accuracy. This article is part of the themed issue 'Supersensing through industrial process tomography'. PMID:27185961

  10. Measurement of multidimensional ion velocity distributions by optical tomography

    NASA Astrophysics Data System (ADS)

    Koslover, R.; McWilliams, R.

    1986-10-01

    The development of a new diagnostic capable of measuring plasma ion distributions as a function of all three velocity-space coordinates is reported. The diagnostic makes use of laser-induced fluorescence (LIF) and computer-assisted image reconstruction techniques. LIF yields high-resolution, nonperturbing measurements of one-dimensional distributions that are integrated in two directions through three-dimensional velocity space. Computer tomography allows for the unambiguous determinations of the complete ion velocity distribution. In addition to a description of the diagnostic, examples of recovered distributions obtained from experiments are given, and the effects of the major steps in the data processing are discussed.

  11. Simultaneous inversion for velocity and attenuation by waveform tomography

    NASA Astrophysics Data System (ADS)

    Gao, Fengxia; Wang, Yanghua

    2016-08-01

    Seismic waveform tomography can invert for the velocity and attenuation (Q- 1) variations simultaneously. For this simultaneous inversion, we propose two strategies for waveform tomography. First, we analyze the contributions of the real part and the imaginary part of the gradients, associated with the velocity and attenuation parameters respectively, and determine that the combination of the real part of the gradient subvector for the velocity parameter and the imaginary part of the gradient subvector for the attenuation parameter would produce an optimal inversion result. Second, we attempt to balance the sensitivities of the objective function to the velocity and the attenuation parameters. Considering the magnitude differences between these two-type parameters in the simultaneous inversion, we apply preliminarily a normalization to both the velocity model and the attenuation model. However, for balancing their sensitivities, we further adjust the corresponding model updates using a tuning factor. We determine this tuning parameter adaptively, based on the sensitivities of these two parameters, at each iteration. Numerical tests demonstrate the feasibility and reliability of these two strategies in full waveform inversion.

  12. HALO VELOCITY GROUPS IN THE PISCES OVERDENSITY

    SciTech Connect

    Sesar, Branimir; Ivezic, Zeljko; Vivas, A. Katherina; Duffau, Sonia E-mail: zi@u.washington.ed E-mail: sonia.duffau@gmail.co

    2010-07-01

    We report spectroscopic observations of five faint (V {approx} 20) RR Lyrae stars associated with the Pisces overdensity conducted with the Gemini South Telescope. At a heliocentric and galactocentric distance of {approx}80 kpc, this is the most distant substructure in the Galactic halo known to date. We combined our observations with literature data and confirmed that the substructure is composed of two different kinematic groups. The main group contains eight stars and has (V{sub gsr}) = 50 km s{sup -1}, while the second group contains four stars at a velocity of (V{sub gsr}) = -52 km s{sup -1}, where V{sub gsr} is the radial velocity in the galactocentric standard of rest. The metallicity distribution of RR Lyrae stars in the Pisces overdensity is centered on [Fe/H] = -1.5 dex and has a width of 0.3 dex. The new data allowed us to establish that both groups are spatially extended making it very unlikely that they are bound systems, and are more likely to be debris of a tidally disrupted galaxy or galaxies. Due to small sky coverage, it is still unclear whether these groups have the same or different progenitors.

  13. The circular velocity function of group galaxies

    SciTech Connect

    Abramson, Louis E.; Williams, Rik J.; Benson, Andrew J.; Kollmeier, Juna A.; Mulchaey, John S.

    2014-09-20

    A robust prediction of ΛCDM cosmology is the halo circular velocity function (CVF), a dynamical cousin of the halo mass function. The correspondence between theoretical and observed CVFs is uncertain, however: cluster galaxies are reported to exhibit a power-law CVF consistent with N-body simulations, but that of the field is distinctly Schechter-like, flattened compared to ΛCDM expectations at circular velocities v {sub c} ≲ 200 km s{sup –1}. Groups offer a powerful probe of the role environment plays in this discrepancy as they bridge the field and clusters. Here, we construct the CVF for a large, mass- and multiplicity-complete sample of group galaxies from the Sloan Digital Sky Survey. Using independent photometric v {sub c} estimators, we find no transition from field to ΛCDM-shaped CVF above v {sub c} = 50 km s{sup –1} as a function of group halo mass. All groups with 12.4 ≲ log M {sub halo}/M {sub ☉} ≲ 15.1 (Local Group analogs to rich clusters) display similar Schechter-like CVFs marginally suppressed at low v {sub c} compared to that of the field. Conversely, some agreement with N-body results emerges for samples saturated with late-type galaxies, with isolated late-types displaying a CVF similar in shape to ΛCDM predictions. We conclude that the flattening of the low-v {sub c} slope in groups is due to their depressed late-type fractions—environment affecting the CVF only to the extent that it correlates with this quantity—and that previous cluster analyses may suffer from interloper contamination. These results serve as useful benchmarks for cosmological simulations of galaxy formation.

  14. Demonstration of images with negative group velocities.

    PubMed

    Glasser, Ryan T; Vogl, Ulrich; Lett, Paul D

    2012-06-18

    We report the experimental demonstration of the superluminal propagation of multi-spatial-mode images via four-wave mixing in hot atomic vapor, in which all spatial sub-regions propagate with negative group velocities. We investigate the spatial mode properties and temporal reshaping of the fast light images, and show large relative pulse peak advancements of up to 64 % of the input pulse width. The degree of temporal reshaping is quantified and increases as the relative pulse peak advancement increases. When optimized for image quality or pulse advancement, negative group velocities of up to v(g)=-c/880 and v(g)=-c/2180, respectively, are demonstrated when integrating temporally over the entire image. The present results are applicable to temporal cloaking devices that require strong manipulation of the dispersion relation, where one can envision temporally cloaking various spatial regions of an image for different durations. Additionally, the modes involved in a four-wave mixing process similar to the present experiment have been shown to exhibit quantum correlations and entanglement. The results presented here provide insight into how to tailor experimental tests of the behavior of these quantum correlations and entanglement in the superluminal regime. PMID:22714436

  15. Rogue events in the group velocity horizon

    PubMed Central

    Demircan, Ayhan; Amiranashvili, Shalva; Brée, Carsten; Mahnke, Christoph; Mitschke, Fedor; Steinmeyer, Günter

    2012-01-01

    The concept of rogue waves arises from a mysterious and potentially calamitous phenomenon of oceanic surfaces. There is mounting evidence that they are actually commonplace in a variety of different physical settings. A set of defining criteria has been advanced; this set is of great generality and therefore applicable to a wide class of systems. The question arises naturally whether there are generic mechanisms responsible for extreme events in different systems. Here we argue that under suitable circumstances nonlinear interaction between weak and strong waves results in intermittent giant waves with all the signatures of rogue waves. To obtain these circumstances only a few basic conditions must be met. Then reflection of waves at the so-called group-velocity horizon occurs. The connection between rogue waves and event horizons, seemingly unrelated physical phenomena, is identified as a feature common in many different physical systems. PMID:23152941

  16. Explore Seismic Velocity Change Associated with the 2010 Kaohsiung Earthquake by Ambient Noise Tomography

    NASA Astrophysics Data System (ADS)

    Ku, Chin-Shang; Wu, Yih-Min; Huang, Bor-Shouh; Huang, Win-Gee; Liu, Chun-Chi

    2016-04-01

    A ML 6.4 earthquake occurred on 4 March 2010 in Kaohsiung, the southern part of Taiwan, this shallow earthquake is the largest one of that area in the past few years. Some damages occurred on buildings and bridges after the earthquake, obvious surface deformation up to few cm was observed and the transportation including road and train traffic was also affected near the source area. Some studies about monitoring the velocity change induced by the big earthquake were carried out recently, most of studies used cross-correlation of the ambient noise-based method and indicated velocity drop was observed immediately after the big earthquake. However, this method is not able to constrain the depth of velocity change, and need to assume a homogeneous seismic velocity change during the earthquake. In this study, we selected 25 broadband seismic stations in the southern Taiwan and time period is from 2009/03 to 2011/03. Then we explored the velocity change associated with the 2010 Kaohsiung earthquake by applying ambient noise tomography (ANT) method. ANT is a way of using interferometry to image subsurface seismic velocity variations by using surface wave dispersions extracted from the ambient noise cross-correlation of seismic station-pairs, then the 2-D group velocity map with different periods could be extracted. Compare to ambient noise-based cross-correlation analysis, we estimated sensitivity kernel of dispersion curves and converted 2-D group velocity map from "with the period" to "with the depth" to have more constraints on the depth of velocity change. By subtracting shear velocity between "before" and "after" the earthquake, we could explore velocity change associated with the earthquake. Our result shows velocity reduction about 5-10% around the focal depth after the 2010 Kaohsiung earthquake and the post-seismic velocity recovery was observed with time period increasing, which may suggest a healing process of damaged rocks.

  17. Sleipner CCS site: velocity and attenuation model from seismic tomography

    NASA Astrophysics Data System (ADS)

    Rossi, G.; Chadwick, R. A.; Williams, G. A.

    2012-04-01

    The results of the travel-time and frequency shift tomographic inversion of the seismic data from one of the high-resolution lines acquired in 2006 on the Sleipner CO2 geological storage site are here presented. The work has been performed within the European project CO2ReMoVe, to produce an accurate model in-depth, of both seismic velocities and attenuation, to constrain better the quantification studies of the project's partners. Tomographic techniques have the advantage of not assuming horizontal layering or uniform lateral velocities, and of enabling an easy comparison of models, even if resulting from seismic data acquired with different geometries, unavoidable in a time-lapse data set. Through an iterative process, the differences in travel-times between observed direct, reflected or refracted arrivals and the same, calculated on a discrete model, with a ray-tracing based on the Fermat's principle, are minimized. Other minimization procedures provide the reflector/refractor geometries in -depth. Analogously, in attenuation tomography, the minimization process takes into account the observed and calculated spectral-centroid frequency-shift, due to the loss of the highest frequency of the seismic wave, while crossing an attenuating medium. The result is a seismic quality factor (Q) model in-depth, and hence of the attenuation that is known to be more sensitive to subtle changes in physical properties than seismic velocity. The model is across the center of the CO2 plume, on the in-line 1838, and is constituted by nine layers, four resulting by a preliminary analysis of the pre-injection 1994 data set, i.e. seabed, a strong reflection in the overburden and the top and bottom of the Utsira Sand, plus additional five horizons, four of which within Utsira Sands, and one just above the top of it. The layers within the reservoir are very close to each other and in some cases they merge together laterally. The accumulation of CO2 in the uppermost layer of the

  18. Preliminary Shear Velocity Tomography of Mt St Helens, Washington from iMUSH Array

    NASA Astrophysics Data System (ADS)

    Crosbie, K.; Abers, G. A.; Creager, K. C.; Moran, S. C.; Denlinger, R. P.; Ulberg, C. W.

    2015-12-01

    The imaging Magma Under Mount St Helens (iMUSH) experiment will illuminate the crust beneath Mt St Helens volcano. The ambient noise tomography (ANT) component of this experiment measures shear velocity structure, which is more sensitive than P velocity to the presence of melt and other pore fluids. Seventy passive-source broadband seismometers for iMUSH were deployed in the summer of 2014 in a dense array of 100 Km diameter with a 10 km station spacing. We cross correlated ambient noise in 120 s windows and summed the result over many months for pairs of stations. Then frequency-domain methods on these cross correlations are employed to measure the phase velocities (Ekström et al. Geophys Rev Lett, 2009). Unlike velocities attained by group velocity methods, velocities for path lengths as small as one wavelength can be measured, enabling analysis of higher frequency signals and increasing spatial resolution. The minimum station spacing from which signals can be recovered ranges from 12 km at 0.18 Hz, a frequency that dominantly samples the upper crust to 20 km, to 37 km at 0.04 Hz, a frequency sensitive to structure through the crust and uppermost mantle, with lower spacing at higher frequencies. These phase velocities are tomographically inverted to obtain shear velocity maps for each frequency, assuming ray theory. Initial shear velocity maps for frequencies between 0.04-0.18 Hz reveal low-velocity sediments in the Puget Lowland west of Mount St Helens at 0.16-0.18 Hz, and a low velocity zone near 0.10 Hz between Mt Rainier and Mt Adams, east of Mount St Helens. The latter may reflect large-scale crustal plumbing of the arc between volcanic centers. In subsequent analyses these ANT results will be jointly inverted with receiver functions in order to further resolve crustal and upper mantle structure.

  19. DIFFERENTIAL GROUP-VELOCITY DETECTION OF FLUID PATHS

    SciTech Connect

    Leland Timothy Long

    2005-12-20

    For nearly 50 years, surface waves that propagate through near-surface soils have been utilized in engineering for the determination of the small-strain dynamic properties of soils. These techniques, although useful, have not been sufficiently precise to use in detecting the subtle changes in soil properties that accompany short-term changes in fluid content. The differential techniques developed in this research now make it possible to monitor small changes (less than 3 cm) in the water level of shallow soil aquifers. Using inversion techniques and tomography, differential seismic techniques could track the water level distribution in aquifers with water being pumped in or out. Differential surface wave analysis could lead to new ways to monitor reservoir levels and verify hydrologic models. Field data obtained during this investigation have measured changes in surface-wave phase and group velocity before and after major rain events, and have detected subtle changes associated with pumping water into an aquifer and pumping water out of an aquifer. This research has established analysis techniques for observing these changes. These techniques combine time domain measurements to isolate surface wave arrivals with frequency domain techniques to determine the effects as a function of frequency. Understanding the differences in response as a function of wave frequency facilitates the inversion of this data for soil velocity structure. These techniques have also quantified many aspects of data acquisition and analysis that are important for significant results. These include tight control on the character of the source and proper placement of the geophones. One important application is the possibility that surface waves could be used to monitor and/or track fluid movement during clean-up operations, verifying that the fluid reached all affected areas. Extending this to a larger scale could facilitate monitoring of water resources in basins without having to drill many

  20. Crustal and uppermost mantle velocity structure beneath northwestern China from seismic ambient noise tomography

    NASA Astrophysics Data System (ADS)

    Li, Hongyi; Li, S.; Song, X. D.; Gong, M.; Li, X.; Jia, J.

    2012-01-01

    In this paper, we conduct ambient noise seismic tomography of northwestern China and adjacent regions. The data include 9 months (2009 January to 2009 September) three-component continuous data recorded at 146 seismic stations of newly upgraded China Provincial Digital Seismic Networks and regional Kyrgyzstan and Kazakhstan networks. Empirical Rayleigh and Love wave Green's functions are obtained from interstation cross-correlations. Group velocity dispersion curves for both Rayleigh and Love waves between 7 and 50 s periods were measured for each interstation path by applying the multiple-filter analysis method with phase-matched processing. The group velocity maps show clear lateral variations which correlate well with major geological structures and tectonic units in the study region. Shear wave velocity structures are inverted from Rayleigh wave and love wave dispersion maps. The results show that the Tibetan Plateau has a very thick crust with a low-velocity zone in its mid-lower crust. Along the northern margin of the plateau where a steep topographic gradient is present, the low-velocity zone does not extend to the Tarim basin which may indicate that crustal materials beneath the Tarim basin are colder and stronger than beneath the plateau, therefore inhibit the extension of mid-lower crustal flow and deformation of the Tibetan Plateau, resulting in very sharp topography contrasts. In the northeastern margin with a gentle topographic gradient toward the Ordos platform, the low-velocity zone diminishes around the eastern KunLun fault. Meanwhile, our results reveal obvious lateral velocity changes in the crust beneath the Tarim basin. In the upper crust, the Manjaer depression in the eastern Tarim basin is featured with very low velocities and the Bachu uplift in the western Tarim basin with high velocities; in the mid-lower crust, the northern Tarim basin in general displays lower velocities than the southern part along latitude ˜40° N with an east

  1. A 3-D shear velocity model of the southern North American and Caribbean plates from ambient noise and earthquake tomography

    NASA Astrophysics Data System (ADS)

    Gaite, B.; Villaseñor, A.; Iglesias, A.; Herraiz, M.; Jiménez-Munt, I.

    2015-02-01

    We use group velocities from earthquake tomography together with group and phase velocities from ambient noise tomography (ANT) of Rayleigh waves to invert for the 3-D shear-wave velocity structure (5-70 km) of the Caribbean (CAR) and southern North American (NAM) plates. The lithospheric model proposed offers a complete image of the crust and uppermost-mantle with imprints of the tectonic evolution. One of the most striking features inferred is the main role of the Ouachita-Marathon-Sonora orogeny front on the crustal seismic structure of the NAM plate. A new imaged feature is the low crustal velocities along the USA-Mexico border. The model also shows a break of the east-west mantle velocity dichotomy of the NAM and CAR plates beneath the Isthmus of the Tehuantepec and the Yucatan Block. High upper-mantle velocities along the Mesoamerican Subduction Zone coincide with inactive volcanic areas while the lowest velocities correspond to active volcanic arcs and thin lithospheric mantle regions.

  2. Complex group velocity and energy transport in absorbing media.

    PubMed

    Gerasik, Vladimir; Stastna, Marek

    2010-05-01

    Complex group velocity is common in absorbing and active media, yet its precise physical meaning is unclear. While in the case of a nondissipative medium the group velocity of propagating waves Cg=dω/dk is exactly equal to the observable energy velocity (defined as the ratio between the energy flux and the total energy density) Cg=F/E , in a dissipative medium Cg=dω/dk is in general a complex quantity which cannot be associated with the velocity of energy transport. Nevertheless, we find that the complex group velocity may contain information about the energy transport as well as the energy dissipated in the medium. The presented analysis is intended to expound the connection between the complex group velocity and energy transport characteristics for a class of hyperbolic dissipative dynamical systems. Dissipation mechanisms considered herein include viscous and viscoelastic types of damping. Both cases of spatial and temporal decay are discussed. The presented approach stems from the Lagrangian formulation and is illustrated with identities that relate the complex group velocity and energy transport characteristics for the damped Klein-Gordon equation; Maxwell's equations, governing electromagnetic waves in partially conducting media; and Biot's theory, governing acoustic wave propagation in porous solids. PMID:20866345

  3. Group-Velocity-Matched Three Wave Mixing in Birefringent Crystals

    SciTech Connect

    SMITH,ARLEE V.

    2000-12-12

    We show that the combination of pulse-front slant, k-vector tilt, and crystal birefringence often permits exact matching of both phase and group velocities in three wave mixing in birefringent crystals. This makes possible more efficient mixing of short light pulses, and it permits efficient mixing of chirped or broad bandwidth light. We analyze this process and present examples. Differences in the group velocities of the three interacting waves in a nonlinear crystal often limits the effective interaction length. For example, in mixing very short pulses, temporal walk off can stretch the pulses in time unless the crystal is very short. Efficient mixing with such short crystals requires high irradiances, but the irradiances are limited by higher order nonlinear effects such as intensity-dependent refractive index and two-photon absorption. Improved matching of the group velocities can alleviate this problem, allowing longer crystal and lower irradiances. Similarly, for high energy pulses, practical limits on crystal apertures mandate temporally stretching the pulses to reduce irradiances. For the resulting chirped pulses, temporal walk off restricts the chirp range unless the group velocities are well matched. In addition to perfectly matching the group velocities of all three waves, it is sometimes useful to match two velocities, such as the signal and idler in parametric amplification, permitting broadband parametric amplification, or to arrange the velocities of two inputs to bracket the generated sum frequency pulse, giving pulse compression under suitable circumstances.

  4. Filtering for unwrapping noisy Doppler optical coherence tomography images for extended microscopic fluid velocity measurement range.

    PubMed

    Xu, Yang; Darga, Donald; Smid, Jason; Zysk, Adam M; Teh, Daniel; Boppart, Stephen A; Scott Carney, P

    2016-09-01

    In this Letter, we report the first application of two phase denoising algorithms to Doppler optical coherence tomography (DOCT) velocity maps. When combined with unwrapping algorithms, significantly extended fluid velocity dynamic range is achieved. Instead of the physical upper bound, the fluid velocity dynamic range is now limited by noise level. We show comparisons between physical simulated ideal velocity maps and the experimental results of both algorithms. We demonstrate unwrapped DOCT velocity maps having a peak velocity nearly 10 times the theoretical measurement range. PMID:27607963

  5. Rayleigh-wave group velocity distribution in the Antarctic region

    NASA Astrophysics Data System (ADS)

    Kobayashi, Reiji; Zhao, Dapeng

    2004-03-01

    We determined 2D group velocity distribution of Rayleigh waves at periods of 20-150 s in the Antarctic region using a tomographic inversion technique. The data are recorded by both permanent networks and temporary arrays. In East Antarctica the velocities are high at periods of 90-150 s, suggesting that the root of East Antarctica is very deep. The velocities in West Antarctica are low at all periods, which may be related to the volcanic activity and the West Antarctic Rift System. Low velocity anomalies appear at periods of 40-140 s along the Southeastern Indian Ridge and the western part of the Pacific Antarctic Ridge. The velocities are only slightly low around the Atlantic Indian Ridge, Southwestern Indian Ridge, and the eastern part of the Pacific Antarctic Ridge, where the spreading rates are small. Around two hotspots, the Mount Erebus and Balleny Islands, the velocity is low at periods of 50-150 s.

  6. Inverse characterization of plates using zero group velocity Lamb modes.

    PubMed

    Grünsteidl, Clemens; Murray, Todd W; Berer, Thomas; Veres, István A

    2016-02-01

    In the presented work, the characterization of plates using zero group velocity Lamb modes is discussed. First, analytical expressions are shown for the determination of the k-ω location of the zero group velocity Lamb modes as a function of the Poisson's ratio. The analytical expressions are solved numerically and an inverse problem is formulated to determine the unknown wave velocities in plates of known thickness. The analysis is applied to determine the elastic properties of tungsten and aluminum plates based on the experimentally measured frequency spectra. PMID:26527393

  7. ML shear wave velocity tomography for the Iranian Plateau

    NASA Astrophysics Data System (ADS)

    Maheri-Peyrov, Mehdi; Ghods, Abdolreza; Abbasi, Madjid; Bergman, Eric; Sobouti, Farhad

    2016-04-01

    Iranian Plateau reflects several different tectonic styles of collision, and large-scale strike-slip faults. We calculate a high-resolution 2-D ML shear velocity map for the Iranian Plateau to detect lateral crustal thickness changes associated with different tectonic boundaries. The ML velocity is very sensitive to strong lateral variations of crustal thickness and varies between the velocity of Lg and Sn phases. Our data set consists of 65 795 ML amplitude velocity measurements from 2531 precisely relocated events recorded by Iranian networks in the period 1996-2014. Using a constrained least-squares inversion scheme, we inverted the ML velocities for a 2-D shear velocity map of Iran. Our results show that the Zagros and South Caspian Basin (SCB) have shear wave velocities close to the Sn phase, and are thus Lg-blocking regions. High velocities in the High Zagros and the Simply Folded Belt imply significant crustal undulations within these zones. We note that in the central and south Zagros, the velocity border between the Zagros and central Iran is not coincident with the Zagros suture line that marks underthrusting of the Arabian plate beneath central Iran. The low plains of Gilan and Gorgan to the south of the Caspian Sea show high shear velocities similar to the SCB, implying that they are either underlain by an oceanic type crust or a transitional crust with a strong lateral crustal thickness gradient. The Lut block is an Lg-passing block implying that it is not surrounded by any sudden crustal thickness changes along its borders with central Iran. In the Alborz, NW Iran, Kopeh-Dagh, Binalud and most of the central Iran, low shear velocity near the Lg velocity is attributed to smooth or minor Moho undulations within these regions.

  8. Negative Group Velocity in the Absence of Absorption Resonance

    PubMed Central

    Ye, Dexin; Zheng, Guoan; Wang, Jingyu; Wang, Zhiyu; Qiao, Shan; Huangfu, Jiangtao; Ran, Lixin

    2013-01-01

    Scientific community has well recognized that a Lorentzian medium exhibits anomalous dispersion behavior in its resonance absorption region. To satisfy the Krammers-Kronig relation, such an anomalous region has to be accompanied with significant loss, and thus, experimental observations of negative group velocity in this region generally require a gain-assisted approach. In this letter, we demonstrate that the negative group velocity can also be observed in the absence of absorption resonance. We show that the k-surface of a passive uniaxial Lorentzian medium undergoes a distortion near the plasma frequency. This process yields an anomalous dispersion bandwidth that is far away from the absorption resonance region, and enables the observation of negative group velocity at the plasma frequency band. Introducing anomalous dispersion in a well-controlled manner would greatly benefit the research of ultrafast photonics and find potential applications in optical delay lines, optical data storage and devices for quantum information processing. PMID:23568139

  9. Direct ambient noise tomography for 3-D near surface shear velocity structure: methodology and applications

    NASA Astrophysics Data System (ADS)

    Yao, H.; Fang, H.; Li, C.; Liu, Y.; Zhang, H.; van der Hilst, R. D.; Huang, Y. C.

    2014-12-01

    Ambient noise tomography has provided essential constraints on crustal and uppermost mantle shear velocity structure in global seismology. Recent studies demonstrate that high frequency (e.g., ~ 1 Hz) surface waves between receivers at short distances can be successfully retrieved from ambient noise cross-correlation and then be used for imaging near surface or shallow crustal shear velocity structures. This approach provides important information for strong ground motion prediction in seismically active area and overburden structure characterization in oil and gas fields. Here we propose a new tomographic method to invert all surface wave dispersion data for 3-D variations of shear wavespeed without the intermediate step of phase or group velocity maps.The method uses frequency-dependent propagation paths and a wavelet-based sparsity-constrained tomographic inversion. A fast marching method is used to compute, at each period, surface wave traveltimes and ray paths between sources and receivers. This avoids the assumption of great-circle propagation that is used in most surface wave tomographic studies, but which is not appropriate in complex media. The wavelet coefficients of the velocity model are estimated with an iteratively reweighted least squares (IRLS) algorithm, and upon iterations the surface wave ray paths and the data sensitivity matrix are updated from the newly obtained velocity model. We apply this new method to determine the 3-D near surface wavespeed variations in the Taipei basin of Taiwan, Hefei urban area and a shale and gas production field in China using the high-frequency interstation Rayleigh wave dispersion data extracted from ambient noisecross-correlation. The results reveal strong effects of off-great-circle propagation of high-frequency surface waves in these regions with above 30% shear wavespeed variations. The proposed approach is more efficient and robust than the traditional two-step surface wave tomography for imaging complex

  10. Ambient noise surface wave tomography to determine the shallow shear velocity structure at Valhall: depth inversion with a Neighbourhood Algorithm

    NASA Astrophysics Data System (ADS)

    Mordret, A.; Landès, M.; Shapiro, N. M.; Singh, S. C.; Roux, P.

    2014-09-01

    This study presents a depth inversion of Scholte wave group and phase velocity maps obtained from cross-correlation of 6.5 hr of noise data from the Valhall Life of Field Seismic network. More than 2 600 000 vertical-vertical component cross-correlations are computed from the 2320 available sensors, turning each sensor into a virtual source emitting Scholte waves. We used a traditional straight-ray surface wave tomography to compute the group velocity map. The phase velocity maps have been computed using the Eikonal tomography method. The inversion of these maps in depth are done with the Neighbourhood Algorithm. To reduce the number of free parameters to invert, geological a priori information are used to propose a power-law 1-D velocity profile parametrization extended with a gaussian high-velocity layer where needed. These parametrizations allowed us to create a high-resolution 3-D S-wave model of the first 600 m of the Valhall subsurface and to precise the locations of geological structures at depth. These results would have important implication for shear wave statics and monitoring of seafloor subsidence due to oil extraction. The 3-D model could also be a good candidate for a starting model used in full-waveform inversions.

  11. Subduction zones beneath Indonesia imaged by Rayleigh wave phase velocity tomography

    NASA Astrophysics Data System (ADS)

    Liu, F.; Yang, T.; Harmon, N.

    2013-12-01

    Situated at the junction of several tectonic plates including Indian-Australia, Eurasia, and Philippine Sea, the Indonesian archipelago is one of the most tectonically complex regions on earth with subductions, collisions and accretions occurring along and within its boundaries. A high-resolution lithospheric and upper mantle model, therefore, is needed to understand these complex processes beneath this region. We present a phase velocity model derived from teleseismic Rayleigh waves recorded at seismic stations in this region. We use the modified version of the two-plane wave tomography, in which the non-planar effects of surface wave propagation such as multipathing and scattering are accounted for by two plane wave interference and using of finite frequency kernels. We measure the amplitudes and phases at 16 individual periods ranging from 20s to 150s for the fundamental mode of Rayleigh waves at over 30 stations. 254 earthquakes are selected from global events greater than Ms 5.5 in the distance range of 25°- 150°. To account for the wavefield inconsistencies among stations for each earthquake due to the large scale of our study region, we divide the seismic array into 4 groups of stations in the two-plane wave parameter inversion. The phase velocity maps from our preliminary results show coherent features between adjacent periods. The most dominant structure in phase velocity maps for all periods is the strong fast-velocity belts beneath Sunda Trench, Java Trench, Timor Trough and the trenches around Celebes Sea, which shift gradually toward the subduction directions. The strength of the high velocity anomaly varies among trenches, likely suggesting the different age of subducting slabs. In addition, a velocity contrast in the middle of Borneo appears to mark the Lupar Line, a boundary between the stable Sundaland continental core and fragments of ophiolitic and Asian continental material accreted to Borneo during the Cretaceous. The 3-D shear wave structure

  12. SPIDER - IX. Classifying galaxy groups according to their velocity distribution

    NASA Astrophysics Data System (ADS)

    Ribeiro, A. L. B.; de Carvalho, R. R.; Trevisan, M.; Capelato, H. V.; La Barbera, F.; Lopes, P. A. A.; Schilling, A. C.

    2013-09-01

    We introduce a new method to study the velocity distribution of galaxy systems, the Hellinger Distance (HD), designed for detecting departures from a Gaussian velocity distribution. Testing different approaches to measure normality of a distribution, we conclude that HD is the least vulnerable method to type I and II statistical errors. We define a relaxed galactic system as the one with unimodal velocity distribution and a normality deviation below a critical value (HD < 0.05). In this work, we study the Gaussian nature of the velocity distribution of the Berlind group sample, and of the FoF groups from the Millennium simulation. For the Berlind group sample (z < 0.1), 67 per cent of the systems are classified as relaxed, while for the Millennium sample we find 63 per cent (z = 0). We verify that in multi-modal groups the average mass of modes in high-multiplicity (N ≥ 20) systems are significantly larger than in low-multiplicity ones (N < 20), suggesting that groups experience a mass growth at an increasing virialization rate towards z = 0, with larger systems accreting more massive subunits. We also investigate the connection between galaxy properties ([Fe/H], Age, eClass, g - r, Rpetro and <μpetro>) and the Gaussianity of the velocity distribution of the groups. Bright galaxies (Mr ≤ -20.7) residing in the inner and outer regions of groups do not show significant differences in the listed quantities regardless if the group has a Gaussian (G) or a Non-Gaussian (NG) velocity distribution. However, the situation is significantly different when we examine the faint galaxies (-20.7 < Mr ≤ -17.9). In G groups, there is a remarkable difference between the galaxy properties of the inner and outer galaxy populations, testifying how the environment is affecting the galaxies. Instead, in NG groups there is no segregation between the properties of galaxies in the inner and outer regions, showing that the properties of these galaxies still reflect the physical

  13. Absolute velocity measurement using three-beam spectral-domain Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Sharma, P.; Verma, Y.; Kumar, S.; Gupta, P. K.

    2015-09-01

    We report the development of a three-beam spectral-domain Doppler optical coherence tomography setup that allows single interferometer-based measurement of absolute flow velocity. The setup makes use of galvo-based phase shifting to remove complex conjugate mirror artifact and a beam displacer in the sample arm to avoid cross talk image. The results show that the developed approach allows efficient utilization of the imaging range of the spectral-domain optical coherence tomography setup for three-beam-based velocity measurement.

  14. Crosswell seismic studies in gas hydrate-bearing sediments: P wave velocity and attenuation tomography

    NASA Astrophysics Data System (ADS)

    Bauer, K.; Haberland, Ch.; Pratt, R. G.; Ryberg, T.; Weber, M. H.; Mallik Working Group

    2003-04-01

    We present crosswell seismic data from the Mallik 2002 Production Research Well Program, an international research project on Gas Hydrates in the Northwest Territories of Canada. The program participants include 8 partners; The Geological Survey of Canada (GSC), The Japan National Oil Corporation (JNOC), GeoForschungsZentrum Potsdam (GFZ), United States Geological Survey (USGS), United States Department of the Energy (USDOE), India Ministry of Petroleum and Natural Gas (MOPNG)/Gas Authority of India (GAIL) and the Chevron-BP-Burlington joint venture group. The crosswell seismic measurements were carried out by making use of two 1160 m deep observation wells (Mallik 3L-38 and 4L-38) both 45 m from and co-planar with the 1188 m deep production research well (5L-38). A high power piezo-ceramic source was used to generate sweeped signals with frequencies between 100 and 2000 Hz recorded with arrays of 8 hydrophones per depth level. A depth range between 800 and 1150 m was covered, with shot and receiver spacings of 0.75 m. High quality data could be collected during the survey which allow for application of a wide range of crosswell seismic methods. The initial data analysis included suppression of tube wave energy and picking of first arrivals. A damped least-squares algorithm was used to derive P-wave velocities from the travel time data. Next, t* values were derived from the decay of the amplitude spectra, which served as input parameters for a damped least-squares attenuation tomography. The initial results of the P-wave velocity and attenuation tomography reveal significant features reflecting the stratigraphic environment and allow for detection and eventually quantification of gas hydrate bearing sediments. A prominent correlation between P velocity and attenuation was found for the gas hydrate layers. This contradicts to the apparently more meaningful inverse correlation as it was determined for the gas hydrates at the Blake Ridge but supports the results from

  15. On electromagnetic waves with a negative group velocity

    NASA Astrophysics Data System (ADS)

    Makarov, V. P.; Rukhadze, A. A.; Samokhin, A. A.

    2010-12-01

    Recent publications devoted to the electrodynamics of media in which waves with a negative group velocity can exist are discussed. The properties of such waves have been studied from the beginning of the past century, and the most important results in this field were obtained by Soviet physicists in the 1940s-1950s. However, in most recent publications, this circumstance has not been taken into account.

  16. On electromagnetic waves with a negative group velocity

    SciTech Connect

    Makarov, V. P.; Rukhadze, A. A.; Samokhin, A. A.

    2010-12-15

    Recent publications devoted to the electrodynamics of media in which waves with a negative group velocity can exist are discussed. The properties of such waves have been studied from the beginning of the past century, and the most important results in this field were obtained by Soviet physicists in the 1940s-1950s. However, in most recent publications, this circumstance has not been taken into account.

  17. Envelope, group and phase velocities in a nested frequency comb

    NASA Astrophysics Data System (ADS)

    Masuda, Koji; Hendrie, James; Diels, Jean-Claude; Arissian, Ladan

    2016-04-01

    Fabry–Pérot etalons have been traditionally used in a laser cavity to tune the optical frequency. In this work we present the generation of interwoven frequency combs with insertion of an intracavity Fabry–Pérot in a mode-locked laser. A high frequency comb is generated by insertion of an uncoated (low finesse) Fabry–Pérot inside the laser cavity. The intracavity Fabry–Pérot acquires a high finesse from the laser cavity and the velocity of the pulses in the Fabry–Pérot is affected by the laser cavity length, gain and losses, with the dielectric group velocity dk/dΩ playing only a minor role. The output characteristics are explained by the condition that the radiation is simultaneously resonant with the etalon and the laser cavity.

  18. Envelope, group and phase velocities in a nested frequency comb

    NASA Astrophysics Data System (ADS)

    Masuda, Koji; Hendrie, James; Diels, Jean-Claude; Arissian, Ladan

    2016-05-01

    Fabry–Pérot etalons have been traditionally used in a laser cavity to tune the optical frequency. In this work we present the generation of interwoven frequency combs with insertion of an intracavity Fabry–Pérot in a mode-locked laser. A high frequency comb is generated by insertion of an uncoated (low finesse) Fabry–Pérot inside the laser cavity. The intracavity Fabry–Pérot acquires a high finesse from the laser cavity and the velocity of the pulses in the Fabry–Pérot is affected by the laser cavity length, gain and losses, with the dielectric group velocity dk/dΩ playing only a minor role. The output characteristics are explained by the condition that the radiation is simultaneously resonant with the etalon and the laser cavity.

  19. Superfluid phase transition with activated velocity fluctuations: Renormalization group approach.

    PubMed

    Dančo, Michal; Hnatič, Michal; Komarova, Marina V; Lučivjanský, Tomáš; Nalimov, Mikhail Yu

    2016-01-01

    A quantum field model that incorporates Bose-condensed systems near their phase transition into a superfluid phase and velocity fluctuations is proposed. The stochastic Navier-Stokes equation is used for a generation of the velocity fluctuations. As such this model generalizes model F of critical dynamics. The field-theoretic action is derived using the Martin-Siggia-Rose formalism and path integral approach. The regime of equilibrium fluctuations is analyzed within the perturbative renormalization group method. The double (ε,δ)-expansion scheme is employed, where ε is a deviation from space dimension 4 and δ describes scaling of velocity fluctuations. The renormalization procedure is performed to the leading order. The main corollary gained from the analysis of the thermal equilibrium regime suggests that one-loop calculations of the presented models are not sufficient to make a definite conclusion about the stability of fixed points. We also show that critical exponents are drastically changed as a result of the turbulent background and critical fluctuations are in fact destroyed by the developed turbulence fluctuations. The scaling exponent of effective viscosity is calculated and agrees with expected value 4/3. PMID:26871026

  20. Superfluid phase transition with activated velocity fluctuations: Renormalization group approach

    NASA Astrophysics Data System (ADS)

    Dančo, Michal; Hnatič, Michal; Komarova, Marina V.; Lučivjanský, Tomáš; Nalimov, Mikhail Yu.

    2016-01-01

    A quantum field model that incorporates Bose-condensed systems near their phase transition into a superfluid phase and velocity fluctuations is proposed. The stochastic Navier-Stokes equation is used for a generation of the velocity fluctuations. As such this model generalizes model F of critical dynamics. The field-theoretic action is derived using the Martin-Siggia-Rose formalism and path integral approach. The regime of equilibrium fluctuations is analyzed within the perturbative renormalization group method. The double (ɛ ,δ ) -expansion scheme is employed, where ɛ is a deviation from space dimension 4 and δ describes scaling of velocity fluctuations. The renormalization procedure is performed to the leading order. The main corollary gained from the analysis of the thermal equilibrium regime suggests that one-loop calculations of the presented models are not sufficient to make a definite conclusion about the stability of fixed points. We also show that critical exponents are drastically changed as a result of the turbulent background and critical fluctuations are in fact destroyed by the developed turbulence fluctuations. The scaling exponent of effective viscosity is calculated and agrees with expected value 4 /3 .

  1. Seismic velocity structure of the Puget Sound Region from three dimensional nonlinear tomography

    NASA Astrophysics Data System (ADS)

    Symons, Neill Philip

    In this dissertation I describe a non-linear seismic tomography experiment in the Greater Puget Sound Region (GPSR). The GPSR contains portions of three distinct geologic provinces: (1) the Coast Range Province---composed of the Olympic Mountains and the Siletzia terrane lying along the Washington Coast (the western edge of the GPSR). (2) The Puget Lowland---an approximately linear depression that stretches from Oregon's Willamette Valley to the Strait of Georgia in Canada. The Puget Lowland lies in the middle of the GPSR. (3) The Cascade Range---lying along the eastern edge of the GPSR and characterized by extensive episodic volcanism since the later Mesozoic. The result of this study is a three-dimensional model of the P-wave velocity within the GPSR. Interpretation of this model provides information about the subsurface geology in the region. The method used to perform the tomography has been developed as part of this research. The method uses a finite-difference algorithm to calculate seismic travel-times to every point in the region using the full 3-d velocity model. The method is capable of using three different types of data: (1) earthquakes with unknown hypocenters. The earthquake hypocenters are found as part of the model during solution of the tomography problem. (2) Explosions or other seismic events with known locations. (3) External data constraining the seismic velocity at known locations within the model. There is a good correlation between the velocity model derived in this experiment and several known geologic structures in the GPSR, including: the core of the Olympic Mountains; high seismic velocity where the basalt that makes up the Siletzia terrane outcrops; and low-velocity regions at basins under the cities of Seattle, Tacoma, Everett, and Chehalis. The data provides sufficient resolution to delineate the geometry of the contacts between these units within a large portion of the GPSR.

  2. Finite-frequency traveltime tomography of San Francisco Bay region crustal velocity structure

    USGS Publications Warehouse

    Pollitz, F.F.

    2007-01-01

    Seismic velocity structure of the San Francisco Bay region crust is derived using measurements of finite-frequency traveltimes. A total of 57 801 relative traveltimes are measured by cross-correlation over the frequency range 0.5-1.5 Hz. From these are derived 4862 'summary' traveltimes, which are used to derive 3-D P-wave velocity structure over a 341 ?? 140 km2 area from the surface to 25 km depth. The seismic tomography is based on sensitivity kernels calculated on a spherically symmetric reference model. Robust elements of the derived P-wave velocity structure are: a pronounced velocity contrast across the San Andreas fault in the south Bay region (west side faster); a moderate velocity contrast across the Hayward fault (west side faster); moderately low velocity crust around the Quien Sabe volcanic field and the Sacramento River delta; very low velocity crust around Lake Berryessa. These features are generally explicable with surface rock types being extrapolated to depth ???10 km in the upper crust. Generally high mid-lower crust velocity and high inferred Poisson's ratio suggest a mafic lower crust. ?? Journal compilation ?? 2007 RAS.

  3. PICASSO: Shear velocities in the Western Mediterranean from Rayleigh Wave tomography

    NASA Astrophysics Data System (ADS)

    Palomeras, I.; Thurner, S.; Levander, A.

    2012-12-01

    The Western Mediterranean has been affected by complex subduction and slab rollback, simultaneously with compression due to African-European convergence. The deformed region occupies a wide area from the intra-continental Atlas mountain belt in Morocco to the southern Iberian Massif in Spain. Evolutionary models of the Western Mediterranean invoke extensive slab rollback and compression in the Cenozoic, as well as likely upper mantle delamination scenarios during formation of the Alboran domain, the Betics, Rif, and Atlas Mountains. PICASSO (Program to Investigate Convective Alboran Sea System Overturn) is a multidisciplinary, international investigation of the Alboran System and surrounding areas. In this study we have analyzed data from the 95 PICASSO broadband stations with data from the Spanish IberArray and Siberia Array in Spain and Morocco, the University of Muenster array in the Atlas Mountains and the permanent Spanish and Portuguese networks. We present Rayleigh wave tomography results made from 168 teleseimic events recorded by 237 stations from April 2009 to April 2011. We measured Rayleigh phase velocities using the two-plane-wave method to remove complications due to multi-pathing, and finite-frequency kernels to improve lateral resolution. Phase velocities were then inverted for shear velocity structure on a grid of 0.5 by 0.5 degree to form a well-resolved 3D shear velocity model to 230 km depth. Our results show low S-velocities (2.9 km/s) in the crust beneath the Gibraltar Strait. Low upper mantle S-velocities are mapped beneath the Middle and High Atlas at ~60 km depth suggesting an elevated asthenosphere beneath these young mountain belts, in agreement with receiver functions analysis (Thurner et al, this session). Beneath the Western Alboran Sea, upper-mantle velocities change laterally from high velocities (>4.5 km/s) in the east to lower velocities to the west (~4.3 km/s). The Rayleigh wave tomography is consistent with P-tomography that

  4. The crustal and mantle velocity structure in central Asia from 3D traveltime tomography

    NASA Astrophysics Data System (ADS)

    Sun, Y.; Martin, R. V.; Toksoz, M. N.; Pei, S.

    2010-12-01

    The lithospheric structure in central Asia features large blocks such as the Indian plate, the Afghan block, the Turan plate, and the Tarim block. This geologically and tectonically complicated area is also one of the most seismically active regions in the world. We developed P- and S- wave velocity structures of the central Asia in the crust using the traveltime data from Kyrgyzstan, Tajikistan, Kazakhstan, and Uzbek. We chose the events and stations between 32N65E and 45N85E and focused on the areas of Pamir and western Tianshan. In this data set, there are more than 6000 P and S arrivals received at 80 stations from about 300 events. The double difference tomography is applied to relocate events and to invert for seismic structures simultaneously. Our results provide accurate locations of earthquakes and high resolution crustal structure in this region. To extend the model deeper into the mantle through the upper mantle transition zone, ISC/EHB data for P and PP phases are combined with the ABCE data. To counteract the “smearing effect,” the crust and upper mantle velocity structure, derived from regional travel-times, is used. An adaptive grid method based on ray density is used in the inversion. A P-wave velocity model extending down to a depth of 2000 km is obtained. regional-teleseismic tomography provides a high-resolution, 3-D P-wave velocity model for the crust, upper mantle, and the transition zone. The crustal models correlate well with geologic and tectonic features. The upper mantle tomograms show the images of Tian Shan. The slab geometry is quite complex, reflecting the history of the changes in the plate motions and collision processes. Vp/Vs tomography was also determined in the study region, and an attenuation tomography was obtained as well.

  5. Benchmark and combined velocity-space tomography of fast-ion D-alpha spectroscopy and collective Thomson scattering measurements

    NASA Astrophysics Data System (ADS)

    Jacobsen, A. S.; Salewski, M.; Geiger, B.; Korsholm, S. B.; Leipold, F.; Nielsen, S. K.; Rasmussen, J.; Stejner, M.; Weiland, M.; the ASDEX Upgrade Team

    2016-04-01

    We demonstrate the combination of fast-ion D-alpha spectroscopy (FIDA) and collective Thomson scattering (CTS) measurements to determine a common best estimate of the fast-ion velocity distribution function by velocity-space tomography. We further demonstrate a benchmark of FIDA tomography and CTS measurements without using a numerical simulation as common reference. Combined velocity-space tomographies from FIDA and CTS measurements confirm that sawtooth crashes reduce the fast-ion phase-space densities in the plasma center and affect ions with pitches close to one more strongly than those with pitches close to zero.

  6. Seismic Velocity Anomalies beneath Tatun Volcano Group, Northern Taiwan

    NASA Astrophysics Data System (ADS)

    Lin, Tzu-yu; Lin, Cheng-Horng; Yang, Tsanyao Frank; Chang, Li-Chin

    2015-04-01

    Volcanic eruption has been a natural disaster for human society. Taiwan is located in the Pacific Ring of Fire. Although there is no obvious phenomenon of volcanic activity in Taiwan, some volcanoes need to be monitored, especially the Tatun Volcano Group (TVG), which exhibits very active hydrothermal activity, is located on the tip of southwestern Ryukyu arc. TVG is about 15 km north to Taipei, capital of Taiwan, and is nearby two nuclear power plants along the northern coast of Taiwan. If TVG erupts, there must be a serious impact and damage to Taiwan. Since TVG is located within the Yangmingshan National Park, any artificial seismic source is not allowed to estimate possible eruption site and the degree of volcanic disaster. Instead, we use natural seismic waves generated by earthquakes to image the possible velocity anomaly of magma chamber and/or hydrothermal system beneath TVG. We systematically compare the differences of arrival times generated by some local earthquakes and recorded at 42 seismic stations in 2014 for finding any low-velocity zone within the crust. The results show that the arrival times always appeared significant delay at some particular seismic stations, such as Chi-Hsin-Shan (CHS), Siao-You-Keng (SYK) and some other stations at TVG, no matter where the earthquakes occurred. It implies that possible low-velocity zones, which could be the location of magma chamber and/or active hydrothermal system, exist beneath the CHS and SYK areas. This feature is generally consistent with the clustered micro-earthquakes in the shallow crust beneath the CHS area in the last decade.

  7. Crustal velocity structure of Central and Eastern Turkey from ambient noise tomography

    NASA Astrophysics Data System (ADS)

    Warren, Linda M.; Beck, Susan L.; Biryol, C. Berk; Zandt, George; Özacar, A. Arda; Yang, Yingjie

    2013-09-01

    In eastern Turkey, the ongoing convergence of the Arabian and African plates with Eurasia has resulted in the westward extrusion of the Anatolian Plate. To better understand the current state and the tectonic history of this region, we image crust and uppermost mantle structure with ambient noise tomography. Our study area extends from longitudes of 32° to 44°E. We use continuous data from two temporary seismic deployments, our 2006-2008 North Anatolian Fault Passive Seismic Experiment and the 1999-2001 Eastern Turkey Seismic Experiment, as well as from additional seismographs in the region. We compute daily cross-correlations of noise records between all station pairs and stack them over the entire time period for which they are available, as well as in seasonal subsets, to obtain interstation empirical Green's functions. After selecting interstation cross-correlations with high signal-to-noise ratios and measuring interstation phase velocities, we compute phase velocity maps at periods ranging from 8 to 40 s. At all periods, the phase velocity maps are similar for winter and summer subsets of the data, indicating that seasonal variations in noise sources do not bias our results. Across the study area, we invert the phase velocity estimates for shear velocity as a function of depth. The shear velocity model, which extends to 50 km depth, highlights tectonic features apparent at the surface: the Eastern Anatolian Plateau is a prominent low-velocity anomaly whereas the Kirşehir Massif has relatively fast velocities. There is a large velocity jump across the Inner Tauride Suture/Central Anataolian Fault Zone throughout the crust whereas the North Anatolian Fault does not have a consistent signature. In addition, in the southeastern part of our study area, we image a high velocity region below 20 km depth which may be the northern tip of the underthrusting Arabian Plate.

  8. Surface wave phase-velocity tomography based on multichannel cross-correlation

    NASA Astrophysics Data System (ADS)

    Jin, Ge; Gaherty, James B.

    2015-06-01

    We have developed a new method to retrieve seismic surface wave phase velocity using dense seismic arrays. The method measures phase variations between nearby stations based on waveform cross-correlation. The coherence in waveforms between adjacent stations results in highly precise relative phase estimates. Frequency-dependent phase variations are then inverted for spatial variations in apparent phase velocity via the Eikonal equation. Frequency-dependent surface wave amplitudes measured on individual stations are used to correct the apparent phase velocity to account for multipathing via the Helmholtz equation. By using coherence and other data selection criteria, we construct an automated system that retrieves structural phase-velocity maps directly from raw seismic waveforms for individual earthquakes without human intervention. The system is applied to broad-band seismic data from over 800 events recorded on EarthScope's USArray from 2006 to 2014, systematically building up Rayleigh-wave phase-velocity maps between the periods of 20 and 100 s for the entire continental United States. At the highest frequencies, the resulting maps are highly correlated with phase-velocity maps derived from ambient noise tomography. At all frequencies, we observe a significant contrast in Rayleigh-wave phase velocity between the tectonically active western US and the stable eastern US, with the phase velocity variations in the western US being 1-2 times greater. The Love wave phase-velocity maps are also calculated. We find that overtone contamination may produce systemic bias for the Love-wave phase-velocity measurements.

  9. Implementation and characterization of phase-resolved Doppler optical coherence tomography method for flow velocity measurement

    NASA Astrophysics Data System (ADS)

    Pongchalee, Pornthep; Palawong, Kunakorn; Meemon, Panomsak

    2014-06-01

    In this work, the system implementation and characterization of a Phase-Resolved Doppler Optical Coherence Tomography (PR-DOCT) is presented. The phase-resolved Doppler technique was implemented on a custom built Frequency Domain OCT (FD-OCT) that was recently developed at Suranaree University of Technology. Utilizing Doppler phase changed relation in a complex interference signal caused by moving samples, PR-DOCT can produce visualization and characterization of flow activity such as blood flow in biological samples. Here we report the performance of the implemented PR-DOCT system in term of the Velocity Dynamic Range (VDR), which is defined by the range from the minimum to the maximum detectable axial velocity. The minimum detectable velocity was quantified from a histogram distribution of phase difference between consecutive depth-scan signals when performing Doppler imaging of a stationary mirror. By applying a Gaussian curve fitting to the histogram, the Full Width at Half Maximum (FWHM) of the fitted curve was measured to represent the detectable minimum flow velocity of the system. The maximum detectable velocity was limited by the phase wrapping of the Doppler signal, which is governed by the acquisition speed of the system. We demonstrate the 3D Doppler imaging and velocity measurement of feed flow phantom using 100% milk pumped through a microfluidic chip by using a syringe pump system.

  10. Velocity structure of the uppermost mantle beneath East Asia from Pn tomography and its dynamic implications

    NASA Astrophysics Data System (ADS)

