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Sample records for 1d velocity structure

  1. Investigation of 1-D crustal velocity structure beneath Izmir Gulf and surroundings by using local earthquakes

    NASA Astrophysics Data System (ADS)

    Polat, Orhan; Özer, Ćaglar

    2016-04-01

    In this study; we examined one dimensional crustal velocity structure of Izmir gulf and surroundings. We used nearly one thousand high quality (A and B class) earthquake data which recorded by Disaster and Emergency Management Presidency (AFAD) [1], Bogazici University (BU-KOERI) [2] and National Observatory of Athens (NOA) [3,4]. We tried several synthetic tests to understand power of new velocity structure, and examined phase residuals, RMS values and shifting tests. After evaluating these tests; we decided one dimensional velocity structure and minimum 1-D P wave velocities, hypocentral parameter and earthquake locations from VELEST algorithm. Distribution of earthquakes was visibly improved by using new minimum velocity structure.

  2. An approach to jointly invert hypocenters and 1D velocity structure and its application to the Lushan earthquake series

    NASA Astrophysics Data System (ADS)

    Qian, Hui; Mechie, James; Li, Haibing; Xue, Guangqi; Su, Heping; Cui, Xiang

    2016-01-01

    Earthquake location is essential when defining fault systems and other geological structures. Many methods have been developed to locate hypocenters within a 1D velocity model. In this study, a new approach, named MatLoc, has been developed which can simultaneously invert for the locations and origin times of the hypocenters and the velocity structure, from the arrival times of local earthquakes. Moreover, it can invert for layer boundary depths, such as Moho depths, which can be well constrained by the Pm and Pn phases. For this purpose, the package was developed to take into account reflected phases, e.g., the Pm phase. The speed of the inversion is acceptable due to the use of optimized matrix calculations. The package has been used to re-locate the Lushan earthquake series which occurred in Sichuan, China, from April 20 to April 22, 2013. The results obtained with the package show that the Lushan earthquake series defines the dip of the Guankou fault, on which most of the series occurred, to be 39° toward the NW. Further, the surface projection of the Lushan earthquake series is consistent with the regional tectonic strike which is about N45° E.

  3. Forward waveform modelling procedure for 1-D crustal velocity structure and its application to the southern Korean Peninsula

    NASA Astrophysics Data System (ADS)

    Kim, Seongryong; Rhie, Junkee; Kim, Geunyoung

    2011-04-01

    We propose a full-grid search procedure for broad-band waveform modelling to determine a 1-D crustal velocity model. The velocity model can be more constrained because of the use of broad-band waveforms instead of traveltimes for the crustal phases, although only a small number of event-station pairs were employed. Despite the time-consuming nature of the full-grid search method to search the whole model parameter space, the use of an empirical relationship between the P- and S-wave velocities can significantly reduce computation time. The proposed method was applied to a case in the southern Korean Peninsula. Broad-band waveforms obtained from two inland earthquakes that occurred on 2007 January 20 (Mw 4.6) and 2004 April 26 (Mw 3.6) were used to test the method. The three-layers over half-space crustal velocity model of the P- and S-wave velocities was estimated. Comparisons of waveform fitness between the final model and previously published models demonstrate advancements in the average value of waveform fitness for the inland earthquakes. In addition, 1-D velocity models were determined for three distinct tectonic regions, namely, the Gyonggi Massif, the Okcheon Belt and the Gyeongsang Basin, which are all located inside the study area. A comparison between the three models demonstrates that the crustal thickness of the southern Korean Peninsula increases from NW to SE and that the lower crustal composition of the Okcheon belt differs from that of the other tectonic regions.

  4. Brady 1D seismic velocity model ambient noise prelim

    DOE Data Explorer

    Mellors, Robert J.

    2013-10-25

    Preliminary 1D seismic velocity model derived from ambient noise correlation. 28 Green's functions filtered between 4-10 Hz for Vp, Vs, and Qs were calculated. 1D model estimated for each path. The final model is a median of the individual models. Resolution is best for the top 1 km. Poorly constrained with increasing depth.

  5. Intricate heterogeneous structures of the top 300 km of the Earth's inner core inferred from global array data: I. Regional 1D attenuation and velocity profiles

    NASA Astrophysics Data System (ADS)

    Iritani, R.; Takeuchi, N.; Kawakatsu, H.

    2014-05-01

    We apply a waveform inversion method based on simulated annealing to complex core phase data observed by globally deployed seismic arrays, and present regional variation of depth profiles of attenuation and velocity for the top half of the inner core. Whereas measured attenuation parameters exhibit consistent trends for data sampling the eastern hemisphere of the inner core, for the western hemisphere, there is a remarkable difference between data sampling the inner core beneath Africa (W1) and beneath north America (W2). Obtained attenuation profiles suggest that intricate heterogeneities appear to be confined in the top 300 km. The profile for the eastern hemisphere has a high attenuation zone in the top 150 km that gradually diminishes with depth. Conversely, for the western hemisphere, the profile for W1 shows constant low attenuation and that for W2 represents a gradual increase from the inner core boundary to a peak at around 200 km depth. Velocity profiles, obtained from differential traveltimes between PKP(DF) and PKP(CD, BC) phases, for the eastern and western hemispheres are respectively about 0.8% faster and 0.6% slower than the reference model at the top of the inner core, and the difference nearly disappears at about 200 km depth. Our result suggests the presence of intricate quasi-hemispherical structures in the top ˜200-300 km of the inner core.

  6. 1-D seismic velocity model and hypocenter relocation using double difference method around West Papua region

    SciTech Connect

    Sabtaji, Agung E-mail: agung.sabtaji@bmkg.go.id; Nugraha, Andri Dian

    2015-04-24

    West Papua region has fairly high of seismicity activities due to tectonic setting and many inland faults. In addition, the region has a unique and complex tectonic conditions and this situation lead to high potency of seismic hazard in the region. The precise earthquake hypocenter location is very important, which could provide high quality of earthquake parameter information and the subsurface structure in this region to the society. We conducted 1-D P-wave velocity using earthquake data catalog from BMKG for April, 2009 up to March, 2014 around West Papua region. The obtained 1-D seismic velocity then was used as input for improving hypocenter location using double-difference method. The relocated hypocenter location shows fairly clearly the pattern of intraslab earthquake beneath New Guinea Trench (NGT). The relocated hypocenters related to the inland fault are also observed more focus in location around the fault.

  7. Minimum 1D P- and S- Velocity Models for Montenegro and Vicinity

    NASA Astrophysics Data System (ADS)

    Vucic, Ljiljana; Kissling, Edi; Spakman, Wim; Glavatovic, Branislav

    2015-04-01

    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) velocity models in this region. For these reasons, high resolution 3D tomography modeling of this area is considered to be of great importance. As part of preparatory phase for conducting a 3D local earthquake tomography 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 tomography 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 group 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 tomography. As a prerequisite to 3D tomography and for consistent high-precision earthquake locations, a minimum 1D velocity 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 velocity models for the region under study. The minimum 1D models were derived

  8. An improved 1-D seismic velocity model for seismological studies in the Campania-Lucania region (Southern Italy)

    NASA Astrophysics Data System (ADS)

    Matrullo, Emanuela; De Matteis, Raffaella; Satriano, Claudio; Amoroso, Ortensia; Zollo, Aldo

    2013-10-01

    We present a 1-D velocity model of the Earth's crust in Campania-Lucania region obtained by solving the coupled hypocentre-velocity inverse problem for 1312 local earthquakes recorded at a dense regional network. The model is constructed using the VELEST program, which calculates 1-D `minimum' velocity model from body wave traveltimes, together with station corrections, which account for deviations from the simple 1-D structure. The spatial distribution of station corrections correlates with the P-wave velocity variations of a preliminary 3-D crustal velocity model that has been obtained from the tomographic inversion of the same data set of P traveltimes. We found that station corrections reflect not only inhomogeneous near-surface structures, but also larger-scale geological features associated to the transition between carbonate platform outcrops at Southwest and Miocene sedimentary basins at Northeast. We observe a significant trade-off between epicentral locations and station corrections, related to the existence of a thick low-velocity layer to the NE. This effect is taken into account and minimized by re-computing station corrections, fixing the position of a subset of well-determined hypocentres, located in the 3-D tomographic model.

  9. Ion velocity distribution at the termination shock: 1-D PIC simulation

    SciTech Connect

    Lu Quanming; Yang Zhongwei; Lembege, Bertrand

    2012-11-20

    The Voyager 2 (V2) plasma observations of the proton temperature downstream of the quasi-perpendicular heliospheric termination shock (TS) showed that upstream thermal solar wind ions played little role in the shock dissipation mechanism and their downstream temperature is an order of magnitude smaller than predicted by MHD Rankine-Hugoniot conditions. While pickup ions (PUI) are generally expected to play an important role in energy dissipation at the shock, the details remain unclear. Here, one-dimensional (1-D) Particle-in-cell (PIC) code is used to examine kinetic properties and downstream velocity distribution functions of pickup ions (the hot supra-thermal component) and solar wind protons (SWs, the cold component) at the perpendicular heliospheric termination shock. The code treats the pickup ions self-consistently as a third component. Present results show that: (1) both of the incident SWs and PUIs can be separated into two parts: reflected (R) ions and directly transmitted (DT) ions, the energy gain of the R ions at the shock front is much larger than that of the DT ions; (2) the fraction of reflected SWs and their downstream temperature decrease with the relative percentage PUI%; (3) no matter how large the PUI% is, the downstream ion velocity distribution function always can be separated into three parts: 1. a high energy tail (i.e. the wings) dominated by the reflected PUIs, 2. a low energy core mainly contributed by the directly transmitted SWs, and 3. a middle energy part which is a complicated superposition of reflected SWs and directly transmitted PUIs. The significance of the presence of pickup ions on shock front micro-structure and nonstationarity is also discussed.

  10. Rayleigh Wave Dispersion and A 1d S-velocity Model of The Fennoscandian Mantle

    NASA Astrophysics Data System (ADS)

    Funke, S.; Friederich, W.; Sstwg, The

    We derive a Rayleigh wave dispersion curve from surface wave data recorded at the SVEKALAPKO tomographic array deployed in Southern Finland from September 1998 to March 1999. After a suite of processing steps, complex spectral amplitudes of the Rayleigh wave train are determined for each available seismogram. The process- ing includes low-pass filtering, instrument correction, deconvolution using a standard earth model to compress the Rayleigh wave train, computation of Gabor matrices (sonograms) to pick group travel times, and finally estimation of complex spectral amplitudes in a Gaussian time window of frequency-dependent width centered on the group travel time. Spectral amplitude values are only accepted if the signal-to-noise ratio in the considered frequency interval is above a pre-chosen threshold and if the picked group travel time does not deviate too strongly from that predicted by a stan- dard earth model. The final dataset contains spectral amplitude values at 34 selected periods from 52 earthquakes observed at on average 25 stations. For each selected frequency, we determine a phase velocity by fitting plane waves propagating across the array with this velocity to the complex spectral amplitudes of all earthquakes and stations. Errors are estimated with a bootstrap method. We obtain reliable phase velocities in the frequency band from 8 mHz to 50 mHz. Phase veloci- ties for lower frequencies exhibit large errors due to the lack of big earthquakes during the time of deployment. The phase velocities are substantially higher than predicted by standard earth model ak135 below 20 mHz and slightly lower above 25 mHz. We have inverted the dispersion curve for a 1D shear wave velocity model down to about 400 km depth and obtain a 50 km thick crust and a fast upper mantle with a sub- Moho velocity of 4.7 km/s. Our data do not require a low-velocity zone in the upper mantle. Indeed, the dispersion curve can be explained by a nearly straight velocity profile from

  11. Periodic solutions for a 1D-model with nonlocal velocity via mass transport

    NASA Astrophysics Data System (ADS)

    Ferreira, Lucas C. F.; Valencia-Guevara, Julio C.

    2016-05-01

    This paper concerns periodic solutions for a 1D-model with nonlocal velocity given by the periodic Hilbert transform. There is a rich literature showing, via numerics and rigorous analysis, that this model presents singular behavior of solutions. For instance, they can blow up by forming mass-concentration. We develop a global well-posedness theory for periodic measure initial data that allows, in particular, to analyze how the model evolves from those singularities. Our results are based on periodic mass transport theory and the abstract gradient flow theory in metric spaces developed by Ambrosio et al. (2005). A viscous version of the model is also analyzed and inviscid limit properties are obtained.

  12. Effective-range signatures in quasi-1D matter waves: sound velocity and solitons

    NASA Astrophysics Data System (ADS)

    Sgarlata, F.; Mazzarella, G.; Salasnich, L.

    2015-06-01

    We investigate ultracold and dilute bosonic atoms under strong transverse harmonic confinement using a 1D modified Gross-Pitaevskii equation (1D MGPE), which accounts for the energy dependence of the two-body scattering amplitude within an effective-range expansion. We study sound waves and solitons of the quasi-1D system, comparing the 1D MGPE results with the 1D GPE ones. We find that when the finite-size nature of the interaction is taken into account, the speed of sound and the density profiles of both dark and bright solitons show relevant quantitative changes with respect to predictions given by the standard 1D GPE.

  13. Calibration of a 1D Crustal Velocity and Q Model for Ground Motion Simulations in Central and Eastern US

    NASA Astrophysics Data System (ADS)

    Graves, R. W.

    2012-12-01

    I have performed low frequency (f < 1 Hz) ground motion simulations for the 2008 Mw 5.23 Mt. Carmel, Illinois and 2011 Mw 5.74 Mineral, Virginia earthquakes to calibrate a rock-site 1D crustal velocity and Q structure model for central and eastern US (CEUS). For each earthquake, the observed ground motions were simulated at sites extending out to about 900 km from the epicenter. Sites within the Mississippi embayment are not included in the modeling. The initial 1D velocity model was developed by averaging profiles extracted from the CUS V1.3 3D velocity model (Ramirez-Guzman et al, 2012) at each of the recording sites, with the surface shear wave velocity set at 2200 m/s. The Mt. Carmel earthquake is represented as a point double couple (strike=25, dip=90, rake=-175) at a depth of 14 km and a slip-rate function having a Brune corner frequency of 0.89 Hz (Hartzell and Mendoza, 2011). The Mineral earthquake is represented as a point double couple (strike=26, dip=55, rake=108) at a depth of 6 km and a slip-rate function having a corner frequency of 0.50 Hz. Full waveform Green's functions were computed using the FK method of Zhu and Rivera (2002). The initial model does well at reproducing the median level of observed response spectral acceleration (Sa) for most sites out to 300 km at periods of 2 to 5 sec, including the observed flattening in distance attenuation between 70 and 150 km. However, this model under predicts the motions beyond about 400 km distance. Increasing Q in the mid- and lower crust from the original value of 700 to 5000 removes this under prediction of the larger distance motions. Modified Mercalli Intensity (MMI) estimates have been computed from the simulations using the ground motion-intensity conversion equations of Atkinson and Kaka (2007; AK2007) and Dangkua and Cramer (2011; DC2011-ENA) for comparison against the observed "Did You Feel It" intensity estimates. Given the bandwidth limitations of the simulations, I use the conversion

  14. Horizontal Velocity Structure in Waterspouts.

    NASA Astrophysics Data System (ADS)

    Schwiesow, R. L.

    1981-04-01

    We have measured the spatial variation of a single horizontal component of the velocity in a number of waterspouts using an airborne infrared Doppler lidar. In 21 data sets, maximum velocities range from 4.2 to 33.6 m s1 and visible funnel diameters from 6.6 to 90 m. Data were taken at altitudes between 675 m, near cloud base, and 95 m above the surface. The sequences show time development of the velocity as a function of radius at a fixed altitude and the velocity structure at different altitudes and sequential times with a horizontal resolution of 0.75 m between data points. The variation in velocity structure between waterspouts is large, with some showing marked azimuthal asymmetry and mixing with the ambient flow, and others showing multiple concentric vortex shells.

  15. Velocity-dependent quantum phase slips in 1D atomic superfluids.

    PubMed

    Tanzi, Luca; Scaffidi Abbate, Simona; Cataldini, Federica; Gori, Lorenzo; Lucioni, Eleonora; Inguscio, Massimo; Modugno, Giovanni; D'Errico, Chiara

    2016-01-01

    Quantum phase slips are the primary excitations in one-dimensional superfluids and superconductors at low temperatures but their existence in ultracold quantum gases has not been demonstrated yet. We now study experimentally the nucleation rate of phase slips in one-dimensional superfluids realized with ultracold quantum gases, flowing along a periodic potential. We observe a crossover between a regime of temperature-dependent dissipation at small velocity and interaction and a second regime of velocity-dependent dissipation at larger velocity and interaction. This behavior is consistent with the predicted crossover from thermally-assisted quantum phase slips to purely quantum phase slips. PMID:27188334

  16. Velocity-dependent quantum phase slips in 1D atomic superfluids

    PubMed Central

    Tanzi, Luca; Scaffidi Abbate, Simona; Cataldini, Federica; Gori, Lorenzo; Lucioni, Eleonora; Inguscio, Massimo; Modugno, Giovanni; D’Errico, Chiara

    2016-01-01

    Quantum phase slips are the primary excitations in one-dimensional superfluids and superconductors at low temperatures but their existence in ultracold quantum gases has not been demonstrated yet. We now study experimentally the nucleation rate of phase slips in one-dimensional superfluids realized with ultracold quantum gases, flowing along a periodic potential. We observe a crossover between a regime of temperature-dependent dissipation at small velocity and interaction and a second regime of velocity-dependent dissipation at larger velocity and interaction. This behavior is consistent with the predicted crossover from thermally-assisted quantum phase slips to purely quantum phase slips. PMID:27188334

  17. Data Analysis of cGPS stations in central Greece: station velocities and 1-D strain estimates

    NASA Astrophysics Data System (ADS)

    Ganas, Athanassios; Chousianitis, Konstantinos; Gianniou, Michalis

    2013-04-01

    We processed 30-s GPS data from permanent GNSS stations in central Greece, available at NOA since 2006. We obtained position time series along with horizontal and vertical velocities using the Kalman filtering approach and accounting for time-correlated noise content. The station distribution allowed us to draw velocity profiles and to calculate rates of baseline length change (1-D strain). In central Greece, the coherent picture of the velocity pattern for Attica and north-eastern Peloponnese (Corinth) stations (effectively a velocity "plateau" at 30 mm/yr) indicates that these areas belong to the same crustal block, although some internal strain is present within Attica's crust as well as across the Saronic Gulf. Our 1-D strain estimates are in general agreement with geological data (fault slip rates) in central Greece, implying accommodation of this crustal extension along E-W striking active normal faults. Some NE-SW directed shortening is mapped in the wider area to the west of the termination of the North Anatolian Fault (Sporades islands).

  18. 1D crustal structure from quality seismological data for the Cyprus subduction zone

    NASA Astrophysics Data System (ADS)

    Perk, Şükran; Deǧer, Ali; Özbakır, Karabulut, Hayrullah

    2013-04-01

    The eastern Mediterranean is a tectonically complex region, where long-term subduction and accretion processes have shaped the overall evolution. Recently, many seismic tomography studies have shown subducted slabs of the Neo-Tethyan lithosphere, continuing its subduction in the Hellenic trench, stalled in the Cyprus trench and being torn near the intersection between them. Antalya bay is a key region located on the western flank of the Cyprus Subduction Zone (CSZ), close to the junction between the Hellenic and Cyprus Arcs. Here deep earthquakes are nucleated, which otherwise cannot be seen anywhere else along the CSZ. For this reason, we focus our attention specifically to the Antalya Bay area but also the remaining parts of the CSZ. Several regional studies have been carried out to define the velocity structure beneath the region but none have been able to locate the CSZ. One of the main reasons for this was the lack of incorporation of a wide seismic network in those regional studies. We compile a large catalog of seismicity and relocate earthquakes to infer 1D local crustal structure using the clusters of seismicity. We used seismic data between 2005 - 2011 which are recorded at more than 335 seismic stations operated by several agencies and portable deployments. The data-set is composed of over 10,000 events and earthquakes can be grouped in several distinct clusters. We defined five of these clusters, where the total number of events is more than 4500, among which we selected over 2000 events with the highest data quality. 1-D local P-wave velocity models are developed using this high quality data-set and the earthquakes are relocated using the local velocity models. The compiled and reanalyzed data will contribute to perform local earthquake tomography. Moreover, obtained local velocity models represent a fundamental step towards an improved seismic tomography studies in a very crucial region in the eastern Mediterranean.

  19. Seismicity and Improved Velocity Structure in Kuwait

    SciTech Connect

    Gok, R M; Rodgers, A J; Al-Enezi, A

    2006-01-26

    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 groups, 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) velocity 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 group velocities. Crustal structure is capped by the thick ({approx} 7 km) sedimentary rocks of the Arabian Platform underlain by normal velocities 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 group velocities 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 tomography technique (tomoDD) to jointly locate the events and estimate three-dimensional (3D) velocity structure. TomoDD is based on hypoDD relocation algorithm and it makes use of both absolute and

  20. High Resolution Velocity Structure in Eastern Turkey

    SciTech Connect

    Pasyanos, M; Gok, R; Zor, E; Walter, W

    2004-09-03

    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 velocity 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 velocity 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-velocity tradeoff. In order to improve previous velocity 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 groups. We calculated the receiver functions using iterative time-domain deconvolution technique and surface wave group velocity dispersion curves between 10-100 sec. We are making surface wave dispersion measurements at the ETSE stations and have incorporated them into a regional group velocity model. Preliminary results indicate a strong trend in the long period group velocity in the northeast. This indicates slow upper mantle velocities 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

  1. Structural stability of a 1D compressible viscoelastic fluid model

    NASA Astrophysics Data System (ADS)

    Huo, Xiaokai; Yong, Wen-An

    2016-07-01

    This paper is concerned with a compressible viscoelastic fluid model proposed by Öttinger. Although the model has a convex entropy, the Hessian matrix of the entropy does not symmetrize the system of first-order partial differential equations due to the non-conservative terms in the constitutive equation. We show that the corresponding 1D model is symmetrizable hyperbolic and dissipative and satisfies the Kawashima condition. Based on these, we prove the global existence of smooth solutions near equilibrium and justify the compatibility of the model with the Navier-Stokes equations.

  2. Prediction of the expansion velocity of ultracold 1D quantum gases for integrable models

    NASA Astrophysics Data System (ADS)

    Mei, Zhongtao; Vidmar, Lev; Heidrich-Meisner, Fabian; Bolech, Carlos

    In the theory of Bethe-ansatz integrable quantum systems, rapidities play an important role as they are used to specify many-body states. The physical interpretation of rapidities going back to Sutherland is that they are the asymptotic momenta after letting a quantum gas expand into a larger volume rendering it dilute and noninteracting. We exploit this picture to calculate the expansion velocity of a one-dimensional Fermi-Hubbard model by using the distribution of rapidities defined by the initial state. Our results are consistent with the ones from time-dependent density-matrix renormalization. We show in addition that an approximate Bethe-ansatz solution works well also for the Bose-Hubbard model. Our results are of interests for future sudden-expansion experiments with ultracold quantum gases.

  3. High Resolution Velocity Structure in Eastern Turkey

    NASA Astrophysics Data System (ADS)

    Pasyanos, M. E.; Gok, R.; Zor, E.; Walter, W. R.

    2004-12-01

    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 velocity 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 velocity 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-velocity trade-off [Ammon et al., 1990]. In order to improve upon this velocity 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 groups 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 group velocity model for periods between 10 and 100 seconds. Preliminary results indicate a strong trend in the long period group velocities toward the northeast, indicating slow upper mantle velocities 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

  4. Tunable Design of Structural Colors Produced by Pseudo-1D Photonic Crystals of Graphene Oxide.

    PubMed

    Tong, Liping; Qi, Wei; Wang, Mengfan; Huang, Renliang; Su, Rongxin; He, Zhimin

    2016-07-01

    It is broadly observed that graphene oxide (GO) films appear transparent with a thickness of about several nanometers, whereas they appear dark brown or almost black with thickness of more than 1 μm. The basic color mechanism of GO film on a sub-micrometer scale, however, is not well understood. This study reports on GO pseudo-1D photonic crystals (p1D-PhCs) exhibiting tunable structural colors in the visible wavelength range owing to its 1D Bragg nanostructures. Striking structural colors of GO p1D-PhCs could be tuned by simply changing either the volume or concentration of the aqueous GO dispersion during vacuum filtration. Moreover, the quantitative relationship between thickness and reflection wavelength of GO p1D-PhCs has been revealed, thereby providing a theoretical basis to rationally design structural colors of GO p1D-PhCs. The spectral response of GO p1D-PhCs to humidity is also obtained clearly showing the wavelength shift of GO p1D-PhCs at differently relative humidity values and thus encouraging the integration of structural color printing and the humidity-responsive property of GO p1D-PhCs to develop a visible and fast-responsive anti-counterfeiting label. The results pave the way for a variety of potential applications of GO in optics, structural color printing, sensing, and anti-counterfeiting. PMID:27171200

  5. Optical bullets in (2+1)D photonic structures and their interaction with localized defects

    NASA Astrophysics Data System (ADS)

    Dohnal, Tomas

    2005-11-01

    This dissertation studies light propagation in Kerr-nonlinear two dimensional waveguides with a Bragg resonant, periodic structure in the propagation direction. The model describing evolution of the electric field envelopes is the system of 2D Nonlinear Coupled Mode Equations (2D CME). The periodic structure induces a range of frequencies (frequency gap) in which linear waves do not propagate. It is shown that, similarly to the ID case of a fiber grating, the 2D nonlinear system supports localized solitary wave solutions, referred to as 2D gap solitons, which have frequencies inside the linear gap and can travel at, any speed smaller than or equal to the speed of light in the corresponding homogeneous medium. Such solutions are constructed numerically via Newton's iteration. Convergence is obtained only near the upper edge of the gap. Gap solitons with a nonzero velocity are constructed by numerically following a bifurcation curve parameterized by the velocity v. It is shown that gap solitons are saddle points of the corresponding Hamiltonian functional and that no (constrained) local minima of the Hamiltonian exist. The linear stability problem is formulated and reasons for the failure of the standard Hamiltonian PDE approach for determining linear stability are discussed. In the second part of the dissertation interaction of 2D gap solitons with localized defects is studied and trapping of slow enough 2D gap solitons is demonstrated. This study builds on [JOSA B 19, 1635 (2002)], where such trapping of 1D gap solitons is considered. Analogously to this 1D problem trapping in the 2D model is explained as a resonant energy transfer into one or more defect modes existent for the particular defect. For special localized defects exact linear modes are found explicitly via the separation of variables. Numerical computation of linear defect modes is used for more general defects. Corresponding nonlinear modes are then constructed via Newton's iteration by following a

  6. S-wave velocity structure of the North China from inversion of Rayleigh wave phase velocity

    NASA Astrophysics Data System (ADS)

    Chen, Hao-peng; Zhu, Liang-bao; Wang, Qing-dong; Zhang, Pan; Yang, Ying-hang

    2014-07-01

    We constructed the S-wave velocity structure of the crust and uppermost mantle (10-100 km) beneath the North China based on the teleseismic data recorded by 187 portable broadband stations deployed in this region. The traditional two-step inversion scheme was adopted. Firstly, we measured the interstation fundamental Rayleigh wave phase velocity of 10-60 s and imaged the phase velocity distributions using the Tarantola inversion method. Secondly, we inverted the 1-D S-wave velocity structure with a grid spacing of 0.25° × 0.25° and constructed the 3-D S-wave velocity structure of the North China. The 3-D S-wave velocity model provides valuable information about the destruction mechanism and geodynamics of the North China Craton (NCC). The S-wave velocity structures in the northwestern and southwestern sides of the North-South Gravity Lineament (NSGL) are obviously different. The southeastern side is high velocity (high-V) while the northeastern side is low velocity (low-V) at the depth of 60-80 km. The upwelling asthenosphere above the stagnated Pacific plate may cause the destruction of the Eastern Block and form the NSGL. A prominent low-V anomaly exists around Datong from 50 to 100 km, which may due to the upwelling asthenosphere originating from the mantle transition zone beneath the Western Block. The upwelling asthenosphere beneath the Datong may also contribute to the destruction of the Eastern Block. The Zhangjiakou-Penglai fault zone (ZPFZ) may cut through the lithosphere and act as a channel of the upwelling asthenosphere. A noticeable low-V zone also exists in the lower crust and upper mantle lid (30-50 km) beneath the Beijing-Tianjin-Tangshan (BTT) region, which may be caused by the upwelling asthenosphere through the ZPFZ.

  7. Structure and Catalytic Mechanism of Human Steroid 5-Reductase (AKR1D1)

    SciTech Connect

    Costanzo, L.; Drury, J; Christianson, D; Penning, T

    2009-01-01

    Human steroid 5{beta}-reductase (aldo-keto reductase (AKR) 1D1) catalyzes reduction of {Delta}{sup 4}-ene double bonds in steroid hormones and bile acid precursors. We have reported the structures of an AKR1D1-NADP{sup +} binary complex, and AKR1D1-NADP{sup +}-cortisone, AKR1D1-NADP{sup +}-progesterone and AKR1D1-NADP{sup +}-testosterone ternary complexes at high resolutions. Recently, structures of AKR1D1-NADP{sup +}-5{beta}-dihydroprogesterone complexes showed that the product is bound unproductively. Two quite different mechanisms of steroid double bond reduction have since been proposed. However, site-directed mutagenesis supports only one mechanism. In this mechanism, the 4-pro-R hydride is transferred from the re-face of the nicotinamide ring to C5 of the steroid substrate. E120, a unique substitution in the AKR catalytic tetrad, permits a deeper penetration of the steroid substrate into the active site to promote optimal reactant positioning. It participates with Y58 to create a 'superacidic' oxyanion hole for polarization of the C3 ketone. A role for K87 in the proton relay proposed using the AKR1D1-NADP{sup +}-5{beta}-dihydroprogesterone structure is not supported.

  8. Generation of a pseudo-2D shear-wave velocity section by inversion of a series of 1D dispersion curves

    USGS Publications Warehouse

    Luo, Y.; Xia, J.; Liu, J.; Xu, Y.; Liu, Q.

    2008-01-01

    Multichannel Analysis of Surface Waves utilizes a multichannel recording system to estimate near-surface shear (S)-wave velocities from high-frequency Rayleigh waves. A pseudo-2D S-wave velocity (vS) section is constructed by aligning 1D models at the midpoint of each receiver spread and using a spatial interpolation scheme. The horizontal resolution of the section is therefore most influenced by the receiver spread length and the source interval. The receiver spread length sets the theoretical lower limit and any vS structure with its lateral dimension smaller than this length will not be properly resolved in the final vS section. A source interval smaller than the spread length will not improve the horizontal resolution because spatial smearing has already been introduced by the receiver spread. In this paper, we first analyze the horizontal resolution of a pair of synthetic traces. Resolution analysis shows that (1) a pair of traces with a smaller receiver spacing achieves higher horizontal resolution of inverted S-wave velocities but results in a larger relative error; (2) the relative error of the phase velocity at a high frequency is smaller than at a low frequency; and (3) a relative error of the inverted S-wave velocity is affected by the signal-to-noise ratio of data. These results provide us with a guideline to balance the trade-off between receiver spacing (horizontal resolution) and accuracy of the inverted S-wave velocity. We then present a scheme to generate a pseudo-2D S-wave velocity section with high horizontal resolution using multichannel records by inverting high-frequency surface-wave dispersion curves calculated through cross-correlation combined with a phase-shift scanning method. This method chooses only a pair of consecutive traces within a shot gather to calculate a dispersion curve. We finally invert surface-wave dispersion curves of synthetic and real-world data. Inversion results of both synthetic and real-world data demonstrate that

  9. Toward Structural Correctness: Aquatolide and the Importance of 1D Proton NMR FID Archiving

    PubMed Central

    2016-01-01

    The revision of the structure of the sesquiterpene aquatolide from a bicyclo[2.2.0]hexane to a bicyclo[2.1.1]hexane structure using compelling NMR data, X-ray crystallography, and the recent confirmation via full synthesis exemplify that the achievement of “structural correctness” depends on the completeness of the experimental evidence. Archived FIDs and newly acquired aquatolide spectra demonstrate that archiving and rigorous interpretation of 1D 1H NMR data may enhance the reproducibility of (bio)chemical research and curb the growing trend of structural misassignments. Despite being the most accessible NMR experiment, 1D 1H spectra encode a wealth of information about bonds and molecular geometry that may be fully mined by 1H iterative full spin analysis (HiFSA). Fully characterized 1D 1H spectra are unideterminant for a given structure. The corresponding FIDs may be readily submitted with publications and collected in databases. Proton NMR spectra are indispensable for structural characterization even in conjunction with 2D data. Quantum interaction and linkage tables (QuILTs) are introduced for a more intuitive visualization of 1D J-coupling relationships, NOESY correlations, and heteronuclear experiments. Overall, this study represents a significant contribution to best practices in NMR-based structural analysis and dereplication. PMID:26812443

  10. Toward Structural Correctness: Aquatolide and the Importance of 1D Proton NMR FID Archiving.

    PubMed

    Pauli, Guido F; Niemitz, Matthias; Bisson, Jonathan; Lodewyk, Michael W; Soldi, Cristian; Shaw, Jared T; Tantillo, Dean J; Saya, Jordy M; Vos, Klaas; Kleinnijenhuis, Roel A; Hiemstra, Henk; Chen, Shao-Nong; McAlpine, James B; Lankin, David C; Friesen, J Brent

    2016-02-01

    The revision of the structure of the sesquiterpene aquatolide from a bicyclo[2.2.0]hexane to a bicyclo[2.1.1]hexane structure using compelling NMR data, X-ray crystallography, and the recent confirmation via full synthesis exemplify that the achievement of "structural correctness" depends on the completeness of the experimental evidence. Archived FIDs and newly acquired aquatolide spectra demonstrate that archiving and rigorous interpretation of 1D (1)H NMR data may enhance the reproducibility of (bio)chemical research and curb the growing trend of structural misassignments. Despite being the most accessible NMR experiment, 1D (1)H spectra encode a wealth of information about bonds and molecular geometry that may be fully mined by (1)H iterative full spin analysis (HiFSA). Fully characterized 1D (1)H spectra are unideterminant for a given structure. The corresponding FIDs may be readily submitted with publications and collected in databases. Proton NMR spectra are indispensable for structural characterization even in conjunction with 2D data. Quantum interaction and linkage tables (QuILTs) are introduced for a more intuitive visualization of 1D J-coupling relationships, NOESY correlations, and heteronuclear experiments. Overall, this study represents a significant contribution to best practices in NMR-based structural analysis and dereplication. PMID:26812443

  11. Formation of 1D adsorbed water structures on CaO(001)

    NASA Astrophysics Data System (ADS)

    Zhao, Xunhua; Bhattacharya, Saswata; Ghiringhelli, Luca M.; Levchenko, Sergey V.; Scheffler, Matthias

    2015-03-01

    Understanding the interaction of water with oxide surfaces is of fundamental importance for basic and engineering sciences. Recently, a spontaneous formation of one-dimensional (1D) adsorbed water structures have been observed on CaO(001). Interestingly, at other alkaline earth metal oxides, in particular MgO(001) and SrO(001), such structures have not been found experimentally. We calculate the relative stability of adsorbed water structures on the three oxides using density-functional theory combined with the ab initio atomistic thermodynamics. Low-energy structures at different coverages are obtained with a first-principles genetic algorithm. Finite-temperature vibrational spectra are calculated using ab initio molecular dynamics. We find a range of (T, p) conditions where 1D structures are thermodynamically stable on CaO(001). The orientation and vibrational spectra of the 1D structures are in agreement with the experiments. The formation of the 1D structures is found to be actuated by a symmetry breaking in the adsorbed water tetramer, as well as by a balance between water-water and water-substrate interactions, determined by the lattice constant of the oxide.

  12. Relocation of the Waldkirch seismic event, December 5, 2004, with regional 1D- and 3D-velocity models in the presence of upper mantle anisotropy

    NASA Astrophysics Data System (ADS)

    Muench, Thomas; Koch, Manfred; Schlittenhard, Jörg

    2010-05-01

    /VS-ratio across the study area are investigated. Finally a thorough statistical analysis of the hypocentral relocation accuracy and its sensitivity to various observational and model errors is carried out by (1) the classical calculation of covariances and confidence ellipses for the hypocenter and (2) Monte Carlo relocations with random perturbations of the observed arrivaltimes as well as of the choice of the initial hypocenter in the relocation process. The correction of the original phase-data leads to a shift of the hypocenter to about 10 to 15 km depth instead of 0 - 5 km for the uncorrected phases.The importance of the phase correction is also supported by the final RMS which is reduced from 2.22 s to 1.00 s for the isotropic case and, even more so, from 2.29 s to 0.75 s for the anisotropic. The reduced traveltime plots indicate also that a common VP /VS-ratio of 1.72 for both the crust and the upper mantle does not fit the crustal Sg-phases well. From subsequent hypocentral relocations with separate VP/VS-ratio for the crust and the upper mantle optimal values of VP /VS = 1.70 former, respective 1.66 for the latter, are obtained. In a subsequent set of relocations of the Waldkirch event the recently established isotropic and anisotropic 3D- crustal and upper mantle seismic velocity models of (Muench, 2009; Muench et al., 2010) are employed. Compared with the previous 1D hypocentral relocations where the optimal depth range found is 14 to 15 km, those of the 3D models lie about one km higher. The slightly lower depth of the 3D-models is most likely a consequence of traveltime effects of the structural velocity inhomogeneities.

  13. Waveform Constrained Seismic Velocity Structure in Northern California

    NASA Astrophysics Data System (ADS)

    Rhie, J.; Dreger, D. S.

    2001-12-01

    1-D and 2-D S-wave velocity structure from Mammoth Lakes to Yreka is determined by SH waveform modeling and receiver function analysis. Regional broadband waveforms from the 21 September 1993 Klamath Falls (Mw 6.0), the 15 May 1999 Mammoth Lakes (Mw 6.0), and the 10 August 2001 Portola (Mw 5.2) events were well recorded by 4 to 5 BDSN stations that are also located nearly on the same NNW line. This naturally aligned configuration of three local earthquakes and stations provides an excellent opportunity to determine a waveform constrained velocity model along the profile. Before performing the waveform modeling, a receiver function technique is applied to constrain Moho depth at each station. 1-D models are estimated iteratively by forward modeling of the broadband waveforms and the receiver functions. A 2-D model will be determined based on the 1-D results, and will be tested by modeling the broadband waveforms using a finite difference technique.

  14. Canonical decomposition of magnetotelluric responses: Experiment on 1D anisotropic structures

    NASA Astrophysics Data System (ADS)

    Guo, Ze-qiu; Wei, Wen-bo; Ye, Gao-feng; Jin, Sheng; Jing, Jian-en

    2015-08-01

    Horizontal electrical heterogeneity of subsurface earth is mostly originated from structural complexity and electrical anisotropy, and local near-surface electrical heterogeneity will severely distort regional electromagnetic responses. Conventional distortion analyses for magnetotelluric soundings are primarily physical decomposition methods with respect to isotropic models, which mostly presume that the geoelectric distribution of geological structures is of local and regional patterns represented by 3D/2D models. Due to the widespread anisotropy of earth media, the confusion between 1D anisotropic responses and 2D isotropic responses, and the defects of physical decomposition methods, we propose to conduct modeling experiments with canonical decomposition in terms of 1D layered anisotropic models, and the method is one of the mathematical decomposition methods based on eigenstate analyses differentiated from distortion analyses, which can be used to recover electrical information such as strike directions, and maximum and minimum conductivity. We tested this method with numerical simulation experiments on several 1D synthetic models, which turned out that canonical decomposition is quite effective to reveal geological anisotropic information. Finally, for the background of anisotropy from previous study by geological and seismological methods, canonical decomposition is applied to real data acquired in North China Craton for 1D anisotropy analyses, and the result shows that, with effective modeling and cautious interpretation, canonical decomposition could be another good method to detect anisotropy of geological media.

  15. Semiconductor structures for repeated velocity overshoot

    NASA Astrophysics Data System (ADS)

    Cooper, J. A., Jr.; Capasso, F.; Thornber, K. K.

    1982-12-01

    The conditions required for obtaining repeated velocity overshoot in semiconductors are discussed. Two classes of structures that provide these conditions are considered. The structures are seen as holding promise for achieving average drift velocities well in excess of the maximum steady-state velocity over distances ranging from submicron to tens of microns. In structures of the first class, the stairstep in potential is achieved by using a graded bandgap that is similar to the avalanche photodetector described by Williams et al. (1982), where the composition is graded from GaAs to Al(0.2)Ga(0.8)As. The second class of structures uses alternating planar doped charge sheets, as described by Malik et al. (1980).

  16. Uranium(VI) coordination polymers with pyromellitate ligand: Unique 1D channel structures and diverse fluorescence

    SciTech Connect

    Zhang, Yingjie; Bhadbhade, Mohan; Karatchevtseva, Inna; Price, Jason R.; Liu, Hao; Zhang, Zhaoming; Kong, Linggen; Čejka, Jiří; Lu, Kim; Lumpkin, Gregory R.

    2015-03-15

    Three new coordination polymers of uranium(VI) with pyromellitic acid (H{sub 4}btca) have been synthesized and structurally characterized. (ED)[(UO{sub 2})(btca)]·(DMSO)·3H{sub 2}O (1) (ED=ethylenediammonium; DMSO=dimethylsulfoxide) has a lamellar structure with intercalation of ED and DMSO. (NH{sub 4}){sub 2}[(UO{sub 2}){sub 6}O{sub 2}(OH){sub 6}(btca)]·~6H{sub 2}O (2) has a 3D framework built from 7-fold coordinated uranyl trinuclear units and btca ligands with 1D diamond-shaped channels (~8.5 Å×~8.6 Å). [(UO{sub 2}){sub 2}(H{sub 2}O)(btca)]·4H{sub 2}O (3) has a 3D network constructed by two types of 7-fold coordinated uranium polyhedron. The unique μ{sub 5}-coordination mode of btca in 3 enables the formation of 1D olive-shaped large channels (~4.5 Å×~19 Å). Vibrational modes, thermal stabilities and fluorescence properties have been investigated. - Graphical abstract: Table of content: three new uranium(VI) coordination polymers with pyromellitic acid (H{sub 4}btca) have been synthesized via room temperature and hydrothermal synthesis methods, and structurally characterized. Two to three dimensional (3D) frameworks are revealed. All 3D frameworks have unique 1D large channels. Their vibrational modes, thermal stabilities and photoluminescence properties have been investigated. - Highlights: • Three new coordination polymers of U(VI) with pyromellitic acid (H{sub 4}btca). • Structures from a 2D layer to 3D frameworks with unique 1D channels. • Unusual µ{sub 5}-(η{sub 1}:η{sub 2}:η{sub 1}:η{sub 2:}η{sub 1}) coordination mode of btca ligand. • Vibrational modes, thermal stabilities and luminescent properties reported.

  17. Thermodynamic nature of vitrification in a 1D model of a structural glass former

    NASA Astrophysics Data System (ADS)

    Semenov, A. N.

    2015-07-01

    We propose a new spin-glass model with no positional quenched disorder which is regarded as a coarse-grained model of a structural glass-former. The model is analyzed in the 1D case when the number N of states of a primary cell is large. For N → ∞, the model exhibits a sharp freezing transition of the thermodynamic origin. It is shown both analytically and numerically that the glass transition is accompanied by a significant growth of a static length scale ξ pointing to the structural (equilibrium) nature of dynamical slowdown effects in supercooled liquids.

  18. Thermodynamic nature of vitrification in a 1D model of a structural glass former.

    PubMed

    Semenov, A N

    2015-07-28

    We propose a new spin-glass model with no positional quenched disorder which is regarded as a coarse-grained model of a structural glass-former. The model is analyzed in the 1D case when the number N of states of a primary cell is large. For N → ∞, the model exhibits a sharp freezing transition of the thermodynamic origin. It is shown both analytically and numerically that the glass transition is accompanied by a significant growth of a static length scale ξ pointing to the structural (equilibrium) nature of dynamical slowdown effects in supercooled liquids. PMID:26233148

  19. Thermodynamic nature of vitrification in a 1D model of a structural glass former

    SciTech Connect

    Semenov, A. N.

    2015-07-28

    We propose a new spin-glass model with no positional quenched disorder which is regarded as a coarse-grained model of a structural glass-former. The model is analyzed in the 1D case when the number N of states of a primary cell is large. For N → ∞, the model exhibits a sharp freezing transition of the thermodynamic origin. It is shown both analytically and numerically that the glass transition is accompanied by a significant growth of a static length scale ξ pointing to the structural (equilibrium) nature of dynamical slowdown effects in supercooled liquids.

  20. Study of phase transformation and crystal structure for 1D carbon-modified titania ribbons

    SciTech Connect

    Zhou, Lihui Zhang, Fang; Li, Jinxia

    2014-02-15

    One-dimensional hydrogen titanate ribbons were successfully prepared with hydrothermal reaction in a highly basic solution. A series of one-dimensional carbon-modified TiO{sub 2} ribbons were prepared via calcination of the mixture of hydrogen titanate ribbons and sucrose solution under N{sub 2} flow at different temperatures. The phase transformation process of hydrogen titanate ribbons was investigated by in-situ X-ray diffraction at various temperatures. Besides, one-dimensional carbon-modified TiO{sub 2} ribbons calcined at different temperatures were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption isotherms, diffuse reflectance ultraviolet–visible spectroscopy, and so on. Carbon-modified TiO{sub 2} ribbons showed one-dimensional ribbon crystal structure and various crystal phases of TiO{sub 2}. After being modified with carbon, a layer of uniform carbon film was coated on the surface of TiO{sub 2} ribbons, which improved their adsorption capacity for methyl orange as a model organic pollutant. One-dimensional carbon-modified TiO{sub 2} ribbons also exhibited enhanced visible-light absorbance with the increase of calcination temperatures. - Highlights: • The synthesis of 1D carbon-modified TiO{sub 2} ribbons. • The phase transformation of 1D carbon-modified TiO{sub 2} ribbons. • 1D carbon-modified TiO{sub 2} exhibites enhanced visible-light absorbance.

  1. Computational Study and Analysis of Structural Imperfections in 1D and 2D Photonic Crystals

    SciTech Connect

    K.R. Maskaly

    2005-06-01

    increasing RMS roughness. Again, the homogenization approximation is able to predict these results. The problem of surface scratches on 1D photonic crystals is also addressed. Although the reflectivity decreases are lower in this study, up to a 15% change in reflectivity is observed in certain scratched photonic crystal structures. However, this reflectivity change can be significantly decreased by adding a low index protective coating to the surface of the photonic crystal. Again, application of homogenization theory to these structures confirms its predictive power for this type of imperfection as well. Additionally, the problem of a circular pores in 2D photonic crystals is investigated, showing that almost a 50% change in reflectivity can occur for some structures. Furthermore, this study reveals trends that are consistent with the 1D simulations: parameter changes that increase the absolute reflectivity of the photonic crystal will also increase its tolerance to structural imperfections. Finally, experimental reflectance spectra from roughened 1D photonic crystals are compared to the results predicted computationally in this thesis. Both the computed and experimental spectra correlate favorably, validating the findings presented herein.

  2. Fine velocity structures collisional dissipation in plasmas

    NASA Astrophysics Data System (ADS)

    Pezzi, Oreste; Valentini, Francesco; Veltri, Pierluigi

    2016-04-01

    In a weakly collisional plasma, such as the solar wind, collisions are usually considered far too weak to produce any significant effect on the plasma dynamics [1]. However, the estimation of collisionality is often based on the restrictive assumption that the particle velocity distribution function (VDF) shape is close to Maxwellian [2]. On the other hand, in situ spacecraft measurements in the solar wind [3], as well as kinetic numerical experiments [4], indicate that marked non-Maxwellian features develop in the three-dimensional VDFs, (temperature anisotropies, generation of particle beams, ring-like modulations etc.) as a result of the kinetic turbulent cascade of energy towards short spatial scales. Therefore, since collisional effects are proportional to the velocity gradients of the VDF, the collisionless hypothesis may fail locally in velocity space. Here, the existence of several characteristic times during the collisional relaxation of fine velocity structures is investigated by means of Eulerian numerical simulations of a spatially homogeneous force-free weakly collisional plasma. The effect of smoothing out velocity gradients on the evolution of global quantities, such as temperature and entropy, is discussed, suggesting that plasma collisionality can increase locally due to the velocity space deformation of the particle velocity distribution. In particular, by means of Eulerian simulations of collisional relaxation of a spatially homogeneous force-free plasma, in which collisions among particles of the same species are modeled through the complete Landau operator, we show that the system entropy growth occurs over several time scales, inversely proportional to the steepness of the velocity gradients in the VDF. We report clear evidences that fine velocity structures are dissipated by collisions in a time much shorter than global non-Maxwellian features, like, for example, temperature anisotropies. Moreover we indicate that, if small-scale structures

  3. Structural transformation in monolayer materials: a 2D to 1D transformation.

    PubMed

    Momeni, Kasra; Attariani, Hamed; LeSar, Richard A

    2016-07-20

    Reducing the dimensions of materials to atomic scales results in a large portion of atoms being at or near the surface, with lower bond order and thus higher energy. At such scales, reduction of the surface energy and surface stresses can be the driving force for the formation of new low-dimensional nanostructures, and may be exhibited through surface relaxation and/or surface reconstruction, which can be utilized for tailoring the properties and phase transformation of nanomaterials without applying any external load. Here we used atomistic simulations and revealed an intrinsic structural transformation in monolayer materials that lowers their dimension from 2D nanosheets to 1D nanostructures to reduce their surface and elastic energies. Experimental evidence of such transformation has also been revealed for one of the predicted nanostructures. Such transformation plays an important role in bi-/multi-layer 2D materials. PMID:27388501

  4. Vibron properties in quasi 1D molecular structures: the case of two parallel unshifted macromolecuar chains

    NASA Astrophysics Data System (ADS)

    Čevizović, D.; Petković, S.; Galović, S.; Reshetnyak, A.; Chizhov, A.

    2016-01-01

    We study the hopping mechanism of the vibron excitation transport in the system of two parallel unshifted 1D macromolecuar chains in the framework of non-adiabatic polaron theory. We suppose that the vibron interaction with thermal oscillations of the macromolecular structural elements will result in vibron self-trapping and the formation of the partial dressed vibron state. We also suppose that quasiparticle motion takes place via a sequence of random sitejumps, in each of which the quasiparticle can migrate either to the first neighbor site of the macromolecular chain. With use of the modified Holstein polaron model, we calculate the vibron effective mass in dependence of the basic system parameters and temperature. Special attention is paid to the influence of interchain coupling on vibron dressing. We find that for certain values of the system parameters the quasiparticle mass abruptly changes.

  5. Hydrothermal synthesis and structural characterization of two 1-D and 2-D Dawson-based phosphotungstates

    SciTech Connect

    Zhao Junwei; Zheng Shoutian; Liu Wei; Yang Guoyu

    2008-03-15

    Two new Dawson-based phosphotungstates (H{sub 2}en){sub 0.5}H[Cu(en){sub 2}(H{sub 2}O)]{sub 2}{l_brace}[Cu(en){sub 2}]({alpha}{sub 1}-P{sub 2}W{sub 17}CuO{sub 61}){r_brace}.8H{sub 2}O (1) (en=ethylenediamine) and [4,4'-H{sub 2}bpy]{sub 2}{l_brace}[Cu(4,4'-bpy){sub 3}][Cu(4,4'-bpy){sub 4}(H{sub 2}O){sub 2}]{sub 2}[Cu(4,4'-bpy)][{alpha}-P{sub 2}W{sub 1=} 8O{sub 62}]{sub 2}{r_brace}.6H{sub 2}O (2) (4,4'-bpy=4,4'-bipyridine) have been hydrothermally synthesized and structurally characterized. 1 crystallizes in the triclinic space group P-1 with a=11.7626(17), b=13.246(2), c=29.350(5) A, {alpha}=87.355(5), {beta}=79.583(5), {gamma}=66.993(3){sup o}, V=4138.3(11) A{sup 3}, Z=2, GOF=1.089, R{sub 1}=0.0563 and wR{sub 2}=0.1505, whereas 2 belongs to the orthorhombic space group Iba2 with a=22.277(8), b=47.04(2), c=22.153(8) A, V=23215(17) A{sup 3}, Z=4, GOF=1.051, R{sub 1}=0.0627 and wR{sub 2}=0.1477. 1 consists of a 1-D linear chain structure constructed from monocopper{sup II}-substituted Dawson polyoxoanions, while 2 represents the first 2-D sheet-like structure with a (4,4)-connected topological net built up from plenary Dawson-type polyoxoanions and Cu{sup II}-4,4'-bpy complex cations in polyoxometalate chemistry. - Graphical abstract: Two Dawson-based phosphotungstates (H{sub 2}en){sub 0.5}H[Cu(en){sub 2}(H{sub 2}O)]{sub 2}{l_brace}[Cu(en){sub 2}]({alpha}{sub 1}-P{sub 2}W{sub 17}CuO{sub 61}){r_brace}.8H{sub 2}O (1) and [4,4'-H{sub 2}bpy]{sub 2}{l_brace}[Cu(4,4'-bpy){sub 3}][Cu(4,4'-bpy){sub 4}(H{sub 2}O){sub 2}]{sub 2}[Cu(4,4'-bpy)][{alpha}-P{sub 2}W{sub 1=} 8O{sub 62}]{sub 2}{r_brace}.6H{sub 2}O (2) have been hydrothermally synthesized and structurally characterized. 1 consists of a 1-D linear chain structure constructed from monocopper-substituted Dawson polyoxoanions, while 2 represents the first 2-D sheet-like structure with a (4,4)-connected topological net built up from saturated Dawson-type polyoxoanions and Cu{sup II}-4,4'-bpy complex cations in

  6. MAGNETIC CORE SHELL STRUCTURES: from 0D to 1D assembling.

    PubMed

    Ficai, Denisa; Ficai, Anton; Dinu, Elena; Oprea, Ovidiu; Sonmez, Maria; Keler, Memduh Kagan; Sahin, Yesim Muge; Ekren, Nazmi; Inan, Ahmet Talat; Daglilar, Sibel; Gunduz, Oguzhan

    2015-01-01

    Material research and development studies are focused on different techniques of bringing out nanomaterials with desired characteristics and properties. From the point of view of materials development, nowadays scientists are strongly focused on obtaining materials with predefined characteristics and properties. The morphology control seems to be a determinant factor and increasing attention is devoted to this aspect. At this moment it is possible to engineer the material's features by using different methods and materials combination for both medical and industrial applications. In the applications of chemistry and synthesis, biology, mechanics, optics solar cells and microelectronics tailoring the adjustable parameters of stoichiometry, chemical structure, shape and segregation are evaluated and opens new fields. Because of the magnetic features of nanoparticles and durable particle size, less than 100 nm, this study is aiming to describe their uses in practical applications. That's why the whole hydrodynamic magnetic core shell topic will be reviewed on this paper. Additionally, the properties acting in general sight in solid-state physics are utilized for material selection and for defining issue connecting the core, shell structure and their producing properties. Here, in the study of core/shell nanoparticle various physical and chemical synthesis routes and the effect of electrospun method are briefly discussed. Starting from a real void of the scientific literature, the existent data related to the 1D magnetic electrospun materials are reviewed. The perspectives in the medical, environmental or energetic sector is great and bring some real advantages related to the 0D core@shell structures because both mechanical and biological properties are dependent on the morphology of the materials. PMID:26377653

  7. Velocity Structure Determination Through Seismic Waveform Modeling and Time Deviations

    NASA Astrophysics Data System (ADS)

    Savage, B.; Zhu, L.; Tan, Y.; Helmberger, D. V.

    2001-12-01

    Through the use of seismic waveforms recorded by TriNet, a dataset of earthquake focal mechanisms and deviations (time shifts) relative to a standard model facilitates the investigation of the crust and uppermost mantle of southern California. The CAP method of focal mechanism determination, in use by TriNet on a routine basis, provides time shifts for surface waves and Pnl arrivals independently relative to the reference model. These shifts serve as initial data for calibration of local and regional seismic paths. Time shifts from the CAP method are derived by splitting the Pnl section of the waveform, the first arriving Pn to just before the arrival of the S wave, from the much slower surface waves then cross-correlating the data with synthetic waveforms computed from a standard model. Surface waves interact with the entire crust, but the upper crust causes the greatest effect. Whereas, Pnl arrivals sample the deeper crust, upper mantle, and source region. This natural division separates the upper from lower crust for regional calibration and structural modeling and allows 3-D velocity maps to be created using the resulting time shifts. Further examination of Pnl and other arrivals which interact with the Moho illuminate the complex nature of this boundary. Initial attempts at using the first 10 seconds of the Pnl section to determine upper most mantle structure have proven insightful. Two large earthquakes north of southern California in Nevada and Mammoth Lakes, CA allow the creation of record sections from 200 to 600 km. As the paths swing from east to west across southern California, simple 1-D models turn into complex structure, dramatically changing the waveform character. Using finite difference models to explain the structure, we determine that a low velocity zone is present at the base of the crust and extends to 100 km in depth. Velocity variations of 5 percent of the mantle in combination with steeply sloping edges produces complex waveform variations

  8. Crystal Structures of Human TBC1D1 and TBC1D4 (AS160) RabGTPase-activating Protein (RabGAP) Domains Reveal Critical Elements for GLUT4 Translocation

    SciTech Connect

    S Park; W Jin; S Shoelson

    2011-12-31

    We have solved the x-ray crystal structures of the RabGAP domains of human TBC1D1 and human TBC1D4 (AS160), at 2.2 and 3.5 {angstrom} resolution, respectively. Like the yeast Gyp1p RabGAP domain, whose structure was solved previously in complex with mouse Rab33B, the human TBC1D1 and TBC1D4 domains both have 16 {alpha}-helices and no {beta}-sheet elements. We expected the yeast Gyp1p RabGAP/mouse Rab33B structure to predict the corresponding interfaces between cognate mammalian RabGAPs and Rabs, but found that residues were poorly conserved. We further tested the relevance of this model by Ala-scanning mutagenesis, but only one of five substitutions within the inferred binding site of the TBC1D1 RabGAP significantly perturbed catalytic efficiency. In addition, substitution of TBC1D1 residues with corresponding residues from Gyp1p did not enhance catalytic efficiency. We hypothesized that biologically relevant RabGAP/Rab partners utilize additional contacts not described in the yeast Gyp1p/mouse Rab33B structure, which we predicted using our two new human TBC1D1 and TBC1D4 structures. Ala substitution of TBC1D1 Met{sup 930}, corresponding to a residue outside of the Gyp1p/Rab33B contact, substantially reduced catalytic activity. GLUT4 translocation assays confirmed the biological relevance of our findings. Substitutions with lowest RabGAP activity, including catalytically dead RK and Met{sup 930} and Leu{sup 1019} predicted to perturb Rab binding, confirmed that biological activity requires contacts between cognate RabGAPs and Rabs beyond those in the yeast Gyp1p RabGAP/mouse Rab33B structure.

  9. Simulation of unsteady state performance of a secondary air system by the 1D-3D-Structure coupled method

    NASA Astrophysics Data System (ADS)

    Wu, Hong; Li, Peng; Li, Yulong

    2016-02-01

    This paper describes the calculation method for unsteady state conditions in the secondary air systems in gas turbines. The 1D-3D-Structure coupled method was applied. A 1D code was used to model the standard components that have typical geometric characteristics. Their flow and heat transfer were described by empirical correlations based on experimental data or CFD calculations. A 3D code was used to model the non-standard components that cannot be described by typical geometric languages, while a finite element analysis was carried out to compute the structural deformation and heat conduction at certain important positions. These codes were coupled through their interfaces. Thus, the changes in heat transfer and structure and their interactions caused by exterior disturbances can be reflected. The results of the coupling method in an unsteady state showed an apparent deviation from the existing data, while the results in the steady state were highly consistent with the existing data. The difference in the results in the unsteady state was caused primarily by structural deformation that cannot be predicted by the 1D method. Thus, in order to obtain the unsteady state performance of a secondary air system more accurately and efficiently, the 1D-3D-Structure coupled method should be used.

  10. The velocity structure of the lunar crust.

    NASA Technical Reports Server (NTRS)

    Kovach, R. L.; Watkins, J. S.

    1973-01-01

    Seismic refraction data, obtained at the Apollo 14 and 16 sites, when combined with other lunar seismic data, allow a compressional wave velocity profile of the lunar near-surface and crust to be derived. The regolith, although variable in thickness over the lunar surface, possesses surprisingly similar seismic properties. Underlying the regolith at both the Apollo 14 Fra Mauro site and the Apollo 16 Descartes site is low-velocity brecciated material or impact derived debris. Key features of the lunar seismic velocity profile are: (1) velocity increases from 100 to 300 m/sec in the upper 100 m to about 4 km/sec at 5 km depth, (2) a more gradual increase from about 4 km/sec to about 6 km/sec at 25 km depth,(3) a discontinuity at a depth of 25 km, and (4) a constant value of about 7 km/sec at depths from 25 km to about 60 km.

  11. The structure and electronic properties of copper iodide 1D nanocrystals within single walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Kiselev, N. A.; Kumskov, A. S.; Zhigalina, V. G.; Verbitskiy, N. I.; Yashina, L. V.; Chuvilin, A. L.; Vasiliev, A. L.; Eliseev, A. A.

    2013-11-01

    Copper iodide one-dimensional nanocrystals within single walled carbon nanotubes (1D CuI@SWCNTs), i.e. meta-nanotubes [1], were investigated by high resolution electron microscopy (HRTEM). In meta-nanotubes of diameter Dm = 1.3-1.4 nm produced by arc-discharge (AD) method close-packed hexagonal or deformed cubic 1D crystal anion sublattices were observed with cations in octahedral or tetrahedral positions. These two sublattices reversibly transform to one another. In catalysed chemical vapour deposition (CCVD) meta-nanotubes of diameters Dm = 1.5-2.0 nm cubic anion sublattices are formed. For diameters >=2.0 nm three-dimensional (3D) crystallization is observed.

  12. The nebular velocity structure of AG Pegasi

    NASA Technical Reports Server (NTRS)

    Oliversen, Nancy A.; Evans, Nancy R.; Anderson, Christopher M.

    1988-01-01

    Ultraviolet emission of the symbiotic star AG Peg which shows periodic variations in the central radial velocity and total flux of several emission lines was studied. Seventeen high dispersion archival SWP spectra covering the period from 1978.6 to 1986.9 were examined. Gaussian profiles were fit to each of the narrow emission lines of O III, N III, O IV, Si IV, C III, and Si III. Radial velocity curves with an amplitude of 15 to 20 km/sec were measured for the N III 1748.6 A, 1749.7 A lines, the O III 1660.8 A, 1666.2 A lines, and the C III 1908.7 A line. The O IV and Si IV lines were generally too weakly exposed to derive reliable velocity curves, while the Si III line was often overexposed. The N III, O III, and C III line fluxes are correlated with phase. These line flux and velocity changes are consistent with formation of the lines near the red giant.

  13. From 1D chain to 3D network: A theoretical study on TiO2 low dimensional structures

    NASA Astrophysics Data System (ADS)

    Guo, Ling-ju; Zeng, Zhi; He, Tao

    2015-06-01

    We have performed a systematic study on a series of low dimensional TiO2 nanostructures under density functional theory methods. The geometries, stabilities, growth mechanism, and electronic structures of 1D chain, 2D ring, 2D ring array, and 3D network of TiO2 nanostructures are analyzed. Based on the Ti2O4 building unit, a series of 1D TiO2 nano chains and rings can be built. Furthermore, 2D ring array and 3D network nanostructures can be constructed from 1D chains and rings. Among non-periodic TiO2 chain and ring structures, one series of ring structures is found to be more stable. The geometry model of the 2D ring arrays and 3D network structures in this work has provided a theoretical understanding on the structure information in experiments. Based on these semiconductive low dimensional structures, moreover, it can help to understand and design new hierarchical TiO2 nanostructure in the future.

  14. From 1D chain to 3D network: A theoretical study on TiO{sub 2} low dimensional structures

    SciTech Connect

    Guo, Ling-ju; He, Tao; Zeng, Zhi

    2015-06-14

    We have performed a systematic study on a series of low dimensional TiO{sub 2} nanostructures under density functional theory methods. The geometries, stabilities, growth mechanism, and electronic structures of 1D chain, 2D ring, 2D ring array, and 3D network of TiO{sub 2} nanostructures are analyzed. Based on the Ti{sub 2}O{sub 4} building unit, a series of 1D TiO{sub 2} nano chains and rings can be built. Furthermore, 2D ring array and 3D network nanostructures can be constructed from 1D chains and rings. Among non-periodic TiO{sub 2} chain and ring structures, one series of ring structures is found to be more stable. The geometry model of the 2D ring arrays and 3D network structures in this work has provided a theoretical understanding on the structure information in experiments. Based on these semiconductive low dimensional structures, moreover, it can help to understand and design new hierarchical TiO{sub 2} nanostructure in the future.

  15. Inhibition of Human Steroid 5-Reductase (AKR1D1) by Finasteride and Structure of the Enzyme-Inhibitor Complex

    SciTech Connect

    Drury, J.; Di Costanzo, L; Penning, T; Christianson, D

    2009-01-01

    The {Delta}{sup 4}-3-ketosteroid functionality is present in nearly all steroid hormones apart from estrogens. The first step in functionalization of the A-ring is mediated in humans by steroid 5{alpha}- or 5{beta}-reductase. Finasteride is a mechanism-based inactivator of 5{alpha}-reductase type 2 with subnanomolar affinity and is widely used as a therapeutic for the treatment of benign prostatic hyperplasia. It is also used for androgen deprivation in hormone-dependent prostate carcinoma, and it has been examined as a chemopreventive agent in prostate cancer. The effect of finasteride on steroid 5{beta}-reductase (AKR1D1) has not been previously reported. We show that finasteride competitively inhibits AKR1D1 with low micromolar affinity but does not act as a mechanism-based inactivator. The structure of the AKR1D1 {center_dot} NADP{sup +} {center_dot} finasteride complex determined at 1.7 {angstrom} resolution shows that it is not possible for NADPH to reduce the {Delta}{sup 1-2}-ene of finasteride because the cofactor and steroid are not proximal to each other. The C3-ketone of finasteride accepts hydrogen bonds from the catalytic residues Tyr-58 and Glu-120 in the active site of AKR1D1, providing an explanation for the competitive inhibition observed. This is the first reported structure of finasteride bound to an enzyme involved in steroid hormone metabolism.

  16. Structure, electrochemical properties and capacitance performance of polypyrrole electrodeposited onto 1-D crystals of iridium complex

    NASA Astrophysics Data System (ADS)

    Wysocka-Żołopa, Monika; Winkler, Krzysztof

    2015-12-01

    Composites of polypyrrole and one-dimensional iridium complex crystals [(C2H5)4N]0.55[IrCl2(CO)2] were prepared by in situ two-step electrodeposition. Initially, iridium complex crystals were formed during [IrCl2(CO)2]- complex oxidation. Next, pyrrole was electropolymerized on the surface of the iridium needles. The morphology of the composite was investigated by scanning and transmission electron microscopy. At positive potentials, the iridium complex crystals and the polypyrrole were oxidized. In aprotic solvents, oxidation of the iridium complex crystals resulted in their dissolution. In water containing tetra(n-butyl)ammonium chlorides, the 1-D iridium complex crystals were reversibly oxidized. The product of the iridium complex oxidation remained on the electrode surface in crystalline form. The iridium complex needles significantly influenced the redox properties of the polymer. The polypyrrole involved electrode processes become more reversible in presence of crystals of iridium complex. The current of polypyrrole oxidation was higher compared to that of pure polypyrrole and the capacitance properties of the polymer were significantly enhanced. A specific capacitance as high as 590 F g-1 was obtained for a composite of polypyrrole and 1-D crystals of the iridium complex in water containing tetra(n-butyl)ammonium chloride. This value is approximately twice as high as the capacitance of the pure polymer deposited onto the electrode surface.

  17. Site-effect estimations for Taipei Basin based on shallow S-wave velocity structures

    NASA Astrophysics Data System (ADS)

    Chen, Ying-Chi; Huang, Huey-Chu; Wu, Cheng-Feng

    2016-03-01

    Shallow S-wave velocities have been widely used for earthquake ground-motion site characterization. Thus, the S-wave velocity structures of Taipei Basin, Taiwan were investigated using array records of microtremors at 15 sites (Huang et al., 2015). In this study, seven velocity structures are added to the database describing Taipei Basin. Validity of S-wave velocity structures are first examined using the 1D Haskell method and well-logging data at the Wuku Sewage Disposal Plant (WK) borehole site. Basically, the synthetic results match well with the observed data at different depths. Based on S-wave velocity structures at 22 sites, theoretical transfer functions at five different formations of the sedimentary basin are calculated. According to these results, predominant frequencies for these formations are estimated. If the S-wave velocity of the Tertiary basement is assumed to be 1000 m/s, the predominant frequencies of the Quaternary sediments are between 0.3 Hz (WUK) and 1.4 Hz (LEL) in Taipei Basin while the depths of sediments between 0 m (i.e. at the edge of the basin) and 616 m (i.e. site WUK) gradually increase from southeast to northwest. Our results show good agreement with available geological and geophysical information.

  18. Shear wave velocity structures of the Arabian Peninsula

    NASA Astrophysics Data System (ADS)

    Mokhtar, Talal A.; Al-Saeed, Mohammed M.

    1994-02-01

    The shear velocity 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 group velocities indicates that the Arabian shield can be modeled by two layers, each of which is 20 km thick with a shear velocity of 3.61 km/s in the upper crust and 3.88 km/s in the lower crust. The underlying upper mantle velocity is 4.61 km/s. Inversion of both Love and Rayleigh waves group velocities shows that the Arabian platform upper and lower crusts are comparable in their thicknesses to those of the shield, but with shear velocities of 3.4 and 4 km/s, respectively. The upper mantle velocity beneath the platform is 4.4 km/s and the average total thickness of the crust is 45 km.

  19. Upper mantle shear and compressional velocity structures beneath southern Africa

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Wen, L.; Weidner, D.

    2005-12-01

    The velocity structures in the upper mantle play an important role in understanding mantle composition and temperature. In this study, we constrain the fine seismic shear and compressional velocity structures in the upper mantle beneath southern Africa by waveform modeling the seismic data recorded in the Kaapvaal array at the distance range of 9°-28° for an event occurring near Lake Tanganyika in east Africa. We then explore mineralogical models that would explain the inferred seismic structures. The seismic data recorded at this distance range provide excellent sampling of both the SH and P velocity structures in the top 800 km of the mantle. The first direct arrivals in both the P and SH data become weak at an epicentral distance of about 20°, indicating presence of a low velocity zone beneath southern Africa at a depth of about 150 km. In the SH data, the observed travel times of the reflected and triplicated phases off the 410-km discontinuity require a large shear velocity reduction in the low velocity zone and a small shear velocity jump across the 410-km discontinuity; the observed triplications at the 660-km discontinuity require a large shear velocity jump across the 660-km discontinuity. In the P wave data, the observed travel times of the triplication at the 410-km discontinuity suggest a small P wave velocity reduction in the low velocity zone, a large velocity jump across the 410-km discontinuity and a high Vp/Vs ratio in the transition zone; the triplication at the 660-km discontinuity is indiscernible, suggesting a small P wave velocity jump across the 660-km discontinuity. Overall, the seismic data can be explained by a 150-km thick high-velocity lid overlying a low velocity zone between 150 km and 405 km depths with a P wave velocity reduction of -1.5% and an SH wave velocity reduction of -9%, followed by a small shear velocity jump of 3% and a large P velocity jump of 10% across the 410-km discontinuity, a transition zone with a high Vp

  20. Middle and upper crust shear-wave velocity structure of the Chinese mainland

    NASA Astrophysics Data System (ADS)

    Feng, Mei; An, Mei-Jian

    2007-07-01

    In order to give a more reliable shallow crust model for the Chinese mainland, the present study collected many short-period surface wave data which are better sensitive to shallow earth structures. Different from traditional two-step surface wave tomography, we developed a new linearized surface wave dispersion inversion method to directly get a 3D S-wave velocity model in the second step instead of inverting for 1D S-velocity profile cell by cell. We convert all the regionalized dispersions into linear constraints for a 3D S-velocity model. Checkerboard tests show that this method can give reasonable results. The distribution of the middle-and upper-crust shear-wave velocity of the Chinese mainland in our model is strongly heterogeneous and related to different geotectonic terrains. Low-velocity anomalies delineated very well most of the major sedimentary basins of China. And the variation of velocities at different depths gives an indication of basement depth of the basins. The western Tethyan tectonic domain (on the west of the 95°E longitude) is characterized by low velocity, while the eastern Tethyan domain does not show obvious low velocity. Since petroleum resources often distribute in sedimentary basins where low-velocity anomaly appears, the low velocity anomalies in the western Tethyan domain may indicate a better petroleum prospect than in its eastern counterpart. Besides, low velocity anomaly in the western Tethyan domain and around the Xing’an orogenic belt may be partly caused by high crustal temperature. The weak low-velocity belt along ˜105°E longitude corresponds to the N-S strong seismic belt of central China.

  1. Syntheses, structures, and properties of two novel cadmium coordination polymers with 1D and 2D structures

    NASA Astrophysics Data System (ADS)

    Yan, Li; Li, Chuanbi; Zhu, Dongsheng; Xu, Lin

    2011-09-01

    Two novel complexes [Cd 2(MIP) 2(BDC) 2]n ( 1) [MIP = 2-(3-methoxyphenyl)-1H-imidazo[4,5-f][1,10]phenanthroline, BDC = terephthalic acid] and [Cd(IPM)(NDC)]n ( 2) [IPM = 4-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)-2-methoxyphenol, NDC = naphthalene-1,4-dicarboxylic acid] have been synthesized by hydrothermal reaction and characterized by elemental analysis, IR, single-crystal X-ray diffraction and thermogravimetric analysis (TGA). Complex 1 exhibits 1D zigzag chain structure and complex 2 shows 2D layer topology. The intermolecular C sbnd H⋯O interactions extend the complex 1 into 2D networks, and the existing H-bonds further stabilized the complexes 1-2, which can be proved by TGA experiment. Furthermore, the solid-state fluorescence spectrum of the complex 2 was studied, as well as the ligand IPM. The complex 2 exhibits intense broad emission at 540 nm at room temperature, which is red-shifted by 45 nm relative to that of free ligand IPM.

