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Sample records for cataclysmic variables identified

  1. Orbital periods of cataclysmic variables identified by the SDSS. VII. Four new eclipsing systems

    Science.gov (United States)

    Southworth, J.; Copperwheat, C. M.; Gänsicke, B. T.; Pyrzas, S.

    2010-02-01

    We present photometry of nine cataclysmic variable stars identified by the Sloan Digital Sky Survey, aimed at measuring the orbital periods of these systems. Four of these objects show deep eclipses, from which we measure their orbital periods. The light curves of three of the eclipsing systems are also analysed using the lcurve code, and their mass ratios and orbital inclinations determined. SDSS J075059.97+141150.1 has an orbital period of 134.1564 ± 0.0008 min, making it a useful object with which to investigate the evolutionary processes of cataclysmic variables. SDSS J092444.48+080150.9 has a period of 131.2432 ± 0.0014 min and is probably magnetic. The white dwarf ingress and egress phases are very deep and short, and there is no clear evidence that this object has an accretion disc. SDSS J115207.00+404947.8 and SDSS J152419.33+220920.1 are nearly identical twins, with periods of 97.5 ± 0.4 and 93.6 ± 0.5 min and mass ratios of 0.14 ± 0.03 and 0.17 ± 0.03, respectively. Their eclipses have well-defined white dwarf and bright spot ingress and egress features, making them excellent candidates for detailed study. All four of the orbital periods presented here are shorter than the 2-3 h period gap observed in the known population of cataclysmic variables. The reduced observational data presented in this work are available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/510/A100 and at http://www.astro.keele.ac.uk/ jkt/.

  2. Orbital periods of cataclysmic variables identified by the SDSS. VII. Four new eclipsing systems

    CERN Document Server

    Southworth, John; Gansicke, B T; Pyrzas, S

    2009-01-01

    We present photometry of nine cataclysmic variable stars identified by the Sloan Digital Sky Survey, aimed at measuring the orbital periods of these systems. Four of these objects show deep eclipses, from which we measure their orbital periods. The light curves of three of the eclipsing systems are also analysed using the LCURVE code, and their mass ratios and orbital inclinations determined. SDSS J075059.97+141150.1 has an orbital period of 134.1564 +/- 0.0008 min, making it a useful object with which to investigate the evolutionary processes of cataclysmic variables. SDSS J092444.48+080150.9 has a period of 131.2432 +/- 0.0014 min and is probably magnetic. The white dwarf ingress and egress phases are very deep and short, and there is no clear evidence that this object has an accretion disc. SDSS J115207.00+404947.8 and SDSS J152419.33+220920.1 are nearly identical twins, with periods of 97.5 +/- 0.4 and 93.6 +/- 0.5 min and mass ratios of 0.14 +/- 0.03 and 0.17 +/- 0.03, respectively. Their eclipses have w...

  3. Looking for New Cataclysmic Variables

    Science.gov (United States)

    Steiner, J. E.; Cieslinski, D.; Jablonski, F. J.

    1987-05-01

    ABSTRACT. One year ago we have started a program of observations of southern irregular variables of the types L, I and I , selected from the catalogs GCVS and NSV. The goal is to identify new cataclysmic variables and related objects. So far we have done photoelectric photometry of about 350 objects and spectroscopy of 120 of them. Nearly 80% of all observed objects are red giant-like. The other 20% comprise a large variety of types such as T Tauri, Mirae, Cepheids, Planetary Nebulae, etc. Ten new cataclysmic variables and one x-ray binary were also identified. Some of these objects studied in more detail, show interesting behavior. Key o : PHOTOMETRY -- SPECTROSCOPY -- VARIABLES

  4. Observations of GAIA-identified Cataclysmic Variables Using the TUBITAK National Observatory

    Science.gov (United States)

    Esenoglu, Hasan H.; Kirbiyik, Halil; Kaynar, Suleyman; Okuyan, Oguzhan; Hamitoglu, Irek; Galeev, Almaz; Uluc, Kadir; Kocak, Murat; Kilic, Sila E.; Parmaksizoglu, Murat; Erece, Orhan; Ozisik, Tuncay; Gulsecen, Hulusi

    2016-07-01

    TUBITAK National Observatory supports the GAIA alerts with observations using three telescopes (RTT150, T100, T60) at the site with a limited time quota. We have observed 10 variable stars among GAIA sources discovered in the years 2014-2016 that may be candidate Cataclysmic Variables (CVs). Our TUG observations at this stage involve photometry and spectroscopy to aid the identification of these sources. The first preliminary result of our observations of Gaia14aat among them showed a dwarf nova outburst with an amplitude of 2.69 mag. We aim to construct a GAIA astrophysics group to study CVs along with supported studies using the SRG (Spectrum Roentgen Gamma astrophysical observatory) after the year of 2016. These observations will basically involve spectroscopy, narrow-band CCD imaging and photometry using several filters to aid the identification of these sources. RTT150 observations with very narrow filters (like H-alpha, SII, OIII with band width of range of 2 to 5 nm) will reveal whether shell around the SRG sources to aid identification novae among them.

  5. Model for eclipsing cataclysmic variables

    International Nuclear Information System (INIS)

    A new and improved model was developed to derive the elements of eclipsing cataclysmic variables (CVs). Roche geometry was used to simulate the eclipse of a flat accretion disk, which was divided into multiple equipotential rings of black-body spectral contribution. The temperature of each ring was adjusted, using a chi-square fitting routine, until the data and the simulations achieved a best-fit value. Only the rising side of the eclipse light curve was used, in order to avoid asymmetries in the disk produced by the shock bulge and hot spot. Time-resolved spectroscopic data for two eclipsing cataclysmic variables (CVs), LX Serpentis and DQ Herculis, were obtained on the 1.3 meter McGraw-Hill telescope at Kitt Peak, Arizona. Seven sets of eclipse data for each star were phase binned in order to suppress the random variability common to such CV systems. The phase of the Balmer-line eclipse minimum leads photometric minimum by 0.0066 cycles for both CV systems. The phase of the Balmer-line minimum is used as the phase of conjunction in the model. From analysis of the data, a mass ratio of 1.06 +/- 0.1 and an inclination angle of 80 +/- 30 were found for LX Ser, while the results for DQ Her were 0.76 +/- 0.1 and 87 +/- 30, respectively. Two hot, roughly 90000K, rings were found in each accretion disk system

  6. Short-timescale variability in cataclysmic binaries

    International Nuclear Information System (INIS)

    Rapid variability, including flickering and pulsations, has been detected in cataclysmic binaries at optical and x-ray frequencies. In the case of the novalike variable TT Arietis, simultaneous observations reveal that the x-ray and optical flickering activity is strongly correlated, while short period pulsations are observed that occur at the same frequencies in both wavelength bands

  7. GLORIA and Study of Cataclysmic Variables

    Czech Academy of Sciences Publication Activity Database

    Šimon, Vojtěch; Hudec, René

    Prague: Czech Technical University, 2015, s. 303-307. (Acta Polytechnica CTU Proceedings. 2). ISBN 9788001056882. E-ISSN 2336-5382. [Workshop on the golden age of cataclysmic variables and related objects /2./. Palermo (IT), 09.09.2013-14.09.2013] Institutional support: RVO:67985815 Keywords : catalysmic variables * spectroscopy * low-dispersion spectra Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  8. Radio emission of cataclysmic variable stars

    Science.gov (United States)

    Fuerst, E.; Benz, A.; Hirth, W.; Geffert, M.; Kiplinger, A.

    1986-01-01

    Eight cataclysmic variable stars were observed at 6 cm wavelength using the Very Large Array (VLA). The objects were: CN-Ori, SS-Aur, YZ-Cnc, SU-Uma, Z-Cam, V603-Aql, EM-Cyg, and RZ-Sge. Most of these objects were in optical high stage, but none were detected beyond flux limits between 0.1 and 0.3 mJy.

  9. Formation and Evolution of Cataclysmic Variables

    CERN Document Server

    Ritter, H

    2008-01-01

    This article summarizes the basic facts and ideas concerning the formation and evolution of cataclysmic variables (CVs). It is shown why the formation of CVs must involve huge losses of mass and orbital angular momentum, very likely via a common envelope evolution. A brief discussion of the principles of the long-term evolution of semi-detached binaries follows. Finally a brief sketch of CV evolution is given.

  10. Swift J0525.6+2416 and IGR J04571+4527: two new hard X-ray selected magnetic cataclysmic variables identified with XMM-Newton

    CERN Document Server

    Bernardini, F; Mukai, K; Israel, G; Falanga, M; Ramsay, G; Masetti, N

    2015-01-01

    IGR J04571+4527 and Swift J0525.6+2416 are two hard X-ray sources detected in the Swift/BAT and INTEGRAL/IBIS surveys. They were proposed to be magnetic cataclysmic variables of the Intermediate Polar (IP) type, based on optical spectroscopy. IGR J04571+4527 also showed a 1218 s optical periodicity, suggestive of the rotational period of a white dwarf, further pointing towards an IP classification. We here present detailed X-ray (0.3-10 keV) timing and spectral analysis performed with XMM-Newton, complemented with hard X-ray coverage (15-70 keV) from Swift/BAT. These are the first high signal to noise observations in the soft X-ray domain for both sources, allowing us to identify the white dwarf X-ray spin period of Swift J0525.6+2416 (226.28 s), and IGR J04571+4527 (1222.6 s). A model consisting of multi-temperature optically thin emission with complex absorption adequately fits the broad-band spectrum of both sources. We estimate a white dwarf mass of about 1.1 and 1.0 solar masses for IGR J04571+4527 and S...

  11. Hard X-ray properties of magnetic cataclysmic variables

    CERN Document Server

    Scaringi, S; Norton, A J; Knigge, C; Hill, A B; Clark, D J; Dean, A J; McBride, V A; Barlow, E J; Bassani, L; Bazzano, A; Fiocchi, M; Landi, R

    2009-01-01

    Hard X-ray surveys have proven remarkably efficient in detecting intermediate polars and asynchronous polars, two of the rarest type of cataclysmic variable (CV). Here we present a global study of hard X-ray selected intermediate polars and asynchronous polars, focusing particularly on the link between hard X-ray properties and spin/orbital periods. To this end, we first construct a new sample of these objects by cross-correlating candidate sources detected in INTEGRAL/IBIS observations against catalogues of known CVs. We find 23 cataclysmic variable matches, and also present an additional 9 (of which 3 are definite) likely magnetic cataclysmic variables (mCVs) identified by others through optical follow-ups of IBIS detections. We also include in our analysis hard X-ray observations from Swift/BAT and SUZAKU/HXD in order to make our study more complete. We find that most hard X-ray detected mCVs have P_{spin}/P_{orb}<0.1 above the period gap. In this respect we also point out the very low number of detecte...

  12. Novalike Cataclysmic Variables in the Infrared

    CERN Document Server

    Hoard, D W; Howell, Steve B; Wachter, Stefanie; Brinkworth, Carolyn S; Knigge, Christian; Drew, J E; Szkody, Paula; Kafka, S; Belle, Kunegunda; Ciardi, David R; Froning, Cynthia S; van Belle, Gerard T; Pretorius, M L

    2014-01-01

    Novalike cataclysmic variables have persistently high mass transfer rates and prominent steady state accretion disks. We present an analysis of infrared observations of twelve novalikes obtained from the Two Micron All Sky Survey, the Spitzer Space Telescope, and the Wide-field Infrared Survey Explorer All Sky Survey. The presence of an infrared excess at >3-5 microns over the expectation of a theoretical steady state accretion disk is ubiquitous in our sample. The strength of the infrared excess is not correlated with orbital period, but shows a statistically significant correlation (but shallow trend) with system inclination that might be partially (but not completely) linked to the increasing view of the cooler outer accretion disk and disk rim at higher inclinations. We discuss the possible origin of the infrared excess in terms of emission from bremsstrahlung or circumbinary dust, with either mechanism facilitated by the mass outflows (e.g., disk wind/corona, accretion stream overflow, and so on) present...

  13. NSV 1907 - A new eclipsing, nova-like cataclysmic variable

    CERN Document Server

    Hümmerich, Stefan; Hambsch, Franz-Josef; Dubois, Franky; Ashley, Richard; Gänsicke, Boris T; Vanaverbeke, Siegfried; Bernhard, Klaus; Wils, Patrick

    2016-01-01

    NSV 1907, formerly listed as an irregular variable in variability catalogues, was classified as an Algol-type eclipsing binary in the Catalina Surveys Periodic Variable Star Catalogue. We have identified NSV 1907 as an ultraviolet (UV) bright source using measurements from the GALEX space telescope and detected obvious out-of-eclipse variability in archival photometric data from the Catalina Sky Survey, which instigated a closer examination of the object. A spectrum and extensive multicolour photometric observations were acquired, from which we deduce that NSV 1907 is a deeply eclipsing, nova-like cataclysmic variable. Apart from the orbital variations (deep eclipses with a period of P ~ 6.63 hours), changes in mean brightness and irregular short-term variability (flickering) were observed. The presence of a secondary minimum at phase phi ~ 0.5 was established, which indicates a significant contribution of the companion star to the optical flux of the system. We find possible evidence for sinusoidal variation...

  14. Novalike Cataclysmic Variables are Significant Radio Emitters

    CERN Document Server

    Coppejans, Deanne L; Miller-Jones, James C A; Rupen, Michael P; Knigge, Christian; Sivakoff, Gregory R; Groot, Paul J

    2015-01-01

    Radio emission from non-magnetic cataclysmic variables (CVs, accreting white dwarfs) could allow detailed studies of outflows and possibly accretion flows in these nearby, numerous and non-relativistic compact accretors. Up to now, however, very few CVs have been detected in the radio. We have conducted a VLA pilot survey of four close and optically-bright novalike CVs at 6 GHz, detecting three, and thereby doubling the number of radio detections of these systems. RW Sex, V603 Aql and the old nova TT Ari were detected in both of the epochs, while V1084 Her was not detected (to a $3\\sigma$ upper-limit of 7.8 $\\mu\\rm{Jy}\\,\\rm{beam}^{-1}$). These observations clearly show that the sensitivity of previous surveys was typically too low to detect these objects and that non-magnetic CVs can indeed be significant radio emitters. The three detected sources show a range of properties, including flaring and variability on both short ($\\sim$200 s) and longer-term (days) time-scales, as well as circular polarization level...

  15. Doppler Tomography in Cataclysmic Variables: an historical perspective

    OpenAIRE

    Echevarria, J.

    2012-01-01

    To mark the half-century anniversary of this newly-born field of Cataclysmic Variables, a special emphasis is made in this review, on the Doppler Effect as a tool in astrophysics. The Doppler Effect was in fact, discovered almost 170 years ago, and has been since, one of the most important tools which helped to develop modern astrophysics. We describe and discuss here, its use in Cataclysmic Variables which, combined with another important tool, the tomography, first devised for medical purpo...

  16. The Secondary Stars of Cataclysmic Variables

    CERN Document Server

    Knigge, Christian

    2011-01-01

    I review what we know about the donor stars in cataclysmic variables (CVs), focusing particularly on the close link between these binary components and the overall secular evolution of CVs. I begin with a brief overview of the "standard model" of CV evolution and explain why the key observables this model is designed to explain - the period gap and the period minimum -- are intimately connected to the properties of the secondary stars in these systems. CV donors are expected to be slightly inflated relative to isolated, equal-mass main-sequence (MS) stars, and this "donor bloating" has now been confirmed observationally. The empirical donor mass-radius relationship also shows a discontinuity at M_2 = 0.2 M_sun which neatly separates long- and short-period CVs. This is strong confirmation of the basic disrupted magnetic braking scenario for CV evolution. The empirical M_2-R_2 relation can be combined with stellar models to construct a complete, semi-empirical donor sequence for CVs. This sequence provides all ...

  17. Einstein x-ray observations of cataclysmic variables

    International Nuclear Information System (INIS)

    Observations with the imaging x-ray detectors on the Einstein Observatory have led to a large increase in the number of low luminosity x-ray sources known to be associated with cataclysmic variable stars (CVs). The high sensitivity of the Einstein instrumentation has permitted study of their short timescale variability and spectra. The data are adding significantly to our knowledge of the accretion process in cataclysmic variables and forcing some revision in our ideas concerning the origin of the optical variability in these stars

  18. A physical model for the flickering variability in cataclysmic variables

    CERN Document Server

    Scaringi, Simone

    2013-01-01

    Aperiodic broad-band variability (also known as flickering) is observed throughout all types of accreting compact objects. Many statistical properties of this variability can be naturally explained with the fluctuating accretion disk model, where variations in the mass-transfer rate through the disk are modulated on the local viscous timescale and propagate towards the central compact object. Here, a recently developed implementation of the model is applied for the first time to the time-averaged, high-frequency variability of a cataclysmic variable star (MV Lyrae) observed with the Kepler satellite. A qualitatively good fit to the data is achieved, suggesting the presence of geometrically thick inner flow with large viscosity parameter, extending from $\\sim0.12R_{\\odot}$ all the way to the white dwarf surface. A simple spectral model of the system suggests that the geometrically thick component would not contribute much to the observed optical flux originating from the geometrically thin outer disk. Instead,...

  19. Study of Cataclysmic Variables with the Satellites LOFT and Gaia

    Czech Academy of Sciences Publication Activity Database

    Hudec, René; Šimon, Vojtěch

    Prague : Czech Technical University, 2015, s. 297-302. ISBN 9788001056882. E-ISSN 2336-5382. - (Acta Polytechnica CTU Proceedings. 2). [Workshop on the golden age of cataclysmic variables and related objects /2./. Palermo (IT), 09.09.2013-14.09.2013] Institutional support: RVO:67985815 Keywords : catalysmic variables * dwarf novae - * intermediate polar Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  20. Cycles in the cataclysmic variable V795 Herculis

    Czech Academy of Sciences Publication Activity Database

    Šimon, Vojtěch; Polášek, Cyril; Štrobl, Jan; Hudec, René; Blažek, Martin

    2012-01-01

    Roč. 540, April (2012), A15/1-A15/11. ISSN 0004-6361 R&D Projects: GA ČR GA205/08/1207 Institutional research plan: CEZ:AV0Z10030501 Keywords : novae * cataclysmic variables * accretion disks Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 5.084, year: 2012

  1. Are the secondary stars in cataclysmic variables main sequence stars

    Energy Technology Data Exchange (ETDEWEB)

    Echevarria, J.

    1983-01-01

    A spectral type-orbital period relation for cataclysmic variables with main sequence companions is presented. The spectral types of seventeen systems with known orbital periods are derived and compared with the observed ones. The analysis shows that they have in general later spectral types than main sequence stars of the same mass.

  2. Are the secondary stars in cataclysmic variables main sequence stars

    International Nuclear Information System (INIS)

    A spectral type-orbital period relation for cataclysmic variables with main sequence companions is presented. The spectral types of seventeen systems with known orbital periods are derived and compared with the observed ones. The analysis shows that they have in general later spectral types than main sequence stars of the same mass. (author)

  3. Lessons learned from ESA INTEGRAL: cataclysmic variables and blazars

    Czech Academy of Sciences Publication Activity Database

    Hudec, René; Gális, R.; Kocka, Matúš

    2010-01-01

    Roč. 81, č. 1 (2010), s. 320-325. ISSN 0037-8720. [Multifrequency behaviour of high energy cosmic sources. Vulcano, 25.05.2009-30.05. 2009] Institutional research plan: CEZ:AV0Z10030501 Keywords : high-energy sources * cataclysmic variables * INTEGRAL Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  4. On the flickering of hot spots in cataclysmic variables

    International Nuclear Information System (INIS)

    A flickering point source inside a scattering cloud will have its higher flicker frequencies attenuated because of delays caused by multiple scattering of photons in the cloud. The effect of this on the flicker spectrum of a cataclysmic variable is considered. (author)

  5. Doppler Tomography in Cataclysmic Variables: an historical perspective

    CERN Document Server

    Echevarria, J

    2012-01-01

    To mark the half-century anniversary of this newly-born field of Cataclysmic Variables, a special emphasis is made in this review, on the Doppler Effect as a tool in astrophysics. The Doppler Effect was in fact, discovered almost 170 years ago, and has been since, one of the most important tools which helped to develop modern astrophysics. We describe and discuss here, its use in Cataclysmic Variables which, combined with another important tool, the tomography, first devised for medical purposes 70 years ago, helped to devise the astronomical Doppler Tomography, developed only two decades ago. A discussion is made since the first trailed spectra provided a one dimensional analysis of these binaries; on the establishment of a 2D velocity profiling of the accretion discs; and unto modern techniques, which include Roche Tomography, time modulation and 3D imaging.

  6. A search for brown dwarf like secondaries in cataclysmic variables

    Science.gov (United States)

    Mennickent, R. E.; Diaz, M. P.

    2002-11-01

    We present VTL/ISAAC infrared spectroscopy of a sample of short-orbital-period cataclysmic variables that are candidates for harbouring substellar companions. We have detected the K I and Na I absorption lines of the companion star in VY Aqr. The overall spectral distribution in this system is best fitted with an M9.5 type dwarf spectrum, implying a distance of 100 +/- 10 pc. VY Aqr seems to fall far from the theoretical distribution of secondary star temperatures around the orbital period minimum. Fitting of the IR spectral energy distribution (SED) was performed by comparing the observed spectrum with late-type templates. The application of such a spectral fitting procedure suggests that the continuum shape in the 1.1-2.5 μm spectral region in short-orbital-period cataclysmic variables may be a useful indicator of the companion's spectral type. SED fitting for RZ Leo and CU Vel suggests M5-type dwarf companions, and distances of 340 +/- 110 and 150 +/- 50 pc, respectively. These systems may be placed in the upper evolution branch for short-period cataclysmic variables.

  7. Characterization of new hard X-ray Cataclysmic Variables

    CERN Document Server

    Bernardini, F; Falanga, M; Mukai, K; Matt, G; Bonnet-Bidaud, J -M; Masetti, N; Mouchet, M

    2012-01-01

    We aim at characterizing a sample of 9 new hard X-ray selected Cataclysmic Variable (CVs), to unambiguously identify them as magnetic systems of the Intermediate Polar (IP) type. We performed timing and spectral analysis by using X-ray, and simultaneous UV and optical data collected by XMM-Newton, complemented with hard X-ray data provided by INTEGRAL and Swift. The pulse arrival time were used to estimate the orbital periods. The X-ray spectra were fitted using composite models consisting of different absorbing columns and emission components. Strong X-ray pulses at the White Dwarf (WD) spin period are detected and found to decrease with energy. Most sources are spin-dominated systems in the X-rays, though four are beat dominated at optical wavelengths. We estimated the orbital period in all system (except for IGR J16500-3307), providing the first estimate for IGR J08390-4833, IGR J18308-1232, and IGR J18173-2509. All X-ray spectra are multi-temperature. V2069 Cyg and RX J0636+3535 posses a soft X-ray optica...

  8. Cataclysmic variables in Globular clusters: First results on the analysis of the MOCCA simulations database

    CERN Document Server

    Belloni, Diogo; Askar, Abbas; Hypki, Arkadiusz

    2016-01-01

    In this first investigation of the MOCCA database with respect to cataclysmic variables, we found that for models with Kroupa initial distributions, considering the standard value of the efficiency of the common-envelope phase adopted in BSE, no single cataclysmic variable was formed only via binary stellar evolution, i. e., in order to form them, strong dynamical interactions have to take place. Our results also indicate that the population of cataclysmic variables in globular clusters are, mainly, in the last stage of their evolution and observational selection effects can change drastically the expected number and properties of observed cataclysmic variables.

  9. Accretion flows in magnetic cataclysmic variables

    Directory of Open Access Journals (Sweden)

    A. J. Norton

    2004-01-01

    Full Text Available Presentamos los resultados de simulaciones que exploran la variedad de ujos de acreci on posibles en variables catacl smicas magn eticas (mCVs. Nuestras simulaciones evolucionan hasta alcanzar per odos de equilibrio que abarcan 0:01 < Pspin=Porb < 0:6, y los ujos resultantes var an desde sistemas alimentados por disco en Pspin=Porb 0:010:1 a sistemas alimentados por corrientes en Pspin=Porb 0:1 0:5 y sistemas alimentados desde un anillo en el borde exterior del l obulo de Roche de la enana blanca, en Pspin=Porb 0:6.

  10. New results on cataclysmic variables observed by INTEGRAL

    Czech Academy of Sciences Publication Activity Database

    Hudec, René; Šimon, Vojtěch; Münz, Filip

    2008-01-01

    Roč. 8, spec. iss. (2008), s. 259-264. ISSN 1009-9271. [International workshop on multifrequency behaviour of high energy cosmic sources. Vulcano, 28.05.2007-02.06.2007] R&D Projects: GA ČR GA205/05/2167 Grant ostatní: ESA(XE) ESA-PECS INTEGRAL project no. 98023 Institutional research plan: CEZ:AV0Z10030501 Keywords : cataclysmic variables * accretion disks Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.689, year: 2008

  11. The nature of the cataclysmic variable PT Per

    CERN Document Server

    Watson, Mike; MacLeod, Chelsea; Osborne, Julian

    2015-01-01

    We present a study of the cataclysmic variable star PT Per based on archival XMM-Newton X-ray data and new optical spectroscopy from the WHT with ISIS. The X-ray data show deep minima which recur at a period of 82 minutes and a hard, unabsorbed X-ray spectrum. The optical spectra of PT Per show a relatively featureless blue continuum. From an analysis of the X-ray and optical data we conclude that PT Per is likely to be a magnetic cataclysmic variable of the polar class in which the minima correspond to those phase intervals when the accretion column rotates out of the field of view of the observer. We suggest that the optical spectrum, obtained around 4 years after the X-ray coverage, is dominated by the white dwarf in the system, implying that PT Per was in a low accretion state at the time of the observations. An analysis of the likely system parameters for PT Per suggests a distance of $\\approx900$ pc and a very low-mass secondary, consistent with the idea that PT Per is a "period-bounce" binary.

  12. The nature of the cataclysmic variable PT Per

    Science.gov (United States)

    Watson, M. G.; Bruce, A.; MacLeod, C.; Osborne, J. P.; Schwope, A. D.

    2016-05-01

    We present a study of the cataclysmic variable star PT Per based on archival XMM-Newton X-ray data and new optical spectroscopy from the WHT with ISIS. The X-ray data show deep minima which recur at a period of 82 minutes and a hard, unabsorbed X-ray spectrum. The optical spectra of PT Per show a relatively featureless blue continuum. From an analysis of the X-ray and optical data we conclude that PT Per is likely to be a magnetic cataclysmic variable of the polar class in which the minima correspond to those phase intervals when the accretion column rotates out of the field of view of the observer. We suggest that the optical spectrum, obtained around 4 years after the X-ray coverage, is dominated by the white dwarf in the system, implying that PT Per was in a low accretion state at the time of the observations. An analysis of the likely system parameters for PT Per suggests a distance of ≈90 pc and a very low-mass secondary, consistent with the idea that PT Per is a "period-bounce" binary. Matching the observed absorption features in the optical spectrum with the expected Zeeman components constrains the white dwarf polar field to be Bp ≈ 25 - 27 MGauss.

  13. The Magnetic Cataclysmic Variable LSQ1725-64

    CERN Document Server

    Fuchs, J T; Dennihy, E; O'Donoghue, D; Clemens, J C; Reichart, D E; Moore, J P; LaCluyze, A P; Haislip, J B; Ivarsen, K V

    2016-01-01

    We present new photometry and spectroscopy of the 94m eclipsing binary LSQ1725-64 that provide insight into the fundamental parameters and evolutionary state of this system. We confirm that LSQ1725-64 is a magnetic cataclysmic variable whose white dwarf has a surface-averaged magnetic field strength of $12.5 \\pm 0.5$ MG measured from Zeeman splitting. The spectral type and colour of the secondary, as well as the eclipse length, are consistent with other secondaries that have not yet evolved through the period minimum expected for cataclysmic variables. We observe two different states of mass transfer and measure the transition between the two to occur over about 45 orbital cycles. In the low state, we observe photometric variations that we hypothesize to arise predominantly from two previously heated magnetic poles of the white dwarf. Our precise eclipse measurements allow us to determine binary parameters of LSQ1725-64 and we find it contains a high mass ($0.97 \\pm 0.03\\ M_{\\odot}$) white dwarf if we assume ...

  14. Discovery of a new short-period, eclipsing cataclysmic variable

    Science.gov (United States)

    Downes, R. A.; Mateo, M.; Szkody, P.; Jenner, D. C.; Margon, B.

    1986-01-01

    Photometry and spectroscopy of a newly recognized 14th mag eclipsing cataclysmic variable, KPD 1911 + 1212 (= SVS 8130, V1315 Agl) are reported. The system exhibits deep (1.7 mag) eclipses with period 0.1397 day. The spectrum is that of a high-excitation old nova and shows dramatic variability of the emission line strengths through the eclipse. The profiles of the Balmer emission lines are also phase-dependent, with prominent absorption cores appearing briefly near the inferior conjunction of the emission line source. There is no direct evidence for the secondary. A preliminary determination of radial velocity variations at modest spectral resolution yields K = 132 + or - 26 km/s for the Balmer emission lines. A model is presented for the system consistent with current data, which implies a mass for the primary and secondary stars of 0.9 and 0.4 solar mass respectively and in inclination of i = 78 deg.

  15. Exploratory Spectroscopy of Magnetic Cataclysmic Variables Candidates and Other Variable Objects

    OpenAIRE

    De Oliveira, A. S.; Rodrigues, C. V.; CIESLINSKI, D.; Jablonski, F. J.; Silva, K. M. G.; Almeida, L. A.; Rodriguez-Ardila, A.; M.S. Palhares

    2016-01-01

    The increasing number of synoptic surveys made by small robotic telescopes, as the photometric Catalina Real-Time Transient Survey (CRTS), represents a unique opportunity for the discovery of new variable objects, improving the samples of many classes of variables. Our goal is the discovery of new magnetic Cataclysmic Variables (mCVs). They are rare objects, which probe interesting accretion scenarios controlled by the white-dwarf magnetic field. We performed an optical spectroscopic survey t...

  16. Discovery of Fourier-dependent time lags in cataclysmic variables

    CERN Document Server

    Scaringi, S; Groot, P J; Uttley, P; Marsh, T; Knigge, C; Maccarone, T; Dhillon, V S

    2013-01-01

    We report the first study of Fourier-frequency-dependent coherence and phase/time lags at optical wavelengths of cataclysmic variables (MV Lyr and LU Cam) displaying typical flickering variability in white light. Observations were performed on the William Herschel Telescope using ULTRACAM. Lightcurves for both systems have been obtained with the SDSS filters $u'$, $g'$ and $r'$ simultaneously with cadences between $\\approx0.5-2$ seconds, and allow us to probe temporal frequencies between ~10^{-3} Hz and ~1 Hz. We find high levels of coherence between the u', g' and r' lightcurves up to at least ~10^{-2} Hz. Furthermore we detect red/negative lags where the redder bands lag the bluer ones at the lowest observed frequencies. For MV Lyr time lags up to ~3 seconds are observed, whilst LU Cam displays larger time lags of ~10 seconds. Mechanisms which seek to explain red/negative lags observed in X-ray binaries and Active Galactic Nuclei involve reflection of photons generated close to the compact object onto the s...

  17. X-rays from eclipsing cataclysmic variable systems: the eclipse profile

    International Nuclear Information System (INIS)

    A cataclysmic variable is a binary system containing a white dwarf which accretes material from a secondary star through the Roche lobe mechanism. Systems observed at large inclination angles offer the possibility to locate the the X-ray emitting region thus allowing to study the behaviour of systems accreting matter in extreme conditions. We briefly review the main properties of a cataclysmic variable and focus on the information possibly derived by high energy observations.

  18. Detached cataclysmic variables are crossing the orbital period gap

    CERN Document Server

    Zorotovic, Monica; Parsons, Steven G; Gänsicke, Boris T; Hardy, Adam; Agurto-Gangas, Carolina; Gómez-Morán, Ada Nebot; Rebassa-Mansergas, Alberto; Schwope, Axel D

    2016-01-01

    A central hypothesis in the theory of cataclysmic variable (CV) evolution is the need to explain the observed lack of accreting systems in the ~2-3 h orbital period range, known as the period gap. The standard model, disrupted magnetic braking (DMB), reproduces the gap by postulating that CVs transform into inconspicuous detached white dwarf (WD) plus main sequence (MS) systems, which no longer resemble CVs. However, observational evidence for this standard model is currently indirect and thus this scenario has attracted some criticism throughout the last decades. Here we perform a simple but exceptionally strong test of the existence of detached CVs (dCVs). If the theory is correct dCVs should produce a peak in the orbital period distribution of detached close binaries consisting of a WD and an M4-M6 secondary star. We measured six new periods which brings the sample of such binaries with known periods below 10 h to 52 systems. An increase of systems in the ~2-3 h orbital period range is observed. Comparing ...

  19. The formation of Cataclysmic Variables: the influence of nova eruptions

    CERN Document Server

    Nelemans, G; Repetto, S; Toonen, S; Phinney, E S

    2015-01-01

    The theoretical and observed populations of pre-cataclysmic variables (pre-CVs) are dominated by systems with low-mass white dwarfs (WDs), while the WD masses in CVs are typically high. In addition, the space density of CVs is found to be significantly lower than theoretical models. We investigate the influence of nova outbursts on the formation and (initial) evolution of CVs. In particular, we calculate the stability of the mass transfer in case all the material accreted on the WD is lost in classical novae, and part of the energy to eject the material comes from a common-envelope like interaction with the companion. In addition, we study the effect of an asymmetry in the mass ejection, that may lead to small eccentricities in the orbit. We find that a common-envelope like ejection significantly decreases the stability of the mass transfer, in particular for low-mass WD. Similarly, the influence of asymmetric mass loss can be important for short-period systems and even more so for low-mass WD, but likely dis...

  20. IGR J18293-1213 is an eclipsing Cataclysmic Variable

    CERN Document Server

    Clavel, Maïca; Bodaghee, A; Chiu, J -L; Fornasini, F M; Hong, J; Krivonos, R; Ponti, G; Rahoui, F; Stern, D

    2016-01-01

    Studying the population of faint hard X-ray sources along the plane of the Galaxy is challenging because of high-extinction and crowding, which make the identification of individual sources more difficult. IGR J18293-1213 is part of the population of persistent sources which have been discovered by the INTEGRAL satellite. We report on NuSTAR and Swift/XRT observations of this source, performed on 2015 September 11. We detected three eclipsing intervals in the NuSTAR light curve, allowing us to constrain the duration of these eclipses, $\\Delta t = 30.8^{+6.3}_{-0.0}$ min, and the orbital period of the system, $T = 6.92\\pm0.01$ hr. Even though we only report an upper limit on the amplitude of a putative spin modulation, the orbital period and the hard thermal Bremsstrahlung spectrum of IGR J18293-1213 provide strong evidence that this source is a magnetic Cataclysmic Variable (CV). Our NuSTAR and Swift/XRT joint spectral analysis places strong constraints on the white dwarf mass $M_{\\rm wd} = 0.78^{+0.10}_{-0.0...

  1. Cataclysmic Variables observed during K2 Campaigns 0 and 1

    CERN Document Server

    Dai, Zhibin; Garnavich, Peter M; Kennedy, Mark

    2016-01-01

    There are 15 cataclysmic variables (CVs) observed in the first two campaigns of the K2 mission. In this paper, the eight CVs showing distinct features are analyzed in detail. Among these eight, modulations during quiescence are evident at the known orbital periods in the SU UMa stars QZ Vir and RZ Leo, and at our newly determined orbital periods of 1RXS J0632+2536 and WD 1144+011. The periodogram analysis for the quiescent light curve of QZ Vir reveals multi-period modulations and the coexistence of orbital and superhump periods. The phased orbital light curves for the other 3 CVs in quiescence display wide (about half cycle) and shallow (< 0.5 mag) eclipse features. Besides these modulations, their quiescent light curves reveal several transient events: a sudden decrease of system light in 1RXS J0632+2536, a low level flare-like event in QZ Vir, a short brightening event in RZ Leo and a temporary disappearance of the orbital modulation in WD 1144+011. The two known dwarf novae UV Gem and TW Vir and the CV...

  2. An Almost Complete Radio Survey of Magnetic Cataclysmic Variables

    Science.gov (United States)

    Dieck, Christopher A.; Everett Barrett, Paul; Beasley, Anthony J.; Pal Singh, Kulinder; Boboltz, David A.; Godon, Patrick; Mason, Paul A.

    2016-01-01

    This poster presents the results of a radio survey using the Jansky Very Large Array (JVLA) of 129 Magnetic Cataclysmic Variables (MCVs) north of declination -35 deg. 103 hours of observations were performed during the JVLA observing sessions 2013B and 2015A, when the array was mostly in its highest spatial-resolution configurations (i.e., A and B). Most targets were observed twice for 2-5 minutes at each of three frequencies (C, X, and K-bands), although a few targets were also observed at a fourth frequency (Q-band). 22 of the 129 MCVS were detected at one or more frequencies. Of these 22 detections, 15 are new. This number nearly triples the number of MCVs that are known radio sources. Most detections are at the C and X-band frequencies, although three sources were detected at the K-band frequency. One of the K-band frequency detections is the known rapidly-rotating radio source AE Aqr, while the other two are the polars, AI Tri and ST LMi. Of the 22 detected sources, two-thirds are polars (15) and all are believed to be nearby (<200 pc). Except for a few stronger sources, most detections are in the range of 100-200 µJy, which at a distance of 150 pc corresponds roughly to a luminosity of 2x1024 erg/s at the X-band frequency. The results of this survey are encouraging in that more MCVs are likely to be detected as the time on-source increases, since the flux from MCVs is highly variable.

  3. Detached cataclysmic variables are crossing the orbital period gap

    Science.gov (United States)

    Zorotovic, M.; Schreiber, M. R.; Parsons, S. G.; Gänsicke, B. T.; Hardy, A.; Agurto-Gangas, C.; Nebot Gómez-Morán, A.; Rebassa-Mansergas, A.; Schwope, A. D.

    2016-04-01

    A central hypothesis in the theory of cataclysmic variable (CV) evolution is the need to explain the observed lack of accreting systems in the ≃2-3 h orbital period range, known as the period gap. The standard model, disrupted magnetic braking (DMB), reproduces the gap by postulating that CVs transform into inconspicuous detached white dwarf (WD) plus main sequence systems, which no longer resemble CVs. However, observational evidence for this standard model is currently indirect and thus this scenario has attracted some criticism throughout the last decades. Here, we perform a simple but exceptionally strong test of the existence of detached CVs (dCVs). If the theory is correct, dCVs should produce a peak in the orbital period distribution of detached close binaries consisting of a WD and an M4-M6 secondary star. We measured six new periods which brings the sample of such binaries with known periods below 10 h to 52 systems. An increase of systems in the ≃2-3 h orbital period range is observed. Comparing this result with binary population models, we find that the observed peak cannot be reproduced by post-common envelope binaries (PCEBs) alone and that the existence of dCVs is needed to reproduce the observations. Also, the WD mass distribution in the gap shows evidence of two populations in this period range, i.e. PCEBs and more massive dCVs, which is not observed at longer periods. We therefore conclude that CVs are indeed crossing the gap as detached systems, which provides strong support for the DMB theory.

  4. IGR J18293-1213 is an eclipsing Cataclysmic Variable

    Science.gov (United States)

    Clavel, M.; Tomsick, J. A.; Bodaghee, A.; Chiu, J.-L.; Fornasini, F. M.; Hong, J.; Krivonos, R.; Ponti, G.; Rahoui, F.; Stern, D.

    2016-06-01

    Studying the population of faint hard X-ray sources along the plane of the Galaxy is challenging because of high-extinction and crowding, which make the identification of individual sources more difficult. IGR J18293-1213 is part of the population of persistent sources which have been discovered by the INTEGRAL satellite. We report on NuSTAR and Swift/XRT observations of this source, performed on 2015 September 11. We detected three eclipsing intervals in the NuSTAR light curve, allowing us to constrain the duration of these eclipses, Δ t= 30.8^{+6.3}_{-0.0} min, and the orbital period of the system, T = 6.92 ± 0.01 hr. Even though we only report an upper limit on the amplitude of a putative spin modulation, the orbital period and the hard thermal Bremsstrahlung spectrum of IGR J18293-1213 provide strong evidence that this source is a magnetic Cataclysmic Variable (CV). Our NuSTAR and Swift/XRT joint spectral analysis places strong constraints on the white dwarf mass M_wd = 0.78^{+0.10}_{-0.09} M⊙. Assuming that the mass to radius ratio of the companion star M⋆/R⋆ = 1 (solar units) and using T, Δt and Mwd, we derived the mass of the companion star M⋆ = 0.82 ± 0.01 M⊙, the orbital separation of the binary system a = 2.14 ± 0.04 R⊙, and its orbital inclination compared to the line of sight i=(72.2^{+2.4}_{-0.0})± 1.0°.

  5. Cataclysmic Variables Observed During K2 Campaigns 0 and 1

    Science.gov (United States)

    Dai, Zhibin; Szkody, Paula; Garnavich, Peter M.; Kennedy, Mark

    2016-07-01

    There are 15 cataclysmic variables (CVs) observed in the first two campaigns of the K2 mission. In this paper, the eight CVs showing distinct features are analyzed in detail. Among these eight, modulations during quiescence are evident at the known orbital periods in the SU UMa stars QZ Vir and RZ Leo, and at our newly determined orbital periods for 1RXS J0632+2536 and WD 1144+011. The periodogram analysis for the quiescent light curve of QZ Vir reveals multi-period modulations and the coexistence of orbital and superhump periods. The phased orbital light curves for the other three CVs in quiescence display wide (about half cycle) and shallow (events: a sudden decrease of system light in 1RXS J0632+2536, a low-level flare-like event in QZ Vir, a short brightening event in RZ Leo, and a temporary disappearance of the orbital modulation in WD 1144+011. The two known dwarf novae UV Gem and TW Vir and the CVs USNO-B1.01144-00115322 and CSS 130516:111236:111236.7+002807 show outbursts, including one complete and three incomplete normal outbursts and two complete superoutbursts. An incomplete but typical normal outburst confirms the dwarf nova identification of the USNO-B1.01144-00115322. The one complete normal outburst in UV Gem may provide the orbital period, since its modulations are shorter than the previously observed superhump period. The superoutburst of CSS 130516:111236.7+002807, along with the corresponding superhump period, indicates that this object is an SU UMa star. The derived superhump period of CSS 130516:111236:111236.7+002807 is 1.44 hr, implying that this new SU UMa star is close to the period minimum.

  6. The new cataclysmic variable RX J1554.2+2721 in the period gap

    Science.gov (United States)

    Tovmassian, G. H.; Greiner, J.; Zharikov, S. V.; Echevarría, J.; Kniazev, A.

    2001-12-01

    We report on the results of a spectroscopic and photometric study of a new cataclysmic variable, identified as optical counterpart of the X-ray source RX J1554.2+2721 detected by ROSAT. The spectroscopic observations of the relatively bright (16.5') object show systematic radial velocity variations with a semi-amplitude of ~140 km s-1. Besides the clear presence of distinct low and high states there are periodic photometric light variations with an amplitude of about 0.15 mag in the R band. The orbital period is 2.753 hours thus being within the period gap, at its upper border. The flux distribution in the spectrum of the object shows a substantial contribution of a M4 V secondary, and also bears clear signs of cyclotron emission. Thus, we classify the discovered object as a new member of the AM Her class of magnetic cataclysmic variables. This classification is further supported by the soft X-ray spectrum, the characteristic profiles of the emission lines, the tomography map and the shape of the orbital light curve. A simple fitting of the spectrum in the low and high states suggests a reduced mass transfer rate in RX J1554.2+2721, compared to similar objects outside the period gap.

  7. The new cataclysmic variable RX J1554.2+2721 in the period gap

    CERN Document Server

    Tovmassian, G H; Zharikov, S V; Echevarria, J; Kniazev, A Yu

    2001-01-01

    We report on the results of a spectroscopic and photometric study of a new cataclysmic variable, identified as optical counterpart of the X-ray source RX J1554.2+2721 detected by ROSAT. The spectroscopic observations of the relatively bright (~16.5mag) object show systematic radial velocity variations with a semi-amplitude of ~140 km/sec. Besides the clear presence of distinct low and high states there are periodic photometric light variations with an amplitude of about 0.15 magnitude in the R band. The orbital period is 2.753h thus being within the period gap, at its upper border. The flux distribution in the spectrum of the object shows a substantial contribution of a M4V secondary, and also bears clear signs of cyclotron emission. Thus, we classify the discovered object as a new member of the AM Her class of magnetic cataclysmic variables. This classification is further supported by the soft X-ray spectrum, the characteristic profiles of the emission lines, the tomography map and the shape of the orbital l...

  8. Cataclysmic variables as probes of x-ray properties of interstellar grains

    Energy Technology Data Exchange (ETDEWEB)

    Bode, M.F.; Evans, A.; Norwell, G.A.

    1983-01-01

    Interstellar-grain properties have previously been probed at wavelengths ranging from the infrared to the ultraviolet. Recent work by other authors has shown that we may also observe the effects of scattering by such grains at x-ray wavelengths. In this paper we suggest that investigations of the x-ray properties of interstellar grains may profitably be conducted in sight lines to variable sources. Particular emphasis is given in this context to cataclysmic variables and related objects.

  9. XMM-Newton observations of the low-luminosity cataclysmic variable V405 Pegasi

    CERN Document Server

    Schwope, A D; Traulsen, I; Schwarz, R; Granzer, T; Pires, A M; Thorstensen, J R

    2013-01-01

    V405 Peg is a low-luminosity cataclysmic variable (CV) that was identified as the optical counterpart of the bright, high-latitude ROSAT all-sky survey source RBS1955. The system was suspected to belong to a largely undiscovered population of hibernating CVs. Despite intensive optical follow-up its subclass however remained undetermined. We want to further classify V405 Peg and understand its role in the CV zoo via its long-term behaviour, spectral properties, energy distribution and accretion luminosity. We perform a spectral and timing analysis of \\textit{XMM-Newton} X-ray and ultra-violet data. Archival WISE, HST, and Swift observations are used to determine the spectral energy distribution and characterize the long-term variability. The X-ray spectrum is characterized by emission from a multi-temperature plasma. No evidence for a luminous soft X-ray component was found. Orbital phase-dependent X-ray photometric variability by $\\sim50\\%$ occurred without significant spectral changes. No further periodicity...

  10. Analysis of Kepler Light Curve of the Novalike Cataclysmic Variable KIC 8751494

    CERN Document Server

    Kato, Taichi

    2013-01-01

    We analyzed the Kepler light curve of KIC 8751494, the recently recognized novalike cataclysmic variable in the Kepler field. We detected a stable periodicity of 0.114379(1) d, which we identified as being the orbital period. The stronger photometric period around 0.12245 d, which had been detected from the ground-based observation, was found to be variable, and we identified this period as being the positive superhump period. Most unexpectedly, this superhump period showed short-term (10--20 d) and strong variations in period when the object entered a slightly faint state. The fractional superhump excess varied as large as ~30%. The variation of the period very well traced the variation of the brightness of the system. The time-scales of this variation of the superhump period was too slow for the thermal disk instability. We interpret that the period variation was caused by the varying pressure effect on the period of positive superhumps. This finding suggests that the pressure effect, at least in novalike s...

  11. An HST Study of the Ultraviolet Variability of Quiescent Cataclysmic Variables

    Science.gov (United States)

    Szkody, Paula; Mukadam, Anjum S.; Gaensicke, Boris T.; HST 12870 Team

    2016-01-01

    A large HST program in Cycle 20 (PI Gaensicke) was awarded 122 orbits to obtain ultraviolet spectra of 40 cataclysmic variables. While the primary aim of the COS spectra was to obtain the temperature of the white dwarfs in these systems, the time-tag data could also be used to study the variability of each system during the time coverage of the allocated 2-5 HST orbits. This variability could encompass periodic orbital modulations on timescales of hours due to eclipses or hot spots, periodic variability on minute timescales due to white dwarf pulsations or spins, as well as non-periodic variability due to flickering and short term accretion changes. The light curves were created by summing the continuum portions of the spectrum and subtracting the background. Discrete Fourier Transforms were computed to assess any periodic behavior. Our results show that about a third of the systems show periodic behavior, including several new candidate accreting pulsators, several with UV detection of spin periods and eclipses, while the rest show various levels of flickering and minor accretion changes.Support for this work was provided by HST grant GO-12870.

  12. Propeller activated resonances and the fate of short period cataclysmic variables

    CERN Document Server

    Matthews, O M; Wynn, G A; Truss, M R

    2006-01-01

    We show that the combination of a weak magnetic propeller and accretion disc resonances can effectively halt accretion in short period cataclysmic variables for large fractions of their lifetimes. This may help to explain the discrepancy between the observed and predicted orbital period distributions of cataclysmic variables at short periods. Orbital resonances cause the disc to become eccentric, allowing material to fall back onto the donor star or out of the system. A weak magnetic field on a rapidly spinning primary star propels disc material outwards, allowing it to access these resonances. Numerical and analytic calculations show that this state can be long lived (~10^11 yr). This is because the magnetic propeller is required only to maintain access to the resonances, and not to push matter out of the Roche lobe, so that the spin down time-scale is much longer than for a classical propeller model.

  13. Exploratory Spectroscopy of Magnetic Cataclysmic Variables Candidates and Other Variable Objects

    CERN Document Server

    Oliveira, A S; Cieslinski, D; Jablonski, F J; Silva, K M G; Almeida, L A; Rodriguez-Ardila, A; Palhares, M S

    2016-01-01

    The increasing number of synoptic surveys made by small robotic telescopes, as the photometric Catalina Real-Time Transient Survey (CRTS), represents a unique opportunity for the discovery of new variable objects, improving the samples of many classes of variables. Our goal is the discovery of new magnetic Cataclysmic Variables (mCVs). They are rare objects, which probe interesting accretion scenarios controlled by the white-dwarf magnetic field. We performed an optical spectroscopic survey to search for signatures of magnetic accretion on 47 variable objects selected mostly from CRTS. Our sample includes 13 polar strong candidates, from which 5 are new discoveries. Accretion disks seem to be present in other 19 objects. One is a previously known probable intermediate polar. We suggest 8 other objects could also be of this class. In particular, 7 of them have spectra consistent with short-period intermediate polars. We suggest one object is a novalike of the VY~Scl class. We also caught one dwarf nova in erup...

  14. Doppler Tomography of Cataclysmic Variables with a 6.5-m class Telescope

    OpenAIRE

    Echevarría, J.

    2007-01-01

    We are conducting a long-term project of high dispersion spectroscopy (R 20000) to observe and analyze a sample of cataclysmic variables with the 2.1-m telescope at San Pedro Mártir and the echelle spectrograph. The main tool for this analysis is Doppler tomography. In this contribution we summarize our work and pose the question: how can we improve this project with a 6.5-m class telescope?

  15. MOCCA-SURVEY Database I. Accreting White Dwarf Binary Systems in Globular Clusters I. Cataclysmic Variables -- present-day population

    CERN Document Server

    Belloni, Diogo T; Askar, Abbas; Leigh, Nathan; Hypki, Arkadiusz

    2016-01-01

    In this paper, which is the first in a series of papers associated with cataclysmic variables and related objects, we introduce the CATUABA code, a numerical machinery written for analysis of the MOCCA simulations, and show some first results by investigating the present-day population of cataclysmic variables in globular clusters. Emphasis was given on their properties and the observational selection effects when observing and detecting them. In this work we analysed in this work six models, including three with Kroupa distributions of the initial binaries. We found that for models with Kroupa initial distributions, considering the standard value of the efficiency of the common envelope phase adopted in BSE, no single cataclysmic variable was formed only via binary stellar evolution, i. e., in order to form them, strong dynamical interactions have to take place. We show and explain why this is inconsistent with observational and theoretical results. Our results indicate that the population of cataclysmic var...

  16. Kepler observations of the eclipsing cataclysmic variable KIS J192748.53+444724.5

    Science.gov (United States)

    Scaringi, S.; Groot, P. J.; Still, M.

    2013-08-01

    We present results from long-cadence Kepler observations covering 97.6 d of the newly discovered eclipsing cataclysmic variable KIS J192748.53+444724.5/KIC 8625249. We detect deep eclipses of the accretion disc by the donor star every 3.97 h. Additionally, the Kepler observations also cover a full outburst for this cataclysmic variable, making KIS J192748.53+444724.5 the second known eclipsing cataclysmic variable system in the Kepler field of view. We show how in quiescence a significant component associated with the hotspot is visible preceding the eclipse, and that this component is swamped by the brightness increase during the outburst, potentially associated with the accretion disc. Furthermore, we present evidence for accretion disc radius changes during the outburst by analysing the out-of-eclipse light levels and eclipse depth through each orbital cycle. We show how these parameters are linearly correlated in quiescence, and discuss how their evolution during the outburst suggests disc radius changes and/or radial temperature gradient variations in the disc.

  17. Kepler observations of the eclipsing cataclysmic variable KIS J192748.53+444724.5

    CERN Document Server

    Scaringi, S; Still, M

    2013-01-01

    We present results from long cadence Kepler observations covering 97.6 days of the newly discovered eclipsing cataclysmic variable KIS J192748.53+444724.5/KIC 8625249. We detect deep eclipses of the accretion disk by the donor star every 3.97 hours. Additionally, the Kepler observations also cover a full outburst for this cataclysmic variable, making KIS J192748.53+444724.5 the second known eclipsing cataclysmic variable system in the Kepler field of view. We show how in quiescence a significant component associated to the hot-spot is visible preceding the eclipse, and that this component is swamped by the brightness increase during the outburst, potentially associated with the accretion disk. Furthermore we present evidence for accretion disk radius changes during the outburst by analysing the out-of-eclipse light levels and eclipse depth through each orbital cycle. We show how these parameters are linearly correlated in quiescence, and discuss how their evolution during the outburst is suggesting disk radiu...

  18. Probing the Nature of Cataclysmic Variables via Photometric Studies on Multiple Timescales /

    OpenAIRE

    Armstrong, Eve

    2013-01-01

    I examine the structure and evolution of hydrogen- and helium-rich cataclysmic variables (CVs), via their periodic variability captured by long-term time series photometry. Studies to be discussed address one of two sets of question. One set pertains to helium CVs, which are poorly understood relative to their hydrogen-rich counterparts: What is the long-term evolution - in terms of orbital period (Porb) - of He CVs, and what does this imply about the nature of their secondaries? Two methods ...

  19. Detection of the AM Her type cataclysmic variable V834 Cen at radio wavelengths

    International Nuclear Information System (INIS)

    The first detection is reported of the AM Her type cataclysmic variable system V834 Cen at 8.4 GHz, making it the second AM Her system to be detected at radio wavelengths. The radio emission is variable on time-scales as short as 1 min and reaches peak flux densities of 35 mJy. Longer time-scale variations of order of tens of minutes and levels of 12 mJy may be correlated with binary phase. The emission mechanism is probably an electron-cyclotron maser. (author)

  20. AN ONLINE CATALOG OF CATACLYSMIC VARIABLE SPECTRA FROM THE FAR-ULTRAVIOLET SPECTROSCOPIC EXPLORER

    International Nuclear Information System (INIS)

    We present an online catalog containing spectra and supporting information for cataclysmic variables that have been observed with the Far-Ultraviolet Spectroscopic Explorer (FUSE). For each object in the catalog we list some of the basic system parameters such as (R.A., decl.), period, inclination, and white dwarf mass, as well as information on the available FUSE spectra: data ID, observation date and time, and exposure time. In addition, we provide parameters needed for the analysis of the FUSE spectra such as the reddening E(B – V), distance, and state (high, low, intermediate) of the system at the time it was observed. For some of these spectra we have carried out model fits to the continuum with synthetic stellar and/or disk spectra using the codes TLUSTY and SYNSPEC. We provide the parameters obtained from these model fits; this includes the white dwarf temperature, gravity, projected rotational velocity, and elemental abundances of C, Si, S, and N, together with the disk mass accretion rate, the resulting inclination, and model-derived distance (when unknown). For each object one or more figures are provided (as gif files) with line identification and model fit(s) when available. The FUSE spectra and the synthetic spectra are directly available for download as ASCII tables. References are provided for each object, as well as for the model fits. In this article we present 36 objects, and additional ones will be added to the online catalog in the future. In addition to cataclysmic variables, we also include a few related objects, such as a wind-accreting white dwarf, a pre-cataclysmic variable, and some symbiotics.

  1. SW Sex stars, old novae, and the evolution of cataclysmic variables

    CERN Document Server

    Schmidtobreick, Linda

    2014-01-01

    The population of cataclysmic variables with orbital periods right above the period gap are dominated by systems with extremely high mass transfer rates, the so-called SW Sextantis stars. On the other hand, some old novae in this period range which are expected to show high mass transfer rate instead show photometric and/or spectroscopic resemblance to low mass transfer systems like dwarf novae. We discuss them as candidates for so-called hibernating systems, CVs that changed their mass transfer behaviour due to a previously experienced nova outburst. This paper is designed to provide input for further research and discussion as the results as such are still very preliminary.

  2. SPECTROSCOPY OF NEW AND POORLY KNOWN CATACLYSMIC VARIABLES IN THE KEPLER FIELD

    International Nuclear Information System (INIS)

    The NASA Kepler mission has been in science operation since 2009 May and is providing high precision, high cadence light curves of over 150,000 targets. Prior to launch, nine cataclysmic variables were known to lie within Kepler's field of view. We present spectroscopy for seven systems, four of which were newly discovered since launch. All of the stars presented herein have been observed by, or are currently being observed by, the Kepler space telescope. Three historic systems and one new candidate could not be detected at their sky position and two candidates are called into question as to their true identity.

  3. On the eclipsing cataclysmic variable star HBHA 4705-03

    CERN Document Server

    Rutkowski, A; Marsh, T R; Eker, Z

    2013-01-01

    We present observations and analysis of a new eclipsing binary HBHA 4705-03. Using decomposition of the light curve into accretion disk and hot spot components, we estimated photometrically the mass ratio of the studied system to be q=0.62 +-0.07. Other fundamental parameters was found with modeling. This approach gave: white dwarf mass M_1 = (0.8 +- 0.2) M_sun, secondary mass M_2=(0.497 +- 0.05) M_sun, orbital radius a=1.418 R_sun, orbital inclination i = (81.58 +- 0.5) deg, accretion disk radius r_d/a = 0.366 +- 0.002, and accretion rate dot{M} = (2.5 +- 2) * 10^{18}[g/s], (3*10^{-8} [M_sun/yr]). Power spectrum analysis revealed ambiguous low-period Quasi Periodic Oscillations centered at the frequencies f_{1}=0.00076 Hz, f_2=0.00048 Hz and f_3=0.00036 Hz. The B-V=0.04 [mag] color corresponds to a dwarf novae during an outburst. The examined light curves suggest that HBHA 4705-03 is a nova-like variable star.

  4. SWSextantis stars: the dominant population of cataclysmic variables with orbital periods between 3 and 4h

    Science.gov (United States)

    Rodríguez-Gil, P.; Gänsicke, B. T.; Hagen, H.-J.; Araujo-Betancor, S.; Aungwerojwit, A.; Allende Prieto, C.; Boyd, D.; Casares, J.; Engels, D.; Giannakis, O.; Harlaftis, E. T.; Kube, J.; Lehto, H.; Martínez-Pais, I. G.; Schwarz, R.; Skidmore, W.; Staude, A.; Torres, M. A. P.