    Wang, Suyun; Niu, Fenglin; Zhang, Guomin

    2013-01-01

    AbstractEast Asia is one of the most tectonically active regions on Earth's surface due to the collision from the India plate and the suctions induced by the subduction of the Pacific and Philippine plates. To better understand the complicated deformation and active seismicity of the area, we conducted a Pn traveltime <span class="hlt">tomography</span> to estimate the compressive wave speed of the uppermost mantle beneath East Asia. We collected a total of 296,334 Pn arrivals recorded by 1354 stations from 27,777 earthquakes in a rectangular area from 60°E to 145°E in longitude, 15°N to 60°N in latitude. The data set was carefully integrated from three different catalogs after examining potential systematic biases in the catalogs. The inversion results revealed a large-scale <span class="hlt">velocity</span> perturbation in the study area. Pn <span class="hlt">velocity</span> in the region west to ~108°E is approximately 10% higher than that in the east. In each region, stable blocks tend to have high Pn <span class="hlt">velocity</span> while the boundary regions, which show a high level of seismicity and surface deformation, appear to have low Pn <span class="hlt">velocity</span>. We further computed the Benioff strain rate in the two regions and found it correlates negatively with the averaged Pn <span class="hlt">velocity</span>. Our observations here suggest that Pn <span class="hlt">velocity</span>, which is predominantly determined by Moho temperature, is a good indicator of lithosphere strength.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014SolED...6.2971G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SolED...6.2971G"><span id="translatedtitle">A 3-D shear <span class="hlt">velocity</span> model of the southern North America and the Caribbean plates from ambient noise and earthquake <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gaite, B.; Villaseñor, A.; Iglesias, A.; Herraiz, M.; Jiménez-Munt, I.</p> <p>2014-10-01</p> <p>We use <span class="hlt">group</span> <span class="hlt">velocities</span> from earthquake <span class="hlt">tomography</span> together with <span class="hlt">group</span> and phase <span class="hlt">velocities</span> from ambient noise <span class="hlt">tomography</span> (ANT) of Rayleigh-waves to invert for the 3-D shear-wave <span class="hlt">velocity</span> structure (5-70 km) of the Caribbean (CAR) and southern North American (NAM) plates. The lithospheric model proposed offers a complete image of the crust and uppermost-mantle with imprints of the tectonic evolution. One of the most striking features inferred is the main role of the Ouachita-Marathon-Sonora orogeny front on the crustal seismic structure of NAM plate. A new imaged feature is the low crustal <span class="hlt">velocities</span> along USA-Mexico border. The model also shows a break of the E-W mantle <span class="hlt">velocity</span> dichotomy of the NAM and CAR plates beneath the Isthmus of Tehuantepec and Yucatan Block. High upper-mantle <span class="hlt">velocities</span> along the Mesoamerican Subduction Zone coincide with inactive volcanic areas while the lowest <span class="hlt">velocities</span> correspond to active volcanic arcs and thin lithospheric mantle regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.T41F..06Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.T41F..06Z"><span id="translatedtitle">Probing the Detailed Seismic <span class="hlt">Velocity</span> Structure of Subduction Zones Using Advanced Seismic <span class="hlt">Tomography</span> Methods</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, H.; Thurber, C. H.</p> <p>2005-12-01</p> <p>Subduction zones are one of the most important components of the Earth's plate tectonic system. Knowing the detailed seismic <span class="hlt">velocity</span> structure within and around subducting slabs is vital to understand the constitution of the slab, the cause of intermediate depth earthquakes inside the slab, the fluid distribution and recycling, and tremor occurrence [Hacker et al., 2001; Obara, 2002].Thanks to the ability of double-difference <span class="hlt">tomography</span> [Zhang and Thurber, 2003] to resolve the fine-scale structure near the source region and the favorable seismicity distribution inside many subducting slabs, it is now possible to characterize the fine details of the <span class="hlt">velocity</span> structure and earthquake locations inside the slab, as shown in the study of the Japan subduction zone [Zhang et al., 2004]. We further develop the double-difference <span class="hlt">tomography</span> method in two aspects: the first improvement is to use an adaptive inversion mesh rather than a regular inversion grid and the second improvement is to determine a reliable Vp/Vs structure using various strategies rather than directly from Vp and Vs [see our abstract ``Strategies to solve for a better Vp/Vs model using P and S arrival time'' at Session T29]. The adaptive mesh seismic <span class="hlt">tomography</span> method is based on tetrahedral diagrams and can automatically adjust the inversion mesh according to the ray distribution so that the inversion mesh nodes are denser where there are more rays and vice versa [Zhang and Thurber, 2005]. As a result, the number of inversion mesh nodes is greatly reduced compared to a regular inversion grid with comparable spatial resolution, and the tomographic system is more stable and better conditioned. This improvement is quite valuable for characterizing the fine structure of the subduction zone considering the highly uneven distribution of earthquakes within and around the subducting slab. The second improvement, to determine a reliable Vp/Vs model, lies in jointly inverting Vp, Vs, and Vp/Vs using P, S, and S</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JGRB..121.2429F&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JGRB..121.2429F&link_type=ABSTRACT"><span id="translatedtitle">Tomographic Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocities</span> in the Central Valley, California, centered on the Sacramento/San Joaquin Delta</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fletcher, Jon B.; Erdem, Jemile; Seats, Kevin; Lawrence, Jesse</p> <p>2016-04-01</p> <p>If shaking from a local or regional earthquake in the San Francisco Bay region were to rupture levees in the Sacramento/San Joaquin Delta, then brackish water from San Francisco Bay would contaminate the water in the Delta: the source of freshwater for about half of California. As a prelude to a full shear-wave <span class="hlt">velocity</span> model that can be used in computer simulations and further seismic hazard analysis, we report on the use of ambient noise <span class="hlt">tomography</span> to build a fundamental mode, Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> model for the region around the Sacramento/San Joaquin Delta in the western Central Valley, California. Recordings from the vertical component of about 31 stations were processed to compute the spatial distribution of Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocities</span>. Complex coherency between pairs of stations was stacked over 8 months to more than a year. Dispersion curves were determined from 4 to about 18 s. We calculated average <span class="hlt">group</span> <span class="hlt">velocities</span> for each period and inverted for deviations from the average for a matrix of cells that covered the study area. Smoothing using the first difference is applied. Cells of the model were about 5.6 km in either dimension. Checkerboard tests of resolution, which are dependent on station density, suggest that the resolving ability of the array is reasonably good within the middle of the array with resolution between 0.2 and 0.4°. Overall, low <span class="hlt">velocities</span> in the middle of each image reflect the deeper sedimentary syncline in the Central Valley. In detail, the model shows several centers of low <span class="hlt">velocity</span> that may be associated with gross geologic features such as faulting along the western margin of the Central Valley, oil and gas reservoirs, and large crosscutting features like the Stockton arch. At shorter periods around 5.5 s, the model's western boundary between low and high <span class="hlt">velocities</span> closely follows regional fault geometry and the edge of a residual isostatic gravity low. In the eastern part of the valley, the boundaries of the low-<span class="hlt">velocity</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70030816','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70030816"><span id="translatedtitle">Comparative <span class="hlt">velocity</span> structure of active Hawaiian volcanoes from 3-D onshore-offshore seismic <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Park, J.; Morgan, J.K.; Zelt, C.A.; Okubo, P.G.; Peters, L.; Benesh, N.</p> <p>2007-01-01</p> <p>We present a 3-D P-wave <span class="hlt">velocity</span> model of the combined subaerial and submarine portions of the southeastern part of the Island of Hawaii, based on first-arrival seismic <span class="hlt">tomography</span> of marine airgun shots recorded by the onland seismic network. Our model shows that high-<span class="hlt">velocity</span> materials (6.5-7.0??km/s) lie beneath Kilauea's summit, Koae fault zone, and the upper Southwest Rift Zone (SWRZ) and upper and middle East Rift Zone (ERZ), indicative of magma cumulates within the volcanic edifice. A separate high-<span class="hlt">velocity</span> body of 6.5-6.9??km/s within Kilauea's lower ERZ and upper Puna Ridge suggests a distinct body of magma cumulates, possibly connected to the summit magma cumulates at depth. The two cumulate bodies within Kilauea's ERZ may have undergone separate ductile flow seaward, influencing the submarine morphology of Kilauea's south flank. Low <span class="hlt">velocities</span> (5.0-6.3??km/s) seaward of Kilauea's Hilina fault zone, and along Mauna Loa's seaward facing Kao'iki fault zone, are attributed to thick piles of volcaniclastic sediments deposited on the submarine flanks. Loihi seamount shows high-<span class="hlt">velocity</span> anomalies beneath the summit and along the rift zones, similar to the interpreted magma cumulates below Mauna Loa and Kilauea volcanoes, and a low-<span class="hlt">velocity</span> anomaly beneath the oceanic crust, probably indicative of melt within the upper mantle. Around Kilauea's submarine flank, a high-<span class="hlt">velocity</span> anomaly beneath the outer bench suggests the presence of an ancient seamount that may obstruct outward spreading of the flank. Mauna Loa's southeast flank is also marked by a large, anomalously high-<span class="hlt">velocity</span> feature (7.0-7.4??km/s), interpreted to define an inactive, buried volcanic rift zone, which might provide a new explanation for the westward migration of Mauna Loa's current SWRZ and the growth of Kilauea's SWRZ. ?? 2007 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.S53A2787E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.S53A2787E"><span id="translatedtitle">Simultaneous Local and Teleseismic P-Wave <span class="hlt">Velocity</span> <span class="hlt">Tomography</span> in Western Mexico</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Escudero, C. R.; Alarcon, E.; Ochoa, J.; Nuñez-Cornu, F. J.</p> <p>2015-12-01</p> <p>In western Mexico, the subduction of the Rivera and Cocos plates beneath the North America plate has deformed and fragmented the overriding plate, forming several structural rifts and crustal blocks. To improve the current tomographic images of the continental crust and uppermost mantle in this complex area, we used P-wave arrivals of local and teleseismic earthquakes along with the Fast Marching Method <span class="hlt">tomography</span> technique. Our traveltime datasets include 2100 local earthquakes P-wave arrival times and 5,062 P-wave relative arrival time residuals of teleseismic earthquakes. The local earthquake phase picking was manually corrected and the relative arrival time residuals were estimated using the Multi-Channel Cross-Correlation method. All earthquakes occurred between 2006 and 2007 and were recorded by seismic stations deployed during the Mapping the Rivera Subduction Zone (MARS) experiment. The temporal seismic network consisted of 50 stations equipped with Streckeisen STS-2 and Quanterra Q330. We use an iterative nonlinear tomographic procedure and the fast marching method to map the residual patterns as P wave <span class="hlt">velocity</span> anomalies. We followed an inversion scheme consisting of: (1) selection of a local and teleseismic earthquake, (2) estimation of improved 1-D reference <span class="hlt">velocity</span> model, and (3) checkerboard testing to determine the optimum configuration of the <span class="hlt">velocity</span> nodes, and inversion parameters, finally (4) perform final <span class="hlt">tomography</span> and results analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PPCF...58b5012W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PPCF...58b5012W"><span id="translatedtitle">Enhancement of the FIDA diagnostic at ASDEX Upgrade for <span class="hlt">velocity</span> space <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weiland, M.; Geiger, B.; Jacobsen, A. S.; Reich, M.; Salewski, M.; Odstrčil, T.; the ASDEX Upgrade Team</p> <p>2016-02-01</p> <p>Recent upgrades to the FIDA (fast-ion D-alpha) diagnostic at ASDEX Upgrade are discussed. The diagnostic has been extended from three to five line of sight arrays with different angles to the magnetic field, and a spectrometer redesign allows the simultaneous measurement of red- and blue-shifted parts of the Doppler spectrum. These improvements make it possible to reconstruct the 2D fast-ion <span class="hlt">velocity</span> distribution f≤ft(E,{{v}\\parallel}/v\\right) from the FIDA measurements by tomographic inversion under a wide range of plasma parameters. Two applications of the <span class="hlt">tomography</span> are presented: a comparison between the distributions resulting from 60 keV and 93 keV neutral beam injection and a <span class="hlt">velocity</span>-space resolved study of fast-ion redistribution induced by a sawtooth crash inside and outside the sawtooth inversion radius.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoJI.205...51L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoJI.205...51L"><span id="translatedtitle">Global Rayleigh wave phase-<span class="hlt">velocity</span> maps from finite-frequency <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Kui; Zhou, Ying</p> <p>2016-04-01</p> <p>We report global phase-<span class="hlt">velocity</span> maps of fundamental-mode Rayleigh waves at periods between 25 and 100 s based on finite-frequency <span class="hlt">tomography</span>. Rayleigh wave dispersion measurements are made using a multitaper technique for both minor-arc and major-arc wave trains. The global phase-<span class="hlt">velocity</span> maps confirm many features associated with surface tectonics including the ocean-continent dichotomy and the signature of lithospheric cooling in oceanic plates. In addition, the high-resolution phase-<span class="hlt">velocity</span> maps reveal a major change in the distribution of small-scale anomalies in the Pacific at different wave periods. We calculate the global average of Rayleigh wave phase <span class="hlt">velocity</span> in major tectonic regions and show that large discrepancies exist between our model and global crustal and mantle models: (1) In oceanic regions, short-period (<˜40 s) Rayleigh waves are faster than calculations based on models CRUST2.0 and S40RTS. The discrepancies could be explained by a thinner crust or faster wave speeds in the crust or upper mantle. The implementation of model CRUST1.0 significantly improves the agreement, with phase-<span class="hlt">velocity</span> discrepancies less than 0.5 per cent on average. (2) In Archean cratons, Rayleigh wave phase <span class="hlt">velocities</span> in our model are faster than calculations based on model S40RTS at periods longer than ˜40 s; and the global average in orogenic belts is ˜1-2 per cent slower than CRUST1.0 at periods shorter than ˜50 s.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PPCF...58d5016J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PPCF...58d5016J"><span id="translatedtitle">Inversion methods for fast-ion <span class="hlt">velocity</span>-space <span class="hlt">tomography</span> in fusion plasmas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jacobsen, A. S.; Stagner, L.; Salewski, M.; Geiger, B.; Heidbrink, W. W.; Korsholm, S. B.; Leipold, F.; Nielsen, S. K.; Rasmussen, J.; Stejner, M.; Thomsen, H.; Weiland, M.; the ASDEX Upgrade Team</p> <p>2016-04-01</p> <p><span class="hlt">Velocity</span>-space <span class="hlt">tomography</span> has been used to infer 2D fast-ion <span class="hlt">velocity</span> distribution functions. Here we compare the performance of five different tomographic inversion methods: truncated singular value decomposition, maximum entropy, minimum Fisher information and zeroth- and first-order Tikhonov regularization. The inversion methods are applied to fast-ion {{\\text{D}}α} measurements taken just before and just after a sawtooth crash in the ASDEX Upgrade tokamak as well as to synthetic measurements from different test distributions. We find that the methods regularizing by penalizing steep gradients or maximizing entropy perform best. We assess the uncertainty of the calculated inversions taking into account photon noise, uncertainties in the forward model as well as uncertainties introduced by the regularization which allows us to distinguish regions of high and low confidence in the <span class="hlt">tomographies</span>. In high confidence regions, all methods agree that ions with pitch values close to zero, as well as ions with large pitch values, are ejected from the plasma center by the sawtooth crash, and that this ejection depletes the ion population with large pitch values more strongly.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21156393','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21156393"><span id="translatedtitle">Study on creating hydraulic <span class="hlt">tomography</span> for crystalline rock using frequency dependent elastic wave <span class="hlt">velocity</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yoshimura, K.; Sakashita, S.; Ando, K.; Bruines, P.; Blechschmidt, I.; Kickmaier, W.; Onishi, Y.; Nishiyama, S.</p> <p>2007-07-01</p> <p>The objective of this study is to establish a technique to obtain hydraulic conductivity distribution in granite rock masses using seismic <span class="hlt">tomography</span>. We apply the characteristic that elastic wave <span class="hlt">velocity</span> disperses in fully saturated porous media on frequency and this <span class="hlt">velocity</span> dispersion is governed by the hydraulic conductivity - this characteristic has been confirmed in laboratory experiments. The feasibility and design of the field experiment was demonstrated in a first step with numerical simulations. In a second step we applied the technique to the fractured granite at the Grimsel Test Site in Switzerland. The emphasis of the field campaign was on the evaluation of the range of applicability of this technique. The field campaign was structured in three steps, each one corresponding to a larger spatial scale. First, the seismic <span class="hlt">tomography</span> was applied to a small area - the two boreholes were located at a distance of 1.5 m. In the following step, we selected a larger area, in which the distance of the boreholes amounts to 10 m and the field corresponds to a more complex geology. Finally we applied the testing to a field where the borehole distance was of the order of 75 m. We also drilled a borehole to confirm hydraulic characteristic and reviewed hydraulic model in the 1.5 m cross-hole location area. The results from the field campaign are presented and their application to the various fields are discussed and evaluated. (authors)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26977365','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26977365"><span id="translatedtitle">Fully distributed absolute blood flow <span class="hlt">velocity</span> measurement for middle cerebral arteries using Doppler optical coherence <span class="hlt">tomography</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Qi, Li; Zhu, Jiang; Hancock, Aneeka M; Dai, Cuixia; Zhang, Xuping; Frostig, Ron D; Chen, Zhongping</p> <p>2016-02-01</p> <p>Doppler optical coherence <span class="hlt">tomography</span> (DOCT) is considered one of the most promising functional imaging modalities for neuro biology research and has demonstrated the ability to quantify cerebral blood flow <span class="hlt">velocity</span> at a high accuracy. However, the measurement of total absolute blood flow <span class="hlt">velocity</span> (BFV) of major cerebral arteries is still a difficult problem since it is related to vessel geometry. In this paper, we present a volumetric vessel reconstruction approach that is capable of measuring the absolute BFV distributed along the entire middle cerebral artery (MCA) within a large field-of-view. The Doppler angle at each point of the MCA, representing the vessel geometry, is derived analytically by localizing the artery from pure DOCT images through vessel segmentation and skeletonization. Our approach could achieve automatic quantification of the fully distributed absolute BFV across different vessel branches. Experiments on rodents using swept-source optical coherence <span class="hlt">tomography</span> showed that our approach was able to reveal the consequences of permanent MCA occlusion with absolute BFV measurement. PMID:26977365</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active"><span>3</span></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_3 --> <div id="page_4" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active"><span>4</span></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="61"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4771474','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4771474"><span id="translatedtitle">Fully distributed absolute blood flow <span class="hlt">velocity</span> measurement for middle cerebral arteries using Doppler optical coherence <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Qi, Li; Zhu, Jiang; Hancock, Aneeka M.; Dai, Cuixia; Zhang, Xuping; Frostig, Ron D.; Chen, Zhongping</p> <p>2016-01-01</p> <p>Doppler optical coherence <span class="hlt">tomography</span> (DOCT) is considered one of the most promising functional imaging modalities for neuro biology research and has demonstrated the ability to quantify cerebral blood flow <span class="hlt">velocity</span> at a high accuracy. However, the measurement of total absolute blood flow <span class="hlt">velocity</span> (BFV) of major cerebral arteries is still a difficult problem since it is related to vessel geometry. In this paper, we present a volumetric vessel reconstruction approach that is capable of measuring the absolute BFV distributed along the entire middle cerebral artery (MCA) within a large field-of-view. The Doppler angle at each point of the MCA, representing the vessel geometry, is derived analytically by localizing the artery from pure DOCT images through vessel segmentation and skeletonization. Our approach could achieve automatic quantification of the fully distributed absolute BFV across different vessel branches. Experiments on rodents using swept-source optical coherence <span class="hlt">tomography</span> showed that our approach was able to reveal the consequences of permanent MCA occlusion with absolute BFV measurement. PMID:26977365</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24582555','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24582555"><span id="translatedtitle">Corrosion and erosion monitoring in plates and pipes using constant <span class="hlt">group</span> <span class="hlt">velocity</span> Lamb wave inspection.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nagy, Peter B; Simonetti, Francesco; Instanes, Geir</p> <p>2014-09-01</p> <p>Recent improvements in tomographic reconstruction techniques generated a renewed interest in short-range ultrasonic guided wave inspection for real-time monitoring of internal corrosion and erosion in pipes and other plate-like structures. Emerging evidence suggests that in most cases the fundamental asymmetric A0 mode holds a distinct advantage over the earlier market leader fundamental symmetric S0 mode. Most existing A0 mode inspections operate at relatively low inspection frequencies where the mode is highly dispersive therefore very sensitive to variations in wall thickness. This paper examines the potential advantages of increasing the inspection frequency to the so-called constant <span class="hlt">group</span> <span class="hlt">velocity</span> (CGV) point where the <span class="hlt">group</span> <span class="hlt">velocity</span> remains essentially constant over a wide range of wall thickness variation, but the phase <span class="hlt">velocity</span> is still dispersive enough to allow accurate wall thickness assessment from phase angle measurements. This paper shows that in the CGV region the crucial issue of temperature correction becomes especially simple, which is particularly beneficial when higher-order helical modes are also exploited for <span class="hlt">tomography</span>. One disadvantage of working at such relatively high inspection frequency is that, as the slower A0 mode becomes faster and less dispersive, the competing faster S0 mode becomes slower and more dispersive. At higher inspection frequencies these modes cannot be separated any longer based on their vibration polarization only, which is mostly tangential for the S0 mode while mostly normal for the A0 at low frequencies, as the two modes become more similar as the frequency increases. Therefore, we propose a novel method for suppressing the unwanted S0 mode based on the Poisson effect of the material by optimizing the angle of inclination of the equivalent transduction force of the Electromagnetic Acoustic Transducers (EMATs) used for generation and detection purposes. PMID:24582555</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007AGUFM.S23B1388T&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007AGUFM.S23B1388T&link_type=ABSTRACT"><span id="translatedtitle">Development of a State-Wide 3-D Seismic <span class="hlt">Tomography</span> <span class="hlt">Velocity</span> Model for California</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thurber, C. H.; Lin, G.; Zhang, H.; Hauksson, E.; Shearer, P.; Waldhauser, F.; Hardebeck, J.; Brocher, T.</p> <p>2007-12-01</p> <p>We report on progress towards the development of a state-wide tomographic model of the P-wave <span class="hlt">velocity</span> for the crust and uppermost mantle of California. The dataset combines first arrival times from earthquakes and quarry blasts recorded on regional network stations and travel times of first arrivals from explosions and airguns recorded on profile receivers and network stations. The principal active-source datasets are Geysers-San Pablo Bay, Imperial Valley, Livermore, W. Mojave, Gilroy-Coyote Lake, Shasta region, Great Valley, Morro Bay, Mono Craters-Long Valley, PACE, S. Sierras, LARSE 1 and 2, Loma Prieta, BASIX, San Francisco Peninsula and Parkfield. Our beta-version model is coarse (uniform 30 km horizontal and variable vertical gridding) but is able to image the principal features in previous separate regional models for northern and southern California, such as the high-<span class="hlt">velocity</span> subducting Gorda Plate, upper to middle crustal <span class="hlt">velocity</span> highs beneath the Sierra Nevada and much of the Coast Ranges, the deep low-<span class="hlt">velocity</span> basins of the Great Valley, Ventura, and Los Angeles, and a high- <span class="hlt">velocity</span> body in the lower crust underlying the Great Valley. The new state-wide model has improved areal coverage compared to the previous models, and extends to greater depth due to the data at large epicentral distances. We plan a series of steps to improve the model. We are enlarging and calibrating the active-source dataset as we obtain additional picks from investigators and perform quality control analyses on the existing and new picks. We will also be adding data from more quarry blasts, mainly in northern California, following an identification and calibration procedure similar to Lin et al. (2006). Composite event construction (Lin et al., in press) will be carried out for northern California for use in conventional <span class="hlt">tomography</span>. A major contribution of the state-wide model is the identification of earthquakes yielding arrival times at both the Northern California Seismic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.T33E2700C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.T33E2700C"><span id="translatedtitle">Anisotropic Shear-wave <span class="hlt">Velocity</span> Structure of East Asian Upper Mantle from Waveform <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chong, J.; Yuan, H.; French, S. W.; Romanowicz, B. A.; Ni, S.</p> <p>2012-12-01</p> <p>East Asia is a seismically active region featuring active tectonic belts, such as the Himalaya collision zone, western Pacific subduction zones and the Tianshan- Baikal tectonic belt. In this study, we applied full waveform time domain <span class="hlt">tomography</span> to image 3D isotropic, radially and azimuthally anisotropic upper mantle shear <span class="hlt">velocity</span> structure of East Asia. High quality teleseismic waveforms were collected for both permanent and temporary stations in the target and its adjacent regions, providing good ray path coverage of the study region. Fundamental and overtone wave packets, filtered down to 60 sec, were inverted for isotropic and radially anisotropic shear wave structure using normal mode asymptotic coupling theory (NACT: Li and Romanowicz, 1995). Joint inversion of SKS measurements and seismic waveforms was then carried out following the methodology described in (Marone and Romanowicz, 2007). The 3D <span class="hlt">velocity</span> model shows strong lateral heterogeneities in the target region, which correlate well with the surface geology in East Asia. Our model shows that Indian lithosphere has subducted beneath Tibet with a different northern reach from western to eastern Tibet,. We also find variations of the slab geometry in Western Pacific subduction zones. Old and stable regions, such as, Indian shield, Siberia platform, Tarim and Yangtze blocks are found to have higher shear wave <span class="hlt">velocity</span> in the upper mantle. Lower <span class="hlt">velocity</span> anomalies are found in regions like Baikal rift, Tienshan, Indochina block, and the regions along Japan island-Ryukyu Trench and Izu-bonin Trench. The dominant fast and slow <span class="hlt">velocity</span> boundaries in the study region are well correlated with tectonic belts, such as the central Asian orogenic belt and Alty/Qilian-Qinling/Dabie orogenic belt. Our radially anisotropic model shows Vsh> Vsv in oceanic regions and at larger depths(>300km), and Vsv > Vsh in some orogenic zones.. We'll show preliminary results of azimuthally anisotropic joint inversion of SKS</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T51C..07O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T51C..07O"><span id="translatedtitle">Seismic <span class="hlt">velocity</span> variation along the Izu-Bonin arc estaimated from traveltime <span class="hlt">tomography</span> using OBS data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Obana, K.; Tamura, Y.; Takahashi, T.; Kodaira, S.</p> <p>2014-12-01</p> <p>The Izu-Bonin (Ogasawara) arc is an intra-oceanic island arc along the convergent plate boundary between the subducting Pacific and overriding Philippine Sea plates. Recent active seismic studies in the Izu-Bonin arc reveal significant along-arc variations in crustal structure [Kodaira et al., 2007]. The thickness of the arc crust shows a remarkable change between thicker Izu (~30 km) and thinner Bonin (~10 km) arcs. In addition to this, several geological and geophysical contrasts, such as seafloor topography and chemical composition of volcanic rocks, between Izu and Bonin arc have been reported [e.g., Yuasa 1992]. We have conducted earthquake observations using ocean bottom seismographs (OBSs) to reveal seismic <span class="hlt">velocity</span> structure of the crust and mantle wedge in the Izu-Bonin arc and to investigate origin of the along-arc structure variations. We deployed 40 short-period OBSs in Izu and Bonin area in 2006 and 2009, respectively. The OBS data were processed with seismic data recorded at routine seismic stations on Hachijo-jima, Aoga-shima, and Chichi-jima operated by National Research Institute for Earth Science and Disaster Prevention (NIED). More than 5000 earthquakes were observed during about three-months observation period in each experiment. We conducted three-dimensional seismic <span class="hlt">tomography</span> using manually picked P- and S-wave arrival time data. The obtained image shows a different seismic <span class="hlt">velocity</span> structures in the mantle beneath the volcanic front between Izu and Bonin arcs. Low P-wave <span class="hlt">velocity</span> anomalies in the mantle beneath the volcanic front in the Izu arc are limited at depths deeper than those in the Bonin arc. On the other hand, P-wave <span class="hlt">velocity</span> in the low <span class="hlt">velocity</span> anomalies beneath volcanic front in the Bonin arc is slower than that in the Izu arc. These large-scale along-arc structure variations in the mantle could relate to the geological and geophysical contrasts between Izu and Bonin arcs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUSM.S31B..04Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUSM.S31B..04Y"><span id="translatedtitle">P-Wave <span class="hlt">Velocity</span> Structure beneath Eastern Eurasia from Finite Frequency Seismic <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, T.; Shen, Y.; Yang, X.</p> <p>2006-05-01</p> <p>Despite the recent extensive seismic studies, the detailed lithospheric structure and deep mantle dynamic processes beneath eastern Eurasia remain poorly constrained. In this study, we applied the Finite Frequency Seismic <span class="hlt">Tomography</span> (FFST) method, which utilizes the 3D Fréchet sensitivity kernels of the travel times of finite frequency seismic waves to account for wavefront healing and off-ray scattering, to eastern Eurasia. Taking advantage of the broadband feature of seismic records, we measured P wave relative delays times by waveform cross-correlation in three frequency bands (0.03-0.1Hz, 0.1-0.5 Hz and 0.5 to 2.0 Hz), which were inverted jointly to constrain <span class="hlt">velocity</span> heterogeneities with different distances from the central geometric rays. The effect of strong variations in crustal structure beneath this region on travel time data was removed by conducting a frequency dependent crustal correction. A comprehensive dataset, including waveforms from the publicly accessible sources and other seismic networks in the region, were collected for this study. Our preliminary results are consistent with the <span class="hlt">velocity</span> models obtained in previous tomographic studies. A more complete dataset will further improve the resolution of the <span class="hlt">velocity</span> structure beneath eastern Eurasia.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/7149038','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/7149038"><span id="translatedtitle">High-resolution seismic <span class="hlt">tomography</span> of compressional wave <span class="hlt">velocity</span> structure at Newberry Volcano, Oregon Cascade Range</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Achauer, U.; Evans, J.R.; Stauber, D.A.</p> <p>1988-09-10</p> <p>Compressional wave <span class="hlt">velocity</span> structure is determined for the upper crust beneath Newberry Volcano, central Oregon, using a high-resolution active-source seismic-<span class="hlt">tomography</span> method. Newberry Volcano is a bimodal shield volcano east of the axis of the Cascade Range. It is associated both with the Cascade Range and with northwest migrating silicic volcanism in southeast Oregon. High-frequency (approx.7 Hz) crustal phases, nominally Pg and a midcrustal reflected phase, travel upward through a target volume beneath Newberry Volcano to a dense array of 120 seismographs. This arrangement is limited by station spacing to 1- to 2-km resolution in the upper 5 to 6 km of the crust beneath the volcano's summit caldera. The experiment tests the hypothesis that Cascade Range volcanoes are underlain only by small magma chambers. A small low-<span class="hlt">velocity</span> anomaly delineated abosut 3 km below the summit caldera supports this hypothesis for Newberry Volcano and is interpreted as a possible magma chamber of a few to a few tens of km/sup 3/ in volume. A ring-shaped high-<span class="hlt">velocity</span> anomaly nearer the surface coincides with the inner mapped ring fractures of the caldera. It also coincides with a circular gravity high, and we interpret it as largely subsolidus silicic cone sheets. The presence of this anomaly and of silicic vents along the ring fractures suggests that the fractures are a likely eruption path between the small magma chamber and the surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T43B2644P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T43B2644P"><span id="translatedtitle">Rayleigh wave phase <span class="hlt">velocity</span> maps from the ambient noise <span class="hlt">tomography</span> in central Mongolia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pan, J.; Wu, Q.; Gao, M.; Li, Y.; Demberel, S. G.; Munkhuu, U.</p> <p>2013-12-01</p> <p>The study area (103°E-111°E, 44°N-49°N) located in the Mongolian fold belts and situated at the southeast of Baikal rift zone which is known as one of the most active regions on the Earth due to integrated influence of the India-Asia collision and compression and the subduction of the Pacific Plate. Additionally, it also located in the north of South-North earthquake belts of China. So, it is believed to be an ideal site for understanding intraplate dynamics. Seismic ambient noise <span class="hlt">tomography</span> has been performed all over the world these years, and it has been proved it's a powerful way to image and study the structure of crust and uppermost mantle due to its exclusive capability to extract estimated Green's functions for short period surface waves. Compared with traditional earthquake <span class="hlt">tomography</span> methods of surface waves, ambient noise <span class="hlt">tomography</span> hasn't limitations related to the distribution of earthquakes as well as errors in earthquake locations and source mechanisms. A new scientific project was carried out in 2011 by Institute of Geophysics of China Earthquake Administration (IGP-CEA) and Research center of Astronomy and Geophysics of Mongolian Academy of Science (RCAG-MAS). In the seismic sub-project 60 portable seismic stations were deployed in central Mongolia in August 2011. Continuous time-series of vertical component between August 2011 and July 2012 have been collected and cross-correlated to obtain estimated Green's functions (EGF) of Rayleigh wave. Using the frequency and time analysis technique based on continuous wavelet transformation, 1258 of phase <span class="hlt">velocity</span> dispersion curves of Rayleigh wave were extracted from EGFs. High resolution phase <span class="hlt">velocity</span> maps at periods of 5, 10, 20 and 30 s were reconstructed with grid size 0.5°x0.5° by utilizing a generalized 2-D-linear inversion method developed by Ditmar & Yanovskaya. The <span class="hlt">tomography</span> results reveal lateral heterogeneity of shear wave structure in the crust and upper mantle in the study region. For</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.7382C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.7382C"><span id="translatedtitle">Extraction of the local phase <span class="hlt">velocity</span> and the <span class="hlt">group</span> <span class="hlt">velocity</span> from surface noise source in microseismic monitoring.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chmiel, Malgorzata; Roux, Philippe; Bardainne, Thomas</p> <p>2015-04-01</p> <p>The aim of this work is to demonstrate the extraction of the local phase <span class="hlt">velocity</span> and the <span class="hlt">group</span> <span class="hlt">velocity</span> from surface noise source in microseismic monitoring. One of the biggest challenges in microseismic monitoring is surface seismic noise. Microseismic surface studies are often contaminated with instrumental and ambient seismic noise, originating from both natural (wind, rain) and anthropogenic sources (injection, pumps, infrastructure, traffic). The two primary ways to attenuate the undesired surface noise sources are via processing and acquisition strategies. At the acquisition stage, one solution is through the use of patch array. One patch is a <span class="hlt">group</span> of 48 vertical sensors densely distributed on the area of~150m*150m, and one trace is the array of 12 vertical geophones. In the present work, 44 patches were sparsely distributed on a 41 square kilometer area. Benefitting from continuous recording, we used Matched Field Processing (MFP) methods to extract local phase and <span class="hlt">group</span> <span class="hlt">velocities</span> over the whole area. The aim of this technique is to detect and locate uncoherent noise sources while using array-processing methods. The method is based on the comparison between a recorded wave field per patch (the data vector) and a theoretical (or modeled) wave-field (the replica vector) in the frequency domain. The replica vector is a Green's function at a given frequency, which depends on the following parameters: position (x,y) in 2D-grid and a phase <span class="hlt">velocity</span>. The noise source location is obtained by matching the data vector with the replica vector using a linear "low-resolution" algorithm or a nonlinear "high-resolution" adaptive processor. These algorithms are defined for each point in the 2D - grid and for each phase <span class="hlt">velocity</span>. The phase <span class="hlt">velocity</span> per patch is optimal if it maximizes the processor output. As a result, an ambiguity surface is produced which shows the probability of presence of primary noise sources per patch. The combination of all the maps per patch</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011SPIE.8091E..0LW','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011SPIE.8091E..0LW"><span id="translatedtitle">Enhanced joint spectral and time domain optical coherence <span class="hlt">tomography</span> for quantitative flow <span class="hlt">velocity</span> measurement</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Walther, Julia; Koch, Edmund</p> <p>2011-06-01</p> <p>Recently, a new method called joint spectral and time domain optical coherence <span class="hlt">tomography</span> (STdOCT) for flow <span class="hlt">velocity</span> measurement in spectral domain OCT (SD OCT) was presented. This method analyzes the detected timeresolved interference fringe spectra by using a two-dimensional fast Fourier transformation (2D FFT) to determine directly the Doppler frequency shift instead of calculating the phase difference at each depth position of adjacent A-scans. There, it was found that STdOCT is more robust for measurements with low signal to noise ratio than the classic phase-resolved Doppler OCT (DOCT) making it attractive first for imaging fast flow <span class="hlt">velocities</span> at which a strong Doppler angle dependent signal damping occurs due to interference fringe washout and second for investigating large blood vessels with a big diameter and a highly damped signal of blood with increasing depth due to strong scattering and absorption in the near-infrared wavelength range. In the present study, we would like to introduce an enhanced algorithm for STdOCT permitting a more precise flow <span class="hlt">velocity</span> measurement in comparison to the conventional STdOCT. The new method determines the amplitude of the broadened Doppler frequency shift by calculating the center of gravity via the complex analytical signal as a result of the second FFT instead of detecting the maximum intensity signal. Furthermore, the comparison with phase-resolved DOCT was done experimentally by using a flow phantom consisting of a 1% Intralipid emulsion and a 320 μm glass capillary. As a result, the enhanced STdOCT and DOCT processed data are completely equivalent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1610360A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1610360A"><span id="translatedtitle">Surface wave phase <span class="hlt">velocities</span> from 2-D surface wave <span class="hlt">tomography</span> studies in the Anatolian plate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arif Kutlu, Yusuf; Erduran, Murat; Çakır, Özcan; Vinnik, Lev; Kosarev, Grigoriy; Oreshin, Sergey</p> <p>2014-05-01</p> <p>We study the Rayleigh and Love surface wave fundamental mode propagation beneath the Anatolian plate. To examine the inter-station phase <span class="hlt">velocities</span> a two-station method is used along with the Multiple Filter Technique (MFT) in the Computer Programs in Seismology (Herrmann and Ammon, 2004). The near-station waveform is deconvolved from the far-station waveform removing the propagation effects between the source and the station. This method requires that the near and far stations are aligned with the epicentre on a great circle path. The azimuthal difference of the earthquake to the two-stations and the azimuthal difference between the earthquake and the station are restricted to be smaller than 5o. We selected 3378 teleseismic events (Mw >= 5.7) recorded by 394 broadband local stations with high signal-to-noise ratio within the years 1999-2013. Corrected for the instrument response suitable seismogram pairs are analyzed with the two-station method yielding a collection of phase <span class="hlt">velocity</span> curves in various period ranges (mainly in the range 25-185 sec). Diffraction from lateral heterogeneities, multipathing, interference of Rayleigh and Love waves can alter the dispersion measurements. In order to obtain quality measurements, we select only smooth portions of the phase <span class="hlt">velocity</span> curves, remove outliers and average over many measurements. We discard these average phase <span class="hlt">velocity</span> curves suspected of suffering from phase wrapping errors by comparing them with a reference Earth model (IASP91 by Kennett and Engdahl, 1991). The outlined analysis procedure yields 3035 Rayleigh and 1637 Love individual phase <span class="hlt">velocity</span> curves. To obtain Rayleigh and Love wave travel times for a given region we performed 2-D tomographic inversion for which the Fast Marching Surface <span class="hlt">Tomography</span> (FMST) code developed by N. Rawlinson at the Australian National University was utilized. This software package is based on the multistage fast marching method by Rawlinson and Sambridge (2004a, 2004b). The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1076806','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1076806"><span id="translatedtitle">Derivation of site-specific relationships between hydraulic parameters and p-wave <span class="hlt">velocities</span> based on hydraulic and seismic <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Brauchler, R.; Doetsch, J.; Dietrich, P.; Sauter, M.</p> <p>2012-01-10</p> <p>In this study, hydraulic and seismic tomographic measurements were used to derive a site-specific relationship between the geophysical parameter p-wave <span class="hlt">velocity</span> and the hydraulic parameters, diffusivity and specific storage. Our field study includes diffusivity tomograms derived from hydraulic travel time <span class="hlt">tomography</span>, specific storage tomograms, derived from hydraulic attenuation <span class="hlt">tomography</span>, and p-wave <span class="hlt">velocity</span> tomograms, derived from seismic <span class="hlt">tomography</span>. The tomographic inversion was performed in all three cases with the SIRT (Simultaneous Iterative Reconstruction Technique) algorithm, using a ray tracing technique with curved trajectories. The experimental set-up was designed such that the p-wave <span class="hlt">velocity</span> tomogram overlaps the hydraulic tomograms by half. The experiments were performed at a wellcharacterized sand and gravel aquifer, located in the Leine River valley near Göttingen, Germany. Access to the shallow subsurface was provided by direct-push technology. The high spatial resolution of hydraulic and seismic <span class="hlt">tomography</span> was exploited to derive representative site-specific relationships between the hydraulic and geophysical parameters, based on the area where geophysical and hydraulic tests were performed. The transformation of the p-wave <span class="hlt">velocities</span> into hydraulic properties was undertaken using a k-means cluster analysis. Results demonstrate that the combination of hydraulic and geophysical tomographic data is a promising approach to improve hydrogeophysical site characterization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.S41B2744B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.S41B2744B"><span id="translatedtitle">Anisotropic 3-D Crustal <span class="hlt">Velocity</span> Structure of Idaho/ Oregon from a Joint Inversion of <span class="hlt">Group</span> and Phase <span class="hlt">Velocities</span> of Love and Rayleigh Waves from Ambient Seismic Noise: Results from the IDOR Project</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bremner, P. M.; Panning, M. P.; Russo, R.; Mocanu, V. I.; Stanciu, A. C.; Torpey, M. E.; Hongsresawat, S.; VanDecar, J. C.</p> <p>2015-12-01</p> <p>We present new 3-D radially anisotropic and isotropic crustal <span class="hlt">velocity</span> models beneath central Idaho and eastern Oregon. We produced the <span class="hlt">velocity</span> models from Love and horizontal component Rayleigh wave <span class="hlt">group</span> and phase <span class="hlt">velocity</span> measurements on the IDaho/ORegon (IDOR) Passive seismic network, 86 broadband seismic stations, dataset using ambient noise <span class="hlt">tomography</span> and the methods of Gallego et. al (2010) and Lin et. al (2008). We calculated inter-station <span class="hlt">group</span>/phase <span class="hlt">velocities</span> in narrow frequency bands from travel-time measurements of the rotated stacked horizontal component cross-correlations (bandpass filtered between 2 and 30 seconds), which we used to invert for <span class="hlt">velocity</span> structure beneath the network. We derived <span class="hlt">group</span> and phase <span class="hlt">velocity</span> maps for each frequency band using the damped least-squares inversion method of Tarantola (2005), and then jointly inverted for <span class="hlt">velocity</span> with depth. Moho depths are prescribed in the joint inversions based on receiver functions, also from the IDOR seismic data, and provides a starting crustal <span class="hlt">velocity</span> model. Goals of our work include refining models of crustal structure in the accreted Blue Mountain terranes in the western study area; determining the depth extent of the Salmon River Suture/West Idaho Shear Zone (WISZ), which crosses north-south through the middle of the network; determining the architecture of the Idaho batholith, an extensive largely crustal-derived pluton; and examining the nature of the autochthonous (?) North American crust and lithosphere beneath and east of the batholith.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.S33A1754S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.S33A1754S"><span id="translatedtitle">Improved Near-surface <span class="hlt">Velocity</span> Models from Waveform <span class="hlt">Tomography</span> Applied to Vibroseis MCS Reflection Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smithyman, B.; Clowes, R. M.</p> <p>2009-12-01</p> <p>Multichannel vibroseis reflection surveys are prevalent in the land exploration seismic industry because of benefits in speed and cost, along with reduced environmental impact when compared to explosive sources. Since the downgoing energy must travel through the shallow subsurface, an improved model of near-surface <span class="hlt">velocity</span> can in theory substantially improve the resolution of deeper reflections. We describe techniques aimed at allowing the use of vibroseis data for long-offset refraction processing of first-arrival traveltimes and waveforms. Refraction processing of surface vibroseis data is typically limited to near-offset refraction statics. <span class="hlt">Velocity</span> models of the shallow subsurface can be built to facilitate CDP stacking and migration, but these models are typically coarse and of limited use for interpretation. Waveform <span class="hlt">tomography</span> combines inversion of first-arrival traveltime data with full waveform inversion of densely-sampled refracted arrivals. Since inversion of the waveform amplitude and phase is not limited by the ray-theory approximation, identification of low-<span class="hlt">velocity</span> zones and small scattering targets is possible. Incorporating a wide range of offsets is critical for a more complete characterization of the near-surface. Because of the use of a non-linear frequency-domain approach to the solution of this inverse problem, low data frequencies are important in comparison with conventional reflection processing. Through the use of waveform <span class="hlt">tomography</span>, we plan to build useful, detailed near-surface <span class="hlt">velocity</span> models for both the reflection work flow and direct interpretation. Several difficulties exist in first-arrival analysis and waveform inversion of vibroseis data. The mixed-phase vibroseis source signature exhibits variations in phase with offset that are difficult to quantify without detailed a priori knowledge of the near-surface. This causes difficulties with picking and initial model building, which is critical for non-linear waveform inversion. A</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.S31E..05W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.S31E..05W"><span id="translatedtitle">Can we go From Tomographically Determined Seismic <span class="hlt">Velocities</span> to Composition? Amplitude Resolution Issues in Local Earthquake <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wagner, L.</p> <p>2007-12-01</p> <p>There have been a number of recent papers (i.e. Lee (2003), James et al. (2004), Hacker and Abers (2004), Schutt and Lesher (2006)) which calculate predicted <span class="hlt">velocities</span> for xenolith compositions at mantle pressures and temperatures. It is tempting, therefore, to attempt to go the other way ... to use tomographically determined absolute <span class="hlt">velocities</span> to constrain mantle composition. However, in order to do this, it is vital that one is able to accurately constrain not only the polarity of the determined <span class="hlt">velocity</span> deviations (i.e. fast vs slow) but also how much faster, how much slower relative to the starting model, if absolute <span class="hlt">velocities</span> are to be so closely analyzed. While much attention has been given to issues concerning spatial resolution in seismic <span class="hlt">tomography</span> (i.e. what areas are fast, what areas are slow), little attention has been directed at the issue of amplitude resolution (how fast, how slow). <span class="hlt">Velocity</span> deviation amplitudes in seismic <span class="hlt">tomography</span> are heavily influenced by the amount of regularization used and the number of iterations performed. Determining these two parameters is a difficult and little discussed problem. I explore the effect of these two parameters on the amplitudes obtained from the tomographic inversion of the Chile Argentina Geophysical Experiment (CHARGE) dataset, and attempt to determine a reasonable solution space for the low Vp, high Vs, low Vp/Vs anomaly found above the flat slab in central Chile. I then compare this solution space to the range in experimentally determined <span class="hlt">velocities</span> for peridotite end-members to evaluate our ability to constrain composition using tomographically determined seismic <span class="hlt">velocities</span>. I find that in general, it will be difficult to constrain the compositions of normal mantle peridotites using tomographically determined <span class="hlt">velocities</span>, but that in the unusual case of the anomaly above the flat slab, the observed <span class="hlt">velocity</span> structure still has an anomalously high S wave <span class="hlt">velocity</span> and low Vp/Vs ratio that is most</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.S31B4404B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.S31B4404B"><span id="translatedtitle">3-D Crustal <span class="hlt">Velocity</span> Structure of Central Idaho/ Eastern Oregon from Joint Inversion of Rayleigh Wave <span class="hlt">Group</span> and Phase <span class="hlt">Velocities</span> Derived from Ambient Seismic Noise: Newest Results from the IDOR Project</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bremner, P. M.; Panning, M. P.; Russo, R. M.; Mocanu, V. I.; Stanciu, A. C.; Torpey, M. E.; Hongsresawat, S.; VanDecar, J. C.</p> <p>2014-12-01</p> <p>We present the latest 3-D isotropic crustal <span class="hlt">velocity</span> model beneath central Idaho and eastern Oregon. We produced the <span class="hlt">velocity</span> model from vertical component Rayleigh wave <span class="hlt">group</span> and phase <span class="hlt">velocity</span> measurements on data from the IDaho/ORegon (IDOR) Passive seismic network, 86 broadband seismic stations, using ambient noise <span class="hlt">tomography</span> and the methods of Gallego et. al (2010) and Lin et. al (2008). We calculated inter-station <span class="hlt">group</span>/phase <span class="hlt">velocities</span> in narrow frequency bands from travel-time measurements of the stacked cross-correlations (bandpass filtered between 2 and 30 seconds), which we used to invert for <span class="hlt">velocity</span> structure beneath the network. Goals of our work include refining models of crustal structure in the accreted Blue Mountain terranes in the western study area; determining the depth extent of the Salmon River Suture/West Idaho Shear Zone (WISZ), which crosses north-south through the middle of the network; determining the architecture of the Idaho batholith, an extensive largely crustal-derived pluton; and examining the nature of the autochthonous (?) North American crust and lithosphere beneath and east of the batholith. We derived Rayleigh wave <span class="hlt">group</span> and phase <span class="hlt">velocity</span> maps for each frequency band using the damped least-squares inversion method of Tarantola (2005), and then jointly inverted for <span class="hlt">velocity</span> with depth. Moho depths are prescribed in the joint inversions based on receiver functions, also from the IDOR seismic data, and provides a starting crustal <span class="hlt">velocity</span> model. 3-D checkerboard resolution tests indicate lateral resolution of better than 40 km. Preliminary results show higher S wave <span class="hlt">velocities</span> in the western study area, and lower <span class="hlt">velocities</span> in the lower crust on the east side of the network, consistent with Basin-and-Range style extension there. A tabular <span class="hlt">velocity</span> anomaly juxtaposing higher above lower seismic <span class="hlt">velocities</span> dips shallow west in the midcrust on the west side of the network.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012SPIE.8222E..0HD&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012SPIE.8222E..0HD&link_type=ABSTRACT"><span id="translatedtitle">Dual-beam optical coherence <span class="hlt">tomography</span> system for quantification of flow <span class="hlt">velocity</span> in capillary phantoms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Daly, S. M.; Silien, C.; Leahy, M. J.</p> <p>2012-03-01</p> <p>The quantification of (blood) flow <span class="hlt">velocity</span> within the vasculature has potent diagnostic and prognostic potential. Assessment of flow irregularities in the form of increased permeability (micro haemorrhaging), the presence of avascular areas, or conversely the presence of vessels with enlarged or increased tortuosity in the acral regions of the body may provide a means of non-invasive in vivo assessment. If assessment of dermal flow dynamics were performed in a routine manner, the existence and prevalence of ailments such as diabetes mellitus, psoriatic arthritis and Raynaud's condition may be confirmed prior to clinical suspicion. This may prove advantageous in cases wherein the efficacy of a prescribed treatment is dictated by a prompt diagnosis and to alleviate patient discomfort through early detection. Optical Coherence <span class="hlt">Tomography</span> (OCT) is an imaging modality which utilises the principle of optical interferometry to distinguish between spatial changes in refractive index within the vasculature and thus formulate a multi-dimensional representation of the structure of the epi- and dermal skin layers. The use of the Doppler functionality has been the predominant force for the quantification of moving particles within media, elucidated via estimation of the phase shift in OCT A-scans. However, the theoretical formulation for the assessment of these phase shifts dictates that the angle between the incident light source and the vessel under question be known a priori; this may be achieved via excisional biopsy of the tissue segment in question, but is counter to the non-invasive premise of the OCT technique. To address the issue of angular dependence, an alternate means of estimating absolute flow <span class="hlt">velocity</span> is presented. The design and development of a dual-beam (db) system incorporating an optical switch mechanism for signal discrimination of two spatially disparate points enabling quasi-simultaneous multiple specimen scanning is described. A crosscorrelation (c</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeoRL..41.8045W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeoRL..41.8045W"><span id="translatedtitle">Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> distributions for East Asia using ambient seismic noise</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Witek, Michael; van der Lee, Suzan; Kang, Tae-Seob</p> <p>2014-11-01</p> <p>Vertical component data from 206 broadband seismometer stations from Korean networks Korean Institute of Geoscience and Mineral Resources and Korea Meteorological Administration, the Japanese F-net network, and the Chinese New China Digital Seismograph Network and Northeast China Extended Seismic Array network are collected for the year 2011, and the ambient seismic noise is analyzed. Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> distribution maps are created in the period range 10 to 70 s. Our results are largely consistent with previous studies of the area but provide greater detail in the Korean peninsula and the Sea of Japan. Low <span class="hlt">group</span> <span class="hlt">velocities</span> are observed in the Ulleung basin, and the Chubu-Kanto and Kyushu regions in Japan. At 10 s period, sediment basins in the Sea of Japan appear as low <span class="hlt">group</span> <span class="hlt">velocity</span> regions relative to higher <span class="hlt">group</span> <span class="hlt">velocity</span> continental regions. At periods longer than 40 s, a low <span class="hlt">group</span> <span class="hlt">velocity</span> region emerges in the Ulleung basin region, and is bounded by the Korean peninsula.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PApGe.tmp..172O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PApGe.tmp..172O"><span id="translatedtitle">P-Wave <span class="hlt">Velocity</span> <span class="hlt">Tomography</span> from Local Earthquakes in Western Mexico</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ochoa-Chávez, Juan A.; Escudero, Christian R.; Núñez-Cornú, Francisco J.; Bandy, William L.</p> <p>2015-11-01</p> <p>In western Mexico, the subduction of the Rivera and Cocos plates beneath the North America plate has deformed and fragmented the overriding plate, forming several structural rifts and crustal blocks. To obtain a reliable subsurface image of the continental crust and uppermost mantle in this complex area, we used P-wave arrivals of local earthquakes along with the Fast Marching Method <span class="hlt">tomography</span> technique. We followed an inversion scheme consisting of (1) the use of a high-quality earthquake catalog and corrected phase picks, (2) the selection of earthquakes using a maximum location error threshold, (3) the estimation of an improved 1-D reference <span class="hlt">velocity</span> model, and (4) the use of checkerboard testing to determine the optimum configuration of the <span class="hlt">velocity</span> nodes and inversion parameters. Surprisingly, the <span class="hlt">tomography</span> results show a very simple δVp distribution that can be described as being controlled by geologic structures formed during two stages of the separation of the Rivera and Cocos plates. The earlier period represents the initial stages of the separation of the Rivera and Cocos plates beneath western Mexico; the later period represents the more advanced stage of rifting where the Rivera and Cocos plates had separated sufficiently to allow melt to accumulate below the Colima Volcanic complex. During the earlier period (14 or 10-1.6 Ma), NE-SW-oriented structures/lineaments (such as the Southern Colima Rift) were formed as the two plates separated. During the second period (1.6 Ma to the present), the deformation is attributed to magma, generated within and above the tear zone between the Rivera and Cocos plates, rising beneath the region of the Colima Volcanic Complex. The rising magma fractured the overlying crust, forming a classic triple-rift junction geometry. This triple-rift system is confined to the mid- to lower crust perhaps indicating that this rifting process is still in an early stage. This fracturing, along with fluid circulation and associated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70015520','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70015520"><span id="translatedtitle">High <span class="hlt">velocity</span> anomaly beneath the Deccan volcanic province: Evidence from seismic <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Iyer, H.M.; Gaur, V.K.; Rai, S.S.; Ramesh, D.S.; Rao, C.V.R.; Srinagesh, D.; Suryaprakasam, K.</p> <p>1989-01-01</p> <p>Analysis of teleseismic P-wave residuals observed at 15 seismograph stations operated in the Deccan volcanic province (DVP) in west central India points to the existence of a large, deep anomalous region in the upper mantle where the <span class="hlt">velocity</span> is a few per cent higher than in the surrounding region. The seismic stations were operated in three deployments together with a reference station on precambrian granite at Hyderabad and another common station at Poona. The first <span class="hlt">group</span> of stations lay along a west-northwesterly profile from Hyderabad through Poona to Bhatsa. The second <span class="hlt">group</span> roughly formed an L-shaped profile from Poona to Hyderabad through Dharwar and Hospet. The third <span class="hlt">group</span> of stations lay along a northwesterly profile from Hyderabad to Dhule through Aurangabad and Latur. Relative residuals computed with respect to Hyderabad at all the stations showed two basic features: a large almost linear variation from approximately +1s for teleseisms from the north to-1s for those from the southeast at the western stations, and persistance of the pattern with diminishing magnitudes towards the east. Preliminary ray-plotting and three-dimensional inversion of the P-wave residual data delineate the presence of a 600 km long approximately N-S trending anomalous region of high <span class="hlt">velocity</span> (1-4% contrast) from a depth of about 100 km in the upper mantle encompassing almost the whole width of the DVP. Inversion of P-wave relative residuals reveal the existence of two prominent features beneath the DVP. The first is a thick high <span class="hlt">velocity</span> zone (1-4% faster) extending from a depth of about 100 km directly beneath most of the DVP. The second feature is a prominent low <span class="hlt">velocity</span> region which coincides with the westernmost part of the DVP. A possible explanation for the observed coherent high <span class="hlt">velocity</span> anomaly is that it forms the root of the lithosphere which coherently translates with the continents during plate motions, an architecture characteristic of precambrian shields. The low</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active"><span>4</span></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_4 --> <div id="page_5" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="81"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003PhDT........25Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003PhDT........25Y"><span id="translatedtitle">Noninvasive microstructural and <span class="hlt">velocity</span> imaging in humans by color Doppler optical coherence <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yazdanfar, Siavash</p> <p></p> <p>The objective of this dissertation is to develop the optical instrumentation, electronics, and signal processing for high-resolution blood flow imaging using optical coherence <span class="hlt">tomography</span> (OCT) in human subjects. In particular, in vivo OCT blood flow imaging, termed color Doppler OCT (CDOCT), is applied for the first time to measurements in human vasculature of the retina and skin. CDOCT is similar to color Doppler ultrasound, whereas depth-resolved flow information is extracted from reflectivity profiles obtained from phase-sensitive, low-coherence interferometry. Although CDOCT has been demonstrated in tissue-mimicking phantoms and in living animal models, the technique has not yet been extended to blood flow imaging in humans. In this project, CDOCT was integrated with a modified slit lamp biomicroscope for imaging of retinal blood flow, and additional technical requirements necessary for retinal flow imaging were met. This system was used to acquire the first high resolution, cross-sectional images of blood flow with OCT in humans. The image acquisition rate was increased to examine retinal hemodynamics in normal subjects. A method was introduced for improving the <span class="hlt">velocity</span> resolution by approximately two orders of magnitude, down to ˜1 micrometer/sec, by calculating the change in the phase across sequential scans. This technique was used to achieve the highest <span class="hlt">velocity</span> resolution to date in scattering media, and applied to imaging the human microvasculature down to the capillary level. Finally, a modification of CDOCT based on differential phase contrast was introduced for high resolution imaging in the presence of motion artifact. This technique measures the differential Doppler frequency between two beams of orthogonal polarization states that are laterally displaced on the sample. Using polarization diversity detection, the common-mode noise was removed, enabling the measurement of flow in scattering media down to the theoretical frequency resolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.T53D..03Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.T53D..03Y"><span id="translatedtitle">P-Wave <span class="hlt">Velocity</span> Structure Beneath Eastern Eurasia From Finite Frequency Seismic <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, T.; Shen, Y.; Yang, X.</p> <p>2005-12-01</p> <p>Eastern Eurasia is one of the most tectonically complex regions in the world. While the evolution history of continental lithosphere has been well recognized, the fine structure associated with the complicated deformation in this region is far from clear, and deep mantle processes that accompanied shallower lithosphere deformations are poorly understood. In order to improve the resolution of the <span class="hlt">velocity</span> structure in the region, we applied the newly-developed Finite Frequency Seismic <span class="hlt">Tomography</span> (FFST) method, which utilizes the 3D Frechet-Born sensitivity kernels of the travel times of finite frequency seismic waves to account for wavefront healing and off-ray scattering, to eastern Eurasia. In addition to the new technique, we obtained a comprehensive finite-frequency body wave travel time data set from cross-correlation of broadband waveforms. Datasets used in this study include waveforms from the publicly accessible sources (e.g. IRIS, GSN, PASSCAL, and IMS stations) and other seismic networks in the region such as the Japanese Broadband Seismograph Network (F-net), the Japanese International Seismic Network (JISNET), the Taiwan Broadband Seismic Network and China National Digital Seismic Network. Taking advantage of broadband waveforms, we measured relative delays times by waveform cross-correlation in three frequency bands between 0.03 to 2 Hz for P waves. The travel times in the three frequency bands were inverted jointly to take advantage of the `data fusion' made possible by the finite-frequency kernels and separately to understand the resolving power of each data set. Preliminary results are comparable to the <span class="hlt">velocity</span> models obtained in previous tomographic studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015WRR....51.9665R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015WRR....51.9665R"><span id="translatedtitle">Application of acoustic <span class="hlt">tomography</span> to reconstruct the horizontal flow <span class="hlt">velocity</span> field in a shallow river</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Razaz, Mahdi; Kawanisi, Kiyosi; Kaneko, Arata; Nistor, Ioan</p> <p>2015-12-01</p> <p>A novel acoustic tomographic measurement system capable of resolving sound travel time in extremely shallow rivers is introduced and the results of an extensive field measurements campaign are presented and further discussed. Acoustic pulses were transmitted over a wide frequency band of 20-35 kHz between eight transducers for about a week in a meandering reach of theBāsen River, Hiroshima, Japan. The purpose of the field experiment was validating the concept of acoustic <span class="hlt">tomography</span> in rivers for visualizing current fields. The particular novelty of the experiment resides in its unusual tomographic features: subbasin scale (100 m × 270 m) and shallowness (0.5-3.0 m) of the physical domain, frequency of the transmitted acoustic signals (central frequency of 30 kHz), and the use of small sampling intervals (105 s). Inverse techniques with no a priori statistical information were used to estimate the depth-average current <span class="hlt">velocity</span> components from differential travel times. Zeroth-order Tikhonov regularization, in conjunction with L-curve method deployed to stabilize the solution and to determine the weighting factor appearing in the inverse analysis. Concurrent direct environmental measurements were provided in the form of ADCP readings close to the right and left bank. Very good agreement found between along-channel <span class="hlt">velocities</span> larger than 0.2 m/s obtained from the two techniques. Inverted quantities were, however, underestimated, perhaps due to vicinity of the ADCPs to the banks and strong effect of river geometry on the readings. In general, comparing the visualized currents with direct nodal measurements illustrate the plausibility of the tomographically reconstructed flow structures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.1716G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.1716G"><span id="translatedtitle">Can seismic <span class="hlt">tomography</span> detect weak <span class="hlt">velocity</span> changes? The practical application for the volcanoes in the Tohoku region.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gladkov, Valery; Koulakov, Ivan</p> <p>2016-04-01</p> <p>Temporal variations of seismic <span class="hlt">velocities</span> in the active volcanic areas may give us important information about its evolution and development of geologic processes inside it. Usually we use "direct" method to reveal <span class="hlt">velocity</span> changes with use of body wave's data. In this method, a whole period of observations is divided into a several interesting for us periods. For each period, we obtain a seismic <span class="hlt">velocity</span> model by means of seismic <span class="hlt">tomography</span>. Finally, a seismic <span class="hlt">velocity</span> changes between chosen periods is a difference between inverted <span class="hlt">velocity</span> models for these periods. In case of weak <span class="hlt">velocity</span> changes, this approach fails due to factors of varying events location and "event-station" rays distribution which influence can raise a false and apparent <span class="hlt">velocity</span> changes in the model. With the aim to eliminate these factors and to increase the reliability of <span class="hlt">velocity</span> changes detection, we propose an approach, which improves the similarity of datasets used for seismic <span class="hlt">tomography</span> in different time periods by rejection some input events and rays information. We used this approach to the data of the Japan Meteorological Agency, which includes several years before and after the Mw 9.0 Tohoku-Oki event that occurred on 11.03.2011. We performed careful testing using different synthetic models, showing that the selected data subsets reveal weak <span class="hlt">velocity</span> changes with amplitudes above 0.5%. We detected <span class="hlt">velocity</span> reductions of P-waves on 0.8% and S-waves on 0.6% in the central area of Honshu possibly linked with the fluid system properties changes which triggered by Tohoku-Oki earthquake.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993PhDT.......118C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993PhDT.......118C"><span id="translatedtitle">a Renormalization <span class="hlt">Group</span> Calculation of the <span class="hlt">Velocity</span> - and Density-Density Correlation Functions.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cowan, Mark Timothy</p> <p></p> <p>The <span class="hlt">velocity-velocity</span> correlation function of a free field theory is obtained. The renormalization <span class="hlt">group</span>, along with a 4-varepsilon expansion, is then used to find the leading order behavior of the <span class="hlt">velocity-velocity</span> correlation function for an interacting field theory in the high temperature phase near the critical point. The details of the calculation of the density-density correlation function for Hedgehogs, in the context of a free field theory, is presented next. Finally the renormalization <span class="hlt">group</span>, along with a 4-varepsilon expansion, is used to find the leading order behavior of the density-density correlation function for Hedgehogs in an interacting field theory near the critical point.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ApPhL.100w3702R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ApPhL.100w3702R"><span id="translatedtitle">Quantitative imaging of red blood cell <span class="hlt">velocity</span> invivo using optical coherence Doppler <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ren, Hugang; Du, Congwu; Park, Kicheon; Volkow, Nora D.; Pan, Yingtian</p> <p>2012-06-01</p> <p>We present particle counting ultrahigh-resolution optical Doppler <span class="hlt">tomography</span> (pc-μODT) that enables accurate imaging of red blood cell <span class="hlt">velocities</span> (νRBC) of cerebrovascular networks by detecting the Doppler phase transients induced by the passage of a RBC through a capillary. We apply pc-μODT to image the response of capillary νRBC to mild hypercapnia in mouse cortex. The results show that νRBC in normocapnia (νN = 0.72 ± 0.15 mm/s) increased 36.1% ± 5.3% (νH = 0.98 ± 0.29 mm/s) in response to hypercapnia. Due to uncorrected angle effect and low hematocrit (e.g., ˜10%), νRBC directly measured by μODT were markedly underestimated (νN ≈ 0.27 ± 0.03 mm/s, νH ≈ 0.37± 0.05 mm/s). Nevertheless, the measured νRBC increase (35.3%) matched that (36.1% ± 5.3%) by pc-μODT.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.S51A0984R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.S51A0984R"><span id="translatedtitle">Variation of fundamental mode Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion in Iran and the surrounding region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rham, D.; Priestley, K.; Tatar, M.; Paul, A.; Hatzfeld, D.; Radjaee, A.; Nowrouzi, G.; Kaviani, A.; Tiberi, C.</p> <p>2005-12-01</p> <p>We present <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion results from a study of regional fundamental mode Rayleigh waves propagating across Iran and the surrounding region. Data for these measurements come from field deployments within Iran by the University of Cambridge (UK) and the Universite Joseph-Fourier (FRA) in conjunction with International Institute of Earthquake Engineering and Seismology (Iran), within Oman by the Universite Pierre et Marie Curie-Paris (FRA), in addition to data from IRIS and Geofone. 1D path-averaged dispersion measurements have been made for ~800 source-receiver paths using multiple filter analysis. We combine these observations in a tomographic inversion to produce <span class="hlt">group</span> <span class="hlt">velocity</span> images between 15 and 60~s period. Because of the dense path coverage, these images have substantially higher lateral resolution for this region than is currently available from global and regional <span class="hlt">group</span> <span class="hlt">velocity</span> studies. We observe variations in short-period <span class="hlt">group</span> <span class="hlt">velocity</span> which is consistent with the surface geology. Low <span class="hlt">group</span> <span class="hlt">velocity</span> (2.45-2.55~km/s) at short periods (15-20~s) is observed beneath the south Caspian Basin, northern Iran, the Persian Gulf, the Zagros, the Makran, northern Afghanistan and southern Pakistan. Somewhat higher <span class="hlt">group</span> <span class="hlt">velocity</span> (2.60-2.70~km/s) at these periods occurs in central Iran. At intermediate periods (30-40~s) <span class="hlt">group</span> <span class="hlt">velocities</span> over most of the region are low (2.90-3.10~km/s) compared to Arabia. At longer periods (50-60~s) <span class="hlt">group</span> <span class="hlt">velocities</span> remain low (3.35-3.45~km/s) over most of Iran but there is a suggestion of higher <span class="hlt">group</span> <span class="hlt">velocities</span> beneath the northern and central Zagros.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JAG...109..140C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JAG...109..140C"><span id="translatedtitle">Application of seismic <span class="hlt">velocity</span> <span class="hlt">tomography</span> in underground coal mines: A case study of Yima mining area, Henan, China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cai, Wu; Dou, Linming; Cao, Anye; Gong, Siyuan; Li, Zhenlei</p> <p>2014-10-01</p> <p>A better understanding of geological structures, stress regimes, and rock burst risks around longwall mining panels can allow for higher extraction efficiency with reduced safety concerns. In this paper, the stress change of rock mass was first examined by using ultrasonic technique into laboratory-scale rock samples. Subsequently, the active and passive seismic <span class="hlt">velocity</span> tomograms were simultaneously applied into two study cases with field-scale. Similar characteristics can be found between the active and passive <span class="hlt">tomography</span> results. More specifically, in the first case, a geological discontinuity was clearly indicated by a linear image in both active and passive seismic <span class="hlt">tomography</span> results. The results of the second case suggest that seismic <span class="hlt">tomography</span> can be used to infer stress redistribution, and assess rock burst hazard or locate high-seismicity zones. Ultimately, comparisons have been made between the results of active and passive seismic <span class="hlt">tomography</span>. Active <span class="hlt">tomography</span> is found to be better applied in accurately detecting stress distribution and geological structures prior to the extraction of longwall panels, while passive <span class="hlt">tomography</span> has advantages in continuously monitoring the stress changes and assessing rock burst potential during the mining of longwall panels. This study is expected to increase the safety and efficiency of the underground mining.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApPhL.108w1904L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApPhL.108w1904L"><span id="translatedtitle">Simultaneous realization of negative <span class="hlt">group</span> <span class="hlt">velocity</span>, fast and slow acoustic waves in a metamaterial</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Xiao-juan; Xue, Cheng; Fan, Li; Zhang, Shu-yi; Chen, Zhe; Ding, Jin; Zhang, Hui</p> <p>2016-06-01</p> <p>An acoustic metamaterial is designed based on a simple and compact structure of one string of side pipes arranged along a waveguide, in which diverse <span class="hlt">group</span> <span class="hlt">velocities</span> are achieved. Owing to Fabry-Perot resonance of the side pipes, a negative phase time is achieved, and thus, acoustic waves transmitting with negative <span class="hlt">group</span> <span class="hlt">velocities</span> are produced near the resonant frequency. In addition, both fast and slow acoustic waves are also observed in the vicinity of the resonance frequency. The extraordinary <span class="hlt">group</span> <span class="hlt">velocities</span> can be explained based on spectral rephasing induced by anomalous dispersion on the analogy of Lorentz dispersion in electromagnetic waves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeoJI.199.1303F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeoJI.199.1303F"><span id="translatedtitle">Whole-mantle radially anisotropic shear <span class="hlt">velocity</span> structure from spectral-element waveform <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>French, S. W.; Romanowicz, B. A.</p> <p>2014-12-01</p> <p>The radially anisotropic shear <span class="hlt">velocity</span> structure of the Earth's mantle provides a critical window on the interior dynamics of the planet, with isotropic variations that are interpreted in terms of thermal and compositional heterogeneity and anisotropy in terms of flow. While significant progress has been made in the more than 30 yr since the advent of global seismic <span class="hlt">tomography</span>, many open questions remain regarding the dual roles of temperature and composition in shaping mantle convection, as well as interactions between different dominant scales of convective phenomena. We believe that advanced seismic imaging techniques, such as waveform inversion using accurate numerical simulations of the seismic wavefield, represent a clear path forwards towards addressing these open questions through application to whole-mantle imaging. To this end, we employ a `hybrid' waveform-inversion approach, which combines the accuracy and generality of the spectral finite element method (SEM) for forward modelling of the global wavefield, with non-linear asymptotic coupling theory for efficient inverse modelling. The resulting whole-mantle model (SEMUCB-WM1) builds on the earlier successful application of these techniques for global modelling at upper mantle and transition-zone depths (≤800 km) which delivered the models SEMum and SEMum2. Indeed, SEMUCB-WM1 is the first whole-mantle model derived from fully numerical SEM-based forward modelling. Here, we detail the technical aspects of the development of our whole-mantle model, as well as provide a broad discussion of isotropic and radially anisotropic model structure. We also include an extensive discussion of model uncertainties, specifically focused on assessing our results at transition-zone and lower-mantle depths.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006AGUFM.S23D0188R&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006AGUFM.S23D0188R&link_type=ABSTRACT"><span id="translatedtitle">Variation of Fundamental Mode Surface Wave <span class="hlt">Group</span> <span class="hlt">Velocity</span> Dispersion in Iran and the Surrounding Region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rham, D. J.; Preistley, K.; Tatar, M.; Paul, A.</p> <p>2006-12-01</p> <p>We present <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion results from a study of regional fundamental mode Rayleigh and Love waves propagating across Iran and the surrounding region. Data for these measurements comes from field deployments within Iran by the University of Cambridge (GBR) and the Universite Joseph-Fourier (FRA) in conjunction with International Institute of Earthquake Engineering and Seismology (Iran), in addition to data from IRIS and Geofone. 1D path- averaged dispersion measurements have been made for ~5500 source-receiver paths using multiple filter analysis. We combine these observations in a tomographic inversion to produce <span class="hlt">group</span> <span class="hlt">velocity</span> images between 10 and 60 s period. Because of the dense path coverage, these images have substantially higher lateral resolution for this region than is currently available from global and regional <span class="hlt">group</span> <span class="hlt">velocity</span> studies. We observe variations in short-period wave <span class="hlt">group</span> <span class="hlt">velocity</span> which is consistent with the surface geology. Low <span class="hlt">group</span> <span class="hlt">velocities</span> (2.00-2.55 km/s) at short periods (10-20 s), for both Rayleigh and Love waves are observed beneath thick sedimentary deposits; The south Caspian Basin, Black Sea, the eastern Mediterranean, the Persian Gulf, the Makran, the southern Turan shield, and the Indus and Gangetic basins. Somewhat higher <span class="hlt">group</span> <span class="hlt">velocity</span> (2.80-3.15 km/s for Rayleigh, and 3.00-3.40 km/s for Love) at these periods occur in sediment poor regions, such as; the Turkish-Iranian plateau, the Arabian shield, and Kazakhstan. At intermediate periods (30-40 s) <span class="hlt">group</span> <span class="hlt">velocities</span> over most of the region are low (2.65-3.20 km/s for Rayleigh, and 2.80-3.45 km/s for love) compared to Arabia (3.40-3.70 km/s Rayleigh, 3.50-4.0 km/s Love). At longer periods (50-60 s) Love wave <span class="hlt">group</span> <span class="hlt">velocities</span> remain low (3.25-3.70 km/s) over most of Iran, but there are even lower <span class="hlt">velocities</span> (2.80-3.00 km/s) still associated with the thick sediments of the south Caspian basin, the surrounding shield areas have much higher <span class="hlt">group</span> <span class="hlt">velocities</span> (3</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007Optik.118..163L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007Optik.118..163L"><span id="translatedtitle"><span class="hlt">Group</span> <span class="hlt">velocity</span> of the light pulse in an open V-type system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Jingjuan; Fan, Xijun; Tian, Shufen; Liu, Chengpu; Gong, Shangqing; Xu, Zhizhan</p> <p>2007-04-01</p> <p>We investigate the <span class="hlt">group</span> <span class="hlt">velocity</span> of the probe light pulse in an open V-type system with spontaneously generated coherence. We find that, not only varying the relative phase between the probe and driving pulses can but varying the atomic exit rate or incoherent pumping rate also can manipulate dramatically the <span class="hlt">group</span> <span class="hlt">velocity</span>, even make the pulse propagation switching from subluminal to superluminal; the subliminal propagation can be companied with gain or absorption, but the superluminal propagation is always companied with absorption.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/611845','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/611845"><span id="translatedtitle">Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion across Northern Africa, Southern Europe and the Middle East</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>McNamara, D.E.; Walter, W.R.</p> <p>1997-07-15</p> <p>THis report presents preliminary results from a large scale study of surface wave <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion throughout Northern Africa, the Mediterranean, Southern Europe and the Middle East. Our goal is to better define the 3D lithospheric shear-wave <span class="hlt">velocity</span> structure within this region by improving the resolution of global surface wave tomographic studies. We hope to accomplish this goal by incorporating regional data at relatively short periods (less than 40 sec), into the regionalization of lateral <span class="hlt">velocity</span> variation. Due to the sparse distributions of stations and earthquakes throughout the region (Figure 1) we have relied on data recorded at both teleseismic and regions; distances. Also, to date we have concentrated on Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> measurements since valuable measurements can be made without knowledge of the source. In order to obtain Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> throughout the region, vertical component teleseismic and regional seismograms were gathered from broadband, 3-component, digital MEDNET, GEOSCOPE and IRIS stations plus the portable PASSCAL deployment in Saudi Arabia. Figure 1 shows the distribution of earthquakes (black circles) and broadband digital seismic stations (white triangles) throughout southern Europe, the middle east and northern Africa used in this study. The most seismicly active regions of northern Africa are the Atlas mountains of Morocco and Algeria as well as the Red Sea region to the east. Significant seismicity also occurs in the Mediterranean, southern Europe and throughout the high mountains and plateaus of the middle-east. To date, over 1300 seismograms have been analyzed to determine the individual <span class="hlt">group</span> <span class="hlt">velocities</span> of 10-150 second Rayleigh waves. Travel times, for each period, are then inverted in a back projection tomographic method in order to determine the lateral <span class="hlt">group</span> <span class="hlt">velocity</span> variation throughout the region. These results are preliminary, however, Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> maps for a range of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFMNS31B0400G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFMNS31B0400G"><span id="translatedtitle">Use of Seismic Reflection Data and Traveltime <span class="hlt">Tomography</span> to Image the Near Surface <span class="hlt">Velocity</span> Structure in the Mississippi Embayment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ge, J.; Magnani, M.; Waldron, B.; Powell, C.</p> <p>2007-12-01</p> <p>The Memphis aquifer represents one of the highest quality reservoirs of drinking water in the nation and it is separated from the shallow unconfined aquifer by the Upper Claiborne clay. Recent studies show that the confining unit might be discontinuous over the greater Memphis area exposing the Memphis aquifer to potential contamination. We present the results of a seismic reflection profile collected near Memphis, TN with the goal of imaging the structures and potential breaches in the Upper Claiborne confining clay. The imaged area is characterized by a highly heterogeneous shallow <span class="hlt">velocity</span> structure and low P wave <span class="hlt">velocities</span> in the ultrashallow unconsolidated materials. The data were collected using a shotgun source and a 1 m source spacing, 0.25 m receiver spacing and a 168-geophone spread for a max offset of 42 m. Raw seismic data show several reflected arrivals in the first 200ms, widespread ground roll, and air wave energy as well as consistent refracted phases across the 1 km - long profile. In addition to the reflection profile we present the preliminary results of first arrival travel time <span class="hlt">tomography</span> performed along the profile to constrain the <span class="hlt">velocity</span> field in the shallow portion of the profile. The <span class="hlt">velocity</span> was then used to remove the effect of the near surface <span class="hlt">velocity</span> variations. The main data processing steps included elevation statics and frequency and FK filtering. First arrival travel time modeling started with an initial estimate of the 2-layer <span class="hlt">velocity</span> model using the slope/intercept method. We then modeled first-arrival picks on 1095 shot gathers using the Geo TOMO+ package. The algorithm computes travel times by tracing turning rays and is also able to handle raypaths through low-<span class="hlt">velocity</span> zones (blind zones). The final resolution is estimated through a ray-information density map, which shows the cumulative contribution of the ray segments traversing different areas of the model. Synthetic models were generated and tested for the <span class="hlt">tomography</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006JPCM...18.3117B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006JPCM...18.3117B"><span id="translatedtitle">Propagation of smooth and discontinuous pulses through materials with very large or very small <span class="hlt">group</span> <span class="hlt">velocities</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bigelow, Matthew S.; Lepeshkin, Nick N.; Shin, Heedeuk; Boyd, Robert W.</p> <p>2006-03-01</p> <p>We investigate the propagation of optical pulses through two different solid-state optical materials, ruby and alexandrite, for which the <span class="hlt">group</span> <span class="hlt">velocity</span> can be very small (v_{\\mathrm {g}} \\ll c ) or superluminal (v_{\\mathrm {g}} \\gg c or negative). We find that for smooth pulses the fractional delay or advancement is maximized through the use of pulses with durations comparable to the response time of the physical process—coherent population oscillations—that leads to these extreme <span class="hlt">group</span> <span class="hlt">velocities</span>. However, we find that the transmitted pulse shape becomes distorted unless the pulse is much longer or much shorter than this response time. We also investigate the transmission of pulses that possess an abrupt change in pulse amplitude. We find that, to within experimental accuracy, this nearly discontinuous jump propagates at the usual phase <span class="hlt">velocity</span> of light c/n, even though the smoothly varying portions of the pulse propagate at the <span class="hlt">group</span> <span class="hlt">velocity</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003JVGR..122...69S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003JVGR..122...69S"><span id="translatedtitle">Seismic <span class="hlt">velocity</span> structure of the central Taupo Volcanic Zone, New Zealand, from local earthquake <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sherburn, Steven; Bannister, Stephen; Bibby, Hugh</p> <p>2003-03-01</p> <p> are unable to determine whether greywacke, which forms the basement beneath the eastern most part of the TVZ continues further west, or is replaced by a volcanic rock such as andesite which has similar Vp and density. Vp/Vs anomalies are much smaller than Vp anomalies and generally have little spatial relationship to the Vp pattern. There is a widespread decrease in Vp/Vs, from >1.76 to 1.70-1.73, between 4 and 6 km depth over much of the study area and Vp/Vs is high southwest of the Okataina caldera, where Vp is low. Hypocentres calculated using the 3-D <span class="hlt">velocity</span> model differ little from those obtained using a 1-D model with station terms, however, some <span class="hlt">groups</span> of earthquakes are more tightly clustered. Following relocation, there is a slight decrease in the estimated thickness of the seismogenic zone, with 73% of hypocentres between 4 and 7 km depth and a slight increase in the depth of the brittle-ductile transition from 6 to 6.5 km.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.7883S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.7883S"><span id="translatedtitle">Cluster analysis applied to <span class="hlt">velocity</span> and attenuation <span class="hlt">tomography</span>: the case study of Mt. Vesuvius</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Siniscalchi, A.; Bianco, F.; Del Pezzo, E.; de Siena, L.; di Giuseppe, M. G.; Petrillo, Z.</p> <p>2009-04-01</p> <p>The interpretation of the results of seismic <span class="hlt">velocity</span> and attenuation inversion are usually based on the qualitative observation and comparison of the different tomographic images. A promising tool to jointly interpret tomographic models based on different parameters resides in the application of statistical classification methods, such as the k-means clustering method, which minimizes the logic distance among each <span class="hlt">group</span> of observations having homogeneous physical properties and maximizes the same quantity between <span class="hlt">groups</span>. The correlation between the models is subsequently examined and significant classes (volumes of high correlation) are identified. Such technique is able to spatially clusterize the zones having similar characteristics in a statistical sense. Each zone is finally identified by the barycenter (centroid) of the corresponding cluster. The Vp <span class="hlt">velocity</span> and Qp and Qs attenuation structures of Mt. Vesuvius, Italy, have been already qualitatively interpreted by a comparison with other similar investigations. To obtain a more quantitative interpretation gathered in a unified model consistent with the entire dataset, a cluster analysis was applied to this models. An optimizing study on the proper number of classes recognizes five clusters corresponding to separate zones inside the volcano structure. - The first cluster can be considered as a "background" cluster, and corresponds to the areas with "average" seismic properties (mainly located below the topographical interface). - The second cluster defines a spatial pattern corresponding to the residual part of the feeding conduit of the volcano. - The third cluster corresponds to two volumes, the first vertically extended between -1000 and -3000 m above the sea level, North-Eastward the cone; the second, in the same depth range Westward the central cone, and linked to the first one at -2000 m. These two volumes may be associated with hydrothermal basins. - The fourth and fifth clusters are described both by</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27410269','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27410269"><span id="translatedtitle">Momentum-dependent <span class="hlt">group</span> <span class="hlt">velocity</span> of surface plasmon polaritons in two-dimensional metallic nanohole array.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cao, Z L; Ong, H C</p> <p>2016-06-13</p> <p>We determine the momentum-dependent <span class="hlt">group</span> <span class="hlt">velocities</span> of ( ± 1,0) and (0, ± 1) Bloch-like surface plasmon polaritons (SPPs) in two-dimensional Au nanohole array by measuring their propagation lengths and decay lifetimes at different SPP propagation length via angle- and polarization-resolved reflectivity spectroscopy and real- and Fourier-space microscopy. We find the decay length and lifetime, as well as <span class="hlt">group</span> <span class="hlt">velocity</span>, are highly dependent on the propagation direction. In particular, close to the Γ-M direction where two SPPs begin to interfere, the <span class="hlt">group</span> <span class="hlt">velocity</span> decreases due to the increase of the standing wave character. More importantly, the two SPPs are strongly interacted with each other at the Γ-M direction, resulting in forming the dark and bright modes. We find the <span class="hlt">group</span> <span class="hlt">velocity</span> of the dark mode is higher that of the bright mode despite its higher quality factor, or longer decay lifetime. We attribute such difference to the distinct field symmetries of dark and bright modes, yielding different effective indices. While bright mode has fields mostly concentrated at the flat metal region to produce higher effective index and therefore lower <span class="hlt">velocity</span>, the fields of the dark mode are located near the air hole, resulting in higher <span class="hlt">velocity</span>. PMID:27410269</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10171446','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10171446"><span id="translatedtitle">Phase and <span class="hlt">group</span> <span class="hlt">velocities</span> for Lamb waves in DOP-26 iridium alloy sheet</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Simpson, W.A.; McGuire, D.J.</p> <p>1994-07-01</p> <p>The relatively coarse grain structure of iridium weldments limits the ultrasonic inspection of these structures to frequencies in the low megahertz range. As the material thickness is nominally 0.635 mm for clad vent set capsules, the low frequencies involved necessarily entail the generation of Lamb waves m the specimen. These waves are, of course, dispersive and detailed knowledge of both the phase and <span class="hlt">group</span> <span class="hlt">velocities</span> is required in order to determine accurately the location of flaws detected using Lamb waves. Purpose of this study is to elucidate the behavior of Lamb waves propagating in the capsule alloy and to quantify the <span class="hlt">velocities</span> so that accurate flaw location is ensured. We describe a numerical technique for computing the phase <span class="hlt">velocities</span> of Lamb waves (or of any other type of guided wave) and derive the <span class="hlt">group</span> <span class="hlt">velocities</span> from this information. A frequency-domain method is described for measuring <span class="hlt">group</span> <span class="hlt">velocity</span> when multiple Lamb modes are present and mutually interfering in the time domain, and experimental confirmation of the <span class="hlt">group</span> <span class="hlt">velocity</span> is presented for the capsule material.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014GeoJI.199..113M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014GeoJI.199..113M&link_type=ABSTRACT"><span id="translatedtitle">A comprehensive dispersion model of surface wave phase and <span class="hlt">group</span> <span class="hlt">velocity</span> for the globe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ma, Zhitu; Masters, Guy; Laske, Gabi; Pasyanos, Michael</p> <p>2014-10-01</p> <p>A new method is developed to measure Rayleigh- and Love-wave phase <span class="hlt">velocities</span> globally using a cluster analysis technique. This method clusters similar waveforms recorded at different stations from a single event and allows users to make measurements on hundreds of waveforms, which are filtered at a series of frequency ranges, at the same time. It also requires minimal amount of user interaction and allows easy assessment of the data quality. This method produces a large amount of phase delay measurements in a manageable time frame. Because there is a strong trade-off between the isotropic part of the Rayleigh-wave phase <span class="hlt">velocity</span> and azimuthal anisotropy, we include the effect of azimuthal anisotropy in our inversions in order to obtain reliable isotropic phase <span class="hlt">velocity</span>. We use b-splines to combine these isotropic phase <span class="hlt">velocity</span> maps with our previous <span class="hlt">group</span> <span class="hlt">velocity</span> maps to produce an internally consistent global surface wave dispersion model.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_5 --> <div id="page_6" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="101"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790019265','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790019265"><span id="translatedtitle">An examination of a <span class="hlt">group-velocity</span> criterion for the breakdown of an idealized vortex flow</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tsai, C. Y.; Widnall, S. E.</p> <p>1979-01-01</p> <p>The phenomenon of vortex breakdown is believed to be associated with a finite amplitude wave that has become trapped at the critical or breakdown location. The conditions at which the propagating waves become trapped at a certain axial location were examined by use of a <span class="hlt">group-velocity</span> criterion implied by Landahl's general theory of wave trapping. An ideal vortex having constant vorticity and uniform axial <span class="hlt">velocity</span> at the inlet of a slowly diverging duct was studied. The linear wave propagation analysis is applied to the base flow at several axial stations for several values of the ratio of swirl <span class="hlt">velocity</span> to axial <span class="hlt">velocity</span> at the inlet of the divergent duct, assuming a locally parallel flow. The dipsersion relations and hence the <span class="hlt">group</span> <span class="hlt">velocities</span> of both the symmetric (n = 0) and asymmetric modes (n = + or - 1) were investigated. The existence of a critical state in the flow (at which the <span class="hlt">group</span> <span class="hlt">velocity</span> vanishes), and its relationship to the stagnation point on the axis of the duct and to the occurrence of an irregular singularity in the equations governing wave propagation in the flow field are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/678818','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/678818"><span id="translatedtitle">Crust and upper mantle P wave <span class="hlt">velocity</span> structure beneath Valles caldera, New Mexico: Results from the Jemez teleseismic <span class="hlt">tomography</span> experiment</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Steck, Lee K.; Fehler, Michael C.; Roberts, Peter M.; Baldridge, W. Scott; Stafford, Darrik G.; Lutter, William J.; Sessions, Robert</p> <p>1998-10-01</p> <p>New results are presented from the teleseismic component of the Jemez <span class="hlt">Tomography</span> Experiment conducted across Valles caldera in northern New Mexico. We invert 4872 relative {ital P} wave arrival times recorded on 50 portable stations to determine <span class="hlt">velocity</span> structure to depths of 40 km. The three principle features of our model for Valles caldera are: (1) near-surface low <span class="hlt">velocities</span> of {minus}17{percent} beneath the Toledo embayment and the Valle Grande, (2) midcrustal low <span class="hlt">velocities</span> of {minus}23{percent} in an ellipsoidal volume underneath the northwest quadrant of the caldera, and (3) a broad zone of low <span class="hlt">velocities</span> ({minus}15{percent}) in the lower crust or upper mantle. Crust shallower than 20 km is generally fast to the northwest of the caldera and slow to the southeast. Near-surface low <span class="hlt">velocities</span> are interpreted as thick deposits of Bandelier tuff and postcaldera volcaniclastic rocks. Lateral variation in the thickness of these deposits supports increased caldera collapse to the southeast, beneath the Valle Grande. We interpret the midcrustal low-<span class="hlt">velocity</span> zone to contain a minimum melt fraction of 10{percent}. While we cannot rule out the possibility that this zone is the remnant 1.2 Ma Bandelier magma chamber, the eruption history and geochemistry of the volcanic rocks erupted in Valles caldera following the Bandelier tuff make it more likely that magma results from a new pulse of intrusion, indicating that melt flux into the upper crust beneath Valles caldera continues. The low-<span class="hlt">velocity</span> zone near the crust-mantle boundary is consistent with either partial melt in the lower crust or mafic rocks without partial melt in the upper mantle. In either case, this low-<span class="hlt">velocity</span> anomaly indicates that underplating by mantle-derived melts has occurred. {copyright} 1998 American Geophysical Union</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.G11A0913R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.G11A0913R"><span id="translatedtitle">GNSS <span class="hlt">tomography</span>, assembled multi model solution, initial results from first experiment of IAG GNSS <span class="hlt">tomography</span> working <span class="hlt">group</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rohm, W.; Gaiger, A.; Brenot, H.; Bender, M.; Shangguan, M.; Bosy, J.