  2. An approach to control tuning range and speed in 1D ternary photonic band gap material nano-layered optical filter structures electro-optically

    NASA Astrophysics Data System (ADS)

    Zia, Shahneel; Banerjee, Anirudh

    2016-05-01

    This paper demonstrates a way to control spectrum tuning capability in one-dimensional (1D) ternary photonic band gap (PBG) material nano-layered structures electro-optically. It is shown that not only tuning range, but also tuning speed of tunable optical filters based on 1D ternary PBG structures can be controlled Electro-optically. This approach finds application in tuning range enhancement of 1D Ternary PBG structures and compensating temperature sensitive transmission spectrum shift in 1D Ternary PBG structures.

  3. Shallow Seismic Velocity Structure of the Betic Cordillera (Southern Spain) from Modelling of Rayleigh Wave Dispersion

    NASA Astrophysics Data System (ADS)

    Chourak, M.; Corchete, V.; Badal, J.; Gómez, F.; Serón, J.

    2005-07-01

    A detailed dispersion analysis of Rayleigh waves generated by local earthquakes and occasionally by blasts that occurred in southern Spain, was undertaken to obtain the shear-wave velocity structure of the region at shallow depth. Our database includes seismograms generated by 35 seismic events that were recorded by 15 single-component short-period stations from 1990 to 1995. All these events have focal depths less than 10 km and body-wave magnitudes between 3.0 and 4.0, and they were all recorded at distances between 40 and 300 km from the epicentre. We analysed a total of 90 source-station Rayleigh-wave paths. The collected data were processed by standard digital filtering techniques to obtain Rayleigh-wave group-velocity dispersion measurements. The path-averaged group velocities vary from 1.12 to 2.25 km/s within the 1.0-6.0 s period interval. Then, using a stochastic inversion approach we obtained 1-D shear-wave velocity depth models across the study area, which were resolved to a depth of circa 5 km. The inverted shear-wave velocities range approximately between 1.0 and 3.8 km/s with a standard deviation range of 0.05 0.16 km/s, and show significant variations from region to region. These results were combined to produce 3-D images via volumetric modelling and data visualization. We present images that show different shear velocity patterns for the Betic Cordillera. Looking at the velocity distribution at various depths and at vertical sections, we discuss of the study area in terms of subsurface structure and S-wave velocity distribution (low velocity channels, basement depth, etc.) at very shallow depths (0 5 km). Our results characterize the region sufficiently and lead to a correlation of shear-wave velocity with the different geological units features.

  4. Synthesis, crystal structure, and properties of a 1-D terbium-substituted monolacunary Keggin-type polyoxotungstate.

    PubMed

    Ma, Pengtao; Si, Yanan; Wan, Rong; Zhang, Shaowei; Wang, Jingping; Niu, Jingyang

    2015-03-01

    A new 1-D linear chainlike terbium-substituted polyoxometalate [Tb(H2O)2(α-PW11O39)](4-) (1) has been synthesized in aqueous solution and characterized by elemental analysis, inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray powder diffraction (XRPD), IR spectrum, thermal analysis, electrospray ionization mass spectrometry (ESI-MS), and X-ray single-crystal diffraction. X-ray structural analysis reveals that 1 displays a 1-D linear chain containing [Tb(H2O)2(α-PW11O39)](4-) moieties. The Tb(III) cation incorporated into the monolacunary Keggin-type [α-PW11O39](7-) unit resides in a distorted monocapped triangular prismatic geometry and acts as a linker to join two adjacent [α-PW11O39](7-) units to form a 1-D chain structure. Solid-state photoluminescent property of 1 has been investigated at room temperature and the photoluminescent emission mainly results from the synergistic effect of the Tb(III) cation and the Na7[α-PW11O39] precursor. The ESI-MS spectrum of 1 confirms that the polyanion [Tb(H2O)(HPW11O39)](3-) is stable in aqueous solution. PMID:25541394

  5. Synthesis, crystal structure, and properties of a 1-D terbium-substituted monolacunary Keggin-type polyoxotungstate

    NASA Astrophysics Data System (ADS)

    Ma, Pengtao; Si, Yanan; Wan, Rong; Zhang, Shaowei; Wang, Jingping; Niu, Jingyang

    2015-03-01

    A new 1-D linear chainlike terbium-substituted polyoxometalate [Tb(H2O)2(α-PW11O39)]4- (1) has been synthesized in aqueous solution and characterized by elemental analysis, inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray powder diffraction (XRPD), IR spectrum, thermal analysis, electrospray ionization mass spectrometry (ESI-MS), and X-ray single-crystal diffraction. X-ray structural analysis reveals that 1 displays a 1-D linear chain containing [Tb(H2O)2(α-PW11O39)]4- moieties. The Tb(III) cation incorporated into the monolacunary Keggin-type [α-PW11O39]7- unit resides in a distorted monocapped triangular prismatic geometry and acts as a linker to join two adjacent [α-PW11O39]7- units to form a 1-D chain structure. Solid-state photoluminescent property of 1 has been investigated at room temperature and the photoluminescent emission mainly results from the synergistic effect of the TbIII cation and the Na7[α-PW11O39] precursor. The ESI-MS spectrum of 1 confirms that the polyanion [Tb(H2O)(HPW11O39)]3- is stable in aqueous solution.

  6. Structure-based design of novel Chlamydomonas reinhardtii D1-D2 photosynthetic proteins for herbicide monitoring

    PubMed Central

    Rea, Giuseppina; Polticelli, Fabio; Antonacci, Amina; Scognamiglio, Viviana; Katiyar, Prashant; Kulkarni, Sudhir A; Johanningmeier, Udo; Giardi, Maria Teresa

    2009-01-01

    The D1-D2 heterodimer in the reaction center core of phototrophs binds the redox plastoquinone cofactors, QA and QB, the terminal acceptors of the photosynthetic electron transfer chain in the photosystem II (PSII). This complex is the target of the herbicide atrazine, an environmental pollutant competitive inhibitor of QB binding, and consequently it represents an excellent biomediator to develop biosensors for pollutant monitoring in ecosystems. In this context, we have undertaken a study of the Chlamydomonas reinhardtii D1-D2 proteins aimed at designing site directed mutants with increased affinity for atrazine. The three-dimensional structure of the D1 and D2 proteins from C. reinhardtii has been homology modeled using the crystal structure of the highly homologous Thermosynechococcus elongatus proteins as templates. Mutants of D1 and D2 were then generated in silico and the atrazine binding affinity of the mutant proteins has been calculated to predict mutations able to increase PSII affinity for atrazine. The computational approach has been validated through comparison with available experimental data and production and characterization of one of the predicted mutants. The latter analyses indicated an increase of one order of magnitude of the mutant sensitivity and affinity for atrazine as compared to the control strain. Finally, D1-D2 heterodimer mutants were designed and selected which, according to our model, increase atrazine binding affinity by up to 20 kcal/mol, representing useful starting points for the development of high affinity biosensors for atrazine. PMID:19693932

  7. Impulse noise removal using 1-D switching median filter with adaptive scanning order based on structural context of image

    NASA Astrophysics Data System (ADS)

    Koga, Takanori; Suetake, Noriaki

    2015-02-01

    This paper describes the detail-preserving impulse noise removal performance of a one-dimensional (1-D) switching median filter (SMF) applied along an adaptive space-filling curve. Usually, a SMF with a two-dimensional (2-D) filter window is widely used for impulse noise removal while still preserving detailed parts in an input image. However, the noise detector of the 2-D filter does not always distinguish between the original pixels and the noise-corrupted ones perfectly. In particular, pixels constituting thin lines in an input image tend to be incorrectly detected as noise-corrupted pixels, and such pixels are filtered regardless of the necessity of the filtering. To cope with this problem, we propose a new impulse noise removal method based on a 1-D SMF and a space-filling curve which is adaptively drawn using a minimum spanning tree reflecting structural context of an input image.

  8. Hyperfine structures of the nd /sup 1/D(n = 3 - 8) states of /sup 3/He I

    SciTech Connect

    Brooks, R.L.; Streif, V.F.; Berry, H.G.

    1981-01-01

    We have used the beam-foil quantum beat method to measure the hyperfine structure separations F = 3/2 - 5/2 of the 1snd /sup 1/D states (n = 3 - 8) of /sup 3/He I. We observed the single frequency modulated decay curves of the 1s2p /sup 1/P - 1snd /sup 1/D transitions for times after excitation up to 50 ns, corresponding to 4 to 5 modulation periods. The frequencies obtained (with a precision of 2 to 5%) are compared with other experiments and theory. The frequencies are determined mainly by the singlet-triplet energy separations and mixing factors for the He I D-states. The results agree with the same parameters obtained from other recent level-crossing measurements in strong magnetic field mixing of the singlet-triplet states.

  9. Optical reflectance and omnidirectional bandgaps in Fibonacci quasicrystals type 1-D multilayer structures containing exponentially graded material

    NASA Astrophysics Data System (ADS)

    Singh, Bipin K.; Thapa, Khem B.; Pandey, Praveen C.

    2013-06-01

    A theoretical study of optical reflectance and reflection bands of 1-D photonic quasi-crystals (Fibonacci type arrangement) composed of exponentially graded material is presented. The proposed structures consist of two different layers, one of them is of constant refractive index (L) and the other one is of exponentially graded refractive index (S) dielectric materials. Four different generations (2nd, 3rd, 4th and 5th) of the Fibonacci sequence for 10 periods in one dimension (1-D) are considered and compared in view of their optical reflectance and bandgaps for both TE and TM polarisations. Also, we proposed some heterostructures made by the combination of different Fibonacci generations and their periods to obtain suitable omnidirectional reflection band. We used the transfer matrix method (TMM) to obtain the reflectance, bandgaps and omnidirectional reflectional bandgaps (ODR) of such structures in near infrared spectrum (800-2200 nm) at different angles of incidence. We show that ODR exists in these types of structures. The number of ODRs and total bandgap depend on the Fibonacci generations. Extraordinary ODR bandgaps are obtained in the case of heterostructures formed by the combination of different generations of the Fibonacci sequence. The ODR for these structures is similar to the ODR of photonic crystals containing left-handed materials. This work would be useful to study the Fibonacci type photonic crystals having graded index materials and also it will open new window to design several photonic crystal devices like sensors, reflectors, etc. in the infrared region.

  10. Bifurcation Structures in a Family of 1D Discontinuous Linear-Hyperbolic Invertible Maps

    NASA Astrophysics Data System (ADS)

    Makrooni, Roya; Gardini, Laura; Sushko, Iryna

    2015-12-01

    We consider a family of one-dimensional discontinuous invertible maps from an application in engineering. It is defined by a linear function and by a hyperbolic function with real exponent. The presence of vertical and horizontal asymptotes of the hyperbolic branch leads to particular codimension-two border collision bifurcation (BCB) such that if the parameter point approaches the bifurcation value from one side then the related cycle undergoes a regular BCB, while if the same bifurcation value is approached from the other side then a nonregular BCB occurs, involving periodic points at infinity, related to the asymptotes of the map. We investigate the bifurcation structure in the parameter space. Depending on the exponent of the hyperbolic branch, different period incrementing structures can be observed, where the boundaries of a periodicity region are related either to subcritical, or supercritical, or degenerate flip bifurcations of the related cycle, as well as to a regular or nonregular BCB. In particular, if the exponent is positive and smaller than one, then the period incrementing structure with bistability regions is observed and the corresponding flip bifurcations are subcritical, while if the exponent is larger than one, then the related flip bifurcations are supercritical and, thus, also the regions associated with cycles of double period are involved into the incrementing structure.

  11. Design of natural killer T cell activators: Structure and function of a microbial glycosphingolipid bound to mouse CD1d

    PubMed Central

    Wu, Douglass; Zajonc, Dirk M.; Fujio, Masakazu; Sullivan, Barbara A.; Kinjo, Yuki; Kronenberg, Mitchell; Wilson, Ian A.; Wong, Chi-Huey

    2006-01-01

    Natural killer T (NKT) cells provide an innate-type immune response upon T cell receptor interaction with CD1d-presented antigens. We demonstrate through equilibrium tetramer binding and antigen presentation assays with Vα14i-positive NKT cell hybridomas that the Sphingomonas glycolipid α-galacturonosyl ceramide (GalA-GSL) is a NKT cell agonist that is significantly weaker than α-galactosylceramide (α-GalCer), the most potent known NKT agonist. For GalA-GSL, a shorter fatty acyl chain, an absence of the 4-OH on the sphingosine tail and a 6′-COOH group on the galactose moiety account for its observed antigenic potency. We further determined the crystal structure of mCD1d in complex with GalA-GSL at 1.8-Å resolution. The overall binding mode of GalA-GSL to mCD1d is similar to that of the short-chain α-GalCer ligand PBS-25, but its sphinganine chain is more deeply inserted into the F′ pocket due to alternate hydrogen-bonding interactions between the sphinganine 3-OH with Asp-80. Subsequently, a slight lateral shift (>1 Å) of the galacturonosyl head group is noted at the CD1 surface compared with the galactose of α-GalCer. Because the relatively short C14 fatty acid of GalA-GSL does not fully occupy the A′ pocket, a spacer lipid is found that stabilizes this pocket. The lipid spacer was identified by GC/MS as a mixture of saturated and monounsaturated palmitic acid (C16). Comparison of available crystal structures of α-anomeric glycosphingolipids now sheds light on the structural basis of their differential antigenic potency and has led to the design and synthesis of NKT cell agonists with enhanced cell-based stimulatory activities compared with α-GalCer. PMID:16537470

  12. ESTIMATION OF S-WAVE VELOCITY STRUCTURE OF FUKUI PLAIN BASED ON MICROTREMOR ARRAY OBSERVATION

    NASA Astrophysics Data System (ADS)

    Kojima, Keisuke; Moto, Koudai

    The precise evaluations of Quaternary structure of the region are indispensable in order to accurately predict the seismic damage. However, deep borehole, PS-logging and elastic wave exploration have been executed only on limited points around the Fukui Plain. The problem analyzed in this study is statistical estimation of the 3D S-wave velocity structure down to the Tertiary bedrock of the Fukui Plain based on the data from 75 microtremor array observation sites. The Rayleigh wave phase velocities at each array site were calculated by the spatial autocorrelation method. The phase velocities at each site were inverted to a 1D S-wave profile using a genetic inversion. The 3-components single-site microtremor observations were carried out to compensate the array observations. The 3D S-wave velocity structure around the Fukui plain have been interpolated by using Kriging and Co-Kriging techniques. In the Co-Kriging procedure, the correlations between the estimated depths of Quaternary and the observed predominant periods of the sites were taken into account. The validity of the estimated structure from the microtremor observation was confirmed by comparing with the density structure and with the existing PS-logging data.

  13. Collisional Relaxation of Fine Velocity Structures in Plasmas.

    PubMed

    Pezzi, Oreste; Valentini, Francesco; Veltri, Pierluigi

    2016-04-01

    The existence of several characteristic times during the collisional relaxation of fine velocity structures is investigated by means of Eulerian numerical simulations of a spatially homogeneous force-free weakly collisional plasma. The effect of smoothing out velocity gradients on the evolution of global quantities, such as temperature and entropy, is discussed, suggesting that plasma collisionality can locally increase due to velocity space deformations of the particle velocity distribution function. These results support the idea that high-resolution measurements of the particle velocity distribution function are crucial for an accurate description of weakly collisional systems, such as the solar wind, in order to answer relevant scientific questions, related, for example, to particle heating and energization. PMID:27104713

  14. Collisional Relaxation of Fine Velocity Structures in Plasmas

    NASA Astrophysics Data System (ADS)

    Pezzi, Oreste; Valentini, Francesco; Veltri, Pierluigi

    2016-04-01

    The existence of several characteristic times during the collisional relaxation of fine velocity structures is investigated by means of Eulerian numerical simulations of a spatially homogeneous force-free weakly collisional plasma. The effect of smoothing out velocity gradients on the evolution of global quantities, such as temperature and entropy, is discussed, suggesting that plasma collisionality can locally increase due to velocity space deformations of the particle velocity distribution function. These results support the idea that high-resolution measurements of the particle velocity distribution function are crucial for an accurate description of weakly collisional systems, such as the solar wind, in order to answer relevant scientific questions, related, for example, to particle heating and energization.

  15. Extremal inversion of lunar travel time data. [seismic velocity structure

    NASA Technical Reports Server (NTRS)

    Burkhard, N.; Jackson, D. D.

    1975-01-01

    The tau method, developed by Bessonova et al. (1974), of inversion of travel times is applied to lunar P-wave travel time data to find limits on the velocity structure of the moon. Tau is the singular solution to the Clairaut equation. Models with low-velocity zones, with low-velocity zones at differing depths, and without low-velocity zones, were found to be consistent with data and within the determined limits. Models with and without a discontinuity at about 25-km depth have been found which agree with all travel time data to within two standard deviations. In other words, the existence of the discontinuity and its size and location have not been uniquely resolved. Models with low-velocity channels are also possible.

  16. Source Mechanisms, Velocity Structures and Himalaya Tectonics

    NASA Astrophysics Data System (ADS)

    Wu, F. T.; Sheehan, A. F.; Huang, G.; Monsalve, G.

    2003-12-01

    The Himalayan Nepal-Tibet Seismic Experiment (HIMNT; in a region bounded by 26.7 and 29.5 degrees N latitudes and 85 and 88 degrees E longitudes) produced, for the first time, broadband seismic data appropriate for determining earthquake and lithospheric characteristics with a local network astride as well as along the high Himalaya. A suite of studies are being conducted in an attempt to gain subsurface information for a better understanding of the orogenic processes that produced the mountain range. First, it is somewhat surprising that of the 20 earthquakes (M>3.5) for which we are able to use waveform inversion to derive focal mechanisms the great majority of them are tensile types with generally EW oriented T-axes. Some of these events are shallow (~20 km) crustal events and a few are deeper crustal or even upper mantle ones (50-80 km). Several of them appear to be related to the N-S trending graben structures at the surface. Initial attempts at tomography yield structures that generally agree with the the results of receiver function analyses (Schulte-Pelkum, this meeting), with a crust of about 45 km under southern Himalaya and much thicker under the Nothern Himalaya in Tibet. The relocated seismicity using hypoDD (this paper and Monsalve et al., this meeting) lie in well-defined zones. In the region around Mount Everest a zone dips at shallow angle (< 10 degrees) from the Greater Himalaya toward the south can be seen. Under the low foothills in south Nepal steep dipping zones between 30 and 60 km are found in some sections. The seismicity in the upper crust (<30 km) under the high Himalayan range is notable in places but under the eastern part of our network deeper crustal (60 < h < 80 km) concentrate without much shall seismicity. While the shallow (~20 km) reflector from the receiver function analyses can be interpreted as the presence of Indian lithosphere and lends support to the INDEPTH model, the interpretation of seismicity and focal mechanisms

  17. A 3D-1D substitution matrix for protein fold recognition that includes predicted secondary structure of the sequence.

    PubMed

    Rice, D W; Eisenberg, D

    1997-04-11

    In protein fold recognition, a probe amino acid sequence is compared to a library of representative folds of known structure to identify a structural homolog. In cases where the probe and its homolog have clear sequence similarity, traditional residue substitution matrices have been used to predict the structural similarity. In cases where the probe is sequentially distant from its homolog, we have developed a (7 x 3 x 2 x 7 x 3) 3D-1D substitution matrix (called H3P2), calculated from a database of 119 structural pairs. Members of each pair share a similar fold, but have sequence identity less than 30%. Each probe sequence position is defined by one of seven residue classes and three secondary structure classes. Each homologous fold position is defined by one of seven residue classes, three secondary structure classes, and two burial classes. Thus the matrix is five-dimensional and contains 7 x 3 x 2 x 7 x 3 = 882 elements or 3D-1D scores. The first step in assigning a probe sequence to its homologous fold is the prediction of the three-state (helix, strand, coil) secondary structure of the probe; here we use the profile based neural network prediction of secondary structure (PHD) program. Then a dynamic programming algorithm uses the H3P2 matrix to align the probe sequence with structures in a representative fold library. To test the effectiveness of the H3P2 matrix a challenging, fold class diverse, and cross-validated benchmark assessment is used to compare the H3P2 matrix to the GONNET, PAM250, BLOSUM62 and a secondary structure only substitution matrix. For distantly related sequences the H3P2 matrix detects more homologous structures at higher reliabilities than do these other substitution matrices, based on sensitivity versus specificity plots (or SENS-SPEC plots). The added efficacy of the H3P2 matrix arises from its information on the statistical preferences for various sequence-structure environment combinations from very distantly related proteins. It

  18. Three-dimensional P-wave velocity structure of Damavand Volcano, Iran

    NASA Astrophysics Data System (ADS)

    Mostafanejad, A.; Shomali, H.

    2009-04-01

    Damavand volcano is the highest peak in the Middle East ( 5670 m ). It is a large intraplate composite cone representing an accumulation of more than 400 km3 of trachyandesite lavas and pyroclastic material overlying the active fold and-thrust belt of the Alborz Mountains,the range that fringes the southern Caspian Sea. It shows fumarolic activity near the summit but no evidence of eruption in the past 1000 yr. The target region, Damavand volcano, is a Quaternary age volcano laying about 65 km northeast of Tehran metropolitan, Iran. A data set of over 1200 earthquakes recorded on a local 19 station short-period network between 1996 and 2006 provided by the Iranian Seismological Centre (ISC) is used for inversion in a well constrained and worldwide adopted code (SIMULPS). A 3-D velocity model beneath Damavand volcano has been obtained through inversion of P-wave arrivals of local earthquakes. About 1200 seismic events distributed around this volcano from surface up to a depth of about 30 km have been used to infer the P-wave velocity structure. The seismic arrival times were directly inverted using a 1D velocity model optimally representing the background structure. We used different grid spacing that provided detailed images of the volcano in order to investigate whether or not the anomalies are resolved by the data or are artifacts of the inversion. The resolution analysis carefully performed on the model parameters allowed the determination of a more reliable final model that represented the best results for the velocity structure beneath the volcano. The final model revealed an anomalous structure with a high velocity anomaly located beneath the volcano and a low velocity anomaly dominated the shallower depths. The spatial pattern of 3D velocity anomalies resolved in the region appears to be correlated at surface with the distribution of seismicity and major tectonic units and faults.

  19. Structure elucidation of organic compounds from natural sources using 1D and 2D NMR techniques

    NASA Astrophysics Data System (ADS)

    Topcu, Gulacti; Ulubelen, Ayhan

    2007-05-01

    In our continuing studies on Lamiaceae family plants including Salvia, Teucrium, Ajuga, Sideritis, Nepeta and Lavandula growing in Anatolia, many terpenoids, consisting of over 50 distinct triterpenoids and steroids, and over 200 diterpenoids, several sesterterpenoids and sesquiterpenoids along with many flavonoids and other phenolic compounds have been isolated. For Salvia species abietanes, for Teucrium and Ajuga species neo-clerodanes for Sideritis species ent-kaurane diterpenes are characteristic while nepetalactones are specific for Nepeta species. In this review article, only some interesting and different type of skeleton having constituents, namely rearranged, nor- or rare diterpenes, isolated from these species will be presented. For structure elucidation of these natural diterpenoids intensive one- and two-dimensional NMR techniques ( 1H, 13C, APT, DEPT, NOE/NOESY, 1H- 1H COSY, HETCOR, COLOC, HMQC/HSQC, HMBC, SINEPT) were used besides mass and some other spectroscopic methods.

  20. 1D cyanide complexes with 2-pyridinemethanol: Synthesis, crystal structures and spectroscopic properties

    NASA Astrophysics Data System (ADS)

    Sayın, Elvan; Kürkçüoğlu, Güneş Süheyla; Yeşilel, Okan Zafer; Hökelek, Tuncer

    2015-12-01

    Two new one-dimensional coordination polymers, [Cu(hmpH)2Pd(μ-CN)2(CN)2]n (1) and [Cu(hmpH)2Pt(μ-CN)2(CN)2]n (2), (hmpH = 2-pyridinemethanol), have been synthesized and characterized by vibrational (FT-IR and Raman) spectroscopy, single crystal X-ray diffraction, thermal and elemental analyses techniques. Single crystal X-ray diffraction analysis indicates that complexes 1 and 2 are isomorphous and isostructural, and crystallize in the triclinic system and P-1 space group. The Pd(II) or Pt(II) ions are four coordinated with four cyanide-carbon atoms in a square planar geometry. Cu(II) ion displays a distorted octahedral coordination by two N-atoms and two O-atoms of hmpH ligands, two bridging cyanide groups. In one dimensional structure of the complexes, [M(CN)4]2- (M = Pd(II) or Pt(II)) anions and [Cu(hmpH)2]2+ cations are linked via bridging cyanide ligands. In the complexes, the presence of intramolecular C-H⋯M (M = Pd(II) or Pt(II)) interactions with distance values of 3.00-2.95 Å are established, respectively.

  1. Exponents of the spectral functions and dynamical structure factor of the 1D Lieb-Liniger Bose gas

    NASA Astrophysics Data System (ADS)

    Carmelo, J. M. P.; Sacramento, P. D.

    2016-06-01

    We study the (k , ω) -plane finite-energy line shape of the zero-temperature one-boson removal spectral function (ω < 0) , one-boson addition spectral function (ω > 0) , and charge dynamical structure factor (ω > 0) of the 1D Lieb-Liniger Bose gas with repulsive boson interaction c > 0. Our analysis of the problem focuses on the line shape at finite excitation energies in the vicinity of these functions spectrum upper (ω < 0) or lower (ω > 0) threshold. Specifically, we derive the exact momentum, interaction, and density dependences of the exponents controlling such a line shape in each of the N = 1 , 2 , 3 , … momentum subdomains k ∈ [(N - 1) 2 πn , N 2 πn ] . Here n = N / L is the boson density, N the boson number, and L the system length. In the thermodynamic limit considered in our study nearly all spectral weight of the dynamical correlation functions is for large values of n / c contained in the N = 1 momentum subdomain k ∈ [ 0 , 2 πn ] . As n / c decreases a small fraction of that weight is transferred to the remaining set of N = 2 , 3 , 4 , … momentum subdomains, particularly to the N = 2 subdomain. In the case of the momentum subdomain k ∈ [ 0 , 2 πn ] , our exact results agree with those of previous studies. For that subdomain the above exponents are plotted as a function of the momentum for several n / c values. Our derivation of the line shapes of the three dynamical correlation functions relies on the use of a simplified form of the pseudofermion dynamical theory of the fermionic 1D Hubbard model suitably modified in this paper for the 1D Bose gas.

  2. Large-scale shear velocity structure of the upper mantle beneath Europe and surrounding regions

    NASA Astrophysics Data System (ADS)

    Legendre, C. P.; Meier, T. M.; Lebedev, S.; Friederich, W.

    2009-12-01

    The automated multimode waveform inversion technique developed by Lebedev et al. (2005) was applied to available data of broadband stations in Europe and surrounding regions. It performs a fitting of the complete waveform starting from the S-wave onset to the surface wave. Assuming the location and focal mechanism of a considered earthquake as known, the first basic step is to consider each available seismogram separately and to find the 1D-model that can explain the filtered seismogram best. In a second step, each 1D-model serves as a linear constraint in an inversion for a 3D S-wave velocity model of the upper mantle. We collected data for the years from 1990 to 2006 from all permanent stations for which data were available via the data centers of ORFEUS, GEOFON amd IRIS, and from others that build the Virtual European Seismological Network (VEBSN). In addition, we incorporated data from temporary experiments like SVEKALAPKO, TOR and the Eifel plume project as well as permanent stations in France. Just recently we were also able to add the data recorded by the temporary broadband EGELADOS network in the southern Aegean. In this way, a huge data set of about 500000 seismograms came about from which about 60000 1D-models could be constructed. The resulting models exhibit an overwhelming structural detail in relation to the size of the region considered in the inversion. They are to our knowledge the most detailed models of shear wave velocity currently available for the European upper mantle and surroundings. Most prominent features are an extremely sharp demarcation of the East European platform from Western Europe. Narrow high velocity regions follow the Hellenic arc and the Ionian trench toward the north. Whereas high velocities are found beneath the western Alps between about 100 km to 200 km depth, the eastern Alps show a low velocity anomaly at these depths. Low velocity zones are found at depths around 150 km in the Pannonian basin, the back-arc of the

  3. S-wave velocity structure in the SE Tibetan plateau

    NASA Astrophysics Data System (ADS)

    Cai, Yan; Wu, Jianping; Wang, Weilai; Fang, Lihua; Fan, Liping

    2016-05-01

    We use observations recorded by 23 permanent and 99 temporary stations in the SE Tibetan plateau to obtain the S-wave velocity structure along two profiles by applying joint inversion with receiver functions and surface waves. The two profiles cross West Yunnan block (WYB), the Central Yunnan sub-block (CYB), South China block (SCB), and Nanpanjiang basin (NPB). The profile at ~25°N shows that the Moho interface in the CYB is deeper than those in the WYB and the NPB, and the topography and Moho depth have clear correspondence. Beneath the Xiaojiang fault zone (XJF), there exists a crustal low-velocity zone (LVZ), crossing the XJF and expanding eastward into the SCB. The NPB is shown to be of relatively high velocity. We speculate that the eastward extrusion of the Tibetan plateau may pass through the XJF and affect its eastern region, and is resisted by the rigid NPB, which has high velocity. This may be the main cause of the crustal thickening and uplift of the topography. In the Tengchong volcanic area, the crust is shown to have alternate high- and low-velocity layers, and the upper mantle is shown to be of low velocity. We consider that the magma which exists in the crust is from the upper mantle and that the complex crustal velocity structure is related to magmatic differentiation. Between the Tengchong volcanic area and the XJF, the crustal velocity is relatively high. Combining these observations with other geophysical evidence, it is indicated that rock strength is high and deformation is weak in this area, which is why the level of seismicity is quite low. The profile at ~23°N shows that the variation of the Moho depth is small from the eastern rigid block to the western active block with a wide range of LVZs. We consider that deformation to the south of the SE Tibetan Plateau is weak.

  4. S-wave velocity structure in the SE Tibetan plateau

    NASA Astrophysics Data System (ADS)

    Cai, Yan; Wu, Jianping; Wang, Weilai; Fang, Lihua; Fan, Liping

    2016-06-01

    We use observations recorded by 23 permanent and 99 temporary stations in the SE Tibetan plateau to obtain the S-wave velocity structure along two profiles by applying joint inversion with receiver functions and surface waves. The two profiles cross West Yunnan block (WYB), the Central Yunnan sub-block (CYB), South China block (SCB), and Nanpanjiang basin (NPB). The profile at ~25°N shows that the Moho interface in the CYB is deeper than those in the WYB and the NPB, and the topography and Moho depth have clear correspondence. Beneath the Xiaojiang fault zone (XJF), there exists a crustal low-velocity zone (LVZ), crossing the XJF and expanding eastward into the SCB. The NPB is shown to be of relatively high velocity. We speculate that the eastward extrusion of the Tibetan plateau may pass through the XJF and affect its eastern region, and is resisted by the rigid NPB, which has high velocity. This may be the main cause of the crustal thickening and uplift of the topography. In the Tengchong volcanic area, the crust is shown to have alternate high- and low-velocity layers, and the upper mantle is shown to be of low velocity. We consider that the magma which exists in the crust is from the upper mantle and that the complex crustal velocity structure is related to magmatic differentiation. Between the Tengchong volcanic area and the XJF, the crustal velocity is relatively high. Combining these observations with other geophysical evidence, it is indicated that rock strength is high and deformation is weak in this area, which is why the level of seismicity is quite low. The profile at ~23°N shows that the variation of the Moho depth is small from the eastern rigid block to the western active block with a wide range of LVZs. We consider that deformation to the south of the SE Tibetan Plateau is weak.

  5. A review of MBE grown 0D, 1D and 2D quantum structures in a nanowire

    NASA Astrophysics Data System (ADS)

    de la Mata, Maria; Zhou, Xiang; Furtmayr, Florian; Teubert, Jörg; Gradecak, Silvija; Eickhoff, Martin; Fontcuberta i Morral, Anna; Arbiol, Jordi

    2013-05-01

    We review different strategies to achieve a three-dimensional energy bandgap modulation in a nanowire (NW) by the introduction of self-assembled 0D, 1D and 2D quantum structures, quantum dots (QDs), quantum wires (QWRs) and quantum wells (QWs). Starting with the well-known axial, radial (coaxial/prismatic) or polytypic quantum wells in GaN/AlN, GaAs/AlAs or wurtzite/zinc-blende systems, respectively, we move to more sophisticated structures by lowering their dimensionality. New recent approaches developed for the self-assembly of GaN quantum wires and InAs or AlGaAs quantum dots on single nanowire templates are reported and discussed. Aberration corrected scanning transmission electron microcopy is presented as a powerful tool to determine the structure and morphology at the atomic scale allowing for the creation of 3D atomic models that can help us to understand the enhanced optical properties of these advanced quantum structures.

  6. Structural variation from heterometallic cluster-based 1D chain to heterometallic tetranuclear cluster: Syntheses, structures and magnetic properties

    SciTech Connect

    Zhang, Shu-Hua; Zhao, Ru-Xia; Li, He-Ping; Ge, Cheng-Min; Li, Gui; Huang, Qiu-Ping; Zou, Hua-Hong

    2014-08-15

    Using the solvothermal method, we present the comparative preparation of ([Co{sub 3}Na(dmaep){sub 3}(ehbd)(N{sub 3}){sub 3}]·DMF){sub n} (1) and [Co{sub 2}Na{sub 2}(hmbd){sub 4}(N{sub 3}){sub 2}(DMF){sub 2}] (2), where Hehbd is 3-ethoxy-2-hydroxy-benzaldehyde, Hhmbd is 3-methoxy-2-hydroxy-benzaldehyde, and Hdmaep is 2-dimethylaminomethyl-6-ethoxy-phenol, which was synthesized by an in-situ reaction. Complexes 1 and 2 were characterized by elemental analysis, IR spectroscopy, and X-ray single-crystal diffraction. Complex 1 is a novel heterometallic cluster-based 1-D chain and 2 is a heterometallic tetranuclear cluster. The (Co{sub 3}{sup II}Na) and (Co{sub 2}{sup II}Na{sub 2}) cores display dominant ferromagnetic interaction from the nature of the binding modes through μ{sub 1,1,1}-N{sub 3}{sup –} (end-on, EO). - Graphical abstract: Two novel cobalt complexes have been prepared. Compound 1 consists of tetranuclear (Co{sub 3}{sup II}Na) units, which further formed a 1-D chain. Compound 2 is heterometallic tetranuclear cluster. Two complexes display dominant ferromagnetic interaction. - Highlights: • Two new heterometallic complexes have been synthesized by solvothermal method. • The stereospecific blockade of the ligands in the synthesis system seems to be the most important synthetic parameter. • The magnetism studies show that 1 and 2 exhibit ferromagnetic interactions. • Complex 1 shows slowing down of magnetization and not blocking of magnetization.

  7. Lithospheric Velocity Structure Along the Dead Sea Transform From the Joint Inversion of P- and S-Wave Receiver Functions and Dispersion Velocities

    NASA Astrophysics Data System (ADS)

    Julia, J.; Nyblade, A.; Pasyanos, M. E.; Matzel, E.; Rodgers, A.; Al-Amri, A. M.

    2012-12-01

    The Dead Sea Transform (DST) is a ~1000 km long fault system that separates the Arabian and African plates and links the active spreading center of the Red Sea with the continental collision zone in the Zagros mountains. Independent thermo-mechanical modeling had suggested that a mantle plume intruding from the south might have eroded the lithosphere East of the DST, but recent results from a number of temporary seismic deployments in the area have found little variation in lithospheric thickness to support it and proposed that such geodynamic processes might have operated on both sides of the DST. Those lithospheric thickness estimates have been obtained through the stack and migration of Sp conversions in S-receiver functions, which assumes a global background velocity model to calibrate the depth-scale that might not represent mantle structure under the DST accurately. In this study, we obtain lithospheric and sub-lithospheric S-velocity structure under several permanent broadband stations along the DST from the joint inversion of P- and S-wave receiver functions and tomographic surface-wave dispersion velocities. The joint inversion approach simultaneously models S-P times and Ps amplitudes in P-receiver functions, P-S times and Sp amplitudes in S-receiver functions, and fundamental-mode, Rayleigh-wave group velocities, providing local 1D models of S-velocity under individual recording stations. Our velocity models display interesting variations in crustal thickness along the DST, with values under 40 km in the southern portions and values well over 40 km more to the North, near Lebanon. The models also display S-velocity values in the lithospheric mantle that are generally slow, in the 4.3-4.4 km/s range, sometimes overlaying a relatively shallow asthenospheric low velocity channel, above 150 km depth.

  8. Photonic Crystals: Tunable Design of Structural Colors Produced by Pseudo-1D Photonic Crystals of Graphene Oxide (Small 25/2016).

    PubMed

    Tong, Liping; Qi, Wei; Wang, Mengfan; Huang, Renliang; Su, Rongxin; He, Zhimin

    2016-07-01

    The production of structural colors based on graphene oxide (GO) pseudo-one-dimensional photonic crystals (p1D-PhCs) in the visible spectrum is reported on page 3433 by W. Qi and co-workers. The structural colors could be tuned by simply changing either the volume or concentration of the aqueous GO dispersion. Moreover, GO p1D-PhCs exhibit visible and rapid responsiveness to humidity. PMID:27364309

  9. Designed Quasi-1D Potential Structures Realized in Compositionally Graded InAs1-xPx Nanowires.

    PubMed

    Nylund, Gustav; Storm, Kristian; Lehmann, Sebastian; Capasso, Federico; Samuelson, Lars

    2016-02-10

    III-V semiconductor heterostructures are important components of many solid-state optoelectronic devices, but the ability to control and tune the electrical and optical properties of these structures in conventional device geometries is fundamentally limited by the bulk dimensionality and the inability to accommodate lattice-mismatched material combinations. Here we demonstrate how semiconductor nanowires may enable the creation of arbitrarily shaped one-dimensional potential structures for new types of designed device functionality. We describe the controlled growth of stepwise compositionally graded InAs1-xPx heterostructures defined along the axes of InAs nanowires, and we show that nanowires with sawtooth-shaped composition profiles behave as near-ideal unipolar diodes with ratchet-like rectification of the electron transport through the nanowires, in excellent agreement with simulations. This new type of designed quasi-1D potential structure represents a significant advance in band gap engineering and may enable fundamental studies of low-dimensional hot-carrier dynamics, in addition to constituting a platform for implementing novel electronic and optoelectronic device concepts. PMID:26788886

  10. Syntheses, structures, spectroscopic and electrochemical properties of two 1D organic-inorganic CuII-LnIII heterometallic germanotungstates.

    PubMed

    Zhang, Jingli; Li, Jie; Li, Lijie; Zhao, Haozhe; Ma, Pengtao; Zhao, Junwei; Chen, Lijuan

    2013-10-01

    Two organic-inorganic hybrid copper-lanthanide heterometallic germanotungstates KNa2H7[enH2]3[Cu(en)2(H2O)]2[Cu(en)2]2{Cu(en)2[Eu(α-GeW11O39)2]2}·13H2O (1) and Na2H4[Cu(en)2(H2O)]2[Cu(en)2]6[Cu(en)2]{Cu(en)2[La(α-GeW11O39)2]2}·12H2O (2) have been hydrothermally synthesized by reaction of K8Na2[A-α-GeW9O34]·25H2O with CuCl2·2H2O and EuCl3/LaCl3 in the presence of en (en=ethylenediamine) and structurally characterized by elemental analyses, IR spectra and single-crystal X-ray diffraction. 1 exhibits the 1D chain motif built by tetrameric {[Cu(en)2(H2O)]2[Cu(en)2]2{Cu(en)2[Eu(α-GeW11O39)2]2}}(16-) moieties through square antiprismatic K(+) cations while 2 displays the 1D architecture made by tetrameric [[Cu(en)2]6[Cu(en)2]{Cu(en)2[La(α-GeW11O39)2]2}](10-) units via octahedral [Cu(en)2](2+) cations. Furthermore, the solid-state electrochemical and electrocatalytic properties of 1 have been investigated and 1 indicates the good electrocatalytic activity for nitrite reduction. In addition, the photoluminescence property of 1 has been investigated. PMID:23786977

  11. Hierarchical Velocity Structure in the Core of Abell 2597

    NASA Technical Reports Server (NTRS)

    Still, Martin; Mushotzky, Richard

    2004-01-01

    We present XMM-Newton RGS and EPIC data of the putative cooling flow cluster Abell 2597. Velocities of the low-ionization emission lines in the spectrum are blue shifted with respect to the high-ionization lines by 1320 (sup +660) (sub -210) kilometers per second, which is consistent with the difference in the two peaks of the galaxy velocity distribution and may be the signature of bulk turbulence, infall, rotation or damped oscillation in the cluster. A hierarchical velocity structure such as this could be the direct result of galaxy mergers in the cluster core, or the injection of power into the cluster gas from a central engine. The uniform X-ray morphology of the cluster, the absence of fine scale temperature structure and the random distribution of the the galaxy positions, independent of velocity, suggests that our line of sight is close to the direction of motion. These results have strong implications for cooling flow models of the cluster Abell 2597. They give impetus to those models which account for the observed temperature structure of some clusters using mergers instead of cooling flows.

  12. Contrasting 1D tunnel-structured and 2D layered polymorphs of V2O5: relating crystal structure and bonding to band gaps and electronic structure.

    PubMed

    Tolhurst, Thomas M; Leedahl, Brett; Andrews, Justin L; Marley, Peter M; Banerjee, Sarbajit; Moewes, Alexander

    2016-06-21

    New V2O5 polymorphs have risen to prominence as a result of their open framework structures, cation intercalation properties, tunable electronic structures, and wide range of applications. The application of these materials and the design of new, useful polymorphs requires understanding their defining structure-property relationships. We present a characterization of the band gap and electronic structure of nanowires of the novel ζ-phase and the orthorhombic α-phase of V2O5 using X-ray spectroscopy and density functional theory calculations. The band gap is found to decrease from 1.90 ± 0.20 eV in the α-phase to 1.50 ± 0.20 eV in the ζ-phase, accompanied by the loss of the α-phase's characteristic split-off dxy band in the ζ-phase. States of dxy origin continue to dominate the conduction band edge in the new polymorph but the inequivalence of the vanadium atoms and the increased local symmetry of [VO6] octahedra results in these states overlapping with the rest of the V 3d conduction band. ζ-V2O5 exhibits anisotropic conductivity along the b direction, defining a 1D tunnel, in contrast to α-V2O5 where the anisotropic conductivity is along the ab layers. We explain the structural origins of the differences in electronic properties that exist between the α- and ζ-phase. PMID:27230816

  13. Pressure, temperature and plasma frequency effects on the band structure of a 1D semiconductor photonic crystal

    NASA Astrophysics Data System (ADS)

    González, Luz E.; Porras-Montenegro, N.

    2012-01-01

    In this work using the transfer-matrix formalism we study pressure, temperature and plasma frequency effects on the band structure of a 1D semiconductor photonic crystal made of alternating layers of air and GaAs. We have found that the temperature dependence of the photonic band structure is negligible, however, its noticeable changes are due mainly to the variations of the width and the dielectric constant of the layers of GaAs, caused by the applied hydrostatic pressure. On the other hand, by using the Drude's model, we have studied the effects of the hydrostatic pressure by means of the variation of the effective mass and density of the carriers in n-doped GaAs, finding firstly that increasing the amount of n-dopants in GaAs, namely, increasing the plasma frequency, the photonic band structure is shifted to regions of higher frequencies, and secondly the appearance of two regimes of the photonic band structure: one above the plasma frequency with the presence of usual Bragg gaps, and the other, below this frequency, where there are no gaps regularly distributed, with their width diminishing with the increasing of the plasma frequency as well as with the appearance of more bands, but leaving a wide frequency range in the lowest part of the spectrum without accessible photon states. Also, we have found characteristic frequencies in which the dielectric constant equals for different applied pressures, and from which to higher or lower values the photonic band structure inverts its behavior, depending on the value of the applied hydrostatic pressure. We hope this work may be taken into account for the development of new perspectives in the design of new optical devices.

  14. Seismic Velocity structures in Northern Izu-Bonin arc derived from passive OBS observations

    NASA Astrophysics Data System (ADS)

    Obana, K.; Kamiya, S.; Kodaira, S.; Suetsugu, D.; Takahashi, N.; Takahashi, T.; Tamura, Y.; Sakaguchi, H.

    2007-12-01

    The Izu-Bonin Island arc is an oceanic island arc, where the Pacific plate subducts beneath the Philippine Sea plate. Recent active seismic surveys in the Izu-Bonin arc show significant variations in thickness of the middle crust along the volcanic front [Kodaira et al, 2007]. To understand the crustal evolution in the oceanic island arc, we have to clarify structures in the mantle wedge along the arc in addition to the oceanic island arc crust. We conducted seismicity observations to investigate structure variations in northern Izu-Bonin arc using natural earthquakes. A temporal ocean bottom seismograph (OBS) network consists of 40 pop-up type OBSs was deployed in April 2006 between Tori-shima and Hachijo-jima islands. These OBSs were retrieved in July after about 80-day observations. We used continuous seismic data at 36 OBSs and three F-net and Hi-net seismic stations on Hachijo-jima and Aoga-shima islands operated by National Research Institute for Earth Science and Disaster Prevention. During the OBS observations, about 1600 earthquakes were located. These earthquakes clearly show double seismic zone along the subducting Pacific plate. We estimated 1D and 3D P- and S-wave seismic velocity structure using arrival time data of these earthquakes. The 1D velocity model shows that a layer with low Poisson's ratio of 0.24 and high Poisson's ratio of 0.28 corresponds to middle and lower crust, respectively. The low Poisson's ratio layer suggests the granitic middle crust with Vp of ~6km/s. The high Poisson's ratio layer agrees with the gabbroic lower crust as suggested by Kodaira et al. [2007]. Three-dimensional Vp and Vs structures were estimated by 3D tomographic inversion method by Kamiyra and Kobayashi [2000] using the 1D model as an initial model. The estimated 3D model shows structure variations along the volcanic front. We will discuss relationships between the seismic velocity variations and the island arc crust structures in northern Izu- Bonin arc.

  15. Crustal and uppermantle velocity structure of the northern Korean Peninsula constrained by ambient noise cross-correlations

    NASA Astrophysics Data System (ADS)

    Lee, S. J.; Rhie, J.; Kim, S.

    2014-12-01

    The seismic velocity structure of the northern Korean Peninsula has not been well known because available seismic data observed inside the region is very rare. Therefore, constructing a one-dimensional (1-D) reference velocity model will be a meaningful first step to understand the detailed velocity structure and also the tectonic evolution of the region. In this study, we use two-year long (2010-2011) ambient noise data recorded by three component broadband seismometers of KIGAM, KMA, F-net, and IRIS networks surrounding the study area. Ambient noise cross-correlations are calculated for station pairs sampling the study area. Multiple filter technique is applied to measure group and phase velocity dispersions of the fundamental mode Rayleigh and Love waves for period ranges between 5 and 70 s, which are sensitive to shear wave velocities in the crust and uppermost mantle. Recently developed inversion method using the Bayesian technique is applied to estimate 1-D models of shear wave velocities and corresponding uncertainties. Combined with the Markov chain Monte Carlo (MCMC) technique, the posterior probability density is evaluated for given data and the prior. Boundaries, velocities, and anisotropy parameters of layers are searched together on the assumption of the layered half-space model. The used method automatically adjusts the number of layers and degree of data fitting by the Bayesian Information Criterion (BIC) estimation and scaling of the data-covariance matrix, respectively. The estimated anisotropic S-wave velocity model in the crust and upper-mantle can help to investigate tectonic processes of the region. For practical use, our velocity model for the Northern Korean Peninsula can be useful to enhance monitoring power of the underground nuclear tests in given area.

  16. HOTCFGM-1D: A Coupled Higher-Order Theory for Cylindrical Structural Components with Through-Thickness Functionally Graded Microstructures

    NASA Technical Reports Server (NTRS)

    Pindera, Marek-Jerzy; Aboudi, Jacob

    1998-01-01

    The objective of this three-year project was to develop and deliver to NASA Lewis one-dimensional and two-dimensional higher-order theories, and related computer codes, for the analysis, optimization and design of cylindrical functionally graded materials/structural components for use in advanced aircraft engines (e.g., combustor linings, rotor disks, heat shields, blisk blades). To satisfy this objective, a quasi one-dimensional version of the higher-order theory, HOTCFGM-1D, and four computer codes based on this theory, for the analysis, design and optimization of cylindrical structural components functionally graded in the radial direction were developed. The theory is applicable to thin multi-phased composite shell/cylinders subjected to macroscopically axisymmetric thermomechanical and inertial loading applied uniformly along the axial direction such that the overall deformation is characterized by a constant average axial strain. The reinforcement phases are uniformly distributed in the axial and circumferential directions, and arbitrarily distributed in the radial direction, thereby allowing functional grading of the internal reinforcement in this direction.

  17. Shallow velocity structure and hidden faults of Kunming city region

    NASA Astrophysics Data System (ADS)

    Yu, Geng-Xin; Lou, Hai; Wang, Chun-Yong; Fu, Li-Yun; Zhang, Jian-Guo; Qin, Jia-Zheng; Yang, Run-Hai; Li, Hai-Ou

    2008-09-01

    In order to image the 3-D velocity structure of its shallow crust in Kunming region, China, finite-difference seismic tomography is used to invert the seismic data selected carefully from six-shot data. The result lays a foundation for the discussion of the relationship between the obtained velocity structure and the hidden faults, and for the illumination of the depth extents of main active faults surrounding Kunming city. Puduhe-Xishan fault lies on the western margin of the Kunming basin and is just situated on the west edge of the low velocity anomaly zone found at all depth levels. This indicates that this fault is a borderline fault of the Kunming basin. It can be concluded that the fault dips eastwards with a steep angle and its depth extent is large. Puji-Hanjiacun fault and Heilongtan-Guandu fault play a role in controlling the low velocity anomaly zone in middle basin. The depth extents of the two faults are comparatively small, without traversing the interface of basin floor.

  18. Velocity and Attenuation Structure of the Geysers Geothermal Field, California

    SciTech Connect

    Zucca, J. J.; Hutchings, L. J.; Kasameyer, P. W.

    1993-01-01

    The Geysers geothermal field is located in northern California and is one of the world's largest producers of electricity from geothermal energy. The resource consists of primarily dry steam which is produced from a low, porosity fractured graywacke. Over the last several years steam pressure at the Geysers has been dropping. Concern over decline of the resource has prompted research to understand its fundamental nature. A key issue is the distribution of fluid in the matrix of the reservoir rock. In this paper we interpret seismic compressional-wave velocity and attenuation data at the Geysers in terms of the geologic structure and fluid saturation in the reservoir. Our data consist of approximately 300 earthquakes that are of magnitude 1.2 and are distributed in depth between sea level and 2.5 km. Using compressional-wave arrival times, we invert for earthquake location, origin time, and velocity along a three-dimensional grid. Using the initial pulse width of the compressional-wave, we invert for the initial pulse width associated with the source, and the one-dimensional Q structure. We find that the velocity structure correlates with known mapped geologic units, including a velocity high that is correlated with a felsite body at depth that is known from drilling. The dry steam reservoir, which is also known from drilling, is mostly correlated with low velocity. The Q increases with depth to the top of the dry steam reservoir and decreases with depth within the reservoir. The decrease of Q with depth probably indicates that the saturation of the matrix of the reservoir rock increases with depth.

  19. Complete characterization of the constrained geometry bimolecular reaction O({sup 1}D)+N{sub 2}O{yields}NO+NO by three-dimensional velocity map imaging

    SciTech Connect

    Goedecke, Niels; Maul, Christof; Kauczok, Sebastian; Gericke, Karl-Heinz; Chichinin, Alexey I.

    2009-08-07

    The bimolecular reaction O({sup 1}D)+N{sub 2}O{yields}NO+NO was photoinitiated in the (N{sub 2}O){sub 2} dimer at a wavelength of 193 nm and was investigated by three-dimensional (3D) velocity map imaging. State selective 3D momentum vector distributions were monitored and analyzed. For the first time, kinetic energy resolution and stereodynamic information about the reaction under constrained geometry conditions is available. Directly observable NO products exhibit moderate vibrational excitation and are rotationally and translationally cold. Speed and spatial distributions suggest a pronounced backward scattering of the observed products with respect to the direction of motion of the O({sup 1}D) atom. Forward scattered partner products, which are not directly detectable are also translationally cold, but carry very large internal energy as vibration or rotation. The results confirm and extend previous studies on the complex initiated reaction system. The restricted geometry of the van der Waals complex seems to favor an abstraction reaction of the terminal nitrogen atom by the O({sup 1}D) atom, which is in striking contrast to the behavior observed for the unrestricted gas phase reaction under bulk conditions.

  20. Decoupling structural and environmental determinants of sap velocity

    NASA Astrophysics Data System (ADS)

    Caylor, K. K.; Dragoni, D.

    2007-12-01

    Characterization of transpiration based on the water use of individual tress has the advantage of preserving vital information on the plant-environment functional links and flux partitioning between species and landscape areas. Whole-tree transpiration has been estimated by means of sap velocity probes, which offer the dual advantages of practicality and repeatability. However, the assumptions underlying the technique require careful verification in order to determine total sap flow from point-based estimates of sap velocity. Our work presents a novel theoretical framework for the study of individual tree sap flow that incorporates both spatial and temporal variability in sap velocities. The instantaneous sap velocity at any point in the radial profile of xylem tissue is defined as the product of two components: (1) a time-invariant sap velocity distribution linked to the species- specific anatomical and structural properties of the conducting xylem, and (2) a time-varying term linked to the dynamics of the atmospheric water demand and available soil moisture. The separation of structural and temporal variation in sap velocity observations provides a direct mechanism for investigating how sap flow is governed by variation in environmental conditions as well as a means for comparing characteristic rates of plant water use among individuals of varying size. Most critically, this approach allows for a consistent and physically meaningful method for extrapolating point observations of sap velocity across the entire depth of conducting xylem. Experimental evidence supports our theoretical framework in the case of a population of sugar maples in a mixed deciduous forest, where observations were taken from a wide range of tree sizes, under varying soil water availability and atmospheric transpiration demand. We have also applied our approach to a small homogeneous sample of dwarf apple trees in a managed orchard, with favorable results. While these results require further

  1. Thermal Solitons in 1d and 2d Anharmonic Lattices - Solectrons and the Organization of Non-Linear Fluctuations in Long-Living Dynamical Structures

    NASA Astrophysics Data System (ADS)

    Velarde, M. G.; Ebeling, W.; Chetverikov, A. P.

    2013-01-01

    We study the thermal excitation of intrinsic localized modes in the form of solitons in 1d and 2d anharmonic lattices at moderately high temperatures. Such finite-amplitude fluctuations form long-living dynamical structures with life-time in the pico-second range thus surviving a relatively long time in comparison to other thermal fluctuations. Further we discuss the influence of such long-living fluctuations on the dynamics of added excess free electrons. The atomic lattice units are treated as quasi-classical objects interacting by Morse forces and stochastically moving according to Langevin equations. In 2d the atoms are initially organized in a triangular lattice. The electron distributions are in a first estimate represented by equilibrium adiabatic distributions in the actual polarization fields. Computer simulations show that in 2d systems such excitations are moving with supersonic velocities along lattice rows oriented with the cristallographic axes. By following the electron distributions we have also been able to study the excitations of solectron type (electron-soliton dynamic bound states) and estimate their life times.

  2. Automated structure verification based on a combination of 1D (1)H NMR and 2D (1)H - (13)C HSQC spectra.

    PubMed

    Golotvin, Sergey S; Vodopianov, Eugene; Pol, Rostislav; Lefebvre, Brent A; Williams, Antony J; Rutkowske, Randy D; Spitzer, Timothy D

    2007-10-01

    A method for structure validation based on the simultaneous analysis of a 1D (1)H NMR and 2D (1)H - (13)C single-bond correlation spectrum such as HSQC or HMQC is presented here. When compared with the validation of a structure by a 1D (1)H NMR spectrum alone, the advantage of including a 2D HSQC spectrum in structure validation is that it adds not only the information of (13)C shifts, but also which proton shifts they are directly coupled to, and an indication of which methylene protons are diastereotopic. The lack of corresponding peaks in the 2D spectrum that appear in the 1D (1)H spectrum, also gives a clear picture of which protons are attached to heteroatoms. For all these benefits, combined NMR verification was expected and found by all metrics to be superior to validation by 1D (1)H NMR alone. Using multiple real-life data sets of chemical structures and the corresponding 1D and 2D data, it was possible to unambiguously identify at least 90% of the correct structures. As part of this test, challenging incorrect structures, mostly regioisomers, were also matched with each spectrum set. For these incorrect structures, the false positive rate was observed as low as 6%. PMID:17694570

  3. Syntheses, structures, and photoluminescence of d 10 coordination architectures: From 1D to 3D complexes based on mixed ligands

    NASA Astrophysics Data System (ADS)

    Yuan, Gang; Shao, Kui-Zhan; Du, Dong-Ying; Wang, Xin-Long; Su, Zhong-Min

    2011-05-01

    Six new compounds, namely, {[Cd 3(Himpy) 3(tda) 2]·3H 2O} n ( 1), {[Zn 3(bipy) 2(tda) 2(H 2O) 2]·4H 2O} n ( 2), {[Cd 3(bipy) 3(tda) 2]·4H 2O} n ( 3), {[Cd 3(tda) 2(H 2O) 3Cl]·H 2O} n ( 4), {[Zn 2(tz)(tda)(H 2O) 2]·H 2O} n ( 5) and {[Cd 7(pz)(tda) 4(OAc)(H 2O) 7]·3H 2O} n ( 6) [H 3tda = 1H-1,2,3-triazole-4,5-dicarboxylic acid, Himpy = 2-(1H-imidazol-2-yl)pyridine, bipy = 2,2'-bipyridine, Htz = 1H-1,2,4-triazole, H 2pz = piperazine] have been prepared under hydrothermal condition and characterized by elemental analyses, infrared spectroscopy, powder X-ray diffraction and single-crystal X-ray diffraction analyses. Compound 1 is a 1D column-like structure and displays a 3D supramolecular network via the π···π stacking interaction. The compounds 2 and 3 exhibit similar 2D layer-like structure, which further extend to 3D supermolecular structure by the π···π stacking interaction. All of compounds 4- 6 display 3D framework with diverse topology constructed from the tda 3- ligands in different coordination modes and secondary ligands (or bridging atom) connecting metal ions. Furthermore, the thermal stabilities and photoluminescent properties of compounds 1- 6 were studied.

  4. Nonzero Density-Velocity Consistency Relations for Large Scale Structures.

    PubMed

    Rizzo, Luca Alberto; Mota, David F; Valageas, Patrick

    2016-08-19

    We present exact kinematic consistency relations for cosmological structures that do not vanish at equal times and can thus be measured in surveys. These rely on cross correlations between the density and velocity, or momentum, fields. Indeed, the uniform transport of small-scale structures by long-wavelength modes, which cannot be detected at equal times by looking at density correlations only, gives rise to a shift in the amplitude of the velocity field that could be measured. These consistency relations only rely on the weak equivalence principle and Gaussian initial conditions. They remain valid in the nonlinear regime and for biased galaxy fields. They can be used to constrain nonstandard cosmological scenarios or the large-scale galaxy bias. PMID:27588842

  5. Nonzero Density-Velocity Consistency Relations for Large Scale Structures

    NASA Astrophysics Data System (ADS)

    Rizzo, Luca Alberto; Mota, David F.; Valageas, Patrick

    2016-08-01

    We present exact kinematic consistency relations for cosmological structures that do not vanish at equal times and can thus be measured in surveys. These rely on cross correlations between the density and velocity, or momentum, fields. Indeed, the uniform transport of small-scale structures by long-wavelength modes, which cannot be detected at equal times by looking at density correlations only, gives rise to a shift in the amplitude of the velocity field that could be measured. These consistency relations only rely on the weak equivalence principle and Gaussian initial conditions. They remain valid in the nonlinear regime and for biased galaxy fields. They can be used to constrain nonstandard cosmological scenarios or the large-scale galaxy bias.

  6. Velocity Structure in the West Bohemia Seismic Zone: Velocity Models Retrieved from different Earthquake Swarms

    NASA Astrophysics Data System (ADS)

    Alexandrakis, C.; Löberich, E.; Kieslich, A.; Calo, M.; Vavrycuk, V.; Buske, S.

    2015-12-01

    Earthquake swarms, fluid migration and gas springs are indications of the ongoing geodynamic processes within the West Bohemia seismic zone located at the Czech-German border. The possible relationship between the fluids, gas and seismicity is of particular interest and has motivated numerous past, ongoing and future studies, including a multidisciplinary monitoring proposal through the International Continental Scientific Drilling Program (ICDP). The most seismically active area within the West Bohemia seismic zone is located at the Czech town Nový Kostel. The Nový Kostel zone experiences frequent swarms of several hundreds to thousands of earthquakes over a period of weeks to several months. The seismicity is always located in the same area and depth range (~5-15 km), however the activated fault segments and planes differ. For example, the 2008 swarm activated faults along the southern end of the seismic zone, the 2011 swarm activated the northern segment, and the recent 2014 swarm activated the middle of the seismic zone. This indicates changes to the local stress field, and may relate to fluid migration and/or the complicated tectonic situation. The West Bohemia Seismic Network (WEBNET) is ideally located for studying the Nový Kostel swarm area and provides good azimuthal coverage. Here, we use the high quality P- and S-wave arrival picks recorded by WEBNET to calculate swarm-dependent velocity models for the 2008 and 2011 swarms, and an averaged (swarm independent) model using earthquakes recorded between 1991 and 2011. To this end, we use double-difference tomography to calculate P- and S-wave velocity models. The models are compared and examined in terms of swarm-dependent velocities and structures. Since the P-to-S velocity ratio is particularly sensitive to the presence of pore fluids, we derive ratio models directly from the inverted P- and S-wave models in order to investigate the potential influence of fluids on the seismicity. Finally, clustering

  7. Deep Mantle Large Low Shear-Wave Velocity Provinces: Principally Thermal Structures?

    NASA Astrophysics Data System (ADS)

    Davies, R.; Goes, S. D. B.

    2014-12-01

    The two large low shear-wave velocity provinces (LLSVPs) that dominate lower-mantle structure may hold key information on Earth's thermal and chemical evolution. It is generally accepted that these provinces are hotter than background mantle and are likely the main source of mantle plumes. Increasingly, it is also proposed that they hold a dense (primitive and/or recycled) compositional component. The principle evidence that LLSVPs may represent thermo-chemical `piles' comes from seismic constraints, including: (i) their long-wavelength nature; (ii) sharp gradients in shear-wave velocity at their margins; (iii) non-Gaussian distributions of deep mantle shear-wave velocity anomalies; (iv) anti-correlated shear-wave and bulk-sound velocity anomalies (and elevated ratios between shear- and compressional-wave velocity anomalies); (v) anti-correlated shear-wave and density anomalies; and (vi) 1-D/radial profiles of seismic velocity that deviate from those expected for an isochemical, well-mixed mantle. In addition, it has been proposed that hotspots and the reconstructed eruption sites of large igneous provinces correlate in location with LLSVP margins. Here, we review recent results, which indicate that the majority of these constraints do not require thermo-chemical piles: they are equally well (or poorly) explained by thermal heterogeneity alone. Our analyses and conclusions are largely based on comparisons between imaged seismic structure and synthetic seismic structures from a set of thermal and thermo-chemical mantle convection models, which are constrained by 300 Myr of plate motion histories. Modelled physical structure (temperature, pressure and composition) is converted into seismic velocities via a thermodynamic approach that accounts for elastic, anelastic and phase contributions and, subsequently, a tomographic resolution filter is applied to account for the damping and geographic bias inherent to seismic imaging. Our results indicate that, in terms of

  8. P-wave velocity structure beneath the northern Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Park, Y.; Kim, K.; Jin, Y.

    2010-12-01

    We have imaged tomographically the tree-dimensional velocity structure of the upper mantle beneath the northern Antarctic Peninsula using teleseismic P waves. The data came from the seven land stations of the Seismic Experiment in Patagonia and Antarctica (SEPA) campaigned during 1997-1999, a permanent IRIS/GSN station (PMSA), and 3 seismic stations installed at scientific bases, Esperanza (ESPZ), Jubany (JUBA), and King Sejong (KSJ), in South Shetland Islands. All of the seismic stations are located in coast area, and the signal to noise ratios (SNR) are very low. The P-wave model was inverted from 95 earthquakes resulting in 347 ray paths with P- and PKP-wave arrivals. The inverted model shows a strong low velocity anmaly beneath the Bransfield Strait, and a fast anomaly beneath the South Shetland Islands. The low velocity anomaly beneath the Bransfield might be due to a back arc extension, and the fast velocity anomaly beneath the South Shetland Islands could indicates the cold subducted slab.

  9. The Hatteras Front: August 2004 velocity and density structure

    NASA Astrophysics Data System (ADS)

    Savidge, Dana K.; Austin, Jay A.

    2007-07-01

    The Hatteras Front is a persistent mesoscale cross-shelf oriented front off Cape Hatteras, North Carolina. It is the boundary between relatively cool, fresh Mid-Atlantic Bight shelf waters and warmer, saltier shelf waters of the South Atlantic Bight, which both converge along-shelf upon Cape Hatteras year round. The Frontal Interaction Near Cape Hatteras (FINCH) project was conducted in 2004-2005 to intensively sample the Hatteras Front with shipboard ADCP and undulating towed CTD. This paper documents velocity and density structures associated with the cross-shelf oriented zone of Hatteras Front during the August 2004 field season. Property gradients across the Hatteras Front are large, with temperature (T) and salinity (S) differences of ˜4-6°C, 2-5 psu, respectively over distances of 1-2 km. The T and S are not completely compensating, and a strong density (ρ) gradient also exists, with Δρ of ˜2 kg/m3 across a gentler 10 km wide front. The density gradient results in a steric sea-level height gradient of ˜1-2 cm across the Front, which is in approximate geostrophic balance with a surface intensified jet, directed shoreward along the cross-shelf oriented Front. The velocity is sheared with depth at 3.0 × 10-2 to 5.0 × 10-2 s-1 in the upper 5 m of the jet; a rate consistent with the density gradient according to the thermal wind relationship. Shoreward transport of ˜4.8 × 104 m3/s results from the surface intensified jet. The structure of the velocity field associated with the Hatteras Front resembles that of a slope-controlled buoyant plume, as described by Lentz and Helfrich (2002). Velocity and density structures are similar during both advancing (southwestward) and retreating (northeastward) motion of the Front.

  10. Structure of an α-Helical Peptide and Lipopeptide Bound to the Nonclassical Major Histocompatibility Complex (MHC) Class I Molecule CD1d.

    PubMed

    Girardi, Enrico; Wang, Jing; Zajonc, Dirk M

    2016-05-13

    Mouse CD1d is a nonclassical MHC molecule able to present lipids and glycolipids to a specialized subset of T cells known as natural killer T cells. The antigens presented by CD1d have been shown to cover a broad range of chemical structures and to follow precise rules determining the potency of the antigen in the context of T cell activation. Together with lipids, initial reports suggested that CD1d can also bind and present hydrophobic peptides with (F/W)XX(I/L/M)XXW. However, the exact location of peptide binding and the molecular basis for the required motif are currently unknown. Here we present the crystal structure of the first peptide identified to bind CD1d, p99, and show that it binds in the antigen-binding groove of CD1d in a manner compatible with its presentation to T cell receptors. Interestingly, the peptide adopts an α-helical conformation, which orients the motif residues toward its deep binding groove, therefore explaining the molecular requirements for peptide binding. Moreover, we demonstrate that a lipopeptide version of the same peptide is able to bind CD1d in a similar conformation, identifying another class of molecules binding this antigen-presenting molecule. PMID:27006394

  11. Debris velocity of concrete structures subjected to explosive loading

    NASA Astrophysics Data System (ADS)

    Xu, Kai; Lu, Yong

    2006-08-01

    When designing above-ground ammunition storage facilities, one has to take into account the debris hazard resulting from accidental explosions. The purpose of this paper is to develop a predictive method for debris dispersion around an ammunition storage site in case of an accidental detonation in a reinforced concrete storage structure. The concrete slabs/walls break up into debris when it is overloaded by the internal blast. The debris velocity is one of the important parameters to describe the debris dispersion. The parameters that affect the debris velocity are complex. This study adopts the energy approach to simplify the formulation. The failure process in a relatively thin concrete slab/wall is treated using the concept of expansion. Based on energy conservation, a general formula is derived for the debris launch velocity in a cubicle structure subjected to internal blast loading. The dynamic strength of concrete and reinforcement are considered in the fracture process. The analytical results are found to be consistent with the relevant experimental results.

  12. Inference of upper-mantle density structure from seismic velocities

    NASA Astrophysics Data System (ADS)

    Nettles, M.; Dziewonski, A. M.

    2005-12-01

    The inverse problem for the determination of density structure from perturbations in the gravity field is highly nonunique. The combination of gravity data and other observables can, however, be used to make inferences about the Earth's density structure in three dimensions. We use the three-dimensional shear-wave velocity model of Nettles and Dziewonski (2005) to make a forward prediction of the Earth's gravity field using simple assumptions about the relationship between perturbations in shear velocity and density. A scaling factor f=0.25 relating perturbations in shear velocity and density (δ/ρρ = f · δvS/vS) is determined empirically by comparison of observed variations in shear velocity in oceanic regions with density variations predicted from a simple model of conductive cooling. This value agrees well with f=0.27 based on the laboratory results of Jackson et al. (1992). The observed gravity signal in the oceans is explained well by this simple thermal-scaling approach. Behavior in some continental regions, such as the Basin and Range and the East African rift zone, is found to be similar to that in the oceans: the high topography in these regions appears to be supported by hot, low-density mantle underneath, a result also found by Kaban and Mooney (2001) for the Basin and Range. A velocity-to-density scaling relationship based only on thermal considerations is clearly inadequate in regions of continental craton, where such scaling leads to unrealistically large perturbations in the predicted gravity field. This result suggests that non-thermal effects must counteract the high density that would occur due to thermal effects alone, consistent with the suggestion of Jordan (1975) and other workers that density increases due to cool temperatures in the continental roots must be balanced by density decreases due to compositional variations. Using the compositional derivatives for density and shear velocity with respect to Mg# determined by Lee (2003), and an

  13. Nonlinear Landau damping and formation of Bernstein-Greene-Kruskal structures for plasmas with q-nonextensive velocity distributions

    NASA Astrophysics Data System (ADS)

    Raghunathan, M.; Ganesh, R.

    2013-03-01

    In the past, long-time evolution of an initial perturbation in collisionless Maxwellian plasma (q = 1) has been simulated numerically. The controversy over the nonlinear fate of such electrostatic perturbations was resolved by Manfredi [Phys. Rev. Lett. 79, 2815-2818 (1997)] using long-time simulations up to t = 1600 ωp - 1 . The oscillations were found to continue indefinitely leading to Bernstein-Greene-Kruskal (BGK)-like phase-space vortices (from here on referred as "BGK structures"). Using a newly developed, high resolution 1D Vlasov-Poisson solver based on piecewise-parabolic method (PPM) advection scheme, we investigate the nonlinear Landau damping in 1D plasma described by toy q-distributions for long times, up to t = 3000 ωp - 1 . We show that BGK structures are found only for a certain range of q-values around q = 1. Beyond this window, for the generic parameters, no BGK structures were observed. We observe that for values of q < 1 where velocity distributions have long tails, strong Landau damping inhibits the formation of BGK structures. On the other hand, for q > 1 where distribution has a sharp fall in velocity, the formation of BGK structures is rendered difficult due to high wave number damping imposed by the steep velocity profile, which had not been previously reported. Wherever relevant, we compare our results with past work.

  14. Relationships between Th1 or Th2 iNKT Cell Activity and Structures of CD1d-Antigen Complexes: Meta-analysis of CD1d-Glycolipids Dynamics Simulations

    PubMed Central

    Laurent, Xavier; Renault, Nicolas; Farce, Amaury; Chavatte, Philippe; Hénon, Eric

    2014-01-01

    A number of potentially bioactive molecules can be found in nature. In particular, marine organisms are a valuable source of bioactive compounds. The activity of an α-galactosylceramide was first discovered in 1993 via screening of a Japanese marine sponge (Agelas mauritanius). Very rapidly, a synthetic glycololipid analogue of this natural molecule was discovered, called KRN7000. Associated with the CD1d protein, this α-galactosylceramide 1 (KRN7000) interacts with the T-cell antigen receptor to form a ternary complex that yields T helper (Th) 1 and Th2 responses with opposing effects. In our work, we carried out molecular dynamics simulations (11.5 µs in total) involving eight different ligands (conducted in triplicate) in an effort to find out correlation at the molecular level, if any, between chemical modulation of 1 and the orientation of the known biological response, Th1 or Th2. Comparative investigations of human versus mouse and Th1 versus Th2 data have been carried out. A large set of analysis tools was employed including free energy landscapes. One major result is the identification of a specific conformational state of the sugar polar head, which could be correlated, in the present study, to the biological Th2 biased response. These theoretical tools provide a structural basis for predicting the very different dynamical behaviors of α-glycosphingolipids in CD1d and might aid in the future design of new analogues of 1. PMID:25376021

  15. Self-assembly of three new coordination complexes: Formation of 2-D square grid, 1-D chain and tape structures

    NASA Astrophysics Data System (ADS)

    Indrani, Murugan; Ramasubramanian, Ramasamy; Fronczek, Frank R.; Vasanthacharya, N. Y.; Kumaresan, Sudalaiandi

    2009-08-01

    Three distinct coordination complexes, viz., [Co(imi) 2(tmb) 2] ( 1) [where imi = imidazole], {[Ni(tmb) 2(H 2O) 3]·2H 2O} n ( 2) and [Cu 2(μ-tmb) 4(CH 3OH) 2] ( 3), have been synthesized hydrothermally by the reactions of metal acetates, 2,4,6-trimethylbenzoic acid (Htmb) and with or without appropriate amine. The Ni analogue of 1 and the Co analogue of 2 have also been synthesized. X-ray single-crystal diffraction suggests that complex 1 represents discrete mononuclear species and complex 2 represents a 1D chain coordination polymer in which the Ni(II) ions are connected by the bridging water molecules. Complex 3 represents a neutral dinuclear complex. In 1, the central metal ions are associated by the carboxylate moiety and imidazole ligands, whereas the central metal atom is coordinated to the carboxylate moiety and the respective solvent molecules in 2 and 3. In 3, the four 2,4,6-trimethylbenzoate moieties act as a bridge connecting two copper (II) ions and the O atoms of methanol coordinate in an anti arrangement to form a square pyramidal geometry, with the methanol molecule at the apical position. In all the three structures the central metal atom sits on a crystallographic inversion centre. In all the cases, the coordination entities are further organized via hydrogen bonding interactions to generate multifarious supramolecular networks. Complexes 1, 2 and 3 have also been characterized by spectroscopic (UV/Vis and IR) and thermal analysis (TGA). In addition, the complexes were found to exhibit antimicrobial activity.The magnetic susceptibility measurements, measured from 8 to 300 K, revealed antiferromagnetic interactions between the Co(II) ions in compound 1 and the Ni(II) ions in 1a, respectively.