    2007-06-01

    We present time-series optical photometry of five new cataclysmic variables (CVs) identified by the Hamburg Quasar Survey (HQS). The deep eclipses observed in HS 0129+2933 (= TT Tri), HS 0220+0603 and HS 0455+8315 provided very accurate orbital periods of 3.35129827(65), 3.58098501(34) and 3.56937674(26) h, respectively. HS 0805+3822 shows grazing eclipses and has a likely orbital period of 3.2169(2) h. Time-resolved optical spectroscopy of the new CVs (with the exception of HS 0805+3822) is also presented. Radial velocity studies of the Balmer emission lines provided an orbital period of 3.55 h for HS 1813+6122, which allowed us to identify the observed photometric signal at 3.39 h as a negative superhump wave. The spectroscopic behaviour exhibited by all the systems clearly identifies them as new SW Sextantis (SW Sex) stars. HS 0220+0603 shows unusual NII and SiII emission lines suggesting that the donor star may have experienced nuclear evolution via the CNO cycle. These five new additions to the class increase the number of known SW Sex stars to 35. Almost 40 per cent of the total SW Sex population do not show eclipses, invalidating the requirement of eclipses as a defining characteristic of the class and the models based on a high orbital inclination geometry alone. On the other hand, as more SW Sex stars are identified, the predominance of orbital periods in the narrow 3-4.5 h range is becoming more pronounced. In fact, almost half the CVs which populate the 3-4.5 h period interval are definite members of the class. The dominance of SW Sex stars is even stronger in the 2-3 h period gap, where they make up 55 per cent of all known gap CVs. These statistics are confirmed by our results from the HQS CVs. Remarkably, 54 per cent of the Hamburg nova-like variables have been identified as SW Sex stars with orbital periods in the 3-4.5 h range. The observation of this pile-up of systems close to the upper boundary of the period gap is difficult to reconcile with the

  5. KIC 9406652: AN UNUSUAL CATACLYSMIC VARIABLE IN THE KEPLER FIELD OF VIEW

    International Nuclear Information System (INIS)

    KIC 9406652 is a remarkable variable star in the Kepler field of view that shows both very rapid oscillations and long term outbursts in its light curve. We present an analysis of the light curve over quarters 1-15 and new spectroscopy that indicates that the object is a cataclysmic variable with an orbital period of 6.108 hr. However, an even stronger signal appears in the light curve periodogram for a shorter period of 5.753 hr, and we argue that this corresponds to the modulation of flux from the hot spot region in a tilted, precessing disk surrounding the white dwarf star. We present a preliminary orbital solution from radial velocity measurements of features from the accretion disk and the photosphere of the companion. We use a Doppler tomography algorithm to reconstruct the disk and companion spectra, and we also consider how these components contribute to the object's spectral energy distribution from ultraviolet to infrared wavelengths. This target offers us a remarkable opportunity to investigate disk processes during the high mass transfer stage of evolution in cataclysmic variables

  6. A New Cataclysmic Variable RX J0757.0+6306 Candidate for the Shortest Period Intermediate Polar

    CERN Document Server

    Tovmassian, G H; Kroll, P; Szkody, P; Mason, P A; Zickgraf, F J; Krautter, J; Thiering, I; Serrano, A; Howell, S; Ciardi, D R

    1998-01-01

    A new cataclysmic variable is identified as the optical counterpart of the faint and hard X-ray source RX J0757.0+6306 discovered during the ROSAT all-sky survey. Strong double-peaked emission lines bear evidence of an accretion disc via an S-wave which varies with a period of 81 +/- 5 min. We identify this period as the orbital period of the binary system. CCD photometry reveals an additional period of 8.52 +/- 0.15 min. which was stable over four nights. We suggest that RX J0757.0+6306 is possibly an intermediate polar, but we cannot exclude the possibility that it is a member of the SU UMa group of dwarf novae.

  7. Dwarf nova-type cataclysmic variable stars are significant radio emitters

    CERN Document Server

    Coppejans, Deanne L; Miller-Jones, James C A; Rupen, Michael P; Sivakoff, Gregory R; Knigge, Christian; Groot, Paul J; Woudt, Patrick A; Waagen, Elizabeth O; Templeton, Matthew

    2016-01-01

    We present 8--12\\,GHz radio light curves of five dwarf nova (DN) type Cataclysmic Variable stars (CVs) in outburst (RX And, U Gem and Z Cam), or superoutburst (SU UMa and YZ Cnc), increasing the number of radio-detected DN by a factor of two. The observed radio emission was variable on time-scales of minutes to days, and we argue that it is likely to be synchrotron emission. This sample shows no correlation between the radio luminosity and optical luminosity, orbital period, CV class, or outburst type; however higher-cadence observations are necessary to test this, as the measured luminosity is dependent on the timing of the observations in these variable objects. The observations show that the previously detected radio emission from SS Cyg is not unique in type, luminosity (in the plateau phase of the outburst), or variability time-scales. Our results prove that DN, as a class, are radio emitters in outburst.

  8. A search for brown-dwarf like secondaries in cataclysmic variables

    CERN Document Server

    Mennickent, R E

    2002-01-01

    We present VTL/ISAAC infrared spectroscopy of a sample of short orbital period cataclysmic variables which are candidates for harboring substellar companions. We have detected the KI and NaI absorption lines of the companion star in VY Aqr. The overall spectral distribution in this system is best fit with a M9.5 type dwarf spectra, implying a distance of $100 \\pm 10$ pc. VY Aqr seems to fall far from the theoretical distribution of secondary star temperatures around the orbital period minimum. Fitting of the IR spectral energy distribution (SED) was performed by comparing the observed spectrum with late-type templates. The application of such a spectral fitting procedure suggests that the continuum shape in the 1.1-2.5 $\\mu$m spectral region in short orbital period cataclysmic variables may be an useful indicator of the companion spectral type. The SED fitting for RZ Leo and CU Vel suggests M5 type dwarf companions, and distances of 340 $\\pm$ 110 and 150 $\\pm$ 50 pc, respectively. These systems may be placed ...

  9. A search for brown dwarf like secondaries in cataclysmic variables - II

    Science.gov (United States)

    Mennickent, R. E.; Diaz, M. P.; Tappert, C.

    2004-02-01

    We have examined VTL/ISAAC 1-2.5 μm spectroscopy of a sample of short-orbital-period cataclysmic variables which are candidates for harbouring substellar companions. We provide descriptions of the infrared spectra of EI Psc, V834 Cen, WX Cet, VW Hyi, TY PsA and BW Scl. Fitting of the infrared (IR) spectral energy distribution (SED) was performed by comparing the observed spectrum with late-type templates. Absorption features of the secondary star were detected in EI Psc and V834 Cen, consistent with dwarf secondaries of spectral type K 5 +/- 1 and M 8 +/- 0.5, respectively. In addition, we report the first detection of the secondary star in VW Hyi. The SED in this case is well matched by an L 0 +/- 2 type secondary contributing 23 per cent to the overall flux at λ= 1.15 μm. This is a surprising result for a system with a relatively high mass transfer rate. We discuss the implication of our findings on the current scenarios for cataclysmic variable star evolution.

  10. EC 19314 - 5915 - A bright, eclipsing cataclysmic variable from the Edinburgh-Cape Blue Object Survey

    Science.gov (United States)

    Buckley, D. A. H.; O'Donoghue, D.; Kilkenny, D.; Stobie, R. S.; Remillard, R. A.

    1992-01-01

    A deeply eclipsing cataclysmic variable, with an orbital period of 4.75 hr, has been discovered in the southern Edinburgh-Cape Blue Object Survey. The star, EC 19314 - 5915, lies close to the positional constraints of a previously unidentified HEAO-1 hard X-ray source, 1H1930 - 5989. Its optical spectrum is unusual in that it shows, apart from the emission lines characteristic of a novalike, or dwarf nova cataclysmic variable (Balmer, He I and He II), metallic absorption lines typical of a late-G star. The individual time-resolved spectra, with the tertiary absorption lines removed, show absorption reversals in the Balmer emission lines, increasing in strength for the higher series. The Balmer emission radial velocities are therefore severely distorted in comparison to the He II 4686-A emission and He I 4471-A absorption radial velocity curves. An independent distance estimate of about 600 pc is derived for EC19314 - 5915, from the spectroscopic parallax of the third star.

  11. New Cataclysmic Variable 1RXS J015017.0+375614 in Andromeda

    CERN Document Server

    Lazareva, A; Denisenko, D; Kuznetsov, A; Gorbovskoy, E; Lipunov, V

    2013-01-01

    We report the discovery of a new cataclysmic variable in MASTER database which is identical to the faint ROSAT X-ray source 1RXS J015017.0+375614. The object was observed in outbursts to 14.9m on 2012 Nov. 28 and to 14.3m on 2013 Jan. 07, but not detected in course of the routine real-time search. Analysis of the archival MASTER data and CRTS light curve shows the large-amplitude variability from 19.1m at quiescence to 15.4-14.8m in outbursts. The new variable is most likely a dwarf nova of SU UMa subtype with rather frequent normal outbursts and occasional superoutbursts.

  12. 1ES 1113+432: Luminous, soft X-ray outburst from a nearby cataclysmic variable (AR Ursae Majoris)

    Science.gov (United States)

    Remillard, R. A.; Schachter, J. F.; Silber, A. D.; Slane, P.

    1994-01-01

    A remarkable X-ray transient from the Einstein Slew Survey, 1 ES 1113+432, is identified with a nearby, short-period cataclysmic variable. Wenzel (1993) has confirmed that the optical counterpart is the variable star, AR UMa (cataloged as 'semiregular'), erroneously reported 5.7 min southeast of the true position. One of the Einstein slew observations recorded a flux of 43 IPC counts/s, which is an order of magnitude above the flux observed from the brightest cataclysmic variables in other X-ray surveys. The outburst spectrum is extremely 'soft,' with an implied blackbody temperature of approximately 22 eV. The optical counterpart (V = 16.5) exhibits a strong UV component, TiO bands from an M star, and broadened Balmer emission lines. Optical states as bright as V approx. 13 were found on photographs from the Harvard Plate Library, confirming outburst behavior in the optical counterpart. The historical photographic record suggests that 1ES 1113+432 remains in a low-accretion state most of the time. Both of the soft X-ray spectrum and the transitions between high and low-accretion states are suggestive of the AM Her (magnetic) subclass. Photometric observations in the I band show 0.18 mag modulations at a period of 0.966 hr. These are interpreted as ellipsiodal variations in the secondary star for a binary period of 1.932 hr, which is near the lower boundary of the 'period gap' in the histogram, of orbital periods of accreting white dwarfs. Thus 1ES 1113+432 provides the rare opportunity to study a secondary star in a cataclysmic binary that has evolved through the period gap. The optical spectral features from the secondary imply a spectral type of approximately M6 and a distance of approximately 88 pc. The peak luminosity in the soft X-ray component (unabsorbed) is then estimated to be 3 X 10(exp 33) ergs/s, assuming emission from a blackbody slab with a temperature of 22 eV. While this luminosity is higher than previous measures of the soft X-ray component, it

  13. Difference between the optical flickering colours of cataclysmic variables and symbiotic recurrent novae

    CERN Document Server

    Zamanov, R; Latev, G; Stoyanov, K A; Tsvetkova, S V

    2015-01-01

    We performed simultaneous observations in 3 bands (UBV) of the flickering variability of the recurrent novae RS Oph and T CrB at quiescence. Using new and published data, we compare the colours of the flickering in cataclysmic variables and symbiotic recurrent novae. We find a difference between the colours of the flickering source in these two types of accreting white dwarfs. The detected difference is highly significant with $ p-value \\approx 2 \\times 10^{-6}$ for the distributions of $(U-B)_0$ colour and $p \\approx 3 \\times 10^{-5}$ on (U-B) versus (B-V) diagram. The possible physical reasons are briefly discussed. The data are available upon request from the authors.

  14. On the diversity and similarity of outbursts of symbiotic binaries and cataclysmic variables

    CERN Document Server

    Skopal, Augustin

    2015-01-01

    Outbursts in two classes of interacting binary systems, the symbiotic stars (SSs) and the cataclysmic variables (CVs), show a number of similarities in spite of very different orbital periods. Typical values for SSs are in the order of years, whereas for CVs they are of a few hours. Both systems undergo unpredictable outbursts, characterized by a brightening in the optical by 1 - 3 and 7 - 15 mag for SSs and CVs, respectively. By modelling the multiwavelength SED of selected examples from both groups of these interacting binaries, I determine their basic physical parameters at a given time of the outburst evolution. In this way I show that the principal difference between outbursts of these objects is their violence, whereas the ionization structure of their ejecta is basically very similar. This suggests that the mechanism of the mass ejection by the white dwarfs in these systems is also similar.

  15. Tomographic simulations of accretion disks in Cataclysmic Variables - flickering and wind

    CERN Document Server

    Ribeiro, F M A; Ribeiro, Fabiola Mariana A.; Diaz, Marcos P.

    2006-01-01

    Cataclysmic Variables (CVs) are close binary systems where mass is transferred from a red dwarf star to a white dwarf star via an accretion disk. The flickering is observed as stochastic variations in the emitted radiation both in the continuum and in the emission line profiles. The main goal of our simulations is to compare synthetic Doppler maps with observed ones, aiming to constrain the flickering properties and wind parameters. A code was developed which generates synthetic emission line profiles of a geometrically thin and optically thick accretion disk. The simulation allows us to include flares in a particular disk region. The emission line flares may be integrated over arbitrary ``exposure'' times, producing the synthetic line profiles. Flickering Doppler maps are created using such synthetic time series. The presence of a wind inside the Roche lobe was also implemented. Radiative transfer effects in the lines where taken into account in order to reproduce the single peaked line profiles frequently s...

  16. The space density of magnetic and non-magnetic cataclysmic variables, and implications for CV evolution

    CERN Document Server

    Pretorius, Magaretha L

    2014-01-01

    We present constraints on the space densities of both non-magnetic and magnetic cataclysmic variables, and discuss some implications for models of the evolution of CVs. The high predicted non-magnetic CV space density is only consistent with observations if the majority of these systems are extremely faint in X-rays. The data are consistent with the very simple model where long-period IPs evolve into polars and account for the whole short-period polar population. The fraction of WDs that are strongly magnetic is not significantly higher for CV primaries than for isolated WDs. Finally, the space density of IPs is sufficiently high to explain the bright, hard X-ray Galactic Centre source population.

  17. Global MHD Simulations of Accretion Disks in Cataclysmic Variables (CVs): I. The Importance of Spiral Shocks

    CERN Document Server

    Ju, Wenhua; Zhu, Zhaohuan

    2016-01-01

    We present results from the first global 3D MHD simulations of accretion disks in Cataclysmic Variable (CV) systems in order to investigate the relative importance of angular momentum transport via turbulence driven by the magnetorotational instability (MRI) compared to that driven by spiral shock waves. Remarkably, we find that even with vigorous MRI turbulence, spiral shocks are an important component to the overall angular momentum budget, at least when temperatures in the disk are high (so that Mach numbers are low). In order to understand the excitation, propagation, and damping of spiral density waves in our simulations more carefully, we perform a series of 2D global hydrodynamical simulations with various equation of states and both with and without mass inflow via the Lagrangian point (L1). Compared with previous similar studies, we find the following new results. 1) Linear wave dispersion relation fits the pitch angles of spiral density waves very well. 2) We demonstrate explicitly that mass accreti...

  18. Theoretical, numerical and experimental study of accretion shocks dynamics in magnetic cataclysmic variables

    International Nuclear Information System (INIS)

    Magnetic cataclysmic variables are interacting binary Systems containing a highly magnetized white dwarf which accretes material from a companion. Material is led along magnetic field lines and falls onto the magnetic pole(s) supersonically forming an accretion column. As the material hits the surface, a reverse shock is formed and the shocked region is structured by the cooling effect of radiation processes. This work is a multidisciplinary study of the dynamics of the accretion column. Firstly, a numerical study of the accretion column structure at the astrophysical scale is presented. The observational consequences are discussed. This approach is completed by experiments using radiative flows generated by powerful lasers. The relevance of such experiments is based on the establishment of scaling laws. News scaling laws in the frame of radiative ideal or resistive MHD are exposed. The results of the sizing and the interpretation of the POLAR experimental campaign of 2012 on LULI2000 installation are presented. (author)

  19. Time lags of the flickering in cataclysmic variables as a function of wavelength

    CERN Document Server

    Bruch, Albert

    2015-01-01

    Flickering is a ubiquitous phenomenon in cataclysmic variables (CVs). Although the underlying light source is one of the main contributors to the optical radiation, the mechanism leading to flickering is not understood as yet. The present study aims to contribute to the set of boundary conditions, defined by observations, which must be met by physical models that describe the flickering. In particular, time lags in the occurrence of flickering events at different wavelengths over the optical range are examined. To this end, the cross-correlation functions (CCFs) of numerous light curves of a sample of CVs are analysed that were observed simultaneously or quasi-simultaneously in different bands of various photometric systems. Deviations of the maxima of the CCFs from zero time-shift indicate a dependence of the flickering activity on the wavelength in the sense that flickering flares reach their maxima slightly earlier in the blue range than in the red. While the available observational material does not permi...

  20. Plasma Diagnostics in High Resolution X-Ray Spectra of Magnetic Cataclysmic Variables

    Energy Technology Data Exchange (ETDEWEB)

    Mauche, C W

    2001-10-02

    Using the Chandra HETG spectrum of EX Hya as an example, we discuss some of the plasma diagnostics available in high-resolution X-ray spectra of magnetic cataclysmic variables. Specifically, for conditions appropriate to collisional ionization equilibrium plasmas, we discuss the temperature dependence of the H- to He-like line intensity ratios and the density and photoexcitation dependence of the He-like R line ratios and the Fe XVII I(17.10 {angstrom})/I(17.05 {angstrom}) line ratio. We show that the plasma temperature in EX Hya spans the range from {approx}0.5 to {approx}10 keV and that the plasma density n {ge} 2 x 10{sup 14} cm{sup -3}, orders of magnitude greater than that observed in the Sun or other late-type stars.

  1. Short-period cataclysmic variables at Observatorio Astronomico Nacional IA UNAM.

    Science.gov (United States)

    Zharikov, S.

    2014-03-01

    We present results of time-resolved spectroscopy and photometry of faint (∼17-19 mag) Cataclysmic Variable stars with periods around the minimum orbital period (∼80 min). In this work we concentrated to our results of study of CVs systems which have evolved beyond the period minimum (so-called bounce-back systems). Using various instruments attached to 2.1m, 1.5m and 0.84m telescopes of OAN SPM of IA UNAM we explored conditions and structure of accretion disks in those short-period Cataclysmic Variables. We showed that the accretion disk in a system with an extremely low mass ratio (≤0.05) grows in the size reaching 2:1 resonance radius and is relatively cool. The disk in such systems also becomes largely optically thin in the continuum, contributing to the total flux less than the stellar components of the system. In contrast, the viscosity and the temperature in spiral arms formed at the outer edge of the disk are higher and their contribution in continuum plays an increasingly important role. We model such disks and generate light curves which successfully simulate the observed double-humped light curves in the quiescence. Thanks to support of our programs by the Time Allocation Commission of OAN SPM, the perfect astroclimate in the observatory, and the phase-locked method of spectroscopic observations, the significant progress in the study of bounce-back systems using a small size telescope was reached.

  2. Reversibility of time series: revealing the hidden messages in X-ray binaries and cataclysmic variables

    CERN Document Server

    Scaringi, S; Middleton, M

    2014-01-01

    We explore the non-linear, high-frequency, aperiodic variability properties in the three cataclysmic variables MV Lyr, KIC 8751494 and V1504 Cyg observed with Kepler, as well as the X-ray binary Cyg X-1 observed with RXTE. This is done through the use of a high-order Fourier statistic called the bispectrum and its related biphase and bicoherence, as well as the time-skewness statistic. We show how all objects display qualitatively similar biphase trends. In particular all biphase amplitudes are found to be smaller than $\\pi/2$, suggesting that the flux distributions for all sources are positively skewed on all observed timescales, consistent with the log-normal distributions expected from the fluctuating accretion disk model. We also find that for all objects the biphases are positive at frequencies where the corresponding power spectral densities display their high frequency break. This suggests that the noise-like flaring observed is rising more slowly than it is falling, and thus not time-reversible. This ...

  3. On the Effect of Explosive Thermonuclear Burning on the Accreted Envelopes of White Dwarfs in Cataclysmic Variables

    CERN Document Server

    Sion, Edward M

    2014-01-01

    The detection of heavy elements at suprasolar abundances in the atmospheres of some accreting white dwarfs in cataclysmic variables, coupled with the high temperatures needed to produce these elements requires explosive thermonuclear burning. The central temperatures of any formerly more massive secondary stars in CVs undergoing hydrostatic CNO burning are far too low to produce these elements. Evidence is presented that at least some cataclysmic variables contain donor secondaries that have been contaminated by repeated novae ejecta and are transferring this material back to the white dwarf. This scenario does not exclude the channel in which formerly more massive donor stars underwent CNO processing in ystems that underwent thermal timescale mass transfer. Implications for the progenitors of CVs are discussed.

  4. Dwarf Nova Oscillations and Quasi-Periodic Oscillations in Cataclysmic Variables: II. A Low Inertia Magnetic Accretor Model

    OpenAIRE

    Warner, Brian; Woudt, Patrick A.

    2002-01-01

    The Dwarf Nova Oscillations observed in Cataclysmic Variable (CV) stars are interpreted in the context of a Low Inertia Accretor model, in which accretion on to an equatorial belt of the white dwarf primary causes the belt to vary its angular velocity. The rapid deceleration phase is attributed to propellering. Evidence that temporary expulsion rather than accretion of gas occurs during this phase is obtained from the large drop in EUV flux. We show that the QPOs are most probably caused by a...

  5. Interferometric Astrometry with Hubble Space Telescope Fine Guidance Sensor 3:The Parallax of the Cataclysmic Variable TV Columbae

    OpenAIRE

    McArthur, B. E.; Benedict, G. F.; Lee, J.; van Altena, W. F.; Slesnick, C. L.; Rhee, J; Patterson, R. J.; Fredrick, L. W.; Spiesman, W. J.; Nelan, E.; Duncombe, R. L.; Hemenway, P. D.; Jefferys, W. H.; Shelus, P. J.; Franz, O. G.

    2001-01-01

    TV Columbae (TV Col) is a 13th magnitude Intermediate Polar (IP) Cataclysmic Variable (CV), with multiple periods found in the light curves. Past estimates predicted a distance of 400 parsec to greater than 500 parsec. Recently completed Hubble Space Telescope (HST) Fine Guidance Sensor (FGS) interferometric observations allow us to determine the first trigonometric parallax to TV Col. This determination puts the distance of TV Col at 368 -15+17 parsecs. CD-32 2376, a 10th magnitude Tycho Cat...

  6. DISCOVERY AND CHARACTERIZATION OF AN EXTREMELY DEEP-ECLIPSING CATACLYSMIC VARIABLE: LSQ172554.8-643839

    International Nuclear Information System (INIS)

    We report the discovery of an eclipsing cataclysmic variable with eclipse depths >5.7 mag, orbital period 94.657 minutes, and peak brightness V ∼ 18 at J2000 position 17h25m54.s8, -64038'39''. Detected by visual inspection of images from Yale University's QUEST camera on the European Southern Observatory 1.0 m Schmidt telescope at La Silla, we obtained light curves in B, V, R, I, z, and J with SMARTS 1.3 m and 1.0 m telescopes at Cerro Tololo and spectra from 3500 to 9000 A with the SOAR 4.3 m telescope at Cerro Pachon. The optical light curves show a deep, 5-minute eclipse immediately followed by a shallow 38-minute eclipse and then sinusoidal variation. No eclipses appear in J. During the deep eclipse we measure V-J > 7.1, corresponding to a spectral type M8 or later secondary, consistent with the dynamical constraints. The estimated distance is 150 ps. The spectra show strong hydrogen emission lines, Doppler broadened by 600-1300 km s-1, oscillating with radial velocity that peaks at mid deep eclipse with semi-amplitude 500 ± 22 km s-1. We suggest that LSQ172554.8-643839 is a polar with a low-mass secondary viewed at high inclination. No known radio or X-ray source coincides with the new object's location.

  7. Continuous `stunted' outbursts detected from the Cataclysmic Variable KIC 9202990 using Kepler data

    CERN Document Server

    Ramsay, Gavin; Wood, Matt A; Howell, Steve B; Smale, Alan; Still, Martin; Barclay, Tom

    2015-01-01

    Based on early Kepler data, Ostensen et al. (2010) found that KIC 9202990 showed a 4 hr and a two-week photometric period. They suggested the 4 hr period was a signature of an orbital period; the longer period was possibly due to precession of an accretion disk and KIC 9202990 was a cataclysmic variable with an accretion disk which is always in a bright state (a nova-like system). Using the full Kepler dataset on KIC 9202990 which covers 1421 d (Quarter 2--17), and includes 1 min cadence data from the whole of Quarters 5 and 16, we find that the 4 hr period is stable and therefore a signature of the binary orbital period. In contrast, the 10--12 d period is not stable and shows an amplitude between 20--50 percent. This longer period modulation is similar to those nova-like systems which show `stunted' outbursts. We discuss the problems that a precessing disk model has in explaining the observed characteristics and indicate why we favour a stunted outburst model. Although such stunted events are considered to ...

  8. The Photometric Periods of the Nova-Like Cataclysmic Variable LQ Pegasi (PG 2133+115)

    CERN Document Server

    Rude, Gerald D

    2011-01-01

    We present a time-resolved differential photometric study and time series analysis of the nova-like cataclysmic variable star LQ Peg. We discover three periodicities in the photometry, one with a period of 3.42 +/- 0.03 hours, and another with a period of 56.8 +/- 0.01 hours. We interpret these to be the apsidal superhump and precessional periods of the accretion disk, respectively, and predict that the orbital period of LQ Peg is 3.22 +/- 0.03 hours. The third periodicity, with a period of 41.3 +/- 0.01 hours, we interpret to be the nodal precessional period of the accretion disk. We also report a flare that lasted four minutes and had an energy in visible light of (1.2 +/- 0.3) x 10^36 ergs, or 10^4-5 times more energetic than the largest solar flares, comparable to the most energetic visible-light stellar flares known. We calculate the absolute magnitude of LQ Peg to be M_J = 4.78 +/- 0.54, and its distance to be 800 +/- 200 pc.

  9. Roche tomography of cataclysmic variables - VII. The long-term magnetic activity of AE Aqr

    Science.gov (United States)

    Hill, C. A.; Watson, C. A.; Steeghs, D.; Dhillon, V. S.; Shahbaz, T.

    2016-06-01

    We present a long-term study of the secondary star in the cataclysmic variable AE Aqr, using Roche tomography to indirectly image starspots on the stellar surface spanning 8 years of observations. The seven maps show an abundance of spot features at both high and low latitudes. We find that all maps have at least one large high-latitude spot region, and we discuss its complex evolution between maps, as well as its compatibility with current dynamo theories. Furthermore, we see the apparent growth in fractional spot coverage, fs, around 45° latitude over the duration of observations, with a persistently high fs near latitudes of 20°. These bands of spots may form as part of a magnetic activity cycle, with magnetic flux tubes emerging at different latitudes, similar to the `butterfly' diagram for the Sun. We discuss the nature of flux tube emergence in close binaries, as well as the activity of AE Aqr in the context of other stars.

  10. BK Lyncis: The Oldest Old Nova?... And a Bellwether for Cataclysmic-Variable Evolution

    CERN Document Server

    Patterson, Joseph; Kemp, Jonathan; de Miguel, Enrique; Krajci, Thomas; Foote, Jerry; Hambsch, Franz-Josef; Campbell, Tut; Roberts, George; Cejudo, David; Dvorak, Shawn; Vanmunster, Tonny; Koff, Robert; Skillman, David; Harvey, David; Martin, Brian; Rock, John; Boyd, David; Oksanen, Arto; Morelle, Etienne; Ulowetz, Joseph; Kroes, Anthony; Sabo, Richard; Jensen, Lasse

    2012-01-01

    We summarize the results of a 20-year campaign to study the light curves of BK Lyncis, a nova-like star strangely located below the 2-3 hour orbital period gap in the family of cataclysmic variables. Two apparent "superhumps" dominate the nightly light curves - with periods 4.6% longer, and 3.0% shorter, than P_orb. The first appears to be associated with the star's brighter states (V~14), while the second appears to be present throughout and becomes very dominant in the low state (V~15.7). Starting in the year 2005, the star's light curve became indistinguishable from that of a dwarf nova - in particular, that of the ER UMa subclass. Reviewing all the star's oddities, we speculate: (a) BK Lyn is the remnant of the probable nova on 30 December 101, and (b) it has been fading ever since, but has taken ~2000 years for the accretion rate to drop sufficiently to permit dwarf-nova eruptions. If such behavior is common, it can explain other puzzles of CV evolution. One: why the ER UMa class even exists (because all...

  11. X-ray Polarization Signatures of Compton Scattering in Magnetic Cataclysmic Variables

    CERN Document Server

    McNamara, Aimee; Wu, Kinwah

    2008-01-01

    Compton scattering within the accretion column of magnetic cataclysmic variables (mCVs) can induce a net polarization in the X-ray emission. We investigate this process using Monte Carlo simulations and find that significant polarization can arise as a result of the stratified flow structure in the shock-ionized column. We find that the degree of linear polarization can reach levels up to ~8% for systems with high accretion rates and low white-dwarf masses, when viewed at large inclination angles with respect to the accretion column axis. These levels are substantially higher than previously predicted estimates using an accretion column model with uniform density and temperature. We also find that for systems with a relatively low-mass white dwarf accreting at a high accretion rate, the polarization properties may be insensitive to the magnetic field, since most of the scattering occurs at the base of the accretion column where the density structure is determined mainly by bremsstrahlung cooling instead of cy...

  12. The Evolution of Cataclysmic Variables as Revealed by their Donor Stars

    CERN Document Server

    Knigge, Christian; Patterson, Joseph

    2011-01-01

    We reconstruct the evolutionary path followed by cataclysmic variables (CVs) from the observed mass-radius relationship of their donor stars. Along the way, we update the semi-empirical CV donor sequence of Knigge (2006) and present a comprehensive review of the link between CV evolution and donor physics. After calibrating state-of-the art stellar models for use in the CV setting, we fit self-consistent theoretical evolution sequences to the observed donor masses and radii. In the standard model of CV evolution, AML below the period gap is assumed to be driven solely by gravitational radiation (GR), while AML above the gap is usually described by a magnetic braking prescription due to Rappaport, Verbunt & Joss (1983). We find that simple scaled versions of these recipes match the data quite well. However, the optimal scaling factors turn out to be f_GR = 2.47 +/- 0.22 below the gap and f_MB = 0.66 +/- 0.05 above. The implications and applications of our results include: (1) The revised evolution sequence...

  13. The spin periods and magnetic moments of white dwarfs in magnetic cataclysmic variables

    CERN Document Server

    Norton, A; Somerscales, R V

    2004-01-01

    We have used a model of magnetic accretion to investigate the rotational equilibria of magnetic cataclysmic variables (mCVs). The results of our numerical simulations demonstrate that there is a range of parameter space in the P_spin / P_orb versus mu_1 plane at which rotational equilibrium occurs. This has allowed us to calculate the theoretical histogram describing the distribution of magnetic CVs as a function of P_spin / P_orb. We show that this agrees with the observed distribution assuming that the number of systems as a function of white dwarf magnetic moment is distributed approximately according to N(mu_1) d mu_1 proportional to 1/mu_1 d mu_1. The rotational equilibria also allow us to infer approximate values for the magnetic moments of all known intermediate polars. We predict that intermediate polars with mu_1 > 5 x 10^33 G cm^3 and P_orb > 3h will evolve into polars, whilst those with mu_1 3h will either evolve into low field strength polars which are (presumably) unobservable, and possibly EUV ...

  14. Doppler Tomography and Photometry of the Cataclysmic Variable 1RXS J064434.5+334451

    CERN Document Server

    Santisteban, J V Hernández; Michel, R; Costero, R

    2016-01-01

    We have obtained simultaneous photometric and spectroscopic observations of the cataclysmic variable 1RXS J064434.5+334451. We have calibrated the spectra for slit losses using the simultaneous photometry allowing to construct reliable Doppler images from H$\\alpha$ and HeII 4686 emission lines. We have improved the ephemeris of the object based on new photometric eclipse timings, obtaining $HJD = 2453403.759533 + 0.26937446E$. Some eclipses present a clear internal structure which we attribute to a central HeII emission region surrounding the white dwarf, a finding supported by the Doppler tomography. This indicates that the system has a large inclination angle $i=78 \\pm 2^{\\circ}$. We have also analysed the radial velocity curve from the emission lines to measure its semi--amplitude, $K_1$, from H$\\alpha$ and HeII 4686 and derive the masses of the components: $M_1=0.82\\pm0.06$ M$_{\\odot}$, $M_2=0.78\\pm0.04$ M$_{\\odot}$ and their separation $a=2.01\\pm0.06$ $R_{\\odot}$. The Doppler tomography and other observe...

  15. Search for brown-dwarf like secondaries in cataclysmic variables II

    CERN Document Server

    Mennickent, R E; Tappert, C

    2004-01-01

    We have examined VTL/ISAAC 1-2.5 $\\umu$m spectroscopy of a sample of short orbital period cataclysmic variables which are candidates for harboring substellar companions. We provide descriptions of the infrared spectrum of \\hbox{EI Psc}, \\hbox{V834 Cen}, \\hbox{WX Cet}, \\hbox{VW Hyi}, \\hbox{TY PsA} and \\hbox{BW Scl}. Fitting of the IR spectral energy distribution (SED) was performed by comparing the observed spectrum with late-type templates. Absorption features of the secondary star were detected in \\hbox{EI Psc} and \\hbox{V834 Cen}, consistent with dwarf secondaries of spectral type K 5 $\\pm$ 1 and M 8 $\\pm$ 0.5, respectively. In addition, we report the first detection of the secondary star in \\hbox{VW Hyi}. The SED in this case is well matched by an L 0 $\\pm$ 2 type secondary contributing 23 per cent to the overall flux at $\\lambda$ = 1.15 $\\umu$m. This is a surprising result for a system with a relatively high mass transfer rate. We discuss the implication of our findings on the current scenarios for catacl...

  16. Photometry of the eclipsing cataclysmic variable SDSS J152419.33+220920.0

    CERN Document Server

    Michel, R; Hernandez-Santisteban, J V

    2013-01-01

    Aims. We present new photometry of the faint and poorly studied cataclysmic variable SDSS J152419.33+220920.0, analyze its light curve and provide an accurate ephemeris for this system. Methods. Time-resolved CCD differential photometry was carried out using the 1.5m and 0.84m telescopes at the Observatorio Astronomico Nacional at San Pedro Martir. Results. From time-resolved photometry of the system obtained during six nights (covering more than twenty primary eclipse cycles in more than three years), we show that this binary presents a strong primary and a weak secondary modulation. Our light curve analysis shows that only two fundamental frequencies are present, corresponding to the orbital period and a modulation with twice this frequency. We determine the accurate ephemeris of the system to be HJD(eclipse)= 2454967.6750(1) + 0.06531866661(1) E. A double-hump orbital period modulation, a standing feature in several bounce-back systems at quiescence, is present at several epochs. However, we found no other...

  17. Doppler Tomography and Photometry of the Cataclysmic Variable 1RXS J064434.5+334451

    Science.gov (United States)

    Echevarria, Juan

    2015-08-01

    We have obtained simultaneous photometric and spectroscopic observations of the cataclysmic variable 1RXS J064434.5+334451. We have calibrated the spectra for slit losses using the simultaneous photometry. This has been used to construct reliable Doppler images from Hα, Hβ and He II 4686 Å emission lines. We have also analyzed the radial velocity curve of the emission lines to derive its semi-amplitude, and used a co-phasing method to determine the semi-amplitude of the secondary. We have improved the ephemeris of the object based on new photometric eclipse timings to obtain HJD = 2453403.759533 + 0.26937446E. Some eclipses present a clear internal structure which we attribute to a central blob of He II emission surrounding the white dwarf, a finding supported by the Doppler Tomography. This indicates that the system has a large inclination angle i = 78o ± 2. We discuss which radial velocity semi-amplitudes indicator yields a better result for the mass ratio of the system. We derive the masses of the components: M1 = 0.76 ± 0.04 M⊙, M2 = 0.57 ± 0.04 M⊙ and their separation a = 1.92 ± 0.04R⊙ . The Doppler tomography and other observed features in this nova-like system strongly suggests that this is an SW Sex type system.

  18. Two Types of Soft X-ray Spectra in Cataclysmic Variables

    Science.gov (United States)

    White, Nicholas E. (Technical Monitor); Mukai, K.; Kinkhabwala, A.; Peterson, J. R.; Kahn, S. M.; Paerels, F.

    2002-01-01

    We present results of analyses of Chandra HETG soft X-ray spectra (Lambda = 1.5-25 A) of seven cataclysmic variables. We find that these spectra divide unambiguously into two distinct types. Spectra of the first type, consisting of EX Hya, V603 Aql, U Gem, and SS Cyg, are remarkably well fit by a simple cooling flow model, which assumes only steady-state isobaric radiative cooling. This model has only two free parameters, the maximum temperature, kT(sub max), which provides a rough measurement of the depth of the potential well, and the overall normalization, which provides a highly precise measurement of the total accretion rate. Spectra of the second type, consisting of V1223 Sgr, A Psc, and GK Per, are grossly inconsistent with a simple cooling flow model. They instead exhibit a hard continuum, and, in addition, show strong H-like and He-like ion emission but little Fe L-shell emission, which is consistent with expectations for line emission from a photoionized plasma. Using a simple photoionization model, we argue that the observed line emission for these sources can be driven entirely by the hard continuum. The physical significance of these two distinct types of X-ray spectra is also explored.

  19. Suzaku observations of Fe K α line in some Magnetic Cataclysmic Variables

    Science.gov (United States)

    Eze, R. N. C.

    2015-05-01

    We resolved the 6.4 keV, 6.7 keV and 7.0 keV Fe K α lines in 19 Magnetic Cataclysmic Variables (mCVs) observed with the Suzaku satellite. The 6.7 keV and 7.0 keV emission lines are typically created by collisional excitation in the vicinity of the white dwarf arising from the shock front. The 6.4 keV iron emission line in contrast is formed in equilibrium by irradiation of the neutral (or low ionized) iron by a hard X-ray source, as a collisional origin would lead to rapid ionization. We study the emission of these lines in the 19 mCVs and found that the 6.4 keV line emission is likely created by a combination of reflection of hard X-rays from the white dwarf surfaces and absorption-induced fluorescence. Specifically, while absorption-induced fluorescence is dominant in 14 mCVs, there are significant hints that the 6.4 keV line emission arise from the reflection of hard X-rays from the white dwarf surfaces in 5 mCVs. This reflection suggests there could be relevant information about the geometry of the WD in the system encoded in the Fe K α line.

  20. Hubble Space Telescope Observations of the Nova-Like Cataclysmic Variable V348 Puppis

    CERN Document Server

    Froning, C S; Baptista, R

    2003-01-01

    We present time series UV and optical (1150 -- 8000 A) spectrophotometry of the novalike (NL) cataclysmic variable V348 Pup through and after eclipse. Outside of eclipse, the spectrum is characterized by a blue continuum, strong line emission, and a broad dip from 2000 -- 3000 A. The continuum eclipse depth is roughly the same over the entire wavelength range covered and there are no signatures of the WD eclipse in the light curves. Model steady-state accretion disk spectra provide a poor fit to the shape of the UV-optical spectrum outside of eclipse. All of these properties are consistent with a disk that is self-shielding, hiding the inner disk and the white dwarf. In eclipse, the emission lines and the broad dip are occulted less than the continuum, indicating vertical extension in these components. The dip is consistent with the presence of a vertical ``Fe II'' absorbing curtain in the system. Archival UV-optical spectra of the lower-inclination NL UX UMa show a bluer continuum and weaker line emission th...

  1. Roche tomography of cataclysmic variables - VII. The long-term magnetic activity of AE Aqr

    CERN Document Server

    Hill, C A; Steeghs, D; Dhillon, V S; Shahbaz, T

    2016-01-01

    We present a long-term study of the secondary star in the cataclysmic variable AE~Aqr, using Roche tomography to indirectly image starspots on the stellar surface spanning 8~years of observations. The 7 maps show an abundance of spot features at both high and low latitudes. We find that all maps have at least one large high-latitude spot region, and we discuss its complex evolution between maps, as well as its compatibility with current dynamo theories. Furthermore, we see the apparent growth in fractional spot coverage, $f_{\\mathrm{s}}$, around $45^{\\circ}$~latitude over the duration of observations, with a persistently high $f_{\\mathrm{s}}$ near latitudes of $20^{\\circ}$. These bands of spots may form as part of a magnetic activity cycle, with magnetic flux tubes emerging at different latitudes, similar to the `butterfly' diagram for the Sun. We discuss the nature of flux tube emergence in close binaries, as well as the activity of AE~Aqr in the context of other stars.

  2. Population Synthesis of Cataclysmic Variables: I. Inclusion of Detailed Nuclear Evolution

    CERN Document Server

    Goliasch, J

    2016-01-01

    We have carried out an extensive population synthesis study of the ensemble properties of the present-day population of cataclysmic variables (PDCVs) that takes into account the nuclear evolution of high-mass donors close to the bifurcation and dynamical instability limits. Assuming the interrupted magnetic braking paradigm, we confirm many of the general features associated with the observed CV population and find enormous diversity in their secular properties. We predict that nearly half of the non-magnetic CVs with Porb > 6 hours are at least mildly evolved (i.e., greater than one-half of their MS turn-off age). Some of these systems contribute to the observed population of PDCVs in the period gap. We also see an enhancement by up to a factor of two in the probability of detecting CVs at the `minimum period'. This spike is quite narrow (approximately 5 minutes) and is attenuated because of the spectrum of WD masses and partly by the evolution of the donors. Our syntheses imply that there should be a very r...

  3. PHL 1445: An eclipsing cataclysmic variable with a substellar donor near the period minimum

    CERN Document Server

    McAllister, M J; Baraffe, I; Dhillon, V S; Marsh, T R; Bento, J; Bochinski, J; Bours, M C P; Breedt, E; Copperwheat, C M; Hardy, L K; Kerry, P; Parsons, S G; Rostron, J W; Sahman, D I; Savoury, C D J; Tunnicliffe, R L

    2015-01-01

    We present high-speed, three-colour photometry of the eclipsing dwarf nova PHL 1445, which, with an orbital period of 76.3 min, lies just below the period minimum of ~82 min for cataclysmic variable stars. Averaging four eclipses reveals resolved eclipses of the white dwarf and bright spot. We determined the system parameters by fitting a parameterised eclipse model to the averaged lightcurve. We obtain a mass ratio of q = 0.087 +- 0.006 and inclination i = 85.2 +- 0.9 degrees. The primary and donor masses were found to be Mw = 0.73 +- 0.03 Msun and Md = 0.064 +- 0.005 Msun, respectively. Through multicolour photometry a temperature of the white dwarf of Tw = 13200 +- 700 K and a distance of 220 +- 50 pc were determined. The evolutionary state of PHL 1445 is uncertain. We are able to rule out a significantly evolved donor, but not one that is slightly evolved. Formation with a brown dwarf donor is plausible; though the brown dwarf would need to be no older than 600 Myrs at the start of mass transfer, requirin...

  4. ANGULAR MOMENTUM LOSS MECHANISMS IN CATACLYSMIC VARIABLES BELOW THE PERIOD GAP

    International Nuclear Information System (INIS)

    Mass transfer in cataclysmic variables (CVs) is usually considered to be caused by angular momentum loss (AML) driven by magnetic braking and gravitational radiation (GR) above the period gap, and solely by GR below the period gap. The best-fit revised model of CV evolution recently presented by Knigge et al., however, indicates that the AML rate below the period gap is 2.47(± 0.22) times the GR rate, suggesting the existence of some other AML mechanisms. We consider several kinds of consequential AML mechanisms often invoked in the literature: isotropic wind from the accreting white dwarfs, outflows from the Lagrangian points, and the formation of a circumbinary disk. We find that neither isotropic wind from the white dwarf nor outflow from the L1 point can explain the extra AML rate, while outflow from the L2 point or a circumbinary disk can effectively extract the angular momentum provided that ∼(15-45)% of the transferred mass is lost from the binary. A more promising mechanism is a circumbinary disk exerting gravitational torque on the binary. In this case, the mass-loss fraction can be as low as ∼–3.

  5. Angular Momentum Loss Mechanisms in Cataclysmic Variables below the Period Gap

    CERN Document Server

    Shao, Yong

    2011-01-01

    Mass transfer in cataclysmic variables (CVs) is usually considered to be caused by angular momentum loss (AML) driven by magnetic braking and gravitational radiation (GR) above the period gap, and solely by GR below the period gap. The best-fit revised model of CV evolution recently by \\citet{kbp11}, however, indicates that AML rate below the period gap is $2.47(\\pm 0.22)$ times the GR rate, suggesting the existence of some other AML mechanisms. We consider several kinds of consequential AML mechanisms often invoked in the literature: isotropic wind from the accreting white dwarfs, outflows from the Langrangian points, and the formation of a circumbinary disk. We found that neither isotropic wind from the white dwarf nor outflow from the $L_1$ point can explain the extra AML rate, while ouflow from the $L_2$ point or a circumbinary disk can effectively extract the angular momentum provided that $\\sim (15-45)%$ of the transferred mass is lost from the binary. A more promising mechanism is a circumbinary disk e...

  6. Continuous `stunted' outbursts detected from the cataclysmic variable KIC 9202990 using Kepler data

    Science.gov (United States)

    Ramsay, Gavin; Hakala, Pasi; Wood, Matt A.; Howell, Steve B.; Smale, Alan; Still, Martin; Barclay, Thomas

    2016-01-01

    Based on early Kepler data, Østensen et al. found that KIC 9202990 showed a 4-h and a two-week photometric period. They suggested the 4-h period was a signature of an orbital period; the longer period was possibly due to precession of an accretion disc and KIC 9202990 was a cataclysmic variable with an accretion disc which is always in a bright state (a nova-like system). Using the full Kepler data set on KIC 9202990 which covers 1421 d (Quarter 2-17), and includes 1-min cadence data from the whole of Quarters 5 and 16, we find that the 4-h period is stable and therefore a signature of the binary orbital period. In contrast, the 10-12 d period is not stable and shows an amplitude between 20 and 50 per cent. This longer period modulation is similar to those nova-like systems which show `stunted' outbursts. We discuss the problems that a precessing disc model has in explaining the observed characteristics and indicate why we favour a stunted outburst model. Although such stunted events are considered to be related to the standard disc instability mechanism, their origin is not well understood. KIC 9202990 shows the lowest amplitude and shortest period of continuous stunted outburst systems, making it an ideal target to better understand stunted outbursts and accretion instabilities in general.

  7. The Emergence of Negative Superhumps in Cataclysmic Variables: Smoothed Particle Hydrodynamics Simulations

    CERN Document Server

    Thomas, David M

    2016-01-01

    Negative superhumps are believed to arise in cataclysmic variable systems when the accretion disk is tilted with respect to the orbital plane. Slow retrograde precession of the line-of-nodes results in a signal---the negative superhump---with a period slightly less than the orbital period. Previous studies have shown that tilted disks exhibit negative superhumps, but a consensus on how a disk initially tilts has not been reached. Analytical work by Lai suggests that a magnetic field on the primary can lead to a tilt instability in a disk when the dipole moment is offset in angle from the spin axis of the primary and when the primary's spin axis is, itself, not aligned with the angular momentum axis of the binary orbit. However, Lai did not apply his work to the formation of negative superhumps. In this paper, we add Lai's model to an existing smoothed particle hydrodynamics code. Using this code, we demonstrate the emergence of negative superhumps in the "light curve" for a range of magnetic dipole moments. W...

  8. The systemic velocities of four long-period cataclysmic variable stars

    CERN Document Server

    North, R C; Kolb, U; Dhillon, V S; Moran, C K J

    2002-01-01

    Although a large number of orbital periods of cataclysmic variable stars (CVs) have been measured, comparison of period and luminosity distributions with evolutionary theory is affected by strong selection effects. A test has been discovered which is independent of these selection effects and is based upon the kinematics of CVs (Kolb & Stehle, 1996). If the standard models of evolution are correct then long-period (P_orb > 5 hrs) CVs should be typically less than 1.5 Gyr old, and their line-of-sight velocity dispersion ($\\sigma_\\gamma$) should be small. We present results from a pilot study which indicate that this postulate is indeed true. Four long-period dwarf novae (EM Cyg, V426 Oph, SS Cyg and AH Her) were observed over a complete orbit, in order that accurate radial velocities be obtained. We find values of -1.7, 5.4, 15.4 and 1.8 km/s with uncertainties of order 3 km/s, referred to the dynamical Local Standard of Rest (LSR), leading to a dispersion of ~ 8 km/s. Calculation of a 95 per cent confiden...

  9. Optical identification of X-ray source 1RXS J180431.1-273932 as a magnetic cataclysmic variable

    CERN Document Server

    Masetti, N; Parisi, P

    2012-01-01

    The X-ray source 1RXS J180431.1-273932 has been proposed as a new member of the Symbiotic X-ray Binary (SyXB) class of systems, which are composed of a late-type giant which loses matter to an extremely compact object, most likely a neutron star. In this paper we present an optical campaign of imaging plus spectroscopy on selected candidate counterparts of this object; we also reanalyzed the available archival X-ray data collected with XMM-Newton. We found that the brightest optical source inside the 90% X-ray positional error circle is spectroscopically identified as a magnetic cataclysmic variable (CV), most likely of Intermediate Polar type, through the detection of prominent Balmer, He I, He II and Bowen Blend emissions. On either spectroscopic or statistical grounds, we discard as counterparts of the X-ray source the other optical objects in the XMM-Newton error circle. A red giant star of spectral type M5 III is found lying just outside the X-ray position: we consider this latter object as a fore-/backg...

  10. Reversibility of time series: revealing the hidden messages in X-ray binaries and cataclysmic variables

    Science.gov (United States)

    Scaringi, S.; Maccarone, T. J.; Middleton, M.

    2014-11-01

    We explore the non-linear, high-frequency, aperiodic variability properties in the three cataclysmic variables MV Lyr, KIC 8751494 and V1504 Cyg observed with Kepler, as well as the X-ray binary Cyg X-1 observed with RXTE. This is done through the use of a high-order Fourier statistic called the bispectrum and its related biphase and bicoherence, as well as the time-skewness statistic. We show how all objects display qualitatively similar biphase trends. In particular, all biphase amplitudes are found to be smaller than π/2, suggesting that the flux distributions for all sources are positively skewed on all observed time-scales, consistent with the lognormal distributions expected from the fluctuating accretion disc model. We also find that for all objects, the biphases are positive at frequencies where the corresponding power spectral densities display their high-frequency break. This suggests that the noise-like flaring observed is rising more slowly than it is falling, and thus not time-reversible. This observation is also consistent with the fluctuating accretion disc model. Furthermore, we observe the same qualitative biphase trends in all four objects, where the biphases display a distinct decrease at frequencies below the high-frequency break in their respective power spectral densities. This behaviour can also be observed in the time skewness of all four objects. As far as we are aware, there is no immediate explanation for the observed biphase decreases. The biphase decreases may thus suggest that the fluctuating accretion disc model begins to break down at frequencies below the high-frequency break.

  11. The long-term light curve of the cataclysmic variable V794 Aquilae

    Energy Technology Data Exchange (ETDEWEB)

    Honeycutt, R. K. [Astronomy Department, Indiana University, Swain Hall West, Bloomington, IN 47405 (United States); Kafka, S. [Department of Terrestrial Magnetism, Carnegie Inst. of Washington, 5241 Broad Branch Road NW, Washington, DC 20015 (United States); Robertson, J. W., E-mail: honey@astro.indiana.edu, E-mail: skafka@aip.org, E-mail: Jeff.Robertson@atu.edu [Arkansas Tech University, Department of Physical Sciences, 1701 N. Boulder, Russellville, AR 72801-2222 (United States)

    2014-01-01

    The 1990-2012 light curve of the nova-like (NL) cataclysmic variable V794 Aql is studied in order to characterize and better understand the transitions to and from the faint state, and the variations within the bright state. Investigations of earlier portions of this data had concluded that the transitions to the low state were much slower than the rapid recovery, giving a sawtoothed appearance to the light curve. This behavior differs from that of most other VY Scl stars, which led to an interpretation of the large amplitude sawtooths as being due to an accretion disk (AD) instability. However, more recent photometry strongly suggests that the bright state itself has transitions of 1-1.5 mag, and that earlier studies had intermixed these bright state variations with the transitions to the low state. These newly recognized variations within the bright state sometimes appear as small outbursts (OBs) with typical amplitudes of 0.5-1.5 mag and spacings of ∼15-50 days. The rise times of the OBs are 2-3 times faster than the decline times. We argue that the V794 Aql bright state variations are due to AD behavior similar to that seen in dwarf novae, but with varying degrees of stability. Similar regular small OBs have also been reported in other NL CVs, which we compare with V794 Aql. The true deep low states in V794 Aql appear to be normal, having transition speeds and shapes very similar to the transitions in other VY Scl stars.

  12. Global MHD Simulations of Accretion Disks in Cataclysmic Variables. I. The Importance of Spiral Shocks

    Science.gov (United States)

    Ju, Wenhua; Stone, James M.; Zhu, Zhaohuan

    2016-06-01

    We present results from the first global 3D MHD simulations of accretion disks in cataclysmic variable (CV) systems in order to investigate the relative importance of angular momentum transport via turbulence driven by the magnetorotational instability (MRI) compared with that driven by spiral shock waves. Remarkably, we find that even with vigorous MRI turbulence, spiral shocks are an important component of the overall angular momentum budget, at least when temperatures in the disk are high (so that Mach numbers are low). In order to understand the excitation, propagation, and damping of spiral density waves in our simulations more carefully, we perform a series of 2D global hydrodynamical simulations with various equation of states, both with and without mass inflow via the Lagrangian point (L1). Compared with previous similar studies, we find the following new results. (1) The linear wave dispersion relation fits the pitch angles of spiral density waves very well. (2) We demonstrate explicitly that mass accretion is driven by the deposition of negative angular momentum carried by the waves when they dissipate in shocks. (3) Using Reynolds stress scaled by gas pressure to represent the effective angular momentum transport rate {α }{eff} is not accurate when mass accretion is driven by non-axisymmetric shocks. (4) Using the mass accretion rate measured in our simulations to directly measure α defined in standard thin-disk theory, we find 0.02≲ {α }{eff}≲ 0.05 for CV disks, consistent with observed values in quiescent states of dwarf novae. In this regime, the disk may be too cool and neutral for the MRI to operate and spiral shocks are a possible accretion mechanism. However, we caution that our simulations use unrealistically low Mach numbers in this regime and, therefore, future models with more realistic thermodynamics and non-ideal MHD are warranted.

  13. NON-THERMAL EMISSION FROM CATACLYSMIC VARIABLES: IMPLICATIONS ON ASTROPARTICLE PHYSICS

    Directory of Open Access Journals (Sweden)

    Vojtech Šimon

    2013-12-01

    Full Text Available We review the lines of evidence that some cataclysmic variables (CVs are the sources of non-thermal radiation. It was really observed in some dwarf novae in outburst, a novalike CV in the high state, an intermediate polar, polars, and classical novae (CNe during outburst. The detection of this radiation suggests the presence of highly energetic particles in these CVs. The conditions for the observability of this emission depend on the state of activity, and the system parameters. We review the processes and conditions that lead to the production of this radiation in various spectral bands, from gamma-rays including TeV emission to radio. Synchrotron and cyclotron emissions suggest the presence of strong magnetic fields in CV. In some CVs, e.g. during some dwarf nova outbursts, the magnetic field generated in the accretion disk leads to the synchrotron jets radiating in radio. The propeller effect or a shock in the case of the magnetized white dwarf (WD can lead to a strong acceleration of the particles that produce gamma-ray emission via pi0 decay; even Cherenkov radiation is possible. In addition, a gamma-ray production via pi0 decay was observed in the ejecta of an outburst of a symbiotic CN. Nuclear reactions during thermonuclear runaway in the outer layer of the WD undergoing CN outburst lead to the production of radioactive isotopes; their decay is the source of gamma-ray emission. The production of accelerated particles in CVs often has episodic character with a very small duty cycle; this makes their detection and establishing the relation of the behavior in various bands difficult.

  14. Time lags of the flickering in cataclysmic variables as a function of wavelength

    Science.gov (United States)

    Bruch, Albert

    2015-07-01

    Context. Flickering is a ubiquitous phenomenon in cataclysmic variables (CVs). Although the underlying light source is one of the main contributors to the optical radiation, the mechanism leading to flickering is not understood as yet. Aims: The present study aims to contribute to the set of boundary conditions, defined by observations, which must be met by physical models that describe the flickering. In particular, time lags in the occurrence of flickering events at different wavelengths over the optical range are examined. Methods: To this end, the cross-correlation functions (CCFs) of numerous light curves of a sample of CVs are analysed that were observed simultaneously or quasi-simultaneously in different bands of various photometric systems. Results: Deviations of the maxima of the CCFs from zero time-shift indicate a dependence of the flickering activity on the wavelength in the sense that flickering flares reach their maxima slightly earlier in the blue range than in the red. While the available observational material does not permit detecting this individually in all observed systems, the ensemble of all data clearly shows this effect. Particularly instructive are the cases of V603 Aql and TT Ari, where time lags of 15ṣ1 and 4ṣ3, respectively, are observed between the U and R bands. In principle this can be understood if during the development of a flickering flare the radiation characteristics of the light source responsible for flickering change such that in the early phases of a flare more short-wavelength radiation is emitted, and later on, the peak of the emission shifts to the red. Respective scenarios are discussed and shown to be in qualitative and quantitative agreement with observations.

  15. Last Rites for Cataclysmic Variables: Death by Fire, or Ice? (Abstract)

    Science.gov (United States)

    Patterson, J.

    2016-06-01

    (Abstract only) Cataclysmic binaries lose angular momentum as they age, and thus the component stars in the binary spiral ever closer together. As the spiraling-in proceeds, the shrinking Roche lobe "strangles" the donor star, forcing it to transfer mass. Since we can measure the rate of mass transfer pretty well, we know the rate of angular momentum loss pretty well.

  16. Multiwavelength study of RX J2015.6+3711: a magnetic cataclysmic variable with a 2-h spin period

    Science.gov (United States)

    Coti Zelati, F.; Rea, N.; Campana, S.; de Martino, D.; Papitto, A.; Safi-Harb, S.; Torres, D. F.

    2016-02-01

    The X-ray source RX J2015.6+3711 was discovered by ROSAT in 1996 and recently proposed to be a cataclysmic variable (CV). Here, we report on an XMM-Newton observation of RX J2015.6+3711 performed in 2014, where we detected a coherent X-ray modulation at a period of 7196 ± 11 s and discovered other significant (>6σ) small-amplitude periodicities which we interpret as the CV spin period and the sidebands of a possible ˜12-h periodicity, respectively. The 0.3-10 keV spectrum can be described by a power law (Γ = 1.15 ± 0.04) with a complex absorption pattern, a broad emission feature at 6.60 ± 0.01 keV, and an unabsorbed flux of (3.16 ± 0.05) × 10-12 erg cm-2 s-1. We observed a significant spectral variability along the spin phase, which can be ascribed mainly to changes in the density of a partial absorber and the power law normalization. Archival X-ray observations carried out by the Chandra satellite, and two simultaneous X-ray and UV/optical pointings with Swift, revealed a gradual fading of the source in the soft X-rays over the last 13 yr, and a rather stable X-ray-to-optical flux ratio (FX/FV ≈ 1.4-1.7). Based on all these properties, we identify this source with a magnetic CV, most probably of the intermediate polar type. The 2-h spin period makes RX J2015.6+3711, the second slowest rotator of the class, after RX J0524+4244 (`Paloma'; Pspin ˜ 2.3 h). Although we cannot unambiguously establish the true orbital period with these observations, RX J2015.6+3711 appears to be a key system in the evolution of magnetic CVs.