</p> <p>2012-12-01</p> <p>The Global Navigation Satellite Systems (GNSS) troposphere delay, standard product of GNSS processing, among all other applications can be used as a data source for GNSS <span class="hlt">tomography</span>. The path delays in the direction of satellites can be converted to a 3D distribution of atmospheric refractivity (total or wet), or water vapor density using Radon inverse transform. Although problem is linear the ill - conditionedess and ill-posedness of the equations, results in complexity of the problem. In the frame of IAG Sub-Commission SC 4.3 - "Remote sensing and modelling of the atmosphere", we proposed a Working <span class="hlt">Group</span> "Inter-comparison and cross-validation of <span class="hlt">tomography</span> models". The <span class="hlt">group</span> aim is to tackle current challenges of GNSS <span class="hlt">tomography</span> modeling like how to find best way to include space based GNSS observations, to deliver more reliable slant delay processing methods, to test robust algorithms to account for outliers in observations, to determine trustworthy precision and accuracy measures, to address problems linked with near real time processing, and how to provide effective cooperation channels with meteorological agencies. In this study the same GNSS data set has been processed for each tomographic model. To study the differences between obtained solutions, each solution step of GNSS <span class="hlt">tomography</span> has been carefully analyzed. The methodical framework has been developed to allow comprehensive comparison and validation. In the GNSS <span class="hlt">tomography</span> process flow several critical points have been selected, for each node a validation has been performed. This validation was based on meteorological observations carefully selected from in situ measurements, satellite measurements, and Numerical Weather Prediction models. Following nodes of GNSS <span class="hlt">tomography</span> processing have been considered: GNSS raw data processing and preprocessing of path delays, voxel model outline and construction, observation selection, raytracing algorithms, a priori observations, observations noise, inversion</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22058808','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22058808"><span id="translatedtitle">Slow light with low <span class="hlt">group-velocity</span> dispersion at the edge of photonic graphene</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ouyang Chunfang; Dong Biqin; Liu Xiaohan; Zi Jian; Xiong Zhiqiang; Zhao Fangyuan; Hu Xinhua</p> <p>2011-07-15</p> <p>We theoretically study the light propagation at the zigzag edges of a honeycomb photonic crystal (PC), or photonic graphene. It is found that the corresponding edge states have a sinusoidal dispersion similar to those found in PC coupled resonator optical waveguides [CROWs; M. Notomi et al., Nature Photon. 2, 741 (2008)]. The sinusoidal dispersion curve can be made very flat by carefully tuning edge parameters. As a result, low <span class="hlt">group</span> <span class="hlt">velocity</span> and small <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion can be simultaneously obtained for light propagating at the zigzag edge of photonic graphene. Compared with PC CROWs, our slow-light system exhibits no intrinsic radiation loss and has a larger <span class="hlt">group</span> <span class="hlt">velocity</span> bandwidth product. Our results could find applications in on-chip optical buffers and enhanced light-matter interaction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27505834','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27505834"><span id="translatedtitle"><span class="hlt">Group</span> <span class="hlt">velocity</span> locked vector dissipative solitons in a high repetition rate fiber laser.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Luo, Yiyang; Li, Lei; Liu, Deming; Sun, Qizhen; Wu, Zhichao; Xu, Zhilin; Tang, Dingyuan; Fu, Songnian; Zhao, Luming</p> <p>2016-08-01</p> <p>Vectorial nature of dissipative solitons (DSs) with high repetition rate is studied for the first time in a normal-dispersion fiber laser. Despite the fact that the formed DSs are strongly chirped and the repetition rate is greater than 100 MHz, polarization locked and polarization rotating <span class="hlt">group</span> <span class="hlt">velocity</span> locked vector DSs can be formed under 129.3 MHz fundamental mode-locking and 258.6 MHz harmonic mode-locking of the fiber laser, respectively. The two orthogonally polarized components of these vector DSs possess distinctly different central wavelengths and travel together at the same <span class="hlt">group</span> <span class="hlt">velocity</span> in the laser cavity, resulting in a gradual spectral edge and small steps on the optical spectrum, which can be considered as an auxiliary indicator of the <span class="hlt">group</span> <span class="hlt">velocity</span> locked vector DSs. Moreover, numerical simulations well confirm the experimental observations and further reveal the impact of the net cavity birefringence on the properties of the formed vector DSs. PMID:27505834</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4309966','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4309966"><span id="translatedtitle">Observation of Wave Packet Distortion during a Negative-<span class="hlt">Group-Velocity</span> Transmission</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ye, Dexin; Salamin, Yannick; Huangfu, Jiangtao; Qiao, Shan; Zheng, Guoan; Ran, Lixin</p> <p>2015-01-01</p> <p>In Physics, causality is a fundamental postulation arising from the second law of thermodynamics. It states that, the cause of an event precedes its effect. In the context of Electromagnetics, the relativistic causality limits the upper bound of the <span class="hlt">velocity</span> of information, which is carried by electromagnetic wave packets, to the speed of light in free space (c). In anomalously dispersive media (ADM), it has been shown that, wave packets appear to propagate with a superluminal or even negative <span class="hlt">group</span> <span class="hlt">velocity</span>. However, Sommerfeld and Brillouin pointed out that the “front” of such wave packets, known as the initial point of the Sommerfeld precursor, always travels at c. In this work, we investigate the negative-<span class="hlt">group-velocity</span> transmission of half-sine wave packets. We experimentally observe the wave front and the distortion of modulated wave packets propagating with a negative <span class="hlt">group</span> <span class="hlt">velocity</span> in a passive artificial ADM in microwave regime. Different from previous literature on the propagation of superluminal Gaussian packets, strongly distorted sinusoidal packets with non-superluminal wave fronts were observed. This result agrees with Brillouin's assertion, i.e., the severe distortion of seemingly superluminal wave packets makes the definition of <span class="hlt">group</span> <span class="hlt">velocity</span> physically meaningless in the anomalously dispersive region. PMID:25631746</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013SPIE.8694E..03P&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013SPIE.8694E..03P&link_type=ABSTRACT"><span id="translatedtitle">Stiffness matrix determination of composite materials using lamb wave <span class="hlt">group</span> <span class="hlt">velocity</span> measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Putkis, O.; Croxford, A. J.</p> <p>2013-04-01</p> <p>The use of Lamb waves in Non-Destructive Evaluation (NDE) and Structural Health Monitoring (SHM) is gaining popularity due to their ability to travel long distances without significant attenuation, therefore offering large area inspections with a small number of sensors. The design of a Lamb-wave-based NDE/SHM system for composite materials is more complicated than for metallic materials due to the directional dependence of Lamb wave propagation characteristics such as dispersion and <span class="hlt">group</span> <span class="hlt">velocity</span>. Propagation parameters can be theoretically predicted from known material properties, specifically the stiffness matrix and density. However, in practice it is difficult to obtain the stiffness matrix of a particular material or structure with high accuracy, hence introducing errors in theoretical predictions and inaccuracies in the resulting propagation parameters. Measured Lamb wave phase <span class="hlt">velocities</span> can be used to infer the stiffness matrix, but the measurements are limited to the principal directions due to the steering effect (different propagation directions of phase and corresponding <span class="hlt">group</span> <span class="hlt">velocities</span>). This paper proposes determination of the stiffness matrix from the measured <span class="hlt">group</span> <span class="hlt">velocities</span>, which can be unambiguously measured in any direction. A highly anisotropic carbon-fibre-reinforced polymer plate is chosen for the study. The influence of different stiffness matrix elements on the directional <span class="hlt">group</span> <span class="hlt">velocity</span> profile is investigated. Thermodynamic Simulated Annealing (TSA) is used as a tool for inverse, multi variable inference of the stiffness matrix. A good estimation is achieved for particular matrix elements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25631746','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25631746"><span id="translatedtitle">Observation of wave packet distortion during a negative-<span class="hlt">group-velocity</span> transmission.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ye, Dexin; Salamin, Yannick; Huangfu, Jiangtao; Qiao, Shan; Zheng, Guoan; Ran, Lixin</p> <p>2015-01-01</p> <p>In Physics, causality is a fundamental postulation arising from the second law of thermodynamics. It states that, the cause of an event precedes its effect. In the context of Electromagnetics, the relativistic causality limits the upper bound of the <span class="hlt">velocity</span> of information, which is carried by electromagnetic wave packets, to the speed of light in free space (c). In anomalously dispersive media (ADM), it has been shown that, wave packets appear to propagate with a superluminal or even negative <span class="hlt">group</span> <span class="hlt">velocity</span>. However, Sommerfeld and Brillouin pointed out that the "front" of such wave packets, known as the initial point of the Sommerfeld precursor, always travels at c. In this work, we investigate the negative-<span class="hlt">group-velocity</span> transmission of half-sine wave packets. We experimentally observe the wave front and the distortion of modulated wave packets propagating with a negative <span class="hlt">group</span> <span class="hlt">velocity</span> in a passive artificial ADM in microwave regime. Different from previous literature on the propagation of superluminal Gaussian packets, strongly distorted sinusoidal packets with non-superluminal wave fronts were observed. This result agrees with Brillouin's assertion, i.e., the severe distortion of seemingly superluminal wave packets makes the definition of <span class="hlt">group</span> <span class="hlt">velocity</span> physically meaningless in the anomalously dispersive region. PMID:25631746</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4477408','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4477408"><span id="translatedtitle"><span class="hlt">Group</span> <span class="hlt">velocity</span> mismatch-absent nonlinear frequency conversions for mid-infrared femtosecond pulses generation</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zhong, Haizhe; Zhang, Lifu; Li, Ying; Fan, Dianyuan</p> <p>2015-01-01</p> <p>A novel <span class="hlt">group</span> <span class="hlt">velocity</span> mismatch (GVM) absent scheme for nonlinear optical parametric procedure in mid-infrared was developed with type-I quasi phase matching by use of an off-digital nonlinear optical coefficient d31. This was achieved by matching of the <span class="hlt">group</span> <span class="hlt">velocities</span> of the pump and the signal waves, while the phase <span class="hlt">velocities</span> were quasi phase matched. The system employs MgO-doped periodically poled LiNbO3 as the nonlinear medium. Desired <span class="hlt">group-velocity</span> dispersion would be obtained via appropriately temperature regulation. To demonstrate its potential applications in ultrafast mid-infrared pulses generation, aiming at a typical mid-infrared wavelength of ~3.2 μm, design examples of two basic nonlinear frequency conversion procedures are studied for both the narrow-band seeding mid-IR optical parametric amplification (OPA) and the synchronously pumped femtosecond optical parametric oscillation (SPOPO). Compared with the conventional scheme of type-0 QPM, the quantum-efficiency can be more than doubled with nearly unlimited bandwidth. The proposed GVM- absent phase matching design may provide a promising route to efficient and broadband sub-100 fs mid-infrared ultrafast pulses generation without <span class="hlt">group-velocity</span> walk-off. PMID:26099837</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70036347','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70036347"><span id="translatedtitle">Analysis of <span class="hlt">group-velocity</span> dispersion of high-frequency Rayleigh waves for near-surface applications</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Luo, Y.; Xia, J.; Xu, Y.; Zeng, C.</p> <p>2011-01-01</p> <p>The Multichannel Analysis of Surface Waves (MASW) method is an efficient tool to obtain the vertical shear (S)-wave <span class="hlt">velocity</span> profile using the dispersive characteristic of Rayleigh waves. Most MASW researchers mainly apply Rayleigh-wave phase-<span class="hlt">velocity</span> dispersion for S-wave <span class="hlt">velocity</span> estimation with a few exceptions applying Rayleigh-wave <span class="hlt">group-velocity</span> dispersion. Herein, we first compare sensitivities of fundamental surface-wave phase <span class="hlt">velocities</span> with <span class="hlt">group</span> <span class="hlt">velocities</span> with three four-layer models including a low-<span class="hlt">velocity</span> layer or a high-<span class="hlt">velocity</span> layer. Then synthetic data are simulated by a finite difference method. Images of <span class="hlt">group-velocity</span> dispersive energy of the synthetic data are generated using the Multiple Filter Analysis (MFA) method. Finally we invert a high-frequency surface-wave <span class="hlt">group-velocity</span> dispersion curve of a real-world example. Results demonstrate that (1) the sensitivities of <span class="hlt">group</span> <span class="hlt">velocities</span> are higher than those of phase <span class="hlt">velocities</span> and usable frequency ranges are wider than that of phase <span class="hlt">velocities</span>, which is very helpful in improving inversion stability because for a stable inversion system, small changes in phase <span class="hlt">velocities</span> do not result in a large fluctuation in inverted S-wave <span class="hlt">velocities</span>; (2) <span class="hlt">group-velocity</span> dispersive energy can be measured using single-trace data if Rayleigh-wave fundamental-mode energy is dominant, which suggests that the number of shots required in data acquisition can be dramatically reduced and the horizontal resolution can be greatly improved using analysis of <span class="hlt">group-velocity</span> dispersion; and (3) the suspension logging results of the real-world example demonstrate that inversion of <span class="hlt">group</span> <span class="hlt">velocities</span> generated by the MFA method can successfully estimate near-surface S-wave <span class="hlt">velocities</span>. ?? 2011 Elsevier B.V.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21313185','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21313185"><span id="translatedtitle">Phase tunability of <span class="hlt">group</span> <span class="hlt">velocity</span> by modulated-pump-forced coherent population oscillations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Arrieta-Yanez, Francisco; Melle, Sonia; Calderon, Oscar G.; Anton, M. A.; Carreno, F.</p> <p>2009-07-15</p> <p>We propose a technique to obtain slow and fast light propagations based on coherent population oscillations forced by a modulated pump. This mechanism produces an enhancement of 1 order of magnitude of the delay or advancement of light signals. The relative phase between the pumps to the signal fields is used as a knob for changing light propagation from ultraslow <span class="hlt">group</span> <span class="hlt">velocities</span> to negative <span class="hlt">group</span> <span class="hlt">velocities</span>. The experimental realization of the phenomenon was carried out in an erbium-doped fiber amplifier at room temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NJPh...18g3031H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NJPh...18g3031H"><span id="translatedtitle"><span class="hlt">Group</span> <span class="hlt">velocity</span> matching in high-order harmonic generation driven by mid-infrared lasers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hernández-García, C.; Popmintchev, T.; Murnane, M. M.; Kapteyn, H. C.; Plaja, L.; Becker, A.; Jaron-Becker, A.</p> <p>2016-07-01</p> <p>We analyze the role of <span class="hlt">group-velocity</span> matching (GVM) in the macroscopic build up of the high-harmonic signal generated in gas targets at high pressures. A definition of the walk-off length, associated with GVM, in the non-perturbative intensity regime of high-harmonic generation is given. Semiclassical predictions based on this definition are in excellent agreement with full quantum simulations. We demonstrate that <span class="hlt">group</span> <span class="hlt">velocity</span> matching is a relevant factor in high harmonic generation and the isolation of attosecond pulses driven by long wavelength lasers and preferentially selects contributions from the short quantum trajectories.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AIPC..760..970H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AIPC..760..970H"><span id="translatedtitle">Applications of the Zero-<span class="hlt">Group-Velocity</span> Lamb Mode for Air-Coupled Ultrasonic Imaging</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Holland, Stephen D.; Song, Jun-Ho; Evan, Victoria L.; Chimenti, D. E.</p> <p>2005-04-01</p> <p>Airborne ultrasound couples particularly well into plates at the zero-<span class="hlt">group-velocity</span> point of the first order symmetric (S1) Lamb mode. Applications of this mode to ultrasonic imaging of plate-like structures are discussed. The sensitivity and high Q of this mode makes it ideal for imaging. Images from a wide variety of materials and samples, including composites and honeycomb structures are presented. Transmission at the zero-<span class="hlt">group-velocity</span> frequency is shown to be particularly sensitive to nearby flaws and discontinuities, and is therefore suitable for wide-area scanning for cracks or manufacturing flaws.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22072614','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22072614"><span id="translatedtitle"><span class="hlt">Group</span> <span class="hlt">velocity</span> of extraordinary waves in superdense magnetized quantum plasma with spin-1/2 effects</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Li Chunhua; Ren Haijun; Yang Weihong; Wu Zhengwei; Chu, Paul K.</p> <p>2012-12-15</p> <p>Based on the one component plasma model, a new dispersion relation and <span class="hlt">group</span> <span class="hlt">velocity</span> of elliptically polarized extraordinary electromagnetic waves in a superdense quantum magnetoplasma are derived. The <span class="hlt">group</span> <span class="hlt">velocity</span> of the extraordinary wave is modified due to the quantum forces and magnetization effects within a certain range of wave numbers. It means that the quantum spin-1/2 effects can reduce the transport of energy in such quantum plasma systems. Our work should be of relevance for the dense astrophysical environments and the condensed matter physics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25019900','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25019900"><span id="translatedtitle">Measurement of the laser-pulse <span class="hlt">group</span> <span class="hlt">velocity</span> in plasma waveguides.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>van Tilborg, J; Daniels, J; Gonsalves, A J; Schroeder, C B; Esarey, E; Leemans, W P</p> <p>2014-06-01</p> <p>Electrically discharged plasma channels can guide laser pulses, extending the laser-plasma interaction length to many Rayleigh ranges. In applications such as the laser-plasma accelerator, the laser <span class="hlt">group</span> <span class="hlt">velocity</span> in the channel plays a critical role. The laser travel time (and thus the averaged <span class="hlt">group</span> <span class="hlt">velocity</span>) was measured through two-pulse frequency-domain interferometry and was found to depend on the on-axis plasma density and laser spot size. The data is in agreement with theory. PMID:25019900</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.T51B2579P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.T51B2579P"><span id="translatedtitle">Mapping Tectonic features beneath the Gulf of California using Rayleigh and Love Waves <span class="hlt">Group</span> <span class="hlt">Velocities</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Persaud, P.; Di Luccio, F.; Clayton, R. W.</p> <p>2012-12-01</p> <p>This study contributes to our understanding of the Pacific-North America lithospheric structure beneath the Gulf of California and its western and eastern confining regions, by mapping fundamental mode surface wave <span class="hlt">group</span> <span class="hlt">velocities</span>. We measure the dispersion of Rayleigh and Love surface waves to create a series of 2D maps of <span class="hlt">group</span> <span class="hlt">velocities</span>, which provide important information on the earth structure beneath the study region. Although several surface waves studies were published in the last decade, all of them were done using phase <span class="hlt">velocity</span> measurements based on the two stations method. Here we combine dispersion measurements at the regional scale with data at teleseismic distances to provide a more complete dataset for studies of earth structure. We also analyze <span class="hlt">group</span> <span class="hlt">velocities</span> from short to long periods in order to define structural features at both crustal and mantle scales. Our study uses earthquakes recorded by the Network of Autonomously Recording Seismographs (NARS-Baja), a set of 14 broadband seismic stations that flank the Gulf of California. From the NEIC bulletin we selected 140 events recorded by the NARS-Baja array. In order to have dispersion measurements in a wide range of periods, we used regional earthquakes with M > 4.2 and teleseismic events with M > 6.9. We first computed the dispersion curves for the surface wave paths crossing the region. Then, the along path <span class="hlt">group</span> <span class="hlt">velocity</span> measurements for multiple periods are converted into tomographic images using kernels which vary in off-path width with the square root of the period. Dispersion measurements show interesting and consistent features for both Rayleigh and Love waves. At periods equal to or shorter than 15 s, when surface waves are primarily sensitive to shear <span class="hlt">velocity</span> in the upper 15 km of the crust, slow <span class="hlt">group</span> <span class="hlt">velocities</span> beneath the northern-central Gulf reveal the presence of a thick sedimentary layer, relative to the southern Gulf. <span class="hlt">Group</span> <span class="hlt">velocities</span> beneath the northwestern side of Baja</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012GeoJI.189..647W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012GeoJI.189..647W"><span id="translatedtitle">High resolution Rayleigh wave phase <span class="hlt">velocity</span> <span class="hlt">tomography</span> in northern North China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Weilai; Wu, Jianping; Fang, Lihua</p> <p>2012-04-01</p> <p>This study presents the Rayleigh wave phase <span class="hlt">velocity</span> tomographic results in northern North China. The data are from 190 broad-band and 10 very broad-band stations of the North China Seismic Array and 50 permanent stations nearby. All available teleseismic vertical component time-series are used to extract the phase <span class="hlt">velocity</span> dispersion curves of the fundamental mode Rayleigh wave by interstation method. Tomographic maps are obtained at periods of 10, 15, 25 and 60 s with a grid spacing of 0.25°× 0.25°. The short-period phase <span class="hlt">velocity</span> maps show good correlation with the geological and tectonic features. To be specific, lower <span class="hlt">velocities</span> correspond to North China Basin and depression area whereas higher <span class="hlt">velocities</span> are associated with Taihangshan and Yanshan uplifts. At 25 s, there are obvious low-<span class="hlt">velocity</span> anomalies in Jizhong depression and Beijing-Tianjin-Tangshan region, indicating that ascendant low <span class="hlt">velocity</span> channel may be formed beneath these areas and induce the <span class="hlt">velocity</span> difference in the upper crust. The phase <span class="hlt">velocity</span> map at 60 s reflects the upper-mantle information in the study area. High-<span class="hlt">velocity</span> anomalies are observed at Yanshan blocks north to Zhangjiakou-Bohai seismic belt, suggesting that the materials are stable beneath these areas or the asthenosphere is at deeper location. Low-<span class="hlt">velocity</span> anomalies are mainly south to the seismic belt, implying the asthenosphere is shallower and the materials are transformed by the open stretching rift trending NNE, resulting in many NNE-directed fault belts. These structural differences at depth may be controlled by the fault activity and strong tectonic movements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016NatSR...629035B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016NatSR...629035B&link_type=ABSTRACT"><span id="translatedtitle">In vivo label-free measurement of lymph flow <span class="hlt">velocity</span> and volumetric flow rates using Doppler optical coherence <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Blatter, Cedric; Meijer, Eelco F. J.; Nam, Ahhyun S.; Jones, Dennis; Bouma, Brett E.; Padera, Timothy P.; Vakoc, Benjamin J.</p> <p>2016-07-01</p> <p>Direct in vivo imaging of lymph flow is key to understanding lymphatic system function in normal and disease states. Optical microscopy techniques provide the resolution required for these measurements, but existing optical techniques for measuring lymph flow require complex protocols and provide limited temporal resolution. Here, we describe a Doppler optical coherence <span class="hlt">tomography</span> platform that allows direct, label-free quantification of lymph <span class="hlt">velocity</span> and volumetric flow rates. We overcome the challenge of very low scattering by employing a Doppler algorithm that operates on low signal-to-noise measurements. We show that this technique can measure lymph <span class="hlt">velocity</span> at sufficiently high temporal resolution to resolve the dynamic pulsatile flow in collecting lymphatic vessels.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27377852','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27377852"><span id="translatedtitle">In vivo label-free measurement of lymph flow <span class="hlt">velocity</span> and volumetric flow rates using Doppler optical coherence <span class="hlt">tomography</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Blatter, Cedric; Meijer, Eelco F J; Nam, Ahhyun S; Jones, Dennis; Bouma, Brett E; Padera, Timothy P; Vakoc, Benjamin J</p> <p>2016-01-01</p> <p>Direct in vivo imaging of lymph flow is key to understanding lymphatic system function in normal and disease states. Optical microscopy techniques provide the resolution required for these measurements, but existing optical techniques for measuring lymph flow require complex protocols and provide limited temporal resolution. Here, we describe a Doppler optical coherence <span class="hlt">tomography</span> platform that allows direct, label-free quantification of lymph <span class="hlt">velocity</span> and volumetric flow rates. We overcome the challenge of very low scattering by employing a Doppler algorithm that operates on low signal-to-noise measurements. We show that this technique can measure lymph <span class="hlt">velocity</span> at sufficiently high temporal resolution to resolve the dynamic pulsatile flow in collecting lymphatic vessels. PMID:27377852</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.3853P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.3853P"><span id="translatedtitle">Applications of detailed 3D P-wave <span class="hlt">velocity</span> crustal model in Poland for local, regional and global seismic <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Polkowski, Marcin; Grad, Marek</p> <p>2015-04-01</p> <p>The 3D P-wave seismic <span class="hlt">velocity</span> model was obtained by combining data from multiple studies during past 50 years. Data sources included refraction seismology, reflection seismology, geological boreholes, vertical seismic profiling, magnetotellurics and gravimetry. Use of many data sources allowed creation of detailed 3D P-wave <span class="hlt">velocity</span> model that reaches to depth of 60 km and includes 6-layers of sediments and 3-layers of the crust. Purpose of this study is to analyze how 3D model influences local (accuracy of location and source time estimation for local events), regional (identification of wide-angle seismic phases) and global (teleseismic <span class="hlt">tomography</span>) seismic travel times. Additionally we compare results of forward seismic wave propagation with signals observed on short period and broadband stations. National Science Centre Poland provided financial support for this work by NCN grant DEC-2011/02/A/ST10/00284.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_6 --> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4932526','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4932526"><span id="translatedtitle">In vivo label-free measurement of lymph flow <span class="hlt">velocity</span> and volumetric flow rates using Doppler optical coherence <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Blatter, Cedric; Meijer, Eelco F. J.; Nam, Ahhyun S.; Jones, Dennis; Bouma, Brett E.; Padera, Timothy P.; Vakoc, Benjamin J.</p> <p>2016-01-01</p> <p>Direct in vivo imaging of lymph flow is key to understanding lymphatic system function in normal and disease states. Optical microscopy techniques provide the resolution required for these measurements, but existing optical techniques for measuring lymph flow require complex protocols and provide limited temporal resolution. Here, we describe a Doppler optical coherence <span class="hlt">tomography</span> platform that allows direct, label-free quantification of lymph <span class="hlt">velocity</span> and volumetric flow rates. We overcome the challenge of very low scattering by employing a Doppler algorithm that operates on low signal-to-noise measurements. We show that this technique can measure lymph <span class="hlt">velocity</span> at sufficiently high temporal resolution to resolve the dynamic pulsatile flow in collecting lymphatic vessels. PMID:27377852</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1611558B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1611558B"><span id="translatedtitle">The deeper structure of the southern Dead Sea basin derived from neural network analysis of <span class="hlt">velocity</span> and attenuation <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Braeuer, Benjamin; Haberland, Christian; Bauer, Klaus; Weber, Michael</p> <p>2014-05-01</p> <p>The Dead Sea basin is a pull-apart basin at the Dead Sea transform fault, the boundary between the African and the Arabian plates. Though the DSB has been studied for a long time, the available knowledge - based mainly on surface geology, drilling and seismic reflection surveys - gives only a partial picture of its shallow structure. Therefore, within the framework of the international DESIRE (DEad Sea Integrated REsearch) project, a dense temporary local seismological network was operated in the southern Dead Sea area. Within 18 month of recording 650 events were detected. In addition to an already published <span class="hlt">tomography</span> study revealing the distribution of P <span class="hlt">velocities</span> and the Vp/Vs ratios a 2D P-wave attenuation <span class="hlt">tomography</span> (parameter Qp) was performed. The neural network technique of Self-organizing maps (SOM) is used for the joint interpretation of these three parameters (Vp, Vp/Vs, Qp). The resulting clusters in the petrophysical parameter space are assigned to the main lithological units below the southern part of the Dead Sea basin: (1) The basin sediments characterized by strong attenuation, high vp/vs ratios and low P <span class="hlt">velocities</span>. (2) The pre-basin sediments characterized by medium to strong attenuation, low Vp/Vs ratios and medium P <span class="hlt">velocities</span>. (3) The basement characterized by low to moderate attenuation, medium vp/vs ratios and high P <span class="hlt">velocities</span>. Thus, the asymmetric southern Dead Sea basin is filled with basin sediments down to depth of 7 to 12 km. Below the basin sediments, the pre-basin sediments are extending to a depth between 13 and 18 km.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.4786J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.4786J"><span id="translatedtitle">Anisotropic <span class="hlt">velocity</span> structure of the crust and upper mantle in the Taiwan region from local travel time <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jakovlev, Andrey; Koulakov, Ivan; Wu, Yih-Min</p> <p>2014-05-01</p> <p>Taiwan Island located in a contact zone between the Eurasian and Philippine Sea plates, the tectonic processes in this area are mostly controlled by the relative kinematics of these two plates. In the east, the Philippine Sea plate subducts northward under the Eurasian plate along the Ryukyu trench. Off the southern tip of Taiwan, the South China Sea subplate, part of the Eurasian plate, subducts eastward under the Philippine Sea plate underneath the Luzon Island. The Taiwan Island is located at the junction between these two subduction zones. Here we present anisotropic <span class="hlt">velocity</span> model of the crust and upper mantle in the Taiwan region derived from local travel time <span class="hlt">tomography</span>. We use more than 300 000 P and more than 150 000 S rays coming from 12910 earthquakes occurred in the Taiwan region and registered by 816 stations of different local Taiwanese seismic networks. The ANITA algorithm, for iterative nonlinear inversion of local earthquake data in orthorhombic anisotropic media with one predefined vertical orientation, was used for the tomographic inversion. This algorithm presumes anisotropy for only P <span class="hlt">velocity</span> described as horizontally oriented ellipsoid. For S <span class="hlt">velocity</span> we presume an isotropic model. Results show a good agreement with tectonic structure of the region. Obtained isotropic P and S <span class="hlt">velocity</span> models show fit to each other. The most prominent features of the models are Philippine Sea plate characterized by increased <span class="hlt">velocities</span> and decreased <span class="hlt">velocities</span> observed along the Luzon and Ryukyu arcs. We observe that orientation of the fast <span class="hlt">velocity</span> axis within the Philippine Sea plate coincides with direction of its displacement. Along the Luzon and Ryukyu arcs orientation of the fast <span class="hlt">velocities</span> axis coincide with the arcs extension. The results show that upper mantle beneath the eastern Taiwan characterized by decreased <span class="hlt">velocities</span> and N-S orientation of the fast <span class="hlt">velocity</span> axis. The western Taiwan characterized by alteration of the relatively small negative</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=280412','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=280412"><span id="translatedtitle">Breed <span class="hlt">group</span> effects for chute exit <span class="hlt">velocity</span> as an indicator trait for temperament in weaner cattle</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>The objective of this study was to determine breed <span class="hlt">group</span> differences in chute exit <span class="hlt">velocity</span> (CEV) in weaner cattle (n=3176). Data were collected in 2004 through 2008 under procedures of objective 3, Southern Regional Research project S1013 with the following states contributing data: FL, LA, and MS...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeoJI.199.1861D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeoJI.199.1861D"><span id="translatedtitle">Seismic structure beneath the Gulf of California: a contribution from <span class="hlt">group</span> <span class="hlt">velocity</span> measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Di Luccio, F.; Persaud, P.; Clayton, R. W.</p> <p>2014-12-01</p> <p>Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion measurements from local and regional earthquakes are used to interpret the lithospheric structure in the Gulf of California region. We compute <span class="hlt">group</span> <span class="hlt">velocity</span> maps for Rayleigh waves from 10 to 150 s using earthquakes recorded by broad-band stations of the Network of Autonomously Recording Seismographs in Baja California and Mexico mainland, UNM in Mexico, BOR, DPP and GOR in southern California and TUC in Arizona. The study area is gridded in 120 longitude cells by 180 latitude cells, with an equal spacing of 10 × 10 km. Assuming that each gridpoint is laterally homogeneous, for each period the tomographic maps are inverted to produce a 3-D lithospheric shear wave <span class="hlt">velocity</span> model for the region. Near the Gulf of California rift axis, we found three prominent low shear wave <span class="hlt">velocity</span> regions, which are associated with mantle upwelling near the Cerro Prieto volcanic field, the Ballenas Transform Fault and the East Pacific Rise. Upwelling of the mantle at lithospheric and asthenospheric depths characterizes most of the Gulf. This more detailed finding is new when compared to previous surface wave studies in the region. A low-<span class="hlt">velocity</span> zone in northcentral Baja at ˜28ºN which extends east-south-eastwards is interpreted as an asthenospheric window. In addition, we also identify a well-defined high-<span class="hlt">velocity</span> zone in the upper mantle beneath central-western Baja California, which correlates with the previously interpreted location of the stalled Guadalupe and Magdalena microplates. We interpret locations of the fossil slab and slab window in light of the distribution of unique post-subduction volcanic rocks in the Gulf of California and Baja California. We also observe a high-<span class="hlt">velocity</span> anomaly at 50-km depth extending down to ˜130 km near the southwestern Baja coastline and beneath Baja, which may represent another remnant of the Farallon slab.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3149517','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3149517"><span id="translatedtitle">Doppler <span class="hlt">velocity</span> detection limitations in spectrometer-based versus swept-source optical coherence <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hendargo, Hansford C.; McNabb, Ryan P.; Dhalla, Al-Hafeez; Shepherd, Neal; Izatt, Joseph A.</p> <p>2011-01-01</p> <p>Recent advances in Doppler techniques have enabled high sensitivity imaging of biological flow to measure blood <span class="hlt">velocities</span> and vascular perfusion. Here we compare spectrometer-based and wavelength-swept Doppler OCT implementations theoretically and experimentally, characterizing the lower and upper observable <span class="hlt">velocity</span> limits in each configuration. We specifically characterize the washout limit for Doppler OCT, the <span class="hlt">velocity</span> at which signal degradation results in loss of flow information, which is valid for both quantitative and qualitative flow imaging techniques. We also clearly differentiate the washout effect from the separate phenomenon of phase wrapping. We demonstrate that the maximum detectable Doppler <span class="hlt">velocity</span> is determined by the fringe washout limit and not phase wrapping. Both theory and experimental results from phantom flow data and retinal blood flow data demonstrate the superiority of the swept-source technique for imaging vessels with high flow rates. PMID:21833356</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70023092','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70023092"><span id="translatedtitle">P-wave <span class="hlt">velocity</span> structure of the uppermost mantle beneath Hawaii from traveltime <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Tilmann, F.J.; Benz, H.M.; Priestley, K.F.; Okubo, P.G.</p> <p>2001-01-01</p> <p>We examine the P-wave <span class="hlt">velocity</span> structure beneath the island of Hawaii using P-wave residuals from teleseismic earthquakes recorded by the Hawaiian Volcano Observatory seismic network. The station geometry and distribution of events makes it possible to image the <span class="hlt">velocity</span> structure between ~ 40 and 100 km depth with a lateral resolution of ~ 15 km and a vertical resolution of ~ 30 km. For depths between 40 and 80 km, P-wave <span class="hlt">velocities</span> are up to 5 per cent slower in a broad elongated region trending SE-NW that underlies the island between the two lines defined by the volcanic loci. No direct correlation between the magnitude of the lithospheric anomaly and the current level of volcanic activity is apparent, but the slow region is broadened at ~ 19.8??N and narrow beneath Kilauea. In the case of the occanic lithosphere beneath Hawaii, slow seismic <span class="hlt">velocities</span> are likely to be related to magma transport from the top of the melting zone at the base of the lithosphere to the surface. Thermal modelling shows that the broad elongated low-<span class="hlt">velocity</span> zone cannot be explained in terms of conductive heating by one primary conduit per volcano but that more complicated melt pathways must exist.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013GeoJI.192..310D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013GeoJI.192..310D"><span id="translatedtitle">Uppermost mantle seismic <span class="hlt">velocity</span> and anisotropy in the Euro-Mediterranean region from Pn and Sn <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Díaz, J.; Gil, A.; Gallart, J.</p> <p>2013-01-01</p> <p>In the last 10-15 years, the number of high quality seismic stations monitoring the Euro-Mediterranean region has increased significantly, allowing a corresponding improvement in structural constraints. We present here new images of the seismic <span class="hlt">velocity</span> and anisotropy variations in the uppermost mantle beneath this complex area, compiled from inversion of Pn and Sn phases sampling the whole region. The method of Hearn has been applied to the traveltime arrivals of the International Seismological Center catalogue for the time period 1990-2010. A total of 579 753 Pn arrivals coming from 12 377 events recorded at 1 408 stations with epicentral distances between 220 km and 1 400 km have been retained after applying standard quality criteria (maximum depth, minimum number of recordings, maximum residual values …). Our results show significant features well correlated with surface geology and evidence the heterogeneous character of the Euro-Mediterranean lithosphere. The station terms reflect the existence of marked variations in crustal thickness, consistent with available Moho depths inferred from active seismic experiments. The highest Pn <span class="hlt">velocities</span> are observed along a continuous band from the Po Basin to the northern Ionian Sea. Other high <span class="hlt">velocity</span> zones include the Ligurian Basin, the Valencia Trough, the southern Alboran Sea and central part of the Algerian margin. Most significant low-<span class="hlt">velocity</span> values are associated to orogenic belts (Betics, Pyrenees, Alps, Apennines and Calabrian Arc, Dinarides-Hellenides), and low-<span class="hlt">velocity</span> zones are also identified beneath Sardinia and the Balearic Islands. The introduction of an anisotropic term enhances significantly the lateral continuity of the anomalies, in particular in the most active tectonic areas. Pn anisotropy shows consistent orientations subparallel to major orogenic structures, such as Betics, Apennines, Calabrian Arc and Alps. The Sn tomographic image has lower resolution but confirms independently most of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRB..121.3686B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRB..121.3686B"><span id="translatedtitle">Lithospheric shear <span class="hlt">velocity</span> structure of South Island, New Zealand, from amphibious Rayleigh wave <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ball, Justin S.; Sheehan, Anne F.; Stachnik, Joshua C.; Lin, Fan-Chi; Yeck, William L.; Collins, John A.</p> <p>2016-05-01</p> <p>We present a crust and mantle 3-D shear <span class="hlt">velocity</span> model extending well offshore of New Zealand's South Island, imaging the lithosphere beneath the South Island as well as the Campbell and Challenger Plateaus. Our model is constructed via linearized inversion of both teleseismic (18-70 s period) and ambient noise-based (8-25 s period) Rayleigh wave dispersion measurements. We augment an array of 4 land-based and 29 ocean bottom instruments deployed off the South Island's east and west coasts in 2009-2010 by the Marine Observations of Anisotropy Near Aotearoa experiment with 28 land-based seismometers from New Zealand's permanent GeoNet array. Major features of our shear wave <span class="hlt">velocity</span> (Vs) model include a low-<span class="hlt">velocity</span> (Vs < 4.4 km/s) body extending from near surface to greater than 75 km depth beneath the Banks and Otago Peninsulas and high-<span class="hlt">velocity</span> (Vs~4.7 km/s) mantle anomalies underlying the Southern Alps and off the northwest coast of the South Island. Using the 4.5 km/s contour as a proxy for the lithosphere-asthenosphere boundary, our model suggests that the lithospheric thickness of Challenger Plateau and central South Island is substantially greater than that of the inner Campbell Plateau. The high-<span class="hlt">velocity</span> anomaly we resolve at subcrustal depths (>50 km) beneath the central South Island exhibits strong spatial correlation with upper mantle earthquake hypocenters beneath the Alpine Fault. The ~400 km long low-<span class="hlt">velocity</span> zone we image beneath eastern South Island and the inner Bounty Trough underlies Cenozoic volcanics and the locations of mantle-derived helium measurements, consistent with asthenospheric upwelling in the region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5446768','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5446768"><span id="translatedtitle">Teleseismic <span class="hlt">tomography</span> of the compressional wave <span class="hlt">velocity</span> structure beneath the Long Valley region, California</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dawson, P.B.; Evans, J.R.; Iyer, H.M. )</p> <p>1990-07-10</p> <p>In 1982 and 1984 the U.S. Geological Survey used several seismic networks, totaling over 90 stations, to record teleseismic P waves and measure travel time residuals in an area centered on the Long Valley caldera. The authors inverted the travel time residuals to obtain a three-dimensional image of the <span class="hlt">velocity</span> structure with resolution of 5-6 km to depths of 70 km beneath the array. Direct inversion of these data indicates that the 2- to 4-km-thick low-<span class="hlt">velocity</span> caldera fill contaminates the signal from any midcrustal <span class="hlt">velocity</span> anomalies beneath the caldera. Thus two methods were used to strip the effects of the upper crust from the travel time residuals: (1) ray tracing through upper crustal <span class="hlt">velocity</span> models provided by seismic refraction experiments and gravity surveys, and (2) an iterative stripping scheme using the inversion itself. The methods produce essentially identical results and adequately remove the effects of the shallowest crustal structures, including the caldera fill and hydrothermal alteration effects. The resulting stripped models show two well-resolved midcrustal low-<span class="hlt">velocity</span> bodies in the Long Valley region. The first body is centered between 7 and 20 km depth beneath the resurgent dome of the Long Valley caldera and has a volume of 150-600 km{sup 3}. The second, with a similar volume, is centered between 10 and 20 km depth beneath the Mono Craters, about 10 km north of Long Valley. <span class="hlt">Velocity</span> contrasts in both of these bodies are about 6-10%, and the features are interpreted as silicic magma chambers. This experiment does not preclude the presence of additional pockets of magma smaller than 5 km across in the upper crust, particularly beneath the resurgent dome of the caldera (which would be removed with the stripping methods). The high eruptive rate of the Mono Craters and these upper mantle structures suggest that the focus of volcanism is shifting north from Long Valley to the Mono Craters</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013EGUGA..15.4891C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013EGUGA..15.4891C&link_type=ABSTRACT"><span id="translatedtitle">Uppermost mantle <span class="hlt">velocity</span> from Pn <span class="hlt">tomography</span> in the Gulf of Aden</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Corbeau, Jordane; Rolandone, Frédérique; Leroy, Sylvie; Al-Lazki, Ali; Keir, Derek; Stuart, Graham; Stork, Anna</p> <p>2013-04-01</p> <p>We present an analysis of Pn traveltimes to determine lateral variations of <span class="hlt">velocity</span> in the uppermost mantle and crustal thickness beneath the Gulf of Aden and its margins. No detailed tomographic image of the entire Gulf of Aden was available. Previous tomographic studies covered the eastern Gulf of Aden and were thus incomplete or at a large scale with a too low resolution to see the lithospheric structures. From 1990 to 2010, 49206 Pn arrivals were selected from the International Seismological Center catalogue. We also used temporary networks : YOCMAL (Young Conjugate Margins Laboratory) networks with broadband stations located in Oman, Yemen and Socotra from 2003 to 2011, and Djibouti network from 2009 to 2011. From these networks we picked Pn arrivals and selected 4110 rays. Using a least-squares tomographic code (Hearn, 1996), these data were analyzed to solve for <span class="hlt">velocity</span> variations in the mantle lithosphere. We perform different inversions for shorter and longer ray path data sets in order to separate the shallow and deep structure within the mantle lid. In the upper lid, zones of low <span class="hlt">velocity</span> (7.7 km/s) around Sanaa, Aden, Afar, and along the Gulf of Aden are related to active volcanism. Off-axis volcanism and a regional melting anomaly in the Gulf of Aden area may be connected to the Afar plume, and explained by the model of channeling material away from the Afar plume along ridge-axis. Our study validates the channeling model and shows that the influence of the Afar hotspot may extend much farther eastwards along the Aden and Sheba ridges into the Gulf of Aden than previously believed. Still in the upper lid, high Pn <span class="hlt">velocities</span> (>8,2 km/s) are observed in Yemen and may be related to the presence of a magmatic underplating under the volcanic margin of Aden and under the Red Sea margins. In the lower lid, zones of low <span class="hlt">velocities</span> are spatially located differently than in the upper lid. On the Oman margin, a low <span class="hlt">velocity</span> zone (7.6 km/s) suggests deep partial</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.S23C4517I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.S23C4517I"><span id="translatedtitle">3-D P Wave <span class="hlt">Velocity</span> Structure of Marmara Region Using Local Earthquake <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Işık, S. E.; Gurbuz, C.</p> <p>2014-12-01</p> <p>The 3D P wave <span class="hlt">velocity</span> model of upper and lower crust of the Marmara Region between 40.200- 41.200N and 26.500- 30.500E is obtained by tomographic inversion (Simulps) of 47034 P wave arrivals of local earthquakes recorded at 90 land stations between October 2009 and December 2012 and 30 OBO stations and 14162 shot arrivals recorded at 35 OBO stations (Seismarmara Survey, 2001). We first obtained a 1D minimum model with Velest code in order to obtain an initial model for 3D inversion with 648 well located earthquakes located within the study area. After several 3D inversion trials we decided to create a more adequate initial model for 3D inversion. Choosing the initial model we estimated the 3D P wave <span class="hlt">velocity</span> model representing the whole region both for land and sea. The results are tested by making Checkerboard , Restoring Resolution and Characteristic Tests, and the reliable areas of the resulting model is defined in terms of RDE, DWS, SF and Hit count distributions. By taking cross sections from the resulting model we observed the vertical <span class="hlt">velocity</span> change along profiles crossing both land and sea. All the profiles crossing the basins showed that the high <span class="hlt">velocities</span> of lower crust make extensions towards the basin area which looks like the force that gives a shape to the basins. These extensions of lower crust towards the basins appeared with an average <span class="hlt">velocity</span> of 6.3 km/s which might be the result of the deformation due the shearing in the region. It is also interpreted that the development of these high <span class="hlt">velocities</span> coincide with the development of the basins. Thus, both the basins and the high <span class="hlt">velocity</span> zones around them might be resulted from the entrance of the NAF into the Marmara Sea and at the same time a shear regime was dominated due to the resistance of the northern Marmara Region (Yılmaz, 2010). The seismicity is observed between 5 km and 15 km after the 3D location of the earthquakes. The locations of the earthquakes improved and the seismogenic zone</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AIPC.1096.1386I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AIPC.1096.1386I"><span id="translatedtitle">Constant <span class="hlt">Group</span> <span class="hlt">Velocity</span> Ultrasonic Guided Wave Inspection for Corrosion and Erosion Monitoring in Pipes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Instanes, Geir; Pedersen, Audun; Toppe, Mads; Nagy, Peter B.</p> <p>2009-03-01</p> <p>This paper describes a novel ultrasonic guided wave inspection technique for the monitoring of internal corrosion and erosion in pipes, which exploits the fundamental flexural mode to measure the average wall thickness over the inspection path. The inspection frequency is chosen so that the <span class="hlt">group</span> <span class="hlt">velocity</span> of the fundamental flexural mode is essentially constant throughout the wall thickness range of interest, while the phase <span class="hlt">velocity</span> is highly dispersive and changes in a systematic way with varying wall thickness in the pipe. Although this approach is somewhat less accurate than the often used transverse resonance methods, it smoothly integrates the wall thickness over the whole propagation length, therefore it is very robust and can tolerate large and uneven thickness variations from point to point. The constant <span class="hlt">group</span> <span class="hlt">velocity</span> (CGV) method is capable of monitoring the true average of the wall thickness over the inspection length with an accuracy of 1% even in the presence of one order of magnitude larger local variations. This method also eliminates spurious variations caused by changing temperature, which can cause fairly large <span class="hlt">velocity</span> variations, but do not significantly influence the dispersion as measured by the true phase angle in the vicinity of the CGV point. The CGV guided wave CEM method was validated in both laboratory and field tests.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1987PhRvL..58...37M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1987PhRvL..58...37M"><span id="translatedtitle">Laboratory observation of ion conics by <span class="hlt">velocity</span>-space <span class="hlt">tomography</span> of a plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McWilliams, R.; Koslover, R.</p> <p>1987-01-01</p> <p>Laboratory experiments have examined particular elements of proposed mechanisms for ion conic formation seen in the earth's auroral-zone magnetosphere. A laser-induced fluorescence diagnostic measured the ion distribution function at many angles in <span class="hlt">velocity</span> space, allowing tomographic techniques to reconstruct the multidimensional ion distribution function. Ion conics, as well as drifting Maxwellians, were observed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27.6157N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27.6157N"><span id="translatedtitle">3d <span class="hlt">Velocity</span> <span class="hlt">Tomography</span> of The Kos - Nisyros Volcanic Area - East Aegean Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nikolova, S.; Ilinski, D.; Makris, J.; Chonia, T.; Stavrakakis, J.</p> <p></p> <p>Since June 2000, active and passive seismic observations have been carried out by IfG, GeoPro GmbH, Hamburg and Institute of Geodynamics, Athens within the frame of the project GEOWARN (Geo-Spacial Warning Systems Nisyros Volcano, Greece: An Emergency Case Study of the Volcanic Area of Nisyros) supported by the European Community. In the active experiment 48 recording seismic units were deployed and recorded more than 7000 shots in 3D array. The Nisyros volcano has been identified as an apophytic intrusion of much larger volcanic structure with a caldera of 35 km diameter, extending between the southern coasts of the islands of Kos and Nisyros. To obtain 3-D <span class="hlt">velocity</span> structure of the area a tomographic inversion was made using 6800 rays which probed the area with a very high ray density. The method applied and the high accuracy of active tomographic data allowed to resolve the high <span class="hlt">velocity</span> bodies in the caldera. The complex volcanic structure is identified by high <span class="hlt">velocity</span> rocks in- truding through the upper crust and penetrating the volcanic cone to depth of approx. 1.0 km to 1.8 km below the surface. Particularly high <span class="hlt">velocity</span> bodies were identified below the islands of Yali and the central caldera of Nisyros. The high <span class="hlt">velocity</span> bodies at shallow depth were interpreted as high-density cumulates of solidified magma intru- sion in the caldera. These intrusions explain very high temperature of 300C observed in the lower aquifer in the caldera at 1.5 km depth as confirmed by drilling. The vol- canic edifices of Kos, Yali, Nisyros and Strongily are part of a major volcanic caldera nearly 35 km in diameter. This size of the volcanic caldera explains the large volume of ignimbrites erupted 160 000 years ago. By combining geodetic, geophysical, geo- chemical and geological observations it is intended to correlate magma movements and associated changes of physical and chemical parameters of the recent volcanism.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70021644','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70021644"><span id="translatedtitle">P wave crustal <span class="hlt">velocity</span> structure in the greater Mount Rainier area from local earthquake <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Moran, S.C.; Lees, J.M.; Malone, S.D.</p> <p>1999-01-01</p> <p>We present results from a local earthquake tomographic imaging experiment in the greater Mount Rainier area. We inverted P wave arrival times from local earthquakes recorded at permanent and temporary Pacific Northwest Seismograph Network seismographs between 1980 and 1996. We used a method similar to that described by Lees and Crosson [1989], modified to incorporate the parameter separation method for decoupling the hypocenter and <span class="hlt">velocity</span> problems. In the upper 7 km of the resulting model there is good correlation between <span class="hlt">velocity</span> anomalies and surface geology. Many focal mechanisms within the St. Helens seismic zone have nodal planes parallel to the epicentral trend as well as to a north-south trending low-<span class="hlt">velocity</span> trough, leading us to speculate that the trough represents a zone of structural weakness in which a moderate (M 6.5-7.0) earthquake could occur. In contrast, the western Rainier seismic zone does not correlate in any simple way with anomaly patterns or focal mechanism fault planes, leading us to infer that it is less likely to experience a moderate earthquake. A ???10 km-wide low-<span class="hlt">velocity</span> anomaly occurs 5 to 18 km beneath the summit of Mount Rainier, which we interpret to be a signal of a region composed of hot, fractured rock with possible small amounts of melt or fluid. No systematic <span class="hlt">velocity</span> pattern is observed in association with the southern Washington Cascades conductor. A midcrustal anomaly parallels the Olympic-Wallowa lineament as well as several other geophysical trends, indicating that it may play an important role in regional tectonics. Copyright 1999 by the American Geophysical Union.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.S43B4562W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.S43B4562W"><span id="translatedtitle">Seismic <span class="hlt">Velocity</span> and Attenuation <span class="hlt">Tomography</span> of the Tonga Arc and Lau Back-arc Basin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wei, S. S.; Zha, Y.; Wiens, D. A.; Webb, S. C.</p> <p>2014-12-01</p> <p>We apply various techniques to analyze seismic data from the 2009 - 2010 Ridge2000 Lau Spreading Center project to investigate the distribution of partial melt beneath the Tonga arc and Lau back-arc basin. The shear wave <span class="hlt">velocity</span> structure is jointly inverted from the phase <span class="hlt">velocities</span> of teleseismic and ambient-noise Rayleigh waves, as the former is inverted using the two-plane-wave method with finite-frequency kernels, and the latter is obtained from cross-correlation in frequency domain. Additionally, we determine the 3D attenuation structure from t* measurements of P and S waves from local earthquakes. In order to avoid the trade-off between t* and corner frequency, we analyze the spectral ratio of S coda to independently constrain the fc for each event. The QP and QS structures are inverted separately, and QP/QS is jointly inverted from QP and t*(S). Tomographic results show strong signals of low <span class="hlt">velocity</span> and high attenuation within the upper 100-km of the mantle beneath the back-arc basin, suggesting perhaps the lowest shear <span class="hlt">velocity</span> (VSV = 3.5 km/s) and highest seismic attenuation (QP < 35 and QS < 25) known in the mantle. These anomalies require not only the abnormally high temperature but also the existence of partial melt. The inferred partial melt aligns with the spreading centers at shallow depths, but shift westwards away from the slab, implying a passive decompression melting process governed by the mantle wedge flow pattern. The Tonga volcanic arc does not display as strong of <span class="hlt">velocity</span> or attenuation anomalies as the spreading centers, suggesting less magmatism associate with the arc compared to the back-arc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.S41A2351L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.S41A2351L"><span id="translatedtitle">Surface wave <span class="hlt">tomography</span> with USArray: Rayleigh wave phase <span class="hlt">velocity</span>, ellipticity, and local amplification</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, F.; Schmandt, B.; Tsai, V. C.</p> <p>2012-12-01</p> <p>The deployment of the EarthScope/USArray Transportable Array allows detailed empirical study of the surface-wave wavefield on a large scale. In this presentation, we show that three local properties of Rayleigh waves, i.e. phase <span class="hlt">velocity</span>, ellipticity (or H/V ratio), and local amplification, can be determined across the array in the western US between 24 and 100 sec period based on teleseismic measurements. More than 900 earthquakes are analyzed where phase <span class="hlt">velocity</span> and local amplification are determined based on empirical phase travel time and amplitude mapping. The three Rayleigh wave properties, which are all sensitive to the 1D structure beneath each location, have very distinct depth sensitivity to Vs, Vp/Vs ratio, and density. Joint inversion of these quantities therefore reduces the trade-off between the three different parameters at different depths. Including the H/V ratio, in particular, allows the uppermost (0-3 km) crustal <span class="hlt">velocity</span> and density structure to be constrained, and our new results are in excellent agreement with known surface features. Pronounced low Vs, low density, and high Vp/Vs anomalies are imaged in the locations of several major sedimentary basins including the Williston, Powder River, Green River, Denver, and San Juan basins. Preliminary results on the inverted 3D Vs, Vp/Vs ratio, and density structure in the crust and upper mantle will also be discussed. (a)-(c) 30-sec Rayleigh-wave phase <span class="hlt">velocity</span>, local amplification, and H/V ratio observed across USArray in the western US. The red lines denote the tectonic boundaries and the triangles in (b)-(c) shown the stations used. The thick black lines indicate 3-km sediment contours for several major sedimentary basins (WB: Williston Basin; PR: Powder River Basin; GR: Green River Basin; DB: Denver Basin). (d)-(f) The Vs, density, and Vp/Vs ratio in the uppermost crust (0-3 km) inverted by phase <span class="hlt">velocity</span> and H/V ratio measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22043421','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22043421"><span id="translatedtitle"><span class="hlt">Group</span> <span class="hlt">velocity</span> and pulse lengthening of mismatched laser pulses in plasma channels</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Schroeder, C. B.; Benedetti, C.; Esarey, E.; Tilborg, J. van; Leemans, W. P.</p> <p>2011-08-15</p> <p>Analytic solutions are presented to the non-paraxial wave equation describing an ultra-short, low-power, laser pulse propagating in a plasma channel. Expressions for the laser pulse centroid motion and laser <span class="hlt">group</span> <span class="hlt">velocity</span> are derived, valid for matched and mismatched propagation in a parabolic plasma channel, as well as in vacuum, for an arbitrary Laguerre-Gaussian laser mode. The <span class="hlt">group</span> <span class="hlt">velocity</span> of a mismatched laser pulse, for which the laser spot size is strongly oscillating, is found to be independent of propagation distance and significantly less than that of a matched pulse. Laser pulse lengthening of a mismatched pulse owing to laser mode slippage is examined and found to dominate over that due to dispersive pulse spreading for sufficiently long pulses. Analytic results are shown to be in excellent agreement with numerical solutions of the full Maxwell equations coupled to the plasma response. Implications for plasma channel diagnostics are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1048294','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1048294"><span id="translatedtitle"><span class="hlt">Group</span> <span class="hlt">velocity</span> and pulse lengthening of mismatched laser pulses in plasma channels</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Schroeder, Carl; Benedetti, Carlo; Esarey, Eric; van Tilborg, Jeroen; Leemans, Wim</p> <p>2011-07-07</p> <p>Analytic solutions are presented to the non-paraxial wave equation describing an ultra-short, low-power, laser pulse propagating in aplasma channel. Expressions for the laser pulse centroid motion and laser <span class="hlt">group</span> <span class="hlt">velocity</span> are derived, valid for matched and mismatchedpropagation in a parabolic plasma channel, as well as in vacuum, for an arbitrary Laguerre-Gaussian laser mode. The <span class="hlt">group</span> <span class="hlt">velocity</span> of amismatched laser pulse, for which the laser spot size is strongly oscillating, is found to be independent of propagation distance andsignificantly less than that of a matched pulse. Laser pulse lengthening of a mismatched pulse owing to laser mode slippage isexamined and found to dominate over that due to dispersive pulse spreading for sufficiently long pulses. Analytic results are shown tobe in excellent agreement with numerical solutions of the full Maxwell equations coupled to the plasma response. Implications for plasmachannel diagnostics are discussed.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4585822','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4585822"><span id="translatedtitle">Impact of Substrate and Bright Resonances on <span class="hlt">Group</span> <span class="hlt">Velocity</span> in Metamaterial without Dark Resonator</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hokmabadi, Mohammad Parvinnezhad; Kim, Ju-Hyung; Rivera, Elmer; Kung, Patrick; Kim, Seongsin M.</p> <p>2015-01-01</p> <p>Manipulating the speed of light has never been more exciting since electromagnetic induced transparency and its classical analogs led to slow light. Here, we report the manipulation of light <span class="hlt">group</span> <span class="hlt">velocity</span> in a terahertz metamaterial without needing a dark resonator, but utilizing instead two concentric split-ring bright resonators (meta-atoms) exhibiting a bright Fano resonance in close vicinity of a bright Lorentzian resonance to create a narrowband transmittance. Unlike earlier reports, the bright Fano resonance does not stem from an asymmetry of meta-atoms or an interaction between them. Additionally, we develop a method to determine the metamaterial “effective thickness”, which quantifies the influence of the substrate on the metamaterial response and has remained challenging to estimate so far. By doing so, very good agreement between simulated and measured <span class="hlt">group</span> delays and <span class="hlt">velocities</span> is accomplished. The proposed structure and method will be useful in designing optical buffers, delay lines, and ultra-sensitive sensors. PMID:26395071</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960025080','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960025080"><span id="translatedtitle">Are There Optical Solitary Wave Solutions in Linear Media with <span class="hlt">Group</span> <span class="hlt">Velocity</span> Dispersion?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Li, Zhonghao; Zhou, Guosheng</p> <p>1996-01-01</p> <p>A generalized exact optical bright solitary wave solution in a three dimensional dispersive linear medium is presented. The most interesting property of the solution is that it can exist in the normal <span class="hlt">group-velocity</span>-dispersion (GVD) region. In addition, another peculiar feature is that it may achieve a condition of 'zero-dispersion' to the media so that a solitary wave of arbitrarily small amplitude may be propagated with no dependence on is pulse width.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21466497','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21466497"><span id="translatedtitle">Pulsed bismuth fibre laser with the intracavity-compensated <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Krylov, Aleksandr A; Kryukov, P G; Dianov, Evgenii M; Okhotnikov, O G; Guina, M</p> <p>2009-01-31</p> <p>Passive mode locking is achieved in a bismuth-doped fibre laser with the help of a SESAM saturable absorber optimised for operation in the spectra range from 1100 to 1200 nm. Pumping was performed by a 2-W cw ytterbium fibre laser at 1075 nm. The oscillation of the laser with an intracavity <span class="hlt">group-velocity</span>-dispersion compensator based on a pair of diffraction gratings is studied. Laser pulses with the minimum duration of {approx}5 ps are generated. (lasers)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17632631','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17632631"><span id="translatedtitle">Ultrashort Laguerre-Gaussian pulses with angular and <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion compensation.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zeylikovich, I; Sztul, H I; Kartazaev, V; Le, T; Alfano, R R</p> <p>2007-07-15</p> <p>Coherent optical vortices are generated from ultrashort 6.4 fs pulses. Our results demonstrate angular dispersion compensation of ultrashort 6.4 fs Laguerre-Gaussian (LG) pulses as well as what is believed to be the first direct autocorrelation measurement of 80 fs LG amplified pulses. A reflective-mirror-based 4f-compressor is proposed to compensate the angular and <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion of the ultrashort LG pulses. PMID:17632631</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JVGR..301..148V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JVGR..301..148V"><span id="translatedtitle">Three-dimensional <span class="hlt">velocity</span> structure of the Galeras volcano (Colombia) from passive local earthquake <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vargas, Carlos Alberto; Torres, Roberto</p> <p>2015-08-01</p> <p>A three-dimensional estimation of the Vp, Vs and Vp/Vs ratio structure at Galeras volcano was conducted by means of passive local earthquake <span class="hlt">tomography</span>. 14,150 volcano-tectonic events recorded by 58 stations in the seismological network established for monitoring the volcanic activity by the Colombian Geological Survey - Pasto Volcano Observatory between the years 1989 and 2015, were inverted by using the LOTOS code. The seismic events are associated with shear-stress fractures in solid rock as a response to pressure induced by magma flow. <span class="hlt">Tomography</span> resolution tests suggest a depth of imaging that yield 10 km from the summit of the main crater, illuminating a large portion of the volcanic structure and the interaction of tectonic features like the Buesaco and Silvia-Pijao faults. Full catalog tomographic inversion, that represents the stacked image of the volcanic structure or the most permanent features underneath the volcano, shows vertical structures aligned with seismicity beneath the main crater. We hypothesize that these structures correspond to a system of ducts or fractures through which magma and fluid phases flow up from deeper levels toward the top and related with the intersection of the surface traces of the Silvia-Pijao and Buesaco faults.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.4181R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.4181R"><span id="translatedtitle">Joint inversion of P-waveforms from teleseismic events and surface waves <span class="hlt">group</span> <span class="hlt">velocities</span> from ambient seismic noise in Bohemian Massif</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ruzek, Bohuslav</p> <p>2010-05-01</p> <p>Joint inversion of P-waveforms from distant earthquakes recorded by 41 broadband seismic stations located on the territory of Bohemian Massif and Rayleigh/Love <span class="hlt">group</span> <span class="hlt">velocities</span> gained by using cross-correlation technique applied to seismic noise recorded by the same set of broadband stations has been performed. Together with joint inversion also individual inversions using single data sets have been carried out. All computations were arranged inside isotropic, locally 1D layered models. Remarkable result is indication of horizons just above MOHO in the lower crust below some stations where low-<span class="hlt">velocity</span> S-wave channel is needed in order to ensure correct modeling of measured events. This indication follows both from individual and joint inversions. P-waveform inversion is based on using a set of 271 well-recorded teleseismic events from epicentral distances 3000-10000 km. The inversion was originally based on the popular 'receiver function' methodology, but due to the instability of needed deconvolution it was modified. We search for optimum layered <span class="hlt">velocity</span> model, which correctly projects radial to vertical components (and vice versa, deconvolution is no more needed). Regarding second source of data, both Rayleigh and Love surface waves were extracted from seismic noise by using cross-correlation. Long time series covering the period 2001-2009 were processed. Such measurements provide <span class="hlt">group</span> <span class="hlt">velocities</span> between arbitrary pairs of stations. Local <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion curves were computed by using 2D <span class="hlt">tomography</span>-like approach for periods 4-20 s. The subject of inversion (both individual and joint) were just <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion curves. Inversion required exhaustive computations. We used HPC cluster nemo.ig.cas.cz and ANNI inversion software, capable to run in parallel regime.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006JAG....59..337C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006JAG....59..337C"><span id="translatedtitle">Numerical simulation of attenuation and <span class="hlt">group</span> <span class="hlt">velocity</span> of guided ultrasonic wave in grouted rock bolts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cui, Y.; Zou, D. H.</p> <p>2006-08-01</p> <p>In this paper, the guided ultrasonic wave propagating in grouted rock bolts was simulated with finite element method. An 800 mm partially grouted cylindrical rock bolt model was created. Dynamic input signals with frequency from 25 to 100 kHz were used to excite ultrasonic wave. The simulated waveform, <span class="hlt">group</span> <span class="hlt">velocity</span> and amplitude ratio matched well with the experimental results. This model made it possible to study the behaviour of the guided waves in the grouted bolt along its central axis. Analysis of the simulated results showed that the <span class="hlt">group</span> <span class="hlt">velocity</span> in grouted rock bolts is constant along the grouted length, and the boundary effect on the <span class="hlt">group</span> <span class="hlt">velocity</span> is negligible. This paper also presents methods to determine the attenuation coefficient from simulation and to determine the boundary effect on attenuation at the bolt ends. The analysis showed that the attenuation of the guided wave propagating inside the grouted bolts is similar to the theoretical solution in steel bar with infinite length. After correction for the boundary effects the grout length of a grouted rock bolt can be determined using the measured attenuation, with sufficient accuracy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvA..91f3607N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvA..91f3607N"><span id="translatedtitle">Maximum <span class="hlt">group</span> <span class="hlt">velocity</span> in a one-dimensional model with a sinusoidally varying staggered potential</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nag, Tanay; Sen, Diptiman; Dutta, Amit</p> <p>2015-06-01</p> <p>We use Floquet theory to study the maximum value of the stroboscopic <span class="hlt">group</span> <span class="hlt">velocity</span> in a one-dimensional tight-binding model subjected to an on-site staggered potential varying sinusoidally in time. The results obtained by numerically diagonalizing the Floquet operator are analyzed using a variety of analytical schemes. In the low-frequency limit we use adiabatic theory, while in the high-frequency limit the Magnus expansion of the Floquet Hamiltonian turns out to be appropriate. When the magnitude of the staggered potential is much greater or much less than the hopping, we use degenerate Floquet perturbation theory; we find that dynamical localization occurs in the former case when the maximum <span class="hlt">group</span> <span class="hlt">velocity</span> vanishes. Finally, starting from an "engineered" initial state where the particles (taken to be hard-core bosons) are localized in one part of the chain, we demonstrate that the existence of a maximum stroboscopic <span class="hlt">group</span> <span class="hlt">velocity</span> manifests in a light-cone-like spreading of the particles in real space.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27036254','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27036254"><span id="translatedtitle">Backward waves with double zero-<span class="hlt">group-velocity</span> points in a liquid-filled pipe.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cui, Hanyin; Lin, Weijun; Zhang, Hailan; Wang, Xiuming; Trevelyan, Jon</p> <p>2016-03-01</p> <p>Hollow cylinders often exhibit backward propagation modes whose <span class="hlt">group</span> and phase <span class="hlt">velocities</span> have opposite directions, and these exhibit a minimum possible frequency at which the <span class="hlt">group</span> <span class="hlt">velocity</span> vanishes at a nonzero wavenumber. These zero-<span class="hlt">group-velocity</span> (ZGV) points are associated with resonant conditions in the medium. On the basis of ZGV resonances, a non-contact and laser ultrasound technique has been developed to measure elastic constants of hollow pipes. This paper provides a theoretical and numerical investigation of the influence of the contained liquid on backward waves and associated ZGV modes, in order to explore whether this ZGV technique is suitable for in-service non-destructive evaluations of liquid-filled pipes. Dispersion spectra and excitation properties have been analyzed. It is found that the presence of the liquid causes an increased number of backward modes and ZGVs which are highly excitable by a point source. In addition, several guided modes twice undergo a change of sign in the slopes of their dispersion curves, leading to two ZGV points. This phenomenon of double ZGVs in one backward wave, which is caused by strong mode repulsions, has not been found in isotropic hollow cylinders, but it can be observed in a fluid-filled thin-walled pipe. PMID:27036254</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/19550877','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/19550877"><span id="translatedtitle">Time-domain upconversion measurements of <span class="hlt">group-velocity</span> dispersion in quantum cascade lasers.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Choi, Hyunyong; Diehl, Laurent; Capasso, Federico; Bour, David; Corzine, Scott; Zhu, Jintian; Hofler, Gloria; Norris, Theodore B</p> <p>2007-11-26</p> <p>A time-resolved mid-infrared upconversion technique based on sum-frequency generation was applied to measure pulse propagation in lambda approximately 5.0 mum quantum cascade lasers operated in continuous wave at 30 K. The wavelength-dependent propagation delay of femtosecond mid-infrared pulses was measured to determine the total <span class="hlt">group-velocity</span> dispersion. The material and waveguide dispersion were calculated and their contributions to the total <span class="hlt">group-velocity</span> dispersion were found to be relatively small and constant. The small-signal gain dispersion was estimated from a measurement of the electroluminescence spectrum without a laser cavity, and was found to be the largest component of the total GVD. A negative <span class="hlt">group-velocity</span> dispersion of beta2 ( =d2beta/d omega2) approximately - 4.6x10-6 ps2/mum was observed at the peak emission wavelength, and good agreement was found for the measured and calculated pulse-broadening. PMID:19550877</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006GeoRL..33.7303T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006GeoRL..33.7303T"><span id="translatedtitle">Local earthquake (LE) <span class="hlt">tomography</span> with joint inversion for P- and S-wave <span class="hlt">velocities</span> using structural constraints</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tryggvason, Ari; Linde, Niklas</p> <p>2006-04-01</p> <p>In local earthquake (LE) <span class="hlt">tomography</span> for P- and S-wave <span class="hlt">velocities</span> (or Vp/Vs ratios), constraints punishing deviations from a given Vp/Vs ratio are often used. In a synthetic model test we demonstrate that though such constraints inhibit unreasonable Vp/Vs ratio variations, they bias the resulting Vp/Vs ratios. As an alternative approach, structural constraints based on the cross-product of the model gradients can be used to constrain the joint P- and S-wave inversion. We show that the resulting models are as low in artifacts as if a Vp/Vs damping was used, but the resulting Vp/Vs ratios are less biased, which is important for a quantitative interpretation of physical properties and processes in the Earth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSM51F4315S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM51F4315S"><span id="translatedtitle"><span class="hlt">Velocity</span> and Energy Distributions of Water <span class="hlt">Group</span> Ion Around the Enceladus Plume</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sakai, S.; Cravens, T.; Pothapragada, S.; Kumar, A.</p> <p>2014-12-01</p> <p>Enceladus has a dynamic plume on its south pole which is emitting gas, including water vapor, and dust. The gas is ionized by solar EUV radiation and by electron impacts and extends throughout the inner magnetosphere of Saturn. The dust is negatively charged and forms the E ring. Hence, the inner magnetosphere within 10 RS contains a complex mixture of plasma, neutral gas and dust. Cassini observations show that the plasma <span class="hlt">velocities</span> are less than the co-rotation <span class="hlt">velocity</span>. The <span class="hlt">velocity</span> and energy distributions of this need to be explained in order to understand the inner magnetospheric plasma physics. We have investigated the <span class="hlt">velocity</span> and energy distributions of water <span class="hlt">group</span> ions in the vicinity of Enceladus using test particle and Monte Carlo methods including collisional processes such as charge exchange and ion-neutral chemical reaction. The model results will be constrained by neutral and ion composition data from the Cassini Ion and Neutral Mass Spectrometer and ion energy spectra from the Plasma Spectrometer (CAPS). We will also discuss related plasma processed in the Enceladus torus.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.S53F..06M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.S53F..06M"><span id="translatedtitle">A New Global <span class="hlt">Group</span> <span class="hlt">Velocity</span> Dataset for Constraining Crust and Upper Mantle Properties</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ma, Z.; Masters, G.; Laske, G.; Pasyanos, M. E.</p> <p>2010-12-01</p> <p>We are improving our CRUST2.0 to a new LITHO1.0 model, refining the nominal resolution to 1 degree and including lithospheric structure. The new model is constrained by many datasets, including very large datasets of surface wave <span class="hlt">group</span> <span class="hlt">velocity</span> built using a new, efficient measurement technique. This technique starts in a similar fashion to the traditional frequency-time analysis, but instead of making measurements for all frequencies for a single source-station pair, we apply cluster analysis to make measurements for all recordings for a single event at a single target frequency. By changing the nominal frequencies of the bandpass filter, we filter each trace until the centroid frequency of the band-passed spectrum matches the target frequency. We have processed all the LH data from IRIS (and some of the BH data from PASSCAL experiments and the POLARIS network) from 1976 to 2007. The Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> data set is complete from 10mHz to 40mHz at increments of 2.5mHz. The data set has about 330000 measurements for 10 and 20mHz, 200000 for 30mHz and 110000 for 40mHz. We are also building a similar dataset for Love waves, though its size will be about half that of the Rayleigh wave dataset. The SMAD of the <span class="hlt">group</span> arrival time difference between our global dataset and other more regional datasets is about 12 seconds for 20mHz, 9 seconds for 30mHz, and 7 seconds for 40mHz. Though the discrepancies are about twice as big as our measurement precision (estimated by looking at <span class="hlt">group</span> arrival time differences between closely-spaced stations), it is still much smaller than the signal in the data (e.g., the <span class="hlt">group</span> arrival time for 20mHz can differ from the prediction of a 1D Earth by over 250 seconds). The fact that there is no systematic bias between the datasets encourages us to combine them to improve coverage of some key areas. <span class="hlt">Group</span> <span class="hlt">velocity</span> maps inverted from the combined datasets show many interesting signals though the dominant signal is related to variations</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007AAS...210.0801M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007AAS...210.0801M&link_type=ABSTRACT"><span id="translatedtitle">Impact of High <span class="hlt">Velocity</span> Interactions on Galaxy Evolution in Galaxy <span class="hlt">Groups</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Machacek, Marie E.; Jones, C.; Forman, W. R.; Kraft, R. P.; Ashby, M. L.; Hardcastle, M. J.</p> <p>2007-05-01</p> <p>Galaxy interactions in cool <span class="hlt">groups</span> dominate galaxy evolution at high redshift. Observations of galaxies interacting in nearby galaxy <span class="hlt">groups</span>, where the same dynamical processes that transform galaxies at high redshift can be studied in detail, are critical to our understanding of galaxy and <span class="hlt">group</span> evolution. X-ray observations of hot gas features, e.g. surface brightness edges and wakes, reveal that high <span class="hlt">velocity</span> interactions play a significant role in the transformation of galaxies in <span class="hlt">groups</span>, yet, because these encounters are difficult to identify in other wavebands, few have been studied. We present two case studies of high <span class="hlt">velocity</span> galaxy-galaxy and galaxy-gas interactions in galaxy <span class="hlt">groups</span>: NGC4782(3C278) and NGC4783 in LGG316, and NGC6872 and NGC6876 in the Pavo <span class="hlt">group</span>. From Chandra and XMM-Newton X-ray data, we measure the hot gas temperature, density and metal abundance in the galaxies and the intragroup medium (IGM) to characterize the thermodynamic state of the <span class="hlt">group</span>, constrain 3D motions of the galaxies through the IGM, and determine the dominant processes transferring matter and energy between the galaxy and <span class="hlt">group</span> gas. We compare these results with VLA observations of NGC4782/3 and Spitzer IRAC observations of NGC6872 and NGC6876 to study the impact of these interactions on nuclear activity, radio jet evolution, and star formation in these galaxies, and on the heating and enrichment of the IGM. This work was supported in part by the Smithsonian Institution, the Chandra Science Center, NASA contracts AR5-6011X, GO6-7068X, NNX06AG34G, JPL1279244 and the Royal Society.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/20442022','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/20442022"><span id="translatedtitle">Laser ultrasonic inspection of plates using zero-<span class="hlt">group</span> <span class="hlt">velocity</span> lamb modes.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Clorennec, Dominique; Prada, Claire; Royer, Daniel</p> <p>2010-05-01</p> <p>A noncontact laser-based ultrasonic technique is proposed for detecting small plate thickness variations caused by corrosion and adhesive disbond between two plates. The method exploits the resonance at the minimum frequency of the S(1) Lamb mode dispersion curve. At this minimum frequency, the <span class="hlt">group</span> <span class="hlt">velocity</span> vanishes, whereas the phase <span class="hlt">velocity</span> remains finite. The energy deposited by the laser pulse generates a local resonance of the plate. This vibration is detected at the same point by an optical interferometer. First experiments show the ability to image a 1.5-microm deep corroded area on the back side of a 0.5-mm-thick duralumin plate. Because of the finite wavelength of the S(1)- zero <span class="hlt">group</span> <span class="hlt">velocity</span> (ZGV) mode, the spatial resolution is limited to approximately twice the plate thickness. With the same technique we investigate the state of adhesive bonds between duralumin and glass plates. The S(1)-Lamb mode resonance is strongly attenuated when plates are rigidly bonded. In the case of thin adhesive layers, we observed other resonances, associated with ZGV modes of the multi-layer structure, whose frequencies and amplitudes vary with adhesive thickness. Experiments were carried out on real automotive adhesively bonded structures and the results were compared with images obtained by X-ray radiography. PMID:20442022</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.S51A1259I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.S51A1259I"><span id="translatedtitle">P-wave anisotropic <span class="hlt">velocity</span> <span class="hlt">tomography</span> beneath the Japan islands: Large-scale images and details in the Kanto district</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ishise, M.; Koketsu, K.; Miyake, H.; Oda, H.</p> <p>2006-12-01</p> <p>The Japan islands arc is located in the convergence zone of the North American (NA), Amurian (AM), Pacific (PAC) and Philippine Sea (PHS) plates, and its parts are exposed to various tectonic settings. For example, at the Kanto district in its central part, these four plates directly interact with each, so that disastrous future earthquakes are expected along the plate boundaries and within the inland areas. In order to understand this sort of complex tectonic setting, it is necessary to know the seismological structure in various perspectives. We investigate the seismic <span class="hlt">velocity</span> structure beneath the Japan islands in view of P-wave anisotropy. We improved a hitherto-known P-wave <span class="hlt">tomography</span> technique so that the 3-D structure of isotropic and anisotropic <span class="hlt">velocities</span> and earthquake hypocenter locations are determined from P-wave arrival times of local earthquakes [Ishise and Oda, 2005]. In the <span class="hlt">tomography</span> technique, P-wave anisotropy is assumed to hold hexagonal symmetry with horizontal symmetry axis. The P-wave arrival times used in this study are complied in the Japan University Network Earthquake Catalog. The results obtained are summarized as follows; (1) the upper crust anisotropy is governed by the present-day stress field arising from the interaction between the plates surrounding the Japan islands arc, (2) the mantle anisotropy is caused by the present-day mantle flow induced by slab subduction and continental plate motion, (3) the old PAC slab keeps its original slab anisotropy which was captured when the plate was formed, while the youngest part of the PHS slab has lost the original anisotropy during its subduction and has gained new anisotropy which is controlled by the present-day stress field. We also carried out a further study on high-resolution seismic <span class="hlt">tomography</span> for understanding the specific characteristics of the Kanto district. We mostly focused on the elucidation of the dual subduction formed by the PHS and PAC slabs using seismological data</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.S31A2030P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.S31A2030P"><span id="translatedtitle">Three dimensional Rayleigh wave <span class="hlt">velocity</span> model using multimode surface wave <span class="hlt">tomography</span> of Eastern Asia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pandey, S.; Yuan, X.; Debayle, E.; Priestley, K. F.; Kind, R.; Li, X.</p> <p>2010-12-01</p> <p>The collision of the Eurasian plate, Indian plate and Philippine sea plate resulted in the tectonic feature of todays; like mountain ranges, fold belts, sedimentary basins and high plateaus in China and the surrounding region. In the Northern part this region is supposed to get some resistance from the Siberian shield. But the collision of Indian plate has left its major imprints and the consequence of this was the uplift of Himalayan Mountain and Tibetan Plateau. This triple junction scenario is the main cause for many inter and intra-plate earthquake in this region. It is generally agreed that the lithosphere is thick in west China while much of the lithospheric root was lost beneath some cratons in east China. Still it's an open debate whether the lithosphere beneath the Tibetan plateau has doubled its thickness as did the crust above or much of the thickened lithosphere was removed by mantle convection and delamination. In our study we try to determine the three dimensional Sv wave speed and azimuthal anisotropy model by analyzing the vertical component multimode Rayleigh wave seismogram. The data which we used are from broadband stations from in and around China. We construct the three dimensional model in two step procedure. In the first step we use the automated version of the Cara and Leveque [1987] waveform inversion technique in terms of secondary observables for modeling each multimode Rayleigh waveform to determine the path-average mantle Sv wave speed structure. In the second stage we combine the 1-D <span class="hlt">velocity</span> models in a tomographic inversion to obtain the three dimensional Sv wave speed structure and the azimuthal anisotropy as a function of depth. We have taken a source region specific <span class="hlt">velocity</span> structure from the three dimensional model 3SMAC to improve the source excitation computation. We analyzed the seismograms using a modified (smoothed) version of PREM for the upper mantle <span class="hlt">velocity</span> structure both for the reference model used in extracting the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009SPIE.7177E..0YY','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009SPIE.7177E..0YY"><span id="translatedtitle">Simultaneous recovery of chromophore concentrations and ultrasound <span class="hlt">velocity</span> by spectrally resolved photoacoustic <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yuan, Zhen; Zhang, Qizhi; Grobmyer, Stephen; Jiang, Huabei</p> <p>2009-02-01</p> <p>We describe a new spectral approach for inversion of photoacoustic data with multi-wavelength pulsed laser illumination. Multi-spectral PAT provides a means of recovery of different chromophore concentrations and ultrasound <span class="hlt">velocity</span> simultaneously and directly by incorporating prior spectral information into the image reconstruction process. It is demonstrated from simulation tests and small animal experiments that the multi-parameter recovery based on multispectral PAT is reliable and accurate. The reconstructed multiple parameter images may provide us a key tool to quantify physiological function, disease progression, or response to intervention.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22039079','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22039079"><span id="translatedtitle">TWO DISTANT HALO <span class="hlt">VELOCITY</span> <span class="hlt">GROUPS</span> DISCOVERED BY THE PALOMAR TRANSIENT FACTORY</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sesar, Branimir; Cohen, Judith G.; Levitan, David; Kirby, Evan N.; Kulkarni, Shrinivas R.; Prince, Thomas A.; Grillmair, Carl J.; Laher, Russ R.; Surace, Jason A.; Juric, Mario; Ofek, Eran O.</p> <p>2012-08-20</p> <p>We report the discovery of two new halo <span class="hlt">velocity</span> <span class="hlt">groups</span> (Cancer <span class="hlt">groups</span> A and B) traced by eight distant RR Lyrae stars and observed by the Palomar Transient Factory survey at R.A. {approx} 129 Degree-Sign , decl. {approx} 20 Degree-Sign (l {approx} 205 Degree-Sign , b {approx} 32 Degree-Sign ). Located at 92 kpc from the Galactic center (86 kpc from the Sun), these are some of the most distant substructures in the Galactic halo known to date. Follow-up spectroscopic observations with the Palomar Observatory 5.1 m Hale telescope and W. M. Keck Observatory 10 m Keck I telescope indicate that the two <span class="hlt">groups</span> are moving away from the Galaxy at v-bar{sub gsr}{sup A} = 78.0{+-}5.6 km s{sup -1} (Cancer <span class="hlt">group</span> A) and v-bar{sub gsr}{sup B} = 16.3{+-}7.1 km s{sup -1} (Cancer <span class="hlt">group</span> B). The <span class="hlt">groups</span> have <span class="hlt">velocity</span> dispersions of {sigma}{sub v{sub g{sub s{sub r}{sup A}}}} = 12.4{+-}5.0 km s{sup -1} and {sigma}B{sub v{sub g{sub s{sub r}{sup B}}}} =14.9{+-}6.2 km s{sup -1} and are spatially extended (about several kpc), making it very unlikely that they are bound systems, and more likely to be debris of tidally disrupted dwarf galaxies or globular clusters. Both <span class="hlt">groups</span> are metal-poor (median metallicities of [Fe/H]{sup A} = -1.6 dex and [Fe/H]{sup B} = -2.1 dex) and have a somewhat uncertain (due to small sample size) metallicity dispersion of {approx}0.4 dex, suggesting dwarf galaxies as progenitors. Two additional RR Lyrae stars with <span class="hlt">velocities</span> consistent with those of the Cancer <span class="hlt">groups</span> have been observed {approx}25 Degree-Sign east, suggesting possible extension of the <span class="hlt">groups</span> in that direction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004ApJ...610L..17P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004ApJ...610L..17P"><span id="translatedtitle">Where Are the High-<span class="hlt">Velocity</span> Clouds in Local <span class="hlt">Group</span> Analogs?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pisano, D. J.; Barnes, David G.; Gibson, Brad K.; Staveley-Smith, Lister; Freeman, Ken C.; Kilborn, Virginia A.</p> <p>2004-07-01</p> <p>High-<span class="hlt">velocity</span> clouds (HVCs) are clouds of H I seen around the Milky Way with <span class="hlt">velocities</span> inconsistent with Galactic rotation; they have unknown distances and masses and controversial origins. One possibility is that HVCs are associated with the small dark matter halos seen in models of galaxy formation and distributed at distances of 150 kpc to 1 Mpc. We report on our attempts to detect the analogs to such putative extragalactic clouds in three <span class="hlt">groups</span> of galaxies similar to our own Local <span class="hlt">Group</span> using the Australia Telescope National Facility Parkes Telescope and Compact Array. Eleven dwarf galaxies were found, but no H I clouds lacking stars were detected. Using the population of compact HVCs around the Milky Way as a template, we find that our nondetection of analogs implies that they must be clustered within 160 kpc of the Milky Way (and other galaxies) with an average H I mass <~4×105 Msolar at the 95% confidence level. This is in accordance with recent limits derived by other authors. If our <span class="hlt">groups</span> are true analogs to the Local <span class="hlt">Group</span>, then this makes the original Blitz et al. and Braun & Burton picture of HVCs residing out to 1 Mpc from the Milky Way extremely unlikely. The total H I mass in HVCs, <~108 Msolar, implies that there is not a large reservoir of neutral hydrogen waiting to be accreted onto the Milky Way. Any substantial reservoir of baryonic matter must be mostly ionized or condensed enough as to be undetectable.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvB..92l1409B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvB..92l1409B"><span id="translatedtitle">Nonperturbative renormalization <span class="hlt">group</span> calculation of quasiparticle <span class="hlt">velocity</span> and dielectric function of graphene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bauer, Carsten; Rückriegel, Andreas; Sharma, Anand; Kopietz, Peter</p> <p>2015-09-01</p> <p>Using a nonperturbative functional renormalization <span class="hlt">group</span> approach, we calculate the renormalized quasiparticle <span class="hlt">velocity</span> v (k ) and the static dielectric function ɛ (k ) of suspended graphene as functions of an external momentum k . Our numerical result for v (k ) can be fitted by v (k ) /vF=A +B ln(Λ0/k ) , where vF is the bare Fermi <span class="hlt">velocity</span>, Λ0 is an ultraviolet cutoff, and A =1.37 , B =0.51 for the physically relevant value (e2/vF=2.2 ) of the coupling constant. In contrast to calculations based on the static random-phase approximation, we find that ɛ (k ) approaches unity for k →0 . Our result for v (k ) agrees very well with a recent measurement by Elias et al. [Nat. Phys. 7, 701 (2011), 10.1038/nphys2049].</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApPhL.108f1106T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApPhL.108f1106T"><span id="translatedtitle">Reducing the <span class="hlt">group</span> <span class="hlt">velocity</span> of coherent radiation for upconverting the single-cycle electron density modulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tanaka, Takashi</p> <p>2016-02-01</p> <p>We present an interesting property of broadband coherent radiation emitted by a single microbunch, or a single-cycle density modulation in an electron beam passing through an undulator, and describe its application to a frequency upconversion of the single-cycle modulation. This is based on the fact that a monocycle pulse is generated by focusing the coherent radiation with a unit-magnification optical system, which propagates without diffraction like the Bessel beam, at a reduced <span class="hlt">group</span> <span class="hlt">velocity</span> equal to the average electron <span class="hlt">velocity</span> in the undulator. Calculations show that a single microbunch with a length of 46-nm formed in a 2-GeV and 2-kA electron beam can be upconverted to a 4-nm long microbunch through interaction with focused coherent radiation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22066656','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22066656"><span id="translatedtitle">Dynamics of frequency-modulated soliton-like pulses in a longitudinally inhomogeneous, anomalous <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion fibre amplifier</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zolotovskii, Igor' O; Korobko, D A; Okhotnikov, Oleg G; Sysolyatin, A A; Fotiadi, A A</p> <p>2012-09-30</p> <p>We examine conditions for the formation and amplification of frequency-modulated soliton-like pulses in longitudinally inhomogeneous, anomalous <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion fibres. The <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion profiles necessary for the existence and amplification of such pulses in active fibres are identified and the pulse duration and chirp are determined as functions of propagation distance. (optical fibres, lasers and amplifiers. properties and applications)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3673069','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3673069"><span id="translatedtitle">Evaluation of Moisture-Related Attenuation Coefficient and Water Diffusion <span class="hlt">Velocity</span> in Human Skin Using Optical Coherence <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lee, Cheng-Kuang; Tsai, Meng-Tsan; Chang, Feng-Yu; Yang, Chih-Hsun; Shen, Su-Chin; Yuan, Ouyang; Yang, Chih-He</p> <p>2013-01-01</p> <p>In this study, time-resolved optical coherence <span class="hlt">tomography</span> (OCT) scanning images of the process of water diffusion in the skin that illustrate the enhancement in the backscattered intensities due to the increased water concentration are presented. In our experiments, the water concentration in the skin was increased by soaking the hand in water, and the same region of the skin was scanned and measured with the OCT system and a commercial moisture monitor every three minutes. To quantitatively analyze the moisture-related optical properties and the <span class="hlt">velocity</span> of water diffusion in human skin, the attenuation coefficients of the skin, including the epidermis and dermis layers, were evaluated. Furthermore, the evaluated attenuation coefficients were compared with the measurements made using the commercial moisture monitor. The results demonstrate that the attenuation coefficient increases as the water concentration increases. Furthermore, by evaluating the positions of center-of mass of the backscattered intensities from OCT images, the diffusion <span class="hlt">velocity</span> can be estimated. In contrast to the commercial moisture monitor, OCT can provide three-dimensional structural images of the skin and characterize its optical property, which together can be used to observe morphological changes and quantitatively evaluate the moisture-related attenuation coefficients in different skin layers. PMID:23529149</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014JGRB..119..519B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014JGRB..119..519B&link_type=ABSTRACT"><span id="translatedtitle">Phase <span class="hlt">velocity</span> <span class="hlt">tomography</span> of surface waves using ambient noise cross correlation and array processing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boué, Pierre; Roux, Philippe; Campillo, Michel; Briand, Xavier</p> <p>2014-01-01</p> <p>Continuous recordings of ambient seismic noise across large seismic arrays allows a new type of processing using the cross-correlation technique on broadband data. We propose to apply double beamforming (DBF) to cross correlations to extract a particular wave component of the reconstructed signals. We focus here on the extraction of the surface waves to measure phase <span class="hlt">velocity</span> variations with great accuracy. DBF acts as a spatial filter between two distant subarrays after cross correlation of the wavefield between each single receiver pair. During the DBF process, horizontal slowness and azimuth are used to select the wavefront on both subarray sides. DBF increases the signal-to-noise ratio, which improves the extraction of the dispersive wave packets. This combination of cross correlation and DBF is used on the Transportable Array (USArray), for the central U.S. region. A standard model of surface wave propagation is constructed from a combination of the DBF and cross correlations at different offsets and for different frequency bands. The perturbation (phase shift) between each beam and the standard model is inverted. High-resolution maps of the phase <span class="hlt">velocity</span> of Rayleigh and Love waves are then constructed. Finally, the addition of azimuthal information provided by DBF is discussed, to construct curved rays that replace the classical great-circle path assumption.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/19506660','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/19506660"><span id="translatedtitle">Zero-<span class="hlt">group-velocity</span> modes in chalcogenide holey photonic-crystal fibers.