WorldWideScience

Sample records for hgsubscript 1-xcdsubscript xte

  1. Delta XTE Spacecraft Solar Panel Deployment, Hangar AO at Cape Canaveral Air Station

    Science.gov (United States)

    1995-01-01

    The footage shows technicians in the clean room checking and adjusting the deployment mechanism of the solar panel for XTE spacecraft. Other scenes show several technicians making adjustments to software for deployment of the solar panels.

  2. Discovery of a Transient Magnetar: XTE J1810-197

    Science.gov (United States)

    Ibrahim, Alaa I.; Markwardt, Craig B.; Swank, Jean H.; Ransom, Scott; Roberts, Mallory; Kaspi, Victoria; Woods, Peter M.; Safi-Harb, Samar; Balman, Solen; Parke, William C.

    2004-01-01

    We report the discovery of a new X-ray pulsar, XTE J1810-197, that was serendipitously discovered on 2003 July 15 by the Rossi X-Ray Timing Explorer (RXTE) while observing the soft gamma repeater SGR 1806-20. The pulsar has a 5.54 s spin period, a soft X-ray spectrum (with a photon index of approx. = 4). and is detectable in earlier RXTE observations back to 2003 January but not before. These show that a transient outburst began between 2002 November 17 and 2003 January 23 and that the source's persistent X-ray flux has been declining since then. The pulsar exhibits a high spin-down rate P approx.= l0(exp -11) s/s with no evidence of Doppler shifts due to a binary companion. The rapid spin-down rate and slow spin period imply a supercritical characteristic magnetic field B approx. = 3 x l0(exp 14) G and a young age tau less than or = 7600 yr. Follow-up Chandra observations provided an accurate position of the source. Within its error radius, the 1.5 m Russian-Turkish Optical Telescope found a limiting magnitude R(sub c) = 21.5. All such properties are strikingly similar to those of anomalous X-ray pulsars ad soft gamma repeaters, providing strong evidence that the source is a new magnetar. However, archival ASCA and ROSAT observations found the source nearly 2 orders of magnitude fainter. This transient behavior and the observed long-term flux variability of the source in absence of an observed SGR-like burst activity make it the first confirmed transient magnetar and suggest that other neutron stars that share the properties of XTE 51810- 197 during its inactive phase may be unidentified transient magnetars awaiting detection via a similar activity. This implies a larger population of magnetars than previously surmised and a possible evolutionary connection between magnetars and other neutron star families. Subject headings: pulsars: general -pulsars: individual (XTE 51810- 197) - stars: magnetic fields -

  3. LOW-FREQUENCY OSCILLATIONS IN XTE J1550-564

    International Nuclear Information System (INIS)

    Rao Fengyun; Belloni, Tomaso; Stella, Luigi; Zhang Shuangnan; Li Tipei

    2010-01-01

    We present the results of a timing analysis of the low-frequency quasi-periodic oscillation (QPO) in the Rossi X-Ray Timing Explorer data of the black hole binary XTE J1550-564 during its 1998 outburst. The QPO frequency is observed to vary on timescales between ∼100 s and days, correlated with the count rate contribution from the optically thick accretion disk: we studied this correlation and discuss its influence on the QPO width. In all observations, the quality factors (ν 0 /FWHM) of the fundamental and second harmonic peaks were observed to be consistent, suggesting that the quasi-periodic nature of the oscillation is due to frequency modulation. In addition to the QPO and its harmonic peaks, a new 1.5ν component was detected in the power spectra. This component is broad, with a quality factor of ∼0.6. From this, we argue that the peak observed at half the QPO frequency, usually referred to as 'sub-harmonic', could be the fundamental frequency, leading to the sequence 1:2:3:4. We also studied the energy dependence of the timing features and conclude that the two continuum components observed in the power spectrum, although both more intense at high energies, show a different dependence on energy. At low energies, the lowest-frequency component dominates, while at high energies the higher-frequency one has a higher fractional rms. An interplay between these two components was also observed as a function of their characteristic frequency. In this source, the transition between the low/hard state and the hard-intermediate state appears to be a smooth process.

  4. Improved X-ray position for XTE J1701-407

    Science.gov (United States)

    Starling, R.; Evans, P.

    2008-07-01

    We report an improved position for the transient source XTE J1701-407 (Markwardt et al. ATEL #1569, Degenaar et al. ATEL #1572) using Swift XRT data from the recently detected X-ray burst (Markwardt et al. ATEL #1616 ; Linares et al. ATEL #1618).

  5. Further comments on segregation during Bridgman growth of Cd(x)Hg(1-x)Te

    Science.gov (United States)

    Lehoczky, S. L.; Szofran, F. R.

    1984-01-01

    The authors comment on recent papers published by Capper et al. (1983) and Jones et al. (1983) which report and discuss the variation of composition with axial position in Bridgman-grown Cd(x)Hg(1-x)Te alloys. The validity of a diffusion-controlled model for non-mixing growth conditions is particularly noted.

  6. Earlier activity from XTE J1739-302/IGR J17391-3021 detected by INTEGRAL

    DEFF Research Database (Denmark)

    Chenevez, Jérôme; Beckmann, V.; Kuulkers, E.

    2008-01-01

    The recently reported outburst from the supergiant fast X-ray transient XTE J1739-302/IGR J17391-3021 (ATEL #1466) began already about five hours earlier than the Swift/BAT trigger on 2008-04-08. The INTEGRAL/JEM-X monitor detected a flare starting at 16:18 (UTC) on the same day during recent Gal...

  7. Electrodeposition and characterization of CdSe x-Te 1- x semiconducting thin films

    Science.gov (United States)

    Benamar, E.; Rami, M.; Fahoume, M.; Chraibi, F.; Ennaoui, A.

    1999-07-01

    Thin polycrystalline films of cadmium chalcogenides CdSe xTe 1-x ( 0 ≤ x ≤ 1) have been prepared by electrochemical plating on ITO (indium tin oxide) coated glass substrates from an acid sulfate solution at 90 °C. Structural, morphological and compositional studies of the deposited films are reported as a function of the x coefficient. XRD analysis shows that all deposits have a cubic structure with a preferred orientation along the (111) direction. The composition in the films is found to vary linearly with the composition in the solution. The increase in the selenium content x in the CdSe xTe 1-x films decreases the lattice constant and increases the band gap. Nevertheless this latter presents a minimum for x = 0.27.

  8. X-ray Observation of XTE J2012+381 during the 1998 Outburst

    Indian Academy of Sciences (India)

    The outburst of X-ray transient source XTE J2012+381 was detected by the RXTE All-Sky Monitor on 1998 May 24th. Following the outburst, X-ray observations of the source were made in the 2-18keV energy band with the Pointed Proportional Counters of the Indian X-ray Astronomy Experiment (IXAE) on-board the Indian ...

  9. Development of the solar array deployment and drive system for the XTE spacecraft

    Science.gov (United States)

    Farley, Rodger; Ngo, Son

    1995-01-01

    The X-ray Timing Explorer (XTE) spacecraft is a NASA science low-earth orbit explorer-class satellite to be launched in 1995, and is an in-house Goddard Space Flight Center (GSFC) project. It has two deployable aluminum honeycomb solar array wings with each wing being articulated by a single axis solar array drive assembly. This paper will address the design, the qualification testing, and the development problems as they surfaced of the Solar Array Deployment and Drive System.

  10. Band structure of Mgsub(x)Znsub(1-x)Te alloys

    International Nuclear Information System (INIS)

    Laugier, A.; Montegu, B.; Barbier, D.; Chevallier, J.; Guillaume, J.C.; Somogyi, K.

    1980-01-01

    The band structure of Mgsub(x)Znsub(1-x)Te alloys is studied using a double beam wavelength modulated system in first derivative mode. Modulated reflectivity measurements are made from 82 to 300 K within spectral range 2500 to 5400 A. Structures corresponding to the E 0 , E 0 + Δ 0 , E 1 , E 1 + Δ 1 , e 1 and e 1 + Δ 1 critical points are indexed on the basis of existing band calculations for ZnTe. (author)

  11. XTE J1946+274: An Enigmatic X-Ray Pulsar

    Science.gov (United States)

    Wilson, Colleen A.; Finger, Mark H.; Coe, M. J.; Negueruela, Ignacio; Six, N. Frank (Technical Monitor)

    2002-01-01

    XTE J1946+274 = GRO J1944+26 is a 15.8-s X-ray pulsar discovered simultaneously by the Rossi X-ray Timing Explorer (RXTE) and the Burst and Transient Source Experiment (BATSE) in September 1998. Follow-up optical/IR observations resulted in the discovery of a Be star companion. Our pulse timing analysis of BATSE and RXTE data indicates that the orbital period is approximately 169 days. Since its discovery in 1998, XTE J1946+274 has undergone 13 outbursts. These outbursts axe not regularly spaced. They occur approximately twice per orbit and are not locked in orbital phase, unlike most Be/X-ray transient systems. A possible explanation for this is a global-one armed oscillation or density perturbation propagating rapidly in the Be star's disk. We will investigate radial velocity variations in the central peak of the H-alpha line to look for evidence of such a perturbation. From 2001 March-September, we regularly monitored XTE J1946+274 with the RXTE PCA. We will demonstrate that the spectrum appears to be varying with orbital phase, based on the 2001 and 1998 RXTE PCA observations. We will also present histories of pulsed frequency and flux.

  12. A photospheric radius-expansion burst observed from XTE J1701-407 by INTEGRAL: an update on distance

    DEFF Research Database (Denmark)

    Chenevez, Jérôme; Maurizio, F.; Brandt, Søren Kristian

    2010-01-01

    On 2010-08-22 00:56:19 the INTEGRAL Burst Alert System (IBAS) triggered on an event ((GCN 11132, Gotz & Ferrigno, 2009) from the known burst source XTE J1701-407 (Falanga et al., A&A 496, 333, 2009; Linares et al., MNRAS 392, L11, 2009) during an observation of the field around SNR RXJ1713.7-3946...... (Falanga et al., 2009). Light curves of the burst can be obtained from the following adress: ftp://ftp.spacecenter.dk/pub/Jerome/Science/XTE_J1701-407/...

  13. Neutral Hydrogen Absorption Toward XTE J1810-197: the Distance to a Radio-Emitting Magnetar

    OpenAIRE

    Minter, Anthony H.; Camilo, Fernando; Ransom, Scott M.; Halpern, Jules P.; Zimmerman, Neil

    2007-01-01

    We have used the Green Bank Telescope to measure HI absorption against the anomalous X-ray pulsar XTE J1810-197. Assuming a flat rotation curve, we find that XTE J1810-197 is located at a distance of 3.4(+0.5,-0.7) kpc. For a rotation curve that incorporates a model of the Galactic bar, we obtain a distance of 4.0(+0.3,-0.8) kpc. Using a rotation curve that incorporates a model of the Galactic bar and the spiral arms of the Galaxy, the distance is 3.7(+/-0.6) kpc. These values are consistent ...

  14. A Survey of Variable Extragalactic Sources with XTE's All Sky Monitor (ASM)

    Science.gov (United States)

    Jernigan, Garrett

    1998-01-01

    The original goal of the project was the near real-time detection of AGN utilizing the SSC 3 of the ASM on XTE which does a deep integration on one 100 square degree region of the sky. While the SSC never performed sufficiently well to allow the success of this goal, the work on the project has led to the development of a new analysis method for coded aperture systems which has now been applied to ASM data for mapping regions near clusters of galaxies such as the Perseus Cluster and the Coma Cluster. Publications are in preparation that describe both the new method and the results from mapping clusters of galaxies.

  15. Erratum: "Discovery of a Second Millisecond Accreting Pulsar: XTE J1751-305"

    Science.gov (United States)

    Markwardt, Craig; Swank, J. H.; Strohmayer, T. E.; in 'tZand, J. J. M.; Marshall, F. E.

    2007-01-01

    The original Table 1 ("Timing Parameters of XTE J1751-305") contains one error. The epoch of pulsar mean longitude 90deg is incorrect due to a numerical conversion error in the preparation of the original table text. A corrected version of Table 1 is shown. For reference, the epoch of the ascending node is also included. The correct value was used in all of the analysis leading up to the paper. As T(sub 90) is a purely fiducial reference time, the scientific conclusions of the paper are unchanged.

  16. Multistate observations of the Galactic black hole XTE J1752-223: evidence for an intermediate black hole spin

    NARCIS (Netherlands)

    Reis, R.C.; Miller, J.M.; Fabian, A.C.; Cackett, E.M.; Maitra, D.; Reynolds, C.S.; Rupen, M.; Steeghs, D.T.H.; Wijnands, R.

    2011-01-01

    The Galactic black hole candidate XTE J1752−223 was observed during the decay of its 2009 outburst with the Suzaku and XMM-Newton observatories. The observed spectra are consistent with the source being in the ‘intermediate’ and ‘low-hard’ states, respectively. The presence of a strong, relativistic

  17. NuSTAR and SWIFT Observations of the Black Hole Candidate XTE J1908+094 during its 2013 Outburst

    DEFF Research Database (Denmark)

    Tao, Lian; Tomsick, John A.; Walton, Dominic J.

    2015-01-01

    The black hole (BH) candidate XTE J1908+094 went into outburst for the first time since 2003 in 2013 October. We report on an observation with the Nuclear Spectroscopic Telescope Array (NuSTAR) and monitoring observations with Swift during the outburst. NuSTAR caught the source in the soft state...

  18. Radius expansion bursts from the neutron star transient XTE J1701-462; a new distance estimate

    NARCIS (Netherlands)

    Lin, D.; Homan, J.; Remillard, R.; Wijnands, R.

    2007-01-01

    A detailed spectral analysis of the second and third type-I X- ray bursts from the neutron star transient XTE J1701-462 (detected on July 20 and July 25, see also ATel #1165) reveals clear photospheric radius expansion in both of them. The bursts show radius expansion for about 2-3 seconds, with the

  19. Coherence of burst oscillations and accretion-powered pulsations in the accreting millisecond pulsar XTE J1814-338

    NARCIS (Netherlands)

    Watts, A.L.; Patruno, A.; van der Klis, M.

    2008-01-01

    X-ray timing of the accretion-powered pulsations during the 2003 outburst of the accreting millisecond pulsar XTE J1814-338 has revealed variation in the pulse time of arrival residuals. These can be interpreted in several ways, including spin-down and wandering of the fuel impact point around the

  20. Resolved, expanding jets in the Galactic black hole candidate XTE J1908+094

    Science.gov (United States)

    Rushton, A. P.; Miller-Jones, J. C. A.; Curran, P. A.; Sivakoff, G. R.; Rupen, M. P.; Paragi, Z.; Spencer, R. E.; Yang, J.; Altamirano, D.; Belloni, T.; Fender, R. P.; Krimm, H. A.; Maitra, D.; Migliari, S.; Russell, D. M.; Russell, T. D.; Soria, R.; Tudose, V.

    2017-07-01

    Black hole X-ray binaries undergo occasional outbursts caused by changing inner accretion flows. Here we report high angular resolution radio observations of the 2013 outburst of the black hole candidate X-ray binary system XTE J1908+094, using data from the Very Long Baseline Array and European VLBI Network. We show that following a hard-to-soft state transition, we detect moving jet knots that appear asymmetric in morphology and brightness, and expand to become laterally resolved as they move away from the core, along an axis aligned approximately -11° east of north. We initially see only the southern component, whose evolution gives rise to a 15-mJy radio flare and generates the observed radio polarization. This fades and becomes resolved out after 4 days, after which a second component appears to the north, moving in the opposite direction. From the timing of the appearance of the knots relative to the X-ray state transition, a 90° swing of the inferred magnetic field orientation, the asymmetric appearance of the knots, their complex and evolving morphology, and their low speeds, we interpret the knots as working surfaces where the jets impact the surrounding medium. This would imply a substantially denser environment surrounding XTE J1908+094 than has been inferred to exist around the microquasar sources GRS 1915+105 and GRO J1655-40.

  1. The Reawakening of the Sleeping X-ray Pulsar XTE J1946+274

    Science.gov (United States)

    Mueller, Sebastian; Mueller, Sebastian; Kuechnel, Matthias; Fuerst, Felix; Kreykenbohm, Ingo; Sagredo, Macarena; Obst, Maria; Wilms, Joern; Caballero, Isabel; Potttschmidt, Katja; hide

    2012-01-01

    We report on a series of outbursts of the high mass X-ray binary XTE 11946+274 in 2010/2011 as observed with INTEGRAL, RXTE, and Swift. We discuss possible mechanisms resulting in the extraordinary outburst behavior of this source. The X-ray spectra can be described by standard phenomenological models, enhanced by an absorption feature of unknown origin at about 10 keV and a narrow iron K alpha fluorescence line at 6.4keV, which are variable in flux and pulse phase. We find possible evidence for the presence of a cyclotron resonance scattering feature at about 25 keV at the 93% level. The presence of a strong cyclotron line at 35 keV seen in data from the source's 1998 outburst and confirmed by a reanalysis of these data can be excluded. This result indicates that the cyclotron line feature in XTE 11946+274 is variable between individual outbursts.

  2. Discovery of a Second Millesecond Accreting Pulsar: XTE J1751-305

    Science.gov (United States)

    Markwardt, C. B.; Swank, J. H.; Strohmayer, T. E.; intZand, J. J. M.; Marshall, F. E.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We report the discovery by the RXTE PCA of a second transient accreting millisecond pulsar, XTE J1751-305, during regular monitoring observations of the galactic bulge region. The pulsar has a spin frequency of 435 Hz, making it one of the fastest pulsars. The pulsations contain the signature of orbital Doppler modulation, which implies an orbital period of 42 minutes, the shortest orbital period of any known radio or X-ray millisecond pulsar. The mass function, f(sub x) = (1.278 +/- 0.003) x 10 (exp -6) solar mass, yields a minimum mass for the companion of between 0.013 and 0.0017 solar mass depending on the mass of the neutron star. No eclipses were detected. A previous X-ray outburst in June, 1998, was discovered in archival All-Sky Monitor data. Assuming mass transfer in this binary system is driven by gravitational radiation, we constrain the orbital inclination to be in the range 30 deg-85 deg and the companion mass to be 0.013-0.035 solar mass. The companion is most likely a heated helium dwarf. We also present results from the Chandra HRC-S observations which provide the best known position of XTE J1751-305.

  3. Iodine as an oxidant in the topotactic deintercalation of interstitial iron in Fe(1+x)Te.

    Science.gov (United States)

    Rodriguez, Efrain E; Zavalij, Peter; Hsieh, Ping-Yen; Green, Mark A

    2010-07-28

    The layered telluride, Fe(1+x)Te, is a parent compound of the isostructural and superconducting phases, Fe(1+x)(Te, Se, S). Here we show that, through a simple reaction of I(2) vapor with both powder and single crystal samples, the interstitial iron can be removed from the FeTe framework topotactically. Neutron powder diffraction and X-ray single crystal diffraction confirm that the iron being extracted is the partially occupied site that lies between the 2-D blocks of edge-sharing FeTe(4) tetrahedra. The deintercalation process has consequences for both magnetic and crystallographic phase transitions in the compound at low temperatures. This technique could be of use for the tuning of stoichiometry of the superconducting phases and therefore enable more careful studies on how chemical composition affects magnetic and superconducting properties.

  4. Suzaku observation of the eclipsing high mass X-ray binary pulsar XTE J1855-026

    Science.gov (United States)

    Devasia, Jincy; Paul, Biswajit

    2018-02-01

    We report results from analysis performed on an eclipsing supergiant high mass X-ray binary pulsar XTE J1855-026 observed with the X-ray Imaging Spectrometer (XIS) on-board Suzaku Observatory in April 2015. Suzaku observed this source for a total effective exposure of ˜ 87 ks just before an eclipse. Pulsations are clearly observed and the pulse profiles of XTE J1855-026 did not show significant energy dependence during this observation consistent with previous reports. The time averaged energy spectrum of XTE J1855-026 in the 1.0-10.5 keV energy range can be well fitted with a partial covering power law model modified with interstellar absorption along with a black-body component for soft excess and a gaussian for iron fluorescence line emision. The hardness ratio evolution during this observation indicated significant absorption of soft X-rays in some segments of the observation. For better understanding of the reason behind this, we performed time-resolved spectroscopy in the 2.5-10.5 keV energy band which revealed significant variations in the spectral parameters, especially the hydrogen column density and iron line equivalent width with flux. The correlated variations in the spectral parameters indicate towards the presence of clumps in the stellar wind of the companion star accounting for the absorption of low energy X-rays in some time segments.

  5. Photoluminescence from Cd{sub x}Hg{sub 1-x}Te

    Energy Technology Data Exchange (ETDEWEB)

    Breivik, M; Selvig, E; Tonheim, C R; Brendhagen, E; Brudevoll, T; Rheenen, A D van; Steen, H; Nicolas, S; Lorentzen, T; Haakenaasen, R [Norwegian Defence Research Establishment, P O Box 25, N-2027 Kjeller (Norway)], E-mail: magnus.breivik@gmail.com

    2008-03-15

    We present important aspects of photoluminescence (PL) of Cd{sub x}Hg{sub 1-x}Te in the infrared part of the spectrum where background thermal radiation significantly affects the PL spectrum. We show how the background spectrum can be removed from the data. We also show how the wavelength of the excitation laser affects the relative intensity of the PL peaks from a multi-layer structure. Finally, we present temperature dependent PL of a Cd{sub 0.36}Hg{sub 0.64}Te/Cd{sub 0.61}Hg{sub 0.39}Te multiple quantum well structure grown on a 4 {mu}m thick Cd{sub 0.36}Hg{sub 0.64}Te buffer layer. We attribute the low temperature peak from the buffer layer to impurities. The impurity levels are depopulated as the temperature increases, resulting in a decreased PL peak intensity. Above {approx}200 K a band-to-band peak from the buffer layer is observed. The quantum well peak persists up to {approx}200 K.

  6. State transitions in the 2001/2002 outburst of XTE J1650-500

    International Nuclear Information System (INIS)

    Rossi, S.; Homan, J.; Miller, J.M.; Belloni, T.

    2004-01-01

    We present a study of the X-ray transient and black hole candidate XTE J1650-500 during its 2001/2002 outburst. The source made two state transitions between the hard and soft states, at luminosity levels that differ by a factor of ∼5-10. The first transition, between hard and soft, lasted for ∼30 days and showed two parts; one part in which the spectral properties evolve smoothly away from the hard state and another that we identify as the 'steep power law state'. The two parts showed different behavior of the Fe K emission line and QPO frequencies. The second transition, from soft to hard, lasted only ∼15 days and showed no evidence of the presence of the 'steep power law state'. Comparing observations from the early rise and the decay of the outburst, we conclude that the source can be in the hard state in a range of more than 10 4 in luminosity. We briefly discuss the state transitions in the framework of a two-flow model

  7. INTEGRAL confirms that XTE J1728-295 = IGR J17285-2922

    DEFF Research Database (Denmark)

    Turler, Marc; ., .; Brandt, Søren Kristian

    2010-01-01

    -40 keV and 40-80 keV energy bands, respectively. The average ISGRI spectrum can be well described (reduced chi^2 of 0.8 for 8 degrees of freedom) by a simple power-law of index 2.1+/-0.5 (uncertainty at 68% c.l.) and a 20-80 keV flux of 9.8e-11 erg/s/cm^2. The best-determined position with a 90......% confinement radius of 2.8 arcmin (Gros et al., 2003, A&A, L179) is (RA,DEC)=(262.172,-29.325), fully consistent with the location of the Swift/XRT Soft X-ray counterpart (ATel #2824). IGR J17285-2922 was not detected by JEM-X with a 3-sigma upper limit of about 12 mCrab (3-11 keV). This is consistent....... The coincidence of the renewed low-level activity of IGR J17285-2922 in the hard X-rays with the reported X-ray outburst of XTE J1728-295 (ATel #2823) and the positional coincidence with the proposed Soft X-ray counterpart (ATel #2824) strengthen the suggestion that the two sources are actually the same object...

  8. UNDERSTANDING COMPACT OBJECT FORMATION AND NATAL KICKS. II. THE CASE OF XTE J1118 + 480

    International Nuclear Information System (INIS)

    Fragos, T.; Willems, B.; Kalogera, V.; Ivanova, N.; Rockefeller, G.; Fryer, C. L.; Young, P. A.

    2009-01-01

    In recent years, an increasing number of proper motions have been measured for Galactic X-ray binaries. When supplemented with accurate determinations of the component masses, orbital period, and donor effective temperature, these kinematical constraints harbor a wealth of information on the system's past evolution. Here, we consider all this available information to reconstruct the full evolutionary history of the black hole X-ray binary XTE J1118 + 480, assuming that the system originated in the Galactic disk and the donor has solar metallicity. This analysis accounts for four evolutionary phases: mass transfer through the ongoing X-ray phase, tidal evolution before the onset of Roche lobe overflow, motion through the Galactic potential after the formation of the black hole, and binary orbital dynamics due to explosive mass loss and possibly a black hole natal kick at the time of core collapse. We find that right after black hole formation, the system consists of a ≅6.0-10.0 M sun black hole and a ≅1.0-1.6 M sun main-sequence star. We also find that that an asymmetric natal kick is not only plausible but required for the formation of this system, and derive a lower and upper limit on the black hole natal kick velocity magnitude of 80 km s -1 and 310 km s -1 , respectively.

  9. A photospheric radius-expansion burst observed from XTE J1701-407 by INTEGRAL: an update on distance

    Science.gov (United States)

    Chenevez, J.; Falanga, M.; Brandt, S.; Galloway, D.; Kuulkers, E.; Cumming, A.; Schatz, H.; Lund, N.; Ooestbroek, T.; Ferrigno, C.

    2010-08-01

    On 2010-08-22 00:56:19 the INTEGRAL Burst Alert System (IBAS) triggered on an event ((GCN 11132, Gotz & Ferrigno, 2009) from the known burst source XTE J1701-407 (Falanga et al., A&A 496, 333, 2009; Linares et al., MNRAS 392, L11, 2009) during an observation of the field around SNR RXJ1713.7-3946 (PI R. Terrier). As part of our monitoring of long thermonuclear X-ray bursts with INTEGRAL, we have analysed both the JEM-X and ISGRI data covering this event, and we identify it as another type I (thermonuclear) X-ray burst.

  10. Topological crystalline insulator PbxSn1-xTe thin films on SrTiO3 (001 with tunable Fermi levels

    Directory of Open Access Journals (Sweden)

    Hua Guo

    2014-05-01

    Full Text Available In this letter, we report a systematic study of topological crystalline insulator PbxSn1-xTe (0 < x < 1 thin films grown by molecular beam epitaxy on SrTiO3(001. Two domains of PbxSn1-xTe thin films with intersecting angle of α ≈ 45° were confirmed by reflection high energy diffraction, scanning tunneling microscopy, and angle-resolved photoemission spectroscopy (ARPES. ARPES study of PbxSn1-xTe thin films demonstrated that the Fermi level of PbTe could be tuned by altering the temperature of substrate whereas SnTe cannot. An M-shaped valance band structure was observed only in SnTe but PbTe is in a topological trivial state with a large gap. In addition, co-evaporation of SnTe and PbTe results in an equivalent variation of Pb concentration as well as the Fermi level of PbxSn1-xTe thin films.

  11. Cd{sub 1−x}Mn{sub x}Te ultrasmall quantum dots growth in a silicate glass matrix by the fusion method

    Energy Technology Data Exchange (ETDEWEB)

    Dantas, Noelio Oliveira; Lima Fernandes, Guilherme de; Almeida Silva, Anielle Christine [Laboratório de Novos Materiais Isolantes e Semicondutores (LNMIS), Instituto de Física, Universidade Federal de Uberlândia, 38408-100 Uberlândia, MG (Brazil); Baffa, Oswaldo; Gómez, Jorge Antônio [Departamento de Física, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, 14040-901 Ribeirão Preto, SP (Brazil)

    2014-09-29

    In this study, we synthesized Cd{sub 1−x}Mn{sub x}Te ultrasmall quantum dots (USQDs) in SiO{sub 2}-Na{sub 2}CO{sub 3}-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3} glass system using the fusion method. Growth of these Cd{sub 1−x}Mn{sub x}Te USQDs was confirmed by optical absorption, atomic force microscopy (AFM), magnetic force microscopy (MFM), scanning transmission electron microscopy (TEM), and electron paramagnetic resonance (EPR) measurements. The blueshift of absorption transition with increasing manganese concentration gives evidence of incorporation of manganese ions (Mn{sup 2+}) in CdTe USQDs. AFM, TEM, and MFM confirmed, respectively, the formation of high quality Cd{sub 1−x}Mn{sub x}Te USQDs with uniformly distributed size and magnetic phases. Furthermore, EPR spectra showed six lines associated to the S = 5/2 spin half-filled d-state, characteristic of Mn{sup 2+}, and confirmed that Mn{sup 2+} are located in the sites core and surface of the CdTe USQD. Therefore, synthesis of high quality Cd{sub 1−x}Mn{sub x}Te USQDs may allow the control of optical and magnetic properties.

  12. XMM-Newton Spectroscopy of the Accretion-driven Millisecond X-Ray Pulsar XTE J1751-305 in Outburst

    NARCIS (Netherlands)

    Miller, J. M.; Wijnands, R.; Méndez, M.; Kendziorra, E.; Tiengo, A.; van der Klis, M.; Chakrabarty, D.; Gaensler, B. M.; Lewin, W. H. G.

    2003-01-01

    We present an analysis of the first high-resolution spectra measured from an accretion-driven millisecond X-ray pulsar in outburst. We observed XTE J1751-305 with XMM-Newton on 2002 April 7 for approximately 35 ks. Using a simple absorbed blackbody plus power-law model, we measure an unabsorbed flux

  13. Development of CdTe/Cd{sub 1-x}Mg{sub x}Te double barrier, single quantum well heterostructure for resonant tunneling

    Energy Technology Data Exchange (ETDEWEB)

    Reuscher, G.; Keim, M.; Fischer, F.; Waag, A.; Landwehr, G. [Physikalishes Institut der Universitaet Wuerzburg am Hubland, Wuerzburg (Germany)

    1995-12-31

    We report the first observation of resonant tunneling through a CdTe/Cd{sub 1-x}Mg{sub x}Te double barrier, single quantum well heterostructure. Negative differential resistance is observable at temperatures below 230 K, exhibiting a peak to valley ratio of 3:1 at 4.2 K. (author). 16 refs, 2 figs.

  14. Application of the Nonballistic Model to the Black Hole Candidate XTE J1752-223 and the Quasar NRAO 150

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, T. Y.; Gong, B. P., E-mail: bpgong@mail.hust.edu.cn [Department of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2017-02-01

    Optical and radio observations of the black hole candidate XTE J1752-223 have exhibited a slightly curved motion of the jet components, which is associated with its radio light curve. In addition, observations of the quasar NRAO 150 have revealed a core–jet structure wobbling with a high angular speed. In this paper, the phenomena displayed in these two different sources are interpreted as the precession of a bent jet. In such a scenario, hot spots reproduced at different separations from the core precess on the same precession cone, in which different components correspond to different propagation times to the observer. By fitting the kinematics of the components of XTE J1752-223 and its light curve with a curved pattern of precession period 314 days, we find that the propagation time can make an earlier event appear later, and the jet axis can oscillate during its precession. Simulating the quasar NRAO 150 with the same scenario reveals that the knots at larger separation from the core precess at a slower speed than those closer in. A possible mechanism relating to the cooling time of a component is proposed. These three new results are of importance in understanding the physics underlying the curved jet as well as the activity of the central engine of different black hole systems.

  15. Application of the Nonballistic Model to the Black Hole Candidate XTE J1752-223 and the Quasar NRAO 150

    International Nuclear Information System (INIS)

    Zheng, T. Y.; Gong, B. P.

    2017-01-01

    Optical and radio observations of the black hole candidate XTE J1752-223 have exhibited a slightly curved motion of the jet components, which is associated with its radio light curve. In addition, observations of the quasar NRAO 150 have revealed a core–jet structure wobbling with a high angular speed. In this paper, the phenomena displayed in these two different sources are interpreted as the precession of a bent jet. In such a scenario, hot spots reproduced at different separations from the core precess on the same precession cone, in which different components correspond to different propagation times to the observer. By fitting the kinematics of the components of XTE J1752-223 and its light curve with a curved pattern of precession period 314 days, we find that the propagation time can make an earlier event appear later, and the jet axis can oscillate during its precession. Simulating the quasar NRAO 150 with the same scenario reveals that the knots at larger separation from the core precess at a slower speed than those closer in. A possible mechanism relating to the cooling time of a component is proposed. These three new results are of importance in understanding the physics underlying the curved jet as well as the activity of the central engine of different black hole systems.

  16. Energy relaxation in IR laser excited Hg{sub 1-x}Cd{sub x}Te

    Energy Technology Data Exchange (ETDEWEB)

    Storebo, A K; Brudevoll, T [FFI - Norwegian Defence Research Establishment, PO Box 25, NO-2027 Kjeller, Norway NTNU (Norwegian University of Science and Technology) (Norway); Olsen, O; Norum, O C [Department of Physics and Department of Electronics and Telecommunications NO-7491 Trondheim (Norway); Breivik, M, E-mail: asta-katrine.storebo@ffi.n [Department of Electronics and Telecommunications NO-7491 Trondheim (Norway)

    2009-11-15

    IR laser excitation of Hg{sub l-x}Cd{sub x}Te by low-fluence femtosecond and high fluence microsecond pulses was explored for the technologically important alloy fractions x {approx} 0.2 and x {approx} 0.28. We have used first principles (LAPW) electronic structure calculations and finite element modelling, supported by Monte Carlo simulation for the description of femtosecond pulse carrier relaxation and the transport parameters. Laser wavelengths considered were 6.4 - 10.6 {mu}m for x {approx} 0.2 and 3.8 - 4.8 {mu}m for x {approx} 0.28, with an incident 1 microsecond pulse fluence of 2 J/cm{sup 2}. Many energy transfer mechanisms are invoked due to the long timescales of the microsecond pulses, and a main challenge is therefore to elucidate how these interplay in situations away from thermal equilibrium. Mechanisms studied include one- and two-photon absorption (OPA and TPA) across the band gap, inter-valence band absorption (IVA) between light- and heavy hole bands, electron-hole recombination/impact ionization, band gap renormalisation, intra-band free carrier absorption (FCA), excess carrier temperatures, non-equilibrium phonon generation, and refractive index changes. In the high fluence case, lattice temperatures evolve considerably during the laser pulse in response to the heated carriers. The chosen photon energies lie just above the band gap at the starting lattice temperature of 77 K, and nonlinear effects therefore dominate as the material heats up and the band gap begins to exceed the photon energy. Because of the low photon energy we must rely on Auger recombination, inter-valence band absorption and free carrier absorption to heat the carrier plasma. Although some Hg{sub l-x}Cd{sub x}Te material parameters are now relatively well known, existing data for many of the processes are inadequate for cases far away from thermal equilibrium. Furthermore, the role of Auger recombination in relation to non-intrinsic recombination has been a matter of debate

  17. UPPER LIMITS ON PULSED RADIO EMISSION FROM THE 6.85 s X-RAY PULSAR XTE J0103-728 IN THE SMALL MAGELLANIC CLOUD

    International Nuclear Information System (INIS)

    Crawford, Fronefield; Devour, Brian M.; Takacs, Brian P.; Lorimer, Duncan R.; Kondratiev, Vladislav I.

