Science.gov

Sample records for steep spectrum sources

  1. Steep Spectrum Radio Sources in Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Clarke, Tracy E.

    2012-05-01

    Steep spectrum radio emission associated with galaxy clusters comes from compact central active galactic nuclei (AGN) driven radio sources in dense cool core clusters as well as from large regions of diffuse (halo and relic) emission associated with dynamically complex merging systems. These radio halos and relics are best traced at low radio frequencies where details of their morphology, location and spectral index distribution can be used to probe the underlying acceleration mechanism(s) as well as important details of large scale structure formation. Low frequency radio observations also play an important role in the study of AGN feedback into the intracluster medium and the regulation of cooling cores. While spectacular results are coming from the current generation of low frequency instruments, there will soon be a new revolution in studies of steep spectrum sources with the upcoming generation of low frequency interferometers on Earth and ultimately the moon.

  2. 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.

  3. New candidate GHz peaked spectrum and compact steep spectrum sources

    NASA Astrophysics Data System (ADS)

    Edwards, P. G.; Tingay, S. J.

    2004-09-01

    Data from a recent Australia Telescope Compact Array (ATCA) program of multi-frequency, multi-epoch monitoring of 202 active galactic nuclei with declinations <+10o have been searched for GHz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radio sources. Supplementary data at higher and lower frequencies, where available, have been used to further examine the spectral properties of previously reported and new candidate GPS and CSS sources. The ATCA monitoring program has allowed the variability and polarization properties of sources previously reported as GPS and CSS sources, and the majority of new GPS and CSS candidates, to be investigated, confirming that these are useful diagnostics in discriminating genuine GPS and CSS sources from variable sources that display similar spectra only temporarily. GPS sources are confirmed to be generally more compact, and less polarized, than CSS sources, although CSS sources show evidence for being somewhat less variable than GPS sources at 1.4 and 2.5 GHz. In addition, the widths of GPS spectra are examined, and a significant difference is found in the GPS sample of Snellen et al. (2000) between sources with compact double (CD) or compact symmetric object (CSO) morphologies and sources with other morphologies, in that CD and CSO sources have generally narrower spectra. Possible reasons for this difference are considered.

  4. 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

  5. EGRET/COMPTEL Observations of an Unusual, Steep-Spectrum Gamma-Ray Source

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.; Bertsch, D. L.; Hartman, R. C.; Collmar, W.; Johnson, W. N.

    1999-01-01

    During analysis of sources below the threshold of the third EGRET catalog, we have discovered a source, named GRO J1400-3956 based on the best position, with a remarkably steep spectrum. Archival analysis of COMPTEL data shows that the spectrum must have a strong turn-over in the energy range between COMPTEL and EGRET. The EGRET data show some evidence of time variability, suggesting an AGN, but the spectral change of slope is larger than that seen for most gamma-ray blazars. The sharp cutoff resembles the high-energy spectral breaks seen in some gamma-ray pulsars. There have as yet been no OSSE observations of this source.

  6. Compact Steep Spectrum 3CR radio sources - VLBI observations at 18 CM

    NASA Astrophysics Data System (ADS)

    Fanti, C.; Fanti, R.; Parma, P.; Schilizzi, R. T.; van Breugel, W. J. M.

    1985-02-01

    Results of a program to investigate the kiloparsec-sized radio structure of a representative sample of Compact Steep Spectrum (CSS) sources from the 3CR catalog (Jenkins et al., 1977) are presented. Ten objects (3C49,67, 119, 237, 241, 268.3, 287, 303.1, 343, 343.1) have been mapped at 18 cm with a resolution of about 30 marcsec using the European VLBI Network. In some cases the VLBI data have been supplemented by MERLIN observations at the same wavelength to enhance sensitivity to large-scale structure. The overall sizes of the CSS sources range from about 0.1 to 1 or 2 arcsec, corresponding to linear sizes of the order of 1 to 10 kpc. The morphological classification ranges from double to core-jet to complex; CSS quasars are generally core-jets or complex, while CSS radio galaxies are doubles, although not necessarily simple doubles.

  7. 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.

  8. FIRST-based survey of Compact Steep Spectrum sources. II. MERLIN and VLA observations of medium-sized symmetric objects

    NASA Astrophysics Data System (ADS)

    Kunert-Bajraszewska, M.; Marecki, A.; Thomasson, P.; Spencer, R. E.

    2005-09-01

    A new sample of candidate Compact Steep Spectrum (CSS) sources that are much weaker than the CSS source prototypes has been selected from the VLA FIRST catalogue. MERLIN "snapshot" observations of the sources at 5 GHz indicate that six of them have an FR II-like morphology, but are not edge-brightened as is normal for Medium-sized Symmetric Objects (MSOs) and FR IIs. Further observations of these six sources with the VLA at 4.9 GHz and MERLIN at 1.7 GHz, as well as subsequent full-track observations with MERLIN at 5 GHz of what appeared to be the two sources of greatest interest are presented. The results are discussed with reference to the established evolutionary model of CSS sources being young but in which not all of them evolve to become old objects with extended radio structures. A lack of stable fuelling in some of them may result in an early transition to a so-called coasting phase so that they fade away instead of growing to become large-scale objects. It is possible that one of the six sources (1542+323) could be labelled as a prematurely "dying" MSO or a "fader".

  9. FIRST-based survey of compact steep spectrum sources. III. MERLIN and VLBI observations of subarcsecond-scale objects

    NASA Astrophysics Data System (ADS)

    Marecki, A.; Kunert-Bajraszewska, M.; Spencer, R. E.

    2006-04-01

    Context: .According to a generally accepted paradigm, small intrinsic sizes of Compact Steep Spectrum (CSS) radio sources are a direct consequence of their youth, but in later stages of their evolution they are believed to become large-scale sources. However, this notion was established mainly for strong CSS sources.Aims.In this series of papers we test this paradigm on 60 weaker objects selected from the VLA FIRST survey. They have 5-GHz flux densities in the range 150 < S5 GHz < 550 mJy and steep spectra in the range 0.365 ≤ ν ≤ 5 GHz. The present paper is focused on sources that fulfill the above criteria and have angular sizes in the range ~0.2 arcsec -1 arcsec.Methods.Observations of 19 such sources were obtained using MERLIN in "snapshot" mode at 5 GHz. They are presented along with 1.7-GHz VLBA and 5-GHz EVN follow-up snapshot observations made for the majority of them. For one of the sources in this subsample, 1123+340, a full-track 5-GHz EVN observation was also carried out.Results.This study provides an important element to the standard theory of CSS sources, namely that in a number of them the activity of their host galaxies probably switched off quite recently and their further growth has been stopped because of that. In the case of 1123+340, the relic of a compact "dead source" is particularly well preserved by the presence of intracluster medium of the putative cluster of galaxies surrounding it.Conclusions.The observed overabundance of compact sources can readily be explained in the framework of the scenario of "premature" cessation of the activity of the host galaxy nucleus. It could also explain the relatively low radio flux densities of many such sources and, in a few cases, their peculiar, asymmetric morphologies. We propose a new interpretation of such asymmetries based on the light-travel time argument.

  10. VizieR Online Data Catalog: Ultra steep spectrum radio sources (Singh+, 2014)

    NASA Astrophysics Data System (ADS)

    Singh, V.; Beelen, A.; Wadadekar, Y.; Sirothia, S.; Ishwara-Chandra, C. H.; Basu, A.; Omont, A.; McAlpine, K.; Ivison, R. J.; Oliver, S.; Farrah, D.; Lacy, M.

    2014-11-01

    We obtained 325 MHz GMRT observations of the XMM-LSS field over sky area of ~12deg2 with synthesized beamsize ~10.2"x7.9". In the mosaiced 325MHz GMRT image the average noise rms is ~160uJy, while in the central region the average noise-rms reaches to ~120uJy. Our 325MHz observations are one of the deepest low-frequency surveys over such a wide sky area and detect ~2553/3304 radio sources at >=5.0σ with noise rms cut-off <=200/300uJy. (1 data file).

  11. 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.

  12. 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.

  13. An X-ray and radio study of steep-spectrum radio sources. II - Four fields from a 22 MHz polar cap survey

    NASA Technical Reports Server (NTRS)

    Dewdney, P. E.; Mchardy, I.; Willis, A. G.; Harris, D. E.; Costain, C. H.

    1991-01-01

    Four fields containing radio sources with spectral indices greater than unity at low frequencies have been observed over a wide range of radio wavelengths and at X-ray wavelengths. For most of the steep-spectrum sources no optical identifications have been found to the detection limit of the Palomar Schmidt prints, even with the positional precision of about 1 arcsec from VLA maps. This implies that the associated galaxies or clusters lie at a great distance. X-ray emission was not detected from any of the steep-spectrum radio sources. In one case, an extended source appears to be a radio halo in an uncataloged cluster of galaxies at a redshift of 0.125, and it is suggested that this object is a promising candidate for the detection of inverse Compton X-rays, since it is not a high-luminosity source of thermal X-rays.

  14. 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.

  15. SDSS J143244.91+301435.3: a link between radio-loud narrow-line Seyfert 1 galaxies and compact steep-spectrum radio sources?

    NASA Astrophysics Data System (ADS)

    Caccianiga, A.; Antón, S.; Ballo, L.; Dallacasa, D.; Della Ceca, R.; Fanali, R.; Foschini, L.; Hamilton, T.; Kraus, A.; Maccacaro, T.; Mack, K.-H.; Marchã, M. J.; Paulino-Afonso, A.; Sani, E.; Severgnini, P.

    2014-06-01

    We present SDSS J143244.91+301435.3, a new case of a radio-loud narrow-line Seyfert 1 (RL NLS1) with a relatively high radio power (P1.4 GHz = 2.1 × 1025 W Hz-1) and large radio-loudness parameter (R1.4 = 600 ± 100). The radio source is compact with a linear size below ˜1.4 kpc but, in contrast to most of the RL NLS1 discovered so far with such a high R1.4, its radio spectrum is very steep (α = 0.93, Sν ∝ ν-α) and does not support a `blazar-like' nature. Both the small mass of the central supermassive black hole and the high accretion rate relative to the Eddington limit estimated for this object (3.2 × 107 M⊙ and 0.27, respectively, with a formal error of ˜0.4 dex for both quantities) are typical of the NLS1 class. Through modelling the spectral energy distribution of the source, we have found that the galaxy hosting SDSS J143244.91+301435.3 is undergoing quite intense star formation (SFR = 50 M⊙ yr-1), which, however, is expected to contribute only marginally (˜1 per cent) to the observed radio emission. The radio properties of SDSS J143244.91+301435.3 are remarkably similar to those of compact steep-spectrum (CSS) radio sources, a class of active galactic nuclei (AGN) mostly composed of young radio galaxies. This may suggest a direct link between these two classes of AGN, with CSS sources possibly representing the misaligned version (the so-called `parent population') of RL NLS1 showing blazar characteristics.

  16. 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.

  17. The radio-optical correlation in steep-spectrum quasars

    NASA Astrophysics Data System (ADS)

    Serjeant, Stephen; Rawlings, Steve; Lacy, Mark; Maddox, Stephen J.; Baker, Joanne C.; Clements, Dave; Lilje, Per B.

    1998-03-01

    Using complete samples of steep-spectrum quasars, we present evidence for a correlation between radio and optical luminosity which is not caused by selection effects, nor caused by an orientation dependence (such as relativistic beaming), nor a by-product of cosmic evolution. We argue that this rules out models of jet formation in which there are no parameters in common with the production of the optical continuum. This is arguably the most direct evidence to date for a close link between accretion onto a black hole and the fuelling of relativistic jets. The correlation also provides a natural explanation for the presence of aligned optical/radio structures in only the most radio-luminous high-redshift galaxies.

  18. H i Absorption in the Steep-Spectrum Superluminal Quasar 3C 216.

    PubMed

    Pihlström; Vermeulen; Taylor; Conway

    1999-11-01

    The search for H i absorption in strong compact steep-spectrum sources is a natural way to probe the neutral gas contents in young radio sources. In turn, this may provide information about the evolution of powerful radio sources. The recently improved capabilities of the Westerbork Synthesis Radio Telescope have made it possible to detect a 0.31% (19 mJy) deep neutral atomic hydrogen absorption line associated with the steep-spectrum superluminal quasar 3C 216. The redshift (z=0.67) of the source shifts the frequency of the 21 cm line down to the ultra-high-frequency (UHF) band (850 MHz). The exact location of the H i-absorbing gas remains to be determined by spectral line VLBI observations at 850 MHz. We cannot exclude that the gas might be extended on galactic scales, but we think it is more likely to be located in the central kiloparsec. Constraints from the lack of X-ray absorption probably rule out obscuration of the core region, and we argue that the most plausible site for the H i absorption is in the jet-cloud interaction observed in this source.

  19. The steep red spectrum of 1992 AD - An asteroid covered with organic material?

    NASA Technical Reports Server (NTRS)

    Fink, Uwe; Hoffmann, Martin; Grundy, William; Hicks, Michael; Sears, William

    1992-01-01

    The CCD spectrometer reflection spectrum of 1992 AD is characterized by a very steep and constant red slope between 0.5 and 1.0 micron, without absorption or emission features; this slope is steeper than any currently known solar-system object, and cannot be readily matched with conventional silicate or meteoritic materials. Mixtures of tholins, or residues of organic molecules' bombardment by energetic radiation, are suggested as a match for this spectrum.

  20. Steep-Spectrum Radio Emission from the Low-Mass Active Galactic Nucleus GH 10

    NASA Astrophysics Data System (ADS)

    Wrobel, J. M.; Greene, J. E.; Ho, L. C.; Ulvestad, J. S.

    2008-10-01

    GH 10 is a broad-lined active galactic nucleus (AGN) energized by a black hole of mass 800,000 M⊙. It was the only object detected by Greene et al. in their Very Large Array (VLA) survey of 19 low-mass AGNs discovered by Greene & Ho. New VLA imaging at 1.4, 4.9, and 8.5 GHz reveals that GH 10's emission has an extent of less than 320 pc, has an optically thin synchrotron spectrum with a spectral index α = - 0.76 +/- 0.05 (Sν propto ν+ α), is less than 11% linearly polarized, and is steady—although poorly sampled—on timescales of weeks and years. Circumnuclear star formation cannot dominate the radio emission, because the high inferred star formation rate, 18 M⊙ yr-1, is inconsistent with the rate of less than 2 M⊙ yr-1 derived from narrow Hα and [O II] λ3727 emission. Instead, the radio emission must be mainly energized by the low-mass black hole. GH 10's radio properties match those of the steep-spectrum cores of Palomar Seyfert galaxies, suggesting that, like those galaxies, the emission is outflow-driven. Because GH 10 is radiating close to its Eddington limit, it may be a local analog of the starting conditions, or seeds, for supermassive black holes. Future imaging of GH 10 at higher linear resolution thus offers an opportunity to study the relative roles of radiative versus kinetic feedback during black hole growth.

  1. DISCOVERY OF ULTRA-STEEP SPECTRUM GIANT RADIO GALAXY WITH RECURRENT RADIO JET ACTIVITY IN ABELL 449

    SciTech Connect

    Hunik, Dominika; Jamrozy, Marek

    2016-01-20

    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.

  2. The Steepness Ratio Technique: A New Method to Analyze ROSAT All-Sky Survey Extended Sources

    NASA Astrophysics Data System (ADS)

    De Grandi, S.; Molendi, S.; Böhringer, H.; Chincarini, G.; Voges, W.

    1997-09-01

    In this first paper of a series we develop a new technique to analyze clusters of galaxies observed during the ROSAT All-Sky Survey (RASS). We call this method the steepness ratio technique (SRT). The SRT uses the convolution between the real RASS point-spread function and the cluster emission profile assumed to be a β model with the β parameter fixed to the value of 2/3. From the convolved source emission profile the SRT extracts total flux and extension (i.e., core radius) for each cluster. Using the steepness ratio (SR) and a control sample of RASS pointlike sources, we are able to assign to each RASS source a model-independent probability of extension. Potential biases arising from the hypotheses of a β-model emission profile and from a fixed β value are quantified. Tests with control samples of optically identified sources extracted from both the ROSAT survey database and from the ROSAT-PSPC pointed observations archive are performed to check the SRT output. We find that the source properties derived using the SRT on RASS data are consistent with those determined from ROSAT-PSPC pointed observations.

  3. Extragalactic Peaked-spectrum Radio Sources at Low Frequencies

    NASA Astrophysics Data System (ADS)

    Callingham, J. R.; Ekers, R. D.; Gaensler, B. M.; Line, J. L. B.; Hurley-Walker, N.; Sadler, E. M.; Tingay, S. J.; Hancock, P. J.; Bell, M. E.; Dwarakanath, K. S.; For, B.-Q.; Franzen, T. M. O.; Hindson, L.; Johnston-Hollitt, M.; Kapińska, A. D.; Lenc, E.; McKinley, B.; Morgan, J.; Offringa, A. R.; Procopio, P.; Staveley-Smith, L.; Wayth, R. B.; Wu, C.; Zheng, Q.

    2017-02-01

    We present a sample of 1483 sources that display spectral peaks between 72 MHz and 1.4 GHz, selected from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey. The GLEAM survey is the widest fractional bandwidth all-sky survey to date, ideal for identifying peaked-spectrum sources at low radio frequencies. Our peaked-spectrum sources are the low-frequency analogs of gigahertz-peaked spectrum (GPS) and compact-steep spectrum (CSS) sources, which have been hypothesized to be the precursors to massive radio galaxies. Our sample more than doubles the number of known peaked-spectrum candidates, and 95% of our sample have a newly characterized spectral peak. We highlight that some GPS sources peaking above 5 GHz have had multiple epochs of nuclear activity, and we demonstrate the possibility of identifying high-redshift (z > 2) galaxies via steep optically thin spectral indices and low observed peak frequencies. The distribution of the optically thick spectral indices of our sample is consistent with past GPS/CSS samples but with a large dispersion, suggesting that the spectral peak is a product of an inhomogeneous environment that is individualistic. We find no dependence of observed peak frequency with redshift, consistent with the peaked-spectrum sample comprising both local CSS sources and high-redshift GPS sources. The 5 GHz luminosity distribution lacks the brightest GPS and CSS sources of previous samples, implying that a convolution of source evolution and redshift influences the type of peaked-spectrum sources identified below 1 GHz. Finally, we discuss sources with optically thick spectral indices that exceed the synchrotron self-absorption limit.

  4. 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.

  5. Testing for Shock-Heated X-Ray Gas around Compact Steep Spectrum Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Noel-Storr, Jacob; O'Dea, Christopher; Worrall, Diana M.; Clarke, Tracy E.; Tremblay, Grant; Baum, Stefi; Christiansen, Kevin; Mullarkey, Christopher; Mittal, Rupal

    2017-01-01

    We present Chandra and XMM-Newton X-ray, VLA radio, and optical observations of two CSS radio galaxies. B3 1445+410 is a low excitation emission line galaxy with possibly a hybrid FRI/II (or Fat Double) radio morphology. The Chandra observations are point-like and well fit with a power-law consistent with emission from a Doppler boosted core. PKS B1017-325 is a galaxy with a bent double radio morphology. The XMM-Newton observations are consistent with an ISM with a contribution from hot shocked gas. We compile selected radio and X-ray properties of the nine CSS radio galaxies with X-ray detections so far. We find that 1/3 show evidence for hot shocked gas. We note that the counts in the sources are low and the properties of the 3 sources with evidence for hot shocked gas are typical of the other CSS radio galaxies. We suggest that hot shocked gas may be typical of CSS radio galaxies due to their propagation through their host galaxies.

  6. Classification of peaked spectrum sources by using neural networks

    NASA Astrophysics Data System (ADS)

    Vera, R. J. C.; Tornikoski, M.; Lähteenmäki, A.

    2017-07-01

    Compact steep-spectrum sources (CSS), high frequency peakers (HFP), and gigahertz-peaked spectrum sources (GPS) are compact radio sources with an intense emission (O'Dea 1998, and references therein). Morphological studies, dense gas analyses, and surveys suggesting the absence of a halo diffusion emission, suggest the idea that peaked spectrum sources (PSS) are young AGN (see, Fanti et al. 1995; Readhead et al. 1996; Stanghellini et al. 1997; Bicknell et al. 1997). Previously, Torniainen et al. (2008) carried out a study of GPS sources, finding that those sources do not follow a distinct morphological classification. In addition, they found that many blazars in a flaring state are misclassified as GPS sources (Torniainen et al. 2005). These findings compromised the simple vision of the g alaxy-quasar dualism, and the amount of genuine GPS sources. For this reason, we endeavour a new classification of 363 sources with the aim to find new insights about their spectral properties using neural networks. Through clustering methods, we have grouped galaxies that present a set of similar physical properties. In total, 18 physical variables were used for this purpose. In particular, we used Multi-dimensional Scaling (MDS) and t-distributed Stochastic Neighbour Embedding (t-SNE) analyses. Those analyses proved to be robust for analysing data of the order of hundreds of data. From our analyses, we were unable to find a clear classification for PSS. Moreover, new galaxies presented a flat spectra emission, or high variability in the radio emission, compromising their classification as genuine PSS.

  7. Optimization of polyhydroxybutyrate production by Bacillus sp. CFR 256 with corn steep liquor as a nitrogen source.

    PubMed

    Vijayendra, S V N; Rastogi, N K; Shamala, T R; Anil Kumar, P K; Kshama, L; Joshi, G J

    2007-06-01

    Polyhydroxyalkanotes (PHAs), the eco-friendly biopolymers produced by many bacteria, are gaining importance in curtailing the environmental pollution by replacing the non-biodegradable plastics derived from petroleum. The present study was carried out to economize the polyhydroxybutyrate (PHB) production by optimizing the fermentation medium using corn steep liquor (CSL), a by-product of starch processing industry, as a cheap nitrogen source, by Bacillus sp. CFR 256. Response surface methodology (RSM) was used to optimize the fermentation medium using the variables such as corn steep liquor (5-25 g l(-1)), Na(2)HPO(4) 2H(2)O (2.2-6.2 g l(-1)), KH(2)PO(4) (0.5-2.5 g l(-1)), sucrose (5-55 g l(-1)) and inoculum concentration (1-25 ml l(-1)). Central composite rotatable design (CCRD) experiments were carried out to study the complex interactions of the variables.The optimum conditions for maximum PHB production were (g l(-1)): CSL-25, Na(2)HPO(4) 2H(2)O-2.2, KH(2)PO(4) - 0.5, sucrose - 55 and inoculum - 10 (ml l(-1)). After 72 h of fermentation, the amount of PHA produced was 8.20 g l(-1) (51.20% of dry cell biomass). It is the first report on optimization of fermentation medium using CSL as a nitrogen source, for PHB production by Bacillus sp.

  8. Assessment of choroidal thickness before and after steep Trendelenburg position using swept-source optical coherence tomography.

    PubMed

    Rim, Tyler Hyungtaek; Lee, Christopher Seungkyu; Kim, Kangyoon; Kim, Sung Soo

    2015-04-01

    To evaluate changes in choroidal thickness before and after steep Trendelenburg position (STP, 40° head-down) using automated segmentation software to analyse swept-source optical coherence tomography (SS-OCT) data. The eyes of 20 healthy volunteers underwent a three-dimensional wide scanning protocol with SS-OCT (Topcon, Tokyo, Japan) at baseline, immediately after STP was initiated, and 5, 10 and 15 min after STP; blood pressure and heart rate were measured concurrently. The predictive mean difference was calculated using a generalised linear mixed model that adjusted for potential confounders. Mean choroidal thickness significantly and transiently increased immediately (268.18±9.24 μm, p<0.01) and 5 min (264.25±9.30 μm, p=0.03) after STP, relative to baseline (256.51±9.20 μm). However, choroidal thickness decreased by 10 min (262.51±9.34 μm, p=0.15) and 15 min (261.38±9.40 μm, p=0.37) after STP. Mean arterial pressure also transiently increased from baseline (78.2±1.2 mm Hg) immediately after STP (79.9±1.1 mm Hg, p=0.01), but normalised by 5 min after STP (p>0.05 for all comparisons ≥5 min). Choroidal thickness significantly but transiently increases after adopting STP, as evaluated by automated layer segmentation analysis of SS-OCT data. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

  9. Plant Growth Absorption Spectrum Mimicking Light Sources

    PubMed Central

    Jou, Jwo-Huei; Lin, Ching-Chiao; Li, Tsung-Han; Li, Chieh-Ju; Peng, Shiang-Hau; Yang, Fu-Chin; Justin Thomas, K. R.; Kumar, Dhirendra; Chi, Yun; Hsu, Ban-Dar

    2015-01-01

    Plant factories have attracted increasing attention because they can produce fresh fruits and vegetables free from pesticides in all weather. However, the emission spectra from current light sources significantly mismatch the spectra absorbed by plants. We demonstrate a concept of using multiple broad-band as well as narrow-band solid-state lighting technologies to design plant-growth light sources. Take an organic light-emitting diode (OLED), for example; the resulting light source shows an 84% resemblance with the photosynthetic action spectrum as a twin-peak blue dye and a diffused mono-peak red dye are employed. This OLED can also show a greater than 90% resemblance as an additional deeper red emitter is added. For a typical LED, the resemblance can be improved to 91% if two additional blue and red LEDs are incorporated. The approach may facilitate either an ideal use of the energy applied for plant growth and/or the design of better light sources for growing different plants. PMID:28793503

  10. Sediment sources, spatiotemporal variability and rates of fluvial bedload transport in glacier-connected steep mountain valleys in western Norway (Erdalen and Bødalen drainage basins)

    NASA Astrophysics Data System (ADS)

    Beylich, Achim A.; Laute, Katja

    2015-01-01

    Contemporary fluvial bedload transport rates are still very difficult to measure and, as a result of this, in many sites only quantitative data on suspended and solute transport are included in sediment budget studies carried out for defined drainage basin systems. The presented analysis of fluvial bedload dynamics in different defined subsystems of the glacier-connected Erdalen (79.5 km2) and Bødalen (60.1 km2) drainage basins in the steep fjord landscape of western Norway provides insights into (i) detectable relevant sediment sources, (ii) instream channel storage of bedload material, (iii) spatiotemporal variability and controls of bedload transport rates and bedload yields, and (iv) the absolute and relative importance of fluvial bedload transport within the sedimentary budgets of these steep cold climate mountain valleys. Rockfalls, snow avalanches, stream channel bank erosion, and fluvial transfers through small tributaries draining slope systems are relevant sediment sources for fluvial bedload transport in the main stream channels, whereas the main outlet glaciers in both drainage basins are not of importance as all bedload material delivered directly from these outlet glaciers is trapped within proglacial lakes. Narrow valleys within both drainage basin systems are characterized by a higher intensity of slope-channel coupling and display higher rates of sediment supply from slopes into the main stream channels than wider valleys. Snow avalanches are the most important sediment source in Erdalen, whereas fluvial transfers through small tributaries followed by snow avalanches are most important in Bødalen. Longer term, instream channel storage is not of great importance in the steep Bødalen drainage basin but currently plays an important role within the Erdalen drainage basin, which is characterized by a stepped longitudinal main valley bottom profile favoring deposition of bedload material within less steep main channel reaches. The mean annual bedload

  11. 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.

  12. 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.

  13. 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.

  14. Flow Around Steep Topography

    DTIC Science & Technology

    2015-09-30

    Flow around steep topography T. M. Shaun Johnston Scripps Institution of Oceanography University of California, San Diego 9500 Gilman Drive, M...tall, steep, submarine topography and islands. During the Flow Encountering Abrupt Topography (FLEAT) DRI, investigators will determine: • Whether...estimates from making accurate statistical/deterministic predictions at ᝺ km resolution around submarine topography and islands? How can we

  15. Optical design of a digitally spectrum-controllable light source

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Ma, Suodong; Shen, Weimin

    2014-11-01

    Spectrum-controllable light sources are able to generate desired spectrums as specific requirements, which have attracted huge interesting in many fields, e.g. life science, machine vision, defense-related science and technology. A controllable light source in the range from 0.38 to 0.78 μm, which is based on a Digital Micromirror Device (DMD) and an Offner dispersion configuration with a convex grating, is proposed in this paper. Due to its fast speed, high fidelity and simplicity with all spherical elements, the Offner relay is chosen as the dispersion structure compared with other existing spectroscopic configurations. The DMD located on the spectral image plane of the dispersion configuration is used to choose spectral channels according to the desired spectral radiance distribution through modulating micromirrors. The optical system of the proposed digitally spectrum-controllable light source is designed and further simulated by Zemax.

  16. Development of a continuous broad-energy-spectrum electron source

    NASA Technical Reports Server (NTRS)

    Adamo, R. C.; Nanevicz, J. E.

    1985-01-01

    The development of a practical prototype, large-area, continuous-spectrum, multienergy electron source to simulate the lower energy (approx = 1 to 30 keV) portion of the geosynchronous orbit electron environment was investigated. The results of future materials-charging tests using this multienergy source should significantly improve the understanding of actual in-orbit charging processes and should help to resolve some of the descrepancies between predicted and observed spacecraft materials performance.

  17. 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.

  18. What are the gigahertz peaked-spectrum radio sources?

    NASA Technical Reports Server (NTRS)

    O'Dea, C. P.; Baum, S. A.; Stanghellini, C.

    1991-01-01

    The astrophysical implications of recent radio and optical observations of the powerful compact gigahertz peaked-spectrum (GPS) radio sources are discussed. Some tentative conclusions are presented and a scenario based on the existing data is suggested. It is argued that the spectrum is due to synchrotron self-absorption, which is assumed as the basis for the present inferences from the radio spectral shape. The finding that some GPS sources have a very narrow spectral shape is consistent with the hypothesis that there is a narrow range of size scales which dominate the radio luminosity. The highly inverted LF radio spectrum is consistent with the hypothesis that the radio source is tightly confined. The conclusion that the radio polarization of these sources is systematically low is consistent either with a very tangled magnetic field or very large Faraday rotation measures. It is suggested that GPS radio sources are formed when the radio plasma is confined on the scale of the narrow-line region by an unusually dense and clumpy ISM. The existing optical spectroscopic results are also consistent with the existence of a dense and dusty nuclear ISM.

  19. Optical identifications of flat-spectrum radio sources

    SciTech Connect

    Condon, J.J.; Condon, M.A.; Broderick, J.J.; Davis, M.M.

    1983-01-01

    A complete sample of radio sources with S> or =0.3 Jy at 1400 MHz, +24/sup 0/sources were made from the PSS prints on the basis of accurate position coincidence alone. Nearly all sources with ''flat'' high-frequency spectra ..cap alpha..(2695, 8085)<+0.5 are identified, and most of the identifications are QSO candidates. Those sources with flat low-frequency spectra but ..cap alpha..(2695, 8085)> or =+0.5 are usually in empty fields. The lower limits that can be assigned to the radio-optical spectral indices ..cap alpha../sub RO/ of these sources are significantly higher than the median ..cap alpha../sub RO/ of the sources with flat high-frequency spectra, so the optical characteristics of the two classes of radio source are intrinsically different. The radio and optical fluxes of flat-spectrum QSO's appear to be correlated, at least when averaged over 10/sup 2/--10/sup 3/ yr.

  20. 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

  1. 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.

  2. 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.

  3. The power spectrum of the Point Source Catalogue redshift survey

    NASA Astrophysics Data System (ADS)

    Sutherland, W.; Tadros, H.; Efstathiou, G.; Frenk, C. S.; Keeble, O.; Maddox, S.; McMahon, R. G.; Oliver, S.; Rowan-Robinson, M.; Saunders, W.; White, S. D. M.

    1999-09-01

    We measure the redshift-space power spectrum P(k) for the recently completed IRAS Point Source Catalogue (PSC) redshift survey, which contains 14 500 galaxies over 84 per cent of the sky with 60-μm flux >=0.6 Jy. Comparison with simulations shows that our estimated errors on P(k) are realistic, and that systematic errors resulting from the finite survey volume are small for wavenumbers k >~ 0.03 h Mpc^-1. At large scales our power spectrum is intermediate between those of the earlier QDOT and 1.2-Jy surveys, but with considerably smaller error bars; it falls slightly more steeply to smaller scales. We have fitted families of CDM-like models using the Peacock-Dodds formula for non-linear evolution; the results are somewhat sensitive to the assumed small-scale velocity dispersion σ_V. Assuming a realistic σ_V ~ 300 km s^-1 yields a shape parameter Γ ~ 0.25 and normalization bσ_8 ~ 0.75; if σ_V is as high as 600 km s^-1 then Γ = 0.5 is only marginally excluded. There is little evidence for any `preferred scale' in the power spectrum or non-Gaussian behaviour in the distribution of large-scale power.

  4. 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.

  5. 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.

  6. 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.

  7. Broadband Spectral Modeling of the Extreme Gigahertz-peaked Spectrum Radio Source PKS B0008-421

    NASA Astrophysics Data System (ADS)

    Callingham, J. R.; Gaensler, B. M.; Ekers, R. D.; Tingay, S. J.; Wayth, R. B.; Morgan, J.; Bernardi, G.; Bell, M. E.; Bhat, R.; Bowman, J. D.; Briggs, F.; Cappallo, R. J.; Deshpande, A. A.; Ewall-Wice, A.; Feng, L.; Greenhill, L. J.; Hazelton, B. J.; Hindson, L.; Hurley-Walker, N.; Jacobs, D. C.; Johnston-Hollitt, M.; Kaplan, D. L.; Kudrayvtseva, N.; Lenc, E.; Lonsdale, C. J.; McKinley, B.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Oberoi, D.; Offringa, A. R.; Ord, S. M.; Pindor, B.; Prabu, T.; Procopio, P.; Riding, J.; Srivani, K. S.; Subrahmanyan, R.; Udaya Shankar, N.; Webster, R. L.; Williams, A.; Williams, C. L.

    2015-08-01

    large population of GPS sources that have ceased activity, and that a portion of the ultra-steep-spectrum source population could be composed of these GPS sources in a relic phase.

  8. 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.

  9. 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.

  10. Millimeter-wave spectra and variability of bright, compact radio sources

    NASA Technical Reports Server (NTRS)

    Edelson, R. A.

    1987-01-01

    Observations at 2.7 mm and at 1.5 cm were used to study the millimeter spectra and variability of 176 bright, compact radio sources. More than 20 percent of the flat-spectrum sources, but none of the steep-spectrum sources, were seen to vary at 1.5 cm by at least 30 percent over ten months. This is consistent with the hypothesis that flat-spectrum sources are compact and possibly beamed, while steep-spectrum sources are not. These data can also be used to choose sources for VLBI observations and for calibration of millimeter-wave observations.

  11. 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.

  12. Effects of Source Correlations on the Spectrum of Radiated Fields

    DTIC Science & Technology

    1990-09-01

    paraxial approximation, with a known result for far-zone radiant intensity of Gaussian Schell - model sources3. Spectral changes on propagation of...33 2.2 The radiation efficiency of planar Gaussian Schell - model sources ............ 34...increase in the source correlation length. Page 40. Figure 2.5: The radiation efficiency of Gaussian Schell - model sources as a function of the rms

  13. [Development of soft X-ray and vacuum ultraviolet spectrum sources].

    PubMed

    Chen, Bo; Ni, Qi-liang; Cao, Jian-lin; Li, Fu-tian; Chen, Xing-dan

    2005-03-01

    The soft X-ray and vacuum ultraviolet sources developed in CIOMP are presented. The wall-stabilized argon arc source with spectrum stability and repeatability of +/-0.3% is applied to the calibration of spectrum intensity distribution of the vacuum ultraviolet instruments as an absolute standard source. The Penning source, duobplasma source and hollow cathode source are able to produce atomic and ionic line spectra as a wavelength standard source, which covers a few nanometers to several tens nanometers with spectrum radiation stability and repeatability of +/-1.0%. In particular, the low debris laser produced plasma source with liquid aerosol spray target recently developed can emit stronger soft X-ray for soft X-ray lithography and metrology, which has a transfer efficiency as high as 0.75%/2pi x sr/2% bandwidth.

  14. 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…

  15. 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…

  16. 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.

  17. 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.

  18. Physical Conditions in Faint Gigahertz-Peaked Spectrum Radio Sources

    NASA Astrophysics Data System (ADS)

    Tyul'Bashev, S. A.

    2001-06-01

    Weak, compact radio sources (˜100 mJy peak flux, L˜1 10 pc) with their spectral peaks at about a gigahertz are studied, based on the complete sample of 46 radio sources of Snellen, drawn from high-sensitivity surveys, including the low-frequency Westerbork catalog. The physical parameters have been estimated for 14 sources: the magnetic field (H ⊥), the number density of relativistic particles (n e), the energy of the magnetic field , and the energy of relativistic particles (E e). Ten sources have & $E_{H_ bot } ≪ E_e ; , three have approximate equipartition of the energies & (E_{H_ bot } ˜ E_e ) ; , and only one has & E_{H_ bot } ≫ E_e ; . The mean magnetic fields in quasars (10-3 G) and galaxies (10-2 G) have been estimated. The magnetic field appears to be related to the sizes of compact features as & H ˜ 1/sqrt L $ ; .

  19. 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.

  20. 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.

  1. 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.

  2. The Population of KPC-Scale Flat-Spectrum Radio Sources

    NASA Astrophysics Data System (ADS)

    Augusto, Pedro; Wilkinson, Peter N.; Browne, Ian W. A.

    In this paper we present a subsample of 55 flat-spectrum radio sources dominated by (~ 100 mas) kpc-scale structure, selected from a parent sample of 1665 VLA sources. Most are core-jets and 23 are CSO/MSO candidates. Properties of the subsample are discussed.

  3. Energy spectrum of extragalactic gamma-ray sources

    NASA Technical Reports Server (NTRS)

    Protheroe, R. J.

    1985-01-01

    The result of Monte Carlo electron photon cascade calculations for propagation of gamma rays through regions of extragalactic space containing no magnetic field are given. These calculations then provide upper limits to the expected flux from extragalactic sources. Since gamma rays in the 10 to the 14th power eV to 10 to the 17th power eV energy range are of interest, interactions of electrons and photons with the 3 K microwave background radiation are considered. To obtain an upper limit to the expected gamma ray flux from sources, the intergalactic field is assumed to be so low that it can be ignored. Interactions with photons of the near-infrared background radiation are not considered here although these will have important implications for gamma rays below 10 to the 14th power eV if the near infrared background radiation is universal. Interaction lengths of electrons and photons in the microwave background radiation at a temperature of 2.96 K were calculated and are given.

  4. Analysis of x-ray spectrum obtained in electron cyclotron resonance x-ray source

    SciTech Connect

    Baskaran, R.; Selvakumaran, T.S.; Sunil Sunny, C.

    2006-03-15

    The analysis of the x-ray spectrum obtained in electron cyclotron resonance (ECR) x-ray source is carried out. Assuming single-particle motion, the electron acceleration and its final energy are calculated for TE{sub 111} cylindrical cavity field and uniform external dc magnetic field. In the calculation, initial coordinates of 40 000 electrons were uniformly selected over the central plane of the cavity using random number generator. The final energy of each electron when it hits the wall is stored and the electron energy distribution is obtained. Using the general purpose Monte Carlo N-particle transport code version 4A, the geometry of the ECR x-ray source is modeled. The x-ray energy spectrum is calculated for the geometry model and the numerically calculated electron energy distribution. The calculated x-ray spectrum is compared with the experimentally measured x-ray spectrum.

  5. Broadband source spectrum, seismic energy, and stress drop of the 1989 Macquarie Ridge earthquake

    SciTech Connect

    Houston, H. )

    1990-06-01

    The author computes the broadband source spectrum at periods from 1 to 50 seconds using teleseismic P body waves of the May 23, 1989 Macquarie Ridge earthquake (M{sub W} = 8.1) recorded by the GDSN, GEOSCOPE, and IDA networks. The average source spectrum is obtained by windowing, tapering, and Fourier-transforming P waves, removing from the spectra the effects of attenuation, geometrical spreading, and radiation pattern, and averaging logarithmically over the stations. The source spectrum for the strike-slip Macquarie Ridge earthquake is higher than an average source spectrum of seven recent large earthquakes (scaled to be comparable to a M{sub W} = 8.1 earthquake) by a factor of 2 to 3 at periods of 1 to 20 seconds. These other earthquakes were underthrusting events in subduction zones. Using Haskell's formulation assuming a point source with no directivity, she estimates the seismically radiated energy from the source spectrum by integrating the square of the source spectrum in velocity and scaling the result. The seismic energy thus estimated for the Macquarie Ridge earthquake is 3 to 8 {times} 10{sup 23} ergs. An Orowan stress drop can be obtained from the seismic energy and moment. The Orowan stress drop for the Macquarie Ridge earthquake is about 20 to 50 bars, much higher than similarly determined stress drops of other recent large earthquakes. There is a correlation between the Orowan stress drops and time since the last earthquake of comparable or larger magnitude for seven recent large earthquakes. This correlation suggests that a healing process operates that may control the mechanical strength of the fault and is important on time scales of tens to hundreds of years.

  6. Optical Spectra of Candidate International Celestial Reference Frame (ICRF) Flat-spectrum Radio Sources. III.

    NASA Astrophysics Data System (ADS)

    Titov, O.; Pursimo, T.; Johnston, Helen M.; Stanford, Laura M.; Hunstead, Richard W.; Jauncey, David L.; Zenere, Katrina A.

    2017-04-01

    In extending our spectroscopic program, which targets sources drawn from the International Celestial Reference Frame (ICRF) Catalog, we have obtained spectra for ˜160 compact, flat-spectrum radio sources and determined redshifts for 112 quasars and radio galaxies. A further 14 sources with featureless spectra have been classified as BL Lac objects. Spectra were obtained at three telescopes: the 3.58 m European Southern Observatory New Technology Telescope, and the two 8.2 m Gemini telescopes in Hawaii and Chile. While most of the sources are powerful quasars, a significant fraction of radio galaxies is also included from the list of non-defining ICRF radio sources.

  7. 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.

  8. [Method to measure spectrum intensity from laser plasma soft X-ray source].

    PubMed

    Ni, Qi-liang; Gong, Yan; Chen, Bo; Cao, Jian-lin

    2004-01-01

    This paper presents a method to detect and measure spectrum intensity from a laser plasma soft X-ray source. A Channel Electron Multiplier (CEM) and a calibrated silicon photodiode were used as detectors in this method, the former is a nonstandard detector and the latter is a standard one. Charge-sensitive preamplifiers were used for measuring total charges generated by detectors, and a monochromator with high resolution was employed as the spectrometer. The formulae to calculate spectrum intensity from laser plasma soft X-ray source was given, based on the known grating efficiency of the monochromator, CEM's gain and responsivity of the silicon photodiode to photons.

