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Sample records for cataclysmic variables identified

  1. Two Rare Magnetic Cataclysmic Variables with Extreme Cyclotron Features Identified in the Sloan Digital Sky Survey

    CERN Document Server

    Szkody, P; Schmidt, G; Hall, P B; Margon, B; Miceli, A; Subba-Rao, M; Frith, W J; Harris, H; Szkody, Paula; Anderson, Scott F.; Schmidt, Gary; Hall, Patrick B.; Margon, Bruce; Miceli, Antonino; Rao, Mark Subba; Frith, James; Harris, Hugh

    2003-01-01

    Two newly identified magnetic cataclysmic variables discovered in the Sloan Digital Sky Survey (SDSS), SDSSJ155331.12+551614.5 and SDSSJ132411.57+032050.5, have spectra showing highly prominent, narrow, strongly polarized cyclotron humps with amplitudes that vary on orbital periods of 4.39 and 2.6 hrs, respectively. In the former, the spacing of the humps indicates the 3rd and 4th harmonics in a magnetic field of ~60 MG. The narrowness of the cyclotron features and the lack of strong emission lines imply very low temperature plasmas and very low accretion rates, so that the accreting area is heated by particle collisions rather than accretion shocks. The detection of rare systems like these exemplifies the ability of the SDSS to find the lowest accretion rate close binaries.

  2. 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.

  3. 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

  4. ULTRACAM photometry of eclipsing cataclysmic variable stars

    CERN Document Server

    Feline, William James

    2008-01-01

    The accurate determination of the masses of cataclysmic variable stars is critical to our understanding of their origin, evolution and behaviour. Observations of cataclysmic variables also afford an excellent opportunity to constrain theoretical physical models of the accretion discs housed in these systems. In particular, the brightness distributions of the accretion discs of eclipsing systems can be mapped at a spatial resolution unachievable in any other astrophysical situation. This thesis addresses both of these important topics via the analysis of the light curves of six eclipsing dwarf novae, obtained using ULTRACAM, a novel high-speed imaging photometer.

  5. 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.

  6. Cataclysmic Variables from SDSS III. The Third Year

    CERN Document Server

    Szkody, P; Fraser, O J; Silvestri, N M; Bochanski, J J; Wolfe, M A; Agüeros, M A; Warner, B; Woudt, P; Tramposch, J; Homer, L; Schmidt, G; Knapp, G R; Anderson, S F; Covey, K; Harris, H; Hawley, S; Schneider, D P; Voges, W; Brinkmann, J; Szkody, Paula; Henden, Arne; Fraser, Oliver; Silvestri, Nicole; Bochanski, John; Wolfe, Michael A.; Ag\\"ueros, Marcel; Warner, Brian; Woudt, Patrick; Tramposch, Jonica; Homer, Lee; Schmidt, Gary; Knapp, Gillian R.; Anderson, Scott F.; Covey, Kevin; Harris, Hugh; Hawley, Suzanne; Schneider, Donald P.; Voges, Wolfgang

    2004-01-01

    This paper continues the series that identifies new cataclysmic variables found in the Sloan Digital Sky Survey. We present 36 cataclysmic variables and one possible symbiotic star from Sloan spectra obtained during 2002, of which 34 are new discoveries, 2 are known dwarf novae (BC UMa, KS UMa) and one is a known CV identified from the 2dF survey. The positions, colors and spectra of all 37 systems are presented, along with follow-up spectroscopic/photometric observations of 10 systems. As in the past 2 years of data, the new SDSS systems show a large variety of characteristics based on their inclination and magnetic fields, including 3 eclipsing systems, 4 with prominent He II emission, and 15 systems showing features of the underlying stars.

  7. 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...

  8. 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...

  9. 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...

  10. Orbital period changes in cataclysmic variables?

    Science.gov (United States)

    Beuermann, K.; Pakull, M. W.

    1984-07-01

    The authors report observations of times of minima for four eclipsing cataclysmic variables: U Gem, EM Cyg, T Aur, and V2051 Oph. For all systems, no secular changes of the orbital period P were detected. The authors derived 3σ lower limits to the time constant τ = P/Pfor such changes of 1.4×108 years, 7.5×106 yr, 4.4×106 yr and 7.6×105 yr for U Gem, EM Cyg, T Aur, and V2051 Oph, respectively. The corresponding upper limits on the mean mass-transfer rate Mderived on the assumption of mass and angular momentum being conserved are still significantly above independent estimates of M, using accretion disk models. For U Gem the existence of quasiperiodic O-C variations with a time scale of ≡18 yr is confirmed.

  11. Searching for nova shells around cataclysmic variables

    CERN Document Server

    Sahman, D I; Knigge, C; Marsh, T R

    2015-01-01

    We present the results of a search for nova shells around 101 cataclysmic variables (CVs), using Halpha images taken with the 4.2-m William Herschel Telescope (WHT) and the 2.5-m Isaac Newton Telescope Photometric Halpha Survey of the Northern Galactic Plane (IPHAS). Both telescopes are located on La Palma. We concentrated our WHT search on nova-like variables, whilst our IPHAS search covered all CVs in the IPHAS footprint. We found one shell out of the 24 nova-like variables we examined. The newly discovered shell is around V1315 Aql and has a radius of approx.2.5 arcmin, indicative of a nova eruption approximately 120 years ago. This result is consistent with the idea that the high mass-transfer rate exhibited by nova-like variables is due to enhanced irradiation of the secondary by the hot white dwarf following a recent nova eruption. The implications of our observations for the lifetime of the nova-like variable phase are discussed. We also examined 4 asynchronous polars, but found no new shells around an...

  12. 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...

  13. 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...

  14. 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...

  15. Searching for nova shells around cataclysmic variables

    Science.gov (United States)

    Sahman, D. I.; Dhillon, V. S.; Knigge, C.; Marsh, T. R.

    2015-08-01

    We present the results of a search for nova shells around 101 cataclysmic variables (CVs), using H α images taken with the 4.2-m William Herschel Telescope (WHT) and the 2.5-m Isaac Newton Telescope Photometric H α Survey of the Northern Galactic Plane (IPHAS). Both telescopes are located on La Palma. We concentrated our WHT search on nova-like variables, whilst our IPHAS search covered all CVs in the IPHAS footprint. We found one shell out of the 24 nova-like variables we examined. The newly discovered shell is around V1315 Aql and has a radius of ˜2.5 arcmin, indicative of a nova eruption approximately 120 yr ago. This result is consistent with the idea that the high mass-transfer rate exhibited by nova-like variables is due to enhanced irradiation of the secondary by the hot white dwarf following a recent nova eruption. The implications of our observations for the lifetime of the nova-like variable phase are discussed. We also examined four asynchronous polars, but found no new shells around any of them, so we are unable to confirm that a recent nova eruption is the cause of the asynchronicity in the white dwarf spin. We find tentative evidence of a faint shell around the dwarf nova V1363 Cyg. In addition, we find evidence for a light echo around the nova V2275 Cyg, which erupted in 2001, indicative of an earlier nova eruption ˜300 yr ago, making V2275 Cyg a possible recurrent nova.

  16. The Magnetospheric Boundary in Cataclysmic Variables

    CERN Document Server

    Hellier, Coel

    2013-01-01

    The magnetic cataclysmic variables (MCVs) present a wealth of observational diagnostics for studying accretion flows interacting with a magnetosphere. Spin-period pulsations from the rotation of the white dwarf are seen in optical light, in the UV and X-ray bands, and in polarimetry, and modelling these can constrain the size and location of the accretion footprints on the white-dwarf surface. Tracing these back along field lines can tell us about the transition region between the stream or disk and the magnetosphere. Further, optical emission lines give us velocity information, while analysis of eclipses gives spatial information. I discuss MCVs (particularly FO Aqr, V405 Aur, XY Ari and EX Hya, but also mentioning PQ Gem, GK Per, V2400 Oph, HT Cam, TX Col, AO Psc, AE Aqr, WZ Sge, V1223 Sgr and DQ Her), reviewing what observations tell us about the disk-magnetosphere boundary. The spin-period variations are caused by a mixture of geometric effects and absorption by the accretion flow, and appear to show that...

  17. Cataclysmic Variables from SDSS II. The Second Year

    CERN Document Server

    Szkody, P; Silvestri, N M; Henden, A A; Anderson, S F; Frith, W J; Lawton, B; Owens, E; Raymond, S; Schmidt, G; Wolfe, M; Bochanski, J J; Covey, K; Harris, H; Hawley, S; Knapp, G R; Margon, B; Voges, W; Walkowicz, L; Brinkmann, J; Lamb, D Q; Anderson, Scott F.; Bochanski, John; Covey, Kevin; Fraser, Oliver; Frith, James; Harris, Hugh; Hawley, Suzanne; Henden, Arne; Knapp, Gillian R.; Lawton, Brandon; Margon, Bruce; Owens, Ethan; Raymond, Sean; Schmidt, Gary; Silvestri, Nicole; Szkody, Paula; Voges, Wolfgang; Walkowicz, Lucianne; Wolfe, Michael

    2003-01-01

    The first full year of operation following the commissioning year of the Sloan Digital Sky Survey has revealed a wide variety of newly discovered cataclysmic variables. We show the SDSS spectra of forty-two cataclysmic variables observed in 2002, of which thirty-five are new classifications, four are known dwarf novae (CT Hya, RZ Leo, T Leo and BZ UMa), one is a known CV identified from a previous quasar survey (Aqr1) and two are known ROSAT or FIRST discovered CVs (RX J09445+0357, FIRST J102347.6+003841). The SDSS positions, colors and spectra of all forty-two systems are presented. In addition, the results of follow-up studies of several of these objects identify the orbital periods, velocity curves and polarization that provide the system geometry and accretion properties. While most of the SDSS discovered systems are faint (>18th mag) with low accretion rates (as implied from their spectral characteristics), there are also a few bright objects which may have escaped previous surveys due to changes in the ...

  18. 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

  19. 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.

  20. 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)

  1. Spectroscopy of Nine Cataclysmic Variable Stars

    CERN Document Server

    Sheets, H A; Peters, C J; Kapusta, A B; Taylor, C J

    2007-01-01

    We present optical spectroscopy of nine cataclysmic binary stars, mostly dwarf novae, obtained primarily to determine orbital periods Porb. The stars and their periods are LX And, 0.1509743(5) d; CZ Aql, 0.2005(6) d; LU Cam, 0.1499686(4) d; GZ Cnc, 0.0881(4) d; V632 Cyg, 0.06377(8) d; V1006 Cyg, 0.09903(9) d; BF Eri, 0.2708804(4) d; BI Ori, 0.1915(5) d; and FO Per, for which Porb is either 0.1467(4) or 0.1719(5) d. Several of the stars proved to be especially interesting. In BF Eri, we detect the absorption spectrum of a secondary star of spectral type K3 +- 1 subclass, which leads to a distance estimate of approximately 1 kpc. However, BF Eri has a large proper motion (100 mas/yr), and we have a preliminary parallax measurement that confirms the large proper motion and yields only an upper limit for the parallax. BF Eri's space velocity is evidently large, and it appears to belong to the halo population. In CZ Aql, the emission lines have strong wings that move with large velocity amplitude, suggesting a mag...

  2. 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.

  3. Sky surveys of interest for cataclysmic variables

    Science.gov (United States)

    Szkody, Paula

    2016-07-01

    Sky Surveys provide much useful information for finding and understanding catacylsmic variables (CVs). Depending on the length of time the survey runs and the cadence used, the surveys can easily locate novae and dwarf novae based on the amplitude and shape of the light curves. For systems with high inclination or prominent hot spots and periods of hours, some orbital information can be derived from eclipses that are caught or repetitive modulations in the folded light curves. However, in most cases, detailed knowledge of the type of system and its orbital period must come from extended observations at other wavelengths, as most surveys take place in one filter or unfiltered. Currently, we are in the midst of an explosion of recently past, continuing and future plans for sky surveys. The Sloan Digital Sky Survey found about 300 CVs in its Legacy Mode, with small numbers continuing to be added through the extended phases. The CVs were primarily identified through spectroscopic coverage of selected objects from the photometric survey and subsequently found a wide variety of systems (polars, intermediate polars, novalikes, dwarf novae, objects with pulsating white dwarfs) due to spectroscopic differences among these types. The Palomar Transit Factory (PTF), Intermediate PTF and future Zwicky Transient Facilty (ZTF) operate in the same mode of candidate discovery via outbursts followed by spectroscopy for confirmation. The Catalina Real-Time Transient Survey primarily adds dwarf novae that are found from outbursts in the long time span of observations. The Kepler K2 mission operates with a much higher cadence (48-1440 observations/day) but shorter total length (70-80 days) and thus finds CVs through orbital variability as well as those with short outburst intervals. Gaia will provide distances for most of the objects under study, thus locating them in the galaxy. The upcoming Large Synoptic Survey Telescope (LSST) will go much fainter and cover variability on a 10 yr

  4. 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...

  5. 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.

  6. 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 ...

  7. 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.

  8. On the White Dwarf Mass Problem of Cataclysmic Variables

    CERN Document Server

    Liu, Wei-Min

    2016-01-01

    Recent observations show that the white dwarfs (WDs) in cataclysmic Variables (CVs) have an average mass significantly higher than isolated WDs and WDs in post-common envelope binaries (PCEBs), which are thought to the progenitors of CVs. This suggests that either the WDs have grown in mass during the PCEB/CV evolution or the binaries with low-mass WDs are unable to evolve to be CVs. In this paper, we calculate the evolution of accreting WD binaries with updated hydrogen accumulation efficiency and angular momentum loss prescriptions. We show that thermal timescale mass transfer is not effective in changing the average WD mass distribution. The WD mass discrepancy is most likely related to unstable mass transfer in WD binaries in which an efficient mechanism of angular momentum loss is required.

  9. Cataclysmic variables in the SUPERBLINK proper motion survey

    Energy Technology Data Exchange (ETDEWEB)

    Skinner, Julie N.; Thorstensen, John R. [Department of Physics and Astronomy, 6127 Wilder Laboratory, Dartmouth College, Hanover, NH 03755-3528 (United States); Lépine, Sébastien, E-mail: jns@dartmouth.edu [Department of Physics and Astronomy, Georgia State University, 25 Park Place NE, Atlanta, GA 30303 (United States)

    2014-12-01

    We have discovered a new high proper motion cataclysmic variable (CV) in the SUPERBLINK proper motion survey, which is sensitive to stars with proper motions greater than 40 mas yr{sup −1}. This CV was selected for follow-up observations as part of a larger search for CVs selected based on proper motions and their near-UV−V and V−K{sub s} colors. We present spectroscopic observations from the 2.4 m Hiltner Telescope at MDM Observatory. The new CV's orbital period is near 96 minutes, its spectrum shows the double-peaked Balmer emission lines characteristic of quiescent dwarf novae, and its V magnitude is near 18.2. Additionally, we present a full list of known CVs in the SUPERBLINK catalog.

  10. Cataclysmic Variables in the SUPERBLINK Proper Motion Survey

    CERN Document Server

    Skinner, Julie N; Lépine, Sébastien

    2014-01-01

    We have discovered a new high proper motion cataclysmic variable (CV) in the SUPERBLINK proper motion survey, which is sensitive to stars with proper motions greater than 40 mas/yr. This CV was selected for follow-up observations as part of a larger search for CVs selected based on proper motions and their NUV-V and V-K$_{s}$ colors. We present spectroscopic observations from the 2.4m Hiltner Telescope at MDM Observatory. The new CV's orbital period is near 96 minutes, its spectrum shows the double-peaked Balmer emission lines characteristic of quiescent dwarf novae, and its V magnitude is near 18.2. Additionally, we present a full list of known CVs in the SUPERBLINK catalog.

  11. Characterization of New Hard X-ray Cataclysmic Variables

    Science.gov (United States)

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

    2012-01-01

    Aims. We aim at characterizing a sample of nine new hard X-ray selected Cataclysmic Variable (CVs), to unambiguously identify them as magnetic systems of the Intermediate Polar (IP) type. Methods. We performed detailed 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 broad band X-ray spectra were fitted using composite models consisting of different absorbing columns and emission components. Results. 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 IGRJ08390-4833, IGRJ18308-1232, and IGR J18173-2509. All X-ray spectra are multi-temperature. V2069 Cyg and RX J0636+3535 poses a soft X-ray optically thick component at kT approx. 80 eV. An intense K (sub alpha) Fe line at 6.4 keV is detected in all sources. An absorption edge at 0.76 keV from OVII is detected in IGR J08390-4833. The WD masses and lower limits to the accretion rates are also estimated. Conclusions. We found all sources to be IPs. IGR J08390-4833, V2069 Cyg, and IGR J16500-3307 are pure disc accretors, while IGR J18308-1232, IGR J1509-6649, IGR J17195-4100, and RX J0636+3535 display a disc-overflow accretion mode. All sources show a temperature gradient in the post-shock regions and a highly absorbed emission from material located in the pre-shock flow which is also responsible for the X-ray pulsations. Reflection at the WD surface is likely the origin of the fluorescent iron line. There is an increasing evidence for the presence of a warm absorber in IPs, a feature that needs future exploration. The addition of two systems to the subgroup of

  12. 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...

  13. Photometry of some neglected bright cataclysmic variables and candidates

    CERN Document Server

    Bruch, Albert

    2016-01-01

    As part of an effort to better characterize bright cataclysmic variables (CVs) which have received little attention in the past light curves of four confirmed systems (CZ Aql, BO Cet, V380 Oph and EF Tuc) and one candidate (Lib 3) are analyzed. For none of these stars time resolved photometry has been published previously. While no variability was found in the case of Lib 3, which thus cannot be confirmed as a CV, the light curves of all other targets are dominated by strong flickering. Modulations on hourly time scales superimposed on the flickering can probably be related to orbital variations in BO Cet and V380 Oph, but not in CZ Aql and EF Tuc. Variations on the time scale of 10 minutes in CZ Aql, while not yet constituting convincing evidence, together with previous suspicions of a magnetically channeled accretion flow may point at an intermediate polar nature of this star. Some properties of the flickering are quantified in an effort to enlarge the data base for future comparative flickering studies in ...

  14. Excess mid-IR emission in Cataclysmic Variables

    CERN Document Server

    Dubus, G; Kern, B; Taam, R E; Spruit, H C

    2004-01-01

    We present a search for excess mid-IR emission due to circumbinary material in the orbital plane of cataclysmic variables (CVs). Our motivation stems from the fact that the strong braking exerted by a circumbinary (CB) disc on the binary system could explain several puzzles in our current understanding of CV evolution. Since theoretical estimates predict that the emission from a CB disc can dominate the spectral energy distribution (SED) of the system at wavelengths > 5 microns, we obtained simultaneous visible to mid-IR SEDs for eight systems. We report detections of SS Cyg at 11.7 microns and AE Aqr at 17.6 microns, both in excess of the contribution from the secondary star. In AE Aqr, the IR likely originates from synchrotron-emitting clouds propelled by the white dwarf. In SS Cyg, we argue that the observed mid-IR variability is difficult to reconcile with simple models of CB discs and we consider free-free emission from a wind. In the other systems, our mid-IR upper limits place strong constraints on the...

  15. Exploring inside-out Doppler tomography: magnetic cataclysmic variables

    CERN Document Server

    Kotze, Enrico J; McBride, Vanessa A

    2016-01-01

    We present the results of applying our inside-out velocity projection and flux modulation mapping techniques to the Doppler tomography of magnetic cataclysmic variables. The inside-out tomogram is constructed by directly projecting phase-resolved spectra onto the inside-out framework. In addition, our flux modulation mapping technique extracts any information related to the modulation of the line flux by utilising consecutive half-phase tomograms. We apply this to both the standard and the inside-out techniques. Our test cases, the polars HU Aqr and V834 Cen, and the intermediate polar PQ Gem, were chosen because of their known accretion characteristics, namely ballistic, magnetic and curtain dominated accretion, respectively. In all three cases the inside-out tomogram better exposes low-velocity emission details which are overly compacted in the standard tomogram. This is especially apparent for the mid-inclination V834 Cen where the almost blob-like blended lower velocity emission in the standard tomogram i...

  16. 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 ...

  17. Nova-like cataclysmic variables in the infrared

    Energy Technology Data Exchange (ETDEWEB)

    Hoard, D. W. [Eureka Scientific, Inc., Oakland, CA (United States); Long, Knox S. [Space Telescope Science Institute, Baltimore, MD (United States); Howell, Steve B. [NASA Ames Research Center, Moffett Field, CA (United States); Wachter, Stefanie [Max Planck Institut für Astronomie, D-69117 Heidelberg (Germany); Brinkworth, Carolyn S. [Spitzer Science Center, California Institute of Technology, Pasadena, CA (United States); Knigge, Christian [Physics and Astronomy, University of Southampton, Southampton (United Kingdom); Drew, J. E. [Centre for Astrophysics Research, Science and Technology Research Institute, University of Hertfordshire, Hatfield (United Kingdom); Szkody, Paula [Department of Astronomy, University of Washington, Seattle, WA (United States); Kafka, S. [Carnegie Institution of Washington, Department of Terrestrial Magnetism, Washington, DC (United States); Belle, Kunegunda [Los Alamos National Laboratory, Los Alamos, NM (United States); Ciardi, David R. [NASA Exoplanet Science Institute, California Institute of Technology, Pasadena, CA (United States); Froning, Cynthia S. [Center for Astrophysics and Space Astronomy, Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO (United States); Van Belle, Gerard T. [Lowell Observatory, Flagstaff, AZ (United States); Pretorius, M. L., E-mail: hoard@mpia.de [Department of Physics, University of Oxford, Oxford (United Kingdom)

    2014-05-01

    Nova-like (NL) cataclysmic variables have persistently high mass transfer rates and prominent steady state accretion disks. We present an analysis of infrared observations of 12 NLs 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 λ ≳ 3-5 μm 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 in NLs. Our comparison of the relative advantages and disadvantages of either mechanism for explaining the observations suggests that the situation is rather ambiguous, largely circumstantial, and in need of stricter observational constraints.