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Oskooi, Ardavan F; Joannopoulos, J D; Johnson, Steven G</p> <p>2009-06-01</p> <p>We demonstrate that a holey photonic-crystal fiber with chalcogenide-glass index contrast can be designed to have a complete gap at a propagation constant beta = 0 that also extends into the non-zero beta region. This type of bandgap (previously identified only at index contrasts unattainable in glasses) opens up a regime for guiding zero-<span class="hlt">group-velocity</span> modes not possible in holey fibers with the more common finger-like gaps originating from beta-->infinity. Such modes could be used to enhance nonlinear and other material interactions, such as for hollow-core fibers in gas-sensor applications. PMID:19506660</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhRvA..90f2314D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhRvA..90f2314D"><span id="translatedtitle">Phase-noise limitations on single-photon cross-phase modulation with differing <span class="hlt">group</span> <span class="hlt">velocities</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dove, Justin; Chudzicki, Christopher; Shapiro, Jeffrey H.</p> <p>2014-12-01</p> <p>A framework is established for evaluating cphase gates that use single-photon cross-phase modulation (XPM) originating from the Kerr nonlinearity. Prior work [J. H. Shapiro, Phys. Rev. A 73, 062305 (2006), 10.1103/PhysRevA.73.062305], which assumed that the control and target pulses propagated at the same <span class="hlt">group</span> <span class="hlt">velocity</span>, showed that the causality-induced phase noise required by a noninstantaneous XPM response function precluded the possibility of high-fidelity π -radian conditional phase shifts. The framework presented herein incorporates the more realistic case of <span class="hlt">group-velocity</span> disparity between the control and target pulses, as employed in existing XPM-based fiber-optical switches. Nevertheless, the causality-induced phase noise identified by Shapiro [J. H. Shapiro, Phys. Rev. A 73, 062305 (2006), 10.1103/PhysRevA.73.062305] still rules out high-fidelity π -radian conditional phase shifts. This is shown to be so for both a reasonable theoretical model for the XPM response function and for the experimentally measured XPM response function of silica-core fiber.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/20707442','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/20707442"><span id="translatedtitle">Estimation of modal <span class="hlt">group</span> <span class="hlt">velocities</span> with a single receiver for geoacoustic inversion in shallow water.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bonnel, Julien; Nicolas, Barbara; Mars, Jérome I; Walker, Shane C</p> <p>2010-08-01</p> <p>Due to the expense associated with at-sea sensor deployments, a challenge in underwater acoustics has been to develop methods requiring a minimal number of sensors. This paper introduces an adaptive time-frequency signal processing method designed for application to a single source-receiver sensor pair. The method involves the application of conjugate time-frequency warping transforms to improve the SNR and resolution of the time-frequency distribution (TFD) of the measured field. Such refined knowledge of the TFD facilitates efforts to extract tomographic information about the propagation medium. Here the method is applied to the case of modal propagation in a shallow ocean range independent environment to extract a refined TFD. Given knowledge of the source-receiver separation, the refined TFD is used to extract the frequency dependent <span class="hlt">group</span> <span class="hlt">velocities</span> of the individual modal components. The extracted <span class="hlt">group</span> <span class="hlt">velocities</span> are then incorporated into a computationally light tomographic inversion method. Simulated and experimental results are discussed. PMID:20707442</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000AAS...196.2809G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000AAS...196.2809G"><span id="translatedtitle">Are Compact High-<span class="hlt">Velocity</span> Clouds The Missing Local <span class="hlt">Group</span> Satellites?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grebel, E. K.; Braun, R.; Burton, W. B.</p> <p>2000-05-01</p> <p>In contrast to high-<span class="hlt">velocity</span> cloud complexes, isolated compact high-<span class="hlt">velocity</span> clouds (CHVCs) are plausibly at distances of 0.5 to 1 Mpc, show infall motion with respect to the Local <span class="hlt">Group</span> barycenter, are rotationally supported and dark-matter dominated. Are CHVCs the missing Local <span class="hlt">Group</span> satellites predicted by hierarchical clustering scenarios? Are they proto-galactic gas clouds or do they contain stars as well? A failure to detect stars would be a very interesting result in itself: the first discovery of pure HI/dark matter halos prior to star formation, i.e., the most basic of galaxy building blocks. A detection of stars will help to refine the HI distances, augment the faint end of the galaxy luminosity function, and open the way to the study of the stellar populations of a new, very dark type of dwarf galaxy. We present results from a targeted multi-color survey for stars in radio-preselected CHVCs with the Mosaic imagers at NOAO. Our findings seem to indicate the detection of the red giant branch of an old stellar population, but contamination by distant starburst galaxies plays a role as well.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=55078&keyword=seismic+AND+tomography&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=67184562&CFTOKEN=25351295','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=55078&keyword=seismic+AND+tomography&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=67184562&CFTOKEN=25351295"><span id="translatedtitle">SUBSEQUENT FINAL REPORT. SEISMIC SURFACE-WAVE <span class="hlt">TOMOGRAPHY</span> OF WASTE SITES</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>Surface-wave <span class="hlt">group-velocity</span> <span class="hlt">tomography</span> is an efficient way to obtain images of the <span class="hlt">group</span> <span class="hlt">velocity</span> over a test area. Because Rayleigh-wave <span class="hlt">group</span> <span class="hlt">velocity</span> depends on frequency, there are separate images for each frequency. Thus, at each point in these images the <span class="hlt">group</span> <span class="hlt">velocities</span> de...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016OptCo.363...31V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016OptCo.363...31V"><span id="translatedtitle"><span class="hlt">Group</span> <span class="hlt">velocity</span> dispersion of CdSSe/ZnS core-shell colloidal quantum dots measured with white light interferometry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>VanEngen Spivey, Amelia G.</p> <p>2016-03-01</p> <p>We measure the <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion coefficient of CdSSe/ZnS core-shell colloidal quantum dots in liquid suspension in the ∼700-900 nm wavelength range using a white-light Michelson interferometer. Two different sizes of dots are investigated. In both cases, the <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion coefficient decreases with increasing wavelength above the absorption edge in the dots. For quantum dots in which the linear absorption spectrum shows clear peaks, the absorption characteristics of the dots can be used to accurately model the wavelength-dependence of the <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion coefficient.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JOpt...17f5612M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JOpt...17f5612M"><span id="translatedtitle">Phase and <span class="hlt">group</span> <span class="hlt">velocity</span> of focused, pulsed Gaussian beams in the presence and absence of primary aberrations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Major, Balázs; Horváth, Zoltán L.; Porras, Miguel A.</p> <p>2015-06-01</p> <p>This work presents a study on the phase- and <span class="hlt">group-velocity</span> variations of focused, pulsed Gaussian beams during the propagation through the focal region along the optical axis. In the aberration-free case, it is discussed how the wavelength dependence of beam properties alters the <span class="hlt">group</span> <span class="hlt">velocity</span>, and how a chromatic aberration-like effect can arise even when focusing is performed with an element that does not have chromatic aberration. It is also examined what effects primary spherical aberration, astigmatism, coma, curvature of field and distortion, along with chromatic aberration, have on the phase- and <span class="hlt">group-velocity</span> changes occurring during propagation through focus.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.S41B2727K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.S41B2727K&link_type=ABSTRACT"><span id="translatedtitle">A 3D Seismic <span class="hlt">Velocity</span> Model Offshore Southern California from Ambient Noise <span class="hlt">Tomography</span> of the ALBACORE OBS Array</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kohler, M. D.; Bowden, D. C.; Tsai, V. C.; Weeraratne, D. S.</p> <p>2015-12-01</p> <p>The Pacific-North America plate boundary in Southern California extends far west of the coastline, and a 12-month ocean bottom seismometer (OBS) array spanned the western side of the plate boundary to image lithospheric seismic <span class="hlt">velocities</span>. <span class="hlt">Velocities</span> are modeled through stacked cross correlations of ambient noise data. Twelve months of continuous data were used from 22 OBS stations and ~30 coastal and island Southern California Seismic Network stations. Particular attention has been paid to improving signal-to-noise ratios in the noise correlations with OBS stations by removing the effects of instrument tilt and infragravity waves. Different applications of preprocessing techniques allow us to distinguish the fundamental and first higher order Rayleigh modes, especially in deep water OBS pairs where the water layer dominates crustal sensitivity of the fundamental mode. Standard time domain and frequency domain methods are used to examine surface wave dispersion curves for <span class="hlt">group</span> and phase <span class="hlt">velocities</span> between 5 and 50 second periods, and these are inverted for 3D <span class="hlt">velocity</span> structure. The results define the transition in three dimensions from continental lithospheric structure in the near-shore region to oceanic structure west of the continental borderland. While the most prominent features of the model relate to thinning of the crust west of the Patton Escarpment, other notable anomalies are present north-to-south throughout the continental borderland and along the coast from the Los Angeles Basin to the Peninsular Ranges. The <span class="hlt">velocity</span> model will help describe the region's tectonic history, as well as provide new constraints for determination of earthquake relocations and rupture styles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3677104','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3677104"><span id="translatedtitle">Quantitative imaging of cerebral blood flow <span class="hlt">velocity</span> and intracellular motility using dynamic light scattering–optical coherence <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lee, Jonghwan; Radhakrishnan, Harsha; Wu, Weicheng; Daneshmand, Ali; Climov, Mihail; Ayata, Cenk; Boas, David A</p> <p>2013-01-01</p> <p>This paper describes a novel optical method for label-free quantitative imaging of cerebral blood flow (CBF) and intracellular motility (IM) in the rodent cerebral cortex. This method is based on a technique that integrates dynamic light scattering (DLS) and optical coherence <span class="hlt">tomography</span> (OCT), named DLS–OCT. The technique measures both the axial and transverse <span class="hlt">velocities</span> of CBF, whereas conventional Doppler OCT measures only the axial one. In addition, the technique produces a three-dimensional map of the diffusion coefficient quantifying nontranslational motions. In the DLS–OCT diffusion map, we observed high-diffusion spots, whose locations highly correspond to neuronal cell bodies and whose diffusion coefficient agreed with that of the motion of intracellular organelles reported in vitro in the literature. Therefore, the present method has enabled, for the first time to our knowledge, label-free imaging of the diffusion-like motion of intracellular organelles in vivo. As an example application, we used the method to monitor CBF and IM during a brief ischemic stroke, where we observed an induced persistent reduction in IM despite the recovery of CBF after stroke. This result supports that the IM measured in this study represent the cellular energy metabolism-related active motion of intracellular organelles rather than free diffusion of intracellular macromolecules. PMID:23403378</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.T33D2690H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.T33D2690H"><span id="translatedtitle">Spatial variation and azimuthal anisotropy of the Rayleigh phase <span class="hlt">velocity</span> beneath Northeast China revealed by ambient noise eikonal <span class="hlt">tomography</span>: results and implications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Han, J.; Ning, J.; Chen, Y. J.; Niu, F.; Grand, S.; Kawakatsu, H.; Tanaka, S.; Obayashi, M.; Ni, J. F.</p> <p>2012-12-01</p> <p>Northeast China consists of Songliao Basin in its center, the Great Xing'an Range to the west, the Changbaishan volcano to the east and the Archean Sino-Korean Craton to the south. Although it is generally believed that the evolution of the Songliao Basin and the Cenozoic volcanism in NE China are somehow related to the Pacific plate subduction beneath the area, there are no concrete geodynamical explanations of the genesis of the volcanism. Detailed seismic images are needed to understand the deep structures. We conducted a high-resolution Rayleigh wave <span class="hlt">tomography</span> to study the crustal <span class="hlt">velocity</span> and azimuthal anisotropy beneath NE China. We used continuous broadband records of the 120 NECESSArray stations and 266 CEA stations in NE China to construct Green's functions of ray paths between station pairs. We employed the Eikonal <span class="hlt">tomography</span> method developed by Lin et al. (2009) to invert phase <span class="hlt">velocities</span> in the area. At short periods, isotropic <span class="hlt">velocity</span> is clearly correlated with the tectonic units. Songliao basin is characterized with very low <span class="hlt">velocity</span>, while most mountain belts show relatively higher <span class="hlt">velocity</span> except some sporadically distributed small low <span class="hlt">velocity</span> zones to the east of the Dunhua-Mishan fault. As period increases, those sporadically distributed small low <span class="hlt">velocity</span> zones gradually grow larger into several scattered low <span class="hlt">velocity</span> fingers, northwestward. At period of 40 s, those scattered low <span class="hlt">velocity</span> fingers expand into a singular wide low <span class="hlt">velocity</span> anomaly and the image clearly shows the low <span class="hlt">velocity</span> zone beneath the Songliao Basin. This large feature is located around Tanlu fault, Yilan-Yitong fault and Dunhua-Mishan fault and suggests that these faults penetrate through the lithosphere and possibly form the conduits for melting materials. To the west of the Great Xing'an Range, there is another large deep low <span class="hlt">velocity</span> zone. Edge-driven small-scale convection process may be operating beneath the boundary between the hot and cold mantle and causing</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70025993','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70025993"><span id="translatedtitle">Surface wave <span class="hlt">tomography</span> of North America and the Caribbean using global and regional broad-band networks: Phase <span class="hlt">velocity</span> maps and limitations of ray theory</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Godey, S.; Snieder, R.; Villasenor, A.; Benz, H.M.</p> <p>2003-01-01</p> <p>We present phase <span class="hlt">velocity</span> maps of fundamental mode Rayleigh waves across the North American and Caribbean plates. Our data set consists of 1846 waveforms from 172 events recorded at 91 broad-band stations operating in North America. We compute phase <span class="hlt">velocity</span> maps in four narrow period bands between 50 and 150 s using a non-linear waveform inversion method that solves for phase <span class="hlt">velocity</span> perturbations relative to a reference Earth model (PREM). Our results show a strong <span class="hlt">velocity</span> contrast between high <span class="hlt">velocities</span> beneath the stable North American craton, and lower <span class="hlt">velocities</span> in the tectonically active western margin, in agreement with other regional and global surface wave <span class="hlt">tomography</span> studies. We perform detailed comparisons with global model results, which display good agreement between phase <span class="hlt">velocity</span> maps in the location and amplitude of the anomalies. However, forward modelling shows that regional maps are more accurate for predicting waveforms. In addition, at long periods, the amplitude of the <span class="hlt">velocity</span> anomalies imaged in our regional phase <span class="hlt">velocity</span> maps is three time larger than in global phase <span class="hlt">velocity</span> models. This amplitude factor is necessary to explain the data accurately, showing that regional models provide a better image of <span class="hlt">velocity</span> structures. Synthetic tests show that the raypath coverage used in this study enables one to resolve <span class="hlt">velocity</span> features of the order of 800-1000 km. However, only larger length-scale features are observed in the phase <span class="hlt">velocity</span> maps. The limitation in resolution of our maps can be attributed to the wave propagation theory used in the inversion. Ray theory does not account for off-great-circle ray propagation effects, such as ray bending or scattering. For wavelengths less than 1000 km, scattering effects are significant and may need to be considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..18.8180K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..18.8180K&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Group</span> and phase <span class="hlt">velocities</span> from deterministic and ambient sources measured during the AlpArray-EASI experiment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kolínský, Petr; Zigone, Dimitri; Fuchs, Florian; Bianchi, Irene; Qorbani, Ehsan; Apoloner, Maria-Theresia; Bokelmann, Götz; AlpArray-EASI Working Group</p> <p>2016-04-01</p> <p>The Eastern Alpine Seismic Investigation (EASI) was a complementary experiment to the AlpArray project. EASI was composed of 55 broadband seismic stations deployed in a winding swath of 540 km length along longitude 13.350 E from the Czech-German border to the Adriatic Sea. Average north-south inter-station distance was 10 km, the distance of each station to either side of the central line was 6 km. Such a dense linear network allows for surface wave dispersion measurements by both deterministic and ambient noise sources along the same paths. During the experiment (July 2014 - August 2015), three earthquakes ML = 2.6, 2.9 and 4.2 occurred in Austria and Northern Italy only several kilometers off the swath. We measure Rayleigh and Love wave <span class="hlt">group</span> <span class="hlt">velocities</span> between the source and a single station for the recorded earthquakes, as well as phase <span class="hlt">velocities</span> between selected pairs of stations using the standard two-station method. We also calculate cross-correlations of ambient noise between selected pairs of stations and we determine the corresponding <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion curves. We propose a comparison of phase <span class="hlt">velocities</span> between two stations measured from earthquakes with <span class="hlt">group</span> <span class="hlt">velocities</span> obtained from cross-correlations for the same station pairs. We also compare <span class="hlt">group</span> <span class="hlt">velocities</span> measured at single station using earthquakes, which occurred along the swath, with <span class="hlt">group</span> <span class="hlt">velocities</span> measured from cross-correlations. That way we analyze <span class="hlt">velocities</span> of both deterministic and ambient noise reconstructed surface waves propagating along the same path. We invert the resulting dispersion curves for 1D shear wave <span class="hlt">velocity</span> profiles with depth and we compile a quasi-2D <span class="hlt">velocity</span> model along the EASI swath.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhyB..452...92A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhyB..452...92A"><span id="translatedtitle">Dynamical diffusion and renormalization <span class="hlt">group</span> equation for the Fermi <span class="hlt">velocity</span> in doped graphene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ardenghi, J. S.; Bechthold, P.; Jasen, P.; Gonzalez, E.; Juan, A.</p> <p>2014-11-01</p> <p>The aim of this work is to study the electron transport in graphene with impurities by introducing a generalization of linear response theory for linear dispersion relations and spinor wave functions. Current response and density response functions are derived and computed in the Boltzmann limit showing that in the former case a minimum conductivity appears in the no-disorder limit. In turn, from the generalization of both functions, an exact relation can be obtained that relates both. Combining this result with the relation given by the continuity equation it is possible to obtain general functional behavior of the diffusion pole. Finally, a dynamical diffusion is computed in the quasistatic limit using the definition of relaxation function. A lower cutoff must be introduced to regularize infrared divergences which allow us to obtain a full renormalization <span class="hlt">group</span> equation for the Fermi <span class="hlt">velocity</span>, which is solved up to order O(ℏ2).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApPhL.105b1605M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApPhL.105b1605M"><span id="translatedtitle">Non contact probing of interfacial stiffnesses between two plates by zero-<span class="hlt">group</span> <span class="hlt">velocity</span> Lamb modes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mezil, Sylvain; Laurent, Jérôme; Royer, Daniel; Prada, Claire</p> <p>2014-07-01</p> <p>A non contact technique using zero-<span class="hlt">group</span> <span class="hlt">velocity</span> (ZGV) Lamb modes is developed to probe the bonding between two solid plates coupled by a thin layer. The layer thickness is assumed to be negligible compared with the plate thickness and the acoustic wavelength. The coupling layer is modeled by a normal and a tangential spring to take into account the normal and shear interfacial stresses. Theoretical ZGV frequencies are determined for a symmetrical bi-layer structure and the effect of the interfacial stiffnesses on the cut-off and ZGV frequencies are evaluated. Experiments are conducted with two glass plates bonded by a drop of water, oil, or salol, leading to a few micrometer thick layer. An evaluation of normal and shear stiffnesses is obtained using ZGV resonances locally excited and detected with laser ultrasonic techniques.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhyU...55.1239L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhyU...55.1239L"><span id="translatedtitle">Angular beam width of a slit-diffracted wave with noncollinear <span class="hlt">group</span> and phase <span class="hlt">velocities</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lock, Edwin H.</p> <p>2012-12-01</p> <p>Taking magnetostatic surface wave diffraction as an example, this paper theoretically investigates the 2D diffraction pattern arising in the far-field region of a ferrite slab in the case of a plane wave with noncollinear <span class="hlt">group</span> and phase <span class="hlt">velocities</span> incident on a wide, arbitrarily oriented slit in an opaque screen. A universal analytical formula for the angular width of a diffracted beam is derived, which is valid for magnetostatic and other types of waves in anisotropic media and structures (including metamaterials) in 2D geometries. It is shown that the angular width of a diffracted beam in an anisotropic medium can not only take values greater or less than \\lambda _0/D (where \\lambda _0 is the incident wavelength, and D is the slit width), but can also be zero under certain conditions.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUSMSM32A..06S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUSMSM32A..06S"><span id="translatedtitle">Fast Reconnection Rates Based on <span class="hlt">Group</span> <span class="hlt">Velocity</span> Cones: Whistler Regime and Pair Plasmas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Singh, N.</p> <p>2009-05-01</p> <p>Based on the <span class="hlt">group</span> <span class="hlt">velocity</span> vector of the whistler mode, we predict the range of whistler-regime reconnection rate depending on the half width (w) of the current sheet (CS. During the reconnection process electromagnetic perturbations (EMPs) are generated in the localized diffusion region (DR, which acts like an antenna and radiates whistler waves for certain range of CS widths. The reconnection structure (exhaust) is approximately the radiation pattern of the DR antenna and it is determined by the <span class="hlt">group</span> <span class="hlt">velocity</span> directions. Since the whistler waves originate from the electromagnetic perturbations (EMPs) localized in the DR, we calculate R over a range of the discrete values of the perpendicular wave number (k'') contained in the Fourier spectrum of the EMPs. We have used such calculations to determine the reconnection rates <R> averaged over the wave number spectrum of a Gaussian shaped EMP as a function of the CS width. We find that <R> has a fairly constant value at <R> ˜ 0.23 for CS widths in the range 0.4 < w/di ˜ 1 and for w < 0.3di it decreases with decreasing w and it attains a value <R> ˜ 0.06 in an extremely thin CS with w ˜ 0.05di, where di is the ion skin depth. We compare the values of <R> and R with those found from simulations and experiments, and find them in good agreement. We also report the properties of the whistler waves radiated from the DR into the exhaust region. We also demonstrate that our theoretical method developed for whistler regime reconnection could be easily adopted to predict fast reconnection rates in pair plasmas, which support inertial Alfven waves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26473520','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26473520"><span id="translatedtitle">Swimming Training Assessment: The Critical <span class="hlt">Velocity</span> and the 400-m Test for Age-<span class="hlt">Group</span> Swimmers.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zacca, Rodrigo; Fernandes, Ricardo Jorge P; Pyne, David B; Castro, Flávio Antônio de S</p> <p>2016-05-01</p> <p>Zacca, R, Fernandes, RJP, Pyne, DB, and Castro, FAdS. Swimming training assessment: the critical <span class="hlt">velocity</span> and the 400-m test for age-<span class="hlt">group</span> swimmers. J Strength Cond Res 30(5): 1365-1372, 2016-To verify the metabolic responses of oxygen consumption (V[Combining Dot Above]O2), heart rate (HR), blood lactate concentrations [La], and rate of perceived exertion (RPE) when swimming at an intensity corresponding to the critical <span class="hlt">velocity</span> (CV) assessed by a 4-parameter model (CV4par), and to check the reliability when using only a single 400-m maximal front crawl bout (T400) for CV4par assessment in age-<span class="hlt">group</span> swimmers. Ten age-<span class="hlt">group</span> swimmers (14-16 years old) performed 50-, 100-, 200-, 400- (T400), 800-, and 1,500-m maximal front crawl bouts to calculate CV4par. V[Combining Dot Above]O2, HR, [La], and RPE were measured immediately after bouts. Swimmers then performed 3 × 10-minute front crawl (45 seconds rest) at CV4par. V[Combining Dot Above]O2, HR, [La], and RPE were measured after 10 minutes of rest (Rest), warm-up (Pre), each 10-minute repetition, and at the end of the test (Post). CV4par was 1.33 ± 0.08 m·s. V[Combining Dot Above]O2, HR, [La], and RPE were similar between first 10-minute and Post time points in the 3 × 10-minute protocol. CV4par was equivalent to 92 ± 2% of the mean swimming speed of T400 (v400) for these swimmers. CV4par calculated through a single T400 (92%v400) showed excellent agreement (r = 0.30; 95% CI: -0.04 to 0.05 m·s, p = 0.39), low coefficient of variation (2%), and root mean square error of 0.02 ± 0.01 m·s when plotted against CV4par assessed through a 4-parameter model. These results generated the equation CV4par = 0.92 × v400. A single T400 can be used reliably to estimate the CV4par typically derived with 6 efforts in age-<span class="hlt">group</span> swimmers. PMID:26473520</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27410366','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27410366"><span id="translatedtitle">Design of chirped distributed Bragg reflector for octave-spanning frequency <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion compensation in terahertz quantum cascade laser.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Xu, Chao; Ban, Dayan</p> <p>2016-06-13</p> <p>The strategies and approaches of designing chirped Distributed Bragg Reflector for <span class="hlt">group</span> <span class="hlt">velocity</span> compensation in metal-metal waveguide terahertz quantum cascade laser are investigated through 1D and 3D models. The results show the depth of the corrugation periods plays an important role on achieving broad-band <span class="hlt">group</span> <span class="hlt">velocity</span> compensation in terahertz range. However, the deep corrugation also brings distortion to the <span class="hlt">group</span> delay behavior. A two-section chirped DBR is proposed to provide smoother <span class="hlt">group</span> delay compensation while still maintain the broad frequency range (octave) operation within 2 THz to 4 THz. PMID:27410366</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.S42B..02B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.S42B..02B"><span id="translatedtitle">Three-Dimensional Seismic <span class="hlt">Velocity</span> Structure in a High-Injection Region in The Northwest Geysers, California, from Standard and Double-Difference Seismic <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boyle, K. L.; Jarpe, S.</p> <p>2011-12-01</p> <p>The Northwest Geysers contains some of the highest-volume injection and production wells in the Geysers geothermal field. These wells coincide spatially with dense clusters of microseismicity with exception of a sub-region central to several injectors which has shown lower rates of seismicity over the past 10 years. This low-seismicity region is underlain by a cluster of deep seismicity extending up to 4.2km below sea level (b.s.l.). The low-seismicity region has been imaged to 610 m resolution using passive-source 3D seismic <span class="hlt">tomography</span> and co-location of hypocenters. The results indicate a low-<span class="hlt">velocity</span> (2.9 km/s) anomaly that extends from the surface to approximately 1.5km b.s.l. in both P- and S- <span class="hlt">velocity</span> models. It lies just above and to the Northwest of the low-seismicity region. The high-injection/production region is bounded on the southeast by higher <span class="hlt">velocities</span> (range 4.0 km/s to 5.3 km/s), although it is dominated by <span class="hlt">velocities</span> in the 3.8 km/s range. The low-<span class="hlt">velocity</span> feature persists over our 5-year study period from 2005 to 2010, but appears to diminish spatially in 2010. Mean <span class="hlt">velocity</span> values vary nominally from year to year, as do the extent of high and low <span class="hlt">velocity</span> regions, but it is yet unknown whether this effect is temporal, an artifact of topography, or related to differences in data quality during different monitoring periods. The the low-<span class="hlt">velocity</span> feature is being confirmed and re-imaged using double-difference <span class="hlt">tomography</span> with a node-spacing of 150 m, and the feature's evolution over time will be correlated with injection and production rates in the surrounding area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21301438','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21301438"><span id="translatedtitle">ARE NEWLY DISCOVERED H I HIGH-<span class="hlt">VELOCITY</span> CLOUDS MINIHALOS IN THE LOCAL <span class="hlt">GROUP</span>?</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Giovanelli, Riccardo; Haynes, Martha P.; Adams, Elizabeth A. K.; Kent, Brian R. E-mail: haynes@astro.cornell.edu E-mail: bkent@nrao.edu</p> <p>2010-01-01</p> <p>A set of H I sources extracted from the north Galactic polar region by the ongoing ALFALFA survey has properties that are consistent with the interpretation that they are associated with isolated minihalos in the outskirts of the Local <span class="hlt">Group</span> (LG). Unlike objects detected by previous surveys, such as the compact high-<span class="hlt">velocity</span> clouds of Braun and Burton, the H I clouds found by ALFALFA do not violate any structural requirements or halo scaling laws of the {lambda}CDM structure paradigm, nor would they have been detected by extant H I surveys of nearby galaxy <span class="hlt">groups</span> other than the LG. At a distance of d Mpc, their H I masses range between 5 x 10{sup 4} d {sup 2} and 10{sup 6} d {sup 2} M {sub sun} and their H I radii between <0.4d and 1.6d kpc. If they are parts of gravitationally bound halos, the total masses would be on the order of 10{sup 8}-10{sup 9} M {sub sun}, their baryonic content would be significantly smaller than the cosmic fraction of 0.16 and present in a ionized gas phase of mass well exceeding that of the neutral phase. This study does not however prove that the minihalo interpretation is unique. Among possible alternatives would be that the clouds are shreds of the Leading Arm of the Magellanic Stream.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016SPIE.9719E..0OB&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016SPIE.9719E..0OB&link_type=ABSTRACT"><span id="translatedtitle">Label-free in-vivo measurement of lymph flow <span class="hlt">velocity</span> using Doppler optical coherence <span class="hlt">tomography</span> (Conference Presentation)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Blatter, Cedric; Meijer, Eelco F. J.; Nam, Ahhyun S.; Jones, Dennis; Padera, Timothy P.; Vakoc, Benjamin J.</p> <p>2016-03-01</p> <p>Alterations in lymphatic network function contribute to the lymphedema development, cancer progression and impairment in regional immune function. However, there are limited tools available to directly measure lymphatic vessel function and transport in vivo. Existing approaches such as fluorescence recovery after photo-bleaching (FRAP) require injection of exogenous labels which intrinsically alter the physiology of the local lymphatic network. A label-free approach to imaging lymph flow in vivo would provide direct and unaltered measurements of lymphatic vessel transport and could catalyze research in lymphatic biology. Here, we demonstrate and validate the use of Doppler optical coherence <span class="hlt">tomography</span> (DOCT) to measure lymph flow in vivo at speeds as low as 50µm/s. Compared to blood, lymph is relatively acellular (under normal conditions), but contains similar soluble components to blood plasma. We demonstrate that the small but detectable scattering signal from lymph can be used to extract fluid <span class="hlt">velocity</span> using a dedicated algorithm optimized for Doppler analysis in low signal-to-noise settings (0 to 6 dB typical). We demonstrate the accuracy of this technique by comparing DOCT to FRAP measurements, using an intralipid lymph proxy in microfluidic devices and in vivo in the mouse ear. Finally, we demonstrate the label free measurement of lymph speed in the hind-limb of mice with a temporal resolution of 0.25s that agree well with prior literature reports. We anticipate that DOCT can become a powerful new tool in preclinical lymphatic biology research—including the relationship between lymphatic function and metastasis formation—with the potential to later expand also to clinical settings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016OptCo.371..196I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016OptCo.371..196I"><span id="translatedtitle">Dependence of light pulse propagation on its temporal width: Transition from <span class="hlt">group</span> <span class="hlt">velocity</span> to c-propagation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ignesti, Emilio; Tommasi, Federico; Fini, Lorenzo; Cavalieri, Stefano</p> <p>2016-07-01</p> <p>We show how the <span class="hlt">velocity</span> of an optical pulse propagating through a dispersive medium depends on the pulse duration. A transition from the <span class="hlt">group</span> <span class="hlt">velocity</span> for long pulses to the in-vacuum <span class="hlt">velocity</span> for short pulses is shown both in experimental results and in theoretical predictions. The temporal duration of the experimental pulses are 150 ps and 3.5 ns. A description of the pulse propagation in terms of the time "center of mass" of the energy flow allows an intuitive overview of the results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4882591','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4882591"><span id="translatedtitle">Subluminal <span class="hlt">group</span> <span class="hlt">velocity</span> and dispersion of Laguerre Gauss beams in free space</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bareza, Nestor D.; Hermosa, Nathaniel</p> <p>2016-01-01</p> <p>That the speed of light in free space c is constant has been a pillar of modern physics since the derivation of Maxwell and in Einstein’s postulate in special relativity. This has been a basic assumption in light’s various applications. However, a physical beam of light has a finite extent such that even in free space it is by nature dispersive. The field confinement changes its wavevector, hence, altering the light’s <span class="hlt">group</span> <span class="hlt">velocity</span> vg. Here, we report the subluminal vg and consequently the dispersion in free space of Laguerre-Gauss (LG) beam, a beam known to carry orbital angular momentum. The vg of LG beam, calculated in the paraxial regime, is observed to be inversely proportional to the beam’s divergence θ0, the orbital order ℓ and the radial order p. LG beams of higher orders travel relatively slower than that of lower orders. As a consequence, LG beams of different orders separate in the temporal domain along propagation. This is an added effect to the dispersion due to field confinement. Our results are useful for treating information embedded in LG beams from astronomical sources and/or data transmission in free space. PMID:27231195</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015OptCo.353...96M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015OptCo.353...96M&link_type=ABSTRACT"><span id="translatedtitle">Generation of tunable ultrafast ultraviolet third harmonic by collinear compensation of <span class="hlt">group-velocity</span> mismatch</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meng, Xianghao; Liu, Huagang; Huang, Jianhong; Wu, Hongchun; Deng, Jing; Dai, Shutao; Weng, Wen; Lin, Wenxiong</p> <p>2015-10-01</p> <p>We demonstrate a high efficient frequency tripling configuration of Ti: sapphire amplifier system for wavelength-tunable ultrafast ultraviolet laser generation. A new nonlinear crystal Ba1-xB2-y-zO4SixAlyGaz and a type-II phase-matched β-BaB2O4 crystal are employed for the second and the third harmonic generation, respectively. Significant improvement in conversion efficiency of frequency tripling is achieved by using a 65°-cut, 3-mm-long β-BaB2O4 crystal as the collinear <span class="hlt">group</span> <span class="hlt">velocity</span> compensation plate. Tunable ultraviolet pulse within the wavelength range from 256.7 to 276.7 nm have been produced, with a maximum average power of 212 mW, corresponding to a conversion efficiency of 8.48% for the third harmonic generation with 2.5 W fundamental power. The maximum pulse energy of the third harmonic is up to 0.21 mJ and it is estimated that the peak power is above 1 GW at 266.7 nm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008PhRvE..78a1117D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008PhRvE..78a1117D&link_type=ABSTRACT"><span id="translatedtitle">Transport in a Lévy ratchet: <span class="hlt">Group</span> <span class="hlt">velocity</span> and distribution spread</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dybiec, B.; Gudowska-Nowak, E.; Sokolov, I. M.</p> <p>2008-07-01</p> <p>We consider the motion of an overdamped particle in a periodic potential lacking spatial symmetry under the influence of symmetric, white, Lévy noise, being a minimal setup for a “Lévy ratchet.” Due to the nonthermal character of the Lévy noise, the particle exhibits a motion with a preferred direction even in the absence of whatever additional time-dependent forces. The examination of the Lévy ratchet has to be based on the characteristics of directionality which are different from typically used measures such as mean current and the dispersion of particle positions, since these become inappropriate when the moments of the noise diverge. To overcome this problem, we discuss robust measures of directionality of transport such as the position of the median of the particle displacement distribution characterizing the <span class="hlt">group</span> <span class="hlt">velocity</span> and the interquantile distance giving the measure of the distribution width. Moreover, we analyze the behavior of splitting probabilities for leaving an interval of a given length, unveiling qualitative differences between the noises with Lévy indices below and above unity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27231195','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27231195"><span id="translatedtitle">Subluminal <span class="hlt">group</span> <span class="hlt">velocity</span> and dispersion of Laguerre Gauss beams in free space.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bareza, Nestor D; Hermosa, Nathaniel</p> <p>2016-01-01</p> <p>That the speed of light in free space c is constant has been a pillar of modern physics since the derivation of Maxwell and in Einstein's postulate in special relativity. This has been a basic assumption in light's various applications. However, a physical beam of light has a finite extent such that even in free space it is by nature dispersive. The field confinement changes its wavevector, hence, altering the light's <span class="hlt">group</span> <span class="hlt">velocity</span> vg. Here, we report the subluminal vg and consequently the dispersion in free space of Laguerre-Gauss (LG) beam, a beam known to carry orbital angular momentum. The vg of LG beam, calculated in the paraxial regime, is observed to be inversely proportional to the beam's divergence θ0, the orbital order ℓ and the radial order p. LG beams of higher orders travel relatively slower than that of lower orders. As a consequence, LG beams of different orders separate in the temporal domain along propagation. This is an added effect to the dispersion due to field confinement. Our results are useful for treating information embedded in LG beams from astronomical sources and/or data transmission in free space. PMID:27231195</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016NatSR...626842B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016NatSR...626842B&link_type=ABSTRACT"><span id="translatedtitle">Subluminal <span class="hlt">group</span> <span class="hlt">velocity</span> and dispersion of Laguerre Gauss beams in free space</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bareza, Nestor D.; Hermosa, Nathaniel</p> <p>2016-05-01</p> <p>That the speed of light in free space c is constant has been a pillar of modern physics since the derivation of Maxwell and in Einstein’s postulate in special relativity. This has been a basic assumption in light’s various applications. However, a physical beam of light has a finite extent such that even in free space it is by nature dispersive. The field confinement changes its wavevector, hence, altering the light’s <span class="hlt">group</span> <span class="hlt">velocity</span> vg. Here, we report the subluminal vg and consequently the dispersion in free space of Laguerre-Gauss (LG) beam, a beam known to carry orbital angular momentum. The vg of LG beam, calculated in the paraxial regime, is observed to be inversely proportional to the beam’s divergence θ0, the orbital order ℓ and the radial order p. LG beams of higher orders travel relatively slower than that of lower orders. As a consequence, LG beams of different orders separate in the temporal domain along propagation. This is an added effect to the dispersion due to field confinement. Our results are useful for treating information embedded in LG beams from astronomical sources and/or data transmission in free space.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.S41A2350J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.S41A2350J"><span id="translatedtitle">Constraints on Crustal Shear Wave <span class="hlt">Velocity</span> Structure beneath Central Tibet from 3-D Multi-scale Finite-frequency Rayleigh Wave Travel-time <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jheng, Y.; Hung, S.; Zhou, Y.; Chang, Y.</p> <p>2012-12-01</p> <p>Surface wave travel-time <span class="hlt">tomography</span> has been widely used as a powerful strategy to image shear wave <span class="hlt">velocity</span> structure of the Earth's crust and upper mantle, providing comparable information other than body wave <span class="hlt">tomography</span>. Traditionally, lateral variations of dispersive phase <span class="hlt">velocities</span> are first obtained at multiple frequencies and then used to invert for shear wave <span class="hlt">velocity</span> with 1-D depth-dependent sensitivity kernels. However, this approach runs short on considering the directional- and depth-dependence of scattering while surface wave propagating through laterally heterogeneous Earth. To refrain from these shortcomings, we here provide a fully 3-D finite-frequency method based on the Born scattering theory formulated with surface wave mode summation, and apply it to regional fundamental Rayleigh wave travel-time <span class="hlt">tomography</span> in central Tibet. Our data were collected from Project Hi-CLIMB, which deployed an N-S trending linear array of over 100 broadband seismic stations with a large aperture of 800 km and very dense spacing of ~3-8 km across the Lhasa and Qiangtang terranes during 2004-2005. We follow a standard procedure of ambient noise cross correlation to extract empirical Green's functions of fundamental Rayleigh waves at 10-33 s between station pairs. A multi-taper method is employed to measure the phase differences as a function of period between observed and synthetic Rayleigh waves as well as the corresponding sensitivity kernels for the measured phase delays to 3-D shear wave <span class="hlt">velocity</span> perturbations in a spherically-symmetric model suitable for central Tibet. A wavelet-based, multi-scale parameterization is invoked in the tomographic inversion to deal with the intrinsically multi-scale nature of unevenly distributed data and resolve the structure with data-adaptive spectral and spatial resolutions. The preliminary result shows that to the north of the Banggong-Nujiang suture (BNS), the crustal shear wave <span class="hlt">velocity</span> beneath the Qiangtang terrane is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24247747','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24247747"><span id="translatedtitle">In vitro and in vivo three-dimensional <span class="hlt">velocity</span> vector measurement by three-beam spectral-domain Doppler optical coherence <span class="hlt">tomography</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Trasischker, Wolfgang; Werkmeister, René M; Zotter, Stefan; Baumann, Bernhard; Torzicky, Teresa; Pircher, Michael; Hitzenberger, Christoph K</p> <p>2013-11-01</p> <p>We developed a three-beam Doppler optical coherence <span class="hlt">tomography</span> (OCT) system that enables measurement of the <span class="hlt">velocity</span> vector of moving particles in three-dimensions (3-D). The spatial orientation as well as the magnitude of motion can be determined without prior knowledge of the geometry of motion. The system combines three spectral-domain OCT interferometers whose sample beams are focused at the sample by a common focusing lens at three different angles. This provides three spatially independent <span class="hlt">velocity</span> components simultaneously from which the <span class="hlt">velocity</span> vector can be reconstructed. We demonstrate the system in a simple test object (rotating disc), a flow phantom, and for blood flow measurements in the retina of a healthy human subject. Measurements of blood flow at a venous bifurcation achieve a good agreement between in- and outflow and demonstrate the reliability of the method. PMID:24247747</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25836695','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25836695"><span id="translatedtitle">Patient <span class="hlt">grouping</span> for dose surveys and establishment of diagnostic reference levels in paediatric computed <span class="hlt">tomography</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vassileva, J; Rehani, M</p> <p>2015-07-01</p> <p>There has been confusion in literature on whether paediatric patients should be <span class="hlt">grouped</span> according to age, weight or other parameters when dealing with dose surveys. The present work aims to suggest a pragmatic approach to achieve reasonable accuracy for performing patient dose surveys in countries with limited resources. The analysis is based on a subset of data collected within the IAEA survey of paediatric computed <span class="hlt">tomography</span> (CT) doses, involving 82 CT facilities from 32 countries in Asia, Europe, Africa and Latin America. Data for 6115 patients were collected, in 34.5 % of which data for weight were available. The present study suggests that using four age <span class="hlt">groups</span>, <1, >1-5, >5-10 and >10-15 y, is realistic and pragmatic for dose surveys in less resourced countries and for the establishment of DRLs. To ensure relevant accuracy of results, data for >30 patients in a particular age <span class="hlt">group</span> should be collected if patient weight is not known. If a smaller sample is used, patient weight should be recorded and the median weight in the sample should be within 5-10 % from the median weight of the sample for which the DRLs were established. Comparison of results from different surveys should always be performed with caution, taking into consideration the way of <span class="hlt">grouping</span> of paediatric patients. Dose results can be corrected for differences in patient weight/age <span class="hlt">group</span>. PMID:25836695</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T11C2452Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T11C2452Y"><span id="translatedtitle">Upper-mantle <span class="hlt">velocity</span> models beneath the east Qingling orogenic belt from finite-frequency <span class="hlt">tomography</span> of a portable seismic array</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Y.; Chen, Y. J.; An, M.; Feng, Y.; Liang, X.; Dong, S.</p> <p>2013-12-01</p> <p>The east Qinling orogenic belt is located between the North China Craton and the South China Block, and is also at the northeastern boundary of Tibetan Plateau. A temporal seismic array of over 110 portable seismic stations was deployed by Peking University and the Chinese Academy of Geological Sciences (CAGS) from July 2011 to October 2013 to study the complex tectonics of this region. We used earthquake data recorded at 65 stations from this array between July 2011 and October 2012 to image the seismic <span class="hlt">velocity</span> variations of the region using finite-frequency <span class="hlt">tomography</span> method. The travel times used in the inversion contain 10876 P-waves and 5945 S-waves at 3 different frequencies. Preliminary results show that <span class="hlt">velocity</span> structures of P-waves and S-waves are quite similar. The upper mantle <span class="hlt">velocities</span> under the east Qinling orogenic belt are higher in general in the east than that in the west at depth around 80 km. A higher <span class="hlt">velocity</span> anomaly is observed under the southern Ordos plateau from 40 km to 360km deep and a low <span class="hlt">velocity</span> anomaly is seen beneath the Taihang uplift from the depth of 40km to the depth of 200km. These <span class="hlt">velocity</span> anomalies in the lithosphere and the upper mantle will be interpreted with the geologic observations and tectonic process of the region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT.......331A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT.......331A"><span id="translatedtitle">Multi-Scale Imaging of the Fault Zone <span class="hlt">Velocity</span> Structure: Double-difference <span class="hlt">Tomography</span>, Inversion of Fault Zone Headwaves, and Fault Zone Sensitivity Kernels</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Allam, Amir A.</p> <p></p> <p>In spite of the close relationship between fault zone structure and earthquake mechanics, fault zone structure at seismogenic depths remains poorly understood. How does localization of the primary slip zone vary with depth? Is there a signature of broad persistent damage zones at seismogenic depths? How does fault zone structure merge with regional structure? To answer these questions, we utilize multiple imaging techniques. We apply high-resolution double-difference <span class="hlt">tomography</span> to the San Jacinto fault zone, invert for <span class="hlt">velocity</span> structure along the Hayward fault using fault zone head waves, and use analytical results for idealized geometries to validate sensitivity kernels of fault zone phases for use in adjoint tomographic inversions. Double-difference <span class="hlt">tomography</span> uses the arrival times of P and S waves to invert simultaneously for compressional <span class="hlt">velocity</span>, shear wave <span class="hlt">velocity</span>, and source location in three dimensions. We present results in the southern California plate-boundary area, with a focus on the San Jacinto fault zone, which incorporate arrival times of 247,472 P- and 105,448 S-wave picks for 5493 earthquakes recorded at 139 stations. Starting with a layered 1D model, and continuing in later iterations with various updated initial models, we invert the data for Vp and Vs in a 270 km long, 105 km wide and 35 km deep volume using a spatially variable grid with higher density around the San Jacinto. Our final <span class="hlt">velocity</span> results show zones of low-<span class="hlt">velocity</span> and high Vp/Vs ratios associated with various fault strands and sedimentary basins, along with clear <span class="hlt">velocity</span> contrasts across the San Jacinto. While both features are limited to the upper 10km, the low <span class="hlt">velocity</span> zones generally have higher amplitude and broader distribution in geometrically complex areas, while the <span class="hlt">velocity</span> contrasts are more pronounced for Vp than Vs. Along the Hayward fault in the San Francisco Bay region, we identify fault zone head waves at eight stations on the northeastern side of the fault</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1175404','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1175404"><span id="translatedtitle">Dielectric waveguide with transverse index variation that support a zero <span class="hlt">group</span> <span class="hlt">velocity</span> mode at a non-zero longitudinal wavevector</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Ibanescu, Mihai; Joannopoious, John D.; Fink, Yoel; Johnson, Steven G.; Fan, Shanhui</p> <p>2005-06-21</p> <p>Optical components including a laser based on a dielectric waveguide extending along a waveguide axis and having a refractive index cross-section perpendicular to the waveguide axis, the refractive index cross-section supporting an electromagnetic mode having a zero <span class="hlt">group</span> <span class="hlt">velocity</span> for a non-zero wavevector along the waveguide axis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JAESc.115..273C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JAESc.115..273C"><span id="translatedtitle">Crustal S-wave structure beneath Eastern Black Sea Region revealed by Rayleigh-wave <span class="hlt">group</span> <span class="hlt">velocities</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Çınar, Hakan; Alkan, Hamdi</p> <p>2016-01-01</p> <p>In this study, the crustal S-wave structure beneath the Eastern Black Sea Region (including the Eastern Black Sea Basin (EBSB) and Eastern Pontides (EP)) has been revealed using inversion of single-station, fundamental-mode Rayleigh-wave <span class="hlt">group</span> <span class="hlt">velocities</span> in the period range of 4-40 seconds. We used digital broadband recordings of 13 regional earthquakes that recently occurred in the easternmost EBSB recorded at stations of the Kandilli Observatory and Earthquake Research Institute (KOERI). The average <span class="hlt">group-velocity</span>-dispersion curves were generated from 26 paths for the EBSB, and 16 paths for the EP, and they were inverted to determine the average 1-D shear-wave structure of the region. We have created a pseudo-section, roughly depicting the crustal structure of the region based on the <span class="hlt">group</span> <span class="hlt">velocity</span> inversion results of all station-earthquake paths. The thickness of the sedimentary layer reaches 12 km in the center of EBSB (Vs = 2.5-3.1 km/s) and decreases 4 km in the EP. There is a thin sedimentary layer in the EP (Vs = 2.7 km/s). A consolidated thin crust that exists in the EBSB possesses a high seismic <span class="hlt">velocity</span> (Vs = 3.8 km/s). While a thin (∼26 km) and transitional crust exists beneath the EBSB, a thick (about 42 km) continental crust exists beneath the EP where the Conrad is clearly seen at about a 24 km depth. Thick continental crust in the EP region is clearly distinguished from a gradational <span class="hlt">velocity</span> change (Vs = 3.4-3.8 km/s). The Moho dips approximately southwards, and the Vs <span class="hlt">velocity</span> (4.25-4.15 km/s) beneath the Moho discontinuity decreases from the EBSB to the EP in the N-S direction. This may be an indication of a southward subduction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26548467','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26548467"><span id="translatedtitle">[(18)F]-<span class="hlt">Group</span> 13 fluoride derivatives as radiotracers for positron emission <span class="hlt">tomography</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chansaenpak, Kantapat; Vabre, Boris; Gabbaï, François P</p> <p>2016-02-21</p> <p>The field of (18)F chemistry is rapidly expanding because of the use of this radionuclide in radiotracers for positron emission <span class="hlt">tomography</span> (PET). Until recently, most [(18)F]-radiotracers were generated by the direct attachment of (18)F to a carbon in the organic backbone of the radiotracer. The past decade has witnessed the emergence of a new strategy based on the formation of an (18)F-<span class="hlt">group</span> 13 element bond. This approach, which is rooted in the field of fluoride anion complexation/coordination chemistry, has led to the development of a remarkable family of boron, aluminium and gallium [(18)F]-fluoride anion complexing agents which can be conjugated with peptides and small molecules to generate disease specific PET radiotracers. This review is dedicated to the chemistry of these <span class="hlt">group</span> 13 [(18)F]-fluorides anion complexing agents and their use in PET. Some of the key fluoride-binding motifs covered in this review include the trifluoroborate unit bound to neutral or cationic electron deficient backbones, the BF2 unit of BODIPY dyes, and AlF or GaF3 units coordinated to multidentate Lewis basic ligands. In addition to describing how these moieties can be converted into their [(18)F]-analogs, this review also dicusses their incorporation into bioconjugates for application in PET. PMID:26548467</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016IJTP...55.2942Q&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016IJTP...55.2942Q&link_type=ABSTRACT"><span id="translatedtitle">Phase Control of <span class="hlt">Group</span> <span class="hlt">Velocity</span> in a Doppler-Broadened Λ-Type Three-Level System</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Qiu, Tian-Hui; Xie, Min</p> <p>2016-06-01</p> <p>We theoretically investigate the phase control role on the <span class="hlt">group</span> <span class="hlt">velocity</span> of a weak probe field in a Doppler-broadened Λ-type three-level atomic system with the spontaneously generated coherence effect enhanced by an incoherence pump. We find that the absorption-dispersion of the probe field behaves phase and Doppler broadening-dependent phenomena, and testify that the quite large <span class="hlt">group</span> index can be realized. The <span class="hlt">group</span> <span class="hlt">velocity</span> of the probe field can be switched from subluminal to superluminal or vice versa by modulating the relative phase of the two applied light fields. In contrast to the counterpropagating setting, the copropagating case is more suitable for the purpose considered in this paper due to the effectiveness of Doppler-free.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ApJ...753....8V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ApJ...753....8V"><span id="translatedtitle">The M31 <span class="hlt">Velocity</span> Vector. II. Radial Orbit toward the Milky Way and Implied Local <span class="hlt">Group</span> Mass</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>van der Marel, Roeland P.; Fardal, Mark; Besla, Gurtina; Beaton, Rachael L.; Sohn, Sangmo Tony; Anderson, Jay; Brown, Tom; Guhathakurta, Puragra</p> <p>2012-07-01</p> <p>We determine the <span class="hlt">velocity</span> vector of M31 with respect to the Milky Way and use this to constrain the mass of the Local <span class="hlt">Group</span>, based on Hubble Space Telescope proper-motion measurements of three fields presented in Paper I. We construct N-body models for M31 to correct the measurements for the contributions from stellar motions internal to M31. This yields an unbiased estimate for the M31 center-of-mass motion. We also estimate the center-of-mass motion independently, using the kinematics of satellite galaxies of M31 and the Local <span class="hlt">Group</span>, following previous work but with an expanded satellite sample. All estimates are mutually consistent, and imply a weighted average M31 heliocentric transverse <span class="hlt">velocity</span> of (vW , vN ) = (- 125.2 ± 30.8, -73.8 ± 28.4) km s-1. We correct for the reflex motion of the Sun using the most recent insights into the solar motion within the Milky Way, which imply a larger azimuthal <span class="hlt">velocity</span> than previously believed. This implies a radial <span class="hlt">velocity</span> of M31 with respect to the Milky Way of V rad, M31 = -109.3 ± 4.4 km s-1, and a tangential <span class="hlt">velocity</span> of V tan, M31 = 17.0 km s-1, with a 1σ confidence region of V tan, M31 <= 34.3 km s-1. Hence, the <span class="hlt">velocity</span> vector of M31 is statistically consistent with a radial (head-on collision) orbit toward the Milky Way. We revise prior estimates for the Local <span class="hlt">Group</span> timing mass, including corrections for cosmic bias and scatter, and obtain M LG ≡ M MW, vir + M M31, vir = (4.93 ± 1.63) × 1012 M ⊙. Summing known estimates for the individual masses of M31 and the Milky Way obtained from other dynamical methods yields smaller uncertainties. Bayesian combination of the different estimates demonstrates that the timing argument has too much (cosmic) scatter to help much in reducing uncertainties on the Local <span class="hlt">Group</span> mass, but its inclusion does tend to increase other estimates by ~10%. We derive a final estimate for the Local <span class="hlt">Group</span> mass from literature and new considerations of M LG = (3.17 ± 0.57) × 1012 M </p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22036965','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22036965"><span id="translatedtitle">THE M31 <span class="hlt">VELOCITY</span> VECTOR. II. RADIAL ORBIT TOWARD THE MILKY WAY AND IMPLIED LOCAL <span class="hlt">GROUP</span> MASS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Van der Marel, Roeland P.; Sohn, Sangmo Tony; Anderson, Jay; Brown, Tom; Fardal, Mark; Besla, Gurtina; Beaton, Rachael L.; Guhathakurta, Puragra</p> <p>2012-07-01</p> <p>We determine the <span class="hlt">velocity</span> vector of M31 with respect to the Milky Way and use this to constrain the mass of the Local <span class="hlt">Group</span>, based on Hubble Space Telescope proper-motion measurements of three fields presented in Paper I. We construct N-body models for M31 to correct the measurements for the contributions from stellar motions internal to M31. This yields an unbiased estimate for the M31 center-of-mass motion. We also estimate the center-of-mass motion independently, using the kinematics of satellite galaxies of M31 and the Local <span class="hlt">Group</span>, following previous work but with an expanded satellite sample. All estimates are mutually consistent, and imply a weighted average M31 heliocentric transverse <span class="hlt">velocity</span> of (v{sub W} , v{sub N} ) = (- 125.2 {+-} 30.8, -73.8 {+-} 28.4) km s{sup -1}. We correct for the reflex motion of the Sun using the most recent insights into the solar motion within the Milky Way, which imply a larger azimuthal <span class="hlt">velocity</span> than previously believed. This implies a radial <span class="hlt">velocity</span> of M31 with respect to the Milky Way of V{sub rad,M31} = -109.3 {+-} 4.4 km s{sup -1}, and a tangential <span class="hlt">velocity</span> of V{sub tan,M31} = 17.0 km s{sup -1}, with a 1{sigma} confidence region of V{sub tan,M31} {<=} 34.3 km s{sup -1}. Hence, the <span class="hlt">velocity</span> vector of M31 is statistically consistent with a radial (head-on collision) orbit toward the Milky Way. We revise prior estimates for the Local <span class="hlt">Group</span> timing mass, including corrections for cosmic bias and scatter, and obtain M{sub LG} {identical_to} M{sub MW,vir} + M{sub M31,vir} = (4.93 {+-} 1.63) Multiplication-Sign 10{sup 12} M{sub Sun }. Summing known estimates for the individual masses of M31 and the Milky Way obtained from other dynamical methods yields smaller uncertainties. Bayesian combination of the different estimates demonstrates that the timing argument has too much (cosmic) scatter to help much in reducing uncertainties on the Local <span class="hlt">Group</span> mass, but its inclusion does tend to increase other estimates by {approx}10%. We</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013GeoJI.194..961O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013GeoJI.194..961O"><span id="translatedtitle">The uppermost mantle shear wave <span class="hlt">velocity</span> structure of eastern Africa from Rayleigh wave <span class="hlt">tomography</span>: constraints on rift evolution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>O'Donnell, J. P.; Adams, A.; Nyblade, A. A.; Mulibo, G. D.; Tugume, F.</p> <p>2013-08-01</p> <p>An expanded model of the 3-D shear wave <span class="hlt">velocity</span> structure of the uppermost mantle beneath eastern Africa has been developed using earthquakes recorded by the AfricaArray East African Seismic Experiment in conjunction with data from permanent stations and previously deployed temporary stations. The combined data set comprises 331 earthquakes recorded on a total of 95 seismic stations spanning Kenya, Uganda, Tanzania, Zambia and Malawi. In this study, data from 149 earthquakes were used to determine fundamental-mode Rayleigh wave phase <span class="hlt">velocities</span> at periods ranging from 20 to 182 s using the two-plane wave method, and then combined with the similarly processed published measurements and inverted for a 3-D shear wave <span class="hlt">velocity</span> model of the uppermost mantle. New features in the model include (1) a low-<span class="hlt">velocity</span> region in western Zambia, (2) a high-<span class="hlt">velocity</span> region in eastern Zambia, (3) a low-<span class="hlt">velocity</span> region in eastern Tanzania and (4) low-<span class="hlt">velocity</span> regions beneath the Lake Malawi rift. When considered in conjunction with mapped seismicity, these results support a secondary western rift branch striking southwestwards from Lake Tanganyika, likely exploiting the relatively weak lithosphere of the southern Kibaran Belt between the Bangweulu Block and the Congo Craton. We estimate a lithospheric thickness of ˜150-200 km for the substantial fast shear wave anomaly imaged in eastern Zambia, which may be a southward subsurface extension of the Bangweulu Block. The low-<span class="hlt">velocity</span> region in eastern Tanzania suggests that the eastern rift branch trends southeastwards offshore eastern Tanzania coincident with the purported location of the northern margin of the proposed Ruvuma microplate. Pronounced <span class="hlt">velocity</span> lows along the Lake Malawi rift are found beneath the northern and southern ends of the lake, but not beneath the central portion of the lake.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Ap.....59..246E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Ap.....59..246E"><span id="translatedtitle">Kinematics and <span class="hlt">Velocity</span> Ellipsoid Parameters of Stellar <span class="hlt">Groups</span> and Open Star Clusters: II Cool Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Elsanhoury, W. H.</p> <p>2016-06-01</p> <p>Based on the galactic space <span class="hlt">velocity</span> components (U, V, W) and with aid of the vector and matrix analyses, we computed the <span class="hlt">velocity</span> ellipsoid parameters for 790 late-type stars from CoRoT (Convection, Rotation and Transits) observations and 290 L dwarf stars. We ran the calculations for spectral types F, G, and K for late-type stars and L0, L1, L2, and L3 for L dwarf stars. We found that the ratio of the middle to the major axis in the galaxy ranged from 0.35 to 0.73. The vertex deviation from the galactic center was very small for the samples under investigation, which agrees well with earlier calculations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005PhRvE..72a6604M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005PhRvE..72a6604M"><span id="translatedtitle">Causal determination of acoustic <span class="hlt">group</span> <span class="hlt">velocity</span> and frequency derivative of attenuation with finite-bandwidth Kramers-Kronig relations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mobley, Joel; Waters, Kendall R.; Miller, James G.</p> <p>2005-07-01</p> <p>Kramers-Kronig (KK) analyses of experimental data are complicated by the extrapolation problem, that is, how the unexamined spectral bands impact KK calculations. This work demonstrates the causal linkages in resonant-type data provided by acoustic KK relations for the <span class="hlt">group</span> <span class="hlt">velocity</span> (cg) and the derivative of the attenuation coefficient (α') (components of the derivative of the acoustic complex wave number) without extrapolation or unmeasured parameters. These relations provide stricter tests of causal consistency relative to previously established KK relations for the phase <span class="hlt">velocity</span> (cp) and attenuation coefficient (α) (components of the undifferentiated acoustic wave number) due to their shape invariance with respect to subtraction constants. For both the <span class="hlt">group</span> <span class="hlt">velocity</span> and attenuation derivative, three forms of the relations are derived. These relations are equivalent for bandwidths covering the entire infinite spectrum, but differ when restricted to bandlimited spectra. Using experimental data from suspensions of elastic spheres in saline, the accuracy of finite-bandwidth KK predictions for cg and α' is demonstrated. Of the multiple methods, the most accurate were found to be those whose integrals were expressed only in terms of the phase <span class="hlt">velocity</span> and attenuation coefficient themselves, requiring no differentiated quantities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T41D2929B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T41D2929B"><span id="translatedtitle">Lithospheric Shear <span class="hlt">Velocity</span> Structure of South Island, New Zealand from Rayleigh Wave <span class="hlt">Tomography</span> of Amphibious Array Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ball, J. S.; Sheehan, A. F.; Stachnik, J. C.; Lin, F. C.; Collins, J. A.</p> <p>2015-12-01</p> <p>We present the first 3D shear <span class="hlt">velocity</span> model extending well offshore of New Zealand's South Island, imaging the lithosphere beneath Campbell and Challenger plateaus. Our model is constructed via linearized inversion of both teleseismic (18 -70 s period) and ambient noise-based (8 - 25 s period) Rayleigh wave dispersion measurements. We augment an array of 29 ocean-bottom instruments deployed off the South Island's east and west coasts in 2009-2010 with 28 New Zealand land-based seismometers. The ocean-bottom seismometers and 4 of the land seismometers were part of the Marine Observations of Anisotropy Near Aotearoa (MOANA) experiment, and the remaining land seismometers are from New Zealand's permanent GeoNet array. Major features of our shear wave <span class="hlt">velocity</span> (Vs) model include a low-<span class="hlt">velocity</span> (Vs<4.3km/s) body extending to at least 75km depth beneath the Banks and Otago peninsulas, a high-<span class="hlt">velocity</span> (Vs~4.7km/s) upper mantle anomaly underlying the Southern Alps to a depth of 100km, and discontinuous lithospheric <span class="hlt">velocity</span> structure between eastern and western Challenger Plateau. Using the 4.5km/s contour as a proxy for the lithosphere-asthenosphere boundary, our model suggests that the lithospheric thickness of Challenger Plateau is substantially greater than that of Campbell Plateau. The high-<span class="hlt">velocity</span> anomaly we resolve beneath the central South Island exhibits strong spatial correlation with subcrustal earthquake hypocenters along the Alpine Fault (Boese et al., 2013). The ~400km-long low <span class="hlt">velocity</span> zone we image beneath eastern South Island underlies Cenozoic volcanics and mantle-derived helium observations (Hoke et al., 2000) on the surface. The NE-trending low-<span class="hlt">velocity</span> zone dividing Challenger Plateau in our model underlies a prominent magnetic discontinuity (Sutherland et al., 1999). The latter feature has been interpreted to represent a pre-Cretaceous crustal boundary, which our results suggest may involve the entire mantle lithosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GGG....16..681B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GGG....16..681B"><span id="translatedtitle">P and S <span class="hlt">velocity</span> <span class="hlt">tomography</span> of the Mariana subduction system from a combined land-sea seismic deployment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barklage, Mitchell; Wiens, Douglas A.; Conder, James A.; Pozgay, Sara; Shiobara, Hajime; Sugioka, Hiroko</p> <p>2015-03-01</p> <p>Seismic imaging provides an opportunity to constrain mantle wedge processes associated with subduction, volatile transport, arc volcanism, and back-arc spreading. We investigate the seismic <span class="hlt">velocity</span> structure of the upper mantle across the Central Mariana subduction system using data from the 2003-2004 Mariana Subduction Factory Imaging Experiment, an 11 month deployment consisting of 20 broadband seismic stations installed on islands and 58 semibroadband ocean bottom seismographs. We determine the three-dimensional VP and VP/VS structure using over 25,000 local and over 2000 teleseismic arrival times. The mantle wedge is characterized by slow <span class="hlt">velocity</span> and high VP/VS beneath the fore arc, an inclined zone of slow <span class="hlt">velocity</span> underlying the volcanic front, and a strong region of slow <span class="hlt">velocity</span> beneath the back-arc spreading center. The slow <span class="hlt">velocities</span> are strongest at depths of 20-30 km in the fore arc, 60-70 km beneath the volcanic arc, and 20-30 km beneath the spreading center. The fore-arc slow <span class="hlt">velocity</span> anomalies occur beneath Big Blue seamount and are interpreted as resulting from mantle serpentinization. The depths of the maximum <span class="hlt">velocity</span> anomalies beneath the arc and back arc are nearly identical to previous estimates of the final equilibrium depths of mantle melts from thermobarometry, strongly indicating that the low-<span class="hlt">velocity</span> zones delineate regions of melt production in the mantle. The arc and back-arc melt production regions are well separated at shallow depths, but may be connected at depths greater than 80 km.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JGRB..120.1708A&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JGRB..120.1708A&link_type=ABSTRACT"><span id="translatedtitle">Lithospheric instability and the source of the Cameroon Volcanic Line: Evidence from Rayleigh wave phase <span class="hlt">velocity</span> <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Adams, Aubreya N.; Wiens, Douglas A.; Nyblade, Andrew A.; Euler, Garrett G.; Shore, Patrick J.; Tibi, Rigobert</p> <p>2015-03-01</p> <p>The Cameroon Volcanic Line (CVL) is a 1800 km long volcanic chain, extending SW-NE from the Gulf of Guinea into Central Africa, that lacks the typical age progression exhibited by hot spot-related volcanic tracks. This study investigates the upper mantle seismic structure beneath the CVL and surrounding regions to constrain the origin of volcanic lines that are poorly described by the classic plume model. Rayleigh wave phase <span class="hlt">velocities</span> are measured at periods from 20 to 182 s following the two-plane wave methodology, using data from the Cameroon Seismic Experiment, which consists of 32 broadband stations deployed between 2005 and 2007. These phase <span class="hlt">velocities</span> are then inverted to build a model of shear wave <span class="hlt">velocity</span> structure in the upper mantle beneath the CVL. Results show that phase <span class="hlt">velocities</span> beneath the CVL are reduced at all periods, with average <span class="hlt">velocities</span> beneath the CVL deviating more than -2% from the regional average and +4% beneath the Congo Craton. This distinction is observed for all periods but is less pronounced for the longest periods measured. Inversion for shear wave <span class="hlt">velocity</span> structure indicates a tabular low <span class="hlt">velocity</span> anomaly directly beneath the CVL at depths of 50 to at least 200 km and a sharp vertical boundary with faster <span class="hlt">velocities</span> beneath the Congo Craton. These observations demonstrate widespread infiltration or erosion of the continental lithosphere beneath the CVL, most likely caused by mantle upwelling associated with edge-flow convection driven by the Congo Craton or by lithospheric instabilities that develop due to the nearby edge of the African continent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006GGG.....7.7005W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006GGG.....7.7005W"><span id="translatedtitle">P and S <span class="hlt">velocity</span> structure of the upper mantle beneath the Transantarctic Mountains, East Antarctic craton, and Ross Sea from travel time <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Watson, Timothy; Nyblade, Andrew; Wiens, Douglas A.; Anandakrishnan, Sridhar; Benoit, Margaret; Shore, Patrick J.; Voigt, Donald; Vandecar, John</p> <p>2006-07-01</p> <p>P and S wave travel times from teleseismic earthquakes recorded by the Transantarctic Mountains Seismic Experiment (TAMSEIS) have been used to tomographically image upper mantle structure beneath portions of the Transantarctic Mountains (TAM), the East Antarctic (EA) craton, and the West Antarctic rift system (WARS) in the vicinity of Ross Island, Antarctica. The TAM form a major tectonic boundary that divides the stable EA craton and the tectonically active WARS. Relative arrival times were determined using a multichannel cross-correlation technique on teleseismic P and S phases from earthquakes with mb ≥ 5.5. 3934 P waves were used from 322 events, and 2244 S waves were used from 168 events. Relative travel time residuals were inverted for upper mantle structure using VanDecar's method. The P wave <span class="hlt">tomography</span> model reveals a low-<span class="hlt">velocity</span> anomaly in the upper mantle of approximately δVp = -1 to -1.5% in the vicinity of Ross Island extending laterally 50 to 100 km beneath the TAM from the coast, placing the contact between regions of fast and slow <span class="hlt">velocities</span> well inland from the coast beneath the TAM. The magnitude of the low-<span class="hlt">velocity</span> anomaly in the P wave model appears to diminish beneath the TAM to the north and south of Ross Island. The depth extent of the low-<span class="hlt">velocity</span> anomaly is not well constrained, but it probably is confined to depths above ˜200 km. The S wave model, within resolution limits, is consistent with the P wave model. The low-<span class="hlt">velocity</span> anomaly within the upper mantle can be attributed to a 200-300 K thermal anomaly, consistent with estimates obtained from seismic attenuation measurements. The presence of a thermal anomaly of this magnitude supports models invoking a thermal buoyancy contribution to flexurally driven TAM uplift, at least in the Ross Island region of the TAM. Because the magnitude of the anomaly to the north and south of Ross Island may diminish, the thermal contribution to the uplift of the TAM could be variable along strike</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1810068S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1810068S"><span id="translatedtitle">Crustal high-<span class="hlt">velocity</span> anomaly at the East European Craton margin in SE Poland (TESZ) modelled by 3-D seismic <span class="hlt">tomography</span> of refracted and reflected arrivals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Środa, Piotr; Dec, Monika</p> <p>2016-04-01</p> <p>The area of Trans-European Suture Zone in SE Poland represents a contact of major tectonic units of different consolidation age - from the Precambrian East European Craton, through Palaeozoic West European Platform to Cenozoic Carpathian orogen. The region was built by several phases of crustal accretion, which resulted in a complex collage of tectonic blocks. In 2000, this region was studied by several seismic wide-angle profiles of CELEBRATION 2000 experiment, providing a dense coverage of seismic data in SE Poland and allowing for detailed investigations of the crustal structure and properties in this area. Beneath the marginal part of the EEC, the 2-D modelling of in-line data form several CELEBRATION profiles revealed a prominent high P-wave <span class="hlt">velocity</span> anomaly in the upper crust, with Vp of 6.7-7.1 km/s, starting at 10-16 km depth (e.g., Środa et al., 2006). Anomalously high <span class="hlt">velocities</span> are observed in the area located approximately beneath Lublin trough, to the NE of Teisseyre-Tornquist Zone. Based on 3-D <span class="hlt">tomography</span> of first arrivals of in- and off-line CELEBRATION 2000 recordings (Malinowski et al., 2008), elevated <span class="hlt">velocities</span> are also reported in the same area and seem to continue to the SW, off the craton margin. Gravimetric modelling also revealed anomalously high density in the same region at similar depths. High seismic <span class="hlt">velocities</span> and densities are interpreted as indicative for a pronounced mafic intrusion, possibly related to extensional processes at the EEC margin. Previous 3-D models of the high-<span class="hlt">velocity</span> intrusion were based on first arrivals (crustal refractions) only. In this study, also off-line reflections (not modelled up to now) are used, in order to enlarge the data set and to better constrain the geometry and properties of the <span class="hlt">velocity</span> anomaly. A code for 3-D joint tomographic inversion of refracted and reflected arrivals, with model parametrization allowing for <span class="hlt">velocity</span> discontinuities was used (Rawlinson, 2007). With this approach, besides the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2939199','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2939199"><span id="translatedtitle">Fundus Autofluorescence and Optical Coherence <span class="hlt">Tomography</span> of Congenital <span class="hlt">Grouped</span> Albinotic Spots</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kim, David Y.; Hwang, John C.; Moore, Anthony T.; Bird, Alan C.; Tsang, Stephen H.</p> <p>2010-01-01</p> <p>Purpose To describe fundus autofluorescence (FAF) and optical coherence <span class="hlt">tomography</span> (OCT) in a series of patients with congenital <span class="hlt">grouped</span> albinotic spots (CGAS). Methods Three eyes of three patients with CGAS were evaluated with FAF and OCT imaging to evaluate the nature of the albinotic spots. Results In all three eyes with CGAS, FAF imaging revealed autofluorescent spots corresponding to the albinotic spots seen on stereo biomicroscopy. One eye also had additional spots detected on FAF imaging that were not visible on stereo biomicroscopy or color fundus photographs. FAF imaging of the spots demonstrated decreased general autofluorescence as well as decreased peripheral autofluorescence surrounding central areas of retained or increased autofluorescence. OCT revealed a disruption in signal from the hyper-reflective layer corresponding to the photoreceptor inner and outer segment junction as well as increased signal backscattering from the choroid in the area of the spots. Fluorescein angiography (FA) demonstrated early and stable hyperfluorescence of the spots without leakage. Conclusion In this case series, FAF demonstrated decreased autofluorescence of the spots consistent with focal RPE atrophy or abnormal material blocking normal autofluorescence as well as areas of increased autofluorescence suggesting RPE dysfunction. OCT and FA findings suggest photoreceptor and RPE layer abnormalities. FAF and OCT are useful noninvasive diagnostic adjuncts that can aid in the diagnosis of GCAS, help determine extent of disease, and contribute to our understanding of its pathophysiology. PMID:20539258</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.S51B4461P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.S51B4461P"><span id="translatedtitle">Shear <span class="hlt">velocity</span> model for the westernmost Mediterranean from ambient noise and ballistic finite-frequency Rayleigh wave <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Palomeras, I.; Villasenor, A.; Thurner, S.; Levander, A.; Gallart, J.; Harnafi, M.</p> <p>2014-12-01</p> <p>The westernmost Mediterranean comprises the Iberian Peninsula and Morocco, separated by the Alboran Sea and the Algerian Basin. From north to south this region consists of the Pyrenees, resulting from Iberia-Eurasia collision; the Iberian Massif, which has been undeformed since the end of the Paleozoic; the Central System and Iberian Chain, regions with intracontinental Oligocene-Miocene deformation; the Gibraltar Arc (Betics, Rif and Alboran terranes), resulting from post-Oligocene subduction roll-back; and the Atlas Mountains. We analyzed data from recent broad-band array deployments and permanent stations in the area (IberArray and Siberia arrays, the PICASSO array, the University of Munster array, and the Spanish, Portuguese and Moroccan National Networks) to characterize its lithospheric structure. The combined array of 350 stations has an average interstation spacing of ~60 km. We calculated the Rayleigh waves phase <span class="hlt">velocities</span> from ambient noise (periods 4 to 40 s) and teleseismic events (periods 20 to 167 s). We inverted the phase <span class="hlt">velocities</span> to obtain a shear <span class="hlt">velocity</span> model for the lithosphere to ~200 km depth. Our results correlate well with the surface expression of the main structural units with higher crustal <span class="hlt">velocity</span> for the Iberian Massif than for the Alpine Iberia and Atlas Mountains. The Gibraltar Arc has lower crustal shear <span class="hlt">velocities</span> than the regional average at all crustal depths. It also shows an arc shaped anomaly with high upper mantle <span class="hlt">velocities</span> (>4.6 km/s) at shallow depths (<65 km) interpreted as the subducting Alboran slab. The hanging slab is depressing the crust of the Gibraltar arc to ~55 km depth, as seen in receiver function data and active source seismic profiles. Low upper mantle <span class="hlt">velocities</span> (<4.2 km/s) are observed beneath the Atlas, the northeastern end of the Betic Mountains and the Late Cenozoic volcanic fields in Iberia and Morocco, indicative of high temperatures at relatively shallow depths, and suggesting that the lithosphere</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22113687','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22113687"><span id="translatedtitle">Light bullets and supercontinuum spectrum during femtosecond pulse filamentation under conditions of anomalous <span class="hlt">group-velocity</span> dispersion in fused silicalicati</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chekalin, Sergei V; Kompanets, V O; Smetanina, E O; Kandidov, V P</p> <p>2013-04-30</p> <p>We report the results of theoretical and experimental research on spectrum transformation and spatiotemporal distribution of the femtosecond laser radiation intensity during filamentation in fused silica. The formation of light bullets with a high power density is first observed in a femtosecond laser pulse in the anomalous <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion regime at a wavelength of 1800 nm. The minimum duration of the light bullet is about two oscillation cycles of the light field. (extreme light fields and their applications)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JAP...117h4305M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JAP...117h4305M"><span id="translatedtitle">Reduction of heat capacity and phonon <span class="hlt">group</span> <span class="hlt">velocity</span> in silicon nanowires</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marchbanks, Christopher; Wu, Zhigang</p> <p>2015-02-01</p> <p>We report on ab initio linear-response calculations of lattice vibrations in narrow silicon nanowires on the order of 1 nm along the [001], [011], and [111] growth directions. The confinement and nanowire structure substantially alter phonon distributions, resulting in an 15% to 23% reduction in heat capacity and an averaged decrease of 31% in acoustic <span class="hlt">velocities</span> compared with bulk silicon. Based on these, we estimate an improvement up to 4 fold on thermoelectric performance due solely to the modified lattice vibrations in narrow silicon nanowires over bulk silicon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EP%26S...68..132P&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EP%26S...68..132P&link_type=ABSTRACT"><span id="translatedtitle">Investigating P- and S-wave <span class="hlt">velocity</span> structure beneath the Marmara region (Turkey) and the surrounding area from local earthquake <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Polat, Gulten; Özel, Nurcan Meral; Koulakov, Ivan</p> <p>2016-07-01</p> <p>We investigated the crustal structure beneath the Marmara region and the surrounding area in the western part of the North Anatolian fault zone. These areas have high seismicity and are of critical significance to earthquake hazards. The study was based on travel-time <span class="hlt">tomography</span> using local moderate and micro-earthquakes occurring in the study area recorded by the Multi-Disciplinary Earthquake Research in High Risk Regions of Turkey project and Kandilli Observatory and Earthquake Research Institute. We selected 2131 earthquakes and a total of 92,858 arrival times, consisting of 50,044 P-wave and 42,814 S-wave arrival times. We present detailed crustal structure down to 50 km depth beneath the Marmara region for P- and S-wave <span class="hlt">velocities</span> using the LOTOS code based on iterative inversion. We used the distributions of the resulting seismic parameters ( Vp, Vs) to pick out significant geodynamical features. The high-<span class="hlt">velocity</span> anomalies correlate well with fracturing segments of the North Anatolian fault. High seismicity is mostly concentrated in these segments. In particular, low <span class="hlt">velocities</span> were observed beneath the central Marmara Sea at 5 km depth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.9513M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.9513M"><span id="translatedtitle">Full waveform seismic modelling of Chalk <span class="hlt">Group</span> rocks from the Danish North Sea - implications for <span class="hlt">velocity</span> analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Montazeri, Mahboubeh; Moreau, Julien; Uldall, Anette; Nielsen, Lars</p> <p>2015-04-01</p> <p>This study aims at understanding seismic wave propagation in the fine-layered Chalk <span class="hlt">Group</span>, which constitutes the main reservoir for oil and gas production in the Danish North Sea. The starting point of our analysis is the Nana-1XP exploration well, which shows strong seismic contrasts inside the Chalk <span class="hlt">Group</span>. For the purposes of seismic waveform modelling, we here assume a one-dimensional model with homogeneous and isotropic layers designed to capture the main fluctuations in petrophysical properties observed in the well logs. The model is representative of the stratigraphic sequences of the area and it illustrates highly contrasting properties of the Chalk <span class="hlt">Group</span>. Finite-difference (FD) full wave technique, both acoustic and elastic equations are applied to the model. <span class="hlt">Velocity</span> analysis of seismic data is a crucial step for stacking, multiple suppression, migration, and depth conversion of the seismic record. Semblance analysis of the synthetic seismic records shows strong amplitude peaks outside the expected range for the time interval representing the Chalk <span class="hlt">Group</span>, especially at the base. The various synthetic results illustrate the occurrence and the impact of different types of waves including multiples, converted waves and refracted waves. The interference of these different wave types with the primary reflections can explain the strong anomalous amplitudes in the semblance plot. In particular, the effect of strongly contrasting thin beds plays an important role in the generation of the high anomalous amplitude values. If these anomalous amplitudes are used to pick the <span class="hlt">velocities</span>, it would impede proper stacking of the data and may result in sub-optimal migration and depth conversion. Consequently this may lead to erroneous or sub-optimal seismic images of the Chalk <span class="hlt">Group</span> and the underlying layers. Our results highlight the importance of detailed <span class="hlt">velocity</span> analysis and proper picking of <span class="hlt">velocity</span> functions in the Chalk <span class="hlt">Group</span> intervals. We show that application of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016GeoJI.205..715W&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016GeoJI.205..715W&link_type=ABSTRACT"><span id="translatedtitle">Correction of phase <span class="hlt">velocity</span> bias caused by strong directional noise sources in high-frequency ambient noise <span class="hlt">tomography</span>: a case study in Karamay, China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Kai; Luo, Yinhe; Yang, Yingjie</p> <p>2016-05-01</p> <p>We collect two months of ambient noise data recorded by 35 broad-band seismic stations in a 9 × 11 km area (1-3 km station interval) near Karamay, China, and do cross-correlation of noise data between all station pairs. Array beamforming analysis of the ambient noise data shows that ambient noise sources are unevenly distributed and the most energetic ambient noise mainly comes from azimuths of 40°-70°. As a consequence of the strong directional noise sources, surface wave components of the cross-correlations at 1-5 Hz show clearly azimuthal dependence, and direct dispersion measurements from cross-correlations are strongly biased by the dominant noise energy. This bias renders that the dispersion measurements from cross-correlations do not accurately reflect the interstation <span class="hlt">velocities</span> of surface waves propagating directly from one station to the other, that is, the cross-correlation functions do not retrieve empirical Green's functions accurately. To correct the bias caused by unevenly distributed noise sources, we adopt an iterative inversion procedure. The iterative inversion procedure, based on plane-wave modeling, includes three steps: (1) surface wave <span class="hlt">tomography</span>, (2) estimation of ambient noise energy and biases and (3) phase <span class="hlt">velocities</span> correction. First, we use synthesized data to test the efficiency and stability of the iterative procedure for both homogeneous and heterogeneous media. The testing results show that: (1) the amplitudes of phase <span class="hlt">velocity</span> bias caused by directional noise sources are significant, reaching ˜2 and ˜10 per cent for homogeneous and heterogeneous media, respectively; (2) phase <span class="hlt">velocity</span> bias can be corrected by the iterative inversion procedure and the convergence of inversion depends on the starting phase <span class="hlt">velocity</span> map and the complexity of the media. By applying the iterative approach to the real data in Karamay, we further show that phase <span class="hlt">velocity</span> maps converge after 10 iterations and the phase <span class="hlt">velocity</span> maps obtained using</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010GeoJI.183.1061T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010GeoJI.183.1061T"><span id="translatedtitle">Structure of the crust beneath Cameroon, West Africa, from the joint inversion of Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocities</span> and receiver functions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tokam, Alain-Pierre K.; Tabod, Charles T.; Nyblade, Andrew A.; Julià, Jordi; Wiens, Douglas A.; Pasyanos, Michael E.</p> <p>2010-11-01</p> <p>The Cameroon Volcanic Line (CVL) consists of a linear chain of Tertiary to Recent, generally alkaline, volcanoes that do not exhibit an age progression. Here we study crustal structure beneath the CVL and adjacent regions in Cameroon using 1-D shear wave <span class="hlt">velocity</span> models obtained from the joint inversion of Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocities</span> and P-receiver functions for 32 broad-band seismic stations deployed between 2005 January and 2007 February. We find that (1) crustal thickness (35-39km) and <span class="hlt">velocity</span> structure is similar beneath the CVL and the Pan African Oubanguides Belt to the south of the CVL, (2) crust is thicker (43-48km) under the northern margin of the Congo Craton and is characterized by shear wave <span class="hlt">velocities</span> >=4.0kms-1 in its lower part and (3) crust is thinner (26-31km) under the Garoua rift and the coastal plain. In addition, a fast <span class="hlt">velocity</span> layer (Vs of 3.6-3.8kms-1) in the upper crust is found beneath many of the seismic stations. Crustal structure beneath the CVL and the Oubanguides Belt is very similar to Pan African crustal structure in the Mozambique Belt, and therefore it appears not to have been modified significantly by the magmatic activity associated with the CVL. The crust beneath the coastal plain was probably thinned during the opening of the southern Atlantic Ocean, while the crust beneath the Garoua rift was likely thinned during the formation of the Benue Trough in the early Cretaceous. We suggest that the thickened crust and the thick mafic lower crustal layer beneath the northern margin of the Congo Craton may be relict features from a continent-continent collision along this margin during the formation of Gondwana.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012JSMME...6..678C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012JSMME...6..678C&link_type=ABSTRACT"><span id="translatedtitle">Damage Evaluation of Unsaturated Polyester Resin Using Zero-<span class="hlt">Group</span> <span class="hlt">Velocity</span> Lamb Waves in Non-Contact Matter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cho, Hideo; Oka, Daichi; Matsuo, Takuma</p> <p></p> <p>In this study we attempted to evaluate the degree of degradation of an unsaturated polyester resin when it was degraded by exposing it to hot water at 90°C, using the frequency of zero-<span class="hlt">group-velocity</span> (ZGV) Lamb waves. The energy of ZGV Lamb waves does not propagate while the phase <span class="hlt">velocity</span> remains finite. We generated ZGV Lamb waves with a Q-switched YAG laser and detected them with a focused air-coupled transducer at the same area of an irradiation point of the YAG laser in con-contact matter. A change in measured frequencies of ZGV Lamb waves decreased with increase of exposed period to hot water and are corresponding to the change in Young's modulus and thickness of the plate near the exposed surface</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMMR13A2255G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMMR13A2255G"><span id="translatedtitle">3D Anisotropic <span class="hlt">Velocity</span> <span class="hlt">Tomography</span> of a Water Saturated Rock under True-Triaxial Stress in the Laboratory</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghofrani Tabari, M.; Goodfellow, S. D.; Nasseri, M. B.; Young, R.</p> <p>2013-12-01</p> <p>A cubic specimen of water saturated Fontainebleau Sandstone is tested in the laboratory under true-triaxial loading where three different principal stresses are applied under drained conditions. Due to the loading arrangement, closure and opening of the pre-existing cracks in the rock, as well as creation and growth of the aligned cracks cause elliptical anisotropy and distributed heterogeneities. A Geophysical Imaging Cell equipped with an Acoustic Emission monitoring system is employed to image <span class="hlt">velocity</span> structure of the sample during the experiment through repeated transducer to transducer non-destructive ultrasonic surveys. Apparent P-wave <span class="hlt">velocities</span> along the rock body are calculated in different directions and shown in stereonet plots which demonstrate an overall anisotropy of the sample. The apparent <span class="hlt">velocities</span> in the main three orthogonal cubic directions are used as raw data for building a mean spatial distribution model of anisotropy ratios. This approach is based on the concept of semi-principal axes in an elliptical anisotropic model and appointing two ratios between the three orthogonal <span class="hlt">velocities</span> in each of the cubic grid cells. The spatial distribution model of anisotropy ratios are used to calculate the anisotropic ray-path segment matrix elements (Gij). These contain segment lengths of the ith ray in the jth cell in three dimensions where, length of each ray in each cell is computed for one principal direction based on the dip and strike of the ray and these lengths differ from the ones in an isotropic G Matrix. 3D strain of the squeezed rock and the consequent geometrical deformation is also included in the ray-path segment matrix. A Singular Value Decomposition (SVD) method is used for inversion from the data space of apparent <span class="hlt">velocities</span> to the model space of P-wave propagation <span class="hlt">velocities</span> in the three principal directions. Finally, spatial variation and temporal evolution of induced damages in the rock, representing uniformly distributed or</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1818160P&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1818160P&link_type=ABSTRACT"><span id="translatedtitle">Lithospheric structure of the westernmost Mediterranean inferred from finite frequency Rayleigh wave <span class="hlt">tomography</span> S-<span class="hlt">velocity</span> model.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Palomeras, Imma; Villasenor, Antonio; Thurner, Sally; Levander, Alan; Gallart, Josep; Harnafi, Mimoun</p> <p>2016-04-01</p> <p>The Iberian Peninsula and Morocco, separated by the Alboran Sea and the Algerian Basin, constitute the westernmost Mediterranean. From north to south this region consists of the Pyrenees, the result of interaction between the Iberian and Eurasian plates; the Iberian Massif, a region that has been undeformed since the end of the Paleozoic; the Central System and Iberian Chain, regions with intracontinental Oligocene-Miocene deformation; the Gibraltar Arc (Betics, Rif and Alboran terranes) and the Atlas Mountains, resulting from post-Oligocene subduction roll-back and Eurasian-Nubian plate convergence. In this study we analyze data from recent broad-band array deployments and permanent stations on the Iberian Peninsula and in Morocco (Spanish IberArray and Siberia arrays, the US PICASSO array, the University of Munster array, and the Spanish, Portuguese, and Moroccan National Networks) to characterize its lithospheric structure. The combined array of 350 stations has an average interstation spacing of ~60 km, comparable to USArray. We have calculated the Rayleigh waves phase <span class="hlt">velocities</span> from ambient noise for short periods (4 s to 40 s) and teleseismic events for longer periods (20 s to 167 s). We inverted the phase <span class="hlt">velocities</span> to obtain a shear <span class="hlt">velocity</span> model for the lithosphere to ~200 km depth. The model shows differences in the crust for the different areas, where the highest shear <span class="hlt">velocities</span> are mapped in the Iberian Massif crust. The crustal thickness is highly variable ranging from ~25 km beneath the eastern Betics to ~55km beneath the Gibraltar Strait, Internal Betics and Internal Rif. Beneath this region a unique arc shaped anomaly with high upper mantle <span class="hlt">velocities</span> (>4.6 km/s) at shallow depths (<65 km) is observed. We interpret this body as the subducting Alboran slab that is depressing the crust of the western Gibraltar arc to ~55 km depth. Low upper mantle <span class="hlt">velocities</span> (<4.2 km/s) are observed beneath the Atlas, the northeastern end of the Betic Mountains and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70170508','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70170508"><span id="translatedtitle">Three-dimensional seismic <span class="hlt">velocity</span> structure of Mauna Loa and Kilauea volcanoes in Hawaii from local seismic <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Lin, Guoqing; Shearer, Peter M.; Matoza, Robin S.; Okubo, Paul G.; Amelung, Falk</p> <p>2016-01-01</p> <p>We present a new three-dimensional seismic <span class="hlt">velocity</span> model of the crustal and upper mantle structure for Mauna Loa and Kilauea volcanoes in Hawaii. Our model is derived from the first-arrival times of the compressional and shear waves from about 53,000 events on and near the Island of Hawaii between 1992 and 2009 recorded by the Hawaiian Volcano Observatory stations. The Vp model generally agrees with previous studies, showing high-<span class="hlt">velocity</span> anomalies near the calderas and rift zones and low-<span class="hlt">velocity</span> anomalies in the fault systems. The most significant difference from previous models is in Vp/Vs structure. The high-Vp and high-Vp/Vs anomalies below Mauna Loa caldera are interpreted as mafic magmatic cumulates. The observed low-Vp and high-Vp/Vs bodies in the Kaoiki seismic zone between 5 and 15 km depth are attributed to the underlying volcaniclastic sediments. The high-Vp and moderate- to low-Vp/Vs anomalies beneath Kilauea caldera can be explained by a combination of different mafic compositions, likely to be olivine-rich gabbro and dunite. The systematically low-Vp and low-Vp/Vs bodies in the southeast flank of Kilauea may be caused by the presence of volatiles. Another difference between this study and previous ones is the improved Vp model resolution in deeper layers, owing to the inclusion of events with large epicentral distances. The new <span class="hlt">velocity</span> model is used to relocate the seismicity of Mauna Loa and Kilauea for improved absolute locations and ultimately to develop a high-precision earthquake catalog using waveform cross-correlation data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRB..119.4377L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRB..119.4377L"><span id="translatedtitle">Three-dimensional seismic <span class="hlt">velocity</span> structure of Mauna Loa and Kilauea volcanoes in Hawaii from local seismic <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, Guoqing; Shearer, Peter M.; Matoza, Robin S.; Okubo, Paul G.; Amelung, Falk</p> <p>2014-05-01</p> <p>We present a new three-dimensional seismic <span class="hlt">velocity</span> model of the crustal and upper mantle structure for Mauna Loa and Kilauea volcanoes in Hawaii. Our model is derived from the first-arrival times of the compressional and shear waves from about 53,000 events on and near the Island of Hawaii between 1992 and 2009 recorded by the Hawaiian Volcano Observatory stations. The Vp model generally agrees with previous studies, showing high-<span class="hlt">velocity</span> anomalies near the calderas and rift zones and low-<span class="hlt">velocity</span> anomalies in the fault systems. The most significant difference from previous models is in Vp/Vs structure. The high-Vp and high-Vp/Vs anomalies below Mauna Loa caldera are interpreted as mafic magmatic cumulates. The observed low-Vp and high-Vp/Vs bodies in the Kaoiki seismic zone between 5 and 15 km depth are attributed to the underlying volcaniclastic sediments. The high-Vp and moderate- to low-Vp/Vs anomalies beneath Kilauea caldera can be explained by a combination of different mafic compositions, likely to be olivine-rich gabbro and dunite. The systematically low-Vp and low-Vp/Vs bodies in the southeast flank of Kilauea may be caused by the presence of volatiles. Another difference between this study and previous ones is the improved Vp model resolution in deeper layers, owing to the inclusion of events with large epicentral distances. The new <span class="hlt">velocity</span> model is used to relocate the seismicity of Mauna Loa and Kilauea for improved absolute locations and ultimately to develop a high-precision earthquake catalog using waveform cross-correlation data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA....11836J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA....11836J"><span id="translatedtitle">SERAPIS project - 3D imaging of the Campi Flegrei caldera (southern Italy) : high resolution P-wave <span class="hlt">velocity</span> <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Judenherc, S.; Zollo, A.; Auger, E.; Boschi, L.; Satriano, C.; Serapis Working Group</p> <p>2003-04-01</p> <p>In September 2001, the SERAPIS project was carried out as an extended active seismic survey in the gulfs of Naples and Pozzuoli. A dense array of 60 three-component on-land stations and 72 sea bottom seismographs (OBS) have been deployed to record more than 5000 air gun shots at a spacing of about 125~m. As a preliminary analysis, the first P-arrival times of a the small offset data in the central part of the region has been inverted using the codes of H.M. Benz. The linearized iterative inversion of 38000 arrival times provided a >80% variance reduction with a node spacing of 250m. At the first order, our model shows a 2-layer structure : low <span class="hlt">velocity</span> volcanic sediments (2.5-3.5km/s) lying on an inclined high <span class="hlt">velocity</span> limestone platform (>6km/s). The caldera itself is very well identified, the rim is characterized by a 500-1000m upward shift of the <span class="hlt">velocity</span> isolines. The whole dataset is expected to provide a wider image with the same resolution (250m). It includes the detailed shape of the refractor beneath the caldera as well as its irregularities out of the bay which have been observered in the seismic sections.