  9. Inhomogeneity in cosmic ray sources as the origin of the electron spectrum and the PAMELA anomaly.

    PubMed

    Shaviv, Nir J; Nakar, Ehud; Piran, Tsvi

    2009-09-11

    We show that inhomogeneity of cosmic ray (CR) sources, due to the concentration of supernova remnants (SNRs) towards the galactic spiral arms, can naturally explain the anomalous increase in the positron/electron ratio observed by PAMELA. We consistently recover the observed positron fraction between 1 and 100 GeV using SNRs as the sole source of CRs. The contribution of a few known nearby SNRs dominates the CR electron spectrum above approximately 100 GeV, leading to the relatively flat spectrum observed by Fermi and to the sharp cutoff observed by H.E.S.S.

  10. Naturally inflating on steep potentials through electromagnetic dissipation

    SciTech Connect

    Anber, Mohamed M.; Sorbo, Lorenzo

    2010-02-15

    In models of natural inflation, the inflaton is an axionlike particle. Unfortunately, axion potentials in UV-complete theories appear to be too steep to drive inflation. We show that, even for a steep potential, natural inflation can occur if the coupling between axion and gauge fields is taken into account. Because of this coupling, quanta of the gauge field are produced by the rolling of the axion. If the coupling is large enough, such a dissipative effect slows down the axion, leading to inflation even for a steep potential. The spectrum of perturbations is quasiscale invariant, but in the simplest construction its amplitude is larger than 10{sup -5}. We discuss a possible way out of this problem.

  11. OpenMS-Simulator: an open-source software for theoretical tandem mass spectrum prediction.

    PubMed

    Wang, Yaojun; Yang, Fei; Wu, Peng; Bu, Dongbo; Sun, Shiwei

    2015-04-02

    Tandem mass spectrometry (MS/MS) acts as a key technique for peptide identification. The MS/MS-based peptide identification approaches can be categorized into two families, namely, de novo and database search. Both of the two types of approaches can benefit from an accurate prediction of theoretical spectrum. A theoretical spectrum consists of m/z and intensity of possibly occurring ions, which are estimated via simulating the spectrum generating process. Extensive researches have been conducted for theoretical spectrum prediction; however, the prediction methods suffer from low prediciton accuracy due to oversimplifications in the spectrum simulation process. In the study, we present an open-source software package, called OpenMS-Simulator, to predict theoretical spectrum for a given peptide sequence. Based on the mobile-proton hypothesis for peptide fragmentation, OpenMS-Simulator trained a closed-form model for the intensity ratio of adjacent y ions, from which the whole theoretical spectrum can be constructed. On a collection of representative spectra datasets with annotated peptide sequences, experimental results suggest that OpenMS-Simulator can predict theoretical spectra with considerable accuracy. The study also presents an application of OpenMS-Simulator: the similarity between theoretical spectra and query spectra can be used to re-rank the peptide sequence reported by SEQUEST/X!Tandem. OpenMS-Simulator implements a novel model to predict theoretical spectrum for a given peptide sequence. Compared with existing theoretical spectrum prediction tools, say MassAnalyzer and MSSimulator, our method not only simplifies the computation process, but also improves the prediction accuracy. Currently, OpenMS-Simulator supports the prediction of CID and HCD spectrum for peptides with double charges. The extension to cover more fragmentation models and support multiple-charged peptides remains as one of the future works.

  12. 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.

  13. The Parkes quarter-Jansky flat-spectrum sample. I. Sample selection and source identifications

    NASA Astrophysics Data System (ADS)

    Jackson, C. A.; Wall, J. V.; Shaver, P. A.; Kellermann, K. I.; Hook, I. M.; Hawkins, M. R. S.

    2002-04-01

    We present a new sample of quarter-Jansky flat-spectrum radio sources selected to search for high-redshift quasars and to study the evolution of the flat-spectrum quasar population. The sample comprises 878 radio sources selected from the Parkes catalogues with spectral indices alpha 5 GHz_2.7 GHz >=-0.4 where Snu ~ nu alpha . The sample covers all right ascensions and the declination range from -80fdg0 to +2fdg5 , excluding low galactic latitudes (mid b mid < 10deg) and the Magellanic Cloud regions. We have obtained improved radio source positions, firstly to reconfirm the majority of the existing identifications, and secondly, using digitized sky-survey data and deep B, Gunn-i and Gunn-z CCD-imaging, to find optical identifications for 223 previously-unidentified sources. We present the final catalogue of 878 flat-spectrum sources: 827 are compact radio sources identified with galaxies, quasars and BL Lac objects, 38 have either extended radio structure or are identified with Galactic objects (PN, HII or non-compact radio source), 4 are obscured by Galactic stars, and 9 (1 per cent of the total sample) remain unidentified. Full Appendices A-D are only available in electronic form at http://www.edpsciences.org

  14. A Survey of Information Source Preferences of Parents of Individuals with Autism Spectrum Disorder.

    PubMed

    Gibson, Amelia N; Kaplan, Samantha; Vardell, Emily

    2017-07-01

    For parents of children with an Autism spectrum disorder (ASD), high quality, easily accessible information and a strong peer network can be the key to raising a happy, healthy child, and maintaining family well-being and emotional resilience. This article reports the findings of an anonymous survey examining the information source preferences for 935 parents of individuals with ASDs in North Carolina. Data indicates that parents show similar information seeking patterns across the age spectrum, that availability of information (as indicated by overall information source selection) decrease as children age. It also shows that parents rely heavily on local sources of information, preferring them to nonlocal sources (such as the internet) for many types of information.

  15. Regularized least-squares migration of simultaneous-source seismic data with adaptive singular spectrum analysis.

    PubMed

    Li, Chuang; Huang, Jian-Ping; Li, Zhen-Chun; Wang, Rong-Rong

    2017-01-01

    Simultaneous-source acquisition has been recognized as an economic and efficient acquisition method, but the direct imaging of the simultaneous-source data produces migration artifacts because of the interference of adjacent sources. To overcome this problem, we propose the regularized least-squares reverse time migration method (RLSRTM) using the singular spectrum analysis technique that imposes sparseness constraints on the inverted model. Additionally, the difference spectrum theory of singular values is presented so that RLSRTM can be implemented adaptively to eliminate the migration artifacts. With numerical tests on a flat layer model and a Marmousi model, we validate the superior imaging quality, efficiency and convergence of RLSRTM compared with LSRTM when dealing with simultaneous-source data, incomplete data and noisy data.

  16. 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.

  17. 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…

  18. A Survey of Information Source Preferences of Parents of Individuals with Autism Spectrum Disorder

    ERIC Educational Resources Information Center

    Gibson, Amelia N.; Kaplan, Samantha; Vardell, Emily

    2017-01-01

    For parents of children with an Autism spectrum disorder (ASD), high quality, easily accessible information and a strong peer network can be the key to raising a happy, healthy child, and maintaining family well-being and emotional resilience. This article reports the findings of an anonymous survey examining the information source preferences for…

  19. 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…

  20. Observations of VLA-FIRST/GB6 Inverted-Spectrum Radio Sources

    NASA Astrophysics Data System (ADS)

    Guerra, E. J.; Haarsma, D. B.; Partridge, R. B.

    1998-12-01

    Extragalactic radio sources with spectral peaks above 4.8 GHz are difficult to detect on the basis of available surveys since the highest radio frequency survey of any substantial solid angle is the Green Bank 6 cm (GB6) survey. Until surveys at higher frequencies are performed, selecting sources with inverted spectra between 1.4 GHz and 4.8 GHz (increasing flux with increasing frequency) is the most promising method of detecting Gigahertz Peaked Spectrum (GPS) sources with peak frequencies above 4.8 GHz. Many models of radio source evolution predict the existence of such GPS sources as the precursors of other classes of radio sources. The radio spectra and other properties of these ``extreme'' GPS sources may be used to constrain such models. Extreme GPS sources can be a significant foreground for cosmic microwave background (CMB) anisotropy experiments (such as the MAP and Planck Surveyor satellites) because a steeply rising spectrum can mimic the Rayleigh-Jeans portion of the CMB spectrum. Extrapolating radio source counts from lower frequencies is risky, since available surveys are at frequencies approximately 20 to 100 times lower than those used in CMB anisotropy experiments. The source counts and spectral indices of discrete radio sources between 20 GHz and 100 GHz are open and important questions for CMB anisotropy experiments, and necessary ingredients for foreground subtraction if results from these experiments are to be used to accurately determine cosmological parameters. A sample was carefully selected from the cross-correlation of the VLA FIRST (February 1998 release) and GB6 surveys. For our purposes, a source is defined as inverted when alpha_ {1.4-4.8}>0.4, where S ~ nu (alpha ) . Data cuts have been enforced to minimize the effects of confused or extended sources and insure reliable spectral indices. The remaining sample contains 308 inverted-spectrum radio sources. Observations at 21 GHz are scheduled in November 1998 at the 140-foot telescope

  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. Extension of the angular spectrum method to calculate pressure from a spherically curved acoustic source.

    PubMed

    Vyas, Urvi; Christensen, Douglas A

    2011-11-01

    The angular spectrum method is an accurate and computationally efficient method for modeling acoustic wave propagation. The use of the typical 2D fast Fourier transform algorithm makes this a fast technique but it requires that the source pressure (or velocity) be specified on a plane. Here the angular spectrum method is extended to calculate pressure from a spherical transducer-as used extensively in applications such as magnetic resonance-guided focused ultrasound surgery-to a plane. The approach, called the Ring-Bessel technique, decomposes the curved source into circular rings of increasing radii, each ring a different distance from the intermediate plane, and calculates the angular spectrum of each ring using a Fourier series. Each angular spectrum is then propagated to the intermediate plane where all the propagated angular spectra are summed to obtain the pressure on the plane; subsequent plane-to-plane propagation can be achieved using the traditional angular spectrum method. Since the Ring-Bessel calculations are carried out in the frequency domain, it reduces calculation times by a factor of approximately 24 compared to the Rayleigh-Sommerfeld method and about 82 compared to the Field II technique, while maintaining accuracies of better than 96% as judged by those methods for cases of both solid and phased-array transducers.

  3. Spectrum synthesis for a spectrally tunable light source based on a DMD-convex grating Offner configuration

    NASA Astrophysics Data System (ADS)

    Ma, Suodong; Pan, Qiao; Shen, Weimin

    2016-09-01

    As one kind of light source simulation devices, spectrally tunable light sources are able to generate specific spectral shape and radiant intensity outputs according to different application requirements, which have urgent demands in many fields of the national economy and the national defense industry. Compared with the LED-type spectrally tunable light source, the one based on a DMD-convex grating Offner configuration has advantages of high spectral resolution, strong digital controllability, high spectrum synthesis accuracy, etc. As a key link of the above type light source to achieve target spectrum outputs, spectrum synthesis algorithm based on spectrum matching is therefore very important. An improved spectrum synthesis algorithm based on linear least square initialization and Levenberg-Marquardt iterative optimization is proposed in this paper on the basis of in-depth study of the spectrum matching principle. The effectiveness of the proposed method is verified by a series of simulations and experimental works.

  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 dosimetry, moderated energy spectrum, and neutron capture therapy for californium-252 medical sources

    NASA Astrophysics Data System (ADS)

    Rivard, Mark Joseph

    Examination of neutron dosimetry for 252Cf has been conducted using calculative and experimental means. Monte Carlo N-Particle (MCNP) transport code was used in a distributed computing environment as a parallel virtual machine (PVM) to determine the absorbed neutron dose and neutron energy spectrum from 252Cf in a variety of clinically relevant materials. Herein, a Maxwellian spectrum was used to model the 252Cf neutron emissions within these materials. 252Cf mixed-field dosimetry of Applicator Tube (AT) type sources was measured using 1.0 and 0.05 cm3 tissue-equivalent ion chambers and a miniature GM counter. A dosimetry protocol was formulated similar that of ICRU 45. The 252Cf AT neutron dosimetry was determined in the cylindrical coordinate system formalism recommended by the AAPM Task Group 43. These results demonstrated the overwhelming dependence of dosimetry on the source geometry factor as there was no significant neutron attenuation within the source or encapsulation. Gold foils and TLDs were used to measure the thermal flux in the vicinity of 252Cf AT sources to compare with the results calculated using MCNP. As the fast neutron energy spectrum did not markedly changed at increasing distances from the AT source, neutron dosimetry results obtained with paired ion chambers using fixed sensitivity factors agreed well with MCNP results and those in the literature. Calculations of moderated 252Cf neutron energy spectrum with various loadings of 10B and 157Gd were performed, in addition to analysis of neutron capture therapy dosimetry with these isotopes. Radiological concerns such as personnel exposure and shielding of 252Cf emissions were examined. Feasibility of a high specific-activity 252Cf HDR source was investigated through radiochemical and metallurgical studies using stand-ins such as Tb, Gd and 249Cf. Issues such as capsule burst strength due to helium production for a variety of proposed HDR sources were addressed. A recommended 252Cf source

  6. 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.

  7. 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

  8. VLBI observations of nineteen GHz-peaked-spectrum radio sources at 1.6 GHz

    NASA Astrophysics Data System (ADS)

    Liu, X.; Cui, L.; Luo, W.-F.; Shi, W.-Z.; Song, H.-G.

    2007-07-01

    Aims and Methods: We present the results of VLBI observations of nineteen GHz-peaked-spectrum (GPS) radio sources at 1.6 GHz. Of them, 15 sources are selected from the Parkes half-jansky (PHJ) sample (Snellen et al. 2002, MNRAS, 337, 981), and 4 others are from our previous observation list. We aimed at imaging the structure of GPS sources, searching for compact symmetric objects (CSOs) and studying the absorption for the convex radio spectra of GPS sources. Results: We obtained total-intensity 1.6 GHz VLBI images of 17 sources for the first time. Of them, 80% show a mini-double-lobe radio structure, indicating that they are CSOs or candidates, and their host AGNs could be edge-on to us. This result suggests that there is a high incidence of mini double-lobe sources (or CSOs) in the PHJ sample. The sources J0323+0534, J1135-0021, J1352+0232, J2058+0540, J2123-0112, and J2325-0344 are classified as CSOs with measured redshift, showing double-lobe structure with sizes of <1 kpc. Three sources J1057+0012, J1600-0037, and J1753+2750 are considered as core-jet sources according to their morphologies and flux variability.

  9. Evaluation of the beta energy spectrum from a distributed uranium mill tailings source

    SciTech Connect

    Reif, R.H.; Martz, D.E.; Carlson, D.S.; Turner, J.B. )

    1993-10-01

    The beta energy spectra from uranium mill tailings, 90Sr with different absorber thicknesses, and a uranium metal slab were measured and compared to select an appropriate beta source for calibrating a personal dosimeter to measure shallow dose equivalent when exposed to uranium mill tailings. The measured beta energy spectrum from the 90Sr source, with a 111 mg cm-2 cover thickness, was selected as a possible calibration source for a personnel dosimeter. The dose equivalent rate to the skin at 1 cm from a distributed tailings source of infinite thickness, with a 226Ra activity of 56 Bq g-1 (1.5 x 10(3) pCi g-1), was measured to be 0.024 mSv h-1 (2.4 mrem h-1).

  10. Evaluation of the beta energy spectrum from a distributed uranium mill tailings source.

    PubMed

    Reif, R H; Martz, D E; Carlson, D S; Turner, J B

    1993-10-01

    The beta energy spectra from uranium mill tailings, 90Sr with different absorber thicknesses, and a uranium metal slab were measured and compared to select an appropriate beta source for calibrating a personal dosimeter to measure shallow dose equivalent when exposed to uranium mill tailings. The measured beta energy spectrum from the 90Sr source, with a 111 mg cm-2 cover thickness, was selected as a possible calibration source for a personnel dosimeter. The dose equivalent rate to the skin at 1 cm from a distributed tailings source of infinite thickness, with a 226Ra activity of 56 Bq g-1 (1.5 x 10(3) pCi g-1), was measured to be 0.024 mSv h-1 (2.4 mrem h-1).

  11. Source spectrum and source time function of volcanic tremor determined with a dense seismic network near the summit crater of Izu-Oshima volcano, Japan

    NASA Astrophysics Data System (ADS)

    Oikawa, Jun; Ida, Yoshiaki; Yamaoka, Koshun

    1994-05-01

    Digital seismic records of episodic volcanic tremor, obtained with a dense seismic network near the summit crater of Izu-Oshima volcano, were analyzed to determine source spectrum and source time function. Source spectrum and transfer function could be separated because the seismic records showed a systematic change with distance from the source. The source spectrum of velocity amplitude had a different frequency, f, dependence above and below a corner frequency of 8 to 10 Hz. At high ranges, the spectrum was proportional to f(exp -2), while at low ranges, it was proportional to f(exp 2). Inversion of this frequency-dependent source spectrum yields a source time function that can be represented by an impulse that attenuates in about 0.1 s. Repeated impulses could explain observed volcanic tremor that persists for many minutes or longer and that have complicated phase spectra. The source spectrum gives an energy release rate of about 5.2 x 10(exp 2) J/s, so that the total energy released is about 1.0 x 10(exp 5) J during a tremor episode of about 3 min at Izu-Oshima. Such energy release is comparable to the seismic energy released by an earthquake of magnitude 0.1.

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

    SciTech Connect

    Kneller, James P.; Kabadi, Neel V.

    2015-07-16

    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. Furthermore, 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.

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

    DOE PAGES

    Kneller, James P.; Kabadi, Neel V.

    2015-07-16

    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. Inmore » 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. Furthermore, 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.« less

  14. 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.

  15. 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.

  16. 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.

  17. [Decomposition and analysis of the natural source SLF spectrum using curvelet transform method].

    PubMed

    Jiang, Hong-bo; Chen, Chao; Qin, Qi-ming

    2012-02-01

    Because natural source super low frequency (SLF) electromagnetic detection equipment receives wideband multi-source signal, how to decompose the signal to filter out the interference signal was a key factor for the application of natural source SLF electromagnetic detection technology. In the present article, the detection equipment developed by Peking University was used to survey the coal bed methane data in the Qinshui basin, Shanxi province, and the curvelet transform method was employed to decompose those data. The analysis results indicated that the high-frequency information coming from the decomposition is the interference signals mainly generated by lightning in the atmospheric and directly received by the detection equipment, while the low frequency signal mainly contains the target information. So the reconstructed curve based on the low-frequency information was more favorable for the interpretation of the target, compared with the original spectrum curve. But the curvelet transform method could not remove the artificial frequency signal.

  18. Tachyon inflation with steep potentials

    NASA Astrophysics Data System (ADS)

    Rezazadeh, K.; Karami, K.; Hashemi, S.

    2017-05-01

    Within the framework of tachyon inflation, we consider different steep potentials and check their viability in light of the Planck 2015 data. We see that in this scenario, the inverse power-law potential V (ϕ )=V0(ϕ /ϕ0)-n with n =2 leads to the power-law inflation with the scale factor a (t )∝tq where q >1 , while with n <2 , it gives rise to the intermediate inflation with the scale factor a (t )∝exp (A tf) where A >0 and 0 2 can be compatible with the 95% CL region of Planck 2015 TT, TE, EE +lowP data. We further conclude that the exponential potential V (ϕ )=V0e-ϕ /ϕ0, the inverse cosh potential V (ϕ )=V0/cosh (ϕ /ϕ0), and the mutated exponential potential V (ϕ )=V0[1 +(n -1 )-(n -1 )(ϕ /ϕ0)n] e-ϕ /ϕ0 with n =4 , can be consistent with the 95% CL region of Planck 2015 TT, TE, EE +lowP data. Moreover, using the r -ns constraints on the model parameters, we also estimate the running of the scalar spectral index d ns/d ln k and the local non-Gaussianity parameter fNLlocal. We find that the lower and upper bounds evaluated for these observables are compatible with the Planck 2015 results.

  19. Study on the test of transient ultraviolet spectrum for remote extended area sources with spectrometer

    NASA Astrophysics Data System (ADS)

    Li, Hongguang; Yang, Hongru; Wu, Baoning; Chang, Weijun; Bai, Zhao; Yin, Qingyan

    2010-10-01

    Spectral radiation intensity measurement at ultraviolet wavelengths is important for the material composition analysis of transient extended area light sources. Here we developed transient ultraviolet multi-spectral spectrometer which is utilized to measure relative spectral radiation intensity distributions of remote transient as well as steady-state extended area light sources in the wavelength range (0.22-0.40) μm. Simultaneously the device also shows different spectral radiation intensity distribution curve of the transient radiation source along with time changes. This spectrometer consists of mobile collimation lens, Cassegrain imaging system, grating spectrograph, high speed data acquisition system and computer software. Since ultraviolet spectral radiation is severely absorbed in air transmission, firstly the Cassegrain system which has high reflectance in ultraviolet wavelength range is used to image the extended area light source onto the entrance slit of spectrograph, in order to markedly improve the light gathering power of the device. The spectrograph uses plane blazed grating to disperse spectrums which are focalized as the focal plane for detection by ultraviolet response enhancing array CCD detector. Secondly, to resolve spectrum acquisition problem of nanosecond transient light sources, we adopt CCD drive technology programmed by CPLD and fixed phasic high speed data acquisition method. Finally, the spectral distortion of the spectrograph is reduced by using non-parametric kernel regression de-noising algorithm and convolution algorithm in order to improve the spectral resolving power of the device. So we experimentalize for spectral radiation intensity distributions of remote transient and steady-state extended area light sources, then the uncertainty of measurement results is analyzed.

  20. DETECTORS AND EXPERIMENTAL METHODS: Measurement of the neutron spectrum of a Pu-C source with a liquid scintillator

    NASA Astrophysics Data System (ADS)

    Wang, Song-Lin; Huang, Han-Xiong; Ruan, Xi-Chao; Li, Xia; Bao, Jie; Nie, Yang-Bo; Zhong, Qi-Ping; Zhou, Zu-Ying; Kong, Xiang-Zhong

    2009-05-01

    The neutron response function for a BC501A liquid scintillator (LS) has been measured using a series of monoenergetic neutrons produced by the p-T reaction. The proton energies were chosen such as to produce neutrons in the energy range of 1 to 20 MeV. The principles of the technique of unfolding a neutron energy spectrum by using the measured neutron response function and the measured Pulse Height (PH) spectrum is briefly described. The PH spectrum of neutrons from the Pu-C source, which will be used for the calibration of the reactor antineutrino detectors for the Daya Bay neutrino experiment, was measured and analyzed to get the neutron energy spectrum. Simultaneously the neutron energy spectrum of an Am-Be source was measured and compared with other measurements as a check of the result for the Pu-C source. Finally, an error analysis and a discussion of the results are given.

  1. The hidden nuclear spectrum of the luminous IRAS source FSC 10214+4724

    NASA Technical Reports Server (NTRS)

    Jannuzi, Buell T.; Elston, Richard; Schmidt, Gary D.; Smith, Paul S.; Stockman, H. S.

    1994-01-01

    Optical spectropolarimetry of the luminous IRAS source FSC 10214+4724 (z=2.286) reveals that the strong (approximately 17%) linear polarization detected by Lawrence et al. is shared by both the narrow ultraviolet (UV) emission lines and the underlying continuum. This observation and the brightness of the source rule out synchrotron emission and dichroic extinction by dust as the polarizing mechanism, leaving scattering as the only plausible cause of the polarized emission. The narrowness of the lines requires that the scatterers be dust grains or cool (below 1.6 x 10(exp 4) K) electrons. We can recover the spectrum that is incident on the scattering medium provided we make some reasonable assumptions regarding the source geometry. The scattered UV spectrum has a power-law index alpha of -1.2 plus or minus 0.6 (F(sub nu) varies as nu(sup alpha)), steeper than would be expected from a young burst of star formation but similar to that of many active galactic nucleus (AGNs).

  2. Diffraction based method to reconstruct the spectrum of the Thomson scattering x-ray source

    NASA Astrophysics Data System (ADS)

    Chi, Zhijun; Yan, Lixin; Zhang, Zhen; Zhou, Zheng; Zheng, Lianmin; Wang, Dong; Tian, Qili; Wang, Wei; Nie, Zan; Zhang, Jie; Du, Yingchao; Hua, Jianfei; Shi, Jiaru; Pai, Chihao; Lu, Wei; Huang, Wenhui; Chen, Huaibi; Tang, Chuanxiang

    2017-04-01

    As Thomson scattering x-ray sources based on the collision of intense laser and relativistic electrons have drawn much attention in various scientific fields, there is an increasing demand for the effective methods to reconstruct the spectrum information of the ultra-short and high-intensity x-ray pulses. In this paper, a precise spectrum measurement method for the Thomson scattering x-ray sources was proposed with the diffraction of a Highly Oriented Pyrolytic Graphite (HOPG) crystal and was demonstrated at the Tsinghua Thomson scattering X-ray source. The x-ray pulse is diffracted by a 15 mm (L) ×15 mm (H)× 1 mm (D) HOPG crystal with 1° mosaic spread. By analyzing the diffraction pattern, both x-ray peak energies and energy spectral bandwidths at different polar angles can be reconstructed, which agree well with the theoretical value and simulation. The higher integral reflectivity of the HOPG crystal makes this method possible for single-shot measurement.

  3. 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.

  4. Sound Spectrum Influences Auditory Distance Perception of Sound Sources Located in a Room Environment

    PubMed Central

    Spiousas, Ignacio; Etchemendy, Pablo E.; Eguia, Manuel C.; Calcagno, Esteban R.; Abregú, Ezequiel; Vergara, Ramiro O.

    2017-01-01

    Previous studies on the effect of spectral content on auditory distance perception (ADP) focused on the physically measurable cues occurring either in the near field (low-pass filtering due to head diffraction) or when the sound travels distances >15 m (high-frequency energy losses due to air absorption). Here, we study how the spectrum of a sound arriving from a source located in a reverberant room at intermediate distances (1–6 m) influences the perception of the distance to the source. First, we conducted an ADP experiment using pure tones (the simplest possible spectrum) of frequencies 0.5, 1, 2, and 4 kHz. Then, we performed a second ADP experiment with stimuli consisting of continuous broadband and bandpass-filtered (with center frequencies of 0.5, 1.5, and 4 kHz and bandwidths of 1/12, 1/3, and 1.5 octave) pink-noise clips. Our results showed an effect of the stimulus frequency on the perceived distance both for pure tones and filtered noise bands: ADP was less accurate for stimuli containing energy only in the low-frequency range. Analysis of the frequency response of the room showed that the low accuracy observed for low-frequency stimuli can be explained by the presence of sparse modal resonances in the low-frequency region of the spectrum, which induced a non-monotonic relationship between binaural intensity and source distance. The results obtained in the second experiment suggest that ADP can also be affected by stimulus bandwidth but in a less straightforward way (i.e., depending on the center frequency, increasing stimulus bandwidth could have different effects). Finally, the analysis of the acoustical cues suggests that listeners judged source distance using mainly changes in the overall intensity of the auditory stimulus with distance rather than the direct-to-reverberant energy ratio, even for low-frequency noise bands (which typically induce high amount of reverberation). The results obtained in this study show that, depending on the spectrum

  5. Flat-spectrum radio source C1 in M33 is a background radio galaxy

    SciTech Connect

    Reynolds, S.P.; Fix, J.D.

    1988-10-01

    A candidate Crab-like supernova remnant in M33 discovered in a high-resolution survey of compact radio sources (Reynolds and Fix, 1987) has been observed. VLA observations at 1465 and 4885 MHz show that it is simply the flat-spectrum core of a completely normal double-lobed radio galaxy. This eliminates the last candidate Crab-like object in M33 whose size and brightness do not at all resemble those of the Crab Nebula, and confirms the dearth of Crab-like supernova remnants reported earlier. 7 references.

  6. Sound Spectrum Influences Auditory Distance Perception of Sound Sources Located in a Room Environment.

    PubMed

    Spiousas, Ignacio; Etchemendy, Pablo E; Eguia, Manuel C; Calcagno, Esteban R; Abregú, Ezequiel; Vergara, Ramiro O

    2017-01-01

    Previous studies on the effect of spectral content on auditory distance perception (ADP) focused on the physically measurable cues occurring either in the near field (low-pass filtering due to head diffraction) or when the sound travels distances >15 m (high-frequency energy losses due to air absorption). Here, we study how the spectrum of a sound arriving from a source located in a reverberant room at intermediate distances (1-6 m) influences the perception of the distance to the source. First, we conducted an ADP experiment using pure tones (the simplest possible spectrum) of frequencies 0.5, 1, 2, and 4 kHz. Then, we performed a second ADP experiment with stimuli consisting of continuous broadband and bandpass-filtered (with center frequencies of 0.5, 1.5, and 4 kHz and bandwidths of 1/12, 1/3, and 1.5 octave) pink-noise clips. Our results showed an effect of the stimulus frequency on the perceived distance both for pure tones and filtered noise bands: ADP was less accurate for stimuli containing energy only in the low-frequency range. Analysis of the frequency response of the room showed that the low accuracy observed for low-frequency stimuli can be explained by the presence of sparse modal resonances in the low-frequency region of the spectrum, which induced a non-monotonic relationship between binaural intensity and source distance. The results obtained in the second experiment suggest that ADP can also be affected by stimulus bandwidth but in a less straightforward way (i.e., depending on the center frequency, increasing stimulus bandwidth could have different effects). Finally, the analysis of the acoustical cues suggests that listeners judged source distance using mainly changes in the overall intensity of the auditory stimulus with distance rather than the direct-to-reverberant energy ratio, even for low-frequency noise bands (which typically induce high amount of reverberation). The results obtained in this study show that, depending on the spectrum of

  7. 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

  8. 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.

  9. Percent Agricultural Land Cover on Steep Slopes

    EPA Pesticide Factsheets

    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 surface water. Agricultural land cover on steep slopes (AGSL) is the percent of agriculture on slopes greater than or equal to 9%. More information about these resources, including the variables used in this study, may be found here: https://edg.epa.gov/data/Public/ORD/NERL/ReVA/ReVA_Data.zip.

  10. Initial study of the optical spectrum of the ISIS H- ion source plasma.

    PubMed

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

    2012-02-01

    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(-) 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%.

  11. 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%.

  12. [DWT-iPLS applied in the infrared diffuse reflection spectrum of hydrocarbon source rocks].

    PubMed

    Song, Ning; Xu, Xiao-xuan; Wu, Zhong-chen; Zhang, Cun-zhou; Wang, Bin

    2008-08-01

    Infrared spectroscopy is useful to monitor the quality of products on-line, or to quality multivariate properties simultaneously. The IR spectrometer satisfies the requirements of users who want to have quantitative product information in real-time because the instrument provides the information promptly and easily. However, Samples that are measured using diffuse reflectance often exhibit significant differences in the spectra due to the non-homogeneous distribution of the particles. In fact, multiple spectral measurements of the same sample can look completely different. In many cases, the scattering can be an overpowering contributor to the spectrum, sometimes accounting for most of the variance in the data. Although the degree of scattering is dependent on the wavelength of the light that is used and the particle size and refractive index of the sample, the scattering is not uniform throughout the spectrum. Typically, this appears as a baseline shift, tilt and sometimes curvature, where the degree of influence is more pronounced at the longer-wavelength end of the spectrum. The diffuse reflection spectrum is unsatisfactory and the calibration may provide unsatisfactory prediction results. So we must use some methods to remove the effects of the scattering for multivariate calibration of IR spectral signals. Discrete wavelet transform (DWT) is a good method to remove the effects of the scattering for multivariate calibration of IR spectral signals. By using DWT on individual signals as a preprocessing method in regression modeling on IR spectra, good compression is achieved with almost no loss of information, the low-frequency varying background and the high-frequency noise be removed simultaneously. In this report, we use the iPLS method to establish the calibration models of hydrocarbon source rocks. iPLS is a new regression method and the authors can get better results by using DTW- iPLS.

  13. 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.

  14. 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.

  15. 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…

  16. 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…

  17. 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…

  18. 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…

  19. 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…

  20. 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.

  1. 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.

  2. Aerogel Cherenkov detector for characterizing the intense flash x-ray source, Cygnus, spectrum

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Herrmann, H. W.; McEvoy, A. M.; Young, C. S.; Hamilton, C.; Schwellenbach, D. D.; Malone, R. M.; Kaufman, M. I.; Smith, A. S.

    2016-11-01

    An aerogel Cherenkov detector is proposed to measure the X-ray energy spectrum from the Cygnus—intense flash X-ray source operated at the Nevada National Security Site. An array of aerogels set at a variety of thresholds between 1 and 3 MeV will be adequate to map out the bremsstrahlung X-ray production of the Cygnus, where the maximum energy of the spectrum is normally around 2.5 MeV. In addition to the Cherenkov radiation from aerogels, one possible competing light-production mechanism is optical transition radiation (OTR), which may be significant in aerogels due to the large number of transitions from SiO2 clusters to vacuum voids. To examine whether OTR is a problem, four aerogel samples were tested using a mono-energetic electron beam (varied in the range of 1-3 MeV) at NSTec Los Alamos Operations. It was demonstrated that aerogels can be used as a Cherenkov medium, where the rate of the light production is about two orders magnitude higher when the electron beam energy is above threshold.

  3. Aerogel Cherenkov detector for characterizing the intense flash x-ray source, Cygnus, spectrum

    SciTech Connect

    Kim, Y. Herrmann, H. W.; McEvoy, A. M.; Young, C. S.; Hamilton, C.; Schwellenbach, D. D.; Malone, R. M.; Kaufman, M. I.; Smith, A. S.

    2016-11-15

    An aerogel Cherenkov detector is proposed to measure the X-ray energy spectrum from the Cygnus—intense flash X-ray source operated at the Nevada National Security Site. An array of aerogels set at a variety of thresholds between 1 and 3 MeV will be adequate to map out the bremsstrahlung X-ray production of the Cygnus, where the maximum energy of the spectrum is normally around 2.5 MeV. In addition to the Cherenkov radiation from aerogels, one possible competing light-production mechanism is optical transition radiation (OTR), which may be significant in aerogels due to the large number of transitions from SiO{sub 2} clusters to vacuum voids. To examine whether OTR is a problem, four aerogel samples were tested using a mono-energetic electron beam (varied in the range of 1–3 MeV) at NSTec Los Alamos Operations. It was demonstrated that aerogels can be used as a Cherenkov medium, where the rate of the light production is about two orders magnitude higher when the electron beam energy is above threshold.

  4. The 4-8 micron spectrum of the infrared source W33 A

    NASA Technical Reports Server (NTRS)

    Soifer, B. T.; Puetter, R. C.; Russell, R. W.; Willner, S. P.; Harvey, P. M.; Gillett, F. C.

    1979-01-01

    The spectrum of the highly obscured infrared source W33 A from 4.5 to 8 microns is measured in order to investigate the intervening cold, dense interstellar material. Spectrophotometry at a relative spectral resolution of about 0.015 by an airborne filter-wheel infrared spectrometer reveals strong absorption features at 4.61, 5.99 and 6.78 microns. The absorption at 4.61 microns is attributed primarily to the fundamental vibration-rotation band of CO at a column density (at least 10 to the 19th/sq cm) which is 10% of the carbon inferred from silicate abundances. The strengths and line widths of the absorption agt 5.99 and 6.78 microns are interpreted as evidence of absorption in the resonance bands of carbonyl, carbon-carbon double, methyl and methylene bonds of hydrocarbons associated with interstellar dust.

  5. The 4-8 micron spectrum of the infrared source W33 A

    NASA Technical Reports Server (NTRS)

    Soifer, B. T.; Puetter, R. C.; Russell, R. W.; Willner, S. P.; Harvey, P. M.; Gillett, F. C.

    1979-01-01

    The spectrum of the highly obscured infrared source W33 A from 4.5 to 8 microns is measured in order to investigate the intervening cold, dense interstellar material. Spectrophotometry at a relative spectral resolution of about 0.015 by an airborne filter-wheel infrared spectrometer reveals strong absorption features at 4.61, 5.99 and 6.78 microns. The absorption at 4.61 microns is attributed primarily to the fundamental vibration-rotation band of CO at a column density (at least 10 to the 19th/sq cm) which is 10% of the carbon inferred from silicate abundances. The strengths and line widths of the absorption agt 5.99 and 6.78 microns are interpreted as evidence of absorption in the resonance bands of carbonyl, carbon-carbon double, methyl and methylene bonds of hydrocarbons associated with interstellar dust.

  6. Pion transverse-momentum spectrum, elliptic flow, and Hanbury-Brown-Twiss interferometry in a viscous granular source model

    NASA Astrophysics Data System (ADS)

    Yang, Jing; Zhang, Wei-Ning; Ren, Yan-Yu

    2017-08-01

    We examine the evolution of quark-gluon plasma (QGP) droplets with viscous hydrodynamics and analyze the pion transverse-momentum spectrum, elliptic flow, and Hanbury-Brown-Twiss (HBT) interferometry in a granular source model consisting of viscous QGP droplets. The shear viscosity of the QGP droplet speeds up and slows down the droplet evolution in the central and peripheral regions of the droplet, respectively. The effect of the bulk viscosity on the evolution is negligible. Although there are viscous effects on the droplet evolution, the pion momentum spectrum and elliptic flow change little for granular sources with and without viscosity. On the other hand, the influence of viscosity on HBT radius R out is considerable. It makes R out decrease in the granular source model. We determine the model parameters of granular sources using the experimental data of pion transverse-momentum spectrum, elliptic flow, and HBT radii together, and investigate the effects of viscosity on the model parameters. The results indicate that the granular source model may reproduce the experimental data of pion transverse-momentum spectrum, elliptic flow, and HBT radii in heavy-ion collisions of Au-Au at and Pb-Pb at in different centrality intervals. The viscosity of the droplet leads to an increase in the initial droplet radius and a decrease of the source shell parameter in the granular source model. Supported by National Natural Science Foundation of China (11675034, 11275037)

  7. Determination of neutron spectrum outside the lateral shielding of Taiwan Photon Source using high-sensitivity Bonner cylinders

    NASA Astrophysics Data System (ADS)

    Lin, Yu-Chi; Chen, Ang-Yu; Liu, Joseph; Lee, Kuo-Wei; Sheu, Rong-Jiun

    2017-09-01

    A homemade Bonner cylinder spectrometer was used to determine the neutron spectrum from thermal energy up to several GeV at a heavily-shielded light source facility. The spectrometer, similar to the design of Bonner spheres, features high sensitivity of neutron detection because of using a long cylindrical 3He proportional counter. The spectrum measurement was performed during the facility commissioning by intentionally parking the injected electrons at the septum of the storage ring. Based on a high-fidelity FLUKA simulation, the predicted neutron spectrum at the location of measurement was adopted as the initial guess of spectrum unfolding. The unfolded result indicated an underestimation of the calculated neutron spectrum in the high-energy portion, leading to a substantial revision of the neutron dose rate at the location.

  8. 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.

  9. 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.

  10. On the relation between steep monoclinal flexure zones and steep hydraulic gradients.

    PubMed

    Yechieli, Y; Kafri, U; Wollman, S; Lyakhovsky, V; Weinberger, R

    2007-01-01

    Steep hydraulic gradients are found in association with steep monoclinal flexures. However, the physics of the reduction of the hydraulic conductivity, which is responsible for the steep gradients, has seldom been studied. We present results of hydrological and mechanical modeling aiming to study the effect of such steep hydraulic gradients demonstrated in the Judea Group Aquifer system, Israel. The hydrological configuration of steep dips and anisotropy between flows parallel and perpendicular to the bedding planes was simulated using the FEFLOW code. It exhibited a situation whereby part of the flow is oblique to the bedding planes and therefore some steepening of the hydraulic gradients occurred due to actual conductivity reduction. However, this reduction is not enough to account for the steeper gradients observed. The effect of a deep-seated reverse fault under the monocline on the permeability distribution within the structure was examined by numerical mechanical simulations. It exhibited a compressional stress distribution in the steep part of the monocline, which, due to shortening and closure of joints and voids, is presumably responsible for a significant pressure-induced permeability reduction. This process by itself in a layered structure, including interlayering of thin marl layers, could be responsible for the steep hydraulic gradients in the steep part of the monocline.

  11. Obscured flat spectrum radio active galactic nuclei as sources of high-energy neutrinos

    NASA Astrophysics Data System (ADS)

    Maggi, G.; Buitink, S.; Correa, P.; de Vries, K. D.; Gentile, G.; Tavares, J. León; Scholten, O.; van Eijndhoven, N.; Vereecken, M.; Winchen, T.

    2016-11-01

    Active galactic nuclei (AGN) are believed to be one of the main source candidates for the high-energy (TeV-PeV) cosmic neutrino flux recently discovered by the IceCube neutrino observatory. Nevertheless, several correlation studies between AGN and the cosmic neutrinos detected by IceCube show no significance. Therefore, in this article we consider a specific subclass of AGN for which an increased neutrino production is expected. This subclass contains AGN for which their high-energy jet is pointing toward Earth. Furthermore, we impose the condition that the jet is obscured by gas or dust surrounding the AGN. A method is presented to determine the total column density of the obscuring medium, which is probed by determining the relative x-ray attenuation with respect to the radio flux as obtained from the AGN spectrum. The total column density allows us to probe the interaction of the jet with the surrounding matter, which leads to additional neutrino production. Finally, starting from two different source catalogs, this method is applied to specify a sample of low redshift radio galaxies for which an increased neutrino production is expected.

  12. Evolution of and High-Energy Emission from GHz-Peaked Spectrum Sources

    NASA Astrophysics Data System (ADS)

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

    2008-06-01

    Here we discuss evolution and broadband emission of compact (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 hot spot of a jet to expanding lobes, taking into account their adiabatic energy losses, as well as radiative cooling. This allows us to discuss the broadband 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 upscattering 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 γ-ray instruments. In particular, we suggest that GPS radio galaxies should constitute a relatively numerous class of extragalactic sources detected by GLAST.

  13. 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.

  14. The Galactic Center EGRET Source and the Broad-band Spectrum of SGR A East

    NASA Astrophysics Data System (ADS)

    Fatuzzo, M.; Melia, F.; Yusef-Zadeh, F.; Markoff, S.

