Science.gov

Sample records for steep spectrum sources

  1. IONIZED OUTFLOWS FROM COMPACT STEEP SPECTRUM SOURCES

    SciTech Connect

    Shih, Hsin-Yi; Stockton, Alan; Kewley, Lisa E-mail: stockton@ifa.hawaii.edu

    2013-08-01

    Massive outflows are known to exist, in the form of extended emission-line regions (EELRs), around about one-third of powerful FR II radio sources. We investigate the origin of these EELRs by studying the emission-line regions around compact-steep-spectrum (CSS) radio galaxies that are younger (10{sup 3}-10{sup 5} yr old) versions of the FR II radio galaxies. We have searched for and analyzed the emission-line regions around 11 CSS sources by taking integral field spectra using Gemini Multi-Object Spectrograph on Gemini North. We fit the [O III] {lambda}5007 line and present the velocity maps for each detected emission-line region. We find, in most cases, that the emission-line regions have multi-component velocity structures with different velocity dispersions and/or flux distributions for each component. The velocity gradients of the emission-line gas are mostly well aligned with the radio axis, suggesting a direct causal link between the outflowing gas and the radio jets. The complex velocity structure may be a result of different driving mechanisms related to the onset of the radio jets. We also present the results from the line-ratio diagnostics we used to analyze the ionization mechanism of the extended gas, which supports the scenario where the emission-line regions are ionized by a combination of active galactic nucleus radiation and shock excitation.

  2. The discovery of diffuse steep spectrum sources in Abell 2256

    NASA Astrophysics Data System (ADS)

    van Weeren, R. J.; Intema, H. T.; Oonk, J. B. R.; Röttgering, H. J. A.; Clarke, T. E.

    2009-12-01

    Context: Hierarchical galaxy formation models indicate that during their lifetime galaxy clusters undergo several mergers. An example of such a merging cluster is Abell 2256. Here we report on the discovery of three diffuse radio sources in the periphery of Abell 2256, using the Giant Metrewave Radio Telescope (GMRT). Aims: The aim of the observations was to search for diffuse ultra-steep spectrum radio sources within the galaxy cluster Abell 2256. Methods: We have carried out GMRT 325 MHz radio continuum observations of Abell 2256. V, R and I band images of the cluster were taken with the 4.2 m William Herschel Telescope (WHT). Results: We have discovered three diffuse elongated radio sources located about 1 Mpc from the cluster center. Two are located to the west of the cluster center, and one to the southeast. The sources have a measured physical extent of 170, 140 and 240 kpc, respectively. The two western sources are also visible in deep low-resolution 115-165 MHz Westerbork Synthesis Radio Telescope (WSRT) images, although they are blended into a single source. For the combined emission of the blended source we find an extreme spectral index (α) of -2.05 ± 0.14 between 140 and 351 MHz. The extremely steep spectral index suggests these two sources are most likely the result of adiabatic compression of fossil radio plasma due to merger shocks. For the source to the southeast, we find that {α < -1.45} between 1369 and 325 MHz. We did not find any clear optical counterparts to the radio sources in the WHT images. Conclusions: The discovery of the steep spectrum sources implies the existence of a population of faint diffuse radio sources in (merging) clusters with such steep spectra that they have gone unnoticed in higher frequency (⪆1 GHz) observations. Simply considering the timescales related to the AGN activity, synchrotron losses, and the presence of shocks, we find that most massive clusters should possess similar sources. An exciting possibility

  3. Radio properties of Compact Steep Spectrum and GHz-Peaked Spectrum radio sources

    NASA Astrophysics Data System (ADS)

    Orienti, M.

    2016-02-01

    Compact steep spectrum (CSS) and GHz-peaked spectrum (GPS) radio sources represent a large fraction of the extragalactic objects in flux density-limited samples. They are compact, powerful radio sources whose synchrotron peak frequency ranges between a few hundred MHz to several GHz. CSS and GPS radio sources are currently interpreted as objects in which the radio emission is in an early evolutionary stage. In this contribution I review the radio properties and the physical characteristics of this class of radio sources, and the interplay between their radio emission and the ambient medium of the host galaxy.

  4. A sample of southern Compact Steep Spectrum radio sources: The VLBI observations

    NASA Astrophysics Data System (ADS)

    Tzioumis, A.; King, E.; Morganti, R.; Dallacasa, D.; Tadhunter, C.; Fanti, C.; Reynolds, J.; Jauncey, D.; Preston, R.; McCulloch, P.; Tingay, S.; Edwards, P.; Costa, M.; Jones, D.; Lovell, J.; Clay, R.; Meier, D.; Murphy, D.; Gough, R.; Ferris, R.; White, G.; Jones, P.

    2002-09-01

    A small sample of 7 southern Compact Steep Spectrum (CSS) radio sources has been selected as part of the study of a larger flux-limited complete sample of radio sources. High resolution images, using the VLBI network in the southern hemisphere and the high resolution MERLIN array, are presented for all sources in the CSS sample. The overall morphology of each source consists of well-defined double lobes but with substantial diffuse and extended components present. In the majority of cases only a fraction of the total flux density is detected on the VLBI baselines, indicating the presence of larger extended radio structures. However, all sources are unresolved at arcsecond scales and are of sub-galactic size, with linear size in the range 0.1-2 kpc. The radio properties of the sources agree well with CSS sources in other samples. Based on observations with the Southern Hemisphere VLBI Network (SHEVE) and the MERLIN.

  5. VizieR Online Data Catalog: Ultra-steep spectrum radio sources (Gopal-Krishna+, 2005)

    NASA Astrophysics Data System (ADS)

    Gopal-Krishna; Ledoux, C.; Melnick, J.; Giraud, E.; Kulkarni, V.; Altieri, B.

    2006-09-01

    We present the results of radio (VLA) and optical (ESO/La Silla) imaging of a sample of 52 radio sources having an ultra-steep radio spectrum with {alpha} mostly steeper than -1.1 at decimetre wavelengths (median {alpha}=-1.22). Radio-optical overlays are presented to an astrometric accuracy of ~1". For 41 of the sources, radio spectral indices are newly determined using unpublished observations made with the 100-m Effelsberg radio telescope. For 14 of the sources identified with relatively brighter optical counterparts, spectroscopic observations were also carried out at La Silla and their redshifts are found to lie in the range 0.4 to 2.6. (2 data files).

  6. A plethora of diffuse steep spectrum radio sources in Abell 2034 revealed by LOFAR

    NASA Astrophysics Data System (ADS)

    Shimwell, T. W.; Luckin, J.; Brüggen, M.; Brunetti, G.; Intema, H. T.; Owers, M. S.; Röttgering, H. J. A.; Stroe, A.; van Weeren, R. J.; Williams, W. L.; Cassano, R.; de Gasperin, F.; Heald, G. H.; Hoang, D. N.; Hardcastle, M. J.; Sridhar, S. S.; Sabater, J.; Best, P. N.; Bonafede, A.; Chyży, K. T.; Enßlin, T. A.; Ferrari, C.; Haverkorn, M.; Hoeft, M.; Horellou, C.; McKean, J. P.; Morabito, L. K.; Orrù, E.; Pizzo, R.; Retana-Montenegro, E.; White, G. J.

    2016-06-01

    With Low-Frequency Array (LOFAR) observations, we have discovered a diverse assembly of steep spectrum emission that is apparently associated with the intracluster medium (ICM) of the merging galaxy cluster Abell 2034. Such a rich variety of complex emission associated with the ICM has been observed in few other clusters. This not only indicates that Abell 2034 is a more interesting and complex system than previously thought but it also demonstrates the importance of sensitive and high-resolution, low-frequency observations. These observations can reveal emission from relativistic particles which have been accelerated to sufficient energy to produce observable emission or have had their high energy maintained by mechanisms in the ICM. The most prominent feature in our maps is a bright bulb of emission connected to two steep spectrum filamentary structures, the longest of which extends perpendicular to the merger axis for 0.5 Mpc across the south of the cluster. The origin of these objects is unclear, with no shock detected in the X-ray images and no obvious connection with cluster galaxies or AGNs. We also find that the X-ray bright region of the cluster coincides with a giant radio halo with an irregular morphology and a very steep spectrum. In addition, the cluster hosts up to three possible radio relics, which are misaligned with the cluster X-ray emission. Finally, we have identified multiple regions of emission with a very steep spectral index that seem to be associated with either tailed radio galaxies or a shock.

  7. Clustering and Light Profiles of Galaxies in the Environment of 20 Ultra-Steep-Spectrum Radio Sources

    NASA Astrophysics Data System (ADS)

    Bornancini, Carlos G.; Martínez, Héctor J.; Lambas, Diego G.; de Vries, Wim; van Breugel, Wil; De Breuck, Carlos; Minniti, Dante

    2004-02-01

    We have analyzed galaxy properties in the neighborhood of 20 ultra-steep-spectrum (USS) radio sources taken from the Westerbork in the Southern Hemisphere (WISH) catalog of De Breuck and coworkers. Galaxies in these USS fields were identified in deep observations that were carried out in the K' band using the OSIRIS imager at the CTIO 4 m telescope. We find a statistically significant signal of clustering around our sample of USS sources. The angular extension of the detected USS source-galaxy clustering is θc~20'', corresponding to a spatial scale of ~120 h-1 kpc, assuming the sources are at z~1 in an Ωm=0.3, ΩΛ=0.7 model universe. These results are in agreement with those obtained by Best for radio galaxy-galaxy correlation, and Best and coworkers for radio-loud AGN-galaxy correlation. We have also analyzed the light distribution of the galaxies by fitting Sérsic's law profiles. Our results show no significant dependence of the galaxy shape parameters on the projected distance to the USS source. Based on observations obtained at Cerro Tololo Inter-American Observatory (CTIO), a division of the National Optical Astronomy Observatory (NOAO), which is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.

  8. ULTRA STEEP SPECTRUM RADIO SOURCES IN THE LOCKMAN HOLE: SERVS IDENTIFICATIONS AND REDSHIFT DISTRIBUTION AT THE FAINTEST RADIO FLUXES

    SciTech Connect

    Afonso, J.; Bizzocchi, L.; Grossi, M.; Messias, H.; Fernandes, C. A. C.; Ibar, E.; Ivison, R. J.; Simpson, C.; Chapman, S.; Gonzalez-Solares, E.; Jarvis, M. J.; Rottgering, H.; Norris, R. P.; Dunlop, J.; Best, P.; Pforr, J.; Vaccari, M.; Seymour, N.; Farrah, D.; Huang, J.-S.; and others

    2011-12-20

    Ultra steep spectrum (USS) radio sources have been successfully used to select powerful radio sources at high redshifts (z {approx}> 2). Typically restricted to large-sky surveys and relatively bright radio flux densities, it has gradually become possible to extend the USS search to sub-mJy levels, thanks to the recent appearance of sensitive low-frequency radio facilities. Here a first detailed analysis of the nature of the faintest USS sources is presented. By using Giant Metrewave Radio Telescope and Very Large Array radio observations of the Lockman Hole at 610 MHz and 1.4 GHz, a sample of 58 USS sources, with 610 MHz integrated fluxes above 100 {mu}Jy, is assembled. Deep infrared data at 3.6 and 4.5 {mu}m from the Spitzer Extragalactic Representative Volume Survey (SERVS) are used to reliably identify counterparts for 48 (83%) of these sources, showing an average total magnitude of [3.6]{sub AB} = 19.8 mag. Spectroscopic redshifts for 14 USS sources, together with photometric redshift estimates, improved by the use of the deep SERVS data, for a further 19 objects, show redshifts ranging from z = 0.1 to z = 2.8, peaking at z {approx} 0.6 and tailing off at high redshifts. The remaining 25 USS sources, with no redshift estimate, include the faintest [3.6] magnitudes, with 10 sources undetected at 3.6 and 4.5 {mu}m (typically [3.6] {approx}> 22-23 mag from local measurements), which suggests the likely existence of higher redshifts among the sub-mJy USS population. The comparison with the Square Kilometre Array Design Studies Simulated Skies models indicates that Fanaroff-Riley type I radio sources and radio-quiet active galactic nuclei may constitute the bulk of the faintest USS population, and raises the possibility that the high efficiency of the USS technique for the selection of high-redshift sources remains even at the sub-mJy level.

  9. LOFAR Low-band Antenna Observations of the 3C 295 and Boötes Fields: Source Counts and Ultra-steep Spectrum Sources

    NASA Astrophysics Data System (ADS)

    van Weeren, R. J.; Williams, W. L.; Tasse, C.; Röttgering, H. J. A.; Rafferty, D. A.; van der Tol, S.; Heald, G.; White, G. J.; Shulevski, A.; Best, P.; Intema, H. T.; Bhatnagar, S.; Reich, W.; Steinmetz, M.; van Velzen, S.; Enßlin, T. A.; Prandoni, I.; de Gasperin, F.; Jamrozy, M.; Brunetti, G.; Jarvis, M. J.; McKean, J. P.; Wise, M. W.; Ferrari, C.; Harwood, J.; Oonk, J. B. R.; Hoeft, M.; Kunert-Bajraszewska, M.; Horellou, C.; Wucknitz, O.; Bonafede, A.; Mohan, N. R.; Scaife, A. M. M.; Klöckner, H.-R.; van Bemmel, I. M.; Merloni, A.; Chyzy, K. T.; Engels, D.; Falcke, H.; Pandey-Pommier, M.; Alexov, A.; Anderson, J.; Avruch, I. M.; Beck, R.; Bell, M. E.; Bentum, M. J.; Bernardi, G.; Breitling, F.; Broderick, J.; Brouw, W. N.; Brüggen, M.; Butcher, H. R.; Ciardi, B.; de Geus, E.; de Vos, M.; Deller, A.; Duscha, S.; Eislöffel, J.; Fallows, R. A.; Frieswijk, W.; Garrett, M. A.; Grießmeier, J.; Gunst, A. W.; Hamaker, J. P.; Hassall, T. E.; Hörandel, J.; van der Horst, A.; Iacobelli, M.; Jackson, N. J.; Juette, E.; Kondratiev, V. I.; Kuniyoshi, M.; Maat, P.; Mann, G.; McKay-Bukowski, D.; Mevius, M.; Morganti, R.; Munk, H.; Offringa, A. R.; Orrù, E.; Paas, H.; Pandey, V. N.; Pietka, G.; Pizzo, R.; Polatidis, A. G.; Renting, A.; Rowlinson, A.; Schwarz, D.; Serylak, M.; Sluman, J.; Smirnov, O.; Stappers, B. W.; Stewart, A.; Swinbank, J.; Tagger, M.; Tang, Y.; Thoudam, S.; Toribio, C.; Vermeulen, R.; Vocks, C.; Zarka, P.

    2014-10-01

    We present Low Frequency Array (LOFAR) Low Band observations of the Boötes and 3C 295 fields. Our images made at 34, 46, and 62 MHz reach noise levels of 12, 8, and 5 mJy beam-1, making them the deepest images ever obtained in this frequency range. In total, we detect between 300 and 400 sources in each of these images, covering an area of 17-52 deg2. From the observations, we derive Euclidean-normalized differential source counts. The 62 MHz source counts agree with previous GMRT 153 MHz and Very Large Array 74 MHz differential source counts, scaling with a spectral index of -0.7. We find that a spectral index scaling of -0.5 is required to match up the LOFAR 34 MHz source counts. This result is also in agreement with source counts from the 38 MHz 8C survey, indicating that the average spectral index of radio sources flattens toward lower frequencies. We also find evidence for spectral flattening using the individual flux measurements of sources between 34 and 1400 MHz and by calculating the spectral index averaged over the source population. To select ultra-steep spectrum (α < -1.1) radio sources that could be associated with massive high-redshift radio galaxies, we compute spectral indices between 62 MHz, 153 MHz, and 1.4 GHz for sources in the Boötes field. We cross-correlate these radio sources with optical and infrared catalogs and fit the spectral energy distribution to obtain photometric redshifts. We find that most of these ultra-steep spectrum sources are located in the 0.7 <~ z <~ 2.5 range.

  10. LOFAR low-band antenna observations of the 3C 295 and Boötes fields: source counts and ultra-steep spectrum sources

    SciTech Connect

    Van Weeren, R. J.; Williams, W. L.; Röttgering, H. J. A.; Rafferty, D. A.; Van der Tol, S.; Tasse, C.; Heald, G.; White, G. J.; Shulevski, A.; Best, P.; Intema, H. T.; Bhatnagar, S.; Reich, W.; Steinmetz, M.; Van Velzen, S.; Enßlin, T. A.; Prandoni, I.; Brunetti, G.; De Gasperin, F.; Jamrozy, M.; and others

    2014-10-01

    We present Low Frequency Array (LOFAR) Low Band observations of the Boötes and 3C 295 fields. Our images made at 34, 46, and 62 MHz reach noise levels of 12, 8, and 5 mJy beam{sup –1}, making them the deepest images ever obtained in this frequency range. In total, we detect between 300 and 400 sources in each of these images, covering an area of 17-52 deg{sup 2}. From the observations, we derive Euclidean-normalized differential source counts. The 62 MHz source counts agree with previous GMRT 153 MHz and Very Large Array 74 MHz differential source counts, scaling with a spectral index of –0.7. We find that a spectral index scaling of –0.5 is required to match up the LOFAR 34 MHz source counts. This result is also in agreement with source counts from the 38 MHz 8C survey, indicating that the average spectral index of radio sources flattens toward lower frequencies. We also find evidence for spectral flattening using the individual flux measurements of sources between 34 and 1400 MHz and by calculating the spectral index averaged over the source population. To select ultra-steep spectrum (α < –1.1) radio sources that could be associated with massive high-redshift radio galaxies, we compute spectral indices between 62 MHz, 153 MHz, and 1.4 GHz for sources in the Boötes field. We cross-correlate these radio sources with optical and infrared catalogs and fit the spectral energy distribution to obtain photometric redshifts. We find that most of these ultra-steep spectrum sources are located in the 0.7 ≲ z ≲ 2.5 range.

  11. Compact steep-spectrum sources as the parent population of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies

    NASA Astrophysics Data System (ADS)

    Berton, M.; Caccianiga, A.; Foschini, L.; Peterson, B. M.; Mathur, S.; Terreran, G.; Ciroi, S.; Congiu, E.; Cracco, V.; Frezzato, M.; La Mura, G.; Rafanelli, P.

    2016-06-01

    Narrow-line Seyfert 1 galaxies (NLS1s) are an interesting subclass of active galactic nuclei (AGN), which tipically does not exhibit any strong radio emission. Seven percent of them, though, are radio-loud and often show a flat radio-spectrum (F-NLS1s). This, along to the detection of γ-ray emission coming from them, is usually interpreted as a sign of a relativistic beamed jet oriented along the line of sight. An important aspect of these AGN that must be understood is the nature of their parent population, in other words how do they appear when observed under different angles. In the recent literature it has been proposed that a specific class of radio-galaxies, compact-steep sources (CSS) classified as high excitation radio galaxies (HERG), can represent the parent population of F-NLS1s. To test this hypothesis in a quantitative way,in this paper we analyzed the only two statistically complete samples of CSS/HERGs and F-NLS1s available in the literature. We derived the black hole mass and Eddington ratio distributions, and we built for the first time the radio luminosity function of F-NLS1s. Finally, we applied a relativistic beaming model to the luminosity function of CSS/HERGs, and compared the result with the observed function of F-NLS1s. We found that compact steep-spectrum sources are valid parent candidates and that F-NLS1s, when observed with a different inclination, might actually appear as CSS/HERGs.

  12. BROADBAND JET EMISSION IN YOUNG AND POWERFUL RADIO SOURCES: THE CASE OF THE COMPACT STEEP SPECTRUM QUASAR 3C 186

    SciTech Connect

    Migliori, Giulia; Siemiginowska, Aneta; Celotti, Annalisa

    2012-04-20

    We present the X-ray analysis of a deep ({approx}200 ks) Chandra observation of the compact steep spectrum radio-loud quasar 3C 186 (z = 1.06) and investigate the contribution of the unresolved radio jet to the total X-ray emission. The spectral analysis is not conclusive on the origin of the bulk of the X-ray emission. In order to examine the jet contribution to the X-ray flux, we model the quasar spectral energy distribution, adopting several scenarios for the jet emission. For the values of the main physical parameters favored by the observables, a dominant role of the jet emission in the X-ray band is ruled out when a single-zone (leptonic) scenario is adopted, even including the contribution of the external photon fields as seed photons for inverse Compton emission. We then consider a structured jet, with the blazar component that-although not directly visible in the X-ray band-provides an intense field of seed synchrotron photons Compton-scattered by electrons in a mildly relativistic knot. In this case, the whole X-ray emission can be accounted for if we assume a blazar luminosity within the range observed from flat spectrum radio quasars. The X-ray radiative efficiency of such a (structured) jet is intimately related to the presence of a complex velocity structure. The jet emission can provide a significant contribution in X-rays if it decelerates within the host galaxy on kiloparsec scales. We discuss the implications of this model in terms of jet dynamics and interaction with the ambient medium.

  13. CHANDRA VIEW OF THE ULTRA-STEEP SPECTRUM RADIO SOURCE IN A2443: MERGER SHOCK-INDUCED COMPRESSION OF FOSSIL RADIO PLASMA?

    SciTech Connect

    Clarke, T. E.; Randall, S. W.; Sarazin, C. L.; Blanton, E. L.; Giacintucci, S.

    2013-08-01

    We present a new Chandra X-ray observation of the intracluster medium in the galaxy cluster A2443, hosting an ultra-steep spectrum radio source. The data reveal that the intracluster medium is highly disturbed. The thermal gas in the core is elongated along a northwest to southeast axis and there is a cool tail to the north. We also detect two X-ray surface brightness edges near the cluster core. The edges appear to be consistent with an inner cold front to the northeast of the core and an outer shock front to the southeast of the core. The southeastern edge is coincident with the location of the radio relic as expected for shock (re)acceleration or adiabatic compression of fossil relativistic electrons.

  14. AN X-RAY COOLING-CORE CLUSTER SURROUNDING A LOW-POWER COMPACT STEEP SPECTRUM RADIO SOURCE 1321+045

    SciTech Connect

    Kunert-Bajraszewska, M.; Siemiginowska, A.; Labiano, A.

    2013-07-20

    We discovered an X-ray cluster in a Chandra observation of the compact steep spectrum (CSS) radio source 1321+045 (z = 0.263). CSS sources are thought to be young radio objects at the beginning of their evolution and can potentially test the cluster heating process. 1321+045 is a relatively low-luminosity source and its morphology consists of two radio lobes on the opposite sides of a radio core with no evidence for jets or hotspots. The optical emission line ratios are consistent with an interstellar medium dominated by active galactic nucleus photoionization with a small contribution from star formation, and no contributions from shocks. Based on these ratios, we classify 1321+045 as a low excitation galaxy (LEG) and suggest that its radioactivity is in a coasting phase. The X-ray emission associated with the radio source is detected with 36.1 {+-} 8.3 counts, but the origin of this emission is highly uncertain. The current X-ray image of the cluster does not show any signatures of a radio source impact on the cluster medium. Chandra detects the cluster emission at >3{sigma} level out to {approx}60'' (240 kpc). We obtain the best-fit beta model parameters of the surface brightness profile of {beta} = 0.58 {+-} 0.2 and a core radius of 9.4{sup +1.1}{sub -0.9} arcsec. The average temperature of the cluster is equal to kT = 4.4{sup +0.5}{sub -0.3} keV, with a temperature and cooling profile indicative of a cooling core. We measure the cluster luminosity L{sub (0.5-2{sub keV)}} = 3 Multiplication-Sign 10{sup 44} erg s{sup -1} and mass 1.5 Multiplication-Sign 10{sup 14} M{sub Sun}.

  15. Jet evolution in Steep Spectrum Radio Quasars: a multiwavelength study

    NASA Astrophysics Data System (ADS)

    Torresi, Eleonora; Grandi, Paola

    2013-12-01

    Thanks to the Fermi γ-ray satellite, it is now confirmed that Misaligned Active Galactic Nuclei (MAGN), i.e. radio galaxies and steep spectrum radio quasars, are a new class of GeV emitters. In this work we present the first γ-ray and multiwavelength study of the two steep spectrum radio quasars, i.e. 3C 207 and 3C 380, belonging to the MAGN sample. From the γ -ray variability study we estimate the physical size of the zone where high-energy photons are dissipated: for both sources this region should be very compact, not larger than 0.05 pc. As a successive step, we build multiwavelength light curves of 3C 207 and 3C 380 to search for possible simultaneous outbursts in different wavebands with the aim of localizing the compact emitting region. This is an important issue with strong impact on theoretical models: indeed, knowing where highenergy photons are dissipated (at sub-pc or pc-scale) provides information on the nature of the seed photons involved in the production of the GeV radiation.

  16. DEEP 1.4 GHz FOLLOW-UP OF THE STEEP SPECTRUM RADIO HALO IN A521

    SciTech Connect

    Dallacasa, D.; Macario, G.; Setti, G.; Brunetti, G.; Cassano, R.; Venturi, T.; Giacintucci, S.; Kassim, N. E.; Lane, W.

    2009-07-10

    In a recent paper, we reported on the discovery of a radio halo with very steep spectrum in the merging galaxy cluster A521 through observations with the Giant Metrewave Radio Telescope. We showed that the steep spectrum of the halo is inconsistent with a secondary origin of the relativistic electrons and supports a turbulent acceleration scenario. At that time, due to the steep spectrum, the available observations at 1.4 GHz (archival NRAO-Very Large Array-VLA-CnB-configuration data) were not adequate to accurately determine the flux density associated with the radio halo. In this paper, we report the detection at 1.4 GHz of the radio halo in A521 using deep VLA observations in the D configuration. We use these new data to confirm the steep spectrum of the object. We consider A521 the prototype of a population of very steep spectrum halos. This population is predicted assuming that turbulence plays an important role in the acceleration of relativistic particles in galaxy clusters, and we expect it will be unveiled by future surveys at low frequencies with the LOFAR and LWA radio telescopes.

  17. Discovery of Ultra-steep Spectrum Giant Radio Galaxy with Recurrent Radio Jet Activity in Abell 449

    NASA Astrophysics Data System (ADS)

    Hunik, Dominika; Jamrozy, Marek

    2016-01-01

    We report a discovery of a 1.3 Mpc diffuse radio source with extremely steep spectrum fading radio structures in the vicinity of the Abell 449 cluster of galaxies. Its extended diffuse lobes are bright only at low radio frequencies and their synchrotron age is about 160 Myr. The parent galaxy of the extended relic structure, which is the dominant galaxy within the cluster, is starting a new jet activity. There are three weak X-rays sources in the vicinity of the cluster as found in the ROSAT survey, however it is not known if they are connected with this cluster of galaxies. Just a few radio galaxy relics are currently known in the literature, as finding them requires sensitive and high angular resolution low-frequency radio observations. Objects of this kind, which also are starting a new jet activity, are important for understanding the life cycle and evolution of active galactic nuclei. A new 613 MHz map as well as the archival radio data pertaining to this object are presented and analyzed.

  18. Spectroscopic Observations of Steep Spectrum Narrow-Line Seyfert 1 Galaxies

    NASA Technical Reports Server (NTRS)

    Leighly, Karen

    1999-01-01

    ROSAT observations of narrow-line Seyfert 1s found consistently steep spectra and rapid variability, but ASCA observations show more diversity, very different to classical Seyfert 1s. However, in 3 NLS1s, ASCA finds common characteristics of these exciting new class of AGN (active galactic nuclei): a very strong high temperature soft excess, weak hard tail, a possible blue shifted ionized oxygen edge, and rapid large amplitude variability characterized by flares and quiescent periods. It is necessary to observe many more such objects in order to understand the physical processes underlying the different phenomenology in ASCA. ASCA observations of two NLS1s discovered by ROSAT's all sky survey were proposed and an observation of one of these objects, RX J0439-45, was awarded. The results of spectral and variability analysis are included in Leighly 1999ab, and preliminary results are found in Leighly 1998ab.

  19. VizieR Online Data Catalog: Compact steep spectrum new sample (Kunert-Bajraszewska+, 2010)

    NASA Astrophysics Data System (ADS)

    Kunert-Bajraszewska, M.; Gawronski, M. P.; Labiano, A.; Siemiginowska, A.

    2013-08-01

    Using the final release of FIRST, combined with the Green Bank 6-cm (GB6) survey at 4.85GHz, we looked for unresolved, isolated sources, that is, more compact than the FIRST beam (5.4-arcsec), and surrounded by an empty field (we adopted 1-arcmin as the radius of that field). We required that the redshifts of the objects identified with radio sources were known, and we extracted these from the National Aeronautics and Space Administration (NASA)/Infrared Processing and Analysis Center (IPAC) Extragalactic Data base (NED) and the Sloan Digital Sky Survey (SDSS). (3 data files).

  20. Use of corn steep liquor as an economical nitrogen source for biosuccinic acid production by Actinobacillus succinogenes

    NASA Astrophysics Data System (ADS)

    Tan, J. P.; Jahim, J. M.; Wu, T. Y.; Harun, S.; Mumtaz, T.

    2016-06-01

    Expensive raw materials are the driving force that leads to the shifting of the petroleum-based succinic acid production into bio-based succinic acid production by microorganisms. Cost of fermentation medium is among the main factors contributing to the total production cost of bio-succinic acid. After carbon source, nitrogen source is the second largest component of the fermentation medium, the cost of which has been overlooked for the past years. The current study aimed at replacing yeast extract- a costly nitrogen source with corn steep liquor for economical production of bio-succinic acid by Actinobacillus succinogenes 130Z. In this study, a final succinic acid concentration of 20.6 g/L was obtained from the use of corn steep liquor as the nitrogen source, which was comparable with the use of yeast extract as the nitrogen source that had a final succinate concentration of 21.4 g/l. In terms of economical wise, corn steep liquor was priced at 200 /ton, which was one fifth of the cost of yeast extract at 1000 /ton. Therefore, corn steep liquor can be considered as a potential nitrogen source in biochemical industries instead of the costly yeast extract.

  1. WIND DIRECTION EFFECTS ON DISPERSION FROM SOURCES DOWNWIND OF STEEP HILLS

    EPA Science Inventory

    A previous experimental study of the nsture of dispersion from point sources downwind of three-dimensional hills of various crosswind aspect ratio (spanwise breadth/ height) has been extended to the case when the approaching wind is not normal to the spanwise axis of the hill. Su...

  2. Universal energy spectrum from point sources

    NASA Technical Reports Server (NTRS)

    Tomozawa, Yukio

    1992-01-01

    The suggestion is made that the energy spectrum from point sources such as galactic black hole candidates (GBHC) and active galactic nuclei (AGN) is universal on the average, irrespective of the species of the emitted particles, photons, nucleons, or others. The similarity between the observed energy spectra of cosmic rays, gamma-rays, and X-rays is discussed. In other words, the existing data for gamma-rays and X-rays seem to support the prediction. The expected data from the Gamma Ray Observatory are to provide a further test.

  3. STEEP32 computer code

    NASA Technical Reports Server (NTRS)

    Goerke, W. S.

    1972-01-01

    A manual is presented as an aid in using the STEEP32 code. The code is the EXEC 8 version of the STEEP code (STEEP is an acronym for shock two-dimensional Eulerian elastic plastic). The major steps in a STEEP32 run are illustrated in a sample problem. There is a detailed discussion of the internal organization of the code, including a description of each subroutine.

  4. Source-to-sink sediment transfers, environmental engineering and hazard mitigation in the steep Var River catchment, French Riviera, southeastern France

    NASA Astrophysics Data System (ADS)

    Anthony, Edward J.; Julian, Maurice

    1999-12-01

    Steep coastal margins are potentially subject to mass wasting processes involving notable landslide activity and sediment evacuation downstream by steep-gradient streams. Sediment transfer from short source-to-sink segments, coupled with mountain hydrological regimes, regulate patterns of river channel aggradation and coastal sediment supply in such geomorphic settings. On the steep French Riviera margin, sediment transfers from existing landslides or from various minor mass wasting processes to stream channels may result following bursts of heavy, concentrated rainfall. High-magnitude flooding and massive sediment transport downstream are generally related to unpredictable extreme rainfalls. Both mass movements and channel sediment storage pose serious hazards to downvalley settlements and infrastructure. A consideration of channel sediment storage patterns in the Var River catchment, the most important catchment in this area, highlights two important shortcomings relative to environmental engineering and hazard mitigation practices. In the first place, the appreciation of geomorphic processes is rather poor. This is illustrated by the undersized nature of engineering works constructed to mitigate hazards in the upstream bedload-dominated channels, and by the unforeseen effects that ten rock dams, constructed in the early 1970s, have had on downstream and coastal sediment storage and on sediment dispersal patterns and, consequently, valley flooding. Secondly, planners and environmental engineers have lacked foresight in valley and coastal management issues on this steep setting, notably as regards the reclaimed areas of the lower Var channel and delta liable to flooding. Urbanization and transport and environmental engineering works have progressively affected patterns of storage and transport of fine-grained sediments in the lower Var channel and delta. Meanwhile the problems raised by these changes have not been adequately addressed in terms of scientific

  5. Measures of the Glottal Source Spectrum

    ERIC Educational Resources Information Center

    Kreiman, Jody; Gerratt, Bruce R.; Antonanzas-Barroso, Norma

    2007-01-01

    Purpose: Many researchers have studied the acoustics, physiology, and perceptual characteristics of the voice source, but despite significant attention, it remains unclear which aspects of the source should be quantified and how measurements should be made. In this study, the authors examined the relationships among a number of existing measures…

  6. Flat spectrum multicomponent radio sources - Cosmic conspiracy or geometry

    SciTech Connect

    Pacholczyk, A.G.

    1981-01-01

    Compact radio sources which do not exhibit currently large flux density variations, are often characterized by spectra nearly flat over a wide range of wavelengths. Cotton et al. (1980) recently reported the results of the VLBI multifrequency interferometric and total flux density observations of a typical representative of the flat spectrum class of sources, a BL Lacertae object PKS 0735+178. If 0735+178 is indeed representative of flat spectrum sources, then some mechanism causing the component production and energy loss to be balanced must be operative among this type of radio source to maintain a flat spectrum over at least certain periods of time. This effect is referred to as 'cosmic conspiracy'. It is suggested that the flatness of spectra of this class of radio sources may be related to a specific symmetry in the radio structure, namely, to a predominantly linear, one-dimensional evolution of radio radiating material, rather than spherical, three-dimensional evolution.

  7. Corn steep liquor and fermented ammoniated condensed whey as protein sources for lactating cows and yearling heifers grazing winter native range

    SciTech Connect

    Wagner, J.J.; Lusby, K.S.; Horn, G.W.; Dvorak, M.J.

    1982-06-01

    Corn steep liquor (CSL) and fermented ammoniated condensed whey (FACW) were compared to cottonseed meal (CSM) as protein sources for wintering 61 lactating first-calf Hereford heifers and 32 yearling Hereford heifers on native range. Cattle were allotted by weight and individually fed 6 days per week for 12 weeks one of four protein treatments: negative control (NC), positive control (PC), CSL and FACW to provide .7, 1.5, .15 and 1.5 lb crude protein (CP) per day, respectively, to the lacating heifers and .2, .4, .4 and .4lb cP per day, respectively, to the yearling heifers. CMS was supplied in the CSL and FACW treatments at the same level as in the negative control. Lactating heifers fed the NC lost more (P less than .005) weight and body condition (120 lb and 1.6 units) than those fed the PC (45.8 lb and .9 units). Weight and condition losses were similar (P more than .05) for lactating heifers fed PC, CSL and FACW. Yearling heifers fed the NC lost more (P less than .005) weight than those fed the PC (49.4 vs 10.6 lb). Yearling heifers fed CSL and FACW gained more (P less than .005) weight than those fed the PC (17.6 and 9.3 vs - 10.6 lb). Feeding CSL resulted in signficantly lower rumen pH, lower ruminal acetate and higher ruminal butyrate, isovalerate and caproate levels than did feeding either control. Supplementing with FACW produced significantly lower rumen pH, higher rumen ammonia and soluble carbohydrate levels, lower ruminal acetate, and higher ruminal propionate and butyrate concentrations than did either control supplement. Corn steep liquor and FDCW appear to be effective protein sources for cows and heifers grazing winter native range.

  8. The Steep Nekhoroshev's Theorem

    NASA Astrophysics Data System (ADS)

    Guzzo, M.; Chierchia, L.; Benettin, G.

    2016-03-01

    Revising Nekhoroshev's geometry of resonances, we provide a fully constructive and quantitative proof of Nekhoroshev's theorem for steep Hamiltonian systems proving, in particular, that the exponential stability exponent can be taken to be {1/(2nα_1\\cdotsα_{n-2}}) ({α_i}'s being Nekhoroshev's steepness indices and {n ≥ 3} the number of degrees of freedom). On the base of a heuristic argument, we conjecture that the new stability exponent is optimal.

  9. Aeroacoustic source spectrum for fricative consonant speech sounds

    NASA Astrophysics Data System (ADS)

    Leonard, Daniel; Krane, Michael

    2008-11-01

    The aeroacoustic source spectrum is experimentally determined for flow within an open-ended duct. The source region comprises a jet, formed at a constriction within the duct, which then interacts with an obstacle placed further downstream. The physical model dimensions are commensurate with a life-size vocal tract to enable study of the physics of human speech sound production. Two methods are used to estimate the aeroacoustic source spectrum. The first estimate results from inverse-filtering radiated sound measured outside the duct. The transfer function between the source and microphone locations is constructed from two-microphone-method measurements of the acoustic field inside the duct. The second estimate uses measurements of the jet flow near the obstacle as input to aeroacoustic theory. Comparison of the two estimates is presented.

  10. Can the cosmic x ray and gamma ray background be due to reflection of a steep power law spectrum and Compton scattering by relativistic electrons?

    NASA Technical Reports Server (NTRS)

    Zycki, Piotr T.; Zdziarski, Andrzej A.; Svensson, Roland

    1991-01-01

    We reconsider the recent model for the origin in the cosmic X-ray and gamma-ray background by Rogers and Field. The background in the model is due to an unresolved population of AGNs. An individual AGN spectrum contains three components: a power law with the energy index of alpha = 1.1, an enhanced reflection component, and a component from Compton scattering by relativistic electrons with a low energy cutoff at some minimum Lorentz factor, gamma(sub min) much greater than 1. The MeV bump seen in the gamma-ray background is then explained by inverse Compton emission by the electrons. We show that the model does not reproduce the shape of the observed X-ray and gamma-ray background below 10 MeV and that it overproduces the background at larger energies. Furthermore, we find the assumptions made for the Compton component to be physically inconsistent. Relaxing the inconsistent assumptions leads to model spectra even more different from that of the observed cosmic background. Thus, we can reject the hypothesis that the high-energy cosmic background is due to the described model.

  11. Cosmic ray injection spectrum at the galactic sources

    NASA Astrophysics Data System (ADS)

    Lagutin, Anatoly; Tyumentsev, Alexander; Volkov, Nikolay

    The spectra of cosmic rays measured at Earth are different from their source spectra. A key to understanding this difference, being crucial for solving the problem of cosmic-ray origin, is the determination of how cosmic-ray (CR) particles propagate through the turbulent interstellar medium (ISM). If the medium is a quasi-homogeneous the propagation process can be described by a normal diffusion model. However, during a last few decades many evidences, both from theory and observations, of the existence of multiscale structures in the Galaxy have been found. Filaments, shells, clouds are entities widely spread in the ISM. In such a highly non-homogeneous (fractal-like) ISM the normal diffusion model certainly is not kept valid. Generalization of this model leads to what is known as "anomalous diffusion". The main goal of the report is to retrieve the cosmic ray injection spectrum at the galactic sources in the framework of the anomalous diffusion (AD) model. The anomaly in this model results from large free paths ("Levy flights") of particles between galactic inhomogeneities. In order to evaluate the CR spectrum at the sources, we carried out new calculation of the CR spectra at Earth. AD equation in terms of fractional derivatives have been used to describe CR propagation from the nearby (r≤1 kpc) young (t≤ 1 Myr) and multiple old distant (r > 1 kpc) sources. The assessment of the key model parameters have been based on the results of the particles diffusion in the cosmic and laboratory plasma. We show that in the framework of the anomalous diffusion model the locally observed basic features of the cosmic rays (difference between spectral exponents of proton, He and other nuclei, "knee" problem, positron to electron ratio) can be explained if the injection spectrum at the main galactic sources of cosmic rays has spectral exponent p˜ 2.85. The authors acknowledge support from The Russian Foundation for Basic Research grant No. 14-02-31524.

  12. What are the megahertz peaked-spectrum sources?

    NASA Astrophysics Data System (ADS)

    Coppejans, Rocco; Cseh, Dávid; van Velzen, Sjoert; Falcke, Heino; Intema, Huib T.; Paragi, Zsolt; Müller, Cornelia; Williams, Wendy L.; Frey, Sándor; Gurvits, Leonid I.; Körding, Elmar G.

    2016-07-01

    Megahertz peaked-spectrum (MPS) sources have spectra that peak at frequencies below 1 GHz in the observer's frame and are believed to be radio-loud active galactic nuclei (AGN). We recently presented a new method to search for high-redshift AGN by identifying unusually compact MPS sources. In this paper, we present European VLBI Network (EVN) observations of 11 MPS sources which we use to determine their sizes and investigate the nature of the sources with ˜10 mas resolution. Of the 11 sources, we detect 9 with the EVN. Combining the EVN observations with spectral and redshift information, we show that the detected sources are all AGN with linear sizes smaller than 1.1 kpc and are likely young. This shows that low-frequency colour-colour diagrams are an easy and efficient way of selecting small AGN and explains our high detection fraction (82 per cent) in comparison to comparable surveys. Finally we argue that the detected sources are all likely compact symmetric objects and that none of the sources are blazars.

  13. Modeling runoff and erosion risk in a~small steep cultivated watershed using different data sources: from on-site measurements to farmers' perceptions

    NASA Astrophysics Data System (ADS)

    Auvet, B.; Lidon, B.; Kartiwa, B.; Le Bissonnais, Y.; Poussin, J.-C.

    2015-09-01

    This paper presents an approach to model runoff and erosion risk in a context of data scarcity, whereas the majority of available models require large quantities of physical data that are frequently not accessible. To overcome this problem, our approach uses different sources of data, particularly on agricultural practices (tillage and land cover) and farmers' perceptions of runoff and erosion. The model was developed on a small (5 ha) cultivated watershed characterized by extreme conditions (slopes of up to 55 %, extreme rainfall events) on the Merapi volcano in Indonesia. Runoff was modelled using two versions of STREAM. First, a lumped version was used to determine the global parameters of the watershed. Second, a distributed version used three parameters for the production of runoff (slope, land cover and roughness), a precise DEM, and the position of waterways for runoff distribution. This information was derived from field observations and interviews with farmers. Both surface runoff models accurately reproduced runoff at the outlet. However, the distributed model (Nash-Sutcliffe = 0.94) was more accurate than the adjusted lumped model (N-S = 0.85), especially for the smallest and biggest runoff events, and produced accurate spatial distribution of runoff production and concentration. Different types of erosion processes (landslides, linear inter-ridge erosion, linear erosion in main waterways) were modelled as a combination of a hazard map (the spatial distribution of runoff/infiltration volume provided by the distributed model), and a susceptibility map combining slope, land cover and tillage, derived from in situ observations and interviews with farmers. Each erosion risk map gives a spatial representation of the different erosion processes including risk intensities and frequencies that were validated by the farmers and by in situ observations. Maps of erosion risk confirmed the impact of the concentration of runoff, the high susceptibility of long steep

  14. Contrasting Crustal Structure Across a Steep Accretionary Margin in Idaho-Oregon, Illuminated by EarthScope IDOR Controlled-Source Seismic Data

    NASA Astrophysics Data System (ADS)

    Davenport, K. K.; Hole, J. A.; Harder, S. H.; Tikoff, B.

    2014-12-01

    The U.S. Cordillera in Idaho and Oregon is the location of an unusually steep tectonic boundary between relatively juvenile accreted island-arc terranes and Precambrian North American craton. Accretion occurred in the Mesozoic, forming the Salmon River suture zone. Following accretion, transpressional deformation in the Cretaceous shortened and steepened the suture zone along the western Idaho shear zone (WISZ) into a narrow boundary less than 10km wide at the surface. The region was later modified by emplacement of the Idaho batholith, Challis volcanism, the Columbia River Basalts, and Basin and Range-style extension. The EarthScope IDOR project acquired a controlled-source seismic survey across this region with a 430-km refraction and wide-angle reflection line. It utilized 2555 vertical component seismometer stations to record 8 explosive shots, as well as many hours of continuous recording for background seismicity and ambient noise. Travel-time tomography and reflection modeling have been used to produce a preliminary seismic velocity model of the whole crust.There are significant differences between the seismic velocity, mid-crustal boundaries, and crustal thickness seen in the accreted terranes west of the WISZ and those seen in the Idaho batholith and Precambrian craton to the east. The crust west of the WISZ is characterized by faster velocities consistent with mafic oceanic-arc crust, while the crust east of the WISZ has a slower velocity consistent with primarily felsic, continental-affinity crust. Numerous wide-angle seismic reflections are observed on both sides of the WISZ. To the west, there is a lower-crustal reflector that produces a stronger reflection amplitude than the Moho. Beneath the Idaho batholith and Challis volcanics to the east, several smaller-amplitude wide-angle reflections indicate complexity in mid-crustal structure. Thickness of the crust east of the WISZ is 6-12 km greater than the crust to the west, and Moho reflections near the

  15. Flat-spectrum radio sources - Cosmic conspiracy or relativistic neutrons?

    NASA Technical Reports Server (NTRS)

    Giovanoni, Peter M.; Kazanas, Demosthenes

    1990-01-01

    The intensity spectrum of the core of radio-loud AGN varies smoothly from 10 exp 8.5 to 10 to the 16th Hz, and is flat between 10 to the 9th and 10 to the 10th Hz, implying that a single emission mechanism is responsible. It is proposed here that energy is transported from the central source by relativistic neutrons which travel freely over a large volume and decay into relativistic protons. The protons produce secondary electrons which generate the observed radiation. The photon spectra thus produced are largely model-independent and flat.

  16. Dose rate constant and energy spectrum of interstitial brachytherapy sources.

    PubMed

    Chen, Z; Nath, R

    2001-01-01

    In the past two years, several new manufacturers have begun to market low-energy interstitial brachytherapy seeds containing 125I and 103Pd. Parallel to this development, the National Institute of Standards and Technology (NIST) has implemented a modification to the air-kerma strength (S(K)) standard for 125I seeds and has also established an S(K) standard for 103Pd seeds. These events have generated a considerable number of investigations on the determination of the dose rate constants (inverted V) of interstitial brachytherapy seeds. The aim of this work is to study the general properties underlying the determination of dose rate constant and to develop a simple method for a quick and accurate estimation of dose rate constant. As the dose rate constant of clinical seeds is defined at a fixed reference point, we postulated that dose rate constant may be calculated by treating the seed as an effective point source when the seed's source strength is specified in S(K) and its source characteristics are specified by the photon energy spectrum measured in air at the reference point. Using a semi-analytic approach, an analytic expression for dose rate constant was derived for point sources with known photon energy spectra. This approach enabled a systematic study of dose rate constant as a function of energy. Using the measured energy spectra, the calculated dose rate constant for 125I model 6711 and 6702 seeds and for 192Ir seed agreed with the AAPM recommended values within +/-1%. For the 103Pd model 200 seed, the agreement was 5% with a recently measured value (within the +/-7% experimental uncertainty) and was within 1% with the Monte Carlo simulations. The analytic expression for dose rate constant proposed here can be evaluated using a programmable calculator or a simple spreadsheet and it provides an efficient method for checking the measured dose rate constant for any interstitial brachytherapy seed once the energy spectrum of the seed is known. PMID:11213926

  17. Source parameters derived from seismic spectrum in the Jalisco block

    NASA Astrophysics Data System (ADS)

    Gutierrez, Q. J.; Escudero, C. R.; Nunez-Cornu, F. J.

    2012-12-01

    The direct measure of the earthquake fault dimension represent a complicated task nevertheless a better approach is using the seismic waves spectrum. With this method we can estimate the dimensions of the fault, the stress drop and the seismic moment. The study area comprises the complex tectonic configuration of Jalisco block and the subduction of the Rivera plate beneath the North American plate; this causes that occur in Jalisco some of the most harmful earthquakes and other related natural disasters. Accordingly it is important to monitor and perform studies that helps to understand the physics of earthquake rupture mechanism in the area. The main proposue of this study is estimate earthquake seismic source parameters. The data was recorded by the MARS network (Mapping the Riviera Subduction Zone) and the RESAJ network. MARS had 51 stations and settled in the Jalisco block; that is delimited by the mesoamerican trench at the west, the Colima grabben to the south, and the Tepic-Zacoalco to the north; for a period of time, of January 1, 2006 until December 31, 2007 Of this network was taken 104 events, the magnitude range of these was between 3 to 6.5 MB. RESJAL has 10 stations and is within the state of Jalisco, began to record since October 2011 and continues to record. We firs remove the trend, the mean and the instrument response, then manually chosen the S wave, then the multitaper method was used to obtain the spectrum of this wave and so estimate the corner frequency and the spectra level. We substitude the obtained in the equations of the Brune model to calculate the source parameters. Doing this we obtained the following results; the source radius was between .1 to 2 km, the stress drop was between .1 to 2 MPa.

  18. Flat-Spectrum Radio Sources as Likely Counterparts of Unidentified INTEGRAL Sources (Research Note)

    NASA Technical Reports Server (NTRS)

    Molina, M.; Landi, R.; Bassani, L.; Malizia, A.; Stephen, J. B.; Bazzano, A.; Bird, A. J.; Gehrels, N.

    2012-01-01

    Many sources in the fourth INTEGRAL/IBIS catalogue are still unidentified since they lack an optical counterpart. An important tool that can help in identifying and classifying these sources is the cross-correlation with radio catalogues, which are very sensitive and positionally accurate. Moreover, the radio properties of a source, such as the spectrum or morphology, could provide further insight into its nature. In particular, flat-spectrum radio sources at high Galactic latitudes are likely to be AGN, possibly associated to a blazar or to the compact core of a radio galaxy. Here we present a small sample of 6 sources extracted from the fourth INTEGRAL/IBIS catalogue that are still unidentified or unclassified, but which are very likely associated with a bright, flat-spectrum radio object. To confirm the association and to study the source X-ray spectral parameters, we performed X-ray follow-up observations with Swift/XRT of all objects. We report in this note the overall results obtained from this search and discuss the nature of each individual INTEGRAL source. We find that 5 of the 6 radio associations are also detected in X-rays; furthermore, in 3 cases they are the only counterpart found. More specifically, IGR J06073-0024 is a flat-spectrum radio quasar at z = 1.08, IGR J14488-4008 is a newly discovered radio galaxy, while IGR J18129-0649 is an AGN of a still unknown type. The nature of two sources (IGR J07225-3810 and IGR J19386-4653) is less well defined, since in both cases we find another X-ray source in the INTEGRAL error circle; nevertheless, the flat-spectrum radio source, likely to be a radio loud AGN, remains a viable and, in fact, a more convincing association in both cases. Only for the last object (IGR J11544-7618) could we not find any convincing counterpart since the radio association is not an X-ray emitter, while the only X-ray source seen in the field is a G star and therefore unlikely to produce the persistent emission seen by INTEGRAL.

  19. Robot Would Climb Steep Terrain

    NASA Technical Reports Server (NTRS)

    Kennedy, Brett; Ganino, Anthony; Aghazarian, Hrand; Hogg, Robert; McHerny, Michael; Garrett, Michael

    2007-01-01

    This brief describes the steep terrain access robot (STAR) -- a walking robot that has been proposed for exploring steep terrain on remote planets. The STAR would be able to climb up or down on slopes as steep as vertical, and even beyond vertical to overhangs. Its system of walking mechanisms and controls would be to react forces and maintain stability. To enable the STAR to anchor itself in the terrain on steep slopes to maintain stability and react forces, it would be necessary to equip the tips of the walking legs with new ultrasonic/ sonic drill corers (USDCs) and to develop sensors and control algorithms to enable robust utilization of the USDCs.

  20. MASKING VERSUS REMOVING POINT SOURCES IN CMB DATA: THE SOURCE-CORRECTED WMAP POWER SPECTRUM FROM NEW EXTENDED CATALOG

    SciTech Connect

    Scodeller, Sandro; Hansen, Frode K. E-mail: frodekh@astro.uio.no

    2012-12-20

    In Scodeller et al., a new and extended point source catalog obtained from the Wilkinson Microwave Anisotropy Probe (WMAP) seven-year data was presented. It includes most of the sources included in the standard WMAP seven-year point source catalogs as well as a large number of new detections. Here, we study the effects on the estimated CMB power spectrum when taking the newly detected point sources into consideration. We create point source masks for all the 2102 sources that we detected as well as a smaller one for the 665 sources detected in the Q, V, and W bands. We also create WMAP7 maps with point sources subtracted in order to compare with the spectrum obtained with source masks. The extended point source masks and point source cleaned WMAP7 maps are made publicly available. Using the proper residual correction, we find that the CMB power spectrum obtained from the point source cleaned map without any source mask is fully consistent with the spectrum obtained from the masked map. We further find that the spectrum obtained masking all 2102 sources is consistent with the results obtained using the standard WMAP seven-year point source mask (KQ85y7). We also verify that the removal of point sources does not introduce any skewness.

  1. Gamma ray cosmology: The extra galactic gamma spectrum and methods to detect the underlying source

    NASA Technical Reports Server (NTRS)

    Cline, David B.

    1990-01-01

    The possible sources of extragalactic gamma rays and methods to distinguish the different sources are discussed. The sources considered are early universe decays and annihilation of Particles, active galactic nuclei (AGN) sources, and baryon-antibaryon annihilation in a baryon symmetric cosmology. The energy spectrum and possible angular fluctuations due to these sources are described.

  2. Megahertz peaked-spectrum sources in the Boötes field I - a route towards finding high-redshift AGN

    NASA Astrophysics Data System (ADS)

    Coppejans, Rocco; Cseh, David; Williams, Wendy L.; van Velzen, Sjoert; Falcke, Heino

    2015-06-01

    We present a 324.5 MHz image of the National Optical Astronomy Observatory Boötes field that was made using Very Large Array P-band observations. The image has a resolution of 5.6 × 5.1 arcsec, a radius of 2.05° and a central noise of ˜0.2 mJy beam-1. Both the resolution and noise of the image are an order of magnitude better than what was previously available at this frequency and will serve as a valuable addition to the already extensive multiwavelength data that are available for this field. The final source catalogue contains 1370 sources and has a median 325-1400 MHz spectral index of -0.72. Using a radio colour-colour diagram of the unresolved sources in our catalogue, we identify 33 megahertz peaked-spectrum (MPS) sources. Based on the turnover frequency linear size relation for the gigahertz peaked-spectrum and compact steep-spectrum sources, we expect that the MPS sources that are compact on scales of tens of milliarcseconds should be young radio loud active galactic nuclei at high (z > 2) redshifts. Of the 33 MPS sources, we were able to determine redshifts for 24, with an average redshift of 1.3. Given that five of the sources are at z > 2, that the four faint sources for which we could not find redshifts are likely at even higher redshifts and that we could only select sources that are compact on a scale of ˜5 arcsec, there is encouraging evidence that the MPS method can be used to search for high-redshift sources.

  3. Measuring the activity of a 51Cr neutrino source based on the gamma-radiation spectrum

    NASA Astrophysics Data System (ADS)

    Gorbachev, V. V.; Gavrin, V. N.; Ibragimova, T. V.; Kalikhov, A. V.; Malyshkin, Yu. M.; Shikhin, A. A.

    2015-12-01

    A technique for the measurement of activities of intense β sources by measuring the continuous gamma-radiation (internal bremsstrahlung) spectra is developed. A method for reconstructing the spectrum recorded by a germanium semiconductor detector is described. A method for the absolute measurement of the internal bremsstrahlung spectrum of 51Cr is presented.

  4. Parent Perspectives on Sources of Information about Autism Spectrum Disorder Interventions in Australia

    ERIC Educational Resources Information Center

    Carlon, Sarah; Stephenson, Jennifer; Carter, Mark

    2015-01-01

    Extant research on sources of information about interventions used by parents of children with autism spectrum disorder (ASD) has provided a general overview of sources used. However, it has provided little insight into why parents view certain sources as reliable or trustworthy, or how useful parents found the information provided to them by the…

  5. Flicker of extragalactic radio sources at two frequencies

    SciTech Connect

    Simonetti, J.H.; Cordes, J.M.; Heeschen, D.S.

    1985-09-01

    Dual-frequency observations of flat and steep-spectrum extragalactic radio sources made at Arecibo Observatory over a 20-day period are analyzed. As first reported by Heeschen (1982, 1984), flat-spectrum sources generally have larger intensity variations than steep-spectrum ones. A structure function analysis demonstrates a qualitative difference in the time series of the sources. The case against interstellar scintillation is examined, including a review of applicable scintillation theory. Relativistic source motion is treated as a solution to the brightness-temperature problems which arise if the variations are assumed intrinsic to the sources. 16 references.

  6. Modulation transfer function analysis for a digitally spectrum-controllable light source

    NASA Astrophysics Data System (ADS)

    Ma, Suodong; Wang, Yan; Pan, Qiao; Shen, Weimin

    2015-08-01

    Owing to the ability of generating designated spectrums as special requirements, spectrum-controllable light source has attracted huge interesting in several fields, e.g. medical science, industrial detection, defense-related testing. In principle, optical performance of a spectrum-controllable light source can be predicted by some transfer functions of the corresponding system, e.g. modulation transfer function (MTF). Unfortunately, the aforementioned research work is still lacking at present although it is meaningful for the optical design and evaluation of this new kind of light sources. Hence, a MTF model for a modified version of our previously-proposed spectrum-controllable light source system based on a Digital Micromirror Device (DMD) and an Offner dispersion configuration with a convex grating is deduced as an example. Related preliminary analyses have been present in this paper as well.

  7. Contribution from cosmological scalar perturbations to the angular velocity spectrum of extragalactic sources

    SciTech Connect

    Marakulin, A. O. Sazhina, O. S.; Sazhin, M. V.

    2012-07-15

    The possibility of the influence of adiabatic scalar perturbations on the angular velocity spectrum of extragalactic sources is considered. The multipole expansion coefficients of the angular velocity field in terms of vector spherical harmonics are calculated. We show that there is no contribution from adiabatic perturbations to the angular spectrum for a spatially flat Universe at the dusty stage, while there is a contribution only to the electric multiple coefficients at the stage of {Lambda}-term domination. The cases of long-wavelength and short-wavelength perturbations are considered separately. The relationship between the multipole angular velocity spectrum and the primordial scalar perturbation spectrum is discussed.

  8. Contribution from cosmological scalar perturbations to the angular velocity spectrum of extragalactic sources

    NASA Astrophysics Data System (ADS)

    Marakulin, A. O.; Sazhina, O. S.; Sazhin, M. V.

    2012-07-01

    The possibility of the influence of adiabatic scalar perturbations on the angular velocity spectrum of extragalactic sources is considered. The multipole expansion coefficients of the angular velocity field in terms of vector spherical harmonics are calculated. We show that there is no contribution from adiabatic perturbations to the angular spectrum for a spatially flat Universe at the dusty stage, while there is a contribution only to the electric multiple coefficients at the stage of Λ-term domination. The cases of long-wavelength and short-wavelength perturbations are considered separately. The relationship between the multipole angular velocity spectrum and the primordial scalar perturbation spectrum is discussed.

  9. Direct measurement of aeroacoustic source spectrum due to a jet/wall interaction

    NASA Astrophysics Data System (ADS)

    Lani, Shane; Krane, Michael

    2009-11-01

    The aeroacoustic source spectrum due to a turbulent jet passing over an obstruction is found experimentally. The model consists of a constriction and planar obstacle in a duct with dimensions commensurate with the those of a human vocal tract. An unsteady jet formed at a constriction interacts with a planar obstruction downstream with the jet normal to the planar surface. The aeroacoustic source spectrum is found both by measuring the unsteady force imparted on the planar obstruction as well as measuring radiated sound outside the duct. A comparison of the force spectrum to the inverse-filtered radiated sound measurements will be presented.

  10. Measurement of an inverse Compton scattering source local spectrum using k-edge filters

    SciTech Connect

    Golosio, Bruno; Oliva, Piernicola; Carpinelli, Massimo; Endrizzi, Marco; Delogu, Pasquale; Pogorelsky, Igor; Yakimenko, Vitaly

    2012-04-16

    X-ray sources based on the inverse Compton scattering process are attracting a growing interest among scientists, due to their extremely fast pulse, quasi-monochromatic spectrum, and relatively high intensity. The energy spectrum of the x-ray beam produced by inverse Compton scattering sources in a fixed observation direction is a quasi-monochromatic approximately Gaussian distribution. The mean value of this distribution varies with the scattering polar angle between the electron beam direction and the x-ray beam observation direction. Previous works reported experimental measurements of the mean energy as a function of the polar angle. This work introduces a method for the measurement of the whole local energy spectrum (i.e., the spectrum in a fixed observation direction) of the x-ray beam yielded by inverse Compton scattering sources, based on a k-edge filtering technique.

  11. THE COMPLEX X-RAY SPECTRUM OF THE SEFYERT 1.5 SOURCE NGC 6860

    SciTech Connect

    Winter, Lisa M.; Mushotzky, Richard

    2010-08-10

    The X-ray spectrum of the Seyfert 1.5 source NGC 6860 is among the most complex of the sources detected in the Swift Burst Alert Telescope all-sky survey. A short XMM-Newton follow-up observation of the source revealed a flat spectrum both above and below 2 keV. To uncover the complexity of the source, in this paper we analyze both a 40 ks Suzaku and a 100 ks XMM-Newton observation of NGC 6860. While the spectral state of the source changed between the newer observations presented here and the earlier short XMM-Newton spectrum-showing a higher flux and a steeper power-law component-the spectrum of NGC 6860 is still complex with clearly detected warm absorption signatures. We find that a two-component warm ionized absorber is present in the soft spectrum, with column densities of about 10{sup 20} and 10{sup 21} cm{sup -2}, ionization parameters of {xi} = 180 and 45 erg s{sup -1}, and outflow velocities for each component in the range of {approx}0-300 km s{sup -1}. Additionally, in the hard spectrum we find a broad ({approx}11, 000 km s{sup -1}) Fe K{alpha} emission line, redshifted by {approx}2800 km s{sup -1}.

  12. Source to detector spectrum transformation and its inverse for the Pegasus Z-pinch

    SciTech Connect

    Matuska, W.; Lee, Huan; Hockaday, R.; Peterson, D.

    1993-05-01

    We have developed a ray-tracing code which enables us to calculate the spectrum from a 2-D source simulation and compare directly with experimental data. This code also allows us to study the various spectral components which can potentially be used to determine the source from measured data.

  13. Source to detector spectrum transformation and its inverse for the Pegasus Z-pinch

    SciTech Connect

    Matuska, W.; Lee, Huan; Hockaday, R.; Peterson, D.

    1993-01-01

    We have developed a ray-tracing code which enables us to calculate the spectrum from a 2-D source simulation and compare directly with experimental data. This code also allows us to study the various spectral components which can potentially be used to determine the source from measured data.

  14. ON THE INJECTION SPECTRUM OF RELATIVISTIC ELECTRONS IN HIGH-REDSHIFT RADIO GALAXIES

    SciTech Connect

    Gopal-Krishna; Mhaskey, Mukul

    2012-01-01

    We point out that the remarkable linearity of the ultra-steep radio spectra of high-redshift radio galaxies reflects a previously reported general trend for powerful radio galaxies, according to which the spectral curvature is less for sources having steeper spectra (measured near rest-frame 1 GHz). We argue based on existing theoretical and observational evidence that it is premature to conclude that the particle acceleration mechanism in sources having straight, ultra-steep radio spectra gives rise to an ultra-steep injection spectrum of the radiating electrons. In empirical support for this we show that the estimated injection spectral indices available for a representative sample of 35 compact steep spectrum radio sources are not correlated with their rest-frame (intrinsic) rotation measures, which are known to be typically large, indicating a dense environment, as is also the case for high-z radio galaxies.

  15. An equivalent n-source for WGPu derived from a spectrum-shifted PuBe source

    NASA Astrophysics Data System (ADS)

    Ghita, Gabriel; Sjoden, Glenn; Baciak, James; Walker, Scotty; Cornelison, Spring

    2008-04-01

    We have designed, built, and laboratory-tested a unique shield design that transforms the complex neutron spectrum from PuBe source neutrons, generated at high energies, to nearly exactly the neutron signature leaking from a significant spherical mass of weapons grade plutonium (WGPu). This equivalent "X-material shield assembly" (Patent Pending) enables the harder PuBe source spectrum (average energy of 4.61 MeV) from a small encapsulated standard 1-Ci PuBe source to be transformed, through interactions in the shield, so that leakage neutrons are shifted in energy and yield to become a close reproduction of the neutron spectrum leaking from a large subcritical mass of WGPu metal (mean energy 2.11 MeV). The utility of this shielded PuBe surrogate for WGPu is clear, since it directly enables detector field testing without the expense and risk of handling large amounts of Special Nuclear Materials (SNM) as WGPu. Also, conventional sources using Cf-252, which is difficult to produce, and decays with a 2.7 year half life, could be replaced by this shielded PuBe technology in order to simplify operational use, since a sealed PuBe source relies on Pu-239 (T½=24,110 y), and remains viable for more than hundreds of years.

  16. The Low-frequency Radio Catalog of Flat-spectrum Sources

    NASA Astrophysics Data System (ADS)

    Massaro, F.; Giroletti, M.; D'Abrusco, R.; Masetti, N.; Paggi, A.; Cowperthwaite, Philip S.; Tosti, G.; Funk, S.

    2014-07-01

    A well known property of the γ-ray sources detected by Cos-B in the 1970s, by the Compton Gamma-Ray Observatory in the 1990s, and recently by the Fermi observations is the presence of radio counterparts, particularly for those associated with extragalactic objects. This observational evidence is the basis of the radio-γ-ray connection established for the class of active galactic nuclei known as blazars. In particular, the main spectral property of the radio counterparts associated with γ-ray blazars is that they show a flat spectrum in the GHz frequency range. Our recent analysis dedicated to search blazar-like candidates as potential counterparts for the unidentified γ-ray sources allowed us to extend the radio-γ-ray connection in the MHz regime. We also showed that blazars below 1 GHz maintain flat radio spectra. Thus, on the basis of these new results, we assembled a low-frequency radio catalog of flat-spectrum sources built by combining the radio observations of the Westerbork Northern Sky Survey and of the Westerbork in the southern hemisphere catalog with those of the NRAO Very Large Array Sky survey (NVSS). This could be used in the future to search for new, unknown blazar-like counterparts of γ-ray sources. First, we found NVSS counterparts of Westerbork Synthesis Radio Telescope radio sources, and then we selected flat-spectrum radio sources according to a new spectral criterion, specifically defined for radio observations performed below 1 GHz. We also described the main properties of the catalog listing 28,358 radio sources and their logN-logS distributions. Finally, a comparison with the Green Bank 6 cm radio source catalog was performed to investigate the spectral shape of the low-frequency flat-spectrum radio sources at higher frequencies.

  17. THE LOW-FREQUENCY RADIO CATALOG OF FLAT-SPECTRUM SOURCES

    SciTech Connect

    Massaro, F.; Giroletti, M.; D'Abrusco, R.; Paggi, A.; Cowperthwaite, Philip S.; Masetti, N.; Tosti, G.; Funk, S.

    2014-07-01

    A well known property of the γ-ray sources detected by Cos-B in the 1970s, by the Compton Gamma-Ray Observatory in the 1990s, and recently by the Fermi observations is the presence of radio counterparts, particularly for those associated with extragalactic objects. This observational evidence is the basis of the radio-γ-ray connection established for the class of active galactic nuclei known as blazars. In particular, the main spectral property of the radio counterparts associated with γ-ray blazars is that they show a flat spectrum in the GHz frequency range. Our recent analysis dedicated to search blazar-like candidates as potential counterparts for the unidentified γ-ray sources allowed us to extend the radio-γ-ray connection in the MHz regime. We also showed that blazars below 1 GHz maintain flat radio spectra. Thus, on the basis of these new results, we assembled a low-frequency radio catalog of flat-spectrum sources built by combining the radio observations of the Westerbork Northern Sky Survey and of the Westerbork in the southern hemisphere catalog with those of the NRAO Very Large Array Sky survey (NVSS). This could be used in the future to search for new, unknown blazar-like counterparts of γ-ray sources. First, we found NVSS counterparts of Westerbork Synthesis Radio Telescope radio sources, and then we selected flat-spectrum radio sources according to a new spectral criterion, specifically defined for radio observations performed below 1 GHz. We also described the main properties of the catalog listing 28,358 radio sources and their logN-logS distributions. Finally, a comparison with the Green Bank 6 cm radio source catalog was performed to investigate the spectral shape of the low-frequency flat-spectrum radio sources at higher frequencies.

  18. The Integrated X-Ray Spectrum of Galactic Populations of Luminous Supersoft X-Ray Sources

    NASA Technical Reports Server (NTRS)

    DiStefano, R.; Becker, C. M.; Fabbiano, G.

    1996-01-01

    We compute the composite X-ray spectrum of a population of unresolved SSS's in a spiral galaxy such as our own or M31. The sources are meant to represent the total underlying population corresponding to all sources which have bolometric luminosities in the range of 10(exp 37) - 10(exp 38) ergs/s and kT on the order of tens of eV. These include close-binary supersoft sources, symbiotic novae, and planetary nebulae, for example. In order to determine whether the associated X-ray signal would be detectable, we also 'seed' the galaxy with other types of X-ray sources, specifically low-mass X-ray binaries (LMXB's) and high-mass X-ray binaries (HMXB's). We find that the total spectrum due to SSS's, LMXB's, and HMXB's exhibits a soft peak which owes its presence to the SSS population. Preliminary indications are that this soft peak may be observable.

  19. Neutron energy spectrum characterization on TMR-1 at the Indiana University neutron source

    NASA Astrophysics Data System (ADS)

    Halstead, Matthew R.; Lee, Sangjin; Petrosky, James; Bickley, Abigail; Sokol, Paul

    The energy spectrum of the Neutron Radiation Effects Program (NREP) beam line, Target-Moderator-Reflector-1 (TMR-1), at Indiana University has not been previously characterized. The facility has a unique proton source with variable pulse length (15-600 ms) and energy (13 MeV). Thus, it can produce a unique and tailored neutron beam when incident on a beryllium target. Through a combination of MCNP-X particle simulations, neutron activation experiments, and application of a spectrum unfolding code (SAND-II), the neutron source is characterized. Eight activation foils and wires were irradiated in the target area and the gamma activity measured. This information was used in an unfolding code, SAND-II, to deconvolve the spectrum, using the MCNP simulations as a basis for the spectral fitting.

  20. Examining the Clinical Correlates of Autism Spectrum Disorder in Youth by Ascertainment Source

    ERIC Educational Resources Information Center

    Joshi, Gagan; Faraone, Stephen V.; Wozniak, Janet; Petty, Carter; Fried, Ronna; Galdo, Maribel; Furtak, Stephannie L.; McDermott, Katie; Epstien, Cecily; Walker, Rosemary; Caron, Ashley; Feinberg, Leah; Biederman, Joseph

    2014-01-01

    To examine whether presentation of autism spectrum disorder (ASD) and associated patterns of psychiatric comorbidity and dysfunction vary by referral source. ASD youth referred to a specialized ambulatory program for ASD (N = 143) were compared to ASD youth referred to a general child psychiatry clinic (N = 217). More ASD clinic youth met criteria…

  1. Investigation of the neutron spectrum of americium-beryllium sources by Bonner sphere spectrometry

    NASA Astrophysics Data System (ADS)

    Bedogni, R.; Domingo, C.; Roberts, N.; Thomas, D. J.; Chiti, M.; Esposito, A.; Garcia, M. J.; Gentile, A.; Liu, Z. Z.; de-San-Pedro, M.

    2014-11-01

    Americium-beryllium neutron sources are certainly the most widely used in neutron dosimetry laboratories, basically due to their long half-life and their energy distribution, which covers the energy domain of interest for many applications in ambient and personal dosimetry. Nevertheless, the spectrum of this source depends on the materials and dimension of the capsule and on the amount and physical-chemical properties of the active material, thus affecting relevant quantities such as the spectrum-averaged fluence-to-dose equivalent conversion coefficient. A EURAMET (European Association of National Metrology Institutes) project (n. 1104) was initiated to experimentally investigate how the neutron spectrum changes for different source sizes and encapsulations with a view to providing improved data for a planned revision of the ISO 8529 Standard Series. The experimental campaign was carried out in the low scatter facility at NPL. Here three different Bonner sphere spectrometers, BSSs, were exposed to the neutron fields produced by three different neutron sources formats: one X3 capsule (1 Ci) and two X14 capsules (10 Ci and 15 Ci). The specific advantage of the BSS is the large sensitivity to low-energy neutrons (E<0.1 MeV) which is the component expected to be most affected by the capsule-to-capsule variations and the component which is least well known. This paper summarises the results of the campaign with emphasis on (1) estimating the low-energy component of the Am-Be neutron spectrum, according to the encapsulation type; (2) evaluating the coherence between the Bonner spheres data and the previous studies performed with high-resolution spectrometers but limited in energy to E>0.1 MeV; (3) understanding whether the ISO-recommended Am-Be spectrum needs to be amended, and for which source formats.

  2. Pulsar candidates towards Fermi unassociated sources

    NASA Astrophysics Data System (ADS)

    Frail, D. A.; Mooley, K. P.; Jagannathan, P.; Intema, H. T.

    2016-09-01

    We report on a search for steep spectrum radio sources within the 95 per cent confidence error ellipses of the Fermi unassociated sources from the Large Area Telescope (LAT). Using existing catalogues and the newly released Giant Metrewave Radio Telescope all-sky survey at 150 MHz, we identify compact radio sources that are bright at MHz frequencies but faint or absent at GHz frequencies. Such steep spectrum radio sources are rare and constitute a sample of pulsar candidates, selected independently of period, dispersion measure, interstellar scattering and orbital parameters. We find point-like, steep spectrum candidates towards 11 Fermi sources. Based on the gamma-ray/radio positional coincidence, the rarity of such radio sources, and the properties of the 3FGL sources themselves, we argue that many of these sources could be pulsars. They may have been missed by previous radio periodicity searches due to interstellar propagation effects or because they lie in an unusually tight binary. If this hypothesis is correct, then renewed gamma-ray and radio periodicity searches at the positions of the steep spectrum radio sources may reveal pulsations.

  3. Correlation equation for the marine drag coefficient and wave steepness

    NASA Astrophysics Data System (ADS)

    Foreman, Richard J.; Emeis, Stefan

    2012-09-01

    This work questions, starting from dimensional considerations, the generality of the belief that the marine drag coefficient levels off with increasing wind speed. Dimensional analysis shows that the drag coefficient scales with the wave steepness as opposed to a wave-age scaling. A correlation equation is employed here that uses wave steepness scaling at low aspect ratios (inverse wave steepnesses) and a constant drag coefficient at high aspect ratios. Invoked in support of the correlation are measurements sourced from the literature and at the FINO1 platform in the North Sea. The correlation equation is then applied to measurements recorded from buoys during the passage of hurricanes Rita, Katrina (2005) and Ike (2008). Results show that the correlation equation anticipates the expected levelling off in deeper water, but a drag coefficient more consistent with a Charnock type relation is also possible in more shallower water. Some suggestions are made for proceeding with a higher-order analysis than that conducted here.

  4. Algorithm for Building a Spectrum for NREL's One-Sun Multi-Source Simulator: Preprint

    SciTech Connect

    Moriarty, T.; Emery, K.; Jablonski, J.

    2012-06-01

    Historically, the tools used at NREL to compensate for the difference between a reference spectrum and a simulator spectrum have been well-matched reference cells and the application of a calculated spectral mismatch correction factor, M. This paper describes the algorithm for adjusting the spectrum of a 9-channel fiber-optic-based solar simulator with a uniform beam size of 9 cm square at 1-sun. The combination of this algorithm and the One-Sun Multi-Source Simulator (OSMSS) hardware reduces NREL's current vs. voltage measurement time for a typical three-junction device from man-days to man-minutes. These time savings may be significantly greater for devices with more junctions.

  5. Neutron energy spectrum adjustment using deposited metal films on Teflon in the miniature neutron source reactor.

    PubMed

    Nassan, L; Abdallah, B; Omar, H; Sarheel, A; Alsomel, N; Ghazi, N

    2016-01-01

    The focus of this article was on the experimental estimation of the neutron energy spectrum in the inner irradiation site of the miniature neutron source reactor (MNSR), using, for the first time, a selected set of deposited metal films on Teflon (DMFTs) neutron detectors. Gold, copper, zinc, titanium, aluminum, nickel, silver, and chromium were selected because of the dependence of their neutron cross-sections on neutron energy. Emphasis was placed on the usability of this new type of neutron detectors in the total neutron energy spectrum adjustment. The measured saturation activities per target nucleus values of the DMFTs, and the calculated neutron spectrum in the inner irradiation site using the MCNP-4C code were used as an input for the STAY'SL computer code during the adjustment procedure. The agreement between the numerically calculated and experimentally adjusted spectra results was discussed. PMID:26562448

  6. The nuclear region of low luminosity flat radio spectrum sources. II. Emission-line spectra

    NASA Astrophysics Data System (ADS)

    Gonçalves, A. C.; Serote Roos, M.