    2009-01-01

    X-ray pulsations with a 6.85 s period were recently detected in the Small Magellanic Cloud (SMC) and were subsequently identified as originating from the Be/X-ray binary system XTE J0103-728. The recent localization of the source of the X-ray emission has made a targeted search for radio pulsations from this source possible. The detection of pulsed radio emission from XTE J0103-728 would make it only the second system after PSR B1259-63 that is both a Be/X-ray binary and a radio pulsar. We observed XTE J0103-728 in 2008 February with the Parkes 64 m radio telescope soon after the identification of the source of X-ray pulsations was reported in order to search for corresponding radio pulsations. We used a continuous 6.4 hr observation with a 256 MHz bandwidth centered at 1390 MHz using the center beam of the Parkes multibeam receiver. In the subsequent data analysis, which included a folding search, a Fourier search, a fast-folding algorithm search, and a single pulse search, no pulsed signals were found for trial dispersion measures (DMs) between 0 and 800 pc cm -3 . This DM range easily encompasses the expected values for sources in the SMC. We place an upper limit of ∼45 mJy kpc 2 on the luminosity of periodic radio emission from XTE J0103-728 at the epoch of our observation, and we compare this limit to a range of luminosities measured for PSR B1259-63, the only Be/X-ray binary currently known to emit radio pulses. We also compare our limit to the radio luminosities of neutron stars having similarly long spin periods to XTE J0103-728. Since the radio pulses from PSR B1259-63 are eclipsed and undetectable during the portion of the orbit near periastron, repeated additional radio search observations of XTE J0103-728 may be valuable if it is undergoing similar eclipsing and if such observations are able to sample the orbital phase of this system well.

  18. USA Observation of Spectral and Timing Evolution During the 2000 Outburst of XTE J1550--564

    Energy Technology Data Exchange (ETDEWEB)

    Reilly, Kaice T

    2002-12-06

    We report on timing and spectral observations of the 2000 outburst of XTE J1550--564 made by the Unconventional Stellar Aspect (USA) Experiment on board the Advanced Research and Global Observation Satellite (ARGOS). We observe a low-frequency quasi-periodic oscillation (LFQPO) with a centroid frequency that tends to increase with increasing flux and a fractional rms amplitude which is correlated with the hardness ratio. Several high-frequency quasi-periodic oscillations (HFQPO) were detected by RXTE, during periods where the LFQPO is seen to be weakening or not detectable at all. The evolution of the hardness ratio (4-16 keV/1-4 keV) with time and source flux is examined. The hardness-intensity diagram (HID) shows a cyclical movement in the counterclockwise direction and possibly indicates the presence of two independent accretion flows: a thin disk and a hot sub-Keplerian flow.

  19. Observation of variable pre-eclipse dips and disk winds in the eclipsing LMXB XTE J1710-281

    Science.gov (United States)

    Raman, Gayathri; Maitra, Chandreyee; Paul, Biswajit

    2018-04-01

    We report the first detection of highly ionized Fe species in the X-ray spectrum of the eclipsing and dipping Low Mass X-ray Binary XTE J1710-281. Using archival Chandra and Suzaku observations, we have carried out a spectro-timing analysis of the source during three different epochs. We compare the average orbital profile and obtain differences in pre-eclipse dip morphologies between different observation epochs. We observe an orbit to orbit evolution of the dips for the first time in this source in both the Chandra observations, reflecting changes in the structure of the accretion disc in timescales of hours. We further perform intensity resolved spectroscopy for both the Chandra and the Suzaku data to characterize the changes in the spectral parameters from the persistent to the dipping intervals. We find that the absorbers responsible for the dips, can be best described using a partially ionized partial covering absorber, with an ionization parameter, log(ξ) of ˜2. The photon index of the source remained at ˜2 during both the Chandra and the Suzaku observations. In the 0.6-9 keV Suzaku spectra, we detect a broad 0.72 keV Fe L-alpha emission line complex and two narrow absorption lines at ˜6.60 keV and ˜7.01 keV. The highly ionized Fe line signatures, being an indicator of accretion disc-winds, has been observed for the first time in XTE J1710-281.

  20. Effect of magnetic field on the donor impurity in CdTe/Cd{sub 1-x}Mn{sub x}Te quantum well wire

    Energy Technology Data Exchange (ETDEWEB)

    Kalpana, P.; Nithiananthi, P.; Jayakumar, K., E-mail: kjkumar-gri@rediffmail.com [Nanostructure Lab, Department of Physics, Gandhigram Rural University, Gandhigram – 624 302, Tamilnadu (India); Reuben, A. Merwyn Jasper D. [Department of Physics, School of Engineering, Saveetha University, Thandalam, Chennai-600104, TamilNadu (India)

    2016-05-23

    The donor impurity binding energy in CdTe / Cd{sub 1-x}Mn{sub x}Te QWW with square well confinement along x – direction and parabolic confinement along y – direction under the influence of externally applied magnetic field has been computed using variational principle in the effective mass approximation. The spin polaronic shift has also been computed. The results are presented and discussed.

  1. Limits on the quiescent radio emission from the black hole binaries GRO J1655−40 and XTE J1550−564

    NARCIS (Netherlands)

    Calvelo, D.E.; Fender, R.P.; Russell, D.M.; Gallo, E.; Corbel, S.; Tzioumis, A.K.; Bell, M.E.; Lewis, F.; Maccarone, T.J.

    2010-01-01

    We present the results of radio observations of the black hole binaries GRO J1655−40 and XTE J1550−564 in quiescence, with the upgraded Australia Telescope Compact Array. Neither system was detected. Radio flux density upper limits (3σ) of 26 μJy (at 5.5 GHz), 47 μJy (at 9 GHz) for GRO J1655−40 and

  2. A study of the cross-correlation and time lag in black hole X-ray binary XTE J1859+226

    Science.gov (United States)

    Pei, Songpeng; Ding, Guoqiang; Li, Zhibing; Lei, Yajuan; Yuen, Rai; Qu, Jinlu

    2017-07-01

    With Rossi X-ray Timing Explorer (RXTE) data, we systematically study the cross-correlation and time lag in all spectral states of black hole X-ray binary (BHXB) XTE J1859+226 in detail during its entire 1999-2000 outburst that lasted for 166 days. Anti-correlations and positive correlations and their respective soft and hard X-ray lags are only detected in the first 100 days of the outburst when the luminosity is high. This suggests that the cross-correlations may be related to high luminosity. Positive correlations are detected in every state of XTE J1859+226, viz., hard state, hard-intermediate state (HIMS), soft-intermediate state (SIMS) and soft state. However, anti-correlations are only detected in HIMS and SIMS, anti-correlated hard lags are only detected in SIMS, while anti-correlated soft lags are detected in both HIMS and SIMS. Moreover, the ratio of the observations with anti-correlated soft lags to hard lags detected in XTE J1859+226 is significantly different from that in neutron star low-mass X-ray binaries (NS LMXBs). So far, anti-correlations are never detected in the soft state of BHXBs but detected in every branch or state of NS LMXBs. This may be due to the origin of soft seed photons in BHXBs is confined to the accretion disk and, for NS LMXBs, from both accretion disk and the surface of the NS. We notice that the timescale of anti-correlated time lags detected in XTE J1859+226 is similar with that of other BHXBs and NS LMXBs. We suggest that anti-correlated soft lag detected in BHXB may result from fluctuation in the accretion disk as well as NS LMXB.

  3. The influence of hydrostatic pressure on the I-U characteristic of Pb/sub 1-x/Sn/sub x/Te diodes

    International Nuclear Information System (INIS)

    Hoerstel, W.; Kraak, W.; Rudolph, A.F.

    1983-01-01

    The influence of hydrostatic pressure and temperature on the I-U characteristic of Pb/sub 1-x/Sn/sub x/Te diodes has been investigated. The measurements have been carried out under hydrostatic pressure of 95 to 1070 MPa. The experimental results obtained differ from the predictions of the recombination-tunneling model. Formally it is possible to describe the deviation by a voltage dependence of the concentration of the active traps per unit area in the junction

  4. Electron beam induced Hg desorption and the electronic structure of the Hg depleted surface of Hg1/sub -//sub x/Cd/sub x/Te

    International Nuclear Information System (INIS)

    Shih, C.K.; Friedman, D.J.; Bertness, K.A.; Lindau, I.; Spicer, W.E.; Wilson, J.A.

    1986-01-01

    Auger electron spectroscopy (AES), x-ray photoemission spectroscopy (XPS), low energy electron diffraction (LEED), and angle-resolved ultraviolet photoemission spectroscopy (ARPES) were used to study the electron beam induced Hg desorption from a cleaved (110)Hg/sub 1-//sub x/Cd/sub x/Te surface and the electronic structure of the Hg depleted surface. Solid state recrystallized Hg/sub 1-//sub x/Cd/sub x/Te single crystals were used. It was found that the electron beam heating dominated the electron beam induced Hg desorption on Hg/sub 1-//sub x/Cd/sub x/Te. At the electron beam energy used, the electron beam heating extended several thousand angstroms deep. However, the Hg depletion saturated after a few monolayers were depleted of Hg atoms. At the initial stage of Hg loss (only 3%), the surface band bends upward (more p type). The ARPES spectrum showed the loss of some E vs k dispersion after 22% Hg atoms were removed from the surface region, and no dispersion was observed after 43% Hg atoms were removed. These results have important implications on the electronic structure of the surfaces and interfaces of which the stoichiometry is altered

  5. X-Ray Timing and Spectral Observations of Galactic Black Hole Candidate XTE J1550--564 During Outburst

    Energy Technology Data Exchange (ETDEWEB)

    Reilly, Kaice T

    2002-12-11

    Soft X-ray transients (SXTs), a sub-class of low-mass X-ray binaries (LMXBs), provide a unique opportunity to test General Relativity and to probe fundamental physics under conditions terrestrially unattainable. SXT outbursts are of great interest because they allow the study of LMXBs under a wide range of accretion rates. The majority of known SXTs contain black holes, therefore SXT outbursts are key to understanding accretion physics around black holes and in active galactic nuclei, which are thought to contain supermassive, M {approx} 10{sup 6} - 10{sup 10} M{circle_dot}, where M{circle_dot} is one solar mass, central compact objects. These compact objects are most likely black holes, which exhibit, on a much larger scale, accretion physics similar to that around black holes in SXTs. In this work, the timing and spectral properties of the SXT and microquasar XTE J1550-564 during outburst are studied. Observations made by the Unconventional Stellar Aspect (USA) Experiment on board the Advanced Research and Global Observation Satellite (ARGOS) are emphasized. USA data show a low-frequency quasi-periodic oscillation (LFQPO) with a centroid frequency that tends to increase with increasing USA flux and a fractional rms amplitude which is correlated with the USA hardness ratio (4-16 keV/1-4 keV). Several high-frequency quasi-periodic oscillations (HFQPOs) were detected by the Rossi X-ray Timing Explorer (RXTE), during periods where the LFQPO is seen to be weakening or not detectable at all. The evolution of the USA hardness ratio with time and source flux is examined. The hardness-intensity diagram shows counterclockwise cyclical evolution and possibly indicates the presence of two independent accretion flows: a geometrically thin, optically thick accretion disk and a hot sub-Keplerian flow.

  6. Accretion flow dynamics during 1999 outburst of XTE J1859+226—modeling of broadband spectra and constraining the source mass

    Science.gov (United States)

    Nandi, Anuj; Mandal, S.; Sreehari, H.; Radhika, D.; Das, Santabrata; Chattopadhyay, I.; Iyer, N.; Agrawal, V. K.; Aktar, R.

    2018-05-01

    We examine the dynamical behavior of accretion flow around XTE J1859+226 during the 1999 outburst by analyzing the entire outburst data (˜166 days) from RXTE Satellite. Towards this, we study the hysteresis behavior in the hardness intensity diagram (HID) based on the broadband (3-150 keV) spectral modeling, spectral signature of jet ejection and the evolution of Quasi-periodic Oscillation (QPO) frequencies using the two-component advective flow model around a black hole. We compute the flow parameters, namely Keplerian accretion rate (\\dot{m}d), sub-Keplerian accretion rate (\\dot{m}h), shock location (rs) and black hole mass (M_{bh}) from the spectral modeling and study their evolution along the q-diagram. Subsequently, the kinetic jet power is computed as L^{obs}_{jet} ˜3-6 ×10^{37} erg s^{-1} during one of the observed radio flares which indicates that jet power corresponds to 8-16% mass outflow rate from the disc. This estimate of mass outflow rate is in close agreement with the change in total accretion rate (˜14%) required for spectral modeling before and during the flare. Finally, we provide a mass estimate of the source XTE J1859+226 based on the spectral modeling that lies in the range of 5.2-7.9 M_{⊙} with 90% confidence.

  7. Effects of deposition temperatures on structure and physical properties of Cd 1-xZn xTe films prepared by RF magnetron sputtering

    Science.gov (United States)

    Zeng, Dongmei; Jie, Wanqi; Zhou, Hai; Yang, Yingge

    2010-02-01

    Cd 1-xZn xTe films were deposited by RF magnetron sputtering from Cd 0.9Zn 0.1Te crystals target at different substrate temperatures (100-400 °C). The effects of the deposition temperature on structure and physical properties of Cd 1-xZn xTe films have been studied using X-ray diffraction (XRD), step profilometer, atomic force microscopy (AFM), ultraviolet spectrophotometer and Hall effect measurements. X-ray studies suggest that the deposited films were polycrystalline with preferential (1 1 1) orientation. AFM micrographs show that the grain size was changed from 50 to 250 nm with the increase of deposition temperatures, the increased grain size may result from kinetic factors during sputtering growth. The optical transmission data indicate that shallow absorption edge occurs in the range of 744-835 nm and that the optical absorption coefficient is varied with the increase of deposition temperatures. In Hall Effect measurements, the sheet resistivities of the deposited films are 3.2×10 8, 3.0×10 8, 1.9×10 8 and 1.1×10 8 Ohm/sq, which were decreased with the increase of substrate temperatures. Analysis of the resistivity of films depended on the substrate temperatures is discussed.

  8. Erratum: "Photoionization Modeling of Oxygen K Absorption in the Interstellar Medium, the Chandra Grating Spectra of XTE J1817-330" (2013, Apj, 768, 60)

    Science.gov (United States)

    Gatuzz, E.; Garcia, J.; Mendoza, C.; Kallman, Timothy R.; Witthoeft, Michael C.; Lohfink, A.; Bautista, M. A.; Palmeri, P.; Quinet, P.

    2013-01-01

    In the published version of this paper, there are some minor inaccuracies in the absorption-line wavelengths listed in Table 4 as a result of a faulty reduction procedure of the Obs6615 spectrum. The shifts have been detected in a comparison with the wavelengths listed for this spectrum in the Chandra Transmission Grating Catalog and Archive (TGCat8). They are due to incorrect centroid positions of the zero-order image in both reductions as determined by the tgdetect utility which, when disentangled, yield the improved line positions of the amended Table 4 given below. It must also be pointed out that other quantitative findings of the original paper: 1. Table 5, p. 9: the column density (NH), ionization parameter, oxygen abundance of the warmabs model and the normalization and photon index of the power-law model; 2. Table 6, p. 9: the hydrogen column density of the warmabs fit; 3. Table 7, p. 9: the present oxygen equivalent widths of XTE J1817-330; and 4. Table 8, p. 10: the present oxygen column densities of XTE J1817-330 derived from both the curve of growth and warmabs model fit have been revised in the new light and are, within the estimated uncertainty ranges, in good accord with the new rendering.

  9. In-Flight Observations of Long-Term Single Event Effect(SEE)Performance on Orbview-2 and Xray Timing Explorer(XTE)Solid State Recorders (SSR)

    Science.gov (United States)

    Poivey, Christian; Barth, Janet L.; LaBel, Ken A.; Gee, George; Safren, Harvey

    2003-01-01

    This paper presents Single Event Effect (SEE) in-flight data on Solid State Recorders (SSR) that have been collected over a long period of time for two NASA spacecraft: Orbview-2 and XTE. SEE flight data on solid-state memories give an opportunity to study the behavior in space of SEE sensitive commercial devices. The actual Single Event Upset (SEU) rates can be compared with the calculated rates based on environment models and ground test data. The SEE mitigation schemes can also be evaluated in actual implementation. A significant amount of data has already been published concerning observed SEE effects on memories in space. However, most of the data presented cover either a short period of time or a small number of devices. The data presented here has been collected on a large number of devices during several years. This allows statistically significant information about the effect of space weather fluctuations on SEU rates, and the effectiveness of SEE countermeasures used to be analyzed. Only Orbview-2 data is presented in this summary. XTE data will be included in the final paper.

  10. Photoionization Modeling of Oxygen K Absorption in the Interstellar Medium: The Chandra Grating Spectra of XTE J1817-330

    Science.gov (United States)

    Gatuzz, E.; Garcia, J.; Menodza, C.; Kallman, T. R.; Witthoeft, M.; Lohfink, A.; Bautista, M. A.; Palmeri, P.; Quinet, P.

    2013-01-01

    We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra towards the X-ray low-mass binary XTE J1817-330. The 11-25 A broadband is described with a simple absorption model that takes into account the pileup effect and results in an estimate of the hydrogen column density. The oxygen K-edge region (21-25 A) is fitted with the physical warmabs model, which is based on a photoionization model grid generated with the XSTAR code with the most up-to-date atomic database. This approach allows a benchmark of the atomic data which involves wavelength shifts of both the K lines and photoionization cross sections in order to fit the observed spectra accurately. As a result we obtain: a column density of N(sub H) = 1.38 +/- 0.01 x 10(exp 21) cm(exp -2); ionization parameter of log xi = .2.70 +/- 0.023; oxygen abundance of A(sub O) = 0.689(exp +0.015./-0.010); and ionization fractions of O I/O = 0.911, O II/O = 0.077, and O III/O = 0.012 that are in good agreement with previous studies. Since the oxygen abundance in warmabs is given relative to the solar standard of Grevesse and Sauval (1998), a rescaling with the revision by Asplund et al. (2009) yields A(sub O) = 0.952(exp +0.020/-0.013, a value close to solar that reinforces the new standard. We identify several atomic absorption lines.K-alpha , K-beta, and K-gamma in O I and O II; and K-alpha in O III, O VI, and O VII--last two probably residing in the neighborhood of the source rather than in the ISM. This is the first firm detection of oxygen K resonances with principal quantum numbers n greater than 2 associated to ISM cold absorption.

  11. Photoionization Modeling of Oxygen K Absorption in the Interstellar Medium:. [The Chandra Grating Spectra of XTE J1817-330

    Science.gov (United States)

    Gatuzz, E.; Garcia, J.; Mendoza, C.; Kallman, T. R.; Witthoeft, M.; Lohfink, A.; Bautista, M. A.; Palmeri, P.; Quinet, P.

    2013-01-01

    We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra toward the X-ray low-mass binary XTE J1817-330. The 11-25 Angstrom broadband is described with a simple absorption model that takes into account the pile-up effect and results in an estimate of the hydrogen column density. The oxygen K-edge region (21-25 Angstroms) is fitted with the physical warmabs model, which is based on a photoionization model grid generated with the xstar code with the most up-to-date atomic database. This approach allows a benchmark of the atomic data which involves wavelength shifts of both the K lines and photoionization cross sections in order to fit the observed spectra accurately. As a result we obtain a column density of N(sub H) = 1.38 +/- 0.01 × 10(exp 21) cm(exp -2); an ionization parameter of log xi = -2.70 +/- 0.023; an oxygen abundance of A(sub O) = 0.689 (+0.015/-0.010); and ionization fractions of O(sub I)/O = 0.911, O(sub II)/O = 0.077, and O(sub III)/O = 0.012 that are in good agreement with results from previous studies. Since the oxygen abundance in warmabs is given relative to the solar standard of Grevesse & Sauval, a rescaling with the revision by Asplund et al. yields A(sub O) = 0.952(+0.020/-0.013), a value close to solar that reinforces the new standard.We identify several atomic absorption lines-K(alpha), K(beta), and K(gamma) in O(sub I) and O(sub II) and K(alpha) in O(sub III), O(sub VI), and O(sub VII)-the last two probably residing in the neighborhood of the source rather than in the ISM. This is the first firm detection of oxygen K resonances with principal quantum numbers n greater than 2 associated with ISM cold absorption.

  12. PHOTOIONIZATION MODELING OF OXYGEN K ABSORPTION IN THE INTERSTELLAR MEDIUM: THE CHANDRA GRATING SPECTRA OF XTE J1817-330

    International Nuclear Information System (INIS)

    Gatuzz, E.; Mendoza, C.; García, J.; Lohfink, A.; Kallman, T. R.; Witthoeft, M.; Bautista, M. A.; Palmeri, P.; Quinet, P.

    2013-01-01

    We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra toward the X-ray low-mass binary XTE J1817-330. The 11-25 Å broadband is described with a simple absorption model that takes into account the pile-up effect and results in an estimate of the hydrogen column density. The oxygen K-edge region (21-25 Å) is fitted with the physical warmabs model, which is based on a photoionization model grid generated with the XSTAR code with the most up-to-date atomic database. This approach allows a benchmark of the atomic data which involves wavelength shifts of both the K lines and photoionization cross sections in order to fit the observed spectra accurately. As a result we obtain a column density of N H = 1.38 ± 0.01 × 10 21 cm –2 ; an ionization parameter of log ξ = –2.70 ± 0.023; an oxygen abundance of A O = 0.689 +0.015 -0.010 ; and ionization fractions of O I/O = 0.911, O II/O = 0.077, and O III/O = 0.012 that are in good agreement with results from previous studies. Since the oxygen abundance in warmabs is given relative to the solar standard of Grevesse and Sauval, a rescaling with the revision by Asplund et al. yields A O =0.952 +0.020 -0.013 , a value close to solar that reinforces the new standard. We identify several atomic absorption lines—Kα, Kβ, and Kγ in O I and O II and Kα in O III, O VI, and O VII—the last two probably residing in the neighborhood of the source rather than in the ISM. This is the first firm detection of oxygen K resonances with principal quantum numbers n > 2 associated with ISM cold absorption.

  13. High-energy observations of the state transition of the X-ray nova and black hole candidate XTE J1720-318

    DEFF Research Database (Denmark)

    Bel, M.C.; Rodriguez, J.; Sizun, P.

    2004-01-01

    We report the results of extensive high-energy observations of the X-ray transient and black hole candidate XTE J1720-318 performed with INTEGRAL, XMM-Newton and RXTE. The source, which underwent an X-ray outburst in 2003 January, was observed in February in a spectral state dominated by a soft......, typical of a black-hole binary in the so-called High/Soft State. We then followed the evolution of the source outburst over several months using the INTEGRAL Galactic Centre survey observations. The source became active again at the end of March: it showed a clear transition towards a much harder state...... of the black hole X-ray novae class which populate our galactic bulge and we discuss its properties in the frame of the spectral models used for transient black hole binaries....

  14. Excitation density dependence of the photoluminescence from Cd{sub x}Hg{sub 1-x}Te multiple quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Tonheim, C R; Selvig, E; Nicolas, S; Breivik, M; Haakenaasen, R [Norwegian Defence Research Establishment, PO Box 25, N-2027 Kjeller (Norway); Gunnaes, A E [Department of Physics, University of Oslo, Boks 1048 Blindern, N-0316 Oslo (Norway)], E-mail: celin.tonheim@ffi.no

    2008-03-15

    A study of the photoluminescence from a four-period Cd{sub x}Hg{sub 1-x}Te multiple quantum well structure at 11 K as a function of excitation density is presented. High-resolution X-ray diffraction and transmission electron microscopy revealed that the quantum well structure is of high quality. This was supported by the narrow photoluminescence peak originating in the ground state electron - heavy hole transition, with a full width at half maximum of only 7.4 meV for an excitation density of 1.3 W/cm{sup 2}. When the excitation density was increased from 1.3 to 23.4 W/cm{sup 2}, the peak position was shifted toward higher energy by 2.6 meV and the full width at half maximum increased from 7.4 to 10.9 meV.

  15. Below-gap absorption and precipitation in n-type Hg/sub 1-x/Cd/sub x/Te

    International Nuclear Information System (INIS)

    Qian Dingrong

    1986-01-01

    Free electron absorption spectra due to the scattering on optical phonons, acoustic phonons, and ionized impurities are calculated using Haga and Kimura's theory and Tang's two-mode Callen effective charges taking into account the nonparabolicity of the conduction band and the two-mode behaviour of the optical phonons of Hg/sub 1-x/Cd/sub x/Te. Free hole absorption spectra including both intra- and inter-band absorptions are also calculated. In addition, extinction spectra due to the absorption and scattering of light by precipitates of Te and HgTe in the crystal are included so as to give a good account for the measured below-gap absorption spectra. Therefore, the specific precipitates, their concentration and size distribution are obtained from the fits to the absorption spectra measured at 100 and 300 K for two samples. (author)

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

    Science.gov (United States)

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

    2010-01-01

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

  17. The Drop of the Coherence of the Lower Kilohertz Quasi-periodic Brightness Variations is Also Observed in XTE J1701-462

    Science.gov (United States)

    Barret, D.; Bachetti, M.; Miller, M. Coleman

    2011-02-01

    We investigate the quality factor and root mean square (rms) amplitude of the lower kilohertz quasi-periodic brightness variations (kHz QPOs) from XTE J1701-462, a unique X-ray source which was observed in both the so-called Z and atoll states. Correcting for the frequency drift of the QPO, we show that, as in all sources for which such a correction can be applied, the quality factor and rms amplitude drops sharply above a critical frequency. For XTE J1701-462, this frequency is estimated to be ~800 Hz, where the quality factor reaches a maximum of ~200 (e.g., a value consistent with the one observed from more classical systems, such as 4U 1636-536). Such a drop has been interpreted as the signature of the innermost stable circular orbit, and that interpretation is consistent with the observations we report here. The kHz QPOs in the Z state are much less coherent and lower amplitude than they are in the atoll state. We argue that the change of the QPO properties between the two source states is related to the change of the scale height of the accretion disk; a prediction of the toy model proposed by Barret et al. As a by-product of our analysis, we also increased the significance of the upper kHz QPO detected in the atoll phase up to 4.8σ (single trial significance) and show that the frequency separation (266.5 ± 13.1 Hz) is comparable with the one measured from simultaneous twin QPOs in the Z phase.

  18. THE TRANSIENT ACCRETING X-RAY PULSAR XTE J1946+274: STABILITY OF X-RAY PROPERTIES AT LOW FLUX AND UPDATED ORBITAL SOLUTION

    Energy Technology Data Exchange (ETDEWEB)

    Marcu-Cheatham, Diana M.; Pottschmidt, Katja [CRESST and Department of Physics, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250 (United States); Kühnel, Matthias; Müller, Sebastian; Falkner, Sebastian; Kreykenbohm, Ingo [Dr. Karl Remeis-Observatory and ECAP, University Erlangen-Nuremberg, Sternwartstr. 7, Bamberg (Germany); Caballero, Isabel [Laboratoire AIM, CEA/IRFU, CNRS/INSU, Université Paris Diderot, CEA DSM/IRFU/SAp, F-91191 Gif-sur-Yvette (France); Finger, Mark H. [Universities Space Research Association, National Space Science and Technology Center, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Jenke, Peter J. [University of Alabama in Huntsville, 301 Sparkman Drive, Huntsville, AL 35899 (United States); Wilson-Hodge, Colleen A. [Astrophysics Office, ZP 12, NASA Marshall Space Flight Center, Huntsville, AL 35812 (United States); Fürst, Felix [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Grinberg, Victoria [Massachusetts Institute of Technology, Kavli Institute for Astrophysics, Cambridge, MA 02139 (United States); Hemphill, Paul B.; Rothschild, Richard E. [University of California, San Diego, Center for Astrophysics and Space Sciences, 9500 Gilman Drive, La Jolla, CA 92093-0424 (United States); Klochkov, Dmitry [Institut für Astronomie und Astrophysik, Universität Tübingen (IAAT), Sand 1, Tübingen (Germany); Terada, Yukikatsu [Graduate School of Science and Engineering, Saitama University, 255 Simo-Ohkubo, Sakura-ku, Saitama City, Saitama 338-8570 (Japan); and others

    2015-12-10

    We present a timing and spectral analysis of the X-ray pulsar XTE J1946+274 observed with Suzaku during an outburst decline in 2010 October and compare with previous results. XTE J1946+274 is a transient X-ray binary consisting of a Be-type star and a neutron star with a 15.75 s pulse period in a 172 days orbit with 2–3 outbursts per orbit during phases of activity. We improve the orbital solution using data from multiple instruments. The X-ray spectrum can be described by an absorbed Fermi–Dirac cut-off power-law model along with a narrow Fe Kα line at 6.4 keV and a weak Cyclotron Resonance Scattering Feature (CRSF) at ∼35 keV. The Suzaku data are consistent with the previously observed continuum flux versus iron line flux correlation expected from fluorescence emission along the line of sight. However, the observed iron line flux is slightly higher, indicating the possibility of a higher iron abundance or the presence of non-uniform material. We argue that the source most likely has only been observed in the subcritical (non-radiation dominated) state since its pulse profile is stable over all observed luminosities and the energy of the CRSF is approximately the same at the highest (∼5 × 10{sup 37} erg s{sup −1}) and lowest (∼5 × 10{sup 36} erg s{sup −1}) observed 3–60 keV luminosities.

  19. Spin effects in high- and low-field magnetotransport experiments in semimagnetic Cd{sub 1-x}Mn{sub x}Te heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Betthausen, Christian

    2012-07-09

    Within the framework of this PhD we report on the very first observation of the fractional Quantum Hall Effect (FQHE) in both, a non-magnetic CdTe and a semimagnetic Cd{sub 1-x}Mn{sub x}Te quantum well device. To our knowledge, this constitutes the first demonstration of this effect in the II-VI material family. Furthermore, our results reveal that the formation of fractional Quantum Hall states is not inhibited by the presence of magnetic impurities in a quantum structure. The second part of this thesis addresses an alternative route to realize efficient spin transistor action. Typically, spin transistor designs relying on spin-orbit interaction principally suffer from low signal levels due to limitations in spin injection efficiency and fast spin decay. Here we present an approach to realize spin transistor action in systems where spin information is protected by propagating it adiabatically. This is achieved by inducing tunable diabatic Landau-Zener transitions that lead to a backscattering of spins and hence allow controlling the transmission of spin-polarized charge carriers through the device, i.e. switching between 'on' and 'off' states. We demonstrate the validity of our approach in a Cd{sub 1-x}Mn{sub x}Te diluted magnetic semiconductor quantum well structure where efficient spin transport is observed over device distances of 50 {mu}m. In contrast to other spin transistor designs we find that our concept is exceptionally tolerant against disorder.

  20. Paramagnetic behavior at room temperature of Zn{sub 1−x}Mn{sub x}Te nanocrystals grown in a phosphate glass matrix by the fusion method

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Alessandra S., E-mail: alessandra@mestrado.ufu.br [Universidade Federal de Uberlândia, Instituto de Física, Laboratório de Novos Materiais Isolantes e Semicondutores (LNMIS), Uberlândia CEP: 38400-902 (Brazil); Franco, Adolfo; Pelegrini, Fernando [Instituto de Física, Universidade Federal de Goiás, C. P. 131, 74001-970 Goiânia, GO (Brazil); Dantas, Noelio O. [Universidade Federal de Uberlândia, Instituto de Física, Laboratório de Novos Materiais Isolantes e Semicondutores (LNMIS), Uberlândia CEP: 38400-902 (Brazil)

    2015-10-25

    This work reports on the synthesis and characterization of Zn{sub 1−x}Mn{sub x}Te nanocrystals (NCs) with Mn doping concentration x varying from 0.000 to 0.800. Physical properties of samples were studied by transmission electron microscopy, magnetic force microscopy, vibrating sample magnetometry and electron paramagnetic resonance spectroscopy. Room temperature experiments revealed the size of NCs, the growth of magnetization and non-linear dependence of magnetic susceptibility on the concentration of Mn{sup 2+} ions; samples with low concentrations revealed the presence of ions in the interior and near the surface of the NCs. The results obtained confirm the paramagnetic behavior of Zn{sub 1−x}Mn{sub x}Te NCs at room temperature.

  1. Solubility limit of Mn{sup 2+} ions in Zn{sub 1−x}Mn{sub x}Te nanocrystals grown within an ultraviolet-transparent glass template

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Alessandra dos Santos, E-mail: alemestrado@gmail.com [Universidade Federal de Uberlândia, Laboratório de Novos Materiais Isolantes e Semicondutores (LNMIS), Instituto de Física (Brazil); Silva, Sebastião William da; Morais, Paulo Cesar de [Universidade de Brasília, Núcleo de Física Aplicada, Instituto de Física (Brazil); Dantas, Noelio Oliveira [Universidade Federal de Uberlândia, Laboratório de Novos Materiais Isolantes e Semicondutores (LNMIS), Instituto de Física (Brazil)

    2016-05-15

    This paper reports on the synthesis of Zn{sub 1−x}Mn{sub x}Te nanocrystals (NCs) (with 0 ≤ x ≤ 0.800) within a PZABP glass system (P{sub 2}O{sub 5}–ZnO–Al{sub 2}O{sub 3}–BaO–PbO) using the fusion method. The as-grown samples were investigated by optical absorption measurements, atomic force microscopy, X-ray diffraction, and Raman spectroscopy. The mean radius of the as-produced NCs (around R ≈ 2.2 nm) was well below the exciton Bohr radius of the bulk ZnTe (5.2 nm). All the characterization techniques employed in this report confirmed the successful inclusion of Mn{sup 2+} ions in the ZnTe-based NCs (Zn{sub 1−x}Mn{sub x}Te NCs) up to the nominal solubility limit of x = 0.100. Above this solubility limit (around x = 0.100), one can observe the formation of MnO and α-MnO{sub 2} NCs, since the nucleation rate for the formation of these NCs is greater than that of Zn{sub 1−x}Mn{sub x}Te NCs, at high x concentrations.Graphical abstract.