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17325457','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17325457"><span id="translatedtitle">Autopsy radiography: digital radiographs (DR) vs multidetector computed <span class="hlt">tomography</span> (MDCT) in high-<span class="hlt">velocity</span> gunshot-wound victims.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Harcke, H Theodore; Levy, Angela D; Abbott, Robert M; Mallak, Craig T; Getz, John M; Champion, Howard R; Pearse, Lisa</p> <p>2007-03-01</p> <p>This study compared full-body digital radiography (DR) with multidetector computed <span class="hlt">tomography</span> (MDCT) in the postmortem evaluation of gunshot wound (GSW) victims. Thirteen consecutive male GSW victims (mean age, 27 years) had full-body DR and MDCT prior to routine autopsy. DR successfully identified all metallic fragments, but MDCT was superior in its ability to precisely determine location because it provided 3-dimensional anatomic localization. In all cases, MDCT more accurately assessed organ injuries and wound tracks. Both DR and MDCT are limited in classifying multiple wounds and major vessel injury, but MDCT is generally superior to DR. MDCT shows significant advantages over DR in the forensic evaluation of GSW victims. This is particularly advantageous for the pathologist retrieving metallic fragments and for describing fracture detail accurately. Use of MDCT instead of radiographs will require medical examiners to become familiar with reading cross-sectional images. PMID:17325457</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19810002129','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19810002129"><span id="translatedtitle">First Scientific Working <span class="hlt">Group</span> Meeting of Airborne Doppler Lidar Wind <span class="hlt">Velocity</span> Measurement Program</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kaufman, J. W. (Editor)</p> <p>1980-01-01</p> <p>The purpose of the first scientific working <span class="hlt">group</span> meeting was fourfold: (1) to identify flight test options for engineering verification of the MSFC Doppler Lidar; (2) to identify flight test options for gathering data for scientific/technology applications; (3) to identify additional support equipment needed on the CV 990 aircraft for the flight tests; and (4) to identify postflight data processing and data sets requirements. The working <span class="hlt">group</span> identified approximately ten flight options for gathering data on atmospheric dynamics processes, including turbulence, valley breezes, and thunderstorm cloud anvil and cold air outflow dynamics. These test options will be used as a basis for planning the fiscal year 1981 tests of the Doppler Lidar system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/22344142','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/22344142"><span id="translatedtitle">Modulational instability in a silicon-on-insulator directional coupler: role of the coupling-induced <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ding, W; Staines, O K; Hobbs, G D; Gorbach, A V; de Nobriga, C; Wadsworth, W J; Knight, J C; Skryabin, D V; Strain, M J; Sorel, M; De La Rue, R M</p> <p>2012-02-15</p> <p>We report frequency conversion experiments in silicon-on-insulator (SOI) directional couplers. We demonstrate that the evanescent coupling between two subwavelength SOI waveguides is strongly dispersive and significantly modifies modulational instability (MI) spectra through the coupling induced <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion (GVD). As the separation between two 380-nm-wide silicon photonic wires decreases, the increasing dispersion of the coupling makes the GVD in the symmetric supermode more normal and suppresses the bandwidth of the MI gain observed for larger separations. PMID:22344142</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/19829441','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/19829441"><span id="translatedtitle">Temporal compression of cw diode-laser output into short pulses with cesium-vapor <span class="hlt">group-velocity</span> dispersion.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Choi, K; Menders, J; Ross, D; Korevaar, E</p> <p>1993-11-15</p> <p>Using a technique similar to chirped pulse compression, we have compressed the 50-mW cw output of a diode laser into pulses of greater than 500-mW peak power and less than 400-ps duration. By applying a small current modulation to the diode, we induced a small wavelength modulation in the vicinity of the 6s(1/2)-to-6p(3/2) cesium resonance transition at 852 nm. <span class="hlt">Group-velocity</span> dispersion on propagation through a cesium vapor cell then led to pulse compression. We developed a simple model to make predictions of output pulse shapes by using different modulation waveforms. PMID:19829441</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17471707','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17471707"><span id="translatedtitle">Finite-bandwidth Kramers-Kronig relations for acoustic <span class="hlt">group</span> <span class="hlt">velocity</span> and attenuation derivative applied to encapsulated microbubble suspensions.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mobley, Joel</p> <p>2007-04-01</p> <p>Kramers-Kronig (KK) analyses of experimental data are complicated by the conflict between the inherently bandlimited data and the requirement of KK integrals for a complete infinite spectrum of input information. For data exhibiting localized extrema, KK relations can provide accurate transforms over finite bandwidths due to the local-weighting properties of the KK kernel. Recently, acoustic KK relations have been derived for the determination of the <span class="hlt">group</span> <span class="hlt">velocity</span> (cg) and the derivative of the attenuation coefficient (alpha') (components of the derivative of the acoustic complex wave number). These relations are applicable to bandlimited data exhibiting resonant features without extrapolation or unmeasured parameters. In contrast to twice-subtracted finite-bandwidth KK predictions for phase <span class="hlt">velocity</span> and attenuation coefficient (components of the undifferentiated wave number), these more recently derived relations for cg and alpha' provide stricter tests of causal consistency because the resulting shapes are invariant with respect to subtraction constants. The integrals in these relations can be formulated so that they only require the phase <span class="hlt">velocity</span> and attenuation coefficient data without differentiation. Using experimental data from suspensions of encapsulated microbubbles, the finite-bandwidth KK predictions for cg and alpha' are found to provide an accurate mapping of the primary wave number quantities onto their derivatives. PMID:17471707</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.T23A1991A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.T23A1991A"><span id="translatedtitle">3-D P-wave <span class="hlt">velocity</span> structure and seismicity in Central Costa Rica from Local Earthquake <span class="hlt">Tomography</span> using an amphibic network</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arroyo, I.; Husen, S.; Flueh, E.; Alvarado, G. E.</p> <p>2008-12-01</p> <p>The Central Pacific sector of the erosional margin in Costa Rica shows a high seismicity rate, coincident with the subduction of rough-relief ocean floor, and generates earthquakes up to Mw 7. Precise earthquake locations and detailed knowledge of the 3-D <span class="hlt">velocity</span> structure provide key insights into the dynamics of subduction zones. To this end, we performed a 3-D Local Earthquake <span class="hlt">Tomography</span> using P-wave traveltimes from 595 selected events recorded by a seismological network of off- and onshore stations, deployed for 6 months in the area. The results reflect the complexity associated to subduction of bathymetric highs and the transition from normal to thickened oceanic crust (Cocos Ridge). The slab is imaged as a high-<span class="hlt">velocity</span> anomaly with a band of low <span class="hlt">velocities</span> (LVB) on top enclosing the intraslab events deeper than ~30 km. Below the margin slope, the LVB is locally thickened by at least two seamounts. We observe an abrupt, eastward widening of the LVB, preceded by a low-<span class="hlt">velocity</span> anomaly under the continental shelf, which we interpret as a big seamount. The thickening coincides with an inverted basin at the inner forearc and a low-<span class="hlt">velocity</span> anomaly under it. The latter appears in a sector where blocks of inner forearc are uplifted, possibly by underplating of eroded material against the base of the crust. The anomaly promotes seismicity by high-friction with the upper plate, and could be linked to a Mw 6.4 earthquake in 2004. In the west part of the area, the interplate seismicity forms a cluster beneath the continental shelf. Its updip limit coincides with the 150° C isotherm and an increase in Vp along the plate boundary. This further supports a proposed model in which the seismicity onset along the plate interface is mainly due to a decrease in the abundance of the fluids released by subducted sediments. Higher seismicity rates locally concur with seamounts present at the seismogenic zone, while seamounts under the margin slope may shallow the onset of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APhy...61..231B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APhy...61..231B"><span id="translatedtitle">Reconstruction of the sound <span class="hlt">velocity</span> and absorption spatial distributions in soft biological tissue phantoms from experimental ultrasound <span class="hlt">tomography</span> data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Burov, V. A.; Zotov, D. I.; Rumyantseva, O. D.</p> <p>2015-03-01</p> <p>The paper is devoted to implementing in a specific tomographic device a two-step algorithm designed to reconstruct the spatial distributions of the sound <span class="hlt">velocity</span> and absorption coefficient, primarily in soft biological tissues. To generate the input data of the first and second steps, a correlation algorithm is used based on determination of the time shift in the signal propagation time in the presence of an object. The results of reconstruction are presented, which are based on data measured for objects-phantoms using a developed experimental ultrasound tomograph model. We discuss problems that arise during reconstruction with a low resolution at the first step of the algorithm, and we demonstrate the high spatial resolving power achieved at the second step.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013ApJ...768...77A&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013ApJ...768...77A&link_type=ABSTRACT"><span id="translatedtitle">A Catalog of Ultra-compact High <span class="hlt">Velocity</span> Clouds from the ALFALFA Survey: Local <span class="hlt">Group</span> Galaxy Candidates?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Adams, Elizabeth A. K.; Giovanelli, Riccardo; Haynes, Martha P.</p> <p>2013-05-01</p> <p>We present a catalog of 59 ultra-compact high <span class="hlt">velocity</span> clouds (UCHVCs) extracted from the 40% complete ALFALFA HI-line survey. The ALFALFA UCHVCs have median flux densities of 1.34 Jy km s-1, median angular diameters of 10', and median <span class="hlt">velocity</span> widths of 23 km s-1. We show that the full UCHVC population cannot easily be associated with known populations of high <span class="hlt">velocity</span> clouds. Of the 59 clouds presented here, only 11 are also present in the compact cloud catalog extracted from the commensal GALFA-HI survey, demonstrating the utility of this separate dataset and analysis. Based on their sky distribution and observed properties, we infer that the ALFALFA UCHVCs are consistent with the hypothesis that they may be very low mass galaxies within the Local Volume. In that case, most of their baryons would be in the form of gas, and because of their low stellar content, they remain unidentified by extant optical surveys. At distances of ~1 Mpc, the UCHVCs have neutral hydrogen (H I) masses of ~105-106 M ⊙, H I diameters of ~2-3 kpc, and indicative dynamical masses within the H I extent of ~107-108 M ⊙, similar to the Local <span class="hlt">Group</span> ultra-faint dwarf Leo T. The recent ALFALFA discovery of the star-forming, metal-poor, low mass galaxy Leo P demonstrates that this hypothesis is true in at least one case. In the case of the individual UCHVCs presented here, confirmation of their extragalactic nature will require further work, such as the identification of an optical counterpart to constrain their distance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22126806','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22126806"><span id="translatedtitle">A CATALOG OF ULTRA-COMPACT HIGH <span class="hlt">VELOCITY</span> CLOUDS FROM THE ALFALFA SURVEY: LOCAL <span class="hlt">GROUP</span> GALAXY CANDIDATES?</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Adams, Elizabeth A. K.; Giovanelli, Riccardo; Haynes, Martha P. E-mail: riccardo@astro.cornell.edu</p> <p>2013-05-01</p> <p>We present a catalog of 59 ultra-compact high <span class="hlt">velocity</span> clouds (UCHVCs) extracted from the 40% complete ALFALFA HI-line survey. The ALFALFA UCHVCs have median flux densities of 1.34 Jy km s{sup -1}, median angular diameters of 10', and median <span class="hlt">velocity</span> widths of 23 km s{sup -1}. We show that the full UCHVC population cannot easily be associated with known populations of high <span class="hlt">velocity</span> clouds. Of the 59 clouds presented here, only 11 are also present in the compact cloud catalog extracted from the commensal GALFA-HI survey, demonstrating the utility of this separate dataset and analysis. Based on their sky distribution and observed properties, we infer that the ALFALFA UCHVCs are consistent with the hypothesis that they may be very low mass galaxies within the Local Volume. In that case, most of their baryons would be in the form of gas, and because of their low stellar content, they remain unidentified by extant optical surveys. At distances of {approx}1 Mpc, the UCHVCs have neutral hydrogen (H I) masses of {approx}10{sup 5}-10{sup 6} M{sub Sun }, H I diameters of {approx}2-3 kpc, and indicative dynamical masses within the H I extent of {approx}10{sup 7}-10{sup 8} M{sub Sun }, similar to the Local <span class="hlt">Group</span> ultra-faint dwarf Leo T. The recent ALFALFA discovery of the star-forming, metal-poor, low mass galaxy Leo P demonstrates that this hypothesis is true in at least one case. In the case of the individual UCHVCs presented here, confirmation of their extragalactic nature will require further work, such as the identification of an optical counterpart to constrain their distance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010SoPh..265..245J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010SoPh..265..245J"><span id="translatedtitle">Inclusion of In-Situ <span class="hlt">Velocity</span> Measurements into the UCSD Time-Dependent <span class="hlt">Tomography</span> to Constrain and Better-Forecast Remote-Sensing Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jackson, B. V.; Hick, P. P.; Bisi, M. M.; Clover, J. M.; Buffington, A.</p> <p>2010-08-01</p> <p>The University of California, San Diego (UCSD) three-dimensional (3-D) time-dependent <span class="hlt">tomography</span> program has been used successfully for a decade to reconstruct and forecast coronal mass ejections from interplanetary scintillation observations. More recently, we have extended this <span class="hlt">tomography</span> technique to use remote-sensing data from the Solar Mass Ejection Imager (SMEI) on board the Coriolis spacecraft; from the Ootacamund (Ooty) radio telescope in India; and from the European Incoherent SCATter (EISCAT) radar telescopes in northern Scandinavia. Finally, we intend these analyses to be used with observations from the Murchison Widefield Array (MWA), or the LOw Frequency ARray (LOFAR) now being developed respectively in Australia and Europe. In this article we demonstrate how in-situ <span class="hlt">velocity</span> measurements from the Advanced Composition Explorer (ACE) space-borne instrumentation can be used in addition to remote-sensing data to constrain the time-dependent tomographic solution. Supplementing the remote-sensing observations with in-situ measurements provides additional information to construct an iterated solar-wind parameter that is propagated outward from near the solar surface past the measurement location, and throughout the volume. While the largest changes within the volume are close to the radial directions that incorporate the in-situ measurements, their inclusion significantly reduces the uncertainty in extending these measurements to global 3-D reconstructions that are distant in time and space from the spacecraft. At Earth, this can provide a finely-tuned real-time measurement up to the latest time for which in-situ measurements are available, and enables more-accurate forecasting beyond this than remote-sensing observations alone allow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMDI41A4314L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMDI41A4314L"><span id="translatedtitle">Layer Stripping Forward <span class="hlt">Tomography</span> with S, ScS, and Sdiff phases to sharpen images of deep mantle shear <span class="hlt">velocity</span> heterogeneity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lai, H.; Garnero, E.; Zhao, C.</p> <p>2014-12-01</p> <p>The Earth's deep mantle has been shown to be heterogeneous at a wide spectrum of scales, from fine scale (e.g.,1-10 km) to degree 2 low <span class="hlt">velocity</span> provinces (1000's of km lateral scale). Principle structures include large low shear <span class="hlt">velocity</span> provinces (LLSVPs) beneath the Pacific Ocean and Africa and southern Atlanic Ocean, and a circum-Pacific higher <span class="hlt">velocity</span> band. At intermediate scales, structures include D" discontinuities and details associated with LLSVPs, such as sharp sides. Shorter scales include ultra-low <span class="hlt">velocity</span> zones (ULVZs) and regions of scattering of high frequency waves. In this study we seek to improve upon our knowledge of global intermediate and small-scale shear wave structure in the lower mantle with an iterative Layer-Stripping Forward <span class="hlt">Tomography</span> approach. This approach iteratively updates a starting tomographic model by mapping travel time residuals (between observations and predictions) from the surface (using shallow S wave phase) down to lowermost mantle depths (using deep S waves, ScS waves, and Sdiff waves). Modifications to the uppermost mantle are primarily aimed at properly correcting deep phases for shallow heterogeneity. Relatively uniform coverage of the deepest mantle is achieved with Sdiff. The core-reflected ScS contributes most strongly to our knowledge of shorter scale heterogeneity, but coverage is more limited that with Sdiff. Deep mantle S waves provide information on the vertical extent of lowermost mantle heterogeneity (e.g., LLSVPs), but similar to ScS, coverage is limited to source-receiver pairs with the proper distance range. We collected near 1200 global earthquakes global earthquakes from the last two decades, with depths greater than 30 km, and focused on data with clear and impulsive phases. In a semi-automatic scheme, we measured all S, ScS, and Sdiff times and document waveshape stability by constructing a mean shape of each phase for each event. Cross-correlation coefficients between individual records and the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27523454','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27523454"><span id="translatedtitle">Defining risk <span class="hlt">groups</span> of patients with cancer of unknown primary site and cervical nodal metastases by F-18 fluorodeoxyglucose positron emission <span class="hlt">tomography</span> and computed <span class="hlt">tomography</span> imaging.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Su, Yung-Yueh; Chen, Shih-Shin; Hsieh, Chia-Hsun; Liao, Chun-Ta; Lin, Chien-Yu; Kang, Chung-Jan; Yen, Tzu-Chen</p> <p>2016-08-01</p> <p>We sought to investigate the clinical utility of F-18 fluorodeoxyglucose (FDG) positron emission <span class="hlt">tomography</span> and computed <span class="hlt">tomography</span> (PET/CT) in Taiwanese patients with cancer of unknown primary site (CUP) and cervical nodal metastases. We also aimed to study the impact of F-18 FDG PET/CT on clinical treatment priority in this patient <span class="hlt">group</span>. Between September 2006 and May 2014, patients with CUP and cervical nodal metastases who underwent F-18 FDG PET/CT imaging study were retrospectively identified. The clinicopathological risk factors and PET parameters were analyzed in relation to 2-year overall survival (OS) rates using univariate and multivariate analyses. Two-year OS curves were plotted with the Kaplan-Meier method. Of the eligible patients (n = 54), 12 (22.2%) had distant metastases (DM) at presentation. A total of 13 (24.1%) and 15 (27.8%) primary tumors were identified by FDG PET/CT imaging and an additional triple biopsy, respectively. The results of multivariate analysis identified smoking [p = 0.033, 95% confidence interval (CI) = 1.197-40.342], a maximum standardized uptake value (SUVmax) of cervical nodes ≥ 14.2 (p = 0.035, 95% CI = 1.134-28.029), and DM at presentation (p = 0.031, 95% CI = 1.257-114.854) as independent predictors of 2-year OS. Specifically, patients who carried ≥ 2 risk factors showed poorer outcomes (70.3% vs. 11.8%, p < 0.001). Fifteen study patients (27.8%) had their treatment modified by FDG PET/CT findings. We conclude that FDG PET/CT is clinically useful in CUP patients not only for tumor staging, but also for modifying treatment regimens. PMID:27523454</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26233023','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26233023"><span id="translatedtitle">Experimental and numerical study of the excitability of zero <span class="hlt">group</span> <span class="hlt">velocity</span> Lamb waves by laser-ultrasound.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Grünsteidl, Clemens M; Veres, István A; Murray, Todd W</p> <p>2015-07-01</p> <p>The excitability of zero <span class="hlt">group</span> <span class="hlt">velocity</span> (ZGV) Lamb waves using a pulsed laser source is investigated experimentally and through numerical simulation. Experimentally, a laser based ultrasonic technique is used to find the optical spot size on the sample surface that allows an optimal coupling of the optical energy into the ZGV mode. Numerical simulations, using the time domain finite differences technique, are carried out to model the thermoelastic generation process by laser irradiation and the propagation of the generated acoustic waves. The experimental results are in good agreement with the numerical predictions. The experimentally and numerically obtained responses of the plate are investigated by a short-time Fourier transform. The responses show that the source diameter does not affect the fundamental behavior of the temporal decay of the ZGV mode. PMID:26233023</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22395863','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22395863"><span id="translatedtitle">Filamentation of a phase-modulated pulse under conditions of normal, anomalous and zero <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chekalin, S V; Kompanets, V O; Smetanina, E O; Spirkov, A I; Kandidov, V P</p> <p>2014-06-30</p> <p>We have investigated experimentally and numerically the influence of the initial temporal phase modulation of a pulse on the spatiotemporal intensity distribution and the frequency-angular spectrum of femtosecond laser pulses with self-channelling in a condensed medium. We have detected a decrease in the intensity of divergent anti-Stokes frequency components during filamentation of radiation under conditions of normal <span class="hlt">group-velocity</span> dispersion (GVD) and strong phase modulation. In the zero-GVD regime under conditions of the phase modulation of radiation, the spatiotemporal transformation of the pulse is similar to that in the normal-GVD regime, which leads to a qualitative change in the supercontinuum spectrum. In the anomalous-GVD regime, a sequence of 'light bullets' is formed in the filament for both a phase-modulated and a transform-limited pulse. (extreme light fields and their applications)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25121882','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25121882"><span id="translatedtitle">Measurement of <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion in a solid-core photonic crystal fiber filled with a nematic liquid crystal.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wahle, Markus; Kitzerow, Heinz</p> <p>2014-08-15</p> <p>Liquid crystal-filled photonic crystal fibers (PCFs) are promising candidates for electrically tunable integrated photonic devices. In this Letter, we present <span class="hlt">group</span> <span class="hlt">velocity</span> measurements on such fibers. A large mode area PCF, LMA8, was infiltrated with the liquid crystal mixture, E7. The measurements were performed with an interferometric setup. The fiber exhibits several spectral transmission windows in the visible wavelength regime that originate from the bandgap guiding mechanism. The dispersion of these windows is very unusual compared to typical fibers. Our measurements show that it can change from -2500 ps km(-1) nm(-1) to +2500 ps km(-1) nm(-1) within a spectral range of only 15 nm. This leads to multiple zero dispersion wavelengths in the visible wavelength range. PMID:25121882</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22130462','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22130462"><span id="translatedtitle"><span class="hlt">Group</span> <span class="hlt">velocity</span> dispersion and relativistic effects on the wakefield induced by chirped laser pulse in parabolic plasma channel</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sohbatzadeh, F.; Akou, H.</p> <p>2013-04-15</p> <p>The excitation of wake field plasma waves by a short laser pulse propagating through a parabolic plasma channel is studied. The laser pulse is assumed to be initially chirped. In this regard, the effects of initial and induced chirp on the plasma wake field as well as the laser pulse parameters are investigated. The <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion and nonlinear relativistic effects were taken into account to evaluate the excited wake field in two dimension using source dependent expansion method. Positive, negative, and un-chirped laser pulses were employed in numerical code to evaluate the effectiveness of the initial chirp on 2-D wake field excitation. Numerical results showed that for laser irradiances exceeding 10{sup 18}W/cm{sup 2}, an intense laser pulse with initial positive chirp generates larger wake field compared to negatively and un-chirped pulses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhPl...20d3101S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhPl...20d3101S"><span id="translatedtitle"><span class="hlt">Group</span> <span class="hlt">velocity</span> dispersion and relativistic effects on the wakefield induced by chirped laser pulse in parabolic plasma channel</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sohbatzadeh, F.; Akou, H.</p> <p>2013-04-01</p> <p>The excitation of wake field plasma waves by a short laser pulse propagating through a parabolic plasma channel is studied. The laser pulse is assumed to be initially chirped. In this regard, the effects of initial and induced chirp on the plasma wake field as well as the laser pulse parameters are investigated. The <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion and nonlinear relativistic effects were taken into account to evaluate the excited wake field in two dimension using source dependent expansion method. Positive, negative, and un-chirped laser pulses were employed in numerical code to evaluate the effectiveness of the initial chirp on 2-D wake field excitation. Numerical results showed that for laser irradiances exceeding 1018W/cm2, an intense laser pulse with initial positive chirp generates larger wake field compared to negatively and un-chirped pulses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014QuEle..44..577C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014QuEle..44..577C"><span id="translatedtitle">Filamentation of a phase-modulated pulse under conditions of normal, anomalous and zero <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chekalin, S. V.; Smetanina, E. O.; Spirkov, A. I.; Kompanets, V. O.; Kandidov, V. P.</p> <p>2014-06-01</p> <p>We have investigated experimentally and numerically the influence of the initial temporal phase modulation of a pulse on the spatiotemporal intensity distribution and the frequency-angular spectrum of femtosecond laser pulses with self-channelling in a condensed medium. We have detected a decrease in the intensity of divergent anti-Stokes frequency components during filamentation of radiation under conditions of normal <span class="hlt">group-velocity</span> dispersion (GVD) and strong phase modulation. In the zero-GVD regime under conditions of the phase modulation of radiation, the spatiotemporal transformation of the pulse is similar to that in the normal-GVD regime, which leads to a qualitative change in the supercontinuum spectrum. In the anomalous-GVD regime, a sequence of 'light bullets' is formed in the filament for both a phase-modulated and a transform-limited pulse.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.S41B2742K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.S41B2742K&link_type=ABSTRACT"><span id="translatedtitle">New Observations of Seismic <span class="hlt">Group</span> <span class="hlt">Velocities</span> in the Western Solomon Islands from Cross-Correlation of Ambient Seismic Noise</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ku, C. S.; You, S. H.; Kuo, Y. T.; Huang, B. S.; Wu, Y. M.; Chen, Y. G.; Taylor, F. W.</p> <p>2015-12-01</p> <p>A MW 8.1 earthquake occurred on 1 April 2007 in the western Solomon Islands. Following this event, a damaging tsunami was induced and hit the Island Gizo where the capital city of Western Province of Solomon Islands located. Several buildings of this city were destroyed and several peoples lost their lives during this earthquake. However, during this earthquake, no near source seismic instrument has been installed in this region. The seismic evaluations for the aftershock sequence, the possible earthquake early warning and tsunami warning were unavailable. For the purpose of knowing more detailed information about seismic activity in this region, we have installed 9 seismic stations (with Trillium 120PA broadband seismometer and Q330S 24bit digitizer) around the rupture zone of the 2007 earthquake since September of 2009. Within a decade, it has been demonstrated both theoretically and experimentally that the Green's function or impulse response between two seismic stations can be retrieved from the cross-correlation of ambient noise. In this study, 6 stations' observations which are more complete during 2011/10 ~ 2012/12 period, were selected for the purpose of the cross-correlation analysis of ambient seismic noise. The <span class="hlt">group</span> <span class="hlt">velocities</span> at period 2-20 seconds of 15 station-pairs were extracted by using multiple filter technique (MFT) method. The analyzed results of this study presented significant results of <span class="hlt">group</span> <span class="hlt">velocities</span> with higher frequency contents than other studies (20-60 seconds in usually cases) and opened new opportunities to study the shallow crustal structure of the western Solomon Islands.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22036442','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22036442"><span id="translatedtitle">Simultaneous measurement of <span class="hlt">group</span> refractive index and thickness of optical samples using optical coherence <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cheng, Hsu-Chih; Liu, Yi-Cheng</p> <p>2010-02-10</p> <p>Optical coherence <span class="hlt">tomography</span> (OCT), based on a Michelson interferometer and utilizing low coherence light as the optical source, is a novel technique for the noninvasive imaging of optical scattering media. A simple OCT scheme based on a 3x3 fiber coupler is presented for the simultaneous measurement of the refractive index and thickness of optical samples. The proposed system enables the refractive index and thickness to be determined without any prior knowledge of the sample parameters and is characterized by a simple and compact configuration, a straightforward measurement procedure, and a low cost. The feasibility of the proposed approach is demonstrated experimentally using BK7 and B270 optical glass samples.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008GeoJI.175..689S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008GeoJI.175..689S"><span id="translatedtitle">P- and SV-<span class="hlt">velocity</span> structure of the South Portuguese Zone fold-and-thrust belt, SW Iberia, from traveltime <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmelzbach, C.; Zelt, C. A.; Juhlin, C.; Carbonell, R.</p> <p>2008-11-01</p> <p>Imaging the architecture of the shallow crust of the South Portuguese Zone fold-and-thrust belt is essential to extend surface mapped geological information to depth and to help in developing models of the ore-bearing Iberian Pyrite Belt part of the Variscan orogeny. The recently acquired IBERSEIS seismic-reflection data set provides, for the first time, detailed images of the entire crust, but source-generated noise masks the earliest reflections and limits the shallowest observed signals to depths >500m. We inverted P- and SV first-arrival traveltimes for the smoothest minimum-structure <span class="hlt">velocity</span> models, imaging the shallowest few hundreds of metres along four in total ~60-km-long profiles. A comparison of a 2-D and 2.5-D (3-D forward and 2-D inverse problem) crooked-line inversion scheme revealed that the crooked-line geometry has a negligible effect on the final images. Resolution of the final preferred models was assessed on the basis of an extensive series of checkerboard tests, showing a slightly lower resolution capability of the SV-data due to greater data uncertainty, fewer number of picks and more limited source-receiver offsets compared with the P-data. The preferred final models compare favourably with the mapped surface geology, showing relatively high and uniform <span class="hlt">velocities</span> (>5.25kms-1) for the flysch <span class="hlt">group</span> in the southern part of the investigation area. Low <span class="hlt">velocities</span> (~4.5kms-1) are found for the `La Puebla de Guzman antiform' in the centre of the investigation area, where the phyllite-quartzite <span class="hlt">group</span> is exposed. <span class="hlt">Velocities</span> fluctuate the most along the northernmost ~20km. <span class="hlt">Velocity</span> variations reflect more the state of tectonic deformation than being directly correlated with the mapped lithologies. Based on a comparison with coincident seismic-reflection data along the southern half of the area, we suggest that two areas of low to intermediate ratios (~1.85-1.9) correspond to occurrences of thick and less deformed flysch-<span class="hlt">group</span> units, whereas high</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1010842','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1010842"><span id="translatedtitle">Structure of the Crust beneath Cameroon, West Africa, from the Joint Inversion of Rayleigh Wave <span class="hlt">Group</span> <span class="hlt">Velocities</span> and Receiver Functions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tokam, A K; Tabod, C T; Nyblade, A A; Julia, J; Wiens, D A; Pasyanos, M E</p> <p>2010-02-18</p> <p> Cameroon using 1-D shear wave <span class="hlt">velocity</span> models obtained from the joint inversion of Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocities</span> and P-receiver functions for 32 broadband seismic stations. From the 1-D shear wave <span class="hlt">velocity</span> models, we obtain new insights into the composition and structure of the crust and upper mantle across Cameroon. After briefly reviewing the geological framework of Cameroon, we describe the data and the joint inversion method, and then interpret variations in crustal structure found beneath Cameroon in terms of the tectonic history of the region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.T51A0304T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.T51A0304T"><span id="translatedtitle">A Detailed 3D Seismic <span class="hlt">Velocity</span> Structure of the Subducting Pacific Slab Beneath Hokkaido, Tohoku and Kanto, Japan, by Double-Difference <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tsuji, Y.; Nakajima, J.; Kita, S.; Okada, T.; Matsuzawa, T.; Hasegawa, A.</p> <p>2007-12-01</p> <p>Three-dimensional heterogeneous structure beneath northeastern (NE) Japan has been investigated by previous studies and an inclined seismic low-<span class="hlt">velocity</span> zone is imaged in the mantle wedge sub-parallel to the down-dip direction of the subducting slab (Zhao et al., 1992, Nakajima et al., 2001). However, the heterogeneous structure within the slab has not been well studied even though it is very important to understand the whole process of water transportation from the slab to the surface. Here we show a detailed 3D seismic <span class="hlt">velocity</span> structure within the subducted Pacific slab around Japan and propose a water-transportation path from the slab to the mantle wedge. In this study, we estimated 3D <span class="hlt">velocity</span> structure within the Pacific slab by the double-difference <span class="hlt">tomography</span> (Zhang and Thurber, 2003). We divided the study area, from Hokkaido to Kanto, into 6 areas due to the limitation of memory and computation time. In each area, arrival-time data of 7,500-17,000 events recorded at 70-170 stations were used in the analysis. The total number of absolute travel-time data was about 140,000-312,000 for P wave and 123,000-268,000 for S wave, and differential data were about 736,000-1,920,000 for P wave and 644,000-1,488,000 for S wave. Horizontal and vertical grid separations are 10-25 km and 6.5 km, respectively. RMS residuals of travel times for P wave decreased from 0.23s to 0.09s and for S wave from 0.35s to 0.13s. The obtained results are as follows: (1) a remarkable low-Vs zone exists in the uppermost part of the subducting slab, (2) it extends down to a depth of about 80 km, (3) the termination of this low-Vs zone almost corresponds to the "seismic belt" recently detected in the upper plane of the double seismic zone (Kita et al.,2006; Hasegawa et al., 2007), (4) at depths deeper than 80 km, a low-Vs and high-Vp/Vs zone is apparently distributed in the mantle wedge, immediately above the slab crust. We consider that these features reflect water-transportation processes</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24921834','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24921834"><span id="translatedtitle">Tamm plasmon-polariton with negative <span class="hlt">group</span> <span class="hlt">velocity</span> induced by a negative index meta-material capping layer at metal-Bragg reflector interface.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Liu, Cunding; Kong, Mingdong; Li, Bincheng</p> <p>2014-05-01</p> <p>Influence of a negative refractive index meta-material (NIM) capping layer on properties of Tamm plasmon-polariton at the interface of metal-Bragg reflector structure is investigated. Conditions for excitation of the plasmon-polariton is determined from reflectivity mapping calculation and analyzed with cavity mode theory. For specific thicknesses of capping layers, Tamm plasmon-polariton with negative <span class="hlt">group</span> <span class="hlt">velocity</span> is revealed in a wide region of frequency. Different from backward optical propagation induced by negative effective-<span class="hlt">group</span>-refractive-index in dispersive media, negative <span class="hlt">group</span> <span class="hlt">velocity</span> of Tamm plasmon-polariton results from opposite signs of cross-section-integrated field energy and Poynting vector. PMID:24921834</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvA..93b3834C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvA..93b3834C"><span id="translatedtitle">Modulation instability in noninstantaneous Kerr media with walk-off and cross-phase modulation for mixed <span class="hlt">group-velocity</span>-dispersion regimes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Canabarro, Askery; Santos, B.; de Lima Bernardo, B.; Moura, André L.; Soares, W. C.; de Lima, E.; Gléria, Iram; Lyra, M. L.</p> <p>2016-02-01</p> <p>Taking into account relaxing Kerr nonlinearity and walk-off effects, the conditions and gain spectra of cross-phase modulation-induced modulational instability (XPM-MI) of two incoherently copropagating optical waves of different frequencies and same polarization are investigated. We devote particular attention to the mixed case in which one pulse propagates under the normal <span class="hlt">group-velocity</span> dispersion (GVD) regime, while the second one is under an anomalous GVD regime. We unveil that in the limit of an instantaneuous nonlinear response, the typical frequency with maximum gain converges to a finite value in the mixed GDV regime, while it continuously grows with the <span class="hlt">group-velocity</span> mismatch in the normal GVD regime. As a result, the maximum gain typically decreases with the <span class="hlt">group-velocity</span> mismatch in the mixed regime, contrasting with the opposite trend in the normal GVD regime. Further, we show that besides the mode having maximum gain at a frequency decaying with 1 /τ1 /3 in the slow response limit, there is a second mode having maximum gain with a distinct scaling behavior Ωmax∝1 /τ in the absence of <span class="hlt">group-velocity</span> mismatch. The associated maximum gains scale, respectively, as 1 /τ2 /3 and 1 /τ , thus signaling the corresponding quadratic and linear dispersion relation of these modes in the low-frequency limit. A detailed analysis of the influence of the nonlinear response time and <span class="hlt">group-velocity</span> dispersion on the MI gain spectrum is also provided.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013Tectp.602...38W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013Tectp.602...38W"><span id="translatedtitle">New constraints on the 3D shear wave <span class="hlt">velocity</span> structure of the upper mantle underneath Southern Scandinavia revealed from non-linear <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wawerzinek, B.; Ritter, J. R. R.; Roy, C.</p> <p>2013-08-01</p> <p>We analyse travel times of shear waves, which were recorded at the MAGNUS network, to determine the 3D shear wave <span class="hlt">velocity</span> (vS) structure underneath Southern Scandinavia. The travel time residuals are corrected for the known crustal structure of Southern Norway and weighted to account for data quality and pick uncertainties. The resulting residual pattern of subvertically incident waves is very uniform and simple. It shows delayed arrivals underneath Southern Norway compared to fast arrivals underneath the Oslo Graben and the Baltic Shield. The 3D upper mantle vS structure underneath the station network is determined by performing non-linear travel time <span class="hlt">tomography</span>. As expected from the residual pattern the resulting tomographic model shows a simple and continuous vS perturbation pattern: a negative vS anomaly is visible underneath Southern Norway relative to the Baltic Shield in the east with a contrast of up to 4% vS and a sharp W-E dipping transition zone. Reconstruction tests reveal besides vertical smearing a good lateral reconstruction of the dipping vS transition zone and suggest that a deep-seated anomaly at 330-410 km depth is real and not an inversion artefact. The upper part of the reduced vS anomaly underneath Southern Norway (down to 250 km depth) might be due to an increase in lithospheric thickness from the Caledonian Southern Scandes in the west towards the Proterozoic Baltic Shield in Sweden in the east. The deeper-seated negative vS anomaly (330-410 km depth) could be caused by a temperature anomaly possibly combined with effects due to fluids or hydrous minerals. The determined simple 3D vS structure underneath Southern Scandinavia indicates that mantle processes might influence and contribute to a Neogene uplift of Southern Norway.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70025699','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70025699"><span id="translatedtitle">Seismic <span class="hlt">velocity</span> anisotropy and heterogeneity beneath the Mantle Electromagnetic and <span class="hlt">Tomography</span> Experiment (MELT) region of the East Pacific Rise from analysis of P and S body waves</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hammond, W.C.; Toomey, D.R.</p> <p>2003-01-01</p> <p>We use teleseismic P and S delay times and shear wave splitting measurements to constrain isotropic and anisotropic heterogeneity in the mantle beneath the southern East Pacific Rise (SEPR). The data comprise 462 P and S delay times and 18 shear wave splitting observations recorded during the Mantle Electromagnetic and <span class="hlt">Tomography</span> (MELT) Experiment. We estimate the mantle melt content (F) and temperature (T) variation from the isotropic <span class="hlt">velocity</span> variation. Our results indicate that the maximum variation in F beneath our array is between zero and ???1.2%, and maximum variation in T is between zero and ???100 K. We favor an explanation having partial contributions from both T and F. We approximate the seismic anisotropy of the upper mantle with hexagonal symmetry, consistent with the assumption of two dimensionality of mantle flow. Our new tomographic technique uses a nonlinear inversion of P and slow S polarization delay times to simultaneously solve for coupled VP and VS heterogeneity throughout the model and for the magnitude of anisotropy within discrete domains. The domain dimensions and the dip of the anisotropy are fixed for each inversion but are varied in a grid search, obtaining the misfit of the models to the body wave delay data and to split times of vertically propagating S waves. The data misfit and the isotropic heterogeneity are sensitive to domain dimensions and dip of anisotropy. In a region centered beneath the SEPR the best average dip of the hexagonal symmetry axis is horizontal or dipping shallowly (<30??) west. Given the resolution of our data, a subaxial region characterized by vertically aligned symmetry axes may exist but is limited to be <80 km deep. We infer that the mantle flow beneath the SEPR is consistent with shallow asthenospheric return flow from the direction of the South Pacific superswell.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/966531','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/966531"><span id="translatedtitle">Developing regionalized models of lithospheric thickness and <span class="hlt">velocity</span> structure across Eurasia and the Middle East from jointly inverting P-wave and S-wave receiver functions with Rayleigh wave <span class="hlt">group</span> and phase <span class="hlt">velocities</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Julia, J; Nyblade, A; Hansen, S; Rodgers, A; Matzel, E</p> <p>2009-07-06</p> <p>In this project, we are developing models of lithospheric structure for a wide variety of tectonic regions throughout Eurasia and the Middle East by regionalizing 1D <span class="hlt">velocity</span> models obtained by jointly inverting P-wave and S-wave receiver functions with Rayleigh wave <span class="hlt">group</span> and phase <span class="hlt">velocities</span>. We expect the regionalized <span class="hlt">velocity</span> models will improve our ability to predict travel-times for local and regional phases, such as Pg, Pn, Sn and Lg, as well as travel-times for body-waves at upper mantle triplication distances in both seismic and aseismic regions of Eurasia and the Middle East. We anticipate the models will help inform and strengthen ongoing and future efforts within the NNSA labs to develop 3D <span class="hlt">velocity</span> models for Eurasia and the Middle East, and will assist in obtaining model-based predictions where no empirical data are available and for improving locations from sparse networks using kriging. The codes needed to conduct the joint inversion of P-wave receiver functions (PRFs), S-wave receiver functions (SRFs), and dispersion <span class="hlt">velocities</span> have already been assembled as part of ongoing research on lithospheric structure in Africa. The methodology has been tested with synthetic 'data' and case studies have been investigated with data collected at an open broadband stations in South Africa. PRFs constrain the size and S-P travel-time of seismic discontinuities in the crust and uppermost mantle, SRFs constrain the size and P-S travel-time of the lithosphere-asthenosphere boundary, and dispersion <span class="hlt">velocities</span> constrain average S-wave <span class="hlt">velocity</span> within frequency-dependent depth-ranges. Preliminary results show that the combination yields integrated 1D <span class="hlt">velocity</span> models local to the recording station, where the discontinuities constrained by the receiver functions are superimposed to a background <span class="hlt">velocity</span> model constrained by the dispersion <span class="hlt">velocities</span>. In our first year of this project we will (i) generate 1D <span class="hlt">velocity</span> models for open broadband seismic stations in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.S31B2233K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.S31B2233K"><span id="translatedtitle">Variable feeding regimes of the Kluchevskoy <span class="hlt">group</span> volcanoes (Kamchatka, Russia) derived from time-dependent seismic <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Koulakov, I.; Gordeev, E.; Dobretsov, N. L.; Vernikovsky, V. A.; Senyukov, S.; Jakovlev, A.</p> <p>2011-12-01</p> <p>We present the results of time-dependent local earthquake <span class="hlt">tomography</span> for the Kluchevskoy <span class="hlt">group</span> of volcanoes in Kamchatka. We consider the time period from 2001 to 2008, which covers several stages of activity for Kluchevskoy and Bezymyanny volcanoes. During the entire period, we robustly observe a mantle channel below 25 km depth with anomalously high Vp/Vs values (up to 2.2), which is interpreted to be the main feeding source of the volcanoes of the <span class="hlt">group</span>. In the crust, we derived complex structure that varies over the observation time. During the pre-eruptive period, we detected two levels of magma sources: one in the middle crust and one just below Kluchevskoy volcano. In 2005, a year of powerful eruptions of Kluchevskoy and Besymyanny volcanoes, we observe a general increase in Vp/Vs throughout the crust. In the relaxation period following the eruption, the Vp/Vs values are generally low, and no anomalous zones in the crust are observed. We propose that very rapid variations in Vp/Vs are most likely due to abrupt changes in stress and deformation regime, which cause fracturing and the active transport of fluids. This causes positive feedback, and the excessive stresses in the crust lead to volcanic eruptions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23037310','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23037310"><span id="translatedtitle">Synthesis of [(18)F]SiFB: a prosthetic <span class="hlt">group</span> for direct protein radiolabeling for application in positron emission <span class="hlt">tomography</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kostikov, Alexey P; Chin, Joshua; Orchowski, Katy; Schirrmacher, Esther; Niedermoser, Sabrina; Jurkschat, Klaus; Iovkova-Berends, Liuba; Wängler, Carmen; Wängler, Björn; Schirrmacher, Ralf</p> <p>2012-11-01</p> <p>N-Succinimidyl 3-(di-tert-butyl[(18)F]fluorosilyl)benzoate ([(18)F]SiFB) is a highly reactive prosthetic <span class="hlt">group</span> for radiolabeling of proteins for use in positron emission <span class="hlt">tomography</span> (PET). It is similar to N-succinimidyl-4-[(18)F]fluorobenzoate ([(18)F]SFB), the 'gold-standard' prosthetic <span class="hlt">group</span> for protein (18)F-labeling, but can be synthesized using a much shorter and technically easier procedure. A recently reported simple procedure to obtain anhydrous (18)F- by avoiding time-consuming azeotropic drying is applied with a slight modification to prevent basic hydrolysis of the active N-hydroxysuccinimide (NHS) ester moiety of [(18)F]SiFB. The labeling of [(18)F]SiFB is performed by a fast (18)F-(19)F isotopic exchange (IE) reaction at room temperature (20-25 °C) within 30 min. [(18)F]SiFB is purified using a C18 cartridge instead of HPLC, further decreasing the overall time required for protein labeling. High specific activities > 18.5 GBq μmol(-1) (> 500 Ci mmol(-1)) can be obtained. Finally, incubation of [(18)F]SiFB with the desired protein in an aqueous solution at pH 9, followed by HPLC purification, provides the final solution of the labeled protein ready for in vivo applications. PMID:23037310</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4510826','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4510826"><span id="translatedtitle">Visceral adipose tissue influences on coronary artery calcification at young and middle-age <span class="hlt">groups</span> using computed <span class="hlt">tomography</span> angiography</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Abazid, Rami M.; Kattea, M. Obadah; Sayed, Sawsan; Saqqah, Hanaa; Qintar, Mohammed; Smettei, Osama A.</p> <p>2015-01-01</p> <p>Purpose: The purpose of the study was to evaluate the impact of excessive visceral adipose tissue (VAT) on subclinical coronary atherosclerosis and coronary artery calcifications (CAC) in young and middle-age <span class="hlt">groups</span> using multislice computed <span class="hlt">tomography</span>. Methods: This study is a single center, cross-sectional study. Eligible patients (n = 159), who under the age of 61 years, with chest pain and mild to moderate probability to have coronary artery disease (CAD) were enrolled. Coronary calcium score and epicardial adipose tissue (EAT) were measured at the level of the left main coronary artery while VAT was measured at the level of the iliac crest. Results: The average age was (48 ± 8 years). The mean VAT was (38 ± 21 cm2) with no significant difference between men and women (38 ± 22 vs. 37 ± 19 P = 0.8) respectively. Student's t-test analysis showed significantly higher VAT in patients with detectable CAC than patients with no CAC (48 ± 24 vs. 33 ± 18 P = 0.00002), respectively. Univariate regression analysis showed that VAT and EAT, are strong predictor for CAC (hazard ratio [HR] 1.034, 95% confidence interval [CI: 1.016–1.052]. P <0.001 and [HR] 1.344, 95% CI: [1.129–1.601] P = 0.001), respectively. Conclusion: Excessive VAT is significantly associated with positive CAC. VAT can strongly predict subclinical CAD in individuals at young and middle-age <span class="hlt">groups</span>. PMID:26229760</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUSM.S51A..02D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUSM.S51A..02D"><span id="translatedtitle">Toward Improved Methods of Estimating Attenuation, Phase and <span class="hlt">Group</span> <span class="hlt">velocity</span> of surface waves observed on Shallow Seismic Records</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Diallo, M. S.; Holschneider, M.; Kulesh, M.; Scherbaum, F.; Ohrnberger, M.; Lück, E.</p> <p>2004-05-01</p> <p>This contribution is concerned with the estimate of attenuation and dispersion characteristics of surface waves observed on a shallow seismic record. The analysis is based on a initial parameterization of the phase and attenuation functions which are then estimated by minimizing a properly defined merit function. To minimize the effect of random noise on the estimates of dispersion and attenuation we use cross-correlations (in Fourier domain) of preselected traces from some region of interest along the survey line. These cross-correlations are then expressed in terms of the parameterized attenuation and phase functions and the auto-correlation of the so-called source trace or reference trace. Cross-corelation that enter the optimization are selected so as to provide an average estimate of both the attenuation function and the phase (<span class="hlt">group</span>) <span class="hlt">velocity</span> of the area under investigation. The advantage of the method over the standard two stations method using Fourier technique is that uncertainties related to the phase unwrapping and the estimate of the number of 2π cycle skip in the phase phase are eliminated. However when mutliple modes arrival are observed, its become merely impossible to obtain reliable estimate the dipsersion curves for the different modes using optimization method alone. To circumvent this limitations we using the presented approach in conjunction with the wavelet propagation operator (Kulesh et al., 2003) which allows the application of band pass filtering in (ω -t) domain, to select a particular mode for the minimization. Also by expressing the cost function in the wavelet domain the optimization can be performed either with respect to the phase, the modulus of the transform or a combination of both. This flexibility in the design of the cost function provides an additional mean of constraining the optimization results. Results from the application of this dispersion and attenuation analysis method are shown for both synthetic and real 2D shallow</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.S41B2725W&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.S41B2725W&link_type=ABSTRACT"><span id="translatedtitle">Application of the energy reassignment method to measure accurate Rayleigh and Love wave <span class="hlt">group</span> <span class="hlt">velocities</span> from ambient seismic noise cross-correlations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Witek, M.; Kang, T. S.; van der Lee, S.</p> <p>2015-12-01</p> <p>We have collected three-component data from 122 Korean accelerometer stations for the month of December in 2014. We apply similar techniques described by Zha et al. (2013) to retrieve accurate station orientation angles, in order to rotate the horizontal component data into the radial and transverse frame of reference, and for subsequent measurement of Love wave <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion. We simultaneously normalize all three components of a daily noise record via the frequency-time normalization (FTN) method. Each component is divided by the average signal envelope in an effort to retain relative amplitude information between all three components. Station orientations are found by a grid search for the orientation azimuth which maximizes the coherency between the radial-vertical cross-correlation and the Hilbert transformed vertical-vertical cross-correlation. After measuring orientation angles, we cross-correlate and rotate the data. Typically, the <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion curves are measured using the frequency time analysis technique (FTAN), effectively producing spectrograms with significant uncertainty in the time-frequency plane. The spectrogram approach retains only the amplitude information of the short-time Fourier transform (STFT). However, Kodera et al (1976) show that by taking into account the phase information, the concepts of instantaneous frequency and <span class="hlt">group</span>-time delay can be used to compute the first moment of the signal power in the frequency and time domains. During energy reassignment, the signal power calculated using the STFT at a point (t0,f0t_0, f_0) is reassigned to the location of the first moment (t^g,f^ihat{t}_g,hat{f}_i), where t^ghat{t}_g is the <span class="hlt">group</span>-time delay and f^ihat{f}_i is the instantaneous frequency. We apply the method of energy reassignment to produce precise Rayleigh and Love wave <span class="hlt">group</span> <span class="hlt">velocity</span> measurements in the frequency range 0.1 - 1.0 Hz. Tests on synthetic data show more accurate retrieval of <span class="hlt">group</span> <span class="hlt">velocities</span> at</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27203477','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27203477"><span id="translatedtitle">Empirical validation of statistical parametric mapping for <span class="hlt">group</span> imaging of fast neural activity using electrical impedance <span class="hlt">tomography</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Packham, B; Barnes, G; Dos Santos, G Sato; Aristovich, K; Gilad, O; Ghosh, A; Oh, T; Holder, D</p> <p>2016-06-01</p> <p>Electrical impedance <span class="hlt">tomography</span> (EIT) allows for the reconstruction of internal conductivity from surface measurements. A change in conductivity occurs as ion channels open during neural activity, making EIT a potential tool for functional brain imaging. EIT images can have  >10 000 voxels, which means statistical analysis of such images presents a substantial multiple testing problem. One way to optimally correct for these issues and still maintain the flexibility of complicated experimental designs is to use random field theory. This parametric method estimates the distribution of peaks one would expect by chance in a smooth random field of a given size. Random field theory has been used in several other neuroimaging techniques but never validated for EIT images of fast neural activity, such validation can be achieved using non-parametric techniques. Both parametric and non-parametric techniques were used to analyze a set of 22 images collected from 8 rats. Significant <span class="hlt">group</span> activations were detected using both techniques (corrected p  <  0.05). Both parametric and non-parametric analyses yielded similar results, although the latter was less conservative. These results demonstrate the first statistical analysis of such an image set and indicate that such an analysis is an approach for EIT images of neural activity. PMID:27203477</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013AGUFM.S33A2400C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013AGUFM.S33A2400C&link_type=ABSTRACT"><span id="translatedtitle">Constructing a starting 3D shear <span class="hlt">velocity</span> model with sharp interfaces for SEM-based upper mantle <span class="hlt">tomography</span> in North America</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Calo, M.; Bodin, T.; Yuan, H.; Romanowicz, B. A.; Larmat, C. S.; Maceira, M.</p> <p>2013-12-01</p> <p>Seismic <span class="hlt">tomography</span> is currently evolving towards 3D earth models that satisfy full seismic waveforms at increasingly high frequencies. This evolution is possible thanks to the advent of powerful numerical methods such as the Spectral Element Method (SEM) that allow accurate computation of the seismic wavefield in complex media, and the drastic increase of computational resources. However, the production of such models requires handling complex misfit functions with more than one local minimum. Standard linearized inversion methods (such as gradient methods) have two main drawbacks: 1) they produce solution models highly dependent on the starting model; 2) they do not provide a means of estimating true model uncertainties. However, these issues can be addressed with stochastic methods that can sample the space of possible solutions efficiently. Such methods are prohibitively challenging computationally in 3D, but increasingly accessible in 1D. In previous work (Yuan and Romanowicz, 2010; Yuan et al., 2011) we developed a continental scale anisotropic upper mantle model of north America based on a combination of long period seismic waveforms and SKS splitting measurements, showing the pervasive presence of layering of anisotropy in the cratonic lithosphere with significant variations in depth of the mid-lithospheric boundary. The radial anisotropy part of the model has been recently updated using the spectral element method for forward wavefield computations and waveform data from the latest deployments of USarray (Yuan and Romanowicz, 2013). However, the long period waveforms (periods > 40s) themselves only provide a relatively smooth view of the mantle if the starting model is smooth, and the mantle discontinuities necessary for geodynamical interpretation are not imaged. Increasing the frequency of the computations to constrain smaller scale features is possible, but challenging computationally, and at the risk of falling in local minima of the misfit function. In</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...819..133A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...819..133A"><span id="translatedtitle">The Radial and Rotational <span class="hlt">Velocities</span> of PSO J318.5338-22.8603, a Newly Confirmed Planetary-mass Member of the β Pictoris Moving <span class="hlt">Group</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Allers, K. N.; Gallimore, J. F.; Liu, Michael C.; Dupuy, Trent J.</p> <p>2016-03-01</p> <p>PSO J318.5338-22.8603 is an extremely red planetary-mass object that has been identified as a candidate member of the β Pictoris moving <span class="hlt">group</span> based on its spatial position and tangential <span class="hlt">velocity</span>. We present a high-resolution K-band spectrum of PSO J318.5338-22.8603. Using a forward modeling Markov Chain Monte Carlo approach, we report the first measurement of the radial <span class="hlt">velocity</span> and v sin(i) of PSO J318.5-22, -{6.0}-1.1+0.8 km s-1, and {17.5}-2.8+2.3 km s-1, respectively. We calculate the space <span class="hlt">velocity</span> and position of PSO J318.5-22 and confirm that it is a member of the β Pictoris moving <span class="hlt">group</span>. Adopting an age of 23 ± 3 Myr for PSO J318.5-22, we determine a mass of 8.3 ± 0.5 MJup and an effective temperature of {1127}-26+24 K using evolutionary models. PSO J318.5338-22.8603 is intermediate in mass and temperature to the directly imaged planets β Pictoris b and 51 Eridani b, making it an important benchmark object in the sequence of the planetary-mass members of the β Pictoris moving <span class="hlt">group</span>. Combining our v sin(i) measurement with recent photometric variability data, we constrain the inclination of PSO J318.5-22 to >29° and its rotational period to 5-10.2 hr. The equatorial <span class="hlt">velocity</span> of PSO J318.5-22 indicates that its rotation is consistent with an extrapolation of the <span class="hlt">velocity</span>-mass relationship for solar system planets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3220670','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3220670"><span id="translatedtitle">Better Safe than Sorry - Socio-Spatial <span class="hlt">Group</span> Structure Emerges from Individual Variation in Fleeing, Avoidance or <span class="hlt">Velocity</span> in an Agent-Based Model</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Evers, Ellen; de Vries, Han; Spruijt, Berry M.; Sterck, Elisabeth H. M.</p> <p>2011-01-01</p> <p>In <span class="hlt">group</span>-living animals, such as primates, the average spatial <span class="hlt">group</span> structure often reflects the dominance hierarchy, with central dominants and peripheral subordinates. This central-peripheral <span class="hlt">group</span> structure can arise by self-organization as a result of subordinates fleeing from dominants after losing a fight. However, in real primates, subordinates often avoid interactions with potentially aggressive <span class="hlt">group</span> members, thereby preventing aggression and subsequent fleeing. Using agent-based modeling, we investigated which spatial and encounter structures emerge when subordinates also avoid known potential aggressors at a distance as compared with the model which only included fleeing after losing a fight (fleeing model). A central-peripheral <span class="hlt">group</span> structure emerged in most conditions. When avoidance was employed at small or intermediate distances, centrality of dominants emerged similar to the fleeing model, but in a more pronounced way. This result was also found when fleeing after a fight was made independent of dominance rank, i.e. occurred randomly. Employing avoidance at larger distances yielded more spread out <span class="hlt">groups</span>. This provides a possible explanation of larger <span class="hlt">group</span> spread in more aggressive species. With avoidance at very large distances, spatially and socially distinct subgroups emerged. We also investigated how encounters were distributed amongst <span class="hlt">group</span> members. In the fleeing model all individuals encountered all <span class="hlt">group</span> members equally often, whereas in the avoidance model encounters occurred mostly among similar-ranking individuals. Finally, we also identified a very general and simple mechanism causing a central-peripheral <span class="hlt">group</span> structure: when individuals merely differed in <span class="hlt">velocity</span>, faster individuals automatically ended up at the periphery. In summary, a central-peripheral <span class="hlt">group</span> pattern can easily emerge from individual variation in different movement properties in general, such as fleeing, avoidance or <span class="hlt">velocity</span>. Moreover, avoidance behavior also</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MPLB...2950104J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MPLB...2950104J"><span id="translatedtitle">Controlling of <span class="hlt">group</span> <span class="hlt">velocity</span> via terahertz signal radiation in a defect medium doped by four-level InGaN/GaN quantum dot nanostructure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jafarzadeh, Hossein; Sangachin, Elnaz Ahmadi; Asadpour, Seyyed Hossein</p> <p>2015-07-01</p> <p>In this paper, we propose a novel scheme for controlling the <span class="hlt">group</span> <span class="hlt">velocity</span> of transmitted and reflected pulse from defect medium doped with four-level InGaN/GaN quantum dot nanostructure. Quantum dot nanostructure is designed numerically by Schrödinger and Poisson equations which solve self consistently. By size control of quantum dot and external voltage, one can design a four-level quantum dot with appropriate energy levels which can be suitable for controlling the <span class="hlt">group</span> <span class="hlt">velocity</span> of pulse transmission and reflection from defect slab with terahertz signal field. It is found that in the presence and absence of terahertz signal field the behaviors of transmission and reflection pulses are completely different. Moreover, it is shown that for strong terahertz signal field, by changing the thickness of the slab, simultaneous peak and dip for transmission and reflection pulse are obtained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21576540','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21576540"><span id="translatedtitle">THE M81 <span class="hlt">GROUP</span> DWARF IRREGULAR GALAXY DDO 165. I. HIGH-<span class="hlt">VELOCITY</span> NEUTRAL GAS IN A POST-STARBURST SYSTEM</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cannon, John M.; Most, Hans P.; Skillman, Evan D.; Weisz, Daniel R.; Warren, Steven R.; Cook, David; Dolphin, Andrew E.; Kennicutt, Robert C.; Lee, Janice; Seth, Anil; Walter, Fabian E-mail: skillman@astro.umn.edu E-mail: warren@astro.umn.edu E-mail: adolphin@raytheon.com E-mail: jlee@obs.carnegiescience.edu E-mail: walter@mpia.de</p> <p>2011-07-01</p> <p>We present new multi-configuration Very Large Array H I spectral line observations of the M81 <span class="hlt">group</span> dwarf irregular post-starburst galaxy DDO 165. The H I morphology is complex, with multiple column density peaks surrounding a large region of very low H I surface density that is offset from the center of the stellar distribution. The bulk of the neutral gas is associated with the southern section of the galaxy; a secondary peak in the north contains {approx}15% of the total H I mass. These components appear to be kinematically distinct, suggesting that either tidal processes or large-scale blowout have recently shaped the interstellar medium (ISM) of DDO 165. Using spatially resolved position-<span class="hlt">velocity</span> maps, we find multiple localized high-<span class="hlt">velocity</span> gas features. Cross-correlating with radius-<span class="hlt">velocity</span> analyses, we identify eight shell/hole structures in the ISM with a range of sizes ({approx}400-900 pc) and expansion <span class="hlt">velocities</span> ({approx}7-11 km s{sup -1}). These structures are compared with narrow- and broadband imaging from the Kitt Peak National Observatory and the Hubble Space Telescope (HST). Using the latter data, recent works have shown that DDO 165's previous 'burst' phase was extended temporally ({approx}>1 Gyr). We thus interpret the high-<span class="hlt">velocity</span> gas features, H I holes, and kinematically distinct components of the galaxy in the context of the immediate effects of 'feedback' from recent star formation (SF). In addition to creating H I holes and shells, extended SF events are capable of creating localized high-<span class="hlt">velocity</span> motion of the surrounding interstellar material. A companion paper connects the energetics from the H I and HST data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.2714L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.2714L"><span id="translatedtitle">Lithospheric structure across the central Tien Shan constrained by gravity anomalies and joint inversions of receiver function and Rayleigh <span class="hlt">group</span> <span class="hlt">velocity</span> data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Yonghua; Shi, Lei; Gao, Jiayi</p> <p>2016-04-01</p> <p>Shear wave <span class="hlt">velocity</span> structure across the central Tien Shan orogeny was generated by jointly inverting Rayleigh wave phase and <span class="hlt">group</span> <span class="hlt">velocity</span> with teleseismic P-wave receiver functions at 40 broad band seismic stations of the MANAS project. The inferred seismic structure was validated by forward modeling of the complete Bouguer anomaly data. The joint inversion result reveals larger crust thicknesses beneath the Kokshaal (~68-72 km) and Kyrgyz ranges (~62-64 km), while other units have crustal thicknesses between 48 and 58 km. A fast <span class="hlt">velocity</span> layer (Vs = 3.6-3.9 km/s) in the upper crust is found in some seismic stations within the Kazakh Shield. Our models show the presence of high <span class="hlt">velocity</span> and density layers in the lowermost crust throughout the region, consistent with the presence of mafic/ultramafic lithologies. The large crustal thickness is associated with a thickened mafic layer in the lower crust, indicating that the thickened crust may be partly caused by magmatic underplating. The low <span class="hlt">velocity</span> and density anomaly in the middle crust, and low upper mantle <span class="hlt">velocity</span> observed in our model beneath the middle Tien Shan reflects the presence of partial melt in the crust due to the intrusion of hot mantle material. The lack of correlation between Moho depth and topography, together with the gravity results, suggests that the topographic compensation in the central Tien Shan is not confined to the crust. This requires significant support from the mantle to account for the relative high elevation of the middle Tien Shan.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014GeoJI.198..978A&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014GeoJI.198..978A&link_type=ABSTRACT"><span id="translatedtitle">Seismic <span class="hlt">velocity</span> structure in the Hot Springs and Trifurcation areas of the San Jacinto fault zone, California, from double-difference <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Allam, A. A.; Ben-Zion, Y.; Kurzon, I.; Vernon, F.</p> <p>2014-08-01</p> <p>We present tomographic images of crustal <span class="hlt">velocity</span> structures in the complex Hot Springs and Trifurcation areas of the San Jacinto Fault Zone (SJFZ) based on double-difference inversions of earthquake arrival times. We invert for VP, VS and hypocentre location within 50 × 50 × 20 km3 volumes, using 266 969 P and 148 249 S arrival times. We obtain high-fidelity images of seismic <span class="hlt">velocities</span> with resolution on the order of a few kilometres from 2 to 12 km depth and validate the results using checkerboard tests. Due to the relatively large proportion of S-wave arrival times, we also obtain stable maps of VP/VS ratios in both regions. The <span class="hlt">velocity</span> of the Trifurcation Area as a whole is lower than adjacent unfaulted material. We interpret a 4-km-wide low <span class="hlt">velocity</span> zone with high VP/VS ratio in the trifurcation itself as related to fault zone damage. We also observe clear <span class="hlt">velocity</span> contrasts across the Buck Ridge, Clark and Coyote Creek segments of the SJFZ. The Anza segment of the SJFZ, to the NW of the trifurcation area, displays a strong (up to 27 per cent) contrast of VS from 2 to 9 km depth. In the Hot Springs area, a low <span class="hlt">velocity</span> zone between the Claremont and Casa Loma Strands narrows with depth, with clear <span class="hlt">velocity</span> contrasts observed across both segments. A roughly 10-km-wide zone of low <span class="hlt">velocity</span> and low VP/VS ratio at the NW tip of the Hot Springs fault is indicative of either unconsolidated sediments associated with the San Jacinto basin, or fluid-filled cracks within a broad deformation zone. High VP/VS ratios along the Anza segment could indicate a preferred nucleation location for future large earthquakes, while the across-fault <span class="hlt">velocity</span> contrast suggests a preferred northwest rupture propagation direction for such events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ArMiS..57..139H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ArMiS..57..139H"><span id="translatedtitle">Passive seismic <span class="hlt">velocity</span> <span class="hlt">tomography</span> and geostatistical simulation on longwall mining panel / Tomografia pasywna pola prędkości i symulacje geostatystyczne w obrębie pola ścianowego</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hosseini, Navid; Oraee, Kazem; Shahriar, Kourosh; Goshtasbi, Kamran</p> <p>2012-10-01</p> <p>Generally, the accurate determination of the stress in surrounding rock mass of underground mining area has an important role in stability and ground control. In this paper stress redistribution around the longwall face has been studied using passive seismic <span class="hlt">velocity</span> <span class="hlt">tomography</span> based on Simultaneous Iterative Reconstructive Technique (SIRT) and Sequential Gaussian Simulation (SGS). The mining-induced microseismic events are used as a passive source. Since such sources are used, the ray coverage is insufficient and in order to resolve this deficiency, the wave <span class="hlt">velocity</span> is estimated in a denser network and by the SGS method. Consequently the three-dimensional images of wave <span class="hlt">velocity</span> are created and sliced into the coal seam. To analyze the variations of stress around the panel during the study period, these images are interpreted. Results show that the state of stress redistribution around the longwall panel can be deduced from these <span class="hlt">velocity</span> images. In addition, movements of the stressed zones, including front and side abutments and the goaf area, along the longwall face are evident. The applied approach illustrated in this paper can be used as a useful method to monitoring the stress changes around the longwall face continuously. This can have significant safety implications and contribute to improvements in operational productivity</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JGRB..121.4408K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JGRB..121.4408K&link_type=ABSTRACT"><span id="translatedtitle">Application of repeated passive source travel time <span class="hlt">tomography</span> to reveal weak <span class="hlt">velocity</span> changes related to the 2011 Tohoku-Oki Mw 9.0 earthquake</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Koulakov, Ivan; Gladkov, Valery; El Khrepy, Sami; Al-Arifi, Nassir; Fathi, Ismail Husain</p> <p>2016-06-01</p> <p>Temporal changes of seismic <span class="hlt">velocities</span> may provide important information on the processes that occur inside the Earth. However, using body wave data with passive sources faces the problem of an uneven distribution of rays, which may cause artifacts with stronger amplitudes than the actual <span class="hlt">velocity</span> changes in the Earth. We propose an algorithm for the selection of similar data sets in different time periods that minimize the artifacts related to variable data distributions. In this study, we used the data of the Japan Meteorological Agency for several years before and after the Mw 9.0 Tohoku-Oki event that occurred on 11 March 2011. We performed careful testing using different synthetic models, showing that the selected data subsets allow detecting weak <span class="hlt">velocity</span> changes with amplitudes above 0.2%. The analysis of the experimental data revealed important features associated with the stress and deformation distributions after the megathrust event. In the upper crust, we found a large zone along the coast with significant P <span class="hlt">velocity</span> increase likely caused by compression of crustal rocks. This zone was cut by several elongated anomalies with local <span class="hlt">velocity</span> decrease coinciding with the limits of the maximum slip area. These anomalies possibly mark the areas of major ruptures and deformations after the Tohoku-Oki earthquake. In the coupling zone at a depth of 40 km, we observe a <span class="hlt">velocity</span> decrease in the area of the Mw 7.7 aftershock representing strong fracturing in the focal zone. Beneath the volcanic arc, we observe significant (up to 0.5%) decrease of P <span class="hlt">velocity</span> but less prominent S <span class="hlt">velocity</span> changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/20831323','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/20831323"><span id="translatedtitle">On the relation between the microscopic structure and the sound <span class="hlt">velocity</span> anomaly in elemental melts of <span class="hlt">groups</span> IV, V, and VI.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Greenberg, Yaron; Yahel, Eyal; Caspi, El'ad N; Beuneu, Brigitte; Dariel, Moshe P; Makov, Guy</p> <p>2010-09-01</p> <p>The sound <span class="hlt">velocity</span> of some liquid elements of <span class="hlt">groups</span> IV, V, and VI, as reported in the literature, displays anomalous features that set them apart from other liquid metals. In an effort to determine a possible common origin of these anomalies, extensive neutron diffraction measurements of liquid Bi and Sb were carried out over a wide temperature range. The structure factors of liquid Sb and Bi were determined as a function of temperature. The structure of the two molten metals was carefully analyzed with respect to peak locations, widths, and coordination numbers in their respective radial distribution function. The width of the peaks in the radial distribution functions was not found to increase and even decreased within a certain temperature range. This anomalous temperature dependence of the peak widths correlates with the anomalous temperature dependence of the sound <span class="hlt">velocity</span>. This correlation may be accounted for by increased rigidity of the liquid structure with temperature. A phenomenological correlation between the peak width and the sound <span class="hlt">velocity</span> is suggested for metallic melts and is found to agree with available data for normal and anomalous elemental liquids in <span class="hlt">groups</span> IV-VI. PMID:20831323</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70036677','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70036677"><span id="translatedtitle">Volcano-tectonic implications of 3-D <span class="hlt">velocity</span> structures derived from joint active and passive source <span class="hlt">tomography</span> of the island of Hawaii</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Park, J.; Morgan, J.K.; Zelt, C.A.; Okubo, P.G.</p> <p>2009-01-01</p> <p>We present a <span class="hlt">velocity</span> model of the onshore and offshore regions around the southern part of the island of Hawaii, including southern Mauna Kea, southeastern Hualalai, and the active volcanoes of Mauna Loa, and Kilauea, and Loihi seamount. The <span class="hlt">velocity</span> model was inverted from about 200,000 first-arrival traveltime picks of earthquakes and air gun shots recorded at the Hawaiian Volcano Observatory (HVO). Reconstructed volcanic structures of the island provide us with an improved understanding of the volcano-tectonic evolution of Hawaiian volcanoes and their interactions. The summits and upper rift zones of the active volcanoes are characterized by high-<span class="hlt">velocity</span> materials, correlated with intrusive magma cumulates. These high-<span class="hlt">velocity</span> materials often do not extend the full lengths of the rift zones, suggesting that rift zone intrusions may be spatially limited. Seismicity tends to be localized seaward of the most active intrusive bodies. Low-<span class="hlt">velocity</span> materials beneath parts of the active rift zones of Kilauea and Mauna Loa suggest discontinuous rift zone intrusives, possibly due to the presence of a preexisting volcanic edifice, e.g., along Mauna Loa beneath Kilauea's southwest rift zone, or alternatively, removal of high-<span class="hlt">velocity</span> materials by large-scale landsliding, e.g., along Mauna Loa's western flank. Both locations also show increased seismicity that may result from edifice interactions or reactivation of buried faults. New high-<span class="hlt">velocity</span> regions are recognized and suggest the presence of buried, and in some cases, previously unknown rift zones, within the northwest flank of Mauna Loa, and the south flanks of Mauna Loa, Hualalai, and Mauna Kea. Copyright 2009 by the American Geophysical Union.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013AGUFM.T53D2609A&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013AGUFM.T53D2609A&link_type=ABSTRACT"><span id="translatedtitle">Seismic <span class="hlt">velocity</span> structure in the Hemet Stepover and Trifurcation Areas of the San Jacinto Fault Zone from double-difference earthquake <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Allam, A. A.; Ben-Zion, Y.; Vernon, F.; Kurzon, I.</p> <p>2013-12-01</p> <p>We present tomographic images of crustal <span class="hlt">velocity</span> structures in the Hemet Stepover and Trifurcation areas of the San Jacinto Fault Zone (SJFZ) based on double-difference inversions of earthquake arrival times. We discretize both regions with a horizontal 250m grid spacing and a vertical 500m spacing within 50km by 50km by 20km volumes. We invert for VP, VS, and hypocenter location using data from 16064 earthquakes recorded at 136 stations. In total, we use 266,969 P and 148,249 S arrivals to constrain the seismic <span class="hlt">velocity</span> structures in the two regions. With large numbers of both arrivals, we are able to obtain images of VP and VS at similar resolutions, enabling us to make spatial maps of and interpret the VP/VS ratios. Though ray coverage is limited at shallow depths, we obtain high-fidelity images of seismic <span class="hlt">velocities</span> from 2 to 12 km, and validate the results using checkerboard tests. The tomographic images indicate that the <span class="hlt">velocity</span> of the trifurcation area as a whole is lower than adjacent unfaulted material. We interpret a 4km-wide low <span class="hlt">velocity</span> zone in the trifurcation itself as fault zone damage related due to high VP/VS ratio. We also observe clear <span class="hlt">velocity</span> contrasts across the Buck Ridge, Clark, and Coyote Creek segments of the SJFZ. The Anza segment of the SJFZ, to the NW of the trifurcation area, displays a strong (up to 27%) contrast of VS from 2km to 9km. In the Hemet Stepover, a low <span class="hlt">velocity</span> zone between the Claremont and Casa Loma Strands narrows with depth, with clear <span class="hlt">velocity</span> contrasts observed across both segments. A roughly 10km-wide zone of low <span class="hlt">velocity</span> and low VP/VS ratio at the NW tip of the Hot Springs fault is indicative of either unconsolidated sediments associated with the San Jacinto basin, or fluid-filled cracks within a broad deformation zone. Relocated seismicity tends to align with the surface traces of the various fault strands, though it is offset to the northeast of the Casa Loma-Clark strand and to the southwest of the Hot Springs</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T11B2434P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T11B2434P"><span id="translatedtitle">Crustal and upper mantle shear <span class="hlt">velocities</span> of Iberia, the Alboran Sea, and North Africa from ambient noise and ballistic finite-frequency Rayleigh wave <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Palomeras, I.; Villasenor, A.; Thurner, S.; Levander, A.; Gallart, J.; mimoun, H.</p> <p>2013-12-01</p> <p>The complex Mesozoic-Cenozoic Alpine deformation in the western Mediterranean extends from the Pyrenees in northern Spain to the Atlas Mountains in southern Morocco. The Iberian plate was accreted to the European plate in late Cretaceous, resulting in the formation of the Pyrenees. Cenozoic African-European convergence resulted in subduction of the Tethys oceanic plate beneath Europe. Rapid Oligocene slab rollback from eastern Iberia spread eastward and southward, with the trench breaking into three segments by the time it reached the African coast. One trench segment moved southwestward and westward creating the Alboran Sea, floored by highly extended continental crust, and building the encircling Betics Rif mountains comprising the Gibraltar arc, and the Atlas mountains, which formed as the inversion of a Jurassic rift. A number of recent experiments have instrumented this region with broad-band arrays (the US PICASSO array, Spanish IberArray and Siberia arrays, the University of Munster array), which, including the Spanish, Portuguese, and Moroccan permanent networks, provide a combined array of 350 stations having an average interstation spacing of ~60 km. Taking advantage of this dense deployment, we have calculated the Rayleigh waves phase <span class="hlt">velocities</span> from ambient noise for short periods (4 s to 40 s) and teleseismic events for longer periods (20 s to 167 s). Approximately 50,000 stations pairs were used to measure the phase <span class="hlt">velocity</span> from ambient noise and more than 160 teleseismic events to measure phase <span class="hlt">velocity</span> for longer periods. The inversion of the phase <span class="hlt">velocity</span> dispersion curves provides a 3D shear <span class="hlt">velocity</span> for the crust and uppermost mantle. Our results show differences between the various tectonic regions that extend to upper mantle depths (~200 km). In Iberia we obtain, on average, higher upper mantle shear <span class="hlt">velocities</span> in the western Variscan region than in the younger eastern part. We map high upper mantle <span class="hlt">velocities</span> (>4.6 km/s) beneath the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009SPIE.7258E..35G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009SPIE.7258E..35G"><span id="translatedtitle">A cardiac phantom study on quantitative correction of coronary calcium score on multi-detector, dual source, and electron beam <span class="hlt">tomography</span> for <span class="hlt">velocity</span>, calcification density, and acquisition time</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Greuter, Marcel J. W.; Groen, Jaap M.; Nicolai, Lieuwe J.; Dijkstra, Hildebrand; Oudkerk, Matthijs</p> <p>2009-02-01</p> <p>Objective: To quantify the influence of <span class="hlt">velocity</span>, calcification density and acquisition time on coronary calcium determination using multi-detector CT, dual-source CT and EBT. Materials and Methods: Artificial arteries with four calcifications of increasing density were attached to a robotic arm to which a linear movement was applied between 0 and 120 mm/s (step 10 mm/s). The phantom was scanned five times on 64-slice MDCT, DSCT and EBT using a standard acquisition protocol and the average Agatston score was determined. Results: Increasing motion artifacts were observed at increasing <span class="hlt">velocities</span> on all scanners, with increasing severity from EBT to DSCT to 64-slice MDCT. The Agatston score showed a linear dependency on <span class="hlt">velocity</span> from which a correction factor was derived. This correction factor showed a linear dependency on calcification density (0.92<=R2<=0.95). The slope and offset of this correction factor also showed a linear dependency on acquisition time (0.84<=R2<=0.86). Conclusion: The Agatston score is highly dependent on the average density of individual calcifications. The dependency of the Agatston score on <span class="hlt">velocity</span> shows a linear behaviour on calcification density. A quantitative method could be derived which corrects the measured calcium score for the influence of <span class="hlt">velocity</span>, calcification density and acquisition time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70014405','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70014405"><span id="translatedtitle">Active high-resolution seismic <span class="hlt">tomography</span> of compressional wave <span class="hlt">velocity</span> and attenuation structure at Medicine Lake Volcano, northern California Cascade Range</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Evans, J.R.; Zucca, J.J.</p> <p>1988-01-01</p> <p>Medicine Lake volcano is a basalt through rhyolite shield volcano of the Cascade Range, lying east of the range axis. The Pg wave from eight explosive sources which has traveled upward through the target volume to a dense array of 140 seismographs provides 1- to 2-km resolution in the upper 5 to 7 km of the crust beneath the volcano. The experiment tests the hypothesis that Cascade Range volcanoes of this type are underlain only by small silicic magma chambers. We image a low-<span class="hlt">velocity</span> low-Q region not larger than a few tens of cubic kilometers in volume beneath the summit caldera, supporting the hypothesis. A shallower high-<span class="hlt">velocity</span> high-density feature, previously known to be present, is imaged for the first time in full plan view; it is east-west elongate, paralleling a topographic lineament between Medicine Lake volcano and Mount Shasta. Differences between this high-<span class="hlt">velocity</span> feature and the equivalent feature at Newberry volcano, a volcano in central regon resembling Medicine Lake volcano, may partly explain the scarcity of surface hydrothermal features at Medicine Lake volcano. A major low-<span class="hlt">velocity</span> low-Q feature beneath the southeast flank of the volcano, in an area with no Holocene vents, is interpreted as tephra, flows, and sediments from the volcano deeply ponded on the downthrown side of the Gillem fault. A high-Q normal-<span class="hlt">velocity</span> feature beneath the north rim of the summit caldera may be a small, possibly hot, subsolidus intrusion. A high-<span class="hlt">velocity</span> low-Q region beneath the eastern caldera may be an area of boiling water between the magma chamber and the ponded east flank material. -from Authors</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=20930&keyword=seismic+AND+tomography&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=67184562&CFTOKEN=25351295','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=20930&keyword=seismic+AND+tomography&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=67184562&CFTOKEN=25351295"><span id="translatedtitle">FINAL REPORT. SEISMIC SURFACE-WAVE <span class="hlt">TOMOGRAPHY</span> OF WASTE SITES</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>The objective of this study was to develop analysis programs for surface-wave <span class="hlt">group-velocity</span> <span class="hlt">tomography</span> and apply these to three test areas. We succeeded by obtaining data covering two square areas that were 30 meters on a side and one that was 16 meters on a side, in addition to...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70017441','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70017441"><span id="translatedtitle">Three dimensional images of geothermal systems: local earthquake P-wave <span class="hlt">velocity</span> <span class="hlt">tomography</span> at the Hengill and Krafla geothermal areas, Iceland, and The Geysers, California</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Julian, B.R.; Prisk, A.; Foulger, G.R.; Evans, J.R.</p> <p>1993-01-01</p> <p>Local earthquake <span class="hlt">tomography</span> - the use of earthquake signals to form a 3-dimensional structural image - is now a mature geophysical analysis method, particularly suited to the study of geothermal reservoirs, which are often seismically active and severely laterally inhomogeneous. Studies have been conducted of the Hengill (Iceland), Krafla (Iceland) and The Geysers (California) geothermal areas. All three systems are exploited for electricity and/or heat production, and all are highly seismically active. Tomographic studies of volumes a few km in dimension were conducted for each area using the method of Thurber (1983).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoJI.201..783A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoJI.201..783A"><span id="translatedtitle">Crustal and uppermost mantle structure in the Middle East: assessing constraints provided by jointly modelling Ps and Sp receiver functions and Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion curves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Agrawal, Mohit; Pulliam, Jay; Sen, Mrinal K.; Dutta, Utpal; Pasyanos, Michael E.; Mellors, Robert</p> <p>2015-05-01</p> <p>Seismic <span class="hlt">velocity</span> models are found, along with uncertainty estimates, for 11 sites in the Middle East by jointly modelling Ps and Sp receiver functions and surface (Rayleigh) wave <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion. The approach performs a search for models that satisfy goodness-of-fit criteria guided by a variant of simulated annealing and uses statistical tools to assess these products of searches. These tools, a parameter correlation matrix and marginal posterior probability density (PPD) function, allow us to evaluate quantitatively the constraints that each data type imposes on model parameters and to identify portions of each model that are well-constrained relative to other portions. This joint modelling technique, which we call `multi-objective optimization for seismology', does not require a good starting solution, although such a model can be incorporated easily, if available, and can reduce the computation time significantly. Applying the process described above to broadband seismic data reveals that crustal thickness varies from 15 km beneath Djibouti (station ATD) to 45 km beneath Saudi Arabia (station RAYN). A pronounced low <span class="hlt">velocity</span> zone for both Vp and Vs is present at a depth of ˜12 km beneath station KIV located in northern part of greater Caucasus, which may be due to the presence of a relatively young volcano. Similarly, we also noticed a 6-km-thick low <span class="hlt">velocity</span> zone for Vp beginning at 20 km depth beneath seismic station AGIN, on the Anatolian plateau, while positive <span class="hlt">velocity</span> gradients prevail elsewhere in eastern Turkey. Beneath station CSS, located in Cyprus, an anomalously slow layer is found in the uppermost mantle, which may indicate the presence of altered lithospheric material. Crustal P- and S-wave <span class="hlt">velocities</span> beneath station D2, located in the northeastern portion of central Zagros, range between 5.2-6.2 and 3.2-3.8 km s-1, respectively. In Oman, we find a Moho depth of 34.0 ± 1.0 km and 25.0 ± 1.0 to 30.0 ± 1.0 km beneath stations S02 and S</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21124380','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21124380"><span id="translatedtitle">In Patients Experiencing Biochemical Failure After Radiotherapy, Pretreatment Risk <span class="hlt">Group</span> and PSA <span class="hlt">Velocity</span> Predict Differences in Overall Survival and Biochemical Failure-Free Interval</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Soto, Daniel E. Andridge, Rebecca R.; Pan, Charlie C.; Williams, Scott G.; Taylor, Jeremy M.G.; Sandler, Howard M.</p> <p>2008-08-01</p> <p>Purpose: To characterize the demographics and survival outcomes of localized prostate cancer patients who developed biochemical failure (BF) according to a prostate-specific antigen (PSA) nadir plus 2 ng/mL. Methods and Materials: We identified 375 prostate cancer patients who had undergone external beam radiotherapy without androgen deprivation therapy but with sufficient PSA data to study PSA kinetics. Of these patients, we identified 82 with BF. The pretreatment PSA <span class="hlt">velocity</span> was calculated for each patient. Results: For the BF cohort, 26% were low-risk and 74% were intermediate- or high-risk patients. Of the 82 BF patients, 16 (20%) were noted to have both low-risk disease and a pretreatment low PSA <span class="hlt">velocity</span> of {<=}2 ng/mL/y (termed 'low-risk low-<span class="hlt">velocity</span>' [LRLV]). The remaining BF patients had either intermediate- or high-risk features or a high PSA <span class="hlt">velocity</span> >2 ng/mL/y (termed 'higher risk' [HR]). For patients who had BF, the LRLV <span class="hlt">group</span> had a delayed median time to BF of 55 months compared with 33 months for the HR patients (p = 0.04). With a median clinical follow-up of 112 months, the 5-year overall survival rate was 100% for the LRLV BF patients vs. 84% for the HR patients (p = 0.02). Conclusions: We observed that LRLV BF patients represent a sizeable proportion of all patients with treatment failure. However, when comparing LRLV BF with HR BF patients, the former had significantly better overall survival and a longer interval to BF. This suggests that not all BF events are equivalent and emphasizes the challenges associated with using BF alone as a surrogate for a survival endpoint.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011SPIE.7914E..22B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011SPIE.7914E..22B"><span id="translatedtitle"><span class="hlt">Group-velocity</span> dispersion in multimode photonic crystal fibers measured using time-domain white-light interferometry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Böswetter, Pascal; Baselt, Tobias; Ebert, Frank; Basan, Fabiola; Hartmann, Peter</p> <p>2011-02-01</p> <p>Optical fibers are used in various applications, e. g. optical communication, material processing, as a laser medium or to generate efficient supercontinua. For most of these applications the knowledge of the dispersion is an essential prerequisite. The dispersion and modal properties of photonic crystal fibers (PCF) strongly depend on the hole diameter and pitch. Since fabrication tolerances affect the structure of the photonic lattice, the dispersion behavior as well as the number of guided transverse modes can differ from numerical calculations. Dispersion measurement of singlemode photonic crystal fibers has been well described in recent papers. However, the determination of dispersion in the presence of higher-order modes is much more difficult. To measure the dispersion of optical fibers with high accuracy, a time-domain white-light interferometer based on a Mach-Zehnder interferometer is presented. The experimental setup allows to determine the wavelength-dependent differential <span class="hlt">group</span> delay of light travelling through conventional fibers and PCFs within the wavelength range from VIS to NIR. Interferences appear due to superposition of two laser beams, one propagating through the tested fiber and the other travelling through air. Measuring the different <span class="hlt">group</span> delays of a step-index fiber shows the sufficient accuracy of the interferometer. This paper demonstrates a simple yet effective way to suppress higher-order modes, making it possible to measure the chromatic dispersion of singlemode as well as multimode fibers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012SPIE.8553E..0QD','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012SPIE.8553E..0QD"><span id="translatedtitle">Recent advances in optical coherence <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ding, Zhihua; Wang, Chuan; Shen, Yi; Huang, Liangming; Wu, Lan; Du, Chixin</p> <p>2012-12-01</p> <p>This paper reports recent advances in spectral domain Doppler optical coherence <span class="hlt">tomography</span> (SD-DOCT) in our <span class="hlt">group</span>. A high speed SD-DOCT system is developed and applied to animal study and microchip evaluation. Further improvements concerning SD-DOCT are presented, those including higher-order cross-correlation for phase retrieval, transit-time analysis for <span class="hlt">velocity</span> quantification, and orthogonal dispersive SD-OCT for depth extension.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016A%26A...592A.145A&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016A%26A...592A.145A&link_type=ABSTRACT"><span id="translatedtitle">Observations of asymmetric <span class="hlt">velocity</span> fields and gas cooling in the NGC 4636 galaxy <span class="hlt">group</span> X-ray halo</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ahoranta, Jussi; Finoguenov, Alexis; Pinto, Ciro; Sanders, Jeremy; Kaastra, Jelle; de Plaa, Jelle; Fabian, Andrew</p> <p>2016-08-01</p> <p>Aims: This study aims to probe the thermodynamic properties of the hot intragroup medium (IGM) plasma in the core regions of the NGC 4636 galaxy <span class="hlt">group</span> by detailed measurements of several emission lines and their relative intensities. Methods: We analyzed deep XMM-Newton Reflection Grating Spectrometer (RGS) data in five adjacent spectral regions in the central parts of the NGC 4636 galaxy <span class="hlt">group</span>. We examined the suppression of the Fe xvii resonance line (15.01 Å) as compared to the forbidden lines of the same ion (17.05 Å and 17.10 Å). The presence and radial dependence of the cooling flow was investigated through spectral modeling. Parallel analysis with deep Chandra Advances CCD Imaging Spectrometer (ACIS) data was conducted to gain additional information about the thermodynamical properties of the IGM. Results: The plasma at the <span class="hlt">group</span> center to the north shows efficient Fe xvii ion resonant scattering, yielding (Iλ17.05 + Iλ17.10) /Iλ15.01 line ratios up to 2.9 ± 0.4, corresponding toabout twice the predicted line ratio. In contrast, no resonant scattering was detected at the south side. The regions featuring resonant scattering coincide with those embodying large amounts of cool (kT ≲ 0.4 keV) gas phases, and the spectral imprints of cooling gas with a total mass deposition rate of ~0.8 M⊙ yr-1 within the examined region of 2.4' × 5.0'. Conclusions: We interpret the results as possible evidence of asymmetric turbulence distribution in the NGC 4636 IGM: turbulence dominates the gas dynamics to the south, while collective gas motions characterize the dynamics to the north. X-ray images show imprints of energetic AGN at both sides, yet we find evidence of turbulence heating at the south and gas cooling at the north of the core. We infer that the observed asymmetry may be the result of the specific observation angle to the source, or arise from the turbulence driven by core sloshing at south side.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.usgs.gov/of/2012/1191/OF12-1191.pdf','USGSPUBS'); return false;" href="http://pubs.usgs.gov/of/2012/1191/OF12-1191.pdf"><span id="translatedtitle">Measurement of near-surface seismic compressional wave <span class="hlt">velocities</span> using refraction <span class="hlt">tomography</span> at a proposed construction site on the Presidio of Monterey, California</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Powers, Michael H.; Burton, Bethany L.</p> <p>2012-01-01</p> <p>The U.S. Army Corps of Engineers is determining the feasibility of constructing a new barracks building on the U.S. Army Presidio of Monterey in Monterey, California. Due to the presence of an endangered orchid in the proposed area, invasive techniques such as exploratory drill holes are prohibited. To aid in determining the feasibility, budget, and design of this building, a compressional-wave seismic refraction survey was proposed by the U.S. Geological Survey as an alternative means of investigating the depth to competent bedrock. Two sub-parallel profiles were acquired along an existing foot path and a fence line to minimize impacts on the endangered flora. The compressional-wave seismic refraction <span class="hlt">tomography</span> data for both profiles indicate that no competent rock classified as non-rippable or marginally rippable exists within the top 30 feet beneath the ground surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011Tectp.512....1M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011Tectp.512....1M"><span id="translatedtitle">Seismic imaging of the 2001 Bhuj Mw7.7 earthquake source zone: b-value, fractal dimension and seismic <span class="hlt">velocity</span> <span class="hlt">tomography</span> studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mandal, Prantik; Rodkin, Mikhail V.