Constraints on the galactic population of TeV pulsar wind nebulae using Fermi Large Area Telescope observations

DOE PAGES

Acero, F.; Ackermann, M.; Ajello, M.; ...

2013-07-29

Pulsar wind nebulae (PWNe) have been established as the most populous class of TeV γ-ray emitters. Since launch, the Fermi Large Area Telescope (LAT) has identified five high-energy (100 MeV < E < 100 GeV) γ-ray sources as PWNe and detected a large number of PWN candidates, all powered by young and energetic pulsars. The wealth of multi-wavelength data available and the new results provided by Fermi-LAT give us an opportunity to find new PWNe and to explore the radiative processes taking place in known ones. The TeV γ-ray unidentified (UNID) sources are the best candidates for finding new PWNe.more » Using 45 months of Fermi-LAT data for energies above 10 GeV, an analysis was performed near the position of 58 TeV PWNe and UNIDs within 5° of the Galactic plane to establish new constraints on PWN properties and find new clues on the nature of UNIDs. Of the 58 sources, 30 were detected, and this work provides their γ-ray fluxes for energies above 10 GeV. The spectral energy distributions and upper limits, in the multi-wavelength context, also provide new information on the source nature and can help distinguish between emission scenarios, i.e., between classification as a pulsar candidate or as a PWN candidate. Six new GeV PWN candidates are described in detail and compared with existing models. As a result, a population study of GeV PWN candidates as a function of the pulsar/PWN system characteristics is presented.« less

Moderator design studies for a new neutron reference source based on the D–T fusion reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mozhayev, Andrey V.; Piper, Roman K.; Rathbone, Bruce A.

2016-06-01

The radioactive isotope Californium-252 (252Cf) is relied upon internationally as a neutron calibration source for ionizing radiation dosimetry because of its high specific activity. The source may be placed within a heavy-water (D2O) moderating sphere to produce a softened spectrum representative of neutron fields common to commercial nuclear power plant environments, among others. Due to termination of the U.S. Department of Energy loan/lease program in 2012, the expense of obtaining 252Cf sources has undergone a significant increase, rendering high output sources largely unattainable. On the other hand, the use of neutron generators in research and industry applications has increased dramaticallymore » in recent years. Neutron generators based on deuterium-tritium (D-T) fusion reaction provide high neutron fluence rates and, therefore, could possibly be used as a replacement for 252Cf. To be viable, the 14.6 MeV D-T output spectrum must be significantly moderated to approximate common workplace environments. This paper presents the results of an effort to select appropriate moderating materials and design a configuration to reshape the primary neutron field toward a spectrum approaching that from a nuclear power plant workplace. A series of Monte-Carlo (MCNP) simulations of single layer high- and low-Z materials are used to identify initial candidate moderators. Candidates are refined through a similar series of simulations involving combinations of 2 to 5 different materials. The simulated energy distribution using these candidate moderators are rated in comparison to a target spectrum. Other properties, such as fluence preservation and/or enhancement, prompt gamma production and other characteristics are also considered.« less

Hard X-ray imaging of the Galactic black hole candidate GX 339 - 4

NASA Technical Reports Server (NTRS)

Covault, C. E.; Grindlay, J. E.; Manandhar, R. P.

1992-01-01

Imaging and spectral observations in the energy range 25-250 keV of the black hole candidate GX 339 - 4 have been obtained with the Energetic X-ray Imaging Telescope Experiment. Observations were made during a balloon flight from Alice Springs, Australia on UT 1989 May 8-10. A single source of nearly 6-sigma significance is detected near the center of the 3.4-deg field of view with a position consistent with GX 339 - 4. This is the first imaging observation of GX 339 - 4 at hard X-ray energies. This result confirms previously reported results from nonimaging experiments showing significant hard X-ray flux up to greater than about 60 keV, with a power-law spectral fit similar to the other black hole candidates such as Cygnus X - 1. The source may have been in an outburst state similar to that recently detected with BATSE on GRO.

Micro-Power Sources Enabling Robotic Outpost Based Deep Space Exploration

NASA Technical Reports Server (NTRS)

West, W. C.; Whitacre, J. F.; Ratnakumar, B. V.; Brandon, E. J.; Studor, G. F.

2001-01-01

Robotic outpost based exploration represents a fundamental shift in mission design from conventional, single spacecraft missions towards a distributed risk approach with many miniaturized semi-autonomous robots and sensors. This approach can facilitate wide-area sampling and exploration, and may consist of a web of orbiters, landers, or penetrators. To meet the mass and volume constraints of deep space missions such as the Europa Ocean Science Station, the distributed units must be fully miniaturized to fully leverage the wide-area exploration approach. However, presently there is a dearth of available options for powering these miniaturized sensors and robots. This group is currently examining miniaturized, solid state batteries as candidates to meet the demand of applications requiring low power, mass, and volume micro-power sources. These applications may include powering microsensors, battery-backing rad-hard CMOS memory and providing momentary chip back-up power. Additional information is contained in the original extended abstract.

A novel method for transient detection in high-cadence optical surveys. Its application for a systematic search for novae in M 31

NASA Astrophysics Data System (ADS)

Soraisam, Monika D.; Gilfanov, Marat; Kupfer, Thomas; Masci, Frank; Shafter, Allen W.; Prince, Thomas A.; Kulkarni, Shrinivas R.; Ofek, Eran O.; Bellm, Eric

2017-03-01

Context. In the present era of large-scale surveys in the time domain, the processing of data, from procurement up to the detection of sources, is generally automated. One of the main challenges in the astrophysical analysis of their output is contamination by artifacts, especially in the regions of high surface brightness of unresolved emission. Aims: We present a novel method for identifying candidates for variable and transient sources from the outputs of optical time-domain survey data pipelines. We use the method to conduct a systematic search for novae in the intermediate Palomar Transient Factory (iPTF) observations of the bulge part of M 31 during the second half of 2013. Methods: We demonstrate that a significant fraction of artifacts produced by the iPTF pipeline form a locally uniform background of false detections approximately obeying Poissonian statistics, whereas genuine variable and transient sources, as well as artifacts associated with bright stars, result in clusters of detections whose spread is determined by the source localization accuracy. This makes the problem analogous to source detection on images produced by grazing incidence X-ray telescopes, enabling one to utilize the arsenal of powerful tools developed in X-ray astronomy. In particular, we use a wavelet-based source detection algorithm from the Chandra data analysis package CIAO. Results: Starting from 2.5 × 105 raw detections made by the iPTF data pipeline, we obtain approximately 4000 unique source candidates. Cross-matching these candidates with the source-catalog of a deep reference image of the same field, we find counterparts for 90% of the candidates. These sources are either artifacts due to imperfect PSF matching or genuine variable sources. The remaining approximately 400 detections are transient sources. We identify novae among these candidates by applying selection cuts to their lightcurves based on the expected properties of novae. Thus, we recovered all 12 known novae (not counting one that erupted toward the end of the survey) registered during the time span of the survey and discovered three nova candidates. Our method is generic and can be applied to mining any target out of the artifacts in optical time-domain data. As it is fully automated, its incompleteness can be accurately computed and corrected for.

Efficient high-power narrow-linewidth all-fibred linearly polarized ytterbium laser source

NASA Astrophysics Data System (ADS)

Bertrand, Anthony; Liégeois, Flavien; Hernandez, Yves; Giannone, Domenico

2012-06-01

We report on experimental results on a high power, all-fibred, linearly polarized, mode-locked laser at 1.03 μm. The laser generates pulses of 40 ps wide at a repetition rate of 52 MHz, exhibiting 12 kW peak power. Dispersion in optical fibres is controlled to obtain both high power and narrow spectral linewidth. The average output power reached is 25 W with a spectral linewidth of 380 pm and a near diffraction limit beam (M2 < 1.2). This laser is an ideal candidate for applications like IR spectroscopy, where high peak power and narrow linewidth are required for subsequent wavelength conversion.

Blazars in Hard X-rays

NASA Astrophysics Data System (ADS)

Ghisellini, Gabriele

2009-05-01

Although blazars are thought to emit most of their luminosity in the γ-ray band, there are subclasses of them very prominent in hard X-rays. These are the best candidates to be studied by Simbol-X. They are at the extremes of the blazar sequence, having very small or very high jet powers. The former are the class of TeV emitting BL Lacs, whose synchrotron emission often peaks at tens of keV or more. The latter are the blazars with the most powerful jets, have high black hole masses accreting at high (i.e. close to Eddington) rates. These sources are predicted to have their high energy peak even below the MeV band, and therefore are very promising candidates to be studied with Simbol-X.

Helium-3 and helium-4 acceleration by high power laser pulses for hadron therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bulanov, S. S.; Esarey, E.; Schroeder, C. B.

The laser driven acceleration of ions is considered a promising candidate for an ion source for hadron therapy of oncological diseases. Though proton and carbon ion sources are conventionally used for therapy, other light ions can also be utilized. Whereas carbon ions require 400 MeV per nucleon to reach the same penetration depth as 250 MeV protons, helium ions require only 250 MeV per nucleon, which is the lowest energy per nucleon among the light ions (heavier than protons). This fact along with the larger biological damage to cancer cells achieved by helium ions, than that by protons, makes thismore » species an interesting candidate for the laser driven ion source. Two mechanisms (magnetic vortex acceleration and hole-boring radiation pressure acceleration) of PW-class laser driven ion acceleration from liquid and gaseous helium targets are studied with the goal of producing 250 MeV per nucleon helium ion beams that meet the hadron therapy requirements. We show that He3 ions, having almost the same penetration depth as He4 with the same energy per nucleon, require less laser power to be accelerated to the required energy for the hadron therapy.« less

Helium-3 and helium-4 acceleration by high power laser pulses for hadron therapy

DOE PAGES

Bulanov, S. S.; Esarey, E.; Schroeder, C. B.; ...

2015-06-24

The laser driven acceleration of ions is considered a promising candidate for an ion source for hadron therapy of oncological diseases. Though proton and carbon ion sources are conventionally used for therapy, other light ions can also be utilized. Whereas carbon ions require 400 MeV per nucleon to reach the same penetration depth as 250 MeV protons, helium ions require only 250 MeV per nucleon, which is the lowest energy per nucleon among the light ions (heavier than protons). This fact along with the larger biological damage to cancer cells achieved by helium ions, than that by protons, makes thismore » species an interesting candidate for the laser driven ion source. Two mechanisms (magnetic vortex acceleration and hole-boring radiation pressure acceleration) of PW-class laser driven ion acceleration from liquid and gaseous helium targets are studied with the goal of producing 250 MeV per nucleon helium ion beams that meet the hadron therapy requirements. We show that He3 ions, having almost the same penetration depth as He4 with the same energy per nucleon, require less laser power to be accelerated to the required energy for the hadron therapy.« less

Lunar Surface Stirling Power Systems Using Isotope Heat Sources

NASA Technical Reports Server (NTRS)

Schmitz, Paul C.; Penswick, L. Barry; Shaltens, Richard K.

2010-01-01

For many years, NASA has used the decay of plutonium-238 (Pu-238) (in the form of the General Purpose Heat Source (GPHS)) as a heat source for Radioisotope Thermoelectric Generators (RTGs), which have provided electrical power for many NASA missions. While RTGs have an impressive reliability record for the missions in which they have been used, their relatively low thermal to electric conversion efficiency and the scarcity of plutonium-238 (Pu-238) has led NASA to consider other power conversion technologies. NASA is considering returning both robotic and human missions to the lunar surface and, because of the long lunar nights (14.75 Earth days), isotope power systems are an attractive candidate to generate electrical power. NASA is currently developing the Advanced Stirling Radioisotope Generator (ASRG) as a candidate higher efficiency power system that produces greater than 160 W with two GPHS modules at the beginning of life (BOL) (32% efficiency). The ASRG uses the same Pu-238 GPHS modules, which are used in RTG, but by coupling them to a Stirling convertor provides a four-fold reduction in the number of GPHS modules. This study considers the use of americium-241 (Am-241) as a substitute for the Pu-238 in Stirling- convertor-based Radioisotope Power Systems (RPS) for power levels from tens of watts to 5 kWe. The Am-241 is used as a substitute for the Pu-238 in GPHS modules. Depending on power level, different Stirling heat input and removal systems are modeled. It was found that substituting Am-241 GPHS modules into the ASRG reduces power output by about one-fifth while maintaining approximately the same system mass. In order to obtain the nominal 160 W of electrical output of the Pu-238 ASRG requires 10 Am-241 GPHS modules. Higher power systems require changing from conductive coupling heat input and removal from the Stirling convertor to either pumped loops or heat pipes. Liquid metal pumped loops are considered as the primary heat transportation on the hot end and water pumped loop/heat pipe radiator is considered for the heat rejection side for power levels above 1 kWe.

Camelot-a novel concept for a multiterawatt pulse power generator for single pulse, burst, or repetetion rate operation. Special report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stewart, A.G.

1981-04-01

Superpower pulse generators are fast establishing themselves internationally as candidates for employment in a wide variety of military applications including electronic warfare and jamming, high energy beam weapons, and nuclear weapons effects simulation. Unfortunately, existing multimegajoule pulse power generators such as AURORA do not satisfy many Department of Defense goals for field-adaptable weapon systems-for example, repetition (rep) rate operation, high reliabilty, long life, ease of operation, and low maintenance. The Camelot concept is a multiterawatt rep ratable pulse power source, adaptable to a wide range of output parameters-both charged particles and photons. An analytical computer model has been developed tomore » predict the power flowing through the device. A 5-year development program, culminating in a source region electromagnetic pulse simulator, is presented.« less

New Active Remote-sensing Capabilities: Laser Ablation Spectrometer and Lidar Atmospheric Species Profile Measurements

NASA Technical Reports Server (NTRS)

DeYoung, R. J.; Bergstralh, J. T.

2005-01-01

Introduction: With the anticipated development of high-capacity fission power and electric propulsion for deep-space missions, it will become possible to propose experiments that demand higher power than current technologies (e.g. radioisotope power sources) provide. Jupiter Icy Moons Orbiter (JIMO), the first mission in the Project Prometheus program, will explore the icy moons of Jupiter with a suite of high-capability experiments that take advantage of the high power levels (and indirectly, the high data rates) that fission power affords. This abstract describes two high-capability active-remote-sensing experiments that will be logical candidates for subsequent Prometheus-class missions.

Gamma ray monitoring of a AGN and galactic black hole candidates by the Compton Gamma Ray Observatory

NASA Technical Reports Server (NTRS)

Skelton, R. T.; Ling, James C.; Wheaton, William A.; Harmon, Alan; Fishman, G. J.; Meegan, C. A.; Paciesas, William S.; Gruber, Duane E.; Rubin, Brad; Wilson, R. B.

1992-01-01

The Compton Gamma-Ray Observatory's Burst and Transient Source Experiment (BATSE) has a powerful capability to provide nearly uninterrupted monitoring in the 25 keV-10 MeV range of both active galactic nuclei (AGN) and galactic black hole candidates (GBHC) such as Cygnus X-1, using the occultation of cosmic sources by the Earth. Since the Crab is detected by the BATSE Large Area Detectors with roughly 25(sigma) significance in the 15-125 keV range in a single rise or set, a variation by a factor of two of a source having one-tenth the strength of Cygnus X-1 should be detectable within a day. Methods of modeling the background are discussed which will increase the accuracy, sensitivity, and reliability of the results beyond those obtainable from a linear background fit with a single rise or set discontinuity.

Discovery of three strongly lensed quasars in the Sloan Digital Sky Survey

NASA Astrophysics Data System (ADS)

Williams, P. R.; Agnello, A.; Treu, T.; Abramson, L. E.; Anguita, T.; Apostolovski, Y.; Chen, G. C.-F.; Fassnacht, C. D.; Hsueh, J. W.; Lemaux, B. C.; Motta, V.; Oldham, L.; Rojas, K.; Rusu, C. E.; Shajib, A. J.; Wang, X.

2018-06-01

We present the discovery of three quasar lenses in the Sloan Digital Sky Survey, selected using two novel photometry-based selection techniques. The J0941+0518 system, with two point sources separated by 5.46 arcsec on either side of a galaxy, has source and lens redshifts 1.54 and 0.343. Images of J2257+2349 show two point sources separated by 1.67 arcsec on either side of an E/S0 galaxy. The extracted spectra show two images of the same quasar at zs = 2.10. SDSS J1640+1045 has two quasar spectra at zs = 1.70 and fits to the SDSS and Pan-STARRS images confirm the presence of a galaxy between the two point sources. We observed 56 photometrically selected lens candidates in this follow-up campaign, confirming three new lenses, re-discovering one known lens, and ruling out 36 candidates, with 16 still inconclusive. This initial campaign demonstrates the power of purely photometric selection techniques in finding lensed quasars.

On the inorganic carriers of the 21 micron emission feature in post-AGB stars

NASA Astrophysics Data System (ADS)

Zhang, Ke; Jiang, Biwei; Li, Aigen

2008-10-01

The mysterious 21 μm emission feature seen in only 12 C-rich proto-planetary nebulae (PPNe) remains unidentified since its discovery in 1989. Over a dozen materials have been suggested as the carrier candidates while none of them has received general acceptance. We investigate the inorganic carrier candidates by applying the observational constraints of the feature strength and associated features. It is found that: (1) three candidates, TiC clusters, fullerenes with Ti impurity atoms, and SiS2, are not abundant enough to account for the emission power of the 21 μm band, (2) five candidates, doped-SiC, SiO2-mantled SiC dust, carbon and silicon mixtures, Fe2O3, and Fe3O4, all show associated features which are either not detected in the 21 μm sources or detected but with a much lower strength, and (3) FeO, which satisfies the abundance constraints, does not display any associated features which are not seen in the 21 μm sources. Moreover, FeO is more likely to survive in the C-rich environment than Fe2O3 and Fe3O4. Thus FeO seems to be the most plausible one among the inorganic carrier candidates.

XMM-Newton Archival Study of the ULX Population in Nearby Galaxies

NASA Technical Reports Server (NTRS)

Winter, Lisa M.; Mushotzky, Richard F.; Reynolds, christopher S.

2006-01-01

We present the results of an archival XMM-Newton study of the bright X-ray point sources (L(sub X) greater than 10(exp 38 erg per second)) in 32 nearby galaxies. From our list of approximately 100 point sources, we attempt to determine if there is a low-state counterpart to the Ultraluminous X-ray (ULX) population, searching for a soft-hard state dichotomy similar to that known for Galactic X-ray binaries and testing the specific predictions of the IMBH hypothesis. To this end, we searched for low-state objects, which we defined as objects within our sample which had a spectrum well fit by a simple absorbed power law, and high-state objects, which we defined as objects better fit by a combined blackbody and a power law. Assuming that low-state)) objects accrete at approximately 10% of the Eddington luminosity (Done & Gierlinski 2003) and that high-state objects accrete near the Eddington luminosity we further divided our sample of sources into low and high state ULX sources. We classify 16 sources as low-state ULXs and 26 objects as high-state ULXs. As in Galactic black hole systems, the spectral indices, GAMMA, of the lowstate objects, as well as the luminosities, tend to be lower than those of the high-state objects. The observed range of blackbody temperatures for the high state is 0.1-1 keV, with the most luminous systems tending toward the lowest temperatures. We therefore divide our high-state ULXs into candidate IMBHs (with blackbody temperatures of approximately 0.1 keV) and candidate stellar mass BHs (with blackbody temperatures of approximately 1.0 keV). A subset of the candidate stellar mass BHs have spectra that are well-fit by a Comptonization model, a property similar of Galactic BHs radiating in the very-high state near the Eddington limit.

Baryons in the relativistic jets of the stellar-mass black-hole candidate 4U 1630-47.

PubMed

Trigo, María Díaz; Miller-Jones, James C A; Migliari, Simone; Broderick, Jess W; Tzioumis, Tasso

2013-12-12

Accreting black holes are known to power relativistic jets, both in stellar-mass binary systems and at the centres of galaxies. The power carried away by the jets, and, hence, the feedback they provide to their surroundings, depends strongly on their composition. Jets containing a baryonic component should carry significantly more energy than electron-positron jets. Energetic considerations and circular-polarization measurements have provided conflicting circumstantial evidence for the presence or absence of baryons in jets, and the only system in which they have been unequivocally detected is the peculiar X-ray binary SS 433 (refs 4, 5). Here we report the detection of Doppler-shifted X-ray emission lines from a more typical black-hole candidate X-ray binary, 4U 1630-47, coincident with the reappearance of radio emission from the jets of the source. We argue that these lines arise from baryonic matter in a jet travelling at approximately two-thirds the speed of light, thereby establishing the presence of baryons in the jet. Such baryonic jets are more likely to be powered by the accretion disk than by the spin of the black hole, and if the baryons can be accelerated to relativistic speeds, the jets should be strong sources of γ-rays and neutrino emission.

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.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Titov, O.; Stanford, Laura M.; Pursimo, T.

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 radiomore » sources.« less

Analysis of Chemical, REP, and SEP missions to the Trojan asteroids

NASA Technical Reports Server (NTRS)

Bonfiglio, Eugene P.; Oh, David; Yen, Chen-Wan

2005-01-01

Recent studies suggest significant benefits from using 1st and 2nd generation Radioisotope Power Systems (RPS) as a power source for electric propulsion (EP) missions to the outer planets. This study focuses on trajectories to the Trojan asteroids. A high level analysis is performed with chemical trajectories to determine potential canidates for REP trajectory optimization. Extensive analysis of direct trajectories using REP is performed on these candidates. Solar Electric Propulsion (SEP) trajectories are also considered for comparison against REP trajectories.

Observations of a nearby filament of galaxy clusters with the Sardinia Radio Telescope

NASA Astrophysics Data System (ADS)

Vacca, Valentina; Murgia, M.; Loi, F. Govoni F.; Vazza, F.; Finoguenov, A.; Carretti, E.; Feretti, L.; Giovannini, G.; Concu, R.; Melis, A.; Gheller, C.; Paladino, R.; Poppi, S.; Valente, G.; Bernardi, G.; Boschin, W.; Brienza, M.; Clarke, T. E.; Colafrancesco, S.; Enßlin, T.; Ferrari, C.; de Gasperin, F.; Gastaldello, F.; Girardi, M.; Gregorini, L.; Johnston-Hollitt, M.; Junklewitz, H.; Orrù, E.; Parma, P.; Perley, R.; Taylor, G. B.

2018-05-01

We report the detection of diffuse radio emission which might be connected to a large-scale filament of the cosmic web covering a 8° × 8° area in the sky, likely associated with a z≈0.1 over-density traced by nine massive galaxy clusters. In this work, we present radio observations of this region taken with the Sardinia Radio Telescope. Two of the clusters in the field host a powerful radio halo sustained by violent ongoing mergers and provide direct proof of intra-cluster magnetic fields. In order to investigate the presence of large-scale diffuse radio synchrotron emission in and beyond the galaxy clusters in this complex system, we combined the data taken at 1.4 GHz with the Sardinia Radio Telescope with higher resolution data taken with the NRAO VLA Sky Survey. We found 28 candidate new sources with a size larger and X-ray emission fainter than known diffuse large-scale synchrotron cluster sources for a given radio power. This new population is potentially the tip of the iceberg of a class of diffuse large-scale synchrotron sources associated with the filaments of the cosmic web. In addition, we found in the field a candidate new giant radio galaxy.

Satellite Power Systems (SPS) concept definition study, exhibit C. Volume 1: Executive summary

NASA Technical Reports Server (NTRS)

Hanley, G. M.

1979-01-01

The Department of Energy (DOE) is currently conducting an evaluation of approaches to provide energy to meet demands in the post-2000 time period. The Satellite Power System (SPS) is a candidate for producing significant quantities of base-load power using solar energy as the source. The SPS concept is illustrated for a solar photovoltaic concept. A satellite, located at geosynchronous orbit, converts solar energy to dc electrical energy using large solar arrays. This study is a continuing effort to provide system definition data to aid in the evaluation of the SPS concept.

Comparative study of blue laser diode driven cerium-doped single crystal phosphors in application of high-power lighting and display technologies

NASA Astrophysics Data System (ADS)

Balci, Mustafa H.; Chen, Fan; Cunbul, A. Burak; Svensen, Øyvind; Akram, M. Nadeem; Chen, Xuyuan

2018-02-01

Cerium-doped single crystals (Ce:LuAG, Ce:YAG, Ce:GAGG, Ce:GdYAG) have been investigated as stationary phosphor candidates for blue laser driven solid-state lighting without heat sink. The luminous properties of the single crystals are superior compared to the commercial ceramic powder phosphor wheels (Ce3+: Y3Al5O12). The high-power blue laser diode driven temperature increase of the crystals versus quantum efficiency is experimentally measured and discussed. We have carried out realistic measurements at high excitation power levels and at high temperatures. Limitation of phosphors as stationary sources is determined for commercial usage. The measurements were done without any heat sink to see the relative comparison of SCPs in the worst-case scenarios. The results indicate that Gd and Ga addition decreases the luminescence quenching temperature. Based on their superior properties, these single crystals can serve as potential phosphor candidates for high-power blue diode laser driven picture projectors for the green and red channels.

Extended VHE γ-ray emission towards SGR1806-20 and stellar cluster C1 1806-20

NASA Astrophysics Data System (ADS)

Rowell, Gavin; de Naurois, Mathieu; Ataï, Arache Djannati; Gallant, Yves; H.E.S.S. Collaboration

2012-12-01

We report the discovery, with the H.E.S.S. telescopes, of steady and extended VHE γ-ray emission towards the magnetar candidate SGR 1806-20 and parent stellar cluster C1 1806-20. Preliminary analysis suggests the VHE γ-ray flux of this source, designated HESS J1808-204 is a few×10-13 ph cm-2 s-1 TeV-1 at 1 TeV with a power-law photon spectral index Γ = 2.4+/-0.2. The instrinsic extension and orientation matches that of the synchrotron radio nebula G10.0-0.3 which may be powered by the luminous blue variable star LBV 1806-20, a prominent member of the C1 1806-20 cluster. From the energetics of the combined VHE, X-ray, and nearby Fermi-LAT GeV emission, magnetar magnetic energy may be a dominant source of energy over spin-down power, should SGR 1806-20 power the source. Alternatively, C1 1806-20 and/or LBV 1806-20 by itself, via stellar winds, could supply sufficient energy.

A search for faint high-redshift radio galaxy candidates at 150 MHz

NASA Astrophysics Data System (ADS)

Saxena, A.; Jagannathan, P.; Röttgering, H. J. A.; Best, P. N.; Intema, H. T.; Zhang, M.; Duncan, K. J.; Carilli, C. L.; Miley, G. K.

2018-04-01

Ultrasteep spectrum (USS) radio sources are good tracers of powerful radio galaxies at z > 2. Identification of even a single bright radio galaxy at z > 6 can be used to detect redshifted 21 cm absorption due to neutral hydrogen in the intervening intergalactic medium. Here we describe a new sample of high-redshift radio galaxy (HzRG) candidates constructed from the TIFR GMRT Sky Survey First Alternative Data Release survey at 150 MHz. We employ USS selection (α ≤ -1.3) in ˜10 000 deg2, in combination with strict size selection and non-detections in all-sky optical and infrared surveys. We apply flux density cuts that probe a unique parameter space in flux density (50 mJy < S150 < 200 mJy) to build a sample of 32 HzRG candidates. Follow-up Karl G. Jansky Very Large Array (VLA) observations at 1.4 GHz with an average beam size of 1.3 arcsec revealed ˜ 48 per cent of sources to have a single radio component. P-band (370 MHz) imaging of 17 of these sources revealed a flattening radio SED for 10 sources at low frequencies, which is expected from compact HzRGs. Two of our sources lie in fields where deeper multiwavelength photometry and ancillary radio data are available and for one of these we find a best-fitting photo-z of 4.8 ± 2.0. The other source has zphot = 1.4 ± 0.1 and a small angular size (3.7 arcsec), which could be associated with an obscured star-forming galaxy or with a `dead' elliptical. One USS radio source not part of the HzRG sample but observed with the VLA none the less is revealed to be a candidate giant radio galaxy with a host galaxy photo-z of 1.8 ± 0.5, indicating a size of 875 kpc.

Gamma-ray monitoring of AGN and galactic black hole candidates by the Gamma-Ray Observatory

NASA Technical Reports Server (NTRS)

Wheaton, Wm. A.; Ling, James C.; Skelton, R. T.; Harmon, Alan; Fishman, Gerald J.; Meegan, Charles A.; Paciesas, William S.; Rubin, Brad; Wilson, Robert B.; Gruber, Duane E.

1992-01-01

The Burst and Transient Spectroscopy Experiment (BATSE) on the Compton Gamma-Ray Observatory has a powerful capability to provide nearly uninterrupted monitoring in the 25 keV-10 MeV range of both AGN and Galactic black hole candidates such as Cygnus X-1, using the occultation of cosmic sources by the Earth. Progress in background modeling indicates that the data accept region, or fit window tau, around the occultation step can be substantially increased over that conservatively assumed in earlier estimates of BATSE's Earth occultation sensitivity. We show samples of large-tau fits to background and source edges. As a result we expect to be able to perform long-term monitoring of Cygnus X-1 and many of the brighter AGN for the duration of the CGRO mission.

Free-piston Stirling Engine system considerations for various space power applications

NASA Technical Reports Server (NTRS)

Dochat, George R.; Dhar, Manmohan

1991-01-01

Free-Piston Stirling Engines (FPSE) have the potential to provide high reliability, long life, and efficient operation. Therefore, they are excellent candidates for the dynamic power conversion module of a space-based, power-generating system. FPSE can be coupled with many potential heat sources (radioisotope, solar, or nuclear reactor), various heat input systems (pumped loop, heat pipe), heat rejection (pumped loop or heat pipe), and various power management and distribution systems (ac, dc, high or low voltage, and fixed or variable load). This paper reviews potential space missions that can be met using free-piston Stirling engines and discusses options of various system integration approaches. This paper briefly outlines the program and recent progress.

Robo-AO Kepler Asteroseismic Survey. I. Adaptive Optics Imaging of 99 Asteroseismic Kepler Dwarfs and Subgiants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schonhut-Stasik, Jessica S.; Baranec, Christoph; Huber, Daniel

We used the Robo-AO laser adaptive optics (AOs) system to image 99 main sequence and subgiant stars that have Kepler -detected asteroseismic signals. Robo-AO allows us to resolve blended secondary sources at separations as close as ∼0.″15 that may contribute to the measured Kepler light curves and affect asteroseismic analysis and interpretation. We report eight new secondary sources within 4.″0 of these Kepler asteroseismic stars. We used Subaru and Keck AOs to measure differential infrared photometry for these candidate companion systems. Two of the secondary sources are likely foreground objects, while the remaining six are background sources; however, we cannotmore » exclude the possibility that three of the objects may be physically associated. We measured a range of i ′-band amplitude dilutions for the candidate companion systems from 0.43% to 15.4%. We find that the measured amplitude dilutions are insufficient to explain the previously identified excess scatter in the relationship between asteroseismic oscillation amplitude and the frequency of maximum power.« less

High-Temperature Phase Change Materials (PCM) Candidates for Thermal Energy Storage (TES) Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gomez, J. C.

2011-09-01

It is clearly understood that lower overall costs are a key factor to make renewable energy technologies competitive with traditional energy sources. Energy storage technology is one path to increase the value and reduce the cost of all renewable energy supplies. Concentrating solar power (CSP) technologies have the ability to dispatch electrical output to match peak demand periods by employing thermal energy storage (TES). Energy storage technologies require efficient materials with high energy density. Latent heat TES systems using phase change material (PCM) are useful because of their ability to charge and discharge a large amount of heat from amore » small mass at constant temperature during a phase transformation like melting-solidification. PCM technology relies on the energy absorption/liberation of the latent heat during a physical transformation. The main objective of this report is to provide an assessment of molten salts and metallic alloys proposed as candidate PCMs for TES applications, particularly in solar parabolic trough electrical power plants at a temperature range from 300..deg..C to 500..deg.. C. The physical properties most relevant for PCMs service were reviewed from the candidate selection list. Some of the PCM candidates were characterized for: chemical stability with some container materials; phase change transformation temperatures; and latent heats.« less

Organic Materials Ionizing Radiation Susceptibility for the Outer Planet/Solar Probe Radioisotope Power Source

NASA Technical Reports Server (NTRS)

Golliher, Eric L.; Pepper, Stephen V.

2001-01-01

The Department of Energy is considering the current Stirling Technology Corporation 55 We Stirling Technology Demonstration Convertor as a baseline option for an advanced radioisotope power source for the Outer Planets/Solar Probe project of Jet Propulsion Laboratory and other missions. However, since the Technology Demonstration Convertor contains organic materials chosen without any special consideration of flight readiness, and without any consideration of the extremely high radiation environment of Europa, a preliminary investigation was performed to address the radiation susceptibility of the current organic materials used in the Technology Demonstration Convertor. This report documents the results of the investigation. The results of the investigation show that candidate replacement materials have been identified to be acceptable in the harsh Europa radiation environment.

Social Psychological Exchange of Interpersonal Power and Obligation between U.S. Army Infantry Superordinates and Subordinates

DTIC Science & Technology

1976-06-11

Model (RPM) 21 Leadership Styles ..... 24 Followership Styles 33 Role Relationships Between Styles .... 39 Summary . hi 3. METHODOLOGY 42...48 Hypotheses . 49 4. FINDINGS AND DISCUSSION 55 Leadership Styles 55 Followership Styles ..... 62 Background variables 65 Source...for differences in leadership styles of noncommissioned officers, officer candidates, and commissioned officers . . 57 Mean scores and standard

The NASA space power technology program

NASA Technical Reports Server (NTRS)

Stephenson, R. Rhoads

1992-01-01

NASA has a broad technology program in the field of space power. This paper describes that program, including the roles and responsibilities of the various NASA field centers and major contractors. In the power source area, the paper discusses the SP-100 Space Nuclear Power Project, which has been under way for about seven years and is making substantial progress toward development of components for a 100-kilowatt power system that can be scaled to other sizes. This system is a candidate power source for nuclear electric propulsion, as well as for a power plant for a lunar base. In the energy storage area, the paper describes NASA's battery- and fuel-cell development programs. NASA is actively working on NiCd, NiH2, and lithium batteries. A status update is also given on a U.S. Air Force-sponsored program to develop a large (150 ampere-hour) lithium-thionyl chloride battery for the Centaur upper-stage launch vehicle. Finally, the area of power management and distribution (PMAD) is addressed, including power system components such as solid-state switches and power integrated circuits. Automated load management and other computer-controlled functions offer considerable payoffs. The state of the art in space power is described, along with NASA's medium- and long-term goals in the area.

Lunar Surface Stirling Power Systems Using Am-241

NASA Technical Reports Server (NTRS)

Schmitz, Paul C.; Penswick, L. Barry; Shaltens, Richard K.

2009-01-01

For many years NASA has used the decay of Pu-238 (in the form of the General Purpose Heat Source (GPHS)) as a heat source for Radioisotope Thermoelectric Generators (RTG), which have provided electrical power for many NASA missions. While RTG's have an impressive reliability record for the missions in which they have been used, their relatively low thermal to electric conversion efficiency (-5% efficiency) and the scarcity of Plutoinium-238 (Pu-238) has led NASA to consider other power conversion technologies. NASA is considering returning both robotic and human missions to the lunar surface and, because of the long lunar nights (14 earth days) isotope power systems are an attractive candidate to generate electrical power. NASA is currently developing the Advanced Stirling Radioisotope Generator (ASRG) as a candidate higher efficiency power system that produces greater than 160 watts with 2 GPHS modules at the beginning of life (BOL) (-30% efficiency). The ASRG uses the same Pu-238 GPHS modules, which are used in RTG, but by coupling them to a Stirling convertor provides a 4-fold reduction in the number of GPHS modules. This study considers the use of Americium 241 (Am-241) as a substitute for the Pu-238 in Stirling convertor based Radioisotope Power Systems (RPS) for power levels from 1 O's of watts to 5 kWe. The Am-241 is used as a replacement for the Pu-238 in GPHS modules. Depending on power level, different Stirling heat input and removal systems are modeled. It was found that substituting Am-241 GPHS modules into the ASRG reduces power output by about 1/5 while maintaining approximately the same system mass. In order to obtain the nominal 160 watts electrical output of the Pu-238 ASRG requires 10 Am-241 GPHS modules. Higher power systems require changing from conductive coupling heat input and removal from the Stirling convertor to either pumped loops or heat pipes. Liquid metal pumped loops are considered as the primary heat transportation on the hot end and water pumped loop/heat pipe radiator is considered for the heat rejection side for power levels above 1 kWe.

Wavelet-Transform-Based Power Management of Hybrid Vehicles with Multiple On-board Energy Sources Including Fuel Cell, Battery and Ultracapacitor

DTIC Science & Technology

2008-09-12

considered to be promising for application as distributed generation sources due to high efficiency and compactness [1-2], [21-24]. The PEMFC is...also a primary candidate for environment-friendly vehicles. The nomenclatures of the PEMFC are as follows: B , C : Constants to calculate the...0 O H H-O H-O 1 2 N I q q r r FU = (10) The block diagram of the PEMFC model based on the above equations is shown in Fig

Polarization-maintaining performance of large effective area, higher order modes fiber in a coiled configuration

NASA Astrophysics Data System (ADS)

Ahmad, Raja; Nicholson, Jeffrey W.; Abedin, Kazi S.; Westbrook, Paul S.; Headley, Clifford; Wisk, Patrick W.; Monberg, Eric M.; Yan, Man F.; DiGiovanni, David J.

2018-02-01

Scaling the power-level of fiber sources has many practical advantages, while also enabling fundamental studies on the light-matter interaction in amorphous guiding media. In order to scale the power-level of fiber-sources without encountering nonlinear impairments, a strategy is to increase the effective-area of the guided optical-mode. Increasing the effective-area of the fundamental mode in a fiber, however, presents the challenges of increased susceptibility to mode-distortion and effective-area-reduction under the influence of bends. Therefore, higher-order-mode (HOM) fibers, which guide light in large effective-area (Aeff) Bessel-like modes, are a good candidate for scaling the power-level of robust fiber-sources. Many applications of high-power fiber-sources also demand a deterministic control on the polarization-state of light. Furthermore, a polarization-maintaining (PM)-type HOM fiber can afford the added possibility of coherent-beam combination and polarization multiplexing of high-power fiber-lasers. Previously, we reported polarization-maintaining operation in a 1.3 m length of PM-HOM fiber that was held straight. The PM-HOM fiber guided Bessel-like modes with Aeff ranging from 1200-2800 μm2. In this work, we report, for the first time, that the polarization-extinction-ratio (PER) of the HOM exceeds 10 dB in an 8 m long fiber that is coiled down to a diameter of 40 cm. This opens a path towards compact and polarization-controlled high-power fiber-systems.

The US Army Foreign Comparative Test fuel cell program

NASA Astrophysics Data System (ADS)

Bostic, Elizabeth; Sifer, Nicholas; Bolton, Christopher; Ritter, Uli; Dubois, Terry

The US Army RDECOM initiated a Foreign Comparative Test (FCT) Program to acquire lightweight, high-energy dense fuel cell systems from across the globe for evaluation as portable power sources in military applications. Five foreign companies, including NovArs, Smart Fuel Cell, Intelligent Energy, Ballard Power Systems, and Hydrogenics, Inc., were awarded competitive contracts under the RDECOM effort. This paper will report on the status of the program as well as the experimental results obtained from one of the units. The US Army has interests in evaluating and deploying a variety of fuel cell systems, where these systems show added value when compared to current power sources in use. For low-power applications, fuel cells utilizing high-energy dense fuels offer significant weight savings over current battery technologies. This helps reduce the load a solider must carry for longer missions. For high-power applications, the low operating signatures (acoustic and thermal) of fuel cell systems make them ideal power generators in stealth operations. Recent testing has been completed on the Smart Fuel Cell A25 system that was procured through the FCT program. The "A-25" is a direct methanol fuel cell hybrid and was evaluated as a potential candidate for soldier and sensor power applications.

Hunting for treasures among the Fermi unassociated sources: A multiwavelength approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Acero, F.; Ojha, R.; Donato, D.

2013-12-20

The Fermi Gamma-Ray Space Telescope has been detecting a wealth of sources where the multiwavelength counterpart is either inconclusive or missing altogether. We present a combination of factors that can be used to identify multiwavelength counterparts to these Fermi unassociated sources. This approach was used to select and investigate seven bright, high-latitude unassociated sources with radio, UV, X-ray, and γ-ray observations. As a result, four of these sources are candidates to be active galactic nuclei, and one to be a pulsar, while two do not fit easily into these known categories of sources. The latter pair of extraordinary sources mightmore » reveal a new category subclass or a new type of γ-ray emitter. These results altogether demonstrate the power of a multiwavelength approach to illuminate the nature of unassociated Fermi sources.« less

Characterisation of flash X-ray source generated by Kali-1000 Pulse Power System

NASA Astrophysics Data System (ADS)

Satyanarayana, N.; Durga Prasada Rao, A.; Mittal, K. C.

2016-02-01

The electron beam-driven Rod Pinch Diode (RPD) is presently fielded on KALI-1000 Pulse Power System at Bhabha Atomic Research Centre, Visakhapatnam and is a leading candidate for future flash X-ray radiographic sources. The diode is capable of producing less than 2-mm radiation spot sizes and greater than 350 milli rads of dose measured at 1 m from the X-ray source. KALI-1000 Pulse Power Source is capable of delivering up to 600 kV using a Tesla Transformer with Demineralized Insulated Transmission Line (DITL), the diode typically operates between 250-330 kV . Since the radiation dose has a power-law dependence on diode voltage, this limits the dose production on KALI-1000 system. Radiation dose with angular variation is measured using thermoluminescent detectors (TLD's) and the X-ray spot size is measured using pin hole arrangement with image plate (IP) to obtain the time-integrated source profile as well as a time-resolved spot diagnostic. An X-ray pinhole camera was used to pick out where the energetic e-beam connects to the anode. Ideally the diode should function such that the radiation is emitted from the tip. The camera was mounted perpendicular to the machine's axis to view the radiation from the tip. Comparison of the spot sizes of the X-ray sources obtained by the pin hole and rolled edge arrangements was carried and results obtained by both the techniques are with in ± 10% of the average values.

A Search for Technosignatures from 14 Planetary Systems in the Kepler Field with the Green Bank Telescope at 1.15–1.73 GHz

NASA Astrophysics Data System (ADS)

Margot, Jean-Luc; Greenberg, Adam H.; Pinchuk, Pavlo; Shinde, Akshay; Alladi, Yashaswi; Prasad MN, Srinivas; Bowman, M. Oliver; Fisher, Callum; Gyalay, Szilard; McKibbin, Willow; Miles, Brittany; Nguyen, Donald; Power, Conor; Ramani, Namrata; Raviprasad, Rashmi; Santana, Jesse; Lynch, Ryan S.

2018-05-01

Analysis of Kepler mission data suggests that the Milky Way includes billions of Earth-sized planets in the habitable zone of their host stars. Current technology enables the detection of technosignatures emitted from a large fraction of the Galaxy. We describe a search for technosignatures that is sensitive to Arecibo-class transmitters located within ∼420 ly of Earth and transmitters that are 1000 times more effective than Arecibo within ∼13000 ly of Earth. Our observations focused on 14 planetary systems in the Kepler field and used the L-band receiver (1.15–1.73 GHz) of the 100 m diameter Green Bank Telescope. Each source was observed for a total integration time of 5 minutes. We obtained power spectra at a frequency resolution of 3 Hz and examined narrowband signals with Doppler drift rates between ±9 Hz s‑1. We flagged any detection with a signal-to-noise ratio in excess of 10 as a candidate signal and identified approximately 850,000 candidates. Most (99%) of these candidate signals were automatically classified as human-generated radio-frequency interference (RFI). A large fraction (>99%) of the remaining candidate signals were also flagged as anthropogenic RFI because they have frequencies that overlap those used by global navigation satellite systems, satellite downlinks, or other interferers detected in heavily polluted regions of the spectrum. All 19 remaining candidate signals were scrutinized and none were attributable to an extraterrestrial source.

Mapping Compound Cosmic Telescopes Containing Multiple Projected Cluster-scale Halos

NASA Astrophysics Data System (ADS)

Ammons, S. Mark; Wong, Kenneth C.; Zabludoff, Ann I.; Keeton, Charles R.

2014-01-01

Lines of sight with multiple projected cluster-scale gravitational lenses have high total masses and complex lens plane interactions that can boost the area of magnification, or étendue, making detection of faint background sources more likely than elsewhere. To identify these new "compound" cosmic telescopes, we have found directions in the sky with the highest integrated mass densities, as traced by the projected concentrations of luminous red galaxies (LRGs). We use new galaxy spectroscopy to derive preliminary magnification maps for two such lines of sight with total mass exceeding ~3 × 1015 M ⊙. From 1151 MMT Hectospec spectra of galaxies down to i AB = 21.2, we identify two to three group- and cluster-scale halos in each beam. These are well traced by LRGs. The majority of the mass in beam J085007.6+360428 (0850) is contributed by Zwicky 1953, a massive cluster at z = 0.3774, whereas beam J130657.5+463219 (1306) is composed of three halos with virial masses of 6 × 1014-2 × 1015 M ⊙, one of which is A1682. The magnification maps derived from our mass models based on spectroscopy and Sloan Digital Sky Survey photometry alone display substantial étendue: the 68% confidence bands on the lens plane area with magnification exceeding 10 for a source plane of zs = 10 are [1.2, 3.8] arcmin2 for 0850 and [2.3, 6.7] arcmin2 for 1306. In deep Subaru Suprime-Cam imaging of beam 0850, we serendipitously discover a candidate multiply imaged V-dropout source at z phot = 5.03. The location of the candidate multiply imaged arcs is consistent with the critical curves for a source plane of z = 5.03 predicted by our mass model. Incorporating the position of the candidate multiply imaged galaxy as a constraint on the critical curve location in 0850 narrows the 68% confidence band on the lens plane area with μ > 10 and zs = 10 to [1.8, 4.2] arcmin2, an étendue range comparable to that of MACS 0717+3745 and El Gordo, two of the most powerful single cluster lenses known. The significant lensing power of our beams makes them powerful probes of reionization and galaxy formation in the early universe.

iPTF report of bright transients

NASA Astrophysics Data System (ADS)

Cannella, Chris; Kuesters, Daniel; Ferretti, Raphael; Blagorodnova, Nadejda; Adams, Scott; Kupfer, Thomas; Neill, James D.; Walters, Richard; Yan, Lin; Kulkarni, Shri

2017-02-01

The intermediate Palomar Transient Factory (iPTF; ATel #4807) reports the following bright ( Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R), and RB5 (Wozniak et al. 2013AAS...22143105W).

Time-dependent Modeling of Pulsar Wind Nebulae

NASA Astrophysics Data System (ADS)

Vorster, M. J.; Tibolla, O.; Ferreira, S. E. S.; Kaufmann, S.

2013-08-01

A spatially independent model that calculates the time evolution of the electron spectrum in a spherically expanding pulsar wind nebula (PWN) is presented, allowing one to make broadband predictions for the PWN's non-thermal radiation. The source spectrum of electrons injected at the termination shock of the PWN is chosen to be a broken power law. In contrast to previous PWN models of a similar nature, the source spectrum has a discontinuity in intensity at the transition between the low- and high-energy components. To test the model, it is applied to the young PWN G21.5-0.9, where it is found that a discontinuous source spectrum can model the emission at all wavelengths better than a continuous one. The model is also applied to the unidentified sources HESS J1427-608 and HESS J1507-622. Parameters are derived for these two candidate nebulae that are consistent with the values predicted for other PWNe. For HESS J1427-608, a present day magnetic field of B age = 0.4 μG is derived. As a result of the small present day magnetic field, this source has a low synchrotron luminosity, while remaining bright at GeV/TeV energies. It is therefore possible to interpret HESS J1427-608 within the ancient PWN scenario. For the second candidate PWN HESS J1507-622, a present day magnetic field of B age = 1.7 μG is derived. Furthermore, for this candidate PWN a scenario is favored in the present paper in which HESS J1507-622 has been compressed by the reverse shock of the supernova remnant.

Finding Minimum-Power Broadcast Trees for Wireless Networks

NASA Technical Reports Server (NTRS)

Arabshahi, Payman; Gray, Andrew; Das, Arindam; El-Sharkawi, Mohamed; Marks, Robert, II

2004-01-01

Some algorithms have been devised for use in a method of constructing tree graphs that represent connections among the nodes of a wireless communication network. These algorithms provide for determining the viability of any given candidate connection tree and for generating an initial set of viable trees that can be used in any of a variety of search algorithms (e.g., a genetic algorithm) to find a tree that enables the network to broadcast from a source node to all other nodes while consuming the minimum amount of total power. The method yields solutions better than those of a prior algorithm known as the broadcast incremental power algorithm, albeit at a slightly greater computational cost.

Wavelength stabilized DBR high power diode laser using EBL optical confining grating technology

NASA Astrophysics Data System (ADS)

Paoletti, R.; Codato, S.; Coriasso, C.; Gotta, P.; Meneghini, G.; Morello, G.; De Melchiorre, P.; Riva, E.; Rosso, M.; Stano, A.; Gattiglio, M.

2018-02-01

This paper reports a DBR High Power Diode Laser (DBR-HPDL) realization, emitting up to 10W in the 920 nm range. High spectral purity (90% power in about 0.5 nm), and wavelength stability versus injected current (about 5 times more than standard FP laser) candidates DBR-HPDL as a suitable device for wavelength stabilized pump source, and high brightness applications exploiting Wavelength Division Multiplexing. Key design aspect is a multiple-orders Electron Beam Lithography (EBL) optical confining grating, stabilizing on same wafer multiple wavelengths by a manufacturable and reliable technology. Present paper shows preliminary demonstration of wafer with 3 pitches, generating DBRHPDLs 2.5 nm spaced.

Finding gene regulatory network candidates using the gene expression knowledge base.

PubMed

Venkatesan, Aravind; Tripathi, Sushil; Sanz de Galdeano, Alejandro; Blondé, Ward; Lægreid, Astrid; Mironov, Vladimir; Kuiper, Martin

2014-12-10

Network-based approaches for the analysis of large-scale genomics data have become well established. Biological networks provide a knowledge scaffold against which the patterns and dynamics of 'omics' data can be interpreted. The background information required for the construction of such networks is often dispersed across a multitude of knowledge bases in a variety of formats. The seamless integration of this information is one of the main challenges in bioinformatics. The Semantic Web offers powerful technologies for the assembly of integrated knowledge bases that are computationally comprehensible, thereby providing a potentially powerful resource for constructing biological networks and network-based analysis. We have developed the Gene eXpression Knowledge Base (GeXKB), a semantic web technology based resource that contains integrated knowledge about gene expression regulation. To affirm the utility of GeXKB we demonstrate how this resource can be exploited for the identification of candidate regulatory network proteins. We present four use cases that were designed from a biological perspective in order to find candidate members relevant for the gastrin hormone signaling network model. We show how a combination of specific query definitions and additional selection criteria derived from gene expression data and prior knowledge concerning candidate proteins can be used to retrieve a set of proteins that constitute valid candidates for regulatory network extensions. Semantic web technologies provide the means for processing and integrating various heterogeneous information sources. The GeXKB offers biologists such an integrated knowledge resource, allowing them to address complex biological questions pertaining to gene expression. This work illustrates how GeXKB can be used in combination with gene expression results and literature information to identify new potential candidates that may be considered for extending a gene regulatory network.

Long-Term Spectral and Timing Behavior of the Black Hole Candidate XTE J1908+094

NASA Technical Reports Server (NTRS)

Gogus, Ersin; Finger, Mark H.; Kouveliotou, Chryssa; Woods, Peter M.; Patel, Sandeep K.; Ruppen, Michael; Swank, Jean H.; Markwardt, Craig B.; VanDerKlis, Michiel

2004-01-01

We present the long-term X-ray light curves and detailed spectral and timing analyses of XTE J1908+094 using the Rossi X-Ray Timing Explorer Proportional Counter Array observations covering two outbursts in 2002 and early 2003. At the onset of the first outburst, the source was found in a spectrally low/hard state lasting for approx.40 days, followed by a 3 day long transition to the high/soft state. The source flux (in 2- 10 keV) reached approx.100 mcrab on 2002 April 6, then decayed rapidly. In power spectra, we detect strong band-limited noise and varying low- frequency quasi-periodic oscillations that evolved from approx.0.5 to approx.5 Hz during the initial low/hard state of the source. We find that the second outburst closely resembled the spectral evolution of the first. The X-ray transient s overall outburst characteristics led us to classify XTE J1908+094 as a black hole candidate. Here we also derive precise X-ray position of the source using Chandra observations that were performed during the decay phase of the first outburst and following the second outburst.

Analysis of High Switching Frequency Quasi-Z-Source Photovoltaic Inverter Using Wide Bandgap Devices

NASA Astrophysics Data System (ADS)

Kayiranga, Thierry

Power inverters continue to play a key role in todays electrical system more than ever. Power inverters employ power semiconductors to converter direct current (DC) into alternating current (AC). The performance of the semiconductors is based on speed and efficiency. Until recently, Silicon (Si) semiconductors had been established as mature. However, the continuous optimization and improvements in the production process of Si to meet today technology requirements have pushed Si materials to their theoretical limits. In an effort to find a suitable replacement, wide bandgap devices mainly Gallium Nitride (GaN) and Silicon Carbide (SiC), have proved to be excellent candidates offering high operation temperature, high blocking voltage and high switching frequency; of which the latter makes GaN a better candidate in high switching low voltage in Distributed Generations (DG). The single stage Quasi-Z-Source Inverter (qZSI) is also able to draw continuous and constant current from the source making ideal for PV applications in addition to allowing shoot-through states. The qZSI find best applications in medium level ranges where multiples qZS inverters can be cascaded (qZS-CMI) by combining the benefit of the qZSI, boost capabilities and continuous and constant input current, and those of the CMI, low output harmonic content and independent MPPT. When used with GaN devices operating at very high frequency, the qZS network impedance can be significantly reduced. However, the impedance network becomes asymmetric. The asymmetric impedance network (AIN-qZSI) has several advantages such as increased power density, increases system lifetime, small size volume and size making it more attractive for module integrated converter (MIC) concepts. However, there are technical challenges. With asymmetric component, resonance is introduced in the system leading to more losses and audible noise. With small inductances, new operation states become available further increasing the system complexity. This report investigates the AIN-qZSI and present solutions to aforementioned issues.

Discovery of the First Quadruple Gravitationally Lensed Quasar Candidate with Pan-STARRS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berghea, C. T.; Nelson, George J.; Dudik, R. P.

We report the serendipitous discovery of the first gravitationally lensed quasar candidate from Pan-STARRS. The grizy images reveal four point-like images with magnitudes between 14.9 and 18.1 mag. The colors of the point sources are similar, and they are more consistent with quasars than with stars or galaxies. The lensing galaxy is detected in the izy bands, with an inferred photometric redshift of ∼0.6, lower than that of the point sources. We successfully model the system with a singular isothermal ellipsoid with shear, using the relative positions of the five objects as constraints. While the brightness ranking of the pointmore » sources is consistent with that of the model, we find discrepancies between the model-predicted and observed fluxes, likely due to microlensing by stars and millilensing due to the dark matter substructure. In order to fully confirm the gravitational lens nature of this system and add it to the small but growing number of the powerful probes of cosmology and astrophysics represented by quadruply lensed quasars, we require further spectroscopy and high-resolution imaging.« less

Research on radiation induced laser plasmas

NASA Technical Reports Server (NTRS)

Schneider, R. T.; Rowe, M. J.; Carter, B. D.; Walters, R. A.; Cox, J. D.; Liang, R.; Roxey, T.; Zapata, L.

1979-01-01

The development of high power nuclear pumped lasers is discussed. The excitation mechanism of continuous wave (CW) HeNe nuclear pumped lasers is studied and a CO2 nuclear pumped laser is used to demonstrate the CW output in the order of watts. The assumption that high power densities are only achievable by volume fission fragment sources is used to identify laser gases which are compatible with UF6 by excited states lifetime measurements. The examination of Xe2, XeF, and KrF under nuclear irradiation to determine if they are good candidates for nuclear-pumped lasers is described.

Solar powered Stirling cycle electrical generator

NASA Technical Reports Server (NTRS)

Shaltens, Richard K.

1991-01-01

Under NASA's Civil Space Technology Initiative (CSTI), the NASA Lewis Research Center is developing the technology needed for free-piston Stirling engines as a candidate power source for space systems in the late 1990's and into the next century. Space power requirements include high efficiency, very long life, high reliability, and low vibration. Furthermore, system weight and operating temperature are important. The free-piston Stirling engine has the potential for a highly reliable engine with long life because it has only a few moving parts, non-contacting gas bearings, and can be hermetically sealed. These attributes of the free-piston Stirling engine also make it a viable candidate for terrestrial applications. In cooperation with the Department of Energy, system designs are currently being completed that feature the free-piston Stirling engine for terrestrial applications. Industry teams were assembled and are currently completing designs for two Advanced Stirling Conversion Systems utilizing technology being developed under the NASA CSTI Program. These systems, when coupled with a parabolic mirror to collect the solar energy, are capable of producing about 25 kW of electricity to a utility grid. Industry has identified a niche market for dish Stirling systems for worldwide remote power application. They believe that these niche markets may play a major role in the introduction of Stirling products into the commercial market.

On the carriers of the 21μm emission feature in post-asymptotic giant branch stars

NASA Astrophysics Data System (ADS)

Zhang, Ke; Jiang, B. W.; Li, Aigen

2009-07-01

The mysterious 21μm emission feature seen in sixteen C-rich proto-planetary nebulae (PPNe) remains unidentified since its discovery in 1989. Over a dozen of materials are suggested as the carrier candidates. In this work, we quantitatively investigate eight inorganic and one organic carrier candidates in terms of elemental abundance constraints, while previous studies mostly focus on their spectral profiles (which could be largely affected by grain size, shape and clustering effects). It is found that: (1) five candidates (TiC nanoclusters, fullerenes coordinated with Ti atoms, SiS2, doped-SiC and SiO2-coated SiC dust) violate the abundance constraints (i.e. they require too much Ti, S or Si to account for the emission power of the 21μm band, (2) three candidates (carbon and silicon mixtures, Fe2O3 and Fe3O4), while satisfying the abundance constraints, exhibit secondary features which are not detected in the 21μm sources and (3) nano FeO, neither exceeding the abundance budget nor producing undetected secondary features, seems to be a viable candidate, supporting the suggestions of Posch, Mutschke & Andersen.

Recent advances on enzymatic glucose/oxygen and hydrogen/oxygen biofuel cells: Achievements and limitations

NASA Astrophysics Data System (ADS)

Cosnier, Serge; J. Gross, Andrew; Le Goff, Alan; Holzinger, Michael

2016-09-01

The possibility of producing electrical power from chemical energy with biological catalysts has induced the development of biofuel cells as viable energy sources for powering portable and implanted electronic devices. These power sources employ biocatalysts, called enzymes, which are highly specific and catalytic towards the oxidation of a biofuel and the reduction of oxygen or hydrogen peroxide. Enzymes, on one hand, are promising candidates to replace expensive noble metal-based catalysts in fuel cell research. On the other hand, they offer the exciting prospect of a new generation of fuel cells which harvest energy from body fluids. Biofuel cells which use glucose as a fuel are particularly interesting for generating electricity to power electronic devices inside a living body. Hydrogen consuming biofuel cells represent an emerging alternative to platinum catalysts due to comparable efficiencies and the capability to operate at lower temperatures. Currently, these technologies are not competitive with existing commercialised fuel cell devices due to limitations including insufficient power outputs and lifetimes. The advantages and challenges facing glucose biofuel cells for implantation and hydrogen biofuel cells will be summarised along with recent promising advances and the future prospects of these exotic energy-harvesting devices.

A Chandra X-Ray Study of NGC 1068 IL the Luminous X-Ray Source Population

NASA Technical Reports Server (NTRS)

Smith, David A.; Wilson, Andrew S.

2003-01-01

We present an analysis of the compact X-ray source population in the Seyfert 2 galaxy NGC 1068, imaged with a approx. 50 ks Chandra observation. We find a total of 84 compact sources on the S3 chip, of which 66 are located within the 25.0 B-mag/arcsec isophote of the galactic disk of NGC 1068. Spectra have been obtained for the 21 sources with at least 50 counts and modeled with both multicolor disk blackbody and power-law models. The power-law model provides the better description of the spectrum for 18 of these sources. For fainter sources, the spectral index has been estimated from the hardness ratio. Five sources have 0.4 - 8 keV intrinsic luminosities greater than 10(exp 39)ergs/ s, assuming that their emission is isotropic and that they are associated with NGC 1068. We refer to these sources as intermediate-luminosity X-ray objects (ISOs). If these five sources are X-ray binaries accreting with luminosities that are both sub-Eddington and isotropic, then the implied source masses are approx greater than 7 solar mass, and so they are inferred to be black holes. Most of the spectrally modeled sources have spectral shapes similar to Galactic black hole candidates. However, the brightest compact source in NGC 1068 has a spectrum that is much harder than that found in Galactic black hole candidates and other ISOs. The brightest source also shows large amplitude variability on both short-term and long-term timescales, with the count rate possibly decreasing by a factor of 2 in approx. 2 ks during our Chundra observation, and the source flux decreasing by a factor of 5 between our observation and the grating observations taken just over 9 months later. The ratio of the number of sources with luminosities greater than 2.1 x 10(exp 38) ergs/s in the 0.4 - 8 keV band to the rate of massive (greater than 5 solar mass) star formation is the same, to within a factor of 2, for NGC 1068, the Antennae, NGC 5194 (the main galaxy in M51), and the Circinus galaxy. This suggests that the rate of production of X-ray binaries per massive star is approximately the same for galaxies with currently active star formation, including "starbursts."

A High Performance H2-Cl2 Fuel Cell for Space Power Applications

NASA Technical Reports Server (NTRS)

Anderson, Everett B.; Taylor, E. Jennings; Wilemski, Gerald; Gelb, Alan

1993-01-01

NASA has numerous airborne/spaceborne applications for which high power and energy density power sources are needed. The proton exchange membrane fuel cell (PEMFC) is an attractive candidate for such a power source. PEMFC's offer many advantages for airborne/spaceborne applications. They have high power and energy densities, convert fuel to electrical power with high efficiency at both part and full load, and can rapidly startup and shutdown. In addition, PEMFC's are lightweight and operate silently. A significant impediment to the attainment of very high power and energy densities by PEMFC's is their current exclusive reliance on oxygen as the oxidant. Conventional PEMFC's oxidize hydrogen at the anode and reduce oxygen at the cathode. The electrode kinetics of oxygen reduction are known to be highly irreversible, incurring large overpotential losses. In addition, the modest open circuit potential of 1.2V for the H2-O2 fuel cell is unattainable due to mixed potential effects at the oxygen electrode. Because of the high overpotential losses, cells using H2 and O2 are capable of achieving high current densities only at very low cell voltages, greatly curtailing their power output. Based on experimental work on chlorine reduction in a gas diffusion electrode, we believe significant increases in both the energy and power densities of PEMFC systems can be achieved by employing chlorine as an alternative oxidant.

YSO jets in the Galactic plane from UWISH2 - V. Jets and outflows in M17

NASA Astrophysics Data System (ADS)

Samal, M. R.; Chen, W. P.; Takami, M.; Jose, J.; Froebrich, D.

2018-07-01

Jets and outflows are the first signposts of stellar birth. Emission in the H2 1-0 S(1) line at 2.122- μm is a powerful tracer of shock excitation in these objects. Here we present the analysis of 2.0 × 0.8 deg2 data from the UK Wide-field Infrared Survey for H2 (UWISH2) in the 1-0 S(1) line to identify and characterize the outflows of the M17 complex. We uncover 48 probable outflows, of which 93 per cent are new discoveries. We identified driving source candidates for 60 per cent of outflows. Among the driving source candidate young stellar objects (YSOs), 90 per cent are protostars and the remaining 10 per cent are Class II YSOs. In comparison with results from other surveys, we suggest that H2 emission fades very quickly as the objects evolve from protostars to pre-main-sequence stars. We fit spectral energy distribution (SED) models to 14 candidate outflow-driving sources and conclude that the outflows of our sample are mostly driven by moderate-mass YSOs that are still actively accreting from their protoplanetary disc. We examined the spatial distribution of the outflows with the gas and dust distribution of the complex and observed that the filamentary dark cloud M17SWex, located on the south-western side of the complex, is associated with a greater number of outflows. We find that our results corroborate previous suggestions that, in the M17 complex, M17SWex is the most active site of star formation. Several of our newly identified outflow candidates are excellent targets for follow-up studies to understand better the very early phase of protostellar evolution.

iPTF Discoveries of Recent Type Ia Supernovae

NASA Astrophysics Data System (ADS)

Papadogiannakis, S.; Taddia, F.; Petrushevska, T.; Ferretti, R.; Fremling, C.; Karamehmetoglu, E.; Nyholm, A.; Roy, R.; Hangard, L.; Vreeswijk, P.; Horesh, A.; Manulis, I.; Rubin, A.; Yaron, O.; Leloudas, G.; Khazov, D.; Soumagnac, M.; Knezevic, S.; Johansson, J.; Nir, G.; Cao, Y.; Blagorodnova, N.; Kulkarni, S.

2016-05-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following Type Ia SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artefacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W).

iPTF Discoveries of Recent Core-Collapse Supernovae

NASA Astrophysics Data System (ADS)

Taddia, F.; Ferretti, R.; Papadogiannakis, S.; Petrushevska, T.; Fremling, C.; Karamehmetoglu, E.; Nyholm, A.; Roy, R.; Hangard, L.; Horesh, A.; Khazov, D.; Knezevic, S.; Johansson, J.; Leloudas, G.; Manulis, I.; Rubin, A.; Soumagnac, M.; Vreeswijk, P.; Yaron, O.; Bar, I.; Cao, Y.; Kulkarni, S.; Blagorodnova, N.

2016-05-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following core-collapse SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W).

iPTF Discoveries of Recent Core-Collapse Supernovae

NASA Astrophysics Data System (ADS)

Taddia, F.; Ferretti, R.; Fremling, C.; Karamehmetoglu, E.; Nyholm, A.; Papadogiannakis, S.; Petrushevska, T.; Roy, R.; Hangard, L.; De Cia, A.; Vreeswijk, P.; Horesh, A.; Manulis, I.; Sagiv, I.; Rubin, A.; Yaron, O.; Leloudas, G.; Khazov, D.; Soumagnac, M.; Bilgi, P.

2015-04-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following Core-Collapse SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W).

iPTF Discoveries of Recent Type Ia Supernova

NASA Astrophysics Data System (ADS)

Petrushevska, T.; Ferretti, R.; Fremling, C.; Hangard, L.; Karamehmetoglu, E.; Nyholm, A.; Papadogiannakis, S.; Roy, R.; Horesh, A.; Khazov, D.; Knezevic, S.; Johansson, J.; Leloudas, G.; Manulis, I.; Rubin, A.; Soumagnac, M.; Vreeswijk, P.; Yaron, O.; Bilgi, P.; Cao, Y.; Duggan, G.; Lunnan, R.; Andreoni, I.

2015-10-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following Type Ia SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W).

iPTF Discoveries of Recent SNe Ia

NASA Astrophysics Data System (ADS)

Ferretti, R.; Fremling, C.; Johansson, J.; Karamehmetoglu, E.; Migotto, K.; Nyholm, A.; Papadogiannakis, S.; Taddia, F.; Petrushevska, T.; Roy, R.; Ben-Ami, S.; De Cia, A.; Dzigan, Y.; Horesh, A.; Khazov, D.; Manulis, I.; Rubin, A.; Sagiv, I.; Vreeswijk, P.; Yaron, O.; Bilgi, P.; Cao, Y.; Duggan, G.

2015-02-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following Type Ia SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W).

iPTF Discoveries of Recent Type Ia Supernovae

NASA Astrophysics Data System (ADS)

Papadogiannakis, S.; Taddia, F.; Ferretti, R.; Fremling, C.; Karamehmetoglu, E.; Petrushevska, T.; Nyholm, A.; Roy, R.; Hangard, L.; Vreeswijk, P.; Horesh, A.; Manulis, I.; Rubin, A.; Yaron, O.; Leloudas, G.; Khazov, D.; Soumagnac, M.; Knezevic, S.; Johansson, J.; Lunnan, R.; Blagorodnova, N.; Cao, Y.; Cenk, S. B.

2016-01-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following Type Ia SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W).

iPTF Discoveries of Recent Type Ia Supernovae

NASA Astrophysics Data System (ADS)

Ferretti, R.; Fremling, C.; Hangard, L.; Karamehmetoglu, E.; Nyholm, A.; Papadogiannakis, S.; Petrushevska, T.; Roy, R.; Taddia, F.; Horesh, A.; Khazov, D.; Knezevic, S.; Leloudas, G.; Manulis, I.; Rubin, A.; Soumagnac, M.; Vreeswijk, P.; Yaron, O.; Cao, Y.; Duggan, G.; Lunnan, R.; Blagorodnova, N.

2015-11-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following Type Ia SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W).

iPTF Discoveries of Recent Core-Collapse Supernovae

NASA Astrophysics Data System (ADS)

Taddia, F.; Ferretti, R.; Fremling, C.; Karamehmetoglu, E.; Nyholm, A.; Papadogiannakis, S.; Petrushevska, T.; Roy, R.; Hangard, L.; Vreeswijk, P.; Horesh, A.; Manulis, I.; Rubin, A.; Yaron, O.; Leloudas, G.; Khazov, D.; Soumagnac, M.; Knezevic, S.; Johansson, J.; Duggan, G.; Lunnan, R.; Cao, Y.

2015-09-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following Core-Collapse SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W).

iPTF Discovery of Recent Type Ia Supernovae

NASA Astrophysics Data System (ADS)

Hangard, L.; Ferretti, R.; Fremling, C.; Karamehmetoglu, E.; Nyholm, A.; Papadogiannakis, S.; Petrushevska, T.; Roy, R.; Bar, I.; Horesh, A.; Johansson, J.; Khazov, D.; Knezevic, S.; Leloudas, G.; Manulis, I.; Rubin, A.; Soumagnac, M.; Vreeswijk, P.; Yaron, O.; Cao, Y.; Kulkarni, S.; Lunnan, R.; Ravi, V.; Vedantham, H. K.; Yan, L.

2016-04-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following Type Ia SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W).

iPTF Discoveries of Recent Core-Collapse Supernovae

NASA Astrophysics Data System (ADS)

Taddia, F.; Ferretti, R.; Fremling, C.; Karamehmetoglu, E.; Nyholm, A.; Papadogiannakis, S.; Petrushevska, T.; Roy, R.; Hangard, L.; Vreeswijk, P.; Horesh, A.; Manulis, I.; Rubin, A.; Yaron, O.; Leloudas, G.; Khazov, D.; Soumagnac, M.; Knezevic, S.; Johansson, J.; Lunnan, R.; Cao, Y.; Miller, A.

2015-11-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following Core-Collapse SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W).

iPTF Discoveries of Recent Type Ia Supernovae

NASA Astrophysics Data System (ADS)

Petrushevska, T.; Ferretti, R.; Fremling, C.; Hangard, L.; Karamehmetoglu, E.; Nyholm, A.; Papadogiannakis, S.; Roy, R.; Horesh, A.; Khazov, D.; Knezevic, S.; Johansson, J.; Leloudas, G.; Manulis, I.; Rubin, A.; Soumagnac, M.; Vreeswijk, P.; Yaron, O.; Bilgi, P.; Cao, Y.; Duggan, G.; Lunnan, R.

2016-02-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following Type Ia SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W).

iPTF Discovery of Recent Type Ia Supernovae

NASA Astrophysics Data System (ADS)

Hangard, L.; Taddia, F.; Ferretti, R.; Papadogiannakis, S.; Petrushevska, T.; Fremling, C.; Karamehmetoglu, E.; Nyholm, A.; Roy, R.; Horesh, A.; Khazov, D.; Knezevic, S.; Johansson, J.; Leloudas, G.; Manulis, I.; Rubin, A.; Soumagnac, M.; Vreeswijk, P.; Yaron, O.; Bar, I.; Lunnan, R.; Cenk, S. B.

2016-02-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following Type Ia SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W).

iPTF Discoveries of Recent Type Ia Supernovae

NASA Astrophysics Data System (ADS)

Papadogiannakis, S.; Fremling, C.; Hangard, L.; Karamehmetoglu, E.; Nyholm, A.; Ferretti, R.; Petrushevska, T.; Roy, R.; Taddia, F.; Bar, I.; Horesh, A.; Johansson, J.; Knezevic, S.; Leloudas, G.; Manulis, I.; Nir, G.; Rubin, A.; Soumagnac, M.; Vreeswijk, P.; Yaron, O.; Arcavi, I.; Howell, D. A.; McCully, C.; Hosseinzadeh, G.; Valenti, S.; Blagorodnova, N.; Cao, Y.; Duggan, G.; Ravi, V.; Lunnan, R.

