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Sample records for closely spaced quasar

  1. Close companions to two high-redshift quasars

    SciTech Connect

    McGreer, Ian D.; Fan, Xiaohui; Bian, Fuyan; Strauss, Michael A.; Haiman, Zoltàn; Richards, Gordon T.; Jiang, Linhua; Schneider, Donald P.

    2014-10-01

    We report the serendipitous discoveries of companion galaxies to two high-redshift quasars. SDSS J025617.7+001904 is a z = 4.79 quasar included in our recent survey of faint quasars in the SDSS Stripe 82 region. The initial MMT slit spectroscopy shows excess Lyα emission extending well beyond the quasar's light profile. Further imaging and spectroscopy with LBT/MODS1 confirms the presence of a bright galaxy (i {sub AB} = 23.6) located 2'' (12 kpc projected) from the quasar with strong Lyα emission (EW{sub 0} ≈ 100 Å) at the redshift of the quasar, as well as faint continuum. The second quasar, CFHQS J005006.6+344522 (z = 6.25), is included in our recent HST SNAP survey of z ∼ 6 quasars searching for evidence of gravitational lensing. Deep imaging with ACS and WFC3 confirms an optical dropout ∼4.5 mag fainter than the quasar (Y {sub AB} = 25) at a separation of 0.''9. The red i {sub 775} – Y {sub 105} color of the galaxy and its proximity to the quasar (5 kpc projected if at the quasar redshift) strongly favor an association with the quasar. Although it is much fainter than the quasar, it is remarkably bright when compared to field galaxies at this redshift, while showing no evidence for lensing. Both systems may represent late-stage mergers of two massive galaxies, with the observed light for one dominated by powerful ongoing star formation and for the other by rapid black hole growth. Observations of close companions are rare; if major mergers are primarily responsible for high-redshift quasar fueling then the phase when progenitor galaxies can be observed as bright companions is relatively short.

  2. Quasar Astrophysics with the Space Interferometry Mission

    NASA Technical Reports Server (NTRS)

    Unwin, Stephen; Wehrle, Ann; Meier, David; Jones, Dayton; Piner, Glenn

    2007-01-01

    Optical astrometry of quasars and active galaxies can provide key information on the spatial distribution and variability of emission in compact nuclei. The Space Interferometry Mission (SIM PlanetQuest) will have the sensitivity to measure a significant number of quasar positions at the microarcsecond level. SIM will be very sensitive to astrometric shifts for objects as faint as V = 19. A variety of AGN phenomena are expected to be visible to SIM on these scales, including time and spectral dependence in position offsets between accretion disk and jet emission. These represent unique data on the spatial distribution and time dependence of quasar emission. It will also probe the use of quasar nuclei as fundamental astrometric references. Comparisons between the time-dependent optical photocenter position and VLBI radio images will provide further insight into the jet emission mechanism. Observations will be tailored to each specific target and science question. SIM will be able to distinguish spatially between jet and accretion disk emission; and it can observe the cores of galaxies potentially harboring binary supermassive black holes resulting from mergers.

  3. Low-redshift quasars in the SDSS Stripe 82. Host galaxy colours and close environment

    NASA Astrophysics Data System (ADS)

    Bettoni, D.; Falomo, R.; Kotilainen, J. K.; Karhunen, K.; Uslenghi, M.

    2015-12-01

    We present a photometrical and morphological multicolour study of the properties of low-redshift (z < 0.3) quasar hosts based on a large and homogeneous data set of quasars derived from the Sloan Digital Sky Survey (DR7). We used quasars that were imaged in the SDSS Stripe82 that is up to 2 mag deeper than standard Sloan images. This sample is part of a larger data set of ˜400 quasars at z < 0.5 for which both the host galaxies and their galaxy environments were studied. For 52 quasars, we undertake a study of the colour of the host galaxies and of their close environments in the u, g, r, i and z bands. We are able to resolve almost all the quasars in the sample in the filters g, r, i and z and also in u for about 50 per cent of the targets. We found that the mean colours of the QSO host galaxy (g - i = 0.82 ± 0.26; r - i = 0.26 ± 0.16 and u - g = 1.32 ± 0.25) are very similar to the values of a sample of inactive galaxies matched in terms of redshift and galaxy luminosity with the quasar sample. There is a suggestion that the most massive QSO hosts have bluer colours. Both quasar hosts and the comparison sample of inactive galaxies have candidates of close (<50 kpc) companion galaxies for ˜30 per cent of the sources with no significant difference between active and inactive galaxies. We do not find significant correlation between the central black hole (BH) mass and the quasar host luminosity that appears to be extra luminous at a given BH mass with respect to the local relation (MBH - Mhost) for inactive galaxies. This confirms previous suggestion that a substantial disc component, not correlated with the BH mass, is present in the galaxies hosting low-z quasars. These results support a scenario where the activation of the nucleus has negligible effects on the global structural and photometrical properties of the hosting galaxies.

  4. Hubble Space Telescope Images of Nearby Luminous Quasars. 2; Results for Eight Quasars and Tests of the Detection Sensitivity

    NASA Technical Reports Server (NTRS)

    Bahcall, John N.; Kirhakos, Sofia; Schneider, Donald P.

    1995-01-01

    Observations with the Wide-Field Camera of the Hubble Space Telescope (HST) are presented for eight intrinsically luminous quasars with redshifts between 0.16 and 0.29. These observations, when combined with a similar HST study of the quasar PKS 2349-014, show that luminous nearby quasars exist in a variety of environments. Seven companion galaxies brighter than M(V) = 16.5 (H(sub 0) = 100 km s(sup -1) Mpc(sup -1), Omega(sub 0) = 1.0) lie within a projected distance of 25 kpc of the quasars; three of the companions are located closer than 3'' (6 kpc projected distance) from the quasars, well within the volume that would be enclosed by a typical L* host galaxy. The observed association of quasars and companion galaxies is statistically significant and may he an important element in the luminous-quasar phenomenon. Apparent host galaxies are detected for three of the quasars: PG 1116+215, 3C 273, and PG 1444+407; the hosts have an average absolute magnitude of about 0.6 mag brighter than L*. The agreement between the previously published major-axis directions in ground-based images and in the present HST images of 3C 273 and PG 1444+407 constitutes important evidence supporting the reality of these candidate host galaxies. Upper limits are placed on the visual-band brightnesses of representative galactic hosts for all the quasars. These limits are established by placing galaxy images obtained with HST underneath the quasars and measuring at what faintness level the known galaxies are detected. On average, the HST spirals would have been detected if they were as faint as 1 mag below L*, and the early-type galaxies could have been detected down to a brightness level of about L*, where L* is the Schechter characteristic luminosity of field galaxies. Smooth, featureless galaxy models (exponential disks or de Vaucouleurs profiles) are fitted to the residual light after a best-fitting point source is subtracted from the quasar images. The results show that smooth spiral

  5. Hubble Space Telescope Imaging of Post-starburst Quasars

    NASA Astrophysics Data System (ADS)

    Cales, S. L.; Brotherton, M. S.; Shang, Zhaohui; Bennert, Vardha Nicola; Canalizo, G.; Stoll, R.; Ganguly, R.; Vanden Berk, D.; Paul, C.; Diamond-Stanic, A.

    2011-11-01

    We present images of 29 post-starburst quasars (PSQs) from a Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) Wide Field Channel Snapshot program. These broadlined active galactic nuclei (AGNs) possess the spectral signatures of massive (M burst ~ 1010 M sun), moderate-aged stellar populations (hundreds of Myr). Thus, their composite nature provides insight into the AGN-starburst connection. We measure quasar-to-host galaxy light contributions via semi-automated two-dimensional light profile fits of point-spread-function-subtracted images. We examine the host morphologies and model the separate bulge and disk components. The HST/ACS-F606W images reveal an equal number of spiral (13/29) and early-type (13/29) hosts, with the remaining three hosts having indeterminate classifications. AGNs hosted by early-type galaxies have on average greater luminosity than those hosted by spiral galaxies. Disturbances such as tidal tails, shells, star-forming knots, and asymmetries are seen as signposts of interaction/merger activity. Disturbances like these were found in 17 of the 29 objects and are evenly distributed among early-type and spiral galaxies. Two of these systems are clearly merging with their companions. Compared to other AGNs of similar luminosity and redshift, these PSQs have a higher fraction of early-type hosts and disturbances. Our most luminous objects with disturbed early-type host galaxies appear to be consistent with merger products. Thus, these luminous galaxies may represent a phase in an evolutionary scenario for merger-driven activity. Our less luminous objects appear to be consistent with Seyfert galaxies not requiring triggering by major mergers. Many of these Seyferts are barred spiral galaxies.

  6. HUBBLE SPACE TELESCOPE IMAGING OF POST-STARBURST QUASARS

    SciTech Connect

    Cales, S. L.; Brotherton, M. S.; Shang Zhaohui; Bennert, Vardha Nicola; Canalizo, G.; Stoll, R.; Ganguly, R.; Vanden Berk, D.; Paul, C.; Diamond-Stanic, A. E-mail: mbrother@uwyo.edu E-mail: bennert@physics.ucsb.edu E-mail: stoll@astronomy.ohio-state.edu E-mail: daniel.vandenberk@email.stvincent.edu E-mail: aleks@ucsd.edu

    2011-11-10

    We present images of 29 post-starburst quasars (PSQs) from a Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) Wide Field Channel Snapshot program. These broadlined active galactic nuclei (AGNs) possess the spectral signatures of massive (M{sub burst} {approx} 10{sup 10} M{sub sun}), moderate-aged stellar populations (hundreds of Myr). Thus, their composite nature provides insight into the AGN-starburst connection. We measure quasar-to-host galaxy light contributions via semi-automated two-dimensional light profile fits of point-spread-function-subtracted images. We examine the host morphologies and model the separate bulge and disk components. The HST/ACS-F606W images reveal an equal number of spiral (13/29) and early-type (13/29) hosts, with the remaining three hosts having indeterminate classifications. AGNs hosted by early-type galaxies have on average greater luminosity than those hosted by spiral galaxies. Disturbances such as tidal tails, shells, star-forming knots, and asymmetries are seen as signposts of interaction/merger activity. Disturbances like these were found in 17 of the 29 objects and are evenly distributed among early-type and spiral galaxies. Two of these systems are clearly merging with their companions. Compared to other AGNs of similar luminosity and redshift, these PSQs have a higher fraction of early-type hosts and disturbances. Our most luminous objects with disturbed early-type host galaxies appear to be consistent with merger products. Thus, these luminous galaxies may represent a phase in an evolutionary scenario for merger-driven activity. Our less luminous objects appear to be consistent with Seyfert galaxies not requiring triggering by major mergers. Many of these Seyferts are barred spiral galaxies.

  7. A census of quasar-intrinsic absorption in the Hubble Space Telescope archive: systems from high-resolution echelle spectra

    NASA Astrophysics Data System (ADS)

    Ganguly, Rajib; Lynch, Ryan S.; Charlton, Jane C.; Eracleous, Michael; Tripp, Todd M.; Palma, Christopher; Sembach, Kenneth R.; Misawa, Toru; Masiero, Joseph R.; Milutinovic, Nikola; Lackey, Benjamin D.; Jones, Therese M.

    2013-10-01

    We present a census of zabs ≲ 2 intrinsic (those showing partial coverage) and associated (zabs ˜ zem) quasar absorption-line systems detected in the Hubble Space Telescope archive of Space Telescope Imaging Spectrograph echelle spectra. This work complements the Misawa et al. survey of 2 < zem < 4 quasars that selects systems using similar techniques. We confirm the existence of so-called strong N V intrinsic systems (where the equivalent width of H I Lyα is small compared to N V λ1238) presented in that work, but find no convincing cases of `strong C IV' intrinsic systems at low redshift/luminosity. Moreover, we also report on the existence of `strong O VI' systems. From a comparison of partial coverage results as a function of ion, we conclude that systems selected by the N V ion have the highest probability of being intrinsic. By contrast, the C IV and O VI ions are poor selectors. Of the 30 O VI systems tested, only two of the systems in the spectrum on 3C 351 show convincing evidence for partial coverage. However, there is an ˜3σ excess in the number of absorbers near the quasar redshift (|Δv| ≤ 5000 km s-1) over absorbers at large redshift differences. In at least two cases, the associated O VI systems are known not to arise close to the accretion disc of the quasar.

  8. The Hubble Space Telescope Quasar Absorption Line Key Project. 10: Galactic H I 21 centimeter emission toward 143 quasars and active Galactic nuclei

    NASA Technical Reports Server (NTRS)

    Lockman, Felix J.; Savage, Blair D.

    1995-01-01

    Sensitive H I 21 cm emission line spectra have been measured for the directions to 143 quasars and active galactic nuclei (AGNs) chosen from the observing lists for the Hubble Space Telescope (HST) Quasar Absorption Line Key Project. Narrow-band and wide-band data were obtained with the National Radio Astronomy Observatory (NRAO) 43 m radio telescope for each object. The narrow-band data have a velocity resolution of 1 km/s, extend from -220 to +170 km/s, and are corrected for stray 21 cm radiation. The wide-band data have a resolution of 4 km/s and extend from -1000 to +1000 km/s. The data are important for the interpretation of ultraviolet absorption lines near zero redshift in Key Project spectra. Twenty-two percent of the quasars lie behind Galactic high-velocity H I clouds with absolute value of V(sub LSR) greater than 100 km/s whose presence can increase the equivalent width of interstellar absorption lines significantly. This paper contains the emission spectra and measures of the H I velocities and column densities along the sight line to each quasar. We discuss how the measurements can be used to estimate the visual and ultraviolet extinction toward each quasar and to predict the approximate strength of the strong ultraviolet resonance lines of neutral gas species in the HST Key Project spectra.

  9. HUBBLE SPACE TELESCOPE NARROWBAND SEARCH FOR EXTENDED Ly{alpha} EMISSION AROUND TWO z > 6 QUASARS

    SciTech Connect

    Decarli, Roberto; Walter, Fabian; Yang Yujin; Hennawi, Joseph F.; Rix, Hans-Walter; Venemans, Bram P.; Carilli, Chris L.; Fan Xiahoui; Kurk, Jaron; Riechers, Dominik; Strauss, Michael A.

    2012-09-10

    We search for extended Ly{alpha} emission around two z > 6 quasars, SDSS J1030+0524 (z = 6.309) and SDSS J1148+5251 (z = 6.419) using Wide Field Camera 3 narrowband filters on board the Hubble Space Telescope. For each quasar, we collected two deep, narrowband images, one sampling the Ly{alpha} line+continuum at the quasar redshifts and one of the continuum emission redward of the line. After carefully modeling the point-spread function, we find no evidence for extended Ly{alpha} emission. These observations set 2{sigma} limits of L(Ly{alpha}, extended) <3.2 Multiplication-Sign 10{sup 44} erg s{sup -1} for J1030+0524 and L(Ly{alpha}, extended) <2.5 Multiplication-Sign 10{sup 44} erg s{sup -1} for J1148+5251. Given the star formation rates typically inferred from (rest-frame) far-infrared measurements of z {approx} 6 quasars, these limits are well below the intrinsic bright Ly{alpha} emission expected from the recombination of gas photoionized by the quasars or by the star formation in the host galaxies, and point toward significant Ly{alpha} suppression or dust attenuation. However, small extinction values have been observed along the line of sight to the nuclei, thus reddening has to be coupled with other mechanisms for Ly{alpha} suppression (e.g., resonance scattering). No Ly{alpha} emitting companions are found, down to a 5{sigma} sensitivity of {approx}1 Multiplication-Sign 10{sup -17} erg s{sup -1} cm{sup -2} arcsec{sup -2} (surface brightness) and {approx}5 Multiplication-Sign 10{sup -17} erg s{sup -1} cm{sup -2} (assuming point sources).

  10. A Long-Term Space Astrophysics Research Program: The Evolution of the Quasar Continuum

    NASA Technical Reports Server (NTRS)

    Elvis, M.; Oliversen, Ronald K. (Technical Monitor)

    2001-01-01

    Four papers have been written. One reports on the major study funded by this grant: a pan-chromatic study of the quasar continuum at redshift 3. Two others make use of the quasar continuum shapes to find the minimum total accretion luminosity of the Universe, and hence the efficiency and spin of supermassive black holes; the second shows that the reemission of absorbed quasar radiation alleviates a major problem with galaxy formation and the FIR background. The last paper recognizes the role quasars may play in the initial formation of dust in the early Universe. The major study of a sample of z=3 and its comparison with a sample of z=0.l quasars across the whole X-ray to radio spectrum was completed and accepted for publication in ApJ Supplements. This study comprises the thesis work of Olga Kuhn. The two samples are matched in evolved luminosity, and so should be sampling the same black hole population at different z, and in different accretion states. Despite this no strong differences were found between the samples, except in the 'small bump' region of the optical/UV. This region is dominated by FeII emission, and may indicate abundance evolution in quasars. The lack of overall spectral changes argues strongly against a single population of quasars fading over cosmic time, and for a multiple generation, or multiple outburst model for quasars. A study of the total luminosity absorbed from quasars and re-emitted in the infrared produced two results (reported in two papers): The minimum intrinsic luminosity/Gpc(3) from AGN compared with the measured mass density in supermassive black holes [Gpc(-3)] requires a conversion efficiency of accreted mass into luminosity of greater than 15%. Non-rotating black holes cannot exceed 5% efficiency, while rapidly rotating black holes can reach 47%. Hence our result requires that most supermassive black holes must be rapidly rotating. The second result comes from considering the contribution that the re-radiated quasar

  11. Early Fermi Gamma-ray Space Telescope Observations of the Quasar 3C454.3

    SciTech Connect

    Abdo, A

    2009-05-07

    This is the first report of Fermi Gamma-ray Space Telescope observations of the quasar 3C 454.3, which has been undergoing pronounced long-term outbursts since 2000. The data from the Large Area Telescope (LAT), covering 2008 July 7-October 6, indicate strong, highly variable {gamma}-ray emission with an average flux of {approx} 3 x 10{sup -6} photons cm{sup -2} s{sup -1}, for energies > 100 MeV. The {gamma}-ray flux is variable, with strong, distinct, symmetrically-shaped flares for which the flux increases by a factor of several on a time scale of about three days. This variability indicates a compact emission region, and the requirement that the source is optically thin to pair-production implies relativistic beaming with Doppler factor {delta} > 8, consistent with the values inferred from VLBI observations of superluminal expansion ({delta} {approx} 25). The observed {gamma}-ray spectrum is not consistent with a simple power-law, but instead steepens strongly above {approx} 2 GeV, and is well described by a broken power-law with photon indices of {approx} 2.3 and {approx} 3.5 below and above the break, respectively. This is the first direct observation of a break in the spectrum of a high luminosity blazar above 100 MeV, and it is likely direct evidence for an intrinsic break in the energy distribution of the radiating particles. Alternatively, the spectral softening above 2GeV could be due to -ray absorption via photonphoton pair production on the soft X-ray photon field of the host AGN, but such an interpretation would require the dissipation region to be located very close ({approx}< 100 gravitational radii) to the black hole, which would be inconsistent with the X-ray spectrum of the source.

  12. A possible close supermassive black-hole binary in a quasar with optical periodicity.

    PubMed

    Graham, Matthew J; Djorgovski, S G; Stern, Daniel; Glikman, Eilat; Drake, Andrew J; Mahabal, Ashish A; Donalek, Ciro; Larson, Steve; Christensen, Eric

    2015-02-01

    Quasars have long been known to be variable sources at all wavelengths. Their optical variability is stochastic and can be due to a variety of physical mechanisms; it is also well-described statistically in terms of a damped random walk model. The recent availability of large collections of astronomical time series of flux measurements (light curves) offers new data sets for a systematic exploration of quasar variability. Here we report the detection of a strong, smooth periodic signal in the optical variability of the quasar PG 1302-102 with a mean observed period of 1,884 ± 88 days. It was identified in a search for periodic variability in a data set of light curves for 247,000 known, spectroscopically confirmed quasars with a temporal baseline of about 9 years. Although the interpretation of this phenomenon is still uncertain, the most plausible mechanisms involve a binary system of two supermassive black holes with a subparsec separation. Such systems are an expected consequence of galaxy mergers and can provide important constraints on models of galaxy formation and evolution. PMID:25561176

  13. Quasars, Redshifts and Controversies

    NASA Astrophysics Data System (ADS)

    Arp, Halton C.

    1988-09-01

    Introduction; 1. Distance of quasars; 2. The battle over statistics; 3. Galaxies visibly connected to quasars; 4. Certain galaxies with many quasars; 5. Distribution of quasars in space; 6. Galaxies with excess redshift; 7. Small excess redshifts, the local group of galaxies, and quantization of redshifts; 8. Correcting intrinsic redshifts and identifying hydrogen clouds within nearby groups of galaxies; 9. Ejection from galaxies; 10. The sociology of the controversy; 11. Interpretations; Glossary; Index.

  14. 46 CFR 72.15-15 - Ventilation for closed spaces.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 3 2010-10-01 2010-10-01 false Ventilation for closed spaces. 72.15-15 Section 72.15-15... ARRANGEMENT Ventilation § 72.15-15 Ventilation for closed spaces. (a) All enclosed spaces within the vessel... spaces and for closing all doorways, ventilators and annular spaces around funnels and other openings...

  15. 46 CFR 72.15-15 - Ventilation for closed spaces.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 3 2013-10-01 2013-10-01 false Ventilation for closed spaces. 72.15-15 Section 72.15-15... ARRANGEMENT Ventilation § 72.15-15 Ventilation for closed spaces. (a) All enclosed spaces within the vessel... spaces and for closing all doorways, ventilators and annular spaces around funnels and other openings...

  16. 46 CFR 72.15-15 - Ventilation for closed spaces.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 3 2012-10-01 2012-10-01 false Ventilation for closed spaces. 72.15-15 Section 72.15-15... ARRANGEMENT Ventilation § 72.15-15 Ventilation for closed spaces. (a) All enclosed spaces within the vessel... spaces and for closing all doorways, ventilators and annular spaces around funnels and other openings...

  17. 46 CFR 72.15-15 - Ventilation for closed spaces.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 3 2014-10-01 2014-10-01 false Ventilation for closed spaces. 72.15-15 Section 72.15-15... ARRANGEMENT Ventilation § 72.15-15 Ventilation for closed spaces. (a) All enclosed spaces within the vessel... spaces and for closing all doorways, ventilators and annular spaces around funnels and other openings...

  18. 46 CFR 72.15-15 - Ventilation for closed spaces.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 3 2011-10-01 2011-10-01 false Ventilation for closed spaces. 72.15-15 Section 72.15-15... ARRANGEMENT Ventilation § 72.15-15 Ventilation for closed spaces. (a) All enclosed spaces within the vessel... spaces and for closing all doorways, ventilators and annular spaces around funnels and other openings...

  19. 78 FR 53497 - Commercial Space Transportation Advisory Committee; Closed Session

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-29

    ... Federal Aviation Administration Commercial Space Transportation Advisory Committee; Closed Session AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of Commercial Space Transportation Advisory... closed session of the Commercial Space Transportation Advisory Committee (COMSTAC). The special...

  20. The Hubble Space Telescope quasar absorption line key project. II - Data calibration and absorption-line selection

    NASA Technical Reports Server (NTRS)

    Schneider, Donald P.; Hartig, George F.; Jannuzi, Buell T.; Kirhakos, Sofia; Saxe, David H.; Weymann, Ray J.; Bahcall, John N.; Bergeron, Jacqueline; Boksenberg, Alec; Sargent, W. L. W.

    1993-01-01

    We present the observational and data processing aspects of the Hubble Space Telescope Quasar Absorption Line Key Project. Topics discussed include the observational technique, calibration of the data, software that simulates the data, the automated procedure used to identify and characterize the absorption features, and the determination of the sensitivity limits of the survey.

  1. Controlled Microbial Cenoses in Closed Spaces

    NASA Astrophysics Data System (ADS)

    Somova, Lydia; Mikheeva, Galina

    Controlled microbial cenoses have good prospects in closed spaces: for air treatment in LSS and cellars industrial premises; for sewage treatment in LSS; for increase of productivity and protect of plants from infections in LSS. Possible methods of formation of microbiocenoses are: selection, autoselection, artificial formation taking into account their biochemical properties and metabolic interactions. Experimental microbiocenoses, has been produced on the basis of natural association of microorganisms by long cultivation on specially developed medium. Dominating groups are bacteria of genera: Lactobacillus, Streptococcus, Leuconostoc, Bidobac-terium, Rhodopseudomonas and yeast of genera: Kluyveromyces, Saccharomyces and Torulop-sis. Microbiocenoses do not contain pathogenic and conditionally pathogenic microorganisms, they possess opposing and probiotic properties. Different examples of microbial cenoses actions are to be presented in the paper.

  2. A NEW METHOD TO DIRECTLY MEASURE THE JEANS SCALE OF THE INTERGALACTIC MEDIUM USING CLOSE QUASAR PAIRS

    SciTech Connect

    Rorai, Alberto; Hennawi, Joseph F.; White, Martin

    2013-10-01

    Although the baryons in the intergalactic medium (IGM) trace dark matter fluctuations on megaparsec scales, on smaller scales ∼100 kpc, fluctuations are suppressed because the finite temperature gas is pressure supported against gravity, analogous to the classical Jeans argument. This Jeans filtering scale, which quantifies the small-scale structure of the IGM, has fundamental cosmological implications. First, it provides a thermal record of heat injected by ultraviolet photons during cosmic reionization events, and thus constrains the thermal and reionization history of the universe. Second, the Jeans scale determines the clumpiness of the IGM, a critical ingredient in models of cosmic reionization. Third, it sets the minimum mass scale for gravitational collapse from the IGM, and hence plays a pivotal role in galaxy formation. Unfortunately, it is extremely challenging to measure the Jeans scale via the standard technique of analyzing purely longitudinal Lyα forest spectra, because the thermal Doppler broadening of absorption lines along the line-of-sight, is highly degenerate with Jeans smoothing. In this work, we show that the Jeans filtering scale can be directly measured by characterizing the coherence of correlated Lyα forest absorption in close quasar pairs, with separations small enough ∼100 kpc to resolve it. We present a novel technique for this purpose, based on the probability density function (PDF) of phase angle differences of homologous longitudinal Fourier modes in close quasar pair spectra. A Bayesian formalism is introduced based on the phase angle PDF, and Markov Chain Monte Carlo techniques are used to characterize the precision of a hypothetical Jeans scale measurement, and explore degeneracies with other thermal parameters governing the IGM. A semi-analytical model of the Lyα forest is used to generate a large grid (500) of thermal models from a dark matter only simulation. Our full parameter study indicates that a realistic sample of

  3. A Long-Term Space Astrophysics Research Program. The Evolution of the Quasar Continuum

    NASA Technical Reports Server (NTRS)

    Elvis, M.

    1998-01-01

    The grant "The Evolution of the Quasar Continuum" resulted in over 53 published referred papers and conference proceedings. The more significant of these papers are listed below, and abstracts are attached. The papers address a wide range of issues involving the evolution of quasars, their electromagnetic emissions, and their environment, from nearby low luminosity Seyfert galaxies to quasars at the highest redshifts. Primarily observational in content the work nonetheless included theoretical studies of quasar accretion disks that attempt to explain the observed time variability of quasars, and the overall 'demographics' of the quasar population. The work carried out under this grant has laid a strong foundation for ongoing and future research with AXAF, HST and other new facilities.

  4. A Long-Term Space Astrophysics Research Program: The Evolution of the Quasar Continuum

    NASA Technical Reports Server (NTRS)

    Elvis, M.; Oliversen, Ronald K. (Technical Monitor)

    2002-01-01

    Four papers have been written. One reports on the major study funded by this grant: a pan-chromatic study of the quasar continuum at redshift 3. Two others make use of the quasar continuum shapes to find the minimum total accretion luminosity of the Universe, and hence the efficiency and spin of supermassive black holes; the second shows that the reemission of absorbed quasar radiation alleviates a major problem with galaxy formation and the FIR background. The last paper recognizes the role quasars may play in the initial formation of dust in the early Universe.

  5. 46 CFR 190.15-10 - Ventilation for closed spaces.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Ventilation for closed spaces. 190.15-10 Section 190.15... CONSTRUCTION AND ARRANGEMENT Ventilation § 190.15-10 Ventilation for closed spaces. (a) All enclosed spaces... chemical laboratories, scientific laboratories, chemical storerooms, and machinery spaces and for...

  6. 46 CFR 190.15-10 - Ventilation for closed spaces.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 7 2013-10-01 2013-10-01 false Ventilation for closed spaces. 190.15-10 Section 190.15... CONSTRUCTION AND ARRANGEMENT Ventilation § 190.15-10 Ventilation for closed spaces. (a) All enclosed spaces... chemical laboratories, scientific laboratories, chemical storerooms, and machinery spaces and for...

  7. 46 CFR 190.15-10 - Ventilation for closed spaces.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 7 2014-10-01 2014-10-01 false Ventilation for closed spaces. 190.15-10 Section 190.15... CONSTRUCTION AND ARRANGEMENT Ventilation § 190.15-10 Ventilation for closed spaces. (a) All enclosed spaces... chemical laboratories, scientific laboratories, chemical storerooms, and machinery spaces and for...

  8. 46 CFR 190.15-10 - Ventilation for closed spaces.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 7 2012-10-01 2012-10-01 false Ventilation for closed spaces. 190.15-10 Section 190.15... CONSTRUCTION AND ARRANGEMENT Ventilation § 190.15-10 Ventilation for closed spaces. (a) All enclosed spaces... chemical laboratories, scientific laboratories, chemical storerooms, and machinery spaces and for...

  9. 46 CFR 190.15-10 - Ventilation for closed spaces.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 7 2011-10-01 2011-10-01 false Ventilation for closed spaces. 190.15-10 Section 190.15... CONSTRUCTION AND ARRANGEMENT Ventilation § 190.15-10 Ventilation for closed spaces. (a) All enclosed spaces... chemical laboratories, scientific laboratories, chemical storerooms, and machinery spaces and for...

  10. Weak bump quasars

    NASA Technical Reports Server (NTRS)

    Wilkes, B. J.; Mcdowell, J.

    1994-01-01

    Research into the optical, ultraviolet and infrared continuum emission from quasars and their host galaxies was carried out. The main results were the discovery of quasars with unusually weak infrared emission and the construction of a quantitative estimate of the dispersion in quasar continuum properties. One of the major uncertainties in the measurement of quasar continuum strength is the contribution to the continuum of the quasar host galaxy as a function of wavelength. Continuum templates were constructed for different types of host galaxy and individual estimates made of the decomposed quasar and host continua based on existing observations of the target quasars. The results are that host galaxy contamination is worse than previously suspected, and some apparent weak bump quasars are really normal quasars with strong host galaxies. However, the existence of true weak bump quasars such as PHL 909 was confirmed. The study of the link between the bump strength and other wavebands was continued by comparing with IRAS data. There is evidence that excess far infrared radiation is correlated with weaker ultraviolet bumps. This argues against an orientation effect and implies a probable link with the host galaxy environment, for instance the presence of a luminous starburst. However, the evidence still favors the idea that reddening is not important in those objects with ultraviolet weak bumps. The same work has led to the discovery of a class of infrared weak quasars. Pushing another part of the envelope of quasar continuum parameter space, the IR-weak quasars have implications for understanding the effects of reddening internal to the quasars, the reality of ultraviolet turnovers, and may allow further tests of the Phinney dust model for the IR continuum. They will also be important objects for studying the claimed IR to x-ray continuum correlation.

  11. 46 CFR 92.15-10 - Ventilation for closed spaces.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Ventilation for closed spaces. 92.15-10 Section 92.15-10... CONSTRUCTION AND ARRANGEMENT Ventilation § 92.15-10 Ventilation for closed spaces. (a) Except as noted in paragraph (c) of this section, all enclosed spaces within the vessel shall be properly vented or...

  12. 46 CFR 92.15-10 - Ventilation for closed spaces.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 4 2014-10-01 2014-10-01 false Ventilation for closed spaces. 92.15-10 Section 92.15-10... CONSTRUCTION AND ARRANGEMENT Ventilation § 92.15-10 Ventilation for closed spaces. (a) Except as noted in paragraph (c) of this section, all enclosed spaces within the vessel shall be properly vented or...

  13. 46 CFR 92.15-10 - Ventilation for closed spaces.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 4 2012-10-01 2012-10-01 false Ventilation for closed spaces. 92.15-10 Section 92.15-10... CONSTRUCTION AND ARRANGEMENT Ventilation § 92.15-10 Ventilation for closed spaces. (a) Except as noted in paragraph (c) of this section, all enclosed spaces within the vessel shall be properly vented or...

  14. 46 CFR 92.15-10 - Ventilation for closed spaces.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 4 2013-10-01 2013-10-01 false Ventilation for closed spaces. 92.15-10 Section 92.15-10... CONSTRUCTION AND ARRANGEMENT Ventilation § 92.15-10 Ventilation for closed spaces. (a) Except as noted in paragraph (c) of this section, all enclosed spaces within the vessel shall be properly vented or...

  15. 46 CFR 92.15-10 - Ventilation for closed spaces.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Ventilation for closed spaces. 92.15-10 Section 92.15-10... CONSTRUCTION AND ARRANGEMENT Ventilation § 92.15-10 Ventilation for closed spaces. (a) Except as noted in paragraph (c) of this section, all enclosed spaces within the vessel shall be properly vented or...

  16. A long-term space astrophysics research program: The evolution of the quasar continuum

    NASA Technical Reports Server (NTRS)

    Elvis, M.

    1993-01-01

    The research program supported by this grant now has great momentum. Numerous papers are in progress, and a strong multi-wavelength observing program is rapidly accumulating data on samples of high redshift quasars across the spectrum. ROSAT spectra of quasars continue to yield surprises. Of four z = 3 quasars with X-ray spectra, three show strong absorption. This contrasts strongly with the situation for luminous AGN at low redshifts where fewer than 1 in 20 show X-ray absorption. A new site for this absorption is probably needed, either around the quasar (e.g. in a cluster cooling flow) or along the line of sight (e.g. in a Damped Lyman-alpha system). The unabsorbed quasar allows limits on the physical conditions in a damped Lyman-alpha cloud to be calculated, and will allow a X-ray Gunn-Peterson test to be applied that will limit the fraction of the closure mass in an intergalactic medium. The X-ray spectral indices of these z = 3 quasars show no change from those of similar objects at low z, suggesting that 'short-lifetime' models apply. Eight other z = 3-4 quasars have been detected and their energy distributions from X-rays to Infrared (using new infrared spectrographs) have been compiled. These are now being compared with the low z continua from the 'Atlas of Quasar Energy Distributions' to search for evolutionary changes. The discovery of a likely warm absorber in 3C351 made recognition of another example simple. Also, modeling of the conditions in the absorber in 3C351 using the OVI absorption line from HST and the high ionization emission lines, suggests that the broad line region is indeed the origin of the warm absorber in this quasar, and by extension, others. Warm absorbers can now be used as a new diagnostic of this region. The X-ray spectrum of a 'Red Quasar', 3C212, has a cut-off spectrum, which could be fitted by an absorbed power-law, or more remarkably, by an unabsorbed black body. Using our quasi-simultaneous optical data and photoionization

  17. Hubble Space Telescope Close to Capture

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Hubble Space Telescope (HST), with its normal routine temporarily interrupted, is about to be captured by the Space Shuttle Columbia prior to a week of servicing and upgrading by the STS-109 crew. The telescope was captured by the shuttle's Remote Manipulator System (RMS) robotic arm and secured on a work stand in Columbia's payload bay where 4 of the 7-member crew performed 5 space walks completing system upgrades to the HST. Included in those upgrades were: The replacement of the solar array panels; replacement of the power control unit (PCU); replacement of the Faint Object Camera (FOC) with a new advanced camera for Surveys (ACS); and installation of the experimental cooling system for the Hubble's Near-Infrared Camera and Multi-object Spectrometer (NICMOS), which had been dormant since January 1999 when its original coolant ran out. The Marshall Space Flight Center had the responsibility for the design, development, and construction of the the HST, which is the most complex and sensitive optical telescope ever made, to study the cosmos from a low-Earth orbit. Launched March 1, 2002, the STS-109 HST servicing mission lasted 10 days, 22 hours, and 11 minutes. It was the 108th flight overall in NASA's Space Shuttle Program.

  18. A transformer of closely spaced pulsed waveforms

    NASA Technical Reports Server (NTRS)

    Niedra, J.

    1970-01-01

    Passive circuit, using diodes, transistors, and magnetic cores, transforms the voltage of repetitive positive or negative pulses. It combines a pulse transformer with switching devices to effect a resonant flux reset and can transform various pulsed waveforms that have a nonzero average value and are relatively cosely spaced in time.