</p> <p>2011-11-01</p> <p>We use precisely located aftershocks of the 2001 Mw7.7 Bhuj earthquake (2001-2009) to explore the structure of the Kachchh seismic zone by mapping the 3-D distributions of b-value, fractal dimension (D) and seismic <span class="hlt">velocities</span>. From frequency-magnitude analysis, we find that the catalog is complete above Mw = 3.0. Thus, we analyze 2159 aftershocks with Mw ≥ 3.0 to estimate the 3-D distribution of b-value and fractal dimensions using maximum-likelihood and spatial correlation dimension approaches, respectively. Our results show an area of high b-, D- and Vp/Vs ratio values at 15-35 km depth in the main rupture zone (MRZ), while relatively low b- and D values characterize the surrounding rigid regions and Gedi fault (GF) zone. We propose that higher material heterogeneities in the vicinity of the MRZ and/or circulation of deep aqueous fluid/volatile CO 2 is the main cause of the increased b-, D- and Vp/Vs ratio values at 15-35 km depth. Seismic <span class="hlt">velocity</span> images also show some low <span class="hlt">velocity</span> zones continuing in to the deep lower crust, supporting the existence of circulation of deep aqueous fluid / volatile CO 2 in the region (probably released from the eclogitasation of olivine rich lower crustal rocks). The presence of number of high and low <span class="hlt">velocity</span> patches further reveals the heterogeneous and fractured nature of the MRZ. Interestingly, we observe that Aki (1981)'s relation (D = 2b) is not valid for the spatial b-D correlation of the events in the GF (D 2 = 1.2b) zone. However, the events in the MRZ (D 2 = 1.7b) show a fair agreement with the D = 2b relationship while the earthquakes associated with the remaining parts of the aftershock zone (D 2 = 1.95b) show a strong correlation with the Aki (1981)'s relationship. Thus, we infer that the remaining parts of the aftershock zone are probably behaving like locked un-ruptured zones, where larger stresses accumulate. We also propose that deep fluid involvement may play a key role in generating seismic activity in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22356642','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22356642"><span id="translatedtitle">BANYAN. III. Radial <span class="hlt">velocity</span>, rotation, and X-ray emission of low-mass star candidates in nearby young kinematic <span class="hlt">groups</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Malo, Lison; Artigau, Étienne; Doyon, René; Lafrenière, David; Albert, Loïc; Gagné, Jonathan E-mail: doyon@astro.umontreal.ca</p> <p>2014-06-10</p> <p>Based on high-resolution spectra obtained with PHOENIX at Gemini-South, CRIRES at VLT-UT1, and ESPaDOnS at the Canada-France-Hawaii Telescope, we present new measurements of the radial and projected rotational <span class="hlt">velocities</span> of 219 low-mass stars. The target likely membership was initially established using the Bayesian analysis tool recently presented in Malo et al., taking into account only the position, proper motion, and photometry of the stars to assess their membership probability. In the present study, we include radial <span class="hlt">velocity</span> as an additional input to our analysis, and in doing so we confirm the high membership probability for 130 candidates: 27 in β Pictoris, 22 in Tucana-Horologium, 25 in Columba, 7 in Carina, 18 in Argus and 18 in AB Doradus, and 13 with an ambiguous membership. Our analysis also confirms the membership of 57 stars proposed in the literature. A subsample of 16 candidates was observed at 3 or more epochs, allowing us to discover 6 new spectroscopic binaries. The fraction of binaries in our sample is 25%, consistent with values in the literature. Of the stars in our sample, 20% show projected rotational <span class="hlt">velocities</span> (vsin i) higher than 30 km s{sup –1} and therefore are considered as fast rotators. A parallax and other youth indicators are still needed to fully confirm the 130 highly probable candidates identified here as new bona fide members. Finally, based on the X-ray emission of bona fide and highly probable <span class="hlt">group</span> members, we show that for low-mass stars in the 12-120 Myr age range, the X-ray luminosity is an excellent indicator of youth and better than the more traditionally used R {sub X} parameter, the ratio of X-ray to bolometric luminosity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26723309','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26723309"><span id="translatedtitle">Effect of refracted light distribution on the photoelastic generation of zero-<span class="hlt">group</span> <span class="hlt">velocity</span> Lamb modes in optically low-absorbing plates.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Raetz, Samuel; Laurent, Jérôme; Dehoux, Thomas; Royer, Daniel; Audoin, Bertrand; Prada, Claire</p> <p>2015-12-01</p> <p>Zero-<span class="hlt">group</span> <span class="hlt">velocity</span> (ZGV) Lamb modes are associated with sharp local acoustic resonances and allow, among other features, local measurement of Poisson's ratio. While the thermoelastic generation of Lamb waves in metal plates has been widely studied, the case of materials of low-optical absorption remains unexplored. In materials such as glasses, the generation of bulk elastic waves has been demonstrated to be sensitive to the refracted light distribution. In this paper, a detailed analysis of the effect of light refraction on the laser-based generation of ZGV Lamb modes is presented. Experiments are performed on a bare glass plate without the need for an additional layer for light absorption or reflection. Using an appropriate tilted volume source, it is shown that the laser-ultrasonic technique allows non-contact measurement of the Poisson's ratio. PMID:26723309</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.S23B1379Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.S23B1379Y"><span id="translatedtitle">Multi-scale Finite-Frequency Travel-time <span class="hlt">Tomography</span> Applied to Imaging 3-D <span class="hlt">Velocity</span> Structure of the Upper Mantle Beneath the Southwest United States</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yin, Y.; Hung, S.</p> <p>2007-12-01</p> <p>Seismic tomographic imaging has played a key component to unravel the deep processes that caused the surface morphology and rift magmatism in the southwest United States. Several studies used teleseismic body- wave arrivals recorded by the La Ristra experiment, a dense broadband array of 950-km in length deployed during 1999-2001 and run through the Great Plains, the Rio Grande Rift, and the Colorado Plateau, to construct a 2-D tomographic image of the upper mantle structure beneath this linear array (e.g., Gao et al., 2004). However, because of the inevitable smoothing and damping imposed in the tomographic model, the resulting <span class="hlt">velocity</span> contrast is too weak to explain distinct P and S waveform changes across the array (Song and Helmberger, 2007). In this study, we include all the data from the La Ristra and available nearby arrays and reexamine finite- frequency travel time delays measured by inter-station cross correlation of waveforms at both high- (0.3-2 Hz for P and 0.1-0.5 Hz for S) and low-frequencies (0.03-0.125 Hz for P and 0.03-0.1 Hz for S). Differing from the previous models that rely on classical ray theory and simple grid parameterization, our inversion considers more realistic 3-D sensitivity kernels for relative travel-time delays and a wavelet-based, multi-scale parameterization that enables to yield robust features with spatially-varying resolutions. Our preliminary P-wave model reveals a prominent low-<span class="hlt">velocity</span> zone extending from near surface to the depth of 300 km beneath the Rio Grande Rift, while the upper mantle which underlies the Great Plains and the Colorado Plateau is seismically fast. We will demonstrate the difference and improvement of 3-D tomographic models through the use of finite-frequency kernels and multi-scale parameterization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4073226','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4073226"><span id="translatedtitle">Doppler Optical Coherence <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Leitgeb, Rainer A.; Werkmeister, René M.; Blatter, Cedric; Schmetterer, Leopold</p> <p>2014-01-01</p> <p>Optical Coherence <span class="hlt">Tomography</span> (OCT) has revolutionized ophthalmology. Since its introduction in the early 1990s it has continuously improved in terms of speed, resolution and sensitivity. The technique has also seen a variety of extensions aiming to assess functional aspects of the tissue in addition to morphology. One of these approaches is Doppler OCT (DOCT), which aims to visualize and quantify blood flow. Such extensions were already implemented in time domain systems, but have gained importance with the introduction of Fourier domain OCT. Nowadays phase-sensitive detection techniques are most widely used to extract blood <span class="hlt">velocity</span> and blood flow from tissues. A common problem with the technique is that the Doppler angle is not known and several approaches have been realized to obtain absolute <span class="hlt">velocity</span> and flow data from the retina. Additional studies are required to elucidate which of these techniques is most promising. In the recent years, however, several <span class="hlt">groups</span> have shown that data can be obtained with high validity and reproducibility. In addition, several <span class="hlt">groups</span> have published values for total retinal blood flow. Another promising application relates to non-invasive angiography. As compared to standard techniques such as fluorescein and indocyanine-green angiography the technique offers two major advantages: no dye is required and depth resolution is required is provided. As such Doppler OCT has the potential to improve our abilities to diagnose and monitor ocular vascular diseases. PMID:24704352</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24704352','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24704352"><span id="translatedtitle">Doppler optical coherence <span class="hlt">tomography</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Leitgeb, Rainer A; Werkmeister, René M; Blatter, Cedric; Schmetterer, Leopold</p> <p>2014-07-01</p> <p>Optical Coherence <span class="hlt">Tomography</span> (OCT) has revolutionized ophthalmology. Since its introduction in the early 1990s it has continuously improved in terms of speed, resolution and sensitivity. The technique has also seen a variety of extensions aiming to assess functional aspects of the tissue in addition to morphology. One of these approaches is Doppler OCT (DOCT), which aims to visualize and quantify blood flow. Such extensions were already implemented in time domain systems, but have gained importance with the introduction of Fourier domain OCT. Nowadays phase-sensitive detection techniques are most widely used to extract blood <span class="hlt">velocity</span> and blood flow from tissues. A common problem with the technique is that the Doppler angle is not known and several approaches have been realized to obtain absolute <span class="hlt">velocity</span> and flow data from the retina. Additional studies are required to elucidate which of these techniques is most promising. In the recent years, however, several <span class="hlt">groups</span> have shown that data can be obtained with high validity and reproducibility. In addition, several <span class="hlt">groups</span> have published values for total retinal blood flow. Another promising application relates to non-invasive angiography. As compared to standard techniques such as fluorescein and indocyanine-green angiography the technique offers two major advantages: no dye is required and depth resolution is required is provided. As such Doppler OCT has the potential to improve our abilities to diagnose and monitor ocular vascular diseases. PMID:24704352</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.S41A2701C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.S41A2701C"><span id="translatedtitle">Crustal Structure of the PARANÁ Basin from Ambient Noise <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Collaço, B.; Assumpcao, M.</p> <p>2015-12-01</p> <p>Conventional seismic <span class="hlt">tomography</span> tends to have poor resolution in regions of low seismicity where good path coverage is not always possible. Previous studies carried out in South America did not map clearly some areas of the continent, such as the southern part of the Paraná basin, because of insufficient number of crossing paths. To describe the crustal structure of the whole Paraná basin, in addition to data obtained by the analysis of Andean earthquakes, we used dispersion curves from ambient noise correlation between pairs of seismographic stations, a technique known by Ambient Noise <span class="hlt">Tomography</span> (ANT). The obtained <span class="hlt">group</span> <span class="hlt">velocity</span> maps for South America correspond well with the main geological provinces of the continent: low <span class="hlt">velocities</span> under the Andes and sedimentary basins and high <span class="hlt">velocities</span> in cratonic regions. Inversion of the <span class="hlt">group</span> <span class="hlt">velocities</span> for the Paraná Basin were carried out with the following results: a) crustal thicknesses tend to be 45 km; b) high <span class="hlt">velocity</span> anomalies for the uppermost mantle, which agree with previous studies consistent with the presence of a cratonic nucleus in the basin, particularly beneath its northern part. However, our surface wave <span class="hlt">tomography</span> had no resolution to say whether such a nucleus is intact.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PApGe.tmp...95S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PApGe.tmp...95S"><span id="translatedtitle">Ambient Seismic Noise <span class="hlt">Tomography</span> of a High Loess Bank at Dunaszekcső (Hungary)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Szanyi, Gyöngyvér; Gráczer, Zoltán; Győri, Erzsébet; Kaláb, Zdeněk; Lednická, Markéta</p> <p>2016-05-01</p> <p>High loess banks along the right side of the Danube in Hungary are potential subjects of landslides. Small scale ambient seismic noise <span class="hlt">tomography</span> was used at the Dunaszekcső high bank. The aim of the study was to map near surface <span class="hlt">velocity</span> anomalies since we assume that the formation of tension cracks—which precede landslides—are represented by low <span class="hlt">velocities</span>. Mapping Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> distribution can help to image intact and creviced areas and identify the most vulnerable sections. The study area lies at the top of the Castle Hill of Dunaszekcső, which was named after Castellum Lugio, a fortress of Roman origin. The presently active head scarp was formed in April 2011, and our study area was chosen to be at its surroundings. Cross-correlation functions of ambient noise recordings were used to retrieve the dispersion curves, which served as the input of the <span class="hlt">group</span> <span class="hlt">velocity</span> <span class="hlt">tomography</span>. Phase cross-correlation and time-frequency phase weighted stacking was applied to calculate the cross-correlation functions. The average Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> at the high loess bank was found to be 171 ms^{-1} . The <span class="hlt">group</span> <span class="hlt">velocity</span> map at a 0.1 s period revealed a low-<span class="hlt">velocity</span> region, whose location coincides with a highly creviced area, where slope failure takes place along a several meter wide territory. Another low <span class="hlt">velocity</span> region was found, which might indicate a previously unknown loosened domain. The highest <span class="hlt">velocities</span> were observed at the supposed remnants of Castellum Lugio.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PApGe.173.2913S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PApGe.173.2913S&link_type=ABSTRACT"><span id="translatedtitle">Ambient Seismic Noise <span class="hlt">Tomography</span> of a Loess High Bank at Dunaszekcső (Hungary)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Szanyi, Gyöngyvér; Gráczer, Zoltán; Győri, Erzsébet; Kaláb, Zdeněk; Lednická, Markéta</p> <p>2016-08-01</p> <p>Loess high banks along the right side of the Danube in Hungary are potential subjects of landslides. Small scale ambient seismic noise <span class="hlt">tomography</span> was used at the Dunaszekcső high bank. The aim of the study was to map near surface <span class="hlt">velocity</span> anomalies since we assume that the formation of tension cracks—which precede landslides—are represented by low <span class="hlt">velocities</span>. Mapping Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> distribution can help to image intact and creviced areas and identify the most vulnerable sections. The study area lies at the top of the Castle Hill of Dunaszekcső, which was named after Castellum Lugio, a fortress of Roman origin. The presently active head scarp was formed in April 2011, and our study area was chosen to be at its surroundings. Cross-correlation functions of ambient noise recordings were used to retrieve the dispersion curves, which served as the input of the <span class="hlt">group</span> <span class="hlt">velocity</span> <span class="hlt">tomography</span>. Phase cross-correlation and time-frequency phase weighted stacking was applied to calculate the cross-correlation functions. The average Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> at the loess high bank was found to be 171 ms^{-1}. The <span class="hlt">group</span> <span class="hlt">velocity</span> map at a 0.1 s period revealed a low-<span class="hlt">velocity</span> region, whose location coincides with a highly creviced area, where slope failure takes place along a several meter wide territory. Another low <span class="hlt">velocity</span> region was found, which might indicate a previously unknown loosened domain. The highest <span class="hlt">velocities</span> were observed at the supposed remnants of Castellum Lugio.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25537816','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25537816"><span id="translatedtitle">Nasal endoscopy and paranasal sinus computerised <span class="hlt">tomography</span> (CT) findings in an Irish cystic fibrosis adult patient <span class="hlt">group</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Casserly, P; Harrison, M; O'Connell, O; O'Donovan, N; Plant, B J; O'Sullivan, P</p> <p>2015-11-01</p> <p>Cystic fibrosis (CF) is a common inherited disorder in Caucasians in Ireland having the highest reported incidence. CF has well-recognised clinical sequelae in several physiological systems. Its' impact on the sinonasal system is less well established. We evaluated symptoms, endoscopic and computerised tomographic (CT) findings in an Irish adult CF <span class="hlt">group</span> with the aim of characterising the relationship between these clinical features in an Irish CF <span class="hlt">group</span>. Adult CF patients attending a specialist clinic underwent prospective evaluation of sinonasal symptoms using a specifically designed questionnaire. They subsequently underwent nasoendoscopy and CT scanning of their paranasal sinuses. Abnormalities identified were quantified using established radiological (Lund-Mackay) and endoscopic (Lund-Kennedy) scoring systems. The relationship between symptoms of chronic rhinosinusitis (CRS), endoscopic findings and CT abnormalities were then compared. Sixty-three CF patients (n = 63) were studied. 29 patients had a CT scan. Thirty-three CF patients (52%) had no symptoms of CRS. Fifty CF patients (80% of CF <span class="hlt">group</span>) had evidence of CRS on nasoendoscopy including thirteen patients (20%) with nasal polyposis. 98% of patients scanned have positive findings on CT scan. There was no significant difference between symptomatic and asymptomatic CF <span class="hlt">groups</span> with respect to their Lund-Kennedy endoscopic score or their Lund-Mackay CT score. 86% demonstrated one or more hypoplastic sinus. There was no increased incidence of hypoplastic sinuses amongst Δf508 homozygotes than other mutation <span class="hlt">groups</span>. PMID:25537816</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AIPC.1335.1365A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AIPC.1335.1365A"><span id="translatedtitle">Modification of the Zero <span class="hlt">Group</span> <span class="hlt">Velocity</span> (impact Echo) Resonance Frequency in the Presence of Voids for the Inspection of Tendon Ducts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abraham, O.; Popovics, J. S.; Cottineau, L.-M.</p> <p>2011-06-01</p> <p>Non-destructive testing of the civil engineering infrastructure for diagnosis, residual service life estimation and/or structural health monitoring, is increasing in importance and need. For example, post-tensioned concrete bridges may be subject to sudden collapse due to tendon breakage. In France, tendon ducts are currently investigated with gamma ray radiometry, but alternative non ionizing techniques are currently sought. Since the mid-nineties, the impact echo method has been proposed to detect voids in tendon ducts, where a void indicates a possible location for tendon corrosion and rupture. The impact echo method is currently used in civil engineering to determine thicknesses or depths by measuring the resonance frequency of the S1 Lamb mode associated to its zero <span class="hlt">group</span> <span class="hlt">velocity</span> (ZGV) frequency. A downward shift of the ZGV frequency is commonly associated with the presence of an internal void, but evidence of such phenomena in case of fully filled ducts calls for deeper physical insight. In this paper we show impact-echo results obtained with a laser interferometer on a 0.25 m thick concrete test wall containing filled and partially or fully empty ducts, with both thin and thick duct walls. The data corroborate ZGV frequency shift to the modification of the local stiffness of the wall.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4668428','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4668428"><span id="translatedtitle">An Open Label Parallel <span class="hlt">Group</span> Study to Assess the Effects of Amlodipine and Cilnidipine on Pulse Wave <span class="hlt">Velocity</span> and Augmentation Pressures in Mild to Moderate Essential Hypertensive Patients</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Rajashekar, Sujith Tumkur; Buchineni, Madhavulu; Meriga, Rajesh Kumar; Reddy, Chirra Bhakthavasthala; Kumar, Kolla Praveen</p> <p>2015-01-01</p> <p>Introduction Hypertension is a major cardiovascular risk factor, which affects both large and small arteries. Because of the associated morbidity and mortality and the cost to society, it is an important public health challenge. Population based studies have reported that large artery stiffness is an important determinant of cardiovascular events and mortality in general population and in patients with hypertension. This study was designed to compare the effects of 8 weeks blood pressure control using Amlodepine and cilnidipine on haemodynamic parameters and vascular indices in mild to moderate hypertensive patients. Materials and Methods A total of 60 patients were enrolled in the study. Thirty patients were randomly allocated to either Amlodipine 5 mg OD or Cilnidipine 10 mg OD for duration of eight weeks. Blood Pressure (BP), Heart Rate (HR), carotid-femoral Pulse Wave <span class="hlt">Velocity</span> (cf PWV), Augmentation Index (AIx) and Aortic augmentation pressure (AoAP) were measured at baseline and at the end of eight weeks. Results The mean change in the central artery stiffness from baseline to week-8 in the Amlodipine <span class="hlt">group</span> as compared to Cilnidipine <span class="hlt">group</span> cf PWV -139.3±27.7 vs. -234.1±74.8 cm/s p=<0.0001, AoAP -3.8±1.5 vs. -5.6±3.3 mm of Hg p=0.008 and AIx -6.8±2.4 vs. -10.8±4.4 %, p=<0.0001 respectively. Conclusion This study showed that the L/N-type calcium channel antagonist Cilnidipine has a similar antihypertensive action to Amlodipine, but is superior in improving the arterial stiffness. PMID:26676157</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AGUFM.S52F0702B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AGUFM.S52F0702B"><span id="translatedtitle">Refining Estimates of the Seismic <span class="hlt">Velocities</span> of the Crust and Upper Mantle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>BARMIN, M.; SHAPIRO, N. M.; Ritzwoller, M. H.; Levin, V.; Park, J.</p> <p>2001-12-01</p> <p>We discuss recent efforts to improve a global shear-<span class="hlt">velocity</span> model of the crust and upper mantle by advancing surface wave methodology as well as by introducing new types of geophysical data in the inversion. The primary data-set used to construct the model consists of broad-band Rayleigh and Love wave <span class="hlt">group-velocity</span> (CU-Boulder) and phase-<span class="hlt">velocity</span> (Harvard, Utrecht) dispersion curves. The first step of the inversion is surface wave <span class="hlt">tomography</span> in which <span class="hlt">group</span> and phase <span class="hlt">velocity</span> maps are constructed. We present a new method of surface wave <span class="hlt">tomography</span> called "diffraction <span class="hlt">tomography</span>" that is based on a physical model of the surface wave Fresnel zone rather than on ray-theory and ad hoc regularization. Diffraction <span class="hlt">tomography</span> accounts for path-length dependent sensitivity, wave-form healing and associated diffraction effects, and provides a more accurate assessment of spatially variable resolution than traditional tomographic methods. The second step is Monte-Carlo inversion of the dispersion maps for an ensemble of acceptable shear <span class="hlt">velocity</span> models of the crust and uppermost mantle. Because surface waves have limited vertical resolution, we apply constraints on the model derived from other types of geophysical observations. We consider two types of additional data: teleseismic receiver functions and heat flow measurements. Receivers functions are formed by P-S converted waves that arise from sharp boundaries close to the Earth's surface, and thus provide important constraints on the crustal structure. Their use in the inversion mitigates the tradeoff between the crust (where surface waves have poor sensitivity) and the deeper part of the model. Heat-flow data constrain mantle shear <span class="hlt">velocities</span> through the conversion of heat-flow into temperature and subsequently into shear <span class="hlt">velocity</span> at the top of the upper mantle. We present results from the joint inversion and discuss how the combination of different types of data reduces both uncertainties and systematic bias in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/781156','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/781156"><span id="translatedtitle">Seismic Surface-Wave <span class="hlt">Tomography</span> of Waste Sites - Final Report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Long, Timothy L.</p> <p>2000-09-14</p> <p>The objective of this study was to develop analysis programs for surface-wave <span class="hlt">group-velocity</span> <span class="hlt">tomography</span>, and apply these to three test areas. We succeeded by obtaining data covering two square areas that were 30 meters on a side, and a third area that was 16 meters on a side, in addition to a collaborative effort wherein we processed data from the Oak Ridge National Laboratory site. At all sites, usable <span class="hlt">group</span> <span class="hlt">velocities</span> were obtained for frequencies from 16 to 50 Hz using a sledgehammer source. The resulting tomographic images and <span class="hlt">velocity</span> anomalies were sufficient to delineate suspected burial trenches (one 4-meters deep) and anomalous <span class="hlt">velocity</span> structure related to rocks and disturbed soil. The success was not uniform because in portions of one area the inversion for shear-wave structure became unstable. More research is needed to establish a more robust inversion technique.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PASP..124.1159W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PASP..124.1159W"><span id="translatedtitle">Accurate <span class="hlt">Group</span> Delay Measurement for Radial <span class="hlt">Velocity</span> Instruments Using the Dispersed Fixed Delay Interferometer Method. II. Application of Heterodyne Combs Using an External Interferometer Filter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Ji; Ge, Jian; Wan, Xiaoke; De Lee, Nathan; Lee, Brian</p> <p>2012-11-01</p> <p>A fixed delay interferometer is the key component in a DFDI (dispersed fixed delay interferometer) instrument for an exoplanet search using the radial <span class="hlt">velocity</span> (RV) technique. Although the <span class="hlt">group</span> delay (GD) of the interferometer can be measured with white light combs (WLCs), the measurement precision is limited by the comb visibility, and the wavelength coverage is constrained by the comb sampling. For instance, this method can calibrate only half of the SDSS-III MARVELS spectra and reach a precision of 2.2 m s-1. This article introduces an innovative method using a sine source for precision delay calibration over very broad wavelengths. The sine source is made of a monolithic Michelson interferometer fed with white light. The interferometer modulated white light (in a sinusoidal form) is fed into a DFDI instrument for calibration. Due to an optimal GD of the sine source, Fourier components from the DFDI interferometer, the sine source, and their frequency beating can be clearly separated and effectively extracted with a chirped Fourier transform to allow precision measurements of the interferometer GD over the entire range of operation wavelengths. The measurements of the MARVELS interferometer with a sine source show that this new calibration method has improved the wavelength coverage by a factor of 2 and the precision by a factor of 3. The RV measurement error induced by GD measurement uncertainties is controlled to be less than 1 m s-1, which has met the requirements for MARVELS moderate-to-high Doppler precision (~5-30 m s-1) for exoplanet search around V ~ 8-12 solar-type stars. Heterodyne combs using an external interferometer source can be applied in other areas of optics measurement and calibration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/806810','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/806810"><span id="translatedtitle">Seismic Surface-Wave <span class="hlt">Tomography</span> of Waste Sites</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Leland Timothy Long</p> <p>2002-12-17</p> <p>Surface-wave <span class="hlt">group-velocity</span> <span class="hlt">tomography</span> is an efficient way to obtain images of the <span class="hlt">group</span> <span class="hlt">velocity</span> over a test area. Because Rayleigh-wave <span class="hlt">group</span> <span class="hlt">velocity</span> depends on frequency, there are separate images for each frequency. Thus, at each point in these images the <span class="hlt">group</span> <span class="hlt">velocities</span> define a dispersion curve, a curve that relates <span class="hlt">group</span> <span class="hlt">velocity</span> to frequency. The objective of this study has been to find an accurate and efficient way to find the shear-wave structure from these dispersion curves. The conventional inversion techniques match theoretical and observed dispersion curves to determine the structure. These conventional methods do not always succeed in correctly differentiating the fundamental and higher modes, and for some <span class="hlt">velocity</span> structures can become unstable. In this research a perturbation technique was developed. The perturbation method allows the pre-computation of a global inversion matrix which improves efficiency in obtaining solutions for the structure. Perturbation methods are stable and mimic the averaging process in wave propagation; hence. leading to more accurate solutions. Finite difference techniques and synthetic trace generation techniques were developed to define the perturbations. A new differential trace technique was developed for slight variations in dispersion. The improvements in analysis speed and the accuracy of the solution could lead to real-time field analysis systems, making it possible to obtain immediate results or to monitor temporal change in structure, such as might develop in using fluids for soil remediation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4275164','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4275164"><span id="translatedtitle">Radiolabeling of Poly(lactic-co-glycolic acid) (PLGA) Nanoparticles with Biotinylated F-18 Prosthetic <span class="hlt">Groups</span> and Imaging of Their Delivery to the Brain with Positron Emission <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2015-01-01</p> <p>The avidin–biotin interaction permits rapid and nearly irreversible noncovalent linkage between biotinylated molecules and avidin-modified substrates. We designed a biotinylated radioligand intended for use in the detection of avidin-modified polymer nanoparticles in tissue with positron emission <span class="hlt">tomography</span> (PET). Using an F-18 labeled prosthetic <span class="hlt">group</span>, [18F]4-fluorobenzylamine, and a commercially available biotin derivate, NHS-PEG4-biotin, [18F]-fluorobenzylamide-poly(ethylene glycol)4-biotin ([18F]NPB4) was prepared with high purity and specific activity. The attachment of the [18F]NPB4 radioligand to avidin-modified poly(lactic-co-glycolic acid) (PLGA) nanoparticles was tested by using PET imaging to measure the kinetics of convection-enhanced delivery (CED) of nanoparticles of varying size to the rat brain. PET imaging enabled the direct observation of nanoparticle delivery by measurement of the spatial volume of distribution of radiolabeled nanoparticles as a function of time, both during and after the infusion. This work thus validates new methods for radiolabeling PEG-biotin derivatives and also provides insight into the fate of nanoparticles that have been infused directly into the brain. PMID:25322194</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25322194','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25322194"><span id="translatedtitle">Radiolabeling of poly(lactic-co-glycolic acid) (PLGA) nanoparticles with biotinylated F-18 prosthetic <span class="hlt">groups</span> and imaging of their delivery to the brain with positron emission <span class="hlt">tomography</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sirianni, Rachael W; Zheng, Ming-Qiang; Patel, Toral R; Shafbauer, Thomas; Zhou, Jiangbing; Saltzman, W Mark; Carson, Richard E; Huang, Yiyun</p> <p>2014-12-17</p> <p>The avidin-biotin interaction permits rapid and nearly irreversible noncovalent linkage between biotinylated molecules and avidin-modified substrates. We designed a biotinylated radioligand intended for use in the detection of avidin-modified polymer nanoparticles in tissue with positron emission <span class="hlt">tomography</span> (PET). Using an F-18 labeled prosthetic <span class="hlt">group</span>, [(18)F]4-fluorobenzylamine, and a commercially available biotin derivate, NHS-PEG4-biotin, [(18)F]-fluorobenzylamide-poly(ethylene glycol)4-biotin ([(18)F]NPB4) was prepared with high purity and specific activity. The attachment of the [(18)F]NPB4 radioligand to avidin-modified poly(lactic-co-glycolic acid) (PLGA) nanoparticles was tested by using PET imaging to measure the kinetics of convection-enhanced delivery (CED) of nanoparticles of varying size to the rat brain. PET imaging enabled the direct observation of nanoparticle delivery by measurement of the spatial volume of distribution of radiolabeled nanoparticles as a function of time, both during and after the infusion. This work thus validates new methods for radiolabeling PEG-biotin derivatives and also provides insight into the fate of nanoparticles that have been infused directly into the brain. PMID:25322194</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015PhDT.........4H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015PhDT.........4H&link_type=ABSTRACT"><span id="translatedtitle">Enhanced monitoring of hazardous waste site remediation: Electrical conductivity <span class="hlt">tomography</span> and citizen monitoring of remediation through the EPA's community advisory <span class="hlt">group</span> program</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hort, Ryan D.</p> <p></p> <p>In situ chemical oxidation using permanganate has become a common method for degrading trichloroethene (TCE) in contaminated aquifers. Its effectiveness, however, is dependent upon contact between the oxidant and contaminant. Monitoring permanganate movement after injection is often hampered by aquifer heterogeneity and insufficient well coverage. Time lapse electrical conductivity <span class="hlt">tomography</span> increases the spatial extent of monitoring beyond well locations. This technique can create two- or three-dimensional images of the electrical conductivity within the aquifer to monitor aquifer chemistry changes caused by permanganate injection and oxidation reactions. In-phase and quadrature electrical conductivity were measured in homogeneous aqueous and porous media samples to determine the effects of TCE and humate oxidation by permanganate on both measures of conductivity. Further effects of clean sand, 10% kaolinite (v/v), and 10% smectite (v/v) on both types of conductivity were studied as well. Finally, in-phase electrical conductivity was measured over time after injecting permanganate solution into two-dimensional tanks containing artificial groundwater with and without TCE to observe the movement of the permanganate plume and its interaction with TCE and to examine the effectiveness of time-lapse conductivity <span class="hlt">tomography</span> for monitoring the plume's movement. In-phase electrical conductivity after oxidation reactions involving permanganate, TCE, and humate could be accurately modeled in homogeneous batch samples. Use of forward modeling of in-phase conductivity from permanganate concentrations may be useful for improving recovery of conductivity values during survey inversion, but further work is needed combining the chemistry modeling with solute transport models. Small pH-related quadrature conductivity decreases were observed after TCE oxidation, and large quadrature conductivity increases were observed as a result of sodium ion addition; however, quadrature</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.S31D..06B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.S31D..06B"><span id="translatedtitle">Transdimensional Seismic <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bodin, T.; Sambridge, M.</p> <p>2009-12-01</p> <p>In seismic imaging the degree of model complexity is usually determined by manually tuning damping parameters within a fixed parameterization chosen in advance. Here we present an alternative methodology for seismic travel time <span class="hlt">tomography</span> where the model complexity is controlled automatically by the data. In particular we use a variable parametrization consisting of Voronoi cells with mobile geometry, shape and number, all treated as unknowns in the inversion. The reversible jump algorithm is used to sample the transdimensional model space within a Bayesian framework which avoids global damping procedures and the need to tune regularisation parameters. The method is an ensemble inference approach, as many potential solutions are generated with variable numbers of cells. Information is extracted from the ensemble as a whole by performing Monte Carlo integration to produce the expected Earth model. The ensemble of models can also be used to produce <span class="hlt">velocity</span> uncertainty estimates and experiments with synthetic data suggest they represent actual uncertainty surprisingly well. In a transdimensional approach, the level of data uncertainty directly determines the model complexity needed to satisfy the data. Intriguingly, the Bayesian formulation can be extended to the case where data uncertainty is also uncertain. Experiments show that it is possible to recover data noise estimate while at the same time controlling model complexity in an automated fashion. The method is tested on synthetic data in a 2-D application and compared with a more standard matrix based inversion scheme. The method has also been applied to real data obtained from cross correlation of ambient noise where little is known about the size of the errors associated with the travel times. As an example, a tomographic image of Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> for the Australian continent is constructed for 5s data together with uncertainty estimates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.S31A2034C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.S31A2034C"><span id="translatedtitle">Surface Wave <span class="hlt">Tomography</span> of the Region Between Korea and Taiwan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cho, K.; Lee, S.</p> <p>2010-12-01</p> <p>Surface wave <span class="hlt">tomography</span> of the region between Korea and Taiwan has been investigated by inverting the path-averaged <span class="hlt">group-velocity</span> dispersion characteristic curves of surface waves obtained from big events and ambient noise. 219 seismograms from 19 events of magnitude greater than 6.0 that occurred in Taiwan from 1999 to 2007 have been recorded at three-component broadband seismic stations of Korea Institute of Geosciences and Mineral Resources-Korea Earthquake Research Center(KIGAM-KERC) and ambient noise signals during 2004 and 2005 have been recorded at three-component broadband <span class="hlt">velocity</span> and accelerometer stations of Korea Meteorological Administration(KMA) seismic network. 1928 Green’s functions have been obtained from very long ambient noise signals by seismic interferometry. Horizontal components of big event seismograms and ambient noise Green's functions have been rotated along great circle path to obtain Rayleigh-and Love-waves. In periods between 5 and 100 sec, <span class="hlt">group</span> <span class="hlt">velocities</span> of Rayleigh-and Love-waves have been computed using multiple filter technique(MFT). The tomographic inversion technique used has inverted all periods simultaneously to provide a smooth dispersion curve as a function of period and a smooth spatial image. Surface wave <span class="hlt">tomography</span> inverted from the path-averaged <span class="hlt">group</span> <span class="hlt">velocity</span> data provides detailed tectonic information of East China Sea.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013GeoJI.193.1627M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013GeoJI.193.1627M"><span id="translatedtitle">Near-surface study at the Valhall oil field from ambient noise surface wave <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mordret, A.; Landès, M.; Shapiro, N. M.; Singh, S. C.; Roux, P.; Barkved, O. I.</p> <p>2013-06-01</p> <p>We used 6 hr of continuous seismic noise records from 2320 four-component sensors of the Valhall `Life of Field Seismic' network to compute cross-correlations (CCs) of ambient seismic noise. A beamforming analysis showed that at low frequencies (below 2 Hz) the seismic noise sources were spatially homogeneously distributed, whereas at higher frequencies (2-30 Hz), the dominant noise source was the oil platform at the centre of the network. Here, we performed an ambient noise surface wave <span class="hlt">tomography</span> at frequencies below 2 Hz. We used vertical-component geophones CCs to extract and measure the Scholte waves <span class="hlt">group</span> <span class="hlt">velocities</span> dispersion curves that were then processed with a set of quality criteria and inverted to build <span class="hlt">group</span> <span class="hlt">velocity</span> maps of the Valhall area. Although Scholte wave <span class="hlt">group</span> <span class="hlt">velocity</span> depends on S wave, our <span class="hlt">group</span> <span class="hlt">velocity</span> maps show features similar to that was previously obtained from P-wave <span class="hlt">velocity</span> full-waveform inversion of an active seismic data set. Since the dominant noise source at high frequency (above 3 Hz) was the oil platform, we determined a 2-D S-wave <span class="hlt">velocity</span> model along a profile aligned with the platform by inverting <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion curves of Love waves from transverse-component geophones CCs. We found that S-wave <span class="hlt">velocity</span> down to 20 m was low and varied along the profile, and could be used to estimate S-wave static.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.6492V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.6492V"><span id="translatedtitle">Minimum 1D P- and S- <span class="hlt">Velocity</span> Models for Montenegro and Vicinity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vucic, Ljiljana; Kissling, Edi; Spakman, Wim; Glavatovic, Branislav</p> <p>2015-04-01</p> <p>The territory of Montenegro and its vicinity are characterized by high-seismicity rate and very complex tectonics. Namely, southern Adria microplate subducts beneath Eurasia, forming the Dinarides fold-and-thrust belt which spreads through whole Montenegro and the western Balkans. Present-day lithosphere structure of the Adria-Dinarides collision zone in general is not constrained very well and, consequently, there is a lack of three-dimensional (3D) <span class="hlt">velocity</span> models in this region. For these reasons, high resolution 3D <span class="hlt">tomography</span> modeling of this area is considered to be of great importance. As part of preparatory phase for conducting a 3D local earthquake <span class="hlt">tomography</span> study, a substantial amount of waveform data was collected, from all surroundings national seismic networks including 130 seismic stations from 11 countries. The data set comprises waveforms from 1452 earthquakes in the region recorded during time period 1990 - 2014. The collected data were obtained in different formats and the data base was harmonized by converting and integrating all data to miniseed format. The potential resolution of collected data for seismic <span class="hlt">tomography</span> purpose was analyzed by ray density testing, using specially developed software for this specific purpose. The result is expressed as the number of rays between selected <span class="hlt">group</span> of earthquake hypocenters and seismic stations, penetrating through the 3D model of the Earth crust and it documents the great potential of the data set for 3D seismic <span class="hlt">tomography</span>. As a prerequisite to 3D <span class="hlt">tomography</span> and for consistent high-precision earthquake locations, a minimum 1D <span class="hlt">velocity</span> model has been calculated. The data set of around 400 earthquakes was selected from the main database and consistent wave onsets picking was performed, including seismic phase interpretation and its quality assessment. This highly consistent travel time data set is used for calculation of 1D <span class="hlt">velocity</span> models for the region under study. The minimum 1D models were derived</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997A%26A...319..811B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997A%26A...319..811B"><span id="translatedtitle">High S/N Echelle spectroscopy in young stellar <span class="hlt">groups</span>. II. Rotational <span class="hlt">velocities</span> of early-type stars in SCO OB2.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brown, A. G. A.; Verschueren, W.</p> <p>1997-03-01</p> <p>We investigate the rotational <span class="hlt">velocities</span> of early-type stars in the Sco OB2 association. We measure v.sin(i) for 156 established and probable members of the association. The measurements are performed with three different techniques, which are in increasing order of expected v.sin(i): 1) converting the widths of spectral lines directly to v.sin(i), 2) comparing artificially broadened spectra of low v.sin(i) stars to the target spectrum, 3) comparing the HeI λ4026 line profile to theoretical models. The sample is extended with literature data for 47 established members of Sco OB2. Analysis of the v.sin(i) distributions shows that there are no significant differences between the subgroups of Sco OB2. We find that members of the binary population of Sco OB2 on the whole rotate more slowly than the single stars. In addition, we find that the B7-B9 single star members rotate significantly faster than their B0-B6 counterparts. We test various hypotheses for the distribution of v.sin(i) in the association. The results show that we cannot clearly exclude any form of random distribution of the direction and/or magnitude of the intrinsic rotational <span class="hlt">velocity</span> vector. We also investigate the effects of rotation on colours in the Walraven photometric system. We show that positions of B7-B9 single dwarfs above the main sequence are a consequence of rotation. This establishes the influence of rotation on the Walraven colours, due primarily to surface gravity effects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014GeoJI.197.1236L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014GeoJI.197.1236L&link_type=ABSTRACT"><span id="translatedtitle">Adaptive ambient noise <span class="hlt">tomography</span> and its application to the Garlock Fault, southern California</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Peng; Lin, Guoqing</p> <p>2014-05-01</p> <p>Traditional ambient noise <span class="hlt">tomography</span> methods using regular grid nodes are often ill posed because the inversion grids do not always represent the distribution of ray paths. Large grid spacing is usually used to reduce the number of inversion parameters, which may not be able to solve for small-scale <span class="hlt">velocity</span> structure. We present a new adaptive <span class="hlt">tomography</span> method with irregular grids that provides a few advantages over the traditional methods. First, irregular grids with different sizes and shapes can fit the ray distribution better and the traditionally ill-posed problem can become more stable owing to the different parametrizations. Secondly, the data in the area with dense ray sampling will be sufficiently utilized so that the model resolution can be greatly improved. Both synthetic and real data are used to test the newly developed <span class="hlt">tomography</span> algorithm. In synthetic data tests, we compare the resolution and stability of the traditional and adaptive methods. The results show that adaptive <span class="hlt">tomography</span> is more stable and performs better in improving the resolution in the area with dense ray sampling. For real data, we extract the ambient noise signals of the seismic data near the Garlock Fault region, obtained from the Southern California Earthquake Data Center. The resulting <span class="hlt">group</span> <span class="hlt">velocity</span> of Rayleigh wave is well correlated with the geological structures. High-<span class="hlt">velocity</span> anomalies are shown in the cold southern Sierra Nevada, the Tehachapi Mountains and the Western San Gabriel Mountains. In contrast, low <span class="hlt">velocity</span> values are prominent in the southern San Joaquin Valley and western Mojave.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007pmia.book..367C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007pmia.book..367C"><span id="translatedtitle">Computed <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Castellano, Isabel; Geleijns, Jacob</p> <p></p> <p>After its clinical introduction in 1973, computed <span class="hlt">tomography</span> developed from an x-ray modality for axial imaging in neuroradiology into a versatile three dimensional imaging modality for a wide range of applications in for example oncology, vascular radiology, cardiology, traumatology and even in interventional radiology. Computed <span class="hlt">tomography</span> is applied for diagnosis, follow-up studies and screening of healthy subpopulations with specific risk factors. This chapter provides a general introduction in computed <span class="hlt">tomography</span>, covering a short history of computed <span class="hlt">tomography</span>, technology, image quality, dosimetry, room shielding, quality control and quality criteria.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGE....13..146R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGE....13..146R"><span id="translatedtitle">Reflection seismic waveform <span class="hlt">tomography</span> of physical modelling data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rao, Y.; Wang, Y.; Zhang, Z. D.; Ning, Y. C.; Chen, X. H.; Li, J. Y.</p> <p>2016-04-01</p> <p>Waveform <span class="hlt">tomography</span> is commonly tested using numerically generated synthetic seismic data, before the method is applied to field seismic data. However, there are often noticeable differences between idealized synthetic data and real field data, and many factors in the field data, such as noise, irregular source/receiver geometry, affect the inversion solutions. For exploring the potential of reflection seismic waveform <span class="hlt">tomography</span>, we presented a more realistic test than the synthetic data test, by applying it to physical modelling data, to reconstruct a laboratorial model with complex <span class="hlt">velocity</span> variation. First, we provided a formulation of the perfectly matched layer absorbing boundary condition, associated with the second-order acoustic wave equation, in order to suppress artificial reflections from subsurface model boundaries in seismic waveform simulation and <span class="hlt">tomography</span>. Then, we demonstrated the successful implementation of a layer-striping inversion scheme applicable to reflection seismic waveform <span class="hlt">tomography</span>. Finally, we confirmed the effectiveness of frequency <span class="hlt">grouping</span>, rather than a single frequency at each iteration, a strategy specifically for the frequency-domain waveform <span class="hlt">tomography</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMNS41B3836L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMNS41B3836L"><span id="translatedtitle">Probing Near Surface Shear <span class="hlt">Velocity</span> Structure from Ambient Noise in Hefei Urban Area</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, C.; Yao, H.; Fang, H.</p> <p>2014-12-01</p> <p>Ambient noise <span class="hlt">tomography</span> has widely been used to achieve high resolution 3-D crustal <span class="hlt">velocity</span> structure. Recently, various studies also indicate that high-frequency surface wave signals can be extracted from cross correlation of ambient noise. So it makes ambient noise <span class="hlt">tomography</span> capable to investigate near surface <span class="hlt">velocity</span> structure. This is important for studies related to strong motion estimation due to earthquakes and characterization of structure in oil and gas exploration fields. Here we investigate near surface 3-D <span class="hlt">velocity</span> structure using high-frequency (0.5 - 2 Hz) ambient noise <span class="hlt">tomography</span> in the urban area of Hefei city, Anhui province in eastern China. We collected continuous ambient noise data of two weeks from 17 stations in the center of city with a lateral scale about 5 km by 7 km. The S-transform technique is used to stack vertical-component cross-correlation functions from hourly data, which yields much higher SNR of the high frequency surface waves than traditional linear stack. We developed a ray-tracing based iterative surface wave <span class="hlt">tomography</span> method with spatial smoothing constraints (model regularization) based on ray path density.This method is used to construct frequency-dependent phase <span class="hlt">velocity</span> maps in the study area, which can account for the effect of ray bending in the tomographic inversion. We also developed a new direct surface wave inversion method to iteratively invert surface wave dispersion data of all paths for 3-D variations of shear wave <span class="hlt">velocity</span> in the study area without the intermediate step of phase or <span class="hlt">group</span> <span class="hlt">velocity</span> maps.The method uses frequency dependent propagation paths and a wavelet-based sparsity-constrained <span class="hlt">tomography</span> inversion. Hefei city is located in a basin and its southern suburb close to the Chao Lake, the fifth largest lake in China. The inversion results show that the north part has much higher <span class="hlt">velocity</span>(~2.5 km/s) in the top several hundred meters than the south part(~0.8 km/s), basically consistent with the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/80189','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/80189"><span id="translatedtitle">Seismic crosshole curved ray reflection plus transmission <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wu, L.; Song, W.; Zhang, M.</p> <p>1994-12-31</p> <p>This paper provides a new seismic crosshole <span class="hlt">tomography</span> method, Curved Ray Reflection + Transmission <span class="hlt">Tomography</span> (CCRTT). The method could enhance the resolution of oil and gas reservoir beds <span class="hlt">tomography</span> image, and it is suitable for the area with thin reservoir beds and high <span class="hlt">velocity</span> contrast between the adjacent beds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21322426','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21322426"><span id="translatedtitle">Is the misalignment of the Local <span class="hlt">Group</span> <span class="hlt">velocity</span> and the dipole generated by the 2MASS Redshift Survey typical in {lambda} cold dark matter and the halo model of galaxies?</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Erdogdu, Pirin; Lahav, Ofer</p> <p>2009-08-15</p> <p>We predict the acceleration of the Local <span class="hlt">Group</span> generated by the 2MASS Redshift Survey within the framework of {lambda} cold dark matter and the halo model of galaxies. We show that as the galaxy fluctuations derived from the halo model have more power on small scales compared with the mass fluctuations, the misalignment angle between the CMB <span class="hlt">velocity</span> vector and the 2MASS Redshift Survey dipole is in reasonable agreement with the observed 21 deg. This statistical analysis suggests that it is not necessary to invoke a hypothetical nearby galaxy or a distant cluster to explain this misalignment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.S51C1280Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.S51C1280Z"><span id="translatedtitle">Constrained Deformable-Layer <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, H.</p> <p>2006-12-01</p> <p>The improvement on traveltime <span class="hlt">tomography</span> depends on improving data coverage and tomographic methodology. The data coverage depends on the spatial distribution of sources and stations, as well as the extent of lateral <span class="hlt">velocity</span> variation that may alter the raypaths locally. A reliable tomographic image requires large enough ray hit count and wide enough angular range between traversing rays over the targeted anomalies. Recent years have witnessed the advancement of traveltime <span class="hlt">tomography</span> in two aspects. One is the use of finite frequency kernels, and the other is the improvement on model parameterization, particularly that allows the use of a priori constraints. A new way of model parameterization is the deformable-layer <span class="hlt">tomography</span> (DLT), which directly inverts for the geometry of <span class="hlt">velocity</span> interfaces by varying the depths of grid points to achieve a best traveltime fit. In contrast, conventional grid or cell <span class="hlt">tomography</span> seeks to determine <span class="hlt">velocity</span> values of a mesh of fixed-in-space grids or cells. In this study, the DLT is used to map crustal P-wave <span class="hlt">velocities</span> with first arrival data from local earthquakes and two LARSE active surveys in southern California. The DLT solutions along three profiles are constrained using known depth ranges of the Moho discontinuity at 21 sites from a previous receiver function study. The DLT solutions are generally well resolved according to restoration resolution tests. The patterns of 2D DLT models of different profiles match well at their intersection locations. In comparison with existing 3D cell <span class="hlt">tomography</span> models in southern California, the new DLT models significantly improve the data fitness. In comparison with the multi-scale cell <span class="hlt">tomography</span> conducted for the same data, while the data fitting levels of the DLT and the multi-scale cell <span class="hlt">tomography</span> models are compatible, the DLT provides much higher vertical resolution and more realistic description of the undulation of <span class="hlt">velocity</span> discontinuities. The constraints on the Moho depth</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMDI43B..01S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMDI43B..01S"><span id="translatedtitle">Origin of the Low <span class="hlt">Velocity</span> Zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stixrude, L. P.; Lithgow-Bertelloni, C. R.</p> <p>2014-12-01</p> <p>The origin of the low <span class="hlt">velocity</span> zone is still not well understood, although the mechanisms responsible have important implications for the thermal evolution of the Earth and the origin of plate tectonics. The null hypothesis (a geotherm consisting of an adiabat and a conductive thermal boundary layer, and free of melt, water, and attenuation) accounts for many properties of the low <span class="hlt">velocity</span> zone, including the depth at which the minimum <span class="hlt">velocity</span> occurs and its variation with age, but the value of the minimum <span class="hlt">velocity</span> is greater than that seen by seismology (the <span class="hlt">velocity</span> deficit). Attenuation, as found in global seismic attenuation <span class="hlt">tomography</span>, can explain much of the <span class="hlt">velocity</span> deficit, but still leaves two features of the boundaries of the low <span class="hlt">velocity</span> zone unexplained: an apparently abrupt upper boundary to the low <span class="hlt">velocity</span> (G discontinuity, sometimes also associated with the "lithosphere-asthenosphere boundary"), and a high gradient zone beneath in which <span class="hlt">velocity</span> increases with depth very rapidly. Here we show that by adding to the null hypothesis attenuation as recently measured experimentally, the entire <span class="hlt">velocity</span> deficit is explained. Moreover, the upper boundary of the low <span class="hlt">velocity</span> zone is remarkably abrupt, although possibly less sharp than receiver function analyses indicate. The high gradient zone is explained by variations in the entropy with depth, i.e. cooling with increasing depth at depths beneath the low <span class="hlt">velocity</span> zone, a property of the geotherm that is expected on the basis of mantle convection simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22391598','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22391598"><span id="translatedtitle">The preliminary results: Seismic ambient noise Rayleigh wave <span class="hlt">tomography</span> around Merapi volcano, central Java, Indonesia</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Trichandi, Rahmantara; Yudistira, Tedi; Nugraha, Andri Dian; Zulhan, Zulfakriza; Saygin, Erdinc</p> <p>2015-04-24</p> <p>Ambient noise <span class="hlt">tomography</span> is relatively a new method for imaging the shallow structure of the Earth subsurface. We presents the application of this method to produce a Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> maps around the Merapi Volcano, Central Java. Rayleigh waves <span class="hlt">group</span> <span class="hlt">velocity</span> maps were reconstructed from the cross-correlation of ambient noise recorded by the DOMERAPI array which consists 43 broadband seismometers. In the processing stage, we first filtered the observation data to separatethe noise from the signal that dominated by the strong volcanic activities. Next, we cross-correlate the filtered data and stack to obtain the Green’s function for all possible station pairs. Then we carefully picked the peak of each Green’s function to estimate the dispersion trend and appliedMultiple Filter Technique to obtain the dispersion curve. Inter-station <span class="hlt">group</span> <span class="hlt">velocity</span> curvesare inverted to produceRayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> maps for periods 1 to 10 s. The resulted Rayleigh <span class="hlt">group</span> <span class="hlt">velocity</span> maps show the interesting features around the Merapi Volcano which generally agree with the previous studies. Merapi-Lawu Anomaly (MLA) is emerged as a relatively low anomaly in our <span class="hlt">group</span> <span class="hlt">velocity</span> maps.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/928149','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/928149"><span id="translatedtitle">Seismicity and Improved <span class="hlt">Velocity</span> Structure in Kuwait</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gok, R M; Rodgers, A J; Al-Enezi, A</p> <p>2006-01-26</p> <p>The Kuwait National Seismic Network (KNSN) began operation in 1997 and consists of nine three-component stations (eight short-period and one broadband) and is operated by the Kuwait Institute for Scientific Research. Although the region is largely believed to be aseismic, considerable local seismicity is recorded by KNSN. Seismic events in Kuwait are clustered in two main <span class="hlt">groups</span>, one in the south and another in the north. The KNSN station distribution is able to capture the southern cluster within the footprint of the network but the northern cluster is poorly covered. Events tend to occur at depths ranging from the free surface to about 20 km. Events in the northern cluster tend to be deeper than those in south, however this might be an artifact of the station coverage. We analyzed KNSN recordings of nearly 200 local events to improve understanding of seismic events and crustal structure in Kuwait, performing several analyses with increasing complexity. First, we obtained an optimized one-dimensional (1D) <span class="hlt">velocity</span> model for the entire region using the reported KNSN arrival times and routine locations. The resulting model is consistent with a recently obtained model from the joint inversion of receiver functions and surface wave <span class="hlt">group</span> <span class="hlt">velocities</span>. Crustal structure is capped by the thick ({approx} 7 km) sedimentary rocks of the Arabian Platform underlain by normal <span class="hlt">velocities</span> for stable continental crust. Our new model has a crustal thickness of 44 km, constrained by an independent study of receiver functions and surface wave <span class="hlt">group</span> <span class="hlt">velocities</span> by Pasyanos et al (2006). Locations and depths of events after relocation with the new model are broadly consistent with those reported by KISR, although a few events move more than a few kilometers. We then used a double-difference <span class="hlt">tomography</span> technique (tomoDD) to jointly locate the events and estimate three-dimensional (3D) <span class="hlt">velocity</span> structure. TomoDD is based on hypoDD relocation algorithm and it makes use of both absolute and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1810335K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1810335K"><span id="translatedtitle">Trans-dimensional ambient noise <span class="hlt">tomography</span> of the northeast Asia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, Seongryong; Tkalčić, Hrvoje; Rhie, Junkee; Chen, Youlin</p> <p>2016-04-01</p> <p>A trans-dimensional and hierarchical Bayesian <span class="hlt">tomography</span> is performed to estimate spatial variations of shear wave <span class="hlt">velocity</span> and provide the uncertainty in the northeast Asia region from the ambient noise data. The method accounts for irregular data distribution and sensitivity using adaptive partition property of Voronoi cells. Importantly, the number of basis functions used to parameterise the Earth model in the inversion and the level of data noise are implicitly balanced by the information contained in the data (and treated as free parameters in the inversions). Thereby more reliable models and their rigorous uncertainties are estimated by avoiding over- or under-estimation and explicit regularisation. We measure Rayleigh wave phase and <span class="hlt">group</span> <span class="hlt">velocity</span> (8-70 s) for available inter-station paths between more than 300 broadband stations. The obtained <span class="hlt">group</span> and phase <span class="hlt">velocity</span> maps reveal characteristic features beneath the former (East Sea also known as Japan Sea) and the current back-arc (Okinawa trough) regions, where relatively high and low <span class="hlt">velocities</span> are estimated at intermediate (20-40 s) and longer periods (50-60 s), respectively. We observe that the low <span class="hlt">velocity</span> anomalies extend to beneath intraplate volcanoes in the northeast China and the Korean Peninsula. Based on the depth sensitivity of surface wave dispersions and previous geological evidences, we argue that the intraplate volcanism in this region might be influenced by sub-lithospheric processes related to the subduction of the Pacific and Philippine Sea plates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.S23D2775L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.S23D2775L&link_type=ABSTRACT"><span id="translatedtitle">Ambient seismic noise <span class="hlt">tomography</span> of Jeju Island, South Korea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, S. J.; Rhie, J.; Kim, S.; Kang, T. S.; Kim, Y.</p> <p>2015-12-01</p> <p>Jeju Island, formed by Cenozoic basaltic eruptions, is an island off the southern coast of the Korean Peninsula. This volcanic island is far from the plate boundaries and the fundamental cause of the volcanic activity in this region is not understood well. To understand the origin of the island, resolving the detailed seismic <span class="hlt">velocity</span> structures is crucial. Therefore, we applied ambient noise <span class="hlt">tomography</span> to study the <span class="hlt">velocity</span> structures of the island. Continuous waveform data recorded at 20 temporary and 3 permanent broad-band seismic stations are used. The <span class="hlt">group</span> and phase <span class="hlt">velocity</span> dispersion curves of the fundamental mode Rayleigh waves are extracted from cross-correlograms for 253 station pairs by adopting multiple filter technique. The fast marching method and the subspace method are jointly applied to construct 2-D <span class="hlt">group</span> and phase <span class="hlt">velocity</span> maps for periods ranging between 1 and 15 s. 1-D shear wave <span class="hlt">velocity</span> models and their uncertainties are estimated by the Bayesian technique. The optimal number of the layers are determined at the end of the burn-in period based on the Bayesian Information Criteria (BIC). Final 3-D <span class="hlt">velocity</span> model of the island is constructed by compiling 1-D models. In our 3-D model, a distinct low <span class="hlt">velocity</span> anomaly appears beneath Mt. Halla from surface to about 6 km depth. The surficial extent of the anomaly is more or less consistent with the surface geologic feature of the third-stage basaltic eruption reported by previous studies but the vertical extension of the anomaly is not well constrained. To improve the <span class="hlt">velocity</span> model, especially enhance the vertical resolution of the anomaly, we will apply joint analysis of the surface wave dispersions and teleseismic receiver functions. The improved model will provide more information to infer the tectonic or volcanic implications of the anomaly and unravel the origin of the strange volcanic island in South Korea.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.S13B2840Z&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.S13B2840Z&link_type=ABSTRACT"><span id="translatedtitle">Microseismic <span class="hlt">Velocity</span> Imaging of the Fracturing Zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, H.; Chen, Y.</p> <p>2015-12-01</p> <p>Hydraulic fracturing of low permeability reservoirs can induce microseismic events during fracture development. For this reason, microseismic monitoring using sensors on surface or in borehole have been widely used to delineate fracture spatial distribution and to understand fracturing mechanisms. It is often the case that the stimulated reservoir volume (SRV) is determined solely based on microseismic locations. However, it is known that for some fracture development stage, long period long duration events, instead of microseismic events may be associated. In addition, because microseismic events are essentially weak and there exist different sources of noise during monitoring, some microseismic events could not be detected and thus located. Therefore the estimation of the SRV is biased if it is solely determined by microseismic locations. With the existence of fluids and fractures, the seismic <span class="hlt">velocity</span> of reservoir layers will be decreased. Based on this fact, we have developed a near real time seismic <span class="hlt">velocity</span> <span class="hlt">tomography</span> method to characterize <span class="hlt">velocity</span> changes associated with fracturing process. The method is based on double-difference seismic <span class="hlt">tomography</span> algorithm to image the fracturing zone where microseismic events occur by using differential arrival times from microseismic event pairs. To take into account varying data distribution for different fracking stages, the method solves the <span class="hlt">velocity</span> model in the wavelet domain so that different scales of model features can be obtained according to different data distribution. We have applied this real time <span class="hlt">tomography</span> method to both acoustic emission data from lab experiment and microseismic data from a downhole microseismic monitoring project for shale gas hydraulic fracturing treatment. The <span class="hlt">tomography</span> results from lab data clearly show the <span class="hlt">velocity</span> changes associated with different rock fracturing stages. For the field data application, it shows that microseismic events are located in low <span class="hlt">velocity</span> anomalies. By</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/264569','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/264569"><span id="translatedtitle">Pseudolocal <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Katsevich, A.J.; Ramm, A.G.</p> <p>1996-07-23</p> <p>Local tomographic data is used to determine the location and value of a discontinuity between a first internal density of an object and a second density of a region within the object. A beam of radiation is directed in a predetermined pattern through the region of the object containing the discontinuity. Relative attenuation data of the beam is determined within the predetermined pattern having a first data component that includes attenuation data through the region. The relative attenuation data is input to a pseudo-local <span class="hlt">tomography</span> function, where the difference between the internal density and the pseudo-local <span class="hlt">tomography</span> function is computed across the discontinuity. The pseudo-local <span class="hlt">tomography</span> function outputs the location of the discontinuity and the difference in density between the first density and the second density. 7 figs.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/870532','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/870532"><span id="translatedtitle">Pseudolocal <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Katsevich, Alexander J.; Ramm, Alexander G.</p> <p>1996-01-01</p> <p>Local tomographic data is used to determine the location and value of a discontinuity between a first internal density of an object and a second density of a region within the object. A beam of radiation is directed in a predetermined pattern through the region of the object containing the discontinuity. Relative attenuation data of the beam is determined within the predetermined pattern having a first data component that includes attenuation data through the region. The relative attenuation data is input to a pseudo-local <span class="hlt">tomography</span> function, where the difference between the internal density and the pseudo-local <span class="hlt">tomography</span> function is computed across the discontinuity. The pseudo-local <span class="hlt">tomography</span> function outputs the location of the discontinuity and the difference in density between the first density and the second density.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21140555','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21140555"><span id="translatedtitle">Superluminal <span class="hlt">group</span> <span class="hlt">velocity</span> in a birefringent crystal</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Halvorsen, Tore Gunnar; Leinaas, Jon Magne</p> <p>2008-02-15</p> <p>We examine the effect of superluminal signal propagation through a birefringent crystal, where the effect is not due to absorption or reflection, but to the filtration of a special polarization component. We first examine the effect by a stationary phase analysis, with results consistent with those of an earlier analysis of the system. We supplement this analysis by considering the transit of a Gaussian wave and find bounds for the validity of the stationary phase result. The propagation of the Gaussian wave is illustrated by figures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002InvPr..18.1795L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002InvPr..18.1795L"><span id="translatedtitle">Ultrasonic Lamb wave <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Leonard, Kevin R.; Malyarenko, Eugene V.; Hinders, Mark K.</p> <p>2002-12-01</p> <p>Nondestructive evaluation (NDE) of aerospace structures using traditional methods is a complex, time-consuming process critical to maintaining mission readiness and flight safety. Limited access to corrosion-prone structure and the restricted applicability of available NDE techniques for the detection of hidden corrosion or other damage often compound the challenge. In this paper we discuss our recent work using ultrasonic Lamb wave <span class="hlt">tomography</span> to address this pressing NDE technology need. Lamb waves are ultrasonic guided waves, which allow large sections of aircraft structures to be rapidly inspected for structural flaws such as disbonds, corrosion and delaminations. Because the <span class="hlt">velocity</span> of Lamb waves depends on thickness, for example, the travel times of the fundamental Lamb modes can be converted into a thickness map of the inspection region. However, extracting quantitative information from Lamb wave data has always involved highly trained personnel with a detailed knowledge of mechanical waveguide physics. Our work focuses on tomographic reconstruction to produce quantitative maps that can be easily interpreted by technicians or fed directly into structural integrity and lifetime prediction codes. Laboratory measurements discussed here demonstrate that Lamb wave <span class="hlt">tomography</span> using a square perimeter array of transducers with algebraic reconstruction <span class="hlt">tomography</span> is appropriate for detecting flaws in aircraft materials. The speed and fidelity of the reconstruction algorithms as well as practical considerations for person-portable array-based systems are discussed in this paper.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PApGe.tmp...88B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PApGe.tmp...88B"><span id="translatedtitle">Regional Ambient Noise <span class="hlt">Tomography</span> in the Eastern Alps of Europe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Behm, Michael; Nakata, Nori; Bokelmann, Götz</p> <p>2016-05-01</p> <p>We present results from ambient noise <span class="hlt">tomography</span> applied to temporary seismological stations in the easternmost part of the Alps and their transition to the adjacent tectonic provinces (Vienna Basin, Bohemian Massif, Southern Alps, Dinarides). By turning each station into a virtual source, we recover surface waves in the frequency range between 0.1 and 0.6 Hz, which are sensitive to depths of approximately 2-15 km. The utilization of horizontal components allows for the analysis of both Rayleigh and Love waves with comparable signal-to-noise ratio. Measured <span class="hlt">group</span> wave dispersion curves between stations are mapped to local cells by means of a simultaneous inverse reconstruction technique. The spatial reconstruction for Love-wave <span class="hlt">velocities</span> fails in the central part of the investigated area, and we speculate that a heterogeneous noise source distribution is the cause for the failure. Otherwise, the obtained <span class="hlt">group</span> <span class="hlt">velocity</span> maps correlate well with surface geology. Inversion of Rayleigh-wave <span class="hlt">velocities</span> for shear-wave <span class="hlt">velocities</span> along a vertical N-S section stretching from the Bohemian Massif through the Central Alps to the Southern Alps and Dinarides reveals a mid-crustal low-<span class="hlt">velocity</span> anomaly at the contact between the Bohemian Massif and the Alps, which shows a spatial correlation with the P-wave <span class="hlt">velocity</span> structure and the low-frequency component of the magnetic anomaly map. Our study is validated by the analysis of resolution and accuracy, and we further compare the result to shear-wave <span class="hlt">velocity</span> models estimated from other active and passive experiments in the area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PApGe.173.2813B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PApGe.173.2813B&link_type=ABSTRACT"><span id="translatedtitle">Regional Ambient Noise <span class="hlt">Tomography</span> in the Eastern Alps of Europe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Behm, Michael; Nakata, Nori; Bokelmann, Götz</p> <p>2016-08-01</p> <p>We present results from ambient noise <span class="hlt">tomography</span> applied to temporary seismological stations in the easternmost part of the Alps and their transition to the adjacent tectonic provinces (Vienna Basin, Bohemian Massif, Southern Alps, Dinarides). By turning each station into a virtual source, we recover surface waves in the frequency range between 0.1 and 0.6 Hz, which are sensitive to depths of approximately 2-15 km. The utilization of horizontal components allows for the analysis of both Rayleigh and Love waves with comparable signal-to-noise ratio. Measured <span class="hlt">group</span> wave dispersion curves between stations are mapped to local cells by means of a simultaneous inverse reconstruction technique. The spatial reconstruction for Love-wave <span class="hlt">velocities</span> fails in the central part of the investigated area, and we speculate that a heterogeneous noise source distribution is the cause for the failure. Otherwise, the obtained <span class="hlt">group</span> <span class="hlt">velocity</span> maps correlate well with surface geology. Inversion of Rayleigh-wave <span class="hlt">velocities</span> for shear-wave <span class="hlt">velocities</span> along a vertical N-S section stretching from the Bohemian Massif through the Central Alps to the Southern Alps and Dinarides reveals a mid-crustal low-<span class="hlt">velocity</span> anomaly at the contact between the Bohemian Massif and the Alps, which shows a spatial correlation with the P-wave <span class="hlt">velocity</span> structure and the low-frequency component of the magnetic anomaly map. Our study is validated by the analysis of resolution and accuracy, and we further compare the result to shear-wave <span class="hlt">velocity</span> models estimated from other active and passive experiments in the area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Seismic+AND+waves&id=EJ307310','ERIC'); return false;" href="http://eric.ed.gov/?q=Seismic+AND+waves&id=EJ307310"><span id="translatedtitle">Seismic <span class="hlt">Tomography</span>.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Anderson, Don L.; Dziewonski, Adam M.</p> <p>1984-01-01</p> <p>Describes how seismic <span class="hlt">tomography</span> is used to analyze the waves produced by earthquakes. The information obtained from the procedure can then be used to map the earth's mantle in three dimensions. The resulting maps are then studied to determine such information as the convective flow that propels the crustal plates. (JN)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JSeis..17..385P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JSeis..17..385P"><span id="translatedtitle">Imaging heterogeneity of the crust adjacent to the Dead Sea fault using ambient seismic noise <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pinsky, Vladimir; Meirova, Tatiana; Levshin, Anatoli; Hofstetter, Abraham; Kraeva, Nadezda; Barmin, Mikhail</p> <p>2013-04-01</p> <p>For the purpose of studying the Earth's crust by means of <span class="hlt">tomography</span>, we investigated cross-correlation functions emerging from long-term observations of propagating ambient seismic noise at pairs of broadband stations in Israel and Jordan. The data was provided by the eight permanent broadband stations of the Israel Seismic Network evenly distributed over Israel and the 30 stations of the DESERT2000 experiment distributed across the Arava Fault (South of the Dead Sea basin). To eliminate the influence of earthquakes and explosions, we have applied the methodology of Bensen et al. (Geophys J Int 169:1239-1260, 2007), including bandpass filtering and amplitude normalization in time and frequency domain. The cross-correlation functions estimated from continuous recordings of a few months were used to extract Rayleigh waves <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion curves using automatic version of the frequency-time analysis procedure. Subsequently, these curves have been converted into the Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> maps in the period range 5-20 s and S waves <span class="hlt">velocity</span> maps in the depth range 5-15 km. In these maps, four <span class="hlt">velocity</span> anomalies are prominent. Two of them are outlined by the previous reflection-refraction profiles and body wave <span class="hlt">tomography</span> studies, i.e. a low <span class="hlt">velocity</span> anomaly corresponds to the area of the extremely deep (down to 14 km) sedimentary infill in the Southern Dead Sea Basin and a high <span class="hlt">velocity</span> anomaly in the Southern Jordan corresponds to the area of the Precambrian crystalline rocks of the Nubian Shield on the flanks of the Red Sea. The two other anomalies have not been reported before - the high <span class="hlt">velocity</span> zone close to the Beersheba city and the low <span class="hlt">velocity</span> anomaly in the region of Samaria-Carmel mountains - Southern Galilee. They have relatively low resolution and hence need further investigations for approving and contouring. The highest contrast between the average Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> (2.7 km/s) and the anomalies is 10-13 %, comparable, however</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014NatSR...4E4711B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014NatSR...4E4711B"><span id="translatedtitle">Correlative <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Burnett, T. L.; McDonald, S. A.; Gholinia, A.; Geurts, R.; Janus, M.; Slater, T.; Haigh, S. J.; Ornek, C.; Almuaili, F.; Engelberg, D. L.; Thompson, G. E.; Withers, P. J.</p> <p>2014-04-01</p> <p>Increasingly researchers are looking to bring together perspectives across multiple scales, or to combine insights from different techniques, for the same region of interest. To this end, correlative microscopy has already yielded substantial new insights in two dimensions (2D). Here we develop correlative <span class="hlt">tomography</span> where the correlative task is somewhat more challenging because the volume of interest is typically hidden beneath the sample surface. We have threaded together x-ray computed <span class="hlt">tomography</span>, serial section FIB-SEM <span class="hlt">tomography</span>, electron backscatter diffraction and finally TEM elemental analysis all for the same 3D region. This has allowed observation of the competition between pitting corrosion and intergranular corrosion at multiple scales revealing the structural hierarchy, crystallography and chemistry of veiled corrosion pits in stainless steel. With automated correlative workflows and co-visualization of the multi-scale or multi-modal datasets the technique promises to provide insights across biological, geological and materials science that are impossible using either individual or multiple uncorrelated techniques.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24736640','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24736640"><span id="translatedtitle">Correlative <span class="hlt">tomography</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Burnett, T L; McDonald, S A; Gholinia, A; Geurts, R; Janus, M; Slater, T; Haigh, S J; Ornek, C; Almuaili, F; Engelberg, D L; Thompson, G E; Withers, P J</p> <p>2014-01-01</p> <p>Increasingly researchers are looking to bring together perspectives across multiple scales, or to combine insights from different techniques, for the same region of interest. To this end, correlative microscopy has already yielded substantial new insights in two dimensions (2D). Here we develop correlative <span class="hlt">tomography</span> where the correlative task is somewhat more challenging because the volume of interest is typically hidden beneath the sample surface. We have threaded together x-ray computed <span class="hlt">tomography</span>, serial section FIB-SEM <span class="hlt">tomography</span>, electron backscatter diffraction and finally TEM elemental analysis all for the same 3D region. This has allowed observation of the competition between pitting corrosion and intergranular corrosion at multiple scales revealing the structural hierarchy, crystallography and chemistry of veiled corrosion pits in stainless steel. With automated correlative workflows and co-visualization of the multi-scale or multi-modal datasets the technique promises to provide insights across biological, geological and materials science that are impossible using either individual or multiple uncorrelated techniques. PMID:24736640</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3988479','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3988479"><span id="translatedtitle">Correlative <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Burnett, T. L.; McDonald, S. A.; Gholinia, A.; Geurts, R.; Janus, M.; Slater, T.; Haigh, S. J.; Ornek, C.; Almuaili, F.; Engelberg, D. L.; Thompson, G. E.; Withers, P. J.</p> <p>2014-01-01</p> <p>Increasingly researchers are looking to bring together perspectives across multiple scales, or to combine insights from different techniques, for the same region of interest. To this end, correlative microscopy has already yielded substantial new insights in two dimensions (2D). Here we develop correlative <span class="hlt">tomography</span> where the correlative task is somewhat more challenging because the volume of interest is typically hidden beneath the sample surface. We have threaded together x-ray computed <span class="hlt">tomography</span>, serial section FIB-SEM <span class="hlt">tomography</span>, electron backscatter diffraction and finally TEM elemental analysis all for the same 3D region. This has allowed observation of the competition between pitting corrosion and intergranular corrosion at multiple scales revealing the structural hierarchy, crystallography and chemistry of veiled corrosion pits in stainless steel. With automated correlative workflows and co-visualization of the multi-scale or multi-modal datasets the technique promises to provide insights across biological, geological and materials science that are impossible using either individual or multiple uncorrelated techniques. PMID:24736640</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010JPhCS.224a2030B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010JPhCS.224a2030B&link_type=ABSTRACT"><span id="translatedtitle">Tidal volume (TV) post-process obtained with electrical impedance <span class="hlt">tomography</span> on a <span class="hlt">group</span> of chronic obstructive pulmonary disease (COPD) patients. Use of adjust equations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Balleza, Marco; Anton, Daniel; Casan, Pere; Riu, Pere</p> <p>2010-04-01</p> <p>Equations used to estimate ventilation out of EIT images, validated on healthy volunteers show a significant bias and a larger variance when were applied on a COPD patients <span class="hlt">group</span>. The differences in estimation values were found to be highly correlated with anthropometric parameters. Two <span class="hlt">groups</span> of 13 and 4 COPD male patients (FEV1/FVC<70% and FVC >= 80%) were used in this study. We have measured different anthropometric parameters like age, weight, height and skinfolds. The EIT system (TIE4sys) and a pneumotach were simultaneously connected to monitor tidal volume. The main anthropometric parameters values of 13 COPD patients were: age: 67±9 years, height: 1.65±0.05 m, weight: 72±11 kg, BMI: 26.4±3.3 and the subscapular skinfold thickness was 23±9mm. The mean tidal volume estimated with TIE4sys and the pneumotach were: 0.580±0.212 L and 0.774±0.173 L r = 0.861 (p<0.01). The mean difference was 0.196±0.096 L (p0.01). On this <span class="hlt">group</span> we have found out an adjust equation and we have validated it on an independent <span class="hlt">group</span> of 4 COPD patients. The equation was Diff=-1478+15.6(weight). The mean tidal volume values obtained with pneumotach and TIE4sys on the second <span class="hlt">group</span> of COPD patients (M:4) were: 0.798±0.395 L and 0.732±0.327 L. The mean of the differences was 0.066±0.114L. The differences of determinations estimated with pneumotach and TIE4sys can be attributed to changes of anthropometric characteristics like subscapular skinfold.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ExG....45...86C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ExG....45...86C"><span id="translatedtitle">Discovery of a surface wave <span class="hlt">velocity</span> anomaly in the West Sea of South Korea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cho, Kwang Hyun</p> <p>2014-01-01</p> <p>Imaging of Rayleigh- and Love-wave <span class="hlt">velocities</span> is very important in detecting geophysical anomalies within the earth. Surface wave <span class="hlt">velocity</span> imaging studies using ambient noise have provided enhanced and detailed images of <span class="hlt">velocity</span> anomalies for sedimentary basins, hotspots, and volcanoes in various regions of the Earth (Yang et al., 2008). Cross-correlations of ambient noises observed from the Korea Meteorological Administration (KMA) seismic network provide the short-period Rayleigh-and Love-wave dispersion characteristics of the Korean Peninsula (Cho et al., 2007). Signal whitening and multiple-filter analysis are used to equalise power in signals from different times before noise processing, such as cross-correlation and stacking to extract <span class="hlt">group</span> <span class="hlt">velocities</span> from the estimated Green's functions, which are then used to image the spatially varying dispersion at periods between 1 and 5 s. The analysis method and data used in this paper are the same as those of Cho et al. (2007) except for the addition of the dataset of a new station, HUK. However, this paper notes that Rayleigh- and Love-wave <span class="hlt">velocity</span> images in short periods show a very different <span class="hlt">group</span> <span class="hlt">velocity</span> image for the north-eastern area of the HUK station because additional data was analysed. This <span class="hlt">velocity</span> anomaly corresponds with the residual anomaly of gravity <span class="hlt">tomography</span> obtained in prior studies (Yu and Min, 2005; Kim and Oh, 2007). Our results show that a fracture zone concerning the Permo-Triassic collision (Choi et al., 2006; Kwon et al., 2009) exists below the north-eastern sea of the HUK station. In addition, recent studies (de Ridder and Dellinger, 2011; de Ridder and Biondi, 2013; Mordret et al., 2011, 2013a, 2013b, 2013c; Bussat and Kugler, 2011) regarding ambient noise <span class="hlt">tomography</span> in hydro-carbon fields show that the anomaly might have resulted from the hydro-carbon reservoir. In the near future, the ambient noise <span class="hlt">tomography</span> (ANT) method can replace seismic survey dominantly using body waves to find</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27.3798S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27.3798S"><span id="translatedtitle"><span class="hlt">Velocity</span> Inhomogeneity of The Seismic Focal Zone In Kamchatka</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sanina, I.; Gontovaya, L.; Levina, V.; Stepanova, M.</p> <p></p> <p>Kamchatka is situated in the junction zone of Kuril-Kamchatka and Aleutian island arcs. According to P.R.Vogt et.al the geometry of this conjunction is determined by the Hawaiian-Emperor Volcanic Seamount Chain. The Kluchevsky volcanic <span class="hlt">group</span> be- longs to intersection of these structures on the Kamchatka Peninsula. Due to high yield of magmatic material this <span class="hlt">group</span> can be considered as one of the so-called hot spots on Earth. We studied the <span class="hlt">velocity</span> structure of the Earth's crust and upper mantle in the transition zone continent-Pacific Ocean up to the depth about 120 km. 3-D <span class="hlt">veloc</span>- ity structure is reconstructed by seismic <span class="hlt">tomography</span> method (SSA modification). We used regional catalogue of Kamchatka earthquakes for the period 1975-1999 recorded by 35 seismological stations within the territory of Kamchatka (Kuril-Kamchatka is- land arc) and the Bering Island. Data are carefully selected according to special re- quirements on depth, magnitude, accuracy in coordinates and origin time. The amount of data provides high resolution of observation pattern and accuracy of obtained <span class="hlt">veloc</span>- ity residuals. Distributions of Vp and Vs <span class="hlt">velocities</span> are presented for the depth ranges 0-20, 20-35, 35-60, 60-90 and 90-120 km, and for vertical crossections along and across the Kuril-Kamchatka island arc. Significant lateral and vertical inhomogeneity of the seismic focal zone is revealed. We identify narrow steep dipping low <span class="hlt">velocity</span> zones, related to deep faults with continuation on the Peninsula. These zones sepa- rate crust and mantle blocks with high contrast within the focal layer. Usually strong earthquakes are related to these boundaries. The conjunction zone of the island arc and the Emperor fault (its continuation under Kamchatka) coincides with the low <span class="hlt">velocity</span> zone in the mantle at depth 60-90 km, continued in the continental block. A chain of volcanoes oriented across Eastern-Kamchatka volcanic belt is related to this zone. Volcanic belt on the whole is shifted westwards in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.8259G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.8259G"><span id="translatedtitle">Ambient noise <span class="hlt">tomography</span> of the western Corinth Rift, Greece</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Giannopoulos, Dimitrios; Rivet, Diane; Sokos, Efthimios; Deschamps, Anne; Paraskevopoulos, Paraskevas; Lyon-Caen, Hélène; Pascal, Bernard; Tselentis, G.-Akis</p> <p>2016-04-01</p> <p>The Corinth Rift separates Peloponnesus to the south from main-land Greece to the north. It is one of the most active extensional intra-continental rifts in the world, with geodetically measured rates of extension varying from ~5 mm/yr at the eastern part to ~15 mm/yr at the western part. This work presents a first attempt to study the crustal <span class="hlt">velocity</span> structure of the western Corinth Rift using ambient noise recordings. We used 3 yrs (01/2012-12/2014) of continuous waveform data recorded at 24 stations from the Corinth Rift Laboratory (CRL) and the Hellenic Unified Seismological Network (HUSN). All available vertical component time-series were cross-correlated to extract Rayleigh wave Green's functions. <span class="hlt">Group</span> <span class="hlt">velocity</span> dispersion curves between 0.5 and 7 s period were measured for each station pair by applying frequency-time analysis and then inverted to build <span class="hlt">group</span> <span class="hlt">velocity</span> maps of the study area. At the studied periods, the northern coast of the Corinth Rift is generally imaged as a region of elevated seismic <span class="hlt">velocities</span> compared to the southern coast. More specifically, low <span class="hlt">velocities</span> are observed in areas of Plio-Quaternary syn-rift sediments such as off-shore regions of the rift, the Mornos delta and a large part of the southern coast. Higher <span class="hlt">velocities</span> are observed in pre-rift basement structures which are dominated mostly by carbonates. The preliminary results demonstrate good agreement with the major geological features of the area and agree relatively well with previous local earthquake <span class="hlt">tomography</span> studies. This work will be the base for further investigations towards the study of the Corinth Rift structure using long time-series of ambient noise data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3348750','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3348750"><span id="translatedtitle">Treatment Protocol for High <span class="hlt">Velocity</span>/High Energy Gunshot Injuries to the Face</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Peled, Micha; Leiser, Yoav; Emodi, Omri; Krausz, Amir</p> <p>2011-01-01</p> <p>Major causes of facial combat injuries include blasts, high-<span class="hlt">velocity</span>/high-energy missiles, and low-<span class="hlt">velocity</span> missiles. High-<span class="hlt">velocity</span> bullets fired from assault rifles encompass special ballistic properties, creating a transient cavitation space with a small entrance wound and a much larger exit wound. There is no dispute regarding the fact that primary emergency treatment of ballistic injuries to the face commences in accordance with the current advanced trauma life support (ATLS) recommendations; the main areas in which disputes do exist concern the question of the timing, sequence, and modes of surgical treatment. The aim of the present study is to present the treatment outcome of high-<span class="hlt">velocity</span>/high-energy gunshot injuries to the face, using a protocol based on the experience of a single level I trauma center. A <span class="hlt">group</span> of 23 injured combat soldiers who sustained bullet and shrapnel injuries to the maxillofacial region during a 3-week regional military conflict were evaluated in this study. Nine patients met the inclusion criteria (high-<span class="hlt">velocity</span>/high-energy injuries) and were included in the study. According to our protocol, upon arrival patients underwent endotracheal intubation and were hemodynamically stabilized in the shock-trauma unit and underwent total-body computed <span class="hlt">tomography</span> with 3-D reconstruction of the head and neck and computed <span class="hlt">tomography</span> angiography. All patients underwent maxillofacial surgery upon the day of arrival according to the protocol we present. In view of our treatment outcomes, results, and low complication rates, we conclude that strict adherence to a well-founded and structured treatment protocol based on clinical experience is mandatory in providing efficient, appropriate, and successful treatment to a relatively large <span class="hlt">group</span> of patients who sustain various degrees of maxillofacial injuries during a short period of time. PMID:23449809</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23449809','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23449809"><span id="translatedtitle">Treatment protocol for high <span class="hlt">velocity</span>/high energy gunshot injuries to the face.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Peled, Micha; Leiser, Yoav; Emodi, Omri; Krausz, Amir</p> <p>2012-03-01</p> <p>Major causes of facial combat injuries include blasts, high-<span class="hlt">velocity</span>/high-energy missiles, and low-<span class="hlt">velocity</span> missiles. High-<span class="hlt">velocity</span> bullets fired from assault rifles encompass special ballistic properties, creating a transient cavitation space with a small entrance wound and a much larger exit wound. There is no dispute regarding the fact that primary emergency treatment of ballistic injuries to the face commences in accordance with the current advanced trauma life support (ATLS) recommendations; the main areas in which disputes do exist concern the question of the timing, sequence, and modes of surgical treatment. The aim of the present study is to present the treatment outcome of high-<span class="hlt">velocity</span>/high-energy gunshot injuries to the face, using a protocol based on the experience of a single level I trauma center. A <span class="hlt">group</span> of 23 injured combat soldiers who sustained bullet and shrapnel injuries to the maxillofacial region during a 3-week regional military conflict were evaluated in this study. Nine patients met the inclusion criteria (high-<span class="hlt">velocity</span>/high-energy injuries) and were included in the study. According to our protocol, upon arrival patients underwent endotracheal intubation and were hemodynamically stabilized in the shock-trauma unit and underwent total-body computed <span class="hlt">tomography</span> with 3-D reconstruction of the head and neck and computed <span class="hlt">tomography</span> angiography. All patients underwent maxillofacial surgery upon the day of arrival according to the protocol we present. In view of our treatment outcomes, results, and low complication rates, we conclude that strict adherence to a well-founded and structured treatment protocol based on clinical experience is mandatory in providing efficient, appropriate, and successful treatment to a relatively large <span class="hlt">group</span> of patients who sustain various degrees of maxillofacial injuries during a short period of time. PMID:23449809</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1982WRR....18.1157D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1982WRR....18.1157D"><span id="translatedtitle">Pore <span class="hlt">Velocity</span> Estimation Uncertainties</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Devary, J. L.; Doctor, P. G.</p> <p>1982-08-01</p> <p>Geostatistical data analysis techniques were used to stochastically model the spatial variability of groundwater pore <span class="hlt">velocity</span> in a potential waste repository site. Kriging algorithms were applied to Hanford Reservation data to estimate hydraulic conductivities, hydraulic head gradients, and pore <span class="hlt">velocities</span>. A first-order Taylor series expansion for pore <span class="hlt">velocity</span> was used to statistically combine hydraulic conductivity, hydraulic head gradient, and effective porosity surfaces and uncertainties to characterize the pore <span class="hlt">velocity</span> uncertainty. Use of these techniques permits the estimation of pore <span class="hlt">velocity</span> uncertainties when pore <span class="hlt">velocity</span> measurements do not exist. Large pore <span class="hlt">velocity</span> estimation uncertainties were found to be located in the region where the hydraulic head gradient relative uncertainty was maximal.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/80209','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/80209"><span id="translatedtitle">Reservoir characterization with sequential Gaussian simulation constrained by diffraction <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lo, T.W.; Bermawi, A.</p> <p>1994-12-31</p> <p>A geostatistical approach for reservoir characterization that honors both surface seismic data and wireline data is described. It first computes a <span class="hlt">velocity</span> profiles with seismic diffraction <span class="hlt">tomography</span>, then, performs kriging with an external drift and sequential Gaussian simulation using the <span class="hlt">velocity</span> profiles as soft data and the sonic logs as hard data. The product is a <span class="hlt">velocity</span> profile with a resolution as high as that of the smoothed sonic logs, showing lateral <span class="hlt">velocity</span> variations constrained by surface seismic data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.T33D2444G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.T33D2444G"><span id="translatedtitle">Structure of the crust beneath Cameroon (West Africa) revealed by ambient noise <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guidarelli, M.; Zandomeneghi, D.; Aoudia, A.</p> <p>2011-12-01</p> <p>As Cameroon is characterized by moderate seismicity, mainly restricted to Mt. Cameroon, the study of crust and uppermost mantle with traditional seismic <span class="hlt">tomography</span> methods can be very limited. We use the ambient noise surface wave <span class="hlt">tomography</span> to overcome the limitations of traditional methods and fully exploit the Cameroon network data. By cross-correlating six months of continuous seismic noise records from 32 broadband stations distributed across Cameroon, we have been able to measure Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> in the period range 5-35 s, sensitive to approximately the upper 40 km of the crust, for about 300 station-to-station paths. We first apply a dispersion analysis using the frequency-time analysis to obtain the <span class="hlt">group</span> <span class="hlt">velocity</span> of the fundamental mode of Rayleigh waves for periods ranging from 5 to 35 sec. We then invert path-averaged dispersion curves to obtain 2D maps, on a 0.5 ° x0.5 ° nodal grid, of <span class="hlt">group</span> <span class="hlt">velocity</span> for discrete periods using a method that is the generalization to two dimensions of the Backus and Gilbert method. We obtain tomographic <span class="hlt">group</span> <span class="hlt">velocity</span> maps of the Cameroon crust that image the main tectonic features of the Cameroon crust, with an unprecedented detail on the major West Africa tectonic feature, known as Cameroon Volcanic Line. Through Cameroon, the anomaly maps clearly show both higher- and slower-than-average <span class="hlt">velocities</span>, marking a variety of geological/tectonic features. In the period range 10-20 s, which corresponds to crustal depths, the most evident features are: the high <span class="hlt">velocity</span> region, wide and composite, in southern Cameroon in clear spatial correspondence with the Congo Craton; the low <span class="hlt">velocity</span> in the central-eastern part of the country corresponding to the Adamawa Plateau; a strong low <span class="hlt">velocity</span> anomaly beneath Mt. Cameroon that persists up to 25 s period; and low <span class="hlt">group</span> <span class="hlt">velocities</span> along the border with Nigeria. Based on our new results and integrated with precedent studies we discuss the origin of the Cameroon</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.texasheart.org/HIC/Topics/Diag/diag_oct.cfm','NIH-MEDLINEPLUS'); return false;" href="http://www.texasheart.org/HIC/Topics/Diag/diag_oct.cfm"><span id="translatedtitle">Optical Coherence <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>... Cardiac Magnetic Resonance Imaging (MRI and MRA) Computed <span class="hlt">Tomography</span> (CT) Scan Diagnostic Tests and Procedures Echocardiography Electrocardiogram ... Ultrasound Nuclear Stress Test Nuclear Ventriculography Positron Emission <span class="hlt">Tomography</span> (PET) Stress ... Optical Coherence <span class="hlt">Tomography</span> | ...</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2996539','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2996539"><span id="translatedtitle">ASCI 2010 contrast media guideline for cardiac imaging: a report of the Asian Society of Cardiovascular Imaging cardiac computed <span class="hlt">tomography</span> and cardiac magnetic resonance imaging guideline working <span class="hlt">group</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kitagawa, Kakuya; Tsai, I-Chen; Chan, Carmen; Yu, Wei; Yong, Hwan Seok; Choi, Byoung Wook</p> <p>2010-01-01</p> <p>The use of contrast media for cardiac imaging becomes increasing as the widespread of cardiac CT and cardiac MR. A radiologist needs to carefully consider the indication and the injection protocol of contrast media to be used as well as the possibility of adverse effect. There are several guidelines for contrast media in western countries. However, these are focusing the adverse effect of contrast media. The Asian Society of Cardiovascular Imaging, the only society dedicated to cardiovascular imaging in Asia, formed a Working <span class="hlt">Group</span> and created a guideline, which summarizes the integrated knowledge of contrast media for cardiac imaging. In cardiac imaging, coronary artery evaluation is feasible by non-contrast MR angiography, which can be an alternative examination in high risk patients for the use of iodine contrast media. Furthermore, the body habitus of Asian patients is usually smaller than that of their western counterparts. This necessitates modifications in the injection protocol and in the formula for calculation of estimated glomerular filtration rate. This guideline provided fundamental information for the use of contrast media for Asian patients in cardiac imaging. PMID:20931289</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://medlineplus.gov/ency/article/003927.htm','NIH-MEDLINEPLUS'); return false;" href="https://medlineplus.gov/ency/article/003927.htm"><span id="translatedtitle">Nerve conduction <span class="hlt">velocity</span></span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>... page: //medlineplus.gov/ency/article/003927.htm Nerve conduction <span class="hlt">velocity</span> To use the sharing features on this page, please enable JavaScript. Nerve conduction <span class="hlt">velocity</span> (NCV) is a test to see how ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.S42B..01Y&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.S42B..01Y&link_type=ABSTRACT"><span id="translatedtitle">Unraveling overtone interferences in Love-wave phase <span class="hlt">velocity</span> measurements by array-based radon transform</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Y.; Luo, Y.