    1999-06-01

    High energy (30 MeV - 10 GeV) emission associated with a Galactic Center source has recently been observed by EGRET on board the Compton Gamma-ray Observatory. Continuum low-frequency radio observations of the Galactic Center reveal the presence of several viable source candidates, one of which is a prominent elliptical shell structure known as Sgr A East. Although morphologically similar to supernova remnants (SNRs), its inferred energetics and size appear to be extreme and have generated some uncertainty regarding this interpretation. Additionally, the radio spectral index determined from 6 cm and 20 cm observations of Sgr A East (~ 1) differs from the indices normally found for SNRs (~ 0.5). This difference is quite significant given that the corresponding index for the electron distribution for Sgr A East is then ~3 (versus ~2 for SNRs) and therefore unlike that thought to be produced directly from the shock acceleration processes believed to occur in such an environment. Regardless, recent observations of this region at 1720 MHz (the transition frequency of OH maser emission) have revealed the presence of several maser spots, suggesting a kinship between Sgr A East and three EGRET SNRs also observed at 1720 MHz: IC443, W28 and W44. This possible kinship suggests that Sgr A East could be the source of the EGRET emission. We show here that the pion-production and decay mechanism invoked to account for gamma-ray emission from SNRs can also naturally account for the radio through TeV spectrum of Sgr A East (including the EGRET data). The differences between the spectral features of Sgr A East and the other SNRs then results from the differences between the underlying energetics and the properties of the surrounding interstellar medium.

  15. 30 CFR 816.107 - Backfilling and grading: Steep slopes.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Backfilling and grading: Steep slopes. 816.107... ACTIVITIES § 816.107 Backfilling and grading: Steep slopes. (a) Surface mining activities on steep slopes... section except where mining is conducted on flat or gently rolling terrain with an occasional steep...

  16. Interrill soil erosion processes on steep slopes

    USDA-ARS?s Scientific Manuscript database

    To date interrill erosion processes and regimes are not fully understood. The objectives are to 1) identify the erosion regimes and limiting processes between detachment and transport on steep slopes, 2) characterize the interactive effects between rainfall intensity and flow depth on sediment trans...

  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. 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.

  19. 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.

  20. 30 CFR 817.107 - Backfilling and grading: Steep slopes.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Backfilling and grading: Steep slopes. 817.107 Section 817.107 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE... ACTIVITIES § 817.107 Backfilling and grading: Steep slopes. (a) Underground mining activities on steep...

  1. Flat-spectrum radio sources from the Parkes 2.7 GHz survey - A study of a complete sample

    NASA Technical Reports Server (NTRS)

    Savage, Ann; Jauncey, David L.; White, Graeme L.; Peterson, Bruce A.; Peters, W. L.; Gulkis, Samuel

    1990-01-01

    A complete sample, taken from the Parkes 2.7 GHz catalog, of flat-spectrum radio sources with flux densities greater than 0.5 Jy is described. The sample covers all right ascensions and declinations for +10 deg to -45 deg, excluding the Galactic plane, and contains 403 sources. Attention is drawn to the advantages of radio surveys over optical surveys. The survey is used to highlight some selection effects found in optical surveys. How this sample can be used to give information on the early universe is discussed.

  2. 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".

  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. Radio spectra of extragalactic sources and the relativistic beaming model

    NASA Astrophysics Data System (ADS)

    Eckart, A.; Hummel, C. A.; Witzel, A.

    1989-07-01

    Multiepoch radio spectra of 308 extragalactic radio sources taken from the 1-Jy catalog (Kuhr et al., 1981) are analyzed, correlating the spectral index, spectral curvature, and degree of variability. These quantities are statistically interdependent, and their distributions can be used to distinguish between galaxies, quasars, optically violent variable sources, and BL Lac objects. These spectral associations are explained using a relativistic beaming model involving a nonvariable steep spectrum component and a core component with an inverted spectrum exhibiting an intrinsic variability of about 30 percent. At 5 GHz, the flux density ratio of the core component (seen at an angle of 90 deg) to the steep-spectrum component is about 0.03 or larger.

  5. A method of manufacturing planar gamma-sources with controlled spectrum

    NASA Astrophysics Data System (ADS)

    Uvarov, V. L.; Dikiy, N. P.; Dovbnya, A. N.; Lyashko, Yu. V.; Tenishev, A. Eh.

    2017-09-01

    Planar γ-sources with manipulated number, position and intensity of spectral bands within the span 24…122 keV have been fabricated and examined. Every source comprises a stack of the foils from inactive elementary substances and planar single-photon γ-sources. As the latter ones, the sources on the basis of the 57Co and 179Ta isotopes produced at an electron accelerator are used.

  6. 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.

  7. Accurately computing the optical pathlength difference for a michelson interferometer with minimal knowledge of the source spectrum.

    PubMed

    Milman, Mark H

    2005-12-01

    Astrometric measurements using stellar interferometry rely on precise measurement of the central white light fringe to accurately obtain the optical pathlength difference of incoming starlight to the two arms of the interferometer. One standard approach to stellar interferometry uses a channeled spectrum to determine phases at a number of different wavelengths that are then converted to the pathlength delay. When throughput is low these channels are broadened to improve the signal-to-noise ratio. Ultimately the ability to use monochromatic models and algorithms in each of the channels to extract phase becomes problematic and knowledge of the spectrum must be incorporated to achieve the accuracies required of the astrometric measurements. To accomplish this an optimization problem is posed to estimate simultaneously the pathlength delay and spectrum of the source. Moreover, the nature of the parameterization of the spectrum that is introduced circumvents the need to solve directly for these parameters so that the optimization problem reduces to a scalar problem in just the pathlength delay variable. A number of examples are given to show the robustness of the approach.

  8. Steep extinction towards GRB 140506A reconciled from host galaxy observations: Evidence that steep reddening laws are local

    NASA Astrophysics Data System (ADS)

    Heintz, K. E.; Fynbo, J. P. U.; Jakobsson, P.; Krühler, T.; Christensen, L.; Watson, D.; Ledoux, C.; Noterdaeme, P.; Perley, D. A.; Rhodin, H.; Selsing, J.; Schulze, S.; Tanvir, N. R.; Møller, P.; Goldoni, P.; Xu, D.; Milvang-Jensen, B.

    2017-05-01

    We present the spectroscopic and photometric late-time follow-up of the host galaxy of the long-duration Swift γ-ray burst GRB 140506A at z = 0.889. The optical and near-infrared afterglow of this GRB had a peculiar spectral energy distribution (SED) with a strong flux-drop at 8000 Å (4000 Å rest-frame) suggesting an unusually steep extinction curve. By analysing the contribution and physical properties of the host galaxy, we here aim at providing additional information on the properties and origin of this steep, non-standard extinction. We find that the strong flux-drop in the GRB afterglow spectrum at <8000 Å and rise at <4000 Å (observers frame) is well explained by the combination of a steep extinction curve along the GRB line of sight and contamination by the host galaxy light at short wavelengths so that the scenario with an extreme 2175 Å extinction bump can be excluded. We localise the GRB to be at a projected distance of approximately 4 kpc from the centre of the host galaxy. Based on emission-line diagnostics of the four detected nebular lines, Hα, Hβ, [O ii] and [O iii], we find the host to be a modestly star forming (SFR = 1.34 ± 0.04 M⊙ yr-1) and relatively metal poor (Z=0.35+0.15-0.11 Z⊙) galaxy with a large dust content, characterised by a measured visual attenuation of AV = 1.74 ± 0.41 mag. We compare the host to other GRB hosts at similar redshifts and find that it is unexceptional in all its physical properties. We model the extinction curve of the host-corrected afterglow and show that the standard dust properties causing the reddening seen in the Local Group are inadequate in describing the steep drop. We thus conclude that the steep extinction curve seen in the afterglow towards the GRB is of exotic origin and issightline-dependent only, further confirming that this type of reddening is present only at very local scales and that it is solely a consequence of the circumburst environment. Based on observations carried out under

  9. Multicore fiber-Bragg-grating-based directional curvature sensor interrogated by a broadband source with a sinusoidal spectrum.

    PubMed

    Zheng, Di; Madrigal, Javier; Chen, Hailan; Barrera, David; Sales, Salvador

    2017-09-15

    A simple, spectral-drift-insensitive interrogation scheme for a multicore fiber Bragg grating (FBG)-based directional curvature sensor is proposed. The basic principle is to transform the wavelength shift of FBGs into the reflected power variation, which is accomplished by utilizing a broadband source with a sinusoidal spectrum. The closed-form expression of the relationship between the reflected power of the FBG and the corresponding peak wavelength is derived for the first time, to the best of our knowledge; therefore, the peak wavelength of the FBG can be precisely interrogated by using a single photodiode. The experimental results show that, with respect to conventional wavelength measurement by an optical spectrum analyzer, the demodulated wavelength error by our proposed interrogation scheme is within ±20  pm. The proposed scheme is further extended to interrogate the direction and curvature using a multicore FBG-based curvature sensor; the interrogated curvature with an error less than 8% is achieved.

  10. 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.

  11. 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.

  12. 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

    2016-12-01

    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, 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 and megahertz peaked-spectrum sources.

  13. Bed load fluctuations in a steep channel

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    Bed load transport rate fluctuations have been observed over time in steep rivers and flumes with wide grain size distributions even under constant sediment feeding and water discharge. The observed bed load transport rate pulses are periodic and a consequence of grain sorting. Moreover, the presence of large, relatively immobile boulders, such as erratic stones, which are often present in mountain streams, has an impact on flow conditions. The detailed analysis of a 13 h laboratory experiment is presented in this paper. Boulders were randomly placed in a flume with a steep slope (6.7%), and water and sediment were constantly supplied to the flume. Along with the sediment transport and bulk mean flow velocity, the boulder protrusion, boulder surface, and number of hydraulic jumps, which are indicators of the channel morphology, were measured regularly during the experiment. Periodic bed load transport rate pulses are clearly visible in the data collected during this long-duration experiment, along with correlated fluctuations in the flow velocity and bed morphology. The links among the bulk velocity, the time evolution of the morphology variables, and the bed load transport rate are analyzed via correlational analysis, showing that the fluctuations are strongly related. A phase analysis of all observed variables is performed, and the average shapes of the time cycles of the fluctuations are shown. Observations indicate that the detected periodic fluctuations correspond to different bed states. Furthermore, the grain size distribution through the channel, which varies in time and space, clearly influences these bed load transport rate pulses. Finally, known bed load transport rate formulae are tested, showing that only the application of a drag shear stress allows a correct estimation of the time fluctuations.

  14. 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.

  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. Relevance of aerosol size spectrum analysis as support to qualitative source apportionment studies.

    PubMed

    Manigrasso, M; Febo, A; Guglielmi, F; Ciambottini, V; Avino, P

    2012-11-01

    This work presents a diagnostic methodology in support to source apportionment studies to identify remote and local pollution sources. It is based on the temporal analysis of both PM size distributions and PM size fraction correlation along with natural radioactivity measurements as index of Planetary Boundary Layer dynamic. A correlation drop is indicative of changing aerosol sources. When this observation is coupled with decreasing level of natural radioactivity and increasing aerosol concentration, be it coarse or fine, it is indicative of the inflow of remote polluted air masses. The methodology defines in which size range operates the contribution of remote pollution sources. It was applied to two PM10 pollution episodes: the first involved the advection of coarse PM, the second entailed the inflow of two air masses, one transporting coarse dust and the other fine PM. Dust models and backward trajectories analysis confirmed such results, indicating the air mass provenience.

  17. Identifying a Damped Lyman Alpha Source in the Spectrum of Quasar SDSS J233544.18+150118.3

    NASA Astrophysics Data System (ADS)

    Browning, Benjamin; Takamiya, Marianne Y.; Chun, Mark Richard; Kulkarni, Varsha P.; Gharanfoli, Soheila

    2014-06-01

    We present the nebular properties of a DLA along the line-of-sight of the quasar SDSS J233544.18+150118.3. We obtained two IFU spectra with UH 2.2m/SNIFS approximately 4 arcseconds south of the quasar. A careful analysis of the sky spectra surrounding the DLA then allowed us to generate a high SNR sky spectrum. Through a close examination of our reduced images, we have successfully identified a faint but distinct source of [OII] emission at the same redshift reported elsewhere for the damped Lyman-Alpha absorption lines in the quasar's spectrum. Further investigation also revealed the presence of lower intensity H-beta emission lines at the same redshift. Based on the relative intensities of the [OII] and H-beta lines in the spectrum of this relatively dim intervening galaxy, we present some initial conclusions regarding nebular abundance and star formation rate in this newly identified galaxy, and how its properties compare with a representative sample of galaxies at similar redshifts and luminosities.

  18. Recognition memory and source memory in autism spectrum disorder: A study of the intention superiority and enactment effects.

    PubMed

    Grainger, Catherine; Williams, David M; Lind, Sophie E

    2016-06-22

    It is well established that neurotypical individuals generally show better memory for actions they have performed than actions they have observed others perform or merely read about, a so-called 'enactment effect'. Strikingly, research has also shown that neurotypical individuals demonstrate superior memory for actions they intend to perform in the future (but have not yet performed), an effect commonly known as the 'intention superiority effect'. Although the enactment effect has been studied among people with autism spectrum disorder, this study is the first to investigate the intention superiority effect in this disorder. This is surprising given the potential importance this issue has for general theory development, as well as for clinical practice. As such, this study aimed to assess the intention superiority and enactment effects in 22 children with autism spectrum disorder, and 20 intelligence quotient/age-matched neurotypical children. The results showed that children with autism spectrum disorder demonstrated not only undiminished enactment effects in recognition and source memory, but also (surprisingly for some theories) typical intention superiority effects. The implications of these results for theory, as well as clinical practice, are discussed.

  19. Cylindrical angular spectrum using Fourier coefficients of point light source and its application to fast hologram calculation.

    PubMed

    Oh, Seungtaik; Jeong, Il Kwon

    2015-11-16

    We will introduce a new simple analytic formula of the Fourier coefficient of the 3D field distribution of a point light source to generate a cylindrical angular spectrum which captures the object wave in 360° in the 3D Fourier space. Conceptually, the cylindrical angular spectrum can be understood as a cylindrical version of the omnidirectional spectral approach of Sando et al. Our Fourier coefficient formula is based on an intuitive observation that a point light radiates uniformly in all directions. Our formula is defined over all frequency vectors lying on the entire sphere in the 3D Fourier space and is more natural and computationally more efficient for all around recording of the object wave than that of the previous omnidirectional spectral method. A generalized frequency-based occlusion culling method for an arbitrary complex object is also proposed to enhance the 3D quality of a hologram. As a practical application of the cylindrical angular spectrum, an interactive hologram example is presented together with implementation details.

  20. Birth prevalence of autism spectrum disorders in the San Francisco Bay area by demographic and ascertainment source characteristics.

    PubMed

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

    2011-10-01

    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 the state-wide Department of Developmental Services. In adjusted models, we found a male:female ratio of 6:1, a doubling of ASD prevalence among children of older mothers (40+), and lower prevalence with lower paternal education. Children of Black or Hispanic mothers had lower prevalence than those of White, non-Hispanic mothers, but these differences were attenuated after adjustment. Prevalence in children of Asian mothers was similar to Whites. Potential under-counting is discussed.

  1. 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

  2. Effect of source spectrum on sound localization in an everyday reverberant room.

    PubMed

    Ihlefeld, Antje; Shinn-Cunningham, Barbara G

    2011-07-01

    Two experiments explored how frequency content impacts sound localization for sounds containing reverberant energy. Virtual sound sources from thirteen lateral angles and four distances were simulated in the frontal horizontal plane using binaural room impulse responses measured in an everyday office. Experiment 1 compared localization judgments for one-octave-wide noise centered at either 750 Hz (low) or 6000 Hz (high). For both band-limited noises, perceived lateral angle varied monotonically with source angle. For frontal sources, perceived locations were similar for low- and high-frequency noise; however, for lateral sources, localization was less accurate for low-frequency noise than for high-frequency noise. With increasing source distance, judgments of both noises became more biased toward the median plane, an effect that was greater for low-frequency noise than for high-frequency noise. In Experiment 2, simultaneous presentation of low- and high-frequency noises yielded performance that was less accurate than that for high-frequency noise, but equal to or better than for low-frequency noise. Results suggest that listeners perceptually weight low-frequency information heavily, even in reverberant conditions where high-frequency stimuli are localized more accurately. These findings show that listeners do not always optimally adjust how localization cues are integrated over frequency in reverberant settings. © 2011 Acoustical Society of America

  3. Effect of source spectrum on sound localization in an everyday reverberant room

    PubMed Central

    Ihlefeld, Antje; Shinn-Cunningham, Barbara G.

    2011-01-01

    Two experiments explored how frequency content impacts sound localization for sounds containing reverberant energy. Virtual sound sources from thirteen lateral angles and four distances were simulated in the frontal horizontal plane using binaural room impulse responses measured in an everyday office. Experiment 1 compared localization judgments for one-octave-wide noise centered at either 750 Hz (low) or 6000 Hz (high). For both band-limited noises, perceived lateral angle varied monotonically with source angle. For frontal sources, perceived locations were similar for low- and high-frequency noise; however, for lateral sources, localization was less accurate for low-frequency noise than for high-frequency noise. With increasing source distance, judgments of both noises became more biased toward the median plane, an effect that was greater for low-frequency noise than for high-frequency noise. In Experiment 2, simultaneous presentation of low- and high-frequency noises yielded performance that was less accurate than that for high-frequency noise, but equal to or better than for low-frequency noise. Results suggest that listeners perceptually weight low-frequency information heavily, even in reverberant conditions where high-frequency stimuli are localized more accurately. These findings show that listeners do not always optimally adjust how localization cues are integrated over frequency in reverberant settings. PMID:21786902

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

    SciTech Connect

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

    2016-02-15

    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 H{sub 2} 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.

  5. Ionized gas in the Irr galaxy IC 10: The emission spectrum and ionization sources

    NASA Astrophysics Data System (ADS)

    Arkhipova, V. P.; Egorov, O. V.; Lozinskaya, T. A.; Moiseev, A. V.

    2011-02-01

    We present the observations of the Irr galaxy IC 10 at the 6-m SAO telescope with the panoramic Multi-Pupil Fiber Spectrograph (MPFS). Based on the results of these observations and our long-slit spectroscopy performed previously, we have investigated the ionized-gas emission spectrum in the region of intense star formation and refined the gas metallicity estimates. We show that the “diagnostic diagrams” constructed from our observations agree best with the new improved ionization models by Martin-Manjon et al. Using these models, we have determined the electron density and gas ionization parameter and ionizing-cluster characteristics, the age and mass, from the spectra of the investigated HII regions. The cluster ages and masses are shown to be within the ranges 2.5-5 Myr and (0.2-1) × 105 M ⊗, respectively.

  6. Radio, millimeter-submillimeter, and infrared spectra of flat-spectrum extragalactic radio sources

    NASA Technical Reports Server (NTRS)

    Bloom, Steven D.; Marscher, Alan P.; Gear, Walter K.; Terasranta, Harri; Valtaoja, Esko; Aller, Hugh D.; Aller, Margo F.

    1994-01-01

    We present radio to submillimeter-wave continuum spectra of 44 bright, compact extragalactic radio sources with flat spectra at centimeter wavelengths ('blazars'). Infrared J, H, and K flux densities are added to the spectra of six of these objects. These spectra are useful in comparisons of x-ray and gamma-ray measurements with the multiwaveband properties of blazars. A number of the objects have been detected as strong, hard gamma-ray sources by the Compton Gamma Ray Observatory (CGRO). The millimeter-wave spectra of the gamma-ray bright blazars we observe are flatter on average than for the sample as a whole.

  7. Development of Forced Patches in Steep Channels

    NASA Astrophysics Data System (ADS)

    Monsalve Sepulveda, A.; Yager, E. M.

    2012-12-01

    Bed surface patchiness occurs in most gravel-bedded rivers. This spatial variability in grain size and sorting impacts bed load transport. Laboratory experiments have shown that patches can arise from a local sediment transport-supply imbalance, grain to grain interactions or size-selective cross-stream transport in the presence of topographically forced heterogeneous flow fields. It is still unknown if these mechanisms can explain the formation of patches in high gradient channels with large roughness elements, which create spatial and temporal variations in depth, velocity and shear stress and alter pressure gradients, centrifugal forces, boundary friction and along and cross-stream changes in fluid momentum. To understand how these forced patches (spatially persistent due to strong topographic controls) form, a set of flume experiments using staggered immobile boulders and steep slopes wasconducted through different stages of patch evolution, starting from a flat uniform bed until patch geometry was stable in time and sediment fluxes were in equilibrium. Areas, changes in elevation, stream and crosswise sediment fluxes, and grains size distributions for patches located upstream, downstream and between boulders were measured for five different discharges. Flow field properties were obtained using a quasi-three-dimensional model to explain the influence of different components of the momentum equations on patch formation and evolution. We present these flume measurements and numerical modeling results to determine how the formation of patches is influenced by immobile boulders and the relative submergence of these roughness elements.

  8. 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.

  9. Novel, High-power, Mid-infrared Optical Source for the 5-12 Micron Spectrum

    DTIC Science & Technology

    2011-12-01

    mid‐IR nonlinear crystals of MgO:PPLN, MgO:sPPLT, and CdSiP2 together with fiber and solid‐ state  laser  technology at 1064 nm as the  pump  source...based on parametric generation and oscillation in the latest class of mid-IR nonlinear materials in combination with the most advanced lasers pump ...Distribution A: Approved for pubic release: distribution is unlimited. 2 1. Fiber- laser - pumped , multiwatt, near- to mid-infrared, continuous-wave optical

  10. Variability in the X-ray Spectrum of the Stable Calibration Source Capella

    NASA Astrophysics Data System (ADS)

    Raassen, T.

    2006-08-01

    The X-ray calibration source Capella has been extensively observed by Chandra and XMM-Newton since 1999, the year of the launches of the two satellites. We have investigated eleven X-ray spectra obtained by LETGS aboard Chandra over the last 5 years. Variability of the zeroth order count rate (lightcurve) as well as variability of the line fluxes of highly ionized iron features (FeXVIII-XXI) is established. The fluxes have been compared with measured line fluxes from EUVE observations between 1992 and 1995. A strong resemblance between variations in the period 1992-1995 and the period 2000-2005 is noticed.

  11. Polarization properties of extragalactic radio sources and their contribution to microwave polarization fluctuations

    NASA Astrophysics Data System (ADS)

    Mesa, D.; Baccigalupi, C.; De Zotti, G.; Gregorini, L.; Mack, K.-H.; Vigotti, M.; Klein, U.

    2002-12-01

    We investigate the statistical properties of the polarized emission of extragalactic radio sources and estimate their contribution to the power spectrum of polarization fluctuations in the microwave region. The basic ingredients of our analysis are the NVSS polarization data, the multifrequency study of polarization properties of the B3-VLA sample (Mack et al. \\cite{Mack2002}) which has allowed us to quantify Faraday depolarization effects, and the 15 GHz survey by Taylor et al. (\\cite{Taylor2001}), which has provided strong constraints on the high-frequency spectral indices of sources. The polarization degree of both steep- and flat-spectrum sources at 1.4 GHz is found to be anti-correlated with the flux density. The median polarization degree at 1.4 GHz of both steep- and flat-spectrum sources brighter than S(1.4 GHz)=80 mJy is =~ 2.2%. The data by Mack et al. (\\cite{Mack2002}) indicate a substantial mean Faraday depolarization at 1.4 GHz for steep spectrum sources, while the depolarization is undetermined for most flat/inverted-spectrum sources. Exploiting this complex of information we have estimated the power spectrum of polarization fluctuations due to extragalactic radio sources at microwave frequencies. We confirm that extragalactic sources are expected to be the main contaminant of Cosmic Microwave Background (CMB) polarization maps on small angular scales. At frequencies <30 GHz the amplitude of their power spectrum is expected to be comparable to that of the E-mode of the CMB. At higher frequencies, however, the CMB dominates.

  12. A "looming bias" in spatial hearing? Effects of acoustic intensity and spectrum on categorical sound source localization.

    PubMed

    McCarthy, Lisa; Olsen, Kirk N

    2017-01-01

    Continuous increases of acoustic intensity (up-ramps) can indicate a looming (approaching) sound source in the environment, whereas continuous decreases of intensity (down-ramps) can indicate a receding sound source. From psychoacoustic experiments, an "adaptive perceptual bias" for up-ramp looming tonal stimuli has been proposed (Neuhoff, 1998). This theory postulates that (1) up-ramps are perceptually salient because of their association with looming and potentially threatening stimuli in the environment; (2) tonal stimuli are perceptually salient because of an association with single and potentially threatening biological sound sources in the environment, relative to white noise, which is more likely to arise from dispersed signals and nonthreatening/nonbiological sources (wind/ocean). In the present study, we extrapolated the "adaptive perceptual bias" theory and investigated its assumptions by measuring sound source localization in response to acoustic stimuli presented in azimuth to imply looming, stationary, and receding motion in depth. Participants (N = 26) heard three directions of intensity change (up-ramps, down-ramps, and steady state, associated with looming, receding, and stationary motion, respectively) and three levels of acoustic spectrum (a 1-kHz pure tone, the tonal vowel /ә/, and white noise) in a within-subjects design. We first hypothesized that if up-ramps are "perceptually salient" and capable of eliciting adaptive responses, then they would be localized faster and more accurately than down-ramps. This hypothesis was supported. However, the results did not support the second hypothesis. Rather, the white-noise and vowel conditions were localized faster and more accurately than the pure-tone conditions. These results are discussed in the context of auditory and visual theories of motion perception, auditory attentional capture, and the spectral causes of spatial ambiguity.

  13. 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.

  14. 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.

  15. Channel Steepness and Longitudinal Profile Evaluation Along the Northern California Coast

    NASA Astrophysics Data System (ADS)

    Fisher, A. C. N.; Belmont, P.; MacDonald, L. H.

    2016-12-01

    Rivers along the northern California coast have been subjected to high levels of tectonic activity (uplift and subsidence) as well as a century and a half of timber harvest, both of which can increase sediment loads in rivers. Excessive sedimentation has caused many of these rivers to be listed as impaired under the Clean Water Act. Discerning natural versus anthropogenic sources of sediment is essential for informing future policy and management decisions. The purpose of this study is to quantify regional trends in river channel steepness and concavity as well as identify reach-scale discontinuities (i.e., anomalous increases or decreases in slope) in river longitudinal profiles. We extracted longitudinal elevation profiles for 14 coastal rivers from Eureka to Crescent City in order to locate knickpoints (anomalous changes in slope that may indicate significant transitions in sediment transport processes and/or tectonic boundaries). Further, we computed the normalized steepness index (Ksn) throughout the river networks. Results indicate generally higher steepness in the northern portion of the study area, suggesting higher rates of tectonic uplift. Most coastal rivers exhibit anomalously low steepness proximate to the coast, with a few key exceptions.

  16. Vorticity Dynamics of Cross-isobath Geostrophic Transport in the Stratified Steep and Concave Shelves

    NASA Astrophysics Data System (ADS)

    Jianping, G.; Hui, C. W.

    2016-02-01

    We investigated the variability and the physics of cross-isobath transport that lead to the formation of prominent upwelling centers in the steep shelf to the east of Hainan Island (EHI) and in the ambient shallow Gulf of Zhanjiang (GOZ). In situ measurements and a three-dimensional modeling showed that strengthened upslope transport of cold deep waters occurred in these two shelves, which are characterized by steep slope and concaving isobaths, respectively. The major driving force for these shoreward cross-isobath transports were not from the bottom frictional dynamics, but from the along-isobath pressure gradient force (PGF) as a result of the flow response to the variable shelf topography. The physical origins of the PGF of these prominent upwelling centers, however, were dynamically different. We found that the sources of the PGF were the Modified Joint Effect Baroclinicity and Relief (MJEBAR) due to importance of baroclinicity in the steep EHI and the net water-column stress curl in the concaving GOZ. The along-shelf geostrophic current that maintains the flow-topography interaction for the formation of the PGF was determined by the competing slope and baroclinic effects in EHI and by the cross-isobath changing bottom pressure in GOZ. Based on depth-integrated vorticity dynamics for a stratified and free-surface sea, this study illustrates the contrasting forcing functions of the three-dimensional circulation over the steep and shallow concaving shelves.

  17. Active Galactic Nuclei Selected from GALEX Spectroscopy: The Ionizing Source Spectrum at z ~ 1

    NASA Astrophysics Data System (ADS)

    Barger, Amy J.; Cowie, Lennox L.

    2010-08-01

    We use a complete sample of Lyα-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 Å) at z ~ 1. Our sample consists of 139 sources selected in the redshift range z = 0.65-1.25 in the near-ultraviolet (NUV; 2371 Å central wavelength) channel. The area covered is 8.2 deg2 to a NUV magnitude of 20.5 (AB) and 0.92 deg2 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 Å 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 ~ 1 in a fully self-consistent way. Based in part on data obtained from the Multimission Archive at the Space Telescope Science Institute (STScI). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for Multimission Archive at STScI (MAST) for non-HST data is provided by the NASA Office of Space Science via grant NAG5-7584 and by other grants and contracts. Based in part on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation.

  18. Percent Agricultural Land Cover on Steep Slopes (Future)

    EPA Pesticide Factsheets

    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 surface water. Agricultural land cover on steep slopes (AGSL) is the percent of agriculture on slopes greater than or equal to 9%. More information about these resources, including the variables used in this study, may be found here: https://edg.epa.gov/data/Public/ORD/NERL/ReVA/ReVA_Data.zip.

  19. Very high energy gamma-rays from flat spectrum radio quasars

    NASA Astrophysics Data System (ADS)

    Lindfors, Elina

    2015-03-01

    The detection of Flat Spectrum Radio Quasars (FSRQs) in the Very High Energy (VHE, E>100 GeV) range is challenging, mainly because of their steep soft spectra and distance. Nevertheless four FSRQs are now known to be VHE emitters. The detection of the VHE γ-rays has challenged the emission models of these sources. The sources are also found to exhibit very different behavior. I will give an overview of what is known about the VHE emission of these sources and about the multiwavelength signatures that are connected to the VHE gamma-ray emission.

  20. 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.

  1. Steep front short duration low voltage impulse performance of distribution transformers

    SciTech Connect

    Burrage, L.M.; Veverka, E.F.; McConnell, B.W.

    1987-01-01

    An extensive literature search of steep front short duration (SFSD) impulse sources, their characteristics and effect on power system equipment has led to the specification of a test program to evaluate key apparatus and insulations. Distribution transformers, although not overly susceptible to impulse damage, have been selected as one of the candidate apparatus for low and high voltage SFSD impulse tests. This paper covers the low voltage SFSD impulse response of conventional oil insulated shell form and core form distribution transformers.

  2. 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.

  3. 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.

  4. 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.

  5. An event-related source localization study of response monitoring and social impairments in autism spectrum disorder.

    PubMed

    Santesso, Diane L; Drmic, Irene E; Jetha, Michelle K; Bryson, Susan E; Goldberg, Joel O; Hall, Geoffrey B; Mathewson, Karen J; Segalowitz, Sidney J; Schmidt, Louis A

    2011-02-01

    A number of studies suggest anterior cingulate cortex (ACC) abnormalities in autism spectrum disorder (ASD), which might underlie response monitoring and social impairments exhibited by children and adolescents with ASD. The goal of the present study was to extend this work by examining error and correct response monitoring using event-related potentials (ERN, Pe, CRN) and LORETA source localization in high functioning adults with ASD and controls. Adults with ASD showed reduced ERN and Pe amplitudes and reduced rostral ACC activation compared with controls. Adults with ASD also showed less differentiation between error and correct ERP components. Social impairments and higher overall autism symptoms were related to reduced rostral ACC activity at the time of the ERN, particularly in adults with ASD. These findings suggest that reduced ACC activity may reflect a putative brain mechanism involved in the origins and maintenance of social impairments and raise the possibility of the presence of stable brain-behavior relation impairment across development in some individuals with ASD.

  6. Continuation of the Pursuit of the Far-Infrared Spectrum of Ncncs, at the Canadian Light Source

    NASA Astrophysics Data System (ADS)

    Winnewisser, Manfred; Winnewisser, Brenda P.; De Frank, C. Lucia; Tokaryk, Dennis W.; Ross, Stephen C.; Billinghurst, Brant E.

    2013-06-01

    The molecule cyanogen iso-thiocyanate, NCNCS, has proved to be the most revealing model system for studying the effects of molecular quantum monodromy. In two previous measuring campaigns in May 2011 and May 2012 at the Canadian Light Source (CLS) at the University of Saskatchewan we have obtained a rich collection of high-resolution infrared band systems for both S(CN)_{2} and its isomer NCNCS which is our target molecule. We found experimentally that NCNCS is the more stable isomer. Some results for S(CN)_{2} are reported in the adjacent talk in this session. However, the isomerization between S(CN)_{2} and NCNCS and other reaction products make the attainment of a pure sample of NCNCS difficult and time consuming. We have not yet obtained a satisfactory high-resolution recording of the quasi-linear bending mode in the far infrared in the two allotments of beam time so far available to us. Our theoretical preparations for the project include recent refinements of predictions of intensities in the low-lying bending mode band system, which will be shown. The experimental aspects of obtaining an optimal sample of NCNCS in order to observe the rotational resolved spectrum in the CLS campaign scheduled for May 2013, and an initial report of the results, will also be discussed. B. P. Winnewisser, M. Winnewisser, I. R. Medvedev, F. C. {De Lucia}, S. C. Ross and J. Koput, Phys. Chem. Chem. Phys., {12}, 8158 (2010)

  7. 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…

  8. 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…

  9. Radio-Optical Analysis of Extended Radio Sources in the First Look Survey Field

    NASA Astrophysics Data System (ADS)

    Paulo, C. M.; Prandoni, I.; Morganti, R.; Cress, C. M.

    2010-05-01

    We combine 610 MHz GMRT data, 1.4 GHz VLA data, and 1.4 GHz WSRT observations, encompassing a ~ 4 square degree field centered on the verification strip of the Spitzer First Look Survey field, to study radio sources down to fluxes of about 0.1 mJy. The spectral index (Figure 1) analysis shows that the majority of multi-component sources are steep-spectrum sources. Nevertheless the spread in the spectral distribution is wide, with a significant number of ultra-steep, flat or inverted sources, possibly indicating a wider range of accretion modes in fainter samples. By cross-correlating 107 multi-component radio sources with the optical catalogues of Marleau et al. (2007) and Papovich et al. (2006), 23 objects were identified.

  10. Fermi LAT detection of renewed GeV gamma-ray activity associated with the flat-spectrum radio source PKS 2247-131

    NASA Astrophysics Data System (ADS)

    Gasparrini, D.

    2016-10-01

    The Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope, has observed a renewed strong gamma-ray activity from a source positionally consistent with the flat-spectrum radio source PKS 2247-131 with coordinates RA=342.4983854 deg, Dec=-12.8546736 deg (J2000; Beasley et al. 2002, ApJS, 141, 13). Fermi-LAT already reported a flare on ATel #9285 but this source is not in any published LAT catalog and was not detected by AGILE or EGRET.

  11. 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.

  12. 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.

  13. Calculating bed load transport in steep boulder bed channels

    NASA Astrophysics Data System (ADS)

    Yager, E. M.; Kirchner, J. W.; Dietrich, W. E.

    2007-07-01

    Steep, rough channels occupy a large fraction of the total channel length in mountainous regions. Most sediment mobilized on hillslopes must pass through these streams before reaching lower-gradient channels. Steep channels have wide grain size distributions that are composed of finer, more mobile sediment and large, rarely mobile grains. The large grains can bear a significant portion of the total shear stress and thereby reduce the stress available to move the finer sediment. Conventional bed load transport equations often overpredict the sediment flux in steep channels by several orders of magnitude. We hypothesize that sediment transport equations overpredict the sediment flux because they do not (1) account for the stress borne by rarely mobile grains, (2) differentiate between highly and rarely mobile sediment, and (3) account for the limited availability of mobile sediment. Here we modify a conventional bed load transport equation to include these three effects. We use measurements of the flow, bed properties, and sediment flux in a small, steep flume to test this equation. We supply gravel at a constant rate through fields of regularly spaced immobile spheres and measure the bed coverage by gravel and sphere protrusion (the percent of the sphere that protrudes above the gravel deposit). For a given sphere spacing, the proportion of the bed covered by gravel increases and the sphere protrusion decreases with greater sediment supply. Thus bed coverage and immobile grain protrusion may serve as proxies for sediment availability in steep, rough streams. Unlike most transport equations that we tested, our modified bed load equation predicts sediment fluxes to within an order of magnitude of the measured values. Our results demonstrate that accurately predicting bed load transport in steep, rough streams may require accounting for the effects of local sediment availability (coverage by mobile sediment) and drag due to rarely mobile particles.

  14. Distribution transformer performance when subjected to steep front impulses

    SciTech Connect

    Burrage, L.M.; Shaw, J.H. . Thomas A. Edison Technical Center); McConnell, B.W. )

    1990-04-01

    The experimental method and the results of subjecting arrester protected pole type distribution transformers to the combined stresses caused by the conducted steep front impulse and rated 60 Hz voltages are described. Comparisons are drawn between these results and those of similar experiments on unenergized distribution transformers. It is concluded that tank mounted direct connected arresters provide a high degree of protection to these transformers, tank mounted externally gapped or crossarm mounted arresters may not provide sufficient protection; internal transformer insulation system failures caused by the steep front impulse do not necessarily result in immediate catastrophic failures of the transformers.

  15. Routing Bedload Sediment Through River Networks Draining Steep Uplands

    NASA Astrophysics Data System (ADS)

    Cui, Y.; Dietrich, W. E.; Parker, G.

    2001-12-01

    River networks draining mountainous landscapes receive episodic and spatially variable sediment supply. The network structure itself imposes a distinct sediment loading structure in which steep, coarse bedded tributaries deliver significant point loads to less steep main stems. Landslides that fail directly into the main stem also introduce large local loads. These sediment pulses then become attenuated during downstream transport due to storage and particle breakdown. For both theoretical and practical reasons (e.g. dam removal, polluted sediment management, hillslope erosion management, and stream restoration) we need to be able to predict the downstream transit time of particles and quantify the controls on rates of signal attenuation downstream. Here we report a new, mechanistic numerical model for bedload routing that accounts for vertical storage, particle attrition, and stochastic sediment input and flow regime. The model uses observed channel slopes and channel widths. Flow is estimated through the network using drainage-area scaled annual flow duration. Sediment input varies around long-term average value by factors of a random number that co-varies with the randomly chosen flow duration curves and an independently selected random number, and input occurs along the channel banks and channel head. Debris flow transport is not considered. Simulations reported here were performed with data from the Noyo River, California as the prototype. Sample runs of the models revealed several important phenomena, many of which are fundamentally important in guiding future model development in mountain watersheds: a) in landscapes underlain by mechanically weak bedrock, particle attrition is probably the most important mechanism with which the bedload sediment is transported out of the system; b) due to particle attrition, bedload transport flux may decrease in the downstream direction even with the increased drainage area from tributary contributions, indicating the

  16. Sediment transport dynamics in steep, tropical volcanic catchments

    NASA Astrophysics Data System (ADS)

    Birkel, Christian; Solano Rivera, Vanessa; Granados Bolaños, Sebastian; Brenes Cambronero, Liz; Sánchez Murillo, Ricardo; Geris, Josie

    2017-04-01

    How volcanic landforms in tropical mountainous regions are eroded, and how eroded materials move through these mostly steep landscapes from the headwaters to affect sediment fluxes are critical to water resources management in their downstream rivers. Volcanic landscapes are of particular importance because of the short timescales (< years) over which they transform. Owing to volcanism and seismic activity, landslides and other mass movements frequently occur. These processes are amplified by high intensity precipitation inputs resulting in significant, but natural runoff, erosion and sediment fluxes. Sediment transport is also directly linked to carbon and solute export. However, knowledge on the sediment sources and transport dynamics in the humid tropics remains limited and their fluxes largely unquantified. In order to increase our understanding of the dominant erosion and sediment transport dynamics in humid tropical volcanic landscapes, we conducted an extensive monitoring effort in a pristine and protected (biological reserve Alberto Manuel Brenes, ReBAMB) tropical forest catchment (3.2 km2), located in the Central Volcanic Cordillera of Costa Rica (Figure 1A). Typical for tropical volcanic and montane regions, deeply incised V-form headwaters (Figure 1B) deliver the majority of water (>70%) and sediments to downstream rivers. At the catchment outlet (Figure 1C) of the San Lorencito stream, we established high temporal resolution (5min) water quantity and sediment monitoring (turbidity). We also surveyed the river network on various occasions to characterize fluvial geomorphology including material properties. We could show that the rainfall-runoff-sediment relationships and their characteristic hysteresis patterns are directly linked to variations in the climatic input (storm intensity and duration) and the size, form and mineralogy of the transported material. Such a relationship allowed us to gain the following insights: (i) periodic landslides contribute

  17. Optical spectroscopy of four young radio sources

    NASA Astrophysics Data System (ADS)

    Fan, Xu-Liang; Bai, Jin-Ming; Hu, Chen; Wang, Jian-Guo

    2017-01-01

    We report the optical spectroscopy of four young radio sources which are observed with the Lijiang 2.4 m telescope. The Eddington ratios of these sources are similar with those of narrow-line Seyfert 1 galaxies (NLS1s). Their Fe II emission is strong while [O III] strength is weak. These results confirm the NLS1 features of young radio sources, except that the width of broad Hβ of young radio sources is larger than that of NLS1s. We thus suggest that the young radio sources are the high black hole mass counterparts of steep-spectrum radio-loud NLS1s. In addition, the broad Hβ component of 4C 12.50 is the blue wing of the narrow component, but not from the broad line region.

  18. Felling and bunching small timber on steep slopes.

    Treesearch

    Rodger A. Arola; Edwin S. Miyata; John A. Sturos; Helmuth M. Steinhilb

    1981-01-01

    Discusses the results of a field test of the unique Menzi Muck machine for felling and bunching small trees on steep slopes. Includes the analysis of a detailed time study to determine the productivity, costs, and economic feasibility of this unusual machine.

  19. 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...

  20. 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...

  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, 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...

  3. 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...

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

    USDA-ARS?s Scientific Manuscript database

    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...

  5. 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 MINING ACTIVITIES § 816.107 Backfilling and...

  6. 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 MINING ACTIVITIES § 817.107 Backfilling an...

  7. It's time to look at yarding problems on steep slopes.

    Treesearch

    Robert H. Ruth

    1960-01-01

    In many parts of the Pacific Northwest, logging operations are moving into rugged terrain as access roads probe deeper into the back country. Because of this trend, it's time to look more carefully at steep slopes and decide on the best possible management practices consistent with maximum protection against erosion.

  8. 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.

  9. Direct medical costs and source of cost differences across the spectrum of cognitive decline: A population-based study

    PubMed Central

    Leibson, Cynthia L.; Long, Kirsten Hall; Ransom, Jeanine E.; Roberts, Rosebud O.; Hass, Steven L.; Duhig, Amy M.; Smith, Carin Y.; Emerson, Jane A.; Pankratz, V. Shane; Petersen, Ronald C.