    2004-01-01

    We report on the spectroscopic study of 19 low luminosity Flat Radio Spectrum (LL FRS) sources selected from Marchã's et al. (\\cite{March96}) 200 mJy sample. In the optical, these objects are mainly dominated by the host galaxy starlight. After correcting the data for this effect, we obtain a new set of spectra clearly displaying weak emission lines; such features carry valuable information concerning the excitation mechanisms at work in the nuclear regions of LL FRS sources. We have used a special routine to model the spectra and assess the intensities and velocities of the emission lines; we have analyzed the results in terms of diagnostic diagrams. Our analysis shows that 79% of the studied objects harbour a Low Ionization Nuclear Emission-line Region (or LINER) whose contribution was swamped by the host galaxy starlight. The remaining objects display a higher ionization spectrum, more typical of Seyferts; due to the poor quality of the spectra, it was not possible to identify any possible large Balmer components. The fact that we observe a LINER-type spectrum in LL FRS sources supports the idea that some of these objects could be undergoing an ADAF phase; in addition, such a low ionization emission-line spectrum is in agreement with the black hole mass values and sub-Eddington accretion rates published for some FRS sources. Based on observations collected at the Multiple Mirror Telescope on Mt. Hopkins. Full Fig. 1 is only available in electronic form at http://www.edpsciences.org

  7. PERCENT OF CROPLAND ON STEEP SLOPES

    EPA Science Inventory

    Clearing land for agriculture tends to increase soil erosion. The amount of erosion is related to the steepness of the slope, farming methods used and soil type. High amounts of cropland on steep slopes can increase the amount of soil erosion leading to increased sediment in sur...

  8. PERCENT AGRICULTURAL LAND COVER ON STEEP SLOPES

    EPA Science Inventory

    Clearing land for agriculture tends to increase soil erosion. The amount of erosion is related to the steepness of the slope, farming methods used and soil type. High amounts of agriculture on steep slopes can increase the amount of soil erosion leading to increased sediment in ...

  9. Sensitivity of neutrinos to the supernova turbulence power spectrum: Point source statistics

    NASA Astrophysics Data System (ADS)

    Kneller, James P.; Kabadi, Neel V.

    2015-07-01

    The neutrinos emitted from the proto-neutron star created in a core-collapse supernova must run through a significant amount of turbulence before exiting the star. Turbulence can modify the flavor evolution of the neutrinos imprinting itself upon the signal detected here at Earth. The turbulence effect upon individual neutrinos, and the correlation between pairs of neutrinos, might exhibit sensitivity to the power spectrum of the turbulence, and recent analysis of the turbulence in a two-dimensional hydrodynamical simulation of a core-collapse supernova indicates the power spectrum may not be the Kolmogorov 5 /3 inverse power law as has been previously assumed. In this paper we study the effect of non-Kolmogorov turbulence power spectra upon neutrinos from a point source as a function of neutrino energy and turbulence amplitude at a fixed postbounce epoch. We find the two effects of turbulence upon the neutrinos—the distorted phase effect and the stimulated transitions—both possess strong and weak limits in which dependence upon the power spectrum is absent or evident, respectively. Since neutrinos of a given energy will exhibit these two effects at different epochs of the supernova each with evolving strength, we find there is sensitivity to the power spectrum present in the neutrino burst signal from a Galactic supernova.

  10. Constraining high-redshift X-ray sources with next generation 21-cm power spectrum measurements

    NASA Astrophysics Data System (ADS)

    Ewall-Wice, Aaron; Hewitt, Jacqueline; Mesinger, Andrei; Dillon, Joshua S.; Liu, Adrian; Pober, Jonathan

    2016-05-01

    We use the Fisher matrix formalism and seminumerical simulations to derive quantitative predictions of the constraints that power spectrum measurements on next-generation interferometers, such as the Hydrogen Epoch of Reionization Array (HERA) and the Square Kilometre Array (SKA), will place on the characteristics of the X-ray sources that heated the high-redshift intergalactic medium. Incorporating observations between z = 5 and 25, we find that the proposed 331 element HERA and SKA phase 1 will be capable of placing ≲ 10 per cent constraints on the spectral properties of these first X-ray sources, even if one is unable to perform measurements within the foreground contaminated `wedge' or the FM band. When accounting for the enhancement in power spectrum amplitude from spin temperature fluctuations, we find that the observable signatures of reionization extend well beyond the peak in the power spectrum usually associated with it. We also find that lower redshift degeneracies between the signatures of heating and reionization physics lead to errors on reionization parameters that are significantly greater than previously predicted. Observations over the heating epoch are able to break these degeneracies and improve our constraints considerably. For these two reasons, 21-cm observations during the heating epoch significantly enhance our understanding of reionization as well.

  11. Discovery of the Hard Spectrum VHE γ-Ray Source HESS J1641-463

    NASA Astrophysics Data System (ADS)

    Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Angüner, E. O.; Backes, M.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Birsin, E.; Biteau, J.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Bulik, T.; Carrigan, S.; Casanova, S.; Chadwick, P. M.; Chakraborty, N.; Chalme-Calvet, R.; Chaves, R. C. G.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Cui, Y.; Dalton, M.; Davids, I. D.; Degrange, B.; Deil, C.; deWilt, P.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; O'C. Drury, L.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Edwards, T.; Egberts, K.; Eger, P.; Espigat, P.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gabici, S.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Gottschall, D.; Grondin, M.-H.; Grudzińska, M.; Hadasch, D.; Häffner, S.; Hahn, J.; Harris, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Ivascenko, A.; Jacholkowska, A.; Jahn, C.; Jamrozy, M.; Janiak, M.; Jankowsky, F.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Khélifi, B.; Kieffer, M.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lau, J.; Lefaucheur, J.; Lefranc, V.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Méhault, J.; Meintjes, P. J.; Menzler, U.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Morå, K.; Moulin, E.; Murach, T.; de Naurois, M.; Niemiec, J.; Nolan, S. J.; Oakes, L.; Odaka, H.; Ohm, S.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Parsons, R. D.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Reichardt, I.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Romoli, C.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Salek, D.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sol, H.; Spanier, F.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tluczykont, M.; Trichard, C.; Valerius, K.; van Eldik, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Völk, H. J.; Volpe, F.; Vorster, M.; Vuillaume, T.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; Ward, M.; Weidinger, M.; Weitzel, Q.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zabalza, V.; Zaborov, D.; Zacharias, M.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.; Fukui, Y.; Sano, H.; Fukuda, T.; Yoshiike, S.; H. E. S. S. Collaboration

    2014-10-01

    This Letter reports the discovery of a remarkably hard spectrum source, HESS J1641-463, by the High Energy Stereoscopic System (H.E.S.S.) in the very high energy (VHE) domain. HESS J1641-463 remained unnoticed by the usual analysis techniques due to confusion with the bright nearby source HESS J1640-465. It emerged at a significance level of 8.5 standard deviations after restricting the analysis to events with energies above 4 TeV. It shows a moderate flux level of phi(E>1 TeV) = (3.64 ± 0.44stat ± 0.73sys) × 10-13 cm-2 s-1, corresponding to 1.8% of the Crab Nebula flux above the same energy, and a hard spectrum with a photon index of Γ = 2.07 ± 0.11stat ± 0.20sys. It is a point-like source, although an extension up to a Gaussian width of σ = 3 arcmin cannot be discounted due to uncertainties in the H.E.S.S. point-spread function. The VHE γ-ray flux of HESS J1641-463 is found to be constant over the observed period when checking time binnings from the year-by-year to the 28 minute exposure timescales. HESS J1641-463 is positionally coincident with the radio supernova remnant SNR G338.5+0.1. No X-ray candidate stands out as a clear association; however, Chandra and XMM-Newton data reveal some potential weak counterparts. Various VHE γ-ray production scenarios are discussed. If the emission from HESS J1641-463 is produced by cosmic ray protons colliding with the ambient gas, then their spectrum must extend close to 1 PeV. This object may represent a source population contributing significantly to the galactic cosmic ray flux around the knee.

  12. Contribution from individual nearby sources to the spectrum of high-energy cosmic-ray electrons

    NASA Astrophysics Data System (ADS)

    Sedrati, R.; Attallah, R.

    2014-04-01

    In the last few years, very important data on high-energy cosmic-ray electrons and positrons from high-precision space-born and ground-based experiments have attracted a great deal of interest. These particles represent a unique probe for studying local comic-ray accelerators because they lose energy very rapidly. These energy losses reduce the lifetime so drastically that high-energy cosmic-ray electrons can attain the Earth only from rather local astrophysical sources. This work aims at calculating, by means of Monte Carlo simulation, the contribution from some known nearby astrophysical sources to the cosmic-ray electron/positron spectra at high energy (≥ 10 GeV). The background to the electron energy spectrum from distant sources is determined with the help of the GALPROP code. The obtained numerical results are compared with a set of experimental data.

  13. How steep are the Alps?

    NASA Astrophysics Data System (ADS)

    Robl, Jörg; Prasicek, Günther; Stüwe, Kurt; Hergarten, Stefan

    2014-05-01

    The topography of the European Alps reflects continental collision, crustal thickening and buoyancy driven surface uplift, overprinted by erosional processes. Topographic gradients generally steepen from the valley floors up to about 1500 m - 2000 m followed by an unexpected decrease in slope up to about 2900 m and a further increase to the highest summits of the range. Several studies have interpreted this pattern and the accompanied maximum in the hypsometric curve in terms of either the critical slope stability angle, the prematurity of the Alps caused by recent tectonic uplift, or the effect of the glacial "buzz saw" related to the Pleistocene glaciation cycles. There is consensus that the lithological inventory represents a first order parameter for the steepness of fluvial channels and the angle of hillslopes in steady state and that the response time of a transient landscape is controlled by lithology. In this study we systematically explore the slope-elevation distributions for several hundred continuous domains of the major structural units of the Alps. For this, we apply a novel numerical code to determine the predominant cause for the observed peculiar topography. We compare adjacent alpine domains with contrasting lithology to explore lithological effects on the limiting slope stability angle. We analyze domains with different lithology in the non-glaciated parts of the orogen to highlight the state of maturity related to a recent uplift event. We evaluate the glacial effects on the landscape by the comparison of areas belonging to the same structural units but affected by a variable amount of glacial imprint. The results show that lithology has a major impact on the morphometric characteristics of the European Alps. Adjacent but different structural units show a significant variability in their slope-elevation distributions although they have experienced the same uplift history and the same amount of glacial imprint. This suggests that the response

  14. Partially Absorbed Comptonization Spectrum from the Nearly Edge-on Source X1822-371

    NASA Astrophysics Data System (ADS)

    Iaria, R.; Di Salvo, T.; Burderi, L.; Robba, N. R.

    2001-08-01

    We report the results of a spectral analysis over the range 0.1-200 keV performed on the dipping source X1822-371 observed by BeppoSAX. We find the best fit to the continuum using a partially covered Comptonization model, representing scattering of soft seed photons by electrons at a temperature of ~4.8 keV, without the presence of any soft blackbody emission. The equivalent hydrogen column obtained for the absorbed component is ~4.5×1022 cm-2, an order of magnitude larger than the Galactic absorption for this source, and the covering fraction is ~71%. Because the inclination angle of X1822-371 to the line of sight is ~85°, this model gives a reasonable scenario for the source: the Comptonized spectrum could come from an extended accretion disk corona (ADC), probably the only region that can be directly observed as a result of the high inclination. The excess matter producing the partial covering could be close to the equatorial plane of the system, above the outer disk, occulting the emission from the inner disk and the inner part of the ADC. An iron emission line is also present at ~6.5 keV with an equivalent width of ~150 eV. We argue that this strong iron line cannot be explained as reflection of the Comptonized spectrum by the accretion disk. It is probably produced in the ADC. An emission line at ~1.9 keV (with an equivalent width of ~54 eV) and an absorption edge at ~8.7 keV (with an optical depth of ~0.1) are also required to fit this spectrum. These features are probably produced by highly ionized iron (Fe XXIV) present in the outer part of the ADC, where the plasma density is ~1011-1012 cm-3 and ionized plasma is present.

  15. Measuring the activity of a {sup 51}Cr neutrino source based on the gamma-radiation spectrum

    SciTech Connect

    Gorbachev, V. V. Gavrin, V. N.; Ibragimova, T. V.; Kalikhov, A. V.; Malyshkin, Yu. M.; Shikhin, A. A.

    2015-12-15

    A technique for the measurement of activities of intense β sources by measuring the continuous gamma-radiation (internal bremsstrahlung) spectra is developed. A method for reconstructing the spectrum recorded by a germanium semiconductor detector is described. A method for the absolute measurement of the internal bremsstrahlung spectrum of {sup 51}Cr is presented.

  16. CRATES: An All-Sky Survey of Flat-Spectrum Radio Sources

    SciTech Connect

    Healey, Stephen E.; Romani, Roger W.; Taylor, Gregory B.; Sadler, Elaine M.; Ricci, Roberto; Murphy, Tara; Ulvestad, James S.; Winn, Joshua N.; /MIT

    2007-02-20

    We have assembled an 8.4 GHz survey of bright, flat-spectrum ({alpha} > -0.5) radio sources with nearly uniform extragalactic (|b| > 10{sup o}) coverage for sources brighter than S{sub 4.8 GHz} = 65 mJy. The catalog is assembled from existing observations (especially CLASS and the Wright et al. PMN-CA survey), augmented by reprocessing of archival VLA and ATCA data and by new observations to fill in coverage gaps. We refer to this program as CRATES, the Combined Radio All-sky Targeted Eight GHz Survey. The resulting catalog provides precise positions, sub-arcsecond structures, and spectral indices for some 11,000 sources. We describe the morphology and spectral index distribution of the sample and comment on the survey's power to select several classes of interesting sources, especially high energy blazars. Comparison of CRATES with other high-frequency surveys also provides unique opportunities for identification of high-power radio sources.

  17. Effect of photon energy spectrum on dosimetric parameters of brachytherapy sources

    PubMed Central

    Ghorbani, Mahdi; Davenport, David

    2016-01-01

    Abstract Aim The aim of this study is to quantify the influence of the photon energy spectrum of brachytherapy sources on task group No. 43 (TG-43) dosimetric parameters. Background Different photon spectra are used for a specific radionuclide in Monte Carlo simulations of brachytherapy sources. Materials and methods MCNPX code was used to simulate 125I, 103Pd, 169Yb, and 192Ir brachytherapy sources. Air kerma strength per activity, dose rate constant, radial dose function, and two dimensional (2D) anisotropy functions were calculated and isodose curves were plotted for three different photon energy spectra. The references for photon energy spectra were: published papers, Lawrence Berkeley National Laboratory (LBNL), and National Nuclear Data Center (NNDC). The data calculated by these photon energy spectra were compared. Results Dose rate constant values showed a maximum difference of 24.07% for 103Pd source with different photon energy spectra. Radial dose function values based on different spectra were relatively the same. 2D anisotropy function values showed minor differences in most of distances and angles. There was not any detectable difference between the isodose contours. Conclusions Dosimetric parameters obtained with different photon spectra were relatively the same, however it is suggested that more accurate and updated photon energy spectra be used in Monte Carlo simulations. This would allow for calculation of reliable dosimetric data for source modeling and calculation in brachytherapy treatment planning systems. PMID:27247558

  18. Energy enhancement and spectrum narrowing in terahertz electron sources due to negative mass instability

    NASA Astrophysics Data System (ADS)

    Lurie, Yu.; Bratman, V. L.; Savilov, A. V.

    2016-05-01

    Simulations of coherent spontaneous undulator radiation in a waveguide demonstrate that the use of negative mass instability (NMI) for retaining longitudinal sizes of dense electron bunches, which are formed in laser-driven photoinjectors, allows one to increase power capabilities of a terahertz radiation source by many times. The NMI is realized in an undulator with combined helical and over-resonance uniform longitudinal magnetic fields due to nonisochronous longitudinal oscillations of electrons, whose frequencies increase/decrease with increasing/decreasing particle energy. In such conditions, an effective longitudinal size of the bunches can be preserved at long distance even at an extremely high electron density. Correspondingly, an energy extraction efficiency of more than 20% is revealed at a narrow frequency radiation spectrum, suggesting realization of a compact and powerful THz source.

  19. Initial study of the optical spectrum of the ISIS H{sup -} ion source plasma

    SciTech Connect

    Lawrie, S. R.; Faircloth, D. C.; Philippe, K.

    2012-02-15

    The front end test stand is being constructed at the Rutherford Appleton Laboratory, with the aim of producing a 60 mA, 2 ms, 50 Hz, perfectly chopped H{sup -} ion beam. To meet the beam requirements, a more detailed understanding of the ion source plasma is required. To this end, an initial study is made of the optical spectrum of the plasma using a digital spectrometer. The atomic and molecular emission lines of hydrogen and caesium are clearly distinguished and a quantitative comparison is made when the ion source is run in different conditions. The electron temperature is 0.6 eV and measured line widths vary by up to 75%.

  20. A simplified approach to characterizing a kilovoltage source spectrum for accurate dose computation

    SciTech Connect

    Poirier, Yannick; Kouznetsov, Alexei; Tambasco, Mauro

    2012-06-15

    Purpose: To investigate and validate the clinical feasibility of using half-value layer (HVL) and peak tube potential (kVp) for characterizing a kilovoltage (kV) source spectrum for the purpose of computing kV x-ray dose accrued from imaging procedures. To use this approach to characterize a Varian Registered-Sign On-Board Imager Registered-Sign (OBI) source and perform experimental validation of a novel in-house hybrid dose computation algorithm for kV x-rays. Methods: We characterized the spectrum of an imaging kV x-ray source using the HVL and the kVp as the sole beam quality identifiers using third-party freeware Spektr to generate the spectra. We studied the sensitivity of our dose computation algorithm to uncertainties in the beam's HVL and kVp by systematically varying these spectral parameters. To validate our approach experimentally, we characterized the spectrum of a Varian Registered-Sign OBI system by measuring the HVL using a Farmer-type Capintec ion chamber (0.06 cc) in air and compared dose calculations using our computationally validated in-house kV dose calculation code to measured percent depth-dose and transverse dose profiles for 80, 100, and 125 kVp open beams in a homogeneous phantom and a heterogeneous phantom comprising tissue, lung, and bone equivalent materials. Results: The sensitivity analysis of the beam quality parameters (i.e., HVL, kVp, and field size) on dose computation accuracy shows that typical measurement uncertainties in the HVL and kVp ({+-}0.2 mm Al and {+-}2 kVp, respectively) source characterization parameters lead to dose computation errors of less than 2%. Furthermore, for an open beam with no added filtration, HVL variations affect dose computation accuracy by less than 1% for a 125 kVp beam when field size is varied from 5 Multiplication-Sign 5 cm{sup 2} to 40 Multiplication-Sign 40 cm{sup 2}. The central axis depth dose calculations and experimental measurements for the 80, 100, and 125 kVp energies agreed within 2

  1. DISCOVERY OF THE HARD SPECTRUM VHE γ-RAY SOURCE HESS J1641–463

    SciTech Connect

    Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Bernlöhr, K.; Akhperjanian, A. G.; Angüner, E. O.; Birsin, E.; Backes, M.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Biteau, J.; Boisson, C. E-mail: sabrina.casanova@mpi-hd.mpg.de; Collaboration: H.E.S.S. Collaboration; and others

    2014-10-10

    This Letter reports the discovery of a remarkably hard spectrum source, HESS J1641–463, by the High Energy Stereoscopic System (H.E.S.S.) in the very high energy (VHE) domain. HESS J1641–463 remained unnoticed by the usual analysis techniques due to confusion with the bright nearby source HESS J1640–465. It emerged at a significance level of 8.5 standard deviations after restricting the analysis to events with energies above 4 TeV. It shows a moderate flux level of φ(E>1 TeV) = (3.64 ± 0.44{sub stat} ± 0.73{sub sys}) × 10{sup –13} cm{sup –2} s{sup –1}, corresponding to 1.8% of the Crab Nebula flux above the same energy, and a hard spectrum with a photon index of Γ = 2.07 ± 0.11{sub stat} ± 0.20{sub sys}. It is a point-like source, although an extension up to a Gaussian width of σ = 3 arcmin cannot be discounted due to uncertainties in the H.E.S.S. point-spread function. The VHE γ-ray flux of HESS J1641–463 is found to be constant over the observed period when checking time binnings from the year-by-year to the 28 minute exposure timescales. HESS J1641–463 is positionally coincident with the radio supernova remnant SNR G338.5+0.1. No X-ray candidate stands out as a clear association; however, Chandra and XMM-Newton data reveal some potential weak counterparts. Various VHE γ-ray production scenarios are discussed. If the emission from HESS J1641–463 is produced by cosmic ray protons colliding with the ambient gas, then their spectrum must extend close to 1 PeV. This object may represent a source population contributing significantly to the galactic cosmic ray flux around the knee.

  2. Removing Complications of a Dominant Broad Age Spectrum Source: A New Approach to the Mixing of Detrital Zircons.

    NASA Astrophysics Data System (ADS)

    Wissink, G.; Hoke, G. D.

    2014-12-01

    Detrital zircons are often considered the panacea of provenance analysis but are often limited to inquiry based solely on the presence or absence of populations and thus restricted to qualitative comparisons. However, if one broad age spectrum source dominates a detrital dataset other sources may be obscured. We present a method for removing a broad age spectrum source through a process of randomly drawing grains from the dominant source, pairing them with sample grains and removing matched aged grains. This results in a residual population representing all remaining unassociated ages, which can then be compared to other potential sources using PDP crossplot and likeness comparisons. The sources best matching our post-removal sample are resampled in varying proportions, with the dominant, broad age spectrum source, to recreate the pre-subtraction sample by maximizing the population comparison tests. We test our method with a synthetic dataset of 18, 10,000-grain 'sandstone' populations created from 6 easily differentiable sources and 1 complex source representing the dominant, broad age spectrum source. Synthetic detrital zircon age populations are created by randomly selecting from each of the synthetic populations. This method was able to consistently determine the correct sources and their mixing proportions to within ±10% of the original artificial sandstone proportions. Covariance between the two comparison tests also shows improvement relative to their pre-removal counterparts. Previously published detrital zircon age data from modern sediment samples of the Yangtze River (He et al., 2013) show a dominance of ages commonly attributed to the Triassic Songpan Ganze Terrane, which has a broad age spectrum. We applied our method to these Yangtze age populations in conjunction with 35 potential sources units compiled and consolidated from the literature. Applying this technique to modern Chinese sediments identifies previously unknown contributing sources and

  3. Resting State Functional Connectivity MRI among Spectral MEG Current Sources in Children on the Autism Spectrum.

    PubMed

    Datko, Michael; Gougelet, Robert; Huang, Ming-Xiong; Pineda, Jaime A

    2016-01-01

    Social and communicative impairments are among the core symptoms of autism spectrum disorders (ASD), and a great deal of evidence supports the notion that these impairments are associated with aberrant functioning and connectivity of various cortical networks. The present study explored the links between sources of MEG amplitude in various frequency bands and functional connectivity MRI in the resting state. The goal of combining these modalities was to use sources of neural oscillatory activity, measured with MEG, as functionally relevant seed regions for a more traditional pairwise fMRI connectivity analysis. We performed a seed-based connectivity analysis on resting state fMRI data, using seed regions derived from frequency-specific amplitude sources in resting state MEG data in the same nine subjects with ASD (10-17 years of age). We then compared fMRI connectivity among these MEG-source-derived regions between participants with autism and typically developing, age-matched controls. We used a source modeling technique designed for MEG data to detect significant amplitude sources in six frequency bands: delta (2-4 Hz), theta (4-8 Hz), alpha (8-12 Hz), beta (12-30 Hz), low gamma (30-60 Hz), and high gamma (60-120 Hz). MEG-derived source maps for each participant were co-registered in standard MNI space, and group-level source maps were obtained for each frequency. For each frequency band, the 10 largest clusters resulting from these t-tests were used as regions of interest (ROIs) for the fMRI functional connectivity analysis. Pairwise BOLD signal correlations were obtained between each pair of these ROIs for each frequency band. Each pairwise correlation was compared between the ASD and TD groups using t-tests. We also constrained these pairwise correlations to known network structures, resulting in a follow-up set of correlation matrices specific to each network we considered. Frequency-specific MEG sources had distinct patterns of fMRI resting state functional

  4. Resting State Functional Connectivity MRI among Spectral MEG Current Sources in Children on the Autism Spectrum

    PubMed Central

    Datko, Michael; Gougelet, Robert; Huang, Ming-Xiong; Pineda, Jaime A.

    2016-01-01

    Social and communicative impairments are among the core symptoms of autism spectrum disorders (ASD), and a great deal of evidence supports the notion that these impairments are associated with aberrant functioning and connectivity of various cortical networks. The present study explored the links between sources of MEG amplitude in various frequency bands and functional connectivity MRI in the resting state. The goal of combining these modalities was to use sources of neural oscillatory activity, measured with MEG, as functionally relevant seed regions for a more traditional pairwise fMRI connectivity analysis. We performed a seed-based connectivity analysis on resting state fMRI data, using seed regions derived from frequency-specific amplitude sources in resting state MEG data in the same nine subjects with ASD (10–17 years of age). We then compared fMRI connectivity among these MEG-source-derived regions between participants with autism and typically developing, age-matched controls. We used a source modeling technique designed for MEG data to detect significant amplitude sources in six frequency bands: delta (2–4 Hz), theta (4–8 Hz), alpha (8–12 Hz), beta (12–30 Hz), low gamma (30–60 Hz), and high gamma (60–120 Hz). MEG-derived source maps for each participant were co-registered in standard MNI space, and group-level source maps were obtained for each frequency. For each frequency band, the 10 largest clusters resulting from these t-tests were used as regions of interest (ROIs) for the fMRI functional connectivity analysis. Pairwise BOLD signal correlations were obtained between each pair of these ROIs for each frequency band. Each pairwise correlation was compared between the ASD and TD groups using t-tests. We also constrained these pairwise correlations to known network structures, resulting in a follow-up set of correlation matrices specific to each network we considered. Frequency-specific MEG sources had distinct patterns of fMRI resting

  5. OPTICAL SPECTRA OF CANDIDATE INTERNATIONAL CELESTIAL REFERENCE FRAME (ICRF) FLAT-SPECTRUM RADIO SOURCES

    SciTech Connect

    Titov, O.; Stanford, Laura M.; Johnston, Helen M.; Hunstead, Richard W.; Pursimo, T.; Jauncey, David L.; Maslennikov, K.

    2013-07-01

    Continuing our program of spectroscopic observations of International Celestial Reference Frame (ICRF) sources, we present redshifts for 120 quasars and radio galaxies. Data were obtained with five telescopes: the 3.58 m European Southern Observatory New Technology Telescope, the two 8.2 m Gemini telescopes, the 2.5 m Nordic Optical Telescope (NOT), and the 6.0 m Big Azimuthal Telescope of the Special Astrophysical Observatory in Russia. The targets were selected from the International VLBI Service for Geodesy and Astrometry candidate International Celestial Reference Catalog which forms part of an observational very long baseline interferometry (VLBI) program to strengthen the celestial reference frame. We obtained spectra of the potential optical counterparts of more than 150 compact flat-spectrum radio sources, and measured redshifts of 120 emission-line objects, together with 19 BL Lac objects. These identifications add significantly to the precise radio-optical frame tie to be undertaken by Gaia, due to be launched in 2013, and to the existing data available for analyzing source proper motions over the celestial sphere. We show that the distribution of redshifts for ICRF sources is consistent with the much larger sample drawn from Faint Images of the Radio Sky at Twenty cm (FIRST) and Sloan Digital Sky Survey, implying that the ultra-compact VLBI sources are not distinguished from the overall radio-loud quasar population. In addition, we obtained NOT spectra for five radio sources from the FIRST and NRAO VLA Sky Survey catalogs, selected on the basis of their red colors, which yielded three quasars with z > 4.

  6. Birth Prevalence of Autism Spectrum Disorders in the San Francisco Bay Area by Demographic and Ascertainment Source Characteristics

    ERIC Educational Resources Information Center

    Windham, Gayle C.; Anderson, Meredith C.; Croen, Lisa A.; Smith, Karen S.; Collins, John; Grether, Judith K.

    2011-01-01

    Using standardized methods for multi-source surveillance, we calculated the prevalence of autism spectrum disorders (ASD) among children born in a racially diverse region in 1994 or 1996 as 4.7/1000 live births. Children with ASD before age 9 were identified through chart abstraction at health-related sources; three-quarters were being served by…

  7. Recognition Memory, Self-Other Source Memory, and Theory-of-Mind in Children with Autism Spectrum Disorder

    ERIC Educational Resources Information Center

    Lind, Sophie E.; Bowler, Dermot M.

    2009-01-01

    This study investigated semantic and episodic memory in autism spectrum disorder (ASD), using a task which assessed recognition and self-other source memory. Children with ASD showed undiminished recognition memory but significantly diminished source memory, relative to age- and verbal ability-matched comparison children. Both children with and…

  8. Brief Report: The Role of Task Support in the Spatial and Temporal Source Memory of Adults with Autism Spectrum Disorder

    ERIC Educational Resources Information Center

    Bowler, Dermot M.; Gaigg, Sebastian B.; Gardiner, John M.

    2015-01-01

    Adults with autism spectrum disorder (ASD) show intact recognition (supported procedure) but impaired recall (unsupported procedure) of incidentally-encoded context. Because this has not been demonstrated for temporal source, we compared the temporal and spatial source memory of adults with ASD and verbally matched typical adults. Because of…

  9. Spectrum and anisotropy of cosmic rays at TeV-PeV-energies and contribution of nearby sources

    NASA Astrophysics Data System (ADS)

    Sveshnikova, L. G.; Strelnikova, O. N.; Ptuskin, V. S.

    2013-12-01

    The role of nearby galactic sources, the supernova remnants, in formation of observed energy spectrum and large-scale anisotropy of high-energy cosmic rays is studied. The list of these sources is made up based on radio, X-ray and gamma-ray catalogues. The distant sources are treated statistically as ensemble of sources with random positions and ages. The source spectra are defined based on the modern theory of cosmic ray acceleration in supernova remnants while the propagation of cosmic rays in the interstellar medium is described in the frameworks of galactic diffusion model. Calculations of dipole component of anisotropy are made to reproduce the experimental procedure of "two-dimensional" anisotropy measurements. The energy dependence of particle escape time in the process of acceleration in supernova remnants and the arm structure of sources defining the significant features of anisotropy are also taken into account. The essential new trait of the model is a decreasing number of core collapse SNRs being able to accelerate cosmic rays up to the given energy, that leads to steeper total cosmic ray source spectrum in comparison with the individual source spectrum. We explained simultaneously the new cosmic ray data on the fine structure of all particle spectrum around the knee and the amplitude and direction of the dipole component of anisotropy in the wide energy range 1 TeV-1 EeV. Suggested assumptions do not look exotic, and they confirm the modern understanding of cosmic ray origin.

  10. Diesel engine noise source identification based on EEMD, coherent power spectrum analysis and improved AHP

    NASA Astrophysics Data System (ADS)

    Zhang, Junhong; Wang, Jian; Lin, Jiewei; Bi, Fengrong; Guo, Qian; Chen, Kongwu; Ma, Liang

    2015-09-01

    As the essential foundation of noise reduction, many noise source identification methods have been developed and applied to engineering practice. To identify the noise source in the board-band frequency of different engine parts at various typical speeds, this paper presents an integrated noise source identification method based on the ensemble empirical mode decomposition (EEMD), the coherent power spectrum analysis, and the improved analytic hierarchy process (AHP). The measured noise is decomposed into several IMFs with physical meaning, which ensures the coherence analysis of the IMFs and the vibration signals are meaningful. An improved AHP is developed by introducing an objective weighting function to replace the traditional subjective evaluation, which makes the results no longer dependent on the subject performances and provides a better consistency in the meantime. The proposed noise identification model is applied to identifying a diesel engine surface radiated noise. As a result, the frequency-dependent contributions of different engine parts to different test points at different speeds are obtained, and an overall weight order is obtained as oil pan  >  left body  >  valve chamber cover  >  gear chamber casing  >  right body  >  flywheel housing, which provides an effectual guidance for the noise reduction.

  11. An atomic spectrum recorded with a single-molecule light source

    NASA Astrophysics Data System (ADS)

    Kiefer, Wilhelm; Rezai, Mohammad; Wrachtrup, Jörg; Gerhardt, Ilja

    2016-02-01

    A single molecule under cryogenic conditions allows one to realize an extremely bright and simultaneously narrow-band single-photon source. We present a review on the different excitation schemes of a single molecule and present the corresponding single-photon nature of the emitted light. Single-molecule spectroscopy has been recently interlinked with atomic spectroscopy. This optical interconnect among the different quantum systems might be enhanced by a so-called Faraday anomalous dispersion optical filter—an ideal tool for many experiments in quantum optics. We introduce our theoretical and experimental approach on these filters which are based on hot atomic sodium vapor. The electrical tunability together with the brightness of a single molecule allows us to record a full atomic spectrum of this filter with the single photons originating from a single-molecular emitter.

  12. Confirmation of a conspiracy - Dual-band VLBI maps of the flat-spectrum radio source 2021 + 614

    NASA Technical Reports Server (NTRS)

    Wittels, J. J.; Shapiro, I. I.; Cotton, W. D.

    1982-01-01

    VLBI observations at 3.6 and 13 cm wavelengths of the flat-spectrum radio source 2021 + 614 reveal two components, separated by about 6.5 + or - 0.6 milli-arcseconds along a position angle of 36 deg + or - 6 deg. The dual-band observations show that the two components have spectral indices of opposite signs, indicating that, as for 0735 + 178 (Cotton et al. 1980), the flat spectrum of 2021 + 614 is a result of the superposition of spectra from individual components, each having a peaked spectrum, presumably due to incoherent electron synchrotron radiation. If this situation is typical, then there is too large a percentage of flat-spectrum sources for the individual components in each to have independent characteristics.

  13. White LEDs as broad spectrum light sources for spectrophotometry: demonstration in the visible spectrum range in a diode-array spectrophotometric detector.

    PubMed

    Piasecki, Tomasz; Breadmore, Michael C; Macka, Mirek

    2010-11-01

    Although traditional lamps, such as deuterium lamps, are suitable for bench-top instrumentation, their compatibility with the requirements of modern miniaturized instrumentation is limited. This study investigates the option of utilizing solid-state light source technology, namely white LEDs, as a broad band spectrum source for spectrophotometry. Several white light LEDs of both RGB and white phosphorus have been characterized in terms of their emission spectra and energy output and a white phosphorus Luxeon LED was then chosen for demonstration as a light source for visible-spectrum spectrophotometry conducted in CE. The Luxeon LED was fixed onto the base of a dismounted deuterium (D(2) ) lamp so that the light-emitting spot was geometrically positioned exactly where the light-emitting spot of the original D(2) lamp is placed. In this manner, the detector of a commercial CE instrument equipped with a DAD was not modified in any way. As the detector hardware and electronics remained the same, the change of the deuterium lamp for the Luxeon white LED allowed a direct comparison of their performances. Several anionic dyes as model analytes with absorption maxima between 450 and 600 nm were separated by CE in an electrolyte of 0.01 mol/L sodium tetraborate. The absorbance baseline noise as the key parameter was 5 × lower for the white LED lamp, showing clearly superior performance to the deuterium lamp in the available, i.e. visible part of the spectrum. PMID:21077241

  14. Theoretical investigation of the spectrum and conversion efficiency of short wavelength extreme-ultraviolet light sources based on terbium plasmas

    SciTech Connect

    Sasaki, Akira; Nishihara, Katsunobu; Sunahara, Atsushi; Furukawa, Hiroyuki; Nishikawa, Takeshi; Koike, Fumihiro

    2010-12-06

    The emission spectrum and conversion efficiency of laser-produced terbium plasmas are theoretically investigated on the basis of computational atomic data. The theoretically calculated spectrum reproduces the main peak of observed spectrum at {lambda}=6.5 nm, which originates from 4d-4f transitions of near palladiumlike ions (Tb{sup 19+}). A simple model of the isothermal expansion of terbium plasma suggests that efficient emission can be achieved by pumping the plasma with a laser pulse at an intensity of approximately one order of magnitude greater than that used with tin sources at {lambda}=13.5 nm.

  15. On the Evolution of and High-Energy Emission from GHz-Peaked-Spectrum Sources

    SciTech Connect

    Stawarz, L.; Ostorero, L.; Begelman, M.C.; Moderski, R.; Kataoka, J.; Wagner, S.

    2007-12-18

    Here we discuss evolution and broad-band emission of compact (< kpc) lobes in young radio sources. We propose a simple dynamical description for these objects, consisting of a relativistic jet propagating into a uniform gaseous medium in the central parts of an elliptical host. In the framework of the proposed model, we follow the evolution of ultrarelativistic electrons injected from a terminal hotspot of a jet to expanding lobes, taking into account their adiabatic energy losses as well as radiative cooling. This allows us to discuss the broad-band lobe emission of young radio sources. In particular, we argue that the observed spectral turnover in the radio synchrotron spectra of these objects cannot originate from the synchrotron self-absorption process but is most likely due to free-free absorption effects connected with neutral clouds of interstellar medium engulfed by the expanding lobes and photoionized by active centers. We also find a relatively strong and complex high-energy emission component produced by inverse-Compton up-scattering of various surrounding photon fields by the lobes electrons. We argue that such high energy radiation is strong enough to account for several observed properties of GHz-peaked-spectrum (GPS) radio galaxies at UV and X-ray frequencies. In addition, this emission is expected to extend up to GeV (or possibly even TeV) photon energies and can thus be probed by several modern {gamma}-ray instruments. In particular, we suggest that GPS radio galaxies should constitute a relatively numerous class of extragalactic sources detected by GLAST.

  16. Seismic Monitoring of Bedload Transport in a Steep Mountain Catchment

    NASA Astrophysics Data System (ADS)

    Roth, D. L.; Finnegan, N. J.; Brodsky, E. E.; Turowski, J. M.; Wyss, C. R.; Badoux, A.

    2014-12-01

    Predicting river channel evolution relies on an understanding of when and at what rate coarse sediment moves in a channel. Unfortunately, our predictive abilities are limited by the logistical challenges and potential dangers inherent in current techniques for monitoring sediment transport during flood events, especially in steep, highly active landscapes. However, the use of seismic signals near rivers shows promise as a safe, low-cost method for studying sediment transport in these settings. Seismic signals near rivers are partially generated by both water turbulence and bedload sediment particles impacting the river bed during transport. Here, we attempt to isolate the seismic signatures of discharge and bedload transport in a steep mountain channel by examining high-frequency broadband seismic data from the well-studied Erlenbach stream (local slope of ~10%) in the Swiss Prealps. The extensive monitoring infrastructure and long history of sediment transport data at this field site allow us to independently constrain discharge, precipitation, and bedload transport during flood events over a two month field campaign. We perform a general linear least squares inversion of the seismic data, exploiting times with isolated rain or discharge events, to identify the spectral signals of water turbulence, rain, and bedload sediment transport. We find that the signal generated by rain exhibits a roughly broadband spectrum, while discharge and sediment transport exhibit power primarily in lower frequency bands. Our preliminary results indicate that with only precipitation and discharge data, it is possible to isolate the seismic signal of bedload transport in steep fluvial environments. Seismic studies may therefore have the potential to revolutionize our ability to monitor and understand these environments.

  17. Doppler shift measurement of Balmer-alpha line spectrum emission from a plasma in a negative hydrogen ion source

    SciTech Connect

    Wada, M. Doi, K.; Kisaki, M.; Nakano, H.; Tsumori, K.; Nishiura, M.

    2015-04-08

    Balmer-α light emission from the extraction region of the LHD one-third ion source has shown a characteristic Doppler broadening in the wavelength spectrum detected by a high resolution spectrometer. The spectrum resembles Gaussian distribution near the wavelength of the intensity peak, while it has an additional component of a broader foot. The measured broadening near the wavelength of the intensity peak corresponds to 0.6 eV hydrogen atom temperature. The spectrum exhibits a larger expansion in the blue wing which becomes smaller when the line of sight is tilted toward the driver region from the original observation axis parallel to the plasma grid. A surface collision simulation model predicts the possibility of hydrogen reflection at the plasma grid surface to form a broad Balmer-α light emission spectrum.

  18. Properties of the integrated spectrum of serendipitous 2XMM catalog sources

    NASA Astrophysics Data System (ADS)

    Chaudhary, P.; Brusa, M.; Hasinger, G.; Merloni, A.; Comastri, A.

    2010-07-01

    Aims: Our analysis is aimed at characterizing the properties of the integrated spectrum of active galactic nuclei (AGNs), such as the ubiquity of the Fe Kα emission in AGNs and the dependence of the spectral parameters on the X-ray luminosity and redshift. Methods: We selected 2646 point sources from the 2XMM catalog at high galactic latitude (|BII| > 25 degrees) and with the sum of EPIC-PN and EPIC-MOS 0.2-12 keV counts greater than 1000. Redshifts were obtained for 916 sources from the Nasa's Extragalactic Database. We excluded sources classified as HII regions, groups/clusters, star-forming/starburst galaxies. The final sample consists of 507 AGN. Individual source spectra were summed in the observed frame to compute the integrated spectra in different redshift and luminosity bins over the range 0 < z < 5. Detailed analysis of these spectra used appropriately normalized background spectra and exposure time-weighted response and ancillary files. Results: We find that the narrow Fe Kα line at 6.4 keV is significantly detected up to z = 1. The line equivalent width decreases with increasing X-ray luminosity in the 2-10 keV band (“Iwasawa-Taniguchi effect”). The anticorrelation is characterized by the relation log(EWFe) = (1.66±0.09) + (-0.43±0.07) log(LX,44), where EWFe is the rest frame equivalent width of the neutral iron Kα line in eV and LX,44 is the 2-10 keV X-ray luminosity in units of 1044 erg s-1. The equivalent width is nearly independent of redshift up to z ~ 0.8 with an average value of 101±40 (rms dispersion) eV in the luminosity range 43.5 ≤ log LX ≤ 44.5. Our analysis also confirms the hardening of the spectral indices at low luminosities, implying a dependence of obscuration on luminosity. Conclusions: We confirm that the neutral narrow Fe Kα line is an almost ubiquitous feature of AGNs. We find compelling evidence supporting the “Iwasawa-Taniguchi effect” over a redshift interval larger than probed in any previous study. We detect

  19. Source counts in the chronometric cosmology

    NASA Technical Reports Server (NTRS)

    Wright, Edward L.

    1987-01-01

    The chronometric cosmology (a static, homogeneous, and hence nonevolving model proposed by Segal) is unable to explain the steep number versus flux law N(S) for quasars or extragalactic radio sources. The explanation given by Segal to explain the steep N(S) laws gives at best a small increase over a Euclidean N(S) proportional to S exp-1.5, and requires that the source spectral index be close to but greater than zero to create the effect. For typical radio spectral indices of roughly 0.75, the chronometric model cannot give a quantitative fit to the excess number of 1-3 Jy sources that the standard cosmology attributes to evolution. Thus the chronometric model can explain a steep N(S) law only for flat spectrum sources, while the observations show the steepest N(S) law for steep spectrum sources. Furthermore, the observed N(S) law for ultraviolet excess quasars is steeper than the steepest possible chronometric prediction.

  20. The integrated radio continuum spectrum of M33 - Evidence for free-free absorption by cool ionized gas

    NASA Technical Reports Server (NTRS)

    Israel, F. P.; Mahoney, M. J.; Howarth, N.

    1992-01-01

    We present measurements of the integrated radio continuum flux density of M33 at frequencies between 22 and 610 MHz and discuss the radio continuum spectrum of M33 between 22 MHz and 10 GHz. This spectrum has a turnover between 500 and 900 MHz, depending on the steepness of the high frequency radio spectrum of M33. Below 500 MHz the spectrum is relatively flat. We discuss possible mechanisms to explain this spectral shape and consider efficient free-free absorption of nonthermal emission by a cool (not greater than 1000 K) ionized gas to be a very likely possibility. The surface filling factor of both the nonthermal and the thermal material appears to be small (of order 0.001), which could be explained by magnetic field/density fluctuations in the M 33 interstellar medium. We briefly speculate on the possible presence of a nuclear radio source with a steep spectrum.

  1. Bedload transport calculations for steep streams

    NASA Astrophysics Data System (ADS)

    Rickenmann, D.; Turowski, J. M.; Nitsche, M.; Badoux, A.; Raymond, M.

    2011-12-01

    Due to large flow resistance, bedload transport calculations for steep streams often result in a clear overestimation of observed bedload. This contribution discusses the importance of introducing a proper partitioning of flow resistance for bedload transport calculations for steep streams. Several approaches to account for additional flow resistance were tested. They were used with the same reference bedload transport equation, and the predictions were then compared with bedload observations for a number of mountain streams. To this end, we measured the streambed parameters required for these calculations for flood events in 7 mountain rivers and torrents and for long-term discharge and bedload data of 6 torrents. The streams have channel slopes from 2 to 19 %, catchment areas from 0.5 to 170 km2, and are all located in the Swiss Alps. Some approaches give better predictions for rougher streams and for the extreme flood events than for less rough streams and for the long-term data from the torrents (Nitsche et al., 2011). An example for this prediction pattern is the approach of Yager et al. (2007) which is the one mostly based on physical principles for flow resistance calculations. This approach requires additional field measurements regarding the key roughness parameters. On the other hand considering all the bedload data, the empirical approach of Rickenmann and Recking (2011) appears to give the best overall predictions. This approach has the advantage to be easy to apply. Further bedload transport calculations were made for steep streams upstream of water intakes in the Swiss Alps where information is available on both discharge and annual sediment yield. If no correction for high flow resistance is made, calculated bedload transport rates with many equations tend to result in elevated bedload concentrations which are expected for debris flood or debris flow conditions. Some observations from the widespread flood events of August 2005 in Switzerland

  2. Dipping longwalls in semi-steep seams

    SciTech Connect

    Dietrich, J.; Delcruzel, J.

    1982-07-01

    Use of high productivity equipment designed for level seams gives encouraging results in the semi-steep seams of the Lorraine Basin. In the Lorraine coal basin, this type of coal seam has been mined by ascending horizontal slices with back filling, using two basic methods: (1) multiple front faces in a stepped pattern using drilling, blasting, and timber support. (2) longwall mining to the rise, which is usable in favorable conditions of seam width and ground stability. This method gives face productivities up to 15 metric tons per manshift. The technical progress that has been made in recent years in the area of support, coal cutting, and coal clearance has allowed the mechanization of steep and semi-steep seams. A new method was started in 1981 at the Simon colliery. A caving longwall mining method is used. The dip of the seam averages 33/sup 0/. A two-entry retreat system was selected. The first longwalls were worked at heights of 3 to 3.5 meters (10 to 11 feet). Most of the equipment is similar to that used for mining flat seams. High performance four-leg, self-advancing chock supports are used. In order to meet certain requirements imposed by the dip, the supports have the following particular features: (1) The shields are positioned close to each other to increase support. Also, to reduce caving dangers, side flaps are mounted on the canopy, the rear shield, and the base. (2) The shields are advanced in a staggered fashion to maintain proper roof support after shearing. (3)Telescopic front shields can be brought down onto the spill plates of the conveyor to isolate the face line from the travel way. This provides extra protection against falling materials while giving access to the face.

  3. Rough and Steep Terrain Lunar Surface Mobility

    NASA Technical Reports Server (NTRS)

    Wilcox, Brian

    2005-01-01

    In the summer of 2004, the NASA Exploration Systems Mission Directorate conducted an open call for projects relevant to human and robotic exploration of the Earth-Moon and Mars systems. A project entitled 'Rough and Steep Terrain Lunar Surface Mobility' was submitted by JPL and accepted by NASA. The principal investigator of this project describes the robotic vehicle being developed for this effort, which includes six 'wheels-on-legs' so that it can roll efficiently on relatively smooth terrain but walk (using locked wheels as footpads) when "the going gets rough".

  4. Electron heat transport down steep temperature gradients

    SciTech Connect

    Matte, J.P.; Virmont, J.

    1982-12-27

    Electron heat transport is studied by numerically solving the Fokker-Planck equation, with a spherical harmonic representation of the distribution function. The first two terms (f/sub 0/, f/sub 1/) suffice, even in steep temperature gradients. Deviations from the Spitzer-Haerm law appear for lambda/L/sub T/ ((mean free path)/(temperature gradient length))> or approx. =0.01, as a result of non-Maxwellian f/sub 0/. For lambda/L/sub T/> or approx. =1, the heat flux is (1/3) of the free-streaming value. In intermediate cases, a harmonic law describes well the hottest part of the plasma.

  5. The design of a source to simulate the gamma-ray spectrum emitted by a radioisotope thermoelectric generator

    NASA Technical Reports Server (NTRS)

    Reier, M.

    1972-01-01

    A simulated source was designed to duplicate the gamma spectrum of a uniform cylindrical 2200-watt Pu02 radioisotope thermoelectric generator containing 81% Pu-238 and 1.2 ppm Pu-236. Gamma rays from the decay of Pu-238, Am-241, Pu-239, and the 0-18(alpha,n)Ne-21 reaction were catalogued in broad energy groups. Two 46- and one 22-mc Th-228 sources provided simulation at various times in the life of the fuel capsule up to 18 years, which covers the time span of an outer planet mission. Emission from Th-228 represents the overwhelming contribution of the gamma spectrum after the first few years. The sources, in the form of 13-inch rods, were placed in a concentric hole in a cylinder of depleted uranium, which provided shielding equivalent to the self-shielding of the fuel capsule. The thickness of the U-238 cylinder (0.55cm) was determined by Monte Carlo calculations to insure that the spectrum emerging from the simulated source matched that of the fuel capsule.

  6. H216O absorption spectrum between 22250 and 22800 cm-1: Fourier transform spectroscopy with bright light source

    NASA Astrophysics Data System (ADS)

    Serduykov, V. I.; Sinitsa, L. N.; Vasil'chenko, S. S.; Bykov, A. D.; Kruglova, T. V.; Polovtseva, E. R.; Scherbakov, A. P.

    2014-11-01

    Measurements of water vapor absorption spectra in the visible spectral region near 0.44 mkm are performed using FTspectrometer IFS-125M and Light-emitting diode (LED) as source of radiation. Water vapor spectrum has been obtained by averaging over 17136 scans recorded at 34,8 m optical path length, temperature 24 ± 1 C and pressure of sample 24,8 mBar. Due to strong emission of LED source it was possible to achieve signal-to-noise ratio about 104 and to record weak lines with intensities of 6 10-27 cm/molecule. Comparisons with results of early works are made.

  7. Xenon N4,500 Auger spectrum - a useful calibration source

    SciTech Connect

    Carroll, T.X.; Bozek, J.D.; Kukk, E.; Myrseth, V.; Saethre, L.J.; Thomas, T.D.; Wiesner, Karoline

    2002-02-06

    In the xenon N4,5OO Auger spectrum there are 19 prominent lines ranging from 8 to 36 eV that provide a convenient set of standards for calibrating electron spectrometers. Combining optical data with recent measurements of this spectrum gives energies for these lines that are absolutely accurate to 11 meV. For most lines the relative accuracy is better than 1 meV; for a few it is about 3 meV. The spin-orbit splitting of the xenon 4d lines is measured to be 1979.0 +- 0.5meV.

  8. Robotic chair at steep and narrow stairways

    NASA Astrophysics Data System (ADS)

    Imazato, Masahiro; Yamaguchi, Masahiro; Moromugi, Shunji; Ishimatsu, Takakazu

    2007-12-01

    A robotic chair is developed to support mobility of elderly and disabled people living in the house where steep and narrow stairways are installed. In order to deal with such mobility problem the developed robotic chair has a compact original configuration. The robotic chair vertically moves by actuation of electric cylinders and horizontally moves by push-pull operation given by a care-giver. In order to navigate safely every action of the chair is checked by the operator. Up-and-down motions of the robotic chair on the stairway are executed through combinations of motor and cylinder actuations. Performance of the robotic chair was evaluated through two kinds of experiments. The excellent ability of the robotic chair could be confirmed through these experiments.

  9. Cathode luminescence light source for broadband applications in the visible spectrum

    NASA Technical Reports Server (NTRS)

    Foster, John E. (Inventor)

    2007-01-01

    A device and method for generating cathode luminescence is provided. The device and method generate broad spectrum electromagnetic radiation in the visible. A layer of particles, such as quartz or alumina powder, is exposed to electrons in a plasma discharge. Surface excitation of these particles or the generations/excitation of F-center sites give rise to luminescence.

  10. Measurement of steep aspheric surfaces using an anamorphic probe

    NASA Astrophysics Data System (ADS)

    Biswas, Amiya; Coupland, Jeremy

    2008-04-01

    Synthetic aperture interferometry has been previously proposed as a possible in-process method to measure aspheric form (R. Tomlinson, Appl. Opt.42, 701, 2003.APOPAI0003-693510.1364/AO.42.000701). Preliminary demonstration utilized a scanning probe consisting of a pair of bare single mode fibers to perform source and receive functions. It was found that this probe did not have sufficient numerical aperture (NA) to measure steep surfaces and that simply increasing the NA decreases the light gathering efficiency substantially. In this paper, we introduce supplementary optics to increase the NA, and the light gathering efficiency has been increased by adopting an anamorphic design. A spherical test optic of known form is measured to demonstrate the capability of the new probe design.

  11. Ducted kinetic Alfven waves in plasma with steep density gradients

    SciTech Connect

    Houshmandyar, Saeid; Scime, Earl E.

    2011-11-15

    Given their high plasma density (n {approx} 10{sup 13} cm{sup -3}), it is theoretically possible to excite Alfven waves in a conventional, moderate length (L {approx} 2 m) helicon plasma source. However, helicon plasmas are decidedly inhomogeneous, having a steep radial density gradient, and typically have a significant background neutral pressure. The inhomogeneity introduces regions of kinetic and inertial Alfven wave propagation. Ion-neutral and electron-neutral collisions alter the Alfven wave dispersion characteristics. Here, we present the measurements of propagating kinetic Alfven waves in helium helicon plasma. The measured wave dispersion is well fit with a kinetic model that includes the effects of ion-neutral damping and that assumes the high density plasma core defines the radial extent of the wave propagation region. The measured wave amplitude versus plasma radius is consistent with the pile up of wave magnetic energy at the boundary between the kinetic and inertial regime regions.

  12. Ferroelectric gate tunnel field-effect transistors with low-power steep turn-on

    NASA Astrophysics Data System (ADS)

    Lee, M. H.; Wei, Y.-T.; Lin, J.-C.; Chen, C.-W.; Tu, W.-H.; Tang, M.

    2014-10-01

    Using a ferroelectric PbZrTiO3 gate stack, the range of the steep subthreshold swing in tunnel field-effect transistors was extended by 3.5 orders of magnitude demonstrating an improvement in the swing (by approximately double the slope). The drain conductance (gd) shows only 16% enhancement with large V DS (˜-1.5V) indicates internal voltage amplification with ferroelectric negative capacitance effect beneficial to small lateral drain-source bias voltages (-0.1 V). The concept of coupling the ferroelectric polarization is proposed. The power consumption is also discussed in low-power applications of steep subthreshold slope devices.

  13. Determination of Jet Noise Radiation Source Locations using a Dual Sideline Cross-Correlation/Spectrum Technique

    NASA Technical Reports Server (NTRS)

    Allen, C. S.; Jaeger, S. M.

    1999-01-01

    The goal of our efforts is to extrapolate nearfield jet noise measurements to the geometric far field where the jet noise sources appear to radiate from a single point. To accomplish this, information about the location of noise sources in the jet plume, the radiation patterns of the noise sources and the sound pressure level distribution of the radiated field must be obtained. Since source locations and radiation patterns can not be found with simple single microphone measurements, a more complicated method must be used.

  14. Preferential Transport of Coarse Sediment in Steep Channels

    NASA Astrophysics Data System (ADS)

    Moody, J. A.

    2002-12-01

    Wildfires can change a source-limited system to a transport-limited system especially in steep mountainous terrain where the erosion threshold has been lowered by a wildfire. Such a situation occurred in the Buffalo and Spring Creek watersheds after the 1996 Buffalo Creek Fire, when 1 to 3 m of sediment was deposited in two relatively steep main channels (channel slope equal to 0.02 and 0.04 respectively) after an intense rainstorm of about 110 mm/hour. The bed material was a mixture of coarse grain sizes in both channels. The median size class in Buffalo Creek was 2-4 mm and in Spring Creek it was 4-8 mm. Bedload transport samples were collected in the field using a US BLH-84 sampler for discharge ranging from 0.0036 to 5.2 m3/s. The particle-size distributions for the bedload samples were analyzed to investigate sediment mobility. For each size class, a ratio was calculated equal to the percent of sediment transported divided by the percent of sediment available for transport. The percent available for transport was determined by recalculating the particle-size distribution of the bed material by excluding those sizes that did not move. The average ratio for the median-size class was 1.00 (13 samples) for Buffalo Creek and 0.94 (12 samples) for Spring Creek. In the Buffalo Creek channel, the average ratio for sizes larger than the median size (greater than 2-4 mm) was less than 1.00. Whereas in the Spring Creek channel, the data indicate a preferential transport of sizes larger than the median size with the ratio ranging from 0.86 to 2.22 and averaging 1.42 for the 8-16 mm size class and from 0.37 to 3.86 and averaging 1.28 for the 16-32 mm size class. Possible causes for the difference between Buffalo and Spring Creeks are: 1) the smaller value of the relative roughness (particle diameter/flow depth) in Buffalo Creek, 2) the less steep bed slope in Buffalo Creek, and 3) the difference in the sediment-size distribution

  15. Factors Affecting VUV Emission Spectrum near Lyman-{alpha} from a Hydrogen Plasma Source

    SciTech Connect

    Ogino, K.; Kasuya, T.; Shimamoto, S.; Wada, M.; Kimura, Y.; Nishiura, M.

    2011-09-26

    Vacuum ultra violet (VUV) emission spectra from plasmas near walls of different metallic materials were measured to estimate the effect upon the local production rate of vibrational excited hydrogen molecules due to plasma wall interaction. Among Cu, Mo, Ni, Ta and Ti, the intensity of band spectrum around Lyman-{alpha} had become the largest when Cu wall was used while it was the smallest for Ti. The role of particle reflection from the plasma electrode surface upon the H{sup -} production by a pure electron volume process is discussed.

  16. Modified blackbody radiation spectrum of a selective emitter with application to incandescent light source design.

    PubMed

    Matsumoto, Takahiro; Tomita, Makoto

    2010-06-21

    Using a selective emitter with high emissivity in the visible wavelength region and low emissivity in the infrared wavelength region, we reduced the infrared contribution to the blackbody radiation spectrum and shifted the peak emission to shorter wavelengths. We made precise measurements of thermal radiation loss. The conversion efficiency from input electric power to visible light radiation was quantitatively evaluated with high accuracy. Using the proposed selective emitter, the conversion efficiencies in excess of 95% could be produced. Our conclusions pave the way for the design of incandescent lamps with luminous efficiencies exceeding 400 lm/W. PMID:20588588

  17. A waveguide high-pass filter system for measuring the spectrum of pulsed terahertz sources

    NASA Astrophysics Data System (ADS)

    Glyavin, M. Yu.; Goykhman, M. B.; Gromov, A. V.; Palitsin, A. V.; Panin, A. N.; Rodin, Yu. V.; Fil'chenkov, S. E.

    2016-05-01

    We propose a system for measuring spectra of terahertz (THz) pulses, including single pulses, which is based on high-pass filters (HPFs). The system consists of channels for measuring amplitudes of pulses (initial pulses and those transmitted via HPFs with different cutoff frequencies) and an algorithm for processing of the obtained data. The pulse spectrum is restored by using the iteration method or the amplitude-frequency method. The iteration method of spectrum restoration is applicable in the range of THz pulse durations from 10-9 s to 10-7 s. The amplitude-frequency method is applicable to THz pulses with durations exceeding 10-8 s. The system for measuring of THz pulse spectra was simulated by using the characteristics of specially developed waveguide HPFs. The relative simulation error of determining the central frequency by the amplitude-frequency method is equal to 2 · 10-6 for THz pulse durations of 10-5 s and longer.

  18. Investigation of a complete sample of flat spectrum radio sources from the S5 survey

    NASA Astrophysics Data System (ADS)

    Eckart, A.; Witzel, A.; Biermann, P.; Johnston, K. J.; Simon, R.; Schalinski, C.; Kuhr, H.

    1986-11-01

    An analysis of 13 extragalactic sources of the S5 survey with flux densities greater than or equal to 1 Jy at 4990 MHz, mapped with milliarcsecond resolution at 1.6 and 5 GHz by means of VLBI, is presented. All sources appear to display multiple components dominated in flux density at 6 cm by a core component which is self-absorbed at 18 cm. Comparison of the measured to predicted X-ray flux density of the core radio components suggests that all sources should display bulk relativistic motion with small angles to the line of sight, and four sources show rapid changes in their radio structures which can be interpreted as apparent superliminal motion.

  19. The gamma ray continuum spectrum from the galactic center disk and point sources

    NASA Technical Reports Server (NTRS)

    Gehrels, Neil; Tueller, Jack

    1992-01-01

    A light curve of gamma-ray continuum emission from point sources in the galactic center region is generated from balloon and satellite observations made over the past 25 years. The emphasis is on the wide field-of-view instruments which measure the combined flux from all sources within approximately 20 degrees of the center. These data have not been previously used for point-source analyses because of the unknown contribution from diffuse disk emission. In this study, the galactic disk component is estimated from observations made by the Gamma Ray Imaging Spectrometer (GRIS) instrument in Oct. 1988. Surprisingly, there are several times during the past 25 years when all gamma-ray sources (at 100 keV) within about 20 degrees of the galactic center are turned off or are in low emission states. This implies that the sources are all variable and few in number. The continuum gamma-ray emission below approximately 150 keV from the black hole candidate 1E1740.7-2942 is seen to turn off in May 1989 on a time scale of less than two weeks, significantly shorter than ever seen before. With the continuum below 150 keV turned off, the spectral shape derived from the HEXAGONE observation on 22 May 1989 is very peculiar with a peak near 200 keV. This source was probably in its normal state for more than half of all observations since the mid-1960's. There are only two observations (in 1977 and 1979) for which the sum flux from the point sources in the region significantly exceeds that from 1E1740.7-2942 in its normal state.

  20. ANOMALOUSLY STEEP REDDENING LAW IN QUASARS: AN EXCEPTIONAL EXAMPLE OBSERVED IN IRAS 14026+4341

    SciTech Connect

    Jiang Peng; Zhou Hongyan; Ji Tuo; Shu Xinwen; Liu Wenjuan; Dong Xiaobo; Wang Huiyuan; Wang Tinggui; Wang Jianguo

    2013-06-15

    A fraction of the heavily reddened quasars require a reddening curve that is even steeper than that of the Small Magellanic Cloud. In this paper, we thoroughly characterize the anomalously steep reddening law in quasars via an exceptional example observed in IRAS 14026+4341. By comparing the observed spectrum to the quasar composite spectrum, we derive a reddening curve in the rest-frame wavelength range of 1200-10000 A. It has a steep rise at wavelengths shorter than 3000 A, but no significant reddening at longer wavelengths. The absence of dust reddening in the optical continuum is confirmed by the normal broad-line Balmer decrement (the H{alpha}/H{beta} ratio) in IRAS 14026+4341. The anomalous reddening curve can be satisfactorily reproduced with a dust model containing silicate grains in a power-law size distribution, dn(a)/da{proportional_to}a {sup -1.4}, truncated at a maximum size of a{sub max} = 70 nm. The unusual size distribution may be caused by the destruction of large 'stardust' grains by quasar activities or a different dust formation mechanism (i.e., the in situ formation of dust grains in quasar outflows). It is also possible that the analogies of the dust grains observed near the Galactic center are responsible for the steep reddening curve. In addition, we find that IRAS 14026+4341 is a weak emission-line quasar (i.e., PHL 1811 analogies) with heavy dust reddening and blueshifted broad absorption lines.

  1. Balmer-α spectrum measurements of the LHD one-third ion source

    NASA Astrophysics Data System (ADS)

    Wada, M.; Kenmotsu, T.; Kisaki, M.; Nakano, H.; Nishiura, M.; Tsumori, K.

    2016-02-01

    Wavelength spectra of Balmer-α light from plasmas in the extraction region of the Large Helical Device-R&D negative ion source, or the LHD one-third ion source have exhibited a blue shift as a negative bias voltage was applied to the plasma grid. The blue shift increased as the negative bias voltage with respect to the local plasma potential was increased. The measured spectra were compared with the velocity distributions of surface reflected hydrogen atoms calculated by atomic collisions in amorphous target code. The arc power and the source H2 pressure also affected the shift and broadening in the observed Balmer-α spectra. The possibility of identifying the negative hydrogen ions produced at the low work function plasma grid surface by high resolution spectroscopy is discussed.

  2. Balmer-α spectrum measurements of the LHD one-third ion source.

    PubMed

    Wada, M; Kenmotsu, T; Kisaki, M; Nakano, H; Nishiura, M; Tsumori, K

    2016-02-01

    Wavelength spectra of Balmer-α light from plasmas in the extraction region of the Large Helical Device-R&D negative ion source, or the LHD one-third ion source have exhibited a blue shift as a negative bias voltage was applied to the plasma grid. The blue shift increased as the negative bias voltage with respect to the local plasma potential was increased. The measured spectra were compared with the velocity distributions of surface reflected hydrogen atoms calculated by atomic collisions in amorphous target code. The arc power and the source H2 pressure also affected the shift and broadening in the observed Balmer-α spectra. The possibility of identifying the negative hydrogen ions produced at the low work function plasma grid surface by high resolution spectroscopy is discussed. PMID:26931989

  3. Design and experimental realization of a highly efficient superfluorescent fiber source with flat C-band spectrum

    NASA Astrophysics Data System (ADS)

    Arabanian, Atoosa Sadat; Massudi, Reza

    2015-09-01

    Design and experimental realization of C-band superfluorescent fiber sources using a well-designed high reflector/filter of fiber Bragg grating (FBG) in three configurations, namely double-pass forward (DPF), double-pass backward (DPB), and DPF+DPB, is realized. Using a numerical method, the optimum length and peak absorption coefficient of erbium-doped fiber as well as the optimum specifications of FBG, i.e., its 3-dB bandwidth and central wavelength, are calculated. Our numerical calculations illustrate that an appropriate design may result in a flattened amplified spontaneous emission (ASE) output spectrum with a 3-dB bandwidth of about 22 nm and a central wavelength of 1550 nm. Furthermore, the peak power of the flattened ASE spectrum is 16 dBm larger than the power at a wavelength of 1530 nm that is beneficial for increasing the 3-dB bandwidth. The experimental results show that using an optimum design, there are negligible differences between ASE output spectra acquired by different double-pass configurations. However, the DPB configuration has a higher efficiency as compared with other configurations and can provide a C-band superfluorescent fiber source with a simultaneously good spectral flatness, <0.73 dB, high output power of 12 dBm, and maximum 3-dB bandwidth of about 22 nm.

  4. PERCENT AGRICULTURAL LAND COVER ON STEEP SLOPES (FUTURE)

    EPA Science Inventory

    Clearing land for agriculture tends to increase soil erosion. The amount of erosion is related to the steepness of the slope, farming methods used and soil type. High amounts of agriculture on steep slopes can increase the amount of soil erosion leading to increased sediment in ...

  5. On the nature of bright compact radio sources at z>4.5

    NASA Astrophysics Data System (ADS)

    Coppejans, Rocco; Frey, Sándor; Cseh, Dávid; Müller, Cornelia; Paragi, Zsolt; Falcke, Heino; Gabányi, Krisztina É.; Gurvits, Leonid I.; An, Tao; Titov, Oleg

    2016-09-01

    High-redshift radio-loud quasars are used to, among other things, test the predictions of cosmological models, set constraints on black hole growth in the early universe and understand galaxy evolution. Prior to this paper, 20 extragalactic radio sources at redshifts above 4.5 have been imaged with very long baseline interferometry (VLBI). Here we report on observations of an additional ten z > 4.5 sources at 1.7 and 5 GHz with the European VLBI Network (EVN), thereby increasing the number of imaged sources by 50 per cent. Combining our newly observed sources with those from the literature, we create a substantial sample of 30 z > 4.5 VLBI sources, allowing us to study the nature of these objects. Using spectral indices, variability and brightness temperatures, we conclude that of the 27 sources with sufficient information to classify, the radio emission from one source is from star formation, 13 are flat-spectrum radio quasars and 13 are steep-spectrum sources. We also argue that the steep-spectrum sources are off-axis (unbeamed) radio sources with rest-frame self-absorption peaks at or below GHz frequencies and that these sources can be classified as gigahertz peaked-spectrum (GPS) and megahertz peaked-spectrum (MPS) sources.

  6. Disk Reflection Signatures in the Spectrum of the Bright Z-Source GX 340+0

    NASA Astrophysics Data System (ADS)

    D'Aì, A.; Iaria, R.; Di Salvo, T.; Matt, G.; Robba, N. R.

    2009-03-01

    We present the preliminary results of a 50 ks long XMM-Newton observation of the bright Z-source GX 340+0. In this Letter, we focus on the study of a broad asymmetric emission line in the Fe Kα energy band, whose shape is clearly resolved and compatible with a relativistically smeared profile arising from reflection on a hot accretion disk extending close to the central accreting neutron star. By combining temporal and spectral analysis, we are able to follow the evolution of the source along its horizontal branch. However, despite a significant change in the continuum emission and luminosity, the line profile does not show any strong correlated variation. This broad line is produced by recombination of highly ionized iron (Fe XXV) at an inferred inner radius close to 13R g, while the fit requires a high value for the outer disk radius. The inclination of the source is extremely well constrained at 35°, while the emissivity index is -2.50. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.

  7. Potential changes of wave steepness and occurrence of rogue waves

    NASA Astrophysics Data System (ADS)

    Bitner-Gregersen, Elzbieta M.; Toffoli, Alessandro

    2015-04-01

    Wave steepness is an important characteristic of a sea state. It is also well established that wave steepness is one of the parameter responsible for generation of abnormal waves called also freak or rogue waves. The study investigates changes of wave steepness in the past and future wave climate in the North Atlantic. The fifth assessment report IPCC (2013) uses four scenarios for future greenhouse gas concentrations in the atmosphere called Representative Concentration Pathways (RCP). Two of these scenarios RCP 4.5 and RCP 8.5 have been selected to project future wave conditions in the North Atlantic. RCP 4.5 is believed to achieve the political target of a maximum global mean temperature increase of 2° C while RPC 8.5 is close to 'business as usual' and expected to give a temperature increase of 4° C or more. The analysis includes total sea, wind sea and swell. Potential changes of wave steepness for these wave systems are shown and compared with wave steepness derived from historical data. Three historical data sets with different wave model resolutions are used. The investigations show also changes in the mean wind direction as well as in the relative direction between wind sea and swell. Consequences of wave steepness changes for statistics of surface elevation and generation of rogue waves are demonstrated. Uncertainties associated with wave steepness projections are discussed.

  8. Doubly Stochastic Earthquake Source Model: "Omega-Square" Spectrum and Low High-Frequency Directivity Revealed by Numerical Experiments

    NASA Astrophysics Data System (ADS)

    Gusev, A. A.

    2014-10-01

    Since its formulation in 1967-1970, the classical ω -2 model of earthquake source spectrum awaits a consistent theoretical foundation. To obtain one, stochastic elements are incorporated both into the final structure of the fault and into the mode of rupture propagation. The main components of the proposed "doubly stochastic" model are: (1) the Andrews's concept, that local stress drop over a fault is a random self-similar field; (2) the concept of rupture with running slip pulse, after Heaton; (3) the hypothesis that a rupture front is a tortuous, multiply connected ("lacy") fractal polyline that occupies a strip of finite width close to the slip-pulse width; and (4) the assumption that the propagation distance of fault-guided, mostly Rayleigh waves from a failing spot on a fault is determined by the slip-pulse width. Waveforms produced by this model are determined based on the fault asperity failure model after Das and Kostrov. Properties of the model are studied by numerical experiments. At high frequency, simulated source spectra behave as ω -2, and acceleration spectra are flat. Their level, at a given seismic moment and rms stress drop, is inversely related to the relative width of the slip pulse. When this width is relatively low, a well-defined second corner frequency (lower cutoff of acceleration spectrum) is seen. The model shows clear dependence of propagation-related directivity on frequency. Between the first and the second corner frequency, amplitude spectra are strongly enhanced for the forward direction; whereas, above the second corner frequency, directivity is significantly reduced. Still, it is not inhibited totally, suggesting incomplete incoherence of the simulated radiator at high frequencies.

  9. ACTIVE GALACTIC NUCLEI SELECTED FROM GALEX SPECTROSCOPY: THE IONIZING SOURCE SPECTRUM AT z {approx} 1 ,

    SciTech Connect

    Barger, Amy J.; Cowie, Lennox L. E-mail: cowie@ifa.hawaii.ed

    2010-08-01

    We use a complete sample of Ly{alpha}-emission-line-selected active galactic nuclei (AGNs) obtained from nine deep blank fields observed with the grism spectrographs on the Galaxy Evolution Explorer (GALEX) satellite to measure the normalization and the spectral shape of the AGN contribution to the ionizing background (rest-frame wavelengths 700-900 A) at z {approx} 1. Our sample consists of 139 sources selected in the redshift range z = 0.65-1.25 in the near-ultraviolet (NUV; 2371 A central wavelength) channel. The area covered is 8.2 deg{sup 2} to a NUV magnitude of 20.5 (AB) and 0.92 deg{sup 2} at the faintest magnitude limit of 21.8. The GALEX AGN luminosity function agrees well with those obtained using optical and X-ray AGN samples, and the measured redshift evolution of the ionizing volume emissivity is similar to that previously obtained by measuring the GALEX far-ultraviolet (FUV; 1528 A central wavelength) magnitudes of an X-ray-selected sample. For the first time, we are able to construct the shape of the ionizing background at z {approx} 1 in a fully self-consistent way.

  10. Improved numerical modeling of morphodynamics of rivers with steep banks

    NASA Astrophysics Data System (ADS)

    Langendoen, Eddy J.; Mendoza, Alejandro; Abad, Jorge D.; Tassi, Pablo; Wang, Dongchen; Ata, Riadh; El kadi Abderrezzak, Kamal; Hervouet, Jean-Michel

    2016-07-01

    The flow and sediment transport processes near steep streambanks, which are commonly found in meandering, braided, and anastomosing stream systems, exhibit complex patterns that produce intricate interactions between bed and bank morphologic adjustment. Increasingly, multi-dimensional computer models of riverine morphodynamics are used to aid in the study of these processes. A number of depth-averaged two-dimensional models are available to simulate morphologic adjustment of both bed and banks. Unfortunately, these models use overly simplified conceptual models of riverbank erosion, are limited by inflexible structured mesh systems, or are unable to accurately account for the flow and sediment transport adjacent to streambanks of arbitrary geometry. A new, nonlinear model is introduced that resolves these limitations. The model combines the river morphodynamics computer models TELEMAC-2D and SISYPHE of the open source TELEMAC-MASCARET suite of solvers with the bank erosion modules of the CONCEPTS channel evolution computer model. The performance of the new model is evaluated for meander-planform initiation and development. The most important findings are: (1) the model is able to simulate a much greater variety and complexity in meander wavelengths; (2) simulated meander development agrees closely with the unified bar-bend theory of Tubino and Seminara (1990); and (3) the rate of meander planform adjustment is greatly reduced if the wavelength of alternate bars is similar to that of meanders.

  11. Channel erosion in steep gradient, gravel-paved streams

    SciTech Connect

    Lepp, L.R.; Koger, C.J.; Wheeler, J.A.

    1993-12-01

    Discharges were measured in steep gradient (> 5 percent) gravel-paved streams from 1988 to 1991 in order to empirically determine erosional thresholds based on sediment size, related to critical velocity, tractive force, and unit stream power. Results suggest that the empirical relationship between sediment size and unit stream power provides an accurate and simple methodology for determining the minimum erosion threshold discharge for steep gradient streams common in western Washington and other similar mountain terrains.

  12. Steep radio spectra in high-redshift radio galaxies

    NASA Technical Reports Server (NTRS)

    Krolik, Julian H.; Chen, Wan

    1991-01-01

    The generic spectrum of an optically thin synchrotron source steepens by 0.5 in spectral index from low frequencies to high whenever the source lifetime is greater than the energy-loss timescale for at least some of the radiating electrons. Three effects tend to decrease the frequency nu(b) of this spectral bend as the source redshift increases: (1) for fixed bend frequency nu* in the rest frame, nu(b) = nu*/(1 + z); (2) losses due to inverse Compton scattering the microwave background rise with redshift as (1 + z) exp 4, so that, for fixed residence time in the radiating region, the energy of the lowest energy electron that can cool falls rapidly with increasing redshift; and (3) if the magnetic field is proportional to the equipartition field and the emitting volume is fixed or slowly varying, flux-limited samples induce a selection effect favoring low nu* at high z because higher redshift sources require higher emissivity to be included in the sample, and hence have stronger implied fields and more rapid synchrotron losses. A combination of these effects may explain the trend observed in the 3CR sample for higher redshift radio galaxies to have steeper spectra, and the successful use of ultrasteep spectrum surveys to locate high-redshift galaxies.

  13. A Hard Tail in Broad Band Spectrum of Cir X-1: a clue for a Z-source behavior

    NASA Astrophysics Data System (ADS)

    Iaria, R.; Di Salvo, T.; La Barbera, A.; Burderi, L.; Robba, N. R.