  18. ULTRACAM photometry of the eclipsing cataclysmic variable OU Vir

    CERN Document Server

    Feline, W J; Marsh, T R; Stevenson, M J; Watson, C A; Brinkworth, C S

    2004-01-01

    We present high-speed, three-colour photometry of the faint eclipsing cataclysmic variable OU Vir. For the first time in OU Vir, separate eclipses of the white dwarf and bright spot have been observed. We use timings of these eclipses to derive a purely photometric model of the system, obtaining a mass ratio of q = 0.175 +/- 0.025, an inclination of i = 79.2 +/- 0.7 degrees and a disc radius of Rd/a = 0.2315 +/- 0.0150. We separate the white dwarf eclipse from the lightcurve and, by fitting a blackbody spectrum to its flux in each passband, obtain a white dwarf temperature of T = 13900 +/- 600 K and a distance of D = 51 +/- 17 pc. Assuming that the primary obeys the Nauenberg (1972) mass-radius relation for white dwarfs and allowing for temperature effects, we also find a primary mass Mw/Msun = 0.89 +/- 0.20, primary radius Rw/Rsun = 0.0097 +/- 0.0031 and orbital separation a/Rsun = 0.74 +/- 0.05.

  19. Dynamical Formation of Cataclysmic Variables in Globular Clusters

    CERN Document Server

    Hong, Jongsuk; Belloni, Diogo; Giersz, Mirek

    2016-01-01

    The formation and evolution of X-ray sources in globular clusters is likely to be affected by the cluster internal dynamics and the stellar interactions in the cluster dense environment.Several observational studies have revealed a correlation between the number of X-ray sources and the stellar encounter rate and provided evidence of the role of dynamics in the formation of X-ray binaries. We have performed a survey of Monte-Carlo simulations aimed at exploring the connection between the dynamics and formation of cataclysmic variables (CVs) and the origin of the observed correlation between the number of these objects, $N_{\\rm cv}$, and the stellar encounter rate, $\\Gamma$.The results of our simulations show a correlation between $N_{\\rm cv}$ and $\\Gamma$ as found in observational data, illustrate the essential role played by dynamics, and shed light on the dynamical history behind this correlation. CVs in our simulations are more centrally concentrated than single stars with masses close to those of turn-off...

  20. 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...

  1. On the late spectral types of cataclysmic variable secondaries

    CERN Document Server

    Baraffe, I

    2000-01-01

    We investigate why the spectral type of most cataclysmic variable (CV) secondaries is significantly later than that of a ZAMS star with the same mean density. Using improved stellar input physics, tested against observations of low-mass stars at the bottom of the main sequence, we calculate the secular evolution of CVs with low-mass donors. We consider sequences with different mass transfer rates and with a different degree of nuclear evolution of the donor prior to mass transfer. Systems near the upper edge of the gap ($P \\sim 3 - 6$ h) can be reproduced by models with a wide range of mass transfer rates from $1.5 \\times 10^{-9} \\msolyr$ to $10^{-8} \\msolyr$. Evolutionary sequences with a small transfer rate and donors that are substantially evolved off the ZAMS (central hydrogen content $0.05-0.5$) reproduce CVs with late spectral types above $P \\simgr$ 6 h. Systems with the most discrepant (late) spectral type should have the smallest donor mass at any given $P$. Consistency with the period gap suggests th...

  2. 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...

  3. 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.

  4. 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.

  5. 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°.

  6. 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.

    2016-09-01

    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 h. 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. 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°.

  7. 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.

  8. 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...

  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. Cataclysmic Variables from SDSS. VIII. The Final Year (2007-2008)

    CERN Document Server

    Szkody, Paula; Brooks, Keira; Gaensicke, Boris T; Kronberg, Martin; Riecken, Thomas; Ross, Nicholas P; Schmidt, Gary D; Schneider, Donald P; Agueros, Marcel A; Gomez-Moran, Ada N; Knapp, Gillian R; Schreiber, Matthias R; Schwope, Axel D

    2011-01-01

    This paper completes the series of cataclysmic variables (CVs) identified from the Sloan Digital Sky Survey I/II. The coordinates, magnitudes and spectra of 33 CVs are presented. Among the 33 are eight systems known previous to SDSS (CT Ser, DO Leo, HK Leo, IR Com, V849 Her, V405 Peg, PG1230+226 and HS0943+1404), as well as nine objects recently found through various photometric surveys. Among the systems identified since the SDSS are two polar candidates, two intermediate polar candidates and one candidate for containing a pulsating white dwarf. Our followup data have confirmed a polar candidate from Paper VII and determined tentative periods for three of the newly identified CVs. A complete summary table of the 285 CVs with spectra from SDSS I/II is presented as well as a link to an online table of all known CVs from both photometry and spectroscopy that will continue to be updated as future data appear.

  12. CATACLYSMIC VARIABLES FROM THE SLOAN DIGITAL SKY SURVEY. VIII. THE FINAL YEAR (2007-2008)

    Energy Technology Data Exchange (ETDEWEB)

    Szkody, Paula; Anderson, Scott F.; Brooks, Keira; Kronberg, Martin; Riecken, Thomas [Department of Astronomy, University of Washington, Seattle, WA 98195 (United States); Gaensicke, Boris T. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Ross, Nicholas P. [Lawrence Berkeley National Lab, Berkeley, CA 92420 (United States); Schmidt, Gary D. [The University of Arizona, Steward Observatory, Tucson, AZ 85721 (United States); Schneider, Donald P. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Agueeros, Marcel A. [Department of Astronomy, Columbia University, New York, NY 10027 (United States); Gomez-Moran, Ada N.; Schwope, Axel D. [Leibniz-Institut fuer Astrophysik Potsdam (AIP), 14482 Potsdam (Germany); Knapp, Gillian R. [Princeton University Observatory, Princeton, NJ 08544 (United States); Schreiber, Matthias R., E-mail: szkody@astro.washington.edu [Departamento de Fisica y Astronomia, Universidad de Valparaiso (Chile)

    2011-12-15

    This paper completes the series of cataclysmic variables (CVs) identified from the Sloan Digital Sky Survey (SDSS) I/II. The coordinates, magnitudes, and spectra of 33 CVs are presented. Among the 33 are eight systems known prior to SDSS (CT Ser, DO Leo, HK Leo, IR Com, V849 Her, V405 Peg, PG1230+226, and HS0943+1404), as well as nine objects recently found through various photometric surveys. Among the systems identified since the SDSS are two polar candidates, two intermediate polar candidates, and one candidate for containing a pulsating white dwarf. Our follow-up data have confirmed a polar candidate from Paper VII and determined tentative periods for three of the newly identified CVs. A complete summary table of the 285 CVs with spectra from SDSS I/II is presented as well as a link to an online table of all known CVs from both photometry and spectroscopy that will continue to be updated as future data appear.

  13. 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.

  14. 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...

  15. 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?

  16. Observations of the Cataclysmic Variable 1 RXPJ113123+4322.5

    Science.gov (United States)

    Holtgrewe, Kirk S.; Durig, Douglas T.

    We observed the cataclysmic variable star l RXPJ113123+4322.5 while it was undergoing its recent outburst. We collected data using R and V filters, alternating the filters every two minutes. We obtained two to three hour-long data sets on two different nights. The light curve was analyzed using Mathematica. The period determined was near 95 minutes and there was also some indication of a lower amplitude, higher frequency variation.

  17. 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...

  18. 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.

  19. 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...

  20. Abundance Derivations for the Secondary Stars in Cataclysmic Variables from Near-Infrared Spectroscopy

    CERN Document Server

    Harrison, Thomas E

    2016-01-01

    We derive metallicities for 41 cataclysmic variables (CVs) from near-infrared spectroscopy. We use synthetic spectra that cover the 0.8 $\\mu$m $\\leq \\lambda \\leq$ 2.5 $\\mu$m bandpass to ascertain the value of [Fe/H] for CVs with K-type donors, while also deriving abundances for other elements. Using calibrations for determining [Fe/H] from the $K$-band spectra of M-dwarfs, we derive more precise values for T$_{\\rm eff}$ for the secondaries in the shortest period CVs, and examine whether they have carbon deficits. In general, the donor stars in CVs have sub-solar metallicities. We confirm carbon deficits for a large number of systems. CVs with orbital periods $>$ 5 hr are most likely to have unusual abundances. We identify four CVs with CO emission. We use phase-resolved spectra to ascertain the mass and radius of the donor in U Gem. The secondary star in U Gem appears to have a lower {\\it apparent} gravity than a main sequence star of its spectral type. Applying this result to other CVs, we find that the late...

  1. 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 ...

  2. 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)

  3. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Godon, Patrick; Sion, Edward M. [Astronomy and Astrophysics, Villanova University, 800 Lancaster Avenue, Villanova, PA 19085 (United States); Levay, Karen [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Linnell, Albert P.; Szkody, Paula [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195-1580 (United States); Barrett, Paul E. [United States Naval Observatory, Washington, DC 20392 (United States); Hubeny, Ivan [Steward Observatory and Department of Astronomy and Astrophysics, University of Arizona, Tucson, AZ 85721 (United States); Blair, William P., E-mail: patrick.godon@villanova.edu, E-mail: edward.sion@villanova.edu, E-mail: klevay@stsci.edu, E-mail: linnell@astro.washington.edu, E-mail: szkody@astro.washington.edu, E-mail: barrett.paul@usno.navy.mil, E-mail: hubeny@as.arizona.edu, E-mail: wpb@pha.jhu.edu [Henry A. Rowland Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218 (United States)

    2012-12-15

    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.

  5. 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.

  6. Cataclysmic Variables From the Sloan Digital Sky Survey. VI. the Sixth Year (2005)

    Energy Technology Data Exchange (ETDEWEB)

    Szkody, Paula; /Washington U., Seattle, Astron. Dept.; Henden, Arne; /Naval Observ., Flagstaff /AAVSO, Cambridge; Mannikko, Lee; Mukadam, Anjum; /Washington U., Seattle,; Schmidt, Gary D.; /Arizona U., Astron. Dept. - Steward Observ.; Bochanski, John J.; Agueros, Marcel; Anderson, Scott F.; Silvestri, Nicole M.; /Washington U., Seattle,; Dahab, William E.; /Princeton U. Observ.; Oguri, Masamune; /Princeton U. Observ. /KIPAC, Menlo Park; Schneider, Donald P.; /Penn State U., Astron. Astrophys.; Shin,; Strauss, Michael A.; Knapp, Gillian R.; /Princeton U. Observ.; West, Andrew A.; /Washington U., Seattle, Astron. Dept.

    2007-06-15

    The 28 cataclysmic variables found in 2005 in the Sloan Digital Sky Survey are presented with their coordinates, magnitudes and spectra. Five of these systems are previously known CVs (HH Cnc, SX LMi, QZ Ser, RXJ1554.2+2721 and HS1016+3412) and the rest are new discoveries. Additional spectroscopic, photometric and/or polarimetric observations of 10 systems were carried out, resulting in estimates of the orbital periods for seven of the new binaries. The 23 new CVs include one eclipsing system, one new Polar and five systems whose spectra clearly reveal atmospheric absorption lines from the underlying white dwarf.

  7. 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

  8. 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

  9. 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.

  10. 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.

  11. Emission line tomography of the short period cataclysmic variables CC Scl and V2051 Oph

    CERN Document Server

    Longa-Peña, P; Marsh, T

    2014-01-01

    We present time-series spectroscopy of two short period cataclysmic variables, CC Scl and V2051 Oph, to test the efficiency of Doppler tomography-based methods in constraining orbital parameters of evolved cataclysmic variables. We find that the Ca~II triplet lines offer superior diagnostics, revealing emission components from the mass donors and sharp images of the accretion discs. Furthermore, we use Monte-Carlo methods to estimate the uncertainties from ensembles of Doppler maps. We compare our new methods against traditional radial velocity methods and show that they offer a valid route towards system parameter determination. Our analysis of CC Scl suggests a low mass ratio of $q=0.08\\pm0.03$ with a primary velocity of $K_1=37\\pm14$ km/s. This mass ratio is in between the pre- and post-period minimum status, however our $K_1$ solution favours a post-period minimum system. Our derived parameters for V2051 Oph ($q= 0.16\\pm 0.03$, $K_1=97\\pm10$ km/s) are in agreement with the eclipse solution ($q=0.19\\pm0.03...

  12. 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.

  13. 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

  14. MASTER OT J190519.41+301524.4: New Eclipsing Cataclysmic Variable of VY Scl Type

    CERN Document Server

    Martinelli, F

    2016-01-01

    MASTER OT J190519.41+301524.4 was discovered as an optical transient of 15.7m by the Mobile Astronomical System of TElescope-Robots in March 2014. We report the results of photometric observations of this variable performed at Lajatico Astronomical Center in June-July 2015. The light curve is showing deep V-shaped eclipses with an amplitude of two magnitudes. The orbital period was determined to be 0.129694 d (3.113 h). Based on the archival observations and the shape of the orbital curve we suggest that MASTER OT J190519.41+301524.4 is a new cataclysmic variable of VY Scl type ("anti-nova") with an inclination angle close to 90 deg.

  15. SPECTROSCOPIC ORBITAL PERIODS FOR 29 CATACLYSMIC VARIABLES FROM THE SLOAN DIGITAL SKY SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Thorstensen, John R.; Taylor, Cynthia J.; Peters, Christopher S.; Skinner, Julie N. [Department of Physics and Astronomy 6127 Wilder Laboratory, Dartmouth College Hanover, NH 03755-3528 (United States); Southworth, John [Astrophysics Group Keele University Staffordshire ST5 5BG (United Kingdom); Gänsicke, Boris T. [Department of Physics University of Warwick Coventry CV4 7AL (United Kingdom)

    2015-04-15

    We report follow-up spectroscopy of 29 cataclysmic variables from the Sloan Digital Sky Survey (SDSS), 22 of which were discovered by SDSS and seven of which are previously known systems that were recovered in SDSS. The periods for 16 of these objects were included in the tabulation by Gänsicke et al. While most of the systems have periods less than 2 hr, only one has a period in the 80–86 minutes “spike” found by Gänsicke et al., and 11 have periods longer than 3 hr, indicating that the present sample is skewed toward longer-period, higher-luminosity objects. Seven of the objects have spectra resembling dwarf novae, but have apparently never been observed in outburst, suggesting that many cataclysmics with relatively low variability amplitude remain to be discovered. Some of the objects are notable. SDSS J07568+0858 and SDSS J08129+1911 were previously known to have deep eclipses; in addition to spectroscopy, we use archival data from the Catalina Real Time Transient Survey to refine their periods. We give a parallax-based distance of 195 (+54, −39) pc for LV Cnc (SDSS J09197+0857), which at P{sub orb} = 81 m has the shortest orbital period in our sample. SDSS J08091+3814 shows both the spectroscopic phase offset and phase-dependent absorption found in SW Sextantis stars. The average spectra of SDSS J08055+0720 and SDSS J16191+1351 show contributions from K-type secondaries, and SDSS J080440+0239 shows a contribution from an early M star. We use these to constrain the distances. SDSS J09459+2922 has characteristics typical of a magnetic system. SDSS11324+6249 may be a novalike variable, and if so, its orbital period (99 minutes) is unusually short for that subclass.

  16. 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.

  17. 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.

  18. 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...

  19. 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...

  20. A 6.3-h superhump in the cataclysmic variable TV Columbae the longest yet seen

    CERN Document Server

    Retter, A; Augusteijn, T; Naylor, T; Bedding, T R; Bembrick, C; McCormick, J; Velthuis, F

    2002-01-01

    We present results from a two week multi-longitude photometric campaign on TV Col held in 2001 January. The data confirm the presence of a permanent positive superhump found in re-examination of extensive archive photometric data of TV Col. The 6.3-h period is 15 per cent longer than the orbital period and obeys the well known relation between superhump period excess and binary period. At 5.5-h, TV Col has an orbital period longer than any known superhumping cataclysmic variable and, therefore, a mass ratio which might be outside the range at which superhumps can occur according to the current theory. We suggest several solutions for this problem.

  1. 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...

  2. 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.

  3. 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 ...

  4. SDSS J123813.73-033933.0, a cataclysmic variable evolved beyond the period minimum

    CERN Document Server

    Aviles, A; Tovmassian, G; Michel, R; Tapia, M; Roth, M; Neustroev, V; Zurita, C; Andreev, M; Sergeev, A; Pavlenko, E; Tsymbal, V; Anupama, G C; Kamath, U S; Sahu, D K

    2010-01-01

    We present infrared JHK photometry of the cataclysmic variable SDSS J123813.73-033933.0 (SDSS1238)and analyze it along with optical spectroscopy, demonstrating that the binary system is most probably comprised of a massive white dwarf with Teff=12000+/-1000 K and a brown dwarf of spectral type L4. The inferred system parameters suggest that this system may have evolved beyond the orbital period minimum and is a bounce-back system. SDSS1238 stands out among CVs by exhibiting the cyclical variability (brightenings). These are not related to specific orbital phases of the binary system and are fainter than dwarf novae outbursts, that usually occur on longer timescales. This phenomenon has not been observed extensively and, thus, is poor understood. The new time-resolved, multi-longitude photometric observations of SDSS1238 allowed us to observe two consecutive brightenings and to determine their recurrence time. The period analysis of all observed brightenings during 2007 suggests a typical timescale that is clo...

  5. Disk Structure of Cataclysmic Variables in the light of Broadband Noise Characteristics

    Science.gov (United States)

    Balman, Solen

    2016-07-01

    Flicker noise and its variations in accreting systems have been a diagnostic tool in understanding the structure in accretion disks. I study the nature of time variability of brightness of non-magnetic cataclysmic variables. Dwarf novae demonstrate band limited noise in the UV and X-ray energy bands, which can be adequately explained in the framework of the model of propagating fluctuations. The detected frequency breaks in the range (1-6) mHz indicates an optically thick disk truncation in the inner disk of some dwarf novae systems. Analysis of other available data (SS Cyg, SU UMa, WZ Sge, Z Cha) indicate that during the outburst the inner disk radius moves towards the white dwarf and receeds as the outburst declines while changes in the X-ray energy spectrum is also observed. Cross-correlations between the simultaneous Optical, UV and X-ray light curves show time lags in the X-rays consistent with truncated inner optically thick disk. I compare magnetic and nonmagnetic CVs in terms of their broadband noise characteristics and summarize findings regarding broadband noise structure and time lags in other types of nonmagnetic CVs which in general show compliance with the model of propagating fluctuations. In addition, I discuss comparisons with X-ray binaries.

  6. 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.

  7. 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...

  8. 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...

  9. 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...

  10. Cataclysmic Variables and a Candidate Helium White Dwarf in the Globular Cluster NGC 6397

    CERN Document Server

    Edmonds, P D; Cool, A M; Cohn, H N; Lugger, P M; Bailyn, C D; Edmonds, Peter D.; Grindlay, Jonathan E.; Cool, Adrienne M.; Cohn, Haldan N.; Lugger, Phyllis N.; Bailyn, Charles D.

    1999-01-01

    We have used HST/FOS to study faint UV stars in the core of the nearby globular cluster NGC 6397. We confirm the presence of a 4th cataclysmic variable (CV) in NGC 6397 (CV 4), and we use the photometry of Cool et al. (1998) to present evidence that CVs 1--4 all have faint disks and probably low accretion rates. By combining these results with new UV spectra of CV 1 and the published spectra of Grindlay et al. (1995) we present new evidence that CVs 1--3 may be DQ Her systems, and we show that CV 4 may either be a dwarf nova or another magnetic system. Another possibility is that the CVs could be old novae in hibernation between nova eruptions. We also present the first spectrum of a member of a new class of UV bright stars in NGC 6397. These faint, hot stars do not vary, unlike the CVs, and are thus denoted as ``non-flickerers'' (NFs). Like the CVs, their spatial concentration is strongly concentrated toward the cluster center. Using stellar atmosphere models we have determined log g = 6.25, and T_eff = 17,5...

  11. 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 ...

  12. 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.

  13. 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...

  14. 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 ...

  15. 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...

  16. Infrared Spectroscopic Observations of the Secondary Stars of Short Period Sub-Gap Cataclysmic Variables

    CERN Document Server

    Hamilton, Ryan T; Tappert, Claus; Howell, Steve B

    2010-01-01

    We present K-band spectroscopy of short period, "sub-gap" cataclysmic variable (CV) systems obtained using ISAAC on the VLT. We show the infrared spectra (IR) for nine systems below the 2-3 hour period gap: V2051 Oph, V436 Cen, EX Hya, VW Hyi, Z Cha, WX Hyi, V893 Sco, RZ Leo, and TY PsA. We are able to clearly detect the secondary star in all but WX Hyi, V893 Sco, and TY PsA. We present the first direct detection of the secondary stars of V2051 Oph, V436 Cen, and determine new spectral classifications for EX Hya, VW Hyi, Z Cha, and RZ Leo. We find that the CO band strengths of all but Z Cha appear normal for their spectral types, in contrast to their longer period cousins above the period gap. This brings the total number of CVs and pre-CVs with moderate resolution (R >~ 1500) IR spectroscopy to sixty-one systems: nineteen pre-CVs, thirty-one non-magnetic systems, and eleven magnetic or partially magnetic systems. We discuss the trends seen in the IR abundance patterns thus far, and highlight a potential link...

  17. 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...

  18. 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.

