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Sample records for hydrogen-rich magnetic white

  1. Spectropolarimetric Survey of Hydrogen-rich White Dwarf Stars

    Kawka, Adela; Vennes, S.; Schmidt, G. D.; Wickramasinghe, D.T.; Koch, R.

    2007-01-01

    Roč. 654, č. 1 (2007), s. 499-520 ISSN 0004-637X R&D Projects: GA ČR GP205/05/P186 Institutional research plan: CEZ:AV0Z10030501 Keywords : magnetic fields * white dwarf s Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 6.405, year: 2007

  2. A study of high proper-motion white dwarfs - I. Spectropolarimetry of a cool hydrogen-rich sample

    Kawka, Adela; Vennes, Stephane

    2012-01-01

    Roč. 425, č. 2 (2012), s. 1394-1412 ISSN 0035-8711 R&D Projects: GA ČR GAP209/10/0967; GA MŠk(CZ) LC06014 Institutional research plan: CEZ:AV0Z10030501 Keywords : stars * fundamental parameters * magnetic field Subject RIV: BN - Astronomy , Celestial Mechanics, Astrophysics Impact factor: 5.521, year: 2012

  3. Coal pyrolysis under hydrogen-rich gases

    Liao, H.; Sun, C.; Li, B.; Liu, Z. [Chinese Academy of Sciences, Taiyuan (China). State Key Laboratory of Coal Conversion, Institute of Coal Chemistry

    1998-04-01

    To improve the economy of the pyrolysis process by reducing the hydrogen cost, it is suggested to use cheaper hydrogen-rich gases such as coke-oven gas (COG) or synthesis gas (SG) instead of pure hydrogen. The pyrolysis of Chinese Xianfeng lignite which was carried out with real COG and SG at 3-5 MPa, a final temperature of 650{degree}C and a heating rate of 5{degree}C/min in a 10g fixed-bed reactor is compared with coal pyrolysis with pure hydrogen and nitrogen under the same conditions. The results indicate that compared with hydropyrolysis at the same total pressure, the total conversion and tar yields from coal pyrolysis with COG and SG decreases while the unwanted water increases. However, at the same H{sub 2} partial pressure, the tar yields and yields of BBTX, PCX and naphthalene from the pyrolysis of coal with COG and SG are all significantly higher than those of hydropyrolysis. Therefore, it is possible to use COG and SG instead of pure hydrogen. 8 refs., 3 figs., 6 tabs.

  4. Effects of magnetic fields in white dwarfs

    Franzon, Bruno; Schramm, Stefan

    2017-01-01

    We perform calculations of white dwarfs endowed with strong magnetic fields. White dwarfs are the progenitors of supernova Type Ia explosions and they are widely used as candles to show that the Universe is expanding and accelerating. However, observations of ultraluminous supernovae have suggested that the progenitor of such an explosion should be a white dwarf with mass above the well-known Chandrasekhar limit ∼ 1.4 M⊙. In corroboration with other works, but by using a fully general relativistic framework, we obtained also strongly magnetized white dwarfs with masses M ∼ 2.0 M⊙. (paper)

  5. ON THE EVOLUTION OF MAGNETIC WHITE DWARFS

    Tremblay, P.-E. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Fontaine, G.; Brassard, P. [Département de Physique, Université de Montréal, C. P. 6128, Succursale Centre-Ville, Montréal, QC H3C 3J7 (Canada); Freytag, B. [Department of Physics and Astronomy at Uppsala University, Regementsvägen 1, Box 516, SE-75120 Uppsala (Sweden); Steiner, O. [Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, D-79104 Freiburg (Germany); Ludwig, H.-G. [Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Königstuhl 12, D-69117 Heidelberg (Germany); Steffen, M. [Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam (Germany); Wedemeyer, S., E-mail: tremblay@stsci.edu [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, NO-0315 Oslo (Norway)

    2015-10-10

    We present the first radiation magnetohydrodynamic simulations of the atmosphere of white dwarf stars. We demonstrate that convective energy transfer is seriously impeded by magnetic fields when the plasma-β parameter, the thermal-to-magnetic-pressure ratio, becomes smaller than unity. The critical field strength that inhibits convection in the photosphere of white dwarfs is in the range B = 1–50 kG, which is much smaller than the typical 1–1000 MG field strengths observed in magnetic white dwarfs, implying that these objects have radiative atmospheres. We have employed evolutionary models to study the cooling process of high-field magnetic white dwarfs, where convection is entirely suppressed during the full evolution (B ≳ 10 MG). We find that the inhibition of convection has no effect on cooling rates until the effective temperature (T{sub eff}) reaches a value of around 5500 K. In this regime, the standard convective sequences start to deviate from the ones without convection due to the convective coupling between the outer layers and the degenerate reservoir of thermal energy. Since no magnetic white dwarfs are currently known at the low temperatures where this coupling significantly changes the evolution, the effects of magnetism on cooling rates are not expected to be observed. This result contrasts with a recent suggestion that magnetic white dwarfs with T{sub eff} ≲ 10,000 K cool significantly slower than non-magnetic degenerates.

  6. A possible magnetic DA white dwarf

    Wickramasinghe, D.T.; Bessell, M.S.

    1976-01-01

    The spectrum of a peculiar southern white dwarf suspect BPM 25114 is described. A possible magnetic interpretation suggests a DA white dwarf with a field of about 10 7 gauss. The star appears to be both a spectrum variable and perhaps light variable

  7. Polarized radiation in magnetic white dwarfs

    Rosi, L.A.; Zimmerman, R.L.; Kemp, J.C.

    1976-01-01

    A model for magnetic white dwarfs is proposed which attributes the partially polarized light to synchrotron radiation. The source of the radiation is relativistic electrons trapped in the magnetosphere of a white dwarf. The white dwarf's magnetic field is assumed to be dipolar. The Stokes parameters for the synchrotron radiation are tabulated as a function of frequency, observer's orientation, and energy and spatial distribution of the relativistic electrons. The results of the synchrotron calculations are applied to the polarization observations of Grw+70degree8247 and DQ Herculis. This model can account for the major features of the polarized radiation coming from these two magnetic white dwarfs. The calculations predict for Grw+70degree8247 that the surface magnetic field is B/sub s/approximately-less-than4 x 10 6 gauss, that the incident viewing angle is 45degreeapproximately-less-thantheta 0 approximately-less-than75degree, and that the electrons are trapped with nearly an isotropic distribution about the white dwarf. For DQ Herculis the surface magnetic field is B/sub s/approximately-less-than7 x 10 6 gauss and the trapped electrons are confined to a dislike region about the white dwarf. For both cases the density of electrons in the magnetosphere falls in the range of 10 5 approximately-less-thannapproximately-less-than10 7 cm -3 with energies of about 4--35 MeV

  8. Thermonuclear runaways in thick hydrogen rich envelopes of neutron stars

    Starrfield, S. G.; Kenyon, S.; Truran, J. W.; Sparks, W. M.

    1981-01-01

    A Lagrangian, fully implicit, one dimensional hydrodynamic computer code was used to evolve thermonuclear runaways in the accreted hydrogen rich envelopes of 1.0 Msub solar neutron stars with radii of 10 km and 20 km. Simulations produce outbursts which last from about 750 seconds to about one week. Peak effective temeratures and luninosities were 26 million K and 80 thousand Lsub solar for the 10 km study and 5.3 millison and 600 Lsub solar for the 20 km study. Hydrodynamic expansion on the 10 km neutron star produced a precursor lasting about one ten thousandth seconds.

  9. Maximum mass of magnetic white dwarfs

    Paret, Daryel Manreza; Horvath, Jorge Ernesto; Martínez, Aurora Perez

    2015-01-01

    We revisit the problem of the maximum masses of magnetized white dwarfs (WDs). The impact of a strong magnetic field on the structure equations is addressed. The pressures become anisotropic due to the presence of the magnetic field and split into parallel and perpendicular components. We first construct stable solutions of the Tolman-Oppenheimer-Volkoff equations for parallel pressures and find that physical solutions vanish for the perpendicular pressure when B ≳ 10 13 G. This fact establishes an upper bound for a magnetic field and the stability of the configurations in the (quasi) spherical approximation. Our findings also indicate that it is not possible to obtain stable magnetized WDs with super-Chandrasekhar masses because the values of the magnetic field needed for them are higher than this bound. To proceed into the anisotropic regime, we can apply results for structure equations appropriate for a cylindrical metric with anisotropic pressures that were derived in our previous work. From the solutions of the structure equations in cylindrical symmetry we have confirmed the same bound for B ∼ 10 13 G, since beyond this value no physical solutions are possible. Our tentative conclusion is that massive WDs with masses well beyond the Chandrasekhar limit do not constitute stable solutions and should not exist. (paper)

  10. Stable Hydrogen-rich Atmospheres of Young Rocky Planets

    Zahnle, K. J.; Catling, D. C.; Gacesa, M.

    2016-12-01

    SourceURL:file://localhost/Volumes/Lexar/Zahnle_AGU_2016.docx Understanding hydrogen escape is essential to understanding the limits to habitability, both for liquid water where the Sun is bright, but also to assess the true potential of H2 as a greenhouse gas where the Sun is faint. Hydrogen-rich primary atmospheres of Earth-like planets can result either from gravitational capture of solar nebular gases (with helium), or from impact shock processing of a wide variety of volatile-rich planetesimals (typically accompanied by H2O, CO2, and under the right circumstances, CH4). Most studies of hydrogen escape from planets focus on determining how fast the hydrogen escapes. In general this requires solving hydrodynamic equations that take into account the acceleration of hydrogen through a critical transonic point and an energy budget that should include radiative heating and cooling, thermal conduction, the work done in lifting the hydrogen against gravity, and the residual heat carried by the hydrogen as it leaves. But for planets from which hydrogen escape is modest or insignificant, the atmosphere can be approximated as hydrostatic, which is much simpler, and for which a relatively full-featured treatment of radiative cooling by embedded molecules, atoms, and ions such as CO2 and H3+ is straightforward. Previous work has overlooked the fact that the H2 molecule is extremely efficient at exciting non-LTE CO2 15 micron emission, and thus that radiative cooling can be markedly more efficient when H2 is abundant. We map out the region of phase space in which terrestrial planets keep hydrogen-rich atmospheres, which is what we actually want to know for habitability. We will use this framework to reassess Tian et al's (Science 308, pp. 1014-1017, 2005) hypothesis that H2-rich atmospheres may have been rather long-lived on Earth itself. Finally, we will address the empirical observation that rocky planets with thin or negligible atmospheres are rarely or never bigger than

  11. Accretion on to Magnetic White Dwarfs

    Wickramasinghe Dayal

    2014-01-01

    The polars have no counterparts in neutron star systems and their study provides unique insights into the complex nature of the magnetospheric boundary. The observed properties of accretion shocks at the white dwarf surface such as the anomalous soft-X-ray excess and its time variability provide strong support for the hypothesis that under certain circumstances the field channelled funnel flow is “blobby”. This has been attributed to interchange instabilities such as the Magnetic Rayleigh-Taylor instability in the shocked gas at the stream-magnetosphere boundary where the stream fragments into discrete clumps of gas. As the clumps penetrate into the magnetosphere, they are shredded into smaller mass blobs via the Kelvin-Helmholtz instability that then couple on to field lines over an extended inner transition region in the orbital plane. The more massive blobs penetrate deep into the photosphere of the white dwarf releasing their energy as a reprocessed soft-X-ray black body component. Although similar instabilities are expected in the inner transition region in disced accretion albeit on a different scale there has been no direct observational evidence for blobby accretion in the generally lower field and disced IPs.

  12. Magnetic white dwarfs: Observations, theory and future prospects

    García-Berro, Enrique; Kilic, Mukremin; Kepler, Souza Oliveira

    2016-01-01

    Isolated magnetic white dwarfs have field strengths ranging from 103G to 109G, and constitute an interesting class of objects. The origin of the magnetic field is still the subject of a hot debate. Whether these fields are fossil, hence the remnants of original weak magnetic fields amplified during the course of the evolution of the progenitor of white dwarfs, or on the contrary, are the result of binary interactions or, finally, other physical mechanisms that could produce such large magnetic fields during the evolution of the white dwarf itself, remains to be elucidated. In this work, we review the current status and paradigms of magnetic fields in white dwarfs, from both the theoretical and observational points of view.

  13. Structure and stabilization of hydrogen-rich transverse.

    Lyra, Sgouria [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Wilde, B [Georgia Inst. of Technology, Atlanta, GA (United States); Kolla, Hemanth [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Seitzman, J. [Georgia Inst. of Technology, Atlanta, GA (United States); Lieuwen, T. C. [Georgia Inst. of Technology, Atlanta, GA (United States); Chen, Jacqueline H. [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

    2014-07-01

    This paper reports the results of a joint experimental and numerical study of the ow characteristics and flame stabilization of a hydrogen rich jet injected normal to a turbulent, vitiated cross ow of lean methane combustion products. Simultaneous high-speed stereoscopic PIV and OH PLIF measurements were obtained and analyzed alongside three-dimensional direct numerical simulations of inert and reacting JICF with detailed H2/CO chemistry. Both the experiment and the simulation reveal that, contrary to most previous studies of reacting JICF stabilized in low-to-moderate temperature air cross ow, the present conditions lead to an autoigniting, burner-attached flame that initiates uniformly around the burner edge. Significant asymmetry is observed, however, between the reaction zones located on the windward and leeward sides of the jet, due to the substantially different scalar dissipation rates. The windward reaction zone is much thinner in the near field, while also exhibiting significantly higher local and global heat release than the much broader reaction zone found on the leeward side of the jet. The unsteady dynamics of the windward shear layer, which largely control the important jet/cross flow mixing processes in that region, are explored in order to elucidate the important flow stability implications arising in the reacting JICF. Vorticity spectra extracted from the windward shear layer reveal that the reacting jet is globally unstable and features two high frequency peaks, including a fundamental mode whose Strouhal number of ~0.7 agrees well with previous non-reacting JICF stability studies. The paper concludes with an analysis of the ignition, ame stabilization, and global structure of the burner-attached flame. Chemical explosive mode analysis (CEMA) shows that the entire windward shear layer, and a large region on the leeward side of the jet, are highly explosive prior to ignition and are dominated by non-premixed flame structures after

  14. Effects of hydrogen rich water on prolonged intermittent exercise.

    Da Ponte, Alessandro; Giovanelli, Nicola; Nigris, Daniele; Lazzer, Stefano

    2018-05-01

    Recent studies showed a positive effect of hydrogen rich water (HRW) intake on acid-base homeostasis at rest. We investigated 2-weeks of HRW intake on repeated sprint performance and acid-base status during prolonged intermittent cycling exercise. In a cross over single-blind protocol, 8 trained male cyclists (age [mean±SD] 41±7 years, body mass 72.3±4.4 kg, height 1.77±0.04 m, maximal oxygen uptake [V̇O2max] 52.6±4.4 mL·kg-1·min-1) were provided daily with 2 liters of placebo normal water (PLA, pH 7.6, oxidation/reduction potential [ORP] +230 mV, free hydrogen content 0 ppb) or HRW (pH 9.8, ORP -180 mV, free Hydrogen 450 ppb). Tests were performed at baseline and after each period of 2 weeks of treatment. The treatments were counter-balanced and the sequence randomized. The 30-minute intermittent cycling trial consisted in 10 3-minute blocks, each one composed by 90 seconds at 40% V̇O2max, 60 seconds at 60% V̇O2max, 16 seconds all out sprint, and 14 seconds active recovery. Oxygen uptake (V̇O2), heart rate and power output were measured during the whole test, while mean and peak power output (PPO), time to peak power and Fatigue Index (FI) were determined during all the 16 seconds sprints. Lactate, pH and bicarbonate (HCO3-) concentrations were determined at rest and after each sprint on blood obtained by an antecubital vein indwelling catheter. In the PLA group, PPO in absolute values decreased significantly at the 8th and 9th of 10 sprints and in relative values, ΔPPO, decreased significantly at 6th, 8th and 9th of 10 sprints (by mean: -12±5%, Pmay help to maintain PPO in repetitive sprints to exhaustion over 30 minutes.

  15. Effects of Hydrogen-Rich Saline on Hepatectomy-Induced Postoperative Cognitive Dysfunction in Old Mice.

    Tian, Yue; Guo, Shanbin; Zhang, Yan; Xu, Ying; Zhao, Ping; Zhao, Xiaochun

    2017-05-01

    This study aims to investigate the protective effects and underlying mechanisms of hydrogen-rich saline on the cognitive functions of elder mice with partial hepatectomy-induced postoperative cognitive dysfunction (POCD). Ninety-six old male Kunming mice were randomly divided into 4 groups (n = 24 each): control group (group C), hydrogen-rich saline group (group H), POCD group (group P), and POCD + hydrogen-rich saline group (group PH). Cognitive function was subsequently assessed using Morris water-maze (MWM) test. TNF-α and IL-1β levels were measured by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry, along with NF-κB activity determined by ELISA. The morphology of hippocampal tissues were further observed by HE staining. Learning and memory abilities of mice were significantly impaired at day 10 and day 14 post-surgery, as partial hepatectomy significantly prolonged the escape latency, decreased time at the original platform quadrant and frequency of crossing in group P when compared to group C (p hydrogen-rich saline (group PH) partially rescued spatial memory and learning as it shortened escape latency and increased time and crossing frequency of original platform compared to group P (p hydrogen-rich saline. Hydrogen-rich saline can alleviate POCD via inhibiting NF-κB activity in the hippocampus and reducing inflammatory response.

  16. Genesis of magnetic fields in isolated white dwarfs

    Briggs, Gordon P.; Ferrario, Lilia; Tout, Christopher A.; Wickramasinghe, Dayal T.

    2018-05-01

    A dynamo mechanism driven by differential rotation when stars merge has been proposed to explain the presence of strong fields in certain classes of magnetic stars. In the case of the high field magnetic white dwarfs (HFMWDs), the site of the differential rotation has been variously thought to be the common envelope, the hot outer regions of a merged degenerate core or an accretion disc formed by a tidally disrupted companion that is subsequently accreted by a degenerate core. We have shown previously that the observed incidence of magnetism and the mass distribution in HFMWDs are consistent with the hypothesis that they are the result of merging binaries during common envelope evolution. Here we calculate the magnetic field strengths generated by common envelope interactions for synthetic populations using a simple prescription for the generation of fields and find that the observed magnetic field distribution is also consistent with the stellar merging hypothesis. We use the Kolmogorov-Smirnov test to study the correlation between the calculated and the observed field strengths and find that it is consistent for low envelope ejection efficiency. We also suggest that field generation by the plunging of a giant gaseous planet on to a white dwarf may explain why magnetism among cool white dwarfs (including DZ white dwarfs) is higher than among hot white dwarfs. In this picture a super-Jupiter residing in the outer regions of the white dwarf's planetary system is perturbed into a highly eccentric orbit by a close stellar encounter and is later accreted by the white dwarf.

  17. Investigation on the production of hydrogen rich gas in a plasma converter for motorcycle applications

    Horng, R.-F.; Chang, Y.-P.; Wu, S.-C.

    2006-01-01

    A plasma fuel converter producing a hydrogen rich gas fuel has been designed and constructed. The methodology included using a high voltage electric arc generator to ionize the mixture of methane fuel and air, which was then reformed into a hydrogen rich gas. It transpired from the experiment that the higher the arc frequency, the higher was the generated hydrogen concentration, with a maximum concentration of 43 vol.% attained with an arc frequency of 200 Hz and an O/C (O 2 /CH 4 ) ratio of 0.10. The maximum hydrogen yield of 0.55 was obtained with an arc frequency of 200 Hz and an O/C ratio between 0.20 and 0.25. By fueling a four stroke motorcycle engine with the hydrogen rich gas, low emissions during the cold start idle condition can be obtained

  18. Attenuation of cigarette smoke-induced airway mucus production by hydrogen-rich saline in rats.

    Yunye Ning

    Full Text Available BACKGROUND: Over-production of mucus is an important pathophysiological feature in chronic airway disease such as chronic obstructive pulmonary disease (COPD and asthma. Cigarette smoking (CS is the leading cause of COPD. Oxidative stress plays a key role in CS-induced airway abnormal mucus production. Hydrogen protected cells and tissues against oxidative damage by scavenging hydroxyl radicals. In the present study we investigated the effect of hydrogen on CS-induced mucus production in rats. METHODS: Male Sprague-Dawley rats were divided into four groups: sham control, CS group, hydrogen-rich saline pretreatment group and hydrogen-rich saline control group. Lung morphology and tissue biochemical changes were determined by immunohistochemistry, Alcian Blue/periodic acid-Schiff staining, TUNEL, western blot and realtime RT-PCR. RESULTS: Hydrogen-rich saline pretreatment attenuated CS-induced mucus accumulation in the bronchiolar lumen, goblet cell hyperplasia, muc5ac over-expression and abnormal cell apoptosis in the airway epithelium as well as malondialdehyde increase in the BALF. The phosphorylation of EGFR at Tyr1068 and Nrf2 up-regulation expression in the rat lungs challenged by CS exposure were also abrogated by hydrogen-rich saline. CONCLUSION: Hydrogen-rich saline pretreatment ameliorated CS-induced airway mucus production and airway epithelium damage in rats. The protective role of hydrogen on CS-exposed rat lungs was achieved at least partly by its free radical scavenging ability. This is the first report to demonstrate that intraperitoneal administration of hydrogen-rich saline protected rat airways against CS damage and it could be promising in treating abnormal airway mucus production in COPD.

  19. A Common Origin of Magnetism from Planets to White Dwarfs

    Isern, Jordi; Külebi, Baybars [Institut de Ciències de l’Espai (CSIC), Campus UAB, 08193 Cerdanyola (Spain); García-Berro, Enrique [Institut d’Estudis Espacials de Catalunya, Ed. Nexus-201, c/Gran Capità 2-4, E-08034 Barcelona (Spain); Lorén-Aguilar, Pablo [School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL (United Kingdom)

    2017-02-20

    Isolated magnetic white dwarfs have field strengths ranging from kilogauss to gigagauss. However, the origin of the magnetic field has not been hitherto elucidated. Whether these fields are fossil, hence the remnants of original weak magnetic fields amplified during the course of the evolution of their progenitor stars, or are the result of binary interactions, or, finally, they are produced by other internal physical mechanisms during the cooling of the white dwarf itself, remains a mystery. At sufficiently low temperatures, white dwarfs crystallize. Upon solidification, phase separation of its main constituents, {sup 12}C and {sup 16}O, and of the impurities left by previous evolution occurs. This process leads to the formation of a Rayleigh–Taylor unstable liquid mantle on top of a solid core. This convective region, as it occurs in solar system planets like the Earth and Jupiter, can produce a dynamo able to yield magnetic fields of strengths of up to 0.1 MG, thus providing a mechanism that could explain magnetism in single white dwarfs.

  20. Constraining the neutrino magnetic dipole moment from white dwarf pulsations

    Córsico, A.H.; Althaus, L.G.; Bertolami, M.M. Miller; Kepler, S.O.; García-Berro, E.

    2014-01-01

    Pulsating white dwarf stars can be used as astrophysical laboratories to constrain the properties of weakly interacting particles. Comparing the cooling rates of these stars with the expected values from theoretical models allows us to search for additional sources of cooling due to the emission of axions, neutralinos, or neutrinos with magnetic dipole moment. In this work, we derive an upper bound to the neutrino magnetic dipole moment (μ ν ) using an estimate of the rate of period change of the pulsating DB white dwarf star PG 1351+489. We employ state-of-the-art evolutionary and pulsational codes which allow us to perform a detailed asteroseismological period fit based on fully DB white dwarf evolutionary sequences. Plasmon neutrino emission is the dominant cooling mechanism for this class of hot pulsating white dwarfs, and so it is the main contributor to the rate of change of period with time (Pidot) for the DBV class. Thus, the inclusion of an anomalous neutrino emission through a non-vanishing magnetic dipole moment in these sequences notably influences the evolutionary timescales, and also the expected pulsational properties of the DBV stars. By comparing the theoretical Pidot value with the rate of change of period with time of PG 1351+489, we assess the possible existence of additional cooling by neutrinos with magnetic dipole moment. Our models suggest the existence of some additional cooling in this pulsating DB white dwarf, consistent with a non-zero magnetic dipole moment with an upper limit of μ ν  ∼< 10 -11  μ B . This bound is somewhat less restrictive than, but still compatible with, other limits inferred from the white dwarf luminosity function or from the color-magnitude diagram of the Globular cluster M5. Further improvements of the measurement of the rate of period change of the dominant pulsation mode of PG 1351+489 will be necessary to confirm our bound

  1. Magnetic resonance imaging of white matter diseases of prematurity

    Rutherford, Mary A.; Supramaniam, Veena; Ederies, Ashraf; Chew, Andrew; Anjari, Mustafa; Counsell, Serena [Imperial College, Hammersmith Hospital, Robert Steiner MR Unit, MRC Clinical Sciences Centre, London (United Kingdom); Bassi, Laura; Groppo, Michela; Ramenghi, Luca A. [University of Milan, NICU, Institute of Pediatrics and Neonatology, Fondazione IRCCS Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena, Milan (Italy)

    2010-06-15

    Periventricular leucomalacia (PVL) and parenchymal venous infarction complicating germinal matrix/intraventricular haemorrhage have long been recognised as the two significant white matter diseases responsible for the majority of cases of cerebral palsy in survivors of preterm birth. However, more recent studies using magnetic resonance imaging to assess the preterm brain have documented two new appearances, adding to the spectrum of white matter disease of prematurity: punctate white matter lesions, and diffuse excessive high signal intensity (DEHSI). These appear to be more common than PVL but less significant in terms of their impact on individual neurodevelopment. They may, however, be associated with later cognitive and behavioural disorders known to be common following preterm birth. It remains unclear whether PVL, punctate lesions, and DEHSI represent a continuum of disorders occurring as a result of a similar injurious process to the developing white matter. This review discusses the role of MR imaging in investigating these three disorders in terms of aetiology, pathology, and outcome. (orig.)

  2. Magnetically gated accretion in an accreting 'non-magnetic' white dwarf.

    Scaringi, S; Maccarone, T J; D'Angelo, C; Knigge, C; Groot, P J

    2017-12-13

    White dwarfs are often found in binary systems with orbital periods ranging from tens of minutes to hours in which they can accrete gas from their companion stars. In about 15 per cent of these binaries, the magnetic field of the white dwarf is strong enough (at 10 6 gauss or more) to channel the accreted matter along field lines onto the magnetic poles. The remaining systems are referred to as 'non-magnetic', because until now there has been no evidence that they have a magnetic field that is strong enough to affect the accretion dynamics. Here we report an analysis of archival optical observations of the 'non-magnetic' accreting white dwarf in the binary system MV Lyrae, whose light curve displays quasi-periodic bursts of about 30 minutes duration roughly every 2 hours. The timescale and amplitude of these bursts indicate the presence of an unstable, magnetically regulated accretion mode, which in turn implies the existence of magnetically gated accretion, in which disk material builds up around the magnetospheric boundary (at the co-rotation radius) and then accretes onto the white dwarf, producing bursts powered by the release of gravitational potential energy. We infer a surface magnetic field strength for the white dwarf in MV Lyrae of between 2 × 10 4 gauss and 1 × 10 5 gauss, too low to be detectable by other current methods. Our discovery provides a new way of studying the strength and evolution of magnetic fields in accreting white dwarfs and extends the connections between accretion onto white dwarfs, young stellar objects and neutron stars, for which similar magnetically gated accretion cycles have been identified.

  3. Thomson scattering in magnetic fields. [of white dwarf stars

    Whitney, Barbara

    1989-01-01

    The equation of transfer in Thomson scattering atmospheres with magnetic fields is solved using Monte Carlo methods. Two cases, a plane parallel atmosphere with a magnetic field perpendicular to the atmosphere, and a dipole star, are investigated. The wavelength dependence of polarization from plane-parallel atmosphere is qualitatively similar to that observed in the magnetic white dwarf Grw+70 deg 8247, and the field strength determined by the calculation, 320 MG, is quantitatively similar to that determined from the line spectrum. The dipole model does not resemble the data as well as the single plane-parallel atmosphere.

  4. Hydrogen-rich saline ameliorates the severity of L-arginine-induced acute pancreatitis in rats

    Chen, Han; Sun, Yan Ping; Li, Yang; Liu, Wen Wu; Xiang, Hong Gang; Fan, Lie Ying; Sun, Qiang; Xu, Xin Yun; Cai, Jian Mei; Ruan, Can Ping; Su, Ning; Yan, Rong Lin; Sun, Xue Jun; Wang, Qiang

    2010-01-01

    Molecular hydrogen, which reacts with the hydroxyl radical, has been considered as a novel antioxidant. Here, we evaluated the protective effects of hydrogen-rich saline on the L-arginine (L-Arg)-induced acute pancreatitis (AP). AP was induced in Sprague-Dawley rats by giving two intraperitoneal injections of L-Arg, each at concentrations of 250 mg/100 g body weight, with an interval of 1 h. Hydrogen-rich saline (>0.6 mM, 6 ml/kg) or saline (6 ml/kg) was administered, respectively, via tail vein 15 min after each L-Arg administration. Severity of AP was assessed by analysis of serum amylase activity, pancreatic water content and histology. Samples of pancreas were taken for measuring malondialdehyde and myeloperoxidase. Apoptosis in pancreatic acinar cell was determined with terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling technique (TUNEL). Expression of proliferating cell nuclear antigen (PCNA) and nuclear factor kappa B (NF-κB) were detected with immunohistochemistry. Hydrogen-rich saline treatment significantly attenuated the severity of L-Arg-induced AP by ameliorating the increased serum amylase activity, inhibiting neutrophil infiltration, lipid oxidation and pancreatic tissue edema. Moreover, hydrogen-rich saline treatment could promote acinar cell proliferation, inhibit apoptosis and NF-κB activation. These results indicate that hydrogen treatment has a protective effect against AP, and the effect is possibly due to its ability to inhibit oxidative stress, apoptosis, NF-κB activation and to promote acinar cell proliferation.