  16. Imaging of 3-D seismic velocity structure of Southern Sumatra region using double difference tomographic method

    SciTech Connect

    Lestari, Titik; Nugraha, Andri Dian

    2015-04-24

    Southern Sumatra region has a high level of seismicity due to the influence of the subduction system, Sumatra fault, Mentawai fault and stretching zone activities. The seismic activities of Southern Sumatra region are recorded by Meteorological Climatological and Geophysical Agency (MCGA’s) Seismograph network. In this study, we used earthquake data catalog compiled by MCGA for 3013 events from 10 seismic stations around Southern Sumatra region for time periods of April 2009 – April 2014 in order to invert for the 3-D seismic velocities structure (Vp, Vs, and Vp/Vs ratio). We applied double-difference seismic tomography method (tomoDD) to determine Vp, Vs and Vp/Vs ratio with hypocenter adjustment. For the inversion procedure, we started from the initial 1-D seismic velocity model of AK135 and constant Vp/Vs of 1.73. The synthetic travel time from source to receiver was calculated using ray pseudo-bending technique, while the main tomographic inversion was applied using LSQR method. The resolution model was evaluated using checkerboard test and Derivative Weigh Sum (DWS). Our preliminary results show low Vp and Vs anomalies region along Bukit Barisan which is may be associated with weak zone of Sumatran fault and migration of partial melted material. Low velocity anomalies at 30-50 km depth in the fore arc region may indicated the hydrous material circulation because the slab dehydration. We detected low seismic seismicity in the fore arc region that may be indicated as seismic gap. It is coincides contact zone of high and low velocity anomalies. And two large earthquakes (Jambi and Mentawai) also occurred at the contact of contrast velocity.

  17. Imaging of 3-D seismic velocity structure of Southern Sumatra region using double difference tomographic method

    NASA Astrophysics Data System (ADS)

    Lestari, Titik; Nugraha, Andri Dian

    2015-04-01

    Southern Sumatra region has a high level of seismicity due to the influence of the subduction system, Sumatra fault, Mentawai fault and stretching zone activities. The seismic activities of Southern Sumatra region are recorded by Meteorological Climatological and Geophysical Agency (MCGA's) Seismograph network. In this study, we used earthquake data catalog compiled by MCGA for 3013 events from 10 seismic stations around Southern Sumatra region for time periods of April 2009 - April 2014 in order to invert for the 3-D seismic velocities structure (Vp, Vs, and Vp/Vs ratio). We applied double-difference seismic tomography method (tomoDD) to determine Vp, Vs and Vp/Vs ratio with hypocenter adjustment. For the inversion procedure, we started from the initial 1-D seismic velocity model of AK135 and constant Vp/Vs of 1.73. The synthetic travel time from source to receiver was calculated using ray pseudo-bending technique, while the main tomographic inversion was applied using LSQR method. The resolution model was evaluated using checkerboard test and Derivative Weigh Sum (DWS). Our preliminary results show low Vp and Vs anomalies region along Bukit Barisan which is may be associated with weak zone of Sumatran fault and migration of partial melted material. Low velocity anomalies at 30-50 km depth in the fore arc region may indicated the hydrous material circulation because the slab dehydration. We detected low seismic seismicity in the fore arc region that may be indicated as seismic gap. It is coincides contact zone of high and low velocity anomalies. And two large earthquakes (Jambi and Mentawai) also occurred at the contact of contrast velocity.

  18. High Velocity Impact Response of Composite Lattice Core Sandwich Structures

    NASA Astrophysics Data System (ADS)

    Wang, Bing; Zhang, Guoqi; Wang, Shixun; Ma, Li; Wu, Linzhi

    2014-04-01

    In this research, carbon fiber reinforced polymer (CFRP) composite sandwich structures with pyramidal lattice core subjected to high velocity impact ranging from 180 to 2,000 m/s have been investigated by experimental and numerical methods. Experiments using a two-stage light gas gun are conducted to investigate the impact process and to validate the finite element (FE) model. The energy absorption efficiency (EAE) in carbon fiber composite sandwich panels is compared with that of 304 stainless-steel and aluminum alloy lattice core sandwich structures. In a specific impact energy range, energy absorption efficiency in carbon fiber composite sandwich panels is higher than that of 304 stainless-steel sandwich panels and aluminum alloy sandwich panels owing to the big density of metal materials. Therefore, in addition to the multi-functional applications, carbon fiber composite sandwich panels have a potential advantage to substitute the metal sandwich panels as high velocity impact resistance structures under a specific impact energy range.

  19. Imaging shallow velocity structure using ambient noise in urban area

    NASA Astrophysics Data System (ADS)

    Meng, H.; Chen, Y. J.

    2013-12-01

    Vehicle traffic and other human activities provide affluent seismic excitation in urban area. We extract Green's function of surface wave from cross correlation of ambient noise recorded by a small array in schoolyard of Peking University. Although non-isotropic source distribution introduces bias in the Green's function reconstruction, relative steady phase and group velocity map could be estimated from only days' records. The inverted S structure demonstrates agreement with well logging data. This technique could be introduced to engineering for well location optimizing design in noisy urban environment.

  20. A New Mixed Model Based on the Velocity Structure Function

    NASA Astrophysics Data System (ADS)

    Brun, Christophe; Friedrich, Rainer; Da Silva, Carlos B.; Métais, Olivier

    We propose a new mixed model for Large Eddy-Simulation based on the 3D spatial velocity increment. This approach blends the non-linear properties of the Increment model (Brun & Friedrich (2001)) with the eddy viscosity characteristics of the Structure Function model (Métais & Lesieur (1992)). The behaviour of this subgrid scale model is studied both via a priori tests of a plane jet at ReH=3000 and Large Eddy-Simulation of a round jet at ReD=25000. This approach allows to describe both forward and backward energy transfer encountered in transitional shear flows.

  1. Large-scale shear velocity structure of the upper mantle beneath Europe and surrounding regions

    NASA Astrophysics Data System (ADS)

    Legendre, Cédric; Meier, Thomas; Lebedev, Sergei; Friederich, Wolfgang; Egelados Working Group

    2010-05-01

    The automated multimode waveform inversion technique developed by Lebedev et al. (2005) was applied to available data of broadband stations in Europe and surrounding regions. It performs a fitting of the complete waveform starting from the S-wave onset to the surface wave. Assuming the location and focal mechanism of a considered earthquake as known, the first basic step is to consider each available seismogram separately and to find the velocity perturbations that can explain the filtered seismogram best. In a second step, each velocity perturbations serves as a linear constraint in an inversion for a 3D S-wave velocity model of the upper mantle. We collected data for the years from 1990 to 2006 from all permanent stations for which data were available via the data centers of ORFEUS, GEOFON and IRIS, and from others that build the Virtual European Seismological Network (VEBSN). In addition, we incorporated data from temporary experiments like SVEKALAPKO, TOR and the Eifel plume project as well as permanent stations in France. Just recently we were also able to add the data recorded by the temporary broadband EGELADOS network in the southern Aegean. In this way, a huge data set of about 500000 seismograms came about from which about 60000 1D-models could be constructed. The resulting models exhibit an overwhelming structural detail in relation to the size of the region considered in the inversion. They are to our knowledge the most detailed models of shear wave velocity currently available for the European upper mantle and surroundings. Most prominent features are an extremely sharp demarcation of the East European platform from Western Europe. Narrow high velocity regions follow the Hellenic arc and the Ionian trench toward the north. Whereas high velocities are found beneath the western Alps between about 100 km to 200 km depth, the eastern Alps show a low velocity anomaly at these depths. Low velocity zones are found at depths around 150 km in the Pannonian

  2. 3D velocity structure of upper crust beneath NW Bohemia/Vogtland

    NASA Astrophysics Data System (ADS)

    Javad Fallahi, Mohammad; Mousavi, Sima; Korn, Michael; Sens-Schönfelder, Christoph; Bauer, Klaus; Rößler, Dirk

    2013-04-01

    The 3D structure of the upper crust beneath west Bohemia/Vogtland region, analyzed with travel time tomography and ambient noise surface wave tomography using existing data. This region is characterized by a series of phenomena like occurrence of repeated earthquake swarms, surface exhalation, CO2 enriched fluids, mofettes, mineral springs and enhanced heat flow, and has been proposed as an excellent location for an ICDP drilling project targeted to a better understanding of the crust in an active magmatic environment. We performed a 3D tomography using P-and S-wave travel times of local earthquakes and explosions. The data set were taken from permanent and temporary seismic networks in Germany and Czech Republic from 2000 to 2010, as well as active seismic experiments like Celebration 2000 and quarry blasts. After picking P and S wave arrival times, 399 events which were recorded by 9 or more stations and azimuthal gap<160° were selected for inversion. A simultaneous inversion of P and S wave 1D velocity models together with relocations of hypocenters and station corrections was performed. The obtained minimum 1D velocity model was used as starting model for the 3D Vp and Vp/Vs velocity models. P and S wave travel time tomography employs damped least-square method and ray tracing by pseudo-bending algorithm. For model parametrization different cell node spacings have been tested to evaluate the resolution in each node. Synthetic checkerboard tests have been done to check the structural resolution. Then Vp and Vp/Vs in the preferred 3D grid model have been determined. Earthquakes locations in iteration process change till the hypocenter adjustments and travel time residuals become smaller than the defined threshold criteria. Finally the analysis of the resolution depicts the well resolved features for interpretation. We observed lower Vp/Vs ratio in depth of 5-10 km close to the foci of earthquake swarms and higher Vp/Vs ratio is observed in Saxoturingian zone and

  3. The Complex Velocity Structure of the Chromosphere of VV Cephei

    NASA Astrophysics Data System (ADS)

    Bauer, Wendy Hagen; Bennett, Philip D.

    2014-06-01

    The eclipsing binary system VV Cephei consists of an M2 Iab supergiant primary and a hotter, probably B-type main-sequence companion. The last eclipse was observed with the HST-STIS spectrograph at 21 epochs ranging from mid-totality through first quadrature. These observations sampled seven lines of sight through the entire, extended chromosphere of the M supergiant star, beginning shortly after the hot companion emerged from total eclipse. At all seven of these egress epochs, the observed chromospheric absorption line profiles had a typical FWHM of 25-30 km/s. These profiles contained multiple (usually two) components that persisted throughout the chromosphere. The relative strengths of the two components were observed to depend on the ionization level and excitation potential, with the longer-wavelength (red) component tending to be stronger than the shorter-wavelength (blue) component in the higher-ionization and higher-excitation lines, while the strengths of the two components were more similar in lower-excitation features. This behavior suggests the red components form in hotter gas than the blue components. The great width of these chromospheric lines has been attributed both to intrinsic chromospheric turbulence and absorption due to the accelerating stellar wind. Here we present evidence that the complex absorption line profiles observed in the extended chromosphere of VV Cep reflect an intrinsic, coherent, multi-temperature component, azimuthal velocity structure present over the entire height of the M supergiant chromosphere, which is about a stellar radius in extent. This velocity model is inferred from the behavior of weak ultraviolet lines of species including Al I, Ti I, Fe I, Co I, Ni I, and Zr II. We present observations, analysis of the line profile velocity structure, and discuss the implications for driving the stellar wind and associated mass loss.

  4. Developing regionalized models of lithospheric thickness and velocity structure across Eurasia and the Middle East from jointly inverting P-wave and S-wave receiver functions with Rayleigh wave group and phase velocities

    SciTech Connect

    Julia, J; Nyblade, A; Hansen, S; Rodgers, A; Matzel, E

    2009-07-06

    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 velocity models obtained by jointly inverting P-wave and S-wave receiver functions with Rayleigh wave group and phase velocities. We expect the regionalized velocity 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 velocity 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 velocities 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 velocities constrain average S-wave velocity within frequency-dependent depth-ranges. Preliminary results show that the combination yields integrated 1D velocity models local to the recording station, where the discontinuities constrained by the receiver functions are superimposed to a background velocity model constrained by the dispersion velocities. In our first year of this project we will (i) generate 1D velocity models for open broadband seismic stations in the

  5. Gold-induced nanowires on the Ge(100) surface yield a 2D and not a 1D electronic structure

    NASA Astrophysics Data System (ADS)

    de Jong, N.; Heimbuch, R.; Eliëns, S.; Smit, S.; Frantzeskakis, E.; Caux, J.-S.; Zandvliet, H. J. W.; Golden, M. S.

    2016-06-01

    Atomic nanowires on semiconductor surfaces induced by the adsorption of metallic atoms have attracted a lot of attention as possible hosts of the elusive, one-dimensional Tomonaga-Luttinger liquid. The Au/Ge(100) system in particular is the subject of controversy as to whether the Au-induced nanowires do indeed host exotic, 1D (one-dimensional) metallic states. In light of this debate, we report here a thorough study of the electronic properties of high quality nanowires formed at the Au/Ge(100) surface. The high-resolution ARPES data show the low-lying Au-induced electronic states to possess a dispersion relation that depends on two orthogonal directions in k space. Comparison of the E (kx,ky) surface measured using high-resolution ARPES to tight-binding calculations yields hopping parameters in the two different directions that differ by approximately factor of two. Additionally, by pinpointing the Au-induced surface states in the first, second, and third surface Brillouin zones and analyzing their periodicity in k||, the nanowire propagation direction seen clearly in STM can be imported into the ARPES data. We find that the larger of the two hopping parameters corresponds, in fact, to the direction perpendicular to the nanowires (tperp). This proves that the Au-induced electron pockets possess a two-dimensional, closed Fermi surface, and this firmly places the Au/Ge(100) nanowire system outside potential hosts of a Tomonaga-Luttinger liquid. We combine these ARPES data with scanning tunneling spectroscopic measurements of the spatially resolved electronic structure and find that the spatially straight—wirelike—conduction channels observed up to energies of order one electron volt below the Fermi level do not originate from the Au-induced states seen in the ARPES data. The former are rather more likely to be associated with bulk Ge states that are localized to the subsurface region. Despite our proof of the 2D (two-dimentional) nature of the Au

  6. Analysis of the rupture process of the 1995 Kobe earthquake using a 3D velocity structure

    NASA Astrophysics Data System (ADS)

    Guo, Yujia; Koketsu, Kazuki; Ohno, Taichi

    2013-12-01

    A notable feature of the 1995 Kobe (Hyogo-ken Nanbu) earthquake is that violent ground motions occurred in a narrow zone. Previous studies have shown that the origin of such motions can be explained by the 3D velocity structure in this zone. This indicates not only that the 3D velocity structure significantly affects strong ground motions, but also that we should consider its effects in order to determine accurately the rupture process of the earthquake. Therefore, we have performed a joint source inversion of strong-motion, geodetic, and teleseismic data, where 3D Green's functions were calculated for strong-motion and geodetic data in the Osaka basin. Our source model estimates the total seismic moment to be about 2.1 × 1019 N m and the maximum slip reaches 2.9 m near the hypocenter. Although the locations of large slips are similar to those reported by Yoshida et al. (1996), there are quantitative differences between our results and their results due to the differences between the 3D and 1D Green's functions. We have also confirmed that our source model realized a better fit to the strong motion observations, and a similar fit as Yoshida et al. (1996) to the observed static displacements.

  7. Monitoring of concrete structures using the ultrasonic pulse velocity method

    NASA Astrophysics Data System (ADS)

    Karaiskos, G.; Deraemaeker, A.; Aggelis, D. G.; Van Hemelrijck, D.

    2015-11-01

    Concrete is the material most produced by humanity. Its popularity is mainly based on its low production cost and great structural design flexibility. Its operational and ambient loadings including environmental effects have a great impact in the performance and overall cost of concrete structures. Thus, the quality control, the structural assessment, the maintenance and the reliable prolongation of the operational service life of the existing concrete structures have become a major issue. In the recent years, non-destructive testing (NDT) is becoming increasingly essential for reliable and affordable quality control and integrity assessment not only during the construction of new concrete structures, but also for the existing ones. Choosing the right inspection technique is always followed by a compromise between its performance and cost. In the present paper, the ultrasonic pulse velocity (UPV) method, which is the most well known and widely accepted ultrasonic concrete NDT method, is thoroughly reviewed and compared with other well-established NDT approaches. Their principles, inherent limitations and reliability are reviewed. In addition, while the majority of the current UPV techniques are based on the use of piezoelectric transducers held on the surface of the concrete, special attention is paid to a very promising technique using low-cost and aggregate-size piezoelectric transducers embedded in the material. That technique has been evaluated based on a series of parameters, such as the ease of use, cost, reliability and performance.

  8. Sound velocity and structure measurement of silicate glasses under pressure

    NASA Astrophysics Data System (ADS)

    Sakamaki, T.; Kono, Y.; Wang, Y.; Park, C.; Yu, T.; Jing, Z.; Shen, G.

    2012-12-01

    The degree of polymerization in silicate melt/glass is one of the most important parameters to understand the magma behavior. For silicate melts at ambient pressure, the degree of polymerization is highly related to composition, which is quantitatively described by a ratio of non-bridging oxygen (NBO) to tetrahedrally cation (T). In particular, the NBO/T is widely used to obtain viscosity information of various silicate melts and discuss the magma mobility in the Earth's interior. Several viscometry studies reported that polymerized melts showed much higher values of viscosity than those of depolymerized ones. Interestingly, it should be noted that the pressure dependence of the high viscosity of polymerized melts was shown to be negative. This gives important questions of the compression effect on the degree of polymerization and its effects on properties of silicate melts. In this study, we have measured the sound velocity of polymerized glass (jadeite and albite glass: NBO/T=0) and depolymerized glass (diopside glass: NBO/T=2) at pressures up to 10 GPa by using ultrasonic technique and synchrotron radiation with a Paris-Edinburgh press. We have also obtained the X-ray structure factor, S(Q), of these glasses by using energy-dispersive X-ray diffraction method in order to understand structural changes in the intermediate-range order with pressure. All experiments were conducted using a Paris-Edinburgh press, which is installed at the HPCAT 16-BM-B beamline, Advanced Photon Source (APS). High pressure sound velocity measurements were carried out using the ultrasonic pulse-echo-overlap method. Radiography images taken by CCD camera allowed us to calculate the sample length under high pressure. Pressure was determined by the equation of state of gold, which was located below the sample. The scattered X-rays were detected using a Ge solid state detector (Ge-SSD) with a 4096 multi-channel analyzer. Ultrasonic signals were generated and received by a LiNbO3 transducer

  9. Dark matter direct detection with non-Maxwellian velocity structure

    SciTech Connect

    Kuhlen, Michael; Weiner, Neal; Diemand, Jürg; Moore, Ben; Potter, Doug; Stadel, Joachim; Madau, Piero; Zemp, Marcel E-mail: neal.weiner@nyu.edu E-mail: pmadau@ucolick.org E-mail: dpotter@physik.uzh.ch E-mail: mzemp@umich.edu

    2010-02-01

    The velocity distribution function of dark matter particles is expected to show significant departures from a Maxwell-Boltzmann distribution. This can have profound effects on the predicted dark matter - nucleon scattering rates in direct detection experiments, especially for dark matter models in which the scattering is sensitive to the high velocity tail of the distribution, such as inelastic dark matter (iDM) or light (few GeV) dark matter (LDM), and for experiments that require high energy recoil events, such as many directionally sensitive experiments. Here we determine the velocity distribution functions from two of the highest resolution numerical simulations of Galactic dark matter structure (Via Lactea II and GHALO), and study the effects for these scenarios. For directional detection, we find that the observed departures from Maxwell-Boltzmann increase the contrast of the signal and change the typical direction of incoming DM particles. For iDM, the expected signals at direct detection experiments are changed dramatically: the annual modulation can be enhanced by more than a factor two, and the relative rates of DAMA compared to CDMS can change by an order of magnitude, while those compared to CRESST can change by a factor of two. The spectrum of the signal can also change dramatically, with many features arising due to substructure. For LDM the spectral effects are smaller, but changes do arise that improve the compatibility with existing experiments. We find that the phase of the modulation can depend upon energy, which would help discriminate against background should it be found.

  10. Measurement of the differential cross section of the photoinitiated reactive collision of O(1D)+D2 using only one molecular beam: A study by three dimensional velocity mapping

    NASA Astrophysics Data System (ADS)

    Kauczok, S.; Maul, C.; Chichinin, A. I.; Gericke, K.-H.

    2010-06-01

    velocities. Using the benchmark system O(D1)+D2 with N2O as the precursor, we demonstrate that the technique is also applicable in a very general sense (i.e., also with a large spread in reactant velocities, products much faster than reactants) and therefore can be used also if such unfortunate conditions cannot be avoided. Since the resulting distribution of velocities in the laboratory frame is not cylindrically symmetric, three dimensional velocity mapping is the method of choice for the detection of the ionized products. For the reconstruction, the distance between the two laser beams is an important parameter. We have measured this distance using the photodissociation of HBr at 193 nm, detecting the H atoms near 243 nm. The collision energy resulting from the 193 nm photodissociation of N2O is 5.2±1.9 kcal/mol. Our results show a preference for backward scattered D atoms with the OH partner fragment in the high vibrational states (v =4-6), in accord with previously published results claiming the growing importance of a linear abstraction mechanism for collision energies higher than 2.4 kcal/mol.

  11. P Wave Velocity Structure Beneath the Baikal Rift Axis

    NASA Astrophysics Data System (ADS)

    Brazier, R. A.; Nyblade, A. A.; Boman, E. C.

    2001-12-01

    Over 100 p wave travel times from the 1500 km en echelon Baikal Rift system are used in this study.The events range 3 to 13 degrees from Talaya, Russia (TLY) along the axis of southwest northeast trending rift in East Siberia. A Herglotz Wiechert inversion of these events resolved a crust of 6.4 km/s and a gradient in the mantle starting at 35 km depth and 7.7 km/s down to 200 km depth and 8.2 km/s. This is compatible with Gao et al,1994 cross sectional structure which cuts the rift at about 400km from TLY. The Baikal Rift hosts the deepest lake and is the most seismically active rift in the world. It is one of the few continental rifts, it separates the Siberian craton and the Syan-Baikal mobile fold belt. Two events, the March 21 1999 magnitude 5.7 earthquake 638 km from TLY and the November 13th 1995 magnitude 5.9 earthquake 863 km from TLY were modeled for there PnL wave structure using the discrete wavenumber method and the Harvard CMT solutions with adjusted depths from p-pP times. The PnL signals match well. A genetic algorithm will used to perturb the velocity structure and compare to a selection of the events between 3 and 13 degrees many will require moment tensor solutions.

  12. Seismic velocity structure of the central Taupo Volcanic Zone, New Zealand, from local earthquake tomography

    NASA Astrophysics Data System (ADS)

    Sherburn, Steven; Bannister, Stephen; Bibby, Hugh

    2003-03-01

    The 3-D distribution of P-wave velocity (Vp) and the P-wave/S-wave velocity ratio (Vp/Vs) are derived for the crust in the central Taupo Volcanic Zone (TVZ), New Zealand, by tomographic inversion of P- and S-wave arrival time data from local earthquakes. Resolution in the seismogenic mid-crust (4-6 km) is good, but poorer above and below these depths. The 3-D velocity model has several Vp anomalies as large as ±5% in the mid-lower crust (4-10 km) and more than ±10% in the upper crust (0-4 km). The model achieves a 55% reduction in data variance from an initial 1-D model. Young caldera structures, Okataina, Rotorua, and Reporoa, are characterised by low Vp anomalies at a depth of about 4 km and these coincide with large negative residual gravity anomalies. We attribute these anomalies to large volumes of low Vp, low-density, volcaniclastic sediments that have filled these caldera collapse structures. Although there are no Vp anomalies which suggest the presence of molten or semi-molten magma beneath the TVZ, a large, high Vp anomaly of more than +15% and a high Vp/Vs anomaly are observed coincident with a diorite pluton beneath the Ngatamariki geothermal field. However, Vp anomalies cannot be seen beneath the largest geothermal fields, Waimangu, Waiotapu, and Reporoa, and, consequently, if such anomalies exist, they must be below the resolution of our data. A prominent Vp contrast of 5-10% occurs at a depth of about 6 km beneath the boundary between the Taupo-Reporoa Depression and the Taupo Fault Belt (TFB), coincident with the eastern limit of the seismic activity beneath the TFB. We interpret this velocity contrast as being caused by the presence of extensive, non-molten, intrusives beneath the Taupo-Reporoa Depression. We suggest that the high-velocity material beneath the Taupo-Reporoa Depression is isolated from regional extension in the TVZ, and from the resulting faulting and seismicity, which occurs preferentially within the weaker material of the TFB. We

  13. 3-D imaging of large scale buried structure by 1-D inversion of very early time electromagnetic (VETEM) data

    USGS Publications Warehouse

    Aydmer, A.A.; Chew, W.C.; Cui, T.J.; Wright, D.L.; Smith, D.V.; Abraham, J.D.

    2001-01-01

    A simple and efficient method for large scale three-dimensional (3-D) subsurface imaging of inhomogeneous background is presented. One-dimensional (1-D) multifrequency distorted Born iterative method (DBIM) is employed in the inversion. Simulation results utilizing synthetic scattering data are given. Calibration of the very early time electromagnetic (VETEM) experimental waveforms is detailed along with major problems encountered in practice and their solutions. This discussion is followed by the results of a large scale application of the method to the experimental data provided by the VETEM system of the U.S. Geological Survey. The method is shown to have a computational complexity that is promising for on-site inversion.

  14. Joint inversion of surface wave velocity and gravity observations and its application to central Asian basins shear velocity structure

    NASA Astrophysics Data System (ADS)

    Maceira, Monica; Ammon, Charles J.

    2009-02-01

    We implement and apply a method to the jointly inverted of surface wave group velocities and gravity anomalies observations. Surface wave dispersion measurements are sensitive to seismic shear wave velocities, and the gravity measurements supply constraints on rock density variations. Our goal is to obtain a self-consistent three-dimensional shear velocity-density model with increased resolution of shallow geologic structures. We apply the method to investigate the structure of the crust and upper mantle beneath two large central Asian sedimentary basins: the Tarim and Junggar. The basins have thick sediment sections that produce substantial regional gravity variations (up to several hundred milligals). We used gravity observations extracted from the global gravity model derived from the Gravity Recovery and Climate Experiment (GRACE) satellite mission. We combine the gravity anomalies with high-resolution surface wave slowness tomographic maps that provide group velocity dispersion values in the period range between 8 and 100 s for a grid of locations across central Asia. To integrate these data, we use a relationship between seismic velocity and density constructed through the combination of two empirical relations. One determined by Nafe and Drake, most appropriate for sedimentary rocks, and a linear Birch's law, more applicable to denser rocks (the basement). An iterative, damped least squares inversion including smoothing is used to jointly model both data sets, using shear velocity variations as the primary model parameters. Results show high upper mantle shear velocities beneath the Tarim basin and suggest differences in lower crust and upper mantle shear velocities between the eastern and western Tarim.

  15. Four 1-D metal-organic polymers self-assembled from semi-flexible benzimidazole-based ligand: Syntheses, structures and fluorescent properties

    NASA Astrophysics Data System (ADS)

    Zhou, Chun-lin; Wang, Shi-min; Liu, Sai-nan; Yu, Tian-tian; Li, Rui-ying; Xu, Hong; Liu, Zhong-yi; Sun, Huan; Cheng, Jia-jia; Li, Jin-peng; Hou, Hong-wei; Chang, Jun-biao

    2016-08-01

    Four one-dimensional (1-D) metal-organic polymers based on methylene-bis(1,1‧-benzimidazole)(mbbz), namely, {[Hg(mbbz)(SCN)2]·1/3H2O}n (1), [Co(mbbz)(Cl)2]n (2), {[Co(mbbz)(SO4)]·CH3OH}n (3) and {[Zn(mbbz)(SO4)]·CH3OH}n (4) have been successfully synthesized and structurally characterized. Single-crystal X-ray diffraction reveals that polymers 1 and 2 exhibit interesting 1-D double helical chain structures, while polymers 3 and 4 are 1-D double chain structures due to the bridging effect of mbbz ligands and sulfate anions. These polymers containing the mbbz-based ligand have a high degree of dependence on the corresponding counter anions. Furthermore, the fluorescence properties of the four polymers were also investigated in the solid state, showing the fluorescence signal changes in comparing with that of free ligand mbbz.

  16. Seismic Velocity Structure and Depth-Dependence of Anisotropy in the Red Sea and Arabian Shield from Surface Wave Analysis

    SciTech Connect

    Hansen, S; Gaherty, J; Schwartz, S; Rodgers, A; Al-Amri, A

    2007-07-25

    We investigate the lithospheric and upper mantle structure as well as the depth-dependence of anisotropy along the Red Sea and beneath the Arabian Peninsula using receiver function constraints and phase velocities of surface waves traversing two transects of stations from the Saudi Arabian National Digital Seismic Network. Frequency-dependent phase delays of fundamental-mode Love and Rayleigh waves, measured using a cross-correlation procedure, require very slow shear velocities and the presence of anisotropy throughout the upper mantle. Linearized inversion of these data produce path-averaged 1D radially anisotropic models with about 4% anisotropy in the lithosphere, increasing to about 4.8% anisotropy across the lithosphere-asthenosphere boundary (LAB). Models with reasonable crustal velocities in which the mantle lithosphere is isotropic cannot satisfy the data. The lithospheric lid, which ranges in thickness from about 70 km near the Red Sea coast to about 90 km beneath the Arabian Shield, is underlain by a pronounced low-velocity zone with shear velocities as low as 4.1 km/s. Forward models, which are constructed from previously determined shear-wave splitting estimates, can reconcile surface and body wave observations of anisotropy. The low shear velocity values are similar to many other continental rift and oceanic ridge environments. These low velocities combined with the sharp velocity contrast across the LAB may indicate the presence of partial melt beneath Arabia. The anisotropic signature primarily reflects a combination of plate- and density-driven flow associated with active rifting processes in the Red Sea.

  17. 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.

  18. Crustal S-wave structure beneath Eastern Black Sea Region revealed by Rayleigh-wave group velocities

    NASA Astrophysics Data System (ADS)

    Çınar, Hakan; Alkan, Hamdi

    2016-01-01

    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 group velocities 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 group-velocity-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 group velocity 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 velocity (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 velocity change (Vs = 3.4-3.8 km/s). The Moho dips approximately southwards, and the Vs velocity (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.

  19. Syntheses, crystal structures and properties of two 1-D cadmium(II) coordination polymers based on 1,1'-(1,3-propanediyl)bis-1H-benzimidazole

    SciTech Connect

    Yang Huaixia; Meng Xiangru; Liu Yun; Hou Hongwei Fan Yaoting; Shen Xiaoqing

    2008-09-15

    The combination of framework-builders 1,1'-(1,3-propanediyl)bis-1H-benzimidazole (pbbm), Cd(II) ion and framework-regulator ClO{sub 4}{sup -} or SO{sub 4}{sup 2-} provides two new coordination polymers [Cd(pbbm){sub 2}(ClO{sub 4}){sub 2}]{sub n}(1) and {l_brace}[Cd(pbbm)SO{sub 4}(H{sub 2}O){sub 2}].CH{sub 3}OH{r_brace}{sub n}(2). Both of them display 1-D chain framework, but their detailed structures are clearly different from each other. 1 displays a 1-D ribbon of rings framework, 2 features an interesting infinite 1-D looped chain structure composed of two kinds of rings, the smaller 8-membered ring and the larger 20-membered ring. The antimicrobial activities of the two polymers were tested by the agar diffusion method and the results indicated that they exhibited antimicrobial activities against bacterial strands. The measurement of the non-isothermal kinetics of the thermal decomposition of 2 reveals that there are at least three steps that occur in its decomposition process. - Graphical abstract: Two new Cd(II)-containing complexes have been synthesized and characterized by single-crystal X-ray diffraction. The antimicrobial activity and the non-isothermal kinetics of the thermal decomposition of the polymers were also investigated. Display Omitted.

  20. Syntheses, crystal structures and luminescent properties of two new 1D d {sup 1} coordination polymers constructed from 2,2'-bibenzimidazole and 1,4-benzenedicarboxylate

    SciTech Connect

    Wen Lili; Li Yizhi; Dang Dongbin; Tian Zhengfang; Ni Zhaoping; Meng Qingjin . E-mail: mengqj@nju.edu.cn

    2005-11-15

    Two novel interesting d {sup 1} metal coordination polymers, [Zn(H{sub 2}bibzim)(BDC)] {sub n} (1) and [Cd(H{sub 2}bibzim)(BDC)] {sub n} (2) [H{sub 2}bibzim=2,2'-bibenzimidazole, BDC=1,4-benzenedicarboxylate] have been synthesized under solvothermal conditions and structurally characterized. Both 1 and 2 are constructed from infinite neutral zigzag-like one-dimensional (1D) chains. The {pi}-{pi} interactions and interchain hydrogen-bonding interactions further extend the 1D arrangement to generate a 3D supramolecular architecture for 1 and 2. Both complexes have high thermal stability and display strong blue fluorescent emissions in the solid state upon photo-excitation at 365 nm at room temperature. They are the first two examples that 2,2'-bibenzimidazole has been introduced into the d {sup 1} coordination polymeric framework.

  1. Superconducting accelerating structures for very low velocity ion beams

    SciTech Connect

    Xu, J.; Shepard, K.W.; Ostroumov, P.N.; Fuerst, J.D.; Waldschmidt, G.; Gonin, I.V.; /Fermilab

    2008-01-01

    This paper presents designs for four types of very-low-velocity superconducting accelerating cavity capable of providing several MV of accelerating potential per cavity, and suitable for particle velocities in the range 0.006 < v/c < 0.06. Superconducting TEM-class cavities have been widely applied to CW acceleration of ion beams. SC linacs can be formed as an array of independently-phased cavities, enabling a variable velocity profile to maximize the output energy for each of a number of different ion species. Several laboratories in the US and Europe are planning exotic beam facilities based on SC linacs. The cavity designs presented here are intended for the front-end of such linacs, particularly for the post-acceleration of rare isotopes of low charge state. Several types of SC cavities have been developed recently to cover particle velocities above 0.06c. Superconducting four-gap quarter-wave resonators for velocities 0.008 < {beta} = v/c < 0.05 were developed about two decades ago and have been successfully operated at the ATLAS SC linac at Argonne National Laboratory. Since that time, progress in simulation tools, cavity fabrication and processing have increased SC cavity gradients by a factor of 3-4. This paper applies these tools to optimize the design of a four-gap quarter-wave resonator for exotic beam facilities and other low-velocity applications.

  2. Structure of the crust beneath Cameroon, West Africa, from the joint inversion of Rayleigh wave group velocities and receiver functions

    NASA Astrophysics Data System (ADS)

    Tokam, Alain-Pierre K.; Tabod, Charles T.; Nyblade, Andrew A.; Julià, Jordi; Wiens, Douglas A.; Pasyanos, Michael E.

    2010-11-01

    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 velocity models obtained from the joint inversion of Rayleigh wave group velocities 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 velocity 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 velocities >=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 velocity 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.

  3. Velocity structure in long period variable star atmospheres

    NASA Technical Reports Server (NTRS)

    Pilachowski, C.; Wallerstein, G.; Willson, L. A.

    1980-01-01

    A regression analysis of the dependence of absorption line velocities on wavelength, line strength, excitation potential, and ionization potential is presented. The method determines the region of formation of the absorption lines for a given data and wavelength region. It is concluded that the scatter which is frequently found in velocity measurements of absorption lines in long period variables is probably the result of a shock of moderate amplitude located in or near the reversing layer and that the frequently observed correlation of velocity with excitation and ionization are a result of the velocity gradients produced by this shock in the atmosphere. A simple interpretation of the signs of the coefficients of the regression analysis is presented in terms of preshock, post shock, or across the shock, together with criteria for evaluating the validity of the fit. The amplitude of the reversing layer shock is estimated from an analysis of a series of plates for four long period variable stars along with the most probable stellar velocity for these stars.

  4. New method for computation of band structures in 1D photonic crystals based on the Fresnel equations

    NASA Astrophysics Data System (ADS)

    Roshan Entezar, S.

    2013-02-01

    In this paper, we present a new method for calculation of band structure in one-dimensional bilayer photonic crystals, based on the Fresnel equations. We derive a new relation to obtain the band structure without using the Floquet theorem. It is shown that this relation can be simplified under the assumption that the single-path phase-shift acquired through the individual layers of the photonic crystal be equal to ? . The results obtained by our method are compared with the ones obtained from the transfer matrix method to show that they are exactly identical.

  5. Syntheses, crystal structures, and characterization of three 1D, 2D and 3D complexes based on mixed multidentate N- and O-donor ligands

    SciTech Connect

    Yang, Huai-Xia; Liang, Zhen; Hao, Bao-Lian; Meng, Xiang-Ru

    2014-10-15

    Three new 1D to 3D complexes, namely, ([Ni(btec)(Himb){sub 2}(H{sub 2}O){sub 2}]·6H{sub 2}O){sub n} (1), ([Cd(btec){sub 0.5}(imb)(H{sub 2}O)]·1.5H{sub 2}O){sub n} (2), and ([Zn(btec){sub 0.5}(imb)]·H{sub 2}O){sub n} (3) (H{sub 4}btec=1,2,4,5-benzenetetracarboxylic acid, imb=2-(1H-imidazol-1-methyl)-1H-benzimidazole) have been synthesized by adjusting the central metal ions. Single-crystal X-ray diffraction analyses reveal that complex 1 possesses a 1D chain structure which is further extended into the 3D supramolecular architecture via hydrogen bonds. Complex 2 features a 2D network with Schla¨fli symbol (5{sup 3}·6{sup 2}·7)(5{sup 2}·6{sup 4}). Complex 3 presents a 3D framework with a point symbol of (4·6{sup 4}·8)(4{sup 2}·6{sup 2}·8{sup 2}). Moreover, their IR spectra, PXRD patterns, thermogravimetric curves, and luminescent emissions were studied at room temperature. - Graphical abstract: Three new 1D to 3D complexes with different structural and topological motifs have been obtained by modifying the central metal ions. Additionally, their IR, TG analyses and fluorescent properties are also investigated. - Highlights: • Three complexes based on mixed multidentate N- and O-donor ligands. • The complexes are characterized by IR, luminescence and TGA techniques. • Benzenetetracarboxylates display different coordination modes in complexes 1–3. • Changing the metal ions can result in complexes with completely different structures.

  6. Crystal Structure of Human Liver delta {4}-3-Ketosteroid 5 beta-Reductase (AKR1D1) and Implications for Substrate Binding and Catalysis

    SciTech Connect

    Di Costanzo,L.; Drury, J.; Penning, T.; Christianson, D.

    2008-01-01

    AKR1D1 (steroid 5{beta}-reductase) reduces all 4-3-ketosteroids to form 5{beta}-dihydrosteroids, a first step in the clearance of steroid hormones and an essential step in the synthesis of all bile acids. The reduction of the carbon-carbon double bond in an a,{beta}-unsaturated ketone by 5{beta}-reductase is a unique reaction in steroid enzymology because hydride transfer from NADPH to the {beta}-face of a 4-3-ketosteroid yields a cis-A/B-ring configuration with an {approx}90 bend in steroid structure. Here, we report the first x-ray crystal structure of a mammalian steroid hormone carbon-carbon double bond reductase, human 4-3-ketosteroid 5{beta}-reductase (AKR1D1), and its complexes with intact substrates. We have determined the structures of AKR1D1 complexes with NADP+ at 1.79- and 1.35- Angstroms resolution (HEPES bound in the active site), NADP+ and cortisone at 1.90- Angstroms resolution, NADP+ and progesterone at 2.03- Angstroms resolution, and NADP+ and testosterone at 1.62- Angstroms resolution. Complexes with cortisone and progesterone reveal productive substrate binding orientations based on the proximity of each steroid carbon-carbon double bond to the re-face of the nicotinamide ring of NADP+. This orientation would permit 4-pro-(R)-hydride transfer from NADPH. Each steroid carbonyl accepts hydrogen bonds from catalytic residues Tyr58 and Glu120. The Y58F and E120A mutants are devoid of activity, supporting a role for this dyad in the catalytic mechanism. Intriguingly, testosterone binds nonproductively, thereby rationalizing the substrate inhibition observed with this particular steroid. The locations of disease-linked mutations thought to be responsible for bile acid deficiency are also revealed.

  7. Seismic imaging for velocity and attenuation structure in geothermal fields

    SciTech Connect

    Zucca, J.J. ); Evans, J.R. )

    1989-06-01

    We have applied the attenuation inversion technique developed by Evans and Zucca (1988) to a seismic tomographic data set taken at Newberry Volcano by Achauer et al. (1988). Our preliminary results suggest that the interpretation of the velocity data by Achauer et al. that a magma chamber is present 3 km beneath the caldera is not confirmed by the attenuation data.

  8. Upper-mantle velocity structure beneath the Siberian platform

    NASA Astrophysics Data System (ADS)

    Priestley, Keith; Cipar, John; Egorkin, Anatoli; Pavlenkova, Nina

    1994-08-01

    We present a new velocity model for the continental upper mantle beneath central Siberia based on observations of the 1982'RIFT'Deep Seismic Sounding (DSS) profile. Three Peaceful Nuclear Explosions (PNE) were detonated to provide energy for the 2600 km long profile that extends from the Yamal Peninsula to the Mongolian border SE of Lake Baikal. In this paper, we model seismic recordings from the northernmost explosion since data from that shot shows unambiguous arrivals from the mantle-transition-zone discontinuities. The analysis combines forward-traveltime modelling and waveform matching using reflectivity synthetic seismograms. Our model for the lithosphere has velocities of 8.25-8.20 km s-1 from the Moho to 117 km depth. Between 117 and 123 km depth, a strong velocity gradient (8.30-8.53 km s-1) is required while a moderate gradient (8.53-8.55 km s-1) exists between 123 and 136 km depth. A low-velocity zone from 136 to 210 km depth terminates this phase arrival branch. The gradient again rises between 210 and 233 km and depth, culminating in a high-gradient zone (8.63-8.80 km s-1) between 233 and 235 km depth. Below the high-gradient zone, more moderate gradient (8.80-8.85 km s-1) is required from 235 to 253 km depth, terminating in a zone of lower velocity (8.62-8.64 km s-1) from 253 to 400 km depth. The upper-mantle transition zone consists of two high-gradient zones separated by a more moderate gradient. The upper zone is best modelled as a 35 km thick velocity gradient (8.64-9.45 km s-1) from 400 to 435 km depth. The existence of the velocity gradient is based on the observation that arrivals from this feature can be identified starting at 1580 km range and rapidly become prominent with increasing distance. A model with a first-order discontinuity predicts significant arrivals at ranges closer than 1580 km. Our observations contain no compelling evidence for a 520 km discontinuity, although a small discontinuity cannot be ruled out. The lower

  9. Propagation of the Ultra-Short Laser Pulses Through the Helical 1D Photonic Crystal Structure with Twist Defect

    NASA Astrophysics Data System (ADS)

    Antonov, Dmitrii V.; Iegorov, Roman

    2016-02-01

    The presence of the photonic band-gap is a featured property of the cholesteric liquid crystals (CLC). It can be practically realized for almost any reasonable wavelengths with very high degree of tunability. We have investigated theoretically the influence of the twist defect of the CLC helical structure onto the bandwidth-limited ultra-short laser pulse propagating inside the photonic band-gap. The changes of both pulse duration and peak power with defect angle were observed together with pulse acceleration and retardation for a case of normal incidence of the light.

  10. A time series generalized functional model based method for vibration-based damage precise localization in structures consisting of 1D, 2D, and 3D elements

    NASA Astrophysics Data System (ADS)

    Sakaris, C. S.; Sakellariou, J. S.; Fassois, S. D.

    2016-06-01

    This study focuses on the problem of vibration-based damage precise localization via data-based, time series type, methods for structures consisting of 1D, 2D, or 3D elements. A Generalized Functional Model Based method is postulated based on an expanded Vector-dependent Functionally Pooled ARX (VFP-ARX) model form, capable of accounting for an arbitrary structural topology. The FP model's operating parameter vector elements are properly constrained to reflect any given topology. Damage localization is based on operating parameter vector estimation within the specified topology, so that the location estimate and its uncertainty bounds are statistically optimal. The method's effectiveness is experimentally demonstrated through damage precise localization on a laboratory spatial truss structure using various damage scenarios and a single pair of random excitation - vibration response signals in a low and limited frequency bandwidth.

  11. Structural and Magnetic Behavior of a Quasi-1D Antiferromagnetic Chain Compound Cu(NCS)(2)(PYZ)

    SciTech Connect

    Bordallo, H. N.; Chapon, L. C.; Manson, Jamie L; Qualls, J. S.; Hall, D.; Argyriou, D. N.

    2003-01-01

    Synchrotron X-ray diffraction (XRD) and neutron powder diffraction (NPD) were used to determine the structure of Cu(NCS){sub 2}(pyz) (pyz=pyrazine=C{sub 4}N{sub 2}H{sub 4}), which consists of a stacking of Cu-pyz-Cu chains. While NPD measurements showed no evidence of long-range magnetic ordering, the temperature dependence of the magnetic susceptibility and magnetization suggests that the system can be adequately described on the local scale as a spin-1/2 antiferromagnet (AFM) chain with an intrachain exchange interaction J/k{sub B} = -8 K ({approx}0.7 meV). Comparison of isothermal magnetization data acquired up to 30 T at 1.6 K to a linear chain model shows excellent agreement, making this material a nearly ideal example of an isotropic Heisenberg AFM chain.

  12. Tuning the structures based on polyoxometalates from 1-D to 2-D by using different secondary organic ligands.

    PubMed

    Hu, Yang-Yang; Xiao-Zhang; Zhao, De-Chuan; Guo, Hai-Yang; Fu, Li-Wei; Guo, Lan-Lan; Cui, Xiao-Bing; Huo, Qi-Sheng; Xu, Ji-Qing

    2015-09-01

    Six new organic-inorganic hybrid compounds based on [XM12O40](4-) (X = heteroatom, M = metal atom), namely [Cu(pic)2][H2XM12O40]·2Hapy·2apy (X = Si, M = W for , X = Ge, M = W for and X = Si, M = Mo for ), [Cu(2,2'-bpy)2][Cu(2,2'-bpy)(H2O)][Cu(pic)2]0.5[XM12O40]·nH2O (X = Si, M = Mo, n = 0.5 for , X = Ge, M = W, n = 1 for ) and [Cu(phen)(H2O)]2[Cu(pic)2][GeW12O40]·2.5H2O () (pic = deprotonated picolinic acid, apy = 2-aminopyridine, 2,2'-bpy = 2,2'-bipyridine, phen = phenanthroline), have been synthesized and characterized by IR, UV-Vis, XRD, cyclic voltammetric measurements and single crystal X-ray diffraction analysis. Single crystal X-ray analysis reveals that compounds are isomorphous and isostructural, in which each is based on [H2XM12O40](2-) and [Cu(pic)2]. Compounds and are also isomorphous and isostructural, of which the structures are more interesting than those of compounds . Both structures are constructed from [XM12O40](4-) and metal mixed-organic-ligand complexes. Compound is also constructed from Keggin ions and metal mixed-organic-ligand complexes, which are, however, thoroughly different from those of compounds and . The photodegradation properties of compounds have been analyzed. Compounds also exhibit rapid absorption properties for RhB (Rhodamine B). Detailed analysis of the photodegradation properties of compounds reveals that the molybdate POM has stronger degradation ability for RhB than the tungstate one. PMID:26223513

  13. Large-scale shear velocity structure of the upper mantle beneath Europe and surrounding regions

    NASA Astrophysics Data System (ADS)

    Legendre, C.; Meier, T.; Lebedev, S.; Friederich, W.

    2009-04-01

    The automated multimode waveform inversion technique developed by Lebedev et al., (2005) was applied to available data of broadband stations in Europe and surrounding regions. The Automated Multimode Inversion Method (AMI) foots on an inversion technique originally invented by Nolet (1991) which he called partitioned waveform inversion. It performs a fitting of the complete waveform starting from the S-wave onset to the surface wave. Assuming that the location and focal mechanism of a considered earthquake are known, the first basic step is to consider each available seismogram separately and to to derive from it linear constrains, which are later used to construct the 3D-model. Inversion parameters are variations of shear velocity in the mantle and Moho depth. The theoretical background of AMI is the pure-path approximation which assumes propagation of waves in and around the vertical plane containing source and receiver. AMI extends the partitioned waveform inversion to a completely automated procedure with automated data quality checks and an automated assessment of the quality of fit obtain when determining the linear constrains from the observed seismogram. In this way, large volumes of data can be efficiently inverted for 3D-mantle structure. We collected all available data for the years from 1990 to 2007 from permanent stations in and around Europe via the data centers of ORFEUS, GEOFON and IRIS. In addition, we incorporated data from temporary experiments like ETSE array, SVEKALAPKO, TOR and the Eifel plume project. Just recently we were also able to add the data recorded by the EGELADOS network from the GEOFON data archive. In this way, a huge data set of about 500.000 seismograms came about from which about 65.000 1D-models could be constructed. The reduction of usable seismograms is caused by (1) mislocation or/and errors in the CMT solutions, (2) the rigorous automatic quality checks implemented in AMI, and (3) the elimination of seismograms for which

  14. Shear Wave Velocity Structure of Southern African Crust: Evidence for Compositional Heterogeneity within Archaean and Proterozoic Terrains

    SciTech Connect

    Kgaswane, E M; Nyblade, A A; Julia, J; Dirks, P H H M; Durrheim, R J; Pasyanos, M E

    2008-11-11

    Crustal structure in southern Africa has been investigated by jointly inverting receiver functions and Rayleigh wave group velocities for 89 broadband seismic stations spanning much of the Precambrian shield of southern Africa. 1-D shear wave velocity profiles obtained from the inversion yield Moho depths that are similar to those reported in previous studies and show considerable variability in the shear wave velocity structure of the lower part of the crust between some terrains. For many of the Archaean and Proterozoic terrains in the shield, S velocities reach 4.0 km/s or higher over a substantial part of the lower crust. However, for most of the Kimberley terrain and adjacent parts of the Kheis Province and Witwatersrand terrain, as well as for the western part of the Tokwe terrain, mean shear wave velocities of {le} 3.9 km/s characterize the lower part of the crust along with slightly ({approx}5 km) thinner crust. These findings indicate that the lower crust across much of the shield has a predominantly mafic composition, except for the southwest portion of the Kaapvaal Craton and western portion of the Zimbabwe Craton, where the lower crust is intermediate-to-felsic in composition. The parts of the Kaapvaal Craton underlain by intermediate-to-felsic lower crust coincide with regions where Ventersdorp rocks have been preserved, and thus we suggest that the intermediate-to-felsic composition of the lower crust and the shallower Moho may have resulted from crustal melting during the Ventersdorp tectonomagmatic event at c. 2.7 Ga and concomitant crustal thinning caused by rifting.

  15. Determination of a three-dimensional velocity structure for the Southeastern of Mexico, by means of seismic ray tracing.

    NASA Astrophysics Data System (ADS)

    Rodriguez-Perez, Q.; Valdes-Gozalez, C.

    2007-05-01

    The objective of the present study is to obtain a three-dimensional velocity structure for three different tectonic provinces (Oaxaca, Chiapas and north of Guatemala). The Southeastern of Mexico is a seismic active region, in which several geologic structures of great importance are located: the Tehuantepec ridge, the Central-American volcanic arc, the Chiapas batholit, the extension of the Motagua-Polochic fault system, and also the existance of complex tectonostratigrafic terrenes at cortical level. In this area of study, there are a considerable number of tectonic studies and cortical velocity models (1D). For this reason is desired to obtain a three-dimensional realistic velocity model that agrees with the results obtained in previous studies. To make it posible, a preliminary velocity model has been proposed and has been discretized, and is now at the test stage. Also the geometry of the Cocos plate is determined (variation of the subduction angle) and we will try to obtain the interaction between the Motagua-Polochic fault system and the previously described subduction provinces. We will use P and S waves, from local and regional earthquakes from 1994 to 2004 reported by National Seismological Service (SSN) in eight broadband seismic stations in the Southeastern of Mexico (CCIG, CMIG, EVV, HUIG, OXIG, SCX TPX, TUIG). In the study earthquake relocalizations with the DD method will be performed, and a 3-D ray tracing will be used to test the seismic model. The 3-D velocity model will allow us to better understand the wave propagation characteristics, and apply them to the mitigation of the seismic risk in the region. 1. Earth Science Graduate Program. UNAM. 2. Institute of Geophysics. UNAM.

  16. Structural Insights into the Binding of Vascular Endothelial Growth Factor-B by VEGFR-1D2

    PubMed Central

    Iyer, Shalini; Darley, Paula I.; Acharya, K. Ravi

    2010-01-01

    The formation of blood vessels (angiogenesis) is a highly orchestrated sequence of events involving crucial receptor-ligand interactions. Angiogenesis is critical for physiological processes such as development, wound healing, reproduction, tissue regeneration, and remodeling. It also plays a major role in sustaining tumor progression and chronic inflammation. Vascular endothelial growth factor (VEGF)-B, a member of the VEGF family of angiogenic growth factors, effects blood vessel formation by binding to a tyrosine kinase receptor, VEGFR-1. There is growing evidence of the important role played by VEGF-B in physiological and pathological vasculogenesis. Development of VEGF-B antagonists, which inhibit the interaction of this molecule with its cognate receptor, would be important for the treatment of pathologies associated specifically with this growth factor. In this study, we present the crystal structure of the complex of VEGF-B with domain 2 of VEGFR-1 at 2.7 Å resolution. Our analysis reveals that each molecule of the ligand engages two receptor molecules using two symmetrical binding sites. Based on these interactions, we identify the receptor-binding determinants on VEGF-B and shed light on the differences in specificity towards VEGFR-1 among the different VEGF homologs. PMID:20501651

  17. Crustal velocity structure north of the Mendocino triple junction

    NASA Astrophysics Data System (ADS)

    Beaudoin, Bruce C.; Magee, Marian; Benz, Harley

    1994-10-01

    A 140-km-long refraction/wide-angle reflection profile recently recorded by Stanford University and the U.S. Geological Survey imaged the subducting Gorda slab beneath northern California. The profile, which is subparallel to the coast from Cape Mendocino northward, indicates that the North American plate is 13- to 14-km-thick along the coast north of Cape Mendocino. The crust is characterized by relatively uniform, low velocities of less than or = 6 km/s interpreted as Franciscan rocks. Two strong reflections define the upper and lower boundaries of the subducting Gorda crust. Our data indicate that the subducting Gorda crust thickens northward from Cape Mendocino from 7-km-thick just north of Cape Mendocino to 10-km-thick 120 km to the north. This change in thickness is coincident with a change in velocity from 6.7 km/s south to 6.2 km/s north. Mantle velocities of 7.7 km/s are observed for offsets greater than c. 80 km. We interpret our model to indicate that the Gorda slab is not imbricated on a crustal scale beneath our profile, that sediments and/or a tectonically thickened oceanic layer 2 are present to the north but not in the vicinity of Cape Mendocino, and that proximity to the Mendocino triple junction affects the way sediments are subducted.

  18. The preliminary results: Internal seismic velocity structure imaging beneath Mount Lokon

    SciTech Connect

    Firmansyah, Rizky; Nugraha, Andri Dian; Kristianto

    2015-04-24

    Historical records that before the 17{sup th} century, Mount Lokon had been dormant for approximately 400 years. In the years between 1350 and 1400, eruption ever recorded in Empung, came from Mount Lokon’s central crater. Subsequently, in 1750 to 1800, Mount Lokon continued to erupt again and caused soil damage and fall victim. After 1949, Mount Lokon dramatically increased in its frequency: the eruption interval varies between 1 – 5 years, with an average interval of 3 years and a rest interval ranged from 8 – 64 years. Then, on June 26{sup th}, 2011, standby alert set by the Center for Volcanology and Geological Hazard Mitigation. Peak activity happened on July 4{sup th}, 2011 that Mount Lokon erupted continuously until August 28{sup th}, 2011. In this study, we carefully analyzed micro-earthquakes waveform and determined hypocenter location of those events. We then conducted travel time seismic tomographic inversion using SIMULPS12 method to detemine Vp, Vs and Vp/Vs ratio structures beneath Lokon volcano in order to enhance our subsurface geological structure. During the tomographic inversion, we started from 1-D seismic velocities model obtained from VELEST33 method. Our preliminary results show low Vp, low Vs, and high Vp/Vs are observed beneath Mount Lokon-Empung which are may be associated with weak zone or hot material zones. However, in this study we used few station for recording of micro-earthquake events. So, we suggest in the future tomography study, the adding of some seismometers in order to improve ray coverage in the region is profoundly justified.

  19. The preliminary results: Internal seismic velocity structure imaging beneath Mount Lokon

    NASA Astrophysics Data System (ADS)

    Firmansyah, Rizky; Nugraha, Andri Dian; Kristianto

    2015-04-01

    Historical records that before the 17th century, Mount Lokon had been dormant for approximately 400 years. In the years between 1350 and 1400, eruption ever recorded in Empung, came from Mount Lokon's central crater. Subsequently, in 1750 to 1800, Mount Lokon continued to erupt again and caused soil damage and fall victim. After 1949, Mount Lokon dramatically increased in its frequency: the eruption interval varies between 1 - 5 years, with an average interval of 3 years and a rest interval ranged from 8 - 64 years. Then, on June 26th, 2011, standby alert set by the Center for Volcanology and Geological Hazard Mitigation. Peak activity happened on July 4th, 2011 that Mount Lokon erupted continuously until August 28th, 2011. In this study, we carefully analyzed micro-earthquakes waveform and determined hypocenter location of those events. We then conducted travel time seismic tomographic inversion using SIMULPS12 method to detemine Vp, Vs and Vp/Vs ratio structures beneath Lokon volcano in order to enhance our subsurface geological structure. During the tomographic inversion, we started from 1-D seismic velocities model obtained from VELEST33 method. Our preliminary results show low Vp, low Vs, and high Vp/Vs are observed beneath Mount Lokon-Empung which are may be associated with weak zone or hot material zones. However, in this study we used few station for recording of micro-earthquake events. So, we suggest in the future tomography study, the adding of some seismometers in order to improve ray coverage in the region is profoundly justified.

  20. A relation among geology, tectonics, and velocity structure, western to central Nevada Basin and Range

    USGS Publications Warehouse

    Catchings, R.D.

    1992-01-01

    In the northwestern to central Nevada Basin and Range, there are correlations between velocity and specific geologic structures of the crust. Mapped range-bounding faults at the surface can be traced to appreciable (10km) depths based on velocity variations and are consistent with subsurface projections of the faults based on seismic reflection images. Correlations between velocity and the surface geology show that in the upper crust the pre-Cenozoic rocks are underlain by high-velocity rocks, whereas the Tertiary ranges are underlain by lower-velocity rocks to depths as great as 10 km. The regional seismicity pattern is consistent with this interpretation, as earthquakes are largely confined within or near the base of the low-velocity rocks. These low-velocity, highly fractured rocks are laterally distributed in discrete zones, suggesting that extension is not uniformly distributed but occurs in discrete, highly extended zones. -from Author

  1. Syntheses, crystal structures, and characterization of three 1D, 2D and 3D complexes based on mixed multidentate N- and O-donor ligands

    NASA Astrophysics Data System (ADS)

    Yang, Huai-Xia; Liang, Zhen; Hao, Bao-Lian; Meng, Xiang-Ru

    2014-10-01

    Three new 1D to 3D complexes, namely, {[Ni(btec)(Himb)2(H2O)2]·6H2O}n (1), {[Cd(btec)0.5(imb)(H2O)]·1.5H2O}n (2), and {[Zn(btec)0.5(imb)]·H2O}n (3) (H4btec=1,2,4,5-benzenetetracarboxylic acid, imb=2-(1H-imidazol-1-methyl)-1H-benzimidazole) have been synthesized by adjusting the central metal ions. Single-crystal X-ray diffraction analyses reveal that complex 1 possesses a 1D chain structure which is further extended into the 3D supramolecular architecture via hydrogen bonds. Complex 2 features a 2D network with Schla¨fli symbol (53·62·7)(52·64). Complex 3 presents a 3D framework with a point symbol of (4·64·8)(42·62·82). Moreover, their IR spectra, PXRD patterns, thermogravimetric curves, and luminescent emissions were studied at room temperature.

  2. The velocity field under breaking waves: coherent structures and turbulence

    NASA Astrophysics Data System (ADS)

    Melville, W. Kendall; Veron, Fabrice; White, Christopher J.

    2002-03-01

    Digital particle image velocimetry (DPIV) measurements of the velocity field under breaking waves in the laboratory are presented. The region of turbulent fluid directly generated by breaking is too large to be imaged in one video frame and so an ensemble-averaged representation of the flow is built up from a mosaic of image frames. It is found that breaking generates at least one coherent vortex that slowly propagates downstream at a speed consistent with the velocity induced by its image in the free surface. Both the kinetic energy of the flow and the vorticity decay approximately as t[minus sign]1. The Reynolds stress of the turbulence also decays as t[minus sign]1 and is, within the accuracy of the measurements, everywhere negative, consistent with downward transport of streamwise momentum. Estimates of the mometum flux from waves to currents based on the measurements of the Reynolds stress are consistent with earlier estimates. The implications of the measurements for breaking in the field are discussed. Based on geometrical optics and wave action conservation, we suggest that the presence of the breaking-induced vortex provides an explanation for the suppression of short waves by breaking. Finally, in Appendices, estimates of the majority of the terms in the turbulent kinetic energy budget are presented at an early stage in the evolution of the turbulence, and comparisons with independent acoustical measurements of breaking are presented.

  3. Crystal Structure of Human Liver [delta][superscript 4]-3-Ketosteroid 5[beta]-Reductase (AKR1D1) and Implications for Substrate Binding and Catalysis

    SciTech Connect

    Di Costanzo, Luigi; Drury, Jason E.; Penning, Trevor M.; Christianson, David W.

    2008-07-15

    AKR1D1 (steroid 5{beta}-reductase) reduces all {Delta}{sup 4}-3-ketosteroids to form 5{beta}-dihydrosteroids, a first step in the clearance of steroid hormones and an essential step in the synthesis of all bile acids. The reduction of the carbon-carbon double bond in an {alpha}{beta}-unsaturated ketone by 5{beta}-reductase is a unique reaction in steroid enzymology because hydride transfer from NADPH to the {beta}-face of a {Delta}{sup 4}-3-ketosteroid yields a cis-A/B-ring configuration with an {approx}90{sup o} bend in steroid structure. Here, we report the first x-ray crystal structure of a mammalian steroid hormone carbon-carbon double bond reductase, human {Delta}{sup 4}-3-ketosteroid 5{beta}-reductase (AKR1D1), and its complexes with intact substrates. We have determined the structures of AKR1D1 complexes with NADP{sup +} at 1.79- and 1.35-{angstrom} resolution (HEPES bound in the active site), NADP{sup +} and cortisone at 1.90-{angstrom} resolution, NADP{sup +} and progesterone at 2.03-{angstrom} resolution, and NADP{sup +} and testosterone at 1.62-{angstrom} resolution. Complexes with cortisone and progesterone reveal productive substrate binding orientations based on the proximity of each steroid carbon-carbon double bond to the re-face of the nicotinamide ring of NADP{sup +}. This orientation would permit 4-pro-(R)-hydride transfer from NADPH. Each steroid carbonyl accepts hydrogen bonds from catalytic residues Tyr{sup 58} and Glu{sup 120}. The Y58F and E120A mutants are devoid of activity, supporting a role for this dyad in the catalytic mechanism. Intriguingly, testosterone binds nonproductively, thereby rationalizing the substrate inhibition observed with this particular steroid. The locations of disease-linked mutations thought to be responsible for bile acid deficiency are also revealed.

  4. Three Dimensional velocity Structure in the New Madrid and Other SCR Seismic Zones

    NASA Astrophysics Data System (ADS)

    Powell, C. A.

    2002-12-01

    Recent tomographic inversions of travel time data accumulated for active SCR seismic zones have revealed strong velocity contrasts that appear to control the distribution of seismicity. Velocity images have been obtained for the New Madrid seismic zone (NMSZ), the eastern Tennessee seismic zone (ETSZ), and the Charlevoix seismic zone (CSZ). We have also obtained a preliminary velocity model for the aftershock region associated with the Mw=7.7 January 26th Bhuj, India earthquake. Both P and S waves were inverted for velocity structure in the NMSZ. High velocity bodies were imaged and are interpreted to be intrusions associated with the axis and edge of the Reelfoot graben. Low velocities were imaged near the intersection of the long NE arm of seismicity and the NW trending arm; the low velocities are attributed to highly fractured, fluid saturated crust and are associated with shallow earthquake swarms. In general, earthquakes tend to avoid regions with higher than average velocities and concentrate in areas of low velocity or along the edges of high velocity zones. Similar results were obtained for both the ETSZ and the CSZ. A prominent low-velocity zone was detected in the ETSZ; most earthquakes occur in rocks that surround the lowest-velocity regions. An elongated, high velocity region is present at mid-crustal depths in the CSZ; earthquakes avoid the high velocity body and separate into two bands, one on either side of the feature. Larger earthquakes (exceeding magnitude 4) have occurred along the northern edge of the high velocity region. Our results suggest that earthquakes in SCR seismic zones tend to occur in rocks where strain energy is concentrating. This observation is consistent with results from high resolution tomographic images of fault zones in California.

  5. Lithospheric Shear Velocity and Discontinuity Structure of Hudson Bay from S-to-P Receiver Functions and Jointly Inverted P-to-S Receiver Functions and Rayleigh Wave Phase Velocities.

    NASA Astrophysics Data System (ADS)

    Porritt, R. W.; Miller, M. S.; Darbyshire, F. A.

    2014-12-01

    Hudson Bay overlies some of the thickest Precambrian lithosphere on Earth, whose internal structures contain important clues to the earliest workings of plate formation. The Hudson Bay Lithospheric Experiment (HuBLE) has thus far constrained its seismic wavespeed, anisotropy, and discontinuity structures. However, previous work has either focused on a single imaging method or briefly compared two independent methods. In this study, we combine surface wave dispersion curves with P to S receiver functions (PRF) to jointly invert for 1D shear velocity, and also compute independent S to P receiver functions (SRF) using teleseismic earthquakes recorded at 36 broadband seismic stations from the HuBLE experiment and 9 additional regional stations. High shear velocities are observed to depths of 200-300 km in the region, indicating a thick depleted lithospheric keel, with maximum thickness in the center of Hudson Bay. The 1D shear velocity profiles typically exhibit a low-velocity zone in the lower crust, consistent with the hypothesis of post-orogenic or syn-orogenic lower crustal flow or the tectonic burial of metasediments. Observations of a flat Moho in the Rae domain of northwestern Hudson Bay are consistent with an Archean-aged crust, which has remained unaltered since formation. Structures observed within the mantle lithosphere in the depth-stacked S to P receiver functions appear to dip from the Hearne domain towards the Rae domain, suggestive of lithospheric formation through plate tectonic processes. This implies that plate tectonic processes were in action during the Archean when these provinces formed.

  6. Investigation of structural heterogeneity at the SPE site using combined P–wave travel times and Rg phase velocities

    DOE PAGESBeta

    Rowe, Charlotte A.; Patton, Howard J.

    2015-10-01

    Here, we present analyses of the 2D seismic structure beneath Source Physics Experiments (SPE) geophone lines that extended radially at 100 m spacing from 100 to 2000 m from the source borehole. With seismic sources at only one end of the geophone lines, standard refraction profiling methods cannot resolve seismic velocity structures unambiguously. In previous work, we demonstrated overall agreement between body-wave refraction modeling and Rg dispersion curves for the least complex of the five lines. A more detailed inspection supports a 2D reinterpretation of the structure. We obtained Rg phase velocity measurements in both the time and frequency domains,more » then used iterative adjustment of the initial 1D body-wave model to predict Rg dispersion curves to fit the observed values. Our method applied to the most topographically severe of the geophone lines is supplemented with a 2D ray-tracing approach, whose application to P-wave arrivals supports the Rg analysis. In addition, midline sources will allow us to refine our characterization in future work.« less

  7. Upper-crustal velocity structure near Coalinga, as determined from seismic-refraction data

    SciTech Connect

    Walter, A.W.

    1990-01-01

    The May 2 earthquake (M{sub L} = 6.7) was unexpected in that it occurred at the structural transition between the southern Diablo Range and the San Joaquin Valley, part of the 500-km-long Coast Ranges-Great Valley boundary. Since 1981, the US Geological Survey (USGS) has been acquiring both seismic reflection and refraction data along profiles that cross this boundary. The occurrence of the May 2 earthquake provided motivation to acquire additional seismic reflection and refraction data in the hypocentral region with the goal of understanding the structural relations responsible for the unexpected seismicity. This understanding is needed to assess the probability of large earthquakes occurring elsewhere along the Coast Ranges-Great Valley boundary. Sections of this paper describe the following: geologic setting; seismic-refraction experiment, including the east-west profile, northwest-southeast profile, quality of seismic data, velocity modeling, east-west velocity model, and northwest-southeast velocity model; comparison of the velocity models at their point of intersection; comparison between the Coalinga velocity models and the velocity model derived for profile SJ-6; comparison between the refraction velocity structure and nearby seismic-reflection profiles; relation between Coalinga seismicity and the velocity structure; and a summary of modeling results.

  8. Three-dimensional P and S wave velocity structure of Redoubt Volcano, Alaska

    USGS Publications Warehouse

    Benz, H.M.; Chouet, B.A.; Dawson, P.B.; Lahr, J.C.; Page, R.A.; Hole, J.A.

    1996-01-01

    The three-dimensional P and S wave structure of Redoubt Volcano, Alaska, and the underlying crust to depths of 7-8 km is determined from 6219 P wave and 4008 S wave first-arrival times recorded by a 30-station seismograph network deployed on and around the volcano. First-arrival times are calculated using a finite-difference technique, which allows for flexible parameterization of the slowness model and easy inclusion of topography and source-receiver geometry. The three-dimensional P wave velocity structure and hypocenters are determined simultaneously, while the three-dimensional S wave velocity model is determined using the relocated seismicity and an initial S wave velocity model derived from the P wave velocity model assuming an average Vp/Vs ratio of 1.78. Convergence is steady with approximately 73% and 52% reduction in P and S wave arrival time RMS, respectively, after 10 iterations. The most prominent feature observed in the three-dimensional velocity models derived for both P and S waves is a relative low-velocity, near-vertical, pipelike structure approximately 1 km in diameter that extends from 1 to 6 km beneath sea level. This feature aligns axially with the bulk of seismicity and is interpreted as a highly fractured and altered zone encompassing a magma conduit. The velocity structure beneath the north flank of the volcano between depths of 1 and 6 km is characterized by large lateral velocity variations. High velocities within this region are interpreted as remnant dikes and sills and low velocities as regions along which magma migrates. No large low-velocity body suggestive of a magma chamber is resolved in the the upper 7-8 km of the crust.

  9. Determination of Bedrock Variations and S-wave Velocity Structure in the NW part of Turkey for Earthquake Hazard Mitigation

    NASA Astrophysics Data System (ADS)

    Ozel, A. O.; Arslan, M. S.; Aksahin, B. B.; Genc, T.; Isseven, T.; Tuncer, M. K.

    2015-12-01

    Tekirdag region (NW Turkey) is quite close to the North Anatolian Fault which is capable of producing a large earthquake. Therefore, earthquake hazard mitigation studies are important for the urban areas close to the major faults. From this point of view, integration of different geophysical methods has important role for the study of seismic hazard problems including seismotectonic zoning. On the other hand, geological mapping and determining the subsurface structure, which is a key to assist management of new developed areas, conversion of current urban areas or assessment of urban geological hazards can be performed by integrated geophysical methods. This study has been performed in the frame of a national project, which is a complimentary project of the cooperative project between Turkey and Japan (JICA&JST), named as "Earthquake and Tsunami Disaster Mitigation in the Marmara Region and Disaster Education". With this principal aim, this study is focused on Tekirdag and its surrounding region (NW of Turkey) where some uncertainties in subsurface knowledge (maps of bedrock depth, thickness of quaternary sediments, basin geometry and seismic velocity structure,) need to be resolved. Several geophysical methods (microgravity, magnetic and single station and array microtremor measurements) are applied and the results are evaluated to characterize lithological changes in the region. Array microtremor measurements with several radiuses are taken in 30 locations and 1D-velocity structures of S-waves are determined by the inversion of phase velocities of surface waves, and the results of 1D structures are verified by theoretical Rayleigh wave modelling. Following the array measurements, single-station microtremor measurements are implemented at 75 locations to determine the predominant frequency distribution. The predominant frequencies in the region range from 0.5 Hz to 8 Hz in study area. On the other hand, microgravity and magnetic measurements are performed on

  10. 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.

  11. Mononuclear, dinuclear and 1-D polymeric complexes of Cd(II) of a pyridyl pyrazole ligand: Syntheses, crystal structures and photoluminescence studies

    NASA Astrophysics Data System (ADS)

    Das, Kinsuk; Konar, Saugata; Jana, Atanu; Barik, Anil Kumar; Roy, Sangita; Kar, Susanta Kumar

    2013-03-01

    The syntheses, crystal structures and photoluminescence properties of four new Cd(II) complexes are reported using strongly coordinating ligand 3,5-dimethyl-1-(2'-pyridyl) pyrazole (L) in presence of anionic ancillary bridging ligands as nitrite, chloride and dicyanamide. Among the complexes two (1 and 2) are monomeric, 3 is μ2 - chloro bridged dimer and the last one (4) is a mixed alternate chloro - end to end (EE) dicyanamide bridged 1D polymer. All the four complexes have been X-ray crystallographically characterized. The ligand L behaves as a potent bidentate neutral N, N donor. Geometrical diversity of Cd(II) complexes is due to no loss or gain of crystal field stability with the variation of geometry. Consequently the stability of a structure depends on steric requirements. The ligand L shows considerable fluorescence and all four complexes in methanol exhibit interesting photoluminescence properties with different emission intensities. The band maxima and fluorescence efficiency (in methanol) are found to be dependent on the coordination chromophore and structural rigidity induced by the incorporated Cd(II) ion. Among the synthesized complexes 1 exhibits the highest fluorescence intensity in methanol.