  2. Study of the Mg incorporation in CdTe for developing wide band gap Cd{sub 1-x}Mg{sub x}Te thin films for possible use as top-cell absorber in a tandem solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, Omar S. [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, 62580 Temixco, Morelos (Mexico); Universidad Politecnica del Estado de Guerrero, Comunidad de Puente Campuzano, C.P. 40325 Taxco de Alarcon, Guerrero (Mexico); Millan, Aduljay Remolina [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, 62580 Temixco, Morelos (Mexico); Huerta, L.; Santana, G. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico. C.P 04510 Mexico D.F. (Mexico); Mathews, N.R.; Ramon-Garcia, M.L.; Morales, Erik R. [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, 62580 Temixco, Morelos (Mexico); Mathew, X., E-mail: xm@cie.unam.mx [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, 62580 Temixco, Morelos (Mexico)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Thin films of Cd{sub 1-x}Mg{sub x}Te with high spatial uniformity and band gap in the range of 1.6-1.96 eV were deposited by vacuum co-evaporation of CdTe and Mg. Black-Right-Pointing-Pointer Obtained Cd{sub 1-x}Mg{sub x}Te films have the structural characteristics of the CdTe, evidence of the change in atomic scattering due to incorporation of Mg was observed. Black-Right-Pointing-Pointer XRD and XPS data confirmed the incorporation of Mg in the lattice of CdTe. Black-Right-Pointing-Pointer SEM images revealed the impact of Mg incorporation on the morphology of the films, the changes in grain size and grain morphology are noticeable. - Abstract: Thin films of Cd{sub 1-x}Mg{sub x}Te with band gap in the range of 1.6-1.96 eV were deposited by vacuum co-evaporation of CdTe and Mg on glass substrates heated at 300 Degree-Sign C. Different experimental techniques such as XRD, UV-vis spectroscopy, SEM, and XPS were used to study the effect of Mg incorporation into the lattice of CdTe. The band gap of the films showed a clear tendency to increase as the Mg content in the film is increased. The Cd{sub 1-x}Mg{sub x}Te films maintain all the structural characteristics of the CdTe, however, diminishing of intensity for the XRD patterns is observed due to both change in preferential orientation and change in atomic scattering due to the incorporation of Mg. SEM images showed significant evidences of morphological changes due to the presence of Mg. XRD, UV-vis spectroscopy, and XPS data confirmed the incorporation of Mg in the lattice of CdTe. The significant increase in band gap of CdTe due to incorporation of Mg suggests that the Cd{sub 1-x}Mg{sub x}Te thin film is a candidate material to use as absorber layer in the top-cell of a tandem solar cell.

  3. Chevrel-phase solid solution Mo 6Se 8- xTe x. Study of its superconducting, magnetic and NMR properties

    Science.gov (United States)

    Hamard1a, C.; Auffret, V.; Peña, O.; Le Floch, M.; Nowak, B.; Wojakowski, A.

    2000-09-01

    The Chevrel-phase solid solution Mo 6Se 8-Mo 6Te 8 was studied by X-ray diffraction, AC and DC magnetic susceptibility and 77Se and 125Te NMR spectroscopy. From the smooth evolution of the lattice parameters and superconducting critical temperatures, a progressive substitution of selenium atoms by tellurium is shown, on the whole range of composition 0⩽ x⩽8, in the formulation Mo 6Se 8- xTe x: the unit-cell volume increases linearly because of the larger ionic size of tellurium, while Tc decreases rapidly (from 6.45 down to 0 K) because of the different formal oxidation states of the anions and a probable evolution of the Fermi level in the density of states. Results of magnetic susceptibility support this model and suggest the inhibition of the intrinsic metallic behavior with increasing x. The NMR spectra of the binaries Mo 6Se 8 and Mo 6Te 8 reveal two significant features, attributed to two different chalcogen positions in the R 3¯ symmetry. At low Se contents in Mo 6Se 8- xTe x ( x=7.5, 7 and 6), selenium first fills the two X(2) sites along the three-fold axis (2c positions), and then it becomes statistically distributed over the general 6f positions, leading to broad 77Se NMR lines. On the other hand, substitution of Te atoms in Mo 6Se 8 seems to occur in a random way, creating large perturbations on the 125Te NMR spectra, over the whole range of x. Theoretical analysis based on the presence of two anisotropic lines (of axial and non-axial symmetries, respectively) allowed us to estimate their anisotropy factors and to perfectly simulate the frequency response of both Mo 6Se 8 and Mo 6Te 8 binaries. Analysis of the Knight shift anisotropy leads us to conclude about the importance of the molybdenum z 2 molecular orbital contribution which controls the Mo-X dipolar interactions.

  4. Synthesis, characterization and performance of Cd{sub 1−x}In{sub x}Te compound for solar cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Shenouda, Atef Y., E-mail: ayshenouda@yahoo.com [Central Metallurgical R and D Institute (CMRDI), Tebbin, P.O. Box 87 Helwan, Cairo 11412 (Egypt); Rashad, Mohamed M. [Central Metallurgical R and D Institute (CMRDI), Tebbin, P.O. Box 87 Helwan, Cairo 11412 (Egypt); Chow, Lee [Department of Physics, University of Central Florida, Orlando, FL 32816 (United States)

    2013-06-25

    Highlights: ► Cd{sub 1−x}In{sub x}Te samples were synthesized by wet chemical method using NaBH{sub 4} for reduction. ► The band gap energy was achieved to be 1.37 eV with Cd{sub 0.6}In{sub 0.4}Te. ► The highest photovoltaic response was achieved by a power conversion efficiency of 1.89% with Cd{sub 0.6}In{sub 0.4}Te. -- Abstract: Cd{sub 1−x}In{sub x}Te (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) samples have been synthesized chemically using wet chemical method from precursor compounds, CdSO{sub 4}, InCl{sub 3}, and TeCl{sub 4}. The hydroxide form of the solution mixture was obtained by using ammonia solution and the pH of the mixture was adjusted to 9. A suitable amount of NaBH{sub 4} solution was added to reduce the hydroxide phase to the metalloid alloy. The crystal structure has been studied using powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. The 300 °C annealed samples revealed a cubic crystal structure. The morphology of the prepared samples is very fine and the average diameter is between 1 and 2.5 μm. The optical properties were determined using UV–vis–NIR spectrophotometer and band gap energy of 1.37 eV for Cd{sub 0.6}In{sub 0.4}Te was obtained. The best photovoltaic conversion efficiency of 1.89% was obtained for the Cd{sub 0.6}In{sub 0.4}Te sample with a short circuit current density (J{sub sc}) of 15.3 mA cm{sup −2}, an open circuit voltage (V{sub oc}) of 0.668 V, and a filling factor (FF) of 69.31%.

  5. First-principles calculations of a half-metallic ferromagnet zinc blende Zn{sub 1−x}V{sub x}Te

    Energy Technology Data Exchange (ETDEWEB)

    El Amine Monir, M.; Baltache, H. [Laboratoire de Physique Quantique de la Modélisation Mathématique (LPQ3M), Université de Mascara, 29000 (Algeria); Khenata, R., E-mail: khenata_rabah@yahoo.fr [Laboratoire de Physique Quantique de la Modélisation Mathématique (LPQ3M), Université de Mascara, 29000 (Algeria); Murtaza, G. [Materials Modeling Laboratory, Department of Physics, Islamia College University, Peshawar (Pakistan); Azam, Sikander [New Technologies-Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic); Bouhemadou, A. [Laboratory for Developing New Materials and their Characterization, Department of Physics, Faculty of Science, University Setif 1, 19000 Setif (Algeria); Al-Douri, Y. [Institute of Nano Electronic Engineering, University Malaysia Perlis, 01000 Kangar, Perlis (Malaysia); Bin Omran, S. [Department of Physics and Astronomy, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Ali, Roshan [Materials Modeling Lab, Department of Physics, Post Graduate Jahanzeb College, Swat (Pakistan)

    2015-03-15

    First-principles calculations have been used to study the structural, elastic, electronic, magnetic and thermal properties of zinc blende Zn{sub 1−x}V{sub x}Te for x=0, 0.25, 0.50, 0.75 and 1 using the full-potential linearized augmented plane wave method (FP-LAPW) based on spin-polarized density functional theory (DFT). The electronic exchange-correlation potential is approached using the spin generalized gradient approximation (spin-GGA). The structural properties of the Zn{sub 1−x}V{sub x}Te alloys (x=0, 0.25, 0.50, 0.75 and 1) are given for the lattice constants and the bulk moduli and their pressure derivatives. The elastic constants C{sub 11}, C{sub 12} and C{sub 44} are calculated using numerical first-principles calculations implemented in the WIEN2k package. An analysis of the band structures and the densities of states reveals that Zn{sub 0.50}V{sub 0.50}Te and Zn{sub 0.75}V{sub 0.25}Te exhibit a half-metallic character, while Zn{sub 0.25}V{sub 0.75}Te is nearly half-metallic. The band structure calculations are used to estimate the spin-polarized splitting energies Δ{sub x}(d) and Δ{sub x}(pd) produced by the V(3d)-doped and s(p)–d exchange constants N{sub 0α} (conduction band) and N{sub 0β} (valence band). The p–d hybridization reduces the magnetic moment of V from its atomic charge value of 3µ{sub B} and creates small local magnetic moments on the nonmagnetic Zn and Te sites. Finally, we present the thermal effect on the macroscopic properties of these alloys, such as the thermal expansion coefficient, heat capacity and Debye temperature, based on the quasi-harmonic Debye model. - Highlights: • Some physical properties of Vanadium doped ZnTe have been investigated. • Structural parameters for the parent compounds compare well with the available data. • The elastic and thermal properties are studied for the first time.

  6. Study of the aqueous synthesis, optical and electrochemical characterization of alloyed Zn{sub x}Cd{sub 1-x}Te nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Matos, Charlene Regina Santos [Postgraduate Program in Materials Science and Engineering, Federal University of Sergipe, São Cristóvão, SE (Brazil); Candido, Luan P.M.; Souza, Helio Oliveira [Department of Chemistry, Federal University of Sergipe, São Cristóvão, SE (Brazil); Pereira da Costa, Luiz [Institute of Technology and Research (ITP), Tiradentes University, Aracaju, SE (Brazil); Sussuchi, Eliana Midori [Department of Chemistry, Federal University of Sergipe, São Cristóvão, SE (Brazil); Gimenez, Iara F., E-mail: gimenez@ufs.br [Postgraduate Program in Materials Science and Engineering, Federal University of Sergipe, São Cristóvão, SE (Brazil); Department of Chemistry, Federal University of Sergipe, São Cristóvão, SE (Brazil); Postgraduate Program in Chemistry, Federal University of Sergipe, São Cristóvão, SE (Brazil)

    2016-08-01

    The effects of experimental factors such as initial reaction pH, capping ligand, and heating method on the optical and electrochemical properties of aqueous alloyed Zn{sub x}Cd{sub 1-x}Te nanocrystals were evaluated. Here the type of capping ligand (glutathione GSH and 3-mercaptopropionic acid MPA) was found to be the most significant factor in controlling the range of photoluminescence emission. Also a pronounced pH effect on the emission wavelength has been verified in the presence of GSH, in contrast to MPA for which only a minor pH effect was observed. The heating method (microwave or hydrothermal) was found to be irrelevant for the emission wavelength at the conditions studied. The electrochemical characterization in aqueous medium (cyclic voltammetry and differential pulse voltammetry) evidenced a good correlation between electrochemical and optical band gap values and allowed estimation of band edge positions. - Highlights: • ZnCdTe quantum dots were obtained by aqueous synthesis. • Nature of capping ligand was the most relevant factor. • Optical and electrochemical band gaps were well correlated.

  7. Reformulated tight binding calculation for band discontinuity at CdTe/Hg {sub x}Cd{sub 1-x}Te heterointerfaces and their type I-type III transitions

    Energy Technology Data Exchange (ETDEWEB)

    Ekpunobi, A.J. [Department of Physics and Industrial Physics, Nnamdi Azikiwe University, P.M.B. 5025, Awka, Anambra State (Nigeria)

    2005-02-25

    A recently reformulated tight binding method is used to calculate the valence band discontinuity at the CdTe/Hg {sub x}Cd{sub 1-x}Te interface in the s{sup 2}p{sup 2} configuration. The calculated valence band discontinuity of 0.31 eV at CdTe/HgTe interface is in good agreement with self-consistent calculation and accepted experimental value. Calculations were extended to alloy interfaces, which enabled the investigation of the band-offset problem at the transition point. Both valence band discontinuity ratio and conduction band discontinuity ratio show inflexions at the transition point.

  8. Energy scaling of the "heartbeat" pulse width of GRS 1915+105, IGR J17091-3624, and MXB 1730-335 from Rossi-XTE observations

    Science.gov (United States)

    Maselli, A.; Capitanio, F.; Feroci, M.; Massa, F.; Massaro, E.; Mineo, T.

    2018-04-01

    We investigate some key aspects of the "heartbeat" variability consisting of series of bursts with a slow rise and a fast decay, thus far detected only in GRS 1915+105, IGR J17091-3624, and MXB 1730-335. A previous analysis based on BeppoSAX data of GRS 1915+105 revealed a hard-X delay (HXD), that is a lag of the burst rise at higher energies with respect to lower ones; this leads to narrower pulse widths, w, at higher energies. We here use some light curves of Rossi-XTE observations of GRS 1915+105 for a deeper analysis of this effect and search for its presence in those extracted from some IGR J17091-3624 and MXB 1730-335 observations performed with the same satellite. Our results show that, at variance with GRS 1915+105, no HXD is evident in the light curves of MXB 1730-335 and only a marginal HXD may be argued for IGR J17091-3624. For GRS 1915+105 we find a decreasing trend of the pulse width with energy following a power law w = A ṡ E-s with an index s ≈ 0.8. Furthermore, we confirm the increase of the HXD with the recurrence time Trec of the bursts in each series that was already found in previous works using BeppoSAX data. Based on a spectral analysis of these three sources we conclude that the differences highlighted in the properties of the "heartbeat" variability are probably related to the different accreting compact object and the eventual presence of a corona in these binary interacting systems.

  9. Optical spectra of Zn{sub 1-x}Be{sub x}Te mixed crystals determined by IR-VIS-UV ellipsometry and photoluminescence measurements

    Energy Technology Data Exchange (ETDEWEB)

    Wronkowska, A.A., E-mail: aleksandra.wronkowska@utp.edu.p [Institute of Mathematics and Physics, University of Technology and Life Sciences, S. Kaliskiego 7, PL-85796 Bydgoszcz (Poland); Arwin, H. [Department of Physics, Chemistry and Biology, Linkoeping University, SE-58183 Linkoeping (Sweden); Firszt, F.; Legowski, S. [Institute of Physics, Nicholas Copernicus University, Grudziadzka 5, PL-87100 Torun (Poland); Wronkowski, A.; Skowronski, L. [Institute of Mathematics and Physics, University of Technology and Life Sciences, S. Kaliskiego 7, PL-85796 Bydgoszcz (Poland)

    2011-02-28

    Spectroscopic ellipsometry in the photon energy range from 0.04 eV to 6.50 eV is used for investigation of the optical response of Zn{sub 1-x}Be{sub x}Te crystals grown by a high-pressure Bridgman method in the composition range x {<=} 0.12. Infrared spectra display absorption bands centred between 411 cm{sup -1} and 420 cm{sup -1} associated with BeTe-type optical phonon modes. The positions of the transverse-optical and longitudinal-optical phonon modes have been found by modelling the line shape of the complex dielectric functions, {epsilon}-tilde and Im(-{epsilon}-tilde{sup -1}), using a classical damped Lorentzian oscillator approach. Ellipsometric measurements in the VIS-UV range allow determination of the fundamental energy-gap (E{sub 0}) and the higher threshold energies (E{sub 1}, E{sub 1} + {Delta}{sub 1}, E{sub 2}) originating from the band edge and spin-orbit splitting critical points. We have found that the Be content x = 0.12 causes an increase of the fundamental energy gap about 0.15 eV at room temperature when compared to the E{sub 0} = 2.23 eV of ZnTe crystal at the same temperature. Photoluminescence spectra were measured in the temperature range from 30 K to room temperature. Luminescence at temperature T > 200 K is very weak. The peak positions of the exciton emission lines agree well with the E{sub 0} band-gaps derived from ellipsometric data if corrected for their temperature dependence.

  10. Phonon spectra in the parent superconducting iron-tuned telluride F e1 +xTe from inelastic neutron scattering and ab initio calculations

    Science.gov (United States)

    Zbiri, Mohamed; Viennois, Romain

    2017-10-01

    We report inelastic neutron scattering measurements of phonon spectra in the parent superconductor iron-tuned chalcogenide F e1 +xTe for two different x contents (x ≤0.11 ) using neutron time-of-flight technique. Thermal neutron spectroscopy allowed the collection of the low-temperature Stokes spectra over an extended Q range at 2, 40, and 120 K, hence covering both the magnetic monoclinic and the paramagnetic tetragonal phases, whereas cold neutrons allowed the measurement of high-resolution anti-Stokes spectra at 140, 220, and 300 K, thus covering the tetragonal phase. Our results evidence a spin-phonon coupling behavior towards the observed noticeable temperature-dependent change of the Stokes spectra across the transition temperatures. On the other hand, the anti-Stokes spectra reveal a pronounced hardening of the low-energy, acoustic region of the phonon spectrum upon heating, indicating a strong anharmonicity and a subtle dependence of phonons on structural evolution within the tetragonal phase. Experimental results are accompanied by ab initio calculations of phonon spectra of the tetragonal stoichiometric phase for a comparison with the high-resolution anti-Stokes spectra. Calculations included different density functional methods. Spin polarization and van der Waals interaction were either considered or neglected, individually or concomitantly, in order to study their respective effect on lattice dynamics description. Our results suggest that including van der Waals interaction has only a slight effect on phonon dynamics; however, phonon spectra are better described when spin polarization is included in a cooperative way with van der Waals interactions.

  11. Reanalysis of the RXTE observations of the black-hole candidate XTE J1650-500 in the 2001/2002 outburst

    International Nuclear Information System (INIS)

    Yan Lihong; Wang Jiancheng

    2012-01-01

    We present the results of the spectral fits made to 59 Rossi X-ray Timing Explorer (RXTE) observations of the Galactic X-Ray Black-Hole Candidate XTE J1650-500 covering the first 30d of its 2001/2002 outburst when the source was in a transition from the hard state to the soft state. The photon spectra can be well fitted with a phenomenological model of a power-law/cutoff power-law and a physical model of bulk-motion Comptonization. The spectral properties smoothly evolve away from the hard state and then stay in the soft state. The fitting results of the physical model reveal the peak of the burst had a flux of 2.90 × 10 −8 erg cm −2 s −1 in the 2–100 keV energy range and was observed on 2001 Sep. 9; it transitioned to the hard state. The total flux decays by a factor of ∼3 as it evolves into the soft state. The photon index Γ increases from ∼1.5 in the hard state and stays at ∼2.5 in the soft state. We found that the effective area of the high-energy X-ray emission region (the Compton cloud) decreases, i.e. the area of the Compton cloud decreases by a factor of ∼23 during the transition from the hard state to the soft state. Combining the new radio and quasi-periodic oscillation studies, the model of total flux in the 2–100 keV energy range, the jet emission and the timing analysis during the state transition, we suggest a possible geometry and evolution for the (jet+corona+disk) system, like that proposed by Kalemci et al. based on enhanced lags and peak frequency shift during the transition.

  12. XTE J1701-462 AND ITS IMPLICATIONS FOR THE NATURE OF SUBCLASSES IN LOW-MAGNETIC-FIELD NEUTRON STAR LOW-MASS X-RAY BINARIES

    International Nuclear Information System (INIS)

    Homan, Jeroen; Fridriksson, Joel K.; Remillard, Ronald A.; Lewin, Walter H. G.; Van der Klis, Michiel; Wijnands, Rudy; Altamirano, Diego; Mendez, Mariano; Lin Dacheng; Casella, Piergiorgio; Belloni, Tomaso M.

    2010-01-01

    We report on an analysis of Rossi X-Ray Timing Explorer data of the transient neutron star low-mass X-ray binary (NS-LMXB) XTE J1701-462, obtained during its 2006-2007 outburst. The X-ray properties of the source changed between those of various types of NS-LMXB subclasses. At high luminosities, the source switched between two types of Z source behavior and at low luminosities we observed a transition from Z source to atoll source behavior. These transitions between subclasses primarily manifest themselves as changes in the shapes of the tracks in X-ray color-color (CD) and hardness-intensity diagrams (HID), but they are accompanied by changes in the kHz quasi-periodic oscillations, broadband variability, burst behavior, and/or X-ray spectra. We find that for most of the outburst the low-energy X-ray flux is a good parameter to track the gradual evolution of the tracks in CD and HID, allowing us to resolve the evolution of the source in greater detail than before and relate the observed properties to other NS-LMXBs. We further find that during the transition from Z to atoll, characteristic behavior known as the atoll upper banana can equivalently be described as the final stage of a weakening Z source flaring branch, thereby blurring the line between the two subclasses. Our findings strongly suggest that the wide variety in behavior observed in NS-LXMBs with different luminosities can be linked through changes in a single variable parameter, namely the mass accretion rate, without the need for additional differences in the neutron star parameters or viewing angle. We briefly discuss the implications of our findings for the spectral changes observed in NS-LMXBs and suggest that, contrary to what is often assumed, the position along the color-color tracks of Z sources is not determined by the instantaneous mass accretion rate.

  13. High power pulse electron beam modification and ion implantation of Hg{sub 1-x}Cd{sub x}Te crystals

    Energy Technology Data Exchange (ETDEWEB)

    Vojtsekhovskij, A V; Remnev, G E [Tomsk Polytechnic Univ. (Russian Federation). Nuclear Physics Inst.; Opekunov, M S; Kokhanenko, A P; Korotaev, A G; Denisov, Yu A; Oucherenko, D A [Tomsk State Univ. (Russian Federation). Dept. of Radiophysics

    1997-12-31

    Hg{sub 1-x}Cd{sub x}Te (MCT) samples (x = 0.21 - 0.22) were irradiated by pulse electron beams at doses of 10{sup 13} to 10{sup 17} cm{sup -2}. The electron beams possessed the following parameters: 500 keV electron energy (30-40 A/cm{sup 2} electron current density, 60-80 ns current pulse); 200 keV electron energy (8- 10 A/cm{sup 2} electron current density, 100-200 ns current pulse). The electric conductivity and recombination of modified samples were investigated by the Hall effect and photoconductivity methods. For the 200 keV electron energy beam irradiation, the n-type surface regions were obtained under threshold mechanisms of donor defect generation. For the 500 keV electron energy beam irradiation, the maximum value of charge carrier lifetimes occur in the p- to n-type conductivity conversion range for the initial p-type crystals due to the conductivity compensation. MCT samples (x = 0.21 - 0.22) were implanted with Al ions at doses of 10{sup 12}-10{sup 16} cm{sup -2}. The ion beams possessed the following parameters: (1-10) A/cm{sup 2} ion current density, (100-200) ns current pulse; (150-450) keV Al ion (Al{sup +},Al{sup ++}, Al{sup +++}). The ion distribution and doping profiles were investigated by PIGE and Hall effect methods. Comparison between MCT samples after power pulse ion implantation and after standard ion implantation demonstrates differences in ion distribution, doping profiles and defect formation radiation mechanisms. (author). 3 figs., 8 refs.

  14. Rossi X-Ray Timing Explorer Observations of the First Transient Z Source XTE J1701-462: Shedding New Light on Mass Accretion in Luminous Neutron Star X-Ray Binaries

    Science.gov (United States)

    Homan, Jeroen; van der Klis, Michiel; Wijnands, Rudy; Belloni, Tomaso; Fender, Rob; Klein-Wolt, Marc; Casella, Piergiorgio; Méndez, Mariano; Gallo, Elena; Lewin, Walter H. G.; Gehrels, Neil

    2007-02-01

    We report on the first 10 weeks of RXTE observations of the X-ray transient XTE J1701-462 and conclude that it had all the characteristics of the neutron star Z sources, i.e., the brightest persistent neutron star low-mass X-ray binaries. These include the typical Z-shaped tracks traced out in X-ray color diagrams and the variability components detected in the power spectra, such as kHz QPOs and normal and horizontal branch oscillations. XTE J1701-462 is the first transient Z source and provides unique insights into mass accretion rate (m˙) and luminosity dependencies in neutron star X-ray binaries. As its overall luminosity decreased, we observed a switch between two types of Z source behavior, with the branches of the Z track changing their shape and/or orientation. We interpret this as an extreme case of the more moderate long-term changes seen in the persistent Z sources and suggest that they result from changes in m˙. We also suggest that the Cyg-like Z sources (Cyg X-2, GX 5-1, and GX 340+0) are substantially more luminous (>50%) than the Sco-like Z sources (Sco X-1, GX 17+2, and GX 349+2). Adopting a possible explanation for the behavior of kHz QPOs, which involves a prompt as well as a filtered response to changes in m˙, we further propose that changes in m˙ can explain both movement along the Z track and changes in the shape of the Z track. We discuss some consequences of this and consider the possibility that the branches of the Z will smoothly evolve into the branches observed in X-ray color diagrams of the less luminous atoll sources, although not in a way that was previously suggested.

  15. A PROPELLER-EFFECT INTERPRETATION OF MAXI/GSC LIGHT CURVES OF 4U 1608-52 AND Aql X-1 AND APPLICATION TO XTE J1701-462

    Energy Technology Data Exchange (ETDEWEB)

    Asai, K.; Matsuoka, M.; Mihara, T.; Sugizaki, M.; Serino, M. [MAXI Team, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Nakahira, S. [ISS Science Project Office, ISAS, JAXA, 2-1-1 Sengen, Tsukuba, Ibaraki 305-8505 (Japan); Negoro, H. [Department of Physics, Nihon University, 1-8-14 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8308 (Japan); Ueda, Y. [Department of Astronomy, Kyoto University, Kitashirakawa, Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan); Yamaoka, K., E-mail: kazumi@crab.riken.jp [Institute of Space and Astronautical Science, JAXA, 3-1-1 Yoshino-dai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)

    2013-08-20

    We present the luminosity dwell-time distributions during the hard states of two low-mass X-ray binaries containing a neutron star (NS), 4U 1608-52 and Aql X-1, observed with MAXI/GSC. The luminosity distributions show a steep cutoff on the low-luminosity side at {approx}1.0 Multiplication-Sign 10{sup 36} erg s{sup -1} in both sources. The cutoff implies a rapid luminosity decrease in their outburst decay phases and this decrease can be interpreted as being due to the propeller effect. We estimate the surface magnetic field of 4U 1608-52 to be (0.5-1.6) Multiplication-Sign 10{sup 8} G and Aql X-1 to be (0.6-1.9) Multiplication-Sign 10{sup 8} G from the cutoff luminosity and apply the same propeller mechanism to the similar rapid luminosity decrease observed in the transient Z source, XTE J1701-462, with RXTE/ASM. Assuming that the spin period of the NS is on the order of milliseconds, the observed cutoff luminosity implies a surface magnetic field on the order of 10{sup 9} G.

  16. Properties of the relaxation time distribution underlying the Kohlrausch-Williams-Watts photoionization of the DX centers in Cd{sub 1-x}Mn{sub x}Te mixed crystals

    Energy Technology Data Exchange (ETDEWEB)

    Trzmiel, J; Weron, K; Placzek-Popko, E [Institute of Physics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Janczura, J [Hugo Steinhaus Center for Stochastic Methods and Institute of Mathematics and Computer Science, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland)

    2009-08-26

    In this paper we clarify the relationship between the relaxation rate and relaxation time distributions underlying the Kohlrausch-Williams-Watts (KWW) photoconductivity build-ups in indium- and gallium-doped Cd{sub 1-x}Mn{sub x}Te mixed crystals. We discuss the role of asymptotic properties of the corresponding probability density functions. We show that the relaxation rate distribution, as a completely asymmetric alpha-stable distribution, leads to an infinite mean value of the effective relaxation rate. In contrast, the relaxation time distribution related to it leads to a finite mean value of the effective relaxation time. It follows from the experimental data analysis that for all the investigated samples the KWW exponent alpha decreases linearly with increasing photon flux in the range of (0.6-0.99) and its values are more spread in the case of gallium-doped material. We also observe a linear dependence of the mean relaxation time on the characteristic material time constant, which is consistent with the theoretical model.

  17. Development of a highly efficient conversion electron Moessbauer spectroscopy (CEMS) detector for low temperature (<20 K) measurements and tests on Fe / (Eu{sub x}Pb{sub 1-x})Te bilayers; Desenvolvimento de um detector de alta eficiencia para espectroscopia Moessbauer de eletrons de conversao (CEMS) a baixas temperaturas (<20K) e testes em bicamadas Fe / (Eu{sub x}Pb{sub 1-x})Te

    Energy Technology Data Exchange (ETDEWEB)

    Pombo, Carlos Jose da Silva Matos

    2006-07-01

    The {sup 57}Fe Moessbauer spectroscopy is a nuclear, non-destructive technique used for the investigation of structural, magnetic and hyperfine properties of several materials. It is a powerful tool in characterizing materials in physics, metallurgy, geology and biology field areas, especially magnetic materials, alloys and minerals containing Fe. Lately, the Conversion Electron Moessbauer Spectroscopy (CEMS) is widely used in making studies on ultra-thin magnetic films, as well as other nanostructured materials. In case of magnetic nanostructures, low temperature (LT) studies are especially important due to the possibility of dealing with superparamagnetic effects. In this work it was developed a CEMS measurement system for low temperatures (<20 K) based on a solid-state electron multiplier (Channeltron{sup R}) and an optical cryostat (Model SVT-400, Janis Research Co, USA), from which the project was originally conceived at the Applied Physics / Moessbauer spectroscopy Department from University of Duisburg-Essen, Germany. The LT-CEMS system was fully built, tested and successfully applied in a preliminary characterization of Fe/(Eu{sub x}Pb{sub 1-x})Te(111) bilayers with use of a 15 angstrom, {sup 57} Fe probe layer, with reasonable results at sample temperatures as low as 8 K. (author)

  18. Pb{sub 1–x}Eu{sub x}Te alloys (0 ⩽ x ⩽ 1) as materials for vertical-cavity surface-emitting lasers in the mid-infrared spectral range of 4–5 μm

    Energy Technology Data Exchange (ETDEWEB)

    Pashkeev, D. A., E-mail: d.pashkeev@gmail.com; Selivanov, Yu. G.; Chizhevskii, E. G.; Zasavitskiy, I. I. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

    2016-02-15

    The optical properties of epitaxial layers and heterostructures based on Pb{sub 1–x}Eu{sub x}Te alloys (0 ⩽ x ⩽ 1) are analyzed in the context of designing Bragg mirrors and vertical-cavity surface-emitting lasers for the midinfrared spectral range. It is shown that the optimal heteropair for laser microcavities is Pb{sub 1–x}Eu{sub x}Te(x ≈ 0.06)/EuTe. On the basis of this heteropair, highly reflective Bragg mirrors consisting of just three periods and featuring a reflectance of R ⩾ 99.8% at the center of the stop band are grown by molecular-beam epitaxy on BaF{sub 2} (111) substrates. Single-mode optically pumped vertical-cavity surface-emitting lasers for the 4–5 μm spectral range operating at liquid-nitrogen temperatures are demonstrated.

  19. XTE J1701-407 INTEGRAL and Swift observations

    DEFF Research Database (Denmark)

    Soldi, S.; Beckmann, V.; Eckert, D.

    2008-01-01

    :27 with an on-source time of 1.7 ksec. The combined spectrum of Swift/XRT and IBIS/ISGRI (33 ksec) can be represented by an absorbed power law with intrinsic NH = 2.2e22 1/cm^2 and photon index 2.1 ± 0.1. The model flux in the 2-50 keV band is 3e-10 erg/cm^2/sec. Assuming a maximum distance of 6 kpc (Linares et...

  20. Photoluminescence from CdxHg1-xTe

    International Nuclear Information System (INIS)

    Breivik, M; Selvig, E; Tonheim, C R; Brendhagen, E; Brudevoll, T; Rheenen, A D van; Steen, H; Nicolas, S; Lorentzen, T; Haakenaasen, R

    2008-01-01

    We present important aspects of photoluminescence (PL) of Cd x Hg 1-x Te in the infrared part of the spectrum where background thermal radiation significantly affects the PL spectrum. We show how the background spectrum can be removed from the data. We also show how the wavelength of the excitation laser affects the relative intensity of the PL peaks from a multi-layer structure. Finally, we present temperature dependent PL of a Cd 0.36 Hg 0.64 Te/Cd 0.61 Hg 0.39 Te multiple quantum well structure grown on a 4 μm thick Cd 0.36 Hg 0.64 Te buffer layer. We attribute the low temperature peak from the buffer layer to impurities. The impurity levels are depopulated as the temperature increases, resulting in a decreased PL peak intensity. Above ∼200 K a band-to-band peak from the buffer layer is observed. The quantum well peak persists up to ∼200 K

  1. INTEGRAL detects the recurrent transients XTE J1709-267 and XTE J1739-285 in outburst

    DEFF Research Database (Denmark)

    Sanchez-Fernandez, C.; Chenevez, Jérôme; Pavan, L.

    2012-01-01

    in the 20-40 keV band. We estimate a rough flux of ~8 mCrab (5 sigma) for an effective ISGRI exposure time of 21 ks. A preliminary spectral fit to the JEM-X data is consistent with an absorbed disk blackbody model of temperature ~2.2 keV. The onset of this outburst was also detected by MAXI http://maxi.riken.jp/top/index.php...

  2. The determination of the surface potential for the CdxHg1-xTe crystals and the V-CdxHg1-xTe and Ni-V-CdxMg1-xTe structures

    International Nuclear Information System (INIS)

    Veliyulin, Eh.I.; Ragimova, R.A.; Mamedov, A.A.

    1996-01-01

    Surface potential of semiconductor crystals n-Cd x Hg 1-x Te (unannealed and annealed in mercury vapors) and of the structures V-Cd x Hg 1-x Te, Ni-V-Cd x Hg 1-x Te has been defined using spectroscopy of weak-field electric reflection. It is shown that a deep penetration of vanadium atoms in near the surface region of the crystal occurs in the structures on the basis of unannealed Cd x Hg 1-x Te. 1 ref.; 4 figs

  3. The new intermediate long-bursting source XTE J1701-407

    DEFF Research Database (Denmark)

    Falanga, M.; Cumming, A.; Bozzo, E.

    2009-01-01

    functions with e-folding times of tau(1) = 40 +/- 3 s and tau(2) = 221 +/- 9 s. The bursts occurred at a persistent luminosity of L-per = 8.3 x 10(36) erg s(-1) (approximate to 2.2% of the Eddington luminosity). For the intermediate long-burst, the mass accretion rate per unit area onto the neutron star...

  4. Exciton luminescence in CdxMn1-xTe compounds

    International Nuclear Information System (INIS)

    Caraman, M.; Gashin, P.; Metelitsa, Snejana; Nicorici, Valentina; Nicorici, A.