  19. ULTRACAM photometry of the eclipsing cataclysmic variables GY Cnc, IR Com and HT Cas

    CERN Document Server

    Feline, W J; Marsh, T R; Watson, C A; Littlefair, S P

    2005-01-01

    We present high-speed, three-colour photometry of the eclipsing cataclysmic variables GY Cnc, IR Com and HT Cas. We find that the sharp eclipses in GY Cnc and IR Com are due to eclipses of the white dwarf. There is some evidence for a bright spot on the edge of the accretion disc in GY Cnc, but not in IR Com. Eclipse mapping of HT Cas is presented which shows changes in the structure of the quiescent accretion disc. Observations in 2002 show the accretion disc to be invisible except for the presence of a bright spot at the disc edge. 2003 observations, however, clearly show a bright inner disc and the bright spot to be much fainter than in 2002. Although no outburst was associated with either set of quiescent observations, the system was ~0.6 mJy brighter in 2003, mainly due to the enhanced emission from the inner disc. We propose that these changes are due to variations in the mass transfer rate from the secondary star and through the disc. The disc colours indicate that it is optically thin in both its inne...

  20. ULTRACAM photometry of the eclipsing cataclysmic variables XZ Eri and DV UMa

    CERN Document Server

    Feline, W J; Marsh, T R; Brinkworth, C S

    2004-01-01

    We present high-speed, three-colour photometry of the faint eclipsing cataclysmic variables XZ Eri and DV UMa. We determine the system parameters through two techniques: first, timings of the eclipse contact phases of the white dwarf and bright-spot using the derivative of the light curve; and secondly, a parameterized model of the eclipse fitted to the observed light curve by chi-squared minimisation. For both objects, we prefer the latter method, as it is less affected by photon noise and rapid flickering. For XZ Eri we obtain a mass ratio q = 0.1098 +/- 0.0017 and an orbital inclination i = 80.16 +/- 0.09 degrees. For DV UMa we derive figures of q = 0.1506 +/- 0.0009 and i = 84.24 +/- 0.07 degrees. The secondary star in XZ Eri has a very low mass Mr/Msun = 0.0842 +/- 0.0024, placing it close to the upper limit on the mass of a brown dwarf.

  1. 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...

  2. An Online Catalog of Cataclysmic Variable Spectra from the Far Ultraviolet Spectroscopic Explorer

    CERN Document Server

    Godon, P; Levay, K; Linnell, A P; Szkody, P; Barrett, P E; Hubeny, I; Blair, W P

    2012-01-01

    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 (RA,Dec), period, inclination, 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 inclinati...

  3. 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.

  4. 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.

  5. Evolution of Cataclysmic Variables and Related Binaries Containing a White-Dwarf

    CERN Document Server

    Kalomeni, B; Rappaport, S; Molnar, M; Quintin, J; Yakut, K

    2016-01-01

    We present a binary evolution study of cataclysmic variables (CVs) and related systems with white dwarf accretors, including for example, AM CVn systems, classical novae, supersoft X-ray sources, and systems with giant donor stars. Our approach intentionally avoids the complications associated with population synthesis algorithms thereby allowing us to present the first truly comprehensive exploration of all of the subsequent binary evolution pathways that ZACVs might follow (assuming fully non-conservative, Roche-lobe overflow onto an accreting WD) using the sophisticated binary stellar evolution code MESA. The grid consists of 56,000 initial models, including 14 white dwarf accretor masses, 43 donor-star masses ($0.1-4.7$ $M_{\\odot}$), and 100 orbital periods. We explore evolution tracks in the orbital period and donor-mass ($P_{\\rm orb}-M_{\\rm don}$) plane in terms of evolution dwell times, masses of the white dwarf accretor, accretion rate, and chemical composition of the center and surface of the donor s...

  6. 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.

  7. 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...

  8. Radial velocity studies of HeII and Hβ emission from cataclysmic variables

    Science.gov (United States)

    Schwarz, C.; Montgomery, M. M.

    2014-02-01

    Radial velocity (RV) plots of HeII and Hβ emission lines from non-magnetic Cataclysmic Variable (CV) systems are frequently fit with a sin curve but sometimes contain outlying data points around phase ϕ∼1.0. A lack of consensus exists on the origin of these outlying points. In this work, we develop an analytical model that is based upon our 3D Smoothed Particle Hydrodynamic (SPH) numerical model to simulate these RV curves. Our chosen targets are CV SW Sextanis-like systems UX Uma and RW Tri as well as SU UMa dwarf novae systems Hα0242-28 and 1RXSJ1808+10, which have secondary-to-primary mass ratios of q = (0.43, 0.86, 0.27, 0.18), respectively. In our model, we include disk eccentricity, inclination angle, degree of disk-tilt, bright spot (s), and/or gas stream overflow. Our model provides good non-sinusoidal fits to the observed RV data, including outlying data points near ϕ∼1.0, suggesting these excess points may be caused by gas-stream overflow.

  9. An investigation of a magnetic cataclysmic variable with a period of 14.1 ks

    CERN Document Server

    Wang, Song; Zhang, Chuan-peng; Liu, Ji-feng

    2016-01-01

    Magnetic cataclysmic variables (CVs) contain a white dwarf with magnetic field strong enough to control the accretion flow from a late type secondary. In this paper, we discover a magnetic CV (CXOGSG J215544.4+380116) from the $Chandra$ archive data. The X-ray light curves show a significant period of 14.1 ks, and the X-ray spectra can be described by a multi-temperature hot thermal plasma, suggesting the source as a magnetic CV. The broad dip in the X-ray light curve is due to the eclipse of the primary magnetic pole, and the additional dip in the bright phase of the soft and medium bands may be caused by the accretion stream crossing our line of sight to the primary pole. Follow-up optical spectra show features of an M2--M4 dwarf dominating the red band and a WD which is responsible for the weak upturn in the blue band. The mass ($\\sim$ 0.4 $M_{\\odot}$) and radius ($\\sim$ 0.4 $R_{\\odot}$) for the M dwarf are obtained using CV evolution models and empirical relations between the orbital period and the mass/r...

  10. 1RXSJ173021.5-055933: a cataclysmic variable with a fast-spinning magnetic white dwarf

    CERN Document Server

    De Martino, D; Mukai, K; Bonnet-Bidaud, J -M; Falanga, M; Gänsicke, B T; Haberl, F; Marsh, T R; Mouchet, M; Littlefair, S P; Dhillon, V

    2008-01-01

    We present the first X-ray observations with the XMM-Newton and INTEGRAL satellites of the recently discovered cataclysmic variable 1RXSJ173021.5-055933, together with simultaneous UV and coordinated optical photometry aiming at characterising its broad-band temporal and spectral properties and classifying this system as a magnetic one. We find that the X-ray light curve is dominated by the 128s spin period of the accreting white dwarf in contrast to the far-UV range, which turns out to be unmodulated at a 3sigma level. Near-UV and optical pulses are instead detected at twice the spin frequency. We identify the contributions from two accreting poles that imply a moderately inclined dipole field allowing, one pole to dominate at energies at least up to 10keV, and a secondary that instead is negligible above 5keV. X-ray spectral analysis reveals the presence of multiple emission components consisting of optically thin plasma with temperatures ranging from 0.17keV to 60keV and a hot blackbody at ~90eV. The spect...

  11. 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...

  12. 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.

  13. 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.

  14. 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.

  15. Physical parameters and orbital period variation of a newly discovered cataclysmic variable GSC 4560–02157

    Science.gov (United States)

    Han, Zhong-Tao; Qian, Sheng-Bang; Voloshina, Irina; Metlov, Vladimir G.; Zhu, Li-Ying; Li, Lin-Jia

    2016-10-01

    GSC 4560–02157 is a new eclipsing cataclysmic variable with an orbital period of 0.265359 days. By using the published V ‑ and R ‑ band data together with our observations, we discovered that the O ‑ C curve of GSC 4560–02157 may show a cyclic variation with a period of 3.51 years and an amplitude of 1.40 min. If this variation is caused by a light travel-time effect via the existence of a third body, then its mass can be derived as M 3 sin i' ≈ 91.08 M Jup, and it should be a low-mass star. In addition, several physical parameters were measured. The color of the secondary star was determined to be V ‑ R = 0.77(±0.03) which corresponds to a spectral type of K2–3. The secondary star's mass was estimated as M 2 = 0.73(±0.02) M ⊙ by combing the derived V ‑ R value around phase 0 with the assumption that it obeys the mass-luminosity relation for main sequence stars. This mass is consistent with the mass—period relation for CV donor stars. For the white dwarf, the eclipse durations and contacts of the white dwarf yield an upper limit on the white dwarf's radius corresponding to a lower limit on mass of M 1 ≈ 0.501 M ⊙. The overestimated radius and previously published spectral data indicate that the boundary layer may have a very high temperature.

  16. 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.

  17. 1H 1752 + 081: an eclipsing cataclysmic variable with a small accretion disk

    Science.gov (United States)

    Silber, Andrew D.; Remillard, Ronald A.; Horne, Keith; Bradt, Hale V.

    1994-04-01

    We announce the discovery of an eclipsing nova-like cataclysmic variable (CV) as the optical counterpart to the HEAO 1 X-ray source 1H1752 + 081. This CV has an orbital period of 1.882801 hr, a high equivalent width of H-beta, and an average mv of 16.4 out of the eclipse. A geometric model is constructed from observations of the eclipse ingress and egress in many optical bandpasses. The broad-band emission originates primarily in two regions; the disk/accretion stream 'hot spot' and a compact central component, which may be a spot on the white dwarf surface, the entire white dwarf surface or the boundary layer between the accretion disk and the white dwarf surface. Based on the durations and offsets of the two eclipses we determined the mass ratio q = 2.5 +/- 0.6 and the angle of inclination i = 77 deg +/- 2 deg. If the central component is the entire white dwarf surface the masses of the stars are M1 = 0.80 +/- 0.06 solar masses and M2 = 0.32 +/- 0.06 solar masses. The disk is faint and small (RD = 0.25 +/- 0.05 rL1, where rL1 is the distance from the primary to the L1 point), compared to other eclipsing CVs. The small disk may result from the removal of angular momentum from the accretion disk by the magnetic field of the white dwarf; this CV may be a DQ Her type with a slowly rotating white dwarf. The emission-line velocities do not show the 'Z-wave' expected from the eclipse of a Keplerian accretion disk, nor do they have the correct phasing to originate near the white dwarf. The most likely origin of the line emission is the hot spot. The secondary star is visible at wavelengths greater than or equal to 6000 A during eclipse. We estimate a spectral type approximately M6 which, together with the observed m1 = 16.94 during eclipse, results in a distance estimate of 150 +/- 27 pc.

  18. The space density and X-ray luminosity function of non-magnetic cataclysmic variables

    Science.gov (United States)

    Pretorius, Magaretha L.; Knigge, Christian

    2012-01-01

    We combine two complete, X-ray flux-limited surveys, the ROSAT Bright Survey (RBS) and the ROSAT North Ecliptic Pole (NEP) survey, to measure the space density (ρ) and X-ray luminosity function (Φ) of non-magnetic cataclysmic variables (CVs). The combined survey has a flux limit of FX≳ 1.1 × 10-12 erg cm-2 s-1 over most of its solid angle of just over ?, but is as deep as ≃10-14 erg cm-2 s-1 over a small area. The CV sample that we construct from these two surveys contains 20 non-magnetic systems. We carefully include all sources of statistical error in calculating ρ and Φ by using Monte Carlo simulations; the most important uncertainty proves to be the often large errors in distances estimates. If we assume that the 20 CVs in the combined RBS and NEP survey sample are representative of the intrinsic population, the space density of non-magnetic CVs is ?. We discuss the difficulty in measuring Φ in some detail - in order to account for biases in the measurement, we have to adopt a functional form for Φ. Assuming that the X-ray luminosity function of non-magnetic CVs is a truncated power law, we constrain the power-law index to -0.80 ± 0.05. It seems likely that the two surveys have failed to detect a large, faint population of short-period CVs, and that the true space density may well be a factor of 2 or 3 larger than what we have measured; this is possible, even if we only allow for undetected CVs to have X-ray luminosities in the narrow range 28.7 log(LX/erg s-1) < 29.7. However, ρ as high as 2 × 10-4 pc-3 would require that the majority of CVs has X-ray luminosities below LX= 4 × 1028 erg s-1 in the 0.5-2.0 keV band.

  19. Archival Ultraviolet Spectroscopic Analysis of Disk-Dominated Cataclysmic Variables: The Importance of the Boundary Layer

    Science.gov (United States)

    Godon, Patrick

    We propose to carry out a systematic ultraviolet (UV) spectral analysis of 43 disk- dominated systems in cataclysmic variable (CV) binaries with the inclusion of the contribution from the boundary layer, from NASA UV Space Missions such as HST, FUSE, HUT, IUE and ORFEUS. The mass accretion in CVs is a badly needed parameter to verify the theory of the evolution of CVs, to understand the accretion process itself and the disk instability. However, many disk-dominated systems unexpectedly prove impossible to model using only standard accretion disks and white dwarfs in combination. Our objective is to overcome this difficulty by modeling the UV spectrum of the boundary layer between the star and disk, including its effect on the spectrum of the disk and star for the first time. This will provide the first step needed for the improvement of the disk model in UV spectroscopic analysis of disk-dominated systems in CVs. At the same time the results of this spectral analysis will provide information on the boundary layer and accretion disk of these systems. As a by-product, we will create a web-based catalog of all the archival UV spectra of disk-dominated CVs, which will be added and fused to our existing and growing web-based catalog of FUSE spectra of CVs. Since the WD is the most common end-product of stellar evolution (approx 90% of all the stars in the Galaxy have or will evolve into white dwarfs), and the accretion disk is the most common universal structure resulting from mass transfer with angular momentum, and since both can be directly viewed in CVs in the ultraviolet (UV), an understanding of the consequences of accretion in these systems is the first step in a global understanding of accretion in other systems throughout the universe. These include Young Stellar Objects, galactic binaries (accretion onto neutron stars and black holes) and the most difficult to study, Active Galactic Nuclei. In addition, the formation history of WDs is closely linked to the

  20. 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...

  1. 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...

  2. 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...

  3. Probing Accretion in Magnetic Cataclysmic Variables from High Time Resolution Optical Photometry and X-ray Observations from ASTROSAT

    Science.gov (United States)

    Buckley, David; Marsh, Tom; Revnivtsev, Mikhail; Bonnet-Bidaud, Jean-Marc; Mouchet, Martine; Pal Singh, Kulinder; Semena, Andrey; Dhillon, Vik; Breytenbach, Hannes; Irawati, Puji; Potter, Stephen

    2016-07-01

    We present results from an on-going program of high speed CCD photometry of magnetic cataclysmic variables (mCVs) aimed at characterizing their high frequency (˜0.1-10 Hz) optical variability. In particular, we have been actively attempting to detect Quasi-Periodic Oscillations in many Polars, indicative of shock instabilities in their accretion columns. We have used a variety of instruments for this purpose, including the EM-CCD based SHOC camera on the SAAO 1.9-m telescope, SALTICAM and BVIT on SALT and Ultraspec on the TNO 2.5-m telescope. While we have detected QPOs seen before in the systems V834 Cen and VV Pup, we have only found evidence for one new detection, namely for 2MASS J19283247-5001344, an eclipsing polar. This may indicate that QPOs are somewhat of a rarity in Polars. We have also seen evidence for lower frequency QPOs, with characteristic timescales of 10s of seconds to several minutes. In addition, we have been investigating the nature of the breaks in the Power Density Spectra (νF_ν) power law for Intermediate Polars (e.g. EX Hya). This may give clues to the size of the inner radius of the accretion disc, where the magnetosphere begins to dominate the accretion flow. Finally, results of our recent ASTROSAT program on mCVs will be discussed.

  4. 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.

  5. Using Gaussian processes to model light curves in the presence of flickering: the eclipsing cataclysmic variable ASASSN-14ag

    CERN Document Server

    McAllister, M J; Dhillon, V S; Marsh, T R; Ashley, R P; Bours, M C P; Breedt, E; Hardy, L K; Hermes, J J; Kengkriangkrai, S; Kerry, P; Rattanasoon, S; Sahman, D I

    2016-01-01

    The majority of cataclysmic variable (CV) stars contain a stochastic noise component in their light curves, commonly referred to as flickering. This can significantly affect the morphology of CV eclipses and increases the difficulty in obtaining accurate system parameters with reliable errors through eclipse modelling. Here we introduce a new approach to eclipse modelling, which models CV flickering with the help of Gaussian processes (GPs). A parameterised eclipse model - with an additional GP component - is simultaneously fit to 8 eclipses of the dwarf nova ASASSN-14ag and system parameters determined. We obtain a mass ratio $q$ = 0.149 $\\pm$ 0.016 and inclination $i$ = 83.4 $^{+0.9}_{-0.6}$ $^{\\circ}$. The white dwarf and donor masses were found to be $M_{w}$ = 0.63 $\\pm$ 0.04 $M_{\\odot}$ and $M_{d}$ = 0.093 $^{+0.015}_{-0.012}$ $M_{\\odot}$, respectively. A white dwarf temperature $T_{w}$ = 14000 $^{+2200}_{-2000}$ K and distance $d$ = 146 $^{+24}_{-20}$ pc were determined through multicolour photometry. W...

  6. 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...

  7. 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...

  8. 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.

  9. A Critical Examination of the Paradigm for the 2-3 Hour Period Gap in Cataclysmic Variables

    CERN Document Server

    Howell, S B; Rappaport, S; Howell, Steve B.; Nelson, Lorne A.

    2000-01-01

    We critically examine the basic paradigm for the origin of the 2-3 hr period gap in cataclysmic variables (CVs). We carry out an extensive population synthesis study of CVs starting from ~ 3 x 10^6 primordial binaries, and evolving some ~ 2 x 10^4 surviving systems through their CV phase. In particular we study current-epoch distributions of CVs in the $\\dot M-P_{orb}$, R_{2}-P_{orb}, M_{2}-P_{orb}, q-P_{orb}, T_{eff}-P_{orb}, and L_{2}-P_{orb} planes, where $\\dot M$ is the mass transfer rate, q is the mass ratio M_2/M_1, and M_2, R_2, T_{eff}, and L_2 are the donor star mass, radius, effective temperature, and luminosity, respectively. This work presents a new perspective on theoretical studies of the long-term evolution of CVs. In particular, we show that if the current paradigm is correct, the secondary masses in CVs just above the period gap should be as much as ~ 50% lower than would be inferred if one assumes a main-sequence radius-mass relation for the donor star.

  10. UNAMBIGUOUS DETECTION OF REFLECTION IN MAGNETIC CATACLYSMIC VARIABLES: JOINT NuSTAR–XMM-NEWTON OBSERVATIONS OF THREE INTERMEDIATE POLARS

    Energy Technology Data Exchange (ETDEWEB)

    Mukai, K. [CRESST and X-ray Astrophysics Laboratory, NASA/GSFC, Greenbelt, MD 20771 (United States); Rana, V. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Bernardini, F. [New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi (United Arab Emirates); De Martino, D., E-mail: Koji.Mukai@nasa.gov [INAF—Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, I-80131 Napoli (Italy)

    2015-07-10

    In magnetic cataclysmic variables (CVs), X-ray emission regions are located close to the white dwarf surface, which is expected to reflect a significant fraction of intrinsic X-rays above 10 keV, producing a Compton reflection hump. However, up to now, a secure detection of this effect in magnetic CVs has largely proved elusive because of the limited sensitivity of non-imaging X-ray detectors. Here we report our analysis of joint NuSTAR–XMM-Newton observations of three magnetic CVs, V709 Cas, NY Lup, and V1223 Sgr. The improved hard X-ray sensitivity of the imaging NuSTAR data has resulted in the first robust detection of Compton hump in all three objects, with amplitudes of ∼1 or greater in NY Lup, and likely <1.0 in the other two. We also confirm earlier reports of a strong spin modulation above 10 keV in V709 Cas, and we report the first detection of small spin amplitudes in the others. We interpret this as due to different height of the X-ray emitting region among these objects. A height of ∼0.2 white dwarf radii provides a plausible explanation for the low reflection amplitude of V709 Cas. Since emission regions above both poles are visible at certain spin phases, this can also explain the strong hard X-ray spin modulation. A shock height of ∼0.05 white dwarf radii can explain our results on V1223 Sgr, while the shock height in NY Lup appears negligible.

  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. The X-ray properties of the magnetic Cataclysmic Variable UU Col

    CERN Document Server

    De Martino, D; Mukai, K; Bonnet-Bidaud, J M; Burwitz, V; Gänsicke, B T; Haberl, F; Mouchet, M

    2006-01-01

    XMM-Newton observations aimed at determining for the first time the broad-band X-ray properties of the faint high galactic latitude Intermediate Polar UU Col are presented. We performed X-ray timing analysis in different energy ranges of the EPIC cameras which reveals the dominance of the 863s white dwarf rotational period. The spin pulse is strongly energy dependent. Weak variabilities at the beat 935s and at the 3.5hr orbital periods are also observed, but the orbital modulation is detected only below 0.5keV. Simultaneous UV and optical photometry shows that the spin pulse is anti-phased with respect to the hard X-rays. Analysis of the EPIC and RGS spectra reveals the complexity of the X-ray emission, being composed of a soft 50eV black--body component and two optically thin emission components at 0.2keV and 11keV strongly absorbed by dense material with an equivalent hydrogen column density of 10**(23)cm**(-2) partially (50%) covering the X-ray source. The complex X-ray and UV/optical temporal behaviour in...

  13. Wavelets with Ridges: A High-Resolution Representation of Cataclysmic Variable Time-Series

    CERN Document Server

    Blackman, Claire

    2010-01-01

    Quasi-periodic oscillations and dwarf nova oscillations occur in dwarf novae and nova-like variables during outburst and occasionally during quiescence, and have analogues in high-mass X-ray binaries and black-hole candidates. The frequent low coherence of quasi-period oscillations and dwarf nova oscillations can make detection with standard time-series tools such as periodograms problematic. This paper develops tools to analyse quasi-periodic brightness oscillations. We review the use of time-frequency representations in the astronomical literature, and show that representations such as the Choi-Williams Distribution and Zhao-Atlas-Marks Representation, which are best suited to high signal-to-noise data, cannot be assumed a priori to be the best techniques for our data, which have a much higher noise level and lower coherence. This leads us to a detailed analysis of the time-frequency resolution and statistical properties of six time-frequency representations. We conclude that the wavelet scalogram, with the...