  12. 3-D seismic velocity and attenuation structures in the geothermal field

    SciTech Connect

    Nugraha, Andri Dian; Syahputra, Ahmad; Fatkhan,; Sule, Rachmat

    2013-09-09

    We conducted delay time tomography to determine 3-D seismic velocity structures (Vp, Vs, and Vp/Vs ratio) using micro-seismic events in the geothermal field. The P-and S-wave arrival times of these micro-seismic events have been used as input for the tomographic inversion. Our preliminary seismic velocity results show that the subsurface condition of geothermal field can be fairly delineated the characteristic of reservoir. We then extended our understanding of the subsurface physical properties through determining of attenuation structures (Qp, Qs, and Qs/Qp ratio) using micro-seismic waveform. We combined seismic velocities and attenuation structures to get much better interpretation of the reservoir characteristic. Our preliminary attanuation structures results show reservoir characterization can be more clearly by using the 3-D attenuation model of Qp, Qs, and Qs/Qp ratio combined with 3-D seismic velocity model of Vp, Vs, and Vp/Vs ratio.

  13. Estimation of shallow S-wave velocity structure and site response characteristics by microtremor array measurements in Tekirdag region, NW Turkey

    NASA Astrophysics Data System (ADS)

    Karagoz, Ozlem; Chimoto, Kosuke; Citak, Seckin; Ozel, Oguz; Yamanaka, Hiroaki; Hatayama, Ken

    2015-11-01

    In this study, we aimed to explore the S-wave velocity structure of shallow soils using microtremors in order to estimate site responses in Tekirdag and surrounding areas (NW Turkey). We collected microtremor array data at 44 sites in Tekirdag, Marmara Ereglisi, Corlu, and Muratlı. The phase velocities of Rayleigh waves were estimated from the microtremor data using a Spatial Autocorrelation method. Then, we applied a hybrid genetic simulated annealing algorithm to obtain a 1D S-wave velocity structure at each site. Comparison between the horizontal-to-vertical ratio of microtremors and computed ellipticities of the fundamental mode Rayleigh waves showed good agreement with validation models. The depth of the engineering bedrock changed from 20 to 50 m in the Tekirdag city center and along the coastline with a velocity range of 700-930 m/s, and it ranged between 10 and 65 m in Marmara Ereglisi. The average S-wave velocity of the engineering bedrock was 780 m/s in the region. We obtained average S-wave velocities in the upper 30 m to compare site amplifications. Empirical relationships between the AVs30, the site amplifications, and also average topographic slopes were established for use in future site effects microzonation studies in the region.

  14. Structure of the Crust beneath Cameroon, West Africa, from the Joint Inversion of Rayleigh Wave Group Velocities and Receiver Functions

    SciTech Connect

    Tokam, A K; Tabod, C T; Nyblade, A A; Julia, J; Wiens, D A; Pasyanos, M E

    2010-02-18

    Cameroon using 1-D shear wave velocity models obtained from the joint inversion of Rayleigh wave group velocities and P-receiver functions for 32 broadband seismic stations. From the 1-D shear wave velocity 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.

  15. Knot structures in jets formed by a two-mode ejection velocity time-variability

    NASA Astrophysics Data System (ADS)

    Raga, A. C.; Rodríguez-Ramírez, J. C.; Cantó, J.; Velázquez, P. F.

    2015-11-01

    We present a 1D analytic model for the formation of working surfaces along a jet produced by an outflow source with a double-sinusoidal mode ejection velocity variability. We succeed in obtaining simple expressions for the distance of formation and for the initial velocity jump across the `fast-mode' working surfaces, which are modulated by the phase of the `slow mode'. These results can be straightforwardly applied to interpret observations of Herbig-Haro jets showing a chain of aligned knots close to the source, and large `heads' at greater distances, for which a two-mode ejection variability is likely to be applicable. We use our new analytic model to interpret observations of the externally photoionized HH 333 jet.

  16. Numerical study on the velocity structure around tidal fronts in the Yellow Sea

    NASA Astrophysics Data System (ADS)

    Liu, Guimei; Wang, Hui; Sun, Song; Han, Boping

    2003-05-01

    The velocity components across tidal fronts are examined using the Blumberg and Mellor 3-D nonlinear numerical coastal circulation model incorporated with the Mellor and Yamada level 2.5 turbulent closure model based on the reasonable model output of the M2 tide and density residual currents. In the numerical experiments, upwelling motion appears around all the fronts with different velocity structures, accounting for surface cold water around the fronts. The experiments also suggest that the location and formation of fronts are closely related to topography and tidal mixing, as is the velocity structure around the front.

  17. Velocity Structure and Plasma Properties in Halo CMEs

    NASA Technical Reports Server (NTRS)

    Wagner, William (Technical Monitor); Raymond, John C.

    2003-01-01

    We have identified a set of 23 Halo CMEs through July 2002 and 21 Partial Halo CMEs from the LASCO Halo CME Mail Archive for which Ultraviolet Coronagraph Spectrometer (UVCS) spectra exist. For each event we have collected basic information such as the event speed, whether or not UVCS caught the bright front, lines detected, Doppler shift and associated flare class. We have also obtained excellent observations of some of the spectacular events in November 2003, and we have made theoretical calculations pertaining to CME expansion at the heights observed by UVCS. We first analyzed the halo CMEs on 21 April and 24 August 2002 and the partial halo on 23 July 2002, because the X-class flares associated with these CMEs were extensively observed by RHESSI and other instruments as part of the MAX MILLENIUM campaign. These very fast CMEs showed extremely violent disruption of the pre-CME streamers, little or no cool prominence material, and the unusual (for UVCS heights) hot emission line [Fe XVIII]. Results, including a discussion of the current sheet interpretation for the [Fe XVIII] emission, are published in Raymond et al. and presented at the Fall 2002 AGU meeting and the solar physics summer school in L'Aquila, Italy. We are currently preparing two papers on the Dec. 28, 2000 partial halo event. This event was chosen to take advantage of the SEP event measured by WIND and ACE, and because a Type II radio burst coincides with the time that broad, blue-shifted O VI emission appeared in the UVCS spectra. One paper deals with a new density and velocity diagnostic for very fast CMEs; pumping of O VI lambda 1032 by Ly beta and pumping of O VI lambda 1038 by O VI lambda 1032. The other discusses physics of the shock wave and association with the SEP event. In the coming year we plan to expand the list of Halo and Partial Halo events observed by UVCS through the end of 2003. We will look at those events as a class to search for correlation between UV spectral characteristics

  18. Amplitude Anomalies of S Waves Caused by Low Shear Velocity Structures at the Base of the Mantle

    NASA Astrophysics Data System (ADS)

    To, A.; Capdeville, Y.; Romanowicz, B. A.

    2015-12-01

    Previous studies have shown that the direct S and Sdiff waveforms of earthquakes in Papua New Guinea region recorded by seismographs in Northern America are distorted due to sampling slow shear velocity anomalies at the base of the mantle. The emergence of postcursours to the S/Sdiff waves and the travel time anomalies have been reasonably explained by placing a ultra low velocity zone (ULVZ) in southwest of Hawaii. In this study, we focused on the amplitude anomalies of the S/Sdiff waveforms. The direct S phase show very low amplitude at stations in Southern California, at the distance and azimuth around 90 and 55 degrees from the earthquake. The amplitude is as low as 10% of the synthetic amplitude of a standard 1D model, especially at higher frequency range above 0.025 Hz. We first checked and confirmed that the anomalies are not due to errors in the focal mechanism, which is used to calculate the reference synthetic waveforms. Also we checked that the amplitude anomalies are unlikely to be caused by the structures near the earthquake or near the stations, by looking at the amplitude of the depth phases or waveforms of other earthquakes. We assumed that the anomalies are produced by the focusing and defocusing effect of sampling 3D heterogeneous at the base of the mantle, and searched for the causal structures. Full 3D synthetic waveforms are calculated down to 8 seconds for tens of structural models with slow anomalies of different size and velocity reduction placed on the core-mantle boundary (CMB). The result shows that existing tomographic models do not fully explain the observed amplitude anomalies. Stronger shear velocity anomalies are required. The previously proposed thin large ULVZ placed on the CMB southwest of Hawaii partly explains the observed amplitude reduction, even at the distance as short as 90 degrees from the earthquake. This result indicates the significance of finite frequency effect of the ULVZ structure to the S waves, since the ray

  19. Structural variation from 1D to 3D: effects of ligands and solvents on the construction of lead(II)-organic coordination polymers.

    PubMed

    Yang, Jin; Li, Guo-Dong; Cao, Jun-Jun; Yue, Qi; Li, Guang-Hua; Chen, Jie-Sheng

    2007-01-01

    A series of Pb(II) coordination polymers [Pb(ndc)(dpp)] (1), [Pb(ndc)(ptcp)].0.5 H2O (2), [Pb(ndc)(dppz)] (3), [Pb(ndc)(tcpn)(2)] (4), [Pb2(ndc)2(tcpp)] (5), [Pb(Hndc)2].H2O (6), [Pb(ndc)(dma)] (7), [Pb(bdc)(dma)] (8), [Pb(trans-chdc)(H2O)] (9), and [Pb2(cis-chdc)2].NH(CH3)2 (10), where ndc=1,4-naphthalenedicarboxylate, dpp=4,7-diphenyl-1,10-phenanthroline, ptcp=2-phenyl-1H-1,3,7,8-tetraazacyclopenta[l]phenanthrene, dppz=dipyrido[3,2-a:2',3'-c]phenazine, tcpn=2-(1H-1,3,7,8-tetraazacyclopenta[l]phenanthren-2-yl)naphthol, tcpp=4-(1H-1,3,7,8-tetraazacyclopenta[l]phenanthren-2-yl)phenol, dma=N,N-dimethylacetamide, bdc=1,4-benzenedicarboxylate, and chdc=1,4-cyclohexanedicarboxylate, have been synthesized from a hydrothermal or solvothermal reaction system by varying the ligands or the solvents. Compounds 1-5 crystallize with an N-donor chelating ligand and an aromatic dicarboxylate linker. Compounds 1-4 are 1D polymers with different pi-pi stacking interactions, whereas compound 5 consists of 2D layers. The structures of compounds 7, 8, and 10 are 3D frameworks formed by connection of the Pb(II) centers by organic acid ligands. Compound 7 is chiral although the ndc ligand is achiral, while the framework of 8 is a typical 3D (3,4)-connected net. Compound 10 is the first example of Pb(II) wheel cluster [Pb(8)O(8)] units bridged by carboxylate groups. Compound 6 contains 1D chains which are further extended to a 3D structure by pi-pi interactions. Compound 9 consists of a 2D network constructed by Pb(II) centers and trans-chdc ligands. The structural differences between 7 and 8 and between 9 and 10 indicate the importance of solvents for framework formation of the coordination polymers. By varying the solvent the cis and trans conformations of H(2)chdc in 9 and 10 were separated completely. The photoluminescence and nonlinear optical properties of the coordination polymers have also been investigated. PMID:17212363

  20. Density, Velocity and Ionization Structure in Accretion-Disc Winds

    NASA Technical Reports Server (NTRS)

    Sonneborn, George (Technical Monitor); Long, Knox

    2004-01-01

    This was a project to exploit the unique capabilities of FUSE to monitor variations in the wind- formed spectral lines of the luminous, low-inclination, cataclysmic variables(CV) -- RW Sex. (The original proposal contained two additional objects but these were not approved.) These observations were intended to allow us to determine the relative roles of density and ionization state changes in the outflow and to search for spectroscopic signatures of stochastic small-scale structure and shocked gas. By monitoring the temporal behavior of blue-ward extended absorption lines with a wide range of ionization potentials and excitation energies, we proposed to track the changing physical conditions in the outflow. We planned to use a new Monte Carlo code to calculate the ionization structure of and radiative transfer through the CV wind. The analysis therefore was intended to establish the wind geometry, kinematics and ionization state, both in a time-averaged sense and as a function of time.

  1. Line-of-sight velocity as a tracer of coronal cavity magnetic structure

    NASA Astrophysics Data System (ADS)

    Bak-Steslicka, Urszula; Gibson, Sarah; Chmielewska, Ewa

    2016-03-01

    We present a statistical analysis of 66 days of observations of quiescent (non-erupting) coronal cavities and associated velocity and thermal structures. We find that nested rings of LOS-oriented velocity are common in occurrence and spatially well correlated with cavities observed in emission. We find that the majority of cavities possess multiple rings, and a range in velocity on the order of several km/sec. We find that the tops of prominences lie systematically below the cavity center and location of largest Doppler velocity. Finally, we use DEM analysis to consider the temperature structure of two cavities in relation to cavity, prominence, and flows. These observations yield new constraints on the magnetic structure of cavities, and on the conditions leading up to solar eruptions.

  2. Using seismically constrained magnetotelluric inversion to recover velocity structure in the shallow lithosphere

    NASA Astrophysics Data System (ADS)

    Moorkamp, M.; Fishwick, S.; Jones, A. G.

    2015-12-01

    Typical surface wave tomography can recover well the velocity structure of the upper mantle in the depth range between 70-200km. For a successful inversion, we have to constrain the crustal structure and assess the impact on the resulting models. In addition,we often observe potentially interesting features in the uppermost lithosphere which are poorly resolved and thus their interpretationhas to be approached with great care.We are currently developing a seismically constrained magnetotelluric (MT) inversion approach with the aim of better recovering the lithospheric properties (and thus seismic velocities) in these problematic areas. We perform a 3D MT inversion constrained by a fixed seismic velocity model from surface wave tomography. In order to avoid strong bias, we only utilize information on structural boundaries to combine these two methods. Within the region that is well resolved by both methods, we can then extract a velocity-conductivity relationship. By translating the conductivitiesretrieved from MT into velocities in areas where the velocity model is poorly resolved, we can generate an updated velocity model and test what impactthe updated velocities have on the predicted data.We test this new approach using a MT dataset acquired in central Botswana over the Okwa terrane and the adjacent Kaapvaal and Zimbabwe Cratons togetherwith a tomographic models for the region. Here, both datasets have previously been used to constrain lithospheric structure and show some similarities.We carefully asses the validity of our results by comparing with observations and petrophysical predictions for the conductivity-velocity relationship.

  3. Upper mantle structure of central and West Antarctica from array analysis of Rayleigh wave phase velocities

    NASA Astrophysics Data System (ADS)

    Heeszel, David S.; Wiens, Douglas A.; Anandakrishnan, Sridhar; Aster, Richard C.; Dalziel, Ian W. D.; Huerta, Audrey D.; Nyblade, Andrew A.; Wilson, Terry J.; Winberry, J. Paul

    2016-03-01

    The seismic velocity structure of Antarctica is important, both as a constraint on the tectonic history of the continent and for understanding solid Earth interactions with the ice sheet. We use Rayleigh wave array analysis methods applied to teleseismic data from recent temporary broadband seismograph deployments to image the upper mantle structure of central and West Antarctica. Phase velocity maps are determined using a two-plane wave tomography method and are inverted for shear velocity using a Monte Carlo approach to estimate three-dimensional velocity structure. Results illuminate the structural dichotomy between the East Antarctic Craton and West Antarctica, with West Antarctica showing thinner crust and slower upper mantle velocity. West Antarctica is characterized by a 70-100 km thick lithosphere, underlain by a low-velocity zone to depths of at least 200 km. The slowest anomalies are beneath Ross Island and the Marie Byrd Land dome and are interpreted as upper mantle thermal anomalies possibly due to mantle plumes. The central Transantarctic Mountains are marked by an uppermost mantle slow-velocity anomaly, suggesting that the topography is thermally supported. The presence of thin, higher-velocity lithosphere to depths of about 70 km beneath the West Antarctic Rift System limits estimates of the regionally averaged heat flow to less than 90 mW/m2. The Ellsworth-Whitmore block is underlain by mantle with velocities that are intermediate between those of the West Antarctic Rift System and the East Antarctic Craton. We interpret this province as Precambrian continental lithosphere that has been altered by Phanerozoic tectonic and magmatic activity.

  4. Mantle shear-wave velocity structure beneath the Hawaiian hot spot.

    PubMed

    Wolfe, Cecily J; Solomon, Sean C; Laske, Gabi; Collins, John A; Detrick, Robert S; Orcutt, John A; Bercovici, David; Hauri, Erik H

    2009-12-01

    Defining the mantle structure that lies beneath hot spots is important for revealing their depth of origin. Three-dimensional images of shear-wave velocity beneath the Hawaiian Islands, obtained from a network of sea-floor and land seismometers, show an upper-mantle low-velocity anomaly that is elongated in the direction of the island chain and surrounded by a parabola-shaped high-velocity anomaly. Low velocities continue downward to the mantle transition zone between 410 and 660 kilometers depth, a result that is in agreement with prior observations of transition-zone thinning. The inclusion of SKS observations extends the resolution downward to a depth of 1500 kilometers and reveals a several-hundred-kilometer-wide region of low velocities beneath and southeast of Hawaii. These images suggest that the Hawaiian hot spot is the result of an upwelling high-temperature plume from the lower mantle. PMID:19965755

  5. Three dimensional P-wave velocity structure at Popocatépetl Volcano, Mexico

    NASA Astrophysics Data System (ADS)

    Berger, P.; Valdes-Gonzales, C. M.

    2009-12-01

    Popocatépetl Volcano is an active andesitic stratovolcano (5460m) of the Trans Mexican Volcanic Belt that has been erupting since December 1994. We used three-dimensional seismic tomography to detect variations in the P-wave velocity structure during three different volcanic cycles, which are separated by the two largest eruptions that occurred at Popocatépetl on June 30th, 1997 and January 22nd, 2001. The start of the first dataset is defined by the eruption in June 1996; the last dataset ends with the eruption in September 2003. The P-wave velocity structure of the volcano has been determined to 10 km depth below the summit using nearly 4000 P-arrival times from about 900 volcano tectonic events recorded on a local 10-station network. The Root Mean Square (RMS) of the arrival time residuals was reduced by 22% - 30% from the initial RMS of about 0.30 s, after running seven iterations of our tomography code. In the three eruption cycles, we observe velocity structures which complement the results of former studies, as well as image previously unrecognized velocity anomalies. We observe velocity changes of ~1km/s in certain areas before and after large eruptions. We compare the tomographic results with geologic, geophysical and geochemical investigations and interpret low velocity zones as fractured rock (SE-zone) or as thermally disturbed zones including hot rock and melt (below the crater region and north flank), from which unexpected future eruptions or flank collapses may occur. High velocity zones are interpreted as roofs of magma reservoirs, old dike systems or relicts of the ancient volcano. The observed changes in velocity anomalies before and after large eruptions, determined by four-dimensional tomography, indicate a change in the internal volcanic fluid-filled structures during volcanic eruptions and show the need for time-resolved geophysical techniques when investigating volcanic structures.

  6. Forest-atmosphere BVOC exchange in diverse and structurally complex canopies: 1-D modeling of a mid-successional forest in northern Michigan

    NASA Astrophysics Data System (ADS)

    Bryan, Alexander M.; Cheng, Susan J.; Ashworth, Kirsti; Guenther, Alex B.; Hardiman, Brady S.; Bohrer, Gil; Steiner, Allison L.

    2015-11-01

    Foliar emissions of biogenic volatile organic compounds (BVOC)-important precursors of tropospheric ozone and secondary organic aerosols-vary widely by vegetation type. Modeling studies to date typically represent the canopy as a single dominant tree type or a blend of tree types, yet many forests are diverse with trees of varying height. To assess the sensitivity of biogenic emissions to tree height variation, we compare two 1-D canopy model simulations in which BVOC emission potentials are homogeneous or heterogeneous with canopy depth. The heterogeneous canopy emulates the mid-successional forest at the University of Michigan Biological Station (UMBS). In this case, high-isoprene-emitting foliage (e.g., aspen and oak) is constrained to the upper canopy, where higher sunlight availability increases the light-dependent isoprene emission, leading to 34% more isoprene and its oxidation products as compared to the homogeneous simulation. Isoprene declines from aspen mortality are 10% larger when heterogeneity is considered. Overall, our results highlight the importance of adequately representing complexities of forest canopy structure when simulating light-dependent BVOC emissions and chemistry.

  7. Forest-atmosphere BVOC exchange in diverse and structurally complex canopies: 1-D modeling of a mid-successional forest in northern Michigan

    SciTech Connect

    Bryan, Alexander M.; Cheng, Susan J.; Ashworth, Kirsti; Guenther, Alex B.; Hardiman, Brady; Bohrer, Gil; Steiner, A. L.

    2015-11-01

    Foliar emissions of biogenic volatile organic compounds (BVOC)dimportant precursors of tropospheric ozone and secondary organic aerosolsdvary widely by vegetation type. Modeling studies to date typi-cally represent the canopy as a single dominant tree type or a blend of tree types, yet many forests are diverse with trees of varying height. To assess the sensitivity of biogenic emissions to tree height vari-ation, we compare two 1-D canopy model simulations in which BVOC emission potentials are homo-geneous or heterogeneous with canopy depth. The heterogeneous canopy emulates the mid-successional forest at the University of Michigan Biological Station (UMBS). In this case, high-isoprene-emitting fo-liage (e.g., aspen and oak) is constrained to the upper canopy, where higher sunlight availability increases the light-dependent isoprene emission, leading to 34% more isoprene and its oxidation products as compared to the homogeneous simulation. Isoprene declines from aspen mortality are 10% larger when heterogeneity is considered. Overall, our results highlight the importance of adequately representing complexities of forest canopy structure when simulating light-dependent BVOC emissions and chemistry.

  8. Pore-scale intermittent velocity structure underpinning anomalous transport through 3-D porous media

    NASA Astrophysics Data System (ADS)

    Kang, Peter K.; Anna, Pietro; Nunes, Joao P.; Bijeljic, Branko; Blunt, Martin J.; Juanes, Ruben

    2014-09-01

    We study the nature of non-Fickian particle transport in 3-D porous media by simulating fluid flow in the intricate pore space of real rock. We solve the full Navier-Stokes equations at the same resolution as the 3-D micro-CT (computed tomography) image of the rock sample and simulate particle transport along the streamlines of the velocity field. We find that transport at the pore scale is markedly anomalous: longitudinal spreading is superdiffusive, while transverse spreading is subdiffusive. We demonstrate that this anomalous behavior originates from the intermittent structure of the velocity field at the pore scale, which in turn emanates from the interplay between velocity heterogeneity and velocity correlation. Finally, we propose a continuous time random walk model that honors this intermittent structure at the pore scale and captures the anomalous 3-D transport behavior at the macroscale.

  9. Density and velocity fine structure enhancement in oceanic eddies

    NASA Astrophysics Data System (ADS)

    Miller, Jerry L.; Evans, David L.

    1985-05-01

    Advection-diffusion models of the oceanic thermocline require a global ocean, mean vertical eddy diffusivity of about 1 cm2 s-1; however, maximum values estimated from microstructure measurements at mid-gyre locations are generally smaller and, occasionally, 1-2 orders of magnitude less, depending on the particular assumptions made by individual analysts. Mesoscale features are high kinetic energy sources, which may fuel vertical mixing mechanisms on fine structure scales, resulting in local enhancements of eddy diffusivity above the canonical value of 1 cm2 s-1. The effects of one such mechanism, the Kelvin-Helmholtz instability, are assessed for a Gulf Stream ring and a mid-thermocline eddy. The necessary Richardson numbers are computed from Yvette profiles obtained in these features and are accurate to within about 10% for Ri = 1, and more accurate at the critical value Ri = 0.25. A plausible extension of the Miles-Howard theorem for a nonparallel shear flow is formulated for a two-dimensional perturbation. The shear appropriate for this Richardson number calculation is well approximated by the total shear for slowly depth-varying direction, as is the case for the vast majority of the data. Upper and lower bounds on the vertical scale for the Richardson number calculation are set by the shear spectra and the Ozmidov scale. Median Richardson number was lower toward the center of the eddy because of a large decrease in Brunt-Vaisala frequency (N2) and was depressed on the fringes by high shear. Lower median Ri is also found at the center of the ring as a result of low N2. Lower bounds on vertical eddy diffusivity are estimated based on the assumptions of a simple, mixing-length model and of complete mixing of each region where Ri is less than 0.25. The spatial distribution of this quantity within the eddy and the ring mirrors that of median Ri. Values range from Az ˜ 1.1 cm2 s-1 near the center of the eddy and 0.90 cm2 s-1 near the center of the ring to zero in

  10. Impact velocity vs target hardness relationships for equivalent response of cask structures

    SciTech Connect

    Chen, T.F.; Chen, J.C.; Witte, M.C.; Fischer, L.E.

    1993-06-01

    In this paper, impact velocity vs. target hardness relationships for cask structures are reviewed. The relationships are based on equivalent cask responses in terms of equal deceleration or similar cask damages. By examining several past cask or container tests as well as some analytical results, some conclusions can be drawn about the relationship between target hardness and equivalent impact velocities. This relationship clearly shows that the cask response to impact is cask-dependent and that the rigid sphere impact model results in an unconservative estimate of equivalent velocity.

  11. CELFE/NASTRAN Code for the Analysis of Structures Subjected to High Velocity Impact

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.

    1978-01-01

    CELFE (Coupled Eulerian Lagrangian Finite Element)/NASTRAN Code three-dimensional finite element code has the capability for analyzing of structures subjected to high velocity impact. The local response is predicted by CELFE and, for large problems, the far-field impact response is predicted by NASTRAN. The coupling of the CELFE code with NASTRAN (CELFE/NASTRAN code) and the application of the code to selected three-dimensional high velocity impact problems are described.

  12. A Initio Mr-Rci Calculations of ((n - 1)D + Ns)(n) Atomic Bound States: Application to Hyperfine Structure and Electron Affinity Studies.

    NASA Astrophysics Data System (ADS)

    Datta, Debasis

    Systematic inclusion of many-body effects in open d and f subshell atoms has long been known as a formidable challenge in atomic structure theory. Due to the presence of competing relativistic effects in such systems, an appropriate theoretical approach needs to incorporate electron correlation within the framework of the Special Theory of Relativity. To this aim, the Relativistic Configuration Interaction methodology as developed by Beck and others has been extended and applied to multi-reference situations in ((n - 1)d + ns) ^{rm N} type valence configurations. Specific focus has been on the hyperfine structure and electron affinity studies of the transition metal ions and the rare earths respectively. Energies and magnetic dipole and electric quadrupole hyperfine structure constants of all the fifteen Zr II (4d + 5s)^3 J = 0.5, 1.5 levels and the twenty one Nb II (4d + 5s)^4 J = 2 levels have been determined with unprecedented accuracies. The average errors in energy are 0.087 eV and 0.050 eV for Zr II J = 3/2 & 1/2 respectively while that for the ten bottom levels of Nb II J = 2 is 0.055 eV. For the levels known experimentally, the corresponding errors in magnetic dipole hyperfine structure constants are 9.2%, 31.8% and 3.8%. Quite a few of the many-body hyperfine constant values exhibit striking improvements over the Multi-Configurational Dirac Fock values. A new value of nuclear quadrupole moment has also been predicted for Zr II. In all cases certain previous level assignments have been corrected and five previously unknown levels have been identified in Nb II. The rigorous systematics of the many-body effects important for the energy level and hyperfine structure of these systems has been presented including core-valence and core-core effects. Contrary to the conventional wisdom and theoretical predictions of the last decade, the attachment of an f electron has been discarded as the most likely mechanism for the formation of Lanthanide and Actinide negative

  13. PKP Waveform Complexity and Its Implications to Fine Structure Near the Edge of African Large Low Shear Velocity Province

    NASA Astrophysics Data System (ADS)

    Song, Teh-Ru Alex; Tanaka, Satoru; Takeuchi, Nozomu

    2010-05-01

    and receiver-side structure do not play a predominant role in generating these anomalous PKPab waveforms. We then look into structural anomaly near the core-mantle-boundary (CMB) since PKPab grazes the CMB at a very shallow angle and it can effectively interact with it and possibly produce anomalous PKPab waveforms. We first explore 1-D model space by introducing velocity anomaly directly above the CMB, with a velocity perturbation up to a few tens of percents in S wave velocity and P wave velocity. We calculate synthetics up to 2 Hz by Direct Solution Method (DSM) and Reflectivity Method to examine waveform anomaly at long period band (0.01-0.2 Hz) as well as short-period band (0.5-2 Hz). Our preliminary result indicates that the model with a thin (~ 15 km) ultra-low velocity zone (ULVZ, 30% reduction in P wave and S wave velocity) is capable of reproducing characteristics of these anomalous PKPab waveforms at both frequency bands. The pierce points of PKPab in the source side at CMB are near the southeast Indian Ocean where S wave velocity is only slightly faster than PREM. On the other hand, the pierce points in the receiver side are at the eastern edge of the African Large Low Shear Velocity Province (LLSVP). One interesting feature of our ULVZ model is that dlnVs/dlnVp is about 1, which is different from most ULVZ models where dlnVs/dlnVp is about 3.

  14. Synthesis, crystal structures and magnetic properties of mer-cyanideiron(III)-based 1D heterobimetallic cyanide-bridged chiral coordination polymers.

    PubMed

    Zhang, Daopeng; Zhuo, Shuping; Zhang, Hongyan; Wang, Ping; Jiang, Jianzhuang

    2015-03-14

    Two pairs of cyanide-bridged Fe(III)–Mn(III)/Cu(II) chiral enantiomer coordination polymers {[Mn(S,S/R,R-Salcy)(CH3OH)2]{[Mn(S,S/R,R-Salcy)][Fe(bbp)(CN)3]}}2n (1,2) (bbp = bis(2-benzimidazolyl)pyridine dianion) and {[Cu(S,S/R,R-Chxn)2]2[Fe2(tbbp)(CN)6]}n (3,4) (tbbp = tetra(3-benzimidazolyl)-4,4′-bipyridine tetraanion) have been successfully prepared by employing mer-tricyanometallate [PPh4]2[Fe(bbp)(CN)3] or the newly bimetallic mer-cyanideiron(III) precursor K4[Fe2(tbbp)(CN)6] as building blocks and with chiral manganese(III)/copper(II) compounds as assemble segments. The four complexes have been characterized by elemental analysis, IR spectroscopy, circular dichroism (CD) and magnetic circular dichroism (MCD) spectra. Single X-ray diffraction reveals that complexes 1 and 2 possess a single anionic chain structure consisting of the asymmetric chiral {[Mn(S,S/R,R-Salcy)][Fe(bbp)(CN)3]}2(2−) unit with free [Mn(S,S/R,R-Salcy)](+) as balanced cations. The cyanide-bridged Fe(III)–Cu(II) complexes 3 and 4 can be structurally characterized as neutral ladder-like double chains composed of the alternating cyanide-bridged Fe–Cu units. Our investigation of magnetic susceptibilities reveals the antiferromagnetic coupling between the cyanide-bridged Fe(III) and Mn(III)/Cu(II) ions for complexes 1–4. These results have been further confirmed by theoretical simulation through numerical matrix diagonalization techniques using a Fortran program or a uniform chain model, leading to the coupling constants J = −7.36 cm(−1), D = −1.52 cm(−1) (1) and J = −4.35 cm(−1) (3), respectively. PMID:25661782

  15. Attenuation and Velocity Structure in Spain and Morocco: Distinguishing Between Water, Temperature, and Partial Melt

    NASA Astrophysics Data System (ADS)

    Bezada, M. J.; Humphreys, E.

    2014-12-01

    Temperature, melt fraction, and water content affect seismic velocity and attenuation differently. Both are sensitive to temperature, but velocity is more sensitive to melt fraction and attenuation is thought to be more sensitive to water content. For these reasons, combining attenuation measurements with tomographic imaging of velocity structure can help untangle these fields and better resolve lithospheric structure and physical state. We map variations in attenuation beneath Spain and northern Morocco using teleseismic data generated by more than a dozen teleseismic deep-focus earthquakes recorded on a dense array of stations. For each event, we first estimate the source from the best quality recordings. We then apply an attenuation operator to the source estimate, using a range of t* values, to match the record at each station. We invert for a smooth map of t* from the ensemble of measurements. The spatial patterns in t* correlate very well with the tectonic domains in Spain and Morocco. In particular, areas in Spain that resisted deformation during the Variscan and Alpine orogenies produce very little attenuation. Comparing the attenuation map with seismic velocity structure we find that, in Morocco, some areas with strong low-velocity anomalies and recent volcanism do not cause high attenuation. These observations suggest that water content is a more likely cause for seismic attenuation in the study area than temperature, and that the non-attenuative low-velocity anomalies in Morocco are produced by partial mel.

  16. 3-D P Wave Velocity Structure of Marmara Region Using Local Earthquake Tomography

    NASA Astrophysics Data System (ADS)

    Işık, S. E.; Gurbuz, C.

    2014-12-01

    The 3D P wave velocity 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 velocity 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 velocity change along profiles crossing both land and sea. All the profiles crossing the basins showed that the high velocities 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 velocity 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 velocities coincide with the development of the basins. Thus, both the basins and the high velocity 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

  17. Velocity structure of a bottom simulating reflector offshore Peru: Results from full waveform inversion

    USGS Publications Warehouse

    Pecher, I.A.; Minshull, T.A.; Singh, S.C.; Von Huene, R.

    1996-01-01

    Much of our knowledge of the worldwide distribution of submarine gas hydrates comes from seismic observations of Bottom Simulating Reflectors (BSRs). Full waveform inversion has proven to be a reliable technique for studying the fine structure of BSRs using the compressional wave velocity. We applied a non-linear full waveform inversion technique to a BSR at a location offshore Peru. We first determined the large-scale features of seismic velocity variations using a statistical inversion technique to maximise coherent energy along travel-time curves. These velocities were used for a starting velocity model for the full waveform inversion, which yielded a detailed velocity/depth model in the vicinity of the BSR. We found that the data are best fit by a model in which the BSR consists of a thin, low-velocity layer. The compressional wave velocity drops from 2.15 km/s down to an average of 1.70 km/s in an 18m thick interval, with a minimum velocity of 1.62 km/s in a 6 m interval. The resulting compressional wave velocity was used to estimate gas content in the sediments. Our results suggest that the low velocity layer is a 6-18 m thick zone containing a few percent of free gas in the pore space. The presence of the BSR coincides with a region of vertical uplift. Therefore, we suggest that gas at this BSR is formed by a dissociation of hydrates at the base of the hydrate stability zone due to uplift and subsequently a decrease in pressure.

  18. Regional P wave velocity structure of the Northern Cascadia Subduction Zone

    USGS Publications Warehouse

    Ramachandran, K.; Hyndman, R.D.; Brocher, T.M.

    2006-01-01

    This paper presents the first regional three-dimensional, P wave velocity model for the Northern Cascadia Subduction. Zone (SW British Columbia and NW Washington State) constructed through tomographic inversion of first-arrival traveltime data from active source experiments together with earthquake traveltime data recorded at permanent stations. The velocity model images the structure of the subducting Juan de Fuca plate, megathrust, and the fore-arc crust and upper mantle. Beneath southern Vancouver Island the megathrust above the Juan de Fuca plate is characterized by a broad zone (25-35 km depth) having relatively low velocities of 6.4-6.6 km/s. This relative low velocity zone coincides with the location of most of the episodic tremors recently mapped beneath Vancouver Island, and its low velocity may also partially reflect the presence of trapped fluids and sheared lower crustal rocks. The rocks of the Olympic Subduction Complex are inferred to deform aseismically as evidenced by the lack of earthquakes withi the low-velocity rocks. The fore-arc upper mantle beneath the Strait of Georgia and Puget Sound is characterized by velocities of 7.2-7.6 km/s. Such low velocities represent regional serpentinization of the upper fore-arc mantle and provide evidence for slab dewatering and densification. Tertiary sedimentary basins in the Strait of Georgia and Puget Lowland imaged by the velocity model lie above the inferred region of slab dewatering and densification and may therefore partly result from a higher rate of slab sinking. In contrast, sedimentary basins in the Strait of Juan de Fuca lie in a synclinal depression in the Crescent Terrane. The correlation of in-slab earthquake hypocenters M>4 with P wave velocities greater than 7.8 km/s at the hypocenters suggests that they originate near the oceanic Moho of the subducting Juan de Fuca plate. Copyright 2006 by the American Geophysical Union.

  19. 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.

  20. Three-dimensional seismic velocity structure of the San Francisco Bay area

    NASA Astrophysics Data System (ADS)

    Hole, J. A.; Brocher, T. M.; Klemperer, S. L.; Parsons, T.; Benz, H. M.; Furlong, K. P.

    2000-06-01

    Seismic travel times from the northern California earthquake catalogue and from the 1991 Bay Area Seismic Imaging Experiment (BASIX) refraction survey were used to obtain a three-dimensional model of the seismic velocity structure of the San Francisco Bay area. Nonlinear tomography was used to simultaneously invert for both velocity and hypocenters. The new hypocenter inversion algorithm uses finite difference travel times and is an extension of an existing velocity tomography algorithm. Numerous inversions were performed with different parameters to test the reliability of the resulting velocity model. Most hypocenters were relocated <2 km from their catalogue locations. Large lateral velocity variations at shallow (<4 km) depth correlate with known surface geology, including low-velocity Cenozoic sedimentary basins, high-velocity Cenozoic volcanic rocks, and outcrop patterns of the major Mesozoic geologic terranes. Salinian arc rocks have higher velocities than the Franciscan melange, which in turn are faster than Great Valley Sequence forearc rocks. The thickess of low-velocity sediment is defined, including >12 km under the Sacramento River Delta, 6 km beneath Livermore Valley, 5 km beneath the Santa Clara Valley, and 4 km beneath eastern San Pablo Bay. The Great Valley Sequence east of San Francisco Bay is 4-6 km thick. A relatively high velocity body exists in the upper 10 km beneath the Sonoma volcanic field, but no evidence for a large intrusion or magma chamber exists in the crust under The Geysers or the Clear Lake volcanic center. Lateral velocity contrasts indicate that the major strike-slip faults extend sub vertically beneath their surface locations through most of the crust. Strong lateral velocity contrasts of 0.3-0.6 km/s are observed across the San Andreas Fault in the middle crust and across the Hayward, Rogers Creek, Calaveras, and Greenville Faults at shallow depth. Weaker velocity contrasts (0.1-0.3 km/s) exist across the San Andreas, Hayward

  1. Heterobridged dinuclear, tetranuclear, dinuclear-based 1-d, and heptanuclear-based 1-D complexes of copper(II) derived from a dinucleating ligand: syntheses, structures, magnetochemistry, spectroscopy, and catecholase activity.

    PubMed

    Majumder, Samit; Sarkar, Sohini; Sasmal, Sujit; Sañudo, E Carolina; Mohanta, Sasankasekhar

    2011-08-15

    The work in this paper presents syntheses, characterization, crystal structures, variable-temperature/field magnetic properties, catecholase activity, and electrospray ionization mass spectroscopic (ESI-MS positive) study of five copper(II) complexes of composition [Cu(II)(2)L(μ(1,1)-NO(3))(H(2)O)(NO(3))](NO(3)) (1), [{Cu(II)(2)L(μ-OH)(H(2)O)}(μ-ClO(4))](n)(ClO(4))(n) (2), [{Cu(II)(2)L(NCS)(2)}(μ(1,3)-NCS)](n) (3), [{Cu(II)(2)L(μ(1,1)-N(3))(ClO(4))}(2)(μ(1,3)-N(3))(2)] (4), and [{Cu(II)(2)L(μ-OH)}{Cu(II)(2)L(μ(1,1)-N(3))}{Cu(II)(μ(1,1)-N(3))(4)(dmf)}{Cu(II)(2)(μ(1,1)-N(3))(2)(N(3))(4)}](n)·ndmf (5), derived from a new compartmental ligand 2,6-bis[N-(2-pyridylethyl)formidoyl]-4-ethylphenol, which is the 1:2 condensation product of 4-ethyl-2,6-diformylphenol and 2-(2-aminoethyl)pyridine. The title compounds are either of the following nuclearities/topologies: dinuclear (1), dinuclear-based one-dimensional (2 and 3), tetranuclear (4), and heptanuclear-based one-dimensional (5). The bridging moieties in 1-5 are as follows: μ-phenoxo-μ(1,1)-nitrate (1), μ-phenoxo-μ-hydroxo and μ-perchlorate (2), μ-phenoxo and μ(1,3)-thiocyanate (3), μ-phenoxo-μ(1,1)-azide and μ(1,3)-azide (4), μ-phenoxo-μ-hydroxo, μ-phenoxo-μ(1,1)-azide, and μ(1,1)-azide (5). All the five compounds exhibit overall antiferromagnetic interaction. The J values in 1-4 have been determined (-135 cm(-1) for 1, -298 cm(-1) for 2, -105 cm(-1) for 3, -119.5 cm(-1) for 4). The pairwise interactions in 5 have been evaluated qualitatively to result in S(T) = 3/2 spin ground state, which has been verified by magnetization experiment. Utilizing 3,5-di-tert-butyl catechol (3,5-DTBCH(2)) as the substrate, catecholase activity of all the five complexes have been checked. While 1 and 3 are inactive, complexes 2, 4, and 5 show catecholase activity with turn over numbers 39 h(-1) (for 2), 40 h(-1) (for 4), and 48 h(-1) (for 5) in dmf and 167 h(-1) (for 2) and 215 h(-1) (for 4) in acetonitrile

  2. Seismic wave velocity of rocks in the Oman ophiolite: constraints for petrological structure of oceanic crust

    NASA Astrophysics Data System (ADS)

    Saito, S.; Ishikawa, M.; Shibata, S.; Akizuki, R.; Arima, M.; Tatsumi, Y.; Arai, S.

    2010-12-01

    Evaluation of rock velocities and comparison with velocity profiles defined by seismic refraction experiments are a crucial approach for understanding the petrological structure of the crust. In this study, we calculated the seismic wave velocities of various types of rocks from the Oman ophiolite in order to constrain a petrological structure of the oceanic crust. Christensen & Smewing (1981, JGR) have reported experimental elastic velocities of rocks from the Oman ophiolite under oceanic crust-mantle conditions (6-430 MPa). However, in their relatively low-pressure experiments, internal pore-spaces might affect the velocity and resulted in lower values than the intrinsic velocity of sample. In this study we calculated the velocities of samples based on their modal proportions and chemical compositions of mineral constituents. Our calculated velocities represent the ‘pore-space-free’ intrinsic velocities of the sample. We calculated seismic velocities of rocks from the Oman ophiolite including pillow lavas, dolerites, plagiogranites, gabbros and peridotites at high-pressure-temperature conditions with an Excel macro (Hacker & Avers 2004, G-cubed). The minerals used for calculations for pillow lavas, dolerites and plagiogranites were Qtz, Pl, Prh, Pmp, Chl, Ep, Act, Hbl, Cpx and Mag. Pl, Hbl, Cpx, Opx and Ol were used for the calculations for gabbros and peridotites. Assuming thermal gradient of 20° C/km and pressure gradient of 25 MPa/km, the velocities were calculated in the ranges from the atmospheric pressure (0° C) to 200 MPa (160° C). The calculation yielded P-wave velocities (Vp) of 6.5-6.7 km/s for the pillow lavas, 6.6-6.8 km/s for the dolerites, 6.1-6.3 km/s for the plagiogranites, 6.9-7.5 km/s for the gabbros and 8.1-8.2 km/s for the peridotites. On the other hand, experimental results reported by Christensen & Smewing (1981, JGR) were 4.5-5.9 km/s for the pillow lavas, 5.5-6.3 km/s for the dolerites, 6.1-6.3 km/s for the plagiogranites, 6

  3. Shear wave velocity structure in North America from large-scale waveform inversions of surface waves

    USGS Publications Warehouse

    Alsina, D.; Woodward, R.L.; Snieder, R.K.

    1996-01-01

    A two-step nonlinear and linear inversion is carried out to map the lateral heterogeneity beneath North America using surface wave data. The lateral resolution for most areas of the model is of the order of several hundred kilometers. The most obvious feature in the tomographic images is the rapid transition between low velocities in the technically active region west of the Rocky Mountains and high velocities in the stable central and eastern shield of North America. The model also reveals smaller-scale heterogeneous velocity structures. A high-velocity anomaly is imaged beneath the state of Washington that could be explained as the subducting Juan de Fuca plate beneath the Cascades. A large low-velocity structure extends along the coast from the Mendocino to the Rivera triple junction and to the continental interior across the southwestern United States and northwestern Mexico. Its shape changes notably with depth. This anomaly largely coincides with the part of the margin where no lithosphere is consumed since the subduction has been replaced by a transform fault. Evidence for a discontinuous subduction of the Cocos plate along the Middle American Trench is found. In central Mexico a transition is visible from low velocities across the Trans-Mexican Volcanic Belt (TMVB) to high velocities beneath the Yucatan Peninsula. Two elongated low-velocity anomalies beneath the Yellowstone Plateau and the eastern Snake River Plain volcanic system and beneath central Mexico and the TMVB seem to be associated with magmatism and partial melting. Another low-velocity feature is seen at depths of approximately 200 km beneath Florida and the Atlantic Coastal Plain. The inversion technique used is based on a linear surface wave scattering theory, which gives tomographic images of the relative phase velocity perturbations in four period bands ranging from 40 to 150 s. In order to find a smooth reference model a nonlinear inversion based on ray theory is first performed. After

  4. Shear wave velocity structure in North America from large-scale waveform inversions of surface waves

    NASA Astrophysics Data System (ADS)

    Alsina, D.; Woodward, R. L.; Snieder, R. K.

    1996-07-01

    A two-step nonlinear and linear inversion is carried out to map the lateral heterogeneity beneath North America using surface wave data. The lateral resolution for most areas of the model is of the order of several hundred kilometers. The most obvious feature in the tomographic images is the rapid transition between low velocities in the tectonically active region west of the Rocky Mountains and high velocities in the stable central and eastern shield of North America. The model also reveals smaller-scale heterogeneous velocity structures. A high-velocity anomaly is imaged beneath the state of Washington that could be explained as the subducting Juan de Fuca plate beneath the Cascades. A large low-velocity structure extends along the coast from the Mendocino to the Rivera triple junction and to the continental interior across the southwestern United States and northwestern Mexico. Its shape changes notably with depth. This anomaly largely coincides with the part of the margin where no lithosphere is consumed since the subduction has been replaced by a transform fault. Evidence for a discontinuous subduction of the Cocos plate along the Middle American Trench is found. In central Mexico a transition is visible from low velocities across the Trans-Mexican Volcanic Belt (TMVB) to high velocities beneath the Yucatan Peninsula. Two elongated low-velocity anomalies beneath the Yellowstone Plateau and the eastern Snake River Plain volcanic system and beneath central Mexico and the TMVB seem to be associated with magmatism and partial melting. Another low-velocity feature is seen at depths of approximately 200 km beneath Florida and the Atlantic Coastal Plain. The inversion technique used is based on a linear surface wave scattering theory, which gives tomographic images of the relative phase velocity perturbations in four period bands ranging from 40 to 150 s. In order to find a smooth reference model a nonlinear inversion based on ray theory is first performed. After

  5. Dinuclear and 1D iron(III) Schiff base complexes bridged by 4-salicylideneamino-1,2,4-triazolate: X-ray structures and magnetic properties.

    PubMed

    Herchel, Radovan; Pavelek, Lubomír; Trávníček, Zdeněk

    2011-11-28

    Four new iron(III) complexes were obtained by the reaction of 4-salicylideneamino-1,2,4-triazole (Hsaltrz) and selected dinuclear μ-oxo-bridged iron(III) Schiff base complexes [{FeL(4)}(2)(μ-O)], where L(4) represents a terminal tetradentate dianionic Schiff-base ligand. X-ray structural analysis revealed a novel bridging mode of κN,κO of the saltrz ligand to form dinuclear complexes [{Fe(salen)(μ-saltrz)}(2)]·CH(3)OH (1) (H(2)salen = N,N'-ethylenebis(salicylimine)) and [{Fe(salpn)(μ-saltrz)}(2)] (2) (H(2)salpn = N,N'-1,2-propylenbis(salicylimine)), whereas one-dimensional (1D) zig-zag chains were formed in the case of [{Fe(salch)(μ-saltrz)}·0.5CH(3)OH](n) (3) (H(2)salch = N,N'-cyclohexanebis(salicylimine)) and [Fe(salophen)(μ-saltrz)](n) (4) (H(2)salophen = N,N'-o-phenylenebis(salicylimine)). It was also shown that the rigidity of the terminal ligand L(4) can be considered as the key factor for the molecular dimensionality of the products. The thorough magnetic analysis based on SQUID experiments, including the isotropic exchange and the zero-field splitting of both temperature and field dependent data, was performed for dimeric (1 and 2) and also for polymeric compounds (3 and 4) and revealed weak antiferromagnetic exchange mediated by the saltrz anions with much larger D-parameter (|D|≫|J|). PMID:21968851

  6. Shear-wave velocity structure of the crust and uppermost mantle in the Shanxi rift zone

    NASA Astrophysics Data System (ADS)

    Song, Meiqing; Zheng, Yong; Liu, Chun; Li, Li; Wang, Xia

    2015-04-01

    The Shanxi rift zone is one of the largest and active Cenozoic grabens in the world, studying the velocity structure of the crust and upper mantle in this region may help us to understand the mechanisms of rift processes and the seismogenic environment of active seismicity in continental rifts. In this work, using the broadband seismic data of Shanxi, Hebei, Henan, Shaanxi provinces, and the Inner Mongolia Autonomous Region from February 2009 to November 2011, we have picked out 350 high-quality phase velocity dispersion curves of fundamental mode Rayleigh waves at periods from 8 to 75 s, and Rayleigh wave phase velocity maps have been constructed from 8 to 75 s period with horizontal resolution ranging from 40 to 50 km by two-station surface-wave tomography. Then, using a genetic algorithm, a 3D shear-wave speed model of the crust and uppermost mantle have been derived from these maps with a spatial resolution of 0.4° × 0.4°. Four characteristics can be outlined from the results: (1) Except in the Datong volcanic zone, in the depth range of 11-30 km, the location of a transition zone between the high- and low-velocity regions is in agreement with the seismicity pattern in the study region, and the earthquakes are mostly concentrated near this transition zone; (2) In the depth range of 31-40 km, shear-wave velocities are higher to the south of the Taiyuan Basin and lower to the north, which is similar to the distribution pattern of Moho depth variations in the Shanxi region; (3) The shear-wave velocity pattern of higher velocities to the south of 38°N and lower velocities to the north is found to be consistent with that from the upper crustal levels to depth of 70 km. At the deeper depths, the spatial scale of the low-velocity anomalies zone in the north is gradually shrinking with depth increasing, the low-velocity anomalies are gradually disappearing beneath the Datong volcanic zone at the depth of 151-200 km. We proposed that the root of the Datong volcano

  7. Shallow velocity structure in the Imperial Valley region of Southern California

    NASA Astrophysics Data System (ADS)

    Ma, Y.; Stock, J. M.; Hole, J. A.; Fuis, G. S.

    2013-12-01

    The Imperial Valley, located south of the Salton Sea of Southern California, contains a pull-apart basin formed by the on-going oblique extension between the southernmost San Andreas fault and the northern Imperial fault. In this very seismically active area, the earthquakes tend to occur in the form of seismic swarms (e.g. events in August 2012), often related to the geothermal systems in the valley. Previous active seismic studies (e.g. Fuis et al. 1979, Parsons and McCarthy 1996) have revealed major crustal structures including the shallow basin structures in the valley and surroundings, based primarily on 2D models. A better 3D structure model is still awaiting construction to provide improved information on the location of earthquakes, faults, fault-zone properties, and the evolution of the basin. The 2011 Salton Seismic Imaging Project (SSIP) deployed a seismic array at 2-km grid spacing in the central northern part of the valley (Line 11), and three longer seismic lines across the valley with active sources (Lines 1, 2, and 3). Here we will present the shallow (to 8-km depth) 3D structure in this region obtained by modeling the traveltimes of the first arrivals in these recordings and from earlier experiments. We have processed arrivals from all shots at all receivers, from the SSIP dataset, in the region south of the Salton Sea. Relevant data from the 1979 Imperial Valley experiment has also been used. The 3D structure of the valley was inverted from the surface to 8-km depth using the technique of Hole (1992). On average, the velocity increases rapidly from ~2 km/s at the surface to 5.6 km/s at 5 km depth, a velocity range corresponding to the unmetamorphosed sediments (Fuis et al. 1984). Below 5-km depth, velocity increases slowly to 6.3 km/s at 8-km depth, a velocity range corresponding to the metasedimentary rocks, or 'basement' (Fuis et al. 1984). In depth slices, geothermal areas are characterized by high velocity zones. Specifically, we observe a

  8. Second derivatives of the flutter velocity and the optimization of aircraft structures.

    NASA Technical Reports Server (NTRS)

    Rudisill, C. S.; Bhatia, K. G.

    1972-01-01

    Equations for the second partial derivatives of the eigenvalues of the flutter equation along with the equations for finding the second partial derivatives of the flutter velocity of an aircraft structure with respect to the structural parameters are derived. These partial derivatives are used to develop expressions for the step size in a projected gradient search along a constant mass hyperlane. A projected gradient search along with a gradient mass and a gradient velocity search is used to minimize the mass of a box beam which supports a lifting surface.

  9. Shallow velocity structure and Poisson's ratio at the Tarzana, California, strong-motion accelerometer site

    USGS Publications Warehouse

    Catchings, R.D.; Lee, W.H.K.

    1996-01-01

    The 17 January 1994, Northridge, California, earthquake produced strong ground shaking at the Cedar Hills Nursery (referred to here as the Tarzana site) within the city of Tarzana, California, approximately 6 km from the epicenter of the mainshock. Although the Tarzana site is on a hill and is a rock site, accelerations of approximately 1.78 g horizontally and 1.2 g vertically at the Tarzana site are among the highest ever instrumentally recorded for an earthquake. To investigate possible site effects at the Tarzana site, we used explosive-source seismic refraction data to determine the shallow (<70 m) P- and S-wave velocity structure. Our seismic velocity models for the Tarzana site indicate that the local velocity structure may have contributed significantly to the observed shaking. P-wave velocities range from 0.9 to 1.65 km/sec, and S-wave velocities range from 0.20 and 0.6 km/sec for the upper 70 m. We also found evidence for a local S-wave low-velocity zone (LVZ) beneath the top of the hill. The LVZ underlies a CDMG strong-motion recording site at depths between 25 and 60 m below ground surface (BGS). Our velocity model is consistent with the near-surface (<30 m) P- and S-wave velocities and Poisson's ratios measured in a nearby (<30 m) borehole. High Poisson's ratios (0.477 to 0.494) and S-wave attenuation within the LVZ suggest that the LVZ may be composed of highly saturated shales of the Modelo Formation. Because the lateral dimensions of the LVZ approximately correspond to the areas of strongest shaking, we suggest that the highly saturated zone may have contributed to localized strong shaking. Rock sites are generally considered to be ideal locations for site response in urban areas; however, localized, highly saturated rock sites may be a hazard in urban areas that requires further investigation.

  10. Upper mantle seismic velocity structure beneath the Kenya Rift and the Arabian Shield

    NASA Astrophysics Data System (ADS)

    Park, Yongcheol

    Upper mantle structure beneath the Kenya Rift and Arabian Shield has been investigated to advance our understanding of the origin of the Cenozoic hotspot tectonism found there. A new seismic tomographic model of the upper mantle beneath the Kenya Rift has been obtained by inverting teleseismic P-wave travel time residuals. The model shows a 0.5--1.5% low velocity anomaly below the Kenya Rift extending to about 150 km depth. Below ˜150 km depth, the anomaly broadens to the west toward the Tanzania Craton, suggesting a westward dip to the structure. The P- and S-wave velocity structure beneath the Arabian Shield has been investigated using travel-time tomography. Models for the seismic velocity structure of the upper mantle between 150 and 400 depths reveal a low velocity region (˜1.5% in the P model and ˜3% in the S model) trending NW-SE along the western side of the Arabian Shield and broadening to the northeast beneath the MMN volcanic line. The models have limited resolution above 150 km depth everywhere under the Shield, and in the middle part of the Shield the resolution is limited at all depths. Rayleigh wave phase velocity measurements have been inverted to image regions of the upper mantle under the Arabian Shield not well resolved by the body wave tomography. The shear wave velocity model obtained shows upper mantle structure above 200 km depth. A broad low velocity region in the lithospheric mantle (depths of ≤ ˜100 km) across the Shield is observed, and below ˜150 km depth a region of low shear velocity is imaged along the Red Sea coast and MMN volcanic line. A westward dipping low velocity zone beneath the Kenya Rift is consistent with an interpretation by Nyblade et al. [2000] suggesting that a plume head is located under the eastern margin of the Tanzania Craton, or alternatively a superplume rising from the lower mantle from the west and reaching the surface under Kenya [e.g., Debayle et al., 2001; Grand et al., 1997; Ritsema et al., 1999]. For

  11. 3-D Velocity Structure of Southwestern British Columbia and Northern Washington

    NASA Astrophysics Data System (ADS)

    Ramachandran, K.; Ramachandran, K.; Spence, G. D.; Dosso, S.; Hyndman, R. D.; Hyndman, R. D.; Brocher, T. M.; Fisher, M. M.

    2001-12-01

    A seismic tomography analysis in S.W. British Columbia and N. Washington has been used to define the velocity structure of the forearc crust and underlying subducting Juan de Fuca plate, and to obtain precise earthquake locations. First arrival travel-times from earthquakes and from the large airgun array used in the `Seismic Hazards Investigation of Puget Sound' (SHIPS) 1998 experiment, were simultaneously inverted for hypocentral parameters and velocity structure. Approximately 16,000 picks from 1,400 earthquakes recorded at 46 permanent stations, and 35,000 picks from the SHIPS experiment were used in the inversion. The velocity model was parameterized in the forward/inverse step by a node/cell spacing of 3 X 3 X 3 km over a volume of 360 X 450 X 93 km depth. The starting and final RMS travel time misfits were 479 ms and 120 ms respectively. Checkerboard tests conducted on the final velocity model imply good lateral resolution ranging from 30 to 50 km. The SHIPS airgun data mainly constrained the upper ~12 km and the earthquake data the deeper structure. The high velocity mafic Crescent Terrane that dips beneath the margin is well mapped in the velocity model on a regional scale. Its thickness beneath southern Vancouver Island is interpreted to reach ~20 km. Three high velocity structures above the subducting Juan de Fuca plate, having mafic to ultramafic velocities of 7.25-7.5 km/s, occur beneath southern Vancouver Island and Puget Sound at a depth of ~25 km. They may be associated with deeper parts of the Crescent Terrane, or with structures such as seamounts on the subducting Juan de Fuca plate. At the southern tip of Vancouver Islands, the Leech River Fault, Southern Whidbey Island Fault, and the Devils Mountain Fault appear to correlate with mapped seismicity. The subducting Juan de Fuca plate is well mapped beneath southern Vancouver Island, Olympic Peninsula, Strait of Georgia, and Puget Sound. The velocity model identifies the steepening dip in the

  12. Joint inversion for 3-dimensional S-velocity mantle structure along the Tethyan margin

    NASA Astrophysics Data System (ADS)

    Chang, S.; van der Lee, S.; Flanagan, M. P.; Bedle, H.; Marone, F.; Matzel, E. M.; Pasyanos, M. E.; Rodgers, A. J.; Romanowicz, B.; Schmid, C.

    2007-12-01

    For purposes of studying the lateral heterogeneity as well as for ultimately predicting seismograms for the region which extends from the western Mediterranean region to the Hindu Kush, we construct a new 3-D S-velocity model by jointly inverting regional waveforms, surface wave group velocity measurements, teleseismic S arrival times, and crustal thickness estimates from receiver functions, refraction lines, and gravity surveys. We can expect better resolution for the resulting model than when using individual data set, because these data types have complementary resolving power for crust and mantle structures, vertical and lateral variations, shallow and deep mantle features, local and global structure, and are jointly inverted to image the complexity of this tectonically diverse area. We have fitted the waveforms of regional S and Rayleigh waves from over 3800 seismograms using Partitioned Waveform Inversion. We have accumulated over 3000 crustal thicknesses from receiver functions, gravity measurements, and refraction profiles. We have measured Rayleigh wave group velocities for hundreds of new paths recorded at the MIDSEA stations and combined them with thousands of existing paths transecting the region. We have over 5000 teleseismic S arrival times measured through cross correlation and 200,000 more from picks originally reported to the ISC. We scale the resulting S-velocity model to a P-velocity model using observed relations between S and P delay times as well as mineral physics. We then update the P-model using P delay times and compare the result to existing P-velocity models of the region. We discuss features of our new model, which includes oceanic structure, cratons, subducting slabs that penetrate into the lower mantle and others that do not, low-velocity mantle plumes, rifts, plateaus, and basins.

  13. LOCA hydroloads calculations with multidimensional nonlinear fluid/structure interaction. Volume 1: STEALTH 1D single-phase fluid studies. Final report. [PWR

    SciTech Connect

    Santee, G.E. Jr.; Mortensen, G.A.; Caraher, D.L.

    1980-04-01

    This report, which is the first in a series of reports for RP-1065, describes the first step in the stepwise approach for developing the methodology to assess the hydroloads on a large PWR during the subcooled portions of a hypothetical LOCA. The first step in the methodology considers enhancements and special modifications to the 1D STEALTH computer code in order that acoustic phenomena in piping and vessel networks may be simulated. The resulting code is termed 1D STEALTH-HYDRO. The 1D STEALTH-HYDRO enhancements consist of three control volume models to simulate area changes, orifices, and tees in piping networks. The theory of the control volume models is described.

  14. Effect of Anisotropic Velocity Structure on Acoustic Emission Source Location during True-Triaxial Deformation Experiments

    NASA Astrophysics Data System (ADS)

    Ghofrani Tabari, Mehdi; Goodfellow, Sebastian; Young, R. Paul

    2016-04-01

    Although true-triaxial testing (TTT) of rocks is now more extensive worldwide, stress-induced heterogeneity due to the existence of several loading boundary effects is not usually accounted for and simplified anisotropic models are used. This study focuses on the enhanced anisotropic velocity structure to improve acoustic emission (AE) analysis for an enhanced interpretation of induced fracturing. Data from a TTT on a cubic sample of Fontainebleau sandstone is used in this study to evaluate the methodology. At different stages of the experiment the True-Triaxial Geophysical Imaging Cell (TTGIC), armed with an ultrasonic and AE monitoring system, performed several velocity surveys to image velocity structure of the sample. Going beyond a hydrostatic stress state (poro-elastic phase), the rock sample went through a non-dilatational elastic phase, a dilatational non-damaging elasto-plastic phase containing initial AE activity and finally a dilatational and damaging elasto-plastic phase up to the failure point. The experiment was divided into these phases based on the information obtained from strain, velocity and AE streaming data. Analysis of the ultrasonic velocity survey data discovered that a homogeneous anisotropic core in the center of the sample is formed with ellipsoidal symmetry under the standard polyaxial setup. Location of the transducer shots were improved by implementation of different velocity models for the sample starting from isotropic and homogeneous models going toward anisotropic and heterogeneous models. The transducer shot locations showed a major improvement after the velocity model corrections had been applied especially at the final phase of the experiment. This location improvement validated our velocity model at the final phase of the experiment consisting lower-velocity zones bearing partially saturated fractures. The ellipsoidal anisotropic velocity model was also verified at the core of the cubic rock specimen by AE event location of

  15. Upper-crustal velocity structure along 150 km of the Mendeleev Ridge from tomographic inversion of long-offset refraction data collected during HLY0602

    NASA Astrophysics Data System (ADS)

    Vermeesch, P. M.; van Avendonk, H. J.; Lawver, L. A.

    2007-12-01

    In the summer of 2006 we acquired a unique seismic refraction data set on the Chukchi Borderlands and Mendeleev Ridge utilizing USCGC Healy and two helicopters. The array on the Mendeleev Ridge consisted of 14 instrument sites with 12 km spacing between instruments. On every site we deployed a Sea-Ice Seismometer (S- IS) especially designed for this experiment in the ice-covered part of the Arctic Ocean. Each S-IS contained a vertical component geophone that was buried in the ice and a hydrophone that was hanging from the ice edge in the water. From the 14 instrument sites, 10 contained useful data with refracted crustal arrivals up to offsets of 40 km. Because of extensive drifting of the receivers (40 km in 5 days and containing numerous loops), and because of the irregular geometry of airgun shots due to the problems of sailing through ice-covered seas, a 3D ray-shooting code was developed to calculate ray paths within a 3D velocity model that extends along 150 km in the X- direction and along 35 km in the Y-direction. Using the velocity model proposed by Lebedeva-Ivanova et al. (2006) we observe that the maximum depth of our calculated ray paths is 11 km below sealevel. Using all the available data, the Root Mean Square (RMS) difference between observed and calculated travel-times is of the order of 500 ms. Initially a simple 1D travel-time inversion was developed to constrain the velocity structure of the basement underneath a layer of water (3D) and a layer of sediment (1D). This inversion was carried out on 2 pairs of receivers: one pair in the NNE and one more towards the SSW part of the line. Inversion of S-IS 45N-42 (NNE) results in a model with a velocity of 5.5 km s-1 at the top of the basement, slowly increasing to a velocity of 5.7 km s-1 at 3 km below the top of the basement (RMS = 117 ms). Inversion of S-IS 49-45S (SSW) results in a model with a velocity of 4.8 km s-1 at the top of the basement, increasing to a velocity of 5.9 km s-1 at 3 km below

  16. Velocity Structure of the Rifted Crust in the Northwestern Ross Sea, From Seismic Refraction Data

    NASA Astrophysics Data System (ADS)

    Selvans, M. M.; Stock, J. M.; Clayton, R. W.; Cande, S. C.; Davey, F. J.

    2007-12-01

    Extension in the West Antarctic Rift System produced the Transantarctic Mountains, deep sedimentary basins in the Ross Sea, and the Adare Trough spreading center (43 to 26 Ma). The Adare Basin and Northern Basin are located at the northwesternmost extent of this region of deformation, and are generally assumed to be oceanic and continental crust respectively. Their boundary therefore provides an ideal study area for linking the styles of extension in the two types of crust. We process seismic refraction data collected during research cruise NBP0701 to determine 2D crustal velocity models along four seismic lines at the margin of the Adare and Northern Basins. The 48 closely-spaced sonobuoy records included in this study provide continuous refraction data coverage; three of these lines have reversed sonobuoy records. Finite difference modeling of the individual sonobuoys provides accuracy in our interpreted layer velocities, confidence in tracing refracted arrivals back to their associated reflections in the sonobuoy records, and the ability to match these reflected arrivals with the multi- channel seismic reflection data. Preliminary results from the line trending perpendicular to the margin of the Adare and Northern Basins show no change in crustal velocity structure from one basin to the other, with nearly flat velocity contours along the entire line. An apparent velocity of 8000 m/s is observed along this line in the Northern Basin. A comparable layer velocity is not detected in the sonobuoy record shot in the reverse direction, so this velocity could be due to local basement topography. Alternatively, the high velocity may indicate mantle material, and an unusually thin crust at that location. We model structural layers and associated velocities below the sea floor in order to better understand the physical structure and deformational history of the crust in the northwestern Ross Sea. The velocity horizons determined from this data set provide model constraints

  17. Velocity Structure of the Rifted Crust in the Northwestern Ross Sea, From Seismic Refraction Data

    NASA Astrophysics Data System (ADS)

    Selvans, M. M.; Stock, J. M.; Clayton, R. W.; Cande, S. C.; Davey, F. J.

    2004-12-01

    Extension in the West Antarctic Rift System produced the Transantarctic Mountains, deep sedimentary basins in the Ross Sea, and the Adare Trough spreading center (43 to 26 Ma). The Adare Basin and Northern Basin are located at the northwesternmost extent of this region of deformation, and are generally assumed to be oceanic and continental crust respectively. Their boundary therefore provides an ideal study area for linking the styles of extension in the two types of crust. We process seismic refraction data collected during research cruise NBP0701 to determine 2D crustal velocity models along four seismic lines at the margin of the Adare and Northern Basins. The 48 closely-spaced sonobuoy records included in this study provide continuous refraction data coverage; three of these lines have reversed sonobuoy records. Finite difference modeling of the individual sonobuoys provides accuracy in our interpreted layer velocities, confidence in tracing refracted arrivals back to their associated reflections in the sonobuoy records, and the ability to match these reflected arrivals with the multi- channel seismic reflection data. Preliminary results from the line trending perpendicular to the margin of the Adare and Northern Basins show no change in crustal velocity structure from one basin to the other, with nearly flat velocity contours along the entire line. An apparent velocity of 8000 m/s is observed along this line in the Northern Basin. A comparable layer velocity is not detected in the sonobuoy record shot in the reverse direction, so this velocity could be due to local basement topography. Alternatively, the high velocity may indicate mantle material, and an unusually thin crust at that location. We model structural layers and associated velocities below the sea floor in order to better understand the physical structure and deformational history of the crust in the northwestern Ross Sea. The velocity horizons determined from this data set provide model constraints

  18. Probing Near Surface Shear Velocity Structure from Ambient Noise in Hefei Urban Area

    NASA Astrophysics Data System (ADS)

    Li, C.; Yao, H.; Fang, H.

    2014-12-01

    Ambient noise tomography has widely been used to achieve high resolution 3-D crustal velocity 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 tomography capable to investigate near surface velocity 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 velocity structure using high-frequency (0.5 - 2 Hz) ambient noise tomography 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 tomography method with spatial smoothing constraints (model regularization) based on ray path density.This method is used to construct frequency-dependent phase velocity 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 velocity in the study area without the intermediate step of phase or group velocity maps.The method uses frequency dependent propagation paths and a wavelet-based sparsity-constrained tomography 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 velocity(~2.5 km/s) in the top several hundred meters than the south part(~0.8 km/s), basically consistent with the

  19. 2D and 3D Shear-Wave Velocity Structure to >1 Km Depth from Ambient and Active Surface Waves: Three "Deep Remi" Case Studies

    NASA Astrophysics Data System (ADS)

    Louie, J. N.; Pancha, A.; Pullammanappallil, S. K.

    2014-12-01

    Refraction microtermor routinely assesses 1D and 2D velocity-depth profiles to shallow depths of approximately 100 m primarily for engineering applications. Estimation of both shallow and deep (>100 m) shear-velocity structure are key elements in the assessment of urban areas for potential earthquake ground shaking, damage, and the calibration of recorded ground motions. Three independent studies investigated the ability of the refraction microtremor technology to image deep velocity structure, to depths exceeding 1 km (Deep ReMi). In the first study, we were able to delineate basin thicknesses of up to 900 m and the deep-basin velocity structure beneath the Reno-area basin. Constraints on lateral velocity changes in 3D as well as on velocity profiles extended down to 1500 m, and show a possible fault offset. This deployment used 30 stand-alone wireless instruments mated to 4.5 Hz geophones, along each of five arrays 2.9 to 5.8 km long. Rayleigh-wave dispersion was clear at frequencies as low as 0.5 Hz using 120 sec ambient urban noise records. The results allowed construction of a 3D velocity model, vetted by agreement with gravity studies. In a second test, a 5.8 km array delimited the southern edge of the Tahoe Basin, with constraints from gravity. There, bedrock depth increased by 250 m in thickness over a distance of 1600 m, with definition of the velocity of the deeper basin sediments. The third study delineated the collapse region of an underground nuclear explosion within a thick sequence of volcanic extrusives, using a shear-wave minivibe in a radial direction, and horizontal geophones. Analysis showed the cavity extends to 620 m depth, with a width of 180 m and a height of 220 m. Our results demonstrate that deep velocity structure can be recovered using ambient noise. This technique offers the ability to define 2D and 3D structural representations essential for seismic hazard evaluation.

  20. Two-station phase velocity determination for structure in North Africa

    SciTech Connect

    Hazler, S; Pasyanos, M; Sheehan, A; Walter, W

    1999-07-28

    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 velocity 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 velocity 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 velocity 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 velocity dispersion curve. Phase velocity 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 velocity structure of the lithosphere and can be used in combination with additional independent seismic observations (e.g. Pn tomography, surface wave group velocity tomography, receiver functions, etc.) to construct reliable velocity models. We compare velocities 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

  1. Offshore Southern California lithospheric velocity structure from noise cross-correlation functions

    NASA Astrophysics Data System (ADS)

    Bowden, D. C.; Kohler, M. D.; Tsai, V. C.; Weeraratne, D. S.

    2016-05-01

    A new shear wave velocity model offshore Southern California is presented that images plate boundary deformation including both thickening and thinning of the crustal and mantle lithosphere at the westernmost edge of the North American continent. The Asthenospheric and Lithospheric Broadband Architecture from the California Offshore Region Experiment (ALBACORE) ocean bottom seismometer array, together with 65 stations of the onshore Southern California Seismic Network, is used to measure ambient noise correlation functions and Rayleigh wave dispersion curves which are inverted for 3-D shear wave velocities. The resulting velocity model defines the transition from continental lithosphere to oceanic, illuminating the complex history and deformation in the region. A transition to the present-day strike-slip regime between the Pacific and North American Plates resulted in broad deformation and capture of the now >200 km wide continental shelf. Our velocity model suggests the persistence of the uppermost mantle volcanic processes associated with East Pacific Rise spreading adjacent to the Patton Escarpment, which marks the former subduction of Farallon Plate underneath North America. The most prominent of these seismic structures is a low-velocity anomaly underlying the San Juan Seamount, suggesting ponding of magma at the base of the crust, resulting in thickening and ongoing adjustment of the lithosphere due to the localized loading. The velocity model also provides a robust framework for future earthquake location determinations and ground-shaking simulations for risk estimates.

  2. The effects of structural setting on the azimuthal velocities of blast induced ground motion in perlite

    SciTech Connect

    Beattie, S.G.

    1995-02-01

    A series of small scale explosive tests were performed during the spring of 1994 at a perlite mine located near Socorro, NM. The tests were designed to investigate the azimuthal or directional relationship between small scale geologic structures such as joints and the propagation of explosively induced ground motion. Three shots were initiated within a single borehole located at ground zero (gz) at depths varying from the deepest at 83 m (272 ft) to the shallowest at 10 m (32 ft). The intermediate shot was initiated at a depth of 63 m (208 ft). An array of three component velocity and acceleration transducers were placed in two concentric rings entirely surrounding the single shot hole at 150 and 300 azimuths as measured from ground zero. Data from the transducers was then used to determine the average propagation velocity of the blast vibration through the rock mass at the various azimuths. The rock mass was mapped to determine the prominent joint orientations (strike and dip) and the average propagation velocities were correlated with this geologic information. The data from these experiments shows that there is a correlation between the orientation of prominent joints and the average velocity of ground motion. It is theorized that this relationship is due to the relative path the ground wave follows when encountering a joint or structure within the rock mass. The more prominent structures allow the wave to follow along their strike thereby forming a sort of channel or path of least resistance and in turn increasing the propagation velocity. Secondary joints or structures may act in concert with more prominent features to form a network of channels along which the wave moves more freely than it may travel against the structure. The amplitudes of the ground motion was also shown to vary azimuthally with the direction of the most prominent structures.