    2000-10-01

    We report on the spectral analysis of the peculiar source Cir X--1 observed by the BeppoSAX satellite when the X-ray source was near the periastron. A flare lasting ~ 6 x 103 s is present at the beginning of the observation. The luminosity during the persistent emission is 1 x 1038 erg s-1, while during the flare is 2 x 1038 erg s-1. The broad band (0.1--100 keV) energy spectrum is well fitted by a model consisting of Comptonization of soft photons, with a temperature of ~ 0.4 keV, by electrons at a temperature of ~ 1 keV, and a power-law component, with photon index ~ 3, dominant at energies higher than 10 keV. This component is present out the flare, contributing to ~ 4% of the total luminosity, while during the flare its addition is not statistically significant. An absorption edge at ~ 8.4 keV, with optical depth ~ 1, corresponding to the K-edge of Fe XXIII--XXV, and an iron emission line at 6.7 keV are also present. The iron line energy is in agreement with the ionization level of the absorbtion edge. The hydrogen column deduced from the absorption edge is ~ 1024 cm-2,two order of magnitude larger than the absorption measured in this source. We calculated the radius of the region originating the comptonized seed photons, RW ~ 150 km. We propose a scenario where RW is the inner disk radius, a highly ionized torus surrounds the accretion disk and a magnetospere is large up to RW. The absorption edge, the emission line could originate in the photoionized torus present in the outer edge of the accretion disk, while the comptonized component originates in an inner region of the disk.

  14. 318-MHz variability of complete samples of extragalactic radio sources

    NASA Technical Reports Server (NTRS)

    Dennison, B.; Broderick, J. J.; Ledden, J. E.; Odell, S. L.; Condon, J. J.

    1981-01-01

    It is found by a low-frequency variability survey, involving two- and three-epoch, 318-MHz observations of extragalactic sources in samples complete to 3 Jy at 1400 MHz and 1 Jy at 5000 MHz, that steep-spectrum sources do not seem to vary while all flat-spectrum sources exhibit low-frequency variability greater than 8% over about 5 yr. It is also found that the flat-spectrum sources with inverted spectra show the largest fractional variations, and that there is a correlation between the incidence of low-frequency variability and the determination that a source is an optically violent variable. These statistical properties are consistent with models which invoke radio and optical emission relativistic beaming.

  15. Remotely sensed biomass over steep slopes: An evaluation among successional stands of the Atlantic Forest, Brazil

    NASA Astrophysics Data System (ADS)

    Barbosa, Jomar Magalhães; Melendez-Pastor, Ignacio; Navarro-Pedreño, Jose; Bitencourt, Marisa Dantas

    2014-02-01

    Remotely sensed images have been widely used to model biomass and carbon content on large spatial scales. Nevertheless, modeling biomass using remotely sensed data from steep slopes is still poorly understood. We investigated how topographical features affect biomass estimation using remotely sensed data and how such estimates can be used in the characterization of successional stands in the Atlantic Rainforest in southeastern Brazil. We estimated forest biomass using a modeling approach that included the use of both satellite data (LANDSAT) and topographic features derived from a digital elevation model (TOPODATA). Biomass estimations exhibited low error predictions (Adj. R2 = 0.67 and RMSE = 35 Mg/ha) when combining satellite data with a secondary geomorphometric variable, the illumination factor, which is based on hill shading patterns. This improved biomass prediction helped us to determine carbon stock in different forest successional stands. Our results provide an important source of modeling information about large-scale biomass in remaining forests over steep slopes.

  16. Measurement of the neutron spectrum and ambient neutron dose rate equivalent from the small 252Cf source at 1 meter

    SciTech Connect

    Radev, R.

    2015-07-07

    NASA Langley Research Center requested a measurement of the neutron spectral distribution and fluence from the 252Cf source (model NS-120, LLNL serial # 7001677, referred as the SMALL Cf source) and determination of the ambient neutron dose rate equivalent and kerma at 100 cm for the Radiation Budget Instrument Experiment (Rad-X). The dosimetric quantities should be based on the neutron spectrum and the current neutron-to-dose conversion coefficients.

  17. Predictors of Age of Diagnosis for Children with Autism Spectrum Disorder: The Role of a Consistent Source of Medical Care, Race, and Condition Severity

    ERIC Educational Resources Information Center

    Emerson, Natacha D.; Morrell, Holly E. R.; Neece, Cameron

    2016-01-01

    Having a consistent source of medical care may facilitate diagnosis of autism spectrum disorders (ASD). This study examined predictors of age of ASD diagnosis using data from the 2011-2012 National Survey of Children's Health. Using multiple linear regression analysis, age of diagnosis was predicted by race, ASD severity, having a consistent…

  18. VLA observations of unidentified Leiden-Berkeley Deep-Survey sources - Luminosity and redshift dependence of spectral properties

    NASA Technical Reports Server (NTRS)

    Kapahi, Vijay K.; Kulkarni, Vasant K.

    1990-01-01

    VLA observations of a complete subset of the Leiden-Berkeley Deep Survey sources that have S(1.4 GHz) greater than 10 mJy and are not optically identified down to F=22 mag are reported. By comparing the spectral and structural properties of the sources with samples from the literature, an attempt was made to disentangle the luminosity and redshift dependence of the spectral indices of extended emission in radio galaxies and of the incidence of compact steep-spectrum sources. It is found that the fraction of compact sources among those with a steep spectrum is related primarily to redshift, being much larger at high redshifts for sources of similar radio luminosity. Only a weak and marginally significant dependence of spectral indices of the extended sources on luminosity and redshift is found in samples selected at 1.4 and 2.7 GHz. It is pointed out that the much stronger correlation of spectral indices with luminosity may be arising partly from spectral curvature, and partly due to the preferential inclusion of very steep-spectrum sources from high redshift in low-frequency surveys.

  19. Measurement of the Neutron Spectrum of the HB-4 Cold Source at the High Flux Isotope Reactor at Oak Ridge National Laboratory

    NASA Astrophysics Data System (ADS)

    Robertson, J. L.; Iverson, E. B.

    2009-08-01

    Measurements of the cold neutron spectrum from the super critical hydrogen cold source at the High Flux Isotope Reactor at Oak Ridge National Laboratory were made using time-of-flight spectroscopy. Data were collected at reactor power levels of 8.5MW, 42.5MW and 85MW. The moderator temperature was also varied. Data were collected at 17K and 25K while the reactor power was at 8.5MW, 17K and 25K while at 42.5MW and 18K and 22K while at 85MW. The purpose of these measurements was to characterize the brightness of the cold source and to better understand the relationship between reactor power, moderator temperature, and cold neutron production. The authors will discuss the details of the measurement, the changes observed in the neutron spectrum, and the process for determining the source brightness from the measured neutron intensity.

  20. Photomorphogenesis and photoassimilation in soybean and sorghum grown under broad spectrum or blue-deficient light sources

    NASA Technical Reports Server (NTRS)

    Britz, S. J.; Sager, J. C.; Knott, W. M. (Principal Investigator)

    1990-01-01

    The role of blue light in plant growth and development was investigated in soybean (Glycine max [L.] Merr. cv Williams) and sorghum (Sorghum bicolor [L.] Moench. cv Rio) grown under equal photosynthetic photon fluxes (approximately 500 micromoles per square meter per second) from broad spectrum daylight fluorescent or blue-deficient, narrow-band (589 nanometers) low pressure sodium (LPS) lamps. Between 14 and 18 days after sowing, it was possible to relate adaptations in photosynthesis and leaf growth to dry matter accumulation. Soybean development under LPS light was similar in several respects to that of shaded plants, consistent with an important role for blue light photoreceptors in regulation of growth response to irradiance. Thus, soybeans from LPS conditions partitioned relatively more growth to leaves and maintained higher average leaf area ratios (mean LAR) that compensated lower net assimilation rates (mean NAR). Relative growth rates were therefore comparable to plants from daylight fluorescent lamps. Reductions in mean NAR were matched by lower rates of net photosynthesis (A) on an area basis in the major photosynthetic source (first trifoliolate) leaf. Lower A in soybean resulted from reduced leaf dry matter per unit leaf area, but lower A under LPS conditions in sorghum correlated with leaf chlorosis and reduced total nitrogen (not observed in soybean). In spite of a lower A, mean NAR was larger in sorghum from LPS conditions, resulting in significantly greater relative growth rates (mean LAR was approximately equal for both light conditions). Leaf starch accumulation rate was higher for both species and starch content at the end of the dark period was elevated two- and three-fold for sorghum and soybean, respectively, under LPS conditions. Possible relations between starch accumulation, leaf export, and plant growth in response to spectral quality were considered.

  1. 30 CFR 785.15 - Steep slope mining.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Steep slope mining. 785.15 Section 785.15 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR SURFACE COAL MINING AND RECLAMATION OPERATIONS PERMITS AND COAL EXPLORATION SYSTEMS UNDER REGULATORY...

  2. 30 CFR 785.15 - Steep slope mining.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Steep slope mining. 785.15 Section 785.15 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR SURFACE COAL MINING AND RECLAMATION OPERATIONS PERMITS AND COAL EXPLORATION SYSTEMS UNDER REGULATORY...

  3. 30 CFR 785.15 - Steep slope mining.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Steep slope mining. 785.15 Section 785.15 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR SURFACE COAL MINING AND RECLAMATION OPERATIONS PERMITS AND COAL EXPLORATION SYSTEMS UNDER REGULATORY...

  4. 30 CFR 785.15 - Steep slope mining.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Steep slope mining. 785.15 Section 785.15 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR SURFACE COAL MINING AND RECLAMATION OPERATIONS PERMITS AND COAL EXPLORATION SYSTEMS UNDER REGULATORY...

  5. 30 CFR 785.15 - Steep slope mining.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Steep slope mining. 785.15 Section 785.15 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR SURFACE COAL MINING AND RECLAMATION OPERATIONS PERMITS AND COAL EXPLORATION SYSTEMS UNDER REGULATORY...

  6. Improved numerical modelling of morphodynamics of rivers with steep banks

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The flow and sediment transport processes near steep streambanks, which are commonly found in meandering, braided, and anastomosing stream systems, exhibit complex patterns. The interactions between bed and bank morphologic adjustment, and their governing processes are still not well understood. Inc...

  7. 30 CFR 816.107 - Backfilling and grading: Steep slopes.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Backfilling and grading: Steep slopes. 816.107 Section 816.107 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PERMANENT PROGRAM PERFORMANCE STANDARDS PERMANENT PROGRAM PERFORMANCE STANDARDS-SURFACE...

  8. 30 CFR 817.107 - Backfilling and grading: Steep slopes.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Backfilling and grading: Steep slopes. 817.107 Section 817.107 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PERMANENT PROGRAM PERFORMANCE STANDARDS PERMANENT PROGRAM PERFORMANCE STANDARDS-UNDERGROUND...

  9. 166. Big Laurel Mountain Viaduct. View of the steep slope ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    166. Big Laurel Mountain Viaduct. View of the steep slope upon which the steel pier is built. The construction of this viaduct eliminated either a large scar of fill, helping to preserve the mountainside. Facing north. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

  10. Measurement of steep edges and undercuts in confocal microscopy.

    PubMed

    Mueller, T; Jordan, M; Schneider, T; Poesch, A; Reithmeier, E

    2016-05-01

    Confocal microscopy is widely used to measure the surface topography of specimen with a precision in the micrometer range. The measurement uncertainty and quality of the acquired data of confocal microscopy depends on various effects, such as optical aberrations, vibrations of the measurement setup and variations in the surface reflectivity. In this article, the influence of steep edges and undercuts on measurement results is examined. Steep edges on the specimen's surface lead to a reduced detector signal which influences the measurement accuracy and undercuts cause surface regions, which cannot be captured in a measurement. The article describes a method to overcome the negative effects of steep edges and undercuts by capturing several measurements of the surface with different angles between the surface and the optical axis of the objective. An algorithm is introduced which stitches different angle measurements together without knowledge of the exact position and orientation of the rotation axis. Thus, the measurement uncertainty due to steep edges and undercuts can be avoided without expensive high-precision rotation stages and time consuming adjustment of the measurement setup. PMID:27011256

  11. Ultraprecision machining of steep aspheric parts with large sagittal height

    NASA Astrophysics Data System (ADS)

    Mu, Lin; Zhao, Rui; Xin, Qiming

    2009-05-01

    Problems occurred during machining steep aspheric parts with large sagittal height on double-spindle diamond turning machine are presented and the main reasons of the problems are described. And methods of solving these problems are also suggested. When we machine steep aspheric parts with large sagittal height on a 2 axis diamond turning machine, we have such problems as difficult control of part edge accuracy, poor roughness and rapid wear of the cutting tool. The main reasons for these problems lie in: 1) Measurement. To make accurate measurements, the measurement range of the profilometer must fall within the sagittal heights of the aspheric parts, and the measurement angle must also meet the requirements, an insufficient measurement angle, for example, will have a big impact on the measurement and fabrication accuracy of such parts; and 2) Machine and tool, firstly, the diamond cutting tool will suffer a very big force when turning the edge section, resulting in bigger micro-vibration in the tool and tool post, thus affecting the part accuracy and surface roughness. Secondly, the machine itself has location errors in axes X and Z during the processing, leading to the severest destruction in the steep section of the aspheric part by their resultant force. Lastly, anisotropy of diamond cutting tool hardness. The indentation hardness of the diamond is maximum in the direction of <1.0.0> of face (100) and the front clearance has the best strength at tool point in the direction of <1.0.0>. When cutting a steep aspheric part with large sagittal height, a bigger included angle of the diamond tool point arc will be used, and there will be a more deviation from the <1.0.0> lattice direction. So the tool hardness is consistently decreased, resulting in a rapid wear of the cutting tool when turning the steep section of the aspheric part, thus the accuracy and roughness in machining an aspheric part become more difficult to control. The paper is concluded with the

  12. PI: An open-source software package for validation of the SEQUEST result and visualization of mass spectrum

    PubMed Central

    2011-01-01

    Background Tandem mass spectrometry (MS/MS) has emerged as the leading method for high- throughput protein identification in proteomics. Recent technological breakthroughs have dramatically increased the efficiency of MS/MS data generation. Meanwhile, sophisticated algorithms have been developed for identifying proteins from peptide MS/MS data by searching available protein sequence databases for the peptide that is most likely to have produced the observed spectrum. The popular SEQUEST algorithm relies on the cross-correlation between the experimental mass spectrum and the theoretical spectrum of a peptide. It utilizes a simplified fragmentation model that assigns a fixed and identical intensity for all major ions and fixed and lower intensity for their neutral losses. In this way, the common issues involved in predicting theoretical spectra are circumvented. In practice, however, an experimental spectrum is usually not similar to its SEQUEST -predicted theoretical one, and as a result, incorrect identifications are often generated. Results Better understanding of peptide fragmentation is required to produce more accurate and sensitive peptide sequencing algorithms. Here, we designed the software PI of novel and exquisite algorithms that make a good use of intensity property of a spectrum. Conclusions We designed the software PI with the novel and effective algorithms which made a good use of intensity property of the spectrum. Experiments have shown that PI was able to validate and improve the results of SEQUEST to a more satisfactory degree. PMID:21672262

  13. Calculation of the expected output spectrum for a mid-infrared supercontinuum source based on As ₂ S₃ chalcogenide photonic crystal fibers.

    PubMed

    Weiblen, R J; Docherty, A; Menyuk, C R; Shaw, L B; Sanghera, J S; Aggarwal, I D

    2014-09-01

    We computationally investigate supercontinuum generation in an As ₂ S₃ solid core photonic crystal fiber (PCF) with a hexagonal cladding of air holes. With a goal of obtaining a supercontinuum output spectrum that can predict what might be seen in an experiment, we investigate the spectral and statistical behavior of a mid-infrared supercontinuum source using a large ensemble average of 10⁶ realizations, in which the input pulse duration and energy vary. The output spectrum is sensitive to small changes (0.1%) in these pulse parameters. We show that the spectrum can be divided into three regions with distinct characteristics: a short-wavelength region with high correlation, a middle-wavelength region with minimal correlation, and a long-wavelength region where the behavior is dominated by a few rare large-bandwidth events. We show that statistically significant fluctuations exist in the experimentally expected output spectrum and that we can reproduce an excellent match to that spectrum with a converged shape and bandwidth using 5000 realizations. PMID:25321598

  14. Surprises from a Deep ASCA Spectrum of the Broad Absorption Line Quasar PHL 5200

    NASA Technical Reports Server (NTRS)

    Mathur, Smita; Matt, G.; Green, P. J.; Elvis, M.; Singh, K. P.

    2002-01-01

    We present a deep (approx. 85 ks) ASCA observation of the prototype broad absorption line quasar (BALQSO) PHL 5200. This is the best X-ray spectrum of a BALQSO yet. We find the following: (1) The source is not intrinsically X-ray weak. (2) The line-of-sight absorption is very strong, with N(sub H) = 5 x 10(exp 23)/sq cm. (3) The absorber does not cover the source completely; the covering fraction is approx. 90%. This is consistent with the large optical polarization observed in this source, implying multiple lines of sight. The most surprising result of this observation is that (4) the spectrum of this BALQSO is not exactly similar to other radio-quiet quasars. The hard X-ray spectrum of PHL 5200 is steep, with the power-law spectral index alpha approx. 1.5. This is similar to the steepest hard X-ray slopes observed so far. At low redshifts, such steep slopes are observed in narrow-line Seyfert 1 (NLS1) galaxies, believed to be accreting at a high Eddington rate. This observation strengthens the analogy between BALQSOs and NLS1 galaxies and supports the hypothesis that BALQSOs represent an early evolutionary state of quasars. It is well accepted that the orientation to the line of sight determines the appearance of a quasar: age seems to play a significant role as well.

  15. On the existence of smooth Cauchy steep time functions

    NASA Astrophysics Data System (ADS)

    Minguzzi, E.

    2016-06-01

    A simple proof (based on results in Chruściel et al 2015 Ann. Henri Poincaré arXiv:1301.2909) is given that every globally hyperbolic spacetime admits a smooth Cauchy steep time function. This result is useful in order to show that globally hyperbolic spacetimes can be isometrically embedded in Minkowski spacetimes and that they split as a product. The proof is based on a recent result on the differentiability of Geroch’s volume functions.

  16. Emplacement and composition of steep-sided domes on Venus

    NASA Astrophysics Data System (ADS)

    Stofan, Ellen R.; Anderson, Steven W.; Crown, David A.; Plaut, Jeffrey J.

    2000-11-01

    Steep-sided domes on Venus have surface characteristics that can provide information on their emplacement, including relatively smooth upper surfaces, radial and polygonal fracture patterns, and pits. These characteristics indicate that domes have surface crusts which are relatively unbroken, have mobile interiors after emplacement, and preserve fractures from only late in their history in response to endogenous growth or sagging of the dome surface. We have calculated the time necessary to form a 12-cm-thick crust for basalt and rhyolite under current terrestrial and Venusian ambient conditions. A 12-cm-thick crust will form in all cases in <10 hours. Although Venusian lava flows should develop a brittle carapace during emplacement, only late-stage brittle fractures are preserved at steep-sided domes. We favor an emplacement model where early-formed surface crusts are entrained or continually annealed as they deform to accommodate dome growth. Entrainment and annealing of fractures are not mutually exclusive processes and thus may both be at work during steep-sided dome emplacement. Our results are most consistent with basaltic compositions, as rhyolitic lavas would quickly form thick crusts which would break into large blocks that would be difficult to entrain or anneal. However, if Venus has undergone large temperature excursions in the past (producing ambient conditions of 800-1000 K [e.g., Bullock and Grinspoon, 1996, 1998]), rhyolitic lavas would be unable to form crusts at high surface temperatures and could produce domes with surface characteristics consistent with those of Venusian steep-sided domes.

  17. Sidewall spacer optimization for steep switching junctionless transistors

    NASA Astrophysics Data System (ADS)

    Gupta, Manish; Kranti, Abhinav

    2016-06-01

    In this work, we analyze the impact of a high permittivity (high-κ) sidewall spacer and gate dielectric on the occurrence of sub-60 mV/decade subthreshold swing (S-swing) in symmetrical junctionless (JL) double gate (DG) transistors. It is shown that steep S-swing values (≤10 mV/decade) can be achieved in JL devices with a combination of a high permittivity (high-κ) gate dielectric and a narrow low permittivity (low-κ) sidewall spacer. Implementation of a wider high-κ spacer will diminish the degree of impact ionization by the influence of the fringing component of the gate electric field, and will not be useful for steep off-to-on current transition. A wider spacer with low-κ and a narrow spacer with high-κ permittivity will be useful to limit the latching effect that can occur at lower temperatures (250 K). For high temperature operation, the decrease in the impact ionization rate can be compensated by designing a JL transistor with a thicker silicon film. The work demonstrates opportunities to enhance impact ionization at sub bandgap voltages, and proposes optimal guidelines for selecting a sidewall spacer to facilitate steep switching in JL transistors.

  18. Formation mechanism of steep wave front in magnetized plasmas

    SciTech Connect

    Sasaki, M. Kasuya, N.; Itoh, S.-I.; Kobayashi, T.; Arakawa, H.; Itoh, K.; Fukunaga, K.; Yamada, T.; Yagi, M.

    2015-03-15

    Bifurcation from a streamer to a solitary drift wave is obtained in three dimensional simulation of resistive drift waves in cylindrical plasmas. The solitary drift wave is observed in the regime where the collisional transport is important as well as fluctuation induced transport. The solitary drift wave forms a steep wave front in the azimuthal direction. The phase of higher harmonic modes are locked to that of the fundamental mode, so that the steep wave front is sustained for a long time compared to the typical time scale of the drift wave oscillation. The phase entrainment between the fundamental and second harmonic modes is studied, and the azimuthal structure of the stationary solution is found to be characterized by a parameter which is determined by the deviation of the fluctuations from the Boltzmann relation. There are two solutions of the azimuthal structures, which have steep wave front facing forward and backward in the wave propagation direction, respectively. The selection criterion of these solutions is derived theoretically from the stability of the phase entrainment. The simulation result and experimental observations are found to be consistent with the theoretical prediction.

  19. The BL LAC phenomenon: X-ray observations of transition objects and determination of the x-ray spectrum of a complete sample of flat-spectrum radio sources

    NASA Technical Reports Server (NTRS)

    Worrall, Diana M.

    1994-01-01

    This report summarizes the activities related to two ROSAT investigations: (1) x-ray properties of radio galaxies thought to contain BL Lac type nuclei; and (2) x-ray spectra of a complete sample of flat-spectrum radio sources. The following papers describing the research are provided as attachments: Multiple X-ray Emission Components in Low Power Radio Galaxies; New X-ray Results on Radio Galaxies; Analysis Techniques for a Multiwavelength Study of Radio Galaxies; Separation of X-ray Emission Components in Radio Galaxies; X-ray Emission in Powerful Radio Galaxies and Quasars; Extended and Compact X-ray Emission in Powerful Radio Galaxies; and X-ray Spectra of a Complete Sample of Extragalactic Core-dominated Radio Sources.

  20. The spectral variability of the GHZ-Peaked spectrum radio source PKS 1718-649 and a comparison of absorption models

    SciTech Connect

    Tingay, S. J.; Macquart, J.-P.; Wayth, R. B.; Trott, C. M.; Emrich, D.; Collier, J. D.; Wong, G. F.; Rees, G.; Stevens, J.; Carretti, E.; Callingham, J. R.; Gaensler, B. M.; McKinley, B.; Briggs, F.; Bernardi, G.; Bowman, J. D.; Cappallo, R. J.; Corey, B. E.; Deshpande, A. A.; Goeke, R.; and others

    2015-02-01

    Using the new wideband capabilities of the ATCA, we obtain spectra for PKS 1718-649, a well-known gigahertz-peaked spectrum radio source. The observations, between approximately 1 and 10 GHz over 3 epochs spanning approximately 21 months, reveal variability both above the spectral peak at ∼3 GHz and below the peak. The combination of the low- and high-frequency variability cannot be easily explained using a single absorption mechanism, such as free–free absorption or synchrotron self-absorption. We find that the PKS 1718-649 spectrum and its variability are best explained by variations in the free–free optical depth on our line of sight to the radio source at low frequencies (below the spectral peak) and the adiabatic expansion of the radio source itself at high frequencies (above the spectral peak). The optical depth variations are found to be plausible when X-ray continuum absorption variability seen in samples of active galactic nuclei is considered. We find that the cause of the peaked spectrum in PKS 1718-649 is most likely due to free–free absorption. In agreement with previous studies, we find that the spectrum at each epoch of observation is best fit by a free–free absorption model characterized by a power-law distribution of free–free absorbing clouds. This agreement is extended to frequencies below the 1 GHz lower limit of the ATCA by considering new observations with Parkes at 725 MHz and 199 MHz observations with the newly operational Murchison Widefield Array. These lower frequency observations argue against families of absorption models (both free–free and synchrotron self-absorption) that are based on simple homogenous structures.

  1. The X-ray source Serpens X-1 - Ariel 5 observations and discussion of models for the spectrum and time variability

    NASA Technical Reports Server (NTRS)

    Coe, M. J.; Engel, A. R.; Quenby, J. J.; Carpenter, G. F.; Bell-Burnell, S. J.; Davison, P. J. N.

    1978-01-01

    Experimental data from Ariel 5 on the spectral shape and time variability of Ser X-1 are presented, and possible explanations for the observations are discussed in terms of current theoretical suggestions for source emission. The observations are summarized in the form of a light curve for 3-7.6-keV photons. The data are fitted with a power law of index -2.3, which yields a hydrogen column density of (1.1 + or - 0.4) x 10 to the 22nd power atoms/sq cm. No persistent periodicity of amplitude greater than 5% of the steady flux is found, but evidence of statistically significant burst activity is obtained. Various emission mechanisms are considered for the time-averaged spectrum and the X-ray bursts. It is suggested that the inverse Compton mechanism is a likely cause for the emission from this source and that the source is radiating near the Eddington limit.

  2. Discovery and Monitoring of a New Black Hole Candidate XTE J1752-223 with RXTE: RMS Spectrum Evolution, BH Mass and the Source Distance

    NASA Technical Reports Server (NTRS)

    Shaposhinikov, Nikolai; Markwardt, Craig; Swank, Jean; Krimm, Hans

    2010-01-01

    We report on the discovery and monitoring observations of a new galactic black hole candidate XTE J1752-223 by Rossi X-ray Timing Explorer (RXTE). The new source appeared on the X-ray sky on October 21 2009 and was active for almost 8 months. Phenomenologically, the source exhibited the low-hard/highsoft spectral state bi-modality and the variability evolution during the state transition that matches standard behavior expected from a stellar mass black hole binary. We model the energy spectrum throughout the outburst using a generic Comptonization model assuming that part of the input soft radiation in the form of a black body spectrum gets reprocessed in the Comptonizing medium. We follow the evolution of fractional root-mean-square (RMS) variability in the RXTE/PCA energy band with the source spectral state and conclude that broad band variability is strongly correlated with the source hardness (or Comptonized fraction). We follow changes in the energy distribution of rms variability during the low-hard state and the state transition and find further evidence that variable emission is strongly concentrated in the power-law spectral component. We discuss the implication of our results to the Comptonization regimes during different spectral states. Correlations of spectral and variability properties provide measurements of the BH mass and distance to the source. The spectral-timing correlation scaling technique applied to the RXTE observations during the hardto- soft state transition indicates a mass of the BH in XTE J1752-223 between 8 and 11 solar masses and a distance to the source about 3.5 kiloparsec.

  3. Radiation detector spectrum simulator

    DOEpatents

    Wolf, Michael A.; Crowell, John M.

    1987-01-01

    A small battery operated nuclear spectrum simulator having a noise source nerates pulses with a Gaussian distribution of amplitudes. A switched dc bias circuit cooperating therewith generates several nominal amplitudes of such pulses and a spectral distribution of pulses that closely simulates the spectrum produced by a radiation source such as Americium 241.

  4. Radiation detector spectrum simulator

    DOEpatents

    Wolf, M.A.; Crowell, J.M.

    1985-04-09

    A small battery operated nuclear spectrum simulator having a noise source generates pulses with a Gaussian distribution of amplitudes. A switched dc bias circuit cooperating therewith to generate several nominal amplitudes of such pulses and a spectral distribution of pulses that closely simulates the spectrum produced by a radiation source such as Americium 241.

  5. Transient river response, captured by channel steepness and its concavity

    NASA Astrophysics Data System (ADS)

    Vanacker, Veerle; von Blanckenburg, Friedhelm; Govers, Gerard; Molina, Armando; Campforts, Benjamin; Kubik, Peter W.

    2015-01-01

    Mountain rivers draining tropical regions are known to be great conveyor belts carrying efficiently more than half of the global sediment flux to the oceans. Many tropical mountain areas are located in tectonically active belts where the hillslope and stream channel morphology are rapidly evolving in response to changes in base level. Here, we report basin-wide denudation rates for an east-west transect through the tropical Andes. Hillslope and channel morphology vary systematically from east to west, reflecting the transition from high relief, strongly dissected topography in the escarpment zones into relatively low relief topography in the inter-Andean valley. The spatial pattern of differential denudation rates reflects the transient adjustment of the landscape to rapid river incision following tectonic uplift and river diversion. In the inter-Andean valley, upstream of the wave of incision, slopes and river channels display a relatively smooth, concave-up morphology and denudation rates (time scale of 104-105 a) are consistently low (3 to 200 mm/ka). In contrast, slopes and river channels of rejuvenated basins draining the eastern cordillera are steep to very steep; and the studied drainage basins show a wide range of denudation rate values (60 to 400 mm/ka) that increase systematically with increasing basin mean slope gradient, channel steepness, and channel convexity. Drainage basins that are characterised by strong convexities in their river longitudinal profiles systematically have higher denudation rates. As such, this is one of the first studies that provides field-based evidence of a correlation between channel concavity and basin mean denudation rates, consistent with process-based fluvial incision models.

  6. Check dams effects on sediment transport in steep slope flume

    NASA Astrophysics Data System (ADS)

    Piton, Guillaume; Recking, Alain

    2014-05-01

    Depending on many influences (geology, relief, hydrology, land use, etc.) some mountainous watershed are prone to cause casualties and facilities damages. Large amounts of sediments episodically released by torrents are often the biggest problem in torrent related hazard mitigation. Series of transversal structures as check dams and ground sills are often used in the panel of risk mitigation technics. A large literature exits on check dams and it mainly concerns engineering design, e.g. toe scouring, stability stress diagram, changes in upper and lower reaches equilibrium slopes. Check dams in steep slope rivers constitute fixed points in the bed profile and prevent general bed incision. However their influence on sediment transport once they are filled is not yet clear. Two flume test campaigns, synthetize in Table 1, were performed to investigate this question: Table 1 : experiment plan Run (duration) Ref1 (50h)CD1a (30h)CD1b (30h)Ref2 (92h)CD2 (18h) Solid feeding discharge (g.s^-1) 44 44 44 60 60 Number of check dams none 1 3 none 2 A nearly 5-m-long, 10-cm-wide and 12%-steep flume was used. The water discharge was set to 0,55 l/s in all runs. A mixture of poorly sorted natural sediments with diameters between 0.8 and 40 mm was used. An open solid-discharge-feeding circuit kept the inlet sediment flux constant during all experiments. As both feeding rates did not present variation, changes in outlet solid discharge were assumed to be due to bed variations in the bed storage. We observed strong fluctuations of solid flux and slope in each reaches of all runs between: (i) steep aggradating armoured bed and (ii) less steep and finer bed releasing bedload sheets during erosion events and inducing bedload pulses. All experiments showed consistent results: transported volume associated with erosion event decreased with the length between two subsequent check dams. Solid transversal structures shorten the upstream erosion-propagation and avoid downstream change in the

  7. Field experiments of nonlocal sediment transport on a steep hillslope

    NASA Astrophysics Data System (ADS)

    DiBiase, R.; Booth, A. M.; Ganti, V.; Scheingross, J. S.; Lamb, M. P.

    2014-12-01

    Steep rocky hillslopes dominate the areal extent of rapidly uplifting mountain ranges, and pose a significant hazard to encroaching population centers. Existing models for hillslope sediment transport developed for soil-mantled landscapes are poorly suited to explain the evolution of steep hillslopes characterized by: (1) intermittent or patchy soil cover, (2) slopes that exceed the angle of repose, and (3) transport events that often involve long travel distances. Recently, nonlocal formulations of hillslope sediment transport laws that account for long travel distances have been proposed to overcome the limitations of traditional continuum-based models. However, their application to natural landscapes has been limited owing to few field constraints on key parameters, and computational difficulties expanding the framework to two-dimensions. To address this knowledge gap, we performed a series of field experiments on natural hillslopes to inform a simple particle-based model of hillslope sediment transport. We compiled the distribution of average velocity and transport distance for over 300 stones ranging in diameter from 2-10 cm using a video camera and laser range-finder. To characterize surface roughness, we used a tripod-based laser scanner to generate a 1 cm-resolution digital elevation model of each 30 m long hillslope. We find that hillslope travel distance follows a heavy-tailed distribution that varies systematically with the ratio of particle diameter to roughness height, in general agreement to published laboratory experiments. Mean particle velocity ranges from 1-3 m/s and scales weakly with distance traveled. Our modeling exercise reveals three key effects that should be included in any treatment of steep hillslope evolution: (1) there is a strong grain-size and surface roughness dependence on sediment transport distance, (2) sediment storage on slopes steeper than the angle of repose is possible due to vegetation or topographic roughness, and (3

  8. Photon energy spectrum emitted by a novel polymer-encapsulated {sup 103}Pd source and its effect on the dose rate constant

    SciTech Connect

    Khan, Sabrina; Chen, Zhe Jay; Nath, Ravinder

    2008-04-15

    Two independent groups have published intrinsic dosimetry parameters for the recently introduced OptiSeed{sup 103} interstitial brachytherapy source which contains {sup 103}Pd encapsulated by a novel polymer shell. The dose rate constant ({lambda}) reported by the two groups, however, differed by more than 6% and there is currently no AAPM recommended consensus value for this source in clinical dosimetry. The aim of this work was to perform an independent determination of {lambda} for the OptiSeed{sup 103} source using a recently developed photon spectrometry technique. Three OptiSeed{sup 103} sources (model 1032P) with known air-kerma strength were used in this study. The photon energy spectrum emitted along the radial direction on the source's bisector was measured in air using a high-resolution intrinsic germanium spectrometer designed and established for low-energy brachytherapy source spectrometry. The dose rate constant of each source was determined from its emitted energy spectrum and the spatial distribution of radioactivity in the source. Unlike other sources made with traditional titanium encapsulation, the photons emitted by the OptiSeed{sup 103} sources exhibited only slight spectral hardening, yielding a relative energy spectrum closer to that emitted by bare {sup 103}Pd. The dose rate constant determined by the photon spectrometry technique for water was 0.664{+-}0.025 cGy h{sup -1} U{sup -1}. This value agreed, within experimental uncertainties, with the Monte Carlo-calculated value ({sub MC}{lambda}) of 0.665{+-}0.014 cGy h{sup -1} U{sup -1} and the TLD-measured value (with a Monte Carlo-calculated solid-phantom-to-water conversion factor) of 0.675{+-}0.051 cGy h{sup -1} U{sup -1} reported by Wang and Hertel [Appl. Radiat. Isot. 63, 311-321 (2005)]. However, it differed by -6.7% from the {sub MC}{lambda} of 0.712{+-}0.043 cGy h{sup -1} U{sup -1} reported by Bernard and Vynckier [Phys. Med. Biol. 50, 1493-1504 (2005)]. The results obtained in this

  9. Steep microbial boundstone-dominated platform margins—examples and implications

    NASA Astrophysics Data System (ADS)

    Kenter, Jeroen A. M.; Harris, Paul M. (Mitch); Della Porta, Giovanna

    2005-07-01

    Seaward progradation of several kilometers has been documented mostly for leeward margin low-angle carbonate slope systems with a dominant platform top sediment source. However, steep and high-relief margins fronting deep basins can also prograde and as such are somewhat perplexing. Characteristics of two prograding Carboniferous examples provide a model which may apply elsewhere: (1) outcrops in Asturias, northern Spain serve as important analogs for (2) hydrocarbon reservoirs in steep-sided isolated platforms of the North Caspian Basin, Kazakhstan, such as Tengiz. Seismic and well data from Tengiz corroborate outcrop patterns for slope development, showing progradation of up to 5 and more than 10 km, respectively, despite the high-relief (up to 600 m) and steep (˜20-35°) nature of these margins. The two examples share a highly productive microbial boundstone factory extending from the platform break down the slope to nearly 300 m (or more) depth and a lower slope dominated by (mega)breccias and grain flow deposits derived from the margin and slope itself. The broad depth range of microbial boundstone increases the potential for production during both lowstands and high stands of sea level and thereby facilitates progradation independent from platform-top-derived sediment. Rapid in situ lithification of the boundstone provides stability to the steep slopes, but also leads to readjustment through shearing and avalanching. What controls the microbial cement boundstone formation remains a debate but its presence is a key factor controlling the progradational geometry of these and possibly other margins. This new model of "slope" shedding has implications for slope readjustment processes and resulting architecture, sequence stratigraphic interpretation, reservoir characterization, and reservoir modeling. Especially the isotropic character of microbial boundstone will reduce the potential for coherent seismic reflections to develop and possibly invoke, under certain

  10. Computing nonhydrostatic shallow-water flow over steep terrain

    USGS Publications Warehouse

    Denlinger, R.P.; O'Connell, D. R. H.

    2008-01-01

    Flood and dambreak hazards are not limited to moderate terrain, yet most shallow-water models assume that flow occurs over gentle slopes. Shallow-water flow over rugged or steep terrain often generates significant nonhydrostatic pressures, violating the assumption of hydrostatic pressure made in most shallow-water codes. In this paper, we adapt a previously published nonhydrostatic granular flow model to simulate shallow-water flow, and we solve conservation equations using a finite volume approach and an Harten, Lax, Van Leer, and Einfeldt approximate Riemann solver that is modified for a sloping bed and transient wetting and drying conditions. To simulate bed friction, we use the law of the wall. We test the model by comparison with an analytical solution and with results of experiments in flumes that have steep (31??) or shallow (0.3??) slopes. The law of the wall provides an accurate prediction of the effect of bed roughness on mean flow velocity over two orders of magnitude of bed roughness. Our nonhydrostatic, law-of-the-wall flow simulation accurately reproduces flume measurements of front propagation speed, flow depth, and bed-shear stress for conditions of large bed roughness. ?? 2008 ASCE.

  11. Steep dose gradients for simultaneous integrated boost IMRT.

    PubMed

    Bratengeier, Klaus; Meyer, Jürgen; Schwab, Franz; Vordermark, Dirk; Flentje, Michael

    2009-01-01

    Steep dose gradients between two planning target volumes (PTVs) as may be required for simultaneous integrated boosts (SIB) should be an option provided by IMRT algorithms. The aim was to analyse the geometry of the SIB problem and to implement the results in an algorithm for IMRT segment generation denoted two-step intensity modulated radiotherapy (2-Step IMRT). It was hypothesized that a gap between segments directed to the inner and the outer PTV would steepen the dose gradient. The mathematical relationships were derived from the individual dose levels and the geometry (diameters) of the PTVs. The results generated by means of 2-Step IMRT segments were equivalent or better than the segment generation using a commercial IMRT planning system. The dose to both the inner and the outer PTV was clearly more homogeneous and the composite objective value was the lowest. The segment numbers were lower or equal--with better sparing of the surrounding tissue. In summary, it was demonstrated that 2-Step IMRT was able to achieve steep dose gradients for SIB constellations. PMID:19678528

  12. The Role of a Steepness Parameter in the Exponential Stability of a Model Problem. Numerical Aspects

    NASA Astrophysics Data System (ADS)

    Todorovic, N.

    2011-06-01

    The Nekhoroshev theorem considers quasi integrable Hamiltonians providing stability of actions in exponentially long times. One of the hypothesis required by the theorem is a mathematical condition called steepness. Nekhoroshev conjectured that different steepness properties should imply numerically observable differences in the stability times. After a recent study on this problem (Guzzo et al. 2011, Todorovic et al. 2011) we show some additional numerical results on the change of resonances and the diffusion laws produced by the increasing effect of steepness. The experiments are performed on a 4-dimensional steep symplectic map designed in a way that a parameter smoothly regulates the steepness properties in the model.

  13. Typhoon-Mediated Organic Carbon Export in the Western Pacific: The Role of Steep Mountainous Rivers

    NASA Astrophysics Data System (ADS)

    Hemingway, J. D.; Galy, V.; Hilton, R. G.; Hovius, N.

    2014-12-01

    Steep, mountainous rivers draning recently uplifted lithology on high standing islands within the Inter Tropical Convergence Zone export a disproportionately high amount of sediment given their small area; up to 20% of global export in 3% of the total exorheic land area. Typhoons strongly influence climate in this region, leading to increased sediment discharge, hyperpycnal flow, and efficient deposition of terrestrial particulate organic carbon in marine sediments. If this material escapes benthic remineralization - as is expected due to the lack of a continental shelf - typhoon mediated export of plant-derived POC is a net atmospheric CO2 sink. Here we report results from high-resolution (~hours) sampling on the LiWu River, Taiwan, during three sequential typhoons in 2008, and re-examine previous soil samples using more in-depth methods. Using a combination of bulk carbon isotopes (δ13C, ∆14C), vascular plant biomarker concentrations and δ13C, and ramped oxidation radiocarbon analysis, we describe the source and age of exported POC over a range of discharge conditions. We show that previous results indicating an increase in biospheric POC export during typhoons is an oversimplification; pre-aged soil OC complicates export. We offer an updated view of steep, mountainous rivers as a negative feedback loop to increased atmospheric CO2 and estimate for the first time the contribution and residence time of pre-aged soil OC in such a system.

  14. Predictors of Age of Diagnosis for Children with Autism Spectrum Disorder: The Role of a Consistent Source of Medical Care, Race, and Condition Severity.

    PubMed

    Emerson, Natacha D; Morrell, Holly E R; Neece, Cameron

    2016-01-01

    Having a consistent source of medical care may facilitate diagnosis of autism spectrum disorders (ASD). This study examined predictors of age of ASD diagnosis using data from the 2011-2012 National Survey of Children's Health. Using multiple linear regression analysis, age of diagnosis was predicted by race, ASD severity, having a consistent source of care (CSC), and the interaction between these variables after controlling for birth cohort, birth order, poverty level, parental education, and health insurance. While African American children were diagnosed earlier than Caucasians, this effect was moderated by ASD severity and CSC. Having a CSC predicted earlier diagnosis for Caucasian but not African American children. Both physician and parent behaviors may contribute to diagnostic delays in minority children. PMID:26280401

  15. Classification of Power Density Spectrum Features and Estimation of the δ-invariant Value for the Z Source GX 340+0

    NASA Astrophysics Data System (ADS)

    Titarchuk, Lev; Osherovich, Vladimir

    2001-07-01

    We present a theoretical analysis of Rossi X-Ray Timing Explorer data of Z source GX 340+0 obtained by Jonker et al. In the frameworks of the recently formulated transition layer model, the δ-angle is an angle between the neutron star (NS) magnetospheric axis and the disk (presumably NS rotational) axis. We determine the angle δ=6.3d+/-0.3d, which is a combination of the simultaneously observed kilohertz quasi-periodic and horizontal-branch oscillation frequencies. While these three frequencies change by a factor of 3 or more, their δ-combination stays almost constant. GX 340+0 is the fourth source (in addition to 4U 0614+09, Scorpius X-1, and 4U 1702-42) for which δ has been determined. With one (constrained) parameter, at most, we make a complete classification of six observed power spectral features, including the two kilohertz frequencies, the first and second harmonics of the horizontal-branch oscillation frequency, the low-frequency noise component, and the break frequencies. We demonstrate that a new component discovered by Jonker et al. in the GX 340+0 power spectrum is related to the viscous-frequency branch that has in fact been reported earlier in 4U 1728-34 by Ford & van der Klis. Finally, we reclassify several previously misidentified features in the power spectrum.

  16. Parameterization of the sediment transport in steep channels with boulders

    NASA Astrophysics Data System (ADS)

    Ghilardi, Tamara; Franca, Mário J.; Schleiss, Anton

    2015-04-01

    The presence of large relatively immobile boulders in steep mountain rivers is generally not taken into account in the development of equations to predict the bedload, leading to overestimates of the bedload rate by several times when applied to mountain rivers. Sediment transport in steep channels with boulders is herein investigated using 41 laboratory experiments carried out on a steep (longitudinal inclination of 6.7 to 13%), 8 m long (7 m usable) and 0.25 m wide, tilting flume. The experiments were made for varying flume slopes and boulder configurations (combination of boulder dimensionless distance and diameter), and for several sediment supply conditions. 35 experiments are made with boulders and six experiments without boulders. Boulders are herein defined as elements that although not transported by the flow, may move several times their diameter during experiments, mainly due to the scour holes formed around them. Water and poorly sorted sediments are constantly supplied at the flume inlet. Bedload at the channel downstream section, bulk flow velocities and morphological parameters are measured regularly during the experiments. The poorly sorted sediments (d50=9.3 mm, d65=11.9 mm, d30=7.1 mm, d84=16.6 mm, and d90=19.0 mm) are constantly fed into the system by a calibrated sediment feeder situated upstream, and recirculated during the experiments. The experiments show that the sediment transport capacity clearly decreases with the dimensionless boulder distance and is better estimated in terms of critical discharge for incipient motion of mobile sediments than in terms of critical bed shear stress. The channel longitudinal slope shows the strongest impact on the transport capacity, namely in what concerns the critical discharge for beginning of motion. In addition, it is also shown that the sediment transport decreases with boulder density. A sediment transport formula based on excess discharge relative to a critical value, which depends not only on the

  17. Environmental Illumination and Human Behavior: The Effects of Spectrum of Light Source on Human Performance in a University Setting.

    ERIC Educational Resources Information Center

    Kleiber, Douglas A.; And Others

    Two experiments tested the general question of whether a more "natural" artificial light (Vita-Lite) would have any different effects on classroom behavior and the ability to study than would a traditional (cool-white) light source. Fifty-nine undergraduates took part in the first experiment that utilized an 8-week counterbalanced design.…

  18. The composite broad band spectrum of Cir X-1 at the periastron: a peculiar Z-source

    NASA Astrophysics Data System (ADS)

    Iaria, R.; di Salvo, T.; Burderi, L.; La Barbera, N.; Robba, N. R.

    2001-09-01

    We report on the spectral analysis of the peculiar source Cir X-1 observed by the BeppoSAX satellite when the X-ray source was near the periastron. A flare lasting ~6×103s is present at the beginning of the observation. We produced broad band (0.1 - 100 keV) energy spectra during the flare and the persistent emission. At low energies the continuum is well fitted by a model consisting of Comptonization of soft photons, with a temperature of ~0.4 keV, by electrons at a temperature of ~1 keV. Out of the flare a power-law component, with photon index ~3, is dominant at energies higher than 10 keV. This component contributes to ~4% of the total luminosity. During the flare its addition is not statistically significant. Similar hard components have been recently observed in other Z-sources, sometimes related to the position of the source in the color-color diagram. An interesting possibility is that these components are due to the presence of jet emission.

  19. Corn steep liquor as a cost-effective nutrition adjunct in high-performance Zymomonas ethanol fermentations

    SciTech Connect

    Lawford, H.G.; Rousseau, J.D.

    1997-12-31

    The ethanologenic bacterium Zymomonas mobilis has been demonstrated to possess several fermentation performance characteristics that are superior to yeast. In a recent survey conducted by the National Renewable Energy Laboratory (NREL), Zymomonas was selected as the most promising host for improvement by genetic engineering directed to pentose metabolism for the production of ethanol from lignocellulosic biomass and wastes. Minimization of costs associated with nutritional supplements and seed production is essential for economic large-scale production of fuel ethanol. Corn steep liquor (CSL) is a byproduct of corn wet-milling and has been used as a fermentation nutrient supplement in several different fermentations. This study employed pH-controlled batch fermenters to compare the growth and fermentation performance of Z. mobilis in glucose media with whole and clarified corn steep liquor as sole nutrient source, and to determine minimal amounts of CSL required to sustain high-performance fermentation. 44 refs., 8 figs., 2 tabs.

  20. EPA External Research Grants Program Faces Steep Budget Cuts

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2004-03-01

    The Bush administration's proposed budget cuts to the Environmental Protection Agency's research grants program, Science to Achieve Results (STAR), came under criticism at hearing of the Science Subcommittee on Environment, Technology and Standards of U.S. House of Representatives. The hearing was held 11 March. Subcommittee members and several witnesses said that a proposed $36 million cut to the STAR's fiscal year 2005 budget-compared to the FY2004 proposed budget-is too steep. They said the proposed $65 million budget-which would represents a cut of 30% from the previous fiscal year-would harm the program, as well as the agency's ability to receive outside research advice on a range of cutting-edge environmental issues. Funding for STAR graduate fellowships also would be cut by 3.1%, compared to the enacted level for FY2004.

  1. An important erosion process on steep burnt hillslopes

    NASA Astrophysics Data System (ADS)

    Langhans, Christoph; Nyman, Petter; Noske, Philip; Lane, Patrick; Sheridan, Gary

    2016-04-01

    Steep forested hillslopes often display a high degree of armouring where diffusive erosion processes preferentially remove the fine fraction of the surface soil. High infiltration capacities, hydraulic resistance to overland flow and physical anchoring by cover plants and litter mean that even the most extreme rainfall events usually do not erode the armouring substantially. We argue that fire (wild or planned) is essential to the mobilization and transport of the armouring by increasing the rates of overland flow and decreasing trapping opportunities. We present evidence of the types of erosion that lead to the stripping of the surface armouring using post-event surveys and high-rate overland flow experiments. The type of erosion depends on the relative abundance of non-cohesive surface material to overland flow, but we found that a particular type of transport dominates that has no representation in current erosion models: On steep slopes overland flow can lead to incipient motion of individual stones that transfer their momentum to other stones leading to a rapid mobilization of the whole non-cohesive, armoured surface layer. Once in motion, the layer quickly separates out into a granular flow front and liquefied body, akin to debris flows in channels. Depending on the size of the event, these hillslope debris flows (HDF) either get trapped or enter into the channel, stripping the hillslope of most armouring on their way. They provide channels with the material and shear stress needed to erode into the channel bed, increasing the risk of channel debris flows. We present a simple physical model of HDF initiation, movement, and possible re-mobilization on hillslopes that was derived from debris flow theory. Understanding this process, its frequency, and magnitude are important for assessing the role of fire in landscape evolution and risk to humans through debris flow impacts.

  2. Cooperative Three-Robot System for Traversing Steep Slopes

    NASA Technical Reports Server (NTRS)

    Stroupe, Ashley; Huntsberger, Terrance; Aghazarian, Hrand; Younse, Paulo; Garrett, Michael

    2009-01-01

    Teamed Robots for Exploration and Science in Steep Areas (TRESSA) is a system of three autonomous mobile robots that cooperate with each other to enable scientific exploration of steep terrain (slope angles up to 90 ). Originally intended for use in exploring steep slopes on Mars that are not accessible to lone wheeled robots (Mars Exploration Rovers), TRESSA and systems like TRESSA could also be used on Earth for performing rescues on steep slopes and for exploring steep slopes that are too remote or too dangerous to be explored by humans. TRESSA is modeled on safe human climbing of steep slopes, two key features of which are teamwork and safety tethers. Two of the autonomous robots, denoted Anchorbots, remain at the top of a slope; the third robot, denoted the Cliffbot, traverses the slope. The Cliffbot drives over the cliff edge supported by tethers, which are payed out from the Anchorbots (see figure). The Anchorbots autonomously control the tension in the tethers to counter the gravitational force on the Cliffbot. The tethers are payed out and reeled in as needed, keeping the body of the Cliffbot oriented approximately parallel to the local terrain surface and preventing wheel slip by controlling the speed of descent or ascent, thereby enabling the Cliffbot to drive freely up, down, or across the slope. Due to the interactive nature of the three-robot system, the robots must be very tightly coupled. To provide for this tight coupling, the TRESSA software architecture is built on a combination of (1) the multi-robot layered behavior-coordination architecture reported in "An Architecture for Controlling Multiple Robots" (NPO-30345), NASA Tech Briefs, Vol. 28, No. 10 (October 2004), page 65, and (2) the real-time control architecture reported in "Robot Electronics Architecture" (NPO-41784), NASA Tech Briefs, Vol. 32, No. 1 (January 2008), page 28. The combination architecture makes it possible to keep the three robots synchronized and coordinated, to use data

  3. Development of the MICROMEGAS detector for measuring the energy spectrum of alpha particles by using a 241Am source

    NASA Astrophysics Data System (ADS)

    Kim, Do Yoon; Ham, Cheolmin; Shin, Jae Won; Park, Tae-Sun; Hong, Seung-Woo; Andriamonje, Samuel; Kadi, Yacine; Tenreiro, Claudio

    2016-05-01

    We have developed MICROMEGAS (MICRO MEsh GASeous) detectors for detecting a particles emitted from an 241Am standard source. The voltage applied to the ionization region of the detector is optimized for stable operation at room temperature and atmospheric pressure. The energy of a particles from the 241Am source can be varied by changing the flight path of the a particle from the 241Am source. The channel numbers of the experimentally-measured pulse peak positions for different energies of the a particles are associated with the energies deposited by the alpha particles in the ionization region of the detector as calculated by using GEANT4 simulations; thus, the energy calibration of the MICROMEGAS detector for a particles is done. For the energy calibration, the thickness of the ionization region is adjusted so that a particles may completely stop in the ionization region and their kinetic energies are fully deposited in the region. The efficiency of our MICROMEGAS detector for a particles under the present conditions is found to be ~97.3%.

  4. A Giant Metrewave Radio Telescope search for associated H I 21 cm absorption in high-redshift flat-spectrum sources

    NASA Astrophysics Data System (ADS)

    Aditya, J. N. H. S.; Kanekar, Nissim; Kurapati, Sushma

    2016-02-01

    We report results from a Giant Metrewave Radio Telescope search for `associated' redshifted H I 21 cm absorption from 24 active galactic nuclei (AGNs), at 1.1 < z < 3.6, selected from the Caltech-Jodrell Bank Flat-spectrum (CJF) sample. 22 out of 23 sources with usable data showed no evidence of absorption, with typical 3σ optical depth detection limits of ≈0.01 at a velocity resolution of ≈30 km s-1. A single tentative absorption detection was obtained at z ≈ 3.530 towards TXS 0604+728. If confirmed, this would be the highest redshift at which H I 21 cm absorption has ever been detected. Including 29 CJF sources with searches for redshifted H I 21 cm absorption in the literature, mostly at z < 1, we construct a sample of 52 uniformly selected flat-spectrum sources. A Peto-Prentice two-sample test for censored data finds (at ≈3σ significance) that the strength of H I 21 cm absorption is weaker in the high-z sample than in the low-z sample; this is the first statistically significant evidence for redshift evolution in the strength of H I 21 cm absorption in a uniformly selected AGN sample. However, the two-sample test also finds that the H I 21 cm absorption strength is higher in AGNs with low ultraviolet or radio luminosities, at ≈3.4σ significance. The fact that the higher luminosity AGNs of the sample typically lie at high redshifts implies that it is currently not possible to break the degeneracy between AGN luminosity and redshift evolution as the primary cause of the low H I 21 cm opacities in high-redshift, high-luminosity AGNs.

  5. Dosimetry in steep dose-rate gradient radiation fields: A challenge in clinical applications

    SciTech Connect

    Massillon-JL, G.

    2010-12-07

    The fundamental goal of radiotherapy is to reduce the damage to normal tissue and optimize the dose to the tumor with an associated high probability of cure. Because of this, an accurate and precise knowledge of the radiation dose distribution delivered around the tumor volume during radiotherapy treatments such as stereotactic radiosurgery, intensity modulated radiotherapy or brachytherapy with low-energy X-ray and beta particle sources is of great importance. However, in each of these radiation fields, there exists a steep dose-rate gradient which makes it very difficult to perform accurate dose measurements. In this work, the physics phenomena involved in the energy absorption for each of these situations are discussed, and a brief revision of what the Medical Physics community is doing is presented.

  6. Dosimetry in steep dose-rate gradient radiation fields: A challenge in clinical applications

    NASA Astrophysics Data System (ADS)

    Massillon-JL, G.

    2010-12-01

    The fundamental goal of radiotherapy is to reduce the damage to normal tissue and optimize the dose to the tumor with an associated high probability of cure. Because of this, an accurate and precise knowledge of the radiation dose distribution delivered around the tumor volume during radiotherapy treatments such as stereotactic radiosurgery, intensity modulated radiotherapy or brachytherapy with low-energy X-ray and beta particle sources is of great importance. However, in each of these radiation fields, there exists a steep dose-rate gradient which makes it very difficult to perform accurate dose measurements. In this work, the physics phenomena involved in the energy absorption for each of these situations are discussed, and a brief revision of what the Medical Physics community is doing is presented.

  7. 2D simulation of granular flow over irregular steep slopes using global and local coordinates

    NASA Astrophysics Data System (ADS)

    Juez, C.; Murillo, J.; García-Navarro, P.

    2013-12-01

    In this work approximate augmented Riemann solvers are formulated providing appropriate numerical schemes for mathematical models of granular flow on irregular steep slopes. Fluxes and source terms are discretized to ensure steady state configurations including correct modeling of start/stop flow conditions, both in a global and a local system of coordinates. The weak solutions presented involve the effect of bed slope in pressure distribution and frictional effects by means of the adequate gravity acceleration components. The numerical solvers proposed are first tested against 1D cases with exact solution and then their results are compared with experimental data in order to check the suitability of the mathematical models described in this work. Comparisons between results provided when using global and local system of coordinates are presented. The obtained results point out that both the global and the local system of coordinates can be used to predict faithfully the overall behavior of the phenomena considered in this work.

  8. Radio continuum spectra of gigahertz-peaked spectrum galaxies

    NASA Astrophysics Data System (ADS)

    Torniainen, I.; Tornikoski, M.; Lähteenmäki, A.; Aller, M. F.; Aller, H. D.; Mingaliev, M. G.

    2007-07-01

    Context: Recent studies have shown that a remarkable share of quasars classified in the literature as gigahertz-peaked spectrum (GPS) sources and high frequency peakers (HFPs) are actually flaring flat-spectrum sources or blazars. Thus, at least among the quasar-type samples, genuine GPS sources and HFPs seem to be rare. Aims: We have studied variability and the shape of the radio continuum spectra of a sample of 96 galaxy-type GPS sources and HFPs in order to find out whether there is a similar contamination in the galaxy-type samples. Methods: We collected radio data for the sample from the literature, our long-term monitoring campaigns, and recent observations, and then plotted the radio continuum spectra. We also calculated the peak frequencies, the spectral indices, and the variability indices, and finally classified the sources according to these parameters. Results: About 30% of the galaxies in our sample are clearly GPS sources, for another ~30% there are not enough data for a solid classification, and the rest are flat- or steep-spectrum sources. Conclusions: The galaxy-type GPS samples seem to be cleaner than the quasar-type, but there is also a remarkable contamination of other source types among the galaxies. However, there may be a strong selection effect, originating from the different selection criteria of the original samples, which must be taken into consideration when comparing the results of this and our previous study. Both simultaneous spectra and long-term monitoring are essential when classifying convex-spectrum sources. However, even monitoring for several years may not reveal the variable nature of a source with a convex radio spectrum. Figures 4 to 9 are only available in electronic form at http://www.aanda.org Table 2 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/469/451

  9. EMERGENCY ROOM: AN UNRECOGNIZED SOURCE OF EXTENDED-SPECTRUM β-LACTAMASE PRODUCING ESCHERICHIA COLI AND KLEBSIELLA PNEUMONIAE.

    PubMed

    Pornsinchai, Pornsook; Chongtrakool, Piriyaporn; Diraphat, Pornphan; Siripanichgon, Kanokrat; Malathum, Kumthorn

    2015-01-01

    Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae are the leading causes of hospital-associated infections, but community-acquired cases are increasingly being reported. This study determined the prevalence of ESBL-producing E. coli and K. pneumoniae carriers, their bla genes and risk factors of 452 patients admitted to the emergency room (ER) of Ramathibodi Hospital, Mahidol University, Bangkok, Thailand between April and August 2011. Prevalence of ESBL-producing E. coli and K. pneumoniae from rectal swabs was 16.5% and 1.0%, respectively. Factors associated with ESBL-producing carriers were a previous history of hospital admission (p = 0.001) and visits to health care facilities (p = 0.002) during the previous 3 months. All ESBL-producing isolates were susceptible to imipenem, meropenem and ertapenem. The majority (78%) of ESBL-producing E. coli isolates showed very high resistance to cefotaxime and ceftriaxone (MIC50 and MIC90 > 256 µg/ml). ESBL-producing E. coli harbored chromosomal blaTEM (96%), blaCTX-M (70%) and blaSHV (1%), while 8%, 73% and 3%, respectively, were located on plasmid. The prevalence of these genes in ESBL-producing K. pneumoniae was 75%, 50% and 25%, respectively on chromosome; and 100%, 25% and 50%, respectively on plasmid. Nucleotide sequence analysis revealed that these bla genes were of the type blaTEM-1' blaTEM-116' blaCTX-M-15' blaCTX-M-161' blaSHV-12, blaSHV-28 and blaSHV-148. Detailed epidemiologic and clinical characteristics of ER patients with history of prior hospital visits should be carried out to identify the ESBL-producing organisms they have acquired in order to institute appropriate treatment for these patients as well as control measures against further dissemination of these life-threatening organisms. PMID:26513905

  10. Lead distribution and possible sources along vertical zone spectrum of typical ecosystems in the Gongga Mountain, eastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Luo, Ji; Tang, Ronggui; Sun, Shouqin; Yang, Dandan; She, Jia; Yang, Peijun

    2015-08-01

    A total of 383 samples from soil, plant, litterfall and precipitation in four typical ecosystems of Gongga Mountain were collected. Pb concentrations of samples were measured and analyzed. The results showed mean Pb concentrations in different soil layers were in the order of O > A > C, and mean Pb concentrations of the aboveground parts of plant was 3.60 ± 2.54 mg kg-1, with the minimum value of 0.77 mg kg-1 and the maximum value of 10.90 mg kg-1. Pb concentrations in soil's O-horizon and A-horizon showed a downward trend with increasing elevation (the determination coefficient R2 was 0.9478, 0.7918 and 0.9759 respectively). In contrast to other soil layers, the level of Pb concentrations in O-horizon (incomplete decomposition) was significantly high. Litterfall decomposition, atmospheric deposition and the unique climate could be main factors leading high Pb accumulation in soil's O-horizon. What's more, significant correlation (R2 = 0.8126, P < 0.05) was found between Pb concentrations in fine roots and soil's A-horizon confirms that fine roots could adsorb and accumulate Pb materials in soil. In general, the fact that Pb inputted into the typical ecosystems in the Gongga Mountain via long-range transportation and deposition of the atmosphere from external Pb sources could be confirmed by the HYSPLIT model and the ratio of CPb/CAl in plants (leaves) and CPb/CAl in litterfall. The mining activities and increasing anthropogenic activities (tourism development) could be main sources of Pb in this area. In order to better understand Pb sources and eco-risks of these typical ecosystems, litterfall decomposition characteristics, biomass of productivity of forest ecosystem, Pb isotopic tracing among air mass, twigs, leaves, litterfall and O-horizon soil in this vertical belt should also be taken into consideration.

  11. Taking the Radio Blinders Off of M83: A Wide Spectrum Analysis of the Historical Point Source Population

    NASA Astrophysics Data System (ADS)

    Stockdale, Christopher; Keefe, Clayton; Nichols, Michael; Rujevcan, Colton; Blair, William P.; Cowan, John J.; Godfrey, Leith; Miller-Jones, James; Kuntz, K. D.; Long, Knox S.; Maddox, Larry A.; Plucinsky, Paul P.; Pritchard, Tyler A.; Soria, Roberto; Whitmore, Bradley C.; Winkler, P. Frank

    2015-01-01

    We present low frequency observations of the grand design spiral galaxy, M83, using the C and L bands of the Karl G. Jansky Very Large Array (VLA). With recent optical (HST) and X-ray (Chandra) observations and utilizing the newly expanded bandwidth of the VLA, we are exploring the radio spectral properties of the historical radio point sources in M83. These observations allow us to probe the evolution of supernova remnants (SNRs) and to find previously undiscovered SNRs. These observations represent the fourth epoch of deep VLA observations of M83. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities.

  12. Spatial Distribution of Acid Neutralizing Processes in Steep Headwater Catchments in Tanakami Mountains, Central Japan

    NASA Astrophysics Data System (ADS)

    Asano, Y.; Uchida, T.; Ohte, N.; Tani, M.

    2001-05-01

    The areas characterized by steep slope, thin soils, and unreactive bedrock types are often considered as acid-sensitive. The purpose of this study is to investigate the spatial distribution of acid neutralizing processes in steep headwater catchment in the humid temperate region, and to discuss the long-term change in acid neutralizing processes associated with the forest growth and soil development. The observations were conducted at two adjacent unchannelled steep catchment, Fudoji (0.10ha) and Rachidani (0.18ha). Two catchments share similar climatic condition and the same bedrock geology (granite). The mean hollow gradient is 37degrees in Fudoji and 34degrees in Rachidani. Fudoji is forested with mean soil depth of 77cm, while Rachidani is non-vegetated with mean soil depth of about 10cm. In both catchments, hydrometric and isotopic measurements illustrated the substantial downward water flux into the bedrock in upslope area and emerging of this water from bedrock to soil layer within 2m from the perennial spring points. The mean pH of soil water and groundwater were dispersed over a wide range of 4.00 to 5.84 in Fudoji and 5.29 to 6.28 in Rachidani, while stream pHs converged very closely to neutral value in two catchments. In both catchments, major H+ sources distributed at the near-surface soil layer and the intensity of internal H+ production was greater in forested Fudoji than non-vegetated Rachidani, attributed to the biological cycles in forest ecosystems. Calculation of budget for base cations (Na+, K+, Ca2+ and Mg2+) presented that 72 to 84 percent (Fudoji) and 34percent (Rachidani) of the net base cation production in each catchment was derived from the bedrock, indicating that a considerable amount of the H+ was consumed within the bedrock. Moreover, the H+ consumption rate per unit volume of soil in Fudoji was almost one order of magnitude smaller than that of Rachidani. These results suggested that the dominant H+ sink in catchments shifted from

  13. Geotechnical properties of cemented sands in steep slopes

    USGS Publications Warehouse

    Collins, B.D.; Sitar, N.

    2009-01-01

    An investigation into the geotechnical properties specific to assessing the stability of weakly and moderately cemented sand cliffs is presented. A case study from eroding coastal cliffs located in central California provides both the data and impetus for this study. Herein, weakly cemented sand is defined as having an unconfined compressive strength (UCS) of less than 100 kPa, and moderately cemented sand is defined as having UCS between 100 and 400 kPa. Testing shows that both materials fail in a brittle fashion and can be modeled effectively using linear Mohr-Coulomb strength parameters, although for weakly cemented sands, curvature of the failure envelope is more evident with decreasing friction and increasing cohesion at higher confinement. Triaxial tests performed to simulate the evolving stress state of an eroding cliff, using a reduction in confinement-type stress path, result in an order of magnitude decrease in strain at failure and a more brittle response. Tests aimed at examining the influence of wetting on steep slopes show that a 60% decrease in UCS, a 50% drop in cohesion, and 80% decrease in the tensile strength occurs in moderately cemented sand upon introduction to water. In weakly cemented sands, all compressive, cohesive, and tensile strength is lost upon wetting and saturation. The results indicate that particular attention must be given to the relative level of cementation, the effects of groundwater or surficial seepage, and the small-scale strain response when performing geotechnical slope stability analyses on these materials. ?? 2009 ASCE.

  14. Radar scattering properties of steep-sided domes on Venus

    NASA Technical Reports Server (NTRS)

    Ford, Peter G.

    1994-01-01

    More than 100 quasi-circular steep-sided volcanic domes, with diameters ranging from 6 to 60 km, have been observed on the surface of Venus by the Magellan radar mapper. Assuming that they have the shape of a solidified high-viscosity Newtonian fluid, their radar scattering properties can be studied in detail from Magellan images, since a typical radar swath resolves each dome into several tens of thousands of measurements of radar cross section at incidence angles varying fom 15 deg to 55 deg. Through examination of 20 domes in detail, it appears that many of those situated on lava plains scatter radar in a manner that is indistinguishable from that of the surrounding material, suggesting that either (1) they were formed of a relatively high-density high-viscosity material, e.g., andesite, rather than a lower-density one, e.g., rhyolite or dacite; or (2) that their surfaces share a common origin with those of their surroundings, e.g., through in situ weathering or aeolian deposition.

  15. Buoyant Turbulent Kinetic Energy Production in Steep-Slope Katabatic Flow

    NASA Astrophysics Data System (ADS)

    Oldroyd, Holly J.; Pardyjak, Eric R.; Higgins, Chad W.; Parlange, Marc B.

    2016-07-01

    We develop several critical concepts that should be considered when interpreting, modelling and designing future experiments for flows over sloping terrain. Vertical buoyancy fluxes in katabatic flows can be positive and a source of turbulent kinetic energy (TKE) despite the statically stable, thermal stratification that drives these flows. This phenomenon occurs when the ratio of along-slope to slope-normal kinematic heat fluxes is greater than the cotangent of the slope angle, suggesting a critical value of slope-angle steepness found in earlier studies. We provide field-data-based evidence that the along-slope heat flux may dominate the variables in this inequality, and therefore in generating buoyant TKE production or suppression over a steep slope. These data show the along-slope heat flux can be more variable and significantly larger in magnitude than the slope-normal component. The gradient Richardson number does not include the effects of the along-slope buoyancy; furthermore, none of the canonical stability parameters can properly reflect the TKE redistribution from turbulent transport divergence and the sink of TKE in cases of counter-gradient momentum fluxes, which we frequently observe near the peak of the katabatic jet. In such cases, canonical stability parameters inadequately represent the physical mechanisms associated with stability. These results have broad implications related to accurately modelling turbulence and surface exchanges over sloping terrain and illustrate the need to more thoroughly investigate the along-slope heat flux and its drivers, the meaning and definitions of stability, and the effects of non-local turbulent transport.

  16. A novel ultra steep dynamically reconfigurable electrostatically doped silicon nanowire Schottky Barrier FET

    NASA Astrophysics Data System (ADS)

    Singh, Sangeeta; Sinha, Ruchir; Kondekar, P. N.

    2016-05-01

    In this paper, an ultra steep, symmetric and dynamically configurable, electrostatically doped silicon nanowire Schottky FET (E-SiNW-SB-FET) based on dopant-free technology is investigated. It achieves the ultra steep sub-threshold slope (SS) due to the cumulative effect of weak impact-ionization induced positive feedback and electrostatic modulation of Schottky barrier heights at both source and drain terminals. It consists of axial nanowire heterostructure (silicide-intrinsic silicon-silicide) with three independent all-around gates, two gates are polarity control gates for dynamically reconfiguring the device polarity by modulating the effective Schottky barrier heights and a control gate switches the device ON and OFF. The most interesting features of the proposed structure are simplified fabrication process as the state-of-the-art for ion implantation and high thermal budget no more required for annealing. It is highly immune to process variations, doping control issues and random dopant fluctuations (RDF) and there are no mobility degradation issues related to high doping. A calibrated 3-D TCAD simulation results exhibit the SS of 2 mV/dec for n-type E-SiNW-SB-FET and 9 mV/dec for p-type E-SiNW-SB-FET for about five decades of current. Further, it resolves all the reliability related issues of IMOS as hot electron effects are no more limiting our device performance. It offers significant drive current of the order of 10-5-10-4 A and magnificently high ION/IOFF ratio of ∼108 along with the inherent advantages of symmetric device structure for its circuit realization.

  17. On the determination of the cosmic infrared background radiation from the high-energy spectrum of extragalactic gamma-ray sources

    NASA Technical Reports Server (NTRS)

    Dwek, Eli; Slavin, Jonathan

    1994-01-01

    In a recent paper Stecker, De Jager, & Salamon have suggested using the observed approximately MeV to TeV spectra of extragalactic gamma-ray sources as probes of the local density of the cosmic infrared background radiation (CIBR) and have subsequently claimed a first possible measurement of the CIBR from the analysis of the gamma-ray spectrum of Mrk 421 (De Jager, Stecker, & Salamon). The CIBR from normal galaxies consists of two components: a stellar emission component (CIBRs), and a thermal dust emission component (CIBRd). Photons with energies in the approximately 0.1-2 TeV range interact primarily with the CIBRs, whereas interactions with CIBRd dominate the absorption of photons in the approximately 2-100 TeV energy range. SDS 92 and DSS94 considered only the interaction of the gamma-rays with the dust emission component of the CIBR. We present here an improved analysis of the absorption of extragalactic TeV gamma rays by the CIBR, taking the dual nature of its origin into account. Applying the analysis to the observed gamma-ray spectrum of Mrk 421, a BL Lac object at z = 0.031, we find agreement with DSS94 tentative evidence for absorption by the CINRs. Our analysis therefore limits the detection of the CIBR to the approximately 15-40 micron wavelength regime which, considering the uncertainties in the highest energy (greater than 4 TeV) data and ion the possibility of absorption inside the source, many turn out to be an upper limit on its energy density. At shorter wavelengths (lambda approximately = 1-15 microns), where the gamma-ray interactions are dominated by the CIBRs, our analysis definitely yields only an upper limit on the energy density of the CIBR. In contrast, DSS94 have claimed a possible first measurement of the CIBR over the entire 1-120 micron wavelength region. The upper limit on the CIBRs and tentative detection of the CIBRd are consistent with normal galaxies contributing most of the energy to the CIBR, and constrain the contribution of

  18. Measuring noise equivalent irradiance of a digital short-wave infrared imaging system using a broadband source to simulate the night spectrum

    NASA Astrophysics Data System (ADS)

    Green, John R.; Robinson, Timothy

    2015-05-01

    There is a growing interest in developing helmet-mounted digital imaging systems (HMDIS) for integration into military aircraft cockpits. This interest stems from the multiple advantages of digital vs. analog imaging such as image fusion from multiple sensors, data processing to enhance the image contrast, superposition of non-imaging data over the image, and sending images to remote location for analysis. There are several properties an HMDIS must have in order to aid the pilot during night operations. In addition to the resolution, image refresh rate, dynamic range, and sensor uniformity over the entire Focal Plane Array (FPA); the imaging system must have the sensitivity to detect the limited night light available filtered through cockpit transparencies. Digital sensor sensitivity is generally measured monochromatically using a laser with a wavelength near the peak detector quantum efficiency, and is generally reported as either the Noise Equivalent Power (NEP) or Noise Equivalent Irradiance (NEI). This paper proposes a test system that measures NEI of Short-Wave Infrared (SWIR) digital imaging systems using a broadband source that simulates the night spectrum. This method has a few advantages over a monochromatic method. Namely, the test conditions provide spectrum closer to what is experienced by the end-user, and the resulting NEI may be compared directly to modeled night glow irradiance calculation. This comparison may be used to assess the Technology Readiness Level of the imaging system for the application. The test system is being developed under a Cooperative Research and Development Agreement (CRADA) with the Air Force Research Laboratory.

  19. Numerical calculations of spectral turnover and synchrotron self-absorption in CSS and GPS radio sources

    NASA Astrophysics Data System (ADS)

    Jeyakumar, S.

    2016-06-01

    The dependence of the turnover frequency on the linear size is presented for a sample of Giga-hertz Peaked Spectrum and Compact Steep Spectrum radio sources derived from complete samples. The dependence of the luminosity of the emission at the peak frequency with the linear size and the peak frequency is also presented for the galaxies in the sample. The luminosity of the smaller sources evolve strongly with the linear size. Optical depth effects have been included to the 3D model for the radio source of Kaiser to study the spectral turnover. Using this model, the observed trend can be explained by synchrotron self-absorption. The observed trend in the peak-frequency-linear-size plane is not affected by the luminosity evolution of the sources.

  20. Effect of steeping conditions on the amylolytic development of some Nigerian improved sorghum cultivars.

    PubMed

    Ukwuru, M U

    2010-01-01

    Nigerian improved sorghum cultivars 'L538', 'YG5760', 'L1499', 'SSH1' and 'SSH3' were investigated for the effect of steeping conditions on their amylolytic development. The grains were steeped using 3 steep regimes SR 1, SR 2 and SR 3 which involved steeping and re-steeping in cold distilled and de-ionized water for 36, 45 and 54 h respectively. Grains in each SR were divided into 4 portions and further steeped for 6 h using final warm steep temperatures (FWST) of 30, 35, 40 and 45°C. α-and β-Amylase as well as diastatic activity were determined at different FWST. SR and FWST were correlated with enzyme development. Steeping conditions significantly (p<0.05) affected amylolytic development of the sorghum malts. Optimum moisture content (48%) was obtained at FWST of 35°C. α-Amylase was the predominant enzyme. All enzyme activities were at a peak at FWST of 30 and 35°C and at SR 2. The highest enzyme activity was recorded by cultivar 'YG5760' malt-(α-amylase 272, β-Amylase 169 μg equivalent glucose). High relationship existed between α-amylase and moderate relationship between β-Amylase and SR. Similar relationship existed between enzyme development and FWST. PMID:23572602

  1. Parent population of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies

    NASA Astrophysics Data System (ADS)

    Berton, M.; Foschini, L.; Ciroi, S.; Cracco, V.; La Mura, G.; Lister, M. L.; Mathur, S.; Peterson, B. M.; Richards, J. L.; Rafanelli, P.