    2015-01-01

    BACKGROUND Objective cost estimates and source of cost differences are needed across the spectrum of cognition, including cognitively normal (CN), mild-cognitive-impairment (MCI), newly-discovered dementia, and prevalent dementia. METHODS Subjects were a subset of the Mayo Clinic Study of Aging stratified-random sampling of Olmsted County, MN, residents aged 70-89 years. A neurologist reviewed provider-linked medical records to identify prevalent-dementia (review date=index). Remaining subjects were invited to participate in prospective clinical/neuropsychological assessments; participants were categorized as CN, MCI, or newly-discovered-dementia (assessment date=index). Costs for medical services/procedures 1-year pre-index (excluding indirect and long-term care costs) were estimated using line-item provider-linked administrative data. We estimated contributions of care-delivery site and comorbid conditions (including and excluding neuropsychiatric diagnoses) to between-category cost differences. RESULTS Annual mean medical costs for CN, MCI, newly-discovered-dementia, and prevalent-dementia were $6,042, $6,784, $9,431, $11,678 respectively. Hospital inpatient costs contributed 70% of total costs for prevalent dementia and accounted for differences between CN and both prevalent and newly-discovered dementia. Ambulatory costs accounted for differences between CN and MCI. Age-, sex-, education-adjusted differences reached significance for CN versus newly-discovered and prevalent-dementia and for MCI versus prevalent-dementia. After considering all comorbid diagnoses, between-category differences were reduced (e.g., prevalent-dementia minus MCI (from $4,842 to $3,575); newly-discovered-dementia minus CN (from $3,578 to$711). Following exclusion of neuropsychiatric diagnoses from comorbidity adjustment, between-category differences tended to revert to greater differences. CONCLUSIONS Cost estimates did not differ significantly between CN and MCI. Substantial

  10. Radio Sources in Low-Luminosity Active Galactic Nuclei. I. VLA Detections of Compact, Flat-Spectrum Cores

    NASA Astrophysics Data System (ADS)

    Nagar, Neil M.; Falcke, Heino; Wilson, Andrew S.; Ho, Luis C.

    2000-10-01

    We report a high-resolution (0.2"), 15 GHz survey of a sample of 48 low-luminosity active galactic nuclei with the Very Large Array.5 Compact radio emission has been detected above a flux density of 1.1 mJy in 57% (17 of 30) of low-ionization nuclear emission-line region (LINER) nuclei and low-luminosity Seyfert galaxies. The 2 cm radio power is significantly correlated with the emission-line ([O I] λ6300) luminosity. Using radio fluxes at other frequencies from the literature, we find that at least 15 of the 18 detected radio cores have a flat to inverted spectrum (α>=-0.3, Sν~να). While the present observations are consistent with the radio emission originating in star-forming regions (the brightness temperatures are >=102.5-4.5 K), higher resolution radio observations of 10 of the detected sources, reported in an accompanying paper, show that the cores are very compact (<~1 pc), of high brightness temperature (Tb>~108 K), and probably synchrotron self-absorbed, ruling out a starburst origin. Thus, our results suggest that at least 50% of low-luminosity Seyfert galaxies and LINERs in the sample are accretion powered, with the radio emission presumably coming from jets or advection-dominated accretion flows. We have detected only 1 of 18 ``transition'' (i.e., LINER+H II) nuclei observed, indicating that their radio cores are significantly weaker than those of ``pure'' LINERs. Compact 2 cm radio cores are found in both type 1 (i.e., with broad Hα) and type 2 (without broad Hα) nuclei. There is weak evidence, limited in significance by small numbers, that low-luminosity active galactic nuclei with compact radio cores exhibit radio ejecta preferentially aligned along the rotation axis of the galaxy disk. If this result were confirmed by a larger sample, it would lend support to the idea that the misalignment of accretion disks with the galaxy stellar disk in more luminous Seyfert galaxies is a result of radiation-pressure-induced warping of their accretion

  11. The broad band X-ray spectrum of SN 1978k and two other luminous X-ray sources in the spiral galaxy NGC 1313

    NASA Technical Reports Server (NTRS)

    Petre, Robert; Okada, Kyoko; Mihara, Tatehiro; Makishima, Kazuo; Colbert, Edward J. M.

    1994-01-01

    We present preliminary results of our analysis of the Advanced Satellite for Cosmology and Astrophysics (ASCA) PV phase observation of the nearby spiral galaxy NGC 1313. ASCA cleanly resolves the three previously known luminous sources, one of which is the very luminous supernova, SN 1978k. The spectrum of SN 1978k is described by either a power law with a photon index gamma approximately 2.2 or a thermal model with temperature kT approximately 3.0 keV and abundances Z approximately 0.2 Z(sun). There is no evidence for strong line emission from it or from the other two sources. The spectrum of SN 1978k arises either in shocked gas in extreme departure from ionization equilibrium or from synchrotron processes associated with a newborn pulsar. A second source, near the galactic center, is well-fit by a power-law with a photon index of approximately 1.8. It is possibly an active nucleus-like source, but physically displaced from the optical nucleus of the galaxy. The spectrum of the third source, located 8 kpc south of the nucleus, along with the absence of an optical counterpart, suggests that it is a low mass X-ray binary; but its high X-ray luminosity clouds this interpretation. This observation demonstrates the ability of ASCA to perform effective broad band spectroscopic measurements of sources at a 2-10 keV flux level of 5 x 10(exp -13) erg cm(exp -2) s(exp -1).

  12. Steep Decay Phase Shaped by the Curvature Effect. II. Spectral Evolution

    NASA Astrophysics Data System (ADS)

    Lin, Da-Bin; Mu, Hui-Jun; Liang, Yun-Feng; Liu, Tong; Gu, Wei-Min; Lu, Rui-Jing; Wang, Xiang-Gao; Liang, En-Wei

    2017-05-01

    We derive a simple analytical formula to describe the evolution of spectral index β in the steep decay phase shaped by the curvature effect with the assumption that the spectral parameters and Lorentz factor of the jet shell are the same for different latitudes. Here, the value of β is estimated in the 0.3-10 keV energy band. For a spherical thin shell with a cutoff power-law (CPL) intrinsic radiation spectrum, the spectral evolution can be read as a linear function of observer time. For the situation with the Band function intrinsic radiation spectrum, the spectral evolution may be complex. If the observed break energy of the radiation spectrum is larger than 10 keV, the spectral evolution is the same as that shaped by jet shells with a CPL spectrum. If the observed break energy is less than 0.3 keV, the value of β would be a constant. For others, the spectral evolution can be approximated as a logarithmal function of the observer time in general.

  13. Nocturnal winds over steep terrain: Turbulence structure and modeling challenges

    NASA Astrophysics Data System (ADS)

    Oldroyd, H. J.; Pardyjak, E.; Higgins, C. W.; Parlange, M. B.

    2016-12-01

    The presence of steep terrain poses several challenges to numerical modeling of turbulent surface-atmospheric exchanges, ranging from difficulties associated with the numerical grid (e.g., insufficient resolution and overstretching) to violating key assumptions (e.g., horizontal terrain) necessary for traditional parameterizations to hold. We present observations of the turbulence structure in nocturnal slope flows over steep (35.5 degree), alpine terrain in Val Ferret, Switzerland to highlight specific modeling challenges arising from deviating from the horizontal-terrain assumption. Under clear-sky conditions, we observe two distinct flow regimes with mean winds directed down the slope: (1) buoyancy-driven, `katabatic flow', for which an elevated velocity maximum (katabatic jet peak) is observed and (2) `downslope winds', for which larger-scale forcing prevents formation of a katabatic jet. These distinct flow regimes exhibit very different vertical turbulence structures. For example, the katabatic jet strongly modulates momentum and buoyancy fluxes and can vary in sign when compared to the downslope wind regime or traditional horizontal, stable boundary layer flows. Hence, improved numerical forecasting models should seek the capabilities to accurately reproduce these varied regimes. Additional modeling challenges posed by steep-slope flows are that turbulent fluxes rarely exhibit a constant-flux-type surface layer, in violation to another key assumption for most turbulence parameterizations (e.g., Monin-Obukhov similarity based wall models and turbulence closure models). Finally, we show that the traditional (horizontal terrain) concept of atmospheric stability can become unclear for flows over steep terrain, which can further complicate stability-based numerical modeling. Hence, we additionally propose key areas for future research toward improving modeling capabilities over steep terrain.

  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. 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.

  16. Evolution of luminous IRAS sources - CCD imaging

    NASA Technical Reports Server (NTRS)

    Hutchings, J. B.; Neff, S. G.

    1991-01-01

    The paper presents optical imaging of a sample of 64 luminous IRAS galaxies which cover a wide range of IRAS spectra and luminosity and also include a range of optical types. The objects are almost all in current or recent tidal interaction. The connections between the strength and age of the interaction, the IR spectrum and luminosity, and the optical colors, and other properties of the galaxies are discussed. The principal result is that the powerful IR sources with steep IR spectra are stronger and dynamically younger interacting systems, while the flat IR spectrum objects are older. Star formation, dust obscuration, and the timescales for nuclear activity compared with IR and tidal events are discussed, and a self-consistent evolution scenario connecting the luminous IR sources is described.

  17. 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.

  18. Prediction of Sediment Transport in Steep Boulder-bed Channels

    NASA Astrophysics Data System (ADS)

    Yager, E.; Kirchner, J. W.; Dietrich, W. E.; Furbish, D. J.

    2002-12-01

    Most sediment in mountainous terrain must first travel through steep, rough channels before reaching lower-gradient streams. Predicting flow and sediment transport rates through steep channels is problematic. Conventional transport equations, developed for lower-gradient reaches, typically over-predict sediment flux in these streams by several orders of magnitude. We hypothesize that current transport equations do not apply in steep, rough channels because 1) they do not account for the stress borne by large, relatively immobile grains, 2) they do not differentiate between seasonally and rarely mobile sediment 3) they assume an unlimited sediment supply. We have developed and tested a transport equation that incorporates the effects of large roughness elements and variable sediment supply. Measurements of the spacing, diameter, and protrusion of immobile grains, combined with channel slope, water discharge, and mobile grain size, are used to predict transport rates in steep channels. We partition the total shear stress between that borne by the exposed immobile grains and that borne by the finer, more mobile bed. We then modify a traditional bedload transport equation to use only the stress on the mobile fraction, rather than the total stress. To account for the limited supply of mobile sediment, we scale the predicted transport rate by the proportion of the bed occupied by the mobile fraction. We tested this theory in a 15 cm wide flume set at a gradient of ten percent. For each run, 3.7 mm gravel was fed at a constant rate through a bed of regularly spaced immobile spheres (30 mm diameter). To evaluate our model over a range of conditions, we varied the sphere spacing and sediment supply between experimental runs. The proportion of the bed occupied by the mobile fraction increased with sediment supply. Thus, bed coverage by mobile sediment may serve as a proxy for sediment supply in steep, rough streams. Sediment transport rates predicted by our modified bedload

  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. Flight dynamics of rotorcraft in steep high-g turns

    NASA Technical Reports Server (NTRS)

    Chen, R. T. N.

    1982-01-01

    An analyticl procedure developed to permit a systematic examination of rotorcraft flight dynamics in steep high-g turns is presented. The procedure is used in a numerical investigation of a tilt-rotor aircraft and three single-rotor helicopters that have different types of main rotor systems. The results indicate (1) that strong coupling in longitudinal and lateral-directional motions exists for these rotorcraft in high-g turns; (2) that for single-rotor helicopters, the direction of turn has a significant influence on flight dynamics; and (3) that a stability and control augmentation system that is designed on the basis of standard small-disturbance equations of motion from steady straight and level flight and that otherwise performs satisfactorily in operations near 1 g, becomes significantly degraded in steep turning flight.

  1. Damage mechanisms and influence of gradation for steep riprap

    SciTech Connect

    Rohan, K.; Belfadhel, M.B.; Lefebvre, G. ); Dascal, O. )

    1994-03-01

    Model tests in a laboratory flume were performed to verify certain hypotheses put forward to explain steep riprap behavior observed in the field at several embankment dam sites. The laboratory study has focused on riprap degradation under wave attack, and on the influence of fine blocks incorporated into riprap. Unlike flatter riprap, steep riprap is characterized by a low rate of damage until a point of acceleration, after which damage progresses rapidly. At that stage, damage is characterized by sliding and crumbling, which results in an upward propagation of damage toward the crest. The inclusion of a portion of small blocks into the riprap significantly reduces the stability of seep riprap. This detrimental effect is gradually reduced as the riprap slope becomes flatter.

  2. 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.

  3. 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.

  4. Katabatic flow observations over a steep alpine slope

    NASA Astrophysics Data System (ADS)

    Oldroyd, Holly; Pardyjak, Eric; Calaf, Marc; Giometto, Marco; Huwald, Hendrik; parlange, Marc

    2013-04-01

    Katabatic flows, or downslope drainage flows, are thermally driven winds generated over sloping terrain when the surface is colder than the adjacent air and synoptic forcing is weak. This near-surface temperature inversion generates a buoyancy field such that denser, cooler air near the surface tends to sink down the slope and form the katabatic flow. Often these flows can be exploited for wind energy, and they are important in predicting pollution transport in mountainous regions and the formation of large cold air pools in valleys and basins. Mean characteristics of katabatic flows over gentle slopes are well documented. However, small-scale observations of turbulence inside the katabatic jet are less common, especially over very steep slopes in highly complex topography. Summertime measurements over a steep slope (36.5°) in a narrow alpine valley (Val Ferret, Switzerland) were taken with the aim of better understanding the near-surface turbulent fluxes that govern the local slope flows. Here, a weak katabatic jet with a height less than 1 m characterizes the mean flow. High-resolution, near-surface temperature measurements suggest a shallow internal boundary layer within the katabatic layer. Additionally, the turbulent heat flux varies significantly over the 6 m measurement layer. Hence, Monin-Obukhov Similarity theory (MOST) may be invalid for steep slopes. Turbulent statistics such as velocity and temperature variances, fluxes of momentum and heat, turbulence kinetic energy (TKE), and turbulent Prandtl number are compared to those obtained in large eddy simulations (LES) of idealized steep sloping terrain.

  5. 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.

  6. 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.

  7. Steep waves in free-surface flow past narrow topography

    NASA Astrophysics Data System (ADS)

    Wade, Stephen L.; Binder, Benjamin J.; Mattner, Trent W.; Denier, James P.

    2017-06-01

    In this work, we compute steep forced solitary wave solutions for the problem of free-surface flow over a localised topographic disturbance in an otherwise flat horizontal channel bottom. A single forced solitary wave and a double-crested forced solitary wave solution are shown to exist, both of which approach the Stokes limiting configuration of an included angle of 12 0° and a stagnation point at the wave crests. The solution space for the topographically forced problem is compared to that found in Wade et al. ["On the free-surface flow of very steep forced solitary waves," J. Fluid Mech. 739, 1-21 (2014)], who considered forcing due to a localised distribution of pressure applied to the free surface. The main feature that differentiates the two types of forcing is an additional solution that exists in the pressure-forced problem, a steep wave with a cusp at a single wave crest. Our numerical results suggest that this cusped-wave solution does not exist in the topographically forced problem.

  8. 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.

  9. DISCOVERY AND MONITORING OF A NEW BLACK HOLE CANDIDATE XTE J1752-223 WITH RXTE: RMS SPECTRUM EVOLUTION, BLACK HOLE MASS, AND THE SOURCE DISTANCE

    SciTech Connect

    Shaposhnikov, Nikolai

    2010-11-10

    We report on the discovery and monitoring observations of a new galactic black hole (BH) candidate XTE J1752-223 by Rossi X-ray Timing Explorer (RXTE). The new source appeared on the X-ray sky on 2009 October 21 and was active for almost 8 months. Phenomenologically, the source exhibited the low-hard/high-soft spectral state bi-modality and the variability evolution during the state transition that matches standard behavior expected from a stellar mass BH 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 blackbody 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 broadband 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 hard-to-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 of about 3.5 kpc.

  10. Results on the primary CR spectrum and composition reconstructed with the SPHERE-2 detector

    NASA Astrophysics Data System (ADS)

    Antonov, R. A.; Beschapov, S. P.; Bonvech, E. A.; Chernov, D. V.; Dzhatdoev, T. A.; Finger, Mir; Finger, Mix; Galkin, V. I.; Kabanova, N. V.; Petkun, A. S.; Podgrudkov, D. A.; Roganova, T. M.; Shaulov, S. B.; Sysoeva, T. I.

    2013-02-01

    First preliminary results of the balloon-borne experiment SPHERE-2 on the all-nuclei primary cosmic rays (PCR) spectrum and primary composition are presented. The primary spectrum in the energy range 1016-5 · 1017 eV was reconstructed using characteristics of Vavilov-Cherenkov radiation of extensive air showers (EAS), reflected from a snow surface. Several sources of systematic uncertainties of the spectrum were analysed. A method for separation of the primary nuclei' groups based on the lateral distribution function' (LDF) steepness parameter is presented. Preliminary estimate of the mean light nuclei' fraction f30-150 at energies 3 · 1016-1.5 · 1017 eV was performed and yielded f30-150 = (21±11) %.

  11. Multifrequency polarimetry of a complete sample of PACO radio sources

    NASA Astrophysics Data System (ADS)

    Galluzzi, V.; Massardi, M.; Bonaldi, A.; Casasola, V.; Gregorini, L.; Trombetti, T.; Burigana, C.; De Zotti, G.; Ricci, R.; Stevens, J.; Ekers, R. D.; Bonavera, L.; di Serego Alighieri, S.; Liuzzo, E.; López-Caniego, M.; Mignano, A.; Paladino, R.; Toffolatti, L.; Tucci, M.

    2017-03-01

    We present high-sensitivity polarimetric observations (σP ≃0.6 mJy) in six bands covering the 5.5-38 GHz range of a complete sample of 53 compact extragalactic radio sources brighter than 200 mJy at 20 GHz. The observations, carried out with the Australia Telescope Compact Array, achieved a 91 per cent detection rate (at 5σ). Within this frequency range, the spectra of about 95 per cent of sources are well fitted by double power laws, both in total intensity and in polarization, but the spectral shapes are generally different in the two cases. Most sources were classified as either steep- or peaked-spectrum but less than 50 per cent have the same classification in total and in polarized intensity. No significant trends of the polarization degree with flux density or with frequency were found. The mean variability index in total intensity of steep-spectrum sources increases with frequency for a 4-5 yr lag, while no significant trend shows up for the other sources and for the 8 yr lag. In polarization, the variability index, which could be computed only for the 8 yr lag, is substantially higher than in total intensity and has no significant frequency dependence.

  12. 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

  13. Stability of steep gravity capillary solitary waves in deep water

    NASA Astrophysics Data System (ADS)

    Calvo, David C.; Akylas, T. R.

    2002-02-01

    The stability of steep gravity capillary solitary waves in deep water is numerically investigated using the full nonlinear water-wave equations with surface tension. Out of the two solution branches that bifurcate at the minimum gravity capillary phase speed, solitary waves of depression are found to be stable both in the small-amplitude limit when they are in the form of wavepackets and at finite steepness when they consist of a single trough, consistent with observations. The elevation-wave solution branch, on the other hand, is unstable close to the bifurcation point but becomes stable at finite steepness as a limit point is passed and the wave profile features two well-separated troughs. Motivated by the experiments of Longuet-Higgins & Zhang (1997), we also consider the forced problem of a localized pressure distribution applied to the free surface of a stream with speed below the minimum gravity capillary phase speed. We find that the finite-amplitude forced solitary-wave solution branch computed by Vanden-Broeck & Dias (1992) is unstable but the branch corresponding to Rayleigh’s linearized solution is stable, in agreement also with a weakly nonlinear analysis based on a forced nonlinear Schrödinger equation. The significance of viscous effects is assessed using the approach proposed by Longuet-Higgins (1997): while for free elevation waves the instability predicted on the basis of potential-flow theory is relatively weak compared with viscous damping, the opposite turns out to be the case in the forced problem when the forcing is strong. In this régime, which is relevant to the experiments of Longuet-Higgins & Zhang (1997), the effects of instability can easily dominate viscous effects, and the results of the stability analysis are used to propose a theoretical explanation for the persistent unsteadiness of the forced wave profiles observed in the experiments.

  14. 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.

  15. Flow during the evening transition over steep alpine slopes

    NASA Astrophysics Data System (ADS)

    Parlange, M. B.; Nadeau, D. F.; Pardyjak, E.; Oldroyd, H. J.; Calaf Bracons, M.; Daniels, M. H.; Higgins, C. W.; Huwald, H.

    2011-12-01

    In steep alpine environments, surface heating and cooling plays an important role on the wind circulation, turbulence and flow patterns. These circulations undergo a strong diurnal cycle, with upslope winds during the day and drainage winds at night. Little is known about the transition between these two wind regimes over very steep slopes due to the difficulties involved with making field measurements. In both summers 2010 and 2011, we conducted a field campaign on a steep, west-facing slope of the Swiss Alps (Val Ferret, Valais) to study the evening transition of slope flows. Two eddy-covariance towers and two weather stations were installed on an experimental transect with slopes ranging from 20° to 45°. Large-scale valley circulations were observed with tethered balloon profiling and a wind lidar. The results show that topographic shading controls the daytime slope flow destruction and initiation of the evening transition. Following the movement of a 'shading front', the incoming shortwave radiation decreases by several hundreds of W/m2 in just a few minutes. The associated reduction in skin temperatures is substantial, and reductions on the order of 10°C in less than 10 min can be observed. This is followed by an early-evening calm period with light wind speeds and very small turbulent kinetic energy (TKE). Finally, growing from the surface upwards, a shallow, local katabatic flow (skin flow) forms. Additionally, an analysis of the TKE budget close to the surface shows that the buoyancy flux overpowers the shear production in the last hours before the local sunset, while at night shear production dominates the TKE budget.

  16. 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.

  17. 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.

  18. 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

  19. Wave Reflection on a Two-Slope Steep Beach

    DTIC Science & Technology

    2012-03-01

    ABSTRACT (maximum 200 words) Wave reflection of sea-swell (0.05–0.20 Hz) energy on a two-slope (1/7.6 nearshore and 1/19 offshore) steep beach with no...offshore components to determine reflection. The long data set captured a wide range of wave conditions at various tidal stages. Observations show low...amplitude long period waves produced energy reflection coefficients up to 80%, with most in the 30–50% range. There was a measured increase in the

  20. Global dynamics for steep nonlinearities in two dimensions

    NASA Astrophysics Data System (ADS)

    Gedeon, Tomáš; Harker, Shaun; Kokubu, Hiroshi; Mischaikow, Konstantin; Oka, Hiroe

    2017-01-01

    This paper discusses a novel approach to obtaining mathematically rigorous results on the global dynamics of ordinary differential equations. We study switching models of regulatory networks. To each switching network we associate a Morse graph, a computable object that describes a Morse decomposition of the dynamics. In this paper we show that all smooth perturbations of the switching system share the same Morse graph and we compute explicit bounds on the size of the allowable perturbation. This shows that computationally tractable switching systems can be used to characterize dynamics of smooth systems with steep nonlinearities.

  1. Katabatic flows over steep alpine slopes covered with short vegetation

    NASA Astrophysics Data System (ADS)

    Oldroyd, H. J.; Katul, G. G.; Pardyjak, E.; Huwald, H.; Parlange, M. B.

    2013-12-01

    Katabatic flows are high density air flows traversing down a slope under the action of a gravitational force. These flows can be exploited for wind energy and are gaining importance in predicting scalar transport (e.g. pollutants, water vapor, CO2 drainage) within mountainous regions and in forming large cold air pools in valleys and basins. Summertime measurements over a steep slope in a narrow alpine valley (Val Ferret, Switzerland) were collected so as to explore the components of the mean longitudinal momentum balance leading to the formation of the katabatic jet. During clear-sky nights with weak synoptic forcing, observations show a strong, near-surface temperature gradient and a subsequent, weak katabatic jet with a peak velocity at less than 1 m from the surface. Two distinct log-linear layers, both in mean velocity and in temperature, characterize the katabatic jet layer (up to ~6 m) where fluxes of heat and momentum vary with height. This departure from the so-called constant-stress region typifies difficulties in modeling and predicting flows over steep topography. To circumvent some of these difficulties, a one-dimensional model for the vertical flux gradient that couples momentum and thermal balances was used to predict the mean velocity and turbulent flux profiles for katabatic flows over steep, vegetated slopes. The model predicts realistic profiles of heat and momentum fluxes in comparison with the field measurements. For example, in the case of the modeled momentum flux, the sign of the flux changes at the height of peak velocity and the higher gradient near the surface is well reproduced. It is conjectured that unsteadiness in synoptic scale conditions can be partly accommodated via a dynamic mean horizontal pressure gradient at a point. Order of magnitude calculations suggest that this term can be larger than the so-called thermal wind term when the katabatic flow is sufficiently shallow, as is the case on steep slopes. This model may serve as a

  2. 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

  3. Magnetic Field Disorder and Faraday Effects on the Polarization of Extragalactic Radio Sources

    NASA Astrophysics Data System (ADS)

    Lamee, Mehdi; Rudnick, Lawrence; Farnes, Jamie S.; Carretti, Ettore; Gaensler, B. M.; Haverkorn, Marijke; Poppi, Sergio

    2016-09-01

    We present a polarization catalog of 533 extragalactic radio sources that have a 2.3 GHz total intensity above 420 mJy from the S-band Polarization All Sky Survey, S-PASS, with corresponding 1.4 GHz polarization information from the NRAO VLA Sky Survey, NVSS. We studied the selection effects and found that fractional polarization, π, of radio objects at both wavelengths depends on the spectral index, the source magnetic field disorder, the source size, and depolarization. The relationship between depolarization, spectrum, and size shows that depolarization occurs primarily in the source vicinity. The median {π }2.3 of resolved objects in NVSS is approximately two times larger than that of unresolved sources. Sources with little depolarization are ∼2 times more polarized than both highly depolarized and re-polarized sources. This indicates that intrinsic magnetic field disorder is the dominant mechanism responsible for the observed low fractional polarization of radio sources at high frequencies. We predict that number counts from polarization surveys will be similar at 1.4 GHz and at 2.3 GHz, for fixed sensitivity, although ∼10% of all sources may currently be missing because of strong depolarization. Objects with {π }1.4≈ {π }2.3≥slant 4 % typically have simple Faraday structures, so they are most useful for background samples. Almost half of flat-spectrum (α ≥slant -0.5) and ∼25% of steep-spectrum objects are re-polarized. Steep-spectrum, depolarized sources show a weak negative correlation of depolarization with redshift in the range 0 < z < 2.3. Previous non-detections of redshift evolution are likely due the inclusion of re-polarized sources as well.

  4. Orographic Precipitation Changes and Shallow Landslide-Derived Sediment in Steep Landscapes

    NASA Astrophysics Data System (ADS)

    Bellugi, D. G.; O'Gorman, P. A.; Perron, J. T.; Milledge, D.

    2014-12-01

    Rainfall-triggered shallow landslides are both a hazard and a major source of sediment in steep landscapes. Extreme precipitation events are expected to change under climate warming, but we have limited understanding of their effect on the relative abundance, size, and spatial distribution of landslides. In particular, changes in orographic precipitation may alter landslide distributions in steep landscapes. Recent theory suggests a significant downwind shift in orographic precipitation under a warming climate, causing larger fractional changes on leeward than on windward slopes. This may prove particularly relevant on the west coast of the USA where mountain ranges are oriented perpendicular to the moisture-laden prevailing winds coming from the Pacific. We analyze precipitation data from regional climate models (NARCCAP) under a high-end emissions scenario (IPCC A2). Preliminary results show that mean winter precipitation over the contiguous United States increases by roughly 2% over both low and high elevation regions in the simulations between the periods 1971-2000 to 2041-2070, but much larger fractional changes (~ triple) are found on leeward slopes. For the same periods, we find that extremes have greater fractional changes in intensity than the mean, and that these changes increase with return period. Similar trends emerge in the West Coast, but with bigger differences between windward and leeward slopes, which increase with return period. Moreover, while leeward increases are large for 30-year events (14%-19%), they are marked even for 2-year events (7-12%). This could significantly impact the frequency and magnitude of shallow landslides in steep landscapes affected by orographic precipitation. We test this hypothesis by applying a new catchment-scale model, which predicts both landslide location and size, to an intensively investigated study site in the Oregon Coast Range, where a ten-year landslide inventory has been mapped onto high

  5. The 9Be(d,n) 10B-reaction as intense neutron source with continuous energy spectrum

    NASA Astrophysics Data System (ADS)

    Baumann, F. M.; Domogala, G.; Freiesleben, H.; Paul, H. J.; Puhlvers, S.; Sohlbach, H.

    1986-06-01

    Neutron energy spectra produced by deuterons of 3 to 8 MeV in a thick 9Be-target were measured at various scattering angles. Significant angle dependences were observed. Angular distributions of the most energetic neutrons produced in thin 9Be targets can be described quantitatively in DWBA, which is an indication for a direct reaction mechanism. As a consequence all but 0°-neutrons are polarized to a certain extent. Also presented is the neutron energy spectrum of 7Li(d,n) 8Be at 0° produced in a thick 7Li-target. The potential of these intense 0°-neutron beams with continuous energy distributions is demonstrated by a measurement of the neutron absorption cross section of natural carbon.

  6. Using repeat lidar to estimate sediment transport in a steep stream

    NASA Astrophysics Data System (ADS)

    Anderson, Scott; Pitlick, John

    2014-03-01

    Sediment fluxes in steep mountain streams remain difficult to quantify, despite their importance in geomorphology, ecology, and hazard analysis. In this work, aerial lidar surveys, acquired in 2002, 2008, and 2012, are used to quantify such fluxes in Tahoma Creek, a proglacial stream on Mount Rainier, Washington. As these surveys encompass all coarse sediment sources in the basin, we are able to translate geomorphic change into total bed material transport volumes for the time steps between surveys. By assuming that the relationship between daily sediment transport and daily mean discharge is of the form Qs=a(Q-Qc)b, our two observed total loads and estimates of daily mean discharge allow us to numerically solve for values of a and b to create a bed material sediment rating curve. Comparisons of our transport estimates with sediment deposition in a downstream reservoir indicate that our transport estimates and derived rating curve are reasonable. The method we present thus represents a plausible means of estimating transport rates in energetic settings or during extreme events, applicable whenever at least two cumulative sediment loads and the driving hydrology are known. We use these results to assess the performance of several bed load transport equations. The equations generally overpredict transport at low to moderate flows but significantly underpredict transport rates during an extreme event. Using a critical shear stress value appropriate for steep streams improves agreement at lower flows, whereas a shear-partitioning technique accounting for form drag losses significantly underpredicts transport at all flows.

  7. Measurements and analysis of bremsstrahlung x-ray spectrum obtained in NANOGAN electron cyclotron resonance ion source

    SciTech Connect

    Baskaran, R.; Selvakumaran, T. S.; Rodrigues, G.; Kanjilal, D.; Roy, A.

    2008-02-15

    From the ECR plasma, hot electrons leak across the magnetic lines of force and by striking the plasma chamber produce bremsstrahlung x-rays. The wall bremsstrahlung gives information on the confinement status of hot electron. In our studies, experimental measurements are carried out in NANOGAN electron cyclotron resonance (ECR) ion source for the wall bremsstrahlung x-rays and the results are presented. While optimizing a particular charge state in ECR ion source, experimental parameters are adjusted to get a maximum current. The wall bremsstrahlung components are studied in these cases for understanding the hot electron confinement conditions.

  8. 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.

  9. 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.

  10. Designing steep, sharp patterns on uniformly ion-bombarded surfaces

    PubMed Central

    Perkinson, Joy C.; Aziz, Michael J.; Brenner, Michael P.; Holmes-Cerfon, Miranda

    2016-01-01

    We propose and experimentally test a method to fabricate patterns of steep, sharp features on surfaces, by exploiting the nonlinear dynamics of uniformly ion-bombarded surfaces. We show via theory, simulation, and experiment that the steepest parts of the surface evolve as one-dimensional curves that move in the normal direction at constant velocity. The curves are a special solution to the nonlinear equations that arises spontaneously whenever the initial patterning on the surface contains slopes larger than a critical value; mathematically they are traveling waves (shocks) that have the special property of being undercompressive. We derive the evolution equation for the curves by considering long-wavelength perturbations to the one-dimensional traveling wave, using the unusual boundary conditions required for an undercompressive shock, and we show this equation accurately describes the evolution of shapes on surfaces, both in simulations and in experiments. Because evolving a collection of one-dimensional curves is fast, this equation gives a computationally efficient and intuitive method for solving the inverse problem of finding the initial surface so the evolution leads to a desired target pattern. We illustrate this method by solving for the initial surface that will produce a lattice of diamonds connected by steep, sharp ridges, and we experimentally demonstrate the evolution of the initial surface into the target pattern. PMID:27698147

  11. Global theory to understand toroidal drift waves in steep gradient

    NASA Astrophysics Data System (ADS)

    Xie, Hua-sheng; Li, Bo

    2016-08-01

    Toroidal drift waves with unconventional mode structures and non-ground eigenstates, which differ from a typical ballooning structure mode, are found to be important recently by large scale global gyrokinetic simulations and especially become dominant at strong gradient edge plasmas [cf. H. S. Xie and Y. Xiao, Phys. Plasmas 22, 090703 (2015)]. The global stability and mode structures of drift wave in this steep edge density and temperature gradients are examined by both direct numerical solutions of a model two-dimensional eigen equation and analytical theory employing WKB-ballooning approach. Theory agrees with numerical solutions quite well. Our results indicate that (i) non-ground eigenstates and unconventional mode structures generally exist and can be roughly described by two parameters "quantum number" l and ballooning angle ϑk , (ii) local model can overestimate the growth rate largely, say, >50 % , and (iii) the narrow steep equilibrium profile leads to twisting (triangle-like) radial mode structures. With velocity space integral, semi-local theory predicts that the critical jump gradient of the most unstable ion temperature gradient mode from ground state l = 0 to non-ground state l = 1 is LT-1R ˜50 . These features can have important consequences to turbulent transport.

  12. Enhanced stochastic fluctuations to measure steep adhesive energy landscapes.

    PubMed

    Haider, Ahmad; Potter, Daniel; Sulchek, Todd A

    2016-12-13

    Free-energy landscapes govern the behavior of all interactions in the presence of thermal fluctuations in the fields of physical chemistry, materials sciences, and the biological sciences. From the energy landscape, critical information about an interaction, such as the reaction kinetic rates, bond lifetimes, and the presence of intermediate states, can be determined. Despite the importance of energy landscapes to understanding reaction mechanisms, most experiments do not directly measure energy landscapes, particularly for interactions with steep force gradients that lead to premature jump to contact of the probe and insufficient sampling of transition regions. Here we present an atomic force microscopy (AFM) approach for measuring energy landscapes that increases sampling of strongly adhesive interactions by using white-noise excitation to enhance the cantilever's thermal fluctuations. The enhanced fluctuations enable the recording of subtle deviations from a harmonic potential to accurately reconstruct interfacial energy landscapes with steep gradients. Comparing the measured energy landscape with adhesive force measurements reveals the existence of an optimal excitation voltage that enables the cantilever fluctuations to fully sample the shape and depth of the energy surface.

  13. Enhanced stochastic fluctuations to measure steep adhesive energy landscapes

    PubMed Central

    Haider, Ahmad; Potter, Daniel; Sulchek, Todd A.

    2016-01-01

    Free-energy landscapes govern the behavior of all interactions in the presence of thermal fluctuations in the fields of physical chemistry, materials sciences, and the biological sciences. From the energy landscape, critical information about an interaction, such as the reaction kinetic rates, bond lifetimes, and the presence of intermediate states, can be determined. Despite the importance of energy landscapes to understanding reaction mechanisms, most experiments do not directly measure energy landscapes, particularly for interactions with steep force gradients that lead to premature jump to contact of the probe and insufficient sampling of transition regions. Here we present an atomic force microscopy (AFM) approach for measuring energy landscapes that increases sampling of strongly adhesive interactions by using white-noise excitation to enhance the cantilever’s thermal fluctuations. The enhanced fluctuations enable the recording of subtle deviations from a harmonic potential to accurately reconstruct interfacial energy landscapes with steep gradients. Comparing the measured energy landscape with adhesive force measurements reveals the existence of an optimal excitation voltage that enables the cantilever fluctuations to fully sample the shape and depth of the energy surface. PMID:27911778

  14. 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.

  15. Comprehensive evaluation of high-steep slope stability and optimal high-steep slope design by 3D physical modeling

    NASA Astrophysics Data System (ADS)

    Lai, Xing-ping; Shan, Peng-fei; Cai, Mei-feng; Ren, Fen-hua; Tan, Wen-hui

    2015-01-01

    High-steep slope stability and its optimal excavation design in Shuichang open pit iron mine were analyzed based on a large 3D physical simulation technique. An optimal excavation scheme with a relatively steeper slope angle was successfully implemented at the northwest wall between Nos. 4 and 5 exploration lines of Shuichang Iron Mine, taking into account the 3D scale effect. The physico-mechanical properties of rock materials were obtained by laboratory tests conducted on sample cores from exploration drilling directly from the iron mine. A porous rock-like composite material was formed for the model, and the mechanical parameters of the material were assessed experimentally; specifically, the effect of water on the sample was quantitatively determined. We adopted an experimental setup using stiff modular applied static loading to carry out a visual excavation of the slope at a random depth. The setup was equipped with acoustic emission (AE) sensors, and the experiments were monitored by crack optical acquirement, ground penetrating radar, and close-field photogrammetry to investigate the mechanisms of rock-mass destabilization in the high-steep slope. For the complex study area, the model results indicated a clear correlation between the model's destabilization resulting from slope excavation and the collected monitoring information. During the model simulation, the overall angle of the slope increased by 1-6 degrees in different sections. Dramatically, the modeled excavation scheme saved over 80 million tons of rock from extraction, generating enormous economic and ecological benefits.

  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. 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.

  18. 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.

  19. Classification and analysis of corn steep liquor by UPLC/Q-TOF MS and HPLC.

    PubMed

    Xiao, Xue; Hou, Yuanyuan; Liu, Yang; Liu, Yanjie; Zhao, Hongzhi; Dong, Linyi; Du, Jun; Wang, Yiming; Bai, Gang; Luo, Guoan

    2013-03-30

    Corn steep liquor (CSL), an important raw material with high nutritional value, serves as a nitrogen source in the fermentation industry. The CSL quality directly affects the yield and quality of fermentation products. In this work, a fingerprinting technique was used to identify the potential markers of CSL. Forty-two CSL samples from different manufacturers were profiled by ultra-performance liquid chromatography with tandem quadrupole time-of-flight mass spectrometry. Sixteen compounds, almost all of which were amino acids and their derivatives, were considered as the potential markers. Then, o-phthalaldehyde-9-fluorenylmethyl chloroformate precolumn derivatization by high-performance liquid chromatography was performed to identify the free amino acids in CSL. Principal component analysis (PCA) was used to distinguish among the samples from different manufacturers. The results demonstrated that the fingerprinting technique combined with PCA analysis was a powerful tool for determining the CSL quality.

  20. 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.

  1. What controls channel form in steep mountain streams?

    NASA Astrophysics Data System (ADS)

    Palucis, M. C.; Lamb, M. P.

    2017-07-01

    Steep mountain streams have channel morphologies that transition from alternate bar to step-pool to cascade with increasing bed slope, which affect stream habitat, flow resistance, and sediment transport. Experimental and theoretical studies suggest that alternate bars form under large channel width-to-depth ratios, step-pools form in near supercritical flow or when channel width is narrow compared to bed grain size, and cascade morphology is related to debris flows. However, the connection between these process variables and bed slope—the apparent dominant variable for natural stream types—is unclear. Combining field data and theory, we find that certain bed slopes have unique channel morphologies because the process variables covary systematically with bed slope. Multiple stable states are predicted for other ranges in bed slope, suggesting that a competition of underlying processes leads to the emergence of the most stable channel form.

  2. Active Flows on Steep Slopes in Ganges Chasma

    NASA Image and Video Library

    2017-05-31

    This image from NASA's Mars Reconnaissance Orbiter covers a steep west-facing slope in southwestern Ganges Chasma, north of the larger canyons of Valles Marineris. The spot was targeted both for the bedrock exposures and to look for active slope processes. We see two distinct flow deposits: lobate flows that are relatively bright, sometimes with dark fringes, and very thin brownish lines that resemble recurring slope lineae (or 'RSL'). Both flows emanate from rocky alcoves. The RSL are superimposed on the lobate deposits (perhaps rocky debris flows), so they are younger and more active. The possible role of water in forming the debris flows and RSL are the subjects of continuing debate among scientists. We will acquire more images here to see if the candidate RSL are active. https://photojournal.jpl.nasa.gov/catalog/PIA21651

  3. De-icers derived from corn steep water.

    PubMed

    Yang, Byung Yun; Montgomery, Rex

    2003-12-01

    Corn steep water (CSW) and other byproducts derived from fermentations and sugar productions are presently forming the base of compositions for de-icing and anti-icing materials. Since the de-icing and anti-icing values are in part a colligative property, increase in the molar concentration of ionic species has been frequently necessary to decrease further the freezing point of this byproducts stream. In the present study this has been achieved by the generation of biodegradable organic acid salts in situ, without the use of chloride or other inorganic salts, by the alkaline degradation of reducing sugars added to corn steep water, which alone is not an efficient de-icer. Reducing sugars, such as glucose, react with alkali metal hydroxides to produce principally hydroxy carboxylic acids that react with the alkali metal hydroxide to form a mixture of organic acid salts. The ionic strength of the resulting solution is increased since each sugar molecule produces nearly two acid molecules upon degradation. The ionic strength necessary to achieve the desired freezing point depression is determined by the amount and concentration of the alkali metal hydroxide used, with the necessary counter anions being derived from the degradation of the reducing sugar. The amount of the sugar used is that required to result in a near to neutral final solution. The well-known anti-corrosive property of CSW is used in the de-icer preparations, either by conducting the alkaline degradation of the sugar in this medium, or by using water for the degradation of the sugar followed by dilution of the resulting solution with CSW to adjust the viscosity of the final solution to meet the requirements for spraying. The monovalent metal hydroxides are more efficient in producing de-icer solutions than the divalent metal hydroxides.