  3. Three-Dimensional Shear Wave Velocity Structure of the Peru Flat Slab Subduction Segment

    NASA Astrophysics Data System (ADS)

    Knezevic Antonijevic, S.; Wagner, L. S.; Beck, S. L.; Zandt, G.; Long, M. D.

    2012-12-01

    Recent studies focused on flat slab subduction segments in central Chile (L. S. Wagner, 2006) and Alaska (B. R. Hacker and G. A. Aber, 2012) suggest significant differences in seismic velocity structures, and hence, composition in the mantle wedge between flat and normal "steep" subducting slabs. Instead of finding the low velocities and high Vp/Vs ratios common in normal subduction zones, these studies find low Vp, high Vs, and very low Vp/Vs above flat slabs. This may indicate the presence of dry, cold material in the mantle wedge. In order to investigate the seismic velocities of the upper mantle above the Peruvian flat segment, we have inverted for 2D Rayleigh wave phase velocity maps using data from the currently deployed 40 station PULSE seismic network and some adjacent stations from the CAUGHT seismic network. We then used the sensitivity of surface waves to shear wave velocity structure with depth to develop a 3D shear wave velocity model. This model will allow us to determine the nature of the mantle lithosphere above the flat slab, and how this may have influenced the development of local topography. For example, dry conditions (high Vs velocities) above the flat slab would imply greater strength of this material, possibly making it capable of causing further inland overthrusting, while wet conditions (low Vs) would imply weaker material. This could provide some insight into the ongoing debate over whether the Fitzcarrald arch (along the northern most flank of the Altiplano) could be a topographical response to the subducted Nazca ridge hundred kilometers away from the trench (N. Espurt, 2012, P. Baby, 2005, V. A. Ramos, 2012) or not (J. Martinod, 2005, M. Wipf, 2008, T. Gerya, 2008).

  4. Damage tolerance of composite sandwich structures subjected to projectile impact. [of low velocity foreign object

    NASA Technical Reports Server (NTRS)

    Sharma, A. V.

    1979-01-01

    An experimental investigation was conducted to evaluate the effect of low velocity projectile impact on the strength carrying ability of secondary aerospace structural components fabricated with graphite/epoxy composite materials. The preload and the impact energy combinations necessary to cause catastrophic failure were determined. Those specimens that survived the projectile impact were evaluated for the residual strength.

  5. Teleseismic array analysis of upper mantle compressional velocity structure. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Walck, M. C.

    1984-01-01

    Relative array analysis of upper mantle lateral velocity variations in southern California, analysis techniques for dense data profiles, the P-wave upper mantle structure beneath an active spreading center: the Gulf of California, and the upper mantle under the Cascade ranges: a comparison with the Gulf of California are presented.

  6. Gas-rich and gas-poor structures through the stream velocity effect

    NASA Astrophysics Data System (ADS)

    Popa, Cristina; Naoz, Smadar; Marinacci, Federico; Vogelsberger, Mark

    2016-08-01

    Using adiabatic high-resolution numerical simulations, we quantify the effect of the streaming motion of baryons with respect to dark matter at the time of recombination on structure formation and evolution. Formally a second-order effect, the baryonic stream velocity has proven to have significant impact on dark matter halo abundance, as well as on the gas content and morphology of small galaxy clusters. In this work, we study the impact of stream velocity on the formation and gas content of haloes with masses up to 109 M⊙, an order of magnitude larger than previous studies. We find that the non-zero stream velocity has a sizable impact on the number density of haloes with masses ≲ few × 107 M⊙ up to z = 10, the final redshift of our simulations. Furthermore, the gas stream velocity induces a suppression of the gas fraction in haloes, which at z = 10 is ˜10 per cent for objects with M ˜ 107 M⊙, as well as a flattening of the gas density profiles in the inner regions of haloes. We further identify and study the formation, in the context of a non-zero stream velocity, of moderately long lived gas-dominated structures at intermediate redshifts 10 < z < 20, which Naoz and Narayan have recently proposed as potential progenitors of globular clusters.

  7. Gas-rich and gas poor structures through the stream velocity effect

    NASA Astrophysics Data System (ADS)

    Popa, Cristina; Naoz, Smadar; Marinacci, Federico; Vogelsberger, Mark

    2016-05-01

    Using adiabatic high-resolution numerical simulations we quantify the effect of the streaming motion of baryons with respect to dark matter at the time of recombination on structure formation and evolution. Formally a second order effect, the baryonic stream velocity has proven to have significant impact on dark matter halo abundance, as well as on the gas content and morphology of small galaxy clusters. In this work, we study the impact of stream velocity on the formation and gas content of haloes with masses up to 109M⊙, an order of magnitude larger than previous studies. We find that the non-zero stream velocity has a sizable impact on the number density of haloes with masses ≲ few× 107M⊙ up to z = 10, the final redshift of our simulations. Furthermore, the gas stream velocity induces a suppression of the gas fraction in haloes, which at z=10 is ˜10% for objects with M ˜ 107M⊙, as well as a flattening of the gas density profiles in the inner regions of haloes. We further identify and study the formation, in the context of a non-zero stream velocity, of moderately long lived gas dominated structures at intermediate redshifts 10 < z < 20, which Naoz and Narayan have recently proposed as potential progenitors of globular clusters.

  8. P-wave velocity structure of the uppermost mantle beneath Hawaii from traveltime tomography

    USGS Publications Warehouse

    Tilmann, F.J.; Benz, H.M.; Priestley, K.F.; Okubo, P.G.

    2001-01-01

    We examine the P-wave velocity 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 velocity 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 velocities 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 velocities 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-velocity zone cannot be explained in terms of conductive heating by one primary conduit per volcano but that more complicated melt pathways must exist.

  9. 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

  10. Shear velocity structure of the Tyrrhenian region in relation to volcanism and tectonics

    NASA Astrophysics Data System (ADS)

    Paulssen, H.; Greve, S.

    2012-12-01

    We present a detailed 3D shear velocity model of the Tyrrhenian Sea and surrounding onshore areas down to about 160 km depth. The high resolution of the model is achieved through the measurement of interstation Rayleigh wave dispersion curves in a small regional setting with dense station coverage. The most noticeable structure is a pronounced, nearly ringshaped low velocity region at about 80 km depth surrounding the Tyrrhenian Sea: from Corsica to the western part of the Italian mainland, continuing to the western part of Sicily and Sardinia. The thickness of this low velocity region is constrained to a maximum of 40 km, and it is independent of the chosen inversion parameters or the background model. The low values of the shear velocity suggest the presence of fluids or melt. The lateral extent of the low velocity region beneath the Italian mainland is well correlated with the locations of subduction-related volcanism, but there is also a striking continuation of the anomalous low-velocity region along the Northern Tyrrhenian Sea towards (and beneath) the island of Corsica. The recent (<5 Ma) magmatism along the Italian peninsula and the older (5-9 Ma) magmatism of the Northern Tyrrhenian Sea are associated with the subduction of the Adriatic slab beneath the Apennines, indicating mantle contamination with continental crustal material. Slab rollback, the eastward migration of the Adriatic subduction zone during the last 15 My, has been invoked to explain the eastward decrease in the age of the volcanism along the Northern Tyrrhenian Sea. Our seismic results now suggest that the anomalous mantle is still present beneath Corsica and the Northern Tyrrhenian Sea, although it does not produce any active volcanism anymore. The picture for the Southern Tyrrhenian Sea is different. Intriguingly, the sublithospheric low velocity anomaly does not continue to southeasternmost part of the Tyrrhenian Sea where the volcanism of the Aeolian arc is related to subduction of the

  11. Seismic Noise Analysis to Constrain Shallow Velocity Structure in the southern San Andreas Fault Region

    NASA Astrophysics Data System (ADS)

    Tsang, Stephanie D.

    The seismic velocity structure in the southern San Andreas Fault region is characterized by a known, distinct seismic velocity contrast on opposite sides of the fault, with a thick sedimentary region on the west side (Salton Sea area). Reverberations would affect the duration of shaking for El Centro, Mexicali, and other communities in the Coachella Valley and Imperial Valley. Furthermore, there are other areas where deep basins are bounded by faults that could have similar effects. Therefore, being able to determine the 3D structure is a critical facet of assessing the overall seismic hazard for structures on such basins. By utilizing the particle motion of surface waves, we are able extract useful information about the S-wave velocity structure. To accomplish this, we measured Rayleigh-wave ellipticity of continuous broadband data from 2010 to 2014 for 67 stations within the Southern California Seismic Network (SCSN). Measurements of Rayleigh-wave ellipticity were computed as the ratio between the vertical and horizontal amplitudes. Regional variations in the Rayleigh-wave ellipticity measurements at frequencies of 0.10 Hz up to and including 0.30 Hz illuminate small ellipticity values (i.e. horizontal elongation in Rayleigh-wave particle motion) across the entire frequency band in the regions specific to the thick sedimentary region. In this region, minimum ellipticity values (<0.20) observed at 0.10 Hz, 0.15 Hz, and at 0.20 Hz show a gradual increase up to 0.60 between 0.25 Hz to 0.40 Hz. In most areas exterior to the thick sedimentary region, ellipticity values are generally constant across the frequency band and are significantly higher (>0.90). The observed, small ellipticity values, which are characteristic of a slow velocity layer at shallow depths (upper 5-10 km), could have significant implications on the S-wave velocity structure. As the ZH-Ratio method is highly sensitive to the near-surface structure, combination of the ellipticity data with phase

  12. Controlling the stability of both the structure and velocity of domain walls in magnetic nanowires

    NASA Astrophysics Data System (ADS)

    Brandão, J.; Atkinson, D.

    2016-08-01

    For magnetic nanowire devices, the precise control of both domain wall (DW) motion and pinning behaviour is essential for reliable functional performance. The domain wall velocity and wall structure are typically sensitive to the driving field or spin-polarized current, and the pinning behaviour depends on the walls' structure and chirality, leading to variability in behaviour. Here, a systematic study combining experimental measurements and micromagnetic simulations of planar nanowires with small fixed-angle structural modulations on both edges was undertaken to study the domain wall reversal regime. A phase diagram for the reversal field as a function of modulation amplitude was obtained that shows that three DW reversal regime. A range of field and modulation amplitudes were identified in which stable DW reversal occurs, where the wall velocity is constant as a function of field and the wall structure is stable, which is well suited to applications.

  13. Multiple triangulation analysis: application to determine the velocity of 2-D structures

    NASA Astrophysics Data System (ADS)

    Zhou, X.-Z.; Zong, Q.-G.; Wang, J.; Pu, Z. Y.; Zhang, X. G.; Shi, Q. Q.; Cao, J. B.

    2006-11-01

    In order to avoid the ambiguity of the application of the Triangulation Method (multi-spacecraft timing method) to two-dimensional structures, another version of this method, the Multiple Triangulation Analysis (MTA) is used, to calculate the velocities of these structures based on 4-point measurements. We describe the principle of MTA and apply this approach to a real event observed by the Cluster constellation on 2 October 2003. The resulting velocity of the 2-D structure agrees with the ones obtained by some other methods fairly well. So we believe that MTA is a reliable version of the Triangulation Method for 2-D structures, and thus provides us a new way to describe their motion.

  14. A new family of 1D, 2D and 3D frameworks aggregated from Ni5, Ni4 and Ni7 building units: synthesis, structure, and magnetism.

    PubMed

    Liu, Ya-Hui; Lu, Li-Ping; Zhu, Miao-Li; Feng, Si-Si; Su, Feng

    2016-05-31

    Three new Ni(ii)-clusters based on a Y-shaped ligand (biphenyl-3,4',5-tricarboxylate, H3BPT), [Ni5(HBPT)4(OH)2(H2O)12]n (), [Ni4(BPT)2(OH)2(H2O)6]n·4nH2O (), and [Ni7(BPT)2(1,4-bib)2(OH)6(HCO2)2]n·3nH2O () (1,4-bib = 1,4-bi(1H-imidazol-1-yl)benzene), have been synthesized under solvothermal conditions. They were studied by infrared spectroscopy (IR), single crystal X-ray diffraction, thermogravimetric analysis (TGA), and magnetochemistry. The complexes contain low nuclear Ni-clusters as building units (BUs). Structurally, in , the cluster BUs of [Ni5(μ3-OH)2](8+) can be viewed as two reverse triangles sharing a common vertex, which are connected by the partially deprotonated μ2-η(1):η(1)-HBPT(2-) forming 1D chains. The BUs of [Ni4(μ3-OH)2](6+) clusters in can be considered as two reverse triangles sharing a common edge and extended by deprotonated μ6-η(1):η(1):η(1):η(1):η(2)-BPT(3-) constructing a 2D framework. The 3D framework of complex consists of a [Ni7(μ3-OH)4(R-COO)7(HCO2)3] cluster BUs with fully deprotonated μ5-η(1):η(1):η(1):η(1):η(1):η(1)-BPT(3-) and 1,4-bib ligands. In addition, TGA reveals that the complexes are stable in the range of 293-548 K. Magnetostructural analyses indicate ferromagnetic coupling of J1 = 1.85(3) and J2 = 2.25(4) cm(-1) in and J = 5.76(6) cm(-1) in , whereas magnetic parameters J1 = -2.64(3), J2 = -23.22(19) and J3 = 12.02(5) cm(-1) indicate an alternating magnetic chain (AF/F) in . PMID:27180871

  15. Rayleigh wave phase velocities, shear wave structure and azimuthal anisotropy beneath southern California

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Forsyth, D. W.

    2003-12-01

    We use normal mode Rayleigh wave phase and amplitude data recorded at the TriNet network in southern California to invert for phase velocities at periods from 25 to 143 s. These phase velocities were used to obtain 3-D S-wave velocity structure in the upper mantle. Phase velocities on the Pacific plate side of the plate boundary are systematically higher than on the North American side, suggesting that seismic velocity contrast between these two plates extends to the upper mantle. In the upper mantle, there is a pronounced low velocity anomaly beneath the Long Valley/Mono Lake region, which has not been observed by previous tomographic studies. This low velocity anomaly is consistent with melting extending to the base of the crust beneath this part of the western Basin and Range province, as suggested based on the composition of late Cenozoic basalts (Wang et al., JGT, 2002). There is a high velocity anomaly under the Transverse Range and a slightly slow velocity anomaly under the Salton Trough, both of which have been observed in previous body and/or surface wave tomographic studies. Assuming uniform anisotropic structure in the whole study area, the strength of anisotropy is about 2.5% at all periods. However, the fast direction varies with period. The fast direction of apparent anisotropy is nearly W-E at periods less than 50 s, consistent with the fast polarization axis of SKS splitting measurements in Southern California. At periods larger than 67s, the fast direction changes to NW-SE, subparallel to the plate boundary. This two-layer azimuthal anisotropy structure is in contrast to the one-layer SKS splitting model for southern California, implying that lateral heterogeneity may affect the apparent anisotropy of long-period surface waves. If anisotropy is allowed to vary laterally in our models, we find a minimum in azimuthal anisotropy in the vicinity of the Transverse Range, suggesting possible more vertical alignment of the olivine a-axis in a region of

  16. Crustal shear velocity structure in the Southern Lau Basin constrained by seafloor compliance

    NASA Astrophysics Data System (ADS)

    Zha, Yang; Webb, Spahr C.

    2016-05-01

    Seafloor morphology and crustal structure vary significantly in the Lau back-arc basin, which contains regions of island arc formation, rifting, and seafloor spreading. We analyze seafloor compliance: deformation under long period ocean wave forcing, at 30 ocean bottom seismometers to constrain crustal shear wave velocity structure along and across the Eastern Lau Spreading Center (ELSC). Velocity models obtained through Monte Carlo inversion of compliance data show systematic variation of crustal structure in the basin. Sediment thicknesses range from zero thickness at the ridge axis to 1400 m near the volcanic arc. Sediment thickness increases faster to the east than to the west of the ELSC, suggesting a more abundant source of sediment near the active arc volcanoes. Along the ELSC, upper crustal velocities increase from the south to the north where the ridge has migrated farther away from the volcanic arc front. Along the axial ELSC, compliance analysis did not detect a crustal low-velocity body, indicating less melt in the ELSC crustal accretion zone compared to the fast spreading East Pacific Rise. Average upper crust shear velocities for the older ELSC crust produced when the ridge was near the volcanic arc are 0.5-0.8 km/s slower than crust produced at the present-day northern ELSC, consistent with a more porous extrusive layer. Crust in the western Lau Basin, which although thought to have been produced through extension and rifting of old arc crust, is found to have upper crustal velocities similar to older oceanic crust produced at the ELSC.

  17. Teleseismic tomography of the compressional wave velocity structure beneath the Long Valley region, California

    SciTech Connect

    Dawson, P.B.; Evans, J.R.; Iyer, H.M. )

    1990-07-10

    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 velocity 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-velocity caldera fill contaminates the signal from any midcrustal velocity 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 velocity 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-velocity 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. Velocity 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

  18. Liquid structure and temperature invariance of sound velocity in supercooled Bi melt

    SciTech Connect

    Emuna, M.; Mayo, M.; Makov, G.; Greenberg, Y.; Caspi, E. N.; Yahel, E.; Beuneu, B.

    2014-03-07

    Structural rearrangement of liquid Bi in the vicinity of the melting point has been proposed due to the unique temperature invariant sound velocity observed above the melting temperature, the low symmetry of Bi in the solid phase and the necessity of overheating to achieve supercooling. The existence of this structural rearrangement is examined by measurements on supercooled Bi. The sound velocity of liquid Bi was measured into the supercooled region to high accuracy and it was found to be invariant over a temperature range of ∼60°, from 35° above the melting point to ∼25° into the supercooled region. The structural origin of this phenomenon was explored by neutron diffraction structural measurements in the supercooled temperature range. These measurements indicate a continuous modification of the short range order in the melt. The structure of the liquid is analyzed within a quasi-crystalline model and is found to evolve continuously, similar to other known liquid pnictide systems. The results are discussed in the context of two competing hypotheses proposed to explain properties of liquid Bi near the melting: (i) liquid bismuth undergoes a structural rearrangement slightly above melting and (ii) liquid Bi exhibits a broad maximum in the sound velocity located incidentally at the melting temperature.

  19. Do Invertebrate Activity and Current Velocity Affect Fungal Assemblage Structure in Leaves?

    NASA Astrophysics Data System (ADS)

    Ferreira, Verónica; Graça, Manuel A. S.

    2006-02-01

    In this study we assessed the effect of current velocity and shredder presence, manipulated in artificial channels, on the structure of the fungal assemblage colonizing alder (Alnus glutinosa (L.) Gaertner) leaves incubated in coarse and fine mesh bags. Fungal sporulation rates, cumulative conidial production and number of species of aquatic hyphomycetes were higher in leaves exposed to high rather than to low current velocity. The opposite was observed regarding Simpson's index (D) on the fungal assemblage. Some species of aquatic hyphomycetes were consistently stimulated in high current channels. No effect of shredders or of mesh type was observed.

  20. Lithospheric Velocity Structure of the Anatolain plateau-Caucasus-Caspian Regions

    SciTech Connect

    Gok, R; Mellors, R J; Sandvol, E; Pasyanos, M; Hauk, T; Yetirmishli, G; Teoman, U; Turkelli, N; Godoladze, T; Javakishvirli, Z

    2009-04-15

    Anatolian Plateau-Caucasus-Caspian region is an area of complex structure accompanied by large variations in seismic wave velocities. Despite the complexity of the region little is known about the detailed lithospheric structure. Using data from 29 new broadband seismic stations in the region, a unified velocity structure is developed using teleseismic receiver functions and surface waves. Love and Rayleigh surface waves dispersion curves have been derived from event-based analysis and ambient-noise correlation. We jointly inverted the receiver functions with the surface wave dispersion curves to determine absolute shear wave velocity and important discontinuities such as sedimentary layer, Moho, lithospheric-asthenospheric boundary. We combined these new station results with Eastern Turkey Seismic Experiment results (29 stations). Caspian Sea and Kura basin underlained by one of the thickest sediments in the world. Therefore, short-period surface waves are observed to be very slow. The strong crustal multiples in receiver functions and the slow velocities in upper crust indicate the presence of thick sedimentary unit (up to 20 km). Crustal thickness varies from 34 to 52 km in the region. The thickest crust is in Lesser Caucasus and the thinnest is in the Arabian Plate. The lithospheric mantle in the Greater Caucasus and the Kura depression is faster than the Anatolian Plateau and Lesser Caucasus. This possibly indicates the presence of cold lithosphere. The lower crust is slowest in the northeastern part of the Anatolian Plateau where Holocene volcanoes are located.

  1. Experimental investigation on structures and velocity of liquid jets in a supersonic crossflow

    SciTech Connect

    Wang, Zhen-guo Wu, Liyin; Li, Qinglian; Li, Chun

    2014-09-29

    Particle image velocimetry was applied in the study focusing on the structure and velocity of water jets injected into a Ma = 2.1 crossflow. The instantaneous structures of the jet, including surface waves in the near-injector region and vortices in the far-field, were visualized clearly. Spray velocity increases rapidly to 66% of the mainstream velocity in the region of x/d < 15, owing to the strong gas-liquid interaction near the orifice. By contrast, the velocity grows slowly in the far-field region, where the liquid inside the spray is accelerated mainly by the continuous driven force provided by the mainstream with the gas-liquid shear. The injection and atomization of liquid jet in a supersonic crossflow serves as a foundation of scramjet combustion process, by affecting the combustion efficiency and some other performances. With various forces acting on the liquid jet (Mashayek et al. [AIAA J. 46, 2674–2686 (2008)] and Wang et al. [AIAA J. 50, 1360–1366 (2012)]), the atomization process involves very complex flow physics. These physical processes include strong vortical structures, small-scale wave formation, stripping of small droplets from the jet surface, formations of ligaments, and droplets with a wide range of sizes.

  2. Multi-scale compressional wave velocity structure of the San Gregorio Fault zone

    NASA Astrophysics Data System (ADS)

    Gettemy, G. L.; Tobin, H. J.; Hole, J. A.; Sayed, A. Y.

    2004-03-01

    Understanding fault architecture at multiple scales is crucial to delineate in situ fault zone physical properties and rupture dynamics through modeling and geophysical imaging/monitoring. An exposure of the active large-offset, strike-slip San Gregorio Fault at Moss Beach, CA provides a unique field site to relate the well-mapped fault zone architecture with compressional wave velocity (Vp) structure measured at centimeter to meter scales. Laboratory ultrasonic velocities of fault zone samples, adjusted for fluid-related frequency and structural dispersion, indicate that (i) a seismic velocity reduction of ~30% characterizes the central smectite-rich clay gouge relative to the rocks 100 m away in the relatively undeformed host rocks, and (ii) the across-fault velocity profile trends for the seismic to ultrasonic bandwidth correlate almost exactly to the previously mapped macroscale fault zone structure. These results highlight the value of conducting multiscaled investigations when measuring fault zone properties defined by physical elements at multiple scale lengths.

  3. The anisotropy1 D604N Mutation in the Arabidopsis Cellulose Synthase1 Catalytic Domain Reduces Cell Wall Crystallinity and the Velocity of Cellulose Synthase Complexes1[W][OA

    PubMed Central

    Fujita, Miki; Himmelspach, Regina; Ward, Juliet; Whittington, Angela; Hasenbein, Nortrud; Liu, Christine; Truong, Thy T.; Galway, Moira E.; Mansfield, Shawn D.; Hocart, Charles H.; Wasteneys, Geoffrey O.

    2013-01-01

    Multiple cellulose synthase (CesA) subunits assemble into plasma membrane complexes responsible for cellulose production. In the Arabidopsis (Arabidopsis thaliana) model system, we identified a novel D604N missense mutation, designated anisotropy1 (any1), in the essential primary cell wall CesA1. Most previously identified CesA1 mutants show severe constitutive or conditional phenotypes such as embryo lethality or arrest of cellulose production but any1 plants are viable and produce seeds, thus permitting the study of CesA1 function. The dwarf mutants have reduced anisotropic growth of roots, aerial organs, and trichomes. Interestingly, cellulose microfibrils were disordered only in the epidermal cells of the any1 inflorescence stem, whereas they were transverse to the growth axis in other tissues of the stem and in all elongated cell types of roots and dark-grown hypocotyls. Overall cellulose content was not altered but both cell wall crystallinity and the velocity of cellulose synthase complexes were reduced in any1. We crossed any1 with the temperature-sensitive radial swelling1-1 (rsw1-1) CesA1 mutant and observed partial complementation of the any1 phenotype in the transheterozygotes at rsw1-1’s permissive temperature (21°C) and full complementation by any1 of the conditional rsw1-1 root swelling phenotype at the restrictive temperature (29°C). In rsw1-1 homozygotes at restrictive temperature, a striking dissociation of cellulose synthase complexes from the plasma membrane was accompanied by greatly diminished motility of intracellular cellulose synthase-containing compartments. Neither phenomenon was observed in the any1 rsw1-1 transheterozygotes, suggesting that the proteins encoded by the any1 allele replace those encoded by rsw1-1 at restrictive temperature. PMID:23532584

  4. First high resolution P wave velocity structure beneath Tenerife Island, (Canary Islands, Spain)

    NASA Astrophysics Data System (ADS)

    Garcia-Yeguas, Araceli; Ivan, Koulakov; Ibañez Jesus, M.; Valenti, Sallarès.

    2010-05-01

    3D velocity structure distribution has been imaged for first time using high resolution traveltime seismic tomography of the active volcano of Tenerife Island (Canary Islands, Spain). It is located in the Atlantic Ocean. In this island is situated the Teide stratovolcano (3718 m high) that is part of the Cañadas-Teide-Pico Viejo volcanic complex. Las Cañadas is a caldera system more than 20 kilometers wide where at least four distinct caldera processes have been identified. Evidence for many explosive eruptions in the volcanic complex has been found; the last noticeable explosive eruption (sub-plinean) occurred at Montaña Blanca around 2000 years ago. During the last 300 years, six effusive eruptions have been reported, the last of which took place at Chinyero Volcano on 18 November 1909. In January 2007, a seismic active experiment was carried out as part of the TOM-TEIDEVS project. About 6850 air gun shots were fired on the sea and recorded on a dense local seismic land network consisting of 150 independent (three component) seismic stations. The good quality of the recorded data allowed identifying P-wave arrivals up to offsets of 30-40 km obtaining more than 63000 traveltimes used in the tomographic inversion. The images have been obtained using ATOM-3D code (Koulakov, 2009). This code uses ray bending algorithms in the ray tracing for the forward modelling and in the inversion step it uses gradient methods. The velocity models show a very heterogeneous upper crust that is usual in similar volcanic environment. The tomographic images points out the no-existence of a magmatic chamber near to the surface and below Pico Teide. The ancient Las Cañadas caldera borders are clearly imaged featuring relatively high seismic velocity. Moreover, we have found a big low velocity anomaly in the northwest dorsal of the island. The last eruption took place in 1909 in this area. Furthermore, in the southeast another low velocity anomaly has been imaged. Several resolution

  5. Upper mantle P velocity structure beneath the Baikal Rift from modeling regional seismic data

    NASA Astrophysics Data System (ADS)

    Brazier, Richard A.; Nyblade, Andrew A.

    2003-02-01

    Uppermost mantle P wave velocity structure beneath the Baikal rift and southern margin of the Siberian Platform has been investigated by using a grid search method to model Pnl waveforms from two moderate earthquakes recorded by station TLY at the southwestern end of Lake Baikal. The results yielded a limited number of successful models which indicate the presence of upper mantle P wave velocities beneath the rift axis and the margin of the platform that are 2-5% lower than expected. The magnitude of the velocity anomalies and their location support the presence of a thermal anomaly that extends laterally beyond the rift proper, possibly created by small-scale convection or a plume-like, thermal upwelling.

  6. Upper-ocean velocity structure of Gulf Stream warm-core ring 82B

    NASA Technical Reports Server (NTRS)

    Joyce, T. M.; Kennelly, M. A.

    1985-01-01

    Acoustic-Doppler current profiling of warm-core ring (WCR) 82B revealed changes in the velocity structure over much of the ring's 7-month lifespan. As ring diameter decreased, peak speeds in the high-velocity region decreased from 0.8 m/s in April 1982 to 0.5 m/s in August 1982. Azimuthally averaged velocities revealed the core of WCR 82B to be in near solid-body rotation, with little measurable horizontal divergence at 100 m. In addition, potential vorticity was conserved in the ring core despite interactions with the Gulf Stream and large changes in ring size. Deviations from symmetry in WCR 82B were caused by superposition with the shelf-slope front, small cyclonic eddies, and upper-layer mean flow.

  7. Seismic structure beneath the Gulf of California: a contribution from group velocity measurements

    NASA Astrophysics Data System (ADS)

    Di Luccio, F.; Persaud, P.; Clayton, R. W.

    2014-12-01

    Rayleigh wave group velocity dispersion measurements from local and regional earthquakes are used to interpret the lithospheric structure in the Gulf of California region. We compute group velocity 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 velocity model for the region. Near the Gulf of California rift axis, we found three prominent low shear wave velocity 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-velocity 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-velocity 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-velocity 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.

  8. The lithospheric shear-wave velocity structure of Saudi Arabia: Young volcanism in an old shield

    NASA Astrophysics Data System (ADS)

    Tang, Zheng; Julià, Jordi; Mai, P. Martin

    2016-04-01

    We are utilizing receiver function and surface wave dispersion data to investigate the lithospheric shear-wave velocity 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 velocity-depth profiles by jointly inverting teleseismic P-receiver functions and Rayleigh wave group velocities at 56 broadband stations deployed by the Saudi Geological Survey (SGS). Our results reveal significant lateral variations in crustal thickness, S-velocity, 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-velocities 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-velocity structures, Vp/Vs ratios, and upper-mantle lid velocities support the hypothesis of lateral mantle flow from the Afar and (perhaps

  9. Unveiling the Detailed Density and Velocity Structures of the Protostellar Core B335

    NASA Astrophysics Data System (ADS)

    Kurono, Yasutaka; Saito, Masao; Kamazaki, Takeshi; Morita, Koh-Ichiro; Kawabe, Ryohei

    2013-03-01

    We present an observational study of the protostellar core B335 harboring a low-mass Class 0 source. The observations of the H13CO+(J = 1-0) line emission were carried out using the Nobeyama 45 m telescope and Nobeyama Millimeter Array. Our combined image of the interferometer and single-dish data depicts detailed structures of the dense envelope within the core. We found that the core has a radial density profile of n(r)vpropr -p and a reliable difference in the power-law indices between the outer and inner regions of the core: p ≈ 2 for r >~ 4000 AU and p ≈ 1.5 for r <~ 4000 AU. The dense core shows a slight overall velocity gradient of ~1.0 km s-1 over the scale of 20, 000 AU across the outflow axis. We believe that this velocity gradient represents a solid-body-like rotation of the core. The dense envelope has a quite symmetrical velocity structure with a remarkable line broadening toward the core center, which is especially prominent in the position-velocity diagram across the outflow axis. The model calculations of position-velocity diagrams do a good job of reproducing observational results using the collapse model of an isothermal sphere in which the core has an inner free-fall region and an outer region conserving the conditions at the formation stage of a central stellar object. We derived a central stellar mass of ~0.1 M ⊙, and suggest a small inward velocity, v_{r ≥ r_inf}˜ 0 km s^{-1} in the outer core at >~ 4000 AU. We concluded that our data can be well explained by gravitational collapse with a quasi-static initial condition, such as Shu's model, or by the isothermal collapse of a marginally critical Bonnor-Ebert sphere.

  10. Upper Mantle Seismic Velocity Structure Beneath Eastern Africa and the Origin of Cenozoic Extensional Tectonism (Invited)

    NASA Astrophysics Data System (ADS)

    Nyblade, A.; Julia, J.; Adams, A. N.; Mulibo, G. D.; Tugume, F. A.

    2009-12-01

    The seismic structure of the upper mantle beneath eastern Africa will be reviewed using results from body wave tomography, surface wave tomography, and images of the 410 and 660 km discontinuities. Most of the data used for obtaining these results come from temporary deployments of broadband seismic stations in Ethiopia, Kenya, Uganda and Tanzania over the past decade. The ensemble of seismic results point to a deep-seated low velocity zone beneath the East African rift system that extends from the uppermost mantle, through the upper mantle, and into the mantle transition zone. The low velocity anomaly may also extend through the mantle transition zone and link with the low velocity zone in the lower mantle under southern Africa, commonly referred to as the African Superplume. This is in contrast to southern Africa, were there is little evidence for a pronounced low velocity anomaly in the upper mantle. The existence of a seismic low velocity zone beneath eastern African that extends to depths of more than 500 km supports the possibility that there is a geodynamic connection between the African Superplume and the origin of Cenozoic extensional tectonism in eastern Africa.

  11. One dimensional P wave velocity structure of the crust beneath west Java and accurate hypocentre locations from local earthquake inversion

    SciTech Connect

    Supardiyono; Santosa, Bagus Jaya

    2012-06-20

    A one-dimensional (1-D) velocity model and station corrections for the West Java zone were computed by inverting P-wave arrival times recorded on a local seismic network of 14 stations. A total of 61 local events with a minimum of 6 P-phases, rms 0.56 s and a maximum gap of 299 Degree-Sign were selected. Comparison with previous earthquake locations shows an improvement for the relocated earthquakes. Tests were carried out to verify the robustness of inversion results in order to corroborate the conclusions drawn out from our reasearch. The obtained minimum 1-D velocity model can be used to improve routine earthquake locations and represents a further step toward more detailed seismotectonic studies in this area of West Java.

  12. Seismic structure and ultra-low velocity zones at the base of the Earth’s mantle beneath Southeast Asia

    NASA Astrophysics Data System (ADS)

    Yao, Jiayuan; Wen, Lianxing

    2014-08-01

    We constrain seismic structure and ultra-low velocity zones near the Earth’s core-mantle boundary (CMB) beneath Southeast Asia. We first determine the average shear-velocity structure near the CMB in the region based on travel-time analysis of S, ScS, P and ScP phases. We then map seismic scattering in the lowermost mantle using the PKP precursors observed at the USArray. The inferred average shear-velocity perturbations in the lowermost 200 km of the mantle range from about -6% to 6%, and exhibit a complex geographic distribution of alternate low- and high-velocity patches adjacent to each other, surrounded by a high-velocity anomaly in the south. The inferred strong seismic scatterers exhibit a crescent shape distributed from the South China Sea to the Maluku Islands and coincide with the westernmost low-velocity patch, suggesting that the strong scatterers represent ultra-low velocity zones (ULVZs). We suggest that the seismic structure in the region likely results from a complex interaction between a downwelling and a low-velocity region near the CMB. The downwelling (the high-velocity patches) displaces the low-velocity region into many low-velocity patches and pushes the ULVZs to the edge of the low-velocity region.

  13. Impact of acoustic velocity structure to measurement of ocean bottom crustal deformation

    NASA Astrophysics Data System (ADS)

    Ikuta, R.; Tadokoro, K.; Okuda, T.; Sugimoto, S.; Watanabe, T.; Eto, S.; Ando, M.

    2010-12-01

    We are developing a geodetic method of monitoring crustal deformation under the ocean using kinematic GPS and acoustic ranging. The goal of our research is to achieve sub-centimeter accuracy in measuring oceanic crustal deformation by a very short-time measurement like 10 hours. In this study, we focused on lateral variation of acoustic velocity structure in seawater and introduced an inclined acoustic velocity structure model to improve accuracy of the measurement. We have a few measurement sites along Nankai trough, Japan. In each sites, we deployed a trio of transponders on ocean floor (seafloor benchmark units) within distance comparable with the depth. An ultrasonic signal is generated from a surface vessel drifting over the benchmark unit, which is received and replied by the benchmark unit. In this system, both acoustic velocity structure and the benchmark unit positions were determined simultaneously for the each measurement using a tomographic technique. This tomographic technique was adopted on an assumption that the acoustic velocity structure is horizontally layered and changes only in time, not in space. Ikuta et al., (AGU fall meeting 2009) reported an approach to improve accuracy of benchmark positioning using a new additional assumption. The additional assumption was that the configuration of the transponders trio constituting one benchmark unit does not change. They determined the time evolution of weight center for the fixed transponder triangle between different measurements using all repetitively obtained data sets at once. This is contrasting to the previous method in which each data set for different measurement was solved independently. This assumption worked well in reducing number of unknown parameters. As a result, repeatability of benchmark positioning improved from 5 cm to 3 cm. We conducted numerical experiments synthesizing acoustic travel-time data to evaluate the robustness of this new approach. When acoustic travel-time data is

  14. IRIS and the S-velocity structure of the North American upper mantle

    NASA Astrophysics Data System (ADS)

    van der Lee, S.; Frederiksen, A. W.

    2004-12-01

    Owing to its US-based origin and resulting seismogram holdings the Data Management Center (DMC) of the Incorporated Research Institutions for Seismology (IRIS) has greatly facilitated waveform tomographic studies worldwide, and for North America in particular. We report on one such undertaking, in which nearly one and a half thousand seismograms from the IRIS DMC and the Canadian National Seismic Network have been interactively analyzed and used in a Partitioned Waveform Inversion for a tomographic model for the three-dimensional S-velocity structure of the North American upper mantle. A predecessor (NA95) of this new model is consistent with global tomographic models and revealed additional detail such as an upper-mantle component of subducted Farallon lithosphere, an enigmatic structure for the Wyoming lithosphere, and a V-shaped dent in the new England cratonic lithosphere. These details in turn helped spark additional IRIS activity in the form of further analyses of the data holdings of the DMC and PASSCAL experiments addressing these details. The new model provides relatively high-resolution images of the high-velocity rigid root beneath the Canadian shield and central US, which extends to depths of 200-300 km, the low velocities beneath the tectonically active Cordillera and the continent west of it, which also reach depths of 200-300 km, and details herein such as those mentioned above. Below these structures, high-velocity features in the transition zone are not as steep as but in line with the dipping high-velocity Farallon slab imaged in the lower mantle with tomographic methods that include teleseismic body waves. Increased accuracy in the new model, relative to its predecessors, is largely a result of extending the data base that constrains it. We checked the effects of using sensitivity kernels that cover elliptical areas around the great circles and found that they do not lead to better a posteriori data fits.

  15. Three-dimensional seismic velocity structure of the San Francisco Bay area

    USGS Publications Warehouse

    Hole, J.A.; Brocher, T.M.; Klemperer, S.L.; Parsons, T.; Benz, H.M.; Furlong, K.P.

    2000-01-01

    Seismic travel times from the northern California earthquake catalogue and from the 1991 Bay Area Seismic Imaging Experiment (BASIX) refraction survey were used to obtain a three-dimensional model of the seismic velocity structure of the San Francisco Bay area. Nonlinear tomography was used to simultaneously invert for both velocity and hypocenters. The new hypocenter inversion algorithm uses finite difference travel times and is an extension of an existing velocity tomography algorithm. Numerous inversions were performed with different parameters to test the reliability of the resulting velocity model. Most hypocenters were relocated 12 km under the Sacramento River Delta, 6 km beneath Livermore Valley, 5 km beneath the Santa Clara Valley, and 4 km beneath eastern San Pablo Bay. The Great Valley Sequence east of San Francisco Bay is 4-6 km thick. A relatively high velocity body exists in the upper 10 km beneath the Sonoma volcanic field, but no evidence for a large intrusion or magma chamber exists in the crust under The Geysers or the Clear Lake volcanic center. Lateral velocity contrasts indicate that the major strike-slip faults extend subvertically beneath their surface locations through most of the crust. Strong lateral velocity contrasts of 0.3-0.6 km/s are observed across the San Andreas Fault in the middle crust and across the Hayward, Rogers Creek, Calaveras, and Greenville Faults at shallow depth. Weaker velocity contrasts (0.1-0.3 km/s) exist across the San Andreas, Hayward, and Rogers Creek Faults at all other depths. Low spatial resolution evidence in the lower crust suggests that the top of high-velocity mafic rocks gets deeper from west to east and may be offset under the major faults. The data suggest that the major strike-slip faults extend subvertically through the middle and perhaps the lower crust and juxtapose differing lithology due to accumulated strike-slip motion. The extent and physical properties of the major geologic units as

  16. 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.

  17. Structural Integrity Of Low-Velocity Impacted C/SIC Ceramic Matrix Composites

    NASA Astrophysics Data System (ADS)

    Knoche, R.; Drose, A.

    2012-07-01

    Carbon fibre reinforced silicon carbide (C/SiC) ceramic matrix composites (CMC) are most favourable for thermal protection systems & hot structures in re-entry vehicles since they offer superior heat resistance, high specific strength as well as a low coefficient of temperature expansion (CTE). To ensure the structural integrity of these C/SiC structures and thus mission safety all potential degradation effects during manufacturing and lifetime have to be considered. One of the most probable defects which may harm the structural integrity significantly can be caused by low-velocity impacts (LVI) which may occur during transportation and integration by e.g. dropping of tools. Thus the present study focuses on the residual mechanical and thermo-mechanical performance of C/SiC composites after being exposed to a low-velocity impact in terms of initial and residual mechanical performance, changes in microstructure, as well as thermo-mechanical performance through exposing specimens to multiple experimentally simulated re-entries. The results reveal the impact characteristics and damage mechanisms of C/SiC CMC exposed to a low-velocity impact and evidence the functional reliability as well as the damage tolerance of the C/SiC material investigated.

  18. Complete regional waveform modeling to estimate seismic velocity structure and source parameters for CTBT monitoring

    SciTech Connect

    Bredbeck, T; Rodgers, A; Walter, W

    1999-07-23

    The velocity structures and source parameters estimated by waveform modeling provide valuable information for CTBT monitoring. The inferred crustal and uppermost mantle structures advance understanding of tectonics and guides regionalization for event location and identification efforts. Estimation of source parameters such as seismic moment, depth and mechanism (whether earthquake, explosion or collapse) is crucial to event identification. In this paper we briefly outline some of the waveform modeling research for CTBT monitoring performed in the last year. In the future we will estimate structure for new regions by modeling waveforms of large well-observed events along additional paths. Of particular interest will be the estimation of velocity structure in aseismic regions such as most of Africa and the Former Soviet Union. Our previous work on aseismic regions in the Middle East, north Africa and south Asia give us confidence to proceed with our current methods. Using the inferred velocity models we plan to estimate source parameters for smaller events. It is especially important to obtain seismic moments of earthquakes for use in applying the Magnitude-Distance Amplitude Correction (MDAC; Taylor et al., 1999) to regional body-wave amplitudes for discrimination and calibrating the coda-based magnitude scales.

  19. Multi-Scale Imaging of the Fault Zone Velocity Structure: Double-difference Tomography, Inversion of Fault Zone Headwaves, and Fault Zone Sensitivity Kernels

    NASA Astrophysics Data System (ADS)

    Allam, Amir A.

    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 tomography to the San Jacinto fault zone, invert for velocity 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 tomography uses the arrival times of P and S waves to invert simultaneously for compressional velocity, shear wave velocity, 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 velocity results show zones of low-velocity and high Vp/Vs ratios associated with various fault strands and sedimentary basins, along with clear velocity contrasts across the San Jacinto. While both features are limited to the upper 10km, the low velocity zones generally have higher amplitude and broader distribution in geometrically complex areas, while the velocity 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

  20. Double-Layer ULVZ Shear Velocity Structure Imaged With Stacked ScS Data

    NASA Astrophysics Data System (ADS)

    Avants, M.; Lay, T.; Garnero, E.

    2005-12-01

    The ultra-low velocity zone (ULVZ) has been imaged as a thin (5-40 km thick) layer just above the core-mantle boundary (CMB), with P and S velocities reduced by up to 10 and 30%, respectively. Accurate characterization of the ULVZ is important, as it may relate to, for example, the role of the lowermost mantle in Earth's evolution, mantle and outer core convection, the geodynamo, and heat flux into the mantle. A direct measurement of S velocity in the ULVZ, independent of the P-wave velocity, is needed to better constrain ULVZ properties. We establish tangential component ScS data as a new probe of ULVZ shear velocity properties. Lowermost mantle structure beneath the central Pacific is studied using data from 38 deep focus Tonga-Fiji earthquakes, recorded by dense broadband seismic networks in western North America. Our data set consists of 442 instrument-deconvolved displacement seismograms, which are additionally deconvolved by average source-time functions (source wavelets) constructed for each event, in order to equalize the signals and to extend the signal bandwidth to high frequencies. The resulting traces are used in a double-beam stacking approach to enhance the signal-to-noise ratio of any coherent precursory reflections of the wide-angle transverse component ScS data, which should be detectable if ULVZ structure is present beneath our central Pacific study region. Our stacks reveal two distinct ScS precursors, which indicate a double layer ULVZ structure in this region. Both layers show strong lateral variations in shear velocity reduction (dVs) and thickness. The deeper ULVZ layer is well modeled by dVs drops varying from 3.3-7.4% (relative to PREM) with a thickness range of 24-30 km. The overlying layer has dVs reductions from 0.8-2.0% (relative to PREM), and 60-86 km thickness. Thus the imaged 2-layered ULVZ has dVs reductions far milder than previous studies (10-30%), which have argued for a partial melt origin to the ULVZ. Finer subdivisions of data

  1. Shear wave velocity structure of the Anatolian Plate: anomalously slow crust in southwestern Turkey

    NASA Astrophysics Data System (ADS)

    Delph, Jonathan R.; Biryol, C. Berk; Beck, Susan L.; Zandt, George; Ward, Kevin M.

    2015-07-01

    The Anatolian Plate is composed of different lithospheric blocks and ribbon continents amalgamated during the closure of the Paleotethys Ocean and Neotethys Ocean along a subduction margin. Using ambient noise tomography, we investigate the crustal and uppermost mantle shear wave velocity structure of the Anatolian Plate. A total of 215 broad-band seismic stations were used spanning 7 yr of recording to compute 13 778 cross-correlations and obtain Rayleigh wave dispersion measurements for periods between 8 and 40 s. We then perform a shear wave inversion to calculate the seismic velocity structure of the crust and uppermost mantle. Our results show that the overall crustal shear wave velocities of the Anatolian crust are low (˜3.4 km s-1), indicative of a felsic overall composition. We find that prominent lateral seismic velocity gradients correlate with Tethyan suture zones, supporting the idea that the neotectonic structures of Turkey are exploiting the lithospheric weaknesses associated with the amalgamation of Anatolia. Anomalously slow shear wave velocities (˜3.15 km s-1 at 25 km) are located in the western limb of the Isparta Angle in southwestern Turkey. In the upper crust, we find that these low shear wave velocities correlate well with the projected location of a carbonate platform unit (Bey Dağlari) beneath the Lycian Nappe complex. In the lower crust and upper mantle of this region, we propose that the anomalously slow velocities are due to the introduction of aqueous fluids related to the underplating of accretionary material from the underthrusting of a buoyant, attenuated continental fragment similar to the Eratosthenes seamount. We suggest that this fragment controlled the location of the formation of the Subduction-Transform Edge Propagator fault in the eastern Aegean Sea during rapid slab rollback of the Aegean Arc in early Miocene times. Lastly, we observe that the uppermost mantle beneath continental Anatolia is generally slow (˜4.2 km s-1

  2. Seismic velocity structure in the western part of Nankai subduction zone

    NASA Astrophysics Data System (ADS)

    Yamamoto, Y.; Obana, K.; Takahashi, T.; Nakanishi, A.; Kodaira, S.; Kaneda, Y.

    2011-12-01

    In the Nankai Trough, three major seismogenic zones of megathrust earthquake exist (Tokai, Tonankai and Nankai earthquake regions). The Hyuga-nada region was distinguished from these seismogenic zones because of the lack of megathrust earthquake. However, recent studies show the possibility of simultaneous rupture of the Nankai and Hyuga-nada segments was also pointed out [e.g., Furumura et al, 2010 JGR]. Because seismic velocity structure is one of the useful and basic information for understanding the possibility of seismic linkage of Nankai and Hyuga-nada segments, Japan Agency for Marine-Earth Science and Technology has been carried out a series of wide-angle active source surveys and local seismic observations among the three major seismogenic zones and Hyuga-nada segment from 2008, as a part of "Research concerning Interaction Between the Tokai, Tonankai and Nankai Earthquakes' funded by Ministry of Education, Culture, Sports, Science and Technology, Japan". We are performing two set of three-dimensional seismic velocity tomographic inversions, one is in the Hyuga-nada region and the other is western part of the coseismic rupture area of 1946 Nankai earthquake, to discuss the relationship between the structural heterogeneities and the location of segment boundary between Hyuga-nada and Nankai segment. For the analysis of Hyuga-nada segment, we used both active and passive source data. The obtained velocity model clearly showed the subducted Kyushu-Palau ridge as thick low velocity Philippine Sea slab in the southwestern part. Our velocity image also indicates that "the thin oceanic crust zone" located between Nankai segment and Kyushu-Palau Ridge segment, founded by Nakanishi et al [2010, AGU] by analyzing of the active source survey, continuously exists from trough axis to near the coastline of Kyushu Island. The overriding plate just above the coseismic slip area of 1968 Hyuga-nada earthquake shows relatively high velocity. Although the tomographic study in

  3. Role of microscopic properties in the evolution of large scale internal structure in the UltraLow Velocity Zones

    NASA Astrophysics Data System (ADS)

    Baruah, Amiya; Hier-Majumder, Saswata

    2016-04-01

    Seismic observations at the Earth's core -mantle boundary show regions marked by anomalously low shear (30%) and compressional wave (10%) speeds, called UltraLow Velocity Zones (ULVZs). These ULVZs are characterized by their low topography (few tens of km above the core-mantle boundary) spanning few thousand of km in length and possible presence of partial melting, and a 8-10% increase in density compared to the surrounding mantle materials and low viscosity. Current understanding attributes presence of partial melt in the ULVZs for its low viscosity. Recent studies have shown that such rheology can be explained by the presence of Fe-rich phases, which does not require the presence of partial melt in the system. Ascent of such a dense, low viscosity material from the core-mantle boundary is mechanically difficult. Earlier studies have shown mantle convection as the guiding factor in controlling the flow and geometry of the ULVZs, without any quantification about their internal structure. There have been some recent studies in 1D and 2D, which models ULVZs as multiphase system. However, there is no numerical model that shows the evolution of ULVZs in 3D and development of the internal structures within these zones. Rock deformation experiments and theoretical analysis explicitly show that the melt-volume fraction and the dihedral angle have strong effect on the melt topology and seismic properties in partially molten systems like ULVZs. Employing these well constrained microstructural properties, the present study aims to explore the complex three-dimensional internal structure within the patchy ULVZs geometry. Our two-phase finite element model shows that the partial melt segregate within the ULVZ as a function of strong deformation in the matrix.

  4. Measurement of flow velocity profiles in tank structures using the prototype device OCM Pro LR.

    PubMed

    Klepiszewski, K; Teufel, M; Seiffert, S; Henry, E

    2011-01-01

    Generally, studies investigating the treatment efficiency of tank structures for storm water or waste water treatment observe pollutant flows in connection with conditions of hydraulic loading. Further investigations evaluate internal processes in tank structures using computational fluid dynamic (CFD) modelling or lab scale tests. As flow paths inside of tank structures have a considerable influence on the treatment efficiency, flow velocity profile (FVP) measurements can provide a possibility to calibrate CFD models and contribute to a better understanding of pollutant transport processes in these structures. This study focuses on tests carried out with the prototype FVP measurement device OCM Pro LR by NIVUS in a sedimentation tank with combined sewer overflow (CSO) situated in Petange, Luxembourg. The OCM Pro LR measurement system analyses the echo of ultrasonic signals of different flow depths to get a detailed FVP. A comparison of flow velocity measured by OCM Pro LR with a vane measurement showed good conformity. The FVPs measured by OCM Pro LR point out shortcut flows within the tank structure during CSO events, which could cause a reduction of the cleaning efficiency of the structure. The results prove the applicability of FVP measurements in large-scale structures. PMID:22053484

  5. Seismic velocity structure and microearthquake source properties at The Geysers, California, geothermal area

    SciTech Connect

    O'Connell, D.R.

    1986-12-01

    The method of progressive hypocenter-velocity inversion has been extended to incorporate S-wave arrival time data and to estimate S-wave velocities in addition to P-wave velocities. S-wave data to progressive inversion does not completely eliminate hypocenter-velocity tradeoffs, but they are substantially reduced. Results of a P and S-wave progressive hypocenter-velocity inversion at The Geysers show that the top of the steam reservoir is clearly defined by a large decrease of V/sub p//V/sub s/ at the condensation zone-production zone contact. The depth interval of maximum steam production coincides with minimum observed V/sub p//V/sub s/, and V/sub p//V/sub s/ increses below the shallow primary production zone suggesting that reservoir rock becomes more fluid saturated. The moment tensor inversion method was applied to three microearthquakes at The Geysers. Estimated principal stress orientations were comparable to those estimated using P-wave firstmotions as constraints. Well constrained principal stress orientations were obtained for one event for which the 17 P-first motions could not distinguish between normal-slip and strike-slip mechanisms. The moment tensor estimates of principal stress orientations were obtained using far fewer stations than required for first-motion focal mechanism solutions. The three focal mechanisms obtained here support the hypothesis that focal mechanisms are a function of depth at The Geysers. Progressive inversion as developed here and the moment tensor inversion method provide a complete approach for determining earthquake locations, P and S-wave velocity structure, and earthquake source mechanisms.

  6. 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.

  7. High-Resolution Inverse-Based Determination of Seismic-Velocity Structure in Basins

    NASA Astrophysics Data System (ADS)

    Akcelik, V.; Bielak, J.; Epanomeritakis, I.; Ghattas, O.

    2004-12-01

    Starting with the pioneering work of Aki, Christoffersson, and Husebye in 1976, there has been an increasing interest in developing inversion techniques for determining the three-dimensional crustal velocity structure in seismic regions. In this paper we describe a methodology that capitalizes on recent advances in optimization methods to adapt, extend, and refine powerful nonlinear Newton-Krylov adjoint-based inverse wave propagation algorithms to two- and three-dimensional velocity structure and kinematic source inversion problems. We present results of high resolution models for two-dimensional sedimentary valleys undergoing antiplane motion, and three dimensional acoustic approximations of models of the San Fernando Valley using parallel scalable inversion algorithms that overcome many of the difficulties particular to inverse heterogeneous wave propagation problems.

  8. Peeling linear inversion of upper mantle velocity structure with receiver functions

    NASA Astrophysics Data System (ADS)

    Shen, Xuzhang; Zhou, Huilan

    2012-02-01

    A peeling linear inversion method is presented to study the upper mantle (from Moho to 800 km depth) velocity structures with receiver functions. The influences of the crustal and upper mantle velocity ratio error on the inversion results are analyzed, and three valid measures are taken for its reduction. This method is tested with the IASP91 and the PREM models, and the upper mantle structures beneath the stations GTA, LZH, and AXX in northwestern China are then inverted. The results indicate that this inversion method is feasible to quantify upper mantle discontinuities, besides the discontinuities between 3 h M ( h M denotes the depth of Moho) and 5 h M due to the interference of multiples from Moho. Smoothing is used to overcome possible false discontinuities from the multiples and ensure the stability of the inversion results, but the detailed information on the depth range between 3 h M and 5 h M is sacrificed.

  9. Design and test of a superconducting structure for high-velocity ions

    SciTech Connect

    Delayen, J.R.; Kennedy, W.L.; Roche, C.T.

    1992-01-01

    Following the successful development of a niobium coaxial half-wave structure we have designed, built and tested a new half-wave geometry: the spoke resonator. This geometry is better suited for high frequency resonators and for the acceleration of high velocity ions. The prototype cavity is a 2-gap structure resonating at 855 MHz, and optimized for particle velocity of 0.30 c. It is easier to manufacture than the coaxial half-wave resonator and the geometry can be straightforwardly extended to multigap designs. Rf-tests have been performed on this cavity both prior to and after high temperature annealing. An accelerating gradient of 7.2 MV/m (cw) and 7.8 MV/m (pulsed) was observed at 4.2 K. After annealing, a low power Q{sub 0} of 1.2 {times}10{sup 8} was observed with small Q degradation due to field emission at high accelerating fields.

  10. Design and test of a superconducting structure for high-velocity ions

    SciTech Connect

    Delayen, J.R.; Kennedy, W.L.; Roche, C.T.

    1992-10-01

    Following the successful development of a niobium coaxial half-wave structure we have designed, built and tested a new half-wave geometry: the spoke resonator. This geometry is better suited for high frequency resonators and for the acceleration of high velocity ions. The prototype cavity is a 2-gap structure resonating at 855 MHz, and optimized for particle velocity of 0.30 c. It is easier to manufacture than the coaxial half-wave resonator and the geometry can be straightforwardly extended to multigap designs. Rf-tests have been performed on this cavity both prior to and after high temperature annealing. An accelerating gradient of 7.2 MV/m (cw) and 7.8 MV/m (pulsed) was observed at 4.2 K. After annealing, a low power Q{sub 0} of 1.2 {times}10{sup 8} was observed with small Q degradation due to field emission at high accelerating fields.

  11. 3-D Crustal Velocity Structure Across the Vrancea Zone in Romania, Derived From Seismic Data

    NASA Astrophysics Data System (ADS)

    Landes, M.; Hauser, F.; Popa, M.

    2002-12-01

    The Vrancea zone in the south-eastern Carpathians is one of the most active seismic zones in Europe. In order to study the crustal and upper-mantle structure in this region, two seismic refraction/wide-angle reflection experiments were carried out in 1999 and 2001. The 1999 campaign comprised a 320 km long N-S profile and a 80 km long transverse profile (E-W). All shots were recorded simultaneously on both profiles. The profile conducted in 2001 extended in E-W direction from the Hungarian border across the Vrancea zone to the Black Sea. We present an application of a 3-D refraction and reflection tomography algorithm (Hole 1992, 1995), elaborating the crustal velocity and interface structure within a 115 x 235 km wide region around the Vrancea zone. In order to enhance the model resolution, first arrival data from local earthquakes of the CALIXTO-99 teleseismic project were also included. The results indicate a high-velocity structure beneath the northern part of the Vrancea zone extending from shallow levels to depths of about 11 km. This structure may be related to the Trotus and Capidava-Ovidiu faults, which converge to the north of it. The high-velocity region is surrounded by the lower velocity Focsani and Brasov basins. The sedimentary succession beneath the southern part of the model extends to 18 km depth, while in the north sediment thickness varies between 10 and 15 km. Further results of the interface modelling of prominent reflections show that the mid-crustal and Moho interfaces shallow northwards from 30 km to 22 km and from 42 km to 38 km, respectively. This correlates well with previous results of Hauser et al. (2001).

  12. 3-D Isotropic and Anisotropic S-velocity Structure in the North American Upper Mantle

    NASA Astrophysics Data System (ADS)

    Yuan, H.; Marone, F.; Romanowicz, B.; Abt, D.; Fischer, K.

    2008-12-01

    The tectonic diversity of the North American continent has led to a number of geological, tectonic and geodynamical models, many of which can be better tested with high resolution 3-d tomographic models of the isotropic and anisotropic mantle structure of the continent. In the framework of non-linear asymptotic coupling theory (NACT), we recently developed tools to invert long period seismic waveforms combined with SKS splitting data, for both isotropic and radial and azimuthal anisotropic S-wave velocity structure in the upper mantle at the continental scale (Marone et al., 2007; Marone and Romanowicz, 2007). Striking differences in both isotropic and anisotropic velocity structure were observed: beneath the high velocity stable cratonic region a distinct two-layer anisotropic domain is present, with the bottom layer fast axis direction aligned with the absolute plate motion, and a shallower lithospheric layer with north pointing fast axis most likely showing records of past tectonic history; under the active western US the direction of tomographically inferred anisotropy is stable with depth and compatible with the absolute plate motion direction. Here we present an updated model which includes nearly five more years of data, including data from newly operative USArray stations, and a somewhat more extended frequency band. Our new model confirms our previous results, and reveals greater yet complex details of the anisotropic velocity structure beneath the western U.S.. We also show initial results of incorporating constraints on the depth to the lithosphere-asthenosphere boundary (LAB) using teleseismic receiver functions. We discuss the different anisotropic domains resolved both laterally and in depth, in the context of tectonic history of the north American continent.

  13. Anisotropic Shear-wave Velocity Structure of East Asian Upper Mantle from Waveform Tomography

    NASA Astrophysics Data System (ADS)

    Chong, J.; Yuan, H.; French, S. W.; Romanowicz, B. A.; Ni, S.

    2012-12-01

    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 tomography to image 3D isotropic, radially and azimuthally anisotropic upper mantle shear velocity 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 velocity 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 velocity in the upper mantle. Lower velocity 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 velocity 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

  14. A 3-D crustal velocity structure across the southeastern Carpathians of Romania

    NASA Astrophysics Data System (ADS)

    Landes, M.; Hauser, F.; Ritter, J. R. R.; Fielitz, W.; Popa, M.

    2003-04-01

    The Vrancea zone in the southeastern Carpathians is one of the most active seismic regions in Europe. In order to study the crustal and upper-mantle structure in this region, two seismic refraction experiments were carried out in 1999 and 2001. The 1999 campaign comprised a 320 km long N-S profile and a 80 km long transverse profile. All shots were recorded simultaneously on both profiles. The profile conducted in 2001 extended in E-W direction from the Hungarian border across the Vrancea zone to the Black Sea. A first ever 3-D crustal velocity model of the south-eastern Carpathians within a 115 x 235 km wide region around the Vrancea zone is presented. This model was generated by application of a 3-D refraction and reflection tomography algorithm (Hole 1992, 1995). In order to enhance the model resolution, first arrival data from local earthquakes were also included. The results indicate a high-velocity structure above the Vrancea zone extending from shallow levels to depths of about 11 km. A possible relation to the Trotus and Capidava-Ovidiu faults, which converge to the north of it, is deemed unlikely. However,the existence of the outstanding high velocities may be explained by crystalline basement thrust onto the sub-Carpathian nappes. The high-velocity region is surrounded by the lower velocity Focsani and Brasov basins. The sedimentary succession beneath the southern part of the model area extends to 18 km depth, while in the north sediment thickness varies between 10 and 15 km. Further results of the interface modelling of prominent reflections show that the mid-crustal and Moho interfaces shallow northwards from 30 km to 22 km and from 42 km to 38 km, respectively.

  15. P-Wave Velocity Structure beneath Eastern Eurasia from Finite Frequency Seismic Tomography

    NASA Astrophysics Data System (ADS)

    Yang, T.; Shen, Y.; Yang, X.

    2006-05-01

    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 Tomography (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 velocity 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 velocity models obtained in previous tomographic studies. A more complete dataset will further improve the resolution of the velocity structure beneath eastern Eurasia.

  16. Connections between density, wall-normal velocity, and coherent structure in a heated turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Saxton-Fox, Theresa; Gordeyev, Stanislav; Smith, Adam; McKeon, Beverley

    2015-11-01

    Strong density gradients associated with turbulent structure were measured in a mildly heated turbulent boundary layer using an optical sensor (Malley probe). The Malley probe measured index of refraction gradients integrated along the wall-normal direction, which, due to the proportionality of index of refraction and density in air, was equivalently an integral measure of density gradients. The integral output was observed to be dominated by strong, localized density gradients. Conditional averaging and Pearson correlations identified connections between the streamwise gradient of density and the streamwise gradient of wall-normal velocity. The trends were suggestive of a process of pick-up and transport of heat away from the wall. Additionally, by considering the density field as a passive marker of structure, the role of the wall-normal velocity in shaping turbulent structure in a sheared flow was examined. Connections were developed between sharp gradients in the density and flow fields and strong vertical velocity fluctuations. This research is made possible by the Department of Defense through the National Defense & Engineering Graduate Fellowship (NDSEG) Program and by the Air Force Office of Scientific Research Grant # FA9550-12-1-0060.

  17. Detailed seismic velocity structure beneath the Hokkaido corner, NE Japan: Collision process of the forearc sliver

    NASA Astrophysics Data System (ADS)

    Kita, S.; Hasegawa, A.; Okada, T.; Nakajima, J.; Matsuzawa, T.; Katsumata, K.

    2010-12-01

    1. Introduction In south-eastern Hokkaido, the Kuril forearc sliver is colliding with the northeastern Japan arc due to the oblique subduction of the Pacific plate. This collision causes the formation of the Hidaka mountain range since the late Miocene (Kimura, 1986) and delamination of the lower-crust materials of the Kuril forearc sliver, which would be expected to descend into the mantle wedge below (e.g., Ito 2000; Ito and Iwasaki, 2002). In this study, we precisely investigated the three-dimensional seismic velocity structure beneath the Hokkaido corner to examine the collision of two forearcs in this area by using both of data from a dense temporary seismic network deployed in this area (Katsumata et al. [2006]) and those from the Kiban observation network, which covers the entire Japanese Islands with a station separation of 15-20 km. 2. Data and method The double-difference tomography method (Zhang and Thurber, 2003; 2006) was applied to a large number of arrival time data of 201,527 for P-waves and 150,963 for S-waves that were recorded at 125 stations from 10,971 earthquakes that occurred from 1999 to 2010. Grid intervals were set at 10 km in the along-arc direction, 12.5 km perpendicular to it, and 5-10 km in the vertical direction. 3. Results and discussion Inhomogeneous seismic velocity structure was clearly imaged in the Hokkaido corner at depths of 0-120 km. A high-velocity anomaly of P- and S- waves with a volume of 20 km x 90 km x 35km was detected just beneath the main zone of the Hidaka metamorphic belt at depths of 0-35 km. This high-velocity anomaly is continuously distributed from the depths of the mantle wedge to the surface. The western edge of the anomaly exactly corresponds to the Hidaka main thrust (HMT) at the surface. The highest velocity value in the anomaly corresponds to those of the uppermost mantle material (e.g. peridotite). The location of them at depths of 0-35km is also consistent with that of the Horoman-Peridotite belt, which

  18. Seismic Velocity Structure and Seismotectonics of the Hayward Fault System, East San Francisco Bay, California

    NASA Astrophysics Data System (ADS)

    Hardebeck, J. L.; Michael, A. J.; Brocher, T. M.

    2004-12-01

    The Hayward Fault is considered the most likely fault in the San Francisco Bay Area, California, to have a major earthquake in the next 30 years, posing a serious earthquake risk to more than 2 million people. In order to accurately evaluate various earthquake scenarios for this fault, it is important to understand its structure, kinematics, and physical properties. We present a new seismological study of the Hayward Fault system, including a new 3D seismic velocity model for the East San Francisco Bay, relocated earthquake hypocenters, and improved focal mechanisms. We use these new constraints on structure and seismicity to study the geometry and kinematics of the Hayward Fault. The new East Bay 3D tomography model, based on travel times from earthquakes and controlled-source experiments, reveals a clear velocity contrast across the Hayward Fault. In the upper 10 km, the P-wave velocity in the Franciscan rocks to the west are up to 0.8 km/s faster than in the Great Valley sequence rocks to the east. Below 10 km, where Franciscan rocks are thought to be present on both sides of the fault, there is negligible contrast. The observed P-wave velocities are comparable with velocities observed in deep boreholes in the East Bay. Anomalously low S-wave velocities are observed east of the Hayward Fault, near the Livermore Basin. We relocated more than 20,000 East Bay earthquakes, 1967-2004, with the 3D model. The events illuminate the Hayward Fault at depth, shifting from near-vertical in the north to steeply east-dipping in the south. New focal mechanisms were also computed, using take-off angles from ray tracing in the 3D seismic velocity model. Previous authors found heterogeneous focal mechanisms along the Hayward Fault near San Leandro, interpreted it as a zone of complex fracturing, and speculated that San Leandro marks a probable boundary for major Hayward Fault earthquakes. We find, however, that our high-quality focal mechanisms for events all along the Hayward

  19. Crustal velocity structure beneath Saurashtra, NW India, through waveform modeling: Implications for magmatic underplating

    NASA Astrophysics Data System (ADS)

    Praveen Kumar, K. A.; Mohan, G.

    2014-01-01

    The Saurashtra peninsula in the northwestern segment of the Deccan volcanic province of India, is characterized by several high gravity and magnetic anomalies, which correspond to mafic crustal intrusions. This study attempts to quantify the alterations to the crust caused by the Deccan volcanism, by estimating the crustal Poisson's ratio, shear wave velocity (Vs) structure and the shear velocity contrast across the Moho, through teleseismic waveform modeling. The P receiver functions (RFs) for six broadband seismic stations were constructed using about 575 high quality (S/N ≥ 2.5) teleseismic waveforms of earthquakes (M ≥ 5.5) recorded during the period 2004-2010. The moveout corrected RF summation stacks were inverted using the Neighborhood algorithm (NA) to estimate the shear velocity structure beneath each station. The crustal thickness is estimated to range from 38 km in western Saurashtra to 33 km close to the southern extension of the Cambay rift. A low velocity zone possibly corresponding to sub-basaltic sediments is detected beneath all the stations. The average crustal Vs and Poisson's ratio are estimated to be 3.68 km/s and 0.276 respectively. The crustal Poisson's ratio indicates an intermediate to mafic composition for the crust. Modeling reveals a relatively high velocity lower crust with an average Vs ≈ 3.88 ± 0.1 km/s which is consistent with the high Vp ≈ 7.1 km/s reported for this region through seismic refraction and wide angle reflection studies, overlying a relatively low velocity (Vs ≈ 4.4 ± 0.1 km/s) upper mantle. The shear velocity contrasts across the Moho, derived from the amplitudes of the P-to-s (Pms) conversions from the Moho range from 0.08 to 0.17 which are much smaller than those (>0.20) observed across the Indian shield, implying a gradational Moho due to underplating. This study reveals that the crust beneath Saurashtra is distinctly different from that of the Archean Indian shield largely due to significant alterations

  20. SIMULATIONS OF EARLY BARYONIC STRUCTURE FORMATION WITH STREAM VELOCITY. II. THE GAS FRACTION

    SciTech Connect

    Naoz, Smadar; Yoshida, Naoki; Gnedin, Nickolay Y.

    2013-01-20

    Understanding the gas content of high-redshift halos is crucial for studying the formation of the first generation of galaxies and reionization. Recently, Tseliakhovich and Hirata showed that the relative 'stream' velocity between the dark matter and baryons at the time of recombination-formally a second-order effect, but an unusually large one-can influence the later structure formation history of the universe. We quantify the effect of the stream velocity on the so-called characteristic mass-the minimum mass of a dark matter halo capable of retaining most of its baryons throughout its formation epoch-using three different high-resolution sets of cosmological simulations (with separate transfer functions for baryons and dark matter) that vary in box size, particle number, and the value of the relative velocity between the dark matter and baryons. In order to understand this effect theoretically, we generalize the linear theory filtering mass to properly account for the difference between the dark matter and baryonic density fluctuation evolution induced by the stream velocity. We show that the new filtering mass provides an accurate estimate for the characteristic mass, while other theoretical ansatzes for the characteristic mass are substantially less precise.

  1. The lithospheric shear-wave velocity structure of Saudi Arabia: Young volcanism in an old shield

    NASA Astrophysics Data System (ADS)

    Tang, Zheng; Julià, Jordi; Zahran, Hani; Mai, P. Martin

    2016-06-01

    We investigate the lithospheric shear-wave velocity structure of Saudi Arabia by conducting H-κ stacking analysis and jointly inverting teleseismic P-receiver functions and fundamental-mode Rayleigh wave group velocities at 56 broadband stations deployed by the Saudi Geological Survey (SGS). The study region, the Arabian plate, is traditionally divided into the western Arabian shield and the eastern Arabian platform: The Arabian shield itself is a complicated mélange of crustal material, composed of several Proterozoic terrains separated by ophiolite-bearing suture zones and dotted by outcropping Cenozoic volcanic rocks (locally known as harrats). The Arabian platform is primarily covered by 8 to 10 km of Paleozoic, Mesozoic and Cenozoic sedimentary rocks. Our results reveal high Vp/Vs ratios in the region of Harrat Lunayyir, which are interpreted as solidified magma intrusions from old magmatic episodes in the shield. Our results also indicate slow velocities and large upper mantle lid temperatures below the southern and northern tips of the Arabian shield, when compared with the values obtained for the central shield. We argue that our inferred patterns of lid velocity and temperature are due to heating by thermal conduction from the Afar plume (and, possibly, the Jordan plume), and that volcanism in western Arabia may result from small-scale adiabatic ascent of magma diapirs.

  2. Compressive strength evaluation of structural lightweight concrete by non-destructive ultrasonic pulse velocity method.

    PubMed

    Bogas, J Alexandre; Gomes, M Glória; Gomes, Augusto

    2013-07-01

    In this paper the compressive strength of a wide range of structural lightweight aggregate concrete mixes is evaluated by the non-destructive ultrasonic pulse velocity method. This study involves about 84 different compositions tested between 3 and 180 days for compressive strengths ranging from about 30 to 80 MPa. The influence of several factors on the relation between the ultrasonic pulse velocity and compressive strength is examined. These factors include the cement type and content, amount of water, type of admixture, initial wetting conditions, type and volume of aggregate and the partial replacement of normal weight coarse and fine aggregates by lightweight aggregates. It is found that lightweight and normal weight concretes are affected differently by mix design parameters. In addition, the prediction of the concrete's compressive strength by means of the non-destructive ultrasonic pulse velocity test is studied. Based on the dependence of the ultrasonic pulse velocity on the density and elasticity of concrete, a simplified expression is proposed to estimate the compressive strength, regardless the type of concrete and its composition. More than 200 results for different types of aggregates and concrete compositions were analyzed and high correlation coefficients were obtained. PMID:23351273

  3. Empirical transfer functions: Application to determination of outermost core velocity structure using SmKS phases

    NASA Astrophysics Data System (ADS)

    Alexandrakis, Catherine; Eaton, David W.

    2007-11-01

    SmKS waves provide good resolution of outer-core velocity structure, but are affected by heterogeneity in the D'' region. We have developed an Empirical Transfer Function (ETF) technique that transforms a reference pulse (here, SmKS) into a target waveform (SKKS) by: (1) time-windowing the respective pulses, (2) applying Wiener deconvolution, and (3) convolving the output with a Gaussian waveform. Common source and path effects are implicitly removed by this process. We combine ETFs from 446 broadband seismograms to produce a global stack, from which S3KS-SKKS differential time can be measured accurately. As a result of stacking, the scatter in our measurements (0.43 s) is much less than the 1.29 s scatter in previous compilations. Although our data do not uniquely constrain outermost core velocities, we show that the fit of most standard models can be improved by perturbing the outermost core velocity. Our best-fitting model is formed using IASP91 with PREM-like velocity at the top of the core.

  4. On the convective velocity of large-scale structures in compressible axisymmetric jets

    NASA Astrophysics Data System (ADS)

    Thurow, Brian S.