    2015-06-01

    Flat-spectrum radio-loud narrow-line Seyfert 1 galaxies (NLS1s) are a recently discovered class of γ-ray emitting active galactic nuclei (AGN), that exhibit some blazar-like properties which are explained with the presence of a relativistic jet viewed at small angles. When blazars are observed at larger angles they appear as radio-galaxies, and we expect to observe an analogue parent population for beamed NLS1s. However, the number of known NLS1s with the jet viewed at large angles is not enough. Therefore, we tried to understand the origin of this deficit. Current hypotheses about the nature of parent sources are steep-spectrum radio-loud NLS1s, radio-quiet NLS1s and disk-hosted radio-galaxies. To test these hypotheses we built three samples of candidate sources plus a control sample, and calculated their black hole mass and Eddington ratio using their optical spectra. We then performed a Kolmogorov-Smirnov statistical test to investigate the compatibility of our different samples with a beamed population. Our results indicate that, when the inclination angle increases, a beamed source appears as a steep-spectrum radio-loud NLS1, or possibly even as a disk-hosted radio-galaxy with low black hole mass and high Eddington ratio. Further investigations, involving larger complete samples and observations at radio frequency, are needed to understand the incidence of disk-hosted radio-galaxies in the parent population, and to assess whether radio-quiet NLS1s can play a role, as well. Appendix A is available in electronic form at http://www.aanda.org

  2. Zellweger Spectrum

    MedlinePlus

    ... the Zellweger spectrum result from defects in the assembly of a cellular structure called the peroxisome, and ... Zellweger spectrum are caused by defects in the assembly of the peroxisome. There are at least 12 ...

  3. Flood and Debris Flow Hazard Predictions in Steep, Burned Landscapes

    NASA Astrophysics Data System (ADS)

    Rengers, Francis; McGuire, Luke; Kean, Jason; Staley, Dennis

    2016-04-01

    scale. The calibrated effective watershed hydraulic conductivity was low for both models, even for storms occurring several months after the fire, consistent with wildfire-induced water-repellency being retained throughout that time. Both models captured the timing of flow peaks, although neither model correctly simulated the flow depth. This study suggests that a kinematic wave model, which is simpler and more computationally efficient, is a justifiable approach for predicting flood and debris flow timing in steep, burned watersheds. By demonstrating the applicability of these models, this study takes an important step towards the development of process-based methods to assess post-wildfire flood and debris flow hazards.

  4. Effect of Wildfire on Sediment Sorting in a Steep Channel

    NASA Astrophysics Data System (ADS)

    Florsheim, J. L.; Chin, A.; O'Hirok, L.; Storesund, R.

    2014-12-01

    Wildfire is an external forcing factor in the landscape. In chaparral environments, wildfire initiates transport of well-sorted fine sediment through dry-ravel processes on hillslopes and facilitates delivery of sediment to stream channels. In turn, this periodic post-fire sediment influx governs sorting of channel-bed material during subsequent floods that mobilize and transport the sediment downstream. We investigated the effects of the May 2013 Springs Wildfire in the Santa Monica Mountains in semi-arid southern California with field measurements and terrestrial LiDAR scanning. Before the fire, sediment sorting within the heterogeneous bed material present in Big Sycamore Creek was controlled by organized step-pool bedforms. Boulders formed steps with relatively finer cobbles, gravel, and sand filling the pools. Before the fire, the grain size distribution present in the substrate between boulder steps was relatively coarse (D84 = 250 mm), in contrast to that in the influx of sediment contributed by post-fire dry-ravel processes deposited at channel margins (D84 = 8 mm). Flow shear stress during one small flood in 2014 (post-fire) was adequate to mobilize fine dry ravel- related sediment. Transport capacity was sufficient to mobilize and transport this sediment within a study reach; however, it was not adequate to flush the fine material downstream. Shear stress required to mobilize sediment contributed by dry ravel was substantially less than that required to transport the substrate material present before the wildfire. The small flood deposited fine sediment (D84 = 16 mm) as flow lost capacity. Resulting deposition buried bedforms, changing the step-pool profile to a plane bed. The relatively poorly sorted, coarse, rough bed changed to a well sorted, fine, smooth, bed. These changes have implications for sediment transport dynamics and aquatic ecology. In steep, semi-arid, chaparral fluvial systems, sediment derived from dry-ravel processes influences the

  5. Mid-Infrared Observations of Class I/Flat-Spectrum Systems in Six Nearby Molecular Clouds

    NASA Astrophysics Data System (ADS)

    Haisch, K.; Barsony, M.; Greene, T.; Ressler, M.

    2005-12-01

    We present the results of new mid-infrared observations of 64 Class I/flat-spectrum objects in the Perseus, Taurus, Chamaeleon I and II, Rho Ophiuchi, and Serpens dark clouds. These objects represent a subset of the young stellar objects (YSOs) from our previous near-infrared multiplicity surveys. We detected 45/48 (94%) of the single sources, 16/16 (100%) of the primary components, and 12/16 (75%) of the secondary/triple components of the binary/multiple objects surveyed. While the composite spectral energy distributions for all of our sample YSOs are either Class I or flat-spectrum, the individual source components typically display Class II, or in one case Class III, spectral indices, and frequently display mixed pairings; Class I objects paired with a flat-spectrum source, or a flat-spectrum source paired with a Class II YSO. Such behavior is not consistent with what one typically finds for T Tauri stars (TTS), where the companion of a classical TTS also tends to be a classical TTS, although other mixed pairings have been previously observed among Class II YSOs. In general, the individual binary/multiple components suffer very similar extinctions, Av, suggesting that most of the line-of-sight material is either in the foreground of the molecular cloud or circumbinary. ISO-Cha I 97 was previously detected as a single star in our near-infrared imaging survey of binary/multiple Class I and flat-spectrum YSOs, however our mid-infrared observations have revealed that this source is in fact binary. With a spectral index of α > 3.9, ISO-Cha I 97 is a member of a rare class of very steep spectral index YSOs, those with α > 3.

  6. What Did We Learn From Chandra, Xmm-Newton And Fermi-Lat About The High Energy Emission In Young Radio Sources?

    NASA Astrophysics Data System (ADS)

    Siemiginowska, Aneta; Guainazzi, M.; Hardcastle, M.; Kelly, B. C.; Kunert-Bajraszewska, M.; Migliori, G.; Sobolewska, M.; Stawarz, L.

    2013-04-01

    Giga-Hertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radio sources comprise a large population of compact objects with radio emission fully contained within the innermost regions of the host galaxy (< a few kpc). Spectral and kinematic age measurements indicate their young age (typically < thousands years and in some cases less a few hundred years). These sources provide the important insights to the initial phase of the jet formation, radio source growth, source evolution and the jet impact on the ISM in the very central regions of the host galaxy. We have obtained Chandra and XMM-Newton observations for a large sample of these sources over several observing cycles. Our most recent Chandra observations targeted Compact Symmetric Objects (CSO) associated with the nuclear regions of nearby galaxies. All these CSO have measured kinematic ages within 100-3000 year old. I will present the results of our ongoing observing program focusing on the high energy properties of these young sources.

  7. Joint distribution of successive wave steepness parameters. [Water wave modeling and effects on offshore oil platforms

    SciTech Connect

    Myrhaug, D. . Dept. of Marine Hydrodynamics); Rue, H. . Division of Industrial Mathematics)

    1993-08-01

    In this paper, a joint distribution of wave steepness parameters for two successive waves is presented. The wave steepness parameters considered herein are the crest front steepness and the total wave steepness. The joint distribution of wave steepness parameters for two successive waves is represented by a two-dimensional Weibull distribution with the parameters [alpha]=0.84 and [beta]=1.40. The application of the results is illustrated by an example. Overall these results seem to be physically sound, although they are valid for the particular sea state chosen. The present approach has some basis in measured wave data, but comparison with data on the joint distribution of steepness parameters for two successive waves are needed before any conclusion can be drawn on the ability of this approach to describe measured wave data. Such a data base should be established from carefully designed field measurements in order to have the possibility to measure nonlinear properties of the waves. However, at present this joint distribution of steepness parameters for two successive waves should represent a useful tool for engineering applications.

  8. Along-Arc and Back-Arc Attenuation, Site Response, and Source Spectrum for the Intermediate-Depth 8 January 2006 M 6.7 Kythera, Greece, Earthquake

    USGS Publications Warehouse

    Boore, D.M.; Skarlatoudis, A.A.; Margaris, B.N.; Costas, B.P.; Ventouzi, C.

    2009-01-01

    An M 6.7 intermediate-depth (66 km), in-slab earthquake occurring near the island of Kythera in Greece on 8 January 2006 was well recorded on networks of stations equipped with acceleration sensors and with broadband velocity sensors. All data were recorded digitally using recording instruments with resolutions ranging from almost 11 to 24 bits. We use data from these networks to study the distance dependence of the horizontal-component Fourier acceleration spectra (FAS) and horizontal-component pseudoabsolute response spectral acceleration (PSA). For purposes of simulating motions in the future, we parameterize the distance decay using several forms of the geometrical-spreading function, for each of which we derive Q as a function of frequency. By extrapolating the distance decay back to 1 km, we obtain a reference spectrum that can be used in future simulations. This spectrum requires a more complicated spectral shape than the classic single-corner-frequency model; in particular, there appears to be an enhancement of motion around 0.2-0.3 Hz that may be due to the radiation of a 3-5 sec pulse from the source. We infer a ??0 value of about 0.055 sec for rock stations and a stress parameter in the range of 400-600 bars. We also find distinctive differences in the site response of stations on soft soil and soil; both the FAS and the 5% damped PSA amplifications have similar peak amplitudes (about 2 and 4 for soil and soft-soil sites, respectively, relative to the rock sites) at similar frequencies (between about 0.4 and 2.0 Hz, with the soft-soil amplifications peaking at somewhat lower frequencies than the soil amplifications). One of the most distinctive features of the data is the clear difference in the motions for along-arc and back-arc stations, with the former being significantly higher than the latter over a broad range of frequencies at distances beyond about 250 km. The motions from the Kythera earthquake are roughly comparable to those from intermediate

  9. Seismic wave propagation in thinly-layered media with steep reflectors

    SciTech Connect

    Deng, H.L.

    1992-05-01

    Seismic waves reflected from steep reflectors in the earth`s subsurface spend a significant amount of time travelling more or less horizontally. Therefore, accurate imaging of steep geologic structure requires knowledge of the behavior of these horizontally propagating waves. In particular, the effect of tunneling on seismic waves propagating in thinly-layered media must be understood. I describe a method for modeling seismic waves traveling in thinly-layered media. This method, a frequency-wavenumber finite-difference scheme coupled with the Born approximation, is useful in studying seismic waves reflected from steep geologic structures.

  10. Seismic wave propagation in thinly-layered media with steep reflectors

    SciTech Connect

    Deng, H.L.

    1992-05-01

    Seismic waves reflected from steep reflectors in the earth's subsurface spend a significant amount of time travelling more or less horizontally. Therefore, accurate imaging of steep geologic structure requires knowledge of the behavior of these horizontally propagating waves. In particular, the effect of tunneling on seismic waves propagating in thinly-layered media must be understood. I describe a method for modeling seismic waves traveling in thinly-layered media. This method, a frequency-wavenumber finite-difference scheme coupled with the Born approximation, is useful in studying seismic waves reflected from steep geologic structures.

  11. The infrared properties of the GPS and CSS radio sources

    NASA Astrophysics Data System (ADS)

    O'Dea, C. P.

    2016-02-01

    I review the results of three Spitzer studies of GHz-Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radio galaxies. The luminosity of the IR continuum and the high ionization lines confirm that some GPS/CSS can have central engines which are similar to those of the extended powerful radio sources. This is consistent with the hypothesis that some GPS/CSS can evolve to become the large-scale sources. Warm H_2 is common in the GPS/CSS sources consistent with feedback via jet-ISM interaction. The GPS/CSS seem to have higher star formation rates than typical (2JY + 3CRR) radio sources. This should be confirmed with a larger sample. If compact sources interact with dense, clumpy star forming clouds and if the interaction with the dense medium sufficiently enhances the radio power, these star forming galaxies with enhanced radio emission will be selected for the current bright samples of GPS and CSS sources. This will increase the number of GPS and CSS sources which are observed to be forming stars. If radio sources have longer lives and/or star formation is more common in large radio galaxies, the need for a new population of star forming compact sources with enhanced radio emission is reduced.

  12. Critical Shields Values in Coarse-Bedded Steep Streams

    NASA Astrophysics Data System (ADS)

    Bunte, K.; Abt, S. R.; Swingle, K. W.; Cenderelli, D. A.; Schneider, J. M.

    2013-12-01

    Critical Shields values for poorly mobile, semi-alluvial mountain streams are not provided by the original Shields diagram and are still debated. This empirical study uses gravel bedload samples collected with unbiasing samplers at 22 stream sites and establishes a relation between instantaneous discharge and the largest sampled bedload particle size for each site. Using relations between flow depth and discharge, critical Shields values for particle sizes corresponding to the bed surface D50, D16, D84, and D50s sizes at each site can be backcomputed from the established critical flow or flow competence relations. Critical Shields values for all bed material particle size percentiles increase with stream gradient Sx and are stratifiable by relative flow depth d/D50 and relative roughness (D84/d) which improves prediction. Critical Shields values for the bed D16 sizes (τ*c16) are approximately three times larger than those for the D50 size (τ*c50), while those for the D84 size (τ*c84) are approximately half of τ*c50. It remains unclear to what extent physical processes or numerical artifacts contribute to determining critical Shields values. Specific critical Shields values are needed to predict the average largest particle size mobile at bankfull flow (DBmax,bf). So far, no Shields values are available for this common task, especially not in poorly mobile semi-alluvial streams. Critical bankfull Shields values (τ*cbf) backcomputed from the largest particles transported at bankfull flow approach τ*c16 at steep gradient streams and τ*c84 at low gradients and therefore increase very steeply with Sx. The relation τ*cbf = f(Sx) is stratified by bed mobility D50/DBmax,bf and predictable if bed mobility can be categorized in the field. Non-critical Shields values (τ*bf50) computed from bankfull flow depth and the bed surface D50 size differ from τ*c50 and from critical bankfull Shields values τ*cbf. Only in bankfull mobile streams where D50/DBmax,bf = 1 can

  13. Wavenumber spectrum of whistler turbulence: Particle-in-cell simulation

    SciTech Connect

    Saito, S.; Gary, S. Peter; Narita, Y.

    2010-12-15

    The forward cascade of decaying whistler turbulence is studied in low beta plasma to understand essential properties of the energy spectrum at electron scales, by using a two-dimensional electromagnetic particle-in-cell (PIC) simulation. This simulation demonstrates turbulence in which the energy cascade rate is greater than the dissipation rate at the electron inertial length. The PIC simulation shows that the magnetic energy spectrum of forward-cascaded whistler turbulence at electron inertial scales is anisotropic and develops a very steep power-law spectrum which is consistent with recent solar wind observations. A comparison of the simulated spectrum with that predicted by a phenomenological turbulence scaling model suggests that the energy cascade at the electron inertial scale depends on both magnetic fluctuations and electron velocity fluctuations, as well as on the whistler dispersion relation. Thus, not only kinetic Alfven turbulence but also whistler turbulence may explain recent solar wind observations of very steep magnetic spectra at short scales.

  14. Cost-effective temporary microirrigation system for grass establishment on environmentally sensitive steep slopes

    SciTech Connect

    Gyasi-Agyei, Y.

    2004-05-15

    An advanced technology cost-effective drip irrigation system design and setup on environmentally sensitive elevated steep slopes (batters) of a coal train derailment site in Central Queensland, Australia, are presented. The final profile of the coal burial site consists of six batters and associated berms with a drop in elevation of about 35 m. A small dam constructed downstream of the confluence of the two main drainage channels at the site supplied water for irrigation of the batters to aid the establishment of grass to control erosion. Water was periodically pumped from the small dam to three storage tanks using a petrol (gas) pump. Three solar pumps drew water from the storage tanks and dam to irrigate the top four batters. Contactors, pressure switches and irrigation control valves in turn shared a single solar power source between the solar pumps. Level balls (floating switches) placed in the storage tanks cut the solar power supply to the pumps when the storage tanks were nearly empty. On the whole, the irrigation system worked very well and excellent grass cover was established within 12 weeks. Given the environmental risks associated with the on-site burying of coal, and the estimated cost of about AU$11.73/m{sup 2} (every 10 years) in maintenance if the railway batters are not treated, the estimated total cost of AU$4.61/m{sup 2} of batter area treated with irrigation, including AU$3.08/m{sup 2} in irrigation cost, is justified.

  15. A steep-slope transistor based on abrupt electronic phase transition

    PubMed Central

    Shukla, Nikhil; Thathachary, Arun V.; Agrawal, Ashish; Paik, Hanjong; Aziz, Ahmedullah; Schlom, Darrell G.; Gupta, Sumeet Kumar; Engel-Herbert, Roman; Datta, Suman

    2015-01-01

    Collective interactions in functional materials can enable novel macroscopic properties like insulator-to-metal transitions. While implementing such materials into field-effect-transistor technology can potentially augment current state-of-the-art devices by providing unique routes to overcome their conventional limits, attempts to harness the insulator-to-metal transition for high-performance transistors have experienced little success. Here, we demonstrate a pathway for harnessing the abrupt resistivity transformation across the insulator-to-metal transition in vanadium dioxide (VO2), to design a hybrid-phase-transition field-effect transistor that exhibits gate controlled steep (‘sub-kT/q') and reversible switching at room temperature. The transistor design, wherein VO2 is implemented in series with the field-effect transistor's source rather than into the channel, exploits negative differential resistance induced across the VO2 to create an internal amplifier that facilitates enhanced performance over a conventional field-effect transistor. Our approach enables low-voltage complementary n-type and p-type transistor operation as demonstrated here, and is applicable to other insulator-to-metal transition materials, offering tantalizing possibilities for energy-efficient logic and memory applications. PMID:26249212

  16. A steep-slope transistor based on abrupt electronic phase transition

    NASA Astrophysics Data System (ADS)

    Shukla, Nikhil; Thathachary, Arun V.; Agrawal, Ashish; Paik, Hanjong; Aziz, Ahmedullah; Schlom, Darrell G.; Gupta, Sumeet Kumar; Engel-Herbert, Roman; Datta, Suman

    2015-08-01

    Collective interactions in functional materials can enable novel macroscopic properties like insulator-to-metal transitions. While implementing such materials into field-effect-transistor technology can potentially augment current state-of-the-art devices by providing unique routes to overcome their conventional limits, attempts to harness the insulator-to-metal transition for high-performance transistors have experienced little success. Here, we demonstrate a pathway for harnessing the abrupt resistivity transformation across the insulator-to-metal transition in vanadium dioxide (VO2), to design a hybrid-phase-transition field-effect transistor that exhibits gate controlled steep (`sub-kT/q') and reversible switching at room temperature. The transistor design, wherein VO2 is implemented in series with the field-effect transistor's source rather than into the channel, exploits negative differential resistance induced across the VO2 to create an internal amplifier that facilitates enhanced performance over a conventional field-effect transistor. Our approach enables low-voltage complementary n-type and p-type transistor operation as demonstrated here, and is applicable to other insulator-to-metal transition materials, offering tantalizing possibilities for energy-efficient logic and memory applications.

  17. Negative Capacitance in Organic/Ferroelectric Capacitor to Implement Steep Switching MOS Devices.

    PubMed

    Jo, Jaesung; Choi, Woo Young; Park, Jung-Dong; Shim, Jae Won; Yu, Hyun-Yong; Shin, Changhwan

    2015-07-01

    Because of the "Boltzmann tyranny" (i.e., the nonscalability of thermal voltage), a certain minimum gate voltage in metal-oxide-semiconductor (MOS) devices is required for a 10-fold increase in drain-to-source current. The subthreshold slope (SS) in MOS devices is, at best, 60 mV/decade at 300 K. Negative capacitance in organic/ferroelectric materials is proposed in order to address this physical limitation in MOS technology. Here, we experimentally demonstrate the steep switching behavior of a MOS device-that is, SS ∼ 18 mV/decade (much less than 60 mV/decade) at 300 K-by taking advantage of negative capacitance in a MOS gate stack. This negative capacitance, originating from the dynamics of the stored energy in a phase transition of a ferroelectric material, can achieve the step-up conversion of internal voltage (i.e., internal voltage amplification in a MOS device). With the aid of a series-connected negative capacitor as an assistive device, the surface potential in the MOS device becomes higher than the applied gate voltage, so that a SS of 18 mV/decade at 300 K is reliably observed. PMID:26103511

  18. Experimental characterization of the Advanced Liquid Hydrogen Cold Neutron Source spectrum of the NBSR reactor at the NIST Center for Neutron Research

    NASA Astrophysics Data System (ADS)

    Cook, J. C.; Barker, J. G.; Rowe, J. M.; Williams, R. E.; Gagnon, C.; Lindstrom, R. M.; Ibberson, R. M.; Neumann, D. A.

    2015-08-01

    The recent expansion of the National Institute of Standards and Technology (NIST) Center for Neutron Research facility has offered a rare opportunity to perform an accurate measurement of the cold neutron spectrum at the exit of a newly-installed neutron guide. Using a combination of a neutron time-of-flight measurement, a gold foil activation measurement, and Monte Carlo simulation of the neutron guide transmission, we obtain the most reliable experimental characterization of the Advanced Liquid Hydrogen Cold Neutron Source brightness to date. Time-of-flight measurements were performed at three distinct fuel burnup intervals, including one immediately following reactor startup. Prior to the latter measurement, the hydrogen was maintained in a liquefied state for an extended period in an attempt to observe an initial radiation-induced increase of the ortho (o)-hydrogen fraction. Since para (p)-hydrogen has a small scattering cross-section for neutron energies below 15 meV (neutron wavelengths greater than about 2.3 Å), changes in the o- p hydrogen ratio and in the void distribution in the boiling hydrogen influence the spectral distribution. The nature of such changes is simulated with a continuous-energy, Monte Carlo radiation-transport code using 20 K o and p hydrogen scattering kernels and an estimated hydrogen density distribution derived from an analysis of localized heat loads. A comparison of the transport calculations with the mean brightness function resulting from the three measurements suggests an overall o- p ratio of about 17.5(±1) % o- 82.5% p for neutron energies<15 meV, a significantly lower ortho concentration than previously assumed.

  19. MEASURING THE JET POWER OF FLAT-SPECTRUM RADIO QUASARS

    SciTech Connect

    Shabala, S. S.; Santoso, J. S.; Godfrey, L. E. H.

    2012-09-10

    We use frequency-dependent position shifts of flat-spectrum radio cores to estimate the kinetic power of active galactic nucleus (AGN) jets. We find a correlation between the derived jet powers and AGN narrow-line luminosity, consistent with the well-known relation for radio galaxies and steep spectrum quasars. This technique can be applied to intrinsically weak jets even at high redshift.

  20. The compact radio structure of radio-loud NLS1 galaxies and the relationship to CSS sources

    NASA Astrophysics Data System (ADS)

    Gu, M.; Chen, Y.; Komossa, S.; Yuan, W.; Shen, Z.

    2016-02-01

    Narrow-line Seyfert 1 galaxies are thought to be young AGNs with relatively small black hole masses and high accretion rates. Radio-loud narrow-line Seyfert 1 galaxies (RLNLS1s) are very special, because some of them show blazar-like characteristics, while others resemble compact steep-spectrum sources. Relativistic jets were shown to exist in a few RLNLS1s based on VLBI observations and confirmed by the gamma-ray flaring of some of them. These properties may possibly be contrary to typical radio-loud AGNs, in light of the low black-hole masses, and high accretion rates. We present the compact radio structure of fourteen RLNLS1 galaxies from Very Long Baseline Array observations at 5 GHz in 2013. Although all these sources are very radio-loud with {R > 100}, their jet properties are diverse, in terms of their milli-arcsecond (mas) scale (pc scale) morphology and their overall radio spectral shape. The core brightness temperatures of our sources are significantly lower than those of blazars, therefore, the beaming effect is generally not significant in our sources, compared to blazars. This implies that the bulk jet speed may likely be low in our sources. The relationship between RLNLS1s and compact steep-spectrum sources, and the implications on jet formation are discussed based on the pc-scale jet properties.

  1. SPECTRUM AND MORPHOLOGY OF THE TWO BRIGHTEST MILAGRO SOURCES IN THE CYGNUS REGION: MGRO J2019+37 AND MGRO J2031+41

    SciTech Connect

    Abdo, A. A.; Abeysekara, U.; Linnemann, J. T.; Allen, B. T.; Aune, T.; Berley, D.; Goodman, J. A.; Bonamente, E.; Galbraith-Frew, J. G.; Huentemeyer, P. H.; Hui, C. M.; Christopher, G. E.; Kolterman, B. E.; Mincer, A. I.; DeYoung, T.; Dingus, B. L.; Hoffman, C. M.; Ellsworth, R. W.; Gonzalez, M. M.; McEnery, J. E. E-mail: petra@mtu.edu; and others

    2012-07-10

    The Cygnus region is a very bright and complex portion of the TeV sky, host to unidentified sources and a diffuse excess with respect to conventional cosmic-ray propagation models. Two of the brightest TeV sources, MGRO J2019+37 and MGRO J2031+41, are analyzed using Milagro data with a new technique, and their emission is tested under two different spectral assumptions: a power law and a power law with an exponential cutoff. The new analysis technique is based on an energy estimator that uses the fraction of photomultiplier tubes in the observatory that detect the extensive air shower. The photon spectrum is measured in the range 1-100 TeV using the last three years of Milagro data (2005-2008), with the detector in its final configuration. An F-test indicates that MGRO J2019+37 is better fit by a power law with an exponential cutoff than by a simple power law. The best-fitting parameters for the power law with exponential cutoff model are a normalization at 10 TeV of 7{sup +5}{sub -2} Multiplication-Sign 10{sup -10} s{sup -1} m{sup -2} TeV{sup -1}, a spectral index of 2.0{sup +0.5}{sub -1.0}, and a cutoff energy of 29{sup +50}{sub -16} TeV. MGRO J2031+41 shows no evidence of a cutoff. The best-fitting parameters for a power law are a normalization of 2.1{sup +0.6}{sub -0.6} Multiplication-Sign 10{sup -10} s{sup -1} m{sup -2} TeV{sup -1} and a spectral index of 3.22{sup +0.23}{sub -0.18}. The overall flux is subject to a {approx}30% systematic uncertainty. The systematic uncertainty on the power-law indices is {approx}0.1. Both uncertainties have been verified with cosmic-ray data. A comparison with previous results from TeV J2032+4130, MGRO J2031+41, and MGRO J2019+37 is also presented.

  2. Spectrum and Morphology of the Two Brightest Milagro Sources in the Cygnus Region: MGRO J2019+37 and MGRO J2031+41

    NASA Technical Reports Server (NTRS)

    Abdo, A. A.; Abeysekara, U.; Allen, B, T.; Aune, T.; Berley, D.; Bonamente, E.; Christopher, G. E.; DeYoung, T.; Dingus, B. L.; Ellsworth, R. W.; Galbraith-Frew, J. G.; Gonzalez, M. M.; Goodman, J. A.; Hoffman, C. M.; Huentemeyer, P. H.; Hui, C. M.; Kolterman, B. E.; Linnemann, J . T.; McEnery, J. E.; Mincer, A. I.; Morgan, T.; Nemethy, P.; Pretz, J.; Ryan, J. M.; Vasileiou, V.

    2012-01-01

    The Cygnus region is a very bright and complex portion of the TeV sky, host to unidentified sources and a diffuse excess with respect to conventional cosmic-ray propagation models. Two of the brightest TeV sources, MGRO J2019+37 and MGRO J2031+41, are analyzed using Milagro data with a new technique, and their emission is tested under two different spectral assumptions: a power law and a power law with an exponential cutoff. The new analysis technique is based on an energy estimator that uses the fraction of photomultiplier tubes in the observatory that detect the extensive air shower. The photon spectrum is measured in the range 1-100 TeV using the last three years of Milagro data (2005-2008), with the detector in its final configuration. An F-test indicates that MGRO J2019+37 is better fit by a power law with an exponential cutoff than by a simple power law. The best-fitting parameters for the power law with exponential cutoff model are a normalization at 10 TeV of 7(sup +5 sub -2) × 10(exp -10)/ s /sq m/ TeV, a spectral index of 2.0(sup +0.5 sub -10), and a cutoff energy of 29(sup +50 sub -16) TeV. MGRO J2031+41 shows no evidence of a cutoff. The best-fitting parameters for a power law are a normalization of 2.1(sup +0.6 sub -0.6) × 10(exp -10)/ s/sq m/ TeV and a spectral index of 3.22(sup +0.23 sub -0.18. The overall flux is subject to a approx.. 30% systematic uncertainty. The systematic uncertainty on the power-law indices is approx. 0.1. Both uncertainties have been verified with cosmic-ray data. A comparison with previous results from TeV J2032+4130, MGRO J2031+41, and MGRO J2019+37 is also presented.

  3. Spectrum Recombination.

    ERIC Educational Resources Information Center

    Greenslade, Thomas B., Jr.

    1984-01-01

    Describes several methods of executing lecture demonstrations involving the recombination of the spectrum. Groups the techniques into two general classes: bringing selected portions of the spectrum together using lenses or mirrors and blurring the colors by rapid movement or foreshortening. (JM)

  4. A Peculiar Class of Debris Disks from Herschel/DUNES: A Steep Fall Off in the Far Infrared

    NASA Technical Reports Server (NTRS)

    Ertel, S.; Wolf, S.; Marshall, J. P.; Eiroa, C.; Augereau, J. C.; Krivov, A. V.; Lohne, T.; Absil, O.; Ardila, D.; Arevalo, M.; Bayo, A.; Bryden, G.; del Burgo, C.; Greaves, J.; Kennedy, G.; Lebreton, J.; Liseau, R.; Maldonado, J.; Montesinos, B.; Mora, A.; Pilbratt, G. L.; Sanz-Forcada, J.; Stapelfeldt, K.; White, G. J.

    2012-01-01

    Context. The existence of debris disks around old main sequence stars is usually explained by continuous replenishment of small dust grains through collisions from a reservoir of larger objects. Aims. We present photometric data of debris disks around HIP 103389 (HD199260), HIP 100350 (HN Peg, HD206860), and HIP 114948 (HD 219482), obtained in the context of our Herschel Open TIme Key Program DUNES (DUst around NEarby Stars). Methods. We used Herschel/PACS to detect the thermal emission of the three debris disks with a 30 sigma sensitivity of a few mJy at l00 micron and 160 micron. In addition, we obtained Herschel/PACS photometric data at 70 micron for HIP 103389. These observations are complemented by a large variety of optical to far-infrared photometric data. Two different approaches are applied to reduce the Herschel data to investigate the impact of data reduction on the photometry. We fit analytical models to the available spectral energy distribution (SED) data using the fitting method of simulated therma1 annealing as well as a classical grid search method. Results. The SEDs of the three disks potentially exhibit an unusually steep decrease at wavelengths >= 70 micron. We investigate the significance of the peculiar shape of these SEDs and the impact on models of the disks provided it is real. Using grain compositions that have been applied successfully for modeling of many other debris disks, our modeling reveals that such a steep decrease of the SEDs in the long wavelength regime is inconsistent with a power-law exponent of the grain size distribution -3.5 expected from a standard equilibrium collisional cascade. In contrast, a steep grain size distribution or, alternatively an upper grain size in the range of few tens of micrometers are implied. This suggests that a very distinct range of grain sizes would dominate the thermal. emission of such disks. However, we demonstrate that the understanding of the data of faint sources obtained with Herschel is

  5. 26.3 MHz radio source survey. III - Correlation with extragalactic X-ray sources

    NASA Technical Reports Server (NTRS)

    Erickson, W. C.; Matthews, T. A.; Viner, M. R.

    1978-01-01

    The correlation between extragalactic X-ray sources and radio sources in a 26.3-MHz catalog is studied. A list of reliably identified sources is developed by examining X-ray, optical, and radio data for those candidate objects that are in or near the X-ray error boxes. The source 3UR 0432+05 is identified with 3C 120, 3UR 1555+27 (identified with A2142) is shown to be a steep-spectrum radio source, and it is found that 86% of the high-galactic-latitude sources can be reliably identified when the X-ray source error areas are no more than 1 sq deg. The results also indicate that: (1) X-ray sources identified with clusters of galaxies as a whole, with individual galaxies in clusters, and with separate isolated galaxies have similar decametric properties in that their spectral indices and radio luminosities fall in the same range; (2) there is a Bautz-Morgan dependence of both the X-ray and the decametric luminosities of clusters and of individual objects in clusters; and (3) the X-ray luminosity of all except compact sources appears to be approximately proportional to the decametric luminosity.

  6. Analysis of Regionally Detected Icequakes Using the STEEP Network, South-Central AK

    NASA Astrophysics Data System (ADS)

    O'Neel, S.; Leblanc, L.; Larsen, C.; Truffer, M.; Hansen, R.; Rupert, N.; Pavlis, G.; None, N.

    2007-12-01

    Glaciers produce seismic energy that is detectable from local to teleseismic distances. Glaciolgical processes including calving, surface crevassing, basal sliding and other, yet unresolved source processes are capable of producing recordable seismicity. Twenty-two broadband sensors deployed in south-central Alaska during the SainT Elias TEctonics and Erosion Project (STEEP) provide an excellent means to study glacier-generated seismicity at regional distances. These instruments surround over 7500 km2 of glacier area including the Bering Glacier, Bagley Icefield and the tidewater calving glaciers of Icy Bay (Yahtse, Guyot, Tyndal). Our analysis shows that icequakes nominally occur several times hourly, and can be separated from tectonic seismicity using their unique spectral characteristics and hypocenter locations. The events typically propagate over 50-75 km distances, but occasionally are recorded at stations over 150 km away from the energy source. Hypocenters for more than 1000 events were manually calculated through a 26-day interval during October 2006, and suggest that a majority of the icequakes are associated with calving at tidewater glaciers that terminate in Icy Bay. Events with similar time and frequency domain characteristics also occur at locations away from calving fronts, but less often, and their mechanical origin remains undetermined. Automated detections from a frequency domain event detector exhibit strong correlation with the handpicked time series, and extend our analysis to all available data collected during 2006. We present the time distribution of several categories of icequakes and compare these distributions to environmental variables such as precipitation, temperature and tides to explore potential forcing for observed variability in icequake occurrence.

  7. Steep REE patterns and enriched Pb isotopes in southern Central American arc magmas: Evidence for forearc subduction erosion?

    NASA Astrophysics Data System (ADS)

    Goss, A. R.; Kay, S. M.

    2006-05-01

    The appearance of adakitic magmas with steep rare earth element (REE) patterns in southern Costa Rica and Panama at ˜4 Ma coincides with the collision of the Cocos Ridge and the inception of slab shallowing along the margin. Distinctly higher 206Pb/204Pb and 208Pb/204Pb ratios in these adakitic lavas than in older Miocene lavas suggest that components enriched in radiogenic Pb also entered the mantle magma source at ˜4 Ma. Published Pb-isotopic data for Central American arc lavas show that a similar radiogenic component is not present in lavas farther north and that maxima in post-Miocene 206Pb/204Pb and 208Pb/204Pb ratios occur in central Costa Rica and western Panama. Cretaceous and early Tertiary ophiolites in the forearc, whose origins have been linked to the Galápagos hot spot, show a similar spatial pattern in Pb isotopic ratios. The incorporation of ophiolitic forearc crust into the mantle wedge by forearc subduction erosion can explain the along-arc spatial and temporal pattern of Pb-isotopic ratios in southern Central American arc lavas. Partial melting of crust removed from the base of the forearc and subjected to high-pressure metamorphism in the subduction channel provides an explanation for the steep adakitic REE patterns in some Costa Rican and Panamanian arc lavas.

  8. 3C380 - A powerful radio source seen end-on?

    NASA Astrophysics Data System (ADS)

    Wilkinson, P. N.; Akujor, Chidi E.; Cornwell, T. J.; Saikia, D. J.

    1991-01-01

    New VLA, MERLIN, and VLBI observations are presented for 3C380, a powerful compact steep-spectrum radio source with complex extended structure, in an effort to clarify whether it is a larger source seen end-on or whether it is intrinsically of galactic dimensions and distorted. The extended structure, which could be a pair of overlapping lobes, exhibits a strong depolarization asymmetry of the kind found in powerful double sources, while the core exhibits superluminal motion with v(app) of about 8 c. Therefore 3C380 has features to be expected of a Fanaroff-Riley class II source seen approximately end-on. However, a detailed consideration of the new evidence shows that the source is intrinsically small with an overall extent of 60 kpc or less. This small size, together with several unusual features of the structure, suggests that it may be interacting strongly with the surrounding gas.

  9. A model of the steep power-law spectra and high-frequency quasi-periodic oscillations in luminous black hole X-ray binaries

    NASA Astrophysics Data System (ADS)

    Dexter, Jason; Blaes, Omer

    2014-03-01

    We propose a new model of the steep power-law state of luminous black hole X-ray binaries. The model uses the fact that at high luminosities, the inner radii of radiation pressure dominated accretion discs are expected to (i) become effectively optically thin and (ii) produce significant luminosities. The gas temperature therefore rises sharply inwards, producing local saturated Compton spectra with rapidly increasing peak energies. These spectra sum together to form a steep power-law tail to the spectrum. A given photon energy on this tail corresponds to a narrow range in radius, so that local vertical oscillations of the disc naturally produce high-quality high-frequency quasi-periodic oscillations (HFQPOs) in the hard X-ray band. The two lowest order modes have a robust frequency ratio of sqrt{7/3}˜eq 1.53. This model explains the appearance of steep power-law spectra and HFQPOs at high luminosity, the 3:2 HFQPO frequency ratios, and their association with the power-law spectral component. We predict an increase in QPO quality factor when the power spectrum is restricted to a narrower photon energy band, and an increase in HFQPO frequency at higher X-ray energies or lower luminosities. Future X-ray telescopes could detect additional HFQPOs from higher order modes. We demonstrate how this model could be used to measure black hole spin from HFQPOs, and qualitatively estimate the spin of GRO J1655-40 as a/M ˜ 0.4-0.7.

  10. Technical note: Common characteristics of directional spreading-steepness joint distribution in freak wave events

    NASA Astrophysics Data System (ADS)

    Liu, Shouhua; Li, Yizhen; Yue, Xinyang

    2016-06-01

    Seven freak wave incidents previously documented in the real ocean in combination with model hindcast simulations are used to study the variations associated with freak-wave-related parameters, such as wave steepness, directional spreading, and frequency bandwidth. Unlike the strong correlations between the freak wave parameters and freak waves' occurrence which were obtained in experimental and physical research, the correlations are not clear in the freak waves occurring in the real ocean. Wave directional spreading-steepness joint distribution is introduced and common visual features were found in the joint distribution when freak waves occur among seven "freakish" sea states. The visual features show that freak wave incidents occur when the steepness is large and directional spreading is small. Besides large steepness and small directional spreading, a long-duration, relatively rough sea state is also necessary for the freak wave generation. The joint distribution is more informative than any single statistical wave parameter. The continuous sea states of local large steepness and small directional spreading are supposed to generate freak waves, and two-dimensional distribution visualization is found to be a useful tool for freak waves' forecast. The common visual features of joint distributions supply an important cue for the theoretical and experimental research.

  11. Does perceived steepness deter stair climbing when an alternative is available?

    PubMed

    Eves, Frank F; Thorpe, Susannah K S; Lewis, Amanda; Taylor-Covill, Guy A H

    2014-06-01

    Perception of hill slant is exaggerated in explicit awareness. Proffitt (Perspectives on Psychological Science 1:110-122, 2006) argued that explicit perception of the slant of a climb allows individuals to plan locomotion in keeping with their available locomotor resources, yet no behavioral evidence supports this contention. Pedestrians in a built environment can often avoid climbing stairs, the man-made equivalent of steep hills, by choosing an adjacent escalator. Stair climbing is avoided more by women, the old, and the overweight than by their comparators. Two studies tested perceived steepness of the stairs as a cue that promotes this avoidance. In the first study, participants estimated the steepness of a staircase in a train station (n = 269). Sex, age, height, and weight were recorded. Women, older individuals, and those who were heavier and shorter reported the staircase as steeper than did their comparison groups. In a follow-up study in a shopping mall, pedestrians were recruited from those who chose the stairs and those who avoided them, with the samples stratified for sex, age, and weight status. Participants (n = 229) estimated the steepness of a life-sized image of the stairs they had just encountered, presented on the wall of a vacant shop in the mall. Pedestrians who avoided stair climbing by choosing the escalator reported the stairs as steeper even when demographic differences were controlled. Perceived steepness may to be a contextual cue that pedestrians use to avoid stair climbing when an alternative is available. PMID:24197656

  12. Suspended sediment dynamics in a steep, glacier-fed mountain stream, Place Creek, Canada

    NASA Astrophysics Data System (ADS)

    Richards, G.; Moore, R. D.

    2003-06-01

    This study examined suspended sediment concentration (SSC) during the ablation seasons of 2000 and 2001 in Place Creek, Canada, a steep, glacier-fed mountain stream. Comparison of stream flow in Place Creek with that in an adjacent, almost unglacierized catchment provided a rational basis for separating the ablation seasons into nival, nival-glacial, glacial and autumn recession subseasons. Distinct groupings of points in plots of electrical conductivity against discharge supported the validity of the subseasonal divisions in terms of varying hydrological conditions. Relationships between SSC and discharge (Q) varied between the two study seasons, and between subseasons. Hysteresis in the SSC-Q relationship was evident at both event and weekly time-scales. Some suspended sediment released from pro-glacial Place Lake (the source of Place Creek) appeared to be lost to channel storage at low flows, especially early in the ablation season, with re-entrainment at higher flows. Multiple regression models were derived for the subseasons using predictor variables including Q, Q2, the change in Q over the previous 3 h, cumulative discharge over the ablation season, total precipitation over the previous 24 h and SSC measured at 1500 hours as an index value for each day. The models produced adjusted R2 values ranging from 0·71 to 0·91, and provided tentative insights into the differences in SSC dynamics amongst subseasons. Introduction of the index value of SSC significantly improved the model fit during the nival-glacial and glacial subseasons for both years, as it adjusts the model to the current condition of sediment supply.

  13. The Origin and Consequences of Steep-Sided Crater Lakes on Titan

    NASA Astrophysics Data System (ADS)

    Mitchell, Karl L.; Radebaugh, J.; Wood, C. A.; Lopes, R. M.; Lorenz, R. D.; Lunine, J. I.; Stofan, E. R.; Stiles, B. W.; Hensley, S.; Wall, S. D.; Cassini RADAR Team

    2006-09-01

    Cassini radar imagery obtained during the 22nd July 2006 (T16) Titan fly-by reveals the presence of lakes at >70° N (Wall et al., this volume). Several are in relatively steep-sided depressions, contrasting with other lakes in this region that exhibit no pronounced topography at this scale. We postulate based on the arguments in Wood et al. (this volume) that these depressions existed prior to being filled with fluids, and find that a volcanic origin, rather than chemical dissolution or impact, is most likely. A caldera is the preferred interpretation, on the basis of geomorphology, scale, and the lack of need to introduce novel chemical processes. Despite plentiful lakes in this region, there appear to be relatively few fluvial channels supplying them in contrast with other regions. We suggest that: (1) unlike at lower latitudes, precipitation is dominated by gentle rain, possibly ethane-rich, which would fill lakes gradually without high flow rates characteristic of storms that carve broad river channels; and/or (2) the crust is porous, accommodating sub-surface flow in a manner akin to terrestrial groundwater systems, in which case we might expect lake surfaces to follow an equipotential surface, which should be possible to test with stereo data following future fly-bys. The presence of calderas here, and in the Ta scene, lends credence to the use of terrestrial analogs for volcanic processes on Titan. The implication is that magma stalls at buoyancy/density traps in the upper crust to form magma chambers. If residence times are sufficiently long, then pre-eruptive cooling and differentiation of cryomagmas would occur. Therefore, relative to deeper-sourced eruptions, they would be richer in ammonia and/or methanol, and less prone to solidification during ascent. If volcanic and lacustrine environments are concurrent, then geothermal systems rich in organic materials may provide suitable conditions for the emergence of life.

  14. Persistence and change in the soft X-ray spectrum of the quasar PG 1211 + 143

    NASA Technical Reports Server (NTRS)

    Elvis, Martin; Wilkes, Belinda J.; Giommi, P.; Mcdowell, Jonathan

    1991-01-01

    The present study examines two Einstein and three Exosat observations of PG 1211 + 143 over a 6-yr baseline which show that strong steep-spectrum low-energy X-ray emission is a persistent feature of this quasar. Exosat observations of PG 1211 + 143 detected an increase of a factor of 2.3 in its steep soft X-ray flux during 18 days. It is concluded that the bulk of the soft X-ray emission of PG 1211 + 143 comes from a region less than 5 x 10 to the 16th cm across. In another interval of 193 days, the soft X-rays decreased by a factor of 3.7. In the same interval the hard X-rays decreased by a factor of 1.6 + or - 0.05, which suggests a connection between the two energy regimes and argues against variable absorption causing the soft X-ray variations. It is contended that in order to decrease in luminosity so rapidly, a thermal source in PG 1211 + 143 would have to be optically thick to both electron scattering and free-bound absorption.

  15. Action spectrum for photocarcinogenesis.

    PubMed

    de Gruijl, F R

    1995-01-01

    The wavelength dependence of the carcinogenicity of ultraviolet (UV) radiation needs to be known in order to assess the carcinogenic risks of various UV sources, most notably the different solar UV spectra at ground level under depleting stratospheric ozone. This wavelength dependence cannot be extracted from human data (e.g., from epidemiology); it can, however, be directly obtained from animal experiments. Precise information on the wavelength dependence, the so-called action spectrum, was not available until recently: erythemal or mutagenic action spectra have been used as substitutes. However, experimental data on skin tumors induced in hairless mice (Skh:HR1) with various polychromatic sources have been building up. Our group has found that none of the substitute action spectra yield a statistically acceptable description of our data, and we have, therefore, derived a new action spectrum, dubbed the SCUP action spectrum (SCUP stands for Skin Cancer Utrecht-Philadelphia, because the action spectrum also fits experimental data from the former Skin and Cancer Hospital in Philadelphia). The SCUP action spectrum has a maximum at 293 nm, and in the UVA region above 340 nm the relative carcinogenicity per J/m2 drops to about 10(-4) of this maximum. The effects of an ozone depletion on solar UV doses weighted with these different action spectra are compared: the erythemal and SCUP weighted dose come out as least sensitive with a 1.3% and 1.4% increase, respectively, for every 1% decrease in ozone. PMID:7597292

  16. Chemical weathering and runoff chemistry in a steep headwater catchment

    NASA Astrophysics Data System (ADS)

    Anderson, Suzanne Prestrud; Dietrich, William E.

    2001-07-01

    We present here deductions about the location, rate, and mechanisms of chemical weathering in a small catchment based on a catchment-scale sprinkling experiment. In this experiment demineralized water was applied at an approximately steady rate in the CB1 catchment in the Oregon Coast Range to reach and maintain a quasi-steady discharge for a period of 4 days. Because of nearly steady flow conditions within the catchment, the contribution to solute fluxes from soil and bedrock could be partitioned. One half of the solute flux from the catchment derived from colluvial soil, and one half from weathering in bedrock. This implies more intense weathering in the thin colluvium mantling the catchment than in the thick underlying weathered bedrock. The annual solute flux from the catchment, scaled to the annual runoff from the catchment, is 32 +/- 10 t km-2 year-1, equivalent to published chemical denudation rates for nearby rivers with drainage areas 106 times greater than the experiment site. Soil waters sampled during the sprinkling experiment had steady compositions following a period of transient water flow conditions, implying steady-state chemical evolution in the soil. The waters leached organic anions from shallow depths in the soil, which solubilized aluminium and iron, indicating that podzolization is occurring in these soils. Carbonate dissolution appears to be an important source of solutes from the bedrock, despite being present as only a minor phase in the rock. Water balance suggests that the residence time of water in the catchment is about 2 months, and that typical 24 h storms displace only a fraction of the stored water. A consequence is that runoff chemistry is dominated by old water, which imposes strong limits on the variability of runoff composition.

  17. Enhanced hazard assessment of a steep limestone rock slope above the federal road B 305

    NASA Astrophysics Data System (ADS)

    Sellmeier, Bettina; Krautblatter, Michael; Thuro, Kurosch

    2013-04-01

    Rock fall events of the last years show that in many cases infrastructure like railways, highways and roads are affected, as has been demonstrated by the rock fall in Gurtnellen on June 5th, 2012 with one casualty and on Nov. 14th, 2012. To minimize the rock fall risk it is necessary to analyze, assess and anticipate the processes by means of rock fall modeling. Up to now it is common to perform the determination of input parameters using fact sheets referring to the requirements of the chosen code in terms of input parameters (Dorren 2010, GEOTEST 2006). In many cases it is not sufficient to only attend to the common parameter lists, but it is required to collect enhanced data. In the current project it has been worked out that it is essential to think about the following accessory questions when performing rock fall modeling: • How can we achieve additional knowledge about block sizes by acquiring enhanced data considering the source areas? • How can we round off the input data for rock fall modeling by performing kinematic analysis? • To which extent can the approaches of Barton & Choubey (1977) be an amendment to rockfall modeling? These questions are addressed in a steep forested limestone slope that extends above the federal road B 305 near Ramsau in the Bavarian Alps, 30 km southwest of Salzburg. The extension of the source area was mapped combining the information of hillshades generated of a 1m-DTM and fieldwork. During the project we performed a detailed analysis of the discontinuities in the source area, which implies the evaluation of discontinuity patterns as well as a kinematic analysis (Markland 1972, Talobre 1957). In a second step, we focused on a key object, a single block subject to planar failure, where it was possible to directly enter the detachment surface. We performed an accurate mapping of the release surface with special regard to fracture roughness as well as rock bridges (Barton & Choubey 1977, ISRM 1978 and Woszdilo 1989). The

  18. Rapid spectrum measurement at 3  μm over 100  nm wavelength range using mid-infrared difference frequency generation source.

    PubMed

    Abe, Masashi; Nishida, Yoshiki; Tadanaga, Osamu; Tokura, Akio; Takenouchi, Hirokazu

    2016-04-01

    We demonstrate a broadband rapid scanning light source in the 3-μm region by using difference frequency generation (DFG). The DFG source consists of a module with quasi-phase-matched LiNbO3 ridge waveguides, a 1-μm-band wide swept range laser for the pump source, and a 1.5-μm continuous wave laser for the signal source. The sweep rate and the tuning bandwidth of this source are 20 kHz and 100 nm, respectively. This source enables us to evaluate the temperature dependence of absorbance of methane gas. PMID:27192241

  19. The Lockman Hole project: LOFAR observations and spectral index properties of low-frequency radio sources

    NASA Astrophysics Data System (ADS)

    Mahony, E. K.; Morganti, R.; Prandoni, I.; van Bemmel, I. M.; Shimwell, T. W.; Brienza, M.; Best, P. N.; Brüggen, M.; Rivera, G. Calistro; de Gasperin, F.; Hardcastle, M. J.; Harwood, J. J.; Heald, G.; Jarvis, M. J.; Mandal, S.; Miley, G. K.; Retana-Montenegro, E.; Röttgering, H. J. A.; Sabater, J.; Tasse, C.; van Velzen, S.; van Weeren, R. J.; Williams, W. L.; White, G. J.

    2016-09-01

    The Lockman Hole is a well-studied extragalactic field with extensive multi-band ancillary data covering a wide range in frequency, essential for characterising the physical and evolutionary properties of the various source populations detected in deep radio fields (mainly star-forming galaxies and AGNs). In this paper we present new 150-MHz observations carried out with the LOw Frequency ARray (LOFAR), allowing us to explore a new spectral window for the faint radio source population. This 150-MHz image covers an area of 34.7 square degrees with a resolution of 18.6×14.7 arcsec and reaches an rms of 160 μJy beam-1 at the centre of the field. As expected for a low-frequency selected sample, the vast majority of sources exhibit steep spectra, with a median spectral index of α _{150}^{1400}=-0.78± 0.015. The median spectral index becomes slightly flatter (increasing from α _{150}^{1400}=-0.84 to α _{150}^{1400}=-0.75) with decreasing flux density down to S150 ˜10 mJy before flattening out and remaining constant below this flux level. For a bright subset of the 150-MHz selected sample we can trace the spectral properties down to lower frequencies using 60-MHz LOFAR observations, finding tentative evidence for sources to become flatter in spectrum between 60 and 150 MHz. Using the deep, multi-frequency data available in the Lockman Hole, we identify a sample of 100 Ultra-steep spectrum (USS) sources and 13 peaked spectrum sources. We estimate that up to 21 per cent of these could have z > 4 and are candidate high-z radio galaxies, but further follow-up observations are required to confirm the physical nature of these objects.

  20. Development and Validation of a Low Cost, Flexible, Open Source Robot for Use as a Teaching and Research Tool across the Educational Spectrum

    ERIC Educational Resources Information Center

    Howell, Abraham L.

    2012-01-01

    In the high tech factories of today robots can be used to perform various tasks that span a wide spectrum that encompasses the act of performing high-speed, automated assembly of cell phones, laptops and other electronic devices to the compounding, filling, packaging and distribution of life-saving pharmaceuticals. As robot usage continues to…

  1. Rainfall and sheet power model for interrill erosion in steep slope

    NASA Astrophysics Data System (ADS)

    Shin, Seung Sook; Deog Park, Sand; Nam, Myeong Jun

    2015-04-01

    The two-phase process of interrill erosion consist of the splash and detachment of individual particles from soil mass by impact of raindrops and the transport by erosive running water. Most experimental results showed that the effect of interaction between rainfall impact and surface runoff increases soil erosion in low or gentle slope. Especially, the combination of rain splash and sheet flow is the dominant runoff and erosion mechanism occurring on most steep hillslopes. In this study, a rainfall simulation was conducted to evaluate interrill erosion in steep slope with cover or non-cover. The kinetic energy of raindrops of rainfall simulator was measured by disdrometer used to measure the drop size distribution and velocity of falling raindrops and showed about 0.563 rate of that calculated from empirical equation between rainfall kinetic energy and rainfall intensity. Surface and subsurface runoff and sediment yield depended on rainfall intensity, gradient of slope, and existence of cover. Sediment from steep plots under rainfall simulator is greatly reduced by existence of the strip cover that the kinetic energy of raindrop approximates to zero. Soil erosion in steep slope with non-cover was nearly 4.93 times of that measured in plots with strip cover although runoff was only 1.82 times. The equation of a rainfall and sheet power was used to evaluate sediment yields in steep slope with cover or non-cover. The power model successfully explained physical processes for interrill erosion that combination of raindrop impact and sheet flow increases greatly soil erosion in steep slope. This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology(No. 2013R1A1A3011962).

  2. Search for extreme rotation measures in CSS sources

    NASA Astrophysics Data System (ADS)

    Cotton, W. D.; Kravchenko, E.; Kovalev, Y. Y.; Fomalont, E.

    2016-02-01

    Magnetized plasmas traversed by linearly polarized light will reveal their presence by the frequency dependent Faraday rotation of the angle of polarization. The regions surrounding the black holes powering the jets in AGNs are expected to have dense magnetized plasmas, possibly giving rise to very large Faraday rotations. Compact steep spectrum (CSS) sources are good candidates to search for very large Faraday rotated components as they contain compact emission from close to the black hole and many are strongly depolarized at centimeter wavelengths as expected from strong Faraday effects. We present data on several CSS sources (3C 48, 3C 138, and 3C 147) observed with the VLA at frequencies between 20 and 48 GHz in the most extended configuration. Large, but not excessive rotation measures are reported.

  3. Effects of low frequency ultrasonic treatment on the maturation of steeped greengage wine.

    PubMed

    Zheng, Xinhua; Zhang, Min; Fang, Zhongxiang; Liu, Yaping

    2014-11-01

    To accelerate wine maturation, low frequency ultrasonic waves of 28 kHz and 45 kHz were used to treat the steeped greengage wine. The contents of total acid, total ester, fusel oils and the wine chromaticity were determined before and after the ultrasonic treatment. The volatile compounds were analysed by GC-MS method, and the sensory quality was evaluated by panelist. The results indicated that ultrasonic treatment of the steeped greengage wine at 45 kHz 360 W for 30 min was effective to accelerate the aging process, where the fusel oils and alcohol compounds were significantly reduced and acid and ester compounds were significantly increased. PMID:24874386

  4. Bedload transport in steep glacier-fed streams: from incipient motion to floods

    NASA Astrophysics Data System (ADS)

    Comiti, Francesco; Dell'Agnese, Andrea; Lucia, Ana; Vignoli, Gianluca; Simoni, Silvia; Bertoldi, Walter; Mao, Luca; Macconi, Pierpaolo; Mazzorana, Bruno; Dinale, Roberto

    2015-04-01

    The current understanding of bedload dynamics in mountain channels is rather scarce, and the capability to predict it over a range of discharges and under different morphological conditions is still very poor despite the headways made during the last decade. Indeed, there has been an increased recognition of the highly stochastic nature of bedload transport in steep streams, especially at low to medium flows (i.e. up to ordinary events). On the other hand, considerable efforts have been made to model the effective energy available for bedload in steep channels, in order to reduce the large overestimation in bedload rates produced by transport capacity equations. Nonetheless, because high-gradient channels are notoriously sediment supply-limited, largely varying bedload rates can be observed at the same stream cross-section under nearly identical morphological and hydraulic conditions, as a consequence of different sediment supply regimes/events. Therefore, the use of a single bedload transport equation even for the same stream is becoming strongly questioned by researchers, whereas most river agencies and consultants - and numerical models - still rely on "classical" transport capacity equations. Remarkably, glacial streams offer the possibility to investigate how seasonal changes in sediment supply at the basin scale - deriving from the periglacial and glacial areas - affects bedload transport rates in the main channel. However, little quantitative bedload data from these systems are available. This contribution intends to share the recent results obtained in two glaciarized basins in the Eastern Italian Alps, which range from about 10 km2 (upper Saldur river basin) to 130 km2 (Sulden river basin) in drainage area. Different monitoring methodologies encompassing PIT-tagged clasts tracking (by both portable and stationary antennas), geophone plates, acoustic pipe sensor and direct sampling by portable traps have been deployed in these two mountain streams. Our

  5. Slope, Rate of Change, and Steepness: Do Students Understand These Concepts?

    ERIC Educational Resources Information Center

    Teuscher, Dawn; Reys, Robert E.

    2010-01-01

    How do mathematics teachers introduce the concepts of slope, rate of change, and steepness in their classrooms? Do students understand these concepts as interchangeable or regard them as three different ideas? In this article, the authors report the results of a study of high school Advanced Placement (AP) Calculus students who displayed…

  6. Permafrost in steep bedrock slopes and its temperature-related destabilization following climate change

    NASA Astrophysics Data System (ADS)

    Gruber, S.; Haeberli, W.

    2007-06-01

    Permafrost in steep bedrock is abundant in many cold-mountain areas, and its degradation can cause slope instability that is unexpected and unprecedented in location, magnitude, frequency, and timing. These phenomena bear consequences for the understanding of landscape evolution, natural hazards, and the safe and sustainable operation of high-mountain infrastructure. Permafrost in steep bedrock is an emerging field of research. Knowledge of rock temperatures, ice content, mechanisms of degradation, and the processes that link warming and destabilization is often fragmental. In this article we provide a review and discussion of existing literature and pinpoint important questions. Ice-filled joints are common in bedrock permafrost and possibly actively widened by ice segregation. Broad evidence of destabilization by warming permafrost exists despite problems of attributing individual events to this phenomenon with certainty. Convex topography such as ridges, spurs, and peaks is often subject to faster and deeper thaw than other areas. Permafrost degradation in steep bedrock can be strongly affected by percolating water in fractures. This degradation by advection is difficult to predict and can lead to quick and deep development of thaw corridors along fractures in permafrost and potentially destabilize much greater volumes of rock than conduction would. Although most research on steep bedrock permafrost originates from the Alps, it will likely gain importance in other geographic regions with mountain permafrost.

  7. Does WEPP meet the specificity of soil erosion in steep mountain regions?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We chose the USDA-ARS-WEPP model (Water Erosion Prediction Project) to describe the soil erosion in the Urseren valley (Central Switzerland) as it seems to be one of the most promising models for steep mountain environments. Crucial model parameters were determined in the field (slope, plant species...

  8. Effects of sediment size on transport capacity of overland flow on steep slopes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sediment transport capacity is a key concept to determine rates of detachment and deposition in process-based erosion models. Few studies were conducted to evaluate the effects of sediment size on transport capacity of overland flow on steep slopes. The objective of this study was to investigate the...

  9. Sediment transport and soil detachment on steep slopes: I. Transport capacity estimation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Precise prediction of sediment transport capacity (Tc) is pivotal to develop physically based erosion models. Few data are available for predicting Tc on steep slopes. The objectives of this study were to evaluate the effects of unit flow discharge (q), slope gradient (S), and mean flow velocity on ...

  10. Erosion risk assessment of controlled burning of grasses established on steep slopes

    NASA Astrophysics Data System (ADS)

    Gyasi-Agyei, Yeboah

    2006-02-01

    It is a standard practice to establish grasses on steep slopes (batters) of embankments and cuttings to minimise erosion problems. However, the increase in grass density (high biomass) on the steep slopes poses a greater risk of fire. Controlled burning is a common fuel hazard reduction program employed to minimise the fire risks. The increased risk of erosion on the steep slopes after controlled burning has received little attention if any. This paper assesses the erosion risks associated with controlled burning of grasses established on steep slopes. Grasses, with and without the aid of waste ballast rock mulch, were established on 10 m wide railway embankment batter experiment plots. Two-and-a-half years after the grass establishment, selected plots were controlled burned. Runoff and soil loss from the experimental plots were monitored throughout the 3½-year period of the experiment. After one year the grass cover on the burned plots has hardly exceeded 60%, far below the average pre-burn levels of about 80%. All treatments achieved an incredible soil loss reduction of over 95% (compared with the bare scenario) without controlled burning at the end of the 3½-year period. This percentage value was decreased numerically by 14 where controlled burning was implemented. Compared with the 100% grass cover treatment, runoff rates tripled while erosion rates increased by nine-fold for the waste ballast treatment, and 17-fold for the non-waste ballast treatment, during the first year following controlled burning.

  11. Contour Planting: A Strategy to Reduce Soil Erosion on Steep Slopes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Practices that combine GPS-based guidance for terrain contouring and tillage for runoff detention have potential to increase water infiltration and reduce runoff. The objective of this study was to investigate contour planting as a means to reduce soil erosion on steep slopes of the Columbia Platea...

  12. 4-Hydroxyisoleucine production of recombinant Corynebacterium glutamicum ssp. lactofermentum under optimal corn steep liquor limitation.

    PubMed

    Shi, Feng; Niu, Tengfei; Fang, Huimin

    2015-05-01

    4-Hydroxyisoleucine (4-HIL) is a nonproteinogenic amino acid that exhibits insulinotropic biological activity. Here, L-isoleucine dioxygenase gene (ido) derived from Bacillus thuringiensis YBT-1520 was cloned and expressed in an L-isoleucine-producing strain, Corynebacterium glutamicum ssp. lactofermentum SN01, in order to directly convert its endogenous L-isoleucine (Ile) into 4-HIL through single-step fermentation. The effects of corn steep liquor limitation as well as ido and truncated idoΔ6 overexpression on 4-HIL production were researched. 4-HIL production by ido-overexpressing strain was improved to 65.44 ± 2.27 mM after fermented for 144 h under corn steep liquor-subsufficient condition, obviously higher than that under corn steep liquor-rich and insufficient conditions. The conversion ratio of Ile to 4-HIL increased to 0.85 mol/mol. In addition, 4-HIL production by ido-overexpressing strain was higher than that by idoΔ6-overexpressing strain, in accord with the relatively higher affinity of Ido as compared to IdoΔ6. This research generated a novel system for 4-HIL de novo biosynthesis and demonstrated corn steep liquor limitation as a useful strategy for improving 4-HIL production in recombinant C. glutamicum ssp. lactofermentum. PMID:25725632

  13. A LOFAR view on the duty cycle of young radio sources

    NASA Astrophysics Data System (ADS)

    Brienza, M.; Morganti, R.; Shulevski, A.; Godfrey, L.; Vilchez, N.

    2016-02-01

    Compact Steep Spectrum, Gigahertz Peaked Spectrum, and High Frequency Peak (CSS, GPS, HFP) sources are considered to be young radio sources, but the details of their duty cycle are not well understood. In some cases they are thought to develop in FRI/FRII radio galaxies while in other cases their jets may remain confined within the host galaxy, and some may experience intermittent activity or die prematurely, never reaching the size of large classical double radio galaxies. Studying in a systematic way the presence and the properties of any extended emission surrounding these compact sources can provide firmer constraints on their evolutionary history and on the timescales of activity of the radio source. Remnant emission from previous outbursts is supposed to have very low surface brightness and to be brighter at low frequency. Taking advantage of the unprecedented sensitivity and resolution provided by the Low Frequency Array (LOFAR) we have started a systematic search of new CSS, GPS, and HFP sources with extended emission, as well as a more detailed study of some well-known of these sources. Here we present the key points of our search in the LOFAR fields and a more in-depth analysis on the source B2 0258+35, a CSS source surrounded by a pair of large, diffuse radio lobes. In this way, we aim to provide a better census of restarted sources and a better knowledge of the variety of their duty cycle.

  14. Exploratory 5-micron spectrum of Uranus

    SciTech Connect

    Orton, G.S.; Kaminski, C.D.

    1989-01-01

    The intensity peak at 4.8 microns characterizing the spectrum observed for the disk of Uranus near 5 microns, in June 1987, exhibits steep declines at shorter and longer wavelength. An exploratory discussion is presented of various models in view of these data; it is noted that some component of the radiation must originate near the 140 K atmospheric irrespective of the radiation's origin in sunlight or thermal emission; physical considerations dictate that it be at least partly thermal in origin. One model consistent with the data requires the presence of a cloud top at the 8-bar level. 30 references.

  15. Pseudo 3-D P wave refraction seismic monitoring of permafrost in steep unstable bedrock

    NASA Astrophysics Data System (ADS)

    Krautblatter, Michael; Draebing, Daniel

    2014-02-01

    permafrost in steep rock walls can cause hazardous rock creep and rock slope failure. Spatial and temporal patterns of permafrost degradation that operate at the scale of instability are complex and poorly understood. For the first time, we used P wave seismic refraction tomography (SRT) to monitor the degradation of permafrost in steep rock walls. A 2.5-D survey with five 80 m long parallel transects was installed across an unstable steep NE-SW facing crestline in the Matter Valley, Switzerland. P wave velocity was calibrated in the laboratory for water-saturated low-porosity paragneiss samples between 20°C and -5°C and increases significantly along and perpendicular to the cleavage by 0.55-0.66 km/s (10-13%) and 2.4-2.7 km/s (>100%), respectively, when freezing. Seismic refraction is, thus, technically feasible to detect permafrost in low-porosity rocks that constitute steep rock walls. Ray densities up to 100 and more delimit the boundary between unfrozen and frozen bedrock and facilitate accurate active layer positioning. SRT shows monthly (August and September 2006) and annual active layer dynamics (August 2006 and 2007) and reveals a contiguous permafrost body below the NE face with annual changes of active layer depth from 2 to 10 m. Large ice-filled fractures, lateral onfreezing of glacierets, and a persistent snow cornice cause previously unreported permafrost patterns close to the surface and along the crestline which correspond to active seasonal rock displacements up to several mm/a. SRT provides a geometrically highly resolved subsurface monitoring of active layer dynamics in steep permafrost rocks at the scale of instability.

  16. Egalitarian despots: hierarchy steepness, reciprocity and the grooming-trade model in wild chimpanzees, Pan troglodytes

    PubMed Central

    Kaburu, Stefano S. K.; Newton-Fisher, Nicholas E.

    2014-01-01

    Biological market theory models the action of natural selection as a marketplace in which animals are viewed as traders with commodities to offer and exchange. Studies of female Old World monkeys have suggested that grooming might be employed as a commodity to be reciprocated or traded for alternative services, yet previous tests of this grooming-trade model in wild adult male chimpanzees have yielded mixed results. Here we provide the strongest test of the model to date for male chimpanzees: we use data drawn from two social groups (communities) of chimpanzees from different populations and give explicit consideration to variation in dominance hierarchy steepness, as such variation results in differing conditions for biological markets. First, analysis of data from published accounts of other chimpanzee communities, together with our own data, showed that hierarchy steepness varied considerably within and across communities and that the number of adult males in a community aged 20–30 years predicted hierarchy steepness. The two communities in which we tested predictions of the grooming-trade model lay at opposite extremes of this distribution. Second, in accord with the grooming-trade model, we found evidence that male chimpanzees trade grooming for agonistic support where hierarchies are steep (despotic) and consequent effective support is a rank-related commodity, but not where hierarchies are shallow (egalitarian). However, we also found that grooming was reciprocated regardless of hierarchy steepness. Our findings also hint at the possibility of agonistic competition, or at least exclusion, in relation to grooming opportunities compromising the free market envisioned by biological market theory. Our results build on previous findings across chimpanzee communities to emphasize the importance of reciprocal grooming exchanges among adult male chimpanzees, which can be understood in a biological markets framework if grooming by or with particular individuals is

  17. The relation between superior phacoemulsification incision and steep axis on astigmatic outcomes.

    PubMed

    Özyol, Erhan; Özyol, Pelin

    2012-12-01

    To evaluate the relation between superior phacoemulsification incision and different steep axis on astigmatism outcomes. This prospective, randomized study comprised three groups each with 24 eyes with age-related cataracts and underwent 3.0 mm superior clear corneal incision (CCI). The three groups of the patients were divided by the location of the steep axis. The steep axis was between 0 and 30° in group 1, 31-60° in group 2, 61-90° in group 3. The degree was accepted as the distance from the steep axis to the distal aspect of the wound. Outcome measures were including the changes in mean total astigmatism, surgically-induced astigmatism (SIA), axis deviation, uncorrected visual acuity (UCVA), and best corrected visual acuity (BCVA). Astigmatism was measured by manuel keratometry readings before surgery and day-1, week-1, week-2, week-4 and week-8 postoperatively. The surgically-induced astigmatism was calculated by the vector analysis using the Holladay-Cravy-Koch method. The magnitude of mean total astigmatism was lowest in group 1 and highest in group 3 at 8th week. Surgically-induced astigmatism was 0.52 diopter (D), 0.88 D, 1.03 D in group 1, group 2, and group 3 respectively. The change in SIA was significant in group 1 (P < 0.05). The change in the astigmatic axis deviation was highest in group 1 (31.5 ± 31.3, P < 0.05). The mean UCVA and BCVA were not significant pre and postoperatively between groups (P > 0.05). Axis deviation and SIA were stable after the week-1 and week-2 examinations respectively. Cataract surgery with CCI on or near the steep axis is resulted in decreased SIA and increased axis deviation. PMID:22825889

  18. Deep 20-GHz survey of the Chandra Deep Field South and SDSS Stripe 82: source catalogue and spectral properties

    NASA Astrophysics Data System (ADS)

    Franzen, Thomas M. O.; Sadler, Elaine M.; Chhetri, Rajan; Ekers, Ronald D.; Mahony, Elizabeth K.; Murphy, Tara; Norris, Ray P.; Waldram, Elizabeth M.; Whittam, Imogen H.

    2014-04-01

    We present a source catalogue and first results from a deep, blind radio survey carried out at 20 GHz with the Australia Telescope Compact Array, with follow-up observations at 5.5, 9 and 18 GHz. The Australia Telescope 20 GHz (AT20G) deep pilot survey covers a total area of 5 deg2 in the Chandra Deep Field South and in Stripe 82 of the Sloan Digital Sky Survey. We estimate the survey to be 90 per cent complete above 2.5 mJy. Of the 85 sources detected, 55 per cent have steep spectra (α _{1.4}^{20} < -0.5) and 45 per cent have flat or inverted spectra (α _{1.4}^{20} ≥ -0.5). The steep-spectrum sources tend to have single power-law spectra between 1.4 and 18 GHz, while the spectral indices of the flat- or inverted-spectrum sources tend to steepen with frequency. Among the 18 inverted-spectrum (α _{1.4}^{20} ≥ 0.0) sources, 10 have clearly defined peaks in their spectra with α _{1.4}^{5.5} > 0.15 and α 9^{18} < -0.15. On a 3-yr time-scale, at least 10 sources varied by more than 15 per cent at 20 GHz, showing that variability is still common at the low flux densities probed by the AT20G-deep pilot survey. We find a strong and puzzling shift in the typical spectral index of the 15-20-GHz source population when combining data from the AT20G, Ninth Cambridge and Tenth Cambridge surveys: there is a shift towards a steeper-spectrum population when going from ˜1 Jy to ˜5 mJy, which is followed by a shift back towards a flatter-spectrum population below ˜5 mJy. The 5-GHz source-count model by Jackson & Wall, which only includes contributions from FRI and FRII sources, and star-forming galaxies, does not reproduce the observed flattening of the flat-spectrum counts below ˜5 mJy. It is therefore possible that another population of sources is contributing to this effect.

  19. Fate of Extended-Spectrum β-Lactamase-Producing Escherichia coli from Faecal Sources in Surface Water and Probability of Human Exposure through Swimming.

    PubMed

    Schijven, Jack F; Blaak, Hetty; Schets, Franciska M; de Roda Husman, Ana Maria

    2015-10-01

    The goal of this study was to determine the fate of ESBL-producing Escherichia coli (ESBL-EC) emitted from faecal sources in surface water, and the probability of human exposure through swimming. Concentrations of ESBL-EC were measured in recreational waters and in source waters, being water in ditches surrounding poultry farms and municipal wastewater. Additionally, the potential of ESBL-EC in source waters to reach recreational waters located downstream of these sources was modeled. Modeled ESBL-EC concentrations in recreational waters appeared to be mostly determined by the concentrations in the source waters and by subsequent dilution in surface water, and less by inactivation. The mean (95%) risk of human exposure to ESBL-EC per person per swimming event, as assessed from measured ESBL-EC concentrations in recreational waters, was 0.16 (0.89) for men, 0.13 (0.72) for women and 0.20 (0.95) for children. Similar exposure risks were estimated for hypothetical recreational waters containing 100- or 1000-times diluted source water, located 10 days water travel time downstream of the sources. Human exposure to ESBL-EC through swimming is likely, if recreational waters are located downstream of poultry farms and municipal wastewater discharge points. PMID:26338143

  20. Transport and Export of Coarse Particulate Organic Matter (CPOM) in Steep Streams

    NASA Astrophysics Data System (ADS)

    Bunte, K.; Swingle, K. W.; Turowski, J. M.; Abt, S. R.; Cenderelli, D. A.

    2015-12-01

    Coarse particulate organic material >1 mm (CPOM) comprising mainly leaves, needles, cones, twigs, and decaying wood pieces is an energy source in headwater ecosystems, and CPOM transport of is one form of watershed carbon export. However, sampling methods for instantaneous CPOM transport rates and annual loads are not well developed, and hence not much is known about annual CPOM export from high energy, forested mountain streams. CPOM transport samples were collected over one-month snowmelt highflow seasons in two high-elevation, subalpine, Rocky Mountains streams with snowmelt regimes as well as in a montane torrent in the Swiss Pre-Alps with a pluvio-nival regime. Basin areas ranged from 1 to 13 km2. Bedload traps and automated hanging baskets installed at an overfall, developed for sampling gravel bedload, proved suitable for sampling CPOM transport. Bedload traps with 0.3 by 0.2 m openings are typically deployed for an hour at a time during wadeable flows, collect samples back-to-back, and may trap volumes of up to 20 liters in the attached 1.4 m long nets. At the Swiss site, hanging baskets with a 1 m3 volume are deployed at an overfall in unwadeable flows, and bedload traps in wadeable flows. When flow overtopped bedload traps, CPOM transport rates were adjusted to estimate and add the unsampled CPOM portion traveling higher in the water column; when nets overfilled, CPOM transport rate were adjusted for the reduction in captured transport. CPOM transport rates in consecutive samples were well related to flow but showed pronounced hysteresis over diurnal fluctuations of flow, between consecutive days, and over the rising and falling limbs of the high-flow season. Hysteresis effects require intensive sampling and use of separate rating curves for all rising and falling limbs in order to compute annual CPOM load. Annual CPOM export for the two Rocky Mountain streams was 2.7 and 4 kg/ha/year, but both streams exported 6.5 and 6.6 kg/ha/year per forested portion

  1. The Effect of Steep Topography on Explosion-Generated Seismic Signals

    NASA Astrophysics Data System (ADS)

    Stevens, J. L.; O'Brien, M.