  5. The movie about the magnetism in isolated white dwarfs

    Sliwinski, M. S.; Krzyczkowska, L. I.

    2004-10-01

    We present the movie about magnetism in the isolated white dwarfs. We tried to create a brand new form of presentation of astronomical knowledge. This one was made to show it to the scientists, so we assumed some level of knowledge that was needed to understand the movie. However it still can be a way to arouse interest of non-astronomers (even children) in astronomical research. This could also be the best way to teach young people or help them to understand astronomy and astrophysics that they have to learn at school. Below we report the plot of the movie adding, in some parts, comments that will follow.

  6. Hyperoxygenated hydrogen-rich solution suppresses shock- and resuscitation-induced liver injury.

    Dang, Yangjie; Liu, Ting; Mei, Xiaopeng; Meng, Xiangzhong; Gou, Xingchun; Deng, Bin; Xu, Hao; Xu, Lixian

    2017-12-01

    It is not known whether simultaneous delivery of hydrogen and oxygen can reduce injury caused by hemorrhagic shock and resuscitation (HSR). This study investigated the therapeutic potential of hyperoxygenated hydrogen-rich solution (HHOS), a combined hydrogen/oxygen carrier, in a rat model of HSR-induced liver injury. Rats (n = 60) were randomly divided into 5 groups (n = 6 per group at each time point). One group underwent sham operation, and the others were subjected to severe hemorrhagic shock and then treated with lactated Ringer's solution (LRS), hydrogen-rich solution, hyperoxygenated solution, or HHOS. At 2 and 6 h after resuscitation, blood samples (n = 6) were collected from the femoral artery and serum concentrations of alanine aminotransferase and aspartate aminotransferase (AST) were measured. Rats were then sacrificed, and histopathological changes in the liver were evaluated by quantifying the percentage of apoptotic cells by caspase-3 immunohistochemistry and terminal deoxynucleotidyl transferase dUTP nick-end labeling. Inflammation was assessed by assessing malondialdehyde content and tumor necrosis factor-α, and interleukin (IL)-6 expression. Compared to lactated Ringer's solution, hydrogen-rich solution, or hyperoxygenated solution groups, serum AST and alanine aminotransferase levels and IL-6, tumor necrosis factor-α, and malondialdehyde expression in liver tissue were decreased by HHOS treatment. The number of caspase-3- and terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells was decreased (P < 0.05) by HHOS treatment, 2 and 6 h after resuscitation. HHOS has protective effects against liver injury in a rat model of HSR. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Therapeutic Effects of Hydrogen-Rich Solution on Aplastic Anemia in Vivo

    Sanhu Zhao

    2013-08-01

    Full Text Available Background: Aplasitc anemia (AA is a bone marrow failure syndrome characterized by an immune-mediated destruction of hematopoietic stem cells. Though clinical symptoms could be ameliorated by bone marrow transplantation and/or immunosuppressive therapy, frequent recurrence and especially evolution of clonal hematologic diseases remains problematic clinically. Cytokines such as interferon-γ (INF-γ, tumor necrosis factor-α (TNF-α and interleukin-6 (IL-6 secreted by autologous T cells are closely related with the development of AA. Hydrogen-rich solution was reported to inhibit the levels of cytokines including INF-γ, TNF-α and IL-6 in vivo in recent studies. This study was to investigate the potential therapeutic effects of hydrogen-rich solution on AA in vivo. Methods: AA model was determined in vivo by mice and body weights of the mice were used as the basic physiological index. Peripheral blood cells were calculated to evaluate the hematologic recovery degree. Bone marrow nucleated cells (BMNCs, tissue histology, as well as CFU-S and CFU-GM forming units were used to evaluate the recovery of bone marrow microenvironment. The ratio of CD4+ and CD8+ cells were examined along with cytokine levels in serum to determine the efficacy of H2-rich solution on the affected immunological functions. Results: Body weight and number of peripheral blood cells were significantly improved for mice in the H2-rich solution treated groups as compared with those with AA. The number of BMNCs and CFUs increased markedly and the bone marrow microenvironment was also improved significantly. The experimental group restrained the cell apoptosis, relieved hyperemia and accelerated tissue repair. The number of CD4+ and CD8+ cells as well as the ratio of CD4/CD8 increased to normal gradually, while the levels of TNF-α, IFN-γ, and IL-6 in serum decreased after H2-rich solution treatment. Conclusion: Our study firstly showed that hydrogen-rich solution accelerated the

  8. Suppression of cooling by strong magnetic fields in white dwarf stars.

    Valyavin, G; Shulyak, D; Wade, G A; Antonyuk, K; Zharikov, S V; Galazutdinov, G A; Plachinda, S; Bagnulo, S; Machado, L Fox; Alvarez, M; Clark, D M; Lopez, J M; Hiriart, D; Han, Inwoo; Jeon, Young-Beom; Zurita, C; Mujica, R; Burlakova, T; Szeifert, T; Burenkov, A

    2014-11-06

    Isolated cool white dwarf stars more often have strong magnetic fields than young, hotter white dwarfs, which has been a puzzle because magnetic fields are expected to decay with time but a cool surface suggests that the star is old. In addition, some white dwarfs with strong fields vary in brightness as they rotate, which has been variously attributed to surface brightness inhomogeneities similar to sunspots, chemical inhomogeneities and other magneto-optical effects. Here we describe optical observations of the brightness and magnetic field of the cool white dwarf WD 1953-011 taken over about eight years, and the results of an analysis of its surface temperature and magnetic field distribution. We find that the magnetic field suppresses atmospheric convection, leading to dark spots in the most magnetized areas. We also find that strong fields are sufficient to suppress convection over the entire surface in cool magnetic white dwarfs, which inhibits their cooling evolution relative to weakly magnetic and non-magnetic white dwarfs, making them appear younger than they truly are. This explains the long-standing mystery of why magnetic fields are more common amongst cool white dwarfs, and implies that the currently accepted ages of strongly magnetic white dwarfs are systematically too young.

  9. Effect of bioleaching on hydrogen-rich gas production by steam gasification of sewage sludge

    Li, Hanhui; Chen, Zhihua; Huo, Chan; Hu, Mian; Guo, Dabin; Xiao, Bo

    2015-01-01

    Highlights: • Bioleaching can modify the physicochemical property of sewage sludge. • The enhancement is mainly hydrogen. • Bioleaching can enhance the gas production in gasification of sewage sludge. • Study provides an insight for future application of bioleached sewage sludge. - Abstract: Effect of bioleaching on hydrogen-rich gas production by steam gasification of sewage sludge was carried out in a lab-scale fixed-bed reactor. The influence of sewage sludge solids concentrations (6–14% (w/v) in 2% increments) during the bioleaching process and reactor temperature (600–900 °C in 100 °C increments) on gasification product yields and gas composition were studied. Characterization of samples showed that bioleaching treatment, especially in 6% (w/v) sludge solids concentration, led to metal removal effectively and modifications in the physicochemical property of sewage sludge which was favored for gasification. The maximum gas yield (49.4%) and hydrogen content (46.4%) were obtained at 6% (w/v) sludge solids concentration and reactor temperature of 900 °C. Sewage sludge after the bioleaching treatment may be a feasible feedstock for hydrogen-rich gas product.

  10. Hydrogen-rich saline injection into the subarachnoid cavity within 2 weeks promotes recovery after acute spinal cord injury

    Jian-long Wang

    2015-01-01

    Full Text Available Hydrogen can relieve tissue-damaging oxidative stress, inflammation and apoptosis. Injection of hydrogen-rich saline is an effective method for transporting molecular hydrogen. We hypothesized that hydrogen-rich saline would promote the repair of spinal cord injury induced by Allen′s method in rats. At 0.5, 1, 2, 4, 8, 12 and 24 hours after injury, then once daily for 2 weeks, 0.25 mL/kg hydrogen-rich saline was infused into the subarachnoid space through a catheter. Results at 24 hours, 48 hours, 1 week and 2 weeks after injury showed that hydrogen-rich saline markedly reduced cell death, inflammatory cell infiltration, serum malondialdehyde content, and caspase-3 immunoreactivity, elevated serum superoxide dismutase activity and calcitonin gene-related peptide immunoreactivity, and improved motor function in the hindlimb. The present study confirms that hydrogen-rich saline injected within 2 weeks of injury effectively contributes to the repair of spinal cord injury in the acute stage.

  11. Effectiveness of hydrogen rich water on antioxidant status of subjects with potential metabolic syndrome-an open label pilot study.

    Nakao, Atsunori; Toyoda, Yoshiya; Sharma, Prachi; Evans, Malkanthi; Guthrie, Najla

    2010-03-01

    Metabolic syndrome is characterized by cardiometabolic risk factors that include obesity, insulin resistance, hypertension and dyslipidemia. Oxidative stress is known to play a major role in the pathogenesis of metabolic syndrome. The objective of this study was to examine the effectiveness of hydrogen rich water (1.5-2 L/day) in an open label, 8-week study on 20 subjects with potential metabolic syndrome. Hydrogen rich water was produced, by placing a metallic magnesium stick into drinking water (hydrogen concentration; 0.55-0.65 mM), by the following chemical reaction; Mg + 2H(2)O --> Mg (OH)(2) + H(2). The consumption of hydrogen rich water for 8 weeks resulted in a 39% increase (pfasting glucose levels during the 8 week study. In conclusion, drinking hydrogen rich water represents a potentially novel therapeutic and preventive strategy for metabolic syndrome. The portable magnesium stick was a safe, easy and effective method of delivering hydrogen rich water for daily consumption by participants in the study.

  12. Protective Effects of Hydrogen-Rich Saline Against Lipopolysaccharide-Induced Alveolar Epithelial-to-Mesenchymal Transition and Pulmonary Fibrosis.

    Dong, Wen-Wen; Zhang, Yun-Qian; Zhu, Xiao-Yan; Mao, Yan-Fei; Sun, Xue-Jun; Liu, Yu-Jian; Jiang, Lai

    2017-05-19

    BACKGROUND Fibrotic change is one of the important reasons for the poor prognosis of patients with acute respiratory distress syndrome (ARDS). The present study investigated the effects of hydrogen-rich saline, a selective hydroxyl radical scavenger, on lipopolysaccharide (LPS)-induced pulmonary fibrosis. MATERIAL AND METHODS Male ICR mice were divided randomly into 5 groups: Control, LPS-treated plus vehicle treatment, and LPS-treated plus hydrogen-rich saline (2.5, 5, or 10 ml/kg) treatment. Twenty-eight days later, fibrosis was assessed by determination of collagen deposition, hydroxyproline, and type I collagen levels. Development of epithelial-to-mesenchymal transition (EMT) was identified by examining protein expressions of E-cadherin and α-smooth muscle actin (α-SMA). Transforming growth factor (TGF)-β1 content, total antioxidant capacity (T-AOC), malondialdehyde (MDA) content, catalase (CAT), and superoxide dismutase (SOD) activity were determined. RESULTS Mice exhibited increases in collagen deposition, hydroxyproline, type I collagen contents, and TGF-β1 production in lung tissues after LPS treatment. LPS-induced lung fibrosis was associated with increased expression of α-SMA, as well as decreased expression of E-cadherin. In addition, LPS treatment increased MDA levels but decreased T-AOC, CAT, and SOD activities in lung tissues, indicating that LPS induced pulmonary oxidative stress. Hydrogen-rich saline treatment at doses of 2.5, 5, or 10 ml/kg significantly attenuated LPS-induced pulmonary fibrosis. LPS-induced loss of E-cadherin in lung tissues was largely reversed, whereas the acquisition of α-SMA was dramatically decreased by hydrogen-rich saline treatment. In addition, hydrogen-rich saline treatment significantly attenuated LPS-induced oxidative stress. CONCLUSIONS Hydrogen-rich saline may protect against LPS-induced EMT and pulmonary fibrosis through suppressing oxidative stress.

  13. Hydrogen-rich saline protects retina against glutamate-induced excitotoxic injury in guinea pig.

    Wei, Lihua; Ge, Li; Qin, Shucun; Shi, Yunzhi; Du, Changqing; Du, Hui; Liu, Liwei; Yu, Yang; Sun, Xuejun

    2012-01-01

    Molecular hydrogen (H(2)) is an efficient antioxidant that can selectively reduce hydroxyl radicals and inhibit oxidative stress-induced injuries. We investigated the protective effects and mechanism of hydrogen-rich saline in a glutamate-induced retinal injury model. Retinal excitotoxicity was induced in healthy guinea pigs by injecting glutamate into the vitreous cavity. After 30 min, hydrogen-rich saline was injected into the vitreous cavity, the peritoneal cavity or both. Seven days later, the retinal stress response was evaluated by examining the stress biomarkers, inducible nitric-oxide synthase (iNOS) and glucose-regulated protein 78 (GRP78). The impaired glutamate uptake was assessed by the expression of the excitatory amino acid transporter 1(EAAT-1). The retinal histopathological changes were investigated, focusing on the thicknesses of the entire retina and its inner layer, the number of cells in the retinal ganglion cell layer (GCL) and the ultrastructure of the retinal ganglion cells (RGCs) and glial cells. Compared with the glutamate-induced injury group, the hydrogen-rich saline treatment reduced the loss of cells in the GCL and thinning of the retina and attenuated cellular morphological damage. These improvements were greatest in animals that received H(2) injections into both the vitreous and the peritoneal cavities. The hydrogen-rich saline also inhibited the expression of glial fibrillary acidic protein (GFAP) in Müller cells, CD11b in microglia, and iNOS and GRP78 in glial cells. Moreover, the hydrogen-rich saline increased the expression of EAAT-1. In conclusion, the administration of hydrogen-rich saline through the intravitreal or/and intraperitoneal routes could reduce the retinal excitotoxic injury and promote retinal recovery. This result likely occurs by inhibiting the activation of glial cells, decreasing the production of the iNOS and GRP78 and promoting glutamate clearance. Copyright © 2011 Elsevier Ltd. All rights reserved.

  14. (F)UV Spectral Analysis of Hot, Hydrogen-Rich Central Stars of Planetary Nebulae

    Ziegler, M.; Rauch, T.; Werner, K.; Kruk, J. W.

    2010-11-01

    Metal abundances of CSPNe are not well known although they provide important constraints on AGB nucleosynthesis. We aim to determine metal abundances of two hot, hydrogen-rich CSPNe (namely of A35 and NGC3587, the latter also known as M97 or the Owl Nebula) and to derive Teff and log g precisely from high-resolution, high-S/N (far-) ultraviolet observations obtained with FUSE and HST/STIS. For this purpose, we utilize NLTE model atmospheres calculated with TMAP, the Tübingen Model Atmosphere Package. Due to strong line absorption of the ISM, simultaneous modeling of interstellar features has become a standard tool in our analyses. We present preliminary results, demonstrating the importance of combining stellar and interstellar models, in order to clearly identify and measure the strengths of strategic photospheric lines.

  15. A Review on Preferential Oxidation of Carbon Monoxide in Hydrogen Rich Gases

    A. Mishra

    2011-05-01

    Full Text Available In this review, recent works on the preferential oxidation of carbon monoxide in hydrogen rich gases for fuel cell applications are summarized. H2 is used as a fuel for polymer-electrolyte membrane fuel cell (PEMFC. It is produced by reforming of natural gas or liquid fuels followed by water gas shift reaction. The produced gas consists of H2, CO, and CO2. In which CO content is around 1%, which is highly poisonous for the Pt anode of the PEMFC so that further removal of CO is needed. Catalytic preferential oxidation of CO (CO-PROX is one of the most suitable methods of purification of H2 because of high CO conversion rate at low temperature range, which is preferable for PEMFC operating conditions. Catalysts used for COPROX are mainly noble metal based; gold based and base metal oxide catalysts among them Copper-Ceria based catalysts are the most appropriate due to its low cost, easy availability and result obtained by these catalysts are comparable with the conventional noble metal catalysts. Copyright © 2011 BCREC UNDIP. All rights reserved(Received: 22nd October 2010, Revised: 12nd January 2011, Accepted: 19th January 2011[How to Cite: A. Mishra, R. Prasad. (2011. A Review on Preferential Oxidation of Carbon Monoxide in Hydrogen Rich Gases. Bulletin of Chemical Reaction Engineering & Catalysis, 6 (1: 1-14. doi:10.9767/bcrec.6.1.191.1-14][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.6.1.191.1-14 || or local:  http://ejournal.undip.ac.id/index.php/bcrec/article/view/191] | View in 

  16. The Stability of Hydrogen-Rich Atmospheres of Earth-Like Planets

    Zahnle, Kevin

    2016-01-01

    Understanding hydrogen escape is essential to understanding the limits to habitability, both for liquid water where the Sun is bright, but also to assess the true potential of H2 as a greenhouse gas where the Sun is faint. Hydrogen-rich primary atmospheres of Earth-like planets can result either from gravitational capture of solar nebular gases (with helium), or from impact shock processing of a wide variety of volatile-rich planetesimals (typically accompanied by H2O, CO2, and under the right circumstances, CH4). Most studies of hydrogen escape from planets focus on determining how fast the hydrogen escapes. In general this requires solving hydro- dynamic equations that take into account the acceleration of hydrogen through a critical transonic point and an energy budget that should include radiative heating and cooling, thermal conduction, the work done in lifting the hydrogen against gravity, and the residual heat carried by the hydrogen as it leaves. But for planets from which hydrogen escape is modest or insignificant, the atmosphere can be approximated as hydrostatic, which is much simpler, and for which a relatively full-featured treatment of radiative cooling by embedded molecules, atoms, and ions such as CO2 and H3+ is straightforward. Previous work has overlooked the fact that the H2 molecule is extremely efficient at exciting non-LTE CO2 15 micron emission, and thus that radiative cooling can be markedly more efficient when H2 is abundant. We map out the region of phase space in which terrestrial planets keep hydrogen-rich atmospheres, which is what we actually want to know for habitability. We will use this framework to reassess Tian et al's hypothesis that H2-rich atmospheres may have been rather long-lived on Earth itself. Finally, we will address the empirical observation that rocky planets with thin or negligible atmospheres are rarely or never bigger than 1.6 Earth radii.

  17. Experimental Evaluation of SI Engine Operation Supplemented by Hydrogen Rich Gas from a Compact Plasma Boosted Reformer

    J. B. Green, Jr.; N. Domingo; J. M. E. Storey; R.M. Wagner; J.S. Armfield; L. Bromberg; D. R. Cohn; A. Rabinovich; N. Alexeev

    2000-01-01

    It is well known that hydrogen addition to spark-ignited (SI) engines can reduce exhaust emissions and increase efficiency. Micro plasmatron fuel converters can be used for onboard generation of hydrogen-rich gas by partial oxidation of a wide range of fuels. These plasma-boosted microreformers are compact, rugged, and provide rapid response. With hydrogen supplement to the main fuel, SI engines can run very lean resulting in a large reduction in nitrogen oxides (NO x ) emissions relative to stoichiometric combustion without a catalytic converter. This paper presents experimental results from a microplasmatron fuel converter operating under variable oxygen to carbon ratios. Tests have also been carried out to evaluate the effect of the addition of a microplasmatron fuel converter generated gas in a 1995 2.3-L four-cylinder SI production engine. The tests were performed with and without hydrogen-rich gas produced by the plasma boosted fuel converter with gasoline. A one hundred fold reduction in NO x due to very lean operation was obtained under certain conditions. An advantage of onboard plasma-boosted generation of hydrogen-rich gas is that it is used only when required and can be readily turned on and off. Substantial NO x reduction should also be obtainable by heavy exhaust gas recirculation (EGR) facilitated by use of hydrogen-rich gas with stoichiometric operation

  18. Hydrogen-rich gas as a product of two-stage co-gasification of lignite/waste mixtures

    Straka, Pavel; Bičáková, Olga

    2014-01-01

    Roč. 39, č. 21 (2014), s. 10987-10995 ISSN 0360-3199 Institutional support: RVO:67985891 Keywords : co-gasification * waste plastics * lignite * hydrogen-rich gas Subject RIV: DM - Solid Waste and Recycling Impact factor: 3.313, year: 2014 http://authors.elsevier.com/sd/article/S0360319914014025

  19. SN 2017dio: A Type-Ic Supernova Exploding in a Hydrogen-rich Circumstellar Medium

    Kuncarayakti, Hanindyo; Maeda, Keiichi; Ashall, Christopher J.; Prentice, Simon J.; Mattila, Seppo; Kankare, Erkki; Fransson, Claes; Lundqvist, Peter; Pastorello, Andrea; Leloudas, Giorgos; Anderson, Joseph P.; Benetti, Stefano; Bersten, Melina C.; Cappellaro, Enrico; Cartier, Régis; Denneau, Larry; Della Valle, Massimo; Elias-Rosa, Nancy; Folatelli, Gastón; Fraser, Morgan; Galbany, Lluís; Gall, Christa; Gal-Yam, Avishay; Gutiérrez, Claudia P.; Hamanowicz, Aleksandra; Heinze, Ari; Inserra, Cosimo; Kangas, Tuomas; Mazzali, Paolo; Melandri, Andrea; Pignata, Giuliano; Rest, Armin; Reynolds, Thomas; Roy, Rupak; Smartt, Stephen J.; Smith, Ken W.; Sollerman, Jesper; Somero, Auni; Stalder, Brian; Stritzinger, Maximilian; Taddia, Francesco; Tomasella, Lina; Tonry, John; Weiland, Henry; Young, David R.

    2018-02-01

    SN 2017dio shows both spectral characteristics of a type-Ic supernova (SN) and signs of a hydrogen-rich circumstellar medium (CSM). Prominent, narrow emission lines of H and He are superposed on the continuum. Subsequent evolution revealed that the SN ejecta are interacting with the CSM. The initial SN Ic identification was confirmed by removing the CSM interaction component from the spectrum and comparing with known SNe Ic and, reversely, adding a CSM interaction component to the spectra of known SNe Ic and comparing them to SN 2017dio. Excellent agreement was obtained with both procedures, reinforcing the SN Ic classification. The light curve constrains the pre-interaction SN Ic peak absolute magnitude to be around {M}g=-17.6 mag. No evidence of significant extinction is found, ruling out a brighter luminosity required by an SN Ia classification. These pieces of evidence support the view that SN 2017dio is an SN Ic, and therefore the first firm case of an SN Ic with signatures of hydrogen-rich CSM in the early spectrum. The CSM is unlikely to have been shaped by steady-state stellar winds. The mass loss of the progenitor star must have been intense, \\dot{M}∼ 0.02{({ε }{{H}α }/0.01)}-1 ({v}{wind}/500 km s‑1) ({v}{shock}/10,000 km s‑1)‑3 M ⊙ yr‑1, peaking at a few decades before the SN. Such a high mass-loss rate might have been experienced by the progenitor through eruptions or binary stripping. Based on observations made with the NOT, operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. This work is based (in part) on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile as part of PESSTO, (the Public ESO Spectroscopic Survey for Transient Objects Survey) ESO program 188.D-3003, 191.D-0935, 197.D-1075. Based on observations made with the Liverpool Telescope operated on the

  20. Method of controlling injection of oxygen into hydrogen-rich fuel cell feed stream

    Meltser, Mark Alexander; Gutowski, Stanley; Weisbrod, Kirk

    2001-01-01

    A method of operating a H.sub.2 --O.sub.2 fuel cell fueled by hydrogen-rich fuel stream containing CO. The CO content is reduced to acceptable levels by injecting oxygen into the fuel gas stream. The amount of oxygen injected is controlled in relation to the CO content of the fuel gas, by a control strategy that involves (a) determining the CO content of the fuel stream at a first injection rate, (b) increasing the O.sub.2 injection rate, (c) determining the CO content of the stream at the higher injection rate, (d) further increasing the O.sub.2 injection rate if the second measured CO content is lower than the first measured CO content or reducing the O.sub.2 injection rate if the second measured CO content is greater than the first measured CO content, and (e) repeating steps a-d as needed to optimize CO consumption and minimize H.sub.2 consumption.

  1. Hydrogen-rich gas production by cogasification of coal and biomass in an intermittent fluidized bed.

    Wang, Li-Qun; Chen, Zhao-Sheng

    2013-01-01

    This paper presents the experimental results of cogasification of coal and biomass in an intermittent fluidized bed reactor, aiming to investigate the influences of operation parameters such as gasification temperature (T), steam to biomass mass ratio (SBMR), and biomass to coal mass ratio (BCMR) on hydrogen-rich (H2-rich) gas production. The results show that H2-rich gas free of N2 dilution is produced and the H2 yield is in the range of 18.25~68.13 g/kg. The increases of T, SBMR, and BCMR are all favorable for promoting the H2 production. Higher temperature contributes to higher CO and H2 contents, as well as H2 yield. The BCMR has a weak influence on gas composition, but the yield and content of H2 increase with BCMR, reaching a peak at the BCMR of 4. The H2 content and yield in the product gas increase with SBMR, whilst the content of CO increases first and then decreases correspondingly. At a typical case, the relative linear sensitivity coefficients of H2 production efficiency to T, SBMR, and BCMR were calculated. The results reveal that the order of the influence of the operation parameters on H2 production efficiency is T > SBMR > BCMR.

  2. Plasma steam reforming of E85 for hydrogen rich gas production

    Zhu Xinli; Hoang Trung; Lobban, Lance L; Mallinson, Richard G

    2011-01-01

    E85 (85 vol% ethanol and 15 vol% gasoline) is a partly renewable fuel that is increasing in supply availability. Hydrogen production from E85 for fuel cell or internal combustion engine applications is a potential method for reducing CO 2 emissions. Steam reforming of E85 using a nonthermal plasma (pulse corona discharge) reactor has been exploited at low temperature (200-300 0 C) without external heating, diluent gas, oxidant or catalyst in this work. Several operational parameters, including the discharge current, E85 concentration and feed flow rate, have been investigated. The results show that hydrogen rich gases (63-67% H 2 and 22-29% CO, with small amounts of CO 2 , C 2 hydrocarbons and CH 4 ) can be produced by this method. A comparison with ethanol reforming and gasoline reforming under identical conditions has also been made and the behaviour of E85 reforming is found to be close to that of ethanol reforming with slightly higher C 2 hydrocarbons yields.

  3. A New Analysis of Stark and Zeeman Effects on Hydrogen Lines in Magnetized DA White Dwarfs

    Ny Kieu

    2017-11-01

    Full Text Available White dwarfs with magnetic field strengths larger than 10 T are understood to represent more than 10% of the total population of white dwarfs. The presence of such strong magnetic fields is clearly indicated by the Zeeman triplet structure visible on absorption lines. In this work, we discuss the line broadening mechanisms and focus on the sensitivity of hydrogen lines on the magnetic field. We perform new calculations in conditions relevant to magnetized DA stellar atmospheres using models inspired from magnetic fusion plasma spectroscopy. A white dwarf spectrum from the Sloan Digital Sky Survey (SDSS database is analyzed. An effective temperature is provided by an adjustment of the background radiation with a Planck function, and the magnetic field is inferred from absorption lines presenting a Zeeman triplet structure. An order-of-magnitude estimate for the electron density is also performed from Stark broadening analysis.

  4. Hydrogen-rich saline attenuates anxiety-like behaviors in morphine-withdrawn mice.

    Wen, Di; Zhao, Peng; Hui, Rongji; Wang, Jian; Shen, Qianchao; Gong, Miao; Guo, Hongyan; Cong, Bin; Ma, Chunling

    2017-05-15

    Hydrogen therapy is a new medical approach for a wide range of diseases. The effects of hydrogen on central nervous system-related diseases have recently become increasingly appreciated, but little is known about whether hydrogen affects the morphine withdrawal process. This study aims to investigate the potential effects of hydrogen-rich saline (HRS) administration on naloxone-precipitated withdrawal symptoms and morphine withdrawal-induced anxiety-like behaviors. Mice received gradually increasing doses (25-100 mg/kg, i.p.) of morphine over 3 days. In the naloxone-precipitated withdrawal procedure, the mice were treated with three HRS (20 μg/kg, i.p.) injections, and naloxone (1 mg/kg, i.p.) was given 30 min after HRS administration. Body weight, jumping behavior and wet-dog shakes were immediately assessed. In the spontaneous withdrawal procedure, the mice were treated with HRS (20 μg/kg, i.p.) every 8-h. Mice underwent naloxone-precipitated or spontaneous withdrawal were tested for anxiety-like behaviors in the elevated plus-maze (EPM) and light/dark box (L/D box) paradigm, respectively. In addition, the levels of plasma corticosterone were measured. We found that HRS administration significantly reduced body weight loss, jumping behavior and wet-dog shakes in mice underwent naloxone-precipitated withdrawal, and attenuated anxiety-like behaviors in the EPM and L/D box tests after naloxone-precipitated withdrawal or a 2-day spontaneous withdrawal period. Hypo-activity or motor impairment after HRS administration was not observed in the locomotion tests. Furthermore, HRS administration significantly decreased the levels of corticosterone in morphine-withdrawn mice. These are the first findings to indicate that hydrogen might ameliorate withdrawal symptoms and exert an anxiolytic-like effect in morphine-withdrawal mice. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Influence of the hydrogen-rich on the furnace thermal efficiency

    Lee, Chien-Li; Jou, Chih-Ju G.