    2002-01-01

    The Cd x Mn 1-x Te (0.5 7 W/cm 2 . The luminescence spectra were observed at 78 K. The results of the study had shown that the presence of relatively narrow luminescence peaks localized in the region of the fundamental absorption edge is characteristic for these spectra and for the majority of the crystals a wide maximum in the long wavelength region is observed. The luminescence maxima with an accuracy of ∼ 5 meV correspond to the resonance energy of the excitons of the state with n=1 determined from the absorption spectra. Hence, these maxima can be considered as exciton luminescence stimulated either by the excitons of the state n=1 or bounded to the exciton ionization centers. From the analysis of the absorption and exciton luminescence spectra one can make a conclusion about the fact that the homogeneity extent of the crystals decreases from CdTe to the compounds with x= 0.8 - 0.7 and slightly increases at the x decrease to 0.5. The exciton luminescence lines in CdTe and Cd 0.99 Mn 0.01 Te crystals is shifting by 7 - 10 meV relatively to the lines of free excitons absorption. This fact is explained by the fact that in these crystals, probably, excitons bounding to the lattice inherited defects with the binding energy of 7 - 10 meV participate in the luminescence. In the long wavelength region a wide peak is observed on which the impurity lines are not displayed. In the luminescence spectra of CdTe with 0.1%. As crystals three maxima at 1.51 eV, 1.46 eV and 1.42 eV are revealed. For pure CdTe the maximum at 1.4 eV is also revealed. These maxima are explained by the luminescence through the recombination levels localized at 0.46 eV. (authors)

  5. Electronic properties and charge density of BexZn1− xTe alloys

    Indian Academy of Sciences (India)

    Electronic band structure calculations are performed for the BeZn1−Te (0 ≤ ≤ 1 in steps of 0.2) alloys following the empirical pseudopotential method. The alloying effects are modelled through the modified virtual crystal approximation. Throughout the composition, valence band maximum resides at the point.

  6. Photoconductivity of Se85-xTe15Hgx thin films

    International Nuclear Information System (INIS)

    Chaudhary, Neetu; Bahishti, Adam A.; Zulfequar, M.

    2012-01-01

    The photoconductive properties such as dark conductivity, steady state and transient characteristics of a-Se 85-x Te 15 Hg x thin films, prepared by thermal vacuum evaporation technique have been studied in the temperature range 312-380 K. Analysis of data shows that the activation energy of dark current is greater as compared to the activation energy of photocurrent. The activation energy increases at higher concentration of Hg which shows that the defect density of states decreases. Analysis of intensity dependent photoconductivity shows that the bimolecular recombination is predominant. The transient photoconductivity shows that the carrier lifetime decreases with the increase in Hg concentration and increases at higher concentration of Hg. This decrease is due to the transition trapping process. Further the photosensitivity and carrier lifetime increases at higher concentration of Hg which also confirms that the density of defect states decreases.

  7. Phonon Density of States and Heat Capacity of La3-xTe4

    International Nuclear Information System (INIS)

    Delaire, Olivier A.; May, Andrew F.; McGuire, Michael A.; Porter, Wallace D.; Lucas, Matthew S.; Stone, Matthew B.; Abernathy, Douglas L.; Snyder, G.J.

    2009-01-01

    The phonon density of states (DOS) of La 3-x Te 4 compounds (x=0.0, 0.18, 0.32) was measured at 300, 520, and 780 K, using inelastic neutron scattering. A significant stiffening of the phonon DOS, and a large broadening of features were observed upon introduction of vacancies on La sites (increasing x). Heat capacity measurements were performed at temperatures ∼1.85 ≤ T ≤ 1200 K and were analyzed to quantify the contributions of phonons and electrons. The Debye temperature and the electronic coefficient of heat capacity determined from these measurements are consistent with the neutron scattering results, and with previously reported first-principles calculations. Our results indicate that La vacancies in La 3-x Te 4 strongly scatter phonons, and this source of scattering appears to be independent of temperature. The stiffening of the phonon DOS induced by the introduction of vacancies is explained in terms of the electronic structure and the change in bonding. The temperature dependence of the phonon DOS is captured satisfactorily by the quasiharmonic approximation.

  8. Thermal studies of Se85-xTe15Inx (x = 3,6,9,12) glasses

    International Nuclear Information System (INIS)

    Sushama, D.; George, Achamma; Asokan, S.

    2011-01-01

    Bulk glasses of compositions Se 85-x Te 15 In x (x = 3,6,9,12) are prepared by melt quenching technique and Differential scanning calorimetry (DSC) is employed to study the thermal stability, crystallization mechanism as well as specific heat of these glasses. It is found that the addition of indium increases the glass transition temperature. From the heating rate dependence of the glass transition temperature the activation energy of glass transition is determined using Kissinger's equation for non-isothermal crystallization of materials. An attempt has been made to explain the variation in the value of T c , T p and ΔC p for the composition Se 73 Te 15 In 12 using rigidity percolation threshold (RPT). From the values of (T c -T g ) the stable glass system is determined.

  9. Reduction of thermal conductivity in YxSb2-xTe3 for phase change memory

    Science.gov (United States)

    Li, Zhen; Miao, Naihua; Zhou, Jian; Xu, Huibin; Sun, Zhimei

    2017-11-01

    Thermal conductivity (κ) is one of the fundamental properties of materials for phase change memory (PCM) application, as the set/reset processes strongly depend upon heat dissipation and transport. The κ of phase change materials in both amorphous and crystalline phases should be quite small, because it determines how energy-efficient the PCM device is during programming. At a high temperature, the electronic thermal conductivity (κe) is always notable for semiconductors, which is still lacking for antimony telluride under doping in the literature as far as we know. In this paper, using density functional theory and Boltzmann transport equations, we report calculations of lattice thermal conductivity κL and electronic thermal conductivity κe of the yttrium doped antimony telluride. We show that the average value of thermal conductivity decreases from ˜2.5 W m-1 K-1 for Sb2Te3 to ˜1.5 W m-1 K-1 for Y0.167Sb1.833Te3. This can be attributed to the reduced κL and κe, especially the κe at high temperature (near melting point). We further point out that the increased effective mass of carriers and the flat valance band edge are responsible for the decrease of κe. The reduced thermal conductivity is highly desirable for the decrease of heat dissipation and transport in PCM operations, which can increase the density of memory and reduce energy consumption.

  10. Cd-diffused Pb/sub 1-x/Sn/sub x/Te lasers with high output

    International Nuclear Information System (INIS)

    Lo, W.

    1976-01-01

    Cd-diffused Pb 1 /sub -//subx/Sn/subx/Te (xapprox.0.13) diode lasers have been fabricated with cw output powers of 1.25 mW (single mode) and 2.4 mW (total) at 10.6 μm. These power levels are attributed to the low-temperature Cd diffusion, a new method of growing low-dislocation-density crystals, and to a contact resistance as low as 3x10 -5 Ω cm 2 . Multimode emission spectra are common for cw operation, but reducing the cavity width encourages single-mode emission, indicating the filamentary nature of modes in these devices

  11. Excitation density dependence of the photoluminescence from CdxHg1-xTe multiple quantum wells

    International Nuclear Information System (INIS)

    Tonheim, C R; Selvig, E; Nicolas, S; Breivik, M; Haakenaasen, R; Gunnaes, A E

    2008-01-01

    A study of the photoluminescence from a four-period Cd x Hg 1-x Te multiple quantum well structure at 11 K as a function of excitation density is presented. High-resolution X-ray diffraction and transmission electron microscopy revealed that the quantum well structure is of high quality. This was supported by the narrow photoluminescence peak originating in the ground state electron - heavy hole transition, with a full width at half maximum of only 7.4 meV for an excitation density of 1.3 W/cm 2 . When the excitation density was increased from 1.3 to 23.4 W/cm 2 , the peak position was shifted toward higher energy by 2.6 meV and the full width at half maximum increased from 7.4 to 10.9 meV

  12. Dislocation-free etching figures in crystals of CdxHg1-xTe solid solutions

    International Nuclear Information System (INIS)

    Kholina, E.N.; Khazieva, R.A.; Bursak, S.S.; Nevskij, O.B.; Filatov, A.V.; Popovyan, G.Eh.; Suslov, E.V.; Prijmak, A.N.

    1988-01-01

    Using the method of chemical etching, etching figures formed in areas distributed over Cd x Hg 1-x Te crystal with increased content of impurities consisting of Si,Al,Na,K,Cl,Fe,Ti,Mg and S mainly are revealed. The size of impurity inclusions is >1μm, that is why they cannot be detected either by optical microscopy or local microroentgenospectral analysis. Formation and distribution of impurity inclusions are obviously defined by only the concentration of impurity atoms in the melt. The shape of etching figures does not depend on crystallographical orientation of the crystal-matrix

  13. L'enquista de literatura orala e son contèxte au sègle XX

    OpenAIRE

    Bouvier, Jean-Claude

    2014-01-01

    Après lei folcloristas dau sègle dètz-e-nòu, lo moviment de recèrca sus la literatura orala es contunhat ò puslèu représ a partir deis annadas 1960, dins de condicions que pòdon èstre dichas mai marridas, mai de tot biais nòvas. Dison generalament que la tradicion orala es avanida, çò qu'es verai en partida per lo conte meravilhós. Mai es verai pasmens que de tròç entiers de literatura orala son restats vius (n'en tornarai parlar dins un moment) e es verai tanben que de fòrmas novas de tradic...

  14. Evolution of the complicated decaying branch of the very long outburst in XTE J1701-462

    Czech Academy of Sciences Publication Activity Database

    Šimon, Vojtěch

    2015-01-01

    Roč. 37, May (2015), s. 26-34 ISSN 1384-1076 Grant - others:GA ČR(CZ) GA13-33324S Institutional support: RVO:67985815 Keywords : X-rays * radiation mechanisms * accretion disks Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 1.085, year: 2015

  15. Probing the Optical Properties and Strain-Tuning of Ultrathin Mo1- xW xTe2.

    Science.gov (United States)

    Aslan, Ozgur Burak; Datye, Isha M; Mleczko, Michal J; Sze Cheung, Karen; Krylyuk, Sergiy; Bruma, Alina; Kalish, Irina; Davydov, Albert V; Pop, Eric; Heinz, Tony F

    2018-04-11

    Ultrathin transition metal dichalcogenides (TMDCs) have recently been extensively investigated to understand their electronic and optical properties. Here we study ultrathin Mo 0.91 W 0.09 Te 2 , a semiconducting alloy of MoTe 2 , using Raman, photoluminescence (PL), and optical absorption spectroscopy. Mo 0.91 W 0.09 Te 2 transitions from an indirect to a direct optical band gap in the limit of monolayer thickness, exhibiting an optical gap of 1.10 eV, very close to its MoTe 2 counterpart. We apply tensile strain, for the first time, to monolayer MoTe 2 and Mo 0.91 W 0.09 Te 2 to tune the band structure of these materials; we observe that their optical band gaps decrease by 70 meV at 2.3% uniaxial strain. The spectral widths of the PL peaks decrease with increasing strain, which we attribute to weaker exciton-phonon intervalley scattering. Strained MoTe 2 and Mo 0.91 W 0.09 Te 2 extend the range of band gaps of TMDC monolayers further into the near-infrared, an important attribute for potential applications in optoelectronics.

  16. The frequency-domain relaxation response of gallium doped Cd{sub 1-x}Mn{sub x}Te

    Energy Technology Data Exchange (ETDEWEB)

    Trzmiel, Justyna; Weron, Karina [Institute of Physics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Jurlewicz, Agnieszka [Hugo Steinhaus Center, Institute of Mathematics and Computer Science, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland)

    2010-03-10

    In this paper the complex dielectric permittivity of gallium doped Cd{sub 0.99}Mn{sub 0.01}Te mixed crystals is studied at different temperatures. We observe a two-power-law relaxation pattern with m and n, the low- and high-frequency power-law exponents respectively, satisfying the relation m < 1 - n. To interpret the empirical result we propose a correlated-cluster relaxation mechanism. This approach allows us to find origins of both power-law exponents, m and n.

  17. Accretion torques and motion of the hot spot on the accreting millisecond pulsar XTE J1807-294

    NARCIS (Netherlands)

    Patruno, A.; Hartman, J.M.; Wijnands, R.; Chakrabarty, D.; van der Klis, M.

    2010-01-01

    We present a coherent timing analysis of the 2003 outburst of the accreting millisecond pulsar (AMXP) XTEJ1807-294. We find a 95% confidence interval for the pulse frequency derivative of (+0.7, +4.7) x 10(-14) Hz s(-1) and (-0.6, +3.8) x 10(-14) Hz s(-1) for the fundamental and second harmonics,

  18. Far-infrared phonon spectroscopy of Pb1-xMn xTe layers grown by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Romcevic, N.; Nadolny, A.J.; Romcevic, M.; Story, T.; Taliashvili, B.; Milutinovic, A.; Trajic, J.; Lusakowska, E.; Vasiljevic-Radovic, D.; Domukhovski, V.; Osinniy, V.; Hadzic, B.; Dziawa, P.

    2007-01-01

    In this paper we used far-infrared spectroscopy, reflection high energy electron diffraction (RHEED), X-ray diffraction and atomic force microscopy (AFM) to investigate structural and optical properties of Pb 1-x Mn x Te layers grown by molecular beam epitaxy (MBE). A numerical model for calculating the reflectivity coefficient for complex systems which include films, buffer layer and substrate has been applied. The infrared reflectivity spectra consist of Pb 1-x Mn x Te phonons, which exhibit intermediate one-two mode behavior, and MnTe phonons. A good agreement between calculated and experimental spectra is achieved. We registered the local distribution of Mn impurities depending on substrate type. For films growth on BaF 2 substrate we registered the orthorhombic local structure of MnTe clusters, while in the case of KCl substrate this structure is cubic. The Pb 1-x Mn x Te long wavelength optical phonons were described by the modified Genzel's model

  19. A tool to separate optical/infrared disc and jet emission in X-ray transient outbursts: the colour-magnitude diagrams of XTE J1550-564

    NARCIS (Netherlands)

    Russell, D.M.; Maitra, D.; Dunn, R.J.H.; Fender, R.P.

    2011-01-01

    It is now established that thermal disc emission and non-thermal jet emission can both play a role at optical/infrared (OIR) wavelengths in X-ray transients. The spectra of the jet and disc components differ, as do their dependence on mass accretion properties. Here we demonstrate that the OIR

  20. REPRODUCING THE CORRELATIONS OF TYPE C LOW-FREQUENCY QUASI-PERIODIC OSCILLATION PARAMETERS IN XTE J1550–564 WITH A SPIRAL STRUCTURE

    Energy Technology Data Exchange (ETDEWEB)

    Varniere, Peggy [APC, AstroParticule et Cosmologie, Universite Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire de Paris, Sorbonne Paris Cité, 10, rue Alice Domon et Lonie Duquet, F-75205 Paris Cedex 13 (France); Vincent, Frederic H., E-mail: varniere@apc.univ-paris7.fr [Observatoire de Paris/LESIA, 5, place Jules Janssen, F-92195 Meudon Cedex (France)

    2017-01-10

    While it has been observed that the parameters intrinsic to the type C low-frequency quasi-periodic oscillations are related in a nonlinear manner among themselves, there has been, up to now, no model to explain or reproduce how the frequency, the FWHM, and the rms amplitude of the type C low-frequency quasi-periodic oscillations behave with respect to one another. Here we are using a simple toy model representing the emission from a standard disk and a spiral such as that caused by the accretion–ejection instability to reproduce the overall observed behavior and shed some light on its origin. This allows us to prove the ability of such a spiral structure to be at the origin of flux modulation over more than an order of magnitude in frequency.

  1. Effect of layer composition on band spectrum of CdxHg1-xTe - CdyHg1-yTe-type superlattices

    International Nuclear Information System (INIS)

    Gerchikov, L.G.; Subashiev, A.V.; Salman Dalla

    1993-01-01

    Evolution of energy spectrum of Cd x Hg 1-x Te -Cd y Hg 1-y Te superlattices at variation of layer composition is considered. Transition from 3 type superlattice to 1 type superlattice occurring for y=0.16 is studied comprehensively. In this case, dependence of the width of superlattice forbidden zone on layer thickness is shown to become more smooth, than in CdTe - HgTe superlattice and it gives more possibilities to use such superlattices for making IR phototransistors. 10 refs., 4 figs

  2. Reformulated tight binding calculation for band discontinuity at CdTe/Hg xCd1-xTe heterointerfaces and their type I-type III transitions

    International Nuclear Information System (INIS)

    Ekpunobi, A.J.

    2005-01-01

    A recently reformulated tight binding method is used to calculate the valence band discontinuity at the CdTe/Hg x Cd 1-x Te interface in the s 2 p 2 configuration. The calculated valence band discontinuity of 0.31 eV at CdTe/HgTe interface is in good agreement with self-consistent calculation and accepted experimental value. Calculations were extended to alloy interfaces, which enabled the investigation of the band-offset problem at the transition point. Both valence band discontinuity ratio and conduction band discontinuity ratio show inflexions at the transition point

  3. Development of a highly efficient conversion electron Moessbauer spectroscopy (CEMS) detector for low temperature (xPb1-x)Te bilayers

    International Nuclear Information System (INIS)

    Pombo, Carlos Jose da Silva Matos

    2006-01-01

    The 57 Fe Moessbauer spectroscopy is a nuclear, non-destructive technique used for the investigation of structural, magnetic and hyperfine properties of several materials. It is a powerful tool in characterizing materials in physics, metallurgy, geology and biology field areas, especially magnetic materials, alloys and minerals containing Fe. Lately, the Conversion Electron Moessbauer Spectroscopy (CEMS) is widely used in making studies on ultra-thin magnetic films, as well as other nanostructured materials. In case of magnetic nanostructures, low temperature (LT) studies are especially important due to the possibility of dealing with superparamagnetic effects. In this work it was developed a CEMS measurement system for low temperatures ( R ) and an optical cryostat (Model SVT-400, Janis Research Co, USA), from which the project was originally conceived at the Applied Physics / Moessbauer spectroscopy Department from University of Duisburg-Essen, Germany. The LT-CEMS system was fully built, tested and successfully applied in a preliminary characterization of Fe/(Eu x Pb 1-x )Te(111) bilayers with use of a 15 angstrom, 57 Fe probe layer, with reasonable results at sample temperatures as low as 8 K. (author)

  4. Investigation of the change in CdxHg1-xTe surface chemical structure under processing in N2O and H2 gases activated by a high-frequency discharge

    International Nuclear Information System (INIS)

    Vasil'ev, V.V.; Zakhar'yash, T.I.; Kesler, V.G.; Parm, I.O.; Solov'ev, A.P.

    2001-01-01

    The change in Cd x Hg 1-x Te (CTM) surface chemical composition is investigated during the processing by atomic beams of oxygen and hydrogen, obtained by a method of the electronic impact in a high-frequency plasma (N 2 O and H 2 ). The analysis is carried out using methods of Auger electron spectroscopy and X-ray photoelectron spectroscopy. It is shown that consecutive treatment by beams of atomic oxygen and hydrogen results in removing from the sample surface as carbon impurities so a layer of as-grown oxide and metallic tellurium. It is concluded that the suggested technique of CTM substrate surface pretreatment can be used efficiently in manufacturing semiconductor junctions [ru

  5. Imaging Dirac-mass disorder from magnetic dopant atoms in the ferromagnetic topological insulator Crx(Bi0.1Sb0.9)2-xTe3.

    Science.gov (United States)

    Lee, Inhee; Kim, Chung Koo; Lee, Jinho; Billinge, Simon J L; Zhong, Ruidan; Schneeloch, John A; Liu, Tiansheng; Valla, Tonica; Tranquada, John M; Gu, Genda; Davis, J C Séamus

    2015-02-03

    To achieve and use the most exotic electronic phenomena predicted for the surface states of 3D topological insulators (TIs), it is necessary to open a "Dirac-mass gap" in their spectrum by breaking time-reversal symmetry. Use of magnetic dopant atoms to generate a ferromagnetic state is the most widely applied approach. However, it is unknown how the spatial arrangements of the magnetic dopant atoms influence the Dirac-mass gap at the atomic scale or, conversely, whether the ferromagnetic interactions between dopant atoms are influenced by the topological surface states. Here we image the locations of the magnetic (Cr) dopant atoms in the ferromagnetic TI Cr0.08(Bi0.1Sb0.9)1.92Te3. Simultaneous visualization of the Dirac-mass gap Δ(r) reveals its intense disorder, which we demonstrate is directly related to fluctuations in n(r), the Cr atom areal density in the termination layer. We find the relationship of surface-state Fermi wavevectors to the anisotropic structure of Δ(r) not inconsistent with predictions for surface ferromagnetism mediated by those states. Moreover, despite the intense Dirac-mass disorder, the anticipated relationship [Formula: see text] is confirmed throughout and exhibits an electron-dopant interaction energy J* = 145 meV·nm(2). These observations reveal how magnetic dopant atoms actually generate the TI mass gap locally and that, to achieve the novel physics expected of time-reversal symmetry breaking TI materials, control of the resulting Dirac-mass gap disorder will be essential.

  6. Mercury vacancies as divalent acceptors in Hg{sub y}Te{sub 1} {sub –} {sub y}/Cd{sub x}Hg{sub 1} {sub –} {sub x}Te structures with quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Kozlov, D. V., E-mail: dvkoz@ipmras.ru; Rumyantsev, V. V.; Morozov, S. V.; Kadykov, A. M.; Fadeev, M. A. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Varavin, V. S.; Mikhailov, N. N.; Dvoretsky, S. A. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation); Gavrilenko, V. I. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Teppe, F. [Laboratoire Charles Coulomb (L2C) (France)

    2016-12-15

    A long-wavelength band caused by transitions between states related to the valence band is detected in the photoconductivity spectra of Hg{sub y}Te{sub 1–y}/Cd{sub x}Hg{sub 1–x}Te (CMT) structures with quantum wells. The energy states of mercury vacancies in quantum wells of CMT structures is calculated taking into account a chemical shift. It is shown that the long-wavelength band observed in the photoconductivity spectra of these structures is associated with the ionization of divalent acceptor centers which are such vacancies.

  7. Preparation of CdxHg1-xTe films by the method of vapour-phase epitaxy of HgTe on CdTe substrates with subsequent mutual diffusion

    International Nuclear Information System (INIS)

    Varavin, V.S.; Sidorov, Yu.G.; Remesnik, V.G.; Chikichev, S.I.; Nis, I.E.

    1994-01-01

    Mirror-like HgTe films have been grown on CdTe substrates of various orientations by vapor deposition of HgTe in temperature gradient. Deposition rates fell in the range of 5-12 μm/h. Subsequent annealing has permitted production of Hg 1-x Cd x Te layers about 15 μm in thickness. Canier density in annealed n-type specimens has been found to constitute (1-20)x10 15 cm -3 at carrier mobility of (2-5)x10 4 cm 2 xV -1 xs -1 and in p-type films - (1-5)x10 16 cm -3 and 200-350 cm 2 xV -1 xs -1 (77 K) respectively

  8. Polarity-dependent resistance switching in GeSbTe phase-change thin films : The importance of excess Sb in filament formation

    NARCIS (Netherlands)

    Pandian, Ramanathaswamy; Kooi, Bart J.; Oosthoek, Jasper L. M.; van den Dool, Pim; Palasantzas, George; Pauza, Andrew

    2009-01-01

    We show that polarity-dependent resistance switching in GeSbTe thin films depends strongly on Sb composition by comparing current-voltage characteristics in Sb-excess Ge(2)Sb(2+x)Te(5) and stoichiometric Ge(2)Sb(2)Te(5) samples. This type of switching in Ge(2)Sb(2+x)Te(5) films is reversible with

  9. Black hole and neutron star soft X-ray transients: a hard X-ray view of their outbursts

    International Nuclear Information System (INIS)

    Yu, W.

    2004-01-01

    The RXTE public observations of the outbursts of black hole soft X-ray transients XTE J1550-564, XTE J1859+226, 4U 1630-47, XTE J1118+480, XTE J1650-500, and the neutron star soft X-ray transients 4U 1608-52, Aquila X-1, including a variable 'persistent' neutron star low mass X-ray binary 4U 1705-44, are summarized in this paper. The hard X-ray view of those outbursts, which is quite different from that of the soft X-ray band, suggests that there are several types of outbursts which result in different hard X-ray outburst profile - the outburst profiles are energy dependent. One type is the low/hard state outbursts, the other type is the outburst showing transitions from the low/hard state to the high/soft state, or to the intermediate or to the very high state. The later has an initial low/hard state, introducing the phenomena that the hard X-ray precedes the soft X-ray in the outburst rise. Such outbursts in XTE J1550-564, Aql X-1 and 4U 1705-44 support a two-accretion-flow model which involves one Keplerian disk flow and one sub-Keplerian flow for the initial outburst rise

  10. Continuous brightening of IGR J17473-2721

    DEFF Research Database (Denmark)

    Baldovin Saavedra, C.; Chenevez, Jérôme; Kuulkers, E.

    2008-01-01

    Renewed accretion activity has been reported by Swift/XRT (ATel #1459), XTE/PCA (ATel #1460) and INTEGRAL/IBIS/ISGRI (ATel #1461) from the RXTE transient IGR J17473-2721 (= XTE J1747-274; ATels #467, #498) after the detection of an X-ray burst by SuperAGILE (ATel #1445). From the on-going Galactic...... bulge monitoring program (see ATels #1385, #1461) we report that the transient continues to brighten as seen with IBIS/ISGRI and JEM-X....

  11. Journal of Astrophysics and Astronomy | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Astrophysics and Astronomy. S. Seetha. Articles written in Journal of Astrophysics and Astronomy. Volume 21 Issue 1-2 June 2000 pp 29-38. X-ray Observation of XTE J2012+381 during the 1998 Outburst · S. Naik P. C. Agrawal B. Paul A. R. Rao S. Seetha Κ. Kasturirangan · More Details Abstract ...

  12. P. C. Agrawal

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Astrophysics and Astronomy. P. C. Agrawal. Articles written in Journal of Astrophysics and Astronomy. Volume 21 Issue 1-2 June 2000 pp 29-38. X-ray Observation of XTE J2012+381 during the 1998 Outburst · S. Naik P. C. Agrawal B. Paul A. R. Rao S. Seetha Κ. Kasturirangan · More Details ...

  13. The Correlation between Hard X-Ray Peak Flux and Soft X-Ray Peak Flux in the Outburst Rise of Low-Mass X-Ray Binaries

    NARCIS (Netherlands)

    Yu, W.; van der Klis, M.; Fender, R.P.

    2004-01-01

    We have analyzed Rossi X-Ray Timing Explorer pointed observations of the outbursts of black hole and neutron star soft X-ray transients in which an initial low/hard state, or ``island'' state, followed by a transition to a softer state was observed. In three sources-the black hole transient XTE

  14. Journal of Astrophysics and Astronomy | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... We have investigated the Quasi Periodic Oscillation (QPO) properties of the transient accreting X-ray pulsar XTE J1858 + 034 during the second outburst of this source in April–May 2004. We have used observations made with the Proportional Counter Array (PCA) of the Rossi X-ray Timing Explorer (RXTE) ...

  15. Photovoltaic performance of a Cd{sub 1−x}Mg{sub x}Te/CdS top-cell structure

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, Omar S. [Instituto de Energías Renovables, Universidad Nacional Autónoma de México, Temixco, Morelos 62580 (Mexico); Centro del Cambio Global y la Sustentabilidad en el Sureste, Villahermosa, Tabasco 86080 (Mexico); Regalado-Pérez, E.; Mathews, N.R. [Instituto de Energías Renovables, Universidad Nacional Autónoma de México, Temixco, Morelos 62580 (Mexico); Morales, Erik R. [División Académica de Ingeniería y Arquitectura, Universidad Juárez Autónoma de Tabasco, Cunduacán, Tabasco 86690 (Mexico); Reyes-Coronado, David [Unidad Académica Playa del Carmen, Universidad de Quintana Roo, Playa del Carmen, Quintana Roo 77710 (Mexico); Galvez, Geovanni Hernández [Centro del Cambio Global y la Sustentabilidad en el Sureste, Villahermosa, Tabasco 86080 (Mexico); Mathew, Xavier, E-mail: xm@ier.unam.mx [Instituto de Energías Renovables, Universidad Nacional Autónoma de México, Temixco, Morelos 62580 (Mexico)

    2015-05-01

    In this paper we report the progress in developing a wide band gap alloy material based on CdTe to use as the top-cell absorber in tandem solar cells. High photovoltaic performance for a Cd{sub 1−x}Mg{sub x}Te/CdS top-cell was achieved by tuning the composition of the Cd{sub 1−x}Mg{sub x}Te film, and optimizing the device processing. We have carried out studies on the effect of vapor chloride treatment of the Cd{sub 1−x}Mg{sub x}Te/CdS device and the thermal annealing of the Cu/Au contacts on the opto-electronic properties of the device. With improved contact processing and post deposition treatments, we were able to achieve 9.3% efficiency for a 1.6 eV band gap top-cell; Cd{sub 1−x}Mg{sub x}Te/CdS on conductive glass substrate. - Highlights: • Cd{sub 1−x}Mg{sub x}Te films obtained by co-evaporation of CdTe and Mg • Band gap of Cd{sub 1−x}Mg{sub x}Te can be easily tuned by verifying x. • Band gap of Cd{sub 1−x}Mg{sub x}Te is stable only for short annealing durations. • Obtained efficiency of a Cd{sub 1−x}Mg{sub x}Te based device with a band gap of 1.6 eV is 9.3%.

  16. Hydrostatic pressure study of MBE CdMnTe doped bromine

    Energy Technology Data Exchange (ETDEWEB)

    Szczytko, J.; Wasek, D.; Przybytek, J.; Baj, M. [Institute of Experimental Physics, Warsaw University, Warsaw (Poland); Waag, A. [Physikalisches Institut, Universitaet Wuerzburg, Wuerzburg (Germany)

    1995-12-31

    We present Hall effect and resistivity measurements as a function of pressure performed on MBE-grown Cd{sub 1-x}Mn{sub x}Te (with x=0.14) layer doped with bromine. The experimental data were analysed using positive and negative U model of Br centers. We found that both models could reproduce the experimental points, but in the case of positive U modes - only under assumption that the sample was completely uncompensated. (author). 6 refs, 3 figs.

  17. Hard X-ray activity of IGR J17473-2721

    DEFF Research Database (Denmark)

    Kuulkers, E.; Shaw, S.; Beckmann, V.

    2008-01-01

    Persistent X-ray activity has been reported by Swift/XRT (ATel #1459) and RXTE/PCA (ATel #1460) from the transient IGR J17473-2721 (= XTE J1747-274; ATels #467, #498) after the detection of an X-ray burst by SuperAGILE (ATel #1445). We report the detection of persistent activity at 18-100 keV wit...

  18. Delineation of phase fields at the Te-rich end of the Ru Te binary system

    Science.gov (United States)

    Ali (Basu), M.; Bharadwaj, S. R.; Das, D.

    2005-04-01

    The tellurium rich side of the ruthenium-tellurium binary system was studied by differential thermal analysis. To avoid reported problems of Te loss by evaporation and reactive interference of Te to the thermocouples of the thermal analyzer, the present study made use of specially designed sealed quartz capsules as DTA containers. The thermal analyses were carried out over the compositional range of 0.66 ⩽ xTe ⩽ 1.00 with the help of SETARAM TG/DTA and other indigenously built thermal analyzers available in this laboratory. The thermal data generated for fifteen different compositions were interpreted for the nature of phase transitions occurring at their characteristic temperatures. The Ru-Te binary system was found to have a eutectic transformation at 444 °C at a composition of xTe = 0.918 and a monotectic transformation at 447 °C at a composition of xTe = 0.700. Up to 6 at.% Ru is soluble in Te at about 440 °C.

  19. COMMON PATTERNS IN THE EVOLUTION BETWEEN THE LUMINOUS NEUTRON STAR LOW-MASS X-RAY BINARY SUBCLASSES

    International Nuclear Information System (INIS)

    Fridriksson, Joel K.; Homan, Jeroen; Remillard, Ronald A.

    2015-01-01

    The X-ray transient XTE J1701–462 was the first source observed to evolve through all known subclasses of low-magnetic-field neutron star low-mass X-ray binaries (NS-LMXBs), as a result of large changes in its mass accretion rate. To investigate to what extent similar evolution is seen in other NS-LMXBs we have performed a detailed study of the color–color and hardness–intensity diagrams (CDs and HIDs) of Cyg X-2, Cir X-1, and GX 13+1—three luminous X-ray binaries, containing weakly magnetized neutron stars, known to exhibit strong secular changes in their CD/HID tracks. Using the full set of Rossi X-ray Timing Explorer Proportional Counter Array data collected for the sources over the 16 year duration of the mission, we show that Cyg X-2 and Cir X-1 display CD/HID evolution with close similarities to XTE J1701–462. Although GX 13+1 shows behavior that is in some ways unique, it also exhibits similarities to XTE J1701–462, and we conclude that its overall CD/HID properties strongly indicate that it should be classified as a Z source, rather than as an atoll source. We conjecture that the secular evolution of Cyg X-2, Cir X-1, and GX 13+1—illustrated by sequences of CD/HID tracks we construct—arises from changes in the mass accretion rate. Our results strengthen previous suggestions that within single sources Cyg-like Z source behavior takes place at higher luminosities and mass accretion rates than Sco-like Z behavior, and lend support to the notion that the mass accretion rate is the primary physical parameter distinguishing the various NS-LMXB subclasses

  20. EVIDENCE OF LIGHT-BENDING EFFECTS AND ITS IMPLICATION FOR SPECTRAL STATE TRANSITIONS

    International Nuclear Information System (INIS)

    Reis, R. C.; Miller, J. M.; Reynolds, M. T.; Fabian, A. C.; Walton, D. J.; Steiner, J. F.; Cackett, E.

    2013-01-01

    It has long been speculated that the nature of the hard X-ray corona may be an important second driver of black hole state transitions, in addition to the mass accretion rate through the disk. However, a clear physical picture of coronal changes has not yet emerged. We present results from a systematic analysis of Rossi X-Ray Timing Explorer observations of the stellar-mass black hole binary XTE J1650-500. All spectra with significant hard X-ray detections were fit using a self-consistent, relativistically blurred disk reflection model suited to high ionization regimes. Importantly, we find evidence that both the spectral and timing properties of black hole states may be partially driven by the height of the X-ray corona above the disk, and related changes in how gravitational light bending affects the corona-disk interaction. Specifically, the evolution of the power-law, thermal disk, and relativistically convolved reflection components in our spectral analysis indicates that: (1) the disk inner radius remains constant at r in =1.65 ± 0.08 GM/c 2 (consistent with values found for the ISCO of XTE J1650-500 in other works) throughout the transition from the brighter phases of the low-hard state to the intermediate states (both the hard-intermediate and soft-intermediate), through to the soft state and back; (2) the ratio between the observed reflected X-ray flux and power-law continuum (the 'reflection fraction', R) increases sharply at the transition between the hard-intermediate and soft-intermediate states ('ballistic' jets are sometimes launched at this transition); (3) both the frequency and coherence of the high-frequency quasi-periodic oscillations observed in XTE J1650-500 increase with R. We discuss our results in terms of black hole states and the nature of black hole accretion flows across the mass scale.