  19. Dust in the Quasar Wind (Artist Concept)

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Dusty grains -- including tiny specks of the minerals found in the gemstones peridot, sapphires and rubies -- can be seen blowing in the winds of a quasar, or active black hole, in this artist's concept. The quasar is at the center of a distant galaxy.

    Astronomers using NASA's Spitzer Space Telescope found evidence that such quasar winds might have forged these dusty particles in the very early universe. The findings are another clue in an ongoing cosmic mystery: where did all the dust in our young universe come from?

    Dust is crucial for efficient star formation as it allows the giant clouds where stars are born to cool quickly and collapse into new stars. Once a star has formed, dust is also needed to make planets and living creatures. Dust has been seen as far back as when the universe was less than a tenth of its current age, but how did it get there? Most dust in our current epoch forms in the winds of evolved stars that did not exist when the universe was young.

    Theorists had predicted that winds from quasars growing in the centers of distant galaxies might be a source of this dust. While the environment close to a quasar is too hot for large molecules like dust grains to survive, dust has been found in the cooler, outer regions. Astronomers now have evidence that dust is created in these outer winds.

    Using Spitzer's infrared spectrograph instrument, scientists found a wealth of dust grains in a quasar called PG2112+059 located at the center of a galaxy 8 billion light-years away. The grains - including corundum (sapphires and rubies); forsterite (peridot); and periclase (naturally occurring in marble) - are not typically found in galaxies without quasars, suggesting they might have been freshly formed in the quasar's winds.

  20. Twin Quasars Tango And It's No Mirage

    NASA Astrophysics Data System (ADS)

    2002-03-01

    image of a single quasar into an apparent double has proved fruitless. This led to the speculation that the gravitation light-bending might be caused by a new type of cluster that contained hot gas and dark matter, but failed to ever make stars or galaxies. Such a "dark cluster" would be invisible to optical and ultraviolet telescopes, but would be detectable in X-rays. The Chandra images, the most sensitive ever taken for this type of search, showed no evidence for a massive dark cluster. Further, the X-ray spectra of the two quasars were distinctly different. "This may mean that the pair Q2345+007A,B actually consists of two separate quasars," said Green. "However, a mystery remains. How can two quasars have identical optical spectra - every bump and wiggle? The coincidence seems improbable." One possible explanation is that the quasars are formed close by each other grow up to look alike at optical wavelengths, but that X-rays which probe closer to their central black holes, bring out the individual differences. Chandra observed Q2345+007 on May 26, 2000, for 65,000 seconds using the Advanced CCD Imaging Spectrometer instrument. Scientists from the Harvard-Smithsonian Center for Astrophysics and the National Optical Astronomy Observatory were also members of the research team. The ACIS camera was developed for NASA by Pennsylvania State University, University Park, Pa., and the Massachusetts Institute of Technology, Cambridge, Mass. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. TRW, Inc., Redondo Beach, Calif., is the prime contractor for the spacecraft. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge. The National Optical Astronomy Observatory is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under a cooperative agreement with the National Science Foundation.

  1. Quasars Candidates in the Hubble Deep Field

    NASA Astrophysics Data System (ADS)

    Conti, A.; Kennefick, J. D.; Martini, P. L.; Omser, P. S.

    1996-12-01

    The Hubble Deep Field gives us an unprecedented view of our universe and an opportunity to study a wide range of questions in galaxy evolution and cosmology. Here, we will focus on the search for faint quasars and AGN in the crude combined images using a multicolor imaging analysis that has proven very successful in recent years. To produce a catalog of objects in the field, we used the FOCAS package for object detection with particular care to the set of input parameters used to minimize spurious detections. For each detected source we measured aperture magnitudes in several different apertures using the IRAF PHOT routine. For object classification we have chosen not to use the built in FOCAS routines, instead we have developed classification schemes that closely resemble those of Flynn at al. (1996) to distinguish resolved from unresolved objects in the Hubble Deep Field. We generated synthetic quasar spectra in the range 2.0quasar colors.These colors are used to identify areas of the multicolor space where quasars might be expected. A quasar candidate list is being formed. Routines were developed to determine the completeness of our data to point sources in the observed bands. The data are 50 % complete at 27.0(m) , 28.9(m) ,29.1(m) , 28.2(m) in the F300W (U), F450W (B), F606W (V) and F814W (I) filter respectively. These completeness limits closely approximate the 3sigma detection limit. We will present a list of quasars candidates and compare the results to expectations from previous surveys and extrapolations from current models. Our initial extrapolations, based on the luminosity function of Boyle (1991) and Warren at al. (1994), suggest the Hubble Deep Field may contain of order 10 quasars.

  2. Towards a comprehensive picture of powerful quasars, their host galaxies and quasar winds at z ˜ 0.5

    NASA Astrophysics Data System (ADS)

    Wylezalek, Dominika; Zakamska, Nadia L.; Liu, Guilin; Obied, Georges

    2016-03-01

    Luminous type-2 quasars in which the glow from the central black hole is obscured by dust are ideal targets for studying their host galaxies and the quasars' effect on galaxy evolution. Such feedback appears ubiquitous in luminous obscured quasars where high-velocity-ionized nebulae have been found. We present rest-frame yellow-band (˜5000 Å) observations using the Hubble Space Telescope (HST) for a sample of 20 luminous quasar host galaxies at 0.2 < z < 0.6 selected from the Sloan Digital Sky Survey. For the first time, we combine host galaxy observations with geometric measurements of quasar illumination using blue-band HST observations and [O III] integral field unit observations probing the quasar winds. The HST images reveal bright merger signatures in about half the galaxies; a significantly higher fraction than in comparison inactive ellipticals. We show that the host galaxies are primarily bulge-dominated, with masses close to M*, but belong to <30 per cent of elliptical galaxies that are highly star forming at z ˜ 0.5. Ionized gas signatures are uncorrelated with faint stellar discs (if present), confirming that the ionized gas is not concentrated in a disc. Scattering cones and [O III] ionized gas velocity field are aligned with the forward scattering cones being co-spatial with the blue-shifted side of the velocity field, suggesting the high-velocity gas is indeed photo-ionized by the quasar. Based on the host galaxies' high star formation rates and bright merger signatures, we suggest that this low-redshift outbreak of luminous quasar activity is triggered by recent minor mergers. Combining these novel observations, we present new quasar unification tests, which are in agreement with expectations of the orientation-based unification model for quasars.

  3. A hybrid genetic algorithm for resolving closely spaced objects

    NASA Technical Reports Server (NTRS)

    Abbott, R. J.; Lillo, W. E.; Schulenburg, N.

    1995-01-01

    A hybrid genetic algorithm is described for performing the difficult optimization task of resolving closely spaced objects appearing in space based and ground based surveillance data. This application of genetic algorithms is unusual in that it uses a powerful domain-specific operation as a genetic operator. Results of applying the algorithm to real data from telescopic observations of a star field are presented.

  4. Heat Transfer Analysis of a Closed Brayton Cycle Space Radiator

    NASA Technical Reports Server (NTRS)

    Juhasz, Albert J.

    2007-01-01

    This paper presents a mathematical analysis of the heat transfer processes taking place in a radiator for a closed cycle gas turbine (CCGT), also referred to as a Closed Brayton Cycle (CBC) space power system. The resulting equations and relationships have been incorporated into a radiator sub-routine of a numerical triple objective CCGT optimization program to determine operating conditions yielding maximum cycle efficiency, minimum radiator area and minimum overall systems mass. Study results should be of interest to numerical modeling of closed cycle Brayton space power systems and to the design of fluid cooled radiators in general.

  5. Galaxy Clustering Around Nearby Luminous Quasars

    NASA Technical Reports Server (NTRS)

    Fisher, Karl B.; Bahcall, John N.; Kirhakos, Sofia; Schneider, Donald P.

    1996-01-01

    We examine the clustering of galaxies around a sample of 20 luminous low redshift (z approx. less than 0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope (HST). The HST resolution makes possible galaxy identification brighter than V = 24.5 and as close as 1 min or 2 min to the quasar. We find a significant enhancement of galaxies within a projected separation of approx. less than 100 1/h kpc of the quasars. If we model the QSO/galaxy correlation function as a power law with a slope given by the galaxy/galaxy correlation function, we find that the ratio of the QSO/galaxy to galaxy/galaxy correlation functions is 3.8 +/- 0.8. The galaxy counts within r less than 15 1/h kpc of the quasars are too high for the density profile to have an appreciable core radius (approx. greater than 100 1/h kpc). Our results reinforce the idea that low redshift quasars are located preferentially in groups of 10-20 galaxies rather than in rich clusters. We see no significant difference in the clustering amplitudes derived from radio-loud and radio-quiet subsamples.

  6. Hubble space telescope/cosmic origins spectrograph observations of the quasar Q0302–003: Probing the He II reionization epoch and QSO proximity effects

    SciTech Connect

    Syphers, David; Shull, J. Michael

    2014-03-20

    Q0302–003 (z = 3.2860 ± 0.0005) was the first quasar discovered that showed a He II Gunn-Peterson trough, a sign of incomplete helium reionization at z ≳ 2.9. We present its Hubble Space Telescope/Cosmic Origins Spectrograph far-UV medium-resolution spectrum, which resolves many spectral features for the first time, allowing study of the quasar itself, the intergalactic medium, and quasar proximity effects. Q0302–003 has a harder intrinsic extreme-UV spectral index than previously claimed, as determined from both a direct fit to the spectrum (yielding α{sub ν} ≈ –0.8) and the helium-to-hydrogen ion ratio in the quasar's line-of-sight proximity zone. Intergalactic absorption along this sightline shows that the helium Gunn-Peterson trough is largely black in the range 2.87 < z < 3.20, apart from ionization due to local sources, indicating that helium reionization has not completed at these redshifts. However, we tentatively report a detection of nonzero flux in the high-redshift trough when looking at low-density regions, but zero flux in higher-density regions. This constrains the He II fraction to be about 1% in the low-density intergalactic medium (IGM) and possibly a factor of a few higher in the IGM as a whole, suggesting helium reionization has progressed substantially by z ∼ 3.1. The Gunn-Peterson trough recovers to a He II Lyα forest at z < 2.87. We confirm a transmission feature due to the ionization zone around a z = 3.05 quasar just off the sightline, and resolve the feature for the first time. We discover a similar such feature possibly caused by a luminous z = 3.23 quasar further from the sightline, which suggests that this quasar has been luminous for >34 Myr.

  7. Modal vector estimation for closely spaced frequency modes

    NASA Technical Reports Server (NTRS)

    Craig, R. R., Jr.; Chung, Y. T.; Blair, M.

    1982-01-01

    Techniques for obtaining improved modal vector estimates for systems with closely spaced frequency modes are discussed. In describing the dynamical behavior of a complex structure modal parameters are often analyzed: undamped natural frequency, mode shape, modal mass, modal stiffness and modal damping. From both an analytical standpoint and an experimental standpoint, identification of modal parameters is more difficult if the system has repeated frequencies or even closely spaced frequencies. The more complex the structure, the more likely it is to have closely spaced frequencies. This makes it difficult to determine valid mode shapes using single shaker test methods. By employing band selectable analysis (zoom) techniques and by employing Kennedy-Pancu circle fitting or some multiple degree of freedom (MDOF) curve fit procedure, the usefulness of the single shaker approach can be extended.

  8. Rationale for evaluating a closed food chain for space habitats

    NASA Technical Reports Server (NTRS)

    Modell, M.; Spurlock, J. M.

    1980-01-01

    Closed food cycles for long duration space flight and space habitation are examined. Wash water for a crew of six is economically recyclable after a week, while a total closed loop water system is effective only if the stay exceeds six months' length. The stoichiometry of net plant growth is calculated and it is shown that the return of urine, feces, and inedible plant parts to the food chain, along with the addition of photosynthesis, closes the food chain loop. Scenarios are presented to explore the technical feasibility of achieving a closed loop system. An optimal choice of plants is followed by processing, waste conversion, equipment specifications, and control requirements, and finally, cost-effectiveness.

  9. Hubble Space Telescope Faint Object Spectrograph and ground-based observations of the broad absorption line quasar 0226-1024

    NASA Technical Reports Server (NTRS)

    Korista, Kirk T.; Weymann, Ray J.; Morris, Simon L.; Kopko, Michael, Jr.; Turnshek, David A.; Hartig, George F.; Foltz, Craig B.; Burbidge, E. M.; Junkkarinen, Vesa T.

    1992-01-01

    Faint Object Spectrograph data from the Hubble Space Telescope of the broad absorption line quasar 0226-1024 have revealed the presence of 8-10 absorbing ions between 680 and 1000 A (restframe): C III, N III, N IV, O III, O IV, O VI, S V, S VI, possibly Ne VIII, and possibly O V* arising from a metastable excited state. We also present ground-based optical observations of the broad line troughs for the following ions: H I, C IV, N V, Si IV, and possibly Fe III, S IV, P V, and C III* (also arising from a metastable excited state). The results of this fit are used to estimate the absorbing ionic column densities. There is evidence that the broad absorption line clouds are optically thick and either do not completely cover the continuum source or narrow unresolved lines are present.

  10. Hubble Space Telescope ultraviolet spectroscopy of the highly polarized but quiescent quasar OI 287

    NASA Technical Reports Server (NTRS)

    Antonucci, Robert; Kinney, Anne L.; Hurt, Todd

    1993-01-01

    The quasar OI 287 has a unique combination of properties, including a high and constant optical polarization oriented parallel to the radio axis, a quiescent optical flux, and a lobe-dominant radio source. Previous studies have led to the picture of an edge-on thin dusty torus occulting a featureless continuum (FC) source and a broad line region (BLR) in this object. The FC source and the BLR are seen only in reflected (polarized) light. In the unified models, this makes OI 287 a 'quasar 2', analogous to the type 2 Seyfert galaxies and the narrow-line radio galaxies. Our UV spectrum adds two bits of information consistent with the above ideas. First, the spectrum neither turns up in the UV, as expected for optically thin dust scattering, nor turns down as expected for polarization by dust transmission. It is consistent with reflection by free electrons or optically thick dust. Second, there are in fact blueshifted absorption troughs associated with the C IV 1549 A line, supporting the analogy with BALs, as well as the idea that the BALs are objects which present a nearly edge-on view of a disk structure.

  11. Glycosylation of closely spaced acceptor sites in human glycoproteins

    PubMed Central

    Shrimal, Shiteshu; Gilmore, Reid

    2013-01-01

    Summary Asparagine-linked glycosylation of proteins by the oligosaccharyltransferase (OST) occurs when acceptor sites or sequons (N-x≠P-T/S) on nascent polypeptides enter the lumen of the rough endoplasmic reticulum. Metazoan organisms assemble two isoforms of the OST that have different catalytic subunits (STT3A or STT3B) and partially non-overlapping cellular roles. Potential glycosylation sites move past the STT3A complex, which is associated with the translocation channel, at the protein synthesis elongation rate. Here, we investigated whether close spacing between acceptor sites in a nascent protein promotes site skipping by the STT3A complex. Biosynthetic analysis of four human glycoproteins revealed that closely spaced sites are efficiently glycosylated by an STT3B-independent process unless the sequons contain non-optimal sequence features, including extreme close spacing between sequons (e.g. NxTNxT) or the presence of paired NxS sequons (e.g. NxSANxS). Many, but not all, glycosylation sites that are skipped by the STT3A complex can be glycosylated by the STT3B complex. Analysis of a murine glycoprotein database revealed that closely spaced sequons are surprisingly common, and are enriched for paired NxT sites when the gap between sequons is less than three residues. PMID:24105266

  12. Developing closed life support systems for large space habitats

    NASA Technical Reports Server (NTRS)

    Phillips, J. M.; Harlan, A. D.; Krumhar, K. C.

    1978-01-01

    In anticipation of possible large-scale, long-duration space missions which may be conducted in the future, NASA has begun to investigate the research and technology development requirements to create life support systems for large space habitats. An analysis suggests the feasibility of a regeneration of food in missions which exceed four years duration. Regeneration of food in space may be justified for missions of shorter duration when large crews must be supported at remote sites such as lunar bases and space manufacturing facilities. It is thought that biological components consisting principally of traditional crop and livestock species will prove to be the most acceptable means of closing the food cycle. A description is presented of the preliminary results of a study of potential biological components for large space habitats. Attention is given to controlled ecosystems, Russian life support system research, controlled-environment agriculture, and the social aspects of the life-support system.

  13. Approximating the Generalized Voronoi Diagram of Closely Spaced Objects

    SciTech Connect

    Edwards, John; Daniel, Eric; Pascucci, Valerio; Bajaj, Chandrajit

    2015-06-22

    We present an algorithm to compute an approximation of the generalized Voronoi diagram (GVD) on arbitrary collections of 2D or 3D geometric objects. In particular, we focus on datasets with closely spaced objects; GVD approximation is expensive and sometimes intractable on these datasets using previous algorithms. With our approach, the GVD can be computed using commodity hardware even on datasets with many, extremely tightly packed objects. Our approach is to subdivide the space with an octree that is represented with an adjacency structure. We then use a novel adaptive distance transform to compute the distance function on octree vertices. The computed distance field is sampled more densely in areas of close object spacing, enabling robust and parallelizable GVD surface generation. We demonstrate our method on a variety of data and show example applications of the GVD in 2D and 3D.

  14. Approximating the Generalized Voronoi Diagram of Closely Spaced Objects

    PubMed Central

    Edwards, John; Daniel, Eric; Pascucci, Valerio; Bajaj, Chandrajit

    2016-01-01

    We present an algorithm to compute an approximation of the generalized Voronoi diagram (GVD) on arbitrary collections of 2D or 3D geometric objects. In particular, we focus on datasets with closely spaced objects; GVD approximation is expensive and sometimes intractable on these datasets using previous algorithms. With our approach, the GVD can be computed using commodity hardware even on datasets with many, extremely tightly packed objects. Our approach is to subdivide the space with an octree that is represented with an adjacency structure. We then use a novel adaptive distance transform to compute the distance function on octree vertices. The computed distance field is sampled more densely in areas of close object spacing, enabling robust and parallelizable GVD surface generation. We demonstrate our method on a variety of data and show example applications of the GVD in 2D and 3D. PMID:27540272

  15. Multi-wavelength Monitoring of Lensed Quasars: Deciphering Quasar Structure at Micro-arcseconds Scales

    NASA Astrophysics Data System (ADS)

    Mosquera, Ana; Morgan, Christopher W.; Kochanek, Christopher S.; Dai, Xinyu; Chen, Bin; MacLeod, Chelsea Louise; Chartas, George

    2016-01-01

    Microlensing in multiply imaged gravitationally lensed quasars provides us with a unique tool to zoom in on the structure of AGN and explore their physics in more detail. Microlensing magnification, caused primarily by stars and white dwarfs close to the line of sight towards the lensed quasar images, is seen as uncorrelated flux variations due to the relative motions of the quasar, the lens, its stars, and the observer, and it depends on the structural and dynamical properties of the source and the lens. Since the magnification depends upon the size of the source, we can use microlensing to measure the size of quasar emission regions. In essence, the amplitude of the microlensing variability encodes the source size, with smaller sources showing larger variability amplitudes. Using state of the art microlensing techniques, our team has performed pioneering research in the field based on multi-wavelength space and ground-based observations. Among the most remarkable results, using Chandra observations we have set the first quantitative constraints on the sizes of the X-ray emission regions of quasars. In this work l briefly describe the methodology, the results from our previous multi-wavelength monitoring programs, and the next frontier of exploring the dependence of the structure of the X-ray emission regions on black hole mass and X-ray energy.

  16. Dusty Quasars at High Redshifts

    NASA Astrophysics Data System (ADS)

    Weedman, Daniel; Sargsyan, Lusine

    2016-09-01

    A population of quasars at z ˜ 2 is determined based on dust luminosities νL ν (7.8 μm) that includes unobscured, partially obscured, and obscured quasars. Quasars are classified by the ratio νL ν (0.25 μm)/νL ν (7.8 μm) = UV/IR, assumed to measure obscuration of UV luminosity by the dust that produces IR luminosity. Quasar counts at rest-frame 7.8 μm are determined for quasars in the Boötes field of the NOAO Deep Wide Field Survey using 24 μm sources with optical redshifts from the AGN and Galaxy Evolution Survey (AGES) or infrared redshifts from the Spitzer Infrared Spectrograph. Spectral energy distributions are extended to far-infrared wavelengths using observations from the Herschel Space Observatory Spectral and Photometric Imaging Receiver (SPIRE), and new SPIRE photometry is presented for 77 high-redshift quasars from the Sloan Digital Sky Survey. It is found that unobscured and obscured quasars have similar space densities at rest-frame 7.8 μm, but the ratio L ν (100 μm)/L ν (7.8 μm) is about three times higher for obscured quasars than for unobscured, so that far-infrared or submillimeter quasar detections are dominated by obscured quasars. We find that only ˜5% of high-redshift submillimeter sources are quasars and that existing 850 μm surveys or 2 mm surveys should already have detected sources at z ˜ 10 if quasar and starburst luminosity functions remain the same from z = 2 until z = 10.

  17. SPITZER OBSERVATIONS OF YOUNG RED QUASARS

    SciTech Connect

    Urrutia, Tanya; Lacy, Mark; Spoon, Henrik; Glikman, Eilat; Petric, Andreea; Schulz, Bernhard E-mail: mlacy@nrao.edu E-mail: eilat.glikman@yale.edu E-mail: bschulz@ipac.caltech.edu

    2012-10-01

    We present mid-infrared spectra and photometry of 13 redshift 0.4 < z < 1 dust reddened quasars obtained with Spitzer IRS and MIPS. We compare properties derived from their infrared spectral energy distributions (intrinsic active galactic nucleus (AGN) luminosity and far-infrared luminosity from star formation) to the host luminosities and morphologies from Hubble Space Telescope imaging, and black hole masses estimated from optical and/or near-infrared spectroscopy. Our results are broadly consistent with models in which most dust reddened quasars are an intermediate phase between a merger-driven starburst triggering a completely obscured AGN, and a normal, unreddened quasar. We find that many of our objects have high accretion rates, close to the Eddington limit. These objects tend to fall below the black hole mass-bulge luminosity relation as defined by local galaxies, whereas most of our low accretion rate objects are slightly above the local relation, as typical for normal quasars at these redshifts. Our observations are therefore most readily interpreted in a scenario in which galaxy stellar mass growth occurs first by about a factor of three in each merger/starburst event, followed sometime later by black hole growth by a similar amount. We do not, however, see any direct evidence for quasar feedback affecting star formation in our objects, for example, in the form of a relationship between accretion rate and star formation. Five of our objects, however, do show evidence for outflows in the [O III]5007 A emission line profile, suggesting that the quasar activity is driving thermal winds in at least some members of our sample.

  18. Hilbert-space localization in closed quantum systems

    NASA Astrophysics Data System (ADS)

    Cohen, Doron; Yukalov, Vyacheslav I.; Ziegler, Klaus

    2016-04-01

    Quantum localization within an energy shell of a closed quantum system stands in contrast to the ergodic assumption of Boltzmann, and to the corresponding eigenstate thermalization hypothesis. The familiar case is the real-space Anderson localization and its many-body Fock-space version. We use the term Hilbert-space localization in order to emphasize the more general phase-space context. Specifically, we introduce a unifying picture that extends the semiclassical perspective of Heller, which relates the localization measure to the probability of return. We illustrate our approach by considering several systems of experimental interest, referring in particular to the bosonic Josephson tunneling junction. We explore the dependence of the localization measure on the initial state and on the strength of the many-body interactions using a recursive projection method.

  19. Underwater acoustic source localization using closely spaced hydrophone pairs

    NASA Astrophysics Data System (ADS)

    Sim, Min Seop; Choi, Bok-Kyoung; Kim, Byoung-Nam; Lee, Kyun Kyung

    2016-07-01

    Underwater sound source position is determined using a line array. However, performance degradation occurs owing to a multipath environment, which generates incoherent signals. In this paper, a hydrophone array is proposed for underwater source position estimation robust to a multipath environment. The array is composed of three pairs of sensors placed on the same line. The source position is estimated by performing generalized cross-correlation (GCC). The proposed system is not affected by a multipath time delay because of the close distance between closely spaced sensors. The validity of the array is confirmed by simulation using acoustic signals synthesized by eigenrays.

  20. Predicting Space Weather Effects on Close Approach Events

    NASA Astrophysics Data System (ADS)

    Newman, L.; Besser, R.; Hejduk, M.

    The NASA Robotic Conjunction Assessment Risk Analysis (CARA) team sends ephemeris data to the Joint Space Operations Center (JSpOC) for screening against the high accuracy catalog, then assesses risk posed to protected assets from predicted close approaches. Since most spacecraft supported by the CARA team are located in LEO orbits, atmospheric drag is a primary source of state estimate uncertainty, and drag is directly governed by space weather. At present the actual effect of space weather on atmospheric density cannot be accurately predicted because most atmospheric density models are empirical in nature. The Jacchia-Bowman-HASDM 2009 atmospheric density model used at the JSpOC employs a solar storm active compensation feature that predicts storm sizes and arrival times, and thus the resulting neutral density alterations. With this feature, estimation errors can occur in either direction (i.e., over- or under-estimation of density and thus drag), giving rise to several questions. Does a change in space weather make a close approach safer or riskier? Might performing a maneuver make the approach worse due to uncertainty in predicted location at a given time? What if there are errors in the predicted timing or magnitude of the space weather event? Although the exact effect of a solar storm on atmospheric drag cannot be determined, one can explore the effects of drag perturbations on conjuncting objects' trajectories to determine if a conjunction can become riskier or less risky. The CARA team has constructed a Space Weather Trade-Space tool that systematically alters the drag coefficient of the conjuncting objects and recalculates the probability of collision for each case to determine the effect is likely to have on the collision risk. In addition to a review of the theory and the particulars of the tool, all of the observed output will be explained, along with statistics of their frequency.

  1. The Hubble Space Telescope Quasar Absorption Line Key Project: The Unusual Absorption-Line System in the Spectrum of PG 2302+029--Ejected or Intervening?

    NASA Technical Reports Server (NTRS)

    Jannuzi, B. T.; Hartig, G. F.; Kirhakos, S.; Sargent, W. L. W.; Turnshek, D. A.; Weymann, R. J.; Bahcall, J. N.; Bergeron, J.; Boksenberg, A.; Savage, B. D.; Schneider, D. P.; Wolfe, A. M.

    1996-01-01

    We report the discovery of a high-ionization broad absorption line system at a redshift of z(sub abs) = 0.695 in the spectrum of the z(sub em) = 1.052 radio-quiet quasar PG 2302+029. Broad absorption with FWHM from 3000 to 5000 km/s is detected from C iv, N v, and O vi in Hubble Space Telescope (HST) Faint Object Spectrograph spectra of the quasar. A narrow-line system (FWHM approx. 250 km/s) at z(sub abs) = 0.7016 is resolved from the broad blend and includes absorption by Ly alpha and the C iv, N v, and O vi doublets. No absorption by low-ionization metal species (e.g., Si II and Mg II) is detected in the HST or ground-based spectra for either the broad or the narrow system. The centroids of the broad system lines are displaced by approx. 56,000 km/s to the blue of the quasar's broad emission lines. The reddest extent of the broad-line absorption is more than 50,000 km/s from the quasar. The properties of this system are unprecedented, whether it is an intervening or an ejected system.

  2. Close-up of Shuttle Thermal Tiles in Space

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Launched on July 26, 2005 from the Kennedy Space Center in Florida, STS-114 was classified as Logistics Flight 1. Among the Station-related activities of the mission were the delivery of new supplies and the replacement of one of the orbital outpost's Control Moment Gyroscopes (CMGs). STS-114 also carried the Raffaello Multi-Purpose Logistics Module and the External Stowage Platform-2. A major focus of the mission was the testing and evaluation of new Space Shuttle flight safety, which included new inspection and repair techniques. Upon its approach to the International Space Station (ISS), the Space Shuttle Discovery underwent a photography session in order to assess any damages that may have occurred during its launch and/or journey through Space. The mission's third and final Extra Vehicular Activity (EVA) included taking a close-up look and the repair of the damaged heat shield. Gap fillers were removed from between the orbiter's heat-shielding tiles located on the craft's underbelly. Never before had any repairs been done to an orbiter while still in space. This particular photo was taken by astronaut Stephen K. Robinson, STS-114 mission specialist, whose shadow is visible on the thermal protection tiles, and a portion of the Canadian built Remote Manipulator System (RMS) robotic arm and the Nile River is visible at the bottom.

  3. Hubble Space Telescope faint object spectrograph Quasar Absorption System Snapshot Survey (AbSnap). 1: Astrometric optical positions and finding charts of 269 bright QSO

    NASA Technical Reports Server (NTRS)

    Bowen, David V.; Osmer, Samantha J.; Blades, J. Chris; Tytler, David; Cottrell, Lance; Fan, Xiao-Ming; Lanzetta, Kenneth M.

    1994-01-01

    We present finding charts and optical positions accurate to less than 1 arcsec for 269 bright (V less than or = 18.5) Quasi-Stellar Objects (QSOs). These objects were selected as candidates for the Hubble Space Telescope (HST) Quasar Absorption System Snapshot Survey (AbSnap), a program designed to use the Faint Object Spectrograph (FOS) to obtain short exposure ultraviolet (UV) spectra of bright QSOs. Many quasars were included because of their proximity to bright, low redshift galaxies and positions of these QSOs are measured accurately for the first time. Data were obtained using the digitized sky survey produced by the Space Telescope Science Institute's Guide Stars Selection System Astrometric Support Program.

  4. Heat transfer from cylinders having closely spaced fins

    NASA Technical Reports Server (NTRS)

    Biermann, Arnold E

    1937-01-01

    The heat-transfer coefficients have been determined for five steel cylinders having fins 1.22 inches wide and the spacing between the fins ranging from 0.022 to 0.131 inch. The cylinders were tested with and without baffles in a wind tunnel; they were also tested enclosed in jackets with the cooling air supplied by a blower. A maximum heat transfer was reached at a fin space of about 0.45 inch for the cylinders tested with each of the three methods of cooling investigated. The rise in temperature of the air passing between the fins and the change in flow pattern were found to be important factors limiting the heat transfer that may be obtained by decreasing the fin space. The use of baffles for directing the air around the cylinders with closely spaced fins proved very effective in increasing the over-all heat-transfer coefficient, provided that the spacing was not appreciably less than that for maximum heat transfer.

  5. 78 FR 70093 - Commercial Space Transportation Advisory Committee-Closed Session

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-22

    ... Federal Aviation Administration Commercial Space Transportation Advisory Committee--Closed Session AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of Commercial Space Transportation Advisory... closed session of the Commercial Space Transportation Advisory Committee (COMSTAC). The special...

  6. A Hungry Quasar Caught in the Act

    NASA Astrophysics Data System (ADS)

    2001-05-01

    interaction with the quasar host galaxy. Quasar activity is believed to be triggered by such dramatic events. Since some time, astronomers have therefore been searching for clear evidence for a connection between gravitational interaction and the quasar phenomenon. However, quasars are very bright objects and their light easily outshines all nearby objects. Any companion galaxies and structural features that may indicate interaction are therefore hard to detect. While observations with the Hubble Space Telescope (HST) have much improved our knowledge of the interaction-activity connection in some relatively nearby quasars, it has been difficult to probe the same phenomenon in more distant quasar environments. Such studies clearly require larger telescopes. The observations of the quasar HE 1013-2136 presented here result from a new programme that addresses this issue at earlier cosmic epochs. This 17-mag object is seen in the southern constellation Hydra (The Water Snake) and is located at a distance of about 10 billion light years (the redshift is z = 0.785) PR Photo 20a/01 shows an image of HE 1013-2136 and its immediate surroundings, obtained with the FORS2 multi-mode instrument at the 8.2-m VLT KUEYEN telescope under very good seeing conditions. The image resolution is about 0.6 arcsec, or about 10,000 light-years at the distance of the quasar. The image has been further sharpened by means of image processing software (the Lucy algorithm) in PR Photo 20b/01 , now also showing the distribution of objects very close to the bright quasar image. This impressively illustrates the light gathering and resolution power of the VLT. Tidal forces at HE 1013-2136 The quasar is the point-like object at the center of the images. It is embedded within a complex structure that mainly consists of two arc-like and knotty tails extending in different directions. Such tails are well-known from nearby galaxy interactions, cf. NGC 6872/IC4970 and are a consequence of tidal forces in the

  7. A closed life-support system for space colonies

    NASA Technical Reports Server (NTRS)

    Johnson, R. D.; Jebens, H. J.; Sweet, H. C.

    1977-01-01

    In 1975, a system design study was performed to examine a completely self-contained system for a permanent colony of 10,000 inhabitants in space. Fundamental to this design was the life support system. Since resupply from earth is prohibitive in transportation costs, it was decided to use a closed system with the initial supply of oxygen coming from processing of lunar ores, and the supply of carbon, nitrogen and hydrogen from earth. The problem of life support was treated starting with the nutritional and metabolic requirements for the human population, creating a food and water chain sufficient to supply these demands, adding the additional requirements for the animal and plant sources in the food chain, feeding back useful waste products, supplying water as required from different sources, and closing the loop by processing organic wastes into CO2. This concept places the burden of the system upon plants for O2 generation and waste processing the CO2 generation.

  8. Accumulation of Raman gain between closely spaced pulse pairs.

    PubMed

    Marshall, L R; Piper, J A

    1990-12-01

    The short-pulse conversion efficiency of stimulated Raman scattering in Pb vapor is increased from 15% to 35% by using a novel technique that employs a closely spaced pair of pump pulses. The second pulse scatters off the coherent excitation induced in the medium by the first pulse, with a resultant enhancement in efficiency. To our knowledge these results give the first observation of such long-lived cooperative phenomena in stimulated Raman scattering. We have also observed this phenomenon in H(2) and show that this technique is readily applicable to other Raman-active media. PMID:19771085

  9. NASA Research For Instrument Approaches To Closely Spaced Parallel Runways

    NASA Technical Reports Server (NTRS)

    Elliott, Dawn M.; Perry, R. Brad

    2000-01-01

    Within the NASA Aviation Systems Capacity Program, the Terminal Area Productivity (TAP) Project is addressing airport capacity enhancements during instrument meteorological condition (IMC). The Airborne Information for Lateral Spacing (AILS) research within TAP has focused on an airborne centered approach for independent instrument approaches to closely spaced parallel runways using Differential Global Positioning System (DGPS) and Automatic Dependent Surveillance-Broadcast (ADS-B) technologies. NASA Langley Research Center (LaRC), working in partnership with Honeywell, Inc., completed in AILS simulation study, flight test, and demonstration in 1999 examining normal approaches and potential collision scenarios to runways with separation distances of 3,400 and 2,500 feet. The results of the flight test and demonstration validate the simulation study.

  10. Close Up of Space Shuttle External Tank's Intertank Flange Area

    NASA Technical Reports Server (NTRS)

    2004-01-01

    In NASA's Michoud Assembly Facility in New Orleans, the Space Shuttle External Tank 120 is in position for its new foam application process on the liquid hydrogen tank-to-inter tank flange area, a tank structural connection point. This image is a close-up of the inter tank flange area. The foam will be applied with an enhanced finishing procedure that requires two technicians, one for a new mold-injection procedure to the intertank's ribbing and one for real-time videotaped surveillance of the process. The 120 tank is slated for launch on the Orbiter Discovery scheduled for next Spring. Marshall Space Flight Center played a significant role in the development of the new application process designed to replace the possible debris shedding source previously used. (Lockheed Martin/NASA Michoud)

  11. A Closed Ecological System in a Space Experiment

    NASA Astrophysics Data System (ADS)

    Strauch, S. M.; Schuster, M.; Lebert, M.; Richter, P.; Schmittnagel, M.; Hader, D.-P.

    2008-06-01

    The Russian FOTON-M3 mission, a satellite for mid-length experiments in space and recovery afterwards, included a closed artificial ecosystem (OMEGAHAB for Oreochromis Mossambicus-Euglena Gracilis-Aquatic HABitat) with the photosynthetic flagellate Euglena gracilis as oxygen producer and larvae of Oreochromis mossambicus, a Tilapia species, as consumer. During the 12-day orbital flight the algae were observed 10 minutes per day by means of a miniaturized microscope to analyse their swimming behavior. The fishes were also filmed to monitor their development and movement. An identical experiment was carried out as ground control. A data downlink provided the measured temperature values of the space experiment every day to readjust the temperature of the ground reference in order to eliminate the influence of the different temperature on the velocity of the development of the fishes. The system worked very well and confirmed the design in principle. OMEGAHAB was the most successful German experiment of that kind as yet.