    2016-01-01

    Highlights: • Iν fixed velocity mixing fuel, the flame length is reduced when adding more hydrogen. • Orange-yellowish brightness decrease with increasing tail gas to hydrocarbon fuel. • Adding hydrogen to hydrocarbon fuel will improve the velocity and stability flame. - Abstract: In this research a full-scale furnace is used to recover the hydrogen-rich tail gas as fuel. Adding hydrogen gas to hydrocarbon fuel will reduce the ignition delay of methane, increase the flame velocity and speed up the relatively slow reaction rate of methane to improve the flame stability. The results show that the flame length and orange-yellowish brightness decrease as the amount of tail gas fuel added to the natural gas increases, because of the lower C/H ratio in the flame. Moreover, at a fixed flow rate of hydrocarbon fuel, the moving length of the burning flame is reduced as the amount of hydrogen increases, and thus the visible flame length becomes shorter. Additionally, burning the mixture of tail gas reduces the pressure and increases the gas rising velocity in the furnace radiation and convective zones compared to burning pure tail gas, and thus the gas temperatures in the convective zone and in the flue are raised. The furnace convective zone temperature and the flue gas temperature are 793.6 °C and 350.7 °C, respectively, for burning the mixture fuel (45 vol. % tail gas + 55 vol. % natural gas) vs. 648.5 °C and 346.3 °C for burning the pure tail gas.

  6. Decoration of carbon nano surfaces with hydrogen and hydrogen rich molecules

    Zöttl, S.

    2013-01-01

    The use of helium nano droplets as a matrix to investigate different atomic and molecular samples is a well established experimental technique. The unique properties of helium allow for different analytical methods and at the same time provide a stable ambient temperature. Cluster growth inside helium nano droplets can be accomplished by repeatedly doping the droplets with sample particles in a controlled environment. The experimental work represented in this thesis was performed using helium nano droplets to create clusters of fullerenes like C 60 and C 70 . The adsorption properties of these fullerene clusters regarding hydrogen and hydrogen rich molecules have been subject to investigation. The observed results suggest that curved carbon nano surfaces offer higher storage densities than planar graphite surfaces. The use of C 60 as a model carbon nano structure provides a well understood molecule for testing and evaluating computational methods to calculate surface properties of various carbon nano materials. The cost effective storage of hydrogen for mobile applications plays a key role in the development of alternatives to fossil fuels. For that reason, the application of carbon nano materials to store hydrogen by adsorption has attracted much scientific attention lately. The insights gained in the presented thesis contribute to the collective efforts and deliver more refined tools to estimate the adsorption properties of future carbon nano materials. In addition to the aforementioned, a time-of-flight mass spectrometer for educational purpose has been designed and constructed in the framework of my PhD thesis. The instrument is successfully used in various lab courses and information on the setup can be found in the Appendix of this work. (author) [de

  7. Stripped-envelope supernova SN 2004dk is now interacting with hydrogen-rich circumstellar material

    Mauerhan, Jon C.; Filippenko, Alexei V.; Zheng, WeiKang; Brink, Thomas; Graham, Melissa L.; Shivvers, Isaac; Clubb, Kelsey

    2018-05-01

    The dominant mechanism and time scales over which stripped-envelope supernovae (SNe) progenitor stars shed their hydrogen envelopes are uncertain. Observations of Type Ib and Ic SNe at late phases could reveal the optical signatures of interaction with distant circumstellar material (CSM) providing important clues on the origin of the necessary pre-SN mass loss. We report deep late-time optical spectroscopy of the Type Ib explosion SN 2004dk 4684 days (13 years) after discovery. We detect strong Hα emission with an intermediate line width of ˜400 km s-1 and luminosity ˜2.5 × 1039 erg s-1, signaling that the SN blast wave has caught up with the hydrogen-rich CSM lost by the progenitor system. The line luminosity is the highest ever reported for a SN at this late stage. Prominent emission features of He I, Fe, and Ca are also detected. The spectral characteristics are consistent with CSM energized by the forward shock, and resemble the late-time spectra of the persistently interacting Type IIn SNe 2005ip and 1988Z. We suggest that the onset of interaction with H-rich CSM was associated with a previously reported radio rebrightening at ˜1700 days. The data indicate that the mode of pre-SN mass loss was a relatively slow dense wind that persisted millennia before the SN, followed by a short-lived Wolf-Rayet phase that preceded core-collapse and created a cavity within an extended distribution of CSM. We also present new spectra of SNe 2014C, PTF11iqb, and 2009ip, all of which also exhibit continued interaction with extended CSM distributions.

  8. Alleviation of cadmium toxicity in Medicago sativa by hydrogen-rich water

    Cui, Weiti; Gao, Cunyi; Fang, Peng [College of Life Sciences, Nanjing Agricultural University, Nanjing 210095 (China); Lin, Guoqing [Laboratory Center of Life Sciences, Co. Laboratory of Nanjing Agricultural University and Carl Zeiss Far East, Nanjing Agricultural University, Nanjing 210095 (China); Shen, Wenbiao, E-mail: wbshenh@njau.edu.cn [College of Life Sciences, Nanjing Agricultural University, Nanjing 210095 (China)

    2013-09-15

    Highlights: • HRW can alleviate Cd-induced alfalfa seedling growth inhibition and DNA laddering. • HRW alleviates Cd-induced oxidative stress by activating antioxidant enzymes. • Cd uptake in alfalfa seedling roots was decreased by HRW. • HRW can re-establish glutathione homeostasis under Cd stress. -- Abstract: Hydrogen gas (H{sub 2}) induces plant tolerance to several abiotic stresses, including salinity and paraquat exposure. However, the role of H{sub 2} in cadmium (Cd)-induced stress amelioration is largely unknown. Here, pretreatment with hydrogen-rich water (HRW) was used to characterize physiological roles and molecular mechanisms of H{sub 2} in the alleviation of Cd toxicity in alfalfa plants. Our results showed that the addition of HRW at 10% saturation significantly decreased contents of thiobarbituric acid reactive substances (TBARS) caused by Cd, and inhibited the appearance of Cd toxicity symptoms, including the improvement of root elongation and seedling growth. These responses were related to a significant increase in the total or isozymatic activities of representative antioxidant enzymes, or their corresponding transcripts. In vivo imaging of reactive oxygen species (ROS), and the detection of lipid peroxidation and the loss of plasma membrane integrity provided further evidence for the ability of HRW to improve Cd tolerance significantly, which was consistent with a significant enhancement of the ratio of reduced/oxidized (homo)glutathione ((h)GSH). Additionally, plants pretreated with HRW accumulated less amounts of Cd. Together, this study suggested that the usage of HRW could be an effective approach for Cd detoxification and could be explored in agricultural production systems.

  9. Alleviation of cadmium toxicity in Medicago sativa by hydrogen-rich water

    Cui, Weiti; Gao, Cunyi; Fang, Peng; Lin, Guoqing; Shen, Wenbiao

    2013-01-01

    Highlights: • HRW can alleviate Cd-induced alfalfa seedling growth inhibition and DNA laddering. • HRW alleviates Cd-induced oxidative stress by activating antioxidant enzymes. • Cd uptake in alfalfa seedling roots was decreased by HRW. • HRW can re-establish glutathione homeostasis under Cd stress. -- Abstract: Hydrogen gas (H 2 ) induces plant tolerance to several abiotic stresses, including salinity and paraquat exposure. However, the role of H 2 in cadmium (Cd)-induced stress amelioration is largely unknown. Here, pretreatment with hydrogen-rich water (HRW) was used to characterize physiological roles and molecular mechanisms of H 2 in the alleviation of Cd toxicity in alfalfa plants. Our results showed that the addition of HRW at 10% saturation significantly decreased contents of thiobarbituric acid reactive substances (TBARS) caused by Cd, and inhibited the appearance of Cd toxicity symptoms, including the improvement of root elongation and seedling growth. These responses were related to a significant increase in the total or isozymatic activities of representative antioxidant enzymes, or their corresponding transcripts. In vivo imaging of reactive oxygen species (ROS), and the detection of lipid peroxidation and the loss of plasma membrane integrity provided further evidence for the ability of HRW to improve Cd tolerance significantly, which was consistent with a significant enhancement of the ratio of reduced/oxidized (homo)glutathione ((h)GSH). Additionally, plants pretreated with HRW accumulated less amounts of Cd. Together, this study suggested that the usage of HRW could be an effective approach for Cd detoxification and could be explored in agricultural production systems

  10. Hydrogen-rich water affected blood alkalinity in physically active men.

    Ostojic, Sergej M; Stojanovic, Marko D

    2014-01-01

    Possible appliance of effective and safe alkalizing agent in the treatment of metabolic acidosis could be of particular interest to humans experiencing an increase in plasma acidity, such as exercise-induced acidosis. In the present study we tested the hypothesis that the daily oral intake of 2L of hydrogen-rich water (HRW) for 14 days would increase arterial blood alkalinity at baseline and post-exercise as compared with the placebo. This study was a randomized, double blind, placebo-controlled trial involving 52 presumably healthy physically active male volunteers. Twenty-six participants received HRW and 26 a placebo (tap water) for 14 days. Arterial blood pH, partial pressure for carbon dioxide (pCO2), and bicarbonates were measured at baseline and postexercise at the start (day 0) and at the end of the intervention period (day 14). Intake of HRW significantly increased fasting arterial blood pH by 0.04 (95% confidence interval; 0.01 - 0.08; p < 0.001), and postexercise pH by 0.07 (95% confidence interval; 0.01 - 0.10; p = 0.03) after 14 days of intervention. Fasting bicarbonates were significantly higher in the HRW trial after the administration regimen as compared with the preadministration (30.5 ± 1.9 mEq/L vs. 28.3 ± 2.3 mEq/L; p < 0.0001). No volunteers withdrew before the end of the study, and no participant reported any vexatious side effects of supplementation. These results support the hypothesis that HRW administration is safe and may have an alkalizing effect in young physically active men.

  11. Beneficial effects of hydrogen-rich saline on early burn-wound progression in rats.

    Song Xue Guo

    Full Text Available Deep burn wounds undergo a dynamic process known as wound progression that results in a deepening and extension of the initial burn area. The zone of stasis is more likely to develop more severe during wound progression in the presence of hypoperfusion. Hydrogen has been reported to alleviate injury triggered by ischaemia/reperfusion and burns in various organs by selectively quenching oxygen free radicals. The aim of this study was to investigate the possible protective effects of hydrogen against early burn-wound progression.Deep-burn models were established through contact with a boiled, rectangular, brass comb for 20 s. Fifty-six Sprague-Dawley rats were randomly divided into sham, burn plus saline, and burn plus hydrogen-rich saline (HS groups with sacrifice and analysis at various time windows (6 h, 24 h, 48 h post burn. Indexes of oxidative stress, apoptosis and autophagy were measured in each group. The zone of stasis was evaluated using immunofluorescence staining, ELISA, and Western blot to explore the underlying effects and mechanisms post burn.The burn-induced increase in malondialdehyde was markedly reduced with HS, while the activities of endogenous antioxidant enzymes were significantly increased. Moreover, HS treatment attenuated increases in apoptosis and autophagy postburn in wounds, according to the TUNEL staining results and the expression analysis of Bax, Bcl-2, caspase-3, Beclin-1 and Atg-5 proteins. Additionally, HS lowered the level of myeloperoxidase and expression of TNF-α, IL-1β, and IL-6 in the zone of stasis while augmenting IL-10. The elevated levels of Akt phosphorylation and NF-κB p65 expression post burn were also downregulated by HS management.Hydrogen can attenuate early wound progression following deep burn injury. The beneficial effect of hydrogen was mediated by attenuating oxidative stress, which inhibited apoptosis and inflammation, and the Akt/NF-κB signalling pathway may be involved in regulating the

  12. Co-pyrolysis of waste tire/coal mixtures for smokeless fuel, maltenes and hydrogen-rich gas production

    Bičáková, Olga; Straka, Pavel

    2016-01-01

    Roč. 116, MAY 15 (2016), s. 203-213 ISSN 0196-8904 Grant - others:OPPK(XE) CZ.2.16/3.1.00/21538 Program:OPPK Institutional support: RVO:67985891 Keywords : waste tires * coal * co-pyrolysis * smokeless fuel * tar * hydrogen -rich gas Subject RIV: DM - Solid Waste and Recycling Impact factor: 5.589, year: 2016 http://www.sciencedirect.com/science/article/pii/S0196890416300991

  13. Features of the mass transfer in magnetic cataclysmic variables with fast-rotating white dwarfs

    Isakova Polina

    2014-01-01

    Full Text Available The flow structure in magnetic cataclysmic variables was investigated taking into account the effects of strong magnetic field and fast rotation of the white dwarf. We modeled the AE Aqr system as a unique object that has the rotation period of the white dwarf is about 1000 times shorter than the orbital period of the binary system. Observations show that in spite of fast rotation of the white dwarf some part of the stream from the inner Lagrange point comes into the Roche lobe region. We analyzed possible mechanisms preventing material to outflow from the system.

  14. Oral intake of hydrogen-rich water ameliorated chlorpyrifos-induced neurotoxicity in rats

    Wang, Tingting; Zhao, Ling; Liu, Mengyu; Xie, Fei; Ma, Xuemei, E-mail: xmma@bjut.edu.cn; Zhao, Pengxiang; Liu, Yunqi; Li, Jiala; Wang, Minglian; Yang, Zhaona; Zhang, Yutong

    2014-10-01

    Chronic exposure to low-levels of organophosphate (OP) compounds, such as chlorpyrifos (CPF), induces oxidative stress and could be related to neurological disorders. Hydrogen has been identified as a novel antioxidant which could selectively scavenge hydroxyl radicals. We explore whether intake of hydrogen-rich water (HRW) can protect Wistar rats from CPF-induced neurotoxicity. Rats were gavaged daily with 6.75 mg/kg body weight (1/20 LD{sub 50}) of CPF and given HRW by oral intake. Nissl staining and electron microscopy results indicated that HRW intake had protective effects on the CPF-induced damage of hippocampal neurons and neuronal mitochondria. Immunostaining results showed that the increased glial fibrillary acidic protein (GFAP) expression in astrocytes induced by CPF exposure can be ameliorated by HRW intake. Moreover, HRW intake also attenuated CPF-induced oxidative stress as evidenced by enhanced level of MDA, accompanied by an increase in GSH level and SOD and CAT activity. Acetylcholinesterase (AChE) activity tests showed significant decrease in brain AChE activity after CPF exposure, and this effect can be ameliorated by HRW intake. An in vitro study demonstrated that AChE activity was more intense in HRW than in normal water with or without chlorpyrifos-oxon (CPO), the metabolically-activated form of CPF. These observations suggest that HRW intake can protect rats from CPF-induced neurotoxicity, and the protective effects of hydrogen may be mediated by regulating the oxidant and antioxidant status of rats. Furthermore, this work defines a novel mechanism of biological activity of hydrogen by directly increasing the AChE activity. - Highlights: • Hydrogen molecules protect rats from CPF-induced damage of hippocampal neurons. • The increased GFAP expression induced by CPF can also be ameliorated by hydrogen. • Hydrogen molecules attenuated the increase in CPF-induced oxidative stress. • Hydrogen molecules attenuated AChE inhibition in vivo

  15. Oral intake of hydrogen-rich water ameliorated chlorpyrifos-induced neurotoxicity in rats

    Wang, Tingting; Zhao, Ling; Liu, Mengyu; Xie, Fei; Ma, Xuemei; Zhao, Pengxiang; Liu, Yunqi; Li, Jiala; Wang, Minglian; Yang, Zhaona; Zhang, Yutong

    2014-01-01

    Chronic exposure to low-levels of organophosphate (OP) compounds, such as chlorpyrifos (CPF), induces oxidative stress and could be related to neurological disorders. Hydrogen has been identified as a novel antioxidant which could selectively scavenge hydroxyl radicals. We explore whether intake of hydrogen-rich water (HRW) can protect Wistar rats from CPF-induced neurotoxicity. Rats were gavaged daily with 6.75 mg/kg body weight (1/20 LD 50 ) of CPF and given HRW by oral intake. Nissl staining and electron microscopy results indicated that HRW intake had protective effects on the CPF-induced damage of hippocampal neurons and neuronal mitochondria. Immunostaining results showed that the increased glial fibrillary acidic protein (GFAP) expression in astrocytes induced by CPF exposure can be ameliorated by HRW intake. Moreover, HRW intake also attenuated CPF-induced oxidative stress as evidenced by enhanced level of MDA, accompanied by an increase in GSH level and SOD and CAT activity. Acetylcholinesterase (AChE) activity tests showed significant decrease in brain AChE activity after CPF exposure, and this effect can be ameliorated by HRW intake. An in vitro study demonstrated that AChE activity was more intense in HRW than in normal water with or without chlorpyrifos-oxon (CPO), the metabolically-activated form of CPF. These observations suggest that HRW intake can protect rats from CPF-induced neurotoxicity, and the protective effects of hydrogen may be mediated by regulating the oxidant and antioxidant status of rats. Furthermore, this work defines a novel mechanism of biological activity of hydrogen by directly increasing the AChE activity. - Highlights: • Hydrogen molecules protect rats from CPF-induced damage of hippocampal neurons. • The increased GFAP expression induced by CPF can also be ameliorated by hydrogen. • Hydrogen molecules attenuated the increase in CPF-induced oxidative stress. • Hydrogen molecules attenuated AChE inhibition in vivo and in

  16. Hydrogen-Rich Water Intake Accelerates Oral Palatal Wound Healing via Activation of the Nrf2/Antioxidant Defense Pathways in a Rat Model

    Orihuela-Campos, Rita Cristina; Fukui, Makoto; Ito, Hiro-O

    2016-01-01

    The wound healing process attempts to restore the integrity and function of the injured tissue. Additionally, proinflammatory cytokines, growth factors, and oxidative stress play important roles in wound healing. The aim of this study was to determine whether hydrogen-rich water intake induces the activation of the Nrf2/antioxidant defense pathway in rat palatal tissue, thereby reducing systemic oxidative stress and proinflammatory cytokine levels and promoting healing-associated genes. A circular excisional wound was created in the oral palatal region, and the wound healing process was observed. The rats were divided into two experimental groups in which either hydrogen-rich water or distilled water was consumed. In the drinking hydrogen-rich water, the palatal wound healing process was accelerated compared to that in the control group. As molecular hydrogen upregulated the Nrf2 pathway, systemic oxidative stresses were decreased by the activation of antioxidant activity. Furthermore, hydrogen-rich water intake reduced proinflammatory cytokine levels and promoted the expression of healing-associated factors in rat palatal tissue. In conclusion, hydrogen-rich water intake exhibited multiple beneficial effects through activation of the Nrf2/antioxidant defense pathway. The results of this study support the hypothesis that oral administration of hydrogen-rich water benefits the wound healing process by decreasing oxidative stress and inflammatory responses. PMID:26798423

  17. Infrared photometry of cool white dwarfs

    Wickramasinghe, D.T.; Allen, D.A.; Bessell, M.S.

    1982-01-01

    The results are presented of a search for the effects of pressure induced H 2 dipole opacity on the infrared JHK magnitudes of cool white dwarfs. LHS 1126 is found to be a very cool (Tsub(e) approximately 4250 K) DC white dwarf with a H rich atmospheric composition dominated by H 2 dipole opacity in the infrared. JHK photometry also favours a H rich atmospheric composition for the DK white dwarfs LP 658-2 and W 489. The surprisingly high proportion of hydrogen rich white dwarfs in the sample appears to suggest that the mechanism which inhibits the accretion of hydrogen in the hotter helium stars becomes less effective at low (Tsub(e) approximately 3 + ion in cool hydrogen rich white dwarf atmospheres is pointed out and it is suggested that the opacity due to this ion may be responsible for the blanketing observed in the U and B magnitudes of some cool white dwarfs. (author)

  18. The cool magnetic DAZ white dwarf NLTT 10480

    Kawka, Adela; Vennes, Stephane

    2011-01-01

    Roč. 532, August (2011), A7/1-A7/8 ISSN 0004-6361 R&D Projects: GA AV ČR(CZ) IAA300030908; GA AV ČR IAA301630901; GA ČR GAP209/10/0967; GA MŠk(CZ) LC06014 Institutional research plan: CEZ:AV0Z10030501 Keywords : white dwarfs * individual star NLTT 10480 Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.587, year: 2011

  19. Diffusion-weighted magnetic resonance imaging of cerebral white matter development

    Prayer, Daniela.; Prayer, Lucas

    2003-01-01

    Diffusion-weighted magnetic resonance imaging (DWI) has become a sensitive tool to monitor white matter development. Different applications of diffusion-weighted techniques provide information about premyelinating, myelinating, and postmyelinating states of white matter maturation. Mirroring maturational processes on the cellular level, DWI has to be regarded as a morphological method as well as a functional instrument, giving insight into molecular processes during the formation of axons and myelin sheets and into the steric arrangement of white matter tracts the formation of which is strongly influenced by their function

  20. Diffusion-weighted magnetic resonance imaging of cerebral white matter development

    Prayer, Daniela. E-mail: daniela.prayer@univie.ac.at; Prayer, Lucas

    2003-03-01

    Diffusion-weighted magnetic resonance imaging (DWI) has become a sensitive tool to monitor white matter development. Different applications of diffusion-weighted techniques provide information about premyelinating, myelinating, and postmyelinating states of white matter maturation. Mirroring maturational processes on the cellular level, DWI has to be regarded as a morphological method as well as a functional instrument, giving insight into molecular processes during the formation of axons and myelin sheets and into the steric arrangement of white matter tracts the formation of which is strongly influenced by their function.

  1. Particular features of conditioned electrodefensive reflex in white rats on background of constant magnetic field

    Shust, I.V.; Galantyuk, S.I.; Cheretyanko, Yu.V.

    Study of the influence of magnetic fields upon the higher nervous activity of man and animals has long been attracting the attention of researchers. It is indicated in the literature that magnetic fields inhibit development of conditioned reflexes in planarians, fishes, and mammals. However, there are data of opposite nature as well, indicating accelerated development of the avoidance reflex in animals exposed previously to a magnetic field. Researchers studied formation of a conditioned electrodefensive reflex (CER) in white rats exposed to a constant magnetic field (CMF), and the influence of a vitamin preparation - galascorbin - on formation of the CER in animals exposed to a CMF.

  2. Effects of hydrogen-rich saline on endotoxin-induced uveitis

    Wei-ming Yan

    2017-01-01

    Full Text Available The therapeutic effects of hydrogen-rich saline (HRS have been reported for a wide range of diseases mainly via selectively reducing the amount of reactive oxygen species. Oxidative stress plays an important role in the pathogenesis of uveitis and endotoxin-induced uveitis (EIU. In this study, we investigated whether HRS can mitigate EIU in rats. Sprague-Dawley rats were randomly divided into Norm group, Model group, HRS group, dexamethasone (DEX group, and rats in the latter three groups were injected with equal amount of lipopolysaccharide (LPS to induce EIU of different severities (by 1 mg/kg of LPS, or 1/8 mg/kg of LPS. Rats in HRS group were injected with HRS intraperitoneally at three different modes to purse an ameliorating effect of EIU (10 mL/kg of HRS immediately after injection of 1 mg/kg of LPS, 20 mL/kg of HRS once a day for 1 week before injection of 1 mg/kg of LPS and at 0, 0.5, 1, 2, 6, 8, 12 hours after LPS administration, or 20 mL/kg of HRS once a day for 1 week before injection of 1/8 mg/kg of LPS, and at 0, 0.5, 1, 2, 6, 8, 12, 24 hours and once a day for 3 weeks after LPS administration. Rats of DEX group were injected with 1 mL/kg of DEX solution intraperitoneally immediately after LPS administration. Rats in Norm and Model groups did not receive any treatment. All rats were examined under slit lamp microscope and graded according to the clinical signs of uveitis. Electroretinogram, quantitative analysis of protein in aqueous humor (AqH and histological examination of iris and ciliary body were also carried out. Our results showed that HRS did not obviously ameliorate the signs of uveitis under slit lamp examination and the inflammatory cells infiltration around iris and cilliary body of EIU induced by 1 mg/kg or 1/8 mg/kg of LPS (P > 0.05, while DEX significantly reduced the inflammation reflected by the above two indicators (P 0.05, while DEX had an obvious therapeutic effect (P < 0.05. However, HRS exerted an inhibition

  3. Hydrogen-rich saline inhibits tobacco smoke-induced chronic obstructive pulmonary disease by alleviating airway inflammation and mucus hypersecretion in rats.

    Liu, Zibing; Geng, Wenye; Jiang, Chuanwei; Zhao, Shujun; Liu, Yong; Zhang, Ying; Qin, Shucun; Li, Chenxu; Zhang, Xinfang; Si, Yanhong

    2017-09-01

    Chronic obstructive pulmonary disease induced by tobacco smoke has been regarded as a great health problem worldwide. The purpose of this study is to evaluate the protective effect of hydrogen-rich saline, a novel antioxidant, on chronic obstructive pulmonary disease and explore the underlying mechanism. Sprague-Dawley rats were made chronic obstructive pulmonary disease models via tobacco smoke exposure for 12 weeks and the rats were treated with 10 ml/kg hydrogen-rich saline intraperitoneally during the last 4 weeks. Lung function testing indicated hydrogen-rich saline decreased lung airway resistance and increased lung compliance and the ratio of forced expiratory volume in 0.1 s/forced vital capacity in chronic obstructive pulmonary disease rats. Histological analysis revealed that hydrogen-rich saline alleviated morphological impairments of lung in tobacco smoke-induced chronic obstructive pulmonary disease rats. ELISA assay showed hydrogen-rich saline lowered the levels of pro-inflammatory cytokines (IL-8 and IL-6) and anti-inflammatory cytokine IL-10 in bronchoalveolar lavage fluid and serum of chronic obstructive pulmonary disease rats. The content of malondialdehyde in lung tissue and serum was also determined and the data indicated hydrogen-rich saline suppressed oxidative stress reaction. The protein expressions of mucin MUC5C and aquaporin 5 involved in mucus hypersecretion were analyzed by Western blot and ELISA and the data revealed that hydrogen-rich saline down-regulated MUC5AC level in bronchoalveolar lavage fluid and lung tissue and up-regulated aquaporin 5 level in lung tissue of chronic obstructive pulmonary disease rats. In conclusion, these results suggest that administration of hydrogen-rich saline exhibits significant protective effect on chronic obstructive pulmonary disease through alleviating inflammation, reducing oxidative stress and lessening mucus hypersecretion in tobacco smoke-induced chronic obstructive pulmonary disease rats

  4. White-dwarf rotational equilibria in magnetic cataclysmic variable stars

    Warner, B. (Cape Town Univ. (South Africa). Dept. of Astronomy Australian National Univ., Canberra (Australia). Dept. of Mathematics); Wickramasinghe, D.T. (Australian National Univ., Canberra (Australia). Dept. of Mathematics)

    1991-02-01

    The magnetic cataclysmic variable stars (polars, intermediate polars and DQ Her stars) are grouped about three lines in the orbital period-spin period diagram. This segregation is shown to be the consequence of competition between braking and accretion torques when combined with the effects of cyclical variations in rate of mass transfer. (author).

  5. Reduction of greenhouse gas emission on a medium-pressure boiler using hydrogen-rich fuel control

    Hsieh, S.-C.; Jou, Chih-Ju G.