</p> <p>2015-12-01</p> <p>Surface waves contain fundamental mode and higher modes, which could interfere with each other. Different modes of surface waves have completely different sensitivities to earth structures. If they are not properly separated, the inverted Earth structures using surface waves could be biased. Especially, for Love waves propagating over oceanic paths, the <span class="hlt">group</span> <span class="hlt">velocities</span> of fundamental mod and first/second overtoneS are overlapped with each at periods shorter than 100 sec, resulting in strong overtone interferences in seismograms. Most surface wave <span class="hlt">tomography</span> studies use dispersion curves of fundamental modes in imaging. One challenge in surface wave <span class="hlt">tomography</span> is to accurately measure the fundamental-mode phase <span class="hlt">velocities</span> and avoid the contamination by overtones. In this study, we develop an effective way by applying Linear Radon Transform (LRT) to a seismic array to separate fundamental-mode surface waves from higher modes. We apply this method to both synthetic data and real surface waves from USArray. Analysis on synthetic seismograms shows that two-station measurements on reconstructed data obtained after mode separation can completely retrieve the fundamental-mode Love-wave phase <span class="hlt">velocities</span>. Results on USArray data show that higher mode contamination effects reach up to ˜10-15 percent for two-station and array-based measurements of Love waves, while two-station measurements on mode-separated data obtained by LRT are very close to the predicted values from a global dispersion model of GDM52, demonstrating that the contamination of overtones on fundamental-mode Love wave phase <span class="hlt">velocity</span> measurements is effectively mitigated by the LRT method and accurate fundamental-mode Love-wave phase <span class="hlt">velocities</span> can be measured.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/14579','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/14579"><span id="translatedtitle">Two-station phase <span class="hlt">velocity</span> determination for structure in North Africa</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hazler, S; Pasyanos, M; Sheehan, A; Walter, W</p> <p>1999-07-28</p> <p>The seismic structure of North Africa is poorly understood due to the relative paucity of stations and seismicity when compared to other continental regions of the world. A better understanding of the <span class="hlt">velocity</span> structure in this area will allow improved models of travel times and regional phase amplitudes. Such models will improve location and identification capability in this region leading to more effective monitoring of the Comprehensive Nuclear-Test-Ban Treaty. Using regional-to-teleseismic Rayleigh and Love waves that traverse the area we can obtain information about the region's seismic structure by examining phase <span class="hlt">velocity</span> as a function of period. We utilize earthquakes from the tectonically active regions bounding North Africa (Mediterranean, Red Sea, East African Rift, and Mid-Atlantic Ridge) recorded at broadband seismic stations distributed throughout the region. A two-station method is utilized to determine phase <span class="hlt">velocity</span> information along the interstation segment of the ray path. The two-station method provides particular advantage in this region as it dramatically increases the number of events available to provide pure North African sampling. Bandpass filters are applied to the seismograms so that peaks and troughs may be correlated. The phase is unwrapped and a difference curve computed. The difference curve is then converted to a phase <span class="hlt">velocity</span> dispersion curve. Phase <span class="hlt">velocity</span> curves are constructed in the range of 10 to 120 seconds. Rayleigh and Love waves in this period range are most sensitive to the shear <span class="hlt">velocity</span> structure of the lithosphere and can be used in combination with additional independent seismic observations (e.g. Pn <span class="hlt">tomography</span>, surface wave <span class="hlt">group</span> <span class="hlt">velocity</span> <span class="hlt">tomography</span>, receiver functions, etc.) to construct reliable <span class="hlt">velocity</span> models. We compare <span class="hlt">velocities</span> computed in this study to those generated from well known models for similar tectonic regions throughout the world in order to better define the tectonic setting of North Africa</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.S43B2546C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.S43B2546C"><span id="translatedtitle">Crustal Structure of the PARANÁ Basin from Ambient Noise <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Collaço, B.; Assumpcao, M.; Rosa, M. L.; Sanchez, G.</p> <p>2013-12-01</p> <p>Previous surface-wave <span class="hlt">tomography</span> in South America (SA) (e.g., Feng et al., 2004; 2007) mapped the main large-scale features of the continent, such as the high lithospheric <span class="hlt">velocities</span> in cratonic areas and low <span class="hlt">velocities</span> in the Patagonian province. However, more detailed features such as the Paraná Basin, have not been mapped with good resolution because of poor path coverage, i.e. classic surface- wave <span class="hlt">tomography</span> has low resolution in low-seismicity areas, like Brazil and the Eastern Argentina. Crustal structure in Southern Brazil is poorly known. Most paths used by Feng et al. (2007) in this region are roughly parallel, which prevents good spatial resolution in tomographic inversions. This work is part of a major project that will increase knowledge of crustal structure in Southern Brazil and Eastern Argentina and is being carried out by IAG-USP (Brazil) in collaboration with UNLP and INPRES (Argentina). To improve resolution for the Paraná Basin we used inter-station dispersion curves derived from correlation of ambient noise for new stations deployed with the implementation of the Brazilian Seismic Network (Pirchiner et al. 2011). This technique, known as ambient noise <span class="hlt">tomography</span> (ANT), was first applied by Shapiro et al. (2005) and is now expanding rapidly, especially in areas with high density of seismic stations (e.g. Bensen et al. 2007, Lin et al. 2008, Moschetti et al. 2010). ANT is a well-established method to estimate short period (< 20s) and intermediate periods (20 - 50s) surface wave speeds both in regional or continental scales (Lin et al. 2008). ANT data processing in this work was similar to the one described by Bensen et al. 2007, in four major steps with addition of a data inversion step. <span class="hlt">Group</span> <span class="hlt">velocities</span> between pairs of stations were derived from correlation of two years of ambient noise in the period range 5 to 60 s. The dispersion curves measurements were made using a modified version of PGSWMFA (PGplot Surface Wave Multiple Filter Analysis</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003AGUFM.S32B0847M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003AGUFM.S32B0847M"><span id="translatedtitle">Bayesian Approach to Short Period Slowness <span class="hlt">Tomography</span> in Central Asia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maceira, M.; Taylor, S. R.; Ammon, C. J.</p> <p>2003-12-01</p> <p>We are investigating the utility of short-period, high-resolution surface-wave slowness maps for lowering detection thresholds and allowing for discrimination of explosions and earthquakes at lower magnitudes (3.0-4.8). We focus on the region of central Asia between 69 and 108 degrees east longitude and 29 and 54 degrees north latitude. We retrieved broadband waveform data from more than 1,100 events that occurred between January 1997 and May 2002. Waveforms were obtained from four different networks comprising 13 individual stations. Using multiple-filter and phase-matched filter techniques, we measured the dispersion characteristics of the signals between 6 and 30 seconds. These Rayleigh-wave <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion curves were used to compute high-resolution, half a degree cell size, slowness tomographic maps for each period. We adopted a Bayesian <span class="hlt">tomography</span> method to solve the equation that relates travel-time data with the slowness structure. We used a declustering technique to minimize the effect of event clusters on the results. Our model is similar, to some extent, to the a priori model, but contains more structure and the cell size is smaller (0.5 compared to 1 degree cell size for the a priori model). The tomographic patterns correlate well with known geologic and tectonic features in the area. Accumulations of relatively young sediments across Eurasia are greater than on any other continent due to the continuing rapid uplift across much of central Asia. The short periods are primarily sensitive to upper crustal structures. The tomographic images display low <span class="hlt">velocities</span> associated with the known sedimentary basins - Tarim, Junggar and Quaidam basins - in the area of central Asia under study. High <span class="hlt">velocities</span> are associated with mountainous tectonic features such as the Tien Shan. We validated our maps using Rayleigh <span class="hlt">group-velocity</span> dispersion curves for 640 events that occurred on the region of interest between January 1993 and December 1996. We analyzed</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19780002503','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19780002503"><span id="translatedtitle">Dust particle <span class="hlt">velocity</span> measurement</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Thielman, L. O.</p> <p>1976-01-01</p> <p>A laser Doppler velocimeter was used to measure the <span class="hlt">velocity</span> distributions for particles entering a vacuum chamber from the atmosphere through calibrated leaks. The relative number of particles per <span class="hlt">velocity</span> interval was obtained for particulates of three size distributions and two densities passing through six different leak geometries. The <span class="hlt">velocity</span> range 15 to 320 meters per second was investigated. Peak particle <span class="hlt">velocities</span> were found to occur in the 15 to 150 meters per second range depending upon type of particle and leak geometry. A small fraction of the particles were found to have <span class="hlt">velocities</span> in the 150 to 320 meters per second range.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5017736','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5017736"><span id="translatedtitle">Dry deposition <span class="hlt">velocities</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sehmel, G.A.</p> <p>1984-03-01</p> <p>Dry deposition <span class="hlt">velocities</span> are very difficult to predict accurately. In this article, reported values of dry deposition <span class="hlt">velocities</span> are summarized. This summary includes values from the literature on field measurements of gas and particle dry deposition <span class="hlt">velocities</span>, and the uncertainties inherent in extrapolating field results to predict dry deposition <span class="hlt">velocities</span> are discussed. A new method is described for predicting dry deposition <span class="hlt">velocity</span> using a least-squares correlation of surface mass transfer resistances evaluated in wind tunnel experiments. 14 references, 4 figures, 1 table.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21491616','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21491616"><span id="translatedtitle">Pelvic Lymph Node Status Assessed by 18F-Fluorodeoxyglucose Positron Emission <span class="hlt">Tomography</span> Predicts Low-Risk <span class="hlt">Group</span> for Distant Recurrence in Locally Advanced Cervical Cancer: A Prospective Study</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kang, Sokbom; Park, Jung-Yeol; Lim, Myung-Chul; Song, Yong-Joong; Park, Se-Hyun; Kim, Seok-Ki; Chung, Dae-Chul; Seo, Sang-Soo; Kim, Joo-Young; Park, Sang-Yoon</p> <p>2011-03-01</p> <p>Purpose: To develop a prediction model to identify a low-risk <span class="hlt">group</span> for distant recurrence in patients with locally advanced cervical cancer treated by concurrent chemoradiation. Methods and Materials: Prospectively, 62 patients with locally advanced cervical cancer were recruited as a training cohort. Clinical variables and parameters obtained from positron emission <span class="hlt">tomography</span> (PET) and magnetic resonance imaging were analyzed by logistic regression. For the test set, 54 patients were recruited independently. To identify the low-risk <span class="hlt">group</span>, negative likelihood ratio (LR) less than 0.2 was set to be a cutoff. Results: Among the training cohort, multivariate logistic analysis revealed that advanced International Federation of Gynecology and Obstetrics (FIGO) stage and a high serum squamous cancer cell (SCC) antigen level were significant risk factors (p = 0.015 and 0.025, respectively). Using the two parameters, criteria to determine a low-risk subset for distant recurrence were postulated: (1) FIGO Stage IIB or less and (2) pretreatment SCC < 2.4 (Model A). Positive pelvic node on PET completely predicted all cases with distant recurrence and thus was considered as another prediction model (Model B). In the test cohort, although Model A did not showed diagnostic performance, Model B completely predicted all cases with distant recurrence and showed a sensitivity of 100% with negative LR of 0. Across the training and test cohort (n = 116), the false negative rate was 0 (95% confidence interval 0%-7.6%). Conclusions: Positive pelvic node on PET is a useful marker in prediction of distant recurrence in patients with locally advanced cervical cancer who are treated with concurrent chemoradiation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoJI.200.1538L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoJI.200.1538L"><span id="translatedtitle">Local earthquake <span class="hlt">tomography</span> of Scotland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Luckett, Richard; Baptie, Brian</p> <p>2015-03-01</p> <p>Scotland is a relatively aseismic region for the use of local earthquake <span class="hlt">tomography</span>, but 40 yr of earthquakes recorded by a good and growing network make it possible. A careful selection is made from the earthquakes located by the British Geological Survey (BGS) over the last four decades to provide a data set maximising arrival time accuracy and ray path coverage of Scotland. A large number of 1-D <span class="hlt">velocity</span> models with different layer geometries are considered and differentiated by employing quarry blasts as ground-truth events. Then, SIMULPS14 is used to produce a robust 3-D tomographic P-wave <span class="hlt">velocity</span> model for Scotland. In areas of high resolution the model shows good agreement with previously published interpretations of seismic refraction and reflection experiments. However, the model shows relatively little lateral variation in seismic <span class="hlt">velocity</span> except at shallow depths, where sedimentary basins such as the Midland Valley are apparent. At greater depths, higher <span class="hlt">velocities</span> in the northwest parts of the model suggest that the thickness of crust increases towards the south and east. This observation is also in agreement with previous studies. Quarry blasts used as ground truth events and relocated with the preferred 3-D model are shown to be markedly more accurate than when located with the existing BGS 1-D <span class="hlt">velocity</span> model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.8678J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.8678J"><span id="translatedtitle">3D <span class="hlt">velocity</span> structure of upper crust beneath NW Bohemia/Vogtland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Javad Fallahi, Mohammad; Mousavi, Sima; Korn, Michael; Sens-Schönfelder, Christoph; Bauer, Klaus; Rößler, Dirk</p> <p>2013-04-01</p> <p> surrounding area. Surface wave <span class="hlt">tomography</span> using ambient noise provides additional constraints on shear <span class="hlt">velocities</span>. The detailed knowledge of the 3D structure is essential to select the optimal future borehole locations. we use the vertical and transverse component ambient noise data to estimate both Rayleigh and Love waves from ambient noise cross-correlation waveforms to investigate the crustal seismic structure of W-Bohemia/Vogtland. More than 2000 Rayleigh and Love <span class="hlt">group-velocity</span> dispersion curves are obtained by time-frequency analysis of stacked ambient noise cross-correlation functions between station pairs. We used the data between 2002 and 2004 recorded at 43 seismic stations from BOHEMA experiment and between 2006 and 2008 recorded at 79 seismic stations from permanent station networks of Germany, Czech Academy of Sciences (WEBNET) and PASSEQ experiments. At each period between 1 and 10 s, <span class="hlt">group</span> <span class="hlt">velocity</span> maps are constructed, all corresponding to different sampling depths, and thus together giving an indication of the 3D shear wave <span class="hlt">velocity</span> structure extending to a depth of about 15 km.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.S34B..02Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.S34B..02Z"><span id="translatedtitle">Broadband Finite Frequency Ambient Noise <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, K.; Yang, Y.; Luo, Y.; Xie, J.</p> <p>2015-12-01</p> <p>Ambient noise <span class="hlt">tomography</span> (ANT) has become a popular method to study the crustal and uppermost mantle structure of the earth in recent years due to its exclusive capability to extract short-period surface wave signals. Most of ANT are based on ray theory that assumes interstation surface waves from ambient noise are mainly sensitive to a narrow zone alone the ray path from one station to the other. Recently, many studies have demonstrated that long-period Rayleigh wave signal with high SNR can be obtained from cross-correlation of ambient noise data and could be used to do long period surface ware <span class="hlt">tomography</span>. In order to obtain accurate phase <span class="hlt">velocity</span> maps using long period surface waves from ambient noise, frequency effects must be considered in <span class="hlt">tomography</span>. In this study, we investigate the feasibility of finite frequency ANT by calculating 2-D phase sensitivity kernel based on Born approximation. In calculating 2D sensitivity kernels for empirical Green's functions extracted from cross-correlations between a pair of stations, one station is regarded as receiver and the other as virtual source. Based on the 2D finite frequency sensitivity kennels, we develop a finite frequency ambient noise <span class="hlt">tomography</span> method to construct Rayleigh wave phase <span class="hlt">velocity</span> maps. To demonstrate the feasibility of our developed method, we apply the method to empirical Green's functions extracted from cross-correlations of USArray noise data to construct phase <span class="hlt">velocity</span> maps at 20-150 sec periods. Our resulting phase <span class="hlt">velocity</span> maps are very similar to earthquake-based phase <span class="hlt">velocity</span> maps with almost zero means and 20-30 m/s stand deviations of differences. Major tectonic features in USA are well revealed in our phase <span class="hlt">velocity</span> maps.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011orol.book..743W&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011orol.book..743W&link_type=ABSTRACT"><span id="translatedtitle">Photoacoustic <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Lihong V.</p> <p></p> <p>Photoacoustic <span class="hlt">tomography</span> (PAT) refers to imaging that is based on the photoacoustic effect. Although the photoacoustic effect as a physical phenomenon was first reported on by Alexander Graham Bell in 1880 [1], PAT as an imaging technology was developed only after the advent of ultrasonic transducers, computers, and lasers [2-31]. A review on biomedical photoacoustics is available [32]. The motivation for PAT is to combine optical-absorption contrast with ultrasonic spatial resolution for deep imaging in the optical quasi-diffusive or diffusive regime. In PAT, the tissue is irradiated by usually a short-pulsed laser beam to achieve a thermal and acoustic impulse response (Fig. 19.1). Locally absorbed light is converted into heat, which is further converted to a pressure rise via thermo-elastic expansion. The initial pressure rise - determined by the local optical absorption coefficient (μ â ), fluence (ψ) and other thermal and mechanical properties - propagates as an ultrasonic wave, which is referred to as a photoacoustic wave.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.S33A2062R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.S33A2062R"><span id="translatedtitle">Crustal structure of the Pannonian-Carpathian region, Central Europe, from ambient noise <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ren, Y.; Stuart, G. W.; Houseman, G. A.; Carpathian Basins Project Working Group</p> <p>2010-12-01</p> <p>The Pannonian Basin of Central Europe is a major extensional basin surrounded by the Carpathian Mountains. During the evolution of the Carpathian-Pannonian region, extension of the crust and lithosphere created several inter-related basins of which the Pannonian basin is the largest. Imaging the seismic <span class="hlt">velocity</span> structure of the crust and the upper mantle may help us understand the structure and geodynamic evolution of this part of central Europe. Here, we use ambient noise <span class="hlt">tomography</span> to investigate the crust and uppermost mantle structure in the region. We have collected and processed continuous data from 56 temporary stations deployed in the Carpathian Basins Project (CBP) for 16 months (2005-2007) and 41 permanent broadband stations; this dataset enables the most well-resolved images of the S-wave structure of the region yet obtained. We computed the cross-correlation between vertical component seismograms from pairs of stations and stacked the correlated waveforms over 1-2 years to estimate the Rayleigh wave Green’s function. Frequency-time analysis is used to measure the <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion curves, which are then inverted for the <span class="hlt">group</span> <span class="hlt">velocity</span> maps. Our 4-10 s <span class="hlt">group</span> <span class="hlt">velocity</span> maps exhibit low <span class="hlt">velocity</span> anomalies which clearly defined the major sediment depo-centers in the Carpathian region. A broad low <span class="hlt">velocity</span> anomaly in the center of the 5 s <span class="hlt">group</span> <span class="hlt">velocity</span> map can be associated with the Pannonian Basin, whereas an anomaly in the southeastern region is related to the Moesian platform. Further east, the Vienna Basin can also be seen on our maps. A fast anomaly in the central region can be associated with the Mid-Hungarian line. At periods from 18 to 24 seconds, <span class="hlt">group</span> <span class="hlt">velocities</span> become increasingly sensitive to crustal thickness. The maps also reveal low-<span class="hlt">velocity</span> anomalies associated with the Carpathians. The low <span class="hlt">velocity</span> anomalies are probably caused by deeper crustal roots beneath the mountain ranges which occur due to isostatic compensation. CBP</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1811696F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1811696F"><span id="translatedtitle"><span class="hlt">Velocity</span> gradients in the Earth's upper mantle: insights from higher mode surface waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fishwick, Stewart; Maupin, Valerie; Afonso, Juan Carlos</p> <p>2016-04-01</p> <p>The majority of seismic tomographic models of the uppermost mantle beneath Precambrian regions show a positive <span class="hlt">velocity</span> gradient from the Moho to depths of around 100 km. It is becoming increasingly well recognised that this gradient is not readily compatible with simple models of a craton with constant composition and a steady-state geotherm and more complex compositional variations are invoked to explain this feature. At these depths most of the models are dominated by data from fundamental mode surface waves, and the combination of the sensitivity kernels alongside the choice of model parameterisation means that the <span class="hlt">velocity</span> gradient could be an artefact of the particular inversion. Indeed, recent work using thermodynamically consistent <span class="hlt">velocity</span> models suggests that in some cases there is not a requirement of this style of gradient. We investigate this aspect of the mantle structure further by returning to the Sa phase. This phase can be considered as the build up of a wave packet due to the overlapping <span class="hlt">group</span> <span class="hlt">velocities</span> of higher modes at periods of around 8 - 30 s. Using the Australian shield as a test-case we compare waveforms built from three different styles of <span class="hlt">velocity</span> model. Firstly, the 1D model AU3 (Gaherty & Jordan, 1995) which did incorporate the Sa phase as part of the waveform in their modelling. Secondly, recent tomographic models of the Australian continent are used, which include no a priori information from the phase. Thirdly, a thermodynamically consistent <span class="hlt">velocity</span> model that fits the broad dispersion characteristics of the <span class="hlt">tomography</span> is tested. Finally, these synthetic waveforms are compared to real data crossing the Australian shield. The results illustrate small, but clear, variations in waveform dependent on the <span class="hlt">velocity</span> structure. Complicating factors in any analysis involve the importance of having good knowledge of the crustal structure and a very accurate source depth (particularly if this is similar to the average crustal thickness).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JOpt...17d5605S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JOpt...17d5605S"><span id="translatedtitle">Modifications of intensity-interferometric spectral-domain optical coherence <span class="hlt">tomography</span> with dispersion cancellation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shirai, Tomohiro</p> <p>2015-04-01</p> <p>Intensity-interferometric spectral-domain (SD) optical coherence <span class="hlt">tomography</span> (OCT) developed recently enables axial-scan-free cross-sectional imaging with <span class="hlt">group-velocity</span> dispersion cancellation and a factor-of-\\sqrt{2} resolution improvement. This paper is concerned with a simple and practical method of realizing OCT of this kind. Specifically, we demonstrate theoretically and experimentally that intensity-interferometric SD-OCT can be realized in a simple way by means of a slightly modified conventional SD-OCT setup.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1510067R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1510067R"><span id="translatedtitle">Geodynamical Interpretation of Crustal and Mantle Shear-Wave <span class="hlt">Velocity</span> Structures Beneath the Carpathian-Pannonian Region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ren, Yong; Stuart, Graham; Houseman, Gregory; Grecu, Bogdan; Ionescu, Constantin; Hegedüs, Endre; Radovanović, Slavica; Shen, Yang; South Carpathian Project working Group</p> <p>2013-04-01</p> <p>The Carpathian-Pannonian system of Eastern and Central Europe represents a unique opportunity to study the interaction between surface tectonic processes involving convergence and extension, and convective processes in the upper mantle. The South Carpathian Project (SCP), a major temporary deployment (2009-2011) of seismic broadband systems extending across the eastern Pannonian Basin and the South Carpathian Mountains was set up with the purpose of bringing constraints on the geodynamical processes that have shaped the region. Imaging the seismic <span class="hlt">velocity</span> structure of the crust and the upper mantle helps us to understand the structure and geodynamical evolution of this part of central Europe. Here, we present high-resolution images of both crustal and upper mantle shear-wave <span class="hlt">velocity</span> structures beneath the Carpathian-Pannonian region using surface waves obtained from ambient noise <span class="hlt">tomography</span>, and finite-frequency teleseismic <span class="hlt">tomography</span> using S-wave arrivals, from 54 stations of the South Carpathian Project (SCP, 2009-2011), 56 stations of the Carpathian Basins Project (CBP, 2005-2007) and 131 national network broadband stations. For ambient noise <span class="hlt">tomography</span>, we computed cross-correlations of vertical component continuous ambient seismic noise recordings for all possible pairs of stations and stacked the correlated waveforms over 1-2 years for the temporary stations and up to 5 years for permanent stations to estimate Rayleigh wave empirical Green's functions. Over 5700 final Rayleigh wave Green's functions were selected for the measurement of <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion curves between 4s and 40s using the multiple-filter analysis technique. <span class="hlt">Group</span> <span class="hlt">velocity</span> maps are first computed on a grid discretized with 0.2°x0.2° steps from a non-linear 2-D tomographic inversion of measured <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion curves. We then inverted the Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> at each location to obtain the 3-D shear-wave <span class="hlt">velocity</span> structure of the crust and uppermost mantle beneath</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19900040580&hterms=Angular+velocity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DTitle%26N%3D0%26No%3D10%26Ntt%3DAngular%2Bvelocity','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19900040580&hterms=Angular+velocity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DTitle%26N%3D0%26No%3D10%26Ntt%3DAngular%2Bvelocity"><span id="translatedtitle">Angular <span class="hlt">velocity</span> discrimination</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kaiser, Mary K.</p> <p>1990-01-01</p> <p>Three experiments designed to investigate the ability of naive observers to discriminate rotational <span class="hlt">velocities</span> of two simultaneously viewed objects are described. Rotations are constrained to occur about the x and y axes, resulting in linear two-dimensional image trajectories. The results indicate that observers can discriminate angular <span class="hlt">velocities</span> with a competence near that for linear <span class="hlt">velocities</span>. However, perceived angular rate is influenced by structural aspects of the stimuli.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1813547Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1813547Z"><span id="translatedtitle">Seismic <span class="hlt">Tomography</span> Around the Eastern Edge of the Alps From Ambient-Noise-Based Rayleigh Waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zigone, Dimitri; Fuchs, Florian; Kolinsky, Petr; Gröschl, Gidera; Apoloner, Maria-Theresia; Qorbani, Ehsan; Schippkus, Sven; Löberich, Eric; Bokelmann, Götz; AlpArray Working Group</p> <p>2016-04-01</p> <p>Inspecting ambient noise Green's functions is an excellent tool for monitoring the quality of seismic data, and for swiftly detecting changes in the configuration of a seismological station. Those Green's functions readily provide stable information about structural variations near the Earth's surface. We apply the technique to a network consisting of about 40 broadband stations in the area of the Easternmost Alps, in particular those operated by the University of Vienna (AlpArrayAustria) and the Vienna University of Technology. Those data are used to estimate Green's functions between station pairs; the Green's function consist mainly of surface waves, and we use them to investigate crustal structure near the Eastern edge of the Alps. To obtain better signal-to-noise ratios in the noise correlation functions, we adopt a procedure using short time windows (2 hr). Energy tests are performed on the data to remove effects of transient sources and instrumental problems. The resulting 9-component correlation tensor is used to make travel time measurements on the vertical, radial and transverse components. Those measurements can be used to evaluate dispersion using frequency-time analysis for periods between 5-30 seconds. After rejecting paths without sufficient signal-to-noise ratio, we invert the <span class="hlt">velocity</span> measurements using the Barmin et al. (2001) approach on a 10 km grid size. The obtained <span class="hlt">group</span> <span class="hlt">velocity</span> maps reveal complex structures with clear <span class="hlt">velocity</span> contrasts between sedimentary basins and crystalline rocks. The Bohemian Massif and the Northern Calcareous Alps are associated with fast-<span class="hlt">velocity</span> bodies. By contrast, the Vienna Basin presents clear low-<span class="hlt">velocity</span> zones with <span class="hlt">group</span> <span class="hlt">velocities</span> down to 2 km/s at period of 7 s. The <span class="hlt">group</span> <span class="hlt">velocities</span> are then inverted to 3D images of shear wave speeds using the linear inversion method of Herrmann (2013). The results highlight the complex crustal structure and complement earthquake <span class="hlt">tomography</span> studies in the region. Updated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011BAAA...54..155F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011BAAA...54..155F"><span id="translatedtitle">About measuring <span class="hlt">velocity</span> dispersions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fellhauer, M.</p> <p></p> <p>A lot of our knowledge about the dynamics and total masses of pressure dominated stellar systems relies on measuring the internal <span class="hlt">velocity</span> disper- sion of the system. We assume virial equilibrium and that we are able to measure only the bound stars of the system without any contamination. This article shows how likely it is to measure the correct <span class="hlt">velocity</span> dispersion in reality. It will show that as long as we have small samples of <span class="hlt">velocity</span> mea- surements the distribution of possible outcomes can be very large and as soon as we have a source of error the <span class="hlt">velocity</span> dispersion can wrong by several standard deviations especially in large samples.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4478850','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4478850"><span id="translatedtitle">Effects of damping-off caused by Rhizoctonia solani anastomosis <span class="hlt">group</span> 2-1 on roots of wheat and oil seed rape quantified using X-ray Computed <span class="hlt">Tomography</span> and real-time PCR</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Sturrock, Craig J.; Woodhall, James; Brown, Matthew; Walker, Catherine; Mooney, Sacha J.; Ray, Rumiana V.</p> <p>2015-01-01</p> <p>Rhizoctonia solani is a plant pathogenic fungus that causes significant establishment and yield losses to several important food crops globally. This is the first application of high resolution X-ray micro Computed <span class="hlt">Tomography</span> (X-ray μCT) and real-time PCR to study host–pathogen interactions in situ and elucidate the mechanism of Rhizoctonia damping-off disease over a 6-day period caused by R. solani, anastomosis <span class="hlt">group</span> (AG) 2-1 in wheat (Triticum aestivum cv. Gallant) and oil seed rape (OSR, Brassica napus cv. Marinka). Temporal, non-destructive analysis of root system architectures was performed using RooTrak and validated by the destructive method of root washing. Disease was assessed visually and related to pathogen DNA quantification in soil using real-time PCR. R. solani AG2-1 at similar initial DNA concentrations in soil was capable of causing significant damage to the developing root systems of both wheat and OSR. Disease caused reductions in primary root number, root volume, root surface area, and convex hull which were affected less in the monocotyledonous host. Wheat was more tolerant to the pathogen, exhibited fewer symptoms and developed more complex root systems. In contrast, R. solani caused earlier damage and maceration of the taproot of the dicot, OSR. Disease severity was related to pathogen DNA accumulation in soil only for OSR, however, reductions in root traits were significantly associated with both disease and pathogen DNA. The method offers the first steps in advancing current understanding of soil-borne pathogen behavior in situ at the pore scale, which may lead to the development of mitigation measures to combat disease influence in the field. PMID:26157449</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26157449','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26157449"><span id="translatedtitle">Effects of damping-off caused by Rhizoctonia solani anastomosis <span class="hlt">group</span> 2-1 on roots of wheat and oil seed rape quantified using X-ray Computed <span class="hlt">Tomography</span> and real-time PCR.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sturrock, Craig J; Woodhall, James; Brown, Matthew; Walker, Catherine; Mooney, Sacha J; Ray, Rumiana V</p> <p>2015-01-01</p> <p>Rhizoctonia solani is a plant pathogenic fungus that causes significant establishment and yield losses to several important food crops globally. This is the first application of high resolution X-ray micro Computed <span class="hlt">Tomography</span> (X-ray μCT) and real-time PCR to study host-pathogen interactions in situ and elucidate the mechanism of Rhizoctonia damping-off disease over a 6-day period caused by R. solani, anastomosis <span class="hlt">group</span> (AG) 2-1 in wheat (Triticum aestivum cv. Gallant) and oil seed rape (OSR, Brassica napus cv. Marinka). Temporal, non-destructive analysis of root system architectures was performed using RooTrak and validated by the destructive method of root washing. Disease was assessed visually and related to pathogen DNA quantification in soil using real-time PCR. R. solani AG2-1 at similar initial DNA concentrations in soil was capable of causing significant damage to the developing root systems of both wheat and OSR. Disease caused reductions in primary root number, root volume, root surface area, and convex hull which were affected less in the monocotyledonous host. Wheat was more tolerant to the pathogen, exhibited fewer symptoms and developed more complex root systems. In contrast, R. solani caused earlier damage and maceration of the taproot of the dicot, OSR. Disease severity was related to pathogen DNA accumulation in soil only for OSR, however, reductions in root traits were significantly associated with both disease and pathogen DNA. The method offers the first steps in advancing current understanding of soil-borne pathogen behavior in situ at the pore scale, which may lead to the development of mitigation measures to combat disease influence in the field. PMID:26157449</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1992ppln.symp..181D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1992ppln.symp..181D"><span id="translatedtitle"><span class="hlt">VELOC</span> - A new kind of information system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dittloff, H. J.; Keuser, H.; Langer, H.</p> <p></p> <p>Based on the Global Positioning System (GPS), <span class="hlt">VELOC</span> (Vehicle Location) is designed to be a vehicle information system for fleet management adaptable to various user <span class="hlt">groups</span>, e.g., haulage and delivery companies, and service enterprises with vehicle fleets. The needs of these <span class="hlt">groups</span> vary with respect to position accuracy, position update rate, and type of communication. The authors describe the requirements, specifications, and performance of <span class="hlt">VELOC</span>. Special emphasis is placed on some substantial features of the <span class="hlt">VELOC</span> center, namely the integration of DGPS, a comfortable user interface, and handling of vehicle positions on digital maps.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoJI.204.1222H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoJI.204.1222H"><span id="translatedtitle">Global <span class="hlt">tomography</span> using seismic hum</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haned, A.; Stutzmann, E.; Schimmel, M.; Kiselev, S.; Davaille, A.; Yelles-Chaouche, A.</p> <p>2016-02-01</p> <p>We present a new upper-mantle tomographic model derived solely from hum seismic data. Phase correlograms between station pairs are computed to extract phase-coherent signals. Correlograms are then stacked using the time-frequency phase-weighted stack method to build-up empirical Green's functions. <span class="hlt">Group</span> <span class="hlt">velocities</span> and uncertainties are measured in the wide period band of 30-250 s, following a resampling approach. Less data are required to extract reliable <span class="hlt">group</span> <span class="hlt">velocities</span> at short periods than at long periods, and 2 yr of data are necessary to measure reliable <span class="hlt">group</span> <span class="hlt">velocities</span> for the entire period band. <span class="hlt">Group</span> <span class="hlt">velocities</span> are first regionalized and then inverted versus depth using a simulated annealing method in which the number and shape of splines that describes the S-wave <span class="hlt">velocity</span> model are variable. The new S-wave <span class="hlt">velocity</span> tomographic model is well correlated with models derived from earthquakes in most areas, although in India, the Dharwar craton is shallower than in other published models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22342134','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22342134"><span id="translatedtitle">Galaxy <span class="hlt">groups</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Brent Tully, R.</p> <p>2015-02-01</p> <p>Galaxy <span class="hlt">groups</span> can be characterized by the radius of decoupling from cosmic expansion, the radius of the caustic of second turnaround, and the <span class="hlt">velocity</span> dispersion of galaxies within this latter radius. These parameters can be a challenge to measure, especially for small <span class="hlt">groups</span> with few members. In this study, results are gathered pertaining to particularly well-studied <span class="hlt">groups</span> over four decades in <span class="hlt">group</span> mass. Scaling relations anticipated from theory are demonstrated and coefficients of the relationships are specified. There is an update of the relationship between light and mass for <span class="hlt">groups</span>, confirming that <span class="hlt">groups</span> with mass of a few times 10{sup 12}M{sub ⊙} are the most lit up while <span class="hlt">groups</span> with more and less mass are darker. It is demonstrated that there is an interesting one-to-one correlation between the number of dwarf satellites in a <span class="hlt">group</span> and the <span class="hlt">group</span> mass. There is the suggestion that small variations in the slope of the luminosity function in <span class="hlt">groups</span> are caused by the degree of depletion of intermediate luminosity systems rather than variations in the number per unit mass of dwarfs. Finally, returning to the characteristic radii of <span class="hlt">groups</span>, the ratio of first to second turnaround depends on the dark matter and dark energy content of the universe and a crude estimate can be made from the current observations of Ω{sub matter}∼0.15 in a flat topology, with a 68% probability of being less than 0.44.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AJ....149...54T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AJ....149...54T"><span id="translatedtitle">Galaxy <span class="hlt">Groups</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tully, R. Brent</p> <p>2015-02-01</p> <p>Galaxy <span class="hlt">groups</span> can be characterized by the radius of decoupling from cosmic expansion, the radius of the caustic of second turnaround, and the <span class="hlt">velocity</span> dispersion of galaxies within this latter radius. These parameters can be a challenge to measure, especially for small <span class="hlt">groups</span> with few members. In this study, results are gathered pertaining to particularly well-studied <span class="hlt">groups</span> over four decades in <span class="hlt">group</span> mass. Scaling relations anticipated from theory are demonstrated and coefficients of the relationships are specified. There is an update of the relationship between light and mass for <span class="hlt">groups</span>, confirming that <span class="hlt">groups</span> with mass of a few times {{10}12}{{M}⊙ } are the most lit up while <span class="hlt">groups</span> with more and less mass are darker. It is demonstrated that there is an interesting one-to-one correlation between the number of dwarf satellites in a <span class="hlt">group</span> and the <span class="hlt">group</span> mass. There is the suggestion that small variations in the slope of the luminosity function in <span class="hlt">groups</span> are caused by the degree of depletion of intermediate luminosity systems rather than variations in the number per unit mass of dwarfs. Finally, returning to the characteristic radii of <span class="hlt">groups</span>, the ratio of first to second turnaround depends on the dark matter and dark energy content of the universe and a crude estimate can be made from the current observations of {{Ω}matter}˜ 0.15 in a flat topology, with a 68% probability of being less than 0.44.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016GeoJI.204.1756G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016GeoJI.204.1756G&link_type=ABSTRACT"><span id="translatedtitle">Ambient noise <span class="hlt">tomography</span> of the Cameroon Volcanic Line and Northern Congo craton: new constraints on the structure of the lithosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guidarelli, M.; Aoudia, A.</p> <p>2016-03-01</p> <p>We investigate the lithospheric structure of Cameroon inverting Rayleigh waves obtained from the cross-correlation of ambient seismic noise. We correlate seismic records between 32 broad-band stations and we obtain good quality Rayleigh waves for 310 interstation paths. We measure <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion curves from the reconstructed Rayleigh waves in the period range 10-35 s and we invert the <span class="hlt">group</span> <span class="hlt">velocities</span> for tomographic images. After the <span class="hlt">tomography</span> the <span class="hlt">group</span> <span class="hlt">velocities</span> are then inverted, together with longer period <span class="hlt">group</span> <span class="hlt">velocity</span> measurements from existing literature, to compute a 3-D S-wave <span class="hlt">velocity</span> model of the Cameroon lithosphere down to 100 km depth. Our results provide an unprecedented mapping of the physical properties of the different crustal units and their correlations with surface geology, as well as with mantle lithospheric variations. The Cameroon Volcanic Line (CVL) appears as a segmented feature exhibiting different physical properties along strike. The active Mt Cameroon volcano is underlain by very low <span class="hlt">velocities</span>, unlike the other segments of the CVL. The along-strike variations in crustal structure suggest that lateral heterogeneities in lithospheric thickness and physical properties have influenced the location and distribution of magmatism. The crust beneath the Central African Shear Zone exhibits a sizeable low <span class="hlt">velocity</span> anomaly. The lithosphere beneath Cameroon is characterised by a heterogeneous crust with a relatively constant thickness and a low <span class="hlt">velocity</span> uppermost mantle at the edge of the Congo Craton. Our results favour processes combining small-scale upwelling at the edge of a thick lithosphere and reactivation of Precambrian basement structures to explain the distribution of Holocene-Recent magmatism and plateau uplift. Our results also indicate that Mt Cameroon and surroundings areas are the most at risk zones for magmatic activity during this stage of CVL development.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeoJI.198..637N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeoJI.198..637N"><span id="translatedtitle">Rayleigh wave <span class="hlt">tomography</span> of the British Isles from ambient seismic noise</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nicolson, Heather; Curtis, Andrew; Baptie, Brian</p> <p>2014-08-01</p> <p>We present the first Rayleigh wave <span class="hlt">group</span> speed maps of the British Isles constructed from ambient seismic noise. The maps also constitute the first surface wave <span class="hlt">tomography</span> study of the crust under the British Isles at a relatively high resolution. We computed interferometric, interstation Rayleigh waves from vertical component records of ambient seismic noise recorded on 63 broad-band and short-period stations across the UK and Ireland. <span class="hlt">Group</span> <span class="hlt">velocity</span> measurements were made from the resulting surface wave dispersion curves between 5 and 25 s using a multiple phase-matched filter method. Uncertainties in the <span class="hlt">group</span> <span class="hlt">velocities</span> were computed by calculating the standard deviation of four dispersion curves constructed by stacking a random selection of daily cross-correlations. Where an uncertainty could not be obtained for a ray path using this method, we estimated it as a function of the interreceiver distance. <span class="hlt">Group</span> <span class="hlt">velocity</span> maps were computed for 5-25-s period using the Fast Marching forward solution of the eikonal equation and iterative, linearized inversion. At short and intermediate periods, the maps show remarkable agreement with the major geological features of the British Isles including: terrane boundaries in Scotland; regions of late Palaeozoic basement uplift; areas of exposed late Proterozoic/early Palaeozoic rocks in southwest Scotland, northern England and northwest Wales and, sedimentary basins formed during the Mesozoic such as the Irish Sea Basin, the Chester Basin, the Worcester Graben and the Wessex Basin. The maps also show a consistent low-<span class="hlt">velocity</span> anomaly in the region of the Midlands Platform, a Proterozoic crustal block in the English Midlands. At longer periods, which are sensitive <span class="hlt">velocities</span> in the lower crustal/upper mantle, the maps suggest that the depth of Moho beneath the British Isles decreases towards the north and west. Areas of fast <span class="hlt">velocity</span> in the lower crust also coincide with areas thought to be associated with underplating of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19730027981&hterms=terminal+velocity&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dterminal%2Bvelocity','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19730027981&hterms=terminal+velocity&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dterminal%2Bvelocity"><span id="translatedtitle">Ice crystal terminal <span class="hlt">velocities</span>.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Heymsfield, A.</p> <p>1972-01-01</p> <p>Terminal <span class="hlt">velocities</span> of different ice crystal forms were calculated, using the most recent ice crystal drag coefficients, aspect ratios, and densities. The equations derived were primarily for use in calculating precipitation rates by sampling particles with an aircraft in cirrus clouds, and determining particle size in cirrus clouds by Doppler radar. However, the equations are sufficiently general for determining particle terminal <span class="hlt">velocity</span> at any altitude, and almost any crystal type. Two sets of equations were derived. The 'general' equations provide a good estimate of terminal <span class="hlt">velocities</span> at any altitude. The 'specific' equations are a set of equations for ice crystal terminal <span class="hlt">velocities</span> at 1000 mb. The calculations are in good agreement with terminal <span class="hlt">velocity</span> measurements. The results from the present study were also compared to prior calculations by others and seem to give more reasonable results, particularly at higher altitudes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930053862&hterms=rifle&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Drifle','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930053862&hterms=rifle&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Drifle"><span id="translatedtitle">Stepwise shockwave <span class="hlt">velocity</span> determinator</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Roth, Timothy E.; Beeson, Harold</p> <p>1992-01-01</p> <p>To provide an uncomplicated and inexpensive method for measuring the far-field <span class="hlt">velocity</span> of a surface shockwave produced by an explosion, a stepwise shockwave <span class="hlt">velocity</span> determinator (SSVD) was developed. The <span class="hlt">velocity</span> determinator is constructed of readily available materials and works on the principle of breaking discrete sensors composed of aluminum foil contacts. The discrete sensors have an average breaking threshold of approximately 7 kPa. An incremental output step of 250 mV is created with each foil contact breakage and is logged by analog-to-digital instrumentation. <span class="hlt">Velocity</span> data obtained from the SSVD is within approximately 11 percent of the calculated surface shockwave <span class="hlt">velocity</span> of a muzzle blast from a 30.06 rifle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.T11D2928B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.T11D2928B&link_type=ABSTRACT"><span id="translatedtitle">The Crustal Structure of the Eastern Tennessee Seismic Zone Imaged by means of Seismic Noise <span class="hlt">Tomography</span> and Potential Fields Inversion Methods</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brandmayr, E.; Arroucau, P.; Kuponiyi, A.; Vlahovic, G.</p> <p>2015-12-01</p> <p>We investigate the crustal structure of the Eastern Tennessee Seismic Zone (ETSZ) by means of <span class="hlt">group</span> <span class="hlt">velocity</span> <span class="hlt">tomography</span> maps from seismic noise data analysis and potential fields inversion with the located Euler deconvolution method. Preliminary <span class="hlt">tomography</span> results show that, in the uppermost crust, the New York-Alabama (NY-AL) magnetic lineament surface projection represents the boundary between a low <span class="hlt">velocity</span> anomaly to the NW of the lineament and a high <span class="hlt">velocity</span> anomaly to the SE of it. The low <span class="hlt">velocity</span> anomaly migrates towards SE with increasing depth, suggesting a possible SE dipping weak structure in which most of the seismic activity takes place. Inversion of magnetic field data shows that the top of the magnetic basement ranges between 5 and 10 km of depth in the Valley and the Ridge physiographic province while it is shallower (less than 2 km of depth) and locally outcropping in the Blue Ridge province and in the Cumberland Plateau province. The estimated depth of the top of the magnetic basement is in general agreement with existing sedimentary cover map of the broad study area, although the local features of the ETSZ presented in this work are not resolved by previous studies due to poor resolution. The correlation between the magnetic signature and the position of the seismic <span class="hlt">velocity</span> anomalies support the interpretation of the low <span class="hlt">velocity</span> zone as a major basement fault, trending NE-SW and juxtaposing Granite-Rhyolite basement to the NW from Grenville southern Appalachian basement to the SE, of which the NY-AL magnetic lineament is the projection on the surface. In order to better constrain our interpretation, inversion of <span class="hlt">tomography</span> results to obtain absolute shear waves <span class="hlt">velocity</span> models will be performed as a next step.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T23B2581W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T23B2581W"><span id="translatedtitle">Lithospheric structure of the Illinois Basin from teleseismic P-wave <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wilson, B.; Gilbert, H. J.; Hamburger, M. W.; Merrell, T.; Pavlis, G. L.; Sherrill, E.</p> <p>2013-12-01</p> <p>We examine heterogeneity of the crust and upper mantle associated with a major intracratonic basin, using arrival time data from a regional EarthScope experiment extending across the western margin of the Illinois Basin. We measured 24,062 P-wave residuals associated with 399 teleseismic events recorded from January 2012 to March 2013 by 122 stations in the Illinois Basin region. We used data from the Ozark Illinois INdiana Kentucky (OIINK) Flexible Array, the permanent New Madrid Seismic Network, and a portion of the Earthscope Transportable Array. Precise relative arrival times were determined using array cross-correlation methods. We plotted the measured arrivals as residual maps to identify first order patterns of <span class="hlt">velocity</span> heterogeneity and to fix outliers. These data were then inverted for P-wave <span class="hlt">velocity</span> using non-linear <span class="hlt">tomography</span> code developed by Steven Roecker. Our preliminary results indicate the upper 200 km of the mantle can be characterized by two blocks with a transition zone centered roughly parallel to the Ohio River boundary of Illinois and Kentucky. Estimated P-wave <span class="hlt">velocities</span> are higher in Kentucky, located southeast of the transition zone compared to Missouri and Illinois, located northwest. We caution that at this stage our <span class="hlt">tomography</span> model may be biased as we have not accounted for variations in crustal structure or applied corrections associated with the Illinois Basin. Parallel work with receiver functions by our <span class="hlt">group</span> and the known geometry of the Illinois Basin will be used to calculate these corrections and modify the tomographic model accordingly.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.radiologyinfo.org/en/info.cfm?pg=spinect','NIH-MEDLINEPLUS'); return false;" href="http://www.radiologyinfo.org/en/info.cfm?pg=spinect"><span id="translatedtitle">Computed <span class="hlt">Tomography</span> (CT) - Spine</span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>... News Physician Resources Professions Site Index A-Z Computed <span class="hlt">Tomography</span> (CT) - Spine Computed <span class="hlt">tomography</span> (CT) of the spine is a diagnostic imaging ... Spine? What is CT Scanning of the Spine? Computed <span class="hlt">tomography</span>, more commonly known as a CT or CAT ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000AAS...197.0426S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000AAS...197.0426S"><span id="translatedtitle">FAME Radial <span class="hlt">Velocity</span> Survey</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Salim, S.; Gould, A.</p> <p>2000-12-01</p> <p>Full-Sky Astrometric Mapping Explorer (FAME) belongs to a new generation of astrometry satellites and will probe the surrounding space some 20 times deeper than its predecessor Hipparcos. As a result we will acquire precise knowledge of 5 out of 6 components of phase-space for millions of stars. The remaining coordinate, radial <span class="hlt">velocity</span>, will remain unknown. In this study, we look at how the knowledge of radial <span class="hlt">velocity</span> affects the determination of the structure of the Galaxy, and its gravitational potential. We therefore propose a radial <span class="hlt">velocity</span> survey of FAME stars, and discuss its feasibility and technical requirements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvB..93w5425S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvB..93w5425S"><span id="translatedtitle">Multilogarithmic <span class="hlt">velocity</span> renormalization in graphene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sharma, Anand; Kopietz, Peter</p> <p>2016-06-01</p> <p>We reexamine the effect of long-range Coulomb interactions on the quasiparticle <span class="hlt">velocity</span> in graphene. Using a nonperturbative functional renormalization <span class="hlt">group</span> approach with partial bosonization in the forward scattering channel and momentum transfer cutoff scheme, we calculate the quasiparticle <span class="hlt">velocity</span>, v (k ) , and the quasiparticle residue, Z , with frequency-dependent polarization. One of our most striking results is that v (k ) ∝ln[Ck(α ) /k ] where the momentum- and interaction-dependent cutoff scale Ck(α ) vanishes logarithmically for k →0 . Here k is measured with respect to one of the charge neutrality (Dirac) points and α =2.2 is the strength of dimensionless bare interaction. Moreover, we also demonstrate that the so-obtained multilogarithmic singularity is reconcilable with the perturbative expansion of v (k ) in powers of the bare interaction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.nlm.nih.gov/medlineplus/ency/article/003927.htm','NIH-MEDLINEPLUS'); return false;" href="https://www.nlm.nih.gov/medlineplus/ency/article/003927.htm"><span id="translatedtitle">Nerve conduction <span class="hlt">velocity</span></span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>Nerve conduction <span class="hlt">velocity</span> (NCV) is a test to see how fast electrical signals move through a nerve. ... normal body temperature. Being too cold slows nerve conduction. Tell your doctor if you have a cardiac ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930091260','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930091260"><span id="translatedtitle">Investigation of Slipstream <span class="hlt">Velocity</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Crowley, J W , Jr</p> <p>1925-01-01</p> <p>These experiments were made at the request of the Bureau of Aeronautics, Navy Department, to investigate the <span class="hlt">velocity</span> of the air in the slipstream in horizontal and climbing flight to determine the form of expression giving the slipstream <span class="hlt">velocity</span> in terms of the airspeed of the airplane. The method used consisted in flying the airplane both on a level course and in climb at full throttle and measuring the slipstream <span class="hlt">velocity</span> at seven points in the slipstream for the whole speed range of the airplane in both conditions. In general the results show that for both condition, horizontal and climbing flights, the slipstream <span class="hlt">velocity</span> v subscript 3 and airspeed v can be represented by straight lines and consequently the equations are of the form: v subscript s = mv+b where m and b are constant. (author)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19940009164&hterms=Gun&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DGun','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19940009164&hterms=Gun&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DGun"><span id="translatedtitle">High <span class="hlt">Velocity</span> Gas Gun</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1988-01-01</p> <p>A video tape related to orbital debris research is presented. The video tape covers the process of loading a High <span class="hlt">Velocity</span> Gas Gun and firing it into a mounted metal plate. The process is then repeated in slow motion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=loudspeaker&pg=2&id=EJ124867','ERIC'); return false;" href="http://eric.ed.gov/?q=loudspeaker&pg=2&id=EJ124867"><span id="translatedtitle"><span class="hlt">Velocity</span> of Sound</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Gillespie, A.</p> <p>1975-01-01</p> <p>Describes a method for the determination of the <span class="hlt">velocity</span> of sound using a dual oscilloscope on which is displayed the sinusoidal input into a loudspeaker and the signal picked up by a microphone. (GS)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/405606','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/405606"><span id="translatedtitle">Application of seismic <span class="hlt">tomography</span> in underground mining</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Scott, D.F.; Williams, T.J.; Friedel, M.J.</p> <p>1996-12-01</p> <p>Seismic <span class="hlt">tomography</span>, as used in mining, is based on the principle that highly stressed rock will demonstrate relatively higher P-wave <span class="hlt">velocities</span> than rock under less stress. A decrease or increase in stress over time can be verified by comparing successive tomograms. Personnel at the Spokane Research Center have been investigating the use of seismic <span class="hlt">tomography</span> to identify stress in remnant ore pillars in deep (greater than 1220 in) underground mines. In this process, three-dimensional seismic surveys are conducted in a pillar between mine levels. A sledgehammer is used to generate P-waves, which are recorded by geophones connected to a stacking signal seismograph capable of collecting and storing the P-wave data. Travel times are input into a spreadsheet, and apparent <span class="hlt">velocities</span> are then generated and merged into imaging software. Mine workings are superimposed over apparent P-wave <span class="hlt">velocity</span> contours to generate a final tomographic image. Results of a seismic tomographic survey at the Sunshine Mine, Kellogg, ED, indicate that low-<span class="hlt">velocity</span> areas (low stress) are associated with mine workings and high-<span class="hlt">velocity</span> areas (higher stress) are associated with areas where no mining has taken place. A high stress gradient was identified in an area where ground failed. From this tomographic survey, as well, as four earlier surveys at other deep underground mines, a method was developed to identify relative stress in remnant ore pillars. This information is useful in making decisions about miner safety when mining such ore pillars.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JSAES..66....1R&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JSAES..66....1R&link_type=ABSTRACT"><span id="translatedtitle">Thin crust beneath the Chaco-Paraná Basin by surface-wave <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rosa, María Laura; Collaço, Bruno; Assumpção, Marcelo; Sabbione, Nora; Sánchez, Gerardo</p> <p>2016-03-01</p> <p>We present the results of surface-wave <span class="hlt">group</span> <span class="hlt">velocity</span> <span class="hlt">tomography</span> for South America, using dispersion curves from a) regional earthquakes recorded at permanent and portable stations and b) inter-station cross-correlation of ambient noise for stations in and around the Paraná and Chaco-Paraná basins, achieving better path coverage and a more azimuthally uniform distribution. A 2D <span class="hlt">group</span> <span class="hlt">velocity</span> tomographic inversion, using two different smoothing criteria (first- and second-derivative smoothing) was performed in the period 10-150 s for the Rayleigh wave and 10-90 s for the Love wave, displayed improved resolution in northern Argentina and southern Brazil, compared with previous studies. A grid-search method was applied to estimate sediment, crustal thickness and upper mantle Sn <span class="hlt">velocity</span> maps for the Chaco-Paraná basin. Our results obtained from a more complete dataset reveal an average crustal thickness for the Chaco-Paraná basin of about 35 km, reaching approximately 28-30 km beneath the northern region. S-wave <span class="hlt">velocities</span> in the uppermost mantle are about 2% lower than IASP91 model, especially for the northern region, suggesting a shallower asthenosphere. These results are consistent with previous estimates, but are more robust because we used a larger dataset and tested different inversion constraints.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PApGe.172.1007Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PApGe.172.1007Z"><span id="translatedtitle">Seismic <span class="hlt">Tomography</span> of the Southern California Plate Boundary Region from Noise-Based Rayleigh and Love Waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zigone, Dimitri; Ben-Zion, Yehuda; Campillo, Michel; Roux, Philippe</p> <p>2015-05-01</p> <p>We use cross-correlations of ambient seismic noise between pairs of 158 broadband and short-period sensors to investigate <span class="hlt">velocity</span> structure over the top 5-10 km of the crust in the Southern California plate boundary region around the San Jacinto Fault Zone (SJFZ). From the 9-component correlation tensors associated with all station pairs we derive dispersion curves of Rayleigh and Love wave <span class="hlt">group</span> <span class="hlt">velocities</span>. The dispersion results are inverted first for Rayleigh and Love waves <span class="hlt">group</span> <span class="hlt">velocity</span> maps on a 1.5 × 1.5 km2 grid that includes portions of the SJFZ, the San Andreas Fault (SAF), and the Elsinore fault. We then invert these maps to 3D shear wave <span class="hlt">velocities</span> in the top ~7 km of the crust. The distributions of the Rayleigh and Love <span class="hlt">group</span> <span class="hlt">velocities</span> exhibit 2θ azimuthal anisotropy with fast directions parallel to the main faults and rotations in complex areas. The reconstructed 3D shear <span class="hlt">velocity</span> model reveals complex shallow structures correlated with the main geological units, and strong <span class="hlt">velocity</span> contrasts across various fault sections along with low-<span class="hlt">velocity</span> damage zones and basins. The SJFZ is marked by a clear <span class="hlt">velocity</span> contrast with higher V s values on the NE block for the section SE of the San Jacinto basin and a reversed contrast across the section between the San Jacinto basin and the SAF. <span class="hlt">Velocity</span> contrasts are also observed along the southern parts on the SAF and the Elsinore fault, with a faster southwest block in both cases. The region around the Salton Trough is associated with a significant low-<span class="hlt">velocity</span> zone. Strong <span class="hlt">velocity</span> reductions following flower-shape with depth are observed extensively around both the SJFZ and the SAF, and are especially prominent in areas of geometrical complexity. In particular, the area between the SJFZ and the SAF is associated with an extensive low-<span class="hlt">velocity</span> zone correlated with diffuse seismicity at depth, and a similar pattern including correlation with deep diffuse seismicity is observed on a smaller scale in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014E%26PSL.408..378O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014E%26PSL.408..378O"><span id="translatedtitle">Crustal and uppermost mantle <span class="hlt">velocity</span> structure and its relationship with the formation of ore districts in the Middle-Lower Yangtze River region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ouyang, Longbin; Li, Hongyi; Lü, Qingtian; Yang, Yingjie; Li, Xinfu; Jiang, Guoming; Zhang, Guibin; Shi, Danian; Zheng, Dan; Sun, Sanjian; Tan, Jing; Zhou, Ming</p> <p>2014-12-01</p> <p>In this study, we conduct ambient noise <span class="hlt">tomography</span> and teleseismic two-plane-wave <span class="hlt">tomography</span> to probe the crustal and uppermost mantle structures in the Middle-Lower Yangtze River region. The data used include 14 months (from July 2012 to August 2013) of continuous vertical component ambient noise data and 219 teleseismic earthquakes recorded at 138 broadband seismic stations from Chinese provincial networks and 19 temporary seismic stations deployed by China University of Geosciences (Beijing). First, we apply ambient noise <span class="hlt">tomography</span> to the collected ambient noise data to generate Rayleigh wave <span class="hlt">group</span> and phase <span class="hlt">velocity</span> maps at 5-42 s periods and two-plane-wave <span class="hlt">tomography</span> method to earthquake data to generate intermediate-to-long period phase <span class="hlt">velocity</span> maps at 20-143 s periods. We then combine the short-to-intermediate period <span class="hlt">velocity</span> maps from ambient noise and the intermediate-to-long period phase <span class="hlt">velocity</span> maps from earthquake data to generate broadband phase <span class="hlt">velocity</span> maps at periods from 5 to 143 s. By inverting these 5-143 s Rayleigh wave <span class="hlt">velocity</span> maps, we construct a 3-D shear wave <span class="hlt">velocity</span> model from the surface to ∼250 km depth in the Middle-Lower Yangtze River region. The 3-D model shows that in the upper crust, the basin regions, including the JiangHan, HeHuai, SuBei, HeFei and NanYang basins, are all featured with low <span class="hlt">velocities</span>, and the mountain regions with high <span class="hlt">velocities</span>. In the uppermost mantle, a low-<span class="hlt">velocity</span> zone at ∼100-200 km depth is observed beneath the Middle-Lower Yangtze River Metallogenic Belt. Moreover, our tomographic results show that the NingWu and NingZhen ore districts are clearly characterized by the strongest low <span class="hlt">velocity</span> anomaly in the uppermost mantle at ∼70-200 km depth. The depth extent of the low-<span class="hlt">velocity</span> zone becomes shallower and the amplitude of low <span class="hlt">velocity</span> anomaly becomes larger from the southwest JiuRui ore district to northeast NingWu ore districts. The change pattern of the low-<span class="hlt">velocity</span> zone in the depth extent</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013GeoJI.195.1351R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013GeoJI.195.1351R"><span id="translatedtitle">Crustal structure of the Carpathian-Pannonian region from ambient noise <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ren, Yong; Grecu, Bogdan; Stuart, Graham; Houseman, Gregory; Hegedüs, Endre; South Carpathian Project Working Group</p> <p>2013-11-01</p> <p>We use ambient noise <span class="hlt">tomography</span> to investigate the crust and uppermost mantle structure beneath the Carpathian-Pannonian region of Central Europe. Over 7500 Rayleigh wave empirical Green's functions are derived from interstation cross-correlations of vertical component ambient seismic noise recordings (2005-2011) using a temporary network of 54 stations deployed during the South Carpathian Project (2009-2011), 56 temporary stations deployed in the Carpathian Basins Project (2005-2007) and 100 permanent and regional broad-band stations. Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion curves (4-40 s) are determined using the multiple-filter analysis technique. <span class="hlt">Group</span> <span class="hlt">velocity</span> maps are computed on a grid of 0.2° × 0.2° from a non-linear 2-D tomographic inversion using the subspace method. We then inverted the <span class="hlt">group</span> <span class="hlt">velocity</span> maps for the 3-D shear wave <span class="hlt">velocity</span> structure of the crust and uppermost mantle beneath the region. Our shear wave <span class="hlt">velocity</span> model provides a uniquely complete and relatively high-resolution view of the crustal structure in the Carpathian-Pannonian region, which in general is validated by comparison with previous studies using other methods to probe the crustal structure. At shallow depths (<10 km) we find relatively high <span class="hlt">velocities</span> below where basement is exposed (e.g. Bohemian Massif, Eastern Alps, most of Carpathians, Apuseni Mountains and Trans-Danubian Ranges) whereas sedimentary areas (e.g. Vienna, Pannonian, Transylvanian and Foçsani Basins) are associated with low <span class="hlt">velocities</span> of well defined depth extent. The mid to lower crust (16-34 km) below the Mid-Hungarian Line is associated with a broad NE-SW trending relatively fast anomaly, flanked to the NW by an elongated low-<span class="hlt">velocity</span> region beneath the Trans-Danubian Ranges. In the lowermost crust and uppermost mantle (between 30 and 40 km), relatively low <span class="hlt">velocities</span> are observed beneath the Bohemian Massif and Eastern Alps but the most striking features are the broad low <span class="hlt">velocity</span> regions beneath the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.S54B..01D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.S54B..01D"><span id="translatedtitle"><span class="hlt">Velocity</span> Based Modulus Calculations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dickson, W. C.</p> <p>2007-12-01</p> <p>A new set of equations are derived for the modulus of elasticity E and the bulk modulus K which are dependent only upon the seismic wave propagation <span class="hlt">velocities</span> Vp, Vs and the density ρ. The three elastic moduli, E (Young's modulus), the shear modulus μ (Lamé's second parameter) and the bulk modulus K are found to be simple functions of the density and wave propagation <span class="hlt">velocities</span> within the material. The shear and elastic moduli are found to equal the density of the material multiplied by the square of their respective wave propagation-<span class="hlt">velocities</span>. The bulk modulus may be calculated from the elastic modulus using Poisson's ratio. These equations and resultant values are consistent with published literature and values in both magnitude and dimension (N/m2) and are applicable to the solid, liquid and gaseous phases. A 3D modulus of elasticity model for the Parkfield segment of the San Andreas Fault is presented using data from the wavespeed model of Thurber et al. [2006]. A sharp modulus gradient is observed across the fault at seismic depths, confirming that "variation in material properties play a key role in fault segmentation and deformation style" [Eberhart-Phillips et al., 1993] [EPM93]. The three elastic moduli E, μ and K may now be calculated directly from seismic pressure and shear wave propagation <span class="hlt">velocities</span>. These <span class="hlt">velocities</span> may be determined using conventional seismic reflection, refraction or transmission data and techniques. These <span class="hlt">velocities</span> may be used in turn to estimate the density. This allows <span class="hlt">velocity</span> based modulus calculations to be used as a tool for geophysical analysis, modeling, engineering and prospecting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/44952','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/44952"><span id="translatedtitle">Elastic constants and <span class="hlt">velocity</span> surfaces of indurated anisotropic shales</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Johnston, J.E.; Christensen, N.I.</p> <p>1994-09-01</p> <p>The <span class="hlt">velocities</span> of two Devonian-Mississippian shales have been measured to confining pressures of 200 MPa in a laboratory study of anisotropy and wave propagation. Both samples were found to be transversely isotropic at elevated pressures with the main symmetry axis perpendicular to bedding. The elastic constants of the shales were used to calculate phase and <span class="hlt">group</span> <span class="hlt">velocity</span> surfaces as a function of angle to the bedding normal. Multiple <span class="hlt">velocity</span> measurements in non-symmetry directions, not undertaken in previously published studies of shales, have been used to confirm features observed on calculated <span class="hlt">velocity</span> surfaces. It is demonstrated that <span class="hlt">velocities</span> measured in non-symmetry directions are phase <span class="hlt">velocities</span>. <span class="hlt">Group</span> <span class="hlt">velocities</span> were found to be significantly lower than the corresponding phase <span class="hlt">velocities</span> of the shales due to their high anisotropies. Shear wave splitting was found to be negligible for propagation directions within approximately 30{degrees} of the bedding normals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeoJI.196.1162S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeoJI.196.1162S"><span id="translatedtitle">Shallow crustal structures of the Tehran basin in Iran resolved by ambient noise <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shirzad, Taghi; Hossein Shomali, Z.</p> <p>2014-02-01</p> <p>In this study, we present an application of the ambient noise <span class="hlt">tomography</span> (ANT) to study the near-surface geological structures of the metropolitan Tehran/Iran region. Short-period fundamental mode Rayleigh wave Green's functions were estimated using cross-correlations of the vertical component of the ambient noise from 2009 October to 2011 May using a variety of seismic sensors, for example, accelerometers and seismometers, deployed in the Tehran area. Standard common low frequency processing procedures were applied to the cross-correlations, and shorter time-windows comprising 10-min segments were used in the processing step to enhance the time resolution of the signal in the frequency range of interest (1-10 s). Stacking was also conducted using the rms of the estimated empirical Green's functions. Our results demonstrate that ambient seismic noise <span class="hlt">tomography</span> is a viable technique at periods of 1-10 s in length, even when different sensor types are present. Analysis of the empirical Green's functions indicates that the dominant sources of ambient seismic noise originated from the same origin, and no significant seasonal or spatial variations in the ambient noise sources were observed. Multiple-filter analysis was used to extract the <span class="hlt">group</span> <span class="hlt">velocities</span> from the estimated empirical Green's functions, which were then inverted to image the spatially varying dispersion at periods of lengths between 1 and 7 s using tomographic inversion of the traveltimes estimated for each frequency. The resulting <span class="hlt">group</span> <span class="hlt">velocity</span> maps show high correlations with known geological and tectonic features of the study region. In general, most of the Tehran basin, with certain exceptions, could be clearly resolved with low <span class="hlt">group</span> <span class="hlt">velocities</span>, whereas the mountain ranges were found to be correlated with high <span class="hlt">group</span> <span class="hlt">velocities</span>. In the Tehran basin, for 2 and 3 s periods, the low-<span class="hlt">velocity</span> zone deepens towards the south-southwest, which reflects thicker sediments in the southern part of the basin</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1168946','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1168946"><span id="translatedtitle">Turbocharging Quantum <span class="hlt">Tomography</span>.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Blume-Kohout, Robin J; Gamble, John King,; Nielsen, Erik; Maunz, Peter Lukas Wilhelm; Scholten, Travis L.; Rudinger, Kenneth Michael</p> <p>2015-01-01</p> <p>Quantum <span class="hlt">tomography</span> is used to characterize quantum operations implemented in quantum information processing (QIP) hardware. Traditionally, state <span class="hlt">tomography</span> has been used to characterize the quantum state prepared in an initialization procedure, while quantum process <span class="hlt">tomography</span> is used to characterize dynamical operations on a QIP system. As such, <span class="hlt">tomography</span> is critical to the development of QIP hardware (since it is necessary both for debugging and validating as-built devices, and its results are used to influence the next generation of devices). But <span class="hlt">tomography</span> su %7C ers from several critical drawbacks. In this report, we present new research that resolves several of these flaws. We describe a new form of <span class="hlt">tomography</span> called gate set <span class="hlt">tomography</span> (GST), which unifies state and process <span class="hlt">tomography</span>, avoids prior methods critical reliance on precalibrated operations that are not generally available, and can achieve unprecedented accuracies. We report on theory and experimental development of adaptive <span class="hlt">tomography</span> protocols that achieve far higher fidelity in state reconstruction than non-adaptive methods. Finally, we present a new theoretical and experimental analysis of process <span class="hlt">tomography</span> on multispin systems, and demonstrate how to more e %7C ectively detect and characterize quantum noise using carefully tailored ensembles of input states.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016GeoJI.204.1565D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016GeoJI.204.1565D&link_type=ABSTRACT"><span id="translatedtitle">Ambient noise <span class="hlt">tomography</span> of the East African Rift in Mozambique</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Domingues, Ana; Silveira, Graça; Ferreira, Ana M. G.; Chang, Sung-Joon; Custódio, Susana; Fonseca, João F. B. D.</p> <p>2016-03-01</p> <p>Seismic ambient noise <span class="hlt">tomography</span> is applied to central and southern Mozambique, located in the tip of the East African Rift (EAR). The deployment of MOZART seismic network, with a total of 30 broad-band stations continuously recording for 26 months, allowed us to carry out the first tomographic study of the crust under this region, which until now remained largely unexplored at this scale. From cross-correlations extracted from coherent noise we obtained Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion curves for the period range 5-40 s. These dispersion relations were inverted to produce <span class="hlt">group</span> <span class="hlt">velocity</span> maps, and 1-D shear wave <span class="hlt">velocity</span> profiles at selected points. High <span class="hlt">group</span> <span class="hlt">velocities</span> are observed at all periods on the eastern edge of the Kaapvaal and Zimbabwe cratons, in agreement with the findings of previous studies. Further east, a pronounced slow anomaly is observed in central and southern Mozambique, where the rifting between southern Africa and Antarctica created a passive margin in the Mesozoic, and further rifting is currently happening as a result of the southward propagation of the EAR. In this study, we also addressed the question concerning the nature of the crust (continental versus oceanic) in the Mozambique Coastal Plains (MCP), still in debate. Our data do not support previous suggestions that the MCP are floored by oceanic crust since a shallow Moho could not be detected, and we discuss an alternative explanation for its ocean-like magnetic signature. Our <span class="hlt">velocity</span> maps suggest that the crystalline basement of the Zimbabwe craton may extend further east well into Mozambique underneath the sediment cover, contrary to what is usually assumed, while further south the Kaapval craton passes into slow rifted crust at the Lebombo monocline as expected. The sharp passage from fast crust to slow crust on the northern part of the study area coincides with the seismically active NNE-SSW Urema rift, while further south the Mazenga graben adopts an N-S direction</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27179476','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27179476"><span id="translatedtitle">Quantitative <span class="hlt">velocity</span> modulation spectroscopy.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hodges, James N; McCall, Benjamin J</p> <p>2016-05-14</p> <p><span class="hlt">Velocity</span> Modulation Spectroscopy (VMS) is arguably the most important development in the 20th century for spectroscopic study of molecular ions. For decades, interpretation of VMS lineshapes has presented challenges due to the intrinsic covariance of fit parameters including <span class="hlt">velocity</span> modulation amplitude, linewidth, and intensity. This limitation has stifled the growth of this technique into the quantitative realm. In this work, we show that subtle changes in the lineshape can be used to help address this complexity. This allows for determination of the linewidth, intensity relative to other transitions, <span class="hlt">velocity</span> modulation amplitude, and electric field strength in the positive column of a glow discharge. Additionally, we explain the large homogeneous component of the linewidth that has been previously described. Using this component, the ion mobility can be determined. PMID:27179476</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860023223','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860023223"><span id="translatedtitle">Fluidic angular <span class="hlt">velocity</span> sensor</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Berdahl, C. M. (Inventor)</p> <p>1986-01-01</p> <p>A fluidic sensor providing a differential pressure signal proportional to the angular <span class="hlt">velocity</span> of a rotary input is described. In one embodiment the sensor includes a fluid pump having an impeller coupled to a rotary input. A housing forming a constricting fluid flow chamber is connected to the fluid input of the pump. The housing is provided with a fluid flow restrictive input to the flow chamber and a port communicating with the interior of the flow chamber. The differential pressure signal measured across the flow restrictive input is relatively noise free and proportional to the square of the angular <span class="hlt">velocity</span> of the impeller. In an alternative embodiment, the flow chamber has a generally cylindrical configuration and plates having flow restrictive apertures are disposed within the chamber downstream from the housing port. In this embodiment, the differential pressure signal is found to be approximately linear with the angular <span class="hlt">velocity</span> of the impeller.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JChPh.144r4201H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JChPh.144r4201H"><span id="translatedtitle">Quantitative <span class="hlt">velocity</span> modulation spectroscopy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hodges, James N.; McCall, Benjamin J.</p> <p>2016-05-01</p> <p><span class="hlt">Velocity</span> Modulation Spectroscopy (VMS) is arguably the most important development in the 20th century for spectroscopic study of molecular ions. For decades, interpretation of VMS lineshapes has presented challenges due to the intrinsic covariance of fit parameters including <span class="hlt">velocity</span> modulation amplitude, linewidth, and intensity. This limitation has stifled the growth of this technique into the quantitative realm. In this work, we show that subtle changes in the lineshape can be used to help address this complexity. This allows for determination of the linewidth, intensity relative to other transitions, <span class="hlt">velocity</span> modulation amplitude, and electric field strength in the positive column of a glow discharge. Additionally, we explain the large homogeneous component of the linewidth that has been previously described. Using this component, the ion mobility can be determined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015sf2a.conf..221S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015sf2a.conf..221S"><span id="translatedtitle">MSE <span class="hlt">velocity</span> survey</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schimd, C.; Courtois, H.; Koda, J.</p> <p>2015-12-01</p> <p>A huge <span class="hlt">velocity</span> survey based on the Maunakea Spectroscopic Explorer facility (MSE) is proposed, aiming at investigating the structure and dynamics of the cosmic web over 3π steradians up to ˜1 Gpc and at unprecedented spatial resolution, its relationship with the galaxy formation process, and the bias between galaxies and dark matter during the last three billions years. The cross-correlation of <span class="hlt">velocity</span> and density fields will further allow the probe any deviation from General Relativity by measuring the the linear-growth rate of cosmic structures at precision competitive with high-redshift spectroscopic redshift surveys.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050031077','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050031077"><span id="translatedtitle">DVL Angular <span class="hlt">Velocity</span> Recorder</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Liebe, Wolfgang</p> <p>1944-01-01</p> <p>In many studies, especially of nonstationary flight motion, it is necessary to determine the angular <span class="hlt">velocities</span> at which the airplane rotates about its various axes. The three-component recorder is designed to serve this purpose. If the angular <span class="hlt">velocity</span> for one flight attitude is known, other important quantities can be derived from its time rate of change, such as the angular acceleration by differentiations, or - by integration - the angles of position of the airplane - that is, the angles formed by the airplane axes with the axis direction presented at the instant of the beginning of the motion that is to be investigated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5249531','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/5249531"><span id="translatedtitle"><span class="hlt">Velocity</span> pump reaction turbine</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>House, P.A.</p> <p></p> <p>An expanding hydraulic/two-phase <span class="hlt">velocity</span> pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This <span class="hlt">velocity</span> pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/864862','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/864862"><span id="translatedtitle"><span class="hlt">Velocity</span> pump reaction turbine</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>House, Palmer A.</p> <p>1984-01-01</p> <p>An expanding hydraulic/two-phase <span class="hlt">velocity</span> pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This <span class="hlt">velocity</span> pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/864222','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/864222"><span id="translatedtitle"><span class="hlt">Velocity</span> pump reaction turbine</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>House, Palmer A.</p> <p>1982-01-01</p> <p>An expanding hydraulic/two-phase <span class="hlt">velocity</span> pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This <span class="hlt">velocity</span> pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JVGR..200..234B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JVGR..200..234B"><span id="translatedtitle">Seismic <span class="hlt">tomography</span> at Popocatépetl volcano, Mexico</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Berger, Pia; Got, Jean-Luc; González, Carlos Valdés; Monteiller, Vadim</p> <p>2011-03-01</p> <p>We performed the first 3D seismic <span class="hlt">tomography</span> of the Popocatépetl volcano, Mexico, from the inversion of the P-wave arrival times of nearly 1500 earthquakes recorded by up to 11 seismic stations of the permanent CENAPRED-SSN network. We used the Bayesian tomographic algorithm developed by Monteiller et al. (2005) to perform this P-wave travel-time <span class="hlt">tomography</span> and carefully choose optimal regularization hyper-parameters. Sensitivity tests show that the inversion is correctly constrained under the volcano from - 1 to 4 km depth b.s.l.. At these depths, the optimal tomographic model mainly shows low-<span class="hlt">velocity</span> volumes surrounded by higher-<span class="hlt">velocity</span> volumes. Lateral heterogeneity is strong: the variation of the P-wave <span class="hlt">velocity</span> may reach up to ± 20% of the average value at a given depth. Low-<span class="hlt">velocity</span> volumes correlate well with results from former geological and geophysical studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2647010','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2647010"><span id="translatedtitle">Prospects of photoacoustic <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Wang, Lihong V.</p> <p>2008-01-01</p> <p>Commercially available high-resolution three-dimensional optical imaging modalities—including confocal microscopy, two-photon microscopy, and optical coherence tomography—have fundamentally impacted biomedicine. Unfortunately, such tools cannot penetrate biological tissue deeper than the optical transport mean free path (∼1 mm in the skin). Photoacoustic <span class="hlt">tomography</span>, which combines strong optical contrast and high ultrasonic resolution in a single modality, has broken through this fundamental depth limitation and achieved superdepth high-resolution optical imaging. In parallel, radio frequency-or microwave-induced thermoacoustic <span class="hlt">tomography</span> is being actively developed to combine radio frequency or microwave contrast with ultrasonic resolution. In this Vision 20∕20 article, the prospects of photoacoustic <span class="hlt">tomography</span> are envisaged in the following aspects: (1) photoacoustic microscopy of optical absorption emerging as a mainstream technology, (2) melanoma detection using photoacoustic microscopy, (3) photoacoustic endoscopy, (4) simultaneous functional and molecular photoacoustic <span class="hlt">tomography</span>, (5) photoacoustic <span class="hlt">tomography</span> of gene expression, (6) Doppler photoacoustic <span class="hlt">tomography</span> for flow measurement, (7) photoacoustic <span class="hlt">tomography</span> of metabolic rate of oxygen, (8) photoacoustic mapping of sentinel lymph nodes, (9) multiscale photoacoustic imaging in vivo with common signal origins, (10) simultaneous photoacoustic and thermoacoustic <span class="hlt">tomography</span> of the breast, (11) photoacoustic and thermoacoustic <span class="hlt">tomography</span> of the brain, and (12) low-background thermoacoustic molecular imaging. PMID:19175133</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3775479','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3775479"><span id="translatedtitle">Meaning of Interior <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Wang, Ge; Yu, Hengyong</p> <p>2013-01-01</p> <p>The classic imaging geometry for computed <span class="hlt">tomography</span> is for collection of un-truncated projections and reconstruction of a global image, with the Fourier transform as the theoretical foundation that is intrinsically non-local. Recently, interior <span class="hlt">tomography</span> research has led to theoretically exact relationships between localities in the projection and image spaces and practically promising reconstruction algorithms. Initially, interior <span class="hlt">tomography</span> was developed for x-ray computed <span class="hlt">tomography</span>. Then, it has been elevated as a general imaging principle. Finally, a novel framework known as “omni-tomography” is being developed for grand fusion of multiple imaging modalities, allowing tomographic synchrony of diversified features. PMID:23912256</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=terminal&id=EJ1007732','ERIC'); return false;" href="http://eric.ed.gov/?q=terminal&id=EJ1007732"><span id="translatedtitle">Modeling Terminal <span class="hlt">Velocity</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Brand, Neal; Quintanilla, John A.</p> <p>2013-01-01</p> <p>Using a simultaneously falling softball as a stopwatch, the terminal <span class="hlt">velocity</span> of a whiffle ball can be obtained to surprisingly high accuracy with only common household equipment. This classroom activity engages students in an apparently daunting task that nevertheless is tractable, using a simple model and mathematical techniques at their…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1131963','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1131963"><span id="translatedtitle">Double-Difference <span class="hlt">Tomography</span> for Sequestration MVA</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Westman, Erik</p> <p>2008-12-31</p> <p>Analysis of synthetic data was performed to determine the most cost-effective tomographic monitoring system for a geologic carbon sequestration injection site. Double-difference tomographic inversion was performed on 125 synthetic data sets: five stages of CO2 plume growth, five seismic event regions, and five geophone arrays. Each resulting <span class="hlt">velocity</span> model was compared quantitatively to its respective synthetic <span class="hlt">velocity</span> model to determine an accuracy value. The results were examined to determine a relationship between cost and accuracy in monitoring, verification, and accounting applications using double-difference <span class="hlt">tomography</span>. The geophone arrays with widely-varying geophone locations, both laterally and vertically, performed best. Additionally, double difference seismic <span class="hlt">tomography</span> was performed using travel time data from a carbon sequestration site at the Aneth oil field in southeast Utah as part of a Department of Energy initiative on monitoring, verification, and accounting (MVA) of sequestered CO2. A total of 1,211 seismic events were recorded from a borehole array consisting of 22 geophones. Artificial <span class="hlt">velocity</span> models were created to determine the ease with which different CO2 plume locations and sizes can be detected. Most likely because of the poor geophone arrangement, a low <span class="hlt">velocity</span> zone in the Desert Creek reservoir can only be detected when regions of test site containing the highest ray path coverage are considered. MVA accuracy and precision may be improved through the use of a receiver array that provides more comprehensive ray path coverage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15004851','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15004851"><span id="translatedtitle">Regional Body-Wave Corrections and Surface-Wave <span class="hlt">Tomography</span> Models to Improve Discrimination</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Walter, W R; Pasyanos, M E; Rodgers, A J; Meyeda, K M; Sicherman, A</p> <p>2003-07-18</p> <p> multivariate combinations of ratios for their discrimination power. We also make use of the MDAC2 spectra and the noise spectra to determine the expected signal-to-noise value of each phase and use that to optimize the multivariate discriminants as a function of location. We quantify the discrimination power using the misidentified event trade-off curves and an equi-probable measure. In addition to the traditional phases, we are also exploring the application of coda amplitudes in discrimination. Coda-derived spectra can be peaked due to Rg-to-coda scattering, which can indicate an unusually shallow source. For surface waves we have a new high-resolution regional Rayleigh-Wave <span class="hlt">tomography</span> for the Yellow Sea and Korean Peninsula Region, based on measuring thousands of seismograms. We also continue to make new measurements for our regional Rayleigh and Love wave <span class="hlt">group</span> <span class="hlt">velocity</span> <span class="hlt">tomography</span> models of Western Eurasia and North Africa. These <span class="hlt">tomography</span> models provide high-resolution maps of <span class="hlt">group</span> <span class="hlt">velocity</span> from 10- to 100-s period. The maps also provide estimates of the expected phase spectra of new events that can be used in phase-match filters to compress the expected signals and improve the signal-to-noise ratio on surface wave magnitude (Ms) estimates. Phase match filters in combination with regional Ms formulas can significantly lower the threshold at which Ms can be measured, extending the Ms-mb discriminant. We have measured Ms in western Eurasia for thousands of events at tens of stations, with and without phase match filtering, and found a marked improvement in discrimination. Here we start to quantify the improvement to both discrimination performance and the Ms threshold reduction. The <span class="hlt">group</span> <span class="hlt">velocity</span> models also provide constraints on <span class="hlt">velocity</span> structure, particularly in low seismicity regions. For example we are working with Dr. Bob Henmann and Dr. Charles Ammon to combine <span class="hlt">tomography</span> derived <span class="hlt">group</span> <span class="hlt">velocity</span> curves with station based receiver functions in joint inversions to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T11F..03D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T11F..03D"><span id="translatedtitle">Ambient Noise <span class="hlt">Tomography</span> of the East African Rift System in Mozambique</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Domingues, A.; Chamussa, J.; Silveira, G. M.; Custodio, S.; Lebedev, S.; Chang, S.; Ferreira, A. M.; Fonseca, J. F.</p> <p>2013-12-01</p> <p>A wide range of studies has shown that the cross-correlation of ambient noise can provide an estimate of the Greens functions between pairs of stations. Project MOZART (funded by FCT, Lisbon, PI J. Fonseca) deployed 30 broadband (120s) seismic stations from the SEIS-UK Pool in Central Mozambique and NE South Africa, with the purpose of studying the East African Rift System (EARS) in Mozambique. We applied the Ambient Noise <span class="hlt">Tomography</span> (ANT) method to broadband seismic data recorded from March 2011 until July 2012. Cross-correlations were computed between all pairs of stations, and from these we obtained Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion curves for all interstation paths, in the period range from 3 to 50 seconds. We tested various approaches for pre-processing the ambient noise data regarding time-domain and spectral normalisation, as well as the use of phase cross-correlations. Moreover, we examined the robustness of our dispersion maps by splitting our dataset into various sub-sets of Green's functions with similar paths and by quantifying the differences between the dispersion maps obtained from the various sub-sets of data. We find that while the geographical distribution of the <span class="hlt">group</span> <span class="hlt">velocity</span> anomalies is well constrained, the amplitudes of the anomalies are slightly less robust. We performed a three-dimensional inversion to obtain the S-wave <span class="hlt">velocity</span> of the crust and upper mantle. In addition, our preliminary results show a good correlation between the Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> and the geology of Mozambique. In order to extend the investigation to longer periods and, thus, to be able to look into the lithosphere-asthenosphere depth range in the upper mantle, we apply a recent implementation of the surface-wave two-station method (teleseismic interferometry) and augment our dataset with Rayleigh wave phase <span class="hlt">velocities</span> curves in broad period ranges.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JPhCS.602a2039M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JPhCS.602a2039M"><span id="translatedtitle">Optical Coherence <span class="hlt">Tomography</span> Velocimetry with Complex Fluids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Malm, A.; Waigh, T. A.; Jaradat, S.; Tomlin, R.</p> <p>2015-04-01</p> <p>We present recent results obtained with an Optical Coherence <span class="hlt">Tomography</span> Velocimetry technique. An optical interferometer measures the <span class="hlt">velocity</span> of a sheared fluid at specific depths of the sample using the coherence length of the light source. The technique allows the dynamics of 3 pico liter volumes to be probed inside opaque complex fluids. In a study of opaque starch suspensions, classical bulk rheology experiments show non-linear shear thickening, whereas observations of the <span class="hlt">velocity</span> profiles as a function of distance across the gap show Newtonian behavior. The ability of the technique to measure <span class="hlt">velocity</span> fluctuations is also discussed for the case of polyacrylamide samples which were observed to display shear banding behavior. A relationship between the viscoelasticity of the sample and the size of the apparent fluctuations is observed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994Tectp.230..105M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994Tectp.230..105M"><span id="translatedtitle">Shear wave <span class="hlt">velocity</span> structures of the Arabian Peninsula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mokhtar, Talal A.; Al-Saeed, Mohammed M.</p> <p>1994-02-01</p> <p>The shear <span class="hlt">velocity</span> structures of the different tectonic provinces of the Arabian Peninsula has been studied using surface wave data recorded by the RYD (Riyadh) station. The inversion of Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocities</span> indicates that the Arabian shield can be modeled by two layers, each of which is 20 km thick with a shear <span class="hlt">velocity</span> of 3.61 km/s in the upper crust and 3.88 km/s in the lower crust. The underlying upper mantle <span class="hlt">velocity</span> is 4.61 km/s. Inversion of both Love and Rayleigh waves <span class="hlt">group</span> <span class="hlt">velocities</span> shows that the Arabian platform upper and lower crusts are comparable in their thicknesses to those of the shield, but with shear <span class="hlt">velocities</span> of 3.4 and 4 km/s, respectively. The upper mantle <span class="hlt">velocity</span> beneath the platform is 4.4 km/s and the average total thickness of the crust is 45 km.