2016-03-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following Type Ia SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W).

iPTF discoveries of recent type Ia supernovae

NASA Astrophysics Data System (ADS)

Papadogiannakis, S.; Ferretti, R.; Fremling, C.; Hangard, L.; Karamehmetoglu, E.; Nyholm, A.; Petrushevska, T.; Roy, R.; De Cia, A.; Vreeswijk, P.; Horesh, A.; Manulis, I.; Sagiv, I.; Rubin, A.; Yaron, O.; Leloudas, G.; Khazov, D.; Soumagnac, M.; Knezevic, S.; Cenko, S. B.; Capone, J.; Bartakk, M.

2015-09-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following Type Ia SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W).

iPTF Discovery of Recent Type Ia Supernova

NASA Astrophysics Data System (ADS)

Hangard, L.; Petrushevska, T.; Papadogiannakis, S.; Ferretti, R.; Fremling, C.; Karamehmetoglu, E.; Nyholm, A.; Roy, R.; Horesh, A.; Khazov, D.; Knezevic, S.; Johansson, J.; Leloudas, G.; Manulis, I.; Rubin, A.; Soumagnac, M.; Vreeswijk, P.; Yaron, O.; Kasliwal, M.

2015-10-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following Type Ia SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W).

iPTF Discoveries of Recent Type Ia Supernovae

NASA Astrophysics Data System (ADS)

Petrushevska, T.; Ferretti, R.; Fremling, C.; Hangard, L.; Karamehmetoglu, E.; Nyholm, A.; Papadogiannakis, S.; Roy, R.; Horesh, A.; Khazov, D.; Knezevic, S.; Johansson, J.; Leloudas, G.; Manulis, I.; Rubin, A.; Soumagnac, M.; Vreeswijk, P.; Yaron, O.; Bilgi, P.; Cao, Y.; Duggan, G.; Lunnan, R.; Neill, J. D.; Walters, R.

2016-04-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following Type Ia SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W).

iPTF Discoveries of Recent Type Ia Supernovae

NASA Astrophysics Data System (ADS)

Papadogiannakis, S.; Taddia, F.; Petrushevska, T.; Fremling, C.; Hangard, L.; Johansson, J.; Karamehmetoglu, E.; Migotto, K.; Nyholm, A.; Roy, R.; Ben-Ami, S.; De Cia, A.; Dzigan, Y.; Horesh, A.; Khazov, D.; Soumagnac, M.; Manulis, I.; Rubin, A.; Sagiv, I.; Vreeswijk, P.; Yaron, O.; Bond, H.; Bilgi, P.; Cao, Y.; Duggan, G.

2015-03-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following Type Ia SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W).

iPTF Discovery of Recent Type Ia Supernovae

NASA Astrophysics Data System (ADS)

Hangard, L.; Ferretti, R.; Papadogiannakis, S.; Petrushevska, T.; Fremling, C.; Karamehmetoglu, E.; Nyholm, A.; Roy, R.; Horesh, A.; Khazov, D.; Knezevic, S.; Johansson, J.; Leloudas, G.; Manulis, I.; Rubin, A.; Soumagnac, M.; Vreeswijk, P.; Yaron, O.; Cook, D.

2015-12-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following Type Ia SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W).

iPTF Discoveries of Recent Type Ia Supernova

NASA Astrophysics Data System (ADS)

Petrushevska, T.; Ferretti, R.; Fremling, C.; Hangard, L.; Karamehmetoglu, E.; Nyholm, A.; Papadogiannakis, S.; Roy, R.; Horesh, A.; Khazov, D.; Knezevic, S.; Johansson, J.; Leloudas, G.; Manulis, I.; Rubin, A.; Soumagnac, M.; Vreeswijk, P.; Yaron, O.; Bilgi, P.; Cao, Y.; Duggan, G.; Lunnan, R.; Jencson, J.

2015-11-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following Type Ia SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W).

Continued X-ray Monitoring of Magnetar Candidate SWIFT J1822.3-1606

NASA Astrophysics Data System (ADS)

Scholz, P.; Livingstone, M. A.; Kaspi, V. M.

2011-08-01

We report on Swift/XRT and RXTE/PCA observations of the new 8.4-s Galactic magnetar candidate SWIFT J1822.3-1606, also referred to as SGR J1822.3-1606 (ATELs #3488, #3489, #3490, #3493, #3495, #3496, #3501, #3503, #3543). The persistent X-ray flux from the source continues to fade in ongoing XRT monitoring observations. For data in the MJD range 55757 to 55781, the best-fit power-law index, alpha, for the decay of the absorbed 1-10 keV flux is -0.47 ± 0.02, assuming a decay of functional form F(t) = F0 + F0*(t-T)^alpha, where T is the epoch of the Swift/BAT trigger (ATEL #3488).

Thermal power systems small power systems applications project. Volume 2: Detailed report

NASA Technical Reports Server (NTRS)

Marriott, A. T.

1979-01-01

Small power system technology as applied to power plants up to 10 MW in size was considered. Markets for small power systems were characterized and cost goals were established for the project. Candidate power plant system design concepts were selected for evaluation and preliminary performance and cost assessments were made. Breakeven capital costs were determined for leading contenders among the candidate systems. The potential use of small power systems in providing part of the demand for pumping power by the extensive aqueduct system of California, was studied. Criteria and methodologies were developed for the ranking of candidate power plant system design concepts. Experimental power plant concepts of 1 MW rating were studied to define a power plant configuration for subsequent detail design construction, testing and evaluation. Site selection criteria and ground rules were developed.

Application of the monolithic solid oxide fuel cell to space power systems

NASA Astrophysics Data System (ADS)

Myles, Kevin M.; Bhattacharyya, Samit K.

1991-01-01

The monolithic solid-oxide fuel cell (MSOFC) is a promising electrochemical power generation device that is currently under development at Argonne National Laboratory. The extremely high power density of the MSOFC leads to MSOFC systems that have sufficiently high energy densities that they are excellent candidates for a number of space missions. The fuel cell can also be operated in reverse, if it can be coupled to an external power source, to regenerate the fuel and oxidant from the water product. This feature further enhances the potential mission applications of the MSOFC. In this paper, the current status of the fuel cell development is presented—the focus being on fabrication and currently achievable performance. In addition, a specific example of a space power system, featuring a liquid metal cooled fast spectrum nuclear reactor and a monolithic solid oxide fuel cell, is presented to demonstrate the features of an integrated system.

THE CHANDRA SURVEY OF THE COSMOS FIELD. II. SOURCE DETECTION AND PHOTOMETRY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Puccetti, S.; Vignali, C.; Cappelluti, N.

2009-12-01

The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8 Ms, Chandra program that covers the central contiguous {approx}0.92 deg{sup 2} of the COSMOS field. C-COSMOS is the result of a complex tiling, with every position being observed in up to six overlapping pointings (four overlapping pointings in most of the central {approx}0.45 deg{sup 2} area with the best exposure, and two overlapping pointings in most of the surrounding area, covering an additional {approx}0.47 deg{sup 2}). Therefore, the full exploitation of the C-COSMOS data requires a dedicated and accurate analysis focused on three main issues: (1) maximizing the sensitivity when themore » point-spread function (PSF) changes strongly among different observations of the same source (from {approx}1 arcsec up to {approx}10 arcsec half-power radius); (2) resolving close pairs; and (3) obtaining the best source localization and count rate. We present here our treatment of four key analysis items: source detection, localization, photometry, and survey sensitivity. Our final procedure consists of a two step procedure: (1) a wavelet detection algorithm to find source candidates and (2) a maximum likelihood PSF fitting algorithm to evaluate the source count rates and the probability that each source candidate is a fluctuation of the background. We discuss the main characteristics of this procedure, which was the result of detailed comparisons between different detection algorithms and photometry tools, calibrated with extensive and dedicated simulations.« less

Scuba: scalable kernel-based gene prioritization.

PubMed

Zampieri, Guido; Tran, Dinh Van; Donini, Michele; Navarin, Nicolò; Aiolli, Fabio; Sperduti, Alessandro; Valle, Giorgio

2018-01-25

The uncovering of genes linked to human diseases is a pressing challenge in molecular biology and precision medicine. This task is often hindered by the large number of candidate genes and by the heterogeneity of the available information. Computational methods for the prioritization of candidate genes can help to cope with these problems. In particular, kernel-based methods are a powerful resource for the integration of heterogeneous biological knowledge, however, their practical implementation is often precluded by their limited scalability. We propose Scuba, a scalable kernel-based method for gene prioritization. It implements a novel multiple kernel learning approach, based on a semi-supervised perspective and on the optimization of the margin distribution. Scuba is optimized to cope with strongly unbalanced settings where known disease genes are few and large scale predictions are required. Importantly, it is able to efficiently deal both with a large amount of candidate genes and with an arbitrary number of data sources. As a direct consequence of scalability, Scuba integrates also a new efficient strategy to select optimal kernel parameters for each data source. We performed cross-validation experiments and simulated a realistic usage setting, showing that Scuba outperforms a wide range of state-of-the-art methods. Scuba achieves state-of-the-art performance and has enhanced scalability compared to existing kernel-based approaches for genomic data. This method can be useful to prioritize candidate genes, particularly when their number is large or when input data is highly heterogeneous. The code is freely available at https://github.com/gzampieri/Scuba .

Project on Elite Athlete Commitment (PEAK): IV. identification of new candidate commitment sources in the sport commitment model.

PubMed

Scanlan, Tara K; Russell, David G; Scanlan, Larry A; Klunchoo, Tatiana J; Chow, Graig M

2013-10-01

Following a thorough review of the current updated Sport Commitment Model, new candidate commitment sources for possible future inclusion in the model are presented. They were derived from data obtained using the Scanlan Collaborative Interview Method. Three elite New Zealand teams participated: amateur All Black rugby players, amateur Silver Fern netball players, and professional All Black rugby players. An inductive content analysis of these players' open-ended descriptions of their sources of commitment identified four unique new candidate commitment sources: Desire to Excel, Team Tradition, Elite Team Membership, and Worthy of Team Membership. A detailed definition of each candidate source is included along with example quotes from participants. Using a mixed-methods approach, these candidate sources provide a basis for future investigations to test their viability and generalizability for possible expansion of the Sport Commitment Model.

Application of Biomass from Palm Oil Mill for Organic Rankine Cycle to Generate Power in North Sumatera Indonesia

NASA Astrophysics Data System (ADS)

Nur, T. B.; Pane, Z.; Amin, M. N.

2017-03-01

Due to increasing oil and gas demand with the depletion of fossil resources in the current situation make efficient energy systems and alternative energy conversion processes are urgently needed. With the great potential of resources in Indonesia, make biomass has been considered as one of major potential fuel and renewable resource for the near future. In this paper, the potential of palm oil mill waste as a bioenergy source has been investigated. An organic Rankine cycle (ORC) small scale power plant has been preliminary designed to generate electricity. The working fluid candidates for the ORC plant based on the heat source temperature domains have been investigated. The ORC system with a regenerator has higher thermal efficiency than the basic ORC system. The study demonstrates the technical feasibility of ORC solutions in terms of resources optimizations and reducing of greenhouse gas emissions.

Candidate high-z protoclusters among the Planck compact sources, as revealed by Herschel-SPIRE

NASA Astrophysics Data System (ADS)

Greenslade, J.; Clements, D. L.; Cheng, T.; De Zotti, G.; Scott, D.; Valiante, E.; Eales, S.; Bremer, M. N.; Dannerbauer, H.; Birkinshaw, M.; Farrah, D.; Harrison, D. L.; Michałowski, M. J.; Valtchanov, I.; Oteo, I.; Baes, M.; Cooray, A.; Negrello, M.; Wang, L.; van der Werf, P.; Dunne, L.; Dye, S.

2018-05-01

By determining the nature of all the Planck compact sources within 808.4 deg2 of large Herschel surveys, we have identified 27 candidate protoclusters of dusty star-forming galaxies (DSFGs) that are at least 3σ overdense in either 250, 350, or 500 μm sources. We find roughly half of all the Planck compact sources are resolved by Herschel into multiple discrete objects, with the other half remaining unresolved by Herschel. We find a significant difference between versions of the Planck catalogues, with earlier releases hosting a larger fraction of candidate protoclusters and Galactic cirrus than later releases, which we ascribe to a difference in the filters used in the creation of the three catalogues. We find a surface density of DSFG candidate protoclusters of (3.3 ± 0.7) × 10-2 sources deg-2, in good agreement with previous similar studies. We find that a Planck colour selection of S857/S545 < 2 works well to select candidate protoclusters, but can miss protoclusters at z < 2. The Herschel colours of individual candidate protocluster members indicate our candidate protoclusters all likely all lie at z > 1. Our candidate protoclusters are a factor of 5 times brighter at 353 GHz than expected from simulations, even in the most conservative estimates. Further observations are needed to confirm whether these candidate protoclusters are physical clusters, multiple protoclusters along the line of sight, or chance alignments of unassociated sources.

iPTF Discoveries of Recent Type Ia Supernovae

NASA Astrophysics Data System (ADS)

Petrushevska, T.; Ferretti, R.; Fremling, C.; Hangard, L.; Johansson, J.; Migotto, K.; Nyholm, A.; Papadogiannakis, S.; Ben-Ami, S.; De Cia, A.; Dzigan, Y.; Horesh, A.; Leloudas, G.; Manulis, I.; Rubin, A.; Sagiv, I.; Vreeswijk, P.; Yaron, O.; Cao, Y.; Perley, D.; Miller, A.; Waszczak, A.; Kasliwal, M. M.; Hosseinzadeh, G.; Cenko, S. B.; Quimby, R.

2015-05-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following Type Ia SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W). See ATel #7112 for additional details.

Milagro Observations of Potential TeV Emitters

NASA Technical Reports Server (NTRS)

Abdo, A. A.; Abeysekara, A. U.; Allen, B. T.; Aune, T.; Barber, A. S.; Berley, D.; Braun, J.; Chen, C.; Christopher, G. E.; DeYoung, T.;

High-energy neutrinos from FR0 radio galaxies?

NASA Astrophysics Data System (ADS)

Tavecchio, F.; Righi, C.; Capetti, A.; Grandi, P.; Ghisellini, G.

2018-04-01

The sources responsible for the emission of high-energy (≳100 TeV) neutrinos detected by IceCube are still unknown. Among the possible candidates, active galactic nuclei with relativistic jets are often examined, since the outflowing plasma seems to offer the ideal environment to accelerate the required parent high-energy cosmic rays. The non-detection of single-point sources or - almost equivalently - the absence, in the IceCube events, of multiplets originating from the same sky position - constrains the cosmic density and the neutrino output of these sources, pointing to a numerous population of faint sources. Here we explore the possibility that FR0 radio galaxies, the population of compact sources recently identified in large radio and optical surveys and representing the bulk of radio-loud AGN population, can represent suitable candidates for neutrino emission. Modelling the spectral energy distribution of an FR0 radio galaxy recently associated with a γ-ray source detected by the Large Area Telescope onboard Fermi, we derive the physical parameters of its jet, in particular the power carried by it. We consider the possible mechanisms of neutrino production, concluding that pγ reactions in the jet between protons and ambient radiation is too inefficient to sustain the required output. We propose an alternative scenario, in which protons, accelerated in the jet, escape from it and diffuse in the host galaxy, producing neutrinos as a result of pp scattering with the interstellar gas, in strict analogy with the processes taking place in star-forming galaxies.

Hunting for swinging millisecond pulsars with XMM-Newton

NASA Astrophysics Data System (ADS)

Papitto, Alessandro

2013-10-01

The recent XMM discovery of a millisecond pulsar swinging between an accretion- powered (X-ray) and a rotation-powered (radio) pulsar state provided the final evidence of the evolutionary link between these two classes, demonstrating that transitions between the two states can be observed over of a few weeks. We propose a ToO program (made of 3 triggers of 60 ks, over a 3years timescale) aimed at detecting X-ray accretion powered pulsations in sources already known as ms radio pulsars. Candidates are restricted to black widows and redbacks, systems in an evolutionary phase that allows state transitions. Enlarging the number of systems in this transitional phase is crucial to test binary evolution theories, and to study the disk-field interaction over a large range of mass accretion rates.

The high-energy X-ray spectrum of black hole candidate GX 339-4 during a transition

NASA Technical Reports Server (NTRS)

Dolan, J. F.; Crannell, C. J.; Dennis, B. R.; Orwig, L. E.

1987-01-01

The X-ray emitting system GX 339-4 contains one of the prime candidates for a stellar mass-sized black hole. Determining the observational similarities and differences between the members of this group is of value in specifying which characteristics can be used to identify systems containing a black hole, especially those for which no mass determination can be made. The first observations of the E greater than 20 keV spectrum of GX 339-4 during a transition between luminosity states are reported here. The hard spectral state is the lower luminosity state of the system. GX 339-4 has a power-low spectrum above 20 keV which pivots during transitions between distinct luminosity states. The only other X-ray sources known to exhibit this behavior, Cyg XR-1 and (probably) A0620-00, are leading candidates for systems containing a black hole component based on their measured spectrocopic mass function.

POWERFUL HIGH-ENERGY EMISSION OF THE REMARKABLE BL Lac OBJECT S5 0716+714

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vittorini, V.; Chen, A. W.; Ferrari, A.

BL Lac objects of the intermediate subclass (IBLs) are known to emit a substantial fraction of their power in the energy range 0.1-10 GeV. Detecting gamma-ray emission from such sources provides therefore a direct probe of the emission mechanisms and of the underlying powerhouse. The gamma-ray satellite, AGILE, detected the remarkable IBL S5 0716+714 (z approx = 0.3) during a high state in the period from 2007 September-October, marked by two very intense flares reaching peak fluxes of 200 x 10{sup -8} photons cm{sup -2} s{sup -1} above 100 MeV, with simultaneous optical and X-ray observations. We present here amore » theoretical model for the two major flares and discuss the overall energetics of the source. We conclude that 0716+714 is among the brightest BL Lac's ever detected at gamma-ray energies. Because of its high power and lack of signs for ongoing accretion or surrounding gas, the source is an ideal candidate to test the maximal power extractable from a rotating supermassive black hole via the pure Blandford-Znajek (BZ) mechanism. We find that during the 2007 gamma-ray flares 0716+714 approached or just exceeded the upper limit set by BZ for a black hole of mass 10{sup 9} M{sub sun}.« less

On the Relation of Silicates and SiO Maser in Evolved Stars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jiaming; Jiang, Biwei, E-mail: bjiang@bnu.edu.cn

2017-04-01

The SiO molecule is one of the candidates for the seed of silicate dust in the circumstellar envelope of evolved stars, but this opinion is challenged. In this work we investigate the relation of the SiO maser emission power and the silicate dust emission power. With both our own observation by using the PMO/Delingha 13.7 m telescope and archive data, a sample is assembled of 21 SiO v  = 1, J  = 2 − 1 sources and 28 SiO v  = 1, J  = 1 − 0 sources that exhibit silicate emission features in the ISO /SWS spectrum as well. The analysis of their SiO maser and silicatemore » emission power indicates a clear correlation, which is not against the hypothesis that the SiO molecules are the seed nuclei of silicate dust. On the other hand, no correlation is found between SiO maser and silicate crystallinity, which may imply that silicate crystallinity does not correlate with mass-loss rate.« less

MAMBO observations at 240GHz of optically obscured Spitzer sources: source clumps and radio activity at high redshift

NASA Astrophysics Data System (ADS)

Andreani, P.; Magliocchetti, M.; de Zotti, G.

2010-01-01

Optically very faint (R > 25.5) sources detected by the Spitzer Space Telescope at 24μm represent a very interesting population at redshift z ~ (1.5-3). They exhibit strong clustering properties, implying that they are hosted by very massive haloes, and their mid-infrared emission could be powered by either dust-enshrouded star formation and/or by an obscured active galactic nucleus (AGN). We report observations carried out with the Max Planck Millimetre Bolometer (MAMBO) array at the IRAM 30-m antenna on Pico Veleta of a candidate protocluster with five optically obscured sources selected from the 24-μm Spitzer sample of the First-Look Survey. Interestingly, these sources appear to lie on a high-density filament aligned with the two radio jets of an AGN. Four out of five of the observed sources were detected. We combine these measurements with optical, infrared and radio observations to probe the nature of the candidate protocluster members. Our preliminary conclusions can be summarized as follows: the spectral energy distributions (SEDs) of all sources include both AGN and starburst contributions; the AGN contribution to the bolometric luminosities ranges between 14 and 26 per cent of the total. Such a contribution is enough for the AGN to dominate the emission at 5.8, 8 and 24μm, while the stellar component, inferred from SED fitting, prevails at 1.25mm and at λ < 4.5μm. The present analysis suggests a coherent interplay at high z between extended radio activity and the development of filamentary large-scale structures.

Advances in macrocyclic peptide-based antibiotics.

PubMed

Luther, Anatol; Bisang, Christian; Obrecht, Daniel

2018-06-01

Macrocyclic peptide-based natural products have provided powerful new antibiotic drugs, drug candidates, and scaffolds for medicinal chemists as a source of inspiration to design novel antibiotics. While most of those natural products are active mainly against Gram-positive pathogens, novel macrocyclic peptide-based compounds have recently been described, which exhibit potent and specific activity against some of the most problematic Gram-negative ESKAPE pathogens. This mini-review gives an up-date on recent developments. Copyright © 2017 Elsevier Ltd. All rights reserved.

SGR 1822-1606 (Swift J1822.3-1606): X-ray spectrum and refined spin period from Swift XRT analysis

NASA Astrophysics Data System (ADS)

Esposito, P.; Rea, N.; Israel, G. L.

2011-07-01

We have analysed 1.6 ks s of Photon Counting (PC) XRT data of the new SGR/magnetar candidate Swift J1822.3-1606 (Cummings et al. GCN #12159), including the first 0.6 ks on which Pagani et al. reported in GCN #12163. We found that the source spectrum is well described by a power-law plus blackbody model, modified for the interstellar absorption (reduced chi-squared = 1.04 for 97 degrees of freedom).

Analysis of the Execution of Counter-Drug Strategy in Bolivia Using the Low Intensity Conflict Imperatives

DTIC Science & Technology

1992-06-05

constant encouragement, and Dr. Graham Turbiville who added the academic focus and perspective to the paper. I especially thank my wife whu was introduced...boundaries became a source of conflict especially when mineral riches were involved. In 1879, Bolivia and Peru went to war with Chile over Bolivian claims...La Paz: Comision Episcopal de Educacion , 1981) pp. 277. 25 candidate. The incumbent president refused to allow Paz Estenssoro to assume power and

The Ultra-Luminous X-ray Source Population from the Chandra Archive of Galaxies

NASA Technical Reports Server (NTRS)

Swartz, Douglas A.; Ghosh, Kajal K.; Tennant, Allen F.; Wu, Kinwah

2004-01-01

One hundred fifty-four discrete non-nuclear Ultra-Luminous X-ray (ULX) sources, with spectroscopically-determined intrinsic X-ray luminosities greater than 1 e39 ergs/s, are identified in 82 galaxies observed with Chandra's Advanced CCD Imaging Spectrometer. Source positions, X-ray luminosities, and spectral and timing characteristics are tabulated. Statistical comparisons between these X-ray properties and those of the weaker discrete sources in the same fields (mainly neutron star and stellar-mass black hole binaries) are made. Sources above approximately le38 ergs per second display similar spatial, spectral, color, and variability distributions. In particular, there is no compelling evidence in the sample for a new and distinct class of X-ray object such as the intermediate-mass black holes. 83% of ULX candidates have spectra that can be described as absorbed power laws with index = 1.74 and column density = 2.24e21 l per square centimeter, or approximately 5 times the average Galactic column. About 20% of the ULX's have much steeper indices indicative of a soft, and likely thermal, spectrum. The locations of ULXs in their host galaxies are strongly peaked towards their galaxy centers. The deprojected radial distribution of the ULX candidates is somewhat steeper than an exponential disk, indistinguishable from that of the weaker sources. About 5--15% of ULX candidates are variable during the Chandra observations (which average 39.5 ks). Comparison of the cumulative X-ray luminosity functions of the ULXs to Chandra Deep Field results suggests approximately 25% of the sources may be background objects including 14% of the ULX candidates in the sample of spiral galaxies and 44% of those in elliptical galaxies implying the elliptical galaxy ULX population is severely compromised by background active galactic nuclei. Correlations with host galaxy properties confirm the number and total X-ray luminosity of the ULXs are associated with recent star formation and with galaxy merging and interactions. The preponderance of ULXs in star-forming galaxies as well as their similarities to less-luminous sources suggest they originate in a young but short-lived population such as the high-mass X-ray binaries with a smaller contribution (based on spectral slope) from recent supernovae. The number of ULXs in elliptical galaxies scales with host galaxy mass and can be explained most simply as the high-luminosity end of the low-mass X-ray binary population.

Speaking truth to power: the effect of candid feedback on how individuals with power allocate resources.

PubMed

Oc, Burak; Bashshur, Michael R; Moore, Celia

2015-03-01

Subordinates are often seen as impotent, able to react to but not affect how powerholders treat them. Instead, we conceptualize subordinate feedback as an important trigger of powerholders' behavioral self-regulation and explore subordinates' reciprocal influence on how powerholders allocate resources to them over time. In 2 experiments using a multiparty, multiround dictator game paradigm, we found that when subordinates provided candid feedback about whether they found prior allocations to be fair or unfair, powerholders regulated how self-interested their allocations were over time. However, when subordinates provided compliant feedback about powerholders' prior allocation decisions (offered consistently positive feedback, regardless of the powerholders' prior allocation), those powerholders made increasingly self-interested allocations over time. In addition, we showed that guilt partially mediates this relationship: powerholders feel more guilty after receiving negative feedback about an allocation, subsequently leading to a less self-interested allocation, whereas they feel less guilty after receiving positive feedback about an allocation, subsequently taking more for themselves. Our findings integrate the literature on upward feedback with theory about moral self-regulation to support the idea that subordinates are an important source of influence over those who hold power over them. PsycINFO Database Record (c) 2015 APA, all rights reserved.

Satellite power system operations

NASA Technical Reports Server (NTRS)

Pugh, F. L.; Gordon, A. I.

1980-01-01

A projection of the electrical energy demands over the next 30 to 50 years, coupled with reasonable assessments of known or developable energy sources, indicates that a shortage of electrical energy will occur about the turn of the century. Recognizing the criticality of such a shortage, the Department of Energy is currently evaluating alternative power generation concepts. One of these candidate concepts is the Satellite Power System. The power levels considered during the evaluation of the various satellite systems have ranged from 5 to 10 GW. It is apparent that, with this power level, both the satellite and the rectenna must be very large and encompass a large number of complex operational system activities. Major elements of the Satellite Power System (SPS) consist of a power satellite placed in a geosynchronous equatorial orbit, and a dedicated ground receiving station (GRS) located at a selected site within the continental United States. The nominal power output of the SPS is established at 5 gigawatts (5 million kilowatts) although, because of various system constraints or losses, it may actually produce between 4 and 5 gigawatts.

Voronoi Diagram Based Optimization of Dynamic Reactive Power Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Weihong; Sun, Kai; Qi, Junjian

2015-01-01

Dynamic var sources can effectively mitigate fault-induced delayed voltage recovery (FIDVR) issues or even voltage collapse. This paper proposes a new approach to optimization of the sizes of dynamic var sources at candidate locations by a Voronoi diagram based algorithm. It first disperses sample points of potential solutions in a searching space, evaluates a cost function at each point by barycentric interpolation for the subspaces around the point, and then constructs a Voronoi diagram about cost function values over the entire space. Accordingly, the final optimal solution can be obtained. Case studies on the WSCC 9-bus system and NPCC 140-busmore » system have validated that the new approach can quickly identify the boundary of feasible solutions in searching space and converge to the global optimal solution.« less

X-ray spectral variability of Seyfert 2 galaxies

NASA Astrophysics Data System (ADS)

Hernández-García, L.; Masegosa, J.; González-Martín, O.; Márquez, I.

2015-07-01

Context. Variability across the electromagnetic spectrum is a property of active galactic nuclei (AGN) that can help constrain the physical properties of these galaxies. Nonetheless, the way in which the changes happen and whether they occur in the same way in every AGN are still open questions. Aims: This is the third in a series of papers with the aim of studying the X-ray variability of different families of AGN. The main purpose of this work is to investigate the variability pattern(s) in a sample of optically selected Seyfert 2 galaxies. Methods: We use the 26 Seyfert 2s in the Véron-Cetty and Véron catalog with data available from Chandra and/or XMM-Newton public archives at different epochs, with timescales ranging from a few hours to years. All the spectra of the same source were simultaneously fitted, and we let different parameters vary in the model. Whenever possible, short-term variations from the analysis of the light curves and/or long-term UV flux variations were studied. We divided the sample into Compton-thick and Compton-thin candidates to account for the degree of obscuration. When transitions between Compton-thick and thin were obtained for different observations of the same source, we classified it as a changing-look candidate. Results: Short-term variability at X-rays was studied in ten cases, but variations are not found. From the 25 analyzed sources, 11 show long-term variations. Eight (out of 11) are Compton-thin, one (out of 12) is Compton-thick, and the two changing-look candidates are also variable. The main driver for the X-ray changes is related to the nuclear power (nine cases), while variations at soft energies or related to absorbers at hard X-rays are less common, and in many cases these variations are accompanied by variations in the nuclear continuum. At UV frequencies, only NGC 5194 (out of six sources) is variable, but the changes are not related to the nucleus. We report two changing-look candidates, MARK 273 and NGC 7319. Conclusions: A constant reflection component located far away from the nucleus plus a variable nuclear continuum are able to explain most of our results. Within this scenario, the Compton-thick candidates are dominated by reflection, which suppresses their continuum, making them seem fainter, and they do not show variations (except MARK 3), while the Compton-thin and changing-look candidates do. Appendices are available in electronic form at http://www.aanda.org

Thermal Analysis of AlGaN/GaN High-Electron-Mobility Transistor and Its RF Power Efficiency Optimization with Source-Bridged Field-Plate Structure.

PubMed

Kwak, Hyeon-Tak; Chang, Seung-Bo; Jung, Hyun-Gu; Kim, Hyun-Seok

2018-09-01

In this study, we consider the relationship between the temperature in a two-dimensional electron gas (2-DEG) channel layer and the RF characteristics of an AlGaN/GaN high-electron-mobility transistor by changing the geometrical structure of the field-plate. The final goal is to achieve a high power efficiency by decreasing the channel layer temperature. First, simulations were performed to compare and contrast the experimental data of a conventional T-gate head structure. Then, a source-bridged field-plate (SBFP) structure was used to obtain the lower junction temperature in the 2-DEG channel layer. The peak electric field intensity was reduced, and a decrease in channel temperature resulted in an increase in electron mobility. Furthermore, the gate-to-source capacitance was increased by the SBFP structure. However, under the large current flow condition, the SBFP structure had a lower maximum temperature than the basic T-gate head structure, which improved the device electron mobility. Eventually, an optimum position of the SBFP was used, which led to higher frequency responses and improved the breakdown voltages. Hence, the optimized SBFP structure can be a promising candidate for high-power RF devices.

The Top 10 List of Gravitational Lens Candidates from the HUBBLE SPACE TELESCOPE Medium Deep Survey

NASA Astrophysics Data System (ADS)

Ratnatunga, Kavan U.; Griffiths, Richard E.; Ostrander, Eric J.

1999-05-01

A total of 10 good candidates for gravitational lensing have been discovered in the WFPC2 images from the Hubble Space Telescope (HST) Medium Deep Survey (MDS) and archival primary observations. These candidate lenses are unique HST discoveries, i.e., they are faint systems with subarcsecond separations between the lensing objects and the lensed source images. Most of them are difficult objects for ground-based spectroscopic confirmation or for measurement of the lens and source redshifts. Seven are ``strong lens'' candidates that appear to have multiple images of the source. Three are cases in which the single image of the source galaxy has been significantly distorted into an arc. The first two quadruply lensed candidates were reported by Ratnatunga et al. We report on the subsequent eight candidates and describe them with simple models based on the assumption of singular isothermal potentials. Residuals from the simple models for some of the candidates indicate that a more complex model for the potential will probably be required to explain the full structural detail of the observations once they are confirmed to be lenses. We also discuss the effective survey area that was searched for these candidate lens objects.

In vitro production of huperzine A, a promising drug candidate for Alzheimer's disease.

PubMed

Ma, Xiaoqiang; Gang, David R

2008-07-01

Alzheimer's disease (AD) is growing in impact on human health. With no known cure, AD is one of the most expensive diseases in the world to treat. Huperzine A (HupA), a anti-AD drug candidate from the traditional Chinese medicine Qian Ceng Ta (Huperzia serrata), has been shown to be a powerful and selective inhibitor of acetylcholinesterase and has attracted widespread attention because of its unique pharmacological activities and low toxicity. As a result, HupA is becoming an important lead compound for drugs to treat AD. HupA is obtained naturally from very limited and slowly growing natural resources, members of the Huperziaceae. Unfortunately, the content of HupA is very low in the raw plant material. This has led to strong interest in developing sources of HupA. We have developed a method to propagate in vitro tissues of Phlegmariurus squarrosus, a member of the Huperziaceae, that produce high levels of HupA. The in vitro propagated tissues produce even higher levels of HupA than the natural plant, and may represent an excellent source for HupA.

Fermi-LAT Constraints on the Pulsar Wind Nebula Nature of HESS J1857+026

NASA Technical Reports Server (NTRS)

Rousseau, R.; Grondin, M.-H.; VanEtten, A.; Lemoine-Goumard, M.; Bogdanov, S.; Hessels, J. W. T.; Kaspi, V. M.; Arzoumanian, Z.; Camilo, F.; Casandjian, J. M.;

Fermi-LAT constraints on the pulsar wind nebula nature of HESS J1857+026

NASA Astrophysics Data System (ADS)

Rousseau, R.; Grondin, M.-H.; Van Etten, A.; Lemoine-Goumard, M.; Bogdanov, S.; Hessels, J. W. T.; Kaspi, V. M.; Arzoumanian, Z.; Camilo, F.; Casandjian, J. M.; Espinoza, C. M.; Johnston, S.; Lyne, A. G.; Smith, D. A.; Stappers, B. W.; Caliandro, G. A.

2012-08-01

Context. Since its launch, the Fermi satellite has firmly identified 5 pulsar wind nebulae plus a large number of candidates, all powered by young and energetic pulsars. HESS J1857 + 026 is a spatially extended γ-ray source detected by H.E.S.S. and classified as a possible pulsar wind nebula candidate powered by PSR J1856 + 0245. Aims: We search for γ-ray pulsations from PSR J1856+0245 and explore the characteristics of its associated pulsar wind nebula. Methods: Using a rotational ephemeris obtained from the Lovell telescope at Jodrell Bank Observatory at 1.5 GHz, we phase-fold 36 months of γ-ray data acquired by the Large Area Telescope (LAT) aboard Fermi. We also perform a complete γ-ray spectral and morphological analysis. Results: No γ-ray pulsations were detected from PSR J1856+0245. However, significant emission is detected at a position coincident with the TeV source HESS J1857 + 026. The γ-ray spectrum is well described by a simple power-law with a spectral index of Γ = 1.53 ± 0.11stat ± 0.55syst and an energy flux of G(0.1-100 GeV) = (2.71 ± 0.52stat ± 1.51syst) × 10-11 erg cm-2 s-1. The γ-ray luminosity is LPWNγ (0.1-100 GeV)=(2.5 ± 0.5stat ± 1.5syst) × 1035 (d/9 kpc)2 erg s-1, assuming a distance of 9 kpc. This implies a γ-ray efficiency of ~5% for Ė = 4.6 × 1036 erg s-1, in the range expected for pulsar wind nebulae. Detailed multi-wavelength modeling provides new constraints on its pulsar wind nebula nature.

X-ray Properties of an Unbiased Hard X-ray Detected Sample of AGN

NASA Technical Reports Server (NTRS)

Winter, Lisa M.; Mushotzky, Richard F.; Tueller, Jack; Markwardt, Craig

2007-01-01

The SWIFT gamma ray observatory's Burst Alert Telescope (BAT) has detected a sample of active galactic nuclei (AGN) based solely on their hard X-ray flux (14-195keV). In this paper, we present for the first time XMM-Newton X-ray spectra for 22 BAT AGXs with no previously analyzed X-ray spectra. If our sources are a representative sample of the BAT AGN, as we claim, our results present for the first time global X-ray properties of an unbiased towards absorption (n(sub H) < 3 x 10(exp 25)/sq cm), local (< z >= 0.03), AGN sample. We find 9/22 low absorption (n(sub H) < 10(exp 23)/sq cm), simple power law model sources, where 4 of these sources have a statistically significant soft component. Among these sources, we find the presence of a warm absorber statistically significant for only one Seyfert 1 source, contrasting with the ASCA results of Reynolds (1997) and George et al. (1998), who find signatures of warm absorption in half or more of their Seyfert 1 samples at similar redshifts. Additionally, the remaining sources (13122) have more complex spectra, well-fit by an absorbed power law at E > 2.0 keV. Five of the complex sources (NGC 612, ESO 362-G018, MRK 417, ESO 506-G027, and NGC 6860) are classified as Compton-thick candidates. Further, we find four more sources (SWIFT J0641.3+3257, SWIFT J0911.2+4533, SWIFT J1200.8+0650, and NGC 4992) with properties consistent with the hidden/buried AGN reported by Ueda et al. (2007). Finally, we include a comparison of the XMM EPIC spectra with available SWIFT X-ray Telescope (XRT) observations. From these comparisons, we find 6/16 sources with varying column densities, 6/16 sources with varying power law indices, and 13/16 sources with varying fluxes, over periods of hours to months. Flux and power law index are correlated for objects where both parameters vary.

Origins of sharp cosmic-ray electron structures and the DAMPE excess

NASA Astrophysics Data System (ADS)

Huang, Xian-Jun; Wu, Yue-Liang; Zhang, Wei-Hong; Zhou, Yu-Feng

2018-05-01

Nearby sources may contribute to cosmic-ray electron (CRE) structures at high energies. Recently, the first DAMPE results on the CRE flux hinted at a narrow excess at energy ˜1.4 TeV . We show that in general a spectral structure with a narrow width appears in two scenarios. The first is spectrum broadening for the continuous sources with a δ -function-like injection spectrum. In this scenario, a finite width can develop after propagation through the Galaxy, which can reveal the distance of the source. Well-motivated sources include minispikes and subhalos formed by dark matter (DM) particles χs which annihilate directly into e+e- pairs. The second is phase-space shrinking for burstlike sources with a power-law-like injection spectrum. The spectrum after propagation can shrink at a cooling-related cutoff energy and form a sharp spectral peak. The peak can be more prominent due to the energy-dependent diffusion. In this scenario, the width of the excess constrains both the power index and the distance of the source. Possible such sources are pulsar wind nebulae (PWNe) and supernova remnants (SNRs). We analysis the DAMPE excess and find that the continuous DM sources should be fairly close within ˜0.3 kpc , and the annihilation cross sections are close to the thermal value. For the burstlike source, the narrow width of the excess suggests that the injection spectrum must be hard with power index significantly less than two, the distance is within ˜(3 - 4 ) kpc , and the age of the source is ˜0.16 Myr . In both scenarios, large anisotropies in the CRE flux are predicted. We identify possible candidates of minispike and PWN sources in the current Fermi-LAT 3FGL and ATNF catalog, respectively. The diffuse γ -rays from these sources can be well below the Galactic diffuse γ -ray backgrounds and less constrained by the Fermi-LAT data, if they are located at the low Galactic latitude regions.

Inversion of Acoustic and Electromagnetic Recordings for Mapping Current Flow in Lightning Strikes

NASA Astrophysics Data System (ADS)

Anderson, J.; Johnson, J.; Arechiga, R. O.; Thomas, R. J.

2012-12-01

Acoustic recordings can be used to map current-carrying conduits in lightning strikes. Unlike stepped leaders, whose very high frequency (VHF) radio emissions have short (meter-scale) wavelengths and can be located by lightning-mapping arrays, current pulses emit longer (kilometer-scale) waves and cannot be mapped precisely by electromagnetic observations alone. While current pulses are constrained to conductive channels created by stepped leaders, these leaders often branch as they propagate, and most branches fail to carry current. Here, we present a method to use thunder recordings to map current pulses, and we apply it to acoustic and VHF data recorded in 2009 in the Magdalena mountains in central New Mexico, USA. Thunder is produced by rapid heating and expansion of the atmosphere along conductive channels in response to current flow, and therefore can be used to recover the geometry of the current-carrying channel. Toward this goal, we use VHF pulse maps to identify candidate conductive channels where we treat each channel as a superposition of finely-spaced acoustic point sources. We apply ray tracing in variable atmospheric structures to forward model the thunder that our microphone network would record for each candidate channel. Because multiple channels could potentially carry current, a non-linear inversion is performed to determine the acoustic source strength of each channel. For each combination of acoustic source strengths, synthetic thunder is modeled as a superposition of thunder signals produced by each channel, and a power envelope of this stack is then calculated. The inversion iteratively minimizes the misfit between power envelopes of recorded and modeled thunder. Because the atmospheric sound speed structure through which the waves propagate during these events is unknown, we repeat the procedure on many plausible atmospheres to find an optimal fit. We then determine the candidate channel, or channels, that minimizes residuals between synthetic and acoustic recordings. We demonstrate the usefulness of this method on both intracloud and cloud-to-ground strikes, and discuss factors affecting our ability to replicate recorded thunder.

Star Formation and Young Population of the H II Complex Sh2-294

NASA Astrophysics Data System (ADS)

Samal, M. R.; Pandey, A. K.; Ojha, D. K.; Chauhan, N.; Jose, J.; Pandey, B.

2012-08-01

The Sh2-294 H II region ionized by a single B0V star features several infrared excess sources, a photodissociation region, and also a group of reddened stars at its border. The star formation scenario in this region seems to be quite complex. In this paper, we present follow-up results of Sh2-294 H II region at 3.6, 4.5, 5.8, and 8.0 μm observed with the Spitzer Space Telescope Infrared Array Camera (IRAC), coupled with H2 (2.12 μm) observation, to characterize the young population of the region and to understand its star formation history. We identified 36 young stellar object (YSO, Class I, Class II, and Class I/II) candidates using IRAC color-color diagrams. It is found that Class I sources are preferentially located at the outskirts of the H II region and associated with enhanced H2 emission; none of them are located near the central cluster. Combining the optical to mid-infrared (MIR) photometry of the YSO candidates and using the spectral energy distribution fitting models, we constrained stellar parameters and the evolutionary status of 33 YSO candidates. Most of them are interpreted by the model as low-mass (<4 M ⊙) YSOs; however, we also detected a massive YSO (~9 M ⊙) of Class I nature, embedded in a cloud of visual extinction of ~24 mag. Present analysis suggests that the Class I sources are indeed a younger population of the region relative to Class II sources (age ~ 4.5 × 106 yr). We suggest that the majority of the Class I sources, including the massive YSOs, are second-generation stars of the region whose formation is possibly induced by the expansion of the H II region powered by a ~4 × 106 yr B0 main-sequence star.

STAR FORMATION AND YOUNG POPULATION OF THE H II COMPLEX Sh2-294

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samal, M. R.; Pandey, A. K.; Chauhan, N.

The Sh2-294 H II region ionized by a single B0V star features several infrared excess sources, a photodissociation region, and also a group of reddened stars at its border. The star formation scenario in this region seems to be quite complex. In this paper, we present follow-up results of Sh2-294 H II region at 3.6, 4.5, 5.8, and 8.0 {mu}m observed with the Spitzer Space Telescope Infrared Array Camera (IRAC), coupled with H{sub 2} (2.12 {mu}m) observation, to characterize the young population of the region and to understand its star formation history. We identified 36 young stellar object (YSO, Classmore » I, Class II, and Class I/II) candidates using IRAC color-color diagrams. It is found that Class I sources are preferentially located at the outskirts of the H II region and associated with enhanced H{sub 2} emission; none of them are located near the central cluster. Combining the optical to mid-infrared (MIR) photometry of the YSO candidates and using the spectral energy distribution fitting models, we constrained stellar parameters and the evolutionary status of 33 YSO candidates. Most of them are interpreted by the model as low-mass (<4 M{sub Sun }) YSOs; however, we also detected a massive YSO ({approx}9 M{sub Sun }) of Class I nature, embedded in a cloud of visual extinction of {approx}24 mag. Present analysis suggests that the Class I sources are indeed a younger population of the region relative to Class II sources (age {approx} 4.5 Multiplication-Sign 10{sup 6} yr). We suggest that the majority of the Class I sources, including the massive YSOs, are second-generation stars of the region whose formation is possibly induced by the expansion of the H II region powered by a {approx}4 Multiplication-Sign 10{sup 6} yr B0 main-sequence star.« less

Description of the SSF PMAD DC testbed control system data acquisition function

NASA Technical Reports Server (NTRS)

Baez, Anastacio N.; Mackin, Michael; Wright, Theodore

1992-01-01

The NASA LeRC in Cleveland, Ohio has completed the development and integration of a Power Management and Distribution (PMAD) DC Testbed. This testbed is a reduced scale representation of the end to end, sources to loads, Space Station Freedom Electrical Power System (SSF EPS). This unique facility is being used to demonstrate DC power generation and distribution, power management and control, and system operation techniques considered to be prime candidates for the Space Station Freedom. A key capability of the testbed is its ability to be configured to address system level issues in support of critical SSF program design milestones. Electrical power system control and operation issues like source control, source regulation, system fault protection, end-to-end system stability, health monitoring, resource allocation, and resource management are being evaluated in the testbed. The SSF EPS control functional allocation between on-board computers and ground based systems is evolving. Initially, ground based systems will perform the bulk of power system control and operation. The EPS control system is required to continuously monitor and determine the current state of the power system. The DC Testbed Control System consists of standard controllers arranged in a hierarchical and distributed architecture. These controllers provide all the monitoring and control functions for the DC Testbed Electrical Power System. Higher level controllers include the Power Management Controller, Load Management Controller, Operator Interface System, and a network of computer systems that perform some of the SSF Ground based Control Center Operation. The lower level controllers include Main Bus Switch Controllers and Photovoltaic Controllers. Power system status information is periodically provided to the higher level controllers to perform system control and operation. The data acquisition function of the control system is distributed among the various levels of the hierarchy. Data requirements are dictated by the control system algorithms being implemented at each level. A functional description of the various levels of the testbed control system architecture, the data acquisition function, and the status of its implementationis presented.

Thermionic/AMTEC cascade converter concept for high-efficiency space power

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hagan, T.H. van; Smith, J.N. Jr.; Schuller, M.

1996-12-31

This paper presents trade studies that address the use of the thermionic/AMTEC cell--a cascaded, high-efficiency, static power conversion concept that appears well-suited to space power applications. Both the thermionic and AMTEC power conversion approaches have been shown to be promising candidates for space power. Thermionics offers system compactness via modest efficiency at high heat rejection temperatures, and AMTEC offers high efficiency at modest heat rejection temperature. From a thermal viewpoint the two are ideally suited for cascaded power conversion: thermionic heat rejection and AMTEC heat source temperatures are essentially the same. In addition to realizing conversion efficiencies potentially as highmore » as 35--40%, such a cascade offers the following perceived benefits: survivability; simplicity; technology readiness; and technology growth. Mechanical approaches and thermal/electric matching criteria for integrating thermionics and AMTEC into a single conversion device are described. Focusing primarily on solar thermal space power applications, parametric trends are presented to show the performance and cost potential that should be achievable with present-day technology in cascaded thermionic/AMTEC systems.« less

NuSTAR Observations of Two New Black Hole X-ray Binary Candidates within 1 pc of Sgr A*

NASA Astrophysics Data System (ADS)

Hord, Benjamin; Hailey, Charles; Mori, Kaya; Mandel, Shifra

2018-01-01

Remarkably, two new X-ray transients were discovered in outburst within ~1 pc of the Galactic Center by the Swift X-ray Telescope in the first half of 2016. A few weeks after each outburst began, NuSTAR ToO observations were triggered for both of the objects. These sources have no known counterparts at other energies. Both objects exhibit relativistically broadened Fe lines in their spectra and possible quasi-periodic oscillations (QPO) in their power spectra, which are features seen in many black hole X-ray binaries. Combined with the fact that there have been no previously observed large outbursts at these positions over the decade of the Swift X-ray Telescope galactic center monitoring campaign, these sources make for prime black hole binary candidates (BHC) rather than neutron star low-mass X-ray binaries (NS-LMXB), which have a known short (<~5 year) recurrence time. We will present 3-79 keV NuSTAR spectra and timing analysis of these sources that supports a black hole binary interpretation over a neutron star scenario. These new BHC, combined with at least one other previously discovered BHC near the Galactic Center, hint at a potentially substantive black hole population in the vicinity of the supermassive black hole at Sgr A*.

Thermal power systems, small power systems application project. Volume 1: Executive summary

NASA Technical Reports Server (NTRS)

Marriott, A. T.

1979-01-01

Current small power system technology as applied to power plants up to 10 MWe in size was assessed. Markets for small power systems were characterized and cost goals were established. Candidate power plant system design concepts were selected for evaluation and preliminary performance and cost assessments were made. Economic studies were conducted and breakeven capital costs were determined for leading contenders among the candidate systems. An application study was made of the potential use of small power systems in providing part of the demand for pumping power by the extensive aqueduct system of California, estimated to be 1000 MWe by 1985. Criteria and methodologies were developed for application to the ranking of candidate power plant system design concepts. Experimental power plants concepts of 1 MWe rating were studied leading toward the definition of a power plant configuration for subsequent detail design, construction, testing and evaluation as Engineering Experiment No. 1 (EE No. 1). Site selection criteria and ground rules for the solicitation of EE No. 1 site participation proposals by DOE were developed.

A study of the far infrared counterparts of new candidates for planetary nebulae

NASA Astrophysics Data System (ADS)

Iyengar, K. V. K.

1986-05-01

The IRAS Point Source Catalog was searched for infrared counterparts of the fourteen new candidates for planetary nebulae of low surface brightness detected by Hartl and Tritton (1985). Five of these candidates were identified with sources in the Catalog. All five nebulae are found in regions of high cirrus flux at 100 microns, and all have both point sources and small size extended sources with numbers varying from field to field. The infrared emission from these nebulae is connected with dust temperatures of about 100 K, characteristic of planetary nebulae.

Power system requirements and definition for lunar and Mars outposts

NASA Technical Reports Server (NTRS)

Petri, D. A.; Cataldo, R. L.; Bozek, J. M.

1990-01-01

Candidate power systems being considered for outpost facilities (stationary power systems) and vehicles (mobile systems) are discussed, including solar, chemical, isotopic, and reactor. The current power strategy was an initial outpost power system composed of photovoltaic arrays for daytime energy needs and regenerative fuel cells for power during the long lunar night. As day and night power demands grow, the outpost transitions to nuclear-based power generation, using thermoelectric conversion initially and evolving to a dynamic conversion system. With this concept as a guideline, a set of requirements has been established, and a reference definition of candidate power systems meeting these requirements has been identified.

1WHSP: An IR-based sample of ~1000 VHE γ -ray blazar candidates

DOE PAGES

Arsioli, B.; Fraga, B.; Giommi, P.; ...

2015-06-23

Context. Blazars are the dominant type of extragalactic sources at microwave and at γ-ray energies. In the most energetic part of the electromagnetic spectrum (E > ≳ 100 GeV) a large fraction of high Galactic latitude sources are blazars of the High Synchrotron Peaked (HSP) type, that is BL Lac objects with synchrotron power peaking in the UV or in the X-ray band. Building new large samples of HSP blazars is key to understand the properties of jets under extreme conditions, and to study the demographics and the peculiar cosmological evolution of these sources. Aims. HSP blazars are remarkably rare,more » with only a few hundreds of them expected to be above the sensitivity limits of currently available surveys, some of which include hundreds of millions of sources. To find these very uncommon objects, we have devised a method that combines ALLWISE survey data with multi-frequency selection criteria. Methods. The sample was defined starting from a primary list of infrared colour-colour selected sources from the ALLWISE all sky survey database, and applying further restrictions on IR-radio and IR-X-ray flux ratios. Using a polynomial fit to the multi-frequency data (radio to X-ray) we estimated synchrotron peak frequencies and fluxes of each object. Results. We assembled a sample including 992 sources, which is currently the largest existing list of confirmed and candidates HSP blazars. All objects are expected to radiate up to the highest γ-ray photon energies. In fact, 299 of these are confirmed emitters of GeV γ-ray photons (based on Fermi-LAT catalogues), and 36 have already been detected in the TeV band. The majority of sources in the sample are within reach of the upcoming Cherenkov Telescope Array (CTA), and many may be detectable even by the current generation of Cherenkov telescopes during flaring episodes. The sample includes 425 previously known blazars, 151 new identifications, and 416 HSP candidates (mostly faint sources) for which no optical spectra is available yet. The full 1WHSP catalogue is on-line at http://www.asdc.asi.it/1whsp/ providing a direct link to the SED building tool where multifrequency data for each source can be easily visualised.« less

VizieR Online Data Catalog: Planck high-z source candidates catalog (PHZ) (Planck+, 2016)

NASA Astrophysics Data System (ADS)

Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoit-Levy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Burigana, C.; Butler, R. C.; Calabrese, E.; Catalano, A.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombo, L. P. L.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; De Rosa, A.; de Zotti, G.; Delabrouille, J.; Dickinson, C.; Diego, J. M.; Dole, H.; Dore, O.; Douspis, M.; Ducout, A.; Dupac, X.; Elsner, F.; Ensslin, T. A.; Eriksen, H. K.; Falgarone, E.; Finelli, F.; Flores-Cacho, I.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Galeotta, S.; Galli, S.; Ganga, K.; Giard, M.; Giraud-Heraud, Y.; Gjerlow, E.; Gonzalez-Nuevo, J.; Gorski, K. M.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Hansen, F. K.; Harrison, D. L.; Helou, G.; Hernandez-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Keihanen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vornle, M.; Lopez-Caniego, M.; Lubin, P. M.; Macias-Perez, J. F.; Maffei, B.; Maggio, G.; Maino, D.; Mandolesi, N.; Mangilli, A.; Maris, M.; Martin, P. G.; Martinez-Gonzalez, E.; Masi, S.; Matarrese, S.; Melchiorri, A.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschenes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Nati, F.; Natoli, P.; Nesvadba, N. P. H.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Pagano, L.; Pajot, F.; Paoletti, D.; Partridge, B.; Pasian, F.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Pettorino, V.; Piacentini, F.; Piat, M.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Pratt, G. W.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rubino-Martin, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savelainen, M.; Savini, G.; Scott, D.; Spencer, L. D.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Turler, M.; Umana, G.; Valenziano, L.; Valiviita, J.; van Tent, F.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Welikala, N.; Yvon, D.; Zacchei, A.; Zonca, A.

2016-11-01

We present in this work the Planck List of Highredshift Source Candidates (the "PHZ"), which includes 2151 sources distributed over 26% of the sky, with redshifts likely to be greater than 2. (2 data files).

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.

Status of Brayton Cycle Power Conversion Development at NASA GRC

NASA Technical Reports Server (NTRS)

Mason, Lee S.; Shaltens, Richard K.; Dolce, James L.; Cataldo, Robert L.

2002-01-01

The NASA Glenn Research Center (GRC) is pursuing the development of Brayton cycle power conversion for various NASA initiatives. Brayton cycle power systems offer numerous advantages for space power generation including high efficiency, long life, high maturity, and broad scalability. Candidate mission applications include surface rovers and bases, advanced propulsion vehicles, and earth orbiting satellites. A key advantage is the ability for Brayton converters to span the wide range of power demands of future missions from several kilowatts to multi-megawatts using either solar, isotope, or reactor heat sources. Brayton technology has been under development by NASA since the early 1960's resulting in engine prototypes in the 2 to 15 kW-class that have demonstrated conversion efficiency of almost 30% and cumulative operation in excess of 40,000 hours. Present efforts at GRC are focusing on a 2 kW testbed as a proving ground for future component advances and operational strategies, and a 25 kW engine design as a modular building block for 100 kW-class electric propulsion and Mars surface power applications.

Reliability Issues in Stirling Radioisotope Power Systems

NASA Technical Reports Server (NTRS)

Schreiber, Jeffrey; Shah, Ashwin

2005-01-01

Stirling power conversion is a potential candidate for use in a Radioisotope Power System (RPS) for space science missions because it offers a multifold increase in the conversion efficiency of heat to electric power and reduced requirement of radioactive material. Reliability of an RPS that utilizes Stirling power conversion technology is important in order to ascertain long term successful performance. Owing to long life time requirement (14 years), it is difficult to perform long-term tests that encompass all the uncertainties involved in the design variables of components and subsystems comprising the RPS. The requirement for uninterrupted performance reliability and related issues are discussed, and some of the critical areas of concern are identified. An overview of the current on-going efforts to understand component life, design variables at the component and system levels, and related sources and nature of uncertainties are also discussed. Current status of the 110 watt Stirling Radioisotope Generator (SRG110) reliability efforts is described. Additionally, an approach showing the use of past experience on other successfully used power systems to develop a reliability plan for the SRG110 design is outlined.

Reliability Issues in Stirling Radioisotope Power Systems

NASA Technical Reports Server (NTRS)

Shah, Ashwin R.; Schreiber, Jeffrey G.

2004-01-01

Stirling power conversion is a potential candidate for use in a Radioisotope Power System (RPS) for space science missions because it offers a multifold increase in the conversion efficiency of heat to electric power and reduced requirement of radioactive material. Reliability of an RPS that utilizes Stirling power conversion technology is important in order to ascertain long term successful performance. Owing to long life time requirement (14 years), it is difficult to perform long-term tests that encompass all the uncertainties involved in the design variables of components and subsystems comprising the RPS. The requirement for uninterrupted performance reliability and related issues are discussed, and some of the critical areas of concern are identified. An overview of the current on-going efforts to understand component life, design variables at the component and system levels, and related sources and nature of uncertainties are also discussed. Current status of the 110 watt Stirling Radioisotope Generator (SRG110) reliability efforts is described. Additionally, an approach showing the use of past experience on other successfully used power systems to develop a reliability plan for the SRG110 design is outlined.

A variable ULX and possible IMBH candidate in M51a

NASA Astrophysics Data System (ADS)

Earnshaw, Hannah M.; Roberts, Timothy P.; Heil, Lucy M.; Mezcua, Mar; Walton, Dominic J.; Done, Chris; Harrison, Fiona A.; Lansbury, George B.; Middleton, Matthew J.; Sutton, Andrew D.

2016-03-01

Ultraluminous X-ray source (ULX)-7, in the northern spiral arm of M51, demonstrates unusual behaviour for an ULX, with a hard X-ray spectrum but very high short-term variability. This suggests that it is not in a typical ultraluminous state. We analyse the source using archival data from XMM-Newton, Chandra and NuSTAR, and by examining optical and radio data from HST and Very Large Array. Our X-ray spectral analysis shows that the source has a hard power-law spectral shape with a photon index Γ ˜ 1.5, which persists despite the source's X-ray luminosity varying by over an order of magnitude. The power spectrum of the source features a break at 6.5^{+0.5}_{-1.1} × 10-3 Hz, from a low-frequency spectral index of α _1={-}0.1^{+0.5}_{-0.2} to a high-frequency spectral index of α _2=6.5^{+0.05}_{-0.14}, making it analogous to the low-frequency break found in the power spectra of low/hard state black holes (BHs). We can take a lower frequency limit for a corresponding high-frequency break to calculate a BH mass upper limit of 1.6 × 103 M⊙. Using the X-ray/radio Fundamental Plane, we calculate another upper limit to the BH mass of 3.5 × 104 M⊙ for a BH in the low/hard state. The hard spectrum, high rms variability and mass limits are consistent with ULX-7 being an intermediate-mass BH; however we cannot exclude other interpretations of this source's interesting behaviour, most notably a neutron star with an extreme accretion rate.

Power line identification of millimeter wave radar based on PCA-GS-SVM

NASA Astrophysics Data System (ADS)

Fang, Fang; Zhang, Guifeng; Cheng, Yansheng

2017-12-01

Aiming at the problem that the existing detection method can not effectively solve the security of UAV's ultra low altitude flight caused by power line, a power line recognition method based on grid search (GS) and the principal component analysis and support vector machine (PCA-SVM) is proposed. Firstly, the candidate line of Hough transform is reduced by PCA, and the main feature of candidate line is extracted. Then, upport vector machine (SVM is) optimized by grid search method (GS). Finally, using support vector machine classifier optimized parameters to classify the candidate line. MATLAB simulation results show that this method can effectively identify the power line and noise, and has high recognition accuracy and algorithm efficiency.

Phenome-driven disease genetics prediction toward drug discovery.

PubMed

Chen, Yang; Li, Li; Zhang, Guo-Qiang; Xu, Rong

2015-06-15

Discerning genetic contributions to diseases not only enhances our understanding of disease mechanisms, but also leads to translational opportunities for drug discovery. Recent computational approaches incorporate disease phenotypic similarities to improve the prediction power of disease gene discovery. However, most current studies used only one data source of human disease phenotype. We present an innovative and generic strategy for combining multiple different data sources of human disease phenotype and predicting disease-associated genes from integrated phenotypic and genomic data. To demonstrate our approach, we explored a new phenotype database from biomedical ontologies and constructed Disease Manifestation Network (DMN). We combined DMN with mimMiner, which was a widely used phenotype database in disease gene prediction studies. Our approach achieved significantly improved performance over a baseline method, which used only one phenotype data source. In the leave-one-out cross-validation and de novo gene prediction analysis, our approach achieved the area under the curves of 90.7% and 90.3%, which are significantly higher than 84.2% (P < e(-4)) and 81.3% (P < e(-12)) for the baseline approach. We further demonstrated that our predicted genes have the translational potential in drug discovery. We used Crohn's disease as an example and ranked the candidate drugs based on the rank of drug targets. Our gene prediction approach prioritized druggable genes that are likely to be associated with Crohn's disease pathogenesis, and our rank of candidate drugs successfully prioritized the Food and Drug Administration-approved drugs for Crohn's disease. We also found literature evidence to support a number of drugs among the top 200 candidates. In summary, we demonstrated that a novel strategy combining unique disease phenotype data with system approaches can lead to rapid drug discovery. nlp. edu/public/data/DMN © The Author 2015. Published by Oxford University Press.

Investigating powerful jets in radio-loud narrow-line Seyfert 1s

DOE PAGES

Orienti, M.; D'Ammando, F.; Larsson, J.; ...

2015-09-14

Here, we report results on multiband observations from radio to γ-rays of the two radio-loud narrow-line Seyfert 1 (NLSy1) galaxies PKS 2004-447 and J1548+3511. Furthermore, both sources show a core–jet structure on parsec scale, while they are unresolved at the arcsecond scale. The high core dominance and the high variability brightness temperature make these NLSy1 galaxies good γ-ray source candidates. Fermi-Large Area Telescope detected γ-ray emission only from PKS 2004-447, with a γ-ray luminosity comparable to that observed in blazars. There was no γ-ray emission observed for J1548+3511. Both sources are variable in X-rays. J1548+3511 shows a hardening of themore » spectrum during high activity states, while PKS 2004-447 has no spectral variability. A spectral steepening likely related to the soft excess is hinted below 2 keV for J1548+3511, while the X-ray spectra of PKS 2004-447 collected by XMM–Newton in 2012 are described by a single power law without significant soft excess. No additional absorption above the Galactic column density or the presence of an Fe line is detected in the X-ray spectra of both sources.« less

Development of a solar-powered residential air conditioner: System optimization preliminary specification

NASA Technical Reports Server (NTRS)

Rousseau, J.; Hwang, K. C.

1975-01-01

Investigations aimed at the optimization of a baseline Rankine cycle solar powered air conditioner and the development of a preliminary system specification were conducted. Efforts encompassed the following: (1) investigations of the use of recuperators/regenerators to enhance the performance of the baseline system, (2) development of an off-design computer program for system performance prediction, (3) optimization of the turbocompressor design to cover a broad range of conditions and permit operation at low heat source water temperatures, (4) generation of parametric data describing system performance (COP and capacity), (5) development and evaluation of candidate system augmentation concepts and selection of the optimum approach, (6) generation of auxiliary power requirement data, (7) development of a complete solar collector-thermal storage-air conditioner computer program, (8) evaluation of the baseline Rankine air conditioner over a five day period simulating the NASA solar house operation, and (9) evaluation of the air conditioner as a heat pump.

NuSTAR AND SWIFT OBSERVATIONS OF THE BLACK HOLE CANDIDATE XTE J1908+094 DURING ITS 2013 OUTBURST

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tao, Lian; Walton, Dominic J.; Fürst, Felix

2015-09-20

The black hole (BH) candidate XTE J1908+094 went into outburst for the first time since 2003 in 2013 October. We report on an observation with the Nuclear Spectroscopic Telescope Array (NuSTAR) and monitoring observations with Swift during the outburst. NuSTAR caught the source in the soft state: the spectra show a broad relativistic iron line, and the light curves reveal a ∼40 ks flare, with the count rate peaking about 40% above the non-flare level and with significant spectral variation. A model combining a multi-temperature thermal component, a power law, and a reflection component with an iron line provides amore » good description of the NuSTAR spectrum. Although relativistic broadening of the iron line is observed, it is not possible to constrain the BH spin with these data. The variability of the power-law component, which can also be modeled as a Comptonization component, is responsible for the flux and spectral change during the flare, suggesting that changes in the corona (or possibly continued jet activity) are the likely cause of the flare.« less

System diagnostics using qualitative analysis and component functional classification

DOEpatents

Reifman, J.; Wei, T.Y.C.

1993-11-23

A method for detecting and identifying faulty component candidates during off-normal operations of nuclear power plants involves the qualitative analysis of macroscopic imbalances in the conservation equations of mass, energy and momentum in thermal-hydraulic control volumes associated with one or more plant components and the functional classification of components. The qualitative analysis of mass and energy is performed through the associated equations of state, while imbalances in momentum are obtained by tracking mass flow rates which are incorporated into a first knowledge base. The plant components are functionally classified, according to their type, as sources or sinks of mass, energy and momentum, depending upon which of the three balance equations is most strongly affected by a faulty component which is incorporated into a second knowledge base. Information describing the connections among the components of the system forms a third knowledge base. The method is particularly adapted for use in a diagnostic expert system to detect and identify faulty component candidates in the presence of component failures and is not limited to use in a nuclear power plant, but may be used with virtually any type of thermal-hydraulic operating system. 5 figures.

System diagnostics using qualitative analysis and component functional classification

DOEpatents

Reifman, Jaques; Wei, Thomas Y. C.

1993-01-01

A method for detecting and identifying faulty component candidates during off-normal operations of nuclear power plants involves the qualitative analysis of macroscopic imbalances in the conservation equations of mass, energy and momentum in thermal-hydraulic control volumes associated with one or more plant components and the functional classification of components. The qualitative analysis of mass and energy is performed through the associated equations of state, while imbalances in momentum are obtained by tracking mass flow rates which are incorporated into a first knowledge base. The plant components are functionally classified, according to their type, as sources or sinks of mass, energy and momentum, depending upon which of the three balance equations is most strongly affected by a faulty component which is incorporated into a second knowledge base. Information describing the connections among the components of the system forms a third knowledge base. The method is particularly adapted for use in a diagnostic expert system to detect and identify faulty component candidates in the presence of component failures and is not limited to use in a nuclear power plant, but may be used with virtually any type of thermal-hydraulic operating system.

A Search for FRB 121102-like Persistent Radio-luminous Sources—Candidates and Implications for the FRB Rate and Searches

NASA Astrophysics Data System (ADS)

Ofek, Eran O.

2017-09-01

The localization of the repeating fast radio burst (FRB), FRB 121102, suggests that it is associated with a persistent radio-luminous compact source in the FRB host galaxy. Using the FIRST radio catalog, I present a search for luminous persistent sources in nearby galaxies, with radio luminosities > 10 % of the FRB 121102 persistent source luminosity. The galaxy sample contains about 30% of the total galaxy g-band luminosity within < 108 Mpc, in a footprint of 10,600 deg2. After rejecting sources likely due to active galactic nuclei activity or background sources, I am left with 11 candidates that are presumably associated with galactic disks or star-formation regions. At least some of these candidates are likely to be due to chance alignment. In addition, I find 85 sources within 1\\prime\\prime of galactic nuclei. Assuming that the radio persistent sources are not related to galactic nuclei and that they follow the galaxy g-band light, the 11 sources imply a 95% confidence upper limit on the space density of luminous persistent sources of ≲ 5× {10}-5 Mpc-3, and that at any given time only a small fraction of galaxies host a radio-luminous persistent source (≲ {10}-3 {L}* -1). Assuming a persistent source lifetime of 100 years, this implies a birth rate of ≲ 5× {10}-7 yr-1 Mpc-3. Given the FRB volumetric rate, and assuming that all FRBs repeat and are associated with persistent radio sources, this sets a lower limit on the rate of FRB events per persistent source of ≳ 0.8 yr-1. I argue that these 11 candidates are good targets for FRB searches and I estimate the FRB event rate from these candidates.

Can we observe neutrino flares in coincidence with explosive transients?

NASA Astrophysics Data System (ADS)

Guépin, C.; Kotera, K.

2017-12-01

The new generation of powerful instruments is reaching sensitivities and temporal resolutions that will allow multi-messenger astronomy of explosive transient phenomena, with high-energy neutrinos as a central figure. We derive general criteria for the detectability of neutrinos from powerful transient sources for given instrument sensitivities. In practice, we provide the minimum photon flux necessary for neutrino detection based on two main observables: the bolometric luminosity and the time variability of the emission. This limit can be compared to the observations in specified wavelengths in order to target the most promising sources for follow-ups. Our criteria can also help distinguishing false associations of neutrino events with a flaring source. We find that relativistic transient sources such as high- and low-luminosity gamma-ray bursts (GRBs), blazar flares, tidal disruption events, and magnetar flares could be observed with IceCube, as they have a good chance to occur within a detectable distance. Of the nonrelativistic transient sources, only luminous supernovae appear as promising candidates. We caution that our criterion should not be directly applied to low-luminosity GRBs and type Ibc supernovae, as these objects could have hosted a choked GRB, leading to neutrino emission without a relevant counterpart radiation. We treat the concrete example of PKS 1424-418 major outburst and the possible association with an IceCube event IC 35.

Identification and properties of host galaxies of RCR radio sources

NASA Astrophysics Data System (ADS)

Zhelenkova, O. P.; Soboleva, N. S.; Majorova, E. K.; Temirova, A. V.

2013-01-01

FIRST and NVSS radio maps are used to cross identify the radio sources of the RCR catalog, which is based on observational data obtained in several runs of the "Cold" survey, with the SDSS and DPOSS digital optical sky surveys and the 2MASS, LAS UKIDSS, and WISE infrared surveys. Digital images in various filters and the coadded gri-band SDSS images, red and infrared DPOSS images, JHK-band UKIDSS images, and JHK-band 2MASS images are analyzed for the sources with no optical candidates found in the above catalogs. Our choice of optical candidates was based on the data on the structure of the radio source, its photometry, and spectroscopy (where available). We found reliable identifications for 86% of the radio sources; possible counterparts for 8% of the sources, and failed to find any optical counterparts for 6% of the sources because their host objects proved to be fainter than the limiting magnitude of the corresponding surveys. A little over half of all the identifications proved to be galaxies; about one quarter were quasars, and the types of the remaining objects were difficult to determine because of their faintness. A relation between the luminosity and the radioloudness index was derived and used to estimate the 1.4 and 3.94 GHz luminosities for the sources with unknown redshifts. We found 3% and 60% of all the RCR radio sources to be FRI-type objects ( L ≲ 1024 W/Hz at 1.4 GHz) and powerful FRII-type galaxies ( L ≳ 1026.5 W/Hz), respectively, whereas the rest are sources including objects of the FRI, FRII, and mixed FRI-FRII types. Unlike quasars, galaxies show a trend of decreasing luminosity with decreasing flux density. Note that identification would be quite problematic without the software and resources of the virtual observatory.

Search for and detection of pulsars inmonitoring observations at 111 MHz

NASA Astrophysics Data System (ADS)

Tyul'bashev, S. A.; Tyul'bashev, V. S.; Kitaeva, M. A.; Chernyshova, A. I.; Malofeev, V. M.; Chashei, I. V.; Shishov, V. I.; Dagkesamanskii, R. D.; Klimenko, S. V.; Nikitin, I. N.; Nikitina, L. D.