  12. The Extremes of Quasar Variability

    NASA Astrophysics Data System (ADS)

    Stern, Daniel

    2016-04-01

    Variability is one of the key observational properties of quasars, and it can be used as a probe of their fueling, physics, and evolution. A new generation of synoptic sky surveys, in combination with the novel data analytics tools, offers unprecedented data sets for the studies of quasars in the time domain. I will illustrate this with examples from the Catalina Real-Time Transient Survey (CRTS), which has an open and growing archive of 500 million light curves, including 350,000 spectroscopically confirmed quasars, with the time baselines ranging from 10 minutes to 10 years. I will discuss a new approach to discover quasars using a combination of variability and mid-IR colors from WISE, which results in a catalog of over a million quasar candidates. I will then discuss quasars with extreme, anomolous light curves, including quasars that have gone through extreme brightening events over the past decade with concordant large changes in their spectroscopic properties. I will also discuss a small subset of quasars with periodic light curves which we interpret as a signature of close (milliparsec scale) supermassive black hole (SMBH) binaries.

  13. CFD simulation of boundary effects on closely spaced jets

    NASA Astrophysics Data System (ADS)

    Shrivastava, Ishita; Adams, Eric

    2015-11-01

    In coastal areas characterized by shallow water depth, industrial effluents are often diluted using multiple closely spaced jets. Examples of such effluents include brine from desalination plants, treated wastewater from sewage treatment plants and heated water from thermal power plants. These jets are arranged in various orientations, such as unidirectional diffusers and rosette groups, to maximize mixing with ambient water. Due to effects of dynamic pressure, the jets interact with each other leading to mixing characteristics which are quite different from those of individual jets. The effect of mutual interaction is exaggerated under confinement, when a large number of closely spaced jets discharge into shallow depth. Dilution through an outfall, consisting of multiple jets, depends on various outfall and ambient parameters. Here we observe the effects of shoreline proximity, in relation to diffuser length and water depth, on the performance of unidirectional diffusers discharging to quiescent water. For diffusers located closer to shore, less dilution is observed due to the limited availability of ambient water for dilution. We report on the results of Computational Fluid Dynamics (CFD) simulations and compare the results with experimental observations.

  14. HUBBLE'S 100,000TH EXPOSURE CAPTURES IMAGE OF DISTANT QUASAR

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Hubble Space Telescope achieved its 100,000th exposure June 22 with a snapshot of a quasar that is about 9 billion light-years from Earth. The Wide Field and Planetary Camera 2 clicked this image of the quasar, the bright object in the center of the photo. The fainter object just above it is an elliptical galaxy. Although the two objects appear to be close to each other, they are actually separated by about 2 billion light-years. Located about 7 billion light-years away, the galaxy is almost directly in front of the quasar. Astronomer Charles Steidel of the California Institute of Technology in Pasadena, Calif., indirectly discovered the galaxy when he examined the quasar's light, which contained information about the galaxy's chemical composition. The reason, Steidel found, was that the galaxy was absorbing the light at certain frequencies. The astronomer is examining other background quasars to determine which kinds of galaxies absorb light at the same frequencies. Steidel also was somewhat surprised to discover that the galaxy is an elliptical, rather than a spiral. Elliptical galaxies are generally believed to contain very little gas. However, this elliptical has a gaseous 'halo' and contains no visible stars. Part of the halo is directly in front of the quasar. The bright object to the right of the quasar is a foreground star. The quasar and star are separated by billions of light-years. The quasar looks as bright as the star because it produces a tremendous amount of light from a compact source. The 'disturbed-looking' double spiral galaxy above the quasar also is in the foreground. Credit: Charles Steidel (California Institute of Technology, Pasadena, CA) and NASA. Image files in GIF and JPEG format and captions may be accessed on Internet via anonymous ftp from ftp.stsci.edu in /pubinfo.

  15. Predicting Space Weather Effects on Close Approach Events

    NASA Technical Reports Server (NTRS)

    Hejduk, Matthew D.; Newman, Lauri K.; Besser, Rebecca L.; Pachura, Daniel A.

    2015-01-01

    The NASA Robotic Conjunction Assessment Risk Analysis (CARA) team sends ephemeris data to the Joint Space Operations Center (JSpOC) for conjunction assessment screening against the JSpOC high accuracy catalog and then assesses risk posed to protected assets from predicted close approaches. Since most spacecraft supported by the CARA team are located in LEO orbits, atmospheric drag is the primary source of state estimate uncertainty. Drag magnitude and uncertainty is directly governed by atmospheric density and thus space weather. At present the actual effect of space weather on atmospheric density cannot be accurately predicted because most atmospheric density models are empirical in nature, which do not perform well in prediction. The Jacchia-Bowman-HASDM 2009 (JBH09) atmospheric density model used at the JSpOC employs a solar storm active compensation feature that predicts storm sizes and arrival times and thus the resulting neutral density alterations. With this feature, estimation errors can occur in either direction (i.e., over- or under-estimation of density and thus drag). Although the exact effect of a solar storm on atmospheric drag cannot be determined, one can explore the effects of JBH09 model error on conjuncting objects' trajectories to determine if a conjunction is likely to become riskier, less risky, or pass unaffected. The CARA team has constructed a Space Weather Trade-Space tool that systematically alters the drag situation for the conjuncting objects and recalculates the probability of collision for each case to determine the range of possible effects on the collision risk. In addition to a review of the theory and the particulars of the tool, the different types of observed output will be explained, along with statistics of their frequency.

  16. Performance of a simple closed aquatic ecosystem (CAES) in space

    NASA Astrophysics Data System (ADS)

    Wang, G.-H.; Li, G.-B.; Hu, C.-X.; Liu, Y.-D.; Song, L.-R.; Tong, G.-H.; Liu, X.-M.; Cheng, E.-T.

    2004-01-01

    A simple Closed Aquatic Ecosystem (CAES) consisting of single-celled green algae ( Chlorella pyrenoidosa, producer), a spiral snail ( Bulinus australianus, consumer) and a data acquisition and control unit was flown on the Chinese Spacecraft SHENZHOU-II in January 2001 for 7 days. In order to study the effect of microgravity on the operation of CAES, a 1 g centrifuge reference group in space, a ground 1 g reference group and a ground 1 g centrifuge reference group (1.4 g group) were run concurrently. Real-time data about algae biomass (calculated from transmission light intensity), temperature, light and centrifugation of the CAES were logged at minute intervals. It was found that algae biomass of both the microgravity group and the ground 1 g centrifuge reference group (1.4 g) fluctuated during the experiment, but the algae biomass of the 1 g centrifuge reference group in space and the ground 1 g reference group increased during the experiment. The results may be attributable to influences of microgravity and 1.4 g gravity on the algae and snails metabolisms. Microgravity is the main factor to affect the operation of CAES in space and the contribution of microgravity to the effect was also estimated. These data may be valuable for the establishment of a complex CELSS in the future.

  17. Quasars Probing Quasars. VI. Excess H I Absorption within One Proper Mpc of z ~ 2 Quasars

    NASA Astrophysics Data System (ADS)

    Prochaska, J. Xavier; Hennawi, Joseph F.; Lee, Khee-Gan; Cantalupo, Sebastiano; Bovy, Jo; Djorgovski, S. G.; Ellison, Sara L.; Lau, Marie Wingyee; Martin, Crystal L.; Myers, Adam; Rubin, Kate H. R.; Simcoe, Robert A.

    2013-10-01

    With close pairs of quasars at different redshifts, a background quasar sightline can be used to study a foreground quasar's environment in absorption. We use a sample of 650 projected quasar pairs to study the H I Lyα absorption transverse to luminous, z ~ 2 quasars at proper separations of 30 kpc < R < 1 Mpc. In contrast to measurements along the line-of-sight, regions transverse to quasars exhibit enhanced H I Lyα absorption and a larger variance than the ambient intergalactic medium, with increasing absorption and variance toward smaller scales. Analysis of composite spectra reveals excess absorption characterized by a Lyα equivalent width profile W = 2.3 Å (R /100 kpc)-0.46. We also observe a high (sime 60%) covering factor of strong, optically thick H I absorbers (H I column N_{H\\,\\scriptsize{I}}>10^{17.3}\\, cm^{-2}) at separations R < 200 kpc, which decreases to ~20% at R ~= 1 Mpc, but still represents a significant excess over the cosmic average. This excess of optically thick absorption can be described by a quasar-absorber cross-correlation function ξQA(r) = (r/r 0)γ with a large correlation length r_0=12.5^{+2.7}_{-1.4}\\, h^{-1}\\ Mpc (comoving) and \\gamma =1.68^{+0.14}_{-0.30}. The H I absorption measured around quasars exceeds that of any previously studied population, consistent with quasars being hosted by massive dark matter halos M halo ≈ 1012.5 M ⊙ at z ~ 2.5. The environments of these massive halos are highly biased toward producing optically thick gas, and may even dominate the cosmic abundance of Lyman limit systems and hence the intergalactic opacity to ionizing photons at z ~ 2.5. The anisotropic absorption around quasars implies the transverse direction is much less likely to be illuminated by ionizing radiation than the line-of-sight.

  18. 3. A Closed Aquatic System for Space and Earth Application

    NASA Astrophysics Data System (ADS)

    Slenzka, K.; Duenne, M.; Jastorff, B.; Ranke, J.; Schirmer, M.

    Increased durations in space travel as well as living in extreme environments are requiring reliable life support systems in general and bioregenerative ones in detail. Waste water management, air revitalization and food production are obviously center goals in this research, however, in addition a potential influence by chemicals, drugs etc. released to the closed environment must be considered. On this basis ecotoxicological data become more and more important for CELSS (Closed Ecological Life Support System) development and performance. The experiences gained during the last years in our research group lead to the development of an aquatic habitat, called AquaHab (formerly CBRU), which is a closed, self-sustaining system with a total water volume of 9 liters. In the frame program of a R&D project funded by the state of Bremen and OHB System, AquaHab is under adaptation to become an ecotoxicological research unit containing for example Japanese Medaka or Zebra Fish, amphipods, water snails and water plants. Test runs were standardized and analytical methods were developed. Beside general biological and water chemical parameters, activity measurements of biotransforming enzymes (G6PDH, CytP450-Oxidase, Peroxidase) and cell viability tests as well as residual analysis of the applied substance and respective metabolites were selected as evaluation criteria. In a first series of tests low doses effects of TBT (Tributyltin, 0.1 to 20 μgTBT/l nominal concentration) were analyzed. The AquaHab and data obtained for applied environmental risk assessment will be presented at the assembly.

  19. Hubble Space Telescope Observations of the Luminous IRAS Source FSC 10214+4724: A Gravitationally Lensed Infrared Quasar

    NASA Technical Reports Server (NTRS)

    Eisenhardt, Peter R.; Armus, Lee; Hogg, David W.; Soifer, B. T.; Neugebauer, G.; Werner, Michael W.

    1996-01-01

    With a redshift of 2.3, the IRAS source FSC 10214+4724 is apparently one of the most luminous objects known in the universe. We present an image of FSC 10214+4724 at 0.8 pm obtained with the Hubble Space Telescope (HST) WFPC2 Planetary Camera. The source appears as an unresolved (less then 0.06) arc 0.7 long, with significant substructure along its length. The center of curvature of the arc is located near an elliptical galaxy 1.18 to the north. An unresolved component 100 times fainter than the arc is clearly detected on the opposite side of this galaxy. The most straightforward interpretation is that FSC 10214+4724 is gravitationally lensed by the foreground elliptical galaxy, with the faint component a counter-image of the IRAS source. The brightness of the arc in the HST image is then magnified by approx. 100, and the intrinsic source diameter is approx. 0.0l (80 pc) at 0.25 microns rest wavelength. The bolometric luminosity is probably amplified by a smaller factor (approx. 30) as a result of the larger extent expected for the source in the far-infrared. A detailed lensing model is presented that reproduces the observed morphology and relative flux of the arc and counterimage and correctly predicts the position angle of the lensing galaxy. The model also predicts reasonable values for the velocity dispersion, mass, and mass-to-light ratio of the lensing galaxy for a wide range of galaxy redshifts. A redshift for the lensing galaxy of -0.9 is consistent with the measured surface brightness profile from the image, as well as with the galaxy's spectral energy distribution. The background lensed source has an intrinsic luminosity approx. 2 x 10(exp 13) L(solar mass) and remains a highly luminous quasar with an extremely large ratio of infrared to optical/ultraviolet luminosity.

  20. Various Approaches for Targeting Quasar Candidates

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Zhao, Y.

    2015-09-01

    With the establishment and development of space-based and ground-based observational facilities, the improvement of scientific output of high-cost facilities is still a hot issue for astronomers. The discovery of new and rare quasars attracts much attention. Different methods to select quasar candidates are in bloom. Among them, some are based on color cuts, some are from multiwavelength data, some rely on variability of quasars, some are based on data mining, and some depend on ensemble methods.

  1. Active galactic nucleus and quasar science with aperture masking interferometry on the James Webb Space Telescope

    SciTech Connect

    Ford, K. E. Saavik; McKernan, Barry; Sivaramakrishnan, Anand; Martel, André R.; Koekemoer, Anton; Lafrenière, David; Parmentier, Sébastien

    2014-03-10

    Due to feedback from accretion onto supermassive black holes (SMBHs), active galactic nuclei (AGNs) are believed to play a key role in ΛCDM cosmology and galaxy formation. However, AGNs extreme luminosities and the small angular size of their accretion flows create a challenging imaging problem. We show that the James Webb Space Telescope's Near Infrared Imager and Slitless Spectrograph (JWST-NIRISS) Aperture Masking Interferometry (AMI) mode will enable true imaging (i.e., without any requirement of prior assumptions on source geometry) at ∼65 mas angular resolution at the centers of AGNs. This is advantageous for studying complex extended accretion flows around SMBHs and in other areas of angular-resolution-limited astrophysics. By simulating data sequences incorporating expected sources of noise, we demonstrate that JWST-NIRISS AMI mode can map extended structure at a pixel-to-pixel contrast of ∼10{sup –2} around an L = 7.5 point source, using short exposure times (minutes). Such images will test models of AGN feedback, fueling, and structure (complementary with ALMA observations), and are not currently supported by any ground-based IR interferometer or telescope. Binary point source contrast with NIRISS is ∼10{sup –4} (for observing binary nuclei in merging galaxies), significantly better than current ground-based optical or IR interferometry. JWST-NIRISS's seven-hole non-redundant mask has a throughput of 15%, and utilizes NIRISS's F277W (2.77 μm), F380M (3.8 μm), F430M (4.3 μm), and F480M (4.8 μm) filters. NIRISS's square pixels are 65 mas per side, with a field of view ∼2' × 2'. We also extrapolate our results to AGN science enabled by non-redundant masking on future 2.4 m and 16 m space telescopes working at long-UV to near-IR wavelengths.

  2. Possibility of graphene growth by close space sublimation.

    PubMed

    Sopinskyy, Mykola V; Khomchenko, Viktoriya S; Strelchuk, Viktor V; Nikolenko, Andrii S; Olchovyk, Genadiy P; Vishnyak, Volodymyr V; Stonis, Viktor V

    2014-01-01

    Carbon films on the Si/SiO2 substrate are fabricated using modified method of close space sublimation at atmospheric pressure. The film properties have been characterized by micro-Raman and X-ray photoelectron spectroscopy and monochromatic ellipsometry methods. Ellipsometrical measurements demonstrated an increase of the silicon oxide film thickness in the course of manufacturing process. The XPS survey spectra of the as-prepared samples indicate that the main elements in the near-surface region are carbon, silicon, and oxygen. The narrow-scan spectra of C1s, Si2p, O1s regions indicate that silicon and oxygen are mainly in the SiOx (x ≈ 2) oxide form, whereas the main component of C1s spectrum at 284.4 eV comes from the sp2-hybridized carbon phase. Micro-Raman spectra confirmed the formation of graphene films with the number of layers that depended on the distance between the graphite source and substrate. PMID:24731549

  3. Insulators and Materials for Closed-Spaced Thermoelectric Modules

    SciTech Connect

    Donald P. Snowden

    2003-07-20

    The primary goal of this Phase I program has been accomplished: to demonstrate a ceramic, injection-molded eggcrate which will form the support structure for a close-spaced thermoelectric module which can operate at significantly higher temperatures than presently possible with such modules. It has been shown that yttria-stabilized zirconia is compatible at high temperatures with typical thermoelectric materials (TAGS, SnTE and PbTe) and that it can serve as a barrier between them to preclude cross-contamination and doping of the constituents of one leg type by those from the other. Using a 2 x 2 ceramic eggcrate, thermally sprayed molybdenum electrodes have been deposited on a test module which effectively seal each pocket, further reducing the possibility of migration of elements. Based on these results the next tasks are to refine the design of the injection tool and the injection parameters to produce consistent results and to allow increase in the size of the module to that on which commercial, high-temperature thermoelectric modules can be based. In addition, development of the fabrication techniques for segmented thermoelectric legs for use with these ceramic eggcrates at high temperatures must be continued.

  4. Close-spaced vapor transport of II-VI semiconductors

    NASA Astrophysics Data System (ADS)

    Perrier, Gerard

    1991-12-01

    The close spaced vapor transport (CSVT) is an efficient and cost-effective technique that allows the growth of polycrystalline as well as epitaxial thin layers of semiconductors. It has been applied to II-VI materials, especially to zinc and cadmium chalcogenides. A summary table including the deposition parameters, i.e., the nature of the ambient gas, the temperature of the source, the temperature difference between source and substrate, and the values of the growth rates measured on various substrates is presented for ZnS, ZnSe, ZnTe, CdS, CdSe, and CdTe. Experimental results concerning the growth of ZnSe on GaAs substrates are also reported. The CSVT system uses an Ar atmosphere and the working temperature is ca. 825 degree(s)C. The temperatures of source and substrate are measured during deposition and growth rates of the ZnSe films are studied as a function of the reciprocal temperature of the substrate surface for GaAs and quartz (inert) substrates. The measured values of the growth rate are compared to the theoretical ones given by the reaction-limited model and the diffusion-limited model. The validity of the models is discussed in terms of the nature of the molecules participating in the transport.

  5. A DISTANT QUASAR'S BRILLIANT LIGHT

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The arrow in this image, taken by a ground-based telescope, points to a distant quasar, the brilliant core of an active galaxy residing billions of light-years from Earth. As light from this faraway object travels across space, it picks up information on galaxies and the vast clouds of material between galaxies as it moves through them. The Space Telescope Imaging Spectrograph aboard NASA's Hubble Space Telescope decoded the quasar's light to find the spectral 'fingerprints' of highly ionized (energized) oxygen, which had mixed with invisible clouds of hydrogen in intergalactic space. The quasar's brilliant beam pierced at least four separate filaments of the invisible hydrogen laced with the telltale oxygen. The presence of oxygen between the galaxies implies there are huge quantities of hydrogen in the universe. Credits: WIYN Telescope at Kitt Peak National Observatory in Arizona. The telescope is owned and operated by the University of Wisconsin, Indiana University, Yale University, and the National Optical Astronomy Observatories.

  6. Locating star-forming regions in quasar host galaxies

    NASA Astrophysics Data System (ADS)

    Young, J. E.; Eracleous, M.; Shemmer, O.; Netzer, H.; Gronwall, C.; Lutz, Dieter; Ciardullo, R.; Sturm, Eckhard

    2014-02-01

    We present a study of the morphology and intensity of star formation in the host galaxies of eight Palomar-Green quasars using observations with the Hubble Space Telescope. Our observations are motivated by recent evidence for a close relationship between black hole growth and the stellar mass evolution in its host galaxy. We use narrow-band [O II]λ3727, Hβ, [O III]λ5007 and Paα images, taken with the Wide Field Planetary Camera 2 and NICMOS instruments, to map the morphology of line-emitting regions, and, after extinction corrections, diagnose the excitation mechanism and infer star-formation rates. Significant challenges in this type of work are the separation of the quasar light from the stellar continuum and the quasar-excited gas from the star-forming regions. To this end, we present a novel technique for image decomposition and subtraction of quasar light. Our primary result is the detection of extended line-emitting regions with sizes ranging from 0.5 to 5 kpc and distributed symmetrically around the nucleus, powered primarily by star formation. We determine star-formation rates of the order of a few tens of M⊙ yr-1. The host galaxies of our target quasars have stellar masses of the order of 1011 M⊙ and specific star-formation rates on a par with those of M82 and luminous infrared galaxies. As such they fall at the upper envelope or just above the star-formation mass sequence in the specific star formation versus stellar mass diagram. We see a clear trend of increasing star-formation rate with quasar luminosity, reinforcing the link between the growth of the stellar mass of the host and the black hole mass found by other authors.

  7. 76 FR 4412 - Commercial Space Transportation Advisory Committee-Closed Session

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-25

    ... TRANSPORTATION Federal Aviation Administration Commercial Space Transportation Advisory Committee--Closed Session AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of Commercial Space Transportation... 102-3.160, notice is hereby given of a special closed session of the Commercial Space...

  8. NEAR-INFRARED IMAGING OF A z = 6.42 QUASAR HOST GALAXY WITH THE HUBBLE SPACE TELESCOPE WIDE FIELD CAMERA 3

    SciTech Connect

    Mechtley, M.; Windhorst, R. A.; Cohen, S. H.; Jansen, R. A.; Scannapieco, E.; Ryan, R. E.; Koekemoer, A. M.; Schneider, G.; Fan, X.; Hathi, N. P.; Keel, W. C.; Roettgering, H.; Schneider, D. P.; Strauss, M. A.; Yan, H. J.

    2012-09-10

    We report on deep near-infrared F125W (J) and F160W (H) Hubble Space Telescope Wide Field Camera 3 images of the z = 6.42 quasar J1148+5251 to attempt to detect rest-frame near-ultraviolet emission from the host galaxy. These observations included contemporaneous observations of a nearby star of similar near-infrared colors to measure temporal variations in the telescope and instrument point-spread function (PSF). We subtract the quasar point source using both this direct PSF and a model PSF. Using direct subtraction, we measure an upper limit for the quasar host galaxy of m{sub J} > 22.8 and m{sub H} > 23.0 AB mag (2 {sigma}). After subtracting our best model PSF, we measure a limiting surface brightness from 0.''3 to 0.''5 radius of {mu}{sub J} > 23.5 and {mu}{sub H} > 23.7 AB mag arcsec{sup -2} (2 {sigma}). We test the ability of the model subtraction method to recover the host galaxy flux by simulating host galaxies with varying integrated magnitude, effective radius, and Sersic index, and conducting the same analysis. These models indicate that the surface brightness limit ({mu}{sub J} > 23.5 AB mag arcsec{sup -2}) corresponds to an integrated upper limit of m{sub J} > 22-23 AB mag, consistent with the direct subtraction method. Combined with existing far-infrared observations, this gives an infrared excess log (IRX) > 1.0 and corresponding ultraviolet spectral slope {beta} > -1.2 {+-} 0.2. These values match those of most local luminous infrared galaxies, but are redder than those of almost all local star-forming galaxies and z {approx_equal} 6 Lyman break galaxies.

  9. Paired quasars near NGC 2639 - Evidence for quasars in superclusters

    NASA Technical Reports Server (NTRS)

    Ford, H.; Ciardullo, R.; Harms, R.

    1983-01-01

    Arp (1979, 1980) has found quasars with similar redshifts which appear to be paired across low-redshift galaxies. Arp concludes that the pairings provide evidence for an association between high-redshift quasars and a small, low-redshift galaxy. Oort et al. (1981) suggested an alternative hypothesis to explain the close redshift pairs. They proposed that the two closest pairs are in superclusters at the cosmological distances implied by the quasars' redshifts. The low-redshift quasar pair U7/U10 (0.303/0.305) is close enough to allow detection of any associated clusters of galaxies on deep red photographs. The present investigation had originally the objective to test the supercluster hypothesis by searching for faint clusters which might comprise a supercluster at z approximately 0.3. Unfortunately, the disappearance of the pairs makes it impossible to test the hypothesis in this field. The search for a supercluster at z = 0.30 revealed a faint rich cluster of galaxies near the quasar U10 (z = 0.305). It was found that U10 is not associated with the cluster.

  10. OH maser observations using the Russian interferometric network ``Quasar'' in preparation for scientific observations with the space mission RadioAstron.

    NASA Astrophysics Data System (ADS)

    Litovchenko, I. D.; Alakoz, A. V.; Kostenko, V. I.; Lihachev, S. F.; Finkelstein, A. M.; Ipatov, A. V.

    2012-07-01

    We present results of a VLBI experiment at a wavelength of 18 cm, which simulates the ground-space interferometer with space link to RadioAstron. An array of five antennas was used, four of them are located in the Russian Federation, plus the the 32-m radio telescope in Medicine (Italy). The 22-m radio telescope in Pushchino (Moscow Region) acted in place of the space arm. It has an effective area of 100 square meters. The three other Russian 32-m antennas are operated by the Institute of Applied Astronomy RAS; they are located at Badary, Svetloe and Zelenchukskaya (interferometer network ``Quasar''). The maximum base-line, Badary-Svetloe, was about 4402 km, providing an angular resolution of about 0.009 arc seconds at a wavelength of 18 cm. The duration of the experiment was 10 hours on 02/03 February 2011. The program of observations included quasars 3C273, 3C279, 3C286 and the maser source - W3(OH). W3(OH) was observed only by the Russian telescopes and was investigated at the frequency of the 1665 MHz main line. The data were recorded on the MK5 recorder (32-m radio telescopes) and the RDR system (RadioAstron Digital Recorder) in Pushchino. The low SEFD (system equivalence of flux density) of Pushchino emulated the RadioAstron antenna. Correlation was performed with the universal software correlator of the AstroSpace Center of Lebedev Physical Institute. The correlator output format is compatible with that used by the AIPS package, which was used for data analysis. After analyzing the correlated data we obtained relative coordinates of the maser components. The main results are tabulated and presented in the figures. The data quality is sufficient for astrophysical analysis and comparison with previous observations of maser source W3(OH) on VLBI networks EVN and VLBA.

  11. Space ecosynthesis: An approach to the design of closed ecosystems for use in space

    NASA Technical Reports Server (NTRS)

    Macelroy, R. D.; Averner, M. M.

    1978-01-01

    The use of closed ecological systems for the regeneration of wastes, air, and water is discussed. It is concluded that such systems, if they are to be used for the support of humans in space, will require extensive mechanical and physico-chemical support. The reason for this is that the buffering capacity available in small systems is inadequate, and that natural biological and physical regulatory mechanisms rapidly become inoperative. It is proposed that mathematical models of the dynamics of a closed ecological system may provide the best means of studying the initial problems of ecosystem closure. A conceptual and mathematical model of a closed ecosystem is described which treats the biological components as a farm, calculates the rates of flow of elements through the system by mass-balance techniques and control theory postulates, and can evaluate the requirements for mechanical buffering activities. It is suggested that study of the closure of ecosystems can significantly aid in the establishment of general principles of ecological systems.

  12. The Hubble Space Telescope quasar absorption line key project. 6: Properties of the metal-rich systems

    NASA Technical Reports Server (NTRS)

    Bergeron, Jacqueline; Petitjean, Patrick; Sargent, W. L. W.; Bahcall, John N.; Boksenberg, Alec; Hartig, George F.; Jannuzi, Buell T.; Kirhakos, Sofia; Savage, Blair D.; Schneider, Donald P.

    1994-01-01

    We present an analysis of the properties of a sample of 18 metal-rich, low-redshift z(sub abs) much less than z(sub em) absorbers seen in low- and medium-resolution spectra obtained for the Quasar Absorption Line Key Project with the Hubble Space Telescope Faint Object Spectrograph (HST/FOS). For most of the C IV and Lyman-limit systems, observations in the optical wavelength range of the expected associated Mg II absorption are available. As at high redshift (z approximately 2), there are two subclasses of absorbers which are characterized by the presence or absence of MG II absorption. However, some low-redshift Mg II and Fe absorptions originate from regions optically thin to UV ionizing photons and thus, at low redshift, the low-ionization systems do not always trace high opacities, as is the case at high redshift. This implies that the mean ionization state of metal-rich, optically thin absorbing clouds falls with decreasing redshift, which is consistent with the hypothesis that the gas is photoionized by the metagalactic UV background radiation field. Two main constraints are derived from the analysis of the Lyman-limit sample, assuming photoionization models are valid. First, a low opacity to ionizing photons (tau(sub LL) approximately less than 1), as observed for several Mg II-Fe II systems at z approximately 0.5, sets limits on the ionization level of hydrogen, thus on the total hydrogen column density and the heavy element abundances, (Z/H) approximately -0.5 to -0.3. Second, the dimensions of individual Mg II clouds are smaller than at high redshift by a factor 3-10. At z approximately greater than 0.6, the O VI absorption doublet is detected in four of the five z(sub abs) much less than z(sub em) systems for which the O VI wavelength range has been observed, whereas the associated N V doublet is detected in only two cases. This suggests that the presence of a high-ionization O VI phase is a general property of z approximately 0.6-1 absorption systems

  13. Information for Lateral Aircraft Spacing Enabling Closely-Spaced Runway Operations During Instrument-Weather Conditions

    NASA Technical Reports Server (NTRS)

    Thrush, Trent; Pritchett, Amy; Johnson, Eric; Hansman, R. John; Shafto, Michael (Technical Monitor)

    1994-01-01

    In an effort to increase airport capacity, the U.S. plans on investing nearly $6 billion a year to properly maintain and improve the nation's major airports. Current FAA standards however, require a reduction in terminal operations during instrument-weather conditions at many airports, causing delays and reducing airport capacity. NASA, in cooperation with the FAA, has developed the Terminal Area Productivity Program to achieve clear-weather capacity in instrument- weather conditions for all phases of flight. This paper describes a series of experiments planned to investigate the conceptual design of different systems that provide information to flight crews regarding nearby traffic during the approach phase of flight. The purpose of this investigation is to identify and evaluate different display and auditory interfaces to the crew for use in closely-spaced parallel runway operations. Three separate experiments are planned for the investigation. The first two experiments will be conducted using part-task flight simulators located at the MIT Aeronautical Systems Laboratory and at NASA Ames. The third experiment will be conducted in the Advanced Concepts Flight Simulator, a generic "glass-cockpit" simulator at NASA Ames. Subjects for each experiment will be current glass-cockpit pilots from major U.S. air carriers. Subject crews will fly several experimental scenarios in which pseudo-aircraft are "blundered" into the subject aircraft simulation. Runway spacing, longitudinal aircraft separation, aircraft performance and traffic information will be varied. Analyses of the subject reaction times in evading the blundering aircraft and the resulting closest points of approach will be conducted. This paper presents a preliminary examination of the data recorded during the part-task experiments. The impact of traffic information on closely-spaced parallel runway operations is discussed, cockpit displays to aid these operations are examined, and topics for future research

  14. The Hubble Space Telescope quasar absorption line key project. v. redshift evolution of lyman limit absorption in the spectra of a large sample of quasars

    NASA Technical Reports Server (NTRS)

    Stengler-Larrea, Erik A.; Boksenberg, Alec; Steidel, Charles, C.; Sargent, W. L. W.; Bacall, John N.; Bergeron, Jacqueline; Hartig, George F.; Jannuzi, Buell T.; Kirhakos, Sofia; Savage, Blair D.

    1995-01-01

    Using a sample of 119 QSOs, containing objects we have selected having previously available high quality ground-based and IUE spectral observations, together with Hubble Space Telescope (HST) observations of 26 QSOs from Bahcall et al. (1993, 1995) and Impey et al. (1995) and new optical observations of 41 objects by Steidel & Sargent (1995), we study the redshift evolution of Lyman limit absorption systems (LLSs; tau greater than 1.0) over the reshift range 0.32 less than or equal to z(sub LLS) less than or equal to 4.11. The HST observations significantly improve the determination of the low redshift (0.4 less than or equal to z(sub LLS) less than or equal to 1.4) distribution. We find the effect which may have been responsible for the apparent strong evolution at a(sub LLS) greater than or equal to 2.5 found by Lanzetta (1991), which led him to consider a broken, not single power law as a better description of the redshift distribution of LLSs. After removing objects which may bias our sample, leaving a total of 169 QSOs, we find the distribution is well described by a single power law, and obtain for the number density as a function of redshift the form N(z) = N(sub 0)(1 + z)(exp gamma) with gamma = 1.50 =/- 0.39 and N(sub 0) = 0.25(sup -0.10)(sub +0.17), consistent with a constant comoving density of absorbers in a Firedmann universe with q(sub 0) = 0 but indicating evolution if q(sub 0) = 1/2.

  15. The Hubble Space Telescope quasar absorption line key project. v. redshift evolution of lyman limit absorption in the spectra of a large sample of quasars

    NASA Astrophysics Data System (ADS)

    Stengler-Larrea, Erik A.; Boksenberg, Alec; Steidel, Charles C.; Sargent, W. L. W.; Bahcall, John N.; Bergeron, Jacqueline; Hartig, George F.; Jannuzi, Buell T.; Kirhakos, Sofia; Savage, Blair D.; Schneider, Donald P.; Turnshek, David A.; Weymann, Ray J.

    1995-05-01

    Using a sample of 119 QSOs, containing objects we have selected having previously available high quality ground-based and IUE spectral observations, together with Hubble Space Telescope (HST) observations of 26 QSOs from Bahcall et al. (1993, 1995) and Impey et al. (1995) and new optical observations of 41 objects by Steidel & Sargent (1995), we study the redshift evolution of Lyman limit absorption systems (LLSs; tau greater than 1.0) over the reshift range 0.32 less than or equal to zLLS less than or equal to 4.11. The HST observations significantly improve the determination of the low redshift (0.4 less than or equal to zLLS less than or equal to 1.4) distribution. We find the effect which may have been responsible for the apparent strong evolution at aLLS greater than or equal to 2.5 found by Lanzetta (1991), which led him to consider a broken, not single power law as a better description of the redshift distribution of LLSs. After removing objects which may bias our sample, leaving a total of 169 QSOs, we find the distribution is well described by a single power law, and obtain for the number density as a function of redshift the form N(z) = N0(1 + z)gamma with gamma = 1.50 =/- 0.39 and N0 = 0.25-0.10+0.17, consistent with a constant comoving density of absorbers in a Firedmann universe with q0 = 0 but indicating evolution if q0 = 1/2.

  16. Plants for space plantations. [crops for closed life support systems

    NASA Technical Reports Server (NTRS)

    Nikishanova, T. I.

    1978-01-01

    Criteria for selection of candidate crops for closed life support systems are presented and discussed, and desired characteristics of candidate higher plant crops are given. Carbohydrate crops, which are most suitable, grown worldwide are listed and discussed. The sweet potato, ipomoea batatas Poir., is shown to meet the criteria to the greatest degree, and the criteria are recommended as suitable for initial evaluation of candidate higher plant crops for such systems.

  17. Noncontact Friction and Force Fluctuations between Closely Spaced Bodies

    SciTech Connect

    Stipe, B. C.; Mamin, H. J.; Stowe, T. D.; Kenny, T. W.; Rugar, D.

    2001-08-27

    Noncontact friction between a Au(111) surface and an ultrasensitive gold-coated cantilever was measured as a function of tip-sample spacing, temperature, and bias voltage using observations of cantilever damping and Brownian motion. The importance of the inhomogeneous contact potential is discussed and comparison is made to measurements over dielectric surfaces. Using the fluctuation-dissipation theorem, the force fluctuations are interpreted in terms of near-surface fluctuating electric fields interacting with static surface charge.

  18. Ultra Reliable Closed Loop Life Support for Long Space Missions

    NASA Technical Reports Server (NTRS)

    Jones, Harry W.; Ewert, Michael K.

    2010-01-01

    Spacecraft human life support systems can achieve ultra reliability by providing sufficient spares to replace all failed components. The additional mass of spares for ultra reliability is approximately equal to the original system mass, provided that the original system reliability is not too low. Acceptable reliability can be achieved for the Space Shuttle and Space Station by preventive maintenance and by replacing failed units. However, on-demand maintenance and repair requires a logistics supply chain in place to provide the needed spares. In contrast, a Mars or other long space mission must take along all the needed spares, since resupply is not possible. Long missions must achieve ultra reliability, a very low failure rate per hour, since they will take years rather than weeks and cannot be cut short if a failure occurs. Also, distant missions have a much higher mass launch cost per kilogram than near-Earth missions. Achieving ultra reliable spacecraft life support systems with acceptable mass will require a well-planned and extensive development effort. Analysis must determine the reliability requirement and allocate it to subsystems and components. Ultra reliability requires reducing the intrinsic failure causes, providing spares to replace failed components and having "graceful" failure modes. Technologies, components, and materials must be selected and designed for high reliability. Long duration testing is needed to confirm very low failure rates. Systems design should segregate the failure causes in the smallest, most easily replaceable parts. The system must be designed, developed, integrated, and tested with system reliability in mind. Maintenance and reparability of failed units must not add to the probability of failure. The overall system must be tested sufficiently to identify any design errors. A program to develop ultra reliable space life support systems with acceptable mass should start soon since it must be a long term effort.