  4. Geomorphic response detection and quantification in a steep forested torrent

    NASA Astrophysics Data System (ADS)

    Bezak, Nejc; Grigillo, Dejan; Urbančič, Tilen; Mikoš, Matjaž; Petrovič, Dušan; Rusjan, Simon

    2017-08-01

    Extreme events such as flash floods and debris flows are frequent phenomena that occur in steep torrential catchments; these kinds of events can cause notable geomorphic changes. Repeated terrestrial laser scanning (TLS) surveys were performed in a steep forested catchment of the Kuzlovec torrent (drainage area 0.7 km2) in central Slovenia, where a 200-m long section of the torrent was scanned in 2013, 2014, and 2015. The main aim of this study was to perform the geomorphic response detection in the torrent due to hydro-meteorological events of different magnitudes. After applying several pre-processing steps, digital terrain models (DTMs) with a cell resolution of 5 cm were produced. The geomorphic change detection was performed using the DTM of Difference approach (DoD). Several above-average flow events occurred in the period from 2013 to 2015 (some of them can be regarded as floods). The 2014 August extreme flash flood that was initiated by the rainfall event with a return period exceeding 100 years, where maximum 1-minute rainfall intensities were up to 288 mm/h, led to erosion rates of an order of magnitude higher than average annual erosion rates. Moreover, the analysis of the geomorphic changes shows that the August 2014 flash flood caused intense sediment transport processes that resulted in the changes at the location of the main stream channel thalweg and reduced channel roughness. The unit stream power for the scanned section of the torrent was assessed to be approximately 500 W/m2 during this extreme event. This is above the thresholds that were suggested to differentiate between the situations where significant geomorphic changes can occur and the situations where geomorphic changes are not notable.

  5. 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.

  6. HOTSPUR progress report: neutron source spectrum characterization, and /sup 6/Li(n,x. cap alpha. ) and /sup 7/Li(n,x. cap alpha. ) cross section determination

    SciTech Connect

    Goldberg, E.; Haight, R.

    1984-04-02

    As a prerequisite to high accuracy measurements involving the bulk configuration of /sup 6/LiD we must have a good grasp of the details of the RTNS-I neutron source energy spectrum. Experiments to this end involving neutron yield vs deuteron energy, ratios of foil activation of selected elements, and pulse height distributions of a Si surface barrier detector are described. With this knowledge, the /sup 4/He-production cross sections for /sup 6/Li and /sup 7/Li are found experimentally to be 0.512b and 0.336b, respectively, at anti E/sub N/ = 15.0 MeV in free-field geometry. 14 references.

  7. 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

  8. 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.

  9. Chandra Discovery of Intervening, Local and Intrinsic Highly Ionized Absorption in an extremely bright high resolution X-ray spectrum of an Extragalactic Source

    NASA Astrophysics Data System (ADS)

    Nicastro, F.; Elvis, M.; Fang, T.; Mathur, S.; Siemiginowska, A.; Zezas, A.

    2003-03-01

    In this contribution we present the brightest high resolution X-ray spectrum ever taken for an extragalactic source. Following our ToO request, Chandra observed the blazar Mkn 421 (z=0.03) during an exceptionally high-luminosity flare. The observation lasted about 100 ks, during which the source reached a flux level of > 0.1 Crab in the 0.5-2 keV band This allowed us to collect 4.2 million counts in the 1st-order ACIS-LETG spectrum of Mkn 421, and more than 3000 counts per resolution elements at the rest frame wavelength of the OVII Kα resonant transitions (21.6 Å). A forest of very weak (EW=3.1-10 mÅ) resonant absorption lines is detected from the rest frame wavelength of the OVII Kα all the way down to the position of the OVII Kα line at the source redshift. We identify these lines as due to: (a) Local Group Warm-Hot Intergalactic Medium (WHIM) absorption, (b) intervening WHIM absorption at redshifts z=0.01 (associated with faint H Lyα absorption) and z=0.025, and (c) intrinsic source absorption. The strongest of these systems is associated with the local WHIM first discovered along the line of sight to PKS 2155-304 (Nicastro et al., 2002, 2003), and now observed (always with consistent gas properties) along all the lines of sight for which Chandra high resolution spectra with sufficient signal to noise ratio are available. The faintest systems (probing OVII column densities as low as 1015 cm-2) are those identified as due to the two intervening WHIM systems. If both these identification are correct this discovery implies a number of intervening OVII WHIM systems per unit redshift of dN/dz(NOVII>1015) = 75, about 3-4 times larger than the corresponding number estimated for OVI systems in the local Universe (down to OVI EW of 60 mÅ). The WHIM baryon fraction implied depends slightly on the ionization correction applied, and ranges between 40 % and 60 % of the total baryons at z<2, so confirming hydrodynamical simulation predictions and accounting for all of

  10. Quantification of fluvial bedload transport in glacier-connected steep mountain catchments in western Norway

    NASA Astrophysics Data System (ADS)

    Beylich, Achim A.; Laute, Katja

    2015-04-01

    Contemporary fluvial bedload transport rates are still very difficult to measure and, as a result of this, in many sites only quantitative data on fluvial suspended and solute transport are included in sediment budget studies carried out for defined drainage basin systems. During the years 2010-2013 detailed field measurements with portable impact sensors as a non-invasive technique for indirectly determining fluvial bedload transport intensity were conducted in two instrumented drainage basin systems (Erdalen and Bødalen) in the fjord landscape in western Norway. The collected impact sensor field data were calibrated with laboratory flume experiments, and the data from the impact sensor field measurements and the flume experiments were combined with field data from continuous discharge monitoring, repeated surveys of channel morphometry and sediment texture, particle tracer measurements, Helley-Smith samplings, underwater video filming and biofilm analyses. The combination of methods and techniques applied provides insights into the temporal variability and intensity of fluvial bedload transport in the selected mountain streams of both drainage basin systems. The conducted analysis of fluvial bedload dynamics in different defined subsystems of Erdalen (79.5 km2) and Bødalen (60.1 km2) provides information on (i) detectable relevant sediment sources, (ii) instream channel storage of bedload material, (iii) spatiotemporal variability and controls of bedload transport rates and bedload yields, and (iv) the absolute and relative importance of fluvial bedload transport within the sedimentary budgets of these steep cold climate mountain catchments. Rockfalls, snow avalanches, stream channel bank erosion, and fluvial transfers through small tributaries draining slope systems are relevant sediment sources for fluvial bedload transport in the main stream channels, whereas the main outlet glaciers in both catchment systems are not of importance as all bedload material

  11. The fading of Cassiopeia A, and improved models for the absolute spectrum of primary radio calibration sources

    NASA Astrophysics Data System (ADS)

    Trotter, A. S.; Reichart, D. E.; Egger, R. E.; Stýblová, J.; Paggen, M. L.; Martin, J. R.; Dutton, D. A.; Reichart, J. E.; Kumar, N. D.; Maples, M. P.; Barlow, B. N.; Berger, T. A.; Foster, A. C.; Frank, N. R.; Ghigo, F. D.; Haislip, J. B.; Heatherly, S. A.; Kouprianov, V. V.; LaCluyzé, A. P.; Moffett, D. A.; Moore, J. P.; Stanley, J. L.; White, S.

    2017-08-01

    Based on 5 yr of observations with the 40-foot telescope at Green Bank Observatory (GBO), Reichart & Stephens found that the radio source Cassiopeia A had either faded more slowly between the mid-1970s and late 1990s than Baars et al. had found it to be fading between the late 1940s and mid-1970s, or that it had rebrightened and then resumed fading sometime between the mid-1970s and mid-1990s, in the L band (1.4 GHz). Here, we present 15 additional years of observations of Cas A and Cyg A with the 40-foot in the L band, and three and a half additional years of observations of Cas A, Cyg A, Tau A and Vir A with GBO's recently refurbished 20-m telescope in the L and X (9 GHz) bands. We also present a more sophisticated analysis of the 40-foot data, and a reanalysis of the Baars et al. data, which reveals small, but non-negligible differences. We find that overall, between the late 1950s and late 2010s, Cas A faded at an average rate of 0.670 ± 0.019 per cent yr-1 in the L band, consistent with Reichart & Stephens. However, we also find, at the 6.3σ credible level, that it did not fade at a constant rate. Rather, Cas A faded at a faster rate through at least the late 1960s, rebrightened (or at least faded at a much slower rate), and then resumed fading at a similarly fast rate by, at most, the late 1990s. Given these differences from the original Baars et al. analysis, and given the importance of their fitted spectral and temporal models for flux-density calibration in radio astronomy, we update and improve on these models for all four of these radio sources. In doing so, we additionally find that Tau A is fading at a rate of 0.102^{+0.042}_{-0.043} per cent yr-1 in the L band.

  12. Spectrum 101: An Introduction to Spectrum Management

    DTIC Science & Technology

    2004-03-01

    This interference can come from another friendly source, a host or neighboring nation source, or an enemy jammer . The DoD has a Joint Spectrum...users, demonstrate this concept. Wireless local area networks (LANs), Bluetooth devices, cordless phones, and microwave ovens all share the same

  13. Time-resolved electronic Raman spectrum of terbium aluminum garnet excited with visible and UV laser sources

    NASA Astrophysics Data System (ADS)

    Myslynski, P.; Koningstein, J. A.

    1987-05-01

    Excitation profiles for the intensities of electronic Raman transitions between crystal field components of the 7F 6 and 7F 5 manifolds of terbium aluminum garnet are recorded for excitation in the spectral region where absorption bands due to levels of the 5D 4 manifold occur. The intensities of the electronic transitions are not enhanced which is thought to be caused by the small values of electric dipole matrix elements of the resonating electronic states in comparison to the values of such elements to other intermediate states which occur in the expression for the scattering tensor. Fluorescence from the 5D 4 levels is induced and resonance fluorescence are time resolved with respect to the Raman transitions. We report electronic Raman transitions excited with the 308.0 nm line of an XeCl excimer laser. As opposed to excitation with visible laser sources, transitions are recorded which terminate on all the crystal field levels of the 7F 5…0 levels. In addition, fluorescence from 5D 3 to the ground state of terbium aluminum garnet is also observed.

  14. Ice motion and seismic activity on a steep temporate glacier tongue

    NASA Astrophysics Data System (ADS)

    Dalban Canassy, Pierre; Faillettaz, Jerome; Funk, Martin

    2010-05-01

    Ice motion and seismic activity on a steep temporate glacier (Triftgletscher, Bernese Alps, Switzerland) Pierre Dalban Canassy*, Jerome Faillettaz* and Martin Funk* * Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zurich, CH-8092 Zurich, Switzerland (dalban@vaw.baug.ethz.ch) In the last 15 years Triftgletscher (Bernese Alps, Switzerland) has substantially retreated (several hundreds of meters) from the riegel and a proglacial lake containing 6.106 m3 water has been formed in the glacier forefield. Because of the glacier retreat, especially the thinning of the lower flat tongue, the stability of the steep section behind it is affected. The consequence is that the likelihood of large ice avalanches starting from the steep section will increase. The recent intensive glacier thinning in the lower tongue area of 6-10 m.a-1 has even worsened the situation because the runout path of the ice avalanches has become steeper. Ice avalanches with several millions of m3 triggering impulse waves by plunguing into the lake can be the consequence. The aim of our study is to improve the understanding of the mechanisms leading to such instabilities and to develop a predictive method based on both seismic and photogrammetric surveys. The seismic recording is performed with help of 3 geophones installed on the rock on both sides of the serac fall allowing a continuous record. We are able to highlight seismic events by applying an automatic detection procedure, to locate their sources and also to evaluate the released energy of each detected icequake. The most part of these events are due to crack openings and falls of ice chunks, but we could also isolate specific events corresponding to stick-slip motions. The latter seem to play a significant role in the destabilization of the ice mass and represent valuable precursors to break-off episodes. The 2D picture analysis is achieved by analysing photographs taken every day at the same time by an automatic camera installed in

  15. 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

  16. 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

  17. Relative roughness controls on incipient sediment motion in steep channels

    NASA Astrophysics Data System (ADS)

    Prancevic, J.; Lamb, M. P.; Fuller, B. M.

    2012-12-01

    For over eight decades, researchers have noted an appreciable increase in the nondimensional shear stress (Shields number) at initiation of fluvial bedload transport with increasing bed slope. The precise cause of the trend, however, is obscured by the covariance of several factors with increased slope: a greater downstream component of the gravity acting on the grains and fluid, changes in bed morphology, increased grainsize relative to the channel width that may lead to grain bridging, and increased grainsize relative to flow depth (relative roughness) that may change flow hydraulics and particle buoyancy. Here, we report on ongoing laboratory experiments spanning a wide range of bed slopes (2% to 67%) designed to isolate these variables and determine the true cause of heightened critical Shields numbers on steep slopes. First, we eliminated bed morphology as a factor by using only planar beds. To investigate the effect of grain bridging, we used two different channel widths, representing width-to-grainsize ratios of 23:1 and 9:1. Finally, to separate the effects of slope from relative roughness, we compared incipient motion conditions for acrylic particles (submerged specific gravity of 0.15) to natural siliciclastic gravel (submerged specific gravity of 1.65). Different particle densities allowed us to explore incipient motion as a function of relative roughness, independent of channel slope, because lighter particles move at shallower flow depths than heavier ones of the same size. Results show that both materials exhibit a positive trend between bed slope and critical Shields number despite the existence of planar beds for all slopes. Furthermore, changing the grainsize-to-width ratio had a negligible effect on this trend. For all slopes, the critical Shields number for bedload transport was higher for the acrylic particles than for gravel, indicating that relative roughness has a strong control on incipient sediment motion independent of channel slope. These

  18. 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.

    2016-12-01

    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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Steep gravity-capillary waves within the internal resonance regime

    NASA Astrophysics Data System (ADS)

    Perlin, Marc; Ting, Chao-lung

    1992-11-01

    Steep gravity-capillary waves are studied experimentally in a channel. The range of cyclic frequencies investigated is 6.94-9.80 Hz; namely, the high-frequency portion of the regime of internal resonances according to the weakly nonlinear theory (Wilton's ripples). These wave trains are stable according to the nonlinear Schrödinger equation. The experimental wave trains are generated by large, sinusoidal oscillations of the wavemaker. A comparison is made between the measured wave fields and the (symmetric) numerical solutions of Schwartz and Vanden-Broeck [J. Fluid Mech. 95, 119 (1979)], Chen and Saffman [Stud. Appl. Math. 60, 183 (1979); 62, 95 (1980)], and Huh (Ph.D. dissertation, University of Michigan, 1991). The waves are shown to be of slightly varying asymmetry as they propagate downstream. Their symmetric parts, isolated by determining the phase which provides the smallest mean-square antisymmetric part, compare favorably with the ``gravity-type'' wave solutions determined by numerical computations. The antisymmetric part of the wave profile is always less than 30% of the peak-to-peak height of the symmetric part. As nonlinearity is increased, the amplitudes of the short-wave undulations in the trough of the primary wave increase; however, there are no significant changes in these short-wave frequencies. The lowest frequency primary-wave experiments, which generate the highest frequency short-wave undulations, exhibit more rapid viscous decay of these high-frequency waves than do the higher-frequency primary wave experiments.

  4. 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.

  5. How Phytoplankton Membranes Cope With Steep Ionic Strength (Salinity) Gradient?

    NASA Astrophysics Data System (ADS)

    Gasparovic, B.; Sesar, T.; Cankovic, M.; Ljubešić, Z.; Hrustić, E.; Zhu, Z.; Zhang, R.; Du, J.

    2016-02-01

    We report on phytoplankton accommodation on stressful conditions being steep ionic strength, i.e. salinity, changes, the conditions regularly found in the estuaries. We aimed defining how lipid composition of phytoplankton membrane structure is accommodated to prevent spontaneous osmosis. Salinity-dependent lipid profiles for particulate lipid extracts from blooming periods of the two opposing estuaries: eutrophic and polluted Wenchang River Estuary and pristine oligotrophic/mesotrophic Krka River Estuary were characterized by thin layer chromatography (TLC). The composition of phytoplankton pigments which was analyzed by high performance liquid chromatography. Domination of pigment Fucoxanthin in both estuaries indicates diatoms were major blooming group. While total particulate lipid concentration was almost an order of magnitude higher in the Wenchang River estuary (on average 238 µg/L) than in the Krka River Estuary (on average 36 µg/L), the lipid composition was similar. This implies that salinity stress is the main influential factor on phytoplankton lipid composition rather than availability of nutrients. Details on the lipid composition that follow salinity changes will be discussed.

  6. Antioxidative properties of phenolic antioxidants isolated from corn steep liquor.

    PubMed

    Niwa, T; Doi, U; Kato, Y; Osawa, T

    2001-01-01

    With the immersion of corn into dilute sulfur oxide during starch-manufacturing processes, corn steep liquor (CSL) remains as leftover material. CSL is often used for fermentation, but its components are not fully understood. To determine the properties of CSL, 12 p-coumaric acid-related compounds were isolated from an ethyl acetate extract of CSL with the guidance of antioxidative activity on the rabbit erythrocyte membrane ghost system. The activity of these compounds was compared against oxidative damages, and it was elucidated that the activity of p-coumaric acid derivatives was mainly affected by their functional groups at the 3-position and less by the conjugated side chain. Moreover, p-coumaric acid derivatives exhibited inhibitory activity stronger than that of tocopherols and ascorbic acid on peroxynitrite-mediated lipoprotein nitration. These findings that p-coumaric acid derivatives, which might play a beneficial role against oxidative damage, exist in CSL suggest this byproduct might be a useful resource of phenolic antioxidants.

  7. Imported poultry meat as a source of extended-spectrum cephalosporin-resistant CMY-2-producing salmonella heidelberg and s. minnesota in european union, 2014-2015.

    PubMed

    Campos, Joana; Mourão, Joana; Silveira, Leonor; Saraiva, Margarida; Correia, Cristina Belo; Maçãs, Ana Paula; Peixe, Luísa; Antunes, Patrícia

    2017-09-14

    Extended-spectrum cephalosporin (ESC)-resistant Salmonella has been described at low level in EU, nevertheless the increasing importation of poultry meat could be an important source of epidemic strains carrying ESC-resistant genes. We evaluated ESC resistance and characterized genetic platforms as well as the clonal relatedness of Salmonella isolates from poultry meat products imported into Portugal. All Salmonella isolates recovered from samples of fresh meat destined to be imported into the EU in the scope of Portuguese official border control between 2014 and 2015 were studied. Susceptibility to antibiotics and detection of β-lactamase production was performed by disk diffusion/microdilution methods. Molecular studies included detection of genes encoding for qAmpC and extended-spectrum β-lactamases, plasmid-mediated quinolone resistance and other antibiotic resistance by PCR/sequencing and clonality by MLST and XbaI-PFGE. Plasmid characterization was assessed by conjugation assays, replicon typing (PCR-PBRT/pMLST) and hybridization experiments (I-CeuI/S1-PFGE nuclease). Salmonella belonged to S. Heidelberg (n=6; ST15/eBG26) and S. Minnesota (n=1; ST548/eBG77) serotypes and presented multidrug-resistant profiles, including to ESC and/or fluoroquinolones. All but one carried blaCMY-2 gene, located on two epidemic plasmids, IncA/C (ST2-n=5) or a transferable IncI1 (ST12-n=1). S. Heidelberg was associated with 5 PFGE-types, including one similar to an American epidemic clone. This study reveals imported poultry products as a source of uncommon and/or invasive ESC resistant Salmonella strains in EU. The increase of those clinically-relevant poultry-related serotypes in Europe, as described here, must be taken into account in the current monitoring of antibiotic resistance trends and in re-evaluation of food regulations. Copyright © 2017 Elsevier B.V. and International Society of Chemotherapy. All rights reserved.

  8. Delineation of preventative landslide buffers along steep streamside slopes in northern California

    Treesearch

    Jason S. Woodward; David W. Lamphear; Matthew R. House

    2012-01-01

    Green Diamond Resource Co (GDRCo) applies tree retention buffers to steep slopes along fish bearing (Class I) and non-fish bearing (Class II) streams that are in addition to the standard riparian management zones associated with timber harvest plans. These Steep Streamside Slope (SSS) buffers were designed to reduce the amount of sediment delivering to watercourses as...

  9. Evaluating survey instruments and methods in a steep channel

    NASA Astrophysics Data System (ADS)

    Scott, Daniel N.; Brogan, Daniel J.; Lininger, Katherine B.; Schook, Derek M.; Daugherty, Ellen E.; Sparacino, Matthew S.; Patton, Annette I.

    2016-11-01

    Methods for surveying and analyzing channel bed topography commonly lack a rigorous characterization of their appropriateness for project objectives. We compare four survey methods: a hand level, two different methods of surveying with a laser rangefinder, and a real-time kinematic GNSS (RTK-GNSS) to explore their accuracy in determining channel bed slope and roughness for a study reach in a small, dry, steep channel. Additionally, we evaluate the variability among four operators for each survey technique. Two methods of calculating reach slope were computed: a regression on the channel profile and a calculation using only survey endpoints. Using data from the RTK-GNSS as our accuracy reference, the hand level and two-person laser rangefinder surveying systems performed with high accuracy (< 5% error in estimating slope, < 10% error in estimating roughness), while the one-person laser rangefinder survey system performed with considerably lower accuracy (up to 54% error in roughness and slope). Variability between operators was found to be very low (coefficients of variation ranged from 0.001 to 0.046) for all survey systems except the one-person laser rangefinder system, suggesting that survey data collected by different operators can be validly compared. Due to reach-scale concavity, calculating slope using a regression produced significantly different values than those obtained by using only survey endpoints, suggesting that caution must be taken in choosing the most appropriate method of calculating slope for a given project objective. We present recommendations for choosing appropriate survey and analysis methods to accomplish various surveying objectives.

  10. Sediment yields from small, steep coastal watersheds of California

    USGS Publications Warehouse

    Warrick, Jonathan A.; Melack, John M.; Goodridge, Blair M.

    2015-01-01

    Global inventories of sediment discharge to the ocean highlight the importance of small, steep watersheds (i.e., those having drainage areas less than 100,000 km2 and over 1000 m of relief) that collectively provide a dominant flux of sediment. The smallest of these coastal watersheds (e.g., those that have drainage areas less than 1000 km2) can represent a large portion of the drainage areas of active margin coasts, such as California’s coast, but remain almost universally unmonitored. Here we report on the suspended-sediment discharge of several small coastal watersheds (10-56 km2) of the Santa Ynez Mountains, California, that were found to have ephemeral discharge and suspended-sediment concentrations ranging between 1 and over 200,000 mgL-1. Sediment concentrations were weakly correlated with discharge (r2 = 0.10–0.25), and all types of hysteresis patterns were observed during high flows (clockwise, counterclockwise, no hysteresis, and complex). Sediment discharge varied strongly with time and was measurably elevated in one watershed following a wildfire. Although sediment yields varied by over 100-fold across the watersheds (e.g., 15 – 2100 tkm-2 yr -1during the relatively wet 2005 water year), the majority of sediment discharge (65-80%) occurred during only 1% of the time for all watersheds. Furthermore, sampling of dozens of high flow events provides evidence that sediment yields were generally related to peak discharge yields, although these relationships were not consistent across the watersheds. These results suggest that small watersheds of active margins can provide large fluxes of sediment to the coast, but that the rates and timing of this sediment discharge is more irregular in time – and thus more difficult to characterize – than the better monitored and studied watersheds that are 1000-100,000 km2.

  11. Extended-Spectrum beta (β)-Lactamases and Antibiogram in Enterobacteriaceae from Clinical and Drinking Water Sources from Bahir Dar City, Ethiopia.

    PubMed

    Abera, Bayeh; Kibret, Mulugeta; Mulu, Wondemagegn

    2016-01-01

    The spread of Extended-Spectrum beta (β)-Lactamases (ESBL)-producing Enterobacteriaceae has become a serious global problem. ESBL-producing Enterobacteriaceae vary based on differences in antibiotic use, nature of patients and hospital settings. This study was aimed at determining ESBL and antibiogram in Enterobacteriaceae isolates from clinical and drinking water sources in Bahir Dar City, Northwest Ethiopia. Enterobacteriaceae species were isolated from clinical materials and tap water using standard culturing procedures from September 2013 to March 2015. ESBL-producing-Enterobacteriaceae were detected using double-disk method by E-test Cefotaxim/cefotaxim+ clavulanic acid and Ceftazidime/ceftazidime+ clavulanic acid (BioMerieux SA, France) on Mueller Hinton agar (Oxoid, UK). Overall, 274 Enterobacteriaceae were isolated. Of these, 210 (44%) were from patients and 64 (17.1%) were from drinking water. The median age of the patients was 28 years. Urinary tract infection and blood stream infection accounted for 60% and 21.9% of Enterobacteriaceae isolates, respectively. Klebsiella pneumoniae was isolated from 9 (75%) of neonatal sepsis. The overall prevalence of ESBL-producing Enterobacteriaceae in clinical and drinking water samples were 57.6% and 9.4%, respectively. The predominant ESBL-producers were K. pneumoniae 34 (69.4%) and Escherichia coli 71 (58.2%). Statistically significant associations were noted between ESBL-producing and non- producing Enterobacteriaceae with regard to age of patients, infected body sites and patient settings (P = 0.001). ESBL-producing Enterobacteriaceae showed higher levels of resistance against chloramphenicol, ciprofloxacin and cotrimoxazole than non-ESBL producers (P = 0.001). ESBL-producing Enterobacteriaceae coupled with high levels of other antimicrobials become a major concern for treatment of patients with invasive infections such as blood stream infections, neonatal sepsis and urinary tract infections. ESBL

  12. The role of drinking water sources, consumption of vegetables and seafood in relation to blood arsenic concentrations of Jamaican children with and without Autism Spectrum Disorders.

    PubMed

    Rahbar, Mohammad H; Samms-Vaughan, Maureen; Ardjomand-Hessabi, Manouchehr; Loveland, Katherine A; Dickerson, Aisha S; Chen, Zhongxue; Bressler, Jan; Shakespeare-Pellington, Sydonnie; Grove, Megan L; Bloom, Kari; Wirth, Julie; Pearson, Deborah A; Boerwinkle, Eric

    2012-09-01

    Arsenic is a toxic metal with harmful effects on human health, particularly on cognitive function. Autism Spectrum Disorders (ASDs) are lifelong neurodevelopmental and behavioral disorders manifesting in infancy or early childhood. We used data from 130 children between 2 and 8 years (65 pairs of ASD cases with age- and sex-matched control), to compare the mean total blood arsenic concentrations in children with and without ASDs in Kingston, Jamaica. Based on univariable analysis, we observed a significant difference between ASD cases and controls (4.03 μg/L for cases vs. 4.48 μg/L for controls, P<0.01). In the final multivariable General Linear Model (GLM), after controlling for car ownership, maternal age, parental education levels, source of drinking water, consumption of "yam, sweet potato, or dasheen", "carrot or pumpkin", "callaloo, broccoli, or pak choi", cabbage, avocado, and the frequency of seafood consumption per week, we did not find a significant association between blood arsenic concentrations and ASD status (4.36 μg/L for cases vs. 4.65 μg/L for controls, P=0.23). Likewise, in a separate final multivariable GLM, we found that source of drinking water, eating avocado, and eating "callaloo, broccoli, or pak choi" was significantly associated with higher blood arsenic concentrations (all three P<0.05). Based on our findings, we recommend assessment of arsenic levels in water, fruits, and vegetables, as well as increased awareness among the Jamaican population regarding potential risks for various exposures to arsenic.

  13. The role of drinking water sources, consumption of vegetables and seafood in relation to blood arsenic concentrations of Jamaican children with and without Autism Spectrum Disorders

    PubMed Central

    Rahbar, Mohammad H.; Samms-Vaughan, Maureen; Ardjomand-Hessabi, Manouchehr; Loveland, Katherine A.; Dickerson, Aisha S.; Chen, Zhongxue; Bressler, Jan; Shakespeare-Pellington, Sydonnie; Grove, Megan L.; Bloom, Kari; Wirth, Julie; Pearson, Deborah A.; Boerwinkle, Eric

    2012-01-01

    Arsenic is a toxic metal with harmful effects on human health, particularly on cognitive function. Autism Spectrum Disorders (ASDs) are lifelong neurodevelopmental and behavioral disorders manifesting in infancy or early childhood. We used data from 130 children between 2-8 years (65 pairs of ASD cases with age- and sex-matched control), to compare the mean total blood arsenic concentrations in children with and without ASDs in Kingston, Jamaica. Based on univariable analysis, we observed a significant difference between ASD cases and controls (4.03μg/L for cases vs. 4.48μg/L for controls, P < 0.01). In the final multivariable General Linear Model (GLM), after controlling for car ownership, maternal age, parental education levels, source of drinking water, consumption of “yam, sweet potato, or dasheen”, “carrot or pumpkin”, “callaloo, broccoli, or pak choi”, cabbage, avocado, and the frequency of seafood consumption per week, we did not find a significant association between blood arsenic concentrations and ASD status (4.36μg/L for cases vs. 4.65μg/L for controls, P = 0.23). Likewise, in a separate final multivariable GLM, we found that source of drinking water, eating avocado, and eating “callaloo, broccoli, or pak choi” were significantly associated with higher blood arsenic concentrations (all three P < 0.05). Based on our findings, we recommend assessment of arsenic levels in water, fruits, and vegetables, as well as increased awareness among the Jamaican population regarding potential risks for various exposures to arsenic. PMID:22819887

  14. Contaminated sinks in intensive care units: an underestimated source of extended-spectrum beta-lactamase-producing Enterobacteriaceae in the patient environment.

    PubMed

    Roux, D; Aubier, B; Cochard, H; Quentin, R; van der Mee-Marquet, N

    2013-10-01

    Extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBLE) outbreaks in intensive care units (ICUs) associated with contaminated handwashing sinks have been reported. To conduct a regional study to assess whether handwashing sinks in 135 ICU patient rooms are a potential source of contamination, and to identify factors associated with an increased risk of sink contamination. A multicentre study was conducted in 13 ICUs, including microbiological testing for ESBLE contamination at 185 sinks. The micro-organisms isolated were analysed using randomly amplified polymorphic DNA analysis to assess clonal spread in ICUs. Data were collected to document the use of each sink, factors that may contribute to contamination of clinical areas near to the sinks, and routine cleansing procedures for the sinks. Fifty-seven sinks were contaminated (31%) with ESBLE, mostly Klebsiella (N = 33) and Enterobacter (N = 18). In two ICUs, a high contamination rate was associated with clonal spread of an epidemic isolate. Risk factors for contamination of and by handwashing sinks were frequent: 81 sinks (44%) were used for handwashing as well as the disposal of body fluids; splash risk was identified for 67 sinks (36%), among which 23 were contaminated by ESBLE. Routine sink disinfection was frequent (85%), mostly daily (75%), and involved quaternary ammonium compounds (41%) or bleach (21%). A lower sink contamination rate was significantly associated with use of the sink being restricted to handwashing and to daily sink disinfection using bleach. In ICUs, contaminated sinks are a potential source of ESBLE in the environment of the patient, a problem that may be underestimated by ICU teams. Relatively simple measures may result in a rapid improvement of the situation, and a significant decrease of the risk of exposure of ICU patients to multiresistant Enterobacteriaceae. Copyright © 2013 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.

  15. Extended-Spectrum beta (β)-Lactamases and Antibiogram in Enterobacteriaceae from Clinical and Drinking Water Sources from Bahir Dar City, Ethiopia

    PubMed Central

    Abera, Bayeh; Kibret, Mulugeta; Mulu, Wondemagegn

    2016-01-01

    Background The spread of Extended-Spectrum beta (β)-Lactamases (ESBL)-producing Enterobacteriaceae has become a serious global problem. ESBL-producing Enterobacteriaceae vary based on differences in antibiotic use, nature of patients and hospital settings. This study was aimed at determining ESBL and antibiogram in Enterobacteriaceae isolates from clinical and drinking water sources in Bahir Dar City, Northwest Ethiopia. Methods Enterobacteriaceae species were isolated from clinical materials and tap water using standard culturing procedures from September 2013 to March 2015. ESBL-producing-Enterobacteriaceae were detected using double-disk method by E-test Cefotaxim/cefotaxim+ clavulanic acid and Ceftazidime/ceftazidime+ clavulanic acid (BioMerieux SA, France) on Mueller Hinton agar (Oxoid, UK). Results Overall, 274 Enterobacteriaceae were isolated. Of these, 210 (44%) were from patients and 64 (17.1%) were from drinking water. The median age of the patients was 28 years. Urinary tract infection and blood stream infection accounted for 60% and 21.9% of Enterobacteriaceae isolates, respectively. Klebsiella pneumoniae was isolated from 9 (75%) of neonatal sepsis. The overall prevalence of ESBL-producing Enterobacteriaceae in clinical and drinking water samples were 57.6% and 9.4%, respectively. The predominant ESBL-producers were K. pneumoniae 34 (69.4%) and Escherichia coli 71 (58.2%). Statistically significant associations were noted between ESBL-producing and non- producing Enterobacteriaceae with regard to age of patients, infected body sites and patient settings (P = 0.001). ESBL-producing Enterobacteriaceae showed higher levels of resistance against chloramphenicol, ciprofloxacin and cotrimoxazole than non-ESBL producers (P = 0.001) Conclusions ESBL-producing Enterobacteriaceae coupled with high levels of other antimicrobials become a major concern for treatment of patients with invasive infections such as blood stream infections, neonatal sepsis and urinary

  16. Tunable high-power narrow-spectrum external-cavity diode laser at 675 nm as a pump source for UV generation.

    PubMed

    Chi, Mingjun; Jensen, Ole Bjarlin; Erbert, Götz; Sumpf, Bernd; Petersen, Paul Michael

    2011-01-01

    High-power narrow-spectrum diode laser systems based on tapered gain media in an external cavity are demonstrated at 675 nm. Two 2 mm long amplifiers are used, one with a 500 μm long ridge-waveguide section (device A), the other with a 750 μm long ridge-waveguide section (device B). Laser system A based on device A is tunable from 663 to 684 nm with output power higher than 0.55 W in the tuning range; as high as 1.25 W output power is obtained at 675.34 nm. The emission spectral bandwidth is less than 0.05 nm throughout the tuning range, and the beam quality factor M(2) is 2.07 at an output power of 1.0 W. Laser system B based on device B is tunable from 666 to 685 nm. As high as 1.05 W output power is obtained around 675.67 nm. The emission spectral bandwidth is less than 0.07 nm throughout the tuning range, and the beam quality factor M(2) is 1.13 at an output power of 0.93 W. Laser system B is used as a pump source for the generation of 337.6 nm UV light by single-pass frequency doubling in a bismuth triborate (BIBO) crystal. An output power of 109 μW UV light, corresponding to a conversion efficiency of 0.026% W(-1), is attained.

  17. 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.

  18. Utilization of corn steep liquor for biosynthesis of pullulan, an important exopolysaccharide.

    PubMed

    Sharma, Nishat; Prasad, G S; Choudhury, Anirban Roy

    2013-03-01

    Five different agricultural wastes viz. rice bran oil cake, soya bean oil cake, cotton seed oil cake, mustard seed oil cake and corn steep liquor (CSL) were evaluated for their use as nutrient along with 15% (w/v) glucose as carbon source for biosynthesis of pullulan using Aureobasidium pullulans RBF 4A3. Among the selected agricultural wastes, CSL was found to be the best and supported production of 77.92gL(-1) pullulan under un-optimized conditions. Single point optimization technique resulted in increase in 18% pullulan (88.59gL(-1)) production. The process was successfully validated in a 7-L fermenter and a process economic analysis has suggested that use of CSL as nutrient may result in 3-fold reduction of cost of raw materials for pullulan production as compared to a process where conventional nitrogen sources were used. These observations may be helpful in development of a cost effective process for pullulan production. Copyright © 2012 Elsevier Ltd. All rights reserved.

  19. 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

  20. 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.

  1. 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

  2. Zellweger Spectrum

    MedlinePlus

    ... Resources Conference News Contact Us Donate The Zellweger Spectrum Zellweger Syndrome, Neonatal Adrenoleukodystrophy (NALD), and Infantile Refsum’s ... of severity of disease. What causes the Zellweger spectrum of diseases? As we mentioned, disorders of the ...

  3. 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.

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

    NASA Astrophysics Data System (ADS)

    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.; Hüntemeyer, 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.; Saz Parkinson, P. M.; Shoup, A.; Sinnis, G.; Smith, A. J.; Vasileiou, V.; Walker, G. P.; Williams, D. A.; Yodh, G. B.

    2012-07-01

    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+5 -2 × 10-10 s-1 m-2 TeV-1, a spectral index of 2.0+0.5 -1.0, and a cutoff energy of 29+50 -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+0.6 -0.6 × 10-10 s-1 m-2 TeV-1 and a spectral index of 3.22+0.23 -0.18. The overall flux is subject to a ~30% systematic uncertainty. The systematic uncertainty on the power-law indices is ~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.

  5. 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

  6. Terrestrial reproduction as an adaptation to steep terrain in African toads.

    PubMed

    Liedtke, H Christoph; Müller, Hendrik; Hafner, Julian; Penner, Johannes; Gower, David J; Mazuch, Tomáš; Rödel, Mark-Oliver; Loader, Simon P

    2017-03-29

    How evolutionary novelties evolve is a major question in evolutionary biology. It is widely accepted that changes in environmental conditions shift the position of selective optima, and advancements in phylogenetic comparative approaches allow the rigorous testing of such correlated transitions. A longstanding question in vertebrate biology has been the evolution of terrestrial life histories in amphibians and here, by investigating African bufonids, we test whether terrestrial modes of reproduction have evolved as adaptations to particular abiotic habitat parameters. We reconstruct and date the most complete species-level molecular phylogeny and estimate ancestral states for reproductive modes. By correlating continuous habitat measurements from remote sensing data and locality records with life-history transitions, we discover that terrestrial modes of reproduction, including viviparity evolved multiple times in this group, most often directly from fully aquatic modes. Terrestrial modes of reproduction are strongly correlated with steep terrain and low availability of accumulated water sources. Evolutionary transitions to terrestrial modes of reproduction occurred synchronously with or after transitions in habitat, and we, therefore, interpret terrestrial breeding as an adaptation to these abiotic conditions, rather than an exaptation that facilitated the colonization of montane habitats. © 2017 The Author(s).

  7. Ducted kinetic Alfvén waves in plasma with steep density gradients

    NASA Astrophysics Data System (ADS)

    Houshmandyar, Saeid; Scime, Earl E.

    2011-11-01

    Given their high plasma density (n ˜ 1013 cm-3), it is theoretically possible to excite Alfvén waves in a conventional, moderate length (L ˜ 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 Alfvén wave propagation. Ion-neutral and electron-neutral collisions alter the Alfvén wave dispersion characteristics. Here, we present the measurements of propagating kinetic Alfvén 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.

  8. 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.

  9. 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.

  10. Polarization dependence of light scattered from rough surfaces with steep slopes

    NASA Astrophysics Data System (ADS)

    O'Donnell, Kevin A.; Knotts, Michael E.

    1991-11-01

    We discuss measurements of the infrared scattering properties of one- and two-dimensional conducting randomly rough surfaces. The surfaces are fabricated in photoresist and are checked with a stylus profilometer to verify that the surface statistics agree with the desired results. For surfaces that have steep slopes and lateral scale sizes comparable to the illumination wavelength, we observe strongly enhanced backscattering toward the source. These observations are shown to be strongly dependent on polarization. In the case of a one- dimensional surface, four distinct quantities appear in the Stokes scattering matrix, and examples of measurements of these quantities are presented. For the case of a two- dimensionally rough surface it is discussed that, even if the incident field is purely linearly polarized, the scattered light consists of both polarized and randomly polarized components. In the backscattering region, the polarized component contains linear, elliptical, and even nearly circular polarization states at various field angles. These data are interpreted and are consistent with the statistical isotropy of the surface.

  11. 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

    2015-07-08

    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.

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

    PubMed

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

    2015-08-07

    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.

  13. Waste Soybean Oil and Corn Steep Liquor as Economic Substrates for Bioemulsifier and Biodiesel Production by Candida lipolytica UCP 0998.

    PubMed

    Souza, Adriana Ferreira; Rodriguez, Dayana M; Ribeaux, Daylin R; Luna, Marcos A C; Lima E Silva, Thayse A; Andrade, Rosileide F Silva; Gusmão, Norma B; Campos-Takaki, Galba M

    2016-09-23

    Almost all oleaginous microorganisms are available for biodiesel production, and for the mechanism of oil accumulation, which is what makes a microbial approach economically competitive. This study investigated the potential that the yeast Candida lipolytica UCP0988, in an anamorphous state, has to produce simultaneously a bioemulsifier and to accumulate lipids using inexpensive and alternative substrates. Cultivation was carried out using waste soybean oil and corn steep liquor in accordance with 2² experimental designs with 1% inoculums (10⁷ cells/mL). The bioemulsifier was produced in the cell-free metabolic liquid in the late exponential phase (96 h), at Assay 4 (corn steep liquor 5% and waste soybean oil 8%), with 6.704 UEA, IE24 of 96.66%, and showed an anionic profile. The emulsion formed consisted of compact small and stable droplets (size 0.2-5 µm), stable at all temperatures, at pH 2 and 4, and 2% salinity, and showed an ability to remove 93.74% of diesel oil from sand. The displacement oil (ODA) showed 45.34 cm² of dispersion (central point of the factorial design). The biomass obtained from Assay 4 was able to accumulate lipids of 0.425 g/g biomass (corresponding to 42.5%), which consisted of Palmitic acid (28.4%), Stearic acid (7.7%), Oleic acid (42.8%), Linoleic acid (19.0%), and γ-Linolenic acid (2.1%). The results showed the ability of C. lipopytica to produce both bioemulsifier and biodiesel using the metabolic conversion of waste soybean oil and corn steep liquor, which are economic renewable sources.

  14. Waste Soybean Oil and Corn Steep Liquor as Economic Substrates for Bioemulsifier and Biodiesel Production by Candida lipolytica UCP 0998

    PubMed Central

    Souza, Adriana Ferreira; Rodriguez, Dayana M.; Ribeaux, Daylin R.; Luna, Marcos A. C.; Lima e Silva, Thayse A.; Andrade, Rosileide F. Silva; Gusmão, Norma B.; Campos-Takaki, Galba M.