2017-10-01

In the course of monitoring interplanetary scintillations of a large number of sources using the Big Scanning Antenna of the Lebedev Physical Institute, a search for pulsars with periods ≥0.4 s at declinations -9◦ < δ < 42◦ and right ascensions 0h < α < 24h was simultaneously carried out. The search was conducted using four years of observations carried out at 110.25MHz in six frequency channels making up a 2.5 MHz band and having a time resolution of 100 ms. The initial identification of pulsar candidates was done using Fourier power spectra averaged over the entire observational period; the pulsar candidates were then verified using observations with higher frequency and time resolution: 32 frequency channels and a time resolution of 12.5 ms. Eighteen new pulsars were discovered in the studied area, whose main characteristics are presented.

A Search for the X-ray Counterpart of the Unidentified Gamma-ray Source 3EG J2020+4017 (2CG078+2)

NASA Technical Reports Server (NTRS)

Weisskopf, Martin; Swartz, Douglas A.; Carraminana, Alberto; Carrasco, Luis; Kaplan, David L.; Becker, Werner; Elsner, Ronald F.; Kanbach, Gottfried; ODell, Stephen L.; Tennant, Allyn F.

2006-01-01

We report observations with the Chandra X-ray Observatory of a field in the gamma-Cygni supernova remnant (SNR78.2+2.1) centered on the cataloged location of the unidentified, bright gamma-ray source 3EG J2020+4017. In this search for an X-ray counterpart to the gamma-ray source, we detected 30 X-ray sources. Of these, we found 17 strong-candidate counterparts in optical (visible through near-infrared) cataloged and an additional 3 through our optical observations. Based upon colors and (for several objects) optical spectra, nearly all the optically identified objects appear to be reddened main-sequence stars: None of the X-ray sources with an optical counterpart is a plausible X-ray counterpart to 3EG J2020+4017-if that gamma-ray source is a spin-powered pulsar. Many of the 10 X-ray sources lacking optical counterparts are likely (extragalactic) active galactic nuclei, based upon the sky density of such sources. Although one of the 10 optically unidentified X-ray sources could be the gamma-ray source, there is no auxiliary evidence supporting such an identification

Cognitive Styles in Admission Procedures for Assessing Candidates of Architecture

ERIC Educational Resources Information Center

Casakin, Hernan; Gigi, Ariela

2016-01-01

Cognitive style has a strong predictive power in academic and professional success. This study investigated the cognitive profile of candidates studying architecture. Specifically, it explored the relation between visual and verbal cognitive styles, and the performance of candidates in admission procedures. The cognitive styles of candidates who…

A universal procedure for evaluation and application of surge-protective devices

NASA Technical Reports Server (NTRS)

1980-01-01

The source, nature, and frequency of occurrence of transients must be identified and a representative standard test wave chosen for proof testing. The performance of candidate suppressor devices then can be evaluated against the withstand goals set for the equipment. The various suppressors divide into two classes of generic behavior. The key to a universal procedure for evaluating both classes lies in representing transients as quasi-current sources of defined current impulse duration. The available surge current is established by the Thevenin equivalent transient voltage and source impedance. A load line drawn on the V-I characteristic graph of the suppressor quickly determines the clamping voltage and peak current. These values then can be compared to the requirement. The deposited energy and average power dissipation for multiple transients also can be calculated. The method is illustrated with a design example for motor vehicle alternator load dump suppression.

A circumstellar molecular gas structure associated with the massive young star Cepheus A-HW 2

NASA Technical Reports Server (NTRS)

Torrelles, Jose M.; Rodriguez, Luis F.; Canto, Jorge; Ho, Paul T. P.

1993-01-01

We report the detection via VLA-D observations of ammonia of a circumstellar high-density molecular gas structure toward the massive young star related to the object Cepheus A-HW 2, a firm candidate for the powering source of the high-velocity molecular outflow in the region. We suggest that the circumstellar molecular gas structure could be related to the circumstellar disk previously suggested from infrared, H2O, and OH maser observations. We consider as a plausible scenario that the double radio continuum source of HW 2 could represent the ionized inner part of the circumstellar disk, in the same way as proposed to explain the double radio source in L1551. The observed motions in the circumstellar molecular gas can be produced by bound motions (e.g., infall or rotation) around a central mass of about 10-20 solar masses (B0.5 V star or earlier).

Research and characterisation of blazar candidates among the Fermi/LAT 3FGL catalogue using multivariate classifications

NASA Astrophysics Data System (ADS)

Lefaucheur, Julien; Pita, Santiago

2017-06-01

Context. In the recently published 3FGL catalogue, the Fermi/LAT collaboration reports the detection of γ-ray emission from 3034 sources obtained after four years of observations. The nature of 1010 of those sources is unknown, whereas 2023 have well-identified counterparts in other wavelengths. Most of the associated sources are labelled as blazars (1717/2023), but the BL Lac or FSRQ nature of 573 of these blazars is still undetermined. Aims: The aim of this study was two-fold. First, to significantly increase the number of blazar candidates from a search among the large number of Fermi/LAT 3FGL unassociated sources (case A). Second, to determine the BL Lac or FSRQ nature of the blazar candidates, including those determined as such in this work and the blazar candidates of uncertain type (BCU) that are already present in the 3FGL catalogue (case B). Methods: For this purpose, multivariate classifiers - boosted decision trees and multilayer perceptron neural networks - were trained using samples of labelled sources with no caution flag from the 3FGL catalogue and carefully chosen discriminant parameters. The decisions of the classifiers were combined in order to obtain a high level of source identification along with well controlled numbers of expected false associations. Specifically for case A, dedicated classifications were generated for high (| b | >10◦) and low (| b | ≤10◦) galactic latitude sources; in addition, the application of classifiers to samples of sources with caution flag was considered separately, and specific performance metrics were estimated. Results: We obtained a sample of 595 blazar candidates (high and low galactic latitude) among the unassociated sources of the 3FGL catalogue. We also obtained a sample of 509 BL Lacs and 295 FSRQs from the blazar candidates cited above and the BCUs of the 3FGL catalogue. The number of expected false associations is given for different samples of candidates. It is, in particular, notably low ( 9/425) for the sample of high-latitude blazar candidates from case A. Full Tables 5 and 7 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/602/A86

NuSTAR Hard X-Ray Observation of the Gamma-Ray Binary Candidate HESS J1832-093

NASA Astrophysics Data System (ADS)

Mori, Kaya; Gotthelf, E. V.; Hailey, Charles J.; Hord, Ben J.; de Oña Wilhelmi, Emma; Rahoui, Farid; Tomsick, John A.; Zhang, Shuo; Hong, Jaesub; Garvin, Amani M.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Harrison, Fiona A.; Stern, Daniel; Zhang, William W.

2017-10-01

We present a hard X-ray observation of the TeV gamma-ray binary candidate HESS J1832-093, which is coincident with the supernova remnant G22.7-0.2, using the Nuclear Spectroscopic Telescope Array. Non-thermal X-ray emission from XMMU J183245-0921539, the X-ray source associated with HESS J1832-093, is detected up to ˜30 keV and is well-described by an absorbed power-law model with a best-fit photon index {{Γ }}=1.5+/- 0.1. A re-analysis of archival Chandra and XMM-Newton data finds that the long-term X-ray flux increase of XMMU J183245-0921539 is {50}-20+40 % (90% C.L.), much less than previously reported. A search for a pulsar spin period or binary orbit modulation yields no significant signal to a pulse fraction limit of {f}p< 19 % in the range 4 ms < P< 40 ks. No red noise is detected in the FFT power spectrum to suggest active accretion from a binary system. While further evidence is required, we argue that the X-ray and gamma-ray properties of XMMU J183245-0921539 are most consistent with a non-accreting binary generating synchrotron X-rays from particle acceleration in the shock formed as a result of the pulsar and stellar wind collision. We also report on three nearby hard X-ray sources, one of which may be associated with diffuse emission from a fast-moving supernova fragment interacting with a dense molecular cloud.

Voices of Teacher Candidates of Color on White Race Evasion: "I Worried about My Safety!"

ERIC Educational Resources Information Center

Amos, Yukari Takimoto

2016-01-01

This qualitative study investigated the negative impacts minority teacher candidates receive from white teacher candidates in a required multicultural education class. The findings reveal that four teacher candidates of color had difficulty positioning themselves among the overwhelming silencing power of whiteness in the class. The white students…

Progress in CPI Microwave Tube Development

NASA Astrophysics Data System (ADS)

Wright, Edward L.; Bohlen, Heinz

2006-01-01

CPI continues its role as a leading supplier of state-of-the-art, high-power microwave tubes; from linear beam, velocity- and density-modulated devices, to high frequency gyro-devices. Klystrons are the device-of-choice for many high-power microwave applications, and can provide multi-megawatts to multi-kilowatts of power from UHF to W-band, respectively. A number of recent and on-going developments will be described. At UHF frequencies, the inductive output tube (IOT) has replaced the klystron for terrestrial NTSC and HDTV broadcast, due to its high efficiency and linearity, and is beginning to see use in scientific applications requiring 300 kW or less. Recent advances have enabled use well into L-band. CPI has developed a number of multiple-beam amplifiers. The VKL-8301 multiple-beam klystron (MBK) was built for the TESLA V/UV and x-ray FEL projects, and is a candidate RF source for the International Linear Collider (ILC). We have also contributed to the development of the U.S. Naval Research Laboratory (NRL) high-power fundamental-mode S-band MBK. The VHP-8330B multiple-beam, high-order mode (HOM) IOT shows great promise as a compact, CW UHF source for high power applications. These topics will be discussed, along with CPI's development capabilities for new and novel applications. Most important is our availability to provide design and fabrication services to organizations requiring CPI's manufacturing and process control infrastructure to build and test state-of-the-art devices.

Reviews of a Diode-Pumped Alkali Laser (DPAL): a potential high powered light source

NASA Astrophysics Data System (ADS)

Cai, He; Wang, You; Han, Juhong; An, Guofei; Zhang, Wei; Xue, Liangping; Wang, Hongyuan; Zhou, Jie; Gao, Ming; Jiang, Zhigang

2015-03-01

Diode pumped alkali vapor lasers (DPALs) were first developed by in W. F. Krupke at the beginning of the 21th century. In the recent years, DPALs have been rapidly developed because of their high Stokes efficiency, good beam quality, compact size and near-infrared emission wavelengths. The Stokes efficiency of a DPAL can achieve a miraculous level as high as 95.3% for cesium (Cs), 98.1% for rubidium (Rb), and 99.6% for potassium (K), respectively. The thermal effect of a DPAL is theoretically smaller than that of a normal diode-pumped solid-state laser (DPSSL). Additionally, generated heat of a DPAL can be removed by circulating the gases inside a sealed system. Therefore, the thermal management would be relatively simple for realization of a high-powered DPAL. In the meantime, DPALs combine the advantages of both DPSSLs and normal gas lasers but evade the disadvantages of them. Generally, the collisionally broadened cross sections of both the D1 and the D2 lines for a DPAL are much larger than those for the most conventional solid-state, fiber and gas lasers. Thus, DPALs provide an outstanding potentiality for realization of high-powered laser systems. It has been shown that a DPAL is now becoming one of the most promising candidates for simultaneously achieving good beam quality and high output power. With a lot of marvelous merits, a DPAL becomes one of the most hopeful high-powered laser sources of next generation.

Ultra-low noise supercontinuum source for ultra-high resolution optical coherence tomography at 1300 nm

NASA Astrophysics Data System (ADS)

Gonzalo, I. B.; Maria, M.; Engelsholm, R. D.; Feuchter, T.; Leick, L.; Moselund, P. M.; Podoleanu, A.; Bang, O.

2018-02-01

Supercontinuum (SC) sources are of great interest for many applications due to their ultra-broad optical bandwidth, good beam quality and high power spectral density [1]. In particular, the high average power over large bandwidths makes SC light sources excellent candidates for ultra-high resolution optical coherence tomography (UHR-OCT) [2-5]. However, conventional SC sources suffer from high pulse-to-pulse intensity fluctuations as a result of the noise-sensitive nonlinear effects involved in the SC generation process [6-9]. This intensity noise from the SC source can limit the performance of OCT, resulting in a reduced signal-to-noise ratio (SNR) [10-12]. Much work has been done to reduce the noise of the SC sources for instance with fiber tapers [7,8] or increasing the repetition rate of the pump laser for averaging in the spectrometer [10,12]. An alternative approach is to use all-normal dispersion (ANDi) fibers [13,14] to generate SC light from well-known coherent nonlinear processes [15-17]. In fact, reduction of SC noise using ANDi fibers compared to anomalous dispersion SC pumped by sub-picosecond pulses has been recently demonstrated [18], but a cladding mode was used to stabilize the ANDi SC. In this work, we characterize the noise performance of a femtosecond pumped ANDi based SC and a commercial SC source in an UHR-OCT system at 1300 nm. We show that the ANDi based SC presents exceptional noise properties compared to a commercial source. An improvement of 5 dB in SNR is measured in the UHR-OCT system, and the noise behavior resembles that of a superluminiscent diode. This preliminary study is a step forward towards development of an ultra-low noise SC source at 1300 nm for ultra-high resolution OCT.

Fermi -LAT constraints on the pulsar wind nebula nature of HESS J1857+026

DOE PAGES

Rousseau, R.; Grondin, M. -H.; Van Etten, A.; ...

2012-07-17

Since its launch, the Fermi satellite has firmly identified 5 pulsar wind nebulae plus a large number of candidates, all powered by young and energetic pulsars. HESS J1857 + 026 is a spatially extended γ-ray source detected by H.E.S.S. and classified as a possible pulsar wind nebula candidate powered by PSR J1856 + 0245. Here, we search for γ-ray pulsations from PSR J1856+0245 and explore the characteristics of its associated pulsar wind nebula. Using a rotational ephemeris obtained from the Lovell telescope at Jodrell Bank Observatory at 1.5 GHz, we phase-fold 36 months of γ-ray data acquired by the Large Area Telescope (LAT) aboard Fermi. We also perform a complete γ-ray spectral and morphological analysis. No γ-ray pulsations were detected from PSR J1856+0245. But, significant emission is detected at a position coincident with the TeV source HESS J1857 + 026. The γ-ray spectrum is well described by a simple power-law with a spectral index of Γ = 1.53 ± 0.11 stat ± 0.55 syst and an energy flux of G(0.1–100 GeV) = (2.71 ± 0.52 stat ± 1.51 syst) × 10 -11 erg cm -2 s -1. The γ-ray luminosity is L PWN γ (0.1–100 GeV)=(2.5 ± 0.5 stat ± 1.5 syst) × 10 35 (d/9 kpc) 2 erg s -1, assuming a distance of 9 kpc. This implies a γ-ray efficiency of ~5% formore » $$\\dot{E}$$ = 4.6 × 10 36 erg s -1, in the range expected for pulsar wind nebulae. This detailed multi-wavelength modeling provides new constraints on its pulsar wind nebula nature.« less

Unidentified Gamma-Ray Sources: Hunting Gamma-Ray Blazars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Massaro, F.; D'Abrusco, R.; Tosti, G.

2012-04-02

One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of the unidentified {gamma}-ray sources (UGSs). Despite the large improvements of Fermi in the localization of {gamma}-ray sources with respect to the past {gamma}-ray missions, about one third of the Fermi-detected objects are still not associated to low energy counterparts. Recently, using the Wide-field Infrared Survey Explorer (WISE) survey, we discovered that blazars, the rarest class of Active Galactic Nuclei and the largest population of {gamma}-ray sources, can be recognized and separated from other extragalactic sources on the basis of their infrared (IR) colors. Basedmore » on this result, we designed an association method for the {gamma}-ray sources to recognize if there is a blazar candidate within the positional uncertainty region of a generic {gamma}-ray source. With this new IR diagnostic tool, we searched for {gamma}-ray blazar candidates associated to the UGS sample of the second Fermi {gamma}-ray catalog (2FGL). We found that our method associates at least one {gamma}-ray blazar candidate as a counterpart each of 156 out of 313 UGSs analyzed. These new low-energy candidates have the same IR properties as the blazars associated to {gamma}-ray sources in the 2FGL catalog.« less

UNIDENTIFIED {gamma}-RAY SOURCES: HUNTING {gamma}-RAY BLAZARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Massaro, F.; Ajello, M.; D'Abrusco, R.

2012-06-10

One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of unidentified {gamma}-ray sources (UGSs). Despite the major improvements of Fermi in the localization of {gamma}-ray sources with respect to the past {gamma}-ray missions, about one-third of the Fermi-detected objects are still not associated with low-energy counterparts. Recently, using the Wide-field Infrared Survey Explorer survey, we discovered that blazars, the rarest class of active galactic nuclei and the largest population of {gamma}-ray sources, can be recognized and separated from other extragalactic sources on the basis of their infrared (IR) colors. Based on this result, wemore » designed an association method for the {gamma}-ray sources to recognize if there is a blazar candidate within the positional uncertainty region of a generic {gamma}-ray source. With this new IR diagnostic tool, we searched for {gamma}-ray blazar candidates associated with the UGS sample of the second Fermi {gamma}-ray LAT catalog (2FGL). We found that our method associates at least one {gamma}-ray blazar candidate as a counterpart to each of 156 out of 313 UGSs analyzed. These new low-energy candidates have the same IR properties as the blazars associated with {gamma}-ray sources in the 2FGL catalog.« less

System design impacts on optimization of the advanced radioisotope power system (ARPS) AMTEC cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hendricks, T.J.; Huang, C.

1998-07-01

Several NASA deep space missions require Advanced Radioisotope Power Systems (ARPS) to supply spacecraft power for various internal functions and mission instruments and experiments. AMTEC (Alkali-Metal Thermal-Electric Conversion) power conversion is the DOE-selected technology for an advanced, next- generation RPS to power these spacecraft. Advanced Modular Power Systems, Inc. (AMPS) has begun investigating the design of an AMTEC-based ARPS using the General Purpose Heat Source (GPHS) and the latest PX-5 AMTEC cell technology with refractory materials in critical components. This paper presents and discusses the system design methodology, and results of important system design tradeoffs and system design impacts onmore » the ARPS AMTEC cell design. This work investigated dual 2-GPHS system configurations and 4-GPHS system configurations with 16 side-mounted AMTEC cells operating at beginning-of-mission (BOM) and end-of-mission (EOM) GPHS heat dissipation conditions. Current design studies indicate using a refractory material AMTEC cell with 8-BASE tubes, 5.0 inches long, and 1.75 inches diameter in the 4-GPHS system configuration is the strongest design candidate to satisfy system performance requirements.« less

Gene screening of Wharton's jelly derived stem cells.

PubMed

Mechiche Alami, S; Velard, F; Draux, F; Siu Paredes, F; Josse, J; Lemaire, F; Gangloff, S C; Graesslin, O; Laurent-Maquin, D; Kerdjoudj, H

2014-01-01

Stem cells are the most powerful candidate for the treatment of various diseases. Suitable stem cell source should be harvested with minimal invasive procedure, found in great quantity, and transplanted with no risk of immune response and tumor formation. Fetal derived stem cells have been introduced as an excellent alternative to adult and embryonic stem cells use, but unfortunately, their degree of "stemness" and molecular characterization is still unclear. Several studies have been performed deciphering whether fetal stem cells meet the needs of regenerative medicine. We believe that a transcriptomic screening of Wharton's jelly stem cells will bring insights on cell population features.

A novel method for preparing microfibrillated cellulose from bamboo fibers

NASA Astrophysics Data System (ADS)

Dat Nguyen, Huu; Thanh Thuy Mai, Thi; Bich Nguyen, Ngoc; Duy Dang, Thanh; Loan Phung Le, My; Dang, Tan Tai; Tran, Van Man

2013-03-01

The bamboo fiber is a potential candidate for biomass and power source application. In this study, microfibrillated cellulose (MFC) is prepared from raw fibers of bamboo tree (Bambusa Blumeana J A & J H Schultes) by an alkali treatment at room temperature in association with a bleaching treatment followed by a sulfuric acid hydrolysis. Field-emission scanning electron microscopy (FESEM) images indicated that final products ranged from 20 to 40 nm in diameter. The chemical composition measurement and Fourier transform infrared (FTIR) spectroscopy showed that both hemicellulose and lignin are mostly removed in the MFC. The x-ray diffraction (XRD) results also show that MFC has crystallinity of more than 70%. The thermogravimetric analysis (TGA) curves revealed that cellulose microfibers have a two-step thermal decomposition behavior owing to the attachment of sulfated groups onto the cellulose surface in the hydrolysis process with sulfuric acid. The obtained MFCs may have potential applications in alternative power sources as biomass, in pharmaceutical and optical industries as additives, as well as in composite fields as a reinforcement phase.

Probing the Nature of Short Swift Bursts via Deep INTEGRAL Monitoring of GRB 050925

NASA Technical Reports Server (NTRS)

Sakamoto, T.; Barbier, L.; Barthelmy, S. D.; Cummings, J. R.; Fenimore, E. E.; Gehrels, N.; Krimm, H. A.; Markwardt, C. B.; Palmer, D. M.; Parsons, A. M.;

A Targeted Search for Point Sources of EeV Photons with the Pierre Auger Observatory

NASA Astrophysics Data System (ADS)

Aab, A.; Abreu, P.; Aglietta, M.; Samarai, I. Al; Albuquerque, I. F. M.; Allekotte, I.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Anastasi, G. A.; Anchordoqui, L.; Andrada, B.; Andringa, S.; Aramo, C.; Arqueros, F.; Arsene, N.; Asorey, H.; Assis, P.; Aublin, J.; Avila, G.; Badescu, A. M.; Balaceanu, A.; Barreira Luz, R. J.; Beatty, J. J.; Becker, K. H.; Bellido, J. A.; Berat, C.; Bertaina, M. E.; Bertou, X.; Biermann, P. L.; Billoir, P.; Biteau, J.; Blaess, S. G.; Blanco, A.; Blazek, J.; Bleve, C.; Boháčová, M.; Boncioli, D.; Bonifazi, C.; Borodai, N.; Botti, A. M.; Brack, J.; Brancus, I.; Bretz, T.; Bridgeman, A.; Briechle, F. L.; Buchholz, P.; Bueno, A.; Buitink, S.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, L.; Cancio, A.; Canfora, F.; Caramete, L.; Caruso, R.; Castellina, A.; Cataldi, G.; Cazon, L.; Chavez, A. G.; Chinellato, J. A.; Chudoba, J.; Clay, R. W.; Colalillo, R.; Coleman, A.; Collica, L.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cooper, M. J.; Coutu, S.; Covault, C. E.; Cronin, J.; D'Amico, S.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; de Jong, S. J.; De Mauro, G.; de Mello Neto, J. R. T.; De Mitri, I.; de Oliveira, J.; de Souza, V.; Debatin, J.; Deligny, O.; Di Giulio, C.; Di Matteo, A.; Díaz Castro, M. L.; Diogo, F.; Dobrigkeit, C.; D'Olivo, J. C.; Dorosti, Q.; dos Anjos, R. C.; Dova, M. T.; Dundovic, A.; Ebr, J.; Engel, R.; Erdmann, M.; Erfani, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Falcke, H.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Fick, B.; Figueira, J. M.; Filipčič, A.; Fratu, O.; Freire, M. M.; Fujii, T.; Fuster, A.; Gaior, R.; García, B.; Garcia-Pinto, D.; Gaté, F.; Gemmeke, H.; Gherghel-Lascu, A.; Ghia, P. L.; Giaccari, U.; Giammarchi, M.; Giller, M.; Głas, D.; Glaser, C.; Golup, G.; Gómez Berisso, M.; Gómez Vitale, P. F.; González, N.; Gorgi, A.; Gorham, P.; Grillo, A. F.; Grubb, T. D.; Guarino, F.; Guedes, G. P.; Hampel, M. R.; Hansen, P.; Harari, D.; Harrison, T. A.; Harton, J. L.; Haungs, A.; Hebbeker, T.; Heck, D.; Heimann, P.; Herve, A. E.; Hill, G. C.; Hojvat, C.; Holt, E.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huege, T.; Hulsman, J.; Insolia, A.; Isar, P. G.; Jandt, I.; Jansen, S.; Johnsen, J. A.; Josebachuili, M.; Kääpä, A.; Kambeitz, O.; Kampert, K. H.; Katkov, I.; Keilhauer, B.; Kemp, E.; Kemp, J.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Krause, R.; Krohm, N.; Kuempel, D.; Kukec Mezek, G.; Kunka, N.; Kuotb Awad, A.; LaHurd, D.; Lauscher, M.; Legumina, R.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; Lopes, L.; López, R.; López Casado, A.; Luce, Q.; Lucero, A.; Malacari, M.; Mallamaci, M.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Mariş, I. C.; Marsella, G.; Martello, D.; Martinez, H.; Martínez Bravo, O.; Masías Meza, J. J.; Mathes, H. J.; Mathys, S.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Mayotte, E.; Mazur, P. O.; Medina, C.; Medina-Tanco, G.; Melo, D.; Menshikov, A.; Micheletti, M. I.; Middendorf, L.; Minaya, I. A.; Miramonti, L.; Mitrica, B.; Mockler, D.; Mollerach, S.; Montanet, F.; Morello, C.; Mostafá, M.; Müller, A. L.; Müller, G.; Muller, M. A.; Müller, S.; Mussa, R.; Naranjo, I.; Nellen, L.; Nguyen, P. H.; Niculescu-Oglinzanu, M.; Niechciol, M.; Niemietz, L.; Niggemann, T.; Nitz, D.; Nosek, D.; Novotny, V.; Nožka, H.; Núñez, L. A.; Ochilo, L.; Oikonomou, F.; Olinto, A.; Palatka, M.; Pallotta, J.; Papenbreer, P.; Parente, G.; Parra, A.; Paul, T.; Pech, M.; Pedreira, F.; Pȩkala, J.; Pelayo, R.; Peña-Rodriguez, J.; Pereira, L. A. S.; Perlín, M.; Perrone, L.; Peters, C.; Petrera, S.; Phuntsok, J.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Porowski, C.; Prado, R. R.; Privitera, P.; Prouza, M.; Quel, E. J.; Querchfeld, S.; Quinn, S.; Ramos-Pollan, R.; Rautenberg, J.; Ravignani, D.; Revenu, B.; Ridky, J.; Risse, M.; Ristori, P.; Rizi, V.; Rodrigues de Carvalho, W.; Rodriguez Fernandez, G.; Rodriguez Rojo, J.; Rogozin, D.; Roncoroni, M. J.; Roth, M.; Roulet, E.; Rovero, A. C.; Ruehl, P.; Saffi, S. J.; Saftoiu, A.; Salamida, F.; Salazar, H.; Saleh, A.; Salesa Greus, F.; Salina, G.; Sánchez, F.; Sanchez-Lucas, P.; Santos, E. M.; Santos, E.; Sarazin, F.; Sarmento, R.; Sarmiento, C. A.; Sato, R.; Schauer, M.; Scherini, V.; Schieler, H.; Schimp, M.; Schmidt, D.; Scholten, O.; Schovánek, P.; Schröder, F. G.; Schulz, A.; Schulz, J.; Schumacher, J.; Sciutto, S. J.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sigl, G.; Silli, G.; Sima, O.; Śmiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sonntag, S.; Sorokin, J.; Squartini, R.; Stanca, D.; Stanič, S.; Stasielak, J.; Stassi, P.; Strafella, F.; Suarez, F.; Suarez Durán, M.; Sudholz, T.; Suomijärvi, T.; Supanitsky, A. D.; Swain, J.; Szadkowski, Z.; Taboada, A.; Taborda, O. A.; Tapia, A.; Theodoro, V. M.; Timmermans, C.; Todero Peixoto, C. J.; Tomankova, L.; Tomé, B.; Torralba Elipe, G.; Travnicek, P.; Trini, M.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van Aar, G.; van Bodegom, P.; van den Berg, A. M.; van Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Varner, G.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Vergara Quispe, I. D.; Verzi, V.; Vicha, J.; Villaseñor, L.; Vorobiov, S.; Wahlberg, H.; Wainberg, O.; Walz, D.; Watson, A. A.; Weber, M.; Weindl, A.; Wiencke, L.; Wilczyński, H.; Winchen, T.; Wirtz, M.; Wittkowski, D.; Wundheiler, B.; Yang, L.; Yelos, D.; Yushkov, A.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zepeda, A.; Zimmermann, B.; Ziolkowski, M.; Zong, Z.; Zuccarello, F.

2017-03-01

Simultaneous measurements of air showers with the fluorescence and surface detectors of the Pierre Auger Observatory allow a sensitive search for EeV photon point sources. Several Galactic and extragalactic candidate objects are grouped in classes to reduce the statistical penalty of many trials from that of a blind search and are analyzed for a significant excess above the background expectation. The presented search does not find any evidence for photon emission at candidate sources, and combined p-values for every class are reported. Particle and energy flux upper limits are given for selected candidate sources. These limits significantly constrain predictions of EeV proton emission models from non-transient Galactic and nearby extragalactic sources, as illustrated for the particular case of the Galactic center region.

Associating Fast Radio Bursts with Extragalactic Radio Sources: General Methodology and a Search for a Counterpart to FRB 170107

NASA Astrophysics Data System (ADS)

Eftekhari, T.; Berger, E.; Williams, P. K. G.; Blanchard, P. K.

2018-06-01

The discovery of a repeating fast radio burst (FRB) has led to the first precise localization, an association with a dwarf galaxy, and the identification of a coincident persistent radio source. However, further localizations are required to determine the nature of FRBs, the sources powering them, and the possibility of multiple populations. Here we investigate the use of associated persistent radio sources to establish FRB counterparts, taking into account the localization area and the source flux density. Due to the lower areal number density of radio sources compared to faint optical sources, robust associations can be achieved for less precise localizations as compared to direct optical host galaxy associations. For generally larger localizations that preclude robust associations, the number of candidate hosts can be reduced based on the ratio of radio-to-optical brightness. We find that confident associations with sources having a flux density of ∼0.01–1 mJy, comparable to the luminosity of the persistent source associated with FRB 121102 over the redshift range z ≈ 0.1–1, require FRB localizations of ≲20″. We demonstrate that even in the absence of a robust association, constraints can be placed on the luminosity of an associated radio source as a function of localization and dispersion measure (DM). For DM ≈1000 pc cm‑3, an upper limit comparable to the luminosity of the FRB 121102 persistent source can be placed if the localization is ≲10″. We apply our analysis to the case of the ASKAP FRB 170107, using optical and radio observations of the localization region. We identify two candidate hosts based on a radio-to-optical brightness ratio of ≳100. We find that if one of these is indeed associated with FRB 170107, the resulting radio luminosity (1029‑ 4 × 1030 erg s‑1 Hz‑1, as constrained from the DM value) is comparable to the luminosity of the FRB 121102 persistent source.

SLD-MOSCNT: A new MOSCNT with step-linear doping profile in the source and drain regions

NASA Astrophysics Data System (ADS)

Tahne, Behrooz Abdi; Naderi, Ali

2017-01-01

In this paper, a new structure, step-linear doping MOSCNT (SLD-MOSCNT), is proposed to improve the performance of basic MOSCNTs. The basic structure suffers from band to band tunneling (BTBT). We show that using SLD profile for source and drain regions increases the horizontal distance between valence and conduction bands at gate to source/drain junction which reduces BTBT probability. SLD performance is compared with other similar structures which have recently been proposed to reduce BTBT such as MOSCNT with lightly-doped drain and source (LDDS), and with double-light doping in source and drain regions (DLD). The obtained results using a nonequilibrium Green’s function (NEGF) method show that the SLD-MOSCNT has the lowest leakage current, power consumption and delay time, and the highest current ratio and voltage gain. The ambipolar conduction in the proposed structure is very low and can be neglected. In addition, these structures can improve short-channel effects. Also, the investigation of cutoff frequency of the different structures shows that the SLD has the highest cutoff frequency. Device performance has been investigated for gate length from 8 to 20 nm which demonstrates all discussions regarding the superiority of the proposed structure are also valid for different channel lengths. This improvement is more significant especially for channel length less than 12 nm. Therefore, the SLD can be considered as a candidate to be used in the applications with high speed and low power consumption.

Milagro Observations of Potential TeV Emitters

NASA Astrophysics Data System (ADS)

Abeysekara, Anushka; Linnemann, James

2012-03-01

We searched for point sources in Milagro sky maps at the locations in four catalogs of potential TeV emitting sources. Our candidates are selected from the Fermi 2FGL pulsars, Fermi 2FGL extragalactic sources, TeVCat extragalactic sources, and from the BL Lac TeV Candidate list published by Costamante and Ghisellini in 2002. The False Discovery Rate (FDR) statistical procedure is used to select the sources. The FDR procedure controls the fraction of false detections. Our results are presented in this talk.

An evaluation of talker localization based on direction of arrival estimation and statistical sound source identification

NASA Astrophysics Data System (ADS)

Nishiura, Takanobu; Nakamura, Satoshi

2002-11-01

It is very important to capture distant-talking speech for a hands-free speech interface with high quality. A microphone array is an ideal candidate for this purpose. However, this approach requires localizing the target talker. Conventional talker localization algorithms in multiple sound source environments not only have difficulty localizing the multiple sound sources accurately, but also have difficulty localizing the target talker among known multiple sound source positions. To cope with these problems, we propose a new talker localization algorithm consisting of two algorithms. One is DOA (direction of arrival) estimation algorithm for multiple sound source localization based on CSP (cross-power spectrum phase) coefficient addition method. The other is statistical sound source identification algorithm based on GMM (Gaussian mixture model) for localizing the target talker position among localized multiple sound sources. In this paper, we particularly focus on the talker localization performance based on the combination of these two algorithms with a microphone array. We conducted evaluation experiments in real noisy reverberant environments. As a result, we confirmed that multiple sound signals can be identified accurately between ''speech'' or ''non-speech'' by the proposed algorithm. [Work supported by ATR, and MEXT of Japan.

DEEP NEAR-IR OBSERVATIONS OF THE GLOBULAR CLUSTER M4: HUNTING FOR BROWN DWARFS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dieball, A.; Bedin, L. R.; Knigge, C.

2016-01-20

We present an analysis of deep Hubble Space Telescope (HST)/Wide Field Camera 3 near-IR (NIR) imaging data of the globular cluster (GC) M4. The best-photometry NIR color–magnitude diagram (CMD) clearly shows the main sequence extending toward the expected end of the hydrogen-burning limit and going beyond this point toward fainter sources. The white dwarf (WD) sequence can be identified. As such, this is the deepest NIR CMD of a GC to date. Archival HST optical data were used for proper-motion cleaning of the CMD and for distinguishing the WDs from brown dwarf (BD) candidates. Detection limits in the NIR aremore » around F110W ≈ 26.5 mag and F160W ≈ 27 mag, and in the optical around F775W ≈ 28 mag. Comparing our observed CMDs with theoretical models, we conclude that we have reached beyond the H-burning limit in our NIR CMD and are probably just above or around this limit in our optical–NIR CMDs. Thus, any faint NIR sources that have no optical counterpart are potential BD candidates, since the optical data are not deep enough to detect them. We visually inspected the positions of NIR sources that are fainter than the H-burning limit in F110W and for which the optical photometry did not return a counterpart. We found in total five sources for which we did not get an optical measurement. For four of these five sources, a faint optical counterpart could be visually identified, and an upper optical magnitude was estimated. Based on these upper optical magnitude limits, we conclude that one source is likely a WD, one source could be either a WD or BD candidate, and the remaining two sources agree with being BD candidates. No optical counterpart could be detected for just one source, which makes this source a good BD candidate. We conclude that we found in total four good BD candidates.« less

ITO-MgF2 Film Development for PowerSphere Polymer Surface Protection

NASA Technical Reports Server (NTRS)

Hambourger, Paul D.; Kerslake, Thomas W.; Waters, Deborah L.

2004-01-01

Multi-kilogram class microsatellites with a PowerSphere electric power system are attractive for fulfilling a variety of potential NASA missions. However, PowerSphere polymer surfaces must be coated with a film that has suitable electrical sheet resistivity for electrostatic discharge control, be resistant to atomic oxygen attack, be transparent to ultraviolet light for composite structure curing and resist ultraviolet light induced darkening for efficient photovoltaic cell operation. In addition, the film must be tolerant of polymer layer folding associated with launch stowage of PowerSphere inflatable structures. An excellent film material candidate to meet these requirements is co-sputtered, indium oxide (In2O3) - tin oxide (SnO2), known as 'ITO', and magnesium fluoride (MgF2). While basic ITO-MgF2 film properties have been the subject of research over the last decade, further research is required in the areas of film durability for space-inflatable applications and precise film property control for large scale commercial production. In this paper, the authors present film durability results for a folded polymer substrate and film resistance to vacuum UV darkening. The authors discuss methods and results in the area of film sheet resistivity measurement and active control, particularly dual-channel, plasma emission line measurement of ITO and MgF2 plasma sources. ITO-MgF2 film polymer coupon preparation is described as well as film deposition equipment, procedures and film characterization. Durability testing methods are also described. The pre- and post-test condition of the films is assessed microscopically and electrically. Results show that an approx. 500A ITO-18vol% MgF2 film is a promising candidate to protect PowerSphere polymer surfaces for Earth orbit missions. Preliminary data also indicate that in situ film measurement methods are promising for active film resistivity control in future large scale production. Future film research plans are also discussed.

Difference Imaging of Lensed Quasar Candidates in the Sloan Digital Sky Survey Supernova Survey Region

NASA Astrophysics Data System (ADS)

Lacki, Brian C.; Kochanek, Christopher S.; Stanek, Krzysztof Z.; Inada, Naohisa; Oguri, Masamune

2009-06-01

Difference imaging provides a new way to discover gravitationally lensed quasars because few nonlensed sources will show spatially extended, time variable flux. We test the method on the fields of lens candidates in the Sloan Digital Sky Survey (SDSS) Supernova Survey region from the SDSS Quasar Lens Search (SQLS) and one serendipitously discovered lensed quasar. Starting from 20,536 sources, including 49 SDSS quasars, 32 candidate lenses/lensed images, and one known lensed quasar, we find that 174 sources including 35 SDSS quasars, 16 candidate lenses/lensed images, and the known lensed quasar are nonperiodic variable sources. We can measure the spatial structure of the variable flux for 119 of these variable sources and identify only eight as candidate extended variables, including the known lensed quasar. Only the known lensed quasar appears as a close pair of sources on the difference images. Inspection of the remaining seven suggests they are false positives, and only two were spectroscopically identified quasars. One of the lens candidates from the SQLS survives our cuts, but only as a single image instead of a pair. This indicates a false positive rate of order ~1/4000 for the method, or given our effective survey area of order 0.82 deg2, ~5 per deg2 in the SDSS Supernova Survey. The fraction of quasars not found to be variable and the false positive rate would both fall if we had analyzed the full, later data releases for the SDSS fields. While application of the method to the SDSS is limited by the resolution, depth, and sampling of the survey, several future surveys such as Pan-STARRS, LSST, and SNAP will significantly improve on these limitations.

Applications of thermal energy storage in the cement industry

NASA Technical Reports Server (NTRS)

Jaeger, F. A.; Beshore, D. G.; Miller, F. M.; Gartner, E. M.

1978-01-01

In the manufacture of cement, literally trillions of Btu's are rejected to the environment each year. The purpose of this feasibility study program was to determine whether thermal energy storage could be used to conserve or allow alternative uses of this rejected energy. This study identifies and quantifies the sources of rejected energy in the cement manufacturing process, established use of this energy, investigates various storage system concepts, and selects energy conservation systems for further study. Thermal performance and economic analyses are performed on candidate storage systems for four typical cement plants representing various methods of manufacturing cement. Through the use of thermal energy storage in conjunction with waste heat electric power generation units, an estimated 2.4 x 10 to the 13th power Btu/year, or an equivalent on investment of the proposed systems are an incentive for further development.

How multiple causes combine: independence constraints on causal inference.

PubMed

Liljeholm, Mimi

2015-01-01

According to the causal power view, two core constraints-that causes occur independently (i.e., no confounding) and influence their effects independently-serve as boundary conditions for causal induction. This study investigated how violations of these constraints modulate uncertainty about the existence and strength of a causal relationship. Participants were presented with pairs of candidate causes that were either confounded or not, and that either interacted or exerted their influences independently. Consistent with the causal power view, uncertainty about the existence and strength of causal relationships was greater when causes were confounded or interacted than when unconfounded and acting independently. An elemental Bayesian causal model captured differences in uncertainty due to confounding but not those due to an interaction. Implications of distinct sources of uncertainty for the selection of contingency information and causal generalization are discussed.

The Chaotic Light Curves of Accreting Black Holes

NASA Technical Reports Server (NTRS)

Kazanas, Demosthenes

2007-01-01

We present model light curves for accreting Black Hole Candidates (BHC) based on a recently developed model of these sources. According to this model, the observed light curves and aperiodic variability of BHC are due to a series of soft photon injections at random (Poisson) intervals and the stochastic nature of the Comptonization process in converting these soft photons to the observed high energy radiation. The additional assumption of our model is that the Comptonization process takes place in an extended but non-uniform hot plasma corona surrounding the compact object. We compute the corresponding Power Spectral Densities (PSD), autocorrelation functions, time skewness of the light curves and time lags between the light curves of the sources at different photon energies and compare our results to observation. Our model reproduces the observed light curves well, in that it provides good fits to their overall morphology (as manifest by the autocorrelation and time skewness) and also to their PSDs and time lags, by producing most of the variability power at time scales 2 a few seconds, while at the same time allowing for shots of a few msec in duration, in accordance with observation. We suggest that refinement of this type of model along with spectral and phase lag information can be used to probe the structure of this class of high energy sources.

Investigation of a family of power conditioners integrated into a utility grid: final report Category I

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wood, P.; Putkovich, R.P.

1981-07-01

A study was conducted of the requirements for and technologies applicable to power conditioning equipment in residential solar photovoltaic systems. A survey of companies known or thought to manufacture power conditioning equipment was conducted to asses the technology. Technical issues regarding ac and dc interface requirements were studied. A baseline design was selected to be a good example of existing technology which would not need significant development effort for its implementation. Alternative technologies are evaluated to determine which meet the baseline specification, and their costs and losses are evaluated. Areas in which cost improvements can be obtained are studied, andmore » the three best candidate technologies--the current-sourced converter, the HF front end converter, and the programmed wave converter--are compared. It is concluded that the designs investigated will meet, or with slight improvement could meet, short term efficiency goals. Long term efficiency goals could be met if an isolation transformer were not required in the power conditioning equipment. None of the technologies studied can meet cost goals unless further improvements are possible. (LEW)« less

A High Performance Delta-Sigma Modulator for Neurosensing

PubMed Central

Xu, Jian; Zhao, Menglian; Wu, Xiaobo; Islam, Md. Kafiul; Yang, Zhi

2015-01-01

Recorded neural data are frequently corrupted by large amplitude artifacts that are triggered by a variety of sources, such as subject movements, organ motions, electromagnetic interferences and discharges at the electrode surface. To prevent the system from saturating and the electronics from malfunctioning due to these large artifacts, a wide dynamic range for data acquisition is demanded, which is quite challenging to achieve and would require excessive circuit area and power for implementation. In this paper, we present a high performance Delta-Sigma modulator along with several design techniques and enabling blocks to reduce circuit area and power. The modulator was fabricated in a 0.18-μm CMOS process. Powered by a 1.0-V supply, the chip can achieve an 85-dB peak signal-to-noise-and-distortion ratio (SNDR) and an 87-dB dynamic range when integrated over a 10-kHz bandwidth. The total power consumption of the modulator is 13 μW, which corresponds to a figure-of-merit (FOM) of 45 fJ/conversion step. These competitive circuit specifications make this design a good candidate for building high precision neurosensors. PMID:26262623

A Targeted Search for Point Sources of EeV Photons with the Pierre Auger Observatory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aab, A.; Abreu, P.; Aglietta, M.

Simultaneous measurements of air showers with the fluorescence and surface detectors of the Pierre Auger Observatory allow a sensitive search for EeV photon point sources. Several Galactic and extragalactic candidate objects are grouped in classes to reduce the statistical penalty of many trials from that of a blind search and are analyzed for a significant excess above the background expectation. The presented search does not find any evidence for photon emission at candidate sources, and combined p-values for every class are reported. Particle and energy flux upper limits are given for selected candidate sources. Lastly, these limits significantly constrain predictionsmore » of EeV proton emission models from non-transient Galactic and nearby extragalactic sources, as illustrated for the particular case of the Galactic center region.« less

A Targeted Search for Point Sources of EeV Photons with the Pierre Auger Observatory

DOE PAGES

Aab, A.; Abreu, P.; Aglietta, M.; ...

2017-03-09

Simultaneous measurements of air showers with the fluorescence and surface detectors of the Pierre Auger Observatory allow a sensitive search for EeV photon point sources. Several Galactic and extragalactic candidate objects are grouped in classes to reduce the statistical penalty of many trials from that of a blind search and are analyzed for a significant excess above the background expectation. The presented search does not find any evidence for photon emission at candidate sources, and combined p-values for every class are reported. Particle and energy flux upper limits are given for selected candidate sources. Lastly, these limits significantly constrain predictionsmore » of EeV proton emission models from non-transient Galactic and nearby extragalactic sources, as illustrated for the particular case of the Galactic center region.« less

A Targeted Search for Point Sources of EeV Photons with the Pierre Auger Observatory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aab, A.; Abreu, P.; Aglietta, M.

Simultaneous measurements of air showers with the fluorescence and surface detectors of the Pierre Auger Observatory allow a sensitive search for EeV photon point sources. Several Galactic and extragalactic candidate objects are grouped in classes to reduce the statistical penalty of many trials from that of a blind search and are analyzed for a significant excess above the background expectation. The presented search does not find any evidence for photon emission at candidate sources, and combined p -values for every class are reported. Particle and energy flux upper limits are given for selected candidate sources. These limits significantly constrain predictionsmore » of EeV proton emission models from non-transient Galactic and nearby extragalactic sources, as illustrated for the particular case of the Galactic center region.« less

Lunar mass spectrometer test program

NASA Technical Reports Server (NTRS)

Torney, F. L.; Dobrott, J. R.

1972-01-01

The procedures are described along with results obtained in a test program conducted to demonstrate the performance of a candidate lunar mass spectrometer. The instrument was designed to sample and measure gases believed to exist in the lunar atmosphere at the surface. The subject instrument consists of a cold cathode ion source, a small quadrupole mass analyzer and an off axis electron multiplier ion counting detector. The major program emphasis was placed on demonstrating instrument resolution, sensitivity and S/N ratio over the mass range 0-150 amu and over a partial pressure range from 10 to the minus 9th power to 10 to the minus 13th power torr. Ultrahigh vacuum tests were conducted and the minimum detectable partial pressure for neon, argon, krypton and xenon was successfully determined for the spectrometer using isotopes of these gases. With the exception of neon, the minimum detectable partial pressure is approximately 4 x 10 to the minus 14th power torr for the above gases.

The Serendip II design. [narrowband astronautical radio signal search for extraterrestrial intelligence

NASA Technical Reports Server (NTRS)

Werthimer, D.; Tarter, J.; Bowyer, S.

1985-01-01

Serendip II is an automated system designed to perform a real time search for narrow band radio signals in the spectra of sources in a regularly scheduled, non-Seti, astronomical observing program. Because Serendip II is expected to run continuously without requiring dedicated observing time, it is hoped that a large portion of the sky will be surveyed at high sensitivity and low cost. Serendip II will compute the power spectrum using a 65,536 channel fast Fourier transform processor with a real time bandwidth of 128 KHz and 2 Hz per channel resolution. After searching for peaks in a 100 KHz portion of the radio telescope's IF band, Serendip II will move to the next 100 KHz portion using a programmable frequency synthesizer; when the whole IF band has been scanned, the process will start again. Unidentified peaks in the power spectra are candidates for further study and their celestial coordinates will be recorded along with the time and power, IF and RF frequency, and bandwidth of the peak.

Narrow-stripe broad-area lasers with distributed-feedback surface gratings as brilliant sources for high power spectral beam combining systems

NASA Astrophysics Data System (ADS)

Decker, J.; Crump, P.; Fricke, J.; Wenzel, H.; Maaβdorf, A.; Erbert, G.; Tränkle, G.

2014-03-01

Laser systems based on spectral beam combining (SBC) of broad-area (BA) diode lasers are promising tools for material processing applications. However, the system brightness is limited by the in-plane beam param- eter product, BPP, of the BA lasers, which operate with a BPP of < 3mm-mrad. The EU project BRIDLE (www.bridle.eu) is developing novel diode laser sources for such systems, and several technological advances are sought. For increased system brightness and optimal ber-coupling the diode lasers should operate with reduced BPP and vertical far eld angle (95% power content), μV 95. The resulting diode lasers are fabricated as mini- bars for reduced assembly costs. Gratings are integrated into the mini-bar, with each laser stripe emitting at a different wavelength. In this way, each emitter can be directed into a single bre via low-cost dielectric filters. Distributed-feedback narrow-stripe broad-area (DFB-NBA) lasers are promising candidates for these SBC sys- tems. We review here the design process and performance achieved, showing that DFB-NBA lasers with stripe width, W = 30 μm, successfully cut of higher-order lateral modes, improving BPP. Uniform, surface-etched, 80th-order Bragg gratings are used, with weak gratings essential for high e ciency. To date, such DFB-NBA sources operate with < 50% effciency at output power, Pout < 6 W, with BPP < 1.8 mm-mrad and offV 95 36 . The emission wavelength is about 970 nm and the spectral width is < 0.7 nm (95% power). The BPP is half that of a DFB-BA lasers with W = 90 um. We conclude with a review of options for further performance improvements.

Diverse Long-Term Variability of Five Candidate High-Mass X-Ray Binaries from Swift Burst Alert Telescope Observations

NASA Technical Reports Server (NTRS)

Corbet, Robin H. D.; Coley, Joel B.; Krimm, Hans A.

2017-01-01

We present an investigation of long-term modulation in the X-ray light curves of five little-studied candidate high-mass X-ray binaries using the Swift Burst Alert Telescope (SWIFT-BAT). IGR J14488-5942 and AX J1700.2-4220 show strong modulation at periods of 49.6 and 44 days, respectively, which are interpreted as orbital periods of Be star systems. For IGR J14488-5942, observations with the Swift X-ray Telescope show a hint of pulsations at 33.4 seconds. For AX J1700.2-4220, 54 second-pulsations were previously found with XMM-Newton. Swift J1816.7-1613 exhibits complicated behavior. The strongest peak in the power spectrum is at a period near 150 days, but this conflicts with a determination of a period of 118.5 days by La Parola et al. AX J1820.5-1434 has been proposed to exhibit modulation near 54 days, but the extended BAT observations suggest modulation at slightly longer than double this at approximately 111 days. There appears to be a long-term change in the shape of the modulation near 111 days, which may explain the apparent discrepancy. The X-ray pulsar XTE J1906+090,which was previously proposed to be a Be star system with an orbital period of approximately 30 days from pulse timing, shows peaks in the power spectrum at 81 and 173 days. The origins of these periods are unclear, although theymight be the orbital period and a superorbital period respectively. For all five sources, the long-term variability, together with the combination of orbital and proposed pulse periods, suggests that the sources contain Be starmass donors.

Diverse Long-term Variability of Five Candidate High-mass X-Ray Binaries from Swift Burst Alert Telescope Observations

NASA Astrophysics Data System (ADS)

Corbet, Robin H. D.; Coley, Joel B.; Krimm, Hans A.

2017-09-01

We present an investigation of long-term modulation in the X-ray light curves of five little-studied candidate high-mass X-ray binaries using the Swift Burst Alert Telescope. IGR J14488-5942 and AX J1700.2-4220 show strong modulation at periods of 49.6 and 44 days, respectively, which are interpreted as orbital periods of Be star systems. For IGR J14488-5942, observations with the Swift X-ray Telescope show a hint of pulsations at 33.4 s. For AX J1700.2-4220, 54 s pulsations were previously found with XMM-Newton. Swift J1816.7-1613 exhibits complicated behavior. The strongest peak in the power spectrum is at a period near 150 days, but this conflicts with a determination of a period of 118.5 days by La Parola et al. AX J1820.5-1434 has been proposed to exhibit modulation near 54 days, but the extended BAT observations suggest modulation at slightly longer than double this at approximately 111 days. There appears to be a long-term change in the shape of the modulation near 111 days, which may explain the apparent discrepancy. The X-ray pulsar XTE J1906+090, which was previously proposed to be a Be star system with an orbital period of ˜30 days from pulse timing, shows peaks in the power spectrum at 81 and 173 days. The origins of these periods are unclear, although they might be the orbital period and a superorbital period respectively. For all five sources, the long-term variability, together with the combination of orbital and proposed pulse periods, suggests that the sources contain Be star mass donors.

Diverse Long-Term Variability of Five Candidate High-Mass X-ray Binaries from Swift Burst Alert Telescope Observations

NASA Astrophysics Data System (ADS)

Corbet, Robin; Coley, Joel Barry; Krimm, Hans A.

2017-08-01

We present an investigation of long-term modulation in the X-ray light curves of five little-studied candidate high-mass X-ray binaries using the Swift Burst Alert Telescope. IGR J14488-5942 and AX J1700.2-4220 show strong modulation at periods of 49.6 and 44 days, respectively, which are interpreted as orbital periods of Be star systems. For IGR J14488-5942, observations with Swift X-ray Telescope show a hint of pulsations at 33.4 s. For AX J1700.2-4220, 54 s pulsations were previously found with XMM-Newton. Swift J1816.7-1613 exhibits complicated behavior. The strongest peak in the power spectrum is at a period near 150 days, but this conflicts with a determination of a period of 118.5 days by La Parola et al. (2014). AX J1820.5-1434 has been proposed to exhibit modulation near 54 days, but the extended BAT observations suggest modulation at slightly longer than double this at approximately 111 days. There appears to be a long-term change in the shape of the modulation near 111 days, which may explain the apparent discrepancy. The X-ray pulsar XTE J1906+090, which was previously proposed to be a Be star system with an orbital period of ˜30 days from pulse timing, shows peaks in the power spectrum at 81 and 173 days. The origins of these periods are unclear, although they might be the orbital period and a superorbital period respectively. For all five sources, the long-term variability, together with the combination of orbital and proposed pulse periods, suggests that the sources contain Be star mass donors.

Starburst or AGN dominance in submm-luminous candidate AGN

NASA Astrophysics Data System (ADS)

Coppin, Kristen; Alexander, Dave; Aretxaga, Itziar; Blain, Andrew; Chapman, Scott; Clements, Dave; Dunlop, James; Dunne, Loretta; Dye, Simon; Farrah, Duncan; Hughes, David; Ivison, Rob; Kim, Sungeun; Menendez-Delmestre, Karin; Oliver, Sebastian; Page, Mat; Pope, Alexandra; Rowan-Robinson, Michael; Scott, Douglas; Smail, Ian; Swinbank, Mark; Vaccari, Mattia; van Kampen, Eelco

2008-03-01

It is widely believed that starbursts/ULIRGs and AGN activity are triggered by galaxy interactions and merging; and sub-mm selected galaxies (SMGs) seem to be simply high redshift ULIRGs, observed near the peak of activity. In this evolutionary picture every SMG would host an AGN, which would eventually grow a black hole strong enough to blow off all of the gas and dust leaving an optically luminous QSO. In order to probe this evolutionary sequence, a crucial sub-sample to focus on would be the 'missing link' sources, which demonstrate both strong starburst and AGN signatures and to determine if the starburst is the main power source even in SMGs when we have evidence that an AGN is present. The best way to determine if a dominant AGN is present is to look in the mid-IR for their signatures, since often even deep X-ray observations miss identifying the presence of AGN in heavily dust-obscured SMGs. We have selected a sample of SMGs which are good candidates for harboring powerful AGN on the basis of their IRAC colours (S8um/S4.5um>2). Once we confirm these SMGs are AGN-dominated, we can then perform an audit of the energy balance between star-formation and AGN within this special sub-population of SMGs where the BH has grown appreciably to begin heating the dust emission. The proposed observations with IRS will probe the physics of how SMGs evolve from a cold-dust starburst-dominated ULIRG to an AGN/QSO by measuring the level of the mid-IR continuum, PAH luminosity, and Si absorption in these intermediate `transitory' AGN/SMGs.

Disc-jet Coupling in the 2009 Outburst of the Black Hole Candidate H1743-322

NASA Technical Reports Server (NTRS)

Miller-Jones, J. C. A.; Sivakoff, G. R.; Altamirano, D.; Coriat, M.; Corbel, S.; Dhawan, V.; Krimm, H. A.; Remillard, R. A.; Rupen, M. P.; Russell, D. M.;

Cluster candidates around low-power radio galaxies at z ∼ 1-2 in cosmos

DOE Office of Scientific and Technical Information (OSTI.GOV)

Castignani, G.; Celotti, A.; De Zotti, G.

2014-09-10

We search for high-redshift (z ∼1-2) galaxy clusters using low power radio galaxies (FR I) as beacons and our newly developed Poisson probability method based on photometric redshift information and galaxy number counts. We use a sample of 32 FR Is within the Cosmic Evolution Survey (COSMOS) field from the Chiaberge et al. catalog. We derive a reliable subsample of 21 bona fide low luminosity radio galaxies (LLRGs) and a subsample of 11 high luminosity radio galaxies (HLRGs), on the basis of photometric redshift information and NRAO VLA Sky Survey radio fluxes. The LLRGs are selected to have 1.4 GHzmore » rest frame luminosities lower than the fiducial FR I/FR II divide. This also allows us to estimate the comoving space density of sources with L {sub 1.4} ≅ 10{sup 32.3} erg s{sup –1} Hz{sup –1} at z ≅ 1.1, which strengthens the case for a strong cosmological evolution of these sources. In the fields of the LLRGs and HLRGs we find evidence that 14 and 8 of them reside in rich groups or galaxy clusters, respectively. Thus, overdensities are found around ∼70% of the FR Is, independently of the considered subsample. This rate is in agreement with the fraction found for low redshift FR Is and it is significantly higher than that for FR IIs at all redshifts. Although our method is primarily introduced for the COSMOS survey, it may be applied to both present and future wide field surveys such as Sloan Digital Sky Survey Stripe 82, LSST, and Euclid. Furthermore, cluster candidates found with our method are excellent targets for next generation space telescopes such as James Webb Space Telescope.« less

A Targeted Search for Point Sources of EeV Neutrons

NASA Astrophysics Data System (ADS)

Aab, A.; Abreu, P.; Aglietta, M.; Ahlers, M.; Ahn, E. J.; Samarai, I. Al; Albuquerque, I. F. M.; Allekotte, I.; Allen, J.; Allison, P.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Alves Batista, R.; Ambrosio, M.; Aminaei, A.; Anchordoqui, L.; Andringa, S.; Aramo, C.; Arqueros, F.; Asorey, H.; Assis, P.; Aublin, J.; Ave, M.; Avenier, M.; Avila, G.; Badescu, A. M.; Barber, K. B.; Bäuml, J.; Baus, C.; Beatty, J. J.; Becker, K. H.; Bellido, J. A.; Berat, C.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blanco, F.; Blanco, M.; Bleve, C.; Blümer, H.; Boháčová, M.; Boncioli, D.; Bonifazi, C.; Bonino, R.; Borodai, N.; Brack, J.; Brancus, I.; Brogueira, P.; Brown, W. C.; Buchholz, P.; Bueno, A.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, B.; Caccianiga, L.; Candusso, M.; Caramete, L.; Caruso, R.; Castellina, A.; Cataldi, G.; Cazon, L.; Cester, R.; Chavez, A. G.; Cheng, S. H.; Chiavassa, A.; Chinellato, J. A.; Chudoba, J.; Cilmo, M.; Clay, R. W.; Cocciolo, G.; Colalillo, R.; Collica, L.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cooper, M. J.; Coutu, S.; Covault, C. E.; Criss, A.; Cronin, J.; Curutiu, A.; Dallier, R.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; De Domenico, M.; de Jong, S. J.; de Mello Neto, J. R. T.; De Mitri, I.; de Oliveira, J.; de Souza, V.; del Peral, L.; Deligny, O.; Dembinski, H.; Dhital, N.; Di Giulio, C.; Di Matteo, A.; Diaz, J. C.; Díaz Castro, M. L.; Diep, P. N.; Diogo, F.; Dobrigkeit, C.; Docters, W.; D'Olivo, J. C.; Dong, P. N.; Dorofeev, A.; Dova, M. T.; Ebr, J.; Engel, R.; Erdmann, M.; Erfani, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Facal San Luis, P.; Falcke, H.; Fang, K.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferguson, A. P.; Fernandes, M.; Fick, B.; Figueira, J. M.; Filevich, A.; Filipčič, A.; Fox, B. D.; Fratu, O.; Fröhlich, U.; Fuchs, B.; Fuji, T.; Gaior, R.; García, B.; Garcia Roca, S. T.; Garcia-Gamez, D.; Garcia-Pinto, D.; Garilli, G.; Gascon Bravo, A.; Gate, F.; Gemmeke, H.; Ghia, P. L.; Giaccari, U.; Giammarchi, M.; Giller, M.; Glaser, C.; Glass, H.; Gomez Albarracin, F.; Gómez Berisso, M.; Gómez Vitale, P. F.; Gonçalves, P.; Gonzalez, J. G.; Gookin, B.; Gorgi, A.; Gorham, P.; Gouffon, P.; Grebe, S.; Griffith, N.; Grillo, A. F.; Grubb, T. D.; Guardincerri, Y.; Guarino, F.; Guedes, G. P.; Hansen, P.; Harari, D.; Harrison, T. A.; Harton, J. L.; Hasankiadeh, Q. D.; Haungs, A.; Hebbeker, T.; Heck, D.; Heimann, P.; Herve, A. E.; Hill, G. C.; Hojvat, C.; Hollon, N.; Holt, E.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huber, D.; Huege, T.; Insolia, A.; Isar, P. G.; Islo, K.; Jandt, I.; Jansen, S.; Jarne, C.; Josebachuili, M.; Kääpä, A.; Kambeitz, O.; Kampert, K. H.; Kasper, P.; Katkov, I.; Kégl, B.; Keilhauer, B.; Keivani, A.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Krause, R.; Krohm, N.; Krömer, O.; Kruppke-Hansen, D.; Kuempel, D.; Kunka, N.; La Rosa, G.; LaHurd, D.; Latronico, L.; Lauer, R.; Lauscher, M.; Lautridou, P.; Le Coz, S.; Leão, M. S. A. B.; Lebrun, D.; Lebrun, P.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; López, R.; Lopez Agüera, A.; Louedec, K.; Lozano Bahilo, J.; Lu, L.; Lucero, A.; Ludwig, M.; Lyberis, H.; Maccarone, M. C.; Malacari, M.; Maldera, S.; Maller, J.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Marin, V.; Mariş, I. C.; Marsella, G.; Martello, D.; Martin, L.; Martinez, H.; Martínez Bravo, O.; Martraire, D.; Masías Meza, J. J.; Mathes, H. J.; Mathys, S.; Matthews, A. J.; Matthews, J.; Matthiae, G.; Maurel, D.; Maurizio, D.; Mayotte, E.; Mazur, P. O.; Medina, C.; Medina-Tanco, G.; Melissas, M.; Melo, D.; Menichetti, E.; Menshikov, A.; Messina, S.; Meyhandan, R.; Mićanović, S.; Micheletti, M. I.; Middendorf, L.; Minaya, I. A.; Miramonti, L.; Mitrica, B.; Molina-Bueno, L.; Mollerach, S.; Monasor, M.; Monnier Ragaigne, D.; Montanet, F.; Morello, C.; Moreno, J. C.; Mostafá, M.; Moura, C. A.; Muller, M. A.; Müller, G.; Münchmeyer, M.; Mussa, R.; Navarra, G.; Navas, S.; Necesal, P.; Nellen, L.; Nelles, A.; Neuser, J.; Niechciol, M.; Niemietz, L.; Niggemann, T.; Nitz, D.; Nosek, D.; Novotny, V.; Nožka, L.; Ochilo, L.; Olinto, A.; Oliveira, M.; Ortiz, M.; Pacheco, N.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Palmieri, N.; Papenbreer, P.; Parente, G.; Parra, A.; Pastor, S.; Paul, T.; Pech, M.; Peķala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Pesce, R.; Petermann, E.; Peters, C.; Petrera, S.; Petrolini, A.; Petrov, Y.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Porcelli, A.; Porowski, C.; Privitera, P.; Prouza, M.; Purrello, V.; Quel, E. J.; Querchfeld, S.; Quinn, S.; Rautenberg, J.; Ravel, O.; Ravignani, D.; Revenu, B.; Ridky, J.; Riggi, S.; Risse, M.; Ristori, P.; Rizi, V.; Roberts, J.; Rodrigues de Carvalho, W.; Rodriguez Cabo, I.; Rodriguez Fernandez, G.; Rodriguez Rojo, J.; Rodríguez-Frías, M. D.; Ros, G.; Rosado, J.; Rossler, T.; Roth, M.; Roulet, E.; Rovero, A. C.; Rühle, C.; Saffi, S. J.; Saftoiu, A.; Salamida, F.; Salazar, H.; Salesa Greus, F.; Salina, G.; Sánchez, F.; Sanchez-Lucas, P.; Santo, C. E.; Santos, E.; Santos, E. M.; Sarazin, F.; Sarkar, B.; Sarmento, R.; Sato, R.; Scharf, N.; Scherini, V.; Schieler, H.; Schiffer, P.; Schmidt, A.; Scholten, O.; Schoorlemmer, H.; Schovánek, P.; Schulz, A.; Schulz, J.; Sciutto, S. J.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sidelnik, I.; Sigl, G.; Sima, O.; Śmiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sorokin, J.; Squartini, R.; Srivastava, Y. N.; Stanič, S.; Stapleton, J.; Stasielak, J.; Stephan, M.; Stutz, A.; Suarez, F.; Suomijärvi, T.; Supanitsky, A. D.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Szuba, M.; Taborda, O. A.; Tapia, A.; Tartare, M.; Thao, N. T.; Theodoro, V. M.; Tiffenberg, J.; Timmermans, C.; Todero Peixoto, C. J.; Toma, G.; Tomankova, L.; Tomé, B.; Tonachini, A.; Torralba Elipe, G.; Torres Machado, D.; Travnicek, P.; Trovato, E.; Tueros, M.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van Aar, G.; van den Berg, A. M.; van Velzen, S.; van Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Varner, G.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Verzi, V.; Vicha, J.; Videla, M.; Villaseñor, L.; Vlcek, B.; Wahlberg, H.; Wainberg, O.; Walz, D.; Watson, A. A.; Weber, M.; Weidenhaupt, K.; Weindl, A.; Werner, F.; Whelan, B. J.; Widom, A.; Wiencke, L.; Wilczyńska, B.; Wilczyński, H.; Will, M.; Williams, C.; Winchen, T.; Wittkowski, D.; Wundheiler, B.; Wykes, S.; Yamamoto, T.; Yapici, T.; Younk, P.; Yuan, G.; Yushkov, A.; Zamorano, B.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zaw, I.; Zepeda, A.; Zhou, J.; Zhu, Y.; Zimbres Silva, M.; Ziolkowski, M.; Auger Collaboration101, The Pierre

2014-07-01

A flux of neutrons from an astrophysical source in the Galaxy can be detected in the Pierre Auger Observatory as an excess of cosmic-ray air showers arriving from the direction of the source. To avoid the statistical penalty for making many trials, classes of objects are tested in combinations as nine "target sets," in addition to the search for a neutron flux from the Galactic center or from the Galactic plane. Within a target set, each candidate source is weighted in proportion to its electromagnetic flux, its exposure to the Auger Observatory, and its flux attenuation factor due to neutron decay. These searches do not find evidence for a neutron flux from any class of candidate sources. Tabulated results give the combined p-value for each class, with and without the weights, and also the flux upper limit for the most significant candidate source within each class. These limits on fluxes of neutrons significantly constrain models of EeV proton emission from non-transient discrete sources in the Galaxy.

A CMOS Low-Power Optical Front-End for 5 Gbps Applications

NASA Astrophysics Data System (ADS)

Zohoori, Soorena; Dolatshahi, Mehdi

2018-01-01

In this paper, a new low-power optical receiver front-end is proposed in 90 nm CMOS technology for 5 Gb/s AApplications. However, to improve the gain-bandwidth trade-off, the proposed Trans-Impedance Amplifier (TIA) uses an active modified inverter-based topology followed by a common-source amplifier, which uses active inductive peaking technique to enhance the frequency bandwidth in an increased gain level for a reasonable power consumption value. The proposed TIA is analyzed and simulated in HSPICE using 90 nm CMOS technology parameters. Simulation results show a 53.5dBΩ trans-impedance gain, 3.5 GHz frequency bandwidth, 16.8pA/√Hz input referred noise, and 1.28 mW of power consumption at 1V supply voltage. The Optical receiver is completed using three stages of differential limiting amplifiers (LAs), which provide 27 dB voltage gain while consume 3.1 mW of power. Finally, the whole optical receiver front-end consumes only 5.6 mW of power at 1 V supply and amplifies the input signal by 80 dB, while providing 3.7 GHz of frequency bandwidth. Finally, the simulation results indicate that the proposed optical receiver is a proper candidate to be used in a low-power 5 Gbps optical communication system.

Meta-analysis of heterogeneous data sources for genome-scale identification of risk genes in complex phenotypes.

PubMed

Pers, Tune H; Hansen, Niclas Tue; Lage, Kasper; Koefoed, Pernille; Dworzynski, Piotr; Miller, Martin Lee; Flint, Tracey J; Mellerup, Erling; Dam, Henrik; Andreassen, Ole A; Djurovic, Srdjan; Melle, Ingrid; Børglum, Anders D; Werge, Thomas; Purcell, Shaun; Ferreira, Manuel A; Kouskoumvekaki, Irene; Workman, Christopher T; Hansen, Torben; Mors, Ole; Brunak, Søren

2011-07-01

Meta-analyses of large-scale association studies typically proceed solely within one data type and do not exploit the potential complementarities in other sources of molecular evidence. Here, we present an approach to combine heterogeneous data from genome-wide association (GWA) studies, protein-protein interaction screens, disease similarity, linkage studies, and gene expression experiments into a multi-layered evidence network which is used to prioritize the entire protein-coding part of the genome identifying a shortlist of candidate genes. We report specifically results on bipolar disorder, a genetically complex disease where GWA studies have only been moderately successful. We validate one such candidate experimentally, YWHAH, by genotyping five variations in 640 patients and 1,377 controls. We found a significant allelic association for the rs1049583 polymorphism in YWHAH (adjusted P = 5.6e-3) with an odds ratio of 1.28 [1.12-1.48], which replicates a previous case-control study. In addition, we demonstrate our approach's general applicability by use of type 2 diabetes data sets. The method presented augments moderately powered GWA data, and represents a validated, flexible, and publicly available framework for identifying risk genes in highly polygenic diseases. The method is made available as a web service at www.cbs.dtu.dk/services/metaranker. © 2011 Wiley-Liss, Inc.

X-rays and gamma-rays from accretion flows onto black holes in Seyferts and X-ray binaries

NASA Technical Reports Server (NTRS)

Zdziarski, Andrzej A.; Johnson, W. Neil; Poutanen, Juri; Magdziarz, Pawel; Gierlinski, Marek

1997-01-01

Observations and theoretical models of X-ray/gamma ray spectra of radio quiet Seyfert galaxies and Galactic black hole candidates are reviewed. The spectra from these objects share the following characteristics: an underlying power law with a high energy cutoff above 200 keV; a Compton reflection component with a Fe K alpha line, and a low energy absorption by intervening cold matter. The X-ray energy spectral index, alpha, is typically in the range between 0.8 and 1 in Seyfert spectra, and that of the hard state spectra of the black hole candidates Cygnus X-1 and GX 339-4 is typically between 0.6 and 0.8. The Compton reflection component corresponds with cold matter covering a solid angle of between 0.8pi and 2pi as seen from the X-ray source. The broadband spectra of both classes of sources are well fitted by Compton upscattering of soft photons in thermal plasma. The fits yield a thermal plasma temperature of 100 keV and the Thomson optical depth of 1. All the spectra presented are cut off before the electron rest energy 511 keV, indicating that electron/positron pair production is an important process.