  14. 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...

  15. 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.

  16. 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.

  17. Roche tomography of cataclysmic variables -- II. Images of the secondary stars in AM Her, QQ Vul, IP Peg and HU Aqr

    CERN Document Server

    Watson, C A; Rutten, R G M; Schwope, A D

    2003-01-01

    We present a set of Roche tomography reconstructions of the secondary stars in the cataclysmic variables AM Her, QQ Vul, IP Peg and HU Aqr. The image reconstructions show distinct asymmetries in the irradiation pattern for all four systems which can be attributed to shielding of the secondary star by the accretion stream/column in AM Her, QQ Vul and HU Aqr, and increased irradiation by the bright spot in IP Peg. We use the entropy landscape technique to derive accurate system parameters (M1, M2, i and gamma) for the four binaries. In principle, this technique should provide the most reliable mass determinations available, since the intensity distribution across the secondary star is known. We also find that the intensity distribution can systematically affect the value of gamma derived from circular orbit fits to radial velocity variations.

  18. 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...

  19. 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...

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

    Science.gov (United States)

    Belloni, Diogo; Giersz, Mirek; Rocha-Pinto, Helio J.; Leigh, Nathan W. C.; Askar, Abbas

    2016-10-01

    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 (≲ 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 illustrate that, due mainly to unstable mass transfer, some CVs that form in our simulations are destroyed before the present-day. Finally, some field CVs might have originated from GCs, as found in our simulations, although the fraction of such escapers should be small relative to the entire Galactic field CV population.

  1. 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…

  2. 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.

  3. 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...

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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).

  9. 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.

  10. 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,…

  11. 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...

  12. Examining Preservice Science Teachers' Skills of Formulating Hypotheses and Identifying Variables

    Science.gov (United States)

    Aydogdu, Bülent

    2015-01-01

    The aim of this study is to examine preservice science teachers' skills of formulating hypotheses and identifying variables. The research has a phenomenological research design. The data was gathered qualitatively. In this study, preservice science teachers were first given two scenarios (Scenario-1 & Scenario-2) containing two different…

  13. Cluster analysis for identifying sub-groups and selecting potential discriminatory variables in human encephalitis

    Directory of Open Access Journals (Sweden)

    Crowcroft Natasha S

    2010-12-01

    Full Text Available Abstract Background Encephalitis is an acute clinical syndrome of the central nervous system (CNS, often associated with fatal outcome or permanent damage, including cognitive and behavioural impairment, affective disorders and epileptic seizures. Infection of the central nervous system is considered to be a major cause of encephalitis and more than 100 different pathogens have been recognized as causative agents. However, a large proportion of cases have unknown disease etiology. Methods We perform hierarchical cluster analysis on a multicenter England encephalitis data set with the aim of identifying sub-groups in human encephalitis. We use the simple matching similarity measure which is appropriate for binary data sets and performed variable selection using cluster heatmaps. We also use heatmaps to visually assess underlying patterns in the data, identify the main clinical and laboratory features and identify potential risk factors associated with encephalitis. Results Our results identified fever, personality and behavioural change, headache and lethargy as the main characteristics of encephalitis. Diagnostic variables such as brain scan and measurements from cerebrospinal fluids are also identified as main indicators of encephalitis. Our analysis revealed six major clusters in the England encephalitis data set. However, marked within-cluster heterogeneity is observed in some of the big clusters indicating possible sub-groups. Overall, the results show that patients are clustered according to symptom and diagnostic variables rather than causal agents. Exposure variables such as recent infection, sick person contact and animal contact have been identified as potential risk factors. Conclusions It is in general assumed and is a common practice to group encephalitis cases according to disease etiology. However, our results indicate that patients are clustered with respect to mainly symptom and diagnostic variables rather than causal agents

  14. 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.

  15. 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...

  16. 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.

  17. 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

  18. 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.

  19. Superhumps in Cataclysmic Binaries. XXV. q_crit, epsilon(q), and Mass-Radius

    CERN Document Server

    Patterson, J; Harvey, D; Fried, R; Rea, R; Monard, B; Cook, L; Skillman, D R; Vanmunster, T; Bolt, G; Armstrong, E; McCormick, J; Krajci, T; Jensen, L; Gunn, J; Butterworth, N D; Foote, J; Bos, M; Masi, G; Warhurst, P; Patterson, Joseph; Kemp, Jonathan; Harvey, David; Fried, Robert; Rea, Robert; Monard, Berto; Cook, Lewis; Skillman, David; Vanmunster, Tonny; Bolt, Greg; Armstrong, Eve; Cormick, Jennie Mc; Krajci, Thomas; Jensen, Lasse; Gunn, Jerry; Butterworth, Neil; Foote, Jerry; Bos, Marc; Masi, Gianluca; Warhurst, Paul

    2005-01-01

    We report on successes and failures in searching for positive superhumps in cataclysmic variables, and show the superhumping fraction as a function of orbital period. Basically, all short-period systems do, all long-period systems don't, and a 50% success rate is found at P_orb=3.1+-0.2 hr. We can use this to measure the critical mass ratio for the creation of superhumps. With a mass-radius relation appropriate for cataclysmic variables, and an assumed mean white-dwarf mass of 0.75 M_sol, we find a mass ratio q_crit=0.35+-0.02. We also report superhump studies of several stars of independently known mass ratio: OU Virginis, XZ Eridani, UU Aquarii, and KV UMa (= XTE J1118+480). The latter two are of special interest, because they represent the most extreme mass ratios for which accurate superhump measurements have been made. We use these to improve the epsilon(q) calibration, by which we can infer the elusive q from the easy-to-measure epsilon (the fractional period excess of P_superhump over P_orb). This rela...

  20. Moving to Second-Stage Treatments Faster: Identifying Midtreatment Tailoring Variables for Youth with Anxiety Disorders.

    Science.gov (United States)

    Pettit, Jeremy W; Silverman, Wendy K; Rey, Yasmin; Marin, Carla; Jaccard, James

    2016-01-01

    The current study presents an approach for empirically identifying tailoring variables at midtreatment of cognitive behavioral therapy (CBT) protocols for youth with anxiety disorders that can be used to guide moves to second-stage treatments. Using 2 independent data sets (Study 1 N = 240, M age = 9.86 years; Study 2 N = 341; M age = 9.53 years), we examined treatment response patterns after 8 sessions of CBT (i.e., CBT midtreatment). We identified and replicated 3 classes of response patterns at CBT midtreatment: Early Responders, Partial Responders, and Nonresponders. Class membership at CBT midtreatment was predictive of outcome at CBT posttreatment. Receiver operating characteristics curves were used to derive guidelines to optimize accuracy of assignment to classes at CBT midtreatment. These findings support the promise of treatment response at CBT midtreatment to identify tailoring variables for use in abbreviating first-stage treatments and facilitating moves to second-stage treatments.

  1. 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.

  2. Detection of accretion X-rays from QS Vir: cataclysmic or a lot of hot air?

    CERN Document Server

    Matranga, Marco; Kashyap, Vinay; Steeghs, Danny

    2012-01-01

    An XMM-Newton observation of the nearby "pre-cataclysmic" short-period (P_orb = 3.62 hr) binary QS Vir (EC 13471-1258) revealed regular narrow X-ray eclipses when the white dwarf passed behind its M2-4 dwarf companion. The X-ray emission provides a clear signature of mass transfer and accretion onto the white dwarf. The low-resolution XMM-Newton EPIC spectra are consistent with a cooling flow model and indicate an accretion rate of Mdot= 1.7\\times10^-13M\\odot/yr. At 48 pc distant, QS Vir is then the second nearest accreting cataclysmic variable known, with one of the lowest accretion rates found to date for a non-magnetic system. To feed this accretion through a wind would require a wind mass loss rate of Mdot ~ 2 \\times 10^-12M\\odot/yr if the accretion efficiency is of the order of 10%. Consideration of likely mass loss rates for M dwarfs suggests this is improbably high and pure wind accretion unlikely. A lack of accretion disk signatures also presents some difficulties for direct Roche lobe overflow. We sp...

  3. 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...

  4. 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 ...

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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.

  11. Detection limits of tidal-wetland sequences to identify variable rupture modes of megathrust earthquakes

    Science.gov (United States)

    Shennan, Ian; Garrett, Ed; Barlow, Natasha

    2016-10-01

    Recent paleoseismological studies question whether segment boundaries identified for 20th and 21st century great, >M8, earthquakes persist through multiple earthquake cycles or whether smaller segments with different boundaries rupture and cause significant hazards. The smaller segments may include some currently slipping rather than locked. In this review, we outline general principles regarding indicators of relative sea-level change in tidal wetlands and the conditions in which paleoseismic indicators must be distinct from those resulting from non-seismic processes. We present new evidence from sites across southcentral Alaska to illustrate different detection limits of paleoseismic indicators and consider alternative interpretations for marsh submergence and emergence. We compare predictions of coseismic uplift and subsidence derived from geophysical models of earthquakes with different rupture modes. The spatial patterns of agreement and misfits between model predictions and quantitative reconstructions of coseismic submergence and emergence suggest that no earthquake within the last 4000 years had a pattern of rupture the same as the Mw 9.2 Alaska earthquake in 1964. From the Alaska examples and research from other subduction zones we suggest that If we want to understand whether a megathrust ruptures in segments of variable length in different earthquakes, we need to be site-specific as to what sort of geological-based criteria eliminate the possibility of a particular rupture mode in different earthquakes. We conclude that coastal paleoseismological studies benefit from a methodological framework that employs rigorous evaluation of five essential criteria and a sixth which may be very robust but only occur at some sites: 1 - lateral extent of peat-mud or mud-peat couplets with sharp contacts; 2 - suddenness of submergence or emergence, and replicated within each site; 3 - amount of vertical motion, quantified with 95% error terms and replicated within each

  12. 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...

  13. 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...

  14. Transient changes in intercellular protein variability identify sources of noise in gene expression.

    Science.gov (United States)

    Singh, Abhyudai

    2014-11-01

    Protein levels differ considerably between otherwise identical cells, and these differences significantly affect biological function and phenotype. Previous work implicated various noise mechanisms that drive variability in protein copy numbers across an isogenic cell population. For example, transcriptional bursting of mRNAs has been shown to be a major source of noise in the expression of many genes. Additional expression variability, referred to as extrinsic noise, arises from intercellular variations in mRNA transcription and protein translation rates attributed to cell-to-cell differences in cell size, abundance of ribosomes, etc. We propose a method to determine the magnitude of different noise sources in a given gene of interest. The method relies on blocking transcription and measuring changes in protein copy number variability over time. Our results show that this signal has sufficient information to quantify both the extent of extrinsic noise and transcription bursting in gene expression. Moreover, if the mean mRNA count is known, then the relative contributions of transcription versus translation rate fluctuations to extrinsic noise can also be determined. In summary, our study provides an easy-to-implement method for characterizing noisy protein expression that complements existing techniques for studying stochastic dynamics of genetic circuits.

  15. 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.

  16. Using Multiple-Variable Matching to Identify Cultural Sources of Differential Item Functioning

    Science.gov (United States)

    Wu, Amery D.; Ercikan, Kadriye

    2006-01-01

    Identifying the sources of differential item functioning (DIF) in international assessments is very challenging, because such sources are often nebulous and intertwined. Even though researchers frequently focus on test translation and content area, few actually go beyond these factors to investigate other cultural sources of DIF. This article…

  17. 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…

  18. 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

  19. 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'…

  20. 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.

  1. 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...

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

    Energy Technology Data Exchange (ETDEWEB)

    Peter Jaffe; Herschel Rabitz

    2003-02-14

    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

  3. 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

  4. DETECTION OF ACCRETION X-RAYS FROM QS Vir: CATACLYSMIC OR A LOT OF HOT AIR?

    Energy Technology Data Exchange (ETDEWEB)

    Matranga, Marco; Drake, Jeremy J.; Kashyap, Vinay [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Steeghs, Danny, E-mail: mmatranga@cfa.harvard.edu [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom)

    2012-03-10

    An XMM-Newton observation of the nearby 'pre-cataclysmic' short-period (P{sub orb} = 3.62 hr) binary QS Vir (EC 13471-1258) revealed regular narrow X-ray eclipses when the white dwarf passed behind its M2-4 dwarf companion. The X-ray emission provides a clear signature of mass transfer and accretion onto the white dwarf. The low-resolution XMM-Newton EPIC spectra are consistent with a cooling flow model and indicate an accretion rate of M-dot = 1.7 Multiplication-Sign 10{sup -13} M{sub sun} yr{sup -1}. At 48 pc distant, QS Vir is then the second nearest accreting cataclysmic variable known, with one of the lowest accretion rates found to date for a non-magnetic system. To feed this accretion through a wind would require a wind mass-loss rate of M-dot {approx}2 Multiplication-Sign 10{sup -12} M{sub sun} yr{sup -1} if the accretion efficiency is of the order of 10%. Consideration of likely mass-loss rates for M dwarfs suggests this is improbably high and pure wind accretion unlikely. A lack of accretion disk signatures also presents some difficulties for direct Roche lobe overflow. We speculate that QS Vir is on the verge of Roche lobe overflow, and that the observed mass transfer could be supplemented by upward chromospheric flows on the M dwarf, analogous to spicules and mottles on the Sun, that escape the Roche surface to be subsequently swept up into the white dwarf Roche lobe. If so, QS Vir would be in a rare evolutionary phase lasting only a million years. The X-ray luminosity of the M dwarf estimated during primary eclipse is L{sub X} = 3 Multiplication-Sign 10{sup 28} erg s{sup -1}, which is consistent with that of rapidly rotating 'saturated' K and M dwarfs.

  5. 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 ...

  6. 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....

  7. 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_{\

  8. 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.

  9. Unraveling the complexity of the zoo community: identifying the variables related to conservation performance in zoological parks.

    Science.gov (United States)

    Fàbregas, María C; Guillén-Salazar, Federico; Garcés-Narro, Carlos

    2012-01-01

    Zoological parks make up a highly heterogeneous community. Ranging from small collections at shopping malls to highly developed bioparks, their contribution to conservation is expected to vary enormously. Although several studies have focused on assessing such contribution, the parameters used frequently do not apply when considering more modest zoos. The goals of this study are to determine, within the wide range of zoos, which type tend to fulfill the conservation mission of modern zoos and to identify the variables associated to their conservation performance. We used the requirements demanded by the European Community Zoos Directive 1999/22/EC, relating to the keeping of wild animals in zoological parks, to assess conservation performance in 72% of officially registered Spanish zoos. Sampled zoos were classified into groups according to their common characteristics, and then the variables related to how they met each of the Directive's requirements in the groups were assessed. We found that private zoological parks with large zoological collections, located within metropolitan areas, and members of a zoo association tended to fulfill the requirements. Being a member of a zoo association was the variable that better explained fulfillment of the requirements among the evaluated zoos. Data revealed that zoos not meeting any requirement were few, although those meeting all of them were not frequent. The requirement related to adequate record keeping showed the lowest level of fulfillment. We discuss the implications of our results and propose measures of change in order to promote the contribution of zoos to biodiversity conservation.

  10. 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.

  11. 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)

  12. A magnetic accretion switch in pre-cataclysmic binaries?

    CERN Document Server

    Drake, Jeremy J; Takei, Dai; Gaensicke, Boris

    2014-01-01

    We have investigated the mass accretion rate implied by published surface abundances of Si and C in the white dwarf component of the 3.62 hr period pre-cataclysmic binary and planet host candidate QS Vir (DA+M2-4). Diffusion timescales for gravitational settling imply $\\dot{M} \\sim 10^{-16}M_\\odot$ yr$^{-1}$ for the 1999 epoch of the observations, which is three orders of magnitude lower than measured from a 2006 {\\it XMM-Newton} observation. This is the first time that large accretion rate variations have been seen in a detached pre-CV. A third body in a 14 yr eccentric orbit suggested in a recent eclipse timing study is too distant to perturb the central binary sufficiently to influence accretion. A hypothetical coronal mass ejection just prior to the {\\it XMM-Newton} observation might explain the higher accretion rate, but the implied size and frequency of such events appear too great. We suggest accretion is most likely modulated by a magnetic cycle on the secondary acting as a wind "accretion switch", a ...

  13. 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.

  14. 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

  15. THE USE OF PRINCIPAL COMPONENT ANALYSIS IN IDENTIFYING AND INTEGRATING VARIABLES RELATED TO FORAGE QUALITY AND METHANE PRODUCTION

    Directory of Open Access Journals (Sweden)

    A. Jayanegara

    2014-10-01

    Full Text Available This research was aimed to explore the use of multivariate statistics i.e. principal componentanalysis (PCA in identifying and integrating variables related to forage quality and ruminal methaneproduction, and in classifying forage species into both characteristics. Seventeen plants were used as adatabase for the above mentioned purposes. Plant samples were determined for their chemicalcomposition, cumulative gas production (represents the nutrient degradation and methane productionafter 24 hours of fermentation period using the Hohenheim gas test. The results showed that the PCAcould clearly identify factors related to forage quality and methane production and separated them intodifferent principal components (PC. The obtained PC1 was related to methane production andsubstantially influenced positively by crude protein, NDF, ADF (positive, total phenols, total tannins,condensed tannins and tannin activity (negative. On the other hand, the obtained PC2 was related tocumulative gas production (forage quality and substantially influenced by crude protein (positive,NDF, ADF and condensed tannins (negative. Classification and screening of forages that have highquality and low methane production are possible using the PCA technique. Rhenum undulatum,Peltiphyllum peltatum and Rhus typhina were found to have such desired characteristics.

  16. 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.

  17. 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.

  18. Identifying environmental variables explaining genotype-by-environment interaction for body weight of rainbow trout (Onchorynchus mykiss): reaction norm and factor analytic models

    NARCIS (Netherlands)

    Sae-Lim, P.; Komen, J.; Kause, A.; Mulder, H.A.

    2014-01-01

    Background: Identifying the relevant environmental variables that cause GxE interaction is often difficult when they cannot be experimentally manipulated. Two statistical approaches can be applied to address this question. When data on candidate environmental variables are available, GxE interaction

  19. 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.

  20. 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

  1. 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...

  2. 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...

  3. The Time Domain Spectroscopic Survey: Variable Selection and Anticipated Results

    Science.gov (United States)

    Morganson, Eric; Green, Paul J.; Anderson, Scott F.; Ruan, John J.; Myers, Adam D.; Eracleous, Michael; Kelly, Brandon; Badenes, Carlos; Bañados, Eduardo; Blanton, Michael R.; Bershady, Matthew A.; Borissova, Jura; Nielsen Brandt, William; Burgett, William S.; Chambers, Kenneth; Draper, Peter W.; Davenport, James R. A.; Flewelling, Heather; Garnavich, Peter; Hawley, Suzanne L.; Hodapp, Klaus W.; Isler, Jedidah C.; Kaiser, Nick; Kinemuchi, Karen; Kudritzki, Rolf P.; Metcalfe, Nigel; Morgan, Jeffrey S.; Pâris, Isabelle; Parvizi, Mahmoud; Poleski, Radosław; Price, Paul A.; Salvato, Mara; Shanks, Tom; Schlafly, Eddie F.; Schneider, Donald P.; Shen, Yue; Stassun, Keivan; Tonry, John T.; Walter, Fabian; Waters, Chris Z.

    2015-06-01

    We present the selection algorithm and anticipated results for the Time Domain Spectroscopic Survey (TDSS). TDSS is an Sloan Digital Sky Survey (SDSS)-IV Extended Baryon Oscillation Spectroscopic Survey (eBOSS) subproject that will provide initial identification spectra of approximately 220,000 luminosity-variable objects (variable stars and active galactic nuclei across 7500 deg2 selected from a combination of SDSS and multi-epoch Pan-STARRS1 photometry. TDSS will be the largest spectroscopic survey to explicitly target variable objects, avoiding pre-selection on the basis of colors or detailed modeling of specific variability characteristics. Kernel Density Estimate analysis of our target population performed on SDSS Stripe 82 data suggests our target sample will be 95% pure (meaning 95% of objects we select have genuine luminosity variability of a few magnitudes or more). Our final spectroscopic sample will contain roughly 135,000 quasars and 85,000 stellar variables, approximately 4000 of which will be RR Lyrae stars which may be used as outer Milky Way probes. The variability-selected quasar population has a smoother redshift distribution than a color-selected sample, and variability measurements similar to those we develop here may be used to make more uniform quasar samples in large surveys. The stellar variable targets are distributed fairly uniformly across color space, indicating that TDSS will obtain spectra for a wide variety of stellar variables including pulsating variables, stars with significant chromospheric activity, cataclysmic variables, and eclipsing binaries. TDSS will serve as a pathfinder mission to identify and characterize the multitude of variable objects that will be detected photometrically in even larger variability surveys such as Large Synoptic Survey Telescope.

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

    NARCIS (Netherlands)

    T. Huysegoms; M. Snoeck; G. Dedene; A. Goderis; F. Stumpe

    2013-01-01

    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

  5. 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.

  6. Sagittal otolith size and shape variability to identify geographical intraspecific differences in three species of the genus Merluccius

    OpenAIRE

    Torres, G. J.; Lombarte, Antoni; Morales-nin, Beatriz

    2000-01-01

    A study was carried out on the morphology (size and shape) of the saccular otolith (sagitta) by means of image analysis on three species of the genus Merluccius (M. gayi, M. hubbsi and M. merluccius). By digitization of the sagittae, morphometry and outline (Fourier harmonic) as form descriptor measurements were obtained, that were subsequently analysed by means of multivariant methods, allowing the intraspecific variability to be quantified. The differences in the intraspecific sagittal otol...