    2016-01-01

    Almost all oleaginous microorganisms are available for biodiesel production, and for the mechanism of oil accumulation, which is what makes a microbial approach economically competitive. This study investigated the potential that the yeast Candida lipolytica UCP0988, in an anamorphous state, has to produce simultaneously a bioemulsifier and to accumulate lipids using inexpensive and alternative substrates. Cultivation was carried out using waste soybean oil and corn steep liquor in accordance with 22 experimental designs with 1% inoculums (107 cells/mL). The bioemulsifier was produced in the cell-free metabolic liquid in the late exponential phase (96 h), at Assay 4 (corn steep liquor 5% and waste soybean oil 8%), with 6.704 UEA, IE24 of 96.66%, and showed an anionic profile. The emulsion formed consisted of compact small and stable droplets (size 0.2–5 µm), stable at all temperatures, at pH 2 and 4, and 2% salinity, and showed an ability to remove 93.74% of diesel oil from sand. The displacement oil (ODA) showed 45.34 cm2 of dispersion (central point of the factorial design). The biomass obtained from Assay 4 was able to accumulate lipids of 0.425 g/g biomass (corresponding to 42.5%), which consisted of Palmitic acid (28.4%), Stearic acid (7.7%), Oleic acid (42.8%), Linoleic acid (19.0%), and γ-Linolenic acid (2.1%). The results showed the ability of C. lipopytica to produce both bioemulsifier and biodiesel using the metabolic conversion of waste soybean oil and corn steep liquor, which are economic renewable sources. PMID:27669227

  15. Propagation of hydrological modeling uncertainties on bed load transport simulations in steep mountain streams

    NASA Astrophysics Data System (ADS)

    Eichner, Bernhard; Koller, Julian; Kammerlander, Johannes; Schöber, Johannes; Achleitner, Stefan

    2017-04-01

    As mountain streams are sources of both, water and sediment, they are strongly influencing the whole downstream river network. Besides large flood flow events, the continuous transport of sediments during the year is in the focus of this work. Since small mountain streams are usually not measured, spatial distributed hydrological models are used to assess the internal discharges triggering the sediment transport. In general model calibration will never be perfect and is focused on specific criteria such as mass balance or peak flow, etc. The remaining uncertainties influence the subsequent applications, where the simulation results are used. The presented work focuses on the question, how modelling uncertainties in hydrological modelling impact the subsequent simulation of sediment transport. The applied auto calibration by means of MonteCarlo Simulation optimizes the model parameters for different aspects (efficiency criteria) of the runoff time series. In this case, we investigated the impacts of different hydrological criteria on a subsequent bed load transport simulation in catchment of the Längentaler Bach, a small catchment in the Stubai Alps. The used hydrologic model HQSim is a physically based semi-distributed water balance model. Different hydrologic response units (HRU), which are characterized by elevation, orientation, vegetation, soil type and depth, drain with various delay into specified river reaches. The runoff results of the Monte-Carlo simulation are evaluated in comparison to runoff gauge, where water is collected by the Tiroler Wasserkraft AG (TIWAG). Using the Nash-Sutcliffe efficiency (NSE) on events and main runoff period (summer), the weighted root mean squared error (RMSE) on duration curve and a combination of different criteria, a set of best fit parametrization with varying runoff series was received as input for the bed load transport simulation. These simulations are performed with sedFlow, a tool especially developed for bed load

  16. Numerical verification of the steepness of three and four degrees of freedom Hamiltonian systems

    NASA Astrophysics Data System (ADS)

    Schirinzi, Gabriella; Guzzo, Massimiliano

    2015-01-01

    We describe a new algorithm for the numerical verification of steepness, a necessary property for the application of Nekhoroshev's theorem, of functions of three and four variables. Specifically, by analyzing the Taylor expansion of order four, the algorithm analyzes the steepness of functions whose Taylor expansion of order three is not steep. In this way, we provide numerical evidence of steepness of the Birkhoff normal form around the Lagrangian equilibrium points L4-L5 of the spatial restricted three-body problem (for the only value of the reduced mass for which the Nekhoroshev stability was still unknown), and of the four-degrees-of-freedom Hamiltonian system obtained from the Fermi-Pasta-Ulam problem by setting the number of particles equal to four.

  17. 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.; Calistro Rivera, G.; 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.

    2016-12-01

    The Lockman Hole is a well-studied extragalactic field with extensive multi-band ancillary data covering a wide range in frequency, essential for characterizing 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 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.

  18. The electrical breakdown characteristics of oil-paper insulation under steep front impulse voltages

    SciTech Connect

    Vandermaar, A.J.; Wang, M.; Neilson, J.B. ); Srivastava, K.D. )

    1994-10-01

    Disconnecting switch operations in gas insulated equipment cause transient voltages with rise times as steep as 5 to 20 nanoseconds and magnitudes as high as 2.5 pu. There is very little information on the effect of these transients on oil-paper insulated equipment. There have been reports, however of transformer and bushing failures caused by these transients. The electrical breakdown characteristics of oil-paper insulation under steep front impulse were studied in this project, which was co-sponsored by the Canadian Electrical Association and B.C. Hydro. V[sub 50] (50% breakdown probability voltage) breakdown data was obtained with steep front (10 ns/2500 [mu]s), lightning and switching impulse waveforms. Insulation breakdown voltage vs breakdown time (V-t) data and multiple impulse breakdown data were obtained with the steep front impulse waveform. The V[sub 50] results showed that the breakdown strengths were lower for steep front impulses than for lightning impulses. The multiple impulse breakdown results showed that oil-paper insulation breakdown strength can be lower than 100 kV/mm. These results are alarming, since they suggest that oil-paper insulated equipment subjected to steep front transients will fail at voltages below the lightning impulse design level (BIL). The Volt-time data had a discontinuity. The breakdown process at risetime below about 50 ns was different from the breakdown process at rise times above 50 ns.

  19. 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.; hide

    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

  20. A peculiar class of debris disks from Herschel/DUNES. A steep fall off in the far infrared

    NASA Astrophysics Data System (ADS)

    Ertel, S.; Wolf, S.; Marshall, J. P.; Eiroa, C.; Augereau, J.-C.; Krivov, A. V.; Löhne, T.; Absil, O.; Ardila, D.; Arévalo, 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.

    2012-05-01

    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 (HD 199260), HIP 107350 (HN Peg, HD 206860), 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 3σ sensitivity of a few mJy at 100 μm and 160 μm. In addition, we obtained Herschel/PACS photometric data at 70 μm 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 thermal 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 μm. 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 still incomplete

  1. Forecasting of radiation hazard: 2. On-line determination of diffusion coefficient in the interplanetary space, time of ejection and energy spectrum at the source; on-line using of neutron monitor and satellite data

    NASA Astrophysics Data System (ADS)

    Dorman, L. I.; Iucci, N.; Murat, M.; Parisi, M.; Pustil'Nik, L. A.; Sternlieb, A.; Villoresi, G.; Zukerman, I. G.

    In Paper 1 [Dorman, L.I., Pustil’nik, L.A., Sternlieb, A., Zukerman, I.G. Forecasting of Radiation Hazard: 1. Alerts on Great FEP Events Beginning; Probabilities of False and Missed Alerts; on-Line Determination of Solar Energetic Particle Spectrum by using Spectrographic Method, Paper tCOSPAR tPSW1-0022-04, This Issue, 2005] it was described the behavior of programs “FEP-Search” and “FEP-Research/Spectrum” estimating, on the basis of on-line one-minute NM data, the beginning of event and FEP spectrum out of the Earth’s magnetosphere. We show that after these two steps it is possible to determine the time of ejection, diffusion coefficient in the interplanetary space, and energy spectrum at the source of FEP. We consider the following possibilities: (1) one of the above parameters is unknown; (2) two parameters are unknown; (3) all three parameters are unknown. We show that in the first case it is necessary to determine the energy spectrum of FEP on the Earth in two different times and automatically, from two equations, the unknown parameter can be determined (energy spectrum at the source or diffusion coefficient, or time of ejection; the determination is done by one equation, and the other is used for control of the model). In the second case it is necessary to determine the energy spectrum of FEP on the Earth in three different times and from three equations two parameters can be determined automatically (for example, the energy spectrum at the source and diffusion coefficient in the interplanetary space). In the third case, by using data for four different times all three unknown parameters can be determined (time of ejection, diffusion coefficient in the interplanetary space and energy spectrum at the source of FEP), and one equation can be used for control of the model. We describe in detail the algorithms of the programs “FEP-Research/Time of Ejection”, “FEP-Research/Source” and “FEP-Research/Diffusion”. We show the behavior of these

  2. Batch and repeated batch production of L (+)-lactic acid by Enterococcus faecalis RKY1 using wood hydrolyzate and corn steep liquor.

    PubMed

    Wee, Y-J; Yun, J-S; Kim, D; Ryu, H-W

    2006-06-01

    Lactic acid production was investigated for batch and repeated batch cultures of Enterococcus faecalis RKY1, using wood hydrolyzate and corn steep liquor. When wood hydrolyzate (equivalent to 50 g l(-1) glucose) supplemented with 15-60 g l(-1) corn steep liquor was used as a raw material for fermentation, up to 48.6 g l(-1) of lactic acid was produced with, volumetric productivities ranging between 0.8 and 1.4 g l(-1 )h(-1). When a medium containing wood hydrolyzate and 15 g l(-1) corn steep liquor was supplemented with 1.5 g l(-1) yeast extract, we observed 1.9-fold and 1.6-fold increases in lactic acid productivity and cell growth, respectively. In this case, the nitrogen source cost for producing 1 kg lactic acid can be reduced to 23% of that for fermentation from wood hydrolyzate using 15 g l(-1) yeast extract as a single nitrogen source. In addition, lactic acid productivity could be maximized by conducting a cell-recycle repeated batch culture of E. faecalis RKY1. The maximum productivity for this process was determined to be 4.0 g l(-1 )h(-1).

  3. 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.

  4. 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)

  5. 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)

  6. 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…

  7. 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…

  8. 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.

  9. Improvement of Rainfall Simulation on the Steep Edge of the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Li, J.; Yu, R.; Zhang, Y.; Chen, H.

    2016-12-01

    Overestimation of precipitation over steep mountains has been a long-lasting bias in many climate models. After replacing the semi-Lagrangian method with a finite-difference approach for trace transport algorithm (the two-step shape preserving scheme, TSPAS), the modified NCAR CAM5 (M-CAM5) with high horizontal resolution results in a significant improvement of simulation in precipitation over the steep edge of the Tibetan Plateau. The M-CAM5 restrains the "overshoot" of water vapor to the high-altitude region of the windward slopes and significantly reduces the overestimation of precipitation in areas above 2000 m along the southern edge of the Tibetan Plateau. More moisture are left in the low-altitude region on the slope where used to present dry biases in CAM5. The excessive (insufficient) amount of precipitation over the higher (lower) part of the steep slope is partially caused by the multi-grid water vapor transport in CAM5, which leads to spurious accumulation of water vapor at cold and high-altitude grids. Benefited from calculation of transport grid by grid in TSPAS and detailed description of steep mountains by the high-resolution model, M-CAM5 moves water vapor and precipitation downward over windward slopes and presents a more realistic simulation. Results in this study indicate that in addition to the development of physical parameterization schemes, the dynamical process should also be reconsidered in order to improve the climate simulation over steep mountains.

  10. Flow, Sediment Transport, and Erosion in Steep Mountain Channels: an Alpine Symphony

    NASA Astrophysics Data System (ADS)

    Kirchner, J. W.; Beer, A. R.; Heimann, F.; Rickenmann, D.; Schneider, J. M.; von Boetticher, A.; Turowski, J. M.

    2015-12-01

    Steep headwater channels comprise a large fraction of the total channel length in mountainous regions. They control the transport of water, solutes, and sediments to larger rivers downstream, and regulate the erosional development of many mountain landscapes. Flow and transport processes in these steep channels contrast with those in their lower-gradient counterparts. Steep streams have complex bed morphology, with large roughness relative to the flow depth, and the flow is likewise complex, often comprising a variable mixture of air and water. Here we present several examples from Switzerland highlighting recent research into hydraulics, sediment transport, and bedrock erosion in steep Alpine channels. The Riedbach presents a striking natural experiment, in which the channel gradient steepens from roughly 3% to more than 40% in less than 1km, while the discharge, flow width, and sediment transport rates remain roughly constant. Measurements at the Riedbach illustrate the self-adjustment of flow velocity and bed roughness in steep mountain channels. Data from the Erlenbach, an intensively instrumented stream in the Alpine foothills, illustrate how the bed configuration of such streams regulates the relationship between flow and sediment transport. Field studies at the Gornera illustrate how flow patterns control the spatial distribution of bedrock erosion in this glacier-fed stream in the shadow of the Matterhorn. We present an overview of these studies and discuss their implications.

  11. Impact of the steepness of the slope on the biomechanics of World Cup slalom skiers.

    PubMed

    Supej, Matej; Hébert-Losier, Kim; Holmberg, Hans-Christer

    2015-04-01

    Numerous environmental factors can affect alpine-ski-racing performance, including the steepness of the slope. However, little research has focused on this factor. Accordingly, the authors' aim was to determine the impact of the steepness of the slope on the biomechanics of World Cup slalom ski racers. The authors collected 3-dimensional kinematic data during a World Cup race from 10 male slalom skiers throughout turns performed on a relatively flat (19.8°) and steep (25.2°) slope under otherwise similar course conditions. Kinematic data revealed differences between the 2 slopes regarding the turn radii of the skis and center of gravity, velocity, acceleration, and differential specific mechanical energy (all P < .001). Ground-reaction forces (GRFs) also tended toward differences (P = .06). Examining the time-course behaviors of variables during turn cycles indicated that steeper slopes were associated with slower velocities but greater accelerations during turn initiation, narrower turns with peak GRFs concentrated at the midpoint of steering, more pronounced lateral angulations of the knees and hips at the start of steering that later became less pronounced, and overall slower turns that involved deceleration at completion. Consequently, distinct energy-dissipation-patterns were apparent on the 2 slope inclines, with greater pregate and lesser postgate dissipation on the steeper slope. The steepness of the slope also affected the relationships between mechanical skiing variables. The findings suggest that specific considerations during training and preparation would benefit the race performance of slalom skiers on courses involving sections of varying steepness.

  12. 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.

  13. 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.

  14. Crustal Structure and Deformation of the Yakutat Microplate: New Insights From STEEP Marine Seismic Reflection Data

    NASA Astrophysics Data System (ADS)

    Lowe, L. A.; Gulick, S. P.; Christeson, G.; van Avendonk, H.; Reece, R.; Elmore, R.; Pavlis, T.

    2008-12-01

    In fall 2008, we will conduct an active source marine seismic experiment of the offshore Yakutat microplate in the northern Gulf of Alaska. The survey will be conducted aboard the academic research vessel, R/V Marcus Langseth, collecting deep-penetrating multi-channel seismic reflection survey using an 8-km, 640 channel hydrophone streamer and a 6600 cu. in., 36 airgun array. The survey is the concluding data acquisition phase for the ST. Elias Erosion and tectonics Project (STEEP), a multi-institution NSF-Continental Dynamics project investigating the interplay of climate and tectonics in the Chugach-St. Elias Mountains in southern Alaska. The experiment will also provide important site survey information for possible future Integrated Ocean Drilling Program investigations. Two profiles coincident with wide-angle refraction data (see Christeson, et al., this session) will image structural changes across the Dangerous River Zone from east to west and the Transition Fault from south to north. We will also image the western portion of the Transition Fault to determine the nature of faulting along this boundary including whether or not the Pacific Plate is underthrusting beneath the Yakutat microplate as part of this collision. Our westernmost profile will image the Kayak Island Zone, typically described as the northern extension of the Aleutian megathrust but which may be a forming suture acting as a deformation backstop for the converging Yakutat and North American plates. Profiles across the Pamplona Zone, the current Yakutat-North America deformation front, will further constrain relative timing of structural development and the depth of deformation on the broad folds and thrust faults that comprise the area. This new dataset will allow further insight into regional tectonics of the St. Elias region as well as provide more detail regarding the development of the south Alaskan margin during major Plio-Pleistocene glacial- interglacial periods.

  15. 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

  16. A steep peripheral ring in irregular cornea topography, real or an instrument error?

    PubMed

    Galindo-Ferreiro, Alicia; Galvez-Ruiz, Alberto; Schellini, Silvana A; Galindo-Alonso, Julio

    2016-01-01

    To demonstrate that the steep peripheral ring (red zone) on corneal topography after myopic laser in situ keratomileusis (LASIK) could possibly due to instrument error and not always to a real increase in corneal curvature. A spherical model for the corneal surface and modifying topography software was used to analyze the cause of an error due to instrument design. This study involved modification of the software of a commercially available topographer. A small modification of the topography image results in a red zone on the corneal topography color map. Corneal modeling indicates that the red zone could be an artifact due to an instrument-induced error. The steep curvature changes after LASIK, signified by the red zone, could be also an error due to the plotting algorithms of the corneal topographer, besides a steep curvature change.

  17. A Millisecond Pulsar Discovery in a Survey of Unidentified Fermi γ-Ray Sources with LOFAR

    NASA Astrophysics Data System (ADS)

    Pleunis, Z.; Bassa, C. G.; Hessels, J. W. T.; Kondratiev, V. I.; Camilo, F.; Cognard, I.; Grießmeier, J.-M.; Stappers, B. W.; van Amesfoort, A. S.; Sanidas, S.

    2017-09-01

    Using LOFAR, we have performed a very-low-frequency (115‑155 MHz) radio survey for millisecond pulsars (MSPs). The survey targeted 52 unidentified Fermi γ-ray sources. Employing a combination of coherent and incoherent dedispersion, we have mitigated the dispersive effects of the interstellar medium while maintaining sensitivity to fast-spinning pulsars. Toward 3FGL J1553.1+5437 we have found PSR J1552+5437, the first MSP to be discovered (through its pulsations) at a radio frequency <200 MHz. PSR J1552+5437 is an isolated MSP with a 2.43 ms spin period and a dispersion measure of 22.9 pc cm‑3. The pulsar has a very steep radio spectral index (α < -2.8 ± 0.4). We obtain a phase-connected timing solution combining the 0.74 years of radio observations with γ-ray photon arrival times covering 7.5 years of Fermi observations. We find that the radio and γ-ray pulse profiles of PSR J1552+5437 appear to be nearly aligned. The very steep spectrum of PSR J1552+5437, along with other recent discoveries, hints at a population of radio MSPs that have been missed in surveys using higher observing frequencies. Detecting such steep spectrum sources is important for mapping the population of MSPs down to the shortest spin periods, understanding their emission in comparison to slow pulsars, and quantifying the prospects for future surveys with low-frequency radio telescopes like SKA-Low and its precursors.

  18. 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.

  19. Bed load transport in a very steep mountain stream (Riedbach, Switzerland): Measurement and prediction

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    Compared to lower-gradient channels, steep mountain streams typically have rougher beds and shallower flow depths, making macro-scale flow resistance (due to, e.g., immobile boulders and irregular bedforms) more important as controls on sediment transport. The marked differences in hydraulics, flow resistance, and grain mobility between steep and lower-gradient streams raise the question of whether the same equations can predict bed load transport rates across wide ranges of channel gradients. We studied a steep, glacier-fed mountain stream (Riedbach, Ct. Valais, Switzerland) that provides a natural experiment for exploring how stream gradients affect bed load transport rates. The streambed gradient increases over a 1 km stream reach by roughly one order of magnitude (from 3% to 38%), while flow discharge and width remain approximately constant. Sediment transport rates were determined in the 3% reach using Bunte bed load traps and in the 38% reach using the Swiss plate geophone system. Despite a ten-fold increase in bed gradient, bed load transport rates did not increase substantially. Observed transport rates for these two very different bed gradients could be predicted reasonably well by using a flow resistance partitioning approach to account for increasing bed roughness (D84 changes from 0.17 m to 0.91 m) within a fractional bed load transport equation. This suggests that sediment transport behavior across this large range of steep slopes agrees with patterns established in previous studies for both lower-gradient and steep reaches, and confirms the applicability of the flow resistance and bed load transport equations at very steep slopes.

  20. 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).

  1. 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.

  2. 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

  3. 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.

  4. The radio spectral energy distribution of infrared-faint radio sources

    NASA Astrophysics Data System (ADS)

    Herzog, A.; Norris, R. P.; Middelberg, E.; Seymour, N.; Spitler, L. R.; Emonts, B. H. C.; Franzen, T. M. O.; Hunstead, R.; Intema, H. T.; Marvil, J.; Parker, Q. A.; Sirothia, S. K.; Hurley-Walker, N.; Bell, M.; Bernardi, G.; Bowman, J. D.; Briggs, F.; Cappallo, R. J.; Callingham, J. R.; Deshpande, A. A.; Dwarakanath, K. S.; For, B.-Q.; Greenhill, L. J.; Hancock, P.; Hazelton, B. J.; Hindson, L.; Johnston-Hollitt, M.; Kapińska, A. D.; Kaplan, D. L.; Lenc, E.; Lonsdale, C. J.; McKinley, B.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Morgan, J.; Oberoi, D.; Offringa, A.; Ord, S. M.; Prabu, T.; Procopio, P.; Udaya Shankar, N.; Srivani, K. S.; Staveley-Smith, L.; Subrahmanyan, R.; Tingay, S. J.; Wayth, R. B.; Webster, R. L.; Williams, A.; Williams, C. L.; Wu, C.; Zheng, Q.; Bannister, K. W.; Chippendale, A. P.; Harvey-Smith, L.; Heywood, I.; Indermuehle, B.; Popping, A.; Sault, R. J.; Whiting, M. T.

    2016-10-01

    Context. Infrared-faint radio sources (IFRS) are a class of radio-loud (RL) active galactic nuclei (AGN) at high redshifts (z ≥ 1.7) that are characterised by their relative infrared faintness, resulting in enormous radio-to-infrared flux density ratios of up to several thousand. Aims: Because of their optical and infrared faintness, it is very challenging to study IFRS at these wavelengths. However, IFRS are relatively bright in the radio regime with 1.4 GHz flux densities of a few to a few tens of mJy. Therefore, the radio regime is the most promising wavelength regime in which to constrain their nature. We aim to test the hypothesis that IFRS are young AGN, particularly GHz peaked-spectrum (GPS) and compact steep-spectrum (CSS) sources that have a low frequency turnover. Methods: We use the rich radio data set available for the Australia Telescope Large Area Survey fields, covering the frequency range between 150 MHz and 34 GHz with up to 19 wavebands from different telescopes, and build radio spectral energy distributions (SEDs) for 34 IFRS. We then study the radio properties of this class of object with respect to turnover, spectral index, and behaviour towards higher frequencies. We also present the highest-frequency radio observations of an IFRS, observed with the Plateau de Bure Interferometer at 105 GHz, and model the multi-wavelength and radio-far-infrared SED of this source. Results: We find IFRS usually follow single power laws down to observed frequencies of around 150 MHz. Mostly, the radio SEDs are steep (α < -0.8; %), but we also find ultra-steep SEDs (α < -1.3; %). In particular, IFRS show statistically significantly steeper radio SEDs than the broader RL AGN population. Our analysis reveals that the fractions of GPS and CSS sources in the population of IFRS are consistent with the fractions in the broader RL AGN population. We find that at least % of IFRS contain young AGN, although the fraction might be significantly higher as suggested by

  5. 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.

  6. Energy spectrum based calculation of the half and the tenth value layers for brachytherapy sources using a semiempirical parametrized mass attenuation coefficient formulism.

    PubMed

    Yue, Ning J

    2008-06-01

    As different types of radionuclides (e.g., 131Cs source) are introduced for clinical use in brachytherapy, the question is raised regarding whether a relatively simple method exists for the derivation of values of the half value layer (HVL) or the tenth value layer (TVL). For the radionuclide that has been clinically used for years, such as 125I and 103Pd, the sources have been manufactured and marketed by several vendors with different designs and structures. Because of the nature of emission of low energy photons for these radionuclides, energy spectra of the sources are very dependent on their individual designs. Though values of the HVL or the TVL in certain commonly used shielding materials are relatively small for these low energy photon emitting sources, the question remains how the variations in energy spectra affect the HVL (or TVL) values and whether these values can be calculated with a relatively simple method. A more fundamental question is whether a method can be established to derive the HVL (TVL) values for any brachytherapy sources and for different materials in a relatively straightforward fashion. This study was undertaken to answer these questions. Based on energy spectra, a well established semiempirical mass attenuation coefficient computing scheme was utilized to derive the HVL (TVL) values of different materials for different types of brachytherapy sources. The method presented in this study may be useful to estimate HVL (TVL) values of different materials for brachytherapy sources of different designs and containing different radionuclides.

  7. Energy spectrum based calculation of the half and the tenth value layers for brachytherapy sources using a semiempirical parametrized mass attenuation coefficient formulism

    SciTech Connect

    Yue, Ning J.

    2008-06-15

    As different types of radionuclides (e.g., {sup 131}Cs source) are introduced for clinical use in brachytherapy, the question is raised regarding whether a relatively simple method exists for the derivation of values of the half value layer (HVL) or the tenth value layer (TVL). For the radionuclide that has been clinically used for years, such as {sup 125}I and {sup 103}Pd, the sources have been manufactured and marketed by several vendors with different designs and structures. Because of the nature of emission of low energy photons for these radionuclides, energy spectra of the sources are very dependent on their individual designs. Though values of the HVL or the TVL in certain commonly used shielding materials are relatively small for these low energy photon emitting sources, the question remains how the variations in energy spectra affect the HVL (or TVL) values and whether these values can be calculated with a relatively simple method. A more fundamental question is whether a method can be established to derive the HVL (TVL) values for any brachytherapy sources and for different materials in a relatively straightforward fashion. This study was undertaken to answer these questions. Based on energy spectra, a well established semiempirical mass attenuation coefficient computing scheme was utilized to derive the HVL (TVL) values of different materials for different types of brachytherapy sources. The method presented in this study may be useful to estimate HVL (TVL) values of different materials for brachytherapy sources of different designs and containing different radionuclides.

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

    USDA-ARS?s Scientific Manuscript database

    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...

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

    USDA-ARS?s Scientific Manuscript database

    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...

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

    Treesearch

    T.J. Voltz; M.N. Gooseff; A.S. Ward; K. Singha; M. Fitzgerald; T. Wagener

    2013-01-01

    Patterns 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,...

  11. X-ray refraction effect and density determination of steep-gradient, high-density plasma

    NASA Astrophysics Data System (ADS)

    Miyanaga, N.; Kato, Y.; Yamanaka, C.

    1982-12-01

    X-ray defraction due to the steep density gradient of a laser-produced plasma has been observed. Distribution of the density gradient was determined from the measured refraction angle. Estimation of the radial density profile and the density scale length in the high-density region near the ablation surface are presented.

  12. Inactivation of tannins in milled sorghum grain through steeping in dilute NaOH solution.

    PubMed

    Adetunji, Adeoluwa I; Duodu, Kwaku G; Taylor, John R N

    2015-05-15

    Steeping milled sorghum in up to 0.4% NaOH was investigated as a method of tannin inactivation. NaOH steeping substantially reduced assayable total phenols and tannins in both Type III and Type II sorghums and with Type III sorghum caused a 60-80% reduction in α-amylase inhibition compared to a 20% reduction by water steeping. NaOH treatment also reduced starch liquefaction time and increased free amino nitrogen. Type II tannin sorghum did not inhibit α-amylase and consequently the NaOH treatment had no effect. HPLC and LC-MS of the tannin extracts indicated a general trend of increasing proanthocyanidin/procyanidin size with increasing NaOH concentration and steeping time, coupled with a reduction in total area of peaks resolved. These show that the NaOH treatment forms highly polymerised tannin compounds, too large to assay and to interact with the α-amylase. NaOH pre-treatment of Type III sorghums could enable their utilisation in bioethanol production.

  13. Hardwood silviculture and skyline yarding on steep slopes: economic and environmental impacts

    Treesearch

    John E. Baumgras; Chris B. LeDoux

    1995-01-01

    Ameliorating the visual and environmental impact associated with harvesting hardwoods on steep slopes will require the efficient use of skyline yarding along with silvicultural alternatives to clearcutting. In evaluating the effects of these alternatives on harvesting revenue, results of field studies and computer simulations were used to estimate costs and revenue for...

  14. 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.

  15. Influence of starch steeping period on dimensionless disintegration values of a paracetamol tablet formulation.

    PubMed

    Alebiowu, Gbenga; Adeyemi, Ayoade O

    2009-01-01

    In this study, tapioca starches obtained after different steeping periods, i.e. TS 24, TS 48 and TS 72, were used as disintegrants with corn starch BP as the standard disintegrant in a paracetamol tablet formulation. Two dimensionless disintegration quantities, T(N) and T(C) were used in the determination of the influence that steeping period of starch disintegrant would have on the crushing strength friability-disintegration time ratio (CSFR/DT). These quantities were used to assess the influence of steeping period, relative density and disintegrant concentration on CSFR/DT as well as to compare disintegrant efficiency. The results suggest that the CSFR/DT is more dependent on the disintegrant concentration than on steeping period and relative density. The study further showed that TS 72 is a more reliable disintegrant because its activity would not be influenced by changes in relative density of tablets. This work concludes that the T(N) would be more useful for quantitative assessment while T(C) is more relevant for qualitative assessment.

  16. 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…

  17. 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…

  18. Fast Back-Propagation Learning Using Steep Activation Functions and Automatic Weight

    Treesearch

    Tai-Hoon Cho; Richard W. Conners; Philip A. Araman

    1992-01-01

    In this paper, several back-propagation (BP) learning speed-up algorithms that employ the ãgainä parameter, i.e., steepness of the activation function, are examined. Simulations will show that increasing the gain seemingly increases the speed of convergence and that these algorithms can converge faster than the standard BP learning algorithm on some problems. However,...

  19. A sediment transport model for incision of gullies on steep topography

    Treesearch

    Erkan Istanbulluoglu; David G. Tarboton; Robert T. Pack; Charles H. Luce

    2003-01-01

    We have conducted surveys of gullies that developed in a small, steep watershed in the Idaho Batholith after a severe wildfire followed by intense precipitation. We measured gully length and cross sections to estimate the volumes of sediment loss due to gully formation. These volume estimates are assumed to provide an estimate of sediment transport capacity at each...

  20. PI3-kinase signaling contributes to orientation in shallow gradients and enhances speed in steep chemoattractant gradients.

    PubMed

    Bosgraaf, Leonard; Keizer-Gunnink, Ineke; Van Haastert, Peter J M

    2008-11-01

    Dictyostelium cells that chemotax towards cAMP produce phosphatidylinositol (3,4,5)-trisphosphate [PtdIns(3,4,5)P(3)] at the leading edge, which has been implicated in actin reorganization and pseudopod extension. However, in the absence of PtdIns(3,4,5)P(3) signaling, cells will chemotax via alternative pathways. Here we examined the potential contribution of PtdIns(3,4,5)P(3) to chemotaxis of wild-type cells. The results show that steep cAMP gradients (larger than 10% concentration difference across the cell) induce strong PtdIns(3,4,5)P(3) patches at the leading edge, which has little effect on the orientation but strongly enhances the speed of the cell. Using a new sensitive method for PtdIns(3,4,5)P(3) detection that corrects for the volume of cytosol in pixels at the boundary of the cell, we show that, in shallow cAMP gradient (less than 5% concentration difference across the cell), PtdIns(3,4,5)P(3) is still somewhat enriched at the leading edge. Cells lacking PI3-kinase (PI3K) activity exhibit poor chemotaxis in these shallow gradients. Owing to the reduced speed and diminished orientation of the cells in steep and shallow gradients, respectively, cells lacking PtdIns(3,4,5)P(3) signaling require two- to six-fold longer times to reach a point source of chemoattractant compared with wild-type cells. These results show that, although PI3K signaling is dispensable for chemotaxis, it gives the wild type an advantage over mutant cells.

  1. Spatial Patterns of Channel Steepness in the Central Rockies: Do River Profiles Record Landscape Evolution Forcing By Yellowstone Dynamic Topography?

    NASA Astrophysics Data System (ADS)

    Guerrero, E. F.; Meigs, A.; Kirby, E.; Gregg, P. M.

    2014-12-01

    Numerous investigations demonstrate that mantle convective processes affect the surface topography of the overriding plate. 'Positive dynamic topography' refers to the surface expression of mantle upwelling. An advecting wave of dynamic topographic surface uplift plate is thought to result from migration of North America relative to the Yellowstone hotspot. Advection of positive dynamic topography through an overriding plate disturbs the landscape by a combination of a change in surface uplift rate and tilting. Identification of dynamic topography's contribution to evolution of the greater Yellowstone region's landscape, however, is complicated by the polygenetic regional topography that results from glaciation, bimodal volcanism, Basin and Range extension, early Cenozoic arc volcanism, and Laramide contraction. Our model, which is parameterized to Yellowstone but doesn't include climate variations, suggests contribution of the dynamic topography erosional signal should decrease from 0.1mm/yr to 0.5 mm/yr at a 100km radius from the hotspot uplift source. The cosmogenic chronology that we are building to constrain spatial patterns of incision in the Bighorn Basin indicates that there is differential incision occurring in the Bighorn basin. Rates vary from 2.8mm/yr in the western basin, which is closer to Yellowstone to 1.1mm/yr in the eastern basin. Global cooling and its effects at the Plio-Pleistocene transition is thought to be the dominant control on the region's erosional regime. However, the magnitude of the contribution from Yellowstone dynamic topography to the regional landscape evolution is still unknown because published incision rates lack the resolution to differentiate between incision forcing mechanisms. Bedrock stream profile analysis is powerful tool for determining spatial patterns of surface deformation. We compare results for normalized channel steepness indices across various basins in the Central Rockies and Greater Yellowstone area with

  2. Morphometric and meteorological controls on recent snow avalanche distribution and activity at hillslopes in steep mountain valleys in western Norway

    NASA Astrophysics Data System (ADS)

    Laute, Katja; Beylich, Achim A.

    2014-08-01

    Snow avalanches are common phenomena in Norway. Controlling factors of snow avalanche distribution and activity, and the relative importance of snow avalanches regarding contemporary sedimentary mass transfers were explored within two steep, parabolic-shaped and glacier-connected tributary valleys (Erdalen and Bødalen) in western Norway. Mapping of distribution, extent and the entire path lengths of snow avalanches was combined with spatial data analysis (GIS and DEM computing) of morphometric controls. The timing and frequency of snow avalanches were explored by correlating meteorological data with high-resolution monitoring data of snow avalanche events. Sediment masses annually transferred by snow avalanches along hillslopes and from hillslopes into stream channels were estimated. A high inter-annual variability of avalanche activity and a wide spectrum of avalanche sizes and types ranging from small to extreme-sized events were found for the four-year investigation period 2009-2012. Spatial distribution of snow avalanches is governed by the topographical factors valley orientation, slope aspect, relative slope height and rockwall morphometry whereas timing and frequency of snow avalanches are controlled by snowfall intensity, periods with strong winds combined with a prevalent wind direction or sharp air temperature changes within short time periods. Snow avalanches represent one of the dominant denudational processes and have a high relative importance regarding sedimentary mass transfers within the two mountain valleys Erdalen and Bødalen in western Norway.

  3. Haemodynamics and cardiac function during robotic-assisted laparoscopic prostatectomy in steep Trendelenburg position.

    PubMed

    Haas, Sebastian; Haese, Alexander; Goetz, Alwin E; Kubitz, Jens C

    2011-12-01

    Robotic-assisted laparoscopic prostatectomy (RALP) is usually performed in steep Trendelenburg position, which can be associated with cardiac impairment due to positioning and capnoperitoneum. This study investigated haemodynamic consequences and cardiac function in this type of surgery and evaluated the hypothesis that steep Trendelenburg position and capnoperitoneum results in haemodynamic and ventricular impairment. 10 patients (ASA I-III) scheduled for RALP in steep Trendelenburg position with capnoperitoneum were prospectively studied. Heart rate (HR), mean arterial pressure (MAP) and central venous pressure (CVP) were recorded. Stroke volume variation (SVV) and cardiac output (CO) were measured using pulse-contour analysis. Further, cardiac function was assessed using trans-oesophageal echocardiography before positioning (T1) and 10 min (T2) and 60 min (T3) after implementation of steep Trendelenburg position and capnoperitoneum. HR did not change statistically. MAP (T1, 69.7 ± 1.55; T2, 82.9 ± 3.05; T3, 79.4 ± 2.18 mmHg), CVP (T1, 7.7 ± 1.3; T2, 17.3 ± 2.01; T3, 16.9 ± 1.66 mmHg) and CO (T1, 4.0 ± 0.15; T2, 4.9 ± 0.26; T3, 4.9 ± 0.36 l/min) increased significantly at T2 and T3. Echocardiography showed no deterioration of left or right ventricular function. In one patient with pre-existing mitral valve insufficiency (I°) an aggravation of the insufficiency (III°) was observed. No other valve dysfunctions were observed. The steep Trendelenburg position may improve haemodynamic function and does not deteriorate left or right ventricular function during RALP. However, mitral valve insufficiency may be aggravated by positioning and capnoperitoneum. Copyright © 2011 John Wiley & Sons, Ltd.

  4. Prevalence and Associations of Steep Cornea/Keratoconus in Greater Beijing. The Beijing Eye Study

    PubMed Central

    Xu, Liang; Wang, Ya Xing; Guo, Yin; You, Qi Sheng; Jonas, Jost B.

    2012-01-01

    Purpose To evaluate the prevalence and associated factors of steep cornea/keratoconus in the adult Chinese population. Methods The population-based Beijing Eye Study 2011 included 3468 individuals with a mean age of 64.6±9.8 years (range: 50–93 years). A detailed ophthalmic examination was performed including optical low-coherence reflectometry. Steep cornea/keratoconus were defined as an anterior corneal refractive power exceeding 48 diopters. Results Mean refractive power of the cornea was 43.16±1.45 diopters (range: 36.51 to 48.46 diopters; flattest meridian) and 43.98±1.52 diopters (range: 37.00 to 52.88 diopters; steepest meridian). A steep cornea/keratoconus defined as corneal refractive power of ≥48 diopters and ≥49 diopters was detected in 27 subjects (prevalence rate: 0.9±0.2%) and 6 (0.2± 0.1%) subjects, respectively. Presence of steep cornea/keratoconus was associated with shorter axial length (P<0.001), smaller interpupillary distance (P = 0.038), lower best corrected visual acuity (P = 0.021), higher cylindrical refractive error (P<0.001) and more myopic refractive error (P<0.001). It was not significantly associated with gender, body height, psychic depression, cognitive function, blood concentrations of glucose, lipids, creatinine and C-reactive protein, blood pressure and quality of life score, nor with intraocular pressure, dry eye feeling, and lens thickness. Conclusions A steep cornea/keratoconus defined as corneal refractive power of 48+ diopters has a prevalence of 0.9±0.2% among Chinese aged 50 years and above. Its prevalence was significantly associated with the ocular parameters of shorter axial length, smaller interpupillary distance, higher cylindrical and myopic refractive error and lower best corrected visual acuity, however, with none of the systemic parameters tested. PMID:22792169

  5. 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.

  6. 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

  7. Steep Decay Phase Shaped by the Curvature Effect. I. Flux Evolution

    NASA Astrophysics Data System (ADS)

    Lin, Da-Bin; Mu, Hui-Jun; Lu, Rui-Jing; Liu, Tong; Gu, Wei-Min; Liang, Yun-Feng; Wang, Xiang-Gao; Liang, En-Wei

    2017-05-01

    The curvature effect may be responsible for the steep decay phase observed in gamma-ray bursts. To test the curvature effect with observations, the zero time point t 0 adopted to plot the observer time and flux on a logarithmic scale should be appropriately selected. In practice, however, the true t 0 cannot be directly constrained from the data. Thus, we move t 0 to a certain time in the steep decay phase, which can be easily identified. In this situation, we derive an analytical formula to describe the flux evolution of the steep decay phase. The analytical formula reads as {F}ν \\propto {(1+{\\tilde{t}}{obs}/{\\tilde{t}}c)}-α , with α ({\\tilde{t}}{obs})=2+{\\int }0{log(1+{\\tilde{t}}{obs}/{\\tilde{t}}c)} β (τ )d[{log}(1+τ /{\\tilde{t}}c)]/{log}(1+{\\tilde{t}}{obs}/{\\tilde{t}}c), where F ν is the flux observed at frequency ν, {\\tilde{t}}{obs} is the observer time by setting t 0 at a certain time in the steep decay phase, β is the spectral index estimated around ν, and {\\tilde{t}}c is the decay timescale of the phase with {\\tilde{t}}{obs}≥slant 0. We test the analytical formula with the data from numerical calculations. It is found that the analytical formula presents a good estimate of the evolution of the flux shaped by the curvature effect. Our analytical formula can be used to confront the curvature effect with observations and estimate the decay timescale of the steep decay phase.

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

    PubMed

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

    2015-01-01

    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 a

  9. Using Local Radiation MHD Simulations to Attempt to Understand the Very High/Steep Power Law State of Black Hole X-ray Binaries

    NASA Astrophysics Data System (ADS)

    Blaes, Omer

    Stellar mass black holes in certain types of binary systems accrete matter from their companion stars through rotating, turbulent flows known as accretion disks. These disks are observed by space X-ray missions to have a number of distinct spectral/variability states, the most mysterious one being the very high/steep power law state that generally occurs at very high luminosities. This state is particularly interesting as it exhibits unique quasi-periodic oscillations observed in the X-rays that, if understood, might help us directly measure the properties of the black hole spacetime. Radiation pressure is an important physical process at such high luminosities, and modifies the character of the accretion disk in a number of unique ways. One of the ways that it does this is that it enables turbulent speeds in the disk to exceed thermal speeds of electrons, thereby introducing a completely new radiation process - turbulent Comptonization. This radiation process is promising for explaining the unique spectral characteristics of the very high/steep power law state. We will test this hypothesis by making detailed calculations of the emergent radiation spectrum from numerical simulation data of the turbulence in local patches of the disk at high levels of radiation pressure. These will be the first detailed theoretical calculations of turbulent Comptonization, which should be an important process for modeling NASA data from high luminosity black hole accretion. We hope that this will shed light on the nature of the mysterious very high/steep power law state. The research will form the basis of the PhD thesis of a graduate student, in line with NASA's educational and training objectives.

  10. How to Include Steep Bank Retreat in 2D/3D Morphological Models?

    NASA Astrophysics Data System (ADS)

    Jagers, B.; Spruyt, A.; Mosselman, E.