A NuSTAR OBSERVATION OF THE GAMMA-RAY-EMITTING X-RAY BINARY AND TRANSITIONAL MILLISECOND PULSAR CANDIDATE 1RXS J154439.4–112820

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bogdanov, Slavko

I present a 40 ks Nuclear Spectroscopic Telescope Array observation of the recently identified low-luminosity X-ray binary and transitional millisecond pulsar (tMSP) candidate 1RXS J154439.4 112820, which is associated with the high-energy γ -ray source 3FGL J1544.6 1125. The system is detected up to ∼30 keV with an extension of the same power-law spectrum and rapid large-amplitude variability between two flux levels observed in soft X-rays. These findings provide further evidence that 1RXS J154439.4 112820 belongs to the same class of objects as the nearby bona fide tMSPs PSR J1023+0038 and XSS J12270 4859 and therefore almost certainly hosts amore » millisecond pulsar accreting at low luminosity. I also examine the long-term accretion history of 1RXS J154439.4 112820 based on archival optical, ultraviolet, X-ray, and γ -ray light curves covering approximately the past decade. Throughout this period, the source has maintained similar flux levels at all wavelengths, which is an indication that it has not experienced prolonged episodes of a non-accreting radio pulsar state but may spontaneously undergo such events in the future.« less

Discovery of a Pulsar Wind Nebula Candidate in the Cygnus Loop

NASA Technical Reports Server (NTRS)

Katsuda, Satoru; Tsunemi, Hiroshi; Mori, Koji; Uchida, Hiroyuki; Petre, Robert; Yamada, Shin'ya; Tamagawa, Toru

2012-01-01

We report on a discovery of a diffuse nebula containing a point-like source in the southern blowout region of the Cygnus Loop supernova remnant, based on Suzaku and XMM-Newton observations. The X-ray spectra from the nebula and the point-like source are well represented by an absorbed power-law model with photon indices of 2.2+/-0.1 and 1.6+/-0.2, respectively. The photon indices as well as the flux ratio of F(sub nebula)/F(sub point-like) approx. 4 lead us to propose that the system is a pulsar wind nebula, although pulsations have not yet been detected. If we attribute its origin to the Cygnus Loop supernova, then the 0.5-8 keV luminosity of the nebula is computed to be 2.1x10(exp 31)(d/540pc)(exp 2)ergss/2, where d is the distance to the Loop. This implies a spin-down loss-energy E approx. 2.6x10(exp 35)(d/540pc)(exp 2)ergs/s. The location of the neutron star candidate, approx.2deg away from the geometric center of the Loop, implies a high transverse velocity of approx.1850(theta/2deg)(d/540pc)(t/10kyr)/k/s assuming the currently accepted age of the Cygnus Loop.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nyland, Kristina; Marvil, Josh; Young, Lisa M.

We present the results of deep, high-resolution, 5 GHz Expanded Very Large Array (EVLA) observations of the nearby, dwarf lenticular galaxy and intermediate-mass black hole candidate (M{sub BH} {approx} 4.5 Multiplication-Sign 10{sup 5} M{sub Sun }), NGC 404. For the first time, radio emission at frequencies above 1.4 GHz has been detected in this galaxy. We found a modestly resolved source in the NGC 404 nucleus with a total radio luminosity of 7.6 {+-} 0.7 Multiplication-Sign 10{sup 17} W Hz{sup -1} at 5 GHz and a spectral index from 5 to 7.45 GHz of {alpha} = -0.88 {+-} 0.30. NGCmore » 404 is only the third central intermediate-mass black hole candidate detected in the radio regime with subarcsecond resolution. The position of the radio source is consistent with the optical center of the galaxy and the location of a known, hard X-ray point source (L{sub X} {approx} 1.2 Multiplication-Sign 10{sup 37} erg s{sup -1}). The faint radio and X-ray emission could conceivably be produced by an X-ray binary, star formation, a supernova remnant, or a low-luminosity active galactic nucleus powered by an intermediate-mass black hole. In light of our new EVLA observations, we find that the most likely scenario is an accreting intermediate-mass black hole, with other explanations being either incompatible with the observed X-ray and/or radio luminosities or statistically unlikely.« less

Search for Candidate Objects with the Sunyaev–Zeldovich Effect in the Radio Source Vicinities—galaxies: clusters: general

NASA Astrophysics Data System (ADS)

Verkhodanov, O. V.; Verkhodanova, N. V.; Ulakhovich, O. S.; Solovyov, D. I.; Khabibullina, M. L.

2018-01-01

Based on the data from the Westerbork Northern Sky Survey performed at a frequency of 325 MHz in the range of right ascensions 0h ≤ α < 2h and declinations 29° < δ < 78° and using multi-frequency Planck maps, we selected candidate objects with the Sunyaev-Zeldovich effect. The list of the most probable candidates includes 381 sources. It is shown that the search for such objects can be accelerated by using a priori data on the negative level of fluctuations in the CMB map with removed low multipoles in the direction to radio sources.

HERSCHEL-ATLAS: TOWARD A SAMPLE OF {approx}1000 STRONGLY LENSED GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gonzalez-Nuevo, J.; Lapi, A.; Bressan, S.

2012-04-10

While the selection of strongly lensed galaxies (SLGs) with 500 {mu}m flux density S{sub 500} > 100 mJy has proven to be rather straightforward, for many applications it is important to analyze samples larger than the ones obtained when confining ourselves to such a bright limit. Moreover, only by probing to fainter flux densities is it possible to exploit strong lensing to investigate the bulk of the high-z star-forming galaxy population. We describe HALOS (the Herschel-ATLAS Lensed Objects Selection), a method for efficiently selecting fainter candidate SLGs, reaching a surface density of {approx_equal} 1.5-2 deg{sup -2}, i.e., a factor ofmore » about 4-6 higher than that at the 100 mJy flux limit. HALOS will allow the selection of up to {approx}1000 candidate SLGs (with amplifications {mu} {approx}> 2) over the full H-ATLAS survey area. Applying HALOS to the H-ATLAS Science Demonstration Phase field ({approx_equal} 14.4 deg{sup 2}) we find 31 candidate SLGs, whose candidate lenses are identified in the VIKING near-infrared catalog. Using the available information on candidate sources and candidate lenses we tentatively estimate a {approx_equal} 72% purity of the sample. As expected, the purity decreases with decreasing flux density of the sources and with increasing angular separation between candidate sources and lenses. The redshift distribution of the candidate lensed sources is close to that reported for most previous surveys for lensed galaxies, while that of candidate lenses extends to redshifts substantially higher than found in the other surveys. The counts of candidate SLGs are also in good agreement with model predictions. Even though a key ingredient of the method is the deep near-infrared VIKING photometry, we show that H-ATLAS data alone allow the selection of a similarly deep sample of candidate SLGs with an efficiency close to 50%; a slightly lower surface density ({approx_equal} 1.45 deg{sup -2}) can be reached with a {approx}70% efficiency.« less

Identifying the TeV gamma-ray source MGRO J2228+61, FINALLY!

NASA Astrophysics Data System (ADS)

Aliu, Ester

2012-09-01

New VERITAS observations of MGRO J2228+61 allow us to associate its TeV emission with the enigmatic radio supernova remnant SNR G106.3+2.7. This remnant is part of a large complex that includes the Boomerang pulsar and nebula. The reduced field suggests that the TeV emission is not powered by the Boomerang, but instead associated with a much larger remnant. A recent SUZAKU X-ray observation of the smaller gamma-ray error box reveals two possible pulsar candidates. We propose short ACIS exposures to identify these sources to determine if one or both can be responsible for the gamma-ray emission. This will allow us to address the long standing problem on the nature of both MGRO J2228+61 and SNR G106.3+2.7.

XMM-Newton Observation of IGR J18538-0102 and an Optical/IR Candidate

NASA Astrophysics Data System (ADS)

Halpern, J. P.; Gotthelf, E. V.

2010-02-01

We observed the X-ray counterpart of IGR J18538-0102 (Stephen et al., ATel #2441) in a pointed observation with XMM-Newton on 2004 October 8. This apparently steady source (in an 8 ks exposure) can be fitted with a power-law model of photon index 1.7+/-0.1, NH = (1.5+/-0.2)e22 cm-2, and unabsorbed 1-10 keV flux 5.6e-12 erg cm-2 s-1. Its coordinates 18h53m48.50s, -01d02'30.0" (J2000), with 90% confidence error radius of 3.2", coincide with an object in the 2MASS Point Source Catalog at 18h53m48.48s, -01d02'29.6" of magnitudes H=14.00+/-0.05 and K=12.50+/-0.05.

Probing the Metal Enrichment of the Intergalactic Medium at z = 5-6 Using the Hubble Space Telescope

NASA Astrophysics Data System (ADS)

Cai, Zheng; Fan, Xiaohui; Dave, Romeel; Finlator, Kristian; Oppenheimer, Ben

2017-11-01

We test the galactic outflow model by probing associated galaxies of four strong intergalactic C IV absorbers at z = 5-6 using the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) ramp narrowband filters. The four strong C IV absorbers reside at z = 5.74, 5.52, 4.95, and 4.87, with column densities ranging from N C IV = 1013.8 to 1014.8 cm-2. At z = 5.74, we detect an I-dropout Lyα emitter (LAE) candidate with a projected impact parameter of 42 physical kpc from the C IV absorber. This LAE candidate has a Lyα-based star formation rate (SFRLyα ) of 2 M ⊙ yr-1 and a UV-based SFR of 4 M ⊙ yr-1. Although we cannot completely rule out that this I-dropout emitter may be an [O II] interloper, its measured properties are consistent with the C IV powered galaxy at z = 5.74. For C IV absorbers at z = 4.95 and z = 4.87, although we detect two LAE candidates with impact parameters of 160 and 200 kpc, such distances are larger than that predicted from the simulations. Therefore, we treat them as nondetections. For the system at z = 5.52, we do not detect LAE candidates, placing a 3σ upper limit of SFRLyα ≈ 1.5 M ⊙ yr-1. In summary, in these four cases, we only detect one plausible C IV source at z = 5.74. Combining the modest SFR of the one detection and the three nondetections, our HST observations strongly support that smaller galaxies (SFRLyα ≲ 2 M ⊙ yr-1) are main sources of intergalactic C IV absorbers, and such small galaxies play a major role in the metal enrichment of the intergalactic medium at z ≳ 5.

Phenome-driven disease genetics prediction toward drug discovery

PubMed Central

Chen, Yang; Li, Li; Zhang, Guo-Qiang; Xu, Rong

2015-01-01

Motivation: Discerning genetic contributions to diseases not only enhances our understanding of disease mechanisms, but also leads to translational opportunities for drug discovery. Recent computational approaches incorporate disease phenotypic similarities to improve the prediction power of disease gene discovery. However, most current studies used only one data source of human disease phenotype. We present an innovative and generic strategy for combining multiple different data sources of human disease phenotype and predicting disease-associated genes from integrated phenotypic and genomic data. Results: To demonstrate our approach, we explored a new phenotype database from biomedical ontologies and constructed Disease Manifestation Network (DMN). We combined DMN with mimMiner, which was a widely used phenotype database in disease gene prediction studies. Our approach achieved significantly improved performance over a baseline method, which used only one phenotype data source. In the leave-one-out cross-validation and de novo gene prediction analysis, our approach achieved the area under the curves of 90.7% and 90.3%, which are significantly higher than 84.2% (P < e−4) and 81.3% (P < e−12) for the baseline approach. We further demonstrated that our predicted genes have the translational potential in drug discovery. We used Crohn’s disease as an example and ranked the candidate drugs based on the rank of drug targets. Our gene prediction approach prioritized druggable genes that are likely to be associated with Crohn’s disease pathogenesis, and our rank of candidate drugs successfully prioritized the Food and Drug Administration-approved drugs for Crohn’s disease. We also found literature evidence to support a number of drugs among the top 200 candidates. In summary, we demonstrated that a novel strategy combining unique disease phenotype data with system approaches can lead to rapid drug discovery. Availability and implementation: nlp.case.edu/public/data/DMN Contact: rxx@case.edu PMID:26072493

EnRICH: Extraction and Ranking using Integration and Criteria Heuristics.

PubMed

Zhang, Xia; Greenlee, M Heather West; Serb, Jeanne M

2013-01-15

High throughput screening technologies enable biologists to generate candidate genes at a rate that, due to time and cost constraints, cannot be studied by experimental approaches in the laboratory. Thus, it has become increasingly important to prioritize candidate genes for experiments. To accomplish this, researchers need to apply selection requirements based on their knowledge, which necessitates qualitative integration of heterogeneous data sources and filtration using multiple criteria. A similar approach can also be applied to putative candidate gene relationships. While automation can assist in this routine and imperative procedure, flexibility of data sources and criteria must not be sacrificed. A tool that can optimize the trade-off between automation and flexibility to simultaneously filter and qualitatively integrate data is needed to prioritize candidate genes and generate composite networks from heterogeneous data sources. We developed the java application, EnRICH (Extraction and Ranking using Integration and Criteria Heuristics), in order to alleviate this need. Here we present a case study in which we used EnRICH to integrate and filter multiple candidate gene lists in order to identify potential retinal disease genes. As a result of this procedure, a candidate pool of several hundred genes was narrowed down to five candidate genes, of which four are confirmed retinal disease genes and one is associated with a retinal disease state. We developed a platform-independent tool that is able to qualitatively integrate multiple heterogeneous datasets and use different selection criteria to filter each of them, provided the datasets are tables that have distinct identifiers (required) and attributes (optional). With the flexibility to specify data sources and filtering criteria, EnRICH automatically prioritizes candidate genes or gene relationships for biologists based on their specific requirements. Here, we also demonstrate that this tool can be effectively and easily used to apply highly specific user-defined criteria and can efficiently identify high quality candidate genes from relatively sparse datasets.

Spitzer Photometry of WISE-Selected Brown Dwarf and Hyper-Lumninous Infrared Galaxy Candidates

NASA Technical Reports Server (NTRS)

Griffith, Roger L.; Kirkpatrick, J. Davy; Eisenhardt, Peter R. M.; Gelino, Christopher R.; Cushing, Michael C.; Benford, Dominic; Blain, Andrew; Bridge, Carrie R.; Cohen, Martin; Cutri, Roc M.;

The Parsec-Scale Morphology of Southern GPS Sources

NASA Astrophysics Data System (ADS)

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

2016-12-01

Multi-frequency, multi-epoch ATCA observations of a sample of AGN resulted in the identification of nine new candidate Giga-hertz Peaked Spectrum sources. Here, we present Long Baseline Array observations at 4.8 GHz of the four candidates with no previously published VLBI image, and consider these together with previously published VLBI images of the other five sources. We find core-jet or compact double morphologies dominate, with further observations required to distinguish between these two possibilities for some sources. One of the nine candidates, PKS 1831-711, displays appreciable variability, suggesting its GPS spectrum is more ephemeral in nature. We focus in particular on the apparent relationship between a narrow spectral width and `compact double' parsec-scale morphology, finding further examples, but also exceptions to this trend. An examination of the VLBI morphologies high-redshift (z > 3) sub-class of GPS sources suggests that core-jet morphologies predominate in this class.

International Data on Radiological Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martha Finck; Margaret Goldberg

2010-07-01

ABSTRACT The mission of radiological dispersal device (RDD) nuclear forensics is to identify the provenance of nuclear and radiological materials used in RDDs and to aid law enforcement in tracking nuclear materials and routes. The application of databases to radiological forensics is to match RDD source material to a source model in the database, provide guidance regarding a possible second device, and aid the FBI by providing a short list of manufacturers and distributors, and ultimately to the last legal owner of the source. The Argonne/Idaho National Laboratory RDD attribution database is a powerful technical tool in radiological forensics. Themore » database (1267 unique vendors) includes all sealed sources and a device registered in the U.S., is complemented by data from the IAEA Catalogue, and is supported by rigorous in-lab characterization of selected sealed sources regarding physical form, radiochemical composition, and age-dating profiles. Close working relationships with global partners in the commercial sealed sources industry provide invaluable technical information and expertise in the development of signature profiles. These profiles are critical to the down-selection of potential candidates in either pre- or post- event RDD attribution. The down-selection process includes a match between an interdicted (or detonated) source and a model in the database linked to one or more manufacturers and distributors.« less

Heat engine development for solar thermal power systems

NASA Astrophysics Data System (ADS)

Pham, H. Q.; Jaffe, L. D.

The parabolic dish solar collector systems for converting sunlight to electrical power through a heat engine will, require a small heat engine of high performance long lifetime to be competitive with conventional power systems. The most promising engine candidates are Stirling, high temperature Brayton, and combined cycle. Engines available in the current market today do not meet these requirements. The development of Stirling and high temperature Brayton for automotive applications was studied which utilizes much of the technology developed in this automotive program for solar power engines. The technical status of the engine candidates is reviewed and the components that may additional development to meet solar thermal system requirements are identified.

A deep NuSTAR observation of M51: Investigating its Compton-thick nucleus, LINER companion and ULXs above 10 keV

NASA Astrophysics Data System (ADS)

Brightman, Murray; Annuar, Ady; Alexander, David M.; Earnshaw, Hannah; Gandhi, Poshak; Hornschemeier, Ann E.; Lehmer, Bret; Ptak, Andrew; Rangelov, Blagoy; Roberts, Tim P.; Stern, Daniel; Zezas, Andreas

2017-08-01

We present the results from a deep 200ks observation of M51 with NuSTAR. This observation was taken simultaneously with Chandra to provide soft-X-ray-coverage as well as to resolve the different point sources. We detect the Compton-thick nucleus of M51a, the LINER nucleus of M51b and several ultraluminous X-ray sources located in the galaxies above 10 keV. From X-ray torus modeling, we find that the covering factor of the torus in the nucleus of M51a is ~40% and supports a decline in the obscured fration at low X-ray luminosities. We find that the X-ray spectrum of the intermediate mass black hole candidate, ULX-7, is consistent with a power-law up to high energies, supporting its IMBH status. We further resolve the nucleus of M51b into two X-ray sources with Chandra, and measure its X-ray luminosity.

A 12 GHz wavelength spacing multi-wavelength laser source for wireless communication systems

NASA Astrophysics Data System (ADS)

Peng, P. C.; Shiu, R. K.; Bitew, M. A.; Chang, T. L.; Lai, C. H.; Junior, J. I.

2017-08-01

This paper presents a multi-wavelength laser source with 12 GHz wavelength spacing based on a single distributed feedback laser. A light wave generated from the distributed feedback laser is fed into a frequency shifter loop consisting of 50:50 coupler, dual-parallel Mach-Zehnder modulator, optical amplifier, optical filter, and polarization controller. The frequency of the input wavelength is shifted and then re-injected into the frequency shifter loop. By re-injecting the shifted wavelengths multiple times, we have generated 84 optical carriers with 12 GHz wavelength spacing and stable output power. For each channel, two wavelengths are modulated by a wireless data using the phase modulator and transmitted through a 25 km single mode fiber. In contrast to previously developed schemes, the proposed laser source does not incur DC bias drift problem. Moreover, it is a good candidate for radio-over-fiber systems to support multiple users using a single distributed feedback laser.

A search for long-time-scale, low-frequency radio transients

NASA Astrophysics Data System (ADS)

Murphy, Tara; Kaplan, David L.; Croft, Steve; Lynch, Christene; Callingham, J. R.; Bannister, Keith; Bell, Martin E.; Hurley-Walker, Natasha; Hancock, Paul; Line, Jack; Rowlinson, Antonia; Lenc, Emil; Intema, H. T.; Jagannathan, P.; Ekers, Ronald D.; Tingay, Steven; Yuan, Fang; Wolf, Christian; Onken, Christopher A.; Dwarakanath, K. S.; For, B.-Q.; Gaensler, B. M.; Hindson, L.; Johnston-Hollitt, M.; Kapińska, A. D.; McKinley, B.; Morgan, J.; Offringa, A. R.; Procopio, P.; Staveley-Smith, L.; Wayth, R.; Wu, C.; Zheng, Q.

2017-04-01

We present a search for transient and highly variable sources at low radio frequencies (150-200 MHz) that explores long time-scales of 1-3 yr. We conducted this search by comparing the TIFR GMRT Sky Survey Alternative Data Release 1 (TGSS ADR1) and the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey catalogues. To account for the different completeness thresholds in the individual surveys, we searched for compact GLEAM sources above a flux density limit of 100 mJy that were not present in the TGSS ADR1; and also for compact TGSS ADR1 sources above a flux density limit of 200 mJy that had no counterpart in GLEAM. From a total sample of 234 333 GLEAM sources and 275 612 TGSS ADR1 sources in the overlap region between the two surveys, there were 99 658 GLEAM sources and 38 978 TGSS ADR sources that passed our flux density cut-off and compactness criteria. Analysis of these sources resulted in three candidate transient sources. Further analysis ruled out two candidates as imaging artefacts. We analyse the third candidate and show it is likely to be real, with a flux density of 182 ± 26 mJy at 147.5 MHz. This gives a transient surface density of ρ = (6.2 ± 6) × 10-5 deg-2. We present initial follow-up observations and discuss possible causes for this candidate. The small number of spurious sources from this search demonstrates the high reliability of these two new low-frequency radio catalogues.

Antiproton signatures from astrophysical and dark matter sources at the galactic center

NASA Astrophysics Data System (ADS)

Cembranos, J. A. R.; Gammaldi, V.; Maroto, A. L.

2015-03-01

The center of our Galaxy is a complex region characterized by extreme phenomena. The presence of the supermassive Sagittarius A* black hole, a high dark matter density and an even higher baryonic density are able to produce very energetic processes. Indeed, high energetic gamma-rays have been observed by different telescopes, although their origin is not clear. In this work, we estimate the possible antiproton flux component associated with this signal. The expected secondary astrophysical antiproton background already saturates the observed data. It implies that any other important astrophysical source leads to an inconsistent excess. We estimate the sensitivity of PAMELA to this new primary antiproton source, which depends on the diffusion model and its spectral features. In particular, we consider antiproton spectra described by a power-law, a monochromatic signal and a Standard Model particle-antiparticle channel production. This latter spectrum is typical in the production from annihilating or decaying dark matter. We pay particular attention to the case of a heavy dark matter candidate, which could be associated with the High Energy Stereoscopic System (HESS) data observed from the J1745-290 source.

Computers for real time flight simulation: A market survey

NASA Technical Reports Server (NTRS)

Bekey, G. A.; Karplus, W. J.

1977-01-01

An extensive computer market survey was made to determine those available systems suitable for current and future flight simulation studies at Ames Research Center. The primary requirement is for the computation of relatively high frequency content (5 Hz) math models representing powered lift flight vehicles. The Rotor Systems Research Aircraft (RSRA) was used as a benchmark vehicle for computation comparison studies. The general nature of helicopter simulations and a description of the benchmark model are presented, and some of the sources of simulation difficulties are examined. A description of various applicable computer architectures is presented, along with detailed discussions of leading candidate systems and comparisons between them.

Design of Power System Architectures for Small Spacecraft Systems

NASA Technical Reports Server (NTRS)

Momoh, James A.; Subramonian, Rama; Dias, Lakshman G.

1996-01-01

The objective of this research is to perform a trade study on several candidate power system architectures for small spacecrafts to be used in NASA's new millennium program. Three initial candidate architectures have been proposed by NASA and two other candidate architectures have been proposed by Howard University. Howard University is currently conducting the necessary analysis, synthesis, and simulation needed to perform the trade studies and arrive at the optimal power system architecture. Statistical, sensitivity and tolerant studies has been performed on the systems. It is concluded from present studies that certain components such as the series regulators, buck-boost converters and power converters can be minimized while retaining the desired functionality of the overall architecture. This in conjunction with battery scalability studies and system efficiency studies have enabled us to develop more economic architectures. Future studies will include artificial neural networks and fuzzy logic to analyze the performance of the systems. Fault simulation studies and fault diagnosis studies using EMTP and artificial neural networks will also be conducted.

OPTICAL SPECTROSCOPIC OBSERVATIONS OF GAMMA-RAY BLAZAR CANDIDATES. VI. FURTHER OBSERVATIONS FROM TNG, WHT, OAN, SOAR, AND MAGELLAN TELESCOPES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Álvarez Crespo, N.; Massaro, F.; Milisavljevic, D.

Blazars, one of the most extreme classes of active galaxies, constitute so far the largest known population of γ-ray sources, and their number is continuously growing in the Fermi catalogs. However, in the latest release of the Fermi catalog there is still a large fraction of sources that are classified as blazar candidates of uncertain type (BCUs) for which optical spectroscopic observations are necessary to confirm their nature and their associations. In addition, about one-third of the γ-ray point sources listed in the Third Fermi-LAT Source Catalog (3FGL) are still unassociated and lacking an assigned lower-energy counterpart. Since 2012 wemore » have been carrying out an optical spectroscopic campaign to observe blazar candidates to confirm their nature. In this paper, the sixth of the series, we present optical spectroscopic observations for 30 γ-ray blazar candidates from different observing programs we carried out with the Telescopio Nazionale Galileo, William Herschel Telescope, Observatorio Astronómico Nacional, Southern Astrophysical Research Telescope, and Magellan Telescopes. We found that 21 out of 30 sources investigated are BL Lac objects, while the remaining targets are classified as flat-spectrum radio quasars showing the typical broad emission lines of normal quasi-stellar objects. We conclude that our selection of γ-ray blazar candidates based on their multifrequency properties continues to be a successful way to discover potential low-energy counterparts of the Fermi unidentified gamma-ray sources and to confirm the nature of BCUs.« less

VizieR Online Data Catalog: New gamma-ray blazar candidates in the 3PBC (Maselli+, 2013)

NASA Astrophysics Data System (ADS)

Maselli, A.; Massaro, F.; Cusumano, G.; D'Abrusco, R.; La Parola, V.; Paggi, A.; Segreto, A.; Smith, H. A.; Tosti, G.

2013-06-01

We searched for γ-ray blazar candidates among the 382 unidentified hard X-ray sources of the third Palermo BAT Catalog (3PBC) obtained from the analysis of 66 months of Swift Burst Alert Telescope (BAT) survey data and listing 1586 sources. We adopted a recently developed association method based on the peculiar infrared colors that characterize the γ-ray blazars included in the second catalog of active galactic nuclei detected by the Fermi Large Area Telescope. We used this method exploiting the data of the all-sky survey performed by the Wide-field Infrared Survey Explorer (WISE) to establish correspondences between unidentified 3PBC sources and WISE γ-ray blazar candidates located within the BAT positional uncertainty region at a 99% confidence level. We obtained a preliminary list of candidates for which we analyzed all the available data in the Swift archive to complement the information in the literature and in the radio, infrared, and optical catalogs with the information on their optical-UV and soft X-ray emission. Requiring the presence of radio and soft X-ray counterparts consistent with the infrared positions of the selected WISE sources, as well as a blazar-like radio morphology, we finally obtained a list of 24 γ-ray blazar candidates. (2 data files).

Searching for New γ-Ray Blazar Candidates in the Third Palermo BAT Hard X-Ray Catalog with WISE

NASA Astrophysics Data System (ADS)

Maselli, A.; Massaro, F.; Cusumano, G.; D'Abrusco, R.; La Parola, V.; Paggi, A.; Segreto, A.; Smith, Howard A.; Tosti, G.

2013-06-01

We searched for γ-ray blazar candidates among the 382 unidentified hard X-ray sources of the third Palermo BAT Catalog (3PBC) obtained from the analysis of 66 months of Swift Burst Alert Telescope (BAT) survey data and listing 1586 sources. We adopted a recently developed association method based on the peculiar infrared colors that characterize the γ-ray blazars included in the second catalog of active galactic nuclei detected by the Fermi Large Area Telescope. We used this method exploiting the data of the all-sky survey performed by the Wide-field Infrared Survey Explorer (WISE) to establish correspondences between unidentified 3PBC sources and WISE γ-ray blazar candidates located within the BAT positional uncertainty region at a 99% confidence level. We obtained a preliminary list of candidates for which we analyzed all the available data in the Swift archive to complement the information in the literature and in the radio, infrared, and optical catalogs with the information on their optical-UV and soft X-ray emission. Requiring the presence of radio and soft X-ray counterparts consistent with the infrared positions of the selected WISE sources, as well as a blazar-like radio morphology, we finally obtained a list of 24 γ-ray blazar candidates.

Stirling Isotope Power Systems for Stationary and Mobile Lunar Applications

NASA Technical Reports Server (NTRS)

Schmitz, Paul C.; Penswick, L. Barry; Shaltens, Richard K.

2007-01-01

The NASA Exploration Systems Architecture Study (ESAS) places a significant emphasis on the development of a wide range of capabilities on the lunar surface as a stepping-stone to further space exploration. An important aspect of developing these capabilities will be the availability of reliable, efficient, and low-mass power systems to support both stationary and mobile applications. One candidate system to provide electrical power is made by coupling the General Purpose Heat Source (GPHS) with a high-performance Stirling convertor. In this paper we explore the practical power range of GPHS/Stirling convertor systems all with conductively coupled hot-end designs for use on the lunar surface. Design and off-design operations during the life of the convertor are studied in addition to considering these varying conditions on system. Unique issues concerning Stirling convertor configurations, integration of the GPHS with the Stirling convertor, controller operation, waste heat rejection, and thermal protection are explored. Of particular importance in the evaluation process is a thorough understanding of the interactions between the wide range of unique lunar environments and the selection of key systems operating characteristics and the power systems design. Additionally, as power levels rise the interface between the GPHS and Stirling and the Stirling and the radiator begins to dominate system mass and material selection becomes more important.

Liquid-fueled SOFC power sources for transportation

NASA Astrophysics Data System (ADS)

Myles, K. M.; Doshi, R.; Kumar, R.; Krumpelt, M.

Traditionally, fuel cells have been developed for space or stationary terrestrial applications. As the first commercial 200-kW systems were being introduced by ONSI and Fuji Electric, the potentially much larger, but also more challenging, application in transportation was beginning to be addressed. As a result, fuel cell-powered buses have been designed and built, and R&D programs for fuel cell-powered passenger cars have been initiated. The engineering challenge of eventually replacing the internal combustion engine in buses, trucks, and passenger cars with fuel cell systems is to achieve much higher power densities and much lower costs than obtainable in systems designed for stationary applications. At present, the leading fuel cell candidate for transportation applications is, without question, the polymer electrolyte fuel cell (PEFC). Offering ambient temperature start-up and the potential for a relatively high power density, the polymer technology has attracted the interest of automotive manufacturers worldwide. But the difficulties of fuel handling for the PEFC have led to a growing interest in exploring the prospects for solid oxide fuel cells (SOFCs) operating on liquid fuels for transportation applications. Solid oxide fuel cells are much more compatible with liquid fuels (methanol or other hydrocarbons) and are potentially capable of power densities high enough for vehicular use. Two SOFC options for such use are discussed in this report.

Cross Matching as Strategy to Find Radio Stars

NASA Astrophysics Data System (ADS)

Christian, Tiffany; Kimball, Amy

2018-01-01

Using cross-matching between the FIRST (20cm) and GPS1 (optical) catalogs, we identified possible radio star candidates. This is an extension of earlier work by Kimball et al. (2009), who sought to identify radiostar candidates by cross-matching the FIRST (radio)and SDSS (optical) catalogs, but did not include the consideration of stellar proper motions. We used proper motions from GPS1 to match with FIRST radio sources; the region of sky where they overlap contains ~900,000 FIRST sources and several million GPS1 sources. We used WISE near-infrared and PanSTARRS optical information to identify matches that have stellar colors. Our selection constraints identified 6 stars (spectroscopically confirmed) as radio star candidates. They are faint in the radio (<1 mJy) indicating we may be searching at the limits of the radio survey. Other candidates had no spectral confirmation or object type identification in SIMBAD, which would make them ideal for follow up radio observations. However, random analysis indicated that many other possible candidates were random associations, which may also be true for these 6 stars.

The use of a multidimensional space for fusion candidate representation in a maritime domain awareness application

NASA Astrophysics Data System (ADS)

Lefebvre, Eric; Helleur, Christopher; Kashyap, Nathan

2008-03-01

Maritime surveillance of coastal regions requires operational staff to integrate a large amount of information from a variety of military and civilian sources. The diverse nature of the information sources makes complete automation difficult. The volume of vessels tracked and the number of sources makes it difficult for the limited operation centre staff to fuse all the information manually within a reasonable timeframe. In this paper, a conceptual decision space is proposed to provide a framework for automating the process of operators integrating the sources needed to maintain Maritime Domain Awareness. The decision space contains all potential pairs of ship tracks that are candidates for fusion. The location of the candidate pairs in this defined space depends on the value of the parameters used to make a decision. In the application presented, three independent parameters are used: the source detection efficiency, the geo-feasibility, and the track quality. One of three decisions is applied to each candidate track pair based on these three parameters: 1. to accept the fusion, in which case tracks are fused in one track, 2. to reject the fusion, in which case the candidate track pair is removed from the list of potential fusion, and 3. to defer the fusion, in which case no fusion occurs but the candidate track pair remains in the list of potential fusion until sufficient information is provided. This paper demonstrates in an operational setting how a proposed conceptual space is used to optimize the different thresholds for automatic fusion decision while minimizing the list of unresolved cases when the decision is left to the operator.

The first catalog of active galactic nuclei detected by the FERMI large area telescope

DOE PAGES

Abdo, A. A.; Ackermann, M.; Ajello, M.; ...

2010-04-29

Here, we present the first catalog of active galactic nuclei (AGNs) detected by the Large Area Telescope (LAT), corresponding to 11 months of data collected in scientific operation mode. The First LAT AGN Catalog (1LAC) includes 671 γ-ray sources located at high Galactic latitudes (|b|>10°) that are detected with a test statistic greater than 25 and associated statistically with AGNs. Some LAT sources are associated with multiple AGNs, and consequently, the catalog includes 709 AGNs, comprising 300 BL Lacertae objects, 296 flat-spectrum radio quasars, 41 AGNs of other types, and 72 AGNs of unknown type. We also classify the blazarsmore » based on their spectral energy distributions as archival radio, optical, and X-ray data permit. In addition to the formal 1LAC sample, we provide AGN associations for 51 low-latitude LAT sources and AGN "affiliations" (unquantified counterpart candidates) for 104 high-latitude LAT sources without AGN associations. The overlap of the 1LAC with existing γ-ray AGN catalogs (LBAS, EGRET, AGILE, Swift, INTEGRAL, TeVCat) is briefly discussed. Various properties—such as γ-ray fluxes and photon power-law spectral indices, redshifts, γ-ray luminosities, variability, and archival radio luminosities—and their correlations are presented and discussed for the different blazar classes. Lastly, we compare the 1LAC results with predictions regarding the γ-ray AGN populations, and we comment on the power of the sample to address the question of the blazar sequence.« less

A Common Calibration Source Framework for Fully-Polarimetric and Interferometric Radiometers

NASA Technical Reports Server (NTRS)

Kim, Edward J.; Davis, Brynmor; Piepmeier, Jeff; Zukor, Dorothy J. (Technical Monitor)

2000-01-01

Two types of microwave radiometry--synthetic thinned array radiometry (STAR) and fully-polarimetric (FP) radiometry--have received increasing attention during the last several years. STAR radiometers offer a technological solution to achieving high spatial resolution imaging from orbit without requiring a filled aperture or a moving antenna, and FP radiometers measure extra polarization state information upon which entirely new or more robust geophysical retrieval algorithms can be based. Radiometer configurations used for both STAR and FP instruments share one fundamental feature that distinguishes them from more 'standard' radiometers, namely, they measure correlations between pairs of microwave signals. The calibration requirements for correlation radiometers are broader than those for standard radiometers. Quantities of interest include total powers, complex correlation coefficients, various offsets, and possible nonlinearities. A candidate for an ideal calibration source would be one that injects test signals with precisely controllable correlation coefficients and absolute powers simultaneously into a pair of receivers, permitting all of these calibration quantities to be measured. The complex nature of correlation radiometer calibration, coupled with certain inherent similarities between STAR and FP instruments, suggests significant leverage in addressing both problems together. Recognizing this, a project was recently begun at NASA Goddard Space Flight Center to develop a compact low-power subsystem for spaceflight STAR or FP receiver calibration. We present a common theoretical framework for the design of signals for a controlled correlation calibration source. A statistical model is described, along with temporal and spectral constraints on such signals. Finally, a method for realizing these signals is demonstrated using a Matlab-based implementation.

A search for cataclysmic binaries containing strongly magnetic white dwarfs

NASA Technical Reports Server (NTRS)

Bond, H. E.; Chanmugam, G.

1982-01-01

The AM Herculis type binaries which contain accreting white dwarfs with surface magnetic fields of a few times 10 to the seventh power gauss were studied. If white dwarfs in cataclysmic binaries have a range of field strengths similar to that among single white dwarfs. AM Her like systems should exist with fields as high as 3 x 10 to the eighth power gauss. It is suggested that such objects will not have the strong optical polarization of the AM Her variables; however, they exhibit high harmonic cyclotron emission, making them spectacular UV sources. We made IUE observations of seven candidate cataclysmic variables selected for optical similarity to AM Her binaries. Although all seven objects were detected in the UV, none display unusually strong UV continua. It is suggested that the distribution of magnetic field strengths among single white dwarfs may be different from that among binaries.

Investigation of a family of power conditioners integrated into a utility grid: Category 1

NASA Astrophysics Data System (ADS)

Wood, P.; Putkovich, R. P.

1981-07-01

Technical issues regarding ac and dc interface requirements were studied. A baseline design was selected to be a good example of existing technology which would not need significant development effort for its implementation in residential solar photovoltaic systems. Alternative technologies are evaluated to determine which meet the baseline specification, and their costs and losses are evaluated. Areas in which cost improvements can be obtained are studied, and the three best candidate technologies--the current sourced converter, the HF front end converter, and the programmed wave converter--are compared. It is concluded that the designs investigated will meet, or with slight improvement could meet, short term efficiency goals. Long term efficiency goals could be met if an isolation transformer were not required in the power conditioning equipment. None of the technologies studied can meet cost goals unless further improvements are possible.

A nuclear driven metallic vapor MHD coupled with MPD thrusters

NASA Technical Reports Server (NTRS)

Anghaie, Samim; Kumar, Ratan

1991-01-01

Nuclear energy as a source of power for space missions, represents an enabling technology for advanced and ambitious space applications. Nuclear fuel in a gaseous or liquid form has been configured as a promising and practical candidate in this regard. The present study investigates and performs a feasibility analysis of an innovative concept for space power generation and propulsion. The system embodies a conceptual nuclear reactor with an MHD generator and coupled to MPD thrusters. The reactor utilizes liquid uranium in droplet form as fuel and superheated metallic vapor as the working fluid. This ultrahigh temperature vapor core reactor brings forward varied and challenging technical issues, and it has been addressed to in this paper. A parametric study of the conceived system has been performed in a qualitative and quantitative manner. Preliminary results show enough promise for further indepth analysis of this novel system.

Electrode performance parameters for a radioisotope-powered AMTEC for space power applications

NASA Technical Reports Server (NTRS)

Underwood, M. L.; O'Connor, D.; Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Bankston, C. P.

1992-01-01

The alkali metal thermoelastic converter (AMTEC) is a device for the direct conversion of heat to electricity. Recently a design of an AMTEC using a radioisotope heat source was described, but the optimum condenser temperature was hotter than the temperatures used in the laboratory to develop the electrode performance model. Now laboratory experiments have confirmed the dependence of two model parameters over a broader range of condenser and electrode temperatures for two candidate electrode compositions. One parameter, the electrochemical exchange current density at the reaction interface, is independent of the condenser temperature, and depends only upon the collision rate of sodium at the reaction zone. The second parameter, a morphological parameter, which measures the mass transport resistance through the electrode, is independent of condenser and electrode temperatures for molybdenum electrodes. For rhodium-tungsten electrodes, however, this parameter increases for decreasing electrode temperature, indicating an activated mass transport mechanism such as surface diffusion.

Dark Matter interpretation of low energy IceCube MESE excess

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chianese, M.; Miele, G.; Morisi, S., E-mail: chianese@na.infn.it, E-mail: miele@na.infn.it, E-mail: stefano.morisi@na.infn.it

2017-01-01

The 2-years MESE IceCube events show a slightly excess in the energy range 10–100 TeV with a maximum local statistical significance of 2.3σ, once a hard astrophysical power-law is assumed. A spectral index smaller than 2.2 is indeed suggested by multi-messenger studies related to p - p sources and by the recent IceCube analysis regarding 6-years up-going muon neutrinos. In the present paper, we propose a two-components scenario where the extraterrestrial neutrinos are explained in terms of an astrophysical power-law and a Dark Matter signal. We consider both decaying and annihilating Dark Matter candidates with different final states (quarks andmore » leptons) and different halo density profiles. We perform a likelihood-ratio analysis that provides a statistical significance up to 3.9σ for a Dark Matter interpretation of the IceCube low energy excess.« less

An image-based search for pulsars among Fermi unassociated LAT sources

NASA Astrophysics Data System (ADS)

Frail, D. A.; Ray, P. S.; Mooley, K. P.; Hancock, P.; Burnett, T. H.; Jagannathan, P.; Ferrara, E. C.; Intema, H. T.; de Gasperin, F.; Demorest, P. B.; Stovall, K.; McKinnon, M. M.

2018-03-01

We describe an image-based method that uses two radio criteria, compactness, and spectral index, to identify promising pulsar candidates among Fermi Large Area Telescope (LAT) unassociated sources. These criteria are applied to those radio sources from the Giant Metrewave Radio Telescope all-sky survey at 150 MHz (TGSS ADR1) found within the error ellipses of unassociated sources from the 3FGL catalogue and a preliminary source list based on 7 yr of LAT data. After follow-up interferometric observations to identify extended or variable sources, a list of 16 compact, steep-spectrum candidates is generated. An ongoing search for pulsations in these candidates, in gamma rays and radio, has found 6 ms pulsars and one normal pulsar. A comparison of this method with existing selection criteria based on gamma-ray spectral and variability properties suggests that the pulsar discovery space using Fermi may be larger than previously thought. Radio imaging is a hitherto underutilized source selection method that can be used, as with other multiwavelength techniques, in the search for Fermi pulsars.

Hard X-ray spectra of neutron stars and black hole candidates

NASA Technical Reports Server (NTRS)

Durouchoux, P.; Mahoney, W.; Clenet, Y.; Ling, J.; Wallyn, P.; Wheaton, W.; Corbet, S.; Chapuis, C.

1997-01-01

The hard X-ray behavior of several X-ray binary systems containing a neutron star or a black hole candidate is analyzed in an attempt to determine the specific signature of these categories of compact objects. Limiting the consideration to two subclasses of neutron stars, Atoll sources and non-pulsating Z sources, it appears that only the Atoll sources have a spectral behavior similar to black holes. It is proposed that Atoll sources are weakly magnetized neutron stars, whereas Z sources are small radius moderate magnetized neutron stars. Large magnetic fields funnel the accreting matter, thus preventing spherical accretion and free fall if the neutron star radius is smaller than the last stable accreting orbit. Weak magnetic fields do not have this effect, and blackbody soft photons from the stellar surface are upscattered on the relativistic infalling matter, leading to excess hard X-rays. This excess is visible in two of the observed Atoll sources and in the spectrum of a black hole candidate. In the case of a Z source, a lack of photons was remarked, providing a possible signature to distinguish between these classes of objects.

Near-infrared counterparts to the Galactic Bulge Survey X-ray source population

NASA Astrophysics Data System (ADS)

Greiss, S.; Steeghs, D.; Jonker, P. G.; Torres, M. A. P.; Maccarone, T. J.; Hynes, R. I.; Britt, C. T.; Nelemans, G.; Gänsicke, B. T.

2014-03-01

We report on the near-infrared matches, drawn from three surveys, to the 1640 unique X-ray sources detected by Chandra in the Galactic Bulge Survey (GBS). This survey targets faint X-ray sources in the bulge, with a particular focus on accreting compact objects. We present all viable counterpart candidates and associate a false alarm probability (FAP) to each near-infrared match in order to identify the most likely counterparts. The FAP takes into account a statistical study involving a chance alignment test, as well as considering the positional accuracy of the individual X-ray sources. We find that although the star density in the bulge is very high, ˜90 per cent of our sources have an FAP <10 per cent, indicating that for most X-ray sources, viable near-infrared counterparts candidates can be identified. In addition to the FAP, we provide positional and photometric information for candidate counterparts to ˜95 per cent of the GBS X-ray sources. This information in combination with optical photometry, spectroscopy and variability constraints will be crucial to characterize and classify secure counterparts.

MOLGENIS/connect: a system for semi-automatic integration of heterogeneous phenotype data with applications in biobanks.

PubMed

Pang, Chao; van Enckevort, David; de Haan, Mark; Kelpin, Fleur; Jetten, Jonathan; Hendriksen, Dennis; de Boer, Tommy; Charbon, Bart; Winder, Erwin; van der Velde, K Joeri; Doiron, Dany; Fortier, Isabel; Hillege, Hans; Swertz, Morris A

2016-07-15

While the size and number of biobanks, patient registries and other data collections are increasing, biomedical researchers still often need to pool data for statistical power, a task that requires time-intensive retrospective integration. To address this challenge, we developed MOLGENIS/connect, a semi-automatic system to find, match and pool data from different sources. The system shortlists relevant source attributes from thousands of candidates using ontology-based query expansion to overcome variations in terminology. Then it generates algorithms that transform source attributes to a common target DataSchema. These include unit conversion, categorical value matching and complex conversion patterns (e.g. calculation of BMI). In comparison to human-experts, MOLGENIS/connect was able to auto-generate 27% of the algorithms perfectly, with an additional 46% needing only minor editing, representing a reduction in the human effort and expertise needed to pool data. Source code, binaries and documentation are available as open-source under LGPLv3 from http://github.com/molgenis/molgenis and www.molgenis.org/connect : m.a.swertz@rug.nl Supplementary data are available at Bioinformatics online. © The Author 2016. Published by Oxford University Press.

MOLGENIS/connect: a system for semi-automatic integration of heterogeneous phenotype data with applications in biobanks

PubMed Central

Pang, Chao; van Enckevort, David; de Haan, Mark; Kelpin, Fleur; Jetten, Jonathan; Hendriksen, Dennis; de Boer, Tommy; Charbon, Bart; Winder, Erwin; van der Velde, K. Joeri; Doiron, Dany; Fortier, Isabel; Hillege, Hans

2016-01-01

Motivation: While the size and number of biobanks, patient registries and other data collections are increasing, biomedical researchers still often need to pool data for statistical power, a task that requires time-intensive retrospective integration. Results: To address this challenge, we developed MOLGENIS/connect, a semi-automatic system to find, match and pool data from different sources. The system shortlists relevant source attributes from thousands of candidates using ontology-based query expansion to overcome variations in terminology. Then it generates algorithms that transform source attributes to a common target DataSchema. These include unit conversion, categorical value matching and complex conversion patterns (e.g. calculation of BMI). In comparison to human-experts, MOLGENIS/connect was able to auto-generate 27% of the algorithms perfectly, with an additional 46% needing only minor editing, representing a reduction in the human effort and expertise needed to pool data. Availability and Implementation: Source code, binaries and documentation are available as open-source under LGPLv3 from http://github.com/molgenis/molgenis and www.molgenis.org/connect. Contact: m.a.swertz@rug.nl Supplementary information: Supplementary data are available at Bioinformatics online. PMID:27153686

Bright Merger-nova Emission Powered by Magnetic Wind from a Newborn Black Hole

NASA Astrophysics Data System (ADS)

Ma, Shuai-Bing; Lei, Wei-Hua; Gao, He; Xie, Wei; Chen, Wei; Zhang, Bing; Wang, Ding-Xiong

2018-01-01

Mergers of neutron star–neutron star (NS–NS) or neutron star–black hole (NS–BH) binaries are candidate sources of gravitational waves (GWs). At least a fraction of the merger remnants should be a stellar mass BH with sub-relativistic ejecta. A collimated jet is launched via the Blandford–Znajek mechanism from the central BH to trigger a short gamma-ray burst (sGRB). At the same time, a near-isotropic wind may be driven by the Blandford–Payne mechanism (BP). In previous work, additional energy injection to the ejecta from the BP mechanism was ignored, and radioactive decay has long been thought to be the main source of the kilonova energy. In this Letter, we propose that the wind driven by the BP mechanism from the newborn BH’s disk can heat up and push the ejecta during the prompt emission phase or even at late times when there is fall-back accretion. Such a BP-powered merger-nova could be bright in the optical band even for a low-luminosity sGRB. The detection of a GW merger event with a BH clearly identified as a remnant, accompanied by a bright merger-nova, would provide robust confirmation of our model.

Constraints on cosmic ray and PeV neutrino production in blazars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, B. Theodore; Li, Zhuo, E-mail: zhangbing91@pku.edu.cn, E-mail: zhuo.li@pku.edu.cn

2017-03-01

IceCube has detected a cumulative flux of PeV neutrinos, which origin is unknown. Blazars, active galactic nuclei with relativistic jets pointing to us, are long and widely expected to be one of the strong candidates of high energy neutrino sources. The neutrino production depends strongly on the cosmic ray power of blazar jets, which is largely unknown. The recent null results in stacking searches of neutrinos for several blazar samples by IceCube put upper limits on the neutrino fluxes from these blazars. Here we compute the cosmic ray power and PeV neutrino flux of Fermi-LAT blazars, and find that themore » upper limits for known blazar sources give stringent constraint on the cosmic ray loading factor of blazar jets (i.e., the ratio of the cosmic ray to bolometric radiation luminosity of blazar jets), ξ{sub cr} ∼< (2–10)ζ{sup −1} (with ζ ∼< 1 the remained fraction of cosmic ray energy when propagate into the blazar broad line region) for flat cosmic ray spectrum, and that the cumulative PeV neutrino flux contributed by all-sky blazars is a fraction ∼< (10–50)% of the IceCube detected flux.« less

Toward realizing high power semiconductor terahertz laser sources at room temperature

NASA Astrophysics Data System (ADS)

Razeghi, Manijeh

2011-05-01

The terahertz (THz) spectral range offers promising applications in science, industry, and military. THz penetration through nonconductors (fabrics, wood, plastic) enables a more efficient way of performing security checks (for example at airports), as illegal drugs and explosives could be detected. Being a non-ionizing radiation, THz radiation is environment-friendly enabling a safer analysis environment than conventional X-ray based techniques. However, the lack of a compact room temperature THz laser source greatly hinders mass deployment of THz systems in security check points and medical centers. In the past decade, tremendous development has been made in GaAs/AlGaAs based THz Quantum Cascade Laser (QCLs), with maximum operating temperatures close to 200 K (without magnetic field). However, higher temperature operation is severely limited by a small LO-phonon energy (~ 36 meV) in this material system. With a much larger LO-phonon energy of ~ 90 meV, III-Nitrides are promising candidates for room temperature THz lasers. However, realizing high quality material for GaN-based intersubband devices presents a significant challenge. Advances with this approach will be presented. Alternatively, recent demonstration of InP based mid-infrared QCLs with extremely high peak power of 120 W at room temperature opens up the possibility of producing high power THz emission with difference frequency generation through two mid-infrared wavelengths.

Teacher Candidates' Questions within the Context of an Educational Psychology Course

ERIC Educational Resources Information Center

Gallagher, Tiffany L.

2009-01-01

The belief systems with which teacher candidates enter their preservice programs powerfully shape their perceptions about teaching and learning. Data were gathered from 412 teacher candidates over the course of 5 academic years. Each of the participants posed 2 questions at the beginning of their course that they would like to be answered during…

Association of candidate genes with drought tolerance traits in diverse perennial ryegrass accessions

Treesearch

Xiaoqing Yu; Guihua Bai; Shuwei Liu; Na Luo; Ying Wang; Douglas S. Richmond; Paula M. Pijut; Scott A. Jackson; Jianming Yu; Yiwei Jiang

2013-01-01

Drought is a major environmental stress limiting growth of perennial grasses in temperate regions. Plant drought tolerance is a complex trait that is controlled by multiple genes. Candidate gene association mapping provides a powerful tool for dissection of complex traits. Candidate gene association mapping of drought tolerance traits was conducted in 192 diverse...

Riemann-Hilbert technique scattering analysis of metamaterial-based asymmetric 2D open resonators

NASA Astrophysics Data System (ADS)

Kamiński, Piotr M.; Ziolkowski, Richard W.; Arslanagić, Samel

2017-12-01

The scattering properties of metamaterial-based asymmetric two-dimensional open resonators excited by an electric line source are investigated analytically. The resonators are, in general, composed of two infinite and concentric cylindrical layers covered with an infinitely thin, perfect conducting shell that has an infinite axial aperture. The line source is oriented parallel to the cylinder axis. An exact analytical solution of this problem is derived. It is based on the dual-series approach and its transformation to the equivalent Riemann-Hilbert problem. Asymmetric metamaterial-based configurations are found to lead simultaneously to large enhancements of the radiated power and to highly steerable Huygens-like directivity patterns; properties not attainable with the corresponding structurally symmetric resonators. The presented open resonator designs are thus interesting candidates for many scientific and engineering applications where enhanced directional near- and far-field responses, tailored with beam shaping and steering capabilities, are highly desired.

Searching for Super Massive Binary Black Holes in the VLBA Calibrator Survey

NASA Astrophysics Data System (ADS)

High, Brittney C.; Peck, Alison B.; Beasley, Anthony J.

2016-01-01

Due to its incredible resolving power, the Very Long Baseline Array (VLBA) allows astronomers to view radio emission from celestial objects in incredible detail. This makes the VLBA the best instrument for studying the dynamics of active galactic nuclei, or compact regions at the centers of galaxies where black holes are thought to reside. Since most galaxies harbor supermassive black holes at their centers, and some galaxies merge with others, supermassive binary black hole systems arise. Though a number of these systems have been found, only one system contains black holes within 10 pc apart. During the summer, we analyzed new observations from the VLBA Calibrator Survey (VCS) on approximately 2200 sources in the hopes of detecting more close supermassive binary black hole candidates. Here we present the results from reducing and categorizing these sources. We also discuss the importance of the VCS and its role in enabling observations of the most distant celestial objects.

Development of a High-Average-Power Compton Gamma Source for Lepton Colliders

NASA Astrophysics Data System (ADS)

Pogorelsky, Igor; Polyanskiy, Mikhail N.; Yakimenko, Vitaliy; Platonenko, Viktor T.

2009-01-01

Gamma- (γ-) ray beams of high average power and peak brightness are of demand for a number of applications in high-energy physics, material processing, medicine, etc. One of such examples is gamma conversion into polarized positrons and muons that is under consideration for projected lepton colliders. A γ-source based on the Compton backscattering from the relativistic electron beam is a promising candidate for this application. Our approach to the high-repetition γ-source assumes placing the Compton interaction point inside a CO2 laser cavity. A laser pulse interacts with periodical electron bunches on each round-trip inside the laser cavity producing the corresponding train of γ-pulses. The round-trip optical losses can be compensated by amplification in the active laser medium. The major challenge for this approach is in maintaining stable amplification rate for a picosecond CO2-laser pulse during multiple resonator round-trips without significant deterioration of its temporal and transverse profiles. Addressing this task, we elaborated on a computer code that allows identifying the directions and priorities in the development of such a multi-pass picosecond CO2 laser. Proof-of-principle experiments help to verify the model and show the viability of the concept. In these tests we demonstrated extended trains of picosecond CO2 laser pulses circulating inside the cavity that incorporates the Compton interaction point.

Air Force electrochemical power research and technology program for space applications

NASA Technical Reports Server (NTRS)

Allen, Douglas

1987-01-01

An overview is presented of the existing Air Force electrochemical power, battery, and fuel cell programs for space application. Present thrusts are described along with anticipated technology availability dates. Critical problems to be solved before system applications occur are highlighted. Areas of needed performance improvement of batteries and fuel cells presently used are outlined including target dates for key demonstrations of advanced technology. Anticipated performance and current schedules for present technology programs are reviewed. Programs that support conventional military satellite power systems and special high power applications are reviewed. Battery types include bipolar lead-acid, nickel-cadmium, silver-zinc, nickel-hydrogen, sodium-sulfur, and some candidate advanced couples. Fuel cells for pulsed and transportation power applications are discussed as are some candidate advanced regenerative concepts.

Applying design principles to fusion reactor configurations for propulsion in space

NASA Technical Reports Server (NTRS)

Carpenter, Scott A.; Deveny, Marc E.; Schulze, Norman R.

1993-01-01

The application of fusion power to space propulsion requires rethinking the engineering-design solution to controlled-fusion energy. Whereas the unit cost of electricity (COE) drives the engineering-design solution for utility-based fusion reactor configurations; initial mass to low earth orbit (IMLEO), specific jet power (kW(thrust)/kg(engine)), and reusability drive the engineering-design solution for successful application of fusion power to space propulsion. We applied three design principles (DP's) to adapt and optimize three candidate-terrestrial-fusion-reactor configurations for propulsion in space. The three design principles are: provide maximum direct access to space for waste radiation, operate components as passive radiators to minimize cooling-system mass, and optimize the plasma fuel, fuel mix, and temperature for best specific jet power. The three candidate terrestrial fusion reactor configurations are: the thermal barrier tandem mirror (TBTM), field reversed mirror (FRM), and levitated dipole field (LDF). The resulting three candidate space fusion propulsion systems have their IMLEO minimized and their specific jet power and reusability maximized. We performed a preliminary rating of these configurations and concluded that the leading engineering-design solution to space fusion propulsion is a modified TBTM that we call the Mirror Fusion Propulsion System (MFPS).

SEARCHING FOR NEW {gamma}-RAY BLAZAR CANDIDATES IN THE THIRD PALERMO BAT HARD X-RAY CATALOG WITH WISE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maselli, A.; Cusumano, G.; La Parola, V.

We searched for {gamma}-ray blazar candidates among the 382 unidentified hard X-ray sources of the third Palermo BAT Catalog (3PBC) obtained from the analysis of 66 months of Swift Burst Alert Telescope (BAT) survey data and listing 1586 sources. We adopted a recently developed association method based on the peculiar infrared colors that characterize the {gamma}-ray blazars included in the second catalog of active galactic nuclei detected by the Fermi Large Area Telescope. We used this method exploiting the data of the all-sky survey performed by the Wide-field Infrared Survey Explorer (WISE) to establish correspondences between unidentified 3PBC sources andmore » WISE {gamma}-ray blazar candidates located within the BAT positional uncertainty region at a 99% confidence level. We obtained a preliminary list of candidates for which we analyzed all the available data in the Swift archive to complement the information in the literature and in the radio, infrared, and optical catalogs with the information on their optical-UV and soft X-ray emission. Requiring the presence of radio and soft X-ray counterparts consistent with the infrared positions of the selected WISE sources, as well as a blazar-like radio morphology, we finally obtained a list of 24 {gamma}-ray blazar candidates.« less

Analysis of the QTL for sleep homeostasis in mice: Homer1a is a likely candidate.

PubMed

Mackiewicz, M; Paigen, B; Naidoo, N; Pack, A I

2008-03-14

Electroencephalographic oscillations in the frequency range of 0.5-4 Hz, characteristic of slow-wave sleep (SWS), are often referred to as the delta oscillation or delta power. Delta power reflects sleep intensity and correlates with the homeostatic response to sleep loss. A published survey of inbred strains of mice demonstrated that the time course of accumulation of delta power varied among inbred strains, and the segregation of the rebound of delta power in BxD recombinant inbred strains identified a genomic region on chromosome 13 referred to as the delta power in SWS (or Dps1). The quantitative trait locus (QTL) contains genes that modify the accumulation of delta power after sleep deprivation. Here, we narrow the QTL using interval-specific haplotype analysis and present a comprehensive annotation of the remaining genes in the Dps1 region with sequence comparisons to identify polymorphisms within the coding and regulatory regions. We established the expression pattern of selected genes located in the Dps1 interval in sleep and wakefulness in B6 and D2 parental strains. Taken together, these steps reduced the number of potential candidate genes that may underlie the accumulation of delta power after sleep deprivation and explain the Dps1 QTL. The strongest candidate gene is Homer1a, which is supported by expression differences between sleep and wakefulness and the SNP polymorphism in the upstream regulatory regions.

Dark matter and the first stars

NASA Astrophysics Data System (ADS)

Spolyar, Douglas

The first stars in the universe (Pop. III stars) mark the birth of the visible and dynamical universe, which we are familiar with: stars galaxies, clusters, etc. They are also important for reionizing the universe, creating the metals needed for subsequent populations of stars and not to mention us. They are possible seeds for super massive black holes which power quasars and are found at the center of galaxies such as the Milky Way galaxy. In this thesis, we argue that if DM is a Weakly Interacting Massive Particle (WIMP), then DM can be an important heat source for the first stars. WIMPs are arguably from a particle physics perspective the most popular DM candidate and are being looked for in numerous experiments such as LHC, CDMS, and GLAST. DM heating would dramatically change the nature of the first stars. Stars powered by DM are larger and cooler than typical Pop. III stars. These differences would alter the metals and abundances produced by the first stars, the ionization history of the universe, and alter the formation of later stellar populations. Effects caused by stars powered by dark matter may also be tested with 21 cm line Tomography, JWST, 30 meter telescopes, Planck, and GLAST. This thesis has been written with an anthology in mind. Thus the thesis will be organized into an introduction followed by a series of papers which will illuminate the effects which DM can have on the first stars. The first paper will argue that DM can dramatically change the formation of the first stars. The second paper discusses DM capture as an important source of DM for the first stars. The third paper tests the effectiveness of the Blumenthal method. The fourth and fifth papers look at the effects of DM upon the evolution of Pop. III stars. As a note, primordial black holes are also a popular DM candidate. The final paper looks at primordial black hole's effect upon the first stars. Thus, we argue that DM in the guise of WIMPs and primordial black holes can dramatically alter the nature of the first stars.

CS Emission Near MIR-bubbles

NASA Astrophysics Data System (ADS)

Watson, C.; Devine, Kathryn; Quintanar, N.; Candelaria, T.

2016-02-01

We survey 44 young stellar objects located near the edges of mid-IR-identified bubbles in CS (1-0) using the Green Bank Telescope. We detect emission in 18 sources, indicating young protostars that are good candidates for being triggered by the expansion of the bubble. We calculate CS column densities and abundances. Three sources show evidence of infall through non-Gaussian line-shapes. Two of these sources are associated with dark clouds and are promising candidates for further exploration of potential triggered star formation. We obtained on-the-fly maps in CS (1-0) of three sources, showing evidence of significant interactions between the sources and the surrounding environment.

Starship Sails Propelled by Cost-Optimized Directed Energy

NASA Astrophysics Data System (ADS)

Benford, J.

Microwave and laser-propelled sails are a new class of spacecraft using photon acceleration. It is the only method of interstellar flight that has no physics issues. Laboratory demonstrations of basic features of beam-driven propulsion, flight, stability (`beam-riding'), and induced spin, have been completed in the last decade, primarily in the microwave. It offers much lower cost probes after a substantial investment in the launcher. Engineering issues are being addressed by other applications: fusion (microwave, millimeter and laser sources) and astronomy (large aperture antennas). There are many candidate sail materials: carbon nanotubes and microtrusses, beryllium, graphene, etc. For acceleration of a sail, what is the cost-optimum high power system? Here the cost is used to constrain design parameters to estimate system power, aperture and elements of capital and operating cost. From general relations for cost-optimal transmitter aperture and power, system cost scales with kinetic energy and inversely with sail diameter and frequency. So optimal sails will be larger, lower in mass and driven by higher frequency beams. Estimated costs include economies of scale. We present several starship point concepts. Systems based on microwave, millimeter wave and laser technologies are of equal cost at today's costs. The frequency advantage of lasers is cancelled by the high cost of both the laser and the radiating optic. Cost of interstellar sailships is very high, driven by current costs for radiation source, antennas and especially electrical power. The high speeds necessary for fast interstellar missions make the operating cost exceed the capital cost. Such sailcraft will not be flown until the cost of electrical power in space is reduced orders of magnitude below current levels.

Ultra-low input power long-wavelength GaSb type-I laser diodes at 2.7-3.0 μm

NASA Astrophysics Data System (ADS)

Vizbaras, Augustinas; Greibus, Mindaugas; Dvinelis, Edgaras; Trinkūnas, Augustinas; Kovalenkovas, Deividas; Šimonytė, Ieva; Vizbaras, Kristijonas

2014-02-01

Mid-infrared spectral region (2-4 μm) is gaining significant attention recently due to the presence of numerous enabling applications in the field of gas sensing, medical, environmental and defense applications. Major requirement for these applications is the availability of laser sources in this spectral window. Type-I GaSb-based laser diodes are ideal candidates for these applications being compact, electrically pumped, power efficient and able to operate at room temperature in continuous-wave. Moreover, due to the nature of type-I transition; these devices have a characteristic low operation voltage, typically below 1 V, resulting in low power consumption, and high-temperature of operation. In this work, we present recent progress of 2.7 μm - 3.0 μm wavelength single-spatial mode GaSb type-I laser diode development at Brolis Semiconductors. Experimental device structures were grown by solid-source multi-wafer MBE, consisting of an active region with 2 compressively strained (~1.3 %-1.5 %) GaInAsSb quantum wells with GaSb barriers for 2.7 μm devices and quinternary AlGaInAsSb barriers for 3.0 μm devices. Epi-wafers were processed into a narrow-ridge (2-4 μm) devices and mounted p-side up on CuW heatsink. Devices exhibited very low CW threshold powers of < 100 mW, and single spatial mode (TE00) operation with room-temperature output powers up to 40 mW in CW mode. Operating voltage was as low as 1.2 V at 1.2 A. As-cleaved devices worked CW up to 50 deg C.

In Silico Gene Prioritization by Integrating Multiple Data Sources

PubMed Central

Zhou, Yingyao; Shields, Robert; Chanda, Sumit K.; Elston, Robert C.; Li, Jing

2011-01-01

Identifying disease genes is crucial to the understanding of disease pathogenesis, and to the improvement of disease diagnosis and treatment. In recent years, many researchers have proposed approaches to prioritize candidate genes by considering the relationship of candidate genes and existing known disease genes, reflected in other data sources. In this paper, we propose an expandable framework for gene prioritization that can integrate multiple heterogeneous data sources by taking advantage of a unified graphic representation. Gene-gene relationships and gene-disease relationships are then defined based on the overall topology of each network using a diffusion kernel measure. These relationship measures are in turn normalized to derive an overall measure across all networks, which is utilized to rank all candidate genes. Based on the informativeness of available data sources with respect to each specific disease, we also propose an adaptive threshold score to select a small subset of candidate genes for further validation studies. We performed large scale cross-validation analysis on 110 disease families using three data sources. Results have shown that our approach consistently outperforms other two state of the art programs. A case study using Parkinson disease (PD) has identified four candidate genes (UBB, SEPT5, GPR37 and TH) that ranked higher than our adaptive threshold, all of which are involved in the PD pathway. In particular, a very recent study has observed a deletion of TH in a patient with PD, which supports the importance of the TH gene in PD pathogenesis. A web tool has been implemented to assist scientists in their genetic studies. PMID:21731658

Study of switching transients in high frequency converters

NASA Technical Reports Server (NTRS)

Zinger, Donald S.; Elbuluk, Malik E.; Lee, Tony

1993-01-01

As the semiconductor technologies progress rapidly, the power densities and switching frequencies of many power devices are improved. With the existing technology, high frequency power systems become possible. Use of such a system is advantageous in many aspects. A high frequency ac source is used as the direct input to an ac/ac pulse-density-modulation (PDM) converter. This converter is a new concept which employs zero voltage switching techniques. However, the development of this converter is still in its infancy stage. There are problems associated with this converter such as a high on-voltage drop, switching transients, and zero-crossing detecting. Considering these problems, the switching speed and power handling capabilities of the MOS-Controlled Thyristor (MCT) makes the device the most promising candidate for this application. A complete insight of component considerations for building an ac/ac PDM converter for a high frequency power system is addressed. A power device review is first presented. The ac/ac PDM converter requires switches that can conduct bi-directional current and block bi-directional voltage. These bi-directional switches can be constructed using existing power devices. Different bi-directional switches for the converter are investigated. Detailed experimental studies of the characteristics of the MCT under hard switching and zero-voltage switching are also presented. One disadvantage of an ac/ac converter is that turn-on and turn-off of the switches has to be completed instantaneously when the ac source is at zero voltage. Otherwise shoot-through current or voltage spikes can occur which can be hazardous to the devices. In order for the devices to switch softly in the safe operating area even under non-ideal cases, a unique snubber circuit is used in each bi-directional switch. Detailed theory and experimental results for circuits using these snubbers are presented. A current regulated ac/ac PDM converter built using MCT's and IGBT's is evaluated.

Multi-mode evaluation of power-maximizing cross-flow turbine controllers

DOE PAGES

Forbush, Dominic; Cavagnaro, Robert J.; Donegan, James; ...

2017-09-21

A general method for predicting and evaluating the performance of three candidate cross-flow turbine power-maximizing controllers is presented in this paper using low-order dynamic simulation, scaled laboratory experiments, and full-scale field testing. For each testing mode and candidate controller, performance metrics quantifying energy capture (ability of a controller to maximize power), variation in torque and rotation rate (related to drive train fatigue), and variation in thrust loads (related to structural fatigue) are quantified for two purposes. First, for metrics that could be evaluated across all testing modes, we considered the accuracy with which simulation or laboratory experiments could predict performancemore » at full scale. Second, we explored the utility of these metrics to contrast candidate controller performance. For these turbines and set of candidate controllers, energy capture was found to only differentiate controller performance in simulation, while the other explored metrics were able to predict performance of the full-scale turbine in the field with various degrees of success. Finally, effects of scale between laboratory and full-scale testing are considered, along with recommendations for future improvements to dynamic simulations and controller evaluation.« less

Multi-mode evaluation of power-maximizing cross-flow turbine controllers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forbush, Dominic; Cavagnaro, Robert J.; Donegan, James

A general method for predicting and evaluating the performance of three candidate cross-flow turbine power-maximizing controllers is presented in this paper using low-order dynamic simulation, scaled laboratory experiments, and full-scale field testing. For each testing mode and candidate controller, performance metrics quantifying energy capture (ability of a controller to maximize power), variation in torque and rotation rate (related to drive train fatigue), and variation in thrust loads (related to structural fatigue) are quantified for two purposes. First, for metrics that could be evaluated across all testing modes, we considered the accuracy with which simulation or laboratory experiments could predict performancemore » at full scale. Second, we explored the utility of these metrics to contrast candidate controller performance. For these turbines and set of candidate controllers, energy capture was found to only differentiate controller performance in simulation, while the other explored metrics were able to predict performance of the full-scale turbine in the field with various degrees of success. Finally, effects of scale between laboratory and full-scale testing are considered, along with recommendations for future improvements to dynamic simulations and controller evaluation.« less

Prevalence and associations of anisometropia with spherical ametropia, cylindrical power, age, and sex in refractive surgery candidates.

PubMed

Linke, Stephan J; Richard, Gisbert; Katz, Toam

2011-09-29

To analyze the prevalence and associations of anisometropia with spherical ametropia, astigmatism, age, and sex in a refractive surgery population. Medical records of 27,070 eyes of 13,535 refractive surgery candidates were reviewed. Anisometropia, defined as the absolute difference in mean spherical equivalent powers between right and left eyes, was analyzed for subjective (A(subj)) and cycloplegic refraction (A(cycl)). Correlations between anisometropia (>1 diopter) and spherical ametropia, cylindrical power, age, and sex, were analyzed using χ² and nonparametric Kruskal-Wallis or Mann-Whitney tests and binomial logistic regression analyses. Power vector analysis was applied for further analysis of cylindrical power. Prevalence of A(subj) was 18.5% and of A(cycl) was 19.3%. In hyperopes, logistic regression analysis revealed that only spherical refractive error (odds ratio [OR], 0.72) and age (OR, 0.97) were independently associated with anisometropia. A(subj) decreased with increasing spherical ametropia and advancing age. Cylindrical power and sex did not significantly affect A(subj). In myopes all explanatory variables (spherical power OR, 0.93; cylindrical power OR, 0.75; age OR, 1.02; sex OR, 0.8) were independently associated with anisometropia. Cylindrical power was most strongly associated with anisometropia. Advancing age and increasing spherical/cylindrical power correlated positively with increasing anisometropia in myopic subjects. Female sex was more closely associated with anisometropia. This large-scale retrospective analysis confirmed an independent association between anisometropia and both spherical ametropia and age in refractive surgery candidates. Notably, an inverse relationship between these parameters in hyperopes was observed. Cylindrical power and female sex were independently associated with anisometropia in myopes.

iPTF discovery and identification of bright transients

NASA Astrophysics Data System (ADS)

Adams, Scott; Karamehmetoglu, Emir; Roy, Rupak; Neill, James D.; Walters, Richard; Cook, Dave; Kupfer, Thomas; Cannella, Chris; Blagorodnova, Nadejda; Yan, Lin; Kasliwal, Mansi; Kulkarni, Shri

2017-02-01

The intermediate Palomar Transient Factory (ATel #4807) reports the discovery of the following bright transients. We report as ATel alerts all objects brighter than 19 mag. Our discoveries are reported in two filters: sdss-g and Mould-I, denoted as g and I. All magnitudes are obtained using difference image photometry based on the PTFIDE pipeline described in Masci et al. 2016.Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R), and RB5 (Wozniak et al. 2013AAS...22143105W).

75 FR 1831 - Seeks Qualified Candidates for the Advisory Committee on Reactor Safeguards

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-13

... renewal, power uprates, and the use of mixed oxide and high burnup fuels. An increased emphasis is being... race, color, religion, national origin, sex, age, or disabilities. Candidates must be citizens of the...