    2015-12-01

    Nuclear monitoring requires a detailed understanding of the physical factors that affect seismic signals. Nuclear tests have frequently been performed in locations with strong topography, and we are performing a series of calculations to determine the effects of topography on seismic signals. We examined the effect of depth beneath a mountainside or other steep slope on seismic waves by performing three 3D nonlinear calculations. The first is placed beneath a mountain; the second is higher and inside the mountain; the third is beneath a flat surface. We find that generation of long period surface waves is strongly dependent on location relative to the slope. Long period surface waves are generated almost entirely by the static horizontal displacement in the upper few hundred meters below the surface. If the explosion is inside the mountain and close enough to the free surface that stress is relieved by the sides of the mountain, then subsurface horizontal displacement is reduced and surface wave amplitudes are reduced dramatically. However, for explosions that are below the mountain, long period surface waves are increased in amplitude. In contrast, regional P and S phases are slightly larger for the explosion in the mountain than beneath it, especially for paths that go across the mountain. Otherwise, there is little difference in regional phases between the flat and topographic calculations. Far field P body waves are slightly enhanced by the presence of the mountain due to reduction of the pP interference. Far field SV body waves are reduced in amplitude relative to the flat case because the pS phase which is very strong for a flat surface is reduced in amplitude for the mountain. Far field SH waves which do not exist for the flat surface are comparable in amplitude to SV for the mountain cases. Nonlinear calculations with topography are difficult because the grid must be brought into gravitational equilibrium before the explosion calculation can be started. We

  2. Singular-Spectrum Analysis and Wavelet Analysis of the Variability of the Extragalactic Radio Sources 3C 120 and CTA 102

    NASA Astrophysics Data System (ADS)

    Donskikh, G. I.; Ryabov, M. I.; Sukharev, A. L.; Aller, M.

    2016-06-01

    This is a study of the variability of the fluxes of radio emission from the quasar CTA 102 and the radio galaxy 3C 120 based on data from the University of Michigan Radio Astronomy Observatory (UMRAO, Ann Arbor). The data were obtained at three frequencies (14.5, 8, and 4.8 GHz) with the 26-m radio telescope. Two mutually complementary methods were used for the analysis: wavelet analysis and singular spectrum analysis. Wavelet analysis is based on the Fourier transform, while singular-spectrum analysis does not use an analyzing function. Long-duration components of the variability in the range of ~4-11 years were found for 3C 120 and ~1.5-3 years, for CTA 102. The short-duration components of the variability are characterized by periods of ~0.7-3.4 years for 3C 120 and ~0.5-0.8 years for CTA 102. These data were also compared with VLBI charts from the MOJAVE archive for studying the evolution of the components in the jets of the quasars studied here.

  3. Combining Information from Multiple Sources for the Diagnosis of Autism Spectrum Disorders for Toddlers and Young Preschoolers from 12 to 47 Months of Age

    PubMed Central

    Kim, So Hyun; Lord, Catherine

    2011-01-01

    Background Purpose of this study was to systematically examine combined use of the Autism Diagnostic Interview-Revised (ADI-R) and Autism Diagnostic Observation Schedule (ADOS) for children under age 4 using newly developed and revised diagnostic algorithms. Methods Single and combined use of the ADI-R and ADOS algorithms were compared to clinical best estimate diagnoses for 435 children with Autism Spectrum Disorders (ASD), 113 children with non-spectrum disorders, and 47 children with typical development from 12 to 47 months of age. Sequential strategies to reach a diagnostic decision by prioritizing administrations of instruments were also evaluated. Results Well-balanced sensitivities and specificities above 80% were obtained for ASD diagnoses using both instruments. Specificities significantly improved when both instruments were used compared to one. Scores that can be used to systematically prioritize administrations of instruments were identified. Conclusions The ADI-R and ADOS make independent, additive contributions to more accurate diagnostic decisions for clinicians evaluating toddlers and young preschoolers with ASD. Sequential assessment strategies using the scores identified may be appropriate for some children. PMID:21883205

  4. The Planck-ATCA Co-eval Observations project: analysis of radio source properties between 5 and 217 GHz

    NASA Astrophysics Data System (ADS)

    Massardi, Marcella; Bonaldi, Anna; Bonavera, Laura; De Zotti, Gianfranco; Lopez-Caniego, Marcos; Galluzzi, Vincenzo

    2016-01-01

    The Planck-ATCA Co-eval Observations (PACO) project has yielded observations of 464 sources with the Australia Telescope Compact Array (ATCA) between 4.5 and 40 GHz. The main purpose of the project was to investigate the spectral properties of mm-selected radio sources at frequencies below and overlapping with the ESA's Planck satellite frequency bands, minimizing the variability effects by observing almost simultaneously with the first two Planck all-sky surveys. In this paper we present the whole catalogue of observations in total intensity. By comparing PACO with the various measures of Planck Catalog of Compact Sources (PCCS) flux densities we found the best consistency with the PCCS `detection pipeline' photometry (DETFLUX) that we used to investigate the spectral properties of sources from 5 to 217 GHz. Of our sources, 91 per cent have remarkably smooth spectrum, well described by a double power-law over the full range. This suggests a single emitting region, at variance with the notion that `flat' spectra result from the superposition of the emissions from different compact regions, self-absorbed up to different frequencies. Most of the objects show a spectral steepening above ≃30 GHz, consistent with synchrotron emission becoming optically thin. Thus, the classical dichotomy between flat-spectrum/compact and steep-spectrum/extended radio sources, well established at cm wavelengths, breaks down at mm wavelengths. The mm-wave spectra do not show indications of the spectral break expected as the effect of `electron ageing', suggesting young source ages.

  5. Vegetation controls on sediment storage and release on steep, rocky hillslopes

    NASA Astrophysics Data System (ADS)

    DiBiase, R. A.; Lamb, M. P.; Heimsath, A. M.; Whipple, K. X.

    2012-12-01

    Quantifying the processes and rates of regolith production, storage, and transport is essential to understanding hillslope response to tectonic, climatic, and anthropogenic forcing. While considerable progress has been made towards interpreting soil mantled landscapes, there are few models to explain steep, bedrock hillslopes that lack a continuous soil cover. Yet, these steep landscapes pose significant risk to encroaching population centers, and are particularly sensitive to the influence of earthquakes, fire, and climate change. Here we focus on a steep, tectonically active landscape in the San Gabriel Mountains of California to document the spatial distribution and controls on sediment cover in bedrock landscapes. A thin but patchy soil cover persists across the range, despite the widespread occurrence of slopes steeper than the angle of repose and long term erosion rates exceeding 1 mm/yr. We address the problem of sediment storage on steep hillslopes using a combination of high-resolution topographic analysis, detailed mapping of hillslope bedrock exposure, and new field measurements of sediment accumulations behind vegetation dams on slopes ranging from 35 to 45 degrees. Using LiDAR-derived slope measurements and high resolution panoramic photographs, we show that rock exposure increases systematically with published cosmogenic erosion rates, suggesting that steep, threshold hillslopes are more sensitive in recording tectonic signals than previously thought. The primary mechanism for enabling sediment storage on slopes that exceed the angle of repose appears to be the presence of vegetation dams that trap dry ravel. Measurements of pile volumes in the field show a scaling consistent with angle-of-repose wedges whose size depends on vegetation basal width and local slope. Similar measurements on slopes burned by wildfire indicate an average loss of 80% of stored sediment, and highlight the importance of the post-fire loss of hillslope sediment storage

  6. Fission Spectrum

    DOE R&D Accomplishments Database

    Bloch, F.; Staub, H.

    1943-08-18

    Measurements of the spectrum of the fission neutrons of 25 are described, in which the energy of the neutrons is determined from the ionization produced by individual hydrogen recoils. The slow neutrons producing fission are obtained by slowing down the fast neutrons from the Be-D reaction of the Stanford cyclotron. In order to distinguish between fission neutrons and the remaining fast cyclotron neutrons both the cyclotron current and the pusle amplifier are modulated. A hollow neutron container, in which slow neutrons have a lifetime of about 2 milliseconds, avoids the use of large distances. This method results in much higher intensities than the usual modulation arrangement. The results show a continuous distribution of neutrons with a rather wide maximum at about 0.8 MV falling off to half of its maximum value at 2.0 MV. The total number of netrons is determined by comparison with the number of fission fragments. The result seems to indicate that only about 30% of the neutrons have energies below .8 MV. Various tests are described which were performed in order to rule out modification of the spectrum by inelastic scattering. Decl. May 4, 1951

  7. The discovery of a hard X-ray component in the horizontal branch spectrum of the Z source GX 17+2

    NASA Astrophysics Data System (ADS)

    di Salvo, T.; Stella, L.; Robba, N. R.; Burderi, L.; van der Klis, M.

    2001-09-01

    We report on a long BeppoSAX (0.1 - 200 keV energy range) observation of the Z-source GX 17+2. The source was on Horizontal and Normal branches of the hardness-intensity diagram. Energy spectra were selected based on the source position in this diagram. The spectral continuum is well described by the sum of a ~0.6 keV blackbody and a Comptonized component, resulting from upscattering of ~1 keV seed photons by electrons at a temperature of ~3 keV and optical depth of ~10. Iron K-line and edge were also present at energies ~6.7 and ~8.5 keV, respectively, corresponding to high ionization stages (Fe XXIII-XXV). In the spectra of the Horizontal branch a hard tail was clearly detected at energies above ~30 keV. It can be fit to a power law of photon index ~2.7, contributing ~8% of the source flux. This component gradually disappears as the source moved towards the Normal branch. We discuss the similarities with spectra of accreting black holes and implications on spectral models.

  8. The peculiar radio source M17 JVLA 35

    SciTech Connect

    Rodríguez, L. F.; Carrasco-González, C.; Montes, G.; Tapia, M.

    2014-07-01

    M17 JVLA 35 is a radio source detected in projection against the M17 H II region. In recent observations, its spectrum between 4.96 and 8.46 GHz was found to be positive and very steep, with α ≥ 2.9 ± 0.6 (S {sub ν}∝ν{sup α}). Here we present Very Large Array observations made in the 18.5 to 36.5 GHz region that indicate a spectral turnover at ∼13 GHz and a negative spectral index (α ≅ –2.0) at higher frequencies. The spectrum is consistent with that of an extragalactic high frequency peaker (HFP). However, M17 JVLA 35 has an angular size of ∼0.''5 at 8.46 GHz, while HFPs have extremely compact, milliarcsecond dimensions. We discuss other possible models for the spectrum of the source and do not find them feasible. Finally, we propose that M17 JVLA 35 is indeed an HFP but that its angular size becomes broadened by plasma scattering as its radiation travels across M17. If our interpretation is correct, accurate measurements of the angular size of M17 JVLA 35 across the centimeter range should reveal the expected ν{sup –2} dependence.

  9. Faraday rotation from magnesium II absorbers toward polarized background radio sources

    SciTech Connect

    Farnes, J. S.; O'Sullivan, S. P.; Corrigan, M. E.; Gaensler, B. M.

    2014-11-01

    Strong singly ionized magnesium (Mg II) absorption lines in quasar spectra typically serve as a proxy for intervening galaxies along the line of sight. Previous studies have found a correlation between the number of these Mg II absorbers and the Faraday rotation measure (RM) at ≈5 GHz. We cross-match a sample of 35,752 optically identified non-intrinsic Mg II absorption systems with 25,649 polarized background radio sources for which we have measurements of both the spectral index and RM at 1.4 GHz. We use the spectral index to split the resulting sample of 599 sources into flat-spectrum and steep-spectrum subsamples. We find that our flat-spectrum sample shows significant (∼3.5σ) evidence for a correlation between Mg II absorption and RM at 1.4 GHz, while our steep-spectrum sample shows no such correlation. We argue that such an effect cannot be explained by either luminosity or other observational effects, by evolution in another confounding variable, by wavelength-dependent polarization structure in an active galactic nucleus, by the Galactic foreground, by cosmological expansion, or by partial coverage models. We conclude that our data are most consistent with intervenors directly contributing to the Faraday rotation along the line of sight, and that the intervening systems must therefore have coherent magnetic fields of substantial strength ( B-bar =1.8±0.4 μG). Nevertheless, the weak nature of the correlation will require future high-resolution and broadband radio observations in order to place it on a much firmer statistical footing.

  10. Design and manufacture of a bandpass filter with high transmittance and steep edge on both sides

    NASA Astrophysics Data System (ADS)

    Wang, Ruisheng; Lü, Shaobo; Yin, Xiaojun; Zhao, Shuaifeng; Sun, Yan

    2016-01-01

    By using Nb2O5 and SiO2 as the coating material, a 152 layers (12 cavities) bandpass film stack with steep edge on both sides was designed. Multiple thickness control methods, including direct optical monitoring control and time control were used in coating strategy. To confirm the feasibility of this coating strategy, a process simulation was performed using Simulator software, and the simulation result indicated that relative thickness errors for all layers were less than ±0.1%. A bandpass filter with this film stack on one side was manufactured by using a plasma assisted reactive magnetic sputtering coating machine. The measuring result shows that the peak transmittance of the filter (without AR on backside) is up to 95.4%, and the steepness of both blocking slope are less than λ/100.

  11. Empirical statistics: V Evidence on the extent of the steepness bias in visual estimation of trends.

    PubMed

    Bailey, C D

    1996-06-01

    The existence of a pervasive and pronounced steepness bias in visually fitting a line to data in a scattergraph was investigated. 262 undergraduate business students were asked to fit lines visually to scattergraphs, to correspond to a least squares regression fit. These visually estimated lines strongly overestimated the steepness of the actual trend. As visual inspection of data is an important step for the detection of linear trends and outliers prior to regression analysis, this bias in subjective perception of the line may result in inappropriate deletion or retention of outliers, transferring the subjective bias into the results of least squares regression. In addition, textbooks on management accounting discuss the use of visually fitted lines to estimate cost behavior. PMID:8774007

  12. Topographic optical profilometry of steep slope micro-optical transparent surfaces.

    PubMed

    Antón, Juan Carlos Martínez; Alonso, Jose; Pedrero, Jose Antonio Gómez

    2015-04-01

    Optical profilometers based on light reflection may fail at surfaces presenting steep slopes and highly curved features. Missed light, interference and diffraction at steps, peaks and valleys are some of the reasons. Consequently, blind areas or profile artifacts may be observed when using common reflection micro-optical profilometers (confocal, scanning interferometers, etc…). The Topographic Optical Profilometry by Absorption in Fluids (TOPAF) essentially avoids these limitations. In this technique an absorbing fluid fills the gap between a reference surface and the surface to profile. By comparing transmission images at two different spectral bands we obtain a reliable topographic map of the surface. In this contribution we develop a model to obtain the profile under micro-optical observation, where high numerical aperture (NA) objectives are mandatory. We present several analytical and experimental results, validating the technique's capabilities for profiling steep slopes and highly curved micro-optical surfaces with nanometric height resolution. PMID:25968777

  13. IMF or Abundance Variations? Steep Gradients at the Centers of Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    McConnell, Nicholas J.; Lu, Jessica R.; Mann, Andrew

    2016-01-01

    We present high signal-to-noise spectra for six early-type galaxies with Keck/LRIS, covering 350-1050 nm and probing spatial scales from 100 pc to several kpc. Some of our objects exhibit steep absorption-line gradients within the central ~300 pc, indicating a rapid increase in [Na/Fe] and [N/Fe] toward the galaxy center. While stellar population synthesis (SPS) modeling may address whether the stellar initial mass function (IMF) varies as a function of radius, we caution that the competing effects of chemical abundance variations and IMF variations demands extreme care in interpreting SPS models of integrated-light spectra. The steep abundance variations themselves may offer insight to star formation and gas retention in progenitors of today's early-type galaxies, including the possible overabundance of stars above ~3 Msun.

  14. Conversion of Impulse Voltage Generator Into Steep Wave Impulse Test-Equipment

    NASA Astrophysics Data System (ADS)

    Khan, Mohammed Zaid; Tanwar, Surender Singh; Dayama, Ravindra; Choudhary, Rahul Raj; Mangal, Ravindra

    This paper demonstrates the alternative measures to generate the Steep wave impulse by using Impulse Voltage Generator (IVG) for high voltage testing of porcelain insulators. The modification of IVG by incorporating compensation of resistor, inductor, and capacitor has been achieved and further performance of the modified system has been analyzed by applying the generated lightning impulse and analyzing the electrical characteristics of impulse waves under standard lightning and fast rise multiple lightning waveform to determine the effect to improve rise time. The advantageous results have been received and being reported such as increase in overshoot compensation, increase in capacitive and inductive load ranges. Such further reduces the duration of oscillations of standard impulse voltages. The reduction in oscillation duration of steep front impulse voltages may be utilized in up gradation of Impulse Voltage Generator System. Stray capacitance could further be added in order to get the minimized difference of measurement between simulation and the field establishment.

  15. Turbulent flows over a modeled steep topography in a thermally-stratified boundary layer.

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Markfort, Corey; Porté-Agel, Fernando

    2015-11-01

    Turbulent flows with features of separation and reattachment, induced by topography of steep slopes, have been very challenging to predict using numerical models. The geometry of the topography, surface roughness and temperature along with the inflow characteristics (velocity, turbulence level, and atmospheric thermal stability) play important roles in determining onset of separation, reattachment location and momentum and heat flux distribution. To address the coupled effects of steep slope and thermal stability on turbulent flows over topography, series of wind-tunnel measurements of velocity fields, temperature and heat fluxes will be presented. Results will demonstrate the turbulent flow properties, including the size of the separation bubble, separated shear layers and the boundary layer recovery in different cases. Focus will be placed on correlation of momentum and heat flux distribution in the wake and turbulent kinetic energy transport.

  16. Streptomyces misionensis PESB-25 Produces a Thermoacidophilic Endoglucanase Using Sugarcane Bagasse and Corn Steep Liquor as the Sole Organic Substrates

    PubMed Central

    Rezende, Raquel de Carvalho; Gravina-Oliveira, Mônica Pires; Pereira, Pedro Henrique Freitas; do Nascimento, Rodrigo Pires; Bon, Elba Pinto da Silva; Macrae, Andrew; Coelho, Rosalie Reed Rodrigues

    2013-01-01

    Streptomyces misionensis strain PESB-25 was screened and selected for its ability to secrete cellulases. Cells were grown in a liquid medium containing sugarcane bagasse (SCB) as carbon source and corn steep liquor (CSL) as nitrogen source, whose concentrations were optimized using response surface methodology (RSM). A peak of endoglucanase accumulation (1.01 U·mL−1) was observed in a medium with SCB 1.0% (w/v) and CSL 1.2% (w/v) within three days of cultivation. S. misionensis PESB-25 endoglucanase activity was thermoacidophilic with optimum pH and temperature range of 3.0 to 3.6 and 62° to 70°C, respectively. In these conditions, values of 1.54 U mL−1 of endoglucanase activity were observed. Moreover, Mn2+ was demonstrated to have a hyperactivating effect on the enzyme. In the presence of MnSO4 (8 mM), the enzyme activity increased threefold, up to 4.34 U·mL−1. Mn2+ also improved endoglucanase stability as the catalyst retained almost full activity upon incubation at 50°C for 4 h, while in the absence of Mn2+, enzyme activity decreased by 50% in this same period. Three protein bands with endoglucanase activity and apparent molecular masses of 12, 48.5 and 119.5 kDa were detected by zymogram. PMID:23586048

  17. The Role of Prospection in Steep Temporal Reward Discounting in Gambling Addiction

    PubMed Central

    Wiehler, Antonius; Bromberg, Uli; Peters, Jan

    2015-01-01

    Addiction and pathological gambling (PG) have been consistently associated with high impulsivity and a steep devaluation of delayed rewards, a process that is known as temporal discounting (TD). Recent studies indicated that enhanced episodic future thinking (EFT) results in less impulsive TD in healthy controls (HCs). In a separate line of research, it has been suggested that non-linearities in time perception might contribute to reward devaluation during inter-temporal choice. Therefore, in addition to deficits in valuation processes and executive control, impairments in EFT and non-linearities in time perception have been hypothesized to contribute to steep TD in addiction. In this study, we explore such a potential association of impairments in EFT and time perception with steep TD in PG. We investigated 20 PGs and 20 matched HCs. TD was assessed via a standard computerized binary choice task. EFT was measured using a variation of the Autobiographical Memory Interview by Levine et al. (1). Time perception was assessed with a novel task, utilizing a non-linear rating procedure via circle-size adjustments. Groups did not differ in baseline EFT. In both groups, a power law accounted time perception best, and the degree of non-linearity in time perception correlated with discounting across groups. A multiple regression analysis across all predictors and covariates revealed that only group status (PG/HC) and depression were significantly associated with discounting behavior such that PG increased TD and depression attenuated TD. Our findings speak against the idea that steep TD in PG is due to a skewed perception of time or impairments in EFT, at least under the present task conditions. The lack of overall group differences in EFT does not rule out the possibility of more complex interactions of EFT and decision-making. These interactions might be diminished in pathological gambling or addiction more generally, when other task configurations are used. PMID:26379558

  18. Bacterial Diversity and Mycotoxin Reduction During Maize Fermentation (Steeping) for Ogi Production.

    PubMed

    Okeke, Chiamaka A; Ezekiel, Chibundu N; Nwangburuka, Cyril C; Sulyok, Michael; Ezeamagu, Cajethan O; Adeleke, Rasheed A; Dike, Stanley K; Krska, Rudolf

    2015-01-01

    Bacterial diversity and community structure of two maize varieties (white and yellow) during fermentation/steeping for ogi production, and the influence of spontaneous fermentation on mycotoxin reduction in the gruel were studied. A total of 142 bacterial isolates obtained at 24-96 h intervals were preliminarily identified by conventional microbiological methods while 60 selected isolates were clustered into 39 OTUs consisting of 15 species, 10 genera, and 3 phyla by 16S rRNA sequence analysis. Lactic acid bacteria constituted about 63% of all isolated bacteria and the genus Pediococcus dominated (white maize = 84.8%; yellow maize = 74.4%). Pediococcus acidilactici and Lactobacillus paraplantarum were found at all steeping intervals of white and yellow maize, respectively, while P. claussenii was present only at the climax stage of steeping white maize. In both maize varieties, P. pentosaceus was found at 24-72 h. Mycotoxin concentrations (μg/kg) in the unsteeped grains were: white maize (aflatoxin B1 = 0.60; citrinin = 85.8; cyclopiazonic acid = 23.5; fumonisins (B1/B2/B3) = 68.4-483; zearalenone = 3.3) and yellow maize (aflatoxins (B1/B2/M1) = 22.7-513; citrinin = 16,800; cyclopiazonic acid = 247; fumonisins (B1/B2/B3) = 252-1,586; zearalenone = 205). Mycotoxins in both maize varieties were significantly (p < 0.05) reduced across steeping periods. This study reports for the first time: (a) the association of L. paraplantarum, P. acidilactici, and P. claussenii with ogi production from maize, (b) citrinin occurrence in Nigerian maize and ogi, and PMID:26697001

  19. Bacterial Diversity and Mycotoxin Reduction During Maize Fermentation (Steeping) for Ogi Production

    PubMed Central

    Okeke, Chiamaka A.; Ezekiel, Chibundu N.; Nwangburuka, Cyril C.; Sulyok, Michael; Ezeamagu, Cajethan O.; Adeleke, Rasheed A.; Dike, Stanley K.; Krska, Rudolf

    2015-01-01

    Bacterial diversity and community structure of two maize varieties (white and yellow) during fermentation/steeping for ogi production, and the influence of spontaneous fermentation on mycotoxin reduction in the gruel were studied. A total of 142 bacterial isolates obtained at 24–96 h intervals were preliminarily identified by conventional microbiological methods while 60 selected isolates were clustered into 39 OTUs consisting of 15 species, 10 genera, and 3 phyla by 16S rRNA sequence analysis. Lactic acid bacteria constituted about 63% of all isolated bacteria and the genus Pediococcus dominated (white maize = 84.8%; yellow maize = 74.4%). Pediococcus acidilactici and Lactobacillus paraplantarum were found at all steeping intervals of white and yellow maize, respectively, while P. claussenii was present only at the climax stage of steeping white maize. In both maize varieties, P. pentosaceus was found at 24–72 h. Mycotoxin concentrations (μg/kg) in the unsteeped grains were: white maize (aflatoxin B1 = 0.60; citrinin = 85.8; cyclopiazonic acid = 23.5; fumonisins (B1/B2/B3) = 68.4–483; zearalenone = 3.3) and yellow maize (aflatoxins (B1/B2/M1) = 22.7–513; citrinin = 16,800; cyclopiazonic acid = 247; fumonisins (B1/B2/B3) = 252–1,586; zearalenone = 205). Mycotoxins in both maize varieties were significantly (p < 0.05) reduced across steeping periods. This study reports for the first time: (a) the association of L. paraplantarum, P. acidilactici, and P. claussenii with ogi production from maize, (b) citrinin occurrence in Nigerian maize and ogi, and (c) aflatoxin M1, citrinin and cyclopiazonic acid degradation/loss due to fermentation in traditional cereal-based fermented food. PMID:26697001

  20. Numerical errors in the presence of steep topography: analysis and alternatives

    SciTech Connect

    Lundquist, K A; Chow, F K; Lundquist, J K

    2010-04-15

    It is well known in computational fluid dynamics that grid quality affects the accuracy of numerical solutions. When assessing grid quality, properties such as aspect ratio, orthogonality of coordinate surfaces, and cell volume are considered. Mesoscale atmospheric models generally use terrain-following coordinates with large aspect ratios near the surface. As high resolution numerical simulations are increasingly used to study topographically forced flows, a high degree of non-orthogonality is introduced, especially in the vicinity of steep terrain slopes. Numerical errors associated with the use of terrainfollowing coordinates can adversely effect the accuracy of the solution in steep terrain. Inaccuracies from the coordinate transformation are present in each spatially discretized term of the Navier-Stokes equations, as well as in the conservation equations for scalars. In particular, errors in the computation of horizontal pressure gradients, diffusion, and horizontal advection terms have been noted in the presence of sloping coordinate surfaces and steep topography. In this work we study the effects of these spatial discretization errors on the flow solution for three canonical cases: scalar advection over a mountain, an atmosphere at rest over a hill, and forced advection over a hill. This study is completed using the Weather Research and Forecasting (WRF) model. Simulations with terrain-following coordinates are compared to those using a flat coordinate, where terrain is represented with the immersed boundary method. The immersed boundary method is used as a tool which allows us to eliminate the terrain-following coordinate transformation, and quantify numerical errors through a direct comparison of the two solutions. Additionally, the effects of related issues such as the steepness of terrain slope and grid aspect ratio are studied in an effort to gain an understanding of numerical domains where terrain-following coordinates can successfully be used and

  1. Steep-sided domes on Venus - Characteristics, geologic setting, and eruption conditions from Magellan data

    NASA Technical Reports Server (NTRS)

    Pavri, Betina; Head, James W., III; Klose, K. B.; Wilson, Lionel

    1992-01-01

    A survey of more than 95 percent of the Venus surface reveals 145 steep-sided domes which can be subdivided into a variety of morphologic forms, the most common being shaped like inverted bowls or flat-topped domes. Results of a preliminary analysis of the distribution and geologic setting of the domes are presented. The relation of the domes to analogous terrestrial features is examined, and possible models for their mode of emplacement are outlined.

  2. The effect of steepness of temporal resource gradients on spatial root allocation

    PubMed Central

    Novoplansky, Ariel; Ovadia, Ofer

    2011-01-01

    Plants are able to discriminately allocate greater biomass to organs that grow under higher resource levels. Recent evidence demonstrates that split-root plants also discriminately allocate more resources to roots that grow under dynamically improving nutrient levels, even when their other roots grow in richer patches. Here, we further tested whether, besides their responsiveness to the direction of resource gradients, plants are also sensitive to the steepness of environmental trajectories. Split-root Pisum sativum plants were grown so that one of their roots developed under constantly-high nutrient levels and the other root was subjected to dynamically improving nutrient levels of variable steepness. As expected, plants usually allocated a greater proportion of their biomass to roots that developed under constantly high resource availability; however, when given a choice, they allocated greater biomass to roots that initially experienced relatively low but steeply improving nutrient availabilities than to roots that developed under continuously-high nutrient availability. Such discrimination was not observed when the roots in the poor patch experienced only gentler improvements in nutrient availability. The results are compatible with the notion that responsiveness to the direction and steepness of environmental gradients could assist annual plants to increase their performance by anticipating resource availabilities foreseeable before the end of the growing season. The results exemplify the ability of plants to integrate and utilize environmental information and execute adaptive behaviors which, until recently, were attributed only to animals with central nervous systems. PMID:22019637

  3. Process analysis, quantification and modelling of erosion on steep unvegetated hillslopes:

    NASA Astrophysics Data System (ADS)

    Neugirg, Fabian; Kaiser, Andreas; Schindewolf, Marcus; Schmidt, Jürgen; Becht, Michael; Haas, Florian

    2016-04-01

    Soil erosion is a problem in many parts of the world. While in agricultural environments the geomorphological drivers of soil erosion are well known, the process understanding in steep alpine environments is still lacking. Steep hillslopes in different climatic settings distributed in Germany and Italy were monitored for at least three years in order to gain better knowledge in the evolution of the unvegetated slopes. The monitoring setup was mainly based on terrestrial laserscanning (TLS) and was expanded with other monitoring methods, like aerial- and terrestrial-based structure from motion, aerial images and airborne laser scanning data. TLS data were mainly used to analyse processes on plot or hillslope scale. In order to regionalize these values, we used two different modelling approaches: a rule-based statistical and the physical-based model Erosion 3D. The latter one had to be adopted from flat agricaltural areas to steep slopes. Parameters for modeling purposes were acquired by field work. Therefore an established rainfall simulator was customized for the application in alpine terrain. The results showed clear differences in the seasonal behaviour of the acting geomorphological processes in nearly all study areas. Furthermore a quantification was possible for each process involved in hillslope development. Additionally, both models showed that an adaptation to the hillslopes was possible and provided satisfying results in all research areas. This presentation aims at summarizing the findings and key results of the three year study period.

  4. Self-adjustment of stream bed roughness and flow velocity in a steep mountain channel

    NASA Astrophysics Data System (ADS)

    Schneider, Johannes M.; Rickenmann, Dieter; Turowski, Jens M.; Kirchner, James W.

    2015-10-01

    Understanding how channel bed morphology affects flow conditions (and vice versa) is important for a wide range of fluvial processes and practical applications. We investigated interactions between bed roughness and flow velocity in a steep, glacier-fed mountain stream (Riedbach, Ct. Valais, Switzerland) with almost flume-like boundary conditions. Bed gradient increases along the 1 km study reach by roughly 1 order of magnitude (S = 3-41%), with a corresponding increase in streambed roughness, while flow discharge and width remain approximately constant due to the glacial runoff regime. Streambed roughness was characterized by semivariograms and standard deviations of point clouds derived from terrestrial laser scanning. Reach-averaged flow velocity was derived from dye tracer breakthrough curves measured by 10 fluorometers installed along the channel. Commonly used flow resistance approaches (Darcy-Weisbach equation and dimensionless hydraulic geometry) were used to relate the measured bulk velocity to bed characteristics. As a roughness measure, D84 yielded comparable results to more laborious measures derived from point clouds. Flow resistance behavior across this large range of steep slopes agreed with patterns established in previous studies for both lower-gradient and steep reaches, regardless of which roughness measures were used. We linked empirical critical shear stress approaches to the variable power equation for flow resistance to investigate the change of bed roughness with channel slope. The predicted increase in D84 with increasing channel slope was in good agreement with field observations.

  5. Evaluation of sediment transport in steep channels combining sediment impact sensors, tracer stones and TLS

    NASA Astrophysics Data System (ADS)

    Harb, Gabriele; Schneider, Josef; Sass, Oliver; Stangl, Johannes

    2016-04-01

    Torrential floods combined with sediment transport presents major hazards to human life and infrastructure in alpine catchments. Despite the importance of sediment transport due to the large damage caused in case of flood events, we lack data on sediment movement and sediment transport rates in steep channels and torrents to improve the understanding of sediment transport processes in this areas. This paper presents an improved application of sediment impact sensors (SIS) integrated in a unique measurement system in an Alpine catchment in Austria consisting of meteorological stations, runoff gauges and tracer stones. In addition sediment availability, mobilization and accumulation have been mapped and quantified by means of terrestrial laser scanning (TLS) and structure from motion using unmanned aerial vehicles (UAVs). Additionally a numerical model was used to simulate the bed load transport rates in the torrent. This contribution focuses on field measurements of bed load transport rates in steep channels based on SIS data, tracer stone data, bed load measurements, precipitation and discharge data. The measurement data was compared to several sediment transport formulae for steep slopes and validated with the observed deposited amount of sediment in the sediment retention basin at the outlet of the catchment.

  6. Functional and evolutionary correlations of steep leaf angles in the mexical shrubland.

    PubMed

    Valiente-Banuet, Alfonso; Verdú, Miguel; Valladares, Fernando; García-Fayos, Patricio

    2010-05-01

    In the evergreen shrubland vegetation of Mexico (mexical), most of the species are sclerophyllous woody plants with steep leaf angles. This architectural pattern has been interpreted as a strategy to cope with water shortages and high radiation. However, the current association between evergreenness and steep leaf angles across mexical plant species could be the result of an adaptive association achieved through correlated evolutionary change between both traits or, alternatively, may be the result of common evolutionary ancestry. In this study, we quantified leaf angle in 28 dominant species under a phylogenetic framework and evaluated the functional implications of the observed range of leaf angles in terms of leaf temperature, water potentials and transpiration by combining manipulative experiments restraining leaves horizontally with microclimatic and stomatal conductance measurements in selected species and energy balance calculations. Horizontally restrained leaves exhibited reduced water potentials and stomatal conductances, and significantly increased temperatures and transpiration rates. Steeply inclined leaves operated near air temperatures and could sustain relatively high stomatal conductances during the dry season since they were associated with low transpiration rates. Phylogenetic analyses showed that steep leaf angles evolved in a correlated fashion in evergreen species. The functional consequences of leaf angle together with the phylogenetic analysis indicate the adaptive nature of this trait which allows the evergreen species to cope with arid conditions and therefore to persist within the mexical community. PMID:19956973

  7. Experimental investigation of steep-front short duration (SFSD) surge effects on power systems components

    SciTech Connect

    Miller, D.B.

    1992-05-01

    Results are reported from experiments in which steep-front, short- duration (SFSD) voltage impulses were imposed on various electrical distribution components. These pulses were generated by switching a section of charged, high voltage coaxial cable across the component under study. Components included underground distribution cable, terminators, insulators and arresters. SFSD voltage needed to flashover 15 kV polyethylene cable with a single pulse is approximately 625 kV peak. Strength of polyethylene cable decreases with increasing number of SFSD pulses, indicating cumulative degradation of the polymer. For 15 kV and 25 kV cable terminators, the SFSD CFO was over twice the rated standard lightning BIL for the same units. Similarly, porcelain suspension insulators required more than a doubling of voltage to decrease time to flashover from 1 microsecond to .1 microsecond. Arresters were found to respond rapidly to steep-front current pulses, but the arrester material itself was found to result in a higher discharge voltage for SFSD pulses. Arresters also showed a delay in turn-on of current following the arrival of a steep-front voltage surge.

  8. Temperature and Time of Steeping Affect the Antioxidant Properties of White, Green, and Black Tea Infusions.

    PubMed

    Hajiaghaalipour, Fatemeh; Sanusi, Junedah; Kanthimathi, M S

    2016-01-01

    Tea (Camellia sinensis) is the most highly consumed beverage in the world next to water. The common way of preparation is steeping in hot water which is varying for different type of tea. We investigated the antioxidant properties of 6 type of tea leaves under different time and temperatures of extraction method used. In general, all samples tested in this study demonstrated high levels of antioxidant capacity and antioxidant activity. The results indicate that the antioxidants activity is significantly affected by time and temperature of steeping and the highest was depending on the variety. White state values, green and black teas showed different levels of antioxidants under different extraction conditions. Overall, the highest activity for white tea was in prolonged hot and in some assays prolonged hot and cold extracts, whereas for green tea the highest activity observed in prolonged cold steeping while, for black tea was in short hot water infusion. The results of this study showed the antioxidant capacity of white and green tea was greater than black tea. PMID:26613545

  9. Thermal stability effects on the separated flow over a steep 2-D hill

    NASA Astrophysics Data System (ADS)

    Zhang, W.; Porte-Agel, F.

    2012-12-01

    Transport of momentum and scalars in turbulent boundary-layer flows over complex topography has been of great interest in the atmospheric sciences and wind engineering communities. Applications include but are not limited to weather forecasting, air pollution dispersion, aviation safety control, and wind energy project planning. Linear models have been well accepted to predict boundary-layer flows over topography with gentle slope. However, once the slope of the topography is sufficientlyo steep that flow separation occurs, linear models are not applicable. Modeling the turbulent transport of momentum and scalars in such flows has to be achieved through non-linear models, such as Reynolds-averaged Navier-Stokes solvers and large-eddy simulations (LES). Dynamics of the separated boundary-layer flows over steep topography is affected by the shape and size of the topography, surface characteristics (e.g., roughness and temperature) and atmospheric thermal stability. Most wind-tunnel experiments of boundary-layer flows over idealized topography (e.g. 2-D or 3-D hills, axisymmetric bumps) do not take thermal stability effects into account due to difficulty of physical simulation. We conducted comprehensive experimental investigation of stably- and unstably- stratified boundary layers over a steep 2-D hill in the thermally-controlled boundary-layer wind tunnel at the Saint Anthony Falls Laboratory. The 2-D model hill has a steepest slope of 0.73 and its shape follows a cosine square function: h=Hcos^2 (πx/L) for -L/2 ≤ x ≤ L/2 , where the maximum height H is 7 cm and the total width L is 15 cm. High-resolution Particle Image Velocimetry (PIV) provides dynamic information of the separated shear layer, the recirculation zone and flow reattachment. Turbulent momentum and scalar (heat) fluxes were characterized up to the top of the thermal boundary layer using a triple-wire (cross-wire and cold-wire) anemometer. Results indicate that promoted and suppressed turbulence

  10. Bedform migration in steep channels: from local avalanches to large scale changes

    NASA Astrophysics Data System (ADS)

    Mettra, F.; Heyman, J.; Ancey, C.

    2013-12-01

    Many studies have emphasized the strength of bedload transport fluctuations in steep streams, especially at low and intermediate transport conditions (relative to the threshold of incipient motion). The origins of these fluctuations, which appear on a wide range of time scales, are still not well understood. In this study, we present the data obtained from a 2D idealized laboratory experiment with the objective of simultaneously recording the channel bed evolution and bedload transport rate at a high temporal resolution. A 3-m long by 8-cm wide transparent flume filled with well-sorted natural gravel (d50=6.5 mm) was used. An efficient technique using accelerometers has been developed to record the arrival time of every particle at the outlet of the flume for long experimental durations (up to a few days). In addition, bed elevation was monitored using cameras filming from the side of the channel, allowing the observation of global aggradation/degradation as well as bedform migration. The experimental parameters were the water discharge, the flume inclination (from 2° to 5°) and the constant feeding rate of sediments. Large-scale bed evolution showed successive aggradation and rapid degradation periods. Indeed, the measured global channel slope, i.e. mean slope over the flume length, fluctuated continuously within a range sometimes wider than 1° (experimental parameters were constant over the entire run). The analysis of these fluctuations provides evidence that steep channels behave like metastable systems, similarly to grain piles. The metastable effects increased for steeper channels and lower transport conditions. In this measurement campaign, we mainly observed upstream-migrating antidunes. For each run, various antidune heights and celerities were measured. On average, the mean antidune migration rate increased with decreasing channel slope and increasing sediment feeding rate. Relatively rare tall and fast-moving antidunes appeared more frequently at high

  11. Carrying a biological "backpack": Quasi-experimental effects of weight status and body fat change on perceived steepness.

    PubMed

    Taylor-Covill, Guy A H; Eves, Frank F

    2016-03-01

    The apparent steepness of hills and stairs is overestimated in explicit perception. These overestimations are malleable in that when physiological resources are compromised, apparent steepness is further overestimated. An alternative explanation of these experimental findings attributes them to demand characteristics. This article tests the relationship between estimated steepness and naturally occurring differences in body composition. A quasi-experimental field study revealed more exaggerated reports of staircase steepness in overweight than in healthy-weight participants in a situation where experimental demand would be an implausible explanation for any differences. A longitudinal follow-up study used dual X-ray absorptiometry to objectively measure participants' body composition at the beginning and end of a weight-loss program (N = 52). At baseline, higher levels of body fat were associated with steeper explicit estimates of staircase steepness. At follow-up, changes in body fat were associated with changes in estimated steepness such that a loss of fat mass co-occurred with shallower estimates. Discussion focuses on the malleability of perceived steepness at an individual level and the implication of these findings for the debate surrounding "embodied" models of perception. (PsycINFO Database Record PMID:26414167

  12. Evidence of Spin and Energy Extraction in a Galactic Black Hole Candidate: The XMM-Newton/EPIC-pn Spectrum of XTE J1650-500

    NASA Astrophysics Data System (ADS)

    Miller, J. M.; Fabian, A. C.; Wijnands, R.; Reynolds, C. S.; Ehle, M.; Freyberg, M. J.; van der Klis, M.; Lewin, W. H. G.; Sanchez-Fernandez, C.; Castro-Tirado, A. J.

    2002-05-01

    We observed the Galactic black hole candidate XTE J1650-500 early in its fall of 2001 outburst with the XMM-Newton European Photon Imaging pn Camera (EPIC-pn). The observed spectrum is consistent with the source having been in the ``very high'' state. We find a broad, skewed Fe Kα emission line that suggests the primary in this system may be a Kerr black hole and that indicates a steep disk emissivity profile that is hard to explain in terms of a standard accretion disk model. These results are quantitatively and qualitatively similar to those from an XMM-Newton observation of the Seyfert galaxy MCG -6-30-15. The steep emissivity in MCG -6-30-15 may be explained by the extraction and dissipation of rotational energy from a black hole with nearly maximal angular momentum or from material in the plunging region via magnetic connections to the inner accretion disk. If this process is at work in both sources, an exotic but fundamental general relativistic prediction may be confirmed across a factor of 106 in black hole mass. We discuss these results in terms of the accretion flow geometry in stellar-mass black holes and the variety of enigmatic phenomena often observed in the very high state.

  13. Evidence of Spin and Energy Extraction in a Galactic Black Hole Candidate: The XMM-NEWTON/EPIC SPECTRUM of XTE 11650-500

    NASA Technical Reports Server (NTRS)

    Miller, J. M.; Fabian, A. C.; Wunands, R.; Reynolds, C. S.; Ehle, M.; Freyberg, M. J.; VanDerKlis, M.; Lewin, W. H. G.; Sanchez-Fernandez, C.; Castro-Tirado, A. J.

    2002-01-01

    We observed the Galactic black hole candidate XTE J1650-500 early in its fall of 2001 outburst with the XMM-Newton European Photon Imaging pn Camera (EPIC-pn). The observed spectrum is consistent with the source having been in the very high state. We h d a broad, skewed Fe Kar emission line that suggests the primary in this system may be a Kerr black hole and that indicates a steep disk emissivity profile that is hard to explain in terms of a standard accretion disk model. These results are quantitatively and qualitatively similar to those from an XMM-Newton observation of the Seyfert galaxy MCG -6-30-15. The steep emissivity in MCG -6-30-15 may be explained by the extraction and dissipation of rotational energy from a black hole with nearly maximal angular momentum or from material in the plunging region via magnetic connections to the inner accretion disk. If this process is at work in both sources, an exotic but fundamental general relativistic prediction may be confirmed across a factor of l0(exp 6) in black hole mass. We discuss these results in terms of the accretion flow geometry in stellar-mass black holes and the variety of enigmatic phenomena often observed in the very high state.

  14. THE 3-5 {mu}m SPECTRUM OF NGC 1068 AT HIGH ANGULAR RESOLUTION: DISTRIBUTION OF EMISSION AND ABSORPTION FEATURES ACROSS THE NUCLEAR CONTINUUM SOURCE

    SciTech Connect

    Geballe, T. R.; Mason, R. E.; Rodriguez-Ardila, A.; Axon, D. J.

    2009-08-20

    We report moderate resolution 3-5 {mu}m spectroscopy of the nucleus of NGC 1068 obtained at 0.''3 (20 pc) resolution with the spectrograph slit aligned approximately along the ionization cones of the active galactic nucleus. The deconvolved full width at half-maximum of the nuclear continuum source in this direction is 0.''3. Four coronal lines of widely different excitations were detected; the intensity of each peaks near radio knot C, approximately 0.''3 north of the infrared continuum peak, where the radio jet changes direction. Together with the broadened line profiles observed near that location, this suggests that shock ionization is the dominant excitation mechanism of the coronal lines. The depth of the 3.4 {mu}m hydrocarbon absorption is maximum at and just south of the continuum peak, similar to the 10 {mu}m silicate absorption. That and the similar and rapid variations of the optical depths of both features across the nucleus suggest that substantial portions of both arise in a dusty environment just in front of the continuum source(s). A new and tighter limit is set on the column density of CO. Although clumpy models of the dust screen might explain the shallowness of the silicate feature, the presence of the 3.4 {mu}m feature and the absence of CO are strongly reminiscent of Galactic diffuse cloud environments and a consistent explanation for them and the observed silicate feature is found if all three phenomena occur in such an environment, existing as close as 10 pc to the central engine.

  15. Ultra high energy cosmic rays: implications of Auger data for source spectra and chemical composition

    NASA Astrophysics Data System (ADS)

    Aloisio, R.; Berezinsky, V.; Blasi, P.

    2014-10-01

    We use a kinetic-equation approach to describe the propagation of ultra high energy cosmic ray protons and nuclei and calculate the expected spectra and mass composition at the Earth for different assumptions on the source injection spectra and chemical abundances. When compared with the spectrum, the elongation rate Xmax(E) and dispersion σ(Xmax) as observed with the Pierre Auger Observatory, several important consequences can be drawn: a) the injection spectra of nuclei must be very hard, ~ E-γ with γ~ 1- 1.6; b) the maximum energy of nuclei of charge Z in the sources must be ~ 5Z× 1018 eV, thereby not requiring acceleration to extremely high energies; c) the fit to the Auger spectrum can be obtained only at the price of adding an ad hoc light extragalactic component with a steep injection spectrum ~ E-2.7). In this sense, at the ankle EA≈ 5× 1018 eV) all the components are of extragalactic origin, thereby suggesting that the transition from Galactic to extragalactic cosmic rays occurs below the ankle. Interestingly, the additional light extragalactic component postulated above compares well, in terms of spectrum and normalization, with the one recently measured by KASCADE-Grande.

  16. Ultra high energy cosmic rays: implications of Auger data for source spectra and chemical composition

    SciTech Connect

    Aloisio, R.; Blasi, P.

    2014-10-01

    We use a kinetic-equation approach to describe the propagation of ultra high energy cosmic ray protons and nuclei and calculate the expected spectra and mass composition at the Earth for different assumptions on the source injection spectra and chemical abundances. When compared with the spectrum, the elongation rate X{sub max}(E) and dispersion σ(X{sub max}) as observed with the Pierre Auger Observatory, several important consequences can be drawn: a) the injection spectra of nuclei must be very hard, ∼ E{sup -γ} with γ∼ 1- 1.6; b) the maximum energy of nuclei of charge Z in the sources must be ∼ 5Z× 10{sup 18} eV, thereby not requiring acceleration to extremely high energies; c) the fit to the Auger spectrum can be obtained only at the price of adding an ad hoc light extragalactic component with a steep injection spectrum ∼ E{sup -2.7}). In this sense, at the ankle E{sub A}≈ 5× 10{sup 18} eV) all the components are of extragalactic origin, thereby suggesting that the transition from Galactic to extragalactic cosmic rays occurs below the ankle. Interestingly, the additional light extragalactic component postulated above compares well, in terms of spectrum and normalization, with the one recently measured by KASCADE-Grande.

  17. Assess the impact of the steep-front, short duration impulse on electric power system insulation: Phase 1, Final report

    SciTech Connect

    Burrage, L.M.; Hettwer, P.F.; Howells, E.; Veverka, E.F.; Smith, I.D.; Nelson, J.K.; Dugan, R.C.

    1987-02-01

    Concern has been expressed with respect to the dielectric integrity of today's power systems and power system components when subjected to steep front, short duration (SFSD) impulse. Impulses of this type are characterized by voltage rise times of 10 to 250 ns and durations to several ..mu..s. A review of the literature on SFSD impulse and its associated impact on the insulating systems used in power system apparatus was completed. SFSD impulse was found to be the result of several sources including both lightning and nuclear electromagnetic pulse (EMP) and may contribute to the so called anomalous behavior or failure of electrical apparatus. The insulation systems used in power system apparatus were ranked with respect to vulnerability to SFSD impulse. The power insulating systems believes to be at greatest risk are the porcelain/air structural insulation (line insulation) and the paper/oil/enamel systems (transformers). Events reported in the open literature as anomalous behavior or failure were cataloged and characterized. The bibliography is available as a separate report.

  18. Assignment of high-lying bending mode levels in the threshold photoelectron spectrum of NH2: a comparison between pyrolysis and fluorine-atom abstraction radical sources.

    PubMed

    Holzmeier, F; Lang, M; Fischer, I; Hemberger, P; Garcia, G A; Tang, X; Loison, J-C

    2015-07-15

    In this manuscript we present threshold photoelectron spectra (TPES) of the amidogen radical, NH2, recorded at two vacuum ultraviolet synchrotron radiation beamlines, the DESIRS beamline of Synchrotron SOLEIL and the VUV beamline of the Swiss Light Source (SLS). Amidogen radicals were generated by two different methods, (a) H-atom abstraction of ammonia in a fluorine microwave discharge flow tube and (b) flash pyrolysis of methylhydrazine and diphenylmethylamine. Due to the large geometry change upon photoionization from the bent neutral molecule NH2 (X[combining tilde] (2)B1) to the quasi-linear cation NH2(+) (X[combining tilde] (3)B1), significant activity in the bending vibration υ2(+) of NH2(+) (X[combining tilde] (3)B1) is observed in the TPES. Transitions into a large number of υ2(+), Ka(+) levels of the cation are resolved. PMID:26146367

  19. Time-series analysis on bed morphology affected by debris flows along a headwater steep channel in Ohya-kuzure landslide, central Japan

    NASA Astrophysics Data System (ADS)

    Hayakawa, Y. S.; Imaizumi, F.; Hotta, N.; Tsunetaka, H.

    2013-12-01

    Deformation of steep terrain has been occurring since the formation of Ohyakuzure landslide in 1707. Although erosion controls in recent decades have resulted in vegetation recovery in downstream portions of the landslide terrain, hillslope erosion and debris flows frequently occur in uppermost steep subwatersheds in the landslide area to yield vast amount of sediment downstream. Ichino-sawa subwatershed in the landslide terrain, where detailed monitoring of debris flows and related topographic changes have previously been performed, has particularly steep slopes, and geomorphic processes therein have been quite active. Freeze-thaw weathering of fractured bedrock on hillslopes made of shale and sandstone frequently occurs in winter to spring season, and resultant sediment particles are provided into channel beds, which act as a source of debris flows that frequently occurs in summer season with heavy or accumulated rainfalls. High-resolution assessment of erosion/deposition patterns in channel bed of the Ichinosawa catchment was performed using multi-temporal terrestrial laser scanning data covering 3 seasons for 2 years. Seasonal changes in spatial distribution of erosion and deposition in the channel bed is quantified using a 0.1-m DEM converted from the original point cloud by TLS. The multi-temporal datasets provides an estimate of annual sediment storage and yield on the order of 1,000 - 5,000 m3. Analysis of changes in elevation by transverse and longitudinal profiles shows contrasting patterns of erosion and deposition along the studied reach: in particular, changes in bed elevation is found to be less in a 50-m long reach, whose downstream part seems bounded by valley narrowing and a knickpoint. Several topographic metrics, including stream gradient, surface roughness and topographic openness, were examined to estimate the characteristics of differing transport processes induced by debris flows along the reaches.

  20. The Performance of RAMS in Representing the Convective Boundary Layer Structure in a Very Steep Valley

    SciTech Connect

    De Wekker, Stephan; Steyn, D. G.; Fast, Jerome D.; Rotach, Mathias W.; Zhong, Shiyuan

    2005-04-01

    Data from a comprehensive field study in the Riviera Valley of Southern Switzerland are used to investigate convective boundary layer structure in a steep valley and to evaluate wind and temperature fields, convective boundary layer height, and surface sensible heat fluxes as predicted by the mesoscale model RAMS. Current parameterizations of surface and boundary layer processes in RAMS, as well as in other mesoscale models, are based on scaling laws strictly valid only for flat topography and uniform land cover. Model evaluation is required to investigate whether this limits the applicability of RAMS in steep, inhomogeneous terrain. One clear-sky day with light synoptic winds is selected from the field study. Observed temperature structure across and along the valley is nearly homogeneous while wind structure is complex with a wind speed maximum on one side of the valley. Upvalley flows are not purely thermally driven and mechanical effects near the valley entrance also affect the wind structure. RAMS captured many of the observed boundary layer characteristics within the steep valley. The wind field, temperature structure, and convective boundary layer height in the valley are qualitatively simulated by RAMS, but the horizontal temperature structure across and along the valley is less homogeneous in the model than in the observations. The model reproduced the observed net radiation, except around sunset and sunrise when RAMS does not take into account the shadows cast by the surrounding topography. The observed sensible heat fluxes fall within the range of simulated values at grid points surrounding the measurement sites. Some of the scatter between observed and simulated turbulent sensible heat fluxes are due to sub-grid scale effects related to local topography.

  1. Comparison of Scheimpflug imaging parameters between steep and keratoconic corneas of Caucasian eyes

    PubMed Central

    Huseynova, Tukezban; Abdulaliyeva, Farah; Lanza, Michele

    2016-01-01

    Purpose To compare the keratometric and pachymetric parameters of healthy eyes with those affected by steep cornea and keratoconus (KC) using Scheimpflug camera. Setting Briz-L Eye Clinic, Baku, Azerbaijan. Design A cross-sectional study. Methods In this study, 49 KC (Amsler–Krumeich stage 1) eyes and 36 healthy eyes were enrolled. A complete ophthalmic evaluation and a Scheimpflug camera scan were performed in every eye included in the study. Tomographic parameters such as parameters from the front and back cornea, maximum keratometry reading (Kmax), corneal volume (CV), anterior chamber volume (ChV), anterior chamber depth (ACD), anterior chamber angle (AC angle), keratometric power deviation (KPD), maximum front elevation (Max FE), and maximum back elevation (Max BE), as well as pachymetric progression indices (PPI), Ambrosio relational thickness (ART), index of surface variance (ISV), index of vertical asymmetry (IVA), center keratoconus index (CKI), index of height asymmetry (IHA), index of height decentration (IHD), and radius minimum (RM) were collected and statistically compared between the two groups. Results PPI, ART, ISV, IVA, CKI, IHA, IHD, and RM parameter values were significantly different (P<0.05) between the KC and healthy eyes. There were no significant differences in K mean and Q values of the frontal corneal parameters, as well as in Kmax, AC angle, RM, back, and front astigmatism, between stage 1 keratoconic and normal Caucasian eyes with steep cornea. All other parameters such as K mean and Q values of the back corneal parameters, Max FE, Max BE, ACD, ChV, and CV showed significant differences between the groups (P<0.05 for all). Conclusion Scheimpflug imaging is able to detect corneal morphological differences between stage 1 KC eyes and healthy eyes with steep cornea, in Caucasians. PMID:27099469

  2. Mechanism of generating fast electrons by an intense laser at a steep overdense interface.

    PubMed

    May, J; Tonge, J; Fiuza, F; Fonseca, R A; Silva, L O; Ren, C; Mori, W B

    2011-08-01

    The acceleration and heating of electrons by an intense laser normally incident on a steep overdense plasma interface is investigated using the particle-in-cell code osiris. Energetic electrons are generated by the laser's electric field in the vacuum region within λ/4 of the surface. Only those electrons which originate within the plasma with a sufficiently large transverse momentum can escape the plasma. This mechanism relies on the standing wave structure created by the incoming and reflected wave and is therefore very different for linear and circularly polarized light. PMID:21929052

  3. In situ measurements of particle friction angles in steep, narrow channels

    NASA Astrophysics Data System (ADS)

    Prancevic, J.; Lamb, M. P.

    2013-12-01

    The persistent observation that sediment requires increased fluid stresses to move on steeper channels has inspired a wide range of explanations, which can loosely be divided into those that invoke increased grain stability (friction angle, φ) and those that require altered flow hydraulics in steep channels. Measurements of bulk fluid forces over a wide range of channel slopes (θ ≤ 22°) have been obtained using laboratory flume experiments that can control for grain stability and show that altered flow hydraulics do play a role in increased critical shear stress. However, measurements of grain stability are almost all limited to channel slopes less than a few degrees. These friction angle studies have been conducted by tilting a fixed gravel bed with a single loose particle until dislodgment, or by directly measuring the forces required to dislodge a particle using a load cell. The latter methodology is less common but offers the advantage of quickly measuring the friction angles of in situ grains in natural river channels. Indeed, it has enabled the collection of extremely large datasets at low slopes [e.g., Johnston et al., 1998]. We are adding to this dataset with measurements from several natural steep channels in the San Gabriel Mountains, CA to test if the particle friction angle changes systematically as a function of slope or width-to-grain size ratio (W/D50), which is thought to determine the propensity for particle jamming. Using a load cell that records peak forces we measure the minimum force required to pull a particle from its pocket in the downstream direction and the particle weight. Particles are sampled over a regular grid and we record the percentage of the particle buried by fines and the qualitative degree of interlocking. Preliminary results from three sites with bed slopes of θ = 2.9°, 3.2°, and 9.0° suggest that the at-a-site variability in friction angle is much higher than between-site variability, and that median values do not

  4. Steep Satellite Altimetry Gradients as a Proxy to the Edge of the Continental Crust

    NASA Astrophysics Data System (ADS)

    Lawver, L. A.; Gahagan, L. M.

    2005-05-01

    Tight-fit plate reconstructions are produced using a global database constrained by marine magnetic anomalies tied to a consistent timescale, paleomagnetic poles, seafloor age dates based on drilling results, and fracture zone and transform fault lineations picked from ship-track and satellite altimetry data. Where a prominent steep gradient in the satellite altimetry data is present near the continental-ocean transition, it is used as a proxy to the continental shelf break [CSB]. Continental block outlines are based on digitization of the steep gradient. In some places, notably off Namibia, there is a very close correlation between that gradient and the ocean-continent boundary deduced from seismic refraction and reflection data. In other regions, there may be some stretched continental crust oceanward of the steep gradient but for reconstruction purposes we assume the crust to be predominantly continental landward of the boundary and oceanic, seaward of the line. Good matchs for conjugate CSBs are found in many places world-wide along passive margins and these will be highlighted. Particularly good matches are observed between the cratonic edges of East Antarctica as determined by sub-ice topographic highs seen along the margins of East Antarctica with respect to Madagascar, Sri Lanka, the southern half of the eastern margin of India, and the region of Australia between 124° E and 133° E along the Great Australian Bight (GAB). There are overlaps of the reconstructed conjugate CSBs, with one overlap between India and East Antarctica (70° E to 85° E) and one between East Antarctica and the western section of the GAB (105° E to 120° E). These two overlaps are coincident with the outer margins of the Lambert Graben - Prydz Bay Basin and the Aurora Subglacial Basin, respectively. It is known that there are substantial glacially-derived sediments prograded off the continental margin onto oceanic crust at Prydz Bay where there may be as much as 200 km in width of

  5. Low-Power RIE of SiO2 in CHF3 To Obtain Steep Sidewalls

    NASA Technical Reports Server (NTRS)

    Turner, Tasha; Wu, Chi

    2003-01-01

    A reactive-ion etching (RIE) process has been developed to enable the formation of holes with steep sidewalls in a layer of silicon dioxide that covers a silicon substrate. The holes in question are through the thickness of the SiO2 and are used to define silicon substrate areas to be etched or to be built upon through epitaxial deposition of silicon. The sidewalls of these holes are required to be vertical in order to ensure that the sidewalls of the holes to be etched in the substrate or the sidewalls of the epitaxial deposits, respectively, also turn out to be vertical.

  6. An exact solution for ideal dam-break floods on steep slopes

    USGS Publications Warehouse

    Ancey, C.; Iverson, R.M.; Rentschler, M.; Denlinger, R.P.

    2008-01-01

    The shallow-water equations are used to model the flow resulting from the sudden release of a finite volume of frictionless, incompressible fluid down a uniform slope of arbitrary inclination. The hodograph transformation and Riemann's method make it possible to transform the governing equations into a linear system and then deduce an exact analytical solution expressed in terms of readily evaluated integrals. Although the solution treats an idealized case never strictly realized in nature, it is uniquely well-suited for testing the robustness and accuracy of numerical models used to model shallow-water flows on steep slopes. Copyright 2008 by the American Geophysical Union.

  7. An episode of steep geomagnetic inclination 120,000 years ago.

    PubMed

    Verosub, K L

    1983-07-22

    The mean inclinations of three sections of 120,000-year-old fine-grained sediments from northern California range from 62 degrees to 66 degrees . These inclinations are significantly steeper than the inclination of the geocentric axial dipole at this site. Because these sediments have probably recorded an actual episode of steep inclination lasting several thousand years, they provide new insights into the significance of mean inclinations shallower than the geocentric axial dipole. Such inclinations are characteristic of fine-grained sediments younger than 35,000 years. The results raise questions about the time-averaged geomagnetic field and about the determination of plate motions from paleomagnetic data. PMID:17798888

  8. Mechanism of generating fast electrons by an intense laser at a steep overdense interface

    SciTech Connect

    May, J.; Tonge, J.; Fiuza, F.; Fonseca, R. A.; Silva, L. O.; Mori, W. B.

    2011-08-15

    The acceleration and heating of electrons by an intense laser normally incident on a steep overdense plasma interface is investigated using the particle-in-cell code osiris. Energetic electrons are generated by the laser's electric field in the vacuum region within {lambda}/4 of the surface. Only those electrons which originate within the plasma with a sufficiently large transverse momentum can escape the plasma. This mechanism relies on the standing wave structure created by the incoming and reflected wave and is therefore very different for linear and circularly polarized light.

  9. Mode and site of acupuncture modulation in the human brain: 3D (124-ch) EEG power spectrum mapping and source imaging.

    PubMed

    Chen, Andrew C N; Liu, Feng-Jun; Wang, Li; Arendt-Nielsen, Lars

    2006-02-15

    This study determined: (a) if acupuncture stimulation at a traditional site might modulate ongoing EEG as compared with stimulation of a control site; (b) if high-frequency vs. low-frequency stimulation could exert differential effects of acupuncture; (c) if the observed effects of acupuncture were specific to certain EEG bands; and (d) if the acupuncture effect could be isolated at a specific scalp field, with its putative underlying intracranial source. Twelve healthy male volunteers (age range 22-35) participated in two experimental sessions separated by 1 week, which involved transcutaneous acupoint stimulation at selected acupoint (Li 4, HeGu) vs. a mock point at the fourth interosseous muscle area on the left hand in high (HF: 100 Hz) vs. low-frequency (LF: 2 Hz) stimulation by counter-balanced order. 124-ch EEG data were used to analyze the Delta, Theta, Alpha-1, Alpha-2, Beta, and Gamma bands. The absolute EEG powers (muv2) at focal maxima across three stages (baseline, stimulation, post) were examined by two-way (condition, stage) repeated measures ANOVA. The activity of the Theta power significantly decreased (P = 0.02), compared with control during HF but not LF stimulation at acupoint stimulation, however, there was no study effect at the mock point. A decreased Theta EEG power was prominent at the frontal midline sites (FCz, Fz) and the contralateral right hemisphere front site (FCC2h). In contrast, the Theta power of low-frequency stimulation showed an increase from the baseline as those in both controlled mock point stimulations. The observed high-frequency acupoint stimulation effects of Theta EEG were only present during, but not after, simulation. The topographic Theta activity was tentatively identified to originate from the intracranial current source in cingulate cortex, likely ACC. It is likely that short-term cortical plasticity occurs during high-frequency but not low-frequency stimulation at the HeGu point, but not mock point. We suggest

  10. Riparian hydraulic gradient and stream-groundwater exchange dynamics in steep headwater valleys

    NASA Astrophysics Data System (ADS)

    Voltz, Thomas; Gooseff, Michael; Ward, Adam S.; Singha, Kamini; Fitzgerald, Michael; Wagener, Thorsten

    2013-06-01

    of riparian hydraulic gradients and stream-groundwater exchange in headwater catchments provide the hydrologic context for important ecological processes. Although the controls are relatively well understood, their dynamics during periods of hydrologic change is not. We investigate riparian hydraulic gradients over three different time scales in two steep, forested, headwater catchments in Oregon (WS01 and WS03) to determine the potential controls of reach-scale valley slope and cross-sectional valley geometry. Groundwater and stream stage data collected at high spatial and temporal resolutions over a period encompassing a 1.25 year storm and subsequent seasonal baseflow recession indicate that hydraulic gradients in both riparian aquifers exhibit strong persistence of down-valley dominance. Responses to rainfall do not support the simple conceptual models of increased riparian hydraulic gradient toward streams. Hydraulic gradient response in WS01 to both the seasonal baseflow recession and the storm suggested the potential for increased stream-groundwater exchange, but there was less evidence for this in WS03. Results from four constant-rate tracer injections in each stream showed a high baseline level of exchange overall, and both a slight seasonal increase (WS01) and slight decrease (WS03) in the riparian intrusion of tracer-labeled stream water as stream discharge receded. These results indicate that steep headwater valley floors host extensive stream water exchange and very little change in the water table gradients over 3 orders of magnitude of stream discharge.

  11. An Inconvenient Sea Truth: Spread, Steepness, and Skewness of Surface Slopes

    NASA Astrophysics Data System (ADS)

    Munk, Walter

    2009-01-01

    Bréon and Henriot (BH) have collected eight million globally distributed satellite images of sunglitter, which yield a few simple, robust rules about the statistics of surface slopes: 1) constant angular spread, 2) linear steepness, and 3) sigmoid (near stepwise) skewness (all with respect to wind speed). Yet the information is sparse because it says nothing about time and space scales. The BH rules are an inconvenient sea truth, too fundamental to be ignored, too incomplete to be understood. With regard to BH rule 1 (BH:1), I suggest that the constant spread is associated with a wake-like geometry of the short gravities. Steepness linearity (BH:2) remains an enigma. Skewness (BH:3) appears to be correlated with a rather sudden onset of breaking for winds above 4 m s-1. I do not think that skewness comes from parasitic capillaries. These are tentative conclusions; I look forward to intensive sea-going experiments over the next few years demolishing the proposed interpretations.

  12. An inconvenient sea truth: spread, steepness, and skewness of surface slopes.

    PubMed

    Munk, Walter

    2009-01-01

    Bréon and Henriot (BH) have collected eight million globally distributed satellite images of sunglitter, which yield a few simple, robust rules about the statistics of surface slopes: 1) constant angular spread, 2) linear steepness, and 3) sigmoid (near stepwise) skewness (all with respect to wind speed). Yet the information is sparse because it says nothing about time and space scales. The BH rules are an inconvenient sea truth, too fundamental to be ignored, too incomplete to be understood. With regard to BH rule 1 (BH:1), I suggest that the constant spread is associated with a wake-like geometry of the short gravities. Steepness linearity (BH:2) remains an enigma. Skewness (BH:3) appears to be correlated with a rather sudden onset of breaking for winds above 4 m s(-1). I do not think that skewness comes from parasitic capillaries. These are tentative conclusions; I look forward to intensive sea-going experiments over the next few years demolishing the proposed interpretations. PMID:21141042

  13. Hot electron generation forming a steep interface in superintense laser-matter interaction

    NASA Astrophysics Data System (ADS)

    Mishra, R.; Sentoku, Y.; Kemp, A. J.

    2009-11-01

    Superintense laser light (>1020 W/cm2) is able to sweep the preplasma over short times and compress the preplasma density gradient typically generated by the prepulse of today's high-intensity, high energy laser systems. Hot electron generation at steep plasma density gradients has been studied in a previous paper [A. J. Kemp, Y. Sentoku, and M. Tabak, Phys. Rev. Lett. 101, 075004 (2008)], which identified a mode of hot electron acceleration that is characterized by the formation of low-density shelf in front of the target. In this paper, we deal with laser incidence on slab target in one-dimensional situation and follow the formation of a steep interface and hot electron acceleration up to later stages of the interaction. We find that a novel mode of absorption appears during which the coupling efficiency drops, while a large number of sub-MeV hot electrons is produced at the interface. These dc-ponderomotive electrons play a dominant role in the bulk heating of solid density targets. We propose an analytical model to describe this absorption mode, explain electron energy spectra, and identify the parameter regime where it appears.

  14. Fully-coupled hydrologic/geomechanical simulations of slope failure in a prototypical steep mountain catchment

    NASA Astrophysics Data System (ADS)

    White, J. A.; Borja, R. I.; Ebel, B. A.; Loague, K.

    2009-12-01

    This work presents a physics-based framework for continuum modeling of hydrologically-driven slope failure. The analyses employ a mixed finite element formulation for variably-saturated geomaterials undergoing elastoplastic deformations. The deforming soil mass is treated as a multiphase continuum, and the governing mass and momentum balance equations are solved in a fully-coupled manner. This tight coupling is necessary to capture key features of slope behavior. To test the coupled formulation, we present a three-dimensional slope analysis motivated by a 1996 landslide that occurred at a steep experimental catchment (CB1) near Coos Bay, Oregon. Simulations are used to quantify the rainfall-induced slope deformation and assess the failure potential. Results of parametric studies suggest that for a steep hillslope underlain by bedrock, similar to the CB1 site, failure would occur by a multiple slide block mechanism, with progressive failure surfaces forming at the bedrock interface and propagating to the surface. Extensive field observations and experimental measurements made at the CB1 site provide a rich data set to calibrate and evaluate the proposed numerical model. We take the opportunity, however, to point out those features of the model that are not well-constrained by available field data, but which may play an important role in determing the timing and location of failure. These observations are used to assess the current state of predictive capability of the slope simulations, and to inform the design of future field experiments.

  15. Experimental study of non-linear loads on vertical cylinders in steep random waves

    SciTech Connect

    Stansberg, C.T.; Huse, E.; Krokstad, J.R.; Lehn, E.

    1995-12-31

    A description of laboratory experiments carried out with fixed, vertical truncated cylinders in irregular waves is given. With a model scale about 1:50, the tested models correspond approximately to North Sea large-volume platform dimensions. Tests with a single cylinder as well as with an array of cylinders are performed. Global horizontal forces and pitch moments on individual cylinders were measured. In the present report, analysis of surge force measurements are presented and discussed. The background of the study is the need for research on the hydrodynamic excitation of ringing phenomena. Thus one has emphasized the study of non-linear high-frequency (HF) force contributions generated by steep random waves. It is observed that although they are negligible in the frequency domain, the magnitude of such force components may be up to 10--20% of the total extreme forces, for this particular cylinder. Tests with the multi-column model show that diffraction effects can be important for the magnitude of the HF excitation, but not for the occurrence and nature of such events in itself. Force measurements on the different individual columns show that the HF force signal due to a particular steep wave passing through the structure, is recognized on all the columns, but shape of the signal changes in space.

  16. Perioperative dorzolamide-timolol intervention for rising intraocular pressure during steep Trendelenburg positioned surgery.

    PubMed

    Molloy, Bonnie; Cong, Xiaomei

    2014-06-01

    Elevated intraocular pressure (IOP) and venous congestion may produce a low ocular perfusion state that can lead to postoperative visual loss (POVL). The literature cites the importance of early IOP reduction to prevent optic nerve damage and visual loss. This study examined dorzolamide hydrochloride and timolol maleate (Cosopt) eyedrops on reducing elevated IOP during laparoscopic surgery with the patient in steep Trendelenburg position. A quasi-experimental study design was used. Subjects involving robotic urologic and gynecologic procedures at 3 separate medical centers were included. The medication was administered topically to both eyes at time points when IOP approached 40 mm Hg. The IOP was measured at 30-minute intervals compared with a supine, anesthetized baseline and final postprocedure supine measurements. A total of 194 patients were recruited, and 63 patients received dorzolamide-timolol treatment when IOP levels reached 38 to 40 mm Hg. Repeated-measures analysis of variance showed that IOP values dropped significantly after drug intervention at 60, 90, and 120 minutes (P < .001). Effect sizes of pharmacologic intervention on IOP reduction were strong (partial eta2 of 0.60 to 0.66). Treatment with dorzolamide-timolol eyedrops significantly reduces elevated IOP of patients who undergo lengthy laparoscopic surgery in the steep Trendelenburg position. PMID:25109158

  17. Predicting Sediment Flux from Hillslopes by Dry Ravel Following Wildfires in Steep Terrain

    NASA Astrophysics Data System (ADS)

    Levina, M.; Lamb, M. P.

    2010-12-01

    Sediment flux from hillslopes to channels increases after fires, and this can lead to debris flows during high intensity rainstorms. Much of this material is transported on steep hillslopes via the process of dry ravel, the rolling, bouncing and sliding of material, which occurs as a result of vegetation loss. Models to predict sediment flux by dry ravel have not been formulated for slopes greater than the angle of repose, and these slopes represent a significant part of the landscape. On these steep slopes we propose that the sediment flux to channels after fires is controlled by the amount of material stored behind vegetation prior to the burn. To test this hypothesis we have performed a series of tilt-table experiments to quantify the amount of sediment stored behind vegetation under a range of slopes, grain sizes, bed roughness, and vegetation widths. Our results show that the volume of the stored material scales with the cube of the width of the vegetation blocking it, but that there are secondary effects when the grain size is comparable to the blocker width. The slope has a much smaller effect on the volume than the width of the blocker, although bed roughness does influence volume at slopes close to the friction angle. Model results might be used to predict sediment fluxes after fires by taking into account the type and density of vegetation and the size distribution of sediment produced on the hillslope.

  18. Wide-field profiling of smooth steep surfaces by structured illumination

    NASA Astrophysics Data System (ADS)

    Wang, Hongting; Tan, Jiubin; Liu, Chenguang; Liu, Jian; Li, Yong

    2016-05-01

    We propose sectioning structured illumination wide-field microscopy (SSIWM) combined with the coating of a readily removable thin fluorescent film (RTFF) for smooth steep surfaces. The profiling of smooth steep surfaces is difficult to achieve using conventional optical systems because these surfaces reflect lights away from the collective lens. In particular, when the angle between optical axis and the normal line of the surface is larger than sin-1(NA), no light reflected from the area can be collected by the collective lens. The proposed method employing an RTFF to the SSIWM can overcome the poor collection barrier and be used to measure the shape of the surface owing to the isotropic incoherent scattering property. Additionally, conventional SSIWM is a promising wide-field imaging technique with high axial sectioning ability and low cost; however, it cannot be introduced to measure a reflective surface because of the non-sectioning characteristic in using a laser (coherent). However, the proposed method can extend the application scope of SSIWM owing to the incoherent property of the coating surface. Simulations and experimental results are presented to show the validity of the proposed method.

  19. Hot electron generation forming a steep interface in superintense laser-matter interaction

    SciTech Connect

    Mishra, R.; Sentoku, Y.; Kemp, A. J.

    2009-11-15

    Superintense laser light (>10{sup 20} W/cm{sup 2}) is able to sweep the preplasma over short times and compress the preplasma density gradient typically generated by the prepulse of today's high-intensity, high energy laser systems. Hot electron generation at steep plasma density gradients has been studied in a previous paper [A. J. Kemp, Y. Sentoku, and M. Tabak, Phys. Rev. Lett. 101, 075004 (2008)], which identified a mode of hot electron acceleration that is characterized by the formation of low-density shelf in front of the target. In this paper, we deal with laser incidence on slab target in one-dimensional situation and follow the formation of a steep interface and hot electron acceleration up to later stages of the interaction. We find that a novel mode of absorption appears during which the coupling efficiency drops, while a large number of sub-MeV hot electrons is produced at the interface. These dc-ponderomotive electrons play a dominant role in the bulk heating of solid density targets. We propose an analytical model to describe this absorption mode, explain electron energy spectra, and identify the parameter regime where it appears.

  20. Modelling Steep Surfaces by Various Configurations of Nadir and Oblique Photogrammetry

    NASA Astrophysics Data System (ADS)

    Casella, V.; Franzini, M.

    2016-06-01

    Among the parts of the territory requiring periodical and careful monitoring, many have steep surfaces: quarries, river basins, land-slides, dangerous mountainsides. Aerial photogrammetry based on lightweight unmanned aircraft systems (UAS) is rapidly becoming the tool of election to survey limited areas of land with a high level of detail. Aerial photogrammetry is traditionally based on vertical images and only recently the use of significantly inclined imagery has been considered. Oblique photogrammetry presents peculiar aspects and offers improved capabilities for steep surface reconstruction. Full comprehension of oblique photogrammetry still requires research efforts and the evaluation of diverse case studies. In the present paper, the focus is on the photogrammetric UAS-based survey of a part of a large sandpit. Various flight configurations are considered: ordinary linear strips, radial strips (as the scarp considered has a semi-circular shape) and curved ones; moreover, nadir looking and oblique image blocks were acquired. Around 300 control points were measured with a topographic total station. The various datasets considered are evaluated in terms of density of the extracted point cloud and in terms of the distance between the reconstructed surface and a number of check points.

  1. Rehabilitation and flood management planning in a steep, boulder-bedded stream.

    PubMed

    Caruso, Brian S; Downs, Peter W

    2007-08-01

    This study demonstrates the integration of rehabilitation and flood management planning in a steep, boulder-bedded stream in a coastal urban catchment on the South Island of New Zealand. The Water of Leith, the primary stream flowing through the city of Dunedin, is used as a case study. The catchment is steep, with a short time of concentration and rapid hydrologic response, and the lower stream reaches are highly channelized with floodplain encroachment, a high potential for debris flows, significant flood risks, and severely degraded aquatic habitat. Because the objectives for rehabilitation and flood management in urban catchments are often conflicting, a number of types of analyses at both the catchment and the reach scales and careful planning with stakeholder consultation were needed for successful rehabilitation efforts. This included modeling and analysis of catchment hydrology, fluvial geomorphologic assessment, analysis of water quality and aquatic ecology, hydraulic modeling and flood risk evaluation, detailed feasibility studies, and preliminary design to optimize multiple rehabilitation and flood management objectives. The study showed that all of these analyses were needed for integrated rehabilitation and flood management and that some incremental improvements in stream ecological health, aesthetics, and public recreational opportunities could be achieved in this challenging environment. These methods should be considered in a range of types of stream rehabilitation projects. PMID:17602254

  2. Evidence for Holocene stability of steep slopes, northern Peruvian Andes, based on soils and radiocarbon dates

    USGS Publications Warehouse

    Miller, D.C.; Birkeland, P.W.; Rodbell, D.T.