  19. Closely Spaced MEG Source Localization and Functional Connectivity Analysis Using a New Prewhitening Invariance of Noise Space Algorithm

    PubMed Central

    Zhang, Junpeng; Cui, Yuan; Deng, Lihua; He, Ling; Zhang, Junran; Zhang, Jing; Zhou, Qun; Liu, Qi; Zhang, Zhiguo

    2016-01-01

    This paper proposed a prewhitening invariance of noise space (PW-INN) as a new magnetoencephalography (MEG) source analysis method, which is particularly suitable for localizing closely spaced and highly correlated cortical sources under real MEG noise. Conventional source localization methods, such as sLORETA and beamformer, cannot distinguish closely spaced cortical sources, especially under strong intersource correlation. Our previous work proposed an invariance of noise space (INN) method to resolve closely spaced sources, but its performance is seriously degraded under correlated noise between MEG sensors. The proposed PW-INN method largely mitigates the adverse influence of correlated MEG noise by projecting MEG data to a new space defined by the orthogonal complement of dominant eigenvectors of correlated MEG noise. Simulation results showed that PW-INN is superior to INN, sLORETA, and beamformer in terms of localization accuracy for closely spaced and highly correlated sources. Lastly, source connectivity between closely spaced sources can be satisfactorily constructed from source time courses estimated by PW-INN but not from results of other conventional methods. Therefore, the proposed PW-INN method is a promising MEG source analysis to provide a high spatial-temporal characterization of cortical activity and connectivity, which is crucial for basic and clinical research of neural plasticity. PMID:26819768

  20. Quantum field theory in spaces with closed timelike curves

    NASA Astrophysics Data System (ADS)

    Boulware, David G.

    1992-11-01

    Gott spacetime has closed timelike curves, but no locally anomalous stress energy. A complete orthonormal set of eigenfunctions of the wave operator is found in the special case of a spacetime in which the total deficit angle is 2π. A scalar quantum field theory is constructed using these eigenfunctions. The resultant interacting quantum field theory is not unitary because the field operators can create real, on-shell, particles in the noncausal region. These particles propagate for finite proper time accumulating an arbitrary phase before being annihilated at the same spacetime point as that at which they were created. As a result, the effective potential within the noncausal region is complex, and probability is not conserved. The stress tensor of the scalar field is evaluated in the neighborhood of the Cauchy horizon; in the case of a sufficiently small Compton wavelength of the field, the stress tensor is regular and cannot prevent the formation of the Cauchy horizon.

  1. The Hubble Space Telescope quasar absorption line key project. III - First observational results on Milky Way gas

    NASA Technical Reports Server (NTRS)

    Savage, Blair D.; Lu, Limin; Bahcall, John N.; Bergeron, Jacqueline; Boksenberg, Alec; Hartig, George F.; Jannuzi, Buell T.; Kirhakos, Sofia; Lockman, Felix J.; Sargent, W. L. W.

    1993-01-01

    Absorption lines found near zero redshift due to Milky Way disk and halo gas in the spectra of 15 quasars observed with the Faint Object Spectrograph (FOS) of the HST at a resolution of about 230 km/s are reported. Results show that Milky Way absorption lines comprise about 44 percent of all absorption lines seen in the first group of Key Project FOS spectra. Milky Way lines were observed for 3C 273 and H1821 + 643. Limits to the Mg-to-H abundance ratio obtained for very high velocity Mg II absorption detections imply gas-phase Mg abundances for the very high velocity gas ranging from more than 0.059 to more than 0.32 times the solar abundance. In all cases where high-velocity H I emission is seen, corresponding high-velocity metal-line absorption is observed.

  2. Nanoscale Engineering of Closely-Spaced Electronic Spins in Diamond.

    PubMed

    Scarabelli, Diego; Trusheim, Matt; Gaathon, Ophir; Englund, Dirk; Wind, Shalom J

    2016-08-10

    Numerous theoretical protocols have been developed for quantum information processing with dipole-coupled solid-state spins. Nitrogen vacancy (NV) centers in diamond have many of the desired properties, but a central challenge has been the positioning of NV centers at the nanometer scale that would allow for efficient and consistent dipolar couplings. Here we demonstrate a method for chip-scale fabrication of arrays of single NV centers with record spatial localization of about 10 nm in all three dimensions and controllable inter-NV spacing as small as 40 nm, which approaches the length scale of strong dipolar coupling. Our approach uses masked implantation of nitrogen through nanoapertures in a thin gold film, patterned via electron-beam lithography and dry etching. We verified the position and spin properties of the resulting NVs through wide-field super-resolution optically detected magnetic resonance imaging. PMID:27428077

  3. Nutritional criteria for closed-loop space food systems

    NASA Technical Reports Server (NTRS)

    Rambaut, P. C.

    1980-01-01

    The nutritional requirements for Skylab crews are summarized as a data base for long duration spaceflight nutrient requirements. Statistically significant increases in energy consumption were detected after three months, along with CO2/O2 exhalation during exercise and thyroxine level increases. Linoleic acid amounting to 3-4 g/day was found to fulfill all fat requirements, and carbohydrate and protein (amino acid) necessities are discussed, noting that vigorous exercise programs avoid deconditioning which enhances nitrogen loss. Urinary calcium losses continued at a rate 100% above a baseline figure, a condition which ingestion of vitamin D2 did not correct. Projections are given that spaceflights lasting more than eight years will necessitate recycling of human waste for nutrient growth, which can be processed into highly efficient space food with a variety of tastes.

  4. XMM-Newton closes in on space's exotic matter

    NASA Astrophysics Data System (ADS)

    2002-11-01

    With ESA's space telescope XMM-Newton, they are now closer to testing this idea. For the first time, XMM-Newton has been able to measure the influence of the gravitational field of a neutron star on the light it emits. This measurement provides much better insight into these objects. Neutron stars are among the densest objects in the Universe. They pack the mass of the sun inside a sphere 10 kilometres across. A sugar cube-sized piece of neutron star weighs over a billion tonnes. Neutron stars are the remnants of exploding stars up to eight times more massive than our Sun. They end their life in a supernova explosion and then collapse under their own gravity. Their interiors may therefore contain a very exotic form of matter. Scientists believe that in a neutron star, the density and the temperatures are similar to those existing a fraction of a second after the Big Bang. They assume that when matter is tightly packed as it is in a neutron star, it goes through important changes. Protons, electrons, and neutrons - the components of atoms - fuse together. It is possible that even the building-blocks of protons and neutrons, the so-called quarks, get crushed together, giving rise to a kind of exotic plasma of 'dissolved' matter. How to find out? Scientists have spent decades trying to identify the nature of matter in neutron stars. To do this, they need to know some important parameters very precisely: if you know a star’s mass and radius, or the relationship between them, you can obtain its compactness. However,no instrument has been advanced enough to perform the measurements needed, until now. Thanks to ESA's XMM-Newton observatory, astronomers have been able for the first time to measure the mass-to-radius ratio of a neutron star and obtain the first clues to its composition. These suggest that the neutron star contains normal, non-exotic matter, although they are not conclusive. The authors say this is a “key first step” and they will keep on with the

  5. Investigations in Time and of Space Using the FIRST Survey: Radio Source Variability and the Evolution of FR II Quasars

    NASA Astrophysics Data System (ADS)

    Thyagarajan, Nithyanandan

    The FIRST survey covered ∼10,000 deg2 of the sky over a decade, providing unprecedented levels of flux density sensitivity (∼ 1 mJy) at 1.4 GHz, uniformity to within 15% (at ∼0.15 mJy rms), 5.4" angular resolution, astrometric accuracy to better than 1" and has cataloged ≳ 800,000 sources. It has made enormous contributions to diverse scientific ends including such subjects as radio source populations, quasars, large-scale structure and clustering of radio sources, gravitational lensing, cosmology, etc. I present the motivation, analysis and results of two projects also intended to demonstrate the power and expand the scope of the FIRST survey's scientific reach. A comprehensive search for variable and transient radio sources has been conducted using the ∼55,000 snapshot images of the FIRST survey. An analysis leading to the discovery of 1,651 variable and transient objects down to mJy levels over a wide range of timescales (few minutes to years) is presented. The multi-wavelength matching for counterparts reveals the diverse classes of objects exhibiting variability. Interestingly, ∼ 60% of the objects in the sample have either no classified counterparts or no corresponding sources at any other wavelength and require multi-wavelength follow-up observations. I discuss these classes of variables and speculate on the identity of objects that lack multi-wavelength counterparts. Thus, the FIRST survey has yielded the largest sample by far of radio variables and transients to date to unprecedented levels of sensitivity and sky coverage and demonstrates the promise of future radio instruments which have transient-detection as one of their key science projects. For decades, radio astronomers have attempted to use double-lobed radio sources to constrain the angular size-redshift (θ - z ) relation and to derive cosmological parameters therefrom. Most of the early attempts have, embarrassingly, shown general consistency with a static Euclidean universe rather

  6. Constraining Sub-parsec Binary Supermassive Black Holes in Quasars with Multi-epoch Spectroscopy. I. The General Quasar Population

    NASA Astrophysics Data System (ADS)

    Shen, Yue; Liu, Xin; Loeb, Abraham; Tremaine, Scott

    2013-09-01

    We perform a systematic search for sub-parsec binary supermassive black holes (BHs) in normal broad-line quasars at z < 0.8, using multi-epoch Sloan Digital Sky Survey (SDSS) spectroscopy of the broad Hβ line. Our working model is that (1) one and only one of the two BHs in the binary is active; (2) the active BH dynamically dominates its own broad-line region (BLR) in the binary system, so that the mean velocity of the BLR reflects the mean velocity of its host BH; (3) the inactive companion BH is orbiting at a distance of a few R BLR, where R BLR ~ 0.01-0.1 pc is the BLR size. We search for the expected line-of-sight acceleration of the broad-line velocity from binary orbital motion by cross-correlating SDSS spectra from two epochs separated by up to several years in the quasar rest frame. Out of ~700 pairs of spectra for which we have good measurements of the velocity shift between two epochs (1σ error ~40 km s-1), we detect 28 systems with significant velocity shifts in broad Hβ, among which 7 are the best candidates for the hypothesized binaries, 4 are most likely due to broad-line variability in single BHs, and the rest are ambiguous. Continued spectroscopic observations of these candidates will easily strengthen or disprove these claims. We use the distribution of the observed accelerations (mostly non-detections) to place constraints on the abundance of such binary systems among the general quasar population. Excess variance in the velocity shift is inferred for observations separated by longer than 0.4 yr (quasar rest frame). Attributing all the excess to binary motion would imply that most of the quasars in this sample must be in binaries, that the inactive BH must be on average more massive than the active one, and that the binary separation is at most a few times the size of the BLR. However, if this excess variance is partly or largely due to long-term broad-line variability, the requirement of a large population of close binaries is much weakened

  7. QUASARS PROBING QUASARS. IV. JOINT CONSTRAINTS ON THE CIRCUMGALACTIC MEDIUM FROM ABSORPTION AND EMISSION

    SciTech Connect

    Hennawi, Joseph F.; Prochaska, J. Xavier

    2013-03-20

    We have constructed a sample of 29 close projected quasar pairs where the background quasar spectrum reveals absorption from optically thick H I gas associated with the foreground quasar. These unique sightlines allow us to study the quasar circumgalactic medium (CGM) in absorption and emission simultaneously, because the background quasar pinpoints large concentrations of gas where Ly{alpha} emission, resulting from quasar-powered fluorescence, resonant Ly{alpha} scattering, and/or cooling radiation, is expected. A sensitive search (1{sigma} surface-brightness limits of SB{sub Ly{alpha}}{approx_equal}3 Multiplication-Sign 10{sup -18} erg s{sup -1} cm{sup -2} arcsec{sup -2}) for diffuse Ly{alpha} emission in the environments of the foreground (predominantly radio-quiet) quasars is conducted using Gemini/GMOS and Keck/LRIS slit spectroscopy. We fail to detect large-scale {approx}100 kpc Ly{alpha} emission, either at the location of the optically thick absorbers or in the foreground quasar halos, in all cases except a single system. We interpret these non-detections as evidence that the gas detected in absorption is shadowed from the quasar UV radiation due to obscuration effects, which are frequently invoked in unified models of active galactic nuclei. Small-scale R {approx}< 50 kpc extended Ly{alpha} nebulosities are detected in 34% of our sample, which are likely the high-redshift analogs of the extended emission-line regions (EELRs) commonly observed around low-redshift (z < 0.5) quasars. This may be fluorescent recombination radiation from a population of very dense clouds with a low covering fraction illuminated by the quasar. We also detect a compact high rest-frame equivalent width (W{sub Ly{alpha}} > 50 A) Ly{alpha}-emitter with luminosity L{sub Ly{alpha}} = 2.1 {+-} 0.32 Multiplication-Sign 10{sup 41} erg s{sup -1} at small impact parameter R = 134 kpc from one foreground quasar, and argue that it is more likely to result from quasar-powered fluorescence

  8. HUBBLE CAPTURES MERGER BETWEEN QUASAR AND GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This NASA Hubble Space Telescope image shows evidence fo r a merger between a quasar and a companion galaxy. This surprising result might require theorists to rethink their explanations for the nature of quasars, the most energetic objects in the universe. The bright central object is the quasar itself, located several billion light-years away. The two wisps on the (left) of the bright central object are remnants of a bright galaxy that have been disrupted by the mutual gravitational attraction between the quasar and the companion galaxy. This provides clear evidence for a merger between the two objects. Since their discovery in 1963, quasars (quasi-stellar objects) have been enigmatic because they emit prodigious amounts of energy from a very compact source. The most widely accepted model is that a quasar is powered by a supermassive black hole in the core of a galaxy. These new observations proved a challenge for theorists as no current models predict the complex quasar interactions unveiled by Hubble. The image was taken with the Wide Field Planetary Camera-2. Credit: John Bahcall, Institute for Advanced Study, NASA.

  9. Weak bump quasars

    NASA Technical Reports Server (NTRS)

    Mcdowell, Jonathan C.; Elvis, Martin; Wilkes, Belinda J.; Willner, Steven P.; Oey, M. S.

    1989-01-01

    The recent emphasis on big bumps dominating the UV continuum of quasars has obscured the facts that bump properties vary widely and that there are objects in which no such component is evident. As part of a survey of quasar continuum spectra, a class of quasars is identified in which the optical-UV continuum big bump feature appears to be weak or absent, relative to both IR and X-ray. These weak bump quasars are otherwise normal objects and constitute a few percent of the quasar population.

  10. Solving Quasars (Part 1)

    SciTech Connect

    Elvis, Martin

    2003-10-29

    Quasars are a frustratingly unsolved problem in astrophysics. For 40 years quasars and AGN have presented an ever-proliferating list of diverse and confusing phenomenology from optical to X-ray wavelengths. The result has been that despite being the most powerful objects in the universe, quasars have been increasingly sidelined in astrophysics. This is unfortunate, as quasars pose major physics, as well as astrophysics puzzles, and should be important in cosmology. The problem, I believe, is not that we do not know enough physics, but rather that we do not have the right geometry. I have proposed a simple geometric and kinematic model that allows all of the quasar diversity to be understood as part of a single structure, the 'Quasar Atmosphere'. This structure suggests a natural physical interpretation, that builds on our understanding of stars (the only fully solved problem in astrophysics), and offers the prospect that we can use quasars for cosmology at last.

  11. GALACTIC-SCALE ABSORPTION OUTFLOW IN THE LOW-LUMINOSITY QUASAR IRAS F04250-5718: HUBBLE SPACE TELESCOPE/COSMIC ORIGINS SPECTROGRAPH OBSERVATIONS

    SciTech Connect

    Edmonds, Doug; Borguet, Benoit; Arav, Nahum; Dunn, Jay P.; Penton, Steve; Kriss, Gerard A.; Korista, Kirk; Bautista, Manuel; Costantini, Elisa; Kaastra, Jelle; Steenbrugge, Katrien; Ignacio Gonzalez-Serrano, J.; Benn, Chris; Aoki, Kentaro; Behar, Ehud; Micheal Crenshaw, D.; Everett, John; Gabel, Jack; Moe, Maxwell; Scott, Jennifer

    2011-09-20

    We present absorption line analysis of the outflow in the quasar IRAS F04250-5718. Far-ultraviolet data from the Cosmic Origins Spectrograph on board the Hubble Space Telescope reveal intrinsic narrow absorption lines from high ionization ions (e.g., C IV, N V, and O VI) as well as low ionization ions (e.g., C II and Si III). We identify three kinematic components with central velocities ranging from {approx}-50 to {approx}-230 km s{sup -1}. Velocity-dependent, non-black saturation is evident from the line profiles of the high ionization ions. From the non-detection of absorption from a metastable level of C II, we are able to determine that the electron number density in the main component of the outflow is {approx}<30 cm{sup -3}. Photoionization analysis yields an ionization parameter log U{sub H} {approx} -1.6 {+-} 0.2, which accounts for changes in the metallicity of the outflow and the shape of the incident spectrum. We also consider solutions with two ionization parameters. If the ionization structure of the outflow is due to photoionization by the active galactic nucleus, we determine that the distance to this component from the central source is {approx}>3 kpc. Due to the large distance determined for the main kinematic component, we discuss the possibility that this outflow is part of a galactic wind.

  12. Near-infrared Photometric Properties of 130,000 Quasars: An SDSS-UKIDSS-matched Catalog

    NASA Astrophysics Data System (ADS)

    Peth, Michael A.; Ross, Nicholas P.; Schneider, Donald P.

    2011-04-01

    We present a catalog of over 130,000 quasar candidates with near-infrared (NIR) photometric properties, with an areal coverage of approximately 1200 deg2. This is achieved by matching the Sloan Digital Sky Survey (SDSS) in the optical ugriz bands to the UKIRT Infrared Digital Sky Survey (UKIDSS) Large Area Survey (LAS) in the NIR YJHK bands. We match the ≈1 million SDSS DR6 Photometric Quasar catalog to Data Release 3 of the UKIDSS LAS (ULAS) and produce a catalog with 130,827 objects with detections in one or more NIR bands, of which 74,351 objects have optical and K-band detections and 42,133 objects have the full nine-band photometry. The majority (~85%) of the SDSS objects were not matched simply because these were not covered by the ULAS. The positional standard deviation of the SDSS Quasar to ULAS matches is δR.A. = 0farcs1370 and δdecl. = 0farcs1314. We find an absolute systematic astrometric offset between the SDSS Quasar catalog and the UKIDSS LAS, of |R.A.offset| = 0farcs025 and |decl.offset| = 0farcs040; we suggest the nature of this offset to be due to the matching of catalog, rather than image, level data. Our matched catalog has a surface density of ≈53 deg-2 for K <= 18.27 objects; tests using our matched catalog, along with data from the UKIDSS Deep Extragalactic Survey, imply that our limiting magnitude is i ≈ 20.6. Color-redshift diagrams, for the optical and NIR, show a close agreement between our matched catalog and recent quasar color models at redshift z <~ 2.0, while at higher redshifts, the models generally appear to be bluer than the mean observed quasar colors. The gJK and giK color spaces are used to examine methods of differentiating between stars and (mid-redshift) quasars, the key to currently ongoing quasar surveys. Finally, we report on the NIR photometric properties of high, z > 4.6, and very high, z > 5.7, redshift previously discovered quasars.

  13. NEAR-INFRARED PHOTOMETRIC PROPERTIES OF 130,000 QUASARS: AN SDSS-UKIDSS-MATCHED CATALOG

    SciTech Connect

    Peth, Michael A.; Ross, Nicholas P.; Schneider, Donald P.

    2011-04-15

    We present a catalog of over 130,000 quasar candidates with near-infrared (NIR) photometric properties, with an areal coverage of approximately 1200 deg{sup 2}. This is achieved by matching the Sloan Digital Sky Survey (SDSS) in the optical ugriz bands to the UKIRT Infrared Digital Sky Survey (UKIDSS) Large Area Survey (LAS) in the NIR YJHK bands. We match the {approx}1 million SDSS DR6 Photometric Quasar catalog to Data Release 3 of the UKIDSS LAS (ULAS) and produce a catalog with 130,827 objects with detections in one or more NIR bands, of which 74,351 objects have optical and K-band detections and 42,133 objects have the full nine-band photometry. The majority ({approx}85%) of the SDSS objects were not matched simply because these were not covered by the ULAS. The positional standard deviation of the SDSS Quasar to ULAS matches is {delta}{sub R.A.} = 0.''1370 and {delta}{sub decl.} = 0.''1314. We find an absolute systematic astrometric offset between the SDSS Quasar catalog and the UKIDSS LAS, of |R.A.{sub offset}| = 0.''025 and |decl.{sub offset}| = 0.''040; we suggest the nature of this offset to be due to the matching of catalog, rather than image, level data. Our matched catalog has a surface density of {approx}53 deg{sup -2} for K {<=} 18.27 objects; tests using our matched catalog, along with data from the UKIDSS Deep Extragalactic Survey, imply that our limiting magnitude is i {approx} 20.6. Color-redshift diagrams, for the optical and NIR, show a close agreement between our matched catalog and recent quasar color models at redshift z {approx}< 2.0, while at higher redshifts, the models generally appear to be bluer than the mean observed quasar colors. The gJK and giK color spaces are used to examine methods of differentiating between stars and (mid-redshift) quasars, the key to currently ongoing quasar surveys. Finally, we report on the NIR photometric properties of high, z > 4.6, and very high, z > 5.7, redshift previously discovered quasars.

  14. Quasar Rain

    NASA Astrophysics Data System (ADS)

    Elvis, Martin

    2015-01-01

    Velocity resolved reverberation mapping (VRRM) has shown clear evidence for inflows in the broad emission line (BEL) region of active galactic nuclei: redshifted BELs at zero lag (AGNs, e.g. Arp 151, Bentz et al. 2010; Grier et al. 2013). While radiative transfer in rotating disks can give shorter red side lags than blue, a zero lag has to be along our line of sight, so it is hard to escape infall. The BEL region is normally considered to be rotating or in outflow so this result is a surprise. Infalling BEL gas cannot fall far without the need to lose angular momentum for accreting gas producing an accretion disk.I suggest that quasar continuum irradiation induced cooling instabilities (Chakravorty et al 2009; Krolik, McKee & Tarter 1981) lead to dense BEL clouds condensing out of the semi-ubiquitous warm absorber (WA) outflows found in AGNs and that these clouds may produce a VRRM inflow signature.Unlike WA gas, dense high column density BEL clouds are hard to accelerate with radiation pressure (Risaliti & Elvis 2010; Mushotzky, Solomon & Strittmatter 1972). BEL clouds will thus stall in the outflow and begin to fall back toward the central black hole after a dynamical time, 'raining out' of the WA medium. If these BEL clouds condense out before these outflows reach escape velocity [v(esc)] then this inflow can potentially produce the observed VRRM signature. As the clouds fall back in they will be moving on elliptical orbits supersonically through the WA gas with Mach number ~(2000 km/s)/(100km/s) ~20. This will produce comet-like structures with narrow opening angles, as seen in asymmetric X-ray absorbing 'eclipses' (Maiolino et al. 2010). They will survive only a few months, as required to avoid forming a disk. For this picture to work the condensation time must be less than the acceleration time to v(esc) and the destruction time must be longer than the dynamical time.

  15. A state-space dynamical representation for multibody mechanical systems. II - Systems with closed loops

    NASA Astrophysics Data System (ADS)

    Schwertassek, R.; Roberson, R. E.

    1984-05-01

    The dynamical equations of motion of a multibody system are reduced to state-space equations in the computer-oriented multibody formalism of Roberson and Wittenberg (1966), extending the analysis of Schwertassek and Roberson (1983) to systems with closed loops. The multibody spacecraft model of Kane and Levinson (1980) and Schiehlen and Kreuzer (1977) is analyzed as an example. The closed-loop equations permit the use of the MULTIBODY computer code (Schwertassek, 1978) to treat such more general systems.

  16. Merging Galaxies Create a Binary Quasar

    NASA Astrophysics Data System (ADS)

    2010-02-01

    Observatory in California indicated that the object was likely a binary quasar in the midst of a galaxy merger. Carnegie's Mulchaey then used the 6.5 meter Baade-Magellan telescope at the Las Campanas observatory in Chile to obtain deeper images and more detailed spectroscopy of the merging galaxies. "Just because you see two galaxies that are close to each other in the sky doesn't mean they are merging," says Mulchaey. "But from the Magellan images we can actually see tidal tails, one from each galaxy, which suggests that the galaxies are in fact interacting and are in the process of merging." Thomas Cox, now a fellow at the Carnegie Observatories, corroborated this conclusion using computer simulations of the merging galaxies. When Cox's model galaxies merged, they showed features remarkably similar to what Mulchaey observed in the Magellan images. "The model verifies the merger origin for this binary quasar system," he says. "It also hints that this kind of galaxy interaction is a key component of the growth of black holes and production of quasars throughout our universe." * The authors of the paper published in the Astrophysical Journal are Paul J. Green of the Harvard-Smithsonian Center for Astrophysics, Adam D. Myers of the University of Illinois at Urbana-Champaign, Wayne A. Barkhouse of the University of North Dakota, John S. Mulchaey of the Observatories of the Carnegie Institution for Science, Vardha N. Bennert of the Department of Physics, University of California, Santa Barbara, Thomas J. Cox of the Observatories of the Carnegie Institution for Science, Thomas L. Aldcroft of the Harvard-Smithsonian Center for Astrophysics, and Joan M. Wrobel of National Radio Astronomy Observatory, Socorro, NM. More information, including images and other multimedia, can be found at: http://chandra.harvard.edu and http://chandra.nasa.gov

  17. Closed Crawl Space Performance: Proof of Concept in the Production Builder Marketplace

    SciTech Connect

    Malkin-Weber, Melissa; Dastur, Cyrus; Mauceri, Maria; Hannas, Benjamin

    2008-10-30

    This overview is intended to be a very concise, limited summary of the key project activities discussed in the detailed report that follows. Due to the large scope of this project, the detailed report is broken into three individually titled sections. Each section repeats key background information, with the goal that the sections will eventually stand alone as complete reports on the major activities of the project. The information presented herein comes from ongoing research, so please note that all observations, findings and recommendations presented are preliminary and subject to change in the future. We invite and welcome your comments and suggestions for improving the project. Advanced Energy completed its first jointly-funded crawl space research project with the Department of Energy in 2005. That project, funded under award number DE-FC26-00NT40995 and titled 'A Field Study Comparison of the Energy and Moisture Performance Characteristics of Ventilated Versus Sealed Crawl Spaces in the South' demonstrated the substantial energy efficiency and moisture management benefits that result from using properly closed crawl space foundations for residential construction instead of traditional wall vented crawl space foundations. Two activities of this first project included (1) an assessment of ten existing homes to document commonly observed energy and moisture failures associated with wall-vented crawl space foundations and (2) a detailed literature review that documented both the history of closed crawl space research and the historical lack of scientific justification for building code requirements for crawl space ventilation. The most valuable activity of the 2005 project proved to be the field demonstration of various closed crawl space techniques, which were implemented in a set of twelve small (1040 square feet), simply designed homes in eastern North Carolina. These homes had matched envelope, mechanical and architectural designs, and comparable performance

  18. Probabilistic Analysis of Impact of Wake Vortices on Closely-Spaced Parallel Approaches

    NASA Technical Reports Server (NTRS)

    Hardy, Gordon H.; Rossow, Vernon J.; Meyn, Larry A.

    2005-01-01

    One of the primary constraints on the capacity of the nation's air transportation system is the landing capacity of its largest airports. Many airports with closely spaced parallel runways suffer a severe runway acceptance rate when the weather conditions do not allow full utilization of these parallel runways. The present requirement for simultaneous independent landings in Instrument Meteorological Conditions, IMC, is at least 4300 feet of lateral runway spacing (as close as 3000 feet for runways with a Precision Runway Monitor). Operations in Visual Meteorological Conditions, VMC, to Closely Spaced Parallel Approaches only require a lateral runway spacing greater than 750 feet. A study by Hardy and Lewis integrated and extended earlier studies and concepts in lateral traffic separation, longitudinal station keeping, wake prediction, wake display, and the concepts of R N P into a preliminary system concept for Closely Spaced Parallel Approaches in IMC. This system allows IMC airport acceptance rates to approach those for VMC. The system concept that was developed, presented traffic and wake information on the NAVigation Display, NAV, and developed operational procedures for a mix of conventional and Runway Independent Aircraft with different approach speeds to Closely Spaced Parallel Runways. This paper first describes some improvements made on the technology needed to better predict and formulate a probabilistic representation for the time-dependent motion and spreading of the hazardous region associated with the lift-generated vortex wakes of preceding aircraft. In this way, the time at which the vortex wakes of leading aircraft intrude into the airspace of adjacent flight-corridor/runway combinations can be more reliably predicted. Such a prediction is needed because it determines restraints to be placed on in-trail separation distances; or, the allowable time intervals between aircraft executing nearly simultaneous landings or takeoffs on very closely-spaced

  19. Strong associated C 4 absorption in low redshift quasars

    NASA Technical Reports Server (NTRS)

    Tytler, David

    1990-01-01

    IUE spectra of quasars were used to determine the frequency of occurrence of strong associated C 4 absorption systems at low red shifts. Four systems are found with rest frame equivalent width (REW) greater than 5 angstroms in the spectra of 38 quasars. This rate of occurrence of 0.12 is not significantly different from the rate of 0.064 determined for high red shift quasars. The detected strong associated systems are all in low red shift quasars which have been imaged from the ground. One of the quasars is unusual, having two nuclei, a close companion and distorted isotopes. Two of the others also have close companion galaxies at projected distances of under 100 kpc. The conclusion was made that a much larger sample is needed.

  20. Infrared weak quasars

    NASA Technical Reports Server (NTRS)

    Mcdowell, J. C.; Elvis, M.; Wilkes, B. J.

    1992-01-01

    Examples of quasars with anomalously weak IR emission are presented, and the effects of starlight subtraction on estimates of the UV and IR component strengths are discussed. Inferred model parameters are very sensitive to the position of the peak of the UV energy distribution. In many low redshift objects the peak is not seen; even in those objects where the turnover is clear, the turnover may not be intrinsic but instead due to reddening within the quasar host galaxy. The small number of unusual quasars with weak IR emission will be of utility as a probe of the quasar phenomenon in the absence of dominant dust reprocessing.

  1. Pilot Non-Conformance to Alerting System Commands During Closely Spaced Parallel Approaches

    NASA Technical Reports Server (NTRS)

    Pritchett, Amy R.; Hansman, R. John

    1997-01-01

    Pilot non-conformance to alerting system commands has been noted in general and to a TCAS-like collision avoidance system in a previous experiment. This paper details two experiments studying collision avoidance during closely-spaced parallel approaches in instrument meteorological conditions (IMC), and specifically examining possible causal factors of, and design solutions to, pilot non-conformance.

  2. Characterizing Quasar Outflows I: Sample, Spectral Measurements

    NASA Astrophysics Data System (ADS)

    Ganguly, Rajib; Christenson, D. H.; Richmond, J. M.; Derseweh, J. A.; Robbins, J. M.; Townsend, S. L.; Stark, M. A.

    2012-05-01

    Galaxy evolution models have shown that quasars are a crucial ingredient in the evolution of massive galaxies. Outflows play a key role in the story of quasars and their host galaxies, by helping regulate the accretion process, the star-formation rate and mass of the host galaxy (i.e., feedback). The prescription for modeling outflows as a contributor to feedback requires knowledge of the outflow velocity, geometry, and column density. In particular, we need to understand how these depend on physical parameters and how much is determined stochastically (and with what distribution). For this purpose, we are examining a sample of 11000 z=1.7-2.0 quasars from the Sloan Digital Sky Survey. This redshift range permits the following from the SDSS spectra: (1) separation of objects that do and do not exhibit outflows; (2) classification/measurement of outflow properties (ionization, velocity, velocity width); and (3) measurements of UV emission line and continuum parameters. In this poster, we subjectively divide these quasars into four categories: broad absorption-line quasars (2700 objects), associated absorption-line quasars (1700 objects), reddened quasars (160 objects), and unabsorbed/unreddened quasars (6300 objects). We present measurements of the absorption (velocities, velocity widths, equivalent widths), composite spectral profiles of outflows as a function of velocity, as well as measurements of the continuum and CIV, MgII, and FeII emission-line properties. In accompanying posters, we add photometry from the rest-frame X-ray (ROSAT and Chandra), EUV (GALEX), optical (2MASS), and infrared (WISE) bands to complete the SED. The continuum and emission-line measurements from the SDSS spectra and accompanying photometry provides estimates on the black hole masses, bolometric luminsosities, and SED. We consider empirically how these affect the outflow properties. This material is based upon work supported by the National Aeronautics and Space Administration under

  3. A Constraint on Quasar Clustering at z = 5 from a Binary Quasar

    NASA Astrophysics Data System (ADS)

    McGreer, Ian D.; Eftekharzadeh, Sarah; Myers, Adam D.; Fan, Xiaohui

    2016-03-01

    We report the discovery of a quasar pair at z = 5 separated by 21″. Both objects were identified as quasar candidates using simple color selection techniques applied to photometric catalogs from the Canada-France-Hawaii Telescope (CFHT) Legacy Survey (CFHTLS). Spectra obtained with the MMT present no discernible offset in redshift between the two objects; on the other hand, there are clear differences in the emission line profiles and in the multiwavelength spectral energy distributions that strongly disfavor the hypothesis that they are gravitationally lensed images of a single quasar. Both quasars are surprisingly bright given their proximity (a projected separation of ˜135 kpc), with i = 19.4 and i = 21.4. Previous measurements of the luminosity function demonstrate that luminous quasars are extremely rare at z = 5 the existence of this pair suggests that quasars have strong small-scale clustering at high redshift. Assuming a real-space correlation function of the form ξ(r) ∝ (r/r0)-2, this discovery implies a correlation length of r0 ≳ 20h-1 Mpc, consistent with a rapid strengthening of quasar clustering at high redshift as seen in previous observations and predicted by theoretical models where feedback effects are inefficient at shutting down black hole growth at high redshift. Observations reported here were obtained at the MMT Observatory, a joint facility of the Smithsonian Institution and the University of Arizona.

  4. Negative Pressure Wound Therapy on Closed Surgical Wounds With Dead Space

    PubMed Central

    Suh, Hyunsuk; Lee, A-Young; Park, Eun Jung; Hong, Joon Pio

    2016-01-01

    Background Closed incisional wound surgery frequently leaves dead space under the repaired skin, which results in delayed healing. The purpose of this study was to evaluate the effect of negative pressure wound therapy (NPWT) on incisional wounds with dead space after primary closure by evaluating the fluid volume through the suction drain, blood flow of the skin, tensile strength, and histology of the wounds. Methods Bilateral 25-cm-long incisional wounds with dead space were created on the back of 6 pigs by partially removing the back muscle and then suturing the skin with nylon sutures. NPWT (experimental group) or gauze dressing (control group) was applied over the closed incision for 7 days. Analysis of the wound included monitoring the amount of closed suction drain, blood perfusion unit, tensile strength of the repaired skin, and histology of the incision site. Results The drainage amount was significantly reduced in the experimental group (49.8 mL) compared to the control group (86.2 mL) (P = 0.046). Skin perfusion was increased in the experimental group with statistical significance compared to the control group (P = 0.0175). Collagen staining was increased in the experimental group. The tensile strength of the incision site was significantly higher in the experimental group (24.6 N at 7 days, 61.67 N at 21 days) compared to the control group (18.26 N at 7 days, 50.05 N at 21 days) (P = 0.02). Conclusion This study explains some of the mechanism for using NPWT in closed incision wounds with dead space. It demonstrates that NPWT significantly reduces drainage amount, increases skin perfusion, increases tensile strength, and has the tendency to promote collagen synthesis for closed wound with dead space indicating enhanced healing. PMID:25003432

  5. Quantum field theory in spaces with closed time-like curves. [Gott space

    SciTech Connect

    Boulware, D.G.

    1992-01-01

    Gott spacetime has closed timelike curves, but no locally anomalous stress-energy. A complete orthonormal set of eigenfunctions of the wave operator is found in the special case of a spacetime in which the total deficit angle is 27[pi]. A scalar quantum field theory is constructed using these eigenfunctions. The resultant interacting quantum field theory is not unitary because the field operators can create real, on-shell, particles in the acausal region. These particles propagate for finite proper time accumulating an arbitrary phase before being annihilated at the same spacetime point as that at which they were created. As a result, the effective potential within the acausal region is complex, and probability is not conserved. The stress tensor of the scalar field is evaluated in the neighborhood of the Cauchy horizon; in the case of a sufficiently small Compton wavelength of the field, the stress tensor is regular and cannot prevent the formation of the Cauchy horizon.