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.3869T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.3869T"><span id="translatedtitle">The lithospheric shear-wave <span class="hlt">velocity</span> structure of Saudi Arabia: Young volcanism in an old shield</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tang, Zheng; Julià, Jordi; Mai, P. Martin</p> <p>2016-04-01</p> <p>We are utilizing receiver function and surface wave dispersion data to investigate the lithospheric shear-wave <span class="hlt">velocity</span> structure of Saudi Arabia. The Arabian plate consists of the western Arabian shield and the eastern Arabian platform. The Arabian shield is a complicated mélange of several Proterozoic terrains, separated by ophiolite-bearing suture zones and dotted by outcropping Cenozoic volcanic rocks (so-called harrats). The Arabian platform is covered by thick Paleozoic, Mesozoic and Cenozoic sedimentary rocks. To understand the geo-dynamics and present-day geology in western Saudi Arabia, the origin and activity of the harrats needs to be investigated: are they controlled primarily by a local mantle plume underneath western Saudi Arabia or by lateral mantle flow from the Afar and (perhaps) Jordan hotspots? In our study, we first estimate Vp/Vs ratios by applying the H-κ stacking technique and construct local shear-wave <span class="hlt">velocity</span>-depth profiles by jointly inverting teleseismic P-receiver functions and Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocities</span> at 56 broadband stations deployed by the Saudi Geological Survey (SGS). Our results reveal significant lateral variations in crustal thickness, S-<span class="hlt">velocity</span>, and bulk Vp/Vs ratio. The Arabian shield has, on average a ~34 km thick crust with Vs ~3.72 km/s and Vp/Vs ~1.73. Thinner crust (~25 - 32 km thick) with strong lateral variations is present along the Red Sea coast. In contrast, the Arabian platform reveals a ~41 km thick crust with Vs ~3.52 km/s and Vp/Vs ~1.77. We find anomalously high Vp/Vs ratios at Harrat Lunayyir, interpreted as solidified magma intrusions. Slow shear-<span class="hlt">velocities</span> in the upper-mantle lid throughout the southernmost and northernmost Arabian shield suggest lateral heating from hot mantle upwellings centered beneath Afar and (perhaps) Jordan. Our findings on crustal S-<span class="hlt">velocity</span> structures, Vp/Vs ratios, and upper-mantle lid <span class="hlt">velocities</span> support the hypothesis of lateral mantle flow from the Afar and (perhaps</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4828413','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4828413"><span id="translatedtitle">Myocardial Tissue Doppler <span class="hlt">Velocity</span> in Child Growth</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Choi, Sun-Ha; Kim, Nam Kyun; Jung, Jo Won; Choi, Jae Young</p> <p>2016-01-01</p> <p>Background In adults, tissue Doppler imaging (TDI) is a recommended component of routine echocardiography. However, TDI <span class="hlt">velocities</span> are less accepted in pediatrics, due to their strong variability and age dependence in children. This study examines the distribution of myocardial tissue Doppler <span class="hlt">velocities</span> in healthy children to assess the effect of age with cardiac growth on the various echocardiographic measurements. Methods Total 144 healthy children were enrolled in this study. They were recruited from the pediatric outpatient clinic for routine well-child visits. The statistical relationships between age and TDI values were analyzed. Also, the statistical relationships between body surface area (BSA) and TDI values, left ventricle end-diastolic dimension (LVEDD) and TDI values were analyzed. Also, we conducted multivariate analysis of cardiac growth parameters such as, age, BSA, LVEDD and TDI <span class="hlt">velocity</span> data. Results All of the age, BSA, and LVEDD had positive correlations with deceleration time (DT), pressure half-time (PHT), peak early diastolic myocardial <span class="hlt">velocity</span>, peak systolic myocardial <span class="hlt">velocity</span>, and had negative correlations with peak late diastolic <span class="hlt">velocity</span> (A) and the ratio of trans-mitral inflow <span class="hlt">velocity</span> to early diastolic <span class="hlt">velocity</span> of mitral annulus (E/E'). In the multivariate analysis, all of the age, BSA, and LVEDD had positive correlations with DT, PHT, and negative correlations with A and E/E'. Conclusion The cardiac growth parameters related alterations of E/E' may suggest that diastolic myocardial <span class="hlt">velocities</span> are cardiac growth dependent, and diastolic function has positive correlation with cardiac growth in pediatric <span class="hlt">group</span>. This cardiac growth related myocardial functional variation would be important for assessment of cardiac involvement either in healthy and sick child. PMID:27081443</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6607747','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6607747"><span id="translatedtitle">Dual seven pinhole <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bizais, Y.; Zubal, I.G.; Rowe, R.W.; Bennett, G.W.; Brill, A.B.</p> <p>1982-01-01</p> <p>Emission <span class="hlt">tomography</span> using two orthogonal sets of projections through seven pinhole collimators is considered. This paper describes the acquisition system, the reconstruction algorithm, presents results obtained in phantom studies, and discusses the advantages and disadvantages of this method over conventional Seven Pinhole <span class="hlt">Tomography</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/80190','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/80190"><span id="translatedtitle">Straight ray <span class="hlt">tomography</span>: Synthetic and real data examples</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bozkurt, G.; Liner, C.L.</p> <p>1994-12-31</p> <p>Crosswell <span class="hlt">tomography</span> is a viable tool for determining detailed P-wave <span class="hlt">velocity</span> structure in the vertical plane between two wells. Seismic data from a West Texas oil field are processed for this purpose. Several geologically significant models are created for testing the accuracy of the method. Synthetic traveltimes corresponding to these models are generated and then inverted for the best image. An iterative straight-ray imaging algorithm is employed for establishing the subsurface <span class="hlt">velocity</span> distribution. A curved-ray solution provided a basis for comparison. The assumption of straight-ray propagation in a medium with low <span class="hlt">velocity</span> contrasts and horizontally oriented target zones provided satisfactory results. However, in the presence of strong <span class="hlt">velocity</span> anomalies or abrupt lateral <span class="hlt">velocity</span> variations, the reconstructed image was distorted due to severe ray bending. When applied to field data with high <span class="hlt">velocity</span> contrasts, straight-ray and curved-ray tomograms displayed similar subsurface features, although the latter had better resolution and image quality.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/11548916','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/11548916"><span id="translatedtitle"><span class="hlt">Velocity</span> specificity, combination training and sport specific tasks.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cronin, J; McNair, P J; Marshall, R N</p> <p>2001-06-01</p> <p>Whether <span class="hlt">velocity</span>-specific resistance training is important for improving functional sporting performance was investigated by studying the effect of isoinertial training <span class="hlt">velocity</span> on netball chest pass throwing <span class="hlt">velocity</span>. Twenty-one female netball players were randomly assigned to a strength-trained <span class="hlt">group</span> (80% 1RM - average training <span class="hlt">velocity</span> = .308 m/s), power-trained <span class="hlt">group</span> (60% 1RM - average training <span class="hlt">velocity</span> = .398 m/s) and a control <span class="hlt">group</span>. Resistance training was combined with sport specific motion training for both <span class="hlt">groups</span> over a ten-week training duration. Pre- and post-training testing revealed that the training <span class="hlt">velocity</span> associated with the strength-trained <span class="hlt">group</span> produced significantly greater improvement in mean volume of weight lifted (85kg) and mean power output (13.25 W) as compared to the power and control <span class="hlt">groups</span> (P< 0.05). The strength-trained and power-trained <span class="hlt">groups</span> significantly improved netball throw <span class="hlt">velocity</span> by 12.4% and 8.8% respectively. There was no significant difference between the two <span class="hlt">groups</span>. The validity of <span class="hlt">velocity</span>-specific training and subsequent adaptations to improve functional sporting performance appears highly questionable, due to the disparity between training <span class="hlt">velocity</span> and actual movement <span class="hlt">velocity</span> (11.38 m x s(-1)) for a given sport specific task such as the netball throw it was proposed that the repeated intent to move an isoinertial load as rapidly as possible coupled with performance of the sport-specific movement promote efficient coordination and activation patterns. Such mechanisms might be more important determinants of sport-specific high <span class="hlt">velocity</span> adaptation. PMID:11548916</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15014178','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15014178"><span id="translatedtitle">High Resolution <span class="hlt">Velocity</span> Structure in Eastern Turkey</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pasyanos, M; Gok, R; Zor, E; Walter, W</p> <p>2004-09-03</p> <p>We investigate the crustal and upper mantle structure of eastern Turkey where the Anatolian, Arabian and Eurasian Plates meet and form a complex tectonic structure. The Bitlis suture is a continental collision zone between the Anatolian plateau and the Arabian plate. Broadband data available through the Eastern Turkey Seismic Experiment (ETSE) provided a unique opportunity for studying the high resolution <span class="hlt">velocity</span> structure. Zor et al. found an average 46 km thick crust in Anatolian plateau using six-layered grid search inversion of the ETSE receiver functions. Receiver functions are sensitive to the <span class="hlt">velocity</span> contrast of interfaces and the relative travel time of converted and reverberated waves between those interfaces. The interpretation of receiver function alone with many-layered parameterization may result in an apparent depth-<span class="hlt">velocity</span> tradeoff. In order to improve previous <span class="hlt">velocity</span> model, we employed the joint inversion method with many layered parameterization of Julia et al. (2000) to the ETSE receiver functions. In this technique, the receiver function and surface-wave observations are combined into a single algebraic equation and each data set is weighted by an estimate of the uncertainty in the observations. We consider azimuthal changes of receiver functions and have stacked them into different <span class="hlt">groups</span>. We calculated the receiver functions using iterative time-domain deconvolution technique and surface wave <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion curves between 10-100 sec. We are making surface wave dispersion measurements at the ETSE stations and have incorporated them into a regional <span class="hlt">group</span> <span class="hlt">velocity</span> model. Preliminary results indicate a strong trend in the long period <span class="hlt">group</span> <span class="hlt">velocity</span> in the northeast. This indicates slow upper mantle <span class="hlt">velocities</span> in the region consistent with Pn, Sn and receiver function results. We started with both the 1-D model that is obtained with the 12 tones dam explosion shot data recorded by ETSE network and the existing receiver function</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015oct..book.2131Y&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015oct..book.2131Y&link_type=ABSTRACT"><span id="translatedtitle">Cardiovascular Optical Coherence <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yonetsu, Taishi; Villiger, Martin; Bouma, Brett E.; Jang, Ik-Kyung</p> <p></p> <p>The potential of optical coherence <span class="hlt">tomography</span> (OCT) for intravascular imaging and assessing the microstructure of atherosclerosis was suggested already by Huang et al. at the very beginning of OCT [1]. For ophthalmology, the eye provides a natural window for OCT to image the retinal microstructure, and OCT has rapidly become the standard imaging modality to diagnose retinal disease and assess disease progression and response to therapy [1, 2]. Intravascular imaging is more invasive by nature and requires imaging through a catheter probe. This has triggered the development of advanced fiber-optic OCT systems with compact, rotating fiber probes, to image the vessel by circumferentially scanning the luminal wall [3, 4]. In 1998, we established the first cardiac OCT research <span class="hlt">group</span> at the Massachusetts General Hospital to explore the clinical applications of OCT. The first imaging of rabbit aorta was reported by Fujimoto et al. [5], followed by the first swine measurements in vivo by Tearney et al. [6], and finally the first assessment of coronary arteries in patients by Jang et al. [7]. The scope of this chapter is to highlight the steps taken to bring intravascular OCT from bench to bedside over the last 15 years. We will give a general description of atherosclerosis and its pathophysiology and the specific technical implementation of OCT for intravascular imaging through a fiber-optic probe. The motivation is to provide sufficient medical details to provide a basic introduction to the terminology, principles, and challenges of intracoronary imaging.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27291488','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27291488"><span id="translatedtitle">Sensitivity to Auditory <span class="hlt">Velocity</span> Contrast.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Locke, Shannon M; Leung, Johahn; Carlile, Simon</p> <p>2016-01-01</p> <p>A natural auditory scene often contains sound moving at varying <span class="hlt">velocities</span>. Using a <span class="hlt">velocity</span> contrast paradigm, we compared sensitivity to <span class="hlt">velocity</span> changes between continuous and discontinuous trajectories. Subjects compared the <span class="hlt">velocities</span> of two stimulus intervals that moved along a single trajectory, with and without a 1 second inter stimulus interval (ISI). We found thresholds were threefold larger for <span class="hlt">velocity</span> increases in the instantaneous <span class="hlt">velocity</span> change condition, as compared to instantaneous <span class="hlt">velocity</span> decreases or thresholds for the delayed <span class="hlt">velocity</span> transition condition. This result cannot be explained by the current static "snapshot" model of auditory motion perception and suggest a continuous process where the percept of <span class="hlt">velocity</span> is influenced by previous history of stimulation. PMID:27291488</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4904411','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4904411"><span id="translatedtitle">Sensitivity to Auditory <span class="hlt">Velocity</span> Contrast</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Locke, Shannon M.; Leung, Johahn; Carlile, Simon</p> <p>2016-01-01</p> <p>A natural auditory scene often contains sound moving at varying <span class="hlt">velocities</span>. Using a <span class="hlt">velocity</span> contrast paradigm, we compared sensitivity to <span class="hlt">velocity</span> changes between continuous and discontinuous trajectories. Subjects compared the <span class="hlt">velocities</span> of two stimulus intervals that moved along a single trajectory, with and without a 1 second inter stimulus interval (ISI). We found thresholds were threefold larger for <span class="hlt">velocity</span> increases in the instantaneous <span class="hlt">velocity</span> change condition, as compared to instantaneous <span class="hlt">velocity</span> decreases or thresholds for the delayed <span class="hlt">velocity</span> transition condition. This result cannot be explained by the current static “snapshot” model of auditory motion perception and suggest a continuous process where the percept of <span class="hlt">velocity</span> is influenced by previous history of stimulation. PMID:27291488</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840009660','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840009660"><span id="translatedtitle">Surface wave <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Anderson, D. L.</p> <p>1984-01-01</p> <p>Vertically polarized shear wave <span class="hlt">velocity</span> (VSV), determined primarily from fundamental mode Rayleigh waves, and the difference between the <span class="hlt">velocity</span> of horizontally polarized shear waves (VSH) and VSV, therefore a measure of anisotropy, are shown.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016SPIE.9707E..0DM&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016SPIE.9707E..0DM&link_type=ABSTRACT"><span id="translatedtitle">Blood flow changes after unilateral carotid artery ligation monitored by optical coherence <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ma, Yushu; Liang, Chengbo; Suo, Yanyan; Zhao, Yuqian; Wang, Yi; Xu, Tao; Wang, Ruikang; Ma, Zhenhe</p> <p>2016-03-01</p> <p>Unilateral carotid artery ligation which could induce adaptive improvement is a classic model that has been widely used to study pathology of ischemic disease. In those studies, blood flow is an important parameter to characterize the ischemia. Optical coherence <span class="hlt">tomography</span> (OCT) is a powerful imaging modality which can provide depth resolved images in biological tissue with high spatial and temporal resolution. SPF rats was anesthetized with isoflurane and divided into two <span class="hlt">groups</span>. In first <span class="hlt">group</span>, bilateral carotid artery was surgically exposed, and then left carotid artery was ligated. Blood flow changes of the contralateral carotid artery was monitored using high speed spectral domain optical coherence <span class="hlt">tomography</span>, including the absolute flow <span class="hlt">velocity</span> and the flow volume. In the other <span class="hlt">group</span>, skull window was opened at the ipsilateral cerebral cortex of ligation and blood supply of small artery was measured before and after the ligation. The measured results demonstrate the blood supply compensation process after unilateral carotid artery ligation. With the superiority of high resolution, OCT is an effective technology in monitoring results of carotid artery after ligation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.usgs.gov/twri/twri3-a17/','USGSPUBS'); return false;" href="http://pubs.usgs.gov/twri/twri3-a17/"><span id="translatedtitle">Acoustic <span class="hlt">velocity</span> meter systems</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Laenen, Antonius</p> <p>1985-01-01</p> <p>Acoustic <span class="hlt">velocity</span> meter (AVM) systems operate on the principles that the point-to-point upstream traveltime of an acoustic pulse is longer than the downstream traveltime and that this difference in traveltime can be accurately measured by electronic devices. An AVM system is capable of recording water <span class="hlt">velocity</span> (and discharge) under a wide range of conditions, but some constraints apply: 1. Accuracy is reduced and performance is degraded if the acoustic path is not a continuous straight line. The path can be bent by reflection if it is too close to a stream boundary or by refraction if it passes through density gradients resulting from variations in either water temperature or salinity. For paths of less than 100 m, a temperature gradient of 0.1' per meter causes signal bending less than 0.6 meter at midchannel, and satisfactory <span class="hlt">velocity</span> results can be obtained. Reflection from stream boundaries can cause signal cancellation if boundaries are too close to signal path. 2. Signal strength is attenuated by particles or bubbles that absorb, spread, or scatter sound. The concentration of particles or bubbles that can be tolerated is a function of the path length and frequency of the acoustic signal. 3. Changes in streamline orientation can affect system accuracy if the variability is random. 4. Errors relating to signal resolution are much larger for a single threshold detection scheme than for multiple threshold schemes. This report provides methods for computing the effect of various conditions on the accuracy of a record obtained from an AVM. The equipment must be adapted to the site. Field reconnaissance and preinstallation analysis to detect possible problems are critical for proper installation and operation of an AVM system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26849582','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26849582"><span id="translatedtitle">Dark Matter <span class="hlt">Velocity</span> Spectroscopy.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Speckhard, Eric G; Ng, Kenny C Y; Beacom, John F; Laha, Ranjan</p> <p>2016-01-22</p> <p>Dark matter decays or annihilations that produce linelike spectra may be smoking-gun signals. However, even such distinctive signatures can be mimicked by astrophysical or instrumental causes. We show that <span class="hlt">velocity</span> spectroscopy-the measurement of energy shifts induced by relative motion of source and observer-can separate these three causes with minimal theoretical uncertainties. The principal obstacle has been energy resolution, but upcoming experiments will have the precision needed. As an example, we show that the imminent Astro-H mission can use Milky Way observations to separate possible causes of the 3.5-keV line. We discuss other applications. PMID:26849582</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvL.116c1301S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvL.116c1301S"><span id="translatedtitle">Dark Matter <span class="hlt">Velocity</span> Spectroscopy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Speckhard, Eric G.; Ng, Kenny C. Y.; Beacom, John F.; Laha, Ranjan</p> <p>2016-01-01</p> <p>Dark matter decays or annihilations that produce linelike spectra may be smoking-gun signals. However, even such distinctive signatures can be mimicked by astrophysical or instrumental causes. We show that <span class="hlt">velocity</span> spectroscopy—the measurement of energy shifts induced by relative motion of source and observer—can separate these three causes with minimal theoretical uncertainties. The principal obstacle has been energy resolution, but upcoming experiments will have the precision needed. As an example, we show that the imminent Astro-H mission can use Milky Way observations to separate possible causes of the 3.5-keV line. We discuss other applications.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016SPIE.9790E..0CS&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016SPIE.9790E..0CS&link_type=ABSTRACT"><span id="translatedtitle">Frequency-domain ultrasound waveform <span class="hlt">tomography</span> breast attenuation imaging</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sandhu, Gursharan Yash Singh; Li, Cuiping; Roy, Olivier; West, Erik; Montgomery, Katelyn; Boone, Michael; Duric, Neb</p> <p>2016-04-01</p> <p>Ultrasound waveform <span class="hlt">tomography</span> techniques have shown promising results for the visualization and characterization of breast disease. By using frequency-domain waveform <span class="hlt">tomography</span> techniques and a gradient descent algorithm, we have previously reconstructed the sound speed distributions of breasts of varying densities with different types of breast disease including benign and malignant lesions. By allowing the sound speed to have an imaginary component, we can model the intrinsic attenuation of a medium. We can similarly recover the imaginary component of the <span class="hlt">velocity</span> and thus the attenuation. In this paper, we will briefly review ultrasound waveform <span class="hlt">tomography</span> techniques, discuss attenuation and its relations to the imaginary component of the sound speed, and provide both numerical and ex vivo examples of waveform <span class="hlt">tomography</span> attenuation reconstructions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.S31A2004S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.S31A2004S"><span id="translatedtitle">Seismic <span class="hlt">Tomography</span> of the South Carpathian System</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stuart, G. W.; Ren, Y.; Dando, B. D.; Houseman, G.; Ionescu, C.; Hegedus, E.; Radovanovic, S.; South Carpathian Project Working Group</p> <p>2010-12-01</p> <p>The South Carpathian Mountain Range is an enigmatic system, which includes one of the most seismically active regions in Europe today. That region, Vrancea in the SE Carpathians, is well studied and its deep structure may be geologically unique, but the mantle structures beneath the western part of the South Carpathian Range are not well resolved by previous tomographic studies. The South Carpathian Project (SCP) is a major temporary deployment (2009-2011) of seismic broadband systems extending across the eastern Pannonian Basin and the South Carpathian Mountains. In this project we aim to map the upper mantle structure in central Europe with the objective of testing geodynamic models of the process that produced extension in the Pannonian, synchronous with convergence and uplift in the Carpathians. Here, we describe initial results of finite-frequency <span class="hlt">tomography</span> using body waves to image the mantle of the region. We have selected teleseismic earthquakes with magnitude greater than 5.9, which occurred between 2005 and 2010. The data were recorded on 57 temporary stations deployed in the South Carpathian Project, 56 temporary stations deployed in the earlier Carpathian Basins Project (CBP), and 41 permanent broadband stations. The differential travel times are measured in high, intermediate and low frequencies (0.5-2.0 Hz, 0.1-0.5 Hz and 0.03-0.1 Hz for both P-wave, 0.1-0.5 Hz, 0.05-0.1 Hz and 0.02-0.05 Hz for S-wave), and are inverted to produce P and S-wave <span class="hlt">velocity</span> maps at different depths in the mantle. An extensive zone of high seismic <span class="hlt">velocities</span> is located in the Mantle Transition zone beneath the Pannonian Basin, and is related to down-welling associated with an earlier phase of continental convergence in the Pannonian region. These results will be used in conjunction with 3D geodynamical modelling to help understand the geological evolution of this region. SCP working <span class="hlt">group</span>: G. Houseman, G. Stuart, Y. Ren, B. Dando, P. Lorinczi, School of Earth and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5867887','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5867887"><span id="translatedtitle">Synthetic RR Lyrae <span class="hlt">velocity</span> curves</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Liu, Tianxing Boston Univ., MA )</p> <p>1991-02-01</p> <p>An amplitude correlation between the pulsation <span class="hlt">velocity</span> curves and visual light curves of ab-type RR Lyrae stars is derived from a large number of RR Lyrae that have high-precision radial-<span class="hlt">velocity</span> and photometric data. Based on the determined AVp, AV ralation, a synthetic radial-<span class="hlt">velocity</span> curve for a typical ab-type RR Lyrae star is constructed. This would be of particular use in determining the systemic <span class="hlt">velocities</span> of RR Lyrae. 17 refs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.T51B1517N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.T51B1517N"><span id="translatedtitle">Ambient Noise <span class="hlt">Tomography</span> of the British Isles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nicolson, H. J.; Curtis, A.; Baptie, B.</p> <p>2009-12-01</p> <p>In recent years, surface wave <span class="hlt">tomography</span> using empirical Green’s functions computed via the ambient noise interferometry method has become an established approach to lithospheric imaging problems. To date, ambient noise <span class="hlt">tomography</span> has been successfully applied to seismometer arrays in the United States, Australia, Iceland, China, South Africa, Europe and the Tibetan Plateau. The basis of the ambient seismic interferometry method is that, by cross-correlating noise data between two seismic stations and stacking over a long enough time period, one can approximate the Green’s Function that would have been recorded at one of the stations if the other had actually been a source. Consequently, one of the main advantages of ambient noise interferometry is that traditional seismic sources such as earthquakes or ballistics are not required; therefore it is ideal for application to seismically quiescent areas such as the British Isles. The British Isles are an archipelago located adjacent to the Eurasian continental shelf in a typically intra-plate setting, formed by a complex amalgamation of several terranes. These range from Laurentian north of the Highland Boundary fault to Avalonian south of the Iapetus Suture and evidence of the regions turbulent geological past can be inferred from its lithospheric structure. Previous studies of the structure of the British Isles considered relatively few seismic stations and/or were limited to using offshore shots, quarry blasts or teleseismic earthquakes as seismic energy sources. We have applied the ambient noise <span class="hlt">tomography</span> method to noise data recorded on approximately 100 broadband and short period seismometers, including many new stations, in the British Isles and mainland Europe. This dense coverage of the British Isles allows us to image the crust and upper mantle <span class="hlt">velocity</span> structure with a horizontal resolution in the region of 100km across the North Sea and 30km in the mainland United Kingdom. Here we present the first</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.T51C2887M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.T51C2887M&link_type=ABSTRACT"><span id="translatedtitle">Rayleigh-wave <span class="hlt">Tomography</span> Study of Northwestern Canada</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McLellan, M. E.; Audet, P.; Schaeffer, A. J.</p> <p>2015-12-01</p> <p>Due to the ongoing collision of the Yakutat block with the North American plate in southeastern Alaska, a significant amount of deformation is occurring in the northern Canadian Cordillera. The stress transfer associated with the accretion of this terrane is believed to be responsible for the seismicity across this widespread region. Estimates of crustal thickness within the Mackenzie and Richardson Mountains provide constraints on models describing the evolution of crustal roots responsible for supporting such belts that transmit tectonic stresses over long distances (>1000 km); unfortunately, current seismic <span class="hlt">velocity</span> models used to map crustal thickness have limited resolution due to sparse coverage by seismograph networks. Here we use data from a new regional seismograph network (Yukon-Northwest Seismograph Network - YNSN) as well as permanent stations to map out crustal structure. Crustal thickness variations can be obtained from 3-D seismic <span class="hlt">velocity</span> models determined from the inversion of surface-wave dispersion data. In this work we present preliminary results of a regional <span class="hlt">tomography</span> study of northwestern Canada, encompassing the northern Canadian Cordillera, using dispersion curves derived from ambient noise cross-correlations in addition to teleseismic two-station interferometry. We collected all available vertical component seismic data from stations located in the Yukon and surrounding regions from the period between June 2012 and June 2015. Using this data set, we first cross-correlated hour-long segments of the ambient seismic noise between all available stations pairs that share common data availability and obtained virtual Rayleigh waves with energy over periods 10-50 s that are predominantly sensitive to crust and uppermost mantle structure. This data set is complemented by Rayleigh-wave dispersion measurements, spanning the period range 25—175 s, derived by cross-correlating vertical component data from teleseismic earthquakes (M>5) lying along</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19940033925&hterms=Michael+Brown&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DMichael%2BBrown','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19940033925&hterms=Michael+Brown&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DMichael%2BBrown"><span id="translatedtitle">The <span class="hlt">velocity</span> distribution of cometary hydrogen - Evidence for high <span class="hlt">velocities</span>?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brown, Michael E.; Spinrad, Hyron</p> <p>1993-01-01</p> <p>The Hamilton Echelle spectrograph on the 3-m Shane telescope at Lick Observatory was used to obtain high-<span class="hlt">velocity</span> and spatial resolution 2D spectra of H-alpha 6563-A emission in Comets Austin and Levy. The presence of the components expected from water dissociation and collisional thermalization in the inner coma is confirmed by the hydrogen <span class="hlt">velocity</span> distribution. In Comet Austin, the potential high-<span class="hlt">velocity</span> hydrogen includes <span class="hlt">velocities</span> of up to about 40 km/s and is spatially symmetric with respect to the nucleus. In Comet Levy, the high-<span class="hlt">velocity</span> hydrogen reaches <span class="hlt">velocities</span> of up to 50 km/s and is situated exclusively on the sunward side of the nucleus. The two distinct signatures of high-<span class="hlt">velocity</span> hydrogen imply two distinct sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T11C2457B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T11C2457B"><span id="translatedtitle">Isotropic Crustal <span class="hlt">Velocity</span> beneath Central Idaho/ Eastern Oregon using Ambient Seismic Noise</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bremner, P. M.; Panning, M. P.; Russo, R.; Mocanu, V. I.; Stanciu, A. C.; Torpey, M.; Hongsresawat, S.</p> <p>2013-12-01</p> <p>We present a new, high resolution isotropic crustal <span class="hlt">velocity</span> model beneath central Idaho and eastern Oregon. We produced the <span class="hlt">velocity</span> model from vertical component Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> measurements on data from the IDaho/ORegon (IDOR) Passive seismic network, 85 3-component broadband seismic stations, using ambient noise <span class="hlt">tomography</span> and the method of Gallego et. al (2010). We calculated inter-station <span class="hlt">group</span> <span class="hlt">velocities</span> in narrow frequency bands from travel-time measurements of the stacked cross-correlations (bandpass filtered between 2 and 30 seconds), which we used to invert for <span class="hlt">velocity</span> structure beneath the network. Goals of our work include refining models of crustal structure in the accreted Blue Mountain terranes in the western study area; determining the depth extent of the Salmon River Suture/ West Idaho Shear Zone (WISZ), which crosses north-south through the middle of the network; determining the architecture of the Idaho batholith, an extensive largely crustal derived pluton; and examining the nature of the autochthonous (?) North American crust and lithosphere beneath the batholith. We cross-correlated seismograms for each IDOR Passive station pair in 24 hr segments, and then band-passed, removed mean and trend, whitened, and progressively stacked these cross-correlated seismograms for the number of days of available data for each station pair. We made travel-time measurements in relative width, narrow frequency bands by picking the peak of the envelope of the stacked seismograms. To overcome the loss of temporal resolution in the narrow bands, we measured 1-sided cross-correlated seismograms made by adding the negative side to the positive side of the stacked seismograms, and multiplying by a step function. We derived Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocity</span> models for each frequency band using the least-squares inversion method of Tarantola (2005). We determined depth sensitivity of the various frequency bands from <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion curves. Similarly</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5602380','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5602380"><span id="translatedtitle">Computing field statics with the help of seismic <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>De Amorim, W.N.; Hubral, P.; Tygel, M.</p> <p>1987-10-01</p> <p>Field static corrections in general need be applied to all onshore seismic reflection data to eliminate the disturbing effects a weathering layer or near-surface low <span class="hlt">velocity</span> zone has on the continuity of deep seismic reflections. The traveltimes of waves refracted at the bottom of the low <span class="hlt">velocity</span> zone (or intermediate refracting interfaces) can often be observed as first breaks on shot records and used to develop a laterally inhomogeneous <span class="hlt">velocity</span> model for this layer, from which the field static corrections can then be obtained. A simple method is described for computing accurate field statics from first breaks. It is based on a linearization principal for traveltimes and leads to the algorithms that are widely and successfully applied within the framework of seismic <span class="hlt">tomography</span>. The authors refine an initial model for the low <span class="hlt">velocity</span> layer (estimated by a standard traveltime inversion technique) by minimizing the errors between the observed first arrivals on field records and those computed by ray theory through an initial model of the low <span class="hlt">velocity</span> layer. Thus, one can include more lateral <span class="hlt">velocity</span> variations within the low <span class="hlt">velocity</span> layers, which are important to obtain good field static corrections. Traditional first break traveltime inversion methods cannot, in general, provide such refined <span class="hlt">velocity</span> values. The technique is successfully applied to seismic data from the Amazon Basin. It is based on a simple model for the low <span class="hlt">velocity</span> layer that consists of an undulating earth surface and one planar horizontal refractor overlain by a laterally changing <span class="hlt">velocity</span> field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/869343','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/869343"><span id="translatedtitle">Unitaxial constant <span class="hlt">velocity</span> microactuator</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>McIntyre, Timothy J.</p> <p>1994-01-01</p> <p>A uniaxial drive system or microactuator capable of operating in an ultra-high vacuum environment. The mechanism includes a flexible coupling having a bore therethrough, and two clamp/pusher assemblies mounted in axial ends of the coupling. The clamp/pusher assemblies are energized by voltage-operated piezoelectrics therewithin to operatively engage the shaft and coupling causing the shaft to move along its rotational axis through the bore. The microactuator is capable of repeatably positioning to sub-manometer accuracy while affording a scan range in excess of 5 centimeters. Moreover, the microactuator generates smooth, constant <span class="hlt">velocity</span> motion profiles while producing a drive thrust of greater than 10 pounds. The system is remotely controlled and piezoelectrically driven, hence minimal thermal loading, vibrational excitation, or outgassing is introduced to the operating environment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014DPS....4630407S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014DPS....4630407S"><span id="translatedtitle">Phobos: Low <span class="hlt">Velocity</span> Impacts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smith, Heather; Lee, Pascal; Hamilton, Douglas</p> <p>2014-11-01</p> <p>Mars’s inner moon, Phobos, is located deep in the planet’s gravity well and orbits far below the planet’s synchronous orbit. Images of the surface of Phobos, in particular from Viking Orbiter 1, MGS, MRO, and MEX, reveal a rich collisional history, including fresh-looking impact craters and subdued older ones, very large impact structures (compared to the size of Phobos), such as Stickney, and much smaller ones.Sources of impactors colliding with Phobos include a priori: A) Impactors from outside the martian system (asteroids, comets, and fragments thereof); B) Impactors from Mars itself (ejecta from large impacts on Mars); and C) Impactors from Mars orbit, including impact ejecta launched from Deimos and ejecta launched from, and reintercepted by, Phobos. In addition to individual craters on Phobos, the networks of grooves on this moon have also been attributed in part or in whole to impactors from some of these sources, particularly B. We report the preliminary results of a systematic survey of the distribution, morphology, albedo, and color characteristics of fresh impact craters and associated ejecta deposits on Phobos. Considering that the different potential impactor sources listed above are expected to display distinct dominant compositions and different characteristic impact <span class="hlt">velocity</span> regimes, we identify specific craters on Phobos that are more likely the result of low <span class="hlt">velocity</span> impacts by impactors derived from Mars orbit than from any alternative sources. Our finding supports the hypothesis that the spectrally “Redder Unit” on Phobos may be a superficial veneer of accreted ejecta from Deimos, and that Phobos’s bulk might be distinct in composition from Deimos.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015A%26A...583A..52M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015A%26A...583A..52M"><span id="translatedtitle">Constraining cosmology with pairwise <span class="hlt">velocity</span> estimator</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ma, Yin-Zhe; Li, Min; He, Ping</p> <p>2015-11-01</p> <p>In this paper, we develop a full statistical method for the pairwise <span class="hlt">velocity</span> estimator previously proposed, and apply Cosmicflows-2 catalogue to this method to constrain cosmology. We first calculate the covariance matrix for line-of-sight <span class="hlt">velocities</span> for a given catalogue, and then simulate the mock full-sky surveys from it, and then calculate the variance for the pairwise <span class="hlt">velocity</span> field. By applying the 8315 independent galaxy samples and compressed 5224 <span class="hlt">group</span> samples from Cosmicflows-2 catalogue to this statistical method, we find that the joint constraint on Ωm0.6h and σ8 is completely consistent with the WMAP 9-year and Planck 2015 best-fitting cosmology. Currently, there is no evidence for the modified gravity models or any dynamic dark energy models from this practice, and the error-bars need to be reduced in order to provide any concrete evidence against/to support ΛCDM cosmology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUSM.S33A..03R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUSM.S33A..03R"><span id="translatedtitle">Crustal thickness beneath the Chaco-Parana basin, NE Argentina, from surface waves and ambient noise <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rosa, M.; Collaco, B.; Sanchez, G.; Assumpcao, M.; Sabbione, N.</p> <p>2013-05-01</p> <p>We present the results of a study of surface-wave dispersion data obtained by <span class="hlt">group</span> <span class="hlt">velocity</span> <span class="hlt">tomography</span>, using seismic data and ambient seismic noise correlation, for the region of the Chaco-Parana basin, a Neopaleozoic intracratonic basin, formed by a complex history of different processes of subsidence. Previous surface waves analysis (e.g., Feng et al., 2004, 2007; Snokes and James, 1997) estimated Moho depth in the central Chaco basin and a low-<span class="hlt">velocity</span> anomaly in the lithospheric mantle. However the seismic structure of the crust and upper mantle remains little characterized across the region due to the rather poor resolution, especially for the south region. The aim of this work is to improve the resolution and fidelity of crustal images obtained from traditional earthquake-based measurements. Hence, we have increased the number of <span class="hlt">group</span> <span class="hlt">velocity</span> measurements using data from regional earthquakes recorded at LPA (La Plata) station, Brazilian Seismic Network stations (BRASIS), permanent (GSN) and portable (BLSP) stations as well as inter-station dispersion curves derived from a dataset of seismic noise recordings from BRASIS, INPRES stations, LPA, CPUP and TRQA stations. The resulting path coverage is denser and displays a more uniform azimuthally distribution producing better tomographic images. The dispersion curves were obtained by a multiple filter technique (Dziewonski et al, 1969) using a phase-matched filter. A 2D <span class="hlt">group</span> <span class="hlt">velocity</span> tomographic inversion was performed, applying a conjugate-gradient method (Paige and Saunders, 1982). The <span class="hlt">group</span> <span class="hlt">velocity</span> maps for 10 to 120 seconds correspond very well to tectonic structures throughout the studied area and the resolution was improved in northern Argentina and southern Brazil by the better seismic ray coverage showing low-<span class="hlt">velocity</span> anomalies in the upper-mantle beneath the Chaco basin, compatible with other dispersion results. The new <span class="hlt">group</span> <span class="hlt">velocity</span> maps were inverted for S <span class="hlt">velocity</span> structures, using a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.5556M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.5556M"><span id="translatedtitle">Seismic <span class="hlt">velocity</span> estimation from wide-angle reflections in sediments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Majdanski, Mariusz</p> <p>2016-04-01</p> <p>Travel time inversion of wide-angle seismic data is well-known technique used in various scales. In specific case of the industrial profiling of a sedimentary layers, where rather flat structures with relatively small <span class="hlt">velocity</span> differences are observed, we propose an extension of standard reflection <span class="hlt">tomography</span> to wide-angle observations. In such conditions wide-angle reflections, and especially one observed at large angles, are dominant. They could be easily interpreted, and combined with observed refractions, gives precise estimation of <span class="hlt">velocities</span>. Such an interpretation is presented based on full spread geometry seismic recording of standard vibroseis sources performing regular reflection seismic works. In the result it was possible to precisely recognize the <span class="hlt">velocity</span> structure in layered media, and also perform its uncertainty analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011OPhy....9..926A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011OPhy....9..926A"><span id="translatedtitle"><span class="hlt">Velocity</span> and <span class="hlt">velocity</span> bounds in static spherically symmetric metrics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arraut, Ivan; Batic, Davide; Nowakowski, Marek</p> <p>2011-08-01</p> <p>We find simple expressions for <span class="hlt">velocity</span> of massless particles with dependence on the distance, r, in Schwarzschild coordinates. For massive particles these expressions give an upper bound for the <span class="hlt">velocity</span>. Our results apply to static spherically symmetric metrics. We use these results to calculate the <span class="hlt">velocity</span> for different cases: Schwarzschild, Schwarzschild-de Sitter and Reissner-Nordström with and without the cosmological constant. We emphasize the differences between the behavior of the <span class="hlt">velocity</span> in the different metrics and find that in cases with naked singularity there always exists a region where the massless particle moves with a <span class="hlt">velocity</span> greater than the <span class="hlt">velocity</span> of light in vacuum. In the case of Reissner-Nordström-de Sitter we completely characterize the <span class="hlt">velocity</span> and the metric in an algebraic way. We contrast the case of classical naked singularities with naked singularities emerging from metric inspired by noncommutative geometry where the radial <span class="hlt">velocity</span> never exceeds one. Furthermore, we solve the Einstein equations for a constant and polytropic density profile and calculate the radial <span class="hlt">velocity</span> of a photon moving in spaces with interior metric. The polytropic case of radial <span class="hlt">velocity</span> displays an unexpected variation bounded by a local minimum and maximum.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JVGR..289..130L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JVGR..289..130L"><span id="translatedtitle">Fall <span class="hlt">velocity</span> of multi-shaped clasts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Le Roux, Jacobus P.</p> <p>2014-12-01</p> <p>Accurate settling <span class="hlt">velocity</span> predictions of differently shaped micro- or macroclasts are required in many branches of science and engineering. Here, a single, dimensionally correct equation is presented that yields a significant improvement on previous settling formulas for a wide range of clast shapes. For smooth or irregular clasts with known axial dimensions, a partially polynomial equation based on the logarithmic values of dimensionless sizes and settling <span class="hlt">velocities</span> is presented, in which the values of only one coefficient and one exponent need to be adapted for different shapes, irrespective of the Reynolds number. For irregular, natural clasts with unknown axial dimensions, a polynomial equation of the same form is applied, but with different coefficients. Comparison of the predicted and measured settling <span class="hlt">velocities</span> of 8 different shape classes as well as natural grains with unknown axial dimensions in liquids, representing a total of 390 experimental data points, shows a mean percentage error of - 0.83% and a combined R2 value of 0.998. The settling data of 169 differently shaped particles of pumice, glass and feldspar falling in air were also analyzed, which demonstrates that the proposed equation is also valid for these conditions. Two additional shape classes were identified in the latter data set, although the resultant equations are less accurate than for liquids. An Excel spreadsheet is provided to facilitate the calculation of fall <span class="hlt">velocities</span> for grains settling individually and in <span class="hlt">groups</span>, or alternatively to determine the equivalent sieve size from the settling <span class="hlt">velocity</span>, which can be used to calibrate settling tubes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeoJI.197..630Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeoJI.197..630Z"><span id="translatedtitle">Upper crustal structure of central Java, Indonesia, from transdimensional seismic ambient noise <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zulfakriza, Z.; Saygin, E.; Cummins, P. R.; Widiyantoro, S.; Nugraha, A. D.; Lühr, B.-G.; Bodin, T.</p> <p>2014-04-01</p> <p>Delineating the crustal structure of central Java is crucial for understanding its complex tectonic setting. However, seismic imaging of the strong heterogeneity typical of such a tectonically active region can be challenging, particularly in the upper crust where <span class="hlt">velocity</span> contrasts are strongest and steep body wave ray paths provide poor resolution. To overcome these difficulties, we apply the technique of ambient noise <span class="hlt">tomography</span> (ANT) to data collected during the Merapi Amphibious Experiment (MERAMEX), which covered central Java with a temporary deployment of over 120 seismometers during 2004 May-October. More than 5000 Rayleigh wave Green's functions were extracted by cross-correlating the noise simultaneously recorded at available station pairs. We applied a fully non-linear 2-D Bayesian probabilistic inversion technique to the retrieved traveltimes. Features in the derived tomographic images correlate well with previous studies, and some shallow structures that were not evident in previous studies are clearly imaged with ANT. The Kendeng Basin and several active volcanoes appear with very low <span class="hlt">group</span> <span class="hlt">velocities</span>, and anomalies with relatively high <span class="hlt">velocities</span> can be interpreted in terms of crustal sutures and/or surface geological features.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930056415&hterms=dum&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Ddum','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930056415&hterms=dum&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Ddum"><span id="translatedtitle">Real <span class="hlt">group</span> <span class="hlt">velocity</span> in a medium with dissipation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Muschietti, L.; Dum, C. T.</p> <p>1993-01-01</p> <p>In order to clarify the role of the imaginary term Im(d(omega)/dk), the motion of a wave packet in a dissipative, homogeneous medium is examined. The integral representation of the packet is analyzed by means of a saddle-point method. It is shown that in a moving frame attached to its maximum the packet looks self-similar. A Gaussian packet keeps its Gaussian identity, as is typical for the case of a nondissipative medium. The central wave number of the packet slowly changes because of a different damping among the Fourier components. Simple 'ray-tracing equations' are derived to follow the packet centers in coordinate and Fourier spaces. The analysis is illustrated with a comparison to geometric optics, and with two applications: the case of a medium with some resonant damping (or growth) and the propagation of whistler waves in a collisional plasma.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoJI.tmp...45Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoJI.tmp...45Y"><span id="translatedtitle">Effect of earthquakes on ambient noise surface wave <span class="hlt">tomography</span> in upper mantle studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yanovskaya, Tatiana; Koroleva, Tatiana; Lyskova, Eugenia</p> <p>2016-03-01</p> <p>Application of the ambient noise surface wave <span class="hlt">tomography</span> method (ANT) for determination of the upper mantle structure requires data on long-periodic noise (T > 40 sec). The ANT technique implies that noise sources are distributed almost uniformly over the surface. This is practically true for short-periodic noise, however it is not so in the case of long periods. In this paper we show that the main contribution to noise at long periods is caused by signals from earthquakes. In some cases they may strongly distort noise cross-correlation. This leads to an incorrect determination of surface wave <span class="hlt">velocity</span> dispersion curves. To minimize such a distortion we propose two means: (1) to use records of noise for the periods when there is no clustering of earthquakes, such as aftershocks of strong events; (2) to stack cross-correlation functions for a period of at least three years in order to achieve sufficient uniformity of earthquake locations. Validity of this approach is demonstrated by ANT results for Europe. Tomographic reconstruction of Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocities</span> for 10-100 sec measured along interstation paths was carried out in a central part of Western Europe where resolving power of the data was the highest. Locally averaged dispersion curves were inverted to vertical S-wave <span class="hlt">velocity</span> sections in this area. The results correspond closely to known features of the structure of the region, namely: strong difference of the crust and upper mantle structure at the opposite sides from the Tornquist-Teisseyre Line down to ˜ 250 km, penetration of high <span class="hlt">velocity</span> material of EEP lithosphere under Carpathians, as well as penetration of low <span class="hlt">velocity</span> asthenospheric layer from the Carpathian region toward the northeast.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016GeoJI.205.1208Y&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016GeoJI.205.1208Y&link_type=ABSTRACT"><span id="translatedtitle">Effect of earthquakes on ambient noise surface wave <span class="hlt">tomography</span> in upper-mantle studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yanovskaya, Tatiana; Koroleva, Tatiana; Lyskova, Eugenia</p> <p>2016-05-01</p> <p>Application of the ambient noise surface wave <span class="hlt">tomography</span> method (ANT) for determination of the upper-mantle structure requires data on long-periodic noise (T > 40 s). The ANT technique implies that noise sources are distributed almost uniformly over the surface. This is practically true for short-periodic noise, however, it is not so in the case of long periods. In this paper we show that the main contribution to noise at long periods is caused by signals from earthquakes. In some cases, they may strongly distort noise cross-correlation. This leads to an incorrect determination of surface wave <span class="hlt">velocity</span> dispersion curves. To minimize such a distortion we propose two means: (1) to use records of noise for the periods when there is no clustering of earthquakes, such as aftershocks of strong events; (2) to stack cross-correlation functions for a period of at least three years in order to achieve sufficient uniformity of earthquake locations. Validity of this approach is demonstrated by ANT results for Europe. Tomographic reconstruction of Rayleigh wave <span class="hlt">group</span> <span class="hlt">velocities</span> for 10-100 s measured along interstation paths was carried out in a central part of Western Europe where resolving power of the data was the highest. Locally averaged dispersion curves were inverted to vertical S-wave <span class="hlt">velocity</span> sections in this area. The results correspond closely to known features of the structure of the region, namely: strong difference of the crust and upper-mantle structure at the opposite sides from the Tornquist-Teisseyre Line down to ˜ 250 km, penetration of high-<span class="hlt">velocity</span> material of East European Platform lithosphere under Carpathians, as well as penetration of low-<span class="hlt">velocity</span> asthenospheric layer from the Carpathian region towards the northeast.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930033803&hterms=Angular+velocity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DTitle%26N%3D0%26No%3D10%26Ntt%3DAngular%2Bvelocity','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930033803&hterms=Angular+velocity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DTitle%26N%3D0%26No%3D10%26Ntt%3DAngular%2Bvelocity"><span id="translatedtitle">Factors influencing perceived angular <span class="hlt">velocity</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kaiser, Mary K.; Calderone, Jack B.</p> <p>1991-01-01</p> <p>Angular <span class="hlt">velocity</span> perception is examined for rotations both in depth and in the image plane and the influence of several object properties on this motion parameter is explored. Two major object properties are considered, namely, texture density which determines the rate of edge transitions for rotations in depth, i.e., the number of texture elements that pass an object's boundary per unit of time, and object size which determines the tangential linear <span class="hlt">velocities</span> and 2D image <span class="hlt">velocities</span> of texture elements for a given angular <span class="hlt">velocity</span>. Results of experiments show that edge-transition rate biased angular <span class="hlt">velocity</span> estimates only when edges were highly salient. Element <span class="hlt">velocities</span> had an impact on perceived angular <span class="hlt">velocity</span>; this bias was associated with 2D image <span class="hlt">velocity</span> rather than 3D tangential <span class="hlt">velocity</span>. Despite these biases judgements were most strongly determined by the true angular <span class="hlt">velocity</span>. Sensitivity to this higher order motion parameter appeared to be good for rotations both in depth (y-axis) and parallel to the line of sight (z-axis).</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015PhDT.......227L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015PhDT.......227L&link_type=ABSTRACT"><span id="translatedtitle">Innovations in seismic <span class="hlt">tomography</span>, their applications and induced seismic events in carbon sequestration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Peng</p> <p></p> <p>This dissertation presents two innovations in seismic <span class="hlt">tomography</span> and a new discovery of induced seismic events associated with CO2 injection at an Enhanced Oil Recovery (EOR) site. The following are brief introductions of these three works. The first innovated work is adaptive ambient seismic noise <span class="hlt">tomography</span> (AANT). Traditional ambient noise <span class="hlt">tomography</span> methods using regular grid nodes are often ill posed because the inversion grids do not always represent the distribution of ray paths. Large grid spacing is usually used to reduce the number of inversion parameters, which may not be able to solve for small-scale <span class="hlt">velocity</span> structure. We present a new adaptive <span class="hlt">tomography</span> method with irregular grids that provides a few advantages over the traditional methods. First, irregular grids with different sizes and shapes can fit the ray distribution better and the traditionally ill-posed problem can become more stable owing to the different parameterizations. Second, the data in the area with dense ray sampling will be sufficiently utilized so that the model resolution can be greatly improved. Both synthetic and real data are used to test the newly developed <span class="hlt">tomography</span> algorithm. In synthetic data tests, we compare the resolution and stability of the traditional and adaptive methods. The results show that adaptive <span class="hlt">tomography</span> is more stable and performs better in improving the resolution in the area with dense ray sampling. For real data, we extract the ambient noise signals of the seismic data near the Garlock Fault region, obtained from the Southern California Earthquake Data Center. The resulting <span class="hlt">group</span> <span class="hlt">velocity</span> of Rayleigh waves is well correlated with the geological structures. High <span class="hlt">velocity</span> anomalies are shown in the cold southern Sierra Nevada, the Tehachapi Mountains and the Western San Gabriel Mountains. The second innovated work is local earthquake <span class="hlt">tomography</span> with full topography (LETFT). In this work, we develop a new three-dimensional local earthquake <span class="hlt">tomography</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT.......227L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT.......227L"><span id="translatedtitle">Innovations in seismic <span class="hlt">tomography</span>, their applications and induced seismic events in carbon sequestration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Peng</p> <p></p> <p>This dissertation presents two innovations in seismic <span class="hlt">tomography</span> and a new discovery of induced seismic events associated with CO2 injection at an Enhanced Oil Recovery (EOR) site. The following are brief introductions of these three works. The first innovated work is adaptive ambient seismic noise <span class="hlt">tomography</span> (AANT). Traditional ambient noise <span class="hlt">tomography</span> methods using regular grid nodes are often ill posed because the inversion grids do not always represent the distribution of ray paths. Large grid spacing is usually used to reduce the number of inversion parameters, which may not be able to solve for small-scale <span class="hlt">velocity</span> structure. We present a new adaptive <span class="hlt">tomography</span> method with irregular grids that provides a few advantages over the traditional methods. First, irregular grids with different sizes and shapes can fit the ray distribution better and the traditionally ill-posed problem can become more stable owing to the different parameterizations. Second, the data in the area with dense ray sampling will be sufficiently utilized so that the model resolution can be greatly improved. Both synthetic and real data are used to test the newly developed <span class="hlt">tomography</span> algorithm. In synthetic data tests, we compare the resolution and stability of the traditional and adaptive methods. The results show that adaptive <span class="hlt">tomography</span> is more stable and performs better in improving the resolution in the area with dense ray sampling. For real data, we extract the ambient noise signals of the seismic data near the Garlock Fault region, obtained from the Southern California Earthquake Data Center. The resulting <span class="hlt">group</span> <span class="hlt">velocity</span> of Rayleigh waves is well correlated with the geological structures. High <span class="hlt">velocity</span> anomalies are shown in the cold southern Sierra Nevada, the Tehachapi Mountains and the Western San Gabriel Mountains. The second innovated work is local earthquake <span class="hlt">tomography</span> with full topography (LETFT). In this work, we develop a new three-dimensional local earthquake <span class="hlt">tomography</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980203096','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980203096"><span id="translatedtitle">Particle <span class="hlt">Velocity</span> Measuring System</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Arndt, G. Dickey (Inventor); Carl, James R. (Inventor)</p> <p>1998-01-01</p> <p>Method and apparatus are provided for determining the <span class="hlt">velocity</span> of individual food particles within a liquid/solid food mixture that is cooked by an aseptic cooking method whereby the food mixture is heated as it flows through a flowline. At least one upstream and at least one downstream microwave transducer are provided to determine the minimum possible travel time of the fastest food particle through the flowline. In one embodiment, the upstream detector is not required. In another embodiment, a plurality of small dipole antenna markers are secured to a plurality of food particles to provide a plurality of signals as the markers pass the upstream and downstream transducers. The dipole antenna markers may also include a non-linear element to reradiate a harmonic frequency of a transmitter frequency. Upstream and downstream transducers include dipole antennas that are matched to the impedance of the food slurry and a signal transmission cable by various impedance matching means including unbalanced feed to the antennas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012EGUGA..1414350H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012EGUGA..1414350H&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Velocity</span> dependant splash behaviour</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hamlett, C. A. E.; Shirtcliffe, N. J.; McHale, G.; Ahn, S.; Doerr, S. H.; Bryant, R.; Newton, M. I.</p> <p>2012-04-01</p> <p>Extreme soil water repellency can occur in nature via condensation of volatile organic compounds released during wildfires and can lead to increased erosion rate. Such extreme water repellent soil can be classified as superhydrophobic and shares similar chemical and topographical features to specifically designed superhydrophobic surfaces. Previous studies using high speed videography to investigate single droplet impact behaviour on artificial superhydrophobic have revealed three distinct modes of splash behaviour (rebound, pinned and fragmentation) which are dependent on the impact <span class="hlt">velocity</span> of the droplet. In our studies, using high-speed videography, we show that such splash behaviour can be replicated on fixed 'model' water repellent soils (hydrophobic glass beads/particles). We show that the type of splash behaviour is dependent on both the size and chemical nature of the fixed particles. The particle shape also influences the splash behaviour as shown by drop impact experiments on fixed sand samples. We have also studied soil samples, as collected from the field, which shows that the type of droplet splash behaviour can lead to enhanced soil particle transport.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/288380','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/288380"><span id="translatedtitle">Metallic glass <span class="hlt">velocity</span> sensor</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Butler, J.L.; Butler, S.C.; Massa, D.P.; Cavanagh, G.H.</p> <p>1996-04-01</p> <p>A metallic glass accelerometer has been developed for use as an underwater sound <span class="hlt">velocity</span> sensor. The device uses the metallic glass material Metglas 2605SC which has been processed to achieve a virgin coupling coefficient of 0.96. The mechanical to electrical conversion is based on the detection of the change in the inductance of the device as a result of bending motion. The detection method uses a carrier frequency signal which is amplitude modulated by the received signal. This scheme was originally described by Wun-Fogle, Savage and Clark [{open_quote}{open_quote}Sensitive wide frequency range magnetostrictive strain gauge,{close_quote}{close_quote} Sensors and Actuators, 1{underscore}2{underscore}, 323{endash}331 (1987)]. The bender is in the form of a three layered laminate with a closed magnetic path window frame structure. The theory of operation along with measured and calculated results are presented for a prototype element with approximate dimensions 1.5{times}1.0{times}0.1 inches. Calculated and measured results agree for a reduced effective coupling coefficient of 0.72 and operation with a carrier field intensity of 0.87 Oe and carrier frequency of 20 kHz. {copyright} {ital 1996 American Institute of Physics.}</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1245828','SCIGOV-DOEDE'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1245828"><span id="translatedtitle">Hydrokinetic canal measurements: inflow <span class="hlt">velocity</span>, wake flow <span class="hlt">velocity</span>, and turbulence</span></a></p> <p><a target="_blank" href="http://www.osti.gov/dataexplorer">DOE Data Explorer</a></p> <p>Gunawan, Budi</p> <p>2014-06-11</p> <p>The dataset consist of acoustic Doppler current profiler (ADCP) <span class="hlt">velocity</span> measurements in the wake of a 3-meter diameter vertical-axis hydrokinetic turbine deployed in Roza Canal, Yakima, WA, USA. A normalized hub-centerline wake <span class="hlt">velocity</span> profile and two cross-section <span class="hlt">velocity</span> contours, 10 meters and 20 meters downstream of the turbine, are presented. Mean <span class="hlt">velocities</span> and turbulence data, measured using acoustic Doppler velocimeter (ADV) at 50 meters upstream of the turbine, are also presented. Canal dimensions and hydraulic properties, and turbine-related information are also included.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFM.S61A1089B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFM.S61A1089B"><span id="translatedtitle">Surface-Wave <span class="hlt">Tomography</span> in Fennoscandia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bruneton, M.; Pedersen, H. A.; Farra, V.</p> <p>2002-12-01</p> <p>We developed a technique based on paraxial ray tracing to obtain 2D phase-<span class="hlt">velocity</span> maps as a function of frequency which can subsequently be inverted for the 3D structure. The major improvement of our method compared to previous ray tracing studies is that we jointly invert for the <span class="hlt">velocity</span> model under the array and the shape of incoming wave fronts, therefore reducing artifacts due to structure outside the study region. The stabilisation of the inversion was performed by imposing a smoothness criteria to the wavefronts and to the phase-<span class="hlt">velocity</span> map. The method was applied to data from the SVEKALAPKO deep seismic experiment, where the central part of the Baltic Shield, in southern Finland, was covered by a regular two-dimensional grid of 46 broad-band stations which operated for six to eight months. This exceptional stations distribution offers the possibility to undertake a high precision surface-wave <span class="hlt">tomography</span>. P-wave and surface-wave <span class="hlt">tomography</span> are complementary as the latter one gives an image of absolute shear-wave velocites with a relatively good vertical resolution. We first selected 69 high quality events with the best possible azimuthal distribution. The arrival times of the fundamental-mode Rayleigh waves as a function of frequency were measured using Wiener filtering. A selection of the data was performed using a minimum signal to noise ratio of 4 and a minimum coherency of 0.95 between the signals recorded by different stations. To obtain an average dispersion curve for the region between 10 and 200 seconds we inverted the data imposing the phase-<span class="hlt">velocity</span> to be quasi constant. This dispersion curve was subsequently inverted for the average shear-wave <span class="hlt">velocity</span> structure as a function of depth. This average structure shows a lithospheric mantle faster than global average models at all resolved depths. The inversion of the same data set was also conducted using weaker constraints to obtain the lateral variations of the phase-<span class="hlt">velocity</span> at each frequency</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26757065','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26757065"><span id="translatedtitle">Coordination pattern of baseball pitching among young pitchers of various ages and <span class="hlt">velocity</span> levels.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Hsiu-Hui; Liu, Chiang; Yang, Wen-Wen</p> <p>2016-09-01</p> <p>This study compared the whole-body movement coordination of pitching among 72 baseball players of various ages and <span class="hlt">velocity</span> levels. Participants were classified as senior, junior, and little according to their age, with each <span class="hlt">group</span> comprising 24 players. The <span class="hlt">velocity</span> levels of the high-<span class="hlt">velocity</span> (the top eight) and low-<span class="hlt">velocity</span> (the lowest eight) <span class="hlt">groups</span> were classified according to their pitching <span class="hlt">velocity</span>. During pitching, the coordinates of 15 markers attached to the major joints of the whole-body movement system were collected for analysis. Sixteen kinematic parameters were calculated to compare the <span class="hlt">groups</span> and <span class="hlt">velocity</span> levels. Principal component analysis (PCA) was conducted to quantify the coordination pattern of pitching movement. The results were as follows: (1) five position and two <span class="hlt">velocity</span> parameters significantly differed among the age <span class="hlt">groups</span>, and two position and one <span class="hlt">velocity</span> parameters significantly differed between the high- and low-<span class="hlt">velocity</span> <span class="hlt">groups</span>. (2) The coordination patterns of pitching movement could be described using three components, of which the eigenvalues and contents varied according to age and <span class="hlt">velocity</span> level. In conclusion, the senior and junior players showed greater elbow angular <span class="hlt">velocity</span>, whereas the little players exhibited a wider shoulder angle only at the beginning of pitching. The players with high <span class="hlt">velocity</span> exhibited higher trunk and shoulder rotation <span class="hlt">velocity</span>. The variations among <span class="hlt">groups</span> found using PCA and kinematics parameter analyses were consistent. PMID:26757065</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27282455','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27282455"><span id="translatedtitle">Differences of bone mineral mass, volumetric bone mineral density, geometrical and structural parameters and derived strength of the tibia between premenopausal and postmenopausal women of different age <span class="hlt">groups</span>: a peripheral Quantitative Computed <span class="hlt">Tomography</span> (pQCT) study.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Stathopoulos, K D; Zoubos, A B; Papaioannou, N A; Mastrokalos, D; Galanos, A; Papagelopoulos, P J; Skarantavos, G</p> <p>2016-01-01</p> <p>Menopause constitutes a significant cause of bone loss, and it is currently debated whether bone mass is preserved or begins to decline substantially before that time in women. We used pQCT of the tibia to estimate differences of bone mineral mass, bone geometry and derived strength between premenopausal and postmenopausal Caucasian women of different age-<span class="hlt">groups</span> per decade of age (20-79y). For each individual, we assessed total, trabecular and cortical bone mineral content (BMC, mg) and volumetric bone mineral density (BMD, mg/cm3); total and cortical cross-sectional areas (CSA, mm2); periosteal circumference (PERI_C, mm); endosteal circumference (ENDO_C, mm); mean cortical thickness (CRT_THK, mm); and Stress-Strain Index (SSI) . Comparisons were made both between premenopausal (N=84) and postmenopausal (N=231) women as distinct <span class="hlt">groups</span>, and among women of the different age-<span class="hlt">groups</span>. Our results indicated that premenopausal women had significantly higher trabecular and cortical BMC and vBMD, with higher cortical CSA, CRT_THK and SSI than postmenopausal women. Moreover, significant differences of trabecular but not cortical BMC, vBMD or SSI were found between women of the younger (<48y) age-<span class="hlt">groups</span>. PERI_C, ENDO_C displayed lower values in the 20-29y <span class="hlt">group</span> and higher values in the 70-79y <span class="hlt">group</span>, denoting significant differences of bone geometry with aging. PMID:27282455</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JOpt...18g5601S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JOpt...18g5601S&link_type=ABSTRACT"><span id="translatedtitle">Improving image quality in intensity-interferometric spectral-domain optical coherence <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shirai, Tomohiro</p> <p>2016-07-01</p> <p>Intensity-interferometric spectral-domain optical coherence <span class="hlt">tomography</span> (I-SD-OCT), devised recently as a classical analog of quantum OCT, enables axially scanless cross-sectional imaging with an immunity to <span class="hlt">group-velocity</span> dispersion and a factor-of-\\sqrt{2} resolution improvement. However, unwanted artifacts inevitably emerge in the resultant image. In this paper, it is demonstrated theoretically and experimentally that such artifacts can be reduced without any difficulty by means of either a mechanical displacement of the detector for capturing spectral intensity patterns or a numerical displacement of the spectral intensity patterns stored in a computer. Furthermore, it is proved that the I-SD-OCT signal can be extracted from the conventional SD-OCT setup under a certain condition. These two features serve to improve the image quality in I-SD-OCT.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.S41B2741V&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.S41B2741V&link_type=ABSTRACT"><span id="translatedtitle">Crustal structure of the Iberian Peninsula and surrounding regions from ambient noise <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Villasenor, A.</p> <p>2015-12-01</p> <p>We present new high-resolution images of the crust in the Iberian Peninsula and surrounding regions using seismic ambient noise. We have compiled continuous recordings of all permanent broadband stations and temporary experiments in the region (IberArray, WILAS, PYROPE, PICASSO) from 2007 to 2014. This dataset consists of more than 400 broadband stations, although not all of them were operating simultaneously. We cross-correlate the three components these continuous recordings between all station pairs to obtain empirical Green's functions (EFGs). From these EGFs we measure <span class="hlt">group</span> and phase <span class="hlt">velocities</span> of the fundamental mode Rayleigh and Love waves, and also obtain estimates of Rayleigh wave ellipticity. We then perform a 2D tomographic inversion of the dispersion measurements to obtain phase and <span class="hlt">group</span> <span class="hlt">velocity</span> maps of Rayleigh and Love waves for periods from 4 to 40 seconds. The short period dispersion and ellipticity maps show excellent correlation with surface features (i.e. sedimentary basins, internal zones of mountain ranges, and stable regions), while maps for longer periods are a good proxy for crustal thickness. Due to the high station density of the dataset used we are able to image the entire Iberian Peninsula with unprecedented resolution, resolving small scale structures such as the West Alboran and Lower Tagus basins, the high anomaly associated with the Ronda-Beni Bousera peridotites, etc. We also investigate the existence of azimuthal anisotropy of Rayleigh wave <span class="hlt">velocities</span> as a function of period (i.e. depth) . Given the good correlation of the new dispersion maps with gravity anomalies, estimates of crustal thickness from receiver functions, and P-wave <span class="hlt">velocities</span> from local earthquake <span class="hlt">tomography</span>, our ultimate objective is to obtain an integrated model of shear-wave structure that fits all these datasets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.T53B0480P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.T53B0480P"><span id="translatedtitle">High Resolution <span class="hlt">Velocity</span> Structure in Eastern Turkey</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pasyanos, M. E.; Gok, R.; Zor, E.; Walter, W. R.</p> <p>2004-12-01</p> <p>We investigate the crust and upper mantle structure of eastern Turkey where the Anatolian, Arabian and Eurasian Plates meet, forming a complex tectonic regime. The Bitlis suture is a continental collision zone between the Anatolian plateau and the Arabian plate. Broadband data available through the Eastern Turkey Seismic Experiment (ETSE) provide a unique opportunity for studying the high resolution <span class="hlt">velocity</span> structure of the region. Zor et al. (2003) found an average 46 km thick crust in the Anatolian plateau using a six-layered grid search inversion of the ETSE receiver functions. Receiver functions are sensitive to the <span class="hlt">velocity</span> contrast of interfaces and the relative travel time of converted and reverberated waves between those interfaces. The interpretation of receiver functions alone, however, may result in an apparent depth-<span class="hlt">velocity</span> trade-off [Ammon et al., 1990]. In order to improve upon this <span class="hlt">velocity</span> model, we have combined the receiver functions with surface wave data using the joint inversion method of Julia et al. (2000). In this technique, the two sets of observations are combined into a single algebraic equation and each data set is weighted by an estimate of the uncertainty in the observations. The receiver functions are calculated using an iterative time-domain deconvolution technique. We also consider azimuthal changes in the receiver functions and have stacked them into different <span class="hlt">groups</span> accordingly. We are improving our surface wave model by making Love and Rayleigh dispersion measurements at the ETSE stations and incorporating them into a regional <span class="hlt">group</span> <span class="hlt">velocity</span> model for periods between 10 and 100 seconds. Preliminary results indicate a strong trend in the long period <span class="hlt">group</span> <span class="hlt">velocities</span> toward the northeast, indicating slow upper mantle <span class="hlt">velocities</span> in the area consistent with Pn, Sn and receiver function results. Starting models used for the joint inversions include both a 1-D model from a 12-ton dam shot recorded by ETSE [Gurbuz et al., 2004] and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.9371A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.9371A"><span id="translatedtitle">Application of Ambient Noise Array <span class="hlt">Tomography</span> on Geotechnical Scales and Comparison with Independent Geophysical Information: A Test for the Thessaloniki Area (Northern Greece)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anthymidis, Marios; Papazachos, Costas; Savvaidis, Alexandros; Theodoulidis, Nikos; Fikos, Ilias</p> <p>2015-04-01</p> <p>Ambient noise array <span class="hlt">tomography</span> has been recently recognized as a promising tool for the study of the shallow 2D/3D geophysical structure. The method basis relies on the implementation of cross-correlation analysis on ambient noise data, which is able to provide the Green's Function of the medium between two spatially separated recording stations (Gouedard et al. 2008). The obtained cross-correlation trace contains information about the <span class="hlt">group</span> and phase <span class="hlt">velocity</span> of the surface waves that are dominant in the ambient noise wavefield. A typical application, similar to larger-scale studies, employs appropriate narrow-band Gaussian filters on the cross-correlation trace (Multiple Filter Analysis), allowing the construction of the <span class="hlt">group</span> <span class="hlt">velocity</span> dispersion curves for selected paths within the study area. An inversion procedure leads to tomographic images (<span class="hlt">group</span> <span class="hlt">velocity</span> maps for specific frequencies), which can be locally inverted to derive 1D shear wave (S-Wave) <span class="hlt">velocity</span> profiles. The superposition of all the local 1D S-Wave <span class="hlt">velocity</span> profiles can potentially lead to a pseudo-3D (or pseudo-2D) <span class="hlt">velocity</span> model for the subsurface structure. In order to study the capability of the ambient noise array <span class="hlt">tomography</span> method to provide reliable geophysical ground models on geotechnical scales in urban environments, a relative small circular array (radius of 500m approximately) incorporating 34 recording stations was installed inside the city of Thessaloniki (Northern Greece). The study area corresponds to the boundary between the geological bedrock and Quaternary/Neogene sediments, with the gneiss bedrock showing a gradual thickness increase from its NE outcrop towards the SW, to the coastline of the city. Large-scale studies in the broader Thessaloniki area (e.g. Anastasiadis et al. 2001, Panou et al. 2005) have showed that the bedrock exhibits a more or less 2D structure in the study area, gradually dipping towards the coastline realizing depths possibly exceeding 200m. Furthermore</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NJPh...18c3024G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NJPh...18c3024G"><span id="translatedtitle">Practical Bayesian <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Granade, Christopher; Combes, Joshua; Cory, D. G.</p> <p>2016-03-01</p> <p>In recent years, Bayesian methods have been proposed as a solution to a wide range of issues in quantum state and process <span class="hlt">tomography</span>. State-of-the-art Bayesian <span class="hlt">tomography</span> solutions suffer from three problems: numerical intractability, a lack of informative prior distributions, and an inability to track time-dependent processes. Here, we address all three problems. First, we use modern statistical methods, as pioneered by Huszár and Houlsby (2012 Phys. Rev. A 85 052120) and by Ferrie (2014 New J. Phys. 16 093035), to make Bayesian <span class="hlt">tomography</span> numerically tractable. Our approach allows for practical computation of Bayesian point and region estimators for quantum states and channels. Second, we propose the first priors on quantum states and channels that allow for including useful experimental insight. Finally, we develop a method that allows tracking of time-dependent states and estimates the drift and diffusion processes affecting a state. We provide source code and animated visual examples for our methods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950040646&hterms=dark+matter+galaxy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Ddark%2Bmatter%2Bgalaxy','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950040646&hterms=dark+matter+galaxy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Ddark%2Bmatter%2Bgalaxy"><span id="translatedtitle"><span class="hlt">Velocity</span> correlations of galaxy clusters</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cen, Renyue; Bahcall, Neta A.; Gramann, Mirt</p> <p>1994-01-01</p> <p>We determine the <span class="hlt">velocity</span> correlation function, pairwise peculiar <span class="hlt">velocity</span> difference, and rms pairwise peculiar <span class="hlt">velocity</span> dispersion of rich clusters of galaxies, as a function of pair separation, for three cosmological models: Omega = 1 and Omega = 0.3 cold dark matter (CDM), and Omega = 0.3 primeval baryonic isocurvature (PBI) models (all flat and Cosmic Background Explorer (COBE)-normalized). We find that close cluster pairs, with separation r is less than or equal to 10/h Mpc, exhibit strong attractive peculiar <span class="hlt">velocities</span> in all models; the cluster pairwise <span class="hlt">velocities</span> depend sensitively on the model. The mean pairwise attractive <span class="hlt">velocity</span> of clusters on 5/h Mpc scale ranges from approximately 1700 km/s for Omega = 1 CDM to approximately 1000 km/s for PBI to approximately 700 km/s for Omega = 0.3 CDM. The small-scale pairwise <span class="hlt">velocities</span> depend also on cluster mass: richer, more massive clusters exhibit stronger attractive <span class="hlt">velocities</span> than less massive clusters. On large scales, from approximately 20 to 200/h Mpc, the cluster peculiar <span class="hlt">velocities</span> are increasingly dominated by bulk and random motions; they are independent of cluster mass. The cluster <span class="hlt">velocity</span> correlation function is negative on small scales for Omega = 1 and Omega = 0.3 CDM, indicating strong pairwise motion relative to bulk motion on small scales; PBI exhibits relatively larger bulk motions. The cluster <span class="hlt">velocity</span> correlation function is positive on very large scales, from r approximately 10/h Mpc to r approximately 200/h Mpc, for all models. These positive correlations, which decrease monotonically with scale, indicate significant bulk motions of clusters up to approximately 200/h Mpc. The strong dependence of the cluster <span class="hlt">velocity</span> functions on models, especially at small separations, makes them useful tools in constraining cosmological models when compared with observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUSM.S31A..01C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUSM.S31A..01C"><span id="translatedtitle">Crustal Structure of the Paraná Basin from Ambient Noise <span class="hlt">Tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Collaco, B.; Rosa, M.; Sanchez, G.; Assumpcao, M.</p> <p>2013-05-01</p> <p>Previous surface-wave <span class="hlt">tomography</span> in South America (e.g., Feng et al., 2004; 2007) mapped the main large-scale features of the continent, such as the high lithospheric <span class="hlt">velocities</span> in cratonic areas and low <span class="hlt">velocities</span> in the Patagonian province. However, more detailed features such as the Chaco and Paraná Basins have not been mapped with good resolution because of poor path coverage. This work is part of a major project to increase knowledge of crustal structure in Southern Brazil and Eastern Argentina, carried out by IAG-USP (Brazil) in collaboration with UNLP and INPRES (Argentina). To improve resolution for the Paraná Basin we used inter-station dispersion curves derived from correlation of ambient noise for new stations deployed with the implementation of the Brazilian Seismic Network (Pirchiner et al. 2011). Ambient noise <span class="hlt">tomography</span> (ANT), was first applied by Shapiro et al. (2005) and is now expanding rapidly, especially in areas with high density of seismic stations (e.g. Bensen et al. 2007, Lin et al. 2008, Moschetti et al. 2010). ANT is a well-established method to estimate short period (< 20s) and intermediate periods (20 - 50s) surface wave speeds both in regional or continental scales (Lin et al. 2008). The ambient noise data was processed as described by Bensen et al. 2007, in four major steps, with addition of a final data inversion step. <span class="hlt">Group</span> <span class="hlt">velocities</span> between pairs of stations were derived from correlation of ambient noise in the period range 5 to 60 s. We used nearly two years of continuous data from INPRES broadband stations, LPA station in La Plata, CPUP in Paraguay, and the recently deployed Brazilian stations in southern Brazil. The dispersion curves were measured with a modified version of PGSWMFA (PGplot Surface Wave Multiple Filter Analysis) code, designed by Chuck Ammon (St. Louis University) and successfully applied by Pasyanos et al. (2001). Our modified version is no more event based and is working now with station pairs. For the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21366931','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21366931"><span id="translatedtitle"><span class="hlt">Velocity</span> Dispersions Across Bulge Types</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fabricius, Maximilian; Bender, Ralf; Hopp, Ulrich; Saglia, Roberto; Drory, Niv; Fisher, David</p> <p>2010-06-08</p> <p>We present first results from a long-slit spectroscopic survey of bulge kinematics in local spiral galaxies. Our optical spectra were obtained at the Hobby-Eberly Telescope with the LRS spectrograph and have a <span class="hlt">velocity</span> resolution of 45 km/s (sigma*), which allows us to resolve the <span class="hlt">velocity</span> dispersions in the bulge regions of most objects in our sample. We find that the <span class="hlt">velocity</span> dispersion profiles in morphological classical bulge galaxies are always centrally peaked while the <span class="hlt">velocity</span> dispersion of morphologically disk-like bulges stays relatively flat towards the center--once strongly barred galaxies are discarded.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70020207','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70020207"><span id="translatedtitle">Nonlinear refraction and reflection travel time <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Zhang, Jiahua; ten Brink, U.S.; Toksoz, M.N.</p> <p>1998-01-01</p> <p>We develop a rapid nonlinear travel time <span class="hlt">tomography</span> method that simultaneously inverts refraction and reflection travel times on a regular <span class="hlt">velocity</span> grid. For travel time and ray path calculations, we apply a wave front method employing graph theory. The first-arrival refraction travel times are calculated on the basis of cell <span class="hlt">velocities</span>, and the later refraction and reflection travel times are computed using both cell <span class="hlt">velocities</span> and given interfaces. We solve a regularized nonlinear inverse problem. A Laplacian operator is applied to regularize the model parameters (cell slownesses and reflector geometry) so that the inverse problem is valid for a continuum. The travel times are also regularized such that we invert travel time curves rather than travel time points. A conjugate gradient method is applied to minimize the nonlinear objective function. After obtaining a solution, we perform nonlinear Monte Carlo inversions for uncertainty analysis and compute the posterior model covariance. In numerical experiments, we demonstrate that combining the first arrival refraction travel times with later reflection travel times can better reconstruct the <span class="hlt">velocity</span> field as well as the reflector geometry. This combination is particularly important for modeling crustal structures where large <span class="hlt">velocity</span> variations occur in the upper crust. We apply this approach to model the crustal structure of the California Borderland using ocean bottom seismometer and land data collected during the Los Angeles Region Seismic Experiment along two marine survey lines. Details of our image include a high-<span class="hlt">velocity</span> zone under the Catalina Ridge, but a smooth gradient zone between. Catalina Ridge and San Clemente Ridge. The Moho depth is about 22 km with lateral variations. Copyright 1998 by the American Geophysical Union.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27.2733B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27.2733B"><span id="translatedtitle">Surface-wave <span class="hlt">Tomography</span> In Fennoscandia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bruneton, M.; Pedersen, H. A.; Farra, V.; Sstwg</p> <p></p> <p>During the SVEKALAPKO deep seismic experiment, the central part of the Baltic Shield, in southern Finland, was covered by a two-dimensional regular grid of 45 broad-band stations, which operated for six to eight months. This exceptional stations distribution offers the possibility to undertake a high precision surface-wave tomogra- phy. P-wave and surface-wave <span class="hlt">tomography</span> are complementary as the later one gives an image in shear-wave <span class="hlt">velocity</span> with a better vertical resolution. The first step of interpreting the surface-waves data set consists of calculating the best 1D model. We selected 26 high quality events and for each one we fit a dispersive plane wave to the measured arrival times of the fundamental mode Rayleigh wave recorded by all stations of the array. The output of this procedure is the average phase-<span class="hlt">velocity</span> dispersion curve. This dispersion curve can be inverted to give a class of shear-wave <span class="hlt">velocity</span> models with depth using a Monte-Carlo algorithm. We developed a technic based on paraxial ray tracing to obtain 2D phase-<span class="hlt">velocity</span> maps as a function of frequency which can subsequently be inverted for the 3D struc- ture. The inversion for phase-<span class="hlt">velocities</span> is iterative and it uses the average dispersion curve measured previously as a starting model. The major improvement of our method compared to previous ray tracing studies is that we jointly invert for the <span class="hlt">velocity</span> model under the array and the shape of incoming wave fronts, therefore reducing artifacts due to structure outside the study region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004SPIE.5559..392B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004SPIE.5559..392B"><span id="translatedtitle">Novel fusion algorithms for medical ultrasound <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bashford, Gregory R.; Morse, Jonathan L.; Melander, Jennifer R.</p> <p>2004-10-01</p> <p>Ultrasound <span class="hlt">tomography</span> is a bioimaging method that combines the geometry of X-ray computed <span class="hlt">tomography</span> with the non-ionizing energy of ultrasound. This modality has potential clinical utility in breast cancer screening and diagnosis. In conventional ultrasound <span class="hlt">tomography</span>, data sets from different interrogation angles are used to reconstruct an estimate of a biomechanical property of the tissue, such as sound <span class="hlt">velocity</span>, in the form of an image. Here we describe an alternative method of reconstruction using novel algorithms which weight the data based on a "quality" score. The quality score is derived from beamforming characteristics, for example, the weighting of angle-dependent data by its distance from the transmit focal zones. The new approach is that for each data set (taken at a different view angle), the reliability of the data (in the range dimension) is assumed to vary. By fusing (combining) the data based on the quality score, a complete image is formed. In this paper, we describe the construction of a rotational translation stage and tissue-mimicking phantoms that are used in conjunction with a commercial medical ultrasound machine to test our reconstruction algorithms. The new algorithms were found to increase the contrast-to-speckle ratio of simulated cysts by 114% from raw data over a 77% improvement by spatial compounding (averaging), and to decrease wire target width by 54% over a 39% reduction by spatial compounding alone. The new method shows promise as a computationally efficient method of improving contrast and resolution in ultrasound images.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6964477','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6964477"><span id="translatedtitle">Emission <span class="hlt">tomography</span> of the kidney</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Teates, C.D.; Croft, B.Y.; Brenbridge, N.A.; Bray, S.T.; Williamson, B.R.</p> <p>1983-12-01</p> <p>Single photon emission computerized <span class="hlt">tomography</span> (SPECT) was done on two patients with suspected renal masses. Nuclear scintigraphy was equivocal on two tumors readily identified by SPECT. Single photon <span class="hlt">tomography</span> is cost effective and increases the reliability of nuclear scintigraphy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/10923876','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/10923876"><span id="translatedtitle"><span class="hlt">Tomography</span> of dispersive media</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ernst; Herman</p> <p>2000-07-01</p> <p>When waves propagate through layered structures, the phase <span class="hlt">velocity</span> is frequency dependent (dispersive). If one wants to reconstruct the <span class="hlt">velocity</span> variations in this medium, conventional traveltime-based tomographic methods cannot be used, since each frequency component has a different traveltime. A tomographic method is presented for reconstructing the phase <span class="hlt">velocity</span> of guided waves in laterally varying media. The dispersive character of guided waves is explicitly accounted for by using a phase-based error criterium instead of "picked" traveltimes. Phase <span class="hlt">velocity</span> and source waveform can be reconstructed to within a few percent, and the algorithm is shown to be robust in the presence of interference noise. When applied to seismic field data, the reconstructed phase <span class="hlt">velocity</span> field correlates well with the topography of the area. PMID:10923876</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/19797654','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/19797654"><span id="translatedtitle">Global surface wave <span class="hlt">tomography</span> using seismic hum.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nishida, Kiwamu; Montagner, Jean-Paul; Kawakatsu, Hitoshi</p> <p>2009-10-01</p> <p>The development of global surface wave <span class="hlt">tomography</span> using earthquakes has been crucial to exploration of the dynamic status of Earth's deep. It is naturally believed that only large earthquakes can generate long-period seismic waves that penetrate deep enough into Earth for such exploration. The discovery of seismic hum, Earth's background free oscillations, which are randomly generated by oceanic and/or atmospheric disturbances, now provides an alternative approach. We present results of global upper-mantle seismic <span class="hlt">tomography</span> using seismic hum and without referring to earthquakes. At periods of 100 to 400 seconds, the phase-<span class="hlt">velocity</span> anomalies of Rayleigh waves are measured by modeling the observed cross-correlation functions between every pair of stations from among 54 globally distributed seismic stations. The anomalies are then inverted to obtain the three-dimensional S-wave <span class="hlt">velocity</span> structure in the upper mantle. Our technique provides a new means for exploring the three-dimensional structure of the interior of terrestrial planets with an atmosphere and/or oceans, particularly Mars. PMID:19797654</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014SPIE.9242E..0RR','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SPIE.9242E..0RR"><span id="translatedtitle">3D acoustic atmospheric <span class="hlt">tomography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rogers, Kevin; Finn, Anthony</p> <p>2014-10-01</p> <p>This paper presents a method for tomographically reconstructing spatially varying 3D atmospheric temperature profiles and wind <span class="hlt">velocity</span> fields based. Measurements of the acoustic signature measured onboard a small Unmanned Aerial Vehicle (UAV) are compared to ground-based observations of the same signals. The frequency-shifted signal variations are then used to estimate the acoustic propagation delay between the UAV and the ground microphones, which are also affected by atmospheric temperature and wind speed vectors along each sound ray path. The wind and temperature profiles are modelled as the weighted sum of Radial Basis Functions (RBFs), which also allow local meteorological measurements made at the UAV and ground receivers to supplement any acoustic observations. <span class="hlt">Tomography</span> is used to provide a full 3D reconstruction/visualisation of the observed atmosphere. The technique offers observational mobility under direct user control and the capacity to monitor hazardous atmospheric environments, otherwise not justifiable on the basis of cost or risk. This paper summarises the tomographic technique and reports on the results of simulations and initial field trials. The technique has practical applications for atmospheric research, sound propagation studies, boundary layer meteorology, air pollution measurements, analysis of wind shear, and wind farm surveys.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.S21B2196N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.S21B2196N"><span id="translatedtitle">Development of the Borehole 2-D Seismic <span class="hlt">Tomography</span> Software Using MATLAB</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nugraha, A. D.; Syahputra, A.; Fatkhan, F.; Sule, R.; Hendriyana, A.</p> <p>2011-12-01</p> <p>We developed 2-D borehole seismic <span class="hlt">tomography</span> software that we called "EARTHMAX-2D <span class="hlt">TOMOGRAPHY</span>" to image subsurface physical properties including P-wave and S-wave <span class="hlt">velocities</span> between two boreholes. We used Graphic User Interface (GUI) facilities of MATLAB programming language to create the software. In this software, we used travel time of seismic waves from source to receiver by using pseudo bending ray tracing method as input for <span class="hlt">tomography</span> inversion. We can also set up a model parameterization, initial <span class="hlt">velocity</span> model, ray tracing processes, conduct borehole seismic <span class="hlt">tomography</span> inversion, and finally visualize the inversion results. The LSQR method was applied to solve of <span class="hlt">tomography</span> inversion solution. We provided the Checkerboard Test Resolution (CTR) to evaluate the model resolution of the <span class="hlt">tomography</span> inversion. As validation of this developed software, we tested it for geotechnical purposes. We then conducted data acquisition in the "ITB X-field" that is located on ITB campus. We used two boreholes that have a depth of 39 meters. Seismic wave sources were generated by impulse generator and sparker and then they were recorded by borehole hydrophone string type 3. Later on, we analyzed and picked seismic arrival time as input for <span class="hlt">tomography</span> inversion. As results, we can image the estimated weathering layer, sediment layer, and basement rock in the field depicted by seismic wave structures. More detailed information about the developed software will be presented. Keywords: borehole, <span class="hlt">tomography</span>, earthmax-2D, inversion</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.S23C2753W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.S23C2753W"><span id="translatedtitle">Wave-equation migration <span class="hlt">velocity</span> inversion using passive seismic sources</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Witten, B.; Shragge, J. C.</p> <p>2015-12-01</p> <p>Seismic monitoring at injection sites (e.g., CO2 sequestration, waste water disposal, hydraulic fracturing) has become an increasingly important tool for hazard identification and avoidance. The information obtained from this data is often limited to seismic event properties (e.g., location, approximate time, moment tensor), the accuracy of which greatly depends on the estimated elastic <span class="hlt">velocity</span> models. However, creating accurate <span class="hlt">velocity</span> models from passive array data remains a challenging problem. Common techniques rely on picking arrivals or matching waveforms requiring high signal-to-noise data that is often not available for the magnitude earthquakes observed over injection sites. We present a new method for obtaining elastic <span class="hlt">velocity</span> information from earthquakes though full-wavefield wave-equation imaging and adjoint-state <span class="hlt">tomography</span>. The technique exploits the fact that the P- and S-wave arrivals originate at the same time and location in the subsurface. We generate image volumes by back-propagating P- and S-wave data through initial Earth models and then applying a correlation-based extended-imaging condition. Energy focusing away from zero lag in the extended image volume is used as a (penalized) residual in an adjoint-state <span class="hlt">tomography</span> scheme to update the P- and S-wave <span class="hlt">velocity</span> models. We use an acousto-elastic approximation to greatly reduce the computational cost. Because the method requires neither an initial source location or origin time estimate nor picking of arrivals, it is suitable for low signal-to-noise datasets, such as microseismic data. Synthetic results show that with a realistic distribution of microseismic sources, P- and S-<span class="hlt">velocity</span> perturbations can be recovered. Although demonstrated at an oil and gas reservoir scale, the technique can be applied to problems of all scales from geologic core samples to global seismology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120009904','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120009904"><span id="translatedtitle">Sodium <span class="hlt">Velocity</span> Maps on Mercury</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Potter, A. E.; Killen, R. M.</p> <p>2011-01-01</p> <p>The objective of the current work was to measure two-dimensional maps of sodium <span class="hlt">velocities</span> on the Mercury surface and examine the maps for evidence of sources or sinks of sodium on the surface. The McMath-Pierce Solar Telescope and the Stellar Spectrograph were used to measure Mercury spectra that were sampled at 7 milliAngstrom intervals. Observations were made each day during the period October 5-9, 2010. The dawn terminator was in view during that time. The <span class="hlt">velocity</span> shift of the centroid of the Mercury emission line was measured relative to the solar sodium Fraunhofer line corrected for radial <span class="hlt">velocity</span> of the Earth. The difference between the observed and calculated <span class="hlt">velocity</span> shift was taken to be the <span class="hlt">velocity</span> vector of the sodium relative to Earth. For each position of the spectrograph slit, a line of <span class="hlt">velocities</span> across the planet was measured. Then, the spectrograph slit was stepped over the surface of Mercury at 1 arc second intervals. The position of Mercury was stabilized by an adaptive optics system. The collection of lines were assembled into an images of surface reflection, sodium emission intensities, and Earthward <span class="hlt">velocities</span> over the surface of Mercury. The <span class="hlt">velocity</span> map shows patches of higher <span class="hlt">velocity</span> in the southern hemisphere, suggesting the existence of sodium sources there. The peak earthward <span class="hlt">velocity</span> occurs in the equatorial region, and extends to the terminator. Since this was a dawn terminator, this might be an indication of dawn evaporation of sodium. Leblanc et al. (2008) have published a <span class="hlt">velocity</span> map that is similar.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRB..120.7068Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRB..120.7068Z"><span id="translatedtitle">Wavelet-based time-dependent travel time <span class="hlt">tomography</span> method and its application in imaging the Etna volcano in Italy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Xin; Zhang, Haijiang</p> <p>2015-10-01</p> <p>It has been a challenge to image <span class="hlt">velocity</span> changes in real time by seismic travel time <span class="hlt">tomography</span>. If more seismic events are included in