  1. COMMON PATTERNS IN THE EVOLUTION BETWEEN THE LUMINOUS NEUTRON STAR LOW-MASS X-RAY BINARY SUBCLASSES

    Energy Technology Data Exchange (ETDEWEB)

    Fridriksson, Joel K. [Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Homan, Jeroen; Remillard, Ronald A., E-mail: J.K.Fridriksson@uva.nl [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)

    2015-08-10

    The X-ray transient XTE J1701–462 was the first source observed to evolve through all known subclasses of low-magnetic-field neutron star low-mass X-ray binaries (NS-LMXBs), as a result of large changes in its mass accretion rate. To investigate to what extent similar evolution is seen in other NS-LMXBs we have performed a detailed study of the color–color and hardness–intensity diagrams (CDs and HIDs) of Cyg X-2, Cir X-1, and GX 13+1—three luminous X-ray binaries, containing weakly magnetized neutron stars, known to exhibit strong secular changes in their CD/HID tracks. Using the full set of Rossi X-ray Timing Explorer Proportional Counter Array data collected for the sources over the 16 year duration of the mission, we show that Cyg X-2 and Cir X-1 display CD/HID evolution with close similarities to XTE J1701–462. Although GX 13+1 shows behavior that is in some ways unique, it also exhibits similarities to XTE J1701–462, and we conclude that its overall CD/HID properties strongly indicate that it should be classified as a Z source, rather than as an atoll source. We conjecture that the secular evolution of Cyg X-2, Cir X-1, and GX 13+1—illustrated by sequences of CD/HID tracks we construct—arises from changes in the mass accretion rate. Our results strengthen previous suggestions that within single sources Cyg-like Z source behavior takes place at higher luminosities and mass accretion rates than Sco-like Z behavior, and lend support to the notion that the mass accretion rate is the primary physical parameter distinguishing the various NS-LMXB subclasses.

  2. Optimization principles for preparation methods and properties of fine ferrite materials

    Science.gov (United States)

    Borisova, N. M.; Golubenko, Z. V.; Kuz'micheva, T. G.; Ol'khovik, L. P.; Shabatin, V. P.

    1992-08-01

    The paper is devoted to the problems of development of fine materials based on Ba-ferrite for vertical magnetic recording in particular. Taking an analogue — BaFe 12-2 xCo xTe xO 19 — we have optimized the melt co-precipitation method and shown a new opportunity to provide chemical homogeneity of microcrystallites by means of cryotechnology. Magnetic characteristics of the magnetic tape experimental sample for digital video recording are presented. A series of principles of consistent control of ferrite powder properties are formulated and illustrated with specific developments.

  3. Defects and diffusion in semiconductors XII

    CERN Document Server

    Fisher, David J

    2010-01-01

    This twelfth volume in the series covering the latest results in the field includes abstracts of papers which have appeared since the publication of Annual Retrospective XI (Volume 282). As well as the 565 semiconductor-related abstracts, the issue includes - in line with the policy of including original papers on all of the major material groups: ""Study of Conduction Mechanism in Amorphous Se85-xTe15Bix Thin Films"" (A.Sharma and P.B.Barman), ""Structure and Optical Properties of Magnetron-Sputtered SiOx Layers with Silicon Nanoparticles"" (L.Khomenkova, N.Korsunska, T.Stara, Y.Goldstein, J.

  4. Magnetic field effect on the Coulomb interaction of acceptors in semimagnetic quantum dot

    Energy Technology Data Exchange (ETDEWEB)

    Kalpana, P.; Merwyn, A.; Nithiananthi, P.; Jayakumar, K., E-mail: kjkumar-gri@rediffmail.com [Nanostructure Lab, Department of Physics, Gandhigram Rural University, Gandhigram-624302 (India); Reuben, Jasper D. [Department of Physics, School of Engineering, Saveetha University, Thandalam, Chennai- 600104 (India)

    2015-06-24

    The Coulomb interaction of holes in a Semimagnetic Cd{sub 1-x}Mn{sub x}Te / CdTe Spherical and Cubical Quantum Dot (SMQD) in a magnetic field is studied using variational approach in the effective mass approximation. Since these holes in QD show a pronounced collective behavior, while distinct single particle phenomena is suppressed, their interaction in confined potential becomes very significant. It has been observed that acceptor-acceptor interaction is more in cubical QD than in spherical QD which can be controlled by the magnetic field. The results are presented and discussed.

  5. Characterization of interfaces in semimagnetic quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt, G.; Kuhn-Heinrich, B.; Zehnder, U.; Ossau, W.; Litz, T.; Waag, A.; Landwehr, G. [Physikalishes Institut der Universitaet Wuerzburg am Hubland, Wuerzburg (Germany)

    1995-12-31

    The interfaces between nonmagnetic CdTe quantum wells and semimagnetic barriers of Cd{sub 1-x}Mn{sub x}Te were investigated for several well widths by low temperature photoluminescence and photoluminescence excitation spectroscopy. Specially designed Cd{sub 1-x}Mn{sub x}/CdTe/Cd{sub 1-y} Mg{sub y}Te structures enable us to distinguish the quality of semimagnetic normal and inverted interfaces. The normal interface shows to better structural quality than the inverted interface. (author). 5 refs, 2 figs, 1 tab.

  6. Atomic-Scale Visualization of Quasiparticle Interference on a Type-II Weyl Semimetal Surface.

    Science.gov (United States)

    Zheng, Hao; Bian, Guang; Chang, Guoqing; Lu, Hong; Xu, Su-Yang; Wang, Guangqiang; Chang, Tay-Rong; Zhang, Songtian; Belopolski, Ilya; Alidoust, Nasser; Sanchez, Daniel S; Song, Fengqi; Jeng, Horng-Tay; Yao, Nan; Bansil, Arun; Jia, Shuang; Lin, Hsin; Hasan, M Zahid

    2016-12-23

    We combine quasiparticle interference simulation (theory) and atomic resolution scanning tunneling spectromicroscopy (experiment) to visualize the interference patterns on a type-II Weyl semimetal Mo_{x}W_{1-x}Te_{2} for the first time. Our simulation based on first-principles band topology theoretically reveals the surface electron scattering behavior. We identify the topological Fermi arc states and reveal the scattering properties of the surface states in Mo_{0.66}W_{0.34}Te_{2}. In addition, our result reveals an experimental signature of the topology via the interconnectivity of bulk and surface states, which is essential for understanding the unusual nature of this material.

  7. Analytical Electron Diffraction from Iii-V and II-Vi Semiconductors

    Science.gov (United States)

    Spellward, Paul

    Available from UMI in association with The British Library. This thesis describes the development and evaluation of a number of new TEM-based techniques for the measurement of composition in ternary III-V and II-VI semiconductors. New methods of polarity determination in binary and ternary compounds are also presented. The theory of high energy electron diffraction is outlined, with particular emphasis on zone axis diffraction from well-defined strings. An account of TEM microstructural studies of Cd_{rm x}Hg _{rm 1-x}Te and CdTe epitaxial layers, which provided the impetus for developing the diffraction-based analytical techniques, is given. The wide range of TEM-based compositional determination techniques is described. The use of HOLZ deficiency lines to infer composition from a lattice parameter measurement is evaluated. In the case of Cd_{ rm x}Hg_{rm 1-x}Te, it is found to be inferior to other techniques developed. Studies of dynamical aspects of HOLZ diffraction can yield information about the dispersion surface from which a measure of composition may be obtained. This technique is evaluated for Al_{rm x}Ga_{rm 1-x} As, in which it is found to be of some use, and for Cd_{rm x}Hg _{rm 1-x}Te, in which the large Debye-Waller factor associated with mercury in discovered to render the method of little value. A number of critical voltages may be measured in medium voltage TEMs. The (111) zone axis critical voltage of Cd_{rm x}Hg _{rm 1-x}Te is found to vary significantly with x and forms the basis of an accurate technique for composition measurement in that ternary compound. Other critical voltage phenomena are investigated. In Al _{rm x}Ga_ {rm 1-x}As and other light ternaries, a non-systematic critical voltage is found to vary with x, providing a good indicator of composition. Critical voltage measurements may be made by conventional CBED or by various other techniques, which may also simultaneously yield information on the spatial variation of composition. The

  8. Double-heterostructure PbSnTe lasers grown by molecular-beam epitaxy with cw operation up to 114 K

    International Nuclear Information System (INIS)

    Walpole, J.N.; Calawa, A.R.; Harman, T.C.; Groves, S.H.

    1976-01-01

    Double-heterostructure Pb/sub 1-x/Sn/sub x/Te lasers with active regions of Pb 0 . 782 Sn 0 . 218 Te have been grown by molecular-beam epitaxy which operate cw up to heat-sink temperatures of 114 0 K. Temperature tuning of the emission from 15.9 to 8.54 μm wavelength is obtained, with emission at 77 0 K near 11.5 μm. The current-voltage characteristics show an abrupt change in slope at threshold, indicating high incremental internal quantum efficiency

  9. Chalcogenhalide cluster rhenium- and molybdenum complexes

    International Nuclear Information System (INIS)

    Fedin, V.P.; Gubin, S.P.; Mishchenko, A.V.; Fedorov, V.E.

    1984-01-01

    The interaction of rhenium- and molybdenum chalcogenhalides with n-donor ligands (L) is studied. At heating Re 3 X 2 Hal 5 complexes up to 100 deg in DMSO in the L presence obtained are the complexes of the 1-6 composition Re 3 X 2 Hal 5 -x Lx DMSO (X=Se, Hal=Cl, L=Et 3 N(1); X=Se, Hal=Cl, L=Bipy(2); X=Se, Hal=Br, L=Et 3 N(3); X=Se, Hal=Br, L=Bipy(4); X=Te, Hal=Br, L=Et 3 N(5); X=Te, Hal=Br, L=(Me 2 NCH 2 ) 2 (6). In the course of boiling of Mo 3 S 7 Hal 4 with PPh 3 in MeCN the Mo 3 S 7 Hal 4 2PPh 3 complexes (Hal=Cl(7); Br(8)) are obtained. For 1 through 8 complexes the chemical analysis data and IR spectra are given. For 4 and 8 complexes the molecular mass is measured. A possible method of obtaining molecular trinuclear clusters from polymer clusters is discussed

  10. Hydrogen-assisted post-growth substitution of tellurium into molybdenum disulfide monolayers with tunable compositions

    Science.gov (United States)

    Yin, Guoli; Zhu, Dancheng; Lv, Danhui; Hashemi, Arsalan; Fei, Zhen; Lin, Fang; Krasheninnikov, Arkady V.; Zhang, Ze; Komsa, Hannu-Pekka; Jin, Chuanhong

    2018-04-01

    Herein we report the successful doping of tellurium (Te) into molybdenum disulfide (MoS2) monolayers to form MoS2x Te2(1-x) alloy with variable compositions via a hydrogen-assisted post-growth chemical vapor deposition process. It is confirmed that H2 plays an indispensable role in the Te substitution into as-grown MoS2 monolayers. Atomic-resolution transmission electron microscopy allows us to determine the lattice sites and the concentration of introduced Te atoms. At a relatively low concentration, tellurium is only substituted in the sulfur sublattice to form monolayer MoS2(1-x)Te2x alloy, while with increasing Te concentration (up to ˜27.6% achieved in this study), local regions with enriched tellurium, large structural distortions, and obvious sulfur deficiency are observed. Statistical analysis of the Te distribution indicates the random substitution. Density functional theory calculations are used to investigate the stability of the alloy structures and their electronic properties. Comparison with experimental results indicate that the samples are unstrained and the Te atoms are predominantly substituted in the top S sublattice. Importantly, such ultimately thin Janus structure of MoS2(1-x)Te2x exhibits properties that are distinct from their constituents. We believe our results will inspire further exploration of the versatile properties of asymmetric 2D TMD alloys.

  11. Synthesis and evaluation of lead telluride/bismuth antimony telluride nanocomposites for thermoelectric applications

    Science.gov (United States)

    Ganguly, Shreyashi; Zhou, Chen; Morelli, Donald; Sakamoto, Jeffrey; Uher, Ctirad; Brock, Stephanie L.

    2011-12-01

    Heterogeneous nanocomposites of p-type bismuth antimony telluride (Bi 2- xSb xTe 3) with lead telluride (PbTe) nanoinclusions have been prepared by an incipient wetness impregnation approach. The Seebeck coefficient, electrical resistivity, thermal conductivity and Hall coefficient were measured from 80 to 380 K in order to investigate the influence of PbTe nanoparticles on the thermoelectric performance of nanocomposites. The Seebeck coefficients and electrical resistivities of nanocomposites decrease with increasing PbTe nanoparticle concentration due to an increased hole concentration. The lattice thermal conductivity decreases with the addition of PbTe nanoparticles but the total thermal conductivity increases due to the increased electronic thermal conductivity. We conclude that the presence of nanosized PbTe in the bulk Bi 2- xSb xTe 3 matrix results in a collateral doping effect, which dominates transport properties. This study underscores the need for immiscible systems to achieve the decreased thermal transport properties possible from nanostructuring without compromising the electronic properties.

  12. The Accuracy Assessment of Determining the Axis of Railway Track Basing on the Satellite Surveying

    Science.gov (United States)

    Koc, Władysław; Specht, Cezary; Chrostowski, Piotr; Palikowska, Katarzyna

    2012-09-01

    In 2009, at the Gdansk University of Technology there have been carried out, for the first time, continuous satellite surveying of railway track by the use of the relative phase method based on geodesic active network ASG-EUPOS and NAVGEO service. Still continuing research works focused on the GNSS multi-receivers platform evaluation for projecting and stock-taking. In order to assess the accuracy of the railway track axis position, the values of deviations of transverse position XTE (Cross Track Error) were evaluated. In order to eliminate the influence of random measurement errors and to obtain the coordinates representing the actual shape of the track, the XTE variable was analyzed by signal analysis methods (Chebyshev low-pass filtering and fast Fourier transform). At the end the paper presents the module of the computer software SATTRACK which currently has been developing at the Gdansk University of Technology. The program serves visualization, assessment and design process of railway track, adapted to the technique of continuous satellite surveying. The module called TRACK STRAIGHT is designed to assess the straight sections. A description of its operation as well as examples of its functions has been presented.

  13. On the Detectability of CO Molecules in the Interstellar Medium via X-Ray Spectroscopy

    Science.gov (United States)

    Joachimi, Katerine; Gatuzz, Efrain; Garcia, Javier; Kallman, Timothy R.

    2016-01-01

    We present a study of the detectability of CO molecules in the Galactic interstellar medium using high-resolution X-ray spectra obtained with the XMM-Newton Reflection Grating Spectrometer. We analysed 10 bright low mass X-ray binaries (LMXBs) to study the CO contribution in their line of sights. A total of 25 observations were fitted with the ISMabs X-ray absorption model which includes photoabsorption cross-sections for Oi, Oii, Oiii and CO. We performed a Monte Carlo (MC) simulation analysis of the goodness of fit in order to estimate the significance of the CO detection. We determine that the statistical analysis prevents a significant detection of CO molecular X-ray absorption features, except for the lines of sight towards XTE J1718-330 and 4U 1636-53. In the case of XTE J1817-330, this is the first report of the presence of CO along its line of sight. Our results reinforce the conclusion that molecules have a minor contribution to the absorption features in the O K-edge spectral region. We estimate a CO column density lower limit to perform a significant detection with XMM-Newton of N(CO) greater than 6 x 10(exp 16) per sq cm for typical exposure times.

  14. Marginal Gap Formation in Approximal "Bulk Fill" Resin Composite Restorations After Artificial Ageing.

    Science.gov (United States)

    Peutzfeldt, A; Mühlebach, S; Lussi, A; Flury, S

    The aim of this in vitro study was to investigate the marginal gap formation of a packable "regular" resin composite (Filtek Supreme XTE [3M ESPE]) and two flowable "bulk fill" resin composites (Filtek Bulk Fill [3M ESPE] and SDR [DENTSPLY DeTrey]) along the approximal margins of Class II restorations. In each of 39 extracted human molars (n=13 per resin composite), mesial and distal Class II cavities were prepared, placing the gingival margins below the cemento-enamel junction. The cavities were restored with the adhesive system OptiBond FL (Kerr) and one of the three resin composites. After restoration, each molar was cut in half in the oro-vestibular direction between the two restorations, resulting in two specimens per molar. Polyvinylsiloxane impressions were taken and "baseline" replicas were produced. The specimens were then divided into two groups: At the beginning of each month over the course of six months' tap water storage (37°C), one specimen per molar was subjected to mechanical toothbrushing, whereas the other was subjected to thermocycling. After artificial ageing, "final" replicas were produced. Baseline and final replicas were examined under the scanning electron microscope (SEM), and the SEM micrographs were used to determine the percentage of marginal gap formation in enamel or dentin. Paramarginal gaps were registered. The percentages of marginal gap formation were statistically analyzed with a nonparametric analysis of variance followed by Wilcoxon-Mann-Whitney tests and Wilcoxon signed rank tests, and all p-values were corrected with the Bonferroni-Holm adjustment for multiple testing (significance level: α=0.05). Paramarginal gaps were analyzed descriptively. In enamel, significantly lower marginal gap formation was found for Filtek Supreme XTE compared to Filtek Bulk Fill ( p=0.0052) and SDR ( p=0.0289), with no significant difference between Filtek Bulk Fill and SDR ( p=0.4072). In dentin, significantly lower marginal gap formation was

  15. Nano-scale pattern formation on the surface of HgCdTe produced by ion bombardment

    Energy Technology Data Exchange (ETDEWEB)

    Smirnov, A.B.; Gudymenko, A.I.; Kladko, V.P.; Korchevyi, A.A.; Savkina, R.K.; Sizov, F.F.; Udovitska, R.S. [V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, Kiev (Ukraine)

    2015-08-15

    Presented in this work are the results concerning formation of nano-scale patterns on the surface of a ternary compound Hg{sub 1-x}Cd{sub x}Te (x ∝ 0.223). Modification of this ternary chalcogenide semiconductor compound was performed using the method of oblique-incidence ion bombardment with silver ions, which was followed by low-temperature treatment. The energy and dose of implanted ions were 140 keV and 4.8 x 10{sup 13} cm{sup -2}, respectively. Atomic force microscopy methods were used for the surface topography characterization. The structural properties of MCT-based structure was analyzed using double and triple crystal X-ray diffraction to monitor the disorder and strain of the implanted region as a function of processing conditions. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Determination of equilibrium phase composition in the Hg-HgTe-CdTe system by ''dew point'' method

    International Nuclear Information System (INIS)

    Vanyukov, A.V.; Krotov, I.I.; Ermakov, A.I.

    1978-01-01

    Using the ''dew point'' method a study has been made of the equilibrium composition of the solid and liquid phases in the Hg-HgTe-CdTe system at 404, 435 and 454 deg C. It has been pointed out that crystallization of cadmium-rich solid solutions of Cdsub(x)Hgsub(1-x) Te takes place from a liquid phase with a much higher concentration of Hg. The activity of Hg in the liquid phase increases along the liquidus isotherm in the direction from section Hg-HgTe to section HgCdTe in accordance with the increase of its concentration. An increase in activity of Hg in the solid phase of Cdsub(x)Hgsub(1-x)Te has been noted with the reduction of its concentration

  17. Where are all the gravastars? Limits upon the gravastar model from accreting black holes

    Energy Technology Data Exchange (ETDEWEB)

    Broderick, Avery E; Narayan, Ramesh [Institute for Theory and Computation, Harvard-Smithsonian Center for Astrophysics, MS 51, 60 Garden Street, Cambridge, MA 02138 (United States)

    2007-02-07

    The gravastar model, which postulates a strongly correlated thin shell of anisotropic matter surrounding a region of anti-de Sitter space, has been proposed as an alternative to black holes. We discuss constraints that present-day observations of well-known black hole candidates place on this model. We focus upon two black hole candidates known to have extraordinarily low luminosities: the supermassive black hole in the galactic centre, Sagittarius A*, and the stellar-mass black hole, XTE J1118 + 480. We find that the length scale for modifications of the type discussed in Chapline et al (2003 Int. J. Mod. Phys. 18 3587-90) must be sub-Planckian.

  18. The Application of Artificial Intelligence to Astronomical Scheduling Problems

    Science.gov (United States)

    Johnston, Mark D.

    1993-01-01

    As artificial intelligence (AI) technology has moved from the research laboratory into more and more widespread use, one of the leading applications in astronomy has been to high-profile observation scheduling. The Spike scheduling system was developed by the Space Telescope Science Institute (STScI) for the purpose of long-range scheduling of Hubble Space Telescope (HST). Spike has been in daily operational use at STScI since well before HST launch in April 1990. The system has also been adapted to schedule other missions: one of these missions (EUVE) is currently operational, while another (ASTRO-D) will be launched in February 1993. Some other future space astronomy missions (XTE, SWAS, and AXAF) are making tentative plans to use Spike. Spike has proven to be a powerful and flexible scheduling framework with applicability to a wide variety of problems.

  19. Resin composites

    DEFF Research Database (Denmark)

    Benetti, Ana Raquel; Peutzfeldt, Anne; Lussi, Adrian

    2014-01-01

    OBJECTIVE: To investigate how the modulus of elasticity of resin composites influences marginal quality in restorations submitted to thermocyclic and mechanical loading. METHODS: Charisma, Filtek Supreme XTE and Grandio were selected as they were found to possess different moduli of elasticity...... of resin composite (p=0.81) on the quality of dentine margins was observed, before or after loading. Deterioration of all margins was evident after loading (p....008). CONCLUSIONS: The resin composite with the highest modulus of elasticity resulted in the highest number of gap-free enamel margins but with an increased incidence of paramarginal enamel fractures. CLINICAL SIGNIFICANCE: The results from this study suggest that the marginal quality of restorations can...

  20. Design principles for HgTe based topological insulator devices

    Science.gov (United States)

    Sengupta, Parijat; Kubis, Tillmann; Tan, Yaohua; Povolotskyi, Michael; Klimeck, Gerhard

    2013-07-01

    The topological insulator properties of CdTe/HgTe/CdTe quantum wells are theoretically studied. The CdTe/HgTe/CdTe quantum well behaves as a topological insulator beyond a critical well width dimension. It is shown that if the barrier (CdTe) and well-region (HgTe) are altered by replacing them with the alloy CdxHg1-xTe of various stoichiometries, the critical width can be changed. The critical quantum well width is shown to depend on temperature, applied stress, growth directions, and external electric fields. Based on these results, a novel device concept is proposed that allows to switch between a normal semiconducting and topological insulator state through application of moderate external electric fields.

  1. Tuning the electrical transport of type II Weyl semimetal WTe2 nanodevices by Mo doping

    Science.gov (United States)

    Fu, Dongzhi; Pan, Xingchen; Bai, Zhanbin; Fei, Fucong; Umana-Membreno, Gilberto A.; Song, Honglian; Wang, Xuelin; Wang, Baigeng; Song, Fengqi

    2018-04-01

    We fabricated nanodevices from MoxW1-xTe2 (x = 0, 0.07, 0.35), and conducted a systematic comparative study of their electrical transport. Magnetoresistance measurements show that Mo doping can significantly suppress mobility and magnetoresistance. The results for the analysis of the two band model show that doping with Mo does not break the carrier balance. Through analysis of Shubnikov-de Haas oscillations, we found that Mo doping also has a strong suppressive effect on the quantum oscillation of the sample, and the higher the ratio of Mo, the fewer pockets were observed in our experiments. Furthermore, the effective mass of electron and hole increases gradually with increasing Mo ratio, while the corresponding quantum mobility decreases rapidly.

  2. Multidirectional channeling analysis of epitaxial CdTe layers using an automatic RBS/channeling system

    Energy Technology Data Exchange (ETDEWEB)

    Wielunski, L S; Kenny, M J [CSIRO, Lindfield, NSW (Australia). Applied Physics Div.

    1994-12-31

    Rutherford Backscattering Spectrometry (RBS) is an ion beam analysis technique used in many fields. The high depth and mass resolution of RBS make this technique very useful in semiconductor material analysis [1]. The use of ion channeling in combination with RBS creates a powerful technique which can provide information about crystal quality and structure in addition to mass and depth resolution [2]. The presence of crystal defects such as interstitial atoms, dislocations or dislocation loops can be detected and profiled [3,4]. Semiconductor materials such as CdTe, HgTe and Hg+xCd{sub 1-x}Te generate considerable interest due to applications as infrared detectors in many technological areas. The present paper demonstrates how automatic RBS and multidirectional channeling analysis can be used to evaluate crystal quality and near surface defects. 6 refs., 1 fig.

  3. Innovation in crystal growth: A personal perspective

    Science.gov (United States)

    Mullin, J. B.

    2008-04-01

    The evolution of crystal growth has been crucially dependent on revolutionary innovations and initiatives involving ideas, technology and communication. A personal perspective is presented on some of these aspects in connection with the early history of semiconductors that have helped evolve our knowledge and advance the science and technology of crystal growth. The presentation considers examples from work on germanium, silicon, indium antimonide, gallium arsenide, indium phosphide, gallium phosphide and mercury cadmium telluride. In connection with metal organic vapour phase epitaxy (MOVPE), the influence of adduct purification for alkyls is noted together with the growth of Hg xCd 1-xTe. The role of crystal growth organisations together with initiatives in the publication of the Journal of Crystal Growth (JCG) and the pivotal role of the International Organisation of Crystal Growth (IOCG) are also highlighted in the quest for scientific excellence.

  4. a Synoptic Study of AN X-Ray Nova in Outburst

    Science.gov (United States)

    McClintock, Jeffrey

    Optical studies of X-ray novae in quiescence have yielded compelling evidence for black holes in binary systems. However, X-ray studies in quiescence are severely constrained by the near absence of high energy emission. Thus, further observational advances in black hole astrophysics require a substantial commitment to observe X-ray novae in outburst in just that spectral range accessible to XTE. We propose an agressive campaign of X-ray observations of the next non-pulsing X-ray nova that rises above 3 Crab at 2-10 keV. We further propose a coordinated and intensive campaign of optical and radio observations covering both hemispheres. The observations will provide a full temporal and spectral view of the outburst cycle.

  5. X-Ray Observations of High-Energy Pulsars: PSR B1951+32 and Geminga

    Science.gov (United States)

    Ho, Cheng

    Observations at frequencies across a wide range of electromagnetic spectra are key to the understanding of the origin and mechanisms of high-energy emissions from pulsars. We propose to observe the high-energy pulsars PSR B1951+32 and Geminga with XTE. These two sources emit X-rays at low enough count rate that we can acquire high resolution timing and spectral data, allowing us to perform detailed analysis on the ground. Staring integration of 10 ksec for each source is requested. Data obtained in these observations, together with those from ROSAT, GRO and a planned project for optical counterpart study at Los Alamos, will provide crucial information to advance high-energy pulsar research.

  6. Multidirectional channeling analysis of epitaxial CdTe layers using an automatic RBS/channeling system

    Energy Technology Data Exchange (ETDEWEB)

    Wielunski, L.S.; Kenny, M.J. [CSIRO, Lindfield, NSW (Australia). Applied Physics Div.

    1993-12-31

    Rutherford Backscattering Spectrometry (RBS) is an ion beam analysis technique used in many fields. The high depth and mass resolution of RBS make this technique very useful in semiconductor material analysis [1]. The use of ion channeling in combination with RBS creates a powerful technique which can provide information about crystal quality and structure in addition to mass and depth resolution [2]. The presence of crystal defects such as interstitial atoms, dislocations or dislocation loops can be detected and profiled [3,4]. Semiconductor materials such as CdTe, HgTe and Hg+xCd{sub 1-x}Te generate considerable interest due to applications as infrared detectors in many technological areas. The present paper demonstrates how automatic RBS and multidirectional channeling analysis can be used to evaluate crystal quality and near surface defects. 6 refs., 1 fig.

  7. Accreting Millisecond Pulsars: Neutron Star Masses and Radii

    Science.gov (United States)

    Strohmayer, Tod

    2004-01-01

    High amplitude X-ray brightness oscillations during thermonuclear X-ray bursts were discovered with the Rossi X-ray Timing Explorer (RXTE) in early 1996. Spectral and timing evidence strongly supports the conclusion that these oscillations are caused by rotational modulation of the burst emission and that they reveal the spin frequency of neutron stars in low mass X-ray binaries. The recent discovery of X-ray burst oscillations from two accreting millisecond pulsars has confirmed this basic picture and provided a new route to measuring neutron star properties and constraining the dense matter equation of state. I will briefly summarize the current observational understanding of accreting millisecond pulsars, and describe recent attempts to determine the mass and radius of the neutron star in XTE J1814-338.

  8. Analysis of the electrical conduction in CdHgTe crystals

    International Nuclear Information System (INIS)

    Dziuba, Z.

    1987-01-01

    The electrical conduction versus magnetic field in p-like CdHgTe samples at 77 K is investigated by analysing the conductivity tensor components. The electrical conduction is mainly due to electrons in the conduction band and low-mobility carriers in an impurity band. In the investigated samples Cd/sub x/Hg/sub 1-x/Te with the composition x approximately 0.17 the concentration of electrons in the conduction band is higher than the intrinsic one and in samples with the composition close to HgTe the concentration of electrons in the conduction band is equal to or lower than the intrinsic one. The model of a half-filled impurity band situated close to the bottom of the conduction band is proposed to account for the concentration of electrons in the conduction band. (author)

  9. Evidence for charge Kondo effect in superconducting Tl-doped PbTe

    Energy Technology Data Exchange (ETDEWEB)

    Fisher, I

    2010-01-11

    We report results of low-temperature thermodynamic and transport measurements of Pb{sub 1-x}Tl{sub x}Te single crystals for Tl concentrations up to the solubility limit of approximately x = 1.5%. For all doped samples, we observe a low-temperature resistivity upturn that scales in magnitude with the Tl concentration. The temperature and field dependence of this upturn are consistent with a charge Kondo effect involving degenerate Tl valence states differing by two electrons, with a characteristic Kondo temperature T{sub K} {approx} 6 K. The observation of such an effect supports an electronic pairing mechanism for superconductivity in this material and may account for the anomalously high T{sub c} values.

  10. Weak Antilocalization in Bi 2 (Se x Te 1– x ) 3 Nanoribbons and Nanoplates

    KAUST Repository

    Cha, Judy J.; Kong, Desheng; Hong, Seung-Sae; Analytis, James G.; Lai, Keji; Cui, Yi

    2012-01-01

    Studying the surface states of Bi 2Se 3 and Bi 2Te 3 topological insulators has proven challenging due to the high bulk carrier density that masks the surface states. Ternary compound Bi 2(Se xTe 1-x) 3 may present a solution to the current materials challenge by lowering the bulk carrier mobility significantly. Here, we synthesized Bi 2(Se xTe 1-x) 3 nanoribbons and nanoplates via vapor-liquid-solid and vapor-solid growth methods where the atomic ratio x was controlled by the molecular ratio of Bi 2Se 3 to Bi 2Te 3 in the source mixture and ranged between 0 and 1. For the whole range of x, the ternary nanostructures are single crystalline without phase segregation, and their carrier densities decrease with x. However, the lowest electron density is still high (∼10 19 cm -3) and the mobility low, suggesting that the majority of these carriers may come from impurity states. Despite the high carrier density, weak antilocalization (WAL) is clearly observed. Angle-dependent magnetoconductance study shows that an appropriate magnetic field range is critical to capture a true, two-dimensional (2D) WAL effect, and a fit to the 2D localization theory gives α of -0.97, suggesting its origin may be the topological surface states. The power law dependence of the dephasing length on temperature is ∼T -0.49 within the appropriate field range (∼0.3 T), again reflecting the 2D nature of the WAL. Careful analysis on WAL shows how the surface states and the bulk/impurity states may interact with each other. © 2012 American Chemical Society.

  11. Enough Is Enough

    Science.gov (United States)

    Barrowman, James

    2003-01-01

    The spacecraft was nearly integrated and had passed some of its early mechanical and electrical testing. One of its instruments, the Proportional Counter Array (PCA), had a gas leak in one of the five proportional counter modules that made up the array. The science division where the instrument was being developed wanted a gas replenishment system added to assure the PCA would last for the entire mission. Adding a gas replenishment system would mean interrupting spacecraft integration and testing; developing a new subsystem and integrating it onto the spacecraft; modifying all the PCA modules; including a complex integration of the instrument onto the spacecraft; and implementing a more complex performance and environmental test process. It was the wrong answer because it made a simple design more complex and added little value to the mission at a major cost in time and dollars. Our mission couldn't afford the additional budget and schedule risks. XTE was the latest of a long line of projects being managed by my Explorer Program Office, but it was unique in being the first project we had agreed to do for a fixed price. NASA HQ agreed, in return, to provide us with the funding profile we needed to make it happen. We were both trying to break the unhealthy spiral in the Explorer program that saw current missions overrunning and pushing subsequent missions downstream to the point where their science was becoming marginal. The science community was upset and wanted better performance from NASA. I summarized my arguments to the director. The Engineering Directorate had taken responsibility for the spacecraft development when we established XTE as an in-house project at Goddard Space Flight Center, and also was supporting the PCA development. "It adds complexity," I reiterated. "It's a significant cost impact for only a marginal reliability increase". His response was music to my ears, "Jim, I won't stand in your way, but you'll have to convince the scientists and

  12. Weak Antilocalization in Bi 2 (Se x Te 1– x ) 3 Nanoribbons and Nanoplates

    KAUST Repository

    Cha, Judy J.

    2012-02-08

    Studying the surface states of Bi 2Se 3 and Bi 2Te 3 topological insulators has proven challenging due to the high bulk carrier density that masks the surface states. Ternary compound Bi 2(Se xTe 1-x) 3 may present a solution to the current materials challenge by lowering the bulk carrier mobility significantly. Here, we synthesized Bi 2(Se xTe 1-x) 3 nanoribbons and nanoplates via vapor-liquid-solid and vapor-solid growth methods where the atomic ratio x was controlled by the molecular ratio of Bi 2Se 3 to Bi 2Te 3 in the source mixture and ranged between 0 and 1. For the whole range of x, the ternary nanostructures are single crystalline without phase segregation, and their carrier densities decrease with x. However, the lowest electron density is still high (∼10 19 cm -3) and the mobility low, suggesting that the majority of these carriers may come from impurity states. Despite the high carrier density, weak antilocalization (WAL) is clearly observed. Angle-dependent magnetoconductance study shows that an appropriate magnetic field range is critical to capture a true, two-dimensional (2D) WAL effect, and a fit to the 2D localization theory gives α of -0.97, suggesting its origin may be the topological surface states. The power law dependence of the dephasing length on temperature is ∼T -0.49 within the appropriate field range (∼0.3 T), again reflecting the 2D nature of the WAL. Careful analysis on WAL shows how the surface states and the bulk/impurity states may interact with each other. © 2012 American Chemical Society.