    2007-01-01

    The increasing emission of greenhouse gases from the combustion of fossil fuel is believed to be responsible for global warming. A study was carried out to probe the influence of replacing fuel gas with hydrogen-rich refinery gas (R.G.) on the reduction of gas emission (CO 2 and NO x ) and energy saving. Test results show that the emission of CO 2 can be reduced by 16.4% annually (or 21,500 tons per year). The NO x emission can be 8.2% lower, or 75 tons less per year. Furthermore, the use of refinery gas leads to a saving of NT$57 million (approximately US$1.73 million) on fuel costs each year. There are no CO 2 , CO, SO x , unburned hydrocarbon, or particles generated from the combustion of added hydrogen. The hydrogen content in R.G. employed in this study was between 50 and 80 mol%, so the C/H ratio of the feeding fuel was reduced. Therefore, the use of hydrogen-rich fuel has practical benefits for both energy saving and the reduction of greenhouse gas emission

  6. Hydrogen-rich saline may be an effective and specific novel treatment for osteoradionecrosis of the jaw

    Chen Y

    2015-10-01

    Full Text Available Yuanli Chen, Chunlin Zong, Yuxuan Guo, Lei Tian Department of Cranio-facial Trauma and Orthognathic Surgery Laboratory of Military Stomatology, School of Stomatology, The Fourth Military Medical University, Shaanxi Key Laboratory of Stomatology, Xi’an, People’s Republic of China Abstract: Hydrogen, a therapeutic medical gas, can exert antioxidant activity via selectively reducing cytotoxic reactive oxygen species such as hydroxyl radicals. Hydrogen-rich saline is an alternative form of molecular hydrogen that has been widely used in many studies, including metabolic syndrome, cerebral, hepatic, myocardial ischemia/reperfusion, and liver injuries with obstructive jaundice, with beneficial results. Osteoradionecrosis of the jaw is a serious complication following radiotherapy for head and neck cancers. It has long been known that most radiation-induced symptoms are caused by free radicals generated by radiolysis of H2O, and the hydroxyl radical is the most reactive of these. Reducing the hydroxyl radical can distinctly improve the protection of cells from radiation damage. We hypothesized that hydrogen-rich saline might be an effective and specific method of managing and preventing osteoradionecrosis of the jaw. Keywords: osteoradionecrosis, hydrogen, reactive oxygen species

  7. The mass limit of white dwarfs with strong magnetic fields in general relativity

    Wen De-Hua; Liu He-Lei; Zhang Xiang-Dong

    2014-01-01

    Recently, U. Das and B. Mukhopadhyay proposed that the Chandrasekhar limit of a white dwarf could reach a new high level (2.58M⊙) if a superstrong magnetic field were considered (Das U and Mukhopadhyay B 2013 Phys. Rev. Lett. 110 071102), where the structure of the strongly magnetized white dwarf (SMWD) is calculated in the framework of Newtonian theory (NT). As the SMWD has a far smaller size, in contrast with the usual expectation, we found that there is an obvious general relativistic effect (GRE) in the SMWD. For example, for the SMWD with a one Landau level system, the super-Chandrasekhar mass limit in general relativity (GR) is approximately 16.5% lower than that in NT. More interestingly, the maximal mass of the white dwarf will be first increased when the magnetic field strength keeps on increasing and reaches the maximal value M = 2.48M⊙ with B D = 391.5. Then if we further increase the magnetic fields, surprisingly, the maximal mass of the white dwarf will decrease when one takes the GRE into account. (geophysics, astronomy, and astrophysics)

  8. Consequence of total lepton number violation in strongly magnetized iron white dwarfs

    Belyaev, V.B. [Bogolyubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna 141980 (Russian Federation); Ricci, P. [Istituto Nazionale di Fisica Nucleare, Sezione di Firenze, I-50019 Sesto Fiorentino (Firenze) (Italy); Šimkovic, F. [Department of Nuclear Physics and Biophysics, Comenius University, Mlynská dolina F1, SK-842 15, Bratislava (Slovakia); Bogolyubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna 141980 (Russian Federation); Adam, J.; Tater, M. [Institute of Nuclear Physics ASCR, CZ-250 68 Řež (Czech Republic); Truhlík, E., E-mail: truhlik@ujf.cas.cz [Institute of Nuclear Physics ASCR, CZ-250 68 Řež (Czech Republic)

    2015-05-15

    The influence of a neutrinoless electron to positron conversion on a cooling of strongly magnetized iron white dwarfs is studied. It is shown that they can be good candidates for soft gamma-ray repeaters and anomalous X-ray pulsars.

  9. Magnetic cation exchange isolation of lysozyme from native hen egg white

    Šafařík, Ivo; Maděrová, Zdeňka; Tokar, O.; Šafaříková, Miroslava

    2007-01-01

    Roč. 45, - (2007), s. 355-359 ISSN 1330-9862 R&D Projects: GA MŠk(CZ) 1P05OC053 Institutional research plan: CEZ:AV0Z60870520 Keywords : magnetic separation * lysozyme * hen egg white Subject RIV: EI - Biotechnology ; Bionics Impact factor: 0.906, year: 2007

  10. Preventive Effects of Drinking Hydrogen-Rich Water on Gingival Oxidative Stress and Alveolar Bone Resorption in Rats Fed a High-Fat Diet.

    Yoneda, Toshiki; Tomofuji, Takaaki; Kunitomo, Muneyoshi; Ekuni, Daisuke; Irie, Koichiro; Azuma, Tetsuji; Machida, Tatsuya; Miyai, Hisataka; Fujimori, Kouhei; Morita, Manabu

    2017-01-13

    Obesity induces gingival oxidative stress, which is involved in the progression of alveolar bone resorption. The antioxidant effect of hydrogen-rich water may attenuate gingival oxidative stress and prevent alveolar bone resorption in cases of obesity. We examined whether hydrogen-rich water could suppress gingival oxidative stress and alveolar bone resorption in obese rats fed a high-fat diet. Male Fischer 344 rats ( n = 18) were divided into three groups of six rats each: a control group (fed a regular diet and drinking distilled water) and two experimental groups (fed a high-fat diet and drinking distilled water or hydrogen-rich water). The level of 8-hydroxydeoxyguanosine was determined to evaluate oxidative stress. The bone mineral density of the alveolar bone was analyzed by micro-computerized tomography. Obese rats, induced by a high-fat diet, showed a higher gingival level of 8-hydroxydeoxyguanosine and a lower level of alveolar bone density compared to the control group. Drinking hydrogen-rich water suppressed body weight gain, lowered gingival level of 8-hydroxydeoxyguanosine, and reduced alveolar bone resorption in rats on a high-fat diet. The results indicate that hydrogen-rich water could suppress gingival oxidative stress and alveolar bone resorption by limiting obesity.

  11. Magnetization transfer changes of grey and white matter in Parkinson's disease

    Tambasco, N.; Mancini, M.L.; Paciaroni, M.; Gallai, V.; Pelliccioli, G.P.; Chiarini, P.; Leone, F.; Montanari, G.E.

    2003-01-01

    Since the attempt to evidence structural brain damage in Parkinson's disease (PD) by conventional magnetic resonance imaging (MRI) is usually disappointing, we have investigated whether the magnetization transfer ratio (MTR) can reflect changes in grey and white matter of PD patients. MTR was quantified in 44 regions of interest (ROIs) in both grey and white matter of 11 non-demented PD patients, ranging from 2 to 4 on the Hoehn and Yahr Scale, and eight age-matched healthy subjects. MTR differences between patients and controls were found in the supratentorial white matter and in the brainstem. In particular, lower MTR values were found in the paraventricular white matter of PD patients (p < 0.05) while no differences were observed in corpus callosum, frontal, parietal, occipital lobes or centrum semiovalis. Lower MTR values were found in substantia nigra (p < 0.001), red nucleus (p < 0.05) and pons (p < 0.05) of the patient group. No differences were discovered in basal ganglia and thalamus. These findings suggest that MTR measurements in the paraventricular white matter and brainstem may help to recognize a marker for probable PD. (orig.)

  12. Energy Levels and Spectral Lines of Li Atoms in White Dwarf Strength Magnetic Fields

    Zhao, L. B.

    2018-04-01

    A theoretical approach based on B-splines has been developed to calculate atomic structures and discrete spectra of Li atoms in a strong magnetic field typical of magnetic white dwarf stars. Energy levels are presented for 20 electronic states with the symmetries 20+, 20‑, 2(‑1)+, 2(‑1)‑, and 2(‑2)+. The magnetic field strengths involved range from 0 to 2350 MG. The wavelengths and oscillator strengths for the electric dipole transitions relevant to these magnetized atomic states are reported. The current results are compared to the limited theoretical data in the literature. A good agreement has been found for the lower energy levels, but a significant discrepancy is clearly visible for the higher energy levels. The existing discrepancies of the wavelengths and oscillator strengths are also discussed. Our investigation shows that the spectrum data of magnetized Li atoms previously published are obviously far from meeting requirements of analyzing discrete atomic spectra of magnetic white dwarfs with lithium atmospheres.

  13. Pilot study: Effects of drinking hydrogen-rich water on muscle fatigue caused by acute exercise in elite athletes

    Aoki Kosuke

    2012-07-01

    Full Text Available Abstract Background Muscle contraction during short intervals of intense exercise causes oxidative stress, which can play a role in the development of overtraining symptoms, including increased fatigue, resulting in muscle microinjury or inflammation. Recently it has been said that hydrogen can function as antioxidant, so we investigated the effect of hydrogen-rich water (HW on oxidative stress and muscle fatigue in response to acute exercise. Methods Ten male soccer players aged 20.9 ± 1.3 years old were subjected to exercise tests and blood sampling. Each subject was examined twice in a crossover double-blind manner; they were given either HW or placebo water (PW for one week intervals. Subjects were requested to use a cycle ergometer at a 75 % maximal oxygen uptake (VO2 for 30 min, followed by measurement of peak torque and muscle activity throughout 100 repetitions of maximal isokinetic knee extension. Oxidative stress markers and creatine kinase in the peripheral blood were sequentially measured. Results Although acute exercise resulted in an increase in blood lactate levels in the subjects given PW, oral intake of HW prevented an elevation of blood lactate during heavy exercise. Peak torque of PW significantly decreased during maximal isokinetic knee extension, suggesting muscle fatigue, but peak torque of HW didn’t decrease at early phase. There was no significant change in blood oxidative injury markers (d-ROMs and BAP or creatine kinease after exercise. Conclusion Adequate hydration with hydrogen-rich water pre-exercise reduced blood lactate levels and improved exercise-induced decline of muscle function. Although further studies to elucidate the exact mechanisms and the benefits are needed to be confirmed in larger series of studies, these preliminary results may suggest that HW may be suitable hydration for athletes.

  14. Ejection of the Massive Hydrogen-rich Envelope Timed with the Collapse of the Stripped SN 2014C

    Margutti, Raffaella [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208 (United States); Kamble, A.; Milisavljevic, D.; Drout, M.; Chakraborti, S.; Kirshner, R.; Parrent, J. T.; Patnaude, D.; Soderberg, A. M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Zapartas, E.; De Mink, S. E. [Anton Pannenkoek Institute for Astronomy, University of Amsterdam, 1090 GE Amsterdam (Netherlands); Chornock, R. [Astrophysical Institute, Department of Physics and Astronomy, 251B Clippinger Lab, Ohio University, Athens, OH 45701 (United States); Risaliti, G. [INAF-Arcetri Astrophysical Observatory, Largo E. Fermi 5, I-50125 Firenze (Italy); Zauderer, B. A. [Center for Cosmology and Particle Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Bietenholz, M. [Department of Physics and Astronomy, York University, Toronto, ON M3J 1P3 (Canada); Cantiello, M. [Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106 (United States); Chomiuk, L. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Fong, W. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Grefenstette, B. [Cahill Center for Astrophysics, 1216 E. California Boulevard, California Institute of Technology, Pasadena, CA 91125 (United States); Guidorzi, C. [University of Ferrara, Department of Physics and Earth Sciences, via Saragat 1, I-44122 Ferrara (Italy); and others

    2017-02-01

    We present multi-wavelength observations of SN 2014C during the first 500 days. These observations represent the first solid detection of a young extragalactic stripped-envelope SN out to high-energy X-rays ∼40 keV. SN 2014C shows ordinary explosion parameters ( E {sub k} ∼ 1.8 × 10{sup 51} erg and M {sub ej} ∼ 1.7 M{sub ⊙}). However, over an ∼1 year timescale, SN 2014C evolved from an ordinary hydrogen-poor supernova into a strongly interacting, hydrogen-rich supernova, violating the traditional classification scheme of type-I versus type-II SNe. Signatures of the SN shock interaction with a dense medium are observed across the spectrum, from radio to hard X-rays, and revealed the presence of a massive shell of ∼1 M {sub ⊙} of hydrogen-rich material at ∼6 × 10{sup 16} cm. The shell was ejected by the progenitor star in the decades to centuries before collapse. This result challenges current theories of massive star evolution, as it requires a physical mechanism responsible for the ejection of the deepest hydrogen layer of H-poor SN progenitors synchronized with the onset of stellar collapse. Theoretical investigations point at binary interactions and/or instabilities during the last nuclear burning stages as potential triggers of the highly time-dependent mass loss. We constrain these scenarios utilizing the sample of 183 SNe Ib/c with public radio observations. Our analysis identifies SN 2014C-like signatures in ∼10% of SNe. This fraction is reasonably consistent with the expectation from the theory of recent envelope ejection due to binary evolution if the ejected material can survive in the close environment for 10{sup 3}–10{sup 4} years. Alternatively, nuclear burning instabilities extending to core C-burning might play a critical role.

  15. Benchmarking DFT and TD-DFT Functionals for the Ground and Excited States of Hydrogen-Rich Peptide Radicals.

    Riffet, Vanessa; Jacquemin, Denis; Cauët, Emilie; Frison, Gilles

    2014-08-12

    We assess the pros and cons of a large panel of DFT exchange-correlation functionals for the prediction of the electronic structure of hydrogen-rich peptide radicals formed after electron attachment on a protonated peptide. Indeed, despite its importance in the understanding of the chemical changes associated with the reduction step, the question of the attachment site of an electron and, more generally, of the reduced species formed in the gas phase through electron-induced dissociation (ExD) processes in mass spectrometry is still a matter of debate. For hydrogen-rich peptide radicals in which several positive groups and low-lying π* orbitals can capture the incoming electron in ExD, inclusion of full Hartree-Fock exchange at long-range interelectronic distance is a prerequisite for an accurate description of the electronic states, thereby excluding several popular exchange-correlation functionals, e.g., B3LYP, M06-2X, or CAM-B3LYP. However, we show that this condition is not sufficient by comparing the results obtained with asymptotically correct range-separated hybrids (M11, LC-BLYP, LC-BPW91, ωB97, ωB97X, and ωB97X-D) and with reference CASSCF-MRCI and EOM-CCSD calculations. The attenuation parameter ω significantly tunes the spin density distribution and the excited states vertical energies. The investigated model structures, ranging from methylammonium to hexapeptide, allow us to obtain a description of the nature and energy of the electronic states, depending on (i) the presence of hydrogen bond(s) around the cationic site(s), (ii) the presence of π* molecular orbitals (MOs), and (iii) the selected DFT approach. It turns out that, in the present framework, LC-BLYP and ωB97 yields the most accurate results.

  16. THE POST-MERGER MAGNETIZED EVOLUTION OF WHITE DWARF BINARIES: THE DOUBLE-DEGENERATE CHANNEL OF SUB-CHANDRASEKHAR TYPE Ia SUPERNOVAE AND THE FORMATION OF MAGNETIZED WHITE DWARFS

    Ji Suoqing; Fisher, Robert T.; García-Berro, Enrique; Tzeferacos, Petros; Jordan, George; Lee, Dongwook; Lorén-Aguilar, Pablo; Cremer, Pascal; Behrends, Jan

    2013-01-01

    Type Ia supernovae (SNe Ia) play a crucial role as standardizable cosmological candles, though the nature of their progenitors is a subject of active investigation. Recent observational and theoretical work has pointed to merging white dwarf binaries, referred to as the double-degenerate channel, as the possible progenitor systems for some SNe Ia. Additionally, recent theoretical work suggests that mergers which fail to detonate may produce magnetized, rapidly rotating white dwarfs. In this paper, we present the first multidimensional simulations of the post-merger evolution of white dwarf binaries to include the effect of the magnetic field. In these systems, the two white dwarfs complete a final merger on a dynamical timescale, and are tidally disrupted, producing a rapidly rotating white dwarf merger surrounded by a hot corona and a thick, differentially rotating disk. The disk is strongly susceptible to the magnetorotational instability (MRI), and we demonstrate that this leads to the rapid growth of an initially dynamically weak magnetic field in the disk, the spin-down of the white dwarf merger, and to the subsequent central ignition of the white dwarf merger. Additionally, these magnetized models exhibit new features not present in prior hydrodynamic studies of white dwarf mergers, including the development of MRI turbulence in the hot disk, magnetized outflows carrying a significant fraction of the disk mass, and the magnetization of the white dwarf merger to field strengths ∼2 × 10 8 G. We discuss the impact of our findings on the origins, circumstellar media, and observed properties of SNe Ia and magnetized white dwarfs

  17. The Post-merger Magnetized Evolution of White Dwarf Binaries: The Double-degenerate Channel of Sub-Chandrasekhar Type Ia Supernovae and the Formation of Magnetized White Dwarfs

    Ji, Suoqing; Fisher, Robert T.; García-Berro, Enrique; Tzeferacos, Petros; Jordan, George; Lee, Dongwook; Lorén-Aguilar, Pablo; Cremer, Pascal; Behrends, Jan

    2013-08-01

    Type Ia supernovae (SNe Ia) play a crucial role as standardizable cosmological candles, though the nature of their progenitors is a subject of active investigation. Recent observational and theoretical work has pointed to merging white dwarf binaries, referred to as the double-degenerate channel, as the possible progenitor systems for some SNe Ia. Additionally, recent theoretical work suggests that mergers which fail to detonate may produce magnetized, rapidly rotating white dwarfs. In this paper, we present the first multidimensional simulations of the post-merger evolution of white dwarf binaries to include the effect of the magnetic field. In these systems, the two white dwarfs complete a final merger on a dynamical timescale, and are tidally disrupted, producing a rapidly rotating white dwarf merger surrounded by a hot corona and a thick, differentially rotating disk. The disk is strongly susceptible to the magnetorotational instability (MRI), and we demonstrate that this leads to the rapid growth of an initially dynamically weak magnetic field in the disk, the spin-down of the white dwarf merger, and to the subsequent central ignition of the white dwarf merger. Additionally, these magnetized models exhibit new features not present in prior hydrodynamic studies of white dwarf mergers, including the development of MRI turbulence in the hot disk, magnetized outflows carrying a significant fraction of the disk mass, and the magnetization of the white dwarf merger to field strengths ~2 × 108 G. We discuss the impact of our findings on the origins, circumstellar media, and observed properties of SNe Ia and magnetized white dwarfs.

  18. THE POST-MERGER MAGNETIZED EVOLUTION OF WHITE DWARF BINARIES: THE DOUBLE-DEGENERATE CHANNEL OF SUB-CHANDRASEKHAR TYPE Ia SUPERNOVAE AND THE FORMATION OF MAGNETIZED WHITE DWARFS

    Ji Suoqing; Fisher, Robert T. [University of Massachusetts Dartmouth, Department of Physics, 285 Old Westport Road, North Dartmouth, MA 02740 (United States); Garcia-Berro, Enrique [Departament de Fisica Aplicada, Universitat Politecnica de Catalunya, c/Esteve Terrades, 5, E-08860 Castelldefels (Spain); Tzeferacos, Petros; Jordan, George; Lee, Dongwook [Center for Astrophysical Thermonuclear Flashes, The University of Chicago, Chicago, IL 60637 (United States); Loren-Aguilar, Pablo [School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL (United Kingdom); Cremer, Pascal [Bethe Center for Theoretical Physics, Universitaet Bonn, Nussallee 12, D-53115 Bonn (Germany); Behrends, Jan [Fachbereich Physik, Freie Universitaet Berlin, Arnimallee 14, D-14195 Berlin (Germany)

    2013-08-20

    Type Ia supernovae (SNe Ia) play a crucial role as standardizable cosmological candles, though the nature of their progenitors is a subject of active investigation. Recent observational and theoretical work has pointed to merging white dwarf binaries, referred to as the double-degenerate channel, as the possible progenitor systems for some SNe Ia. Additionally, recent theoretical work suggests that mergers which fail to detonate may produce magnetized, rapidly rotating white dwarfs. In this paper, we present the first multidimensional simulations of the post-merger evolution of white dwarf binaries to include the effect of the magnetic field. In these systems, the two white dwarfs complete a final merger on a dynamical timescale, and are tidally disrupted, producing a rapidly rotating white dwarf merger surrounded by a hot corona and a thick, differentially rotating disk. The disk is strongly susceptible to the magnetorotational instability (MRI), and we demonstrate that this leads to the rapid growth of an initially dynamically weak magnetic field in the disk, the spin-down of the white dwarf merger, and to the subsequent central ignition of the white dwarf merger. Additionally, these magnetized models exhibit new features not present in prior hydrodynamic studies of white dwarf mergers, including the development of MRI turbulence in the hot disk, magnetized outflows carrying a significant fraction of the disk mass, and the magnetization of the white dwarf merger to field strengths {approx}2 Multiplication-Sign 10{sup 8} G. We discuss the impact of our findings on the origins, circumstellar media, and observed properties of SNe Ia and magnetized white dwarfs.

  19. Seven-Tesla Magnetization Transfer Imaging to Detect Multiple Sclerosis White Matter Lesions.

    Chou, I-Jun; Lim, Su-Yin; Tanasescu, Radu; Al-Radaideh, Ali; Mougin, Olivier E; Tench, Christopher R; Whitehouse, William P; Gowland, Penny A; Constantinescu, Cris S

    2018-03-01

    Fluid-attenuated inversion recovery (FLAIR) imaging at 3 Tesla (T) field strength is the most sensitive modality for detecting white matter lesions in multiple sclerosis. While 7T FLAIR is effective in detecting cortical lesions, it has not been fully optimized for visualization of white matter lesions and thus has not been used for delineating lesions in quantitative magnetic resonance imaging (MRI) studies of the normal appearing white matter in multiple sclerosis. Therefore, we aimed to evaluate the sensitivity of 7T magnetization-transfer-weighted (MT w ) images in the detection of white matter lesions compared with 3T-FLAIR. Fifteen patients with clinically isolated syndrome, 6 with multiple sclerosis, and 10 healthy participants were scanned with 7T 3-dimensional (D) MT w and 3T-2D-FLAIR sequences on the same day. White matter lesions visible on either sequence were delineated. Of 662 lesions identified on 3T-2D-FLAIR images, 652 were detected on 7T-3D-MT w images (sensitivity, 98%; 95% confidence interval, 97% to 99%). The Spearman correlation coefficient between lesion loads estimated by the two sequences was .910. The intrarater and interrater reliability for 7T-3D-MT w images was good with an intraclass correlation coefficient (ICC) of 98.4% and 81.8%, which is similar to that for 3T-2D-FLAIR images (ICC 96.1% and 96.7%). Seven-Tesla MT w sequences detected most of the white matter lesions identified by FLAIR at 3T. This suggests that 7T-MT w imaging is a robust alternative for detecting demyelinating lesions in addition to 3T-FLAIR. Future studies need to compare the roles of optimized 7T-FLAIR and of 7T-MT w imaging. © 2017 The Authors. Journal of Neuroimaging published by Wiley Periodicals, Inc. on behalf of American Society of Neuroimaging.

  20. Fabrication of redox-responsive magnetic protein microcapsules from hen egg white by the sonochemical method.

    Zhong, Shuangling; Cui, Xuejun; Tian, Fangyuan

    2015-01-01

    Redox-responsive magnetic protein microcapsules with Fe3O4 magnetic nanoparticles (MNPs) encapsulated inside have been obtained using a facile, cost-effective and fast sonochemical method from hen egg white proteins. Such prepared redox-responsive magnetic hen egg white protein microcapsules (MHEWPMCs) could be easily manipulated to do magnetic-guided targeting delivery. The synchronous loading of the hydrophobic dye Coumarin 6 as a model of drug into MHEWPMCs was readily achieved during the fabrication of MHEWPMCs by dissolving them into the oil phase before ultrasonication. TEM images indicated that Fe3O4 MNPs were encapsulated in MHEWPMCs. Confocal laser scanning microscopic images indicated that the dye was distributed evenly in the MHEWPMCs and no leakage of dye from the MHEWPMCs was observed due to the protection of protein shells. The MHEWPMCs are potential candidates as attractive carriers for drug targeting delivery and stimuli-responsive release due to their magnetic and redox responsiveness of the disulfide in the microcapsule shells.

  1. Cognitive Function and 3-Tesla Magnetic Resonance Imaging Tractography of White Matter Hyperintensities in Elderly Persons

    Reginold, William; Luedke, Angela C.; Tam, Angela; Itorralba, Justine; Fernandez-Ruiz, Juan; Reginold, Jennifer; Islam, Omar; Garcia, Angeles

    2015-01-01

    Background/Aims: This study used 3-Tesla magnetic resonance imaging (MRI) tractography to determine if there was an association between tracts crossing white matter hyperintensities (WMH) and cognitive function in elderly persons. Methods: Brain T2-weighted fluid-attenuated inversion recovery (FLAIR) and diffusion tensor MRI scans were acquired in participants above the age of 60 years. Twenty-six persons had WMH identified on T2 FLAIR scans. They completed a battery of neuropsychological tes...

  2. Spectral analysis of four surprisingly similar hot hydrogen-rich subdwarf O stars

    Latour, M.; Chayer, P.; Green, E. M.; Irrgang, A.; Fontaine, G.

    2018-01-01

    Context. Post-extreme horizontal branch stars (post-EHB) are helium-shell burning objects evolving away from the EHB and contracting directly towards the white dwarf regime. While the stars forming the EHB have been extensively studied in the past, their hotter and more evolved progeny are not so well characterized. Aims: We perform a comprehensive spectroscopic analysis of four such bright sdO stars, namely Feige 34, Feige 67, AGK+81°266, and LS II+18°9, among which the first three are used as standard stars for flux calibration. Our goal is to determine their atmospheric parameters, chemical properties, and evolutionary status to better understand this class of stars that are en route to become white dwarfs. Methods: We used non-local thermodynamic equilibrium model atmospheres in combination with high quality optical and UV spectra. Photometric data were also used to compute the spectroscopic distances of our stars and to characterize the companion responsible for the infrared excess of Feige 34. Results: The four bright sdO stars have very similar atmospheric parameters with Teff between 60 000 and 63 000 K and log g (cm s-2) in the range 5.9 to 6.1. This places these objects right on the theoretical post-EHB evolutionary tracks. The UV spectra are dominated by strong iron and nickel lines and suggest abundances that are enriched with respect to those of the Sun by factors of 25 and 60. On the other hand, the lighter elements, C, N, O, Mg, Si, P, and S are depleted. The stars have very similar abundances, although AGK+81°266 shows differences in its light element abundances. For instance, the helium abundance of this object is 10 times lower than that observed in the other three stars. All our stars show UV spectral lines that require additional line broadening that is consistent with a rotational velocity of about 25 km s-1. The infrared excess of Feige 34 is well reproduced by a M0 main-sequence companion and the surface area ratio of the two stars

  3. Mapping Magnetic Susceptibility Anisotropies of White Matter in vivo in the Human Brain at 7 Tesla

    Li, Xu; Vikram, Deepti S; Lim, Issel Anne L; Jones, Craig K; Farrell, Jonathan A.D.; van Zijl, Peter C. M.

    2012-01-01

    High-resolution magnetic resonance phase- or frequency- shift images acquired at high field show contrast related to magnetic susceptibility differences between tissues. Such contrast varies with the orientation of the organ in the field, but the development of quantitative susceptibility mapping (QSM) has made it possible to reproducibly image the intrinsic tissue susceptibility contrast. However, recent studies indicate that magnetic susceptibility is anisotropic in brain white matter and, as such, needs to be described by a symmetric second-rank tensor (χ¯¯). To fully determine the elements of this tensor, it would be necessary to acquire frequency data at six or more orientations. Assuming cylindrical symmetry of the susceptibility tensor in myelinated white matter fibers, we propose a simplified method to reconstruct the susceptibility tensor in terms of a mean magnetic susceptibility, MMS = (χ∥ + 2χ⊥)/3 and a magnetic susceptibility anisotropy, MSA = χ∥ − χ⊥, where χ∥ and χ⊥ are susceptibility parallel and perpendicular to the white matter fiber direction, respectively. Computer simulations show that with a practical head rotation angle of around 20°–30°, four head orientations suffice to reproducibly reconstruct the tensor with good accuracy. We tested this approach on whole brain 1×1×1 mm3 frequency data acquired from five healthy subjects at 7 T. The frequency information from phase images collected at four head orientations was combined with the fiber direction information extracted from diffusion tensor imaging (DTI) to map the white matter susceptibility tensor. The MMS and MSA were quantified for regions in several large white matter fiber structures, including the corona radiata, posterior thalamic radiation and corpus callosum. MMS ranged from −0.037 to −0.053 ppm (referenced to CSF being about zero). MSA values could be quantified without the need for a reference and ranged between 0.004 and 0.029 ppm, in line with

  4. (F)UV Spectral Analysis of 15 Hot, Hydrogen-Rich Central Stars of PNe

    Ziegler, Marc

    2013-07-01

    the sample are still too small to start gravitational settling. For the elements C, N, O, Si, P, and S we find increasing abundances with increasing log(Teff^4/g), while the abundances for Ar and Fe decrease. The latter is unexpected as the higher the Teff^4/g ratio, the more the radiative force dominates the gravitational force and, thus, the elements should be kept in the atmosphere. The determined abundances were compared with previous literature values, with abundances predicted from diusion calculations, with abundances from Asymptotic Giant Branch (AGB) nucleosynthesis calculations, and, if available, with abundances found for the corresponding nebulae. The agreement was of mixed quality. The derived Teff and log g values confirmed some literature values while others had to be revised (e.g. for LSS 1362 and NGC1360). However, most of them agree with the previous literature values within the error limits. No difference in Teff can be found for DAO and O(H)-type stars, but O(H)-type stars have a lower log g (5.4 - 6.0) compared to the DAOs (6.5 - 7.4). The exception is the O(H)-type central star of the planetary nebula (CSPN) of Lo 1 with log g = 7.0. A comparison of the positions of each object with stellar evolutionary tracks for post-AGB stars in the log Teff - log g diagram lead to the respective stellar masses. The derived mean mass of the analyzed sample (M = 0.536 ± 0.023 Msol) agrees within the error limits with the expected mean mass for these objects. In the literature M = 0.638 - 0.145 Msol can be found for DA-type white dwarfs, the immediate successors of DAO-type white dwarfs. For two objects (A 35, Sh 2-174) extremely low masses were found. For A35 the derived mass (M_A35 = 0.523 ± 0.05Msol) lies at the lower end of possible masses predicted for post-AGB stars. The very low mass of Sh 2-174 (M_Sh 2-174 = 0.395 ± 0.05Msol) points at Sh 2-174 being a post-extended horizontal branch (EHB) star and not a CSPN. If a stellar mass is too low, it is

  5. Analysis of the brain proton magnetic resonance spectroscopy - differences between normal grey and white matter

    Krukowski, P.; Podgorski, P.; Guzinski, M.; Szewczyk, P.; Sasiadek, M.