  6. QUASARS PROBING QUASARS. VI. EXCESS H I ABSORPTION WITHIN ONE PROPER Mpc OF z ∼ 2 QUASARS

    SciTech Connect

    Prochaska, J. Xavier; Cantalupo, Sebastiano; Lau, Marie Wingyee; Bovy, Jo; Djorgovski, S. G.; Ellison, Sara L.; Martin, Crystal L.; Simcoe, Robert A.

    2013-10-20

    With close pairs of quasars at different redshifts, a background quasar sightline can be used to study a foreground quasar's environment in absorption. We use a sample of 650 projected quasar pairs to study the H I Lyα absorption transverse to luminous, z ∼ 2 quasars at proper separations of 30 kpc < R < 1 Mpc. In contrast to measurements along the line-of-sight, regions transverse to quasars exhibit enhanced H I Lyα absorption and a larger variance than the ambient intergalactic medium, with increasing absorption and variance toward smaller scales. Analysis of composite spectra reveals excess absorption characterized by a Lyα equivalent width profile W = 2.3 Å (R /100 kpc){sup –0.46}. We also observe a high (≅ 60%) covering factor of strong, optically thick H I absorbers (H I column N{sub H{sub I}}>10{sup 17.3} cm{sup -2}) at separations R < 200 kpc, which decreases to ∼20% at R ≅ 1 Mpc, but still represents a significant excess over the cosmic average. This excess of optically thick absorption can be described by a quasar-absorber cross-correlation function ξ{sub QA}(r) = (r/r{sub 0}){sup γ} with a large correlation length r{sub 0} = 12.5{sup +2.7}{sub -1.4} h{sup -1} Mpc (comoving) and γ=1.68{sup +0.14}{sub -0.30}. The H I absorption measured around quasars exceeds that of any previously studied population, consistent with quasars being hosted by massive dark matter halos M{sub halo} ≈ 10{sup 12.5} M{sub ☉} at z ∼ 2.5. The environments of these massive halos are highly biased toward producing optically thick gas, and may even dominate the cosmic abundance of Lyman limit systems and hence the intergalactic opacity to ionizing photons at z ∼ 2.5. The anisotropic absorption around quasars implies the transverse direction is much less likely to be illuminated by ionizing radiation than the line-of-sight.

  7. The Combination Application of Space Filling and Closed Irrigation Suction in Reconstruction of Sacral Decubitus Ulcer

    PubMed Central

    Weizhong, Liang; Zuojun, Zhao; Junling, Wu; Hongmei, Ai

    2014-01-01

    Dead space and poor drainage are the main reasons for intractable sacral decubitus ulcers. The objective of this study was to investigate the effects of treatment for sacral decubitus ulcer using space filling through muscle flap and closed irrigation. A total of 22 patients with serious sacral decubitus ulcer were treated with space filling through muscle flap and closed irrigation. After debridement of the decubitus ulcer, the infected areas over the bony prominence and osseous prominences were debrided. We elevated biceps femoris long head or semitendinosus and semimembranosus muscle. Pedicled by proximal part of muscle, the muscle flap was elevated to cover the ischial tuberosity. Transfusion systems of inflow and outflow drainage were placed between the muscle flap and ischial tuberosity. Wound healing and complications were observed. One wound dehiscence healed after secondary suturing. One wound gradually healed by dressing change after 3 weeks. The other cases had good results. Space filling and closed irrigation were complementary. The use of these two methods simultaneously is useful for the management of sacral decubitus ulcers. PMID:25216432

  8. THE EXTREME ULTRAVIOLET DEFICIT AND MAGNETICALLY ARRESTED ACCRETION IN RADIO-LOUD QUASARS

    SciTech Connect

    Punsly, Brian

    2014-12-20

    The Hubble Space Telescope composite quasar spectra presented in Telfer et al. show a significant deficit of emission in the extreme ultraviolet for the radio-loud component of the quasar population (RLQs) compared to the radio-quiet component of the quasar population. The composite quasar continuum emission between 1100 Å and ∼580 Å is generally considered to be associated with the innermost regions of the accretion flow onto the central black hole. The deficit between 1100 Å and 580 Å in RLQs has a straightforward interpretation as a missing or a suppressed innermost region of local energy dissipation in the accretion flow. It is proposed that this can be the result of islands of large-scale magnetic flux in RLQs that are located close to the central black hole that remove energy from the accretion flow as Poynting flux (sometimes called magnetically arrested accretion). These magnetic islands are natural sites for launching relativistic jets. Based on the Telfer et al. data and the numerical simulations of accretion flows in Penna et al., the magnetic islands are concentrated between the event horizon and an outer boundary of <2.8 M (in geometrized units) for rapidly rotating black holes and <5.5 M for modestly rotating black holes.

  9. Embedded coupled microrings with high-finesse and close-spaced resonances for optical signal processing.

    PubMed

    Souza, Mario C M M; Barea, Luis A M; Vallini, Felipe; Rezende, Guilherme F M; Wiederhecker, Gustavo S; Frateschi, Newton C

    2014-05-01

    Single microring resonators have been used in applications such as wavelength multicasting and microwave photonics, but the dependence of the free spectral range with ring radius imposes a trade-off between the required GHz optical channel spacing, footprint and power consumption. We demonstrate four-channel all-optical wavelength multicasting using only 1 mW of control power, with converted channel spacing of 40-60 GHz. Our device is based on a compact embedded microring design fabricated on a scalable SOI platform. The coexistence of close resonance spacing and high finesse (205) in a compact footprint is possible due to enhanced quality factors (30,000) resulting from the embedded configuration and the coupling-strength dependence of resonance spacing, instead of ring size. In addition, we discuss the possibility of achieving continuously mode splitting from a single-notch resonance up to 40 GHz. PMID:24921744

  10. Properties of closely spaced independently addressable lasers fabricated by impurity-induced disordering

    SciTech Connect

    Thornton, R.L.; Mosby, W.J.; Donaldson, R.M.; Paoli, T.L. )

    1990-04-23

    We describe the fabrication and characteristics of closely spaced (10 {mu}m) dual-beam laser sources by the process of impurity-induced disordering. We present data demonstrating that these devices are capable of high efficiency and reliable operation when operated in a {ital p}-side up configuration. We also show that these devices can be placed in close proximity with a minimal amount of thermal and electrical interaction between devices. These features have significant implications for the realization of high-density arrays of independently addressable lasers for optical interconnection of integrated circuits and optical imaging systems.

  11. PHOTOMETRIC OBSERVATIONS OF SELECTED, OPTICALLY BRIGHT QUASARS FOR SPACE INTERFEROMETRY MISSION AND OTHER FUTURE CELESTIAL REFERENCE FRAMES

    SciTech Connect

    Ojha, Roopesh E-mail: nz@usno.navy.mil E-mail: rgaume@usno.navy.mil

    2009-09-15

    Photometric observations of 235 extragalactic objects that are potential targets for the Space Interferometry Mission (SIM) are presented. Mean B, V, R, I magnitudes at the 5% level are obtained at 1-4 epochs between 2005 and 2007 using the 1 m telescopes at Cerro Tololo Inter-American Observatory and the Naval Observatory Flagstaff Station. Of the 134 sources that have V magnitudes in the Veron and Veron-Cetty catalog, a difference of over 1.0 mag is found for the observed-catalog magnitudes for about 36% of the common sources, and 10 sources show over 3 mag difference. Our first set of observations presented here form the basis of a long-term photometric variability study of the selected reference frame sources to assist in mission target selection and to support QSO multicolor photometric variability studies in general.

  12. Wake Encounter Analysis for a Closely Spaced Parallel Runway Paired Approach Simulation

    NASA Technical Reports Server (NTRS)

    Mckissick,Burnell T.; Rico-Cusi, Fernando J.; Murdoch, Jennifer; Oseguera-Lohr, Rosa M.; Stough, Harry P, III; O'Connor, Cornelius J.; Syed, Hazari I.

    2009-01-01

    A Monte Carlo simulation of simultaneous approaches performed by two transport category aircraft from the final approach fix to a pair of closely spaced parallel runways was conducted to explore the aft boundary of the safe zone in which separation assurance and wake avoidance are provided. The simulation included variations in runway centerline separation, initial longitudinal spacing of the aircraft, crosswind speed, and aircraft speed during the approach. The data from the simulation showed that the majority of the wake encounters occurred near or over the runway and the aft boundaries of the safe zones were identified for all simulation conditions.

  13. THE HISTORY AND ENVIRONMENT OF A FADED QUASAR: HUBBLE SPACE TELESCOPE OBSERVATIONS OF HANNY'S VOORWERP AND IC 2497

    SciTech Connect

    Keel, William C.; Manning, Anna; Lintott, Chris J.; Schawinski, Kevin; Bennert, Vardha N.; Thomas, Daniel; Chojnowski, S. Drew; Van Arkel, Hanny; Lynn, Stuart

    2012-08-15

    We present Hubble Space Telescope imaging and spectroscopy, along with supporting Galaxy Evolution Explorer and ground-based data, for the extended high-ionization cloud known as Hanny's Voorwerp, near the spiral galaxy IC 2497. Wide Field Camera 3 images show complex dust absorption near the nucleus of IC 2497. The galaxy core in these data is, within the errors, coincident with the very long baseline interferometry core component marking the active nucleus. Space Telescope Imaging Spectrograph (STIS) optical spectra show the active galactic nucleus (AGN) to be a type 2 Seyfert galaxy of rather low luminosity. The derived ionization parameter log U = -3.5 is in accordance with the weak X-ray emission from the AGN. We find no high-ionization gas near the nucleus, adding to the evidence that the AGN is currently at a low radiative output (perhaps with the central black hole having switched to a mode dominated by kinetic energy). The nucleus is accompanied by an expanding ring of ionized gas Almost-Equal-To 500 pc in projected diameter on the side opposite Hanny's Voorwerp. Where sampled by the STIS slit, this ring has Doppler offset Almost-Equal-To 300 km s{sup -1} from the nucleus, implying a kinematic age <7 Multiplication-Sign 10{sup 5} years. Narrowband [O III] and H{alpha}+[N II] Advanced Camera for Surveys images show fine structure in Hanny's Voorwerp, including limb-brightened sections suggesting modest interaction with a galactic outflow and small areas where H{alpha} is strong. We identify these latter regions as regions ionized by recent star formation, in contrast to the AGN ionization of the entire cloud. These candidate 'normal' H II regions contain blue continuum objects, whose colors are consistent with young stellar populations; they appear only in a 2 kpc region toward IC 2497 in projection, perhaps meaning that the star formation was triggered by compression from a narrow outflow. The ionization-sensitive ratio [O III]/H{alpha} shows broad bands

  14. A Sample of Quasars with Strong Nitrogen Emission Lines from the Sloan Digital Sky Survey

    NASA Astrophysics Data System (ADS)

    Jiang, Linhua; Fan, Xiaohui; Vestergaard, M.

    2008-06-01

    We report on 293 quasars with strong N IV] λ1486 or N III] λ1750 emission lines (rest-frame equivalent width >3 Å) at 1.7 < z < 4.0 selected from the Sloan Digital Sky Survey (SDSS) Fifth Data Release. These nitrogen-rich (N-rich) objects comprise ~1.1% of the SDSS quasars. The comparison between the N-rich quasars and other quasars shows that the two quasar subsets share many common properties. We also confirm previous results that N-rich quasars have much stronger Lyα and N V λ1240 emission lines. Strong nitrogen emission in all ionization states indicates high overall nitrogen abundances in these objects. We find evidence that the nitrogen abundance is closely related to quasar radio properties. The radio-loud fraction in the N III]-rich quasars is 26% and in the N IV]-rich quasars is 69%, significantly higher than ~8% measured in other quasars with similar redshift and luminosity. Therefore, the high nitrogen abundance in N-rich quasars could be an indicator of a special quasar evolution stage, in which the radio activity is also strong.

  15. BINARY QUASARS AT HIGH REDSHIFT. I. 24 NEW QUASAR PAIRS AT z {approx} 3-4

    SciTech Connect

    Hennawi, Joseph F.; Myers, Adam D.; Shen, Yue; Strauss, Michael A.; Djorgovski, S. G.; Glikman, Eilat; Mahabal, Ashish; Fan Xiaohui; Martin, Crystal L.; Richards, Gordon T.; Schneider, Donald P.; Shankar, Francesco

    2010-08-20

    The clustering of quasars on small scales yields fundamental constraints on models of quasar evolution and the buildup of supermassive black holes. This paper describes the first systematic survey to discover high-redshift binary quasars. Using color-selection and photometric redshift techniques, we searched 8142 deg{sup 2} of Sloan Digital Sky Survey imaging data for binary quasar candidates, and confirmed them with follow-up spectroscopy. Our sample of 27 high-redshift binaries (24 of them new discoveries) at redshifts 2.9 < z < 4.3 with proper transverse separations 10 kpc < R{sub perpendicular} < 650 kpc increases the number of such objects known by an order of magnitude. Eight members of this sample are very close pairs with R{sub perpendicular} < 100 kpc, and of these close systems four are at z>3.5. The completeness and efficiency of our well-defined selection algorithm are quantified using simulated photometry and we find that our sample is {approx}50% complete. Our companion paper uses this knowledge to make the first measurement of the small-scale clustering (R < 1 h {sup -1} Mpc comoving) of high-redshift quasars. High-redshift binaries constitute exponentially rare coincidences of two extreme (M {approx}> 10{sup 9} M {sub sun}) supermassive black holes. At z {approx} 4, there is about one close binary per 10 Gpc{sup 3}, thus these could be the highest sigma peaks, the analogs of superclusters, in the early universe.

  16. Causes and effects of the first quasars.

    PubMed Central

    Rees, M J

    1993-01-01

    The light we observe from the most distant known quasars set out when the Universe was about 200 times denser than it is now and less than one-tenth of its present age. The existence of these objects implies that galaxy formation had already, at that early epoch, proceeded to the stage when massive (>10(8)M[symbol, see text]) objects had accumulated in the centers of at least some young galaxies. A specific model is presented to show that the evolution and luminosity function of quasars are compatible with the cold dark matter cosmogony. Most big galaxies probably passed through a quasar phase; the remnant black holes in nearby galaxies may reveal themselves via the flares that occur whenever a star passes too close to them and gets tidally disrupted. The rich absorption spectra of quasars serve as a probe of the intervening medium. The gas responsible for the Lyman alpha absorption lines may be due to primordial gas gravitationally confined in minihalos of dark matter--shallow potential wells whose evolution and relation to dwarf galaxies are briefly discussed. The patchy heat input into the intergalactic medium from early quasars could modulate the environment in which galaxies form, leading to large-scale spatial correlations in the galaxy distribution. This review concludes with general comments on the prospects for a fully quantitative understanding of galaxy formation. PMID:11607397

  17. Leveraging Spitzer's Legacy: Quasars and Feedback at High Redshift

    NASA Astrophysics Data System (ADS)

    Richards, Gordon; Anderson, Scott; Bauer, Franz; Deo, Rajesh; Fan, Xiaohui; Gallagher, Sarah; Myers, Adam; Strauss, Michael; Zakamska, Nadia

    2009-04-01

    Recent research efforts to understand the evolution of galaxies and quasars are beginning to form a consistent picture. Galaxies and their supermassive black holes grow through mergers, but with decreasing characteristic mass scales over time. Much less, however, is known about the evolution of galaxies at high redshifts and the role played by energy injection from the onset of active black hole growth. Understanding these events requires investigating a statistically significant number of high-redshift quasars and crossing the L* boundary in luminosity. To construct an appropriate data set requires both relatively wide-areas (to find these rare objects) and moderate-depth imaging (to probe below L* in luminosity). Unfortunately, existing optical and MIR surveys fail to meet both of these requirements. Furthermore, both optical and MIR quasar selection are blindest at the most crucial redshifts. Here we propose to address these gaps with targeted IRAC observations of a few hundred high-redshift quasars from the Sloan Digital Sky Survey. Such a sample will enable the construction of a proper training set for the discovery of 2.5quasars through combined optical+MIR (from IRAC channels 1 and 2) selection methods that overcome the limitations inherent to optical and MIR selection alone. By concentrating on SDSS Stripe 82, with sensitivity of i~23, we will learn how to identify high-redshift quasars in other fields over a large range in luminosity. With this knowledge, we will crack open the high-z quasar discovery space within existing IRAC legacy surveys (SWIRE, XFLS, Bootes, COSMOS). With a large sample of high-redshift quasars spanning a large range in luminosity, we can turn the quasar luminosity function and quasar clustering analysis into tools for distinguishing between different evolutionary models and feedback prescriptions. In all, we will observe 330 SDSS quasars using 307 pointings/AORs, totaling 48.5 hours of IRAC time.

  18. Giant scattering cones in obscured quasars

    NASA Astrophysics Data System (ADS)

    Obied, Georges; Zakamska, Nadia L.; Wylezalek, Dominika; Liu, Guilin

    2016-03-01

    We analyse Hubble Space Telescope observations of scattering regions in 20 luminous obscured quasars at 0.24 < z < 0.65 (11 new observations and nine archival ones) observed at rest frame ˜3000 Å. We find spectacular 5-10 kpc-scale scattering regions in almost all cases. The median scattering efficiency at this wavelength (the ratio of observed to estimated intrinsic flux) is 2.3, and 73 per cent of the observed flux at this wavelength is due to scattered light, which if unaccounted for may strongly bias estimates of quasar hosts' star formation rates. Modelling these regions as illuminated dusty cones, we estimate the radial density distributions of the interstellar medium as well as the geometric properties of circumnuclear quasar obscuration - inclinations and covering factors. Small derived opening angles (median half-angle and standard deviation 27° ± 9°) are inconsistent with a 1:1 type 1/type 2 ratio. We suggest that quasar obscuration is patchy and that the observer has an ˜40 per cent chance of seeing a type 1 source even through the obscuration. We estimate median density profile of the scattering medium to be nH = 0.04-0.5 (1 kpc/r)2 cm-3, depending on the method. Quasars in our sample likely exhibit galaxy-wide winds, but if these consist of optically thick clouds then only a small fraction of the wind mass ( ≲ 10 per cent) contributes to scattering.

  19. The Significant Incidents and Close Calls in Human Space Flight Chart: Lessons Learned Gone Viral

    NASA Technical Reports Server (NTRS)

    Wood, Bill; Pate, Dennis; Thelen, David

    2010-01-01

    This presentation will explore the surprising history and events that transformed a mundane spreadsheet of historical spaceflight incidents into a popular and widely distributed visual compendium of lessons learned. The Significant Incidents and Close Calls in Human Space Flight Chart (a.k.a. The Significant Incidents Chart) is a popular and visually captivating reference product that has arisen from the work of the Johnson Space Center (JSC) Safety and Mission Assurance (S&MA) Flight Safety Office (FSO). It began as an internal tool intended to increase our team s awareness of historical and modern space flight incidents. Today, the chart is widely recognized across the agency as a reference tool. It appears in several training and education programs. It is used in familiarization training in the JSC Building 9 Mockup Facility and is seen by hundreds of center visitors each week. The chart visually summarizes injuries, fatalities, and close calls sustained during the continuing development of human space flight. The poster-sized chart displays over 100 total events that have direct connections to human space flight endeavors. The chart is updated periodically. The update process itself has become a collaborative effort. Many people, spanning multiple NASA organizations, have provided suggestions for additional entries. The FSO maintains a growing list of subscribers who have requested to receive updates. The presenters will discuss the origins and motivations behind the significant incidents chart. A review of the inclusion criteria used to select events will be offered. We will address how the chart is used today by S&MA and offer a vision of how it might be used by other organizations now and in the future. Particular emphasis will be placed on features of the chart that have met with broad acceptance and have helped spread awareness of the most important lessons in human spaceflight.

  20. Observed Quasar Structure

    NASA Astrophysics Data System (ADS)

    Schild, Rudolph E.

    2011-05-01

    With the introduction of microlensing (nano-lensing) and reverberation analysis, understanding of the luminous structure surrounding quasars has gone from theoretical speculation to an observer's sport. Micro-lensing with day timescale has demonstrated that quasars have structure on scales of 1 R_G which we attribute to the inner edge of the accretion disc, at central distance 70 R_G in lo-hard state (radio loud) Q0957 quasar, indicated by reverberation. Reverberation of the dominant optical continuum has been detected in all 55 hi-soft quasars with brightness data, originating in the dusty torus observed in UV-optical and IR reverberation. Microlensing simulation compared to brightness monitoring shows that 2/3 of the UV-optical continuum originates in the outer torus. The observed color effects observed in the microlensing support the existence of inner and outer luminous structure.

  1. High Redshift Quasars

    NASA Technical Reports Server (NTRS)

    Elvis, Martin S.

    1996-01-01

    The report for this period includes three papers: 'Associated Absorption at Low and High Redshift'; 'Strong X-ray Absorption in a Broad Absorption Line Quasar: PHL5200'; and 'ASCA and ROSAT X-ray Spectra of High-Redshift Radio-Loud Quasars'. The first gives examples from both low and high redshift for combining information on absorbing material in active galactic nuclei from both x-ray and the UV. The second presents ASCA observations of the z = 1.98 prototype broad absorption line quasar (BALQSO): PHL 5200, detected with both the solid-state imaging spectrometers and the gas imaging spectometers. The third paper presents results on the x-ray properties of 9 high-redshift radio-loud quasars observed by ASCA and ROSAT, including ASCA observations of S5 0014+81 (z = 3.38) and S5 0836+71 (z = 2.17) and ROSAT observations of PKS 2126-158.

  2. Finding Quasars with SNAP

    NASA Astrophysics Data System (ADS)

    Brondel, B. J.; Mufson, S. L.

    2005-12-01

    The Supernova / Acceleration Probe (SNAP) is a planned satellite observatory that will investigate the dark energy by producing imaging data over a large (several square-degree) field of sky that will rival or exceed the Hubble Ultra Deep Field in photometric quality and depth. As such, SNAP is ideally suited for deep surveys as auxiliary science. We discuss application of quasar science techniques to SNAP photometry. Based on a simple photometric quasar / Lyman forest model, we simulate the population of quasars that SNAP will observe and compare the resulting photometry with a population of model stellar photometry. We examine the effectiveness of identifying quasars based only on photometric data by a variety of techniques, most of which were first developed for use with Sloan Digital Sky Survey. Exclusion of the stellar locus in the style of Newberg & Yanni, statistical mapping, and machine learning with neural networks are among the techniques we explore. A photometric redshift calculus is also presented.

  3. Quasars: A Progress Report.

    ERIC Educational Resources Information Center

    Weedman, Daniel

    1988-01-01

    Reports on some of the discoveries over the last quarter century regarding quasars including spectra and energy sources, formation and evolution, and cosmological probes. Describes some of the fundamental mysteries that remain. (CW)

  4. Aeroelastic dynamics of mistuned blade assemblies with closely spaced blade modes

    NASA Technical Reports Server (NTRS)

    Pierre, Christophe; Murthy, Durbha V.

    1993-01-01

    The aeroelastic characteristics of tuned and randomly mistuned blade assemblies which possess two blade-alone natural modes with close frequencies are studied. Modal interactions among the two blade modes are shown to be come extremely significant for small frequency separation. The two distinct loci of the aeroelastic eigenvalues, which characterize an assembly with well separated modes, fully merge into a single root locus as the blade-mode frequency separation vanishes. Also, while in the case of well separated blade modes the introduction of random mistuning into one blade mode affects only the assembly modes which are predominantly of that blade-mode type, mistuning results in the localization of all the assembly modes when the blade-alone natural frequencies are close. Results indicate that in the case of closely-spaced blade modes a single-degree of freedom blade model yields qualitatively erroneous results and that an N-blade assembly with two close blade modes behaves like an equivalent 2Nb-blade assembly with a single blade mode.

  5. Closed Cycle Magnetohydrodynamic Nuclear Space Power Generation Using Helium/Xenon Working Plasma

    NASA Technical Reports Server (NTRS)

    Litchford, R. J.; Harada, N.

    2005-01-01

    A multimegawatt-class nuclear fission powered closed cycle magnetohydrodynamic space power plant using a helium/xenon working gas has been studied, to include a comprehensive system analysis. Total plant efficiency was expected to be 55.2 percent including pre-ionization power. The effects of compressor stage number, regenerator efficiency, and radiation cooler temperature on plant efficiency were investigated. The specific mass of the power generation plant was also examined. System specific mass was estimated to be 3 kg/kWe for a net electrical output power of 1 MWe, 2-3 kg/kWe at 2 MWe, and approx.2 kg/KWe at >3 MWe. Three phases of research and development plan were proposed: (1) Phase I-proof of principle, (2) Phase II-demonstration of power generation, and (3) Phase III-prototypical closed loop test.

  6. Close-spaced vapor transport and photoelectrochemistry of gallium arsenide for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Ritenour, Andrew J.

    The high balance-of-system costs of photovoltaic installations indicate that reductions in absorber cost alone are likely insufficient for photovoltaic electricity to reach grid parity unless energy conversion efficiency is also increased. Technologies which both yield high-efficiency cells (>25%) and maintain low costs are needed. GaAs and related III--V semiconductors are used in the highest-efficiency single- and multi-junction photovoltaics, but the technology is too expensive for non-concentrated terrestrial applications. This is due in part to the limited scalability of traditional syntheses, which rely on expensive reactors and employ toxic and pyrophoric gas-phase precursors such as arsine and trimethyl gallium. This work describes GaAs films made by close-spaced vapor transport, a potentially scalable technique which is carried out at atmospheric pressure and requires only bulk GaAs, water vapor, and a temperature gradient to deposit crystalline films with similar electronic properties to GaAs prepared using traditional syntheses. Although close-spaced vapor transport of GaAs was first developed in 1963, there were few examples of GaAs photovoltaic devices made using this method in the literature at the onset of this project. Furthermore, it was unclear whether close-spaced vapor transport could produce GaAs films appropriate for use in photovoltaics. The goal of this project was to create and study GaAs devices made using close-spaced vapor transport and determine whether the technique could be used for production of grid-connected GaAs photovoltaics. In Chapter I the design of the vapor transport reactor, the chemistry of crystal growth, and optoelectronic characterization techniques are discussed. Chapter II focuses on compositional measurements, doping, and improved electronic quality in CSVT GaAs. Chapter III describes several aspects of the interplay between structure and electronic properties of photoelectrochemical devices. Chapter IV addresses

  7. Induced Recrystallization of CdTe Thin Films Deposited by Close-Spaced Sublimation

    SciTech Connect

    Moutinho, H. R.; Dhere, R. G.; Al-Jassim, M. M.; Levi, D. H.; Kazmerski, L. L.; Mayo, B.

    1998-10-29

    We have deposited CdTe thin films by close-spaced sublimation at two different temperature ranges. The films deposited at the lower temperature partially recrystallized after CdCl{sub 2} treatment at 350 C and completely recrystallized after the same treatment at 400 C. The films deposited at higher temperature did not recrystallize at these two temperatures. These results confirmed that the mechanisms responsible for changes in physical properties of CdTe films treated with CdCl{sub 2} are recrystallization and grain growth, and provided an alternative method to deposit CSS films using lower temperatures.

  8. Induced Recrystallization of CdTe Thin Films Deposited by Close-Spaced Sublimation

    SciTech Connect

    Moutinho, H. R.; Dhere, R. G.; Al-Jassim, M. M.; Levi, D. H.; Kazmerski, L. L.; Mayo, B.

    1998-10-26

    We have deposited CdTe thin films by close-spaced sublimation at two different temperature ranges. The films deposited at the lower temperature partially recrystallized after CdCl2 treatment at 350 C and completely recrystallized after the same treatment at 400 C. The films deposited at higher temperature did not recrystallize at these two temperatures. These results confirmed that the mechanisms responsible for changes in physical properties of CdTe films treated with CdCl2 are recrystallization and grain growth, and provided an alternative method to deposit CSS films using lower temperatures.

  9. Issues in Airborne Systems for Closely-Spaced Parallel Runway Operations

    NASA Technical Reports Server (NTRS)

    Pritchett, A.; Carpenter, B.; Asari, K.; Kuchar, J.; Hansman, R. J.

    1995-01-01

    Efforts to increase airport capacity include studies of aircraft systems that would enable simultaneous approaches to closely spaced parallel runways in Instrument Meteorological Conditions (IMC). The time-critical nature of a parallel approach results in key design issues for current and future collision avoidance systems. These issues are being studied in two ways. First, a part-task flight simulator study has examined the procedural and display issues inherent in such a time-critical task. Second, a prototype collision avoidance logic capable of generating this maneuver guidance has been designed using a recently developed methodology.

  10. Time-resolved photoluminescence of polycrystalline CdTe grown by close-spaced sublimation

    SciTech Connect

    Keyes, B.; Dhere, R.; Ramanathan, K. )

    1994-06-30

    Polycrystalline CdTe has shown great promise as a low-cost material for thin-film, terrestrial photovoltaic applications, with efficiencies approaching 16% achieved with close-spaced sublimation (CSS)-grown CdTe. Due to the inherent complexities of polycrystalline material, much of the progress in this area has occurred through a slow trial-and-error process. This report uses time-resolved photoluminescence (TRPL) to characterize the CdTe material quality as a function of one basic growth parameter---substrate temperature. This characterization is done for two different glass substrate materials, soda-lime silicate and borosilicate.

  11. Evaluating Nextgen Closely Spaced Parallel Operations Concepts with Validated Human Performance Models: Flight Deck Guidelines

    NASA Technical Reports Server (NTRS)

    Hooey, Becky Lee; Gore, Brian Francis; Mahlstedt, Eric; Foyle, David C.

    2013-01-01

    The objectives of the current research were to develop valid human performance models (HPMs) of approach and land operations; use these models to evaluate the impact of NextGen Closely Spaced Parallel Operations (CSPO) on pilot performance; and draw conclusions regarding flight deck display design and pilot-ATC roles and responsibilities for NextGen CSPO concepts. This document presents guidelines and implications for flight deck display designs and candidate roles and responsibilities. A companion document (Gore, Hooey, Mahlstedt, & Foyle, 2013) provides complete scenario descriptions and results including predictions of pilot workload, visual attention and time to detect off-nominal events.

  12. Experimental Studies Of Pilot Performance At Collision Avoidance During Closely Spaced Parallel Approaches

    NASA Technical Reports Server (NTRS)

    Pritchett, Amy R.; Hansman, R. John

    1997-01-01

    Efforts to increase airport capacity include studies of aircraft systems that would enable simultaneous approaches to closely spaced parallel runway in Instrument Meteorological Conditions (IMC). The time-critical nature of a parallel approach results in key design issues for current and future collision avoidance systems. Two part-task flight simulator studies have examined the procedural and display issues inherent in such a time-critical task, the interaction of the pilot with a collision avoidance system, and the alerting criteria and avoidance maneuvers preferred by subjects.

  13. Carbon-Carbon Recuperators in Closed-Brayton-Cycle Nuclear Space Power Systems: A Feasibility Assessment

    NASA Technical Reports Server (NTRS)

    Barrett, Michael J.; Johnson, Paul K.

    2004-01-01

    The feasibility of using carbon-carbon recuperators in closed-Brayton-cycle (CBC) nuclear space power conversion systems (PCS) was assessed. Recuperator performance expectations were forecast based on projected thermodynamic cycle state values for a planetary mission. Resulting thermal performance, mass and volume for a plate-fin carbon-carbon recuperator were estimated and quantitatively compared with values for a conventional offset-strip-fin metallic design. Material compatibility issues regarding carbon-carbon surfaces exposed to the working fluid in the CBC PCS were also discussed.

  14. Quasar counts from variability and color selected samples

    NASA Astrophysics Data System (ADS)

    Andrews, Peter Arthur

    Quasars are among the brightest and most distant objects known, making them intrinsically interesting as well as ideal probes of the history of the universe. Over 23,000 quasars have been found since their discovery four decades ago, but most were identified by various redshift-limited ultraviolet excess methods which excluded extended sources. This prohibits the use of the global quasar sample in a statistical manner for quasar lensing studies. To improve on this situation, the QUEST survey was born, with the goal of finding large numbers of quasars and gravitational lenses using a uniform selection method for cosmology studies. To date, we have completed three years of driftscan imaging observations using the QUEST 16 CCD camera on the 1m Schmidt telescope at Llano del Hato in Venezuela. Presented here are descriptions of the equipment, data, software and selection methods used, our discovered quasar candidates, a list of confirmed quasars, measured quasar surface densities and comparisons with published results. Ten nights of UBUV filter data covering 155 square degrees are analyzed using the traditional UV-excess color-selection method to find low-redshift quasars. From the candidates where we obtained spectroscopy, we measured a low-redshift quasar surface density of 5 +/- 1 per square degree to a B magnitude limit of 19.4. Twenty-five nights of RBRV data taken over three years and covering 250 square degrees are analyzed to find quasars by their variability. To our knowledge the variability portion of our survey is the largest of its kind, using over a dozen nights fully covering most of the huge survey area. Because variability can be used to find quasars uniformly over all redshifts and extended or close groupings of objects are properly treated by our survey, the results here may be less biased with respect to lensed quasars than other selection methods. From the variability candidates where we obtained spectroscopy, we measured a quasar surface density of

  15. Visualizing plasmon coupling in closely spaced chains of Ag nanoparticles by electron energy-loss spectroscopy.

    PubMed

    Song, Fengqi; Wang, Tingyu; Wang, Xuefeng; Xu, Changhui; He, Longbing; Wan, Jianguo; Van Haesendonck, Christian; Ringer, Simon P; Han, Min; Liu, Zongwen; Wang, Guanghou

    2010-02-01

    Anisotropic plasmon coupling in closely spaced chains of Ag nanoparticles is visualized using electron energy-loss spectroscopy in a scanning transmission electron microscope. For dimers as the simplest chain, mapping the plasmon excitations with nanometer spatial resolution and an energy resolution of 0.27 eV intuitively identifies two coupling plasmons. The in-phase mode redshifts from the ultraviolet region as the interparticle spacing is reduced, reaching the visible range at 2.7 eV. Calculations based on the discrete-dipole approximation confirm its optical activeness, where the longitudinal direction is constructed as the path for light transportation. Two coupling paths are then observed in an inflexed four-particle chain. PMID:20077517

  16. Optimizing surface-enhanced Raman scattering by template guided assembling of closely spaced silver nanocluster arrays

    NASA Astrophysics Data System (ADS)

    Xu, C. H.; Xie, B.; Liu, Y. J.; He, L. B.; Han, M.

    2009-04-01

    We present an easy approach to synthesize closely spaced regular arrays of silver nanoclusters, which are self-assembled by depositing gas-phase synthesized metal nanoclusters onto pre-patterned triblock copolymer templates. The array has a high particle density of about 2 ×103 particles per μm2, and an average interparticle space of about 20 nm. The surface plasmon resonance wavelength of the array is tuned due to the interparticle plasmon coupling. High SERS sensitivity for less than one layer trans-1,2-bi-(4-pyridyl) ethylene (BPE) molecule detection, with an enhancement factor of 2.6 ×106, has been demonstrated for a substrate with this array. The enhanced Raman signal was found to be 5 times higher than that measured from the substrate with randomly distributed silver nanoparticles.

  17. Advances in defining a closed Brayton conversion system for future ARIANE 5 space nuclear power applications

    SciTech Connect

    Tilliette, Z.P.

    1987-01-01

    The present European ARIANE space program will expand into the large ARIANE 5 launch vehicle from 1995. It is assumed that important associated missions would require the generation of 200 kWe or more in space during several years at the very beginning of the next century. For this reason, in 1983, the French C.N.E.S. (Centre National d'Etudes Spatiales) and C.E.A. (Commissariat a l'Energie Atomique) have initiated preliminary studies of a space nuclear power system. The currently selected conversion system is a closed Brayton cycle. Reasons for this choice are given: high efficiency of a dynamic system; monophasic, inert working fluid; extensive turbomachinery experience, etc. A key aspect of the project is the adaptation to heat rejection conditions, namely to the radiator geometry which depends upon the dimensions of the ARIANE 5 spacecraft. In addition to usual concepts already studied for space applications, another cycle arrangement is being investigated which could offer satisfactory compromises among many considerations, increase the efficiency of the system, and make it more attractive as far as the specific mass (kg/lWe), the specific radiator area (m/sup 2//kWe), and various technological aspects are concerned. Comparative details are presented.

  18. OBSCURATION BY GAS AND DUST IN LUMINOUS QUASARS

    SciTech Connect

    Usman, S. M.; Murray, S. S.; Hickox, R. C.; Brodwin, M.