    2011-12-01

    State-of-the-art 2D/3D morphological models like open source Delft3D include an increasing number of features, such as multiple cohesive and non-cohesive sediment fractions, bed load and separate suspended load (including density effects), sediment fraction interaction processes such as hiding and exposure, ripple and dune predictors, consolidation, and bed composition stratigraphy. However, this and similar models have been developed for simulating morphological changes under the assumption that horizontal scales are large compared to the vertical scale and that the processes affecting the bed are hence dominantly vertical fluxes. However, near banks and steep slopes the processes have a significant horizontal component: a crucial aspect in the simulation of meandering rivers. Although simple or engineering solutions have been added to many of these models to get some erosion of dry areas, scientifically based bank erosion formulations are generally lacking in these models. Although such formulations may be complex and non-deterministic, that is not the main reason why they haven't been implemented: resolving the shift of bank-lines on the grid is the main problem. Defining bank-lines along the nearest grid lines of a rectangular computational grid leads to staircase lines that impede any reasonable determination of the hydraulic loads on the banks. An adaptive curvilinear boundary-fitted grid may at first glance seem to solve this problem, but arbitrary bank retreat and advance deform such a grid prohibitively within a few bank-line update steps and cause stationary features of the landscape (e.g. a bridge or local sediment composition) to move with the grid or to diffuse due to numerical limitations. We have therefore chosen a new approach in which shifting bank-lines are followed as separate moving objects on a fixed grid, using local immersed-boundary techniques to solve the flow and sediment transport in the vicinity of the bank-lines. We show some results

  11. Bedload Transport on Steep Slopes with Coupled Modeling Based on the Discrete Element Method

    NASA Astrophysics Data System (ADS)

    Chauchat, J.; Maurin, R.; Chareyre, B.; Frey, P.

    2014-12-01

    After more than a century of research, a clear understanding of the physical processes involved in sediment transport problems is still lacking. In particular, modeling of intergranular interactions and fluid-particle interactions in bedload transport need to be improved. In this contribution, we propose a simple numerical model coupling a Discrete Element Method (DEM) for the grain dynamics with a simple 1D vertical fluid phase model inspired from the two-phase approach [1] in order to contribute to this open question. The Reynolds stress is parameterized by a mixing length model which depends on the integral of the grain volume fraction. The coupling between the grains and the fluid phase is essentially achieved through buoyancy and drag forces. The open source DEM code Yade [2] is used with a linear spring-dashpot contact law that allows the description of the behavior of the particles from the quasi-static to the dynamical state. The model is compared with classical results [3] and with particle-scale experimental results obtained in the quasi-2D flume at IRSTEA, Grenoble [4]. We discuss the closures of the model and the sensitivity to the different physical and numerical parameters. [1] Revil-Baudard, T. and J. Chauchat. A two-phase model for sheet flow regime based on dense granular flow rheology. Journal of Geophysical Research: Oceans, 118(2):619-634, 2013. [2] Šmilauer V. , E. Catalano, B. Chareyre, S. Dorofeenko, J. Duriez, A. Gladky, J. Kozicki, C . Modenese, L. Scholtès, L. Sibille, J. Str.nský, and K. Thoeni. Yade Documentation (V. Šmilauer, ed.), The Yade Project, 1st ed., http://yade-dem.org/doc/., 2010. [3] Meyer-Peter, E. and R. Müller. Formulas for bed-load transport. In Proc. 2nd Meeting, pages 39-64. IAHR, 1948. [4] Frey, P. Particle velocity and concentration profiles in bedload experiments on a steep slope. Earth Surface Processes and Landforms, 39(5):646-655, 2014.

  12. 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

  13. 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.

  14. Carbapenems Versus Piperacillin-Tazobactam for Bloodstream Infections of Nonurinary Source Caused by Extended-Spectrum Beta-Lactamase-Producing Enterobacteriaceae.

    PubMed

    Ofer-Friedman, Hadas; Shefler, Coral; Sharma, Sarit; Tirosh, Amit; Tal-Jasper, Ruthy; Kandipalli, Deepthi; Sharma, Shruti; Bathina, Pradeep; Kaplansky, Tamir; Maskit, Moran; Azouri, Tal; Lazarovitch, Tsilia; Zaidenstein, Ronit; Kaye, Keith S; Marchaim, Dror

    2015-08-01

    A recent, frequently quoted study has suggested that for bloodstream infections (BSIs) due to extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL) Escherichia coli, treatment with β-lactam/β-lactamase inhibitors (BLBLIs) might be equivalent to treatment with carbapenems. However, the majority of BSIs originate from the urinary tract. A multicenter, multinational efficacy analysis was conducted from 2010 to 2012 to compare outcomes of patients with non-urinary ESBL BSIs who received a carbapenem (69 patients) vs those treated with piperacillin-tazobactam (10 patients). In multivariate analysis, therapy with piperacillin-tazobactam was associated with increased 90-day mortality (adjusted odds ratio, 7.9, P=.03). For ESBL BSIs of a non-urinary origin, carbapenems should be considered a superior treatment to BLBLIs.

  15. Spectrum Certification

    DTIC Science & Technology

    2010-03-01

    components on a platform, especially for an Unmanned Aerial System (UAS) • Note-To-Holders (NTH) is easier to go through the spectrum certification process... Unmanned Aerial System (UAS) • Application for Equipment Frequency Allocation is required for each RF component i e command and control (C2) link video

  16. Spectrum Management

    NASA Astrophysics Data System (ADS)

    Ghosh, Tapasi

    2002-12-01

    Present day life without the use of radio frequencies is totally unimaginable. The mode of usage of the different frequency bands is diverse and ever-changing with constant development of newer technology. In the midst of all this, there is a minority group of spectrum users who are labeled ``passive''. Radio astronomy and remote sensing groups come under this title, having no control over the signal they try to receive, they are often most vulnerable to interference from man-made radio waves. However, through constant need to develop new techniques to detect very week signal, the research done by these passive users of spectrum often benefits the commercial users. It is therefore of utmost importance that both the active and the passive users of radio spectrum may survive and grow together in a manner of peaceful coexistence. This is the goal of spectrum management. As radio waves ``do not know'' of any national boundaries, such management issues have to be agreed upon globally. The mechanisms that have been set up for such purposes with global and national counterparts is explained. How, as a minority, the interests of radio astronomy may be best served now and in future is also discussed.

  17. Multifrequency VLA observations of PKS 0745 - 191 - The archetypal 'cooling flow' radio source?

    NASA Technical Reports Server (NTRS)

    Baum, S. A.; O'Dea, C. P.

    1991-01-01

    Ninety-, 20-, 6- and 2-cm VLA observations of the high-radio-luminosity cooling-flow radio source PKS 0745 - 191 are presented. The radio source was found to have a core with a very steep spectrum (alpha is approximately -1.5) and diffuse emission with an even steeper spectrum (alpha is approximately -1.5 to -2.3) without clear indications of the jets, hotspots, or double lobes found in the other radio sources of comparable luminosity. It is inferred that the energy to power the radio source comes from the central engine, but the source's structure may be heavily influenced by the past history of the galaxy and the inflowing intracluster medium. It is shown that, while the radio source is energetically unimportant for the cluster as a whole, it is important on the scale of the cooling flow. The mere existence of cosmic rays and magnetic fields within a substantial fraction of the volume inside the cooling radius has important consequences for cooling-flow models.

  18. Multifrequency VLA observations of PKS 0745 - 191 - The archetypal 'cooling flow' radio source?

    NASA Technical Reports Server (NTRS)

    Baum, S. A.; O'Dea, C. P.

    1991-01-01

    Ninety-, 20-, 6- and 2-cm VLA observations of the high-radio-luminosity cooling-flow radio source PKS 0745 - 191 are presented. The radio source was found to have a core with a very steep spectrum (alpha is approximately -1.5) and diffuse emission with an even steeper spectrum (alpha is approximately -1.5 to -2.3) without clear indications of the jets, hotspots, or double lobes found in the other radio sources of comparable luminosity. It is inferred that the energy to power the radio source comes from the central engine, but the source's structure may be heavily influenced by the past history of the galaxy and the inflowing intracluster medium. It is shown that, while the radio source is energetically unimportant for the cluster as a whole, it is important on the scale of the cooling flow. The mere existence of cosmic rays and magnetic fields within a substantial fraction of the volume inside the cooling radius has important consequences for cooling-flow models.

  19. Multifrequency VLA observations of PKS 0745 - 191 - The archetypal 'cooling flow' radio source?

    NASA Astrophysics Data System (ADS)

    Baum, S. A.; O'Dea, C. P.

    1991-06-01

    Ninety-, 20-, 6- and 2-cm VLA observations of the high-radio-luminosity cooling-flow radio source PKS 0745 - 191 are presented. The radio source was found to have a core with a very steep spectrum (alpha is approximately -1.5) and diffuse emission with an even steeper spectrum (alpha is approximately -1.5 to -2.3) without clear indications of the jets, hotspots, or double lobes found in the other radio sources of comparable luminosity. It is inferred that the energy to power the radio source comes from the central engine, but the source's structure may be heavily influenced by the past history of the galaxy and the inflowing intracluster medium. It is shown that, while the radio source is energetically unimportant for the cluster as a whole, it is important on the scale of the cooling flow. The mere existence of cosmic rays and magnetic fields within a substantial fraction of the volume inside the cooling radius has important consequences for cooling-flow models.

  20. 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.

  1. 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.

  2. Radio spectrum surveillance station

    NASA Technical Reports Server (NTRS)

    Hersey, D. R.

    1979-01-01

    The paper presents a general and functional description of a low-cost surveillance station designed as the first phase of NASA's program to develop a radio spectrum surveillance capability for deep space stations for identifying radio frequency interference sources. The station described has identified several particular interferences and is yielding spectral signature data which, after cataloging, will serve as a library for rapid identification of frequently observed interference. Findings from the use of the station are discussed.

  3. 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

  4. Steep subthreshold slope characteristics of body tied to gate NMOSFET in partially depleted SOI

    NASA Astrophysics Data System (ADS)

    Song, Lei; Hu, Zhiyuan; Liu, Zhangli; Xin, Haiwei; Zhang, Zhengxuan; Zou, Shichang

    2017-04-01

    A new body tied to gate (BTG) n-channel metal-oxide-semiconductor field-effect-transistor (NMOSFET) with a diode in partially depleted SOI (PD SOI) is proposed and investigated. We first compare the transfer and output characteristics between the regular and BTG NMOSFETs with grounded body and floating body. The steep subthreshold slope (<6 mV/dec) and low OFF current (∼0.01 pA/μm) of the BTG NMOSFET with floating body are observed at VD = 3.3 V. Mechanisms of the floating body effect (FBE) and the diode are analyzed to explain the outstanding performance. The hysteresis characteristics of BTG NMOSFETs are also presented in comparison to regular ones. Finally, the steep subthreshold characteristics of the BTG NMOSFET with floating body at low drain voltage are studied for ultralow power application.

  5. Research on fast ecological restoration technology of high and steep rocky slope of highway

    NASA Astrophysics Data System (ADS)

    Qin, Xin

    2017-08-01

    Along with the development of the western region, the traffic construction in mountainous areas is booming. In the infrastructure, it produced a large number of secondary bare land. Soil erosion is serious. Based on the literature search and analysis of the domestic and international slope ecological restoration technology, this paper proposes a fast and efficient adaptive highway high steep rock slope ecological restoration technology (it has been authorized by the national patent). And it states the systemic structure, working principle and key construction technology. The ecological restoration technique combines the growth characteristics of the vegetation and the characteristics of the rock mass, which not only improves the survival rate of plants, but also stable slope. The results of this study make up for the shortcomings of the existing ecological restoration technology of slope. Compared with the prior art, which have obvious advantages and suitable for the ecological restoration of high steep rock slope.

  6. 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.

  7. 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.

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

    PubMed

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

    2015-04-06

    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.

  9. Leveling Mountains: Purpose Attenuates Links Between Perceptions of Effort and Steepness.

    PubMed

    Burrow, Anthony L; Hill, Patrick L; Sumner, Rachel

    2016-01-01

    People tend to overestimate the steepness of slopes, especially when they appraise the effort necessary to ascend them as greater. Recent studies, however, suggest the way individuals perceive visual stimuli may rely heavily on their personal motivations. In four studies (N = 517), purpose in life was tested as a motivational framework influencing how appraised effort relates to slope perception. Studies 1 and 2 found the amount of effort participants appraised necessary to ascend several virtual slopes was related to greater overestimation of their steepness. Yet, this relationship was attenuated by purpose assessed both as a disposition and experimental manipulation. Studies 3 and 4 replicated these findings using actual hills, again showing links between the amount of effort thought required to ascend them and their perceived angle were diminished by greater purpose. The discussion addresses implications of purpose as a broad motivational framework that shapes how individuals see their environment.

  10. Electromagnetic spectrum management system

    DOEpatents

    Seastrand, Douglas R.

    2017-01-31

    A system for transmitting a wireless countermeasure signal to disrupt third party communications is disclosed that include an antenna configured to receive wireless signals and transmit wireless counter measure signals such that the wireless countermeasure signals are responsive to the received wireless signals. A receiver processes the received wireless signals to create processed received signal data while a spectrum control module subtracts known source signal data from the processed received signal data to generate unknown source signal data. The unknown source signal data is based on unknown wireless signals, such as enemy signals. A transmitter is configured to process the unknown source signal data to create countermeasure signals and transmit a wireless countermeasure signal over the first antenna or a second antenna to thereby interfere with the unknown wireless signals.

  11. 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

  12. 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

  13. 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.

  14. Satellites and Steep Slopes - the challenge of topography in the Himalaya - Karakorum for cryosphere models

    NASA Astrophysics Data System (ADS)

    Steiner, J. F.; Buri, P.; Miles, E. S.; Immerzeel, W.

    2016-12-01

    The topography in glaciated catchments in the Himalaya - Karakoram range are extreme in a number of aspects that proof to be a challenge for distributed modelling. High altitude regions, where accumulation areas of glaciers are generally located, can at times be very steep, covered in hanging ice and seasonal snow. On the other hand, lower areas, where ablation zones on glacier tongues are located, tend to be very shallow. This has consequences for obtaining glacier areas from satellite derived glacier inventories (e.g. RGI, ICIMOD). As they are taken perpendicular to the center of the earth, these inventories will underestimate the area of steep regions, sometimes quite considerably (Figure 1). This can have consequences for a number of statistics in glaciological modeling, especially when it comes to the relative comparison of accumulation and ablation and hence overall melt from a glacier. Additionally, these steep head walls cause topographic shading. Depending on the exposition of the valley this can result in very divergent amounts of direct solar radiation reaching the glacier surface from valley to valley. Comparisons of melt between different regions and even glaciers have to be taken with considerable caution. Finally, these shallow glacier tongues are increasingly covered in debris. Such glacier surfaces with a debris cover ranging in grain size from sand to boulders several meters in diameter are very hummocky rather than flat bare ice glacier surfaces. This in turn increases local shading but also increases the overall glacier surface. Using high resolution satellite imagery and DEMs ( 5m) from our field site we investigate the effects of areal misrepresentations on the local scale. Decreasing resolution we then take this analysis to the mountain range scale and can identify to what degree these factors are significant and considering literature values determine the quantitative impact for energy and mass balance studies. Figure 1: A schematic

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

    PubMed

    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.

  16. Large sized non-uniform sediment transport at high capacity on steep slopes

    NASA Astrophysics Data System (ADS)

    Fu, X.; Zhang, L.; Duan, J. G.

    2015-12-01

    Transport of large-sized particles such as cobbles in steep streams still remains poorly understood in spite of its importance in mountain stream morphdynamics. Here we explored the law of cobble transport and the effect of cobble existence on gravel bed material transport, using flume experiments with a steep slope (4.9%) and water and sediment constantly supplying. The experiments were conducted in an 8 m long and 0.6 m wide circulating flume with the maximal size up to 90 mm and cobble concentrations in the sediment bed ranging from 22 percent to 6 percent. The sediment transport rate is on the order of 1000 g/m/s, which could be taken as high rate transport compared with existing researches. Bed load transport rate and flow variables were measured after the flume reached an equilibrium state. Bed surface topography was also measured by applying Kinect range camera before and after each run in order to analyze the fractal characteristics of the bed surface under different flow conditions. Critical shear stress of each size friction was estimated from the reference transport method (RTM) and a new hiding function was recommended. Preliminary results show that the bed was nearly in an equal mobility transport regime. We then plot dimensionless fractional transport rate versus dimensionless shear stress and assess the existing bed load transport formulas of non-uniform sediments for their applicability at high sediment transport capacity. This study contributes to the comprehension of high rate sediment transport on steep slopes.

  17. Slope, grain size, and roughness controls on dry sediment transport and storage on steep hillslopes

    NASA Astrophysics Data System (ADS)

    DiBiase, Roman A.; Lamb, Michael P.; Ganti, Vamsi; Booth, Adam M.

    2017-04-01

    Existing hillslope sediment transport models developed for low-relief, soil-mantled landscapes are poorly suited to explain the coupling between steep rocky hillslopes and headwater channels. Here we address this knowledge gap using a series of field and numerical experiments to inform a particle-based model of sediment transport by dry ravel—a mechanism of granular transport characteristic of steep hillslopes. We find that particle travel distance increases as a function of the ratio of particle diameter to fine-scale (<1 m) topographic roughness, in agreement with prior laboratory and field experiments. Contrary to models that assume a fixed critical slope, the particle-based model predicts a broad transition as hillslopes steepen from grain-scale to hillslope-scale mean particle travel distances due to the trapping of sediment on slopes more than threefold steeper than the average friction slope. This transition is further broadened by higher macroscale (>1 m) topographic variability associated with rocky landscapes. Applying a 2-D dry-ravel-routing model to lidar-derived surface topography, we show how spatial patterns of local and nonlocal transport control connectivity between hillslopes and steep headwater channels that generate debris flows through failure of ravel-filled channels following wildfire. Our results corroborate field observations of a patchy transition from soil-mantled to bedrock landscapes and suggest that there is a dynamic interplay between sediment storage, roughness, grain sorting, and transport even on hillslopes that well exceed the angle of repose.

  18. 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.

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

    SciTech Connect

    Miller, D.B. . Dept. of Electrical and Computer Engineering)

    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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  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. 0108 + 388 - A compact double source with surprising properties

    NASA Technical Reports Server (NTRS)

    Baum, S. A.; O'Dea, C. P.; De Bruyn, A. G.; Murphy, D. W.

    1990-01-01

    49 cm, 6 cm, and 20 cm observations of the compact double ratio source 0108 + 388 are presented. Extended emission about 20 deg to the east of the core is detected which resembles a hot spot/lobe with a bridge of emission extending back to the core. This is the first detection of extended emission associated with such a source, and it is inconsistent with the suggestion that such sources are very young classical double radio sources. The inconsistency can be reconciled if the activity in this object is recurrent and the emission is the relic of a previous epoch of activity. Alternatively, the source may be a normal-aged radio galaxy in which most of the radio-emitting plasma is currently unable to escape the nuclear regions of the galaxy. The steep low-frequency spectrum of the core is probably related to the origin of the compact double and suggests that both components are very sharply confined on both their inner and outer edges.

  6. Milli-Arcsecond Morphology and Structural Changes in a Complete Sample of Radio Sources

    NASA Astrophysics Data System (ADS)

    Pearson, T. J.; Readhead, A. C. S.; Barthel, P. D.; Conway, J. E.; Myers, S. T.

    1993-05-01

    We have conducted a VLBI survey of a complete, flux-density--limited sample of 65 extragalactic radio sources, selected at 5 GHz, in order to study their morphology and to look for superluminal motion and other structural changes. First-epoch images of 37 sources were published by Pearson & Readhead (1988, ApJ, 328, 114). Here we present 5-GHz images, with a resolution ~ 1 milliarcsec, taken at three epochs spread over 9 years for each of 25 sources. The majority of the sources have an asymmetric, core-jet morphology. Several of these are superluminal sources in which an emission feature moves outward along the jet at v_app > c (e.g., 0850+581, 1642+690, 1928+738, BL Lac, 3C 216, 3C 345). Several other sources with similar morphology, however, show no changes in relative positions of subcomponents, although subcomponent flux densities do change (e.g., 0711+356, 1652+398, 1823+568). We draw attention to a new class of ``compact symmetric'' objects with double or triple morphology (e.g., 0108+388, 0710+439, 2352+495). We have placed limits < c on relative motion of components in these sources, and they show little if any evidence for relativistic beaming. The central engine appears to lie midway between two lobes ~ 100 pc apart. The sample also includes some compact steep-spectrum sources and other sources that are difficult to classify.

  7. 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.

  8. 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.

  9. 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 (c) 2016 APA, all rights reserved).

  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. 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

  12. 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.

  13. 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

  14. High-cell-density fed-batch culture of Saccharomyces cerevisiae KV-25 using molasses and corn steep liquor.

    PubMed

    Vu, Van Hanh; Kim, Keun

    2009-12-01

    High-cell-density cultivation of yeast was investigated using the agricultural waste products corn steep liquor (CSL) and molasses. The Saccharomyces cerevisiae KV-25 cell mass was significantly dependent on the ratio between C and N sources. The concentrations of molasses and CSL in the culture medium were statistically optimized at 10.25% (v/v) and 16.87% (v/v), respectively, by response surface methodology (RSM). Batch culture in a 5-l stirred tank reactor using the optimized medium resulted in a cell mass production of 36.5 g/l. In the fed-batch culture, the feed phase was preceded by a batch phase using the optimized medium, and a very high dried-cell-mass yield of 187.63 g/l was successfully attained by feeding a mixture of 20% (v/v) molasses and 80% (v/v) CSL at a rate of 22 ml/h. In this system, the production of cell mass depended mainly on the agitation speed, the composition of the feed medium, and the glucose level in the medium, but only slightly on the aeration rate.

  15. Ethanol production from syngas by Clostridium strain P11 using corn steep liquor as a nutrient replacement to yeast extract.

    PubMed

    Maddipati, Prasanth; Atiyeh, Hasan K; Bellmer, Danielle D; Huhnke, Raymond L

    2011-06-01

    The feasibility of replacing yeast extract (YE) by corn steep liquor (CSL), a low cost nutrient source, for syngas fermentation to produce ethanol using Clostridium strain P11 was investigated. About 32% more ethanol (1.7 g L(-1)) was produced with 20 g L(-1) CSL media in 250-mL bottle fermentations compared to media with 1 g L(-1) YE after 360 h. Maximum ethanol concentrations after 360 h of fermentation in a 7.5-L fermentor with 10 and 20 g L(-1) CSL media were 8.6 and 9.6 g L(-1), respectively, which represent 57% and 60% of the theoretical ethanol yields from CO. Only about 6.1 g L(-1) of ethanol was obtained in the medium with 1 g L(-1) YE after 360 h, which represents 53% of the theoretical ethanol yield from CO. The use of CSL also enhanced butanol production by sevenfold compared to YE in bottle fermentations. These results demonstrate that CSL can replace YE as the primary medium component and significantly enhance ethanol production by Clostridium strain P11.

  16. 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.

  17. Imported chicken meat as a potential source of quinolone-resistant Escherichia coli producing extended-spectrum beta-lactamases in the UK.

    PubMed

    Warren, R E; Ensor, V M; O'Neill, P; Butler, V; Taylor, J; Nye, K; Harvey, M; Livermore, D M; Woodford, N; Hawkey, P M

    2008-03-01

    Escherichia coli producing CTX-M-15 enzyme began to rapidly spread in the UK from around 2003 but other types also occur, notably CTX-M-14. We examined breasts from UK-reared (n = 62) and imported (n = 27) chickens as potential sources of quinolone-resistant E. coli with bla(CTX-M) genes. A further 40 samples for which the country of rearing could not be identified were examined. During 2006, 129 fresh and frozen chicken breast fillets were purchased from retail outlets in the West Midlands. These were cultured for E. coli on CLED agar containing 8 mg/L ciprofloxacin and carrying a 10 microg cefpodoxime disc. Resistant isolates were identified and typed by RAPD fingerprinting; bla(CTX-M) was identified by PCR and genotyped by reverse-line hybridization. The country of rearing was identified from the packaging for 89 of 129 purchased samples. Only one of the 62 UK-reared chicken samples carried E. coli producing a CTX-M-1 enzyme, whereas 10 of 27 samples reared overseas had E. coli with CTX-M enzymes. Specifically, 4/10 Brazilian, 3/4 Brazilian/Polish/French, and 2/2 Dutch samples had E. coli with CTX-M-2 enzymes. Six of 40 samples for which the country of rearing was not known had producers of CTX-M enzymes, 5 of them with CTX-M-14. Quinolone-resistant E. coli with various CTX-M beta-lactamase genes that are common in human infections worldwide were found in imported chicken breasts, indicating a possible source for gut colonization. Samples from Brazil were commonly positive for E. coli with CTX-M-2, the dominant bla(CTX-M) genotype from human infections in South America, which is currently rare in clinical infections in the UK. CTX-M-15, the dominant CTX-M type in human infections in the UK, was not found in chicken isolates, suggesting that the UK-reared chickens are not a reservoir of CTX-M-15.

  18. A reduced complexity discrete particle model for understanding the sediment dynamics of steep upland river confluences

    NASA Astrophysics Data System (ADS)

    Tancock, M. J.; Lane, S. N.; Hardy, R. J.

    2012-12-01

    There has been a significant amount of research conducted in order to understand the flow fields at natural river confluences. Much of this has been made possible due to advances in the use of Computational Fluid Dynamics (CFD). However, much of this research has been conducted on river confluences with negligible water surface slopes and any understanding of the sediment dynamics is largely implied from the flow fields. Therefore, a key challenge is to understand the flow and sediment dynamics of steep river confluences with dynamic boundaries. Two numerical modelling developments are presented which together are capable of increasing our understanding of the sediment dynamics of steep river confluences. The first is the application of a Height-of-Liquid (HOL) model within a CFD framework to explicitly solve the water surface elevation. This is a time-dependent, multiphase treatment of the fluid dynamics which solves for the change in volume of water and air in each vertical column of the mesh. The second is the development of a reduced complexity discrete particle transport model which uses the change in momentum on a spherical particle to predict the transport paths through the flow field determined from CFD simulations. The performance of the two models is tested using field data from a series of highly dynamic, steep gravel-bed confluences on a braidplain of the Borgne d'Arolla, Switzerland. The HOL model is validated against the water surface elevation and flow velocity data and is demonstrated to provide a reliable representation of the flow field in fast-flowing, supercritical flows. In order to validate the discrete particle model, individual particles were tracked using electronic tacheometry. The model is demonstrated to accurately represent the particle tracks obtained in the field and provides a new methodology to understand the dynamic morphology of braid plains.

  19. Distributed snow and rock temperature modelling in steep rock walls using Alpine3D

    NASA Astrophysics Data System (ADS)

    Haberkorn, Anna; Wever, Nander; Hoelzle, Martin; Phillips, Marcia; Kenner, Robert; Bavay, Mathias; Lehning, Michael

    2017-02-01

    In this study we modelled the influence of the spatially and temporally heterogeneous snow cover on the surface energy balance and thus on rock temperatures in two rugged, steep rock walls on the Gemsstock ridge in the central Swiss Alps. The heterogeneous snow depth distribution in the rock walls was introduced to the distributed, process-based energy balance model Alpine3D with a precipitation scaling method based on snow depth data measured by terrestrial laser scanning. The influence of the snow cover on rock temperatures was investigated by comparing a snow-covered model scenario (precipitation input provided by precipitation scaling) with a snow-free (zero precipitation input) one. Model uncertainties are discussed and evaluated at both the point and spatial scales against 22 near-surface rock temperature measurements and high-resolution snow depth data from winter terrestrial laser scans.In the rough rock walls, the heterogeneously distributed snow cover was moderately well reproduced by Alpine3D with mean absolute errors ranging between 0.31 and 0.81 m. However, snow cover duration was reproduced well and, consequently, near-surface rock temperatures were modelled convincingly. Uncertainties in rock temperature modelling were found to be around 1.6 °C. Errors in snow cover modelling and hence in rock temperature simulations are explained by inadequate snow settlement due to linear precipitation scaling, missing lateral heat fluxes in the rock, and by errors caused by interpolation of shortwave radiation, wind and air temperature into the rock walls.Mean annual near-surface rock temperature increases were both measured and modelled in the steep rock walls as a consequence of a thick, long-lasting snow cover. Rock temperatures were 1.3-2.5 °C higher in the shaded and sunny rock walls, while comparing snow-covered to snow-free simulations. This helps to assess the potential error made in ground temperature modelling when neglecting snow in steep bedrock.

  20. Origin of steep-pointed and flat-topped volcanic cones in Southwest volcanic field

    NASA Astrophysics Data System (ADS)

    Fukui, U.; Hirota, F.; Yokose, H.

    2002-12-01

    KR01-12 cruise of Japan Marine Science and Technology Center using ROV KAIKO and its mother ship R/V KAIREI were carried out around Hawaii islands in the early fall of 2001. During this cruise, two dives of ROV KAIKO were made on southwest Oahu volcanic field (K203 and K206).The new Seabeam bathymetry revealed that there are remarkable topographic features: flat-topped volcanic cone, ca.2.5 in diameter and 200m in height; steep pointed cone, ellipsoidal in plain: major axis 2km, minor axis 0.5km; 200-400 m in height. This volcanic topographies are similar to those described in elsewhere e.g., Clague et al., 2001. Flat-topped cones distributed in this area are different from other area in their occurrence. They are accompanied with steep-pointed cone. In order to study the geological and petrological relationship between flat-topped cone and steep-pointed cone, both K203 and K206 have been analyzed by video image, thin sections and bulk rock chemistry. The rocks recovered from K206 and K203 are trachybasalt and basanite respectibly. There is no critical differences between FTVC and SPVCin their bulk chemistry. For example rocks from FTCV are almost identical to the SPCV in SiO2 contents in the same site. Total AK concentration of rocks from FTCV is lower than those of SPVC in K203, but FTVC is higher than SPCV in K206. This result implies that topographical characters are not correlated with bulk chemistry. Both in K206 or K203, rocks collected from SPVC have higher vesicularity, ranging from 20 to 40%, and higher crystallinity in groundmass than those from FTCV. It is suggest that differences in topographical characteristics between FTVC and SPVC are controlled by physical property of the groundmass. That is, the viscosity of magma lead to rise due to exsolution of gas phase from melt.

  1. Enhanced stability of steep channel beds to mass failure and debris flow initiation

    NASA Astrophysics Data System (ADS)

    Prancevic, J.; Lamb, M. P.; Ayoub, F.; Venditti, J. G.

    2015-12-01

    Debris flows dominate bedrock erosion and sediment transport in very steep mountain channels, and are often initiated from failure of channel-bed alluvium during storms. While several theoretical models exist to predict mass failures, few have been tested because observations of in-channel bed failures are extremely limited. To fill this gap in our understanding, we performed laboratory flume experiments to identify the conditions necessary to initiate bed failures in non-cohesive sediment of different sizes (D = 0.7 mm to 15 mm) on steep channel-bed slopes (S = 0.45 to 0.93) and in the presence of water flow. In beds composed of sand, failures occurred under sub-saturated conditions on steep bed slopes (S > 0.5) and under super-saturated conditions at lower slopes. In beds of gravel, however, failures occurred only under super-saturated conditions at all tested slopes, even those approaching the dry angle of repose. Consistent with theoretical models, mass failures under super-saturated conditions initiated along a failure plane approximately one grain-diameter below the bed surface, whereas the failure plane was located near the base of the bed under sub-saturated conditions. However, all experimental beds were more stable than predicted by 1-D infinite-slope stability models. In partially saturated sand, enhanced stability appears to result from suction stress. Enhanced stability in gravel may result from turbulent energy losses in pores or increased granular friction for failures that are shallow with respect to grain size. These grain-size dependent effects are not currently included in stability models for non-cohesive sediment, and they may help to explain better the timing and location of debris flow occurrence.

  2. 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

  3. Evaluation of effective energy for splash and sheet erosion on post-fire steep hillslopes

    NASA Astrophysics Data System (ADS)

    Shin, Seung Sook; Deog Park, Sang; Hwang, Yoonhee

    2017-04-01

    The interrill erosion by raindrop and surface runoff is not separated definitely due to the synchronous interaction of raindrop splash and sheet flow transport. On post-fire steep hillslopes of a various vegetation recovery the interaction is more complex. In this study the effective energies of rainfall and surface runoff were introduced to evaluate the contributions for splash and sheet erosion. The effective kinetic energy of rainfall inducing splash erosion was determined by horizontal component of slope for rainfall kinetic energy deducting energies dissipated by structure of vegetation canopies and a litter layer. The effective potential energy of surface runoff transporting soil particles was derived from potential energy of the available surface water following rain-mass allocations of interception and infiltration. The effective energy for splash and sheet erosion was defined as the sum of the effective kinetic energy of rainfall and effective potential energy of surface runoff. The data observed from experimental plots on steep hillslopes were used to evaluate the effective energies for interrill erosion. While sediment yield on densely vegetated slopes depended greatly on effective kinetic energy, they from hillslopes having sparse coverage were dominated by effective potential energy. The energy dissipated by soil erosion showed the highest correlation coefficient with the effective energy under various cover conditions. The kinetic energy of raindrops was greatly reduced by the litter layer and the potential energy of rainwater decreased predominantly due to infiltration. Effective kinetic energies were generally lower than effective potential energies. The average proportions of effective potential energy to total effective energy were respectively 68.7%, 43.1%, and 49.1% for the plots with low, middle, and high vegetation coverage. The energy efficiency for interrill erosion decreased with increasing vegetation coverage and showed high value under

  4. Anaerobic fermentative production of lactic acid using cheese whey and corn steep liquor.

    PubMed

    Agarwal, Lata; Dutt, Kakoli; Meghwanshi, Gautam K; Saxena, R K

    2008-04-01

    Cheese whey was the most suitable substrate for production of lactic acid under anaerobic conditions by Entercoccus flavescens which, on supplementating with corn steep liquor (5% v/v) and 10 mM CaCO(3) at pH 5.5, 37 degrees C, yielded 12.6 g lactic acid/l in 36 h. Production was scaled up to a 10 l bioreactor under controlled pH and continuous CO(2) supply and gave 28 g lactic acid/l in 30 h resulting in a net 8.7-fold increase in production as compared to unoptimized conditions.

  5. 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.

  6. Evaluation and Advancement of Similarity Scalings for a Steep Alpine Slope

    NASA Astrophysics Data System (ADS)

    Oldroyd, H. J.; Pardyjak, E.; Higgins, C. W.; Parlange, M. B.

    2014-12-01

    Monin-Obukhov similarity theory was initially developed for atmospheric boundary layer flows over flat and statistically homogeneous terrain, and verified with flux and profile measurements over such terrain. Even though 'flat and statistically homogeneous terrain' implies a very strict classification for real terrain to satisfy, Monin-Obukhov similarity theory has been shown to hold for a variety of flow situations outside of the narrow terrain categorizations of flows initially proposed. Furthermore, through the use of extended stability functions, it has been shown to hold even for specialized events in the stable boundary layer such as nonbreaking internal gravity waves and low-level jet formation over relatively flat terrain. The fact that it typically works, is one reason why Monin-Obukhov similarity scaling is so widely used in meteorological and hydrological modeling for real terrain, even when theoretically it should break down. Another reason why it is so widely used (potentially when it is inappropriate) is due to a lack of alternative, or more accurate, methodologies to relate the land surface forcing (boundary conditions) to the atmosphere in models. One such example for which Monin-Obukhov similarity theory has been shown to breakdown is steep slope flows. These steep slope flows are characterized by a very shallow jet layer, over which the fluxes vary by more than 10%, and the traditional 'constant-flux' surface layer is not observed. However, thermally driven slope flows exhibit a jet-like velocity profile. This suggests a 'universal' functionality, which could be revealed with the proper similarity scaling. The current work seeks to evaluate the validity of Monin-Obukhov similarity theory, with and without the extended stability functions and more recent similarity theories, proposed specifically for steep slope flows, using field data taken over a steep (35.5°) slope in Val Ferret, Switzerland. In addition, alternative, empirically driven, flux

  7. 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.

  8. Dynamic changes in phenolic compounds and antioxidant activity in oats (Avena nuda L.) during steeping and germination.

    PubMed

    Xu, Jian Guo; Tian, Cheng Rui; Hu, Qing Ping; Luo, Ji Yang; Wang, Xiang Dong; Tian, Xiang Dong

    2009-11-11

    Samples from naked oat were steeped and germinated under controlled conditions in an incubator. Changes of phenolic compounds and antioxidant activity were investigated in oats during steeping and germination. Results revealed that phenolic compounds and antioxidant activity of oats varied with the difference in steeping and germination stages. Compared with raw grains, short-term steeping treatment did not show significant effects (p > 0.05) on phenolic content. Germination can significantly result in the decrease in bound phenolic and the increase in free and total phenolics. Main phenolic acids and avenanthramides were isolated and quantified by HPLC analysis. During steeping, phenolic acids decreased (p < 0.05); avenanthramide N-(3',4'-dihydroxy)-(E)-cinnamoyl-5-hydroxyanthranilic acid first decreased and then increased (p < 0.05), while avenanthramides N-(4'-hydroxy)-(E)-cinnamoyl-5-hydroxyanthranilic acid and N-(4'-hydroxy-3'-methoxy)-(E)-cinnamoyl-5-hydroxyanthranilic acid did not change significantly (p > 0.05). During germination, gallic and caffeic acids first increased (p < 0.05) and then decreased, whereas p-coumaric and ferulic acids and avenanthramides increased (p < 0.05). Nevertheless, avenanthramides did not change significantly (p > 0.05) during the last stage of germination. Oat extracts exhibited increasing high antioxidant activity with the steeping and germination going on, which may explain that antioxidant activity correlated (p < 0.01) significantly with the content of phenolic compounds.

  9. Optimization of a corn steep medium for production of ethanol from synthesis gas fermentation by Clostridium ragsdalei.

    PubMed

    Saxena, Jyotisna; Tanner, Ralph S

    2012-04-01

    Fermentation of biomass derived synthesis gas to ethanol is a sustainable approach that can provide more usable energy and environmental benefits than food-based biofuels. The effects of various medium components on ethanol production by Clostridium ragsdalei utilizing syngas components (CO:CO(2)) were investigated, and corn steep liquor (CSL) was used as an inexpensive nutrient source for ethanol production by C. ragsdalei. Elimination of Mg(2+), NH(4) (+) and PO(4) (3-) decreased ethanol production from 38 to 3.7, 23 and 5.93 mM, respectively. Eliminating Na(+), Ca(2+), and K(+) or increasing Ca(2+), Mg(2+), K(+), NH(4) (+) and PO(4) (3-) concentrations had no effect on ethanol production. However, increased Na(+) concentration (171 mM) inhibited growth and ethanol production. Yeast extract (0.5 g l(-1)) and trace metals were necessary for growth of C. ragsdalei. CSL alone did not support growth and ethanol production. Nutrients limiting in CSL were trace metals, NH(4) (+) and reducing agent (Cys: cysteine sulfide). Supplementation of trace metals, NH(4) (+) and CyS to CSL (20 g l(-1), wet weight basis) yielded better growth and similar ethanol production as compared to control medium. Using 10 g l(-1), the nutritional limitation led to reduced ethanol production. Higher concentrations of CSL (50 and 100 g l(-1)) were inhibitory for cell growth and ethanol production. The CSL could replace yeast extract, vitamins and minerals (excluding NH(4) (+)). The optimized CSL medium produced 120 and 50 mM of ethanol and acetate, respectively. The CSL could provide as an inexpensive source of most of the nutrients required for the syngas fermentation, and thus could improve the economics of ethanol production from biomass derived synthesis gas by C. ragsdalei.

  10. Hysteresis in both sediment transport and water turbulence contribute to seismic hysteresis in a steep mountain stream

    NASA Astrophysics Data System (ADS)

    Roth, D. L.; Finnegan, N. J.; Brodsky, E. E.; Rickenmann, D.; Turowski, J. M.; Badoux, A.; Gimbert, F.

    2016-12-01

    Hysteresis in the relationship between bedload transport and river stage is a well-documented phenomenon with multiple known causes. Consequently, numerous studies have suggested that hysteresis observed in the relationship between seismic amplitudes recorded near rivers and some measure of flow strength (i.e., discharge or stage) is the signature of bedload transport. We use a metric (Ψ) for the normalized magnitude of hysteresis during individual transport events in the Erlenbach stream (local slope 10%) in the Swiss Prealps to compare hysteresis found in seismic data with hysteresis in in-bed geophone plate system recordings, a well-calibrated proxy for direct sediment transport measurements. We find that while both the geophones and seismometers demonstrate hysteresis, the magnitude and direction of hysteresis are not correlated between these data, indicating that an additional source of hysteresis must be present in the seismic signal. Seismic hysteresis also does not correlate with the magnitude of sediment transport recorded by the geophones, contrary to previous studies' assumptions. Our results indicate that hydrologic sources and changes in water turbulence due to evolving boundary conditions at the bed, rather than changes in sediment transport rates, may sometimes contribute to or even dominate the hysteresis observed in seismic amplitudes near rivers. This appears to be especially relevant in steep rivers where the flow depth is low or comparable to the largest roughness elements on the bed, or where highly turbulent features such as waterfalls or cascades may contribute significantly to the seismic signal. These effects must be better understood in order to determine the extent to which seismic hysteresis may relate to sediment transport rates in different fluvial settings and improve our ability to assess bedload transport and bed evolution through hysteresis in seismic signals near rivers.

  11. 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; hide

    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

  12. 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.

  13. Low-flow hydraulic geometry of small, steep mountain streams in southwest British Columbia

    NASA Astrophysics Data System (ADS)

    Reid, Donald E.; Hickin, Edward J.; Babakaiff, Scott C.

    2010-10-01

    This investigation explores the at-a-station hydraulic geometry (AHG) of small, steep mountain streams at low discharge. Thirteen reaches in five tributaries of Chilliwack River, British Columbia, ranging in size from 12 to 77 km 2 are examined. The resulting data set is composed of eight to twelve measurements of water-surface width, mean depth, and mean velocity at each of 61 cross sections or 625 unique combinations of the three variables. Mean velocity in a given cross section responds most rapidly to changing discharge, and 31 of the 61 cross sections have velocity exponents that are greater than the water-surface width and mean-depth exponents combined. The velocity exponent ( m) averages 0.51, while the mean water-surface width exponent ( b) and mean-depth exponent ( f) average 0.20 and 0.29, respectively. Somewhat surprisingly, the AHG of steep mountain streams can be reasonably predicted from just a few measurements of the primary flow variables and stream discharge. While conditions at the cross section appear predictable from a few measurements, extrapolating the results from one cross section to another in the same reach involves large errors. The section-to-section variability of the exponents and coefficients, even when they are located in similar channel units such as riffles, prevents accurate extrapolation to unmeasured cross sections.

  14. 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.