    2005-12-01

    The role of compressibility on the convective velocity of large-scale structures in axisymmetric jets is studied using a home-built pulse burst laser system and newly developed high-repetition rate experimental diagnostics. In the last decade and a half, a number of researchers have made measurements of the convective velocity of large-scale structures within compressible free shear layers. These measurements, based entirely on flow visualization images, indicate a departure of the convective velocity from its theoretically expected value. This work attempts to explore this in further detail through the acquisition of time-correlated planar velocimetry data in two compressible axisymmetric flow fields. A pulse burst laser system was designed and constructed with the ability to produce a burst of short duration (10 nsec) pulses over a ˜150 microsecond period with inter-pulse timing as low as 1 microsecond (1 MHz). Pulse energies were increased by a factor of five through the addition of a phase conjugate mirror, which eliminates a gain robbing low-energy pedestal superimposed on the burst of pulses. The laser can produce individual pulse with energies over 100 mJ/pulse and 2nd and 3rd harmonic conversion efficiencies reaching 50% and 40%, respectively. In addition, the frequency of the laser is found to fluctuate less than 12 MHz, making it ideal for spectroscopic applications. The application of the pulse burst laser for flow measurements was investigated through the development of MHz rate flow visualization and MHz rate planar Doppler velocimetry (PDV). MHz rate flow visualization is achieved by using a high-repetition rate camera to image laser light scattered from particles in the flow. MHz rate PDV is a spectroscopic technique that uses the laser output at 532 nm, two ultra-high framing rate cameras and a molecular iodine vapor filter to measure the Doppler frequency shift of laser light scattered from seed particles contained in the flow field. The technique

  5. Crustal velocity structure of the Superior and Grenville Provinces of the southeastern Canadian Shield

    NASA Astrophysics Data System (ADS)

    Winardhi, Sonny

    In the summer of 1992, the Lithoprobe Abitibi-Grenville Seismic Refraction Experiment was conducted across the Grenville and Superior Provinces of the Southeastern Canadian Shield. More than 17,000 seismograms were collected during the survey from 44 shot points at an average shot spacing of 30 km and station spacing of 1-1.5 km. Each shot was recorded by 417 instruments, 47 of which were three-component systems which were placed strategically across the Grenville Front. The dense ray coverage in the area allowed us to make a detailed study of the variation of crustal velocities using seismic refraction tomography. The shallow velocity structure under the profiles was mapped using a delay-time analysis of the Psb{g} phases. A study of wide-angle reflected waves from the Moho (Psb{m}P) was carried out to constrain the thickness of the crust and the nature of the crust-mantle boundary. Three-component analysis was also employed to explore the anisotropic nature of the upper crust in the vicinity of the Grenville Front Tectonic Zone. The 2-D tomographic inversion was performed using an iterative conjugate gradient technique, whereas its corresponding uncertainty in the velocity determinations were estimated using a combination of the very fast simulated annealing and calculation of the ray-path density. From the three-component data set, polarization and propagation vectors were extracted. Angular deviations between these two directions (5-15 degrees) were then inverted to give parameters describing the anisotropic nature of the uppermost crust in the vicinity of the receivers. The latter was performed using a non-linear inversion technique utilizing the very fast simulated annealing. The delay-time analysis and tomographic inversion of the data set demonstrate significant lateral and vertical variations in crustal velocities from one terrane to another, with the largest velocity values occurring underneath the Central Gneiss and the Central Metasedimentary Belts

  6. Velocity structure around the Baikal rift zone from teleseismic and local earthquake traveltimes and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Petit, Carole; Koulakov, Ivan; Deverchère, Jacques

    1998-10-01

    We present new results on the velocity structure of the Baikal rift zone, Asia, deduced from a comparative teleseismic and local tomography analysis. The aim of this paper is to better identify the role of deep mantle processes versus that of far-field tectonic effects on the occurrence of extensional tectonics within a continental plate. We use 36000 traveltimes of P-refracted waves from the ISC catalogues and Pg and Pn traveltimes of 578 earthquakes recorded by the Russian regional network to determine a velocity model by the use of local and teleseismic inversion procedures. The models show that some velocity patterns are continuous from the surface down to at least 400 km. Among them, a narrow negative anomaly goes through Mongolia and follows the southern and eastern margins of the Siberian craton: this structure is interpreted as a thin mantle plume rising beneath the rift axis. However, our results do not evidence any wide asthenospheric upwarp at this place. Other velocity anomalies observed near the surface are not deeply rooted. In particular, a negative anomaly is observed at shallow levels (48 km) beneath the northern third of Lake Baikal, which is disconnected from deeper structures. It may be explained by the existence of underplated magmatic material at the bottom of the crust. By comparing the geometry of deep-rooted anomalies to the present-day stress field patterns, we conclude that the sub-lithospheric mantle dynamics is not the main factor controlling extensional processes in the Baikal rift. However, it does contribute to a thermal weakening of the lithosphere along a mechanical discontinuity bounding the Siberian shield. We finally conclude that three favourable conditions are gathered in the Baikal area to generate extension: far-field extensional stress field, mechanical inherited lithospheric weakness and heat supply. Further studies should help to precise the genetic link between these three factors.

  7. A 3-D crustal velocity structure across the Variscides of southwest Ireland

    NASA Astrophysics Data System (ADS)

    Landes, M.; Readman, P. W.; O'Reilly, B. M.; Shannon, P. M.

    2003-04-01

    In the VARNET-96 experiment three seismic refraction profiles were acquired to examine the crustal structure in the south-west of Ireland. The shotpoint geometry allowed for both in-line and off-line fan shot recordings on the three profiles. Results of 3-D inversion modelling illustrate that there is pervasive lateral heterogeneity of the sedimentary and crustal velocity structure south of the Shannon Estuary. Palaeozoic strata at the south coast are about 5-6 km thick associated with the sedimentary infill of the Munster and South Munster Basins. To the north, shallow upper crust in the vicinity of the Killarney-Mallow Fault Zone is followed by a 3-4 km thick sedimentary succession in the Dingle-Shannon Basin. A zone of high-velocity upper crust (6.4-6.6 km/s) beneath the South Munster Basin correlates with a gravity high between the Kenmare-Killarney and the Leinster Granite gravity lows. Other high-velocity zones beneath Dingle Bay and the Kenmare River region may be associated with the deep traces of the Killarney-Mallow Fault Zone and the Cork-Kenmare Line. The 3-D velocity model was taken as a basis for the computation of PmP reflected arrivals from the crust-mantle boundary. The Moho depth varies from 28-29 km at the south coast to 32-33 km beneath the Dingle-Shannon Basin. Pervasive Variscan deformation appears to be confined to the sedimentary and upper crustal structure thus supporting a thin-skinned tectonic model for Variscan deformation. Deep-crustal variations only occur where they can be correlated with major tectonic features such as the Caledonian Iapetus Suture near the Shannon Estuary. The shallowing of the Moho towards the coast may result from Mesozoic crustal extension in the adjacent offshore sedimentary basins.

  8. Acoustic wave velocities in two-dimensional composite structures based on acousto-optical crystals

    NASA Astrophysics Data System (ADS)

    Mal'neva, P. V.; Trushin, A. S.

    2015-04-01

    Sound velocities in two-dimensional composite structures based on isotropic and anisotropic acousto-optical crystals have been determined by numerical simulations. The isotropic materials are represented by fused quartz (SiO2) and flint glass, while anisotropic materials include tetragonal crystals of paratellurite (TeO2) and rutile (TiO2) and a trigonal crystal of tellurium (Te). It is established that the acoustic anisotropy of periodic composite structures strongly depends on both the chemical composition and geometric parameters of components.

  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. New 1-D and 3-D thiocyanatocadmates modified by various amine molecules and Cl(-)/CH3COO(-) ions: synthesis, structural characterization, thermal behavior and photoluminescence properties.

    PubMed

    Guo, Bing; Zhang, Xiao; Wang, Yan-Ning; Huang, Jing-Jing; Yu, Jie-Hui; Xu, Ji-Qing

    2015-03-21

    Under ambient conditions, reactions of CdCl2/Cd(CH3COO)2, SCN(-) and various organic amine molecules in strongly acidic solutions afforded the five new thiocyanatocadmates [H2(abpy)][CdCl2(SCN)2] (abpy = azobispyridine) 1, [H(apy)][Cd(SCN)3] (apy = 4-aminopyridine) 2, [H(ba)]2[CdCl2(SCN)2] (ba = tert-butylamine) 3, [H2(tmen)][Cd3Cl6(SCN)2] (tmen = N,N,N',N'-tetramethylethylenediamine) 4, and [H(dba)]2[Cd2(CH3COO)2(SCN)4] (dba = dibutylamine) 5. In compound 2 only, the CH3COO(-) ions in Cd(CH3COO)2 were completely displaced by SCN(-), producing a chained thiocyanatocadmate [Cd(SCN)3](-). In the other four compounds, the Cl(-) or CH3COO(-) ions appeared in the final inorganic anion frameworks. In compound 1, the Cl(-) ions doubly bridge the Cd(2+) centers, forming a one-dimensional (1-D) infinite chain, and the SCN(-) group exists in a terminal form, whereas in compound 3, the reverse situation is observed. Due to a trans-mode arrangement for two terminal Cl(-) or SCN(-) ions around each Cd(2+) center, the inorganic anion chains in compounds 1 and 3 both show a linear shape. In compound 4, Cd(2+) and Cl(-) first aggregate to form a 1-D endless chain with a composition of Cd3Cl6, which can be described as a linear arrangement of the open double cubanes. SCN(-) serves as the second connector, propagating the Cd3Cl6 chain into a three-dimensional (3-D) network with the occluded H2(tmen)(2+) cations. In compound 5, the SCN(-) groups doubly bridge the Cd(2+) centers, forming a 1-D zigzag-shape chain. The formation of the zigzag chain likely derives from chelation of the CH3COO(-) group to the Cd(2+) center. The thermal behavior and the photoluminescence properties of the title compounds were also investigated. PMID:25669175

  11. P wave crustal velocity structure in the greater Mount Rainier area from local earthquake tomography

    USGS Publications Warehouse

    Moran, S.C.; Lees, J.M.; Malone, S.D.

    1999-01-01

    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 velocity problems. In the upper 7 km of the resulting model there is good correlation between velocity 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-velocity 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-velocity 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 velocity 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.

  12. The shallow velocity structure of the Carboneras fault zone from high-resolution seismic investigations

    NASA Astrophysics Data System (ADS)

    Jones, C.; Nippress, S.; Rietbrock, A.; Faulkner, D. R.; Rutter, E. H.; Haberland, C. A.; Teixido, T.

    2010-12-01

    Understanding and characterizing fault zone structure at depth is vital to predicting the slip behaviour of faults in the brittle crust. The CFZ is a large offset (10s of km) strike-slip fault that constitutes part of the diffuse plate boundary between Africa and Iberia. It has been largely passively exhumed from ca. 4 to 6 km depth. The friable fault zone components are excellently preserved in the region’s semi-arid climate, and consist of multiple strands of phyllosilicate-rich fault gouge ranging from 1 to 20 m in thickness. We conducted four high-resolution seismic refraction tomography lines. Two of these lines crossed the entire width of the fault zone (~1km long) while the remaining lines concentrated on individual fault strands and associated damage zones (~100m long). For each line a combination of seismic sources (accelerated drop weight, sledgehammer and 100g explosives) was used, with 2m-geophone spacing. First breaks have been picked for each of the shot gathers and inputted into a 2D travel time inversion and amplitude-modeling package (Zelt & Smith, 1992) to obtain first break tomography images down to a depth 100m for the longer lines. The fault zone is imaged as a series of low velocity zones associated with the gouge strands, with Vp=1.5-1.75 km/s a velocity reduction of 40-60% compared to the wall-rock velocities (Vp=2.8-3.2km/s). These velocities are consistent with first break tomographic observations across the Dead Sea Transform fault (Haberland et al., 2007), but lower than the velocities imaged along the Punchbowl fault zone (part of the San Andreas system). Along the longer profiles we image multiple fault strands that exhibit a variety of thicknesses (~20-80m).

  13. The transverse velocity and excitation structure of the HH 110 jet

    NASA Astrophysics Data System (ADS)

    Riera, A.; López, R.; Raga, A. C.; Estalella, R.; Anglada, G.

    2003-03-01

    We present long-slit spectroscopic observations of the HH 110 jet obtained with the 4.2 m William Herschel Telescope. We have obtained for the first time, spectra for slit positions along and across the jet axis (at the position of knots B, C, I, J and P) to search for the observational signatures of entrainment and turbulence by studying the kinematics and the excitation structure. We find that the HH 110 flow accelerates from a velocity of 35 km s-1 in knot A up to 110 km s-1 in knot P. We find some systematic trends for the variation of the emission line ratios along the jet. No clear trends for the variation of the radial velocity are seen across the width of the jet beam. The cross sections of the jet show complex radial velocity and line emission structures which differ quite strongly from each other. Based on observations made with the 4.2 m William Herschel Telescope operated on La Palma by the Issac Newton Group of Telescopes at the Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

  14. Analysis of the rotational structure in the high-resolution infrared spectra of cis,cis- and trans,trans-1,4-difluorobutadiene-1-d1 and trans,trans-1,4-difluorobutadiene-1,4-d2

    SciTech Connect

    Craig, Norman C.; Chen, Yihui; Lu, Yuhua; Neese, Christopher F.; Nemchick, Deacon J.; Blake, Thomas A.

    2013-06-01

    Samples of cis,cis- and trans,trans-1,4-difluorobutadiene-1- d1 and of trans,trans-1,4-difluorobutadiene-1,4-d2 have been synthesized, and high-resolution (≤0.0018 cm-1) infrared spectra of these substances have been recorded in the gas phase. Analysis of the rotational structure, mostly in C-type bands, has yielded ground state rotational constants. For the two 1-d1 species more than one band has been analyzed. For the 1,4-d2 species only one band was available for analysis. However, good agreement between the experimental centrifugal distortion constants and those predicted with a B3LYP/cc-pVTZ model give strong support to the analysis of the very dense spectrum. The ground state rotational constants are a contribution to finding semiexperimental equilibrium structures of the two nonpolar isomers of 1,4- difluorobutadiene.

  15. Novel 1D coordination polymer {l_brace}Tm(Piv){sub 3{r_brace}n}: Synthesis, structure, magnetic properties and thermal behavior

    SciTech Connect

    Fomina, Irina; Dobrokhotova, Zhanna; Aleksandrov, Grygory; Emelina, Anna; Bykov, Mikhail; Bogomyakov, Artem; Puntus, Lada; Novotortsev, Vladimir; Eremenko, Igor

    2012-01-15

    The new 1D coordination polymer {l_brace}Tm(Piv){sub 3{r_brace}n} (1), where Piv=OOCBu{sup t-}, was synthesized in high yield (>95%) by the reaction of thulium acetate with pivalic acid in air at 100 Degree-Sign S. According to the X-ray diffraction data, the metal atoms in compound 1 are in an octahedral ligand environment unusual for lanthanides. The magnetic and luminescence properties of polymer 1, it's the solid-phase thermal decomposition in air and under argon, and the thermal behavior in the temperature range of -50 Horizontal-Ellipsis +50 Degree-Sign S were investigated. The vaporization process of complex 1 was studied by the Knudsen effusion method combined with mass-spectrometric analysis of the gas-phase composition in the temperature range of 570-680 K. - Graphical Abstract: Novel 1D coordination polymer {l_brace}Tm(Piv){sub 3{r_brace}n} was synthesized and studied by X-ray diffraction. The magnetic, luminescence properties, the thermal behavior and the volatility for the compound {l_brace}Tm(Piv){sub 3{r_brace}n} were investigated. Black-Small-Square Highlights: Black-Right-Pointing-Pointer We synthesized the coordination polymer {l_brace}Tm(Piv){sub 3{r_brace}n}. Black-Right-Pointing-Pointer Tm atoms in polymer have the coordination number 6. Black-Right-Pointing-Pointer Polymer exhibits blue-color emission at room temperature. Black-Right-Pointing-Pointer Polymer shows high thermal stability and volatility. Black-Right-Pointing-Pointer Polymer has no phase transitions in the range of -50 Horizontal-Ellipsis +50 Degree-Sign S.

  16. Constraints on Crustal Shear Wave Velocity Structure beneath Central Tibet from 3-D Multi-scale Finite-frequency Rayleigh Wave Travel-time Tomography

    NASA Astrophysics Data System (ADS)

    Jheng, Y.; Hung, S.; Zhou, Y.; Chang, Y.

    2012-12-01

    Surface wave travel-time tomography has been widely used as a powerful strategy to image shear wave velocity structure of the Earth's crust and upper mantle, providing comparable information other than body wave tomography. Traditionally, lateral variations of dispersive phase velocities are first obtained at multiple frequencies and then used to invert for shear wave velocity 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 tomography 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 velocity 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 velocity beneath the Qiangtang terrane is

  17. Crustal seismic velocity structure from Eratosthenes Seamount to Hecataeus Rise across the Cyprus Arc, eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Welford, J. Kim; Hall, Jeremy; Hübscher, Christian; Reiche, Sönke; Louden, Keith

    2015-02-01

    Wide-angle reflection/refraction seismic profiles were recorded across the Cyprus Arc, the plate boundary between the African Plate and the Aegean-Anatolian microplate, from the Eratosthenes Seamount to the Hecataeus Rise immediately south of Cyprus. The resultant models were able to resolve detail of significant lateral velocity variations, though the deepest crust and Moho are not well resolved from the seismic data alone. Conclusions from the modelling suggest that (i) Eratosthenes Seamount consists of continental crust but exhibits a laterally variable velocity structure with a thicker middle crust and thinner lower crust to the northeast; (ii) the Hecataeus Rise has a thick sedimentary rock cover on an indeterminate crust (likely continental) and the crust is significantly thinner than Eratosthenes Seamount based on gravity modelling; (iii) high velocity basement blocks, coincident with highs in the magnetic field, occur in the deep water between Eratosthenes and Hecataeus, and are separated and bounded by deep low-velocity troughs and (iv) one of the high velocity blocks runs parallel to the Cyprus Arc, while the other two appear linked based on the magnetic data and run NW-SE, parallel to the margin of the Hecataeus Rise. The high velocity block beneath the edge of Eratosthenes Seamount is interpreted as an older magmatic intrusion while the linked high velocity blocks along Hecataeus Rise are interpreted as deformed remnant Tethyan oceanic crust or mafic intrusives from the NNW-SSE oriented transform margin marking the northern boundary of Eratosthenes Seamount. Eratosthenes Seamount, the northwestern limit of rifted continental crust from the Levant Margin, is part of a jagged rifted margin transected by transform faults on the northern edge of the lower African Plate that is being obliquely subducted under the Aegean-Anatolian upper plate. The thicker crust of Eratosthenes Seamount may be acting as an asperity on the subducting slab, locally locking up

  18. Three-dimensional P and S wave velocity structures of southern Peru and their tectonic implications

    NASA Technical Reports Server (NTRS)

    Cunningham, Paul S.; Roecker, Steven W.; Hatzfeld, Denis

    1986-01-01

    Arrival times of compressional and shear (S) waves from microearthquakes recorded in 1981 by an 18-station regional array are used to study the three-dimensional velocity structure of the crust and upper mantle of the central Andes. The data suggest a crustal thickness of about 40 km beneath the coast, increasing to about 70 km beneath the Cordillera Occidental. The inverse correlation between the dip in the Moho and the dip of the slab may indicate a broad-scale causal relation between the two. S wave velocities in the mantle between 70 and 130 km depth above the 30-degree dipping slab are low, possibly indicating the presence of a partially melted asthenosphere that may be responsible for the magmatic activity recorded in southern Peru.

  19. UNVEILING THE DETAILED DENSITY AND VELOCITY STRUCTURES OF THE PROTOSTELLAR CORE B335

    SciTech Connect

    Kurono, Yasutaka; Saito, Masao; Kamazaki, Takeshi; Morita, Koh-Ichiro; Kawabe, Ryohei

    2013-03-10

    We present an observational study of the protostellar core B335 harboring a low-mass Class 0 source. The observations of the H{sup 13}CO{sup +}(J = 1-0) line emission were carried out using the Nobeyama 45 m telescope and Nobeyama Millimeter Array. Our combined image of the interferometer and single-dish data depicts detailed structures of the dense envelope within the core. We found that the core has a radial density profile of n(r){proportional_to}r {sup -p} and a reliable difference in the power-law indices between the outer and inner regions of the core: p Almost-Equal-To 2 for r {approx}> 4000 AU and p Almost-Equal-To 1.5 for r {approx}< 4000 AU. The dense core shows a slight overall velocity gradient of {approx}1.0 km s{sup -1} over the scale of 20, 000 AU across the outflow axis. We believe that this velocity gradient represents a solid-body-like rotation of the core. The dense envelope has a quite symmetrical velocity structure with a remarkable line broadening toward the core center, which is especially prominent in the position-velocity diagram across the outflow axis. The model calculations of position-velocity diagrams do a good job of reproducing observational results using the collapse model of an isothermal sphere in which the core has an inner free-fall region and an outer region conserving the conditions at the formation stage of a central stellar object. We derived a central stellar mass of {approx}0.1 M{sub Sun }, and suggest a small inward velocity, v{sub r{>=}r{sub i{sub n{sub f}}}}{approx}0 km s{sup -1} in the outer core at {approx}> 4000 AU. We concluded that our data can be well explained by gravitational collapse with a quasi-static initial condition, such as Shu's model, or by the isothermal collapse of a marginally critical Bonnor-Ebert sphere.

  20. 3D P-Wave Velocity Structure of the Crust and Relocation of Earthquakes in 21 the Lushan Source Area

    NASA Astrophysics Data System (ADS)

    Yu, X.; Wang, X.; Zhang, W.

    2014-12-01

    The double difference seismic tomography method is applied to the absolute first arrival P wave arrival times and high quality relative P arrival times of the Lushan seismic sequence to determine the detailed crustal 3D P wave velocity structure and the hypocenter parameters in the Lushan seismic area. The results show that the Lushan mainshock locates at 30.28 N, 103.98 E, with the depth of 16.38 km. The leading edge of aftershock in the northeast of mainshock present a spade with a steep dip angle, the aftershocks' extended length is about 12 km. In the southwest of the Lushan mainshock, the leading edge of aftershock in low velocity zone slope gently, the aftershocks' extended length is about 23 km. The P wave velocity structure of the Lushan seismic area shows obviously lateral heterogeneity. The P wave velocity anomalies represent close relationship with topographic relief and geological structure. In Baoxing area the complex rocks correspond obvious high-velocity anomalies extending down to 15 km depth,while the Cenozoic rocks are correlated with low-velocity anomalies. Our high-resolution tomographic model not only displays the general features contained in the previous models, but also reveals some new features. An obvious high-velocity anomaly is visible in Daxing area. The high-velocity anomalies beneath Baoxing and Daxing connect each other in 10 km depth, which makes the contrast between high and low velocity anomalies more sharp. Above 20 km depth the velocity structure in southwest and northeast segment of the mainshock shows a big difference: low-velocity anomalies are dominated the southwest segment, while high-velocity anomalies rule the northeast segment. The Lushan mainshock locates at the leading edge of a low-velocity anomaly surrounded by the Baoxing and Daxing high-velocity anomalies. The Lushan aftershocks in southwest are distributed in low-velocity anomalies or the transition belt: the footwall represents low-velocity anomalies, while

  1. Surface-wave propagation and phase-velocity structure from observations on the USArray Transportable Array

    NASA Astrophysics Data System (ADS)

    Foster, Anna E.

    We address questions relating to the velocity structure of the Earth in three ways: mapping the phase-velocity structure of the western United States, examining deviations of wave paths due to lateral variations in velocity, and demonstrating that Love wave fundamental-mode phase measurements from array methods can be significantly contaminated by overtone interference, dependent on differences in fundamental-mode and first-overtone phase-velocity structure. All of the studies presented in this work use USArray Transportable Array data, which allow for dense, high-quality measurements at an unprecedented level. To image the uppermost mantle beneath the western US, we improve upon single-station phase measurements by differencing them to produce a baseline data set of phase measurements along inter-station paths, for both Love and Rayleigh waves from 25--100 s. Additional measurements of the arrival angle and local phase velocity are made using a mini-array method similar to beamforming. The arrival-angle measurements are used to correct the two-station baseline measurements and produce a corrected data set. Both the baseline and corrected data sets are separately inverted, producing phase-velocity maps on a 0.5°-by-0.5° grid. We select the corrected maps as the preferred models for Rayleigh waves, with better fits to the data and more consistent measurements. We find that arrival-angle measurements for Love waves may be biased by overtone interference, and hence select the baseline maps as the preferred models for Love waves. The final set of phase-velocity maps is consistent with expectations from known geologic features, and is useful for both calculation of phase for regional paths and studies of radial anisotropy within the region. We use the mini-array method to make observations of the deviations of waves from the great-circle path. Measured arrival angles vary from 0° to +/-15°. We compile results from earthquakes in small source regions, allowing the

  2. Three-dimensional seismic velocity structure in the Sichuan basin, China

    NASA Astrophysics Data System (ADS)

    Wang, Maomao; Hubbard, Judith; Plesch, Andreas; Shaw, John H.; Wang, Lining

    2016-02-01

    We present a new three-dimensional velocity model of the crust in the eastern margin of the Tibetan Plateau. The model describes the velocity structure of the Sichuan basin and surrounding thrust belts. The model consists of 3-D surfaces representing major geologic unit contacts and faults and is parameterized with Vp velocity-depth functions calibrated using sonic logs. The model incorporates data from 1166 oil wells, industry isopach maps, geological maps, and a digital elevation model. The geological surfaces were modeled based on structure contour maps for various units from oil wells and seismic reflection profiles. These surfaces include base Quaternary, Mesozoic, Paleozoic, and Proterozoic horizons. The horizons locally exhibit major offsets that are compatible with the locations and displacements of important faults systems. This layered, upper crustal 3-D model extends down to 10-15 km depth and illustrates lateral and vertical variations of velocity that reflect the complex evolution of tectonics and sedimentation in the basin. The model also incorporates 3-D descriptions of Vs and density for sediments that are obtained from empirical relationships with Vp using direct measurements of these properties in borehole logs. To illustrate the impact of our basin model on earthquake hazards assessment, we use it to calculate ground motions and compare these with observations for the 2013 Lushan earthquake. The result demonstrates the effects of basin amplification in the western Sichuan basin. The Sichuan CVM model is intended to facilitate fault systems analysis, strong ground motion prediction, and earthquake hazards assessment for the densely populated Sichuan region.

  3. Comparison of remotely sensed chlorophyll and Lagrangian Coherent Structures for velocity field validation

    NASA Astrophysics Data System (ADS)

    Goldman, Ron; Efrati, Shai; Lehahn, Yoav; Gertman, Isaac; Heifetz, Eyal

    2014-05-01

    We present a tool for daily validation of modeled or satellite derived velocity fields in the southeastern region of the Mediterranean. Within this tool, spatial patterns of Lagrangian Coherent Structures (LCS) derived from the velocity field are compared to distribution patterns of satellite derived surface chlorophyll. This comparison is advantageous to pollution spread predictions since it compares the location of fronts in passive tracer spread. The suggested methodology is based on Lagrangian tools that were shown to be very effective in reconstructing the specific effect of horizontal stirring on individual oceanic patterns. Lagrangian techniques are based, in general, on the identification of the velocity field characteristics along particle trajectories. They are well suited for diagnosing properties of tracers like chlorophyll, since they allow to quantify the dynamical properties experienced by a parcel of water during its motion. The Lagrangian diagnostics performed in this tool are based on analyzing the spatial structure of LCS from calculation of finite size Lyapunov exponents (FSLE). These LCS induce in advected tracer fields filament patterns with typical length in the range of 10 - 100 km and lifetime in the range of days/weeks (though it can be much longer if the patterns are associated to long-lived and energetic mesoscale features with low temporal variability). Since LCS represent transport barriers and tracer boundaries, they separate between water bodies with possibly different physical - biogeochemical properties. Daily analyses ( available online at http://isramar.ocean.org.il/isramar2009/cosem/fsle.aspx ) of LCS is performed on AVISO altimetry derived velocity fields and on operational numerical circulation forecasts, which are produced as part of the South Eastern Levantine Israeli Prediction System (SELIPS). The LCS analyses are then placed atop maps of surface Chlorophyll concentrations, which is provided within the MyOcean project. A

  4. P-wave velocity structure offshore central Sumatra: implications for compressional and strike-slip faulting

    NASA Astrophysics Data System (ADS)

    Karplus, M.; Henstock, T.; McNeill, L. C.; Vermeesch, P. M. T.; Barton, P. J.

    2014-12-01

    The Sunda subduction zone features significant along-strike structural variability including changes in accretionary prism and forearc morphology. Some of these changes have been linked to changes in megathrust faulting styles, and some have been linked to other thrust and strike-slip fault systems across this obliquely convergent margin (~54-58 mm/yr convergence rate, 40-45 mm/yr subduction rate). We examine these structural changes in detail across central Sumatra, from Siberut to Nias Island, offshore Indonesia. In this area the Investigator Fracture Zone and the Wharton Fossil Ridge, features with significant topography, are being subducted, which may affect sediment thickness variation and margin morphology. We present new seismic refraction P-wave velocity models using marine seismic data collected during Sonne cruise SO198 in 2008. The experiment geometry consisted of 57 ocean bottom seismometers, 23 land seismometers, and over 10,000 air gun shots recorded along ~1750 km of profiles. About 130,000 P-wave first arrival refractions were picked, and the picks were inverted using FAST (First Arrivals Refraction Tomography) 3-D to give a velocity model, best-resolved in the top 25 km. Moho depths, crustal composition, prism geometry, slab dip, and upper and lower plate structures provide insight into the past and present tectonic processes at this plate boundary. We specifically examine the relationships between velocity structure and faulting locations/ styles. These observations have implications for strain-partitioning along the boundary. The Mentawai Fault, located west of the forearc basin in parts of Central Sumatra, has been interpreted variably as a backthrust, strike-slip, and normal fault. We integrate existing data to evaluate these hypotheses. Regional megathrust earthquake ruptures indicate plate boundary segmentation in our study area. The offshore forearc west of Siberut is almost aseismic, reflecting the locked state of the plate interface, which

  5. Velocity and pressure fields associated with near-wall turbulence structures

    NASA Technical Reports Server (NTRS)

    Johansson, Arne V.; Alfredsson, P. Henrik; Kim, John

    1990-01-01

    Computer generated databases containing velocity and pressure fields in three-dimensional space at a sequence of time-steps, were used for the investigation of near-wall turbulence structures, their space-time evolution, and their associated pressure fields. The main body of the results were obtained from simulation data for turbulent channel flow at a Reynolds number of 180 (based on half-channel height and friction velocity) with a grid of 128 x 129 x and 128 points. The flow was followed over a total time of 141 viscous time units. Spanwise centering of the detected structures was found to be essential in order to obtain a correct magnitude of the associated Reynolds stress contribution. A positive wall-pressure peak is found immediately beneath the center of the structure. The maximum amplitude of the pressure pattern was, however, found in the buffer region at the center of the shear-layer. It was also found that these flow structures often reach a maximum strength in connection with an asymmetric spanwise motion, which motivated the construction of a conditional sampling scheme that preserved this asymmetry.

  6. Seismic velocity structure and earthquake relocation for the magmatic system beneath Long Valley Caldera, eastern California

    NASA Astrophysics Data System (ADS)

    Lin, Guoqing

    2015-04-01

    A new three-dimensional (3-D) seismic velocity model and high-precision location catalog for earthquakes between 1984 and 2014 are presented for Long Valley Caldera and its adjacent fault zones in eastern California. The simul2000 tomography algorithm is applied to derive the 3-D Vp and Vp/Vs models using first-arrivals of 1004 composite earthquakes obtained from the original seismic data at the Northern California Earthquake Data Center. The resulting Vp model reflects geological structures and agrees with previous local tomographic studies. The simultaneously resolved Vp/Vs model is a major contribution of this study providing an important complement to the Vp model for the interpretation of structural heterogeneities and physical properties in the study area. The caldera is dominated by low Vp anomalies at shallow depths due to postcaldera fill. High Vp and low Vp/Vs values are resolved from the surface to ~ 3.4 km depth beneath the center of the caldera, corresponding to the structural uplift of the Resurgent Dome. An aseismic body with low Vp and high Vp/Vs anomalies at 4.2-6.2 km depth below the surface is consistent with the location of partial melt suggested by previous studies based on Vp models only and the inflation source locations based on geodetic modeling. The Sierran crystalline rocks outside the caldera are generally characterized with high Vp and low Vp/Vs values. The newly resolved velocity model improves absolute location accuracy for the seismicity in the study area and ultimately provides the basis for a high-precision earthquake catalog based on similar-event cluster analysis and waveform cross-correlation data. The fine-scale velocity structure and precise earthquake relocations are useful for investigating magma sources, seismicity and stress interaction and other seismological studies in Long Valley.

  7. Probing the Detailed Seismic Velocity Structure of Subduction Zones Using Advanced Seismic Tomography Methods

    NASA Astrophysics Data System (ADS)

    Zhang, H.; Thurber, C. H.

    2005-12-01

    Subduction zones are one of the most important components of the Earth's plate tectonic system. Knowing the detailed seismic velocity 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 tomography [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 velocity 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 tomography 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 tomography 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

  8. Investigation of structural heterogeneity at the SPE site using combined P–wave travel times and Rg phase velocities

    SciTech Connect

    Rowe, Charlotte A.; Patton, Howard J.

    2015-10-01

    Here, we present analyses of the 2D seismic structure beneath Source Physics Experiments (SPE) geophone lines that extended radially at 100 m spacing from 100 to 2000 m from the source borehole. With seismic sources at only one end of the geophone lines, standard refraction profiling methods cannot resolve seismic velocity structures unambiguously. In previous work, we demonstrated overall agreement between body-wave refraction modeling and Rg dispersion curves for the least complex of the five lines. A more detailed inspection supports a 2D reinterpretation of the structure. We obtained Rg phase velocity measurements in both the time and frequency domains, then used iterative adjustment of the initial 1D body-wave model to predict Rg dispersion curves to fit the observed values. Our method applied to the most topographically severe of the geophone lines is supplemented with a 2D ray-tracing approach, whose application to P-wave arrivals supports the Rg analysis. In addition, midline sources will allow us to refine our characterization in future work.

  9. Upper Crustal Seismic Velocity Structure of the Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Weekly, R. T.; Wilcock, W. S.; Toomey, D. R.; Hooft, E. E.; Wells, A. E.

    2010-12-01

    We report preliminary results from an active-source seismic tomography experiment that was conducted along the intermediate-spreading Endeavour Segment of the Juan de Fuca Ridge in 2009. The overarching objective of the experiment is to test competing hypotheses for what governs the scale and intensity of magmatic and hydrothermal processes at mid-ocean ridges. Previous models of crustal accretion inferred that ridge-basin topography observed at the Endeavour results from alternating periods of enhanced or reduced magma supply from the mantle. Alternatively, a recent seismic reflection study has imaged a crustal magma chamber underlying the central portion of the Endeavour, which may indicate that variations in seafloor topography instead result from dike-induced faulting that occurs within the upper crust, adjacent to the axial magma chamber. The first model predicts a thicker high-porosity eruptive layer and lower velocities beneath topographic highs, while the second model is compatible with a uniform pattern of volcanic accretion. The experiment used 68 four-component ocean-bottom seismometers (OBSs) at 64 sites to record 5,567 airgun shots from the 6600 in3 airgun array of the R/V Marcus G. Langseth. Three nested shooting grids were collected to image the three-dimensional crustal and upper mantle velocity structure of the segment at multiple spatial scales. We use first-arriving crustal phases (Pg) recorded by the two grids with the densest shot-receiver spacing, the 24 x 8 km2 vent field grid and the 60 x 20 km2 crustal grid, to image the fine-scale (< 1 km) three-dimensional velocity structure of the upper few kilometers of crust at the segment scale. We employ a non-linear tomographic method that utilizes a shortest-path ray-tracing algorithm with columns of nodes sheared vertically to include effects of seafloor topography. To date, we have manually picked 13,000 Pg phases located within 10 km of 17 OBSs. The full analysis will include ~40,000 Pg travel

  10. 3D P-wave velocity structure of the crust and relocation of earthquakes in the Lushan, China, source area

    NASA Astrophysics Data System (ADS)

    Yu, Xiangwei; Wang, Xiaona; Zhang, Wenbo

    2016-04-01

    Many researchers have investigated the Lushan source area with geological and geophysical approaches since the 2013 Lushan, China, earthquake happened. Compared with the previous tomographic studies, we have used a much large data set and an updated tomographic method to determine a small scale three-dimensional P wave velocity structure with spatial resolution less than 5km, which plays the important role for understanding the deep structure and the genetic mechanism beneath the Lushan area. The double difference seismic tomography method is applied to 50,711 absolute first arrival P wave arrival times and 7,294,691 high quality relative P arrival times of 5,285 events of Lushan seismic sequence to simultaneously determine the detailed crustal 3D P wave velocity structure and the hypocenter parameters in the Lushan seismic area. This method takes account of the path anomaly biases explicitly by making full use of valuable information of seismic wave propagation jointly with absolute and relative arrival time data. Our results show that the Lushan mainshock locates at 30.28N, 103.98E, with the depth of 16.38km. The front edge of aftershock in the northeast of mainshock present a spade with a steep dip angle, the aftershocks' extended length is about 12km. In the southwest of Lushan mainshock, the front edge of aftershock in low velocity zone slope gently, the aftershocks' extended length is about 23km. Our high-resolution tomographic model not only displays the general features contained in the previous models, but also reveals some new features. The Tianquan, Shuangshi and Daguan line lies in the transition zone between high velocity anomalies to the southeast and low velocity anomalies to the northwest at the ground surface. An obvious high-velocity anomaly is visible in Daxing area. With the depth increasing, Baoxing high velocity anomaly extends to Lingguan, while the southeast of the Tianquan, Shuangshi and Daguan line still shows low velocity. The high-velocity

  11. DESIGN PACKAGE 1D SYSTEM SAFETY ANALYSIS

    SciTech Connect

    L.R. Eisler

    1995-02-02

    The purpose of this analysis is to systematically identify and evaluate hazards related to the Yucca Mountain Project Exploratory Studies Facility (ESF) Design Package 1D, Surface Facilities, (for a list of design items included in the package 1D system safety analysis see section 3). This process is an integral part of the systems engineering process; whereby safety is considered during planning, design, testing, and construction. A largely qualitative approach was used since a radiological System Safety analysis is not required. The risk assessment in this analysis characterizes the accident scenarios associated with the Design Package 1D structures/systems/components in terms of relative risk and includes recommendations for mitigating all identified risks. The priority for recommending and implementing mitigation control features is: (1) Incorporate measures to reduce risks and hazards into the structure/system/component (S/S/C) design, (2) add safety devices and capabilities to the designs that reduce risk, (3) provide devices that detect and warn personnel of hazardous conditions, and (4) develop procedures and conduct training to increase worker awareness of potential hazards, on methods to reduce exposure to hazards, and on the actions required to avoid accidents or correct hazardous conditions. The scope of this analysis is limited to the Design Package 1D structures/systems/components (S/S/Cs) during normal operations excluding hazards occurring during maintenance and ''off normal'' operations.

  12. Near surface velocity structure of Pacaya volcano using spatial autocorrelation method

    NASA Astrophysics Data System (ADS)

    Kenyon, L. M.; Waite, G. P.; Manzoni, P.

    2011-12-01

    the radial components agrees with the vertical component results although the results are less clear; a similar dispersion curve for Love waves is in development. An inversion of the dispersion curves for a velocity model of the near surface will be presented. Finally, this velocity structure will be used to interpret the origin of three dominant tremor bands at 1.5, 1.9 and 3 Hz.

  13. Quasi-static and multi-site high velocity impact response of composite structures

    NASA Astrophysics Data System (ADS)

    Deka, Lakshya

    Understanding of low and high velocity transverse impact of laminated fiber reinforced composites is of interest in military, aerospace, marine and civilian structures. Recent advances in the field of numerical simulation provide a means of predicting the performance characteristics of layered materials for impact protection. The overall objective of this work is to investigate the behavior of laminated composites which include both thermoplastic and thermoset systems subjected to quasi-static, low and high velocity impact; both from an experimental and numerical modeling view point. To analyze this problem, a series of quasi-static, low and high velocity impact tests have been performed on laminated composite plates namely E-glass/polypropylene, S2-glass/epoxy and carbon/polyphenylene sulphide. To analyze the perforation mechanism, ballistic limit and damage evolution, an explicit three-dimensional finite element code LS-DYNA is used. Selecting proper material models and contact definition is one of the major criteria for obtaining accurate numerical simulation. Material model 162 (MAT 162), a progressive failure model based on modified Hashin's criteria and continuum damage mechanics (CDM) has been assigned to predict failure of the laminate. This approach is used because during transverse impact, a composite laminate undergoes progressive damage. The laminate and the projectile are meshed using brick elements with single integration points. The impact velocity ranges from 180 to 400 m s -1. This work focuses on three main aspects; (i) To obtain static and dynamic material properties to incorporate into the finite element model and predict the ballistic limit of a composite laminate based on the information from quasi-static punch shear test; (ii) To understand penetration, material erosion, ballistic limit and delamination mechanisms for single and multi-site high velocity (or ballistic) impact of composite laminates; (iii) To investigate the different failure

  14. Is there structure in the velocity dispersion maps of turbulent disks?

    NASA Astrophysics Data System (ADS)

    Oliva-Altamirano, P.; Fisher, D.; Glazebrook, K.

    2016-06-01

    Galaxies at z > 1 have shown to be different from galaxies at local redshifts. They have irregular morphologies with prominent star-forming clumps. However, due to the limited resolution of high-redshift observations, it is difficult to disentangle the physical processes that create and destroy star-forming clumps. Leaving many open questions in the study of galaxy evolution. The DYnamics of Newly Assembled Massive Objects (DYNAMO) survey aims to observe local galaxies (z < 0.25) with properties similar to those at high redshift (z˜2). This poster presents the near infrared spectra of 3 DYNAMO objects taken with the OSIRIS integral-field spectrograph on the Keck telescope. The high spatial and spectral resolution of OSIRIS allows us to obtain detailed kinematic maps. We are able to resolve the velocity dispersion of individual star-forming clumps down to sizes of ~300 pc. We find that after removing the systematics there is a significant structure in the velocity dispersion. However, whether there is a correlation between velocity dispersion and star formation, remains an open question. This work aims to disentangle the role of turbulence in the life and dead of star-forming clumps.

  15. Relative velocity of dark matter and baryonic fluids and the formation of the first structures

    NASA Astrophysics Data System (ADS)

    Tseliakhovich, Dmitriy; Hirata, Christopher

    2010-10-01

    At the time of recombination, baryons and photons decoupled and the sound speed in the baryonic fluid dropped from relativistic, ˜c/3, to the thermal velocities of the hydrogen atoms, ˜2×10-5c. This is less than the relative velocities of baryons and dark matter computed via linear perturbation theory, so we infer that there are supersonic coherent flows of the baryons relative to the underlying potential wells created by the dark matter. As a result, the advection of small-scale perturbations (near the baryonic Jeans scale) by large-scale velocity flows is important for the formation of the first structures. This effect involves a quadratic term in the cosmological perturbation theory equations and hence has not been included in studies based on linear perturbation theory. We show that the relative motion suppresses the abundance of the first bound objects, even if one only investigates dark matter haloes, and leads to qualitative changes in their spatial distribution, such as introducing scale-dependent bias and stochasticity. We further discuss the possible observable implications of this effect for high-redshift galaxy clustering and reionization.

  16. High-resolution seismic tomography of compressional wave velocity structure at Newberry Volcano, Oregon Cascade Range

    SciTech Connect

    Achauer, U.; Evans, J.R.; Stauber, D.A.

    1988-09-10

    Compressional wave velocity structure is determined for the upper crust beneath Newberry Volcano, central Oregon, using a high-resolution active-source seismic-tomography 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-velocity 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-velocity 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.

  17. Simulation of High Velocity Impact on Composite Structures - Model Implementation and Validation

    NASA Astrophysics Data System (ADS)

    Schueler, Dominik; Toso-Pentecôte, Nathalie; Voggenreiter, Heinz

    2016-08-01

    High velocity impact on composite aircraft structures leads to the formation of flexural waves that can cause severe damage to the structure. Damage and failure can occur within the plies and/or in the resin rich interface layers between adjacent plies. In the present paper a modelling methodology is documented that captures intra- and inter-laminar damage and their interrelations by use of shell element layers representing sub-laminates that are connected with cohesive interface layers to simulate delamination. This approach allows the simulation of large structures while still capturing the governing damage mechanisms and their interactions. The paper describes numerical algorithms for the implementation of a Ladevèze continuum damage model for the ply and methods to derive input parameters for the cohesive zone model. By comparison with experimental results from gas gun impact tests the potential and limitations of the modelling approach are discussed.

  18. Simulation of High Velocity Impact on Composite Structures - Model Implementation and Validation

    NASA Astrophysics Data System (ADS)

    Schueler, Dominik; Toso-Pentecôte, Nathalie; Voggenreiter, Heinz

    2016-05-01

    High velocity impact on composite aircraft structures leads to the formation of flexural waves that can cause severe damage to the structure. Damage and failure can occur within the plies and/or in the resin rich interface layers between adjacent plies. In the present paper a modelling methodology is documented that captures intra- and inter-laminar damage and their interrelations by use of shell element layers representing sub-laminates that are connected with cohesive interface layers to simulate delamination. This approach allows the simulation of large structures while still capturing the governing damage mechanisms and their interactions. The paper describes numerical algorithms for the implementation of a Ladevèze continuum damage model for the ply and methods to derive input parameters for the cohesive zone model. By comparison with experimental results from gas gun impact tests the potential and limitations of the modelling approach are discussed.

  19. Wind tunnel investigation of the effect of high relative velocities on the structural integrity of birds

    NASA Technical Reports Server (NTRS)

    Bresnahan, D. L.

    1972-01-01

    An experimental investigation was conducted in a supersonic wind tunnel to determine the effect a sudden high velocity headwind had on the physical deformation and structural breakup characteristics of birds. Several sizes of recently killed birds were dropped into the test section at free-stream Mach numbers ranging from 0.2 to 0.8 and photographed with high-speed motion-picture cameras. These conditions simulated flow conditions encountered when birds are ingested into the inlets of high speed aircraft, thereby constituting a safety hazard to the aircraft and its occupants. The investigation shows that, over the range of headwind conditions tested, the birds remained structurally intact and did not suffer any appreciable deformation or structural breakup.

  20. Synthesis, structure and characterization of 4,4‧-bipyridine directed isolated cluster and 1D chain of iron sulfates

    NASA Astrophysics Data System (ADS)

    Xu, Zhiwei; Fu, Yunlong; Zhang, Yu

    2008-03-01

    Two 4,4'-bipyridine directed iron sulfates have been synthesized and characterized by single-crystal X-ray diffraction, infrared spectrum, powder X-ray diffraction, CHN elemental analysis, thermal gravimetric analysis and magnetic analysis. [C 10N 2H 10] 2[Fe 4O 2(SO 4) 6(H 2O) 4]·6H 2O, I, and [C 10N 2H 10][Fe(SO 4) 2(OH)]·H 2O, II, both crystallize in triclinic space group P (No. 2). Crystal data: for I, a = 9.2064(8) Å, b = 11.5548(11) Å, c = 11.8130(11) Å, α = 117.3070(10)°, β = 94.650(2)°, γ = 96.493(2)°, V = 1096.79(17) Å 3, Z = 1; for II, a = 7.0382(9) Å, b = 9.0625(12) Å, c = 11.8903(16) Å, α = 100.145(3)°, β = 98.701(2)°, γ = 91.047(3)°, V = 737.17(17) Å 3, Z = 2. Compound I exhibits a rare discrete sulfated tetra-nuclear iron oxo cluster with a butterfly-type arrangement, and II possesses 1D tancoite-type chains. Magnetic properties analysis of I reveals a transformation from ferromagnetism to antiferromagnetism at about 14 K.

  1. Effect of the band structure in a rigorous two-body model with long-range interactions in 1D optical lattices

    NASA Astrophysics Data System (ADS)

    Kristensen, Tom; Simoni, Andrea; Launay, Jean-Michel

    2016-05-01

    We compute scattering and bound state properties for two ultracold molecules in a pure 1D optical lattice. We introduce reference functions with complex quasi-momentum that naturally account for the effect of excited energy bands. Our exact results for a short-range interaction are first compared with the simplest version of the standard Bose-Hubbard (BH) model. Such comparison allows us to highlight the effect of the excited bands, of the non-on-site interaction and of tunneling with distant neighbor, that are not taken into account in the BH model. The effective interaction can depend strongly on the particle quasi-momenta and can present a resonant behavior even in a deep lattice. As a second step, we study scattering of two polar particles in the optical lattice. Peculiar Wigner threshold laws stem from the interplay of the long range dipolar interaction and the presence of the energy bands. We finally assess the validity of an extended Bose-Hubbard model for dipolar gases based on our exact two-body calculations. This work was supported by the Agence Nationale de la Recherche (Contract No. ANR-12-BS04-0020-01).

  2. Crystal structure, infrared spectra and luminescence of a 1D Cd coordination polymer with 4-nitrophthalic acid and 1,10-phenanthroline monohydrate ligands

    NASA Astrophysics Data System (ADS)

    Han, Li-Juan; Kong, Ya-Jie; Sheng, Ning

    2015-01-01

    A new one-dimensional (1D) coordination polymer, [Cd(NPTA)(1,10-phen)(H2O)] n ( 1) (H2NPTA = 4-nitrophthalic acid; 1,10-phen = 1,10-phenanthroline monohydrate), has been synthesized under hydrothermal conditions and characterized by elemental analysis, single-crystal X-ray diffraction, solid state emission spectra, FT-IR spectra, and thermogravimetric analyses. The compound belongs to triclinic system with space group , and exhibits a one-dimensional linear chain. Each Cd with a strongly distorted octahedral coordination geometry is six-coordinated by two N atoms from one 1,10-phenanthroline ligand, three O atoms from two carboxylate groups of two different NPTA2- ligands and one O atoms from lattice water. Layer supramolecular architecture is formed by medium π-π stacking interactions between two neighboring phenanthroline rings from two independent linear chains. Studies on luminescent property of 1 exhibit the solid state emission originating from an intra ligand π → π* transition of NPTA2- ligand.

  3. Dicynamide bridged two new zig-zag 1-D Zn(II) coordination polymers of pyrimidine derived Schiff base ligands: Synthesis, crystal structures and fluorescence studies

    NASA Astrophysics Data System (ADS)

    Konar, Saugata

    2015-07-01

    Two new zigzag 1-D polymeric Zn(II) coordination polymers {[Zn(L1)(μ1,5-dca)](H2O)}n (1), {[Zn(L2)(μ1,5-dca)](ClO4)}n (2) of two potentially tridentate NNO-, NNN-, donor Schiff base ligands [2-(2-(4,6-dimethylpyrimidin-2-yl)hydrazono)methyl)phenol] (L1), [1-(4,6-dimethylpyrimidin-2-yl)-2-(dipyridin-2ylmethylene)hydrazine] (L2) have been synthesized and characterized by elemental analyses, IR and 1H NMR, fluorescence spectroscopy and single crystal X-ray crystallography. The dicyanamide ions act as linkers (μ1,5 mode) in the formation of these coordination polymers. Both the complexes 1 and 2 have same distorted square pyramidal geometry around the Zn(II) centres. The weak forces like π⋯π, Csbnd H⋯π, anion⋯π interactions lead to various supramolecular architectures. Complex 1 shows high chelation enhanced fluorescence compared to that of 2. The fluorescence spectral changes observed high selectivity towards Zn(II) over other metal ions such as Mn(II), Co(II), Ni(II), Cu(II).

  4. Methods to determine the Orientation and Velocity of 2-D structures based on multi- spacecraft data

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Pu, Z.; Zhou, X.; Wang, J.; Zong, Q.; Shi, Q.

    2006-12-01

    Many techniques have been developed to study the axial orientation and/or velocity of 2-D structures (flux ropes), by analyzing in situ data from single or multiple spacecraft. To obtain the axial orientation, there are magnetic based MVA (BMVA), current based MVA (CMVA), Minimum Direction Derivative (MDD) and Multiple Triangulation Analysis (MTA) as a modified version of timing method. To further calculate the velocity, we have DeHoffmann-Teller analysis, Spatio-Temporal Difference (STD) and several version of timing method including MTA. After a brief introduction on the principle of these methods, we theoretically estimate their error ranges based on modeled structures to examine the validity of these techniques. Because of their different principles, their error bars are shown to be distinct, depending on the parameters (such as radius, model selected and even the satellite crossing path) of the certain structure. The error estimation thus provides us some clue on the selection of methods under different conditions. Some real events are further analyzed using these techniques as the example.

  5. Near-surface velocity structure from borehole and refraction seismic surveys

    SciTech Connect

    Parry, D.; Lawton, D.C.

    1994-12-31

    Seismic refraction and borehole reflection data have been used in conjunction with other geophysical tools to characterize the near-surface geology in the vicinity of a shallow well near Calgary, Alberta. The investigated section is comprised primarily of glacial tills and gravels. Seismic waves generated in the lower gravel units travel as compressional waves up to the till/gravel interface, where they are converted to shear waves upon transmission. Velocity structure from a reverse vertical seismic profile (RVSP) survey agrees closely with that from refraction surveying.

  6. The ultrasonic velocity profile measurement of flow structure in the near field of a square free jet

    NASA Astrophysics Data System (ADS)

    Inoue, Y.; Yamashita, S.; Kondo, K.

    Coherent structures in the near field of a three-dimensional jet have been investigated. Experiments were carried out for a free jet issuing from a square nozzle using a water channel. Instantaneous velocity profiles were obtained in the axial and radial directions by using an ultrasonic velocity profile (UVP) monitor. Axial variations of dominant time-scales of vortex structures were examined from one-dimensional wavelet spectra. Wavenumber-frequency spectra were calculated by two-dimensional Fourier transform along the axial direction in a mixing layer, and it was found that a convective velocity of flow structures was nearly constant independently of their scales in space and time. Coherent structures in the axial direction were investigated in terms of proper orthogonal decomposition (POD). Eigenfunctions are similar to a sinusoidal wave, and reconstructed velocity fields by the lower-order and higher-order POD modes demonstrate large-scale and smaller-scale coherent structures, respectively.

  7. Imaging seismic velocity structure beneath the Iceland hot spot: A finite frequency approach

    NASA Astrophysics Data System (ADS)

    Hung, Shu-Huei; Shen, Yang; Chiao, Ling-Yun

    2004-08-01

    Tomographic models based on hypothetically infinite frequency ray interpretation of teleseismic travel time shifts have revealed a region of relatively low P and S wave speeds extending from shallow mantle to 400 km depth beneath Iceland. In reality, seismic waves have finite frequency bandwidths and undergo diffractive wave front healing. The limitation in ray theory leaves large uncertainties in the determinations of the magnitude and shape of the velocity anomaly beneath Iceland and its geodynamic implications. We developed a tomographic method that utilizes the banana-shaped sensitivity of finite frequency relative travel times from the paraxial kernel theory. Using available seismic data from the ICEMELT and HOTSPOT experiments, we applied the new method to image subsurface velocity structure beneath Iceland. Taking advantage that the sensitivity volume of broadband waveforms varies with frequency, we measured relative delay times in three frequency ranges from 0.03 to 2 Hz for P and 0.02 to 0.5 Hz for S waves. Given similar fit to data, the kernel-based models yield the root-mean-square amplitudes of P and S wave speed perturbations about 2-2.8 times those from ray tomography in the depths of 150-400 km. The kernel-based images show that a columnar low-velocity region having a lateral dimension of ˜250-300 km extends to the base of the upper mantle beneath central Iceland, deeper than that resolved by the ray-based studies. The improved resolution in the upper mantle transition zone is attributed to the deeper crossing of broad off-path sensitivity of travel time kernels than in ray approximation and frequency-dependent wave front healing as an intrinsic measure of the distance from velocity heterogeneity to receivers.

  8. Crustal and upper mantle velocity structure of the Hoggar swell (Central Sahara, Algeria)

    NASA Astrophysics Data System (ADS)

    Ayadi, A.; Dorbath, C.; Lesquer, A.; Bezzeghoud, M.

    2000-02-01

    The Hoggar region is known as one of the most important swells in the African continent. Its altitude culminates at 2908 m in the Tahat hill (Atakor). The Hoggar and other massifs of central Africa (Aı̈r, Eghei, Tibesti, Darfur, Cameroon mount, …) form a system of domal uplifts with similar scale, morphology and volcanic activity. The knowledge of the structure beneath the Hoggar swell will help us to understand the origin of continental swells. In order to get an image of the lithosphere in this region, we have performed a teleseismic field experiment. The 33 short-period seismic stations have been maintained for 2 1/2 month along a 700-km long NNW-SSW profile. This experiment crossed the Central Hoggar and extended northward into the In-Salah Sahara basin which is characterized by high heat flow values of deep origin. The high quality of the data recorded during this experiment allows us to perform a velocity inversion. The Hoggar appears to be characterized by lower mantle velocities. The anomalous zone extends from the upper lithosphere to the mantle. The weak velocity contrast is interpreted in agreement with gravity, geothermal and petrological data as due to extensive mantle modifications inherited from Cenozoic volcanic activity. It confirms that the Hoggar swell is not due to a large-scale uplift of hot asthenospheric materials but corresponds to a now cooled-off modified mantle. On the contrary, local low-velocity zones associated with the Atakor and Tahalra volcanic districts show that hot materials still exist at depths in relation with recent basaltic volcanism.

  9. The head-tail structure of high-velocity clouds. A survey of the northern sky

    NASA Astrophysics Data System (ADS)

    Brüns, C.; Kerp, J.; Kalberla, P. M. W.; Mebold, U.

    2000-05-01

    We present new observational results on high-velocity clouds (HVCs) based on an analysis of the Leiden/Dwingeloo \\ion{HI} survey. We cataloged all HVCs with N_HI>= 1*1019 cm-2 and found 252 clouds that form a representative flux limited sample. The detailed analysis of each individual HVC in this sample revealed a significant number of HVCs (nearly 20%) having simultaneously a velocity and a column density gradient. These HVCs have a cometary appearance in the position-velocity representation and are called henceforward head-tail HVCs (HT HVCs). The head is the region with the highest column density of the HVC, while the column density of the tail is in general much lower (by a factor of 2-4). The absolute majority of the cataloged HVCs belongs to the well known HVC complexes. With exception of the very faint HVC complex L, all HVC complexes contain HT HVCs. The HT HVCs were analyzed statistically with respect to their physical parameters like position, velocity (v_LSR, v_GSR), and column density. We found a linear correlation between the fraction of HVCs having a head-tail structure and the peak column density of the HVCs. While there is no correlation between the fraction of HT HVCs and v_LSR, we found a dependence of the fraction of HT HVCs and v_GSR. There is no significant correlation between the fraction of HT HVCs and the parameters galactic longitude and latitude. The HT HVCs may be interpreted as HVCs that are currently interacting with their ambient medium. In the context of this model the tails represent material that is stripped off from the HVC core. We discuss the implications of this model for galactic and extragalactic HVCs.

  10. 3D Seismic Velocity Structure Around Philippine Sea Slab Subducting Beneath Kii Peninsula, Japan

    NASA Astrophysics Data System (ADS)

    Shibutani, T.; Imai, M.; Hirahara, K.; Nakao, S.

    2013-12-01

    Kii Peninsula is a part of the source area of Nankai Trough megaquakes and the region through which the strong seismic waves propagate to big cities in Kansai such as Osaka, Kyoto, Nara, Kobe, and so on. Moreover, the rupture starting point is thought to be possibly at off the peninsula. Therefore, it is important for simulations of the megaquakes and the strong motions to estimate accurately the configuration of the Philippine Sea slab and the seismic velocity structure around the slab and to investigate properties and conditions of the plate boundary surface. Deep low frequency events (DLFEs) are widely distributed from western Shikoku to central Tokai at 30 - 40 km depths on the plate boundary (Obara, 2002). Results from seismic tomography and receiver function analyses revealed that the oceanic crust of the Philippine Sea plate had a low velocity and a high Vp/Vs ratio (Hirose et al., 2007; Ueno et al., 2008). Hot springs with high 3He/4He ratios are found in an area between central Kinki and Kii Peninsula despite in the forearc region (Sano and Wakita, 1985). These phenomena suggest the process that H2O subducting with the oceanic crust dehydrates at the depths, causes the DLFEs, and moves to shallower depths. We carried out linear array seismic observations in the Kii Peninsula since 2004 in order to estimate the structure of the Philippine Sea slab and the surrounding area. We have performed receiver function analyses for four profile lines in the dipping direction of the slab and two lines in the perpendicular direction so far. We estimated three dimensional shapes of seismic velocity discontinuities such as the continental Moho, the upper surface of the oceanic crust and the oceanic Moho (Imai et al., 2013, this session). In addition, we performed seismic tomography with a velocity model embedded the discontinuities and observed travel times at stations in the linear arrays, and successfully estimated 3D seismic velocity structure around the Philippine Sea

  11. Seismic images of the upper mantle velocities and structure of European mantle lithosphere

    NASA Astrophysics Data System (ADS)

    Plomerova, Jaroslava; Munzarova, Helena; Vecsey, Ludek; Babuska, Vladislav

    2014-05-01

    Tomography images of seismic velocities in the Earth mantle represent significant tool for recovering first order structural features. Regional studies, based on dense networks of temporary stations allow us to focus on structure of the continental upper mantle and to study variations of body-wave velocities in greater detail. However, the standard tomography exhibits only isotropic view of the Earth, whose structure is anisotropic in general, as shown by results of various studies exploiting a broad range of methods, types of waves and scales. We present results of our studies of seismic anisotropy in tectonically different provinces that clearly demonstrate the continental mantle lithosphere consists of domains with different fossil fabrics. We detect anisotropic signal both in teleseismic P-wave travel-time deviations and shear-wave splitting and show changes of the anisotropic parameters across seismic arrays, in which stations with similar characteristics form groups. The geographical variations of seismic-wave anisotropy delimit individual, often sharply bounded domains of the mantle lithosphere, each of them having a consistent fabric. The domains can be modelled in 3D by peridotite aggregates with dipping lineation a or foliation (a,c). These findings allow us to interpret the domains as micro-plate fragments retaining fossil fabrics in the mantle lithosphere, reflecting thus an olivine LPO created before the micro-plates assembled. Modelling anisotropic structure of individual domains of the continental mantle lithosphere helps to decipher boundaries of individual blocks building the continental lithosphere and hypothesize on processes of its formation (Plomerova and Babuska, Lithos 2010). Exploiting the long memory of the deep continental lithosphere fabric, we present the lithosphere-asthenosphere boundary (LAB) as a transition between a fossil anisotropy in the mantle lithosphere and an underlying seismic anisotropy related to the present-day flow in

  12. Crustal velocity structure along the Nagaur Rian sector of the Aravalli fold belt, India, using reflection data

    NASA Astrophysics Data System (ADS)

    Satyavani, N.; Dixit, M. M.; Reddy, P. R.

    2001-05-01

    Deep reflection data was collected along the Nagaur-Nandsi profile, Rajasthan (across the Aravalli fold belt), India, to study the tectonic pattern and evolutionary history of the Northwestern Indian Shield. However, as there was no coincident wide-angle/refraction input/well data input, no velocity picture could be derived to supplement the reflection results. In the present study, as velocity information is very important for a realistic analysis of the reflection time sections, we have used the interval velocity derived from stack velocities (Hubral, P. and Krey, T., 1980. In: Larner, K.I. (Ed.), Interval Velocities from Seismic Reflection Time Measurements. SEG, Tulsa, OK), to arrive at a possible velocity-depth section, along the 90-km Nagaur-Rian sector. This was followed by dynamic forward modeling, using the interval velocity model as the starting model. The resultant velocity depth section has a four-layer structure. One of the layers (third) is a low-velocity layer. The lateral extension of this layer vis-à-vis with other layers is presented, for a better understanding of the structure and tectonics of the Aravalli-Delhi fold belt.

  13. Shear wave velocity structure of the southern African upper mantle with implications for the uplift of southern Africa

    NASA Astrophysics Data System (ADS)

    Adams, Aubreya; Nyblade, Andrew

    2011-08-01

    Broad-band seismic data from the southern African seismic experiment and the AfricaArray network are used to investigate the seismic velocity structure of the upper mantle beneath southern Africa, and in particular beneath the Kaapvaal Craton. A two-plane approximation method that includes a finite frequency sensitivity kernel is employed to measure Rayleigh wave phase velocities, which are inverted to obtain a quasi-3-D shear wave velocity model of the upper mantle. We find phase velocities for the Kaapvaal Craton and surrounding mobile belts that are comparable to those reported by previous studies, and we find little evidence for variation from east to west across the Namaqua-Natal Belt, a region not well imaged in previous studies. A high-velocity upper-mantle lid is found beneath the Kaapvaal Craton and most of southern Africa. For the Kaapvaal Craton, the thickness of the lid (˜150-200 km) is consistent with the lid thicknesses reported in many previous studies. The cratonic lid is underlain by a ˜100-km thick low-velocity zone with a 3.9 per cent maximum velocity reduction. By comparing the velocity model to those published for other Archean cratons, we find few differences, and therefore conclude that there is little evidence in the shear wave velocity structure of the mantle to indicate that the southern African plateau is supported by an upper-mantle thermal anomaly.

  14. A magma-hydrothermal system beneath Hakone volcano, central Japan, revealed by highly resolved velocity structures

    NASA Astrophysics Data System (ADS)

    Yukutake, Yohei; Honda, Ryou; Harada, Masatake; Arai, Ryuta; Matsubara, Makoto

    2015-05-01

    High-resolution images of subsurface structures are necessary to understand the transport processes of crustal fluids from deep magma sources and their relationship to earthquake swarms in active volcanic regions. Based on a seismic tomography approach, we have developed a new model for the magma-hydrothermal system beneath Hakone volcano, central Japan, where shallow earthquake swarms and crustal deformation associated with inflation of an open-crack source are often observed. By applying travel-time data for local earthquakes to a tomographic inversion, we obtained highly resolved seismic velocity structures that show a region of low P-wave velocity (Vp), low S-wave velocity (Vs), and high Vp/Vs ratios at depths of 10-20 km beneath the volcano, corresponding to the location of the open-crack source. We suggest that the high Vp/Vs ratios represent a deep magma chamber with a high concentration of melt and/or fluids. Deep low-frequency earthquakes, located just beneath this high Vp/Vs zone, may indicate that magmatic fluids are supplied from below. Above the high Vp/Vs zone, a region of low Vp, low Vs, and low Vp/Vs ratios exists at depths of 3-10 km, suggesting the presence of crack-filled water or CO2 supplied from the inferred deep magma chamber. Many earthquake swarms occur in this low Vp/Vs zone, indicating that crustal fluids play an important role in generating the swarms. Similar relationships between magma reservoirs, overlying hydrothermal systems, and swarm activity have been reported from other volcanic areas and thus may be a ubiquitous feature beneath active volcanoes.

  15. Attenuation and velocity structure from diffuse coda waves: Constraints from underground array data

    NASA Astrophysics Data System (ADS)

    Galluzzo, Danilo; La Rocca, Mario; Margerin, Ludovic; Del Pezzo, Edoardo; Scarpa, Roberto

    2015-03-01

    An analysis of coda waves excited in the 0.2-20 Hz frequency band and recorded by the underground array Underseis (central Italy) has been performed to constrain both seismic attenuation at regional scale and velocity structure in the Mount Gran Sasso area. Attenuation was estimated with the MLTWA method, and shows a predominance of scattering phenomena over intrinsic absorption. The values of Qi and Qs are compatible with other estimates obtained in similar tectonic environments. Array methods allowed for a detailed study of the propagation characteristics, demonstrating that earthquake coda at frequencies greater than about 6 Hz is composed of only body waves. Coherence and spectral characteristics of seismic waves measured along the coda of local and regional earthquakes indicate that the wavefield becomes fully diffuse only in the late coda. The frequency-dependent energy partitioning between horizontal and vertical components has been also estimated and compared with synthetic values computed in a layered half-space under the diffuse field assumption. This comparison confirms that, for frequencies higher than 6 Hz, the coda appears as a sum of body waves coming from all directions while, in the low frequency range (0.2-2 Hz), the observations can be well explained by a coda wavefield composed of an equipartition mixture of surface and body waves traveling in a multiple-layered medium. A Monte-Carlo inversion has been performed to obtain a set of acceptable velocity models of the upper crust. The present results show that a broadband coda wavefield recorded in an underground environment is useful to constrain both the regional attenuation and the velocity structure of the target area, thereby complementing the results of classical array analysis of the wavefield.

  16. VARNET-96: three-dimensional upper crustal velocity structure of SW Ireland

    NASA Astrophysics Data System (ADS)

    Landes, M.; O'Reilly, B. M.; Readman, P. W.; Shannon, P. M.; Prodehl, C.

    2003-05-01

    During the VARNET-96 seismic experiment three seismic refraction/wide-angle reflection profiles were acquired in order to examine the crustal structure in the southwest of Ireland. A total of 170 seismic stations were used on 300 recording sites. The shotpoint geometry was designed to allow for inline and offline fan shot recordings on the three profiles, using a total of 34 shots. Results from 3-D ray-trace and inversion modelling illustrate the pervasive lateral heterogeneity of the crust south of the Shannon Estuary. About 5 km of interpreted Palaeozoic sediment at the south coast was associated with the sedimentary infill of the Munster and South Munster Basins. This sedimentary layer, which thins to approximately 2 km in the northern Munster Basin, is significantly thinner than previously estimated from geological field studies. High-velocity zones beneath Dingle Bay and the Kenmare River region may be associated with the deep traces of the Killarney-Mallow Fault Zone and the Cork-Kenmare line. A zone of high-velocity upper crust (6.4-6.6 km s-1) beneath the South Munster Basin is found in the area between the Kenmare-Killarney and the Leinster Granite gravity lows. The depth to the Moho varies from approximately 28-29 km at the south coast to approximately 32-33 km in the Dingle-Shannon Basin. The interpretation of the 2-D and 3-D velocity models suggests that Variscan deformation is confined to sedimentary and upper crustal structures in the southwest of Ireland.

  17. The Study on S-Wave Velocity Structure of Upper Crust in Three Gorges Region of Yangtze River

    NASA Astrophysics Data System (ADS)

    Li, X.; Zhu, P.; Zhou, Q.

    2014-12-01

    The profile of S-wave velocity structure along Badong-Maoping-Tumen is presented using the ambient noise data observed at 10 stations from mobile broadband seismic array which is located at Three Gorges Region. All of available vertical component time series during April and May,2011 have been cross-correlated to estimate the empirical Green functions. Group velocity dispersion curves were measured by applying multiple filtering technique. Using these dispersion curves,we obtain high resolution pure-path dispersions at 0.5-10 second periods. The S-wave velocity structure,which was reconstructed by inverting the pure-path dispersions,reveals the velocity variations of upper crust at Three Gorges Region. Main conclusions are as follows:(1)The velocity variations in the study region have a close relationship with the geological structure and the velocity profile suggests a anticline unit which core area is Huangling block;(2)The relative fast velocity variations beneath Jiuwanxi and its surrounding areas may correspond to the geological structure and earthquake activity there;(3) The high velocity of the upper crustal in Sandouping indicates that the Reservoir Dam of Three Gorges is located at a tectonic stable region.

  18. Finite Element Simulation of Low Velocity Impact Damage on an Aeronautical Carbon Composite Structure

    NASA Astrophysics Data System (ADS)

    Lemanle Sanga, Roger Pierre; Garnier, Christian; Pantalé, Olivier

    2016-06-01

    Low velocity barely visible impact damage (BVID) in laminated carbon composite structures has a major importance for aeronautical industries. This contribution leads with the development of finite element models to simulate the initiation and the propagation of internal damage inside a carbon composite structure due by a low velocity impact. Composite plates made from liquid resin infusion process (LRI) have been subjected to low energy impacts (around 25 J) using a drop weight machine. In the experimental procedure, the internal damage is evaluated using an infrared thermographic camera while the indentation depth of the face is measured by optical measurement technique. In a first time we developed a robust model using homogenised shells based on degenerated tri-dimensional brick elements and in a second time we decided to modelize the whole stacking sequence of homogeneous layers and cohesive interlaminar interfaces in order to compare and validate the obtained results. Both layer and interface damage initiation and propagation models based on the Hashin and the Benzeggagh-Kenane criteria have been used for the numerical simulations. Comparison of numerical results and experiments has shown the accuracy of the proposed models.

  19. Convergence of third-order velocity structure functions in axisymmetric turbulence

    NASA Astrophysics Data System (ADS)

    Godeferd, Fabien; Delache, Alexandre

    2011-11-01

    Kolmogorov theory (1941) for isotropic turbulence establishes asymptotic scaling laws for the statistics of n-th order structure functions at high Reynolds number, in terms of dissipation ɛ and separation distance r for the velocity increment δu . A famed relationship is the -4/5 law. When the turbulent flow is anisotropic, due to external distortions (background rotation,...) to inhomogeneities or initial conditions (jets, ``isotropic'' grid turbulence), such laws may fail. We examine the applicability of the K41 predictions for third-order moments of velocity structure functions, and evaluate low Reynolds number effects and anisotropic effects on the departure with the -4/5 law. We consider rotating or stably stratified turbulence, whose statistics are obtained by Direct Numerical Simulations or by a two-point statistical model allowing to reach high Reynolds numbers. We link anisotropic spectral statistics for energy transfer with <(δu) 3 > and derive physical space statistics from spectral data of the statistical model. Although K41 scalings may arguably not apply to anisotropic turbulence, some justifications for anisotropic turbulence statistics can be provided (Taylor et al. PRE 2003) by specific data processing in DNS.

  20. Crustal velocity structure beneath the western Andes of Colombian using receiver-function inversion

    NASA Astrophysics Data System (ADS)

    Monsalve, Hugo; Pacheco, Javier F.; Vargas, Carlos A.; Morales, Yorly A.

    2013-12-01

    Analysis of teleseismic records obtained in two broadband seismic stations of three components located on the Andean region of Colombia is presented in this work. The two stations are located at the Western Cordillera (WC), station BOL, and at the Central Cordillera (CC), station PBLA. The analysis of seismograms was performed by inversion of the receiver functions (RF) in order to obtain the crustal velocity structure beneath the receivers. The receiver function is a spectral ratio obtained from teleseismic earthquakes recorded by broadband seismic stations, which allows the calculation of the velocity structure beneath the receiver by removing source effects in the horizontal components of the seismic traces. Data stacking was performed in order to improve signal to noise ratio and then the data was inverted by using two optimization algorithms: a genetic algorithm (GA), and a simulated annealing algorithm (SA). The present work calculates the receiver functions using teleseismic earthquakes at epicentral distances (Δ) ranging between 30° and 90° and recorded at the two stations within the years 2007 and 2009.