  17. New Close Binary Systems from the SDSS-I (Data Release Five) and the Search for Magnetic White Dwarfs in Cataclysmic Variable Progenitor Systems

    CERN Document Server

    Silvestri, Nicole M; Hawley, Suzanne L; West, Andrew A; Schmidt, Gary D; Liebert, James; Szkody, Paula; Mannikko, Lee; Wolfe, Michael A; Barentine, J C; Brewington, Howard J; Harvanek, Michael; Krzesinski, Jurik; Long, Dan; Schneider, Donald P; Snedden, Stephanie A

    2007-01-01

    We present the latest catalog of more than 1200 spectroscopically-selected close binary systems observed with the Sloan Digital Sky Survey through Data Release Five. We use the catalog to search for magnetic white dwarfs in cataclysmic variable progenitor systems. Given that approximately 25% of cataclysmic variables contain a magnetic white dwarf, and that our large sample of close binary systems should contain many progenitors of cataclysmic variables, it is quite surprising that we find only two potential magnetic white dwarfs in this sample. The candidate magnetic white dwarfs, if confirmed, would possess relatively low magnetic field strengths (B_WD < 10 MG) that are similar to those of intermediate-Polars but are much less than the average field strength of the current Polar population. Additional observations of these systems are required to definitively cast the white dwarfs as magnetic. Even if these two systems prove to be the first evidence of detached magnetic white dwarf + M dwarf binaries, th...

  18. ULTRACAM observations of SDSS J170213.26+322954.1 - an eclipsing cataclysmic variable in the period gap

    CERN Document Server

    Littlefair, S P; Marsh, T R; Gänsicke, B T

    2006-01-01

    We present high-speed, three-colour photometry of the eclipsing cataclysmic variable SDSS J170213.26+322954.1 (hereafter SDSS J1702+3229). This system has an orbital period of 2.4 hours, placing it within the ``period gap'' for cataclysmic variables. We determine the system parameters via a parameterized model of the eclipse fitted to the observed light curve by chi-squared minimization. We obtain a mass ratio of q = 0.215 +/- 0.015 and an orbital inclination i = 82.4 +- 0.4 degrees. The primary mass is M_w = 0.94 +/- 0.01 Msun. The secondary mass and radius are found to be Mr = 0.20 +/- 0.01 Msun and Rr = 0.243 +/- 0.013 Rsun respectively. We find a distance to the system of 440 +/- 30 pc, and an effective temperature for the secondary star of 3800 +/- 100 K (corresponding to a spectral type of M0 +/- 0.5V). Both the distance and effective temperature are consistent with previous values derived via spectroscopy of the red star. The secondary star is significantly less massive than expected for the orbital pe...

  19. Cataclysmic Variables — X-rays and Optical Activity in V1223 Sgr and V709 Cas

    Directory of Open Access Journals (Sweden)

    R. Gális

    2011-01-01

    Full Text Available Intermediate polars are a major fraction of all cataclysmic variables detected by INTEGRAL in hard X-ray. These objects have recently been proposed to be the dominant X-ray source population detected near the Galactic centre, and they also contribute significantly to X-ray diffuse Galactic ridge emission. Nevertheless, only 25% of all known intermediate polars have been detected in hard X-ray. This fact can be related to the activity state of these close interacting binaries.A multi-frequency (from optical to X-ray investigation of intermediate polars is essential for understanding the physical mechanisms responsible for the observed activity of these objects.

  20. Cyclic brightening in the short-period WZ Sge-type cataclysmic variable SDSS J080434.20+510349.2

    CERN Document Server

    Zharikov, S V; Neustroev, V V; Michel, R; Zurita, C; Echevarria, J; Bikmaev, I F; Pavlenko, E P; Jeon, Young- Beom; Valyavin, G G; Aviles, A

    2008-01-01

    We have observed a new cataclysmic variable (CV) SDSS J080434.20+510349.2 and study the origin of a long-term variability found in its light curve. Multi-longitude time-resolved photometric observations were carried out to analyze the uncommon behavior also found recently in two newly discovered CVs. This study of SDSS J080434.20+510349.2 mainly concerns the understanding of the nature of the observed double-humped light curve and its relation to a cyclic brightening occurring during quiescence. The observations were obtained early in 2007, when the object was at about V~17.1, 0.4 mag brighter than the pre-outburst magnitude. The light curve shows a sinusoidal variability with an amplitude of about 0.07 mag and a periodicity of 42.48 min, which is half of the orbital period of the system. In addition, we have observed two "mini-outbursts" of the system up to 0.6 mag, with a duration of about 4 days each. The "mini-outburst" had a symmetric profile and repeated in about 32 days. Subsequent monitoring of the sy...

  1. The post-outburst pulsations of the accreting white dwarf in the cataclysmic variable GW Librae

    CERN Document Server

    Chote, P

    2016-01-01

    We present new time-series photometry of the accreting pulsating white dwarf system GW Librae obtained in 2012 and 2013 at the University of Canterbury Mt John Observatory in New Zealand. Our 2012 data show the return of a $\\sim$19 minute periodicity that was previously detected in 2008. This pulsation mode was a dominant feature of our quality May 2012 data set, which consisted of six contiguous nights; a detailed analysis indicated a degree of frequency variability. We show by comparison with the previously identified pulsation modes that this periodicity is best explained as a new mode, and that the quasi-stability of the periods appears to be a general feature of the pulsations in these systems. We also find a previously unreported 3-hour modulation period, which we believe to be related to the known two and four hour periods of so far unknown origin.

  2. A NEW SUB-PERIOD-MINIMUM CATACLYSMIC VARIABLE WITH PARTIAL HYDROGEN DEPLETION AND EVIDENCE OF SPIRAL DISK STRUCTURE

    Energy Technology Data Exchange (ETDEWEB)

    Littlefield, C.; Garnavich, P.; Magno, K. [Physics Department, University of Notre Dame, Notre Dame, IN 46556 (United States); Applegate, A. [Physics Department, Georgian Court University, Lakewood, NJ 08701 (United States); Pogge, R. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Irwin, J.; Marion, G. H.; Kirshner, R. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Vinko, J. [Department of Optics, University of Szeged, Dom ter 9, H-6720 Szeged (Hungary)

    2013-06-15

    We present time-resolved spectroscopy and photometry of CSS 120422:111127+571239 (=SBS 1108+574), a recently discovered SU UMa-type dwarf nova whose 55 minute orbital period is well below the cataclysmic variable (CV) period minimum of {approx}78 minutes. In contrast with most other known CVs, its spectrum features He I emission of comparable strength to the Balmer lines, implying a hydrogen abundance less than 0.1 of long-period CVs-but still at least 10 times higher than that in AM CVn stars. Together, the short orbital period and remarkable helium-to-hydrogen ratio suggest that mass transfer in CSS 120422 began near the end of the donor star's main-sequence lifetime, meaning that this CV is a strong candidate progenitor of an AM CVn system as described by Podsiadlowski et al. Moreover, a Doppler tomogram of the H{alpha} line reveals two distinct regions of enhanced emission. While one is the result of the stream-disk impact, the other is probably attributable to spiral disk structure generated when material in the outer disk achieves a 2:1 orbital resonance with respect to the donor.

  3. A NEW SUB-PERIOD-MINIMUM CATACLYSMIC VARIABLE WITH PARTIAL HYDROGEN DEPLETION AND EVIDENCE OF SPIRAL DISK STRUCTURE

    International Nuclear Information System (INIS)

    We present time-resolved spectroscopy and photometry of CSS 120422:111127+571239 (=SBS 1108+574), a recently discovered SU UMa-type dwarf nova whose 55 minute orbital period is well below the cataclysmic variable (CV) period minimum of ∼78 minutes. In contrast with most other known CVs, its spectrum features He I emission of comparable strength to the Balmer lines, implying a hydrogen abundance less than 0.1 of long-period CVs—but still at least 10 times higher than that in AM CVn stars. Together, the short orbital period and remarkable helium-to-hydrogen ratio suggest that mass transfer in CSS 120422 began near the end of the donor star's main-sequence lifetime, meaning that this CV is a strong candidate progenitor of an AM CVn system as described by Podsiadlowski et al. Moreover, a Doppler tomogram of the Hα line reveals two distinct regions of enhanced emission. While one is the result of the stream-disk impact, the other is probably attributable to spiral disk structure generated when material in the outer disk achieves a 2:1 orbital resonance with respect to the donor.

  4. Barnes-Evans relations for dwarfs with an application to the determination of distances to cataclysmic variables

    CERN Document Server

    Beuermann, K

    2006-01-01

    Barnes-Evans type relations provide an empirical relationship between the surface brightness of stars and their color. They are widely used for measuring the distances to stars of known radii, as the Roche-lobe filling secondaries in cataclysmic variables (CVs). The calibration of the surface brightness of field dwarfs of near-solar metalicity with spectral types A0 to L8 covers all secondary spectral types detectable in CVs and related objects and will aid in the measurement of their distances. The calibrations are based on the radii of field dwarfs measured by the Infrared Flux Method and by interferometry. Published photometry is used and homogenized to the Cousins Rc and Ic and the CIT JHK photometric systems. The narrow band surface brightness at 7500A is based on our own and published spectrophotometry. Care is taken to select the dwarfs for near-solar metalicity, appropriate to CVs, and to avoid errors caused by unrecognized binarity. Relations are provided for the surface brightness in V, Rc, Ic, J, H...

  5. SDSSJ001153.08-064739.2, a cataclysmic variable with an evolved donor in the period gap

    CERN Document Server

    Rebassa-Mansergas, A; Copperwheat, C M; Justham, S; Gaensicke, B T; Schreiber, M R; Marsh, T R; Dhillon, V S

    2014-01-01

    Secondary stars in cataclysmic variables (CVs) follow a well defined period-density relation. Thus, canonical donor stars in CVs are generally low-mass stars of spectral type M. However, several CVs have been observed containing secondary stars which are too hot for their inferred masses. This particular configuration can be explained if the donor stars in these systems underwent significant nuclear evolution before they reached contact. In this paper we present SDSSJ001153.08-064739.2 as an additional example belonging to this peculiar type of CV and discuss in detail its evolutionary history. We perform spectroscopic and photometric observations and make use of available Catalina Real-Time Transient Survey photometry to measure the orbital period of SDSSJ001153.08-064739.2 as 2.4 hours and estimate the white dwarf (Mwd>0.65Msun) and donor star (0.21Msun

  6. Dwarf Nova Oscillations and Quasi-Periodic Oscillations in Cataclysmic Variables II. A Low Inertia Magnetic Accretor Model

    CERN Document Server

    Warner, B; Warner, Brian; Woudt, Patrick A.

    2002-01-01

    The Dwarf Nova Oscillations observed in Cataclysmic Variable (CV) stars are interpreted in the context of a Low Inertia Accretor model, in which accretion on to an equatorial belt of the white dwarf primary causes the belt to vary its angular velocity. The rapid deceleration phase is attributed to propellering. Evidence that temporary expulsion rather than accretion of gas occurs during this phase is obtained from the large drop in EUV flux. We show that the QPOs are most probably caused by a vertical thickening of the disc, moving as a travelling wave near the inner edge of the disc. This alternately obscures and `reflects' radiation from the central source, and is visible even in quite low inclination systems. A possible excitation mechanism, caused by winding up and reconnection of magnetic field lines, is proposed. We apply the model, deduced largely from VW Hyi observations, to re-interpret observations of SS Cyg, OY Car, UX UMa, V2051 Oph, V436 Cen and WZ Sge. In the last of these we demonstrate the exi...

  7. Dominance of Magnetic Cataclysmic Variables in the Resolved Galactic Ridge X-ray Emission of the Limiting Window

    CERN Document Server

    Hong, JaeSub

    2012-01-01

    The diffuse appearance of the Galactic Ridge X-ray Emission (GRXE) has been puzzling since its discovery due to lack of compelling theories for sustainable hot diffuse X-ray emission in the Galactic plane. Recently (Revnivtsev et al. 2009; R09) claimed that about 90% of the 6.5-7.1 keV X-ray flux from a small section of a low extinction region at 1.4 degree south of the Galactic Center has been resolved to discrete sources with 2-10 keV L_X > 4x10^{-16} erg s cm^-2, using ultra-deep (1 Ms) Chandra ACIS-I observations. They also concluded thatcoronally active stars such as active binaries (ABs) contribute about 60% of the resolved flux. However, our recent discovery of a large population of magnetic cataclysmic variables (MCVs) in the same region suggests their significant role in the resolved hard X-ray flux. In addition, deep X-ray surveys of other several Galactic Bulge fields over the past decade have indicated that MCVs are likely the major contributor in the hard X-ray emission above 2-3 keV. To solve th...

  8. Galactic model parameters of cataclysmic variables: Results from a new absolute magnitude calibration with 2MASS and WISE

    CERN Document Server

    Ozdonmez, A; Bilir, S

    2014-01-01

    In order to determine the spatial distribution, Galactic model parameters and luminosity function of cataclysmic variables (CVs), a $J$-band magnitude limited sample of 263 CVs has been established using a newly constructed period-luminosity-colours (PLCs) relation which includes $J$, $K_{s}$ and $W1$-band magnitudes in 2MASS and WISE photometries, and the orbital periods of the systems. This CV sample is assumed to be homogeneous regarding to distances as the new PLCs relation is calibrated with new or re-measured trigonometric parallaxes. Our analysis shows that the scaleheight of CVs is increasing towards shorter periods, although selection effects for the periods shorter than 2.25 h dramatically decrease the scaleheight: the scaleheight of the systems increases from 192 pc to 326 pc as the orbital period decreases from 12 to 2.25h. The $z$-distribution of all CVs in the sample is well fitted by an exponential function with a scaleheight of 213$^{+11}_{-10}$ pc. However, we suggest that the scaleheight of ...

  9. RX J15542+2721: An Apparently Magnetic Cataclysmic Variable with a 2.53 Hour Orbital Period

    Science.gov (United States)

    Thorstensen, John R.; Fenton, William H.

    2002-01-01

    Time-resolved spectroscopy and photometry of the cataclysmic variable (CV) star RX J15542+2721 show it to have an orbital period of 2.53 hr, putting it in the middle of the so-called CV period gap from 2 to 3 hr. Observations taken 2001 March show it in a low state with relatively weak emission lines and a strong contribution from a secondary star near type M4. Contemporaneous I-band differential photometry shows ellipsoidal variations. In 2001 May the emission lines were stronger and of higher excitation, with prominent He II λ4686, the secondary star less visible, and the ellipsoidal variations masked by flickering. By 2001 June the object had returned to a state similar to the March observations. RX J15542+2721 appears to be an AM Her-type magnetic CV. Archival plate material, although sparse, indicates that the object may spend most of its time close to minimum light. This, and a weak indication of a 2-3 hr ``trough'' in the histogram of AM Her star orbital periods, suggest that the mass transfer rate may be somewhat depressed among AM Her stars in this period range. The spectral type of the secondary and the orbital period are consistent with a distance of roughly 210 pc. A proper motion μ=28+/-4 mas yr-1 is found, corresponding to a transverse velocity ~28 km s-1 at the nominal distance. The radial velocity variations of the M dwarf secondary are detected, and their phase is essentially as expected based on the ellipsoidal variations. The data suggest fairly typical masses for the system components, and a more detailed study might constrain the white dwarf mass rather accurately.

  10. Galactic model parameters of cataclysmic variables: Results from a new absolute magnitude calibration with 2MASS and WISE

    Science.gov (United States)

    Özdönmez, A.; Ak, T.; Bilir, S.

    2015-01-01

    In order to determine the spatial distribution, Galactic model parameters and luminosity function of cataclysmic variables (CVs), a J-band magnitude limited sample of 263 CVs has been established using a newly constructed period-luminosity-colours (PLCs) relation which includes J,Ks and W1-band magnitudes in 2MASS and WISE photometries, and the orbital periods of the systems. This CV sample is assumed to be homogeneous regarding to distances as the new PLCs relation is calibrated with new or re-measured trigonometric parallaxes. Our analysis shows that the scaleheight of CVs is increasing towards shorter periods, although selection effects for the periods shorter than 2.25 h dramatically decrease the scaleheight: the scaleheight of the systems increases from 192 pc to 326 pc as the orbital period decreases from 12 to 2.25 h. The z-distribution of all CVs in the sample is well fitted by an exponential function with a scaleheight of 213-10+11 pc. However, we suggest that the scaleheight of CVs in the Solar vicinity should be ∼300 pc and that the scaleheights derived using the sech2 function should be also considered in the population synthesis models. The space density of CVs in the Solar vicinity is found 5.58(1.35)×10-6 pc-3 which is in the range of previously derived space densities and not in agreement with the predictions of the population models. The analysis based on the comparisons of the luminosity function of white dwarfs with the luminosity function of CVs in this study show that the best fits are obtained by dividing the luminosity functions of white dwarfs by a factor of 350-450.

  11. Doppler Tomography of Cataclysmic Variables with a 6.5-m class Telescope

    OpenAIRE

    Echevarría, J.

    2007-01-01

    Se est llevando a cabo un proyecto a largo plazo de espectroscop a de alta dispersi n (R 20000) para observar y analizar una muestra de variables catacl smicas con el telescopio de 2.1-m en el Observatorio Astron mico Nacional en San Pedro M rtir y el espectr grafo echelle. La herramienta principal para este an lisis es la tomograf a Doppler. En esta contribuci n presentamos nuestro trabajo y abordamos la pregunta: >C mo podr amos mejorar este proyecto con un telescopio de clas...

  12. Doppler Tomography of Cataclysmic Variables with a 6.5-m class Telescope

    Directory of Open Access Journals (Sweden)

    J. Echevarría

    2007-01-01

    Full Text Available Se est llevando a cabo un proyecto a largo plazo de espectroscop a de alta dispersi n (R 20000 para observar y analizar una muestra de variables catacl smicas con el telescopio de 2.1-m en el Observatorio Astron mico Nacional en San Pedro M rtir y el espectr grafo echelle. La herramienta principal para este an lisis es la tomograf a Doppler. En esta contribuci n presentamos nuestro trabajo y abordamos la pregunta: >C mo podr amos mejorar este proyecto con un telescopio de clase 6.5-m?

  13. The optical identification of H2252-035 with a cataclysmic variable

    International Nuclear Information System (INIS)

    An improved position is presented for the X-ray source H2252-033 using the Ariel V Sky Survey Instrument, and precise positioning using the Scanning Modulation Collimator on HEAO-1. The source is identified optically with a 13th magnitude emission-line object, which is probably a white dwarf binary with a well-formed accretion disc, with similarities to the dwarf novae (e.g. SS Cyg) at minimum. (author)

  14. Rotating winds from accretion disks in cataclysmic variables eclipse modeling of V347 Puppis

    CERN Document Server

    Shlosman, I; Mauche, C W; Shlosman, Isaac; Vitello, Peter; Mauche, Christopher W

    1995-01-01

    We study the eclipsing nova-like variable V347 Pup by matching its UV emission line profiles in and out of eclipse to synthetic lines using a 3D kinematic and radiation transfer model. Our results support the accretion disk origin of winds in non-magnetic CVs as opposite to the WD origin. Our main point concerns the importance of rotation for the UV emission line shapes in such systems. In particular, we show that the narrowing of the UV emission lines in V347 Pup during eclipse can be easily explained by the eclipse of the innermost part of the wind by the secondary and the resulting reduction in the contribution of rotational broadening to the width of the lines. During the eclipse, the residual line flux is very sensitive to the maximal temperature of disk radiation. Good fits for reasonable mass-loss rates have been obtained for maximum disk temperatures of 50,000 degrees. This constraint was imposed either by leveling off the inner disk temperature profiles, in agreement with recent observations of some ...

  15. Hydrodynamic Models of Line-Driven Accretion Disk Winds in Cataclysmic Variables

    Directory of Open Access Journals (Sweden)

    Nicolas Antonio Pereyra

    2001-01-01

    Full Text Available We developed several alpha-disk models for line-driven winds from cataclysmi c variables. Using 1-D analytic models we explore the conditions necessary for th e existence of a wind, and the dependence of speed and mass-loss with radius. Using a 2-D isothermal model we explore the effects of centrifugal forces, showing that they cause stream lines to collide producing enhanced density regions in the wind. Without these effects, the mass-loss rates obtained would be too low to produce the optical depths required to explain P-Cygni profiles, showing the necessity of 2-D models. Using a 2-D adiabatic model we calculate mass-losses, terminal velocities, and C IV line profiles for various angles. For a disk with Lsun around a white dwarf of 0.6 Msun and 0.01 Rsun, we obtain dot Mwind=8 × 10-12 Msun yr-1, and a terminal velocity ~ 3000 km s-1. The profiles obtained are consistent with observations, in particular with the absorption of the blue-shifted component, the velocities implied by absorption components, the width of emission components, and the strong dependence with inclination.

  16. Exploring inside-out Doppler tomography: non-magnetic cataclysmic variables

    CERN Document Server

    Kotze, E J; McBride, V A

    2015-01-01

    Doppler tomography is a technique that has revolutionised the interpretation of the phase-resolved spectroscopic observations of interacting binary systems. We present the results of our investigation of reversing the velocity axis to create an inside-out Doppler coordinate framework with the intent to expose overly compacted and enhance washed out emission details in the standard Doppler framework. The inside-out tomogram is constructed independently of the standard tomogram by directly projecting phase-resolved spectra onto an inside-out velocity coordinate frame. For the inside-out framework, the zero-velocity origin is transposed to the outer circumference and the maximum velocities to the origin of the velocity space. We test the technique on a simulated system and two real systems with easily identifiable features, namely the accretion disc and bright spot in WZ Sge, and spiral shocks in IP Peg. Our tests show that there is a redistribution of the relative brightness of emission components throughout th...

  17. V344 LYRAE: A TOUCHSTONE SU UMa CATACLYSMIC VARIABLE IN THE KEPLER FIELD

    International Nuclear Information System (INIS)

    We report on the analysis of the Kepler short-cadence (SC) light curve of V344 Lyr obtained during 2009 June 20 through 2010 March 19 (Q2-Q4). The system is an SU UMa star showing dwarf nova (DN) outbursts and superoutbursts, and promises to be a touchstone for CV studies for the foreseeable future. The system displays both positive and negative superhumps with periods of 2.20 and 2.06 hr, respectively, and we identify an orbital period of 2.11 hr. The positive superhumps have a maximum amplitude of ∼0.25 mag, the negative superhumps have a maximum amplitude of ∼0.8 mag, and the orbital period at quiescence has an amplitude of ∼0.025 mag. The quality of the Kepler data is such that we can test vigorously the models for accretion disk dynamics that have been emerging in the past several years. The SC data for V344 Lyr are consistent with the model that two physical sources yield positive superhumps: early in the superoutburst, the superhump signal is generated by viscous dissipation within the periodically flexing disk, but late in the superoutburst, the signal is generated as the accretion stream bright spot sweeps around the rim of the non-axisymmetric disk. The disk superhumps are roughly anti-phased with the stream/late superhumps. The V344 Lyr data also reveal negative superhumps arising from accretion onto a tilted disk precessing in the retrograde direction and suggest that negative superhumps may appear during the decline of DN outbursts. The period of negative superhumps has a positive P-dot in between outbursts.

  18. X-ray emission line spectroscopy of cataclysmic variables. II. Temperatures and densities from line ratios in the Chandra HETG band

    Energy Technology Data Exchange (ETDEWEB)

    Schlegel, E. M.; Shipley, H. V. [Department of Physics and Astronomy, University of Texas-San Antonio, San Antonio, TX 78249 (United States); Rana, V. R. [Space Radiation Laboratory, Caltech, Pasadena, CA 91125 (United States); Barrett, P. E. [US Naval Observatory, Washington, DC 20392-5420 (United States); Singh, K. P., E-mail: eric.schlegel@utsa.edu, E-mail: vrana@srl.caltech.edu, E-mail: barrett.paul@usno.navy.mil, E-mail: singh@tifr.res.in [Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai (India)

    2014-12-10

    We summarize the results of a line-by-line fitting analysis of the available spectra obtained using the Chandra High-Energy Transmission Grating. We confirm the existence of broad ionization and electron temperature ranges and high number densities in cataclysmic variables (CVs) of all subtypes. Temperatures range from ∼0.4 keV to ∼5-10 keV or more with a broad range detected in any given CV. In other words, single-temperature models do not describe the line emission. Number densities also cover a broad range, from 10{sup 12} to >10{sup 16} cm{sup –3}. We demonstrate that much of the plasma is in a nonequilibrium state; the Fe emission, however, may arise from plasma in the ionization equilibrium.

  19. X-ray emission line spectroscopy of cataclysmic variables. II. Temperatures and densities from line ratios in the Chandra HETG band

    International Nuclear Information System (INIS)

    We summarize the results of a line-by-line fitting analysis of the available spectra obtained using the Chandra High-Energy Transmission Grating. We confirm the existence of broad ionization and electron temperature ranges and high number densities in cataclysmic variables (CVs) of all subtypes. Temperatures range from ∼0.4 keV to ∼5-10 keV or more with a broad range detected in any given CV. In other words, single-temperature models do not describe the line emission. Number densities also cover a broad range, from 1012 to >1016 cm–3. We demonstrate that much of the plasma is in a nonequilibrium state; the Fe emission, however, may arise from plasma in the ionization equilibrium.

  20. Time resolved spectroscopy and photometry of three little known bright cataclysmic variables: LS IV -08$^{\\rm o}$ 3, HQ Monocerotis and ST Chamaeleontis

    CERN Document Server

    Bruch, Albert

    2016-01-01

    As part of a project to better characterize comparatively bright but so far little studied cataclysmic variables in the southern hemisphere, we have obtained spectroscopic and photometric data of the nova-like variables LS IV -08$^{\\rm o}$ 3 and HQ Mon, and of the Z Cam type dwarf nova ST Cha. The spectra of all systems are as expected for their respective types. We derive improved orbital ephemeris of LS IV -08$^{\\rm o}$ 3 and map its accretion disk in the light of the H$\\alpha$ emission using Doppler tomography. We find that the emission has a two component origin, arising in the outer parts of the accretion disk and possibly on the illuminated face of the secondary star. The light curve of LS IV -08$^{\\rm o}$ 3 exhibits a low level of flickering and indications for a modulation on the orbital period. Spectroscopy of HQ Mon suggests an orbital period of $\\approx$5.15 hours which is incompatible with previous (uncertain) estimates. The light curves show the typical low scale flickering of UX UMa type nova-li...

  1. High Speed photometry of faint Cataclysmic Variables I. V359 Cen, XZ Eri, HY Lup, V351 Pup, V630 Sgr, YY Tel, CQ Vel, CE-315

    CERN Document Server

    Woudt, P A; Woudt, Patrick A.; Warner, Brian

    2001-01-01

    The first results of a photometric survey of faint Cataclysmic Variables are presented. V359 Cen is an SU UMa star with a period of 112 min. Even though observed at quiescence, the mass transfer rate in this old nova may be sufficiently high that in such a short period system (with its implied small mass ratio) the disc may be excited into an elliptical shape with the result that the observed brightness modulation gives a superhump period rather than an orbital period. XZ Eri is an eclipsing dwarf nova with an orbital period (P(orb)) of 88.1 min. HY Lup has only slight variability. V351 Pup, the remnant of Nova Puppis 1991, has P(orb) = 2.837 h and a light curve that strongly resembles that of the magnetic Nova Cyg 1975. V630 Sgr is the first nova remnant that has both positive superhumps (P(sh) = 2.980 h) and eclipses (P(orb) = 2.831 h). The YY Tel identification is somewhat uncertain. The correct identification for CQ Vel is provided from discovery of its flickering activity. The light curve of CE-315, a re...

  2. Problems Identifying Independent and Dependent Variables

    Science.gov (United States)

    Leatham, Keith R.

    2012-01-01

    This paper discusses one step from the scientific method--that of identifying independent and dependent variables--from both scientific and mathematical perspectives. It begins by analyzing an episode from a middle school mathematics classroom that illustrates the need for students and teachers alike to develop a robust understanding of…

  3. MOCCA-SURVEY database I. Accreting white dwarf binary systems in globular clusters -- II. Cataclysmic variables -- progenitors and population at birth

    CERN Document Server

    Belloni, Diogo; Rocha-Pinto, Helio J; Leigh, Nathan; Askar, Abbas

    2016-01-01

    This is the second in a series of papers associated with cataclysmic variables (CVs) and related objects, formed in a suite of simulations for globular cluster evolution performed with the MOCCA Monte Carlo code. We study the properties of our simulated CV populations throughout the entire cluster evolution. We find that dynamics extends the range of binary CV progenitor properties, causing CV formation from binary progenitors that would otherwise not become CVs. The CV formation rate in our simulations can be separated into two regimes: an initial burst ($\\lesssim$ 1 Gyr) connected with the formation of the most massive WDs, followed by a nearly constant formation rate. This result holds for all models regardless of the adopted initial conditions, even when most CVs form dynamically. Given the cluster age-dependence of CV properties, we argue that direct comparisons to observed Galactic field CVs could be misleading, since cluster CVs can be up to 4 times older than their field counterparts. Our results also...

  4. Very-high-energy gamma-ray observations of pulsar wind nebulae and cataclysmic variable stars with MAGIC and development of trigger systems for IACTs

    Science.gov (United States)

    Lopez-Coto, Ruben

    2015-07-01

    lowest possible energy threshold with the LSTs of CTA. Together with this work, the trigger of the MAGIC telescopes was improved. We have simulated, tested and commissioned a new concept of stereoscopic trigger. This new system, that uses the information of the position of the showers on each of the MAGIC cameras, is dubbed "Topo-trigger". The scientific fraction of the thesis deals with galactic sources observed with the MAGIC telescopes. In Part III, I talk about the analysis of the VHE γ-ray emission of Pulsar Wind Nebulae (PWNe): the discovery of VHE γ-ray emission from the puzzling PWN 3C 58, the likely remnant of the SN 1181 AD and the weakest PWN detected at VHE to date; the characterization of the VHE tail of the Crab nebula by observing it at the highest zenith angles; and the search for an additional inverse Compton component during the Crab nebula flares reported by Fermi-LAT in the synchrotron regime. Part IV is concerned with searches for VHE γ-ray emission of cataclysmic variable stars. I studied, on a multiwavelength context, the VHE γ-ray nature of the previously claimed pulsed γ-ray emission of the cataclysmic variable AE Aqr. I also performed observations of novae and a dwarf nova to pinpoint the ac- celeration mechanisms taking place in this kind of objects and to discover a putative hadronic component of the soft γ-ray emission. A conclusion chapter summarizes all the work performed and lists prospects related with the topics treated in this thesis.

  5. Time dependence of the UV resonance lines in the cataclysmic variables SU UMa, RX And and 0623+71

    International Nuclear Information System (INIS)

    We present IUE observations of the dwarf novae SU UMa and RX And, and of the nova-like variable 0623 + 71. At the time of observation, SU UMa and RX And were in outburst. All three systems show variability in the wind-formed UV resonance lines of N v λ 1240, Si IV λ 1397 and C IV λ 1549 on timescale of hours. The amplitude of variation is smallest in RX And and largest in 0623 + 71. There is evidence that the variations observed in SU UMa's UV spectrum repeat on the orbital period. Our observations of SU UMa also reveal variability in the continuum flux during the decline from outburst maximum that is much more marked in the UV than at optical wavelengths. (author)

  6. The accretion disk in the post period-minimum cataclysmic variable SDSS J080434.20+510349.2

    CERN Document Server

    Zharikov, S; Aviles, A; Michel, R; Gonzalez-Buitrago, D; Garcia-Diaz, Ma T

    2012-01-01

    This study of SDSS0804 is primarily concerned with the double-hump shape in the light curve and its connection with the accretion disk in this bounce-back system. Time-resolved photometric and spectroscopic observations were obtained to analyze the behavior of the system between superoutbursts. A geometric model of a binary system containing a disk with two outer annuli spiral density waves was applied to explain the light curve and the Doppler tomography. Observations were carried out during 2008-2009, after the object's magnitude decreased to V~17.7(0.1) from the March 2006 eruption. The light curve clearly shows a sinusoid-like variability with a 0.07 mag amplitude and a 42.48 min periodicity, which is half of the orbital period of the system. In Sept. 2010, the system underwent yet another superoutburst and returned to its quiescent level by the beginning of 2012. This light curve once again showed a double-humps, but with a significantly smaller ~0.01mag amplitude. Other types of variability like a "mini...

  7. US 943 - A 19th mag eclipsing cataclysmic variable with a period of 2 hr 3.8 min

    Science.gov (United States)

    Howell, S. B.; Warnock, A.; Mason, K. O.; Reichert, G. A.; Kreidl, T. J.

    1988-01-01

    The high-latitude, V equals about 19.5, blue variable star US 943 is found to be an eclipsing binary with an orbital period of 2.06 hr. The light curve is dominated by an orbital hump which has an amplitude of 0.9 mag in V and is centered about 0.17 orbital cycles before the 1.5-mag deep eclipse. There is evidence that the eclipse has at least two components. The overall appearance of the star is that of a dwarf nova in quiescence, a conclusion that is supported by the observation of a subsequent bright state (V equals about 15) suggesting a dwarf nova outburst.

  8. New Low Accretion-Rate Magnetic Binary Systems and their Significance for the Evolution of Cataclysmic Variables

    CERN Document Server

    Schmidt, G D; Vanlandingham, K M; Anderson, S F; Barentine, J C; Brewington, H J; Hall, P B; Harvanek, M; Kleinman, S J; Krzesínski, J; Long, D; Margon, B; Neilsen, E H; Newman, P R; Nitta, A; Schneider, D P; Snedden, S A

    2005-01-01

    Discoveries of two new white dwarf plus M star binaries with striking optical cyclotron emission features from the Sloan Digital Sky Survey (SDSS) brings to six the total number of X-ray faint, magnetic accretion binaries that accrete at rates 3 hr. Optical surveys for the cyclotron harmonics appear to be the only means of discovery, so the space density of pre-Polars could rival that of Polars, and the binaries provide an important channel of progenitors (in addition to the asynchronous Intermediate Polars). Both physical and SDSS observational selection effects are identified that may help to explain the clumping of all six systems in a narrow range of magnetic field strength around 60 MG.

  9. Swift X-ray telescope observations of the nova-like cataclysmic variables MV Lyr, BZ Cam, and V592 Cas

    International Nuclear Information System (INIS)

    We present a total of ∼45 ks (3 × 15 ks) of Swift X-Ray Telescope (XRT) observations for three nonmagnetic nova-like (NL) cataclysmic variables (CVs; MV Lyr, BZ Cam, V592 Cas) in order to study characteristics of boundary layers (BLs) in CVs. The nonmagnetic NLs are found mostly in a state of high mass accretion rate (≥1 × 10–9 M ☉ yr–1), and some show occasional low states. Using the XRT data, we find optically thin multiple-temperature cooling flow type emission spectra with X-ray temperatures (kT max) of 21-50 keV. These hard X-ray-emitting BLs diverge from simple isobaric cooling flows, indicating X-ray temperatures that are of virial values in the disk. In addition, we detect power-law emission components from MV Lyr and BZ Cam and plausibly from V592 Cas, which may be a result of the Compton scattering of the optically thin emission from the fast wind outflows in these systems and/or Compton upscattering of the soft disk photons. The X-ray luminosities of the (multitemperature) thermal plasma emission in the 0.1-50.0 keV range are (0.9-5.0) × 1032 erg s–1. The ratio of the X-ray and disk luminosities (calculated from the UV-optical wavelengths) yields an efficiency (Lx /L disk) ∼ 0.01-0.001. Given this non-radiative ratio for the X-ray-emitting BLs with no significant optically thick blackbody emission in the soft X-rays (consistent with ROSAT observations), together with the high/virial X-ray temperatures, we suggest that high-state NL systems may have optically thin BLs merged with ADAF-like flows and/or X-ray coronae. In addition, we note that the axisymmetric bipolar and/or rotation-dominated fast-wind outflows detected in these three NLs (particularly BZ Cam and V592 Cas) or some other NL may also be explained in the context of ADAF-like BL regions.

  10. Swift X-ray telescope observations of the nova-like cataclysmic variables MV Lyr, BZ Cam, and V592 Cas

    Energy Technology Data Exchange (ETDEWEB)

    Balman, Şölen [Department of Physics, Middle East Technical University, 06800 Ankara (Turkey); Godon, Patrick; Sion, Edward M., E-mail: solen@astroa.physics.metu.edu.tr, E-mail: patrick.godon@villanova.edu, E-mail: edward.sion@villanova.edu [Astrophysics and Space Sciences, Villanova University, 800 Lancaster Avenue, Villanova, PA 19085 (United States)

    2014-10-10

    We present a total of ∼45 ks (3 × 15 ks) of Swift X-Ray Telescope (XRT) observations for three nonmagnetic nova-like (NL) cataclysmic variables (CVs; MV Lyr, BZ Cam, V592 Cas) in order to study characteristics of boundary layers (BLs) in CVs. The nonmagnetic NLs are found mostly in a state of high mass accretion rate (≥1 × 10{sup –9} M {sub ☉} yr{sup –1}), and some show occasional low states. Using the XRT data, we find optically thin multiple-temperature cooling flow type emission spectra with X-ray temperatures (kT {sub max}) of 21-50 keV. These hard X-ray-emitting BLs diverge from simple isobaric cooling flows, indicating X-ray temperatures that are of virial values in the disk. In addition, we detect power-law emission components from MV Lyr and BZ Cam and plausibly from V592 Cas, which may be a result of the Compton scattering of the optically thin emission from the fast wind outflows in these systems and/or Compton upscattering of the soft disk photons. The X-ray luminosities of the (multitemperature) thermal plasma emission in the 0.1-50.0 keV range are (0.9-5.0) × 10{sup 32} erg s{sup –1}. The ratio of the X-ray and disk luminosities (calculated from the UV-optical wavelengths) yields an efficiency (L{sub x} /L {sub disk}) ∼ 0.01-0.001. Given this non-radiative ratio for the X-ray-emitting BLs with no significant optically thick blackbody emission in the soft X-rays (consistent with ROSAT observations), together with the high/virial X-ray temperatures, we suggest that high-state NL systems may have optically thin BLs merged with ADAF-like flows and/or X-ray coronae. In addition, we note that the axisymmetric bipolar and/or rotation-dominated fast-wind outflows detected in these three NLs (particularly BZ Cam and V592 Cas) or some other NL may also be explained in the context of ADAF-like BL regions.

  11. Terminal Cataclysm Epistemology: A Cataclysm that Never Happened?

    Science.gov (United States)

    Hartmann, W. K.

    2015-07-01

    The "terminal cataclysm" or "late heavy bombardment," concept of the last 40 years exhibits curious epistemology, with changing definitions and inconsistent evidence. A sharp "spike" in solar system basin formation at 3.9 Ga ago is untenable.

  12. Stochastic search variable selection for identifying multiple quantitative trait loci.

    Science.gov (United States)

    Yi, Nengjun; George, Varghese; Allison, David B

    2003-07-01

    In this article, we utilize stochastic search variable selection methodology to develop a Bayesian method for identifying multiple quantitative trait loci (QTL) for complex traits in experimental designs. The proposed procedure entails embedding multiple regression in a hierarchical normal mixture model, where latent indicators for all markers are used to identify the multiple markers. The markers with significant effects can be identified as those with higher posterior probability included in the model. A simple and easy-to-use Gibbs sampler is employed to generate samples from the joint posterior distribution of all unknowns including the latent indicators, genetic effects for all markers, and other model parameters. The proposed method was evaluated using simulated data and illustrated using a real data set. The results demonstrate that the proposed method works well under typical situations of most QTL studies in terms of number of markers and marker density. PMID:12871920

  13. Information-Theoretic Methods for Identifying Relationships among Climate Variables

    CERN Document Server

    Knuth, Kevin H; Rossow, William B

    2014-01-01

    Information-theoretic quantities, such as entropy, are used to quantify the amount of information a given variable provides. Entropies can be used together to compute the mutual information, which quantifies the amount of information two variables share. However, accurately estimating these quantities from data is extremely challenging. We have developed a set of computational techniques that allow one to accurately compute marginal and joint entropies. These algorithms are probabilistic in nature and thus provide information on the uncertainty in our estimates, which enable us to establish statistical significance of our findings. We demonstrate these methods by identifying relations between cloud data from the International Satellite Cloud Climatology Project (ISCCP) and data from other sources, such as equatorial pacific sea surface temperatures (SST).

  14. Identifying relevant positions in proteins by Critical Variable Selection.

    Science.gov (United States)

    Grigolon, Silvia; Franz, Silvio; Marsili, Matteo

    2016-06-21

    Evolution in its course has found a variety of solutions to the same optimisation problem. The advent of high-throughput genomic sequencing has made available extensive data from which, in principle, one can infer the underlying structure on which biological functions rely. In this paper, we present a new method aimed at the extraction of sites encoding structural and functional properties from a set of protein primary sequences, namely a multiple sequence alignment. The method, called critical variable selection, is based on the idea that subsets of relevant sites correspond to subsequences that occur with a particularly broad frequency distribution in the dataset. By applying this algorithm to in silico sequences, to the response regulator receiver and to the voltage sensor domain of ion channels, we show that this procedure recovers not only the information encoded in single site statistics and pairwise correlations but also captures dependencies going beyond pairwise correlations. The method proposed here is complementary to statistical coupling analysis, in that the most relevant sites predicted by the two methods differ markedly. We find robust and consistent results for datasets as small as few hundred sequences that reveal a hidden hierarchy of sites that are consistent with the present knowledge on biologically relevant sites and evolutionary dynamics. This suggests that critical variable selection is capable of identifying a core of sites encoding functional and structural information in a multiple sequence alignment. PMID:26974515

  15. Psychological Variables for Identifying Susceptibility to Mental Disorders in Medical

    Directory of Open Access Journals (Sweden)

    Rosa Sender

    2004-05-01

    Full Text Available Introduction: This study analyses some psychological variables related to susceptibility to mental disorders in medical students. Methods: A sample of 209 first- and second-year medical students was evaluated using the State and Trait Anxiety Inventory (STAI, and three questionnaires: Sensitivity to Punishment and Sensitivity to Reward Questionnaire (SPSRQ, General Health Questionnaire (GHQ-28 and UNCAHS scale of STRAIN. Results: Thirty percent of the students suffered from emotional distress as measured by de GHQ-28, and showed significantly higher scores on trait anxiety, sensitivity to punishment and reward scales, and had higher levels of strain both in the academic environment and their personal life. Women scored significantly higher than men on trait anxiety and sensitivity to reward. Logistical regression found that trait anxiety and strain in non-academic life were the best predictors of the development of a mental disorder. Conclusions: The study confirms the usefulness of the STAI for detecting psychological distress and the validity of the SPSRQ for identifying subjects likely to present emotional distress when facing high environmental demands. Subjects most likely to present with mental illness are those who evaluate their personal (non-academic lives as more stressful.

  16. External and Internal Scanning: Identifying Variables that Affect Your School.

    Science.gov (United States)

    Herman, Jerry J.

    1989-01-01

    Principals and others involved in strategic or operational planning decisions need a data collection process with a systematic internal and external scanning structure. Internal data originate from students, school climate, finance, and human resource variables. External data include demography, government finance and budgetary allocations,…

  17. Psychological Variables for Identifying Susceptibility to Mental Disorders in Medical

    OpenAIRE

    Rosa Sender; Manel Salamero; Manuel Valdés

    2004-01-01

    Introduction: This study analyses some psychological variables related to susceptibility to mental disorders in medical students. Methods: A sample of 209 first- and second-year medical students was evaluated using the State and Trait Anxiety Inventory (STAI), and three questionnaires: Sensitivity to Punishment and Sensitivity to Reward Questionnaire (SPSRQ), General Health Questionnaire (GHQ-28) and UNCAHS scale of STRAIN. Results: Thirty percent of the students suffered from emotional distr...

  18. On the Problem of Identifying the Appropriate Price Variable to Study the Price-Volume Relation

    OpenAIRE

    Imad A Moosa; Talla M. Al-Deehani

    2009-01-01

    Model selection tests and criteria are employed to identify empirically the most appropriate price variable for the purposeof studying the price-volume relation. Five different price variables are considered as explanatory variables in modelselection tests, which are carried out on a bilateral basis using data on stock prices and trading volume in eleven markets/indices. The results show that the most appropriate price variable varies from one market to another although two pricevariables app...

  19. Survey on statistical inferences in weakly-identified instrumental variable models

    OpenAIRE

    Mikusheva, Anna

    2013-01-01

    This paper provides a brief review of the current state of knowledge on the topic of weakly-identified instrumental variable regression. We describe the essence of the problem of weak identification, possible methods for detecting it in applied work as well as methods robust to weak identification. Special attention is devoted to the question of hypothesis testing in the presence of weak identification.

  20. Survey on Statistical Inferences in Weakly-Identified Instrumental Variable Models

    OpenAIRE

    Mikusheva, Anna

    2013-01-01

    This paper provides a brief review of the current state of knowledge on the topic of weakly-identified instrumental variable regression. We describe the essence of the problem of weak identification, possible methods for detecting it in applied work as well as methods robust to weak identification. Special attention is devoted to the question of hypothesis testing in the presence of weak identification.

  1. Identifying Variables Influencing Tenant Affordability to Pay Rent in Ipoh City Council Public Housing

    Directory of Open Access Journals (Sweden)

    Salleh Nor Aini

    2014-01-01

    Full Text Available Affordability reflects the challenges faced by households in balancing the real cost of housing and non housing expenditures against income limitations placed upon the household. Various methods have been introduced to measure housing affordability among households. This study was undertaken to identify the variables influencing tenant affordability to pay rent. Data was obtained through questionnaire distribution on 350 MBI public housing tenants using the strata sampling technique. This study found that only ethnic group variable significantly influenced the ability to pay rent. The study’s findings proved that different ethnic groups faced different housing costs liabilities attributable to different socioeconomic status.

  2. History of the Terminal Cataclysm Concept: A Cataclysm That Never Happened?

    Science.gov (United States)

    Hartmann, William K.

    2014-11-01

    The “terminal cataclysm” (or “late heavy bombardment”) concept of the last 40 years exhibits curious epistemology, with changing definitions and inconsistent evidence.Pre-Apollo evidence showed that the impact rate prior to ~3.5 Ga ago averaged ~150x the post-mare rate [1]. In 1973-4, Tera et al. [2,3] introduced the term “terminal cataclysm,” widespread metamorphism ~3.9 Ga ago, possibly caused by the Imbrium impact [3, p.15], or more likely by “formation of several major basins [in a] short time interval (less than 0.2AE)” [3, p.18]. In 1990, Ryder [4] reported a strong spike in ages for Apollo impact melt rocks ~3.8-4.0 Ga ago, and proposed this as proof that a Moon-wide cataclysmic bombardment occurred at that time, with no earlier cratering. Three inconsistencies soon appeared. (1) In 2002, Cohen et al. [5, also 2002 & 2005] dated lunar meteorite clasts (aiming at non-Apollo lunar regions) and found no spike or anomaly at 3.9 Ga. (Yet they inferred “support for the lunar cataclysm hypothesis.”) (2) The Nice model in early 2000s predicted many planetesimals scattered from the outer to the inner Solar System [6], with a plausible (unconstrained) date of 3.9 Ga - but asteroidal meteorite impact melt clasts (like lunar meteorites) show no spike at 3.9. (3) Meanwhile, reports of pre-4.0 impact melts have increased among upland breccia clasts. Nice and Grand Tack modelers have introduced “sawteeth” spikes before 4.0 and gradual declines after 3.8 (both had been proposed earlier), thus softening the “cataclysm” spike. A 2014 model by Marchi, Bottke, Morbidelli, Kring, et al. [7] illustrates a curve of impact flux vs. time, 4.4 to 3.5 Ga, showing no spike at 3.9 Ga - signaling a possible demise of the terminal cataclysm hypothesis. [1] Hartmann W.K. 1966. Icarus 5, 406-418[2] Tera F. et al. 1973. LPSC abstract, p. 723[3] Tera F. et al. 1974. EPSK 22, 1-21[4] Ryder G. 1990. EOS 71, 313[5] Cohen B., Swindle T., Kring D. 2000. Science 290

  3. Identifying psychosocial variables that predict safer-sex intentions in adolescents and young adults

    Directory of Open Access Journals (Sweden)

    Phil eBrüll

    2016-04-01

    Full Text Available Young people are especially vulnerable to sexually transmitted infections. The triad of deliberate and effective safer-sex behavior encompasses condom use, combined with additional information about a partner’s sexual health, and the kind of sex acts usually performed. To identify psychosocial predictors of young people’s intentions to have safer sex, as related to this triad we conducted an online study with 211 sexually active participants aged between 18 and 24 years. Predictors (i.e. perceived behavioural control, subjective norms and intention taken from Fishbein and Ajzen’s Reasoned Action Approach (RAA, were combined with more distal variables (e.g. behavioral inhibition, sensation seeking, parental monitoring, and knowledge about sexually transmitted infections. Beyond the highly predictive power of RAA variables, additional variance was explained by the number of instances of unprotected sexual intercourse during the last twelve months and reasons for using barrier protection during first sexual intercourse. In particular, past condom nonuse behavior moderated perceived behavioral control related to intended condom use. Further, various distal variables showed significant univariate associations with intentions related to the three behaviors of interest. It may, therefore, be helpful to include measures of past behavior as well as certain additional distal variables in future safer-sex programs designed to promote health sustaining sexual behavior.

  4. An algorithm for identifying symmetric variables in the canonical OR-coincidence algebra system

    Institute of Scientific and Technical Information of China (English)

    Xiao-hua LI; Ji-zhong SHEN

    2014-01-01

    To simplify the process for identifying 12 types of symmetric variables in the canonical OR-coincidence (COC) algebra system, we propose a new symmetry detection algorithm based on OR-NXOR expansion. By analyzing the relationships between the coefficient matrices of sub-functions and the order coefficient subset matrices based on OR-NXOR expansion around two arbitrary logical variables, the constraint conditions of the order coefficient subset matrices are revealed for 12 types of symmetric variables. Based on the proposed constraints, the algorithm is realized by judging the order characteristic square value matrices. The proposed method avoids the transformation process from OR-NXOR expansion to AND-OR-NOT expansion, or to AND-XOR expansion, and solves the problem of completeness in the dj-map method. The application results show that, compared with traditional methods, the new algorithm is an optimal detection method in terms of applicability of the number of logical variables, detection type, and complexity of the identification process. The algorithm has been implemented in C language and tested on MCNC91 benchmarks. Experimental results show that the proposed algorithm is convenient and efficient.

  5. Identifying Psychosocial Variables That Predict Safer Sex Intentions in Adolescents and Young Adults.

    Science.gov (United States)

    Brüll, Phil; Ruiter, Robert A C; Wiers, Reinout W; Kok, Gerjo

    2016-01-01

    Young people are especially vulnerable to sexually transmitted infections (STIs). The triad of deliberate and effective safer sex behavior encompasses condom use, combined with additional information about a partner's sexual health, and the kind of sex acts usually performed. To identify psychosocial predictors of young people's intentions to have safer sex, as related to this triad, we conducted an online study with 211 sexually active participants aged between 18 and 24 years. Predictors [i.e., perceived behavioral control (PBC), subjective norms, and intention] taken from Fishbein and Ajzen's Reasoned Action Approach (RAA), were combined with more distal variables (e.g., behavioral inhibition, sensation seeking, parental monitoring, and knowledge about STIs). Beyond the highly predictive power of RAA variables, additional variance was explained by the number of instances of unprotected sexual intercourse (SI) during the last 12 months and reasons for using barrier protection during first SI. In particular, past condom non-use behavior moderated PBC related to intended condom use. Further, various distal variables showed significant univariate associations with intentions related to the three behaviors of interest. It may, therefore, be helpful to include measures of past behavior as well as certain additional distal variables in future safer sex programs designed to promote health-sustaining sexual behavior. PMID:27148520

  6. Identifying decaying supermassive black hole binaries from their variable electromagnetic emission

    Energy Technology Data Exchange (ETDEWEB)

    Haiman, Zoltan; Menou, Kristen [Department of Astronomy, Columbia University, New York, NY (United States); Kocsis, Bence [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Lippai, Zoltan; Frei, Zsolt [Institute of Physics, Eoetvoes University, Budapest (Hungary)

    2009-05-07

    Supermassive black hole binaries (SMBHBs) with masses in the mass range approx(10{sup 4}-10{sup 7}) M{sub o-dot}/(1 + z), produced in galaxy mergers, are thought to complete their coalescence due to the emission of gravitational waves (GWs). The anticipated detection of the GWs by the future Laser Interferometric Space Antenna (LISA) will constitute a milestone for fundamental physics and astrophysics. While the GW signatures themselves will provide a treasure trove of information, if the source can be securely identified in electromagnetic (EM) bands, this would open up entirely new scientific opportunities, to probe fundamental physics, astrophysics and cosmology. We discuss several ideas, involving wide-field telescopes, that may be useful in locating electromagnetic counterparts to SMBHBs detected by LISA. In particular, the binary may produce a variable electromagnetic flux, such as a roughly periodic signal due to the orbital motion prior to coalescence, or a prompt transient signal caused by shocks in the circumbinary disc when the SMBHB recoils and 'shakes' the disc. We discuss whether these time-variable EM signatures may be detectable, and how they can help in identifying a unique counterpart within the localization errors provided by LISA. We also discuss a possibility of identifying a population of coalescing SMBHBs statistically, in a deep optical survey for periodically variable sources, before LISA detects the GWs directly. The discovery of such sources would confirm that gas is present in the vicinity and is being perturbed by the SMBHB-serving as a proof of concept for eventually finding actual LISA counterparts.

  7. The Lunar Cataclysm and How LRO Can Help Test It

    Science.gov (United States)

    Cohen, Barbara A.

    2009-01-01

    One of the important outstanding goals of lunar science is understanding the bombardment history of the Moon and calibrating the impact flux curve for extrapolation to the Earth and other terrestrial planets. The "terminal lunar cataclysm," a brief but intense period of bombardment about 3.9 billion years ago, is of particular scientific interest. Radiometric dating of lunar impact-melt rocks forms the backbone of the lunar cataclysm hypothesis. A histogram of precise age determinations of impact-melt rocks shows the characteristics of the classic formulation of the lunar cataclysm hypothesis: a sharp peak at 3.9 Ga, a steep decline after 3.9 Ga perhaps only 20-200 Myr long, and few rocks of impact origin prior to 4.0 Ga.

  8. Recent Advances in X-ray Observations of Cataclysmic Variables

    OpenAIRE

    Mukai, K.

    2004-01-01

    A personal selection of noteworthy X-ray results on CVs are presented, with emphasis on XMM-Newton and Chandra observations. Progressing roughly from broad-band view to narrow-band, high spectral resolution studies, I summarize: the energy balance of polars; X-ray confirmation of IPs; eclipses in non-magnetic CVs; search for magnetism in "non-magnetic" CVs; multi-temperature plasma emission from the boundary layer; complex absorption in magnetic CVs; temperature and density diagnostics; and X...

  9. Identifying potential sources of variability between vegetation carbon storage estimates for urban areas

    International Nuclear Information System (INIS)

    Although urbanisation is a major cause of land-use change worldwide, towns and cities remain relatively understudied ecosystems. Research into urban ecosystem service provision is still an emerging field, yet evidence is accumulating rapidly to suggest that the biological carbon stores in cities are more substantial than previously assumed. However, as more vegetation carbon densities are derived, substantial variability between these estimates is becoming apparent. Here, we review procedural differences evident in the literature, which may be drivers of variation in carbon storage assessments. Additionally, we quantify the impact that some of these different approaches may have when extrapolating carbon figures derived from surveys up to a city-wide scale. To understand how/why carbon stocks vary within and between cities, researchers need to use more uniform methods to estimate stores and relate this quantitatively to standardised ‘urbanisation’ metrics, in order to facilitate comparisons. -- Highlights: • Broad-scale spatial data fail to capture the fine-grained urban landcover mosaic. • This can have a large impact when extrapolating carbon densities up to a city-wide value. • We review how methodologies to estimate vegetation carbon vary in the literature. • We need a more uniform method for estimating carbon stores to aid inter-city comparisons. • This will allow the drivers underpinning urban carbon stock variability to be identified. -- As variability between urban vegetation carbon storage estimates is becoming increasingly apparent, we examine potential methodological drivers that may be responsible, and illustrate why a more consistent approach to biological carbon accounting would be beneficial

  10. Identifying Decaying Supermassive Black Hole Binaries from their Variable Electromagnetic Emission

    CERN Document Server

    Haiman, Zoltán; Menou, Kristen; Lippai, Zoltán; Frei, Zsolt

    2008-01-01

    Supermassive black hole binaries (SMBHBs) with masses in the range 10^4-10^7 M_sun/(1+z), produced in galaxy mergers, are thought to complete their coalescence due to the emission of gravitational waves (GWs). The anticipated detection of the GWs by the LISA will constitute a milestone for fundamental physics and astrophysics. While the GW signatures themselves will provide a treasure trove of information, if the source can be securely identified in electromagnetic (EM) bands, this would open up entirely new scientific opportunities, to probe fundamental physics, astrophysics, and cosmology. We discuss several ideas, involving wide-field telescopes, that may be useful in locating electromagnetic counterparts to SMBHBs detected by LISA. In particular, the binary may produce a variable electromagnetic flux, such as a roughly periodic signal due to the orbital motion prior to coalescence, or a prompt transient signal caused by shocks in the circumbinary disk when the SMBHB recoils and "shakes" the disk. We discu...

  11. Lightcurve Classification in Massive Variability Surveys

    CERN Document Server

    Belokurov, V V; Le Du, Y; Belokurov, Vasily; Du, Yann Le

    2002-01-01

    This paper pioneers the use of neural networks to provide a fast and automatic way to classify lightcurves in massive photometric datasets. As an example, we provide a working neural network that can distinguish microlensing lightcurves from other forms of variability, such as eruptive, pulsating, cataclysmic and eclipsing variable stars. The network has five input neurons, a hidden layer of five neurons and one output neuron. The five input variables for the network are extracted by spectral analysis from the lightcurve datapoints and are optimised for the identification of a single, symmetric, microlensing bump. The output of the network is the posterior probability of microlensing. The committee of neural networks successfully passes tests on noisy data taken by the MACHO collaboration. When used to process 5000 lightcurves on a typical tile towards the bulge, the network cleanly identifies the single microlensing event. When fed with a sub-sample of 36 lightcurves identified by the MACHO collaboration as ...