    2010-01-01

    Background: The proton magnetic resonance spectroscopy (HMRS) is a non-invasive diagnostic method that allows for an assessment of the metabolite concentration in tissues. The sources of the strongest resonance signals within the brain are N-acetylaspartate (NAA), creatine (Cr), choline (Cho), myoinositol (mI) and water. The aim of our study was to analyse the ratios of metabolite signals within the brain in HMRS in the healthy population, to define the differences between the grey and white matter spectra. Material/Methods: We studied prospectively 90 subjects aged from 8 to 80 years (mean 43.3 years, SD=17.9), without neurological symptoms or abnormalities in magnetic resonance imaging. In all patients, brain HMRS with Signa HDx 1.5 T MR unit (GE Healthcare) was performed with PRESS sequence, using a single voxel method, at TE of 35 ms and TR of 1500 ms. Spectroscopic evaluation involved voxels placed in the white matter of parietal lobe (PWM) and the grey matter of posterior cingulate gyrus (PGM). On the basis of the intensity of NAA, Cr, Cho, mI and water signals, the proportions of these signals were calculated, as well as the ratio of the analyzed metabolite signal to the sum of signals of NAA, Cho, Cr and mI (%Met) in the PGM and PWM voxels. We compared the proportions in the same patients in PGM and PWM voxels. Results: There has been a statistically significant difference between the proportions of a majority of the metabolite ratios evaluated in PGM and PWM, indicating the higher concentration of NAA, Cr and mI in grey matter, and higher concentration of Cho in white matter. Conclusions: HMRS spectra of the brain grey and white matter differ significantly. The concentrations of NAA, Cr and mI are higher in grey matter, while of choline - in the white matter. (authors)

  6. Bound on the flux of magnetic monopoles from catalysis of nucleon decay in white dwarfs

    Freese, K.; Krasteva, E.

    1999-01-01

    Catalysis of nucleon decay in white dwarfs is used to constrain the abundance of magnetic monopoles arising from grand unified theories. Recent discoveries of the dimmest white dwarf ever observed, WD 1136-286 with L=10 -4.94 L circle-dot , place limits on the monopole flux that are two orders of magnitude stronger than previous bounds from white dwarfs. An abundance of monopoles greater than the new bound would heat this star to a luminosity higher than what is observed. The new bound is (F/cm -2 s -1 sr -1 ) (συ/10 -28 cm 2 ) -20 (υ M /10 -3 c) 2 , where υ M is the monopole velocity in the Galaxy. The limit is improved by including the monopoles captured by the main-sequence progenitor of the white dwarf: (F/cm -2 s -1 sr -1 ) (συ/10 -28 cm 2 ) -21 for 10 17 (10 16 ) GeV monopoles. We also note that the dependence on monopole mass of flux bounds due to catalysis in neutron stars with main sequence accretion has previously been calculated incorrectly [previously the bound has been stated as F(συ/10 -28 cm 2 ) -28 cm -2 s -1 sr -1 ]. We show that the correct bounds are somewhat weaker for monopole mass other than 10 17 GeV. copyright 1999 The American Physical Society

  7. Hydrogen-rich gas production from waste plastics by pyrolysis and low-temperature steam reforming over a ruthenium catalyst

    Namioka, Tomoaki; Saito, Atsushi; Inoue, Yukiharu; Park, Yeongsu; Min, Tai-jin; Roh, Seon-ah; Yoshikawa, Kunio

    2011-01-01

    Operating conditions for low-temperature pyrolysis and steam reforming of plastics over a ruthenium catalyst were investigated. In the range studied, the highest gas and lowest coke fractions for polystyrene (PS) with a 60 g h -1 scale, continuous-feed, two-stage gasifier were obtained with a pyrolyzer temperature of 673 K, steam reforming temperature of 903 K, and weight hourly space velocity (WHSV) of 0.10 g-sample g-catalyst -1 h -1 . These operating conditions are consistent with optimum conditions reported previously for polypropylene. Our results indicate that at around 903 K, the activity of the ruthenium catalyst was high enough to minimize the difference between the rates of the steam reforming reactions of the pyrolysates from polystyrene and polypropylene. The proposed system thus has the flexibility to compensate for differences in chemical structures of municipal waste plastics. In addition, the steam reforming temperature was about 200 K lower than the temperature used in a conventional Ni-catalyzed process for the production of hydrogen. Low-temperature steam reforming allows for lower thermal input to the steam reformer, which results in an increase in thermal efficiency in the proposed process employing a Ru catalyst. Because low-temperature steam reforming can be also expected to reduce thermal degradation rates of the catalyst, the pyrolysis-steam reforming process with a Ru catalyst has the potential for use in small-scale production of hydrogen-rich gas from waste plastics that can be used for power generation.

  8. The production of hydrogen-rich gas by wet sludge pyrolysis using waste heat from blast-furnace slag

    Luo, Siyi; Feng, Yu

    2016-01-01

    Blast furnace (BF) slag, a byproduct of steelmaking industry, contains a large amount of sensible heat and is composed of some metal oxides, which exhibits preferable catalytic performance in improving tar cracking and C_nH_m reforming. This paper presents a heat recovery system from the heat of BF slag, which generates hydrogen-rich gas via the endothermic reactions of sludge pyrolysis. The effects of various parameters including the slag temperature, the mass ratio of slag to sludge (B/S), particle size and feed moisture on product yields and gas characteristics were evaluated separately. It was found that the pyrolysis products distribution was significantly influenced by the BF slag temperature. The differences resulting from varying B/S practically disappear as higher temperature heat carrier is approached. The optimum feed moisture was in favour of sludge pyrolysis by getting char and tar participate in gasification reactions, improving gas yield and quality. BF slag as catalyst can greatly increase H_2 and CO contents of gas by improving tar degradation and reforming of biogas (CO_2 and CH_4). Decreasing the slag particles size was helpful to sludge primary pyrolysis to produce more light gases, less char and condensate, while its effects on gas compositions was not evident. - Highlights: • The sensible heat of molten slag was recovered and converted into combustible gas. • A novel rotary pyrolysis reactor using BF slag as heat carrier was presented. • The moisture in sludge was used as the gasification medium and hydrogen source.

  9. Hydrogen-Rich Syngas Production from Gasification and Pyrolysis of Solar Dried Sewage Sludge: Experimental and Modeling Investigations

    Aïda Ben Hassen Trabelsi

    2017-01-01

    Full Text Available Solar dried sewage sludge (SS conversion by pyrolysis and gasification processes has been performed, separately, using two laboratory-scale reactors, a fixed-bed pyrolyzer and a downdraft gasifier, to produce mainly hydrogen-rich syngas. Prior to SS conversion, solar drying has been conducted in order to reduce moisture content (up to 10%. SS characterization reveals that these biosolids could be appropriate materials for gaseous products production. The released gases from SS pyrolysis and gasification present relatively high heating values (up to 9.96 MJ/kg for pyrolysis and 8.02  9.96 MJ/kg for gasification due to their high contents of H2 (up to 11 and 7 wt%, resp. and CH4 (up to 17 and 5 wt%, resp.. The yields of combustible gases (H2 and CH4 show further increase with pyrolysis. Stoichiometric models of both pyrolysis and gasification reactions were determined based on the global biomass formula, CαHβOγNδSε, in order to assist in the products yields optimization.

  10. Performance and emissions of a supercharged dual-fuel engine fueled by hydrogen-rich coke oven gas

    Roy, M.M.; Tomita, E.; Kawahara, N.; Harada, Y.; Sakane, A. [Okayama University, Okayama (Japan). Dept. of Mechanical Engineering

    2009-12-15

    This study investigated the engine performance and emissions of a supercharged dual-fuel engine fueled by hydrogen-rich coke oven gas and ignited by a pilot amount of diesel fuel. The engine was tested for use as a cogeneration engine, so power output while maintaining a reasonable thermal efficiency was important. Experiments were carried out at a constant pilot injection pressure and pilot quantity for different fuel-air equivalence ratios and at various injection timings without and with exhaust gas recirculation (EGR). The experimental strategy was to optimize the injection timing to maximize engine power at different fuel-air equivalence ratios without knocking and within the limit of the maximum cylinder pressure. The engine was tested first without EGR condition up to the maximum possible fuel-air equivalence ratio of 0.65. A maximum indicated mean effective pressure (IMEP) of 1425 kPa and a thermal efficiency of 39% were obtained. However, the nitrogen oxides (NOx) emissions were high. A simulated EGR up to 50% was then performed to obtain lower NOx emissions. The maximum reduction of NOx was 60% or more maintaining the similar levels of IMEP and thermal efficiency. Two-stage combustion was obtained; this is an indicator of maximum power output conditions and a precursor of knocking combustion.

  11. Dynamical response of the Ising model to the time dependent magnetic field with white noise

    Akıncı, Ümit

    2018-03-01

    The effect of the white noise in time dependent magnetic field on the dynamic behavior of the Ising model has been investigated within the effective field theory based on Glauber type of stochastic process. Discrete white noise has been chosen from both Gaussian and uniform probability distributions. Detailed investigation on probability distribution of dynamical order parameter results that, both type of noise distributions yield the same probability distribution related to the dynamical order parameter, namely Gaussian probability distribution. The variation of the parameters that describe the probability distribution of dynamical order parameter (mean value and standard deviation) with temperature and strength of the noise have been inspected. Also, it has been shown that, rising strength of the noise can induce dynamical phase transition in the system.

  12. Marchiafava-Bignami disease: magnetic resonance imaging findings in corpus callosum and subcortical white matter

    Kawarabuki, Kentaro E-mail: bukky@h2.dion.ne.jp; Sakakibara, Takehiko; Hirai, Makoto; Yoshioka, Yuji; Yamamoto, Yasumasa; Yamaki, Tarumi

    2003-11-01

    A case of Marchiafava-Bignami disease (MBD) is presented using magnetic resonance imaging (MRI). A patient with a long history of alcoholism developed a gait disturbance with involuntary movements at the lower extremities. MRI scans taken at the onset showed no particular abnormalities. He progressed to a coma 10 days later. MRI scans taken 20 days after the onset showed a focal lesion at the genu of the corpus callosum and he was diagnosed as having MBD. In addition, multiple lesions were observed in bilateral frontoparietal subcortical white matter. These lesions demonstrated similar intense MRI signals as the corpus callosum.

  13. The hidden-Markov brain: comparison and inference of white matter hyperintensities on magnetic resonance imaging (MRI)

    Pham, Tuan D.; Salvetti, Federica; Wang, Bing; Diani, Marco; Heindel, Walter; Knecht, Stefan; Wersching, Heike; Baune, Bernhard T.; Berger, Klaus

    2011-02-01

    Rating and quantification of cerebral white matter hyperintensities on magnetic resonance imaging (MRI) are important tasks in various clinical and scientific settings. As manual evaluation is time consuming and imprecise, much effort has been made to automate the quantification of white matter hyperintensities. There is rarely any report that attempts to study the similarity/dissimilarity of white matter hyperintensity patterns that have different sizes, shapes and spatial localizations on the MRI. This paper proposes an original computational neuroscience framework for such a conceptual study with a standpoint that the prior knowledge about white matter hyperintensities can be accumulated and utilized to enable a reliable inference of the rating of a new white matter hyperintensity observation. This computational approach for rating inference of white matter hyperintensities, which appears to be the first study, can be utilized as a computerized rating-assisting tool and can be very economical for diagnostic evaluation of brain tissue lesions.

  14. Si:P as a laboratory analogue for hydrogen on high magnetic field white dwarf stars.

    Murdin, B N; Li, Juerong; Pang, M L Y; Bowyer, E T; Litvinenko, K L; Clowes, S K; Engelkamp, H; Pidgeon, C R; Galbraith, I; Abrosimov, N V; Riemann, H; Pavlov, S G; Hübers, H-W; Murdin, P G

    2013-01-01

    Laboratory spectroscopy of atomic hydrogen in a magnetic flux density of 10(5) T (1 gigagauss), the maximum observed on high-field magnetic white dwarfs, is impossible because practically available fields are about a thousand times less. In this regime, the cyclotron and binding energies become equal. Here we demonstrate Lyman series spectra for phosphorus impurities in silicon up to the equivalent field, which is scaled to 32.8 T by the effective mass and dielectric constant. The spectra reproduce the high-field theory for free hydrogen, with quadratic Zeeman splitting and strong mixing of spherical harmonics. They show the way for experiments on He and H(2) analogues, and for investigation of He(2), a bound molecule predicted under extreme field conditions.

  15. Proton magnetic resonance spectroscopy of periventricular white matter and hippocampus in obstructive sleep apnea patients

    Kızılgöz, Volkan; Aydın, Hasan; Tatar, İdil Güneş; Hekimoğlu, Baki; Ardıç, Sadık; Fırat, Hikmet; Dönmez, Cem

    2013-01-01

    The purpose of this study was to diagnose the hypoxic impairment by Magnetic resonance spectroscopy (MRS), an advanced MR imaging technique, which could not be visualised by routine imaging methods in patients with obstructive sleep apnea (OSA). 20 OSA patients and 5 controls were included in this prospective research. MRS was performed on these 25 subjects to examine cerebral hypoxemia in specific regions (periventricular white matter and both hippocampi). Polysomnography was assumed as the gold standard. Statistical analysis was assessed by Mann-Whitney U test and Receiver operating characteristics (ROC) curve for NAA/Cho, NAA/Cr and Cho/Cr ratios. In the periventricular white matter, NAA/Cho ratio in OSA patients was significantly lower than in the control group (p<0.05). There were no statistical differences between the OSA and the control group for NAA/Cho, NAA/Cr and Cho/Cr ratios for both hippocampal regions. Additionally, Cho/Cr ratio in the periventricular white matter region of OSA group was higher than in the control group (p<0.05). Hypoxic impairment induced by repeated episodes of apnea leads to significant neuronal damage in OSA patients. MRS provides valuable information in the assessment of hypoxic ischemic impairment by revealing important metabolite ratios for the specific areas of the brain

  16. Is white matter affected in adolescents with anorexia nervosa? A study using magnetization transfer imaging.

    Akgül, Sinem; Öz, Ayşegül; Karlı-Oğuz, Kader; Kanbur, Nuray; Derman, Orhan

    2016-01-01

    The aim of the study was to assess potential changes in structural integrity of the brain in adolescent patients with Anorexia Nervosa (AN) using the magnetization transfer imaging technique and re-evaluating after nutritional rehabilitation was accomplished. Magnetization transfer ratio (MTR) was used for the detection and quantification of histological changes to the white matter of 9 adolescents diagnosed with AN at diagnosis and after weight gain. Using the MTR technique 6 regions were measured: the pons, left cerebellar hemisphere, amygdala, thalamus, corona radiata and white matter adjacent to the left dorsolateral prefrontal cortex. Scans from the patients with AN were also compared with scans from an age-matched subset of 9 healthy controls. Compared with control subjects, the MTR of participants with AN was no different either at the early stages of diagnosis (p=0.62) or after weight recovery (p=0.81). Similarly, comparison of MTR between patients with AN at diagnoses compared with MTR after weight recovery yielded no statistically significant difference (P=0.33). We conclude that MTR was not able to detect any neuropathological alterations in adolescent patients with AN at either diagnosis or after nutritional recovery and the achievement of weight gain.

  17. Co-pyrolysis of waste tire/coal mixtures for smokeless fuel, maltenes and hydrogen-rich gas production

    Bičáková, Olga; Straka, Pavel

    2016-01-01

    Highlights: • Co-pyrolysis of waste tires/coal mixtures yields mainly smokeless fuel (55–74 wt%). • Alternatively, the smokeless fuel can serve as carbonaceous sorbent. • The obtained tar contained maltenes (80–85 wt%) and asphaltenes (6–8 wt%). • Tar from co-pyrolysis can serve as heating oil or a source of maltenes for repairing of asphalt surfaces. • The hydrogen-rich gas was obtained (61–65 vol% H_2, 24–25 vol% CH_4, 1.4–2 vol% CO_2). - Abstract: The processing of waste tires with two different types of bituminous coal was studied through the slow co-pyrolysis of 1 kg of waste tire/coal mixtures with 15, 30 and 60 wt% waste tires on a laboratory scale. The waste tire/coal mixtures were pyrolysed using a quartz reactor in a stationary bed. The mixtures were heated at a rate 5 °C/min up to the final temperature of 900 °C with a soaking time of 30 min at the required temperature. The mass balance of the process and the properties of the coke and tar obtained were evaluated, further, the influence of the admixture in the charge on the amount and composition of the obtained coke and tar was determined. It was found that the smokeless fuel/carbonaceous sorbent and a high yield of tar for further use can be obtained through the slow co-pyrolysis. The obtained tars contained mostly maltenes (80–85 wt%). FTIR analysis showed that the maltenes from the co-pyrolysis of coal/waste tires exhibited significantly lower aromaticity as compared with that from coal alone. The gas obtained from pyrolysis or co-pyrolysis of waste tire/coal mixtures contained a high amount of hydrogen (above 60 vol%) and methane (above 20 vol%).

  18. Hydrogen-rich saline controls remifentanil-induced hypernociception and NMDA receptor NR1 subunit membrane trafficking through GSK-3β in the DRG in rats.

    Zhang, Linlin; Shu, Ruichen; Wang, Chunyan; Wang, Haiyun; Li, Nan; Wang, Guolin

    2014-07-01

    Although NMDAR trafficking mediated by GSK-3β involvement in transmission of pronociceptive messages in the spinal cord has been confirmed by our previous studies, whether NMDAR trafficking is implicated in peripheral sensitization remains equivocal. It is demonstrated that inflammation is associated with spinal NMDAR-containing nociceptive neurons activation and the maintenance of opioid induced pain hypersensitivity. However, whether and how hydrogen-rich saline, as an effective anti-inflammatory drug, could prevent hyperalgesia through affecting peripheral sensitization caused by NMDAR activation remains to be explored. To test these effects, hydrogen-rich saline (2.5, 5 or 10 ml/kg) was administrated intraperitoneally after remifentanil infusion, NMDAR antagonist MK-801 or GSK-3β inhibitor TDZD-8 was administrated intravenously before remifentanil infusion in rats. We examined time course of hydrogen concentration in blood after hydrogen-rich saline administration. Mechanical and thermal hyperalgesia were evaluated by measuring PWT and PWL for 48 post-infusion hours, respectively. Western blotting and real-time qPCR assay were applied to analyze the NR1 membrane trafficking, GSK-3β expression and activity in DRG. Inflammatory mediators (TNF-α, IL-1β, and IL-6) expressions in DRG were also analyzed. We found that NR1 membrane trafficking in DRG increased, possibly due to GSK-3β activation after remifentanil infusion. We also discovered that hydrogen-rich saline not 2.5 ml/kg but 5 and 10 ml/kg could dose-dependently attenuate mechanical and thermal hyperalgesia without affecting baseline nociceptive threshold, reduce expressions of inflammatory mediators (TNF-α, IL-1β, and IL-6) and decrease NR1 trafficking mediated by GSK-3β, and minimal effective concentration was observed to be higher than 10 μmol/L, namely peak concentration in arterial blood after administration of HRS 2.5 ml/kg without any influence on hyperalgesia. Our results indicated that

  19. Metric to quantify white matter damage on brain magnetic resonance images

    Valdes Hernandez, Maria del C.; Munoz Maniega, Susana; Anblagan, Devasuda; Bastin, Mark E.; Wardlaw, Joanna M.; Chappell, Francesca M.; Morris, Zoe; Sakka, Eleni; Dickie, David Alexander; Royle, Natalie A.; Armitage, Paul A.; Deary, Ian J.

    2017-01-01

    Quantitative assessment of white matter hyperintensities (WMH) on structural Magnetic Resonance Imaging (MRI) is challenging. It is important to harmonise results from different software tools considering not only the volume but also the signal intensity. Here we propose and evaluate a metric of white matter (WM) damage that addresses this need. We obtained WMH and normal-appearing white matter (NAWM) volumes from brain structural MRI from community dwelling older individuals and stroke patients enrolled in three different studies, using two automatic methods followed by manual editing by two to four observers blind to each other. We calculated the average intensity values on brain structural fluid-attenuation inversion recovery (FLAIR) MRI for the NAWM and WMH. The white matter damage metric is calculated as the proportion of WMH in brain tissue weighted by the relative image contrast of the WMH-to-NAWM. The new metric was evaluated using tissue microstructure parameters and visual ratings of small vessel disease burden and WMH: Fazekas score for WMH burden and Prins scale for WMH change. The correlation between the WM damage metric and the visual rating scores (Spearman ρ > =0.74, p =0.72, p < 0.0001). The repeatability of the WM damage metric was better than WM volume (average median difference between measurements 3.26% (IQR 2.76%) and 5.88% (IQR 5.32%) respectively). The follow-up WM damage was highly related to total Prins score even when adjusted for baseline WM damage (ANCOVA, p < 0.0001), which was not always the case for WMH volume, as total Prins was highly associated with the change in the intense WMH volume (p = 0.0079, increase of 4.42 ml per unit change in total Prins, 95%CI [1.17 7.67]), but not with the change in less-intense, subtle WMH, which determined the volumetric change. The new metric is practical and simple to calculate. It is robust to variations in image processing methods and scanning protocols, and sensitive to subtle and severe white

  20. Metric to quantify white matter damage on brain magnetic resonance images

    Valdes Hernandez, Maria del C.; Munoz Maniega, Susana; Anblagan, Devasuda; Bastin, Mark E.; Wardlaw, Joanna M. [University of Edinburgh, Department of Neuroimaging Sciences, Centre for Clinical Brain Sciences, Edinburgh (United Kingdom); University of Edinburgh, Centre for Cognitive Ageing and Cognitive Epidemiology, Edinburgh (United Kingdom); UK Dementia Research Institute, Edinburgh Dementia Research Centre, London (United Kingdom); Chappell, Francesca M.; Morris, Zoe; Sakka, Eleni [University of Edinburgh, Department of Neuroimaging Sciences, Centre for Clinical Brain Sciences, Edinburgh (United Kingdom); UK Dementia Research Institute, Edinburgh Dementia Research Centre, London (United Kingdom); Dickie, David Alexander; Royle, Natalie A. [University of Edinburgh, Department of Neuroimaging Sciences, Centre for Clinical Brain Sciences, Edinburgh (United Kingdom); University of Edinburgh, Centre for Cognitive Ageing and Cognitive Epidemiology, Edinburgh (United Kingdom); Armitage, Paul A. [University of Sheffield, Department of Cardiovascular Sciences, Sheffield (United Kingdom); Deary, Ian J. [University of Edinburgh, Centre for Cognitive Ageing and Cognitive Epidemiology, Edinburgh (United Kingdom); University of Edinburgh, Department of Psychology, Edinburgh (United Kingdom)

    2017-10-15

    Quantitative assessment of white matter hyperintensities (WMH) on structural Magnetic Resonance Imaging (MRI) is challenging. It is important to harmonise results from different software tools considering not only the volume but also the signal intensity. Here we propose and evaluate a metric of white matter (WM) damage that addresses this need. We obtained WMH and normal-appearing white matter (NAWM) volumes from brain structural MRI from community dwelling older individuals and stroke patients enrolled in three different studies, using two automatic methods followed by manual editing by two to four observers blind to each other. We calculated the average intensity values on brain structural fluid-attenuation inversion recovery (FLAIR) MRI for the NAWM and WMH. The white matter damage metric is calculated as the proportion of WMH in brain tissue weighted by the relative image contrast of the WMH-to-NAWM. The new metric was evaluated using tissue microstructure parameters and visual ratings of small vessel disease burden and WMH: Fazekas score for WMH burden and Prins scale for WMH change. The correlation between the WM damage metric and the visual rating scores (Spearman ρ > =0.74, p < 0.0001) was slightly stronger than between the latter and WMH volumes (Spearman ρ > =0.72, p < 0.0001). The repeatability of the WM damage metric was better than WM volume (average median difference between measurements 3.26% (IQR 2.76%) and 5.88% (IQR 5.32%) respectively). The follow-up WM damage was highly related to total Prins score even when adjusted for baseline WM damage (ANCOVA, p < 0.0001), which was not always the case for WMH volume, as total Prins was highly associated with the change in the intense WMH volume (p = 0.0079, increase of 4.42 ml per unit change in total Prins, 95%CI [1.17 7.67]), but not with the change in less-intense, subtle WMH, which determined the volumetric change. The new metric is practical and simple to calculate. It is robust to variations in

  1. Development of a Low NOx Medium sized Industrial Gas Turbine Operating on Hydrogen-Rich Renewable and Opportunity Fuels

    Srinivasan, Ram

    2013-07-31

    This report presents the accomplishments at the completion of the DOE sponsored project (Contract # DE-FC26-09NT05873) undertaken by Solar Turbines Incorporated. The objective of this 54-month project was to develop a low NOx combustion system for a medium sized industrial gas turbine engine operating on Hydrogen-rich renewable and opportunity Fuels. The work in this project was focused on development of a combustion system sized for 15MW Titan 130 gas turbine engine based on design analysis and rig test results. Although detailed engine evaluation of the complete system is required prior to commercial application, those tasks were beyond the scope of this DOE sponsored project. The project tasks were organized in three stages, Stages 2 through 4. In Stage 2 of this project, Solar Turbines Incorporated characterized the low emission capability of current Titan 130 SoLoNOx fuel injector while operating on a matrix of fuel blends with varying Hydrogen concentration. The mapping in this phase was performed on a fuel injector designed for natural gas operation. Favorable test results were obtained in this phase on emissions and operability. However, the resulting fuel supply pressure needed to operate the engine with the lower Wobbe Index opportunity fuels would require additional gas compression, resulting in parasitic load and reduced thermal efficiency. In Stage 3, Solar characterized the pressure loss in the fuel injector and developed modifications to the fuel injection system through detailed network analysis. In this modification, only the fuel delivery flowpath was modified and the air-side of the injector and the premixing passages were not altered. The modified injector was fabricated and tested and verified to produce similar operability and emissions as the Stage 2 results. In parallel, Solar also fabricated a dual fuel capable injector with the same air-side flowpath to improve commercialization potential. This injector was also test verified to produce 15

  2. NuSTAR and swift observations of the fast rotating magnetized white dwarf AE Aquarii

    Kitaguchi, Takao; An, Hongjun; Beloborodov, Andrei M.

    2014-01-01

    AE Aquarii is a cataclysmic variable with the fastest known rotating magnetized white dwarf (P-spin = 33.08 s). Compared to many intermediate polars, AE Aquarii shows a soft X-ray spectrum with a very low luminosity (L-X similar to 10(31) erg s(-1)). We have analyzed overlapping observations...... of this system with the NuSTAR and the Swift X-ray observatories in 2012 September. We find the 0.5-30 keV spectra to be well fitted by either an optically thin thermal plasma model with three temperatures of 0.75(-0.45)(+0.18), 2.29(-0.82)(+0.96), and 9.33(-2.18)(+6.07) keV, or an optically thin thermal plasma...