  15. Polyphenolic Profile and Antioxidant Activities of Oolong Tea Infusion under Various Steeping Conditions

    PubMed Central

    Su, Xinguo; Duan, Jun; Jiang, Yueming; Duan, Xuewu; Chen, Feng

    2007-01-01

    The phenolic profile and antioxidant activities of oolong tea extract were investigated after tea was steeped in 90 or 100 °C water for 3 or 10 min. The extraction yield increased with increasing temperature and extended steeping time. However, higher temperature and longer time (100 °C water for 10 min) led to loss of phenolics. The aqueous extract of oolong tea (AEOT) at 100 °C for 3 min exhibited the strongest antioxidant activity. The major polyphenolic components of the AEOT were identified as (−)-epigallocatechin (EGC), (−)-epigallocatechin gallate (EGCG) and (−)-epicatechin-3-gallate (ECG). The two major catechins (EGC and EGCG) in the tea infusion contributed significantly to the investigated antioxidant activities [i.e., the 2,2-diphenyl-2-picrylhydrazyl hydrate (DPPH) radical scavenging and superoxide radical scavenging activities] with high correlation values in r = 0.9486 and 0.9327 for the EGC and r = 0.9592 and 0.8718 for the EGCG, respectively.

  16. Transforming gate misalignment into a unique opportunity to facilitate steep switching in junctionless nanotransistors

    NASA Astrophysics Data System (ADS)

    Gupta, Manish; Kranti, Abhinav

    2016-11-01

    In this work, we examine the feasibility of triggering impact ionisation at sub-bandgap voltages through optimal utilisation of structural non-ideality induced electric field redistribution in the semiconductor film for an energy efficient steep switching junctionless (JL) transistor. While misalignment between front and back gates is often considered as a disadvantage due to loss of gate controllability, the work highlights its usefulness and applicability in nanoscale devices to engineer the electric field to enhance the product of current density (J) and electric field (E) and activate impact ionisation at sub-bandgap applied voltages. Results show that intentionally misaligned gates in silicon and germanium based JL devices exhibit an inclined conduction channel and achieve a nearly ideal value of steep subthreshold swing (˜ 1 mV decade-1) at room temperature. The work provides new viewpoints to realise energy efficient JL devices through the sharp increase of drain current from off-state to on-state achieved due to intentional misalignment between front and back gates.

  17. Stability of Steep Gravity--Capillary Solitary Waves in Deep Water

    NASA Astrophysics Data System (ADS)

    Akylas, T. R.; Calvo, D. C.

    2000-11-01

    The stability of steep gravity--capillary solitary waves in deep water is numerically investigated using the full nonlinear water-wave equations with surface tension. As was found in prior work based on model equations for small-amplitude solitary waves in shallow water, out of the two solution branches that bifurcate at the minimum gravity--capillary phase speed, solitary waves of depression again turn out to be stable while those of elevation are unstable to small disturbances. Motivated by the experiments of Longuet-Higgins & Zhang (Phys. Fluids 9:1963--1968, 1997), we also consider the forced problem of a localised pressure distribution applied to the free surface of a stream with speed below the minimum gravity--capillary phase speed. We find that the finite-amplitude forced solitary-wave solution branch computed by Vanden-Broeck & Dias (J. Fluid Mech. 240:549--557, 1992) is unstable but the branch corresponding to Rayleigh's linearised solution is stable. The significance of viscous effects is assessed; the effects of instability in steep waves generally are comparable to, and in some cases greater than, those of dissipation. These findings are discussed in connection with the experimental observations of Longuet-Higgins & Zhang.

  18. 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.

  19. 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.

  20. Rehabilitation and Flood Management Planning in a Steep, Boulder-Bedded Stream

    NASA Astrophysics Data System (ADS)

    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.

  1. Flat-top steep-edge response of photodetetors by circuit control method

    NASA Astrophysics Data System (ADS)

    Wang, Li; Huang, Yongqing; Duan, Xiaofeng; Yan, Qiang; Ren, Xiaomin; Huang, Hui; Wang, Qi; Zhang, Xia

    2010-10-01

    This paper proposes a circuit control method achieving the flat-top steep-edge response of photodetectors. The response is realized using three wavelength selective photodetectors and the circuit which consists of amplifiers, comparators and a AND gate. Two groups of experiments were carried out. In group 1, 0.5dB, 3dB, 20dB bandwidths are 2.76nm, 3.29nm, 4.58nm from 1546nm to 1549.3nm. In group 2, 0.5dB, 3dB, 20dB bandwidths are 3.19nm, 2.89nm, 3.06nm from 1554.8nm to 1557.6nm. The results of experiments show that the desirable flat-top steep-edge response can be gained and the response linewidth is adjustable by selecting different photodetectors, so that the requirement of the WDM system and the network can be met. The method is easy to realize with low cost and has wide application in optical measurements and optical processing etc.

  2. Steep slope flow observations during the morning transition in a narrow alpine valley

    NASA Astrophysics Data System (ADS)

    Oldroyd, H. J.; Pardyjak, E.; Calaf, M.; Nadeau, D. F.; Hultmark, M.; Parlange, M. B.

    2012-12-01

    Thermally driven diurnal patterns of slope and valley flows under weak synoptic forcing have been well documented, and are important to local hydrological processes and pollutant transport. However, the smaller scale turbulent processes driving these patterns have received less attention, especially over steep terrain in complex environments during unsteady, transitional periods. Summertime measurements over a steep slope (~40°) in a narrow alpine valley (Val Ferret, Switzerland) were taken to investigate the underlying physics associated the morning transition from katabatic to anabatic winds. The thermally driven diurnal patterns at this site are characterized by weak downslope flow at night and stronger up-valley winds with an upslope component during the day. The topography of the valley results in uneven heating during the morning transition, and the slope site is one of the last places to receive direct solar radiation. Hence, the relative timing and locations of solar incidence (diffuse and direct) in the valley play an important role in the various mechanisms which breakup the stable stratification and development of the anabatic winds in the valley and at the slope site. In addition, terms in the budget equations of heat, momentum, and turbulence kinetic energy (TKE) are calculated to reveal the balances of forces and energy that drive the flows during the morning transition.

  3. Fast and local non-linear evolution of steep wave-groups on deep water: A comparison of approximate models to fully non-linear simulations

    SciTech Connect

    Adcock, T. A. A.; Taylor, P. H.

    2016-01-15

    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.

  4. On the Nature of Neutral-Line-Associated Radio Sources

    NASA Astrophysics Data System (ADS)

    Yasnov, Leonid V.

    2014-04-01

    A number of authors claimed that radio sources above the neutral line of the magnetic field in solar active regions are due to non-thermal emission. This study shows that the thermal mechanism explains the radio emission from such sources. Models similar to those used for interpreting cyclotron lines were used in this study. Such models account for a steep decline in the spectrum at high frequencies and a low degree of polarization. The magnetic field between the two sunspots with an anti-parallel magnetic field has a lower gradient than the field above the sunspots. This, combined with the possibly high temperature in coronal loops connecting the sunspots, leads to the following conclusions. The optical thickness of the gyroresonance layers is increased and leads to more effective radiation at a harmonic number of 4 or 5. The lower gradient of the field between the sunspots also results in more rapid growth of emission intensity with increasing wavelength in this region than in the regions immediately above the sunspots. Additionally, the spatial averaging of the source structure due to the antenna beam pattern leads to a decrease in the degree of polarization in the region between the sunspots.

  5. Deep observations of the Super-CLASS supercluster at 325 MHz with the GMRT: the low-frequency source catalogue

    NASA Astrophysics Data System (ADS)

    Riseley, C. J.; Scaife, A. M. M.; Hales, C. A.; Harrison, I.; Birkinshaw, M.; Battye, R. A.; Beswick, R. J.; Brown, M. L.; Casey, C. M.; Chapman, S. C.; Demetroullas, C.; Hung, C.-L.; Jackson, N. J.; Muxlow, T.; Watson, B.

    2016-10-01

    We present the results of 325 MHz Giant Metrewave Radio Telescope observations of a supercluster field, known to contain five Abell clusters at redshift z ˜ 0.2. We achieve a nominal sensitivity of 34 μJy beam-1 towards the phase centre. We compile a catalogue of 3257 sources with flux densities in the range 183 μ {Jy}-1.5 {Jy} within the entire ˜6.5 deg2 field of view. Subsequently, we use available survey data at other frequencies to derive the spectral index distribution for a sub-sample of these sources, recovering two distinct populations - a dominant population which exhibit spectral index trends typical of steep-spectrum synchrotron emission, and a smaller population of sources with typically flat or rising spectra. We identify a number of sources with ultrasteep spectra or rising spectra for further analysis, finding two candidate high-redshift radio galaxies and three gigahertz-peaked-spectrum radio sources. Finally, we derive the Euclidean-normalized differential source counts using the catalogue compiled in this work, for sources with flux densities in excess of 223 μJy. Our differential source counts are consistent with both previous observations at this frequency and models of the low-frequency source population. These represent the deepest source counts yet derived at 325 MHz. Our source counts exhibit the well-known flattening at mJy flux densities, consistent with an emerging population of star-forming galaxies; we also find marginal evidence of a downturn at flux densities below 308 μJy, a feature so far only seen at 1.4 GHz.

  6. On the formulation of new explicit conditions for steepness from a former result of N.N. Nekhoroshev

    NASA Astrophysics Data System (ADS)

    Schirinzi, Gabriella; Guzzo, Massimiliano

    2013-07-01

    The application of the Nekhoroshev theorem to many problems arising in different fields of Physics and Astronomy depends on a non-degeneracy property, called steepness, that a suitable Hamiltonian approximation must satisfy. Since steepness is implicitly defined, we have the problem of recognizing whether a given function is steep or not. For this purpose, we here consider some sufficient conditions for steepness provided by Nekhoroshev in 1979, based on the solvability of a collection of systems depending on the number n of degrees of freedom, the derivatives of the function up to a certain order r, and some auxiliary parameters. These conditions are really explicit only for r = 2, corresponding to quasi-convexity, and for r = 3. Instead, for r ⩾ 4, the conditions are implicit, since they require an elaborate computation of the closure of a certain set. In this paper, we first revisit Nekhoroshev's result and we show that the number of parameters in the collections of systems can be suitably reduced. Then, we show that for r = 4 Nekhoroshev's result is interesting only for n = 2, 3, and 4, and in these cases we find explicit conditions for steepness which are formulated in a purely algebraic form.

  7. Dynamic changes in gamma-aminobutyric acid and glutamate decarboxylase activity in oats (Avena nuda L.) during steeping and germination.

    PubMed

    Xu, Jian Guo; Hu, Qing Ping; Duan, Jiang Lian; Tian, Cheng Rui

    2010-09-08

    Gamma-aminobutyric acid (GABA) is the principal inhibitory neurotransmitter in the central nervous system and provides beneficial effects for human and other animals health. To accumulate GABA, samples from two different naked oat cultivars, Baiyan II and Bayou I, were steeped and germinated in an incubator. The content of GABA and glutamic acid as well as the activity of the glutamate decarboxylase (GAD) in oats during steeping and germination were investigated with an amino acid automatic analyzer. Compared with raw groats, an increase in GABA content of oat groats during steeping and germination was continuously observed for two oat cultivars. The activity of GAD increased greatly at the end of steeping and the second stage of germination for Baiyan II and Bayou I, respectively. Glutamic acid content of treated oat groats was significantly lower than that in raw groats until the later period of germination. GABA was correlated (p<0.01) significantly and positively with the glutamic acid rather than GAD activity in the current study. The results indicates that steeping and germination process under highly controlled conditions can effectively accumulate the GABA in oat groats for Baiyan II and Bayou I, which would greatly facilitate production of nutraceuticals or food ingredients that enable consumers to gain greater access to the health benefits of oats. However, more assays need to be further performed with more oat cultivars.

  8. 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.

  9. 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.

  10. Arc magmatism associated with steep subduction: Insights from trace element and Sr-Nd-Hf-B isotope systematics

    NASA Astrophysics Data System (ADS)

    Zhang, Yunying; Yuan, Chao; Sun, Min; Long, Xiaoping; Wang, Yunpeng; Jiang, Yingde; Lin, Zhengfan

    2017-03-01

    Subduction zones are the major sites for elemental cycling via slab dehydration and subsequent mantle metasomatism and melting. However, the nature of slab fluids associated with steep subduction remains largely unknown. To clarify this issue, we present an integrated study for Late Paleozoic (318-312 Ma) intermediate dykes from the Beishan orogenic collage, NW China. The dykes consist mainly of dioritic and granodioritic rocks. The dioritic dykes exhibit typical subduction-like geochemical signatures, together with relatively high Mg#, high ɛNd(t) and ɛHf(t), and low initial Sr isotopes, suggesting that they originated probably from a subduction-modified mantle. The granodioritic dykes exhibit high Mg#, high Sr/Y, La/Yb, and Na2O/K2O ratios, low Y and Yb contents, and mid-ocean ridge basalt-like Sr-Nd isotopes and high zircon ɛHf(t), similar to slab-derived adakite, indicating that they were likely formed by partial melting of subducted oceanic crust. The coeval adakitic and normal dioritic dykes reflect a thermal anomaly that was probably caused by rollback of subducted oceanic slab. The dioritic dykes have δ11B values from -7.7 to -6.4‰, whereas the adakitic dykes have relatively high δ11B values from -6.9 to -4.4‰. The δ11B values of adakitic dykes are lower than those of typical altered oceanic crust, in agreement with the expected loss of 11B from subducted oceanic slab during early subduction. Results of a mixing model suggest that the mantle source of the dioritic dykes has been hybridized by 11B-depleted fluids expelled from a highly dehydrated slab at deep depth, owing to the high-angle dip of the subducting oceanic slab.

  11. 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.

  12. Fast, three-dimensional, MR Imaging for polymer gel dosimetric applications involving high dose and steep dose gradients

    NASA Astrophysics Data System (ADS)

    Sandilos, Panagiotis; Baras, Panagiotis; Georgiou, Evangelos; Dardoufas, Konstantinos; Karaiskos, Pantelis; Papagiannis, Panagiotis; Paschalis, Theodoros; Tatsis, Elias; Torrens, Michael; Vlahos, Lampros

    2006-12-01

    Polymer gels constitute water equivalent integrating detectors, which, combined with magnetic resonance imaging (MRI), can provide accurate three dimensional (3D) dose distributions in contemporary radiotherapy applications where the small field dimensions and steep dose gradients induce limitations to conventional dosimeters. One of the main obstacles for adapting the method for routine use in the clinical setting is the cost effectiveness of the MRI readout method. Currently, optimized Carr-Purcell-Meiboom-Gill (CPMG) multiple spin echo imaging pulse sequences are commonly used which however result in long imaging times. This work evaluates the efficiency of 3D, dual-echo, k-space segmented turbo spin echo (TSE) scanning sequences for accurate dosimetry with sub-millimetre spatial resolution in strenuous radiation therapy applications. PABIG polymer gel dosimeters were irradiated with an 192Ir High Dose Rate brachytherapy source, the 4 mm and 8 mm collimator helmets of a gamma knife unit and a custom made x-knife collimator of 1 cm diameter. Profile and dose distribution measurements using TSE are benchmarked against corresponding findings obtained by the commonly used, but time consuming, CPMG sequence as well as treatment planning calculations, Monte Carlo (MC) simulations and film measurements. The implementation of a high Turbo factor was found to provide comparable accuracy, allowing a 64-fold MRI scan acceleration compared to conventional multi-echo sequences. The availability of TSE sequences in typical MRI installations greatly facilitates the introduction of polymer gel dosimetry in the clinical environment as a practicable tool for the determination of full 3D dose distributions in contemporary radiotherapy applications.

  13. Discovery of a Highly Variable Dipping Ultraluminous X-Ray Source in M94

    NASA Astrophysics Data System (ADS)

    Lin, Dacheng; Irwin, Jimmy A.; Webb, Natalie A.; Barret, Didier; Remillard, Ronald A.

    2013-12-01

    We report the discovery of a new ultraluminous X-ray source (ULX) 2XMM J125048.6+410743 within the spiral galaxy M94. The source has been observed by ROSAT, Chandra, and XMM-Newton on several occasions, exhibiting as a highly variable persistent source or a recurrent transient with a flux variation factor of gsim100, a high duty cycle (at least ~70%), and a peak luminosity of L X ~ 2 × 1039 erg s-1 (0.2-10 keV, absorbed). In the brightest observation, the source is similar to typical low-luminosity ULXs, with the spectrum showing a high-energy cutoff but harder than that from a standard accretion disk. There are also sporadical short dips, accompanied by spectral softening. In a fainter observation with L X ~ 3.6 × 1038 erg s-1, the source appears softer and is probably in the thermal state seen in Galactic black hole X-ray binaries (BHBs). In an even fainter observation (L X ~ 9 × 1037 erg s-1), the spectrum is harder again, and the source might be in the steep-power-law state or the hard state of BHBs. In this observation, the light curve might exhibit ~7 hr (quasi-)periodic large modulations over two cycles. The source also has a possible point-like optical counterpart from Hubble Space Telescope images. In terms of the colors and the luminosity, the counterpart is probably a G8 supergiant or a compact red globular cluster containing ~2 × 105 K dwarfs, with some possible weak UV excess that might be ascribed to accretion activity. Thus, our source is a candidate stellar-mass BHB with a supergiant companion or with a dwarf companion residing in a globular cluster. Our study supports that some low-luminosity ULXs are supercritically accreting stellar-mass BHBs.

  14. A preliminary attempt to interpret the power spectrum of the solar five minute oscillations in terms of the global oscillation model

    NASA Technical Reports Server (NTRS)

    Kesley, D. A.

    1980-01-01

    The observed power spectrum of the solar five minute oscillations is discussed from the viewpoint that the oscillations are excited by turbulent convection. The observations place significant constraints on the theory and suggest constraints on the solar model structure. It is shown that the steep low frequency side of the peak in the power spectrum is more readily explained if the mixing length is greater than one scale height. The high frequency end of the power spectrum is also discussed.

  15. 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.

  16. 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.

  17. 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.

  18. Operation regimes and electrical transport of steep slope Schottky Si-FinFETs

    NASA Astrophysics Data System (ADS)

    Jeon, Dae-Young; Zhang, Jian; Trommer, Jens; Park, So Jeong; Gaillardon, Pierre-Emmanuel; De Micheli, Giovanni; Mikolajick, Thomas; Weber, Walter M.

    2017-02-01

    In the quest for energy efficient circuits, considerable focus has been given to steep slope and polarity-controllable devices, targeting low supply voltages and reduction of transistor count. The recently proposed concept of the three-independent gated Si-FinFETs with Schottky-barriers (SBs) has proven to bring both functionalities even in a single device. However, the complex combination of transport properties including Schottky emission and weak impact ionization as well as the body effect makes the design of such devices challenging. In this work, we perform a deep electrical characterization analysis to visualize and decouple the different operation regimes and electrical properties of the SB Si-FinFETs using a graphical transport map. From these, we give important guidelines for the design of future devices.

  19. 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.

  20. Non-linear random wave kinematics models verified against measurements in steep waves

    SciTech Connect

    Stansberg, C.T.

    1996-12-31

    Measurements from an earlier experiment on random wave kinematics are compared to four different numerical wave models. The models are: Second-order random wave model, Hybrid wave model, Wheeler stretching, and a modified Wheeler stretching method. Wave elevation, horizontal fluid particle velocities and corresponding accelerations in steep individual waves are included in the comparison. Spatial velocity profiles, as well as time history profiles showing the kinematics at certain fixed vertical levels, are shown. It is found that the second order and the hybrid wave models generally predict the measured kinematics (velocities as well as accelerations) reasonably well. The Wheeler stretching method predicts velocities quite well at the free surface of crest peaks, while it underpredicts the velocities further below in the wave zone fluid. With the modified Wheeler stretching procedure this is improved.

  1. 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.

  2. 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

  3. Steep switching characteristics of single-gated feedback field-effect transistors

    NASA Astrophysics Data System (ADS)

    Kim, Minsuk; Kim, Yoonjoong; Lim, Doohyeok; Woo, Sola; Cho, Kyoungah; Kim, Sangsig

    2017-02-01

    In this study, we propose newly designed feedback field-effect transistors that utilize the positive feedback of charge carriers in single-gated silicon channels to achieve steep switching behaviors. The band diagram, I-V characteristics, subthreshold swing, and on/off current ratio are analyzed using a commercial device simulator. Our proposed feedback field-effect transistors exhibit subthreshold swings of less than 0.1 mV dec-1, an on/off current ratio of approximately 1011, and an on-current of approximately 10-4 A at room temperature, demonstrating that the switching characteristics are superior to those of other silicon-based devices. In addition, the device parameters that affect the device performance, hysteresis characteristics, and temperature-dependent device characteristics are discussed in detail.

  4. 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.

  5. Simulation of cable and winding response to steep-fronted voltage waves

    SciTech Connect

    Hyypio, D.B.

    1995-12-31

    The detrimental effect of steep-fronted voltage waves impinging on machine windings has become a subject of concern with the advent of fast switching IGBT inverters. A simulation model using finite difference techniques has been developed which predicts observed phenomena such as machine terminal overvoltage transients and nonuniform voltage distribution within the winding. This analysis tool, unlike previous methods discussed under the background survey section of the paper, includes the feeder cable as part of the simulation to reveal the effect of its characteristic impedance and length upon the temporal machine winding voltage distribution. Simulation results are compared to actual measurement. The use of this tool in inverter waveshaping, cable selection and winding design is briefly considered.

  6. 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.

  7. Development of a digital integrated automatic landing system /DIALS/ for steep approach and landing

    NASA Technical Reports Server (NTRS)

    Halyo, N.; Hueschen, R. M.

    1981-01-01

    This paper describes the development of a three-dimensional digital integrated automatic landing system (DIALS) for a small commercial jet transport. The system uses the Microwave Landing System (MLS), body-mounted accelerometers, as well as on-board sensors usually available on commercial aircraft, but does not require inertial platforms. The system development uses modern digital control techniques. The phases of flight considered are the localizer and glideslope capture, which may be performed simultaneously or sequentially, localizer and glideslope track (hold), crab/decrab, and flare to touchdown. The system captures, tracks and flares from steep glideslopes (2.5 - 5.5 deg) selected prior to glideslope capture. The results of a nonlinear simulation are presented.

  8. 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.

  9. Utilization of the buffering capacity of corn steep liquor in bacterial cellulose production by Acetobacter xylinum.

    PubMed

    Noro, N; Sugano, Y; Shoda, M

    2004-04-01

    Acetobacter xylinum BPR2001 produces water-insoluble bacterial cellulose (BC). Using a pH sensor for the accurate control of pH, which is one of the most critical factors for efficient BC production, is difficult especially in a baffled shake-flask and an airlift reactor. The buffering capacity of corn steep liquor (CSL) was estimated by measuring beta (buffering capacity) values in advance and was used to maintain the pH within the optimal range during the production of BC. When CSL was added to either a shake-flask, a stirred-tank reactor or an airlift reactor, BC production was almost the same as that in cultivations where pH was controlled manually or by a pH sensor.

  10. Collisionless absorption of light waves incident on overdense plasmas with steep density gradients

    SciTech Connect

    Yang, T.Y.B.; Kruer, W.L.; Langdon, A.B.

    1995-07-31

    Collisionless absorption of laser light incident on overdense plasmas with steep density gradients is studied analytically and numerically. For the normal incidence case, it is shown that both sheath inverse bremsstrahlung and the anomalous skin effect are limiting cases of the same collisionless absorption mechanism. Using particle-in-cell (PIC) plasma simulations, the effects of finite sheath-transit time and finite density gradient are investigated. The analyses are extended to oblique incident cases. For p-polarized obliquely incident light, the results are significantly different from those for the normal incidence case. Most noticeable is the absorption enhancement for the p-polarized light due to the interaction of the electrons with the normal (parallel to the density gradient) component of the laser electric field in the sheath region.

  11. 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.

  12. 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

  13. Rainfall-Runoff and Slope Failure in a Steep, Tropical Landscape

    NASA Astrophysics Data System (ADS)

    Deane, J.; Freyberg, D. L.

    2016-12-01

    Tropical forests are often located on short, steep slopes with pronounced heterogeneity in vegetation over small distances. Further, they are distinguished from their temperate counterparts by a thinner organic horizon, and large interannual and subseasonal variability in precipitation. However, hydrologic processes in tropical watersheds are difficult to quantify and study because of data scarcity, accessibility difficulties and complex topography. As a result, there has been little work on disentangling the effects of spatial and temporal heterogeneity on flow generation and slope failure on tropical hillslopes. In this work we analyze the connections between terrain properties, subsurface formation, land cover, and precipitation variability in changing water table dynamics at the interface between a thin soil mantle and underlying bedrock. We have developed a fully distributed integrated hydrologic model at two different scales: 1) a 100 m idealized hillslope (1 m model grid size) representative of physiographic regions on tropical islands and 2) a 48 sq. km tropical island watershed in Trinidad and Tobago (30 m model grid size) using ParFlow.CLM. Additionally, we couple Parflow to an infinite slope stability module to investigate the initiation of rainfall induced landslides under different precipitation scenarios. The characteristic hillslopes are used to used to generalize the near subsurface response of a soil-saprolite aquifer to a range of landscape properties. In particular, we investigate the role of mean slope, soil properties and road cuts in altering the partitioning of runoff and infiltration, and increasing slope stability. Moving from the idealized models to the steep tropical watershed, we evaluate the effects of different land cover and precipitation scenarios—consistent with climate change projections—on flooding and hillslope failure incidence.

  14. Distribution of the failure scars on the steep loess slope: influences of topography and rainfall

    NASA Astrophysics Data System (ADS)

    Xu, Xiang-Zhou; Ma, Yu-Lei; Wang, Wen-Jun; Zhang, Hong-Wu

    2017-04-01

    The failure scar morphologies have long been a controversial topic on the Loess Plateau of China. However, the lack of normative data tests has hampered this vital field of research in the area. This study conducted a series of experiments in the laboratory to observe the sliding surfaces of different slope geometries and rainfalls and then performed a sensitivity analysis to quantitatively explore the triggering mechanisms of failure scars on the steep loess slope. The following six types of failure scar were found: translational face (Tf), upper concave (Uc), lower concave (Lc), polygonal-side (Ps), convex (Co) and irregular appearance (Ia). The sum occurrences of gravity erosion in an experiment corresponding to the failure scars Tf, Lc, Uc, Ia, Ps and Co amounted to 46, 27, 21, 3, 2 and 1% of the total, respectively. Meanwhile, the aggregate amounts of gravity erosion in an experiment corresponding to the failure scars Tf, Uc, Lc, Ps, Ia and Co amounted to 59, 18, 17, 3, 2 and 1% of the total. This implies that Tf, Uc and Lc were three major types of failure scar happening in the processes of gravity erosion on the steep loess slope, and especially the Tf was the most decisive one. For the occurrence in an experiment, the sensitivity parameters of slope height, slope gradient, rainfall duration and rainfall intensity on Tf, Lc, Uc, Ia, Ps and Co were comparable, which were from 0.3 to 4.0. Nevertheless, for the total amount in an experiment, the sensitivity parameters on Tf of slope gradient and rainfall intensity are outstanding, which were 5.5 and 3.7, respectively. That's to say, a relative dangerous failure scar, Tf, might appear if the slope grew steeper, or the rainfall became more intensive. The results provide an important implication for controlling the gravity erosion on gully slopes on the Loess Plateau.

  15. Quantifying irreversible movement in steep, fractured bedrock permafrost on Matterhorn (CH)

    NASA Astrophysics Data System (ADS)

    Weber, Samuel; Beutel, Jan; Faillettaz, Jérome; Hasler, Andreas; Krautblatter, Michael; Vieli, Andreas

    2017-02-01

    Understanding rock slope kinematics in steep, fractured bedrock permafrost is a challenging task. Recent laboratory studies have provided enhanced understanding of rock fatigue and fracturing in cold environments but were not successfully confirmed by field studies. This study presents a unique time series of fracture kinematics, rock temperatures and environmental conditions at 3500 m a. s. l. on the steep, strongly fractured Hörnligrat of the Matterhorn (Swiss Alps). Thanks to 8 years of continuous data, the longer-term evolution of fracture kinematics in permafrost can be analyzed with an unprecedented level of detail. Evidence for common trends in spatiotemporal pattern of fracture kinematics could be found: a partly reversible seasonal movement can be observed at all locations, with variable amplitudes. In the wider context of rock slope stability assessment, we propose separating reversible (elastic) components of fracture kinematics, caused by thermoelastic strains, from the irreversible (plastic) component due to other processes. A regression analysis between temperature and fracture displacement shows that all instrumented fractures exhibit reversible displacements that dominate fracture kinematics in winter. Furthermore, removing this reversible component from the observed displacement enables us to quantify the irreversible component. From this, a new metric - termed index of irreversibility - is proposed to quantify relative irreversibility of fracture kinematics. This new index can identify periods when fracture displacements are dominated by irreversible processes. For many sensors, irreversible enhanced fracture displacement is observed in summer and its initiation coincides with the onset of positive rock temperatures. This likely indicates thawing-related processes, such as meltwater percolation into fractures, as a forcing mechanism for irreversible displacements. For a few instrumented fractures, irreversible displacements were found at the

  16. Impacts of rainfall and inflow on rill formation and erosion processes on steep hillslopes

    NASA Astrophysics Data System (ADS)

    Tian, Pei; Xu, Xinyi; Pan, Chengzhong; Hsu, Kuolin; Yang, Tiantian

    2017-05-01

    Limited information has isolated the impacts of rainfall on rill formation and erosion on steep hillslopes where upslope inflow simultaneously exists. Field simulation experiments were conducted on steep hillslopes (26°) under rainfall (60 mm h-1), inflow (6, 12, 18, 24, 30, 36 L min-1 m-1), and combination of rainfall and inflow to explore the impacts of rainfall on rill formation, and the interaction between rainfall and inflow on soil erosion. Rainfall decreased soil infiltration rate (10%-26%) mainly due to soil crust by raindrop impact. Rainfall strengthened rill formation, which behaved in the increment in rill width (5%-26%), length (4%-22%), and depth (3%-22%), but this increment decreased as inflow rates increased. Additionally, the contribution of rainfall on rill formation was most significant at the initial stage, followed by the final stage and active period of rill development. Rainfall increased rill erosion (8%-80%) and interrill erosion (36%-64%), but it played a dominant role in increasing interrill erosion under relatively high inflow rates. The most sensitive hydrodynamic parameter to soil erosion was shear stress and stream power under inflow and 'inflow + rainfall' conditions, respectively. For the lowest inflow rate, the reduction in soil loss by interaction between rainfall and inflow accounted for 20% of total soil loss, indicating a negative interaction. However, such interaction became positive with increasing inflow rates. The contribution rate to rill erosion by the interaction was greater than that of interrill erosion under relatively low inflow rates. Our results provide a better understanding of hillslope soil erosion mechanism.

  17. Model simulations of flood and debris flow timing in steep catchments after wildfire

    NASA Astrophysics Data System (ADS)

    Rengers, F. K.; McGuire, L. A.; Kean, J. W.; Staley, D. M.; Hobley, D. E. J.

    2016-08-01

    Debris flows are a typical hazard on steep slopes after wildfire, but unlike debris flows that mobilize from landslides, most postwildfire 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.

  18. Seismic Component of the STEEP Project, Alaska: Results of the Second Field Season

    NASA Astrophysics Data System (ADS)

    Ruppert, N. A.; Hansen, R. A.; Estes, S. A.; Lafevers, M.; Sandru, J.; Fowler, M.; Pavlis, G.; Bauer, M.; Growdon, M. A.; Lowe, L.

    2006-12-01

    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 a passive seismic experiment utilizing the IRIS PASSCAL Program instruments. A total of 22 new, broadband, seismic stations have been installed in the St. Elias region. All use Freewave IP radios to provide telemetry to a DSL, a DDS or one of three VSAT, connections that provide continuous data transmission to Fairbanks. The data are also recorded local disk storage using Quanterra packet balers. The telemetry data are recorded in real time and used in standard data processing at the Alaska Earthquake Information Center. The network is proving clear improvements in detection and location capabilities for events in the St. Elias region. Processing of teleseismic data is ongoing for estimates of crustal thickness using receiver functions and mantle anisotropy with shear wave splitting. Since the beginning of the new STEEP network installations in July, 2005, the AEIC has located over 400 events in the area, the largest having a magnitude of 3.7. Majority of the events have shallow crustal depths. The deepest events (down to 64 km) are located in the northwestern part of the project area near Wrangell volcanoes. The newly recorded earthquakes follow the pattern of the long term seismicity trend. They mostly cluster in the Icy Bay-Yakutat Bay area, along the central part of the Chugach-St. Elias fault system, and near the Duke River fault. A number of glacial quakes have also been located with the newly installed network. These events primarily concentrate in the Icy Bay area.

  19. 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

  20. 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.

  1. Stochastic predictions of bedload flux and sediment availability in steep channels

    NASA Astrophysics Data System (ADS)

    Yager, E. M.; Turowski, J. M.; Rickenmann, D.; McArdell, B. W.

    2010-12-01

    The sediment supply to steep streams (gradients >3%) is highly episodic and is partially a function of the magnitude and timing of landslides and debris flows. In these channels, clusters and steps of large boulders move only during infrequent, extreme flow events, and significantly alter the flow hydraulics and the transport of the more mobile gravel. Bedload flux predictions are often inaccurate in these streams because they do not account for the influence of the immobile boulders and the highly variable sediment supply. In a steep (10% gradient) channel, we measured the grain-size distribution of the relatively mobile sediment, bedload transport rates and the boulder-step protrusion, grain size, and spacing over a period of 6 years, which encompassed two extreme events (recurrence interval ~50 years) that reorganized boulder steps. The sediment availability on the bed and subsequent bedload fluxes increased after each extreme event because of greater hillslope sediment supply, and reduced bed armoring and particle interlocking. The boulder step protrusion was a power function of the bedload flux; protrusion increased with lower sediment availability. We have previously developed a bedload transport equation that accounts for the influence of boulder steps on the flow hydraulics. Here, we incorporate a stochastic function for protrusion, to estimate the sediment availability during any flow event, in our bedload transport equation. Sediment transport predictions were within an order of magnitude of the measured values if they incorporated a variable protrusion. Use of a constant protrusion caused the predicted bedload fluxes to systematically over- or under- estimate the measured values. Furthermore, sediment transport equations were more accurate if they used sediment and roughness parameters (e.g. area occupied by steps, grain size of mobile gravel and steps, step height) that were representative of the bed conditions for each event. This suggests that

  2. 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.

  3. Lensing corrections to features in the angular two-point correlation function and power spectrum

    SciTech Connect

    LoVerde, Marilena; Hui, Lam; Gaztanaga, Enrique

    2008-01-15

    It is well known that magnification bias, the modulation of galaxy or quasar source counts by gravitational lensing, can change the observed angular correlation function. We investigate magnification-induced changes to the shape of the observed correlation function w({theta}), and the angular power spectrum C{sub l}, paying special attention to the matter-radiation equality peak and the baryon wiggles. Lensing effectively mixes the correlation function of the source galaxies with that of the matter correlation at the lower redshifts of the lenses distorting the observed correlation function. We quantify how the lensing corrections depend on the width of the selection function, the galaxy bias b, and the number count slope s. The lensing correction increases with redshift and larger corrections are present for sources with steep number count slopes and/or broad redshift distributions. The most drastic changes to C{sub l} occur for measurements at high redshifts (z > or approx. 1.5) and low multipole moment (l < or approx. 100). For the source distributions we consider, magnification bias can shift the location of the matter-radiation equality scale by 1%-6% at z{approx}1.5 and by z{approx}3.5 the shift can be as large as 30%. The baryon bump in {theta}{sup 2}w({theta}) is shifted by < or approx. 1% and the width is typically increased by {approx}10%. Shifts of > or approx. 0.5% and broadening > or approx. 20% occur only for very broad selection functions and/or galaxies with (5s-2)/b > or approx. 2. However, near the baryon bump the magnification correction is not constant but is a gently varying function which depends on the source population. Depending on how the w({theta}) data is fitted, this correction may need to be accounted for when using the baryon acoustic scale for precision cosmology.

  4. Integrated geophysics reveals a steep lithologic boundary and Moho offset at the western Idaho shear zone that strongly influenced later tectonic events

    NASA Astrophysics Data System (ADS)

    Davenport, K. K.; Ghanekar, S.; Stanciu, A. C.; Bremner, P. M.; Hole, J. A.; Tikoff, B.; Russo, R. M.

    2016-12-01

    Multiple geophysical data sets from the EarthScope Idaho-Oregon (IDOR) project were integrated to examine crustal structure and composition across the boundary between accreted terranes and the Precambrian craton in Idaho and Oregon. New results from controlled-source seismic S-wave data and gravity data are incorporated with previous results from controlled-source seismic P-waves, broadband seismic receiver functions, and broadband ambient noise surface waves. The geophysical data constrain the deeper structure of the western Idaho shear zone (WISZ), imaging a near-vertical, through-going structure that juxtaposes different seismic velocities and densities throughout the crust and offsets the Moho by 7-8 km. Previous work suggested that the WISZ, which formed when transpressional deformation overprinted the original terrane-craton suture, was less steep at depth or was offset within the crust. West of the WISZ, the crust of the Blue Mountains Province oceanic accreted terranes is characterized by faster seismic velocities and higher densities, intermediate lithology with a mafic lower crust, and a shallower, 30 km deep Moho. East of the WISZ the crust of the Precambrian craton and the Idaho batholith has slower seismic velocities, lower densities, felsic lithology with an intermediate-composition lower crust, and a deeper 35-40 km Moho. The juxtaposition of crustal blocks with distinctly contrasting lithologies created a fundamental rheologic boundary that strongly influenced the response of the crust to subsequent tectonic events, including emplacement of the Idaho batholith and the Columbia River basalts, and Basin and Range extension. The strong contrast across the WISZ restricted these tectonic events to primarily one side or the other, and has likely contributed to the survival of this steep vertical boundary and Moho offset through the later tectonic and heating events.

  5. MAGIC observations and multifrequency properties of the flat spectrum radio quasar 3C 279 in 2011

    SciTech Connect

    Aleksic, J.

    2014-07-01

    Aims. We present a study of the very high energy (VHE; E>100 GeV) γ-ray emission of the blazar PKS 1424+240 observed with the MAGIC telescopes. The primary aim of this paper is the multiwavelength spectral characterization and modeling of this blazar, which is made particularly interesting by the recent discovery of a lower limit of its redshift of z ≥ 0.6 and makes it a promising candidate to be the most distant VHE source. Methods. The source has been observed with the MAGIC telescopes in VHE rays for a total observation time of ~33.6 h from 2009 to 2011. A detailed analysis of its γ-ray spectrum and time evolution has been carried out. Moreover, we have collected and analyzed simultaneous and quasi-simultaneous multiwavelength data. Results. The source was marginally detected in VHE rays during 2009 and 2010, and later, the detection was confirmed during an optical outburst in 2011. The combined significance of the stacked sample is ~7.2σ. The differential spectra measured during the different campaigns can be described by steep power laws with the indices ranging from 3.5 ± 1.2 to 5.0 ± 1.7. The MAGIC spectra corrected for the absorption due to the extragalactic background light connect smoothly, within systematic errors, with the mean spectrum in 2009-2011 observed at lower energies by the Fermi-LAT. The absorption-corrected MAGIC spectrum is flat with no apparent turn down up to 400 GeV. The multiwavelength light curve shows increasing flux in radio and optical bands that could point to a common origin from the same region of the jet. The large separation between the two peaks of the constructed non-simultaneous spectral energy distribution also requires an extremely high Doppler factor if an one zone synchrotron self-Compton model is applied. We find that a two-component synchrotron self-Compton model describes the spectral energy distribution of the source well, if the source is located at z ~ 0.6.

  6. MAGIC observations and multifrequency properties of the flat spectrum radio quasar 3C 279 in 2011

    DOE PAGES

    Aleksic, J.

    2014-07-01

    Aims. We present a study of the very high energy (VHE; E>100 GeV) γ-ray emission of the blazar PKS 1424+240 observed with the MAGIC telescopes. The primary aim of this paper is the multiwavelength spectral characterization and modeling of this blazar, which is made particularly interesting by the recent discovery of a lower limit of its redshift of z ≥ 0.6 and makes it a promising candidate to be the most distant VHE source. Methods. The source has been observed with the MAGIC telescopes in VHE rays for a total observation time of ~33.6 h from 2009 to 2011. Amore » detailed analysis of its γ-ray spectrum and time evolution has been carried out. Moreover, we have collected and analyzed simultaneous and quasi-simultaneous multiwavelength data. Results. The source was marginally detected in VHE rays during 2009 and 2010, and later, the detection was confirmed during an optical outburst in 2011. The combined significance of the stacked sample is ~7.2σ. The differential spectra measured during the different campaigns can be described by steep power laws with the indices ranging from 3.5 ± 1.2 to 5.0 ± 1.7. The MAGIC spectra corrected for the absorption due to the extragalactic background light connect smoothly, within systematic errors, with the mean spectrum in 2009-2011 observed at lower energies by the Fermi-LAT. The absorption-corrected MAGIC spectrum is flat with no apparent turn down up to 400 GeV. The multiwavelength light curve shows increasing flux in radio and optical bands that could point to a common origin from the same region of the jet. The large separation between the two peaks of the constructed non-simultaneous spectral energy distribution also requires an extremely high Doppler factor if an one zone synchrotron self-Compton model is applied. We find that a two-component synchrotron self-Compton model describes the spectral energy distribution of the source well, if the source is located at z ~ 0.6.« less

  7. 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.

  8. 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

  9. Effects of alternative steeping methods on composition, antioxidant property and colour of green, black and oolong tea infusions.

    PubMed

    Lantano, Claudia; Rinaldi, Massimiliano; Cavazza, Antonella; Barbanti, Davide; Corradini, Claudio

    2015-12-01

    Cold water steeping is reported to maximise tea health benefits, but requires long infusion time. In this work, the employment of a brief hot infusion step followed by ice addition was evaluated. The comparison of this innovative method with hot and cold steeping was investigated on green, black and oolong teas. Catechins, xanthines and gallic acid content, antioxidant power, total phenolics and colour analysis were evaluated. Hot infusion shown rapid extractive power, but relevant compound degradation. On the contrary, cold infusion extracted higher level of healthy molecules with slow kinetic. The innovative method achieved in short time similar properties of cold infusion in terms of antioxidant power. As for bioactive compounds, such as gallic acid and epigallocatechin gallate, highest values, about double than in hot infusion, were recorded for green and black teas. This steeping method may represent an alternative approach for industrial beverage preparation.

  10. 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.

  11. 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