  12. Identifying the variables associated with pain during transrectal ultrasonography of the prostate

    Directory of Open Access Journals (Sweden)

    Hou CP

    2015-08-01

    Full Text Available Chen-Pang Hou,1,2 Yu-Hsiang Lin,1,2 Meng-Chiao Hsieh,3 Chien-Lun Chen,1,2 Phei-Lang Chang,1,2 Ying-Chen Huang,2 Ke-Hung Tsui1,21Department of Urology, Chang Gung Memorial Hospital at Linkou, 2School of Medicine, Chang Gung University, 3Division of Colon and Rectal Surgery, Department of Surgery, Chang Gung Memorial Hospital at Chiayi, Chang Gung University, Kwei-Shan, Tao-Yuan, Taiwan Objective: The purpose of this study was to prospectively investigate the degree of pain experienced by the patients receiving transrectal ultrasonography (TRUS of the prostate by applying a visual analog scale. We also identified the clinical parameters influencing pain during the TRUS examination.Materials and methods: Records were obtained from a prospective database for male patients who received TRUS of prostate in the outpatient department of Chang Gung Memorial Hospital, Taiwan, from January 2014 to June 2014. The patients underwent a detailed physical examination and medical history review. Immediately after the TRUS examination, the patients completed questionnaires based on a ten-point visual analog pain scale. The variables of interest were age, body mass index, prostate volume, prostate sagittal length, prostate-specific antigen, previous TRUS experience, external hemorrhoids, anal surgical history, prostate calcification, and image artifact caused by stool in the rectum. All variables were correlated to the visual analog scale by applying multivariate regression analysis.Results: By using linear regression analysis, we identified the independent factors that affected the pain score during the TRUS examination. The patients who received the examination for the first time or had longer prostate sagittal lengths, external hemorrhoids, anal surgical history, or stool stored in the rectum experienced more pain during the TRUS examination. Furthermore, the pain was reduced when we provided the patients with a detailed explanation before the procedure and

  13. Automatic classifier based on heart rate variability to identify fallers among hypertensive subjects.

    Science.gov (United States)

    Melillo, Paolo; Jovic, Alan; De Luca, Nicola; Pecchia, Leandro

    2015-08-01

    Accidental falls are a major problem of later life. Different technologies to predict falls have been investigated, but with limited success, mainly because of low specificity due to a high false positive rate. This Letter presents an automatic classifier based on heart rate variability (HRV) analysis with the goal to identify fallers automatically. HRV was used in this study as it is considered a good estimator of autonomic nervous system (ANS) states, which are responsible, among other things, for human balance control. Nominal 24 h electrocardiogram recordings from 168 cardiac patients (age 72 ± 8 years, 60 female), of which 47 were fallers, were investigated. Linear and nonlinear HRV properties were analysed in 30 min excerpts. Different data mining approaches were adopted and their performances were compared with a subject-based receiver operating characteristic analysis. The best performance was achieved by a hybrid algorithm, RUSBoost, integrated with feature selection method based on principal component analysis, which achieved satisfactory specificity and accuracy (80 and 72%, respectively), but low sensitivity (51%). These results suggested that ANS states causing falls could be reliably detected, but also that not all the falls were due to ANS states. PMID:26609412

  14. Identifying variably saturated water-flow patterns in a steep hillslope under intermittent heavy rainfall

    Science.gov (United States)

    El-Kadi, A. I.; Torikai, J.D.

    2001-01-01

    The objective of this paper is to identify water-flow patterns in part of an active landslide, through the use of numerical simulations and data obtained during a field study. The approaches adopted include measuring rainfall events and pore-pressure responses in both saturated and unsaturated soils at the site. To account for soil variability, the Richards equation is solved within deterministic and stochastic frameworks. The deterministic simulations considered average water-retention data, adjusted retention data to account for stones or cobbles, retention functions for a heterogeneous pore structure, and continuous retention functions for preferential flow. The stochastic simulations applied the Monte Carlo approach which considers statistical distribution and autocorrelation of the saturated conductivity and its cross correlation with the retention function. Although none of the models is capable of accurately predicting field measurements, appreciable improvement in accuracy was attained using stochastic, preferential flow, and heterogeneous pore-structure models. For the current study, continuum-flow models provide reasonable accuracy for practical purposes, although they are expected to be less accurate than multi-domain preferential flow models.

  15. A multivariate and stochastic approach to identify key variables to rank dairy farms on profitability.

    Science.gov (United States)

    Atzori, A S; Tedeschi, L O; Cannas, A

    2013-05-01

    The economic efficiency of dairy farms is the main goal of farmers. The objective of this work was to use routinely available information at the dairy farm level to develop an index of profitability to rank dairy farms and to assist the decision-making process of farmers to increase the economic efficiency of the entire system. A stochastic modeling approach was used to study the relationships between inputs and profitability (i.e., income over feed cost; IOFC) of dairy cattle farms. The IOFC was calculated as: milk revenue + value of male calves + culling revenue - herd feed costs. Two databases were created. The first one was a development database, which was created from technical and economic variables collected in 135 dairy farms. The second one was a synthetic database (sDB) created from 5,000 synthetic dairy farms using the Monte Carlo technique and based on the characteristics of the development database data. The sDB was used to develop a ranking index as follows: (1) principal component analysis (PCA), excluding IOFC, was used to identify principal components (sPC); and (2) coefficient estimates of a multiple regression of the IOFC on the sPC were obtained. Then, the eigenvectors of the sPC were used to compute the principal component values for the original 135 dairy farms that were used with the multiple regression coefficient estimates to predict IOFC (dRI; ranking index from development database). The dRI was used to rank the original 135 dairy farms. The PCA explained 77.6% of the sDB variability and 4 sPC were selected. The sPC were associated with herd profile, milk quality and payment, poor management, and reproduction based on the significant variables of the sPC. The mean IOFC in the sDB was 0.1377 ± 0.0162 euros per liter of milk (€/L). The dRI explained 81% of the variability of the IOFC calculated for the 135 original farms. When the number of farms below and above 1 standard deviation (SD) of the dRI were calculated, we found that 21

  16. 2MASS J22560844+5954299: the newly discovered cataclysmic star with the deepest eclipse

    Science.gov (United States)

    Kjurkchieva, D.; Khruzina, T.; Dimitrov, D.; Groebel, R.; Ibryamov, S.; Nikolov, G.

    2015-12-01

    Context. The SW Sex stars are assumed to represent a distinguished stage in cataclysmic variable (CV) evolution, making it especially important to study them. Aims: We discovered a new cataclysmic star and carried out prolonged and precise photometric observations, as well as medium-resolution spectral observations. Modelling these data allowed us to determine the physical parameters and to establish its peculiarities. Methods: To obtain a light curve solution we used model whose emission sources are a white dwarf surrounded by an accretion disk with a hot spot, a gaseous stream near the disk's lateral side, and a secondary star filling its Roche lobe. The obtained physical parameters are compared with those of other SW Sex-subtype stars. Results: The newly discovered cataclysmic variable 2MASS J22560844+5954299 shows the deepest eclipse amongst the known nova-like stars. It was reproduced by totally covering a very luminous accretion disk by a red secondary component. The temperature distribution of the disk is flatter than that of steady-state disk. The target is unusual with the combination of a low mass ratio q ~ 1.0 (considerably below the limit q = 1.2 of stable mass transfer of CVs) and an M-star secondary. The intensity of the observed three emission lines, Hα, He 5875, and He 6678, sharply increases around phase 0.0, accompanied by a Doppler jump to the shorter wavelength. The absence of eclipses of the emission lines and their single-peaked profiles means that they originate mainly in a vertically extended hot-spot halo. The emission Hα line reveals S-wave wavelength shifts with semi-amplitude of around 210 km s-1 and phase lag of 0.03. Conclusions: The non-steady-state emission of the luminous accretion disk of 2MASS J22560844+5954299 was attributed to the low viscosity of the disk matter caused by its unusually high temperature. The star shows all spectral properties of an SW Sex variable apart from the 0.5 central absorption. Based on data collected

  17. ASAS-SN 13cl : A Newly-Discovered Cataclysmic Binary with an Anomalously Warm Secondary

    CERN Document Server

    Thorstensen, John R

    2015-01-01

    The spectrum of the recently discovered cataclysmic variable star (CV) ASAS-SN 13cl shows that a secondary star with spectral type K4 (+- 2 subclasses) contributes roughly half the optical light. The radial velocities of the secondary are modulated on an orbital period P_orb = 4.86 hr with a velocity semiamplitude K = 246 +- 9 km/s, and the light curve shows ellipsoidal variations and an apparent grazing eclipse. At this orbital period, the secondary stars in most CVs are substantially cooler, with spectral types near M3. ASN-13cl therefore joins the small group of CVs with anomalously warm secondary stars, which apparently form when the onset of mass transfer occurs after the secondary has undergone significant nuclear evolution.

  18. Identifying market segments in consumer markets: variable selection and data interpretation

    OpenAIRE

    Tonks, D G

    2004-01-01

    Market segmentation is often articulated as being a process which displays the recognised features of classical rationalism but in part; convention, convenience, prior experience and the overarching impact of rhetoric will influence if not determine the outcomes of a segmentation exercise. Particular examples of this process are addressed critically in this paper which concentrates on the issues of variable choice for multivariate approaches to market segmentation and also the methods used fo...

  19. Psychological Variables for Identifying Susceptibility to Mental Disorders in Medical Students at the University of Barcelona

    OpenAIRE

    Sender, Rosa; Salamero, Manel; Vallés, Antoni; Valdés, Manuel

    2009-01-01

    Introduction: This study analyses some psychological variables related to susceptibility to mental disorders in medical students. Methods: A sample of 209 first- and second-year medical students was evaluated using the State and Trait Anxiety Inventory (STAI), and three questionnaires: Sensitivity to Punishment and Sensitivity to Reward Questionnaire (SPSRQ), General Health Questionnaire (GHQ-28) and UNCAHS scale of STRAIN. Results: Thirty percent of the students suffered from emotional distr...

  20. Interannual and Spatial Variability of Global Ocean Heat/Freshwater Content Identified from GTSPP

    Science.gov (United States)

    Chu, P. C.; Sun, C.

    2013-12-01

    Global Temperature and Salinity Profile Program (GTSPP) is a cooperative international project since 1990. The GTSPP handles all temperature and salinity profile data including XBT, CTDs, thermistor chain data, and Argo observations. Near-real time gridded (T, S) dataset was established from GTSPP since 1990 with horizontal resolution of (1o×1o) and temporal increment of 1 month using the recently developed optimal spectral decomposition (OSD) method. With this new monthly varying gridded dataset, the upper ocean (surface to 300 m depth) heat content OHC300 and freshwater content FWC300 were calculated at each horizontal grid point. The empirical orthogonal function (EOF) analysis was conducted on the temporally varying global 2D OHC300 anomaly relative to its seasonal variation. A new phenomenon, global ocean tripole, was discovered. The EOF-1 mode (44.2% variance) represents the classical El Nino/La Nina phenomenon. The EOF-2 mode (14.6%) represents the Indian Ocean Dipole mode and the El Nino Modoki. Its features and connection to climate variability is also discussed. The empirical orthogonal function (EOF) analysis was conducted on the temporally varying global 2D FWC300 anomaly relative to its seasonal variation. The EOF-1 mode (73.7% variance) represents near global-scale variability with the largest anomaly appearing in the Indian Ocean near southeast of Africa. The first principal component (PC1) shows decadal variability. The temporal-spatial variability represented by the EOF-1 mode shows rapid increasing of global FWC300 from 1999 to 2005 and sustaining the high values after 2005. Interpretations of the observational results to recent global warming will also be presented.

  1. Multiple time scales in cataclysmic binaries. The low-field magnetic dwarf nova DO Draconis

    CERN Document Server

    Andronov, I L; Han, W; Kim, Y; Yoon, J -N

    2008-01-01

    We study the variability of the cataclysmic variable DO Dra, on time-scales of between minutes and decades. The characteristic decay time dt/dm=0.902(3) days/mag was estimated from our 3 nights of CCD R observations. The quiescent data show a photometric wave with a cycle about 303(15)d. We analyzed the profile of the composite (or mean) outburst. We discovered however, that a variety of different outburst heights and durations had occurred, contrary to theoretical predictions. With increasing maximum brightness, we find that the decay time also increases; this is in contrast to the model predictions, which indicate that outbursts should have a constant shape. This is interpreted as representing the presence of outburst-to-outburst variability of the magnetospheric radius. A presence of a number of missed weak narrow outbursts is predicted from this statistical relationship. A new type of variability is detected, during 3 subsequent nights in 2007: periodic (during one nightly run) oscillations with rapidly-d...

  2. The Quest for Identifying BY Draconis Stars within a Data Set of 3,548 Candidate Cepheid Variable Stars (Abstract)

    Science.gov (United States)

    Johnson, J.

    2016-06-01

    (Abstract only) A spreadsheet of 3,548 automatically classified candidate Cepheid variable stars from the ASAS (All Sky Automated Survey) photometry data was provided to AAVSO (American Association of Variable Star Observers) members for analysis. It was known that the computer filters had significantly overpopulated the list. Patrick Wils originally investigated a small subset of the data using 2MASS, PPMXL, and ROTSE data, and discovered that the vast majority of the 84 candidates he surveyed appeared to have been misidentified, demonstrating the need to reclassify these variables. The most common misidentification seemed to be of BY Draconis stars (K and M spotted dwarfs), which led to an ongoing project to systematically identify BY Draconis stars from this data set. The stars are sorted using the International Variable Star Index (VSX) information and ASAS light curves to search for prior reclassification by other authors in the time since the initial population of the candidate list (e.g. using ROTSE data), along with infrared photometry (2MASS) and proper motion (PPMXL) data. An analysis of light curves and phase plots using the AAVSO software vstar is the final step in identifying potential BY Draconis stars. The goal of this project has been to submit updated identifications for these stars to VSX. This final presentation on this project will identify the last set of reclassified BY Draconis stars and discuss future directions for this research.

  3. Identifying the most informative variables for decision-making problems – a survey of recent approaches and accompanying problems

    Czech Academy of Sciences Publication Activity Database

    Pudil, Pavel; Somol, Petr

    2008-01-01

    Roč. 16, č. 4 (2008), s. 37-55. ISSN 0572-3043 R&D Projects: GA MŠk 1M0572 Grant ostatní: GA MŠk(CZ) 2C06019 Institutional research plan: CEZ:AV0Z10750506 Keywords : variable selection * decision making Subject RIV: BD - Theory of Information http://library.utia.cas.cz/separaty/2008/RO/pudil-identifying%20the%20most%20informative%20variables%20for%20decision-making%20problems%20a%20survey%20of%20recent%20approaches%20and%20accompanying%20problems.pdf

  4. Identifying Students' Learning Style Preferences Regarding Some Variables in the EFL Classroom: The Case of Turkey

    Science.gov (United States)

    Yilmaz, Cevdet; Genc, Salih Zeki

    2010-01-01

    During the past decade, the identification of students' learning style preferences has gained importance in educational research. This study aimed at identifying the individual perceptions of the learner style preferences of Turkish EFL learners. Using learning style preference categories and a 28-item language learning preference questionnaire…

  5. Predicting General Academic Performance and Identifying the Differential Contribution of Participating Variables Using Artificial Neural Networks

    Science.gov (United States)

    Musso, Mariel F.; Kyndt, Eva; Cascallar, Eduardo C.; Dochy, Filip

    2013-01-01

    Many studies have explored the contribution of different factors from diverse theoretical perspectives to the explanation of academic performance. These factors have been identified as having important implications not only for the study of learning processes, but also as tools for improving curriculum designs, tutorial systems, and students'…

  6. Identifying Psychosocial Variables That Predict Safer Sex Intentions in Adolescents and Young Adults

    NARCIS (Netherlands)

    Brüll, Phil; Ruiter, Robert A C; Wiers, Reinout W; Kok, Gerjo

    2016-01-01

    Young people are especially vulnerable to sexually transmitted infections (STIs). The triad of deliberate and effective safer sex behavior encompasses condom use, combined with additional information about a partner's sexual health, and the kind of sex acts usually performed. To identify psychosocia

  7. Identifying spatial variability of groundwater discharge in a wetland stream using a distributed temperature sensor

    Science.gov (United States)

    Lowry, C.S.; Walker, J.F.; Hunt, R.J.; Anderson, M.P.

    2007-01-01

    Discrete zones of groundwater discharge in a stream within a peat-dominated wetland were identified on the basis of variations in streambed temperature using a distributed temperature sensor (DTS). The DTS gives measurements of the spatial (??1 m) and temporal (15 min) variation of streambed temperature over a much larger reach of stream (>800 m) than previous methods. Isolated temperature anomalies observed along the stream correspond to focused groundwater discharge zones likely caused by soil pipes within the peat. The DTS also recorded variations in the number of temperature anomalies, where higher numbers correlated well with a gaining reach identified by stream gauging. Focused zones of groundwater discharge showed essentially no change in position over successive measurement periods. Results suggest DTS measurements will complement other techniques (e.g., seepage meters and stream gauging) and help further improve our understanding of groundwater-surface water dynamics in wetland streams. Copyright 2007 by the American Geophysical Union.

  8. Individual variability in human blood metabolites identifies age-related differences

    OpenAIRE

    Chaleckis, Romanas; MURAKAMI, Itsuo; Takada, Junko; Kondoh, Hiroshi; Yanagida, Mitsuhiro

    2016-01-01

    Human blood provides a rich source of information about metabolites that reflects individual differences in health, disease, diet, and lifestyle. The coefficient of variation for human blood metabolites enriched in red blood cells or plasma was quantified after careful preparation. We identified 14 age-related metabolites. Metabolites that decline strikingly in the elderly include antioxidants and compounds involved in high physical activity, including carnosine, UDP-acetyl-glucosamine, ophth...

  9. A formal method for identifying distinct states of variability in time-varying sources: SgrA* as an example

    CERN Document Server

    Meyer, L; Longstaff, F A; Ghez, A M

    2014-01-01

    Continuously time variable sources are often characterized by their power spectral density and flux distribution. These quantities can undergo dramatic changes over time if the underlying physical processes change. However, some changes can be subtle and not distinguishable using standard statistical approaches. Here, we report a methodology that aims to identify distinct but similar states of time variability. We apply this method to the Galactic supermassive black hole, where 2.2 um flux is observed from a source associated with SgrA*, and where two distinct states have recently been suggested. Our approach is taken from mathematical finance and works with conditional flux density distributions that depend on the previous flux value. The discrete, unobserved (hidden) state variable is modeled as a stochastic process and the transition probabilities are inferred from the flux density time series. Using the most comprehensive data set to date, in which all Keck and a majority of the publicly available VLT dat...

  10. Superhumps in Cataclysmic Binaries. XXIII. V442 Ophiuchi and RX J1643.7+3402

    CERN Document Server

    Patterson, J; Thorstensen, J R; Harvey, D; Skillman, D R; Fried, R E; Monard, B; O'Donoghue, D; Beshore, E; Martin, B; Niarchos, P; Vanmunster, T; Foote, J; Bolt, G; Rea, R; Cook, L; Butterworth, N D; Wood, M; Patterson, Joseph; Fenton, William; Thorstensen, John; Harvey, David; Skillman, David; Fried, Robert; Monard, Berto; Donoghue, Darragh O'; Beshore, Edward; Martin, Brian; Niarchos, Panos; Vanmunster, Tonny; Foote, Jerry; Bolt, Greg; Rea, Robert; Cook, Lewis; Butterworth, Neil; Wood, Matt

    2002-01-01

    We report the results of long observing campaigns on two novalike variables: V442 Ophiuchi and RX J1643.7+3402. These stars have high-excitation spectra, complex line profiles signifying mass loss at particular orbital phases, and similar orbital periods (respectively 0.12433 and 0.12056 d). They are well-credentialed members of the SW Sex class of cataclysmic variables. Their light curves are also quite complex. V442 Oph shows periodic signals with periods of 0.12090(8) and 4.37(15) days, and RX J1643.7+3402 shows similar signals at 0.11696(8) d and 4.05(12) d. We interpret these short and long periods respectively as a "negative superhump" and the wobble period of the accretion disk. The superhump could then possibly arise from the heating of the secondary (and structures fixed in the orbital frame) by inner-disk radiation, which reaches the secondary relatively unimpeded since the disk is not coplanar. At higher frequencies, both stars show another type of variability: quasi-periodic oscillations (QPOs) wi...

  11. Spatial and Temporal Dust Source Variability in Northern China Identified Using Advanced Remote Sensing Analysis

    Science.gov (United States)

    Taramelli, A.; Pasqui, M.; Barbour, J.; Kirschbaum, D.; Bottai, L.; Busillo, C.; Calastrini, F.; Guarnieri, F.; Small, C.

    2013-01-01

    The aim of this research is to provide a detailed characterization of spatial patterns and temporal trends in the regional and local dust source areas within the desert of the Alashan Prefecture (Inner Mongolia, China). This problem was approached through multi-scale remote sensing analysis of vegetation changes. The primary requirements for this regional analysis are high spatial and spectral resolution data, accurate spectral calibration and good temporal resolution with a suitable temporal baseline. Landsat analysis and field validation along with the low spatial resolution classifications from MODIS and AVHRR are combined to provide a reliable characterization of the different potential dust-producing sources. The representation of intra-annual and inter-annual Normalized Difference Vegetation Index (NDVI) trend to assess land cover discrimination for mapping potential dust source using MODIS and AVHRR at larger scale is enhanced by Landsat Spectral Mixing Analysis (SMA). The combined methodology is to determine the extent to which Landsat can distinguish important soils types in order to better understand how soil reflectance behaves at seasonal and inter-annual timescales. As a final result mapping soil surface properties using SMA is representative of responses of different land and soil cover previously identified by NDVI trend. The results could be used in dust emission models even if they are not reflecting aggregate formation, soil stability or particle coatings showing to be critical for accurately represent dust source over different regional and local emitting areas.

  12. Trace Metal Bioremediation: Assessment of Model Components from Laboratory and Field Studies to Identify Critical Variables

    International Nuclear Information System (INIS)

    The objective of this project was to gain an insight into the modeling support needed for the understanding, design, and operation of trace metal/radionuclide bioremediation. To achieve this objective, a workshop was convened to discuss the elements such a model should contain. A ''protomodel'' was developed, based on the recommendations of the workshop, and was used to perform sensitivity analysis as well as some preliminary simulations in support for bioremediation test experiments at UMTRA sites. To simulate the numerous biogeochemical processes that will occur during the bioremediation of uranium contaminated aquifers, a time-dependent one-dimensional reactive transport model has been developed. The model consists of a set of coupled, steady state mass balance equations, accounting for advection, diffusion, dispersion, and a kinetic formulation of the transformations affecting an organic substrate, electron acceptors, corresponding reduced species, and uranium. This set of equations is solved numerically, using a finite element scheme. The redox conditions of the domain are characterized by estimating the pE, based on the concentrations of the dominant terminal electron acceptor and its corresponding reduced specie. This pE and the concentrations of relevant species are passed to a modified version of MINTEQA2, which calculates the speciation and solubilities of the species of interest. Kinetics of abiotic reactions are described as being proportional to the difference between the actual and equilibrium concentration. A global uncertainty assessment, determined by Random Sampling High Dimensional Model Representation (RS-HDMR), was performed to attain a phenomenological understanding of the origins of output variability and to suggest input parameter refinements as well as to provide guidance for field experiments to improve the quality of the model predictions. Results indicated that for the usually high nitrate contents found ate many DOE sites, overall

  13. Authentic early experience in Medical Education: a socio-cultural analysis identifying important variables in learning interactions within workplaces.

    Science.gov (United States)

    Yardley, Sarah; Brosnan, Caragh; Richardson, Jane; Hays, Richard

    2013-12-01

    This paper addresses the question 'what are the variables influencing social interactions and learning during Authentic Early Experience (AEE)?' AEE is a complex educational intervention for new medical students. Following critique of the existing literature, multiple qualitative methods were used to create a study framework conceptually orientated to a socio-cultural perspective. Study participants were recruited from three groups at one UK medical school: students, workplace supervisors, and medical school faculty. A series of intersecting spectra identified in the data describe dyadic variables that make explicit the parameters within which social interactions are conducted in this setting. Four of the spectra describe social processes related to being in workplaces and developing the ability to manage interactions during authentic early experiences. These are: (1) legitimacy expressed through invited participation or exclusion; (2) finding a role-a spectrum from student identity to doctor mindset; (3) personal perspectives and discomfort in transition from lay to medical; and, (4) taking responsibility for 'risk'-moving from aversion to management through graded progression of responsibility. Four further spectra describe educational consequences of social interactions. These spectra identify how the reality of learning is shaped through social interactions and are (1) generic-specific objectives, (2) parallel-integrated-learning, (3) context specific-transferable learning and (4) performing or simulating-reality. Attention to these variables is important if educators are to maximise constructive learning from AEE. Application of each of the spectra could assist workplace supervisors to maximise the positive learning potential of specific workplaces. PMID:23212811

  14. Deep radio imaging of 47 Tuc identifies the peculiar X-ray source X9 as a new black hole candidate

    OpenAIRE

    Miller-Jones, J.C.A.; Strader, J.; Heinke, C. O.; Maccarone, T.J.; van den Berg, M; Knigge, C.; Chomiuk, L.; Noyola, E.; Russell, T.D.; Seth, A.C.; Sivakoff, G.R.

    2015-01-01

    We report the detection of steady radio emission from the known X-ray source X9 in the globular cluster 47 Tuc. With a double-peaked C iv emission line in its ultraviolet spectrum providing a clear signature of accretion, this source had been previously classified as a cataclysmic variable. In deep ATCA (Australia Telescope Compact Array) imaging from 2010 and 2013, we identified a steady radio source at both 5.5 and 9.0 GHz, with a radio spectral index (defined as S??????) of ? = ?0.4 ± 0.4....

  15. Deep radio imaging of 47 Tuc identifies the peculiar X-ray source X9 as a new black hole candidate

    CERN Document Server

    Miller-Jones, J C A; Heinke, C O; Maccarone, T J; Berg, M van den; Knigge, C; Chomiuk, L; Noyola, E; Russell, T D; Seth, A C; Sivakoff, G R

    2015-01-01

    We report the detection of steady radio emission from the known X-ray source X9 in the globular cluster 47 Tuc. With a double-peaked C IV emission line in its ultraviolet spectrum providing a clear signature of accretion, this source had been previously classified as a cataclysmic variable. In deep ATCA imaging from 2010 and 2013, we identified a steady radio source at both 5.5 and 9.0 GHz, with a radio spectral index (defined as $S_{\

  16. HIGHLY VARIABLE OBJECTS IN THE PALOMAR-QUEST SURVEY: A BLAZAR SEARCH USING OPTICAL VARIABILITY

    International Nuclear Information System (INIS)

    We identify 3113 highly variable objects in 7200 deg2 of the Palomar-QUEST (PQ) Survey, which each varied by more than 0.4 mag simultaneously in two broadband optical filters on timescales from hours to roughly 3.5 years. The primary goal of the selection is to find blazars by their well-known violent optical variability. Because most known blazars have been found in radio and/or X-ray wavelengths, a sample discovered through optical variability may have very different selection effects, elucidating the range of behavior possible in these systems. A set of blazars selected in this unusual manner will improve our understanding of the physics behind this extremely variable and diverse class of active galactic nucleus (AGN). The object positions, variability statistics, and color information are available using the PQ CasJobs server. The time domain is just beginning to be explored over large sky areas; we do not know exactly what a violently variable sample will hold. About 20% of the sample has been classified in the literature; over 70% of those objects are known or likely AGNs. The remainder largely consists of a variety of variable stars, including a number of RR Lyrae and cataclysmic variables.

  17. 2MASSJ22560844+5954299: the newly discovered cataclysmic star with the deepest eclipse

    CERN Document Server

    Kjurkchieva, D; Dimitrov, D; Groebel, R; Ibryamov, S; Nikolov, G

    2015-01-01

    Context: The SW Sex stars are assumed to represent a distinguished stage in CV evolution, making it especially important to study them. Aims: We discovered a new cataclysmic star and carried out prolonged and precise photometric observations, as well as medium-resolution spectral observations. Modelling these data allowed us to determine the psysical parameters and to establish its peculiarities. Results: The newly discovered vataclysmic variable 2MASSJ22560844+5954299 shows the deepest eclipse amongst the known nova-like stars. It was reproduced by totally covering a very luminous accretion disk by a red secondary component. The temperature distribution of the disk is flatter than that of steady-state disk. The target is unusual with the combination of a low mass ratio q~1.0 (considerably below the limit q=1.2 of stable mass transfer of CVs) and an M-star secondary. The intensity of the observed three emission lines, H_alpha, He 5875, and He 6678, sharply increases around phase 0.0, accompanied by a Doppler ...

  18. Detailed Mid- and Far-Ultraviolet Model Spectra for Accretion Disks in Cataclysmic Binaries

    CERN Document Server

    Wade, R A; Wade, Richard A.; Hubeny, Ivan

    1998-01-01

    We present a large grid of computed far- and mid-ultraviolet spectra (850 Angstroms to 2000 Angstroms) of the integrated light from steady-state accretion disks in luminous cataclysmic variables. The spectra are tabulated at 0.25 Angstrom intervals with an adopted FWHM resolution of 1.0 Angstrom, so they are suitable for use with observed spectra from a variety of modern space-borne observatories. Twenty-six different combinations of white dwarf mass M(wd) and mass accretion rate dM/dt are considered, and spectra are presented for six different disk inclinations, i. The disk models are computed self-consistently in the plane-parallel approximation, assuming LTE and vertical hydrostatic equilibrium, by solving simultaneously the radiative transfer, hydrostatic equilibrium, and energy balance equations. Irradiation from external sources is neglected. Local spectra of disk annuli are computed taking into account line transitions from elements 1-28 (H through Ni). Limb darkening as well as Doppler broadening and ...

  19. A Trip to the Cataclysmic Binary Zoo: Detailed Follow-Up of 35 Recently-Discovered Systems

    CERN Document Server

    Thorstensen, John R; Weil, Kathryn E

    2016-01-01

    We report follow-up studies of 35 recently-discovered cataclysmic variables (CVs), 32 of which were found in large, automated synoptic sky surveys. The objects were selected for observational tractability. For 34 of the objects we present mean spectra and spectroscopic orbital periods, and for one more we give an eclipse-based period. Thirty-two of the period determinations are new, and three of these refine published estimates based on superhump periods. The remaining three of our determinations confirm previously published periods. Twenty of the stars are confirmed or suspected dwarf novae with periods shorter than 3 hours, but we also find three apparent polars (AM Her stars), and six systems with P > 5 h, five of which have secondary stars visible in their spectra, from which we estimate distances when possible. The orbital period distribution of this sample is very similar to that of previously discovered CVs.

  20. A case study on variability management in software product lines: identifying why real-life projects fail

    Directory of Open Access Journals (Sweden)

    Tom Huysegoms

    2013-01-01

    Full Text Available Economies of scale can be seen as some kind of “holy grail” in state of the art literature on the development of sets of related software systems. Software product line methods are often mentioned in this context, due to the variability management aspects they propose, in order to deal with sets of related software systems. They realize the sought-after reusability. Both variability management and software product lines already have a strong presence in theoretical research, but in real-life software product line projects trying to obtain economies of scale still tend to fall short of target. The objective of this paper is to study this gap between theory and reality through a case study in order to see why such gap exists, and to find a way to bridge this gap. Through analysis of the causes of failure identified by the stakeholders in the case study, the underlying problem, which is found to be located in the requirements engineering phase, is crystallized. The identification of a framework describing the problems will provide practitioners with a better focus for future endeavors in the field of software product lines, so that economies of scale can be achieved.

  1. Inter-sport variability of muscle volume distribution identified by segmental bioelectrical impedance analysis in four ball sports

    Directory of Open Access Journals (Sweden)

    Yamada Y

    2013-04-01

    Full Text Available Yosuke Yamada,1,2 Yoshihisa Masuo,3 Eitaro Nakamura,4 Shingo Oda5 1Laboratory of Sports and Health Science, Kyoto Prefectural University of Medicine, Kyoto, Japan; 2Japan Society for the Promotion of Science, Tokyo, Japan; 3Waseda University Research Institute for Elderly Health, Saitama, Japan; 4Department of Sport Science, Kyoto Iken College of Medicine and Health, Kyoto, Japan; 5Faculty of Health and Well-being, Kansai University, Osaka, Japan Abstract: The aim of this study was to evaluate and quantify differences in muscle distribution in athletes of various ball sports using segmental bioelectrical impedance analysis (SBIA. Participants were 115 male collegiate athletes from four ball sports (baseball, soccer, tennis, and lacrosse. Percent body fat (%BF and lean body mass were measured, and SBIA was used to measure segmental muscle volume (MV in bilateral upper arms, forearms, thighs, and lower legs. We calculated the MV ratios of dominant to nondominant, proximal to distal, and upper to lower limbs. The measurements consisted of a total of 31 variables. Cluster and factor analyses were applied to identify redundant variables. The muscle distribution was significantly different among groups, but the %BF was not. The classification procedures of the discriminant analysis could correctly distinguish 84.3% of the athletes. These results suggest that collegiate ball game athletes have adapted their physique to their sport movements very well, and the SBIA, which is an affordable, noninvasive, easy-to-operate, and fast alternative method in the field, can distinguish ball game athletes according to their specific muscle distribution within a 5-minute measurement. The SBIA could be a useful, affordable, and fast tool for identifying talents for specific sports. Keywords: discriminant analysis, cluster and factor analysis, segmental bioelectrical impedance analysis, baseball, lacrosse

  2. On the masses and the evolution of cataclysmic binaries

    International Nuclear Information System (INIS)

    Masses of cataclysmic binaries (CB's) are derived from observational data (published earlier) and a theoretical relation between the secondary's mass and the period. It is found that the mass ratios of CB's having a relatively massive main sequence secondary (i.e. M2 > approximately 0.9 mass of the sun, corresponding to periods larger than about 7 hr) are not far from being unity. The assumption of a mass ratio near to unity throughout for CB's removes the discrepancy between the mean mass of single white dwarfs and the mean mass of white dwarfs in CB's. A lower limit for the mass ratios of long-living systems (being less than, but near to unity) is found from the discussion of the stability against mass exchange. An evolutionary scheme for CB's based on present stellar evolution theories is sketched. According to this scheme, WUMa systems have probably to be excluded as possible progenitors of CB's. However, the typical configuration of a CB could easily be understood as the result of an evolution of type C of a close binary undergoing mass exchange during the primary's red giant phase, connected with substantial losses of mass and angular momentum from the system. (author)

  3. Identifying the sources driving observed PM2.5 variability over Halifax, Nova Scotia, during BORTAS-B

    Directory of Open Access Journals (Sweden)

    A. J. Wheeler

    2013-02-01

    Full Text Available The source attribution of observed variability of total PM2.5 concentrations over Halifax, Nova Scotia was investigated between 11 July–26 August 2011 using measurements of PM2.5 mass and PM2.5 chemical composition (black carbon, organic matter, anions, cations and 33 elements. This was part of the BORTAS-B (quantifying the impact of BOReal forest fires on Tropospheric oxidants using aircraft and satellites experiment, which investigated the atmospheric chemistry and transport of seasonal boreal wild fire emissions over eastern Canada in 2011. The US EPA Positive Matrix Factorization (PMF receptor model was used to determine the average mass (percentage source contribution over the 45 days, which was estimated to be: Long-Range Transport (LRT Pollution 1.75 μg m−3 (47%, LRT Pollution Marine Mixture 1.0 μg m−3 (27.9%, Vehicles 0.49 μg m−3 (13.2%, Fugitive Dust 0.23 μg m−3 (6.3%, Ship Emissions 0.13 μg m−3 (3.4% and Refinery 0.081 μg m−3 (2.2%. The PMF model describes 87% of the observed variability in total PM2.5 mass (bias = 0.17 and RSME = 1.5 μg m−3. The factor identifications are based on chemical markers, and they are supported by air mass back trajectory analysis and local wind direction. Biomass burning plumes, found by other surface and aircraft measurements, were not significant enough to be identified in this analysis. This paper presents the results of the PMF receptor modelling, providing valuable insight into the local and upwind sources impacting surface PM2.5 in Halifax during the BORTAS-B mission.

  4. Identifying the sources driving observed PM2.5 temporal variability over Halifax, Nova Scotia, during BORTAS-B

    Directory of Open Access Journals (Sweden)

    M. D. Gibson

    2013-07-01

    Full Text Available The source attribution of observed variability of total PM2.5 concentrations over Halifax, Nova Scotia, was investigated between 11 July and 26 August 2011 using measurements of PM2.5 mass and PM2.5 chemical composition (black carbon, organic matter, anions, cations and 33 elements. This was part of the BORTAS-B (quantifying the impact of BOReal forest fires on Tropospheric oxidants using Aircraft and Satellites experiment, which investigated the atmospheric chemistry and transport of seasonal boreal wildfire emissions over eastern Canada in 2011. The US EPA Positive Matrix Factorization (PMF receptor model was used to determine the average mass (percentage source contribution over the 45 days, which was estimated to be as follows: long-range transport (LRT pollution: 1.75 μg m−3 (47%; LRT pollution marine mixture: 1.0 μg m−3 (27.9%; vehicles: 0.49 μg m−3 (13.2%; fugitive dust: 0.23 μg m−3 (6.3%; ship emissions: 0.13 μg m−3 (3.4%; and refinery: 0.081 μg m−3 (2.2%. The PMF model describes 87% of the observed variability in total PM2.5 mass (bias = 0.17 and RSME = 1.5 μg m−3. The factor identifications are based on chemical markers, and they are supported by air mass back trajectory analysis and local wind direction. Biomass burning plumes, found by other surface and aircraft measurements, were not significant enough to be identified in this analysis. This paper presents the results of the PMF receptor modelling, providing valuable insight into the local and upwind sources impacting surface PM2.5 in Halifax and a vital comparative data set for the other collocated ground-based observations of atmospheric composition made during BORTAS-B.

  5. Reducing the devastating effects of cataclysmic events: Cooperation

    International Nuclear Information System (INIS)

    Natural calamities, including earthquakes, land sinkings, volcanos, floods, tsunamis, hurricanes, avalanches, lightnings, forest fires, are discussed. Their devastating effects can be alleviated by cooperative efforts, sometimes international, among all concerned. The successful earthquake management of the Haicheng event is discussed as an example. Now the authors have environmental calamities, including erosion floods, dam failures, acid rain, ozone depletion, and the global greenhouse effect. There are empirical and theoretical questions about whether the greenhouse effect leads to global warming or polar ice melting. The warming prediction was based on model calculation with an incorrect boundary condition. When corrected with the right boundary condition, the models predict ice melting. The same is borne out in independent static and dynamic theories. Thus, there will be no greenhouse warming, only a sea level rise of up to 200 feet, which is much worse. The only way out is replacing fossil fuels by nuclear power. The nuclear fear is analyzed in terms of the Don Quixote syndrome and Laplace dictum. The lessons of Three Mile Island and Chernobyl actually strengthen the case of nuclear safety. New reactor technology and design will make it even safer. After 250 years of studying the history of the earth, geologists are now able to show that it is nothing but a long series of gradual changes and violent events. What was true in the past will remain so in the future, and cataclysms will occur again and again. Earthquakes, land subsidence and volcanic eruptions; flood and drought; the tsunami, tropical cyclones and avalanches; lightning and forest fires; have occurred ever since mountains, oceans, rivers, atmosphere, and ice sheets have been on the earth, and they will continue to happen

  6. Heart Rate Variability as an Alternative Indicator for Identifying Cardiac Iron Status in Non-Transfusion Dependent Thalassemia Patients.

    Directory of Open Access Journals (Sweden)

    Karn Wijarnpreecha

    Full Text Available Iron-overload cardiomyopathy is a major cause of death in thalassemia patients due to the lack of an early detection strategy. Although cardiac magnetic resonance (CMR T2* is used for early detection of cardiac iron accumulation, its availability is limited. Heart rate variability (HRV has been used to evaluate cardiac autonomic function and found to be depressed in thalassemia. However, its direct correlation with cardiac iron accumulation has never been investigated. We investigated whether HRV can be used as an alternative indicator for early identification of cardiac iron deposition in thalassemia patients.Ninety-nine non-transfusion dependent thalassemia patients (23.00 (17.00, 32.75 years, 35 male were enrolled. The correlation between HRV recorded using 24-hour Holter monitoring and non-transferrin bound iron (NTBI, hemoglobin (Hb, serum ferritin, LV ejection fraction (LVEF, and CMR-T2* were determined.The median NTBI value was 3.15 (1.11, 6.59 μM. Both time and frequency domains of HRV showed a significant correlation with the NTBI level, supporting HRV as a marker of iron overload. Moreover, the LF/HF ratio showed a significant correlation with CMR-T2* with the receiver operating characteristic (ROC curve of 0.684±0.063, suggesting that it could represent the cardiac iron deposit in thalassemia patients. HRV was also significantly correlated with serum ferritin and Hb.This novel finding regarding the correlation between HRV and CMR-T2* indicates that HRV could be a potential marker in identifying early cardiac iron deposition prior to the development of LV dysfunction, and may be used as an alternative to CMR-T2* for screening cardiac iron status in thalassemia patients.

  7. An entropy-based input variable selection approach to identify equally informative subsets for data-driven hydrological models

    Science.gov (United States)

    Karakaya, Gulsah; Taormina, Riccardo; Galelli, Stefano; Damla Ahipasaoglu, Selin

    2015-04-01

    Input Variable Selection (IVS) is an essential step in hydrological modelling problems, since it allows determining the optimal subset of input variables from a large set of candidates to characterize a preselected output. Interestingly, most of the existing IVS algorithms select a single subset, or, at most, one subset of input variables for each cardinality level, thus overlooking the fact that, for a given cardinality, there can be several subsets with similar information content. In this study, we develop a novel IVS approach specifically conceived to account for this issue. The approach is based on the formulation of a four-objective optimization problem that aims at minimizing the number of selected variables and maximizing the prediction accuracy of a data-driven model, while optimizing two entropy-based measures of relevance and redundancy. The redundancy measure ensures that the cross-dependence between the variables in a subset is minimized, while the relevance measure guarantees that the information content of each subset is maximized. In addition to the capability of selecting equally informative subsets, the approach is characterized by two other properties, namely 1) the capability of handling nonlinear interactions between the candidate input variables and preselected output, and 2) computational efficiency. These properties are guaranteed by the adoption of Extreme Learning Machine and Borg MOEA as data-driven model and heuristic optimization procedure, respectively. The approach is demonstrated on a long-term streamflow prediction problem, with the input dataset including both hydro-meteorological variables and climate indices representing dominant modes of climate variability. Results show that the availability of several equally informative subsets allows 1) determining the relative importance of each candidate input, thus supporting the understanding of the underlying physical processes, and 2) finding a better trade-off between multiple

  8. Offshore limit of coastal ocean variability identified from hydrography and altimeter data in the eastern Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Antony, M.K.; Swamy, G.N.; Somayajulu, Y.K.

    In this communication, we describe a hitherto-unknown offshore limit to the coastal ocean variability signatures away from the continental shelf in the eastern Arabian Sea, based on hydrographic observations and satellite altimeter (TOPEX...

  9. A human volunteer study to identify variability in performance in the cognitive domain of the postoperative quality of recovery scale

    OpenAIRE

    Royse, C. F.; Newman, S P; Williams, Z.; Wilkinson, D. J.

    2013-01-01

    Background: The Postoperative Quality of Recovery Scale found lower than anticipated recovery in the cognitive domain. The definition of cognitive recovery did not allow for performance variability, and may have been too sensitive. This study aimed to examine variability in cognitive performance in volunteers. Methods: One hundred forty-three volunteers completed the cognitive domain questions at baseline, after 15 min and 40 min, and on days 1 and 3. Delivery via face-to-face interview w...

  10. Identifying Trainees' Computer Self-Efficacy in Relation to Some Variables: The Case of Turkish EFL Trainees

    Science.gov (United States)

    Inal, Sevim

    2015-01-01

    The purpose of this study was to define the self-efficacy perception of Turkish ELT students and examine the relationship between their self-efficacy and such variables as grade level, computer ownership, first time computer use, and frequency of internet and computer use. The participants are 305 Turkish ELT trainees at Dokuz Eylul University,…

  11. Can coordination variability identify performance factors and skill level in competitive sport? The case of race walking

    Institute of Scientific and Technical Information of China (English)

    Dario Cazzola; Gaspare Pavei; Ezio Preatoni

    2016-01-01

    Background: Marginal changes in the execution of competitive sports movements can represent a significant change for performance success. However, such differences may emerge only at certain execution intensities and are not easily detectable through conventional biomechanical techniques. This study aimed to investigate if and how competition standard and progression speed affect race walking kinematics from both a conventional and a coordination variability perspective. Methods: Fifteen experienced athletes divided into three groups (elite, international, and national) were studied while race walking on a treadmill at two different speeds (12.0 and 15.5 km/h). Basic gait parameters, the angular displacement of the pelvis and lower limbs, and the variability in continuous relative phase between six different joint couplings were analyzed. Results: Most of the spatio-temporal, kinematic, and coordination variability measures proved sensitive to the change in speed. Conversely, non-linear dynamics measures highlighted differences between athletes of different competition standard when conventional analytical tools were not able to discriminate between different skill levels. Continuous relative phase variability was higher for national level athletes than international and elite in two couplings (pelvis obliquity—hip flex/extension and pelvis rotation—ankle dorsi/plantarflexion) and gait phases (early stance for the first coupling, propulsive phase for the second) that are deemed fundamental for correct technique and performance. Conclusion: Measures of coordination variability showed to be a more sensitive tool for the fine detection of skill-dependent factors in competitive race walking, and showed good potential for being integrated in the assessment and monitoring of sports motor abilities.

  12. Identifying drivers for the intra-urban spatial variability of airborne particulate matter components and their interrelationships

    Science.gov (United States)

    Wu, Hao; Reis, Stefan; Lin, Chun; Beverland, Iain J.; Heal, Mathew R.

    2015-07-01

    The aim of this work was to compare the variability in an urban area of fine particles (PM2.5), ultrafine particles (UFP) and black carbon (BC) and to evaluate the relationship between each particle metric and potential factors (local traffic, street topography and synoptic meteorology) contributing to the variability. Concentrations of the three particle metrics were quantified using portable monitors through a combination of mobile and static measurements in the city of Edinburgh, UK. The spatial variability of UFP and BC was large, of similar magnitude and about 3 times higher than the spatial variability of PM0.5-2.5 (the PM size fraction actually quantified in this work). Highest inter-daily variability was observed for PM0.5-2.5, which was approximately 2 times higher than inter-daily variability of BC and UFP. Elevated concentrations of UFP and BC were observed along streets with high traffic volumes whereas PM0.5-2.5 showed less variation between streets and a footpath without road traffic. Both BC and UFP were significantly correlated with traffic counts, while no significant correlation between PM0.5-2.5 and traffic counts was observed. BC was significantly correlated with UFP, with significantly different regression slopes between working days and non-working days implying that the increased number of diesel powered heavy goods vehicles during working days contributed more to BC than to UFP. It is concluded that variations in BC and UFP concentrations were mainly determined by the nearby traffic count and varying background concentrations between days, while variation in PM0.5-2.5 concentration was mainly associated with regional sources. These findings imply the need for different policies for managing human exposure to these different particle components: control of much BC and UFP appears to be manageable at local scale by restricting traffic emissions; however, abatement of PM2.5 requires a more strategic approach, in cooperation with other regions

  13. Identifying the odds ratio estimated by a two-stage instrumental variable analysis with a logistic regression model*

    OpenAIRE

    Burgess, Stephen

    2013-01-01

    Adjustment for an uncorrelated covariate in a logistic regression changes the true value of an odds ratio for a unit increase in a risk factor. Even when there is no variation due to covariates, the odds ratio for a unit increase in a risk factor also depends on the distribution of the risk factor. An instrumental variable can be used to consistently estimate a causal effect in the presence of arbitrary confounding. With a logistic outcome model, we show that the simple ratio or two-stage ins...

  14. How Methodology Decisions Affect the Variability of Schools Identified as Beating the Odds. REL 2015-071.rev

    Science.gov (United States)

    Abe, Yasuyo; Weinstock, Phyllis; Chan, Vincent; Meyers, Coby; Gerdeman, R. Dean; Brandt, W. Christopher

    2015-01-01

    A number of states and school districts have identified schools that perform better than expected, given the populations they serve, in order to recognize school performance or to learn from local school practices and policies. These schools have been labeled "beating the odds," "high-performing/high-poverty,"…

  15. Identifying Variables Responsible for Clustering in Discriminant Analysis of Data from Infrared Microspectroscopy of a Biological Sample

    NARCIS (Netherlands)

    Martin, Francis L.; German, Matthew J.; Wit, Ernst; Fearn, Thomas; Ragavan, Narasimhan; Pollock, Hubert M.

    2007-01-01

    In the biomedical field, infrared (IR) spectroscopic studies can involve the processing of data derived from many samples, divided into classes such as category of tissue (e.g., normal or cancerous) or patient identity. We require reliable methods to identify the class-specific information on which

  16. Identifying Critical Factors of Sale Failure on Commercial Property Types, Shop Houses by Using Multi Attribute Variable Technique

    OpenAIRE

    N.I. Mohamad; N. M. Tawil; I.M. Usman; M. M. Tahir

    2014-01-01

    The focus of this research is to identify the critical factors of shop houses sale failure in Bandar Baru Nilai and further up to discover the critical factors of sale failure of commercial property types, shop houses in new township as report by valuation and Property services department (JPPH) showed 5,931 units of shop houses in Malaysia is currently completed but remained unsold where Johor was recorded as the highest with unsold units followed by Negeri Sembilan. Bandar Baru Nilai (a dis...

  17. Incidental Breast Lesions Identified by 18F-FDG PET/CT: Which Clinical Variables Differentiate between Benign and Malignant Breast Lesions?

    OpenAIRE

    Shin, Kyung Min; Kim, Hye Jung; Jung, Su Jin; Lim, Hyo Soon; Lee, Sang Woo; Cho, Seung Hyun; Jang, Yun-Jin; Lee, Hui Joong; Kim, Gab Chul; Jung, Jin Hyang; Park, Ji Young

    2015-01-01

    Purpose The aim of our study was to evaluate the risk of malignancy and to determine which clinical variables differentiate between benign and malignant focal breast lesions found incidentally on 18F-flourodeoxyglucose positron emission tomography and computed tomography (FDG PET/CT). Methods From March 2005 to October 2011, 21,224 women with no history of breast cancer underwent FDG PET/CT at three university-affiliated hospitals. We retrospectively identified 214 patients with incidental fo...

  18. Shrinking a large dataset to identify variables associated with increased risk of Plasmodium falciparum infection in Western Kenya.

    Science.gov (United States)

    Tremblay, M; Dahm, J S; Wamae, C N; De Glanville, W A; Fèvre, E M; Döpfer, D

    2015-12-01

    Large datasets are often not amenable to analysis using traditional single-step approaches. Here, our general objective was to apply imputation techniques, principal component analysis (PCA), elastic net and generalized linear models to a large dataset in a systematic approach to extract the most meaningful predictors for a health outcome. We extracted predictors for Plasmodium falciparum infection, from a large covariate dataset while facing limited numbers of observations, using data from the People, Animals, and their Zoonoses (PAZ) project to demonstrate these techniques: data collected from 415 homesteads in western Kenya, contained over 1500 variables that describe the health, environment, and social factors of the humans, livestock, and the homesteads in which they reside. The wide, sparse dataset was simplified to 42 predictors of P. falciparum malaria infection and wealth rankings were produced for all homesteads. The 42 predictors make biological sense and are supported by previous studies. This systematic data-mining approach we used would make many large datasets more manageable and informative for decision-making processes and health policy prioritization. PMID:25876816

  19. Identifying Critical Factors of Sale Failure on Commercial Property Types, Shop Houses by Using Multi Attribute Variable Technique

    Directory of Open Access Journals (Sweden)

    N.I. Mohamad

    2014-04-01

    Full Text Available The focus of this research is to identify the critical factors of shop houses sale failure in Bandar Baru Nilai and further up to discover the critical factors of sale failure of commercial property types, shop houses in new township as report by valuation and Property services department (JPPH showed 5,931 units of shop houses in Malaysia is currently completed but remained unsold where Johor was recorded as the highest with unsold units followed by Negeri Sembilan. Bandar Baru Nilai (a district of Negeri Sembilan is chosen as research sample for unsold shop houses units due to its strategic location which is near to KLIA, International Sepang Circuit, educational instituitions and surrounded by housing scheme but yet still has numbers of unsold units. Data of the research is obtained from literature review and survey question between developers, local authority, purchasers/tenant and local residents. Relative Importance Index (RII method is applied in identifying the critical factor of shop houses sale failure. Generally, the factors of sale failure are economy, demography, politic, location and access, public and basic facilities, financial loan, physical of product, current stock of shop houses upon completion, future potential of subsale and rental, developer’s background, promotion and marketing, speculation and time.

  20. The Size of the Emitting Region in the Magnetic Eclipsing Cataclysmic Variable Stars

    CERN Document Server

    Andrych, Kateryna D

    2015-01-01

    We discuss a method for determination of the size of the emitting region close to the compact star in a binary system with eclipses by a secondary, which fills its Roche lobe. The often used approach is to model the Roche lobe by a sphere with the "effective radius" corresponding to the volume of the Roche lobe. This approach leads to a 4-6% overestimate of the radius, if taking into account the angular dimensions of the Roche lobe seen form the compact star. Andronov (1992) had shown that the projection of the Roche lobe onto the celestial sphere is close to an ellipse and had tabulated these dimensions as a function of the mass ratio. Also he published the coefficients of the approximation similar to that of the Eggleton (1983) for the "sphere corresponding to the same volume". We compare results obtained for the "circle+circle", "ellipse+circle" and "ellipse+point" approximations of the projections of the red dwarf and a white dwarf, respectively. Results are applied to the recently discovered eclipsing po...

  1. Features of the matter flows in the peculiar cataclysmic variable AE Aquarii

    Science.gov (United States)

    Isakova, P. B.; Ikhsanov, N. R.; Zhilkin, A. G.; Bisikalo, D. V.; Beskrovnaya, N. G.

    2016-05-01

    The structure ofmatter flows in close binary systems in which one of the components is a rapidly rotating magnetic white dwarf is studied. Themain example considered is the AEAquarii system; the period of the white dwarf's rotation is about a factor of 1000 shorter than the orbital period, and the magnetic field on the white-dwarf surface is of order 50MG. The matter flows in this system were analyzed via numerical solution of a systemofmagnetohydrodynamical equatons. These computations show that the white dwarf's magnetic field does not significantly influence the velocity field of the matter in its Roche lobe in the case of a laminar flow regime, so that the field does not hinder the formation of a transient disk (ring) surrounding the magnetosphere. However, the efficiency of the energy and angular-momentum exchange between the white dwarf and the surrounding matter increases considerably with the development of turbulent motions in the matter, accelerating the matter at the magnetosphere boundary and leading to a high escape rate from the system. The time scales for the system's transition between the laminar and turbulent modes are close to those for the transition of AE Aquarii between its quiet and active phases.

  2. Features of the Matter Flows in the Peculiar Cataclysmic Variable AE Aquarii

    CERN Document Server

    Isakova, P B; Zhilkin, A G; Bisikalo, D V; Beskrovnaya, N G

    2016-01-01

    The structure of plasma flows in close binary systems in which one of the components is a rapidly rotating magnetic white dwarf is studied. The main example considered is the AE Aquarii system; the spin period of the white dwarf is about a factor of 1000 shorter than the orbital period, and the magnetic field on the white dwarf surface is of order of 50 MG. The mass transfer in this system was analyzed via numerical solution of the system of MHD equations. These computations show that the magnetic field of the white dwarf does not significantly influence the velocity field of the material in its Roche lobe in the case of laminar flow regime, so that the field does not hinder the formation of a transient disk (ring) surrounding the magnetosphere. However, the efficiency of the energy and angular momentum exchange between the white dwarf and the surrounding material increases considerably with the development of turbulent motions in the matter, resulting in its acceleration at the magnetospheric boundary and fu...

  3. Roche tomography of cataclysmic variables - V. A high-latitude star-spot on RU Pegasi

    CERN Document Server

    Dunford, Alexander; Smith, Robert Connon

    2012-01-01

    We present Roche tomograms of the secondary star in the dwarf nova system RU Pegasi derived from blue and red arm ISIS data taken on the 4.2-m William Herschel Telescope. We have applied the entropy landscape technique to determine the system parameters and obtained component masses of M1 = 1.06 Msun, M2 = 0.96 Msun, an orbital inclination angle of i = 43 degrees, and an optimal systemic velocity of gamma = 7 km/s. These are in good agreement with previously published values. Our Roche tomograms of the secondary star show prominent irradiation of the inner Lagrangian point due to illumination by the disc and/or bright spot, which may have been enhanced as RU Peg was in outburst at the time of our observations.We find that this irradiation pattern is axi-symmetric and confined to regions of the star which have a direct view of the accretion regions. This is in contrast to previous attempts to map RU Peg which suggested that the irradiation pattern was non-symmetric and extended beyond the terminator. We also d...

  4. On the SW Sex-Type Eclipsing Cataclysmic Variable SDSS0756+0858

    CERN Document Server

    Tovmassian, Gagik; Gonzalez-Buitrago, Diego; Zharikov, Sergey; García-Díaz, Maria Teresa

    2014-01-01

    We conducted a spectroscopic and photometric study of SDSS J075653.11+085831. X-ray observations were also attempted. We determined the orbital period of this binary system to be 3.29 hours. It is a deep eclipsing system, whose spectra shows mostly single peaked Balmer emission lines and a quite intense He II line. There is also the presence of faint (often double peaked) He I emission lines as well as several absorption lines; Mg I being the most prominent. All these features point towards affiliation of this object to the growing number of SW Sex-type objects. We developed a phenomenological model of a SW Sex system to reproduce the observed photometric and spectral features.

  5. Fe Line Diagnostics of Cataclysmic Variables and Galactic Ridge X-ray Emission

    CERN Document Server

    Xu, Xiao-jie; Li, Xiang-Dong

    2016-01-01

    The properties of the Galactic Ridge X-ray Emission (GRXE) observed in the 2-10 keV band place fundamental constraints on various types of X-ray sources in the Milky Way. Although the primarily discrete origin of the emission is now well established, the responsible populations of these sources remain uncertain, especially at relatively low fluxes. To provide insights into this issue, we systematically characterize the Fe emission line properties of the candidate types of the sources in the solar neighborhood and compare them with those measured for the GRXE. Our source sample includes 6 symbiotic stars (SSs), 16 intermediate polars (IPs), 3 polars, 16 quiescent dwarf novae (DNe) and 4 active binaries (ABs). We find that the mean equivalent width ($EW_{6.7}$) of the 6.7-keV line and the mean 7.0/6.7-keV line ratio are $107\\pm16.0$ eV and $0.71\\pm 0.04$ for intermediate polars and $221\\pm 135$ eV and $0.44\\pm 0.14$ for polars, respectively, which are all substantially different from those ($490\\pm15 $~eV and $...

  6. Time-Resolved HST Spectroscopy of Four Eclipsing Magnetic Cataclysmic Variables

    CERN Document Server

    Schmidt, G D; Schmidt, Gary D.

    2000-01-01

    Time-resolved HST UV eclipse spectrophotometry is presented for the magnetic CVs V1309 Ori, MN Hya, V2301 Oph, and V1432 Aql. Separation of the light curves into wavebands allows the multiple emission components to be distinguished. Photospheric hot spots are detected in V1309 Ori and V2301 Oph. The emission- line spectra of V1309 Ori and MN Hya are unusual, with the strength of N V 1240 and N IV 1718 suggesting an overabundance of nitrogen. Three epochs of observation of the asynchronous V1432 Aql cover ~1/3 of a 50-day lap cycle between the white dwarf spin and binary orbit. The light curves vary from epoch to epoch and as a function of waveband. The dereddened UV spectrum is extremely bright and the spectral energy distribution coupled with the duration of eclipse ingress indicate that the dominant source of energy is a hot (T~35,000K) white dwarf. Undiminished line emission through eclipse indicates that the eclipse is caused by the accretion stream, not the secondary star. The hot white dwarf, combined w...