  3. Magnetization transfer imaging of periventricular white matter lesions in patients with multi-infarct dementia

    Hanyu, Haruo; Imon, Yukari; Asano, Tetsuichi; Iwamoto, Toshihiko; Takasaki, Masaru

    1998-01-01

    Using magnetization transfer (MT) imaging, we studied the underlying pathological conditions of periventricular hyperintense (PVH) white matter changes seen on T2-weighted MR images of patients with multi-infarct dementia. Twenty-two patients with multiple lacunar infarcts and PVH lesions, including 11 with dementia (diagnosed as multi-infarct dementia) and 11 without dementia, and 10 control subjects (with multiple lacunes, but no PVH lesion) were studied using the MT technique. MT ratios (MTRs) were calculated for PVH lesions (normal-appearing frontal white matter in controls) and the genu of the corpus callosum. Signal intensities on T2-weighted images in PVH lesions of patients were significantly higher than those in normal-appearing white matter of controls, while there were no significant differences in signal intensity in the genu of the corpus callosum among the dementia, non-dementia and control groups. However, MTRs in patients with PVH lesions were significantly lower than those in controls, and MTRs in demented patients were significantly lower than those in non-demented patients. Moreover, MTRs in the genu of the corpus callosum of demented patients were significantly lower than in those in non-demented patients and controls. MTRs in PVH lesions and the genu of the corpus callosum significantly correlated with Hasegawa's dementia scale score. These results suggest that there is some difference in histopathologic changes of PVH lesions between demented and non-demented patients and that the pathological substrate in the corpus callosum may play a role in inducing cognitive decline. Studies with MT imaging may allow the characterization of different pathological conditions that cannot be visualized by conventional MRI. (author)

  4. Theoretical models of highly magnetic white dwarf stars that violate the Chandrasekhar Limit

    Shah, Hridaya

    2017-08-01

    Until recently, white dwarf (WD) stars were believed to be no more massive than 1.44 solar masses (M ⊙ ). This belief has been changed now with the observations of over-luminous or 'peculiar' Type la supernovae that have lead researchers to hypothesize the existence of WDs in the mass range 2.4 - 2.8 M ⊙ . This discovery also raises some doubt over the reliability of the Type Ia supernova as a standard candle. It is thought that these super-massive WDs are their most likely progenitors and that they probably have a very strong magnetic field inside them. A degenerate electron gas in a magnetic field, such as that present inside this star, will be Landau quantized. Magnetic field changes the momentum space of electrons which in turn changes their density of states (DOS) and that in turn changes the equation of state (EoS) of matter inside the star, as opposed to that without a field. When this change in the DOS is taken into account and a link between the DOS and the EoS is established, as is done in this work, I find a physical reason behind the theoretical mass-radius (M-R) relations of a super-massive WD. I start with different equations of state with at most three Landau levels occupied and then construct stellar models of magnetic WDs (MWDs) using the same. I also show the M-R relations of these stars for a particular chosen value of maximum electron Fermi energy. Once a multiple Landau level system of electrons is considered, I find that it leads to such an EoS that gives multiple branches in the MR relations. Super-massive MWDs are obtained only when the Landau level occupancy is limited to just one level and some of the mass values fall within the mass range given above.

  5. Activation of auditory white matter tracts as revealed by functional magnetic resonance imaging

    Tae, Woo Suk [Kangwon National University, Neuroscience Research Institute, School of Medicine, Chuncheon (Korea, Republic of); Yakunina, Natalia; Nam, Eui-Cheol [Kangwon National University, Neuroscience Research Institute, School of Medicine, Chuncheon (Korea, Republic of); Kangwon National University, Department of Otolaryngology, School of Medicine, Chuncheon, Kangwon-do (Korea, Republic of); Kim, Tae Su [Kangwon National University Hospital, Department of Otolaryngology, Chuncheon (Korea, Republic of); Kim, Sam Soo [Kangwon National University, Neuroscience Research Institute, School of Medicine, Chuncheon (Korea, Republic of); Kangwon National University, Department of Radiology, School of Medicine, Chuncheon (Korea, Republic of)

    2014-07-15

    The ability of functional magnetic resonance imaging (fMRI) to detect activation in brain white matter (WM) is controversial. In particular, studies on the functional activation of WM tracts in the central auditory system are scarce. We utilized fMRI to assess and characterize the entire auditory WM pathway under robust experimental conditions involving the acquisition of a large number of functional volumes, the application of broadband auditory stimuli of high intensity, and the use of sparse temporal sampling to avoid scanner noise effects and increase signal-to-noise ratio. Nineteen healthy volunteers were subjected to broadband white noise in a block paradigm; each run had four sound-on/off alternations and was repeated nine times for each subject. Sparse sampling (TR = 8 s) was used. In addition to traditional gray matter (GM) auditory center activation, WM activation was detected in the isthmus and midbody of the corpus callosum (CC), tapetum, auditory radiation, lateral lemniscus, and decussation of the superior cerebellar peduncles. At the individual level, 13 of 19 subjects (68 %) had CC activation. Callosal WM exhibited a temporal delay of approximately 8 s in response to the stimulation compared with GM. These findings suggest that direct evaluation of the entire functional network of the central auditory system may be possible using fMRI, which may aid in understanding the neurophysiological basis of the central auditory system and in developing treatment strategies for various central auditory disorders. (orig.)

  6. Activation of auditory white matter tracts as revealed by functional magnetic resonance imaging

    Tae, Woo Suk; Yakunina, Natalia; Nam, Eui-Cheol; Kim, Tae Su; Kim, Sam Soo

    2014-01-01

    The ability of functional magnetic resonance imaging (fMRI) to detect activation in brain white matter (WM) is controversial. In particular, studies on the functional activation of WM tracts in the central auditory system are scarce. We utilized fMRI to assess and characterize the entire auditory WM pathway under robust experimental conditions involving the acquisition of a large number of functional volumes, the application of broadband auditory stimuli of high intensity, and the use of sparse temporal sampling to avoid scanner noise effects and increase signal-to-noise ratio. Nineteen healthy volunteers were subjected to broadband white noise in a block paradigm; each run had four sound-on/off alternations and was repeated nine times for each subject. Sparse sampling (TR = 8 s) was used. In addition to traditional gray matter (GM) auditory center activation, WM activation was detected in the isthmus and midbody of the corpus callosum (CC), tapetum, auditory radiation, lateral lemniscus, and decussation of the superior cerebellar peduncles. At the individual level, 13 of 19 subjects (68 %) had CC activation. Callosal WM exhibited a temporal delay of approximately 8 s in response to the stimulation compared with GM. These findings suggest that direct evaluation of the entire functional network of the central auditory system may be possible using fMRI, which may aid in understanding the neurophysiological basis of the central auditory system and in developing treatment strategies for various central auditory disorders. (orig.)

  7. Incidental white matter lesions identified on magnetic resonance images of normal Japanese individuals; Correlation with age and hypertension

    Oyama, Hirofumi; Kida, Yoshihisa; Tanaka, Takayuki; Iwakoshi, Takanori; Niwa, Masahiro; Kobayashi, Tatsuya [Komaki City Hospital, Hokkaido (Japan)

    1994-05-01

    Incidental white matter high-intensity lesions are frequently seen on T[sub 2]-weighted magnetic resonance (MR) images of the brain in older people. The incidence increases with advancing age or hypertension. Brain MR images of 59 normal individuals were examined to analyze this phenomenon. The total number of white matter high-intensity lesions correlated significantly with age (p=0.004) or systolic blood pressure (p=0.03). The 60- to 69-year-old group demonstrated a very close correlation of white matter lesions with systolic (p=0.02) and diastolic blood pressure (p=0.01), in contrast to the 50- to 59-year-old group. Hypertensive subjects in their 60s are thought to develop more white matter lesions than subjects in their 50s. (author).

  8. [The protection of hydrogen-rich saline on a rat dry eye model induced by scopolamine hydrobromide].

    Chu, Y Y; Hua, N; Ru, Y S; Zhao, S Z

    2017-05-11

    Objective: To evaluate the effect of hydrogen-rich saline (HRS) on dry eye rats induced by subcutaneous injection of scopolamine hydrobromide. Methods: Experiment research. Thirty female Wistar rats at about six weeks old were randomly divided into the normal group, dry eye group, HRS eyedrops group, normal saline eyedrops group (NS), HRS intraperitoneal injection group and NS intraperitoneal injection group, with 5 rats in each group. The dry eye was induced by subcutaneous injection of scopolamine hydrobromide in the latter five groups. The clinical signs of dry eye such as tear volume (SⅠt), tear break-up time (BUT) and corneal epithelial fluorescein staining scores were evaluated on day 7, 14, 21 and 28. On the 28th day, ten eyes in each group were enucleated and processed for paraffin sections for HE, PAS and immunohistochemistry stainings. Analysis of variance was used to test the data, and independent samples t -test was used for comparison between the two groups. Two-way repeated measure ANOVA was used to compare the difference among groups at different time points, one-way ANOVA was used to test the comparisons of the clinical signs at one time, and LSD was used to for comparison between two groups. Results: Before and after the experiment of the day 7, 14, 21, 28, the values of SIt in HRS eyedrops group and HRS intraperitoneal injection group were respectively:(3.625±1.157),(3.313±0.704),(3.250±0.535),(3.313±0.372), (3.375±0.582)mm and (3.500±1.019), (2.893±0.656), (3.321±0.668), (3.179±0.575), (3.214±0.871)mm. The values of BUT were respectively: (2.750±0.707), (2.688±0.594), (2.813±0.753), (3.000±0.756), (2.750±0.707)s and (3.000±0.679), (2.321±0.464), (2.750±0.753), (3.214±0.699), (2.679±0.608)s. The values of fluorescein staining score were respectively: (6.250±0.707), (8.875±0.641), (8.750±0.707), (9.250±0.463), (8.250±1.282) and (6.000±0.679), (9.143±1.027), (8.857±0.770), (9.143±0.949), (8.500±0.760). The difference

  9. Hydrogen-rich Water Exerting a Protective Effect on Ovarian Reserve Function in a Mouse Model of Immune Premature Ovarian Failure Induced by Zona Pellucida 3

    He, Xin; Wang, Shu-Yu; Yin, Cheng-Hong; Wang, Tong; Jia, Chan-Wei; Ma, Yan-Min

    2016-01-01

    Background: Premature ovarian failure (POF) is a disease that affects female fertility but has few effective treatments. Ovarian reserve function plays an important role in female fertility. Recent studies have reported that hydrogen can protect male fertility. Therefore, we explored the potential protective effect of hydrogen-rich water on ovarian reserve function through a mouse immune POF model. Methods: To set up immune POF model, fifty female BALB/c mice were randomly divided into four groups: Control (mice consumed normal water, n = 10), hydrogen (mice consumed hydrogen-rich water, n = 10), model (mice were immunized with zona pellucida glycoprotein 3 [ZP3] and consumed normal water, n = 15), and model-hydrogen (mice were immunized with ZP3 and consumed hydrogen-rich water, n = 15) groups. After 5 weeks, mice were sacrificed. Serum anti-Müllerian hormone (AMH) levels, granulosa cell (GC) apoptotic index (AI), B-cell leukemia/lymphoma 2 (Bcl-2), and BCL2-associated X protein (Bax) expression were examined. Analyses were performed using SPSS 17.0 (SPSS Inc., Chicago, IL, USA) software. Results: Immune POF model, model group exhibited markedly reduced serum AMH levels compared with those of the control group (5.41 ± 0.91 ng/ml vs. 16.23 ± 1.97 ng/ml, P = 0.033) and the hydrogen group (19.65 ± 7.82 ng/ml, P = 0.006). The model-hydrogen group displayed significantly higher AMH concentrations compared with that of the model group (15.03 ± 2.75 ng/ml vs. 5.41 ± 0.91 ng/ml, P = 0.021). The GC AI was significantly higher in the model group (21.30 ± 1.74%) than those in the control (7.06 ± 0.27%), hydrogen (5.17 ± 0.41%), and model-hydrogen groups (11.24 ± 0.58%) (all P hydrogen group compared with that of the hydrogen group (11.24 ± 0.58% vs. 5.17 ± 0.41%, P = 0.021). Compared with those of the model group, ovarian tissue Bcl-2 levels increased (2.18 ± 0.30 vs. 3.01 ± 0.33, P = 0.045) and the Bax/Bcl-2 ratio decreased in the model-hydrogen group

  10. Hydrogen-rich medium protects mouse embryonic fibroblasts from oxidative stress by activating LKB1-AMPK-FoxO1 signal pathway.

    Lee, Jihyun; Yang, Goowon; Kim, Young-Joo; Tran, Quynh Hoa; Choe, Wonchae; Kang, Insug; Kim, Sung Soo; Ha, Joohun

    2017-09-23

    Persistent oxidative stress is recognized as a major cause of many pathological conditions as well as ageing. However, most clinical trials of dietary antioxidants have failed to produce successful outcomes in treating oxidative stress-induced diseases. Molecular hydrogen (H 2 ) has recently received considerable attention as a therapeutic agent owing to its novel antioxidant properties, a selective scavenger of hydroxyl and peroxynitrite radicals. Beyond this, numerous reports support that H 2 can modulate the activity of various cellular signal pathways. However, its effect on AMP-activated protein kinase (AMPK) signal pathway, a central regulator of energy hemostasis, has remained almost elusive. Here, we report that hydrogen-rich medium activated LKB1-AMPK signal pathway without ATP depletion, which in turn induced FoxO1-dependent transcription of manganese superoxide dismutase and catalase in mouse embryonic fibroblasts. Moreover, hydrogen-rich media effectively reduced the level of reactive oxygen species in cells treated with hydrogen peroxide and protected these cells from apoptosis in an AMPK-dependent manner. These results suggest that the LKB1-AMPK-FoxO1 signaling pathway is a critical mediator of the antioxidant properties of H 2 , further supporting the idea that H 2 acts as a signaling molecule to serve various physiological functions. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Cognitive Function and 3-Tesla Magnetic Resonance Imaging Tractography of White Matter Hyperintensities in Elderly Persons

    William Reginold

    2015-10-01

    Full Text Available Background/Aims: This study used 3-Tesla magnetic resonance imaging (MRI tractography to determine if there was an association between tracts crossing white matter hyperintensities (WMH and cognitive function in elderly persons. Methods: Brain T2-weighted fluid-attenuated inversion recovery (FLAIR and diffusion tensor MRI scans were acquired in participants above the age of 60 years. Twenty-six persons had WMH identified on T2 FLAIR scans. They completed a battery of neuropsychological tests and were classified as normal controls (n = 15 or with Alzheimer's dementia (n = 11. Tractography was generated by the Fiber Assignment by Continuous Tracking method. All tracts that crossed WMH were segmented. The average fractional anisotropy and average mean diffusivity of these tracts were quantified. We studied the association between cognitive test scores with the average mean diffusivity and average fractional anisotropy of tracts while controlling for age, total WMH volume and diagnosis. Results: An increased mean diffusivity of tracts crossing WMH was associated with worse performance on the Wechsler Memory Scale-III Longest Span Forward (p = 0.02. There was no association between the fractional anisotropy of tracts and performance on cognitive testing. Conclusion: The mean diffusivity of tracts crossing WMH measured by tractography is a novel correlate of performance on the Wechsler Memory Scale-III Longest Span Forward in elderly persons.

  12. Cognitive Function and 3-Tesla Magnetic Resonance Imaging Tractography of White Matter Hyperintensities in Elderly Persons.

    Reginold, William; Luedke, Angela C; Tam, Angela; Itorralba, Justine; Fernandez-Ruiz, Juan; Reginold, Jennifer; Islam, Omar; Garcia, Angeles

    2015-01-01

    This study used 3-Tesla magnetic resonance imaging (MRI) tractography to determine if there was an association between tracts crossing white matter hyperintensities (WMH) and cognitive function in elderly persons. Brain T2-weighted fluid-attenuated inversion recovery (FLAIR) and diffusion tensor MRI scans were acquired in participants above the age of 60 years. Twenty-six persons had WMH identified on T2 FLAIR scans. They completed a battery of neuropsychological tests and were classified as normal controls (n = 15) or with Alzheimer's dementia (n = 11). Tractography was generated by the Fiber Assignment by Continuous Tracking method. All tracts that crossed WMH were segmented. The average fractional anisotropy and average mean diffusivity of these tracts were quantified. We studied the association between cognitive test scores with the average mean diffusivity and average fractional anisotropy of tracts while controlling for age, total WMH volume and diagnosis. An increased mean diffusivity of tracts crossing WMH was associated with worse performance on the Wechsler Memory Scale-III Longest Span Forward (p = 0.02). There was no association between the fractional anisotropy of tracts and performance on cognitive testing. The mean diffusivity of tracts crossing WMH measured by tractography is a novel correlate of performance on the Wechsler Memory Scale-III Longest Span Forward in elderly persons.

  13. Magnetic resonance and cranial ultrasound characteristics of periventricular white matter abnormalities in newborn infants

    Childs, Anne-Marie; Cornette, Luc; Ramenghi, Luca A.; Tanner, Steven F.; Arthur, Rosemary J.; Martinez, Delia; Levene, Malcolm I.

    2001-01-01

    OBJECTIVE: To characterize the range of abnormalities within the periventricular white matter (PVWM) in a cohort of newborns using magnetic resonance (MR) brain imaging and to compare the focal MR abnormalities with the cranial ultrasound (CUS) findings. METHODS: Retrospective study of MR brain and CUS findings of infants born in the 18-month period 1998-1999. PVWM abnormalities were identified by MR and focal lesions were characterized by size, number and distribution using a grading scale. Correspondence with CUS findings was assessed. RESULTS: 175 MR examinations corresponding to n = 105 preterm infants, (median GA 28, range 23-36 weeks) and n = 25 term infants (median GA 39, range 37-42 weeks) were analysed for PVWM abnormalities. In the preterm group, MR demonstrated a normal PVWM in n = 76, focal areas of altered signal intensity (SI) in PVWM in n = 26 and venous infarction inn 3. In the term group, MR demonstrated a normal PVWM in n = 15, focal areas of altered SI in PVWM in n = 4, oedematous PVWM in n = 2 and a middle cerebral artery infarction in n = 4. All infants with normal MR had normal CUS findings. A focal PVWM SI abnormality detectable on MR corresponded with an abnormality on CUS in only n = 10/30. CONCLUSIONS: MR appears considerably more sensitive than CUS in demonstrating the existence and extent of focal PVWM lesions in newborn infants. Satisfactory correspondence between the two imaging investigations is obtained only for cystic PVWM lesions. Childs, A.-M. et al. (2001)

  14. NuSTAR AND SWIFT Observations of the Fast Rotating Magnetized White Dwarf AE Aquarii

    Kitaguchi, Takao; An, Hongjun; Beloborodov, Andrei M.; Gotthelf, Eric V.; Hayashi, Takayuki; Kaspi, Victoria M.; Rana, Vikram R.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; hide

    2014-01-01

    AE Aquarii is a cataclysmic variable with the fastest known rotating magnetized white dwarf (P(sub spin) = 33.08 s). Compared to many intermediate polars, AE Aquarii shows a soft X-ray spectrum with a very low luminosity (LX (is) approximately 10(exp 31) erg per second). We have analyzed overlapping observations of this system with the NuSTAR and the Swift X-ray observatories in 2012 September. We find the 0.5-30 keV spectra to be well fitted by either an optically thin thermal plasma model with three temperatures of 0.75(+0.18 / -0.45), 2.29(+0.96 / -0.82), and 9.33 (+6.07 / -2.18) keV, or an optically thin thermal plasma model with two temperatures of 1.00 (+0.34 / -0.23) and 4.64 (+1.58 / -0.84) keV plus a power-law component with photon index of 2.50 (+0.17 / -0.23). The pulse profile in the 3-20 keV band is broad and approximately sinusoidal, with a pulsed fraction of 16.6% +/- 2.3%. We do not find any evidence for a previously reported sharp feature in the pulse profile.

  15. Determination of the orientation of the white dwarf's magnetic axis from X-ray orbital light curves

    Andronov, I.L.

    1986-01-01

    The directional pattern of soft X-ray radiation produced in a ''polar cap'' on the white dwarf's surface is calculated taking into account the absorption in the axially symmetrical accretion column, homogeneous along its height. An algorithm for the determination of orientation of the magnetic axis of a compact star from orbital curves of soft X-ray flux, is suggested. The values of the orbital inclination i (51 deg <=i<64 deg) and the angle between the rotational and magnetic axes σ (30 deg <=σ<=34 deg) were calculated for the polar AM Herculis for different values of model parameters

  16. Mean magnetic susceptibility regularized susceptibility tensor imaging (MMSR-STI) for estimating orientations of white matter fibers in human brain.

    Li, Xu; van Zijl, Peter C M

    2014-09-01

    An increasing number of studies show that magnetic susceptibility in white matter fibers is anisotropic and may be described by a tensor. However, the limited head rotation possible for in vivo human studies leads to an ill-conditioned inverse problem in susceptibility tensor imaging (STI). Here we suggest the combined use of limiting the susceptibility anisotropy to white matter and imposing morphology constraints on the mean magnetic susceptibility (MMS) for regularizing the STI inverse problem. The proposed MMS regularized STI (MMSR-STI) method was tested using computer simulations and in vivo human data collected at 3T. The fiber orientation estimated from both the STI and MMSR-STI methods was compared to that from diffusion tensor imaging (DTI). Computer simulations show that the MMSR-STI method provides a more accurate estimation of the susceptibility tensor than the conventional STI approach. Similarly, in vivo data show that use of the MMSR-STI method leads to a smaller difference between the fiber orientation estimated from STI and DTI for most selected white matter fibers. The proposed regularization strategy for STI can improve estimation of the susceptibility tensor in white matter. © 2014 Wiley Periodicals, Inc.

  17. Quasi-periodic oscillations in accreting magnetic white dwarfs. II. The asset of numerical modelling for interpreting observations

    Busschaert, C.; Falize, É.; Michaut, C.; Bonnet-Bidaud, J.-M.; Mouchet, M.

    2015-07-01

    Context. Magnetic cataclysmic variables are close binary systems containing a strongly magnetized white dwarf that accretes matter coming from an M-dwarf companion. The high magnetic field strength leads to the formation of an accretion column instead of an accretion disk. High-energy radiation coming from those objects is emitted from the column close to the white dwarf photosphere at the impact region. Its properties depend on the characteristics of the white dwarf and an accurate accretion column model allows the properties of the binary system to be inferred, such as the white dwarf mass, its magnetic field, and the accretion rate. Aims: We study the temporal and spectral behaviour of the accretion region and use the tools we developed to accurately connect the simulation results to the X-ray and optical astronomical observations. Methods: The radiation hydrodynamics code Hades was adapted to simulate this specific accretion phenomena. Classical approaches were used to model the radiative losses of the two main radiative processes: bremsstrahlung and cyclotron. Synthetic light curves and X-ray spectra were extracted from numerical simulations. A fast Fourier analysis was performed on the simulated light curves. The oscillation frequencies and amplitudes in the X-ray and optical domains are studied to compare those numerical results to observational ones. Different dimensional formulae were developed to complete the numerical evaluations. Results: The complete characterization of the emitting region is described for the two main radiative regimes: when only the bremsstrahlung losses and when both cyclotron and bremsstrahlung losses are considered. The effect of the non-linear cooling instability regime on the accretion column behaviour is analysed. Variation in luminosity on short timescales (~1 s quasi-periodic oscillations) is an expected consequence of this specific dynamic. The importance of secondary shock instability on the quasi-periodic oscillation

  18. Magnetic resonance spectroscopy of normal appearing white matter in early relapsing-remitting multiple sclerosis: correlations between disability and spectroscopy

    Foronda Jesus

    2004-06-01

    Full Text Available Abstract Background What currently appears to be irreversible axonal loss in normal appearing white matter, measured by proton magnetic resonance spectroscopy is of great interest in the study of Multiple Sclerosis. Our aim is to determine the axonal damage in normal appearing white matter measured by magnetic resonance spectroscopy and to correlate this with the functional disability measured by Multiple Sclerosis Functional Composite scale, Neurological Rating Scale, Ambulation Index scale, and Expanded Disability Scale Score. Methods Thirty one patients (9 male and 22 female with relapsing remitting Multiple Sclerosis and a Kurtzke Expanded Disability Scale Score of 0–5.5 were recruited from four hospitals in Andalusia, Spain and included in the study. Magnetic resonance spectroscopy scans and neurological disability assessments were performed the same day. Results A statistically significant correlation was found (r = -0.38 p Conclusions There is correlation between disability (measured by Expanded Disability Scale Score and the NAA/Cr ratio in normal appearing white matter. The lack of correlation between the NAA/Cr ratio and the Multiple Sclerosis Functional Composite score indicates that the Multiple Sclerosis Functional Composite is not able to measure irreversible disability and would be more useful as a marker in stages where axonal damage is not a predominant factor.

  19. Component masses of young, wide, non-magnetic white dwarf binaries in the Sloan Digital Sky Survey Data Release 7

    Baxter, R. B.; Dobbie, P. D.; Parker, Q. A.; Casewell, S. L.; Lodieu, N.; Burleigh, M. R.; Lawrie, K. A.; Külebi, B.; Koester, D.; Holland, B. R.

    2014-06-01

    We present a spectroscopic component analysis of 18 candidate young, wide, non-magnetic, double-degenerate binaries identified from a search of the Sloan Digital Sky Survey Data Release 7 (DR7). All but two pairings are likely to be physical systems. We show SDSS J084952.47+471247.7 + SDSS J084952.87+471249.4 to be a wide DA + DB binary, only the second identified to date. Combining our measurements for the components of 16 new binaries with results for three similar, previously known systems within the DR7, we have constructed a mass distribution for the largest sample to date (38) of white dwarfs in young, wide, non-magnetic, double-degenerate pairings. This is broadly similar in form to that of the isolated field population with a substantial peak around M ˜ 0.6 M⊙. We identify an excess of ultramassive white dwarfs and attribute this to the primordial separation distribution of their progenitor systems peaking at relatively larger values and the greater expansion of their binary orbits during the final stages of stellar evolution. We exploit this mass distribution to probe the origins of unusual types of degenerates, confirming a mild preference for the progenitor systems of high-field-magnetic white dwarfs, at least within these binaries, to be associated with early-type stars. Additionally, we consider the 19 systems in the context of the stellar initial mass-final mass relation. None appear to be strongly discordant with current understanding of this relationship.

  20. Magnetism, X-rays and accretion rates in WD 1145+017 and other polluted white dwarf systems

    Farihi, J.; Fossati, L.; Wheatley, P. J.; Metzger, B. D.; Mauerhan, J.; Bachman, S.; Gänsicke, B. T.; Redfield, S.; Cauley, P. W.; Kochukhov, O.; Achilleos, N.; Stone, N.

    2018-02-01

    This paper reports circular spectropolarimetry and X-ray observations of several polluted white dwarfs including WD 1145+017, with the aim to constrain the behaviour of disc material and instantaneous accretion rates in these evolved planetary systems. Two stars with previously observed Zeeman splitting, WD 0322-019 and WD 2105-820, are detected above 5σ and 〈Bz〉 > 1 kG, while WD 1145+017, WD 1929+011, and WD 2326+049 yield (null) detections below this minimum level of confidence. For these latter three stars, high-resolution spectra and atmospheric modelling are used to obtain limits on magnetic field strengths via the absence of Zeeman splitting, finding B* Earth composition material falling on to the magnetic polar regions of white dwarfs, where X-rays and cyclotron radiation may contribute to accretion luminosity. This analysis is applied to X-ray data for WD 1145+017, WD 1729+371, and WD 2326+049, and the upper bound count rates are modelled with spectra for a range of plasma kT = 1-10 keV in both the magnetic and non-magnetic accretion regimes. The results for all three stars are consistent with a typical dusty white dwarf in a steady state at 108-109 g s-1. In particular, the non-magnetic limits for WD 1145+017 are found to be well below previous estimates of up to 1012 g s-1, and likely below 1010 g s-1, thus suggesting the star-disc system may be average in its evolutionary state, and only special in viewing geometry.

  1. Magnetic resonance imaging of white matter injury after radio- and chemotherapy

    Jurkiewicz, E.; Pakula-Kosciesza, I.; Bekiesinska-Figatowska, M.; Wagiel, K.; Wagiel, E.; Perek-Polnik, M.; Walecki, J.

    2004-01-01

    To describe MR symptomatology of radio- and chemotherapy-induced leukoencephalopathy and to assess the usefulness of 1H MRS in differential diagnosis of these lesions. The material consists of 44 patients (18 females, 26 males), aged 3-54 years, treated for brain and face tumors (29 cases), other tumors (2) and after CNS prophylaxis for acute lymphoblastic leukemia (13). 1H MRS was performed in 6 cases. Two 1,5 T and one 0,5 T scanners were used. We observed diffuse lesions, hyperintense on T2-weighted images, in the periventricular white matter and centrum semiovale in 14 cases, in 5 also in the cerebellum and brainstem, subcortical in 1. Focal lesions were found in periventricular location in 16 cases, in the corpus callosum in 1 and in 1 the foci were disseminated. No mass effect and no contrast enhancement were observed in these cases. Marked mass effect and contrast enhancement were found in 2 cases, slight mass effect without CE in 2. In these 4 cases and in other 2 with neurological symptoms, 1H MRS was performed: in 2 cases the spectrum was close to that of normal tissue, in 1 suggestive of a tumor, in 3 the spectrum was abnormal but atypical of a tumor. Follow-up studies showed regression of the lesions and of the spectral abnormalities. In 1 case necrotizing leucoencephalopathy and secondary tumor, in 7 - calcificatons, in 7 - parenchymal hematomas were found. Magnetic resonance allows detection of side effects of radio- and chemotherapy, even in asymptomatic patients. In patients with neurological signs MRI allows differentiation of chemo-, radiotherapy-induced leucoencephalopathy and neo plasmatic infiltration with high probability. 1H MRS plays an important role in differential diagnosis in unclear cases with mass effect and contrast enhancement. The results of MRI and 1H MRS should be considered in correlation with clinical findings. (author)

  2. Catalytic steam gasification of biomass in fluidized bed at low temperature: Conversion from livestock manure compost to hydrogen-rich syngas

    Xiao, Xianbin; Le, Duc Dung; Li, Liuyun; Meng, Xianliang; Cao, Jingpei; Morishita, Kayoko; Takarada, Takayuki

    2010-01-01

    Utilizing large amounts of animal waste as a source of renewable energy has the potential to reduce its disposal problems and associated pollution issues. Gasification characteristics of the manure compost make it possible for low temperature gasification. In this paper, an energy efficient approach to hydrogen-rich syngas from manure compost is represented at relatively low temperature, around 600 o C, in a continuous-feeding fluidized bed reactor. The effects of catalyst performance, reactor temperature, steam, and reaction type on gas yield, gas composition, and carbon conversion efficiency are discussed. The Ni-Al 2 O 3 catalyst simultaneously promotes tar cracking and steam reforming. Higher temperature contributes to higher gas yield and carbon conversion. The steam introduction increases hydrogen yield, by steam reforming and water-gas shift reaction. Two-stage gasification is also tried, showing the advantage of better catalyst utilization and enhancing the catalytic reactions to some extent.