Understanding nature's particle accelerators using high energy gamma-ray survey instruments

NASA Astrophysics Data System (ADS)

Abeysekara, Anushka Udara

Nature's particle accelerators, such as Pulsars, Pulsar Wind Nebulae, Active Galactic Nuclei and Supernova Remnants accelerate charged particles to very high energies that then produce high energy photons. The particle acceleration mechanisms and the high energy photon emission mechanisms are poorly understood phenomena. These mechanisms can be understood either by studying individual sources in detail or, alternatively, using the collective properties of a sample of sources. Recent development of GeV survey instruments, such as Fermi-LAT, and TeV survey instruments, such as Milagro, provides a large sample of high energy gamma-ray flux measurements from galactic and extra-galactic sources. In this thesis I provide constraints on GeV and TeV radiation mechanisms using the X-ray-TeV correlations and GeV-TeV correlations. My data sample was obtained from three targeted searches for extragalactic sources and two targeted search for galactic sources, using the existing Milagro sky maps. The first extragalactic candidate list consists of Fermi-LAT GeV extragalactic sources, and the second extragalactic candidate list consists of TeVCat extragalactic sources that have been detected by Imaging Atmospheric Cerenkov Telescopes (IACTs). In both extragalactic candidate lists Markarian 421 was the only source detected by Milagro. A comparison between the Markarian 421 time-averaged flux, measured by Milagro, and the flux measurements of transient states, measured by IACTs, is discussed. The third extragalactic candidate list is a list of potential TeV emitting BL Lac candidates that was synthesized using X-ray observations of BL Lac objects and a Synchrotron Self-Compton model. Milagro's sensitivity was not sufficient to detect any of those candidates. However, the 95% confidence flux upper limits of those sources were above the predicted flux. Therefore, these results provide evidence to conclude that the Synchrotron Self-Compton model for BL Lac objects is still a viable model. Targeted searches for galactic candidates were able to measure TeV emission associated with 14 Fermi-LAT GeV pulsars. In this thesis I also presented a new multi-wavelength technique that I developed to isolate the flux correlation factor (fΩ ) of pulsars as a function of pulsar spin down luminosity. The correlation between fΩ and pulsar spin-down luminosity for a Fermi-LAT GeV pulsar sample was measured using the measurements obtained in the Milagro targeted search performed for galactic sources and from the literature. The measured correlation has some features that favor the Outer Gap model over the Polar Cap, Slot Gap and One Pole Caustic models for pulsar emission in the energy range of 0.1 to 100 GeV. However, these simulated models failed to explain many other important pulsar population characteristics. Therefore, further improvements on the galactic pulsar population simulations are needed to provide tighter constraints.

Negative ion beam development at Cadarache (invited)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simonin, A.; Bucalossi, J.; Desgranges, C.

1996-03-01

Neutral beam injection (NBI) is one of the candidates for plasma heating and current drive in the new generation of large magnetic fusion devices (ITER). In order to produce the required deuterium atom beams with energies of 1 MeV and powers of tens of MW, negative D{sup {minus}} ion beams are required. For this purpose, multiampere D{sup {minus}} beam production and 1 MeV electrostatic acceleration is being studied at Cadarache. The SINGAP experiment, a 1 MeV 0.1 A D{sup {minus}} multisecond beam accelerator facility, has recently started operation. It is equipped with a Pagoda ion source, a multiaperture 60 keVmore » preaccelerator and a 1 MV 120 mA power supply. The particular feature of SINGAP is that the postaccelerator merges the 60 keV beamlets, aiming at accelerating the whole beam to 1 MeV in a single gap. The 1 MV level was obtained in less than 2 weeks, the accumulated voltage on-time of being {approximately}22 min. A second test bed MANTIS, is devoted to the development of multiampere D{sup {minus}} sources. It is capable of driving discharges with current up to 2500 A at arc voltages up to 150 V. A large multicusp source has been tested in pure volume and cesiated operation. With cesium seeding, an accelerated D{sup {minus}} beam current density of up to 5.2 mA/cm{sup 2} (2 A of D{sup {minus}}) was obtained. A modification of the extractor is underway in order to improve this performance. A 3D Monte Carlo code has been developed to simulate the negative ion transport in magnetized plasma sources and optimize magnetic field configuration of the large area D{sup {minus}} sources. {copyright} {ital 1996 American Institute of Physics.}« less

ALMA’s Polarized View of 10 Protostars in the Perseus Molecular Cloud

NASA Astrophysics Data System (ADS)

Cox, Erin G.; Harris, Robert J.; Looney, Leslie W.; Li, Zhi-Yun; Yang, Haifeng; Tobin, John J.; Stephens, Ian

2018-03-01

We present 870 μm ALMA dust polarization observations of 10 young Class 0/I protostars in the Perseus Molecular Cloud. At ∼0.″35 (80 au) resolution, all of our sources show some degree of polarization, with most (9/10) showing significantly extended emission in the polarized continuum. Each source has incredibly intricate polarization signatures. In particular, all three disk-candidates have polarization vectors roughly along the minor axis, which is indicative of polarization produced by dust scattering. On ∼100 au scales, the polarization is at a relatively low level (≲1%) and is quite ordered. In sources with significant envelope emission, the envelope is typically polarized at a much higher (≳5%) level and has a far more disordered morphology. We compute the cumulative probability distributions for both the small (disk-scale) and large (envelope-scale) polarization percentage. We find that the two are intrinsically different, even after accounting for the different detection thresholds in the high/low surface brightness regions. We perform Kolmogorov–Smirnov and Anderson–Darling tests on the distributions of angle offsets of the polarization from the outflow axis. We find disk-candidate sources are different from the non-disk-candidate sources. We conclude that the polarization on the 100 au scale is consistent with the signature of dust scattering for disk-candidates and that the polarization on the envelope-scale in all sources may come from another mechanism, most likely magnetically aligned grains.

Saturation analysis of ChIP-seq data for reproducible identification of binding peaks

PubMed Central

Hansen, Peter; Hecht, Jochen; Ibrahim, Daniel M.; Krannich, Alexander; Truss, Matthias; Robinson, Peter N.

2015-01-01

Chromatin immunoprecipitation coupled with next-generation sequencing (ChIP-seq) is a powerful technology to identify the genome-wide locations of transcription factors and other DNA binding proteins. Computational ChIP-seq peak calling infers the location of protein–DNA interactions based on various measures of enrichment of sequence reads. In this work, we introduce an algorithm, Q, that uses an assessment of the quadratic enrichment of reads to center candidate peaks followed by statistical analysis of saturation of candidate peaks by 5′ ends of reads. We show that our method not only is substantially faster than several competing methods but also demonstrates statistically significant advantages with respect to reproducibility of results and in its ability to identify peaks with reproducible binding site motifs. We show that Q has superior performance in the delineation of double RNAPII and H3K4me3 peaks surrounding transcription start sites related to a better ability to resolve individual peaks. The method is implemented in C+l+ and is freely available under an open source license. PMID:26163319

Landfill site selection by using geographic information systems

NASA Astrophysics Data System (ADS)

Şener, Başak; Süzen, M. Lütfi; Doyuran, Vedat

2006-01-01

One of the serious and growing potential problems in most large urban areas is the shortage of land for waste disposal. Although there are some efforts to reduce and recover the waste, disposal in landfills is still the most common method for waste destination. An inappropriate landfill site may have negative environmental, economic and ecological impacts. Therefore, it should be selected carefully by considering both regulations and constraints on other sources. In this study, candidate sites for an appropriate landfill area in the vicinity of Ankara are determined by using the integration of geographic information systems and multicriteria decision analysis (MCDA). For this purpose, 16 input map layers including topography, settlements (urban centers and villages), roads (Highway E90 and village roads), railways, airport, wetlands, infrastructures (pipelines and power lines), slope, geology, land use, floodplains, aquifers and surface water are prepared and two different MCDA methods (simple additive weighting and analytic hierarchy process) are implemented to a geographical information system. Comparison of the maps produced by these two different methods shows that both methods yield conformable results. Field checks also confirm that the candidate sites agree well with the selected criteria.

A search for debris disks in the Herschel-ATLAS

NASA Astrophysics Data System (ADS)

Thompson, M. A.; Smith, D. J. B.; Stevens, J. A.; Jarvis, M. J.; Vidal Perez, E.; Marshall, J.; Dunne, L.; Eales, S.; White, G. J.; Leeuw, L.; Sibthorpe, B.; Baes, M.; González-Solares, E.; Scott, D.; Vieiria, J.; Amblard, A.; Auld, R.; Bonfield, D. G.; Burgarella, D.; Buttiglione, S.; Cava, A.; Clements, D. L.; Cooray, A.; Dariush, A.; de Zotti, G.; Dye, S.; Eales, S.; Frayer, D.; Fritz, J.; Gonzalez-Nuevo, J.; Herranz, D.; Ibar, E.; Ivison, R. J.; Lagache, G.; Lopez-Caniego, M.; Maddox, S.; Negrello, M.; Pascale, E.; Pohlen, M.; Rigby, E.; Rodighiero, G.; Samui, S.; Serjeant, S.; Temi, P.; Valtchanov, I.; Verma, A.

2010-07-01

Aims: We aim to demonstrate that the Herschel-ATLAS (H-ATLAS) is suitable for a blind and unbiased survey for debris disks by identifying candidate debris disks associated with main sequence stars in the initial science demonstration field of the survey. We show that H-ATLAS reveals a population of far-infrared/sub-mm sources that are associated with stars or star-like objects on the SDSS main-sequence locus. We validate our approach by comparing the properties of the most likely candidate disks to those of the known population. Methods: We use a photometric selection technique to identify main sequence stars in the SDSS DR7 catalogue and a Bayesian Likelihood Ratio method to identify H-ATLAS catalogue sources associated with these main sequence stars. Following this photometric selection we apply distance cuts to identify the most likely candidate debris disks and rule out the presence of contaminating galaxies using UKIDSS LAS K-band images. Results: We identify 78 H-ATLAS sources associated with SDSS point sources on the main-sequence locus, of which two are the most likely debris disk candidates: H-ATLAS J090315.8 and H-ATLAS J090240.2. We show that they are plausible candidates by comparing their properties to the known population of debris disks. Our initial results indicate that bright debris disks are rare, with only 2 candidates identified in a search sample of 851 stars. We also show that H-ATLAS can derive useful upper limits for debris disks associated with Hipparcos stars in the field and outline the future prospects for our debris disk search programme. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Using Multi-Media Projects to Foster Teacher Candidates' Multiple Literacy Skills

ERIC Educational Resources Information Center

Lawrence, Salika A.

2010-01-01

This article describes the strategies used to incorporate multi-modal technology literacy experiences into a graduate level course for literacy specialists. The candidates created a multi-media project in response to literature. Their projects revealed that the teacher candidates used a variety of sources to create the project but the Internet was…

Perspective on the Cosmic-ray Electron Spectrum above TeV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, Kun; Wang, Bing-Bing; Bi, Xiao-Jun

2017-02-20

The AMS-02 has measured the cosmic-ray electron (plus positron) spectrum up to ∼TeV with unprecedented precision. The spectrum can be well described by a power law without any obvious features above 10 GeV. The satellite instrument Dark Matter Particle Explorer (DAMPE), which was launched a year ago, will measure the electron spectrum up to 10 TeV with high-energy resolution. The cosmic electrons beyond TeV may be attributed to few local cosmic-ray sources, such as supernova remnants. Therefore, spectral features, such as cut-off and bumps, can be expected at high energies. In this work, we provide a careful study on themore » perspective of the electron spectrum beyond TeV. We first examine our astrophysical source models on the latest leptonic data of AMS-02 to give a self-consistent picture. Then we focus on the discussion about the candidate sources, which could be electron contributors above TeV. Depending on the properties of the local sources (especially on the nature of Vela), DAMPE may detect interesting features in the electron spectrum above TeV in the future.« less

Occultations of Astrophysical Radio Sources as Probes of Planetary Environments: A Case Study of Jupiter and Possible Applications to Exoplanets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Withers, Paul; Vogt, Marissa F.

Properties of planetary atmospheres, ionospheres, and magnetospheres are difficult to measure from Earth. Radio occultations are a common method for measuring these properties, but they traditionally rely on radio transmissions from a spacecraft near the planet. Here, we explore whether occultations of radio emissions from a distant astrophysical radio source can be used to measure magnetic field strength, plasma density, and neutral density around planets. In a theoretical case study of Jupiter, we find that significant changes in polarization angle due to Faraday rotation occur for radio signals that pass within 10 Jupiter radii of the planet and that significantmore » changes in frequency and power occur from radio signals that pass through the neutral atmosphere. There are sufficient candidate radio sources, such as pulsars, active galactic nuclei, and masers, that occultations are likely to occur at least once per year. For pulsars, time delays in the arrival of their emitted pulses can be used to measure plasma density. Exoplanets, whose physical properties are very challenging to observe, may also occult distant astrophysical radio sources, such as their parent stars.« less

Antiproton signatures from astrophysical and dark matter sources at the galactic center

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cembranos, J.A.R.; Gammaldi, V.; Maroto, A.L., E-mail: cembra@ucm.es, E-mail: vivigamm@ucm.es, E-mail: maroto@fis.ucm.es

2015-03-01

The center of our Galaxy is a complex region characterized by extreme phenomena. The presence of the supermassive Sagittarius A* black hole, a high dark matter density and an even higher baryonic density are able to produce very energetic processes. Indeed, high energetic gamma-rays have been observed by different telescopes, although their origin is not clear. In this work, we estimate the possible antiproton flux component associated with this signal. The expected secondary astrophysical antiproton background already saturates the observed data. It implies that any other important astrophysical source leads to an inconsistent excess. We estimate the sensitivity of PAMELAmore » to this new primary antiproton source, which depends on the diffusion model and its spectral features. In particular, we consider antiproton spectra described by a power-law, a monochromatic signal and a Standard Model particle-antiparticle channel production. This latter spectrum is typical in the production from annihilating or decaying dark matter. We pay particular attention to the case of a heavy dark matter candidate, which could be associated with the High Energy Stereoscopic System (HESS) data observed from the J1745-290 source.« less

XTE J1908+094

NASA Technical Reports Server (NTRS)

Woods, P. M.; Kouveliotou, C.; Finger, M. H.; Gogus, E.; Swank, J.; Markwardt, C.; Strohmayer, T.; Six, N. Frank (Technical Monitor)

2002-01-01

Goddard Space Flight Center reports the serendipitous discovery of a new x-ray transient, XTE J1908+094, in RXTE (Rossi X-ray Timing Explorer) PCA (Proportional Counter Array) observations of the soft-gamma-ray repeater SGR 1900+14, triggered following the burst activity on Feb. 17-18 (GCN 1253). These observations failed to detect the 5.2-s SGR pulsations, pointing towards a possible new source as the origin of the high x-ray flux. An RXTE PCA scan of the region around SGR 1900+14 on Feb. 21 was consistent with emission only from known sources (and no new sources). However, the scans required SGR 1900+14 to be 20 times brighter than its quiescent flux level (GCN 1256). A Director's Discretionary Time Chandra observation on Mar. 11 showed that the SGR was quiescent and did not reveal any new source within the Chandra ACIS (Advanced CCD (charge coupled device) Imaging Spectrometer) field-of-view. A subsequent RXTE PCA scan on Mar. 17, taken in combination with the first scan, required that a new source be included in the fit. The best-fit position is R.A. 19h 08m 50s, Decl. = +9 22 deg .5 (equinox J2000.0; estimated 2 deg systematic error radius), or approximately 24 deg away from the SGR source. The source spectrum (2-30 kev) can be best fit with a power-law function including photoelectric absorption (column density N_h = 2.3 x 10(exp 22), photon index = 1.55). Iron line emission is present, but may be due to the Galactic ridge. Between Feb. 19 and Mar. 17, the source flux (2-10 keV) has risen from 26 to 64 mCrab. The power spectrum is flat between 1 mHz and 0.1 Hz, falling approximately as 1/f**0.5 up to 1 Hz. At 1 Hz is seen a broad quasiperiodic oscillation peak and a break to a 1/f**2 power law, which continues to 4 Hz. The fractional rms (root mean square) amplitude from 1 mHz to 4 Hz is 43 percent. No coherent pulsations are seen between 0.001 and 1024 Hz. The authors conclude that XTE J1908+094 is a new blackhole candidate.

A 1.1-1.9 GHz SETI Survey of the Kepler Field. I. A Search for Narrow-band Emission from Select Targets

NASA Astrophysics Data System (ADS)

Siemion, Andrew P. V.; Demorest, Paul; Korpela, Eric; Maddalena, Ron J.; Werthimer, Dan; Cobb, Jeff; Howard, Andrew W.; Langston, Glen; Lebofsky, Matt; Marcy, Geoffrey W.; Tarter, Jill

2013-04-01

We present a targeted search for narrow-band (<5 Hz) drifting sinusoidal radio emission from 86 stars in the Kepler field hosting confirmed or candidate exoplanets. Radio emission less than 5 Hz in spectral extent is currently known to only arise from artificial sources. The stars searched were chosen based on the properties of their putative exoplanets, including stars hosting candidates with 380 K > T eq > 230 K, stars with five or more detected candidates or stars with a super-Earth (R p < 3 R ⊕) in a >50 day orbit. Baseband voltage data across the entire band between 1.1 and 1.9 GHz were recorded at the Robert C. Byrd Green Bank Telescope between 2011 February and April and subsequently searched offline. No signals of extraterrestrial origin were found. We estimate that fewer than ~1% of transiting exoplanet systems host technological civilizations that are radio loud in narrow-band emission between 1 and 2 GHz at an equivalent isotropically radiated power (EIRP) of ~1.5 × 1021 erg s-1, approximately eight times the peak EIRP of the Arecibo Planetary Radar, and we limit the number of 1-2 GHz narrow-band-radio-loud Kardashev type II civilizations in the Milky Way to be {<}10^{-6}\\ M^{-1}_\\odot. Here we describe our observations, data reduction procedures and results.

Probing the Metal Enrichment of the Intergalactic Medium at z = 5–6 Using the Hubble Space Telescope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, Zheng; Fan, Xiaohui; Dave, Romeel

We test the galactic outflow model by probing associated galaxies of four strong intergalactic C iv absorbers at z = 5–6 using the Hubble Space Telescope ( HST ) Advanced Camera for Surveys (ACS) ramp narrowband filters. The four strong C iv absorbers reside at z = 5.74, 5.52, 4.95, and 4.87, with column densities ranging from N {sub Civ} = 10{sup 13.8} to 10{sup 14.8} cm{sup −2}. At z = 5.74, we detect an i-dropout Ly α emitter (LAE) candidate with a projected impact parameter of 42 physical kpc from the C iv absorber. This LAE candidate has amore » Ly α -based star formation rate (SFR{sub Lyα} ) of 2 M {sub ⊙} yr{sup −1} and a UV-based SFR of 4 M {sub ⊙} yr{sup −1}. Although we cannot completely rule out that this i-dropout emitter may be an [O ii] interloper, its measured properties are consistent with the C iv powered galaxy at z = 5.74. For C iv absorbers at z = 4.95 and z = 4.87, although we detect two LAE candidates with impact parameters of 160 and 200 kpc, such distances are larger than that predicted from the simulations. Therefore, we treat them as nondetections. For the system at z = 5.52, we do not detect LAE candidates, placing a 3 σ upper limit of SFR{sub Lyα} ≈ 1.5 M {sub ⊙} yr{sup −1}. In summary, in these four cases, we only detect one plausible C iv source at z = 5.74. Combining the modest SFR of the one detection and the three nondetections, our HST observations strongly support that smaller galaxies (SFR{sub Lyα} ≲ 2 M {sub ⊙} yr{sup −1}) are main sources of intergalactic C iv absorbers, and such small galaxies play a major role in the metal enrichment of the intergalactic medium at z ≳ 5.« less

Discovery of localized TeV gamma-ray sources and diffuse TeV gamma-ray emission from the galactic plane with Milagro using a new background rejection technique

NASA Astrophysics Data System (ADS)

Abdo, Aws Ahmad

2007-08-01

Very high energy gamma-rays can be used to probe some of the most powerful astrophysical objects in the universe, such as active galactic nuclei, supernova remnants and pulsar-powered nebulae. The diffuse gamma radiation arising from the interaction of cosmic-ray particles with matter and radiation in the Galaxy is one of the few probes available to study the origin of cosmic- rays. Milagro is a water Cherenkov detector that continuously views the entire overhead sky. The large field-of-view combined with the long observation time makes Milagro the most sensitive instrument available for the study of large, low surface brightness sources such as the diffuse gamma radiation arising from interactions of cosmic radiation with interstellar matter. In this thesis I present a new background rejection technique for the Milagro detector through the development of a new gamma hadron separation variable. The Abdo variable, A 4 , coupled with the weighting analysis technique significantly improves the sensitivity of the Milagro detector. This new analysis technique resulted in the first discoveries in Milagro. Four localized sources of TeV gamma-ray emission have been discovered, three of which are in the Cygnus region of the Galaxy and one closer to the Galactic center. In addition to these localized sources, a diffuse emission of TeV gamma-rays has been discovered from the Cygnus region of the Galaxy as well. However, the TeV gamma-ray flux as measured at ~12 TeV from the Cygnus region exceeds that predicted from a conventional model of cosmic-ray production and propagation. This observation indicates the existence of either hard-spectrum cosmic-ray sources and/or other sources of TeV gamma rays in the region. Other TeV gamma-ray source candidates with post-trial statistical significances of > 4s have also been observed in the Galactic plane.

The Predictive Power of the Self-Efficacy Beliefs of Physical Education Candidate Teachers on Their Attitudes towards the Assessment and Evaluation in Education

ERIC Educational Resources Information Center

Varol, Yaprak Kalemoglu

2016-01-01

The aim of the research is to examine relationship between self-efficacy beliefs and attitudes for assessment and evaluation of physical education candidate teachers. In this research, the relational model has been used. Study group consists of 86 women (48%), 93 men (52%) and total 179 physical education teacher candidates (M[subscript age] =…

Galactic SNR Candidates in the ROSAT All-Sky Survey

NASA Technical Reports Server (NTRS)

Schaudel, Daniel; Becker, Werner; Voges, Wolfgand; Reich, Wolfgang; Weisskopf, Martin; Six, N. Frank (Technical Monitor)

2001-01-01

Identified radio supernova remnants (SNRS) in the Galaxy comprise an incomplete sample of the SNR population due to various selection effects. ROSAT performed the first all-sky survey with an imaging X-ray telescope, and thus provides another window for finding SNRS and compact objects that may reside within them. Performing a search for extended X-ray sources in the ROSAT all-sky survey database about 350 objects were identified as SNR candidates in recent years. Continuing this systematic search, we have reanalyzed the ROSAT all-sky survey (BASS) data of these candidates and correlated the results with radio surveys like NVSS, ATNF, Molonglo, and Effelsberg. A further correlation with SIMBAD and NED were used for subsequent identification purpose. About 50 of the 350 candidates turned out to be likely galaxies or clusters of galaxies. We found 14 RASS sources which are very promising SNR candidates and are currently subject of further follow-up studies. We will provide the details of the identification campaign and present first results.

VizieR Online Data Catalog: A spectral approach to transit timing variations (Ofir+, 2018)

NASA Astrophysics Data System (ADS)

Ofir, A.; Xie, J.-W.; Jiang, C.-F.; Sari, R.; Aharonson, O.

2018-03-01

We used Kepler Data Release 24 as the source data and the Kepler Objects of Interest (KOIs) table downloaded from the NExSci archive on 2015 December 25 as the source of list of candidate signals, and processed 4706 object not dispositioned as "false positive". We remove eclipsing binaries from the candidates list (see section 4.1 for further details). (1 data file).

Improved selection criteria for H II regions, based on IRAS sources

NASA Astrophysics Data System (ADS)

Yan, Qing-Zeng; Xu, Ye; Walsh, A. J.; Macquart, J. P.; MacLeod, G. C.; Zhang, Bo; Hancock, P. J.; Chen, Xi; Tang, Zheng-Hong

2018-05-01

We present new criteria for selecting H II regions from the Infrared Astronomical Satellite (IRAS) Point Source Catalogue (PSC), based on an H II region catalogue derived manually from the all-sky Wide-field Infrared Survey Explorer (WISE). The criteria are used to augment the number of H II region candidates in the Milky Way. The criteria are defined by the linear decision boundary of two samples: IRAS point sources associated with known H II regions, which serve as the H II region sample, and IRAS point sources at high Galactic latitudes, which serve as the non-H II region sample. A machine learning classifier, specifically a support vector machine, is used to determine the decision boundary. We investigate all combinations of four IRAS bands and suggest that the optimal criterion is log(F_{60}/F_{12})≥ ( -0.19 × log(F_{100}/F_{25})+ 1.52), with detections at 60 and 100 {μ}m. This selects 3041 H II region candidates from the IRAS PSC. We find that IRAS H II region candidates show evidence of evolution on the two-colour diagram. Merging the WISE H II catalogue with IRAS H II region candidates, we estimate a lower limit of approximately 10 200 for the number of H II regions in the Milky Way.

Breeding Vegetables with Increased Content in Bioactive Phenolic Acids.

PubMed

Kaushik, Prashant; Andújar, Isabel; Vilanova, Santiago; Plazas, Mariola; Gramazio, Pietro; Herraiz, Francisco Javier; Brar, Navjot Singh; Prohens, Jaime

2015-10-09

Vegetables represent a major source of phenolic acids, powerful antioxidants characterized by an organic carboxylic acid function and which present multiple properties beneficial for human health. In consequence, developing new varieties with enhanced content in phenolic acids is an increasingly important breeding objective. Major phenolic acids present in vegetables are derivatives of cinnamic acid and to a lesser extent of benzoic acid. A large diversity in phenolic acids content has been found among cultivars and wild relatives of many vegetable crops. Identification of sources of variation for phenolic acids content can be accomplished by screening germplasm collections, but also through morphological characteristics and origin, as well as by evaluating mutations in key genes. Gene action estimates together with relatively high values for heritability indicate that selection for enhanced phenolic acids content will be efficient. Modern genomics and biotechnological strategies, such as QTL detection, candidate genes approaches and genetic transformation, are powerful tools for identification of genomic regions and genes with a key role in accumulation of phenolic acids in vegetables. However, genetically increasing the content in phenolic acids may also affect other traits important for the success of a variety. We anticipate that the combination of conventional and modern strategies will facilitate the development of a new generation of vegetable varieties with enhanced content in phenolic acids.

Galactic supernova remnant candidates discovered by THOR

NASA Astrophysics Data System (ADS)

Anderson, L. D.; Wang, Y.; Bihr, S.; Rugel, M.; Beuther, H.; Bigiel, F.; Churchwell, E.; Glover, S. C. O.; Goodman, A. A.; Henning, Th.; Heyer, M.; Klessen, R. S.; Linz, H.; Longmore, S. N.; Menten, K. M.; Ott, J.; Roy, N.; Soler, J. D.; Stil, J. M.; Urquhart, J. S.

2017-09-01

Context. There is a considerable deficiency in the number of known supernova remnants (SNRs) in the Galaxy compared to that expected. This deficiency is thought to be caused by a lack of sensitive radio continuum data. Searches for extended low-surface brightness radio sources may find new Galactic SNRs, but confusion with the much larger population of H II regions makes identifying such features challenging. SNRs can, however, be separated from H II regions using their significantly lower mid-infrared (MIR) to radio continuum intensity ratios. Aims: Our goal is to find missing SNR candidates in the Galactic disk by locating extended radio continuum sources that lack MIR counterparts. Methods: We use the combination of high-resolution 1-2 GHz continuum data from The HI, OH, Recombination line survey of the Milky Way (THOR) and lower-resolution VLA 1.4 GHz Galactic Plane Survey (VGPS) continuum data, together with MIR data from the Spitzer GLIMPSE, Spitzer MIPSGAL, and WISE surveys to identify SNR candidates. To ensure that the candidates are not being confused with H II regions, we exclude radio continuum sources from the WISE Catalog of Galactic H II Regions, which contains all known and candidate H II regions in the Galaxy. Results: We locate 76 new Galactic SNR candidates in the THOR and VGPS combined survey area of 67.4° > ℓ > 17.5°, | b | ≤ 1.25° and measure the radio flux density for 52 previously-known SNRs. The candidate SNRs have a similar spatial distribution to the known SNRs, although we note a large number of new candidates near ℓ ≃ 30°, the tangent point of the Scutum spiral arm. The candidates are on average smaller in angle compared to the known regions, 6.4' ± 4.7' versus 11.0' ± 7.8', and have lower integrated flux densities. Conclusions: The THOR survey shows that sensitive radio continuum data can discover a large number of SNR candidates, and that these candidates can be efficiently identified using the combination of radio and MIR data. If the 76 candidates are confirmed as true SNRs, for example using radio polarization measurements or by deriving radio spectral indices, this would more than double the number of known Galactic SNRs in the survey area. This large increase would still, however, leave a discrepancy between the known and expected SNR populations of about a factor of two.

Unveiling the AGN in IC 883: discovery of a parsec-scale radio jet

NASA Astrophysics Data System (ADS)

Romero-Cañizales, C.; Alberdi, A.; Ricci, C.; Arévalo, P.; Pérez-Torres, M. Á.; Conway, J. E.; Beswick, R. J.; Bondi, M.; Muxlow, T. W. B.; Argo, M. K.; Bauer, F. E.; Efstathiou, A.; Herrero-Illana, R.; Mattila, S.; Ryder, S. D.

2017-05-01

IC 883 is a luminous infrared galaxy (LIRG) classified as a starburst-active galactic nucleus (AGN) composite. In a previous study, we detected a low-luminosity AGN (LLAGN) radio candidate. Here, we report on our radio follow-up at three frequencies that provides direct and unequivocal evidence of the AGN activity in IC 883. Our analysis of archival X-ray data, together with the detection of a transient radio source with luminosity typical of bright supernovae, gives further evidence of the ongoing star formation activity, which dominates the energetics of the system. At sub-parsec scales, the radio nucleus has a core-jet morphology with the jet being a newly ejected component showing a subluminal proper motion of 0.6-1 c. The AGN contributes less than 2 per cent of the total IR luminosity of the system. The corresponding Eddington factor is ˜10-3, suggesting this is a low-accretion rate engine, as often found in LLAGNs. However, its high bolometric luminosity (˜1044 erg s-1) agrees better with a normal AGN. This apparent discrepancy may just be an indication of the transition nature of the nucleus from a system dominated by star formation, to an AGN-dominated system. The nucleus has a strongly inverted spectrum and a turnover at ˜4.4 GHz, thus qualifying as a candidate for the least luminous (L5.0 GHz ˜ 6.3 × 1028 erg s-1 Hz-1) and one of the youngest (˜3 × 103 yr) gigahertz-peaked spectrum (GPS) sources. If the GPS origin for the IC 883 nucleus is confirmed, then advanced mergers in the LIRG category are potentially key environments to unveil the evolution of GPS sources into more powerful radio galaxies.

Point X-ray sources in the SNR G 315.4-2.30 (MSH 14-63, RCW 86)

NASA Astrophysics Data System (ADS)

Gvaramadze, V. V.; Vikhlinin, A. A.

2003-04-01

We report the results of a search for a point X-ray source (stellar remnant) in the southwest protrusion of the supernova remnant G 315.4-2.30 (MSH 14-63, RCW 86) using the archival data of the Chandra X-ray Observatory. The search was motivated by a hypothesis that G 315.4-2.30 is the result of an off-centered cavity supernova explosion of a moving massive star, which ended its evolution just near the edge of the main-sequence wind-driven bubble. This hypothesis implies that the southwest protrusion in G 315.4-2.30 is the remainder of a pre-existing bow shock-like structure created by the interaction of the supernova progenitor's wind with the interstellar medium and that the actual location of the supernova blast center is near the center of this hemispherical structure. We have discovered two point X-ray sources in the ``proper" place. One of the sources has an optical counterpart with the photographic magnitude 13.38+/-0.40, while the spectrum of the source can be fitted with an optically thin plasma model. We interpret this source as a foreground active star of late spectral type. The second source has no optical counterpart to a limiting magnitude ~ 21. The spectrum of this source can be fitted almost equally well with several simple models (power law: photon index =1.87; two-temperature blackbody: kT1 =0.11 keV, R1 =2.34 km and kT2 =0.71 keV, R2 =0.06 km; blackbody plus power law: kT =0.07 keV, photon index =2.3). We interpret this source as a candidate stellar remnant (neutron star), while the photon index and non-thermal luminosity of the source (almost the same as those of the Vela pulsar and the recently discovered pulsar PSR J 0205+6449 in the supernova remnant 3C 58) suggest that it can be a young ``ordinary" pulsar.

Gas Foil Bearing Misalignment and Unbalance Effects

NASA Technical Reports Server (NTRS)

Howard, Samuel A.

2008-01-01

The effects of misalignment and unbalance on gas foil bearings are presented. The future of U.S. space exploration includes plans to conduct science missions aboard space vehicles, return humans to the Moon, and place humans on Mars. All of these endeavors are of long duration, and require high amounts of electrical power for propulsion, life support, mission operations, etc. One potential source of electrical power of sufficient magnitude and duration is a nuclear-fission-based system. The system architecture would consist of a nuclear reactor heat source with the resulting thermal energy converted to electrical energy through a dynamic power conversion and heat rejection system. Various types of power conversion systems can be utilized, but the Closed Brayton Cycle (CBC) turboalternator is one of the leading candidates. In the CBC, an inert gas heated by the reactor drives a turboalternator, rejects excess heat to space through a heat exchanger, and returns to the reactor in a closed loop configuration. The use of the CBC for space power and propulsion is described in more detail in the literature (Mason, 2003). In the CBC system just described, the process fluid is a high pressure inert gas such as argon, krypton, or a helium-xenon mixture. Due to the closed loop nature of the system and the associated potential for damage to components in the system, contamination of the working fluid is intolerable. Since a potential source of contamination is the lubricant used in conventional turbomachinery bearings, Gas Foil Bearings (GFB) have high potential for the rotor support system. GFBs are compliant, hydrodynamic journal and thrust bearings that use a gas, such as the CBC working fluid, as their lubricant. Thus, GFBs eliminate the possibility of contamination due to lubricant leaks into the closed loop system. Gas foil bearings are currently used in many commercial applications, both terrestrial and aerospace. Aircraft Air Cycle Machines (ACMs) and ground-based microturbines have demonstrated histories of successful long-term operation using GFBs (Heshmat et al., 2000). Small aircraft propulsion engines, helicopter gas turbines, and high-speed electric motors are potential future applications.

Electrode performance parameters for a radioisotope-powered AMTEC for space power applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Underwood, M.L.; O'Connor, D.; Williams, R.M.

1992-08-01

The alkali metal thermoelastic converter (AMTEC) is a device for the direct conversion of heat to electricity. Recently a design of an AMTEC using a radioisotope heat source was described, but the optimum condenser temperature was hotter than the temperatures used in the laboratory to develop the electrode performance model. Now laboratory experiments have confirmed the dependence of two model parameters over a broader range of condenser and electrode temperatures for two candidate electrode compositions. One parameter, the electrochemical exchange current density at the reaction interface, is independent of the condenser temperature, and depends only upon the collision rate ofmore » sodium at the reaction zone. The second parameter, a morphological parameter, which measures the mass transport resistance through the electrode, is independent of condenser and electrode temperatures for molybdenum electrodes. For rhodium-tungsten electrodes, however, this parameter increases for decreasing electrode temperature, indicating an activated mass transport mechanism such as surface diffusion. 21 refs.« less

Energy saving through LED in signaling functions for automotive exterior lighting

NASA Astrophysics Data System (ADS)

Bony, Alexis; Hamami, Khaled; Tebbe, Frank; Mertens, Jens

2011-05-01

Safety considerations have always driven the way for improving exterior automotive lighting legal requirements. With the recent adoption of day-time running lamps for passenger cars, the steadily increasing need for reduction of vehicle power consumption has led to the introduction of LED-based day-time running lamps. Solutions with incandescent bulbs have also been implemented, as they present price advantages while offering limited design perspectives. In the meantime, technology developments has turned LED sources into ideal candidates for daytime running lamps by increasing their lumen per watt efficiency ratio towards values around 100 lm/W or higher. In this work, taking as an example the new Mercedes-Benz roadster SLK (R172), we present the first single LED daytime- running lamp, with a total power consumption below 5W per vehicle. After reviewing legal requirements, the optical and electronic concepts are discussed. Details on the tail lamp LED functions are also discussed, and particularly the advantages from the realization of fog lamp with LEDs.

On the modulation of low-frequency quasi-periodic oscillations in black hole transients

NASA Astrophysics Data System (ADS)

Pawar, Devraj D.; Motta, Sara; Shanthi, K.; Bhattacharya, Dipankar; Belloni, Tomaso

2015-04-01

We studied the properties of the low-frequency quasi-periodic oscillations detected in a sample of six black hole candidates (XTE J1550-564, H 1743-322, XTE J1859+226, 4U 1630-47, GX 339-4, XTE J1650-500) observed by the Rossi XTE satellite. We analysed the relation between the full width at half-maximum and the frequency of all the narrow peaks detected in power density spectra where a type-C QPO is observed. Our goal was to understand the nature of the modulation of the signal by comparing the properties of different harmonic peaks in the power density spectrum. We find that for the sources in our sample the width of the fundamental and of the first harmonic are compatible with a frequency modulation, while that of the sub-harmonic is independent of frequency, possibly indicating the presence of an additional modulation in amplitude. We compare our results with those obtained earlier from GRS 1915+105 and XTE J1550-564.

Using woven carbon fiber fabric to construct gradient porous structure for passive direct methanol fuel cells

NASA Astrophysics Data System (ADS)

Yuan, Wei; Hu, Jinyi; Zhou, Bo; Deng, Jun; Zhang, Zhaochun; Tang, Yong

2015-09-01

The passive direct methanol fuel cell (DMFC) is a promising candidate power source for portable applications but has to deal with many technical challenges before practical use. This study presents a preliminary investigation on the use of a woven carbon fiber fabric (WCFF) for constructing a gradient porous structure based on the traditional design. The WCFF, carbon paper and carbon-black micro porous layer (MPL) combine into a carbon-based assembly which acts as a mass-transfer-controlling medium at the anode of a passive DMFC. Results show that this novel setup is able to significantly improve the cell performance and facilitate high-concentration operation. A maximum power density of 16.4 mWcm-2 is obtained when two layers of the WCFF are used at a methanol concentration of 8M. This work provides an effective method for using concentrated methanol with no need for major change of the fuel cell configuration.

High energy density aluminum-oxygen cell

NASA Technical Reports Server (NTRS)

Rudd, E. J.; Gibbons, D. W.

1993-01-01

An alternative to a secondary battery as the power source for vehicle propulsion is a fuel cell. An example of this is the metal-air fuel cell using metals such as aluminum, zinc, or iron. Aluminum is a particularly attractive candidate, having high energy and power densities, being environmentally acceptable, and having a large, established industrial base for production and distribution. An aluminum-oxygen system is currently under development for a UUV test vehicle, and recent work has focussed upon low corrosion aluminum alloys and an electrolyte management system for processing the by-products of the energy-producing reactions. This paper summarizes the progress made in both areas. Anode materials capable of providing high utilization factors over current densities ranging from S to 150 mA/sq cm have been identified. These materials are essential to realizing an acceptable mission life for the UUV. With respect to the electrolyte management system, a filter/precipitator unit has been successfully operated for over 250 hours in a large scale, half-cell system.

Aiding Design of Wave Energy Converters via Computational Simulations

NASA Astrophysics Data System (ADS)

Jebeli Aqdam, Hejar; Ahmadi, Babak; Raessi, Mehdi; Tootkaboni, Mazdak

2015-11-01

With the increasing interest in renewable energy sources, wave energy converters will continue to gain attention as a viable alternative to current electricity production methods. It is therefore crucial to develop computational tools for the design and analysis of wave energy converters. A successful design requires balance between the design performance and cost. Here an analytical solution is used for the approximate analysis of interactions between a flap-type wave energy converter (WEC) and waves. The method is verified using other flow solvers and experimental test cases. Then the model is used in conjunction with a powerful heuristic optimization engine, Charged System Search (CSS) to explore the WEC design space. CSS is inspired by charged particles behavior. It searches the design space by considering candidate answers as charged particles and moving them based on the Coulomb's laws of electrostatics and Newton's laws of motion to find the global optimum. Finally the impacts of changes in different design parameters on the power takeout of the superior WEC designs are investigated. National Science Foundation, CBET-1236462.

Establishment of a Comprehensive List of Candidate Antiaging Medicinal Herb Used in Korean Medicine by Text Mining of the Classical Korean Medical Literature, “Dongeuibogam,” and Preliminary Evaluation of the Antiaging Effects of These Herbs

PubMed Central

Choi, Moo Jin; Choi, Byung Tae; Shin, Hwa Kyoung; Shin, Byung Cheul; Han, Yoo Kyoung; Baek, Jin Ung

2015-01-01

The major objectives of this study were to provide a list of candidate antiaging medicinal herbs that have been widely utilized in Korean medicine and to organize preliminary data for the benefit of experimental and clinical researchers to develop new drug therapies by analyzing previous studies. “Dongeuibogam,” a representative source of the Korean medicine literature, was selected to investigate candidate antiaging medicinal herbs and to identify appropriate terms that describe the specific antiaging effects that these herbs are predicted to elicit. In addition, we aimed to review previous studies that referenced the selected candidate antiaging medicinal herbs. From our chosen source, “Dongeuibogam,” we were able to screen 102 terms describing antiaging effects, which were further classified into 11 subtypes. Ninety-seven candidate antiaging medicinal herbs were selected using the criterion that their antiaging effects were described using the same terms as those employed in “Dongeuibogam.” These candidates were classified into 11 subtypes. Of the 97 candidate antiaging medicinal herbs selected, 47 are widely used by Korean medical doctors in Korea and were selected for further analysis of their antiaging effects. Overall, we found an average of 7.7 previous studies per candidate herb that described their antiaging effects. PMID:25861371

Finding the rarest objects in the universe: A new, efficient method for discovering BL Lacertae objects

NASA Technical Reports Server (NTRS)

Stocke, John; Perlman, Eric; Granados, Arno; Schachter, Jonathan; Elvis, Martin; Urry, Meg; Impey, Chris; Smith, Paul

1993-01-01

We present a new, efficient method for discovering new BL Lac Objects based upon the results of the Einstein Extended Medium Sensitivity Survey (EMSS). We have found that all x-ray selected BL Lacs are radio emitters, and further, that in a 'color-color' diagram (radio/optical and optical/x-ray) the BL Lac Objects occupy an area distinct from both radio loud quasars and the radio quiet QSOs and Seyferts which dominate x-ray selected samples. After obtaining radio counterparts via VLA 'snapshot' observations of a large sample of unidentified x-ray sources, the list of candidates is reduced. These candidates then can be confirmed with optical spectroscopy and/or polarimetry. Since greater than 70 percent of these sources are expected to be BL Lacs, the optical observations are very efficient. We have tested this method using unidentified sources found in the Einstein Slew Survey. The 162 Slew Survey x-ray source positions were observed with the VLA in a mixed B/C configuration at 6 cm resulting in 60 detections within 1.5 position error circle radii. These x-ray/optical/radio sources were then plotted, and 40 BL Lac candidates were identified. To date, 10 candidates have been spectroscopically observed resulting in 10 new BL Lac objects! Radio flux, optical magnitude, and polarization statistics (obtained in white light with the Steward Observatory 2.3 m CCD polarimeter) for each are given.

Novel aqueous dual-channel aluminum-hydrogen peroxide battery

NASA Astrophysics Data System (ADS)

Marsh, Catherine; Licht, Stuart

1994-06-01

A dual-channel aluminum hydrogen peroxide battery is introduced with an open-circuit voltage of 1.9 volts, polarization losses of 0.9 mV cm(exp 2) mA(exp -1), and power densities of 1 W/cm(exp 2). Catholyte and anolyte cell compartments are separated by an Ir/Pd modified porous nickel cathode. Separation of catholyte and anolyte chambers prevents hydrogen peroxide poisoning of the aluminum anode. The battery is expressed by aluminum oxidation and aqueous solution phase hydrogen peroxide reduction for an overall battery discharge consisting of 2Al + 3H2O2 + 2OH(-) yields 2AlO2(-) + 4H2O E = 2.3 V. The search for electrical propulsion sources which fit the requirements for electrically powered vehicles has blurred the standard characteristics associated with electrochemical storage systems. Presently, electrochemical systems comprised of mechanically rechargeable primary batteries, secondary batteries, and fuel cells are candidates for electrochemical propulsion sources. While important advances in energy and power density continue for nonaqueous and molten electrolytes, aqueous electrolyte batteries often have an advantage in simplicity, conductivity, cost effectiveness, and environmental impact. Systems coupling aluminum anodes and aqueous electrolytes have been investigated. These systems include: aluminum/silver oxide, aluminum/manganese dioxide, aluminum air, aluminum/hydrogen peroxide aqueous batteries, and the recently introduced aluminum/ferricyanide and aluminum sulfur aqueous batteries. Conventional aqueous systems such as the nickel cadmium and lead-acid batteries are characterized by their relatively low energy densities and adverse environmental impact. Other systems have substantially higher theoretical energy capacities. While aluminum-silver oxide has demonstrated the highest steady-state power density, its high cost is an impediment for widespread utilization for electric propulsion.

USSR Report Engineering and Equipment.

DTIC Science & Technology

1987-05-04

Korenev , et al. ; ENERGETICHESKOYE STROITELSTVO, No 7, Jul 86) 33 Improving Fire Protection of Cables in Electric Power Plants (S.Ye. Korshunov...Russian No 7, Jul 86 pp 32-33 {Article by V.D. Likhachev, candidate of technical sciences, K.I. Korenev , candidate of technical sciences, K.I. Chikvaidze

Prospects for Attractive Fusion Power

NASA Astrophysics Data System (ADS)

Najmabadi, Farrokh

2006-10-01

During the past ten years, the ARIES Team, a national team involving universities, national laboratories, and industry, has studied a variety of magnetic fusion power plants (tokamaks, stellarators, ST, and RFP). In this paper, we present the top-level requirements and goals for commercial fusion power plants developed with consultation with US utilities and industry. We will review several ARIES designs and discuss the candidate options for physics operation regime as well engineering design of various components (e.g., choice of structural material, coolant, breeder). For each option, we will discuss (1) the potential to satisfy the requirements and goals, and (2) the critical R&D needs. In particular, we will discuss fusion R&D issues which are similar to those of advanced fission systems. For tokamaks, our results indicate that dramatic improvement over first-stability operation can be obtained through either utilization of high-field magnets (e.g., high-temperature superconductors) or operation in advanced-tokamak modes (e.g., reversed-shear). In particular, if full benefits of reversed-shear operation are realized, as is assumed in ARIES-AT, tokamak power plants will have a cost of electricity competitive with other sources of electricity. Emerging technologies such as advanced Baryon cycle, high-temperature superconductor, and advanced manufacturing techniques can improve the cost and attractiveness of fusion plants.

RELICS: Strong-lensing Analysis of the Massive Clusters MACS J0308.9+2645 and PLCK G171.9‑40.7

NASA Astrophysics Data System (ADS)

Acebron, Ana; Cibirka, Nathália; Zitrin, Adi; Coe, Dan; Agulli, Irene; Sharon, Keren; Bradač, Maruša; Frye, Brenda; Livermore, Rachael C.; Mahler, Guillaume; Salmon, Brett; Umetsu, Keiichi; Bradley, Larry; Andrade-Santos, Felipe; Avila, Roberto; Carrasco, Daniela; Cerny, Catherine; Czakon, Nicole G.; Dawson, William A.; Hoag, Austin T.; Huang, Kuang-Han; Johnson, Traci L.; Jones, Christine; Kikuchihara, Shotaro; Lam, Daniel; Lovisari, Lorenzo; Mainali, Ramesh; Oesch, Pascal A.; Ogaz, Sara; Ouchi, Masami; Past, Matthew; Paterno-Mahler, Rachel; Peterson, Avery; Ryan, Russell E.; Sendra-Server, Irene; Stark, Daniel P.; Strait, Victoria; Toft, Sune; Trenti, Michele; Vulcani, Benedetta

2018-05-01

Strong gravitational lensing by galaxy clusters has become a powerful tool for probing the high-redshift universe, magnifying distant and faint background galaxies. Reliable strong-lensing (SL) models are crucial for determining the intrinsic properties of distant, magnified sources and for constructing their luminosity function. We present here the first SL analysis of MACS J0308.9+2645 and PLCK G171.9‑40.7, two massive galaxy clusters imaged with the Hubble Space Telescope, in the framework of the Reionization Lensing Cluster Survey (RELICS). We use the light-traces-mass modeling technique to uncover sets of multiply imaged galaxies and constrain the mass distribution of the clusters. Our SL analysis reveals that both clusters have particularly large Einstein radii (θ E > 30″ for a source redshift of z s = 2), providing fairly large areas with high magnifications, useful for high-redshift galaxy searches (∼2 arcmin2 with μ > 5 to ∼1 arcmin2 with μ > 10, similar to a typical Hubble Frontier Fields cluster). We also find that MACS J0308.9+2645 hosts a promising, apparently bright (J ∼ 23.2–24.6 AB), multiply imaged high-redshift candidate at z ∼ 6.4. These images are among the brightest high-redshift candidates found in RELICS. Our mass models, including magnification maps, are made publicly available for the community through the Mikulski Archive for Space Telescopes.

An Integrative Account of Constraints on Cross-Situational Learning

PubMed Central

Yurovsky, Daniel; Frank, Michael C.

2015-01-01

Word-object co-occurrence statistics are a powerful information source for vocabulary learning, but there is considerable debate about how learners actually use them. While some theories hold that learners accumulate graded, statistical evidence about multiple referents for each word, others suggest that they track only a single candidate referent. In two large-scale experiments, we show that neither account is sufficient: Cross-situational learning involves elements of both. Further, the empirical data are captured by a computational model that formalizes how memory and attention interact with co-occurrence tracking. Together, the data and model unify opposing positions in a complex debate and underscore the value of understanding the interaction between computational and algorithmic levels of explanation. PMID:26302052

Demonstration of a High Open-Circuit Voltage GaN Betavoltaic Microbattery

NASA Astrophysics Data System (ADS)

Cheng, Zai-Jun; San, Hai-Sheng; Chen, Xu-Yuan; Liu, Bo; Feng, Zhi-Hong

2011-07-01

A high open-circuit voltage betavoltaic microbattery based on a GaN p-i-n diode is demonstrated. Under the irradiation of a 4×4 mm2 planar solid 63Ni source with an activity of 2 mCi, the open-circuit voltage Voc of the fabricated single 2×2mm2 cell reaches as high as 1.62 V, the short-circuit current density Jsc is measured to be 16nA/cm2. The microbattery has a fill factor of 55%, and the energy conversion efficiency of beta radiation into electricity reaches to 1.13%. The results suggest that GaN is a highly promising potential candidate for long-life betavoltaic microbatteries used as power supplies for microelectromechanical system devices.

Ground Demonstration of Planetary Gas Lidar Based on Optical Parametric Amplifier

NASA Technical Reports Server (NTRS)

Numata, Kenji; Riris, Haris; Li, Steve; Wu, Stewart; Kawa, Stephen R.; Krainak, Michael; Abshire, James

2012-01-01

We report on the development effort of a nanosecond-pulsed optical parametric amplifier (OPA) for remote trace gas measurements for Mars and Earth. The OPA output has high spectral purity and is widely tunable both at near-infrared and mid-infrared wavelengths, with an optical-optica1 conversion efficiency of up to approx 39 %. Using this laser source, we demonstrated open-path measurements of CH4 (3291 nm and 1651 nm), CO2 (1573 nm), H2O (1652 nm), and CO (4764 nm) on the ground. The simplicity, tunability. and power scalability of the OPA make it a strong candidate for general planetary lidar instruments, which will offer important information on the origins of the planet's geology, atmosphere, and potential for biology,

Discovery of Gamma-Ray Emission from the Supernova Remnant Kes 17 with Fermi Large Area Telescope

NASA Astrophysics Data System (ADS)

Wu, J. H. K.; Wu, E. M. H.; Hui, C. Y.; Tam, P. H. T.; Huang, R. H. H.; Kong, A. K. H.; Cheng, K. S.

2011-10-01

We report the discovery of GeV emission at the position of supernova remnant Kes 17 by using the data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. Kes 17 can be clearly detected with a significance of ~12σ in the 1-20 GeV range. Moreover, a number of γ-ray sources were detected in its vicinity. The γ-ray spectrum of Kes 17 can be described well by a simple power law with a photon index of Γ ~ 2.4. Together with the multiwavelength evidence for its interactions with the nearby molecular cloud, the γ-ray detection suggests that Kes 17 is a candidate acceleration site for cosmic rays.

FinFET-based Miller encoder for UHF and SHF RFID application

NASA Astrophysics Data System (ADS)

Srinivasulu, Avireni; Sravanthi, G.; Sarada, M.; Pal, Dipankar

2018-01-01

This paper proposes a T-flip-flop and a Miller encoder design for ultra-high frequency and super high frequency, radio-frequency identification (RFID) application using FinFETs. Miller encoder is used in magnetic recording, in optical domain and also in RFID. Performance of the proposed circuit was examined by installing the model parameters of 20-nm FinFET (obtained from open source) on Cadence platform with +0.4 V supply rail at frequencies of 1, 2 and 10 GHz. Simulation results have confirmed that proposed Miller encoder offers a simpler design with reduced transistor count and gives lower power dissipation, higher frequency range of operation at lower supply rail as compared to other candidate designs. Proposed design also promises less propagation delay.

Extreme Blazars Studied With Fermi -Lat And Suzaku : 1es 0347–121 And Blazar Candidate Hess J1943+213

DOE PAGES

Tanaka, Y. T.; Stawarz, Ł.; Finke, J.; ...

2014-05-14

We report on our study of high-energy properties of two peculiar TeV emitters: the “extreme blazar" 1ES 0347-121 and the “extreme blazar candidate" HESS J1943+213 located near the Galactic Plane. Both objects are characterized by quiescent synchrotron emission with flat spectra extending up to the hard X-ray range, and both were reported to be missing GeV counterparts in the Fermi-LAT 2–year Source Catalog. We analyze a 4.5 year accumulation of the Fermi-LAT data, resulting in the detection of 1ES 0347-121 in the GeV band, as well as in improved upper limits for HESS J1943+213. We also present the analysis resultsmore » of newly acquired Suzaku data for HESS J1943+213. The X-ray spectrum is well represented by a single power law extending up to 25 keV with photon index 2.00±0.02 and a moderate absorption in excess of the Galactic value, in agreementwith previous X-ray observations. No short-term X-ray variability was found over the 80 ks duration of the Suzaku exposure. Under the blazar hypothesis, we modeled the spectral energy distributions of 1ES 0347-121 and HESS J1943+213, and derived constraints on the intergalactic magnetic field strength and source energetics. We conclude that although the classification of HESS J1943+213 has not yet been determined, the blazar hypothesis remains the most plausible option, since in particular the broad-band spectra of the two analyzed sources along with the source model parameters closely resemble each other, and the newly available WISE and UKIDSS data for HESS J1943+213 are consistent with the presence of an elliptical host at the distance of approximatel ~ 600Mpc.« less

Extreme Blazars Studied with Fermi-LAT and Suzaku: 1ES 0347-121 and Blazar Candidate HESS J1943+213

NASA Astrophysics Data System (ADS)

Tanaka, Y. T.; Stawarz, Ł.; Finke, J.; Cheung, C. C.; Dermer, C. D.; Kataoka, J.; Bamba, A.; Dubus, G.; De Naurois, M.; Wagner, S. J.; Fukazawa, Y.; Thompson, D. J.

2014-06-01

We report on our study of high-energy properties of two peculiar TeV emitters: the "extreme blazar" 1ES 0347-121 and the "extreme blazar candidate" HESS J1943+213 located near the Galactic plane. Both objects are characterized by quiescent synchrotron emission with flat spectra extending up to the hard X-ray range, and both were reported to be missing GeV counterparts in the Fermi Large Area Telescope (LAT) two-year Source Catalog. We analyze a 4.5 yr accumulation of the Fermi-LAT data, resulting in the detection of 1ES 0347-121 in the GeV band, as well as in improved upper limits for HESS J1943+213. We also present the analysis results of newly acquired Suzaku data for HESS J1943+213. The X-ray spectrum is well represented by a single power law extending up to 25 keV with photon index 2.00 ± 0.02 and a moderate absorption in excess of the Galactic value, which is in agreement with previous X-ray observations. No short-term X-ray variability was found over the 80 ks duration of the Suzaku exposure. Under the blazar hypothesis, we modeled the spectral energy distributions of 1ES 0347-121 and HESS J1943+213, and we derived constraints on the intergalactic magnetic field strength and source energetics. We conclude that although the classification of HESS J1943+213 has not yet been determined, the blazar hypothesis remains the most plausible option since, in particular, the broadband spectra of the two analyzed sources along with the source model parameters closely resemble each other, and the newly available Wide-field Infrared Survey Explorer and UKIRT Infrared Deep Sky Survey data for HESS J1943+213 are consistent with the presence of an elliptical host at the distance of approximately ~600 Mpc.

Radio Follow-up on All Unassociated Gamma-Ray Sources from the Third Fermi Large Area Telescope Source Catalog

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schinzel, Frank K.; Petrov, Leonid; Taylor, Gregory B.

The third Fermi Large Area Telescope γ -ray source catalog (3FGL) contains over 1000 objects for which there is no known counterpart at other wavelengths. The physical origin of the γ -ray emission from those objects is unknown. Such objects are commonly referred to as unassociated and mostly do not exhibit significant γ -ray flux variability. We performed a survey of all unassociated γ -ray sources found in 3FGL using the Australia Telescope Compact Array and Very Large Array in the range 4.0–10.0 GHz. We found 2097 radio candidates for association with γ -ray sources. The follow-up with very longmore » baseline interferometry for a subset of those candidates yielded 142 new associations with active galactic nuclei that are γ -ray sources, provided alternative associations for seven objects, and improved positions for another 144 known associations to the milliarcsecond level of accuracy. In addition, for 245 unassociated γ -ray sources we did not find a single compact radio source above 2 mJy within 3 σ of their γ -ray localization. A significant fraction of these empty fields, 39%, are located away from the Galactic plane. We also found 36 extended radio sources that are candidates for association with a corresponding γ -ray object, 19 of which are most likely supernova remnants or H ii regions, whereas 17 could be radio galaxies.« less

The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Search for [CII] Line and Dust Emission in 6

NASA Astrophysics Data System (ADS)

Aravena, M.; Decarli, R.; Walter, F.; Bouwens, R.; Oesch, P. A.; Carilli, C. L.; Bauer, F. E.; Da Cunha, E.; Daddi, E.; Gónzalez-López, J.; Ivison, R. J.; Riechers, D. A.; Smail, I.; Swinbank, A. M.; Weiss, A.; Anguita, T.; Bacon, R.; Bell, E.; Bertoldi, F.; Cortes, P.; Cox, P.; Hodge, J.; Ibar, E.; Inami, H.; Infante, L.; Karim, A.; Magnelli, B.; Ota, K.; Popping, G.; van der Werf, P.; Wagg, J.; Fudamoto, Y.

2016-12-01

We present a search for [C II] line and dust continuum emission from optical dropout galaxies at z > 6 using ASPECS, our Atacama Large Millimeter submillimeter Array Spectroscopic Survey in the Hubble Ultra-deep Field (UDF). Our observations, which cover the frequency range of 212-272 GHz, encompass approximately the range of 6 < z < 8 for [C II] line emission and reach a limiting luminosity of L [C II] ˜ (1.6-2.5) × 108 L ⊙. We identify 14 [C II] line emitting candidates in this redshift range with significances >4.5σ, two of which correspond to blind detections with no optical counterparts. At this significance level, our statistical analysis shows that about 60% of our candidates are expected to be spurious. For one of our blindly selected [C II] line candidates, we tentatively detect the CO(6-5) line in our parallel 3 mm line scan. None of the line candidates are individually detected in the 1.2 mm continuum. A stack of all [C II] candidates results in a tentative detection with S 1.2 mm = 14 ± 5 μJy. This implies a dust-obscured star-formation rate (SFR) of (3 ± 1) M ⊙ yr-1. We find that the two highest-SFR objects have candidate [C II] lines with luminosities that are consistent with the low-redshift L [C II] versus SFR relation. The other candidates have significantly higher [C II] luminosities than expected from their UV-based SFR. At the current sensitivity, it is unclear whether the majority of these sources are intrinsically bright [C II] emitters, or spurious sources. If only one of our line candidates was real (a scenario greatly favored by our statistical analysis), we find a source density for [C II] emitters at 6 < z < 8 that is significantly higher than predicted by current models and some extrapolations from galaxies in the local universe.

Search for diffuse neutrino flux from astrophysical sources with MACRO

NASA Astrophysics Data System (ADS)

MACRO Collaboration; Ambrosio, M.; Antolini, R.; Auriemma, G.; Bakari, D.; Baldini, A.; Barbarino, G. C.; Barish, B. C.; Battistoni, G.; Becherini, Y.; Bellotti, R.; Bemporad, C.; Bernardini, P.; Bilokon, H.; Bloise, C.; Bower, C.; Brigida, M.; Bussino, S.; Cafagna, F.; Calicchio, M.; Campana, D.; Carboni, M.; Caruso, R.; Cecchini, S.; Cei, F.; Chiarella, V.; Choudhary, B. C.; Coutu, S.; Cozzi, M.; de Cataldo, G.; Dekhissi, H.; de Marzo, C.; de Mitri, I.; Derkaoui, J.; de Vincenzi, M.; di Credico, A.; Erriquez, O.; Favuzzi, C.; Forti, C.; Fusco, P.; Giacomelli, G.; Giannini, G.; Giglietto, N.; Giorgini, M.; Grassi, M.; Grillo, A.; Guarino, F.; Gustavino, C.; Habig, A.; Hanson, K.; Heinz, R.; Iarocci, E.; Katsavounidis, E.; Katsavounidis, I.; Kearns, E.; Kim, H.; Kyriazopoulou, S.; Lamanna, E.; Lane, C.; Levin, D. S.; Lipari, P.; Longley, N. P.; Longo, M. J.; Loparco, F.; Maaroufi, F.; Mancarella, G.; Mandrioli, G.; Margiotta, A.; Marini, A.; Martello, D.; Marzari-Chiesa, A.; Mazziotta, M. N.; Michael, D. G.; Monacelli, P.; Montaruli, T.; Monteno, M.; Mufson, S.; Musser, J.; Nicolò, D.; Nolty, R.; Orth, C.; Osteria, G.; Palamara, O.; Patera, V.; Patrizii, L.; Pazzi, R.; Peck, C. W.; Perrone, L.; Petrera, S.; Pistilli, P.; Popa, V.; Rainò, A.; Reynoldson, J.; Ronga, F.; Rrhioua, A.; Satriano, C.; Scapparone, E.; Scholberg, K.; Sciubba, A.; Serra, P.; Sioli, M.; Sirri, G.; Sitta, M.; Spinelli, P.; Spinetti, M.; Spurio, M.; Steinberg, R.; Stone, J. L.; Sulak, L. R.; Surdo, A.; Tarlè, G.; Togo, V.; Vakili, M.; Walter, C. W.; Webb, R.

2003-04-01

Many galactic and extragalactic astrophysical sources are currently considered promising candidates as high-energy neutrino emitters. Astrophysical neutrinos can be detected as upward-going muons produced in charged-current interactions with the medium surrounding the detector. The expected neutrino fluxes from various models start to dominate on the atmospheric neutrino background at neutrino energies above some tens of TeV. We present the results of a search for an excess of high-energy upward-going muons among the sample of data collected by MACRO during ~5.8 years of effective running time. No significant evidence for this signal was found. As a consequence, an upper limit on the flux of upward-going muons from high-energy neutrinos was set at the level of 1.7×10-14 cm-2s-1sr-1. The corresponding upper limit for the diffuse neutrino flux was evaluated assuming a neutrino power law spectrum. Our result was compared with theoretical predictions and upper limits from other experiments.

Ultra-compact Watt-level flat supercontinuum source pumped by noise-like pulse from an all-fiber oscillator.

PubMed

Chen, He; Zhou, Xuanfeng; Chen, Sheng-Ping; Jiang, Zong-Fu; Hou, Jing

2015-12-28

We demonstrate Watt-level flat visible supercontinuum (SC) generation in photonic crystal fibers, which is directly pumped by broadband noise-like pulses from an Yb-doped all-fiber oscillator. The novel SC generator is featured with elegant all-fiber-integrated architecture, high spectral flatness and high efficiency. Wide optical spectrum spanning from 500 nm to 2300 nm with 1.02 W optical power is obtained under the pump of 1.4 W noise-like pulse. The flatness of the spectrum in the range of 700 nm~1600 nm is less than 5 dB (including the pump residue). The exceptional simplicity, economical efficiency and the comparable performances make the noise-like pulse oscillator a competitive candidate to the widely used cascade amplified coherent pulse as the pump source of broadband SC. To the best of our knowledge, this is the first demonstration of SC generation which is directly pumped by an all-fiber noise-like pulse oscillator.

PSPICE controlled-source models of analogous circuit for Langevin type piezoelectric transducer

NASA Astrophysics Data System (ADS)

Chen, Yeongchin; Wu, Menqjiun; Liu, Weikuo

2007-02-01

The design and construction of wide-band and high efficiency acoustical projector has long been considered an art beyond the capabilities of many smaller groups. Langevin type piezoelectric transducers have been the most candidate of sonar array system applied in underwater communication. The transducers are fabricated, by bolting head mass and tail mass on both ends of stacked piezoelectric ceramic, to satisfy the multiple, conflicting design for high power transmitting capability. The aim of this research is to study the characteristics of Langevin type piezoelectric transducer that depend on different metal loading. First, the Mason equivalent circuit is used to model the segmented piezoelectric ceramic, then, the impedance network of tail and head masses is deduced by the Newton’s theory. To obtain the optimal solution to a specific design formulation, PSPICE controlled-source programming techniques can be applied. A valid example of the application of PSPICE models for Langevin type transducer analysis is presented and the simulation results are in good agreement with the experimental measurements.

Negative ion source development for a photoneutralization based neutral beam system for future fusion reactors

NASA Astrophysics Data System (ADS)

Simonin, A.; Agnello, R.; Bechu, S.; Bernard, J. M.; Blondel, C.; Boeuf, J. P.; Bresteau, D.; Cartry, G.; Chaibi, W.; Drag, C.; Duval, B. P.; de Esch, H. P. L.; Fubiani, G.; Furno, I.; Grand, C.; Guittienne, Ph; Howling, A.; Jacquier, R.; Marini, C.; Morgal, I.

2016-12-01

In parallel to the developments dedicated to the ITER neutral beam (NB) system, CEA-IRFM with laboratories in France and Switzerland are studying the feasibility of a new generation of NB system able to provide heating and current drive for the future DEMOnstration fusion reactor. For the steady-state scenario, the NB system will have to provide a high NB power level with a high wall-plug efficiency (η ˜ 60%). Neutralization of the energetic negative ions by photodetachment (so called photoneutralization), if feasible, appears to be the ideal solution to meet these performances, in the sense that it could offer a high beam neutralization rate (>80%) and a wall-plug efficiency higher than 60%. The main challenge of this new injector concept is the achievement of a very high power photon flux which could be provided by 3 MW Fabry-Perot optical cavities implanted along the 1 MeV D- beam in the neutralizer stage. The beamline topology is tall and narrow to provide laminar ion beam sheets, which will be entirely illuminated by the intra-cavity photon beams propagating along the vertical axis. The paper describes the present R&D (experiments and modelling) addressing the development of a new ion source concept (Cybele source) which is based on a magnetized plasma column. Parametric studies of the source are performed using Langmuir probes in order to characterize and compare the plasma parameters in the source column with different plasma generators, such as filamented cathodes, radio-frequency driver and a helicon antenna specifically developed at SPC-EPFL satisfying the requirements for the Cybele (axial magnetic field of 10 mT, source operating pressure: 0.3 Pa in hydrogen or deuterium). The paper compares the performances of the three plasma generators. It is shown that the helicon plasma generator is a very promising candidate to provide an intense and uniform negative ion beam sheet.

A deep narrowband survey for planetary nebulae at the outskirts of M 33

NASA Astrophysics Data System (ADS)

Galera-Rosillo, R.; Corradi, R. L. M.; Mampaso, A.

2018-04-01

Context. Planetary nebulae (PNe) are excellent tracers of stellar populations with low surface brightness, and therefore provide a powerful method to detect and explore the rich system of substructures discovered around the main spiral galaxies of the local group. Aim. We searched the outskirts of the local group spiral galaxy M 33 (the Triangulum) for PNe to gain new insights into the extended stellar substructure on the northern side of the disc and to study the existence of a faint classical halo. Methods: The search is based on wide field imaging covering a 4.5 square degree area out to a maximum projected distance of about 40 kpc from the centre of the galaxy. The PN candidates are detected by the combination of images obtained in narrowband filters selecting the [OIII]λ5007 Å and Hα + [NII] nebular lines and in the continuum g' and r' broadband filters. Results: Inside the bright optical disc of M 33, eight new PN candidates were identified, three of which were spectroscopically confirmed. No PN candidates were found outside the limits of the disc. Fourteen additional sources showing [OIII] excess were also discovered. Conclusions: The absence of bright PN candidates in the area outside the galaxy disc covered by this survey sets an upper limit to the luminosity of the underlying population of 1.6 × 107 L⊙, suggesting the lack of a massive classical halo, which is in agreement with the results obtained using the red giant branch population. Based on observations made with the Isaac Newton Telescope and service observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group of Telescopes in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

The DES Bright Arcs Survey: Hundreds of Candidate Strongly Lensed Galaxy Systems from the Dark Energy Survey Science Verification and Year 1 Observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diehl, H. T.; Buckley-Geer, E. J.; Lindgren, K. A.

We report the results of searches for strong gravitational lens systems in the Dark Energy Survey (DES) Science Verification and Year 1 observations. The Science Verification data span approximately 250 sq. deg. with a median i -band limiting magnitude for extended objects (10 σ ) of 23.0. The Year 1 data span approximately 2000 sq. deg. and have an i -band limiting magnitude for extended objects (10 σ ) of 22.9. As these data sets are both wide and deep, they are particularly useful for identifying strong gravitational lens candidates. Potential strong gravitational lens candidate systems were initially identified basedmore » on a color and magnitude selection in the DES object catalogs or because the system is at the location of a previously identified galaxy cluster. Cutout images of potential candidates were then visually scanned using an object viewer and numerically ranked according to whether or not we judged them to be likely strong gravitational lens systems. Having scanned nearly 400,000 cutouts, we present 374 candidate strong lens systems, of which 348 are identified for the first time. We provide the R.A. and decl., the magnitudes and photometric properties of the lens and source objects, and the distance (radius) of the source(s) from the lens center for each system.« less

A Multiwavelength Characterization of Proto-brown-dwarf Candidates in Serpens

NASA Astrophysics Data System (ADS)

Riaz, B.; Vorobyov, E.; Harsono, D.; Caselli, P.; Tikare, K.; Gonzalez-Martin, O.

2016-11-01

We present results from a deep submillimeter survey in the Serpens Main and Serpens/G3-G6 clusters, conducted with the Submillimetre Common-User Bolometer Array (SCUBA-2) at the James Clerk Maxwell Telescope. We have combined near- and mid-infrared spectroscopy, Herschel PACS far-infrared photometry, submillimeter continuum, and molecular gas line observations, with the aim of conducting a detailed multiwavelength characterization of “proto-brown-dwarf” (proto-BD) candidates in Serpens. We have performed continuum and line radiative transfer modeling and have considered various classification schemes to understand the structure and the evolutionary stage of the system. We have identified four proto-BD candidates, of which the lowest-luminosity source has an L bol ˜ 0.05 L ⊙. Two of these candidates show characteristics consistent with Stage 0/I systems, while the other two are Stage I-T/Class Flat systems with tenuous envelopes. Our work has also revealed a ˜20% fraction of misidentified Class 0/I/Flat sources that show characteristics consistent with Class II edge-on disk systems. We have set constraints on the mass of the central object using the measured bolometric luminosities and numerical simulations of stellar evolution. Considering the available gas+dust mass reservoir and the current mass of the central source, three of these candidates are likely to evolve into BDs.