    1993-01-01

    Radiocarbon dating and soil relationships indicate that landscapes in highaltitude glaciated valleys of the northern Peruvian Andes have been remarkably stable during the Holocene. Radiocarbon dates show that deglaciation was underway by 12 ka, and that slopes and alluvial fans at the bases of slopes were essentially stabilized by at least 8 ka. The soils consist of fine-grained loessial A horizons overlying Bw horizons in gravelly till or alluvial-fan gravel. Following deglaciation, widespread gullying took place in till on the steep (maximum angle: 37??) sideslopes of most valleys; the eroded material was deposited as fans at the bases of the slopes. Loess was then deposited as a fairly uniform blanket across most elements of the landscape. Soil formation began during or following loess deposition, and because soil-profile morphology is sufficiently similar at most sites, soil formation has been a dominant process during much of the Holocene. This remarkable stability, especially for such steep slopes, is attributed to a combination of tight packing of the till, permeability of the capping loess, rapid revegetation following ice retreat, and roots from the present grassland vegetation and possibly former forests. ?? 1993.

  3. Rapid growth rates of syndepositional marine aragonite cements in steep marginal slope deposits, Bahamas and Belize

    SciTech Connect

    Grammer, G.M.; Ginsburg, R.N.; Swart, P.K.; McNeill, D.F. . Div. of Marine Geology); Jull, A.J.T. . NSF Accelerator Facility); Prezbindowski, D.R. )

    1993-09-01

    Growth rates of marine botryoidal aragonite cements from steep (35-45[degree]) marginal slope deposits in the Bahamas and Belize have been determined by accelerator mass spectrometer radiocarbon dating of samples taken at the base and top of individual botryoids. The pore-filling cements, which range from approximately 11,000-13,000 years old, grew at average rates of 8-10mm/100 yr with maximum rates > 25mm/100 yr. Radiocarbon dating of coexisting skeletal components indicates that cementation was syndepositional. Microsampling transects across individual botryoids for stable-isotope analyses show little variation in [delta][sup 31]C and [delta][sup 18]O, supporting the conclusion that cementation was extremely rapid. Although the cements show a progressive depletion in isotopic composition of approximately 1[per thousand]([delta][sup 13]C) and 2[per thousand]([delta][sup 18]O) from 13 ka to 11 ka, the average variation ([delta][sub 1]) within individual pore-filling cements, ranging in size 2 mm to 32 mm (bottom to top), was 0.11[per thousand]([delta][sup 13]C) and 0.14[per thousand]([delta][sup 18]O). Results of this study provide the first quantitative data on growth rates of marine carbonate cements in a marginal slope environment. The data indicate that marginal slope deposits may lithify within several tens of years and suggest that geologically instantaneous cementation may be critical in stabilizing steep carbonate slope deposits at or above angles of repose.

  4. Hybrid integrated photodetector with flat-top steep-edge spectral response.

    PubMed

    Fan, Xinye; Huang, Yongqing; Ren, Xiaomin; Duan, Xiaofeng; Hu, Fuquan; Wang, Qi; Cai, Shiwei; Zhang, Xia

    2012-08-20

    Hybrid integrated photodetectors with flat-top steep-edge spectral responses that consist of an Si-based multicavity Fabry-Perot (F-P) filter and an InP-based p-i-n absorption structure (with a 0.2 μm In(0.53)Ga(0.47)As absorption layer), have been designed and fabricated. The performance of the hybrid integrated photodetectors is theoretically investigated by including key factors such as the thickness of each cavity, the pairs of each reflecting mirror, and the thickness of the benzocyclobutene bonding layer. The device is fabricated by bonding an Si-based multicavity F-P filter with an InP-based p-i-n absorption structure. A hybrid integrated photodetector with a peak quantum efficiency of 55% around 1549.2 nm, the -0.5 dB band of 0.43 nm, the 25 dB band of 1.06 nm, and 3 dB bandwidth more than 16 GHz, is simultaneously obtained. Based on multicavity F-P structure, this device has good flat-top steep-edge spectral response. PMID:22907001

  5. Sediment storage by vegetation in steep bedrock landscapes: Theory, experiments, and implications for postfire sediment yield

    NASA Astrophysics Data System (ADS)

    Lamb, Michael P.; Levina, Mariya; Dibiase, Roman A.; Fuller, Brian M.

    2013-06-01

    models for sediment transport on hillslopes are needed for applications ranging from landscape evolution to debris-flow hazards. Progress has been made for soil-mantled landscapes; however, little is known about sediment production and transport in bedrock landscapes that often maintain a patchy soil mantle, even though slopes exceed the angle of repose. Herein we investigate the hypothesis that patchy soil cover is stable on steep slopes due to local roughness such as vegetation dams that trap sediment upslope. To quantify local sediment storage, we developed a new theory and tested it against tilt-table experiments. Results show that trapped sediment volume scales with the cube of dam width. Where the dam width is less than about fifty grain diameters, particle force chains appear to enhance stability, resulting in greater trapped volumes and sediment-pile slopes that exceed the angle of repose. Trapped volumes are greatest for hillslopes that just exceed the friction slope and are independent of hillslope gradient for gradients greater than about twice the friction slope. For neighboring dams spaced less than about five grain diameters apart, grain bridging results in a single sediment pile that is larger than the sum of individual piles. This work provides a mass-conserving framework for quantifying sediment storage and nonlocal transport in bedrock landscapes. Results may explain the rapid increase in sediment yield following wildfire in steep terrain in the absence of rainfall; as sediment dams are incinerated, particles become gravitationally unstable and move rapidly downslope as dry ravel.

  6. Stoppage in Autism Spectrum Disorders.

    PubMed

    Grønborg, Therese K; Hansen, Stefan N; Nielsen, Svend V; Skytthe, Axel; Parner, Erik T

    2015-11-01

    Stoppage refers to changes in reproductive behavior following the birth of a child with a severe disease. The presence of stoppage can bias estimates of sibling recurrence risk if not properly addressed. If stoppage occurs non-randomly (differential stoppage), it is possibly an additional source of bias in sibling recurrence risk estimation. This study investigated whether stoppage occurs in Danish families with a firstborn child diagnosed with autism spectrum disorders, and if stoppage was differential. We found that stoppage occurs moderately in Danish families affected by autism spectrum disorders, and that stoppage is differential. However, differential stoppage is a minor source of estimation bias in Danish sibling recurrence risk studies of autism spectrum disorders. PMID:26077953

  7. Effects of different steeping methods and storage on caffeine, catechins and gallic acid in bag tea infusions.

    PubMed

    Yang, Deng-Jye; Hwang, Lucy Sun; Lin, Jau-Tien

    2007-07-13

    Bag teas, packed 3g of ground black, green, oolong, paochoung and pu-erh tea leaves (the particle size used was 1-2mm), were steeped in 150 mL of 70, 85 or 100 degrees C hot water to study the effects of the number of steeping (the same bag tea was steeped repeatedly eight times, 30s each time, as done in China for making ceremonial tea) and varied steeping durations (0.5-4 min) on caffeine, catechins and gallic acid in tea infusions. The changes in tea infusions during storage at 4 or 25 degrees C for 0-48 h and the variations in these compounds of bag tea infused with 150 mL of 4 or 25 degrees C cold water for 0.5-16 h were also investigated. A HPLC method with a C18 column and a step gradient solvent system consisting of acetonitrile and 0.9% acetic acid in deionized water was used for analysis. Results for all kinds of tea samples showed that the second tea infusion contained the highest contents of caffeine, catechins and gallic acid when bag teas were steeped in 70 degrees C water. It was different from that steeped at 85 and 100 degrees C, the highest contents existed in the first infusion. These compounds decreased gradually in later infusions. Higher amounts of caffeine, catechins and gallic acid could be released from bag teas as hotter water was used. As steeping duration prolonged, these ingredients increased progressively, however, their levels were lower than that cumulated from the infusions with the identical bag tea prepared recurrently at the same temperature and time points. (-)-Gallocatechin gallate and (+)-catechin existed in these tea infusions rarely and could not be detected until a certain amount of them infusing. Except gallic acid that showed a significant increase and caffeine that exhibited no significant change, all kinds of catechins decreased appreciably after tea infusions were stored at 25 degrees C for 36 h; nevertheless, all of them showed no evident changes at 4 degrees C storage. The caffeine, catechins and gallic acid in tea

  8. Autism Spectrum Disorder

    MedlinePlus

    ... Awards Enhancing Diversity Find People About NINDS NINDS Autism Spectrum Disorder Information Page Condensed from Autism Spectrum ... en Español Additional resources from MedlinePlus What is Autism Spectrum Disorder? Autistic disorder (sometimes called autism or ...

  9. Fast and local non-linear evolution of steep wave-groups on deep water: A comparison of approximate models to fully non-linear simulations

    NASA Astrophysics Data System (ADS)

    Adcock, T. A. A.; Taylor, P. H.

    2016-01-01

    The non-linear Schrödinger equation and its higher order extensions are routinely used for analysis of extreme ocean waves. This paper compares the evolution of individual wave-packets modelled using non-linear Schrödinger type equations with packets modelled using fully non-linear potential flow models. The modified non-linear Schrödinger Equation accurately models the relatively large scale non-linear changes to the shape of wave-groups, with a dramatic contraction of the group along the mean propagation direction and a corresponding extension of the width of the wave-crests. In addition, as extreme wave form, there is a local non-linear contraction of the wave-group around the crest which leads to a localised broadening of the wave spectrum which the bandwidth limited non-linear Schrödinger Equations struggle to capture. This limitation occurs for waves of moderate steepness and a narrow underlying spectrum.

  10. A Mid-Infrared Survey of Class I/Flat-Spectrum Binary/Multiple Systems

    NASA Astrophysics Data System (ADS)

    Haisch, Karl E., Jr.; Barsony, M.; Ressler, M. E.; Greene, T. P.

    2006-12-01

    We have obtained new mid-infrared observations of 65 Class I/Flat-Spectrum (F.S.) objects in the Perseus, Taurus, Chamaeleon I and II, Rho Ophiuchi, and Serpens dark clouds. These objects represent a subset of the young stellar objects (YSOs) from our previous near-infrared multiplicity surveys. We detected 45/48 (94%) of the single sources, 16/16 (100%) of the primary components, and 12/16 (75%) of the secondary/triple components of the binary/multiple objects surveyed. The composite spectral energy distributions (SEDs) for all of our sample YSOs are either Class I or F.S., and, in 15/16 multiple systems, at least one of the individual components displays a Class I or F.S. spectral index. However, the occurrence of mixed pairings, such as F.S. with Class I, F.S. with Class II, and, in one case, an F.S. with a Class III (Cha I T33B), is suprisingly frequent. Such behavior is not consistent with that of multiple systems among T Tauri stars (TTS), where the companion of a classical TTS also tends to be a classical TTS, although other mixed pairings have been previously observed among Class II YSOs. Based on an analysis of the spectral indices of the individual binary components, there appears to be a higher proportion of mixed Class I/Flat-Spectrum systems (65-80%) than that of mixed Classical/Weak Lined T Tauri systems (25-40%), demonstrating that the envelopes of Class I/Flat-Spectrum systems are rapidly evolving during this evolutionary phase. We report the discovery of a steep spectral index secondary companion to ISO-Cha I 97 (Alpha > +3.9), detected for the first time via our mid-infrared observations. The secondary component of this system is a member of a rare class (one of four known) of very steep spectral index YSOs, those with Alpha > +3.

  11. Physically-based Hydrologic-response Simulation of a Steep, Zero-Order Catchment

    NASA Astrophysics Data System (ADS)

    Ebel, B. A.; Loague, K. M.; Dietrich, W. E.; Montgomery, D. R.; Torres, R.; Anderson, S. P.; Giambelluca, T. W.; Vanderkwaak, J. E.

    2005-12-01

    Near-surface hydrologic response plays a critical role in landscape evolution, particularly in steep terrain where hydrologically-driven slope instability is the predominant mechanism of sediment removal. Despite the importance of hydrology in governing the timing and extent of slope failure, the majority of slope stability modeling efforts utilize steady-state approximations to the 1D or 2D saturated subsurface flow equations to generate pore pressures. The effort reported here employs the comprehensive, physics-based Integrated Hydrology Model (InHM) to rigorously simulate near-surface hydrologic response. InHM simulates, in a fully-coupled approach, 3D transient variably-saturated flow and solute transport in porous media and macropores and 2D transient flow and solute transport over the land surface and in open channels. Our modeling approach is tested with the extensive data sets from the 860 m2 Coos Bay experimental catchment (CB1) in the Oregon Coast Range for both sprinkling experiments (event-based simulation) and natural storms (continuous simulation). The instrumentation at CB1 for characterizing the spatial and temporal variability in hydrologic response includes an exhaustive array of rain gages, piezometers, tensiometers, TDR wave guide pairs, lysimeters, meteorological sensors, and two weirs all monitored during three, week-long sprinkling experiments. Continuous measurements of rainfall, discharge, and total head (from selected piezometers) are available from 1990 through 1996. Extensive site characterization at CB1 provides high resolution topography and soil characteristics (e.g., geometry/thickness, saturated hydraulic conductivity, soil-water content, porosity, and hysteretic capillary pressure relationships). CB1 provides one of the most comprehensive hydrologic response data sets in existence for a steep catchment that has experienced slope failure. Results from 3D InHM simulations include comparisons of observed versus simulated runoff

  12. Effects of Sediment Patches on Sediment Transport Predictions in Steep Mountain Channels

    NASA Astrophysics Data System (ADS)

    Monsalve Sepulveda, A.; Yager, E.

    2013-12-01

    Bed surface patches occur in most gravel-bedded rivers and in steep streams can be divided between relatively immobile boulders and more mobile patches of cobbles and gravel. This spatial variability in grain size, roughness and sorting impact bed load transport by altering the relative local mobility of different grain sizes and creating complex local flow fields. Large boulders also bear a significant part of the total shear stress and we hypothesize that the remaining shear stress on a given mobile patch is a distribution of values that depend on the local topography, patch type and location relative to the large roughness elements and thalweg. Current sediment transport equations do not account for the variation in roughness, local flow and grain size distributions on and between patches and often use an area-weighted approach to obtain a representative grain size distribution and reach-averaged shear stress. Such equations also do not distinguish between active (patches where at least one grain size is in motion) and inactive patches or include the difference in mobility between patch classes as result of spatial shear stress distributions. To understand the effects of sediment patches on sediment transport in steep channels, we calculated the shear stress distributions over a range of patch classes in a 10% gradient step-pool stream. We surveyed the bed with a high density resolution (every 5 cm in horizontal and vertical directions over a 40 m long reach) using a total station and terrestrial LiDAR, mapped and classified patches by their grain size distributions, and measured water surface elevations and mean velocities for low to moderate flow events. Using these data we calibrated a quasi-three dimensional model (FaSTMECH) to obtain shear stress distributions over each patch for a range of flow discharges. We modified Parker's (1990) equations to use the calculated shear stress distribution, measured grain sizes, and a specific hiding function for each

  13. Physically-based quantitative analysis of soil erosion induced by heavy rainfall on steep slopes

    NASA Astrophysics Data System (ADS)

    Della Sala, Maria; Cuomo, Sabatino; Novità, Antonio

    2014-05-01

    Heavy rainstorms cause either shallow landslides or soil superficial erosion in steep hillslopes covered by coarse unsaturated soils (Cascini et al., 2013), even over large areas (Cuomo and Della Sala, 2013a). The triggering stage of both phenomena is related to ground infiltration, runoff and overland flow (Cuomo and Della Sala, 2013), which are key processes to be investigated. In addition, the mobilization of solid particles deserves a proper physical-based modeling whether a quantitative estimation of solid particles discharge at the outlet of mountain basin is required. In this work, the approaches for soil superficial erosion analysis are firstly reviewed; then, a relevant case study of two medium-sized mountain basins, affected by flow-like phenomena with huge consequences (Cascini et al., 2009) is presented, which motivates a parametric numerical analysis with a physically-based model carried out for a wide class of soil properties and rainfall scenarios (Cuomo et al., 2013b). The achieved results outline that the peak discharge of water and solid particles driven by overland flow depends on rainfall intensity while volumetric solid concentration within the washout is related to the morphometric features of the whole mountain basin. Furthermore, soil suction is outlined as a key factor for the spatial-temporal evolution of infiltration and runoff in the basin, also affecting the discharge of water and solid particles at the outlet of the basin. Based on these insights, selected cases are analyzed aimed to provide a wide class of possible slope erosion scenarios. It is shown that, provided the same amount of cumulated rainfall, the sequence of high and low intensity rainfall events strongly affects the time-discharge at the outlet of the basin without significant variations of the maximum volumetric solid concentration. References Cascini, L., Cuomo, S., Ferlisi, S., Sorbino, G. (2009). Detection of mechanisms for destructive landslides in Campania region

  14. Troll oil pipeline: Assessment of slope and gravel sleeper stability in steep fjord areas

    SciTech Connect

    Eide, A.; Gudmestad, O.T.; Nadim, F.

    1996-12-01

    This paper describes the slope stability evaluation in the steep areas of the Fensfjord. The main focus in the study has been to establish appropriate undrained shear strength for static and dynamic stability analyses, make a reasonable prediction of the earthquake induced permanent deformation and evaluate the post-earthquake static stability. The special laboratory testing and analysis conducted showed that the only consequence of earthquake loading is limited permanent deformations. Analysis of gravel supports on soft clay showed that three supports needed counter fills in order to fulfill the design requirements. At the tunnel entrance point of the pipeline at Mongstad, the soft clay at the seabed had to be excavated in order to attain satisfactory stability for the gravel support.

  15. Interactions of steep and breaking waves with winds and solid bodies

    NASA Astrophysics Data System (ADS)

    Yang, Zixuan; Shen, Lian

    2015-11-01

    The interactions of steep and breaking waves with winds and solid bodies at sea surface is important to many problems in ocean science and engineering. In this study, we perform large-eddy simulations using a finite-difference code with high-performance parallel computing. The air-water interface is captured using a coupled level set and volume of fluid method. A sharp interface immersed boundary method is applied to capture the effect due to the presence of solid bodies. A wall layer model is employed to address high Reynolds numbers. A numerical wave generator is utilized to accurately produce waves with specified parameters. The results are validated for a number of canonical problems, and the performances of different wall-layer model schemes are evaluated using a priori and a posteriori tests. Based on the simulation data, the flow details and interaction mechanisms are analyzed.

  16. Detachment and steep normal faulting in Atlantic oceanic crust west of Africa

    USGS Publications Warehouse

    Reston, T.J.; Ruoff, O.; McBride, J.H.; Ranero, C.R.; White, Robert S.

    1996-01-01

    Improved images of the internal structure of Early Cretaceous North Atlantic crust reveal both probable detachment faults and more steeply dipping normal faults. The detachment faults occur as subhorizontal structures passing ???1.5 km beneath fault blocks without offset; several steeper block-bounding faults appear to detach onto these structures. However, the detachments are bounded to the west (ridgeward) by presumably younger, more steeply west-dipping normal faults. In one possible interpretation, the detachment and the steep faults belong to the same "rolling-hinge" extension system. An intriguing alternative is that a phase of detachment faulting, perhaps related to increased magmatic activity, was succeeded by localized amagmatic extension along steeper and more deeply penetrating faults.

  17. Back bias induced dynamic and steep subthreshold swing in junctionless transistors

    SciTech Connect

    Parihar, Mukta Singh; Kranti, Abhinav

    2014-07-21

    In this work, we analyze back bias induced steep and dynamic subthreshold swing in junctionless double gate transistors operated in the asymmetric mode. This impact ionization induced dynamic subthreshold swing is explained in terms of the ratio between minimum hole concentration and peak electron concentration, and the dynamic change in the location of the conduction channel with applied front gate voltage. The reason for the occurrence of impact ionization at sub-bandgap drain voltages in silicon junctionless transistors is also accounted for. The optimum junctionless transistor operating at a back gate bias of −0.9 V, achieves over 5 orders of change in drain current at a gate overdrive of 200 mV and drain bias of 1 V. These results for junctionless transistors are significantly better than those exhibited by silicon tunnel field effect transistors operating at the same drain bias.

  18. Effects of bedrock groundwater on landslide occurrences in a steep headwater catchment

    NASA Astrophysics Data System (ADS)

    Kosugi, K.; Fujimoto, M.; Sando, Y.; Mizuyama, T.; Kinoshita, A.

    2011-12-01

    Previous studies have shown that the formation of groundwater in the soil mantle greatly affects slope instability on steep landscapes. To predict landslides, mathematical models based on a geographic information system, which organize geographic data such as information on upslope contributing areas and the local slope gradient, have been developed and tested. Although such models can be used to calculate the topographically driven convergence of rainwater and groundwater table developments in the soil mantle, thus providing a spatially distributed prediction of landslide occurrences, the accuracy of these mathematical models is still limited, mainly because they ignore storm responses in underlying bedrock. Recent research has provided credible information on the importance of bedrock groundwater on surface hydrological processes in headwater catchments. To elucidate the effects of bedrock groundwater, the dynamics of bedrock groundwater should be measured directly. However, intensive monitoring of bedrock groundwater is rare in mountains with steep topography. Consequently, how bedrock groundwater controls landslides in a steep headwater catchment is in dispute. In this study, we conducted long-term hydrological observations using densely nested bedrock wells along with monitoring of discharge hydrograph and soil mantle groundwater in a steep headwater catchment underlain by granitic bedrock. Bedrock wells with depths of 7-78 m were drilled at 31 points within the 2.10-ha catchment. Results showed that a hollow of bedrock aquifer was located at a ridge in the surface topography, clearly indicating bedrock groundwater flow across topographic divides. Around a point where the bedrock groundwater exfiltrated, we found scars of landslides. Such landslides cannot be explained by mathematical hydrology models, which calculate the topographically driven convergence of rainwater in the soil mantle. Moreover, at a point along the main hollow of the watershed, we observed

  19. Development of a digital automatic control law for steep glideslope capture and flare

    NASA Technical Reports Server (NTRS)

    Halyo, N.

    1977-01-01

    A longitudinal digital guidance and control law for steep glideslopes using MLS (Microwave Landing System) data is developed for CTOL aircraft using modern estimation and control techniques. The control law covers the final approach phases of glideslope capture, glideslope tracking, and flare to touchdown for automatic landings under adverse weather conditions. The control law uses a constant gain Kalman filter to process MLS and body-mounted accelerometer data to form estimates of flight path errors and wind velocities including wind shear. The flight path error estimates and wind estimates are used for feedback in generating control surface commands. Results of a digital simulation of the aircraft dynamics and the guidance and control law are presented for various wind conditions.

  20. Application of a new cellular model for bedload transporting extreme events at steep slopes

    NASA Astrophysics Data System (ADS)

    Chiari, M.; Scheidl, C.

    2015-10-01

    A cellular model for bedload transport at steep channel gradients and alluvial fans has been developed to simulate lateral distribution of erosion and deposition on alluvial fans of mountain streams. The cellular model, named FluviSed, applies a quasi-steady-state routing of a flood hydrograph over a rectangular grid. Bedload transport is calculated and the morphological changes are updated after each time step. FluviSed is designed to complement existing one-dimensional bedload transport simulation tools by using their outcome as an input for the simulation of inundated areas. The model has been evaluated against TomSed, a one-dimensional bedload transport model. Further, a back-calculation of a laboratory bedload experiment and a real flood event from 2005 at Schnannerbach in Austria are provided to test the model's suitability for reproducing morphological changes caused by flood events at high channel gradients.

  1. Dual-Gate p-GaN Gate High Electron Mobility Transistors for Steep Subthreshold Slope.

    PubMed

    Bae, Jong-Ho; Lee, Jong-Ho

    2016-05-01

    A steep subthreshold slope characteristic is achieved through p-GaN gate HEMT with dual-gate structure. Obtained subthreshold slope is less than 120 μV/dec. Based on the measured and simulated data obtained from single-gate device, breakdown of parasitic floating-base bipolar transistor and floating gate charged with holes are responsible to increase abruptly in drain current. In the dual-gate device, on-current degrades with high temperature but subthreshold slope is not changed. To observe the switching speed of dual-gate device and transient response of drain current are measured. According to the transient responses of drain current, switching speed of the dual-gate device is about 10(-5) sec. PMID:27483846

  2. Mechanics of gravitational spreading of steep-sided ridges («sackung»)

    USGS Publications Warehouse

    Savage, W.Z.; Varnes, D.J.

    1987-01-01

    Large-scale gravitational spreading of steep-sided ridges characterized by linear fissures, trenches, and uphill-facing scarps high on the sides and tops of ridges are known worldwide. Such spreading, termed sackung, is commonly attributed to pervasive plastic deformation of a rock mass, and is here analyzed as such. Beginning with a previously developed exact elastic solution for gravity-induced stresses in a symmetric ridge, stresses calculated from the exact solution are used in the Coulomb failure criterion to determine the extent of ridge failure under self-weight. Finally, when the regions of failure are established, a plastic flow solution is applied to predict the location of and sense of movement on upward-facing scarps near ridge crests and other features common in sackung. ?? 1987 International Assocaition of Engineering Geology.

  3. Impact of steep-front short-duration impulse on electric power system insulation

    SciTech Connect

    Burrage, L M; Veverka, E F; Shaw, J H; McConnell, B W

    1991-04-01

    This research effort required the performance evaluation of three specific insulation systems in common usage by electric power transmission and distribution utilities under stresses imposed by: three characteristic impulse waveforms (two waves representative of steep-front short duration (SFSD) impulses and one representative of lightning), the cumulative effect of multiple shots'' of each pulse, 60 Hz voltage, and, where appropriate, and mechanical load. The insulation systems evaluated are the cellulose-paper/oil combination typical of power transformer and condenser bushing usage, the cellulose-paper/enamel/oil combination used in distribution transformer construction, and the porcelain/air combination representing transmission and distribution line structural insulation. 4 refs., 94 figs., 11 tabs.

  4. Piloted simulator investigations of a civil tilt-rotor aircraft on steep instrument approaches

    NASA Technical Reports Server (NTRS)

    Decker, William A.

    1992-01-01

    NASA-Ames has used its Vertical Motion Simulator to investigate steep-glideslope instrument approaches for a civil transport tilt-rotor aircraft in two different cases: (1) where pilots used raw glideslope and localized error data for 6-25 deg slopes, terminating in slow roll-on landings, and (2) where a flight director commanded manual conversion from fixed-wing to helicopter modes and a deceleration on the glideslope led to a vertical landing on a small urban helipad. In the former, there occurred control problems directly ascribable to the slow approach speed; in the latter, the four-cue flight director's cockpit augmentation furnished adequate pilot ratings up to 15-deg glideslope.

  5. The effects of steep-front, short-duration impulses on power distribution components

    SciTech Connect

    Miller, D.B.; Lux, A.E.; Grzybowski, Stanislaw; Barnes, P.R.

    1989-07-01

    A line type pulser has been developed to test the effects of steep-front, short duration (SFSD) pulses on distribution components. Risetime is 50-100 ns, and pulse duration is on the order of 300 ns. Terminators often shattered or punctured rather than flashing over. Insulator flashover voltage is approximately 1.5 times CFO for standard lightning impulses. Arresters exhibit an inductive character, with SFSD peak voltage at 10 kA approximately 4--5 times the 8 /times/ 20 microsecond 10 kA discharge voltage. Polyethylene insulated cable has a characteristic degradation in which failure voltage decreases with number of SFSD pulses. 7 refs., 12 figs., 2 tabs.

  6. Applications of DBV (design-based verification) for steep ramp-up manufacture

    NASA Astrophysics Data System (ADS)

    Kim, Tae Heon; Han, Dae-Han; Kim, Yong-Hyeon; Han, Min-Chul; Lee, Hong-Ji; Hong, Ae-Ran; Kim, Yoon-Min; Nam, In-Ho; Park, Yong-Jik; Oh, Kyung-Seok

    2011-04-01

    Semiconductor industry has been experiencing rapid and continuous shrinkage of feature size along with Moore's law. As the VLSI technology scales down to sub 40nm process node. Control of critical dimension (CD) and Extraction of Unanticipated weak point pattern effects known as "hot spots" becoming more challenging and difficult. Therefore, experimental full-chip inspection methodologies for Control of critical dimension (CD) and hotspots extraction are necessary in order to reduce Turn-Around-Time (TAT) for steep ramp up Manufacture. In this paper, we introduce the concepts of an innovative reduction Turn-around-time (TAT) in manufacture production with applications of DBV (Design Based Verification). The noble methodologies employed by our own technology with application of DBV are highly advantageous for exactly determining for process judgment go or no-go about wafer process in mass-production of memory device.

  7. Research on the influence of waveguide's exposure steepness on 0.345THz FWGTWT's performance

    NASA Astrophysics Data System (ADS)

    Zhang, Fang; Dong, Zhiwei; Dong, Ye

    2013-08-01

    In the MEMS fabrication process of 0.345THz micro-electric vacuum FWG-TWT, the periodic FWG slow wave structure is assembled by joining two symmetrical metal pieces with grooves. In ideal design, these grooves' profiles should be perpendicular to their symmetrical plane while the device' performance can be best, however those slope angles are actually more than 90 degrees because of their molds' insufficient exposure. This paper does research on the influence of waveguide's exposure steepness on the performance of FWG circuit through theoretical analysis and numerical simulation. The range of slope angle studied in this paper is from 0 to 5 degrees, and as the slope angle becomes larger, electromagnetic signal's transmission attenuation increases. But by adjusting other working parameters of the circuit, the high net gain can be maintained while its bandwidth is going to decrease. These results will be helpful for the experiment.

  8. Laboratory investigation and direct numerical simulation of wind effect on steep surface waves

    NASA Astrophysics Data System (ADS)

    Troitskaya, Yuliya; Sergeev, Daniil; Druzhinin, Oleg; Ermakova, Olga

    2015-04-01

    The small scale ocean-atmosphere interaction at the water-air interface is one of the most important factors determining the processes of heat, mass, and energy exchange in the boundary layers of both geospheres. Another important aspect of the air-sea interaction is excitation of surface waves. One of the most debated open questions of wave modeling is concerned with the wind input in the wave field, especially for the case of steep and breaking waves. Two physical mechanisms are suggested to describe the excitation of finite amplitude waves. The first one is based on the treatment of the wind-wave interaction in quasi-linear approximation in the frameworks of semi-empirical models of turbulence of the low atmospheric boundary layer. An alternative mechanism is associated with separation of wind flow at the crests of the surface waves. The "separating" and "non-separating" mechanisms of wave generation lead to different dependences of the wind growth rate on the wave steepness: the latter predicts a decrease in the increment with wave steepness, and the former - an increase. In this paper the mechanism of the wind-wave interaction is investigated basing on physical and numerical experiments. In the physical experiment, turbulent airflow over waves was studied using the video-PIV method, based on the application of high-speed video photography. Alternatively to the classical PIV technique this approach provides the statistical ensembles of realizations of instantaneous velocity fields. Experiments were performed in a round wind-wave channel at Institute of Applied Physics, Russian Academy of Sciences. A fan generated the airflow with the centerline velocity 4 m/s. The surface waves were generated by a programmed wave-maker at the frequency of 2.5 Hz with the amplitudes of 0.65 cm, 1.4 cm, and 2 cm. The working area (27.4 × 10.7 cm2) was at a distance of 3 m from the fan. To perform the measurements of the instantaneous velocity fields, spherical polyamide

  9. Strong impact of neutrals on anomalous inward drift and width of steep gradient zone

    NASA Astrophysics Data System (ADS)

    Becker, G.

    1999-01-01

    The fundamental properties of the anomalous inward drift and the width of the steep gradient zone in H mode plasmas are explored. A special version of the 1.5-D BALDUR transport code is used to determine the profiles of the electron heat diffusivity and vin/D by transport analysis. The strong rise with radius of vin/D in the edge region is explained by a linear dependence on the neutral deuterium density n0, resulting in a new scaling expression vin(x)/D(x) = F0Zeff(x)n0(x)2x/(ρwxs2). Applying this in simulations reproduces the empirical fit of the vin/D profile not only in the edge plasma but also in the bulk plasma. Modellings with this scaling yield the observed flattening of density profiles with rising line averaged density. The decreasing penetration of deuterium atoms to the core causes a decline of the inward drift. The new scaling is shown to be compatible with gas oscillation experiments, while n0-independent scalings are not. This further explains the strong density profile peaking and rise of vin/D during and after pellet injection by the increase in neutral density. The width of the steep gradient zone is found to be connected with the penetration of neutrals at the edge and the presence of high inward drift velocities. The anomalous inward drift is attributed to ion dynamics, i.e. to the friction between fluctuating deuterons and deuterium atoms diffusing inward. A more general vin/D scaling including impurity effects is presented.

  10. The supercritical pile gamma-ray burst model: The GRB afterglow steep decline and plateau phase

    SciTech Connect

    Sultana, J.; Kazanas, D.

    2013-12-10

    We present a process that accounts for the steep decline and plateau phase of the Swift X-Ray Telescope (XRT) light curves, vexing features of gamma-ray burst (GRB) phenomenology. This process is an integral part of the 'supercritical pile' GRB model, proposed a few years ago to account for the conversion of the GRB kinetic energy into radiation with a spectral peak at E {sub pk} ∼ m{sub e}c {sup 2}. We compute the evolution of the relativistic blast wave (RBW) Lorentz factor Γ to show that the radiation-reaction force due to the GRB emission can produce an abrupt, small (∼25%) decrease in Γ at a radius that is smaller (depending on conditions) than the deceleration radius R{sub D} . Because of this reduction, the kinematic criticality criterion of the 'supercritical pile' is no longer fulfilled. Transfer of the proton energy into electrons ceases and the GRB enters abruptly the afterglow phase at a luminosity smaller by ∼m{sub p} /m{sub e} than that of the prompt emission. If the radius at which this slow-down occurs is significantly smaller than R{sub D} , the RBW internal energy continues to drive the RBW expansion at a constant (new) Γ and its X-ray luminosity remains constant until R{sub D} is reached, at which point it resumes its more conventional decay, thereby completing the 'unexpected' XRT light curve phase. If this transition occurs at R ≅ R{sub D} , the steep decline is followed by a flux decrease instead of a 'plateau,' consistent with the conventional afterglow declines. Besides providing an account of these peculiarities, the model suggests that the afterglow phase may in fact begin before the RBW reaches R ≅ R{sub D} , thus providing novel insights into GRB phenomenology.

  11. Model simulations of flood and debris flow timing in steep catchments after wildfire

    USGS Publications Warehouse

    Rengers, Francis; Mcguire, Luke; Kean, Jason W.; Staley, Dennis M.; Hobley, D.E.J

    2016-01-01

    Debris flows are a typical hazard on steep slopes after wildfire, but unlike debris flows that mobilize from landslides, most post-wildfire debris flows are generated from water runoff. The majority of existing debris-flow modeling has focused on landslide-triggered debris flows. In this study we explore the potential for using process-based rainfall-runoff models to simulate the timing of water flow and runoff-generated debris flows in recently burned areas. Two different spatially distributed hydrologic models with differing levels of complexity were used: the full shallow water equations and the kinematic wave approximation. Model parameter values were calibrated in two different watersheds, spanning two orders of magnitude in drainage area. These watersheds were affected by the 2009 Station Fire in the San Gabriel Mountains, CA, USA. Input data for the numerical models were constrained by time series of soil moisture, flow stage, and rainfall collected at field sites, as well as high-resolution lidar-derived digital elevation models. The calibrated parameters were used to model a third watershed in the burn area, and the results show a good match with observed timing of flow peaks. The calibrated roughness parameter (Manning's $n$) was generally higher when using the kinematic wave approximation relative to the shallow water equations, and decreased with increasing spatial scale. The calibrated effective watershed hydraulic conductivity was low for both models, even for storms occurring several months after the fire, suggesting that wildfire-induced changes to soil-water infiltration were retained throughout that time. Overall the two model simulations were quite similar suggesting that a kinematic wave model, which is simpler and more computationally efficient, is a suitable approach for predicting flood and debris flow timing in steep, burned watersheds.

  12. Rapid measurement of a high step microstructure with 90° steep sidewall.

    PubMed

    Ju, Bing-Feng; Chen, Yuan-Liu; Zhang, Wei; Fang, F Z

    2012-01-01

    A prototype STM system with high aspect ratio measurement capability is developed to fulfill accurate profile measurement of a high step microstructure with 90° steep sidewall. Distinguished from the traditional STM, the new system consists of a long range piezoelectric (PZT) actuator with full stroke of 60 μm as Z-direction servo scanner, a specially customized high aspect ratio STM probe with effective tip length of 300 μm, and an X-Y motorized driven stage for planar scanning. A tilt stage is used to adjust the probe-sample relative angle to compensate the evitable non-parallel effects. Based on the new STM system, sample-tilt-scanning methodology is proposed for eliminating the scanning blind region between the probe and the microstructure. A high step microstructure with height of 23 μm, 90° steep sidewall and width of 50μm has been successfully measured. The slope angle of the sidewall has been achieved to be 85° and the step height at the rising edge and the trench depth at the falling edge are both measured to be 22.96 μm. The whole measuring process only spent less than 10 min. It provides an effective and nondestructive solution for the measurement of high step or deep trench microstructures. In addition, this work also opens the way for further study on sidewall roughness and the tip-sample interaction at the edge of the sidewall, which are highly valuable for fabrication and quality control of high step microstructures. PMID:22299961

  13. Correction of Excessive Precipitation Over Steep and High Mountains in a General Circulation Model

    NASA Technical Reports Server (NTRS)

    Chao, Winston C.

    2012-01-01

    Excessive precipitation over steep and high mountains (EPSM) is a well-known problem in GCMs and meso-scale models. This problem impairs simulation and data assimilation products. Among the possible causes investigated in this study, we found that the most important one, by far, is a missing upward transport of heat out of the boundary layer due to the vertical circulations forced by the daytime upslope winds, which are forced by the heated boundary layer on subgrid-scale slopes. These upslope winds are associated with large subgrid-scale topographic variation, which is found over steep and high mountains. Without such subgridscale heat ventilation, the resolvable-scale upslope flow in the boundary layer generated by surface sensible heat flux along the mountain slopes is excessive. Such an excessive resolvablescale upslope flow combined with the high moisture content in the boundary layer results in excessive moisture transport toward mountaintops, which in turn gives rise to EPSM. Other possible causes of EPSM that we have investigated include 1) a poorly-designed horizontal moisture flux in the terrain-following coordinates, 2) the condition for cumulus convection being too easily satisfied at mountaintops, 3) the presence of conditional instability of the computational kind, and 4) the absence of blocked flow drag. These are all minor or inconsequential. We have parameterized the ventilation effects of the subgrid-scale heated-slope-induced vertical circulation (SHVC) by removing heat from the boundary layer and depositing it in layers higher up when the topographic variance exceeds a critical value. Test results using NASA/Goddard's GEOS-S GCM have shown that this largely solved the EPSM problem.

  14. Steep, cheap and deep: an ideotype to optimize water and N acquisition by maize root systems

    PubMed Central

    Lynch, Jonathan P.

    2013-01-01

    Background A hypothetical ideotype is presented to optimize water and N acquisition by maize root systems. The overall premise is that soil resource acquisition is optimized by the coincidence of root foraging and resource availability in time and space. Since water and nitrate enter deeper soil strata over time and are initially depleted in surface soil strata, root systems with rapid exploitation of deep soil would optimize water and N capture in most maize production environments. • The ideotype Specific phenes that may contribute to rooting depth in maize include (a) a large diameter primary root with few but long laterals and tolerance of cold soil temperatures, (b) many seminal roots with shallow growth angles, small diameter, many laterals, and long root hairs, or as an alternative, an intermediate number of seminal roots with steep growth angles, large diameter, and few laterals coupled with abundant lateral branching of the initial crown roots, (c) an intermediate number of crown roots with steep growth angles, and few but long laterals, (d) one whorl of brace roots of high occupancy, having a growth angle that is slightly shallower than the growth angle for crown roots, with few but long laterals, (e) low cortical respiratory burden created by abundant cortical aerenchyma, large cortical cell size, an optimal number of cells per cortical file, and accelerated cortical senescence, (f) unresponsiveness of lateral branching to localized resource availability, and (g) low Km and high Vmax for nitrate uptake. Some elements of this ideotype have experimental support, others are hypothetical. Despite differences in N distribution between low-input and commercial maize production, this ideotype is applicable to low-input systems because of the importance of deep rooting for water acquisition. Many features of this ideotype are relevant to other cereal root systems and more generally to root systems of dicotyledonous crops. PMID:23328767

  15. The Supercritical Pile Gamma-Ray Burst Model: The GRB Afterglow Steep Decline and Plateau Phase

    NASA Astrophysics Data System (ADS)

    Sultana, J.; Kazanas, D.; Mastichiadis, A.

    2013-12-01

    We present a process that accounts for the steep decline and plateau phase of the Swift X-Ray Telescope (XRT) light curves, vexing features of gamma-ray burst (GRB) phenomenology. This process is an integral part of the "supercritical pile" GRB model, proposed a few years ago to account for the conversion of the GRB kinetic energy into radiation with a spectral peak at E pk ~ mec 2. We compute the evolution of the relativistic blast wave (RBW) Lorentz factor Γ to show that the radiation-reaction force due to the GRB emission can produce an abrupt, small (~25%) decrease in Γ at a radius that is smaller (depending on conditions) than the deceleration radius RD . Because of this reduction, the kinematic criticality criterion of the "supercritical pile" is no longer fulfilled. Transfer of the proton energy into electrons ceases and the GRB enters abruptly the afterglow phase at a luminosity smaller by ~mp /me than that of the prompt emission. If the radius at which this slow-down occurs is significantly smaller than RD , the RBW internal energy continues to drive the RBW expansion at a constant (new) Γ and its X-ray luminosity remains constant until RD is reached, at which point it resumes its more conventional decay, thereby completing the "unexpected" XRT light curve phase. If this transition occurs at R ~= RD , the steep decline is followed by a flux decrease instead of a "plateau," consistent with the conventional afterglow declines. Besides providing an account of these peculiarities, the model suggests that the afterglow phase may in fact begin before the RBW reaches R ~= RD , thus providing novel insights into GRB phenomenology.

  16. The Supercritical Pile Gamma-Ray Burst Model: The GRB Afterglow Steep Decline and Plateau Phase

    NASA Technical Reports Server (NTRS)

    Sultana, Joseph; Kazanas, D.; Mastichiadis, A.

    2013-01-01

    We present a process that accounts for the steep decline and plateau phase of the Swift X-Ray Telescope (XRT) light curves, vexing features of gamma-ray burst (GRB) phenomenology. This process is an integral part of the "supercritical pile" GRB model, proposed a few years ago to account for the conversion of the GRB kinetic energy into radiation with a spectral peak at E(sub pk) is approx. m(sub e)C(exp 2). We compute the evolution of the relativistic blast wave (RBW) Lorentz factor Gamma to show that the radiation-reaction force due to the GRB emission can produce an abrupt, small (approx. 25%) decrease in Gamma at a radius that is smaller (depending on conditions) than the deceleration radius R(sub D). Because of this reduction, the kinematic criticality criterion of the "supercritical pile" is no longer fulfilled. Transfer of the proton energy into electrons ceases and the GRB enters abruptly the afterglow phase at a luminosity smaller by approx. m(sub p)/m(sub e) than that of the prompt emission. If the radius at which this slow-down occurs is significantly smaller than R(sub D), the RBW internal energy continues to drive the RBW expansion at a constant (new) Gamma and its X-ray luminosity remains constant until R(sub D) is reached, at which point it resumes its more conventional decay, thereby completing the "unexpected" XRT light curve phase. If this transition occurs at R is approx. equal to R(sub D), the steep decline is followed by a flux decrease instead of a "plateau," consistent with the conventional afterglow declines. Besides providing an account of these peculiarities, the model suggests that the afterglow phase may in fact begin before the RBW reaches R is approx. equal to R(sub D), thus providing novel insights into GRB phenomenology.

  17. The use of caesium-137 to estimate agricultural erosion on steep slopes in a tropical watershed

    NASA Astrophysics Data System (ADS)

    Nagle, Gregory N.; Lassoie, James P.; Fahey, Timothy J.; McIntyre, Sherwood C.

    2000-04-01

    The estimation of erosion and sediment delivery rates in tropical mountain watersheds is difficult and most of the methods widely used for estimating soil erosion over large areas have serious limitations. The 137Cs approach has potential for quantifying soil erosion because it can provide retrospective estimates of long-term (since 1963) net sediment redistribution relatively quickly. Despite its great potential, 137Cs has not yet been used in an extensive, reconnaissance level survey of erosion in complex tropical mountain environments. The objective of this study was to examine the applicability of the 137Cs method to estimate erosion on steep tropical agricultural lands (23 to 80% slopes) in the Nizao watershed, a humid, tropical mountain area of the Dominican Republic. In this study we (i) examine the variation of 137Cs in ten reference sites - eight coffee groves and two forested sites - and (ii) estimate erosion from 14 cultivated fields.The soil pool of 137Cs ranged from to 150 to 192 mBq cm-2 on reference sites with minimal erosion. Variability among reference sites was less than expected for such complex mountain terrain. The variability within coffee and forested reference (average CV=28%) sites was similar to the variability found on grassland and forested reference sites in the temperate zone.The estimated annual soil loss from 14 sampled fields ranged from 6 to 61 t ha-1 year-1 with an overall mean of 26 t ha-1 year-1. Overall, the soil erosion estimates found using the steep tropical hillsides. These erosion estimates account for soil loss since 1963 only and it seems likely that soil losses may have been much higher in earlier decades immediately after initial forest clearing earlier in the 20th century.

  18. Flood and debris flow interactions with roads promote the invasion of exotic plants along steep mountain streams, western Oregon

    NASA Astrophysics Data System (ADS)

    Watterson, Nicholas A.; Jones, Julia A.

    2006-08-01

    This study examines the interactions among geomorphic and biogeographic processes that govern the invasion by two contrasting exotic plant species—a shrub, scotch broom ( Cytisus scoparius) and an herb, foxglove ( Digitalis purpurea), over several decades of road and stream networks in the H.J. Andrews Experimental Forest in western Oregon. Distributions of C. scoparius and D. purpurea were mapped along hillslopes and streams in 1993, 2002, and 2003. The mapped distributions were related to debris flow pathways and changes in stream morphology interpreted from field surveys and air photos over the period 1993 to 2003. Laboratory trials examined the response of seed germination to scarification (to test effects of transport by debris flows), soaking (to test effects of fluvial transport), and substrate texture (to test effects on establishment). C. scoparius and D. purpurea were present along roads and in clearcuts in the Andrews Forest from the 1970s to 2003, but invaded the stream (Lookout Creek) only after debris flows and floods during an extreme storm in 1996. Laboratory trials demonstrated that seeds could germinate on a variety of substrates after scarification and flood transport. Mapping and air photo/GIS analysis indicated that the distributions of exotic plants were located on freshly scoured bars and floodplains adjacent to the active channel, downstream of seed sources along roads that were connected to the main stem of Lookout Creek by road ditch drainage systems, and debris flow paths. This paper outlines a conceptual model for the invasion of exotic plants, highlighting the connectivity between road and stream networks provided by geomorphic processes in steep forested landscapes.

  19. Cathodoluminescence Spectrum Imaging Software

    Energy Science and Technology Software Center (ESTSC)

    2011-04-07

    The software developed for spectrum imaging is applied to the analysis of the spectrum series generated by our cathodoluminescence instrumentation. This software provides advanced processing capabilities s such: reconstruction of photon intensity (resolved in energy) and photon energy maps, extraction of the spectrum from selected areas, quantitative imaging mode, pixel-to-pixel correlation spectrum line scans, ASCII, output, filling routines, drift correction, etc.

  20. Artificial light sources.

    PubMed

    Anderson, T F

    1986-04-01

    A wide variety of artificial light sources exists for use in the diagnosis and treatment of photosensitivity disorders. A discussion of the advantages and disadvantages of these light sources (including gas discharge arcs, fluorescent lamps, and other apparatus) illustrates the importance of matching the emission spectrum of the light source, the spectral response of the radiometer, and the photobiologic action spectrum. Environmental and occupational exposure to artificial light sources may contribute to photosensitivity disorders. PMID:3955892

  1. When what we need influences what we see: choice of energetic replenishment is linked with perceived steepness.

    PubMed

    Taylor-Covill, Guy A H; Eves, Frank F

    2014-06-01

    The apparent steepness of the locomotor challenge presented by hills and staircases is overestimated in explicit awareness. Experimental evidence suggests the visual system may rescale our conscious experience of steepness in line with available energy resources. Skeptics of this "embodied" view argue that such findings reflect experimental demand. This article tested whether perceived steepness was related to resource choices in the built environment. Travelers in a station estimated the slant angle of a 6.45 m staircase (23.4°) either before (N = 302) or after (N = 109) choosing from a selection of consumable items containing differing levels of energetic resources. Participants unknowingly allocated themselves to a quasi-experimental group based on the energetic resources provided by the item they chose. Consistent with a resource based model, individuals that chose items with a greater energy density, or more rapidly available energy, estimated the staircase as steeper than those opting for items that provided less energetic resources. PMID:24548310

  2. The stratigraphy of the Steep Rock Group, N.W. Ontario, with evidence of a major unconformity

    NASA Technical Reports Server (NTRS)

    Wilks, M. E.; Nisbet, E. G.

    1986-01-01

    The Steep Rock Group is exposed 6 km north of Atikokan, 200 km west of Thunder Bay. It is situated on the southern margin of the Wabigoon Belt of the Archaean Superior Province, N. W. Ontario. Reinvestigation of the geology of the Group has shown that the Group lies unconformably on the Tonalite Complex to the east. This unconformity has been previously suspected, from regional and ine mapping but no conclusive outcrop evidence for its existence has as yet been published. The strike of the group, comprised of Basal Conglomerate, Carbonate Member, Ore Zone and Ashrock is generally north-northwest dipping steeply to the southwest. Of the 7 contacts between the Steep Rock Group and the Tonalite Complex, 3 expose the unconformity (The Headland, S. Roberts Pit, Trueman Point), and 4 are faulted. These three outcrops demonstrate unequivocally that the Steep Rock group was laid down unconformably on the underlying Tonalite Complex, which is circa 3 Ga old.

  3. A Measurement of the Millimeter Emission and the Sunyaev-zel'dovich Effect Associated with Low-frequency Radio Sources

    NASA Technical Reports Server (NTRS)

    Gralla, Megan B.; Crichton, Devin; Marriage, Tobias A.; Mo, Wenli; Aguirre, Paula; Addison, Graeme E.; Asboth, V.; Battaglia, Nick; Bock, James; Bond, J. Richard; Devlin, Mark J.; Duenner, Rolando; Hajian, Amir; Halpern, Mark; Hilton, Matt; Hincks, Adam D.; Hlozek Renee A.; Huffenberger, Kevin M.; Hughes, John P.; Ivison, R. J.; Kosowsky, Arthur; Lin, Yen-Ting; Switzer, Eric R.; Wollack, Edward J.; Zemcov, Michael B.

    2013-01-01

    We present a statistical analysis of the millimeter-wavelength properties of 1.4 GHz-selected sources and a detection of the Sunyaev-Zel'dovich Effect associated with the halos that host them. The Atacama Cosmology Telescope (ACT) has conducted a survey at 148 GHz, 218 GHz and 277 GHz along the celestial equator. Using samples of radio sources selected at 1.4 GHz from the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) Survey and the National Radio Astronomy Observatory Very Large Array Sky Survey (NVSS), we measure the stacked 148, 218 and 277 GHz flux densities for sources with 1.4 GHz flux densities ranging from 5 to 200 mJy. At these flux densities, the radio source population is dominated by active galactic nuclei (AGN), with both steep and at spectrum populations, which have combined radio-to-millimeter spectral indices ranging from 0.5 to 0.95, reecting the prevalence of steep spectrum sources at high flux densities and the presence of at spectrum sources at lower flux densities. The thermal Sunyaev-Zelapos;dovich (SZ) eect associated with the halos that host the AGN is detected at the 5 level through its spectral signature. When we compare the SZ eect with weak lensing measurements of radio galaxies, we find that the relation between the two is consistent with that measured by Planck for local bright galaxies. We present a detection of the SZ eect in some of the lowest mass halos (average M(sub 200) approx. equals 10(exp 13) solar M h(sup-1) (sub 70) ) studied to date. This detection is particularly important in the context of galaxy evolution models, as it confirms that galaxies with radio AGN also typically support hot gaseous halos. With Herschel* observations, we show that the SZ detection is not significantly contaminated by dusty galaxies or by dust associated with the AGN or galaxies hosting the AGN. We show that 5 mJy < S(sub 1:4) < 200 mJy radio sources contribute l(l +1)C(sub l)/(2 pi ) = 0:37+/- 0:03 micro K(exp 2) to the angular

  4. Steep wave, turbulence, and sediment concentration statistics beneath a breaking wave field and their implications for sediment transport

    NASA Astrophysics Data System (ADS)

    Scott, Nicholas V.; Hsu, Tian-Jian; Cox, Daniel

    2009-11-01

    A new methodology based on wavelet analysis is used to estimate steep wave statistics under depth-limited conditions and the corresponding high concentration sediment statistics. Steep waves here are defined as wave crests within the wavelet transform exceeding a root mean square derived acceleration threshold. The method is applied to laboratory data obtained in a large-scale wave-flume experiment conducted in 2005 at Oregon State University's O. H. Hinsdale Wave Research Laboratory from an acoustic Doppler velocimeter and a fiber optic backscatter sensor array above a mobile sand bed. The steep wave and high concentration statistical results for the erosive condition suggest that sand suspensions are intermittent when a wave-breaking timescale (the ratio of breaking wave height and rms wave velocity) is used to detect the concurrence among steep wave, high velocity turbulent fluctuations, and sand concentration events near the bed. More importantly, at 1 cm above the bed, though the accretive case has more steep wave events, the erosive case has more steep waves and concurrent high concentration events, suggesting a more intense breaking wave process near the sensors. The use of a longer time window, based on the dominant wave period in the detection process of steep wave and high concentration events at 1 cm above the bed, does not change the resulting statistics for the erosive condition. However, increased percentages of high concentration events correlated with steep wave and high velocity turbulence events for the accretive condition are obtained. These increased percentages are conjectured to be due to advection of non-local turbulent events and sediment concentration peaks from upstream. A one-dimensional vertical two-phase model for sand transport is modified here to take measured breaking wave turbulence quantities as top boundary conditions to simulate the effect of breaking wave-turbulence on bottom sediment transport. Model results suggest that high

  5. Laboratory investigation and direct numerical simulation of wind effect on steep surface waves

    NASA Astrophysics Data System (ADS)

    Troitskaya, Yuliya; Sergeev, Daniil; Druzhinin, Oleg; Ermakova, Olga

    2015-04-01

    The small scale ocean-atmosphere interaction at the water-air interface is one of the most important factors determining the processes of heat, mass, and energy exchange in the boundary layers of both geospheres. Another important aspect of the air-sea interaction is excitation of surface waves. One of the most debated open questions of wave modeling is concerned with the wind input in the wave field, especially for the case of steep and breaking waves. Two physical mechanisms are suggested to describe the excitation of finite amplitude waves. The first one is based on the treatment of the wind-wave interaction in quasi-linear approximation in the frameworks of semi-empirical models of turbulence of the low atmospheric boundary layer. An alternative mechanism is associated with separation of wind flow at the crests of the surface waves. The "separating" and "non-separating" mechanisms of wave generation lead to different dependences of the wind growth rate on the wave steepness: the latter predicts a decrease in the increment with wave steepness, and the former - an increase. In this paper the mechanism of the wind-wave interaction is investigated basing on physical and numerical experiments. In the physical experiment, turbulent airflow over waves was studied using the video-PIV method, based on the application of high-speed video photography. Alternatively to the classical PIV technique this approach provides the statistical ensembles of realizations of instantaneous velocity fields. Experiments were performed in a round wind-wave channel at Institute of Applied Physics, Russian Academy of Sciences. A fan generated the airflow with the centerline velocity 4 m/s. The surface waves were generated by a programmed wave-maker at the frequency of 2.5 Hz with the amplitudes of 0.65 cm, 1.4 cm, and 2 cm. The working area (27.4 × 10.7 cm2) was at a distance of 3 m from the fan. To perform the measurements of the instantaneous velocity fields, spherical polyamide

  6. Dual-Frequency Observations of 140 Compact, Flat-Spectrum Active Galactic Nuclei for Scintillation-Induced Variability

    NASA Technical Reports Server (NTRS)

    Koay, J. Y.; Macquart, J.- P.; Rickett, B. J.; Bignall, H. E.; Lovell, J. E. J.; Reynolds, C.; Jauncey, D. L.; Pursimo, T.; Kedziora-Chudczer, L.; Ojha, R.

    2012-01-01

    The 4.9 GHz Micro-Arcsecond Scintillation-Induced Variability (MASIV) Survey detected a drop in Interstellar Scintillation (ISS) for sources at red shifts z > or approx. 2, indicating an apparent increase in angular diameter or a decrease in flux density of the most compact components of these sources, relative to their extended emission. This can result from intrinsic source size effects or scatter broadening in the Intergalactic Medium (IGM) , in excess of the expected (1+z)1/2 angular diameter scaling of brightness temperature limited sources resulting from cosmological expansion. We report here 4.9 GHz and 8.4 GHz observations and data analysis for a sample of 140 compact, fiat-spectrum sources which may allow us to determine the origin of this angular diameter-redshift relation by exploiting their different wavelength dependences. In addition to using ISS as a cosmological probe, the observations provide additional insight into source morphologies and the characteristics of ISS. As in the MASIV Survey, the variability of the sources is found to be significantly correlated with line-of-sight H(alpha) intensities, confirming its link with ISS. For 25 sources, time delays of about 0.15 to 3 days are observed between the scintillation patterns at both frequencies, interpreted as being caused by a shift in core positions when probed at different optical depths. Significant correlation is found between ISS amplitudes and source spectral index; in particular, a large drop in ISS amplitudes is observed at alpha < -0.4 confirming that steep spectrum sources scintillate less. We detect a weakened redshift dependence of ISS at 8.4 GHz over that at 4.9 GHz, with the mean variance at 4-day timescales reduced by a factor of 1.8 in the z > 2 sources relative to the z < 2 sources, as opposed to the factor of 3 decrease observed at 4.9 GHz. This suggests scatter broadening in the IGM, but the interpretation is complicated by subtle selection effects that will be explored

  7. DUAL-FREQUENCY OBSERVATIONS OF 140 COMPACT, FLAT-SPECTRUM ACTIVE GALACTIC NUCLEI FOR SCINTILLATION-INDUCED VARIABILITY

    SciTech Connect

    Koay, J. Y.; Macquart, J.-P.; Bignall, H. E.; Reynolds, C.; Rickett, B. J.; Lovell, J. E. J.; Jauncey, D. L.; Pursimo, T.; Kedziora-Chudczer, L.; Ojha, R.

    2011-10-15

    The 4.9 GHz Micro-Arcsecond Scintillation-Induced Variability (MASIV) Survey detected a drop in interstellar scintillation (ISS) for sources at redshifts z {approx}> 2, indicating an apparent increase in angular diameter or a decrease in flux density of the most compact components of these sources relative to their extended emission. This can result from intrinsic source size effects or scatter broadening in the intergalactic medium (IGM) in excess of the expected (1 + z){sup 1/2} angular diameter scaling of brightness temperature limited sources resulting from cosmological expansion. We report here 4.9 GHz and 8.4 GHz observations and data analysis for a sample of 140 compact, flat-spectrum sources which may allow us to determine the origin of this angular diameter-redshift relation by exploiting their different wavelength dependences. In addition to using ISS as a cosmological probe, the observations provide additional insight into source morphologies and the characteristics of ISS. As in the MASIV Survey, the variability of the sources is found to be significantly correlated with line-of-sight H{alpha} intensities, confirming its link with ISS. For 25 sources, time delays of about 0.15-3 days are observed between the scintillation patterns at both frequencies, interpreted as being caused by a shift in core positions when probed at different optical depths. Significant correlation is found between ISS amplitudes and source spectral index; in particular, a large drop in ISS amplitudes is observed at {alpha} < -0.4 confirming that steep spectrum sources scintillate less. We detect a weakened redshift dependence of ISS at 8.4 GHz over that at 4.9 GHz, with the mean variance at four-day timescales reduced by a factor of 1.8 in the z > 2 sources relative to the z < 2 sources, as opposed to the factor of three decrease observed at 4.9 GHz. This suggests scatter broadening in the IGM, but the interpretation is complicated by subtle selection effects that will be

  8. Instream wood in a steep headwater channel: geomorphic significance of large and small wood

    NASA Astrophysics Data System (ADS)

    Galia, Tomáš; Šilhán, Karel; Ruiz-Villanueva, Virginia; Tichavský, Radek

    2016-04-01

    Besides the well-known significance of large wood (LW), also small woody pieces (SW; here defined as pieces with dimensions at least 0.5 m length and 0.05 m diameter), can play an important role in steep narrow headwaters. We inventoried instream wood in the 0.4 km long Mazák headwater channel, Moravskoslezské Beskydy Mts, Czech Republic (2steep adjacent hillslopes (0.6

  9. Early, steep subduction of India beneath Asia required by timing of UHP metamorphism

    NASA Astrophysics Data System (ADS)

    Leech, M. L.; Klemperer, S. L.; Singh, S.; Jain, A. K.

    2004-12-01

    Ultrahigh-pressure (UHP) rocks in the NW Himalaya are the youngest on earth, and allow testing of critical questions of UHP formation and exhumation and the India-Asia collision. The Tso Morari Complex (TMC) is a UHP subduction zone complex in eastern Ladakh in the western Himalaya, south of the Indus-Tsangpo suture zone. New U-Pb SHRIMP data from zircon shows the TMC has a Proterozoic protolith with a Pan-African history, and defines three stages in the Eocene history of the TMC, hence constraining the timing of collision, subduction, and exhumation in the western Himalaya. Our precise new single zircon U-Pb ages indicate that UHP eclogite-facies metamorphism occurred at 53.3±0.7 Ma followed by a HP eclogite-facies event at 50.0±0.6 Ma, and amphibolite-facies metamorphism at 47.5±0.5 Ma. Retrograde zircon growth may result from dehydration reaction-related fluids evolved during exhumation; the intermittent presence of these fluids would allow zircon crystallization during exhumation that would document the changing P-T conditions. Today India subducts beneath Tibet at an angle of only c. 10° ; at this low angle, rocks must travel over 500 km along the subduction thrust to reach the depth of c. 100 km required for UHP metamorphism. Initial collision of India with Asia, based on stratigraphic and paleomagnetic data, is widely cited as being at 55±1 Ma. Here we show that Indian rocks reached UHP depths at 53.3±0.7 Ma. Given the fast India-Asia convergence rate of 69 km/m.y., our result implies an earlier onset of collision (c. 57 Ma) and that UHP rocks must have traveled a short, hence steep path into the mantle. We infer that early continental subduction was at a steep angle, probably vertical, comparable to modern continental subduction in the Hindu Kush.

  10. The Latemar: A flat-topped, steep fronted platform dominated by microbialites and synsedimentary cements

    NASA Astrophysics Data System (ADS)

    Marangon, A.; Gattolin, G.; Della Porta, G.; Preto, N.

    2011-10-01

    Facies analyses on the Latemar isolated carbonate platform suggest a higher proportion of microbial carbonates compared to literature. This is evident especially in the margin-upper slope zone, where microbial boundstone associated with Tubiphytes, calcareous sponges, botryoidal aragonite and radiaxial fibrous cements extended down to 250 m water depth. The Latemar flat-topped high-relief platform has been subdivided into five different facies belts: inner and outermost platform, margin, upper and lower slope. Each facies belt represents subtidal environments except for the inner platform, which is characterized by a peritidal facies association. Point counting analysis was carried out on ca. 90 thin sections to quantify the different platform components. Microbialite and cements are most abundant: they represent, respectively, ca. 40% and ca. 34% of the whole platform volume. These results suggest that carbonate production at Latemar occurred in a M-Factory. Microbial carbonates, as well as early marine cements are most abundant on the upper slope, margin and outermost platform, although microbialites are found in all facies belts. The presence of supratidal sedimentary facies restricted only to the inner platform and of a completely subtidal outermost platform suggests a new depositional profile for the Latemar. The central portion is occupied by the flat platform interior, cyclically subaerially exposed. Facies of the subtidal outermost platform surround the inner platform and display a progressive increase in depth toward the margin. The margin is submerged and essentially constituted by microbial and cement boundstone. The slope is characterized by steep clinoforms (~ 35°) dominated by in situ microbialites in the upper-middle portion (0-250 m depth), evidently precipitated by non light-dependent microbially influenced processes. The lower slope is mostly detrital, poor in platform top-derived sediments and dominated by margin and upper-slope derived rudstone

  11. Tracking water pathways in steep hillslopes by δ18O depth profiles of soil water

    NASA Astrophysics Data System (ADS)

    Mueller, Matthias H.; Alaoui, Abdallah; Kuells, Christoph; Leistert, Hannes; Meusburger, Katrin; Stumpp, Christine; Weiler, Markus; Alewell, Christine

    2014-11-01

    Assessing temporal variations in soil water flow is important, especially at the hillslope scale, to identify mechanisms of runoff and flood generation and pathways for nutrients and pollutants in soils. While surface processes are well considered and parameterized, the assessment of subsurface processes at the hillslope scale is still challenging since measurement of hydrological pathways is connected to high efforts in time, money and personnel work. The latter might not even be possible in alpine environments with harsh winter processes. Soil water stable isotope profiles may offer a time-integrating fingerprint of subsurface water pathways. In this study, we investigated the suitability of soil water stable isotope (δ18O) depth profiles to identify water flow paths along two transects of steep subalpine hillslopes in the Swiss Alps. We applied a one-dimensional advection-dispersion model using δ18O values of precipitation (ranging from -24.7 to -2.9‰) as input data to simulate the δ18O profiles of soil water. The variability of δ18O values with depth within each soil profile and a comparison of the simulated and measured δ18O profiles were used to infer information about subsurface hydrological pathways. The temporal pattern of δ18O in precipitation was found in several profiles, ranging from -14.5 to -4.0‰. This suggests that vertical percolation plays an important role even at slope angles of up to 46°. Lateral subsurface flow and/or mixing of soil water at lower slope angles might occur in deeper soil layers and at sites near a small stream. The difference between several observed and simulated δ18O profiles revealed spatially highly variable infiltration patterns during the snowmelt periods: The δ18O value of snow (-17.7 ± 1.9‰) was absent in several measured δ18O profiles but present in the respective simulated δ18O profiles. This indicated overland flow and/or preferential flow through the soil profile during the melt period. The applied

  12. Tracing bed load sediment using PIT tags in a steep headwater channel.

    NASA Astrophysics Data System (ADS)

    Kubo, Y.; Hiraoka, M.; Gomi, T.; Nidaira, K.; Uchiyama, Y.

    2015-12-01

    Bed load transport in steep headwater channels is complex because of the particle size distribution, topography, channel roughness, and sediment supply from adjacent hillslope. We monitored movement bed load sediment using PIT tags in a steep headwater channel segments. Study area is located in 7.0ha Oobora-sawa observatory from 50km west of Tokyo metropolitan. Annual precipitation is 3000mm and mean temperature is 10°. Annual bed load sediment yields in the study catchment was from 6.5 to 7.6 t/ha/yr. Mean channel gradient is 24° with 0.5m low flow width. The channel is consisted by 0.2 to 1.6m interval of step-pool sequences. Based on pebble count method, D10, D50 and D90 of channel substrate were 8, 28 and 206mm respectively. We deployed 134 bed load tracers with five classes of diameter ranges (Class1:17.7, Class2:24.8, Class3:35.8, Class4:54.1 and Class5:83.8mm). Selected tracers represented from D20 to D77 of channel bed substrates. PIT tags (diameter 2mm, length 9mm and weight 0.1g) were placed into the particles by drilling and refilled with non-corrosive epoxy. We investigated the movement of bed load tracers every major storm event since February 2015. Channel morphology was measured using photographic survey and topographic model was developed using software of Surface from motion (PhotoScan). Mean bed load movement in the 5 storm event with 438 mm total and 33 mm maximum intensity was 168 mm. Then 51 mm of bed load movement occurred in 43 mm total and 16 mm intensity of rainfall. Recurrence interval of the two storm event was 1 and 4 year respectively. Receivable rates of bed load tracers was 70 and 74 % in the two events. Mobilized bed load (7 to 18%) deposited at cascade, pool and riffle, and among step clusters. Mobilized bed load tracers is rather random and we do not find any patterns for particle size for the movement and distance. Our field monitoring showed that bed load tracers were not mobilized for storm events with 10.5mm/h intensity of

  13. New approaches to inferences for steep-sided domes on Venus

    NASA Astrophysics Data System (ADS)

    Quick, Lynnae C.; Glaze, Lori S.; Baloga, Stephen M.; Stofan, Ellen R.

    2016-06-01

    New mathematical approaches for the relaxation and emplacement of viscous lava domes are presented and applied to steep-sided domes on Venus. A similarity solution approach is applied to the governing equation for fluid flow in a cylindrical geometry for two distinct scenarios. In the first scenario, dome relaxation is explored assuming a constant volume of fluid (i.e. lava) has been rapidly emplaced onto the surface. Cooling of lava is represented by a time-variable viscosity and singularities inherent in previous models for dome relaxation have been eliminated. At the onset of relaxation, bulk dynamic viscosities lie in the range between 1010-1016 Pa s, consistent with basaltic-andesite to rhyolitic compositions. Plausible relaxation times range from 5 to 5000 years, depending on initial lava viscosity. The first scenario, however, is only valid during the final stages of dome relaxation and does not consider the time taken for lava to be extruded onto the surface. In the second scenario, emplacement and growth of a steep-sided dome is considered when the volume of lava on the surface increases over time (i.e. time-variable volume approach). The volumetric flowrate may depend on an arbitrary power of the dome thickness, thus embracing Newtonian as well as other rheologies for describing terrestrial and planetary mass flows. The approach can be used to distinguish between basic flowrate models for fluid emplacement. The formalism results in radial expansion of a dome proportional to t1/2, consistent with the diffusive nature of the governing equation. The flow at the front is shown to thicken as the front advances for a constant rate of lava supply. Emplacement times are intimately correlated with the bulk rheology. Comparison of the theoretical profiles with the shape of a typical dome on Venus indicates that a Newtonian bulk rheology is most appropriate, consistent with prior studies. However, results here suggest a bulk dynamic viscosity of 1012-1013 Pa s and

  14. SYNTH: A spectrum synthesizer

    NASA Astrophysics Data System (ADS)

    Hensley, W. K.; McKinnon, A. D.; Miley, H. S.; Panisko, M. E.; Savard, R. M.

    1993-10-01

    A computer code has been written at the Pacific Northwest Laboratory (PNL) to synthesize the results of typical gamma ray spectroscopy experiments. The code, dubbed SYNTH, allows a user to specify physical characteristics of a gamma ray source, the quantity of the nuclides producing the radiation, the source-to-detector distance and the presence of absorbers, the type and size of the detector, and the electronic set up used to gather the data. In the process of specifying the parameters needed to synthesize a spectrum, several interesting intermediate results are produced, including a photopeak transmission function versus energy, a detector efficiency curve, and a weighted list of gamma and x rays produced from a set of nuclides. All of these intermediate results are available for graphical inspection and for printing. SYNTH runs on personal computers. It is menu driven and can be customized to user specifications. SYNTH contains robust support for coaxial germanium detectors and some support for sodium iodide detectors. SYNTH is not a finished product. A number of additional developments are planned. However, the existing code has been compared carefully to spectra obtained from National Institute for Standards and Technology (NIST) certified standards with very favorable results. Examples of the use of SYNTH and several spectral results are presented.

  15. Autism Spectrum Disorder

    MedlinePlus

    Autism spectrum disorder (ASD) is a neurological and developmental disorder that begins early in childhood and lasts throughout a ... and pervasive developmental disorders. It is called a "spectrum" disorder because people with ASD can have a ...

  16. Autism Spectrum Disorder (ASD)

    MedlinePlus

    ... spectrum disorder (ASD) is a group of developmental disabilities that can cause significant social, communication and behavioral ... for autism spectrum disorder (ASD) and other developmental disabilities. More E-mail Your Friends "Children with autism ...

  17. Adapting Tilt Corrections and the Governing Flow Equations for Steep, Fully Three-Dimensional, Mountainous Terrain

    NASA Astrophysics Data System (ADS)

    Oldroyd, Holly J.; Pardyjak, Eric R.; Huwald, Hendrik; Parlange, Marc B.

    2016-06-01

    In recent studies of atmospheric turbulent surface exchange in complex terrain, questions arise concerning velocity-sensor tilt corrections and the governing flow equations for coordinate systems aligned with steep slopes. The standard planar-fit method, a popular tilt-correction technique, must be modified when applied to complex mountainous terrain. The ramifications of these adaptations have not previously been fully explored. Here, we carefully evaluate the impacts of the selection of sector size (the range of flow angles admitted for analysis) and planar-fit averaging time. We offer a methodology for determining an optimized sector-wise planar fit (SPF), and evaluate the sensitivity of momentum fluxes to varying these SPF input parameters. Additionally, we clarify discrepancies in the governing flow equations for slope-aligned coordinate systems that arise in the buoyancy terms due to the gravitational vector no longer acting along a coordinate axis. New adaptions to the momentum equations and turbulence kinetic energy budget equation allow for the proper treatment of the buoyancy terms for purely upslope or downslope flows, and for slope flows having a cross-slope component. Field data show that new terms in the slope-aligned forms of the governing flow equations can be significant and should not be omitted. Since the optimized SPF and the proper alignment of buoyancy terms in the governing flow equations both affect turbulent fluxes, these results hold implications for similarity theory or budget analyses for which accurate flux estimates are important.

  18. The interaction between steep waves and a surface-piercing column.

    PubMed

    Swan, C; Sheikh, R

    2015-01-28

    Experimental observations are presented of a single surface-piercing column subject to a wide range of surface gravity waves. With the column diameter, D, chosen such that the flow lies within the drag-inertia regime, two types of high-frequency wave scattering are identified. The first is driven by the run-up and wash-down on the surface of the column in the vicinity of the upstream and downstream stagnation points. The second concerns the circulation of fluid around the column, leading to the scattering of a pair of non-concentric wavefronts. The phasing of the wave cycle at which this second mode evolves is dependent upon the time taken for fluid to move around the column. This introduces an additional time-scale, explaining why existing diffraction solutions, based upon a harmonic analysis of the incident waves, cannot describe this scattered component. The interaction between the scattered waves and the next (steep) incident wave can produce a large amplification of the scattered waves, particularly the second type. Evidence is provided to show that these interactions can produce highly localized free-surface effects, including vertical jetting, with important implications for the setting of deck elevations, the occurrence of wave slamming and the development of large run-up velocities. PMID:25512588

  19. Evaluation of two cockpit display concepts for civil tiltrotor instrument operations on steep approaches

    NASA Technical Reports Server (NTRS)

    Decker, William A.; Bray, Richard S.; Simmons, Rickey C.; Tucker, George E.

    1993-01-01

    A piloted simulation experiment was conducted using the NASA Ames Research Center Vertical Motion Simulator to evaluate two cockpit display formats designed for manual control on steep instrument approaches for a civil transport tiltrotor aircraft. The first display included a four-cue (pitch, roll, power lever position, and nacelle angle movement prompt) flight director. The second display format provided instantaneous flight path angle information together with other symbols for terminal area guidance. Pilots evaluated these display formats for an instrument approach task which required a level flight conversion from airplane-mode flight to helicopter-mode flight while decelerating to the nominal approach airspeed. Pilots tracked glide slopes of 6, 9, 15 and 25 degrees, terminating in a hover for a vertical landing on a 150 feet square vertipad. Approaches were conducted with low visibility and ceilings and with crosswinds and turbulence, with all aircraft systems functioning normally and were carried through to a landing. Desired approach and tracking performance was achieved with generally satisfactory handling qualities using either display format on glide slopes up through 15 degrees. Evaluations with both display formats for a 25 degree glide slope revealed serious problems with glide slope tracking at low airspeeds in crosswinds and the loss of the intended landing spot from the cockpit field of view.

  20. Steep-Slope Assembly Testing of Clay and Concrete Tile With and Without Cool Pigmented Colors

    SciTech Connect

    Miller, William A

    2005-11-01

    Cool color pigments and sub-tile venting of clay and concrete tile roofs significantly impact the heat flow crossing the roof deck of a steep-slope roof. Field measures for the tile roofs revealed a 70% drop in the peak heat flow crossing the deck as compared to a direct-nailed asphalt shingle roof. The Tile Roofing Institute (TRI) and its affiliate members are keenly interested in documenting the magnitude of the drop for obtaining solar reflectance credits with state and federal "cool roof" building efficiency standards. Tile roofs are direct-nailed or are attached to a deck with batten or batten and counter-batten construction. S-Misson clay and concrete tile roofs, a medium-profile concrete tile roof, and a flat slate tile roof were installed on fully nstrumented attic test assemblies. Temperature measures of the roof, deck, attic, and ceiling, heat flows, solar reflectance, thermal emittance, and the ambient weather were recorded for each of the tile roofs and also on an adjacent attic cavity covered with a conventional pigmented and directnailed asphalt shingle roof. ORNL measured the tile's underside temperature and the bulk air temperature and heat flows just underneath the tile for batten and counter-batten tile systems and compared the results to the conventional asphalt shingle.