  3. Co-pyrolysis of coal with hydrogen-rich gases. 1. Coal pyrolysis under coke-oven gas and synthesis gas

    Liao, H.; Li, B.; Zhang, B. [Chinese Academy of Sciences, Taiyuan (China). State Key Lab. of Coal Conversion

    1998-06-01

    To improve the economics of the hydropyrolysis process, it has been suggested that cheaper hydrogen-rich gases (such as coke oven gas, synthesis gas) could be used instead of pure hydrogen. Pyrolysis of Chinese Xianfeng lignite was carried out with coke oven gas (COG) and synthesis gas (SG) as reactive gases at 0.1-5 MPa and at a final temperature up to 650{degree}C with a heating rate of 5-25{degree}C min{sup -1} in a 10 g fixed-bed reactor. The results indicate that it is possible to use COG and SG instead of pure hydrogen in hydropyrolysis, but that the experimental conditions must be adjusted to optimize the yields of the valuable chemicals. 14 refs., 3 figs., 6 tabs.

  4. A New Stellar Outburst Associated with the Magnetic Activities of the K-type Dwarf in a White Dwarf Binary

    Qian, S.-B.; Han, Z.-T.; Zhang, B.; Zejda, M.; Michel, R.; Zhu, L.-Y.; Zhao, E.-G.; Liao, W.-P.; Tian, X.-M.; Wang, Z.-H.

    2017-10-01

    1SWASP J162117.36+441254.2 was originally classified as an EW-type binary with a period of 0.20785 days. However, it was detected to have undergone a stellar outburst on 2016 June 3. Although the system was later classified as a cataclysmic variable (CV) and the event was attributed as a dwarf nova outburst, the physical reason is still unknown. This binary has been monitored photometrically since 2016 April 19, and many light curves were obtained before, during, and after the outburst. Those light and color curves observed before the outburst indicate that the system is a special CV. The white dwarf is not accreting material from the secondary and there are no accretion disks surrounding the white dwarf. By comparing the light curves obtained from 2016 April 19 to those from September 14, it was found that magnetic activity of the secondary is associated with the outburst. We show strong evidence that the L 1 region on the secondary was heavily spotted before and after the outburst and thus quench the mass transfer, while the outburst is produced by a sudden mass accretion of the white dwarf. These results suggest that J162117 is a good astrophysical laboratory to study stellar magnetic activity and its influences on CV mass transfer and mass accretion.

  5. A New Stellar Outburst Associated with the Magnetic Activities of the K-type Dwarf in a White Dwarf Binary

    Qian, S.-B.; Han, Z.-T.; Zhang, B.; Zhu, L.-Y.; Zhao, E.-G.; Liao, W.-P.; Tian, X.-M.; Wang, Z.-H. [Yunnan Observatories, Chinese Academy of Sciences (CAS), P.O. Box 110, 650011 Kunming (China); Zejda, M. [Department of Theoretical Physics and Astrophysics, Masaryk University, Kotlářská 2, CZ-611 37 Brno (Czech Republic); Michel, R., E-mail: qsb@ynao.ac.cn [Instituto de Astronomía, Universidad Nacional Autónoma de México, Ensenada, Baja California, México (Mexico)

    2017-10-20

    1SWASP J162117.36+441254.2 was originally classified as an EW-type binary with a period of 0.20785 days. However, it was detected to have undergone a stellar outburst on 2016 June 3. Although the system was later classified as a cataclysmic variable (CV) and the event was attributed as a dwarf nova outburst, the physical reason is still unknown. This binary has been monitored photometrically since 2016 April 19, and many light curves were obtained before, during, and after the outburst. Those light and color curves observed before the outburst indicate that the system is a special CV. The white dwarf is not accreting material from the secondary and there are no accretion disks surrounding the white dwarf. By comparing the light curves obtained from 2016 April 19 to those from September 14, it was found that magnetic activity of the secondary is associated with the outburst. We show strong evidence that the L {sub 1} region on the secondary was heavily spotted before and after the outburst and thus quench the mass transfer, while the outburst is produced by a sudden mass accretion of the white dwarf. These results suggest that J162117 is a good astrophysical laboratory to study stellar magnetic activity and its influences on CV mass transfer and mass accretion.

  6. A New Stellar Outburst Associated with the Magnetic Activities of the K-type Dwarf in a White Dwarf Binary

    Qian, S.-B.; Han, Z.-T.; Zhang, B.; Zhu, L.-Y.; Zhao, E.-G.; Liao, W.-P.; Tian, X.-M.; Wang, Z.-H.; Zejda, M.; Michel, R.

    2017-01-01

    1SWASP J162117.36+441254.2 was originally classified as an EW-type binary with a period of 0.20785 days. However, it was detected to have undergone a stellar outburst on 2016 June 3. Although the system was later classified as a cataclysmic variable (CV) and the event was attributed as a dwarf nova outburst, the physical reason is still unknown. This binary has been monitored photometrically since 2016 April 19, and many light curves were obtained before, during, and after the outburst. Those light and color curves observed before the outburst indicate that the system is a special CV. The white dwarf is not accreting material from the secondary and there are no accretion disks surrounding the white dwarf. By comparing the light curves obtained from 2016 April 19 to those from September 14, it was found that magnetic activity of the secondary is associated with the outburst. We show strong evidence that the L 1 region on the secondary was heavily spotted before and after the outburst and thus quench the mass transfer, while the outburst is produced by a sudden mass accretion of the white dwarf. These results suggest that J162117 is a good astrophysical laboratory to study stellar magnetic activity and its influences on CV mass transfer and mass accretion.

  7. The Brain of the Black (Diceros bicornis and White (Ceratotherium simum African Rhinoceroses: Morphology and Volumetrics from Magnetic Resonance Imaging

    Adhil Bhagwandin

    2017-08-01

    Full Text Available The morphology and volumetrics of the understudied brains of two iconic large terrestrial African mammals: the black (Diceros bicornis and white (Ceratotherium simum rhinoceroses are described. The black rhinoceros is typically solitary whereas the white rhinoceros is social, and both are members of the Perissodactyl order. Here, we provide descriptions of the surface of the brain of each rhinoceros. For both species, we use magnetic resonance images (MRI to develop a description of the internal anatomy of the rhinoceros brain and to calculate the volume of the amygdala, cerebellum, corpus callosum, hippocampus, and ventricular system as well as to determine the gyrencephalic index. The morphology of both black and white rhinoceros brains is very similar to each other, although certain minor differences, seemingly related to diet, were noted, and both brains evince the general anatomy of the mammalian brain. The rhinoceros brains display no obvious neuroanatomical specializations in comparison to other mammals previously studied. In addition, the volumetric analyses indicate that the size of the various regions of the rhinoceros brain measured, as well as the extent of gyrification, are what would be predicted for a mammal with their brain mass when compared allometrically to previously published data. We conclude that the brains of the black and white rhinoceros exhibit a typically mammalian organization at a superficial level, but histological studies may reveal specializations of interest in relation to rhinoceros behavior.

  8. Monitoring and modelling of white dwarfs with extremely weak magnetic fields. WD 2047+372 and WD 2359-434

    Landstreet, J. D.; Bagnulo, S.; Valyavin, G.; Valeev, A. F.

    2017-11-01

    Magnetic fields are detected in a few percent of white dwarfs. The number of such magnetic white dwarfs known is now some hundreds. Fields range in strength from a few kG to several hundred MG. Almost all the known magnetic white dwarfs have a mean field modulus ≥1 MG. We are trying to fill a major gap in observational knowledge at the low field limit (≤200 kG) using circular spectro-polarimetry. In this paper we report the discovery and monitoring of strong, periodic magnetic variability in two previously discovered "super-weak field" magnetic white dwarfs, WD 2047+372 and WD 2359-434. WD 2047+372 has a mean longitudinal field that reverses between about -12 and + 15 kG, with a period of 0.243 d, while its mean field modulus appears nearly constant at 60 kG. The observations can be interpreted in terms of a dipolar field tilted with respect to the stellar rotation axis. WD 2359-434 always shows a weak positive longitudinal field with values between about 0 and + 12 kG, varying only weakly with stellar rotation, while the mean field modulus varies between about 50 and 100 kG. The rotation period is found to be 0.112 d using the variable shape of the Hα line core, consistent with available photometry. The field of this star appears to be much more complex than a dipole, and is probably not axisymmetric. Available photometry shows that WD 2359-434 is a light variable with an amplitude of only 0.005 mag; our own photometry shows that if WD 2047+372 is photometrically variable, the amplitude is below about 0.01 mag. These are the first models for magnetic white dwarfs with fields below about 100 kG based on magnetic measurements through the full stellar rotation. They reveal two very different magnetic surface configurations, and that, contrary to simple ohmic decay theory, WD 2359-434 has a much more complex surface field than the much younger WD 2047+372. Based, in part, on observations collected at the European Organisation for Astronomical Research in the

  9. Local Directional Probability Optimization for Quantification of Blurred Gray/White Matter Junction in Magnetic Resonance Image

    Xiaoxia Qu

    2017-09-01

    Full Text Available The blurred gray/white matter junction is an important feature of focal cortical dysplasia (FCD lesions. FCD is the main cause of epilepsy and can be detected through magnetic resonance (MR imaging. Several earlier studies have focused on computing the gradient magnitude of the MR image and used the resulting map to model the blurred gray/white matter junction. However, gradient magnitude cannot quantify the blurred gray/white matter junction. Therefore, we proposed a novel algorithm called local directional probability optimization (LDPO for detecting and quantifying the width of the gray/white matter boundary (GWB within the lesional areas. The proposed LDPO method mainly consists of the following three stages: (1 introduction of a hidden Markov random field-expectation-maximization algorithm to compute the probability images of brain tissues in order to obtain the GWB region; (2 generation of local directions from gray matter (GM to white matter (WM passing through the GWB, considering the GWB to be an electric potential field; (3 determination of the optimal local directions for any given voxel of GWB, based on iterative searching of the neighborhood. This was then used to measure the width of the GWB. The proposed LDPO method was tested on real MR images of patients with FCD lesions. The results indicated that the LDPO method could quantify the GWB width. On the GWB width map, the width of the blurred GWB in the lesional region was observed to be greater than that in the non-lesional regions. The proposed GWB width map produced higher F-scores in terms of detecting the blurred GWB within the FCD lesional region as compared to that of FCD feature maps, indicating better trade-off between precision and recall.

  10. The Assessment of Structural Changes in MS Plaques and Normal Appearing White Matter Using Quantitative Magnetization Transfer Imaging (MTI

    Masoomeh Fooladi

    2007-12-01

    Full Text Available Introduction: Multiple sclerosis (MS is a demyelinating disease of the central nervous system (CNS, affecting mostly young people at a mean age of 30 years. Magnetic resonance imaging (MRI is one of the most specific and sensitive methods in diagnosing and detecting the evolution of multiple sclerosis disease. But it does not have the ability to differentiate between distinct histopathological heterogeneities that occur in MS lesions and brain tissue.Quantitative magnetization transfer imaging (qMTI is a relatively new MRI technique which can be used to examine the pathological processes of the brain parenchyma which occur in MS patients.This quantitative MRI technique can provide more complete information about the extent and nature of the brain tissue destruction in multiple sclerosis, which cannot be detected by conventional MRI. Material and Methods: In this study, twelve patients with relapsing-remitting MS and twelve healthy control subjects underwent conventional MR imaging including: T2-FSE, T1-SE and FLAIR sequences as well as quantitative magnetization transfer imaging. All the focal lesions were identified on T2-weighted images and were classified according to their signal hypointensity on T1-weighted scans. The white matter and MS lesions were segmented using a semi-automated system. MT ratio (MTR histogram analysis was performed for the brain white matter and the average MTR value was calculated for the classified MS lesions. Results: A significant reduction was found in MTR value of the normal appearing white matter (NAWM in patients with relapsing-remitting MS, suggesting that MS is a more diffuse disease, affecting the whole brain tissue. A wide range changes in MTR values can be observed in MS lesions. MTR reduction is correlated with the degree of lesion hypointensity on T1-weighted scans. The lower MTR values of lesions that appear progressively more hypointense on T1-weigted images reflect varying degrees of demyelination and

  11. The distribution of masses and radii of white-dwarf stars

    Shipman, H.L.

    1978-01-01

    The status of determinations of white dwarf radii by model atmosphere methods is reviewed. The results are that (i) the mean radius of a sample of 95 hydrogen-rich stars with parallaxes is 0.0131 R(Sun); (ii) the mean radius of a sample of 13 helium-rich stars is 0.011 R(Sun), indistinguishably different from the radius of the hydrogen-rich stars; and (iii) that the most serious limitation on our knowledge of the mean radius of white dwarfs is the influence of selection effects. An estimate of the selection effects indicates that the true mean white dwarf radius is near 0.011 R(Sun). (Auth.)

  12. Observations of white-light flares in NOAA active region 11515: high occurrence rate and relationship with magnetic transients

    Song, Y. L.; Tian, H.; Zhang, M.; Ding, M. D.

    2018-06-01

    Aims: There are two goals in this study. One is to investigate how frequently white-light flares (WLFs) occur in a flare-productive active region (NOAA active region 11515). The other is to investigate the relationship between WLFs and magnetic transients (MTs). Methods: We used the high-cadence (45 s) full-disk continuum filtergrams and line-of-sight magnetograms taken by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) to identify WLFs and MTs, respectively. Images taken by the Atmospheric Imaging Assembly (AIA) on board SDO were also used to show the flare morphology in the upper atmosphere. Results: We found at least 20 WLFs out of a total of 70 flares above C class (28.6%) in NOAA active region 11515 during its passage across the solar disk (E45°-W45°). Each of these WLFs occurred in a small region, with a short duration of about 5 min. The enhancement of the white-light continuum intensity is usually small, with an average enhancement of 8.1%. The 20 WLFs we observed were found along an unusual configuration of the magnetic field that was characterized by a narrow ribbon of negative field. Furthermore, the WLFs were found to be accompanied by MTs, with radical changes in magnetic field strength (or even a sign reversal) observed during the flare. In contrast, there is no obvious signature of MTs in the 50 flares without white-light enhancements. Conclusions: Our results suggest that WLFs occur much more frequently than previously thought, with most WLFs being fairly weak enhancements. This may explain why WLFs are reported rarely. Our observations also suggest that MTs and WLFs are closely related and appear cospatial and cotemporal, when considering HMI data. A greater enhancement of WL emission is often accompanied by a greater change in the line-of-sight component of the unsigned magnetic field. Considering the close relationship between MTs and WLFs, many previously reported flares with MTs may be WLFs. The movie

  13. Photometric variability in a warm, strongly magnetic DQ white dwarf, SDSS J103655.39+652252.2

    Williams, Kurtis A. [Department of Physics and Astronomy, Texas A and M University-Commerce, P.O. Box 3011, Commerce, TX 75429 (United States); Winget, D. E.; Montgomery, M. H.; Hermes, J. J.; Falcon, Ross E.; Winget, K. I. [Department of Astronomy, University of Texas, 1 University Station C1400, Austin, TX 78712 (United States); Dufour, Patrick [Département de Physique, Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montréal, QC H3C 3J7 (Canada); Kepler, S. O. [Departamento de Astronomia, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9500 Porto Alegre 91501-970, RS (Brazil); Bolte, Michael [UCO/Lick Observatory, University of California, 1156 High St., Santa Cruz, CA 95064 (United States); Rubin, Kate H. R. [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Liebert, James, E-mail: Kurtis.Williams@tamuc.edu, E-mail: jamesliebert@gmail.com [Emeritus, Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States)

    2013-06-01

    We present the discovery of photometric variability in the DQ white dwarf SDSS J103655.39+652252.2 (SDSS J1036+6522). Time-series photometry reveals a coherent monoperiodic modulation at a period of 1115.64751(67) s with an amplitude 0.442% ± 0.024%; no other periodic modulations are observed with amplitudes ≳ 0.13%. The period, amplitude, and phase of this modulation are constant within errors over 16 months. The spectrum of SDSS J1036+6522 shows magnetic splitting of carbon lines, and we use Paschen-Back formalism to develop a grid of model atmospheres for mixed carbon and helium atmospheres. Our models, while reliant on several simplistic assumptions, nevertheless match the major spectral and photometric properties of the star with a self-consistent set of parameters: T {sub eff} ≈ 15, 500 K, log g ≈ 9, log (C/He) = –1.0, and a mean magnetic field strength of 3.0 ± 0.2 MG. The temperature and abundances strongly suggest that SDSS J1036+6522 is a transition object between the hot, carbon-dominated DQs and the cool, helium-dominated DQs. The variability of SDSS J1036+6522 has characteristics similar to those of the variable hot carbon-atmosphere white dwarfs (DQVs), however, its temperature is significantly cooler. The pulse profile of SDSS J1036+6522 is nearly sinusoidal, in contrast with the significantly asymmetric pulse shapes of the known magnetic DQVs. If the variability in SDSS J1036+6522 is due to the same mechanism as other DQVs, then the pulse shape is not a definitive diagnostic on the absence of a strong magnetic field in DQVs. It remains unclear whether the root cause of the variability in SDSS J1036+6522 and the other hot DQVs is the same.

  14. Photometric variability in a warm, strongly magnetic DQ white dwarf, SDSS J103655.39+652252.2

    Williams, Kurtis A.; Winget, D. E.; Montgomery, M. H.; Hermes, J. J.; Falcon, Ross E.; Winget, K. I.; Dufour, Patrick; Kepler, S. O.; Bolte, Michael; Rubin, Kate H. R.; Liebert, James

    2013-01-01

    We present the discovery of photometric variability in the DQ white dwarf SDSS J103655.39+652252.2 (SDSS J1036+6522). Time-series photometry reveals a coherent monoperiodic modulation at a period of 1115.64751(67) s with an amplitude 0.442% ± 0.024%; no other periodic modulations are observed with amplitudes ≳ 0.13%. The period, amplitude, and phase of this modulation are constant within errors over 16 months. The spectrum of SDSS J1036+6522 shows magnetic splitting of carbon lines, and we use Paschen-Back formalism to develop a grid of model atmospheres for mixed carbon and helium atmospheres. Our models, while reliant on several simplistic assumptions, nevertheless match the major spectral and photometric properties of the star with a self-consistent set of parameters: T eff ≈ 15, 500 K, log g ≈ 9, log (C/He) = –1.0, and a mean magnetic field strength of 3.0 ± 0.2 MG. The temperature and abundances strongly suggest that SDSS J1036+6522 is a transition object between the hot, carbon-dominated DQs and the cool, helium-dominated DQs. The variability of SDSS J1036+6522 has characteristics similar to those of the variable hot carbon-atmosphere white dwarfs (DQVs), however, its temperature is significantly cooler. The pulse profile of SDSS J1036+6522 is nearly sinusoidal, in contrast with the significantly asymmetric pulse shapes of the known magnetic DQVs. If the variability in SDSS J1036+6522 is due to the same mechanism as other DQVs, then the pulse shape is not a definitive diagnostic on the absence of a strong magnetic field in DQVs. It remains unclear whether the root cause of the variability in SDSS J1036+6522 and the other hot DQVs is the same.

  15. Alkaline hydrothermal de-ashing and desulfurization of low quality coal and its application to hydrogen-rich gas generation

    Mursito, Anggoro Tri; Hirajima, Tsuyoshi; Sasaki, Keiko

    2011-01-01

    This paper describes experimental research and a fundamental study of alkaline hydrothermal treatment of high-sulfur, high-ash coal from Banten, Java-Indonesia. Experiments were carried out on a laboratory-scale 0.5 L batch reactor. The alkaline hydrothermal treatment gave upgraded clean coal with low sulfur content (about 0.3 wt.%) and low ash content (about 2.1 wt.%). A zero carbon dioxide and pure hydrogen gas were produced at 330 o C by introducing an alkali (sodium hydroxide, NaOH) to the hydrothermal treatment of raw coal. X-ray diffraction (XRD) and X-ray fluorescence (XRF) techniques were used to test for the removal or reduction of major inorganic elements in the coal, and changes in carbon-functional groups and their properties were determined by Fourier transform infrared spectroscopy (FTIR) and Carbon-13 of nuclear magnetic resonance ( 13 C NMR) tests on the product of the hydrothermal upgrading and demineralization process.

  16. White matter magnetic resonance hyperintensities in dementia of the Alzheimer type

    Waldemar, G; Christiansen, P; Larsson, H B

    1994-01-01

    In a prospective MRI study the presence, appearance, volume, and regional cerebral blood flow (rCBF) correlates of periventricular hyperintensities (PVHs) and deep white matter hyperintensities (DWMHs) were examined in 18 patients with probable Alzheimer's disease and in 10 age matched healthy...... in the Alzheimer's disease group (p ... patients had extensive DWMH lesions in the central white matter. In the group of patients with Alzheimer's disease as a whole, the volume of DWMHs correlated well with rCBF in the hippocampal region ( r = -0.72; p

  17. {sup 1}H and {sup 31}P magnetic resonance spectroscopic imaging of white matter signal hyperintensity areas in elderly subjects

    Constans, J M [Department of Veterans Affairs Medical Center and University of California Magnetic Resonance Unit, San Francisco, CA (United States); [California Univ., San Francisco, CA (United States). Dept. of Radiology; Meyerhoff, D J [Department of Veterans Affairs Medical Center and University of California Magnetic Resonance Unit, San Francisco, CA (United States); [California Univ., San Francisco, CA (United States). Dept. of Radiology; Norman, D [California Univ., San Francisco, CA (United States). Dept. of Radiology; Fein, G [Department of Veterans Affairs Psychiatry Service, University of California, San Francisco, California (United States); [University of California, San Francisco, CA (United States). Dept. of Psychiatry; Weiner, M W [Department of Veterans Affairs Medical Center and University of California Magnetic Resonance Unit, San Francisco, CA (United States); [California Univ., San Francisco, CA (United States). Dept. of Radiology; [California Univ., San Francisco, CA (United States). Dept. of Medicine; [DVA Medical Center, Magnetic Resonance Spectroscopy Unit, San Francisco, CA (United States)

    1995-11-01

    White matter signal hyperintensities (WMSH) are commonly seen on MRI of elderly subjects. The purpose of this study was to characterize metabolic changes in the white matter of elderly subjects with extensive WMSH. We used water-suppressed proton ({sup 1}H) magnetic resonance spectroscopic imaging (MRSI) to compare six subjects with extensive WMSH with eight age-matched elderly subjects with minimal or absent WMSH, and phosphorus ({sup 31}P) MRSI to compare nine subjects with extensive WMSH and seven age-matched elderly subjects without extensive WMSH. Relative to region-matched tissue in elderly controls, extensive WMSH were associated with increased signal from choline-containing metabolites, no significant change of signal from N-acetylaspartate, and a trend to a decreased phosphomonoester (PME) resonance. These findings suggest that WMSH may be associated with an alteration of brain myelin phospholipids in the absence of axonal damage. There were no differences in energy phosphates, consistent with lack of ongoing brain ischemia. Within the group with extensive WMSH, PME resonance measures were significantly lower in WMSH than in contralateral normal-appearing white matter. These results provide information on pathophysiology of WMSH and a basis for comparison with WMSH in Alzheimer`s disease, vascular dementia, multiple sclerosis, and other diseases. (orig.). With 4 figs., 4 tabs.

  18. The polluted atmospheres of cool white dwarfs and the magnetic field connection

    Kawka, Adela; Vennes, Stephane

    2014-01-01

    Roč. 439, č. 1 (2014), L90-L94 ISSN 0035-8711 R&D Projects: GA ČR GAP209/12/0217; GA ČR GA13-14581S Institutional support: RVO:67985815 Keywords : white dwarfs * stars: abundances * stars: atmospheres Subject RIV: BN - Astronomy , Celestial Mechanics, Astrophysics Impact factor: 5.107, year: 2014

  19. Association between baseline peri-infarct magnetic resonance spectroscopy and regional white matter atrophy after stroke

    Yassi, Nawaf; Campbell, Bruce C.V.; Davis, Stephen M.; Bivard, Andrew; Moffat, Bradford A.; Steward, Christopher; Desmond, Patricia M.; Churilov, Leonid; Donnan, Geoffrey A.; Parsons, Mark W.

    2016-01-01

    Cerebral atrophy after stroke is associated with poor functional outcome. The prediction and prevention of post-stroke brain atrophy could therefore represent a target for neurorestorative therapies. We investigated the associations between peri-infarct metabolite concentrations measured by quantitative MRS and brain volume change in the infarct hemisphere after stroke. Twenty patients with ischemic stroke were enrolled. Patients underwent 3T-MRI within 1 week of onset, and at 1 and 3 months. At the baseline scan, an MRS voxel was placed manually in the peri-infarct area and another in the corresponding contralateral region. Volumetric analysis of T1 images was performed using two automated processing packages. Changes in gray and white matter volume were assessed as percentage change between 1 and 3 months. Mean concentrations (institutional units) of N-acetylaspartic acid (NAA) (6.1 vs 7.0, p = 0.039), total creatine (Cr+PCr) (5.4 vs 5.8, p = 0.043), and inositol (4.5 vs 5.0, p = 0.014), were significantly lower in the peri-infarct region compared with the contralateral hemisphere. There was a significant correlation between baseline peri-infarct NAA and white matter volume change in the infarct hemisphere between 1 and 3 months, with lower NAA being associated with subsequent white matter atrophy (Spearman's rho = 0.66, p = 0.010). The baseline concentration of Cr+PCr was also significantly correlated with white matter atrophy in the infarct hemisphere (Spearman's rho = 0.59, p = 0.027). Both of these associations were significant after adjustment for the false discovery rate and were validated using the secondary volumetric method. MRS may be useful in the prediction of white matter atrophy post-stroke and in the testing of novel neurorestorative therapies. (orig.)

  20. Association between baseline peri-infarct magnetic resonance spectroscopy and regional white matter atrophy after stroke

    Yassi, Nawaf; Campbell, Bruce C.V.; Davis, Stephen M.; Bivard, Andrew [Melbourne Brain Centre rate at The Royal Melbourne Hospital, Departments of Medicine and Neurology, Parkville, Victoria (Australia); Moffat, Bradford A.; Steward, Christopher; Desmond, Patricia M. [The University of Melbourne, Department of Radiology, The Royal Melbourne Hospital, Parkville (Australia); Churilov, Leonid; Donnan, Geoffrey A. [The University of Melbourne, Florey Institute of Neuroscience and Mental Health, Parkville (Australia); Parsons, Mark W. [University of Newcastle and Hunter Medical Research Institute, Priority Research Centre for Translational Neuroscience and Mental Health, Newcastle (Australia)

    2016-01-15

    Cerebral atrophy after stroke is associated with poor functional outcome. The prediction and prevention of post-stroke brain atrophy could therefore represent a target for neurorestorative therapies. We investigated the associations between peri-infarct metabolite concentrations measured by quantitative MRS and brain volume change in the infarct hemisphere after stroke. Twenty patients with ischemic stroke were enrolled. Patients underwent 3T-MRI within 1 week of onset, and at 1 and 3 months. At the baseline scan, an MRS voxel was placed manually in the peri-infarct area and another in the corresponding contralateral region. Volumetric analysis of T1 images was performed using two automated processing packages. Changes in gray and white matter volume were assessed as percentage change between 1 and 3 months. Mean concentrations (institutional units) of N-acetylaspartic acid (NAA) (6.1 vs 7.0, p = 0.039), total creatine (Cr+PCr) (5.4 vs 5.8, p = 0.043), and inositol (4.5 vs 5.0, p = 0.014), were significantly lower in the peri-infarct region compared with the contralateral hemisphere. There was a significant correlation between baseline peri-infarct NAA and white matter volume change in the infarct hemisphere between 1 and 3 months, with lower NAA being associated with subsequent white matter atrophy (Spearman's rho = 0.66, p = 0.010). The baseline concentration of Cr+PCr was also significantly correlated with white matter atrophy in the infarct hemisphere (Spearman's rho = 0.59, p = 0.027). Both of these associations were significant after adjustment for the false discovery rate and were validated using the secondary volumetric method. MRS may be useful in the prediction of white matter atrophy post-stroke and in the testing of novel neurorestorative therapies. (orig.)