The DES Bright Arcs Survey: Hundreds of Candidate Strongly Lensed Galaxy Systems from the Dark Energy Survey Science Verification and Year 1 Observations

NASA Astrophysics Data System (ADS)

Diehl, H. T.; Buckley-Geer, E. J.; Lindgren, K. A.; Nord, B.; Gaitsch, H.; Gaitsch, S.; Lin, H.; Allam, S.; Collett, T. E.; Furlanetto, C.; Gill, M. S. S.; More, A.; Nightingale, J.; Odden, C.; Pellico, A.; Tucker, D. L.; da Costa, L. N.; Fausti Neto, A.; Kuropatkin, N.; Soares-Santos, M.; Welch, B.; Zhang, Y.; Frieman, J. A.; Abdalla, F. B.; Annis, J.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Burke, D. L.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Cunha, C. E.; D'Andrea, C. B.; Desai, S.; Dietrich, J. P.; Drlica-Wagner, A.; Evrard, A. E.; Finley, D. A.; Flaugher, B.; García-Bellido, J.; Gerdes, D. W.; Goldstein, D. A.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; James, D. J.; Kuehn, K.; Kuhlmann, S.; Lahav, O.; Li, T. S.; Lima, M.; Maia, M. A. G.; Marshall, J. L.; Menanteau, F.; Miquel, R.; Nichol, R. C.; Nugent, P.; Ogando, R. L. C.; Plazas, A. A.; Reil, K.; Romer, A. K.; Sako, M.; Sanchez, E.; Santiago, B.; Scarpine, V.; Schindler, R.; Schubnell, M.; Sevilla-Noarbe, I.; Sheldon, E.; Smith, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Walker, A. R.; DES Collaboration

2017-09-01

We report the results of searches for strong gravitational lens systems in the Dark Energy Survey (DES) Science Verification and Year 1 observations. The Science Verification data span approximately 250 sq. deg. with a median I-band limiting magnitude for extended objects (10σ) of 23.0. The Year 1 data span approximately 2000 sq. deg. and have an I-band limiting magnitude for extended objects (10σ) of 22.9. As these data sets are both wide and deep, they are particularly useful for identifying strong gravitational lens candidates. Potential strong gravitational lens candidate systems were initially identified based on a color and magnitude selection in the DES object catalogs or because the system is at the location of a previously identified galaxy cluster. Cutout images of potential candidates were then visually scanned using an object viewer and numerically ranked according to whether or not we judged them to be likely strong gravitational lens systems. Having scanned nearly 400,000 cutouts, we present 374 candidate strong lens systems, of which 348 are identified for the first time. We provide the R.A. and decl., the magnitudes and photometric properties of the lens and source objects, and the distance (radius) of the source(s) from the lens center for each system.

A MULTIWAVELENGTH CHARACTERIZATION OF PROTO-BROWN-DWARF CANDIDATES IN SERPENS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riaz, B.; Caselli, P.; Vorobyov, E.

2016-11-10

We present results from a deep submillimeter survey in the Serpens Main and Serpens/G3–G6 clusters, conducted with the Submillimetre Common-User Bolometer Array (SCUBA-2) at the James Clerk Maxwell Telescope. We have combined near- and mid-infrared spectroscopy, Herschel PACS far-infrared photometry, submillimeter continuum, and molecular gas line observations, with the aim of conducting a detailed multiwavelength characterization of “proto-brown-dwarf” (proto-BD) candidates in Serpens. We have performed continuum and line radiative transfer modeling and have considered various classification schemes to understand the structure and the evolutionary stage of the system. We have identified four proto-BD candidates, of which the lowest-luminosity source hasmore » an L {sub bol} ∼ 0.05 L {sub ☉}. Two of these candidates show characteristics consistent with Stage 0/I systems, while the other two are Stage I-T/Class Flat systems with tenuous envelopes. Our work has also revealed a ∼20% fraction of misidentified Class 0/I/Flat sources that show characteristics consistent with Class II edge-on disk systems. We have set constraints on the mass of the central object using the measured bolometric luminosities and numerical simulations of stellar evolution. Considering the available gas+dust mass reservoir and the current mass of the central source, three of these candidates are likely to evolve into BDs.« less

Higher Social Intelligence Can Impair Source Memory

ERIC Educational Resources Information Center

Barber, Sarah J.; Franklin, Nancy; Naka, Makiko; Yoshimura, Hiroki

2010-01-01

Source monitoring is made difficult when the similarity between candidate sources increases. The current work examines how individual differences in social intelligence and perspective-taking abilities serve to increase source similarity and thus negatively impact source memory. Strangers first engaged in a cooperative storytelling task. On each…

Systematic search for very-high-energy gamma-ray emission from bow shocks of runaway stars

NASA Astrophysics Data System (ADS)

H.E.S.S. Collaboration; Abdalla, H.; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Andersson, T.; Angüner, E. O.; Arakawa, M.; Arrieta, M.; Aubert, P.; Backes, M.; Balzer, A.; Barnard, M.; Becherini, Y.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Blackwell, R.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Büchele, M.; Bulik, T.; Capasso, M.; Carr, J.; Casanova, S.; Cerruti, M.; Chakraborty, N.; Chalme-Calvet, R.; Chaves, R. C. G.; Chen, A.; Chevalier, J.; Chrétien, M.; Coffaro, M.; Colafrancesco, S.; Cologna, G.; Condon, B.; Conrad, J.; Cui, Y.; Davids, I. D.; Decock, J.; Degrange, B.; Deil, C.; Devin, J.; deWilt, P.; Dirson, L.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; Drury, L. O.'C.; Dutson, K.; Dyks, J.; Edwards, T.; Egberts, K.; Eger, P.; Ernenwein, J.-P.; Eschbach, S.; Farnier, C.; Fegan, S.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Funk, S.; Füßling, M.; Gabici, S.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Gottschall, D.; Goyal, A.; Grondin, M.-H.; Hahn, J.; Haupt, M.; Hawkes, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hinton, J. A.; Hofmann, W.; Hoischen, C.; Holler, M.; Horns, D.; Ivascenko, A.; Iwasaki, H.; Jacholkowska, A.; Jamrozy, M.; Janiak, M.; Jankowsky, D.; Jankowsky, F.; Jingo, M.; Jogler, T.; Jouvin, L.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Katsuragawa, M.; Katz, U.; Kerszberg, D.; Khangulyan, D.; Khélifi, B.; Kieffer, M.; King, J.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Kraus, M.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lau, J.; Lees, J.-P.; Lefaucheur, J.; Lefranc, V.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Leser, E.; Lohse, T.; Lorentz, M.; Liu, R.; López-Coto, R.; Lypova, I.; Marandon, V.; Marcowith, A.; Mariaud, C.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; Meintjes, P. J.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Mohrmann, L.; Morå, K.; Moulin, E.; Murach, T.; Nakashima, S.; de Naurois, M.; Niederwanger, F.; Niemiec, J.; Oakes, L.; O'Brien, P.; Odaka, H.; Öttl, S.; Ohm, S.; Ostrowski, M.; Oya, I.; Padovani, M.; Panter, M.; Parsons, R. D.; Pekeur, N. W.; Pelletier, G.; Perennes, C.; Petrucci, P.-O.; Peyaud, B.; Piel, Q.; Pita, S.; Poon, H.; Prokhorov, D.; Prokoph, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Richter, S.; Rieger, F.; Romoli, C.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Saito, S.; Salek, D.; Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwemmer, S.; Seglar-Arroyo, M.; Settimo, M.; Seyffert, A. S.; Shafi, N.; Shilon, I.; Simoni, R.; Sol, H.; Spanier, F.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stycz, K.; Sushch, I.; Takahashi, T.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tibaldo, L.; Tiziani, D.; Tluczykont, M.; Trichard, C.; Tsuji, N.; Tuffs, R.; Uchiyama, Y.; van der Walt, D. J.; van Eldik, C.; van Rensburg, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Voisin, F.; Völk, H. J.; Vuillaume, T.; Wadiasingh, Z.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zabalza, V.; Zaborov, D.; Zacharias, M.; Zanin, R.; Zdziarski, A. A.; Zech, A.; Zefi, F.; Ziegler, A.; Żywucka, N.

2018-04-01

Context. Runaway stars form bow shocks by ploughing through the interstellar medium at supersonic speeds and are promising sources of non-thermal emission of photons. One of these objects has been found to emit non-thermal radiation in the radio band. This triggered the development of theoretical models predicting non-thermal photons from radio up to very-high-energy (VHE, E ≥ 0.1 TeV) gamma rays. Subsequently, one bow shock was also detected in X-ray observations. However, the data did not allow discrimination between a hot thermal and a non-thermal origin. Further observations of different candidates at X-ray energies showed no evidence for emission at the position of the bow shocks either. A systematic search in the Fermi-LAT energy regime resulted in flux upper limits for 27 candidates listed in the E-BOSS catalogue. Aim. Here we perform the first systematic search for VHE gamma-ray emission from bow shocks of runaway stars. Methods: Using all available archival H.E.S.S. data we search for very-high-energy gamma-ray emission at the positions of bow shock candidates listed in the second E-BOSS catalogue release. Out of the 73 bow shock candidates in this catalogue, 32 have been observed with H.E.S.S. Results: None of the observed 32 bow shock candidates in this population study show significant emission in the H.E.S.S. energy range. Therefore, flux upper limits are calculated in five energy bins and the fraction of the kinetic wind power that is converted into VHE gamma rays is constrained. Conclusions: Emission from stellar bow shocks is not detected in the energy range between 0.14 and 18 TeV.The resulting upper limits constrain the level of VHE gamma-ray emission from these objects down to 0.1-1% of the kinetic wind energy.

A study on various methods of supplying propellant to an orbit insertion rocket engine

NASA Technical Reports Server (NTRS)

Boretz, J. E.; Huniu, S.; Thompson, M.; Pagani, M.; Paulsen, B.; Lewis, J.; Paul, D.

1980-01-01

Various types of pumps and pump drives were evaluated to determine the lightest weight system for supplying propellants to a planetary orbit insertion rocket engine. From these analyses four candidate propellant feed systems were identified. Systems Nos. 1 and 2 were both battery powered (lithium-thionyl-chloride or silver-zinc) motor driven pumps. System 3 was a monopropellant gas generator powered turbopump. System 4 was a bipropellant gas generator powered turbopump. Parameters considered were pump break horsepower, weight, reliability, transient response and system stability. Figures of merit were established and the ranking of the candidate systems was determined. Conceptual designs were prepared for typical motor driven pumps and turbopump configurations for a 1000 lbf thrust rocket engine.

Atomic oxygen effects on candidate coatings for long-term spacecraft in low earth orbit

NASA Technical Reports Server (NTRS)

Lan, E. H.; Smith, Charles A.; Cross, J. B.

1988-01-01

Candidate atomic oxygen protective coatings for long-term low Earth orbit (LEO) spacecraft were evaluated using the Los Alamos National Laboratory O-atom exposure facility. The coatings studied include Teflon, Al2O3, SiO2, and SWS-V-10, a silicon material. Preliminary results indicate that sputtered PTFE Teflon (0.1 micrometers) has a fluence lifetime of 10 to the 19th power O-atoms/cm (2), and sputtered silicon dioxide (0.1 micrometers), aluminum oxide (0.1 micrometers), and SWS-V-10, a silicone, (4 micrometers) have fluence lifetimes of 10 to the 20th power to 10 to the 21st power O-atoms/cm (2). There are large variations in fluence lifetime data for these coatings.

Using gradient-based ray and candidate shadow maps for environmental illumination distribution estimation

NASA Astrophysics Data System (ADS)

Eem, Changkyoung; Kim, Iksu; Hong, Hyunki

2015-07-01

A method to estimate the environmental illumination distribution of a scene with gradient-based ray and candidate shadow maps is presented. In the shadow segmentation stage, we apply a Canny edge detector to the shadowed image by using a three-dimensional (3-D) augmented reality (AR) marker of a known size and shape. Then the hierarchical tree of the connected edge components representing the topological relation is constructed, and the connected components are merged, taking their hierarchical structures into consideration. A gradient-based ray that is perpendicular to the gradient of the edge pixel in the shadow image can be used to extract the shadow regions. In the light source detection stage, shadow regions with both a 3-D AR marker and the light sources are partitioned into candidate shadow maps. A simple logic operation between each candidate shadow map and the segmented shadow is used to efficiently compute the area ratio between them. The proposed method successively extracts the main light sources according to their relative contributions on the segmented shadows. The proposed method can reduce unwanted effects due to the sampling positions in the shadow region and the threshold values in the shadow edge detection.

Planck intermediate results: XXXIX. The Planck list of high-redshift source candidates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ade, P. A. R.; Aghanim, N.; Arnaud, M.

The Planck mission, thanks to its large frequency range and all-sky coverage, has a unique potential for systematically detecting the brightest, and rarest, submillimetre sources on the sky, including distant objects in the high-redshift Universe traced by their dust emission. In this paper, a novel method, based on a component-separation procedure using a combination of Planck and IRAS data, has been validated and characterized on numerous simulations, and applied to select the most luminous cold submillimetre sources with spectral energy distributions peaking between 353 and 857 GHz at 5' resolution. A total of 2151 Planck high-z source candidates (the PHZ)more » have been detected in the cleanest 26% of the sky, with flux density at 545 GHz above 500 mJy. Embedded in the cosmic infrared background close to the confusion limit, these high-z candidates exhibit colder colours than their surroundings, consistent with redshifts z > 2, assuming a dust temperature of T xgal = 35 K and a spectral index of β xgal = 1.5. Exhibiting extremely high luminosities, larger than 10 14L ⊙, the PHZ objects may be made of multiple galaxies or clumps at high redshift, as suggested by a first statistical analysis based on a comparison with number count models. Furthermore, first follow-up observations obtained from optical to submillimetre wavelengths, which can be found in companion papers, have confirmed that this list consists of two distinct populations. A small fraction (around 3%) of the sources have been identified as strongly gravitationally lensed star-forming galaxies at redshift 2 to 4, while the vast majority of the PHZ sources appear as overdensities of dusty star-forming galaxies, having colours consistent with being at z > 2, and may be considered as proto-cluster candidates. The PHZ provides an original sample, which is complementary to the Planck Sunyaev-Zeldovich Catalogue (PSZ2); by extending the population of virialized massive galaxy clusters detected below z < 1.5 through their SZ signal to a population of sources at z > 1.5, the PHZ may contain the progenitors of today’s clusters. Therefore the Planck list of high-redshift source candidates opens a new window on the study of the early stages of structure formation, particularly understanding the intensively star-forming phase at high-z.« less

Planck intermediate results: XXXIX. The Planck list of high-redshift source candidates

DOE PAGES

Ade, P. A. R.; Aghanim, N.; Arnaud, M.; ...

2016-12-12

The Planck mission, thanks to its large frequency range and all-sky coverage, has a unique potential for systematically detecting the brightest, and rarest, submillimetre sources on the sky, including distant objects in the high-redshift Universe traced by their dust emission. In this paper, a novel method, based on a component-separation procedure using a combination of Planck and IRAS data, has been validated and characterized on numerous simulations, and applied to select the most luminous cold submillimetre sources with spectral energy distributions peaking between 353 and 857 GHz at 5' resolution. A total of 2151 Planck high-z source candidates (the PHZ)more » have been detected in the cleanest 26% of the sky, with flux density at 545 GHz above 500 mJy. Embedded in the cosmic infrared background close to the confusion limit, these high-z candidates exhibit colder colours than their surroundings, consistent with redshifts z > 2, assuming a dust temperature of T xgal = 35 K and a spectral index of β xgal = 1.5. Exhibiting extremely high luminosities, larger than 10 14L ⊙, the PHZ objects may be made of multiple galaxies or clumps at high redshift, as suggested by a first statistical analysis based on a comparison with number count models. Furthermore, first follow-up observations obtained from optical to submillimetre wavelengths, which can be found in companion papers, have confirmed that this list consists of two distinct populations. A small fraction (around 3%) of the sources have been identified as strongly gravitationally lensed star-forming galaxies at redshift 2 to 4, while the vast majority of the PHZ sources appear as overdensities of dusty star-forming galaxies, having colours consistent with being at z > 2, and may be considered as proto-cluster candidates. The PHZ provides an original sample, which is complementary to the Planck Sunyaev-Zeldovich Catalogue (PSZ2); by extending the population of virialized massive galaxy clusters detected below z < 1.5 through their SZ signal to a population of sources at z > 1.5, the PHZ may contain the progenitors of today’s clusters. Therefore the Planck list of high-redshift source candidates opens a new window on the study of the early stages of structure formation, particularly understanding the intensively star-forming phase at high-z.« less

THE ABUNDANCE OF X-SHAPED RADIO SOURCES: IMPLICATIONS FOR THE GRAVITATIONAL WAVE BACKGROUND

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roberts, David H.; Saripalli, Lakshmi; Subrahmanyan, Ravi, E-mail: roberts@brandeis.edu

Coalescence of supermassive black holes (SMBHs) in galaxy mergers is potentially the dominant contributor to the low frequency gravitational wave background (GWB). It was proposed by Merritt and Ekers that X-shaped radio galaxies are signposts of such coalescences and that their abundance might be used to predict the magnitude of the GWB. In Roberts et al. we presented radio images of all 52 X-shaped radio source candidates out of the sample of 100 selected by Cheung for which archival VLA data were available. These images indicate that at most 21% of the candidates might be genuine X-shaped radio sources thatmore » were formed by a restarting of beams in a new direction following a major merger. This suggests that fewer than 1.3% of extended radio sources appear to be candidates for genuine axis reorientations (“spin flips”), much smaller than the 7% suggested by Leahy and Parma. Thus, the associated GWB may be substantially smaller than previous estimates. These results can be used to normalize detailed calculations of the SMBH coalescence rate and the GWB.« less

Young Stellar Object Candidates in the Aquila Rift Region

NASA Astrophysics Data System (ADS)

Zhang, Miao-miao; Wang, Hong-chi; Stecklum, B.

2010-10-01

Using the 2m telescope of the Turingia State Observatory at Tauten-berg (TLS), imaging observations in 3 wavebands (H α, R and I) are performed in the 16 fields in the Aquila Rift region. The observed fields cover about 7 square degrees. Excluding the 3 fields with unqualified data, the photometrical analysis is made for the remaining 13 fields, from which point sources are identified, and finally 7 H α emission-line star candidates are identified by color-color diagrams. The 7 candidates are located in five fields. Three of them are located near the Galactic plane, while the galactic latitudes of the rest are greater than 4°. The 2 M ASS counterparts of the point sources are identified, and the properties of the 7 H α emission-line star candidates are further analyzed by using the two-color diagrams. It is found that the near-infrared radiation from these H α emission-line star candidates has no obvious infrared excess, one of them even falls on the main-sequence branch. This indicates that the H α-emissive young stellar objects (YSOs) are not always accompanied with the infrared excess, and that the results of the H α emission line observation and the infrared excess observation are mutually supplemented. If the 7 H α emission-line star candidates are regarded as YSO candidates, then the number of YSOs in the Aquila Rift region is quite small. The further confirmation of these candidates needs subsequent spectral observations.

NuSTAR Hard X-Ray Survey of the Galactic Center Region. II. X-Ray Point Sources

NASA Technical Reports Server (NTRS)

Hong, Jaesub; Mori, Kaya; Hailey, Charles J.; Nynka, Melania; Zhang, Shou; Gotthelf, Eric; Fornasini, Francesca M.; Krivonos, Roman; Bauer, Franz; Perez, Kerstin;

EVN observations of eleven GHz-Peaked-Spectrum radio sources at 2.3/8.4 GHz

NASA Astrophysics Data System (ADS)

Xiang, L.; Dallacasa, D.; Cassaro, P.; Jiang, D.; Reynolds, C.

2005-04-01

We present results of EVN observations of eleven GHz-Peaked-Spectrum (GPS) radio sources at 2.3/8.4 GHz. These sources are from the classical "bright" GPS source samples with peak flux densities > 0.2 Jy and spectral indices α < -0.2 (S ∝ ν-α) in the optically thick regime of their convex spectra. Most of the target sources did not have VLBI images at the time this project started. The aim of the work is to find Compact Symmetric Object (CSO) candidates from the "bright" GPS samples. These CSOs play a key role in understanding the very early stage of the evolution of individual radio galaxies. The reason for investigating GPS source samples is that CSO candidates are more frequently found among this class of radio sources. In fact both classes, GPS and CSO, represent a small fraction of the flux limited and flat-spectrum samples like PR+CJ1 (PR: Pearson-Readhead survey, CJ1: the first Caltech-Jodrell Bank survey) and CJF (the Caltech-Jodrell Bank flat spectrum source survey) with a single digit percentage progressively decreasing with decreasing flux density limit. Our results, with at least 3, but possibly more CSO sources detected among a sample of 11, underline the effectiveness of our approach. The three confirmed CSO sources (1133+432, 1824+271, and 2121-014) are characterized by a symmetric pair of resolved components, each with steep spectral indices. Five further sources (0144+209, 0554-026, 0904+039, 0914+114 and 2322-040) can be considered likely CSO candidates. The remaining three sources (0159+839, 0602+780 and 0802+212) are either of core-jet type or dominated by a single component at both frequencies.

Kernel Machine SNP-set Testing under Multiple Candidate Kernels

PubMed Central

Wu, Michael C.; Maity, Arnab; Lee, Seunggeun; Simmons, Elizabeth M.; Harmon, Quaker E.; Lin, Xinyi; Engel, Stephanie M.; Molldrem, Jeffrey J.; Armistead, Paul M.

2013-01-01

Joint testing for the cumulative effect of multiple single nucleotide polymorphisms grouped on the basis of prior biological knowledge has become a popular and powerful strategy for the analysis of large scale genetic association studies. The kernel machine (KM) testing framework is a useful approach that has been proposed for testing associations between multiple genetic variants and many different types of complex traits by comparing pairwise similarity in phenotype between subjects to pairwise similarity in genotype, with similarity in genotype defined via a kernel function. An advantage of the KM framework is its flexibility: choosing different kernel functions allows for different assumptions concerning the underlying model and can allow for improved power. In practice, it is difficult to know which kernel to use a priori since this depends on the unknown underlying trait architecture and selecting the kernel which gives the lowest p-value can lead to inflated type I error. Therefore, we propose practical strategies for KM testing when multiple candidate kernels are present based on constructing composite kernels and based on efficient perturbation procedures. We demonstrate through simulations and real data applications that the procedures protect the type I error rate and can lead to substantially improved power over poor choices of kernels and only modest differences in power versus using the best candidate kernel. PMID:23471868

Candidates source regions of martian meteorites as identified by OMEGA/MEx

NASA Astrophysics Data System (ADS)

Ody, A.; Poulet, F.; Quantin, C.; Bibring, J.-P.; Bishop, J. L.; Dyar, M. D.

2015-09-01

The objective of this study is to identify and map spectral analogues of some key martian meteorites (basaltic shergottites Los Angeles, Shergotty, QUE 94201, lherzolitic shergottite ALH A77005, Nakhla, Chassigny and the orthopyroxenite ALH 84001) in order to localize terrain candidates for their source regions. We develop a best fit procedure to reproduce the near-infrared (NIR) spectral properties of the martian surface as seen by the hyperspectral imaging spectrometer OMEGA/MEx from the NIR spectra of the martian meteorites. The fitting process is tested and validated, and Root Mean Square (RMS) global maps for each meteorite are obtained. It is found that basaltic shergottites have NIR spectral properties the most representative of the martian surface with the best spectral analogues found in early Hesperian volcanic provinces. Sites with spectral properties similar to those of ALH A77005 are scarce. They are mainly localized in olivine-bearing regions such as Nili Fossae and small Noachian/early Hesperian terrains. The only plausible source region candidate for Chassigny is the Nili Patera caldera dated to 1.6 Ga. Widespread spectral analogues for the ALH 84001 meteorite are found northeast of Syrtis Major and northwest of the Hellas basin. While this distribution is in agreement with the low-calcium-pyroxene-rich composition and old age (4.1 Ga) of this meteorite, the modal mineralogy of these candidates is not consistent with that of this meteorite. No convincing spectral analogue is found for the Amazonian-aged Nakhla meteorite suggesting that its olivine/high-calcium-pyroxene-rich composition could be representative of the Amazonian terrains buried under dust. Finally, some young rayed craters are proposed as possible candidates for source craters of the studied martian meteorites.

High-mass Starless Clumps in the Inner Galactic Plane: The Sample and Dust Properties

NASA Astrophysics Data System (ADS)

Yuan, Jinghua; Wu, Yuefang; Ellingsen, Simon P.; Evans, Neal J., II; Henkel, Christian; Wang, Ke; Liu, Hong-Li; Liu, Tie; Li, Jin-Zeng; Zavagno, Annie

2017-07-01

We report a sample of 463 high-mass starless clump (HMSC) candidates within -60^\\circ < l< 60^\\circ and -1^\\circ < b< 1^\\circ . This sample has been singled out from 10,861 ATLASGAL clumps. None of these sources are associated with any known star-forming activities collected in SIMBAD and young stellar objects identified using color-based criteria. We also make sure that the HMSC candidates have neither point sources at 24 and 70 μm nor strong extended emission at 24 μm. Most of the identified HMSCs are infrared dark, and some are even dark at 70 μm. Their distribution shows crowding in Galactic spiral arms and toward the Galactic center and some well-known star-forming complexes. Many HMSCs are associated with large-scale filaments. Some basic parameters were attained from column density and dust temperature maps constructed via fitting far-infrared and submillimeter continuum data to modified blackbodies. The HMSC candidates have sizes, masses, and densities similar to clumps associated with Class II methanol masers and H II regions, suggesting that they will evolve into star-forming clumps. More than 90% of the HMSC candidates have densities above some proposed thresholds for forming high-mass stars. With dust temperatures and luminosity-to-mass ratios significantly lower than that for star-forming sources, the HMSC candidates are externally heated and genuinely at very early stages of high-mass star formation. Twenty sources with equivalent radii {r}{eq}< 0.15 pc and mass surface densities {{Σ }}> 0.08 g cm-2 could be possible high-mass starless cores. Further investigations toward these HMSCs would undoubtedly shed light on comprehensively understanding the birth of high-mass stars.

Near Real-Time Imaging of the Galactic Plane with BATSE

NASA Technical Reports Server (NTRS)

Harmon, B. A.; Zhang, S. N.; Robinson, C. R.; Paciesas, W. S.; Barret, D.; Grindlay, J.; Bloser, P.; Monnelly, C.

1997-01-01

The discovery of new transient or persistent sources in the hard X-ray regime with the BATSE Earth occultation Technique has been limited previously to bright sources of about 200 mCrab or more. While monitoring known source locations is not a problem to a daily limiting sensitivity of about 75 mCrab, the lack of a reliable background model forces us to use more intensive computer techniques to find weak, previously unknown emission from hard X-ray/gamma sources. The combination of Radon transform imaging of the galactic plane in 10 by 10 degree fields and the Harvard/CFA-developed Image Search (CBIS) allows us to straightforwardly search the sky for candidate sources in a +/- 20 degree latitude band along the plane. This procedure has been operating routinely on a weekly basis since spring 1997. We briefly describe the procedure, then concentrate on the performance aspects of the technique and candidate source results from the search.

Independent Orbiter Assessment (IOA): Weibull analysis report

NASA Technical Reports Server (NTRS)

Raffaelli, Gary G.

1987-01-01

The Auxiliary Power Unit (APU) and Hydraulic Power Unit (HPU) Space Shuttle Subsystems were reviewed as candidates for demonstrating the Weibull analysis methodology. Three hardware components were identified as analysis candidates: the turbine wheel, the gearbox, and the gas generator. Detailed review of subsystem level wearout and failure history revealed the lack of actual component failure data. In addition, component wearout data were not readily available or would require a separate data accumulation effort by the vendor. Without adequate component history data being available, the Weibull analysis methodology application to the APU and HPU subsystem group was terminated.

A Planet Hunters Search of the Kepler TCE Inventory

NASA Astrophysics Data System (ADS)

Schwamb, Meg; Lintott, Chris; Fischer, Debra; Smith, Arfon; Boyajian, Tabetha; Brewer, John; Giguere, Matt; Lynn, Stuart; Schawinski, Kevin; Simpson, Rob; Wang, Ji

2013-07-01

NASA's Kepler spacecraft has spent the past 4 years monitoring ~160,000 stars for the signatures of transiting exoplanets. Planet Hunters (http://www.planethunters.org), part of the Zooniverse (http://www.zooniverse.org) collection of citizen science projects, uses the power of human pattern recognition via the World Wide Web to identify transits in the Kepler public data. We have demonstrated the success of a citizen science approach with the project's discoveries including PH1 b, a transiting circumbinary planet in a four star system., and over 20 previously unknown planet candidates. The Kepler team has released the list of 18,406 potential transit signals or threshold-crossing events (TCEs) identified in Quarters 1-12 (~1000 days) by their automated Transit Planet Search (TPS) algorithm. The majority of these detections found by TPS are triggered by transient events and are not valid planet candidates. To identify planetary candidates from the detected TCEs, a human review of the validation reports, generated by the Kepler pipeline for each TCE, is performed by several Kepler team members. We have undertaken an independent crowd-sourced effort to perform a systematic search of the Kepler Q1-12 TCE list. With the Internet we can obtain multiple assessments of each TCE's data validation report. Planet Hunters volunteers evaluate whether a transit is visible in the Kepler light curve folded on the expected period identified by TPS. We present the first results of this analysis.

A 1.1-1.9 GHz SETI SURVEY OF THE KEPLER FIELD. I. A SEARCH FOR NARROW-BAND EMISSION FROM SELECT TARGETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siemion, Andrew P. V.; Korpela, Eric; Werthimer, Dan

2013-04-10

We present a targeted search for narrow-band (<5 Hz) drifting sinusoidal radio emission from 86 stars in the Kepler field hosting confirmed or candidate exoplanets. Radio emission less than 5 Hz in spectral extent is currently known to only arise from artificial sources. The stars searched were chosen based on the properties of their putative exoplanets, including stars hosting candidates with 380 K > T{sub eq} > 230 K, stars with five or more detected candidates or stars with a super-Earth (R{sub p} < 3 R{sub Circled-Plus }) in a >50 day orbit. Baseband voltage data across the entire bandmore » between 1.1 and 1.9 GHz were recorded at the Robert C. Byrd Green Bank Telescope between 2011 February and April and subsequently searched offline. No signals of extraterrestrial origin were found. We estimate that fewer than {approx}1% of transiting exoplanet systems host technological civilizations that are radio loud in narrow-band emission between 1 and 2 GHz at an equivalent isotropically radiated power (EIRP) of {approx}1.5 Multiplication-Sign 10{sup 21} erg s{sup -1}, approximately eight times the peak EIRP of the Arecibo Planetary Radar, and we limit the number of 1-2 GHz narrow-band-radio-loud Kardashev type II civilizations in the Milky Way to be <10{sup -6} M{sub Sun }{sup -1}. Here we describe our observations, data reduction procedures and results.« less

Efficient electromagnetic source imaging with adaptive standardized LORETA/FOCUSS.

PubMed

Schimpf, Paul H; Liu, Hesheng; Ramon, Ceon; Haueisen, Jens

2005-05-01

Functional brain imaging and source localization based on the scalp's potential field require a solution to an ill-posed inverse problem with many solutions. This makes it necessary to incorporate a priori knowledge in order to select a particular solution. A computational challenge for some subject-specific head models is that many inverse algorithms require a comprehensive sampling of the candidate source space at the desired resolution. In this study, we present an algorithm that can accurately reconstruct details of localized source activity from a sparse sampling of the candidate source space. Forward computations are minimized through an adaptive procedure that increases source resolution as the spatial extent is reduced. With this algorithm, we were able to compute inverses using only 6% to 11% of the full resolution lead-field, with a localization accuracy that was not significantly different than an exhaustive search through a fully-sampled source space. The technique is, therefore, applicable for use with anatomically-realistic, subject-specific forward models for applications with spatially concentrated source activity.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Gui -Liang; Sheng, Tian; Chong, Lina

Sodium-ion batteries (SIBs) have been considered as one of the promising power source candidates for the stationary storage industries owing to the much lower cost of sodium than lithium. It is well-known that the electrode materials largely determine the energy density of the battery systems. However, recent discoveries on the electrode materials showed that most of them present distinct lithium and sodium storage performance, which is not yet well understood. In this work, we performed a comparative understanding on the structural changes of porous cobalt oxide during its electrochemical lithiation and sodiation process by in operando synchrotron small angel X-raymore » scattering, X-ray diffraction, and X-ray absorption spectroscopy. It was found that compared to the lithiation process, the porous cobalt oxide undergoes less pore structure changes, oxidation state, and local structure changes as well as crystal structure evolution during its sodiation process, which is attributed to the intrinsic low sodiation activity of cobalt oxide as evidenced by ab initio molecular dynamics simulations. Moreover, it was indicated that the sodiation activity of metal sulfides is higher than that of metal oxides, indicating a better candidate for SIBs. Furthermore, such understanding is crucial for future design and improvement of high-performance electrode materials for SIBs.« less

75 FR 66168 - Seeks Qualified Candidates for the Advisory Committee on Reactor Safeguards

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-27

... NUCLEAR REGULATORY COMMISSION Seeks Qualified Candidates for the Advisory Committee on Reactor... Reactor Safeguards (ACRS). Submit r[eacute]sum[eacute]s to Ms. Brandi Hamilton, ACRS, Mail Stop T2E-26, U... of existing and proposed nuclear power plants and on the adequacy of proposed reactor safety...

Using Content Acquisition Podcasts to Deliver Core Content to Preservice Teacher Candidates

ERIC Educational Resources Information Center

Kennedy, Michael J.; Kellems, Ryan O.; Thomas, Cathy Newman; Newton, Jennifer R.

2015-01-01

Teacher educators are always looking for instructional strategies that are easy to create and use but are powerful for promoting learning among preservice teacher candidates. Content acquisition podcasts (CAPs) is an example of an instructional strategy that embeds evidence-based instructional design principles to package and deliver critical…

GENIE: a software package for gene-gene interaction analysis in genetic association studies using multiple GPU or CPU cores.

PubMed

Chikkagoudar, Satish; Wang, Kai; Li, Mingyao

2011-05-26

Gene-gene interaction in genetic association studies is computationally intensive when a large number of SNPs are involved. Most of the latest Central Processing Units (CPUs) have multiple cores, whereas Graphics Processing Units (GPUs) also have hundreds of cores and have been recently used to implement faster scientific software. However, currently there are no genetic analysis software packages that allow users to fully utilize the computing power of these multi-core devices for genetic interaction analysis for binary traits. Here we present a novel software package GENIE, which utilizes the power of multiple GPU or CPU processor cores to parallelize the interaction analysis. GENIE reads an entire genetic association study dataset into memory and partitions the dataset into fragments with non-overlapping sets of SNPs. For each fragment, GENIE analyzes: 1) the interaction of SNPs within it in parallel, and 2) the interaction between the SNPs of the current fragment and other fragments in parallel. We tested GENIE on a large-scale candidate gene study on high-density lipoprotein cholesterol. Using an NVIDIA Tesla C1060 graphics card, the GPU mode of GENIE achieves a speedup of 27 times over its single-core CPU mode run. GENIE is open-source, economical, user-friendly, and scalable. Since the computing power and memory capacity of graphics cards are increasing rapidly while their cost is going down, we anticipate that GENIE will achieve greater speedups with faster GPU cards. Documentation, source code, and precompiled binaries can be downloaded from http://www.cceb.upenn.edu/~mli/software/GENIE/.

The II Zw 40 Supernebula: 30 Doradus on Steroids

NASA Astrophysics Data System (ADS)

Leitherer, Claus

2015-10-01

We propose COS G140L spectroscopy of the enigmatic nearby blue compact dwarf galaxy II Zw 40. The galaxy hosts a nuclear super star cluster with a luminosity 10 times that of 30 Doradus, the most powerful giant HII region in the Local Group. The super star cluster has been suggested to be the ionizing source of a supernebula detected via its free-free radiation in the radio. The physical conditions, however, are much more complex, as demonstrated by the detection of the nebular He II and the mid-infrared line of [O IV] 25.9. These lines are unlikely to be related to hot stars and require a different powering source. II Zw 40 shares many similarities with the related blue compact dwarfs NGC 5253 and Henize 2-10, both of which have been studied extensively with HST, yet no ultraviolet spectroscopy has ever been obtained for II Zw 40. This small 4-orbit proposal will provide the necessary UV data to study the massive-star content directly. We will determine reddening, age, and the stellar initial mass function and perform a comparison with the local benchmark 30 Doradus. In particular we will investigate whether the hot stars are able to power the supernebula and the nebular high-excitation lines. Our modeling will utilize the latest generation of stellar evolutionary tracks with and without stellar rotation. If the stars fall short in terms of spectral hardness and luminosity, II Zw 40 may become the second candidate for a central black hole in a young starburst after Henize 2-10.

Magnetospheric Gamma-Ray Emission in Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Katsoulakos, Grigorios; Rieger, Frank M.

2018-01-01

The rapidly variable, very high-energy (VHE) gamma-ray emission from active galactic nuclei (AGNs) has been frequently associated with non-thermal processes occurring in the magnetospheres of their supermassive black holes. The present work aims to explore the adequacy of different gap-type (unscreened electric field) models to account for the observed characteristics. Based on a phenomenological description of the gap potential, we estimate the maximum extractable gap power L gap for different magnetospheric setups, and study its dependence on the accretion state of the source. L gap is found in general to be proportional to the Blandford–Znajek jet power L BZ and a sensitive function of gap size h, i.e., {L}{gap}∼ {L}{BZ}{(h/{r}g)}β , where the power index β ≥slant 1 is dependent on the respective gap setup. The transparency of the vicinity of the black hole to VHE photons generally requires a radiatively inefficient accretion environment and thereby imposes constraints on possible accretion rates, and correspondingly on L BZ. Similarly, rapid variability, if observed, may allow one to constrain the gap size h∼ c{{Δ }}t. Combining these constraints, we provide a general classification to assess the likelihood that the VHE gamma-ray emission observed from an AGN can be attributed to a magnetospheric origin. When applied to prominent candidate sources these considerations suggest that the variable (day-scale) VHE activity seen in the radio galaxy M87 could be compatible with a magnetospheric origin, while such an origin appears less likely for the (minute-scale) VHE activity in IC 310.

GENIE: a software package for gene-gene interaction analysis in genetic association studies using multiple GPU or CPU cores

PubMed Central

2011-01-01

Background Gene-gene interaction in genetic association studies is computationally intensive when a large number of SNPs are involved. Most of the latest Central Processing Units (CPUs) have multiple cores, whereas Graphics Processing Units (GPUs) also have hundreds of cores and have been recently used to implement faster scientific software. However, currently there are no genetic analysis software packages that allow users to fully utilize the computing power of these multi-core devices for genetic interaction analysis for binary traits. Findings Here we present a novel software package GENIE, which utilizes the power of multiple GPU or CPU processor cores to parallelize the interaction analysis. GENIE reads an entire genetic association study dataset into memory and partitions the dataset into fragments with non-overlapping sets of SNPs. For each fragment, GENIE analyzes: 1) the interaction of SNPs within it in parallel, and 2) the interaction between the SNPs of the current fragment and other fragments in parallel. We tested GENIE on a large-scale candidate gene study on high-density lipoprotein cholesterol. Using an NVIDIA Tesla C1060 graphics card, the GPU mode of GENIE achieves a speedup of 27 times over its single-core CPU mode run. Conclusions GENIE is open-source, economical, user-friendly, and scalable. Since the computing power and memory capacity of graphics cards are increasing rapidly while their cost is going down, we anticipate that GENIE will achieve greater speedups with faster GPU cards. Documentation, source code, and precompiled binaries can be downloaded from http://www.cceb.upenn.edu/~mli/software/GENIE/. PMID:21615923

VizieR Online Data Catalog: 231 AGN candidates from the 2FGL catalog (Doert+, 2014)

NASA Astrophysics Data System (ADS)

Doert, M.; Errando, M.

2016-01-01

The second Fermi-LAT source catalog (2FGL; Nolan et al. 2012, cat. J/ApJS/199/31) is the deepest all-sky survey available in the gamma-ray band. It contains 1873 sources, of which 576 remain unassociated. The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope started operations in 2008. In this work, machine-learning algorithms are used to identify unassociated sources in the 2FGL catalog with properties similar to gamma-ray-emitting Active Galactic Nuclei (AGN). This analysis finds 231 high-confidence AGN candidates (see Table3). (1 data file).

Reconstructing gravitational wave source parameters via direct comparisons to numerical relativity II: Applications

NASA Astrophysics Data System (ADS)

O'Shaughnessy, Richard; Lange, Jacob; Healy, James; Carlos, Lousto; Shoemaker, Deirdre; Lovelace, Geoffrey; Scheel, Mark

2016-03-01

In this talk, we apply a procedure to reconstruct the parameters of sufficiently massive coalescing compact binaries via direct comparison with numerical relativity simulations. We illustrate how to use only comparisons between synthetic data and these simulations to reconstruct properties of a synthetic candidate source. We demonstrate using selected examples that we can reconstruct posterior distributions obtained by other Bayesian methods with our sparse grid. We describe how followup simulations can corroborate and improve our understanding of a candidate signal.

Power management system

DOEpatents

Algrain, Marcelo C.; Johnson, Kris W.; Akasam, Sivaprasad; Hoff, Brian D.

2007-10-02

A method of managing power resources for an electrical system of a vehicle may include identifying enabled power sources from among a plurality of power sources in electrical communication with the electrical system and calculating a threshold power value for the enabled power sources. A total power load placed on the electrical system by one or more power consumers may be measured. If the total power load exceeds the threshold power value, then a determination may be made as to whether one or more additional power sources is available from among the plurality of power sources. At least one of the one or more additional power sources may be enabled, if available.

Anion permselective membrane

NASA Technical Reports Server (NTRS)

Alexander, S.; Hodgdon, R. B.

1977-01-01

The objective of NAS 3-20108 was the development and evaluation of improved anion selective membranes useful as efficient separators in a redox power storage cell system being constructed. The program was divided into three parts, (a) optimization of the selected candidate membrane systems, (b) investigation of alternative membrane/polymer systems, and (c) characterization of candidate membranes. The major synthesis effort was aimed at improving and optimizing as far as possible each candidate system with respect to three critical membrane properties essential for good redox cell performance. Substantial improvements were made in 5 candidate membrane systems. The critical synthesis variables of cross-link density, monomer ratio, and solvent composition were examined over a wide range. In addition, eight alternative polymer systems were investigated, two of which attained candidate status. Three other alternatives showed potential but required further research and development. Each candidate system was optimized for selectivity.

SETI Searches for Radio Transients from Kepler Field Planets and Astropulse Candidates

NASA Astrophysics Data System (ADS)

Gautam, Abhimat Krishna; Siemion, Andrew; Korpela, Eric J.; Cobb, Jeff; Lebofsky, Matt; Werthimer, Dan

2014-06-01

We present a search for fast radio transients in targeted observations of planet candidates in the Kepler Field and candidate Astropulse sources.Kepler Field observations were conducted in the band 1.1 and 1.9 GHz using the Green Bank Telescope in Green Bank, West Virginia and are centered on 86 stars hosting candidate planets identified by the Kepler spacecraft. These stars were chosen based on the properties of their putative planetary system thought to be conducive to the development of advanced life, including all systems known (as of May 2011) hosting a Kepler Object of Interest (KOI) with a calculated equilibrium temperature between 230 and 380 K, at least 4 KOIs or a KOI with an inferred radius < 3.0 r_earth and a period > 50 d. The Kepler Field is centered at an intermediate galactic latitude, b = 13.5°, which presents an additional opportunity to detect signals from the older population of millisecond and recycled pulsars located above the galactic plane.The Astropulse radio survey searches for brief wide-band pulses in a 2.5 MHz band centered at 1420 MHz using commensal data recorded from the Arecibo ALFA receiver. In early Astropulse analysis, 108 candidate sources were identified that passed a series of tests designed to eliminate potential sources of radio frequency interference (RFI). We have performed targeted re-observations of these sources at Arecibo over the full (1214-1536 MHz) ALFA band.We have developed a software pipeline to locate fast dispersed transients in these observations, leveraging components of the PRESTO software library. This pipeline consists of finding and removing RFI, conducting de-dispersion to remove the effects of dispersion from the interstellar medium (ISM) on the signal and identifying over- threshold events. We also perform de-dispersion at negative dispersion measures, proposed to be a potential technique for intelligent civilizations to distinguish their emission from natural sources. We carry out both a periodicity and single-pulse search on de-dispersed time series. The outputs from these steps are examined to look for both technological and astrophysical sources of impulsive radio emission.

Fusible heat sink materials - An identification of alternate candidates. [for astronaut thermoregulation in EVA portable life support systems

NASA Technical Reports Server (NTRS)

Selvaduray, Guna; Lomax, Curtis

1991-01-01

Fusible heat sinks are a possible source for thermal regulation of space suited astronauts. An extensive database search was undertaken to identify candidate materials with liquid solid transformations over the temperature range of -18 C to 5 C; and 1215 candidates were identified. Based on available data, 59 candidate materials with thermal storage capability, DeltaH values higher than that of water were identified. This paper presents the methodology utilized in the study, including the decision process used for materials selection.

Herschel Key Program Heritage: a Far-Infrared Source Catalog for the Magellanic Clouds

NASA Astrophysics Data System (ADS)

Seale, Jonathan P.; Meixner, Margaret; Sewiło, Marta; Babler, Brian; Engelbracht, Charles W.; Gordon, Karl; Hony, Sacha; Misselt, Karl; Montiel, Edward; Okumura, Koryo; Panuzzo, Pasquale; Roman-Duval, Julia; Sauvage, Marc; Boyer, Martha L.; Chen, C.-H. Rosie; Indebetouw, Remy; Matsuura, Mikako; Oliveira, Joana M.; Srinivasan, Sundar; van Loon, Jacco Th.; Whitney, Barbara; Woods, Paul M.

2014-12-01

Observations from the HERschel Inventory of the Agents of Galaxy Evolution (HERITAGE) have been used to identify dusty populations of sources in the Large and Small Magellanic Clouds (LMC and SMC). We conducted the study using the HERITAGE catalogs of point sources available from the Herschel Science Center from both the Photodetector Array Camera and Spectrometer (PACS; 100 and 160 μm) and Spectral and Photometric Imaging Receiver (SPIRE; 250, 350, and 500 μm) cameras. These catalogs are matched to each other to create a Herschel band-merged catalog and then further matched to archival Spitzer IRAC and MIPS catalogs from the Spitzer Surveying the Agents of Galaxy Evolution (SAGE) and SAGE-SMC surveys to create single mid- to far-infrared (far-IR) point source catalogs that span the wavelength range from 3.6 to 500 μm. There are 35,322 unique sources in the LMC and 7503 in the SMC. To be bright in the FIR, a source must be very dusty, and so the sources in the HERITAGE catalogs represent the dustiest populations of sources. The brightest HERITAGE sources are dominated by young stellar objects (YSOs), and the dimmest by background galaxies. We identify the sources most likely to be background galaxies by first considering their morphology (distant galaxies are point-like at the resolution of Herschel) and then comparing the flux distribution to that of the Herschel Astrophysical Terahertz Large Area Survey (ATLAS) survey of galaxies. We find a total of 9745 background galaxy candidates in the LMC HERITAGE images and 5111 in the SMC images, in agreement with the number predicted by extrapolating from the ATLAS flux distribution. The majority of the Magellanic Cloud-residing sources are either very young, embedded forming stars or dusty clumps of the interstellar medium. Using the presence of 24 μm emission as a tracer of star formation, we identify 3518 YSO candidates in the LMC and 663 in the SMC. There are far fewer far-IR bright YSOs in the SMC than the LMC due to both the SMC's smaller size and its lower dust content. The YSO candidate lists may be contaminated at low flux levels by background galaxies, and so we differentiate between sources with a high (“probable”) and moderate (“possible”) likelihood of being a YSO. There are 2493/425 probable YSO candidates in the LMC/SMC. Approximately 73% of the Herschel YSO candidates are newly identified in the LMC, and 35% in the SMC. We further identify a small population of dusty objects in the late stages of stellar evolution including extreme and post-asymptotic giant branch, planetary nebulae, and supernova remnants. These populations are identified by matching the HERITAGE catalogs to lists of previously identified objects in the literature. Approximately half of the LMC sources and one quarter of the SMC sources are too faint to obtain accurate ample FIR photometry and are unclassified.

Mode Engineering of Single Photons from Cavity Spontaneous Parametric Down-Conversion Source and Quantum Dots

NASA Astrophysics Data System (ADS)

Paudel, Uttam

Over the past decade, much effort has been made in identifying and characterizing systems that can form a building block of quantum networks, among which semiconductor quantum dots (QD) and spontaneous parametric down-conversion (SPDC) source are two of the most promising candidates. The work presented in this thesis will be centered on investigating and engineering the mentioned systems for generating customizable single photons. A type-II SPDC source can generate a highly flexible pair of entangled photons that can be used to interface disparate quantum systems. In this thesis, we have successfully implemented a cavity-SPDC source that emits polarization correlated photons at 942 nm with a lifetime of 950-1050ps that mode matches closely with InAs/GaAs QD photons. The source emits 80 photon pairs per second per mW pump power within the 150MHz bandwidth. Though the detection of idler photons, the source is capable of emitting heralded photons with g2?0.5 for up to 40 mW pump power. For a low pump power of 5 mW, the heralded g2 is 0.06, indicating that the system is an excellent heralded single photon source. By directly exciting a single QD with cavity-SPDC photons, we have demonstrated a heralded-absorption of SPDC photons by QD, resulting in the coupling of the two systems. Due to the large pump bandwidth, the emitted source is highly multimode in nature, requiring us to post-filter the downconverted field, resulting in a lower photon pair emission rate. We propose placing an intra-cavity etalon to suppress the multi-mode emissions and increase the photon count rate. Understanding and experimentally implementing two-photon interference (HOM) measurements will be crucial for building a scalable quantum network. A detailed theoretical description of HOM measurements is given and is experimentally demonstrated using photons emitted by QD. Through HOM measurements we demonstrated that the QD sample in the study is capable of emitting indistinguishable photons, with the visibility exceeding 95%. As an alternative approach to modifying the spectral mode of single photons, we performed phase modulation of photons emitted by a QD to generate additional sidebands that are separated by several GHz. By performing HOM measurements, we have shown that the central component and the sidebands are in the superposition states and the spectrally modified photons have a well-preserved indistinguishability. Such spectrally engineered photons can be used for phase-encoded cryptography applications. These experimental results should lay the foundations towards building a scalable hybrid quantum network.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Massaro, F.; D’Abrusco, R.; Paggi, A.

The Fermi-Large Area Telescope (LAT) First Source Catalog (1FGL) was released in 2010 February and the Fermi-LAT 2-Year Source Catalog (2FGL) appeared in 2012 April, based on data from 24 months of operation. Since they were released, many follow up observations of unidentified γ-ray sources have been performed and new procedures for associating γ-ray sources with potential counterparts at other wavelengths have been developed. Here we review and characterize all of the associations as published in the 1FGL and 2FGL catalogs on the basis of multifrequency archival observations. In particular, we located 177 spectra for the low-energy counterparts that weremore » not listed in the previous Fermi catalogs, and in addition we present new spectroscopic observations of eight γ-ray blazar candidates. Based on our investigations, we introduce a new counterpart category of “candidate associations” and propose a refined classification for the candidate low-energy counterparts of the Fermi sources. We compare the 1FGL-assigned counterparts with those listed in 2FGL to determine which unassociated sources became associated in later releases of the Fermi catalogs. We also search for potential counterparts to all of the remaining unassociated Fermi sources. Finally, we prepare a refined and merged list of all of the associations of 1FGL plus 2FGL that includes 2219 unique Fermi objects. This is the most comprehensive and systematic study of all the associations collected for the γ-ray sources available to date. We conclude that 80% of the Fermi sources have at least one known plausible γ-ray emitter within their positional uncertainty regions.« less

What can the SEDs of first hydrostatic core candidates reveal about their nature?

NASA Astrophysics Data System (ADS)

Young, Alison K.; Bate, Matthew R.; Mowat, Chris F.; Hatchell, Jennifer; Harries, Tim J.

2018-02-01

The first hydrostatic core (FHSC) is the first stable object to form in simulations of star formation. This stage has yet to be observed definitively, although several candidate FHSCs have been reported. We have produced synthetic spectral energy distributions (SEDs) from 3D hydrodynamical simulations of pre-stellar cores undergoing gravitational collapse for a variety of initial conditions. Variations in the initial rotation rate, radius and mass lead to differences in the location of the SED peak and far-infrared flux. Secondly, we attempt to fit the SEDs of five FHSC candidates from the literature and five newly identified FHSC candidates located in the Serpens South molecular cloud with simulated SEDs. The most promising FHSC candidates are fitted by a limited number of model SEDs with consistent properties, which suggests that the SED can be useful for placing constraints on the age and rotation rate of the source. The sources we consider most likely to be in FHSC phase are B1-bN, CB17-MMS, Aqu-MM1 and Serpens South candidate K242. We were unable to fit SerpS-MM22, Per-Bolo 58 and Chamaeleon-MMS1 with reasonable parameters, which indicates that they are likely to be more evolved.

Restrictive loads powered by separate or by common electrical sources

NASA Technical Reports Server (NTRS)

Appelbaum, J.

1989-01-01

In designing a multiple load electrical system, the designer may wish to compare the performance of two setups: a common electrical source powering all loads, or separate electrical sources powering individual loads. Three types of electrical sources: an ideal voltage source, an ideal current source, and solar cell source powering resistive loads were analyzed for their performances in separate and common source systems. A mathematical proof is given, for each case, indicating the merit of the separate or common source system. The main conclusions are: (1) identical resistive loads powered by ideal voltage sources perform the same in both system setups, (2) nonidentical resistive loads powered by ideal voltage sources perform the same in both system setups, (3) nonidentical resistive loads powered by ideal current sources have higher performance in separate source systems, and (4) nonidentical resistive loads powered by solar cells have higher performance in a common source system for a wide range of load resistances.

A GeV Source in the Direction of Supernova Remnant CTB 37B

NASA Astrophysics Data System (ADS)

Xin, Yu-Liang; Liang, Yun-Feng; Li, Xiang; Yuan, Qiang; Liu, Si-Ming; Wei, Da-Ming

2016-01-01

Supernova remnants (SNRs) are the most attractive candidates for the acceleration sites of Galactic cosmic rays. We report the detection of GeV γ-ray emission with the Pass 8 events recorded by the Fermi Large Area Telescope (Fermi-LAT) in the vicinity of the shell-type SNR CTB 37B that is likely associated with the TeV γ-ray source HESS J1713-381. The photon spectrum of CTB 37B is consistent with a power law with an index of 1.89 ± 0.08 in the energy range of 0.5-500 GeV, and the measured flux connects smoothly with that of HESS J1713-381 at a few hundred GeV. No significant spatial extension and time variation are detected. The multi-wavelength data can be well fitted with either a leptonic model or a hadronic one. However, parameters of both models suggest more efficient particle acceleration than typical SNRs. Meanwhile, the X-ray and γ-ray spectral properties of CTB 37B show that it is an interesting source bridging young SNRs dominated by non-thermal emission and old SNRs interacting with molecular clouds.

Detection of potential periodicities in the unique hard X-ray source Swift J0042.6+4112, dominating the hard X-ray emission in M31

NASA Astrophysics Data System (ADS)

Yukita, Mihoko; Tzanavaris, Panayiotis; Corbet, Robin; Ptak, Andrew; Hornschemeier, Ann; Pottschmidt, Katja; Ballhausen, Ralf; Enoto, Teruaki; Antoniou, Vallia; Lehmer, Bret; Maccarone, Thomas J.; Wik, Daniel; Williams, Ben; Zezas, Andreas

2018-01-01

Recent NuSTAR-Swift observations revealed that a single resolved X-ray source, Swift J0042.6+4112, with Lx of a few times 1038 erg/s dominates the hard X-ray emission from the Andromeda galaxy. HST-based stellar population synthesis modeling combined with the 0.5-50 keV spectral shape suggests that this might be an X-ray pulsar with an intermediate- (or low-) mass donor. Here we further explore the alternative scenario of a symbiotic or ultracompact X-ray binary, based on long-term variability from Swift observations between 2005 and 2016. We find that the soft (0.3-8.0 keV) X-ray flux varies within a factor of 4 but does not exhibit transient behavior. Its power spectrum suggests a 6.1-day period. Additionally, we find a strong 3s-period candidate from both NuSTAR and XMM observations taken in 2017. If interpreted as an orbital and spin period respectively, the source's temporal behavior would not support either the symbiotic or the ultracompact X-ray binary scenario. Rather, it is more consistent with an accreting pulsar with a higher mass donor.

Neutrino diagnostics of ultrahigh energy cosmic ray protons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahlers, Markus; Sarkar, Subir; Anchordoqui, Luis A.

2009-04-15

The energy at which cosmic rays from extra-galactic sources begin to dominate over those from galactic sources is an important open question in astroparticle physics. A natural candidate is the energy at the 'ankle' in the approximately power-law energy spectrum which is indicative of a crossover from a falling galactic component to a flatter extra-galactic component. The transition can occur without such flattening but this requires some degree of conspiracy of the spectral shapes and normalizations of the two components. Nevertheless, it has been argued that extra-galactic sources of cosmic ray protons that undergo interactions on the CMB can reproducemore » the energy spectrum below the ankle if the crossover energy is as low as the 'second knee' in the spectrum. This low crossover model is constrained by direct measurements by the Pierre Auger Observatory, which indicate a heavier composition at these energies. We demonstrate that upper limits on the cosmic diffuse neutrino flux provide a complementary constraint on the proton fraction in ultra-high energy extra-galactic cosmic rays and forthcoming data from IceCube will provide a definitive test of this model.« less

Gas Composition Sensing Using Carbon Nanotube Arrays

NASA Technical Reports Server (NTRS)

Li, Jing; Meyyappan, Meyya

2012-01-01

This innovation is a lightweight, small sensor for inert gases that consumes a relatively small amount of power and provides measurements that are as accurate as conventional approaches. The sensing approach is based on generating an electrical discharge and measuring the specific gas breakdown voltage associated with each gas present in a sample. An array of carbon nanotubes (CNTs) in a substrate is connected to a variable-pulse voltage source. The CNT tips are spaced appropriately from the second electrode maintained at a constant voltage. A sequence of voltage pulses is applied and a pulse discharge breakdown threshold voltage is estimated for one or more gas components, from an analysis of the current-voltage characteristics. Each estimated pulse discharge breakdown threshold voltage is compared with known threshold voltages for candidate gas components to estimate whether at least one candidate gas component is present in the gas. The procedure can be repeated at higher pulse voltages to estimate a pulse discharge breakdown threshold voltage for a second component present in the gas. The CNTs in the gas sensor have a sharp (low radius of curvature) tip; they are preferably multi-wall carbon nanotubes (MWCNTs) or carbon nanofibers (CNFs), to generate high-strength electrical fields adjacent to the tips for breakdown of the gas components with lower voltage application and generation of high current. The sensor system can provide a high-sensitivity, low-power-consumption tool that is very specific for identification of one or more gas components. The sensor can be multiplexed to measure current from multiple CNT arrays for simultaneous detection of several gas components.

QPOs from Random X-ray Bursts around Rotating Black Holes

NASA Technical Reports Server (NTRS)

Kukumura, Keigo; Kazanas, Demosthenes; Stephenson, Gordon

2009-01-01

We continue our earlier studies of quasi-periodic oscillations (QPOs) in the power spectra of accreting, rapidly-rotating black holes that originate from the geometric 'light echoes' of X-ray flares occurring within the black hole ergosphere. Our present work extends our previous treatment to three-dimensional photon emission and orbits to allow for arbitrary latitudes in the positions of the distant observers and the X-ray sources in place of the mainly equatorial positions and photon orbits of the earlier consideration. Following the trajectories of a large number of photons we calculate the response functions of a given geometry and use them to produce model light curves which we subsequently analyze to compute their power spectra and autocorrelation functions. In the case of an optically-thin environment, relevant to advection-dominated accretion flows, we consistently find QPOs at frequencies of order of approximately kHz for stellar-mass black hole candidates while order of approximately mHz for typical active galactic nuclei (approximately equal to 10(exp 7) solar mass) for a wide range of viewing angles (30 degrees to 80 degrees) from X-ray sources predominantly concentrated toward the equator within the ergosphere. As in out previous treatment, here too, the QPO signal is produced by the frame-dragging of the photons by the rapidly-rotating black hole, which results in photon 'bunches' separated by constant time-lags, the result of multiple photon orbits around the hole. Our model predicts for various source/observer configurations the robust presence of a new class of QPOs, which is inevitably generic to curved spacetime structure in rotating black hole systems.

A low-luminosity soft state in the short-period black hole X-ray binary Swift J1753.5-0127

NASA Astrophysics Data System (ADS)

Shaw, A. W.; Gandhi, P.; Altamirano, D.; Uttley, P.; Tomsick, J. A.; Charles, P. A.; Fürst, F.; Rahoui, F.; Walton, D. J.

2016-05-01

We present results from the spectral fitting of the candidate black hole X-ray binary Swift J1753.5-0127 in an accretion state previously unseen in this source. We fit the 0.7-78 keV spectrum with a number of models, however the preferred model is one of a multitemperature disc with an inner disc temperature kTin = 0.252 ± 0.003 keV scattered into a steep power-law with photon index Γ =6.39^{+0.08}_{-0.02} and an additional hard power-law tail (Γ = 1.79 ± 0.02). We report on the emergence of a strong disc-dominated component in the X-ray spectrum and we conclude that the source has entered the soft state for the first time in its ˜10 yr prolonged outburst. Using reasonable estimates for the distance to the source (3 kpc) and black hole mass (5 M⊙), we find the unabsorbed luminosity (0.1-100 keV) to be ≈0.60 per cent of the Eddington luminosity, making this one of the lowest luminosity soft states recorded in X-ray binaries. We also find that the accretion disc extended towards the compact object during its transition from hard to soft, with the inner radius estimated to be R_{in}=28.0^{+0.7}_{-0.4} R_g or ˜12Rg, dependent on the boundary condition chosen, assuming the above distance and mass, a spectral hardening factor f = 1.7 and a binary inclination I = 55°.

Galactic Sources Detected in the NuSTAR Serendipitous Survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tomsick, John A.; Clavel, Maïca; Chiu, Jeng-Lun

The Nuclear Spectroscopic Telescope Array (NuSTAR) provides an improvement in sensitivity at energies above 10 keV by two orders of magnitude over non-focusing satellites, making it possible to probe deeper into the Galaxy and universe. Lansbury and collaborators recently completed a catalog of 497 sources serendipitously detected in the 3–24 keV band using 13 deg{sup 2} of NuSTAR coverage. Here, we report on an optical and X-ray study of 16 Galactic sources in the catalog. We identify 8 of them as stars (but some or all could have binary companions), and use information from Gaia to report distances and X-ray luminositiesmore » for 3 of them. There are 4 CVs or CV candidates, and we argue that NuSTAR J233426–2343.9 is a relatively strong CV candidate based partly on an X-ray spectrum from XMM-Newton . NuSTAR J092418–3142.2, which is the brightest serendipitous source in the Lansbury catalog, and NuSTAR J073959–3147.8 are low-mass X-ray binary candidates, but it is also possible that these 2 sources are CVs. One of the sources is a known high-mass X-ray binary (HMXB), and NuSTAR J105008–5958.8 is a new HMXB candidate that has strong Balmer emission lines in its optical spectrum and a hard X-ray spectrum. We discuss the implications of finding these HMXBs for the surface density (log N –log S ) and luminosity function of Galactic HMXBs. We conclude that with the large fraction of unclassified sources in the Galactic plane detected by NuSTAR in the 8–24 keV band, there could be a significant population of low-luminosity HMXBs.« less

Main drive selection for the Windstorm Simulation Center

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lacy, J.M.; Earl, J.S.

1998-02-01

Operated by the Partnership for Natural Disaster Reduction, the Windstorm Simulation Center (WSC) will be a structural test center dedicated to studying the performance of civil structural systems subjected to hurricanes, tornadoes, and other storm winds. Within the WSC, a bank of high-power fans, the main drive, will produce the high velocity wind necessary to reproduce these storms. Several options are available for the main drive, each with advantages and liabilities. This report documents a study to identify and evaluate all candidates available, and to select the most promising system such that the best possible combination of real-world performance attributesmore » is achieved at the best value. Four broad classes of candidate were identified: electric motors, turbofan aircraft engines, turboshaft aircraft engines, and turboshaft industrial engines. Candidate systems were evaluated on a basis of technical feasibility, availability, power, installed cost, and operating cost.« less

The 25 kW power module evolution study. Part 3: Conceptual designs for power module evolution. Volume 1: Power module evolution

NASA Technical Reports Server (NTRS)

1979-01-01

Candidate power module confugurations which will directly support an evolutionary scenario allowing growth from 25 kW to 100 kW are described. The growth rationale is structured to support a nominal scenario for sortie mission support to the POrbiter and to free-flying payloads during the 1983 to 1990 era.

Colombia - A Case Study in Smart Power

DTIC Science & Technology

2014-05-22

COLOMBIA–A CASE STUDY IN SMART POWER A Monograph by John P. Brady Foreign Service Officer United States Agency for...Colombia–A Case Study in Smart Power 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) John P. Brady...of Candidate: John P. Brady Monograph Title: Colombia–A Case Study in Smart Power Approved by: , Monograph Director Robert W

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seale, Jonathan P.; Meixner, Margaret; Sewiło, Marta

Observations from the HERschel Inventory of the Agents of Galaxy Evolution (HERITAGE) have been used to identify dusty populations of sources in the Large and Small Magellanic Clouds (LMC and SMC). We conducted the study using the HERITAGE catalogs of point sources available from the Herschel Science Center from both the Photodetector Array Camera and Spectrometer (PACS; 100 and 160 μm) and Spectral and Photometric Imaging Receiver (SPIRE; 250, 350, and 500 μm) cameras. These catalogs are matched to each other to create a Herschel band-merged catalog and then further matched to archival Spitzer IRAC and MIPS catalogs from themore » Spitzer Surveying the Agents of Galaxy Evolution (SAGE) and SAGE-SMC surveys to create single mid- to far-infrared (far-IR) point source catalogs that span the wavelength range from 3.6 to 500 μm. There are 35,322 unique sources in the LMC and 7503 in the SMC. To be bright in the FIR, a source must be very dusty, and so the sources in the HERITAGE catalogs represent the dustiest populations of sources. The brightest HERITAGE sources are dominated by young stellar objects (YSOs), and the dimmest by background galaxies. We identify the sources most likely to be background galaxies by first considering their morphology (distant galaxies are point-like at the resolution of Herschel) and then comparing the flux distribution to that of the Herschel Astrophysical Terahertz Large Area Survey (ATLAS) survey of galaxies. We find a total of 9745 background galaxy candidates in the LMC HERITAGE images and 5111 in the SMC images, in agreement with the number predicted by extrapolating from the ATLAS flux distribution. The majority of the Magellanic Cloud-residing sources are either very young, embedded forming stars or dusty clumps of the interstellar medium. Using the presence of 24 μm emission as a tracer of star formation, we identify 3518 YSO candidates in the LMC and 663 in the SMC. There are far fewer far-IR bright YSOs in the SMC than the LMC due to both the SMC's smaller size and its lower dust content. The YSO candidate lists may be contaminated at low flux levels by background galaxies, and so we differentiate between sources with a high (“probable”) and moderate (“possible”) likelihood of being a YSO. There are 2493/425 probable YSO candidates in the LMC/SMC. Approximately 73% of the Herschel YSO candidates are newly identified in the LMC, and 35% in the SMC. We further identify a small population of dusty objects in the late stages of stellar evolution including extreme and post-asymptotic giant branch, planetary nebulae, and supernova remnants. These populations are identified by matching the HERITAGE catalogs to lists of previously identified objects in the literature. Approximately half of the LMC sources and one quarter of the SMC sources are too faint to obtain accurate ample FIR photometry and are unclassified.« less

3FGLzoo: classifying 3FGL unassociated Fermi-LAT γ-ray sources by artificial neural networks

NASA Astrophysics Data System (ADS)

Salvetti, D.; Chiaro, G.; La Mura, G.; Thompson, D. J.

2017-09-01

In its first four years of operation, the Fermi-Large Area Telescope (LAT) detected 3033 γ-ray emitting sources. In the Fermi-LAT Third Source Catalogue (3FGL) about 50 per cent of the sources have no clear association with a likely γ-ray emitter. We use an artificial neural network algorithm aimed at distinguishing BL Lacs from FSRQs to investigate the source subclass of 559 3FGL unassociated sources characterized by γ-ray properties very similar to those of active galactic nuclei. Based on our method, we can classify 271 objects as BL Lac candidates, 185 as FSRQ candidates, leaving only 103 without a clear classification. We suggest a new zoo for γ-ray objects, where the percentage of sources of uncertain type drops from 52 per cent to less than 10 per cent. The result of this study opens up new considerations on the population of the γ-ray sky, and it will facilitate the planning of significant samples for rigorous analyses and multiwavelength observational campaigns.

X-Ray Source Populations in Galaxies Giuseppina Fabbiano

NASA Technical Reports Server (NTRS)

Fabbiano, Giuseppina

1997-01-01

The talk will review the present results on X-ray sources in external galaxies, with particular emphasis on black hole candidates and supersoft sources. These sources will be excellent AXAF targets and it is important that we summarize our knowledge and open issues in time for the AXAF NRA.

MPGD2015: Low-energy electron source to characterize Micromegas/InGrid and study of dE/dx for low energy electrons

NASA Astrophysics Data System (ADS)

Attie, David; Barsuk, Sergey; Bezshyyko, Oleg; Burmistrov, Leonid; Chaus, Andrii; Colas, Paul; Fedorchuk, Oleksii; Golinka-Bezshyyko, Larisa; Haranko, Mykyta; Krylov, Vladyslav; Kubytskyi, Viacheslav; Lopez, Roberto; Monard, Hugues; Sukhonos, Daniil; Titov, Maxim; Tomassini, Davide; Variola, Alessandro; Rodin, Volodymyr

2018-02-01

Insert your english abstract here.A new versatile facility LEETECH for detector R&D, tests and calibration is designed and constructed. It uses electrons produced by the photoinjector PHIL at LAL, Orsay and provides a powerful tool for wide range R&D studies of different detector concepts delivering "monochromatic" samples of low energy electrons with adjustable energy and intensity. Among other innovative instrumentation techniques, LEETECH will be used for testing various gaseous tracking detectors and studying new Micromegas/InGrid concept which has very promising characteristics of spatial resolution and can be a good candidate for particle tracking and identification. In this paper the importance and expected characteristics of such facility based on detailed simulation studies are addressed.

SEARCHES FOR MILLISECOND PULSAR CANDIDATES AMONG THE UNIDENTIFIED FERMI OBJECTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hui, C. Y.; Park, S. M.; Hu, C. P.

2015-08-10

Here we report the results of searching millisecond pulsar (MSP) candidates from the Fermi LAT second source catalog (2FGL). Seven unassociated γ-ray sources in this catalog are identified as promising MSP candidates based on their γ-ray properties. Through the X-ray analysis, we have detected possible X-ray counterparts, localized to an arcsecond accuracy. We have systematically estimated their X-ray fluxes and compared them with the corresponding γ-ray fluxes. The X-ray to γ-ray flux ratios for 2FGL J1653.6-0159 and 2FGL J1946.4-5402 are comparable with the typical value for pulsars. For 2FGL J1625.2-0020, 2FGL J1653.6-0159, and 2FGL J1946.4-5402, their candidate X-ray counterparts aremore » bright enough to perform a detailed spectral and temporal analysis to discriminate their thermal/non-thermal nature and search for the periodic signal. We have also searched for possible optical/IR counterparts at the X-ray positions. For the optical/IR source coincident with the brightest X-ray object associated with 2FGL J1120.0-2204, its spectral energy distribution is comparable with a late-type star. Evidence for the variability has also been found by examining its optical light curve. All the aforementioned 2FGL sources resemble a pulsar in one or more aspects, making them promising targets for follow-up investigations.« less

Nustar and Chandra Insight into the Nature of the 3-40 Kev Nuclear Emission in Ngc 253

NASA Technical Reports Server (NTRS)

Lehmer, Bret D.; Wik, Daniel R.; Hornschemeier, Ann E.; Ptak, Andrew; Antoniu, V.; Argo, M.K.; Bechtol, K.; Boggs, S.; Christensen, F.E.; Craig, W.W.;

Driven by Power? Probe Question and Presentation Format Effects on Causal Judgment

ERIC Educational Resources Information Center

Perales, Jose C.; Shanks, David R.

2008-01-01

It has been proposed that causal power (defined as the probability with which a candidate cause would produce an effect in the absence of any other background causes) can be intuitively computed from cause-effect covariation information. Estimation of power is assumed to require a special type of counterfactual probe question, worded to remove…

Spectral properties of all-active InP-based microring resonator devices

NASA Astrophysics Data System (ADS)

Kapsalis, A.; Alexandropoulos, D.; Mikroulis, S.; Simos, H.; Stamataki, I.; Syvridis, D.; Hamacher, M.; Troppenz, U.; Heidrich, H.