  1. Seismic scattering and velocity structure near the Earth's core-mantle boundary beneath the South China Sea and north Indonesia

    NASA Astrophysics Data System (ADS)

    Yao, J.; Wen, L.

    2013-12-01

    We constrain seismic scatterers near the Earth's core-mantle boundary beneath the South China Sea and north Indonesia using the observed PKP precursory energy and velocity structure in the region using the travel time of the core-reflected phases. The PKP precursor data are collected from the seismic data recorded in the USArray and the core-reflected seismic data include ScS and ScP phases recorded in the China National Digital Seismographic Network, the F-net in Japan, the Global Seismographic Network and several regional arrays. Migration of PKP precursory energy reveals crescent-shaped scatterers distributed from the middle of the South China Sea to the north of Sulawesi Island. ScSH-SH differential-travel-times suggest a complex shear-velocity structure near the core-mantle boundary, changing from a low-velocity patch to a high shear-velocity patch and to another low shear-velocity patch from east to west beneath the middle of the South China Sea. ScP-P differential travel-time residuals reveal a low-velocity patch in northeast of Sulawesi Sea, a high-velocity patch in north of Sulawesi Sea, another low-velocity patch in the middle of Sulawesi Sea and another high-velocity patch in north of the Kalimantan Island. Overall, the seismic structure in the region can be characterized by alternative presence of high- and low-velocity patches near the core-mantle boundary, with the abrupt shear-wave velocity changes between the patches being the source of seismic scattering in the region.

  2. Large-scale power spectrum and structures from the ENEAR galaxy peculiar velocity catalogue

    NASA Astrophysics Data System (ADS)

    Zaroubi, S.; Bernardi, M.; da Costa, L. N.; Hoffman, Y.; Alonso, M. V.; Wegner, G.; Willmer, C. N. A.; Pellegrini, P. S.

    2001-09-01

    We estimate the mass density fluctuations power spectrum (PS) on large scales by applying a maximum likelihood technique to the peculiar velocity data of the recently completed redshift-distance survey of early-type galaxies (hereafter ENEAR). Parametric cold dark matter (CDM)-like models for the PS are assumed, and the best-fitting parameters are determined by maximizing the probability of the model given the measured peculiar velocities of the galaxies, their distances and estimated errors. The method has been applied to CDM models with and without COBE normalization. The general results are in agreement with the high-amplitude power spectra found from similar analyses of other independent all-sky catalogue of peculiar velocity data such as MARK III and SFI, in spite of the differences in the way these samples were selected, the fact that they probe different regions of space and galaxy distances are computed using different distance relations. For example, at k=0.1hMpc-1 the power spectrum value is P(k)Ω1.2=(6.5+/-3)×103(h- 1Mpc)3 and η8≡σ8Ω0.6=1.1- 0.35+0.2 the quoted uncertainties refer to 3σ error level. We also find that, for ΛCDM and OCDM COBE-normalized models, the best-fitting parameters are confined by a contour approximately defined by Ωh1.3=0.377+/-0.08 and Ωh0.88=0.517+/-0.083 respectively. Γ-shape models, free of COBE normalization, result in the weak constraint of Γ>=0.17 and in the rather stringent constraint of η8=1.0+/-0.25. All quoted uncertainties refer to 3σ confidence level (c.l.). The calculated PS has been used as a prior for Wiener reconstruction of the density field at different resolutions and the three-dimensional velocity field within a volume of radius ~80h-1Mpc. All major structures in the nearby Universe are recovered and are well matched to those predicted from all-sky redshift surveys. The robustness of these features has been tested with constrained realizations (CR). Analysis of the reconstructed three

  3. The structural and dynamical aspects of boron nitride nanotubes under high velocity impacts.

    PubMed

    Machado, Leonardo D; Ozden, Sehmus; Tiwary, ChandraSekhar; Autreto, Pedro A S; Vajtai, Robert; Barrera, Enrique V; Galvao, Douglas S; Ajayan, Pulickel M

    2016-06-01

    This communication report is a study on the structural and dynamical aspects of boron nitride nanotubes (BNNTs) shot at high velocities (∼5 km s(-1)) against solid targets. The experimental results show unzipping of BNNTs and the formation of hBN nanoribbons. Fully atomistic reactive molecular dynamics simulations were also carried out to gain insights into the BNNT fracture patterns and deformation mechanisms. Our results show that longitudinal and axial tube fractures occur, but the formation of BN nanoribbons from fractured tubes was only observed for some impact angles. Although some structural and dynamical features of the impacts are similar to the ones reported for CNTs, because BNNTs are more brittle than CNTs this results in a larger number of fractured tubes but with fewer formed nanoribbons. PMID:27189765

  4. Vibrational fine structure of C5 via anion slow photoelectron velocity-map imaging

    NASA Astrophysics Data System (ADS)

    Weichman, Marissa L.; Kim, Jongjin B.; Neumark, Daniel M.

    2013-10-01

    High-resolution anion photoelectron spectra of cryogenically cooled C_5^ - clusters are reported using slow photoelectron velocity-map imaging spectroscopy. We resolve vibronic transitions to the ν2 stretching mode and multiply excited ν5, ν6, and ν7 bending modes of neutral C5 with significantly higher accuracy than previous experiments. Weak transitions to Franck-Condon (FC) forbidden singly excited bending modes are made possible by Herzberg-Teller coupling between electronic states of the neutral cluster. In addition, we resolve vibrational fine structure corresponding to different angular momentum states of multiply excited bending modes. The observation of this multiplet structure, some of which is FC forbidden, is attributed to Renner-Teller coupling between vibrational levels in the C_5^ - ground electronic state.

  5. HIERARCHICAL STRUCTURE OF MAGNETOHYDRODYNAMIC TURBULENCE IN POSITION-POSITION-VELOCITY SPACE

    SciTech Connect

    Burkhart, Blakesley; Lazarian, A.; Goodman, Alyssa; Rosolowsky, Erik

    2013-06-20

    Magnetohydrodynamic turbulence is able to create hierarchical structures in the interstellar medium (ISM) that are correlated on a wide range of scales via the energy cascade. We use hierarchical tree diagrams known as dendrograms to characterize structures in synthetic position-position-velocity (PPV) emission cubes of isothermal magnetohydrodynamic turbulence. We show that the structures and degree of hierarchy observed in PPV space are related to the presence of self-gravity and the global sonic and Alfvenic Mach numbers. Simulations with higher Alfvenic Mach number, self-gravity and supersonic flows display enhanced hierarchical structure. We observe a strong dependency on the sonic and Alfvenic Mach numbers and self-gravity when we apply the statistical moments (i.e., mean, variance, skewness, kurtosis) to the leaf and node distribution of the dendrogram. Simulations with self-gravity, larger magnetic field and higher sonic Mach number have dendrogram distributions with higher statistical moments. Application of the dendrogram to three-dimensional density cubes, also known as position-position-position (PPP) cubes, reveals that the dominant emission contours in PPP and PPV are related for supersonic gas but not for subsonic. We also explore the effects of smoothing, thermal broadening, and velocity resolution on the dendrograms in order to make our study more applicable to observational data. These results all point to hierarchical tree diagrams as being a promising additional tool for studying ISM turbulence and star forming regions for obtaining information on the degree of self-gravity, the Mach numbers and the complicated relationship between PPV and PPP data.

  6. Contrasting sound velocity and intermediate-range structural order between polymerized and depolymerized silicate glasses under pressure

    NASA Astrophysics Data System (ADS)

    Sakamaki, Tatsuya; Kono, Yoshio; Wang, Yanbin; Park, Changyong; Yu, Tony; Jing, Zhicheng; Shen, Guoyin

    2014-04-01

    X-ray diffraction and ultrasonic velocity measurements of three silicate glasses (in jadeite, albite, and diopside compositions) show a sharp contrast in pressure-induced changes in structure and elasticity. With increasing pressure to around 6 GPa, polymerized glasses (jadeite and albite) display large shift in the first sharp diffraction peak (FSDP) in the structure factor, S(Q), to higher-Q values, indicating rapid shrinkage in the intermediate-range ordered (IRO) structure. Above 6 GPa, the shift of FSDP decelerates, suggesting that shrinkage in the IRO structure has been largely completed and the structure evolution is now dominated by the diminution of the interstitial volume in a more densely packed arrangement. Associated with this structural change, sound velocities increase with pressure above 6 GPa. In contrast, the depolymerized diopside glass exhibits smaller changes in the pressure dependence for both sound velocities and FSDP positions. Compared to the polymerized glasses, the velocities are faster and the positions of FSDP appear at higher-Q under the same experimental conditions. The results suggest that the depolymerized diopside glass has an initially denser IRO structure compared to that of the polymerized glasses, and there are no sufficient interstitial voids to shrink. The different behaviors between polymerized and depolymerized glasses are apparently related to the initial linkage of tetrahedra and the pressure-induced structural reactions. These results suggest that under compression up to 10 GPa, the degree of polymerization is a major factor affecting the IRO network structure and the sound velocity of silicate glasses.

  7. Can we trace the eastern Gondwanan margin in Australia? New perspectives from transdimensional inversion of ambient noise for 3D shear velocity structure

    NASA Astrophysics Data System (ADS)

    Pilia, S.; Rawlinson, N.; Direen, N. G.

    2013-12-01

    provides a parsimonious trade-off between data fit and model complexity, rather than adopting the ad hoc regularization often utilized by linearized inversion techniques. After obtaining 2D maps for different periods, these are then discretized into a uniform grid of nodes, each of which has associated group dispersion curve. Subsequently, the group dispersion curve at each node is inverted for 1D shear velocity model using the same robust, data driven Bayesian technique as before. Finally, the 1D models are merged together to achieve the first 3D shear velocity structure beneath southeast Australia, Bass Strait and Tasmania to a depth of 30 km, which is expected to shed new light on the ancient eastern Gondwana margin in Australia. Preliminary results show crustal structure to a high level of detail, particularly in mainland Australia and Tasmania. The transition along the proto-Pacific margin of eastern Gondwana from Precambrian central and western Australia to Paleozoic eastern Australia has been revealed, which appears to follow a trend of relatively low shear velocity that reconnects, across Bass Strait, to the Tamar Fracture System in eastern Tasmania.

  8. Control of coupling in 1D photonic crystal coupled-cavity nano-wire structures via hole diameter and position variation

    NASA Astrophysics Data System (ADS)

    Zain, A. R. Md; De La Rue, R. M.

    2015-12-01

    We have successfully demonstrated close experimental control of the resonance splitting/free spectral range of a coupled micro-cavity one-dimensional photonic crystal/photonic wire device structure based on silicon-on-insulator. Clear splitting of the resonances, with FSR values ranging from 8 nm to 48 nm, was obtained through the use of different hole arrangements within the middle section of the device structures, between the coupled cavities. The results show good agreement with calculations obtained using a finite-difference time-domain simulation approach.

  9. 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).

  10. Structural studies of an arabinan from the stems of Ephedra sinica by methylation analysis and 1D and 2D NMR spectroscopy.

    PubMed

    Xia, Yong-Gang; Liang, Jun; Yang, Bing-You; Wang, Qiu-Hong; Kuang, Hai-Xue

    2015-05-01

    Plant arabinan has important biological activity. In this study, a water-soluble arabinan (Mw∼6.15kDa) isolated from the stems of Ephedra sinica was found to consist of (1→5)-Araƒ, (1→3,5)-Araƒ, T-Araƒ, (1→3)-Araƒ and (1→2,5)-Araƒ residues at proportions of 10:2:3:2:1. A tentative structure was proposed by methylation analysis, nuclear magnetic resonance (NMR) spectroscopy ((1)H NMR, (13)C NMR, DEPT-135, (1)H-(1)H COSY, HSQC, HMBC and ROESY) and literature. The structure proposed includes a branched (1→5)-α-Araf backbone where branching occurs at the O-2 and O-3 positions of the residues with 7.7% and 15.4% of the 1,5-linked α-Araf substituted at the O-2 and O-3 positions. The presence of a branched structure was further observed by atomic force microscopy. This polymer was characterized as having a much longer linear (1→5)-α-Araf backbone as a repeating unit. In particular, the presence of α-Araf→3)-α-Araf-(1→3)-α-Araf-(1→ attached at the O-2 is a new finding. This study may facilitate a deeper understanding of structure-activity relationships of biological polysaccharides from the stems of E. sinica. PMID:25659720

  11. Structures in Ionospheric Number Density and Velocity Associated with Polar Cap Ionization Patches

    NASA Technical Reports Server (NTRS)

    Kivanc, O.; Heelis, R. A.

    1997-01-01

    Spectral characteristics of polar cap F region irregularities on large density gradients associated with polar ionization patches are studied using in situ measurements made by the Dynamics Explorer 2 (DE 2) spacecraft. The 18 patches studied in this paper were identified by the algorithm introduced by Coley and Heelis, and they were encountered during midnight-noon passes of the spacecraft. Density and velocity spectra associated with these antisunward convecting patches are analyzed in detail. Observations indicate the presence of structure on most patches regardless of the distance between the patch and the cusp where they are believed to develop. Existence of structure on both leading and trailing edges is established when such edges exist. Results, which show no large dependence of Delta N/N power on the sign of the edge gradient del N, do not allow the identification of leading and trailing edges of the patch. The Delta N/N is an increasing function of gradient del N regardless of the sign of the gradient. The correlation between Delta N/N and Delta V is generally poor, but for a given intensity in Delta V, Delta N/N maximizes in regions of large gradients in N. There is evidence for the presence of unstructured patches that seem to co-exist with unstructured horizontal velocities. Slightly smaller spectral indices for trailing edges support the presence of the E X B drift instability. Although this instability is found to be operating in some cases, results suggest that stirring may be a significant contributor to kilometer-size structures in the polar cap.

  12. REINTERPRETATION OF SLOWDOWN OF SOLAR WIND MEAN VELOCITY IN NONLINEAR STRUCTURES OBSERVED UPSTREAM OF EARTH'S BOW SHOCK

    SciTech Connect

    Parks, G. K.; Lin, N.; Lee, E.; Hong, J.; Fu, S. Y.; McCarthy, M.; Cao, J. B.; Liu, Y.; Shi, J. K.; Goldstein, M. L.; Canu, P.; Dandouras, I.; Reme, H.

    2013-07-10

    Two of the many features associated with nonlinear upstream structures are (1) the solar wind (SW) mean flow slows down and deviates substantially and (2) the temperature of the plasma increases in the structure. In this Letter, we show that the SW beam can be present throughout the entire upstream event maintaining a nearly constant beam velocity and temperature. The decrease of the velocity is due to the appearance of new particles moving in the opposite direction that act against the SW beam and reduce the mean velocity as computed via moments. The new population, which occupies a larger velocity space, also contributes to the second moment, increasing the temperature. The new particles include the reflected SW beam at the bow shock and another population of lower energies, accelerated nearby at the shock or at the boundary of the nonlinear structures.

  13. Velocity Fields and Structure above LDE arcades: Possible Observational Signatures of Reconnection

    NASA Astrophysics Data System (ADS)

    McKenzie, D. E.

    2000-10-01

    In a growing number of CME events, the X-ray images from Yohkoh SXT reveal velocity fields above the eruption site, directed downward into the top of the flare arcade. These motions, with plane-of-sky speeds typically between 50 -- 500 km s-1, are evidenced by both dark (in X-rays) and bright (i.e., X-ray emitting) features, some of which appear to have a looplike morphology. No counterparts have been detected in simultaneous Hα or EUV imagery. The ``supra-arcade downflows" are tentatively interpreted as resulting from magnetic field line shrinkage, a signature of outflow from reconnection sites above the post-eruption arcade. I will present a summary of the flare events in which these velocity fields have been detected (to date, 17 in the last two years), and movies showing the structure and motion above some of the flare arcades. This work was supported by NASA under Marshall Space Flight Center contract NAS8-40801 with the Lockheed Martin Advanced Technology Center.

  14. Crustal shear-wave velocity structure beneath Sumatra from receiver function modeling

    NASA Astrophysics Data System (ADS)

    Bora, Dipok K.; Borah, Kajaljyoti; Goyal, Ayush

    2016-05-01

    We estimated the shear-wave velocity structure and Vp/Vs ratio of the crust beneath the Sumatra region by inverting stacked receiver functions from five three-component broadband seismic stations, located in diverse geologic setting, using a well known non-linear direct search approach, Neighborhood Algorithm (NA). Inversion results show significant variation of sediment layer thicknesses from 1 km beneath the backarc basin (station BKNI and PMBI) to 3-7 km beneath the coastal part of Sumatra region (station LHMI and MNAI) and Nias island (station GSI). Average sediment layer shear velocity (Vss) beneath all the stations is observed to be less (∼1.35 km/s) and their corresponding Vp/Vs ratio is very high (∼2.2-3.0). Crustal thickness beneath Sumatra region varies between 27 and 35 km, with exception of 19 km beneath Nias island, with average crustal Vs ∼3.1-3.4 km/s (Vp/Vs ∼1.8). It is well known that thick sediments with low Vs (and high Vp/Vs) amplify seismic waves even from a small-magnitude earthquake, which can cause huge damage in the zone. This study can provide the useful information of the crust for the Sumatra region. Since, Sumatra is an earthquake prone zone, which suffered the strong shaking of Great Andaman-Sumatra earthquake; this study can also be helpful for seismic hazard assessment.

  15. Analysis of velocity and thermal structures in a transitionally rough turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Doosttalab, Ali; Dharmarathne, Suranga; Araya, Guillermo; Tutkun, Murat; Adrian, Ronald; Castillo, Luciano

    2015-11-01

    A zero pressure gradient turbulent boundary layer flowing over a transitionally rough surface (24-grit sandpaper) with k+ = 11 and Reynolds numbers based on momentum thickness of around 2400 is studied using direct numerical simulation (DNS). Heat transfer between the isothermal rough surface and the turbulent flow with molecular Prandtl number Pr = 0 . 71 is simulated. The dynamic multi-scale approach developed by Araya et al. (2011) is employed to prescribe realistic time-dependent thermal inflow boundary conditions. Above the roughness sub-layer (3 - 5 k) it is found that statistics of the temperature field, including higher order moments and conditional averages, are the same for the smooth and rough surface flow, showing that the Townsend's Reynolds number similarity hypothesis applies for the thermal field as well as the velocity field for the Reynolds number and k+ considered in this study. Also the velocity and thermal structures of the developing boundary layer were studied by means of multi-point correlations and POD analysis.

  16. Change in the structure of Escherichia coli population related to the settling velocities in karst aquifer

    NASA Astrophysics Data System (ADS)

    Petit, F.; Massei, N.; Berthe, T.; Deloffre, J.; Fournier, M.; Bertel, F.; jolivet, F.; lallemand, H.; Niepceron, F.; Sellier, C.; Benjamin, S.

    2012-04-01

    Change in the structure of Escherichia coli population related to the settling velocities in karst aquifer. Fabienne Petit1, Fanny Bertel2, Florence Jolivet2, Hélène Lallemand2, Fanny Niepceron2, Clémentine Sellier2, Benjamin Smith2, Thierry Berthe, Julien Deloffre1, Matthieu Fournier1,Nicolas Massei 1. 1- Université de Rouen, UMR 6143 M2C, 76821 Mont-Saint-Aignan, France 1- CNRS, UMR 6143 M2C, 76821 Mont-Saint-Aignan, France 1- SFR SCALE, 76821 Mont-Saint-Aignan, France 2 Research project of students from MasterEnvironment ( ESEB University of Rouen) According to the farming or human use of their watershed, the karst aquifers were particularly vulnerable to contamination by fecal bacteria mainly Escherichia coli (E. coli). To date, if E. coli is a commensal bacteria originated from intestinal tracts of humans and vertebrate animals, the water and sediment are also considered as a putative second habitat where some strains could be naturalized. Among the phenotypic characteristics of E.coli, association with particles not only could enhance the survival of some strains but also greatly influenced the particles dynamics. The great genetic diversity of E. coli may explain this variety of lifestyles of this bacteria species. Indeed we have previously shown that in river, the structure of the population of E. coli was not stable, but depended on hydrological conditions (Ratajczak, 2010). In this work we go further into the understanding of the behaviour of E. coli population in karstic hydrosystem by investigating (i) the structure of E. coli population based on the distribution in four main phylo-groups (A, B1, B2, D) according their settling velocities from surface water to groundwater. For this purpose we combined microbiology , microscopy (SEM) and hydrology approaches. During their transfer along the karst hydrosystem, both modalities of the association of E. coli to the particles and, the structure of E. coli population were modified. Settling experiment led

  17. Synthesis, structure, and electrochemistry and magnetic properties of a novel 1D homochiral MnIII(5-Brsalen) coordination polymer with left-handed helical character

    NASA Astrophysics Data System (ADS)

    Dong, Dapeng; Yu, Naisen; Zhao, Haiyan; Liu, Dedi; Liu, Jia; Li, Zhenghua; Liu, Dongping

    2016-01-01

    A novel homochiral manganese (III) Mn(5-Brsalen) coordination polymer with left-handed helical character by spontaneous resolution on crystallization by using Mn(5-Brsalen) and 4,4-bipyridine, [MnIII(5-Brsalen)(4,4-bipy)]·ClO4·CH3OH (1) (4,4-bipy = 4,4-bipyridine) has been synthesized and structurally characterized by X-ray single-crystal diffraction, elemental analysis and infrared spectroscopy. In compound 1, each manganese(III) anion is six-coordinate octahedral being bonded to four atoms of 5-Brsalen ligand in an equatorial plane and two nitrogen atoms from a 4,4-bipyridine ligand in axial positions. The structure of compound 1 can be described a supramolecular 2D-like structure which was formed by the intermolecular π-stacking interactions between the neighboring chains of the aromatic rings of 4,4-bipyridine and 5-Brsalen molecules. UV-vis absorption spectrum, electrochemistry and magnetic properties of the compound 1 have also been studied.

  18. 3D P and S Wave Velocity Structure and Tremor Locations in the Parkfield Region

    NASA Astrophysics Data System (ADS)

    Zeng, X.; Thurber, C. H.; Shelly, D. R.; Bennington, N. L.; Cochran, E. S.; Harrington, R. M.

    2014-12-01

    We have assembled a new dataset to refine the 3D seismic velocity model in the Parkfield region. The S arrivals from 184 earthquakes recorded by the Parkfield Experiment to Record MIcroseismicity and Tremor array (PERMIT) during 2010-2011 were picked by a new S wave picker, which is based on machine learning. 74 blasts have been assigned to four quarries, whose locations were identified with Google Earth. About 1000 P and S wave arrivals from these blasts at permanent seismic network were also incorporated. Low frequency earthquakes (LFEs) occurring within non-volcanic tremor (NVT) are valuable for improving the precision of NVT location and the seismic velocity model at greater depths. Based on previous work (Shelley and Hardebeck, 2010), waveforms of hundreds of LFEs in same family were stacked to improve signal qualify. In a previous study (McClement et al., 2013), stacked traces of more than 30 LFE families at the Parkfileld Array Seismic Observatory (PASO) have been picked. We expanded our work to include LFEs recorded by the PERMIT array. The time-frequency Phase Weight Stacking (tf-PWS) method was introduced to improve the stack quality, as direct stacking does not produce clear S-wave arrivals on the PERMIT stations. This technique uses the coherence of the instantaneous phase among the stacked signals to enhance the signal-to-noise ratio (SNR) of the stack. We found that it is extremely effective for picking LFE arrivals (Thurber et al., 2014). More than 500 P and about 1000 S arrivals from 58 LFE families were picked at the PERMIT and PASO arrays. Since the depths of LFEs are much deeper than earthquakes, we are able to extend model resolution to lower crustal depths. Both P and S wave velocity structure have been obtained with the tomoDD method. The result suggests that there is a low velocity zone (LVZ) in the lower crust and the location of the LVZ is consistent with the high conductivity zone beneath the southern segment of the Rinconada fault that

  19. Shear-wave Velocity Structure of Surabaya, Indonesia, Inferred from Microtremor Observation

    NASA Astrophysics Data System (ADS)

    Deng, X.; Megawati, K.; Yamanaka, H.

    2010-12-01

    Surabaya, the second-largest city of Indonesia, is located on the northern shore of eastern Java at the mouth of the Mas River and along the edge of the Madura Strait. Though there are not many occurrences of large earthquakes, the region has been exposed to moderate earthquakes frequently. Moreover, Surabaya lies over the alluvium deposit that can be critical for the amplification of seismic waves. Towards the southwestern part of the study area, there is the exposure of sedimentary rocks. Shear wave velocity (Vs) is an important parameter for evaluating the dynamic soil behavior of subsurface structures. Small array measurements of microtremor at 36 sites in the city of Surabaya were carried to estimate the shallow Vs profiles for site effect analysis. The spatial autocorrelation coefficient (SPAC) method was used to determine the phase velocity in the period ranging from 0.1 s to 0.5 s and the iterative inversion technique was subsequently applied to determine the Vs profiles at each site. Large array measurements of microtremor at 11 sites were also carried out to estimate deep Vs profiles. Based on the previous shallow Vs profiles from SPAC, the frequency wavenumber (FK) method was subsequently used to determine the phase velocity in the period from 0.5 s to 3 s and depth of soil profiles down to 800 m. Vs30, the average shear wave velocity in the top 30 m of soil profiles, is a representative value to classify the site condition. It was calculated at each site according to definition in the International Building Code (IBC 2006). The maps of site classification are proposed with Kriging interpolations. Site class D is assigned in southwest corner part while site class E is assigned to the rest of Surabaya. The low Vs values confirms well with the loose soil deposit of the area. Additionally, the regression analysis between topographic elevation and Vs in the logarithm shows a linear relationship. However, it is difficult to conclude the relationship between

  20. The Small-Scale Structure of High-Velocity Na I Absorption Toward M81

    NASA Astrophysics Data System (ADS)

    Roth, K. C.; Meyer, D. M.; Lauroesch, J. T.

    2000-12-01

    We present high-resolution (R=20,000) integral field spectra of the Na I absorption toward the nucleus of the nearby spiral galaxy M81 (NGC 3031) obtained in April 2000 with the WIYN 3.5-m telescope and the DensePak fiber optic bundle. Our DensePak map covers the central 27 x 43 arcsec of M81 at a spatial resolution of 4 arcsec which corresponds to a projected length scale of 63 pc at the distance of the galaxy (3.25 Mpc). These data were intended to explore the spatial extent of high-velocity (v = 110-130 km/s) gas seen in Na I, Mg I and Mg II absorption toward SN 1993J by Bowen et al. (1994), which they proposed is due to tidal material associated with interactions between M81 and nearby M82 (Yun, Ho & Lo 1993). No H I gas at these velocities has been detected in 21 cm interferometry maps near the position of SN 1993J (2.6 arcmin SW of the M81 nucleus). Our Na I map of the M81 core shows no evidence of the strong absorption seen at v = 110-130 km/s toward SN 1993J. However, our map does reveal a strong Na I component at v = 220 km/s in several fibers that appears to trace a filamentary structure running from the SW to the NE across the M81 nuclear region. The origin and distance of this filament are unknown. No H I gas at v = 220 km/s has previously been detected in 21 cm studies of the core. At the location of SN 1993J, Bowen et al. measured weak Mg II absorption at this velocity but found no evidence of corresponding Na I absorption. The only known H I gas that corresponds to this velocity in the M81 group are the H I streamers found around M82 by Yun, Ho, & Lo that they interpreted as tidally disrupted M82 disk material.

  1. Joint Inversion of Seismic and Gravity Data for Velocity Structure and Hypocentral Locations of the Colombian Subduction Zone

    NASA Astrophysics Data System (ADS)

    Syracuse, E. M.; Maceira, M.; Prieto, G. A.; Zhang, H.; Ammon, C. J.

    2014-12-01

    Joint inversions of geophysical data recover models that simultaneously fit multiple types of constraints while playing upon the various sensitivities of each data type. Here, we combine body wave arrival times with surface wave dispersion measurements and gravity observations to develop a combined 3D P- and S-wave velocity model for the crust and upper mantle of Colombia. P- and S-wave arrival times were obtained for local earthquakes from instruments in the Colombian National Seismic Network. Rayleigh wave dispersion curves were inverted for using a subset of network stations and larger local earthquakes. Gravity observations were extracted from the global satellite-based model EGM2008. Preliminary results using body waves only show reduced velocities beneath the volcanic arc in the upper 25 km of the crust. Crustal velocities are also reduced from the 1D starting model beneath the Eastern Cordillera in the northern half of the country. Relocations of intermediate-depth seismicity clearly indicate a discontinuity in the slab centered 5° N latitude, where the southern portion of the slab is ~200 km trenchward of the northern portion, coincident with the termination of arc volcanism and in recent years interpreted as due to a slab tear [Vargas and Mann, 2013]. Seismicity below 100 km depth in the southern portion of the subduction zone­­­ is surrounded by a ~100-km-thick region of elevated velocities, associated with the subduction of the Nazca Plate, and embedded within a broader region of reduced velocities. The northern portion of the subduction zone at 100 km depth and below is characterized by a broad region of elevated velocities, which may be consistent with a slab of an old, thickened Caribbean Plate origin. The overlapping of the edges of the Nazca and Caribbean slabs may contribute to the seismicity of the Bucaramanga nest.

  2. Shear-velocity structure, radial anisotropy and dynamics of the Tibetan crust

    NASA Astrophysics Data System (ADS)

    Agius, Matthew R.; Lebedev, Sergei

    2014-12-01

    Geophysical and geological data suggest that Tibetan middle crust is a partially molten, mechanically weak layer, but it is debated whether this low-viscosity layer is present beneath the entire plateau, what its properties are, how it deforms, and what role it has played in the plateau's evolution. Broad-band seismic surface waves yield resolution in the entire depth range of the Tibetan crust and can be used to constrain its shear-wave velocity structure (indicative of crustal composition, temperature and partial melting) and radial anisotropy (indicative of the patterns of deformation). We measured Love- and Rayleigh-wave phase-velocity curves in broad period ranges (up to 7-200 s) for a few tens of pairs and groups of stations across Tibet, combining, in each case, hundreds of interstation measurements, made with cross-correlation and waveform-inversion methods. Shear-velocity profiles were then determined by extensive series of non-linear inversions of the data, designed to constrain the depth-dependent ranges of isotropic-average shear speeds and radial anisotropy. Shear wave speeds within the Tibetan middle crust are anomalously low and, also, show strong lateral variations across the plateau. The lowest mid-crustal shear speeds are found in the north and west of the plateau (˜3.1-3.2 km s-1), within a pronounced low-velocity zone. In southeastern Tibet, crustal shear wave speeds increase gradually towards southeast, whereas in the north, the change across the Kunlun Fault is relatively sharp. The lateral variations of shear speeds within the crust are indicative of those in temperature. A mid-crustal temperature of 800 °C, reported previously, can account for the low shear velocities across Lhasa. In the north, the temperature is higher and exceeds the solidus, resulting in partial melting that we estimate at 3-6 per cent. Strong radial anisotropy is required by the data in western-central Tibet (>5 per cent) but not in northeastern Tibet. The amplitude

  3. Quantification of transition dipole strengths using 1D and 2D spectroscopy for the identification of molecular structures via exciton delocalization: Application to α-helices

    PubMed Central

    Grechko, Maksim; Zanni, Martin T.

    2012-01-01

    Vibrational and electronic transition dipole strengths are often good probes of molecular structures, especially in excitonically coupled systems of chromophores. One cannot determine transition dipole strengths using linear spectroscopy unless the concentration is known, which in many cases it is not. In this paper, we report a simple method for measuring transition dipole moments from linear absorption and 2D IR spectra that does not require knowledge of concentrations. Our method is tested on several model compounds and applied to the amide I′ band of a polypeptide in its random coil and α-helical conformation as modulated by the solution temperature. It is often difficult to confidently assign polypeptide and protein secondary structures to random coil or α-helix by linear spectroscopy alone, because they absorb in the same frequency range. We find that the transition dipole strength of the random coil state is 0.12 ± 0.013 D2, which is similar to a single peptide unit, indicating that the vibrational mode of random coil is localized on a single peptide unit. In an α-helix, the lower bound of transition dipole strength is 0.26 ± 0.03 D2. When taking into account the angle of the amide I′ transition dipole vector with respect to the helix axis, our measurements indicate that the amide I′ vibrational mode is delocalized across a minimum of 3.5 residues in an α-helix. Thus, one can confidently assign secondary structure based on exciton delocalization through its effect on the transition dipole strength. Our method will be especially useful for kinetically evolving systems, systems with overlapping molecular conformations, and other situations in which concentrations are difficult to determine. PMID:23163364

  4. Quantification of transition dipole strengths using 1D and 2D spectroscopy for the identification of molecular structures via exciton delocalization: Application to α-helices

    NASA Astrophysics Data System (ADS)

    Grechko, Maksim; Zanni, Martin T.

    2012-11-01

    Vibrational and electronic transition dipole strengths are often good probes of molecular structures, especially in excitonically coupled systems of chromophores. One cannot determine transition dipole strengths using linear spectroscopy unless the concentration is known, which in many cases it is not. In this paper, we report a simple method for measuring transition dipole moments from linear absorption and 2D IR spectra that does not require knowledge of concentrations. Our method is tested on several model compounds and applied to the amide I' band of a polypeptide in its random coil and α-helical conformation as modulated by the solution temperature. It is often difficult to confidently assign polypeptide and protein secondary structures to random coil or α-helix by linear spectroscopy alone, because they absorb in the same frequency range. We find that the transition dipole strength of the random coil state is 0.12 ± 0.013 D2, which is similar to a single peptide unit, indicating that the vibrational mode of random coil is localized on a single peptide unit. In an α-helix, the lower bound of transition dipole strength is 0.26 ± 0.03 D2. When taking into account the angle of the amide I' transition dipole vector with respect to the helix axis, our measurements indicate that the amide I' vibrational mode is delocalized across a minimum of 3.5 residues in an α-helix. Thus, one can confidently assign secondary structure based on exciton delocalization through its effect on the transition dipole strength. Our method will be especially useful for kinetically evolving systems, systems with overlapping molecular conformations, and other situations in which concentrations are difficult to determine.

  5. Shear wave velocity structure in West Java, Indonesia as inferred from surface wave dispersion

    NASA Astrophysics Data System (ADS)

    Anggono, Titi; Syuhada

    2016-02-01

    We investigated the crust and upper mantle of West Java, Indonesia by measuring the group velocity dispersion of surface waves. We analyzed waveform from four teleseismic earthquake recorded at three 3-component broadband seismometers. We analyzed fundamental mode of Rayleigh and Love waves from vertical, radial, and transverse components using multiple filter technique. We inverted the measured group velocity to obtain shear wave velocity profile down to 200 km depth. We observed low shear wave velocity zone at depth of about 20 km. Shear velocity reduction is estimated to be 18% compared to the upper and lower velocity layer. The low velocity zone might be associated with the subducting slab of Indo-Australian Plate as similar characteristics of low velocity zones also observed at other subducting regions.

  6. On the Velocity Field and the 3D Structure of the Galactic Soccer Ball Abell 43

    NASA Astrophysics Data System (ADS)

    Rauch, Thomas; Werner, Klaus; Ercolano, Barbara; Köppen, Joachim

    2005-11-01

    Planetary nebulae (PNe) and their central stars (CSs) are ideal tools to test evolutionary theory: photospheric properties of their exciting stars give stringent constraints for theoretical predictions of stellar evolution. The nebular abundances display the star's photosphere chemical composition at the time of the nebula's ejection which allows to look back into the history of stellar evolution. More importantly, they even provide a possibility to investigate on the chemical evolution of our Galaxy because most of the nuclear processed material goes back into the interstellar medium via PNe. The recent developments in observation techniques and the new three-dimensional photoionization code MOCASSIN (Ercolano et al. 2003) enable us to analyze PNe properties accurately by the construction of consistent models of PNe and CSs. In addition to PNe imaging and spectroscopy, detailed information about the velocity field within the PNe is a pre-requisite to employ de-projection techniques in modeling the physical structure of the PNe.

  7. Large-scale structure after COBE: Peculiar velocities and correlations of cold dark matter halos

    NASA Technical Reports Server (NTRS)

    Zurek, Wojciech H.; Quinn, Peter J.; Salmon, John K.; Warren, Michael S.

    1994-01-01

    Large N-body simulations on parallel supercomputers allow one to simultaneously investigate large-scale structure and the formation of galactic halos with unprecedented resolution. Our study shows that the masses as well as the spatial distribution of halos on scales of tens of megaparsecs in a cold dark matter (CDM) universe with the spectrum normalized to the anisotropies detected by Cosmic Background Explorer (COBE) is compatible with the observations. We also show that the average value of the relative pairwise velocity dispersion sigma(sub v) - used as a principal argument against COBE-normalized CDM models-is significantly lower for halos than for individual particles. When the observational methods of extracting sigma(sub v) are applied to the redshift catalogs obtained from the numerical experiments, estimates differ significantly between different observation-sized samples and overlap observational estimates obtained following the same procedure.

  8. Syntheses and crystal structures of four 1-D or 2-D coordination polymers based on 1-((benzotriazol-1-yl)methyl)-1 H-1,3-imidazole

    NASA Astrophysics Data System (ADS)

    Zhou, Xiaoli; Li, Weiqiang; Jin, Guanghua; Zhao, Dong; Zhu, Xiaoqing; Meng, Xiangru; Hou, Hongwei

    2011-05-01

    In this paper, four coordination polymers, {[Ag(bmi)]·NO 3} n ( 1), [Co(N 3) 2(bmi) 2] n ( 2), [Cu(SCN) 2(bmi) 2] n ( 3), and {[Cu(bmi) 2(CH 3OH)(H 2O)]·(ClO 4) 2} n ( 4) have been synthesized through the reactions of an unsymmetrical ligand 1-((benzotriazol-1-yl)methyl)-1 H-1,3-imidazole (bmi) with Ag(I), Co(II) and Cu(II) salts at room temperature. X-ray diffraction analyses showed that compound 1 exhibits double-stranded helical chain. Compounds 2- 4 display 2-D rhombus grid network structure. The rhombus grid consists of 32-membered rings, and gives the dimensions of ca. 8.9 × 8.9 Å for compound 2, ca. 10.1 × 10.1 Å for compound 3, and ca. 9.7 × 9.5 Å for compound 4. In addition, the 2-D layers of compound 3 are stacked into 3-D structure via π- π interactions, while the 3-D architecture of compound 4 is realized through complicated hydrogen bonds and π- π interactions. The thermal analyses of compounds 1 and 3 indicate that they have high thermal stability and are stable up to 259 °C.

  9. Three-dimensional upper crustal velocity structure beneath San Francisco Peninsula, California

    NASA Astrophysics Data System (ADS)

    Parsons, Tom; Zoback, Mary Lou

    1997-03-01

    This paper presents new seismic data from, and crustal models of the San Francisco Peninsula. In much of central California the San Andreas fault juxtaposes the Cretaceous granitic Salinian terrane on its west and the Late Mesozoic/Early Tertiary Franciscan Complex on its east. On San Francisco Peninsula, however, the present-day San Andreas fault is completely within a Franciscan terrane, and the Pilarcitos fault, located southwest of the San Andreas, marks the Salinian-Franciscan boundary. This circumstance has evoked two different explanations: either the Pilarcitos is a thrust fault that has pushed Franciscan rocks over Salinian rocks or the Pilarcitos is a transform fault that has accommodated significant right-lateral slip. In an effort to better resolve the subsurface structure of the peninsula faults, we established a temporary network of 31 seismographs arrayed across the San Andreas fault and the subparallel Pilarcitos fault at ˜1-2 km spacings. These instruments were deployed during the first 6 months of 1995 and recorded local earthquakes, air gun sources set off in San Francisco Bay, and explosive sources. Travel times from these sources were used to augment earthquake arrival times recorded by the Northern California Seismic Network and were inverted for three-dimensional velocity structure. Results show lateral velocity changes at depth (˜0.5-7 km) that correlate with downward vertical projections of the surface traces of the San Andreas and Pilarcitos faults. We thus interpret the faults as high-angle to vertical features (constrained to a 70°-110° dip range). From this we conclude that the Pilarcitos fault is probably an important strike-slip fault that accommodated much of the right-lateral plate boundary strain on the peninsula prior to the initiation of the modern-day San Andreas fault in this region sometime after about 3.0 m.y. ago.

  10. P-Wave Velocity Structure Beneath Eastern Eurasia From Finite Frequency Seismic Tomography

    NASA Astrophysics Data System (ADS)

    Yang, T.; Shen, Y.; Yang, X.

    2005-12-01

    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 velocity structure in the region, we applied the newly-developed Finite Frequency Seismic Tomography (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 velocity models obtained in previous tomographic studies.

  11. Structure and Active Stie Residues of Pg1D, an N-Acetyltransferase from the Bacillosamine Synthetic Pathway Required for N-Glycan Synthesis in Campylobacter jejuni

    SciTech Connect

    Rangarajan,E.; Ruane, K.; Sulea, T.; Watson, D.; Proteau, A.; Leclerc, S.; Cygler, M.; Matte, A.; Young, N.

    2008-01-01

    Campylobacter jejuni is highly unusual among bacteria in forming N-linked glycoproteins. The heptasaccharide produced by its pgl system is attached to protein Asn through its terminal 2, 4-diacetamido-2, 4,6-trideoxy-d-Glc (QuiNAc4NAc or N, N'-diacetylbacillosamine) moiety. The crucial, last part of this sugar's synthesis is the acetylation of UDP-2-acetamido-4-amino-2, 4,6-trideoxy-d-Glc by the enzyme PglD, with acetyl-CoA as a cosubstrate. We have determined the crystal structures of PglD in CoA-bound and unbound forms, refined to 1.8 and 1.75 Angstroms resolution, respectively. PglD is a trimer of subunits each comprised of two domains, an N-terminal {alpha}/{beta}-domain and a C-terminal left-handed {beta}-helix. Few structural differences accompany CoA binding, except in the C-terminal region following the {beta}-helix (residues 189-195), which adopts an extended structure in the unbound form and folds to extend the {beta}-helix upon binding CoA. Computational molecular docking suggests a different mode of nucleotide-sugar binding with respect to the acetyl-CoA donor, with the molecules arranged in an 'L-shape', compared with the 'in-line' orientation in related enzymes. Modeling indicates that the oxyanion intermediate would be stabilized by the NH group of Gly143', with His125' the most likely residue to function as a general base, removing H+ from the amino group prior to nucleophilic attack at the carbonyl carbon of acetyl-CoA. Site-specific mutations of active site residues confirmed the importance of His125', Glu124', and Asn118. We conclude that Asn118 exerts its function by stabilizing the intricate hydrogen bonding network within the active site and that Glu124' may function to increase the pKa of the putative general base, His125'.

  12. Optimization of structures to satisfy a flutter velocity constraint by use of quadratic equation fitting. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Motiwalla, S. K.

    1973-01-01

    Using the first and the second derivative of flutter velocity with respect to the parameters, the velocity hypersurface is made quadratic. This greatly simplifies the numerical procedure developed for determining the values of the design parameters such that a specified flutter velocity constraint is satisfied and the total structural mass is near a relative minimum. A search procedure is presented utilizing two gradient search methods and a gradient projection method. The procedure is applied to the design of a box beam, using finite-element representation. The results indicate that the procedure developed yields substantial design improvement satisfying the specified constraint and does converge to near a local optimum.

  13. Imaging 3D anisotropic upper mantle shear velocity structure of Southeast Asia using seismic waveform inversion

    NASA Astrophysics Data System (ADS)

    Chong, J.; Yuan, H.; French, S. W.; Romanowicz, B. A.; Ni, S.

    2011-12-01

    Southeast Asia as a special region in the world which is seismically active and is surrounded by active tectonic belts, such as the Himalaya collision zone, western Pacific subduction zones and the Tianshan- Baikal tectonic belt. Seismic anisotropic tomography can shade light on the complex crust and upper mantle dynamics of this region, which is the subject of much debate. In this study, we applied full waveform time domain tomography to image 3D isotropic and anisotropic upper mantle shear velocity structure of Southeast Asia. Three component waveforms of teleseismic and far regional events (15 degree ≤ Δ≤ 165 degree) with magnitude ranges from Mw6.0 to Mw7.0 are collected from 91 permanent and 438 temporary broadband seismic stations in SE Asia. Wavepackets of both fundamental and overtone modes, filtered between 60 and 400 sec, are selected automatically according to the similarity between data and synthetic waveforms (Panning & Romanowicz, 2006). Wavepackets corresponding to event-station paths that sample the region considered are weighted according to path redundancy and signal to noise ratio. Higher modes and fundamental mode wavepackets are weighted separately in order to enhance the contribution of higher modes which are more sensitive to deeper structure compared to the fundamental mode. Synthetic waveforms and broadband sensitivity kernels are computed using normal mode asymptotic coupling theory (NACT, Li & Romanowicz, 1995). As a starting model, we consider a global anisotropic upper mantle shear velocity model based on waveform inversion using the Spectral Element Method (Lekic & Romanowicz, 2011), updated for more realistic crustal thickness (French et al., 2011) as our starting model, we correct waveforms for the effects of 3D structure outside of the region, and invert them for perturbations in the 3D structure of the target region only. We start with waveform inversion down to 60sec and after several iterations, we include shorter period

  14. Three new 2-D metal-organic frameworks containing 1-D metal chains bridged by N-benzesulfonyl-glutamic acid: Syntheses, crystal structures and properties

    SciTech Connect

    Ma Lufang; Huo Xiankuan; Wang Liya Wang Jiange; Fan Yaoting

    2007-05-15

    To explore the possibility of obtaining the metal-organic frameworks (MOFs) bearing the bsgluH{sub 2} ligand, two new Cd(II) and one Cu(II) coordination polymers, [Cd(bsglu)(bipy)] {sub n} (1), [Cd(bsglu).(H{sub 2}O)] {sub n} (2) and {l_brace}[Cu{sub 2}(bsglu){sub 2}(bipy){sub 2}].4H{sub 2}O{r_brace} {sub n} (3) (bsglu=N-benzesulfonyl-glutamic acid bianion, bipy=2,2'-bipyridine) were synthesized and characterized by IR, elemental analysis and X-ray diffraction analysis. Compounds 1 and 3 exhibit one-dimensional coordination chains, which are further connected to form two-dimensional supramolecular networks through {pi}-{pi} aromatic stacking interactions in a novel zipper-like way. Compound 2 presents a two-dimensional layer structure. To the best of our knowledge, 2 is the first two-dimensional complex formed from transition metal and bsgluH{sub 2} ligand. Interestingly, the bsglu anion exhibits remarkable versatile coordination modes in these complexes. Fluorescent analyses show that 1 exhibits photoluminescence in the solid state. Magnetic measurements for 3 revealed that the Cu(II) chain exhibit a weak antiferromagnetic behavior with a J value of -0.606 cm{sup -1}. - Graphical abstract: Three new complexes, [Cd(bsglu)(bipy)] {sub n} (1), [Cd(bsglu).(H{sub 2}O)] {sub n} (2) and {l_brace}[Cu{sub 2}(bsglu){sub 2}(bipy){sub 2}].4H{sub 2}O{r_brace} {sub n} (3), constructed from Cd(II) or Cu(II) salt with N-benzesulfonyl-glutamic acid were synthesized and characterized. Compounds 1 and 3 exhibit one-dimensional chains which are further connected to form two-dimensional supramolecular networks through {pi}-{pi} aromatic stacking interactions in a novel zipper-like way. Compound 2 presents a two-dimensional layer structure. Luminescence of 1 and magnetic properties of 3 are also investigated.

  15. Moments of the Spin Structure Functions g1p and g1d for 0.05 < Q2 < 3.0 GeV2

    SciTech Connect

    Prok, Yelena; Bosted, Peter; Burkert, Volker; Deur, Alexandre; Dharmawardane, Kahanawita; Dodge, Gail; Griffioen, Keith; Kuhn, Sebastian; Minehart, Ralph; Adams, Gary; Amaryan, Moscov; Amaryan, Moskov; Anghinolfi, Marco; Asryan, G.; Audit, Gerard; Avagyan, Harutyun; Baghdasaryan, Hovhannes; Baillie, Nathan; Ball, J.P.; Ball, Jacques; Baltzell, Nathan; Barrow, Steve; Battaglieri, Marco; Beard, Kevin; Bedlinskiy, Ivan; Bektasoglu, Mehmet; Bellis, Matthew; Benmouna, Nawal; Berman, Barry; Biselli, Angela; Blaszczyk, Lukasz; Boyarinov, Sergey; Bonner, Billy; Bouchigny, Sylvain; Bradford, Robert; Branford, Derek; Briscoe, William; Brooks, William; Bultmann, S.; Bueltmann, Stephen; Butuceanu, Cornel; Calarco, John; Careccia, Sharon; Carman, Daniel; Casey, Liam; Cazes, Antoine; Chen, Shifeng; Cheng, Lu; Cole, Philip; Collins, Patrick; Coltharp, Philip; Cords, Dieter; Corvisiero, Pietro; Crabb, Donald; Crede, Volker; Cummings, John; Dale, Daniel; Dashyan, Natalya; De Masi, Rita; De Vita, Raffaella; De Sanctis, Enzo; Degtiarenko, Pavel; Denizli, Haluk; Dennis, Lawrence; Dhuga, Kalvir; Dickson, Richard; Djalali, Chaden; Doughty, David; Dugger, Michael; Dytman, Steven; Dzyubak, Oleksandr; Egiyan, Hovanes; Egiyan, Kim; Elfassi, Lamiaa; Elouadrhiri, Latifa; Eugenio, Paul; Fatemi, Renee; Fedotov, Gleb; Feldman, Gerald; Fersch, Robert; Feuerbach, Robert; Forest, Tony; Fradi, Ahmed; Funsten, Herbert; Garcon, Michel; Gavalian, Gagik; Gevorgyan, Nerses; Gilfoyle, Gerard; Giovanetti, Kevin; Girod, Francois-Xavier; Goetz, John; Golovach, Evgeny; Gothe, Ralf; Guidal, Michel; Guillo, Matthieu; Guler, Nevzat; Guo, Lei; Gyurjyan, Vardan; Hadjidakis, Cynthia; Hafidi, Kawtar; Hakobyan, Hayk; Hanretty, Charles; Hardie, John; Hassall, Neil; Heddle, David; Hersman, F.; Hicks, Kenneth; Hleiqawi, Ishaq; Holtrop, Maurik; Huertas, Marco; Hyde, Charles; Ilieva, Yordanka; Ireland, David; Ishkhanov, Boris; Isupov, Evgeny; Ito, Mark; Jenkins, David; Jo, Hyon-Suk; Johnstone, John; Joo, Kyungseon; Juengst, Henry; Kalantarians, Narbe; Keith, Christopher; Kellie, James; Khandaker, Mahbubul; Kim, Kui; Kim, Kyungmo; Kim, Wooyoung; Klein, Andreas; Klein, Franz; Klusman, Mike; Kossov, Mikhail; Krahn, Zebulun; Kramer, Laird; Kubarovsky, Valery; Kuhn, Joachim; Kuleshov, Sergey; Kuznetsov, Viacheslav; Lachniet, Jeff; Laget, Jean; Langheinrich, Jorn; Lawrence, Dave; Lima, Ana; Livingston, Kenneth; Lu, Haiyun; Lukashin, K.; MacCormick, Marion; Marchand, Claude; Markov, Nikolai; Mattione, Paul; McAleer, Simeon; McKinnon, Bryan; McNabb, John; Mecking, Bernhard; Mestayer, Mac; Meyer, Curtis; Mibe, Tsutomu; Mikhaylov, Konstantin; Mirazita, Marco; Miskimen, Rory; Mokeev, Viktor; Morand, Ludyvine; Moreno, Brahim; Moriya, Kei; Morrow, Steven; Moteabbed, Maryam; Mueller, James; Munevar Espitia, Edwin; Mutchler, Gordon; Nadel-Turonski, Pawel; Nasseripour, Rakhsha; Niccolai, Silvia; Niculescu, Gabriel; Niculescu, Maria-Ioana; Niczyporuk, Bogdan; Niroula, Megh; Niyazov, Rustam; Nozar, Mina; O'Rielly, Grant; Osipenko, Mikhail; Ostrovidov, Alexander; Park, Kijun; Pasyuk, Evgueni; Paterson, Craig; Anefalos Pereira, S.; Philips, Sasha; Pierce, J.; Pivnyuk, Nikolay; Pocanic, Dinko; Pogorelko, Oleg; Popa, Iulian; Pozdnyakov, Sergey; Preedom, Barry; Price, John; Procureur, Sebastien; Protopopescu, Dan; Qin, Liming; Raue, Brian; Riccardi, Gregory; Ricco, Giovanni; Ripani, Marco; Ritchie, Barry; Rosner, Guenther; Rossi, Patrizia; Rowntree, David; Rubin, Philip; Sabatie, Franck; Salamanca, Julian; Salgado, Carlos; Santoro, Joseph; Sapunenko, Vladimir; Schumacher, Reinhard; Seely, Mikell; Serov, Vladimir; Sharabian, Youri; Sharov, Dmitri; Shaw, Jeffrey; Shvedunov, Nikolay; Skabelin, Alexander; Smith, Elton; Smith, Lee; Sober, Daniel; Sokhan, Daria; Stavinskiy, Aleksey; Stepanyan, Samuel; Stepanyan, Stepan; Stokes, Burnham; Stoler, Paul; Strakovski, Igor; Strauch, Steffen; Suleiman, Riad; Taiuti, Mauro; Tedeschi, David; Tkabladze, Avtandil; Tkachenko, Svyatoslav; Todor, Luminita; Ungaro, Maurizio; V

    2009-02-01

    The spin structure functions $g_1$ for the proton and the deuteron have been measured over a wide kinematic range in $x$ and \\Q2 using 1.6 and 5.7 GeV longitudinally polarized electrons incident upon polarized NH$_3$ and ND$_3$ targets at Jefferson Lab. Scattered electrons were detected in the CEBAF Large Acceptance Spectrometer, for $0.05 < Q^2 < 5 $\\ GeV$^2$ and $W < 3$ GeV. The first moments of $g_1$ for the proton and deuteron are presented -- both have a negative slope at low \\Q2, as predicted by the extended Gerasimov-Drell-Hearn sum rule. The first result for the generalized forward spin polarizability of the proton $\\gamma_0^p$ is also reported, and shows evidence of scaling above $Q^2$ = 1.5 GeV$^2$. Although the first moments of $g_1$ are consistent with Chiral Perturbation Theory (\\ChPT) calculations up to approximately $Q^2 = 0.06$ GeV$^2$, a significant discrepancy is observed between the $\\gamma_0^p$ data and \\ChPT\\ for $\\gamma_0^p$,even at the lowest \\Q2.

  16. Coalescence phenomena in 1D silver nanostructures

    NASA Astrophysics Data System (ADS)

    Gutiérrez-Wing, C.; Pérez-Alvarez, M.; Mondragón-Galicia, G.; Arenas-Alatorre, J.; Gutiérrez-Wing, M. T.; Henk, M. C.; Negulescu, I. I.; Rusch, K. A.

    2009-07-01

    Different coalescence processes on 1D silver nanostructures synthesized by a PVP assisted reaction in ethylene glycol at 160 °C were studied experimentally and theoretically. Analysis by TEM and HRTEM shows different defects found on the body of these materials, suggesting that they were induced by previous coalescence processes in the synthesis stage. TEM observations showed that irradiation with the electron beam eliminates the boundaries formed near the edges of the structures, suggesting that this process can be carried out by the application of other means of energy (i.e. thermal). These results were also confirmed by theoretical calculations by Monte Carlo simulations using a Sutton-Chen potential. A theoretical study by molecular dynamics simulation of the different coalescence processes on 1D silver nanostructures is presented, showing a surface energy driven sequence followed to form the final coalesced structure. Calculations were made at 1000-1300 K, which is near the melting temperature of silver (1234 K). Based on these results, it is proposed that 1D nanostructures can grow through a secondary mechanism based on coalescence, without losing their dimensionality.

  17. Three-dimensional velocity structure of crust and upper mantle in southwestern China and its tectonic implications

    USGS Publications Warehouse

    Wang, Chun-Yong; Chan, W.W.; Mooney, W.D.

    2003-01-01

    Using P and S arrival times from 4625 local and regional earthquakes recorded at 174 seismic stations and associated geophysical investigations, this paper presents a three-dimensional crustal and upper mantle velocity structure of southwestern China (21??-34??N, 97??-105??E). Southwestern China lies in the transition zone between the uplifted Tibetan plateau to the west and the Yangtze continental platform to the east. In the upper crust a positive velocity anomaly exists in the Sichuan Basin, whereas a large-scale negative velocity anomaly exists in the western Sichuan Plateau, consistent with the upper crustal structure under the southern Tibetan plateau. The boundary between these two anomaly zones is the Longmen Shan Fault. The negative velocity anomalies at 50-km depth in the Tengchong volcanic area and the Panxi tectonic zone appear to be associated with temperature and composition variations in the upper mantle. The Red River Fault is the boundary between the positive and negative velocity anomalies at 50-km depth. The overall features of the crustal and the upper mantle structures in southwestern China are a low average velocity, large crustal thickness variations, the existence of a high-conductivity layer in the crust or/and upper mantle, and a high heat flow value. All these features are closely related to the collision between the Indian and the Asian plates.

  18. Probing structure-induced optical behavior in a new class of self-activated luminescent 0D/1D CaWO₄ metal oxide – CdSe nanocrystal composite heterostructures

    SciTech Connect

    Han, Jinkyu; McBean, Coray; Wang, Lei; Hoy, Jessica; Jaye, Cherno; Liu, Haiqing; Li, Zhuo-Qun; Sfeir, Matthew Y.; Fischer, Daniel A.; Taylor, Gordon T.; Misewich, James A.; Wong, Stanislaus S.

    2015-01-30

    In this report, we synthesize and characterize the structural and optical properties of novel heterostructures composed of (i) semiconducting nanocrystalline CdSe quantum dot (QDs) coupled with (ii) both one and zero-dimensional (1D and 0D) motifs of self-activated luminescence CaWO₄ metal oxides. Specifically, ~4 nm CdSe QDs have been anchored onto (i) high-aspect ratio 1D nanowires, measuring ~230 nm in diameter and ~3 μm in length, as well as onto (ii) crystalline 0D nanoparticles (possessing an average diameter of ~ 80 nm) of CaWO₄ through the mediation of 3-mercaptopropionic acid (MPA) as a connecting linker. Composite formation was confirmed by complementary electron microscopy and spectroscopy (i.e. IR and Raman) data. In terms of luminescent properties, our results show that our 1D and 0D heterostructures evince photoluminescence (PL) quenching and shortened PL lifetimes of CaWO₄ as compared with unbound CaWO₄. We propose that a photo-induced electron transfer process occurs from CaWO₄ to CdSe QDs, a scenario which has been confirmed by NEXAFS measurements and which highlights a decrease in the number of unoccupied orbitals in the conduction bands of CdSe QDs. By contrast, the PL signature and lifetimes of MPA-capped CdSe QDs within these heterostructures do not exhibit noticeable changes as compared with unbound MPA-capped CdSe QDs. The striking difference in optical behavior between CaWO₄ nanostructures and CdSe QDs within our heterostructures can be correlated with the relative positions of their conduction and valence energy band levels. In addition, the PL quenching behaviors for CaWO₄ within the heterostructure configuration were examined by systematically varying (i) the quantities and coverage densities of CdSe QDs as well as (ii) the intrinsic morphology (and by extension, the inherent crystallite size) of CaWO₄ itself.

  19. Saturn's auroral/polar H +3 infrared emission . I. General morphology and ion velocity structure

    NASA Astrophysics Data System (ADS)

    Stallard, Tom; Miller, Steve; Melin, Henrik; Lystrup, Makenzie; Dougherty, Michele; Achilleos, Nicholas

    2007-07-01

    We present an analysis of an extensive dataset of observations of the auroral/polar regions of Saturn, carried out in 2004 and 2005 using the high-resolution facility spectrometer CSHELL on the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. The paper outlines the morphology of emission in the H +3νQ(1,0) line at 3.953 μm across the planet's southern auroral/polar region, and gives a description of the main classes of morphology observed. Similarly, it presents the ion velocity as a function of location across the auroral/polar region, with the main classes of structure observed. In presenting these, it sets out the baseline phenomenological parameters, both averaged across our entire dataset and for specific nights, for use in future studies. Averaged across our dataset, the (planetary) west-east infrared H +3 emission profile of Saturn's auroral/polar regions indicates the presence of a clear auroral oval, roughly coincident with that delineated by EUV images, although there is clearly relatively more H +3 emission across the polar cap than would be expected from a straight correlation with the EUV images. The integrated H +3 emission can vary by a factor of ˜50 between observing runs, and a factor of two on a night-to-night basis. Again averaged across our dataset, the lag to co-rotation of ions in the auroral/polar regions is considerable. We also find that the lag to co-rotation shows large variations, and that it is possible to distinguish sub-regions within the auroral/polar region and characterise them by the rate at which the velocity changes as a function of distance from the centre of the planet.

  20. Chicxulub central crater structure: Initial results from physical property measurements and combined velocity and gravity modeling

    NASA Astrophysics Data System (ADS)

    Vermeesch, P. M.; Morgan, J. V.

    2004-07-01

    The Chicxulub crater in Mexico is a nearly pristine example of a large impact crater. Its slow burial has left the central impact basin intact, within which there is an apparently uneroded topographic peak ring. Its burial, however, means that we must rely on drill holes and geophysical data to interpret the crater form. Interpretations of crater structures using geophysical data are often guided by numerical modeling and observations at other large terrestrial craters. However, such endeavors are hindered by uncertainties in current numerical models and the lack of any obvious progressive change in structure with increasing crater size. For this reason, proposed structural models across Chicxulub remain divergent, particularly within the central crater region, where the deepest well is only ~1.6 km deep. The shape and precise location of the stratigraphic uplift are disputed. The spatial extent and distribution of the allogenic impact breccias and melt rocks remain unknown, as do the lithological nature of the peak ring and the mechanism for its formation. The objective of our research is to provide a well-constrained 3D structural and lithological model across the central region of the Chicxulub crater that is consistent with combined geophysical data sets and drill core samples. With this in mind, we present initial physical property measurements made on 18 core samples from the Yaxcopoil-1 (Yax-1) drill hole between 400 and 1500 m deep and present a new density model that is in agreement with both the 3D velocity and gravity data. Future collation of petrophysical and geochemical data from Yax-1 core, as well as further seismic surveys and drilling, will allow us to calibrate our geophysical models-assigning a suite of physical properties to each lithology. An accurate 3D model of Chicxulub is critical to our understanding of large craters and to the constraining of the environmental effects of this impact.

  1. Effect of velocity ratio on coherent-structure dynamics in turbulent free shear layers

    NASA Astrophysics Data System (ADS)

    Suryanarayanan, Saikishan; Narasimha, Roddam

    2014-11-01

    The relevance of the vortex-gas model to the large scale dynamics of temporally evolving turbulent free shear layers has been established by extensive simulations (Phys. Rev. E 89, 013009 (2014)). The effects of velocity ratio (r =U2 /U1) on shear layer dynamics are revealed by spatially evolving vortex-gas shear-layer simulations using a computational model based on Basu et al. (Appl. Math. Modelling 19, (1995)), but with a crucial improvement that ensures conservation of global circulation. The simulations show that the initial conditions and downstream boundaries can significantly affect the flow over substantial part of the domain, but the equilibrium spread rate is a universal function of r, and is within the experimental scatter. The spread in the r = 0 limit is higher than Galilean-transformed temporal value. The present 2D simulations at r = 0 show continuous growth of structures, while merger-dominated evolution is observed for r = 0 . 23 (and higher). These two mechanisms were observed across the same two values of r in the experiments of D'Ovidio & Coats (J. Fluid Mech. 737, 2013), but the continuous growth was instead attributed to mixing-transition and 3D. The 2D mechanisms responsible for the observed continuous growth of structures are analyzed in detail. Supported in part by RN/Intel/4288 and RN/DRDO/4124.

  2. Shear wave velocity analysis of a deep seated gravel landslide structure using the microtremor survey method

    NASA Astrophysics Data System (ADS)

    Su, L.; Xu, X.; Liao, H.; Geng, X.-Y.

    2015-09-01

    The depth and geometry of potential failure surface is the fundamental for evaluating the mechanisms of a landslide. Traditional techniques to acquire information on potential sliding surface are mainly drilling, pitting, and trenching, but these techniques are time consuming and expensive. In this study, microtremor signals and the dispersion curves of surface wave are extracted from the vertical component of microtremor records using the spatial autocorrelation (SPAC) method to estimate shear wave velocity structure. The results suggest that the buried depth of phyllite bedrock is approximately 47.4m, and the thickness of weathered bedrock layer is about 9.9m at about 57.3m deep, which could be interpreted as the potential sliding surface of this landslide, in accordance with borehole data. The microtremor survey method (MSM) is flexible, non-invasive, relatively quick and deployable on the landslide. It clearly demonstrat that it is an effective tool to improve the drilling success rate, and hence allow a large scale and high density investigation of structure characteristics of a deep seated landslide.

  3. Effect of temperature on composite sandwich structures subjected to low velocity impact. [aircraft construction materials

    NASA Technical Reports Server (NTRS)

    Sharma, A. V.

    1980-01-01

    The effect of low velocity projectile impact on sandwich-type structural components was investigated. The materials used in the fabrication of the impact surface were graphite-, Kevlar-, and boron-fibers with appropriate epoxy matrices. The testing of the specimens was performed at moderately low- and high-temperatures as well as at room temperature to assess the impact-initiated strength degradation of the laminates. Eleven laminates with different stacking sequences, orientations, and thicknesses were tested. The low energy projectile impact is considered to simulate the damage caused by runway debris, the dropping of the hand tools during servicing, etc., on the secondary aircraft structures fabricated with the composite materials. The results show the preload and the impact energy combinations necessary to cause catastrophic failure in the laminates tested. A set of faired curves indicating the failure thresholds is shown separately for the tension-and compression-loaded laminates. The specific-strengths and -modulii for the various laminates tested are also given.

  4. Estimation of shallow S-wave velocity structure in the Puli basin, Taiwan, using array measurements of microtremors

    NASA Astrophysics Data System (ADS)

    Wu, Cheng-Feng; Huang, Huey-Chu

    2012-05-01

    The September 21, 1999, Chi-Chi earthquake induced strong shaking, resulting in severe damage in the Puli area. According to Huang and Tarng (2005), the collapse of many structures during the earthquake was very closely related to site effects. Shallow shear-wave velocities are widely used for earthquake ground-motion site characterization. Thus, we investigate S-wave velocity structures for the Puli area by performing microtremor array measurements at 16 sites. Dispersion curves at these sites are calculated using the F-K method (Capon, 1969) for the vertical component; S-wave velocity structures for the Puli area are then estimated by surface wave inversion (Herrmann, 1991). If the S-wave velocity of the bedrock is assumed to be 2000 m/s, the depths of the Quaternary sediments in the Puli area are between 300 m (FAL, PIP) and 870 m (DAH). Moreover, there are 3˜6 distinct interfaces in the shallow velocity structure (0˜1000 m). The depth of the bedrock gradually increases from the edge (SIN, PIP) to the center (PUL, DAH) of the basin and the thickest Quaternary sediments appear near Heng-Chih-Cheng (DAH).

  5. Characterization of Physical Structure from Measurements of Sound Velocity in Aqueous Solutions of Various Saccharides and Alditols.

    NASA Astrophysics Data System (ADS)

    Smith, David Eugene

    Little basic research has been reported on the physical structure of aqueous solutions of saccharides. Sound velocimeters can be used to study physical structure of solutions, non-destructively. The La Place relationship was used to calculate adiabatic compressibility values for solutions from experimentally determined values for sound velocity and density. Using a sound velocimeter, aqueous solutions of twelve alditols and saccharides were studied at various concentrations and temperatures. Data indicated that over most of the temperature range employed (20 to 70 C) adiabatic compressibility of the solutions was the dominant factor in defining sound velocity through and structural rigidity of solution. As concentration of solute increased, more rigid structures were formed in solution, which caused sound velocity values to increase with increasing concentrations of solute; maximum sound velocity values were obtained at progressively lower temperatures. Analysis of data for sound velocity, density and adiabatic compressibility of various solutions provided partial insight into effects of each solute molecule on structure of solutions. A furanose form in a monosaccharide contributed to a more rigid structure than did a pyranose ring when below 30C. At higher temperatures the pyranose ring provided more rigidity than did the furanose ring. Hydroxyl groups in the equatorial position generally contributed more to rigidity of structure than did OH groups in axial positions. Disaccharides contributed differences from the inherent monosaccharides. A (beta) glycosidic linkage provided more structural rigidity of solution than did a linkage. Among the alditols, mannitol and sorbitol contributed very similar characteristics to solutions. Xylitol, in solution provided less rigidity, density and sound velocity than did mannitol-sorbitol in proportion to the lower molecular weight or xylitol. From the data for velocity of sound through single sugar solutions values for

  6. The Boundary Structure in the Analysis of Reversibly Interacting Systems by Sedimentation Velocity

    PubMed Central

    Zhao, Huaying; Balbo, Andrea; Brown, Patrick H.; Schuck, Peter

    2011-01-01

    Sedimentation velocity (SV) experiments of heterogeneous interacting systems exhibit characteristic boundary structures that can usually be very easily recognized and quantified. For slowly interacting systems, the boundaries represent concentrations of macromolecular species and they can be interpreted directly with population models based solely on the mass action law. For fast reactions, migration and chemical reactions are coupled, and different, but equally easily discernable boundary structures appear. However, these features have not been commonly utilized for data analysis, for the lack of an intuitive and computationally simple model. The recently introduced effective particle theory (EPT) provides a suitable framework. Here, we review the motivation and theoretical basis of EPT, and explore practical aspects for its application. We introduce an EPT-based design tool for SV experiments of heterogeneous interactions in the software SEDPHAT. As a practical tool for the first step of data analysis, we describe how the boundary resolution can be further improved in c(s) with a Bayesian adjustment of maximum entropy regularization to the case of heterogeneous interactions between molecules that have been previously studied separately. This can facilitate extracting the characteristic boundary features by integration of c(s) and their assembly into isotherms as a function of total loading concentrations, which are fitted with EPT in a second stage. Methods for addressing concentration errors in isotherms are discussed. Finally, in an experimental model system of alpha-chymotrypsin interacting with soybean trypsin inhibitor, we show that EPT provides an excellent description of the experimental sedimentation boundary structure of fast interacting systems. PMID:21315155

  7. Space Telescope Imaging Spectrograph Observations of the Interstellar Velocity Structure and Chemical Composition toward the Carina Nebula

    NASA Astrophysics Data System (ADS)

    Walborn, Nolan R.; Danks, Anthony C.; Sembach, Kenneth R.; Bohlin, Ralph C.; Jenkins, Edward B.; Gull, Theodore R.; Lindler, Don J.; Feggans, J. Keith; Hulbert, Stephen J.; Linsky, Jeffrey; Hutchings, John B.; Joseph, Charles L.

    1998-01-01

    We have observed the O-type star CPD -59°2603 in the Carina Nebula with the Space Telescope Imaging Spectrograph near-UV and far-UV high-resolution echelles, at a resolving power of ~110,000 (FWHM) and S/N ~ 30. This sight line has complex velocity and excitation structure in the interstellar absorption lines, corresponding to three distinct regions: very high velocity components formed within the nebula; a warm, expanding H II region; and cool, low-velocity gas near the Sun. The Mg I and Mg II profiles show many components, with velocities extending from -235 to +123 km s-1. We have derived physical conditions in the expanding H II region from the Si IV doublet and the excited fine-structure lines of C I. Heavy elements (O, Ni, Cu, Ga) are present in the low-velocity gas, and their abundances indicate depletions consistent with nearby, cool diffuse clouds. 12CO is detected in just one low-velocity component, suggesting different amounts of processing among the clouds near the Sun. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

  8. The ZH ratio method for long-period seismic data: inversion for S-wave velocity structure

    NASA Astrophysics Data System (ADS)

    Yano, Tomoko; Tanimoto, T.; Rivera, L.

    2009-10-01

    The particle motion of surface waves, in addition to phase and group velocities, can provide useful information for S-wave velocity structure in the crust and upper mantle. In this study, we applied a new method to retrieve velocity structure using the ZH ratio, the ratio between vertical and horizontal surface amplitudes of Rayleigh waves. Analysing data from the GEOSCOPE network, we measured the ZH ratios for frequencies between 0.004 and 0.05 Hz (period between 20 and 250s) and inverted them for S-wave velocity structure beneath each station. Our analysis showed that the resolving power of the ZH ratio is limited and final solutions display dependence on starting models; in particular, the depth of the Moho in the starting model is important in order to get reliable results. Thus, initial models for the inversion need to be carefully constructed. We chose PREM and CRUST2.0 in this study as a starting model for all but one station (ECH). The eigenvalue analysis of the least-squares problem that arises for each step of the iterative process shows a few dominant eigenvalues which explains the cause of the inversion's initial-model dependence. However, the ZH ratio is unique in having high sensitivity to near-surface structure and thus provides complementary information to phase and group velocities. Application of this method to GEOSCOPE data suggest that low velocity zones may exist beneath some stations near hotspots. Our tests with different starting models show that the models with low-velocity anomalies fit better to the ZH ratio data. Such low velocity zones are seen near Hawaii (station KIP), Crozet Island (CRZF) and Djibuti (ATD) but not near Reunion Island (RER). It is also found near Echery (ECH) which is in a geothermal area. However, this method has a tendency to produce spurious low velocity zones and resolution of the low velocity zones requires further careful study. We also performed simultaneous inversions for volumetric perturbation and

  9. The uppermost mantle shear wave velocity structure of eastern Africa from Rayleigh wave tomography: constraints on rift evolution

    NASA Astrophysics Data System (ADS)

    O'Donnell, J. P.; Adams, A.; Nyblade, A. A.; Mulibo, G. D.; Tugume, F.

    2013-08-01

    An expanded model of the 3-D shear wave velocity 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 velocities 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 velocity model of the uppermost mantle. New features in the model include (1) a low-velocity region in western Zambia, (2) a high-velocity region in eastern Zambia, (3) a low-velocity region in eastern Tanzania and (4) low-velocity 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-velocity 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 velocity 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.

  10. Study on 3-D velocity structure of crust and upper mantle in Sichuan-yunnan region, China

    USGS Publications Warehouse

    Wang, C.; Mooney, W.D.; Wang, X.; Wu, J.; Lou, H.; Wang, F.