    2014-06-10

    We explore the connection between absorption by neutral gas and extinction by dust in mid-infrared (IR) selected luminous quasars. We use a sample of 33 quasars at redshifts 0.7 < z ≲ 3 in the 9 deg{sup 2} Boötes multiwavelength survey field that are selected using Spitzer Space Telescope Infrared Array Camera colors and are well-detected as luminous X-ray sources (with >150 counts) in Chandra observations. We divide the quasars into dust-obscured and unobscured samples based on their optical to mid-IR color, and measure the neutral hydrogen column density N {sub H} through fitting of the X-ray spectra. We find that all subsets of quasars have consistent power law photon indices Γ ≈ 1.9 that are uncorrelated with N {sub H}. We classify the quasars as gas-absorbed or gas-unabsorbed if N {sub H} > 10{sup 22} cm{sup –2} or N {sub H} < 10{sup 22} cm{sup –2}, respectively. Of 24 dust-unobscured quasars in the sample, only one shows clear evidence for significant intrinsic N {sub H}, while 22 have column densities consistent with N {sub H} < 10{sup 22} cm{sup –2}. In contrast, of the nine dust-obscured quasars, six show evidence for intrinsic gas absorption, and three are consistent with N {sub H} < 10{sup 22} cm{sup –2}. We conclude that dust extinction in IR-selected quasars is strongly correlated with significant gas absorption as determined through X-ray spectral fitting. These results suggest that obscuring gas and dust in quasars are generally co-spatial, and confirm the reliability of simple mid-IR and optical photometric techniques for separating quasars based on obscuration.

  19. Synthesis of Ga 2O 3 chains with closely spaced knots connected by nanowires

    NASA Astrophysics Data System (ADS)

    Dai, L.; You, L. P.; Duan, X. F.; Lian, W. C.; Qin, G. G.

    2004-07-01

    Chains of closely spaced metal or semiconductor particles have potential applications in optoelectronics and single electron devices. We report, for the first time, the synthesis of Ga 2O 3 chains with closely spaced knots connected by nanowires using the thermal evaporation method with a specially designed quartz boat. The Ga 2O 3 chains grew only on the Si substrates where Au catalyst or Ga droplets were coated. The average diameter of the knots is about 450 nm and that of the nanowires is about 50 nm. The selected area electron diffraction of either a knot or a connecting nanowire includes two sets of overlapped single crystal electron diffraction patterns which belong to the [1 0 2] and [1 0 1¯] crystal zone axes of the monoclinic β-Ga 2O 3 phase, respectively. The knot and its neighbor nanowire have the common ( 2¯ 0 1) growth planes at their interface. A mechanism model for the Ga 2O 3 chains synthesis based on the vapor-liquid-solid mechanism is discussed.

  20. Multiport well design for sampling of ground water at closely spaced vertical intervals

    SciTech Connect

    Delin, G.N.; Landon, M.K.

    1996-11-01

    Detailed vertical sampling is useful in aquifers where vertical mixing is limited and steep vertical gradients in chemical concentrations are expected. Samples can be collected at closely spaced vertical intervals from nested wells with short screened intervals. However, this approach may not be appropriate in all situations. An easy-to-construct and easy-to-install multiport sampling well to collect ground-water samples from closely spaced vertical intervals was developed and tested. The multiport sampling well was designed to sample ground water from surficial sand-and-gravel aquifers. The device consists of multiple stainless-steel tubes within a polyvinyl chloride (PVC) protective casing. The tubes protrude through the wall of the PVC casing at the desired sampling depths. A peristaltic pump is used to collect ground-water samples form the sampling ports. The difference in hydraulic head between any two sampling ports can be measured with a vacuum pump and a modified manometer. The usefulness and versatility of this multiport well design was demonstrated at an agricultural research site near Princeton, Minnesota where sampling ports were installed to a maximum depth of about 12 m below land surface. Trace experiments were conducted using potassium bromide to document the degree to which short-circuiting occurred between sampling ports. Samples were successfully collected for analysis of major cations and anions, nutrients, selected herbicides, isotopes, dissolved gases, and chlorofluorocarbon concentrations.

  1. Multiport well design for sampling of ground water at closely spaced vertical intervals

    USGS Publications Warehouse

    Delin, G.N.; Landon, M.K.

    1996-01-01

    Detailed vertical sampling is useful in aquifers where vertical mixing is limited and steep vertical gradients in chemical concentrations are expected. Samples can be collected at closely spaced vertical intervals from nested wells with short screened intervals. However, this approach may not be appropriate in all situations. An easy-to-construct and easy-to-install multiport sampling well to collect ground-water samples from closely spaced vertical intervals was developed and tested. The multiport sampling well was designed to sample ground water from surficial sand-and-gravel aquifers. The device consists of multiple stainless-steel tubes within a polyvinyl chloride (PVC) protective casing. The tubes protrude through the wall of the PVC casing at the desired sampling depths. A peristaltic pump is used to collect ground-water samples from the sampling ports. The difference in hydraulic head between any two sampling ports can be measured with a vacuum pump and a modified manometer. The usefulness and versatility of this multiport well design was demonstrated at an agricultural research site near Princeton, Minnesota where sampling ports were installed to a maximum depth of about 12 m below land surface. Tracer experiments were conducted using potassium bromide to document the degree to which short-circuiting occurred between sampling ports. Samples were successfully collected for analysis of major cations and anions, nutrients, selected herbicides, isotopes, dissolved gases, and chlorofluorcarbon concentrations.

  2. Detecting Space-Time Alternating Biological Signals Close to the Bifurcation Point

    PubMed Central

    Jia, Zhiheng; Bien, Harold; Entcheva, Emilia

    2011-01-01

    Time-alternating biological signals, i.e., alternans, arise in variety of physiological states marked by dynamic instabilities, e.g., period doubling. Normally, a sequence of large–small–large transients, they can exhibit variable patterns over time and space, including spatial discordance. Capture of the early formation of such alternating regions is challenging because of the spatiotemporal similarities between noise and the small-amplitude alternating signals close to the bifurcation point. We present a new approach for automatic detection of alternating signals in large noisy spatiotemporal datasets by exploiting quantitative measures of alternans evolution, e.g., temporal persistence, and by preserving phase information. The technique specifically targets low amplitude, relatively short alternating sequences and is validated by combinatorics-derived probabilities and empirical datasets with white noise. Using high-resolution optical mapping in live cardiomyocyte networks, exhibiting calcium alternans, we reveal for the first time early fine-scale alternans, close to the noise level, which are linked to the later formation of larger regions and evolution of spatially discordant alternans. This robust method aims at quantification and better understanding of the onset of cardiac arrhythmias and can be applied to general analysis of space-time alternating signals, including the vicinity of the bifurcation point. PMID:19695992

  3. CONSTRAINING SUB-PARSEC BINARY SUPERMASSIVE BLACK HOLES IN QUASARS WITH MULTI-EPOCH SPECTROSCOPY. I. THE GENERAL QUASAR POPULATION

    SciTech Connect

    Shen, Yue; Liu, Xin; Loeb, Abraham; Tremaine, Scott

    2013-09-20

    We perform a systematic search for sub-parsec binary supermassive black holes (BHs) in normal broad-line quasars at z < 0.8, using multi-epoch Sloan Digital Sky Survey (SDSS) spectroscopy of the broad Hβ line. Our working model is that (1) one and only one of the two BHs in the binary is active; (2) the active BH dynamically dominates its own broad-line region (BLR) in the binary system, so that the mean velocity of the BLR reflects the mean velocity of its host BH; (3) the inactive companion BH is orbiting at a distance of a few R{sub BLR}, where R{sub BLR} ∼ 0.01-0.1 pc is the BLR size. We search for the expected line-of-sight acceleration of the broad-line velocity from binary orbital motion by cross-correlating SDSS spectra from two epochs separated by up to several years in the quasar rest frame. Out of ∼700 pairs of spectra for which we have good measurements of the velocity shift between two epochs (1σ error ∼40 km s{sup –1}), we detect 28 systems with significant velocity shifts in broad Hβ, among which 7 are the best candidates for the hypothesized binaries, 4 are most likely due to broad-line variability in single BHs, and the rest are ambiguous. Continued spectroscopic observations of these candidates will easily strengthen or disprove these claims. We use the distribution of the observed accelerations (mostly non-detections) to place constraints on the abundance of such binary systems among the general quasar population. Excess variance in the velocity shift is inferred for observations separated by longer than 0.4 yr (quasar rest frame). Attributing all the excess to binary motion would imply that most of the quasars in this sample must be in binaries, that the inactive BH must be on average more massive than the active one, and that the binary separation is at most a few times the size of the BLR. However, if this excess variance is partly or largely due to long-term broad-line variability, the requirement of a large population of close

  4. High Velocity Outflows in Quasars

    NASA Astrophysics Data System (ADS)

    Hamann, Fred; Rodriguez Hidalgo, Paola; Nestor, Daniel

    2006-02-01

    High velocity (HV) outflows are important components of SMBH growth and evolution. The ability of SMBHs to accrete matter and light up as AGN probably requires that outflows are present to carry away angular momentum. Outflows during the luminous AGN phase might also play a critical role in ``unveiling" young dust-enshrouded AGN and in ``polluting" the intergalactic medium with metals at high redshifts. Nonetheless, AGN outflows remain poorly understood. We have begun a program to study a nearly unexplored realm of AGN outflow parameter space: HV winds with v> 10,000 km/s up to v~ 0.2c but small velocity dispersions (narrow absorption lines), such that v/(Delta) v ≫ 1. These extreme outflows have been detected so far in just a few quasars, but they might be ubiquitous if, as expected, the flows subtend a small solid angle as seen from the central engine. Narrow-line HV flows merit specific attention because they pose unique challenges for theoretical models of the wind acceleration, mass loss rates, launch radii, etc. They might also comprise a significant fraction of absorbers previously attributed to unrelated (interveinng) gas or galaxies. We have compiled a list of bright quasars with candidate HV outflow lines (CIV 1550 A) in existing SDSS spectra. We now propose to observe ~50 of these candidates with the 2.1m GoldCam to i) identify/confirm some of the true outflow systems (based on line variability), ii) place a firm lower limit on the fraction of quasars with narrow-line HV outflows, iii) compile a short list of confirmed HV outflow sources for future study, and iv) use the combined SDSS and GoldCam data to measure or constrain basic outflow properties, such as the kinematics, locations, and physical conditions.

  5. Ultraviolet (UV) From Quasars - Skylab Student Experiment ED-23

    NASA Technical Reports Server (NTRS)

    1973-01-01

    This chart describes the Skylab student experiment Ultraviolet (UV) from Quasars, proposed by John C. Hamilton of Aiea, Hawaii. This experiment utilized Skylab's Ultraviolet Stellar Astronomy equipment to photograph quasars in the UV spectrum and compare those images to existing radio and visible data. In March 1972 NASA and the National Science Teachers Association selected 25 experiment proposals for flight on Skylab. Science advisors from the Marshall Space Flight Center aided and assisted the students in developing the proposals for flight on Skylab.

  6. Quasar Absorption Studies

    NASA Technical Reports Server (NTRS)

    Mushotzky, Richard (Technical Monitor); Elvis, Martin

    2004-01-01

    The aim of the proposal is to investigate the absorption properties of a sample of inter-mediate redshift quasars. The main goals of the project are: Measure the redshift and the column density of the X-ray absorbers; test the correlation between absorption and redshift suggested by ROSAT and ASCA data; constrain the absorber ionization status and metallicity; constrain the absorber dust content and composition through the comparison between the amount of X-ray absorption and optical dust extinction. Unanticipated low energy cut-offs where discovered in ROSAT spectra of quasars and confirmed by ASCA, BeppoSAX and Chandra. In most cases it was not possible to constrain adequately the redshift of the absorber from the X-ray data alone. Two possibilities remain open: a) absorption at the quasar redshift; and b) intervening absorption. The evidences in favour of intrinsic absorption are all indirect. Sensitive XMM observations can discriminate between these different scenarios. If the absorption is at the quasar redshift we can study whether the quasar environment evolves with the Cosmic time.

  7. DISCOVERY OF THE DISTURBED RADIO MORPHOLOGY IN THE INTERACTING BINARY QUASAR FIRST J164311.3+315618

    SciTech Connect

    Kunert-Bajraszewska, Magdalena; Janiuk, Agnieszka

    2011-08-01

    We report the high-resolution radio observations and the subsequent analysis of the radio-loud compact steep spectrum quasar FIRST J164311.3+315618, one of the members of a binary system. The second component of the system is a radio-quiet active galactic nucleus. The projected separation of this pair is 2.''3 (15 kpc); it is one of the smallest-known-separation binary quasars. The multi-band images of this binary system made with the Hubble Space Telescope show that the host galaxy of the radio-loud quasar is highly disturbed. The radio observations presented here were made with the Multi-Element Radio-Linked interferometer network (MERLIN) at 1.66 GHz and 5 GHz. We show that the radio morphology of FIRST J164311.3+315618 is complex on both frequencies and exhibits four components that indicate the intermittent activity with a possible rapid change of the jet direction and/or restarting of the jet due to the interaction with the companion. The radio components that are no longer powered by the jet can quickly fade away. We suggest that this makes the potential distortions of the radio structure short-lived phenomena. Our numerical simulations show that the influence of the companion can lead to prolonged current and future activities. FIRST J164311.3+315618 is an unusual and statistically very rare low redshift binary quasar wherein the first close encounter is probably just taking place.

  8. Distributions of Quasar Hosts on the Galaxy Main Sequence Plane

    NASA Astrophysics Data System (ADS)

    Zhang, Zhoujian; Shi, Yong; Rieke, George H.; Xia, Xiaoyang; Wang, Yikang; Sun, Bingqing; Wan, Linfeng

    2016-03-01

    The relation between star formation rates (SFRs) and stellar masses, i.e., the galaxy main sequence, is a useful diagnostic of galaxy evolution. We present the distributions relative to the main sequence of 55 optically selected PG and 12 near-IR-selected Two Micron All Sky Survey (2MASS) quasars at z ≤ 0.5. We estimate the quasar host stellar masses from Hubble Space Telescope or ground-based AO photometry, and the SFRs through the mid-infrared aromatic features and far-IR photometry. We find that PG quasar hosts more or less follow the main sequence defined by normal star-forming galaxies while 2MASS quasar hosts lie systematically above the main sequence. PG and 2MASS quasars with higher nuclear luminosities seem to have higher specific SFRs (sSFRs), although there is a large scatter. No trends are seen between sSFRs and SMBH masses, Eddington ratios, or even morphology types (ellipticals, spirals, and mergers). Our results could be placed in an evolutionary scenario with quasars emerging during the transition from ULIRGs/mergers to ellipticals. However, combined with results at higher redshift, they suggest that quasars can be widely triggered in normal galaxies as long as they contain abundant gas and have ongoing star formation.

  9. A Closed Brayton Power Conversion Unit Concept for Nuclear Electric Propulsion for Deep Space Missions

    NASA Astrophysics Data System (ADS)

    Joyner, Claude Russell; Fowler, Bruce; Matthews, John

    2003-01-01

    In space, whether in a stable satellite orbit around a planetary body or traveling as a deep space exploration craft, power is just as important as the propulsion. The need for power is especially important for in-space vehicles that use Electric Propulsion. Using nuclear power with electric propulsion has the potential to provide increased payload fractions and reduced mission times to the outer planets. One of the critical engineering and design aspects of nuclear electric propulsion at required mission optimized power levels is the mechanism that is used to convert the thermal energy of the reactor to electrical power. The use of closed Brayton cycles has been studied over the past 30 or years and shown to be the optimum approach for power requirements that range from ten to hundreds of kilowatts of power. It also has been found to be scalable to higher power levels. The Closed Brayton Cycle (CBC) engine power conversion unit (PCU) is the most flexible for a wide range of power conversion needs and uses state-of-the-art, demonstrated engineering approaches. It also is in use with many commercial power plants today. The long life requirements and need for uninterrupted operation for nuclear electric propulsion demands high reliability from a CBC engine. A CBC engine design for use with a Nuclear Electric Propulsion (NEP) system has been defined based on Pratt & Whitney's data from designing long-life turbo-machines such as the Space Shuttle turbopumps and military gas turbines and the use of proven integrated control/health management systems (EHMS). An integrated CBC and EHMS design that is focused on using low-risk and proven technologies will over come many of the life-related design issues. This paper will discuss the use of a CBC engine as the power conversion unit coupled to a gas-cooled nuclear reactor and the design trends relative to its use for powering electric thrusters in the 25 kWe to 100kWe power level.

  10. Comparison of Procedures for Dual and Triple Closely Spaced Parallel Runways

    NASA Technical Reports Server (NTRS)

    Verma, Savita; Ballinger, Deborah; Subramanian Shobana; Kozon, Thomas

    2012-01-01

    A human-in-the-loop high fidelity flight simulation experiment was conducted, which investigated and compared breakout procedures for Very Closely Spaced Parallel Approaches (VCSPA) with two and three runways. To understand the feasibility, usability and human factors of two and three runway VCSPA, data were collected and analyzed on the dependent variables of breakout cross track error and pilot workload. Independent variables included number of runways, cause of breakout and location of breakout. Results indicated larger cross track error and higher workload using three runways as compared to 2-runway operations. Significant interaction effects involving breakout cause and breakout location were also observed. Across all conditions, cross track error values showed high levels of breakout trajectory accuracy and pilot workload remained manageable. Results suggest possible avenues of future adaptation for adopting these procedures (e.g., pilot training), while also showing potential promise of the concept.

  11. Homojunction GaAs solar cells grown by close space vapor transport

    SciTech Connect

    Boucher, Jason W.; Ritenour, Andrew J.; Greenaway, Ann L.; Aloni, Shaul; Boettcher, Shannon W.

    2014-06-08

    We report on the first pn junction solar cells grown by homoepitaxy of GaAs using close space vapor transport (CSVT). Cells were grown both on commercial wafer substrates and on a CSVT absorber film, and had efficiencies reaching 8.1%, open circuit voltages reaching 909 mV, and internal quantum efficiency of 90%. The performance of these cells is partly limited by the electron diffusion lengths in the wafer substrates, as evidenced by the improved peak internal quantum efficiency in devices fabricated on a CSVT absorber film. Unoptimized highly-doped n-type emitters also limit the photocurrent, indicating that thinner emitters with reduced doping, and ultimately wider band gap window or surface passivation layers, are required to increase the efficiency.

  12. Performance and Mass Modeling Subtleties in Closed-Brayton-Cycle Space Power Systems

    NASA Technical Reports Server (NTRS)

    Barrett, Michael J.; Johnson, Paul K.

    2006-01-01

    A number of potential NASA missions could benefit from closed-Brayton-cycle (CBC) power conversion systems. The human and robotic mission power applications include spacecraft, surface base, and rover scenarios. Modeling of CBC subsystems allows system engineers, mission planners and project managers to make informed decisions regarding power conversion system characteristics and capabilities. To promote thorough modeling efforts, a critical review of CBC modeling techniques is presented. Analysis of critical modeling elements, component influences and cycle sensitivities is conducted. The analysis leads to quantitative results addressing projections on converter efficiency and overall power conversion system mass. Even moderate modeling errors are shown to easily over-predict converter efficiencies by 30% and underestimate mass estimates by 20%. Both static and dynamic modeling regimes are evaluated. Key considerations in determining model fidelity requirements are discussed. Conclusions and recommendations are presented that directly address ongoing modeling efforts in solar and nuclear space power systems.

  13. Performance and Mass Modeling Subtleties in Closed-Brayton-Cycle Space Power Systems

    NASA Technical Reports Server (NTRS)

    Barrett, Michael J.; Johnson, Paul K.

    2005-01-01

    A number of potential NASA missions could benefit from closed-Brayton-cycle (CBC) power conversion systems. The human and robotic mission power applications include spacecraft, surface base, and rover scenarios. Modeling of CBC subsystems allows system engineers, mission planners and project managers to make informed decisions regarding power conversion system characteristics and capabilities. To promote thorough modeling efforts, a critical review of CBC modeling techniques is presented. Analysis of critical modeling elements, component influences and cycle sensitivities is conducted. The analysis leads to quantitative results addressing projections on converter efficiency and overall power conversion system mass. Even moderate modeling errors are shown to easily over-predict converter efficiencies by 30 percent and underestimate mass estimates by 20 percent. Both static and dynamic modeling regimes are evaluated. Key considerations in determining model fidelity requirements are discussed. Conclusions and recommendations are presented that directly address ongoing modeling efforts in solar and nuclear space power systems.

  14. Growth of CdTe thin films on graphene by close-spaced sublimation method

    SciTech Connect

    Jung, Younghun; Yang, Gwangseok; Kim, Jihyun; Chun, Seungju; Kim, Donghwan

    2013-12-02

    CdTe thin films grown on bi-layer graphene were demonstrated by using the close-spaced sublimation method, where CdTe was selectively grown on the graphene. The density of the CdTe domains was increased with increasing the number of the defective sites in the graphene, which was controlled by the duration of UV exposure. The CdTe growth rate on the bi-layer graphene electrodes was 400 nm/min with a bandgap energy of 1.45–1.49 eV. Scanning electron microscopy, micro-Raman spectroscopy, micro-photoluminescence, and X-ray diffraction technique were used to confirm the high quality of the CdTe thin films grown on the graphene electrodes.

  15. Induced recrystallization of CdTe thin films deposited by close-spaced sublimation

    SciTech Connect

    Moutinho, H.R.; Dhere, R.G.; Al-Jassim, M.M.; Levi, D.H.; Kazmerski, L.L.; Mayo, B.

    1999-03-01

    We have deposited CdTe thin films by close-spaced sublimation at two different temperature ranges. The films deposited at the lower temperature partially recrystallized after CdCl{sub 2} treatment at 350&hthinsp;{degree}C and completely recrystallized after the same treatment at 400&hthinsp;{degree}C. The films deposited at higher temperature did not recrystallize at these two temperatures. These results confirmed that the mechanisms responsible for changes in physical properties of CdTe films treated with CdCl{sub 2} are recrystallization and grain growth, and provided an alternative method to deposit CSS films using lower temperatures. {copyright} {ital 1999 American Institute of Physics.}

  16. Adaptive Filtering for Large Space Structures: A Closed-Form Solution

    NASA Technical Reports Server (NTRS)

    Rauch, H. E.; Schaechter, D. B.

    1985-01-01

    In a previous paper Schaechter proposes using an extended Kalman filter to estimate adaptively the (slowly varying) frequencies and damping ratios of a large space structure. The time varying gains for estimating the frequencies and damping ratios can be determined in closed form so it is not necessary to integrate the matrix Riccati equations. After certain approximations, the time varying adaptive gain can be written as the product of a constant matrix times a matrix derived from the components of the estimated state vector. This is an important savings of computer resources and allows the adaptive filter to be implemented with approximately the same effort as the nonadaptive filter. The success of this new approach for adaptive filtering was demonstrated using synthetic data from a two mode system.

  17. TacSat-2: Path finder for a Close Space Support Asset

    NASA Astrophysics Data System (ADS)

    Bhopale, A.; Finley, C.

    2008-08-01

    With th e launch of TacSat-2, the Oper ationally Responsive Sp ace (O RS) commun ity had its f irst on- orbit asset and opportunity to prove or disprove the premise that small, in expensiv e, and quickly constructed spacecraf t could perform useful operation al missions when needed and for as long as need ed. All of the components of the comp lex TacSat-2 system had to work together to answer the basic questions, "In a crisis, can a lab-developed spacecraf t and ground architecture competen tly p erform th e mission of systems that cost twen ty times the price and tak e four times as long to develop? Mor eover, can th is system actu ally improve on the responsiveness of Nation al Systems to a certain set of underserv ed Oper ational customers?" When all w as said and done, TacSat-2 was a sp acecraf t that h ad to: 1) Carry th irteen tactical and scientific payloads to orbit, many of which doubled as essen tial, non-redundant subsystems; 2) Launch from an unproven launch base on a last minute "rep lacement" launch vehicle; and 3) Fulfill about 140 on-orbit mission requirements. It had tactical sensors, two unproven communication links, numerous next-gen eration single- string componen ts (e.g., h igh-efficiency propulsion system, thin-film so lar arrays, low-power versatile star camera) , and autonomous softw are to mak e the system more friendly and familiar to Tactical, rather than Spacecraf t Op erators. However, the mission was as mu ch about the implementation as it w as about the components. TacSat-2 was designed for and emp loyed with a different concept of operations ( CONOPS) than tradition al N ational Operational Assets. It w as designed to be th e fir st-ev er Clo se Space Support platform and operated in a manner more analogous to Close Air Support aircraf t than to tr aditional spacecraft. Therefore, th e primary objective of the TacSat-2 mission was to use th e TacSat-2 system to id entify those parts of the spacecr aft, ground system, and CON OPS

  18. Principles for RNA metabolism and alternative transcription initiation within closely spaced promoters.

    PubMed

    Chen, Yun; Pai, Athma A; Herudek, Jan; Lubas, Michal; Meola, Nicola; Järvelin, Aino I; Andersson, Robin; Pelechano, Vicent; Steinmetz, Lars M; Jensen, Torben Heick; Sandelin, Albin

    2016-09-01

    Mammalian transcriptomes are complex and formed by extensive promoter activity. In addition, gene promoters are largely divergent and initiate transcription of reverse-oriented promoter upstream transcripts (PROMPTs). Although PROMPTs are commonly terminated early, influenced by polyadenylation sites, promoters often cluster so that the divergent activity of one might impact another. Here we found that the distance between promoters strongly correlates with the expression, stability and length of their associated PROMPTs. Adjacent promoters driving divergent mRNA transcription support PROMPT formation, but owing to polyadenylation site constraints, these transcripts tend to spread into the neighboring mRNA on the same strand. This mechanism to derive new alternative mRNA transcription start sites (TSSs) is also evident at closely spaced promoters supporting convergent mRNA transcription. We suggest that basic building blocks of divergently transcribed core promoter pairs, in combination with the wealth of TSSs in mammalian genomes, provide a framework with which evolution shapes transcriptomes. PMID:27455346

  19. Carbon-Carbon Recuperators in Closed-Brayton-Cycle Space Power Systems

    NASA Technical Reports Server (NTRS)

    Barrett, Michael J.; Johnson, Paul K.

    2006-01-01

    The use of carbon-carbon (C-C) recuperators in closed-Brayton-cycle space power conversion systems was assessed. Recuperator performance was forecast based on notional thermodynamic cycle state values for planetary missions. Resulting thermal performance, mass and volume for plate-fin C-C recuperators were estimated and quantitatively compared with values for conventional offset-strip-fin metallic designs. Mass savings of 40-55% were projected for C-C recuperators with effectiveness greater than 0.9 and thermal loads from 25-1400 kWt. The smaller thermal loads corresponded with lower mass savings; however, at least 50% savings were forecast for all loads above 300 kWt. System-related material challenges and compatibility issues were also discussed.

  20. Carbon-Carbon Recuperators in Closed-Brayton-Cycle Space Power Systems

    NASA Technical Reports Server (NTRS)

    Barrett, Michael J.; Johnson, Paul K.; Naples, Andrew G.

    2006-01-01

    The feasibility of using carbon-carbon (C-C) recuperators in conceptual closed-Brayton-cycle space power conversion systems was assessed. Recuperator performance expectations were forecast based on notional thermodynamic cycle state values for potential planetary missions. Resulting thermal performance, mass and volume for plate-fin C-C recuperators were estimated and quantitatively compared with values for conventional offset-strip-fin metallic designs. Mass savings of 30 to 60 percent were projected for C-C recuperators with effectiveness greater than 0.9 and thermal loads from 25 to 1400 kWt. The smaller thermal loads corresponded with lower mass savings; however, 60 percent savings were forecast for all loads above 300 kWt. System-related material challenges and compatibility issues were also discussed.

  1. The Pan-STARRS1 z>6 quasar survey: More than 100 quasars within the first Gyr of the universe

    NASA Astrophysics Data System (ADS)

    Walter, Fabian; Banados, Eduardo; Venemans, Bram; Decarli, Roberto; Farina, Emanuele; Mazzucchelli, Chiara; Fan, Xiaohui; Chambers, Kenneth C.

    2016-01-01

    Quasars are the most luminous non-transient sources in the Universe. As such, they are ideal probes of the redshift range z=6-7, a critical phase in cosmic history, when the Universe is emerging from the dark ages. Over the last three years we have exploited the Pan-STARRS1 survey, more than doubling the number of known z>5.5 quasars (tripling the number of z>6 quasars in the southern sky, and discovering 4 of the 9 quasars known at z>6.5). This seach significantly extended the sampled parameter space in terms of quasar luminosities and redshift coverage. Pioneering studies already demostrate the intrumental role of QSOs in probing the very early phases of galaxy formation and black hole growth within 1 Gyr from the Big Bang: a) billion solar masses black holes are already in place, b) they are surrounded by massive reservoirs of cold gas, and c) the neutral fraction of the intergalactic medium rapidly drops after z~6, thus marking the end of the epoch of reionization. Our significantly enlarged sample marks the transition phase from studies of individual sources to statistical studies of the high-z quasar population. We present some of the comprehensive multiwavelength characterization of the high-z quasar population and their environment (our on-going efforts include deep NIR spectroscopy, ALMA, NOEMA, HST, Spitzer, and JVLA observations).

  2. Tunneling spectroscopy of close-spaced dangling-bond pairs in Si(001):H

    PubMed Central

    Engelund, Mads; Zuzak, Rafał; Godlewski, Szymon; Kolmer, Marek; Frederiksen, Thomas; García-Lekue, Aran; Sánchez-Portal, Daniel; Szymonski, Marek

    2015-01-01

    We present a combined experimental and theoretical study of the electronic properties of close-spaced dangling-bond (DB) pairs in a hydrogen-passivated Si(001):H p-doped surface. Two types of DB pairs are considered, called “cross” and “line” structures. Our scanning tunneling spectroscopy (STS) data show that, although the spectra taken over different DBs in each pair exhibit a remarkable resemblance, they appear shifted by a constant energy that depends on the DB-pair type. This spontaneous asymmetry persists after repeated STS measurements. By comparison with density functional theory (DFT) calculations, we demonstrate that the magnitude of this shift and the relative position of the STS peaks can be explained by distinct charge states for each DB in the pair. We also explain how the charge state is modified by the presence of the scanning tunneling microscopy (STM) tip and the applied bias. Our results indicate that, using the STM tip, it is possible to control the charge state of individual DBs in complex structures, even if they are in close proximity. This observation might have important consequences for the design of electronic circuits and logic gates based on DBs in passivated silicon surfaces. PMID:26404520

  3. Multi-MW Closed Cycle MHD Nuclear Space Power Via Nonequilibrium He/Xe Working Plasma

    NASA Technical Reports Server (NTRS)

    Litchford, Ron J.; Harada, Nobuhiro

    2011-01-01

    Prospects for a low specific mass multi-megawatt nuclear space power plant were examined assuming closed cycle coupling of a high-temperature fission reactor with magnetohydrodynamic (MHD) energy conversion and utilization of a nonequilibrium helium/xenon frozen inert plasma (FIP). Critical evaluation of performance attributes and specific mass characteristics was based on a comprehensive systems analysis assuming a reactor operating temperature of 1800 K for a range of subsystem mass properties. Total plant efficiency was expected to be 55.2% including plasma pre-ionization power, and the effects of compressor stage number, regenerator efficiency and radiation cooler temperature on plant efficiency were assessed. Optimal specific mass characteristics were found to be dependent on overall power plant scale with 3 kg/kWe being potentially achievable at a net electrical power output of 1-MWe. This figure drops to less than 2 kg/kWe when power output exceeds 3 MWe. Key technical issues include identification of effective methods for non-equilibrium pre-ionization and achievement of frozen inert plasma conditions within the MHD generator channel. A three-phase research and development strategy is proposed encompassing Phase-I Proof of Principle Experiments, a Phase-II Subscale Power Generation Experiment, and a Phase-III Closed-Loop Prototypical Laboratory Demonstration Test.

  4. Einstein spectra of quasars

    NASA Technical Reports Server (NTRS)

    Wilkes, Belinda J.

    1988-01-01

    The results of the initial stage of the CfA survey of quasar energy distributions are reviewed. Einstein imaging proportional counter spectra of 33 quasars have been studied by fitting a single power law slope and absorption by an equivalent column density of neutral hydrogen. Comparison with the higher energy HEAO-A2 data leads to a two-component model for the X-ray spectrum. The X-ray column density is systematically lower than the 21-cm measured Galactic column density along the same line of sight.

  5. THE COLOR VARIABILITY OF QUASARS

    SciTech Connect

    Schmidt, Kasper B.; Rix, Hans-Walter; Knecht, Matthias; Hogg, David W.; Shields, Joseph C.; Maoz, Dan; Bovy, Jo

    2012-01-10

    We quantify quasar color variability using an unprecedented variability database-ugriz photometry of 9093 quasars from Sloan Digital Sky Survey (SDSS) Stripe 82, observed over 8 years at {approx}60 epochs each. We confirm previous reports that quasars become bluer when brightening. We find a redshift dependence of this blueing in a given set of bands (e.g., g and r), but show that it is the result of the flux contribution from less-variable or delayed emission lines in the different SDSS bands at different redshifts. After correcting for this effect, quasar color variability is remarkably uniform, and independent not only of redshift, but also of quasar luminosity and black hole mass. The color variations of individual quasars, as they vary in brightness on year timescales, are much more pronounced than the ranges in color seen in samples of quasars across many orders of magnitude in luminosity. This indicates distinct physical mechanisms behind quasar variability and the observed range of quasar luminosities at a given black hole mass-quasar variations cannot be explained by changes in the mean accretion rate. We do find some dependence of the color variability on the characteristics of the flux variations themselves, with fast, low-amplitude, brightness variations producing more color variability. The observed behavior could arise if quasar variability results from flares or ephemeral hot spots in an accretion disk.

  6. Hubble Space Telescope View of Comet C/Siding Spring during its Close Encounter with Mars

    NASA Astrophysics Data System (ADS)

    Li, J. Y.; Samarasinha, N. H.; Kelley, M. S. P.; Farnham, T. L.; Bodewits, D.; A'Hearn, M. F.; Lisse, C. M.; Delamere, W. A.; Mutchler, M. J.

    2014-12-01

    Comet C/2013 A1 (Siding Spring) is a dynamically new comet whose physical and chemical status should be the least evolved since the formation of cometesimals during the planetary system formation processes. Its close encounter with Mars on October 19, 2014 at a distance of 131,000 km allows for imaging its nucleus and inner coma by MRO/HiRISE at 140 m/pix resolution. Such an encounter offers us the opportunity to do cometary flyby science for a dynamically new comet for the first time ever. Those observations have the potential to advance our understanding of comets in ways similar to previous flyby missions to periodic comets. An extensive observing campaign from many ground- and space-based platforms is supporting the "flyby" observations from Mars spacecraft. We will monitor the comet with Hubble Space Telescope for >24 hrs total observing time around the encounter, to obtain images of the inner coma at ~46 km/pix at the comet. These observations will allow us to perform detailed studies of the morphology of the dust and gas coma of C/Siding Spring, and to connect the observations performed from various platforms at various spatial resolutions and over a long time baseline. The ultimate goal is to correlate large-scale coma behaviors to the nucleus as resolved by MRO/HiRISE. We will report the HST observations and the preliminary results.

  7. Theoretical analysis of surface-plasmon-polariton resonators in free space and close to an interface

    NASA Astrophysics Data System (ADS)

    Jung, Jesper; Søndergaard, Thomas

    2008-04-01

    Surface-plasmon-polariton (SPP) resonators consisting of metal strips in free space, and gap plasmon polariton resonators consisting of a metal strip close to either a block of metal or a metal surface, are studied as optical resonators. The analysis is performed using the Green's function surface integral equation method. For strips in free space, we show how the scattering resonances can be understood, by thinking of the strips as optical resonators for short-range SPPs. The two gap resonator configurations, strip-block and strip-surface, have different structure terminations as the width of the strip and the block are identical whereas the surface is infinite. In the strip-surface configuration, the scattering resonances are broader and red-shifted, compared to the strip-block configuration. This is explained as a consequence of the effective length of the resonator being larger in the strip-surface configuration. By varying the gap size, we study the transition from a SPP resonator to a gap plasmon polariton resonator. In the strip-surface configuration, light can be scattered into both out-of-plane propagating waves and into SPPs that propagate along the surface. For small gaps of a few tens of nanometers, a large enhancement in the scattering cross section is seen due to strong scattering into SPPs.

  8. Phase space matching and finite lifetime effects for top-pair production close to threshold

    SciTech Connect

    Hoang, Andre H.; Reisser, Christoph J.; Ruiz-Femenia, Pedro

    2010-07-01

    The top-pair tt production cross section close to threshold in e{sup +}e{sup -} collisions is strongly affected by the small lifetime of the top quark. Since the cross section is defined through final states containing the top decay products, a consistent definition of the cross section depends on prescriptions of how these final states are accounted for the cross section. Experimentally, these prescriptions are implemented, for example, through cuts on kinematic quantities such as the reconstructed top quark invariant masses. As long as these cuts do not reject final states that can arise from the decay of a top and an antitop quark with a small off-shellness compatible with the nonrelativistic power counting, they can be implemented through imaginary phase space matching conditions in nonrelativistic QCD. The prescription-dependent cross section can then be determined from the optical theorem using the e{sup +}e{sup -} forward scattering amplitude. We compute the phase space matching conditions associated to cuts on the top and antitop invariant masses at next-to-next-to-leading logarithmic order and partially at next-to-next-to-next-to-leading logarithmic order in the nonrelativistic expansion accounting also for higher order QCD effects. Together with finite lifetime and electroweak effects known from previous work, we analyze their numerical impact on the tt cross section. We show that the phase space matching contributions are essential to make reliable nonrelativistic QCD predictions, particularly for energies below the peak region, where the cross section is small. We find that irreducible background contributions associated to final states that do not come from top decays are strongly suppressed and can be neglected for the theoretical predictions.