2006-02-01

Microring resonators are excellent candidates for very large scale photonic integration due to their compactness, and fabrication simplicity. Moreover a wide range of all-optical signal processing functions can be realized due to the resonance effect. Possible applications include filtering, add/drop of optical beams and power switching, as well as more complex procedures including multiplexing, wavelength conversion, and logic operations. All-active ring components based in InGaAsP/InP are possible candidates for laser sources, lossless filters, wavelength converters, etc. Our work is based on measurement, characterization and proposal of possible exploitation of such devices in a variety of applications. We investigate the spectral characteristics of multi-quantum well InGaAsP(λ=1.55μm)/InP microring structures of various ring diameters and different configurations including racetracks with one or two bus waveguides and MMI couplers. The latter configuration has recently exhibited the possibility to obtain tunable active filters as well as tunable laser sources based on all-active ring-bus-coupler structures. In the case of tunable lasers single mode operation has been achieved by obtaining sufficiently high side mode suppression ratio. The tuning capability is attributed to a coupled cavities effect, resembling the case of multi-section DBR lasers. However, in contrast to the latter, the fabrication of microring resonators is considered an easier task, due to a single step growth procedure, although further investigation must be carried out in order to achieve wide range tunability. Detailed mappings of achievable wavelengths are produced for a wide range of injection current values.

Feasibility study on the use of groupware support for NASA source evaluation boards

NASA Technical Reports Server (NTRS)

Bishop, Peter C.; Yoes, Cissy

1991-01-01

Groupware is a class of computer based systems that support groups engaged in a common task (or goal) and that provide an interface to a shared environment. A potential application for groupware is the source evaluation board (SEB) process used in the procurement of government contracts. This study was undertaken to (1) identify parts of the SEB process which are candidates for groupware supports; and (2) identify tools which could be used to support the candidate process. Two processes of the SEB were identified as good candidates for groupware support: (1) document generation - a coordination and communication process required to present and document the findings of an SEB; and (2) group decision making - a highly analytical and integrative decision process requiring a clear and supportable outcome.

Remembering and Voting: Theory and Evidence from Amnesic Patients

PubMed Central

Coronel, Jason C.; Duff, Melissa C.; Warren, David E.; Federmeier, Kara D.; Gonsalves, Brian D.; Tranel, Daniel; Cohen, Neal J.

2013-01-01

One of the most prominent claims to emerge from the field of public opinion is that citizens can vote for candidates whose issue positions best reflect their own beliefs even when they cannot remember previously learned stances associated with the candidates. The current experiment provides a unique and powerful examination of this claim by determining whether individuals with profound amnesia, whose severe memory impairments prevent them from remembering specific issue information associated with any particular candidate, can vote for candidates whose issue positions come closest to their own political views. We report here that amnesic patients, despite not being able to remember any issue information, consistently voted for candidates with favored political positions. Thus, sound voting decisions do not require recall or recognition of previously learned associations between candidates and their issue positions. This result supports a multiple memory systems model of political decision making. PMID:24511170

Improved OSC Amtec generator design to meet goals of JPL's candidate Europa Orbiter mission

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schock, A.; Noravian, H.; Or, C.

1998-07-01

The preceding paper (Paper IECEC.98.244) described OSC's initial designs of AMTEC (Alkali Metal Thermal-to-Electrical Conversion) power systems, consisting of one or two generators, each with 2, 3, or 4 General Purpose Heat Source (GPHS) modules and with 16 refractory AMTEC cells containing 5 Beta Alumina Solid Electrolyte (BASE) tubes; and presented the effect of heat input and voltage output on the generator's BOM evaporator and clad temperatures and on its EOM system efficiency and power output. Comparison of the computed results with JPL's goals for the Europa Orbiter mission showed that all of the initial 16-cell design options yielded eithermore » excessive evaporator and clad temperatures or insufficient EOM power to satisfy the JPL-specified mission goals. The present paper describes modified OSC generator designs with different numbers of AMTEC cells, cell diameters, cell lengths, cell materials, BASE tube lengths, and number of tubes per cell. These efforts succeeded in identifying generator designs with only half the number of AMTEC cells which -- for the same assumptions -- can produce EOM power outputs substantially in excess of JPL's goals for NASA's Europa Orbiter mission while operating well below the prescribed BOM limits on evaporator and clad temperature; and revealed that lowering the emissivity of the generator's housing to raise the cells' condenser temperatures can achieve substantial additional performance improvement. Finally, the paper culminates in programmatic recommendations.« less

Measuring the Spectral Properties of Candidate Mineral Sources of the Venus Radar Anomalies

NASA Astrophysics Data System (ADS)

Kohler, E.; Maturilli, A.; Koulen, J.; Helbert, J.

2016-12-01

Radar mapping of the surface of Venus shows areas of high reflectivity (low emissivity) in the Venusian highlands at altitudes between 2.5-4.75 kilometers. The origin of the radar anomalies found in the highlands remains unclear. Previous experimental research investigated possible materials under simulated Venusian atmospheric and surface conditions, with special emphasis on the combined effect of pressure and temperature, and chemical composition. The results of these studies identified candidate source materials for the radar anomalies. In order to fully be considered a true source candidate the material must have spectroscopic measurements comparable to those measured on the surface of Venus where the high temperature affects spectral characteristics of minerals. The spectroscopic measurements of the previously identified candidate minerals were made at the Planetary Spectroscopy Laboratory (PSL) of DLR in Berlin in an effort to identify the anomaly source. The spectroscopic measurements were made with a FTIR Bruker Vertex 80V evacuated to .1 mbar and using several pairings of detector+beamsplitter to cover the spectral range from 0.2 to 20 µm. Each sample was poured in a stainless steel reflectance cup and measured fresh. Successively each cup was heated (via an induction system) in vacuum (0.07 mbar) at 400°C for 8 hours and measured again in the UV+VIS+MIR spectral range. Three consecutive cycles of heating and measuring reflectance were performed to account for spectral variations arising from the thermal processing of the samples. Heating the samples directly inside the reflectance cups allows to measure every time exactly the same surface, exposed to increasing levels of thermal processing. Results from this study are expected to further constrain the source of the Venus radar anomalies.

Identification of the Hard X-Ray Source Dominating the E > 25 keV Emission of the Nearby Galaxy M31

NASA Technical Reports Server (NTRS)

Yukita, M.; Ptak, A.; Hornschemeier, A. E.; Wik, D.; Maccarone, T.J.; Pottschmidt, Katja; Zezas, A.; Antoniou, V.; Ballhausen, R.; Lehmer, B.D.;

Identification of the Hard X-Ray Source Dominating the E > 25 keV Emission of the Nearby Galaxy M31

NASA Technical Reports Server (NTRS)

Yukita, M.; Ptak, A.; Hornschemeier, A. E.; Wik, D.; Maccarone, T. J.; Pottschmidt, K.; Zezas, A.; Antoniou, V.; Ballhausen, R.; Lehmer, B. D.;

An Overview of Power Capability Requirements for Exploration Missions

NASA Technical Reports Server (NTRS)

Davis, Jose M.; Cataldo, Robert L.; Soeder, James F.; Manzo, Michelle A.; Hakimzadeh, Roshanak

2005-01-01

Advanced power is one of the key capabilities that will be needed to achieve NASA's missions of exploration and scientific advancement. Significant gaps exist in advanced power capabilities that are on the critical path to enabling human exploration beyond Earth orbit and advanced robotic exploration of the solar system. Focused studies and investment are needed to answer key development issues for all candidate technologies before down-selection. The viability of candidate power technology alternatives will be a major factor in determining what exploration mission architectures are possible. Achieving the capabilities needed to enable the CEV, Moon, and Mars missions is dependent on adequate funding. Focused investment in advanced power technologies for human and robotic exploration missions is imperative now to reduce risk and to make informed decisions on potential exploration mission decisions beginning in 2008. This investment would begin the long lead-time needed to develop capabilities for human exploration missions in the 2015 to 2030 timeframe. This paper identifies some of the key technologies that will be needed to fill these power capability gaps. Recommendations are offered to address capability gaps in advanced power for Crew Exploration Vehicle (CEV) power, surface nuclear power systems, surface mobile power systems, high efficiency power systems, and space transportation power systems. These capabilities fill gaps that are on the critical path to enabling robotic and human exploration missions. The recommendations address the following critical technology areas: Energy Conversion, Energy Storage, and Power Management and Distribution.

Corrosion Behavior Of Potential Structural Materials For Use In Nitrate Salts Based Solar Thermal Power Plants

NASA Astrophysics Data System (ADS)

Summers, Kodi

The increasing global demand for electricity is straining current resources of fossil fuels and placing increased pressure on the environment. The implementation of alternative sources of energy is paramount to satisfying global electricity demand while reducing reliance on fossil fuels and lessen the impact on the environment. Concentrated solar power (CSP) plants have the ability to harness solar energy at an efficiency not yet achieved by other technologies designed to convert solar energy to electricity. The problem of intermittency in power production seen with other renewable technologies can be virtually eliminated with the use of molten salt as a heat transfer fluid in CSP plants. Commercial and economic success of CSP plants requires operating at maximum efficiency and capacity which requires high temperature and material reliability. This study investigates the corrosion behavior of structural alloys and electrochemical testing in molten nitrate salts at three temperatures common to CSP plants. Corrosion behavior was evaluated using gravimetric and inductively-coupled plasma optical emission spectroscopy (ICP-OES) analysis. Surface morphology was studied using scanning electron microscopy. Surface oxide structure and chemistry was characterized using X-ray diffraction, Raman spectroscopy, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy. Electrochemical behavior of candidate structural alloys Alloy 4130, austenitic stainless steel 316, and super-austenitic Incoloy 800H was evaluated using potentiodynamic polarization characteristics. It was observed that electrochemical evaluation of these candidate materials correlates well with the corrosion behavior observed from gravimetric and ICP-OES analysis. This study identifies that all three alloys exhibited acceptable corrosion in 300°C molten salt while elevated salt temperatures require the more corrosion resistant alloys, stainless steel 316 and 800H. Characterization of the sample surfaces revealed the presence of spinels at lower temperatures, while Fe2O3 was the dominant iron oxide at higher temperatures for each alloy. It is recommended that accelerated corrosion testing be investigated further to evaluate alloys in other molten salt systems considered for utilization in concentrated solar power plants.

Hybrid power system intelligent operation and protection involving distributed architectures and pulsed loads

NASA Astrophysics Data System (ADS)

Mohamed, Ahmed

Efficient and reliable techniques for power delivery and utilization are needed to account for the increased penetration of renewable energy sources in electric power systems. Such methods are also required for current and future demands of plug-in electric vehicles and high-power electronic loads. Distributed control and optimal power network architectures will lead to viable solutions to the energy management issue with high level of reliability and security. This dissertation is aimed at developing and verifying new techniques for distributed control by deploying DC microgrids, involving distributed renewable generation and energy storage, through the operating AC power system. To achieve the findings of this dissertation, an energy system architecture was developed involving AC and DC networks, both with distributed generations and demands. The various components of the DC microgrid were designed and built including DC-DC converters, voltage source inverters (VSI) and AC-DC rectifiers featuring novel designs developed by the candidate. New control techniques were developed and implemented to maximize the operating range of the power conditioning units used for integrating renewable energy into the DC bus. The control and operation of the DC microgrids in the hybrid AC/DC system involve intelligent energy management. Real-time energy management algorithms were developed and experimentally verified. These algorithms are based on intelligent decision-making elements along with an optimization process. This was aimed at enhancing the overall performance of the power system and mitigating the effect of heavy non-linear loads with variable intensity and duration. The developed algorithms were also used for managing the charging/discharging process of plug-in electric vehicle emulators. The protection of the proposed hybrid AC/DC power system was studied. Fault analysis and protection scheme and coordination, in addition to ideas on how to retrofit currently available protection concepts and devices for AC systems in a DC network, were presented. A study was also conducted on the effect of changing the distribution architecture and distributing the storage assets on the various zones of the network on the system's dynamic security and stability. A practical shipboard power system was studied as an example of a hybrid AC/DC power system involving pulsed loads. Generally, the proposed hybrid AC/DC power system, besides most of the ideas, controls and algorithms presented in this dissertation, were experimentally verified at the Smart Grid Testbed, Energy Systems Research Laboratory. All the developments in this dissertation were experimentally verified at the Smart Grid Testbed.

Biomarker Development for Intraductal Papillary Mucinous Neoplasms Using Multiple Reaction Monitoring Mass Spectrometry.

PubMed

Kim, Yikwon; Kang, MeeJoo; Han, Dohyun; Kim, Hyunsoo; Lee, KyoungBun; Kim, Sun-Whe; Kim, Yongkang; Park, Taesung; Jang, Jin-Young; Kim, Youngsoo

2016-01-04

Intraductal papillary mucinous neoplasm (IPMN) is a common precursor of pancreatic cancer (PC). Much clinical attention has been directed toward IPMNs due to the increase in the prevalence of PC. The diagnosis of IPMN depends primarily on a radiological examination, but the diagnostic accuracy of this tool is not satisfactory, necessitating the development of accurate diagnostic biomarkers for IPMN to prevent PC. Recently, high-throughput targeted proteomic quantification methods have accelerated the discovery of biomarkers, rendering them powerful platforms for the evolution of IPMN diagnostic biomarkers. In this study, a robust multiple reaction monitoring (MRM) pipeline was applied to discovery and verify IPMN biomarker candidates in a large cohort of plasma samples. Through highly reproducible MRM assays and a stringent statistical analysis, 11 proteins were selected as IPMN marker candidates with high confidence in 184 plasma samples, comprising a training (n = 84) and test set (n = 100). To improve the discriminatory power, we constructed a six-protein panel by combining marker candidates. The multimarker panel had high discriminatory power in distinguishing between IPMN and controls, including other benign diseases. Consequently, the diagnostic accuracy of IPMN can be improved dramatically with this novel plasma-based panel in combination with a radiological examination.

Planck intermediate results. XXXIX. The Planck list of high-redshift source candidates

NASA Astrophysics Data System (ADS)

Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Burigana, C.; Butler, R. C.; Calabrese, E.; Catalano, A.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombo, L. P. L.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Dickinson, C.; Diego, J. M.; Dole, H.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Falgarone, E.; Finelli, F.; Flores-Cacho, I.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Galeotta, S.; Galli, S.; Ganga, K.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Hansen, F. K.; Harrison, D. L.; Helou, G.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maggio, G.; Maino, D.; Mandolesi, N.; Mangilli, A.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Melchiorri, A.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Nati, F.; Natoli, P.; Nesvadba, N. P. H.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Pagano, L.; Pajot, F.; Paoletti, D.; Partridge, B.; Pasian, F.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Pettorino, V.; Piacentini, F.; Piat, M.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Pratt, G. W.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savelainen, M.; Savini, G.; Scott, D.; Spencer, L. D.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Türler, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, F.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Welikala, N.; Yvon, D.; Zacchei, A.; Zonca, A.

2016-12-01

The Planck mission, thanks to its large frequency range and all-sky coverage, has a unique potential for systematically detecting the brightest, and rarest, submillimetre sources on the sky, including distant objects in the high-redshift Universe traced by their dust emission. A novel method, based on a component-separation procedure using a combination of Planck and IRAS data, has been validated and characterized on numerous simulations, and applied to select the most luminous cold submillimetre sources with spectral energy distributions peaking between 353 and 857 GHz at 5' resolution. A total of 2151 Planck high-z source candidates (the PHZ) have been detected in the cleanest 26% of the sky, with flux density at 545 GHz above 500 mJy. Embedded in the cosmic infrared background close to the confusion limit, these high-z candidates exhibit colder colours than their surroundings, consistent with redshifts z > 2, assuming a dust temperature of Txgal = 35 K and a spectral index of βxgal = 1.5. Exhibiting extremely high luminosities, larger than 1014L⊙, the PHZ objects may be made of multiple galaxies or clumps at high redshift, as suggested by a first statistical analysis based on a comparison with number count models. Furthermore, first follow-up observations obtained from optical to submillimetre wavelengths, which can be found in companion papers, have confirmed that this list consists of two distinct populations. A small fraction (around 3%) of the sources have been identified as strongly gravitationally lensed star-forming galaxies at redshift 2 to 4, while the vast majority of the PHZ sources appear as overdensities of dusty star-forming galaxies, having colours consistent with being at z > 2, and may be considered as proto-cluster candidates. The PHZ provides an original sample, which is complementary to the Planck Sunyaev-Zeldovich Catalogue (PSZ2); by extending the population of virialized massive galaxy clusters detected below z < 1.5 through their SZ signal to a population of sources at z > 1.5, the PHZ may contain the progenitors of today's clusters. Hence the Planck list of high-redshift source candidates opens a new window on the study of the early stages of structure formation, particularly understanding the intensively star-forming phase at high-z. The catalogue is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/596/A100

Research on power source structure optimization for East China Power Grid

NASA Astrophysics Data System (ADS)

Xu, Lingjun; Sang, Da; Zhang, Jianping; Tang, Chunyi; Xu, Da

2017-05-01

The structure of east china power grid is not reasonable for the coal power takes a much higher proportion than hydropower, at present the coal power takes charge of most peak load regulation, and the pressure of peak load regulation cannot be ignored. The nuclear power, wind power, photovoltaic, other clean energy and hydropower, coal power and wind power from outside will be actively developed in future, which increases the pressure of peak load regulation. According to development of economic and social, Load status and load prediction, status quo and planning of power source and the characteristics of power source, the peak load regulation balance is carried out and put forward a reasonable plan of power source allocation. The ultimate aim is to optimize the power source structure and to provide reference for power source allocation in east china.

TRANSIENT X-RAY SOURCE POPULATION IN THE MAGELLANIC-TYPE GALAXY NGC 55

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jithesh, V.; Wang, Zhongxiang, E-mail: jithesh@shao.ac.cn

2016-04-10

We present the spectral and temporal properties of 15 candidate transient X-ray sources detected in archival XMM-Newton and Chandra observations of the nearby Magellanic-type, SB(s)m galaxy NGC 55. Based on an X-ray color classification scheme, the majority of the sources may be identified as X-ray binaries (XRBs), and six sources are soft, including a likely supernova remnant. We perform a detailed spectral and variability analysis of the data for two bright candidate XRBs. Both sources displayed strong short-term X-ray variability, and their X-ray spectra and hardness ratios are consistent with those of XRBs. These results, combined with their high X-raymore » luminosities (∼10{sup 38} erg s{sup −1}), strongly suggest that they are black hole (BH) binaries. Seven less luminous sources have spectral properties consistent with those of neutron star or BH XRBs in both normal and high-rate accretion modes, but one of them is the likely counterpart to a background galaxy (because of positional coincidence). From our spectral analysis, we find that the six soft sources are candidate super soft sources (SSSs) with dominant emission in the soft (0.3–2 keV) X-ray band. Archival Hubble Space Telescope optical images for seven sources are available, and the data suggest that most of them are likely to be high-mass XRBs. Our analysis has revealed the heterogeneous nature of the transient population in NGC 55 (six high-mass XRBs, one low-mass XRBs, six SSSs, one active galactic nucleus), helping establish the similarity of the X-ray properties of this galaxy to those of other Magellanic-type galaxies.« less

Identification and Classification of Infrared Excess Sources in the Spitzer Enhanced Imaging Products (SEIP) Catalog

NASA Astrophysics Data System (ADS)

Strasburger, David; Gorjian, Varoujan; Burke, Todd; Childs, Linda; Odden, Caroline; Tambara, Kevin; Abate, Antoinette; Akhtar, Nadir; Beach, Skyler; Bhojwani, Ishaan; Brown, Caden; Dear, AnnaMaria; Dumont, Theodore; Harden, Olivia; Joli-Coeur, Laurent; Nahirny, Rachel; Nakahira, Andie; Nix, Sabine; Orgul, Sarp; Parry, Johnny; Picken, John; Taylor, Isabel; Toner, Emre; Turner, Aspen; Xu, Jessica; Zhu, Emily

2015-01-01

The Spitzer Space Telescope's original cryogenic mission imaged roughly 42 million sources, most of which were incidental and never specifically targeted for research. These have now been compiled in the publicly accessible Spitzer Enhanced Imaging Products (SEIP) catalog. The SEIP stores millions of never before examined sources that happened to be in the same field of view as objects specifically selected for study. This project examined the catalog to isolate previously unknown infrared excess (IRXS) candidates. The culling process utilized four steps. First, we considered only those objects with signal to noise ratios of at least 10 to 1 in the following five wavelengths: 3.6, 4.5, 5.8, 8 and 24 microns, which narrowed the source list to about one million. Second, objects were removed from highly studied regions, such as the galactic plane and previously conducted infrared surveys. This further reduced the population of sources to 283,758. Third, the remaining sources were plotted using a [3.6]-[4.5] vs. [8]-[24] color-color diagram to isolate IRXS candidates. Fourth, multiple images of sixty-three outlier points from the extrema of the color-color diagram were examined to verify that the sources had been cross matched correctly and to exclude any candidate sources that may have been compromised due to image artifacts or field crowding. The team will ultimately provide statistics for the prevalence of IRXS sources in the SEIP catalog and provide analysis of those extreme outliers from the main locus of points. This research was made possible through the NASA/IPAC Teacher Archive Research Program (NITARP) and was funded by NASA Astrophysics Data Program.

Radioactivity in the galactic plane

NASA Technical Reports Server (NTRS)

Walraven, G. D.; Haymes, R. C.

1976-01-01

The paper reports the detection of a large concentration of interstellar radioactivity during balloon-altitude measurements of gamma-ray energy spectra in the band between 0.02 and 12.27 MeV from galactic and extragalactic sources. Enhanced counting rates were observed in three directions towards the plane of the Galaxy; a power-law energy spectrum is computed for one of these directions (designated B 10). A large statistical deviation from the power law in a 1.0-FWHM interval centered near 1.16 MeV is discussed, and the existence of a nuclear gamma-ray line at 1.15 MeV in B 10 is postulated. It is suggested that Ca-44, which emits gamma radiation at 1.156 MeV following the decay of radioactive Sc-44, is a likely candidate for this line, noting that Sc-44 arises from Ti-44 according to explosive models of supernova nucleosynthesis. The 1.16-MeV line flux inferred from the present data is shown to equal the predicted flux for a supernova at a distance of approximately 3 kpc and an age not exceeding about 100 years.

High-Efficiency Photovoltaic Devices using Trap-Controlled Quantum-Dot Ink prepared via Phase-Transfer Exchange.

PubMed

Aqoma, Havid; Al Mubarok, Muhibullah; Hadmojo, Wisnu Tantyo; Lee, Eun-Hye; Kim, Tae-Wook; Ahn, Tae Kyu; Oh, Seung-Hwan; Jang, Sung-Yeon

2017-05-01

Colloidal-quantum-dot (CQD) photovoltaic devices are promising candidates for low-cost power sources owing to their low-temperature solution processability and bandgap tunability. A power conversion efficiency (PCE) of >10% is achieved for these devices; however, there are several remaining obstacles to their commercialization, including their high energy loss due to surface trap states and the complexity of the multiple-step CQD-layer-deposition process. Herein, high-efficiency photovoltaic devices prepared with CQD-ink using a phase-transfer-exchange (PTE) method are reported. Using CQD-ink, the fabrication of active layers by single-step coating and the suppression of surface trap states are achieved simultaneously. The CQD-ink photovoltaic devices achieve much higher PCEs (10.15% with a certified PCE of 9.61%) than the control devices (7.85%) owing to improved charge drift and diffusion. Notably, the CQD-ink devices show much lower energy loss than other reported high-efficiency CQD devices. This result reveals that the PTE method is an effective strategy for controlling trap states in CQDs. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Design study and performance analysis of 12S-14P field excitation flux switching motor for hybrid electric vehicle

NASA Astrophysics Data System (ADS)

Husin, Zhafir Aizat; Sulaiman, Erwan; Khan, Faisal; Mazlan, Mohamed Mubin Aizat; Othman, Syed Muhammad Naufal Syed

2015-05-01

This paper presents a new structure of 12slot-14pole field excitation flux switching motor (FEFSM) as an alternative candidate of non-Permanent Magnet (PM) machine for HEV drives. Design study, performance analysis and optimization of field excitation flux switching machine with non-rare-earth magnet for hybrid electric vehicle drive applications is done. The stator of projected machine consists of iron core made of electromagnetic steels, armature coils and field excitation coils as the only field mmf source. The rotor is consisted of only stack of iron and hence, it is reliable and appropriate for high speed operation. The design target is a machine with the maximum torque, power and power density, more than 210Nm, 123kW and 3.5kW/kg, respectively, which competes with interior permanent magnet synchronous machine used in existing hybrid electric vehicle. Some design feasibility studies on FEFSM based on 2D-FEA and deterministic optimization method will be applied to design the proposed machine.

Systems and methods for an integrated electrical sub-system powered by wind energy

DOEpatents

Liu, Yan [Ballston Lake, NY; Garces, Luis Jose [Niskayuna, NY

2008-06-24

Various embodiments relate to systems and methods related to an integrated electrically-powered sub-system and wind power system including a wind power source, an electrically-powered sub-system coupled to and at least partially powered by the wind power source, the electrically-powered sub-system being coupled to the wind power source through power converters, and a supervisory controller coupled to the wind power source and the electrically-powered sub-system to monitor and manage the integrated electrically-powered sub-system and wind power system.

Does Professional Development School Preparation Make a Difference? A Comparison of Three Teacher Candidate Studies

ERIC Educational Resources Information Center

Castle, Sharon; Fox, Rebecca K.; Fuhrman, Caroline

2009-01-01

The article compares three replication studies that explore potential differences between teacher candidates trained in professional development schools and those trained in a traditional program. Data sources included student teaching evaluations (analyzed quantitatively) and portfolio reflections, oral and written (analyzed qualitatively). The…

Culturally Responsive Pedagogy for Teacher Candidates of Color in Teacher Education Programs

ERIC Educational Resources Information Center

Gist, Conra D.

2011-01-01

This dissertation study uses culturally responsive pedagogy as a conceptual framework for exploring how teacher educators structure content, pedagogy, and classroom communities for teacher candidates of color at two model teacher education programs. Using multiple data sources including interviews, focus groups, classroom observations, faculty and…

Intelligent power management in a vehicular system with multiple power sources

NASA Astrophysics Data System (ADS)

Murphey, Yi L.; Chen, ZhiHang; Kiliaris, Leonidas; Masrur, M. Abul

This paper presents an optimal online power management strategy applied to a vehicular power system that contains multiple power sources and deals with largely fluctuated load requests. The optimal online power management strategy is developed using machine learning and fuzzy logic. A machine learning algorithm has been developed to learn the knowledge about minimizing power loss in a Multiple Power Sources and Loads (M_PS&LD) system. The algorithm exploits the fact that different power sources used to deliver a load request have different power losses under different vehicle states. The machine learning algorithm is developed to train an intelligent power controller, an online fuzzy power controller, FPC_MPS, that has the capability of finding combinations of power sources that minimize power losses while satisfying a given set of system and component constraints during a drive cycle. The FPC_MPS was implemented in two simulated systems, a power system of four power sources, and a vehicle system of three power sources. Experimental results show that the proposed machine learning approach combined with fuzzy control is a promising technology for intelligent vehicle power management in a M_PS&LD power system.

Teacher Self-Efficacy Perceptions, Learning Oriented Motivation, Lifelong Learning Tendencies of Candidate Teachers: A Modeling Study

ERIC Educational Resources Information Center

Akyol, Bertan

2016-01-01

Problem Statement: While the concept of professional self-efficacy corresponds to the power and belief employees feel related to tasks they are performing, motivation can be defined as the internal energy which shapes work related behaviors of employees positively. Although there are many features that teachers and candidate teachers must have,…

OPTICAL SPECTROSCOPIC OBSERVATIONS OF GAMMA-RAY BLAZAR CANDIDATES. V. TNG, KPNO, AND OAN OBSERVATIONS OF BLAZAR CANDIDATES OF UNCERTAIN TYPE IN THE NORTHERN HEMISPHERE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Álvarez Crespo, N.; Massaro, F.; Masetti, N.

The extragalactic γ-ray sky is dominated by emission from blazars, a peculiar class of active galactic nuclei. Many of the γ-ray sources included in the Fermi-Large Area Telescope Third Source catalog (3FGL) are classified as blazar candidates of uncertain type (BCUs) because there are no optical spectra available in the literature to confirm their nature. In 2013, we started a spectroscopic campaign to look for the optical counterparts of the BCUs and of the unidentified γ-ray sources to confirm their blazar nature. Whenever possible we also determine their redshifts. Here, we present the results of the observations carried out inmore » the northern hemisphere in 2013 and 2014 at the Telescopio Nazionale Galileo, Kitt Peak National Observatory, and Observatorio Astronómico Nacional in San Pedro Mártir. In this paper, we describe the optical spectra of 25 sources. We confirmed that all of the 15 BCUs observed in our campaign and included in our sample are blazars and we estimated the redshifts for three of them. In addition, we present the spectra for three sources classified as BL Lacs in the literature but with no optical spectra available to date. We found that one of them is a quasar (QSO) at a redshift of z = 0.208 and the other two are BL Lacs. Moreover, we also present seven new spectra for known blazars listed in the Roma-BZCAT that have an uncertain redshift or are classified as BL Lac candidates. We found that one of them, 5BZB J0724+2621, is a “changing look” blazar. According to the spectrum available in the literature, it was classified as a BL Lac, but in our observation we clearly detected a broad emission line that led us to classify this source as a QSO at z = 1.17.« less

Advantage of resonant power conversion in aerospace applications

NASA Technical Reports Server (NTRS)

Hansen, I. G.

1983-01-01

An ultrasonic, sinusoidal aerospace power distribution system is shown to have many advantages over other candidate power systems. These advantages include light weight, ease of fault clearing, versatility in handling many loads including motors, and the capability of production within the limits of present technology. References are cited that demonstrate the state of resonant converter technology and support these conclusions.

A Network Selection Algorithm Considering Power Consumption in Hybrid Wireless Networks

NASA Astrophysics Data System (ADS)

Joe, Inwhee; Kim, Won-Tae; Hong, Seokjoon

In this paper, we propose a novel network selection algorithm considering power consumption in hybrid wireless networks for vertical handover. CDMA, WiBro, WLAN networks are candidate networks for this selection algorithm. This algorithm is composed of the power consumption prediction algorithm and the final network selection algorithm. The power consumption prediction algorithm estimates the expected lifetime of the mobile station based on the current battery level, traffic class and power consumption for each network interface card of the mobile station. If the expected lifetime of the mobile station in a certain network is not long enough compared the handover delay, this particular network will be removed from the candidate network list, thereby preventing unnecessary handovers in the preprocessing procedure. On the other hand, the final network selection algorithm consists of AHP (Analytic Hierarchical Process) and GRA (Grey Relational Analysis). The global factors of the network selection structure are QoS, cost and lifetime. If user preference is lifetime, our selection algorithm selects the network that offers longest service duration due to low power consumption. Also, we conduct some simulations using the OPNET simulation tool. The simulation results show that the proposed algorithm provides longer lifetime in the hybrid wireless network environment.

A Catalog Sample of Low-mass Galaxies Observed in X-Rays with Central Candidate Black Holes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nucita, A. A.; Manni, L.; Paolis, F. De

We present a sample of X-ray-selected candidate black holes in 51 low-mass galaxies with z ≤ 0.055 and masses up to 10{sup 10} M {sub ⊙} obtained by cross-correlating the NASA-SLOAN Atlas with the 3XMM catalog. We have also searched in the available catalogs for radio counterparts of the black hole candidates and find that 19 of the previously selected sources also have a radio counterpart. Our results show that about 37% of the galaxies of our sample host an X-ray source (associated with a radio counterpart) spatially coincident with the galaxy center, in agreement with other recent works. Formore » these nuclear sources, the X-ray/radio fundamental plane relation allows one to estimate the mass of the (central) candidate black holes, which are in the range of 10{sup 4}–2 × 10{sup 8} M {sub ⊙} (with a median value of ≃3 × 10{sup 7} M {sub ⊙} and eight candidates having masses below 10{sup 7} M {sub ⊙}). This result, while suggesting that X-ray emitting black holes in low-mass galaxies may have had a key role in the evolution of such systems, makes it even more urgent to explain how such massive objects formed in galaxies. Of course, dedicated follow-up observations both in the X-ray and radio bands, as well as in the optical, are necessary in order to confirm our results.« less

An Energy Efficient Technique Using Electric Active Shielding for Capacitive Coupling Intra-Body Communication

PubMed Central

Ma, Chao; Huang, Zhonghua; Wang, Zhiqi; Zhou, Linxuan; Li, Yinlin

2017-01-01

Capacitive coupling intra-body communication (CC-IBC) has become one of the candidates for healthcare sensor networks due to its positive prevailing features of energy efficiency, transmission rate and security. Under the CC-IBC scheme, some of the electric field emitted from signal (SIG) electrode of the transmitter will couple directly to the ground (GND) electrode, acting equivalently as an internal impedance of the signal source and inducing considerable energy losses. However, none of the previous works have fully studied the problem. In this paper, the underlying theory of such energy loss is investigated and quantitatively evaluated using conventional parameters. Accordingly, a method of electric active shielding is proposed to reduce the displacement current across the SIG-GND electrodes, leading to less power loss. In addition, the variation of such loss in regard to frequency range and positions on human body was also considered. The theory was validated by finite element method simulation and experimental measurement. The prototype result shows that the receiving power has been improved by approximate 5.5 dBm while the total power consumption is maximally 9 mW less using the proposed technique, providing an energy efficient option in physical layer for wearable and implantable healthcare sensor networks. PMID:28885546

BATSE imaging survey of the Galactic plane

NASA Technical Reports Server (NTRS)

Grindlay, J. E.; Barret, D.; Bloser, P. F.; Zhang, S. N.; Robinson, C.; Harmon, B. A.

1997-01-01

The burst and transient source experiment (BATSE) onboard the Compton Gamma Ray Observatory (CGRO) provides all sky monitoring capability, occultation analysis and occultation imaging which enables new and fainter sources to be searched for in relatively crowded fields. The occultation imaging technique is used in combination with an automated BATSE image scanner, allowing an analysis of large data sets of occultation images for detections of candidate sources and for the construction of source catalogs and data bases. This automated image scanner system is being tested on archival data in order to optimize the search and detection thresholds. The image search system, its calibration results and preliminary survey results on archival data are reported on. The aim of the survey is to identify a complete sample of black hole candidates in the galaxy and constrain the number of black hole systems and neutron star systems.

How to Distinguish Neutron Star and Black Hole X-ray Binaries? Spectral Index and Quasi-Periodic Oscillation Frequency Correlation

NASA Technical Reports Server (NTRS)

Titarchuk, Lev; Shaposhnikov, Nickolai

2005-01-01

Recent studies have revealed strong correlations between 1-10 Hz frequencies of quasiperiodic oscillations (QPOs) and the spectral power law index of several Black Hole (BH) candidate sources when seen in the low/hard state, the steep power-law (soft) state, and in transition between these states. In the soft state these index-QPO frequency correlations show a saturation of the photon index GAMMA approximately equal to 2.7 at high values of the low frequency nu(sub L). This saturation effect was previously identified as a black hole signature. In this paper we argue that this saturation does not occur, at least for one neutron star (NS) source 4U 1728-34, for which the index GAMMA monotonically increases with nu(sub L) to the values of 6 and higher. We base this conclusion on our analysis of approximately 1.5 Msec of RXTE archival data for 4U 1728-34. We reveal the spectral evolution of the Comptonized blackbody spectra when the source transitions from the hard to soft states. The hard state spectrum is a typical thermal Comptonization spectrum of the soft photons which originate in the disk and the NS outer photospheric layers. The hard state photon index is GAMMA approximately 2. The soft state spectrum consists of two blackbody components which are only slightly Comptonized. Thus we can claim (as expected from theory) that in NS sources thermal equilibrium is established for the soft state. To the contrary in BH sources, the equilibrium is never established due to the presence of the BH horizon. The emergent BH spectrum, even in the high/soft state, has a power law component. We also identify the low QPO frequency nu(sub L) as a fundamental frequency of the quasi-spherical component of the transition layer (presumably related to the corona and the NS and disk magnetic closed field lines). The lower frequency nu(sub SL) is identified as the frequency of oscillations of a quasi-cylindrical configuration of the TL (presumably related to the NS and disk magnetic open field lines). We also show that the presence of Fe K(sub alpha), emission-line strengths, QPOs, and the link between them does not depend on radio flux in 4U 1728-34.

Power: a changing commodity.

PubMed

Hage, S J

1991-01-01

"Rapid and tumultuous change in health care as well as business has precipitated a power shift," declares Mr. Hage in this candid discussion of a quality that is both abstract and concrete. Centralized power is no longer the order of the day; in fact, the new stance supports pushing power down into organizations where it can be better used by those closer to the action. The author maintains that effective participants in this new model will learn to share power and respect knowledge as the only tool that wields it.

The HEMP QSO Monitoring Project

NASA Astrophysics Data System (ADS)

Welsh, William F.; Robinson, E. L.

2000-02-01

Many AGN are highly variable sources. Some of these show a pronounced time delay between variations seen in their optical continuum and in their emission lines. ``Echo mapping'' is a technique that uses these time delays to measure the geometry and kinematics of the gas inside the AGN, near the supermassive black hole. The technique is immensely powerful, but the results so far have been modest due to relatively low quality data. We have initiated a long--term project to echo map QSOs. We will examine nearby (but intrinsically faint) QSOs as well as QSOs at high redshift. The high--z QSOs present a problem: it is not known ahead of time which of these are variable sources. Thus we have started a campaign to monitor about 60 high-redshift QSOs for the purpose of determining their variability characteristics. We request SSTO time on the 0.9m telescope for long--term monitoring of high--redshift QSOs to: (i) test their suitability as viable echo mapping candidates; and (ii) measure (for the first time) their variability properties, which is of intrinsic value itself.

Fermi/LAT detection of a transient gamma-ray flare in the vicinity of the binary star DG CVn

DOE PAGES

Loh, Alan; Corbel, Stéphane; Dubus, Guillaume

2017-02-16

Solar flares are regularly detected by the Large Area Telescope (LAT) on board the Fermi satellite, however no γ-ray emission from other stellar eruptions has ever been captured. The Swift detection in 2014 April of a powerful outburst originating from DG CVn, with associated optical and radio emissions, enticed us to search for possible 0.1–100 GeV emission from this flaring nearby binary star using the Fermi/LAT. No γ-ray emission is detected from DG CVn in 2014, but we report a significant γ-ray excess in 2012 November, at a position consistent with that of the binary. There are no reports ofmore » contemporary flaring at other wavelengths from DG CVn or any other source within the error circle of the γ-ray source. As a result, we argue that the γ-ray flare is more likely to have been associated with a background blazar than with DG CVn and identify a candidate for follow-up study.« less

Detailed modelling of a large sample of Herschel sources in the Lockman Hole: identification of cold dust and of lensing candidates through their anomalous SEDs★

NASA Astrophysics Data System (ADS)

Rowan-Robinson, Michael; Wang, Lingyu; Wardlow, Julie; Farrah, Duncan; Oliver, Seb; Bock, Jamie; Clarke, Charlotte; Clements, David; Ibar, Edo; Gonzalez-Solares, Eduardo; Marchetti, Lucia; Scott, Douglas; Smith, Anthony; Vaccari, Mattia; Valtchanov, Ivan

2014-12-01

We have studied in detail a sample of 967 SPIRE sources with 5σ detections at 350 and 500 μm and associations with Spitzer-SWIRE 24 μm galaxies in the HerMES-Lockman survey area, fitting their mid- and far-infrared, and submillimetre, spectral energy distributions (SEDs) in an automatic search with a set of six infrared templates. For almost 300 galaxies, we have modelled their SEDs individually to ensure the physicality of the fits. We confirm the need for the new cool and cold cirrus templates, and also of the young starburst template, introduced in earlier work. We also identify 109 lensing candidates via their anomalous SEDs and provide a set of colour-redshift constraints which allow lensing candidates to be identified from combined Herschel and Spitzer data. The picture that emerges of the submillimetre galaxy population is complex, comprising ultraluminous and hyperluminous starbursts, lower luminosity galaxies dominated by interstellar dust emission, lensed galaxies and galaxies with surprisingly cold (10-13 K) dust. 11 per cent of 500 μm selected sources are lensing candidates. 70 per cent of the unlensed sources are ultraluminous infrared galaxies and 26 per cent are hyperluminous. 34 per cent are dominated by optically thin interstellar dust (`cirrus') emission, but most of these are due to cooler dust than is characteristic of our Galaxy. At the highest infrared luminosities we see SEDs dominated by M82, Arp 220 and young starburst types, in roughly equal proportions.

Search for massive protostellar candidates in the southern hemisphere. I. Association with dense gas

NASA Astrophysics Data System (ADS)

Fontani, F.; Beltrán, M. T.; Brand, J.; Cesaroni, R.; Testi, L.; Molinari, S.; Walmsley, C. M.

2005-03-01

We have observed two rotational transitions of both CS and C17O, and the 1.2 mm continuum emission towards a sample of 130 high-mass protostellar candidates with δ < -30°. This work represents the first step of the extension to the southern hemisphere of a project started more than a decade ago aimed at the identification of massive protostellar candidates. Following the same approach adopted for sources with δ ≥ -30°, we have selected from the IRAS Point Source Catalogue 429 sources which potentially are compact molecular clouds on the basis of their IR colours. The sample has then been divided into two groups according to the colour indices [25 12] and [60 12]: the 298 sources with [25 12] ≥ 0.57 and [60 12] ≥ 1.30 have been called High sources, the remaining 131 have been called Low sources. In this paper, we check the association with dense gas and dust in 130 Low sources. We have obtained a detection rate of ~85% in CS, demonstrating a tight association of the sources with dense molecular clumps. Among the sources detected in CS, ~76% have also been detected in C17O and ~93% in the 1.2 mm continuum. Millimeter-continuum maps show the presence of clumps with diameters in the range 0.2-2 pc and masses from a few M⊙ to 105 M⊙; H2 volume densities computed from CS line ratios lie between ~104.5 and 105.5 cm-3. The bolometric luminosities of the sources, derived from IRAS data, are in the range 103-106 L⊙, consistent with embedded high-mass objects. Based on our results and those found in the literature for other samples of high-mass young stellar objects, we conclude that our sources are massive objects in a very early evolutionary stage, probably prior to the formation of an Hii region. We propose a scenario in which High and Low sources are both made of a massive clump hosting a high-mass protostellar candidate and a nearby stellar cluster. The difference might be due to the fact that the 12 μm IRAS flux, the best discriminant between the two groups, is dominated by the emission from the cluster in Lows and from the massive protostellar object in Highs. Based on results collected at the European Southern Observatory (ESO), La Silla, Chile. Tables [see full text]-[see full text] are only available in electronic form at http://www.edpsciences.org

Passive radio frequency peak power multiplier

DOEpatents

Farkas, Zoltan D.; Wilson, Perry B.

1977-01-01

Peak power multiplication of a radio frequency source by simultaneous charging of two high-Q resonant microwave cavities by applying the source output through a directional coupler to the cavities and then reversing the phase of the source power to the coupler, thereby permitting the power in the cavities to simultaneously discharge through the coupler to the load in combination with power from the source to apply a peak power to the load that is a multiplication of the source peak power.

Performance characterization of mid-infrared difference frequency generation in orientation-patterned gallium phosphide

NASA Astrophysics Data System (ADS)

Wei, Junxiong; Chaitanya Kumar, S.; Ye, Hanyu; Schunemann, Peter G.; Ebrahim-Zadeh, M.

2018-02-01

Orientation-patterned gallium phosphide (OP-GaP) is a recently developed nonlinear material with wide transparency across 0.8-12 μm and high nonlinearity (d14 70 pm/V), which is a promising candidate material for mid-infrared generation. Here we report the full performance characterization of a tunable single-pass nanosecond difference frequency generation (DFG) source based on OP-GaP by mixing the output of a Q-switched Nd:YAG laser at 1.064 μm with the signal from a pulsed MgO:PPLN OPO pumped by the same laser. Using the longest OP-GaP crystal (40 mm) deployed to date, the DFG source provides up to 14 mW of average output power at 2719 nm at 80 kHz repetition rate, with >6 mW across 2492-2782 nm, in TEM00 spatial profile. By performing relevant measurements, detrimental issues such as residual absorption and thermal effects have been studied and confirmed. The temperature and spectral acceptance bandwidths for DFG in the 40-mm-log OP-GaP are measured to be 18 °C and 17 nm, respectively, at 1766 nm. The DFG beam exhibits passive power stability better than 1.7% rms over 1.4 hours at 2774 nm, compared to 1.6% and 0.1% rms for the signal and pump, respectively. The polarization dependence of the input beams on the DFG power has also been systematically investigated, for the first time to our knowledge. Further, we have measured the damage threshold of the OP-GaP crystal to be 0.8 J/cm2 at 1064 nm.

Nustar Reveals the Extreme Properties of the Super-Eddington Accreting Supermassive Black Hole in PG 1247+267

NASA Technical Reports Server (NTRS)

Lanzuisi, G.; Perna, M.; Comastri, A.; Cappi, M.; Dadina, M.; Marinucci, A.; Masini, A.; Matt, G.; Vagnetti, F.; Vignali, C.;

Simulation of a Lunar Surface Base Power Distribution Network for the Constellation Lunar Surface Systems

NASA Technical Reports Server (NTRS)

Mintz, Toby; Maslowski, Edward A.; Colozza, Anthony; McFarland, Willard; Prokopius, Kevin P.; George, Patrick J.; Hussey, Sam W.

2010-01-01

The Lunar Surface Power Distribution Network Study team worked to define, breadboard, build and test an electrical power distribution system consistent with NASA's goal of providing electrical power to sustain life and power equipment used to explore the lunar surface. A testbed was set up to simulate the connection of different power sources and loads together to form a mini-grid and gain an understanding of how the power systems would interact. Within the power distribution scheme, each power source contributes to the grid in an independent manner without communication among the power sources and without a master-slave scenario. The grid consisted of four separate power sources and the accompanying power conditioning equipment. Overall system design and testing was performed. The tests were performed to observe the output and interaction of the different power sources as some sources are added and others are removed from the grid connection. The loads on the system were also varied from no load to maximum load to observe the power source interactions.

Towards disentangling natural and anthropogenic GHG emissions by space-based atmospheric concentration imaging - The CarbonSat Earth Explorer 8 Candidate Mission

NASA Astrophysics Data System (ADS)

Bovensmann, Heinrich; Gerilowski, Konstantin; Krings, Thomas; Reuter, Max; Burrows, John P.; Buchwitz, Michael; Bösch, Hartmut; Brunner, Dominik; Ciais, Philippe; Breon, Francois-Marie; Crisp, David; Dolman, Han; Hayman, Garry; Houweling, Sander; Lichtenberg, Günter; Ingmann, Paul; Meijer, Yasjka

2013-04-01

CarbonSat was selected by ESA as a candidate for the 8 Earth Explorer Opportunity (EE8). The objective of the CarbonSat mission is to determine natural and anthropogenic sources and sinks of the two most important greenhouse gases, carbon dioxide and methane. The unique features of the CarbonSat mission concept are that it offers a combination of high spatial resolution (2 x 2 km2) and broad swath (240 km) to provide global imaging of localised strong emission source areas such as large cities (Megacities), landfills, power plants, volcanoes, etc. and to be able to separate anthropogenic from natural fluxes. In addition, CarbonSat data will also quantify natural fluxes of CO2 and CH4 (biospheric CO2, wetland CH4 etc.) and their changes, to better understand these important sources and sinks and their sensitivity to a changing climate. CarbonSat aims to deliver global data sets of dry column mixing ratios of CO2 and CH4 with high precision (goal: CO2 < 1 ppm, CH4 < 9 ppb) and accuracy. Benefiting from its imaging capabilities, CarbonSat will provide an at least one order of magnitude larger number of cloud free measurements than GOSAT and OCO and one order of magnitude better spatial coverage than OCO. The CarbonSat mission concept builds on the heritage and lessons learned from SCIAMACHY (2002-2012), GOSAT (2009-present) and OCO-2 (2014 onwards) to make scientifically and strategically important measurements of the amounts and distribution of CO2 and CH4 for biogeochemical and climate change research. CarbonSat entered industrial system feasibility activities in 2012, which are supported by scientific studies and campaigns. The current status of the mission concept and selected results from the scientific studies documenting the expected data quality and characteristics will be presented.

Local election: does bureaucracy become one of main political power?

NASA Astrophysics Data System (ADS)

Amin, Muryanto; Musthafa Sembiring, Walid

2018-03-01

This writing aims to analyze the emergence of bureaucracy as one of political power in local level after the local election is held in Indonesia. Due to information authorization, media network, and stable structure, the bureaucracy soon transforms into political power which can compete with the other political power at the local level. In Medan local election in 2010 and 2015 has evidently proven the power of bureaucracy network in winning the bureaucrat-background candidates. As methods of the research, the researcher held a Focus-Group Discussion (FGD) and had an in-depth interview with ten bureaucracy elites in Medan and local political elites. The observation and Focus-Group Discussion (FGD) are analyzed using qualitative analysis technique typology. The result states that the bureaucracy network in Medan has been used in a massive way as the political power of winning. The structure of bureaucracy – from the top to the low – is involved in the winning. The most governmental programs were applied to attract the mass’ sympathy toward the candidates. The bureaucratic proximity to media network is also used to do a campaign in a massive way. The conclusion of the research is that bureaucracy emerges as a new, massive, effective local political power in the local election.

SCUBA and HIRES Results for Protostellar Cores in the MON OB1 Dark Cloud

NASA Astrophysics Data System (ADS)

Wolf-Chase, G.; Moriarty-Schieven, G.; Fich, M.; Barsony, M.

1999-05-01

We have used HIRES-processing of IRAS data and point-source modelling techniques (Hurt & Barsony 1996; O'Linger 1997; Barsony et al. 1998), together with submillimeter continuum imaging using the Submillimeter Common-User Bolometer Array (SCUBA) on the 15-meter James Clerk Maxwell Telescope (JCMT), to search CS cores in the Mon OB1 dark cloud (Wolf-Chase, Walker, & Lada 1995; Wolf-Chase & Walker 1995) for deeply embedded sources. These observations, as well as follow-up millimeter photometry at the National Radio Astronomy Observatory (NRAO) 12-meter telescope on Kitt Peak, have lead to the identification of two Class 0 protostellar candidates, which were previously unresolved from two brighter IRAS point sources (IRAS 06382+0939 & IRAS 06381+1039) in this cloud. Until now, only one Class 0 object had been confirmed in Mon OB1; the driving source of the highly-collimated outflow NGC 2264 G (Ward-Thompson, Eiroa, & Casali 1995; Margulis et al. 1990; Lada & Fich 1996), which lies well outside the extended CS cores. One of the new Class 0 candidates may be an intermediate-mass source associated with an H_2O maser, and the other object is a low-mass source which may be associated with a near-infrared jet, and possibly with a molecular outflow. We report accurate positions for the new Class 0 candidates, based on the SCUBA images, and present new SEDs for these sources, as well as for the brighter IRAS point sources. A portion of this work was performed while GWC held a President's Fellowship from the University of California. MB and GWC gratefully acknowledge financial support from MB's NSF CAREER Grant, AST97-9753229.

Radio Identifications of UGC Galaxies - Starbursts and Monsters

NASA Astrophysics Data System (ADS)

Condon, J. J.; Broderick, J. J.

1995-11-01

Radio identifications of galaxies in the Uppsala General Catalogue of Galaxies with delta < +82 degrees were made from the Green Bank 1400 MHz sky maps. Every source having peak flux density S(P) >= 150 mJy in the approximately 12 arcmin FWHM map point-source response and position < 5 arcmin in both coordinates from the optical position of any UGC galaxy was considered a candidate identification to ensure that very extended (up to 1 Mpc) and asymmetric sources would not be missed. Maps in the literature or new 1.49 GHz VLA C-array maps made with 18 arcsec FWHM resolution were used to confirm or reject candidate identifications. The maps in this directory include both confirmed identifications and candidates rejected because of confusion or low flux density. For more information on this study, please see the following reference: Condon, J. J., and Broderick, J. J., 1988, AJ, 96, 30. The images and related TeX file come from the NRAO CDROM "Images From the Radio Universe" (c. 1992 National Radio Astronomy Observatory, used with permission).

A search for new supernova remnant shells in the Galactic plane with H.E.S.S.

NASA Astrophysics Data System (ADS)

H. E. S. S. Collaboration; Abdalla, H.; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Andersson, T.; Angüner, E. O.; Arakawa, M.; Arrieta, M.; Aubert, P.; Backes, M.; Balzer, A.; Barnard, M.; Becherini, Y.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Blackwell, R.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bonnefoy, S.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Büchele, M.; Bulik, T.; Capasso, M.; Carr, J.; Casanova, S.; Cerruti, M.; Chakraborty, N.; Chaves, R. C. G.; Chen, A.; Chevalier, J.; Coffaro, M.; Colafrancesco, S.; Cologna, G.; Condon, B.; Conrad, J.; Cui, Y.; Davids, I. D.; Decock, J.; Degrange, B.; Deil, C.; Devin, J.; deWilt, P.; Dirson, L.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; Drury, L. O.'C.; Dutson, K.; Dyks, J.; Edwards, T.; Egberts, K.; Eger, P.; Ernenwein, J.-P.; Eschbach, S.; Farnier, C.; Fegan, S.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Funk, S.; Füßling, M.; Gabici, S.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Gottschall, D.; Goyal, A.; Grondin, M.-H.; Hahn, J.; Haupt, M.; Hawkes, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hinton, J. A.; Hofmann, W.; Hoischen, C.; Holch, T. L.; Holler, M.; Horns, D.; Ivascenko, A.; Iwasaki, H.; Jacholkowska, A.; Jamrozy, M.; Janiak, M.; Jankowsky, D.; Jankowsky, F.; Jingo, M.; Jogler, T.; Jouvin, L.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Katsuragawa, M.; Katz, U.; Kerszberg, D.; Khangulyan, D.; Khélifi, B.; King, J.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Kraus, M.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lau, J.; Lees, J.-P.; Lefaucheur, J.; Lefranc, V.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Leser, E.; Lohse, T.; Lorentz, M.; Liu, R.; López-Coto, R.; Lypova, I.; Marandon, V.; Marcowith, A.; Mariaud, C.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; Meintjes, P. J.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Mohrmann, L.; Morå, K.; Moulin, E.; Murach, T.; Nakashima, S.; de Naurois, M.; Niederwanger, F.; Niemiec, J.; Oakes, L.; O'Brien, P.; Odaka, H.; Öttl, S.; Ohm, S.; Ostrowski, M.; Oya, I.; Padovani, M.; Panter, M.; Parsons, R. D.; Pekeur, N. W.; Pelletier, G.; Perennes, C.; Petrucci, P.-O.; Peyaud, B.; Piel, Q.; Pita, S.; Poon, H.; Prokhorov, D.; Prokoph, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Richter, S.; Rieger, F.; Romoli, C.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Saito, S.; Salek, D.; Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwemmer, S.; Seglar-Arroyo, M.; Settimo, M.; Seyffert, A. S.; Shafi, N.; Shilon, I.; Simoni, R.; Sol, H.; Spanier, F.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stycz, K.; Sushch, I.; Takahashi, T.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tibaldo, L.; Tiziani, D.; Tluczykont, M.; Trichard, C.; Tsuji, N.; Tuffs, R.; Uchiyama, Y.; van der Walt, D. J.; van Eldik, C.; van Rensburg, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Voisin, F.; Völk, H. J.; Vuillaume, T.; Wadiasingh, Z.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zabalza, V.; Zaborov, D.; Zacharias, M.; Zanin, R.; Zdziarski, A. A.; Zech, A.; Zefi, F.; Ziegler, A.; Żywucka, N.; Bamba, A.; Fukui, Y.; Sano, H.; Yoshiike, S.

2018-04-01

A search for new supernova remnants (SNRs) has been conducted using TeV γ-ray data from the H.E.S.S. Galactic plane survey. As an identification criterion, shell morphologies that are characteristic for known resolved TeV SNRs have been used. Three new SNR candidates were identified in the H.E.S.S. data set with this method. Extensive multiwavelength searches for counterparts were conducted. A radio SNR candidate has been identified to be a counterpart to HESS J1534-571. The TeV source is therefore classified as a SNR. For the other two sources, HESS J1614-518 and HESS J1912+101, no identifying counterparts have been found, thus they remain SNR candidates for the time being. TeV-emitting SNRs are key objects in the context of identifying the accelerators of Galactic cosmic rays. The TeV emission of the relativistic particles in the new sources is examined in view of possible leptonic and hadronic emission scenarios, taking the current multiwavelength knowledge into account.

JVLA Observations of Young Brown Dwarfs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodríguez, Luis F.; Zapata, Luis A.; Palau, Aina, E-mail: l.rodriguez@crya.unam.mx, E-mail: l.zapata@crya.unam.mx, E-mail: a.palau@crya.unam.mx

We present sensitive 3.0 cm JVLA radio continuum observations of six regions of low-mass star formation that include twelve young brown dwarfs (BDs) and four young BD candidates. We detect a total of 49 compact radio sources in the fields observed, of which 24 have no reported counterparts and are considered new detections. Twelve of the radio sources show variability in timescales of weeks to months, suggesting gyrosynchrotron emission produced in active magnetospheres. Only one of the target BDs, FU Tau A, was detected. However, we detected radio emission associated with two of the BD candidates, WL 20S and CHLTmore » 2. The radio flux densities of the sources associated with these BD candidates are more than an order of magnitude larger than expected for a BD and suggest a revision of their classification. In contrast, FU Tau A falls on the well-known correlation between radio luminosity and bolometric luminosity, suggesting that the emission comes from a thermal jet and that this BD seems to be forming as a scaled-down version of low-mass stars.« less

V/V(max) test applied to SMM gamma-ray bursts

NASA Technical Reports Server (NTRS)

Matz, S. M.; Higdon, J. C.; Share, G. H.; Messina, D. C.; Iadicicco, A.

1992-01-01

We have applied the V/V(max) test to candidate gamma-ray bursts detected by the Gamma-Ray Spectrometer (GRS) aboard the SMM satellite to examine quantitatively the uniformity of the burst source population. For a sample of 132 candidate bursts identified in the GRS data by an automated search using a single uniform trigger criterion we find average V/V(max) = 0.40 +/- 0.025. This value is significantly different from 0.5, the average for a uniform distribution in space of the parent population of burst sources; however, the shape of the observed distribution of V/V(max) is unusual and our result conflicts with previous measurements. For these reasons we can currently draw no firm conclusion about the distribution of burst sources.

Agent-based power sharing scheme for active hybrid power sources

NASA Astrophysics Data System (ADS)

Jiang, Zhenhua

The active hybridization technique provides an effective approach to combining the best properties of a heterogeneous set of power sources to achieve higher energy density, power density and fuel efficiency. Active hybrid power sources can be used to power hybrid electric vehicles with selected combinations of internal combustion engines, fuel cells, batteries, and/or supercapacitors. They can be deployed in all-electric ships to build a distributed electric power system. They can also be used in a bulk power system to construct an autonomous distributed energy system. An important aspect in designing an active hybrid power source is to find a suitable control strategy that can manage the active power sharing and take advantage of the inherent scalability and robustness benefits of the hybrid system. This paper presents an agent-based power sharing scheme for active hybrid power sources. To demonstrate the effectiveness of the proposed agent-based power sharing scheme, simulation studies are performed for a hybrid power source that can be used in a solar car as the main propulsion power module. Simulation results clearly indicate that the agent-based control framework is effective to coordinate the various energy sources and manage the power/voltage profiles.

Microlensing optical depth towards the Galactic Bulge using bright sources from OGLE-II

NASA Astrophysics Data System (ADS)

Sumi, T.; Woźniak, P.; Udalski, A.; Szymański, M.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Zebruń, K.; Szewczyk, O.; Wyrzykowski, L.

2004-12-01

We present a measurement of the microlensing optical depth towards the Galactic Bulge by using bright stars as sources from the central 20 OGLE-II Galactic bulge fields covering a range of 0o

CADDIS Volume 2. Sources, Stressors and Responses: Metals - Point Sources from Industry

EPA Pesticide Factsheets

Introduction to the metals module, when to list metals as a candidate cause, ways to measure metals, simple and detailed conceptual diagrams for metals, metals module references and literature reviews.

Comprehensive Renewable Energy Feasibility Study for Sealaska Corporation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robert Lynette; John Wade: Larry Coupe

2006-06-30

The purposes of this project were: (1) to conduct a comprehensive feasibility study to determine the potential sustainability of wind and/or small hydroelectric power plants on Southeast Alaska native village lands, and (2) to provide the villages with an understanding of the requirements, costs, and benefits of developing and operating wind or small hydroelectric power plants. The program was sponsored by the Tribal Energy program, Office of Energy Efficiency and Renewable Energy, US Department of Energy. The Contractor was Sealaska Corporation, the Regional Native Corporation for Southeast Alaska that includes 12 village/urban corporations. Most villages are isolated from any centralmore » electric transmission and use diesel-electric systems for power generation, making them prime candidates for deploying renewable energy sources. Wind Energy - A database was assembled for all of the candidate sites in SE Alaska, including location, demographics, electricity supply and demand, existing and planned transmission interties with central generation, topographical maps, macro wind data, and contact personnel. Field trips were conducted at the five candidate villages that were deemed most likely to have viable wind resources. Meetings were held with local village and utility leaders and the requirements, costs, and benefits of having local renewable energy facilities were discussed. Two sites were selected for anemometry based on their needs and the probability of having viable wind resources – Yakutat and Hoonah. Anemometry was installed at both sites and at least one year of wind resource data was collected from the sites. This data was compared to long-term data from the closest weather stations. Reports were prepared by meteorologist John Wade that contains the details of the measured wind resources and energy production projections. Preliminary financial analysis of hypothetical wind power stations were prepared to gauge the economic viability of installing such facilities at each site. The average wind resources measured at Yakutat at three sites were very marginal, with an annual average of 4.0 mps (9 mph) at 60 meters above ground level. At Hoonah, the average wind resources measured on the 1,417 ft elevation ridge above the village were very low, with a six-month average of 3.9 mps (8.7 mph) at 60 meters above ground level. The wind resources at both sites were not sufficient to justify installation of wind turbines. In summary, although there are several known windy spots in SE Alaska (e.g., Skagway), we were not able to identify any isolated Native American villages that utilize diesel-electric power generation that have commercially viable wind resources. Small Hydroelectric - The study focused on the communities associated with Sealaska Corporation that use diesel-electric for electricity and have a potential for hydroelectric power generation. Most of them have had at least an assessment of hydroelectric potential, and a few have had feasibility studies of potential hydroelectric projects. Although none of the sites examined are financially viable without substantial grant funding, Hoonah, Kake, and Yakutat appear to have the best potential for new hydro facilities.« less

Detection of X-ray flares from AX J1714.1-3912, the unidentified source near RX J1713.7-3946

NASA Astrophysics Data System (ADS)

Miceli, Marco; Bamba, Aya

2018-04-01

Context. Molecular clouds are predicted to emit nonthermal X-rays when they are close to particle-accelerating supernova remnants (SNRs), and the hard X-ray source AX J1714.1-3912, near the SNR RX J1713.7-3946, has long been considered a candidate for diffuse nonthermal emission associated with cosmic rays diffusing from the remnant to a closeby molecular cloud. Aim. We aim at ascertaining the nature of this source by analyzing two dedicated X-ray observations performed with Suzaku and Chandra. Methods: We extracted images from the data in various energy bands, spectra, and light curves and studied the long-term evolution of the X-ray emission on the basis of the 4.5 yr time separation between the two observations. Results: We found that there is no diffuse emission associated with AX J1714.1-3912, which is instead the point-like source CXOU J171343.9-391205. We discovered rapid time variability (timescale 103 s), together with a high intrinsic absorption and a hard nonthermal spectrum (power law with photon index Γ 1.4). We also found that the X-ray flux of the source drops down by 1-2 orders of magnitude on a timescale of a few years. Conclusions: Our results suggest a possible association between AX J1714.1-3912 and a previously unknown supergiant fast X-ray transient, although further follow-up observations are necessary to prove this association definitively.

Finding False Positives Planet Candidates Due To Background Eclipsing Binaries in K2

NASA Astrophysics Data System (ADS)

Mullally, Fergal; Thompson, Susan E.; Coughlin, Jeffrey; DAVE Team

2016-06-01

We adapt the difference image centroid approach, used for finding background eclipsing binaries, to vet K2 planet candidates. Difference image centroids were used with great success to vet planet candidates in the original Kepler mission, where the source of a transit could be identified by subtracting images of out-of-transit cadences from in-transit cadences. To account for K2's roll pattern, we reconstruct out-of-transit images from cadences that are nearby in both time and spacecraft roll angle. We describe the method and discuss some K2 planet candidates which this method suggests are false positives.

Towards Treating Chemistry Teacher Candidates as Human

ERIC Educational Resources Information Center

Lewthwaite, Brian Ellis

2008-01-01

This research inquiry investigates the factors influencing chemistry teacher candidates' development during their extended practica in the second and final year of an After-Degree Bachelor of Education at a university in central Canada. A variety of data sources are used to identify the risk and protective factors impeding and contributing to the…

Source, Message, Channel and Candidate Image: An Exploratory Study.

ERIC Educational Resources Information Center

Kokkeler, Larry

Designed to explore the relationship between the mass media and candidate image, a single interview questionnaire was prepared to be administered during the two weeks prior to election day, November 7, 1972. It was hypothesized that the amount of information which respondents indicated they received from paid political advertisements, editorials,…

Magnetostrictive direct drive motors

NASA Technical Reports Server (NTRS)

Naik, Dipak; Dehoff, P. H.

1990-01-01

Developing magnetostrictive direct drive research motors to power robot joints is discussed. These type motors are expected to produce extraordinary torque density, to be able to perform microradian incremental steps and to be self-braking and safe with the power off. Several types of motor designs have been attempted using magnetostrictive materials. One of the candidate approaches (the magnetostrictive roller drive) is described. The method in which the design will function is described as is the reason why this approach is inherently superior to the other approaches. Following this, the design will be modelled and its expected performance predicted. This particular candidate design is currently undergoing detailed engineering with prototype construction and testing scheduled for mid 1991.

The Relativistic Iron Line Profile in the Seyfert 1 Galaxy IC4329a

NASA Technical Reports Server (NTRS)

Done, C.; Madejski, G. M.; Zycki, P. T.

2000-01-01

We present simultaneous ASCA and RXTE data on the bright Seyfert 1 galaxy IC4329a. The iron line is significantly broadened, but not to the extent expected from an accretion disk which extends down to the last stable orbit around a black hole. We marginally detect a narrow line component, presumably from the molecular torus, but, even including this gives a line profile from the accretion disk which is significantly narrower that that seen in MCG-6-30-15, and is much more like that seen from the low/hard state galactic black hole candidates. This is consistent with the inner disk being truncated before the last stable orbit, forming a hot flow at small radii as in the ADAF models. However. we cannot rule out the presence of an inner disk which does not contribute to the reflected spectrum. either because of extreme ionisation suppressing the characteristic atomic features of the reflected spectrum or because the X-ray source is intrinsically anisotropic, so it does not illuminate the inner disk. The source was monitored by RXTE every 2 days for 2 months, and these snapshot spectra show that there is intrinsic spectral variability. The data are good enough to disentangle the power law from the reflected continuum and we see that the power law softens as the source brightens. The lack of a corresponding increase in the observed reflected spectrum implies that either the changes in disk inner radial extent/ionization structure are small, or that the variability is actually driven by changes in the seed photons which are decoupled from the hard X-ray mechanism.

New methods to constrain the radio transient rate: results from a survey of four fields with LOFAR.

PubMed

Carbone, D; van der Horst, A J; Wijers, R A M J; Swinbank, J D; Rowlinson, A; Broderick, J W; Cendes, Y N; Stewart, A J; Bell, M E; Breton, R P; Corbel, S; Eislöffel, J; Fender, R P; Grießmeier, J-M; Hessels, J W T; Jonker, P; Kramer, M; Law, C J; Miller-Jones, J C A; Pietka, M; Scheers, L H A; Stappers, B W; van Leeuwen, J; Wijnands, R; Wise, M; Zarka, P

2016-07-01

We report on the results of a search for radio transients between 115 and 190 MHz with the LOw-Frequency ARray (LOFAR). Four fields have been monitored with cadences between 15 min and several months. A total of 151 images were obtained, giving a total survey area of 2275 deg 2 . We analysed our data using standard LOFAR tools and searched for radio transients using the LOFAR Transients Pipeline. No credible radio transient candidate has been detected; however, we are able to set upper limits on the surface density of radio transient sources at low radio frequencies. We also show that low-frequency radio surveys are more sensitive to steep-spectrum coherent transient sources than GHz radio surveys. We used two new statistical methods to determine the upper limits on the transient surface density. One is free of assumptions on the flux distribution of the sources, while the other assumes a power-law distribution in flux and sets more stringent constraints on the transient surface density. Both of these methods provide better constraints than the approach used in previous works. The best value for the upper limit we can set for the transient surface density, using the method assuming a power-law flux distribution, is 1.3 × 10 -3  deg -2 for transients brighter than 0.3 Jy with a time-scale of 15 min, at a frequency of 150 MHz. We also calculated for the first time upper limits for the transient surface density for transients of different time-scales. We find that the results can differ by orders of magnitude from previously reported, simplified estimates.

Investigations on Cs-free alternatives for negative ion formation in a low pressure hydrogen discharge at ion source relevant parameters

NASA Astrophysics Data System (ADS)

Kurutz, U.; Friedl, R.; Fantz, U.

2017-07-01

Caesium (Cs) is applied in high power negative hydrogen ion sources to reduce a converter surface’s work function and thus enabling an efficient negative ion surface formation. Inherent drawbacks with the usage of this reactive alkali metal motivate the search for Cs-free alternative materials for neutral beam injection systems in fusion research. In view of a future DEMOnstration power plant, a suitable material should provide a high negative ion formation efficiency and comply with the RAMI issues of the system: reliability, availability, maintainability, inspectability. Promising candidates, like low work function materials (molybdenum doped with lanthanum (MoLa) and LaB6), as well as different non-doped and boron-doped diamond samples were investigated in this context at identical and ion source relevant parameters at the laboratory experiment HOMER. Negative ion densities were measured above the samples by means of laser photodetachment and compared with two reference cases: pure negative ion volume formation with negative ion densities of about 1× {10}15 {{{m}}}-3 and the effect of H- surface production using an in situ caesiated stainless steel sample which yields 2.5 times higher densities. Compared to pure volume production, none of the diamond samples did exhibit a measurable increase in H- densities, while showing clear indications of plasma-induced erosion. In contrast, both MoLa and LaB6 produced systematically higher densities (MoLa: ×1.60 LaB6: ×1.43). The difference to caesiation can be attributed to the higher work functions of MoLa and LaB6 which are expected to be about 3 eV for both compared to 2.1 eV of a caesiated surface.

Alternate energy source usage methods for in situ heat treatment processes

DOEpatents

Stone, Jr., Francis Marion; Goodwin, Charles R; Richard, Jr., James E

2014-10-14

Systems, methods, and heaters for treating a subsurface formation are described herein. At least one method for providing power to one or more subsurface heaters is described herein. The method may include monitoring one or more operating parameters of the heaters, the intermittent power source, and a transformer coupled to the intermittent power source that transforms power from the intermittent power source to power with appropriate operating parameters for the heaters; and controlling the power output of the transformer so that a constant voltage is provided to the heaters regardless of the load of the heaters and the power output provided by the intermittent power source.

46 CFR 183.310 - Power sources.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 7 2010-10-01 2010-10-01 false Power sources. 183.310 Section 183.310 Shipping COAST...) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.310 Power sources. (a)(1) Each vessel that relies on electricity to power the following loads must be arranged so that the loads can be...

46 CFR 183.310 - Power sources.

Code of Federal Regulations, 2013 CFR

2013-10-01

...) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.310 Power sources. (a)(1) Each vessel that relies on electricity to power the following loads must be arranged so that the loads can be... 46 Shipping 7 2013-10-01 2013-10-01 false Power sources. 183.310 Section 183.310 Shipping COAST...

46 CFR 183.310 - Power sources.

Code of Federal Regulations, 2012 CFR

2012-10-01

...) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.310 Power sources. (a)(1) Each vessel that relies on electricity to power the following loads must be arranged so that the loads can be... 46 Shipping 7 2012-10-01 2012-10-01 false Power sources. 183.310 Section 183.310 Shipping COAST...

46 CFR 183.310 - Power sources.

Code of Federal Regulations, 2014 CFR

2014-10-01

...) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.310 Power sources. (a)(1) Each vessel that relies on electricity to power the following loads must be arranged so that the loads can be... 46 Shipping 7 2014-10-01 2014-10-01 false Power sources. 183.310 Section 183.310 Shipping COAST...