    2002-01-01

    Based on the first arrival P and S data of 4 625 regional earthquakes recorded at 174 stations dispersed in the Yunnan and Sichuan Provinces, the 3-D velocity structure of crust and upper mantle in the region is determined, incorporating with previous deep geophysical data. In the upper crust, a positive anomaly velocity zone exists in the Sichuan basin, whereas a negative anomaly velocity zone exists in the western Sichuan plateau. The boundary between the positive and negative anomaly zones is the Longmenshan fault zone. The images of lower crust and upper mantle in the Longmenshan fault, Xianshuihe fault, Honghe fault and others appear the characteristic of tectonic boundary, indicating that the faults litely penetrate the Moho discontinuity. The negative velocity anomalies at the depth of 50 km in the Tengchong volcanic area and the Panxi tectonic zone appear to be associated with the temperature and composition variations in the upper mantle. The overall features of the crustal and the upper mantle structures in the Sichuan-Yunnan region are the lower average velocity in both crust and uppermost mantle, the large crustal thickness variations, and the existence of high conductivity layer in the crust or/and upper mantle, and higher geothermal value. All these features are closely related to the collision between the Indian and the Asian plates. The crustal velocity in the Sichuan-Yunnan rhombic block generally shows normal.value or positive anomaly, while the negative anomaly exists in the area along the large strike-slip faults as the block boundary. It is conducive to the crustal block side-pressing out along the faults. In the major seismic zones, the seismicity is relative to the negative anomaly velocity. Most strong earthquakes occurred in the upper-mid crust with positive anomaly or normal velocity, where the negative anomaly zone generally exists below.

  11. Shear-wave velocity structure of young Atlantic Lithosphere from dispersion analysis and waveform modelling of Rayleigh waves

    NASA Astrophysics Data System (ADS)

    Grevemeyer, Ingo; Lange, Dietrich; Schippkus, Sven

    2016-04-01

    The lithosphere is the outermost solid layer of the Earth and includes the brittle curst and brittle uppermost mantle. It is underlain by the asthenosphere, the weaker and hotter portion of the mantle. The boundary between the brittle lithosphere and the asthenosphere is call the lithosphere-asthenosphere boundary, or LAB. The oceanic lithosphere is created at spreading ridges and cools and thickens with age. Seismologists define the LAB by the presence of a low shear wave velocity zone beneath a high velocity lid. Surface waves from earthquakes occurring in young oceanic lithosphere should sample lithospheric structure when being recorded in the vicinity of a mid-ocean ridge. Here, we study group velocity and dispersion of Rayleigh waves caused by earthquakes occurring at transform faults in the Central Atlantic Ocean. Earthquakes were recorded either by a network of wide-band (up to 60 s) ocean-bottom seismometers (OBS) deployed at the Mid-Atlantic Ridge near 15°N or at the Global Seismic Network (GSN) Station ASCN on Ascension Island. Surface waves sampling young Atlantic lithosphere indicate systematic age-dependent changes of group velocities and dispersion of Rayleigh waves. With increasing plate age maximum group velocity increases (as a function of period), indicating cooling and thickening of the lithosphere. Shear wave velocity is derived inverting the observed dispersion of Rayleigh waves. Further, models derived from the OBS records were refined using waveform modelling of vertical component broadband data at periods of 15 to 40 seconds, constraining the velocity structure of the uppermost 100 km and hence in the depth interval of the mantle where lithospheric cooling is most evident. Waveform modelling supports that the thickness of lithosphere increases with age and that velocities in the lithosphere increase, too.

  12. Upper Crustal Seismic Structure and Velocity Variations from the Costa Rica Rift to Hole 504B from Multichannel Seismic Reflection and Sonobuoy Data

    NASA Astrophysics Data System (ADS)

    Floyd, J. S.; Carbotte, S. M.; Mutter, J. C.

    2011-12-01

    We present observations from a combined multichannel seismic reflection and sonobuoy refraction survey of the shallow seismic structure of the Costa Rica Rift crust as a function of age, bathymetry, and sedimentation from the rift axis to DSDP/ODP Hole 504B in the Panama Basin. The MCS data were acquired with a 4-km-long, 160 channel hydrophone streamer on two separate segments of leg EW9416 of the R/V Maurice Ewing in 1994, which we call here the northern and Hole 504B MCS survey segments. The northern MCS survey segment covers a ~215-km-long, ~30 km-wide swath from the Costa Rica Rift axis to 5.0 Ma-old crust, located 30.5 km northwest of Hole 504B. It consists of eight ridge-parallel, east-west trending MCS profiles, two ~20 km-long cross-axis profiles and one 214-km-long ridge-perpendicular line that extends from 10.3 km north of the ridge axis to 203 km south of the ridge axis. Upper-crustal velocity constraints are provided by 1-D ray tracing of reflected and refracted waves recorded by 11 sonobuoys with good signal to noise ratios at shot-receiver distances of up 5.3 km to 14.8 km. The Hole 504B segment of the MCS survey covers a 25 km by 25 km area centered around the drill site and consists of six MCS profiles, five north-south lines and one east-west line. Of the six MCS Hole 504B segment profiles, we focus exclusively on the two north-south and east-west oriented profiles that cross DSDP/ODP Hole 504B and allow us to tie seismic observations with physical properties measured at the drill site. Sonobuoy velocities reveal an increase in layer 2A velocities from as low as 3.1 km/s at the ridge axis to 4.6 km/s at 5.3 My-old crust. Velocities at the base of the transition zone to the top of layer 2B range from 5.07 km/s the ridge axis to 6.1 km/s at 5.3 My-old crust, which are very close to transition zone velocities of ~5.3-6.2 km/s found at Hole 504B by Detrick et al. (1998) from tomographic inversion of ocean bottom seismometer data.

  13. Bayesian Inversion for Ultra Low Velocity Zone parameters in the Earth's Lowermost Mantle: Multiple-Layered Structure Confirmed Beneath the East of the Philippines

    NASA Astrophysics Data System (ADS)

    Pachhai, Surya; Tkalcic, Hrvoje; Dettmer, Jan

    2014-05-01

    Ultra low velocity zones (ULVZs) are structures sitting on the top of the core mantle boundary with a strong reduction in P- and S-wave velocity and increased density. ULVZs have been extensively studied using 1-D and 2-D modelling of seismic waves reflected from and transmitted through the core mantle boundary. However, their physical origin and associated dynamics are currently debated. In addition, the forward problem (waveform modelling) is highly non-linear and non-unique with strong correlations between ULVZ parameters. We develop a rigorous Bayesian inversion to address these challenges. Sampling of the posterior probability density (the solution to a Bayesian inverse problem) is based on parallel interacting Markov chains (parallel tempering), which allows efficient sampling of difficult parameter spaces including multiple modes and strong parameter correlations. Uncertainties of ULVZ parameters are naturally addressed by the posterior distribution. In addition, noise on the data (residual errors) is addressed by a hierarchical Bayesian model which estimates the standard deviation from the data. Results are examined in terms of marginal densities of the ULVZ posterior, including profile-marginal and joint-marginal densities. After demonstrating the feasibility of the method with synthetic examples, we apply the hierarchical Bayesian inversion to the waveforms of core reflected phases (ScP) from earthquakes originating in the Indonesian region and recorded on Hi-Net array stations in Japan. These waves sample the CMB beneath the east of the Philippines. The Bayesian information criterion (BIC) is applied to select the optimal parametrization (i.e., the number of layers) from competing ULVZ models. The BIC confirms the existence of a two-layer ULVZ in the lowermost mantle beneath the east of the Philippines. The upper ULVZ layer shows a sharp decrease in P- and S-wave velocity of up to ~11% and ~29%, and an increase in density of up to ~28%. This layer could

  14. Forces Generated by High Velocity Impact of Ice on a Rigid Structure

    NASA Technical Reports Server (NTRS)

    Pereira, J. Michael; Padula, Santo A., II; Revilock, Duane M.; Melis, Matthew E.

    2006-01-01

    Tests were conducted to measure the impact forces generated by cylindrical ice projectiles striking a relatively rigid target. Two types of ice projectiles were used, solid clear ice and lower density fabricated ice. Three forms of solid clear ice were tested: single crystal, poly-crystal, and "rejected" poly-crystal (poly-crystal ice in which defects were detected during inspection.) The solid ice had a density of approximately 56 lb/cu ft (0.9 gm/cu cm). A second set of test specimens, termed "low density ice" was manufactured by molding shaved ice into a cylindrical die to produce ice with a density of approximately 40 lb/cu ft (0.65 gm/cu cm). Both the static mechanical characteristics and the crystalline structure of the ice were found to have little effect on the observed transient response. The impact forces generated by low density ice projectiles, which had very low mechanical strength, were comparable to those of full density solid ice. This supports the hypothesis that at a velocity significantly greater than that required to produce fracture in the ice, the mechanical properties become relatively insignificant, and the impact forces are governed by the shape and mass of the projectile.

  15. Geotechnical stability analysis, fragility of structures and velocity of movement to assess landslides vulnerability

    NASA Astrophysics Data System (ADS)

    Cuanalo, O.; Bernal, E.; Polanco, G.

    2014-09-01

    Landslides are geohazards that can be potential risks to life and property; these phenomena usually cause disasters when they occur in densely populated communities as those that inhabit mountainous and steep regions. Hazard and vulnerability are parameters determined by probability mathematical analysis with values between 0 and 1. When there are no records or enough information regards historical events on the phenomenon in study, that have occurred in a specific area (as in several mountainous regions of Mexico inhabited by ethnic groups), it has the disadvantage of not being able to perform a statistical analysis to properly evaluate the hazard nor the vulnerability. To solve the problem, this paper presents a proposal for evaluating the physical and functional vulnerability of the elements at risk, from two fundamental aspects: (a) the exposure level (EL), and (b) the expected damage degree (EDD). First of these factors is determined by the severity index (SI) and the safety factor from geotechnical stability analysis (SFgeo); the second one from the construction type (degree of fragility of structures) and the velocity that may have the landslide. For evaluating the parameters aforementioned, included tables, graphs and equations proposed by the authors.

  16. Velocity structure of the Long Valley caldera from the inversion of local earthquake P and S travel times

    SciTech Connect

    Romero, A.E. Jr.; McEvilly, T.V.; Majer, E.L.

    1993-11-10

    A high-resolution tomographic study of the Long Valley region began in 1989 with the installation of a special fan array of eight three-component borehole (80-160 m depths) receivers on the northwestern rim of the caldera to provide the data necessary for a joint inversion for hypocenters and the three-dimensional P and S wave velocity structure in and below the caldera. The experiment specifically targeted the subsurface location of the previously inferred magma chamber beneath the Resurgent Dome. Additional coverage was provided by existing US Geological Survey and University of Nevada, Reno seismographic networks. The authors employed the progressive inversion scheme of Thurber, with cubic spline interpolation after Michelini and McEvilly. The final model is based on data from 280 well-distributed local earthquakes. Some 6900 arrival times were used, including about 700 S wave times from the three-component stations. The resulting velocity structure reflects the known geology, defining the low-velocity Sierran block and highland terrane. No isolated distinct low-velocity anomalies are revealed beneath the caldera floor, although a diffuse zone of reduced velocity persists to a depth of about 8 km. These lower velocities may be related to hydrothermal alteration and/or extensive fractures. The Vp/Vs structure contains significant lateral variation within and beneath the caldera to about 8 km depth, and these variations can be related to accepted models of the active geothermal system. The lack of a significant S wave velocity anomaly, along with the normal or low values of the Vp/Vs ratio, argues against the presence of a sizable and distinct magma body at shallow to midcrustal depth beneath Long Valley caldera, although a very low percentage of partial melt cannot be precluded. 37 refs., 7 figs.

  17. Combinatorial variation of structure in considerations of compound lumping in one- and two-dimensional property representations of condensable atmospheric organic compounds. 1. Lumping by 1-D volatility with nC fixed

    NASA Astrophysics Data System (ADS)

    Pankow, James F.; Niakan, Negar; Asher, William E.

    2013-12-01

    Many current models that aim to predict urban and regional levels of organic particulate matter (OPM) use either the 2 product (2p) framework for secondary organic aerosol (SOA) formation, or a static 1-D volatility basis set (1-D-VBS). These approaches assume that: 1) the compounds involved in OPM condensation/evaporation can be lumped simply by volatility with no specificity regarding carbon number nC, MW, or polar functionality; 2) water uptake does not occur; and 3) the compounds are non-ionizing. This work considers the consequences for uniphasic PM caused by the first two assumptions due to effects of the condensed-phase mean molecular weight MWbar and activity coefficients (ζi), including when RH (relative humidity) > 0. Setting nC = 10 for all bins, multiple chemical structures were developed for each bin of a 1-D-VBS for un-aged SOA in the α-pinene/ozone system. For each bin, a group-contribution vapor pressure (pLo) prediction method was used to find multiple structures such that the groups-based log pLo for nC = 10 and variable numbers of aldehyde, ketone, hydroxyl, and carboxylic acid groups agrees, within ±0.5, with the bin volatility. The number of possible combinations with one structure taken from each bin was 17,640. The Raster-Roulette Organic Aerosol (RROA) model was used to calculate the equilibrium mass concentrations (μg m-3) of OPM (Mo) and co-condensed water (Mw) at 25 °C for each combination for ranges of RH and ΔHC (change in parent hydrocarbon concentration). UNIFAC was used to determine the needed values of ζi. Frequency distributions from RROA for Mo, Mw, and the O:C ratio were developed. For Mo levels typical of the ambient atmosphere, then for the 1-D-VBS and all bins constrained at nC = 10, significant RH-induced enhancement of OPM condensation was observed in the distributions. The spread of the distributions was found to increase rapidly as the level of OPM decreased. The within-bin spread of ±0.5 log units in the groups

  18. From 1D chain to 3D network: a new family of inorganic-organic hybrid semiconductors MO3(L)(x) (M = Mo, W; L = organic linker) built on perovskite-like structure modules.

    PubMed

    Zhang, Xiao; Hejazi, Mehdi; Thiagarajan, Suraj J; Woerner, William R; Banerjee, Debasis; Emge, Thomas J; Xu, Wenqian; Teat, Simon J; Gong, Qihan; Safari, Ahmad; Yang, Ronggui; Parise, John B; Li, Jing

    2013-11-20

    MO3 (M = Mo, W) or VI-VI binary compounds are important semiconducting oxides that show great promise for a variety of applications. In an effort to tune and enhance their properties in a systematic manner we have applied a designing strategy to deliberately introduce organic linker molecules in these perovskite-like crystal lattices. This approach has led to a wealth of new hybrid structures built on one-dimensional (1D) and two-dimensional (2D) VI-VI modules. The hybrid semiconductors exhibit a number of greatly improved properties and new functionality, including broad band gap tunability, negative thermal expansion, largely reduced thermal conductivity, and significantly enhanced dielectric constant compared to their MO3 parent phases. PMID:24152119

  19. Whole-mantle radially anisotropic shear velocity structure from spectral-element waveform tomography

    NASA Astrophysics Data System (ADS)

    French, S. W.; Romanowicz, B. A.

    2014-12-01

    The radially anisotropic shear velocity 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 tomography, 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.

  20. Assembly of 1D, 2D and 3D lanthanum(iii) coordination polymers with perchlorinated benzenedicarboxylates: positional isomeric effect, structural transformation and ring-opening polymerisation of glycolide.

    PubMed

    Chen, Sheng-Chun; Dai, An-Qi; Huang, Kun-Lin; Zhang, Zhi-Hui; Cui, Ai-Jun; He, Ming-Yang; Chen, Qun

    2016-02-28

    Utilizing a series of positional isomers of tetrachlorinated benzenedicarboxylic acid ligands, seven La(iii)-based coordination polymers were solvothermally synthesized and structurally characterized. Their structural dimensionalities varying from 1D double chains, to the 2D 3,4,5-connected network, to 3D 6-connected pcu topological nets are only governed by the positions of carboxyl groups on the tetrachlorinated benzene ring. A comprehensive analysis and comparison reveals that the size of the carbonyl solvent molecules (DMF, DEF, DMA, and NMP) can affect the coordination geometries around the La(iii) ions, the coordination modes of carboxylate groups, the packing arrangements, and the void volumes of the overall crystal lattices. One as-synthesized framework further shows an unprecedented structural transformation from a 3D 6-connected network to a 3D 4,5-connected net through the dissolution and reformation pathway in water, suggesting that these easily hydrolyzed lanthanide complexes may serve as precursors to produce new high-dimensional frameworks. The bulk solvent-free melt polymerisation of glycolide utilizing these La(iii) complexes as initiators has been reported herein for the first time. All complexes were found to promote the polymerization of glycolide over a temperature range of 200 to 220 °C, producing poly(glycolic acid) (PGA) with a molecular weight up to 93,280. Under the same experimental conditions, the different catalytic activities for these complexes may result from their structural discrepancy. PMID:26811117

  1. Shear velocity and anisotropy distributions beneath southern Africa's cratons: Lithospheric structure, deformation, LAB and other discontinuities

    NASA Astrophysics Data System (ADS)

    Adam, Joanne; Lebedev, Sergei

    2013-04-01

    Seismic-velocity structure and anisotropy of cratonic lithosphere offer important clues on the enigmatic formation and stabilization of cratons. Broad-band surface waves are highly sensitive to both the isotropic-average shear speeds from the upper crust down to the asthenosphere (characterising the composition and thermal state of the lithosphere) and to radial and azimuthal shear-wave anisotropy (indicative of ancient and recent deformation and flow). Recently, receiver function studies have yielded exciting but puzzling new evidence, revealing multiple discontinuities at different depths within the lithosphere-asthenosphere depth range beneath cratons. While some of the receiver-function signals probably indicate the lithosphere-asthenosphere boundary (LAB), others must be due to sharp radial changes in the mantle-rock composition or anisotropy. We have recently used teleseismic interferometry to measure thousands of inter-station, Rayleigh- and Love-wave, phase-velocity curves across southern Africa (Adam and Lebedev 2012). Here, we invert the very-broadband dispersion data for the profiles of the shear speed and azimuthal and radial anisotropy beneath different parts of the Kaapvaal Craton and the Limpopo Belt. Systematic model space mapping is used to evaluate parameter trade-offs and to ensure the robustness of the anisotropy profiles. Our results, firstly, reconcile the long-debated previous models based on different interpretations of SKS-splitting measurements in southern Africa (one end-member model placing anisotropy primarily into the lithosphere and attributing it to Archean deformation and the other placing it into the asthenosphere, with recently developed fabric). We show that the depth distribution of anisotropy comprises elements of both models: anisotropy in the asthenosphere shows fast-propagation directions parallel to the plate motion; anisotropy in the Limpopo and northern Kaapvaal lithosphere shows fast directions parallel to the Archean

  2. Shear wave velocity, seismic attenuation, and thermal structure of the continental upper mantle

    USGS Publications Warehouse

    Artemieva, I.M.; Billien, M.; Leveque, J.-J.; Mooney, W.D.

    2004-01-01

    Seismic velocity and attenuation anomalies in the mantle are commonly interpreted in terms of temperature variations on the basis of laboratory studies of elastic and anelastic properties of rocks. In order to evaluate the relative contributions of thermal and non-thermal effects on anomalies of attenuation of seismic shear waves, QS-1, and seismic velocity, VS, we compare global maps of the thermal structure of the continental upper mantle with global QS-1 and Vs maps as determined from Rayleigh waves at periods between 40 and 150 S. We limit the comparison to three continental mantle depths (50, 100 and 150 km), where model resolution is relatively high. The available data set does not indicate that, at a global scale, seismic anomalies in the upper mantle are controlled solely by temperature variations. Continental maps have correlation coefficients of <0.56 between VS and T and of <0.47 between QS and T at any depth. Such low correlation coefficients can partially be attributed to modelling arrefacts; however, they also suggest that not all of the VS and QS anomalies in the continental upper mantle can be explained by T variations. Global maps show that, by the sign of the anomaly, VS and QS usually inversely correlate with lithospheric temperatures: most cratonic regions show high VS and QS and low T, while most active regions have seismic and thermal anomalies of the opposite sign. The strongest inverse correlation is found at a depth of 100 km, where the attenuation model is best resolved. Significantly, at this depth, the contours of near-zero QS anomalies approximately correspond to the 1000 ??C isotherm, in agreement with laboratory measurements that show a pronounced increase in seismic attenuation in upper mantle rocks at 1000-1100 ??C. East-west profiles of VS, QS and T where continental data coverage is best (50??N latitude for North America and 60??N latitude for Eurasia) further demonstrate that temperature plays a dominant, but non-unique, role in

  3. Trench-parallel variations in Pacific and Indo-Australian crustal velocity structure due to Louisville Ridge seamount subduction

    NASA Astrophysics Data System (ADS)

    Stratford, W. R.; Knight, T. P.; Peirce, C.; Watts, A. B.; Grevemeyer, I.; Paulatto, M.; Bassett, D.; Hunter, J.; Kalnins, L. M.

    2012-12-01

    Variations in trench and forearc morphology, and lithospheric velocity structure are observed where the Louisville Ridge seamount chain subducts at the Tonga-Kermadec Trench. Subduction of these seamounts has affected arc and back-arc processes along the trench for the last 5 Myr. High subduction rates (80 mm/yr in the north, 55 mm/yr in the south), a fast southwards migrating collision zone (~180 km/myr), and the obliquity of the subducting plate and the seamount chain to the trench, make this an ideal location to study the effects of seamount subduction on lithospheric structure. The "before and after" subduction regions have been targeted by several large-scale geophysical projects in recent years; the most recent being the R/V Sonne cruise SO215 in 2011. The crust and upper mantle velocity structure observed in profiles along strike of the seamount chain and perpendicular to the trench from this study, are compared to a similar profile from SO195, recorded ~100 km to the north. The affects of the passage of the seamounts through the subduction system are indicated by velocity anomalies in the crust and mantle of the overriding plate. Preliminary results indicate that in the present collision zone, mantle velocities (Pn) are reduced by ~5%. Around 100 km to the north, where seamounts are inferred to have subducted ~1 Myr ago, a reduction of 7% in mantle P-wave velocity is observed. The width of the trench slope and elevation of the forearc also vary along strike. At the collision zone a >100 km wide collapse region of kilometre-scale block faults comprise the trench slope, while the forearc is elevated. The elevated forearc has a 5 km think upper crust with a Vp of 2.5-5.5 km/s and the collapse zone also has upper crustal velocities as low as 2.5 km/s. To the east in the Pacific Plate, lower P-wave velocities are also observed and attributed to serpentinization due to deep fracturing in the outer trench high. Large bending faults permeate the crust and the

  4. Effect of structural setting on blast-induced azimuthal velocities and amplitude of ground motions in perlite

    SciTech Connect

    Aimone-Martin, C.T.; Beattie, S.G.

    1996-12-01

    A series of small scale explosive tests were performed at a perlite mine near Socorro, New Mexico. The tests were designed to investigate the azimuthal or directional relationship between small scale geologic structures such as joints and the propagation of explosively-induced ground motions. Three shots were initiated within a single borehole located at ground zero at depths varying from 83 m to 10 m. An array of three component velocity and acceleration transducers were placed in two concentric rings at distances of 20 m and 40 m surrounding the single hole at 7.5{degree}, 15{degree}, and 30{degree} azimuths as measured from ground zero. Data from the transducers were then used to determine the average propagation velocity and waveform characteristics of the blast vibration through the rock mass at the various azimuths. The rock mass was mapped to determine the predominate joint orientations (strike and dip) and the average propagation velocities were correlated with this geologic information. The results showed that there is a correlation between the predominate joint orientation and ground motion amplitudes and velocity. The more predominate geologic structures allow the wave to follow along their strike thereby forming a planar path of least resistance and in turn, allowing higher velocities and amplitudes. Secondary joints or structures may act in concert with more prominent features to form a network of channels or paths along which the wave moves more freely than it may when traveling against the structures. The greatest azimuthal variations in velocity and amplitude was observed for the shallow shot at 10 m depth.

  5. Lithospheric Shear Velocity Structure of South Island, New Zealand from Rayleigh Wave Tomography of Amphibious Array Data

    NASA Astrophysics Data System (ADS)

    Ball, J. S.; Sheehan, A. F.; Stachnik, J. C.; Lin, F. C.; Collins, J. A.

    2015-12-01

    We present the first 3D shear velocity 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 velocity (Vs) model include a low-velocity (Vs<4.3km/s) body extending to at least 75km depth beneath the Banks and Otago peninsulas, a high-velocity (Vs~4.7km/s) upper mantle anomaly underlying the Southern Alps to a depth of 100km, and discontinuous lithospheric velocity 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-velocity 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 velocity 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-velocity 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.

  6. Crust and upper mantle P wave velocity structure beneath Valles caldera, New Mexico: Results from the Jemez teleseismic tomography experiment

    SciTech Connect

    Steck, Lee K.; Fehler, Michael C.; Roberts, Peter M.; Baldridge, W. Scott; Stafford, Darrik G.; Lutter, William J.; Sessions, Robert

    1998-10-01

    New results are presented from the teleseismic component of the Jemez Tomography 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 velocity structure to depths of 40 km. The three principle features of our model for Valles caldera are: (1) near-surface low velocities of {minus}17{percent} beneath the Toledo embayment and the Valle Grande, (2) midcrustal low velocities of {minus}23{percent} in an ellipsoidal volume underneath the northwest quadrant of the caldera, and (3) a broad zone of low velocities ({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 velocities 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-velocity 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-velocity 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-velocity anomaly indicates that underplating by mantle-derived melts has occurred. {copyright} 1998 American Geophysical Union

  7. Use of Seismic Reflection Data and Traveltime Tomography to Image the Near Surface Velocity Structure in the Mississippi Embayment

    NASA Astrophysics Data System (ADS)

    Ge, J.; Magnani, M.; Waldron, B.; Powell, C.

    2007-12-01

    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 velocity structure and low P wave velocities 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 tomography performed along the profile to constrain the velocity field in the shallow portion of the profile. The velocity was then used to remove the effect of the near surface velocity 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 velocity 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-velocity 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 tomography

  8. 3-D velocity structure around tehri region of the garhwal lesser himalaya: constraints on geometry of the underthrusting indian plate

    NASA Astrophysics Data System (ADS)

    Kanaujia, Jyotima; Kumar, Ashwani; Gupta, S. C.

    2016-02-01

    We investigate the upper crustal velocity structure beneath the Tehri region of the Garhwal Himalaya. The investigated region is situated within the 700-km-long central seismic gap of the Himalaya that has experienced three gap-filling earthquakes since 1991 including the recent 2015 Nepal earthquake (Mw 7.8). The local tomographic inversion is based on a dataset of 1365 events collected from January 2008 to December 2012 by a 12-station local network that covers an area of about 100 × 80 km around Tehri Dam. We perform a simultaneous inversion for P- and S-wave velocity anomalies. Tomograms are interpreted in the backdrop of the regional geological and tectonic framework of the region. The spatial distribution of relocated events from the 3- D velocity model has shed new light on the pattern of seismicity in the vicinity of the Main Central thrust (MCT), and has elucidated the structure of the underthrusting Indian plate. Our model exhibits a significant negative velocity anomaly up to ˜5 per cent beneath the central part of the Garhwal Inner Lesser Himalaya, and a P-wave low velocity anomaly near the Chamoli region. The seismicity zone around the Chamoli region may be attributed to the presence of fluid filled rocks. Furthermore, an area with˜3-4 per cent positive velocity anomaly is delineated to the northwest of the Uttarkashi thrust in the vicinity of the MCT. Significant findings of the study include: a flat-ramp-flat type sub-surface geometry of the underthrusting Indian plate below the Garhwal Himalaya, high velocity images representing the trend and configuration of Delhi-Haridwar-ridge below the Sub Himalaya and Lesser Himalaya, and a seismically active zone representing geometrical asperity on the basement thrust in the vicinity of the MCT.

  9. Anisotropic velocity structure of the crust and upper mantle in the Taiwan region from local travel time tomography

    NASA Astrophysics Data System (ADS)

    Jakovlev, Andrey; Koulakov, Ivan; Wu, Yih-Min

    2014-05-01

    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 velocity model of the crust and upper mantle in the Taiwan region derived from local travel time tomography. 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 velocity described as horizontally oriented ellipsoid. For S velocity we presume an isotropic model. Results show a good agreement with tectonic structure of the region. Obtained isotropic P and S velocity models show fit to each other. The most prominent features of the models are Philippine Sea plate characterized by increased velocities and decreased velocities observed along the Luzon and Ryukyu arcs. We observe that orientation of the fast velocity axis within the Philippine Sea plate coincides with direction of its displacement. Along the Luzon and Ryukyu arcs orientation of the fast velocities axis coincide with the arcs extension. The results show that upper mantle beneath the eastern Taiwan characterized by decreased velocities and N-S orientation of the fast velocity axis. The western Taiwan characterized by alteration of the relatively small negative

  10. Probing structure-induced optical behavior in a new class of self-activated luminescent 0D/1D CaWO₄ metal oxide – CdSe nanocrystal composite heterostructures

    DOE PAGESBeta

    Han, Jinkyu; McBean, Coray; Wang, Lei; Hoy, Jessica; Jaye, Cherno; Liu, Haiqing; Li, Zhuo-Qun; Sfeir, Matthew Y.; Fischer, Daniel A.; Taylor, Gordon T.; et al

    2015-01-30

    In this report, we synthesize and characterize the structural and optical properties of novel heterostructures composed of (i) semiconducting nanocrystalline CdSe quantum dot (QDs) coupled with (ii) both one and zero-dimensional (1D and 0D) motifs of self-activated luminescence CaWO₄ metal oxides. Specifically, ~4 nm CdSe QDs have been anchored onto (i) high-aspect ratio 1D nanowires, measuring ~230 nm in diameter and ~3 μm in length, as well as onto (ii) crystalline 0D nanoparticles (possessing an average diameter of ~ 80 nm) of CaWO₄ through the mediation of 3-mercaptopropionic acid (MPA) as a connecting linker. Composite formation was confirmed by complementarymore » electron microscopy and spectroscopy (i.e. IR and Raman) data. In terms of luminescent properties, our results show that our 1D and 0D heterostructures evince photoluminescence (PL) quenching and shortened PL lifetimes of CaWO₄ as compared with unbound CaWO₄. We propose that a photo-induced electron transfer process occurs from CaWO₄ to CdSe QDs, a scenario which has been confirmed by NEXAFS measurements and which highlights a decrease in the number of unoccupied orbitals in the conduction bands of CdSe QDs. By contrast, the PL signature and lifetimes of MPA-capped CdSe QDs within these heterostructures do not exhibit noticeable changes as compared with unbound MPA-capped CdSe QDs. The striking difference in optical behavior between CaWO₄ nanostructures and CdSe QDs within our heterostructures can be correlated with the relative positions of their conduction and valence energy band levels. In addition, the PL quenching behaviors for CaWO₄ within the heterostructure configuration were examined by systematically varying (i) the quantities and coverage densities of CdSe QDs as well as (ii) the intrinsic morphology (and by extension, the inherent crystallite size) of CaWO₄ itself.« less

  11. Seismic velocity structure of the subducting Pacific plate in the Izu-Bonin region

    SciTech Connect

    Iidaka, Takashi; Mizoue, Megumi; Suyehiro, Kiyoshi )

    1992-10-01

    Observed travel time residual data from a spatially dense seismic network above deep earthquakes in the Izu-Bonin region are compared with 3D ray tracing calculations. The data are inconsistent with a homogeneous slab model and consistent with a heterogenous slab model with regional velocity variations. The residual data can be explained by a model that has a velocity gradient within the slab. In the subducting Pacific plate, the velocity near the center of the slab is faster than that near the upper boundary, and gradually decreases toward the bottom of the plate. A model with a velocity decrease of 3 percent, as predicted by a thermal profile, explains the observed data. 52 refs.

  12. Self-powered semi-passive piezoelectric structural damping based on zero-velocity crossing detection

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Yin; Vasic, Dejan; Costa, François; Lee, Chih-Kung; Wu, Wen-Jong

    2013-02-01

    In recent years, semi-passive vibration damping using non-linear synchronized switching methods has been intensively investigated and discussed. In this paper, a self-powered synchronized switch damping on inductor (SSDI) technique based on zero-velocity crossing detection is proposed and investigated. The control signal used to drive the switches is obtained by sensing velocity. A totally self-powered damping system powered by harvested energy using the SSDI technique with velocity sensing and without external power is established. Compared with the conventional technique based on voltage peak detector, this technique does not generate lag in detection of switching time. The theoretical model, the experimental evaluation and the drawback of the self-powered zero-velocity crossing detection switching technique are discussed in this study. The system performance is also compared with the externally powered system.

  13. Comparative velocity structure of active Hawaiian volcanoes from 3-D onshore-offshore seismic tomography

    USGS Publications Warehouse

    Park, J.; Morgan, J.K.; Zelt, C.A.; Okubo, P.G.; Peters, L.; Benesh, N.

    2007-01-01

    We present a 3-D P-wave velocity model of the combined subaerial and submarine portions of the southeastern part of the Island of Hawaii, based on first-arrival seismic tomography of marine airgun shots recorded by the onland seismic network. Our model shows that high-velocity 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-velocity 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 velocities (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-velocity anomalies beneath the summit and along the rift zones, similar to the interpreted magma cumulates below Mauna Loa and Kilauea volcanoes, and a low-velocity anomaly beneath the oceanic crust, probably indicative of melt within the upper mantle. Around Kilauea's submarine flank, a high-velocity 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-velocity 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.

  14. San Andreas fault zone velocity structure at SAFOD at core, log, and seismic scales

    NASA Astrophysics Data System (ADS)

    Jeppson, Tamara N.; Tobin, Harold J.

    2015-07-01

    The San Andreas Fault (SAF), like other mature brittle faults, exhibits a zone of low seismic velocity hypothesized to result from fluid pressure effects and/or development of a damage zone. To address the relative contributions of these mechanisms in developing low-velocity zones, we measured P and S wave velocities ultrasonically at elevated confining and pore pressures on core samples from the San Andreas Fault Observatory at Depth (SAFOD). We compared those data to wireline and seismic-scale velocities to examine the scale dependence of acoustic properties of the fault core and damage zone. Average laboratory P and S wave velocities of the fault gouge at estimated in situ conditions are 3.1 and 1.5 km/s, respectively, consistent with the sonic log from the same intervals. These data show that fault core has intrinsically low velocity, even if no anomalous pore pressure is assumed, due to alteration and mechanical damage. In contrast, laboratory average P and S wave velocities for the damage zone are 4.7 and 2.5 km/s, up to 41% greater than the sonic log in the damage zone. This scale dependence indicates that stress conditions or macroscale features dominate the damage zone's acoustic properties, although velocity dispersion could play a role. Because no pressure anomaly was detected while drilling the SAFOD borehole, we infer that damage at a scale larger than core samples controls the elastic properties of the broader damage zone. This result bolsters other independent lines of evidence that the SAF does not contain major pore fluid overpressure at SAFOD.

  15. Ionic liquid lubrication: influence of ion structure, surface potential and sliding velocity.

    PubMed

    Li, Hua; Rutland, Mark W; Atkin, Rob

    2013-09-21

    Colloid probe atomic force microscopy (AFM) has been employed to investigate the nanotribology of the ionic liquid (IL)-Au(111) interface. Data is presented for four ILs, 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([EMIM] FAP), 1-butyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([BMIM] FAP), 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([HMIM] FAP) and 1-butyl-3-methylimidazolium iodide ([BMIM] I), at different Au(111) surface potentials. Lateral forces vary as a function of applied surface potential and ion structure because the composition of the confined ion layer changes from cation-enriched (at negative potentials) to mixed (at 0 V), and to anion-enriched (at positive potentials). ILs with FAP(-) anions all exhibit similar nanotribology: low friction at negative potentials and higher friction at positive potentials. [BMIM] I displays the opposite behaviour, as an I(-) anion-enriched layer is more lubricating than either the [BMIM](+) or FAP(-) layers. The effect of cation charged group (charge-delocalised versus charged-localised) was investigated by comparing [BMIM] FAP with 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate ([Py(1,4)] FAP). [BMIM] FAP is less lubricating at negative potentials, but more lubricating at positive potentials. This indicated that even at positive potentials the cation concentration in the boundary layer is sufficiently high to influence lubricity. The influence of sliding velocity on lateral force was investigated for the [EMIM] FAP-Au(111) system. At neutral potentials the behaviour is consistent with a discontinuous sliding process. When a positive or negative potential bias is applied, this effect is less pronounced as the colloid probe slides along a better defined ion plane. PMID:23836254

  16. Logarithmic velocity structure in the deep hypolimnetic waters of Lake Michigan

    NASA Astrophysics Data System (ADS)

    Troy, Cary; Cannon, David; Liao, Qian; Bootsma, Harvey

    2016-01-01

    The characteristics of the bottom boundary layer are reported from a Lake Michigan field study carried out in deep hypolimnetic waters (55 m depth) during the stratified period (June-September 2012). The sandy substrate at the measurement site was densely covered with invasive quagga mussels (mean size: 1.6 cm; mean density: 10,000 mussels m-2). The measurements reveal a sluggish, compact bottom boundary layer, with flow speeds at 1 mab less than 5 cm s-1 for most of the period, and a dominance of subinertial energy. A downwelling event caused the largest currents observed during the deployment (10 cm s-1 at 1 mab) and a logarithmic layer thickness of 15 m. In spite of the weak flow, logarithmic profile fitting carried out on high-resolution, near-bed velocity profiles show consistent logarithmic structure (90% of profiles). Flow was dominated by subinertial energy but strong modified by near-inertial waves. Fitted drag coefficients and roughness values are = 0.004 and = 0.12 cm, respectively. These values increase with decreasing flow speed, but approach canonical values for 1 mab flow speeds exceeding 4 cm s-1. The estimated vertical extent of the logarithmic region was compact, with a mean value of 1.2 m and temporal variation that is reasonably described by Ekman scaling, 0.07 /, and the estimated overall Ekman layer thickness was generally less than 10 m. Near-bed dissipation rates inferred from the law of the wall were 10-8-10-7 W kg-1 and turbulent diffusivities were 10-4-10-3 m2s-1.

  17. S-Wave Velocity Structure of the Taiwan Chelungpu Fault Drilling Project (TCDP) Site Using Microtremor Array Measurements

    NASA Astrophysics Data System (ADS)

    Wu, Cheng-Feng; Huang, Huey-Chu

    2015-10-01

    The Taiwan Chelungpu Fault Drilling Project (TCDP) drilled a 2-km-deep hole 2.4 km east of the surface rupture of the 1999 Chi-Chi earthquake ( M w 7.6), near the town of Dakeng. Geophysical well logs at the TCDP site were run over depths ranging from 500 to 1,900 m to obtain the physical properties of the fault zones and adjacent damage zones. These data provide good reference material for examining the validity of velocity structures using microtremor array measurement; therefore, we conduct array measurements for a total of four arrays at two sites near the TCDP drilling sites. The phase velocities at frequencies of 0.2-5 Hz are calculated using the frequency-wavenumber ( f- k) spectrum method. Then the S-wave velocity structures are estimated by employing surface wave inversion techniques. The S-wave velocity from the differential inversion technique gradually increases from 1.52 to 2.22 km/s at depths between 585 and 1,710 m. This result is similar to those from the velocity logs, which range from 1.4 km/s at a depth of 597 m to 2.98 km/s at a depth of 1,705 m. The stochastic inversion results are similar to those from the seismic reflection methods and the lithostratigraphy of TCDP-A borehole, comparatively. These results show that microtremor array measurement provides a good tool for estimating deep S-wave velocity structure.

  18. Regional structural analysis and velocity model (Vp) of the Chittagong-Myanmar Fold and Thrust Belt, Bangladesh

    NASA Astrophysics Data System (ADS)

    Burgi, P.; Hubbard, J.; Peterson, D. E.; Akhter, S. H.

    2015-12-01

    Bangladesh sits on the seismically active Chittagong-Myanmar Fold and Thrust Belt (CMFB), a partially exposed accretionary prism associated with the India-Eurasia collision. Ground shaking due to local and regional earthquakes presents a potential hazard to Bangladesh, one of the most populated areas in the world. In order to constrain this hazard, we first investigate potential seismic sources (active faults), and second we analyze the material through which seismic energy propagates. To address potential earthquake sources, we focus on the Comilla Anticline, which is the frontal-most exposed structure of the CMFB as well as the most proximal to the capital city of Dhaka. We present several industry-acquired and depth-converted seismic reflection profiles, which exhibit an asymmetric detachment fold rising from a relatively deep décollement (5-6 km). Because there is no strong evidence for an associated emergent thrust, this actively growing fold may have low seismic potential. We place this work into a regional context by integrating previous research of CMFB structures to create a regional structural model, which reveals laterally varying wedge geometry. To address ground shaking, the second component of this work, we assess stacking velocities from our seismic reflection data in conjunction with sonic log velocities from several locations in Bangladesh. These data show varying velocity versus depth trends by region. Following similar, data-rich studies performed in the Los Angeles and adjacent basins, we use data and theory-driven fitting techniques to analyze depth-velocity trends for these different regions, and interpolate to create a laterally varying regional seismic velocity model. Velocities generally slow from east to west, consistent with the younging trend as we move from older, exhumed CMFB formations to recent and undeformed deposits.

  19. 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 tomography 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://www.ncbi.nlm.nih.gov/pubmed/26119084','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26119084"><span id="translatedtitle">Synthesis of <span class="hlt">1</span><span class="hlt">D</span> Fe₃O₄/P(MBAAm-co-MAA) nanochains as stabilizers for Ag nanoparticles and templates for hollow mesoporous <span class="hlt">structure</span>, and their applications in catalytic reaction and drug delivery.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Wei; Si, Xiaowei; Liu, Bin; Bian, Guomin; Qi, Yonglin; Yang, Xinlin; Li, Chenxi</p> <p>2015-10-15</p> <p>One-dimensional (<span class="hlt">1</span><span class="hlt">D</span>) magnetic Fe3O4/P(MBAAm-co-MAA) nanochains were prepared by distillation-precipitation polymerization of MBAAm and MAA in the presence of Fe3O4 nanoparticles as building blocks under a magnetic heating stirrer, which played two critical roles: serving as magnetic field to induce the self-assembly of Fe3O4 nanoparticles into <span class="hlt">1</span><span class="hlt">D</span> nanochains and providing thermal energy to induce the polymerization of MAA and MBAAm on the surface of the Fe3O4 nanoparticles. The thickness of the P(MBAAm-co-MAA) layer can be easily tuned by adjusting the successive polymerization steps. The polymer layer that contained carboxyl groups was used as stabilizers for loading Ag nanoparticles and the reaction locus for deposition of outer silica layer via a sol-gel method in presence of C18TMS as the pore directing agent for tri-layer nanochains. The corresponding hollow mesoporous silica nanochains with movable maghemite cores (γ-Fe2O3@mSiO2) were produced after removal of the polymer mid-layer and the alkyl groups of the pore directing agent via calcination of the tri-layer nanochains at high temperature. The Fe3O4/P(MBAAm-co-MAA)/Ag nanochains exhibited a highly catalytic efficiency and well reusable property toward the reduction of nitrophenol. Furthermore, the γ-Fe2O3@mSiO2 nanochains possessed hollow mesoporous <span class="hlt">structure</span> and high specific surface area (197.2 m(2) g(-1)) were used as a drug carrier, which displayed a controlled release property. PMID:26119084</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://www.ncbi.nlm.nih.gov/pubmed/24617285','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24617285"><span id="translatedtitle"><span class="hlt">Structure</span> and thermodynamic properties of (C5H12N)CuBr3: a new weakly coupled antiferromagnetic spin-1/2 chain complex lying in the <span class="hlt">1</span><span class="hlt">D</span>-3D dimensional cross-over regime.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pan, Bingying; Wang, Yang; Zhang, Lijuan; Li, Shiyan</p> <p>2014-04-01</p> <p>Single crystals of a metal organic complex (C5H12N)CuBr3 (C5H12N = piperidinium, pipH for short) have been synthesized, and the <span class="hlt">structure</span> was determined by single-crystal X-ray diffraction. (pipH)CuBr3 crystallizes in the monoclinic group C2/c. Edging-sharing CuBr5 units link to form zigzag chains along the c axis, and the neighboring Cu(II) ions with spin-1/2 are bridged by bibromide ions. Magnetic susceptibility data down to 1.8 K can be well fitted by the Bonner-Fisher formula for the antiferromagnetic spin-1/2 chain, giving the intrachain magnetic coupling constant J ≈ -17 K. At zero field, (pipH)CuBr3 shows three-dimensional (3D) order below TN = 1.68 K. Calculated by the mean-field theory, the interchain coupling constant J' = -0.91 K is obtained and the ordered magnetic moment m0 is about 0.23 μB. This value of m0 makes (pipH)CuBr3 a rare compound suitable to study the <span class="hlt">1</span><span class="hlt">D</span>-3D dimensional cross-over problem in magnetism, since both 3D order and one-dimensional (<span class="hlt">1</span><span class="hlt">D</span>) quantum fluctuations are prominent. In addition, specific heat measurements reveal two successive magnetic transitions with lowering temperature when external field μ0H ≥ 3 T is applied along the a' axis. The μ0H-T phase diagram of (pipH)CuBr3 is roughly constructed. PMID:24617285</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014M%26PS...49.1157K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014M%26PS...49.1157K"><span id="translatedtitle">Density, porosity, mineralogy, and internal <span class="hlt">structure</span> of cosmic dust and alteration of its properties during high-<span class="hlt">velocity</span> atmospheric entry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kohout, T.; Kallonen, A.; Suuronen, J.-P.; Rochette, P.; Hutzler, A.; Gattacceca, J.; Badjukov, D. D.; SkáLa, R.; BöHmová, V.; ČUda, J.</p> <p>2014-07-01</p> <p>X-ray microtomography (XMT), X-ray diffraction (XRD), and magnetic hysteresis measurements were used to determine micrometeorite internal <span class="hlt">structure</span>, mineralogy, crystallography, and physical properties at μm resolution. The study samples include unmelted, partially melted (scoriaceous), and completely melted (cosmic spherules) micrometeorites. This variety not only allows comparison of the mineralogy and porosity of these three micrometeorite types but also reveals changes in meteoroid properties during atmospheric entry at various <span class="hlt">velocities</span>. At low entry <span class="hlt">velocities</span>, meteoroids do not melt and their physical properties do not change. The porosity of unmelted micrometeorites varies considerably (0-12%) with one friable example having porosity around 50%. At higher <span class="hlt">velocities</span>, the range of meteoroid porosity narrows, but average porosity increases (to 16-27%) due to volatile evaporation and partial melting (scoriaceous phase). Metal distribution seems to be mostly unaffected at this stage. At even higher entry <span class="hlt">velocities</span>, complete melting follows the scoriaceous phase. Complete melting is accompanied by metal oxidation and redistribution, loss of porosity (1 ± 1%), and narrowing of the bulk (3.2 ± 0.5 g cm-3) and grain (3.3 ± 0.5 g cm-3) density range. Melted cosmic spherules with a barred olivine <span class="hlt">structure</span> show an oriented crystallographic <span class="hlt">structure</span>, whereas other subtypes do not.</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> <span class="hlt">Structure</span> of Central Idaho/ Eastern Oregon from Joint Inversion of Rayleigh Wave Group 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 group 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 tomography and the methods of Gallego et. al (2010) and Lin et. al (2008). We calculated inter-station group/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> <span class="hlt">structure</span> beneath the network. Goals of our work include refining models of crustal <span class="hlt">structure</span> 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 group 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://pubs.er.usgs.gov/publication/70029117','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70029117"><span id="translatedtitle">Forearc <span class="hlt">structure</span> beneath southwestern British Columbia: A three-dimensional tomographic <span class="hlt">velocity</span> model</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Ramachandran, K.; Dosso, S.E.; Spence, G.D.; Hyndman, R.D.; Brocher, T.M.</p> <p>2005-01-01</p> <p>This paper presents a three-dimensional compressional wave <span class="hlt">velocity</span> model of the forearc crust and upper mantle and the subducting Juan de Fuca plate beneath southwestern British Columbia and the adjoining straits of Georgia and Juan de Fuca. The <span class="hlt">velocity</span> model was constructed through joint tomographic inversion of 50,000 first-arrival times from earthquakes and active seismic sources. Wrangellia rocks of the accreted Paleozoic and Mesozoic island arc assemblage underlying southern Vancouver Island in the Cascadia forearc are imaged at some locations with higher than average lower crustal <span class="hlt">velocities</span> of 6.5-7.2 km/s, similar to observations at other island arc terranes. The mafic Eocene Crescent terrane, thrust landward beneath southern Vancouver Island, exhibits crustal <span class="hlt">velocities</span> in the range of 6.0-6.7 km/s and is inferred to extend to a depth of more than 20 km. The Cenozoic Olympic Subduction Complex, an accretionary prism thrust beneath the Crescent terrane in the Olympic Peninsula, is imaged as a low-<span class="hlt">velocity</span> wedge to depths of at least 20 km. Three zones with <span class="hlt">velocities</span> of 7.0-7.5 km/s, inferred to be mafic and/or ultramafic units, lie above the subducting Juan de Fuca plate at depths of 25-35 km. The forearc upper mantle wedge beneath southeastern Vancouver Island and the Strait of Georgia exhibits low <span class="hlt">velocities</span> of 7.2-7.5 km/s, inferred to correspond to ???20% serpentinization of mantle peridotites, and consistent with similar observations in other warm subduction zones. Estimated dip of the Juan de Fuca plate beneath southern Vancouver Island is ???11??, 16??, and 27?? at depths of 30, 40, and 50 km, respectively. Copyright 2005 by the American Geophysical Union.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27119205','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27119205"><span id="translatedtitle">Cyano-bridged coordination polymer hydrogel-derived Sn-Fe binary oxide nanohybrids with <span class="hlt">structural</span> diversity: from 3D, 2D, to 2D/<span class="hlt">1</span><span class="hlt">D</span> and enhanced lithium-storage performance.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Weiyu; Zhu, Xiaoshu; Chen, Xuguang; Zhou, Yiming; Tang, Yawen; Ding, Liangxin; Wu, Ping</p> <p>2016-05-14</p> <p>Metal oxide nanohybrids with uniform dimensions and controlled architectures possess unique compositional and <span class="hlt">structural</span> superiorities, and thus harbor promising potential for a series of applications in energy, catalysis, and sensing systems. Herein, we propose a facile, general, and scalable cyano-bridged coordination polymer hydrogel-derived thermal-oxidation route for the construction of main-group metal and transition-metal heterometallic oxide nanohybrids with controlled constituents and architectures. The formation of Sn-Fe binary oxide nanohybrids has been demonstrated as an example by using cyano-bridged Sn(iv)-Fe(ii) bimetallic coordination polymer hydrogels (i.e., SnCl4-K4Fe(CN)6 cyanogels, Sn-Fe cyanogels) as precursors. The physicochemical properties of Sn-Fe cyanogels with different Sn/Fe ratios have been systematically examined, and it is found that perfect Sn-Fe cyanogels without unbridged Sn(iv) or Fe(ii) can be formed with Sn/Fe ratios from 2 : 1 to 1 : 2. More importantly, the simple adjustment of Sn/Fe ratios in the Sn-Fe cyanogel precursors can realize flexible dimensional control of the Sn-Fe binary oxide nanohybrids, and 2D/<span class="hlt">1</span><span class="hlt">D</span> SnO2-Fe2O3 hierarchitectures, 2D SnO2-Fe2O3 nanosheets, and 3D SnO2-Fe2O3 networks have been synthesized using the Sn-Fe 1 : 2, Sn-Fe 1 : 1, and Sn-Fe 2 : 1 cyanogels as precursors, respectively. To demonstrate their compositional/<span class="hlt">structural</span> superiorities and potential applications, the lithium-storage utilization of the Sn-Fe binary oxide nanohybrids has been selected as an objective application, and the nanohybrids exhibit Sn/Fe ratio-dependent lithium-storage performance. As a representative example, the 2D/<span class="hlt">1</span><span class="hlt">D</span> SnO2-Fe2O3 hierarchitectures manifest markedly enhanced Li-storage performance in terms of reversible capacities and cycling stability in comparison with their constituent units, i.e., bare SnO2 nanosheets and Fe2O3 nanorods. The proposed cyanogel-derived thermal-oxidation strategy could</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ApPhB.103..271K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ApPhB.103..271K"><span id="translatedtitle">Simultaneous planar measurements of soot <span class="hlt">structure</span> and <span class="hlt">velocity</span> fields in a turbulent lifted jet flame at 3 kHz</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Köhler, M.; Boxx, I.; Geigle, K. P.; Meier, W.</p> <p>2011-05-01</p> <p>We describe a newly developed combustion diagnostic for the simultaneous planar imaging of soot <span class="hlt">structure</span> and <span class="hlt">velocity</span> fields in a highly sooting, lifted turbulent jet flame at 3000 frames per second, or two orders of magnitude faster than "conventional" laser imaging systems. This diagnostic uses short pulse duration (8 ns), frequency-doubled, diode-pumped solid state (DPSS) lasers to excite laser-induced incandescence (LII) at 3 kHz, which is then imaged onto a high framerate CMOS camera. A second (dual-cavity) DPSS laser and CMOS camera form the basis of a particle image <span class="hlt">velocity</span> (PIV) system used to acquire 2-component <span class="hlt">velocity</span> field in the flame. The LII response curve (measured in a laminar propane diffusion flame) is presented and the combined diagnostics then applied in a heavily sooting lifted turbulent jet flame. The potential challenges and rewards of application of this combined imaging technique at high speeds are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21443266','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21443266"><span id="translatedtitle">THREE-DIMENSIONAL <span class="hlt">STRUCTURE</span> OF THE CENTRAL REGION OF NGC 7027: A QUEST FOR TRAILS OF HIGH-<span class="hlt">VELOCITY</span> JETS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Nakashima, Jun-ichi; Kwok, Sun; Zhang Yong; Koning, Nico</p> <p>2010-08-15</p> <p>We report on the results of a radio interferometric observation of NGC 7027 in the CO J = 2-1 and {sup 13}CO J = 2-1 lines. The results are analyzed with morpho-kinematic models developed from the software tool Shape. Our goal is to reveal the morpho-kinematic properties of the central region of the nebula, and to explore the nature of unseen high-<span class="hlt">velocity</span> jets that may have created the characteristic <span class="hlt">structure</span> of the central region consisting of molecular and ionized components. A simple ellipsoidal shell model explains the intensity distribution around the systemic <span class="hlt">velocity</span>, but the high-<span class="hlt">velocity</span> features deviate from the ellipsoidal model. Through the Shape automatic reconstruction model, we found a possible trail of a jet only in one direction, but no other possible holes were created by the passage of a jet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1041979','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1041979"><span id="translatedtitle"><span class="hlt">Structural</span> Electronic and Magnetic Properties of Quasi-<span class="hlt">1</span><span class="hlt">D</span> Quantum Magnets [Ni(HF2)(pyz)2]X (pyz = pyrazine; X = PF6- SbF6-) Exhibiting Ni-FHF-Ni and Ni-pyz-Ni Spin Interactions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>J Manson; S Lapidus; P Stephens; P Peterson; K Carreiro; H Southerland; T Lancaster; S Blundell; A Steele; et al.</p> <p>2011-12-31</p> <p>[Ni(HF{sub 2})(pyz){sub 2}]X {l_brace}pyz = pyrazine; X = PF{sub 6}{sup -} (1), SbF{sub 6}{sup -} (2){r_brace} were <span class="hlt">structurally</span> characterized by synchrotron X-ray powder diffraction and found to possess axially compressed NiN{sub 4}F{sub 2} octahedra. At 298 K, 1 is monoclinic (C2/c) with unit cell parameters, a = 9.9481(3), b = 9.9421(3), c = 12.5953(4) {angstrom}, and {beta} = 81.610(3){sup o} while 2 is tetragonal (P4/nmm) with a = b = 9.9359(3) and c = 6.4471(2) {angstrom} and is isomorphic with the Cu-analogue. Infinite one-dimensional (<span class="hlt">1</span><span class="hlt">D</span>) Ni-FHF-Ni chains propagate along the c-axis which are linked via {mu}-pyz bridges in the ab-plane to afford three-dimensional polymeric frameworks with PF{sub 6}{sup -} and SbF{sub 6}{sup -} counterions occupying the interior sites. A major difference between 1 and 2 is that the Ni-F-H bonds are bent (157{sup o}) in 1 but are linear in 2. Ligand field calculations (LFT) based on an angular overlap model (AOM), with comparison to the electronic absorption spectra, indicate greater {pi}-donation of the HF{sub 2}{sup -} ligand in 1 owing to the bent Ni-F-H bonds. Magnetic susceptibility data for 1 and 2 exhibit broad maxima at 7.4 and 15 K, respectively, and {lambda}-like peaks in dxT/dT at 6.2 and 12.2 K that are ascribed to transitions to long-range antiferromagnetic order (TN). Muon-spin relaxation and specific heat studies confirm these TN's. A comparative analysis of x vs T to various <span class="hlt">1</span><span class="hlt">D</span> Heisenberg/Ising models suggests moderate antiferromagnetic interactions, with the primary interaction strength determined to be 3.05/3.42 K (1) and 5.65/6.37 K (2). However, high critical fields of 19 and 37.4 T obtained from low temperature pulsed-field magnetization data indicate that a single exchange constant (J<span class="hlt">1</span><span class="hlt">D</span>) alone is insufficient to explain the data and that residual terms in the spin Hamiltonian, which could include interchain magnetic couplings (J), as mediated by Ni-pyz-Ni, and single-ion anisotropy (D), must be considered</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1810214W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1810214W"><span id="translatedtitle">3D seismic <span class="hlt">velocity</span> <span class="hlt">structure</span> in the rupture area of the 2014 M8.2 Iquique earthquake in Northern Chile</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Woollam, Jack; Fuenzallida, Amaya; Garth, Tom; Rietbrock, Andreas; Ruiz, Sergio; Tavera, Hernando</p> <p>2016-04-01</p> <p>Seismic <span class="hlt">velocity</span> tomography is one of the key tools in Earth sciences to image the physical properties of the subsurface. In recent years significant advances have been made to image the Chilean subductions zone, especially in the area of the 2010 M8.8 Maule earthquake (e.g. Hicks et al., 2014), providing much needed physical constraints for earthquakes source inversions and rupture models. In 2014 the M8.2 Iquique earthquake struck the northern part of the Chilean subduction zone in close proximity to the Peruvian boarder. The pre- and aftershock sequence of this major earthquake was recorded by a densified seismological network in Northern Chile and Southern Peru, which provides an excellent data set to study in depth the 3D <span class="hlt">velocity</span> <span class="hlt">structure</span> along the subduction megathrust. Based on an automatic event catalogue of nearly 10,000 events spanning the time period March to May 2014 we selected approximately 450 events for a staggered 3D inversion approach. Events are selected to guarantee an even ray coverage through the inversion volume. We only select events with a minimum GAP of 200 to improve depth estimates and therefore increase resolution in the marine forearc. Additionally, we investigate secondary arrivals between the P- and S-wave arrival to improve depth location. Up to now we have processed about 450 events, from which about 150 with at least 30 P- and S-wave observations have been selected for the subsequent 3D tomography. Overall the data quality is very high, which allows arrival time estimates better than 0.05s on average. We will show results from the <span class="hlt">1</span><span class="hlt">D</span>, 2D, and preliminary 3D inversions and discuss the results together with the obtained seismicity distribution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRC..120.4576D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRC..120.4576D"><span id="translatedtitle">Spatial and temporal variability of the <span class="hlt">velocity</span> and hydrographic <span class="hlt">structure</span> in a weakly stratified system, Broad Sound, Casco Bay, Maine</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dzwonkowski, Brian; Pettigrew, Neal R.; Knapp, Stacy R.</p> <p>2015-06-01</p> <p>The <span class="hlt">velocity</span> and hydrographic <span class="hlt">structure</span> across Broad Sound, a north-south orientated subsystem of Casco Bay, ME that lacks continuous coastal boundaries, were characterized using <span class="hlt">velocity</span> observations from two moorings in late summer/fall of 2013 and <span class="hlt">velocity</span> and density observations from a repeat-transect ship survey conducted over a tidal cycle during the same period. At tidal time scales, the system is dominated by a barotropic semidiurnal standing wave with a west to east decrease in tidal amplitude and relatively minimal phase change across the majority of the transect. The stratification (vertical differences of 0.5-1.0 kg m-3) was generally laterally uniform and stronger during the flood phase which is hypothesized to result from stronger offshore stratification. The mean circulation had strong lateral shear with inflow over the deepest point in the bathymetric cross section and eastern slope and outflow over the western slope. There was also vertical shearing of the horizontal <span class="hlt">velocities</span> with stronger northward (or northward trending) <span class="hlt">velocities</span> at depth. The depth-averaged subtidal fluctuations were relatively small (˜2-3 cm s-1) and uncorrelated between mooring sites suggesting the vertically uniform current response associated with remote wind forcing is of limited importance. On the other hand, the depth-dependent <span class="hlt">velocity</span> fluctuations at the subtidal time scale were, in large part (˜36-72%), driven by wind forcing. The net flux ratio, a means of quantifying the relative importance of the vertical and lateral shear in the flow field, was typically ˜0.44 indicating the <span class="hlt">structure</span> of the local wind response favored vertically sheared flow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005JSSCh.178.1929C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005JSSCh.178.1929C&link_type=ABSTRACT"><span id="translatedtitle">The synthesis and <span class="hlt">structure</span> of a chiral <span class="hlt">1</span><span class="hlt">D</span> aluminophosphate chain compound: d-Co(en) 3[AlP 2O 8]·6.5H 2O</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Peng; Li, Jiyang; Yu, Jihong; Wang, Yu; Pan, Qinhe; Xu, Ruren</p> <p>2005-06-01</p> <p>A new chiral one-dimensional (<span class="hlt">1</span><span class="hlt">D</span>) aluminophosphate chain compound [ d-Co(en) 3][AlP 2O 8]·6.5H 2O (designated AlPO-CJ22) has been hydrothermally synthesized by using the optically pure d-Co(en) 3I 3 complex as the template. Single-crystal <span class="hlt">structural</span> analysis reveals that its <span class="hlt">structure</span> is built up from alternating connection of AlO 4 and PO 2(=O 2) tetrahedra to form corner-shared Al 2P 2 four-membered ring (4-MR) chains. The d-Co(en) 33+ complex cations extended along the 2 1 screw axis interact with the inorganic chains through hydrogen-bonds of N⋯O atoms in a helical fashion. Optical rotation measurement shows that AlPO-CJ22 is chiral as with d-Co(en) 33+ complex cations. Crystal data: orthorhombic, I2 12 12 1, a=8.5573(8) Å, b=22.613(2) Å, c=22.605(2) Å, Z=8, R1=0.067, wR2=0.1291, and Flack parameter: -0.02(3). CCDC number: 254179.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016GGG....17.1990H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016GGG....17.1990H&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Velocity</span> <span class="hlt">structure</span> near IODP Hole U1309D, Atlantis Massif, from waveform inversion of streamer data and borehole measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Harding, Alistair J.; Arnulf, Adrien F.; Blackman, Donna K.</p> <p>2016-06-01</p> <p>Seismic full waveform inversion (FWI) is a promising method for determining the detailed <span class="hlt">velocity</span> <span class="hlt">structure</span> of the igneous oceanic crust, especially for locations such as the Mid-Atlantic Ridge with significant lateral heterogeneity and seafloor topography. We examine the accuracy of FWI by inverting, after downward continuation to datum just above the seafloor, a multichannel seismic (MCS) profile from Atlantis Massif oceanic core complex at 30°N that passes close to Integrated Ocean Drilling Program (IODP) Hole U1309D and comparing the results against borehole measurements and existing on-bottom refraction data. The comparisons include the results of IODP Expedition 340T, which extended the sonic logging and vertical seismic profiling to the bottom of the borehole at 1400 m below seafloor. Compared to travel time tomography, the refinement in <span class="hlt">velocity</span> and <span class="hlt">velocity</span> gradient produced by FWI significantly improves the overall match to the borehole measurements, and allows the multilevel pattern of deformation and alteration of the detachment footwall seen in Hole U1309D to be extrapolated across the Central Dome. Prestack depth migration of the profile using the FWI <span class="hlt">velocities</span> reveals the top and edges of the high-<span class="hlt">velocity</span>, gabbroic core of the massif. It also indicates that the comparatively uniform gabbroic rocks drilled at Hole U1309D extend to ˜2.5 km below seafloor but overlie an extended, ˜2 km thick, mantle transition zone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008JGRB..113.6306K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008JGRB..113.6306K"><span id="translatedtitle">Anisotropic shear-wave <span class="hlt">velocity</span> <span class="hlt">structure</span> of the Earth's mantle: A global model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kustowski, B.; EkströM, G.; DziewońSki, A. M.</p> <p>2008-06-01</p> <p>We combine a new, large data set of surface wave phase anomalies, long-period waveforms, and body wave travel times to construct a three-dimensional model of the anisotropic shear wave <span class="hlt">velocity</span> in the Earth's mantle. Our modeling approach is improved and more comprehensive compared to our earlier studies and involves the development and implementation of a new spherically symmetric reference model, simultaneous inversion for <span class="hlt">velocity</span> and anisotropy, as well as discontinuity topographies, and implementation of nonlinear crustal corrections for waveforms. A comparison of our new three-dimensional model, S362ANI, with two other models derived from comparable data sets but using different techniques reveals persistent features: (1) strong, ˜200-km-thick, high-<span class="hlt">velocity</span> anomalies beneath cratons, likely representing the continental lithosphere, underlain by weaker, fast anomalies extending below 250 km, which may represent continental roots, (2) weak <span class="hlt">velocity</span> heterogeneity between 250 and 400 km depths, (3) fast anomalies extending horizontally up to 2000-3000 km in the mantle transition zone beneath subduction zones, (4) lack of strong long-wavelength heterogeneity below 650 km suggesting inhibiting character of the upper mantle-lower mantle boundary, and (5) slow-<span class="hlt">velocity</span> superplumes beneath the Pacific and Africa. The shear wave radial anisotropy is strongest at 120 km depth, in particular beneath the central Pacific. Lateral anisotropic variations appreciably improve the fit to data that are predominantly sensitive to the uppermost and lowermost mantle but not to the waveforms that control the transition zone and midmantle depths. Tradeoffs between lateral variations in <span class="hlt">velocity</span> and anisotropy are negligible in the uppermost mantle but noticeable at the bottom of the mantle.</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> <span class="hlt">structure</span> of South Island, New Zealand, from amphibious Rayleigh wave tomography</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://adsabs.harvard.edu/abs/2006Tectp.420..267A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006Tectp.420..267A"><span id="translatedtitle">Upper-mantle <span class="hlt">velocity</span> <span class="hlt">structure</span> of the lower Great Lakes region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aktas, Kadircan; Eaton, David W.</p> <p>2006-06-01</p> <p>The lithospheric root beneath North America contains a prominent indentation beneath the lower Great Lakes region that is approximately aligned with the track of the New England seamounts. By combining data from the recently installed POLARIS network in southern Ontario, Canada with data acquired in 1996 during the Abitibi-Grenville teleseismic experiment, we have performed a tomographic inversion using 4543 P-wave traveltimes from 213 events (5.0 ≤ mb ≤ 6.6), and 1860 S-wave traveltimes from 98 events (5.0 ≤ mb ≤ 6.6), to obtain high-resolution images of the upper mantle beneath the lower Great Lakes. Two salient features of the 3-D models are: 1) a patchy, NNW-trending low-<span class="hlt">velocity</span> region, and 2) a linear, NE-striking high-<span class="hlt">velocity</span> anomaly. S-wave images show that the low-<span class="hlt">velocity</span> anomaly changes from an arcuate feature at 400-km depth, to a NW-striking linear feature at 100-km depth beneath the Neoproterozoic Ottawa-Bonnechere graben. The linear high-<span class="hlt">velocity</span> anomaly extends to at least 300-km depth and strikes parallel to surface geological belts and the Laurentian continental margin. We interpret the high-<span class="hlt">velocity</span> anomaly as a possible relict slab associated with ca. 1.35-1.3 Ga subduction beneath the Composite Arc Belt, whereas the low-<span class="hlt">velocity</span> anomaly is interpreted as a zone of alteration and metasomatism associated with the ascent of magmas that produced the Late Cretaceous Monteregian plutons. Our data support an interpretation of these plutons as melts generated by the passage of North America across a mantle plume, rather than a far-field response to opening of the North Atlantic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6314574','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6314574"><span id="translatedtitle">Three-dimensional p-<span class="hlt">velocity</span> <span class="hlt">structure</span> of the summit caldera of Newberry Volcano, Oregon</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Stauber, D.A.; Iyer, N.M.; Mooney, W.D.; Dawson, P.B.</p> <p>1985-01-01</p> <p>A three-dimensional high-resolution seismic study of the summit caldera of Newberry Volcano, Oregon, was conducted by the US Geological Survey using an adaptation of the method applied by Mercessian et al. (1984). Preliminary interpretation of the traveltime residuals reveals a ring of high P-<span class="hlt">velocity</span> material coinciding with the inner ring fault system of the caldera in the upper 2 km. A zone of lower P <span class="hlt">velocities</span> extends deeper than 2 km in the center of the caldera. 9 refs., 5 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22218003','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22218003"><span id="translatedtitle">A <span class="hlt">1</span>-<span class="hlt">D</span> dusty plasma photonic crystal</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mitu, M. L.; Ticoş, C. M.; Toader, D.; Banu, N.; Scurtu, A.</p> <p>2013-09-21</p> <p>It is demonstrated numerically that a <span class="hlt">1</span>-<span class="hlt">D</span> plasma crystal made of micron size cylindrical dust particles can, in principle, work as a photonic crystal for terahertz waves. The dust rods are parallel to each other and arranged in a linear string forming a periodic <span class="hlt">structure</span> of dielectric-plasma regions. The dispersion equation is found by solving the waves equation with the boundary conditions at the dust-plasma interface and taking into account the dielectric permittivity of the dust material and plasma. The wavelength of the electromagnetic waves is in the range of a few hundred microns, close to the interparticle separation distance. The band gaps of the <span class="hlt">1</span>-<span class="hlt">D</span> plasma crystal are numerically found for different types of dust materials, separation distances between the dust rods and rod diameters. The distance between levitated dust rods forming a string in rf plasma is shown experimentally to vary over a relatively wide range, from 650 μm to about 1350 μm, depending on the rf power fed into the discharge.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70015514','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70015514"><span id="translatedtitle">Active faulting and deformation of the Coalinga anticline as interpreted from three-dimensional <span class="hlt">velocity</span> <span class="hlt">structure</span> and seismicity</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Eberhart-Phillips, D.</p> <p>1989-01-01</p> <p>This work gives a clear picture of the geometry of aftershock seismicity in a large thrust earthquake. Interpretation of hypocenters and fault plane solutions, from the 1983 Coalinga, Coast Range California, earthquake sequence, in combination with the three-dimensional <span class="hlt">velocity</span> <span class="hlt">structure</span> shows that the active faulting beneath the fold primarily consists of a set of southwest dipping thrusts uplifting blocks of higher-<span class="hlt">velocity</span> material. With the three-dimensional <span class="hlt">velocity</span> model each individual hypocenter moved slightly (0-2km) in accord with the details of the surrounding <span class="hlt">velocity</span> <span class="hlt">structure</span>, so that secondary features in the seismicity pattern are more detailed than with a local one-dimensional model and station corrections. The overall character of the fault plane solutions was not altered by the three-dimensional model, but the more accurate ray paths did result in distinct changes. In particular, the mainshock has a fault plane dipping 30?? southwest instead of the 23?? obtained with the one-dimensional model. -from Author</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Nanos...8.9828Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Nanos...8.9828Z"><span id="translatedtitle">Cyano-bridged coordination polymer hydrogel-derived Sn-Fe binary oxide nanohybrids with <span class="hlt">structural</span> diversity: from 3D, 2D, to 2D/<span class="hlt">1</span><span class="hlt">D</span> and enhanced lithium-storage performance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Weiyu; Zhu, Xiaoshu; Chen, Xuguang; Zhou, Yiming; Tang, Yawen; Ding, Liangxin; Wu, Ping</p> <p>2016-05-01</p> <p>Metal oxide nanohybrids with uniform dimensions and controlled architectures possess unique compositional and <span class="hlt">structural</span> superiorities, and thus harbor promising potential for a series of applications in energy, catalysis, and sensing systems. Herein, we propose a facile, general, and scalable cyano-bridged coordination polymer hydrogel-derived thermal-oxidation route for the construction of main-group metal and transition-metal heterometallic oxide nanohybrids with controlled constituents and architectures. The formation of Sn-Fe binary oxide nanohybrids has been demonstrated as an example by using cyano-bridged Sn(iv)-Fe(ii) bimetallic coordination polymer hydrogels (i.e., SnCl4-K4Fe(CN)6 cyanogels, Sn-Fe cyanogels) as precursors. The physicochemical properties of Sn-Fe cyanogels with different Sn/Fe ratios have been systematically examined, and it is found that perfect Sn-Fe cyanogels without unbridged Sn(iv) or Fe(ii) can be formed with Sn/Fe ratios from 2 : 1 to 1 : 2. More importantly, the simple adjustment of Sn/Fe ratios in the Sn-Fe cyanogel precursors can realize flexible dimensional control of the Sn-Fe binary oxide nanohybrids, and 2D/<span class="hlt">1</span><span class="hlt">D</span> SnO2-Fe2O3 hierarchitectures, 2D SnO2-Fe2O3 nanosheets, and 3D SnO2-Fe2O3 networks have been synthesized using the Sn-Fe 1 : 2, Sn-Fe 1 : 1, and Sn-Fe 2 : 1 cyanogels as precursors, respectively. To demonstrate their compositional/<span class="hlt">structural</span> superiorities and potential applications, the lithium-storage utilization of the Sn-Fe binary oxide nanohybrids has been selected as an objective application, and the nanohybrids exhibit Sn/Fe ratio-dependent lithium-storage performance. As a representative example, the 2D/<span class="hlt">1</span><span class="hlt">D</span> SnO2-Fe2O3 hierarchitectures manifest markedly enhanced Li-storage performance in terms of reversible capacities and cycling stability in comparison with their constituent units, i.e., bare SnO2 nanosheets and Fe2O3 nanorods. The proposed cyanogel-derived thermal-oxidation strategy could open up new</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> <span class="hlt">Structure</span> of Idaho/ Oregon from a Joint Inversion of Group and Phase <span class="hlt">Velocities</span> of Love and Rayleigh Waves from Ambient Seismic Noise: Results from the IDOR Project