  1. Gravitational spreading of steep-sided ridges ("sackung") in Western United States

    USGS Publications Warehouse

    Radbruch-Hall, D. H.; Varnes, D.J.; Savage, W.Z.

    1976-01-01

    Large-scale gravitational spreading and movement along fractures of steep-sided ridges in the mountainous areas of the western United States are characterized by linear fissures, trenches, and uphill-facing scarps on tops and sides of ridges. Spreading appears to take place by movement along disconnected planes and/or by slow plastic deformation of a rock mass. In some places, valleyward squeezing out of weak shales overlain by rigid rocks causes extensional fracturing and outward movement of the rigid layers, as illustrated by extension of two laccoliths overlying Mancos Shale, one at Dolores Peak and another at Crested Butte in western Colorado. Gravitational forces acting on a ridge of more homogeneous material causes tensional spreading of the ridge parallel to its long axis, for example in fractured granitic rock north of Mt. Massive in central Colorado, where a survey course has been established to monitor the movement. Recognition and understanding of these large-scale gravitational features and the mechanism that causes them are pertinent to site selection and design of engineering structures in high mountains. If fractures extend to considerable depth and if movement is continuing, engineering structures in valleys or tunnels through the spreading ridges could be damaged. ?? 1976 International Association of Engineering Geology.

  2. Time series modeling of soil moisture dynamics on a steep mountainous hillside

    NASA Astrophysics Data System (ADS)

    Kim, Sanghyun

    2016-05-01

    The response of soil moisture to rainfall events along hillslope transects is an important hydrologic process and a critical component of interactions between soil vegetation and the atmosphere. In this context, the research described in this article addresses the spatial distribution of soil moisture as a function of topography. In order to characterize the temporal variation in soil moisture on a steep mountainous hillside, a transfer function, including a model for noise, was introduced. Soil moisture time series with similar rainfall amounts, but different wetness gradients were measured in the spring and fall. Water flux near the soil moisture sensors was modeled and mathematical expressions were developed to provide a basis for input-output modeling of rainfall and soil moisture using hydrological processes such as infiltration, exfiltration and downslope lateral flow. The characteristics of soil moisture response can be expressed in terms of model structure. A seasonal comparison of models reveals differences in soil moisture response to rainfall, possibly associated with eco-hydrological process and evapotranspiration. Modeling results along the hillslope indicate that the spatial structure of the soil moisture response patterns mainly appears in deeper layers. Similarities between topographic attributes and stochastic model structures are spatially organized. The impact of temporal and spatial discretization scales on parameter expression is addressed in the context of modeling results that link rainfall events and soil moisture.

  3. The effect of surface cover on infiltration rate in steep forest plantations

    NASA Astrophysics Data System (ADS)

    Hiraoka, M.; Onda, Y.; Kato, H.; Ito, S.; Mizugaki, S.

    2007-12-01

    The Japanese cypress (Hinoki; Chamaecyparis obtusa) is a major commercial tree species in Japan, and without thinning of high-density stands, canopy closure prevents development of understory vegetation. Therefore there is a concern for overlandflow and sediment yield due to infiltration rate lowering from steep hillslopes of Japanese cypress plantation. We developed a light-weight rainfall simulator based on the design of Meyer and Harmon (1979). A flat fan Veejet 80150 spraying nozzle (Spraying systems Co., USA) is mounted on the manifold at 2.13 m high from the plot surface. The nozzle oscillates so that the spray fans swept across the targeting 1m x 1m plot. The Veejet 80150 spraying nozzle produces large raindrops larger than 2 mm in diameter, and can simulate the high raindrop kinetic energy of natural storm. A targeted rainfall rate is 180 mm/h. Total 25 sprinkling experiments have been conducted on 35-degree hillslopes with varying surface cover. We obtained the minimum infiltration rate of 14 mm/h where the surface cover is very little. The infiltration rates were plotted against the total understory vegetation and dry weight of total surface cover including litter. The infiltration rate increased with the increasing total surface cover, and higher regression coefficient is obtained for the case of the total surface cover. These results will contribute to the future modeling studies of overlandflow occurrences for the catchment scales.

  4. B-737 flight test of curved-path and steep-angle approaches using MLS guidance

    NASA Technical Reports Server (NTRS)

    Branstetter, J. R.; White, W. F.

    1989-01-01

    A series of flight tests were conducted to collect data for jet transport aircraft flying curved-path and steep-angle approaches using Microwave Landing System (MLS) guidance. During the test, 432 approaches comprising seven different curved-paths and four glidepath angles varying from 3 to 4 degrees were flown in NASA Langley's Boeing 737 aircraft (Transport Systems Research Vehicle) using an MLS ground station at the NASA Wallops Flight Facility. Subject pilots from Piedmont Airlines flew the approaches using conventional cockpit instrumentation (flight director and Horizontal Situation Indicator (HSI). The data collected will be used by FAA procedures specialists to develop standards and criteria for designing MLS terminal approach procedures (TERPS). The use of flight simulation techniques greatly aided the preliminary stages of approach development work and saved a significant amount of costly flight time. This report is intended to complement a data report to be issued by the FAA Office of Aviation Standards which will contain all detailed data analysis and statistics.

  5. Beach steepness effects on nonlinear infragravity-wave interactions: A numerical study

    NASA Astrophysics Data System (ADS)

    de Bakker, A. T. M.; Tissier, M. F. S.; Ruessink, B. G.

    2016-01-01

    The numerical model SWASH is used to investigate nonlinear energy transfers between waves for a diverse set of beach profiles and wave conditions, with a specific focus on infragravity waves. We use bispectral analysis to study the nonlinear triad interactions, and estimate energy transfers to determine energy flows within the spectra. The energy transfers are divided into four types of triad interactions, with triads including either one, two or three infragravity-frequency components, and triad interactions solely between sea-swell wave frequencies. The SWASH model is validated with a high-resolution laboratory data set on a gently sloping beach, which shows that SWASH is capable of modeling the detailed nonlinear interactions. From the simulations, we observe that especially the beach slope affects nonlinear infragravity-wave interactions. On a low-sloping beach, infragravity-wave energy dominates the water motion close to shore. Here infragravity-infragravity interactions dominate and generate higher harmonics that lead to the steepening of the infragravity wave and eventually breaking, causing large infragravity energy dissipation. On the contrary, on a steep-sloping beach, sea-swell wave energy dominates the water motion everywhere. Here infragravity frequencies interact with the spectral peak and spread energy to a wide range of higher frequencies, with relatively less infragravity energy dissipation. Although both beach types have different nonlinear interaction patterns during infragravity-wave dissipation, the amount of infragravity-wave reflection can be estimated by a single parameter, the normalized bed slope.

  6. Biosurfactant production by Bacillus subtilis using corn steep liquor as culture medium.

    PubMed

    Gudiña, Eduardo J; Fernandes, Elisabete C; Rodrigues, Ana I; Teixeira, José A; Rodrigues, Lígia R

    2015-01-01

    In this work, biosurfactant production by Bacillus subtilis #573 was evaluated using corn steep liquor (CSL) as culture medium. The best results were obtained in a culture medium consisting of 10% (v/v) of CSL, with a biosurfactant production of about 1.3 g/l. To the best of our knowledge, this is the first report describing biosurfactant production by B. subtilis using CSL as culture medium. Subsequently, the effect of different metals (iron, manganese, and magnesium) on biosurfactant production was evaluated using the medium CSL 10%. It was found that for all the metals tested, the biosurfactant production was increased (up to 4.1, 4.4, and 3.5 g/l for iron, manganese, and magnesium, respectively). When the culture medium was supplemented with the optimum concentration of the three metals simultaneously, the biosurfactant production was increased up to 4.8 g/l. Furthermore, the biosurfactant exhibited a good performance in oil recovery assays when compared with chemical surfactants, which suggests its possible application in microbial enhanced oil recovery or bioremediation. PMID:25705209

  7. Sediment dynamics on a steep, megatidal, mixed sand-gravel-cobble beach

    NASA Astrophysics Data System (ADS)

    Hay, A. E.; Zedel, L.; Stark, N.

    2014-08-01

    Results are presented from a pilot study of shore-face sediment dynamics on a steep, poorly sorted, coarse-grained, megatidal beach at the head of the Bay of Fundy, Nova Scotia, Canada. The experiment involved the first field deployment of a prototype wideband, pulse-coherent, bistatic acoustic Doppler profiling system. Measurements of the vertical structure of flow and turbulence above a sloping bed, as well as bed material velocity, demonstrate the capabilities of this instrument vis-à-vis studies of nearshore sediment dynamics at the field scale. The second focus of the paper is the unexpected observation that the surficial sediment median diameter, across the lower two-thirds of the intertidal zone, underwent a pronounced decrease when wave forcing was more energetic, compared to values observed during calmer conditions. The explanation for this result appears to involve the formation - in wave-dominated conditions - of metre-scale wavelength, 20 cm high ripples on the rising tide, which are then planed flat by the swash and/or the shore break on the subsequent ebb.

  8. Biosurfactant production by Bacillus subtilis using corn steep liquor as culture medium

    PubMed Central

    Gudiña, Eduardo J.; Fernandes, Elisabete C.; Rodrigues, Ana I.; Teixeira, José A.; Rodrigues, Lígia R.

    2015-01-01

    In this work, biosurfactant production by Bacillus subtilis #573 was evaluated using corn steep liquor (CSL) as culture medium. The best results were obtained in a culture medium consisting of 10% (v/v) of CSL, with a biosurfactant production of about 1.3 g/l. To the best of our knowledge, this is the first report describing biosurfactant production by B. subtilis using CSL as culture medium. Subsequently, the effect of different metals (iron, manganese, and magnesium) on biosurfactant production was evaluated using the medium CSL 10%. It was found that for all the metals tested, the biosurfactant production was increased (up to 4.1, 4.4, and 3.5 g/l for iron, manganese, and magnesium, respectively). When the culture medium was supplemented with the optimum concentration of the three metals simultaneously, the biosurfactant production was increased up to 4.8 g/l. Furthermore, the biosurfactant exhibited a good performance in oil recovery assays when compared with chemical surfactants, which suggests its possible application in microbial enhanced oil recovery or bioremediation. PMID:25705209

  9. Parameterization of intrawave ripple-averaged sediment pickup above steep ripples

    NASA Astrophysics Data System (ADS)

    Amoudry, L. O.; Souza, A. J.; Thorne, P. D.; Liu, P. L.-F.

    2016-01-01

    Near-bed sediment pickup is critical for predictions of intrawave suspension and in turn net sediment transport in coastal models. In the present study, numerical results from a two-dimensional Reynolds-averaged Navier-Stokes model are used to assess the functional relationship of intrawave ripple-averaged sediment pickup above steep ripples. The numerical model provides intrawave time histories of ripple-averaged near-bed velocities and turbulence, which are qualitatively interrogated to determine pickup functional relationships. Several specific sediment pickup formulations are implemented within the numerical model: expressions relating pickup to near-bed velocity or near-bed turbulent kinetic energy via the bed shear stress; and expressions relating pickup to near-bed shear production of turbulent kinetic energy. These are then tested via model-data comparisons of near-bed suspended sediment concentration. The results show that the traditional functions relating sediment pickup to near-bed velocity cannot lead to reasonable intrawave suspension predictions above vortex ripples under a ripple-averaged framework. Instead, relating sediment pickup to near-bed turbulence quantities, such as turbulent kinetic energy or shear production of turbulent kinetic energy, significantly improves the numerical predictions for these conditions.

  10. A Plausible Explanation for the Steep Redshift Decline in Barred Spirals: Dynamically Hot Disks

    NASA Astrophysics Data System (ADS)

    Sheth, Kartik; Melbourne, J.; Kassin, S.; Elmegreen, D. M.; Elmegreen, B. G.; Athanassoula, E.; Abraham, R. G.; Ellis, R. S.; Weiner, B.

    2012-05-01

    We present the first observational evidence for the inhibition of bar formation in dispersion dominated (dynamically hot) galaxies. We compare the presence of galactic structures (bars) and the host galaxy kinematics in a sample of 200 disk galaxies from the All-Wavelength Extended Groth Strip International Survey (AEGIS) and the Deep Extragalactic Evolutionary Probe 2 (DEEP2) survey. We find that bars are preferentially found in galaxies that lie on the Tully-Fisher relationship and are rotation-dominated, whereas few bars are found in galaxies that are dispersion dominated. The data provide at least one explanation for the steep (x3) decline in the bar fraction from z=0 to z=0.84 previously observed in L* disk galaxies in the COSMOS field. In the COSMOS data, the decline in bars is primarily found in the low mass, late-type systems. A proposed explanation for the trend was that at higher redshifts, lower mass systems were more dispersion dominated because they were more easily harassed by the increased interaction and merger rate. The data presented here provides observational support for this hypothesis.

  11. Preventive Dorzolamide-Timolol for Rising Intraocular Pressure During Steep Trendelenburg Position Surgery.

    PubMed

    Molloy, Bonnie Lee; Cong, Xiamei; Watson, Charles

    2016-06-01

    The study purpose was to evaluate preventive use of dorzolamide-timolol ophthalmic solution (Cosopt) during laparoscopic surgery with the patient in steep Trendelenburg (ST) position. Periorbital swelling, venous congestion, and elevated intraocular pressure (IOP) may produce low ocular perfusion. Prompt IOP reduction is important because 30- to 40-minute episodes of acute IOP elevations can result in retinal ganglion cell dysfunction. Dorzolamide-timolol ophthalmic drops reduce IOP and may ameliorate this effect. A double-blind randomized experimental study was conducted to test the effect of dorzolamide-timolol on IOP elevation during laparoscopic surgeries in ST position. Patients were randomly assigned to receive dorzolamide-timolol treatment or balanced salt solution following anesthesia induction. The IOP levels were measured at baseline and 30-minutes intervals throughout surgery. The generalized estimating equations model was used to analyze treatment and time effects and treatment by time interactions. Ninety patients were recruited, with 46 receiving dorzolamide-timolol treatment and 44 receiving balanced salt solution. Statistical analysis revealed significant treatment and time effects and treatment-time interactions on IOP. Patients' IOP was significantly lower in the treatment group than controls (P < .05 to P < .001). Treatment effects were medium to strong. Prophylactic therapy with dorzolamide-timolol significantly reduced IOP of surgical patients during ST positioning. PMID:27501654

  12. Shallow plumbing and eruptive processes of a scoria cone built on steep terrain

    NASA Astrophysics Data System (ADS)

    Harp, A. G.; Valentine, G. A.

    2015-03-01

    Dark Peak (Lunar Crater Volcanic Field, central Nevada, USA) is an eroded Pliocene, monogenetic basaltic volcano that exposes intrusions while preserving some pyroclastic deposits and lavas, allowing reconstruction of the shallow magma feeding system and its relation to eruptive processes. Variably welded agglomerates record Strombolian and Hawaiian fountaining. Dikes fed degassed magma to a bocca on the lower cone slopes and fed a small lava field. The cone was built on the side of a steep ridge with small side drainages, had a maximum diameter of about 1 km, and was ~ 125 m high above the highest point on the paleotopography. The eruption was fed by an ~ 1 km long, narrow (1-3 m) feeder dike that locally flared in the upper tens of meters to form an ~ 30 m wide conduit around which the cone was built. The conduit shape and the transition depth from feeder dike to conduit are consistent with data from other exposed plumbing systems of small volume basaltic volcanoes that were dominated by magmatic volatile-driven eruption styles, supporting inferences that their conduits are relatively shallow features (upper ~ 150 m).

  13. Properties of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies

    NASA Astrophysics Data System (ADS)

    Foschini, L.; Berton, M.; Caccianiga, A.; Ciroi, S.; Cracco, V.; Peterson, B. M.; Angelakis, E.; Braito, V.; Fuhrmann, L.; Gallo, L.; Grupe, D.; Järvelä, E.; Kaufmann, S.; Komossa, S.; Kovalev, Y. Y.; Lähteenmäki, A.; Lisakov, M. M.; Lister, M. L.; Mathur, S.; Richards, J. L.; Romano, P.; Sievers, A.; Tagliaferri, G.; Tammi, J.; Tibolla, O.; Tornikoski, M.; Vercellone, S.; La Mura, G.; Maraschi, L.; Rafanelli, P.

    2015-03-01

    We have conducted a multiwavelength survey of 42 radio loud narrow-1ine Seyfert 1 galaxies (RLNLS1s), selected by searching among all the known sources of this type and omitting those with steep radio spectra. We analyse data from radio frequencies to X-rays, and supplement these with information available from online catalogues and the literature in order to cover the full electromagnetic spectrum. This is the largest known multiwavelength survey for this type of source. We detected 90% of the sources in X-rays and found 17% at γ rays. Extreme variability at high energies was also found, down to timescales as short as hours. In some sources, dramatic spectral and flux changes suggest interplay between a relativistic jet and the accretion disk. The estimated masses of the central black holes are in the range ~106-8 M⊙, lower than those of blazars, while the accretion luminosities span a range from ~0.01 to ~0.49 times the Eddington limit, with an outlier at 0.003, similar to those of quasars. The distribution of the calculated jet power spans a range from ~1042.6 to ~1045.6 erg s-1, generally lower than quasars and BL Lac objects, but partially overlapping with the latter. Once normalised by the mass of the central black holes, the jet power of the three types of active galactic nuclei are consistent with each other, indicating that the jets are similar and the observational differences are due to scaling factors. Despite the observational differences, the central engine of RLNLS1s is apparently quite similar to that of blazars. The historical difficulties in finding radio-loud narrow-line Seyfert 1 galaxies might be due to their low power and to intermittent jetactivity. Tables 4-9 and Figs. 8-13 are available in electronic form at http://www.aanda.org

  14. The first VLBI image of an infrared-faint radio source

    NASA Astrophysics Data System (ADS)

    Middelberg, E.; Norris, R. P.; Tingay, S.; Mao, M. Y.; Phillips, C. J.; Hotan, A. W.

    2008-11-01

    Context: We investigate the joint evolution of active galactic nuclei and star formation in the Universe. Aims: In the 1.4 GHz survey with the Australia Telescope Compact Array of the Chandra Deep Field South and the European Large Area ISO Survey - S1 we have identified a class of objects which are strong in the radio but have no detectable infrared and optical counterparts. This class has been called Infrared-Faint Radio Sources, or IFRS. 53 sources out of 2002 have been classified as IFRS. It is not known what these objects are. Methods: To address the many possible explanations as to what the nature of these objects is we have observed four sources with the Australian Long Baseline Array. Results: We have detected and imaged one of the four sources observed. Assuming that the source is at a high redshift, we find its properties in agreement with properties of Compact Steep Spectrum sources. However, due to the lack of optical and infrared data the constraints are not particularly strong.

  15. Diffuse radio emission around FR II sources as exemplified by 3C452

    NASA Astrophysics Data System (ADS)

    Wiita, Paul J.; Sirothia, S. K.; Gopal-Krishna, ..

    2014-01-01

    We have discovered a pair of megaparsec size radio lobes of extremely steep spectrum straddling the well-known classical double radio source 3C452. For the past several decades 3C452 has been regarded as a textbook example of an edge-brightened double radio source of Fanaroff-Riley type II (FR II) but we show it to be a bonafide "double-double" radio galaxy (DDRG). The inner double fed by the jets has evolved into a perfectly normal FR II radio source. Thus, 3C452 presents a uniquely robust example of recurrent nuclear activity in which the restarted jets are expanding non-relativistically within the relic synchrotron plasma from an earlier active phase. This situation contrasts markedly with the strikingly narrow inner doubles observed in a few other DDRGs that have been interpreted in terms of compression of the synchrotron plasma of the relic outer lobes at the relativistic bow-shocks driven by the near ballistic propagation of the two inner jets through the relic plasma. We also present additional examples of the occurrence of faded outer lobes around well defined FRII sources, using our deep GMRT images at meter wavelengths processed with AIPS++ software. We also examine the statistics of the occurrence of such sources using a flux density limited sample. A key ramification of our findings are that they caution against the use of FR II classical double radio sources for testing cosmological models and unification schemes for active galactic nuclei.

  16. GPS/CSS radio sources and their relation to other AGN

    NASA Astrophysics Data System (ADS)

    Sadler, E. M.

    2016-02-01

    We are entering a new era of sensitive, large-area and multi-frequency radio surveys that will allow us to identify Gigahertz-Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radio sources over a wide range in radio luminosity and study them within the context of the overall radio-source populations to which they belong. ``Classical'' GPS/CSS objects are extremely luminous radio sources with a compact double morphology, commonly thought to represent the earliest stages in the life cycle of powerful radio galaxies (e.g. O'Dea 1998). It is now becoming easier to identify GPS/CSS candidates with much lower radio luminosity - particularly in the nearby Universe. These less powerful objects, with typical 1.4 GHz radio luminosities of 1023 to 1025 W Hz-1, include peaked-spectrum radio sources with a core-jet morphology on parsec scales as well as high-frequency GPS-like peaked components embedded within lower-frequency extended emission. In the latter case, the presence of a young GPS component may not be evident from low-frequency data alone. Many radio galaxies in the local Universe have a compact (FR-0) morphology, and appear to lack extended radio emission on kiloparsec scales. The relationship of these FR-0 objects to the classical GPS/CSS radio sources remains unclear - some of them may represent short-lived episodes of AGN activity that will not lead to an extended FR-1 or FR-2 radio galaxy. Future wide-band radio surveys will shed more light on this - such surveys should ideally be coordinated to cover the full frequency range from 100 MHz to 100 GHz in order to sample all stages of GPS/CSS evolution in an unbiased way.

  17. Contributions of human activities to suspended-sediment yield during storm events from a steep, small, tropical watershed, American Samoa

    NASA Astrophysics Data System (ADS)

    Messina, A. T.; Biggs, T. W.

    2014-12-01

    Anthropogenic watershed disturbance by agriculture, deforestation, roads, and urbanization can alter the timing, composition, and mass of sediment loads to adjacent coral reefs, causing enhanced sediment stress on corals near the outlets of impacted watersheds like Faga'alu, American Samoa. To quantify the increase in sediment loading to the adjacent priority coral reef experiencing sedimentation stress, suspended-sediment yield (SSY) from undisturbed and human-disturbed portions of a small, steep, tropical watershed was measured during baseflow and storm events of varying magnitude. Data on precipitation, discharge, turbidity, and suspended-sediment concentration (SSC) were collected over three field campaigns and continuous monitoring from January 2012 to March 2014, which included 88 storm events. A combination of paired- and nested-watershed study designs using sediment budget, disturbance ratio, and sediment rating curve methodologies was used to quantify the contribution of human-disturbed areas to total SSY. SSC during base- and stormflows was significantly higher downstream of an open-pit aggregate quarry, indicating the quarry is a key sediment source requiring sediment discharge mitigation. Comparison of event-wise SSY from the upper, undisturbed watershed, and the lower, human-disturbed watershed showed the Lower watershed accounted for more than 80% of total SSY on average, and human activities have increased total sediment loading to the coast by approximately 200%. Four storm characteristics were tested as predictors of event SSY using Pearson's and Spearman's correlation coefficients. Similar to mountainous watersheds in semi-arid and temperate watersheds, SSY from both the undisturbed and disturbed watersheds had the highest correlation with event maximum discharge, Qmax (Pearson's R=0.88 and 0.86 respectively), and were best fit by a power law relationship. The resulting model of event-SSY from Faga'alu is being incorporated as part of a larger

  18. Seismic component of the STEEP project, Alaska: Results of the first field season

    NASA Astrophysics Data System (ADS)

    Hansen, R. A.; Estes, S.; Stachnik, J.; Lafevers, M.; Roush, J.; Sanches, R.; Fuerst, E.; Sandru, J.; Ruppert, N.; Pavlis, G.; Bauer, M.

    2005-12-01

    STEEP (SainT Elias Erosion/tectonics Project) is a five year, multi-disciplinary study that addresses evolution of the highest coastal mountain range on Earth - the St. Elias Mountains of southern Alaska and northwestern Canada. The overall goal of the project is to develop a comprehensive model for the St. Elias orogen that accounts for the interaction of regional plate tectonic processes, structural development, and rapid erosion. The seismic component of this project includes passive seismic experiment utilizing the IRIS PASSCAL Program instruments. The total project consists of 22 new, telemetered, digital broad band seismic stations, most accessible by helicopter only. There are 12 existing short period stations in the area. Eight new stations were installed in the coastal region in June 2005. Freewave IP radios provide the telemetry to the newly installed VSAT at the Bering Glacier camp site. The challenge was to find ice-free locations, on bedrock, large enough to install equipment and still have a helicopter landing zone nearby. The stations consist of Quanterra Q330 digitizers with baler, a STS-2 seismometer installed in a vault, a Freewave IP radio, a Scala 900 Mhz antenna, twenty 100 AH rechargeable batteries with a 2400AH backup Celair primary battery, and three solar panels mounted on hut. The acquired data is recorded in real time at the Alaska Earthquake Information Center located in Fairbanks and is incorporated into the standard data processing procedures. High quality data allows for more reliable automatic earthquake detections in the region with lower magnitude threshold. In addition to tectonic earthquakes, glacial events that occur within the vast ice fields of the region are also regularly detected. Broadband instruments complement regional broadband network for more reliable calculations of the regional moment tensors.

  19. Monitoring of a steep rockfall area experiencing fast displacements in Kåfjord, Northern Norway

    NASA Astrophysics Data System (ADS)

    Dreiås Majala, Gudrun; Harald Blikra, Lars; Skrede, Ingrid; Kristensen, Lene

    2016-04-01

    An unstable rockfall area in Kåfjord, Northern Norway, was recognized during periodic monitoring campaigns in July and early September 2015. The LiSALab ground based Interferometric Synthethic Aperture Radar (GB InSAR) from Ellegi were used. A relatively sharply defined steep area of 1200 m2 (6.000 - 12.000 m3) was documented to be in movement. Norwegian Water Resources and Energy Directorate (NVE) was at this point performing mitigation work in terms of an embarkment within the rockfall run-out area. The monitoring system was reinstalled and adjusted to perform continuous monitoring with an early-warning aim. The section for rockslide management in NVE was responsible for the monitoring and the warning to the municipality and Police. The displacements increased from about 1 mm/day in July to 3 cm/day in mid September. People were evalcuated due to increased velocities the 16th of September. The displacements continued to increase in several stages, and with a distinct accelleration the 2nd of October. The velocity peaked in a short window to more than 200 cm/day, and it ended with a partly frontal and sideway collapse of the unstable area. However, large parts of the area stabilized again, and the run-out lengths from the small rockfalls were limited. The GB InSAR system operated exceptionally well during the event, and were able to follow continuously the displacements during the accelleration stage until collapse as the processing time window was frequently adjusted to the changes in velocity. We were also able to follow inidividual rockfalls from the images - primarily as the rockfall impact points on the slope below showed up clearly on the radar images. The area continued to stabilize due to falling temperatures, and the mitigation work were finished during the fall. The displacements seem to be correlated to the increasing temperatures in late summer and precipitation events.

  20. Optimization of liquid-liquid extraction of biosurfactants from corn steep liquor.

    PubMed

    Vecino, X; Barbosa-Pereira, L; Devesa-Rey, R; Cruz, J M; Moldes, A B

    2015-09-01

    In this work, the optimization of the operational conditions for the chloroform-based extraction of surface-active compounds from corn steep liquor (CSL) was carried out and the nutritional properties of the remnant aqueous phase (CSL-less biosurfactant) was evaluated as microbial fermentation medium. The optimal conditions to obtain biosurfactants from CSL were as follows: chloroform/CSL ratio 2 (v/v), 56 °C at extraction times >30 min. At the optima conditions, 100 % of biosurfactant extract can be obtained from CSL, obtaining 12.0 ± 0.5 g of biosurfactant extract/Kg of CSL. The critical micelle concentration (CMC) of the biosurfactant extract was 399.4 mg L(-1). This value is similar to the CMC of cetrimonium bromide (CTAB), a cationic surfactant used in the formulation of nanoparticles. The extraction of biosurfactant can be also carried out at room temperature although in this case, the extraction yield decreased about 15 %. The extraction of surface-active compounds from agroindustrial streams can suppose important advances for the bio-based surfactants industry. Biosurfactants obtained in this work are not only more eco-friendly than chemical detergents but also can be cost competitive with its chemical counterparts. Furthermore, after the extraction of surface-active compounds, CSL-less biosurfactant was found to be suitable as nutritional supplement for lactic acid bacteria, maintaining its nutritional properties in comparison with regular CSL. PMID:25911424

  1. Steep Decline and Low Hydrocarbon Recovery in Fractured Shale: What and Why?

    NASA Astrophysics Data System (ADS)

    Hu, Q.; Barber, T.; Gao, Z.; Gao, X.; Ewing, R. P.

    2014-12-01

    Since 2000, the technological advances of horizontal drilling and hydraulic fracturing in the United States have led to a dramatic increase in hydrocarbon (gas and oil) production from shale formations, changing the energy landscape in the US and worldwide. Since 2005, the surge in tight oil production from shale formations has provided tremendous optimism regarding future United States hydrocarbon production, unexpectedly becoming the fastest-growing frontier of unconventional resources. According to the Energy Information Administration's newly released report in 2014, US oil output from tight oil prospects will almost double from the 2012 level of 2.5 million barrels per day, to 4.8 by 2019. However, total gas recovery from the Barnett play was reported to be only12-30%, and the tight-oil recovery rate from shale formations is even lower at 5-10%. The main barrier to sustainable development of US shale, the pore structure of the nanopores storing and transporting hydrocarbons, has been quietly ignored. We have studied pore structure, edge-accessible porosity, and how wettability is associated with mineral and organic kerogen phases, from four complementary tests: vacuum saturation with vacuum-pulling on dry shale followed with tracer introduction, tracer diffusion into fluid-saturated shale, fluid and tracer imbibition into partially-saturated shale, and Wood's metal intrusion followed with SEM imaging and elemental mapping. The first three tests use tracer-bearing fluids (API brine or n-decane), with tracer distribution on shale mapped with micro-scale laser ablation-ICP-MS analyses. These innovative approaches indicate the limited accessibility (several millimeters from shale sample edge) and connectivity of nanopores in shales under atmospheric condition, which is linked to the steep initial (e.g., 1st year) decline and low overall recovery because of the limited connection of hydrocarbon molecules in the shale matrix to the stimulated fracture network.

  2. Storm runoff generation at a steep pre-alpine hillslope - transmissivity feedback or organic layer interflow?

    NASA Astrophysics Data System (ADS)

    Schneider, Philipp; Pool, Sandra; Strouhal, Ludek; Seibert, Jan

    2015-04-01

    This study investigated storm runoff generation processes of a pre-alpine hillslope prone to slide. The experimental pasture plot is located in the northern front range of the Swiss Alps on a 30° steep hillslope. A gleysol overlies weathered marlstone and conglomerate of subalpine molasse. We conducted sprinkling experiments on a subplot with variable rainfall intensities. During both experiments fluorescein line-tracer injections into the topsoil, and sodium chloride (NaCl) injections into the sprinkling water were used to monitor flow velocities in the soil. The observed flow velocities for fluorescein in the soil were 1.2 and 1.4 × 10-3 m s-1. The NaCl breakthrough occurred almost simultaneously in all monitored discharge levels (0.05, 0.25 and 1.0 m depth), indicating a high infiltration capacity and efficient lateral drainage of the soil. These initial observations suggested 'transmissivity feedback' (a form of subsurface stormflow described in Nordic catchments by Allan Rhode in 1987) as the dominant storm runoff generation process. However, excavation of dye-stained soil horizons from a brilliant blue tracer experiment completely changed our perceptions of the prevailing storm flow paths and its runoff generation mechanisms. The results highlighted the dominance of 'organic layer interflow', a form of shallow subsurface stormflow at the hillslope. The dye stained the entire topsoil horizon, vertical soil fractures, and macropores (mostly worm burrows) up to 0.5 m depth. Lateral drainage in the subsoil horizons or at the soil-bedrock interface was not observed; drainage was limited to the organic topsoil. The subsoil with its low permeability acted locally as a soil percolation and bedrock exfiltration barrier, producing significant lateral drainage in the organic topsoil and pronounced pore water pressure changes in the bedrock. Reference Rohde, A.: The origin of streamwater traced by Oxygen-18, 260 pp., Uppsala University., 1987.

  3. Scaling relationships between bed load volumes, transport distances, and stream power in steep mountain channels

    NASA Astrophysics Data System (ADS)

    Schneider, Johannes M.; Turowski, Jens M.; Rickenmann, Dieter; Hegglin, Ramon; Arrigo, Sabrina; Mao, Luca; Kirchner, James W.

    2014-03-01

    Bed load transport during storm events is both an agent of geomorphic change and a significant natural hazard in mountain regions. Thus, predicting bed load transport is a central challenge in fluvial geomorphology and natural hazard risk assessment. Bed load transport during storm events depends on the width and depth of bed scour, as well as the transport distances of individual sediment grains. We traced individual gravels in two steep mountain streams, the Erlenbach (Switzerland) and Rio Cordon (Italy), using magnetic and radio frequency identification tags, and measured their bed load transport rates using calibrated geophone bed load sensors in the Erlenbach and a bed load trap in the Rio Cordon. Tracer transport distances and bed load volumes exhibited approximate power law scaling with both the peak stream power and the cumulative stream energy of individual hydrologic events. Bed load volumes scaled much more steeply with peak stream power and cumulative stream energy than tracer transport distances did, and bed load volumes scaled as roughly the third power of transport distances. These observations imply that large bed load transport events become large primarily by scouring the bed deeper and wider, and only secondarily by transporting the mobilized sediment farther. Using the sediment continuity equation, we can estimate the mean effective thickness of the actively transported layer, averaged over the entire channel width and the duration of individual flow events. This active layer thickness also followed approximate power law scaling with peak stream power and cumulative stream energy and ranged up to 0.57 m in the Erlenbach, broadly consistent with independent measurements.

  4. Infiltration and Runoff Measurements on Steep Burned Hillslopes Using a Rainfall Simulator with Variable Rain Intensities

    USGS Publications Warehouse

    Kinner, David A.; Moody, John A.

    2008-01-01

    Multiple rainfall intensities were used in rainfall-simulation experiments designed to investigate the infiltration and runoff from 1-square-meter plots on burned hillslopes covered by an ash layer of varying thickness. The 1-square-meter plots were on north- and south-facing hillslopes in an area burned by the Overland fire northwest of Boulder near Jamestown on the Front Range of Colorado. A single-nozzle, wide-angle, multi-intensity rain simulator was developed to investigate the infiltration and runoff on steep (30- to 40-percent gradient) burned hillslopes covered with ash. The simulated rainfall was evaluated for spatial variability, drop size, and kinetic energy. Fourteen rainfall simulations, at three intensities (about 20 millimeters per hour [mm/h], 35 mm/h, and 50 mm/h), were conducted on four plots. Measurements during and after the simulations included runoff, rainfall, suspended-sediment concentrations, surface ash layer thickness, soil moisture, soil grain size, soil lost on ignition, and plot topography. Runoff discharge reached a steady state within 7 to 26 minutes. Steady infiltration rates with the 50-mm/h application rainfall intensity approached 20?35 mm/h. If these rates are projected to rainfall application intensities used in many studies of burned area runoff production (about 80 mm/h), the steady discharge rates are on the lower end of measurements from other studies. Experiments using multiple rainfall intensities (three) suggest that runoff begins at rainfall intensities around 20 mm/h at the 1-square-meter scale, an observation consistent with a 10-mm/h rainfall intensity threshold needed for runoff initiation that has been reported in the literature.

  5. Timing of deposition and failure of steep carbonate slopes, Tongue of the Ocean, Bahamas

    SciTech Connect

    Grammer, G.M.; Ginsburg, R.N. )

    1991-03-01

    Steep marginal slopes around the Tongue of the Ocean record deposition during the early rise of sea level following the last lowstand some 18,000-21,000 years B.P. Coarse-grained skeletal packstones and grainstones derived from the overlying escarpment were deposited on slopes of 35-45{degree} and rapidly cemented in place. Deposition by rockfall and grainflow processes resulted in a series of elongate lenses oriented parallel to the slope. These lenses are generally less than 0.5 m thick and pinch out downslope within tens of meters. Radiocarbon dating indicates that active deposition on the slopes ceased abruptly about 10,000 years ago as sea level rose above the escarpment and began to flood the top of Great Bahama Bank. Fine-grained, nonskeletal sands and muds derived from the platform are presently by passing these slopes resulting in a 'modern' example of a drowning unconformity. Although these slopes are no longer sites of active deposition, they are still influencing the ultimate record of slope sedimentation. Arcuate, concave-up cracks in the cemented slope indicate zones of weakness and possibly represent areas susceptible to slope failure. These cracks are a few centimeters wide and may extend for tens of meters across the slope. Post-depositional failure of the slope has been observed at several locations. These slide/slump scars are as much as 30 m across and may extend downslope for 70-80 m. Large blocks, some more than 10 m across, derived from failure of the relict slope have been transported for tens or hundreds of meters downslope. The release and transport of such blocks may be one mechanism by which turbidity currents are initiated in deeper slope environments.

  6. Hydro-Mechanical Perturbation of a Steep Hillslope - Failing to Fail a Hillslope

    NASA Astrophysics Data System (ADS)

    Or, D.; Schwarz, M.; Cohen, D.; Michlmayr, G.; Lehmann, P.; Gambazzi, F.; Hofer, M.; Stähli, M.

    2009-04-01

    Rapid shallow landslides are relatively common natural hazards in mountainous regions. The prediction of hydromechanical conditions inducing these events remains a challenge due to complex interactions of soil properties, vegetation and geologic conditions. Shallow landslides in alpine regions occur primarily in slopes steeper than 25 degrees and are triggered most often by heavy rainfall events. Nevertheless, extreme rainfall events on steep slopes >40 degrees in mountainous regions show remarkable stability. To analyze such hillslope response to extreme hydrologic input of long duration, we conducted a field experiment in the Loetschental valley (Wiler, Switzerland) where a small meadow (5 x 10 m) within a forest with soil depth between 0.3 and 1.5 m was instrumented with different sensors to monitor soil water pressure, soil and bedrock water content, electrical resistivity and occurrence of small movements. We applied water using two sprinklers and from a one meter deep trench upslope. Water was applied for two weeks at a rate of 36 L/hr/m2 (corresponding to annual rainfall amount of 860 mm applied in one day). Following this extended period of heavy rainfall, we supplied water to upslope trench (5 m wide and 1 m deep) at maximum rates of 200 L/min (potential seepage rates of 57 m per day!) resulting in surface runoff. Inflow rates less than 30L/min showed no surface runoff. Some tensiometers registered positive pore pressures in the range of 0.2 to 0.8 m of head, however, most of the applied water drained into bedrock and via preferential flow along macropores formed by decaying tree roots and rock fragment skeleton as indicated by geophysical methods and dye tracer experiments. The slope composition (roots, soil and rock fragments) and the interface between soil and bedrock show strong self-organization to maximize drainage capacity thereby reducing mechanical failure potential and landslide risk.

  7. The Divergence of Wear Propagation and Stress at Steep Acetabular Cup Positions Using Ceramic Heads and Sequentially Cross-Linked Polyethylene Liners.

    PubMed

    Zietz, Carmen; Fabry, Christian; Baum, Felix; Bader, Rainer; Kluess, Daniel

    2015-08-01

    The aim of the present wear simulator study was to assess the effect of steep acetabular cup positions on the wear propagation of highly cross-linked-PE (HX-PE) liners. Furthermore, a finite element analysis (FEA) was performed in order to calculate the stress within the HX-PE material in case of steep cup positions under physiological loadings. The higher stress in the HX-PE at a steep acetabular cup position did not result in increased wear in the present wear simulator study. The gravimetrical wear rates at normal (45°) and steep cup inclinations (75°) showed wear amounts of 3.15±0.27mg and 2.18±0.31mg per million cycles (p=0.028), respectively. However, FEA revealed clear increase in stress at the HX-PE liners with respect to steep cup positions. PMID:25770865

  8. An extended steepness model for leg-size determination based on Dachsous/Fat trans-dimer system

    PubMed Central

    Yoshida, Hiroshi; Bando, Tetsuya; Mito, Taro; Ohuchi, Hideyo; Noji, Sumihare

    2014-01-01

    What determines organ size has been a long-standing biological question. Lawrence et al. (2008) proposed the steepness hypothesis suggesting that the protocadherin Dachsous/Fat (Ds/Ft) system may provide some measure of dimension to the cells in relation to the gradient. In this paper we extended the model as a means of interpreting experimental results in cricket leg regeneration. We assumed that (1) Ds/Ft trans-heterodimers or trans-homodimers are redistributed during cell division, and (2) growth would cease when a differential of the dimer across each cell decreases to a certain threshold. We applied our model to simulate the results obtained by leg regeneration experiments in a cricket model. The results were qualitatively consistent with the experimental data obtained for cricket legs by RNA interference methodology. Using our extended steepness model, we provided a molecular-based explanation for leg size determination even in intercalary regeneration and for organ size determination. PMID:24613915

  9. An extended steepness model for leg-size determination based on Dachsous/Fat trans-dimer system.

    PubMed

    Yoshida, Hiroshi; Bando, Tetsuya; Mito, Taro; Ohuchi, Hideyo; Noji, Sumihare

    2014-01-01

    What determines organ size has been a long-standing biological question. Lawrence et al. (2008) proposed the steepness hypothesis suggesting that the protocadherin Dachsous/Fat (Ds/Ft) system may provide some measure of dimension to the cells in relation to the gradient. In this paper we extended the model as a means of interpreting experimental results in cricket leg regeneration. We assumed that (1) Ds/Ft trans-heterodimers or trans-homodimers are redistributed during cell division, and (2) growth would cease when a differential of the dimer across each cell decreases to a certain threshold. We applied our model to simulate the results obtained by leg regeneration experiments in a cricket model. The results were qualitatively consistent with the experimental data obtained for cricket legs by RNA interference methodology. Using our extended steepness model, we provided a molecular-based explanation for leg size determination even in intercalary regeneration and for organ size determination. PMID:24613915

  10. Accelerating Spectrum Sharing Technologies

    SciTech Connect

    Juan D. Deaton; Lynda L. Brighton; Rangam Subramanian; Hussein Moradi; Jose Loera

    2013-09-01

    Spectrum sharing potentially holds the promise of solving the emerging spectrum crisis. However, technology innovators face the conundrum of developing spectrum sharing technologies without the ability to experiment and test with real incumbent systems. Interference with operational incumbents can prevent critical services, and the cost of deploying and operating an incumbent system can be prohibitive. Thus, the lack of incumbent systems and frequency authorization for technology incubation and demonstration has stymied spectrum sharing research. To this end, industry, academia, and regulators all require a test facility for validating hypotheses and demonstrating functionality without affecting operational incumbent systems. This article proposes a four-phase program supported by our spectrum accountability architecture. We propose that our comprehensive experimentation and testing approach for technology incubation and demonstration will accelerate the development of spectrum sharing technologies.

  11. PREDICTING STEEP ESCALATIONS IN ALCOHOL USE OVER THE TEENAGE YEARS: AGE-RELATED VARIATIONS IN KEY SOCIAL INFLUENCES

    PubMed Central

    Chan, Gary C. K.; Kelly, Adrian B.; Toumbourou, John W.; Hemphill, Sheryl A.; Young, Ross McD.; Haynes, Michele A.; Catalano, Richard F.

    2013-01-01

    Aims This study examined how family, peer and school factors are related to different trajectories of adolescent alcohol use at key developmental periods. Design Latent Class Growth Analysis was used to identify trajectories based on five waves of data (from Grade 6 - age 12 to Grade 11 – age 17), with predictors at Grade 5, Grade 7, and Grade 9 included as covariates. Setting Adolescents completed surveys during school hours. Participants 808 students in Victoria, Australia. Measurements Alcohol use trajectories were based on self-reports of 30 day frequency of alcohol use. Predictors included sibling alcohol use, attachment to parents, parental supervision, parental attitudes favorable to adolescent alcohol use, peer alcohol use, and school commitment. Findings 8.2% showed steep escalation in alcohol use. Relative to non-users, steep escalators were predicted by age-specific effects for low school commitment at Grade 7 (p = .031) and parental attitudes at Grade 5 (p = .003), and age-generalized effects for sibling alcohol use (ps = .001/.012/.033 at Grade 5/7/9) and peer alcohol use (ps = .041/.001/.001 at Grade 5/7/9). Poor parental supervision was associated with steep escalators at Grade 9 (p < .001) but not the other grades. Attachment to parents was unrelated to alcohol trajectories. Conclusions Parental disapproval of alcohol use before transition to high school, low school commitment at transition to high school, and sibling and peer alcohol use during adolescence are associated with higher risk of steep escalations in alcohol use. PMID:23834266

  12. High-frequency excess in the radio continuum spectrum of the type-1 Seyfert galaxy NGC 985

    NASA Astrophysics Data System (ADS)

    Doi, Akihiro; Inoue, Yoshiyuki

    2016-08-01

    The Seyfert galaxy NGC 985 is known to show a high-frequency excess in its radio continuum spectrum at a milli-Jansky level on the basis of previous observations at 1.4-15 GHz; a steep spectrum at low frequencies (a spectral index, α = -1.10 ± 0.03) changes at ˜10 GHz into an inverted spectrum at higher frequencies (α = +0.86 ± 0.09). We conduct new observations at 15-43 GHz using the Very Large Array and at 100 GHz using the Nobeyama Millimeter Array. As a result, the high-frequency excess has been confirmed as continuing at even higher radio frequencies, up to 43 GHz. The non-detection at 100 GHz was not so strong a constraint, and therefore the spectral behavior above 43 GHz remains unclear. The astrometric position of the high-frequency excess component coincides with the optical position of the Seyfert nucleus and the low-frequency radio position to an accuracy of 0{^''.}1, corresponding to ˜80 pc; the radio source size is constrained to be <0{^''.}02, corresponding to <16 pc. We discuss the physical origin of the observed high-frequency excess component. Dust emission at the Rayleigh-Jeans regime, free-free emission from X-ray radiating high-temperature plasma, free-free emission from the ensemble of broad-line region clouds, or thermal synchrotron from hot accretion flow cannot be responsible for the observed radio flux. Compact jets under synchrotron self-absorption may be unlikely in terms of observed time scales. Alternatively, we cannot rule out the hypotheses of synchrotron jets free-free absorbed by a circumnuclear photo-ionized region, and self-absorbed nonthermal synchrotron from disk corona, as the origin of the high-frequency excess component.

  13. High-frequency excess in the radio continuum spectrum of the type-1 Seyfert galaxy NGC 985

    NASA Astrophysics Data System (ADS)

    Doi, Akihiro; Inoue, Yoshiyuki

    2016-06-01

    The Seyfert galaxy NGC 985 is known to show a high-frequency excess in its radio continuum spectrum at a milli-Jansky level on the basis of previous observations at 1.4-15 GHz; a steep spectrum at low frequencies (a spectral index, α = -1.10 ± 0.03) changes at ˜10 GHz into an inverted spectrum at higher frequencies (α = +0.86 ± 0.09). We conduct new observations at 15-43 GHz using the Very Large Array and at 100 GHz using the Nobeyama Millimeter Array. As a result, the high-frequency excess has been confirmed as continuing at even higher radio frequencies, up to 43 GHz. The non-detection at 100 GHz was not so strong a constraint, and therefore the spectral behavior above 43 GHz remains unclear. The astrometric position of the high-frequency excess component coincides with the optical position of the Seyfert nucleus and the low-frequency radio position to an accuracy of 0{^''.}1, corresponding to ˜80 pc; the radio source size is constrained to be <0{^''.}02, corresponding to <16 pc. We discuss the physical origin of the observed high-frequency excess component. Dust emission at the Rayleigh-Jeans regime, free-free emission from X-ray radiating high-temperature plasma, free-free emission from the ensemble of broad-line region clouds, or thermal synchrotron from hot accretion flow cannot be responsible for the observed radio flux. Compact jets under synchrotron self-absorption may be unlikely in terms of observed time scales. Alternatively, we cannot rule out the hypotheses of synchrotron jets free-free absorbed by a circumnuclear photo-ionized region, and self-absorbed nonthermal synchrotron from disk corona, as the origin of the high-frequency excess component.

  14. THE HIGH-ENERGY, ARCMINUTE-SCALE GALACTIC CENTER GAMMA-RAY SOURCE

    SciTech Connect

    Chernyakova, M.; Malyshev, D.; Aharonian, F. A.; Crocker, R. M.; Jones, D. I.

    2011-01-10

    Employing data collected during the first 25 months of observations by the Fermi-LAT, we describe and subsequently seek to model the very high energy (>300 MeV) emission from the central few parsecs of our Galaxy. We analyze the morphological, spectral, and temporal characteristics of the central source, 1FGL J1745.6-2900. The data show a clear, statistically significant signal at energies above 10 GeV, where the Fermi-LAT has angular resolution comparable to that of HESS at TeV energies. This makes a meaningful joint analysis of the data possible. Our analysis of the Fermi data (alone) does not uncover any statistically significant variability of 1FGL J1745.6-2900 at GeV energies on the month timescale. Using the combination of Fermi data on 1FGL J1745.6-2900 and HESS data on the coincident, TeV source HESS J1745-290, we show that the spectrum of the central gamma-ray source is inflected with a relatively steep spectral region matching between the flatter spectrum found at both low and high energies. We model the gamma-ray production in the inner 10 pc of the Galaxy and examine cosmic ray (CR) proton propagation scenarios that reproduce the observed spectrum of the central source. We show that a model that instantiates a transition from diffusive propagation of the CR protons at low energy to almost rectilinear propagation at high energies can explain well the spectral phenomenology. We find considerable degeneracy between different parameter choices which will only be broken with the addition of morphological information that gamma-ray telescopes cannot deliver given current angular resolution limits. We argue that a future analysis performed in combination with higher-resolution radio continuum data holds out the promise of breaking this degeneracy.

  15. Effects of feeding different levels of corn steep liquor on the performance of fattening lambs.

    PubMed

    Azizi-Shotorkhoft, A; Sharifi, A; Mirmohammadi, D; Baluch-Gharaei, H; Rezaei, J

    2016-02-01

    This study was conducted to assess the effect of feeding corn steep liquor (CSL) on in vivo digestibility, ruminal pH, ammonia and hydrolytic enzyme activities, blood metabolites, feed intake (FI) and growth performance in fattening lambs. The CSL is a by-product of wet milling process of maize starch industry. The crude protein (CP), rumen-degradable protein (RDP), lactic acid and metabolisable energy contents of this by-product were 420, 324, 200 g/kg dry matter (DM) and 12.6 MJ/kg DM respectively. Twenty-seven male Moghani lambs were assigned randomly into three groups of nine lambs each in a completely randomised design. Three iso-energetic and iso-nitrogenous diets containing different levels (0, 50 or 100 g/kg dry matter) of CSL were offered ad libitum three times a day. Forage to concentrate ratio of the diets was 30:70. With inclusion of CSL in diet, the contents of canola meal, fish meal, wheat bran, corn grain and sugar beet pulp were decreased. The contents of DM, ash-free neutral detergent fibre (NDFom), ether extract, starch, Ca and S were numerically lower, but soluble protein, RDP and non-fibre carbohydrates were greater in the diets containing CSL in comparison with the control diet. The lambs fed with the diets containing CSL had lower [linear (L), p < 0.06] digestibility coefficients of DM and NDFom as compared to those fed with the diet free of CSL. Ruminal ammonia-N concentration increased (L, p < 0.05), but pH decreased (L, p < 0.05) with raising CSL level in diet. Carboxymethyl cellulase and filter paper-degrading activities decreased (L, p < 0.05), while proteases activity increased (L, p < 0.05) as dietary rates of CSL increased. Microcrystalline cellulase and ɑ-amylase activities were similar among the treatments. Within blood metabolites, only urea-N concentration increased (L, p < 0.05) in the lambs receiving CSL as compared to those fed with diet without CSL. Dietary inclusion of CSL resulted in linear decreases (L, p < 0.05) in the

  16. Laboratory Experiments of Tsunami Inundation in Patchy Coastal Forest on a Steep Beach

    NASA Astrophysics Data System (ADS)

    Irish, J. L.; Weiss, R.; Yang, Y.; Zainali, A.; Marivela Colmenarejo, R.

    2014-12-01

    Tsunamis are a leading natural threat to coastal communities, and events such as the 2011 Japan and 2004 Indian Ocean tsunamis caused widespread, crippling damages to coastal infrastructure. Yet, these events also called attention to the role of coastal forest as sustainable mitigation against tsunami hazard. Here, we present large-scale experiments of tsunami runup and withdrawal on a steeply sloping beach in the presence of patchy forest. The forest is modeled using 1.2-m diameter macro-roughness patches of varying resistance were constructed from staggered arrays of 2.7-cm diameter rigid cylinders. Macro-roughness patches were affixed in a staggered arrangement with mean spacing of 3.2 m between patches (Fig. 1). The basin depth and wave height at the wavemaker were 0.73 m and 0.43 m, respectively, such that a broken roller formed offshore of the still-water line. Point measurements of velocity and flow depth were made at twenty locations using co-located acoustic Doppler velocimeters and sonic wave gauges, respectively, in order to construct a flow field in the vicinity of three macro-roughness patches. Simultaneous, high-resolution video was also collected in order to track the runup bore position in time. Analysis of mean flow conditions reveals that patchy roughness induces non-uniform changes in momentum flux throughout the patch array (Fig. 2). During runup, momentum flux is generally reduced in the lee of the patches. However, flow channelization between cross-shore rows of patches leads to an increase in momentum flux. During withdrawal, the strong gravity-driven flows that develop as a result of the steep 1:10 beach lead to an increase in momentum flux in areas behind the patches, which benefited from reduced momentum flux during runup. The experiment findings indicate that flow interactions with the natural environment are indeed complex and that care must be exercised when considering the use of coastal forest as a tsunami bioshield. Acknowledgements

  17. Ridge-Runnel and Swash Dynamics Field Experiment on a Steep Meso-Tidal Beach

    NASA Astrophysics Data System (ADS)

    Figlus, J.; Chardon-Maldonado, P.; Puleo, J. A.

    2014-12-01

    Ridge-runnel (RR) systems are morphological features that may form in the intermittently wet and dry zone of the beach immediately after storm events. Their onshore migration provides a natural way of recovery for an eroded beach but the detailed swash interactions and complex feedback mechanisms between wave dynamics, sediment transport and profile evolution are not well understood and challenging to measure in-situ. During a storm, elevated water levels and large waves can significantly erode the beach profile in a matter of hours through offshore-directed sediment transport. The beach recovery process, on the other hand, occurs over a much longer time period during less intense wave conditions. In the beginning of this 3-week field campaign at South Bethany Beach, Delaware, a Nor'easter, eroded significant portions of this steep, meso-tidal beach and formed a pronounced RR system which then evolved during the less energetic conditions after the storm. An extensive cross-shore array of sensors was installed immediately after the storm measuring near-bed velocity profiles (5 Nortek Vectrino Profilers) and horizontal velocities (6 Sontec Electromagnetic Current Meters; 1 side-looking Nortek Vectrino) suspended sediment concentrations (10 Optical Backscatter Sensors OBS-3+), and pressure fluctuations (7 GE Druck pressure transducers) in the swash zone. Dense topography surveys of the RR system were conducted twice a day during low tide conditions with a Leica RTK GPS rover system. In addition, sediment grab samples along the entire RR cross-section were collected daily. An offshore ADCP with surface wave tracking capability (Nortek 2MHz AWAC AST) measured directional wave spectra and current profiles at a water depth of approximately 6m. The RR system showed rapid onshore migration over the two tide cycles immediately after the storm, followed by a period of vertical ridge accretion of up to 3 ft at certain locations. A first look at the collected data and analysis

  18. Geomorphic Responses to Check-Dam Removal on a Steep Mountain River in Taiwan

    NASA Astrophysics Data System (ADS)

    Wang, H. W.; Kuo, W. C.

    2014-12-01

    dams in Taiwan are located in steep mountainous area with highly variable hydrologic condition, we anticipate the observations will help enhancing future similar dam removal projects.

  19. Quantifying the Temporal and Spatial Response of Channel Steepness to Changes in Rift Basin Architecture

    NASA Astrophysics Data System (ADS)

    Robinson, Scott M.

    Quantifying the temporal and spatial evolution of active continental rifts contributes to our understanding of fault system evolution and seismic hazards. Rift systems also preserve robust paleoenvironmental records and are often characterized by strong climatic gradients that can be used to examine feedbacks between climate and tectonics. In this thesis, I quantify the spatial and temporal history of rift flank uplift by analyzing bedrock river channel profiles along footwall escarpments in the Malawi segment of the East Africa Rift. This work addresses questions that are widely applicable to continental rift settings: (1) Is rift-flank uplift sufficiently described by theoretical elliptical along-fault displacement patterns? (2) Do orographic climate patterns induced by rift topography affect rift-flank uplift or morphology? (3) How do uplift patterns along rift flanks vary over geologic timescales? In Malawi, 100-km-long border faults of alternating polarity bound half-graben sedimentary basins containing up to 4km of basin fill and water depths up to 700m. Orographically driven precipitation produces climatic gradients along footwall escarpments resulting in mean annual rainfall that varies spatially from 800 to 2500 mm. Temporal oscillations in climate have also resulted in lake lowstands 500 m below the modern shoreline. I examine bedrock river profiles crossing the Livingstone and Usisya Border Faults in northern Malawi using the channel steepness index (Ksn) to assess importance of these conditions on rift flank evolution. River profiles reveal a consistent transient pattern that likely preserves a temporal record of slip and erosion along the entire border fault system. These profiles and other topographic observations, along with known modern and paleoenvironmental conditions, can be used to interpret a complete history of rift flank development from the onset of rifting to present. I interpret the morphology of the upland landscape to preserve the onset

  20. Modelling the TSZ power spectrum

    SciTech Connect

    Bhattacharya, Suman; Shaw, Laurie D; Nagai, Daisuke

    2010-01-01

    The structure formation in university is a hierarchical process. As universe evolves, tiny density fluctuations that existed in the early universe grows under gravitational instability to form massive large scale structures. The galaxy clusters are the massive viralized objects that forms by accreting smaller clumps of mass until they collapse under their self-gravity. As such galaxy clusters are the youngest objects in the universe which makes their abundance as a function of mass and redshift, very sensitive to dark energy. Galaxy clusters can be detected by measuring the richness in optical waveband, by measuring the X-ray flux, and in the microwave sky using Sunyaev-Zel'dovich (SZ) effect. The Sunyaev-Zel'dovich (SZ) effect has long been recognized as a powerful tool for detecting clusters and probing the physics of the intra-cluster medium. Ongoing and future experiments like Atacama Cosmology Telescope, the South Pole Telescope and Planck survey are currently surveying the microwave sky to develop large catalogs of galaxy clusters that are uniformly selected by the SZ flux. However one major systematic uncertainties that cluster abundance is prone to is the connection between the cluster mass and the SZ flux. As shown by several simulation studies, the scatter and bias in the SZ flux-mass relation can be a potential source of systematic error to using clusters as a cosmology probe. In this study they take a semi-analytic approach for modeling the intra-cluster medium in order to predict the tSZ power spectrum. The advantage of this approach is, being analytic, one can vary the parameters describing gas physics and cosmology simultaneously. The model can be calibrated against X-ray observations of massive, low-z clusters, and using the SZ power spectrum which is sourced by high-z lower mass galaxy groups. This approach allows us to include the uncertainty in gas physics, as dictated by the current observational uncertainties, while measuring the cosmological

  1. Spectrum formation in superluminous supernovae (Type I)

    NASA Astrophysics Data System (ADS)

    Mazzali, P. A.; Sullivan, M.; Pian, E.; Greiner, J.; Kann, D. A.

    2016-06-01

    The near-maximum spectra of most superluminous supernovae (SLSNe) that are not dominated by interaction with a H-rich circum-stellar medium (SLSN-I) are characterized by a blue spectral peak and a series of absorption lines which have been identified as O II. SN 2011kl, associated with the ultra-long gamma-ray burst GRB111209A, also had a blue peak but a featureless optical/ultraviolet (UV) spectrum. Radiation transport methods are used to show that the spectra (not including SN 2007bi, which has a redder spectrum at peak, like ordinary SNe Ic) can be explained by a rather steep density distribution of the ejecta, whose composition appears to be typical of carbon-oxygen cores of massive stars which can have low metal content. If the photospheric velocity is ˜10 000-15 000 km s-1, several lines form in the UV. O II lines, however, arise from very highly excited lower levels, which require significant departures from local thermodynamic equilibrium to be populated. These SLSNe are not thought to be powered primarily by 56Ni decay. An appealing scenario is that they are energized by X-rays from the shock driven by a magnetar wind into the SN ejecta. The apparent lack of evolution of line velocity with time that characterizes SLSNe up to about maximum is another argument in favour of the magnetar scenario. The smooth UV continuum of SN 2011kl requires higher ejecta velocities (˜20 000 km s-1): line blanketing leads to an almost featureless spectrum. Helium is observed in some SLSNe after maximum. The high-ionization near-maximum implies that both He and H may be present but not observed at early times. The spectroscopic classification of SLSNe should probably reflect that of SNe Ib/c. Extensive time coverage is required for an accurate classification.

  2. The CMBR spectrum

    SciTech Connect

    Stebbins, A.

    1997-05-01

    Here we give an introduction to the observed spectrum of the Cosmic Microwave Background Radiation (CMBR) and discuss what can be learned about it. Particular attention will be given to how Compton scattering can distort the spectrum of the CMBR. An incomplete bibliography of relevant papers is also provided.

  3. Fission Spectrum Related Uncertainties

    SciTech Connect

    G. Aliberti; I. Kodeli; G. Palmiotti; M. Salvatores

    2007-10-01

    The paper presents a preliminary uncertainty analysis related to potential uncertainties on the fission spectrum data. Consistent results are shown for a reference fast reactor design configuration and for experimental thermal configurations. However the results obtained indicate the need for further analysis, in particular in terms of fission spectrum uncertainty data assessment.

  4. Fetal Alcohol Spectrum Disorder

    ERIC Educational Resources Information Center

    Caley, Linda M.; Kramer, Charlotte; Robinson, Luther K.

    2005-01-01

    Fetal alcohol spectrum disorder (FASD) is a serious and widespread problem in this country. Positioned within the community with links to children, families, and healthcare systems, school nurses are a critical element in the prevention and treatment of those affected by fetal alcohol spectrum disorder. Although most school nurses are familiar…

  5. Modeling step-pool systems in steep streams by a cellular automaton sandpile model

    NASA Astrophysics Data System (ADS)

    Saletti, M.; Molnar, P.; Hassan, M. A.; Zimmermann, A. E.; Fraccarollo, L.

    2013-12-01

    downstream end. We parameterize the key processes of grain blocking, the formation of step structures, and their hydraulic-driven collapse by simple intuitive rules. The local interactions in our model, although based on a few simple rules, lead to a complex dynamics, showing fluctuations in sediment transport rates and bed morphology that are typical of natural steep streams (and many physical systems close to a critical state). We compare the results of our model with flume and field data to show how these fluctuations appear in nature as well. References Bak, P., Tang, C., & Weisenfeld, K. (1988). Self-organized criticality. Physical Review A, 38. Church, M., & Zimmermann, A. (2007). Form and stability of step-pool channels: Research progress. Water Resources Research, 43, 1-21. Curran, J. C. (2007). Step - pool formation models and associated step spacing. Earth Surface Processes and Landforms, 32, 1611-1627. Zimmermann, A., Church, M., & Hassan, M. A. (2010). Step-pool stability: Testing the jammed state hypothesis. Journal of Geophysical Research, 115(F2).

  6. Hillslope-channel coupling in a steep Hawaiian catchment accelerates erosion rates over 100-fold

    NASA Astrophysics Data System (ADS)

    Stock, J. D.; Hanshaw, M. N.; Rosener, M.; Schmidt, K. M.; Brooks, B. A.; Tribble, G.; Jacobi, J.

    2009-12-01

    In tropical watersheds, hillslope changes are producing increasing amounts of fine sediment that can be quickly carried to reefs by channels. Suspended sediment concentrations off the reefs of Molokai, Hawaii, chronically exceed a toxic level of 10 mg/L, threatening reef ecosystems. We hypothesize that historic conversion of watersheds from soil creep to overland flow erosion increased both magnitude and frequency of sediment flooding adjacent reefs. We combined surficial and ecological mapping, hillslope and stream gages, and novel sensors to locate, quantify and model the generation of fine sediments polluting the Molokai reef. Ecological and geomorphic mapping from LiDAR and multi-spectral imagery located a subset of overland flow areas with vegetation cover below a threshold value preventing erosion. Here, feral goat grazing exposed cohesive volcanic soils whose low matrix hydraulic conductivities (1-20 mm/hour) promote Horton overland flow erosion. We instrumented steep, barren hillslopes with soil moisture sensors, overland flow meters, Parshall flumes, ISCO sediment samplers, and a rain gage and conducted repeat Tripod LiDAR and infiltration tests. To characterize soil resistance here and elsewhere to overland flow erosion, we deployed a Cohesive Strength Meter (CSM) to simulate the stresses of flowing water. At the 13.5 km 2 watershed mouth we used a USGS stream gage and ISCO sediment sampler to estimate total load. Over 2 years, storms triggered overland flow during rainfall intensities above 10-15 mm/hr. Overland flow meters indicate such flows can be up to 3 cm deep, with a tendency to deepen downslope. CSM tests indicate that these depths are insufficient to erode soils where vegetation is dense, but far above threshold values of 2-3 mm depth for bare soil erosion. Sediment ratings curves for both hillslope and downstream catchment gages show strong clock-wise hysteresis during the first intense storms in the Fall, becoming linear later in the rainy

  7. Dense, gravity-driven granular-liquid flows down steep channels

    NASA Astrophysics Data System (ADS)

    Armanini, A.; Larcher, M.; Nucci, E.

    2011-12-01

    Debris flows are complex natural phenomena, characterized by a mixture of poorly sorted sediments and water driven by gravity. Depending on the size distribution, on the volume concentration of sediments and on the geometry and topography of the channel, flow conditions may be very different, ranging from very fast flows, dominated by granular collisions and by the turbulence on the liquid phase, to very slow and dense flows, dominated by the frictional contacts among the grains. To investigate the basic physics of debris flows, it is very useful to analyze the flow of a mixture of identical spherical particles saturated by water and driven by gravity down a steep channel in steady flow condition (Armanini et al. 2005). The flow presents three regions: an external one, near to the free surface, dominated by nearly instantaneous contacts among the particles (collisional regime), an internal region dominated by prolonged contacts among the particles (frictional regime) and a static bed in which the particles are immobile. The detailed vertical structure of this kind of flows was obtained by means of experiments carried out by Armanini et al. (2005) and Larcher et al. (2007). Armanini et al. (2009) analysed the stratification of rheological mechanisms inside the flow, focusing on the coexistence of frictional and collisional regimes, on the stress transmission inside the flow and on particles kinematics. In particular, it was observed that debris flows may show locally a typical intermittence of the flow regime, switching alternatively from frictional to collisional. While the rheology of the collisional layers is well described by the dense gas analogy (kinetic theory), a persuasive theoretical description of the frictional regime does not yet exist. A Coulombian scheme is often assumed, but this hypothesis is rather limitative because it requires a constant concentration or a distribution of particles concentration known a priori. An interesting scheme of this kind

  8. Displacement of RFID tracers in a steep mountain stream (Rio Cordon, Italy)

    NASA Astrophysics Data System (ADS)

    Rainato, Riccardo; Mao, Luca; Aristide Lenzi, Mario; Picco, Lorenzo

    2015-04-01

    The bedload transport plays a fundamental role in the mountain streams affecting several aspects as morphology and ecological status of the fluvial system, influencing fields as engineering, natural hazard and river management. The monitoring, assessment and quantification of this type of transport is not simple due to impulsive nature that distinguishes it. Moreover, in mountain streams the particle motion is strongly affected by the bed structures as well as by the highly heterogeneous bed material, acting especially through the hiding/exposure, consolidation and embedding effects. Thanks to the assumption that bedload transport may be understood as the result of random individual particle displacements, the sediment tracing method was widely employed in the last years. Such method allow to obtain precious data concerning sediment dynamic in mountain streams, improving the results obtainable by samplers, traps and permanent monitoring stations. In this work, the results obtained by two years of RFID tracers monitoring are presented. This typology of tracers was employed in a steep mountain stream in order to investigate the displacement due to different conditions of hydraulic forcing. The Rio Cordon (northeast Italy) is a typical alpine channel characterized by step-pool and riffle-pool morphology and by a mean slope equal to 13%. The catchment extended 5 km2 exhibits a nivo-pluvial runoff regime. Overall, 250 tracers were seeded in the channel bed, monitoring the travel distance along a study reach 318 m long. For this purpose a mobile antenna in combination with a laser rangefinder were used. The measurement campaign was carried out from 2013 to 2014, performing a survey every 2 months as well as after every flood event occurred. Following such approach 7 tracers monitoring were performed, reaching a mean tracers recovery rate of roughly 65%. During the study period the peak of flood discharges is ranged between 0.85 to 2.10 m3 s-1, therefore allowing to

  9. The optical-ultraviolet-gamma-ray spectrum of 3C 279

    NASA Technical Reports Server (NTRS)

    Netzer, Hagai; Kazanas, D.; Wills, Beverly J.; Wills, D.; Mingsheng, Han; Brotherton, M. S.; Baldwin, J. A.; Ferkand, G. J.; Browne, I. W. A.

    1994-01-01

    We have obtained spectrosocpy of the violently variable quasar 3C 279, simultaneous with gamma-ray observations, in 1992 April. Our combined optical (McDonald Observatory and Cerro Tololo InterAmerican Observatory (CTIO) and ultraviolet (HST) observations, made when the source was faint, show a very steep power-law continuum (F(sub nu) is proportional to nu(exp -1.95), and strong broad emission lines. This is the first time that the broad ultraviolet lines of this object have been measured, and we note several unusual properties of the spectrum. In particular, the profiles of C IV lambda 1549 and Mg II lambda 2798 are asymmetric, with very strong red wings, in contrast to the symmetic profiles of Ly alpha C III lambda 1909, and possible H-beta. The observed asymmetry cannot be explained by a simple outflow associted with the eruption of the source. In addition, the C IV lambda 1549/Ly-alpha and C III lambda 1909/Ly-alpha line intensity ratios are the largest we have observed in out Hubble Space Telescope (HST) sample of more than 30 radio-loud quasars, even though the C III llambda 1909/C IV lambda 1549 ratio is quite typical. 3C 279 was observed in the gamma-ray region by EGRET (Energetic Gamma-Ray Experiment Telescope) at the same time as our optical-ultraviolet observations. The extrapolated ultraviolet continuum falls nine orders of magnitude below the gamma-ray point and we show that this, combined with the optical UV continuum slope, is enough to rule out several synchtoyotron-self-Compton models suggested to explain the multiwavelength spectra of blazars.

  10. Mid-Infrared Observations of Class I/Flat-Spectrum Systems in Six Nearby Molecular Clouds

    NASA Astrophysics Data System (ADS)

    Haisch, Karl E., Jr.; Barsony, Mary; Ressler, Michael E.; Greene, Thomas P.

    2006-12-01

    We have obtained new mid-infrared observations of 65 Class I/flat-spectrum (FS) objects in the Perseus, Taurus, Chamaeleon I and II, ρ Ophiuchi, and Serpens dark clouds. These objects represent a subset of the young stellar objects (YSOs) from our previous near-infrared multiplicity surveys. We detected 45 out of 48 (94%) of the single sources, 16 out of 16 (100%) of the primary components, and 12 out of 16 (75%) of the secondary/triple components of the binary/multiple objects surveyed. One target, IRS 34, a 0.31" separation FS binary, remains unresolved at near-infrared wavelengths. The composite spectral energy distributions for all of our sample YSOs are either Class I or FS, and in 15 out of 16 multiple systems at least one of the individual components displays a Class I or FS spectral index. However, the occurrence of mixed pairings, such as FS with Class I, FS with Class II, and, in one case, an FS with a Class III (Cha I T33B), is suprisingly frequent. Such behavior is not consistent with that of multiple systems among T Tauri stars (TTSs), where the companion of a classical TTS also tends to be a classical TTS, although other mixed pairings have been previously observed among Class II YSOs. Based on an analysis of the spectral indices of the individual binary components, there appears to be a higher proportion of mixed Class I/FS systems (65%-80%) than that of mixed classical and weak-lined TTSs (25%-40%), demonstrating that the envelopes of Class I/FS systems are rapidly evolving during this evolutionary phase. In general, the individual binary/multiple components suffer very similar extinctions, Av, suggesting that most of the line-of-sight material is either in the foreground of the molecular cloud or circumbinary. We report the discovery of a steep spectral index secondary companion to ISO-Cha I 97, detected for the first time via our mid-infrared observations. In our previous near-infrared imaging survey of binary/multiple Class I and FS YSOs, ISO

  11. Consecutive combined response spectrum

    NASA Astrophysics Data System (ADS)

    Xu, Longjun; Zhao, Guochen; Liu, Qingyang; Xie, Yujian; Xie, Lili

    2014-12-01

    Appropriate estimates of earthquake response spectrum are essential for design of new structures, or seismic safety evaluation of existing structures. This paper presents an alternative procedure to construct design spectrum from a combined normalized response spectrum (NRSC) which is obtained from pseudo-velocity spectrum with the ordinate scaled by different peak ground amplitudes (PGA, PGV, PGD) in different period regions. And a consecutive function f( T) used to normalize the ordinates is defined. Based on a comprehensive study of 220 strong ground motions recorded during recent eleven large worldwide earthquakes, the features of the NRSC are discussed and compared with the traditional normalized acceleration, velocity and displacement response spectra (NRSA, NRSV, NRSD). And the relationships between ground amplitudes are evaluated by using a weighted mean method instead of the arithmetic mean. Then the NRSC is used to define the design spectrum with given peak ground amplitudes. At last, the smooth spectrum is compared with those derived by the former approaches, and the accuracy of the proposed spectrum is tested through an analysis of the dispersion of ground motion response spectra.

  12. Production of 1,3-propanediol by Clostridium beijerinckii DSM 791 from crude glycerol and corn steep liquor: Process optimization and metabolic engineering.

    PubMed

    Wischral, Daiana; Zhang, Jianzhi; Cheng, Chi; Lin, Meng; De Souza, Lucas Monteiro Galotti; Pessoa, Fernando L Pellegrini; Pereira, Nei; Yang, Shang-Tian

    2016-07-01

    1,3-Propanediol (1,3-PDO) production from crude glycerol, a byproduct from biodiesel manufacturing, by Clostridium beijerinckii DSM 791 was studied with corn steep liquor as an inexpensive nitrogen source replacing yeast extract in the fermentation medium. A stable, long-term 1,3-PDO production from glycerol was demonstrated with cells immobilized in a fibrous bed bioreactor operated in a repeated batch mode, which partially circumvented the 1,3-PDO inhibition problem. The strain was then engineered to overexpress Escherichia coli gldA encoding glycerol dehydrogenase (GDH) and dhaKLM encoding dihydroxyacetone kinase (DHAK), which increased 1,3-PDO productivity by 26.8-37.5% compared to the wild type, because of greatly increased specific growth rate (0.25-0.40h(-1) vs. 0.13-0.20h(-1) for the wild type). The engineered strain gave a high 1,3-PDO titer (26.1g/L), yield (0.55g/g) and productivity (0.99g/L·h) in fed-batch fermentation. Overexpressing GDH and DHAK was thus effective in increasing 1,3-PDO production from glycerol. PMID:27085150

  13. Determination of main categories of components in corn steep liquor by near-infrared spectroscopy and partial least-squares regression.

    PubMed

    Xiao, Xue; Hou, Yuanyuan; Du, Jun; Liu, Yang; Liu, Yanjie; Dong, Linyi; Liang, Qionglin; Wang, Yiming; Bai, Gang; Luo, Guoan

    2012-08-15

    Corn steep liquor (CSL) is an important raw material that has a high nutritional value and serves as a nitrogen source. This study aimed to develop a fast, versatile, cheap, and environmentally safe analytical method of quantifying the total acidity (TA) of CSL as well as its contents of dry matter (DM), total sugars (TS), total reducing sugars (TRS), total free amino acids (TFAA), total nitrogen (TN), and total sulfite (TSu). The near-infrared (NIR) spectroscopy measurements of 66 samples (22 batches) of CSL were analyzed by partial least-squares regression using several spectral preprocessing methods. Multivariate models developed in the NIR area showed good predictive abilities for DM, TA, TS, TRS, TFAA, TN, and TSu determination. These results confirm the feasibility of the multivariate spectroscopic approach as a replacement for expensive and time-consuming conventional chemical methods. Thus, a convenient and feasible method for the quality control of fermentation raw materials for food additives and fine chemicals, especially in CSL, is established. PMID:22838730

  14. Shuttle spectrum despreader

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The results of the spread spectrum despreader project are reported and three principal products are designed and tested. The products are, (1) a spread spectrum despreader breadboard, (2) associated test equipment consisting of a spectrum spreader and bit reconstruction/error counter and (3) paper design of a Ku-band receiver which would incorporate the despreader as a principal subsystem. The despreader and test set are designed for maximum flexibility. A choice of unbalanced quadriphase or biphase shift keyed data modulation is available. Selectable integration time and threshold voltages on the despreader further lend true usefulness as laboratory test equipment to the delivered hardware.