  7. 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...

  8. Circumbinary Dust in Magnetic Cataclysmic Variables - Bright State of AM Her

    Science.gov (United States)

    Hoard, Donald; Brinkworth, Carolyn; Howell, Steve; Wachter, Stefanie

    2007-07-01

    Observations by the AAVSO during the past several days of the polar AM Herculis show that it may be leaving the "normal" faint state it has occupied during the past ~2 years, and becoming bright. We observed AM Her with IRAC during GO-3 as part of program 30249. That program also included two medium-impact TOO observations to be triggered to re-observe any target of 30249 that changed brightness state during GO-3 from whatever state it was in when its non-TOO observation for 30249 was made. Unfortunately, those TOOs expired at the end of June, at about the same time that AM Her first started to show an indication that it might be getting bright. So, we are requesting a DDT observation, for the same scientific reasons that the TOO observations were requested (and approved) for program 30249 (to be detailed in a follow-on email to the Spitzer Helpdesk). The target is visible to Spitzer until Dec 2007 - we request the DDT observation during IRAC-43 or IRAC-44, in case the high state is of short duration. Total AOR duration will be ~10 minutes. We have requested that the AAVSO alert its members to intensify observations of AM Her so we can confirm with certainty the rise to bright state within the next few days; in the meantime, please consider this TOO request and notify us if it would be approved. By then, we should know if the rise to bright state is real and should be observed.

  9. 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.

  10. 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.

  11. 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...

  12. K-Band Spectroscopy of (Pre-)Cataclysmic Variables: Are Some Donor Stars Really Carbon Poor?

    CERN Document Server

    Howell, Steve B; Szkody, Paula; Silvestri, Nicole M

    2010-01-01

    We present a new sample of $K$-band spectral observations for CVs: non-magnetic and magnetic as well as present day and pre CVs. The purpose of this diverse sample is to address the recent claim that the secondary stars in dwarf novae are carbon deficient, having become so through a far more evolved evolution than the current paradigm predicts. Our new observations, along with previous literature results, span a wide range of orbital period and CV type. In general, dwarf novae in which the secondary star is seen show weak to no CO absorption while polar and pre-CV donor stars appear to have normal CO absorption for their spectral type. However, this is not universal. The presence of normal looking CO absorption in the dwarf nova SS Aur and the hibernating CV QS Vir and a complete lack of CO absorption in the long period polar V1309 Ori cloud the issue. A summary of the literature pointing to non-solar abundances including enhanced NV/CIV ratios is presented. It appears that some CVs have non-solar abundance m...

  13. 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.

  14. 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.

  15. 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...

  16. The space density and X-ray luminosity function of non-magnetic cataclysmic variables

    CERN Document Server

    Pretorius, Magaretha L

    2011-01-01

    We combine two complete, X-ray flux-limited surveys, the ROSAT Bright Survey (RBS) and the ROSAT North Ecliptic Pole (NEP) survey, to measure the space density (\\rho) and X-ray luminosity function (\\Phi) of non-magnetic CVs. The combined survey has a flux limit of F_X \\ga 1.1 \\times 10^{-12} erg cm^{-2}s^{-1} over most of its solid angle of just over 2\\pi, but is as deep as \\simeq 10^{-14} erg cm^{-2}s^{-1} over a small area. The CV sample that we construct from these two surveys contains 20 non-magnetic systems. We carefully include all sources of statistical error in calculating \\rho and \\Phi by using Monte Carlo simulations; the most important uncertainty proves to be the often large errors in distances estimates. If we assume that the 20 CVs in the combined RBS and NEP survey sample are representative of the intrinsic population, the space density of non-magnetic CVs is 4^{+6}_{-2} \\times 10^{-6} pc^{-3}. We discuss the difficulty in measuring \\Phi in some detail---in order to account for biases in the me...

  17. 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...

  18. 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 $...

  19. 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,"…

  20. 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

  1. 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...

  2. 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

  3. 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.

  4. 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...

  5. Cladistic approaches to identifying determinants of variability in multifactorial phenotypes and the evolutionary significance of variation in the human genome.

    Science.gov (United States)

    Templeton, A R

    1996-01-01

    Genetic surveys based on detailed restriction site mapping or DNA sequencing allow one to identify many different classes of mutational change at the molecular level and to estimate the evolutionary history of the genetic variation (a haplotype tree). These two sources of information can be combined in a powerful fashion to test hypotheses about the evolutionary significance of genetic variation and to identify mutations that are associated with diseases. Hypotheses about selection on various classes of genetic variation can be tested by examining the distribution patterns of different mutational classes upon the haplotype tree. The power of this procedure can be enhanced if it is coupled with comparative data from other, closely related species. With respect to disease associations, all mutations that affect phenotypic variation in a population occurred at some point in the evolutionary history of the region of the gene containing the mutations. Even if this evolutionary history is estimated from mutations other than those causing phenotypic effects, the phenotypically important mutations are imbedded in this same evolutionary history. Hence, whole branches (clades) of the haplotype tree should display homogeneous phenotypic effects and this fact is utilized to search for phenotypic associations of haplotypes by using nested clades in a haplotype tree. This procedure has more power than alternatives that do not use evolutionary history, and it avoids several statistical and interpretative problems associated with single-marker analyses. All of these methods could be used more extensively if more human genetic surveys concentrated on greater genetic resolution in small DNA regions and included non-human apes.

  6. Variability in the performance of preventive services and in the degree of control of identified health problems: A primary care study protocol

    Directory of Open Access Journals (Sweden)

    Violan Concepció

    2008-08-01

    Full Text Available Abstract Background Preventive activities carried out in primary care have important variability that makes necessary to know which factors have an impact in order to establish future strategies for improvement. The present study has three objectives: 1 To describe the variability in the implementation of 7 preventive services (screening for smoking status, alcohol abuse, hypertension, hypercholesterolemia, obesity, influenza and tetanus immunization and to determine their related factors; 2 To describe the degree of control of 5 identified health problems (smoking, alcohol abuse, hypertension, hypercholesterolemia and obesity; 3 To calculate intraclass correlation coefficients. Design Multi-centered cross-sectional study of a randomised sample of primary health care teams from 3 regions of Spain designed to analyse variability and related factors of 7 selected preventive services in years 2006 and 2007. At the end of 2008, we will perform a cross-sectional study of a cohort of patients attended in 2006 or 2007 to asses the degree of control of 5 identified health problems. All subjects older than16 years assigned to a randomised sample of 22 computerized primary health care teams and attended during the study period are included in each region providing a sample with more than 850.000 subjects. The main outcome measures will be implementation of 7 preventive services and control of 5 identified health problems. Furthermore, there will be 3 levels of data collection: 1 Patient level (age, gender, morbidity, preventive services, attendance; 2 Health-care professional level (professional characteristics, years working at the team, workload; 3 Team level (characteristics, electronic clinical record system. Data will be transferred from electronic clinical records to a central database with prior encryption and dissociation of subject, professional and team identity. Global and regional analysis will be performed including standard analysis for

  7. Peak flow responses to landscape disturbances caused by the cataclysmic 1980 eruption of Mount St. Helens, Washington

    Science.gov (United States)

    Major, J.J.; Mark, L.E.

    2006-01-01

    Years of discharge measurements that precede and follow the cataclysmic 1980 eruption of Mount St. Helens, Washington, provide an exceptional opportunity to examine the responses of peak flows to abrupt, widespread, devastating landscape disturbance. Multiple basins surrounding Mount St. Helens (300-1300 km2 drainage areas) were variously disturbed by: (1) a debris avalanche that buried 60 km2 of valley; (2) a lateral volcanic blast and associated pyroclastic flow that destroyed 550 km2 of mature forest and blanketed the landscape with silt-capped lithic tephra; (3) debris flows that reamed riparian corridors and deposited tens to hundreds of centimeters of gravelly sand on valley floors; and (4) a Plinian tephra fall that blanketed areas proximal to the volcano with up to tens of centimeters of pumiceous silt, sand, and gravel. The spatially complex disturbances produced a variety of potentially compensating effects that interacted with and influenced hydrological responses. Changes to water transfer on hillslopes and to flow storage and routing along channels both enhanced and retarded runoff. Rapid post-eruption modifications of hillslope surface textures, adjustments of channel networks, and vegetation recovery, in conjunction with the complex nature of the eruptive impacts and strong seasonal variability in regional climate hindered a consistent or persistent shift in peak discharges. Overall, we detected a short-lived (5-10 yr) increase in the magnitudes of autumn and winter peak flows. In general, peak flows were larger, and moderate to large flows (>Q2yr) were more substantively affected than predicted by early modeling efforts. Proportional increases in the magnitudes of both small and large flows in basins subject to severe channel disturbances, but not in basins subject solely to hillslope disturbances, suggest that eruption-induced modifications to flow efficiency along alluvial channels that have very mobile beds differentially affected flows of

  8. Variable Star Network: World Center for Transient Object Astronomy and Variable Stars

    Science.gov (United States)

    Kato, Taichi; Uemura, Makoto; Ishioka, Ryoko; Nogami, Daisaku; Kunjaya, Chatief; Baba, Hajime; Yamaoka, Hitoshi

    2004-03-01

    Variable Star Network (VSNET) is a global professional-amateur network of researchers in variable stars and related objects, particularly in transient objects, such as cataclysmic variables, black-hole binaries, supernovae, and gamma-ray bursts. The VSNET has been playing a pioneering role in establishing the field of transient object astronomy, by effectively incorporating modern advances in observational astronomy and global electronic networks, as well as collaborative progress in theoretical astronomy and astronomical computing. The VSNET is now one of the best-featured global networks in this field of astronomy. We review the historical progress, design concept, associated technology, and a wealth of scientific achievements powered by VSNET.

  9. Factorial kriging and stepwise regression approach to identify environmental factors influencing spatial multi-scale variability of heavy metals in soils.

    Science.gov (United States)

    Lv, Jianshu; Liu, Yang; Zhang, Zulu; Dai, Jierui

    2013-10-15

    The knowledge about spatial variations of heavy metals in soils and their relationships with environmental factors is important for human impact assessment and soil management. Surface soils from Rizhao city, Eastern China with rapid urbanization and industrialization were analyzed for six key heavy metals and characterized by parent material and land use using GIS-based data. Factorial kriging analysis and stepwise multiple regression were applied to examine the scale-dependent relationships among heavy metals and to identify environmental factors affecting spatial variability at each spatial scale. Linear model of coregionalization fitting showed that spatial multi-scale variation of heavy metals in soils consisted of nugget effect, an exponential structure with the range of 12 km (short-range scale), as well as a spherical structure with the range of 36 km (long-range scale). The short-range variation of Cd, Pb and Zn were controlled by land use, with higher values in urban areas as well as cultivated land in mountain area, and were related to human influence; while parent material dominated the long structure variations of these elements. Spatial variations of Cr and Ni were associated with natural geochemical sources at short- and long-range scales. At both two scales, Hg dominated by land use, corresponded well to spatial distributions of urban areas, and was attributed to anthropic emissions and atmosphere deposition. PMID:23973471

  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. New variables in M5 (NGC 5904) and some identification corrections

    CERN Document Server

    Ferro, A Arellano; Giridhar, S; Luna, A; Muneer, S

    2015-01-01

    We report twelve variables not previously detected in the globular cluster M5 (NGC 5904); one SX Phe and eleven semi-regular variables (SR). Their identifications, equatorial coordinates, ephemerides, and light curves are given. Furthermore, we have explored the light curves of a group of stars whose variability has not been confirmed and that are marked as probable non- variables in the CVSGC. Finally, we offer detailed identifications for some of the known variables in crowded regions that were misidentified in previous studies. We shall also address the cases of the cataclysmic variable or U Gem type V101 and of the variable blue straggler V159.

  12. The OmegaWhite survey for Short-Period Variable Stars III: Follow-up Photometric and Spectroscopic Observations

    CERN Document Server

    Macfarlane, S A; Groot, P J; Ramsay, G; Toma, R; Motsoaledi, M; Crause, L A; Gilbank, D G; O'Donoghue, D; Potter, S B; Sickafoose, A A; van Gend, C; Worters, H L

    2016-01-01

    We present photometric and spectroscopic follow-up observations of short-period variables discovered in the OmegaWhite survey: a wide-field high-cadence g-band synoptic survey targeting the Galactic Plane. We have used fast photometry on the SAAO 1.0-m and 1.9-m telescopes to obtain light curves of 27 variables, and use these results to validate the period and amplitude estimates from the OmegaWhite processing pipeline. Furthermore, 57 sources (44 unique, 13 also with new light curves) were selected for spectroscopic follow-up using either the SAAO 1.9-m telescope or the Southern African Large Telescope. We find many of these variables have spectra which are consistent with being delta Scuti type pulsating stars. At higher amplitudes, we detect four possible pulsating white dwarf/subdwarf sources and an eclipsing cataclysmic variable. Due to their rarity, these targets are ideal candidates for detailed follow-up studies. From spectroscopy, we confirm the symbiotic binary star nature of two variables identifie...

  13. 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.

  14. 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

  15. iTREE: Long-term variability of tree growth in a changing environment - identifying physiological mechanisms using stable C and O isotopes in tree rings.

    Science.gov (United States)

    Siegwolf, R. T. W.; Buchmann, N.; Frank, D.; Joos, F.; Kahmen, A.; Treydte, K.; Leuenberger, M.; Saurer, M.

    2012-04-01

    Trees play are a critical role in the carbon cycle - their photosynthetic assimilation is one of the largest terrestrial carbon fluxes and their standing biomass represents the largest carbon pool of the terrestrial biosphere. Understanding how tree physiology and growth respond to long-term environmental change is pivotal to predict the magnitude and direction of the terrestrial carbon sink. iTREE is an interdisciplinary research framework to capitalize on synergies among leading dendroclimatologists, plant physiologists, isotope specialists, and global carbon cycle modelers with the objectives of reducing uncertainties related to tree/forest growth in the context of changing natural environments. Cross-cutting themes in our project are tree rings, stable isotopes, and mechanistic modelling. We will (i) establish a European network of tree-ring based isotope time-series to retrodict interannual to long-term tree physiological changes, (ii) conduct laboratory and field experiments to adapt a mechanistic isotope model to derive plant physiological variables from tree-ring isotopes, (iii) implement this model into a dynamic global vegetation model, and perform subsequent model-data validation exercises to refine model representation of plant physiological processes and (iv) attribute long-term variation in tree growth to plant physiological and environmental drivers, and identify how our refined knowledge revises predictions of the coupled carbon-cycle climate system. We will contribute to i) advanced quantifications of long-term variation in tree growth across Central Europe, ii) novel long-term information on key physiological processes that underlie variations in tree growth, and iii) improved carbon cycle models that can be employed to revise predictions of the coupled carbon-cycle climate system. Hence iTREE will significantly contribute towards a seamless understanding of the responses of terrestrial ecosystems to long-term environmental change, and ultimately

  16. 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...

  17. Coral Luminescence Identifies the Pacific Decadal Oscillation as a Primary Driver of River Runoff Variability Impacting the Southern Great Barrier Reef

    NARCIS (Netherlands)

    Rodriguez-Ramirez, A.; Grove, C.A.; Zinke, J.; Pandolfi, J.M.; Zhao, J.-X.

    2014-01-01

    The Pacific Decadal Oscillation (PDO) is a large-scale climatic phenomenon modulating ocean-atmosphere variability on decadal time scales. While precipitation and river flow variability in the Great Barrier Reef (GBR) catchments are sensitive to PDO phases, the extent to which the PDO influences cor

  18. 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.

  19. 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)

  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. 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.

  2. Compositional variability of ice-rafted debris in Heinrich layers 1 and 2 on the northwest European continental slope identified by environmental magnetic analyses

    Science.gov (United States)

    Walden, John; Wadsworth, Emilie; Austin, William E. N.; Peters, Clare; Scourse, James D.; Hall, Ian R.

    2007-02-01

    The composition of ice-rafted debris (IRD) within a sediment core from the European continental slope (core OMEX-2K; 49° 5 N, 13° 26 W) has been examined using environmental magnetic analyses. The data demonstrate compositional variability of the IRD within Heinrich layers 2 (H2) and 1 (H1) and these differences are most readily explained by changes in the contribution of different IRD sources to the core site. Some IRD within the main Heinrich layers show magnetic signatures that are similar to IRD derived from the Laurentide ice sheet found in cores from within the main North Atlantic IRD-belt. In contrast, other IRD-rich layers, both prior to and within the main Heinrich layers, demonstrate different magnetic behaviour, suggesting a contribution from a non-Laurentide sourced IRD, most likely derived from ice streams discharging from northeast Atlantic ice sheets such as the British and Fennoscandian ice sheets. These data are consistent with published compositional data from the same core and, given the rapid, highly sensitive and non-destructive nature of the method, suggest that environmental magnetic analysis has considerable potential for characterising IRD materials within Heinrich layers for the purposes of defining provenance. Copyright

  3. 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.

  4. Variable Star Network: World Center for Transient Object Astronomy and Variable Stars

    CERN Document Server

    Kato, T; Ishioka, R; Nogami, D; Kunjaya, C; Baba, H; Yamaoka, H

    2003-01-01

    Variable Star Network (VSNET, http://www.kusastro.kyoto-u.ac.jp/vsnet/) is a global professional-amateur network of researchers in variable stars and related objects, particularly in transient objects, such as cataclysmic variables, black hole binaries, supernovae and gamma-ray bursts. The VSNET has been playing a pioneering role in establishing the field of "transient object astronomy", by effectively incorporating modern advance in observational astronomy and global electronic network, as well as collaborative progress in theoretical astronomy and astronomical computing. The VSNET is now one of the best-featured global networks in this field of astronomy. We review on the historical progress, design concept, associated technology, and a wealth of scientific achievements powered by the VSNET.

  5. Variable stars with the Kepler space telescope

    CERN Document Server

    Molnár, László; Plachy, Emese

    2016-01-01

    The Kepler space telescope has revolutionised our knowledge about exoplanets and stars and is continuing to do so in the K2 mission. The exquisite photometric precision, together with the long, uninterrupted observations opened up a new way to investigate the structure and evolution of stars. Asteroseismology, the study of stellar oscillations, allowed us to investigate solar-like stars and to peer into the insides of red giants and massive stars. But many discoveries have been made about classical variable stars too, ranging from pulsators like Cepheids and RR Lyraes to eclipsing binary stars and cataclysmic variables, and even supernovae. In this review, which is far from an exhaustive summary of all results obtained with Kepler, we collected some of the most interesting discoveries, and ponder on the role for amateur observers in this golden era of stellar astrophysics.

  6. 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...

  7. Using Multivariate Statistical and Geostatistical Methods to Identify Spatial Variability of Trace Elements in Agricultural Soils in Dongguan City,Guangdong,China

    Institute of Scientific and Technical Information of China (English)

    Dou Lei; Zhou Yongzhang; Ma Jin; Li Yong; Cheng Qiuming; Xie Shuyun; Du Haiyan; You Yuanhang; Wan Hongfu

    2008-01-01

    Dongguan (东莞) City, located in the Pearl River Delta, South China, is famous for its rapid industrialization in the past 30 years. A total of 90 topsoil samples have been collected from agricultural fields, including vegetable and orchard soils in the city, and eight heavy metals (As, Cu, Cd,Cr, Hg, Ni, Pb, and Zn) and other items (pH values and organic matter) have been analyzed, to evaluate the influence of anthropie activities on the environmental quality of agricultural soils and to identify the spatial distribution of trace elements and possible sources of trace elements. The elements Hg, Pb, and Cd have accumulated remarkably here, incomparison with the soil background content of elements in Guangdong (广东) Province. Pollution is more serious in the western plain and the central region, which are heavily distributed with industries and rivers. Multivariate and geostatistical methods have been applied to differentiate the influences of natural processes and human activities on the pollution of heavy metals in topsoils in the study area. The results of cluster analysis (CA) and factor analysis (FA) show that Ni, Cr, Cu, Zn, and As are grouped in factor F1,Pb in F2, and Cd and Hg in F3, respectively. The spatial pattern of the three factors may be well demonstrated by geostatistical analysis. It is shown that the first factor could be considered as a natural source controlled by parent rocks. The second factor could be referred to as "industrial and traffic pollution sources". The source of the third factor is mainly controlled by long-term anthropic activities ,ad a consequence of agricultural fossil fuel consumption and atmospheric deposition.

  8. 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.

  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. 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.

  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. 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).

  13. 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.

  14. MyNewsFlash: A System for Near Real-Time Variable Star Monitoring and Alerts

    Science.gov (United States)

    Price, A.; Turner, R.; Malatesta, K.; Simonsen, M. A.

    2004-12-01

    MyNewsFlash is an automated and customizable system for distributing timely variable star data. It supplies near real-time reports to the user of the latest activity of a variable star or class of stars. The stars it monitors, the frequency of report delivery, the delivery format, and more features are all completely customizable so the reader receives only reports of information he or she wants and nothing more or less. In addition, manually-generated alerts called Special MyNewsFlashes are occasionally sent out with additional information on special or abnormal behavior of a variable star. MyNewsFlash evolved from the AAVSO News Flash, an electronic publication dedicated to outbursts of popular cataclysmic variable stars

  15. 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...

  16. 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 ...

  17. 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.

  18. ASCA Observations of the Dwarf Novae SS Cyg and VW Hyi And Observations of the Precessing Disk Cataclysmic Variable TV Col

    Science.gov (United States)

    Schlegel, E.; Swank, Jean (Technical Monitor)

    2001-01-01

    The observations for both SS Cyg and VW Hyi were to be scheduled as Targets of Opportunity jointly with other satellites. The VW Hyi observation was obtained jointly with EUVE during a superoutburst. The XTE data were initially processed, revealing no detection. However, the XTE team improved the instrumental background model and distributed it in July 1998. A further improvement was made in August 1999. The improved models allow a better background subtraction, thereby detecting previously un-detected sources.