  9. THE ULTRAVIOLET-TO-MID-INFRARED SPECTRAL ENERGY DISTRIBUTION OF WEAK EMISSION LINE QUASARS

    SciTech Connect

    Lane, Ryan A.; Shemmer, Ohad; Diamond-Stanic, Aleksandar M.; Fan Xiaohui; Anderson, Scott F.; Brandt, W. N.; Schneider, Donald P.; Plotkin, Richard M.; Richards, Gordon T.; Strauss, Michael A. E-mail: ohad@unt.edu

    2011-12-20

    We present Spitzer Space Telescope photometry of 18 Sloan Digital Sky Survey (SDSS) quasars at 2.7 {<=} z {<=} 5.9 which have weak or undetectable high-ionization emission lines in their rest-frame ultraviolet (UV) spectra (hereafter weak-lined quasars, or WLQs). The Spitzer data are combined with SDSS spectra and ground-based, near-infrared (IR) photometry of these sources to produce a large inventory of spectral energy distributions (SEDs) of WLQs across the rest-frame {approx}0.1-5 {mu}m spectral band. The SEDs of our sources are inconsistent with those of BL Lacertae objects which are dominated by synchrotron emission due to a jet aligned close to our line of sight, but are consistent with the SED of ordinary quasars with similar luminosities and redshifts that exhibit a near-to-mid-IR 'bump', characteristic of hot dust emission. This indicates that broad emission lines in WLQs are intrinsically weak, rather than suffering continuum dilution from a jet, and that such sources cannot be selected efficiently from traditional photometric surveys.

  10. An Automated Search for Gravitationally Lensed Quasars in the Sloan Digital Sky Survey

    NASA Astrophysics Data System (ADS)

    Sivakumar, Pranav; Sivakumar, Janani N.; Nebres, Paul J.

    2016-01-01

    Quasar lensing is a powerful tool in deciphering the characteristics of dark matter and dark energy. Given the availability of "big data" on quasars, including the SDSS DR12 and the recently released DES data set, a robust automated algorithm for the detection of lensed quasars is rapidly becoming a necessity. We report results from an automated search for lensed quasars consisting of two complementary algorithms: a morphological algorithm directed at finding wide-separation lens candidates and a PSF-difference-based algorithm aimed at identifying close-separation lens candidates. This research started with a baseline data set of over 450,000 quasars and 996,317 spatial neighbors within 16 arcseconds of each quasar in the SDSS DR12. This threshold can identify quasars lensed by galaxy-scale to cluster-scale matter concentrations. The first part of the automated method matched redshift and color characteristics of images and compared key emission lines in the spectrum of the quasars and their neighbors. The second portion applied image segmentation techniques to deblend close-separation candidates identified as one photometric object by SDSS. Cross-matching with observations of the same targets across other bands of the electromagnetic spectrum and elimination of confirmed binary quasars increased the confidence level of the resulting candidate list. The automated search efficiently produced output consistent with results reported in the literature. In addition, the algorithms identified many new lens candidates not yet reported in the literature which warrant detailed follow-up observations.

  11. Metallicity and Quasar Outflows

    NASA Astrophysics Data System (ADS)

    Wang, Huiyuan; Zhou, Hongyan; Yuan, Weimin; Wang, Tinggui

    2012-06-01

    Correlations of the outflow strength of quasars, as measured by the blueshift and asymmetry index (BAI) of the C IV line, with intensities and ratios of broad emission lines, based on composite quasar spectra built from the Sloan Digital Sky Survey, are investigated. We find that most of the line ratios of other ions to C IV increase prominently with BAI. These behaviors can be well understood in the context of increasing metallicity with BAI. The strength of the dominant coolant, C IV line, decreases, and weak collisionally excited lines increase with gas metallicity as a result of the competition between different line coolants. Using Si IV+O IV]/C IV as an indicator of gas metallicity, we present, for the first time, a strong correlation between the metallicity and the outflow strength of quasars over a wide range of 1.7-6.9 times solar abundance. Our result implies that metallicity plays an important role in the formation of quasar outflows, likely by affecting outflow acceleration. This effect may have a profound impact on galaxy evolution via momentum feedback and chemical enrichment.

  12. METALLICITY AND QUASAR OUTFLOWS

    SciTech Connect

    Wang, Huiyuan; Zhou, Hongyan; Wang, Tinggui; Yuan, Weimin

    2012-06-01

    Correlations of the outflow strength of quasars, as measured by the blueshift and asymmetry index (BAI) of the C IV line, with intensities and ratios of broad emission lines, based on composite quasar spectra built from the Sloan Digital Sky Survey, are investigated. We find that most of the line ratios of other ions to C IV increase prominently with BAI. These behaviors can be well understood in the context of increasing metallicity with BAI. The strength of the dominant coolant, C IV line, decreases, and weak collisionally excited lines increase with gas metallicity as a result of the competition between different line coolants. Using Si IV+O IV]/C IV as an indicator of gas metallicity, we present, for the first time, a strong correlation between the metallicity and the outflow strength of quasars over a wide range of 1.7-6.9 times solar abundance. Our result implies that metallicity plays an important role in the formation of quasar outflows, likely by affecting outflow acceleration. This effect may have a profound impact on galaxy evolution via momentum feedback and chemical enrichment.

  13. Quasar feedback revealed by giant molecular outflows

    NASA Astrophysics Data System (ADS)

    Feruglio, C.; Maiolino, R.; Piconcelli, E.; Menci, N.; Aussel, H.; Lamastra, A.; Fiore, F.

    2010-07-01

    In the standard scenario for galaxy evolution young star-forming galaxies transform into red bulge-dominated spheroids, where star formation has been quenched. To explain this transformation, a strong negative feedback generated by accretion onto a central super-massive black hole is often invoked. The depletion of gas resulting from quasar-driven outflows should eventually stop star-formation across the host galaxy and lead the black hole to “suicide” by starvation. Direct observational evidence for a major quasar feedback onto the host galaxy is still missing, because outflows previously observed in quasars are generally associated with the ionized component of the gas, which only accounts for a minor fraction of the total gas content, and typically occurrs in the central regions. We used the IRAM PdB Interferometer to observe the CO(1-0) transition in Mrk 231, the closest quasar known. Thanks to the wide band we detected broad wings of the CO line, with velocities of up to 750 km s-1 and spatially resolved on the kpc scale. These broad CO wings trace a giant molecular outflow of about 700 M_⊙/year, far larger than the ongoing star-formation rate (~200 M_⊙/year) observed in the host galaxy. This wind will totally expel the cold gas reservoir in Mrk 231 in about 107 yrs, therefore halting the star-formation activity on the same timescale. The inferred kinetic energy in the molecular outflow is ~1.2 × 1044 erg/s, corresponding to a few percent of the AGN bolometric luminosity, which is very close to the fraction expected by models ascribing quasar feedback to highly supersonic shocks generated by radiatively accelerated nuclear winds. Instead, the contribution by the SNe associated with the starburst fall short by several orders of magnitude to account for the kinetic energy observed in the outflow. The direct observational evidence for quasar feedback reported here provides solid support to the scenarios ascribing the observed properties of local massive

  14. Kinematic Modeling of Separation Compression for Paired Approaches to Closely-Spaced Parallel Runways

    NASA Technical Reports Server (NTRS)

    Madden, Michael M.

    2014-01-01

    In a simultaneous paired approach to closely-spaced parallel runways, a pair of aircraft flies in close proximity on parallel approach paths. The longitudinal separation between the aircraft must be maintained within a range that avoids wake encounters and, if one of the aircraft blunders, avoids collision. To increase operational availability, the approach procedure must accommodate a mixture of aircraft sizes and, consequently, approach speeds. In these procedures, the slower aircraft is placed in the lead position. The faster aircraft maintains separation from the slow aircraft in a dependent operation until final approach and flies independently afterward. Due to the higher approach speed of the fast aircraft, longitudinal separation will decrease during final approach. Therefore, the fast aircraft must position itself before the final approach so that it will remain within the safe range of separation as separation decreases. Given the approach geometry and speed schedule for each aircraft, one can use kinematics to estimate the separation loss between a pair of aircraft. A kinematic model can complement fast-time Monte-Carlo simulations of the approach by enabling a tailored reduction in the variation of starting position for the fast aircraft. One could also implement the kinematic model in ground-based or on-board decision support tools to compute the optimal initial separation for a given pair of aircraft. To better match the auto-coupled flight of real aircraft, the paper derives a kinematic model where the speed schedule is flown using equivalent airspeed. The predicted time of flight using the equivalent airspeed kinematic model compares well against a high-fidelity aircraft simulation performing the same approach. This model also demonstrates a modest increase in the predicted loss of separation when contrasted against a kinematic model that assumes the scheduled speed is true airspeed.

  15. The luminosity function of quasars

    NASA Technical Reports Server (NTRS)

    Pei, Yichuan C.

    1995-01-01

    We propose a new evolutionary model for the optical luminosity function of quasars. Our analytical model is derived from fits to the empirical luminosity function estimated by Hartwick and Schade and Warren, Hewett, and Osmer on the basis of more than 1200 quasars over the range of redshifts 0 approximately less than z approximately less than 4.5. We find that the evolution of quasars over this entire redshift range can be well fitted by a Gaussian distribution, while the shape of the luminosity function can be well fitted by either a double power law or an exponential L(exp 1/4) law. The predicted number counts of quasars, as a function of either apparent magnitude or redshift, are fully consistent with the observed ones. Our model indicates that the evolution of quasars reaches its maximum at z approximately = 2.8 and declines at higher redshifts. An extrapolation of the evolution to z approximately greater than 4.5 implies that quasars may have started their cosmic fireworks at z(sub f) approximately = 5.2-5.5. Forthcoming surveys of quasars at these redshifts will be critical to constrain the epoch of quasar formation. All the results we derived are based on observed quasars and are therefore subject to the bias of obscuration by dust in damped Ly alpha systems. Future surveys of these absorption systems at z approximately greater than 3 will also be important if the formation epoch of quasars is to be known unambiguously.

  16. Importance of closely spaced vertical sampling in delineating chemical and microbiological gradients in groundwater studies

    USGS Publications Warehouse

    Smith, R.L.; Harvey, R.W.; LeBlanc, D.R.

    1991-01-01

    Vertical gradients of selected chemical constituents, bacterial populations, bacterial activity and electron acceptors were investigated for an unconfined aquifer contaminated with nitrate and organic compounds on Cape Cod, Massachusetts, U.S.A. Fifteen-port multilevel sampling devices (MLS's) were installed within the contaminant plume at the source of the contamination, and at 250 and 2100 m downgradient from the source. Depth profiles of specific conductance and dissolved oxygen at the downgradient sites exhibited vertical gradients that were both steep and inversely related. Narrow zones (2-4 m thick) of high N2O and NH4+ concentrations were also detected within the contaminant plume. A 27-fold change in bacterial abundance; a 35-fold change in frequency of dividing cells (FDC), an indicator of bacterial growth; a 23-fold change in 3H-glucose uptake, a measure of heterotrophic activity; and substantial changes in overall cell morphology were evident within a 9-m vertical interval at 250 m downgradient. The existence of these gradients argues for the need for closely spaced vertical sampling in groundwater studies because small differences in the vertical placement of a well screen can lead to incorrect conclusions about the chemical and microbiological processes within an aquifer.Vertical gradients of selected chemical constituents, bacterial populations, bacterial activity and electron acceptors were investigated for an unconfined aquifer contaminated with nitrate and organic compounds on Cape Cod, Massachusetts, USA. Fifteen-port multilevel sampling devices (MLS's) were installed within the contaminant plume at the source of the contamination, and at 250 and 2100 m downgradient from the source. Depth profiles of specific conductance and dissolved oxygen at the downgradient sites exhibited vertical gradients that were both steep and inversely related. Narrow zones (2-4 m thick) of high N2O and NH4+ concentrations were also detected within the contaminant plume

  17. Broad-line region physical conditions along the quasar eigenvector 1 sequence

    NASA Astrophysics Data System (ADS)

    Marziani, P.; Sulentic, J. W.; Negrete, C. A.; Dultzin, D.; Zamfir, S.; Bachev, R.

    2010-12-01

    We compare broad emission-line profiles and estimate line ratios for all major emission lines between Lyα and Hβ in a sample of six quasars. The sources were chosen with two criteria in mind: the existence of high-quality optical and ultraviolet spectra and the possibility of sampling the spectroscopic diversity in the 4D eigenvector 1 (4DE1) context. In the latter sense, each source occupies a region (bin) in the full width at half-maximum (FWHM)(Hβ) versus Fe IIopt strength plane that is significantly different from the others. High signal-to-noise ratio Hβ emission-line profiles are used as templates for modelling the other lines (Lyα, C IV λ1549, He II λ1640, Al III λ1860, Si III] λ1892 and Mg II λ2800). We can adequately model all broad lines assuming the existence of three components distinguished by blueshifted, unshifted and redshifted centroids [indicated as a blue component (BLUE), broad component (BC) and very broad component (VBC), respectively]. BC (electron density ne˜ 1012 cm-3, ionization parameter U˜ 10-2 and column density Nc≳ 1023 cm-2) is present in almost all type-1 quasars and therefore corresponds most closely to the classical broad-line emitting region (the reverberating component). The bulk of Mg II λ2800 and Fe II emission also arises in this region. The BLUE emission (log ne˜ 10, log U˜-1 and log Nc < 23) arises in less optically thick gas; it is often thought to arise in an accretion disc wind. The least understood component involves the VBC (high ionization and large column density), which is found in no more than half (but almost all radio-loud) type-1 quasars and luminous Seyfert nuclei. It is perhaps the most distinguishing characteristic of quasars with FWHM (Hβ) ≳ 4000 km s-1 that belong to the so-called population B of our 4DE1 space. Population A quasars [FWHM (Hβ) ≲ 4000 km s-1] are dominated by BC emission in Hβ and BLUE component emission in C IV λ1549 and other high ionization lines. 4DE1 appears to

  18. Heat transport through plasmonic interactions in closely spaced metallic nanoparticle chains

    NASA Astrophysics Data System (ADS)

    Ben-Abdallah, Philippe; Joulain, Karl; Drevillon, Jérémie; Le Goff, Clément

    2008-02-01

    We report a numerical investigation on the heat transfer through one-dimensional arrays of metallic nanoparticles closely spaced in a host material. Our simulations show that the multipolar interactions play a crucial role in the heat transport via collective plasmons. Calculations of the plasmonic thermal conductance and of the thermal conductivity in ballistic and diffusive regimes, respectively, have been carried out. (a) Using the Landauer-Buttiker formalism, we have found that, when the host material dielectric constant takes positive values, the multipolar interactions drastically enhance by several orders of magnitude the ballistic thermal conductance of collective plasmons compared with that of a classical dipolar chain. On the contrary, when the host material dielectric constant takes negative values, we have demonstrated the existence of nonballistic multipolar modes which annihilate the heat transfer through the chains. (b) Using the kinetic theory, we have also examined the thermal behavior of chains in the diffusion approximation. We have shown that the plasmonic thermal conductivity of metallic nanoparticle chains can reach 1% of the bulk metal thermal conductivity. This result could explain the anomalously high thermal conductivity observed in many colloidal suspensions, the so-called nanofluids.

  19. A Preliminary and Simplified Closed Brayton Cycle Modeling for a Space Reactor Application

    SciTech Connect

    Guimaraes, Lamartine Nogueira Frutuoso; Camillo, Giannino Ponchio

    2008-01-21

    The Nuclear Energy Division (ENU) of the Institute for Advanced Studies (IEAv) has started a preliminary design study for a Closed Brayton Cycle Loop (CBCL) aimed at a space reactor application. The main objectives of the study are: 1) to establish a starting concept for the CBCL components specifications, and 2) to build a demonstrative simulator of CBCL. This preliminary design study is developing the CBCL around the NOELLE 60290 turbo machine. The actual nuclear reactor study is being conducted independently. Because of that, a conventional heat source is being used for the CBCL, in this preliminary design phase. This paper describes the steady state simulator of the CBCL operating with NOELLE 60290 turbo machine. In principle, several gases are being considered as working fluid, as for instance: air, helium, nitrogen, CO{sub 2} and gas mixtures such as helium and xenon. However, for this first application pure helium will be used as working fluid. Simplified models of heat and mass transfer were developed to simulate thermal components. Future efforts will focus on implementing a graphical interface to display the thermal process variables in steady state and to keep track of the modifications being implemented at the NOELLE 60290 turbo machine in order to build the CBCL.

  20. Parallel Operation of Multiple Closely Spaced Small Aspect Ratio Rod Pinches

    DOE PAGESBeta

    Harper-Slaboszewicz, Victor J.; Leckbee, Joshua; Bennett, Nichelle; Madrid, Elizabeth A.; Rose, David V.; Thoma, Carsten; Welch, Dale R.; Lake, Patrick W.; McCourt, Andrew L.

    2014-12-10

    A series of simulations and experiments to resolve questions about the operation of arrays of closely spaced small aspect ratio rod pinches has been performed. Design and post-shot analysis of the experimental results are supported by 3D particle-in-cell simulations. Both simulations and experiments support these conclusions. Penetration of current to the interior of the array appears to be efficient, as the current on the center rods is essentially equal to the current on the outer rods. Current loss in the feed due to the formation of magnetic nulls was avoided in these experiments by design of the feed surface ofmore » the cathode and control of the gap to keep the electric fields on the cathode below the emission threshold. Some asymmetry in the electron flow to the rod was observed, but the flow appeared to symmetrize as it reached the end of the rod. Interaction between the rod pinches can be controlled to allow the stable and consistent operation of arrays of rod pinches.« less

  1. Simulated Wake Characteristics Data for Closely Spaced Parallel Runway Operations Analysis

    NASA Technical Reports Server (NTRS)

    Guerreiro, Nelson M.; Neitzke, Kurt W.

    2012-01-01

    A simulation experiment was performed to generate and compile wake characteristics data relevant to the evaluation and feasibility analysis of closely spaced parallel runway (CSPR) operational concepts. While the experiment in this work is not tailored to any particular operational concept, the generated data applies to the broader class of CSPR concepts, where a trailing aircraft on a CSPR approach is required to stay ahead of the wake vortices generated by a lead aircraft on an adjacent CSPR. Data for wake age, circulation strength, and wake altitude change, at various lateral offset distances from the wake-generating lead aircraft approach path were compiled for a set of nine aircraft spanning the full range of FAA and ICAO wake classifications. A total of 54 scenarios were simulated to generate data related to key parameters that determine wake behavior. Of particular interest are wake age characteristics that can be used to evaluate both time- and distance- based in-trail separation concepts for all aircraft wake-class combinations. A simple first-order difference model was developed to enable the computation of wake parameter estimates for aircraft models having weight, wingspan and speed characteristics similar to those of the nine aircraft modeled in this work.

  2. Design of a Simplified Closed Brayton Cycle for a Space Reactor Application

    SciTech Connect

    Guimaraes, Lamartine N. F.; Camillo, Giannino Ponchio; Placco, Guilherme Moreira

    2009-03-16

    The Nuclear Energy Division (ENU) of the Institute for Advanced Studies (IEAv) has started a preliminary design study for a Closed Brayton Cycle Loop (CBCL) aimed at a space reactor application. The main objectives of the study are: 1) to establish a starting concept for the CBCL components specifications, and 2) to build a demonstrative simulator of CBCL. This preliminary design study is been developed around the NOELLE 60290 turbo machine. The actual nuclear reactor study is being conducted independently. Because of that, a conventional heat source is being used for the CBCL, in this preliminary design phase. This paper describes details of the CBCL mechanical design and the steady state simulator of the CBCL operating with NOELLE 60290 turbo machine. In principle, several gases are being considered as working fluid, as for instance: air, helium, nitrogen, CO2 and gas mixtures such as helium and xenon. However, for this first application pure helium will be used as working fluid. Simplified models of heat and mass transfer were developed to simulate thermal components. A new graphical interface was developed for the simulator to display the thermal process variables in steady state and to keep track of the modifications being implemented at the NOELLE 60290 turbo machine in order to build the CBCL. A set of new results are being produced. These new results help to establish the hot and cold source geometry allowing for price estimating costs for building the actual device. These fresh new results will be presented and discussed.

  3. Parallel Operation of Multiple Closely Spaced Small Aspect Ratio Rod Pinches

    SciTech Connect

    Harper-Slaboszewicz, Victor J.; Leckbee, Joshua; Bennett, Nichelle; Madrid, Elizabeth A.; Rose, David V.; Thoma, Carsten; Welch, Dale R.; Lake, Patrick W.; McCourt, Andrew L.

    2014-12-10

    A series of simulations and experiments to resolve questions about the operation of arrays of closely spaced small aspect ratio rod pinches has been performed. Design and post-shot analysis of the experimental results are supported by 3D particle-in-cell simulations. Both simulations and experiments support these conclusions. Penetration of current to the interior of the array appears to be efficient, as the current on the center rods is essentially equal to the current on the outer rods. Current loss in the feed due to the formation of magnetic nulls was avoided in these experiments by design of the feed surface of the cathode and control of the gap to keep the electric fields on the cathode below the emission threshold. Some asymmetry in the electron flow to the rod was observed, but the flow appeared to symmetrize as it reached the end of the rod. Interaction between the rod pinches can be controlled to allow the stable and consistent operation of arrays of rod pinches.

  4. Native Defect Control of CdTe Thin Film Solar Cells by Close-Spaced Sublimation

    NASA Astrophysics Data System (ADS)

    Okamoto, Tamotsu; Kitamoto, Shinji; Yamada, Akira; Konagai, Makoto

    2001-05-01

    The control of native defects in the CdTe thin film solar cells was investigated using a novel source for close-spaced sublimation (CSS) process which was prepared by vacuum evaporation with elemental Cd and Te (evaporated source). The evaporated sources were prepared on glass substrates at room temperature, and the Cd/Te ratio was controlled by varying the Cd and Te beam equivalent pressures. In the cells using the Te-rich source, the conversion efficiency was less than 0.2% because of the extremely low shunt resistance. On the other hand, a conversion efficiency above 15% was obtained by using the Cd-rich source. Capacitance-voltage (C-V) characteristics revealed that the acceptor concentration in the CdTe layer increased with increasing Cd/Te ratio of the evaporated source. Furthermore, photoluminescence spectra implied that the formation of the Cd vacancies in the CdTe layer was suppressed using the Cd-rich source.

  5. Quasars in the COSMOS Field

    NASA Astrophysics Data System (ADS)

    Prescott, M. K. M.; Impey, C. D.; Cool, R. J.; Scoville, N. Z.

    2006-06-01

    We obtained medium-resolution spectra of 336 quasar candidates in the COSMOS HST Treasury field using the MMT 6.5 m telescope and the Hectospec multiobject spectrograph. Candidates were drawn from the Sloan Digital Sky Survey (SDSS) DR1 catalog using quasar flags set by the SDSS multicolor quasar target selection algorithm. In this paper we present our discovery spectra from 1.39 deg2 (69.5% of the COSMOS field) and a discussion of the selection method and yields. We confirmed 95 quasars, including at least two BAL quasars; 80 of these are new quasars that do not appear in previous quasar confirmation follow-up studies. The candidates additionally included 184 compact emission-line galaxies, a third of which are likely type 2 AGNs, and 12 stars. The quasars span a range in magnitude of 18.3quasar surface density from SDSS color selection of 102 deg-2 down to g=22.5 over the entire COSMOS field. This work is the first step toward the eventual goal of setting up a grid of quasar absorption line probes of the 2 deg2 field and of conducting a complete census of supermassive black holes in this well-studied survey region. The total quasar count at the conclusion of this study is 139, making COSMOS one of the most densely sampled regions of sky where a grid of quasar sight lines can be used to probe the intervening volume.

  6. Fifty Years of Quasars: Physical Insights and Potential for Cosmology

    NASA Astrophysics Data System (ADS)

    Sulentic, J. W.; Marziani, P.; Dultzin, D.; D'Onofrio, M.; del Olmo, A.

    2014-12-01

    Last year (2013) was more or less the 50th anniversary of the discovery of quasars. It is an interesting time to review what we know (and don't know) about them both empirically and theoretically. These compact sources involving line emitting plasma show extraordinary luminosities extending to one thousand times that of our Milky Way in emitting volumes of a few solar system diameters (log Lboi= 44.0 - 48.0 erg s-1: D=1-3 light months ~ 103 - 104 gravitational radii). The advent of 8-10 meter class telescopes enables us to study them spectroscopically in ever greater detail. In 2000 we introduced a 4D Eigenvector 1 parameters space involving optical, UV and X- ray measures designed to serve as a 4D equivalent of the 2D H-R diagram so important for depicting the diversity of stellar types and evolutionary states. This diagram has revealed a principal sequence of quasars distinguished by Eddington ratio (proportional to the accretion rate per unit mass). Thus while stellar differences are primarily driven by the mass of a star, quasar differences are apparently driven by the ratio of luminosity-to-mass. Out of this work has emerged the concept of two quasars populations A and B separated at Eddington ratio around 0.2 which maximizes quasar multispectral differences. The mysterious 8% of quasars that are radio-loud belong to population B which are the lowest accretors with the largest black hole masses. Finally we consider the most extreme population A quasars which are the highest accretors and in some cases are among the youngest quasars. We describe how these sources might be exploited as standard candles for cosmology.

  7. Orbital stability of systems of closely-spaced planets, II: configurations with coorbital planets

    NASA Astrophysics Data System (ADS)

    Smith, Andrew W.; Lissauer, Jack J.

    2010-08-01

    We numerically investigate the stability of systems of 1 {M_{oplus}} planets orbiting a solar-mass star. The systems studied have either 2 or 42 planets per occupied semimajor axis, for a total of 6, 10, 126, or 210 planets, and the planets were started on coplanar, circular orbits with the semimajor axes of the innermost planets at 1 AU. For systems with two planets per occupied orbit, the longitudinal initial locations of planets on a given orbit were separated by either 60° (Trojan planets) or 180°. With 42 planets per semimajor axis, initial longitudes were uniformly spaced. The ratio of the semimajor axes of consecutive coorbital groups in each system was approximately uniform. The instability time for a system was taken to be the first time at which the orbits of two planets with different initial orbital distances crossed. Simulations spanned virtual times of up to 1 × 108, 5 × 105, and 2 × 105 years for the 6- and 10-planet, 126-planet, and 210-planet systems, respectively. Our results show that, for a given class of system (e.g., five pairs of Trojan planets orbiting in the same direction), the relationship between orbit crossing times and planetary spacing is well fit by the functional form log( t c / t 0) = b β + c, where t c is the crossing time, t 0 = 1 year, β is the separation in initial orbital semimajor axis (in terms of the mutual Hill radii of the planets), and b and c are fitting constants. The same functional form was observed in the previous studies of single planets on nested orbits (Smith and Lissauer 2009). Pairs of Trojan planets are more stable than pairs initially separated by 180°. Systems with retrograde planets (i.e., some planets orbiting in the opposite sense from others) can be packed substantially more closely than can systems with all planets orbiting in the same sense. To have the same characteristic lifetime, systems with 2 or 42 planets per orbit typically need to have about 1.5 or 2 times the orbital separation as

  8. Physiological Disorders in Closed Environment-Grown Crops for Space Life Support

    NASA Astrophysics Data System (ADS)

    Wheeler, Raymond; Morrow, Robert

    Crop production for life support systems in space will require controlled environments where temperature, humidity, CO2, and light might differ from natural environments where plants evolved. Physiological disorders, i.e., abnormal plant growth and development, can occur under these controlled environments. Among the most common of these disorders are Ca deficiency injuries such as leaf tipburn (e.g., lettuce), blossom-end-rot in fruits (e.g., tomato and pepper), and internal tissue necrosis in fruits or tubers (e.g., cucumber and potato). Increased Ca nutrition to the plants typically has little effect on these disorders, but slowing overall growth or providing better air circulation to increase transpiration can be effective. A second common disorder is oedema or intumescence, which appears as callus-like growth or galls on leaves (e.g., sweetpotato, potato, pepper, and tomato). This disorder can be reduced by increasing the near UV radiation ( 300-400 nm) to the plants. Leaf injury and necrosis can occur under long photoperiods (e.g., tomato, potato, and pepper) and at super-elevated (i.e., ¿ than 4000 mol mol-1) CO2 concentrations (e.g., soybean, potato, and radish), and these can be managed by reducing the photoperiod and CO2 concentration, respectively. Lack of blue light in the spectrum (e.g., under red LEDs or LPS lamps) can result in leggy growth and/or leaves lacking in chlorophyll (e.g., wheat, bean, and radish). Volatile organic compounds (VOCs), most commonly ethylene, can accumulate in tightly closed systems and result in a variety of negative responses. Most of these disorders can be mitigated by altering the environmental set-points or by using more resistant cultivars.

  9. Pilot Non-Conformance to Alerting System Commands During Closely Spaced Parallel Approaches

    NASA Technical Reports Server (NTRS)

    Pritchett, Amy Ruth; Hansman, R. John; Corker, Kevin (Technical Monitor)

    1997-01-01

    Cockpit alerting systems monitor potentially hazardous situations, both inside and outside the aircraft. When a hazard is projected to occur, the alerting system displays alerts and/or command decisions to the pilot. However, pilots have been observed to not conform to alerting system commands by delaying their response or by not following the automatic commands exactly. This non-conformance to the automatic alerting system can reduce its benefit. Therefore, a need exists to understand the causes and effects of pilot non-conformance in order to develop automatic alerting systems whose commands the pilots are more likely to follow. These considerations were examined through flight simulator evaluations of the collision avoidance task during closely spaced parallel approaches. This task provided a useful case-study because the effects of non-conformance can be significant, given the time-critical nature of the task. A preliminary evaluation of alerting systems identified non-conformance in over 40% of the cases and a corresponding drop in collision avoidance performance. A follow-on experiment found subjects' alerting and maneuver selection criteria were consistent with different strategies than those used by automatic systems, indicating the pilot may potentially disagree with the alerting system if the pilot attempts to verify automatic alerts and commanded avoidance maneuvers. A final experiment found supporting automatic alerts with the explicit display of its underlying criteria resulted in more consistent subject reactions. In light of these experimental results, a general discussion of pilot non-conformance is provided. Contributing factors in pilot non-conformance include a lack of confidence in the automatic system and mismatches between the alerting system's commands and the pilots' own decisions based on the information available to them. The effects of non-conformance on system performance are discussed. Possible methods of reconciling mismatches are

  10. CdZnS thin films sublimated by closed space using mechanical mixing: A new approach

    NASA Astrophysics Data System (ADS)

    Mahmood, Waqar; Shah, Nazar Abbas

    2014-06-01

    Cadmium sulfide (CdS) is a prominent material for its tunable band gap used as a window layer in II-VI semiconductor solar cells. The light trapping capability of window layer is one of the powerful tools to enhance the efficiency of the cell. CdS and zinc (Zn) powders were mixed mechanically with different weight percents to make CdZnS (CZS) powder. CZS was deposited onto an ultrasonically cleaned glass substrate using close spaced sublimation (CSS) technique. CZS as-deposited thin films were characterized for structural, surface morphology with energy dispersive X-rays (EDX) and optical properties for the use of window layer in CdS/CdTe based solar cells. The different Zn concentrations in CZS played a vital role on crystallite size in structural analysis and optical properties e.g. transmission, absorption coefficient and energy band gap, etc. The crystallite size of as-deposited CZS thin films were increased as Zn concentration was increased up to certain value. The energy band gap varies from 2.42 eV to 2.57 eV for as-deposited CZS thin films with increasing Zn concentrations and surface morphology changes also. These changes were occurred due to zinc diffusion in CdS thin films. An angle resolved transmission data was taken to check the behavior of CdS and CZS thin film at different angles. A comparative study was carried out between CdS thin films and CZS thin films for the use of good window layer material.

  11. Experimental Study of Collision Detection Schema Used by Pilots During Closely Spaced Parallel Approaches

    NASA Technical Reports Server (NTRS)

    Pritchett, Amy R.; Hansman, R. John

    1996-01-01

    An experimental flight simulator study was conducted to examine the mental alerting logic and thresholds used by subjects to issue an alert and execute an avoidance maneuver. Subjects flew a series of autopilot landing approaches with traffic on a closely-spaced parallel approach; during some runs, the traffic would deviate towards the subject and the subject was to indicate the point when they recognized the potential traffic conflict, and then indicate a direction of flight for an avoidance maneuver. A variety of subjects, including graduate students, general aviation pilots and airline pilots, were tested. Five traffic displays were evaluated, with a moving map TCAS-type traffic display as a baseline. A side-task created both high and low workload situations. Subjects appeared to use the lateral deviation of the intruder aircraft from its approach path as the criteria for an alert regardless of the display available. However, with displays showing heading and/or trend information, their alerting thresholds were significantly lowered. This type of range-only schema still resulted in many near misses, as a high convergence rate was often established by the time of the subject's alert. Therefore, the properties of the intruder's trajectory had the greatest effect on the resultant near miss rate; no display system reliably caused alerts timely enough for certain collision avoidance. Subjects' performance dropped significantly on a side-task while they analyzed the need for an alert, showing alert generation can be a high workload situation at critical times. No variation was found between subjects with and with out piloting experience. These results suggest the design of automatic alerting systems should take into account the range-type alerting schema used by the human, such that the rationale for the automatic alert should be obvious to, and trusted by, the operator. Although careful display design may help generate pilot/automation trust, issues such as user non

  12. Behind the Photos and the Tears: Media Images, Neoliberal Discourses, Racialized Constructions of Space and School Closings in Chicago

    ERIC Educational Resources Information Center

    Allweiss, Alexandra; Grant, Carl A.; Manning, Karla

    2015-01-01

    This critical article provides insights into how media frames influence our understandings of school reform in urban spaces by examining images of students during the 2013 school closings in Chicago. Using visual framing analysis and informed by framing theory and critiques of neoliberalism we seek to explore two questions: (1) What role do media…

  13. The ecology of microorganisms in a small closed system: Potential benefits and problems for space station

    NASA Technical Reports Server (NTRS)

    Rodgers, E. B.

    1986-01-01

    The inevitble presence on the space station of microorganisms associated with crew members and their environment will have the potential for both benefits and a range of problems including illness and corrosion of materials. This report reviews the literature presenting information about microorganisms pertinent to Environmental Control and Life Support (ECLS) on the space station. The perspective of the report is ecological, viewing the space station as an ecosystem in which biological relationships are affected by factors such as zero gravity and by closure of a small volume of space. Potential sites and activities of microorganisms on the space station and their environmental limits, microbial standards for the space station, monitoring and control methods, effects of space factors on microorganisms, and extraterrestrial contamination are discussed.

  14. DISCOVERING THE MISSING 2.2 < z < 3 QUASARS BY COMBINING OPTICAL VARIABILITY AND OPTICAL/NEAR-INFRARED COLORS

    SciTech Connect

    Wu Xuebing; Wang Ran; Bian Fuyan; Jiang Linhua; Fan Xiaohui; Schmidt, Kasper B.

    2011-09-15

    The identification of quasars in the redshift range 2.2 < z < 3 is known to be very inefficient because the optical colors of such quasars are indistinguishable from those of stars. Recent studies have proposed using optical variability or near-infrared (near-IR) colors to improve the identification of the missing quasars in this redshift range. Here we present a case study combining both methods. We select a sample of 70 quasar candidates from variables in Sloan Digital Sky Survey (SDSS) Stripe 82, which are non-ultraviolet excess sources and have UKIDSS near-IR public data. They are clearly separated into two parts on the Y - K/g - z color-color diagram, and 59 of them meet or lie close to a newly proposed Y - K/g - z selection criterion for z < 4 quasars. Of these 59 sources, 44 were previously identified as quasars in SDSS DR7, and 35 of them are quasars at 2.2 < z < 3. We present spectroscopic observations of 14 of 15 remaining quasar candidates using the Bok 2.3 m telescope and the MMT 6.5 m telescope, and successfully identify all of them as new quasars at z = 2.36-2.88. We also apply this method to a sample of 643 variable quasar candidates with SDSS-UKIDSS nine-band photometric data selected from 1875 new quasar candidates in SDSS Stripe 82 given by Butler and Bloom based on the time-series selections, and find that 188 of them are probably new quasars with photometric redshifts at 2.2 < z < 3. Our results indicate that the combination of optical variability and optical/near-IR colors is probably the most efficient way to find 2.2 < z < 3 quasars and is very helpful for constructing a complete quasar sample. We discuss its implications for ongoing and upcoming large optical and near-IR sky surveys.