  13. Color stability of esthetic restorative materials: a spectrophotometric analysis.

    Science.gov (United States)

    Poggio, Claudio; Ceci, Matteo; Beltrami, Riccardo; Mirando, Maria; Wassim, Jaffal; Colombo, Marco

    2016-12-01

    Objective: The aim of this in vitro study was to evaluate the color stability of different restorative materials (one microfilled composite, one nanofilled composite, one nanohybrid composite and one Ormocer-based composite) after exposure to different staining solutions (coffee, coca-cola and red wine). Material and methods: All materials were polymerized into silicon rings (2 mm ×6 mm ×8 mm) to obtain specimens identical in size. Thirty cylindrical specimens of each material were prepared. They were immersed in staining solutions over a 28-day test period. A colorimetric evaluation according to the CIE L*a*b* system was performed by a blind trained operator at 7, 14, 21, 28 days of the staining process. The Shapiro-Wilk test and Kruskal-Wallis ANOVA were applied to assess significant differences among restorative materials. The paired t -test was applied to test which CIE L*a*b* parameters significantly changed after immersion in staining solutions. Results: All restorative materials showed clinically perceptible color differences after immersion in coffee. L* and b* values showed the highest variability. Coca cola and red wine did not influence the color stability for all restorative materials except for Filtek Supreme XTE. Conclusions: Coffee caused a significant color change in all types of tested composite resins. Filtek Supreme XTE demonstrated alone a staining susceptibility to red wine; no other significant differences among the materials were demonstrated. Long-term exposure to some food dyes (coffee in particular) can significantly affect the color stability of modern esthetic restorative materials regardless of materials' different composition.

  14. Repairability of CAD/CAM high-density PMMA- and composite-based polymers.

    Science.gov (United States)

    Wiegand, Annette; Stucki, Lukas; Hoffmann, Robin; Attin, Thomas; Stawarczyk, Bogna

    2015-11-01

    The study aimed to analyse the shear bond strength of computer-aided design and computer-aided manufacturing (CAD/CAM) polymethyl methacrylate (PMMA)- and composite-based polymer materials repaired with a conventional methacrylate-based composite after different surface pretreatments. Each 48 specimens was prepared from six different CAD/CAM polymer materials (Ambarino high-class, artBloc Temp, CAD-Temp, Lava Ultimate, Telio CAD, Everest C-Temp) and a conventional dimethacrylate-based composite (Filtek Supreme XTE, control) and aged by thermal cycling (5000 cycles, 5-55 °C). The surfaces were left untreated or were pretreated by mechanical roughening, aluminium oxide air abrasion or silica coating/silanization (each subgroup n = 12). The surfaces were further conditioned with an etch&rinse adhesive (OptiBond FL) before the repair composite (Filtek Supreme XTE) was adhered to the surface. After further thermal cycling, shear bond strength was tested, and failure modes were assessed. Shear bond strength was statistically analysed by two- and one-way ANOVAs and Weibull statistics, failure mode by chi(2) test (p ≤ 0.05). Shear bond strength was highest for silica coating/silanization > aluminium oxide air abrasion = mechanical roughening > no surface pretreatment. Independently of the repair pretreatment, highest bond strength values were observed in the control group and for the composite-based Everest C-Temp and Ambarino high-class, while PMMA-based materials (artBloc Temp, CAD-Temp and Telio CAD) presented significantly lowest values. For all materials, repair without any surface pretreatment resulted in adhesive failures only, which mostly were reduced when surface pretreatment was performed. Repair of CAD/CAM high-density polymers requires surface pretreatment prior to adhesive and composite application. However, four out of six of the tested CAD/CAM materials did not achieve the repair bond strength of a conventional dimethacrylate

  15. Optimization of Monocrystalline MgxCd1-xTe/MgyCd1-yTe Double-Heterostructure Solar Cells

    Science.gov (United States)

    Becker, Jacob J.

    Polycrystalline CdS/CdTe solar cells continue to dominate the thin-film photovoltaics industry with an achieved record efficiency of over 22% demonstrated by First Solar, yet monocrystalline CdTe devices have received considerably less attention over the years. Monocrystalline CdTe double-heterostructure solar cells show great promise with respect to addressing the problem of low Voc with the passing of the 1 V benchmark. Rapid progress has been made in driving the efficiency in these devices ever closer to the record presently held by polycrystalline thin-films. This achievement is primarily due to the utilization of a remote p-n heterojunction in which the heavily doped contact materials, which are so problematic in terms of increasing non-radiative recombination inside the absorber, are moved outside of the CdTe double heterostructure with two MgyCd1-yTe barrier layers to provide confinement and passivation at the CdTe surfaces. Using this design, the pursuit and demonstration of efficiencies beyond 20% in CdTe solar cells is reported through the study and optimization of the structure barriers, contacts layers, and optical design. Further development of a wider bandgap MgxCd1-xTe solar cell based on the same design is included with the intention of applying this knowledge to the development of a tandem solar cell constructed on a silicon subcell. The exploration of different hole-contact materials--ZnTe, CuZnS, and a-Si:H--and their optimization is presented throughout the work. Devices utilizing a-Si:H hole contacts exhibit open-circuit voltages of up to 1.11 V, a maximum total-area efficiency of 18.5% measured under AM1.5G, and an active-area efficiency of 20.3% for CdTe absorber based devices. The achievement of voltages beyond 1.1V while still maintaining relatively high fill factors with no rollover, either before or after open-circuit, is a promising indicator that this approach can result in devices surpassing the 22% record set by polycrystalline

  16. A non-radial oscillation mode in an accreting millisecond pulsar?

    Energy Technology Data Exchange (ETDEWEB)

    Strohmayer, Tod [Astrophysics Science Division and Joint Space-Science Institute, NASA' s Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Mahmoodifar, Simin [Department of Physics and Joint Space-Science Institute, University of Maryland College Park, MD 20742 (United States)

    2014-03-20

    We present results of targeted searches for signatures of non-radial oscillation modes (such as r- and g-modes) in neutron stars using RXTE data from several accreting millisecond X-ray pulsars (AMXPs). We search for potentially coherent signals in the neutron star rest frame by first removing the phase delays associated with the star's binary motion and computing fast Fourier transform power spectra of continuous light curves with up to 2{sup 30} time bins. We search a range of frequencies in which both r- and g-modes are theoretically expected to reside. Using data from the discovery outburst of the 435 Hz pulsar XTE J1751–305 we find a single candidate, coherent oscillation with a frequency of 0.5727597 × ν{sub spin} = 249.332609 Hz, and a fractional Fourier amplitude of 7.46 × 10{sup –4}. We estimate the significance of this feature at the 1.6 × 10{sup –3} level, slightly better than a 3σ detection. Based on the observed frequency we argue that possible mode identifications include rotationally modified g-modes associated with either a helium-rich surface layer or a density discontinuity due to electron captures on hydrogen in the accreted ocean. In the latter case the presence of sufficient hydrogen in this ultracompact system with a likely helium-rich donor would present an interesting puzzle. Alternatively, the frequency could be identified with that of an inertial mode or a core r-mode modified by the presence of a solid crust; however, the r-mode amplitude required to account for the observed modulation amplitude would induce a large spin-down rate inconsistent with the observed pulse timing measurements. For the AMXPs XTE J1814–338 and NGC 6440 X–2 we do not find any candidate oscillation signals, and we place upper limits on the fractional Fourier amplitude of any coherent oscillations in our frequency search range of 7.8 × 10{sup –4} and 5.6 × 10{sup –3}, respectively. We briefly discuss the prospects and sensitivity for

  17. Possible signature of the magnetic fields related to quasi-periodic oscillations observed in microquasars

    Science.gov (United States)

    Kološ, Martin; Tursunov, Arman; Stuchlík, Zdeněk

    2017-12-01

    The study of quasi-periodic oscillations (QPOs) of X-ray flux observed in the stellar-mass black hole binaries can provide a powerful tool for testing of the phenomena occurring in the strong gravity regime. Magnetized versions of the standard geodesic models of QPOs can explain the observationally fixed data from the three microquasars. We perform a successful fitting of the HF QPOs observed for three microquasars, GRS 1915+105, XTE 1550-564 and GRO 1655-40, containing black holes, for magnetized versions of both epicyclic resonance and relativistic precession models and discuss the corresponding constraints of parameters of the model, which are the mass and spin of the black hole and the parameter related to the external magnetic field. The estimated magnetic field intensity strongly depends on the type of objects giving the observed HF QPOs. It can be as small as 10^{-5} G if electron oscillatory motion is relevant, but it can be by many orders higher for protons or ions (0.02-1 G), or even higher for charged dust or such exotic objects as lighting balls, etc. On the other hand, if we know by any means the magnetic field intensity, our model implies strong limit on the character of the oscillating matter, namely its specific charge.

  18. Ionic electrodeposition of II-VI and III-V compounds. III. Computer simulation of quasi-rest potentials for M/sub 1/X/sub 1/ compounds analogous to CdTe

    International Nuclear Information System (INIS)

    Engelken, R.D.

    1987-01-01

    The quasi-rest potential (QRP) has been proposed as a key quantity in characterizing compound semiconductor (e.g. CdTe) electrodeposition. This article expands the modeling/simulation representative of Cd/sub x/Te in chemical equilibrium to calculate two ''QRP's'': E/sub M/1/sub /, the mixed potential occurring immediately after current interruption and before any relaxation in double layer ion concentration and significant ion exchange/surface stoichiometry change occur, and E/sub M/2/sub /, another mixed potential occurring after the double layer ion concentrations have relaxed to their bulk values but still before any significant surface composition change occurs. Significant predictions include existence of a dramatic negative transition in QRP, with negative-going deposition potential, centered on the potential of perfect stoichiometry (PPS), inequality, in general, between the PPS and E/sub M/1/sub / unless the deposit remains in equilibrium with the electrolyte (no ion exchange at open circuit), negligible sensitivity of QRP-E curves to the activity coefficient parameter implying the importance of the PPS in characterizing compound deposition, and disappearance of the transition structure for sufficiently positive Gibbs free energies

  19. On the Nature of QPO Phase Lags in Black Hole Candidates

    Science.gov (United States)

    Shaposhnikov, Nikolai

    2012-01-01

    Observations of quasi-periodic oscillations (QPOs) in X-ray binaries hold a key to understanding many aspects of these enigmatic systems. Complex appearance of the Fourier phase lags related to QPOs is one of the most puzzling observational effects in accreting black holes. In this Letter we show that QPO properties, including phase lags, can be explained in a framework of a simple scenario, where the oscillating media provides a feedback on the emerging spectrum. We demonstrate that the QPO waveform is presented by the product of a perturbation and a time delayed response factors, where the response is energy dependent. The essential property of this effect is its non-linear and multiplicative nature. Our multiplicative reverberation model successfully describes the QPO components in energy dependent power spectra as well as the appearance of the phase lags between signal in different energy bands. We apply our model to QPOs observed by Rossi X-ray Timing Explorer in BH candidate XTE J1550-564. We briefly discuss the implications of the observed energy dependence of the QPO reverberation times and amplitudes to the nature of the power law spectral component and its variability.

  20. Possible signature of the magnetic fields related to quasi-periodic oscillations observed in microquasars

    Energy Technology Data Exchange (ETDEWEB)

    Kolos, Martin; Tursunov, Arman; Stuchlik, Zdenek [Silesian University in Opava, Institute of Physics and Research Centre of Theoretical Physics and Astrophysics, Faculty of Philosophy and Science, Opava (Czech Republic)

    2017-12-15

    The study of quasi-periodic oscillations (QPOs) of X-ray flux observed in the stellar-mass black hole binaries can provide a powerful tool for testing of the phenomena occurring in the strong gravity regime. Magnetized versions of the standard geodesic models of QPOs can explain the observationally fixed data from the three microquasars. We perform a successful fitting of the HF QPOs observed for three microquasars, GRS 1915+105, XTE 1550-564 and GRO 1655-40, containing black holes, for magnetized versions of both epicyclic resonance and relativistic precession models and discuss the corresponding constraints of parameters of the model, which are the mass and spin of the black hole and the parameter related to the external magnetic field. The estimated magnetic field intensity strongly depends on the type of objects giving the observed HF QPOs. It can be as small as 10{sup -5} G if electron oscillatory motion is relevant, but it can be by many orders higher for protons or ions (0.02-1 G), or even higher for charged dust or such exotic objects as lighting balls, etc. On the other hand, if we know by any means the magnetic field intensity, our model implies strong limit on the character of the oscillating matter, namely its specific charge. (orig.)

  1. Connections Between Jet Formation and Multiwavelength Spectral Evolution in Black Hole Transients

    Science.gov (United States)

    Kakemci, Emrah; Chun, Yoon-Young; Dincer, Tolga; Buxton, Michelle; Tomsick, John A.; Corbel, Stephane; Kaaret, Philip

    2011-01-01

    Multiwavelength observations are the key to understand conditions of jet formation in Galactic black hole transient (GBHT) systems. By studying radio and optical-infrared evolution of such systems during outburst decays, the compact jet formation can be traced. Comparing this with X-ray spectral and timing evolution we can obtain physical and geometrical conditions for jet formation, and study the contribution of jets to X-ray emission. In this work, first X-ray evolution - jet relation for XTE J1752-223 will be discussed. This source had very good coverage in X-rays, optical, infrared and radio. A long exposure with INTEGRAL also allowed us to study gamma-ray behavior after the jet turns on. We will also show results from the analysis of data from GX 339-4 in the hard state with SUZAKU at low flux levels. The fits to iron line fluorescence emission show that the inner disk radius increases by a factor of greater than 27 with respect to radii in bright states. This result, along with other disk radius measurements in the hard state will be discussed within the context of conditions for launching and sustaining jets.

  2. Plutonium oxychalcogenides Pu2O2X (X=O, S, Se, Te) crystal chemistry, magnetic and electrical properties. 5f electrons delocalization

    International Nuclear Information System (INIS)

    Costantini, Jean-Marc.

    1980-05-01

    We have studied the influence of the chalcogen X on the bonding and on the magnetic and electrical properties of the oxychalcogenides Pu 2 O 2 X. These compounds are isostructural with hexagonal La 2 O 3 for X=O, S, Se and with tetragonal La 2 O 2 Te for X=Te. Comparison of Nd 2 O 2 X and Pu 2 O 2 X cell volumes showed that plutonium crystal radius decreases from Pu 2 O 3 through Pu 2 O 2 Te with increasing 5f electrons delocalization and 5f-np overlap. Superexchange interactions through O 2- and X 2- were thought to be responsible for the observed antiferromagnetic ordering. Neel temperatures increase from Pu 2 O 3 through Pu 2 O 2 Te showing that these interactions and subsequent 5f-np covalency are strengthened as chalcogen electronegativity decreases. Hexagonal Pu 2 O 3 is an insulator while the other compounds are semi-conductors with energy gaps around 0.6 eV which were interpreted as the separation between the 6d-7s conduction band and the np valence band. The localized 5f states were located just below the np band, partially overlapping it [fr

  3. Thermoelectric properties of thin film and superlattice structure of IV-VI and V-VI compound semiconductors; Thermoelektrische Eigenschaften duenner Schichten und Uebergitterstrukturen von IV-VI- und V-VI-Verbundhalbleitern

    Energy Technology Data Exchange (ETDEWEB)

    Blumers, Mathias

    2012-02-29

    The basic material property governing the efficiency of thermoelectric applications is the thermoelectric figure of merit Z=S{sup 2}.{sigma}/k, where S is the Seebeck-coefficient, {sigma} is the electrical conductivity and k the thermal conductivity. A promising concept of increasing Z by one and two dimensional quantum well superlattices (QW-SL) was introduced in the early 1990s in terms of theoretical predictions. The realization of such low dimensional systems is done by use of semiconductor compounds with different energy gaps. The ambition of the Nitherma project was to investigate the thermoelectric properties of superlattices and Multi-Quantum-Well-structures (MQW) made of Pb{sub 1-x}Sr{sub x}Te and Bi{sub 2}(Se{sub x}Te{sub 1-x}){sub 3}, respectively. Therefore SL- and MQW-structures of this materials were grown and Z was determined by measuring of S, {sigma} and {kappa} parallel to the layer planes. Aim of this thesis is the interpretation of the transport measurements (S,{sigma},{kappa}) of low dimensional structures and the improvement of preparation and measurement techniques. The influence of low dimensionality on the thermal conductivity in SL- and MQW-structures was investigated by measurements on structures with different layer thicknesses. In addition, measurements of the Seebeck-coefficient were performed, also to verify the results of the participating groups.

  4. Strain effects on electronic structure of Fe{sub 0.75}Ru{sub 0.25}Te

    Energy Technology Data Exchange (ETDEWEB)

    Winiarski, M.J., E-mail: M.Winiarski@int.pan.wroc.pl [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okólna 2, 50-422, Wrocław (Poland); Samsel-Czekała, M. [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okólna 2, 50-422, Wrocław (Poland); Ciechan, A. [Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668, Warsaw (Poland)

    2017-01-15

    Structural and electronic properties of a hypothetical Fe{sub 0.75}Ru{sub 0.25}Te alloy and the parent FeTe compound have been investigated from first principles within the density functional theory (DFT). For both systems the double-stripe antiferromagnetic ground state is predicted at ambient pressure. The incorporation of Ru atoms into FeTe in the nonmagnetic phase leads to a deep valley of density of states in the vicinity of the Fermi level and the DOS at the Fermi level is significantly diminished in the considered solid solution. The single-stripe antiferromagnetic phase in Fe{sub 0.75}Ru{sub 0.25}Te may be induced by tensile strain. These findings suggest that strained thin films of Fe{sub 1−x}Ru{sub x}Te are good candidates for new superconducting Fe-based materials. - Highlights: • Ru-doped FeTe systems are investigated by density-functional theory methods. • Structural and electronic properties of Fe{sub 0.75}Ru{sub 0.25}Te and parent FeTe are studied. • The double-stripe antiferromagnetic ground state is predicted for both systems. • The single-stripe antiferromagnetic phase may be induced by tensile strain. • Tensile strained Fe{sub 0.75}Ru{sub 0.25}Te is a candidate for a new Fe-based superconductor.

  5. The GRB coordinates network (GCN): A status report

    International Nuclear Information System (INIS)

    Barthelmy, S. D.; Takeshima, T.; Butterworth, P.; Cline, T. L.; Gehrels, N.; Marshall, F.; Connaughton, V.; Kippen, R. M.; Kouveliotou, C.; Robinson, C. R.

    1998-01-01

    A review of the GRB Coordinates Network (GCN) will be given. The GCN has recently replaced the BATSE Coordinates Distribution Network (BACODINE), maintaining all of BACODINE's original capabilities and services, but also providing new sources of GRB location information. These are: (1) source locations using the MSFC LOCBURST algorithm, (2) the Rossi-XTE detections (PCA and ASM), (3) the Interplanetary Network (IPN) locations, and (4) CGRO-COMPTEL locations. These new sources of locations are available for distribution in the minutes-to-hours-to-days time delay ranges, and they also have increasingly and significantly reduced error boxes, thus providing a broad range of time delays and error box sizes to fit within the observing capabilities of a broad range of follow-up instruments in the radio, optical, and TeV gamma-ray bands. Extreme-UV transients from ALEXIS are also now distributed. For all sources of location information, all the distribution methods are available (Internet Socket, E-mail, Alpha-numeric and Numeric Pagers, and Phone/modem) and several filters. Sites can choose which sources to receive and what filters to be applied. The GCN web site has been expanded to include a globally inclusive table of locations, light-curves, and fluence information which is automatically updated in real-time

  6. Early NICER Observations of Magnetars and Young Pulsars

    Science.gov (United States)

    Nynka, Melania

    2018-01-01

    Neutron star Interior Composition ExploreR (NICER) is an X-ray telescope attached to the International Space Station (ISS). Launched in June 2017, it is designed to precisely measure the masses and radii of neutron stars (NS) and probe NS equations of state. But its precision timing capabilities and large effective area uniquely position NICER for the study of magnetars. The NICER Magnetar & Magnetosphere (M&M) science working group focuses on studying highly-magnetized neutron stars, a diverse program that includes magnetars, high-B pulsars, rotation powered pulsars, and isolated neutron stars. Our ongoing campaign has already observed targets such as 4U 0142+61, a magnetar in outburst with coincident NuSTAR and Swift observations, the radio rotation powered Vela pulsar PSR B0833-45, and a transient magnetar XTE J1810-197. I will discuss the goals of the M&M program, spectral and temporal results from the observed targets, and an overview of upcoming observations.

  7. Bridgman growth and assessment of CdTe and CdZnTe using the accelerated crucible rotation technique

    Energy Technology Data Exchange (ETDEWEB)

    Capper, P.; Harris, J.E.; O' Keefe, E.; Jones, C.L.; Ard, C.K.; Mackett, P.; Dutton, D. (Philips Infrared Defence Components, Southampton (United Kingdom))

    1993-01-30

    The Bridgman growth process for CdTe has been extended by applying the accelerated crucible rotation technique (ACRT). Modelling using ACRT has been extended to the 50 mm diameter required to produce grains large enough to yield CdTe(and Cd[sub 0.96]Zn[sub 0.04]Te) slices suitable for use in liquid phase epitaxy of Cd[sub x]Hg[sub 1-x]Te (CMT) layers. Two regimes are identified: ACRT parameter combinations which give maximum fluid velocities and that which maintains stable Ekman flow. Growth of crystals shows that larger single crystal regions are obtained when the Ekman flow is stable. Effects of changing the ampoule base shape have also been investigated. Techniques have been developed to produce 20 mm x 30 mm substrates oriented oriented close to the (111) direction. Assessment of these samples has included IR transmission, IR microscopy, defect etching, X-ray topography and X-ray diffraction curve width measurements. Chemical analyses have been carried out to determine impurity levels and matrix element distributions. Good quality CMT epitaxial layers, as demonstrated by good surface topography, electrical data and chemical analyses, have been grown onto material produced in this study. (orig.).

  8. Effect of the value of bond energy on the defect formation in the samples of CdTe - HqTe system under the influence of irradiation

    International Nuclear Information System (INIS)

    Kramchenko, O.A.; Pashkovskij, N.V.

    1984-01-01

    The bonds break energy in solid solutions of the CdTe-HgTe system is calculated. The correctness of the statement that bonds strength in a chemical compound, particularly for the CdTe-HgTe system with decreases with the increase of atomic number. It is shown that in the process of transition from CdTe binary compound to solid solutions of the CdTe-HgTe system a part of Cd atoms is substituted by Hg atoms, which causes relative decrease of the number Cd-Te bonds. At the same time increased is the number of Cd-Te bonds which during irradiation break more probably than the Cd-Te bonds forming however only Frenkel close vapours annihilating during irradiation. During the experiment these defects lead to temperature region washout in which properties reconstruction at isochronous annealing begins. The beginning of annealing is shifted towards higher temperatures which has been observed in the course of investigation. X decrease for the Cdsub(x)Hgsub(1-x)Te solid solution increases the annealing temperature of radiation defects The results of theoretical calculations coincide with the experimental data and permit to confirm that the properties changes arising during irradiation of matters with weak chemical bonds can be conserved only at very low temperatures

  9. Can isolated single black holes produce X-ray novae?

    Science.gov (United States)

    Matsumoto, Tatsuya; Teraki, Yuto; Ioka, Kunihito

    2018-03-01

    Almost all black holes (BHs) and BH candidates in our Galaxy have been discovered as soft X-ray transients, so-called X-ray novae. X-ray novae are usually considered to arise from binary systems. Here, we propose that X-ray novae are also caused by isolated single BHs. We calculate the distribution of the accretion rate from interstellar matter to isolated BHs, and find that BHs in molecular clouds satisfy the condition of the hydrogen-ionization disc instability, which results in X-ray novae. The estimated event rate is consistent with the observed one. We also check an X-ray novae catalogue (Corral-Santana et al.) and find that 16/59 ˜ 0.27 of the observed X-ray novae are potentially powered by isolated BHs. The possible candidates include IGR J17454-2919, XTE J1908-094, and SAX J1711.6-3808. Near-infrared photometric and spectroscopic follow-ups can exclude companion stars for a BH census in our Galaxy.

  10. Theory of deep level trap effects on generation-recombination noise in HgCdTe photoconductors

    International Nuclear Information System (INIS)

    Iverson, A.E.; Smith, D.L.

    1985-01-01

    We present a theory of the effect of deep level centers on the generation-recombination (g-r) noise and responsivity of an intrinsic photoconductor. The deep level centers can influence the g-r noise and responsivity in three main ways: (i) they can shorten the bulk carrier lifetime by Shockley--Read--Hall recombination; (ii) for some values of the capture cross sections, deep level densities, and temperature, the deep levels can trap a significant fraction of the photogenerated minority carriers. This trapping reduces the effective minority carrier mobility and diffusivity and thus reduces the effect of carrier sweep out on both g-r noise and responsivity; (iii) the deep level centers add a new thermal noise source, which results from fluctuations between bound and free carriers. The strength of this new noise source decreases with decreasing temperature at a slower rate than band-to-band thermal g-r noise. Calculations have been performed for a X = 0.21, n-type Hg/sub 1-x/Cd/sub x/Te photoconductor using the parameters of a commonly occurring deep level center in this material. We find that for typical operating conditions photoconductive detector performance begins to degrade as the deep level density begins to exceed 10 16 cm -3

  11. Influence of Cavity Margin Design and Restorative Material on Marginal Quality and Seal of Extended Class II Resin Composite Restorations In Vitro.

    Science.gov (United States)

    Soliman, Sebastian; Preidl, Reinhard; Karl, Sabine; Hofmann, Norbert; Krastl, Gabriel; Klaiber, Bernd

    2016-01-01

    To investigate the influence of three cavity designs on the marginal seal of large Class II cavities restored with low-shrinkage resin composite limited to the enamel. One hundred twenty (120) intact human molars were randomly divided into 12 groups, with three different cavity designs: 1. undermined enamel, 2. box-shaped, and 3. proximal bevel. The teeth were restored with 1. an extra-low shrinkage (ELS) composite free of diluent monomers, 2. microhybrid composite (Herculite XRV), 3. nanohybrid composite (Filtek Supreme XTE), and 4. silorane-based composite (Filtek Silorane). After artificial aging by thermocycling and storage in physiological saline, epoxy resin replicas were prepared. To determine the integrity of the restorations' approximal margins, two methods were sequentially employed: 1. replicas were made of the 120 specimens and examined using SEM, and 2. the same 120 specimens were immersed in AgNO3 solution, and the dye penetration depth was observed with a light microscope. Statistical analysis was performed using the Kruskal-Wallis and the Dunn-Bonferroni tests. After bevel preparation, SEM observations showed that restorations did not exhibit a higher percentage of continuous margin (SEM-analysis; p>0.05), but more leakage was found than with the other cavity designs (pcomposite restorations and is no longer recommended. However, undermined enamel should be removed to prevent enamel fractures.

  12. Search for Nonthermal X-Rays from Supernova Remnant Shells

    Science.gov (United States)

    Petre, R.; Keohane, J.; Hwang, U.; Allen, G.; Gotthelf, E.

    The demonstration by ASCA that the nonthermal X-ray emission from the rim of SN1006 is synchrotron emission from TeV electrons, produced in the same environment responsible for cosmic ray protons and nuclei (Koyama et al. 1995, Nature 378, 255), has stimulated a search for nonthermal X-rays from other remnants. Nonthermal emission has subsequently been found to arise in the shells of at least two other remnants, Cas A and IC 443. In Cas A, a hard tail is detected using ASCA, XTE, and OSSE to energies exceeding 100 keV; the shape of the spectrum rules out all mechanisms except synchrotron radiation. In IC 443, the previously known hard emission has been shown using ASCA to be isolated to a small region along the rim of the remnant, where the shock is interacting most strongly with a molecular cloud. Nonthermal X-ray emission is thought to arise here by enhanced cosmic ray production associated with the shock/cloud interaction (Keohane et al. 1997, ApJ in press). We describe the properties of the nonthermal emission in SN1006, Cas A, and IC 443, and discuss the status of our search for nonthermal emission associated with the shocks of other Galactic and LMC SNR's.

  13. Correlation between some thermo-mechanical and physico-chemical properties in multi-component glasses of Se-Te-Sn-Cd system

    International Nuclear Information System (INIS)

    Kumar, Amit; Mehta, Neeraj

    2017-01-01

    The glass transition phenomenon is guided by the swift cooling of a melt (glass-forming liquid). Consequently, the glass as a final product consists of a considerable number of micro-voids having the size of the order of atomic and/or molecular sizes. The model of free volume fluctuation helps in describing the diverse physico-chemical properties of amorphous materials (like glasses and polymers). This theory is based on the fraction of fluctuation free frozen at the glass transition temperature and it forms a basis for determination of various significant thermo-mechanical properties. In the present work, Vickers hardness test method is employed that provides useful information concerning the mechanical behavior of brittle solids. The present work emphasizes the results of micro-indentation measurements on recently synthesized novel Se_7_8_-_xTe_2_0Sn_2Cd_x glassy system. Basic thermo-mechanical parameters such as micro-hardness, volume (V_h), formation energy (E_h) of micro-voids in the glassy network and modulus of elasticity (E) have been determined and their variation with glass composition has been investigated. (orig.)

  14. Space and Earth Sciences, Computer Systems, and Scientific Data Analysis Support, Volume 1

    Science.gov (United States)

    Estes, Ronald H. (Editor)

    1993-01-01

    This Final Progress Report covers the specific technical activities of Hughes STX Corporation for the last contract triannual period of 1 June through 30 Sep. 1993, in support of assigned task activities at Goddard Space Flight Center (GSFC). It also provides a brief summary of work throughout the contract period of performance on each active task. Technical activity is presented in Volume 1, while financial and level-of-effort data is presented in Volume 2. Technical support was provided to all Division and Laboratories of Goddard's Space Sciences and Earth Sciences Directorates. Types of support include: scientific programming, systems programming, computer management, mission planning, scientific investigation, data analysis, data processing, data base creation and maintenance, instrumentation development, and management services. Mission and instruments supported include: ROSAT, Astro-D, BBXRT, XTE, AXAF, GRO, COBE, WIND, UIT, SMM, STIS, HEIDI, DE, URAP, CRRES, Voyagers, ISEE, San Marco, LAGEOS, TOPEX/Poseidon, Pioneer-Venus, Galileo, Cassini, Nimbus-7/TOMS, Meteor-3/TOMS, FIFE, BOREAS, TRMM, AVHRR, and Landsat. Accomplishments include: development of computing programs for mission science and data analysis, supercomputer applications support, computer network support, computational upgrades for data archival and analysis centers, end-to-end management for mission data flow, scientific modeling and results in the fields of space and Earth physics, planning and design of GSFC VO DAAC and VO IMS, fabrication, assembly, and testing of mission instrumentation, and design of mission operations center.

  15. Deposition of polycrystalline Cd{sub 1-x}Zn{sub x} Te films on ZnTe/graphite and graphite substrates by close-spaced sublimation

    Energy Technology Data Exchange (ETDEWEB)

    Okamoto, Tamotsu; Akiba, Sho; Takahashi, Kohei; Nagatsuka, Satsuki; Kanda, Yohei [Department of Electrical and Electronic Engineering, Kisarazu National College of Technology, 2-11-1 Kiyomidai-higashi, Kisarazu, Chiba 292-0041 (Japan); Tokuda, Satoshi; Kishihara, Hiroyuki; Sato, Toshiyuki [Technology Research Laboratory, Shimadzu Corporation, 3-9-4 Hikaridai, Seika-cho, Soraku-gun, Kyoto 619-0237 (Japan)

    2014-07-15

    The effects of a ZnTe layer on the deposition of a Cd{sub 1-x}Zn{sub x}Te (CZT) layer in the initial stage of the close-spaced sublimation (CSS) deposition were investigated. The deposition rate was almost constant in the initial stage of the CdTe deposition on the ZnTe/graphite substrates. However, the deposition rate within 1 minute was lower than that after 1 minute in the CdTe deposition on graphite substrates. This result suggests that nucleation of CdTe directly deposited on graphite substrate is difficult when compared to that with a ZnTe layer. Furthermore, the effects of CdCl{sub 2} and ZnTe additions to the CdTe sources in the CSS deposition were also investigated. Both the grain size and the intensity of donor-acceptor pair (DAP) emission in photoluminescence (PL) spectra were decreased by the effect of CdCl{sub 2} addition. Zn content in CZT films was controlled by the ZnTe ratio in the CdTe/ZnTe powder sources. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Lifshitz transitions induced by temperature and surface doping in type-II Weyl semimetal candidate T{sub d}-WTe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Qihang; Yang, Lexian [State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics and Collaborative Innovation Center of Quantum Matter, Tsinghua University, Beijing (China); Liu, Zhongkai [School of Physical Science and Technology, ShanghaiTech University and CAS-Shanghai Science Research Center, Shanghai (China); Sun, Yan; Felser, Claudia; Yan, Binghai [Max Planck Institute for Chemical Physics of Solids, Dresden (Germany); Yang, Haifeng [Department of Physics, Clarendon Laboratory, University of Oxford (United Kingdom); Laboratary of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences, Shanghai (China); Jiang, Juan [School of Physical Science and Technology, ShanghaiTech University and CAS-Shanghai Science Research Center, Shanghai (China); Department of Physics, Clarendon Laboratory, University of Oxford (United Kingdom); Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Pohang Accelerator Laboratory POSTECH, Pohang (Korea, Republic of); Mo, Sung-Kwan; Hussain, Zahid [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Qian, Xiaofeng [Department of Materials Science and Engineering, College of Engineering and College of Science, Texas A and M University, College Station, TX (United States); Fu, Liang [Department of Physics, Massachusetts Institute of Technology, Cambridge, MA (United States); Yao, Shuhua; Lu, Minghui [National Laboratory of Solid State Microstructures, Department of Materials Science and Engineering, Nanjing University, Nanjing (China); Chen, Yulin [State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics and Collaborative Innovation Center of Quantum Matter, Tsinghua University, Beijing (China); School of Physical Science and Technology, ShanghaiTech University and CAS-Shanghai Science Research Center, Shanghai (China); Department of Physics, Clarendon Laboratory, University of Oxford (United Kingdom)

    2017-12-15

    Using high resolution angle-resolved photoemission spectroscopy, we systematically investigate the electronic structure of T{sub d}-WTe{sub 2}, which has attracted substantial research attention due to its diverse and fascinating properties, especially the predicted type-II topological Weyl semimetal (TWS) phase. The observed significant lattice contraction and the fact that our ARPES measurements are well reproduced by our ab initio calculations under reduced lattice constants support the theoretical prediction of a type-II TWS phase in T{sub d}-WTe{sub 2} at temperatures below 10 K. We also investigate the evolution of the electronic structure of T{sub d}-WTe{sub 2} and realize two-stage Lifshitz transitions induced by temperature regulation and surface modification, respectively. Our results not only shed light on the understanding of the electronic structure of T{sub d}-WTe{sub 2}, but also provide a promising method to manipulate the electronic structures and physical properties of the type-II TWS T{sub d}-XTe{sub 2}. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Interactive Dynamic Mission Scheduling for ASCA

    Science.gov (United States)

    Antunes, A.; Nagase, F.; Isobe, T.