  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. 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 ...

  1. 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...... 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...

  2. 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.

  3. 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

  4. 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...

  5. 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

  6. 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

  7. 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.

  8. MODELING SUPPLY CHAIN PERFORMANCE VARIABLES

    Directory of Open Access Journals (Sweden)

    Ashish Agarwal

    2005-01-01

    Full Text Available In order to understand the dynamic behavior of the variables that can play a major role in the performance improvement in a supply chain, a System Dynamics-based model is proposed. The model provides an effective framework for analyzing different variables affecting supply chain performance. Among different variables, a causal relationship among different variables has been identified. Variables emanating from performance measures such as gaps in customer satisfaction, cost minimization, lead-time reduction, service level improvement and quality improvement have been identified as goal-seeking loops. The proposed System Dynamics-based model analyzes the affect of dynamic behavior of variables for a period of 10 years on performance of case supply chain in auto business.

  9. 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.

  10. 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.)

  11. 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 ...

  12. 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

  13. 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...

  14. 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...

  15. 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.

  16. Metal alloy identifier

    Science.gov (United States)

    Riley, William D.; Brown, Jr., Robert D.

    1987-01-01

    To identify the composition of a metal alloy, sparks generated from the alloy are optically observed and spectrographically analyzed. The spectrographic data, in the form of a full-spectrum plot of intensity versus wavelength, provide the "signature" of the metal alloy. This signature can be compared with similar plots for alloys of known composition to establish the unknown composition by a positive match with a known alloy. An alternative method is to form intensity ratios for pairs of predetermined wavelengths within the observed spectrum and to then compare the values of such ratios with similar values for known alloy compositions, thereby to positively identify the unknown alloy composition.

  17. Conditional variable importance for random forests

    Directory of Open Access Journals (Sweden)

    Augustin Thomas

    2008-07-01

    Full Text Available Abstract Background Random forests are becoming increasingly popular in many scientific fields because they can cope with "small n large p" problems, complex interactions and even highly correlated predictor variables. Their variable importance measures have recently been suggested as screening tools for, e.g., gene expression studies. However, these variable importance measures show a bias towards correlated predictor variables. Results We identify two mechanisms responsible for this finding: (i A preference for the selection of correlated predictors in the tree building process and (ii an additional advantage for correlated predictor variables induced by the unconditional permutation scheme that is employed in the computation of the variable importance measure. Based on these considerations we develop a new, conditional permutation scheme for the computation of the variable importance measure. Conclusion The resulting conditional variable importance reflects the true impact of each predictor variable more reliably than the original marginal approach.

  18. 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...

  19. A Study of Stellar Photometric Variability Within the Central 4 pc of the Galactic Center with Infrared Image Subtraction

    CERN Document Server

    Peeples, Molly S; De Poy, D L

    2007-01-01

    We present a catalog of 110 variable stars within ~1' of Sgr A* based on image subtraction of near-infrared (H and K) photometry. Our images were obtained over 133 nights from 2000--2002 in H-band and over 134 nights from 2001--2002 in K-band; the typical FWHM is 1.4''. We match the catalog to other near-infrared, X-ray, and radio (i.e., maser) data, and we discuss some of the more interesting objects. The catalog includes 14 periodic sources, several known long-period variables and three new LPV candidates. We associate IRS 10* with OH, SiO, and H2O masers and a bright X-ray point source; this analysis suggests IRS 10* is an AGB star with an accreting companion. Among the approximately 90 newly discovered sources are a probable cataclysmic variable, a potential edge-on contact 84 day period eclipsing binary, and a possible 41 day period pulsating variable.

  20. Random Cell Identifiers Assignment

    Directory of Open Access Journals (Sweden)

    Robert Bestak

    2012-01-01

    Full Text Available Despite integration of advanced functions that enable Femto Access Points (FAPs to be deployed in a plug-and-play manner, the femtocell concept still cause several opened issues to be resolved. One of them represents an assignment of Physical Cell Identifiers (PCIs to FAPs. This paper analyses a random based assignment algorithm in LTE systems operating in diverse femtocell scenarios. The performance of the algorithm is evaluated by comparing the number of confusions for various femtocell densities, PCI ranges and knowledge of vicinity. Simulation results show that better knowledge of vicinity can significantly reduce the number of confusions events.

  1. Cardinality-dependent Variability in Orthogonal Variability Models

    DEFF Research Database (Denmark)

    Mærsk-Møller, Hans Martin; Jørgensen, Bo Nørregaard

    2012-01-01

    by the specific variants being bound, but by their sheer numbers. This paper contributes with an extension to the meta-model underlying the OVM notation, suggesting a notation for the new type of dependency and shows its applicability. The specific case, which initially required this extension, will work......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...

  2. 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...

  3. 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...

  4. 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...

  5. Decomposing global crop yield variability

    Science.gov (United States)

    Ben-Ari, Tamara; Makowski, David

    2014-11-01

    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

  6. 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

  7. 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...

  8. Scoring ordinal variables for constructing composite indicators

    Directory of Open Access Journals (Sweden)

    Marica Manisera

    2013-05-01

    Full Text Available In order to provide composite indicators of latent variables, for example of customer satisfaction, it is opportune to identify the structure of the latent variable, in terms of the assignment of items to the subscales defining the latent variable. Adopting the reflective model, the impact of four different methods of scoring ordinal variables on the identification of the true structure of latent variables is investigated. A simulation study composed of 5 steps is conducted: (1 simulation of population data with continuous variables measuring a two-dimensional latent variable with known structure; (2 draw of a number of random samples; (3 discretization of the continuous variables according to different distributional forms; (4 quantification of the ordinal variables obtained in step (3 according to different methods; (5 construction of composite indicators and verification of the correct assignment of variables to subscales by the multiple group method and the factor analysis. Results show that the considered scoring methods have similar performances in assigning items to subscales, and that, when the latent variable is multinormal, the distributional form of the observed ordinal variables is not determinant in suggesting the best scoring method to use.

  9. 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.

  10. 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.

  11. 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 ...

  12. 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...

  13. Variability as an Operant?

    Science.gov (United States)

    Holth, Per

    2012-01-01

    A series of experiments on operant variability by Neuringer and colleagues (e.g., Neuringer, 1986, 2002; Page & Neuringer, 1985) have been repeatedly cited as showing that behavioral variability can be reinforced by making reinforcement contingent on it. They showed that the degree of variability in pigeons' eight-peck sequences, as measured by U…

  14. 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

  15. 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.

  16. 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).

  17. 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.

  18. Geochemical and isotopic insights into the assembly, evolution and disruption of a magmatic plumbing system before and after a cataclysmic caldera-collapse eruption at Ischia volcano (Italy)

    Science.gov (United States)

    Brown, R. J.; Civetta, L.; Arienzo, I.; D'Antonio, M.; Moretti, R.; Orsi, G.; Tomlinson, E. L.; Albert, P. G.; Menzies, M. A.

    2014-09-01

    New geochemical and isotopic data on volcanic rocks spanning the period ~75-50 ka BP on Ischia volcano, Italy, shed light on the evolution of the magmatic system before and after the catastrophic, caldera-forming Monte Epomeo Green Tuff (MEGT) eruption. Volcanic activity during this period was influenced by a large, composite and differentiating magmatic system, replenished several times with isotopically distinct magmas of deep provenance. Chemical and isotopic variations highlight that the pre-MEGT eruptions were fed by trachytic/phonolitic magmas from an isotopically zoned reservoir that were poorly enriched in radiogenic Sr and became progressively less radiogenic with time. Just prior to the MEGT eruption, the magmatic system was recharged by an isotopically distinct magma, relatively more enriched in radiogenic Sr with respect to the previously erupted magmas. This second magma initially fed several SubPlinian explosive eruptions and later supplied the climactic, phonolitic-to-trachytic MEGT eruption(s). Isotopic data, together with erupted volume estimations obtained for MEGT eruption(s), indicate that >5-10 km3 of this relatively enriched magma had accumulated in the Ischia plumbing system. Geochemical modelling indicates that it accumulated at shallow depths (4-6 km), over a period of ca. 20 ka. After the MEGT eruption, volcanic activity was fed by a new batch of less differentiated (trachyte-latite) magma that was slightly less enriched in radiogenic Sr. The geochemical and Sr-Nd-isotopic variations through time reflect the upward flux of isotopically distinct magma batches, variably contaminated by Hercynian crust at 8-12 km depth. The deep-sourced latitic to trachytic magmas stalled at shallow depths (4-6 km depth), differentiated to phonolite through crystal fractionation and assimilation of a feldspar-rich mush, or ascended directly to the surface and erupted.

  19. What is Optimum Variability?

    Science.gov (United States)

    Schuldberg, David

    2015-10-01

    Guastello (2015a) opened the call for articles for this issue with Goldberger (1991) and colleagues' findings of chaotic variability in healthy heart rate, noting, 'the principle of healthy variability has extended to other biomedical and psychological phenomena.' He suggests a dialectical underpinning for optimal variability involving 'a combination of the minimum entropy or free energy principle that pushes in a downward direction, and Ashby's Law of Requisite Variety that pushes in an upward direction.' Each of the papers in this issue addresses optimal variability across a variety of health-related areas. The present article surveys these seven papers in relation to five conceptual questions about optimal variability: (a) Is variability a positive or a negative, and how are positive things related to health? (b) How shall we define and measure variability? (c) What constitutes an optimum, and how do we locate one? (d) What is the relationship between optimum variability and health? Finally, it touches on (e) What are underlying principles and phenomena behind healthy variability, and can they inform our vocabulary for health? The paper concludes by discussing practical approaches to dealing with optimization. PMID:26375940

  20. The nebular variables

    CERN Document Server

    Glasby, John S

    1974-01-01

    The Nebular Variables focuses on the nebular variables and their characteristics. Discussions are organized by type of nebular variable, namely, RW Aurigae stars, T Orionis stars, T Tauri stars, and peculiar nebular objects. Topics range from light variations of the stars to their spectroscopic and physical characteristics, spatial distribution, interaction with nebulosity, and evolutionary features. This volume is divided into four sections and consists of 25 chapters, the first of which provides general information on nebular variables, including their stellar associations and their classifi

  1. 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.

  2. 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...

  3. Identifying PHM market and network opportunities.

    Science.gov (United States)

    Grube, Mark E; Krishnaswamy, Anand; Poziemski, John; York, Robert W

    2015-11-01

    Two key processes for healthcare organizations seeking to assume a financially sustainable role in population health management (PHM), after laying the groundwork for the effort, are to identify potential PHM market opportunities and determine the scope of the PHM network. Key variables organizations should consider with respect to market opportunities include the patient population, the overall insurance/employer market, and available types of insurance products. Regarding the network's scope, organizations should consider both traditional strategic criteria for a viable network and at least five additional criteria: network essentiality and PHM care continuum, network adequacy, service distribution right-sizing, network growth strategy, and organizational agility.

  4. Variables influencing the frictional behaviour of in vivo human skin

    NARCIS (Netherlands)

    Veijgen, N.K.; Masen, M.A.; Heide, van der E.

    2013-01-01

    In the past decades, skin friction research has focused on determining which variables are important to affect the frictional behaviour of in vivo human skin. Until now, there is still limited knowledge on these variables. This study has used a large dataset to identify the effect of variables on t

  5. Variables influencing the frictional behaviour of in vivo human skin

    NARCIS (Netherlands)

    Veijgen, N.K.; Masen, M.A.; Heide, E. van der

    2013-01-01

    In the past decades, skin friction research has focused on determining which variables are important to affect the frictional behaviour of in vivo human skin. Until now, there is still limited knowledge on these variables.This study has used a large dataset to identify the effect of variables on the

  6. 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.

  7. 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

  8. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Qian, S.-B.; Li, L.-J.; Wang, S.-M.; He, J.-J.; Zhou, X.; Jiang, L.-Q., E-mail: qsb@ynao.ac.cn [Yunnan Observatories, Chinese Academy of Sciences (CAS), P.O. Box 110, 650011 Kunming (China)

    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{sub 2}sini∼0.45(±0.03) M{sub ⊙}). 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.

  10. 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.

  11. 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.

  12. Eternity Variables to Simulate Specifications

    NARCIS (Netherlands)

    Hesselink, WH; Boiten, EA; Moller, B

    2002-01-01

    Simulation of specifications is introduced as a unification and generalization of refinement mappings, history variables, forward simulations, prophecy variables, and backward simulations. Eternity variables are introduced as a more powerful alternative for prophecy variables and backward simulation

  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. 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

  16. 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.

  17. 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.

  18. 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...

  19. 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...

  20. 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 ...

  1. 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.

  2. New criteria to identify spectrum

    DEFF Research Database (Denmark)

    Jensen, Arne; Krishna, M.

    2005-01-01

    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....

  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. 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.

  5. 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...

  6. 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.

  7. 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

  8. 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...... impact in software production. As is also apparent from the call for papers these perspectives focus on qualities such as reuse, adaptability, and maintainability....

  9. 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)

  10. 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.

  11. 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.

  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. 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)

  14. On the Identifiability of the Post-Nonlinear Causal Model

    CERN Document Server

    Zhang, Kun

    2012-01-01

    By taking into account the nonlinear effect of the cause, the inner noise effect, and the measurement distortion effect in the observed variables, the post-nonlinear (PNL) causal model has demonstrated its excellent performance in distinguishing the cause from effect. However, its identifiability has not been properly addressed, and how to apply it in the case of more than two variables is also a problem. In this paper, we conduct a systematic investigation on its identifiability in the two-variable case. We show that this model is identifiable in most cases; by enumerating all possible situations in which the model is not identifiable, we provide sufficient conditions for its identifiability. Simulations are given to support the theoretical results. Moreover, in the case of more than two variables, we show that the whole causal structure can be found by applying the PNL causal model to each structure in the Markov equivalent class and testing if the disturbance is independent of the direct causes for each va...

  15. 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 ...

  16. Individual Identifiability Predicts Population Identifiability in Forensic Microsatellite Markers.

    Science.gov (United States)

    Algee-Hewitt, Bridget F B; Edge, Michael D; Kim, Jaehee; Li, Jun Z; Rosenberg, Noah A

    2016-04-01

    Highly polymorphic genetic markers with significant potential for distinguishing individual identity are used as a standard tool in forensic testing [1, 2]. At the same time, population-genetic studies have suggested that genetically diverse markers with high individual identifiability also confer information about genetic ancestry [3-6]. The dual influence of polymorphism levels on ancestry inference and forensic desirability suggests that forensically useful marker sets with high levels of individual identifiability might also possess substantial ancestry information. We study a standard forensic marker set-the 13 CODIS loci used in the United States and elsewhere [2, 7-9]-together with 779 additional microsatellites [10], using direct population structure inference to test whether markers with substantial individual identifiability also produce considerable information about ancestry. Despite having been selected for individual identification and not for ancestry inference [11], the CODIS markers generate nontrivial model-based clustering patterns similar to those of other sets of 13 tetranucleotide microsatellites. Although the CODIS markers have relatively low values of the F(ST) divergence statistic, their high heterozygosities produce greater ancestry inference potential than is possessed by less heterozygous marker sets. More generally, we observe that marker sets with greater individual identifiability also tend toward greater population identifiability. We conclude that population identifiability regularly follows as a byproduct of the use of highly polymorphic forensic markers. Our findings have implications for the design of new forensic marker sets and for evaluations of the extent to which individual characteristics beyond identification might be predicted from current and future forensic data.

  17. 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.

  18. Validation and Variability

    DEFF Research Database (Denmark)

    Carusi, Annamaria

    2014-01-01

    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...... 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......-facing modelling. I claim that it shows the extent to which experiment-facing modelling and validation require the establishment of criteria for comparing models and experiments that enable them to be linked together. These 'grounds of comparability' are the broad framework in which validation experiments...

  19. 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.

  20. 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)

  1. 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...

  2. 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

  3. Terrestrial Carbon Cycle Variability

    Science.gov (United States)

    Baldocchi, Dennis; Ryu, Youngryel; Keenan, Trevor

    2016-01-01

    A growing literature is reporting on how the terrestrial carbon cycle is experiencing year-to-year variability because of climate anomalies and trends caused by global change. As CO 2 concentration records in the atmosphere exceed 50 years and as satellite records reach over 30 years in length, we are becoming better able to address carbon cycle variability and trends. Here we review how variable the carbon cycle is, how large the trends in its gross and net fluxes are, and how well the signal can be separated from noise. We explore mechanisms that explain year-to-year variability and trends by deconstructing the global carbon budget. The CO 2 concentration record is detecting a significant increase in the seasonal amplitude between 1958 and now. Inferential methods provide a variety of explanations for this result, but a conclusive attribution remains elusive. Scientists have reported that this trend is a consequence of the greening of the biosphere, stronger northern latitude photosynthesis, more photosynthesis by semi-arid ecosystems, agriculture and the green revolution, tropical temperature anomalies, or increased winter respiration. At the global scale, variability in the terrestrial carbon cycle can be due to changes in constituent fluxes, gross primary productivity, plant respiration and heterotrophic (microbial) respiration, and losses due to fire, land use change, soil erosion, or harvesting. It remains controversial whether or not there is a significant trend in global primary productivity (due to rising CO 2, temperature, nitrogen deposition, changing land use, and preponderance of wet and dry regions). The degree to which year-to-year variability in temperature and precipitation anomalies affect global primary productivity also remains uncertain. For perspective, interannual variability in global gross primary productivity is relatively small (on the order of 2 Pg-C y -1) with respect to a large and uncertain background (123 +/- 4 Pg-C y -1), and

  4. 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

  5. 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

  6. 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...

  7. 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.

  8. 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.

  9. 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 ...

  10. 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…

  11. 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…

  12. 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...

  13. Variability and component composition

    NARCIS (Netherlands)

    Storm, T. van der

    2004-01-01

    In component-based product populations, feature models have to be described at the component level to be able to benefit from a product family approach. As a consequence, composition of components becomes very complex. We describe how component-level variability can be managed in the face of compone

  14. Variable rate irrigation

    Science.gov (United States)

    Systems are available to producers to make variable-rate applications of defoliants, fertilizer, lime, pesticides, plant growth regulators, and seed. These systems could potentially offer cost savings to a producer; however, the full potential of the benefits and savings cannot be realized if water ...

  15. 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

  16. 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.

  17. 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...

  18. 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. ...

  19. 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.

  20. 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…

  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. Use of Photogrammetry and Biomechanical Gait analysis to Identify Individuals

    DEFF Research Database (Denmark)

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

    found. Especially the variables located in the frontal plane are interesting due to large inter-individual differences in time course patterns. The variables with high recognition rates seem preferable for use in forensic gait analysis and as input variables to waveform analysis techniques...... such as principal component analysis resulting in marginal scores, which are difficult to interpret individually. Finally, a new gait model is presented based on functional principal component analysis with potentials for detecting individual gait patterns where time course patterns can be marginally interpreted......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...

  4. 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

  5. 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.

  6. 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...

  7. 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 ...

  8. 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.

  9. 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

  10. 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...

  11. 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.

  12. On Complex Random Variables

    Directory of Open Access Journals (Sweden)

    Anwer Khurshid

    2012-07-01

    Full Text Available Normal 0 false false false EN-US X-NONE X-NONE In this paper, it is shown that a complex multivariate random variable  is a complex multivariate normal random variable of dimensionality if and only if all nondegenerate complex linear combinations of  have a complex univariate normal distribution. The characteristic function of  has been derived, and simpler forms of some theorems have been given using this characterization theorem without assuming that the variance-covariance matrix of the vector  is Hermitian positive definite. Marginal distributions of  have been given. In addition, a complex multivariate t-distribution has been defined and the density derived. A characterization of the complex multivariate t-distribution is given. A few possible uses of this distribution have been suggested.

  13. 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.

  14. Classicalization of Quantum Variables

    CERN Document Server

    Koide, T

    2014-01-01

    A systematic procedure to extract classical degrees of freedom in quantum mechanics is formulated using the stochastic variational method. With this classicalization, a hybrid model constructed from quantum and classical variables (quantum-classical hybrids) is derived systematically. In this procedure, conservation laws such as energy are maintained, and Eherefest`s theorem is still satisfied with modification. The criterion for the applicability of quantum-classical hybrids is also investigated.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Revisiting the concept of identifiable neurons.

    Science.gov (United States)

    Bullock, T H

    2000-05-01

    Although eutely in nematodes was known, giant neurons in several taxa and unique motor neurons to leg muscles in decapod crustaceans, the idea that many animals have many identifiable neurons with relatively consistent dynamical properties and connections was only slowly established in the late 1960s and early 1970s. This has to be one of the important quiet revolutions in neurobiology. It stimulated a vast acquisition of specific information and led to some euphoria in the degree and pace of understanding activity of nervous systems and consequent behavior in terms of neuronal connections and properties. Some implications, problems and opportunities for new discovery are developed. The distribution of identifiable neurons among taxa and parts of the nervous system is not yet satisfactorily known. Their evolution may have been a case of several independent inventions. The degree of consistency has been quantified only in a few examples and the plasticity is little known. Identified neurons imply identifiable circuits but whether this extends to discrete systems, functionally definable, seems likely to have several answers in different animals or sites. Very limited attempts have been made to extend the concept to cases of two or ten or a hundred fully equivalent neurons, on all kinds of criteria. These attempts suggest a much smaller redundancy and vaster number of types of neurons than hitherto believed. Theory as well as empirical information has not yet interpreted the range of systems from those with small sets of relatively reliable neurons to those with large numbers of parallel, partially redundant units. The now classical notion of local circuits has to be extended to take account of and find roles for the plethora of integrative variables, of evidence for neural processing independent of spikes and classical synapses, of spatial configurations of terminal arbors and dendritic geometry, of modulators and transmitters, degrees of rhythmicity (regularity

  20. 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.

  1. 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

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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 ...

  7. 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...

  8. 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

  9. 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

  10. 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....... 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...