46 CFR 183.310 - Power sources.

Code of Federal Regulations, 2011 CFR

2011-10-01

...) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.310 Power sources. (a)(1) Each vessel that relies on electricity to power the following loads must be arranged so that the loads can be... 46 Shipping 7 2011-10-01 2011-10-01 false Power sources. 183.310 Section 183.310 Shipping COAST...

49 CFR 193.2613 - Auxiliary power sources.

Code of Federal Regulations, 2011 CFR

2011-10-01

... test must take into account the power needed to start up and simultaneously operate equipment that... 49 Transportation 3 2011-10-01 2011-10-01 false Auxiliary power sources. 193.2613 Section 193.2613...: FEDERAL SAFETY STANDARDS Maintenance § 193.2613 Auxiliary power sources. Each auxiliary power source must...

SS 383: A NEW S-TYPE YELLOW SYMBIOTIC STAR?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baella, N. O.; Pereira, C. B.; Miranda, L. F.

Symbiotic stars are key objects in understanding the formation and evolution of interacting binary systems, and are probably the progenitors of Type Ia supernovae. However, the number of known symbiotic stars is much lower than predicted. We aim to search for new symbiotic stars, with particular emphasis on the S-type yellow symbiotic stars, in order to determine their total population, evolutionary timescales, and physical properties. The Two Micron All Sky Survey (2MASS) (J – H) versus (H – K {sub s}) color-color diagram has been previously used to identify new symbiotic star candidates and show that yellow symbiotics are locatedmore » in a particular region of that diagram. Candidate symbiotic stars are selected on the basis of their locus in the 2MASS (J – H) versus (H – K {sub s}) diagram and the presence of Hα line emission in the Stephenson and Sanduleak Hα survey. This diagram separates S-type yellow symbiotic stars from the rest of the S-type symbiotic stars, allowing us to select candidate yellow symbiotics. To establish the true nature of the candidates, intermediate-resolution spectroscopy is obtained. We have identified the Hα emission line source SS 383 as an S-type yellow symbiotic candidate by its position in the 2MASS color-color diagram. The optical spectrum of SS 383 shows Balmer, He I, He II, and [O III] emission lines, in combination with TiO absorption bands that confirm its symbiotic nature. The derived electron density (≅10{sup 8-9} cm{sup –3}), He I emission line intensity ratios, and position in the [O III] λ5007/Hβ versus [O III] λ4363/Hγ diagram indicate that SS 383 is an S-type symbiotic star, with a probable spectral type of K7-M0 deduced for its cool component based on TiO indices. The spectral type and the position of SS 383 (corrected for reddening) in the 2MASS color-color diagram strongly suggest that SS 383 is an S-type yellow symbiotic. Our result points out that the 2MASS color-color diagram is a powerful tool in identifying new S-type yellow symbiotics.« less

Low Luminosity States of the Black Hole Candidate GX 339-4. 1; ASCA and Simultaneous Radio/RXTE Observations

NASA Technical Reports Server (NTRS)

Wilms, Joern; Nowak, Michael A.; Dove, James B.; Fender, Robert P.; DiMatteo, Tiziana

1998-01-01

We discuss a series of observations of the black hole candidate GX 339-4 in low luminosity, spectrally hard states. We present spectral analysis of three separate archival Advanced Satellite for Cosmology and Astrophysics (ASCA) data sets and eight separate Rossi X-ray Timing Explorer (RXTE) data sets. Three of the RXTE observations were strictly simultaneous with 843 Mega Hertz and 8.3-9.1 Giga Hertz radio observations. All of these observations have (3-9 keV) flux approximately less than 10(exp-9) ergs s(exp-1) CM(exp -2). The ASCA data show evidence for an approximately 6.4 keV Fe line with equivalent width approximately 40 eV, as well as evidence for a soft excess that is well-modeled by a power law plus a multicolor blackbody spectrum with peak temperature approximately equals 150-200 eV. The RXTE data sets also show evidence of an Fe line with equivalent widths approximately equal to 20-1OO eV. Reflection models show a hardening of the RXTE spectra with decreasing X-ray flux; however, these models do not exhibit evidence of a correlation between the photon index of the incident power law flux and the solid angle subtended by the reflector. 'Sphere+disk' Comptonization models and Advection Dominated Accretion Flow (ADAF) models also provide reasonable descriptions of the RXTE data. The former models yield coronal temperatures in the range 20-50 keV and optical depths of r approximately equal to 3. The model fits to the X-ray data, however, do not simultaneously explain the observed radio properties. The most likely source of the radio flux is synchrotron emission from an extended outflow of extent greater than O(10 (exp7) GM/c2).

Fast optical and X-ray variability in the UCXB 4U0614+09

NASA Astrophysics Data System (ADS)

Hakala, P. J.; Charles, P. A.; Muhli, P.

2011-09-01

We present results from several years of fast optical photometry of 4U0614+091 (V1055 Orionis), a candidate ultracompact X-ray binary most likely consisting of a neutron star and a degenerate secondary. We find evidence for strong accretion-driven variability at all epochs, which manifests itself as red noise. This flickering produces transient peaks in the observed power spectrum in the 15-65 min period range. Only in one of our 12 optical data sets can we see evidence for a period that cannot be reproduced using the red noise model. This period of 51 min coincides with the strongest period detected by Shahbaz et al. and can thus be taken as the prime candidate for the orbital period of the system. Furthermore, we find some tentative evidence for the X-ray versus optical flux anticorrelation discovered by Machin et al. using our data together with the all-sky X-ray monitoring data from RXTE/All Sky Monitor. We propose that the complex time series behaviour of 4U0614+09 is a result of drastic changes in the accretion disc geometry/structure on time-scales from hours to days. Finally, we want to draw attention to the interpretation of moderately strong peaks in the power spectra of especially accreting sources. Many of such 'periods' can probably be attributed to the presence of red noise (i.e. correlated events) in the data. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. Uses results provided by the ASM/RXTE teams at MIT and at the RXTE SOF and GOF at NASA's GSFC.

X-ray Binaries in the Central Region of M31

NASA Astrophysics Data System (ADS)

Trudolyubov, Sergey P.; Priedhorsky, W. C.; Cordova, F. A.

2006-09-01

We present the results of the systematic survey of X-ray sources in the central region of M31 using the data of XMM-Newton observations. The spectral properties and variability of 124 bright X-ray sources were studied in detail. We found that more than 80% of sources observed in two or more observations show significant variability on the time scales of days to years. At least 50% of the sources in our sample are spectrally variable. The fraction of variable sources in our survey is much higher than previously reported from Chandra survey of M31, and is remarkably close to the fraction of variable sources found in M31 globular cluster X-ray source population. We present spectral distribution of M31 X-ray sources, based on the spectral fitting with a power law model. The distribution of spectral photon index has two main peaks at 1.8 and 2.3, and shows clear evolution with source luminosity. Based on the similarity of the properties of M31 X-ray sources and their Galactic counterparts, we expect most of X-ray sources in our sample to be accreting binary systems with neutron star and black hole primaries. Combining the results of X-ray analysis (X-ray spectra, hardness-luminosity diagrams and variability) with available data at other wavelengths, we explore the possibility of distinguishing between bright neutron star and black hole binary systems, and identify 7% and 25% of sources in our sample as a probable black hole and neutron star candidates. Finally, we compare the M31 X-ray source population to the source populations of normal galaxies of different morphological type. Support for this work was provided through NASA Grant NAG5-12390. Part of this work was done during a summer workshop ``Revealing Black Holes'' at the Aspen Center for Physics, S. T. is grateful to the Center for their hospitality.

Connecting Past, Present and Future: How African American Teacher Candidates' School Experiences Inform Their Motivations to Teach, Educational Philosophies, and Identities as Future Teachers

ERIC Educational Resources Information Center

Wilson, Brandy

2012-01-01

The stories of students and teacher candidates of Color hold powerful lessons and tremendous insight for educational reform efforts. Yet, rarely do educators and policymakers solicit or critically engage the educational narratives of students of Color. Indeed, despite resurgence in a four-decade long conversation regarding the shortage of teachers…

Fusible pellet transport and storage of heat

NASA Technical Reports Server (NTRS)

Bahrami, P. A.

1982-01-01

A new concept for both transport and storage of heat at high temperatures and heat fluxes is introduced and the first steps in analysis of its feasibility is taken. The concept utilizes the high energy storage capability of materials undergoing change of phase. The phase change material, for example a salt, is encapsulated in corrosion resistant sealed pellets and transported in a carrier fluid to heat source and storage. Calculations for heat transport from a typical solar collector indicate that the pellet mass flow rates are relatively small and that the required pumping power is only a small fraction of the energy transport capability of the system. Salts and eutectic salt mixtures as candidate phase change materials are examined and discussed. Finally, the time periods for melting or solidification of sodium chloride pellets is investigated and reported.

Fusible pellet transport and storage of heat

NASA Astrophysics Data System (ADS)

Bahrami, P. A.

1982-06-01

A new concept for both transport and storage of heat at high temperatures and heat fluxes is introduced and the first steps in analysis of its feasibility is taken. The concept utilizes the high energy storage capability of materials undergoing change of phase. The phase change material, for example a salt, is encapsulated in corrosion resistant sealed pellets and transported in a carrier fluid to heat source and storage. Calculations for heat transport from a typical solar collector indicate that the pellet mass flow rates are relatively small and that the required pumping power is only a small fraction of the energy transport capability of the system. Salts and eutectic salt mixtures as candidate phase change materials are examined and discussed. Finally, the time periods for melting or solidification of sodium chloride pellets is investigated and reported.

Low-Magnetic Magnetars

NASA Astrophysics Data System (ADS)

Turolla, Roberto; Esposito, Paolo

2015-01-01

It is now widely accepted that soft gamma repeaters and anomalous X-ray pulsars are the observational manifestations of magnetars, i.e. sources powered by their own magnetic energy. This view was supported by the fact that these `magnetar candidates' exhibited, without exception, a surface dipole magnetic field (as inferred from the spin-down rate) in excess of the electron critical field (≃4.4 × 1013 G). The recent discovery of fullyqualified magnetars, SGR 0418+5729 and Swift J1822.3-1606, with dipole magnetic field well in the range of ordinary radio pulsars posed a challenge to the standard picture, showing that a very strong field is not necessary for the onset of magnetar activity (chiefly bursts and outbursts). Here we summarise the observational status of the low-magneticfield magnetars and discuss their properties in the context of the mainstream magnetar model and its main alternatives.

The novel top-coat material for RLS trade-off reduction in EUVL

NASA Astrophysics Data System (ADS)

Onishi, Ryuji; Sakamoto, Rikimaru; Fujitani, Noriaki; Endo, Takafumi; Ho, Bang-ching

2012-03-01

For the next generation lithography (NGL), several technologies have been proposed to achieve the 22nm-node devices and beyond. Extreme ultraviolet (EUV) lithography is one of the candidates for the next generation lithography. In EUV light source development, low power is one of the critical issue because of the low throughput, and another issue is Out of Band (OoB) light existing in EUV light. OoB is concerned to be the cause of deterioration for the lithography performance. In order to avoid this critical issue, we focused on development of the resist top coat material with OoB absorption property as Out of Band Protection Layer (OBPL). We designed this material having high absorbance around 240nm wavelength and high transmittance for EUV light. And this material aimed to improve sensitivity, resolution and LWR performance.

Femtosecond laser inscribed cladding waveguides in Nd:YAG ceramics: fabrication, fluorescence imaging and laser performance.

PubMed

Liu, Hongliang; Jia, Yuechen; Vázquez de Aldana, Javier Rodríguez; Jaque, Daniel; Chen, Feng

2012-08-13

We report on the fabrication of depressed cladding waveguide lasers in Nd:YAG (neodymium doped yttrium aluminum garnet, Nd:Y3Al5O12) ceramics microstructured by femtosecond laser pulses. Full control over the confined light spatial distribution is demonstrated by the fabrication of high contrast waveguides with hexagonal, circular and trapezoidal configurations. The confocal fluorescence measurements of the waveguides reveal that the original luminescence features of Nd3+ ions are well-preserved in the waveguide regions. Under optical pump at 808 nm, cladding waveguides showed continuous wave efficient laser oscillation. The maximum output power obtained at 1064.5 nm is ~181 mW with a slope efficiency as high as 44%, which suggests that the fabricated Nd:YAG ceramic waveguides are promising candidates for efficient integrated laser sources.

A comparative assessment of solar thermal electric power plants in the 1-10 MWe range

NASA Technical Reports Server (NTRS)

Rosenberg, L. S.; Revere, W. R.

1981-01-01

The candidate power system technologies were ranked in terms of the cost of electric energy each system produces. In all cases, it was assumed that development programs would result in mature power plant systems that could be commercially manufactured. The results of the study, a brief description of the systems examined, and the methodologies used are presented.

Space Station Freedom primary power wiring requirements

NASA Technical Reports Server (NTRS)

Hill, Thomas J.

1994-01-01

The Space Station Freedom (SSF) Program requirements are a 30 year reliable service life in low Earth orbit in hard vacuum or pressurized module service without detrimental degradation. Specific requirements are outlined in this presentation for SSF primary power and cable insulation. The primary power cable status and the WP-4 planned cable test program are also reviewed along with Rocketdyne-WP04 prime insulation candidates.

Insights into the Distinct Lithiation/Sodiation of Porous Cobalt Oxide by in Operando Synchrotron X-ray Techniques and Ab Initio Molecular Dynamics Simulations.

PubMed

Xu, Gui-Liang; Sheng, Tian; Chong, Lina; Ma, Tianyuan; Sun, Cheng-Jun; Zuo, Xiaobing; Liu, Di-Jia; Ren, Yang; Zhang, Xiaoyi; Liu, Yuzi; Heald, Steve M; Sun, Shi-Gang; Chen, Zonghai; Amine, Khalil

2017-02-08

Sodium-ion batteries (SIBs) have been considered as one of the promising power source candidates for the stationary storage industries owing to the much lower cost of sodium than lithium. It is well-known that the electrode materials largely determine the energy density of the battery systems. However, recent discoveries on the electrode materials showed that most of them present distinct lithium and sodium storage performance, which is not yet well understood. In this work, we performed a comparative understanding on the structural changes of porous cobalt oxide during its electrochemical lithiation and sodiation process by in operando synchrotron small angel X-ray scattering, X-ray diffraction, and X-ray absorption spectroscopy. It was found that compared to the lithiation process, the porous cobalt oxide undergoes less pore structure changes, oxidation state, and local structure changes as well as crystal structure evolution during its sodiation process, which is attributed to the intrinsic low sodiation activity of cobalt oxide as evidenced by ab initio molecular dynamics simulations. Moreover, it was indicated that the sodiation activity of metal sulfides is higher than that of metal oxides, indicating a better candidate for SIBs. Such understanding is crucial for future design and improvement of high-performance electrode materials for SIBs.

Energy stores and switches for rail-launcher systems

NASA Technical Reports Server (NTRS)

Weldon, W. F.; Zowarka, R. C.; Marshall, R. A.

1983-01-01

An overview of existing switch and power supply technology applicable to space launch, a new candidate pulsed power supply for Earth-to-space rail launcher duty, the inverse railgun flux compressor, and a set of switching experiments to study further the feasibility of Earth-to-space launch are discussed.

Megawatt Class Nuclear Space Power Systems (MCNSPS) conceptual design and evaluation report. Volume 2, technologies 1: Reactors, heat transport, integration issues

NASA Technical Reports Server (NTRS)

Wetch, J. R.

1988-01-01

The objectives of the Megawatt Class Nuclear Space Power System (MCNSPS) study are summarized and candidate systems and subsystems are described. Particular emphasis is given to the heat rejection system and the space reactor subsystem.

Energy stores and switches for rail-launcher systems

NASA Astrophysics Data System (ADS)

Weldon, W. F.; Zowarka, R. C.; Marshall, R. A.

An overview of existing switch and power supply technology applicable to space launch, a new candidate pulsed power supply for Earth-to-space rail launcher duty, the inverse railgun flux compressor, and a set of switching experiments to study further the feasibility of Earth-to-space launch are discussed.

Technology survey of electrical power generation and distribution for MIUS application

NASA Technical Reports Server (NTRS)

Gill, W. L.; Redding, T. E.

1975-01-01

Candidate electrical generation power systems for the modular integrated utility systems (MIUS) program are described. Literature surveys were conducted to cover both conventional and exotic generators. Heat-recovery equipment associated with conventional power systems and supporting equipment are also discussed. Typical ranges of operating conditions and generating efficiencies are described. Power distribution is discussed briefly. Those systems that appear to be applicable to MIUS have been indicated, and the criteria for equipment selection are discussed.

Galactic Supernova Remnant Candidates Discovered by THOR

NASA Astrophysics Data System (ADS)

Anderson, Loren; Wang, Yuan; Bihr, Simon; Rugel, Michael; Beuther, Henrik; THOR Team

2018-01-01

There is a considerable deficiency in the number of known supernova remnants (SNRs) in the Galaxy compared to that expected. Searches for extended low-surface brightness radio sources may find new Galactic SNRs, but confusion with the much larger population of HII regions makes identifying such features challenging. SNRs can, however, be separated from HII regions using their significantly lower mid-infrared (MIR) to radio continuum intensity ratios. We use the combination of high-resolution 1-2 GHz continuum data from The HI, OH, Recombination line survey of the Milky Way (THOR) and lower-resolution VLA 1.4 GHz Galactic Plane Survey (VGPS) continuum data, together with MIR data from the Spitzer GLIMPSE, Spitzer MIPSGAL, and WISE surveys to identify SNR candidates. To ensure that the candidates are not being confused with HII regions, we exclude radio continuum sources from the WISE Catalog of Galactic HII Regions, which contains all known and candidate H II regions in the Galaxy. We locate 76 new Galactic SNR candidates in the THOR and VGPS combined survey area of 67.4deg>l>17.5deg, |b|<1.25deg and measure the radio flux density for 52 previously-known SNRs. The candidate SNRs have a similar spatial distribution to the known SNRs, although we note a large number of new candidates near l=30deg, the tangent point of the Scutum spiral arm. The candidates are on average smaller in angle compared to the known regions, 6.4'+/-4.7' versus 11.0'+/-7.8', and have lower integrated flux densities. If the 76 candidates are confirmed as true SNRs, for example using radio polarization measurements or by deriving radio spectral indices, this would more than double the number of known Galactic SNRs in the survey area. This large increase would still, however, leave a discrepancy between the known and expected SNR populations of about a factor of two.

ALMA deep field in SSA22: Blindly detected CO emitters and [C II] emitter candidates

NASA Astrophysics Data System (ADS)

Hayatsu, Natsuki H.; Matsuda, Yuichi; Umehata, Hideki; Yoshida, Naoki; Smail, Ian; Swinbank, A. Mark; Ivison, Rob; Kohno, Kotaro; Tamura, Yoichi; Kubo, Mariko; Iono, Daisuke; Hatsukade, Bunyo; Nakanishi, Kouichiro; Kawabe, Ryohei; Nagao, Tohru; Inoue, Akio K.; Takeuchi, Tsutomu T.; Lee, Minju; Ao, Yiping; Fujimoto, Seiji; Izumi, Takuma; Yamaguchi, Yuki; Ikarashi, Soh; Yamada, Toru

2017-06-01

We report the identification of four millimeter line-emitting galaxies with the Atacama Large Milli/submillimeter Array (ALMA) in SSA22 Field (ADF22). We analyze the ALMA 1.1-mm survey data, with an effective survey area of 5 arcmin2, frequency ranges of 253.1-256.8 and 269.1-272.8 GHz, angular resolution of 0{^''.}7 and rms noise of 0.8 mJy beam-1 at 36 km s-1 velocity resolution. We detect four line-emitter candidates with significance levels above 6σ. We identify one of the four sources as a CO(9-8) emitter at z = 3.1 in a member of the proto-cluster known in this field. Another line emitter with an optical counterpart is likely a CO(4-3) emitter at z = 0.7. The other two sources without any millimeter continuum or optical/near-infrared counterpart are likely to be [C II] emitter candidates at z = 6.0 and 6.5. The equivalent widths of the [C II] candidates are consistent with those of confirmed high-redshift [C II] emitters and candidates, and are a factor of 10 times larger than that of the CO(9-8) emitter detected in this search. The [C II] luminosity of the candidates are 4-7 × 108 L⊙. The star formation rates (SFRs) of these sources are estimated to be 10-20 M⊙ yr-1 if we adopt an empirical [C II] luminosity-SFR relation. One of them has a relatively low S/N ratio, but shows features characteristic of emission lines. Assuming that at least one of the two candidates is a [C II] emitter, we derive a lower limit of [C II]-based star formation rate density (SFRD) at z ˜ 6. The resulting value of >10-2 M⊙ yr-1 Mpc-3 is consistent with the dust-uncorrected UV-based SFRD. Future millimeter/submillimeter surveys can be used to detect a number of high-redshift line emitters, with which to study the star formation history in the early universe.

Finding High Quality Young Star Candidates in Ceph C using X-ray, Optical, and IR data

NASA Astrophysics Data System (ADS)

Orr, Laura; Rebull, Luisa M.; Johnson, Milton; Miller, Alexandra; Aragon Orozco, Anthony; Bakhaj, Benjamin; Bakshian, Jacquelyn; Chiffelle, Elizabeth; DeLint, Arie; Gerber, Stefan; Mader, Jared; Marengo, Amelia; McAdams, Jesse; Montufar, Cassandra; Orr, Quinton; San Emeterio, Lis; Stern, Eliyah; Weisserman, Drew

2017-01-01

We looked for new candidate young stars within the star forming region of Ceph OB3, more specifically in a region of this molecular cloud called Ceph C. While this region lies in the galactic plane and is included in several large surveys, Ceph C has not been well studied in the past and few young stellar objects (YSOs) have been identified there. The YSOVAR team (Rebull et al. 2014) has time-series monitoring data of this region, and in order to understand the diversity of the light curves, it is crucial to understand which objects in the field of view are likely YSOs, and which are foreground/background objects. The goal of our study is to identify candidate YSO sources as well as support the greater understanding of the variety, evolution, and variability of young stars. Our search for young stars includes data in X-ray, optical, and IR. Data points used are from Chandra, SDSS, IPHAS, 2MASS, Spitzer IRAC and MIPS, and WISE, giving us data over many orders of magnitude, 0.001 to 25 microns (0.36 to 25 microns without the X-rays). The catalogs were merged across all available wavelengths. Each source was inspected in all available images to insure good matches and quality of data across wavelengths and to eliminate poor candidates, those with contamination or confusion, and non-YSO objects. Spectral energy distributions (SEDs) for each candidate YSO were constructed and compared to images for greater assessment and reliable YSO identification. Color-color and color-magnitude diagrams have been created for the sources in this region and are used in conjunction with images, SEDs, X-ray, IR excess, and variability properties to identify candidate YSOs. Support provided for this work by the NASA/IPAC Teacher Archive Research Program (NITARP), which receives funding from the NASA ADP program.

LOD score exclusion analyses for candidate QTLs using random population samples.

PubMed

Deng, Hong-Wen

2003-11-01

While extensive analyses have been conducted to test for, no formal analyses have been conducted to test against, the importance of candidate genes as putative QTLs using random population samples. Previously, we developed an LOD score exclusion mapping approach for candidate genes for complex diseases. Here, we extend this LOD score approach for exclusion analyses of candidate genes for quantitative traits. Under this approach, specific genetic effects (as reflected by heritability) and inheritance models at candidate QTLs can be analyzed and if an LOD score is < or = -2.0, the locus can be excluded from having a heritability larger than that specified. Simulations show that this approach has high power to exclude a candidate gene from having moderate genetic effects if it is not a QTL and is robust to population admixture. Our exclusion analysis complements association analysis for candidate genes as putative QTLs in random population samples. The approach is applied to test the importance of Vitamin D receptor (VDR) gene as a potential QTL underlying the variation of bone mass, an important determinant of osteoporosis.

46 CFR 161.013-9 - Independent power source.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 6 2010-10-01 2010-10-01 false Independent power source. 161.013-9 Section 161.013-9...: SPECIFICATIONS AND APPROVAL ELECTRICAL EQUIPMENT Electric Distress Light for Boats § 161.013-9 Independent power source. (a) Each independent power source must be capable of powering the light so that it meets the...

46 CFR 129.310 - Power sources.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 4 2010-10-01 2010-10-01 false Power sources. 129.310 Section 129.310 Shipping COAST... Power Sources and Distribution Systems § 129.310 Power sources. (a)(1) Each vessel that relies on electricity to power the following loads must be arranged so that the loads can be energized from at least two...

46 CFR 129.310 - Power sources.

Code of Federal Regulations, 2011 CFR

2011-10-01

... Power Sources and Distribution Systems § 129.310 Power sources. (a)(1) Each vessel that relies on electricity to power the following loads must be arranged so that the loads can be energized from at least two... 46 Shipping 4 2011-10-01 2011-10-01 false Power sources. 129.310 Section 129.310 Shipping COAST...

46 CFR 129.315 - Power sources for OSVs.

Code of Federal Regulations, 2014 CFR

2014-10-01

... INSTALLATIONS Power Sources and Distribution Systems § 129.315 Power sources for OSVs. (a) The requirements of... 46 Shipping 4 2014-10-01 2014-10-01 false Power sources for OSVs. 129.315 Section 129.315 Shipping... subpart 111.10 of this chapter. (b) If a generator provides electrical power for any system identified as...

46 CFR 129.310 - Power sources.

Code of Federal Regulations, 2014 CFR

2014-10-01

... Power Sources and Distribution Systems § 129.310 Power sources. (a)(1) Each vessel that relies on electricity to power the following loads must be arranged so that the loads can be energized from at least two... 46 Shipping 4 2014-10-01 2014-10-01 false Power sources. 129.310 Section 129.310 Shipping COAST...

46 CFR 129.310 - Power sources.

Code of Federal Regulations, 2012 CFR

2012-10-01

... Power Sources and Distribution Systems § 129.310 Power sources. (a)(1) Each vessel that relies on electricity to power the following loads must be arranged so that the loads can be energized from at least two... 46 Shipping 4 2012-10-01 2012-10-01 false Power sources. 129.310 Section 129.310 Shipping COAST...

46 CFR 129.310 - Power sources.

Code of Federal Regulations, 2013 CFR

2013-10-01

... Power Sources and Distribution Systems § 129.310 Power sources. (a)(1) Each vessel that relies on electricity to power the following loads must be arranged so that the loads can be energized from at least two... 46 Shipping 4 2013-10-01 2013-10-01 false Power sources. 129.310 Section 129.310 Shipping COAST...

OPTICAL SPECTRA OF CANDIDATE SOUTHERN HEMISPHERE INTERNATIONAL CELESTIAL REFERENCE FRAME (ICRF) RADIO SOURCES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Titov, O.; Jauncey, D. L.; Johnston, H. M.

2011-11-15

We present the results of spectroscopic observations of the optical counterparts of 47 southern radio sources from the candidate International Celestial Reference Catalogue as part of a very long baseline interferometry (VLBI) program to strengthen the celestial reference frame, especially in the south. We made the observations with the 3.58 m European Southern Observatory New Technology Telescope. We obtained redshifts for 30 quasars and one radio galaxy, with a further seven objects being probable BL Lac objects with featureless spectra. Of the remainder, four were clear misidentifications with Galactic stars and five had low signal-to-noise spectra and could not bemore » classified. These results, in combination with new VLBI data of the radio sources with redshifts more than 2, add significantly to the existing data needed to refine the distribution of source proper motions over the celestial sphere.« less

ULX spectra revisited: Are accreting, highly magnetized neutron stars the engines of ultraluminous X-ray sources?

NASA Astrophysics Data System (ADS)

Koliopanos, F.; Vasilopoulos, G.; Bachetti, M.; Godet, O.; Webb, N.; Barret, D.

2017-10-01

In light of recent discoveries of pulsating ULXs and recently introduced models placing neutron stars as the central engines of ULXs, we revisit the spectra of seventeen ULXs, in search of indications that favor this hypothesis. To this end we examined the spectra from XMM-Newton observations of all seventeen sources in our sample. For six sources, these were complimented with spectra from public NuSTAR observations. We demonstrate that the notable ({>}6 keV) spectral curvature observed in most ULXs, is most likely due to thermal emission, with T{>} 1keV. More importantly, we find that a double thermal model (comprised of a 'cool' and 'hot' thermal component) - often associated with emission from neutron star X-ray binaries - describes all ULX spectra in our list. We propose that the dual thermal spectrum is the result of accretion onto highly magnetized NSs, as predicted in recent theoretical models (Mushtukov et al. 2017). We further argue that this finding offers an additional and compelling argument in favor of neutron stars as prime candidates for powering ULXs, as has been recently suggested (King & Lasota 2016; King et al. 2017). In my talk I will discuss the implications of our interpretation along with its merits and shortcomings.

Fermi-LAT Search for Pulsar Wind Nebulae around gamma-ray Pulsars

DOE PAGES

Ackermann, M.; Ajello, M.; Baldini, L.; ...

2010-12-13

The high sensitivity of the Fermi-LAT (Large Area Telescope) offers the first opportunity to study faint and extended GeV sources such as pulsar wind nebulae (PWNe). After one year of observation the LAT detected and identified three PWNe: the Crab Nebula, Vela-X, and the PWN inside MSH 15-52. In the meantime, the list of LAT detected pulsars increased steadily. These pulsars are characterized by high energy loss rates (more » $$\\dot{E}$$) from ~3 × 10 33 erg s –1 to 5 × 10 38 erg s –1 and are therefore likely to power a PWN. This paper summarizes the search for PWNe in the off-pulse windows of 54 LAT-detected pulsars using 16 months of survey observations. Ten sources show significant emission, seven of these likely being of magnetospheric origin. The detection of significant emission in the off-pulse interval offers new constraints on the γ-ray emitting regions in pulsar magnetospheres. The three other sources with significant emission are the Crab Nebula, Vela-X, and a new PWN candidate associated with the LAT pulsar PSR J1023–5746, coincident with the TeV source HESS J1023–575. Here, we further explore the association between the HESS and the Fermi source by modeling its spectral energy distribution. Lastly, flux upper limits derived for the 44 remaining sources are used to provide new constraints on famous PWNe that have been detected at keV and/or TeV energies.« less

High-resolution multi-band imaging for validation and characterization of small Kepler planets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Everett, Mark E.; Silva, David R.; Barclay, Thomas

2015-02-01

High-resolution ground-based optical speckle and near-infrared adaptive optics images are taken to search for stars in close angular proximity to host stars of candidate planets identified by the NASA Kepler Mission. Neighboring stars are a potential source of false positive signals. These stars also blend into Kepler light curves, affecting estimated planet properties, and are important for an understanding of planets in multiple star systems. Deep images with high angular resolution help to validate candidate planets by excluding potential background eclipsing binaries as the source of the transit signals. A study of 18 Kepler Object of Interest stars hosting amore » total of 28 candidate and validated planets is presented. Validation levels are determined for 18 planets against the likelihood of a false positive from a background eclipsing binary. Most of these are validated at the 99% level or higher, including five newly validated planets in two systems: Kepler-430 and Kepler-431. The stellar properties of the candidate host stars are determined by supplementing existing literature values with new spectroscopic characterizations. Close neighbors of seven of these stars are examined using multi-wavelength photometry to determine their nature and influence on the candidate planet properties. Most of the close neighbors appear to be gravitationally bound secondaries, while a few are best explained as closely co-aligned field stars. Revised planet properties are derived for each candidate and validated planet, including cases where the close neighbors are the potential host stars.« less

Results of the first Seismometer to Investigate Ice and Ocean Structure (SIIOS) Analogue Mission

NASA Astrophysics Data System (ADS)

Della-Giustina, Daniella; Bray, Veronica; "Hop" Bailey, Samuel; Pettit, Erin; Schmerr, Nicholas; Dahl, Peter; Avenson, Brad; Byrne, Shane; SIIOS Team

2017-10-01

The icy moons of Europa and Enceladus are thought to have global subsurface oceans in contact with mineral-rich interiors, likely providing the ingredients needed for life as we know it. The possibility of life forming in the ocean or in melt pockets, relies on the presence of a source of energy and chemistry for biological molecule formation. A thick, stagnant ice crust would likely prevent transfer of oxidants from the surface to the water, halting the development of life. The ice thickness and structure is therefore one of the most important and controversial topics in astrobiology.The best way to access an icy moon’s interior structure is with a lander-based seismometer. Our team has identified a commercial-off-the-shelf device as a flight-candidate for operation in the extreme environment of the icy moons. Based on estimates of Europan seismicity, the flight candidate device is sensitive enough to detect the ice-water boundary and pockets of liquid within the ice. Its low mass and low power enables deployment of multiple seismometers in a short-baseline array on a lander. The performance, mass, and volume of this device meet or exceed flight requirements identified in lander studies making a field test of these seismometers highly representative of a flight unit developed for an Ocean Worlds mission.We report the results of the first field campaign for the SIIOS Analogue Mission Program (AMP), which has evaluates the performance of the flight candidate seismometer in Ocean World terrestrial analogue environments. In particular, the first SIIOS AMP field exercise is performed at Gulkana Glacier, Alaska. During the summer melt season Gulkana provides kilometer-scale regions of coexisting ice, water, and silicate material, thereby providing areas with the desired analogue seismic contrasts. During this first mission, we have demonstrated device sensitivity to the detection of seismicity from high frequency (> 50 Hz) active and passive sources, the depth of ice-water boundaries, and to the ice properties using a short-baseline (1 m2) seismic array and a “lander-mounted” single station seismometer.

Production of sugarcane and tropical grasses as a renewable energy source. Second annual report, 1978-1979

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1979-01-01

Reseach continued on tropical grasses from Saccharum and related genera as sources of intensively-produced, solar-dried biomass. Categories of candidate grasses include short-, intermediate-, and long-rotation species. These categories are based on the time interval required for maximum dry matter production, and on future management requirements of energy crops for intensive co-production with food crop commodities. Year 1 studies at the greenhouse and field-plot levels were continued and broadened during Year 2. This included candidate screening, importation and quarantine of new clones, breeding, controlled nitrogen and water regimes, chemical growth control, tissue expansion and maturation control, seeding rates, harvest frequency, andmore » variable row spacing. Second-year studies were extended to the project's field-scale and mechanized-harvest phases. These include initial economic anayses for the short-rotation phases. These include initial economic analyses for the short-rotation category of candidate species.« less

Status of the OPERA experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russo, A.

2011-11-23

The OPERA experiment in the underground Gran Sasso Laboratory (LNGS) has been designed to perform the first detection of neutrino oscillations in direct appearance mode in the muon to tau neutrino channel. The detector is hybrid, being made of an emulsion/lead target and of electronic detectors. It is placed in the CNGS neutrino beam 733 km away from the neutrino source. Runs with CNGS neutrinos were successfully carried out from 2008 and the following years. The analysis of a sample of events corresponding to 1.89x10{sup 19} p.o.t. in the CERN CNGS {nu}{sub {mu}} beam yielded the observation of a firstmore » candidate {nu}{sub {tau}} CC interaction. The topology and kinematics of this candidate event is described in detail. The background sources are explained and the significance of the observation of the first {nu}{sub {tau}} event candidate is assessed.« less

Studying the interpretation of dreams in the company of analytic candidates.

PubMed

Levy, Joshua

2009-08-01

Seminars serve as an important, though undervalued, component of psychoanalytic education. The focus of this paper is on the teaching of Freud's The Interpretation of Dreams through a series of seminars presented to analytic candidates at the Toronto Psychoanalytic Institutes. This has been an essential book for introducing generations of candidates to the psychoanalytic concept of the mind and for shaping candidates' understanding and attitudes toward working with their patients' dreams. Four of Freud's basic dream concepts-(1) the method and its application to the exploration of the relationship between manifest and latent dream content, (2) the sources of dreams (day residues), (3) the dream-work, and (4) wish fulfillment-are critically studied in the seminars. Detailed discussion of these basic dream concepts among the candidates and with the teacher, as well as the candidates' feedback at the conclusion of the seminars, are summarized and discussed. Through the teaching and study within the seminar framework of the fundamentals of Freud's dream theory, a shared growth experience results for both teacher and candidates.

Design and optimization of organic rankine cycle for low temperature geothermal power plant

NASA Astrophysics Data System (ADS)

Barse, Kirtipal A.

Rising oil prices and environmental concerns have increased attention to renewable energy. Geothermal energy is a very attractive source of renewable energy. Although low temperature resources (90°C to 150°C) are the most common and most abundant source of geothermal energy, they were not considered economical and technologically feasible for commercial power generation. Organic Rankine Cycle (ORC) technology makes it feasible to use low temperature resources to generate power by using low boiling temperature organic liquids. The first hypothesis for this research is that using ORC is technologically and economically feasible to generate electricity from low temperature geothermal resources. The second hypothesis for this research is redesigning the ORC system for the given resource condition will improve efficiency along with improving economics. ORC model was developed using process simulator and validated with the data obtained from Chena Hot Springs, Alaska. A correlation was observed between the critical temperature of the working fluid and the efficiency for the cycle. Exergy analysis of the cycle revealed that the highest exergy destruction occurs in evaporator followed by condenser, turbine and working fluid pump for the base case scenarios. Performance of ORC was studied using twelve working fluids in base, Internal Heat Exchanger and turbine bleeding constrained and non-constrained configurations. R601a, R245ca, R600 showed highest first and second law efficiency in the non-constrained IHX configuration. The highest net power was observed for R245ca, R601a and R601 working fluids in the non-constrained base configuration. Combined heat exchanger area and size parameter of the turbine showed an increasing trend as the critical temperature of the working fluid decreased. The lowest levelized cost of electricity was observed for R245ca followed by R601a, R236ea in non-constrained base configuration. The next best candidates in terms of LCOE were R601a, R245ca and R600 in non-constrained IHX configuration. LCOE is dependent on net power and higher net power favors to lower the cost of electricity. Overall R245ca, R601, R601a, R600 and R236ea show better performance among the fluids studied. Non constrained configurations display better performance compared to the constrained configurations. Base non-constrained offered the highest net power and lowest LCOE.

Extended VHE γ-ray emission towards SGR1806-20, LBV 1806-20, and stellar cluster Cl* 1806-20

NASA Astrophysics Data System (ADS)

H.E.S.S. Collaboration; Abdalla, H.; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Angüner, E. O.; Arrieta, M.; Aubert, P.; Backes, M.; Balzer, A.; Barnard, M.; Becherini, Y.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Birsin, E.; Blackwell, R.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Bulik, T.; Capasso, M.; Carr, J.; Casanova, S.; Chakraborty, N.; Chalme-Calvet, R.; Chaves, R. C. G.; Chen, A.; Chevalier, J.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Condon, B.; Conrad, J.; Couturier, C.; Cui, Y.; Davids, I. D.; Degrange, B.; Deil, C.; deWilt, P.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; Drury, L. O.'C.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Edwards, T.; Egberts, K.; Eger, P.; Ernenwein, J.-P.; Eschbach, S.; Farnier, C.; Fegan, S.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Funk, S.; Füßling, M.; Gabici, S.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Gottschall, D.; Goyal, A.; Grondin, M.-H.; Grudzińska, M.; Hadasch, D.; Hahn, J.; Hawkes, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hoischen, C.; Holler, M.; Horns, D.; Ivascenko, A.; Jacholkowska, A.; Jamrozy, M.; Janiak, M.; Jankowsky, D.; Jankowsky, F.; Jingo, M.; Jogler, T.; Jouvin, L.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kerszberg, D.; Khélifi, B.; Kieffer, M.; King, J.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Kraus, M.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lau, J.; Lees, J.-P.; Lefaucheur, J.; Lefranc, V.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Leser, E.; Lohse, T.; Lorentz, M.; Liu, R.; Lypova, I.; Marandon, V.; Marcowith, A.; Mariaud, C.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; Meintjes, P. J.; Menzler, U.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Morå, K.; Moulin, E.; Murach, T.; de Naurois, M.; Niederwanger, F.; Niemiec, J.; Oakes, L.; Odaka, H.; Öttl, S.; Ohm, S.; Ostrowski, M.; Oya, I.; Padovani, M.; Panter, M.; Parsons, R. D.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Prokhorov, D.; Prokoph, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Reimer, A.; Reimer, O.; Renaud, M.; de 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.; Sasaki, M.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwemmer, S.; Seyffert, A. S.; Shafi, N.; Shilon, I.; Simoni, R.; 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.; Tuffs, R.; van der Walt, J.; van Eldik, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Voisin, F.; Völk, H. J.; Vuillaume, T.; Wadiasingh, Z.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zabalza, V.; Zaborov, D.; Zacharias, M.; Zdziarski, A. A.; Zech, A.; Zefi, F.; Ziegler, A.; Żywucka, N.

2018-04-01

Using the High Energy Spectroscopic System (H.E.S.S.) telescopes we have discovered a steady and extended very high-energy (VHE) γ-ray source towards the luminous blue variable candidate LBV 1806-20, massive stellar cluster Cl* 1806-20, and magnetar SGR 1806-20. The new VHE source, HESS J1808-204, was detected at a statistical significance of >6σ (post-trial) with a photon flux normalisation (2.9 ± 0.4stat ± 0.5sys) × 10-13 ph cm-2 s-1 TeV-1 at 1 TeV and a power-law photon index of 2.3 ± 0.2stat ± 0.3sys. The luminosity of this source (0.2 to 10 TeV; scaled to distance d = 8.7 kpc) is LVHE 1.6 × 1034(d/8.7 kpc)2 erg s-1. The VHE γ-ray emission is extended and is well fit by a single Gaussian with statistical standard deviation of 0.095° ± 0.015°. This extension is similar to that of the synchrotron radio nebula G10.0-0.3, which is thought to be powered by LBV 1806-20. The VHE γ-ray luminosity could be provided by the stellar wind luminosity of LBV 1806-20 by itself and/or the massive star members of Cl* 1806-20. Alternatively, magnetic dissipation (e.g. via reconnection) from SGR 1806-20 can potentially account for the VHE luminosity. The origin and hadronic and/or leptonic nature of the accelerated particles responsible for HESS J1808-204 is not yet clear. If associated with SGR 1806-20, the potentially young age of the magnetar (650 yr) can be used to infer the transport limits of these particles to match the VHE source size. This discovery provides new interest in the potential for high-energy particle acceleration from magnetars, massive stars, and/or stellar clusters.

14 CFR 25.1310 - Power source capacity and distribution.

Code of Federal Regulations, 2011 CFR

2011-01-01

... certification or under operating rules and that requires a power supply is an “essential load” on the power supply. The power sources and the system must be able to supply the following power loads in probable... source of power is required, after any failure or malfunction in any one power supply system...

14 CFR 25.1310 - Power source capacity and distribution.

Code of Federal Regulations, 2010 CFR

2010-01-01

... certification or under operating rules and that requires a power supply is an “essential load” on the power supply. The power sources and the system must be able to supply the following power loads in probable... source of power is required, after any failure or malfunction in any one power supply system...

Search for gamma-ray emission from Galactic novae with the Fermi -LAT

NASA Astrophysics Data System (ADS)

Franckowiak, A.; Jean, P.; Wood, M.; Cheung, C. C.; Buson, S.

2018-02-01

Context. A number of novae have been found to emit high-energy gamma rays (>100 MeV). However, the origin of this emission is not yet understood. We report on the search for gamma-ray emission from 75 optically detected Galactic novae in the first 7.4 years of operation of the Fermi Large Area Telescope using the Pass 8 data set. Aims: We compile an optical nova catalog including light curves from various resources and estimate the optical peak time and optical peak magnitude in order to search for gamma-ray emission to determine whether all novae are gamma-ray emitters. Methods: We repeated the analysis of the six novae previously identified as gamma-ray sources and developed a unified analysis strategy that we then applied to all novae in our catalog. We searched for emission in a 15 day time window in two-day steps ranging from 20 days before to 20 days after the optical peak time. We performed a population study with Monte Carlo simulations to set constraints on the properties of the gamma-ray emission of novae. Results: Two new novae candidates have been found at 2σ global significance. Although these two novae candidates were not detected at a significant level individually, taking them together with the other non-detected novae, we found a sub-threshold nova population with a cumulative 3σ significance. We report the measured gamma-ray flux for detected sources and flux upper limits for novae without significant detection. Our results can be reproduced by several gamma-ray emissivity models (e.g., a power-law distribution with a slope of 2), while a constant emissivity model (i.e., assuming novae are standard candles) can be rejected.

Search for gamma-ray emission from Galactic novae with the Fermi-LAT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Franckowiak, A.; Jean, P.; Wood, M.

Context. A number of novae have been found to emit high-energy gamma rays (>100 MeV). However, the origin of this emission is not yet understood. We report on the search for gamma-ray emission from 75 optically detected Galactic novae in the first 7.4 years of operation of the Fermi Large Area Telescope using the Pass 8 data set. Aims. We compile an optical nova catalog including light curves from various resources and estimate the optical peak time and optical peak magnitude in order to search for gamma-ray emission to determine whether all novae are gamma-ray emitters. Methods. We repeated themore » analysis of the six novae previously identified as gamma-ray sources and developed a unified analysis strategy that we then applied to all novae in our catalog. We searched for emission in a 15 day time window in two-day steps ranging from 20 days before to 20 days after the optical peak time. We performed a population study with Monte Carlo simulations to set constraints on the properties of the gamma-ray emission of novae. Results. Two new novae candidates have been found at ~ 2σ global significance. Although these two novae candidates were not detected at a significant level individually, taking them together with the other non-detected novae, we found a sub-threshold nova population with a cumulative 3σ significance. We report the measured gamma-ray flux for detected sources and flux upper limits for novae without significant detection. Lastly, our results can be reproduced by several gamma-ray emissivity models (e.g., a power-law distribution with a slope of 2), while a constant emissivity model (i.e., assuming novae are standard candles) can be rejected.« less

Search for gamma-ray emission from Galactic novae with the Fermi-LAT

DOE PAGES

Franckowiak, A.; Jean, P.; Wood, M.; ...

2018-02-05

Context. A number of novae have been found to emit high-energy gamma rays (>100 MeV). However, the origin of this emission is not yet understood. We report on the search for gamma-ray emission from 75 optically detected Galactic novae in the first 7.4 years of operation of the Fermi Large Area Telescope using the Pass 8 data set. Aims. We compile an optical nova catalog including light curves from various resources and estimate the optical peak time and optical peak magnitude in order to search for gamma-ray emission to determine whether all novae are gamma-ray emitters. Methods. We repeated themore » analysis of the six novae previously identified as gamma-ray sources and developed a unified analysis strategy that we then applied to all novae in our catalog. We searched for emission in a 15 day time window in two-day steps ranging from 20 days before to 20 days after the optical peak time. We performed a population study with Monte Carlo simulations to set constraints on the properties of the gamma-ray emission of novae. Results. Two new novae candidates have been found at ~ 2σ global significance. Although these two novae candidates were not detected at a significant level individually, taking them together with the other non-detected novae, we found a sub-threshold nova population with a cumulative 3σ significance. We report the measured gamma-ray flux for detected sources and flux upper limits for novae without significant detection. Lastly, our results can be reproduced by several gamma-ray emissivity models (e.g., a power-law distribution with a slope of 2), while a constant emissivity model (i.e., assuming novae are standard candles) can be rejected.« less

46 CFR 112.20-5 - Failure of power from the normal source or final emergency power source.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 4 2013-10-01 2013-10-01 false Failure of power from the normal source or final emergency power source. 112.20-5 Section 112.20-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING EMERGENCY LIGHTING AND POWER SYSTEMS Emergency Systems Having a Temporary...

46 CFR 112.20-5 - Failure of power from the normal source or final emergency power source.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 4 2014-10-01 2014-10-01 false Failure of power from the normal source or final emergency power source. 112.20-5 Section 112.20-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING EMERGENCY LIGHTING AND POWER SYSTEMS Emergency Systems Having a Temporary...

46 CFR 112.20-5 - Failure of power from the normal source or final emergency power source.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 4 2012-10-01 2012-10-01 false Failure of power from the normal source or final emergency power source. 112.20-5 Section 112.20-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING EMERGENCY LIGHTING AND POWER SYSTEMS Emergency Systems Having a Temporary...

46 CFR 112.20-5 - Failure of power from the normal source or final emergency power source.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 4 2011-10-01 2011-10-01 false Failure of power from the normal source or final emergency power source. 112.20-5 Section 112.20-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING EMERGENCY LIGHTING AND POWER SYSTEMS Emergency Systems Having a Temporary...

46 CFR 112.20-5 - Failure of power from the normal source or final emergency power source.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 4 2010-10-01 2010-10-01 false Failure of power from the normal source or final emergency power source. 112.20-5 Section 112.20-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING EMERGENCY LIGHTING AND POWER SYSTEMS Emergency Systems Having a Temporary...

Probing the gamma-ray emission from HESS J1834-087 using H.E.S.S. and Fermi LAT observations

NASA Astrophysics Data System (ADS)

H. E. S. S. Collaboration; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Angüner, E.; Anton, G.; Backes, M.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Bernlöhr, K.; Birsin, E.; Bissaldi, E.; Biteau, J.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Carrigan, S.; Casanova, S.; Chadwick, P. M.; Chalme-Calvet, R.; Chaves, R. C. G.; Cheesebrough, A.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Cui, Y.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; deWilt, P.; Dickinson, H. J.; Djannati-Ataï, A.; Domainko, W.; 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.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Grondin, M.-H.; Grudzińska, M.; 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.; Jacholkowska, A.; Jahn, C.; Jamrozy, M.; Janiak, M.; Jankowsky, F.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Khélifi, B.; Kieffer, M.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kneiske, T.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lefaucheur, J.; 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.; Moderski, R.; Mohamed, M.; Moulin, E.; Murach, T.; Naumann, C. L.; de Naurois, M.; Niemiec, J.; Nolan, S. J.; Oakes, L.; Odaka, H.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Parsons, R. D.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Raue, M.; Reichardt, I.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Rob, L.; Romoli, C.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sol, H.; 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.; Venter, C.; Viana, A.; Vincent, P.; 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.; Zacharias, M.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.

2015-02-01

Aims: Previous observations with the High Energy Stereoscopic System (H.E.S.S.) have revealed an extended very-high-energy (VHE; E> 100 GeV) γ-ray source, HESS J1834-087, coincident with the supernova remnant (SNR) W41. The origin of the γ-ray emission was investigated in more detail with the H.E.S.S. array and the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope. Methods: The γ-ray data provided by 61 h of observations with H.E.S.S., and four years with the Fermi LAT were analyzed, covering over five decades in energy from 1.8 GeV up to 30 TeV. The morphology and spectrum of the TeV and GeV sources were studied and multiwavelength data were used to investigate the origin of the γ-ray emission toward W41. Results: The TeV source can be modeled with a sum of two components: one point-like and one significantly extended (σTeV = 0.17° ± 0.01°), both centered on SNR W41 and exhibiting spectra described by a power law with index ΓTeV ≃ 2.6. The GeV source detected with Fermi LAT is extended (σGeV = 0.15° ± 0.03°) and morphologically matches the VHE emission. Its spectrum can be described by a power-law model with an index ΓGeV = 2.15 ± 0.12 and smoothly joins the spectrum of the whole TeV source. A break appears in the γ-ray spectra around 100 GeV. No pulsations were found in the GeV range. Conclusions: Two main scenarios are proposed to explain the observed emission: a pulsar wind nebula (PWN) or the interaction of SNR W41 with an associated molecular cloud. X-ray observations suggest the presence of a point-like source (a pulsar candidate) near the center of the remnant and nonthermal X-ray diffuse emission that could arise from the possibly associated PWN. The PWN scenario is supported by the compatible positions of the TeV and GeV sources with the putative pulsar. However, the spectral energy distribution from radio to γ-rays is reproduced by a one-zone leptonic model only if an excess of low-energy electrons is injected following a Maxwellian distribution by a pulsar with a high spin-down power (>1037 erg s-1). This additional low-energy component is not needed if we consider that the point-like TeV source is unrelated to the extended GeV and TeV sources. The interacting SNR scenario is supported by the spatial coincidence between the γ-ray sources, the detection of OH (1720 MHz) maser lines, and the hadronic modeling.

Probing the gamma-ray emission from HESS J1834–087 using H.E.S.S. and FermiLAT observations

DOE PAGES

Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; ...

2015-01-20

Aims. Previous observations with the High Energy Stereoscopic System (H.E.S.S.) have revealed an extended very-high-energy (VHE; E> 100 GeV) γ-ray source, HESS J1834-087, coincident with the supernova remnant (SNR) W41. The origin of the γ-ray emission was investigated in more detail with the H.E.S.S. array and the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope. Methods. For this research, the γ-ray data provided by 61 h of observations with H.E.S.S., and four years with the Fermi LAT were analyzed, covering over five decades in energy from 1.8 GeV up to 30 TeV. The morphology and spectrum of themore » TeV and GeV sources were studied and multiwavelength data were used to investigate the origin of the γ-ray emission toward W41. Results. The TeV source can be modeled with a sum of two components: one point-like and one significantly extended (σ TeV = 0.17° ± 0.01°), both centered on SNR W41 and exhibiting spectra described by a power law with index Γ TeV ≃ 2.6. The GeV source detected with Fermi LAT is extended (σ GeV = 0.15° ± 0.03°) and morphologically matches the VHE emission. Its spectrum can be described by a power-law model with an index Γ GeV = 2.15 ± 0.12 and smoothly joins the spectrum of the whole TeV source. A break appears in the γ-ray spectra around 100 GeV. No pulsations were found in the GeV range. Conclusions. Two main scenarios are proposed to explain the observed emission: a pulsar wind nebula (PWN) or the interaction of SNR W41 with an associated molecular cloud. X-ray observations suggest the presence of a point-like source (a pulsar candidate) near the center of the remnant and nonthermal X-ray diffuse emission that could arise from the possibly associated PWN. The PWN scenario is supported by the compatible positions of the TeV and GeV sources with the putative pulsar. However, the spectral energy distribution from radio to γ-rays is reproduced by a one-zone leptonic model only if an excess of low-energy electrons is injected following a Maxwellian distribution by a pulsar with a high spin-down power (>1037 erg s-1). This additional low-energy component is not needed if we consider that the point-like TeV source is unrelated to the extended GeV and TeV sources. Finally, the interacting SNR scenario is supported by the spatial coincidence between the γ-ray sources, the detection of OH (1720 MHz) maser lines, and the hadronic modeling.« less

Development of a robust space power system decision model

NASA Astrophysics Data System (ADS)

Chew, Gilbert; Pelaccio, Dennis G.; Jacobs, Mark; Stancati, Michael; Cataldo, Robert

2001-02-01

NASA continues to evaluate power systems to support human exploration of the Moon and Mars. The system(s) would address all power needs of surface bases and on-board power for space transfer vehicles. Prior studies have examined both solar and nuclear-based alternatives with respect to individual issues such as sizing or cost. What has not been addressed is a comprehensive look at the risks and benefits of the options that could serve as the analytical framework to support a system choice that best serves the needs of the exploration program. This paper describes the SAIC developed Space Power System Decision Model, which uses a formal Two-step Analytical Hierarchy Process (TAHP) methodology that is used in the decision-making process to clearly distinguish candidate power systems in terms of benefits, safety, and risk. TAHP is a decision making process based on the Analytical Hierarchy Process, which employs a hierarchic approach of structuring decision factors by weights, and relatively ranks system design options on a consistent basis. This decision process also includes a level of data gathering and organization that produces a consistent, well-documented assessment, from which the capability of each power system option to meet top-level goals can be prioritized. The model defined on this effort focuses on the comparative assessment candidate power system options for Mars surface application(s). This paper describes the principles of this approach, the assessment criteria and weighting procedures, and the tools to capture and assess the expert knowledge associated with space power system evaluation. .

A Novel Type of Battery-Supercapacitor Hybrid Device with Highly Switchable Dual Performances Based on a Carbon Skeleton/Mg2Ni Free-Standing Hydrogen Storage Electrode.

PubMed

Li, Na; Du, Yi; Feng, Qing-Ping; Huang, Gui-Wen; Xiao, Hong-Mei; Fu, Shao-Yun

2017-12-27

The sharp proliferation of high power electronics and electrical vehicles has promoted growing demands for power sources with both high energy and power densities. Under these circumstances, battery-supercapacitor hybrid devices are attracting considerable attention as they combine the advantages of both batteries and supercapacitors. Here, a novel type of hybrid device based on a carbon skeleton/Mg 2 Ni free-standing electrode without the traditional nickel foam current collector is reported, which has been designed and fabricated through a dispersing-freeze-drying method by employing reduced graphene oxide (rGO) and multiwalled carbon nanotubes (MWCNTs) as a hybrid skeleton. As a result, the Mg 2 Ni alloy is able to deliver a high discharge capacity of 644 mAh g -1 and, more importantly, a high cycling stability with a retention of over 78% after 50 charge/discharge cycles have been achieved, which exceeds almost all the results ever reported on the Mg 2 Ni alloy. Simultaneously, the electrode could also exhibit excellent supercapacitor performances including high specific capacities (296 F g -1 ) and outstanding cycling stability (100% retention after 100 cycles). Moreover, the hybrid device can switch between battery and supercapacitor modes immediately as needed during application. These features make the C skeleton/alloy electrode a highly promising candidate for battery-supercapacitor hybrid devices with high power/energy density and favorable cycling stability.

Catalytic partial oxidation reforming of hydrocarbon fuels.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahmed, S.

1998-09-21

The polymer electrolyte fuel cell (PEFC) is the primary candidate as the power source for light-duty transportation systems. On-board conversion of fuels (reforming) to supply the required hydrogen has the potential to provide the driving range that is typical of today's automobiles. Petroleum-derived fuels, gasoline or some distillate similar to it, are attractive because of their existing production, distribution, and retailing infrastructure. The fuel may be either petroleum-derived or other alternative fuels such as methanol, ethanol, natural gas, etc. [1]. The ability to use a variety of fuels is also attractive for stationary distributed power generation [2], such as inmore » buildings, or for portable power in remote locations. Argonne National Laboratory has developed a catalytic reactor based on partial oxidation reforming that is suitable for use in light-duty vehicles powered by fuel cells. The reactor has shown the ability to convert a wide variety of fuels to a hydrogen-rich gas at less than 800 C, temperatures that are several hundreds of degrees lower than alternative noncatalytic processes. The fuel may be methanol, ethanol, natural gas, or petroleum-derived fuels that are blends of various hydrocarbons such as paraffins, olefins, aromatics, etc., as in gasoline. This paper will discuss the results obtained from a bench-scale (3-kWe) reactor., where the reforming of gasoline and natural gas generated a product gas that contained 38% and 42% hydrogen on a dry basis at the reformer exit, respectively.« less

Searching for Young Stars in Cepheus C

NASA Astrophysics Data System (ADS)

Evans, Sam; Rebull, Luisa; Rutherford, Thomas; Stalnaker, Olivia; Taylor, John; Efsits, Gabriel; Harl, Linda; Keil, Shayna; Learman, Duncan; Leonard, Liam; Russell, Aaron

2018-01-01

We used archival Herschel Space Observatory data to search for young stellar objects (YSOs) in the Cepheus C region of the molecular cloud Cepheus OB3. Previous work by Gutermuth et al. (2009) identified 114 YSO candidates in this region based on Spitzer/IRAC data. Work by Orr et al. (2016) refined a list of approximately 300 young star candidates to 245 likely YSOs. Our initial search focused on longer infrared wavelength data – Herschel (70, 160, 250, 350, 500 μm) archival data and SCUBA (450, 850 μm) data from the literature (DiFrancesco et al. 2008). Through image inspection and catalog matching, we assembled a list of 54 candidate YSOs detected at wavelengths longer than 22 μm. For each source, we constructed a spectral energy distribution (SED) by aggregating available shorter wavelength data from the literature and assembling photometry from released PACS catalogs, preliminary SPIRE catalogs, and our own photometric measurements. We also created color-color and color-magnitude diagrams to see how these sources compared to each other, other populations of YSOs, and objects in extragalactic regions. Each source was then classified based on its SED shape and its locations on color-color and color-magnitude diagrams. From the initial list of 54 candidates, we suspect all are likely YSOs, some of which are very embedded; ~40% are likely SED Class I or 0. Approximately 20% of the 54 sources have not been previously identified. By beginning the investigation of YSOs in this region, we are adding to the body of YSO knowledge which can be used to understand the process of star formation. This research was made possible through the NASA/IPAC Teacher Archive Research Program (NITARP) and was funded by NASA Astrophysics Data Program.

"They Were Constantly on the Losing Side of Things": The Pedagogical Power of an African-American Teacher Candidate Bearing Witness in Teacher Education

ERIC Educational Resources Information Center

Bryson, Brandy S.

2017-01-01

The stories of students and teacher candidates of Color (Just as singular racial/ethnic identities are capitalized (i.e. African-American, Asian, Latina, Native American etc.), I capitalize Color to honor the various identities that many "non-white" people hold near and dear. I recognize the nuances in doing so- such as the reality that…

Atomic Oxygen Exposure of Power System and other Spacecraft Materials: Results of the EOIM-3 Experiment

NASA Technical Reports Server (NTRS)

Morton, Thomas L.; Ferguson, Dale C.

1997-01-01

In order to test their reactivity with Atomic Oxygen, twenty five materials were flown on the EOIM-3 (Evaluation of Oxygen Interactions with Materials) portion of the STS-46 Mission. These materials include refractory metals, candidate insulation materials, candidate radiator coatings, and a selection of miscellaneous materials. This report documents the results of the pre- and post-flight analysis of these materials.

SEARCHES FOR TIME-DEPENDENT NEUTRINO SOURCES WITH ICECUBE DATA FROM 2008 TO 2012

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aartsen, M. G.; Ackermann, M.; Adams, J.

2015-07-01

In this paper searches for flaring astrophysical neutrino sources and sources with periodic emission with the IceCube neutrino telescope are presented. In contrast to time-integrated searches, where steady emission is assumed, the analyses presented here look for a time-dependent signal of neutrinos using the information from the neutrino arrival times to enhance the discovery potential. A search was performed for correlations between neutrino arrival times and directions, as well as neutrino emission following time-dependent light curves, sporadic emission, or periodicities of candidate sources. These include active galactic nuclei, soft γ-ray repeaters, supernova remnants hosting pulsars, microquasars, and X-ray binaries. Themore » work presented here updates and extends previously published results to a longer period that covers 4 years of data from 2008 April 5 to 2012 May 16, including the first year of operation of the completed 86 string detector. The analyses did not find any significant time-dependent point sources of neutrinos, and the results were used to set upper limits on the neutrino flux from source candidates.« less

Comparative analysis of protein interactome networks prioritizes candidate genes with cancer signatures.

PubMed

Li, Yongsheng; Sahni, Nidhi; Yi, Song

2016-11-29

Comprehensive understanding of human cancer mechanisms requires the identification of a thorough list of cancer-associated genes, which could serve as biomarkers for diagnoses and therapies in various types of cancer. Although substantial progress has been made in functional studies to uncover genes involved in cancer, these efforts are often time-consuming and costly. Therefore, it remains challenging to comprehensively identify cancer candidate genes. Network-based methods have accelerated this process through the analysis of complex molecular interactions in the cell. However, the extent to which various interactome networks can contribute to prediction of candidate genes responsible for cancer is still enigmatic. In this study, we evaluated different human protein-protein interactome networks and compared their application to cancer gene prioritization. Our results indicate that network analyses can increase the power to identify novel cancer genes. In particular, such predictive power can be enhanced with the use of unbiased systematic protein interaction maps for cancer gene prioritization. Functional analysis reveals that the top ranked genes from network predictions co-occur often with cancer-related terms in literature, and further, these candidate genes are indeed frequently mutated across cancers. Finally, our study suggests that integrating interactome networks with other omics datasets could provide novel insights into cancer-associated genes and underlying molecular mechanisms.

Digital Flight Control System Redundancy Study

DTIC Science & Technology

1974-07-01

has its own separate power supr, y . d. Digital Processor The digital processor consists of the followdnq components: (1) Program Counter - This...1-3 Yaw Axis Control 108 1-4 Autothrottle (Airspeed Hold Mode) 109 1-5 Approach Power Compensation 110 1-6 Glideslope Flare 111 I-7 Glideslope Track...considsred to the extent that they imposed constraints on the candidate con- figurations. Cost, size, weight, power , maintainability, survivability and

Thermal control of power supplies with electronic packaging techniques. [using low cost heat pipes

NASA Technical Reports Server (NTRS)

1977-01-01

The integration of low-cost commercial heat pipes in the design of a NASA candidate standard modular power supply with a 350 watt output resulted in a 44% weight reduction. Part temperatures were also appreciably reduced, increasing the environmental capability of the unit. A complete 350- watt modular power converter was built and tested to evaluate thermal performance of the redesigned supply.

A Program of Basic Research for High Power Switching and Other High Power Devices

DTIC Science & Technology

1989-05-23

Physics Topical Group/American Physical Society, Baltimore, Maryland, April 18-21, 1988, Bull. Am. Phys. Soc. 33, 1082 (1988). "New High Power Thyratrons...American Physical Society, Baltimore, Maryland, April 18-21, 1988, Bull. Am. Phys. Soc. 33, 1082 (1988). "A plasma lens candidate with highly stable...April 18-21, 1988, Bull. Am. Phys. Soc. 33. 1082 (1988). "New High Power Thyratrons for High Energy Physics Applications," W. Hartmann, G. Kirkman, M.A

Grid-independent residential power systems

NASA Astrophysics Data System (ADS)

Nelson, Robert E.

1996-02-01

A self-powered, gas-fired, warm air furnace is evaluated as a candidate for the autonomous generation of electrical power. A popular, commercial residential furnace is analyzed for electrical power requirements. Available energy conversion concepts are considered for this application, and the thermophotovoltaic (TPV) option is selected due to reliability and cost. The design and the internal components peculiar to the TPV converter will be covered. Operating results, including NOx emission, will be summarized. This work was sponsored by the Basic Research Group, Gas Research Institute, Chicago, IL.

RITES: Online (Reaching In-service Teachers with Earth Sciences Online)

NASA Astrophysics Data System (ADS)

Baptiste, H.

2003-12-01

The RITES: Online project team (Drs. H. Prentice Baptiste, Susan Brown, Jennifer Villa) believed that the power of technology could not be effectively utilized unless it was grounded in new models of teaching and learning based on a student centered and project based curriculum, that increased opportunities for active, hands-on learning and respect for multiculturalism. We subscribe to an inquiry approach to learning. Specifically, science teaching should actively engage the learners in activities that draw on multiple abilities and learning styles. Recent brain-based research has shown that human beings construct knowledge through actions and interactions within their environment. Learning occurs in communities, and new ideas are linked to previous knowledge and constructed by the learner. Knowledge is acquired by making connections. We believed the aforementioned ideas and points to be equally true for the teacher candidates and inservice teachers participating in the RITES: Online project as well as for their students. The ESSEA science courses were delivered by distance learning via the university WebCt distance education system to teacher candidates (preservice teachers) and inservice teachers. Teacher candidates and inservice teachers were encouraged to use technology when involving their students in science inquiry activities and to record their students' involvement in science activities with digital cameras. Teacher candidates and inservice teachers involve in the ESSEA courses are engaged in earth science inquiry activities relevant to the four spheres (atmosphere, lithosphere, biosphere, hydrosphere) with the students in their classes. This presentation will highlight teacher candidates and inservice teachers in the roles of designer, researcher, and collaborator. Examples of student works will also be a part of the Power point presentation. As a result of our courses our teachers have attained the following positive outcomes: 1) Teacher candidates and inservice teachers are experiencing the inquiry approach to learning about the spheres of our earth. 2) Teacher candidates and inservice teachers are becoming confident in using technology. 3) Teacher candidates and inservice teachers are learning to work cooperatively in-groups and understand what their own students must feel. 4) Teacher candidates and inservice teachers are finding ways to obtain dynamic professional development and not leave their classrooms or homes. 5) Teacher candidates and inservice teachers are developing relationships with other teachers that have an interest in teaching science and a learning community is evolving.

FOUR DUAL AGN CANDIDATES OBSERVED WITH THE VLBA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gabányi, K. É.; Frey, S.; An, T.

According to hierarchical structure formation models, merging galaxies are expected to be seen in different stages of coalescence. However, there are currently no straightforward observational methods to either select or to confirm a large number of dual active galactic nucleus (AGN) candidates. Most attempts involve obtaining a better understanding of double-peaked narrow emission line sources, in order to distinguish the objects for which the emission lines originate from narrow-line kinematics or jet-driven outflows, from those which might harbor dual AGNs. We observed four such candidate sources with the Very Long Baseline Array (VLBA), at 1.5 GHz with a ∼10 masmore » angular resolution, for which the spectral profiles of AGN optical emission suggested the existence of dual AGNs. In SDSS J210449.13–000919.1 and SDSS J23044.82–093345.3 the radio structures are aligned with the optical emission features, thus the double-peaked emission lines might be the results of jet-driven outflows. In the third detected source SDSS J115523.74+150756.9, the radio structure is less extended and is oriented nearly perpendicular to the position angle derived from optical spectroscopy. The fourth source remained undetected with the VLBA, but it was imaged with the Very Large Array at arcsec resolution a few months before our observations, suggesting the existence of an extended radio structure. We did not detect two radio-emitting cores in any of the four sources, a convincing signature of duality.« less

An Ultraviolet-Excess Optical Candidate for the Luminous Globular Cluster X-Ray Source in NGC 1851

NASA Technical Reports Server (NTRS)

Deutsch, Eric W.; Anderson, Scott F.; Margon, Bruce; Downes, Ronald A.

1996-01-01

The intense, bursting X-ray source in the globular cluster NGC 1851 was one of the first cluster sources discovered, but has remained optically unidentified for 25 years. We report here on results from Hubble Space Telescope WFPC2 multicolor images in NGC 1851. Our high spatial resolution images resolve approximately 200 objects in the 3 minute radius Einstein X-ray error circle, 40 times as many as in previous ground-based work. A color-magnitude diagram of the cluster clearly reveals a markedly UV-excess object with B approximately 21, (U - B) approximately -0.9, only 2 minutes from the X-ray position. The UV-excess candidate is 0.12 minutes distant from a second, unremarkable star that is 0.5 mag brighter in B; thus ground-based studies of this field are probably impractical. Three other UV-excess objects are also present among the approximately 16,000 objects in the surveyed region of the cluster, leaving an approximately 5% probability that a UV-excess object has fallen in the X-ray error circle by chance. No variability of the candidate is seen in these data, although a more complete study is required. If this object is in fact the counterpart of the X-ray source, previous inferences that some globular cluster X-ray sources are optically subluminous with respect to low-mass X-ray binaries in the field are now strengthened.

Electrical system architecture

DOEpatents

Algrain, Marcelo C [Peoria, IL; Johnson, Kris W [Washington, IL; Akasam, Sivaprasad [Peoria, IL; Hoff, Brian D [East Peoria, IL

2008-07-15

An electrical system for a vehicle includes a first power source generating a first voltage level, the first power source being in electrical communication with a first bus. A second power source generates a second voltage level greater than the first voltage level, the second power source being in electrical communication with a second bus. A starter generator may be configured to provide power to at least one of the first bus and the second bus, and at least one additional power source may be configured to provide power to at least one of the first bus and the second bus. The electrical system also includes at least one power consumer in electrical communication with the first bus and at least one power consumer in electrical communication with the second bus.

Planetary Nebula Candidates Uncovered with the HASH Research Platform

NASA Astrophysics Data System (ADS)

Fragkou, Vasiliki; Bojičić, Ivan; Frew, David; Parker, Quentin

2017-10-01

A detailed examination of new high quality radio catalogues (e.g. Cornish) in combination with available mid-infrared (MIR) satellite imagery (e.g. Glimpse) has allowed us to find 70 new planetary nebula (PN) candidates based on existing knowledge of their typical colors and fluxes. To further examine the nature of these sources, multiple diagnostic tools have been applied to these candidates based on published data and on available imagery in the HASH (Hong Kong/ AAO/ Strasbourg Hα planetary nebula) research platform. Some candidates have previously-missed optical counterparts allowing for spectroscopic follow-up. Indeed, the single object spectroscopically observed so far has turned out to be a bona fide PN.

Alternate energy source usage for in situ heat treatment processes

DOEpatents

Stone, Jr., Francis Marion; Goodwin, Charles R [League City, TX; Richard, Jr., James

2011-03-22

Systems, methods, and heaters for treating a subsurface formation are described herein. At least one system for providing power to one or more subsurface heaters is described herein. The system may include an intermittent power source; a transformer coupled to the intermittent power source, and a tap controller coupled to the transformer. The transformer may be configured to transform power from the intermittent power source to power with appropriate operating parameters for the heaters. The tap controller may be configured to monitor and control the transformer so that a constant voltage is provided to the heaters from the transformer regardless of the load of the heaters and the power output provided by the intermittent power source.