  15. On the alignment of quasars

    NASA Astrophysics Data System (ADS)

    Zhu, X.-F.

    1986-06-01

    Taking the two Savage-Bolton 5 deg x 5 deg regions of optical quasar patrol as samples, a systematic analysis of the number of aligned quasars was made and compared with the random data generated by Monte Carlo method. The statistical result is that, at least for these two samples, there is no clear evidence for alignment.

  16. On the alignment of quasars

    NASA Astrophysics Data System (ADS)

    Zhu, Xing-fen

    1986-06-01

    Taking the two Savage-Bolton 5° × 5° regions of optical quasar patrol as samples, I made a systematic analysis of the number of aligned quasars and compared with the random data generated by Monte Carlo method. The statistical result is that, at least for these two samples, there is no clear evidence for alignment.

  17. The Circumgalactic Medium of Quasars

    NASA Astrophysics Data System (ADS)

    Hennawi, Joe

    2014-07-01

    I will argue that observations of the diffuse gas in the outskirts of quasar host galaxies, or the so called circumgalactic medium, are essential for understanding how luminous quasars evolve in a cosmological context. Such observations also provide a fruitful comparison to theory, because hydrodynamics at moderate overdensities is much easier to simulate than the complicated processes which trigger quasar activity. A novel technique will be introduced, whereby a foreground quasar can be studied in absorption against a background quasar, resolving scales as small as 30 kpc. This experiment reveals a rich absorption spectrum which contains a wealth of information about the physical conditions of diffuse gas around quasars. Hydrodynamical simulations of the massive dark matter halos which host luminous quasars under predict the amount of cool gas observed in quasar environs by a large factor, challenging our understanding of how massive galaxies form. I will also discuss a very sensitive search for Ly-alpha emission from the same gas which we study in absorption.

  18. QUASAR PG1115+080 AND GRAVITATIONAL LENS

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Left: The light from the single quasar PG 1115+080 is split and distorted in this infrared image. PG 1115+080 is at a distance of about 8 billion light years in the constellation Leo, and it is viewed through an elliptical galaxy lens at a distance of 3 billion light years. The NICMOS frame is taken at a wavelength of 1.6 microns and it shows the four images of the quasar (the two on the left are nearly merging) surrounding the galaxy that causes the light to be lensed. The quasar is a variable light source and the light in each image travels a different path to reach the Earth. The time delay of the variations allows the distance scale to be measured directly. The linear streaks on the image are diffraction artifacts in the NICMOS instrument (NASA/Space Telescope Science Institute). Right: In this NICMOS image, the four quasar images and the lens galaxy have been subtracted, revealing a nearly complete ring of infrared light. This ring is the stretched and amplified starlight of the galaxy that contains the quasar, some 8 billion light years away. (NASA/Space Telescope Science Institute). Credit: Christopher D. Impey (University of Arizona)

  19. Photometric Monitoring of Quasars with Kepler

    NASA Astrophysics Data System (ADS)

    Unwin, Stephen C.; Wehrle, A. E.; Wiita, P. J.; Revalski, M.; Silano, D.; Sprague, D.; Di Lorenzo, P.

    2013-01-01

    We have observed the photometric variability of four flat-spectrum radio quasars, and one radio galaxy (Cyg A) with Kepler, since mid-2010. Kepler’s ability to observe uninterrupted for very extended durations provides a unique opportunity to obtain very long time sequences on active galactic nuclei, something that is hard to do even with dedicated ground-based telescope networks. It allows us to examine these light curves for variability on timescales from hours to weeks, and to probe the physical processes involved in accretion around the central black hole and the organization of some of that energy into jets that ultimately power double-lobed radio sources. Kepler was designed to detect exoplanet transits of stars, and the data analysis pipeline is highly optimized for that purpose. We cannot use the standard analysis tools for the quasi-random variability in quasars, so we re-analysed the raw data, and overcame some of the challenges in calibrating these light curves. We briefly discuss some of the issues in producing calibrated light curves for long timescales. For each quasar we computed power spectra, and found power-law slopes of around -2 for most. Although sensitive to quasi-periodic variations, we did not find any convincing evidence for periodicity in any of our targets. This research was carried out, in part, at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Copyright 2012. California Institute of Technology. Government sponsorship acknowledged.

  20. CONSTRAINTS ON THE FAINT END OF THE QUASAR LUMINOSITY FUNCTION AT z {approx} 5 IN THE COSMOS FIELD

    SciTech Connect

    Ikeda, H.; Matsuoka, K.; Kajisawa, M.; Nagao, T.; Taniguchi, Y.; Shioya, Y.; Enoki, M.; Capak, P.; Masters, D.; Scoville, N. Z.; Civano, F.; Koekemoer, A. M.; Morokuma, T.; Salvato, M.; Schinnerer, E.

    2012-09-10

    We present the result of our low-luminosity quasar survey in the redshift range of 4.5 {approx}< z {approx}< 5.5 in the COSMOS field. Using the COSMOS photometric catalog, we selected 15 quasar candidates with 22 < i' < 24 at z {approx} 5 that are {approx}3 mag fainter than the Sloan Digital Sky Survey quasars in the same redshift range. We obtained optical spectra for 14 of the 15 candidates using FOCAS on the Subaru Telescope and did not identify any low-luminosity type-1 quasars at z {approx} 5, while a low-luminosity type-2 quasar at z {approx} 5.07 was discovered. In order to constrain the faint end of the quasar luminosity function at z {approx} 5, we calculated the 1{sigma} confidence upper limits of the space density of type-1 quasars. As a result, the 1{sigma} confidence upper limits on the quasar space density are {Phi} < 1.33 Multiplication-Sign 10{sup -7} Mpc{sup -3} mag{sup -1} for -24.52 < M{sub 1450} < -23.52 and {Phi} < 2.88 Multiplication-Sign 10{sup -7} Mpc{sup -3} mag{sup -1} for -23.52 < M{sub 1450} < -22.52. The inferred 1{sigma} confidence upper limits of the space density are then used to provide constraints on the faint-end slope and the break absolute magnitude of the quasar luminosity function at z {approx} 5. We find that the quasar space density decreases gradually as a function of redshift at low luminosity (M{sub 1450} {approx} -23), being similar to the trend found for quasars with high luminosity (M{sub 1450} < -26). This result is consistent with the so-called downsizing evolution of quasars seen at lower redshifts.

  1. Being a Closely Spaced Second Child Is Not So Bad. Child-Spacing Effects on Intelligence, Personality, and Social Competence.

    ERIC Educational Resources Information Center

    Nuttall, Ronald L.; Nuttall, Ena Vazquez

    This study focuses on the effects of family size and spacing on intellectual, social, and personality development of children. The sample consisted of 533 suburban, middle class, large family (five or more) and small two child family children. The children, 233 boys and 300 girls, were teenagers attending either junior or senior high school.…

  2. Characterizing Quasar Outflows III: SEDs, and Bolometric Luminosity Estimates

    NASA Astrophysics Data System (ADS)

    Richmond, Joseph; Robbins, J. M.; Ganguly, R.; Stark, M. A.; Christenson, D. H.; Derseweh, J. A.; Townsend, S. L.

    2012-05-01

    Galaxy evolution models have shown that quasars are a crucial ingredient in the evolution of massive galaxies. Outflows play a key role in the story of quasars and their host galaxies, by helping regulate the accretion process, the star-formation rate and mass of the host galaxy (i.e., feedback). The prescription for modeling outflows as a contributor to feedback requires knowledge of the outflow velocity, geometry, and column density. In particular, we need to understand how these depend on physical parameters and how much is determined stochastically (and with what distribution). For this purpose, we are examining a sample of 11000 z=1.7-2.0 quasars from the Sloan Digital Sky Survey. This redshift range permits the following from the SDSS spectra: (1) separation of objects that do and do not exhibit outflows; (2) classification/measurement of outflow properties (ionization, velocity, velocity width); and (3) measurements of UV emission line and continuum parameters. In this poster, we add photometry from both the Two Micron All-Sky Survey (2MASS) and from the Wide-Field Infrared Survey Explorer (WISE). 2MASS photometry covers the rest-frame optical regime of these qusars, while the WISE W1, W2, and W3 bands cover the rest-frame wavelength ranges 0.9-1.27 micron, 1.35-1.75 micron, and 2.52-5.51 micron, respectively. The preliminary release of WISE data cover 3800 of our quasars. In an accompnying poster, we have subjectively divided these quasars into four categories: broad absorption-line quasars (2700 objects), associated absorption-line quasars (1700 objects), reddened quasars (160 objects), and unabsorbed/unreddened quasars (6300 objects). Here, we present average SEDs for these subsamples, estimates of bolometric luminosity, and explore changes in SED based on both outflow properties and quasar physical properties. This material is based upon work supported by the National Aeronautics and Space Administration under Grant No. 09-ADP09-0016 issued through the

  3. Studies of Quasar Outflows

    NASA Technical Reports Server (NTRS)

    Arav, Nahum

    2002-01-01

    The main aim of this research program is to determine the ionization equilibrium and abundances in quasar outflows. Especially in the broad absorption line QSO PG 0946+301. We find that the outflow's metalicity is consistent with being solar, while the abundance ratio of phosphorus to other metals is at least ten times solar. These findings are based on diagnostics that are not sensitive to saturation and partial covering effects in the BALs (Broad Adsorption Lines), which considerably weakened previous claims for enhanced metalicity. Ample evidence for these effects is seen in the spectrum.

  4. 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.

  5. The Hubble Space Telescope Quasar Absorption Line Key Project. XIV. The Evolution of Lyα Absorption Lines in the Redshift Interval z = 0-1.5

    NASA Astrophysics Data System (ADS)

    Weymann, Ray J.; Jannuzi, Buell T.; Lu, Limin; Bahcall, John N.; Bergeron, Jacqueline; Boksenberg, Alec; Hartig, George F.; Kirhakos, Sofia; Sargent, W. L. W.; Savage, Blair D.; Schneider, Donald P.; Turnshek, David A.; Wolfe, Arthur M.

    1998-10-01

    either line misidentification or incomplete spectral coverage. Considering the insensitivity of the equivalent width to large changes in the column density for saturated lines, we suggest that this result is probably attributable to rapid evolution of the very highest column density systems, rather than real differences in metallicity. We find evidence that the rate of evolution increases with increasing equivalent width. We compare our results for the variation of line density with redshift to recent numerical simulations of Lyα absorbers, in particular, to those of Riediger, Petitjean, & Mucket, which extend to zero redshift. We find fairly good agreement between these simulations and our results, though the rapid evolution we find in the Lyα systems containing heavy element ions is not predicted in their models. We speculate that these heavy element-containing Lyα systems involve those clouds closely associated with galaxies, whose column densities are too high and whose sizes are too small to be included in the Riediger et al. simulations. Our results for Lyα lines at the high end of our equivalent width distribution are compatible with the recent analysis of the absorber-galaxy correlation by Chen et al. For the weaker lines, however, our results suggest that whatever association exists between absorbers and galaxies is different from that for the stronger lines. We conclude with some suggestions for further observations. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  6. Potential Sedimentary Evidence of Two Closely Spaced Tsunamis on the West Coast of Aceh, Indonesia

    NASA Astrophysics Data System (ADS)

    Monecke, Katrin; Meilianda, Ella; Rushdy, Ibnu; Moena, Abudzar; Yolanda, Irvan P.

    2016-04-01

    Recent research in the coastal regions of Aceh, Indonesia, an area that was largely affected by the 2004 Sumatra Andaman earthquake and ensuing Indian Ocean tsunami, suggests the possibility that two closely spaced tsunamis occurred at the turn of the 14th to 15th century (Meltzner et al., 2010; Sieh et al., 2015). Here, we present evidence of two buried sand layers in the coastal marshes of West Aceh, possibly representing these penultimate predecessors of the 2004 tsunami. We discovered the sand layers in an until recently inaccessible area of a previously studied beach ridge plain about 15 km North of Meulaboh, West Aceh. Here, the 2004 tsunami left a continuous, typically a few cm thick sand sheet in the coastal hinterland in low-lying swales that accumulate organic-rich deposits and separate the sandy beach ridges. In keeping with the long-term progradation of the coastline, older deposits have to be sought after further inland. Using a hand auger, the buried sand layers were discovered in 3 cores in a flooded and highly vegetated swale in about 1 km distance to the shoreline. The pair of sand layers occurs in 70-100 cm depth and overlies 40-60 cm of dark-brown peat that rests on the basal sand of the beach ridge plain. The lower sand layer is only 1-6 cm thick, whereas the upper layer is consistently thicker, measuring 11-17 cm, with 8-14 cm of peat in between sand sheets. Both layers consist of massive, grey, medium sand and include plant fragments. They show very sharp upper and lower boundaries clearly distinguishing them from the surrounding peat and indicating an abrupt depositional event. A previously developed age model for sediments of this beach ridge plain suggest that this pair of layers could indeed correlate to a nearby buried sand sheet interpreted as tsunamigenic and deposited soon after 1290-1400AD (Monecke et al., 2008). The superb preservation at this new site allows the clear distinction of two depositional events, which, based on a first

  7. Neutrinos from flat-spectrum radio quasars

    NASA Technical Reports Server (NTRS)

    Mannheim, K.; Stanev, T.; Biermann, P. L.

    1992-01-01

    The GRO observation (Hartman et al., 1992) of a very strong flux of gamma rays with an energy index close to 2 from the distant quasar 3C279 and other extragalactic flat-spectrum radio sources is in very good agreement with models that advocate the important role of very high energy protons and nuclei in the energy transport in AGN. Protons and nuclei cool by interactions on the nonthermal fields in the nuclear jet of the AGN and generate gamma ray and neutrino fluxes. Ultra high energy neutrinos could be observed with sensitive air shower experiments in outbursts as powerful as the one seen by GRO.

  8. A Wealth of Dust Grains in Quasar Winds

    NASA Technical Reports Server (NTRS)

    2007-01-01

    [figure removed for brevity, see original site] Click on image for larger poster version

    This plot of data captured by NASA's Spitzer Space Telescope reveals dust entrained in the winds rushing away from a quasar, or growing black hole. The quasar, called PG2112+059, is located deep inside a galaxy 8 billion light-years away. Astronomers believe the dust might have been forged in the winds, which would help explain where dust in the very early universe came from.

    The data were captured by Spitzer's infrared spectrograph, an instrument that splits apart light from the quasar into a spectrum that reveals telltale signs of different minerals. Each type of mineral, or dust grain, has a unique signature, as can be seen in the graph, or spectrum, above.

    The strongest features are from the mineral amorphous olivine, or glass (purple); the mineral forsterite found in sand (blue); and the mineral corundum found in rubies (light blue). The detection of forsterite and corundum is highly unusual in galaxies without quasars. Therefore, their presence is a key clue that these grains might have been created in the quasar winds and not by dying stars as they are in our Milky Way galaxy. Forsterite is destroyed quickly in normal galaxies by radiation, so it must be continually produced to be detected by Spitzer.

    Corundum is hard, and provides a seed that softer, more common minerals usually cover up. As a result, corundum is usually not seen in spectra of galaxies. Since Spitzer did detect the mineral, it is probably forming in a clumpy environment, which is expected in quasar winds. All together, the signatures of the unusual minerals in this spectrum point towards dust grains forming in the winds blowing away from quasars.

  9. Effects of a Closed Space Environment on Gene Expression in Hair Follicles of Astronauts in the International Space Station.

    PubMed

    Terada, Masahiro; Seki, Masaya; Takahashi, Rika; Yamada, Shin; Higashibata, Akira; Majima, Hideyuki J; Sudoh, Masamichi; Mukai, Chiaki; Ishioka, Noriaki

    2016-01-01

    Adaptation to the space environment can sometimes pose physiological problems to International Space Station (ISS) astronauts after their return to earth. Therefore, it is important to develop healthcare technologies for astronauts. In this study, we examined the feasibility of using hair follicles, a readily obtained sample, to assess gene expression changes in response to spaceflight adaptation. In order to investigate the gene expression changes in human hair follicles during spaceflight, hair follicles of 10 astronauts were analyzed by microarray and real time qPCR analyses. We found that spaceflight alters human hair follicle gene expression. The degree of changes in gene expression was found to vary among individuals. In some astronauts, genes related to hair growth such as FGF18, ANGPTL7 and COMP were upregulated during flight, suggesting that spaceflight inhibits cell proliferation in hair follicles. PMID:27029003

  10. Effects of a Closed Space Environment on Gene Expression in Hair Follicles of Astronauts in the International Space Station

    PubMed Central

    Terada, Masahiro; Seki, Masaya; Takahashi, Rika; Yamada, Shin; Higashibata, Akira; Majima, Hideyuki J.; Sudoh, Masamichi; Mukai, Chiaki; Ishioka, Noriaki

    2016-01-01

    Adaptation to the space environment can sometimes pose physiological problems to International Space Station (ISS) astronauts after their return to earth. Therefore, it is important to develop healthcare technologies for astronauts. In this study, we examined the feasibility of using hair follicles, a readily obtained sample, to assess gene expression changes in response to spaceflight adaptation. In order to investigate the gene expression changes in human hair follicles during spaceflight, hair follicles of 10 astronauts were analyzed by microarray and real time qPCR analyses. We found that spaceflight alters human hair follicle gene expression. The degree of changes in gene expression was found to vary among individuals. In some astronauts, genes related to hair growth such as FGF18, ANGPTL7 and COMP were upregulated during flight, suggesting that spaceflight inhibits cell proliferation in hair follicles. PMID:27029003

  11. Do quasars evolve over cosmological time scales?

    NASA Astrophysics Data System (ADS)

    Wampler, E. J.; Ponz, D.

    Systematic biases that are redshift dependent can influence the optical discovery of quasars and the evolution laws derived from counts of quasars. New data and their interpretation for quasars brighter than MB = -24 in the Palomar Bright Quasar Survey (BQS) (Schmidt and Green, 1983) are consistent with no evolution. A comparison of BQS quasars with the brightest quasars from the CTIO Schmidt Telescope Survey (Osmer and Smith, 1980) shows that if q(0) is near zero, the comoving density of bright quasars in a Friedmann cosmology is about 15 times higher for the CTIO survey quasars (mean z of about 2.8) than for the BQS quasars (mean z of about 1.8). In this case spectral evolution is also required since the CTIO quasars have stronger CIV 1548 A lines than the BQS quasars of similar luminosity. Alternatively, if q(0) is taken to be near 1, the CTIO survey quasars would then have a lower luminosity than the BQS quasars and these data would be consistent with no evolution. Strong CIV 1548 A lines for the CTIO quasars would then fit the general correlation between absolute quasar luminosity and emission line strength (Wampler, Gaskell, Burke and Baldwin, 1984).

  12. VTOL in ground effect flows for closely spaced jets. [to predict pressure and upwash forces on aircraft structures

    NASA Technical Reports Server (NTRS)

    Migdal, D.; Hill, W. G., Jr.; Jenkins, R. C.

    1979-01-01

    Results of a series of in ground effect twin jet tests are presented along with flow models for closely spaced jets to help predict pressure and upwash forces on simulated aircraft surfaces. The isolated twin jet tests revealed unstable fountains over a range of spacings and jet heights, regions of below ambient pressure on the ground, and negative pressure differential in the upwash flow field. A separate computer code was developed for vertically oriented, incompressible jets. This model more accurately reflects fountain behavior without fully formed wall jets, and adequately predicts ground isobars, upwash dynamic pressure decay, and fountain lift force variation with height above ground.

  13. Automation of closed environments in space for human comfort and safety

    NASA Technical Reports Server (NTRS)

    1991-01-01

    The results of the second year of a three year design project on the automation of the Environmental Control and Life Support System (ECLSS) of the Space Station Freedom (SSF) are presented. The results are applicable to other space missions that require long duration space habitats. A description of conceptual controls which are developed for the Water Recovery and Management (WRM) Subassembly is given. Mathematical modeling of the Air Revitalization (AR) Subassembly is presented. The work done by the Kansas State University NASA/USRA interdisciplinary student design team is concluded with a discussion of the expert system which was developed for the AR Subassembly.

  14. Quasar variability limits on cosmological density of cosmic strings

    SciTech Connect

    Tuntsov, A. V.; Pshirkov, M. S.

    2010-03-15

    We put robust upper limits on the average cosmological density {Omega}{sub s} of cosmic strings based on the variability properties of a large homogeneous sample of Sloan Digital Sky Survey quasars. We search for an excess of characteristic variations of quasar brightness that are associated with string lensing and use the observed distribution of these variations to constrain the density of strings. The limits obtained do not invoke any clustering of strings. They apply to both open segments and closed loops of strings, usefully extend over a wide range of tensions 10{sup -13}quasar intrinsic variability rather than a mere increase in the volume of data.

  15. Towards an ALHAMBRA quasar catalogue

    NASA Astrophysics Data System (ADS)

    Chaves-Montero, J.; Bonoli, S.

    2015-05-01

    We present the steps towards the identification of quasars in the ALHAMBRA fields using only the ALHAMBRA photospectra. The ALHAMBRA survey (Moles et al. 2005, 2008) uses a set of 20 contiguous optical filters and three infrared filtes (J, H, and Ks). The entire coverage of the optical range and the width of the filters (˜ 300 Å) allowed us to detect emission line quasars and to compute their accurate redshifts. Starting from ˜430 000 sources we ended up with a catalogue of 524 quasar candidates with z>0.8 in an area of 2.79 deg^2. To determine the level of galaxy contamination in our sample and the accuracy of the photo-z we performed a crossmatch between spectroscopically identified objects in another surveys and the ALHAMBRA sources, detecting 1 058 galaxies and 205 quasars. After applying our algorithm none of the galaxies was classified as quasar, the accuracy of the quasar photo-z was σ_{NMAD}=0.010, and the level of quasars with photo-z significantly different to their spec-z (outliers) was 3.12 %.

  16. Selective Growth of CdTe on Nano-patterned CdS via Close-Space Sublimation

    NASA Astrophysics Data System (ADS)

    Aguirre, Brandon A.; Zubia, David; Ordonez, Rafael; Anwar, Farhana; Prieto, Heber; Sanchez, Carlos A.; Salazar, Maria T.; Pimentel, Alejandro. A.; Michael, Joseph R.; Zhou, Xiaowang; Mcclure, John C.; Nielson, Gregory N.; Cruz-Campa, Jose L.

    2014-07-01

    Selective-area deposition of CdTe on CdS via close-space sublimation is used to study the effect of window size (2 μm and 300 nm) on grain growth. The basic fabrication procedures for each of the layers (CdS, SiO2, and CdTe) and for achieving selective-area growth are presented. Selective-area growth of both micro- and nano-scale CdTe islands on CdS substrates using close-spaced sublimation is demonstrated. Scanning electron microscopy and electron backscatter diffraction microstructure analysis show that the micro-scale CdTe islands remain polycrystalline. However, when the island size is reduced to 300 nm, single crystal CdTe can be achieved within the windows. The CdTe grains were most often in the (101) orientation for both the micro- and nano-sized CdTe islands.

  17. Differences in Ambient Polycyclic Aromatic Hydrocarbon Concentrations between Streets and Alleys in New York City: Open Space vs. Semi-Closed Space

    PubMed Central

    Lovinsky-Desir, Stephanie; Miller, Rachel L.; Bautista, Joshua; Gil, Eric N.; Chillrud, Steven N.; Yan, Beizhan; Camann, David; Perera, Frederica P.; Jung, Kyung Hwa

    2016-01-01

    Background: Outdoor ambient polycyclic aromatic hydrocarbon (PAH) concentrations are variable throughout an urban environment. However, little is known about how variation in semivolatile and nonvolatile PAHs related to the built environment (open space vs. semi-closed space) contributes to differences in concentrations. Methods: We simultaneously collected 14, two-week samples of PAHs from the outside of windows facing the front (adjacent to the street) open side of a New York City apartment building and the alley, semi-closed side of the same apartment unit between 2007 and 2012. We also analyzed samples of PAHs measured from 35 homes across Northern Manhattan and the Bronx, 17 from street facing windows with a median floor level of 4 (range 2–26) and 18 from alley-facing windows with a median floor level of 4 (range 1–15). Results: Levels of nonvolatile ambient PAHs were significantly higher when measured from a window adjacent to a street (an open space), compared to a window 30 feet away, adjacent to an alley (a semi-closed space) (street geometric mean (GM) 1.32 ng/m3, arithmetic mean ± standard deviation (AM ± SD) 1.61 ± 1.04 ng/m3; alley GM 1.10 ng/m3, AM ± SD 1.37 ± 0.94 ng/m3). In the neighborhood-wide comparison, nonvolatile PAHs were also significantly higher when measured adjacent to streets compared with adjacent to alley sides of apartment buildings (street GM 1.10 ng/m3, AM ± SD 1.46 ± 1.24 ng/m3; alley GM 0.61 ng/m3, AM ± SD 0.81 ± 0.80 ng/m3), but not semivolatile PAHs. Conclusions: Ambient PAHs, nonvolatile PAHs in particular, are significantly higher when measured from a window adjacent to a street compared to a window adjacent to an alley, despite both locations being relatively close to street traffic. This study highlights small-scale spatial variations in ambient PAH concentrations that may be related to the built environment (open space vs. semi-closed space) from which the samples are measured, as well as the relative distance

  18. A new apparatus for multilayer growth by chemical vapor deposition: The sliding-boat close-spaced technique

    NASA Astrophysics Data System (ADS)

    Yoshikawa, Akihiko; Yoshihara, Seiji; Kasai, Haruo; Nishimaki, Masao

    1980-10-01

    A new apparatus for multilayer growth by chemical vapor deposition, the sliding-boat close-spaced tecnique (SBCST), is presented. The structure of the SBCST growth apparatus is quite similar to that of the conventional liquid phase epitaxy sliding-boat. The possibility of obtaining thin multilayer films by SBCST is shown. Preliminary experimental results for its application to the growth of n-CdS/p-InP heterojunction solar cells are also shown.

  19. The optical variability of the quasar 3C 446

    SciTech Connect

    Barbieri, C.; Vio, R.; Cappellaro, E; Turatto, M Padova Osservatorio Astronomico, Padua )

    1990-08-01

    The optical variability of the quasar 3C 446 is investigated using power spectrum and structure function analysis along with a new set of observations that extend the available data till 1989. No contradiction is found between the PS and SF analyses. The presence of the 1540-day periodicity is strengthened by the occurrence of the 1988 luminosity peak, suggesting that the next burst will occur in the northern spring of 1992. The time series of the quasar is nonstationary. The light variations are determined by a sequence of luminosity bursts, mostly regularly spaced in time and lasting up to 2 yr. 25 refs.

  20. A Hubble Diagram for Quasars

    NASA Astrophysics Data System (ADS)

    Risaliti, Guido; Lusso, Elisabeta

    2015-09-01

    We present a new method to test the cosmological model at high z, and measure the cosmological parameters, based on the non-linear correlation between UV and X-ray luminosity in quasars. While the method can be successfully tested with the data available today, a deep X-ray survey matching the future LSST and Euclid quasar catalogs is needed to achieve a high precision. Athena could provide a Hubble diagram for quasar analogous to that available today for supernovae, but extending up to z>6.

  1. HST/COS OBSERVATIONS OF THIRTEEN NEW He II QUASARS

    SciTech Connect

    Syphers, David; Anderson, Scott F.; Zheng Wei; Meiksin, Avery; Schneider, Donald P.; York, Donald G.

    2012-04-15

    The full reionization of intergalactic helium was a major event in the history of the intergalactic medium (IGM), and UV observations of the He II Gunn-Peterson trough allow us to characterize the end of this process at z {approx} 3. Due to intervening hydrogen absorption, quasars allowing such study are rare, with only 33 known in the literature, and most of those are very recent discoveries. We expand on our previous discovery work, and present 13 new He II quasars with redshifts 2.82 < z < 3.77, here selected with {approx}80% efficiency, and including several that are much brighter than the vast majority of those previously known. This is the largest sample of uniformly observed He II quasars covering such a broad redshift range, and they show evidence of IGM opacity increasing with redshift, as expected for the helium reionization epoch. No evidence of He II Ly{alpha} quasar emission is seen in individual or averaged spectra, posing a problem for standard models of the broad-line region. The current rapid advance in the study of He II quasars has been greatly facilitated by the Cosmic Origins Spectrograph on the Hubble Space Telescope, and we discuss the instrumental and other subtleties that must be taken into account in IGM He II observations.

  2. Performance and Mass Modeling Subtleties in Closed-Brayton-Cycle Space Power Systems

    NASA Technical Reports Server (NTRS)

    Barrett, Michael J.; Johnson, Paul K.

    2005-01-01

    Contents include the following: 1. Closed-Brayton-cycle (CBC) thermal energy conversion is one available option for future spacecraft and surface systems. 2. Brayton system conceptual designs for milliwatt to megawatt power converters have been developed 3. Numerous features affect overall optimized power conversion system performance: Turbomachinery efficiency. Heat exchanger effectiveness. Working-fluid composition. Cycle temperatures and pressures.

  3. Opening and Closing Interactive Spaces: Shaping Four-Year-Old Children's Participation in Two English Settings

    ERIC Educational Resources Information Center

    Payler, Jane

    2007-01-01

    This paper draws on an ESRC-funded study (Payler, 2005) of the sociocultural influences on learning processes of 10 four-year-old children in their second year of the Foundation Stage in England (DfEE, 2000). The children, very close in age, were in one of two early years settings: a pre-school playgroup with a largely invisible pedagogy…

  4. FAR-INFRARED PROPERTIES OF TYPE 1 QUASARS

    SciTech Connect

    Hanish, D. J.; Teplitz, H. I.; Capak, P.; Desai, V.; Armus, L.; Brinkworth, C.; Brooke, T.; Colbert, J.; Fadda, D.; Noriega-Crespo, A.; Paladini, R.; Frayer, D.; Huynh, M.; Lacy, M.; Murphy, E.; Scarlata, C.; Shenoy, S.

    2013-05-01

    We use the Spitzer Space Telescope Enhanced Imaging Products and the Spitzer Archival Far-InfraRed Extragalactic Survey to study the spectral energy distributions (SEDs) of spectroscopically confirmed type 1 quasars selected from the Sloan Digital Sky Survey (SDSS). By combining the Spitzer and SDSS data with the Two Micron All Sky Survey, we are able to construct a statistically robust rest-frame 0.1-100 {mu}m type 1 quasar template. We find that the quasar population is well-described by a single power-law SED at wavelengths less than 20 {mu}m, in good agreement with previous work. However, at longer wavelengths, we find a significant excess in infrared luminosity above an extrapolated power-law, along with significant object-to-object dispersion in the SED. The mean excess reaches a maximum of 0.8 dex at rest-frame wavelengths near 100 {mu}m.

  5. Probability distributions for the magnification of quasars due to microlensing

    NASA Technical Reports Server (NTRS)

    Wambsganss, Joachim

    1992-01-01

    Gravitational microlensing can magnify the flux of a lensed quasar considerably and therefore possibly influence quasar source counts or the observed quasar luminosity function. A large number of distributions of magnification probabilities due to gravitational microlensing for finite sources are presented, with a reasonable coverage of microlensing parameter space (i.e., surface mass density, external shear, mass spectrum of lensing objects). These probability distributions were obtained from smoothing two-dimensional magnification patterns with Gaussian source profiles. Different source sizes ranging from 10 exp 14 cm to 5 x 10 exp 16 cm were explored. The probability distributions show a large variety of shapes. Coefficients of fitted slopes for large magnifications are presented.

  6. Application of Closed Loop Optimal Guidance for a Constant Thrust Space Vehicle

    NASA Astrophysics Data System (ADS)

    Rezaei Darestani, Mahdy; Abbasi Mahale, Mahdi

    2016-01-01

    This research presents derivation and implementation of the explicit guidance problem to steer a space vehicle into exo atmospheric phase of flight to develop three-dimensional optimal trajectory. The proposed guidance algorithm is in association with continuous powered flight of the space vehicle in ascent manoeuvre. Stability, accuracy and simplicity of this approach are the improved developments in comparison with the IGM approach. This algorithm uses the calculus of variation method for the two boundary-value injection problem to generate an optimal trajectory of space vehicle with online generation of steering command to inject to any desired orbit. Here the end conditions have been determined as the orbital height, inclination and eccentricity where the initial conditions are fixed. The simulation results are considered which shows the accuracy and simplicity of this method to reach to the desired orbit in minimum fuel.

  7. Automation of closed environments in space for human comfort and safety

    NASA Technical Reports Server (NTRS)

    1990-01-01

    The results are presented of the first year of a three year project on the automation of the Environmental Control and Life Support System (ECLSS) of the Space Station Freedom (SSF). The results are applicable to other future space mission. The work was done by the Kansas State University NASA/USRA interdisciplinary student design team. The six ECLSS subsystems and how they interact are discussed. Proposed control schemes and their rationale are discussed for the Atmosphere Revitalization (AR) subsystem. Finally, a description of the mathematical models for many components of the ECLSS control system is given.

  8. Through BAL Quasars Brightly

    NASA Technical Reports Server (NTRS)

    Chartas, George

    2003-01-01

    We report on an observation of the broad absorption line (BAL) quasar PG 1115+080 performed with the XMM-Newton observatory. Spectral analysis reveals the second case of a relativistic X-ray-absorbing outflow in a BAL quasar. The first case was revealed in a recent observation of APM 08279+5255 with the Chandra X-Ray Observatory. As in the case of APM 08279+5255, the observed flux of PG 1115+080 is greatly magnified by gravitational lensing. The relatively high redshift (z=1.72) of the quasar places the redshifted energies of resonant absorption features in a sensitive portion of the XMM- Newton spectral response. The spectrum indicates the presence of complex low-energy absorption in the 0.2-0.6 keV observed energy band and high-energy absorption in the 2-5 keV observed energy band. The high-energy absorption is best modeled by two Gaussian absorption lines with rest-frame energies of 7.4 and 9.5 keV. Assuming that these two lines axe produced by resonant absorption due to Fe XXV, we infer that the X-ray absorbers are outflowing with velocities of approx. 0.10c and approx. 0.34c respectively. We have detected significant variability of the energies and widths of the X-ray BALs in PG 1115+080 and APM 08279+5255 over timescales of 19 and 1.8 weeks (proper time), respectively. The BAL variability observed from APM 08279+5255 supports our earlier conclusion that these absorbers are most likely launched at relatively small radii of less than 10(exp 16)(Mbh/M8)(sup 1/2) cm. A comparison of the ionization properties and column densities of the low-energy and high-energy absorbers indicates that these absorbers are likely distinct; however, higher spectral resolution is needed to confirm this result. Finally, we comment on prospects for constraining the kinematic and ionization properties of these X-ray BALs with the next generation of X-ray observatories.

  9. Closely spaced nanomagnets by dual e-beam exposure for low-energy nanomagnet logic

    SciTech Connect

    Shah, Faisal A.; Csaba, Gyorgy; Butler, Katherine; Bernstein, Gary H.

    2013-05-07

    The effect of nanomagnet spacing on required clock field has been studied by micromagnetic simulation for supermalloy (Ni{sub 79}Fe{sub 16}Mo{sub 5}) dots with dimensions 90 Multiplication-Sign 60 Multiplication-Sign 20 nm{sup 3} and 120 Multiplication-Sign 60 Multiplication-Sign 20 nm{sup 3}. Reduction of the inter-magnet spacing for both dimensions has resulted in reduction of the required clock field in the simulation. A dual e-beam exposure technique has been developed to allow fabrication of ultra dense features using conventional poly(methylmethacrylate) e-beam resist. Nanomagnet logic (NML) datalines of supermalloy dots with {approx}10 nm and {approx}15 nm spacing have been fabricated using dual e-beam exposure with a 3{sigma} overlay accuracy of {approx}4 nm. Fabricated NML datalines have been characterized using magnetic force microscopy for various clock fields. Datalines of both spacing have shown proper NML functionality with a clock field as low as 60 mT.

  10. Tropospheric gravity waves observed by three closely-spaced ST radars

    NASA Technical Reports Server (NTRS)

    Carter, D. A.; Eriddle, A. C. AFGARELLO, R.ly stable thro; Eriddle, A. C. AFGARELLO, R.ly stable thro

    1985-01-01

    During a 6 week period in 1982, 3 ST (Stratosphere-Troposphere) radars measured horizontal and vertical wavelengths of small scale tropospheric gravity waves. These 50 MHz, vertically-directed radars were located in a trianglar network with approximately 5 km spacing on the southern coast of France at the mouth of the Rhone River during the ALPEX (Alpine Experiment) program.