  11. 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...

  12. 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…

  13. 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...

  14. Variable speed generator technology options for wind turbine generators

    Science.gov (United States)

    Lipo, T. A.

    1995-01-01

    The electrical system options for variable speed operation of a wind turbine generator are treated in this paper. The key operating characteristics of each system are discussed and the major advantages and disadvantages of each are identified

  15. Differentiating Normal Variability from Inconsistency in Children's Speech: Normative Data

    Science.gov (United States)

    Holm, Alison; Crosbie, Sharon; Dodd, Barbara

    2007-01-01

    Background: In young, typically developing children, some word production variability is expected, but highly inconsistent speech is considered a clinical marker for disorder. Speech-language pathologists need to identify variability versus inconsistency, yet these terms are not clearly differentiated. Not only is it important to identify…

  16. Variables that Discriminate Bulimic from Nonbulimic Adolescent Females.

    Science.gov (United States)

    Post, G.; Crowther, J. H.

    1985-01-01

    A discriminant function analysis identified variables that significantly differentiated bulimic (N=71) from nonbulimic (N=71) adolescent females within a high school setting. These variables included disturbed eating attitudes, negative perception of weight and body image, depressive symptomatology, and alcohol use. Implications for the etiology…

  17. 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…

  18. 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.

  19. How normal is variable, or how variable is normal?

    Science.gov (United States)

    Touwen, B C

    1993-09-01

    Variability is an important property of the central nervous system, and it shows characteristic changes during infancy and childhood. The large amount of variations in the performance of sensomotor functions in infancy is called indiscriminate or primary variability. During toddling age the child develops the capacity to select adaptive variations, and then automatize them: secondary or adaptive variability. The latter is required for the development of motor skills during later preschool age and school age. The question 'How normal is variable or how variable is normal is a wrong question, as any form of variability must be interpreted according to its extent, type and age adequacy. PMID:8275868

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. Chatter Prediction for Variable Pitch and Variable Helix Milling

    Directory of Open Access Journals (Sweden)

    Yong Wang

    2015-01-01

    Full Text Available 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 predicted and observed performance of variable pitch and variable helix against uniform pitch and uniform helix milling is presented. It is shown that variable pitch and variable helix milling can obtain larger stable cutting area than uniform pitch and uniform helix milling. Thus, it is concluded that variable pitch and variable helix milling are an effective way for suppressing chatter.

  5. 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...

  6. Do psychological variables affect early surgical recovery?

    Directory of Open Access Journals (Sweden)

    Michael N Mavros

    Full Text Available 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 16 eligible studies, 15 of which reported a significant association between at least one psychological variable or intervention and an early postoperative outcome. However, most studies also reported psychological factors not influencing surgical recovery and there was significant heterogeneity across the studies. Overall, trait and state anxiety, state anger, active coping, subclinical depression, and intramarital hostility appeared to complicate recovery, while dispositional optimism, religiousness, anger control, low pain expectations, and external locus of control seemed to promote healing. Psychological interventions (guided relaxation, couple support visit, and psychiatric interview also appeared to favor recovery. Psychological factors unrelated to surgical outcomes included loneliness, perceived social support, anger expression, and trait anger. CONCLUSION: Although the heterogeneity of the available evidence precludes any safe conclusions, psychological variables appear to be associated with early surgical recovery; this association could bear important implications for clinical practice. Large clinical trials and further analyses are needed to precisely evaluate the contribution of psychology in surgical recovery.

  7. 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

  8. Identifying sites for elk restoration in Arkansas

    Science.gov (United States)

    Telesco, R.L.; Van Manen, F.T.; Clark, J.D.; Cartwright, Michael E.

    2007-01-01

    We used spatial data to identify potential areas for elk (Cervus elaphus) restoration in Arkansas. To assess habitat, we used locations of 239 elk groups collected from helicopter surveys in the Buffalo National River area of northwestern Arkansas, USA, from 1992 to 2002. We calculated the Mahalanobis distance (D2) statistic based on the relationship between those elk-group locations and a suite of 9 landscape variables to evaluate winter habitat in Arkansas. We tested model performance in the Buffalo National River area by comparing the D2 values of pixels representing areas with and without elk pellets along 19 fixed-width transects surveyed in March 2002. Pixels with elk scat had lower D2 values than pixels in which we found no pellets (logistic regression: Wald χ2 = 24.37, P cover, gently sloping ridge tops and valleys, low human population density, and low road densities. To assess the potential for elk–human conflicts in Arkansas, we used the analytical hierarchy process to rank the importance of 8 criteria based on expert opinion from biologists involved in elk management. The biologists ranked availability of forage on public lands as having the strongest influence on the potential for elk–human conflict (33%), followed by human population growth rate (22%) and the amount of private land in row crops (18%). We then applied those rankings in a weighted linear summation to map the relative potential for elk–human conflict. Finally, we used white-tailed deer (Odocoileus virginianus) densities to identify areas where success of elk restoration may be hampered due to meningeal worm (Parelaphostrongylus tenuis) transmission. By combining results of the 3 spatial data layers (i.e., habitat model, elk–human conflict model, deer density), our model indicated that restoration sites located in west-central and north-central Arkansas were most favorable for reintroduction.

  9. 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...

  10. 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...

  11. Bayesian Variable Selection via Particle Stochastic Search.

    Science.gov (United States)

    Shi, Minghui; Dunson, David B

    2011-02-01

    We focus on Bayesian variable selection in regression models. One challenge is to search the huge model space adequately, while identifying high posterior probability regions. In the past decades, the main focus has been on the use of Markov chain Monte Carlo (MCMC) algorithms for these purposes. In this article, we propose a new computational approach based on sequential Monte Carlo (SMC), which we refer to as particle stochastic search (PSS). We illustrate PSS through applications to linear regression and probit models.

  12. 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.’

  13. Identifying barriers to billing compliance.

    Science.gov (United States)

    Lorence, Daniel P; Ibrahim, Ibrahim Awad

    2003-01-01

    Programs designed toward the control of health care fraud are leading to increasingly aggressive enforcement and prosecutorial efforts by federal regulators, related to over-reimbursement for service providers. Greater penalties for fraudulent practices have been touted as an effective deterrent to practices that encourage, or fail to prevent, incorrect claims for reimbursement. In such a context, this study sought to examine the extent of compliance management barriers through a national survey of all accredited US health information managers, examining likely barriers to payment of health care claims. Using data from a series of surveys on the stated compliance actions of more than 16,000 health care managers, we find that the publication and dissemination of compliance enforcement regulations had a significant effect on the reduction of fraud. Results further suggest that significant non-adoption of proper billing compliance measures continues to occur, despite the existence of counter-fraud prosecution risk designed to enforce proper compliance. Finally, we identify benchmarks of compliance management and show how they vary across demographic, practice setting, and market characteristics. We find significant variation in influence across practice settings and managed care markets. While greater publicity related to proper billing procedures generally leads to greater compliance awareness, this trend may have created pockets of "institutional non-compliance," which result in an increase in the prevalence of non-compliant management actions. As a more general proposition, we find that it is not sufficient to consider compliance actions independent of institutional or industry-wide influences. PMID:12967244

  14. Gait Variability and Multiple Sclerosis

    Directory of Open Access Journals (Sweden)

    Michael J. Socie

    2013-01-01

    Full Text Available Gait variability, that is, fluctuations in movement during walking, is an indicator of walking function and has been associated with various adverse outcomes such as falls. In this paper, current research concerning gait variability in persons with multiple sclerosis (MS is discussed. It is well established that persons with MS have greater gait variability compared to age and gender matched controls without MS. The reasons for the increase in gait variability are not completely understood. Evidence indicates that disability level, assistive device use, attentional requirement, and fatigue are related to gait variability in persons with MS. Future research should address the time-evolving structure (i.e., temporal characteristics of gait variability, the clinical importance of gait variability, and underlying mechanisms that drive gait variability in individuals with MS.

  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. Variable speed controller

    Science.gov (United States)

    Estes, Christa; Spiggle, Charles; Swift, Shannon; Vangeffen, Stephen; Younger, Frank

    1992-01-01

    This report details a new design for a variable speed controller which can be used to operate lunar machinery without the astronaut using his or her upper body. In order to demonstrate the design, a treadle for an industrial sewing machine was redesigned to be used by a standing operator. Since the invention of an electrically powered sewing machine, the operator has been seated. Today, companies are switching from sit down to stand up operation involving modular stations. The old treadle worked well with a sitting operator, but problems have been found when trying to use the same treadle with a standing operator. Emphasis is placed on the ease of use by the operator along with the ergonomics involved. Included with the design analysis are suggestions for possible uses for the speed controller in other applications.

  18. 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...

  19. DNA Microarrays for Identifying Fishes

    Science.gov (United States)

    Nölte, M.; Weber, H.; Silkenbeumer, N.; Hjörleifsdottir, S.; Hreggvidsson, G. O.; Marteinsson, V.; Kappel, K.; Planes, S.; Tinti, F.; Magoulas, A.; Garcia Vazquez, E.; Turan, C.; Hervet, C.; Campo Falgueras, D.; Antoniou, A.; Landi, M.; Blohm, D.

    2008-01-01

    In many cases marine organisms and especially their diverse developmental stages are difficult to identify by morphological characters. DNA-based identification methods offer an analytically powerful addition or even an alternative. In this study, a DNA microarray has been developed to be able to investigate its potential as a tool for the identification of fish species from European seas based on mitochondrial 16S rDNA sequences. Eleven commercially important fish species were selected for a first prototype. Oligonucleotide probes were designed based on the 16S rDNA sequences obtained from 230 individuals of 27 fish species. In addition, more than 1200 sequences of 380 species served as sequence background against which the specificity of the probes was tested in silico. Single target hybridisations with Cy5-labelled, PCR-amplified 16S rDNA fragments from each of the 11 species on microarrays containing the complete set of probes confirmed their suitability. True-positive, fluorescence signals obtained were at least one order of magnitude stronger than false-positive cross-hybridisations. Single nontarget hybridisations resulted in cross-hybridisation signals at approximately 27% of the cases tested, but all of them were at least one order of magnitude lower than true-positive signals. This study demonstrates that the 16S rDNA gene is suitable for designing oligonucleotide probes, which can be used to differentiate 11 fish species. These data are a solid basis for the second step to create a “Fish Chip” for approximately 50 fish species relevant in marine environmental and fisheries research, as well as control of fisheries products. PMID:18270778

  20. 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.

  1. 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…

  2. 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....

  3. 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.

  4. Rainfall variability modelling in Rwanda

    Science.gov (United States)

    Nduwayezu, E.; Kanevski, M.; Jaboyedoff, M.

    2012-04-01

    Support to climate change adaptation is a priority in many International Organisations meetings. But is the international approach for adaptation appropriate with field reality in developing countries? In Rwanda, the main problems will be heavy rain and/or long dry season. Four rainfall seasons have been identified, corresponding to the four thermal Earth ones in the south hemisphere: the normal season (summer), the rainy season (autumn), the dry season (winter) and the normo-rainy season (spring). The spatial rainfall decreasing from West to East, especially in October (spring) and February (summer) suggests an «Atlantic monsoon influence» while the homogeneous spatial rainfall distribution suggests an «Inter-tropical front » mechanism. The torrential rainfall that occurs every year in Rwanda disturbs the circulation for many days, damages the houses and, more seriously, causes heavy losses of people. All districts are affected by bad weather (heavy rain) but the costs of such events are the highest in mountains districts. The objective of the current research is to proceed to an evaluation of the potential rainfall risk by applying advanced geospatial modelling tools in Rwanda: geostatistical predictions and simulations, machine learning algorithm (different types of neural networks) and GIS. The research will include rainfalls variability mapping and probabilistic analyses of extreme events.

  5. 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

  6. Deciphering The Hot Components in Symbiotic Variables: A Brave New Frontier

    Science.gov (United States)

    Sion, Edward

    We propose to investigate the physical properties of the hot components of symbiotic variable stars. They are binary star systems consisting of a red giant and a white dwarf (WD) orbiting each other close enough to interact. Material from the outflowing stellar wind of the red giant accretes onto the white dwarf, and an accretion disk may or may not form. Much of the outflowing red giant wind material forms a large nebula around the binary that is partially ionized by radiation from the accreting WD and from thermonuclear burning at its surface. The exact nature of the hot component, the efficiency of such wind-fed accretion, the rate of accretion onto the WD, whether accretion disks are even present, and why the hot components are so much hotter than their cataclysmic variable cousins, all remain poorly know. All previous attempts to determine WD temperatures, luminosities and accretion rates relied upon the modified Zanstra method and crude black body fitting. To deepen our understanding of the hot components, we propose to apply synthetic spectra for high gravity stars and accretion disks generated from state-of-the-art computer codes to the far ultraviolet archival spectra of 40 symbiotic stars, obtained with the International Ultraviolet Explorer (IUE) and Far Ultraviolet Spectroscopic Explorer (FUSE) spacecrafts. Since the WD is the most common end-product of stellar evolution ( > 95% of all the stars in the Galaxy evolve into white dwarfs), and the accretion disk whether from wind- fed accretion or Roche lobe overflow, is the most common universal structure resulting from mass transfer with angular momentum, and since both can be directly viewed in CVs in the ultraviolet (UV), an understanding of the consequences of accretion in these systems is the first step in a global understanding of accretion in other systems throughout the universe. These include protostellar objects, X-ray binaries (containing neutron star and black hole accretors), active galactic

  7. 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 guide...... 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.......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...

  8. 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

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. 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...

  14. 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...

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. Quasar Classification Using Color and Variability

    Science.gov (United States)

    Peters, Christina M.; Richards, Gordon

    2015-08-01

    We use the Non-parametric Bayesian Classification Kernel Density Estimation (NBC KDE) quasar selection algorithm (Richards et al. 2004) to identify 36,569 type 1 quasar candidates in the Sloan Digital Sky Survey (SDSS) Stripe 82 field using the combination of optical photometry and variability. 5-band coadded optical photometry is taken from the SDSS-I/II 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 using 10 to >100 observations for timescales from ~1 day to ~8 years. Selection was based on a training sample of 13,221 spectroscopically-confirmed type 1 quasars from SDSS-I/II and the Baryon Oscillation Spectroscopic Survey (BOSS). Using variability alone, colors alone, and combining variability and colors we achieve 91%, 93%, and 97% quasar completeness and 98%, 98%, and 97% efficiency respectively, with particular improvement in the selection of quasars at 2.7 < z < 3.5 where quasars and stars have similar optical colors. The 23,043 quasar candidates that are not spectroscopically confirmed reach a depth of coadd i ~ 22: 0 and 21,380 (92.8%) are dimmer than coadded i -band magnitude of 20.2, the cut off for spectroscopic follow-up for SDSSDR7.

  20. The Classificiation of Kepler B star Variables

    CERN Document Server

    McNamara, Bernard J; McKeever, Jean

    2012-01-01

    The light curves of 252 B-star candidates in the Kepler data base are analyzed in a similar fashion to that done by Balona et al. (2011) to further characterize B star variability, increase the sample of variable B stars for future study, and to identify stars whose power spectra include particularly interesting features such as frequency groupings. Stars are classified as either constant light emitters, $\\beta$ Cep stars, slowly pulsating B stars, hybrid pulsators, binaries or stars whose light curves are dominated by rotation (Bin/Rot), hot subdwarfs, or white dwarfs. One-hundred stars in our sample were found to be either light contants or to be variable at a level of less than 0.02 mmag. We increase the number of candidate B-star variables found in the Kepler data base by Balona et al. (2011) in the following fashion: $\\beta$ Cep stars from 0 to 10, slowly pulsating B stars from 8 to 54, hybrid pulsators from 7 to 21, and Bin/Rot stars from 23 to 82. For comparison purposes, approximately 51 SPBs and 6 hy...

  1. 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.

  2. 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...

  3. Usability Evaluation of Variability Modeling by means of Common Variability Language

    Directory of Open Access Journals (Sweden)

    Jorge Echeverria

    2015-12-01

    Full Text Available Common Variability Language (CVL is a recent proposal for OMG's upcoming Variability Modeling standard. CVL models variability in terms of Model Fragments.  Usability is a widely-recognized quality criterion essential to warranty the successful use of tools that put these ideas in practice. Facing the need of evaluating the usability of CVL modeling tools, this paper presents a Usability Evaluation of CVL applied to a Modeling Tool for firmware code of Induction Hobs. This evaluation addresses the configuration, scoping and visualization facets. The evaluation involved the end users of the tool whom are engineers of our Induction Hob industrial partner. Effectiveness and efficiency results indicate that model configuration in terms of model fragment substitutions is intuitive enough but both scoping and visualization require improved tool support. Results also enabled us to identify a list of usability problems which may contribute to alleviate scoping and visualization issues in CVL.

  4. Nursing diagnoses identified in children with acute respiration infection

    Directory of Open Access Journals (Sweden)

    Flávia Paula Magalhães Monteiro

    2006-08-01

    Full Text Available A cross-sectional study developed with 78 children with until five years old, bearers of acute respiration infection interned in pediatric hospital of the periphery of a great city, with the purpose to identify the nursing diagnoses presented by these children. The number of nursing diagnoses, defining characteristics, related factors and risk factors identified and other numerical variables were analyzed based in theirs central tendency and dispersion measures. It was identified a total of 26 nursing diagnoses, 43 related factors, 14 risk factors e 67 defining characteristics. In average, It was found 5,32 nursing diagnoses; 4,10 related factors; 2,03 risk factors and 7,33 defining characteristics. The nursing diagnoses with the biggest proportion were: Ineffective Breathing Pattern, Risk for delayed growth, Ineffective protection and Altered oral mucous membrane. We concluded that children with acute respiration infection present a complex diagnostic frame including human responses of multiples domains.

  5. 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.

  6. Identifying Differences in Cultural Behavior in Online Groups

    Energy Technology Data Exchange (ETDEWEB)

    Gregory, Michelle L.; Engel, David W.; Bell, Eric B.; Mcgrath, Liam R.

    2012-07-23

    We have developed methods to identify online communities, or groups, using a combination of structural information variables and content information variables from weblog posts and their comments to build a characteristic footprint for groups. We have worked with both explicitly connected groups and 'abstract' groups, in which the connection between individuals is in interest (as determined by content based features) and behavior (metadata based features) as opposed to explicit links. We find that these variables do a good job at identifying groups, placing members within a group, and helping determine the appropriate granularity for group boundaries. The group footprint can then be used to identify differences between the online groups. In the work described here we are interested in determining how an individual's online behavior is influenced by their membership in more than one group. For example, individuals belong to a certain culture; they may belong as well to a demographic group, and other 'chosen' groups such as churches or clubs. There is a plethora of evidence surrounding the culturally sensitive adoption, use, and behavior on the Internet. In this work we begin to investigate how culturally defined internet behaviors may influence behaviors of subgroups. We do this through a series of experiments in which we analyze the interaction between culturally defined behaviors and the behaviors of the subgroups. Our goal is to (a) identify if our features can capture cultural distinctions in internet use, and (b) determine what kinds of interaction there are between levels and types of groups.

  7. The variable Crab Nebula

    CERN Document Server

    Tavani, Marco

    2011-01-01

    The remarkable Crab Nebula is powered by an energetic pulsar whose relativistic wind interacts with the inner parts of the Supernova Remnant SN1054. Despite low-intensity optical and X-ray variations in the inner Nebula, the Crab has been considered until now substantially stable at X-ray and gamma-ray energies. This paradigm has been shattered by the AGILE discovery in September 2010 of a very intense transient gamma-ray flare of nebular origin. For the first time, the Crab Nebula was "caught in the act" of accelerating particles up to 10^15 eV within the shortest timescale ever observed in a cosmic nebula (1 day or less). Emission between 50 MeV and a few GeV was detected with a quite hard spectrum within a short timescale. Additional analysis and recent Crab Nebula data lead to identify a total of four major flaring gamma-ray episodes detected by AGILE and Fermi during the period mid-2007/mid-2011. These observations challenge emission models of the pulsar wind interaction and particle acceleration process...

  8. Consistency and variability in functional localisers

    Science.gov (United States)

    Duncan, Keith J.; Pattamadilok, Chotiga; Knierim, Iris; Devlin, Joseph T.

    2009-01-01

    A critical assumption underlying the use of functional localiser scans is that the voxels identified as the functional region-of-interest (fROI) are essentially the same as those activated by the main experimental manipulation. Intra-subject variability in the location of the fROI violates this assumption, reducing the sensitivity of the analysis and biasing the results. Here we investigated consistency and variability in fROIs in a set of 45 volunteers. They performed two functional localiser scans to identify word- and object-sensitive regions of ventral and lateral occipito-temporal cortex, respectively. In the main analyses, fROIs were defined as the category-selective voxels in each region and consistency was measured as the spatial overlap between scans. Consistency was greatest when minimally selective thresholds were used to define “active” voxels (p < 0.05 uncorrected), revealing that approximately 65% of the voxels were commonly activated by both scans. In contrast, highly selective thresholds (p < 10− 4 to 10− 6) yielded the lowest consistency values with less than 25% overlap of the voxels active in both scans. In other words, intra-subject variability was surprisingly high, with between one third and three quarters of the voxels in a given fROI not corresponding to those activated in the main task. This level of variability stands in striking contrast to the consistency seen in retinotopically-defined areas and has important implications for designing robust but efficient functional localiser scans. PMID:19289173

  9. 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.

  10. Variability and Composition of Io's Pele Plume

    Science.gov (United States)

    Jessup, K. L.; Spencer, J.; Yelle, R.