  15. Impact of change in erosion rate and landscape steepness on hillslope and fluvial sediments grain size in the Feather River basin (Sierra Nevada, California)

    NASA Astrophysics Data System (ADS)

    Attal, M.; Mudd, S. M.; Hurst, M. D.; Weinman, B.; Yoo, K.; Naylor, M.

    2015-03-01

    The characteristics of the sediment transported by rivers (e.g. sediment flux, grain size distribution - GSD) dictate whether rivers aggrade or erode their substrate. They also condition the architecture and properties of sedimentary successions in basins. In this study, we investigate the relationship between landscape steepness and the grain size of hillslope and fluvial sediments. The study area is located within the Feather River basin in northern California, and studied basins are underlain exclusively by tonalite lithology. Erosion rates in the study area vary over an order of magnitude, from >250 mm ka-1 in the Feather River canyon to <15 mm ka-1 on an adjacent low-relief plateau. We find that the coarseness of hillslope sediment increases with increasing hillslope steepness and erosion rates. We hypothesise that, in our soil samples, the measured 10-fold increase in D50 and doubling of the amount of fragments larger than 1 mm when slope increases from 0.38 to 0.83 m m-1 is due to a decrease in the residence time of rock fragments, causing particles to be exposed for shorter periods of time to processes that can reduce grain size. For slopes in excess of 0.7 m m-1, landslides and scree cones supply much coarser sediment to rivers, with D50 and D84 more than one order of magnitude larger than in soils. In the tributary basins of the Feather River, a prominent break in slope developed in response to the rapid incision of the Feather River. Downstream of the break in slope, fluvial sediment grain size increases, due to an increase in flow competence (mostly driven by channel steepening) as well as a change in sediment source and in sediment dynamics: on the plateau upstream of the break in slope, rivers transport easily mobilised fine-grained sediment derived exclusively from soils. Downstream of the break in slope, mass wasting processes supply a wide range of grain sizes that rivers entrain selectively, depending on the competence of their flow. Our results

  16. Impact of change in erosion rate and landscape steepness on hillslope and fluvial sediments grain size in the Feather River Basin (Sierra Nevada, California)

    NASA Astrophysics Data System (ADS)

    Attal, M.; Mudd, S. M.; Hurst, M. D.; Weinman, B.; Yoo, K.; Naylor, M.

    2014-10-01

    The characteristics of the sediment transported by rivers (e.g., sediment flux, grain size distribution - GSD -) dictate whether rivers aggrade or erode their substrate. They also condition the architecture and properties of sedimentary successions in basins. In this study, we investigate the relationship between landscape steepness and the grain size of hillslope and fluvial sediments. The study area is located within the Feather River Basin in Northern California, and studied basins are underlain exclusively by tonalite lithology. Erosion rates in the study area vary over an order of magnitude, from > 250 mm ka-1 in the Feather River canyon to < 15 mm ka-1 on an adjacent low relief plateau. We find that the coarseness of hillslope sediment increases with increasing hillslope steepness and erosion rates. We hypothesize that, in our soil samples, the measured ten-fold increase in D50 and doubling of the amount of fragments larger than 1 mm when slope increases from 0.38 to 0.83 m m-1 is due to a decrease in the residence time of rock fragments, causing particles to be exposed for shorter periods of time to processes that can reduce grain size. For slopes in excess of 0.7 m m-1, landslides and scree cones supply much coarser sediment to rivers, with D50 and D84 more than one order of magnitude larger than in soils. In the tributary basins of the Feather River, a prominent break in slope developed in response to the rapid incision of the Feather River. Downstream of the break in slope, fluvial sediment grain size increases, due to an increase in flow competence (mostly driven by channel steepening) but also by a change in sediment source and in sediment dynamics: on the plateau upstream of the break in slope, rivers transport easily mobilised fine-grained sediment derived exclusively from soils. Downstream of the break in slope, mass wasting processes supply a wide range of grain sizes that rivers entrain selectively, depending on the competence of their flow. Our

  17. The solar wind density spectrum near the Sun: Results from Voyager radio measurements

    SciTech Connect

    Coles, W.A.; Liu, W. ); Harmon, J.K.; Martin, C.L. )

    1991-02-01

    Spacecraft radio propagation data are analyzed to estimate the solar wind density fluctuation power spectrum across five decades of spatial wave number. The data were from radio science observations made during superior conjunctions of the Voyager 1 and Voyager 2 spacecrafts in 1979 and 1980. These data were analyzed to yield the wave structure function, a statistic which is related to, but obtained more readily than, the spectrum itself. Structure functions were obtained from a total of 28 observations spanning the heliocentric distance range 7-22 R{sub S}. Each structure function was a composite of two shorter segments estimated, respectively, from phase scintillation and spectral broadening analyses. The composite structure functions tend to be steep (approximately Kolmogorov) at large scales (10{sup 3}-10{sup 6} km) and nearly always show some flattening at smaller scales (10-100 km). The inflection between the steep and flatter regions is abrupt and occurs at scales of 100-300 km. Most of the structure functions also show some turnover at the very smallest scales. These results are in excellent agreement with the spectral shape model proposed by Coles and Harmon (1989). A few transients were seen in the Voyager data which were characterized by an overall increase in power at large scales and a steeping of the structure function at small scales. These transients were similar in appearance to transients reported earlier from Arecibo spectral broadening observations.

  18. 30 GHz observations of sources in the Very Small Array fields

    NASA Astrophysics Data System (ADS)

    Gawroński, M. P.; Peel, M. W.; Lancaster, K.; Battye, R. A.; Birkinshaw, M.; Browne, I. W. A.; Davies, M. L.; Davis, R. J.; Feiler, R.; Franzen, T. M. O.; Génova-Santos, R.; Kus, A. J.; Lowe, S. R.; Pazderska, B. M.; Pazderski, E.; Pooley, G. G.; Roukema, B. F.; Waldram, E. M.; Wilkinson, P. N.

    2010-08-01

    Small angular scale (high l) studies of cosmic microwave background (CMB) anisotropies require accurate knowledge of the statistical properties of extragalactic sources at cm-mm wavelengths. We have used a 30 GHz dual-beam receiver (One Centimetre Receiver Array prototype) on the Toruń 32-m telescope to measure the flux densities of 121 sources in Very Small Array fields selected at 15 GHz with the Ryle Telescope. We have detected 57 sources above a limiting flux density of 5 mJy, of which 31 sources have a flux density greater than 10 mJy, which is our effective completeness limit. From these measurements we derive a surface density of sources above 10 mJy at 30 GHz of 2.2 +/- 0.4 deg-2. This is consistent with the surface density obtained by Mason et al. who observed a large sample of sources selected at a much lower frequency (1.4 GHz). We have also investigated the dependence of the spectral index distribution on flux density by comparing our results with those for sources above 1 Jy selected from the Wilkinson Microwave Anisotropy Probe 22 GHz catalogue. We conclude that the proportion of steep spectrum sources increases with decreasing flux density, qualitatively consistent with the predictions of de Zotti et al. We find no evidence for an unexpected population of sources above our completeness limit of 10 mJy whose spectra rise towards high frequencies, which would affect our ability to interpret current high-resolution CMB observations at 30 GHz and above.

  19. Orbital motions and coherent structures in the internal tide on a steep shelf off the Pacific coast of Mexico

    NASA Astrophysics Data System (ADS)

    Filonov, Anatoliy; Konyaev, Konstantin

    2006-07-01

    Herein we discuss the results of a study of the structure, evolution and break-up of an internal tidal wave under conditions of a steep shelf with a slope close to that of the internal wave characteristic. Measurements were taken in Navidad Bay on Mexico's Pacific Coast. We demonstrate that, under the conditions of homogeneous density stratification, the internal tidal wave releases its energy and collapses due to resonant excitation in a sequence of third tidal harmonics. Those harmonics generate multiscale vertical bilateral steps that follow at regular intervals and feature coherent oscillations in the form of vertical jets that cover the entire water column.

  20. Sensitivity analysis of helicopter IMC decelerating steep approach and landing performance to navigation system parameters. [Instrument Meteorological Conditions

    NASA Technical Reports Server (NTRS)

    Karmali, M. S.; Phatak, A. V.; Bull, J. S.; Peach, L. L.; Demko, P. S.

    1984-01-01

    The present investigation is concerned with a sensitivity analysis of the Decelerated Steep Approach and Landing (DSAL) maneuver to on-board and ground-based navigation system parameters. The Instrument Meteorological Conditions (IMC) DSAL maneuver involves decelerating to zero range rate while tracking the localizer and glideslope. The considered study investigated the performance of the navigation systems using Constant Deceleration Profile (CDP) guidance and a six degrees glideslope trajectory. A closed-loop computer simulation of the UH1H helicopter DSAL system was developed for the sensitivity analysis. Conclusions on system performance parameter sensitivity are discussed.

  1. Detailed documentation of dynamic changes in water depth and surface velocity during large flood at steep mountain stream

    NASA Astrophysics Data System (ADS)

    Asano, Yuko; Uchida, Taro

    2015-04-01

    Understanding discharge capacity of the channel and changes in hydraulic property during large storms are essential for the flash flood prediction, however, those information are limited for the steep mountain channels because of complex nature of steep channels and lack of measured data. Thus, we aimed to obtain detailed water level and surface velocity data during large flood at steep mountain channel and document how complex channel morphology could affect water flows during large storms. We installed water level and surface velocity sensors at cascade and 10m downstream pool cross section of the cascade-pool channel at Aono Research Forest of the Arboricultural Research Institute of The University of Tokyo Forests, in Japan and measured for 1-minutes interval. We could obtain data for storm with total precipitation of 288 mm falling in 59 hours with maximum rainfall intensity of 25 mm/hr on relatively wet condition. During this storm, relative water depth increased from 0.35 to 1.57m and surface velocity increased from 0.35 to 4.15m/s. As expected, changes in water depth, surface velocity and velocity profiles were complex and even different between adjacent cascade and pool cross section. Changes in flow characteristics occurred fist at the cascade when discharge increased to some point, water was suddenly stagnated locally at the foot of the cascade. From this moment, water level increased remarkably but surface velocity and velocity profile stayed almost constant at the cascade cross section. Then, at the downstream pool, when most of rocks were submerged at the mean depth of 0.7m, surface velocity suddenly started to increase remarkably and velocity profile changed, as they might develop negative flow in the lower portion of the profile, but water level did not increase as much. When rainfall diminished, first, surface velocity markedly declined and velocity profile went back to original state at the pool, then submerged flows at the bottom of the cascade

  2. Determinants of peak discharge in steep mountain catchments - Case of the Rift Valley escarpment of Northern Ethiopia

    NASA Astrophysics Data System (ADS)

    Asfaha, Tesfaalem G.; Frankl, Amaury; Haile, Mitiku; Zenebe, Amanuel; Nyssen, Jan

    2015-10-01

    Peak discharge is an important hydrological parameter of mountain torrents. However, due to the flashy and destructive nature of their stream flows, it is usually difficult to understand the hydrological behavior of steep mountain catchments through direct measurements of discharges. In this study, 332 daily peak discharge events from 11 steep (0.27-0.65 m m-1) catchments (0.4-25 km2) were measured in three rainy seasons (2012-2014) with the objective of analyzing runoff response of steep mountain catchments in the western Rift Valley escarpment of Northern Ethiopia. Seven rain gauges were installed at different altitudes (1623-2851 m a.s.l.) in and nearby the catchments. Event peak discharges were calculated using the Manning's equation from daily measurements of maximum discharge height at 11 crest stage gauges. Percentages of land cover classes were detected from high resolution (0.6 m) Google Earth Imagery (February 1, 2014). Morphometric characteristics of the catchments were computed both from ASTER digital elevation model (DEM) and topographic maps. Correlation analysis between average daily precipitation (Pd) and peak discharge (Qp) showed strong positive relation (R2 = 0.32-0.94, P < 0.05) in all the catchments. Catchment-specific peak discharge coefficient (Cp) showed a strong decreasing relation with vegetation cover (R2 = 0.85, P < 0.01), relative distance of vegetation cover from the thalweg (R2 = 0.55, P < 0.01), combined index of vegetation cover and its relative distance from the thalweg (R2 = 0.76, P < 0.01), catchment length (R2 = 0.37, P < 0.05) and time of concentration (R2 = 0.43, P < 0.05). It was correlated positively with catchment slope gradient (R2 = 0.37, P < 0.05) and index of vegetation distribution (R2 = 0.45, P < 0.05). A stepwise multiple regression analysis revealed that 99% (P < 0.01) of the variability of catchment-specific peak discharge coefficient in the catchments can be predicted by vegetation cover and infiltration number

  3. Characterisation of a large aperture steep concave parabolic mirror using SASI based on auto-collimation theory

    NASA Astrophysics Data System (ADS)

    Liu, Bingcai; Li, Bing; Tian, Ailing; Yang, Haoyu; Gao, Fen; Chen, Lei

    2015-01-01

    To characterise a large aperture steep concave parabolic mirror, a new sub-aperture stitching interferometry measurement technology (SASI) based on auto-collimation is proposed. The principle of the stitching process is analysed, and the sub-aperture partitioning for a full aperture of a paraboloid is discussed. Next, the overlapped sampled points between sub-apertures are rectified through sampled points realigned in mesh grids. Finally, two experiments, the SASI based on auto-collimation and the full aperture test, were implemented for a parabolic mirror. The stitching result exhibits good agreement with the full-aperture result.

  4. Development of an optimal automatic control law and filter algorithm for steep glideslope capture and glideslope tracking

    NASA Technical Reports Server (NTRS)

    Halyo, N.

    1976-01-01

    A digital automatic control law to capture a steep glideslope and track the glideslope to a specified altitude is developed for the longitudinal/vertical dynamics of a CTOL aircraft using modern estimation and control techniques. The control law uses a constant gain Kalman filter to process guidance information from the microwave landing system, and acceleration from body mounted accelerometer data. The filter outputs navigation data and wind velocity estimates which are used in controlling the aircraft. Results from a digital simulation of the aircraft dynamics and the control law are presented for various wind conditions.

  5. Development of a digital guidance and control law for steep approach automatic landings using modern control techniques

    NASA Technical Reports Server (NTRS)

    Halyo, N.

    1979-01-01

    The development of a digital automatic control law for a small jet transport to perform a steep final approach in automatic landings is reported along with the development of a steady-state Kalman filter used to provide smooth estimates to the control law. The control law performs the functions of localizer and glides capture, localizer and glideslope track, decrab, and place. The control law uses the microwave landing system position data, and aircraft body-mounted accelerators, attitude and attitude rate information. The results obtained from a digital simulation of the aircraft dynamics, wind conditions, and sensor noises using the control law and filter developed are described.

  6. IRIS Spectrum Line Plot

    NASA Video Gallery

    This video shows a line plot of the spectrum. The spectra here are shown for various locations on the Sun. The changes in the movie are caused by differing physical conditions in the locations. Cre...

  7. Fetal Alcohol Spectrum Disorders

    MedlinePlus

    ... alcohol can cause a group of conditions called fetal alcohol spectrum disorders (FASDs). Effects can include physical and behavioral problems such ... alcohol syndrome is the most serious type of FASD. People with fetal alcohol syndrome have facial abnormalities, ...

  8. Quantum Spread Spectrum Communication

    SciTech Connect

    Humble, Travis S

    2010-01-01

    We demonstrate that spectral teleportation can coherently dilate the spectral probability amplitude of a single photon. In preserving the encoded quantum information, this variant of teleportation subsequently enables a form of quantum spread spectrum communication.

  9. A SSS spectrum of V574 Pup

    NASA Astrophysics Data System (ADS)

    Ness, J.-U.; Starrfield, S.; Schwarz, G.; Osborne, J. P.; Page, K. L.

    2007-12-01

    Two Swift XRT observations of V574 Pup were carried out on 2007 December 7 and 13 with exposure times of 6410 and 5450 seconds, respectively. The average count rate is 0.014±0.001 counts per second. All source photons were registered with energies below 1 keV and the spectrum is consistent with that of a supersoft X-ray source (SSS).

  10. A new principle of coherence in a synchrotron source

    NASA Astrophysics Data System (ADS)

    Singal, Ashok Kumar

    A synchrotron source with a random distribution of velocity vectors for radiating charges will assumedly have no systematic phase relation between radiation fields from individual charges and would thereby give rise to an incoherent emission. It is known that synchrotron radiation mechanism does not allow a MASER type coherent emission. Here we show that a partial coherence due to antenna mechanism can be inherently present in any compact synchrotron source. Synchrotron radiation at an observing frequency selectively arises from relativistic electrons having a narrow range of Lorentz factors and moving in a cone of a narrow opening angle with respect to the line of sight to the observer, and thus having similar velocity vectors. As we show, even opposite charges moving within the cone augment each others radiation fields, contrary to what may be normally expected. The coherence volume grows with wavelength λ as ∝λ^{3}, giving rise to the possibility of coherence occurring at wavelengths larger than a certain value λ_{p} in a source. The coherence resolves many long standing astrophysical problems where theoretical predictions were not borne out by the observational data. For example, the spectrum gets enhanced by a factor ∝λ^{3} in the self-absorbed region. This resolves the observational puzzle of a flat spectrum instead of the theoretical steep slope - known in literature as a ``cosmic conspiracy''. It further explains the brightness temperatures observed in space VLBI up to two orders of magnitude higher than the theoretical incoherent synchrotron limit ˜10^{11.5} K. A simple model for the variability, based on an injection of large number of particles resulting in coherence, explains the observed range of variability time scales (from less than a day to years) and the inferred extremely high brightness temperatures, up to ˜10^{18-19} K, millions of time more than the theoretical limit. Coherence also explains the correlation observed in the optical

  11. Spectrum of carbonaceous-chondrite fission xenon

    NASA Technical Reports Server (NTRS)

    Clayton, D. D.

    1976-01-01

    Estimations of the fission spectrum in xenon isotopes from the progenitor of the strange carbonaceous-chondrite xenon must take account of p-process nucleosynthesis if the latter is the source of anomalous Xe-124, 126. Sample calculations of the p-process yields illustrate the magnitude of the effect, which can greatly increase the estimated Xe-132 fission yield.

  12. MODELING COLLISIONAL CASCADES IN DEBRIS DISKS: STEEP DUST-SIZE DISTRIBUTIONS

    SciTech Connect

    Gaspar, Andras; Psaltis, Dimitrios; Rieke, George H.; Oezel, Feryal E-mail: dpsaltis@as.arizona.edu E-mail: fozel@as.arizona.edu

    2012-07-20

    We explore the evolution of the mass distribution of dust in collision-dominated debris disks, using the collisional code introduced in our previous paper. We analyze the equilibrium distribution and its dependence on model parameters by evolving over 100 models to 10 Gyr. With our numerical models, we confirm that systems reach collisional equilibrium with a mass distribution that is steeper than the traditional solution by Dohnanyi. Our model yields a quasi-steady-state slope of n(m) {approx} m{sup -1.88} [n(a) {approx} a{sup -3.65}] as a robust solution for a wide range of possible model parameters. We also show that a simple power-law function can be an appropriate approximation for the mass distribution of particles in certain regimes. The steeper solution has observable effects in the submillimeter and millimeter wavelength regimes of the electromagnetic spectrum. We assemble data for nine debris disks that have been observed at these wavelengths and, using a simplified absorption efficiency model, show that the predicted slope of the particle-mass distribution generates spectral energy distributions that are in agreement with the observed ones.

  13. The Her X-1 spectrum: A measure of the field near the magnetic poles of a neutron star

    NASA Technical Reports Server (NTRS)

    Boldt, E. A.; Holt, S. S.; Rothschild, R. E.; Serlemitsos, P. J.

    1975-01-01

    The steep high energy cutoff observed in the spectrum for Her X-1 was analyzed in terms of the severely modified Thomson scattering that dominates the radiative transfer in a highly magnetized plasma near the surface of a neutron star. The data indicate a field of about 1013 G near the magnetic poles and the stopping of accreting matter by nuclear collisions in the neighboring plasma.

  14. The Her X-1 spectrum - A measure of the field near the magnetic poles of a neutron star

    NASA Technical Reports Server (NTRS)

    Boldt, E. A.; Holt, S. S.; Rothschild, R. E.; Serlemitsos, P. J.

    1976-01-01

    The steep high energy cutoff observed in the spectrum for Her X-1 is analyzed in terms of the severely modified Thomson scattering that dominates the radiative transfer in a highly magnetized plasma near the surface of a neutron star. The data are shown to indicate a field of about 10 to the 13th G near the magnetic poles and the stopping of accreting matter by nuclear collisions in the neighboring plasma

  15. Steep spatial gradients of volcanic and marine sulfur in Hawaiian rainfall and ecosystems

    USGS Publications Warehouse

    Bern, Carleton R.; Chadwick, Oliver A.; Kendall, Carol; Pribil, Michael J.

    2015-01-01

    Sulfur, a nutrient required by terrestrial ecosystems, is likely to be regulated by atmospheric processes in well-drained, upland settings because of its low concentration in most bedrock and generally poor retention by inorganic reactions within soils. Environmental controls on sulfur sources in unpolluted ecosystems have seldom been investigated in detail, even though the possibility of sulfur limiting primary production is much greater where atmospheric deposition of anthropogenic sulfur is low. Here we measure sulfur isotopic compositions of soils, vegetation and bulk atmospheric deposition from the Hawaiian Islands for the purpose of tracing sources of ecosystem sulfur. Hawaiian lava has a mantle-derived sulfur isotopic composition (δ34S VCDT) of − 0.8‰. Bulk deposition on the island of Maui had a δ34S VCDT that varied temporally, spanned a range from + 8.2 to + 19.7‰, and reflected isotopic mixing from three sources: sea-salt (+ 21.1‰), marine biogenic emissions (+ 15.6‰), and volcanic emissions from active vents on Kilauea Volcano (+ 0.8‰). A straightforward, weathering-driven transition in ecosystem sulfur sources could be interpreted in the shift from relatively low (0.0 to + 2.7‰) to relatively high (+ 17.8 to + 19.3‰) soil δ34S values along a 0.3 to 4100 ka soil age-gradient, and similar patterns in associated vegetation. However, sub-kilometer scale spatial variation in soil sulfur isotopic composition was found along soil transects assumed by age and mass balance to be dominated by atmospheric sulfur inputs. Soil sulfur isotopic compositions ranged from + 8.1 to + 20.3‰ and generally decreased with increasing elevation (0–2000 m), distance from the coast (0–12 km), and annual rainfall (180–5000 mm). Such trends reflect the spatial variation in marine versus volcanic inputs from atmospheric deposition. Broadly, these results illustrate how the sources and magnitude of atmospheric deposition can exert controls

  16. A Bio-Realistic Analog CMOS Cochlea Filter With High Tunability and Ultra-Steep Roll-Off.

    PubMed

    Wang, Shiwei; Koickal, Thomas Jacob; Hamilton, Alister; Cheung, Rebecca; Smith, Leslie S

    2015-06-01

    This paper presents the design and experimental results of a cochlea filter in analog very large scale integration (VLSI) which highly resembles physiologically measured response of the mammalian cochlea. The filter consists of three specialized sub-filter stages which respectively provide passive response in low frequencies, actively tunable response in mid-band frequencies and ultra-steep roll-off at transition frequencies from pass-band to stop-band. The sub-filters are implemented in balanced ladder topology using floating active inductors. Measured results from the fabricated chip show that wide range of mid-band tuning including gain tuning of over 20 dB, Q factor tuning from 2 to 19 as well as the bio-realistic center frequency shift are achieved by adjusting only one circuit parameter. Besides, the filter has an ultra-steep roll-off reaching over 300 dB/dec. By changing biasing currents, the filter can be configured to operate with center frequencies from 31 Hz to 8 kHz. The filter is 9th order, consumes 59.5 ∼ 90.0 μW power and occupies 0.9 mm2 chip area. A parallel bank of the proposed filter can be used as the front-end in hearing prosthesis devices, speech processors as well as other bio-inspired auditory systems owing to its bio-realistic behavior, low power consumption and small size. PMID:25099631

  17. Analysing, quantifying and modelling soil erosion on steep hillslopes in different climatic areas using LiDAR and SFM DEMs

    NASA Astrophysics Data System (ADS)

    Neugirg, Fabian; Haas, Florian; Kaiser, Andreas; Schmidt, Jürgen; Becht, Michael

    2014-05-01

    Soil erosion is a worldwide well known problem and has therefore been subject to various scientific studies, especially on agricultural areas. However soil erosion on steep hillslopes in mountainous drainage basins can be a threat to human infrastructure as it supplies material, e.g. for debris flows to torrents. The study presented here aims to analyse, quantify and model soil erosion on (very) steep hillslopes free of vegetation in different climatic areas ranging from South Germany to Central Italy. Multitemporal digital elevation models were acquired with terrestrial laserscanning and from terrestrial and aerial structure from motion-based imagery. Analysis of erosion is mainly based on slope wash and rill erosion during summer months as well as erosion through freezing and melting processes during winter months in catchments of the Bavarian Alps. Erosional processes in the Mediterranean are mainly controlled by different precipitation regimes throughout the year. Annual erosion and accumulation rates are quantified and used for modelling purposes. First results of the presented project show, that the amount of material eroded is mainly controlled by the size of the sediment contributing area. However there are also other controlling factors, such as slope angle, slope length and vegetation cover which are investigated within this project.

  18. Channel processes following land use changes in a degrading steep headwater stream in North Island, New Zealand

    NASA Astrophysics Data System (ADS)

    Kasai, Mio

    2006-11-01

    In headwater streams in steep land settings, narrow and steep valley floors provide closely coupled relationships between geomorphic components including hillslopes, tributary fans, and channel reaches. These relationships together with small catchment sizes result in episodic changes to the amount of stored sediment in channels. Major sediment inputs follow high magnitude events. Subsequent exponential losses via removal of material can be represented by a relaxation curve. The influence of hillslope and tributary processes on relaxation curves, and that of altered coupling relations between components, were investigated along a 1.3 km reach of a degrading channel in the 4.8 km 2 Weraamaia Catchment, New Zealand. Extensive deforestation in the late 19th and early 20th centuries, followed by invasion of scrubs and reforestation, induced changes to major erosion types from gully complexes to shallow landslides. Changes in the size and pattern of sediment slugs from 1938 to 2002 were analysed from air photographs tied to detailed field measurement. The rate and calibre of sediment flux changed progressively following substantive hillslope input in a storm in 1938. Subsequently, the channel narrowed and incised, decoupling tributary fans from the main stem, thereby scaling down the size of sediment slugs. As a consequence, the dominant influence on the behaviour of sediment slugs and associated relaxation processes, changed from tributary fans to the type and distribution of bedrock outcrops along the reach.

  19. River profile controls on channel morphology, debris flow disturbance, and the spatial extent of salmonids in steep mountain streams

    NASA Astrophysics Data System (ADS)

    May, Christine L.; Lisle, Thomas E.

    2012-12-01

    In the geologically and topographically diverse mountain ranges of the Pacific Northwest, a broad-scale means of prioritizing salmonid habitat conservation areas based on geomorphic process domains is examined. We propose that steepness and concavity indices derived from the relation between drainage area and channel slope provide a means of identifying basins that express different reach-scale morphologies, fish habitat capacity, and risk of episodic disturbance. Strongly concave river profiles that develop in mountainous terrain indicate that almost all of the relief in the drainage network occurs in headwater streams. In these basins a large proportion of the channel network has low-gradient morphologies, which provide favorable habitat for many salmonid species. The severity of pulse disturbances is also reduced because low-gradient main stem channels inhibit debris flow conveyance, and in these networks the distribution of fish can expand into tributaries, allowing for a spatial spreading of risk. In contrast, rivers with poorly concave or steeper profiles have a greater abundance of high gradient reaches that limit the distribution of fish to a small portion of the channel network and facilitate debris flow-passage. The combined influence of a limited spatial distribution of fish and an increased risk of debris flows may cause populations in these basins to be less resilient to pulse disturbances. A case example from the Klamath Mountains, an area with broad variation in the steepness and concavity of river profiles, was used to develop this approach and aid conservation planning for imperiled populations of anadromous salmonids.

  20. The role of log jams and exceptional flood events in mobilizing coarse particulate organic matter in a steep headwater stream

    NASA Astrophysics Data System (ADS)

    Jochner, M.; Turowski, J. M.; Badoux, A.; Stoffel, M.; Rickli, C.

    2015-07-01

    Coarse particulate organic matter (CPOM) fulfills important functions in the physical and ecological system of a stream. CPOM delivery to and export from the stream has implications for the stream's morphology and sediment transport capacity as well as the energy budget and food availability. Export rates of CPOM from mountain catchments have been observed to strongly increase with rising discharge, but the mechanism leading to this strong relationship is unclear. Here, we show that log jams in the Erlenbach, a steep headwater stream in the Swiss Prealps, are an effective barrier for the transport of CPOM pieces, and thus become sites of storage of large quantities of material over time. Exceptional discharge events with return periods exceeding 20 years play a dual role in CPOM transport in the Erlenbach. First, they appear to destroy existing log jams, releasing the stored material (wood and sediment). Second, they intensify channel-hillslope coupling, thereby recruiting new logs to the channel, around which new jams can form. This allows for the formulation of a new, fully episodic end-member in a four-end-member model of CPOM dynamics of steep mountain streams based on wood delivery and export.

  1. Electrical spectrum analysis of operating Hydro Electric machines

    NASA Astrophysics Data System (ADS)

    Timperley, J. E.

    1981-12-01

    The electrical spectrum analysis of the operation of five pumped storage machines is discussed. It was found that machines without electrical problems produced little radio noise, although all machines produced some noise. Severe problems produced severe radio noise. If stator deterioration increases, the noise level increases. Similar machines produce similar electrical spectrum signatures. The general source of discharges can be located. A likelihood of failure can be calculated from spectrum analysis.

  2. Micro acoustic spectrum analyzer

    DOEpatents

    Schubert, W. Kent; Butler, Michael A.; Adkins, Douglas R.; Anderson, Larry F.

    2004-11-23

    A micro acoustic spectrum analyzer for determining the frequency components of a fluctuating sound signal comprises a microphone to pick up the fluctuating sound signal and produce an alternating current electrical signal; at least one microfabricated resonator, each resonator having a different resonant frequency, that vibrate in response to the alternating current electrical signal; and at least one detector to detect the vibration of the microfabricated resonators. The micro acoustic spectrum analyzer can further comprise a mixer to mix a reference signal with the alternating current electrical signal from the microphone to shift the frequency spectrum to a frequency range that is a better matched to the resonant frequencies of the microfabricated resonators. The micro acoustic spectrum analyzer can be designed specifically for portability, size, cost, accuracy, speed, power requirements, and use in a harsh environment. The micro acoustic spectrum analyzer is particularly suited for applications where size, accessibility, and power requirements are limited, such as the monitoring of industrial equipment and processes, detection of security intrusions, or evaluation of military threats.

  3. Goldstone radio spectrum signal identification, March 1980 - March 1982

    NASA Technical Reports Server (NTRS)

    Gaudian, B. A.

    1982-01-01

    The signal identification process is described. The Goldstone radio spectrum environment contains signals that are a potential source of electromagnetic interference to the Goldstone tracking receivers. The identification of these signals is accomplished by the use of signal parameters and environment parameters. Statistical data on the Goldstone radio spectrum environment from 2285 to 2305 MHz are provided.

  4. Broad spectrum solar cell

    DOEpatents

    Walukiewicz, Wladyslaw; Yu, Kin Man; Wu, Junqiao; Schaff, William J.

    2007-05-15

    An alloy having a large band gap range is used in a multijunction solar cell to enhance utilization of the solar energy spectrum. In one embodiment, the alloy is In.sub.1-xGa.sub.xN having an energy bandgap range of approximately 0.7 eV to 3.4 eV, providing a good match to the solar energy spectrum. Multiple junctions having different bandgaps are stacked to form a solar cell. Each junction may have different bandgaps (realized by varying the alloy composition), and therefore be responsive to different parts of the spectrum. The junctions are stacked in such a manner that some bands of light pass through upper junctions to lower junctions that are responsive to such bands.

  5. NREL Spectrum of Innovation

    ScienceCinema

    None

    2013-05-29

    There are many voices calling for a future of abundant clean energy. The choices are difficult and the challenges daunting. How will we get there? The National Renewable Energy Laboratory integrates the entire spectrum of innovation including fundamental science, market relevant research, systems integration, testing and validation, commercialization and deployment. The innovation process at NREL is interdependent and iterative. Many scientific breakthroughs begin in our own laboratories, but new ideas and technologies come to NREL at any point along the innovation spectrum to be validated and refined for commercial use.

  6. Bottomonium spectrum revisited

    NASA Astrophysics Data System (ADS)

    Segovia, Jorge; Ortega, Pablo G.; Entem, David R.; Fernández, Francisco

    2016-04-01

    We revisit the bottomonium spectrum motivated by the recently exciting experimental progress in the observation of new bottomonium states, both conventional and unconventional. Our framework is a nonrelativistic constituent quark model which has been applied to a wide range of hadronic observables from the light to the heavy quark sector, and thus the model parameters are completely constrained. Beyond the spectrum, we provide a large number of electromagnetic, strong and hadronic decays in order to discuss the quark content of the bottomonium states and give more insights about a better way to determine their properties experimentally.

  7. Improving VHF Spectrum Utilization

    NASA Technical Reports Server (NTRS)

    Andro, Monty; Orr, Richard; Foore, Larry; Sheehe, Charles; Freeman, Mark; Nguyen, Thanh; Bretmersky, Steven; Laberge, Chuck; Buchanan, David

    2004-01-01

    Limited VHF communications system capacity and increasing air traffic results in congestion of the aviation VHF spectrum. The voice communications errors and delayed channel access create system congestion and air traffic delays. Regulatory subdivision of bands for specific functions limits flexibility in the frequency usage. The objective of this viewgraph presentation is to identify near/mid/far term technologies to improve the performance and spectrum efficiency of current and emerging VHF communications systems. Select technologies with the highest potential, perform research and development to bring them to implementation stage.

  8. Unveiling Unidentified Fermi Sources

    NASA Astrophysics Data System (ADS)

    Zhang, Lizhong; South Pole Telescope

    2016-01-01

    The Fermi γ-ray Space Telescope (Fermi) has surveyed the entire sky at the highest-energy band of the electromagnetic spectrum. The majority of Fermi sources have counterpart identifications from multi-wavelength large-area surveys, particularly in the radio and x-ray bands. However, around 35% of Fermi sources remain unidentified, a problem exasperated by the low resolution of the telescope. Understanding the nature of unidentified Fermi sources is one of the most pressing problems in γ-ray astronomy. The South Pole Telescope (SPT) has completed a survey covering a 2500 square degrees of the southern extragalactic sky with arcminute resolution at millimeter wavelengths. The mm wavelength is the most efficient means to identify blazars and unidentified Fermi sources. Our analysis shows that the SPT point source catalog provides candidate associations for 40% of the unidentified Fermi sources, showing them to be flat-spectrum radio quasars which are extraordinarily bright at millimeter (mm) wavelengths.

  9. Feeding rolled barley grain steeped in lactic acid modulated energy status and innate immunity in dairy cows.

    PubMed

    Iqbal, S; Zebeli, Q; Mazzolari, A; Dunn, S M; Ametaj, B N

    2010-11-01

    Feeding dairy cows large proportions of cereal grain is commonly associated with rumen acidosis, activation of innate immunity, and perturbation of intermediary metabolism. We previously showed that steeping barley grain in 0.5% lactic acid (LA) decreased the rate of starch degradation, lowered the risk of subacute rumen acidosis, modulated rumen fermentation profile, and increased milk fat content in dairy cows. This study sought to investigate whether feeding of LA-treated barley grain would affect carbohydrate and lipid metabolism as well as innate immunity. Eight rumen-fistulated late-lactation (approximately 217 d in milk, DIM) Holstein cows were randomly assigned, in a 2 × 2 crossover design, to 1 of the 2 dietary treatments consisting of 27% (dry matter basis) rolled barley grain steeped for 48 h in an equal volume (wt/vol) of tap water (CTR) or 0.5% LA (TRT). Each experimental period lasted 21 d, with the first 11 d for diet adaptation. Blood and rumen samples were collected on d 12, 15, 17, and 21 of the experimental period before the morning feeding to evaluate the effects of dietary treatment on preprandial day-to-day variation of plasma and rumen variables. To establish the effect of treatment on diurnal variation of plasma variables, blood samples were collected on the last day of each period at 0, 2, 4, 6, 8, 10, and 12h after the morning feeding (i.e., 0800 h). Results of the day-to-day study showed that cows fed the TRT diet had greater overall preprandial concentrations of glucose, cholesterol, and insulin, and a lower concentration of haptoglobin in plasma. Diurnal data indicated lower concentrations of haptoglobin and serum amyloid A and a tendency for greater plasma lactate in cows fed the TRT diet. A treatment by time interaction was observed for glucose, lactate, insulin, haptoglobin, and lipopolysaccharide-binding protein, suggesting a role for both the processing of grain and the time of sampling on those variables. No effect of diet on

  10. Spatio-temporal variability and rates of fluvial bedload transport in steep mountain catchments in western Norway

    NASA Astrophysics Data System (ADS)

    Beylich, Achim A.; Laute, Katja

    2014-05-01

    The timing and rate of fluvial bedload transport are of central importance within sediment budget studies and in many applications in river science and engineering. Bedload transport rates are very difficult to measure and, in many sites, only suspended load and solute data are included in sediment budget studies. During four years (2010 - 2013) detailed field measurements with portable impact sensors as a non-invasive technique for indirectly determining fluvial bedload transport intensity were conducted at several selected channel stretches within two instrumented and supply-limited drainage basin systems (Erdalen and Bødalen) in the steep fjord landscape in western Norway. The selected stream test stretches where impact sensor field measurements were conducted were located (i) downstream of steep channels in headwater areas of the two drainage basin systems Erdalen and Bødalen, (ii) downstream of selected stream channel segments with temporary in-channel storage of bedload material in Erdalen and Bødalen and (iii) at the outlets of the two drainage basin systems Erdalen and Bødalen. The collected impact sensor field data were calibrated with laboratory flume experiments and were combined with field data from continuous discharge monitoring, repeated surveys of channel morphometry and sediment texture, particle tracer measurements, Helley-Smith samplings, underwater videofilming and biofilm analyses. The combination of methods and techniques applied provides detailed insights into the spatio-temporal variability and rates of fluvial bedload transport within Erdalen and Bødalen. Fluvial bedload transport in steep headwater streams is strongly related to sediment delivery from slopes, especially through fluvial transfers in small creeks draining the slope systems and through snow avalanches in spring and debris flows in fall. Channel reaches with temporary in-channel storage of bedload material in the middle parts of the Erdalen and Bødalen drainage basin

  11. The shape of the primary cosmic ray electron spectrum above 10 GeV

    NASA Technical Reports Server (NTRS)

    Silverberg, R. F.; Ormes, J. F.; Balasubrahmanyan, V. K.

    1974-01-01

    A balloon borne measurement of the cosmic ray electron spectrum above 10 GeV is reported in which two new techniques have been used to remove proton background contamination. First, the depth of the spectrometer on one of the flights was more than 40 radiation lengths, enabling hadronically and electromagnetically induced cascades to be differentiated for a subset of the data. Second, electromagnetic cascade starting points were determined to within about 0.1 radiation lengths based upon a calibration with electrons from 5.4 to 18 GeV at the Stanford Linear Accelerator. The resulting spectrum, when fitted with a power law, is steep, but the fit is marginal. A significantly better fit is achieved by assuming a model in which the spectrum is steepening in the measured region.

  12. High Resolution observation of Ark 564: I. Time-average spectrum

    NASA Astrophysics Data System (ADS)

    Ramírez, J.; Komossa, S.

    2010-07-01

    We present an analysis of a 100 ks X-ray spectrum of the Narrow-Line Seyfert 1 Galaxy Ark 564, which we have taken with the Low Energy Transmission Grating Spectrometer (LETGS) on board the X-ray telescope Chandra. We fit several spectral continuum models to the time-averaged X-ray spectrum of this galaxy, and study the possible origin of the steep soft X-ray spectrum. Also, we characterize the average intrinsic absorption of the system, based on photoionization modeling. Using κ2-statistics, we compare several of these spectral models, and arrive at possible solutions for the description of (1) the intrinsic emission continuum, and (2) the intrinsic absorption of the system.

  13. The Frequency Spectrum Radio.

    ERIC Educational Resources Information Center

    Howkins, John, Ed.

    1979-01-01

    This journal issue focuses on the frequency spectrum used in radio communication and on the World Administrative Radio Conference, sponsored by the International Telecommunication Union, held in Geneva, Switzerland, in the fall of 1979. Articles describe the World Administrative Radio Conference as the most important radio communication conference…

  14. Battlefield spectrum management

    NASA Astrophysics Data System (ADS)

    Sivakumar, C.

    1997-06-01

    Modern tactical communications systems rely on radios to support network and user connectivity. One of the challenges for network planners and managers is to make best use of scarce and vulnerable frequency spectrum resources to support the communication needs of war fighters. With the wide variety of Iris radio types typically to be deployed in the battlefield (ranging from high frequency to super high frequency), a comprehensive suite of tools is necessary to ensure that frequency interference is kept minimum. Without a sophisticated frequency spectrum management system, the most advanced tactical communications systems could be rendered useless, jeopardizing human life and national security. For these reasons, it is important to develop an Iris wide battlefield spectrum management capability that takes full advantage of current frequency spectrum management research and development (R&D), related tools, and supporting technology for assigning frequencies. This session briefly describes various assignment strategies being adopted in the Iris BFSM for overcoming cosite/collocated/farsite interferences along with the propagation models [from high frequency (HF) to super high frequency (SHF)] used for the assignment of frequencies. Also a brief thread outlining the process for generating frequency allocation/assignment request and analysis of frequency interference is discussed.

  15. Charging for Spectrum Use.

    ERIC Educational Resources Information Center

    Geller, Henry; Lampert, Donna

    This paper, the third in a series exploring future options for public policy in the communications and information arenas, argues that the communications spectrum--e.g., public mobile service, private radio, and domestic satellites--is a valuable but limited resource that should benefit all Americans. After a background discussion, it is…

  16. Sinclair ZX Spectrum.

    ERIC Educational Resources Information Center

    Rodwell, Peter

    1982-01-01

    Describes and evaluates the hardware, software, peripheral devices, performance capabilities, and programing capacity of the Sinclair ZX Spectrum microcomputer. The computer's display system, its version of the BASIC programing language, its graphics capabilities, and the unique features of its data entry keyboard are discussed. (JL)

  17. Quenched hadron spectrum of QCD

    SciTech Connect

    Kim, Seyong

    1992-12-01

    We calculate hadron spectrum of quantum chromodynamics without dynamical fermions on a 32{sup 3} {times} 64 lattice volume at {beta} = 6.5. Using two different wall sources of staggered fermion whose mass is 0.01, 0.005 and 0.0025 under the background gauge configurations, we extract local light hadron masses and the {triangle} masses and compare these hadron masses with those from experiments. The numerical simulation is executed on the Intel Touchstone Delta computer. We employ multihit metropolis algorithm with over-relaxation method steps to update gauge field configuration and gauge field configuration are collected at every 1000 sweeps. After the gauge field configuration is fixed to Coulomb gauge, the conjugate gradient method is used for Dirac matrix inversion.

  18. Quenched hadron spectrum of QCD

    SciTech Connect

    Kim, Seyong.

    1992-12-01

    We calculate hadron spectrum of quantum chromodynamics without dynamical fermions on a 32[sup 3] [times] 64 lattice volume at [beta] = 6.5. Using two different wall sources of staggered fermion whose mass is 0.01, 0.005 and 0.0025 under the background gauge configurations, we extract local light hadron masses and the [triangle] masses and compare these hadron masses with those from experiments. The numerical simulation is executed on the Intel Touchstone Delta computer. We employ multihit metropolis algorithm with over-relaxation method steps to update gauge field configuration and gauge field configuration are collected at every 1000 sweeps. After the gauge field configuration is fixed to Coulomb gauge, the conjugate gradient method is used for Dirac matrix inversion.

  19. The role of log jams and exceptional flood events in mobilizing coarse particulate organic matter in a steep headwater stream

    NASA Astrophysics Data System (ADS)

    Jochner, M.; Turowski, J. M.; Badoux, A.; Stoffel, M.; Rickli, C.

    2015-02-01

    Export rates of coarse particulate organic matter (CPOM) from mountain catchments have been observed to strongly increase with rising discharge, but the mechanism leading to this strong relationship is unclear. Here, we show that log jams in the Erlenbach, a steep headwater stream in the Swiss Prealps, are an effective barrier for the transport of CPOM pieces, and thus become sites of storage of large quantities of material over time. Exceptional discharge events with return periods exceeding 20 years play a dual role in CPOM transport. First, they destroy existing log jams, releasing the stored material (wood and sediment). Second, they intensify channel-hillslope coupling, thereby recruiting new logs to the channel, around which new jams can form.

  20. Bed load transport in managed steep-gradient headwater streams of southeastern Alaska

    NASA Astrophysics Data System (ADS)

    Gomi, Takashi; Sidle, Roy C.

    2003-12-01

    Bed load transport was investigated in four headwater streams in southeastern Alaska subjected to different management and disturbance regimes. Bed load yield was positively correlated to peak discharge during the fall 1999 monitoring period. Fine bed load materials (1-11 mm) that were supplied from hillslope sources were equally mobilized during most storm events. Medium-sized bed materials (11-200 m) were only partially mobilized even during large storms, whereas large particles (>200 mm) were immobile and often formed interlocking channel structures. The transport distances of medium-size materials depended on amount of channel obstructions (e.g., woody debris) and sediment supply conditions; both of these factors were influenced by the occurrence of mass movement, timber harvesting, and the related recovery processes. The highest total bed load yield was observed in a channel affected by a debris flow in 1993. Total sediment yields are similar among channels with old-growth, clear cut (logged 4 years before monitoring), and young alder (affected by landslides and debris flows in 1961) riparian stands. By comparing the old-growth and young alder channels, it appears that bed load yield recovers from debris flow disturbances in about 40 years; however, recovery of channel conditions (e.g., reach types and woody debris) may take much longer. Effects of timber harvesting on bed load transport are controlled by sediment linkages between hillslopes and channels related to the occurrence of mass movement.

  1. Bedload Transport Rates and Flux Patterns in a Steep Montane Tropical River - Rio Pacuare, Costa Rica

    NASA Astrophysics Data System (ADS)

    Lind, P.; Fonstad, M. A.; McDowell, P. F.

    2015-12-01

    Humid tropical montane rivers convey large magnitude floods that have the potential to mobilize boulder-sized bed material multiple times during a year. In the montane reaches of the Rio Pacuare active boulder deposits with surface areas of up to 300 x 75 meters influence channel form throughout this otherwise hillslope/bedrock confined river. Therefore, rate of bedload sediment flux occurring within and between river segments and reaches provides insight into the geomorphic sensitivity of the system. The study area (78 km) is divided into five river segments based on channel slope and form. The intense discharge regimes of the Rio Pacuare are off-set by the plentiful sediment inputs sourced from upstream, tributaries, and hillslopes, resulting in a system that is predominantly transport-limited. This research presents bedload sediment transport rates and annual yields calculated at seven representative field sites distributed throughout the study area. Results indicate that the D50 and D84 grain-size fractions are mobilized frequently (annual rate is dependent on timing and frequency of precipitation events). Results also indicate that connectivity between river segments ranges from moderate to high, depending most directly on channel slope. This work utilized a unique mix of traditional grain-size analysis and sediment transport models combined with repeat photogrammetric Structure from Motion (SfM) surveys done pre and post flood event to verify grain size mobilization through high-resolution, 3-D modeling.

  2. Single-centre experience of retroperitoneoscopic approach in urology with tips to overcome the steep learning curve

    PubMed Central

    Srivastava, Aneesh; Sureka, Sanjoy Kumar; Vashishtha, Saurabh; Agarwal, Shikhar; Ansari, Md Saleh; Kumar, Manoj

    2016-01-01

    CONTEXT: The retroperitoneoscopic or retroperitoneal (RP) surgical approach has not become as popular as the transperitoneal (TP) one due to the steeper learning curve. AIMS: Our single-institution experience focuses on the feasibility, advantages and complications of retroperitoneoscopic surgeries (RS) performed over the past 10 years. Tips and tricks have been discussed to overcome the steep learning curve and these are emphasised. SETTINGS AND DESIGN: This study made a retrospective analysis of computerised hospital data of patients who underwent RP urological procedures from 2003 to 2013 at a tertiary care centre. PATIENTS AND METHODS: Between 2003 and 2013, 314 cases of RS were performed for various urological procedures. We analysed the operative time, peri-operative complications, time to return of bowel sound, length of hospital stay, and advantages and difficulties involved. Post-operative complications were stratified into five grades using modified Clavien classification (MCC). RESULTS: RS were successfully completed in 95.5% of patients, with 4% of the procedures electively performed by the combined approach (both RP and TP); 3.2% required open conversion and 1.3% were converted to the TP approach. The most common cause for conversion was bleeding. Mean hospital stay was 3.2 ± 1.2 days and the mean time for returning of bowel sounds was 16.5 ± 5.4 h. Of the patients, 1.4% required peri-operative blood transfusion. A total of 16 patients (5%) had post-operative complications and the majority were grades I and II as per MCC. The rates of intra-operative and post-operative complications depended on the difficulty of the procedure, but the complications diminished over the years with the increasing experience of surgeons. CONCLUSION: Retroperitoneoscopy has proven an excellent approach, with certain advantages. The tips and tricks that have been provided and emphasised should definitely help to minimise the steep learning curve. PMID:27073300

  3. Adaptive Traits Are Maintained on Steep Selective Gradients despite Gene Flow and Hybridization in the Intertidal Zone

    PubMed Central

    Canovas, Fernando; Ferreira Costa, Joana; Serrão, Ester A.; Pearson, Gareth A.

    2011-01-01

    Gene flow among hybridizing species with incomplete reproductive barriers blurs species boundaries, while selection under heterogeneous local ecological conditions or along strong gradients may counteract this tendency. Congeneric, externally-fertilizing fucoid brown algae occur as distinct morphotypes along intertidal exposure gradients despite gene flow. Combining analyses of genetic and phenotypic traits, we investigate the potential for physiological resilience to emersion stressors to act as an isolating mechanism in the face of gene flow. Along vertical exposure gradients in the intertidal zone of Northern Portugal and Northwest France, the mid-low shore species Fucus vesiculosus, the upper shore species Fucus spiralis, and an intermediate distinctive morphotype of F. spiralis var. platycarpus were morphologically characterized. Two diagnostic microsatellite loci recovered 3 genetic clusters consistent with prior morphological assignment. Phylogenetic analysis based on single nucleotide polymorphisms in 14 protein coding regions unambiguously resolved 3 clades; sympatric F. vesiculosus, F. spiralis, and the allopatric (in southern Iberia) population of F. spiralis var. platycarpus. In contrast, the sympatric F. spiralis var. platycarpus (from Northern Portugal) was distributed across the 3 clades, strongly suggesting hybridization/introgression with both other entities. Common garden experiments showed that physiological resilience following exposure to desiccation/heat stress differed significantly between the 3 sympatric genetic taxa; consistent with their respective vertical distribution on steep environmental clines in exposure time. Phylogenetic analyses indicate that F. spiralis var. platycarpus is a distinct entity in allopatry, but that extensive gene flow occurs with both higher and lower shore species in sympatry. Experimental results suggest that strong selection on physiological traits across steep intertidal exposure gradients acts to maintain

  4. Properties of Particle Size Distribution from Milled White Nixtamalized Corn Kernels as a Function of Steeping Time.

    PubMed

    Fernández-Muñoz, J L; Zapata-Torrez, M; Márquez-Herrera, A; Sánchez-Sinencio, F; Mendoza-Álvarez, J G; Meléndez-Lira, M; Zelaya-Ángel, O

    2016-01-01

    This paper focuses on the particle size distribution (PSD) changes during nixtamalized corn kernels (NCK) as a function of the steeping time (ST). The process to obtain powder or corn flour from NCK was as follows: (i) the NCK with different STs were wet-milled in a stone mill, (ii) dehydrated by a Flash type dryer, and (iii) pulverized with a hammer mill and sieved with a 20 mesh. The powder was characterized by measuring the PSD percentage, calcium percentage (CP), peak viscosity at 90°C (PV), and crystallinity percentage (CP). The PSD of the powder as a function of ST was determined by sieving in Ro-TAP equipment. By sieving, five fractions of powder were obtained employing meshes 30, 40, 60, 80, and 100. The final weight of the PSD obtained from the sieving process follows a Gaussian profile with the maximum corresponding to the average particle obtained with mesh 60. The calcium percentage as a function of ST follows a behavior similar to the weight of the PSD. The study of crystallinity versus the mesh number shows that it decreases for smaller mesh number. A similar behavior is observed as steeping time increases, except around ST = 8 h where the gelatinization of starch is observed. The trend of increasing viscosity values of the powder samples occurs when increasing ST and decreasing particle size. The ST significantly changes the crystallinity and viscosity values of the powder and, in both cases, a minimum value is observed in the region 7-9 h. The experimental results show that the viscosity increases (decreases) if the particle size decreases (increases). PMID:27375921

  5. Differences in hydrological responses for different vegetation types on a steep slope on the Loess Plateau, China

    NASA Astrophysics Data System (ADS)

    Duan, Liangxia; Huang, Mingbin; Zhang, Luodan

    2016-06-01

    Extensive vegetation restoration practices have been implemented to control soil erosion on the Loess Plateau, China. However, no strict guidelines are available to determine the most suitable plant species for vegetation restoration within a given area. The objective of this study was to quantify the changes of each component (soil water storage, surface runoff, and actual evapotranspiration) of a water balance model and soil loss over time under eight different vegetation types, and to further determine the optimal vegetation type for soil and water conservation and sustainable ecological restoration on the steep slopes (>25°) on the Loess Plateau. The results indicated that vegetation type substantially affected soil water storage and that the greatest soil water storage in both the shallow (0-2 m) and the deep soil layers (2-5 m) occurred under Bothriochloa ischaemum L. (BOI). Vegetation type also affected surface runoff and soil losses. The most effective vegetation types for reducing soil erosion were BOI and Sea-buckthorn (Hippophae rhamnoides L.), while Chinese pine (Pinus tabulaeformis Carr.) and Chinese pine + Black locust (Robinia pseudoacacia L.) were the most ineffective types. Soil water dynamics and evapotranspiration varied considerably among the different vegetation types. A soil water surplus was only found under BOI, while insufficient water replenishment existed under the other seven vegetation types. The higher water consumption rates of the seven vegetation types could result in soil desiccation, which could lead to severe water stresses that would adversely affect plant growth. This study suggested that both vegetation type and its effect on controlling soil erosion should be considered when implementing vegetation restoration and that BOI should be highly recommended for vegetation restoration on the steep slopes of the Loess Plateau. A similar approach to the one used in this study could be applied to other regions of the world confronted

  6. Properties of Particle Size Distribution from Milled White Nixtamalized Corn Kernels as a Function of Steeping Time

    PubMed Central

    Fernández-Muñoz, J. L.; Zapata-Torrez, M.; Márquez-Herrera, A.; Sánchez-Sinencio, F.; Mendoza-Álvarez, J. G.; Meléndez-Lira, M.; Zelaya-Ángel, O.

    2016-01-01

    This paper focuses on the particle size distribution (PSD) changes during nixtamalized corn kernels (NCK) as a function of the steeping time (ST). The process to obtain powder or corn flour from NCK was as follows: (i) the NCK with different STs were wet-milled in a stone mill, (ii) dehydrated by a Flash type dryer, and (iii) pulverized with a hammer mill and sieved with a 20 mesh. The powder was characterized by measuring the PSD percentage, calcium percentage (CP), peak viscosity at 90°C (PV), and crystallinity percentage (CP). The PSD of the powder as a function of ST was determined by sieving in Ro-TAP equipment. By sieving, five fractions of powder were obtained employing meshes 30, 40, 60, 80, and 100. The final weight of the PSD obtained from the sieving process follows a Gaussian profile with the maximum corresponding to the average particle obtained with mesh 60. The calcium percentage as a function of ST follows a behavior similar to the weight of the PSD. The study of crystallinity versus the mesh number shows that it decreases for smaller mesh number. A similar behavior is observed as steeping time increases, except around ST = 8 h where the gelatinization of starch is observed. The trend of increasing viscosity values of the powder samples occurs when increasing ST and decreasing particle size. The ST significantly changes the crystallinity and viscosity values of the powder and, in both cases, a minimum value is observed in the region 7–9 h. The experimental results show that the viscosity increases (decreases) if the particle size decreases (increases). PMID:27375921

  7. Effects of Stochasticity in Early Life History on Steepness and Population Growth Rate Estimates: An Illustration on Atlantic Bluefin Tuna

    PubMed Central

    Simon, Maximilien; Fromentin, Jean-Marc; Bonhommeau, Sylvain; Gaertner, Daniel; Brodziak, Jon; Etienne, Marie-Pierre

    2012-01-01

    The intrinsic population growth rate (r) of the surplus production function used in the biomass dynamic model and the steepness (h) of the stock-recruitment relationship used in age-structured population dynamics models are two key parameters in fish stock assessment. There is generally insufficient information in the data to estimate these parameters that thus have to be constrained. We developed methods to directly estimate the probability distributions of r and h for the Atlantic bluefin tuna (Thunnus thynnus, Scombridae), using all available biological and ecological information. We examined the existing literature to define appropriate probability distributions of key life history parameters associated with intrinsic growth rate and steepness, paying particular attention to the natural mortality for early life history stages. The estimated probability distribution of the population intrinsic growth rate was weakly informative, with an estimated mean r = 0.77 (±0.53) and an interquartile range of (0.34, 1.12). The estimated distribution of h was more informative, but also strongly asymmetric with an estimated mean h = 0.89 (±0.20) and a median of 0.99. We note that these two key demographic parameters strongly depend on the distribution of early life history mortality rate (M0), which is known to exhibit high year-to-year variations. This variability results in a widely spread distribution of M0 that affects the distribution of the intrinsic population growth rate and further makes the spawning stock biomass an inadequate proxy to predict recruitment levels. PMID:23119063

  8. The Lyα luminosity function at z = 5.7 - 6.6 and the steep drop of the faint end: implications for reionization

    NASA Astrophysics Data System (ADS)

    Santos, Sérgio; Sobral, David; Matthee, Jorryt

    2016-08-01

    We present new results from the widest narrow band survey search for Lyα emitters at z = 5.7, just after reionization. We survey a total of 7 deg2 spread over the COSMOS, UDS and SA22 fields. We find over 11,000 line emitters, out of which 514 are robust Lyα candidates at z = 5.7 within a volume of 6.3 × 106 Mpc3. Our Lyα emitters span a wide range in Lyα luminosities, from faint to bright (LLyα ˜ 1042.5 - 44 erg s-1) and rest-frame equivalent widths (EW0 ˜ 25 - 1000 Å) in a single, homogeneous data-set. By combining all our fields we find that the faint end slope of the z = 5.7 Lyα luminosity function is very steep, with α =-2.3^{+0.4}_{-0.3}. We also present an updated z = 6.6 Lyα luminosity function, based on comparable volumes and obtained with the same methods, which we directly compare with that at z = 5.7. We find a significant decline of the number density of faint Lyα emitters from z = 5.7 to z = 6.6 (by 0.5 ± 0.1 dex), but no evolution at the bright end/no evolution in L★. Faint Lyα emitters at z = 6.6 show much more extended haloes than those at z = 5.7, suggesting that neutral Hydrogen plays an important role, increasing the scattering and leading to observations missing faint Lyα emission within the epoch of reionization. All together, our results suggest that we are observing patchy reionization which happens first around the brightest Lyα emitters, allowing the number densities of those sources to remain unaffected by the increase of neutral Hydrogen fraction from z ˜ 5 to z ˜ 7.

  9. Investigation of real-time microstructure evolution in steep thermal gradients using in-situ spatially resolved X-ray diffraction: A case study for Ti fusion welds

    SciTech Connect

    Ressler, T.; Wong, J.; Elmer, J.W. |

    1998-12-24

    A recently developed spatially resolved X-ray diffraction (SRXRD) technique utilizing intense synchrotron radiation has been refined to yield phase and microstructural information down to 200 {micro}m in spatial extent in materials subjected to steep thermal gradients during processing. This SRXRD technique has been applied to map completely the phases and their solid-state transformation in the so-called heat-affected zone (HAZ) in titanium fusion welds in situ during the welding process. Detailed profile analysis of the SRXRD patterns revealed four principal microstructural regions at temperature in the vicinity of the HAZ surrounding the liquid weld pool: (i) a completely transformed {beta}-Ti zone 2--3 mm adjacent to the liquid weld pool; (ii) a mixed {alpha} + {beta}-it region surrounding the pure {beta}-Ti zone, (iii) a back-transformed {alpha}-Ti zone on the backside of the HAZ where pure {beta}-Ti once existed at temperature well above the {alpha} {r_arrow} {beta} transformation isotherm, and (iv) a more diffused region outside the HAZ where annealing and recrystallization of the {alpha}-it base metal occur. The high-temperature microstructures so derived corroborate well the expected transformation kinetics in pure titanium, and the observed phase transformation boundaries are in good agreement with those predicted from the transformation isotherms calculated from a simplified heat-flow model. Based on a detailed assessment of the SRXRD setup employed, improved experimentations such as a smaller beam spot emitted from third generation synchrotron sources, better mechanical stability (tighter scattering geometry), and use of an area detector would enable more quantitative structural information for future phase dynamics studies exemplified by this work.

  10. Steep Decline and Cessation in Seed Dispersal by Myrmica rubra Ants

    PubMed Central

    2015-01-01

    Myrmecochorous diaspores bear a nutrient-rich appendage, the elaiosome, attractive to ant workers that retrieve them into the nest, detach the elaiosome and reject the seed intact. While this interaction is beneficial for the plant partner by ensuring its seed dispersal, elaiosome consumption has various effects −positive, negative or none − on ants’ demography and survival, depending on both the ant/plant species involved. In this context, the contribution of ants to seed dispersal strongly varies according to the ant/plant pairs considered. In this paper, we investigate whether the dynamics of myrmecochory also vary on a temporal scale, for a given pair of partners: Myrmica rubra ants and Viola odorata seeds. During their first encounter with seeds, ants collect all the diaspores and eat the majority of elaiosomes. Both the harvesting effort and the elaiosome consumption decline when seeds are offered on the next week and completely cease for the following weeks. This is related to a decrease in the number of foragers reaching the food source, as well as to a reduced probability for an ant contacting a seed to retrieve it. Seed retrieval is not reactivated after seven weeks without any encounter with V. odorata seeds. By contrast, naive ant colonies only fed with fruit flies do not show a decline of prey harvesting of which the speed of retrieval even increases over the successive weeks. Myrmecochory may thus be labile at the scale of a fruiting season due to the ability of ants to steeply tune and cease for several months the harvesting of these seemingly poorly rewarding items and to maintain cessation of seed exploitation. The present study emphasizes the importance of a long-lasting follow up of the myrmecochory process, to assess the stability of this ant-plant partnership and to identify mechanisms of adaptive harvesting in ants. PMID:26414161

  11. Crustal Structure of the Yakutat Microplate: Constraints from STEEP Wide-angle Seismic Data

    NASA Astrophysics Data System (ADS)

    Christeson, G. L.; van Avendonk, H.; Gulick, S. P.; Worthington, L.; Pavlis, T.

    2008-12-01

    In Fall 2008 we will conduct a seismic program focusing on the Yakutat microplate. As part of this study we plan to acquire two wide-angle profiles: an onshore-offshore northwest-southeast oriented profile extending from the Bering glacier onto the continental shelf and across the Dangerous River Zone, and an offshore northeast-southwest oriented profile extending from the ocean basin across the Transition fault and into Yakutat Bay. The sound source will be the R/V Langseth's tuned 6600 cu. in., 36 air gun array. Ocean bottom seismometers will be positioned at ~15 km spacing, and Texan seismometers at 1-4 km spacing across the Bering Glacier. Coincident deep-penetrating seismic reflection data will be acquired on the marine portion of both profiles using a 8-km, 640-channel solid hydrophone streamer. Existing models for the Yakutat microplate disagree as to whether it is a continental fragment attached to normal oceanic crust or an oceanic plateau, and if the deep structure changes from west to east across the Dangerous River Zone. In the continental fragment model uplift is concentrated along crustal-scale thrust faulting at the ocean crust boundary (Dangerous River Zone?) resulting in focused and rapid erosion. In the oceanic plateau model more distributed, regional uplift is expected which will produce widespread exhumation with net erosion potentially coupled with glacial cycles. Thus distinguishing between these models, which we expect to accomplish with our planned seismic program, is vital for linking tectonics to erosion on both spatial and temporal scales.

  12. Steep Decline and Cessation in Seed Dispersal by Myrmica rubra Ants.

    PubMed

    Bologna, Audrey; Detrain, Claire

    2015-01-01

    Myrmecochorous diaspores bear a nutrient-rich appendage, the elaiosome, attractive to ant workers that retrieve them into the nest, detach the elaiosome and reject the seed intact. While this interaction is beneficial for the plant partner by ensuring its seed dispersal, elaiosome consumption has various effects -positive, negative or none - on ants' demography and survival, depending on both the ant/plant species involved. In this context, the contribution of ants to seed dispersal strongly varies according to the ant/plant pairs considered. In this paper, we investigate whether the dynamics of myrmecochory also vary on a temporal scale, for a given pair of partners: Myrmica rubra ants and Viola odorata seeds. During their first encounter with seeds, ants collect all the diaspores and eat the majority of elaiosomes. Both the harvesting effort and the elaiosome consumption decline when seeds are offered on the next week and completely cease for the following weeks. This is related to a decrease in the number of foragers reaching the food source, as well as to a reduced probability for an ant contacting a seed to retrieve it. Seed retrieval is not reactivated after seven weeks without any encounter with V. odorata seeds. By contrast, naive ant colonies only fed with fruit flies do not show a decline of prey harvesting of which the speed of retrieval even increases over the successive weeks. Myrmecochory may thus be labile at the scale of a fruiting season due to the ability of ants to steeply tune and cease for several months the harvesting of these seemingly poorly rewarding items and to maintain cessation of seed exploitation. The present study emphasizes the importance of a long-lasting follow up of the myrmecochory process, to assess the stability of this ant-plant partnership and to identify mechanisms of adaptive harvesting in ants. PMID:26414161

  13. Heat transport in steep temperature gradients. I - Small flaring solar loops

    NASA Technical Reports Server (NTRS)

    Smith, D. F.

    1986-01-01

    Results on nonlocal heat transport which properly takes into account the presence of fast electrons with mean free paths much longer than the temperature scale height L are reviewed. In terms of the mean free path for the slow bulk electrons, lambda(s), the nonlocal effects are important whenever lambda(s)/L greater than 0.001, with the following consequences. The heat flux in the hot part of the gradient is reduced relative to the Spitzer-Haerm value q(SH) which does not take into account the heat carried away by the fast electrons. The heat flux in the cold part of the gradient is enhanced relative to the value q(SH) which does not take into account the heat deposited by the fast electrons. These quite general results, which should have several applications in astrophysics, are applied to the problem of thermal hard X-ray burst models. It is shown that heat is not bottled up as effectively as in some past models, and temperatures achieved for realistic energy input rates are consequently not as high. As a result such sources can be effective only in the soft part (10-30 keV) of the hard X-ray range for energy input rates up to 6,400 ergs/cu cm s. The analysis is based on a fluid model and does not consider the X-ray signature of fast electrons which escape to distances far beyond the conduction fronts formed. It is shown that such electrons could at most be effective in the soft part of the hard X-ray range.

  14. A model for the proton spectrum and cosmic ray anisotropy

    NASA Technical Reports Server (NTRS)

    Xu, C.

    1985-01-01

    The problem of the origin of the cosmic rays is still uncertain. As a theory, it should explain the support of particles and energy, the mechanism of acceleration and propagation as well as some important features obtained directly from cosmic ray experiments, such as the power spectrum and the knee. There are two kinds of models for interpreting the knee of the cosmic ray spectrum. One is the leaky box model. Another model suggests that the cut-off rigidity of the main sources causes the knee. The present paper studies the spectrum and the anisotropy of cosmic rays in an isotropic diffuse model with explosive discrete sources in an infinite galaxy.

  15. Chandra Observations of Dying Radio Sources in Galaxy Clusters

    NASA Technical Reports Server (NTRS)

    Murgia, M.; Markevitch, M.; Govoni, F.; Parma, P.; Fanti, R.; de Ruiter, H. R.; Mack, K.-H.

    2012-01-01

    Context. The dying radio sources represent a very interesting and largely unexplored stage of the active galactic nucleus (AGN) evolution. They are considered to be very rare, and almost all of the few known ones were found in galaxy clusters. However, considering the small number detected so far, it has not been possible to draw any firm conclusions about their X-ray environment. Aims. We present X-ray observations performed with the Chandra satellite of the three galaxy clusters Abell 2276, ZwCl 1829.3+6912, and RX J1852.1+5711, which harbor at their center a dying radio source with an ultra-steep spectrum that we recently discovered. Methods. We analyzed the physical properties of the X-ray emitting gas surrounding these elusive radio sources. We determined the global X-ray properties of the clusters, derived the azimuthally averaged profiles of metal abundance, gas temperature, density, and pressure. Furthermore, we estimated the total mass profiles. Results. The large-scale X-ray emission is regular and spherical, suggesting a relaxed state for these systems. Indeed, we found that the three clusters are also characterized by significant enhancements in the metal abundance and declining temperature profiles toward the central region. For all these reasons, we classified RX J1852.1+5711, Abell 2276, and ZwCl 1829.3+6912 as cool-core galaxy clusters. Conclusions. We calculated the non-thermal pressure of the radio lobes assuming that the radio sources are in the minimum energy condition. For all dying sources we found that this is on average about one to two orders of magnitude lower than that of the external gas, as found for many other radio sources at the center of galaxy groups and clusters. We found marginal evidence for the presence of X-ray surface brightness depressions coincident with the fossil radio lobes of the dying sources in A2276 and ZwCl 1829.3+691. We estimated the outburst age and energy output for these two dying sources. The energy power from

  16. Chandra observations of dying radio sources in galaxy clusters

    NASA Astrophysics Data System (ADS)

    Murgia, M.; Markevitch, M.; Govoni, F.; Parma, P.; Fanti, R.; de Ruiter, H. R.; Mack, K.-H.

    2012-12-01

    Context. The dying radio sources represent a very interesting and largely unexplored stage of the active galactic nucleus (AGN) evolution. They are considered to be very rare, and almost all of the few known ones were found in galaxy clusters. However, considering the small number detected so far, it has not been possible to draw any firm conclusions about their X-ray environment. Aims: We present X-ray observations performed with the Chandra satellite of the three galaxy clusters Abell 2276, ZwCl 1829.3+6912, and RX J1852.1+5711, which harbor at their center a dying radio source with an ultra-steep spectrum that we recently discovered. Methods: We analyzed the physical properties of the X-ray emitting gas surrounding these elusive radio sources. We determined the global X-ray properties of the clusters, derived the azimuthally averaged profiles of metal abundance, gas temperature, density, and pressure. Furthermore, we estimated the total mass profiles. Results: The large-scale X-ray emission is regular and spherical, suggesting a relaxed state for these systems. Indeed, we found that the three clusters are also characterized by significant enhancements in the metal abundance and declining temperature profiles toward the central region. For all these reasons, we classified RX J1852.1+5711, Abell 2276, and ZwCl 1829.3+6912 as cool-core galaxy clusters. Conclusions: We calculated the non-thermal pressure of the radio lobes assuming that the radio sources are in the minimum energy condition. For all dying sources we found that this is on average about one to two orders of magnitude lower than that of the external gas, as found for many other radio sources at the center of galaxy groups and clusters. We found marginal evidence for the presence of X-ray surface brightness depressions coincident with the fossil radio lobes of the dying sources in A2276 and ZwCl 1829.3+691. We estimated the outburst age and energy output for these two dying sources. The energy power from

  17. Influences of edges and steep slopes in 3D interference and confocal microscopy

    NASA Astrophysics Data System (ADS)

    Xie, Weichang; Hagemeier, Sebastian; Woidt, Carsten; Hillmer, Harmut; Lehmann, Peter

    2016-04-01

    Optical measurement techniques are widely applied in high-resolution contour, topography and roughness measurement. In this context vertical scanning white-light interferometers and confocal microscopes have become mature instruments over the last decades. The accuracy of measurement results is highly related not only to the type and physical properties of the measuring instruments, but also to the measurement object itself. This contribution focuses on measurement effects occurring at edges and height steps using white-light interferometers of different numerical apertures. If the edge is perfectly perpendicular, batwing effects appear at height steps. These batwings show maximum height if the height-to-wavelength-ratio (HWR) is about one forth or three forth, and they disappear if the HWR value is about an integer multiple of one half. The wavelength that is relevant in this context is the effective wavelength, i.e. the center wavelength of the illuminating light multiplied by a correction factor known as the numerical aperture correction. However, in practice the edges are usually not perfectly perpendicular. In this case, the measurement results depend also on the derivative of the surface height function and they may differ from theory and the prediction according to the HWR value. Measurements of such steps show systematical effects depending on the lateral resolution of the instrument. In this context, a Linnik interferometer with a magnification of 100x and NA = 0.9 is used to characterize the three dimensional topography of more or less rectangular calibration specimens and quasi-perpendicular structures produced by the nanoimprint technology. The Linnik interferometer is equipped with LED light sources emitting at different wavelengths, so that the HWR value can be changed. This is possible since the high NA objective lenses show a rather limited depth of focus such that the temporal coherence gating may be replaced by focal gating in this

  18. Dryout of a Steep Hillslope During Periods of Extended Seasonal Drought

    NASA Astrophysics Data System (ADS)

    Salve, R.; Rempe, D. M.; Dietrich, W. E.

    2011-12-01

    Studies investigating the mechanics of hillslope hydrology typically explore processes that are prominent as precipitation is transformed to runoff. In seasonally water-stressed environments such as arid Mediterranean climates, re-distribution of subsurface moisture during extended periods of seasonal drought is also a significant, though often ignored, component of the hydrologic system. During this period, ground moisture sustains vegetation for upwards of 6 months without replenishment, and researchers have suggested that weathered bedrock is a critical source of water during the summer drought. We have monitored a 4000 m2 hillslope in the Angelo Coast Range Reserve along the Eel River in Northern California to explore hydrologic processes. Since September 2007, devices for tracking saturation changes in soil and rock (e.g., TDR probes, Electrical Resistance Probes, Neutron logging), and climate attributes have been installed throughout the catchment. In addition, 7 deep wells up to nearly 30 m depth were drilled across the hillslope and water levels have been continuously monitored since then. Drilling revealed a thin (< 0.3 m) soil mantle overlying a fractured mudstone weathering profile that extends up to 20 m near the ridgetop and tapers downslope towards a bedrock lined channel named Elder Creek. Baseflow sustains Elder Creek year round. Vegetation at the site is dominated by Pseudostuga menziesii (Douglas Fir), Arbutus menziesii (Madrone), Quercus wislizeni (Interior live oak), Umbellularia californica (California bay), Notholithocarpus densiflorus (Tan-bark oak) and Sequoia sempervirens (Redwood) trees. Average rainfall is about 2 m with nearly all of it occurring between November and April. For approximately six months during the warm summer, there is no recordable precipitation. We have observed that during the long precipitation-free period, there is significant reduction in the amount of water retained in the shallow soil/weathered rock profile, and

  19. Economics of spectrum allocation

    NASA Astrophysics Data System (ADS)

    Melody, W. H.

    The effective and efficient allocation and use of the spectrum can be ensured only by a set of sharing rules that will reflect the interests, values, and power of all affected parties. What is now happening is that the new interests and different values of the developing countries are pressing to change the international sharing rules established by a small group of high-technology nations. It is noted that the latter have established a massive telecommunications infrastructure on the basis of inherited sharing rules that reflect only their interests and a much simplified scarcity problem. Once long-term goals and underlying principles of allocation are established, communication technologies and markets can be directed, through a series of adjustment policies, to achieve them. A crucial first step in the creation of an international information environment in which 'free' flows will be balanced flows is the establishment of a balanced and equitable set of sharing rules for the radio spectrum.

  20. Spread spectrum image steganography.

    PubMed

    Marvel, L M; Boncelet, C R; Retter, C T

    1999-01-01

    In this paper, we present a new method of digital steganography, entitled spread spectrum image steganography (SSIS). Steganography, which means "covered writing" in Greek, is the science of communicating in a hidden manner. Following a discussion of steganographic communication theory and review of existing techniques, the new method, SSIS, is introduced. This system hides and recovers a message of substantial length within digital imagery while maintaining the original image size and dynamic range. The hidden message can be recovered using appropriate keys without any knowledge of the original image. Image restoration, error-control coding, and techniques similar to spread spectrum are described, and the performance of the system is illustrated. A message embedded by this method can be in the form of text, imagery, or any other digital signal. Applications for such a data-hiding scheme include in-band captioning, covert communication, image tamperproofing, authentication, embedded control, and revision tracking. PMID:18267522