  7. On the SW Sex-type eclipsing cataclysmic variable SDSS0756+0858

    International Nuclear Information System (INIS)

    We conducted a spectroscopic and photometric study of SDSS J075653.11+085831. X-ray observations were also attempted. We determined the orbital period of this binary system to be 3.29 hr. It is a deep eclipsing system, whose spectra show mostly single-peaked, Balmer emission lines and a rather intense He II line. There is also the presence of faint (often double-peaked) He I emission lines as well as several absorption lines, Mg I being the most prominent. All of these features point toward the affiliation of this object with the growing number of SW Sex-type objects. We developed a phenomenological model of an SW Sex system to reproduce the observed photometric and spectral features.

  8. Kepler Observations of V447 Lyr: an Eclipsing U Gem Cataclysmic Variable

    Science.gov (United States)

    Ramsay, Gavin; Cannizzo, John K.; Howell, Steve B.; Wood, Matt A.; Still, Martin; Barclay, Thomas; Smale, Alan

    2012-01-01

    We present the results of an analysis of Kepler data covering 1.5 yr of the dwarf nova V447 Lyr. We detect eclipses of the accretion disc by the mass donating secondary star every 3.74 h which is the binary orbital period. V447 Lyr is therefore the first dwarf nova in the Kepler field to show eclipses.We also detect five long outbursts and six short outbursts showing V447 Lyr is a U Gem-type dwarf nova. We show that the orbital phase of the mid-eclipse occurs earlier during outbursts compared to quiescence and that the width of the eclipse is greater during outburst. This suggests that the bright spot is more prominent during quiescence and that the disc is larger during outburst than quiescence. This is consistent with an expansion of the outer disc radius due to the presence of high viscosity material associated with the outburst, followed by a contraction in quiescence due to the accretion of low angular momentum material. We note that the long outbursts appear to be triggered by a short outburst, which is also observed in the super-outbursts of SU UMa dwarf novae as observed using Kepler.

  9. Conserved variation: identifying patterns of stability and variability in BCR and TCR V genes with different diversity and richness metrics

    International Nuclear Information System (INIS)

    The immune system can detect most invading pathogens. The potential for detection of pathogens is dependent on the somatic diversity of the immune repertoires. While it is known that this somatic diversity is carefully generated, it is unclear how the diversity is distributed in the different genes encoding receptors of immune cells. Utilizing different metrics for richness and diversity at the level of small sequence fragments, we present here an analysis of the entire known human germline repertoire as represented by the sequences from the ImMunoGeneTics database of immune receptors. We have developed a fragment sequence quantification analysis to track variation of repertoires with different degrees of precision. Somatic diversity has previously been functionally characterized mostly by division of the V gene sequences into the more conserved and invariant framework (FR) of the receptor and more varied complementarity determining regions (CDR), that interact with the antigen. We find that CDR and FR can be explicitly identified with our sequence fragment diversity quantification technique. In terms of diversity, CDR and FR are especially distinct in B cell V genes. T cell V genes show less of the CDR/FR periodicity but are more diverse overall. Our analysis further shows that there are other areas of diversity outside the CDR and FR that are found widely dispersed in T cell receptor V genes and more tightly focused in FR1 and FR3 in the B cell receptor V genes. The diversity we observe is not dependent on allelic differences nor is this diversity segregated by individual V gene families. We would thus expect that each individual exhibit a diversity equivalent to that of the entire potential repertoire. (paper)

  10. High proper motion objects towards the inner Milky Way: characterisation of newly identified nearby stars from the VISTA Variables in the Via Lactea Survey

    CERN Document Server

    Gromadzki, M; Beamin, J C; Tekola, A; Ramphul, R; Ivanov, V D; Minniti, D; Folkes, S L; Vaisanen, P; Kniazev, A Y; Borissova, J; Parsons, S G; Villanueva, V

    2016-01-01

    The census of the Solar neighbourhood is still incomplete, as demonstrated by recent discoveries of many objects within 5-10 pc from the Sun. The area around the mid-plane and bulge of the Milky Way presents the most difficulties in searches for such nearby objects, and is therefore deficient in the known population. This is largely due to high stellar densities encountered. Spectroscopic, photometric and kinematic characterization of these objects allows better understand the local mass function, the binary fraction, and provides new interesting targets for more detailed studies. We report the spectroscopic follow-up and characterisation of 12 bright high PM objects, identified from the VISTA Variables in Via Lactea survey (VVV). We used the 1.9-m telescope of the South African Astronomical Observatory (SAAO) for low-resolution optical spectroscopy and spectral classification, and the MPG/ESP 2.2m telescope Fiber-fed Extended Range Optical Spectrograph (FEROS) high-resolution optical spectroscopy to obtain t...

  11. Variability of the Accretion Stream in the Eclipsing Polar EP Dra

    OpenAIRE

    Bridge, C. M.; Cropper, Mark; Ramsay, Gavin; de Bruijne, J. H. J.; Reynolds, A.P.; Perryman, M. A. C.

    2003-01-01

    We present the first high time resolution light curves for six eclipses of the magnetic cataclysmic variable EP Dra, taken using the superconducting tunnel junction imager S-Cam2. The system shows a varying eclipse profile between consecutive eclipses over the two nights of observation. We attribute the variable stream eclipse after accretion region ingress to a variation in the amount and location of bright material in the accretion stream. This material creates an accretion curtain as it is...

  12. The first low-mass black hole X-ray binary identified in quiescence outside of a globular cluster

    CERN Document Server

    Tetarenko, B E; Arnason, R M; Miller-Jones, J C A; Repetto, S; Heinke, C O; Maccarone, T J; Chomiuk, L; Sivakoff, G R; Strader, J; Kirsten, F; Vlemmings, W

    2016-01-01

    The observed relation between the X-ray and radio properties of low-luminosity accreting black holes has enabled the identification of multiple candidate black hole X-ray binaries (BHXBs) in globular clusters. Here we report an identification of the radio source VLA J213002.08+120904 (aka M15 S2), recently reported in Kirsten et al. 2014, as a BHXB candidate. They showed that the parallax of this flat-spectrum variable radio source indicates a 2.2$^{+0.5}_{-0.3}$ kpc distance, which identifies it as lying in the foreground of the globular cluster M15. We determine the radio characteristics of this source, and place a deep limit on the X-ray luminosity of $\\sim4\\times10^{29}$ erg s$^{-1}$. Furthermore, we astrometrically identify a faint red stellar counterpart in archival Hubble images, with colors consistent with a foreground star; at 2.2 kpc its inferred mass is 0.1-0.2 $M_{\\odot}$. We rule out that this object is a pulsar, neutron star X-ray binary, cataclysmic variable, or planetary nebula, concluding tha...

  13. Interpopulation Variation in Picrorhiza kurrooa Royle ex Benth-Step Towards Identifying Genetic Variability and Elite Strains for Crop Improvement Study

    OpenAIRE

    B.P. Nautiyal; H Purohit; M.C. Nautiyal

    2008-01-01

    This communication addresses variability at morphological, biochemical and active ingredients level among wild populations of Picrorhiza kurrooa, an important medicinal herb of high altitude region of Himalaya. Variations were observed for microhabitats as well as for two wild strains viz., narrow leaf and broad leaf. Observations suggest variability in vegetative growth while fruits and seeds do not impart significant variation among different populations, microhabitats and strains. Di...

  14. GT2318+620, a variable galactic source with a radio jet

    International Nuclear Information System (INIS)

    A recent galactic survey with the National Radio Astronomy Observatory (NRAO) 91-m telescope revealed a small number of variable radio sources at low galactic latitude. Similar sources within the Galaxy, where they have been identified, are often associated with energetic objects such as X-ray binaries, pulsars, cataclysmic variables and flare stars. One of the new variable sources, GT2318 + 620, is within the error box for the Uhuru X-ray source 4U2316 + 61, and our measurement of the neutral hydrogen absorption towards GT2318 + 620, reported here, indicates that it is a galactic object, at a distance of 3-6 kpc. We also present a high-resolution radio image of the source, which reveals an unresolved core with a jet-like feature extending on either side. GT2318 + 620 is coincident with a star of ∼ 20th magnitude, and we suggest here that it is radio-emitting low-mass X-ray binary. The radio luminosity of GT2318 + 620 is markedly higher than that of Sco X-1, the only other low-mass X-ray binary to show a radio jet; in its radio brightness it resembles SS433, which is remarkable for its relativistic jet motion on arcsecond scales, thought to result from accretion onto a collapsed stellar object. (author)

  15. Compositional and Geochronological Constraints on the Lunar Cataclysm from Planetary Samples

    Science.gov (United States)

    Cohen, Barbara A.

    2008-01-01

    Radiometric dating and compositional clustering of lunar impact-melt rocks form the backbone of the lunar cataclysm hypothesis. Precise age determinations of Apollo and Luna impact-melt rocks define the classic formulation of the cataclysm: a large number of samples 3.9 Ga old, a steep decline after 3.9 Ga, and few impact rocks older than 4.0 Ga. Lunar meteorites more randomly sample the lunar surface, but impact-melt clasts in these rocks show the same apparent age cutoff at 4.0 Ga (though their ages extend approx.500 Myr later). Neither do impact-formed glass spherules and fragments, formed by impacts of all sizes throughout lunar history, predate 4.0 Ga. Geological associations between compositional groups of impact-melt rocks and specific impact basins imply that five large basins formed on the Moon within 200 Myr but a counter-argument postulates they are all products of the Imbrium basin-forming impact; it is not yet proven whether groups of impact melt that are resolvable from each other in age and in trace-element composition represent multiple impacts. The 3.9 Ga age peak and subsequent steep decline are not well mirrored in meteorite data. Radiometric ages in ordinary chondrites and HED meteorites peak around 3.9 Ga but ages older and younger than 3.9 Ga are common. Among Martian meteorites, there is a single impact-related age: ALH 84001 was shocked at 3.92 Ga. Differences in relative impact velocity, impact-melt production, and sampling rate could explain differences between the meteorite and lunar records. One way to anchor the early end of the lunar flux is to directly sample the impact-melt sheet of a large lunar basin distant from Imbrium, such as the South Pole-Aitken basin, where melt rocks probably still resides on the basin floor and could be directly sampled by a human or robotic mission.

  16. Cataclysms and Catastrophes: A Case Study of Improving K-12 Science Education Through a University Partnership

    Science.gov (United States)

    Fennell, T.; Ellins, K. K.; Morris, M.; Christeson, G.

    2003-12-01

    The K-12 science teacher is always seeking ways of improving and updating their curriculum by integrating the latest research into their most effective classroom activities. However, the daily demands of delivering instruction to large numbers of students coupled with the rapid advances in some fields of science can often overwhelm this effort. The NSF-sponsored Cataclysms and Catastrophes curriculum, developed by scientists from the The University of Texas at Austin Institute for Geophysics (UTIG) and Bureau of Economic Geology (BEG), middle and high school teachers, and UT graduate students (NSF GK-12 fellows) working together through the GK-12 program, is a textbook example of how universities can facilitate this quest, benefiting education at both K-12 and university levels. In 1992, "The Great K-T Extinction Debate" was developed as an activity in the Planet Earth class at the Liberal Arts and Science Academy of Austin as an interdisciplinary approach to science. Taking advantage of the media attention generated by the impact scenario for the K-T extinction, the activity consists of students participating in a simulated senate hearing on the potential causes of the K-T extinction and their implications for society today. This activity not only exposes students to the wide range of science involved in understanding mass extinctions, but also to the social, political and economic implications when this science is brought into the public arena and the corresponding use of data in decision making and disaster preparedness. While "The Great K-T Extinction Debate" was always a popular and effective activity with students, it was in desperate need of updating to keep pace with the evolving scientific debate over the cause of the K-T extinction and the growing body of impact evidence discovered over the past decade. By adding two inquiry-based learning activities that use real geophysical data collected by scientists studying the buried Chicxulub feature as a

  17. General Relativity Explains the Shnoll Effect and Makes Possible Forecasting Earthquakes and Weather Cataclysms

    Science.gov (United States)

    Rabounski, Dmitri; Borissova, Larissa

    2014-03-01

    The Shnoll effect is manifested in the fine structure of the noise registered in stable processes, wherein as the magnitude of signal and the average noise remain unchanged. It is periodic fluctuation of the fine structure of the noise according to the cosmic cycles connected with stars, the Sun, and the Moon. The Shnoll effect is explained herein according to General Relativity, as the twin/entangled synchronization states of the observer's reference frame. The states are repeated while the observer travels, in common with the Earth, through the cosmic grid of the geodesic synchronization paths that connect his local reference frame with the reference frames of the other cosmic bodies. These synchronization periods are expected to be existing in the noise of natural processes of any type (physics, biology, social, etc.) and such artificial processes as the random number generation by a computer software. These periods match with the periods of the Shnoll effect. The theory gives not only to explain the Shnoll effect, but also allows forecasting the fluctuations in the stock exchange market, the fluctuations of weather, earthquakes, and other cataclysms.

  18. Generalized Linear Models to Identify Key Hydromorphological and Chemical Variables Determining the Occurrence of Macroinvertebrates in the Guayas River Basin (Ecuador

    Directory of Open Access Journals (Sweden)

    Minar Naomi Damanik-Ambarita

    2016-07-01

    Full Text Available The biotic integrity of the Guayas River basin in Ecuador is at environmental risk due to extensive anthropogenic activities. We investigated the potential impacts of hydromorphological and chemical variables on biotic integrity using macroinvertebrate-based bioassessments. The bioassessment methods utilized included the Biological Monitoring Working Party adapted for Colombia (BMWP-Col and the average score per taxon (ASPT, via an extensive sampling campaign that was completed throughout the river basin at 120 sampling sites. The BMWP-Col classification ranged from very bad to good, and from probable severe pollution to clean water based on the ASPT scores. Generalized linear models (GLMs and sensitivity analysis were used to relate the bioassessment index to hydromorphological and chemical variables. It was found that elevation, nitrate-N, sediment angularity, logs, presence of macrophytes, flow velocity, turbidity, bank shape, land use and chlorophyll were the key environmental variables affecting the BMWP-Col. From the analyses, it was observed that the rivers at the upstream higher elevations of the river basin were in better condition compared to lowland systems and that a higher flow velocity was linked to a better BMWP-Col score. The nitrate concentrations were very low in the entire river basin and did not relate to a negative impact on the macroinvertebrate communities. Although the results of the models provided insights into the ecosystem, cross fold model development and validation also showed that there was a level of uncertainty in the outcomes. However, the results of the models and sensitivity analysis can support water management actions to determine and focus on alterable variables, such as the land use at different elevations, monitoring of nitrate and chlorophyll concentrations, macrophyte presence, sediment transport and bank stability.

  19. Variability of the Accretion Stream in the Eclipsing Polar EP Dra

    CERN Document Server

    Bridge, C M; Ramsay, G; De Bruijne, J H J; Reynolds, A P; Perryman, M A C; Cropper, Mark; Ramsay, Gavin

    2003-01-01

    We present the first high time resolution light curves for six eclipses of the magnetic cataclysmic variable EP Dra, taken using the superconducting tunnel junction imager S-Cam2. The system shows a varying eclipse profile between consecutive eclipses over the two nights of observation. We attribute the variable stream eclipse after accretion region ingress to a variation in the amount and location of bright material in the accretion stream. This material creates an accretion curtain as it is threaded by many field lines along the accretion stream trajectory. We identify this as the cause of absorption evident in the light curves when the system is in a high accretion state. We do not see direct evidence in the light curves for an accretion spot on the white dwarf; however, the variation of the stream brightness with the brightness of the rapid decline in flux at eclipse ingress indicates the presence of some form of accretion region. This accretion region is most likely located at high colatitude on the whit...

  20. Dwarf nova oscillations and quasi-periodic oscillations in cataclysmic variables -- VI. Spin rates, propellering, and coherence

    CERN Document Server

    Warner, Brian

    2007-01-01

    We examine published observations of dwarf nova oscillations (DNOs) on the rise and decline of outbursts and show that their rates of change are in reasonable agreement with those predicted from the magnetic accretion model. We find evidence for propellering in the late stages of outburst of several dwarf novae, as shown by reductions in EUVE fluxes and from rapid increases of the DNO periods. Reanalysis of DNOs observed in TY PsA, which had particularly large amplitudes, shows that the apparent loss of coherence during late decline is better described as a regular switching between two nearby periods. It is partly this and the rapid deceleration in some systems that make the DNOs harder to detect. We suggest that the 28.95 s periodicity in WZ Sge, which has long been a puzzle, is caused by heated regions in the disc, just beyond the corotation radius, which are a consequence of magnetic coupling between the primary and gas in the accretion disc. This leads to a possible new interpretation of the `longer peri...

  1. An infrared and visual study of the structure and variability of the cataclysmic binary V2051 Ophiuchi

    International Nuclear Information System (INIS)

    This paper presents the first infrared (JHK) light curves of the ultra-short-period dwarf nova V2051 Oph in quiescence. Much of the light curve morphology can be attributed to the presence of roughly sinusoidally shaped humps, which appear at different phases in the light curves. The humps consist of material lying close to the white dwarf, that is optically thin in the visual and infrared continua, and is at least as hot as the material in the bulk of the disc. Rapid flares superposed on the humps are optically thick in the infrared, and have a visual to infrared colour temperature of approx. 8000 K. The luminous material in the accretion disc has an infrared brightness temperature exceeding 10 000 K. (author)

  2. DNA methylation patterns in luminal breast cancers differ from non-luminal subtypes and can identify relapse risk independent of other clinical variables.

    Science.gov (United States)

    Kamalakaran, Sitharthan; Varadan, Vinay; Giercksky Russnes, Hege E; Levy, Dan; Kendall, Jude; Janevski, Angel; Riggs, Michael; Banerjee, Nilanjana; Synnestvedt, Marit; Schlichting, Ellen; Kåresen, Rolf; Shama Prasada, K; Rotti, Harish; Rao, Ramachandra; Rao, Laxmi; Eric Tang, Man-Hung; Satyamoorthy, K; Lucito, Robert; Wigler, Michael; Dimitrova, Nevenka; Naume, Bjorn; Borresen-Dale, Anne-Lise; Hicks, James B

    2011-02-01

    The diversity of breast cancers reflects variations in underlying biology and affects the clinical implications for patients. Gene expression studies have identified five major subtypes- Luminal A, Luminal B, basal-like, ErbB2+ and Normal-Like. We set out to determine the role of DNA methylation in subtypes by performing genome-wide scans of CpG methylation in breast cancer samples with known expression-based subtypes. Unsupervised hierarchical clustering using a set of most varying loci clustered the tumors into a Luminal A majority (82%) cluster, Basal-like/ErbB2+ majority (86%) cluster and a non-specific cluster with samples that were also inconclusive in their expression-based subtype correlations. Contributing methylation loci were both gene associated loci (30%) and non-gene associated (70%), suggesting subtype dependant genome-wide alterations in the methylation landscape. The methylation patterns of significant differentially methylated genes in luminal A tumors are similar to those identified in CD24 + luminal epithelial cells and the patterns in basal-like tumors similar to CD44 + breast progenitor cells. CpG islands in the HOXA cluster and other homeobox (IRX2, DLX2, NKX2-2) genes were significantly more methylated in Luminal A tumors. A significant number of genes (2853, p < 0.05) exhibited expression-methylation correlation, implying possible functional effects of methylation on gene expression. Furthermore, analysis of these tumors by using follow-up survival data identified differential methylation of islands proximal to genes involved in Cell Cycle and Proliferation (Ki-67, UBE2C, KIF2C, HDAC4), angiogenesis (VEGF, BTG1, KLF5), cell fate commitment (SPRY1, OLIG2, LHX2 and LHX5) as having prognostic value independent of subtypes and other clinical factors. PMID:21169070

  3. Variation of Surface Air Temperature in Relation to El Nino and Cataclysmic Volcanic Eruptions, 1796-1882

    Science.gov (United States)

    Wilson, Robert M.

    1999-01-01

    During the contemporaneous interval of 1796-1882 a number of significant decreases in temperature are found in the records of Central England and Northern Ireland. These decreases appear to be related to the occurrences of El Nino and/or cataclysmic volcanic eruptions. For example, a composite of residual temperatures of the Central England dataset, centering temperatures on the yearly onsets of 20 El Nino of moderate to stronger strength, shows that, on average, the change in temperature varied by about +/- 0.3 C from normal being warmer during the boreal fall-winter leading up to the El Nino year and cooler during the spring-summer of the El Nino year. Also, the influence of El Nino on Central England temperatures appears to last about 1-2 years. Similarly, a composite of residual temperatures of the Central England dataset, centering temperatures on the month of eruption for 26 cataclysmic volcanic eruptions, shows that, on average, the change in temperature decreased by about 0.1 - 0.2 C, typically, 1-2 years after the eruption, although for specific events, like Tambora, the decrease was considerably greater. Additionally, tropical eruptions appear to produce greater changes in temperature than extratropical eruptions, and eruptions occurring in boreal spring-summer appear to produce greater changes in temperature than those occurring in fall-winter.

  4. Heart rate and heart rate variability assessment identifies individual differences in fear response magnitudes to earthquake, free fall, and air puff in mice.

    Directory of Open Access Journals (Sweden)

    Jun Liu

    Full Text Available Fear behaviors and fear memories in rodents have been traditionally assessed by the amount of freezing upon the presentation of conditioned cues or unconditioned stimuli. However, many experiences, such as encountering earthquakes or accidental fall from tree branches, may produce long-lasting fear memories but are behaviorally difficult to measure using freezing parameters. Here, we have examined changes in heartbeat interval dynamics as physiological readout for assessing fearful reactions as mice were subjected to sudden air puff, free-fall drop inside a small elevator, and a laboratory-version earthquake. We showed that these fearful events rapidly increased heart rate (HR with simultaneous reduction of heart rate variability (HRV. Cardiac changes can be further analyzed in details by measuring three distinct phases: namely, the rapid rising phase in HR, the maximum plateau phase during which HRV is greatly decreased, and the recovery phase during which HR gradually recovers to baseline values. We showed that durations of the maximum plateau phase and HR recovery speed were quite sensitive to habituation over repeated trials. Moreover, we have developed the fear resistance index based on specific cardiac response features. We demonstrated that the fear resistance index remained largely consistent across distinct fearful events in a given animal, thereby enabling us to compare and rank individual mouse's fear responsiveness among the group. Therefore, the fear resistance index described here can represent a useful parameter for measuring personality traits or individual differences in stress-susceptibility in both wild-type mice and post-traumatic stress disorder (PTSD models.

  5. Identifying IGR J14091-6108 as a magnetic CV with a massive white dwarf using X-ray and optical observations

    CERN Document Server

    Tomsick, John A; Krivonos, Roman; Clavel, Maica; Strader, Jay; Chomiuk, Laura

    2016-01-01

    IGR J14091-6108 is a Galactic X-ray source known to have an iron emission line, a hard X-ray spectrum, and an optical counterpart. Here, we report on X-ray observations of the source with XMM-Newton and NuSTAR as well as optical spectroscopy with ESO/VLT and NOAO/SOAR. In the X-rays, this provides data with much better statistical quality than the previous observations, and this is the first report of the optical spectrum. Timing analysis of the XMM data shows a very significant detection of 576.3+/-0.6 s period. The signal has a pulsed fraction of 30%+/-3% in the 0.3-12 keV range and shows a strong drop with energy. The optical spectra show strong emission lines with significant variability in the lines and continuum, indicating that they come from an irradiated accretion disk. Based on these measurements, we identify the source as a magnetic Cataclysmic Variable of Intermediate Polar (IP) type where the white dwarf spin period is 576.3 s. The X-ray spectrum is consistent with the continuum emission mechanis...

  6. Flickering of the symbiotic variable CH Cygni during outburst

    International Nuclear Information System (INIS)

    High-speed and conventional BVRI photometry are reported for the bright symbiotic variable CH Cygni (M6 IIIe), obtained during the course of a recent outburst. Unlike the quiescent symbiotic stars, the presence of flickering similar in nature to that seen in the cataclysmic variables has been confirmed during this active phase. The BVRI photometry for a sample of stars in the field is used to derive the reddening and the distance to CH Cyg. A composite energy distribution is derived from 0.35 to 11.0 μm which clearly establishes the existence of a variable, blue continuum. The lack of variability in the near infrared suggests that the blue continuum arises from a hot companion. A binary model including a subluminous hot companion accreting material from the stellar wind of an SRa variable is discussed to account for the observed photometric properties. (author)

  7. The First Low-mass Black Hole X-Ray Binary Identified in Quiescence Outside of a Globular Cluster

    Science.gov (United States)

    Tetarenko, B. E.; Bahramian, A.; Arnason, R. M.; Miller-Jones, J. C. A.; Repetto, S.; Heinke, C. O.; Maccarone, T. J.; Chomiuk, L.; Sivakoff, G. R.; Strader, J.; Kirsten, F.; Vlemmings, W.

    2016-07-01

    The observed relation between the X-ray and radio properties of low-luminosity accreting black holes (BHs) has enabled the identification of multiple candidate black hole X-ray binaries (BHXBs) in globular clusters (GCs). Here, we report an identification of the radio source VLA J213002.08+120904 (aka M15 S2), recently reported in Kirsten et al., as a BHXB candidate. They showed that the parallax of this flat-spectrum variable radio source indicates a {2.2}-0.3+0.5 kpc distance, which identifies it as lying in the foreground of the GC M15. We determine the radio characteristics of this source and place a deep limit on the X-ray luminosity of ∼4 × 1029 erg s‑1. Furthermore, we astrometrically identify a faint red stellar counterpart in archival Hubble images with colors consistent with a foreground star; at 2.2 kpc, its inferred mass is 0.1–0.2 M ⊙. We rule out that this object is a pulsar, neutron star X-ray binary, cataclysmic variable, or planetary nebula, concluding that VLA J213002.08+120904 is the first accreting BHXB candidate discovered in quiescence outside of a GC. Given the relatively small area over which parallax studies of radio sources have been performed, this discovery suggests a much larger population of quiescent BHXBs in our Galaxy, 2.6 × 104–1.7 × 108 BHXBs at 3σ confidence, than has been previously estimated (∼102–104) through population synthesis.

  8. Optical Studies of 13 Hard X-Ray Selected Cataclysmic Binaries from the Swift-BAT Survey

    Science.gov (United States)

    Halpern, Jules P.; Thorstensen, John R.

    2015-12-01

    From a set of 13 cataclysmic binaries that were discovered in the Swift Burst Alert Telescope (BAT) survey, we conducted time-resolved optical spectroscopy and/or time-series photometry of 11, with the goal of measuring their orbital periods and searching for spin periods. Seven of the objects in this study are new optical identifications. Orbital periods are found for seven targets, ranging from 81 minutes to 20.4 hr. PBC J0706.7+0327 is an AM Herculis star (polar) based on its emission-line variations and large amplitude photometric modulation on the same period. Swift J2341.0+7645 may be a polar, although the evidence here is less secure. Coherent pulsations are detected from two objects, Swift J0503.7-2819 (975 s) and Swift J0614.0+1709 (1412 s and 1530 s, spin and beat periods, respectively), indicating that they are probable intermediate polars (DQ Herculis stars). For two other stars, longer spin periods are tentatively suggested. We also present the discovery of a 2.00 hr X-ray modulation from RX J2015.6+3711, possibly a contributor to Swift J2015.9+3715, and likely a polar. Based on observations obtained at the MDM Observatory, operated by Dartmouth College, Columbia University, Ohio State University, Ohio University, and the University of Michigan.

  9. Optical Studies of Thirteen Hard X-ray Selected Cataclysmic Binaries from the Swift-BAT Survey

    CERN Document Server

    Halpern, J P

    2015-01-01

    From a set of thirteen cataclysmic binaries that were discovered in the Swift Burst Alert Telescope (BAT) survey, we conducted time-resolved optical spectroscopy and/or time-series photometry of eleven, with the goal of measuring their orbital periods and searching for spin periods. Seven of the objects in this study are new optical identifications. Orbital periods are found for seven targets, ranging from 81 minutes to 20.4 hours. PBC J0706.7+0327 is an AM Herculis star (polar) based on its emission-line variations and large amplitude photometric modulation on the same period. Swift J2341.0+7645 may be a polar, although the evidence here is less secure. Coherent pulsations are detected from two objects, Swift J0503.7-2819 (975 s) and Swift J0614.0+1709 (1412 s and 1530 s, spin and beat periods, respectively), indicating that they are probable intermediate polars (DQ Herculis stars). For two other stars, longer spin periods are tentatively suggested. We also present the discovery of a 2.00 hour X-ray modulati...

  10. Magnetostratigraphic evidence from the Cold Creek bar for onset of ice-age cataclysmic floods in eastern Washington during the early Pleistocene

    Energy Technology Data Exchange (ETDEWEB)

    Pluhar, Christopher J.; Bjornstad, Bruce N.; Reidel, Steve P.; Coe, Robert S.; Nelson, Paul B.

    2006-01-01

    This study provides a detailed magnetostratigraphy of sediments composing the Cold Creek cataclysmic flood bar in the Pasco Basin, Washington. Our interpretation suggests onset of Missoula floods or similar events prior to 1.1 myr, later than previously suggested by Bjornstad et al. [Bjornstad B.N., Fecht, K.R., Pluhar, C.J., 2001]. Long history of pre-Wisconsin, Ice Age cataclysmic floods: evidence from southeastern Washington State. [Journal of Geology 109 (6), 695-713]. Nonetheless these data suggest that Channeled Scabland features formed over a much longer timespan than commonly cited, that continental ice sheets of the early Pleistocene reached as far south as those of the late Pleistocene, and that similar physiography existed in eastern Washington and perhaps Montana to both generate and route Missoula-flood-like events. This study adds paleomagnetic polarity results from 213 new samples of silts and sands derived from nine new drill cores penetrating the Cold Creek cataclysmic flood bar to our previous database of 53 samples from four boreholes, resulting in a much more robust and detailed magnetostratigraphy. Rock magnetic studies on these sediments show pure magnetite to be the predominant remanence-carrying magnetic mineral, ruling out widespread remagnetization by secondary mineralization. The magnetostratigraphy at eastern Cold Creek bar is characterized by a normal polarity interval bracketed by reversed polarities. Equating the normal zone with the Jaramillo subchron (0.99-1.07 myr) affords the simplest correlation to the magnetic polarity timescale. Western Cold Creek bar was likely deposited during the Brunhes chron (0-0.78 myr) since it exhibits mainly normal polarities with only two thin reversed-polarity horizons that we interpret as magnetic excursions during the Brunhes.

  11. Magnetostratigraphic evidence from the Cold Creek bar for onset of ice-age cataclysmic floods in eastern Washington during the early Pleistocene

    International Nuclear Information System (INIS)

    This study provides a detailed magnetostratigraphy of sediments composing the Cold Creek cataclysmic flood bar in the Pasco Basin, Washington. Our interpretation suggests onset of Missoula floods or similar events prior to 1.1 myr, later than previously suggested by Bjornstad et al. [Bjornstad B.N., Fecht, K.R., Pluhar, C.J., 2001]. Long history of pre-Wisconsin, Ice Age cataclysmic floods: evidence from southeastern Washington State. [Journal of Geology 109 (6), 695-713]. Nonetheless these data suggest that Channeled Scabland features formed over a much longer timespan than commonly cited, that continental ice sheets of the early Pleistocene reached as far south as those of the late Pleistocene, and that similar physiography existed in eastern Washington and perhaps Montana to both generate and route Missoula-flood-like events. This study adds paleomagnetic polarity results from 213 new samples of silts and sands derived from nine new drill cores penetrating the Cold Creek cataclysmic flood bar to our previous database of 53 samples from four boreholes, resulting in a much more robust and detailed magnetostratigraphy. Rock magnetic studies on these sediments show pure magnetite to be the predominant remanence-carrying magnetic mineral, ruling out widespread remagnetization by secondary mineralization. The magnetostratigraphy at eastern Cold Creek bar is characterized by a normal polarity interval bracketed by reversed polarities. Equating the normal zone with the Jaramillo subchron (0.99-1.07 myr) affords the simplest correlation to the magnetic polarity timescale. Western Cold Creek bar was likely deposited during the Brunhes chron (0-0.78 myr) since it exhibits mainly normal polarities with only two thin reversed-polarity horizons that we interpret as magnetic excursions during the Brunhes

  12. Identifying IGR J14091-6108 as a magnetic CV with a massive white dwarf using X-ray and optical observations

    Science.gov (United States)

    Tomsick, John A.; Rahoui, Farid; Krivonos, Roman; Clavel, Maïca; Strader, Jay; Chomiuk, Laura

    2016-07-01

    INTEGRAL Gamma-Ray (IGR) J14091-6108 is a Galactic X-ray source known to have an iron emission line, a hard X-ray spectrum, and an optical counterpart. Here, we report on X-ray observations of the source with XMM-Newton and NuSTAR as well as optical spectroscopy with European Southern Obseratory/Very Large Telescope and National Optical Astronomy Observatory/Southern Astrophysical Research Telescope. In the X-rays, this provides data with much better statistical quality than the previous observations, and this is the first report of the optical spectrum. Timing analysis of the XMM data shows a very significant detection of 576.3 ± 0.6 s period. The signal has a pulsed fraction of 30 ± 3 per cent in the 0.3-12 keV range and shows a strong drop with energy. The optical spectra show strong emission lines with significant variability in the lines and continuum, indicating that they come from an irradiated accretion disc. Based on these measurements, we identify the source as a magnetic cataclysmic variable of intermediate polar (IP) type where the white dwarf spin period is 576.3 s. The X-ray spectrum is consistent with the continuum emission mechanism being due to thermal bremsstrahlung, but partial covering absorption and reflection are also required. In addition, we use the IP mass model, which suggests that the white dwarf in this system has a high mass, possibly approaching the Chandrasekhar limit.

  13. VizieR Online Data Catalog: Radial velocities of 7 cataclysmic binaries (Halpern+, 2015)

    Science.gov (United States)

    Halpern, J. P.; Thorstensen, J. R.

    2016-04-01

    Our instrumentation, and reduction and analysis procedures are essentially identical to those described in Paper I (Thorstensen et al. 2013, cat. J/AJ/146/107). All of our optical data are from the MDM Observatory (http://mdm.kpno.noao.edu/index/Instrumentation.html), which comprises the 1.3m McGraw-Hill telescope and the 2.4m Hiltner telescope, both on the southwest ridge of Kitt Peak, Arizona. With a single exception, the radial velocity studies to search for the orbital periods were done on the 2.4m, while high-cadence photometry sensitive to spin periods was carried out on the 1.3m. All of our radial velocity studies used the modular spectrograph, as described in Paper I (Thorstensen et al. 2013, cat. J/AJ/146/107). Most of our velocities are from the the 2.4m telescope. Some spectra of Swift J2124.6+0500, and all the data we used for Swift J0939.7-3224, are from the McGraw-Hill 1.3m telescope, again with the modular spectrograph. For four newly identified objects we have only single spectra that were obtained on two observing runs on the 2.4m. These used the Boller and Chivens CCD spectrograph (CCDS) and the Ohio State Multi-Object Spectrograph (OSMOS). Descriptions of these instruments can be found on the MDM Observatory web page (http://mdm.kpno.noao.edu/index/Instrumentation.html). The objects observed are listed in Table1. Table2 lists the radial velocity data, and Table3 gives parameters of the best-fit sinusoids. (3 data files).

  14. Method of Running Sines: Modeling Variability in Long-Period Variables

    CERN Document Server

    Andronov, Ivan L

    2013-01-01

    We review one of complementary methods for time series analysis - the method of "Running Sines". "Crash tests" of the method include signals with a large period variation and with a large trend. The method is most effective for "nearly periodic" signals, which exhibit "wavy shape" with a "cycle length" varying within few dozen per cent (i.e. oscillations of low coherence). This is a typical case for brightness variations of long-period pulsating variables and resembles QPO (Quasi-Periodic Oscillations) and TPO (Transient Periodic Oscillations) in interacting binary stars - cataclysmic variables, symbiotic variables, low-mass X-Ray binaries etc. General theory of "running approximations" was described by Andronov (1997A &AS..125..207A), one of realizations of which is the method of "running sines". The method is related to Morlet-type wavelet analysis improved for irregularly spaced data (Andronov, 1998KFNT...14..490A, 1999sss..conf...57A), as well as to a classical "running mean" (="moving average"). The ...

  15. Extreme Ultraviolet Explorer and Optical Observations of the Magnetic Cataclysmic Variables RX J1015.5+0904 and V405 Auriga (RX J0558+5353)

    Science.gov (United States)

    Szkody, Paula; Armstrong, John; Fried, Robert

    2000-02-01

    We present simultaneous Extreme Ultraviolet Explorer (EUVE) and optical observations of one of the shortest orbital period AM Herculis systems (RX J1015.5+0904) and of one of the intermediate polars which shows a soft X-ray flux (V405 Aur=RX J0558+5353). RX J1015.5+0904 shows a very typical geometry of the accretion area for a one-pole system. The count rate is consistent with a column at the low end of the ROSAT determinations and, therefore, a relatively high temperature for the heated area. Thus, there is every indication that heating operates efficiently even at low accretion rates onto very cool white dwarfs. V405 Aur has a very low count rate, which does not allow a good determination of the spin variation at EUVE wavelengths, although it is obvious in the optical photometry. Doppler tomography of the optical spectra shows a trend of decreasing disk structure and increasing spot structure with increasing excitation, with a change in the location of the primary emitting zone from previous years.

  16. XSS J00564+4548 and IGR J00234+6141 -- new cataclysmic variables from RXTE and INTEGRAL all sky surveys

    CERN Document Server

    Bikmaev, I F; Burenin, R A; Sunyaev, R A

    2006-01-01

    We present the results of optical identification of two X-ray sources from RXTE and INTEGRAL all sky surveys: XSS J00564+4548 and IGR J00234+6141. Using the optical data from Russian-Turkish 1.5-m Telescope (RTT150) and SWIFT X-ray observations, we show that these sources most probably are intermediate polars, i.e. binary systems with accreting white dwarfs with not very strong magnetic field (<~10 MG). Periodical oscillations of optical emission with periods 480 s and 570 s were found. We argue that these periods most probably correspond to the rotating periods of the white dwarfs in these systems. Further optical observations scheduled at RTT150 will allow to study the parameters of these systems in more detail.

  17. Very-high-energy -ray observations of pulsar wind nebulae and cataclysmic variable stars with MAGIC and development of trigger systems for IACTs

    OpenAIRE

    López Coto, Rubén

    2015-01-01

    La historia de la astronomía es tan antigua como alcanzan nuestros registros. Todas las civilizaciones han estado interesadas en el estudio del cielo nocturno, sus objetos y fenómenos. Estas observaciones se realizaron a simple vista hasta el comienzo del siglo XVII, cuando Galileo Galilei empezó a usar un instrumento desarrollado recientemente llamado telescopio. Desde entonces, el rango de longitudes de onda accesible ha ido creciendo, con una explosión en el siglo XX gracias...

  18. Very-high-energy -ray observations of pulsar wind nebulae and cataclysmic variable stars with MAGIC and development of trigger systems for IACTs

    OpenAIRE

    López Coto, Rubén; Fernández Sánchez, Enrique

    2015-01-01

    La historia de la astronomía es tan antigua como alcanzan nuestros registros. Todas las civilizaciones han estado interesadas en el estudio del cielo nocturno, sus objetos y fenómenos. Estas observaciones se realizaron a simple vista hasta el comienzo del siglo XVII, cuando Galileo Galilei empezó a usar un instrumento desarrollado recientemente llamado telescopio. Desde entonces, el rango de longitudes de onda accesible ha ido creciendo, con una explosión en el siglo XX gracias al desarrollo ...

  19. Computing Cosmic Cataclysms

    Science.gov (United States)

    Centrella, Joan M.

    2010-01-01

    The final merger of two black holes releases a tremendous amount of energy, more than the combined light from all the stars in the visible universe. This energy is emitted in the form of gravitational waves, and observing these sources with gravitational wave detectors requires that we know the pattern or fingerprint of the radiation emitted. Since black hole mergers take place in regions of extreme gravitational fields, we need to solve Einstein's equations of general relativity on a computer in order to calculate these wave patterns. For more than 30 years, scientists have tried to compute these wave patterns. However, their computer codes have been plagued by problems that caused them to crash. This situation has changed dramatically in the past few years, with a series of amazing breakthroughs. This talk will take you on this quest for these gravitational wave patterns, showing how a spacetime is constructed on a computer to build a simulation laboratory for binary black hole mergers. We will focus on the recent advances that are revealing these waveforms, and the dramatic new potential for discoveries that arises when these sources will be observed.

  20. Large-scale nucleotide sequence alignment and sequence variability assessment to identify the evolutionarily highly conserved regions for universal screening PCR assay design: an example of influenza A virus.

    Science.gov (United States)

    Nagy, Alexander; Jiřinec, Tomáš; Černíková, Lenka; Jiřincová, Helena; Havlíčková, Martina

    2015-01-01

    The development of a diagnostic polymerase chain reaction (PCR) or quantitative PCR (qPCR) assay for universal detection of highly variable viral genomes is always a difficult task. The purpose of this chapter is to provide a guideline on how to align, process, and evaluate a huge set of homologous nucleotide sequences in order to reveal the evolutionarily most conserved positions suitable for universal qPCR primer and hybridization probe design. Attention is paid to the quantification and clear graphical visualization of the sequence variability at each position of the alignment. In addition, specific problems related to the processing of the extremely large sequence pool are highlighted. All of these steps are performed using an ordinary desktop computer without the need for extensive mathematical or computational skills. PMID:25697651

  1. Identifying High Performance ERP Projects

    OpenAIRE

    Stensrud, Erik; Myrtveit, Ingunn

    2002-01-01

    Learning from high performance projects is crucial for software process improvement. Therefore, we need to identify outstanding projects that may serve as role models. It is common to measure productivity as an indicator of performance. It is vital that productivity measurements deal correctly with variable returns to scale and multivariate data. Software projects generally exhibit variable returns to scale, and the output from ERP projects is multivariate. We propose to use Data Envelopment ...

  2. Sparse Linear Identifiable Multivariate Modeling

    DEFF Research Database (Denmark)

    Henao, Ricardo; Winther, Ole

    2011-01-01

    In this paper we consider sparse and identifiable linear latent variable (factor) and linear Bayesian network models for parsimonious analysis of multivariate data. We propose a computationally efficient method for joint parameter and model inference, and model comparison. It consists of a fully...... Bayesian hierarchy for sparse models using slab and spike priors (two-component δ-function and continuous mixtures), non-Gaussian latent factors and a stochastic search over the ordering of the variables. The framework, which we call SLIM (Sparse Linear Identifiable Multivariate modeling), is validated and...... computational complexity. We attribute this mainly to the stochastic search strategy used, and to parsimony (sparsity and identifiability), which is an explicit part of the model. We propose two extensions to the basic i.i.d. linear framework: non-linear dependence on observed variables, called SNIM (Sparse Non-linear...

  3. Sparse Linear Identifiable Multivariate Modeling

    DEFF Research Database (Denmark)

    Henao, Ricardo; Winther, Ole

    2011-01-01

    In this paper we consider sparse and identifiable linear latent variable (factor) and linear Bayesian network models for parsimonious analysis of multivariate data. We propose a computationally efficient method for joint parameter and model inference, and model comparison. It consists of a fully...... Bayesian hierarchy for sparse models using slab and spike priors (two-component δ-function and continuous mixtures), non-Gaussian latent factors and a stochastic search over the ordering of the variables. The framework, which we call SLIM (Sparse Linear Identifiable Multivariate modeling), is validated and......-linear Identifiable Multivariate modeling) and allowing for correlations between latent variables, called CSLIM (Correlated SLIM), for the temporal and/or spatial data. The source code and scripts are available from http://cogsys.imm.dtu.dk/ slim/. © 2011 Ricardo Henao and Ole Winther....

  4. Currarino syndrome: variability of imaging findings in 22 moleculargenetically identified (HLXB9 mutation) patients from five families; Currarino-Syndrom: Variabilitaet der bildgebenden Befunde bei 22 molekulargenetisch identifizierten (HLXB9-Mutation) Patienten aus fuenf Familien

    Energy Technology Data Exchange (ETDEWEB)

    Riebel, T.; Scheer, I. [Abt. Paediatrische Radiologie d. Klinik fuer Strahlenheilkunde, Charite - Universitaetsmedizin Berlin (Germany); Koechling, J. [Klinik fuer Paediatrie mit Schwerpunkt Onkologie u. Haematologie, Charite - Universitaetsmedizin Berlin (Germany); Oellinger, J. [Klinik fuer Strahlenheilkunde, Charite - Universitaetsmedizin Berlin (Germany); Reis, A. [Inst. fuer Humangenetik, Charite - Universitaetsmedizin Berlin u. Friedrich-Alexander-Univ., Erlangen-Nuernberg (Germany)

    2004-04-01

    Purpose: The imaging documents, obtained in connection with a primarily molecular genetic study on Currarino syndrome, should be evaluated with special respect to the constancy resp. the variability of findings in patients with proven HLBX9 mutations. Methods: In five female non-related index patients with clinicoradiologically diagnosed Currarino syndrome and further 53 members of their families, changes of the homeobox gene HLXB9 had been analysed. Variable mutations of this gene were found in a total of 23 individuals including the five index patients. In 22 of them the preexisting radiological documents could be collected as well as further imaging (plain sacrococcygeal radiography and/or lumbosacral MRI at least) initiated. This was followed by a detailed evaluation of pathological findings in the os sacrum/coccyx as well as in the presacral, the intraspinal, the anorectal, and the urogenital region, finally. Results: Imaging investigations revealed concomitant phenotypic abnormalities in all and even nine clinically asymptomatic individuals with proven HLXB9 mutations. A sacrococcygeal defect of varying intensity was depicted in every case. Complete Currarino triad (i.e. sacrococcygeal defect, presacral mass=anterior meningocele and/or tumor, anorectalmalformation) was only found in the five index patients and three further relatives. In all other cases, one or more of the following anomalies were detected with variable combination and with decreasing frequency: anterior meningocele (12) presacral tumor (11), tethered cord (10), intraspinal lipoma (8), anorectal stenosis/atresia (8), syringocele (5), rectal fistula (3), urogenital (2). (orig.) [German] Ziel: Die im Rahmen einer primaer molekulargenetischen Studie angefertigten ergaenzenden radiologischen Dokumente sollten im Hinblick auf die Konstanz bzw. Variabilitaet der bildgebenden Befunde bei gesichertem Currarino-Syndrom retrospektiv analysiert werden. Methode: Insgesamt 58 Mitglieder aus den Familien

  5. Variability of the Spin Period of the White Dwarf in the Intermediate Polar V405 Aur: Low-Mass Third Body or Precession ?

    CERN Document Server

    Breus, V V; Dubovsky, P; Kolesnikov, S V; Zhuzhulina, E A; Hegedus, T; Beringer, P; Petrik, K; Robertson, J W; Kudzej, I; Shakhovskoy, N M

    2013-01-01

    We present the results of photometric CCD observations of the magnetic cataclysmic variable V405 Aurigae (RX J0558.0+5353 = 1RXS J055800.7+535358) obtained using different instruments. We analysed variability of the spin period of the white dwarf in the V405 Aur (RX J0558.0+5353) system using our observations and previously published maxima timings. The spin period of the system in 2010-2012 is $P=545.4558163(94)$s. As we have gaps in observational data, we present 2 hypotheses of the spin period variability of this system - a cubic ephemeris which may be interpreted by a precession of the magnetic white dwarf or a periodic change with a period of 6.2 years and semi-amplitude of $17.2\\pm1.8$ sec. The periodic variations may be interpreted by a light-time effect caused by a low-mass star ($M_3\\ge0.09M_\\odot$). In this case, the system belongs to a rare class of cataclysmic variables with a third body.

  6. Housekeeping Gene Sequencing and Multilocus Variable-Number Tandem-Repeat Analysis To Identify Subpopulations within Pseudomonas syringae pv. maculicola and Pseudomonas syringae pv. tomato That Correlate with Host Specificity

    Science.gov (United States)

    Gironde, S.

    2012-01-01

    Pseudomonas syringae pv. maculicola causes bacterial spot on Brassicaceae worldwide, and for the last 10 years severe outbreaks have been reported in the Loire Valley, France. P. syringae pv. maculicola resembles P. syringae pv. tomato in that it is also pathogenic for tomato and causes the same types of symptoms. We used a collection of 106 strains of P. syringae to characterize the relationships between P. syringae pv. maculicola and related pathovars, paying special attention to P. syringae pv. tomato. Phylogenetic analysis of gyrB and rpoD gene sequences showed that P. syringae pv. maculicola, which causes diseases in Brassicaceae, forms six genetic lineages within genomospecies 3 of P. syringae strains as defined by L. Gardan et al. (Int. J. Syst. Bacteriol. 49[Pt 2]:469–478, 1999), whereas P. syringae pv. tomato forms two distinct genetic lineages. A multilocus variable-number tandem-repeat (VNTR) analysis (MLVA) conducted with eight minisatellite loci confirmed the genetic structure obtained with rpoD and gyrB sequence analyses. These results provide promising tools for fine-scale epidemiological studies on diseases caused by P. syringae pv. maculicola and P. syringae pv. tomato. The two pathovars had distinct host ranges; only P. syringae pv. maculicola strains were pathogenic for Brassicaceae. A subpopulation of P. syringae pv. maculicola strains that are pathogenic for Pto-expressing tomato plants were shown to lack avrPto1 and avrPtoB or to contain a disrupted avrPtoB homolog. Taking phylogenetic and pathological features into account, our data suggest that the DC3000 strain belongs to P. syringae pv. maculicola. This study shows that P. syringae pv. maculicola and P. syringae pv. tomato appear multiclonal, as they did not diverge from a single common ancestral group within the ancestral P. syringae genomospecies 3, and suggests that pathovar specificity within P. syringae may be due to independent genetic events. PMID:22389364

  7. SDSS J142625.71+575218.3, a Prototype for a New Class of Variable White Dwarf

    CERN Document Server

    Montgomery, M H; Winget, D E; Dufour, Patrick; Degennaro, Steven; Liebert, James

    2008-01-01

    We present the results of a search for pulsations in six of the recently discovered carbon-atmosphere white dwarf ("hot DQ") stars. Based on our theoretical calculations, the star SDSS J142625.71+575218.3 is the only object expected to pulsate. We observe this star to be variable, with significant power at 417.7 s and 208.8 s (first harmonic), making it a strong candidate as the first member of a new class of pulsating white dwarf stars, the DQVs. Its folded pulse shape, however, is quite different from that of other white dwarf variables, and shows similarities with that of the cataclysmic variable AM CVn, raising the possibility that this star may be a carbon-transferring analog of AM CVn stars. In either case, these observations represent the discovery of a new and exciting class of object.

  8. Orbital and spin variability of the Intermediate Polar BG CMi

    CERN Document Server

    Kim, Y G; Park, S S; Jeon, Y B

    2005-01-01

    Results of a CCD study of the variability of the cataclysmic variable BG CMi obtained at the Korean 1.8m telescope in 2002-2005 are presented. The "multi-comparison star" method had been applied for better accuracy estimates. The linear ephemeris based on 19 mean maxima for 2002--2005 is HJD 2453105.31448(6)+0.01057257716(198)(E-764707). The period differs from that predicted by the quadratic ephemeris by Pych et al. (1996) leading to a possible cycle miscount. The statistically optimal ephemeris is a fourth-order polynomial, as a quadratic or even a cubic ephemeris leads to unaceptably large residuals: Min.HJD=$ 2445020.28095(28)+0.0105729609(57)E -1.58(32)\\cdot10^{-13}E^2-5.81(64)\\cdot10^{-19}E^3+4.92(41)\\cdot10^{-25}E^4.$ Thus the rate of the spin-up of the white dwarf is decreasing. An alternative explanation is that the spin-up has been stopped during recent years. The deviations between the amplutudes of the spin variability in V and R, as well as between phases are not statistically significant. Howeve...

  9. WIND VARIABILITY IN BZ CAMELOPARDALIS

    Energy Technology Data Exchange (ETDEWEB)

    Honeycutt, R. K. [Astronomy Department, Indiana University, Swain Hall West, Bloomington, IN 47405 (United States); Kafka, S. [Department of Terrestrial Magnetism, Carnegie Institute of Washington, 5241 Broad Branch Road NW, Washington, DC 2001 (United States); Robertson, J. W., E-mail: honey@astro.indiana.edu, E-mail: skafka@dtm.ciw.edu, E-mail: jrobertson@atu.edu [Department of Physical Sciences, Arkansas Tech University, 1701 North Boulder Avenue, Russellville, AR 72801-2222 (United States)

    2013-02-01

    Sequences of spectra of the nova-like cataclysmic variable (CV) BZ Cam were acquired on nine nights in 2005-2006 in order to study the time development of episodes of wind activity known to occur frequently in this star. We confirm the results of Ringwald and Naylor that the P-Cygni absorption components of the lines mostly evolve from higher expansion velocity to lower velocity as an episode progresses. We also commonly find blueshifted emission components in the H{alpha} line profile, whose velocities and durations strongly suggest that they are also due to the wind. Curiously, Ringwald and Naylor reported common occurrences of redshifted H{alpha} emission components in their BZ Cam spectra. We have attributed these emission components in H{alpha} to occasions when gas concentrations in the bipolar wind (both front side and back side) become manifested as emission lines as they move beyond the disk's outer edge. We also suggest, based on changes in the P-Cygni profiles during an episode, that the progression from larger to smaller expansion velocities is due to the higher velocity portions of a wind concentration moving beyond the edge of the continuum light of the disk first, leaving a net redward shift of the remaining absorption profile. We derive a new orbital ephemeris for BZ Cam, using the radial velocity of the core of the He I {lambda}5876 line, finding P = 0.15353(4). Using this period, the wind episodes in BZ Cam are found to be concentrated near the inferior conjunction of the emission line source. This result helps confirm that the winds in nova-like CVs are often phase dependent, in spite of the puzzling implication that such winds lack axisymmetry. We argue that the radiation-driven wind in BZ Cam receives an initial boost by acting on gas that has been lifted above the disk by the interaction of the accretion stream with the disk, thereby imposing flickering timescales onto the wind events, as well as leading to an orbital modulation of the

  10. Deep radio imaging of 47 Tuc identifies the peculiar X-ray source X9 as a new black hole candidate

    Science.gov (United States)

    Miller-Jones, J. C. A.; Strader, J.; Heinke, C. O.; Maccarone, T. J.; van den Berg, M.; Knigge, C.; Chomiuk, L.; Noyola, E.; Russell, T. D.; Seth, A. C.; Sivakoff, G. R.

    2015-11-01

    We report the detection of steady radio emission from the known X-ray source X9 in the globular cluster 47 Tuc. With a double-peaked C IV emission line in its ultraviolet spectrum providing a clear signature of accretion, this source had been previously classified as a cataclysmic variable. In deep ATCA (Australia Telescope Compact Array) imaging from 2010 and 2013, we identified a steady radio source at both 5.5 and 9.0 GHz, with a radio spectral index (defined as Sν ∝ να) of α = -0.4 ± 0.4. Our measured flux density of 42 ± 4 μJy beam-1 at 5.5 GHz implies a radio luminosity (νLν) of 5.8 × 1027 erg s-1, significantly higher than any previous radio detection of an accreting white dwarf. Transitional millisecond pulsars, which have the highest radio-to-X-ray flux ratios among accreting neutron stars (still a factor of a few below accreting black holes at the same LX), show distinctly different patterns of X-ray and radio variability than X9. When combined with archival X-ray measurements, our radio detection places 47 Tuc X9 very close to the radio/X-ray correlation for accreting black holes, and we explore the possibility that this source is instead a quiescent stellar-mass black hole X-ray binary. The nature of the donor star is uncertain; although the luminosity of the optical counterpart is consistent with a low-mass main-sequence donor star, the mass transfer rate required to produce the high quiescent X-ray luminosity of 1033 erg s-1 suggests the system may instead be ultracompact, with an orbital period of order 25 min. This is the fourth quiescent black hole candidate discovered to date in a Galactic globular cluster, and the only one with a confirmed accretion signature from its optical/ultraviolet spectrum.

  11. Complex variables

    CERN Document Server

    Fisher, Stephen D

    1999-01-01

    The most important topics in the theory and application of complex variables receive a thorough, coherent treatment in this introductory text. Intended for undergraduates or graduate students in science, mathematics, and engineering, this volume features hundreds of solved examples, exercises, and applications designed to foster a complete understanding of complex variables as well as an appreciation of their mathematical beauty and elegance. Prerequisites are minimal; a three-semester course in calculus will suffice to prepare students for discussions of these topics: the complex plane, basic

  12. Identifying climatic drivers of tropical forest dynamics

    Science.gov (United States)

    Aubry-Kientz, M.; Rossi, V.; Wagner, F.; Hérault, B.

    2015-10-01

    In the context of climate change, identifying and then predicting the impacts of climatic drivers on tropical forest dynamics is becoming a matter of urgency. To look at these climate impacts, we used a coupled model of tropical tree growth and mortality, calibrated with forest dynamic data from the 20-year study site of Paracou, French Guiana, in order to introduce and test a set of climatic variables. Three major climatic drivers were identified through the variable selection procedure: drought, water saturation and temperature. Drought decreased annual growth and mortality rates, high precipitation increased mortality rates and high temperature decreased growth. Interactions between key functional traits, stature and climatic variables were investigated, showing best resistance to drought for trees with high wood density and for trees with small current diameters. Our results highlighted strong long-term impacts of climate variables on tropical forest dynamics, suggesting potential deep impacts of climate changes during the next century.

  13. Identifiability in stochastic models

    CERN Document Server

    1992-01-01

    The problem of identifiability is basic to all statistical methods and data analysis, occurring in such diverse areas as Reliability Theory, Survival Analysis, and Econometrics, where stochastic modeling is widely used. Mathematics dealing with identifiability per se is closely related to the so-called branch of ""characterization problems"" in Probability Theory. This book brings together relevant material on identifiability as it occurs in these diverse fields.

  14. Coherence method of identifying signal noise model

    International Nuclear Information System (INIS)

    The noise analysis method is discussed in identifying perturbance models and their parameters by a stochastic analysis of the noise model of variables measured on a reactor. The analysis of correlations is made in the frequency region using coherence analysis methods. In identifying an actual specific perturbance, its model should be determined and recognized in a compound model of the perturbance system using the results of observation. The determination of the optimum estimate of the perturbance system model is based on estimates of related spectral densities which are determined from the spectral density matrix of the measured variables. Partial and multiple coherence, partial transfers, the power spectral densities of the input and output variables of the noise model are determined from the related spectral densities. The possibilities of applying the coherence identification methods were tested on a simple case of a simulated stochastic system. Good agreement was found of the initial analytic frequency filters and the transfers identified. (B.S.)

  15. Cardinality-dependent Variability in Orthogonal Variability Models

    DEFF Research Database (Denmark)

    Mærsk-Møller, Hans Martin; Jørgensen, Bo Nørregaard

    2012-01-01

    During our work on developing and running a software product line for eco-sustainable greenhouse-production software tools, which currently have three products members we have identified a need for extending the notation of the Orthogonal Variability Model (OVM) to support what we refer to as...... cardinality range dependencies. The cardinality-range-dependency type enables expressing that the binding of a certain number of variants to a variation point can influence variability in other places in the model. In other words, we acknowledge that variability can be influenced, not necessarily by the...