    2004-11-01

    The Pele plume is one of the largest and most dynamic of the plumes on Io. While sulfur dioxide (SO2) gas was always assumed to be a constituent of this plume, spectral observations obtained in 1999 were the first to positively identify elemental sulfur (S2) (Spencer et al. 2000) within the Pele plume. The S2/SO2 ratio derived from this observation provided a critical component necessary for the constraint of the magma chemistry and vent conditions of the Pele plume (Zolotov and Fegley 1998). But, because the Pele plume has long been known to be variable in its eruptive behavior, it is not likely that the vent conditions are invariant. Consequently, additional observations were needed to constrain the extent of the variability of the plume's composition and gas abundances. To this end, in February 2003, March 2003 and January 2004 we obtained spectra of Pele with Hubble's Space Telescope Imaging Spectrograph (STIS) in transit of Jupiter, using the 0.1 arcsec slit, for the wavelength region extending from 2100-3100 Å. Contemporaneous with the spectral data we also obtained UV and visible-wavelength images of the plume in reflected sunlight with the Advanced Camera for Surveys (ACS) prior to Jupiter transit, in order to constrain plume dust abundance. The newly acquired STIS data show both the S2 and SO2 absorption signatures, and provide concrete evidence of temporal variability in the abundance of these gases. Likewise, the degree of dust scattering recorded in the ACS data varied as a function of the date of observation. We will present preliminary constraints on the composition and variability of the gas abundances of the Pele plume as recorded within the STIS data. We will also give a brief overview of the variability of the plume dust signatures relative to the gas signatures as a function of time.

  11. 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.

  12. 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.

  13. 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...

  14. Temporal variability in soil hydraulic properties under drip irrigation

    OpenAIRE

    Mubarak, I.; Mailhol, J.C.; R. Angulo-Jaramillo; Ruelle, P.; P. Boivin; 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...

  15. Variable Selection with Exponential Weights and $l_0$-Penalization

    OpenAIRE

    Arias-Castro, Ery; Lounici, Karim

    2012-01-01

    In the context of a linear model with a sparse coefficient vector, exponential weights methods have been shown to be achieve oracle inequalities for prediction. We show that such methods also succeed at variable selection and estimation under the necessary identifiability condition on the design matrix, instead of much stronger assumptions required by other methods such as the Lasso or the Dantzig Selector. The same analysis yields consistency results for Bayesian methods and BIC-type variabl...

  16. 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

  17. Index for Wind Power Variability

    Energy Technology Data Exchange (ETDEWEB)

    Kiviluoma, Juha; Holttinen, Hannele; Cutululis, Nicolaos Antonio; Litong-Palima, Marisciel; Scharff, Richard; Milligan, Michael; Weir, David Edward

    2014-11-13

    Variability of large scale wind power generation is dependent on several factors: characteristics of installed wind power plants, size of the area where the plants are installed, geographic dispersion within that area and its weather regime(s). Variability can be described by ramps in power generation, i.e. changes from time period to time period. Given enough data points, it can be described with a probability density function. This approach focuses on two dimensions of variability: duration of the ramp and probability distribution. This paper proposes an index based on these two dimensions to enable comparisons and characterizations of variability under different conditions. The index is tested with real, large scale wind power generation data from several countries. Considerations while forming an index are discussed, as well as the main results regarding what the drivers of variability experienced for different data.

  18. 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...

  19. Variable stiffness and damping magnetorheological isolator

    Institute of Scientific and Technical Information of China (English)

    Yang ZHOU; Xingyu WANG; Xianzhou ZHANG; Weihua LI

    2009-01-01

    This paper presents the development and characterization of a magnetorheological (MR) fluid-based variable stiffness and damping isolator. The prototype of the MR fluid isolator is fabricated, and its dynamic behavior is measured under various applied magnetic fields. The parameters of the model under various magnetic fields are identified, and the dynamic perfor-mance of the isolator is evaluated in simulation. Experi-mental results indicate that both the stiffness and damping capability of the developed MR isolator can be controlled by an external magnetic field.

  20. 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).

  1. Variable stars in the globular cluster NGC 2419

    CERN Document Server

    Greco, C; Federici, L; Clementini, G; Fabrizio, L D; Baldacci, L; Maio, M; Marconi, M; Musella, I; Stetson, P B

    2005-01-01

    We have used DOLORES at the TNG to obtain B,V time series photometry of NGC 2419, one of the most distant and bright clusters in the Galactic halo. These data will be used to study its variable star population in order to check whether the cluster could be the relic of an extragalactic system accreted by the Milky Way. Using the Image Subtraction technique (Alard 2000) we have identified about 300 candidate variables, many of which are in the cluster central regions. Several of the variables appear to be RR Lyrae stars, but we detected variability also around the tip of the red giant branch, and in other regions of the colour-magnitude diagram. To improve the light curve sampling and to resolve variables in the cluster inner regions, the TNG data were combined with HST archive data. Preliminary results are presented on the light curves from the combined data set.

  2. 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.

  3. 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.

  4. Identifying At-Risk Students in General Chemistry via Cluster Analysis of Affective Characteristics

    Science.gov (United States)

    Chan, Julia Y. K.; Bauer, Christopher F.

    2014-01-01

    The purpose of this study is to identify academically at-risk students in first-semester general chemistry using affective characteristics via cluster analysis. Through the clustering of six preselected affective variables, three distinct affective groups were identified: low (at-risk), medium, and high. Students in the low affective group…

  5. 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....

  6. 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 ...

  7. 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...

  8. Drivers, "Slow" Variables, "Fast" Variables, Shocks, and Resilience

    Directory of Open Access Journals (Sweden)

    Anne-Sophie Crépin

    2012-09-01

    Full Text Available Different uses of the terms "drivers," "variables," and "shocks" cause confusion in the literature and in discussions on the dynamics of ecosystems and social–ecological systems. Three main sources of confusion are unclear definition of the system, unclear definition of the role of people, and confusion between variables and drivers. As a contribution to resolving some of the confusion, we offer one interpretation of how the terms might be used.

  9. 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- ...

  10. 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

  11. Identifying Causal Effects with Computer Algebra

    CERN Document Server

    García-Puente, Luis David; Sullivant, Seth

    2010-01-01

    The long-standing identification problem for causal effects in graphical models has many partial results but lacks a systematic study. We show how computer algebra can be used to either prove that a causal effect can be identified, generically identified, or show that the effect is not generically identifiable. We report on the results of our computations for linear structural equation models, where we determine precisely which causal effects are generically identifiable for all graphs on three and four vertices.

  12. 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....

  13. 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...

  14. 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 ...

  15. 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…

  16. 29 CFR 4010.7 - Identifying information.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 9 2010-07-01 2010-07-01 false Identifying information. 4010.7 Section 4010.7 Labor... DISCLOSURE REQUIREMENTS ANNUAL FINANCIAL AND ACTUARIAL INFORMATION REPORTING § 4010.7 Identifying information..., http://www.pbgc.gov, the following identifying information with respect to each member of the...

  17. 47 CFR 2.926 - FCC identifier.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false FCC identifier. 2.926 Section 2.926... Authorizations § 2.926 FCC identifier. (a) A grant of equipment authorization issued by the Commission will list the validated FCC Identifier consisting of the grantee code assigned by the FCC pursuant to...

  18. De-identifying an EHR Database

    DEFF Research Database (Denmark)

    Lauesen, Søren; Pantazos, Kostas; Lippert, Søren

    2011-01-01

    Abstract. Electronic health records (EHR) contain a large amount of structured data and free text. Exploring and sharing clinical data can improve healthcare and facilitate the development of medical software. However, revealing confidential information is against ethical principles and laws. We de...... lists of identifiers from the database and external resources, define a replacement for each identifier, and replace identifiers in structured data and free text. Some patient records could not be safely de-identified, so the de-identified database has 323,122 patient records with an acceptable degree...

  19. 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.

  20. Electrochromic Variable-Emissivity Surfaces

    Science.gov (United States)

    Rauh, R. David; Cogan, Stuart F.

    1988-01-01

    Temperature controlled by altering infrared radiative properties. Infrared emissivity of electrochromically active layer changed by applying voltage to insert or remove Li atoms electrochemically. Change reversible and continuously variable between specified limits of layered structure.

  1. 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.

  2. 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...

  3. 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...

  4. 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...

  5. Automated Searches for Variable Stars

    CERN Document Server

    Van Noord, Daniel M; Steenwyk, Steven D

    2013-01-01

    With recent developments in imaging and computer technology the amount of available astronomical data has increased dramatically. Although most of these data sets are not dedicated to the study of variable stars much of it can, with the application of proper software tools, be recycled for the discovery of new variable stars. Fits Viewer and Data Retrieval System is a new software package that takes advantage of modern computer advances to search astronomical data for new variable stars. More than 200 new variable stars have been found in a data set taken with the Calvin College Rehoboth Robotic telescope using FVDRS. One particularly interesting example is a very fast subdwarf B with a 95 minute orbital period, the fastest currently known of the HW Vir type.

  6. 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...

  7. Investigation of load reduction for a variable speed, variable pitch, and variable coning wind turbine

    Energy Technology Data Exchange (ETDEWEB)

    Pierce, K. [Univ. of Utah, Salt Lake City, UT (United States)

    1997-12-31

    A two bladed, variable speed and variable pitch wind turbine was modeled using ADAMS{reg_sign} to evaluate load reduction abilities of a variable coning configuration as compared to a teetered rotor, and also to evaluate control methods. The basic dynamic behavior of the variable coning turbine was investigated and compared to the teetered rotor under constant wind conditions as well as turbulent wind conditions. Results indicate the variable coning rotor has larger flap oscillation amplitudes and much lower root flap bending moments than the teetered rotor. Three methods of control were evaluated for turbulent wind simulations. These were a standard IPD control method, a generalized predictive control method, and a bias estimate control method. Each control method was evaluated for both the variable coning configuration and the teetered configuration. The ability of the different control methods to maintain the rotor speed near the desired set point is evaluated from the RMS error of rotor speed. The activity of the control system is evaluated from cycles per second of the blade pitch angle. All three of the methods were found to produce similar results for the variable coning rotor and the teetered rotor, as well as similar results to each other.

  8. Dark Matter with Variable Masses

    OpenAIRE

    Garcia-Bellido, Juan

    1992-01-01

    String effective theories contain a dilaton scalar field which couples to gravity, matter and radiation. In general, particle masses will have different dilaton couplings. We can always choose a conformal frame in which baryons have constant masses while (non--baryonic) dark matter have variable masses, in the context of a scalar--tensor gravity theory. We are interested in the phenomenology of this scenario. Dark matter with variable masses could have a measurable effect on the dynamical mot...

  9. Variable Pricing in Oligopoly Markets

    OpenAIRE

    Frank Bass

    2006-01-01

    Behavioral research has found that consumers respond to variability in prices in addition to price levels. We show that this finding can explain why some firms vary their prices more frequently than others. We examine pricing strategies composed of an average price and price variability and employ logit market share models to analyze equilibrium pricing strategies in an oligopoly. Two competing logit specifications termed price sensitivity and payoff sensitivity are considered and are shown t...

  10. Approaches to variable pay systems

    OpenAIRE

    García-Hernández, Rosa

    2016-01-01

    The general goal of this thesis is to analyze, in some European countries, the connections of Variable Pay Systems with company behaviour, collective bargaining, wage determination and wage inequality. We introduce three different approaches to Variable Pay Systems. First, a company-industry approach in the case of Spain, using a qualitative methodology and analyzing competitiveness, productivity, unit labor cost and collective agreements. Second, a country-collective bargaining approach in t...

  11. Sparse estimation for structural variability

    OpenAIRE

    Singh Rohit; Hosur Raghavendra; Berger Bonnie

    2011-01-01

    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 exp...

  12. Variable rules meet Impoverishment theory

    DEFF Research Database (Denmark)

    Parrott, Jeffrey K.; Nevins, Andrew

    2010-01-01

    This paper revives the sociolinguistic notion of ‘variable rules’ (Labov 1969, Cedergren and Sankoff 1974, Guy 1991) as a specific and restricted mechanism within the theoretical framework of Distributed Morphology (Halle and Marantz 1993, Embick and Noyer 2007). We propose that intra-individual ......This paper revives the sociolinguistic notion of ‘variable rules’ (Labov 1969, Cedergren and Sankoff 1974, Guy 1991) as a specific and restricted mechanism within the theoretical framework of Distributed Morphology (Halle and Marantz 1993, Embick and Noyer 2007). We propose that intra......-individual paradigm ‘leveling’ variation (or, variable syncretism) can be effectively modeled as resulting from post-syntactic feature deletion rules that apply variably. In other words, variable rules enact a structural change only probabilistically, rather than deterministically, when their structural description...... is met. By hypothesis, morphological ‘Impoverishment’ operations (Bonet 1991, Halle 1997, Noyer 1998) are induced by the inherent and universal markedness of particular morphosyntactic features or their combination (Greenberg 1966, Croft 2003). We examine markedness-driven variable Impoverishment through...

  13. Interannual and Interdecadal Variability in Sea Level.

    Science.gov (United States)

    Unal, Yurdanur Sezginer

    The observational data set archived by the Permanent Service for Mean Sea Level (PSMSL) consists of monthly means of sea-level heights at 846 stations. 213 of them are suitable for our purposes. We identified two dominant time scales of El Nino-Southern Oscillation (ENSO) signal, as quasi-biennial and low-frequency (LF) at almost all stations, with the highest amplitudes in the equatorial Pacific and along the west coast of North America. Global sea-level rise, after post-glacial rebound corrections, are 1.620.38 mm/yr. Propagation features of the interannual variability are studied along the coastal sea level stations in five regions: eastern, western, and equatorial Pacific; eastern and western Atlantic. Throughout the Pacific, three dominant spatio-temporal oscillatory patterns are found in the time scales of ENSO variability. In the eastern Pacific, the biennial mode and the 6-yr low-frequency mode propagate poleward. In the western Pacific, interannual oscillation propagates southward in the northern hemisphere but no clear propagation is observed in the southern hemisphere. Equatorward propagation of the biennial signal is very clear in each hemisphere. In the equatorial Pacific, both the quasi -quadrannial and quasi-biennial modes at 10^ circN propagate westward. Strong and weak El Nino years are evident in RSLH reconstructed from the biennial and low-frequency modes. Interannual variability with periods of 3 and 4-8 years is detected in the Atlantic RSLH data. In the eastern Atlantic region, we have found slow propagation of both modes northward and southward, away from 40-45^circN. Sufficiently long and continuous RSLH at 81 stations show interdecadal oscillations with the periods of 9-13 and 18 years. 11.6 and 12.8 years of oscillations are found in the eastern and western Atlantic ocean at latitudes 40^circN-70^ circN and 10^circN -50^circN, respectively. The aforementioned features are simulated with a wind driven ocean model for the periods of 1950 and

  14. Asthma trajectories in early childhood: identifying modifiable factors.

    Directory of Open Access Journals (Sweden)

    Lidia Panico

    Full Text Available BACKGROUND: There are conflicting views as to whether childhood wheezing represents several discreet entities or a single but variable disease. Classification has centered on phenotypes often derived using subjective criteria, small samples, and/or with little data for young children. This is particularly problematic as asthmatic features appear to be entrenched by age 6/7. In this paper we aim to: identify longitudinal trajectories of wheeze and other atopic symptoms in early childhood; characterize the resulting trajectories by the socio-economic background of children; and identify potentially modifiable processes in infancy correlated with these trajectories. DATA AND METHODS: The Millennium Cohort Study is a large, representative birth cohort of British children born in 2000-2002. Our analytical sample includes 11,632 children with data on key variables (wheeze in the last year; ever hay-fever and/or eczema reported by the main carers at age 3, 5 and 7 using a validated tool, the International Study of Asthma and Allergies in Childhood module. We employ longitudinal Latent Class Analysis, a clustering methodology which identifies classes underlying the observed population heterogeneity. RESULTS: Our model distinguished four latent trajectories: a trajectory with both low levels of wheeze and other atopic symptoms (54% of the sample; a trajectory with low levels of wheeze but high prevalence of other atopic symptoms (29%; a trajectory with high prevalence of both wheeze and other atopic symptoms (9%; and a trajectory with high levels of wheeze but low levels of other atopic symptoms (8%. These groups differed in terms of socio-economic markers and potential intervenable factors, including household damp and breastfeeding initiation. CONCLUSION: Using data-driven techniques, we derived four trajectories of asthmatic symptoms in early childhood in a large, population based sample. These groups differ in terms of their socio-economic profiles

  15. Atmospheric variables as driving variables of agricultural and forest ecosystems

    Directory of Open Access Journals (Sweden)

    Luigi Mariani

    Full Text Available Atmospheric variables, which represent meteorology if seen in their instantaneous behavior or climatology if seen in their long time behavior, can be considered among the main driving variables of agricultural and forest ecosystems. In other words meteo-climatic variables determine productivity and quality and territorial specificity of agroforestry productions. On the base of this premise some significant examples are shown in order to describe how different modeling approaches (empirical and mechanistic can improve our degree of description of phenomena and the rationality of our approach to management of agro-ecosystem. The need of strict linkage among agrometeorology and other physical and biological sciences referred to agro-forestry ecosystems is also discussed.

  16. The TAOS Project Stellar Variability II. Detection of 15 Variable Stars

    Energy Technology Data Exchange (ETDEWEB)

    Mondal, S; Lin, C C; Zhang, Z W; Alcock, C; Axelrod, T; Bianco, F B; Byun, Y I; Coehlo, N K; Cook, K H; Dave, R; Kim, D W; King, S K; Lee, T; Lehner, M J; Lin, H C; Marshall, S L; Protopapas, P; Rice, J A; Schwamb, M E; Wang, J H; Wang, S Y; Wen, C Y

    2010-01-28

    The Taiwanese-American Occultation Survey (TAOS) project has collected more than a billion photometric measurements since 2005 January. These sky survey data - covering timescales from a fraction of a second to a few hundred days - are a useful source to study stellar variability. A total of 167 star fields, mostly along the ecliptic plane, have been selected for photometric monitoring with the TAOS telescopes. This paper presents our initial analysis of a search for periodic variable stars from the time-series TAOS data on one particular TAOS field, No. 151 (RA = 17{sup h} 30{sup m} 6.67{sup s}, Dec = 27 degrees, 17 minutes, 30 seconds, J2000), which had been observed over 47 epochs in 2005. A total of 81 candidate variables are identified in the 3 square degree field, with magnitudes in the range 8 < R < 16. On the basis of the periodicity and shape of the lightcurves, 32 variables, 18 of which were previously unknown, are classified as RR Lyrae, Cepheid, {delta} Scuti, SX Phonencis, semi-regular and eclipsing binaries.

  17. Identifying shortage occupations in the UK

    OpenAIRE

    Anna Downs

    2009-01-01

    This article describes the top-down methodology used by the Migration Advisory Committee (MAC) to identify shortage occupations. Identifying shortage occupations is difficult and few countries have attempted to do this in a systematic way. The methodology developed by the MAC to identify shortage occupations is the first to use a comprehensive range of indicators. The methodology dovetails national level top-down data with bottom-up micro-level data and qualitative information from stakeholde...

  18. Determination of set-membership identifiability sets

    OpenAIRE

    Ravanbod-Hosseini, Laleh; Verdière, Nathalie; Jauberthie, Carine

    2014-01-01

    This paper concerns the concept of set-membership identifiability introduced in \\cite{jauberthie}. Given a model, a set-membership identifiable set is a connected set in the parameter domain of the model such that its corresponding trajectories are distinct to trajectories arising from its complementary. For obtaining the so-called set-membership identifiable sets, we propose an algorithm based on interval analysis tools. The proposed algorithm is decomposed into three parts namely {\\it minci...

  19. Identifying multiple submissions in Internet research: preserving data integrity.

    Science.gov (United States)

    Bowen, Anne M; Daniel, Candice M; Williams, Mark L; Baird, Grayson L

    2008-11-01

    Internet-based sexuality research with hidden populations has become increasingly popular. Respondent anonymity may encourage participation and lower social desirability, but associated disinhibition may promote multiple submissions, especially when incentives are offered. The goal of this study was to identify the usefulness of different variables for detecting multiple submissions from repeat responders and to explore incentive effects. The data included 1,900 submissions from a three-session Internet intervention with a pretest and three post-test questionnaires. Participants were men who have sex with men and incentives were offered to rural participants for completing each questionnaire. The final number of submissions included 1,273 "unique", 132 first submissions by "repeat responders" and 495 additional submissions by the "repeat responders" (N = 1,900). Four categories of repeat responders were identified: "infrequent" (2-5 submissions), "persistent" (6-10 submissions), "very persistent" (11-30 submissions), and "hackers" (more than 30 submissions). Internet Provider (IP) addresses, user names, and passwords were the most useful for identifying "infrequent" repeat responders. "Hackers" often varied their IP address and identifying information to prevent easy identification, but investigating the data for small variations in IP, using reverse telephone look up, and patterns across usernames and passwords were helpful. Incentives appeared to play a role in stimulating multiple submissions, especially from the more sophisticated "hackers". Finally, the web is ever evolving and it will be necessary to have good programmers and staff who evolve as fast as "hackers". PMID:18240015

  20. Easy Long-Term Identifiers and the "Data Paper"

    Science.gov (United States)

    Kunze, John

    2011-05-01

    A new publishing paradigm is needed to cope with the deluge of data artifacts produced by data-intensive science, many of which are vital to data re-use and verification of published scientific conclusions. Due to the limitations of traditional publishing, most of these artifacts are not usually disseminated, cited, or preserved. At the California Digital Library (CDL), one promising approach to the problem is to wrap these artifacts in the metaphor of a "data paper", assigning and managing data citations with our EZID (easy-eye-dee) identifier service. A data paper is a somewhat unfamiliar bundle of scholarly output with a familiar facade: minimally, a set of links to archived artifacts and a cover sheet containing familiar elements such as title, authors, date, abstract, and persistent identifier _ just enough to create basic citations, build "overlay journals", and enable discovery of data by internet search engines. Over time, we expect to add elements that permit deeper domain-specific discovery and re-use, such as variable names, methods, etc. At the same time, for data and identifiers that we manage, we will leverage as much domain-agnosticism data and identifier as possible.