    The Japanese X-ray astronomy satellite ASCA (Advanced Satellite for Cosmology and Astrophysics) mission requires scheduling for each 6-month observation phase, further broken down into weekly schedules at a few minutes resolution. Two tools, SPIKE and NEEDLE, written in Lisp and C, use artificial intelligence (AI) techniques combined with a graphic user interface for fast creation and alteration of mission schedules. These programs consider viewing and satellite attitude constraints as well as observer-requested criteria and present an optimized set of solutions for review by the planner. Six-month schedules at 1 day resolution are created for an oversubscribed set of targets by the SPIKE software, originally written for HST and presently being adapted for EUVE, XTE and AXAF. The NEEDLE code creates weekly schedules at 1 min resolution using in-house orbital routines and creates output for processing by the command generation software. Schedule creation on both the long- and short-term scale is rapid, less than 1 day for long-term, and one hour for short-term.

  18. CH Cygni. I. Observational Evidence for a Disk-Jet Connection

    Science.gov (United States)

    Sokoloski, J. L.; Kenyon, S. J.

    2003-02-01

    We investigate the role of accretion in the production of jets in the symbiotic star CH Cygni. Assuming that the rapid stochastic optical variations in CH Cygni come from the accretion disk, as in cataclysmic variables, we use changes in this flickering to diagnose the state of the disk in 1997. At that time, CH Cygni dropped to a very low optical state, and Karovska et al. report that a radio jet was produced. For approximately 1 yr after the jet production, the amplitude of the fastest (timescale of minutes) variations was significantly reduced, although smooth, hour-timescale variations were still present. This light-curve evolution indicates that the inner disk may have been disrupted, or emission from this region suppressed, in association with the mass ejection event. We describe optical spectra that support this interpretation of the flickering changes. The simultaneous state change, jet ejection, and disk disruption suggest a comparison between CH Cygni and some black hole candidate X-ray binaries that show changes in the inner-disk radius in conjunction with discrete ejection events on a wide range of timescales (e.g., the microquasar GRS 1915+105 and XTE J1550-564).

  19. Shocks in the relativistic transonic accretion with low angular momentum

    Science.gov (United States)

    Suková, P.; Charzyński, S.; Janiuk, A.

    2017-12-01

    We perform 1D/2D/3D relativistic hydrodynamical simulations of accretion flows with low angular momentum, filling the gap between spherically symmetric Bondi accretion and disc-like accretion flows. Scenarios with different directional distributions of angular momentum of falling matter and varying values of key parameters such as spin of central black hole, energy and angular momentum of matter are considered. In some of the scenarios the shock front is formed. We identify ranges of parameters for which the shock after formation moves towards or outwards the central black hole or the long-lasting oscillating shock is observed. The frequencies of oscillations of shock positions which can cause flaring in mass accretion rate are extracted. The results are scalable with mass of central black hole and can be compared to the quasi-periodic oscillations of selected microquasars (such as GRS 1915+105, XTE J1550-564 or IGR J17091-3624), as well as to the supermassive black holes in the centres of weakly active galaxies, such as Sgr A*.

  20. Current-Nonlinear Hall Effect and Spin-Orbit Torque Magnetization Switching in a Magnetic Topological Insulator

    Science.gov (United States)

    Yasuda, K.; Tsukazaki, A.; Yoshimi, R.; Kondou, K.; Takahashi, K. S.; Otani, Y.; Kawasaki, M.; Tokura, Y.

    2017-09-01

    The current-nonlinear Hall effect or second harmonic Hall voltage is widely used as one of the methods for estimating charge-spin conversion efficiency, which is attributed to the magnetization oscillation by spin-orbit torque (SOT). Here, we argue the second harmonic Hall voltage under a large in-plane magnetic field with an in-plane magnetization configuration in magnetic-nonmagnetic topological insulator (TI) heterostructures, Crx (Bi1 -ySby )2 -xTe3 /(Bi1 -ySby )2Te3 , where it is clearly shown that the large second harmonic voltage is governed not by SOT but mainly by asymmetric magnon scattering without macroscopic magnetization oscillation. Thus, this method does not allow an accurate estimation of charge-spin conversion efficiency in TI. Instead, the SOT contribution is exemplified by current pulse induced nonvolatile magnetization switching, which is realized with a current density of 2.5 ×1010 A m-2 , showing its potential as a spintronic material.

  1. Excitons in tunnel coupled CdTe and (Cd,Mn)Te quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Terletskii, Oleg; Ryabchenko, Sergiy; Tereshchenko, Oleksandr [Institute of Physics NASU, pr. Nauki 46, 03680 Kyiv (Ukraine); Sugakov, Volodymyr; Vertsimakha, Ganna [Institute for Nuclear Research NASU, pr. Nauki 47, 03680 Kyiv (Ukraine); Karczewski, Grzegorz [Institute of Physics PAS, Al. Lotnikow 32/46, PL-02-668 Warsaw (Poland)

    2017-05-15

    The photoluminescence (PL) from structures containing Cd{sub 0.95}Mn{sub 0.05}Te and CdTe quantum wells (QWs) separated by a narrow (1.94 nm) barrier was studied. The PL lines of comparable intensities from several possible exciton states were observed simultaneously at energy distances substantially exceeding kT. This means that the energy transfer in the studied systems is slower than the radiative recombination of the confined excitons. For the CdTe QW width of about 8.7-9 nm, indirect excitons with the electron and heavy hole chiefly localized in the CdTe and Cd{sub 1-x}Mn{sub x}Te QWs, respectively, were detected in the magnetic field. These indirect excitons have PL energy of about 10-20 meV above the PL line of the direct excitons in the CdTe QW. The observation of the PL from the indirect excitons which are not the lowest excitations in the structure is a distinctive feature of the system. Photoluminescence intensity dependence on the energy and the magnetic field. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Outburst of the 2 s Anomalous X-ray Pulsar 1E 1547.0-5408

    Science.gov (United States)

    Halpern, J. P.; Gotthelf, E. V.; Camilo, F.; Reynolds, J.; Ransom, S. M.

    2008-01-01

    Following our discovery of radio pulsations from the newly recognized anomalous X-ray pulsar (AXP) 1E 1547.0-5408, we initiated X-ray monitoring with the Swift X-ray telescope and obtained a single target-of-opportunity observation with the Newton X-ray Multi-Mirror Mission (XMM-Newton). In comparison with its historic minimum flux of 3 x 10(exp -l3)ergs/sq cm/s, the source was found to be in a record high state, f(sub x)(1-8 keV) = 5 x 10(exp -12)ergs/sq cm/s, or L(sub x) = 1.7 x 10(exp 35)(d/9 kpc )(sup 2)ergs/s, and declining by 25% in 1 month. Extrapolating the decay, we bound the total energy in this outburst to 1042 ergs pulsar, which may indicate a nearly aligned rotator. As also inferred from the transient behavior of XTE J18 10-197, the only other AXP known to emit in the radio, the magnetic field rearrangement responsible for this X-ray outburst of 1E 1547.0-5408 is probably the cause of its radio turn-on.

  3. Effects of Pb doping on the magneto-optical properties of EuPbTe epitaxial films

    Energy Technology Data Exchange (ETDEWEB)

    Heredia, E.; Motisuke, P. [Laboratório Associado de Sensores e Materiais, Instituto Nacional de Pesquisas Espaciais, São José dos Campos, 12227-010 SP (Brazil); Couto, O.D.D. Jr. [Instituto de Física “Gleb Wataghin” – Universidade Estadual de Campinas, Campinas, 13083-859 SP (Brazil); Lang, R. [Instituto de Física “Gleb Wataghin” – Universidade Estadual de Campinas, Campinas, 13083-859 SP (Brazil); Institute of Science and Technology, UNIFESP, São José dos Campos, 12231-280 SP (Brazil); Balanta, M.A.G.; Brasil, M.J.S.P. [Instituto de Física “Gleb Wataghin” – Universidade Estadual de Campinas, Campinas, 13083-859 SP (Brazil); Oliveira Rappl, P.H. de [Laboratório Associado de Sensores e Materiais, Instituto Nacional de Pesquisas Espaciais, São José dos Campos, 12227-010 SP (Brazil); Iikawa, F., E-mail: iikawa@ifi.unicamp.br [Laboratório Associado de Sensores e Materiais, Instituto Nacional de Pesquisas Espaciais, São José dos Campos, 12227-010 SP (Brazil); Instituto de Física “Gleb Wataghin” – Universidade Estadual de Campinas, Campinas, 13083-859 SP (Brazil)

    2015-11-15

    We investigate the magneto-optical properties of magnetic-semiconductor Eu{sub 1−x}Pb{sub x}Te epitaxial layers with Pb contents up to 5%. We show that the inclusion of a small amount of Pb atoms in EuTe affects the optical and magnetic properties of the resulting alloy. The incorporation of Pb gives rise to a reduction of the Néel temperature and of the slope of the giant magneto-red-shift of the magnetic polaron optical emission. All those effects can be understood in terms of the magnetic dilution effect due to the reduced Eu concentration. The introduction of Pb also reveals a splitting of the high emission energy side-band under applied magnetic field, presenting a more complex feature of the band structure of the alloys. Our results cannot be fully explained on the basis of the current theoretical knowledge of the EuTe band structure and, therefore, we expect that they can stimulate future theoretical investigations and encourage applied investigations of spintronic devices based on these materials. - Highlights: • Reduction of the Néel temperature when small amount of Pb is introduced into EuTe. • The saturation magnetic field needed to fully order the magnetic moments of Eu also reduces increasing Pb content. • Splitting of the high energy optical emission line under applied magnetic field, which is more evident for Pb doped samples.

  4. Synthesis of dilute magnetic semiconductors by ion implantation

    International Nuclear Information System (INIS)

    Braunstein, G.H.; Dresselhaus, G.; Withrow, S.P.

    1986-01-01

    We have synthesized layers of CdMnTe by implantation of Mn into CdTe. Samples of CdTe have been implanted with Mn ions of 60 keV energy to fluences in the range 1 x 10 13 cm -2 to 2 x 10 16 cm -2 resulting in local concentrations of up to 10% at the maximum of the Mn distribution. Rutherford backscattering-channeling analysis has been used to study the radiation damage after implantation and after subsequent rapid thermal annealing (RTA). These experiments reveal that RTA for 15 sec at a temperature T greater than or equal to 700 0 C results in the complete recovery of the lattice order, without affecting the stoichiometry of CdTe. Photoluminescence (PL) measurements of a sample showing complete annealing reveal an increase in the band gap corresponding to the synthesis of very dilute (x approx. = 0.004) Cd/sub 1-x/Mn/sub x/Te. A shift of the excitonic PL peak to lower energies is observed when a magnetic field H less than or equal to 1T is applied. These measurements provide clear evidence for the synthesis of a DMS by ion implantation of Mn into CdTe

  5. Temperature Dependences of the Product of the Differential Resistance by the Area in MIS-Structures Based on Cd x Hg1- x Te Grown by Molecularbeam Epitaxy on Alternative Si and GaAs Substrates

    Science.gov (United States)

    Voitsekhovskii, A. V.; Nesmelov, S. N.; Dzyadukh, S. M.; Varavin, V. S.; Vasil'ev, V. V.; Dvoretskii, S. A.; Mikhailov, N. N.; Yakushev, M. V.; Sidorov, G. Yu.

    2017-06-01

    In a temperature range of 9-200 K, temperature dependences of the differential resistance of space-charge region in the strong inversion mode are experimentally studied for MIS structures based on CdxHg1-xTe (x = 0.22-0.40) grown by molecular-beam epitaxy. The effect of various parameters of structures: the working layer composition, the type of a substrate, the type of insulator coating, and the presence of a near-surface graded-gap layer on the value of the product of differential resistance by the area is studied. It is shown that the values of the product RSCRA for MIS structures based on n-CdHgTe grown on a Si(013) substrate are smaller than those for structures based on the material grown on a GaAs(013) substrate. The values of the product RSCRA for MIS structures based on p-CdHgTe grown on a Si(013) substrate are comparable with the value of the analogous parameter for MIS structures based on p-CdHgTe grown on a GaAs(013) substrate.

  6. Refractive index of ternary and quaternary compound semiconductors below the fundamental absorption edge: Linear and nonlinear effects

    International Nuclear Information System (INIS)

    Jensen, B.; Torabi, A.

    1985-01-01

    The index of refraction n is calculated as a function of frequency and mole fraction x for the following compounds: Hg/sub l-x/Cd/sub x/Te, Al/sub x/Ga/sub l-x/As, and In/sub l-x/Ga/sub x/As/sub y/P/sub l-y/ lattice matched to InP. Lattice matching of In/sub l-x/Ga/sub x/As/sub y/P/sub l-y/ to InP requires that x = 0.466 y. The theoretical result for the refractive index is obtained from a quantum mechanical calculation of the dielectric constant of a compound semiconductor. It is given in terms of the basic material parameters of band gap energy, effective electron mass m/sub n/, effective heavy hole mass m/sub rho/, spin orbit splitting energy, lattice constant, and carrier concentration n/sub e/ or rho for n-type or rho-type materials, respectively. If these quantities are known as functions of mole fraction x, there are no adjustable parameters involved. A negative change in the refractive index near the fundamental absorption edge is predicted on passing radiation through a crystal if the change in carrier concentration of the initially unoccupied conduction band is assumed proportional to internal intensity I. Comparison of theory with experimental data is given

  7. Repetitive patterns in rapid optical variations in the nearby black-hole binary V404 Cygni.

    Science.gov (United States)

    Kimura, Mariko; Isogai, Keisuke; Kato, Taichi; Ueda, Yoshihiro; Nakahira, Satoshi; Shidatsu, Megumi; Enoto, Teruaki; Hori, Takafumi; Nogami, Daisaku; Littlefield, Colin; Ishioka, Ryoko; Chen, Ying-Tung; King, Sun-Kun; Wen, Chih-Yi; Wang, Shiang-Yu; Lehner, Matthew J; Schwamb, Megan E; Wang, Jen-Hung; Zhang, Zhi-Wei; Alcock, Charles; Axelrod, Tim; Bianco, Federica B; Byun, Yong-Ik; Chen, Wen-Ping; Cook, Kem H; Kim, Dae-Won; Lee, Typhoon; Marshall, Stuart L; Pavlenko, Elena P; Antonyuk, Oksana I; Antonyuk, Kirill A; Pit, Nikolai V; Sosnovskij, Aleksei A; Babina, Julia V; Baklanov, Aleksei V; Pozanenko, Alexei S; Mazaeva, Elena D; Schmalz, Sergei E; Reva, Inna V; Belan, Sergei P; Inasaridze, Raguli Ya; Tungalag, Namkhai; Volnova, Alina A; Molotov, Igor E; de Miguel, Enrique; Kasai, Kiyoshi; Stein, William L; Dubovsky, Pavol A; Kiyota, Seiichiro; Miller, Ian; Richmond, Michael; Goff, William; Andreev, Maksim V; Takahashi, Hiromitsu; Kojiguchi, Naoto; Sugiura, Yuki; Takeda, Nao; Yamada, Eiji; Matsumoto, Katsura; James, Nick; Pickard, Roger D; Tordai, Tamás; Maeda, Yutaka; Ruiz, Javier; Miyashita, Atsushi; Cook, Lewis M; Imada, Akira; Uemura, Makoto

    2016-01-07

    How black holes accrete surrounding matter is a fundamental yet unsolved question in astrophysics. It is generally believed that matter is absorbed into black holes via accretion disks, the state of which depends primarily on the mass-accretion rate. When this rate approaches the critical rate (the Eddington limit), thermal instability is supposed to occur in the inner disk, causing repetitive patterns of large-amplitude X-ray variability (oscillations) on timescales of minutes to hours. In fact, such oscillations have been observed only in sources with a high mass-accretion rate, such as GRS 1915+105 (refs 2, 3). These large-amplitude, relatively slow timescale, phenomena are thought to have physical origins distinct from those of X-ray or optical variations with small amplitudes and fast timescales (less than about 10 seconds) often observed in other black-hole binaries-for example, XTE J1118+480 (ref. 4) and GX 339-4 (ref. 5). Here we report an extensive multi-colour optical photometric data set of V404 Cygni, an X-ray transient source containing a black hole of nine solar masses (and a companion star) at a distance of 2.4 kiloparsecs (ref. 8). Our data show that optical oscillations on timescales of 100 seconds to 2.5 hours can occur at mass-accretion rates more than ten times lower than previously thought. This suggests that the accretion rate is not the critical parameter for inducing inner-disk instabilities. Instead, we propose that a long orbital period is a key condition for these large-amplitude oscillations, because the outer part of the large disk in binaries with long orbital periods will have surface densities too low to maintain sustained mass accretion to the inner part of the disk. The lack of sustained accretion--not the actual rate--would then be the critical factor causing large-amplitude oscillations in long-period systems.

  8. Black Hole Mass Determination In the X-Ray Binary 4U 1630-47: Scaling of Spectral and Variability Characteristics

    Science.gov (United States)

    Seifina, Elena; Titarchuk, Lev; Shaposhnikov, Nikolai

    2014-01-01

    We present the results of a comprehensive investigation on the evolution of spectral and timing properties of the Galactic black hole candidate 4U 1630-47 during its spectral transitions. In particular, we show how a scaling of the correlation of the photon index of the Comptonized spectral component gamma with low-frequency quasi-periodic oscillations (QPOs), ?(sub L), and mass accretion rate, M, can be applied to the black hole mass and the inclination angle estimates.We analyze the transition episodes observed with the Rossi X-Ray Timing Explorer and BeppoSAX satellites.We find that the broadband X-ray energy spectra of 4U 1630-47 during all spectral states can be modeled by a combination of a thermal component, a Comptonized component, and a red-skewed iron-line component. We also establish that gamma monotonically increases during transition from the low-hard state to the high-soft state and then saturates for high mass accretion rates. The index saturation levels vary for different transition episodes. Correlations of gamma versus ?(sub L) also show saturation at gamma (is) approximately 3. Gamma -M and gamma -?(sub L) correlations with their index saturation revealed in 4U 1630-47 are similar to those established in a number of other black hole candidates and can be considered as an observational evidence for the presence of a black hole in these sources. The scaling technique, which relies on XTE J1550-564, GRO 1655-40, and H1743-322 as reference sources, allows us to evaluate a black hole mass in 4U 1630-47 yielding M(sub BH) (is) approximately 10 +/- 0.1 solar masses and to constrain the inclination angle of i (is) approximately less than 70 deg.

  9. Assembly of cerium(III)-stabilized polyoxotungstate nanoclusters with SeO{sub 3}{sup 2-}/TeO{sub 3}{sup 2-} templates. From single polyoxoanions to inorganic hollow spheres in dilute solution

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Wei-Chao; Wang, Xin-Long; Shao, Kui-Zhan; Su, Zhong-Min; Wang, En-Bo [Institute of Functional Materials Chemistry, Key Laboratory of Polyoxometalate Science of Ministry of Education, Department of Chemistry, Northeast Normal University, Changchun (China); Li, Hao-Long [State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University. Changchun (China)

    2013-08-12

    A versatile one-pot strategy was employed to synthesize three cerium(III)-stabilized polyoxotungstates nanoclusters by combining cerium linkers and SeO{sub 3}{sup 2-}/TeO{sub 3}{sup 2-} heteroanion templates: K{sub 32}Na{sub 16}[{(XO_3)W_1_0O_3_4}{sub 8}{Ce_8(H_2O)_2_0}(WO{sub 2}){sub 4}-(W{sub 4}O{sub 12})].n H{sub 2}O [X=Se, n=81 (1); X=Te, n=114 (2)] and K{sub 12}Na{sub 22}[{(SeO_3)W_1_0O_3_4}{sub 8}{Ce_8(H_2O)_2_0}(WO{sub 2}){sub 4}-{(W_4O_6)Ce_4(H_2O)_1_4(SeO_3)_4(NO_3)_2}] . 79 H{sub 2}O (3), which are the first lanthanide-containing polyoxotungstates with selenium or tellurium heteroatoms. The three clusters were characterized by single-crystal X-ray structure analysis, IR spectroscopy, thermogravimetric/differential thermal analysis, UV/Vis spectroscopy, ESI-MS, and X-ray photoelectron spectroscopy. Their electrochemical, photoluminescence, and magnetic properties were investigated. Their behavior in solution was studied by transmission electron microscopy, which showed that their single polyoxoanions assemble into intact, uniform-sized, purely inorganic hollow spheres in dilute water/acetone solution. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Analysis of long-term monomer elution from bulk-fill and conventional resin-composites using high performance liquid chromatography.

    Science.gov (United States)

    Alshali, Ruwaida Z; Salim, Nesreen A; Sung, Rehana; Satterthwaite, Julian D; Silikas, Nick

    2015-12-01

    The aim of this study was to assess monomer elution from bulk-fill and conventional resin-composites stored in different media using high performance liquid chromatography (HPLC) for up to 3 months. Six bulk-fill (SureFil SDR, Venus Bulk Fill, X-tra base, Filtek Bulk Fill flowable, Sonic Fill, and Tetric EvoCeram Bulk Fill) and eight conventional resin-composites (Grandioso Flow, Venus Diamond Flow, X-Flow, Filtek Supreme XTE, Grandioso, Venus Diamond, TPH Spectrum, and Filtek Z250) were tested. Cylindrical samples (n=5) were immersed in water, 70% ethanol/water solution (70% E/W), and artificial saliva and stored at 37°C for 24h, 1 month, and 3 months. The storage solutions were analysed with HPLC. Data were analysed with repeated measures ANOVA, one-way ANOVA, and Tukey post hoc test at α=0.05. Monomers detected in water and artificial saliva were TEGDMA, DEGDMA, UDMA, and TCD-DI-HEA. No eluted monomers were detected from X-tra base and Sonic fill in these media. All monomers showed a variable extent of elution into 70% E/W with significantly higher amounts than those detected in water and artificial saliva. Significantly higher elution was detected from UDMA-BisEMA based composites compared to BisGMA and BisGMA-BisEMA based systems in 70% E/W. The rate of elution into different media varied between different monomers and was highly dependent on the molecular weight of the eluted compounds. Elution from bulk-fill resin-composites is comparable to that of conventional materials despite their increased increment thickness. Monomer elution is highly dependent on the hydrophobicity of the base monomers and the final network characteristics of the resin-matrix. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  11. Impact of extended defects on recombination in CdTe heterostructures grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Zaunbrecher, Katherine N. [Department of Physics, Colorado State University, Fort Collins, Colorado 80523 (United States); National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Kuciauskas, Darius; Dippo, Pat; Barnes, Teresa M. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Swartz, Craig H.; Edirisooriya, Madhavie; Ogedengbe, Olanrewaju S.; Sohal, Sandeep; Hancock, Bobby L.; LeBlanc, Elizabeth G.; Jayathilaka, Pathiraja A. R. D.; Myers, Thomas H. [Materials Science, Engineering and Commercialization Program, Texas State University, San Marcos, Texas 78666 (United States)

    2016-08-29

    Heterostructures with CdTe and CdTe{sub 1-x}Se{sub x} (x ∼ 0.01) absorbers between two wider-band-gap Cd{sub 1-x}Mg{sub x}Te barriers (x ∼ 0.25–0.3) were grown by molecular beam epitaxy to study carrier generation and recombination in bulk materials with passivated interfaces. Using a combination of confocal photoluminescence (PL), time-resolved PL, and low-temperature PL emission spectroscopy, two extended defect types were identified and the impact of these defects on charge-carrier recombination was analyzed. The dominant defects identified by confocal PL were dislocations in samples grown on (211)B CdTe substrates and crystallographic twinning-related defects in samples on (100)-oriented InSb substrates. Low-temperature PL shows that twin-related defects have a zero-phonon energy of 1.460 eV and a Huang-Rhys factor of 1.50, while dislocation-dominated samples have a 1.473-eV zero-phonon energy and a Huang-Rhys factor of 1.22. The charge carrier diffusion length near both types of defects is ∼6 μm, suggesting that recombination is limited by diffusion dynamics. For heterostructures with a low concentration of extended defects, the bulk lifetime was determined to be 2.2 μs with an interface recombination velocity of 160 cm/s and an estimated radiative lifetime of 91 μs.

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

    Energy Technology Data Exchange (ETDEWEB)

    Corbet, Robin H. D. [University of Maryland, Baltimore County, MD 21250 (United States); Coley, Joel B. [NASA Postdoctoral Program, and Astroparticle Physics Laboratory, Code 661 NASA Goddard Space Flight Center, Greenbelt Road, MD 20771 (United States); Krimm, Hans A., E-mail: corbet@umbc.edu [Universities Space Research Association, 10211 Wincopin Circle, Suite 500, Columbia, MD 21044 (United States)

    2017-09-10

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

  13. Searching for High-energy, Horizon-scale Emissions from Galactic Black Hole Transients during Quiescence

    Energy Technology Data Exchange (ETDEWEB)

    Lin, L. C.-C.; Pu, Hung-Yi; Hirotani, Kouichi; Matsushita, Satoki; Inoue, Makoto [Institute of Astronomy and Astrophysics, Academia Sinica, Taipei 10617, Taiwan (China); Kong, Albert K. H; Chang, Hsiang-Kuang [Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Tam, Pak-Hin T., E-mail: lupin@asiaa.sinica.edu.tw, E-mail: hpu@perimeterinstitute.ca, E-mail: hirotani@tiara.sinica.edu.tw [School of Physics and Astronomy, Sun Yat-Sen University, Zhuhai 519082 (China)

    2017-08-10

    We search for the gamma-ray counterparts of stellar-mass black holes using the long-term Fermi archive to investigate the electrostatic acceleration of electrons and positrons in the vicinity of the event horizon. We achieve this by applying the pulsar outer-gap model to their magnetospheres. When a black hole transient (BHT) is in a low-hard or quiescent state, the radiatively inefficient accretion flow cannot emit enough MeV photons that are required to sustain the force-free magnetosphere in the polar funnel via two-photon collisions. In this charge-starved gap region, an electric field arises along the magnetic field lines to accelerate electrons and positrons into ultra-relativistic energies. These relativistic leptons emit copious Gamma-rays via the curvature and inverse-Compton (IC) processes. It is found that these gamma-ray emissions exhibit a flaring activity when the plasma accretion rate typically stays between 0.01% and 0.005% of the Eddington value for rapidly rotating, stellar-mass black holes. By analyzing the detection limit determined from archival Fermi /Large Area Telescope data, we find that the 7-year averaged duty cycle of such flaring activities should be less than 5% and 10% for XTE J1118+480 and 1A 0620-00, respectively, and that the detection limit is comparable to the theoretical prediction for V404 Cyg. It is predicted that the gap emission can be discriminated from the jet emission if we investigate the high-energy spectral behavior or observe nearby BHTs during deep quiescence simultaneously in infrared wavelength and very-high energies.

  14. 10 microsecond time resolution studies of Cygnus X-1

    Energy Technology Data Exchange (ETDEWEB)

    Wen, H. C. [Stanford Univ., CA (United States)

    1997-06-01

    Time variability analyses have been applied to data composed of event times of X-rays emitted from the binary system Cygnus X-1 to search for unique black hole signatures. The X-ray data analyzed was collected at ten microsecond time resolution or better from two instruments, the High Energy Astrophysical Observatory (HEAO) A-1 detector and the Rossi X-ray Timing Explorer (XTE) Proportional Counter Array (PCA). HEAO A-1 and RXTE/PCA collected data from 1977--79 and from 1996 on with energy sensitivity from 1--25 keV and 2--60 keV, respectively. Variability characteristics predicted by various models of an accretion disk around a black hole have been searched for in the data. Drop-offs or quasi-periodic oscillations (QPOs) in the Fourier power spectra are expected from some of these models. The Fourier spectral technique was applied to the HEAO A-1 and RXTE/PCA data with careful consideration given for correcting the Poisson noise floor for instrumental effects. Evidence for a drop-off may be interpreted from the faster fall off in variability at frequencies greater than the observed breaks. Both breaks occur within the range of Keplerian frequencies associated with the inner edge radii of advection-dominated accretion disks predicted for Cyg X-1. The break between 10--20 Hz is also near the sharp rollover predicted by Nowak and Wagoner`s model of accretion disk turbulence. No QPOs were observed in the data for quality factors Q > 9 with a 95% confidence level upper limit for the fractional rms amplitude at 1.2% for a 16 M⊙ black hole.

  15. Influence of light waves on the thermoelectric power under large magnetic field in III-V, ternary and quaternary materials

    Energy Technology Data Exchange (ETDEWEB)

    Ghatak, K.P. [Department of Electronic Science, The University of Calcutta, 92, Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Bhattacharya, S. [Post Graduate Department of Computer Science, St. Xavier' s College, 30 Park Street, Kolkata 700 016 (India); Pahari, S. [Department of Administration, Jadavpur University, Kolkata 700 032 (India); De, D. [Department of Computer Science and Engineering, West Bengal University of Technology, B. F. 142, Sector I, Salt Lake, Kolkata 700 064 (India); Ghosh, S.; Mitra, M. [Department of Electronics and Telecommunication Engineering, Bengal Engineering and Science University, Howrah 711 103 (India)

    2008-04-15

    We study theoretically the influence of light waves on the thermoelectric power under large magnetic field (TPM) for III-V, ternary and quaternary materials, whose unperturbed energy-band structures, are defined by the three-band model of Kane. The solution of the Boltzmann transport equation on the basis of this newly formulated electron dispersion law will introduce new physical ideas and experimental findings in the presence of external photoexcitation. It has been found by taking n-InAs, n-InSb, n-Hg{sub 1-x}Cd{sub x}Te and n-In{sub 1-x}Ga{sub x}As{sub y}P{sub 1-y} lattice matched to InP as examples that the TPM decreases with increase in electron concentration, and increases with increase in intensity and wavelength, respectively in various manners. The strong dependence of the TPM on both light intensity and wavelength reflects the direct signature of light waves that is in direct contrast as compared with the corresponding bulk specimens of the said materials in the absence of external photoexcitation. The rate of change is totally band-structure dependent and is significantly influenced by the presence of the different energy-band constants. The well-known result for the TPM for nondegenerate wide-gap materials in the absence of light waves has been obtained as a special case of the present analysis under certain limiting conditions and this compatibility is the indirect test of our generalized formalism. Besides, we have also suggested the experimental methods of determining the Einstein relation for the diffusivity:mobility ratio, the Debye screening length and the electronic contribution to the elastic constants for materials having arbitrary dispersion laws. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

  16. Relevant optical properties for direct restorative materials.

    Science.gov (United States)

    Pecho, Oscar E; Ghinea, Razvan; do Amaral, Erika A Navarro; Cardona, Juan C; Della Bona, Alvaro; Pérez, María M

    2016-05-01

    To evaluate relevant optical properties of esthetic direct restorative materials focusing on whitened and translucent shades. Enamel (E), body (B), dentin (D), translucent (T) and whitened (Wh) shades for E (WhE) and B (WhB) from a restorative system (Filtek Supreme XTE, 3M ESPE) were evaluated. Samples (1 mm thick) were prepared. Spectral reflectance (R%) and color coordinates (L*, a*, b*, C* and h°) were measured against black and white backgrounds, using a spectroradiometer, in a viewing booth, with CIE D65 illuminant and d/0° geometry. Scattering (S) and absorption (K) coefficients and transmittance (T%) were calculated using Kubelka-Munk's equations. Translucency (TP) and opalescence (OP) parameters and whiteness index (W*) were obtained from differences of CIELAB color coordinates. R%, S, K and T% curves from all shades were compared using VAF (Variance Accounting For) coefficient with Cauchy-Schwarz inequality. Color coordinates and optical parameters were statistically analyzed using one-way ANOVA, Tukey's test with Bonferroni correction (α=0.0007). Spectral behavior of R% and S were different for T shades. In addition, T shades showed the lowest R%, S and K values, as well as the highest T%, TP an OP values. In most cases, WhB shades showed different color and optical properties (including TP and W*) than their corresponding B shades. WhE shades showed similar mean W* values and higher mean T% and TP values than E shades. When using whitened or translucent composites, the final color is influenced not only by the intraoral background but also by the color and optical properties of multilayers used in the esthetic restoration. Copyright © 2016 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  17. EFFECTS OF ROTATIONALLY INDUCED MIXING IN COMPACT BINARY SYSTEMS WITH LOW-MASS SECONDARIES AND IN SINGLE SOLAR-TYPE STARS

    International Nuclear Information System (INIS)

    Chatzopoulos, E.; Robinson, Edward L.; Wheeler, J. Craig

    2012-01-01

    Many population synthesis and stellar evolution studies have addressed the evolution of close binary systems in which the primary is a compact remnant and the secondary is filling its Roche lobe, thus triggering mass transfer. Although tidal locking is expected in such systems, most studies have neglected the rotationally induced mixing that may occur. Here we study the possible effects of mixing in mass-losing stars for a range of secondary star masses and metallicities. We find that tidal locking can induce rotational mixing prior to contact and thus affect the evolution of the secondary star if the effects of the Spruit-Tayler dynamo are included both for angular momentum and chemical transport. Once contact is made, the effect of mass transfer tends to be more rapid than the evolutionary timescale, so the effects of mixing are no longer directly important, but the mass-transfer strips matter to inner layers that may have been affected by the mixing. These effects are enhanced for secondaries of 1-1.2 M ☉ and for lower metallicities. We discuss the possible implications for the paucity of carbon in the secondaries of the cataclysmic variable SS Cyg and the black hole candidate XTE J1118+480 and for the progenitor evolution of Type Ia supernovae. We also address the issue of the origin of blue straggler stars in globular and open clusters. We find that for models that include rotation consistent with that observed for some blue straggler stars, evolution is chemically homogeneous. This leads to tracks in the H-R diagram that are brighter and bluer than the non-rotating main-sequence turn-off point. Rotational mixing could thus be one of the factors that contribute to the formation of blue stragglers.