  16. Identifying Unknown Proteins

    OpenAIRE

    Barker, Winona C.; Dayhoff, Margaret O.

    1983-01-01

    In this paper we discuss ways to identify a protein, both when its amino acid sequence is known and, particularly, prior to the determination of the complete sequence. If a similar sequence is in the Protein Sequence Database, an unknown may be identified on the basis of partial or ambiguous sequence data, or on the basis of amino acid composition. Identification in the early stages of structural determination can save time and scarce resources by preventing duplicate effort or by suggesting ...

  17. PRACTICAL INSIGHTS FROM OCA VARIABLE COMBINATIONS

    OpenAIRE

    Ozer Itir; Ozkan Ibrahim

    2008-01-01

    This study aims to identify optimum currency areas (OCA) variables that distinguish certain Economic and Monetary Union (EMU) member countries from the other EMU members. In the previous studies, EMU members were identified in the light of criteria suggested by the OCA theory. In this study, in order to obtain additional insights, we analyzed OCA variables and the performance of European countries with respect to these variables. Our analysis shows that some of the EMU member countries are di...

  18. Identifying Knowledge and Communication

    Directory of Open Access Journals (Sweden)

    Eduardo Coutinho Lourenço de Lima

    2006-12-01

    Full Text Available In this paper, I discuss how the principle of identifying knowledge which Strawson advances in ‘Singular Terms and Predication’ (1961, and in ‘Identifying Reference and Truth-Values’ (1964 turns out to constrain communication. The principle states that a speaker’s use of a referring expression should invoke identifying knowledge on the part of the hearer, if the hearer is to understand what the speaker is saying, and also that, in so referring, speakers are attentive to hearers’ epistemic states. In contrasting it with Russell’s Principle (Evans 1982, as well as with the principle of identifying descriptions (Donnellan 1970, I try to show that the principle of identifying knowledge, ultimately a condition for understanding, makes sense only in a situation of conversation. This allows me to conclude that the cooperative feature of communication (Grice 1975 and reference (Clark andWilkes-Gibbs 1986 holds also at the understanding level. Finally, I discuss where Strawson’s views seem to be unsatisfactory, and suggest how they might be improved.

  19. A photometric study of the nova-like variable TT Arietis with the MOST satellite

    CERN Document Server

    Vogt, N; Moffat, A F J; Matthews, J M; Kuschnig, R; Guenther, D B; Rowe, J F; Rucinski, S M; Sasselov, D; Weiss, W W

    2013-01-01

    Variability on all time scales between seconds and decades is typical for cataclysmic variables (CVs). One of the brightest and best studied CVs is TT Ari, a nova-like variable which belongs to the VY Scl subclass, characterized by occasional low states in their light curves. It is also known as a permanent superhumper at high state, revealing "positive" (P_S > P_0) as well as "negative" (P_S < P_0) superhumps, where P_S is the period of the superhump and P_0 the orbital period. TT Ari was observed by the Canadian space telescope MOST for about 230 hours nearly continuously in 2007, with a time resolution of 48 seconds. Here we analyze these data, obtaining a dominant "negative" superhump signal with a period P_S = 0.1331 days and a mean amplitude of 0.09 mag. Strong flickering with amplitudes up to 0.2 mag and peak-to-peak time scales of 15-20 minutes is superimposed on the periodic variations. We found no indications for significant quasi-periodic oscillations with periods around 15 minutes, reported by ...

  20. Disc structure and variability in dwarf novae

    Science.gov (United States)

    Harlaftis, Emilios Theofanus

    An introduction is given to dwarf novae reviewing the current research status in the field. We present IUE observations of Z Cha which support the mass transfer instability as the cause of the superoutbursts observed in SU UMa type dwarf novae. Comparison between the superoutburst and a normal outburst of Z Cha shows that the disc is flatter and has significantly less azimuthal structure than during superoutburst. Z Cha exhibits a soft x-ray deficit during superoutburst compared to OY Car. We find that the secondary star of Z Cha contributes approximately 30 percent of the infrared flux at peak of outburst. The second part of the thesis presents results from the 1988 International Time Project at the Observatorio del Roque de los Muchachos. Investigation of the behavior of SU UMa and YZ Cnc is carried out through the outburst cycle. The secular changes of the equivalent widths of both systems shows an increasing trend even during quiescence and are caused by the continuum decrease. Both systems show a low-velocity emission component which contaminates the wings of the H(alpha) profile. In addition to doppler broadening, the Stark effect is found to cause significant broadening to the line profile. The radial dependence of the emission lines is discussed in relation to other cataclysmic variables. H(alpha) emission from the secondary star of YZ Cnc is found during superoutburst, during outburst and during quiescence after outburst. Photometry during late decline of outburst shows a sinusoidal, weak variation peaking at 0.5 orbital phase and which is related to heating of the red star or to a transient disc event. During quiescence, the flickering is found to be caused by the bright spot. This modulation increases with time and is maximum before the outburst. Doppler tomography of IP Peg during quiescence reveals an emission line distribution not consistent to the standard model. We find Balmer emission from the secondary star, at a level of only 2.5 percent of the

  1. Exploring the crowded central region of 10 Galactic globular clusters using EMCCDs. Variable star searches and new discoveries

    CERN Document Server

    Jaimes, R Figuera; Skottfelt, J; Kains, N; Jørgensen, U G; Horne, K; Dominik, M; Alsubai, K A; Bozza, V; Novati, S Calchi; Ciceri, S; D'Ago, G; Galianni, P; Gu, S -H; Harpsøe, K B W; Haugbølle, T; Hinse, T C; Hundertmark, M; Juncher, D; Korhonen, H; Liebig, C; Mancini, L; Popovas, A; Rabus, M; Rahvar, S; Scarpetta, G; Schmidt, R W; Snodgrass, C; Southworth, J; Starkey, D; Street, R A; Surdej, J; Wang, X -B; Wertz, O

    2015-01-01

    Obtain time-series photometry of the very crowded central regions of Galactic globular clusters with better angular resolution than previously achieved with conventional CCDs on ground-based telescopes to complete, or improve, the census of the variable star population in those stellar systems. Images were taken using the Danish 1.54-m Telescope at the ESO observatory at La Silla in Chile. The telescope was equipped with an electron-multiplying CCD and the short-exposure-time images obtained (10 images per second) were stacked using the shift-and-add technique to produce the normal-exposure-time images (minutes). Photometry was performed via difference image analysis. Automatic detection of variable stars in the field was attempted. The light curves of 12541 stars in the cores of 10 globular clusters were statistically analysed in order to automatically extract the variable stars. We obtained light curves for 31 previously known variable stars (3 L, 2 SR, 20 RR Lyrae, 1 SX Phe, 3 cataclysmic variables, 1 EW a...

  2. Internally readable identifying tag

    International Nuclear Information System (INIS)

    A method of identifying non-metallic objects by means of X-ray equipment is described in detail. A small metal pin with a number of grooves cut in a pre-determined equi-spaced pattern is implanted into the non-metallic object and by decoding the groove patterns using X-ray equipment, the object is uniquely identified. A specific example of such an application is in studying the migratory habits of fish. The pin inserted into the snout of the fish is 0.010 inch in diameter, 0.040 inch in length with 8 possible positions for grooves if spaced 0.005 inch apart. With 6 of the groove positions available for data, the capacity is 26 or 64 combinations; clearly longer pins would increase the data capacity. This method of identification is a major advance over previous techniques which necessitated destruction of the fish in order to recover the identification tag. (UK)

  3. Identifying Fiscal Inflation

    OpenAIRE

    De Graeve, Ferre; Queijo von Heideken, Virginia

    2013-01-01

    Fiscal theorists warn about the risk of future inflation as a consequence of current fiscal imbalances in the US. Because actual inflation remains historically low and data on inflation expectations do not corroborate such risks, warnings for fiscal inflation are often ignored in policy and academic circles. This paper shows that a canonical NK- DSGE model enables identifying an anticipated component of inflation expectations that is closely related to fiscal policy. Estimation results sugges...

  4. On identified predictive control

    Science.gov (United States)

    Bialasiewicz, Jan T.

    1993-01-01

    Self-tuning control algorithms are potential successors to manually tuned PID controllers traditionally used in process control applications. A very attractive design method for self-tuning controllers, which has been developed over recent years, is the long-range predictive control (LRPC). The success of LRPC is due to its effectiveness with plants of unknown order and dead-time which may be simultaneously nonminimum phase and unstable or have multiple lightly damped poles (as in the case of flexible structures or flexible robot arms). LRPC is a receding horizon strategy and can be, in general terms, summarized as follows. Using assumed long-range (or multi-step) cost function the optimal control law is found in terms of unknown parameters of the predictor model of the process, current input-output sequence, and future reference signal sequence. The common approach is to assume that the input-output process model is known or separately identified and then to find the parameters of the predictor model. Once these are known, the optimal control law determines control signal at the current time t which is applied at the process input and the whole procedure is repeated at the next time instant. Most of the recent research in this field is apparently centered around the LRPC formulation developed by Clarke et al., known as generalized predictive control (GPC). GPC uses ARIMAX/CARIMA model of the process in its input-output formulation. In this paper, the GPC formulation is used but the process predictor model is derived from the state space formulation of the ARIMAX model and is directly identified over the receding horizon, i.e., using current input-output sequence. The underlying technique in the design of identified predictive control (IPC) algorithm is the identification algorithm of observer/Kalman filter Markov parameters developed by Juang et al. at NASA Langley Research Center and successfully applied to identification of flexible structures.

  5. Identifying Phronotypes in Psychiatry

    Directory of Open Access Journals (Sweden)

    F. AndrewKozel

    2010-10-01

    Full Text Available Refinements in the methods of diagnosis for psychiatric disorders are critically needed. These new methods should be based on objectively measured brain characteristics that provide clinically useful information. Studying the brain with respect to psychiatric disorders, however, faces numerous challenges. Utilizing techniques learned in other areas of medicine to deal with symptoms that lead to complex disorders can provide insight into improving diagnostic models in psychiatry. Specifically, many areas of medicine use objective measures of an organ’s function or characteristic to guide clinical management of particular subjective complaints. In psychiatry, an objectively measured brain characteristic that provides clinically useful information is proposed to be that person’s “phronotype.” Important requirements to developing phronotypes are discussed. Identifying phronotypes in psychiatry will require a specific investigative approach that must be grounded in rigorous scientific methodology. Successfully developing such markers will have a profound impact on clinical care, clinical research, basic science research, and most importantly the lives of those suffering from these illnesses.

  6. Mutually Unbiased Bases for Continuous Variables

    OpenAIRE

    Weigert, Stefan; Wilkinson, Michael

    2008-01-01

    The concept of mutually unbiased bases is studied for N pairs of continuous variables. To find mutually unbiased bases reduces, for specific states related to the Heisenberg-Weyl group, to a problem of symplectic geometry. Given a single pair of continuous variables, three mutually unbiased bases are identified while five such bases are exhibited for two pairs of continuous variables. For N = 2, the golden ratio occurs in the definition of these mutually unbiased bases suggesting the relevanc...

  7. Quantification of high latitude electric field variability

    OpenAIRE

    Crowley, G.; Hackert, C.L.

    2001-01-01

    Variability in the high latitude electric field has been identified as a major contributor to global Joule heating. Electric field patterns from the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure are used to characterize the E-field temporal variability over the course of 18 hours. The standard deviation of the E-field magnitude on May 4, 1998 often exceeds the average value of the E-field magnitude. A significant fraction of this variability arises from oscillations wit...

  8. Digital Identifier Systems: Comparative Evaluation

    OpenAIRE

    Hamid Reza Khedmatgozar; Mehdi Alipour-Hafezi; Payam Hanafizadeh

    2015-01-01

    Identifier is one of the main elements in identifying an object in digital environment. Digital identifier systems were developed followed by a lot of problems such as violation of persistency and uniqueness of physical identifiers and URL in digital environment. These identifiers try to guarantee uniqueness and persistency of hostnames by using indirect names for Domain Name System (DNS). The main objective of this research is to identify qualified digital identifier system among other syste...

  9. Decomposing global crop yield variability

    International Nuclear Information System (INIS)

    Recent food crises have highlighted the need to better understand the between-year variability of agricultural production. Although increasing future production seems necessary, the globalization of commodity markets suggests that the food system would also benefit from enhanced supplies stability through a reduction in the year-to-year variability. Here, we develop an analytical expression decomposing global crop yield interannual variability into three informative components that quantify how evenly are croplands distributed in the world, the proportion of cultivated areas allocated to regions of above or below average variability and the covariation between yields in distinct world regions. This decomposition is used to identify drivers of interannual yield variations for four major crops (i.e., maize, rice, soybean and wheat) over the period 1961–2012. We show that maize production is fairly spread but marked by one prominent region with high levels of crop yield interannual variability (which encompasses the North American corn belt in the USA, and Canada). In contrast, global rice yields have a small variability because, although spatially concentrated, much of the production is located in regions of below-average variability (i.e., South, Eastern and South Eastern Asia). Because of these contrasted land use allocations, an even cultivated land distribution across regions would reduce global maize yield variance, but increase the variance of global yield rice. Intermediate results are obtained for soybean and wheat for which croplands are mainly located in regions with close-to-average variability. At the scale of large world regions, we find that covariances of regional yields have a negligible contribution to global yield variance. The proposed decomposition could be applied at any spatial and time scales, including the yearly time step. By addressing global crop production stability (or lack thereof) our results contribute to the understanding of a key

  10. The Tabu Search Procedure: An Alternative to the Variable Selection Methods

    Science.gov (United States)

    Mills, Jamie, D.; Olejnik, Stephen, F.; Marcoulides, George, A.

    2005-01-01

    The effectiveness of the Tabu variable selection algorithm, to identify predictor variables related to a criterion variable, is compared with the stepwise variable selection method and the all possible regression approach. Considering results obtained from previous research, Tabu is more successful in identifying relevant variables than the…

  11. Do Psychological Variables Affect Early Surgical Recovery?

    OpenAIRE

    Mavros, Michael N.; Athanasiou, Stavros; Gkegkes, Ioannis D.; Polyzos, Konstantinos A.; Peppas, George; Falagas, Matthew E.

    2011-01-01

    Background Numerous studies have examined the effect of psychological variables on surgical recovery, but no definite conclusion has been reached yet. We sought to examine whether psychological factors influence early surgical recovery. Methods We performed a systematic search in PubMed, Scopus and PsycINFO databases to identify studies examining the association of preoperative psychological variables or interventions with objectively measured, early surgical outcomes. Results We identified 1...

  12. Highly variable cancer subpopulations that exhibit enhanced transcriptome variability and metastatic fitness.

    Science.gov (United States)

    Nguyen, Alexander; Yoshida, Mitsukuni; Goodarzi, Hani; Tavazoie, Sohail F

    2016-01-01

    Individual cells within a tumour can exhibit distinct genetic and molecular features. The impact of such diversification on metastatic potential is unknown. Here we identify clonal human breast cancer subpopulations that display different levels of morphological and molecular diversity. Highly variable subpopulations are more proficient at metastatic colonization and chemotherapeutic survival. Through single-cell RNA-sequencing, inter-cell transcript expression variability is identified as a defining feature of the highly variable subpopulations that leads to protein-level variation. Furthermore, we identify high variability in the spliceosomal machinery gene set. Engineered variable expression of the spliceosomal gene SNRNP40 promotes metastasis, attributable to cells with low expression. Clinically, low SNRNP40 expression is associated with metastatic relapse. Our findings reveal transcriptomic variability generation as a mechanism by which cancer subpopulations can diversify gene expression states, which may allow for enhanced fitness under changing environmental pressures encountered during cancer progression. PMID:27138336

  13. On the area of accretion curtains from fast aperiodic time variability of the intermediate polar EX Hya

    CERN Document Server

    Semena, Andrey N; Buckley, David A H; Kotze, Marissa M; Khabibullin, Ildar I; Breytenbach, Hannes; Gulbis, Amanda A S; Coppejans, Rocco; Potter, Stephen B

    2014-01-01

    We present results of a study of the fast timing variability of the magnetic cataclysmic variable (mCV) EX Hya. It was previously shown that one may expect the rapid flux variability of mCVs to be smeared out at timescales shorter than the cooling time of hot plasma in the post shock region of the accretion curtain near the WD surface. Estimates of the cooling time and the mass accretion rate, thus provide us with a tool to measure the density of the post-shock plasma and the cross-sectional area of the accretion funnel at the WD surface. We have probed the high frequencies in the aperiodic noise of one of the brightest mCV EX Hya with the help of optical telescopes, namely SALT and the SAAO 1.9m telescope. We place upper limits on the plasma cooling timescale $\\tau<$0.3 sec, on the fractional area of the accretion curtain footprint $f<1.6\\times10^{-4}$, and a lower limit on the specific mass accretion rate $\\dot{M}/A \\gtrsim $3 g/sec/cm$^{-2}$. We show that measurements of accretion column footprints v...

  14. Rms-flux relation and fast optical variability simulations of the nova-like system MV Lyr

    CERN Document Server

    Dobrotka, A; Ness, J -U

    2014-01-01

    The stochastic variability (flickering) of the nova-like system (subclass of cataclysmic variable) MV Lyr yields a complicated power density spectrum with four break frequencies. Scaringi et al. (2012) analysed high-cadence Kepler data of MV Lyr, taken almost continuously over 600 days, giving the unique opportunity to study multicomponent Power Density Spectra (PDS) over a wide frequency range. We modelled this variability with our statistical model based on disc angular momentum transport via discrete turbulent bodies with an exponential distribution of the dimension scale. Two different models were used, a full disc (developed from the white dwarf to the outer radius of ~10^10 cm) and a radially thin disc (a ring at a distance of ~10^10 cm from the white dwarf) that imitates an outer disc rim. We succeed in explaining the two lowest observed break frequencies assuming typical values for a disc radius of 0.5 and 0.9 times the primary Roche lobe and an alpha parameter of 0.1-0.4. The highest observed break f...

  15. Lean Thinking in systems with non-negligible process variability

    DEFF Research Database (Denmark)

    Nielsen, Erland Hejn; Simons, David

    2000-01-01

    , Time, Centralisation and Structure. Control focuses on removing variability from the information and physical flows through standardisation of processes. Empirical evidence from automotive after-sales demonstrated that simulation could identify the areas of variability with greatest leverage on cost...

  16. Lean Thinking in Systems with Non-Negligible Process Variability

    DEFF Research Database (Denmark)

    Nielsen, Erland Hejn; Simons, David

    2000-01-01

    , Time, Centralisation and Structure. Control focuses on removing variability from the information and physical flows through standardisation of processes. Empirical evidence from automotive after-sales demonstrated that simulation could identify the areas of variability with greatest leverage on cost...

  17. Sparse estimation for structural variability

    Directory of Open Access Journals (Sweden)

    Singh Rohit

    2011-04-01

    Full Text Available Abstract Background Proteins are dynamic molecules that exhibit a wide range of motions; often these conformational changes are important for protein function. Determining biologically relevant conformational changes, or true variability, efficiently is challenging due to the noise present in structure data. Results In this paper we present a novel approach to elucidate conformational variability in structures solved using X-ray crystallography. We first infer an ensemble to represent the experimental data and then formulate the identification of truly variable members of the ensemble (as opposed to those that vary only due to noise as a sparse estimation problem. Our results indicate that the algorithm is able to accurately distinguish genuine conformational changes from variability due to noise. We validate our predictions for structures in the Protein Data Bank by comparing with NMR experiments, as well as on synthetic data. In addition to improved performance over existing methods, the algorithm is robust to the levels of noise present in real data. In the case of Human Ubiquitin-conjugating enzyme Ubc9, variability identified by the algorithm corresponds to functionally important residues implicated by mutagenesis experiments. Our algorithm is also general enough to be integrated into state-of-the-art software tools for structure-inference.

  18. Variable stars identification in digitized photographic data

    CERN Document Server

    Sokolovsky, K V; Zubareva, A M; Samus, N N; Antipin, S V

    2016-01-01

    We identify 339 known and 316 new variable stars of various types among 250000 lightcurves obtained by digitizing 167 30x30cm photographic plates of the Moscow collection. We use these data to conduct a comprehensive test of 18 statistical characteristics (variability indices) in search for the best general-purpose variability detection statistic. We find that the highest peak on the DFT periodogram, interquartile range, median absolute deviation, and Stetson's L index are the most efficient in recovering variable objects from the set of photographic lightcurves used in our test.

  19. Variability in Race Tests with Heterodera glycines

    OpenAIRE

    Riggs, R. D.; Schmitt, D. P.; Noel, G. R.

    1988-01-01

    Tests of Heterodera glycines on differential host plants to determine races were run in Arkansas, Illinois, and North Carolina to check the uniformity of results of the test. Methods used at the three locations varied somewhat. Results indicate that the race test is highly variable. Isolates previously identified as race 1 were identified as race 1 or race 3; those identified as race 2 were identified in these tests as race 2, 4, 9, or 14; those previously identified as race 3 were identified...

  20. Generalized Instrumental Variable Models

    OpenAIRE

    Chesher, Andrew; Rosen, Adam

    2013-01-01

    The ability to allow for flexible forms of unobserved heterogeneity is an essential ingredient in modern microeconometrics. In this paper we extend the application of instrumental variable (IV) methods to a wide class of problems in which multiple values of unobservable variables can be associated with particular combinations of observed endogenous and exogenous variables. In our Generalized Instrumental Variable (GIV) models, in contrast to traditional IV models, the mapping from unobserved ...

  1. Digital Identifier Systems: Comparative Evaluation

    Directory of Open Access Journals (Sweden)

    Hamid Reza Khedmatgozar

    2015-02-01

    Full Text Available Identifier is one of the main elements in identifying an object in digital environment. Digital identifier systems were developed followed by a lot of problems such as violation of persistency and uniqueness of physical identifiers and URL in digital environment. These identifiers try to guarantee uniqueness and persistency of hostnames by using indirect names for Domain Name System (DNS. The main objective of this research is to identify qualified digital identifier system among other systems. To achieve the research objective, researchers have considered two major steps: first, identifying main criteria for distinguishing digital identifier based on literature review and focus group interview; and second, performing a comparative evaluation on common identifier systems in the world. Findings of first step demonstrated seven main criteria in three domains for distinguishing digital identifier systems: identifier uniqueness and persistency in the identifier features domain, digital identification, digital uniqueness, digital persistency and digital actionability in the digital coverage domain, and globality in the comprehensiveness of scope domain. In the second step, results of the comparative evaluation on common identifier systems indicated that six identifier systems, included, DOI, Handle, UCI, URN, ARK and PURL, are appropriate choices for using as a digital identifier system. Also, according to these results, three identification systems Including NBN, MARIAM and ISNI were identified as suitable choices for digital identification in certain specialized fields. According to many benefits of using these identifiers in important applied fields, such as, digital content chains and networks integration, digital right management, cross referencing, digital libraries and citation analysis, results of this study can help digital environment experts to diagnose digital identifier and their effective use in applied fields.

  2. Exploring the crowded central region of ten Galactic globular clusters using EMCCDs. Variable star searches and new discoveries

    Science.gov (United States)

    Figuera Jaimes, R.; Bramich, D. M.; Skottfelt, J.; Kains, N.; Jørgensen, U. G.; Horne, K.; Dominik, M.; Alsubai, K. A.; Bozza, V.; Calchi Novati, S.; Ciceri, S.; D'Ago, G.; Galianni, P.; Gu, S.-H.; Harpsøe, K. B. W.; Haugbølle, T.; Hinse, T. C.; Hundertmark, M.; Juncher, D.; Korhonen, H.; Mancini, L.; Popovas, A.; Rabus, M.; Rahvar, S.; Scarpetta, G.; Schmidt, R. W.; Snodgrass, C.; Southworth, J.; Starkey, D.; Street, R. A.; Surdej, J.; Wang, X.-B.; Wertz, O.

    2016-04-01

    Aims: We aim to obtain time-series photometry of the very crowded central regions of Galactic globular clusters; to obtain better angular resolution thanhas been previously achieved with conventional CCDs on ground-based telescopes; and to complete, or improve, the census of the variable star population in those stellar systems. Methods: Images were taken using the Danish 1.54-m Telescope at the ESO observatory at La Silla in Chile. The telescope was equipped with an electron-multiplying CCD, and the short-exposure-time images obtained (ten images per second) were stacked using the shift-and-add technique to produce the normal-exposure-time images (minutes). Photometry was performed via difference image analysis. Automatic detection of variable stars in the field was attempted. Results: The light curves of 12 541 stars in the cores of ten globular clusters were statistically analysed to automatically extract the variable stars. We obtained light curves for 31 previously known variable stars (3 long-period irregular, 2 semi-regular, 20 RR Lyrae, 1 SX Phoenicis, 3 cataclysmic variables, 1 W Ursae Majoris-type and 1 unclassified) and we discovered 30 new variables (16 long-period irregular, 7 semi-regular, 4 RR Lyrae, 1 SX Phoenicis and 2 unclassified). Fluxes and photometric measurements for these stars are available in electronic form through the Strasbourg astronomical Data Center. Based on data collected by the MiNDSTEp team with the Danish 1.54m telescope at ESO's La Silla observatory in Chile.Full Table 1 is only available at CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/588/A128

  3. Beyond statistical descriptions of variability

    Science.gov (United States)

    Graham, Matthew; Catalina Real-time Transient Survey Team

    2016-01-01

    The first generation of large synoptic survey archives, such as CRTS, PTF and Pan-STARRs, are now (or soon will be) available to the community, enabling unprecedented systematic searches and studies of variable astrophysical phenomena. These range from moving objects in the Solar System to extreme quasars in the distant universe. However, much of the analyses of these data sets conducted so far have aimed at providing statistical descriptions of the variability. Whilst such parameterizations are useful for feeding classification algorithms, they are not effective at describing the underlying type of variability in the sources or the physical mechanism(s) for it. In this talk, we will discuss new approaches, such as wavelet variance, random matrix theory and echo state networks, that can provide insight into the science of variability rather than just statistically characterizing it. We will pay particular attention to sources exhibiting stochastic variation and how much information about the host system can be determined from their time series. For example, characteristic restframe timescales have been identified in quasars, potentially related to the size of coherent noise fields in the accretion disk. Finally, we will also consider the potential limitations of the next generation surveys, such as LSST and SKA.

  4. Problem of hidden variables

    Science.gov (United States)

    Santos, Emilio

    1992-10-01

    The problem of hidden variables in quantum mechanics is formalized as follows. A general or contextual (noncontextual) hidden-variables theory is defined as a mapping f: Q×M → C (f: Q→C) where Q is the set of projection operators in the appropriate (quantum) Hilbert space, M is the set of maximal Boolean subalgebras of Q and C is a (classical) Boolean algebra. It is shown that contextual (noncontextual) hidden-variables always exist (do not exist).

  5. Variability of Blazars

    Indian Academy of Sciences (India)

    J. H. Fan; Y. Liu; Y. Li; Q. F. Zhang; J. Tao; O. Kurtanidze

    2011-03-01

    Variability is one of the characteristics of blazars. The rapid variability is superposed on the long term variation. In this work, the variability on different time scales, such as intra-day (IDV), short-term (STV) and long-term (LTV) variations are presented for some sources. We also presented our own observations of some selected objects, for which the historical data were compiled for periodicity analysis using several methods. The parameters of the binary black hole system OJ 287 are determined.

  6. VARIABLE TIME DELAY MEANS

    Science.gov (United States)

    Clemensen, R.E.

    1959-11-01

    An electrically variable time delay line is described which may be readily controlled simuitaneously with variable impedance matching means coupied thereto such that reflections are prevented. Broadly, the delay line includes a signal winding about a magnetic core whose permeability is electrically variable. Inasmuch as the inductance of the line varies directly with the permeability, the time delay and characteristic impedance of the line both vary as the square root of the permeability. Consequently, impedance matching means may be varied similariy and simultaneously w:th the electrically variable permeability to match the line impedance over the entire range of time delay whereby reflections are prevented.

  7. A. Variable descriptions

    OpenAIRE

    Hohmann, Sebastian

    2012-01-01

    The appendix lists all variables, or component variables in the case of the institutional variables w and s, together with sources. Detailed descriptions, the wording of which is taken, if possible, directly from the original sources, are also given. Economic variables – dependent name:external_debt_cris source: Reinhart, Camen M. and Kenneth S. Rogoff, From Financial Crash to Debt Crisis, NBER Working Paper 15795, March 2010. Forthcoming in American Economic Review http://terpconnect.umd.edu...

  8. Interplay of Periodic, Cyclic and Stochastic Variability in Selected Areas of the H-R Diagram

    Science.gov (United States)

    Sterken, C.

    2003-03-01

    In 1999, the Ministry of the Flemish Community (Department for Science) allotted a research grant in the framework Bilateral scientific and technological cooperation to a consortium of four astronomical institutes, viz. Vrije Universiteit Brussel (Observational Astronomy), University of Concepcion (Department of Astronomy), Katholieke Universiteit Leuven (Astronomical Institute) and Royal Observatory of Belgium. The project, Long-Term Photometry of Variables, consolidates two decades of scientific collaboration between the Flemish and Chilean partners in the field of long-term monitoring of variable stars (Be stars, cataclysmic variables, S Dor and LBV stars, O stars, WR stars and pulsating main-sequence stars). The allotted grant intended to achieve intensive observing of several key objects selected among some of the most interesting variable stars of the southern hemisphere. The purpose of the present workshop was to comply with the Government's requirement to organise a scientific conference in Flanders in order to debate the scientific outcome of the project along with a broader discussion of related scientific aspects. However, the diversity of research topics dealt with during the course of this project makes it impossible to present a deep view of the field in workshop format. Instead, we decided to concentrate on one common attribute that we all encounter when studying above-mentioned classes of variable stars: the underlying periods and cycles, the methods used to find these cycles, and the associated aspects of interpretation of the oscillations found. The workshop format was a series of invited papers on key topics, supplemented with a number of contributed papers and posters, and ample time for discussions. The meeting consisted of seven sessions, each with a specific theme, viz. history (history of astronomy in Chile, variable star research, etc.), sky surveys, regular variations, non-regular and transient phenomena, chaos (observations), methods and

  9. Software Testing Requires Variability

    DEFF Research Database (Denmark)

    Christensen, Henrik Bærbak

    2003-01-01

    Software variability is the ability of a software system or artefact to be changed, customized or configured for use in a particular context. Variability in software systems is important from a number of perspectives. Some perspectives rightly receive much attention due to their direct economic i...

  10. Microinertia and internal variables

    CERN Document Server

    Berezovski, A

    2015-01-01

    The origin of microinertia of micromorphic theories is investigated from the point of view of non-equilibrium thermodynamics. In the framework of dual internal variables microinertia stems from a thermodynamic equation of state related to the internal variable with the properties of mechanical momentum.

  11. Collective variables and dissipation

    International Nuclear Information System (INIS)

    This course is an introduction to some basic concepts of non-equilibrium statistical mechanics. We put stress on the relevant entropy associated to a set of collective variables, on the meaning of the projection method in Liouville space and its use to establish equations of motion for these variables, and on the interpretation of dissipation in the framework of information theory

  12. Variable Synthetic Capacitance

    Science.gov (United States)

    Kleinberg, L. L.

    1986-01-01

    Feedback amplifier circuit synthesizes electronically variable capacitance. Variable Synthetic Capacitor is amplifier circuit with follower/feedback configuration. Effective input capacitance depends on input set current. If synthetic capacitor is connected across resonant element of oscillator, oscillator frequency controlled via input set current. Circuit especially suitable for fine frequency adjustments of piezoelectric-crystal or inductor/capacitor resonant oscillators.

  13. Tropical North Africa hydro climate variability

    International Nuclear Information System (INIS)

    NCEP/NCAR data are used to study the modulating circulations of the hydro climate of tropical North Africa. Wavelet analysis is used to identify modes of variability of stream flows within the region. Ocean-atmosphere circulation composites are considered to unravel the mechanisms for swing of stream flows. The one of the main finding of the study reveals that hydro climate variability swings within ENSO and decadal timescale. Pacific and Atlantic sea surface temperatures control the hydro climate mode of variability. Associated to Pacific sea surface temperature, the Atlantic Walker Circulation modulates the hydro climate swing of tropical North Africa. The detail result will be discussed.(Author)

  14. K2 Variable Catalogue I: A Catalogue of Variable Stars from K2 Field 0

    CERN Document Server

    Armstrong, D J; Brown, D J A; Kirk, J; Lam, K W F; Pollacco, D L; Spake, J; Walker, S R

    2014-01-01

    We have searched the K2 campaign 0 data for lightcurve variations associated with stellar variability. The results of this search are presented as a catalogue, giving the identifiers of nearly 2500 variable stars in the dataset. We list the detected range of the variation, periodicity if relevant and semi-amplitude. Lightcurves are classified into strictly periodic, quasi-periodic and aperiodic groups. We do not attempt to identify the source of variability, which may arise from pulsation or stellar activity. However, we cross match the objects against variable star related guest observer proposals, specifying the variable type in many cases. At present eclipsing binary stars are not included. Future releases will address each K2 field as it is made available, and may be improved to include more detailed catalogue information and to provide detrended object lightcurves.

  15. New Criteria to Identify Spectrum

    Indian Academy of Sciences (India)

    A Jensen; M Krishna

    2005-05-01

    In this paper we give some new criteria for identifying the components of a probability measure, in its Lebesgue decomposition. This enables us to give new criteria to identify spectral types of self-adjoint operators on Hilbert spaces, especially those of interest.

  16. Detection of the evolutionary stages of variables in M3

    OpenAIRE

    Jurcsik, J.; Benko, J. M.; Bakos, G. A.; Szeidl, B.; Szabo, R.

    2003-01-01

    The large number of variables in M3 provides a unique opportunity to study an extensive sample of variables with the same apparent distance modulus. Recent, high accuracy CCD time series of the variables show that according to their mean magnitudes and light curve shapes, the variables belong to four separate groups. Comparing the properties of these groups (magnitudes and periods) with horizontal branch evolutionary models, we conclude that these samples can be unambiguously identified with ...

  17. Interannual variability in the PFEG coastal upwelling indices

    OpenAIRE

    Parker, Heather A.

    1996-01-01

    Numerous studies examine decadal-scale variability in basin-scale parameters in the Northern Pacific. Characterizing such interannual-to-interdecadal variability is essential to identifying long-term climate changes. The Pacific Fisheries Environmental Group (PFEG) coastal upwelling indices display variability on these time scales and may help explain the mechanisms responsible for such climate variability. ... In this study, examination of 49-year time series of monthly mean upwelling indice...

  18. A close hidden stellar companion to the SX Phe-type variable star DW Psc

    International Nuclear Information System (INIS)

    DW Psc is a high-amplitude SX Phe-type variable with a period of pulsation of 0.05875 days. Using a few newly determined times of maximum light together with those collected from the literature, the changes in the observed-calculated (O-C) diagram are analyzed. It is discovered that the O-C curve of DW Psc shows a cyclic variation with a period of 6.08 years and a semi-amplitude of 0.0066 days. The periodic variation is analyzed for the light travel time effect, which is due to the presence of a stellar companion (M2sini∼0.45(±0.03) M⊙). The two-component stars in the binary system are orbiting each other in an eccentric orbit (e ∼ 0.4) at an orbital separation of about 2.7(±0.3) AU. The detection of a close stellar companion to an SX Phe-type star supports the idea that SX Phe-type pulsating stars are blue stragglers that were formed from the merging of close binaries. The stellar companion has played an important role in the merging of the original binary by removing angular momentum from the central binary during early dynamical interaction or/and late dynamical evolution. After the more massive component in DW Psc evolves into a red giant, the cool close companion should help to remove the giant envelope via possible critical Roche-lobe overflow, and the system may be a progenitor of a cataclysmic variable. The detection of a close stellar companion to DW Psc makes it a very interesting system to study in the future.

  19. A Close Hidden Stellar Companion to the SX Phe-Type Variable Star DW Psc

    Science.gov (United States)

    Qian, S.-B.; Li, L.-J.; Wang, S.-M.; He, J.-J.; Zhou, X.; Jiang, L.-Q.

    2015-01-01

    DW Psc is a high-amplitude SX Phe-type variable with a period of pulsation of 0.05875 days. Using a few newly determined times of maximum light together with those collected from the literature, the changes in the observed-calculated (O-C) diagram are analyzed. It is discovered that the O-C curve of DW Psc shows a cyclic variation with a period of 6.08 years and a semi-amplitude of 0.0066 days. The periodic variation is analyzed for the light travel time effect, which is due to the presence of a stellar companion ({{M}2}sin i˜ 0.45(+/- 0.03) {{M}⊙ }). The two-component stars in the binary system are orbiting each other in an eccentric orbit (e ˜ 0.4) at an orbital separation of about 2.7(±0.3) AU. The detection of a close stellar companion to an SX Phe-type star supports the idea that SX Phe-type pulsating stars are blue stragglers that were formed from the merging of close binaries. The stellar companion has played an important role in the merging of the original binary by removing angular momentum from the central binary during early dynamical interaction or/and late dynamical evolution. After the more massive component in DW Psc evolves into a red giant, the cool close companion should help to remove the giant envelope via possible critical Roche-lobe overflow, and the system may be a progenitor of a cataclysmic variable. The detection of a close stellar companion to DW Psc makes it a very interesting system to study in the future.

  20. Correlated x-ray and optical time variability of TT arietis

    International Nuclear Information System (INIS)

    Simultaneous X-ray and optical photometry of the cataclysmic variable TT Arietis has revealed correlated X-ray and opticl variability over a broad range of time scales. Large amplitude X-ray flickering with a time scale of approx.1000 s persists for the entire observation, is present at all orbital phases, and is correlated with optical flickering. The X-ray flickering is delayed by approx.1 minute with respect to the optical flickering. Transient hard X-ray oscillations with periods approx.32 s, approx.12 s, and approx.9 s and transient optical oscillations with periods approx.32 s and approx.12 s are observed. There is a modulation of the X-ray flux with a period consistent with the orbital period of approximately 200 minutes, but there is no apparent modulation of the X-ray spectrum. The optical flux is modulated with a similar period and may lag the X-ray modulation by approx.0.1 in phase. An X-ray photoelectric absorption event with a duration of about 1000 s is observed. An optical flux decrease of shorter duration (approx.500 s) occurs at the same time. The X-ray spectrum is well fitted by a thermal bremsstrahlung plus Gaunt factor model with kT> or approx. =10 keV, N/sub H/ = 1-2 x 1021 cm-2, and a received flux of approx.2 x 10-11 ergs cm-2 s-1 between 0.2 and 4 keV. The results of our observations suggest that the hard X-ray emission from TT Ari may be produced in a corona above and below the inner accretion disk

  1. VariableR reclustering in multiple top quark events - Oral Presentation

    International Nuclear Information System (INIS)

    VariableR jet reclustering is an innovative technique that allows for the reconstruction of boosted object over a wide range of kinematic regimes. Such capability enables the efficient identification of events with multiple boosted top quarks which is a typical signature for new physics processes such as the production of the supersymmetric partner of the gluon. In order to evaluate the performance of the algorithm, the VariableR reclustered jets are compared with fixed radius reclustered jets. The flexibility of the algorithm is tested by reconstructing both boosted top quarks and boosted W bosons. The VariableR reclustering method is found to be more efficient than the fixed radius algorithm at identifying top quarks and W bosons in events with four top quarks, therefore enhancing the sensitivity for gluino searches.

  2. VariableR Reclustering in Multiple Top Quark and W Boson Events

    Energy Technology Data Exchange (ETDEWEB)

    Hyde, Jeremy [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-08-14

    VariableR jet reclustering is an innovative technique that allows for the reconstruction of boosted object over a wide range of kinematic regimes. Such capability enables the efficient identification of events with multiple boosted top quarks which is a typical signature for new physics processes such as the production of the supersymmetric partner of the gluon. In order to evaluate the performance of the algorithm, the VariableR reclustered jets are compared with fixed radius reclustered jets. The flexibility of the algorithm is tested by reconstructing both boosted top quarks and boosted W bosons. The VariableR reclustering method is found to be more efficient than the fixed radius algorithm at identifying top quarks and W bosons in events with four top quarks, therefore enhancing the sensitivity for gluino searches.

  3. VariableR reclustering in multiple top quark events - Oral Presentation

    Energy Technology Data Exchange (ETDEWEB)

    Hyde, Jeremy; /SLAC

    2015-08-22

    VariableR jet reclustering is an innovative technique that allows for the reconstruction of boosted object over a wide range of kinematic regimes. Such capability enables the efficient identification of events with multiple boosted top quarks which is a typical signature for new physics processes such as the production of the supersymmetric partner of the gluon. In order to evaluate the performance of the algorithm, the VariableR reclustered jets are compared with fixed radius reclustered jets. The flexibility of the algorithm is tested by reconstructing both boosted top quarks and boosted W bosons. The VariableR reclustering method is found to be more efficient than the fixed radius algorithm at identifying top quarks and W bosons in events with four top quarks, therefore enhancing the sensitivity for gluino searches.

  4. Magnetically Controlled Variable Transformer

    Science.gov (United States)

    Kleiner, Charles T.

    1994-01-01

    Improved variable-transformer circuit, output voltage and current of which controlled by use of relatively small current supplied at relatively low power to control windings on its magnetic cores. Transformer circuits of this type called "magnetic amplifiers" because ratio between controlled output power and power driving control current of such circuit large. This ratio - power gain - can be as large as 100 in present circuit. Variable-transformer circuit offers advantages of efficiency, safety, and controllability over some prior variable-transformer circuits.

  5. Matricially free random variables

    CERN Document Server

    Lenczewski, Romuald

    2008-01-01

    We show that the operatorial framework developed by Voiculescu for free random variables can be extended to arrays of random variables whose multiplication imitates matricial multiplication. The associated notion of independence, called matricial freeness, can be viewed as a generalization of both freeness and monotone independence. At the same time, the sums of matricially free random variables, called random pseudomatrices, are closely related to Gaussian random matrices. The main results presented in this paper concern the standard and tracial central limit theorems for random pseudomatrices and the corresponding limit distributions which can be viewed as matricial generalizations of semicirle laws.

  6. Analisis en varias variables

    OpenAIRE

    Stallbohm H., Volker A.

    2006-01-01

    El presente texto ofrece un desarrollo sistemático del cálculo diferencial e integral de funciones en varias variables; es decir funciones con dominio〖 R〗^n (n>2) y contra dominio R^m (m>1). Una diferencia entre el análisis en una variable real y el análisis en varias variables resulta del hecho de que la topología de los subconjuntos en 〖 R〗^n es significativamente más compleja que la topología de la recta. Así los conjuntos convexos en R se clasifican fácilmente mientras que una...

  7. A new extensive catalog of optically variable AGN in the GOODS Fields and a new statistical approach to variability selection

    OpenAIRE

    Villforth, Carolin; Koekemoer, Anton M.; Grogin, Norman A.

    2010-01-01

    Variability is a property shared by practically all AGN. This makes variability selection a possible technique for identifying AGN. Given that variability selection makes no prior assumption about spectral properties, it is a powerful technique for detecting both low-luminosity AGN in which the host galaxy emission is dominating and AGN with unusual spectral properties. In this paper, we will discuss and test different statistical methods for the detection of variability in sparsely sampled d...

  8. The Galex Time Domain Survey. I. Selection And Classification of Over a Thousand Ultraviolet Variable Sources

    Science.gov (United States)

    Gezari, S.; Martin, D. C.; Forster, K.; Neill, J. D.; Huber, M.; Heckman, T.; Bianchi, L.; Morrissey, P.; Neff, S. G.; Seibert, M.; Schiminovich, D.; Wyder, T. K.; Burgett, W. S.; Chambers, K. C.; Kaiser, N.; Magnier, E. A.; Price, P. A.; Tonry, J. L.

    2013-01-01

    We present the selection and classification of over a thousand ultraviolet (UV) variable sources discovered in approximately 40 deg(exp 2) of GALEX Time Domain Survey (TDS) NUV images observed with a cadence of 2 days and a baseline of observations of approximately 3 years. The GALEX TDS fields were designed to be in spatial and temporal coordination with the Pan-STARRS1 Medium Deep Survey, which provides deep optical imaging and simultaneous optical transient detections via image differencing. We characterize the GALEX photometric errors empirically as a function of mean magnitude, and select sources that vary at the 5 sigma level in at least one epoch. We measure the statistical properties of the UV variability, including the structure function on timescales of days and years. We report classifications for the GALEX TDS sample using a combination of optical host colors and morphology, UV light curve characteristics, and matches to archival X-ray, and spectroscopy catalogs. We classify 62% of the sources as active galaxies (358 quasars and 305 active galactic nuclei), and 10% as variable stars (including 37 RR Lyrae, 53 M dwarf flare stars, and 2 cataclysmic variables). We detect a large-amplitude tail in the UV variability distribution for M-dwarf flare stars and RR Lyrae, reaching up to absolute value(?m) = 4.6 mag and 2.9 mag, respectively. The mean amplitude of the structure function for quasars on year timescales is five times larger than observed at optical wavelengths. The remaining unclassified sources include UV-bright extragalactic transients, two of which have been spectroscopically confirmed to be a young core-collapse supernova and a flare from the tidal disruption of a star by dormant supermassive black hole. We calculate a surface density for variable sources in the UV with NUV less than 23 mag and absolute value(?m) greater than 0.2 mag of approximately 8.0, 7.7, and 1.8 deg(exp -2) for quasars, active galactic nuclei, and RR Lyrae stars

  9. THE GALEX TIME DOMAIN SURVEY. I. SELECTION AND CLASSIFICATION OF OVER A THOUSAND ULTRAVIOLET VARIABLE SOURCES

    Energy Technology Data Exchange (ETDEWEB)

    Gezari, S. [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Martin, D. C.; Forster, K.; Neill, J. D.; Morrissey, P.; Wyder, T. K. [Astronomy Department, California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Huber, M.; Burgett, W. S.; Chambers, K. C.; Kaiser, N.; Magnier, E. A.; Tonry, J. L. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Heckman, T.; Bianchi, L. [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Neff, S. G. [Laboratory for Astronomy and Solar Physics, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Seibert, M. [Observatories of the Carnegie Institute of Washington, Pasadena, CA 90095 (United States); Schiminovich, D. [Department of Astronomy, Columbia University, New York, NY 10027 (United States); Price, P. A., E-mail: suvi@astro.umd.edu [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

    2013-03-20

    We present the selection and classification of over a thousand ultraviolet (UV) variable sources discovered in {approx}40 deg{sup 2} of GALEX Time Domain Survey (TDS) NUV images observed with a cadence of 2 days and a baseline of observations of {approx}3 years. The GALEX TDS fields were designed to be in spatial and temporal coordination with the Pan-STARRS1 Medium Deep Survey, which provides deep optical imaging and simultaneous optical transient detections via image differencing. We characterize the GALEX photometric errors empirically as a function of mean magnitude, and select sources that vary at the 5{sigma} level in at least one epoch. We measure the statistical properties of the UV variability, including the structure function on timescales of days and years. We report classifications for the GALEX TDS sample using a combination of optical host colors and morphology, UV light curve characteristics, and matches to archival X-ray, and spectroscopy catalogs. We classify 62% of the sources as active galaxies (358 quasars and 305 active galactic nuclei), and 10% as variable stars (including 37 RR Lyrae, 53 M dwarf flare stars, and 2 cataclysmic variables). We detect a large-amplitude tail in the UV variability distribution for M-dwarf flare stars and RR Lyrae, reaching up to |{Delta}m| = 4.6 mag and 2.9 mag, respectively. The mean amplitude of the structure function for quasars on year timescales is five times larger than observed at optical wavelengths. The remaining unclassified sources include UV-bright extragalactic transients, two of which have been spectroscopically confirmed to be a young core-collapse supernova and a flare from the tidal disruption of a star by dormant supermassive black hole. We calculate a surface density for variable sources in the UV with NUV < 23 mag and |{Delta}m| > 0.2 mag of {approx}8.0, 7.7, and 1.8 deg{sup -2} for quasars, active galactic nuclei, and RR Lyrae stars, respectively. We also calculate a surface density rate in the

  10. The GALEX Time Domain Survey. I. Selection and Classification of Over a Thousand Ultraviolet Variable Sources

    Science.gov (United States)

    Gezari, S.; Martin, D. C.; Forster, K.; Neill, J. D.; Huber, M.; Heckman, T.; Bianchi, L.; Morrissey, P.; Neff, S. G.; Seibert, M.; Schiminovich, D.; Wyder, T. K.; Burgett, W. S.; Chambers, K. C.; Kaiser, N.; Magnier, E. A.; Price, P. A.; Tonry, J. L.

    2013-03-01

    We present the selection and classification of over a thousand ultraviolet (UV) variable sources discovered in ~40 deg2 of GALEX Time Domain Survey (TDS) NUV images observed with a cadence of 2 days and a baseline of observations of ~3 years. The GALEX TDS fields were designed to be in spatial and temporal coordination with the Pan-STARRS1 Medium Deep Survey, which provides deep optical imaging and simultaneous optical transient detections via image differencing. We characterize the GALEX photometric errors empirically as a function of mean magnitude, and select sources that vary at the 5σ level in at least one epoch. We measure the statistical properties of the UV variability, including the structure function on timescales of days and years. We report classifications for the GALEX TDS sample using a combination of optical host colors and morphology, UV light curve characteristics, and matches to archival X-ray, and spectroscopy catalogs. We classify 62% of the sources as active galaxies (358 quasars and 305 active galactic nuclei), and 10% as variable stars (including 37 RR Lyrae, 53 M dwarf flare stars, and 2 cataclysmic variables). We detect a large-amplitude tail in the UV variability distribution for M-dwarf flare stars and RR Lyrae, reaching up to |Δm| = 4.6 mag and 2.9 mag, respectively. The mean amplitude of the structure function for quasars on year timescales is five times larger than observed at optical wavelengths. The remaining unclassified sources include UV-bright extragalactic transients, two of which have been spectroscopically confirmed to be a young core-collapse supernova and a flare from the tidal disruption of a star by dormant supermassive black hole. We calculate a surface density for variable sources in the UV with NUV 0.2 mag of ~8.0, 7.7, and 1.8 deg-2 for quasars, active galactic nuclei, and RR Lyrae stars, respectively. We also calculate a surface density rate in the UV for transient sources, using the effective survey time at the

  11. THE GALEX TIME DOMAIN SURVEY. I. SELECTION AND CLASSIFICATION OF OVER A THOUSAND ULTRAVIOLET VARIABLE SOURCES

    International Nuclear Information System (INIS)

    We present the selection and classification of over a thousand ultraviolet (UV) variable sources discovered in ∼40 deg2 of GALEX Time Domain Survey (TDS) NUV images observed with a cadence of 2 days and a baseline of observations of ∼3 years. The GALEX TDS fields were designed to be in spatial and temporal coordination with the Pan-STARRS1 Medium Deep Survey, which provides deep optical imaging and simultaneous optical transient detections via image differencing. We characterize the GALEX photometric errors empirically as a function of mean magnitude, and select sources that vary at the 5σ level in at least one epoch. We measure the statistical properties of the UV variability, including the structure function on timescales of days and years. We report classifications for the GALEX TDS sample using a combination of optical host colors and morphology, UV light curve characteristics, and matches to archival X-ray, and spectroscopy catalogs. We classify 62% of the sources as active galaxies (358 quasars and 305 active galactic nuclei), and 10% as variable stars (including 37 RR Lyrae, 53 M dwarf flare stars, and 2 cataclysmic variables). We detect a large-amplitude tail in the UV variability distribution for M-dwarf flare stars and RR Lyrae, reaching up to |Δm| = 4.6 mag and 2.9 mag, respectively. The mean amplitude of the structure function for quasars on year timescales is five times larger than observed at optical wavelengths. The remaining unclassified sources include UV-bright extragalactic transients, two of which have been spectroscopically confirmed to be a young core-collapse supernova and a flare from the tidal disruption of a star by dormant supermassive black hole. We calculate a surface density for variable sources in the UV with NUV 0.2 mag of ∼8.0, 7.7, and 1.8 deg–2 for quasars, active galactic nuclei, and RR Lyrae stars, respectively. We also calculate a surface density rate in the UV for transient sources, using the effective survey time at

  12. Author Identifiers in Scholarly Repositories

    CERN Document Server

    Warner, Simeon

    2010-01-01

    Bibliometric and usage-based analyses and tools highlight the value of information about scholarship contained within the network of authors, articles and usage data. Less progress has been made on populating and using the author side of this network than the article side, in part because of the difficulty of unambiguously identifying authors. I briefly review a sample of author identifier schemes, and consider use in scholarly repositories. I then describe preliminary work at arXiv to implement public author identifiers, services based on them, and plans to make this information useful beyond the boundaries of arXiv.

  13. Variable Attitude Test Stand

    Data.gov (United States)

    Federal Laboratory Consortium — The Variable Attitude Test Stand designed and built for testing of the V-22 tilt rotor aircraft propulsion system, is used to evaluate the effect of aircraft flight...

  14. Validation and Variability

    DEFF Research Database (Denmark)

    Carusi, Annamaria

    2014-01-01

    and experimentally inclined modellers on one hand, and attempts to forge new collaborations with medical scientists on the other. Apart from the scientific interest of the population of models approach for tackling variability, the trial also offers a good illustration of the epistemology of experiment......Systems biology is currently making a bid to show that it is able to make an important contribution to personalised or precision medicine. In order to do so, systems biologists need to find a way of tackling the pervasive variability of biological systems that is manifested in the medical domain...... as inter-subject variability. This need is simultaneously social and epistemic: social as systems biologists attempt to engage with the interests and concerns of clinicians and others in applied medical research; epistemic as they attempt to develop new strategies to cope with variability in the validation...

  15. Variable curvature phantom

    International Nuclear Information System (INIS)

    The design of a variable curvature dosimetry phantom is briefly described. The phantom was developed to test the accuracy of the dose modification algorithms used to estimate dose distributions inside patient contours. 1 fig

  16. Variable star data online

    Science.gov (United States)

    Pickard, Roger; Wilson, Andy; Poyner, Gary

    2012-06-01

    Roger Pickard, Andy Wilson and Gary Poyner describe the online database of the British Astronomical Association Variable Star Section, a treasure trove of observations stretching back nearly 125 years.

  17. Identifying Occupationally Specific Affective Behaviors.

    Science.gov (United States)

    Pucel, David J.

    1993-01-01

    Data from two groups of cosmetology instructors (n=15) and two groups of machinist instructors (n=17) validated the Occupational Affective Behavior Analysis instrument as capable of identifying affective behaviors viewed as important to success in a given occupation. (SK)

  18. Algorithms to identify failure pattern

    OpenAIRE

    Poudel, Bhuwan Krishna Som

    2013-01-01

    This project report was written for ?Algorithms to Identify Failure Pattern? at NTNU (Norwegian University of Science and Technology), IME (Faculty of Information Technology, Mathematics and Electrical Engineering) and IDI (Department of Computer Science).In software application, there are three types of failure pattern: point pattern, block pattern and stripe pattern. The purpose of the report is to prepare an algorithm that identifies the pattern in a software application. Only theoretical ...

  19. Calculus of one variable

    CERN Document Server

    Grossman, Stanley I

    1986-01-01

    Calculus of One Variable, Second Edition presents the essential topics in the study of the techniques and theorems of calculus.The book provides a comprehensive introduction to calculus. It contains examples, exercises, the history and development of calculus, and various applications. Some of the topics discussed in the text include the concept of limits, one-variable theory, the derivatives of all six trigonometric functions, exponential and logarithmic functions, and infinite series.This textbook is intended for use by college students.

  20. Variable frequency photonic crystals

    CERN Document Server

    Wu, Xiang-Yao; Liu, Xiao-Jing; Yang, Jing-Hai; Li, Hong; Chen, Wan-Jin

    2015-01-01

    In this paper, we have firstly proposed a new one-dimensional variable frequency photonic crystals (VFPCs), and calculated the transmissivity and the electronic field distribution of VFPCs with and without defect layer, and considered the effect of defect layer and variable frequency function on the transmissivity and the electronic field distribution. We have obtained some new characteristics for the VFPCs, which should be help to design a new type optical devices.

  1. Denominators of cluster variables

    OpenAIRE

    Buan, Aslak Bakke; Marsh, Robert J.; Reiten, Idun

    2007-01-01

    Associated to any acyclic cluster algebra is a corresponding triangulated category known as the cluster category. It is known that there is a one-to-one correspondence between cluster variables in the cluster algebra and exceptional indecomposable objects in the cluster category inducing a correspondence between clusters and cluster-tilting objects. Fix a cluster-tilting object T and a corresponding initial cluster. By the Laurent phenomenon, every cluster variable can be written as a Laurent...

  2. VARIABLE-THROW CAM

    Science.gov (United States)

    Godsil, E.C.; Robinson, E.Y.

    1963-07-16

    A variable-throw cam comprising inner and outer eccentric sleeves which are adjustably locked together is described. The cam throw is varied by unlocking the inner and outer sleeves, rotating the outer sleeve relative to the inner one until the desired throw is obtained, and locking the sleeves together again. The cam is useful in applications wherein a continuously-variable throw is required, e.g., ram-and-die pressing operations, cyclic fatigue testing of materials, etc. (AEC)

  3. Suspended graphene variable capacitor

    OpenAIRE

    AbdelGhany, M.; Mahvash, F.; Mukhopadhyay, M.; Favron, A.; Martel, R; Siaj, M.; Szkopek, T.

    2016-01-01

    The tuning of electrical circuit resonance with a variable capacitor, or varactor, finds wide application with the most important being wireless telecommunication. We demonstrate an electromechanical graphene varactor, a variable capacitor wherein the capacitance is tuned by voltage controlled deflection of a dense array of suspended graphene membranes. The low flexural rigidity of graphene monolayers is exploited to achieve low actuation voltage in an ultra-thin structure. Large arrays compr...

  4. Variability in software engineering paradigms

    OpenAIRE

    Huysegoms, Tom; Snoeck, Monique

    2012-01-01

    The concept of variability is not new in software engineering, but current research mostly remains vague about the overall variability concept when it comes to giving a clear overview of the dimensions of variability. In this paper we evaluate the core variability concept by proposing an overview of the set of definitions concerning variability related concepts and by setting up dimensions of variability. These dimensions represent different possible views on variability for all types of ...

  5. Identifying the structural discontinuities of human interactions

    CERN Document Server

    Grauwin, Sebastian; Sobolevsky, Stanislav; Hövel, Philipp; Simini, Filippo; Vanhoof, Maarten; Smoreda, Zbigniew; Barabasi, Albert-Laszlo; Ratti, Carlo

    2015-01-01

    The idea of a hierarchical spatial organization of society lies at the core of seminal theories in human geography that have strongly influenced our understanding of social organization. In the same line, the recent availability of large-scale human mobility and communication data has offered novel quantitative insights hinting at a strong geographical confinement of human interactions within neighboring regions, extending to local levels within countries. However, models of human interaction largely ignore this effect. Here, we analyze several country-wide networks of telephone calls and uncover a systematic decrease of communication induced by borders which we identify as the missing variable in state-of-the-art models. Using this empirical evidence, we propose an alternative modeling framework that naturally stylize the damping effect of borders. We show that this new notion substantially improves the predictive power of widely used interaction models, thus increasing our ability to predict social activiti...

  6. Identifying important characteristics of municipal carbon footprints

    Energy Technology Data Exchange (ETDEWEB)

    Larsen, Hogne N.; Hertwich, Edgar G. [Industrial Ecology Programme and Department of Energy and Process Engineering, Norwegian University of Science and Technology (NTNU), Realfagbygget E1, NO-7491 Trondheim (Norway)

    2010-11-15

    Local climate action has been identified as a vital contributor to global mitigation of greenhouse gas (GHG) emissions. This paper focuses on the GHG emissions resulting from the provision of local public services, illustrated through the Carbon Footprint (CF) indicator. The CF of all 429 Norwegian municipalities is calculated and compared to variables of interest. Results show that the CF changes significantly depending on size and wealth. Small and/or wealthy municipalities tend to have a much higher CF per capita compared to more populated and/or less wealthy cities. While wealth and CF relate very well linearly, increased population is only beneficial up to a certain size. Results indicate that the CF per capita increases in municipalities with more than {proportional_to}50,000 inhabitants, thus indicating a possible ideal size of municipalities to achieve the optimal municipal CF. (author)

  7. Identifying close binary central stars of PN with Kepler

    CERN Document Server

    De Marco, Orsola; Jacoby, George H; Hillwig, T; Kronberger, M; Howell, Steve B; Reindl, N; Margheim, Steve

    2016-01-01

    Six planetary nebulae (PN) are known in the Kepler space telescope field of view, three newly identified. Of the 5 central stars of PN with useful Kepler data, one, J193110888+4324577, is a short-period, post common envelope binary exhibiting relativistic beaming effects. A second, the central star of the newly identified PN Pa5, has a rare O(He) spectral type and a periodic variability consistent with an evolved companion, where the orbital axis is almost aligned with the line of sight. The third PN, NGC~6826 has a fast rotating central star, something that can only be achieved in a merger. Fourth, the central star of the newly identified PN Kn61, has a PG1159 spectral type and a mysterious semi-periodic light variability which we conjecture to be related to the interplay of binarity with a stellar wind. Finally, the central star of the circular PN A61 does not appear to have a photometric variability above 2 mmag. With the possible exception of the variability of Kn61, all other variability behaviour, wheth...

  8. Cluster analysis of clinical data identifies fibromyalgia subgroups.

    Directory of Open Access Journals (Sweden)

    Elisa Docampo

    Full Text Available INTRODUCTION: Fibromyalgia (FM is mainly characterized by widespread pain and multiple accompanying symptoms, which hinder FM assessment and management. In order to reduce FM heterogeneity we classified clinical data into simplified dimensions that were used to define FM subgroups. MATERIAL AND METHODS: 48 variables were evaluated in 1,446 Spanish FM cases fulfilling 1990 ACR FM criteria. A partitioning analysis was performed to find groups of variables similar to each other. Similarities between variables were identified and the variables were grouped into dimensions. This was performed in a subset of 559 patients, and cross-validated in the remaining 887 patients. For each sample and dimension, a composite index was obtained based on the weights of the variables included in the dimension. Finally, a clustering procedure was applied to the indexes, resulting in FM subgroups. RESULTS: VARIABLES CLUSTERED INTO THREE INDEPENDENT DIMENSIONS: "symptomatology", "comorbidities" and "clinical scales". Only the two first dimensions were considered for the construction of FM subgroups. Resulting scores classified FM samples into three subgroups: low symptomatology and comorbidities (Cluster 1, high symptomatology and comorbidities (Cluster 2, and high symptomatology but low comorbidities (Cluster 3, showing differences in measures of disease severity. CONCLUSIONS: We have identified three subgroups of FM samples in a large cohort of FM by clustering clinical data. Our analysis stresses the importance of family and personal history of FM comorbidities. Also, the resulting patient clusters could indicate different forms of the disease, relevant to future research, and might have an impact on clinical assessment.

  9. Identifying environmental correlates of intraspecific genetic variation.

    Science.gov (United States)

    Harrisson, K A; Yen, J D L; Pavlova, A; Rourke, M L; Gilligan, D; Ingram, B A; Lyon, J; Tonkin, Z; Sunnucks, P

    2016-09-01

    Genetic variation is critical to the persistence of populations and their capacity to adapt to environmental change. The distribution of genetic variation across a species' range can reveal critical information that is not necessarily represented in species occurrence or abundance patterns. We identified environmental factors associated with the amount of intraspecific, individual-based genetic variation across the range of a widespread freshwater fish species, the Murray cod Maccullochella peelii. We used two different approaches to statistically quantify the relative importance of predictor variables, allowing for nonlinear relationships: a random forest model and a Bayesian approach. The latter also accounted for population history. Both approaches identified associations between homozygosity by locus and both disturbance to the natural flow regime and mean annual flow. Homozygosity by locus was negatively associated with disturbance to the natural flow regime, suggesting that river reaches with more disturbed flow regimes may support larger, more genetically diverse populations. Our findings are consistent with the hypothesis that artificially induced perennial flows in regulated channels may provide greater and more consistent habitat and reduce the frequency of population bottlenecks that can occur frequently under the highly variable and unpredictable natural flow regime of the system. Although extensive river regulation across eastern Australia has not had an overall positive effect on Murray cod numbers over the past century, regulation may not represent the primary threat to Murray cod survival. Instead, pressures other than flow regulation may be more critical to the persistence of Murray cod (for example, reduced frequency of large floods, overfishing and chemical pollution). PMID:27273322

  10. Identifying tier one key suppliers.

    Science.gov (United States)

    Wicks, Steve

    2013-01-01

    In today's global marketplace, businesses are becoming increasingly reliant on suppliers for the provision of key processes, activities, products and services in support of their strategic business goals. The result is that now, more than ever, the failure of a key supplier has potential to damage reputation, productivity, compliance and financial performance seriously. Yet despite this, there is no recognised standard or guidance for identifying a tier one key supplier base and, up to now, there has been little or no research on how to do so effectively. This paper outlines the key findings of a BCI-sponsored research project to investigate good practice in identifying tier one key suppliers, and suggests a scalable framework process model and risk matrix tool to help businesses effectively identify their tier one key supplier base. PMID:23615061

  11. Statistical identification of effective input variables

    International Nuclear Information System (INIS)

    A statistical sensitivity analysis procedure has been developed for ranking the input data of large computer codes in the order of sensitivity-importance. The method is economical for large codes with many input variables, since it uses a relatively small number of computer runs. No prior judgemental elimination of input variables is needed. The sceening method is based on stagewise correlation and extensive regression analysis of output values calculated with selected input value combinations. The regression process deals with multivariate nonlinear functions, and statistical tests are also available for identifying input variables that contribute to threshold effects, i.e., discontinuities in the output variables. A computer code SCREEN has been developed for implementing the screening techniques. The efficiency has been demonstrated by several examples and applied to a fast reactor safety analysis code (Venus-II). However, the methods and the coding are general and not limited to such applications

  12. Football refereeing: Identifying innovative methods

    Directory of Open Access Journals (Sweden)

    Reza MohammadKazemi

    2014-08-01

    Full Text Available The aim of the present study is to identify the potentials innovation in football industry. Data were collected from 10 national and international referees, assistant referees and referees’ supervisors in Iran. In this study, technological innovations are identified that assist better refereeing performances. The analysis revealed a significant relationship between using new technologies and referees ‘performance. The results indicate that elite referees, assistant referees and supervisors agreed to use new technological innovations during the game. According to their comments, this kind of technology causes the referees’ performance development.

  13. Variability and Multiwavelength Detected AGN in the GOODS Fields

    OpenAIRE

    Sarajedini, Vicki L.; Koo, David C.; Klesman, Alison J.; Laird, Elise S.; Gonzalez, Pablo G. Perez; Mozena, Mark

    2011-01-01

    We identify 85 variable galaxies in the GOODS North and South fields using 5 epochs of HST ACS V-band (F606W) images spanning 6 months. The variables are identified through significant flux changes in the galaxy's nucleus and represent ~2% of the survey galaxies. With the aim of studying the active galaxy population in the GOODS fields, we compare the variability-selected sample with X-ray and mid-IR AGN candidates. Forty-nine percent of the variables are associated with X-ray sources identif...

  14. Use of Photogrammetry and Biomechanical Gait analysis to Identify Individuals

    DEFF Research Database (Denmark)

    Larsen, Peter Kastmand; Simonsen, Erik Bruun; Lynnerup, Niels

    Photogrammetry and recognition of gait patterns are valuable tools to help identify perpetrators based on surveillance recordings. We have found that stature but only few other measures have a satisfying reproducibility for use in forensics. Several gait variables with high recognition rates were...

  15. Identifying core domains to assess flare in rheumatoid arthritis

    DEFF Research Database (Denmark)

    Bartlett, Susan J; Hewlett, Sarah; Bingham, Clifton O;

    2012-01-01

    For rheumatoid arthritis (RA), there is no consensus on how to define and assess flare. Variability in flare definitions impairs understanding of findings across studies and limits ability to pool results. The OMERACT RA Flare Group sought to identify domains to define RA flares from patient and...

  16. Examination of Leadership Practices of Principals Identified as Servant Leaders

    Science.gov (United States)

    Taylor, Tim; Martin, Barbara N.; Hutchinson, Sandy; Jinks, Michael

    2007-01-01

    The purpose of this study was to examine the leadership practices of principals identified as servant leaders. The conceptual framework used to access the leadership behaviours was the leadership practices advocated by Kouzes and Posner. Statistical analysis included a multivariate test to determine if the demographic variables were significantly…

  17. Identifying Effective Classroom Practices Using Student Achievement Data

    Science.gov (United States)

    Kane, Thomas J.; Taylor, Eric S.; Tyler, John H.; Wooten, Amy L.

    2011-01-01

    Research continues to find large differences in student achievement gains across teachers' classrooms. The variability in teacher effectiveness raises the stakes on identifying effective teachers and teaching practices. This paper combines data from classroom observations of teaching practices and measures of teachers' ability to improve student…

  18. Georeactor Variability and Integrity

    CERN Document Server

    Herndon, J M

    2005-01-01

    As a deep-Earth energy source, the planetocentric nuclear-fission georeactor concept is on a more secure scientific footing than the previous idea related to the assumed growth of the inner core. Unlike previously considered deep-Earth energy sources, which are essentially constant on a human time-scale, variability in nuclear fission reactors can arise from changes in composition and/or position of fuel, moderators, and neutron absorbers. Tantalizing circumstantial evidence invites inquiry into the possibility of short-term planetocentric nuclear fission reactor variability. This brief communication emphasizes the importance of scientific integrity and highlights the possibility of variable georeactor power output so that these might be borne in mind in future investigations, especially those related to the Earth's heat flux.

  19. Identifying the Gifted Child Humorist.

    Science.gov (United States)

    Fern, Tami L.

    1991-01-01

    This study attempted to identify gifted child humorists among 1,204 children in grades 3-6. Final identification of 13 gifted child humorists was determined through application of such criteria as funniness, originality, and exemplary performance or product. The influence of intelligence, development, social factors, sex differences, family…

  20. Identifying, Assisting the Disturbed Adolescent.

    Science.gov (United States)

    Carlson, Patricia L.; Schaefer, William

    1986-01-01

    Educators are in an excellent position to identify seriously troubled young people. Major causes of adolescent problems are discussed, including drugs, parental failure, and biochemical disturbances. Educators can best intervene by becoming aware of support services within their own school and community. (TE)

  1. Identifying Two-Sided Markets

    NARCIS (Netherlands)

    Filistrucchi, L.; Geradin, D.A.A.G.; van Damme, E.E.C.

    2012-01-01

    Abstract: We review the burgeoning literature on two-sided markets focusing on the different definitions that have been proposed. In particular, we show that the well-known definition given by Evans is a particular case of the more general definition proposed by Rochet and Tirole. We then identify t

  2. Identifying high-risk medication

    DEFF Research Database (Denmark)

    Sædder, Eva; Brock, Birgitte; Nielsen, Lars Peter;

    2014-01-01

    salicylic acid, and beta-blockers; 30 drugs or drug classes caused 82 % of all serious MEs. The top ten drugs involved in fatal events accounted for 73 % of all drugs identified. CONCLUSION: Increasing focus on seven drugs/drug classes can potentially reduce hospitalizations, extended hospitalizations...

  3. Can Persistent Identifiers Be Cool?

    Directory of Open Access Journals (Sweden)

    Barbara Bazzanella

    2013-06-01

    Full Text Available The fast growth of scientific and non-scientific digital data, as well as the proliferation of new types of digital content, has led – among many other things – to a lot of innovative work on the concept of the identifier. Digital identifiers have become the key to preserving and accessing content, just as physical identifier tags have been the key to accessing paper-based content and other physical entities for millennia. Two main schools of thought have emerged: on the one hand, librarians and public repositories have pushed the concept of the Persistent Identifier (PI as a way to guarantee long term identification and (sometimes access; on the other hand, the extraordinary success of the web has led several researchers and web experts to push the concept of the Cool URI as the universal mechanism for identifying and accessing digital content. Both views have their pros and cons, but so far (with only a few exceptions the two visions have developed in parallel, sometimes with a subtle underlying hostility.In this paper, we present the evolution of the Entity Name System (ENS, an open service-based platform developed as part of the OKKAM EU co-funded project, which can reconcile these two approaches. The new system, called ENS2.0, is currently under development and will enable data creators and curators to combine the technical strengths and opportunities of the (Semantic Web vision with the organizational, economical and social requirements legitimately raised by the PI community and stakeholders.

  4. Complex variables I essentials

    CERN Document Server

    Solomon, Alan D

    2013-01-01

    REA's Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. Complex Variables I includes functions of a complex variable, elementary complex functions, integrals of complex functions in the complex plane, sequences and series, and poles and r

  5. Applied complex variables

    CERN Document Server

    Dettman, John W

    1965-01-01

    Analytic function theory is a traditional subject going back to Cauchy and Riemann in the 19th century. Once the exclusive province of advanced mathematics students, its applications have proven vital to today's physicists and engineers. In this highly regarded work, Professor John W. Dettman offers a clear, well-organized overview of the subject and various applications - making the often-perplexing study of analytic functions of complex variables more accessible to a wider audience. The first half of Applied Complex Variables, designed for sequential study, is a step-by-step treatment of fun

  6. Rms-flux relation and fast optical variability simulations of the nova-like system MV Lyr

    Science.gov (United States)

    Dobrotka, A.; Mineshige, S.; Ness, J.-U.

    2015-03-01

    The stochastic variability (flickering) of the nova-like system (subclass of cataclysmic variable) MV Lyr yields a complicated power density spectrum with four break frequencies. Scaringi et al. analysed high-cadence Kepler data of MV Lyr, taken almost continuously over 600 d, giving the unique opportunity to study multicomponent Power Density Spectra (PDS) over a wide frequency range. We modelled this variability with our statistical model based on disc angular momentum transport via discrete turbulent bodies with an exponential distribution of the dimension scale. Two different models were used, a full disc (developed from the white dwarf to the outer radius of ˜1010 cm) and a radially thin disc (a ring at a distance of ˜1010 cm from the white dwarf) that imitates an outer disc rim. We succeed in explaining the two lowest observed break frequencies assuming typical values for a disc radius of 0.5 and 0.9 times the primary Roche lobe and an α parameter of 0.1-0.4. The highest observed break frequency was also modelled, but with a rather small accretion disc with a radius of 0.3 times the primary Roche lobe and a high α value of 0.9 consistent with previous findings by Scaringi. Furthermore, the simulated light curves exhibit the typical linear rms-flux proportionality linear relation and the typical log-normal flux distribution. As the turbulent process is generating fluctuations in mass accretion that propagate through the disc, this confirms the general knowledge that the typical rms-flux relation is mainly generated by these fluctuations. In general, a higher rms is generated by a larger amount of superposed flares which is compatible with a higher mass accretion rate expressed by a larger flux.

  7. Household Ownership of Variable Annuities

    OpenAIRE

    Brown, Jeffrey R.; James M. Poterba

    2006-01-01

    Variable annuities have been one of the most rapidly growing financial products of the last two decades. Between 1996 and 2004, nominal sales of variable annuities in the U.S. more than doubled, from $51 billion to $130 billion. Variable annuities now account for approximately nearly two thirds of annuity sales. The investment returns associated with variable annuities resemble those from mutual funds, and variable annuity buyers can select among a range of asset allocation options. Variable ...

  8. Highly Variable Objects in the Palomar-QUEST Survey: A Blazar Search using Optical Variability

    OpenAIRE

    Bauer, Anne; Baltay, Charles; De Coppi, Paolo; Donalek, Ciro; Drake, Andrew; Djorgovski, S. G.; Ellman, Nancy; Glikman, Eilat; Graham, Matthew; Jerke, Jonathan; Mahabal, Ashish; Rabinowitz, David; Scalzo, Richard; Williams, Roy

    2009-01-01

    We identify 3113 highly variable objects in 7200 deg^2 of the Palomar-QUEST (PQ) Survey, which each varied by more than 0.4 mag simultaneously in two broadband optical filters on timescales from hours to roughly 3.5 years. The primary goal of the selection is to find blazars by their well-known violent optical variability. Because most known blazars have been found in radio and/or X-ray wavelengths, a sample discovered through optical variability may have very different selection effects, elu...

  9. Variable speed generators

    CERN Document Server

    Boldea, Ion

    2005-01-01

    With the deregulation of electrical energy production and distribution, says Boldea (Polytechnical Institute, Timisoara, Romania) producers are looking for ways to tailor their electricity for different markets. Variable-speed electric generators are serving that purpose, up to the 400 megavolt ampere unit size, in Japan since 1996 and Germany sinc

  10. Lake Ontario: Nearshore Variability

    Science.gov (United States)

    We conducted a high-resolution survey with towed electronic instrumentation along the Lake Ontario nearshore (720 km) at a 20 meter contour. The survey was conducted September 6-10, 2008 with a shorter 300 km survey conducted August 14-15 for comparing of temporal variability. ...

  11. Several real variables

    CERN Document Server

    Kantorovitz, Shmuel

    2016-01-01

    This undergraduate textbook is based on lectures given by the author on the differential and integral calculus of functions of several real variables. The book has a modern approach and includes topics such as: •The p-norms on vector space and their equivalence •The Weierstrass and Stone-Weierstrass approximation theorems •The differential as a linear functional; Jacobians, Hessians, and Taylor's theorem in several variables •The Implicit Function Theorem for a system of equations, proved via Banach’s Fixed Point Theorem •Applications to Ordinary Differential Equations •Line integrals and an introduction to surface integrals This book features numerous examples, detailed proofs, as well as exercises at the end of sections. Many of the exercises have detailed solutions, making the book suitable for self-study. Several Real Variables will be useful for undergraduate students in mathematics who have completed first courses in linear algebra and analysis of one real variable.

  12. Variable thrust cartridge

    Science.gov (United States)

    Taleyarkhan, Rusi P.

    2000-11-07

    The present invention is a variable thrust cartridge comprising a water-molten aluminum reaction chamber from which a slug is propelled. The cartridge comprises a firing system that initiates a controlled explosion from the reaction chamber. The explosive force provides a thrust to a slug, preferably contained within the cartridge.

  13. Integration i flere variable

    DEFF Research Database (Denmark)

    Markvorsen, Steen

    2010-01-01

    -integralerne. Undervejs introduceres \\texttt{Integrator8}. Det er en pakke med Maple procedurer, som er udviklet specielt med henblik på eksempelbaseret visuel læring af de indledende integrationsbegreber og deres mangfoldige anvendelser. Vi giver eksempler på, hvordan integration i flere variable anvendes til beregning...

  14. Spatial Variability of Rainfall

    DEFF Research Database (Denmark)

    Jensen, N.E.; Pedersen, Lisbeth

    2005-01-01

    As a part of a Local Area Weather Radar (LAWR) calibration exercise 15 km south of Århus, Denmark, the variability in accumulated rainfall within a single radar pixel (500 by 500 m) was measured using nine high-resolution rain gauges. The measured values indicate up to a 100% variation between...

  15. Photometry of variable AFGL sources

    International Nuclear Information System (INIS)

    Results of infrared photometric observations of 63 AFGL sources over the past 9 years are presented. Using these data together with previous measurements of these stars, pulsation periods and mean photometric characteristics are determined. These stars are found to lie midway between optically identified Mira variables and the radio-luminous OH/IR stars in their period distribution and photometric properties. For the sample as a whole, there is no evidence for sudden or transient behavior such as a switch in pulsation mode. Rather, these stars suggest rapid, but continuous, evolution from shorter period Miras with weak mass loss to longer periods and larger mass-loss rates. The carbon-rich stars in the sample have the same period distribution as the oxygen-rich stars. None of the carbon stars have periods as long as those of the very long period radio-luminous OH/IR stars. 61 refs

  16. Photometry of variable AFGL sources

    Science.gov (United States)

    Jones, Terry Jay; Bryja, C. O.; Gehrz, Robert D.; Harrison, Thomas E.; Johnson, Joni J.

    1990-01-01

    Results of infrared photometric observations of 63 AFGL sources over the past 9 years are presented. Using these data together with previous measurements of these stars, pulsation periods and mean photometric characteristics are determined. These stars are found to lie midway between optically identified Mira variables and the radio-luminous OH/IR stars in their period distribution and photometric properties. For the sample as a whole, there is no evidence for sudden or transient behavior such as a switch in pulsation mode. Rather, these stars suggest rapid, but continuous, evolution from shorter period Miras with weak mass loss to longer periods and larger mass-loss rates. The carbon-rich stars in the sample have the same period distribution as the oxygen-rich stars. None of the carbon stars have periods as long as those of the very long period radio-luminous OH/IR stars.

  17. Identifying the Poorest Older Americans

    OpenAIRE

    Fisher, Johathan; Johnson, David; Marchand, Joseph; Smeeding, Timothy; Boyle Torrey, B.

    2009-01-01

    Objectives: Public policies generally target a subset of the population defined as poor or needy, but rarely are people poor or needy in the same way. This is particularly true among older adults, as they have fewer options to compensate for financial decisions made earlier in life. This study investigates poverty among this group in order to identify who among them is financially worst off. Methods: We use 20 years of data from the Consumer Expenditure Survey to examine the income and consum...

  18. Identifying Emotion from Natural Walking

    OpenAIRE

    Cui, Liqing; Li, Shun; Zhang, Wan; Zhang, Zhan; Zhu, Tingshao

    2015-01-01

    Emotion identification from gait aims to automatically determine persons affective state, it has attracted a great deal of interests and offered immense potential value in action tendency, health care, psychological detection and human-computer(robot) interaction.In this paper, we propose a new method of identifying emotion from natural walking, and analyze the relevance between the traits of walking and affective states. After obtaining the pure acceleration data of wrist and ankle, we set a...

  19. Identifying Network Perturbation in Cancer.

    OpenAIRE

    Maxim Grechkin; Logsdon, Benjamin A.; Gentles, Andrew J.; Su-In Lee

    2016-01-01

    We present a computational framework, called DISCERN (DIfferential SparsE Regulatory Network), to identify informative topological changes in gene-regulator dependence networks inferred on the basis of mRNA expression datasets within distinct biological states. DISCERN takes two expression datasets as input: an expression dataset of diseased tissues from patients with a disease of interest and another expression dataset from matching normal tissues. DISCERN estimates the extent to which each ...

  20. Identifying Network Perturbation in Cancer

    OpenAIRE

    Grechkin, Maxim; Logsdon, Benjamin A.; Gentles, Andrew J.; Lee, Su-In

    2016-01-01

    We present a computational framework, called DISCERN (DIfferential SparsE Regulatory Network), to identify informative topological changes in gene-regulator dependence networks inferred on the basis of mRNA expression datasets within distinct biological states. DISCERN takes two expression datasets as input: an expression dataset of diseased tissues from patients with a disease of interest and another expression dataset from matching normal tissues. DISCERN estimates the extent to which each ...

  1. Family and academic performance: identifying high school student profiles

    Directory of Open Access Journals (Sweden)

    Alicia Aleli Chaparro Caso López

    2016-01-01

    Full Text Available The objective of this study was to identify profiles of high school students, based on variables related to academic performance, socioeconomic status, cultural capital and family organization. A total of 21,724 high school students, from the five municipalities of the state of Baja California, took part. A K-means cluster analysis was performed to identify the profiles. The analyses identified two clearly-defined clusters: Cluster 1 grouped together students with high academic performance and who achieved higher scores for socioeconomic status, cultural capital and family involvement, whereas Cluster 2 brought together students with low academic achievement, and who also obtained lower scores for socioeconomic status and cultural capital, and had less family involvement. It is concluded that the family variables analyzed form student profiles that can be related to academic achievement.

  2. Visualizing Multiple Variables Across Scale and Geography.

    Science.gov (United States)

    Goodwin, Sarah; Dykes, Jason; Slingsby, Aidan; Turkay, Cagatay

    2016-01-01

    Comparing multiple variables to select those that effectively characterize complex entities is important in a wide variety of domains - geodemographics for example. Identifying variables that correlate is a common practice to remove redundancy, but correlation varies across space, with scale and over time, and the frequently used global statistics hide potentially important differentiating local variation. For more comprehensive and robust insights into multivariate relations, these local correlations need to be assessed through various means of defining locality. We explore the geography of this issue, and use novel interactive visualization to identify interdependencies in multivariate data sets to support geographically informed multivariate analysis. We offer terminology for considering scale and locality, visual techniques for establishing the effects of scale on correlation and a theoretical framework through which variation in geographic correlation with scale and locality are addressed explicitly. Prototype software demonstrates how these contributions act together. These techniques enable multiple variables and their geographic characteristics to be considered concurrently as we extend visual parameter space analysis (vPSA) to the spatial domain. We find variable correlations to be sensitive to scale and geography to varying degrees in the context of energy-based geodemographics. This sensitivity depends upon the calculation of locality as well as the geographical and statistical structure of the variable. PMID:26390471

  3. Quasar Classification Using Color and Variability

    CERN Document Server

    Peters, Christina M; Myers, Adam D; Strauss, Michael A; Schmidt, Kasper B; Ivezić, Željko; Ross, Nicholas P; MacLeod, Chelsea L; Riegel, Ryan

    2015-01-01

    We conduct a pilot investigation to determine the optimal combination of color and variability information to identify quasars in current and future multi-epoch optical surveys. We use a Bayesian quasar selection algorithm (Richards et al. 2004) to identify 35,820 type 1 quasar candidates in a 239 square degree field of the Sloan Digital Sky Survey (SDSS) Stripe 82, using a combination of optical photometry and variability. Color analysis is performed on 5-band single- and multi-epoch SDSS optical photometry to a depth of r ~22.4. From these data, variability parameters are calculated by fitting the structure function of each object in each band with a power law model using 10 to >100 observations over timescales from ~1 day to ~8 years. Selection was based on a training sample of 13,221 spectroscopically-confirmed type-1 quasars, largely from the SDSS. Using variability alone, colors alone, and combining variability and colors we achieve 91%, 93%, and 97% quasar completeness and 98%, 98%, and 97% efficiency ...

  4. IR spectroscopy of pre-cataclysmic binaries

    CERN Document Server

    Tappert, C; Mennickent, R E

    2004-01-01

    We have taken near-infrared (JHK) spectroscopic data of a sample of pre-CVs, in order to examine them for signatures of nuclear evolution. Here we present preliminary results for the three systems BPM 71214, RR Cae, and RE 1016-053.

  5. Identifying Network Perturbation in Cancer

    Science.gov (United States)

    Logsdon, Benjamin A.; Gentles, Andrew J.; Lee, Su-In

    2016-01-01

    We present a computational framework, called DISCERN (DIfferential SparsE Regulatory Network), to identify informative topological changes in gene-regulator dependence networks inferred on the basis of mRNA expression datasets within distinct biological states. DISCERN takes two expression datasets as input: an expression dataset of diseased tissues from patients with a disease of interest and another expression dataset from matching normal tissues. DISCERN estimates the extent to which each gene is perturbed—having distinct regulator connectivity in the inferred gene-regulator dependencies between the disease and normal conditions. This approach has distinct advantages over existing methods. First, DISCERN infers conditional dependencies between candidate regulators and genes, where conditional dependence relationships discriminate the evidence for direct interactions from indirect interactions more precisely than pairwise correlation. Second, DISCERN uses a new likelihood-based scoring function to alleviate concerns about accuracy of the specific edges inferred in a particular network. DISCERN identifies perturbed genes more accurately in synthetic data than existing methods to identify perturbed genes between distinct states. In expression datasets from patients with acute myeloid leukemia (AML), breast cancer and lung cancer, genes with high DISCERN scores in each cancer are enriched for known tumor drivers, genes associated with the biological processes known to be important in the disease, and genes associated with patient prognosis, in the respective cancer. Finally, we show that DISCERN can uncover potential mechanisms underlying network perturbation by explaining observed epigenomic activity patterns in cancer and normal tissue types more accurately than alternative methods, based on the available epigenomic data from the ENCODE project. PMID:27145341

  6. [Gifted children! How to identify].

    Science.gov (United States)

    Revol, O; Bléandonu, G

    2012-03-01

    Recognizing the intellectually gifted child allows one to anticipate the onset of behavioral disorders and to respond to them so as to improve quality of life for these children and their family. Certain signs can draw attention to this phenomenon. The decisive criterion has always been IQ. The notion of intelligence should be broadened and researchers have adventured beyond the purely intellectual competencies, which value most prominently the educational sphere. In addition, the modeling of high potential is currently renewing the approach to this question. This article takes this complexity into account and presents the main criteria used for identifying intellectually gifted children. PMID:22325457

  7. Rainfall variability and seasonality in northern Bangladesh

    Science.gov (United States)

    Bari, Sheikh Hefzul; Hussain, Md. Manjurul; Husna, Noor-E.-Ashmaul

    2016-05-01

    This paper aimed at the analysis of rainfall seasonality and variability for the northern part of South-Asian country, Bangladesh. The coefficient of variability was used to determine the variability of rainfall. While rainfall seasonality index (SI ) and mean individual seasonality index ( overline{SI_i} ) were used to identify seasonal contrast. We also applied Mann-Kendall trend test and sequential Mann-Kendall test to determine the trend in seasonality. The lowest variability was found for monsoon among the four seasons whereas winter has the highest variability. Observed variability has a decreasing tendency from the northwest region towards the northeast region. The mean individual seasonality index (0.815378 to 0.977228) indicates that rainfall in Bangladesh is "markedly seasonal with a long dry season." It was found that the length of the dry period is lower at the northeastern part of northern Bangladesh. Trend analysis results show no significant change in the seasonality of rainfall in this region. Regression analysis of overline{SI_i} and SI, and longitude and mean individual seasonality index show a significant linear correlation for this area.

  8. Genetic variability of maize pathogens in Serbia

    Directory of Open Access Journals (Sweden)

    Stanković Slavica

    2007-01-01

    Full Text Available Variability of some maize pathogens was identified in the last 50 years of research in Serbia, mostly by their cultural characteristics and susceptibility of test genotypes and only in some cases by determination of mating types, vegetative compatibility or biochemical methods. Although more advanced methods that can determine within population variability at the molecular level were developed, they are still not applied in research in Serbia. The highest variability was determined for maize leaf pathogens - Exserohilum turcicum (Pass. Leonard & Suggs (2 races and Bipolaris zeicola (Stout Shoemaker (2 races, although this variability is significantly lower than the variability of the same pathogens found in the world. Researches conducted with the aim to determine mating types and vegetative compatibility of the Fusarium species, a maize root and stalk pathogen, indicated their high variability in Serbia. Considering the pathogen ability to adapt easily and quickly to new genotypes, agro-ecological conditions and crop practice, a constant surveillance of parasite divergence and epidemiology is necessary in order to avoid detrimental consequences on maize yield and quality.

  9. Variable Permanent Magnet Quadrupole

    Energy Technology Data Exchange (ETDEWEB)

    Mihara, T.; Iwashita, Y.; /Kyoto U.; Kumada, M.; /NIRS, Chiba; Spencer, C.M.; /SLAC

    2007-05-23

    A permanent magnet quadrupole (PMQ) is one of the candidates for the final focus lens in a linear collider. An over 120 T/m strong variable permanent magnet quadrupole is achieved by the introduction of saturated iron and a 'double ring structure'. A fabricated PMQ achieved 24 T integrated gradient with 20 mm bore diameter, 100 mm magnet diameter and 20 cm pole length. The strength of the PMQ is adjustable in 1.4 T steps, due to its 'double ring structure': the PMQ is split into two nested rings; the outer ring is sliced along the beam line into four parts and is rotated to change the strength. This paper describes the variable PMQ from fabrication to recent adjustments.

  10. Variable stiffness torsion springs

    Science.gov (United States)

    Alhorn, Dean C. (Inventor); Polites, Michael E. (Inventor)

    1995-01-01

    In a torsion spring the spring action is a result of the relationships between the torque applied in twisting the spring, the angle through which the torsion spring twists, and the modulus of elasticity of the spring material in shear. Torsion springs employed industrially have been strips, rods, or bars, generally termed shafts, capabable of being flexed by twisting their axes. They rely on the variations in shearing forces to furnish an internal restoring torque. In the torsion springs herein the restoring torque is external and therefore independent of the shearing modulus of elasticity of the torsion spring shaft. Also provided herein is a variable stiffness torsion spring. This torsion spring can be so adjusted as to have a given spring constant. Such variable stiffness torsion springs are extremely useful in gimballed payloads such as sensors, telescopes, and electronic devices on such platforms as a space shuttle or a space station.

  11. EVALUATING THE RETURNS TO VARIABLE RATE NITROGEN APPLICATION

    OpenAIRE

    Roberts, Roland K.; Burton C. English; Mahajanashetti, S.B.

    2000-01-01

    Potential benefits of variable rate nitrogen application are illustrated and information needs identified. Lower costs of precision farming services, higher crop prices, and greater divergence in yield response potentials across management zones reduce the spatial variability required for profitable variable rate application. Information needs include identification and measurement of management zones within a field and estimation of management zone yield response functions, crop and input pr...

  12. Species selection on variability.

    OpenAIRE

    Lloyd, E. A.; Gould, S J

    1993-01-01

    Most analyses of species selection require emergent, as opposed to aggregate, characters at the species level. This "emergent character" approach tends to focus on the search for adaptations at the species level. Such an approach seems to banish the most potent evolutionary property of populations--variability itself--from arguments about species selection (for variation is an aggregate character). We wish, instead, to extend the legitimate domain of species selection to aggregate characters....

  13. Climate Variability Program

    Science.gov (United States)

    Halpern, David (Editor)

    2002-01-01

    The Annual Report of the Climate Variability Program briefly describes research activities of Principal Investigators who are funded by NASA's Earth Science Enterprise Research Division. The report is focused on the year 2001. Utilization of satellite observations is a singularity of research on climate science and technology at JPL (Jet Propulsion Laboratory). Research at JPL has two foci: generate new knowledge and develop new technology.

  14. Variable percentage sampler

    Science.gov (United States)

    Miller, Jr., William H.

    1976-01-01

    A remotely operable sampler is provided for obtaining variable percentage samples of nuclear fuel particles and the like for analyses. The sampler has a rotating cup for a sample collection chamber designed so that the effective size of the sample inlet opening to the cup varies with rotational speed. Samples of a desired size are withdrawn from a flowing stream of particles without a deterrent to the flow of remaining particles.

  15. Variable laser attenuator

    Science.gov (United States)

    Foltyn, Stephen R.

    1988-01-01

    The disclosure relates to low loss, high power variable attenuators comprng one or more transmissive and/or reflective multilayer dielectric filters. The attenuator is particularly suitable to use with unpolarized lasers such as excimer lasers. Beam attenuation is a function of beam polarization and the angle of incidence between the beam and the filter and is controlled by adjusting the angle of incidence the beam makes to the filter or filters. Filters are selected in accordance with beam wavelength.

  16. Variable depth core sampler

    Science.gov (United States)

    Bourgeois, Peter M.; Reger, Robert J.

    1996-01-01

    A variable depth core sampler apparatus comprising a first circular hole saw member, having longitudinal sections that collapses to form a point and capture a sample, and a second circular hole saw member residing inside said first hole saw member to support the longitudinal sections of said first hole saw member and prevent them from collapsing to form a point. The second hole saw member may be raised and lowered inside said first hole saw member.

  17. Variability of calcium absorption

    International Nuclear Information System (INIS)

    Variability in calcium absorption was estimated in three groups of normal subjects in whom Ca absorption was measured by standard isotopic-tracer methods at interstudy intervals ranging from 1 to 4 mo. Fifty absorption tests were performed in 22 subjects. Each was done in the morning after an overnight fast with an identical standard breakfast containing a Ca load of approximately 250 mg. Individual fractional absorption values were normalized to permit pooling of the data. The coefficient of variation (CVs) for absorption for the three groups ranged from 10.57 to 12.79% with the size of the CV increasing with interstudy duration. One other published study presenting replicate absorption values was analyzed in a similar fashion and was found to have a CV of absorption of 9.78%. From these data we estimate that when the standard double-isotope method is used to measure Ca absorption there is approximately 10% variability around any given absorption value within an individual human subject and that roughly two-thirds of this represents real biological variability in absorption

  18. Individual variability in human blood metabolites identifies age-related differences

    Science.gov (United States)

    Murakami, Itsuo; Takada, Junko; Kondoh, Hiroshi; Yanagida, Mitsuhiro

    2016-01-01

    Metabolites present in human blood document individual physiological states influenced by genetic, epigenetic, and lifestyle factors. Using high-resolution liquid chromatography-mass spectrometry (LC-MS), we performed nontargeted, quantitative metabolomics analysis in blood of 15 young (29 ± 4 y of age) and 15 elderly (81 ± 7 y of age) individuals. Coefficients of variation (CV = SD/mean) were obtained for 126 blood metabolites of all 30 donors. Fifty-five RBC-enriched metabolites, for which metabolomics studies have been scarce, are highlighted here. We found 14 blood compounds that show remarkable age-related increases or decreases; they include 1,5-anhydroglucitol, dimethyl-guanosine, acetyl-carnosine, carnosine, ophthalmic acid, UDP-acetyl-glucosamine, N-acetyl-arginine, N6-acetyl-lysine, pantothenate, citrulline, leucine, isoleucine, NAD+, and NADP+. Six of them are RBC-enriched, suggesting that RBC metabolomics is highly valuable for human aging research. Age differences are partly explained by a decrease in antioxidant production or increasing inefficiency of urea metabolism among the elderly. Pearson’s coefficients demonstrated that some age-related compounds are correlated, suggesting that aging affects them concomitantly. Although our CV values are mostly consistent with those CVs previously published, we here report previously unidentified CVs of 51 blood compounds. Compounds having moderate to high CV values (0.4–2.5) are often modified. Compounds having low CV values, such as ATP and glutathione, may be related to various diseases because their concentrations are strictly controlled, and changes in them would compromise health. Thus, human blood is a rich source of information about individual metabolic differences. PMID:27036001

  19. Bayesian Variable Selection to identify QTL affecting a simulated quantitative trait

    NARCIS (Netherlands)

    Schurink, A.; Janss, L.L.G.; Heuven, H.C.M.

    2012-01-01

    Background Recent developments in genetic technology and methodology enable accurate detection of QTL and estimation of breeding values, even in individuals without phenotypes. The QTL-MAS workshop offers the opportunity to test different methods to perform a genome-wide association study on simulat

  20. Bayesian Variable Selection to identify QTL affecting a simulated quantitative trait

    NARCIS (Netherlands)

    Schurink, A.; Janss, L.L.G.; Heuven, H.C.M.

    2012-01-01

    Abstract Background: Recent developments in genetic technology and methodology enable accurate detection of QTL and estimation of breeding values, even in individuals without phenotypes. The QTL-MAS workshop offers the opportunity to test different methods to perform a genome-wide association study

  1. Towards Reducing the Complexity of Enterprise Architectures by Identifying Standard Variants Using Variability Mining

    OpenAIRE

    Wehling, Kenny; Wille, David; Pluchator, Martin; Schaefer, Ina

    2016-01-01

    For decades, Enterprise Architectures (EAs) of car manufacturers have been constantly evolved to respond to growing requirements. As a consequence, EAs have often reached a very high level of complexity, which leads to problems in adapting EAs to new environmental condi­tions. Such a new condition is, for instance, digitalization of society (e.g., social media, Internet of Things) which has a huge effect on the automotive industry and the grown EA. Resulting changes in complex EAs have long i...

  2. Identifying, Categorizing and Setting Variables on Ergonomics Issues in Oil Palm Plantations

    OpenAIRE

    Normala S Govindarajo; Dileep Kumar. M.; Subrahmanium Sri Ramulu

    2014-01-01

    It is an eye opening scenario that Malaysia turned to be one of the major producer and exporter of palm oil. Malaysia has witnessed a dazzling growth of 10.06% of its production recently from 4.05 million hectares in 2005 in an area of 54,000 hectares. Further, the production has enlarged from 94,000 tons in 1960 to 15 million tons in 2005, or by almost 160 times within 45 years-this represents a compound annual growth of 11.93% per year. The oil palm industry is labor intensive, since there ...

  3. An extent of sequence variability of PVY HC-Pro as identified by thermodynamic methods

    Czech Academy of Sciences Publication Activity Database

    Škopek, Josef; Matoušek, Jaroslav

    Prague : Czech University of Agriculture, 2002. s. 56. [Conference of European Foundation for Plant Pathology 'Disease Resistance in Plant Parhology'/6./. 08.09.2002-14.09.2002, Prague] R&D Projects: GA ČR GA522/00/0227; GA AV ČR IBS5051014 Keywords : plant pathology * resistance Subject RIV: EE - Microbiology, Virology

  4. Innovation In The Public Sector: Identifying Variables Useful for Evaluating Anti-Corruption Initiatives

    OpenAIRE

    Jones, L R; Thompson, Fred

    2012-01-01

    Prepared for the 2012 Conference of the International Public Management Network: Innovations in Public Management for Combating Corruption, Hawaii Imin International Conference Center at Jefferson Hall According to the public management reform literature, practitioner experience and research conducted by the authors and others, public organizational innovation appears to depend on a the presence of a specific set of factors that may be controlled or influenced by organizational change spon...

  5. High resolution SNP array profiling identifies variability in retinoblastoma genome stability

    NARCIS (Netherlands)

    Mol, Berber M.; Massink, Maarten P. G.; van der Hout, Annemarie H.; Dommering, Charlotte J.; Zaman, Johannes M. A.; Bosscha, Machteld I.; Kors, Wijnanda A.; Meijers-Heijboer, Hanne E.; Kaspers, Gertjan J. L.; te Riele, Hein; Moll, Annette C.; Cloos, Jacqueline; Dorsman, Josephine C.

    2014-01-01

    Both hereditary and nonhereditary retinoblastoma (Rb) are commonly initiated by loss of both copies of the retinoblastoma tumor suppressor gene (RB1), while additional genomic changes are required for tumor initiation and progression. Our aim was to determine whether there is genomic heterogeneity b

  6. IDENTIFYING SOURCES OF VARIABILITY IN INTERSTITIAL WATER SAMPLING USING THE DIALYSIS (PEEPER) METHOD

    Science.gov (United States)

    The practice of measuring contaminants in interstitial water (IW) during sediment toxicity tests enables researchers to relate contaminant concentrations to organism responses. It is critical that contaminant concentrations are quantified in a precise manner when making these mea...

  7. Improving Students' Understanding of, and Ability to Identify Independent and Dependent Variables

    Science.gov (United States)

    Aldrich, Rosalie S.

    2015-01-01

    Students need to have a basic understanding of research methods before obtaining a communication degree in order to become an intelligent consumer of research--someone who is able to read, understand, explain, and critically evaluate communication and other research reported in scholarly journals as well as in the popular press. These skills are…

  8. Identifying potential sources of variability between vegetation carbon storage estimates for urban areas

    DEFF Research Database (Denmark)

    Davies, Zoe G.; Dallimer, Martin; Edmondson, Jill L.;

    2013-01-01

    Although urbanisation is a major cause of land-use change worldwide, towns and cities remain relatively understudied ecosystems. Research into urban ecosystem service provision is still an emerging field, yet evidence is accumulating rapidly to suggest that the biological carbon stores in cities...

  9. Late quaternary paleo-climatic records from Alaskan Loess: Identifying causes of natural climate variability

    International Nuclear Information System (INIS)

    Magnetic susceptibility profiling and magnetic remanence studies, x-ray sedigraph analysis, scanning electron microscope image studies, tephrochronology, and fission-track dating of thick loess deposits in Alaska reveal a continuous record of the chronology and pattern of past climate changes at high latitudes. Long-term climate changes in Alaska appear to have closely followed global patterns over at least the last 200,000 years. Radiocarbon and fission-track dating demonstrate agreement between the timing of climate changes recorded in terrestrial loess deposits and records from marine and ice cores. Spectral analyses of loess proxy climate time-series reveal power at orbital frequencies, providing evidence for the Milankovitch model of climate change. Many short-term climate events, lasting only 102 - 103 years, are also recorded in loess sections. Some of these short-term events appear to reflect transient changes in global atmospheric CO2 contents of 25-50% documented by studies of ice cores, and provide evidence for changes in the global Greenhouse effect due to natural variations of atmospheric CO2 content

  10. Identifying Process Variables for a Low Atmospheric Pressure Stunning/Killing System

    Science.gov (United States)

    Current systems for pre-slaughter gas stunning/killing of broilers use process gases such as carbon dioxide, argon, or a mixture of these gases with air or oxygen. Both carbon dioxide and argon work by displacing oxygen to induce hypoxia in the bird, leading to unconsciousness and ultimately death....

  11. Individual variability in human blood metabolites identifies age-related differences.

    Science.gov (United States)

    Chaleckis, Romanas; Murakami, Itsuo; Takada, Junko; Kondoh, Hiroshi; Yanagida, Mitsuhiro

    2016-04-19

    Metabolites present in human blood document individual physiological states influenced by genetic, epigenetic, and lifestyle factors. Using high-resolution liquid chromatography-mass spectrometry (LC-MS), we performed nontargeted, quantitative metabolomics analysis in blood of 15 young (29 ± 4 y of age) and 15 elderly (81 ± 7 y of age) individuals. Coefficients of variation (CV = SD/mean) were obtained for 126 blood metabolites of all 30 donors. Fifty-five RBC-enriched metabolites, for which metabolomics studies have been scarce, are highlighted here. We found 14 blood compounds that show remarkable age-related increases or decreases; they include 1,5-anhydroglucitol, dimethyl-guanosine, acetyl-carnosine, carnosine, ophthalmic acid, UDP-acetyl-glucosamine,N-acetyl-arginine,N6-acetyl-lysine, pantothenate, citrulline, leucine, isoleucine, NAD(+), and NADP(+) Six of them are RBC-enriched, suggesting that RBC metabolomics is highly valuable for human aging research. Age differences are partly explained by a decrease in antioxidant production or increasing inefficiency of urea metabolism among the elderly. Pearson's coefficients demonstrated that some age-related compounds are correlated, suggesting that aging affects them concomitantly. Although our CV values are mostly consistent with those CVs previously published, we here report previously unidentified CVs of 51 blood compounds. Compounds having moderate to high CV values (0.4-2.5) are often modified. Compounds having low CV values, such as ATP and glutathione, may be related to various diseases because their concentrations are strictly controlled, and changes in them would compromise health. Thus, human blood is a rich source of information about individual metabolic differences. PMID:27036001

  12. Variable Star Discovery with Ultra-Low Cost Equipment

    Science.gov (United States)

    Paust, Nathaniel; Wilson, Danielle

    2016-06-01

    We present preliminary results of a variable star search using commercial DSLR equipment. The camera in use images the sky at DEC=+44 every ten minutes, day and night. A wide variety of open-source tools, from photo editors to specialty programs like the astrometry.net suite, are used to process the images and identify variable stars.

  13. Gene Variants Associated with Antisocial Behaviour: A Latent Variable Approach

    Science.gov (United States)

    Bentley, Mary Jane; Lin, Haiqun; Fernandez, Thomas V.; Lee, Maria; Yrigollen, Carolyn M.; Pakstis, Andrew J.; Katsovich, Liliya; Olds, David L.; Grigorenko, Elena L.; Leckman, James F.

    2013-01-01

    Objective: The aim of this study was to determine if a latent variable approach might be useful in identifying shared variance across genetic risk alleles that is associated with antisocial behaviour at age 15 years. Methods: Using a conventional latent variable approach, we derived an antisocial phenotype in 328 adolescents utilizing data from a…

  14. Periodic functions with variable period

    OpenAIRE

    Pryjmak, M. V

    2010-01-01

    The examples of rhythmical signals with variable period are considered. The definition of periodic function with the variable period is given as a model of such signals. The examples of such functions are given and their variable periods are written in the explicit form. The system of trigonometric functions with the variable period is considered and its orthogonality is proved. The generalized system of trigonometric functions with the variable period is also suggested; some conditions of it...

  15. Variable Renewable Energy: a Regulatory Roadmap (Fact Sheet)

    Energy Technology Data Exchange (ETDEWEB)

    2014-10-01

    There is not a one-size-fits-all approach to the regulation of variable renewable energy (VRE), but international experience reveals many approaches that are proving successful. Drawing upon research and experiences from various international contexts, the 21st Century Power Partnership in conjunction with the Clean Energy Solutions Center and Clean Energy Regulators Initiative identified key issues and ideas that have emerged as variable deployment has grown. The Power Partnership research, published in 2014, identified four broad categories of regulatory issues.

  16. Spectral Variability of FSRQs

    Indian Academy of Sciences (India)

    Minfeng Gu; Y. L. Ai

    2011-03-01

    The optical variability of 29 flat spectrum radio quasars in SDSS Stripe 82 region are investigated by using DR7 released multi-epoch data. All FSRQs show variations with overall amplitude ranging from 0.24 mag to 3.46 mag in different sources. About half of FSRQs show a bluer-when-brighter trend, which is commonly observed for blazars. However, only one source shows a redder-when-brighter trend, which implies it is rare in FSRQs. In this source, the thermal emission may be responsible for the spectral behaviour.

  17. Complex variables II essentials

    CERN Document Server

    Solomon, Alan D

    2013-01-01

    REA's Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. Complex Variables II includes elementary mappings and Mobius transformation, mappings by general functions, conformal mappings and harmonic functions, applying complex functions to a

  18. Variable leak gas source

    Science.gov (United States)

    Henderson, Timothy M.; Wuttke, Gilbert H.

    1977-01-01

    A variable leak gas source and a method for obtaining the same which includes filling a quantity of hollow glass micro-spheres with a gas, storing said quantity in a confined chamber having a controllable outlet, heating said chamber above room temperature, and controlling the temperature of said chamber to control the quantity of gas passing out of said controllable outlet. Individual gas filled spheres may be utilized for calibration purposes by breaking a sphere having a known quantity of a known gas to calibrate a gas detection apparatus.

  19. Can tests identify creative people?

    Science.gov (United States)

    Bell, Peter M.

    It is always a popular pursuit by academic administrators to assess the creativity or innovative qualities of scientists in order to evaluate their research capabilities. Of course, traditionally such evaluations have been fraught with subjectivity (i.e., innovative scientists are commonly thought to be weird, under 40 years old, independent, risk-taking, etc.), and thus such evaluations have not been highly valued. In recent years, through testing, the American Chemical Society (ACS) has attempted to give respectability to the art of predicting the creativity of a scientist. ACS, which draws its members from both industrial and academic laboratories, held a symposium on the subject of evaluating the creativity of scientists. The proceedings were published by ACS as ‘Innovation and U.S. Research: Problems and Recommendations’ (W. N. Smith and C.F. Larson, eds., 1980). In the proceedings, as reported in the July 1982 Chemtec (all quotes here are from the Chemtec article), A. Nisson was able to identify only the following two-part characteristic of an innovative person: (1) a low threshold to ‘a state of discomfort with some aspect of the order of things, the status quo,’ and (2) ‘an extraordinarily high level of mental stamina enabling him or her to persist until the state of discomfort is removed.’

  20. ENIGMATIC RECURRENT PULSATIONAL VARIABILITY OF THE ACCRETING WHITE DWARF EQ LYN (SDSS J074531.92+453829.6)

    Energy Technology Data Exchange (ETDEWEB)

    Mukadam, Anjum S.; Szkody, Paula [Department of Astronomy, University of Washington, Seattle, WA 98195-1580 (United States); Townsley, D. M.; Brockett, T. [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL 35487 (United States); Gaensicke, B. T.; Parsons, S. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Southworth, J. [Astrophysics Group, Keele University, Staffordshire ST5 5BG (United Kingdom); Hermes, J. J.; Montgomery, M. H.; Winget, D. E.; Harrold, S. [Department of Astronomy, University of Texas at Austin, Austin, TX 78759 (United States); Tovmassian, G.; Zharikov, S. [Observatorio Astronomico Nacional SPM, Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Ensenada, BC (Mexico); Drake, A. J. [Department of Astronomy and the Center for Advanced Computing Research, California Institute of Technology, Pasadena, CA 91225 (United States); Henden, A. [American Association of Variable Star Observers, 25 Birch Street, Cambridge, MA 02138 (United States); Rodriguez-Gil, P. [Departamento de Astrofisica, Universidad de La Laguna, La Laguna, E-38204 Santa Cruz de Tenerife (Spain); Sion, E. M. [Department of Astronomy and Astrophysics, Villanova University, Villanova, PA 19085 (United States); Zola, S.; Szymanski, T. [Astronomical Observatory, Jagiellonian University, ul. Orla 171, PL-30-244 Krakow (Poland); Pavlenko, E. [Crimean Astrophysical Observatory, Crimea 98409 (Ukraine); and others

    2013-09-15

    Photometric observations of the cataclysmic variable EQ Lyn (SDSS J074531.92+453829.6), acquired from 2005 October to 2006 January, revealed high-amplitude variability in the range 1166-1290 s. This accreting white dwarf underwent an outburst in 2006 October, during which its brightness increased by at least five magnitudes, and it started exhibiting superhumps in its light curve. Upon cooling to quiescence, the superhumps disappeared and it displayed the same periods in 2010 February as prior to the outburst within the uncertainties of a couple of seconds. This behavior suggests that the observed variability is likely due to nonradial pulsations in the white dwarf star, whose core structure has not been significantly affected by the outburst. The enigmatic observations begin with an absence of pulsational variability during a multi-site campaign conducted in 2011 January-February without any evidence of a new outburst; the light curve is instead dominated by superhumps with periods in the range of 83-87 minutes. Ultraviolet Hubble Space Telescope time-series spectroscopy acquired in 2011 March reveals an effective temperature of 15,400 K, placing EQ Lyn within the broad instability strip of 10,500-16,000 K for accreting pulsators. The ultraviolet light curve with 90% flux from the white dwarf shows no evidence of any pulsations. Optical photometry acquired during 2011 and Spring 2012 continues to reflect the presence of superhumps and an absence of pulsations. Subsequent observations acquired in 2012 December and 2013 January finally indicate the disappearance of superhumps and the return of pulsational variability with similar periods as previous data. However, our most recent data from 2013 March to May reveal superhumps yet again with no sign of pulsations. We speculate that this enigmatic post-outburst behavior of the frequent disappearance of pulsational variability in EQ Lyn is caused either by heating the white dwarf beyond the instability strip due to an

  1. Exam stressors, modulating variables and academic failure

    OpenAIRE

    Arturo Barraza Macías; Oscar Rodríguez

    2010-01-01

    This research was raised four objectives: a) to establish the profile of stress descriptive review of the higher education students, b) identify areas that cause more stress on the students of higher education when presenting a review c ) distinguish socio-demographic variables and situational which provide significant differences in stress examination of students in higher education d) determining the relationship between stress examination and the number of subjects disapproved of the stude...

  2. Single-molecule dynamics at variable temperatures

    OpenAIRE

    Zondervan, Rob

    2006-01-01

    Single-molecule optics has evolved from a specialized variety of optical spectroscopy at low temperatures into a versatile tool to address questions in physics, chemistry, biology, and materials science. In this thesis, the potential of single-molecule (and ensemble) optical microscopy at variable temperatures is demonstrated: Electron transfer has been identified as a crucial step in the photodynamics of organic fluorophores, and long-term memory effects have been discovered in the relaxatio...

  3. Solar Irradiance Variability

    CERN Document Server

    Solanki, Sami K

    2012-01-01

    The Sun has long been considered a constant star, to the extent that its total irradiance was termed the solar constant. It required radiometers in space to detect the small variations in solar irradiance on timescales of the solar rotation and the solar cycle. A part of the difficulty is that there are no other constant natural daytime sources to which the Sun's brightness can be compared. The discovery of solar irradiance variability rekindled a long-running discussion on how strongly the Sun affects our climate. A non-negligible influence is suggested by correlation studies between solar variability and climate indicators. The mechanism for solar irradiance variations that fits the observations best is that magnetic features at the solar surface, i.e. sunspots, faculae and the magnetic network, are responsible for almost all variations (although on short timescales convection and p-mode oscillations also contribute). In spite of significant progress important questions are still open. Thus there is a debat...

  4. Current Climate Variability & Change

    Science.gov (United States)

    Diem, J.; Criswell, B.; Elliott, W. C.

    2013-12-01

    Current Climate Variability & Change is the ninth among a suite of ten interconnected, sequential labs that address all 39 climate-literacy concepts in the U.S. Global Change Research Program's Climate Literacy: The Essential Principles of Climate Sciences. The labs are as follows: Solar Radiation & Seasons, Stratospheric Ozone, The Troposphere, The Carbon Cycle, Global Surface Temperature, Glacial-Interglacial Cycles, Temperature Changes over the Past Millennium, Climates & Ecosystems, Current Climate Variability & Change, and Future Climate Change. All are inquiry-based, on-line products designed in a way that enables students to construct their own knowledge of a topic. Questions representative of various levels of Webb's depth of knowledge are embedded in each lab. In addition to the embedded questions, each lab has three or four essential questions related to the driving questions for the lab suite. These essential questions are presented as statements at the beginning of the material to represent the lab objectives, and then are asked at the end as questions to function as a summative assessment. For example, the Current Climate Variability & Change is built around these essential questions: (1) What has happened to the global temperature at the Earth's surface, in the middle troposphere, and in the lower stratosphere over the past several decades?; (2) What is the most likely cause of the changes in global temperature over the past several decades and what evidence is there that this is the cause?; and (3) What have been some of the clearly defined effects of the change in global temperature on the atmosphere and other spheres of the Earth system? An introductory Prezi allows the instructor to assess students' prior knowledge in relation to these questions, while also providing 'hooks' to pique their interest related to the topic. The lab begins by presenting examples of and key differences between climate variability (e.g., Mt. Pinatubo eruption) and

  5. Latent cluster analysis of ALS phenotypes identifies prognostically differing groups.

    Directory of Open Access Journals (Sweden)

    Jeban Ganesalingam

    Full Text Available BACKGROUND: Amyotrophic lateral sclerosis (ALS is a degenerative disease predominantly affecting motor neurons and manifesting as several different phenotypes. Whether these phenotypes correspond to different underlying disease processes is unknown. We used latent cluster analysis to identify groupings of clinical variables in an objective and unbiased way to improve phenotyping for clinical and research purposes. METHODS: Latent class cluster analysis was applied to a large database consisting of 1467 records of people with ALS, using discrete variables which can be readily determined at the first clinic appointment. The model was tested for clinical relevance by survival analysis of the phenotypic groupings using the Kaplan-Meier method. RESULTS: The best model generated five distinct phenotypic classes that strongly predicted survival (p<0.0001. Eight variables were used for the latent class analysis, but a good estimate of the classification could be obtained using just two variables: site of first symptoms (bulbar or limb and time from symptom onset to diagnosis (p<0.00001. CONCLUSION: The five phenotypic classes identified using latent cluster analysis can predict prognosis. They could be used to stratify patients recruited into clinical trials and generating more homogeneous disease groups for genetic, proteomic and risk factor research.