  18. Repair bond strength of nanohybrid composite resins with a universal adhesive.

    Science.gov (United States)

    Altinci, Pinar; Mutluay, Murat; Tezvergil-Mutluay, Arzu

    2018-01-01

    Objective: To investigate the repair bond strength of fresh and aged nanohybrid and hybrid composite resins using a universal adhesive (UA). Materials and methods: Fresh and aged substrates were prepared using two nanohybrid (Venus Pearl, Heraus Kulzer; Filtek Supreme XTE, 3 M ESPE) and one hybrid (Z100, 3 M ESPE) composite resin, and randomly assigned to different surface treatments: (1) no treatment (control), (2) surface roughening with 320-grit (SR), (3) SR + UA (iBOND, Heraus Kulzer), (4) SR + Silane (Signum, Ceramic Bond I, Heraeus Kulzer) + UA, (5) SR + Sandblasting (CoJet, 3 M ESPE) + Silane + UA. After surface treatment, fresh composite resin was added to the substrates at 2 mm layer increments to a height of 5 mm, and light cured. Restored specimens were water-stored for 24 h and sectioned to obtain 1.0 × 1.0 mm beams ( n  = 12), and were either water-stored for 24 h at 37 °C, or water-stored for 24 h, and then thermocycled for 6000 cycles before microtensile bond strength (µTBS) testing. Data were analyzed with ANOVA and Tukey's HSD tests ( p  = .05). Results: Combined treatment of SR, sandblasting, silane and UA provided repair bond strength values comparable to the cohesive strength of each tested resin material ( p  composite resins upto 65% ( p  composite repair. Sandblasting and silane application slightly increases the repair strength for all substrate types.

  19. X-Ray Observations of the Black Hole Transient 4U 1630-47 during 2 Years of X-Ray Activity

    Science.gov (United States)

    Tomsick, John A.; Corbel, Stéphane; Goldwurm, Andrea; Kaaret, Philip

    2005-09-01

    The black hole candidate (BHC) X-ray transient 4U 1630-47 continuously produced strong X-ray emission for more than 2 years during its 2002-2004 outburst, which is one of the brightest and longest outbursts ever seen from this source. We use more than 300 observations made with the Rossi X-Ray Timing Explorer (RXTE) to study the source throughout the outburst, along with hard X-ray images from the International Gamma-Ray Astrophysics Laboratory (INTEGRAL), which are critical for interpreting the RXTE data in this crowded field. The source exhibits extreme behaviors, which can be interpreted as an indication that the system luminosity approaches the Eddington limit. For 15 observations, fitting the spectral continuum with a disk-blackbody plus power-law model results in measured inner disk temperatures between 2.7 and 3.8 keV, and such temperatures are only rivaled by the brightest BHC systems, such as GRS 1915+105 and XTE J1550-564. If the high temperatures are caused by the dominance of electron scattering opacity in the inner regions of the accretion disk, it is theoretically required that the source luminosity be considerably higher than 20% of the Eddington limit. We detect a variety of high-amplitude variability, including hard 10-100 s flares, which peak at levels as much as 2-3 times higher than nonflare levels. This flaring occurs at the highest disk luminosities in a regime in which the source deviates from the Ldisk~T4in relationship that is seen at lower luminosities, possibly suggesting that we are seeing transitions between a Shakura & Sunyaev disk and a ``slim'' disk, which is predicted to occur at very high mass accretion rates. The X-ray properties in 2002-2004 are significantly different from those seen during the 1998 outburst, which is the only outburst with detected radio jet emission. Our results support the ``jet line'' concept recently advanced by Fender and coworkers. Our study allows for a test of the quantitative McClintock & Remillard

  20. Six-month color change and water sorption of 9 new-generation flowable composites in 6 staining solutions

    Directory of Open Access Journals (Sweden)

    Maria ARREGUI

    Full Text Available Abstract Color match and water sorption are two factors that affect restorative materials. Discoloration is essential in the lifespan of restorations. The aim of this study was to evaluate color change and water sorption of nine flowable composites at multiple time points over 6 months. 60 samples of each composite were divided into two groups (Color Change and Water Sorption/Solubility. Each Color Change group was divided into six subgroups, which were immersed in distilled water (DW, coffee (CF, Coca-Cola (CC, red wine (RW, tea (TE and orange juice (OJ. The color was measured at the baseline, 1, 2, 3 and 4 weeks, and 3 and 6 months and color change values (ΔE were calculated. Each Water Sorption [WS]/Solubility [WL] group was tested according to ISO 4049:2009. The data were evaluated using two-way ANOVA, Fisher’s post-hoc test and Pearson’s correlation test. The composite with the lowest ΔE differed for each solution: Filtek™ Bulk Fill in DW (∆E = 0.73 (0.17–1.759; Vertise Flow in CF (∆E = 14.75 (7.91–27.41, in TE (∆E = 7.27 (2.81–24.81 and OJ (∆E = 3.17 (0.87–9.92; Tetric EvoFlow® in CC (∆E = 1.27 (0.45–4.02; and Filtek™ Supreme XTE in RW (∆E = 8.88 (5.23–19.59. RW caused the most discoloration (∆E = 23.62 (4.93–51.36. Vertise Flow showed the highest water sorption (WS = 69.10 ± 7.19. The Pearson test showed statistically significant positive correlations between water sorption and solubility and between water sorption and ∆E; the positive solubility-∆E correlation was not statistically significant. The findings suggest that water sorption is one factor associated with the ability of composites to discolor; however, discoloration is a multifactorial problem.

  1. Radiation transport around Kerr black holes

    Science.gov (United States)

    Schnittman, Jeremy David

    This Thesis describes the basic framework of a relativistic ray-tracing code for analyzing accretion processes around Kerr black holes. We begin in Chapter 1 with a brief historical summary of the major advances in black hole astrophysics over the past few decades. In Chapter 2 we present a detailed description of the ray-tracing code, which can be used to calculate the transfer function between the plane of the accretion disk and the detector plane, an important tool for modeling relativistically broadened emission lines. Observations from the Rossi X-Ray Timing Explorer have shown the existence of high frequency quasi-periodic oscillations (HFQPOs) in a number of black hole binary systems. In Chapter 3, we employ a simple "hot spot" model to explain the position and amplitude of these HFQPO peaks. The power spectrum of the periodic X-ray light curve consists of multiple peaks located at integral combinations of the black hole coordinate frequencies, with the relative amplitude of each peak determined by the orbital inclination, eccentricity, and hot spot arc length. In Chapter 4, we introduce additional features to the model to explain the broadening of the QPO peaks as well as the damping of higher frequency harmonics in the power spectrum. The complete model is used to fit the power spectra observed in XTE J1550-564, giving confidence limits on each of the model parameters. In Chapter 5 we present a description of the structure of a relativistic alpha- disk around a Kerr black hole. Given the surface temperature of the disk, the observed spectrum is calculated using the transfer function mentioned above. The features of this modified thermal spectrum may be used to infer the physical properties of the accretion disk and the central black hole. In Chapter 6 we develop a Monte Carlo code to calculate the detailed propagation of photons from a hot spot emitter scattering through a corona surrounding the black hole. The coronal scattering has two major observable

  2. Transport and first-principles study of novel thermoelectric materials

    Science.gov (United States)

    Chi, Hang

    Thermoelectric materials can recover waste industrial heat and convert it to electricity as well as provide efficient local cooling of electronic devices. The efficiency of such environmentally responsible and exceptionally reliable solid state energy conversion is determined by the dimensionless figure-of-merit ZT = alpha2 sigmaT/kappa, where alpha is the Seebeck coefficient, sigma is the electrical conductivity, kappa is the thermal conductivity, and T is the absolute temperature. The goal of the thesis is to (i) illustrate the physics to achieve high ZT of advanced thermoelectric materials and (ii) explore fundamental structure and transport properties in novel condensed matter systems, via an approach combining comprehensive experimental techniques and state-of-the-art first-principles simulation methods. Thermo-galvanomagnetic transport coefficients are derived from Onsager's reciprocal relations and evaluated via solving Boltzmann transport equation using Fermi-Dirac statistics, under the relaxation time approximation. Such understanding provides insights on enhancing ZT through two physically intuitive and very effective routes: (i) improving power factor PF = alpha2sigma; and (ii) reducing thermal conductivity kappa, as demonstrated in the cases of Mg2Si1-xSnx solid solution and Ge/Te double substituted skutterudites CoSb3(1-x)Ge1.5x Te1.5x, respectively. Motivated by recent theoretical predictions of enhanced thermoelectric performance in highly mismatched alloys, ZnTe:N molecular beam epitaxy (MBE) films deposited on GaAs (100) substrates are carefully examined, which leads to a surprising discovery of significant phonon-drag thermopower (reaching 1-2 mV/K-1) at ~13 K. Further systematic study in Bi2Te3 MBE thin films grown on sapphire (0001) and/or BaF2 (111) substrates, reveal that the peak of phonon drag can be tuned by the choice of substrates with different Debye temperatures. Moreover, the detailed transport and structure studies of Bi2-xTl xTe3

  3. Study of high energy emissions from stellar mass accreting holes

    International Nuclear Information System (INIS)

    Cadolle-Bel, Marion

    2006-01-01

    The present work is dedicated to the study of various X-ray binary Systems harbouring accreting stellar mass black holes (or candidates) associated in X-ray binary Systems mainly through the spectral and timing properties of the high energy 3 keV"-"1 MeV emission, sometimes completed by observations performed in radio, near-infrared and optical. The first part is devoted to accretion physics phenomena and the challenges of understanding the X-ray/gamma emission produced with the modeling of such high energy processes. Then I will define in a second part the instruments on board INTEGRAL and the way coded masked aperture is employed. In a third part, I will develop the standard data reduction analysis and my own contribution in improving the usual software before detailing the specific informatics tools I have developed for my own analysis. In the fourth part I will turn towards the deep analysis and interpretations I have performed on several black hole X-ray binary Systems chosen properly: the persistent black hole source Cygnus X-1 which has been studied since several years and surprised us by a high-energy excess detected; two new transient sources which provide interesting information, XTE J1720-318 located in the galactic bulge and SWIFT J1753.5-0127, probably situated in the halo. I will also detail my work on H 1743-322, recently identified by INTEGRAL as the HEAO source discovered in 1977, and on three (almost) persistent micro-quasars with superluminal jets, 1E 1740.7-2942, GRS 1758-258 and GRS 1915+105. I will analyze for each source spectral parameter evolutions and their links with each other during state transitions. I will then discuss the presence of two different X/gamma-ray emitting media with a relatively changing geometry. While establishing a cyclic order for the different variability classes of GRS 1915+105 observed during ten years, I will propose an interpretation for such behaviour, compatible with the theoretical predictions of the

  4. Lead telluride with increased mechanical stability for cylindrical thermoelectric generators; Bleitellurid mit erhoehter mechanischer Stabilitaet fuer zylindrische thermoelektrische Generatoren

    Energy Technology Data Exchange (ETDEWEB)

    Schmitz, Andreas

    2013-04-30

    The aim of this work is to improve the mechanical stability of lead telluride (PbTe), trying to vary its mechanical properties independently from its thermoelectric properties. Thus the influence of material preparation as well as different dopants on the mechanical and thermoelectric properties of lead telluride is being analysed. When using appropriately set process parameters, milling and sintering of lead telluride increases the material's hardness. With sintering temperatures exceeding 300 C stable material of high relative density can be achieved. Milling lead telluride generates lattice defects leading to a reduction of the material's charge carrier density. These defects can be reduced by increased sintering temperatures. Contamination of the powder due to the milling process leads to bloating during thermal cycling and thus reduced density of the sintered material. In addition to that, evaporation of tellurium at elevated temperatures causes instability of the material's thermoelectric properties. Based on the experimental results obtained in this work, the best thermoelectric and mechanical properties can be obtained by sintering coarse powders at around 400 C. Within this work a concept was developed to vary the mechanical properties of lead telluride via synthesis of PbTe with electrically nondoping elements, which thus may keep the thermoelectric properties unchanged. Therefore, the mechanical and thermoelectric properties of Pb{sub 1-x}Ca{sub x}Te were investigated. Doping pure PbTe with calcium causes a significant increase of the material's hardness while only slightly decreasing the charge carrier density and thus keeping the thermoelectric properties apart from a slight reduction of the electrical conductivity nearly unchanged. The abovementioned concept is proven using sodium doped lead telluride, as it is used for thermoelectric generators: The additional doping with calcium again increases the material's hardness while its thermoelectric

  5. Lead telluride with increased mechanical stability for cylindrical thermoelectric generators; Bleitellurid mit erhoehter mechanischer Stabilitaet fuer zylindrische thermoelektrische Generatoren

    Energy Technology Data Exchange (ETDEWEB)

    Schmitz, Andreas

    2013-04-30

    The aim of this work is to improve the mechanical stability of lead telluride (PbTe), trying to vary its mechanical properties independently from its thermoelectric properties. Thus the influence of material preparation as well as different dopants on the mechanical and thermoelectric properties of lead telluride is being analysed. When using appropriately set process parameters, milling and sintering of lead telluride increases the material's hardness. With sintering temperatures exceeding 300 C stable material of high relative density can be achieved. Milling lead telluride generates lattice defects leading to a reduction of the material's charge carrier density. These defects can be reduced by increased sintering temperatures. Contamination of the powder due to the milling process leads to bloating during thermal cycling and thus reduced density of the sintered material. In addition to that, evaporation of tellurium at elevated temperatures causes instability of the material's thermoelectric properties. Based on the experimental results obtained in this work, the best thermoelectric and mechanical properties can be obtained by sintering coarse powders at around 400 C. Within this work a concept was developed to vary the mechanical properties of lead telluride via synthesis of PbTe with electrically nondoping elements, which thus may keep the thermoelectric properties unchanged. Therefore, the mechanical and thermoelectric properties of Pb{sub 1-x}Ca{sub x}Te were investigated. Doping pure PbTe with calcium causes a significant increase of the material's hardness while only slightly decreasing the charge carrier density and thus keeping the thermoelectric properties apart from a slight reduction of the electrical conductivity nearly unchanged. The abovementioned concept is proven using sodium doped lead telluride, as it is used for thermoelectric generators: The additional doping with calcium again increases the material's hardness while

  6. Physics of accretion and ejection processes: a multi-wavelengths study of galactic X-ray binaries

    International Nuclear Information System (INIS)

    Prat, Lionel

    2010-01-01

    This manuscript is dedicated to the study of the accretion and ejection processes in X-ray Binaries, using radio and X-ray observations as well as numerical simulations. The links and interplay between the accretion disc, the corona and the compact jet. In an introductory part, I first describe the main observational and theoretical properties of the X-ray binaries. I especially emphasize the aspects required to understand the work reported in this manuscript. I also describe the main X-ray and radio observatories used during this work. Then, the first part of this manuscript is dedicated to the accretion processes in X-ray Binaries. I use high energy observations to study one High Mass X-ray Binary (IGR J19140+0951) and two Low-Mass X-ray Binaries (XTE J1818-245 and H1743-322). In the case of IGR Jl9140+0951, observations show that the luminosity generated by the accretion processes can deeply alter the stellar wind. In the case of the two Low Mass X-ray Binaries, I estimate several important parameters of the Systems using the behavior of their accretion discs. The second part is dedicated to the interplay between the accretion disc and the other components of the Systems, namely the corona and the compact jet. Using simultaneous X-ray and radio observations, I show that the corona undergo a strong evolution prior to a discrete ejection of matter, in the case of several binary Systems. In the case of GRS 1915+105, evolution of the corona and detection of a discrete ejection appear within a few seconds, while for other sources it takes a few hours. I study also the link between the accretion disc and the compact jet using a correlation between radio and X-ray flux: depending on the System, the link between the accretion energy brought by the accretion disc and the luminosity of the jet is different, indicating that different physical processes are at work. Finally, the third part is dedicated to numerical simulations of the accretion disc, in the case where an

  7. Superficial roughness on composite surface, composite enamel and composite dentin junctions after different finishing and polishing procedures. Part I: roughness after treatments with tungsten carbide vs diamond burs.

    Science.gov (United States)

    Ferraris, Federico; Conti, Alessandro

    2014-01-01

    The aim of this study is to investigate different instruments for finishing composite restorations, as well as examining different surfaces and interfaces of the same restoration. The null hypothesis is represented by the fact that there are no significant differences on roughness of composite restorations finishing between tungsten carbide and diamond burs, furthermore the null hypothesis is that there are no significant differences on roughness between finishing on composite surfaces (C), compositeenamel (CE) and composite-dentin (CD) interfaces. The study was performed on 28 teeth, and class V cavities were prepared on the extracted teeth. Restorations were done in Filtek XTE nanofilled composite (3M Espe) in a standardized method, to then be finished. A comparison was made in the phase 1 between tungsten carbide burs (16 blades), diamond burs (46 μm), with a similar shape by the same manufacturer (Komet). Each surface received 5 bur applications. Consequently, an analysis with a profilometer was performed. Phase 2 involved further confrontation of ulterior finishing with ultrafine tungsten carbide burs (30 blades) and with extra and ultrafine diamond burs (25 and 8 μm) (the same shape as previously mentioned). A second analysis was then performed with a profilometer. All measurements were taken on C surfaces, CE and CD interfaces. Statistical analyses were carried out with c2 test (a = 0.05). The finishing procedures with fine grit or toothing burs gave a better smoothness with tungsten carbide burs compared to diamond burs. While with the ultrafine grit no significant differences were noted between tungsten carbide and diamond burs on the CE and CD interfaces, the diamond bur left less superficial roughness on the C surfaces. With regards to the superficial roughness of the different areas of restoration, it can be concluded that: minor roughness was detected on C surfaces, while the CD interface had the most superficial roughness, regardless of whether the

  8. MO-E-17A-09: Has Cancer Risk for Pediatric CT Increased Or Decreased? An Analysis of Cohort Data From 2004-2013

    International Nuclear Information System (INIS)

    Brady, S; Kaufman, R

    2014-01-01

    Purpose: To analyze CT radiation dosimetry trends in a pediatric population imaged with modern (2004-2013) CT technology Methods: The institutional review board approved this retrospective review. Two cohorts of pediatric patients that received CT scans for treatment or surveillance for Wilms tumor (n=73) or Neuroblastoma (n=74) from 2004–2013 were included in this study. Patients were scanned during this time period on a GE Ultra (8 slice; 2004–2007), a GE VCT (2008–2011), or a GE VCT-XTe (2011–2013). Each patient's individual or combined chest, abdomen, and pelvic CT exams (n=4138) were loaded onto a PACS workstation (Intelerad, Canada) and measured to calculate their effective diameter and SSDE. Patient SSDE was used to estimate patient organ dosimetry based on previously published data. Patient's organ dosimetry were sorted by gender, weight, age, scan protocol (i.e., chest, abdomen, or pelvis), and CT scanner technology and averaged accordingly to calculate population averaged absolute and effective dose values. Results: Patient radiation dose burden calculated for all genders, weights, and ages decreased at a rate of 0.2 mSv/year (4.2 mGy/year; average organ dose) from 2004–2013; overall levels decreased by 50% from 3.0 mSv (60.0 mGy) to 1.5 mSv (25.9 mGy). Patient dose decreased at equal rates for both male and female, and for individual scan protocols. The greatest dose savings was found for patients between 0–4 years old (65%) followed by 5-9 years old (45%), 10–14 years old (30%), and > 14 years old (21%). Conclusion: Assuming a linear-nothreshold model, there always will be potential risk of cancer induction from CT. However, as demonstrated among these patient populations, effective and organ dose has decreased over the last decade; thus, potential risk of long-term side effects from pediatric CT examinations has also been reduced

  9. MO-E-17A-09: Has Cancer Risk for Pediatric CT Increased Or Decreased? An Analysis of Cohort Data From 2004-2013

    Energy Technology Data Exchange (ETDEWEB)

    Brady, S; Kaufman, R [St. Jude Children' s Research Hospital, Memphis, TN (United States)

    2014-06-15

    Purpose: To analyze CT radiation dosimetry trends in a pediatric population imaged with modern (2004-2013) CT technology Methods: The institutional review board approved this retrospective review. Two cohorts of pediatric patients that received CT scans for treatment or surveillance for Wilms tumor (n=73) or Neuroblastoma (n=74) from 2004–2013 were included in this study. Patients were scanned during this time period on a GE Ultra (8 slice; 2004–2007), a GE VCT (2008–2011), or a GE VCT-XTe (2011–2013). Each patient's individual or combined chest, abdomen, and pelvic CT exams (n=4138) were loaded onto a PACS workstation (Intelerad, Canada) and measured to calculate their effective diameter and SSDE. Patient SSDE was used to estimate patient organ dosimetry based on previously published data. Patient's organ dosimetry were sorted by gender, weight, age, scan protocol (i.e., chest, abdomen, or pelvis), and CT scanner technology and averaged accordingly to calculate population averaged absolute and effective dose values. Results: Patient radiation dose burden calculated for all genders, weights, and ages decreased at a rate of 0.2 mSv/year (4.2 mGy/year; average organ dose) from 2004–2013; overall levels decreased by 50% from 3.0 mSv (60.0 mGy) to 1.5 mSv (25.9 mGy). Patient dose decreased at equal rates for both male and female, and for individual scan protocols. The greatest dose savings was found for patients between 0–4 years old (65%) followed by 5-9 years old (45%), 10–14 years old (30%), and > 14 years old (21%). Conclusion: Assuming a linear-nothreshold model, there always will be potential risk of cancer induction from CT. However, as demonstrated among these patient populations, effective and organ dose has decreased over the last decade; thus, potential risk of long-term side effects from pediatric CT examinations has also been reduced.

  10. Comparison of Mechanical Properties of Resin Composites with Resin Modified Glass Ionomers

    Directory of Open Access Journals (Sweden)

    Taha NA

    2015-06-01

    Full Text Available Statement of Problem: There are controversial reports regarding physical and mechanical properties of resin composites and glass ionomer cements. Some revealed higher strength and hardness for resin composites while others showed a comparable value for glass ionomer cements. Evaluation of mechanical properties of different types of resin composites in comparison with resin modified glass ionomers is not widely studied. Objectives: To measure and compare the flexural strength and Vickers hardness of three resin composites and two resins modified glass ionomer cements before and after ageing. Materials and Methods: Three resin composites, i.e. Filtek Supreme XTE (3M ESPE, Ice (SDI, Gradia (GC, and two resins modified glass ionomers, i.e. Fuji II LC (GC and Riva Light Cure (SDI, were selected. Ten barshaped specimens were prepared for each material and cured using LED curing light. After 24 hours storage in distilled water at 37oC, the specimens were randomly divided into two equal groups (n=5. The first group was tested as a baseline and the second group was restored at 37oC for another 29 days. Flexural strength was performed by four-point bending test using universal testing machine at crosshead speed of 0.5mm/min, and the maximum load at failure was recorded. The specimen’s halves were used for evaluating Vickers hardness, using a Digital Hardness Tester (300 g/15 sec and the Vickers hardness number (VHN was recorded. Data were analyzed using one-way analysis of variance (ANOVA, Tukey’s and student’s t-test. Results: After 24 hours of immersion, the highest hardness number was found for Filtek Supreme and Ice and the highest flexural strength was obtained for Gradia. After 30 days of storage, hardness of Fuji II LC and Gradia showed a significant decrease; flexural strength of Ice and Fuji II LC revealed a significant increase while Gradia and Filtek Supreme showed a significant decrease. Conclusions: Resin modified glass ionomers showed

  11. Six-month color change and water sorption of 9 new-generation flowable composites in 6 staining solutions.

    Science.gov (United States)

    Arregui, Maria; Giner, Luis; Ferrari, Marco; Vallés, Marta; Mercadé, Montserrat

    2016-11-28

    Color match and water sorption are two factors that affect restorative materials. Discoloration is essential in the lifespan of restorations. The aim of this study was to evaluate color change and water sorption of nine flowable composites at multiple time points over 6 months. 60 samples of each composite were divided into two groups (Color Change and Water Sorption/Solubility). Each Color Change group was divided into six subgroups, which were immersed in distilled water (DW), coffee (CF), Coca-Cola (CC), red wine (RW), tea (TE) and orange juice (OJ). The color was measured at the baseline, 1, 2, 3 and 4 weeks, and 3 and 6 months and color change values (ΔE) were calculated. Each Water Sorption [WS]/Solubility [WL] group was tested according to ISO 4049:2009. The data were evaluated using two-way ANOVA, Fisher's post-hoc test and Pearson's correlation test. The composite with the lowest ΔE differed for each solution: Filtek™ Bulk Fill in DW (∆E = 0.73 (0.17-1.759)); Vertise Flow in CF (∆E = 14.75 (7.91-27.41)), in TE (∆E = 7.27 (2.81-24.81)) and OJ (∆E = 3.17 (0.87-9.92)); Tetric EvoFlow® in CC (∆E = 1.27 (0.45-4.02)); and Filtek™ Supreme XTE in RW (∆E = 8.88 (5.23-19.59)). RW caused the most discoloration (∆E = 23.62 (4.93-51.36)). Vertise Flow showed the highest water sorption (WS = 69.10 ± 7.19). The Pearson test showed statistically significant positive correlations between water sorption and solubility and between water sorption and ∆E; the positive solubility-∆E correlation was not statistically significant. The findings suggest that water sorption is one factor associated with the ability of composites to discolor; however, discoloration is a multifactorial problem.

  12. "Iron-Clad" Evidence For Spinning Black Hole

    Science.gov (United States)

    2003-09-01

    competing explanations that do not require extreme gravitational effects, and provide the best look yet at the geometry of the space-time around a stellar black hole created by the death of a massive star." The orbit of a particle near a black hole depends on the curvature of space around the black hole, which also depends on how fast the black hole is spinning. A spinning black hole drags space around with it and allows atoms to orbit closer to the black hole than is possible for a non-spinning black hole. The latest Chandra data from Cygnus X-1, the first stellar-size black hole discovered, show that the gravitational effects on the signal from the iron atoms can only be due to relativistic effects, and that some of the atoms are no closer than 100 miles to the black hole. There was no evidence that the Cygnus X-1 black hole is spinning. The XMM-Newton data from the black hole, XTE J1650-500, show a very similar distribution of iron atom X-rays with one important exception. More low energy X-rays from iron atoms are observed, an indication that some X-rays are coming from deep in the gravitational well around the black hole, as close as 20 miles to the black hole event horizon. This black hole must be spinning rapidly. Chandra observations of a third stellar black hole, GX 339-4, have revealed that it is also spinning rapidly, and clouds of warm absorbing gas appear to be flowing away from the black hole at speeds of about three hundred thousand miles per hour. Such warm gas flows have been observed in the vicinity of supermassive black holes. Previous observations of some supermassive black holes by Japan's ASCA satellite, XMM-Newton and Chandra have indicated that they may also be rotating rapidly. The latest results presented by Miller indicate that the peculiar geometry of space around spinning stellar-mass black holes and supermassive black holes is remarkably similar. Stellar and supermassive black holes may be similar in other ways. Powerful jets of high

  13. Appropriate materials and preparation techniques for polycrystalline-thin-film thermophotovoltaic cells

    Science.gov (United States)

    Dhere, Neelkanth G.

    1997-03-01

    Polycrystalline-thin-film thermophotovoltaic (TPV) cells have excellent potential for reducing the cost of TPV generators so as to address the hitherto inaccessible and highly competitive markets such as self-powered gas-fired residential warm air furnaces and energy-efficient electric cars, etc. Recent progress in polycrystalline-thin-film solar cells have made it possible to satisfy the diffusion length and intrinsic junction rectification criteria for TPV cells operating at high fluences. Continuous ranges of direct bandgaps of the ternary and pseudoternary compounds such as Hg1-xCdxTe, Pb1-xCdxTe, Hg1-xZnxTe, and Pb1-xZnxS cover the region of interest of 0.50-0.75 eV for efficient TPV conversion. Other ternary and pseudoternary compounds which show direct bandgaps in most of or all of the 0.50-0.75 eV range are Pb1-xZnxTe, Sn1-xCd2xTe2, Pb1-xCdxSe, Pb1-xZnxSe, and Pb1-xCdxS. Hg1-xCdxTe (with x~0.21) has been studied extensively for infrared detectors. PbTe and Pb1-xSnxTe have also been studied for infrared detectors. Not much work has been carried out on Hg1-xZnxTe thin films. Hg1-xCdxTe and Pb1-xCdxTe alloys cover a wide range of cut-off wavelengths from the far infrared to the near visible. Acceptors and donors are introduced in these materials by excess non-metal (Te) and excess metal (Hg and Pb) respectively. Extrinsic acceptor impurities are Cu, Au, and As while and In and Al are donor impurities. Hg1-xCdxTe thin films have been deposited by isothermal vapor-phase epitaxy (VPE), liquid phase epitaxy (LPE), hot-wall metalorganic chemical vapor deposition (MOCVD), electrodeposition, sputtering, molecular beam epitaxy (MBE), laser-assisted evaporation, and vacuum evaporation with or without hot-wall enclosure. The challenge in the preparation of Hg1-xCdxTe is to provide excess mercury incidence rate, to optimize the deposition parameters for enhanced mercury incorporation, and to achieve the requisite stoichiometry, grain size, and doping. MBE and MOCVD

  14. Faraday Rotation Studies of Indium Antimonide and CADMIUM(1-X) Manganese(x) Telluride

    Science.gov (United States)

    Jimenez Gonzalez, Hector J.

    Brillouin zone as well as the lattice contribution from optical phonons. The multioscillator model explains the measured behavior of the Verdet constant as a function of photon energy for all the above values of x at both temperatures. This model has also been applied successfully to Faraday rotation data for Cd_ {1-x}Mn_{x}Te and Zn_{1-x}Mn _{x}Te from previous studies. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253 -1690.).

  15. Strain-engineering of the topological insulator HgTe

    Energy Technology Data Exchange (ETDEWEB)

    Leubner, Philipp

    2017-07-24

    The subject of this thesis is the control of strain in HgTe thin-film crystals. A major task was the experimental control of the strain in the HgTe films. This was achieved by a new epitaxial approach and confirmed by cristallographic analysis and magneto-transport measurements. In this work, strain was induced in thin films by means of coherent epitaxy on substrate crystals. In principle, compressive strain can be achieved by using an appropriate Cd{sub 1-x}Zn{sub x}Te substrate. This concept was modified and applied in this work. Epilayers have been fabricated by molecular-beam epitaxy (MBE). The growth of thick buffer layers of CdTe on GaAs:Si was established as an alternative to commercial CdTe and Cd{sub 0.96}Zn{sub 0.04}Te substrates. Residual strain was found in the buffer layers, and was attributed to a combination of finite layer thickness and mismatch of the thermal expansion coefficients of CdTe and GaAs. CdTe-Cd{sub 0.5}Zn{sub 0.5}Te strained-layer-superlattices have been grown by a combination of MBE and atomic-layer epitaxy (ALE), and have been analyzed by HRXRD. The crystal quality has been found to degrade with increasing Zn-fraction. HgTe quantum wells (QWs) sandwiched in between CdHgTe barriers have been fabricated in a similar fashion on superlattices and conventional CdTe and Cd{sub 0.96}Zn{sub 0.04}Te substrates. We have determined the QW thickness with an accuracy of ±0.5 nm by an analysis of the beating patterns in the thickness fringes of HRXRD measurements and X-ray reflectometry measurements. We have, for the first time, induced compressive strain in HgTe QWs by an epitaxial technique (i.e. the effective lattice constant of the superlattice is lower compared to the lattice constant of HgTe). The problem of the lattice mismatch between superlattice and barriers has been circumvented by using CdHgTe-ZnHgTe superlattices instead of CdHgTe as a barrier material. Furthermore, the growth of compressively strained HgTe bulk layers (with a

  16. Continuous and rapid synthesis of nanoclusters and nanocrystals using scalable microstructured reactors

    Science.gov (United States)

    Jin, Hyung Dae

    formation mechanism of CuInSe2 nanocrystals for the development of a continuous flow process for their synthesis. It was found that copper-rich CuInSe2 with a sphalerite structure was formed initially followed by the formation of more ordered CuInSe2 at longer reaction times, along with the formation of Cu2Se and In2Se3. It was found that Cu2Se was formed at a much faster rate than In2Se3 under the same reaction conditions. By adjusting the Cu/In precursor ratio, we were able to develop a very rapid and simple synthesis of CuInSe2 nanocrystals using a continuous flow microreactor with a high throughput per reactor volume. The microreactor has a simple design which uses readily available low cost components. It comprised an inner microtube to precisely control the injection of TOPSe into a larger diameter tube that preheated CuCl and InCl3 hot mixture was pumped through. Rapid injection plays an important role in dividing the nucleation and growth process which is crucial in getting narrow size distribution. The design of this microreactor also has the advantages of alleviating sticking of QDs on the growth channel wall since QDs were formed from the center of the reactor. Furthermore, size-controlled synthesis of CuInSe2 nanocrystals was achieved using this reactor simply by adjusting ratio between coordinating solvents. Semiconductors with a direct bandgap between 1 and 2eV including Cu(In,Ga)Se 2 (1.04--1.6eV) and CuIn(Se,S)2 (1.04--1.53eV) are ideal for single junction cells utilize the visible spectrum. However, half of the solar energy available to the Earth lies in the infrared region. Inorganic QD-based solar cells with a decent efficiency near 1.5 mum have been reported. Therefore, syntheses of narrow gap IV-VI (SnTe, PbS, PbSe, PbTe), II-IV (HgTe, CdXHg1-XTe), and III-V (InAs) QDs have attracted significant attention and these materials have potential uses for a variety of other optical, electronic, and optoelectronic applications. SnTe with an energy gap of 0.18e

  17. IUE's treasure-chest of the ultraviolet Universe

    Science.gov (United States)

    1997-11-01

    to 3200 angstrom units, which is blotted out by the Earths atmosphere. Operating far above the atmosphere, IUE generated spectra showing intensities at different wavelengths, coming from the selected objects in the sky. To an astrophysicist, such spectra are much more informative than images, about the mechanisms that produce and dissipate the objects energy. Temperatures, motions, magnetism and chemical composition are all discernable in the ultraviolet spectra. As a result, astronomers have a far better picture of the hot atmospheres of stars than they did before IUE's launch. Even the Sun, a quiet star of moderate size, possesses a very hot atmosphere emitting ultraviolet light, which is now being monitored non-stop by the ESA-NASA solar spacecraft SOHO. Some other stars, ranging from small white dwarfs to large, massive stars, give off ultraviolet emissions from their very hot surfaces. Hot and fierce winds of gas emitted from stars have a profound effect on the lives and environments of the stars, and on any companions caught up in the winds. IUE unmasked the ultraviolet behaviour of a large menagerie of different star types, and astronomers at the Sevilla meeting will discuss profound revisions in astrophysical ideas resulting from the observations. Other participants will review IUE's contribution to new knowledge about galaxies. These vast assemblies of stars also reveal violent behaviour in ultraviolet light. In a special campaign, a multinational team used IUE to observe the stormy galaxy NGC 5548 some 60 times in eight months. As a result, they discovered effects of central outbursts spreading from hot regions at the very core of the galaxy to adjacent cooler regions, in a timescale of weeks. In galaxy NGC 7469, observed simultaneously by IUE and by the X-ray satellite Rossi XTE, the timescale shrank to days. Quasars are erupting galaxies observable at great distances, and their examination by ultraviolet light, by IUE and more recently by the Hubble Space