  6. Quantifying the limits of fingerprint variability.

    Science.gov (United States)

    Fagert, Michael; Morris, Keith

    2015-09-01

    The comparison and identification of fingerprints are made difficult by fingerprint variability arising from distortion. This study seeks to quantify both the limits of fingerprint variability when subject to heavy distortion, and the variability observed in repeated inked planar impressions. A total of 30 fingers were studied: 10 right slant loops, 10 plain whorls, and 10 plain arches. Fingers were video recorded performing several distortion movements under heavy deposition pressure: left, right, up, and down translation of the finger, clockwise and counter-clockwise torque of the finger, and planar impressions. Fingerprint templates, containing 'true' minutiae locations, were created for each finger using 10 repeated inked planar impressions. A minimal amount of variability, 0.18mm globally, was observed for minutiae in repeated inked planar impressions. When subject to heavy distortion minutiae can be displaced by upwards of 3mm and their orientation altered by as much as 30° in relation to their template positions. Minutiae displacements of 1mm and 10° changes in orientation are readily observed. The results of this study will allow fingerprint examiners to identify and understand the degree of variability that can be reasonably expected throughout the various regions of fingerprints. PMID:26197351

  7. Monochromatic and identifiable photons used in photonuclear research

    International Nuclear Information System (INIS)

    A general overview is given of the most common experimental procedures for the production and utilisation of monochromatic and (or) identifiable photon probes actually operational in 1979. Their basic characteristics, merits and drawbacks, together with their respective major domains of experimental physics to which they are usually applied, are also investigated. Methods for producing such monochromatic and (or) identifiable photon probes, with a continuously variable energy from a few MeV up till about 180 GeV, are treated in some detail. Some of the most promising future trends in the ulterior development of such electromagnetic probes are also mentioned

  8. Structural parameter identifiability analysis for dynamic reaction networks

    DEFF Research Database (Denmark)

    Davidescu, Florin Paul; Jørgensen, Sten Bay

    2008-01-01

    A fundamental problem in model identification is to investigate whether unknown parameters in a given model structure potentially can be uniquely recovered from experimental data. This issue of global or structural identifiability is essential during nonlinear first principles model development...... where for a given set of measured variables it is desirable to investigate which parameters may be estimated prior to spending computational effort on the actual estimation. This contribution addresses the structural parameter identifiability problem for the typical case of reaction network models. The...

  9. New Variable Stars in the Globular Cluster NGC 6584

    OpenAIRE

    Toddy, Joseph M.; Johnson, Elliott W.; Darragh, Andrew N.; Murphy, Brian W.

    2012-01-01

    Using the Southeastern Association for Research in Astronomy 0.6 meter telescope located at Cerro Tololo, we searched for variable stars in the southern globular cluster NGC 6584. We obtained images during 8 nights between 28 May and 6 July of 2011. After processing the images, we used the image subtraction package ISIS developed by Alard (2000)to search for the variable stars. We identified a total of 69 variable stars in our 10x10 arcmin^2 field, including 43 variables cataloged by Millis &...

  10. Variability of Optical Counterparts in the Chandra Galactic Bulge Survey

    CERN Document Server

    Britt, Christopher T; Johnson, C B; Baldwin, A; Jonker, P G; Nelemans, G; Torres, M A P; Maccarone, T; Steeghs, D; Greiss, S; Heinke, C; Bassa, C G; Collazzi, A; Villar, A; Gabb, M; Gossen, L

    2014-01-01

    We present optical lightcurves of variable stars consistent with the positions of X-ray sources identified with the Chandra X-ray Observatory for the Chandra Galactic Bulge Survey. Using data from the Mosaic-II instrument on the Blanco 4m Telescope at CTIO, we gathered time-resolved photometric data on timescales from $\\sim2$ hr to 8 days over the $\\frac{3}{4}$ of the X-ray survey containing sources from the initial GBS catalog. Among the lightcurve morphologies we identify are flickering in interacting binaries, eclipsing sources, dwarf nova outbursts, ellipsoidal variations, long period variables, spotted stars, and flare stars. $87\\%$ of X-ray sources have at least one potential optical counterpart. $24\\%$ of these candidate counterparts are detectably variable; a much greater fraction than expected for randomly selected field stars, which suggests that most of these variables are real counterparts. We discuss individual sources of interest, provide variability information on candidate counterparts, and di...

  11. Using novel spectral-timing techniques to probe the rapid variability of X-Ray Binaries

    OpenAIRE

    Wilkinson, Tony

    2011-01-01

    X-ray spectral variability is a powerful probe of the relationship between the accretion disc and corona in accreting compact objects. In this thesis, I present the use of variability techniques to disentangle the different variable components of X-ray spectra. By examining correlated variability over a range of timescales, I identify for the first time evidence of intrinsic disc variability on timescales of seconds. I go on to examine, utilising a range of spectral-timing techniques, the rol...

  12. Rapid VHE variability in blazars

    OpenAIRE

    Volpe, Francesca; Rieger, Frank M.

    2011-01-01

    Active Galactic Nuclei (AGN) are known to show significant variability over a wide frequency range. We review observational results on the variability characteristics of blazars in the very high energy (VHE) domain, focusing on recent findings of rapid VHE variability and evidence for an underlying multiplicative driving process in PKS 2155-304. We explore a physical scenario where the variability is assumed to arise due to accretion disk fluctuations transmitted to the jet, and discuss its i...

  13. Modeling Shared Variables in VHDL

    DEFF Research Database (Denmark)

    Madsen, Jan; Brage, Jens P.

    1994-01-01

    A set of concurrent processes communicating through shared variables is an often used model for hardware systems. This paper presents three modeling techniques for representing such shared variables in VHDL, depending on the acceptable constraints on accesses to the variables. Also a set of...... guidelines for handling atomic updates of multiple shared variables is given. 1 Introduction It is often desirable to partition a computational system into discrete functional units which cooperates to....

  14. The Performance of Variable Annuities

    OpenAIRE

    Michael J. McNamara; Henry R. Oppenheimer

    1991-01-01

    Variable annuities have become increasingly important in retirement plans. This paper provides an examination of the investment performance of variable annuities for the period year-end 1973 to year-end 1988. Returns, risk, and selectivity measures are analyzed for the sample of annuities, for individual variable annuities, and for subsamples of annuities with similar portfolio size and turnover. While the investment returns of variable annuities were greater than inflation over the period, t...

  15. Essential biodiversity variables

    Science.gov (United States)

    Pereira, H.M.; Ferrier, S.; Walters, M.; Geller, G.N.; Jongman, R.H.G.; Scholes, R.J.; Bruford, M.W.; Brummitt, N.; Butchart, S.H.M.; Cardoso, A.C.; Coops, N.C.; Dulloo, E.; Faith, D.P.; Freyhof, J.; Gregory, R.D.; Heip, C.; Höft, R.; Hurtt, G.; Jetz, W.; Karp, D.S.; McGeoch, M.A.; Obura, D.; Onada, Y.; Pettorelli, N.; Reyers, B.; Sayre, R.; Scharlemann, J.P.W.; Stuart, S.N.; Turak, E.; Walpole, M.; Wegmann, M.

    2013-01-01

    Reducing the rate of biodiversity loss and averting dangerous biodiversity change are international goals, reasserted by the Aichi Targets for 2020 by Parties to the United Nations (UN) Convention on Biological Diversity (CBD) after failure to meet the 2010 target (1, 2). However, there is no global, harmonized observation system for delivering regular, timely data on biodiversity change (3). With the first plenary meeting of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) soon under way, partners from the Group on Earth Observations Biodiversity Observation Network (GEO BON) (4) are developing—and seeking consensus around—Essential Biodiversity Variables (EBVs) that could form the basis of monitoring programs worldwide.

  16. Climate variability and change

    International Nuclear Information System (INIS)

    When Australia's climate should not be definite barrier to the population reaching 30 million by 2050, it is recognised that our climate has limited the development of the nation over the past 200 years. Indeed in 1911, based on a comparison of the climate and development between the US and Australia. Griffith Taylor predicted that Australia's population would be 19 million at the end of the 20th century, which is a pretty good 90-year forecast. The climate constraint is not only due to much of the country being semi-arid with an annual rainfall below 400 millimetres, but also due to the large year-to-year variability of rainfall across the country

  17. Strong Decomposition of Random Variables

    DEFF Research Database (Denmark)

    Hoffmann-Jørgensen, Jørgen; Kagan, Abram M.; Pitt, Loren D.;

    2007-01-01

    A random variable X is stongly decomposable if X=Y+Z where Y=Φ(X) and Z=X-Φ(X) are independent non-degenerated random variables (called the components). It is shown that at least one of the components is singular, and we derive a necessary and sufficient condition for strong decomposability of a...... discrete random variable....

  18. Preservice Teachers' Understanding of Variable

    Science.gov (United States)

    Brown, Sue; Bergman, Judy

    2013-01-01

    This study examines the research on middle school students' understanding of variables and explores preservice elementary and middle school teachers' knowledge of variables. According to research studies, middle school students have limited understanding of variables. Many studies have examined the performance of middle school students and offered…

  19. CHARACTERIZING THE OPTICAL VARIABILITY OF BRIGHT BLAZARS: VARIABILITY-BASED SELECTION OF FERMI ACTIVE GALACTIC NUCLEI

    International Nuclear Information System (INIS)

    We investigate the use of optical photometric variability to select and identify blazars in large-scale time-domain surveys, in part to aid in the identification of blazar counterparts to the ∼30% of γ-ray sources in the Fermi 2FGL catalog still lacking reliable associations. Using data from the optical LINEAR asteroid survey, we characterize the optical variability of blazars by fitting a damped random walk model to individual light curves with two main model parameters, the characteristic timescales of variability τ, and driving amplitudes on short timescales σ-circumflex. Imposing cuts on minimum τ and σ-circumflex allows for blazar selection with high efficiency E and completeness C. To test the efficacy of this approach, we apply this method to optically variable LINEAR objects that fall within the several-arcminute error ellipses of γ-ray sources in the Fermi 2FGL catalog. Despite the extreme stellar contamination at the shallow depth of the LINEAR survey, we are able to recover previously associated optical counterparts to Fermi active galactic nuclei with E ≥ 88% and C = 88% in Fermi 95% confidence error ellipses having semimajor axis r < 8'. We find that the suggested radio counterpart to Fermi source 2FGL J1649.6+5238 has optical variability consistent with other γ-ray blazars and is likely to be the γ-ray source. Our results suggest that the variability of the non-thermal jet emission in blazars is stochastic in nature, with unique variability properties due to the effects of relativistic beaming. After correcting for beaming, we estimate that the characteristic timescale of blazar variability is ∼3 years in the rest frame of the jet, in contrast with the ∼320 day disk flux timescale observed in quasars. The variability-based selection method presented will be useful for blazar identification in time-domain optical surveys and is also a probe of jet physics.

  20. Identifying US monetary policy shocks through sign restrictions in dollarized countries

    NARCIS (Netherlands)

    A. Gobbi; T. Willems

    2011-01-01

    Since dollarized countries import US monetary policy, identifying US monetary shocks through sign restrictions on US variables only, does not use all available information. In this paper we therefore include dollarized countries, which enable us to restrict more variables and leave the responses of

  1. PERIODIC AND APERIODIC VARIABILITY IN THE MOLECULAR CLOUD ρ OPHIUCHUS

    International Nuclear Information System (INIS)

    Presented are the results of a near-IR photometric survey of 1678 stars in the direction of the ρ Ophiuchus (ρ Oph) star forming region using data from the 2MASS Calibration Database. For each target in this sample, up to 1584 individual J-, H-, and Ks -band photometric measurements with a cadence of ∼1 day are obtained over three observing seasons spanning ∼2.5 yr; it is the most intensive survey of stars in this region to date. This survey identifies 101 variable stars with ΔKs -band amplitudes from 0.044 to 2.31 mag and Δ(J – Ks ) color amplitudes ranging from 0.053 to 1.47 mag. Of the 72 young ρ Oph star cluster members included in this survey, 79% are variable; in addition, 22 variable stars are identified as candidate members. Based on the temporal behavior of the Ks time-series, the variability is distinguished as either periodic, long time-scale or irregular. This temporal behavior coupled with the behavior of stellar colors is used to assign a dominant variability mechanism. A new period-searching algorithm finds periodic signals in 32 variable stars with periods between 0.49 to 92 days. The chief mechanism driving the periodic variability for 18 stars is rotational modulation of cool starspots while 3 periodically vary due to accretion-induced hot spots. The time-series for six variable stars contains discrete periodic ''eclipse-like'' features with periods ranging from 3 to 8 days. These features may be asymmetries in the circumstellar disk, potentially sustained or driven by a proto-planet at or near the co-rotation radius. Aperiodic, long time-scale variations in stellar flux are identified in the time-series for 31 variable stars with time-scales ranging from 64 to 790 days. The chief mechanism driving long time-scale variability is variable extinction or mass accretion rates. The majority of the variable stars (40) exhibit sporadic, aperiodic variability over no discernable time-scale. No chief variability mechanism

  2. N-variable rational approximants

    International Nuclear Information System (INIS)

    ''Desirable properties'' of a two-variable generalization of Pade approximants are laid down. The ''Chisholm approximants'' are defined and are shown to obey nearly all of these properties; the alternative ways of completing a unique definition are discussed, and the ''prong structure'' of the defining equations is elucidated. Several generalizations and variants of Chisholm approximants are described: N-variable diagonal, 2-variable simple off-diagonal, N-variable simple and general off-diagonal, and rotationally covariant 2-variable approximants. All of the 2-variable approximants are capable of representing singularities of functions of two variables, and of analytically continuing beyond the polycylinder of convergence of the double series. 8 figures

  3. Climate variability and climate change

    International Nuclear Information System (INIS)

    Changes of variability with climate change are likely to have a substantial impact on vegetation and society, rivaling the importance of changes in the mean values themselves. A variety of paleoclimate and future climate simulations performed with the GISS global climate model is used to assess how the variabilities of temperature and precipitation are altered as climate warms or cools. In general, as climate warms, temperature variability decreases due to reductions in the latitudinal temperature gradient and precipitation variability increases together with the intensity of the hydrologic cycle. If future climate projections are accurate, the reduction in temperature variability will be minimized by the rapid change in mean temperatures, but the hydrologic variability will be amplified by increased evapotranspiration. Greater hydrologic variability would appear to pose a potentially severe problem for the next century. 19 refs.; 3 figs.; 2 tabs

  4. Climate variability and climate change

    International Nuclear Information System (INIS)

    Changes of variability with climate change are likely to have a substantial impact on vegetation and society, rivaling the importance of changes in the mean values themselves. A variety of paleoclimate and future climate simulations performed with the GISS global climate model is used to assess how the variabilities of temperature and precipitation are altered as climate warms or cools. In general, as climate warms, temperature variability decreases due to reductions in the latitudinal temperature gradient and precipitation variability increases together with the intensity of the hydrologic cycle. If future climate projections are accurate, the reduction in temperature variability will be minimized by the rapid change in mean temperatures, but the hydrologic variability will be amplified by increased evapotranspiration. Greater hydrologic variability would appear to pose a potentially severe problem for the next century

  5. Identifying periods of drowsy driving using EEG.

    Science.gov (United States)

    Brown, Timothy; Johnson, Robin; Milavetz, Gary

    2013-01-01

    Drowsy driving is a significant contributor to death and injury crashes on our nation's highways. Predictive neurophysiologic/physiologic solutions to reduce these incidences have been proposed and developed. EEG based metrics were found to be promising in initial studies, but remain controversial in their efficacy, primarily due to failures to develop replication studies within the simulation settings used for development, and real-world validation. This analysis sought to address these short comings by assessing the utility of the B-Alert algorithms, in a replication study of driving and drowsiness. Data were collected on the National Advanced Driving Simulator from 72 volunteer drivers exposed to three types of roadways at three times of day representing different levels of drowsiness. EEG metrics, collected using the B-Alert X10 Wireless Headset were evaluated to determine their utility in future predictive studies. The replication of the B-Alert algorithms was a secondary focus for this analysis, resulting in highly variable start times within each time of day segment, leading to EEG data being confounded by the diurnal variations that occur in the basal EEG signal. Regardless of this limitation, the analysis revealed promising outcomes. The EEG based algorithms for sleep onset, drowsiness, as well as fatigue related power spectral bandwidths (i.e. lateral central, and parietal alpha) varied with time of day of the drives. Interestingly, EEG metrics of cognitive workload were also sensative to the terrain of the drives. The replicaiton of the B-Alert algorithms were a secondary focuse in the study design, Taken together, these data indicate great potential of carefully designed studies to utilize neurophysiologic metrics to identify time of day and task and road conditions that may be at greatest risk during fatigued/drowsy periods. PMID:24406950

  6. Utilizing the AAVSO's Variable Star Index (VSX) In Undergraduate Research Projects

    Science.gov (United States)

    Larsen, Kristine

    2016-01-01

    Among the many important services that the American Association of Variable Star Observers (AAVSO) provides to the astronomical community is the Variable Star Index (VSX - https://www.aavso.org/vsx/). This online catalog of variable stars is the repository of data on over 334,000 variable stars, including information on spectral type, range of magnitude, period, and type of variable, among other properties. A number of these stars were identified as being variable through automated telescope surveys, such as ASAS (All Sky Automated Survey). The computer code of this survey classified newly discovered variables as best it could, but a significant number of false classifications have been noted. The reclassification of ASAS variables in the VSX data, as well as a closer look at variables identified as miscellaneous type in VSX, are two of many projects that can be undertaken by interested undergraduates. In doing so, students learn about the physical properties of various types of variable stars as well as statistical analysis and computer software, especially the VStar variable star data visualization and analysis tool that is available to the astronomical community free of charge on the AAVSO website (https://www.aavso.org/vstar-overview). Two such projects are described in this presentation, the first to identify BY Draconis variables erroneously classified as Cepheids in ASAS data, and the second to identify SRD semiregular variables misidentified as "miscellaneous" in VSX.

  7. X-ray variability and period determinations in the eclipsing polar DP Leonis

    Science.gov (United States)

    Robinson, Craig R.; Cordova, France A.

    1994-01-01

    We present an analysis of our ROSAT position sensitive proportional counter (PSPC) observations on the eclipsing magnetic cataclysmic variable DP Leo. The soft X-ray spectrum is modeled by a blackbody of kT = 24.8(sup +2.6 sub -8.1) eV. Severe limits are placed upon the flux from any hard bremsstrahlung component. A strong soft X-ray excess, with respect to hard X-ray emission, is found. The soft X-ray blackbody luminosity is larger than both the cyclotron and bremsstrahlung luminosities. An upper limit of 500 pc is obtained for the system's distance based upon the X-ray absorption (N(sub H) less than 5 x 10(exp 19)/sq cm) and an estimate of 260(sup +150 sub -100) pc is determined from a published measurement of the secondary's flux. For the derived blackbody fit, the bolometric luminosity is found to be L(sub bb, bol) = 1.4(sup +7.1 sub -0.3) x 10(exp 31)(d/260 pc)(exp 2) ergs/s. Absorption by the accretion stream produces an intensity dip prior to each eclipse. Extreme variability in the shape of the light curve from eclipse to eclipse demonstrates that changes in the rate of accretion onto the white dwarf, the sizes of accretion filaments, or variations in the location or amount of absorbing matter in the system occur on timescales shorter than the orbital period (89.8 minutes). No evidence exists for accretion onto the stronger (59 MG) magnetic pole in the ROSAT data. A new ephemeris is presented for the eclipse of the white dwarf emission region by the secondary star and another is produced for the orbital conjunction of the two components. The rotation of the white dwarf is shown to be faster than the orbital period by (5.3 +/- 1.1) x 10(exp -3) s. The origin of the asynchronous rotation may be activity cycle included orbital period variations or oscillations of the white dwarf's main pole about an equilibirium position. The accretion stream is modeled assuming that disruption of the stream along magnetic field lines occurs close to the white dwarf. The ROSAT

  8. Variable angle correlation spectroscopy

    International Nuclear Information System (INIS)

    In this dissertation, a novel nuclear magnetic resonance (NMR) technique, variable angle correlation spectroscopy (VACSY) is described and demonstrated with 13C nuclei in rapidly rotating samples. These experiments focus on one of the basic problems in solid state NMR: how to extract the wealth of information contained in the anisotropic component of the NMR signal while still maintaining spectral resolution. Analysis of the anisotropic spectral patterns from poly-crystalline systems reveal information concerning molecular structure and dynamics, yet in all but the simplest of systems, the overlap of spectral patterns from chemically distinct sites renders the spectral analysis difficult if not impossible. One solution to this problem is to perform multi-dimensional experiments where the high-resolution, isotropic spectrum in one dimension is correlated with the anisotropic spectral patterns in the other dimensions. The VACSY technique incorporates the angle between the spinner axis and the static magnetic field as an experimental parameter that may be incremented during the course of the experiment to help correlate the isotropic and anisotropic components of the spectrum. The two-dimensional version of the VACSY experiments is used to extract the chemical shift anisotropy tensor values from multi-site organic molecules, study molecular dynamics in the intermediate time regime, and to examine the ordering properties of partially oriented samples. The VACSY technique is then extended to three-dimensional experiments to study slow molecular reorientations in a multi-site polymer system

  9. Variables moderadoras del estres

    Directory of Open Access Journals (Sweden)

    María Cristina Richaud de Minzi

    1999-01-01

    Full Text Available El objetivo del presente trabajo es analizar la influenciadel estilo atribucional, la confianza interpersonal y el soporte social sobre la percepción de la amenaza. Se administraron la Escala de Estilo Atribucional; la Manheim Interview 01 Social Support, la Escala de Confianza Interpersonal; y el Inventario de Situaciones y Respuestas de Ansiedad, a 260 sujetos de ambos sexos, de 30 años de edad promedio, de nivel socioeconómico medio, residentes en la ciudad de Buenos Aires. El soporte social no demostró influencia significativa sobre la percepción de la amenaza. Con respecto a la influencia del estilo atribucional se puede decir que las personas indefensas perciben más amenaza, especialmente expresada como ansiedad cognitiva y, en menor grado, como ansiedad motora o conductual. La confianza interpersonal demostró ser una variable importante en la percepción de la amenaza. Los sujetos que presentaron alta desconfianza hacia las personas de su entorno perciben un mundo amenazante, que se manifiesta como ansiedad cognitiva, fisiológica y motora o conductual.

  10. Variable subsistence indemnity

    CERN Document Server

    2000-01-01

    At its meeting on 15 December 1999, the Finance Committee approved, with effect from 1st January 2000, adjustments to the Variable Subsistence Indemnity according to the rates published by the United Nations Organization given in document CERN/FC/4219. This decision maintained the reference method in force since 1983. The Management now proposes to adjust the CERN rates of indemnities, with effect from 1st January 2001, on the basis of the United Nations 2000 rates. The table contained in this document shows the rates for typical destinations, but they are only extracts from the complete UN table. Although a precise estimate of the cost effect for duty travel is difficult to achieve due to currency exchange values, it is probable that this will remain unchanged if calculated in Swiss francs. It may also be noted that, since 1 January this year, Article R IV 1.41 of the Staff Rules and Regulations has been changed in order to formalize the practice of the payment of a lower subsistence indemnity than the appro...

  11. Variable subsistence indemnity

    CERN Document Server

    2001-01-01

    At its meeting on 8 November 2000, the Finance Committee approved, with effect from 1st January 2001, adjustments to the Variable Subsistence Indemnity according to the rates published by the United Nations Organization given in document CERN/FC/4339. This decision maintained the reference method in force since 1983. The Management now proposes to adjust the CERN rates of indemnities, with effect from 1st January 2002, on the basis of the United Nations 2001 rates. Simply to give some examples extracted from the complete United Nations lists, the attached Annex shows the rates for a number of typical CERN duty travel destinations. For those countries concerned, the rates will be expressed in Euros from 2002. It is to be noted that the cost level for most destinations will not change significantly if calculated in Swiss Francs and, in any case, the Management will ensure that the total volume of costs for duty travel is contained within the limits of the 2002 budget. It is also to be noted that, since 1st Janu...

  12. Variable angle correlation spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Y K [Univ. of California, Berkeley, CA (United States)

    1994-05-01

    In this dissertation, a novel nuclear magnetic resonance (NMR) technique, variable angle correlation spectroscopy (VACSY) is described and demonstrated with {sup 13}C nuclei in rapidly rotating samples. These experiments focus on one of the basic problems in solid state NMR: how to extract the wealth of information contained in the anisotropic component of the NMR signal while still maintaining spectral resolution. Analysis of the anisotropic spectral patterns from poly-crystalline systems reveal information concerning molecular structure and dynamics, yet in all but the simplest of systems, the overlap of spectral patterns from chemically distinct sites renders the spectral analysis difficult if not impossible. One solution to this problem is to perform multi-dimensional experiments where the high-resolution, isotropic spectrum in one dimension is correlated with the anisotropic spectral patterns in the other dimensions. The VACSY technique incorporates the angle between the spinner axis and the static magnetic field as an experimental parameter that may be incremented during the course of the experiment to help correlate the isotropic and anisotropic components of the spectrum. The two-dimensional version of the VACSY experiments is used to extract the chemical shift anisotropy tensor values from multi-site organic molecules, study molecular dynamics in the intermediate time regime, and to examine the ordering properties of partially oriented samples. The VACSY technique is then extended to three-dimensional experiments to study slow molecular reorientations in a multi-site polymer system.

  13. Radio Band Observations of Blazar Variability

    Indian Academy of Sciences (India)

    Margo F. Aller; Hugh D. Aller; Philip A. Hughes

    2011-03-01

    The properties of blazar variability in the radio band are studied using the unique combination of temporal resolution from single dish monitoring and spatial resolution from VLBA imaging. Such measurements now available in all four Stokes parameters, together with theoretical simulations, identify the origin of radio band variability and probe the characteristics of the radio jet where the broadband blazar emission originates. Outbursts in total flux density and linear polarization in the optical-to-radio bands are attributed to shocks propagating within the jet spine, in part, based on limited modelling invoking transverse shocks; new radiative transfer simulations allowing for shocks at arbitrary angle to the flow direction confirm this picture by reproducing the observed centimeter-band variations observed more generally, and are of current interest since these shocks may play a role in the -ray flaring detected by Fermi. Recent UMRAO multifrequency Stokes V studies of bright blazars identify the spectral variability properties of circular polarization for the first time and demonstrate that polarity flips are relatively common. All-Stokes data are consistent with the production of circular polarization by linear-to-circular mode conversion in a region that is at least partially selfabsorbed. Detailed analysis of single-epoch, multifrequency, all-Stokes VLBA observations of 3C 279 support this physical picture and are best explained by emission from an electron-proton plasma.

  14. Calculi of meta-variables

    Institute of Scientific and Technical Information of China (English)

    Masahiko SATO; Takafumi SAKURAI; Yukiyoshi KAMEYAMA; Atsushi IGARASH

    2008-01-01

    The notion of meta-variable plays a fun-damental role when we define formal systems such as logical and computational calculi. Yet it has been usually understood only informally as is seen in most textbooks of logic. Based on our observations of the usages of meta-variables in textbooks, we propose two formal systems that have the notion of meta-variable. In both calculi, each variable is given a level (non-negative integer), which classifies variables into object variables (level 0), meta-variables (level 1), metameta-variables (level 2) and so on. Then, simple arity systems are. used to exclude meaningless terms like a meta-level function operating on the metameta-level. A main difference of the two calculi lies in the definitions of substitution. The first calculus uses textual substitution, which can often be found in definitions of quantified formulae: when a term is substituted for a meta-variable, free object-level variables in the term may be captured. The second cal-culus is based on the observation that predicates can be regarded as meta-level functions on object-level terms, hence uses capture-avoiding substitution. We show that both calculi enjoy a number of properties including Church-Rosser and Strong Normalization, which are indispensable when we use them as frameworks to define logical systems.

  15. Variable Cosmological Term

    Science.gov (United States)

    Dymnikova, Irina

    2003-06-01

    In the spherically symmetric case the dominant energy condition, together with the requirement of regularity of a density and finiteness of the mass, defines the family of asymptotically flat globally regular solutions to the Einstein minimally coupled equations which includes the class of metrics asymptotically de Sitter as r --> 0 and asymptotically Schwarzschild as r --> ∞. A source term connects smoothly de Sitter vacuum in the origin with the Minkowski vacuum at infinity and corresponds to anisotropic vacuum defined macroscopically by the algebraic structure of its stress-energy tensor invariant under boosts in the radial direction. Dependently on parameters, geometry describes vacuum nonsingular black and white holes, and self-gravitating particle-like structures. ADM mass for this class is related to both de Sitter vacuum trapped inside an object and to breaking of space-time symmetry. This class of metrics is easily extended to the case of nonzero cosmological constant at infinity. The source term connects then smoothly two de Sitter vacua and corresponds to extension of the Einstein cosmological term Λgμν to an r-dependent cosmological term Λμν. In this approach a constant scalar Λ associated with a vacuum density Λ = 8πGρvac, becomes a tensor component Λtt associated explicitly with a density component of a perfect fluid tensor whose vacuum properties follow from its symmetry and whose variability follows from the Bianchi identities. In this review we outline and discuss Λμν geometry and its applications.

  16. Intraspecific chromosome variability

    Directory of Open Access Journals (Sweden)

    N Dubinin

    2010-12-01

    Full Text Available (Editorial preface. The publication is presented in order to remind us of one of dramatic pages of the history of genetics. It re-opens for the contemporary reader a comprehensive work marking the priority change from plant cytogenetics to animal cytogenetics led by wide population studies which were conducted on Drosophila polytene chromosomes. The year of the publication (1937 became the point of irretrievable branching between the directions of Old World and New World genetics connected with the problems of chromosome variability and its significance for the evolution of the species. The famous book of T. Dobzhansky (1937 was published by Columbia University in the US under the title “Genetics and the origin of species”, and in the shadow of this American ‘skybuilding’ all other works grew dim. It is remarkable that both Dobzhansky and Dubinin come to similar conclusions about the role of chromosomes in speciation. This is not surprising given that they both might be considered as representatives of the Russian genetic school, by their birth and education. Interestingly, Dobzhansky had never referred to the full paper of Dubinin et al. (1937, though a previous short communication in Nature (1936 was included together with all former papers on the related subject. In full, the volume of the original publication printed in the Biological Journal in Moscow comprised 47 pages, in that number 41 pages of the Russian text accompanied by 16 Figs, a table and reference list, and, above all, 6 pages of the English summary. This final part in English is now reproduced in the authors’ version with the only addition being the reference list in the originally printed form.

  17. Population Synthesis for Mira Variables

    Institute of Scientific and Technical Information of China (English)

    Chun-Hua Zhu; Chao-Zheng Zha

    2005-01-01

    By means of a population synthesis code, we investigate the Mira variables. Their birth rate (over 0.65yr-1) and their number (~ 130000) in the Galaxy are estimated. For all possible Mira variables, ranges of their initial masses,pulsating periods, mass losses and lifetimes are given. We check our model with the observed Mira variables near the Sun and our results prove to be valid.

  18. ABOUT PSYCHOLOGICAL VARIABLES IN APPLICATION SCORING MODELS

    Directory of Open Access Journals (Sweden)

    Pablo Rogers

    2015-01-01

    Full Text Available The purpose of this study is to investigate the contribution of psychological variables and scales suggested by Economic Psychology in predicting individuals’ default. Therefore, a sample of 555 individuals completed a self-completion questionnaire, which was composed of psychological variables and scales. By adopting the methodology of the logistic regression, the following psychological and behavioral characteristics were found associated with the group of individuals in default: a negative dimensions related to money (suffering, inequality and conflict; b high scores on the self-efficacy scale, probably indicating a greater degree of optimism and over-confidence; c buyers classified as compulsive; d individuals who consider it necessary to give gifts to children and friends on special dates, even though many people consider this a luxury; e problems of self-control identified by individuals who drink an average of more than four glasses of alcoholic beverage a day.

  19. Variable Speed Rotor System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Variable speed rotors will give helicopters several advantages: higher top speed, greater fuel efficiency, momentary emergency over-power, resonance detuning...

  20. Prioritizing Highway Safety Manual's crash prediction variables using boosted regression trees.

    Science.gov (United States)

    Saha, Dibakar; Alluri, Priyanka; Gan, Albert

    2015-06-01

    The Highway Safety Manual (HSM) recommends using the empirical Bayes (EB) method with locally derived calibration factors to predict an agency's safety performance. However, the data needs for deriving these local calibration factors are significant, requiring very detailed roadway characteristics information. Many of the data variables identified in the HSM are currently unavailable in the states' databases. Moreover, the process of collecting and maintaining all the HSM data variables is cost-prohibitive. Prioritization of the variables based on their impact on crash predictions would, therefore, help to identify influential variables for which data could be collected and maintained for continued updates. This study aims to determine the impact of each independent variable identified in the HSM on crash predictions. A relatively recent data mining approach called boosted regression trees (BRT) is used to investigate the association between the variables and crash predictions. The BRT method can effectively handle different types of predictor variables, identify very complex and non-linear association among variables, and compute variable importance. Five years of crash data from 2008 to 2012 on two urban and suburban facility types, two-lane undivided arterials and four-lane divided arterials, were analyzed for estimating the influence of variables on crash predictions. Variables were found to exhibit non-linear and sometimes complex relationship to predicted crash counts. In addition, only a few variables were found to explain most of the variation in the crash data. PMID:25823903

  1. Variable selection and estimation for longitudinal survey data

    KAUST Repository

    Wang, Li

    2014-09-01

    There is wide interest in studying longitudinal surveys where sample subjects are observed successively over time. Longitudinal surveys have been used in many areas today, for example, in the health and social sciences, to explore relationships or to identify significant variables in regression settings. This paper develops a general strategy for the model selection problem in longitudinal sample surveys. A survey weighted penalized estimating equation approach is proposed to select significant variables and estimate the coefficients simultaneously. The proposed estimators are design consistent and perform as well as the oracle procedure when the correct submodel was known. The estimating function bootstrap is applied to obtain the standard errors of the estimated parameters with good accuracy. A fast and efficient variable selection algorithm is developed to identify significant variables for complex longitudinal survey data. Simulated examples are illustrated to show the usefulness of the proposed methodology under various model settings and sampling designs. © 2014 Elsevier Inc.

  2. Identifying the northernmost summer monsoon location in East Asia

    Institute of Scientific and Technical Information of China (English)

    Hu Haoran; Qian Weihong

    2007-01-01

    An integrated index which can be used to indicate the advance of subtropical summer monsoon in East Asia has been proposed in this paper. The index was combined by three variables including precipitation, wind and pseudo-equivalent potential temperature. The northernmost summer monsoon location (NSML) was identified by using this index annually. It was found that the NSML experienced an interdecadal shift in the period 1977-1979 based on the annual index analysis from 1961 to 2001. A comparison of the NSML with other four summer monsoon indices has also been made. The result showed that the NSML could well represent the interannual and interdecadal variability of summer monsoon precipitation in North China (beyond 35°N), while other four indices could well indicate the precipitation anomalies of East Asian summer monsoon along the Yangtze River valley (around 30°N).

  3. Two methods for studying the X-ray variability

    Science.gov (United States)

    Yan, Shu-Ping; Ji, Li; Méndez, Mariano; Wang, Na; Liu, Siming; Li, Xiang-Dong

    2016-04-01

    The X-ray aperiodic variability and quasi-periodic oscillation (QPO) are the important tools to study the structure of the accretion flow of X-ray binaries. However, the origin of the complex X-ray variability from X-ray binaries remains yet unsolved. We proposed two methods for studying the X-ray variability. One is amplitude-ratio spectrum analysis method. The other is mapping analysis method. Based on the consideration that the aperiodic variability originates from all spectral components whereas the QPO originates from one spectral component, we divided the root-mean-square (rms) amplitude spectrum of the power density spectrum (PDS) broadband noise component by the amplitude spectrum of an accompanying QPO, and first identified a high-frequency (> 10 Hz) aperiodic variability from the accretion disk (Yan et al. 2013). We now present the evolution of the amplitude-ratio spectrum with the cycle phase of the heartbeat state of the microquasar GRS 1915+105. We produced the energy-frequency-power map to investigate the origin of the X-ray variability, and show that most aperiodic X-ray variability is produced in the corona, and the low-frequency aperiodic variability from the corona is significant in the hard phase of the cycle phase of the heartbeat state of GRS 1915+105 while the low-frequency aperiodic variability from the disk and the corona are both significant in the soft phase.

  4. Perceptual mapping of mulitiple variable batteries by plotting supplementary variables in correspondence analysis of rating data

    OpenAIRE

    Torres, Antoni; Velden, Michel

    2005-01-01

    textabstractIn this paper we consider the use of correspondence analysis (CA) of rating data. CA of rating data allows a joint representation of the rated items (e.g. attributes or products) and individuals. However, as the number of individuals increases, the interpretation of the CA map becomes difficult. To overcome this problem, we propose a method that allows the depiction of additional variables, for example, background characteristics that may be of interest in identifying consumer seg...

  5. VARIABILITY IN GROWTH, PIG WEIGHTS AND HOG MARKETING DECISIONS

    OpenAIRE

    Huang, Haixiao; Miller, Gay Y.

    2004-01-01

    Variability in pig growth is an intrinsic characteristic of swine production. The optimal marketing strategies are identified to minimize the negative economic impact of variability for a typical all-in-all-out swine finishing facility using a recent pricing matrix and data featuring swine production in the Midwestern region. Our results show that compared with marketing all pigs from a 1,020 head barn on the same day, marketing pigs in six truckloads on different dates as groups of pigs grow...

  6. Temporal variability in soil hydraulic properties under drip irrigation

    OpenAIRE

    Mubarak, I.; Mailhol, J.C.; R. Angulo-Jaramillo; Ruelle, P.; Boivin, P.; Khaledian, M. R.

    2009-01-01

    Predicting soil hydraulic properties and understanding their temporal variability during the irrigated cropping season are required to mitigate agro-environmental risks. This paper reports field measurements of soil hydraulic properties under two drip irrigation treatments, full (FT) and limited (LT). The objective was to identify the temporal variability of the hydraulic properties of field soil under high-frequency water application during a maize cropping season. Soil hydraulics were chara...

  7. APASS discovery and characterization of 180 variable stars in Aquarius

    Science.gov (United States)

    Munari, Ulisse; Henden, Arne; Frigo, Andrea; Dallaporta, Sergio

    2014-12-01

    During a search for RR Lyr variable stars candidate members of the Aquarius stream, which led to the discovery of 71 such objects, we also discovered an additional 180 variables which are presented in this paper. Of them, 141 were previously reported as variables and 39 are brand new. For all 180 objects, we provide: our epoch photometry, accurate positions, mean magnitude and amplitude of variation in Landolt B,V and Sloan g, r, i bands, cross-identification with WISE, 2MASS and GALEX surveys, accurate BVR_C I_C gri photometric sequences and finding charts identifying the variable and the stars of the photometric sequence provided to support follow-up observations. We carried out a Fourier search on all 39 new variables and found periods for 11 of them.

  8. Variable stars in the open cluster NGC 2141

    CERN Document Server

    Luo, Yanping

    2014-01-01

    We report the results of a search for variable stars in the open cluster NGC 2141. Ten variable stars are detected, among which nine are new variable stars and they are classified as three short period W UMa type eclipsing binaries, two EA type eclipsing binaries, one EB type eclipsing binary, one very short period RS CVn type eclipsing binary, one d type RR Lyrae variable star, and one unknown type variable star. The membership and physical properties are discussed, based on their light curves, positions in the CMDs, spatial locations and periods. A known EB type eclipsing binary is also identified as a blue struggler candidate of the cluster. Furthermore, we find that all eclipsing contact binaries have prominently asymmetric eclipses and O Connell effect (O Connell 1951) which increases with the decrease of the orbital periods. This suggests that the O Connell effect is probably related to the evolution of the orbital period in short period eclipsing binary systems.

  9. WEAK UNCORRELATEDNESS OF RANDOM VARIABLES

    Institute of Scientific and Technical Information of China (English)

    Sofiya Ostrovska

    2006-01-01

    New measures of independence for n random variables, based on their moments, are studied. A scale of degrees of independence for random variables which starts with uncorrelatedness (for n = 2) and finishes at independence is constructed. The scale provides a countable linearly ordered set of measures of independence.

  10. Variability in human body size

    Science.gov (United States)

    Annis, J. F.

    1978-01-01

    The range of variability found among homogeneous groups is described and illustrated. Those trends that show significantly marked differences between sexes and among a number of racial/ethnic groups are also presented. Causes of human-body size variability discussed include genetic endowment, aging, nutrition, protective garments, and occupation. The information is presented to aid design engineers of space flight hardware and equipment.

  11. Students' Misconceptions about Random Variables

    Science.gov (United States)

    Kachapova, Farida; Kachapov, Ilias

    2012-01-01

    This article describes some misconceptions about random variables and related counter-examples, and makes suggestions about teaching initial topics on random variables in general form instead of doing it separately for discrete and continuous cases. The focus is on post-calculus probability courses. (Contains 2 figures.)

  12. Harvested populations are more variable only in more variable environments.

    Science.gov (United States)

    Cameron, Tom C; O'Sullivan, Daniel; Reynolds, Alan; Hicks, Joseph P; Piertney, Stuart B; Benton, Tim G

    2016-06-01

    The interaction between environmental variation and population dynamics is of major importance, particularly for managed and economically important species, and especially given contemporary changes in climate variability. Recent analyses of exploited animal populations contested whether exploitation or environmental variation has the greatest influence on the stability of population dynamics, with consequences for variation in yield and extinction risk. Theoretical studies however have shown that harvesting can increase or decrease population variability depending on environmental variation, and requested controlled empirical studies to test predictions. Here, we use an invertebrate model species in experimental microcosms to explore the interaction between selective harvesting and environmental variation in food availability in affecting the variability of stage-structured animal populations over 20 generations. In a constant food environment, harvesting adults had negligible impact on population variability or population size, but in the variable food environments, harvesting adults increased population variability and reduced its size. The impact of harvesting on population variability differed between proportional and threshold harvesting, between randomly and periodically varying environments, and at different points of the time series. Our study suggests that predicting the responses to selective harvesting is sensitive to the demographic structures and processes that emerge in environments with different patterns of environmental variation. PMID:27516873

  13. Interobserver variability in the evaluation of mismatch repair protein immunostaining

    DEFF Research Database (Denmark)

    Klarskov, Louise Laurberg; Ladelund, Steen; Holck, Susanne;

    2010-01-01

    reliability are lacking. We therefore evaluated interobserver variability among 6 pathologists, 3 experienced gastrointestinal pathologists and 3 residents. In total, 225 immunohistochemically stained colorectal cancers were evaluated as having normal, weak, loss of, or nonevaluable mismatch repair protein...... variability was considerable, though experienced pathologists and residents reached the same level of consensus. Because results from immunohistochemical mismatch repair protein stainings are used for decisions on mutation analysis and as an aid in the interpretation of gene variants of unknown significance...... in hereditary nonpolyposis colorectal cancer, the interobserver variability identified highlights the need for quality assessment programs, including guidelines for classification of different expression patterns....

  14. Psychosocial counselling of identifiable sperm donors

    NARCIS (Netherlands)

    M. Visser; M.H. Mochtar; A.A. de Melker; F. van der Veen; S. Repping; T. Gerrits

    2016-01-01

    STUDY QUESTION: What do identifiable sperm donors feel about psychosocial counselling? SUMMARY ANSWER: Identifiable sperm donors found it important that psychosocial counselling focused on emotional consequences and on rules and regulations and they expected to have access to psychosocial counsellin

  15. NIH Researchers Identify OCD Risk Gene

    Science.gov (United States)

    ... News From NIH NIH Researchers Identify OCD Risk Gene Past Issues / Summer 2006 Table of Contents For ... and Alcoholism (NIAAA) have identified a previously unknown gene variant that doubles an individual's risk for obsessive- ...

  16. The SEDs, Host Galaxies and Environments of Variability Selected AGN in GOODS-S

    OpenAIRE

    Villforth, Carolin; Sarajedini, Vicki; Koekemoer, Anton

    2012-01-01

    Variability selection has been proposed as a powerful tool for identifying both low-luminosity AGN and those with unusual SEDs. However, a systematic study of sources selected in such a way has been lacking. In this paper, we present the multi-wavelength properties of the variability selected AGN in GOODS South. We demonstrate that variability selection indeed reliably identifies AGN, predominantly of low luminosity. We find contamination from stars as well as a very small sample of sources t...

  17. Aggressive and unsportsmanlike behaviours in competitive sports: an analysis of related personal and environmental variables

    OpenAIRE

    Antonia Pelegrín; Sidónio Serpa; Antonio Rosado

    2013-01-01

    This paper gives an analysis of personal and environmental variables related to aggressive and unsportsmanlike behaviours in a sample of Spanish sports competitors. We aim to: 1) ascertain how personality and expression variables relate to trait anger control and unsportsmanlike behaviors, in relation to men and women, age groups and type of sport, 2) identify and analyze the most maladjusted and the most adjusted profiles in a sample of sportsmen and women; 3) identify personality variables ...

  18. INVocD: Identifier Name Vocabulary Dataset

    OpenAIRE

    Butler, Simon; Wermelinger, Michel; Yu, Yijun; Sharp, Helen

    2013-01-01

    NVocD is a dataset of the identifier name declarations and vocabulary found in 60 FLOSS Java projects where the source code structure is recorded and the identifier name vocabulary is made directly available, offering advantages for identifier name research over conventional source code models. The dataset has been used to support a range of research projects from identifier name analysis to concept location, and provides many opportunities to researchers.

  19. GW Librae: A unique laboratory for pulsations in an accreting white dwarf

    CERN Document Server

    Toloza, O; Hermes, J J; Townsley, D M; Schreiber, M R; Szkody, P; Pala, A; Beuermann, K; Bildsten, L; Breedt, E; Cook, M; Godon, P; Henden, A A; Hubeny, I; Knigge, C; Long, K S; Marsh, T R; de Martino, D; Mukadam, A S; Myers, G; Nelson, P; Oksanen, A; Patterson, J; Sion, E M; Zorotovic, M

    2016-01-01

    Non-radial pulsations have been identified in a number of accreting white dwarfs in cataclysmic variables. These stars offer insight into the excitation of pulsation modes in atmospheres with mixed compositions of hydrogen, helium, and metals, and the response of these modes to changes in the white dwarf temperature. Among all pulsating cataclysmic variable white dwarfs, GW Librae stands out by having a well-established observational record of three independent pulsation modes that disappeared when the white dwarf temperature rose dramatically following its 2007 accretion outburst. Our analysis of HST ultraviolet spectroscopy taken in 2002, 2010 and 2011, showed that pulsations produce variations in the white dwarf effective temperature as predicted by theory. Additionally in May~2013, we obtained new HST/COS ultraviolet observations that displayed unexpected behaviour: besides showing variability at ~275s, which is close to the post-outburst pulsations detected with HST in 2010 and 2011, the white dwarf exhi...

  20. Ability of Slovakian Pupils to Identify Birds

    Science.gov (United States)

    Prokop, Pavol; Rodak, Rastislav

    2009-01-01

    A pupil's ability to identify common organisms is necessary for acquiring further knowledge of biology. We investigated how pupils were able to identify 25 bird species following their song, growth habits, or both features presented simultaneously. Just about 19% of birds were successfully identified by song, about 39% by growth habit, and 45% of…

  1. VizieR Online Data Catalog: Mira variables om ROTSE-IIId (Yesilyaprak+, 2012)

    Science.gov (United States)

    Yesilyaprak, C.; Yerli, S. K.; Gucsav, B. B.; Aksaker, N.; Dikicioglu, E.; Helvaci, M.; Coker, D.; Aydin, M. E.; Dincel, B.; Uzun, N.

    2012-03-01

    We have studied the long-term variations of Mira type variables observed with Robotic Optical Transient Search Experiment telescope (ROTSE-IIId) between 2004 and 2009 located at TUBITAK National Observatory (TUG) in Antalya, Turkey. The actual pulsation periods, variability amplitudes, epochs of maximums and light curves of selected 70 Mira type variables already defined in the SIMBAD database were investigated. In these variables, 17 periods are identified for the first time (1 data file).

  2. The significance of demographic factors on key-indicator variables of consumer credit decisions

    OpenAIRE

    Simangaliso Biza-Khupe

    2011-01-01

    The literature on consumer financial behaviour identifies a myriad of factors that influence individuals’ financial decisions and choices. Among the key-indicator variables of consumer credit behaviour are Credit Search, Financial Risk and Credit Terms Considered. These indicator variables have been well researched and measured in the literature. Personal attributes, and in particular demographic variables, have largely been regarded as moderating variables in the literature. Although demogra...

  3. Predicting Securitized Real Estate Returns: Financial and Real Estate Factors vs. Economic Variables

    OpenAIRE

    Serrano, Camilo; Hoesli, Martin E.

    2009-01-01

    Securitized real estate returns have traditionally been forecasted using economic variables. However, no consensus exists regarding the variables to use. Financial and real estate factors have recently emerged as an alternative set of variables useful in forecasting securitized real estate returns. This paper examines whether the predictive ability of the two sets of variables differs. We use fractional cointegration analysis to identify whether long-run nonlinear relations exist between secu...

  4. A general hidden variable model for the two-qubits system

    OpenAIRE

    Ghirardi, GianCarlo; Romano, Raffaele

    2012-01-01

    We generalize Bell's hidden variable model describing the singlet state of a two-qubits system by extending it to arbitrary states and observables. As in the original work, we assume a uniform, state-independent probability distribution for the hidden variables which are identified with the unit vectors of a 3-dimensional real space. By slightly modifying our model, we provide also a minimal hidden variable description of the two-qubits system, relying on a single hidden variable. We discuss ...

  5. IMPACT OF NON PERFORMING ASSETS ON STRATEGIC BANKING VARIABLES IN SELECTED PUBLIC SECTOR BANKS IN INDIA

    OpenAIRE

    GOUR BANDYOPADHYAY

    2013-01-01

    The study uses correlation and regression analysis to examine the impact of Non Performing Assets (NPA) on selected banking variables in two Public Sector Banks (PSBs) in India. Initially to examine degree of association between the strategic banking variables identified, simple correlation co-efficients have been computed and their significance examined. For the purpose of examining impact of NPA on the profitability and other strategic banking variables including time variable, simple li...

  6. Variables influencing victim selection in genocide.

    Science.gov (United States)

    Komar, Debra A

    2008-01-01

    While victims of racially motivated violence may be identified through observation of morphological features, those targeted because of their ethnic, religious, or national identity are not easily recognized. This study examines how perpetrators of genocide recognize their victims. Court documents, including indictments, witness statements, and testimony from the International Criminal Tribunals for Rwanda and the former Yugoslavia (FY) detail the interactions between victim and assailant. A total of 6012 decedents were included in the study; only 20.8% had been positively identified. Variables influencing victim selection in Rwanda included location, segregation, incitement, and prior relationship, while significant factors in FY were segregation, location, age/gender, and social data. Additional contributing factors in both countries included self-identification, victim behavior, linguistic or clothing evidence, and morphological features. Understanding the system of recognition used by perpetrators aids investigators tasked with establishing victim identity in such prosecutions. PMID:18005010

  7. IVOA Identifiers Version 2.0

    CERN Document Server

    Demleitner, Markus; Linde, Tony; Williams, Roy; Noddle, Keith

    2016-01-01

    An IVOA Identifier is a globally unique name for a resource within the Virtual Observatory. This name can be used to retrieve a unique description of the resource from an IVOA-compliant registry or to identify an entity like a dataset or a protocol without dereferencing the identifier. This document describes the syntax for IVOA Identifiers as well as how they are created. The syntax has been defined to encourage global-uniqueness naturally and to maximize the freedom of resource providers to control the character content of an identifier.

  8. Chatter Prediction for Variable Pitch and Variable Helix Milling

    OpenAIRE

    Yong Wang; Taiyong Wang; Zhiqiang Yu; Yue Zhang; Yulong Wang; Hengli Liu

    2015-01-01

    Regenerative chatter is a self-excited vibration that can occur during milling, which shortens the lifetime of the tool and results in unacceptable surface quality. In this paper, an improved semidiscretization method for modeling and simulation with variable pitch and variable helix milling is proposed. Because the delay between each flute varies along the axial depth of the tool in milling, the cutting tool is discrete into some axial layers to simplify calculation. A comparison of the pred...

  9. Variable copy number DNA sequences in rice.

    Science.gov (United States)

    Kikuchi, S; Takaiwa, F; Oono, K

    1987-12-01

    We have cloned two types of variable copy number DNA sequences from the rice embryo genome. One of these sequences, which was cloned in pRB301, was amplified about 50-fold during callus formation and diminished in copy number to the embryonic level during regeneration. The other clone, named pRB401, showed the reciprocal pattern. The copy numbers of both sequences were changed even in the early developmental stage and eliminated from nuclear DNA along with growth of the plant. Sequencing analysis of the pRB301 insert revealed some open reading frames and direct repeat structures, but corresponding sequences were not identified in the EMBL and LASL DNA databases. Sequencing of the nuclear genomic fragment cloned in pRB401 revealed the presence of the 3'rps12-rps7 region of rice chloroplast DNA. Our observations suggest that during callus formation (dedifferentiation), regeneration and the growth process the copy numbers of some DNA sequences are variable and that nuclear integrated chloroplast DNA acts as a variable copy number sequence in the rice genome. Based on data showing a common sequence in mitochondria and chloroplast DNA of maize (Stern and Lonsdale 1982) and that the rps12 gene of tobacco chloroplast DNA is a divided gene (Torazawa et al. 1986), it is suggested that the sequence on the inverted repeat structure of chloroplast DNA may have the character of a movable genetic element. PMID:3481021

  10. Symmetrization of binary random variables

    OpenAIRE

    Kagan, Abram; Mallows, Colin L.; Shepp, Larry A.; Vanderbei, Robert J.; Vardi, Yehuda

    1999-01-01

    A random variable [math] is called an independent symmetrizer of a given random variable [math] if (a) it is independent of [math] and (b) the distribution of [math] is symmetric about [math] . In cases where the distribution of [math] is symmetric about its mean, it is easy to see that the constant random variable [math] is a minimum-variance independent symmetrizer. Taking [math] to have the same distribution as [math] clearly produces a symmetric sum, but it may not be of minimum variance....

  11. Clinical Application of Heart Rate Variability after Acute Myocardial Infarction

    Directory of Open Access Journals (Sweden)

    HeikkiVeliHuikuri

    2012-02-01

    Heart rate (HR variability has been extensively studied in patients surviving an acute myocardial infarction (AMI. The majority of studies have shown that patients with reduced or abnormal HR variability/turbulence have an increased risk of mortality within few years after an AMI. Various measures of HR dynamics, such as time-domain, spectral, and non-linear measures of HR variability, as well as HR turbulence, have been used in risk stratification of post-AMI patients. The prognostic power of various measures, except of those reflecting rapid R-R interval oscillations, has been almost identical, albeit some non-linear HR variability measures, such as short-term fractal scaling exponent, and HR turbulence, have provided somewhat better prognostic information than the others. Abnormal HR variability predicts both sudden and non-sudden cardiac death after AMI. Because of remodeling of the arrhythmia substrate after AMI, early measurement of HR variability to identify those at high risk should likely be repeated later in order to assess the risk of fatal arrhythmia events. Future randomized trials using HR variability/turbulence as one of the pre-defined inclusion criteria will show whether routine measurement of HR variability/turbulence will become a routine clinical tool for risk stratification of post-AMI patients.

  12. Nonlinear stratospheric variability: multifractal detrended fluctuation analysis and singularity spectra

    CERN Document Server

    Badin, Gualtiero

    2015-01-01

    Northern Hemisphere (NH) and Southern Hemisphere (SH) stratospheric variability is studied using Multifractal Detrended Fluctuation Analysis. The analysis is performed for three different variables extracted from four re-analysis products. Three realizations of an idealized numerical model, identifying the role of topographic forcing and seasonal variability, are also considered in order to analyze the ability of the model to reproduce the statistics as observed in the re-analyses. The NH variability is shown to possess a multifractal nature for time scales shorter than about one year. For these time scales, the variability scales in time with a power law close to 3/2, corresponding to a red spectrum. For longer time scales, the NH variability becomes monofractal and scales in time with a power law close to 1/2, corresponding to white noise. SH variability shows a similar transition from multifractal to monofractal variability at annual scales, but with a power law close to 1 for time scales shorter than abou...

  13. Solar Variability and Planetary Climates

    CERN Document Server

    Calisesi, Y; Gray, L; Langen, J; Lockwood, M

    2007-01-01

    Variations in solar activity, as revealed by variations in the number of sunspots, have been observed since ancient times. To what extent changes in the solar output may affect planetary climates, though, remains today more than ever a subject of controversy. In 2000, the SSSI volume on Solar Variability and Climate reviewed the to-date understanding of the physics of solar variability and of the associated climate response. The present volume on Solar Variability and Planetary Climates provides an overview of recent advances in this field, with particular focus at the Earth's middle and lower atmosphere. The book structure mirrors that of the ISSI workshop held in Bern in June 2005, the collection of invited workshop contributions and of complementary introductory papers synthesizing the current understanding in key research areas such as middle atmospheric processes, stratosphere-troposphere dynamical coupling, tropospheric aerosols chemistry, solar storm influences, solar variability physics, and terrestri...

  14. Mirador - Climate Variability and Change

    Data.gov (United States)

    National Aeronautics and Space Administration — Earth Science data access made simple. NASA's role in climate variability study is centered around providing the global scale observational data sets on oceans and...

  15. Manipulating continuous variable photonic entanglement

    International Nuclear Information System (INIS)

    I will review our work on photonic entanglement in the continuous variable regime including both Gaussian and non-Gaussian states. The feasibility and efficiency of various entanglement purification protocols are discussed this context. (author)

  16. Convergence in variable Lebesgue spaces

    OpenAIRE

    Cruz-Uribe, David; SFO; Fiorenza, Alberto

    2010-01-01

    We consider the relationship in the variable Lebesgue space Lp(•)(Ω) between convergence in norm, convergence in modular, and convergence in measure, for both bounded and unbounded exponent functions.

  17. Convergence in variable Lebesque spaces

    OpenAIRE

    Cruz-Uribe, David; Fiorenza, Alberto

    2010-01-01

    We consider the relationship in the variable Lebesgue space $L^{p(\\cdot)}(\\Omega)$ between convergence in norm, convergence in modular, and convergence in measure, for both bounded and unbounded exponent functions.

  18. Climate Impact of Solar Variability

    Science.gov (United States)

    Schatten, Kenneth H. (Editor); Arking, Albert (Editor)

    1990-01-01

    The conference on The Climate Impact of Solar Variability, was held at Goddard Space Flight Center from April 24 to 27, 1990. In recent years they developed a renewed interest in the potential effects of increasing greenhouse gases on climate. Carbon dioxide, methane, nitrous oxide, and the chlorofluorocarbons have been increasing at rates that could significantly change climate. There is considerable uncertainty over the magnitude of this anthropogenic change. The climate system is very complex, with feedback processes that are not fully understood. Moreover, there are two sources of natural climate variability (volcanic aerosols and solar variability) added to the anthropogenic changes which may confuse our interpretation of the observed temperature record. Thus, if we could understand the climatic impact of the natural variability, it would aid our interpretation and understanding of man-made climate changes.

  19. Variable Heat Rejection (VHR) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Develop advanced technologies to enable a variable heat rejection Thermal Control System (TCS) capable of operating through a wide range of thermal environments...

  20. Simulation of truncated normal variables

    OpenAIRE

    Robert, Christian P.

    2009-01-01

    We provide in this paper simulation algorithms for one-sided and two-sided truncated normal distributions. These algorithms are then used to simulate multivariate normal variables with restricted parameter space for any covariance structure.