  1. Two-step gasification of cattle manure for hydrogen-rich gas production: Effect of biochar preparation temperature and gasification temperature.

    Xin, Ya; Cao, Hongliang; Yuan, Qiaoxia; Wang, Dianlong

    2017-10-01

    Two-step gasification process was proposed to dispose cattle manure for hydrogen rich gas production. The effect of temperature on product distribution and biochar properties were first studied in the pyrolysis-carbonization process. The steam gasification of biochar derived from different pyrolysis-carbonization temperatures was then performed at 750°C and 850°C. The biochar from the pyrolysis-carbonization temperatures of 500°C had high carbon content and low volatiles content. According to the results of gasification stage, the pyrolysis-carbonization temperature of 500°C and the gasification temperature of 850°C were identified as the suitable conditions for hydrogen production. We obtained 1.61m 3 /kg of syngas production, 0.93m 3 /kg of hydrogen yield and 57.58% of hydrogen concentration. This study shows that two-step gasification is an efficient waste-to-hydrogen energy process. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Promotion of hydrogen-rich gas and phenolic-rich bio-oil production from green macroalgae Cladophora glomerata via pyrolysis over its bio-char.

    Norouzi, Omid; Jafarian, Sajedeh; Safari, Farid; Tavasoli, Ahmad; Nejati, Behnam

    2016-11-01

    Conversion of Cladophora glomerata (C. glomerata) as a Caspian Sea's green macroalgae into gaseous, liquid and solid products was carried out via pyrolysis at different temperatures to determine its potential for bio-oil and hydrogen-rich gas production for further industrial utilization. Non-catalytic tests were performed to determine the optimum condition for bio-oil production. The highest portion of bio-oil was retrieved at 500°C. The catalytic test was performed using the bio-char derived at 500°C as a catalyst. Effect of the addition of the algal bio-char on the composition of the bio-oil and also gaseous products was investigated. Pyrolysis derived bio-char was characterized by BET, FESEM and ICP method to show its surface area, porosity, and presence of inorganic metals on its surface, respectively. Phenols were increased from 8.5 to 20.76area% by the addition of bio-char. Moreover, the hydrogen concentration and hydrogen selectivity were also enhanced by the factors of 1.37, 1.59 respectively. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Structural, magnetic and electrical characterization of Mg–Ni nano-crystalline ferrites prepared through egg-white precursor

    Gabal, M.A., E-mail: mgabalabdonada@yahoo.com [Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah (Saudi Arabia); Al Angari, Y.M. [Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah (Saudi Arabia); Zaki, H.M. [Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah (Saudi Arabia); Physics Department, Faculty of Science, Zagazig University, Zagazig (Egypt)

    2014-08-01

    Soft Ni–Mg nano-crystalline ferrites with the general formula Ni{sub 1−x}Mg{sub x}Fe{sub 2}O{sub 4} (0≤x≤1) were synthesized through egg-white method. The precursor decomposition was followed by thermal analysis techniques. The obtained ferrites were characterized by X-ray diffraction, Fourier transform infrared and transmission electron microscopy measurements. X-ray diffraction showed the cubic spinel structure with crystallite size variation within the range 20–45 nm. The different structural data obtained were discussed in the view of ionic radii of the entire ions and their distribution within the lattice. The appropriate suggested cation distribution was then confirmed through Fourier transform infrared as well as electrical and magnetic properties measurements. Transmission electron microscopy exhibited a nano-crystal aggregation phenomenon. The observed size of the spherical particles agrees well with that obtained by X-ray diffraction. Hysteresis loop measurements revealed dilution in the obtained magnetic parameters by Mg-substitution due to the preferential occupancy of Mg{sup 2+} ions by the octahedral sites. Ac-electrical conductivity as a function of temperature and frequency exhibited a semi-conducting behavior with conductivity decreases by increasing Mg-content. The change in the slope of the curve indicates the changing in the conduction mechanism from electron hopping to polaron mechanism by increasing temperature. The obtained structural, electrical and magnetic properties were explained based on the cation distribution among tetrahedral and octahedral sites. - Highlights: • Ni–Mg nano-crystalline ferrites were synthesized through egg-white method. • An appropriate cation distribution was suggested. • Conductivity revealed a change in conduction mechanism by increasing temperature. • The effect of Mg-substitution on different properties was studied.

  4. White Matter Brain Lesions in Midlife Familial Hypercholesterolemic Patients at 3-Tesla Magnetic Resonance Imaging

    Schmitz, S.A.; O' Regan, D.P.; Fitzpatrick, J.; Neuwirth, C.; Potter, E.; Tosi, I.; Hajnal, J.V.; Naoumova, R.P. (Imaging Sciences Dept. and Clinical Research Facility, MRC Clinical Sciences Centre, London (GB))

    2008-03-15

    Background: Patients with hypercholesterolemia of 60 years and older have an increased risk for white matter brain lesions and dementia. Purpose: To investigate whether patients with familial hypercholesterolemia (FH) develop white matter lesions at 3-Tesla (T) MRI as early as in midlife. Material and Methods: Non-diabetic, non-smoking, and non-hypertensive heterozygous FH patients on treatment with maximally tolerated dose of a statin for more than 5 years (n = 14) and matched controls (n = 22) aged 25 to 60 years of age were studied. Imaging was performed at 3T with a fluid-attenuated T2-weighted MR pulse sequence and a T1-weighted spin-echo pulse sequence following 10 ml of i.v. gadopentetate dimeglumine. Images were evaluated by two independent readers. Fasting blood samples were taken. Student's t test was employed at P<0.05. Results: Three volunteers and one FH patient had white matter lesions (P<0.53). No other evidence of past ischemic stroke was observed. Mean total serum cholesterol and low-density lipoprotein (LDL) cholesterol were significantly higher in the FH group (6.0+-1.1 vs. 5.1+-0.9 mmol/l, P<0.02 and 4.1+-0.9 vs. 3.1+-0.8 mmol/l, P<0.004, respectively). Conclusion: Heterozygous FH patients on statin treatment in the age range of 25 to 60 years are not at increased risk of white matter lesions at 3T MRI

  5. White Matter Brain Lesions in Midlife Familial Hypercholesterolemic Patients at 3-Tesla Magnetic Resonance Imaging

    Schmitz, S.A.; O'Regan, D.P.; Fitzpatrick, J.; Neuwirth, C.; Potter, E.; Tos i, I.; Hajnal, J.V.; Naoumova, R.P.

    2008-01-01

    Background: Patients with hypercholesterolemia of 60 years and older have an increased risk for white matter brain lesions and dementia. Purpose: To investigate whether patients with familial hypercholesterolemia (FH) develop white matter lesions at 3-Tesla (T) MRI as early as in midlife. Material and Methods: Non-diabetic, non-smoking, and non-hypertensive heterozygous FH patients on treatment with maximally tolerated dose of a statin for more than 5 years (n = 14) and matched controls (n = 22) aged 25 to 60 years of age were studied. Imaging was performed at 3T with a fluid-attenuated T2-weighted MR pulse sequence and a T1-weighted spin-echo pulse sequence following 10 ml of i.v. gadopentetate dimeglumine. Images were evaluated by two independent readers. Fasting blood samples were taken. Student's t test was employed at P<0.05. Results: Three volunteers and one FH patient had white matter lesions (P<0.53). No other evidence of past ischemic stroke was observed. Mean total serum cholesterol and low-density lipoprotein (LDL) cholesterol were significantly higher in the FH group (6.0±1.1 vs. 5.1±0.9 mmol/l, P<0.02 and 4.1±0.9 vs. 3.1±0.8 mmol/l, P<0.004, respectively). Conclusion: Heterozygous FH patients on statin treatment in the age range of 25 to 60 years are not at increased risk of white matter lesions at 3T MRI

  6. Magnetic resonance spectroscopy features of normal-appearing white matter in patients with acute brucellosis

    Kayabas, Uner [Department of Infectious Disease and Clinical Microbiology, Inonu University, Medical Faculty, TR-44280 Malatya (Turkey)], E-mail: ukayabas@inonu.edu.tr; Alkan, Alpay; Firat, Ahmet Kemal; Karakas, Hakki Muammer [Department of Radiology, Inonu University, Medical Faculty, TR-44280 Malatya (Turkey); Bayindir, Yasar; Yetkin, Funda [Department of Infectious Disease and Clinical Microbiology, Inonu University, Medical Faculty, TR-44280 Malatya (Turkey)

    2008-03-15

    We aimed to evaluate whether the subtle metabolic cerebral changes are present in normal-appearing white matter on conventional MRI, in patients with acute brucellosis, by using MR spectroscopy (MRS). Sixteen patients with acute brucellosis and 13 healthy control subjects were investigated with conventional MRI and single-voxel MRS. Voxels were placed in normal-appearing parietal white matter (NAPWM). N-Acetyl aspartate (NAA)/creatine (Cr) and choline (Cho)/Cr ratios were calculated. There was no significant difference between the study subjects and the control group in NAA/Cr ratios obtained from NAPWM. However, the Cho/Cr ratios were significantly higher in patients with acute brucellosis compared to controls (p = 0.01). MRS revealed metabolic changes in normal-appearing white matter of patients with brucellosis. Brucellosis may cause subtle cerebral alterations, which may only be discernible with MRS. Increased Cho/Cr ratio possibly represents an initial phase of inflammation and/or demyelination process of brucellosis.

  7. Magnetic resonance spectroscopy features of normal-appearing white matter in patients with acute brucellosis

    Kayabas, Uner; Alkan, Alpay; Firat, Ahmet Kemal; Karakas, Hakki Muammer; Bayindir, Yasar; Yetkin, Funda

    2008-01-01

    We aimed to evaluate whether the subtle metabolic cerebral changes are present in normal-appearing white matter on conventional MRI, in patients with acute brucellosis, by using MR spectroscopy (MRS). Sixteen patients with acute brucellosis and 13 healthy control subjects were investigated with conventional MRI and single-voxel MRS. Voxels were placed in normal-appearing parietal white matter (NAPWM). N-Acetyl aspartate (NAA)/creatine (Cr) and choline (Cho)/Cr ratios were calculated. There was no significant difference between the study subjects and the control group in NAA/Cr ratios obtained from NAPWM. However, the Cho/Cr ratios were significantly higher in patients with acute brucellosis compared to controls (p = 0.01). MRS revealed metabolic changes in normal-appearing white matter of patients with brucellosis. Brucellosis may cause subtle cerebral alterations, which may only be discernible with MRS. Increased Cho/Cr ratio possibly represents an initial phase of inflammation and/or demyelination process of brucellosis

  8. ESO 439-162/163 - a common proper motion binary formed by a magnetic DQ and a DC type white dwarf

    Ruiz, M.T.; Maza, J.

    1988-01-01

    In the course of a search for faint large proper motion stars, a common proper motion pair was identified having a mu = 0.38 + or - 0.03 arcsec/yr in the direction theta = 233 deg. The stars are separated by 23 arcsec and have apparent visual magnitudes 18.77 and 19.84, respectively. Spectrophotometry of the stars established that the fainter component is a cold DC white dwarf, while the brighter one is a magnetic white dwarf with strong Swan bands of C2 shifted and broadened by an about 10 to the 8th G magnetic field. 6 references

  9. Nuclear magnetic resonance study of diffusion and relaxation in hydrating white cement pastes of different water content

    Nestle, Nikolaus; Galvosas, Petrik; Geier, Oliver; Zimmermann, Christian; Dakkouri, Marwan; Karger, Jorg

    2001-01-01

    While the nuclear spin relaxation time changes in hydrating cement materials have been widely studied by various groups during the last 20 years, data on the self-diffusion behavior of the pore water during hydration of a cement paste are much scarcer. Taking advantage of improved spectrometer hardware for pulsed field gradient diffusometry and a specialized pulse sequence which is designed to compensate the detrimental effects of inner magnetic field gradients in the sample we have studied the water self-diffusion behavior in pastes prepared from white cement at various water/cement ratios. For the same mixtures, studies of the transverse spin relaxation behavior were also conducted. A comparison of the results from both techniques shows that the diffusion coefficient starts to decrease only much later than the relaxation times for all pastes studied. [copyright] 2001 American Institute of Physics

  10. Pathological Assessment of Brain White Matter in Relapsing-Remitting MS Patients using Quantitative Magnetization Transfer Imaging

    Khodarahm Pahlevan

    2011-09-01

    Full Text Available Introduction: Multiple sclerosis (MS is characterized by lesions in the white matter (WM of the central nervous system. Magnetic resonance imaging is the most specific and sensitive method for diagnosis of multiple sclerosis. However, the ability of conventional MRI to show histopathologic heterogeneity of MS lesions is insufficient. Quantitative magnetization transfer imaging (qMTI is a relatively new method to investigate pathologic processes of the brain tissue occurring in MS patients. Material and Methods: Voxel-based analyses allow regional comparisons between groups to be made for the whole brain in a single analysis. This is done by coregistering data from all individual subjects to a reference brain, generally referred to as the "standard space", and then comparing them on a voxel-by-voxel basis. This study aimed to analyze whole-brain quantitative T1 maps, not to find global changes or changes in selected regions, but specifically to investigate the spatial distribution throughout the brain of T1 increases in MS WM with respect to control WM. In this study, 11 healthy controls, 10 relapsing-remitting (RR MS patients and 13 CIS patients were studied using MT-MRI imaging. MT parameters, including magnetization transfer ratio (MTR, magnetization transfer rate between free protons and restricted macromolecular protons, Ksat and longitudinal relaxation times (with and without MT saturation pulse, T1sat and T1free values were evaluated. Results: The results showed that, at a group level, there is widespread involvement of WM throughout the brain in CIS MS and especially in RRMS, where a significant T1 increase was found in 15.58% of WM voxels (normals < RR. Discussion and Conclusion: This study demonstrates that WM in large parts of the brain is susceptible to disease processes in RR and CIS MS

  11. White Matter Integrity in Asperger Syndrome: A Preliminary Diffusion Tensor Magnetic Resonance Imaging Study in Adults

    Bloemen, Oswald J. N.; Deeley, Quinton; Sundram, Fred; Daly, Eileen M.; Barker, Gareth J.; Jones, Derek K.; van Amelsvoort, Therese A. M. J.; Schmitz, Nicole; Robertson, Dene; Murphy, Kieran C.; Murphy, Declan G. M.

    2010-01-01

    Background: Autistic Spectrum Disorder (ASD), including Asperger syndrome and autism, is a highly genetic neurodevelopmental disorder. There is a consensus that ASD has a biological basis, and it has been proposed that it is a "connectivity" disorder. Diffusion Tensor Magnetic Resonance Imaging

  12. Anti-oxidant and anti-inflammatory effects of hydrogen-rich water alleviate ethanol-induced fatty liver in mice.

    Lin, Ching-Pin; Chuang, Wen-Chen; Lu, Fung-Jou; Chen, Chih-Yen

    2017-07-21

    To investigate the effects of hydrogen-rich water (HRW) treatment on prevention of ethanol (EtOH)-induced early fatty liver in mice. In vitro reduction of hydrogen peroxide by HRW was determined with a chemiluminescence system. Female mice were randomly divided into five groups: control, EtOH, EtOH + silymarin, EtOH + HRW and EtOH + silymarin + HRW. Each group was fed a Lieber-DeCarli liquid diet containing EtOH or isocaloric maltose dextrin (control diet). Silymarin was used as a positive control to compare HRW efficacy against chronic EtOH-induced hepatotoxicity. HRW was freshly prepared and given at a dosage of 1.2 mL/mouse trice daily. Blood and liver tissue were collected after chronic-binge liquid-diet feeding for 12 wk. The in vitro study showed that HRW directly scavenged hydrogen peroxide. The in vivo study showed that HRW increased expression of acyl ghrelin, which was correlated with food intake. HRW treatment significantly reduced EtOH-induced increases in serum alanine aminotransferase, aspartate aminotransferase, triglycerol and total cholesterol levels, hepatic lipid accumulation and inflammatory cytokines, including tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-6. HRW attenuated malondialdehyde level, restored glutathione depletion and increased superoxide dismutase, glutathione peroxidase and catalase activities in the liver. Moreover, HRW reduced TNF-α and IL-6 levels but increased IL-10 and IL-22 levels. HRW protects against chronic EtOH-induced liver injury, possibly by inducing acyl ghrelin to suppress the pro-inflammatory cytokines TNF-α and IL-6 and induce IL-10 and IL-22, thus activating antioxidant enzymes against oxidative stress.

  13. XUV-exposed, non-hydrostatic hydrogen-rich upper atmospheres of terrestrial planets. Part I: atmospheric expansion and thermal escape.

    Erkaev, Nikolai V; Lammer, Helmut; Odert, Petra; Kulikov, Yuri N; Kislyakova, Kristina G; Khodachenko, Maxim L; Güdel, Manuel; Hanslmeier, Arnold; Biernat, Helfried

    2013-11-01

    The recently discovered low-density "super-Earths" Kepler-11b, Kepler-11f, Kepler-11d, Kepler-11e, and planets such as GJ 1214b represent the most likely known planets that are surrounded by dense H/He envelopes or contain deep H₂O oceans also surrounded by dense hydrogen envelopes. Although these super-Earths are orbiting relatively close to their host stars, they have not lost their captured nebula-based hydrogen-rich or degassed volatile-rich steam protoatmospheres. Thus, it is interesting to estimate the maximum possible amount of atmospheric hydrogen loss from a terrestrial planet orbiting within the habitable zone of late main sequence host stars. For studying the thermosphere structure and escape, we apply a 1-D hydrodynamic upper atmosphere model that solves the equations of mass, momentum, and energy conservation for a planet with the mass and size of Earth and for a super-Earth with a size of 2 R(Earth) and a mass of 10 M(Earth). We calculate volume heating rates by the stellar soft X-ray and extreme ultraviolet radiation (XUV) and expansion of the upper atmosphere, its temperature, density, and velocity structure and related thermal escape rates during the planet's lifetime. Moreover, we investigate under which conditions both planets enter the blow-off escape regime and may therefore experience loss rates that are close to the energy-limited escape. Finally, we discuss the results in the context of atmospheric evolution and implications for habitability of terrestrial planets in general.

  14. Hydrogen-rich water inhibits glucose and α,β -dicarbonyl compound-induced reactive oxygen species production in the SHR.Cg-Leprcp/NDmcr rat kidney

    Katakura Masanori

    2012-07-01

    Full Text Available Abstract Background Reactive oxygen species (ROS production induced by α,β-dicarbonyl compounds and advanced glycation end products causes renal dysfunction in patients with type 2 diabetes and metabolic syndrome. Hydrogen-rich water (HRW increases the H2 level in blood and tissues, thus reducing oxidative stress in animals as well as humans. In this study, we investigated the effects of HRW on glucose- and α,β-dicarbonyl compound-induced ROS generation in vitro and in vivo. Methods Kidney homogenates from Wistar rats were incubated in vitro with glucose and α,β-dicarbonyl compounds containing HRW, following which ROS levels were measured. In vivo animal models of metabolic syndrome, SHR.Cg-Leprcp/NDmcr rats, were treated with HRW for 16 weeks, following which renal ROS production and plasma and renal α,β-dicarbonyl compound levels were measured by liquid chromatograph mass spectrometer. Results HRW inhibited glucose- and α,β-dicarbonyl compound-induced ROS production in kidney homogenates from Wistar rats in vitro. Furthermore, SHR.Cg-Leprcp/NDmcr rats treated with HRW showed a 34% decrease in ROS production. Moreover, their renal glyoxal, methylglyoxal, and 3-deoxyglucosone levels decreased by 81%, 77%, and 60%, respectively. Positive correlations were found between renal ROS levels and renal glyoxal (r = 0.659, p = 0.008 and methylglyoxal (r = 0.782, p = 0.001 levels. Conclusion These results indicate that HRW inhibits the production of α,β-dicarbonyl compounds and ROS in the kidneys of SHR.Cg-Leprcp/NDmcr rats. Therefore, it has therapeutic potential for renal dysfunction in patient with type 2 diabetes and metabolic syndrome.

  15. A fast spinning magnetic white dwarf in the double degenerate, super-Chandrasekhar system NLTT 12758

    Kawka, Adela; Briggs, G.; Vennes, Stephane; Ferrario, L.; Paunzen, E.; Wickramasinghe, D.T.

    2017-01-01

    Roč. 466, č. 1 (2017), s. 1127-1139 ISSN 0035-8711 R&D Projects: GA ČR GAP209/12/0217; GA ČR GA15-15943S; GA MŠk LG14013; GA MŠk(CZ) LG15010 Institutional support: RVO:67985815 Keywords : close binaries * NLTT 12758 * magnetic field Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 4.961, year: 2016

  16. Anti-N-methyl-D-aspartate receptor encephalitis concomitant with multifocal subcortical white matter lesions on magnetic resonance imaging: a case report and review of the literature.

    Wang, Rui-Jin; Chen, Bu-Dong; Qi, Dong

    2015-07-08

    Anti-N-methyl-D-aspartate receptor encephalitis is a severe autoimmune disorder characterized by severe psychiatric symptoms, seizures, decreased consciousness, autonomic dysregulation, and dyskinesias. Multifocal subcortical white matter lesions on fluid-attenuated inversion recovery and diffuse weighted images have rarely been reported in previous literature, and serial magnetic resonance imaging changes after plasma exchange have not been presented before. A previously healthy 24-year-old Chinese woman presented with acute psychiatric symptoms characterized by fear and agitation followed by decreased consciousness, dyskinesias, and seizures. Magnetic resonance imaging revealed hyperintense lesions on fluid-attenuated inversion recovery and diffuse weighted images in bilateral subcortical white matter. Cerebrospinal fluid analysis revealed a mild pleocytosis with lymphocytic predominance. Protein and glucose levels were normal. Aquaporin-4 antibodies in serum and cerebrospinal fluid were negative. Identification of anti-N-methyl-D-aspartate receptor antibodies in serum and cerebrospinal fluid confirmed the diagnosis of anti-N-methyl-D-aspartate receptor encephalitis. She was initially treated with combined intravenous immunoglobulin and methylprednisolone without improvement. Plasma exchange was then initiated with good response; the patient made a full recovery after several cycles of plasma exchange. Repeat magnetic resonance imaging performed 1 month after plasma exchange showed partial resolution of the hyperintense lesions in bilateral subcortical white matter, and follow-up magnetic resonance imaging 2 months after plasma exchange showed complete resolution. Anti-N-methyl-D-aspartate receptor encephalitis may be concomitant with multifocal subcortical white matter lesions. Such lesions may resolve after appropriate immunotherapy.

  17. White Paper of the Society of Computed Body Tomography and Magnetic Resonance on Dual-Energy CT, Part 2: Radiation Dose and Iodine Sensitivity.

    Foley, W Dennis; Shuman, William P; Siegel, Marilyn J; Sahani, Dushyant V; Boll, Daniel T; Bolus, David N; De Cecco, Carlo N; Kaza, Ravi K; Morgan, Desiree E; Schoepf, U Joseph; Vrtiska, Terri J; Yeh, Benjamin M; Berland, Lincoln L

    This is the second of a series of 4 white papers that represent Expert Consensus Documents developed by the Society of Computed Body Tomography and Magnetic Resonance through its task force on dual-energy computed tomography. This paper, part 2, addresses radiation dose and iodine sensitivity in dual-energy computed tomography.

  18. Late effects of high-dose adjuvant chemotherapy on white and gray matter in breast cancer survivors: Converging results from multimodal magnetic resonance imaging

    de Ruiter, Michiel B.; Reneman, Liesbeth; Boogerd, Willem; Veltman, Dick J.; Caan, Matthan; Douaud, Gwenaëlle; Lavini, Cristina; Linn, Sabine C.; Boven, Epie; van Dam, Frits S. A. M.; Schagen, Sanne B.

    2012-01-01

    The neural substrate underlying cognitive impairments after chemotherapy is largely unknown. Here, we investigated very late (>9 years) effects of adjuvant high-dose chemotherapy on brain white and gray matter in primary breast cancer survivors (n = 17) with multimodal magnetic resonance imaging

  19. The prognostic value of multivoxel magnetic resonance spectroscopy determined metabolite levels in white and grey matter brain tissue for adverse outcome in term newborns following perinatal asphyxia

    van Doormaal, Pieter Jan; Meiners, Linda C.; ter Horst, Hendrik J.; Veere, van der Christa; Sijens, Paul E.

    Magnetic resonance spectroscopy can identify brain metabolic changes in perinatal asphyxia by providing ratios of metabolites, such as choline (Cho), creatine (Cr), N-acetyl aspartate (NAA) and lactate (Lact) [Cho/Cr, Lact/NAA, etc.]. The purpose of this study was to quantify the separate white and

  20. Reduced parietooccipital white matter glutamine measured by proton magnetic resonance spectroscopy in treated graves' disease patients

    Danielsen, Else Rubæk; Elberling, T.V.; Rasmussen, Åse Krogh

    2008-01-01

    CONTEXT: Graves' disease is an autoimmune disease of the thyroid gland. Patients often have affective and cognitive complaints, whether these disappear after treatment remains disputed. OBJECTIVE: Our objective was to evaluate cerebral biochemistry in acute and treated Graves' disease. DESIGN: We...... conducted a prospective study, investigating volunteers once and patients before and 1 yr after treatment. SETTING: The study was performed at a radiology department, a memory disorder clinic, and two endocrinology clinics. PATIENTS AND OTHER PARTICIPANTS: Of 53 consecutively referred, newly diagnosed...... and a battery of biochemical, affective, and cognitive tests were used. RESULTS: Previously reported findings of reduced choline and myo-inositol in acute Graves' disease were confirmed and reversibility was demonstrated. Parieto-occipital white matter glutamine was and remained significantly reduced (P

  1. Unsupervised detection, quantification and localization of white matter hyper-intensities in magnetic resonance imaging

    Gicquel, Sebastien

    1998-01-01

    White matter hyper-intensities (WMH) are punctual ischemic areas, related to arteriosclerosis, visible on T2- and PD-weighted MRI. They are present on elderly normal subjects, and their proportion vary between 27 to 83 % from study to study. This strong variability in their counting is especially caused by human observation, so an unsupervised detection tool is necessary. The method is based on the analysis of Tl-weighted MRI in sagittal orientation, and of T2- and PD-weighted MRI in transaxial orientation of a single subject. Detection of WMH is based on a segmentation phase, and contains a large number of pre- and post-processing. First, a correction of inhomogeneities due to instrumentation is applied, with the modelization of the intensity variations appearing on a homogenous object. and the Computing a correction matrix. The three MRI modalities are then placed in a single referential, using a MRI-PET registration method. The brain is segmented on the Tl-weighted MRI, resulting in a mask used to segment the two others modalities after registration. A multispectral bayesian segmentation algorithm extracts the white matter (WM) and objects likely to be WMH. A set of morphological operations generate an image representing WM and potential WMH. A second segmentation of this image, in two classes, results in a WMH mask. It is then possible to list the WMH, their size, their shape, and their position in the MRI referential. At last, the coordinates of the WMH centers of mass are placed into Talairach space, allowing statistical analysis on a large number of subjects. This method has been in part applied on a data base of 850 subjects. The four steps (correction of inhomogeneities, registration, segmentation of the brain and detection of AC and PC landmarks) result in a global success rate of 90 %. (author) [fr

  2. Hemispheric asymmetries in dorsal language pathway white-matter tracts: A magnetic resonance imaging tractography and functional magnetic resonance imaging study.

    Silva, Guilherme; Citterio, Alberto

    2017-10-01

    Introduction Previous studies have shown that the arcuate fasciculus has a leftward asymmetry in right-handers that could be correlated with the language lateralisation defined by functional magnetic resonance imaging. Nonetheless, information about the asymmetry of the other fibres that constitute the dorsal language pathway is scarce. Objectives This study investigated the asymmetry of the white-matter tracts involved in the dorsal language pathway through the diffusion tensor imaging (DTI) technique, in relation to language hemispheric dominance determined by task-dependent functional magnetic resonance imaging (fMRI). Methods We selected 11 patients (10 right-handed) who had been studied with task-dependent fMRI for language areas and DTI and who had no language impairment or structural abnormalities that could compromise magnetic resonance tractography of the fibres involved in the dorsal language pathway. Laterality indices (LI) for fMRI and for the volumes of each tract were calculated. Results In fMRI, all the right-handers had left hemispheric lateralisation, and the ambidextrous subject presented right hemispheric dominance. The arcuate fasciculus LI was strongly correlated with fMRI LI ( r = 0.739, p = 0.009), presenting the same lateralisation of fMRI in seven subjects (including the right hemispheric dominant). It was not asymmetric in three cases and had opposite lateralisation in one case. The other tracts presented predominance for rightward lateralisation, especially superior longitudinal fasciculus (SLF) II/III (nine subjects), but their LI did not correlate (directly or inversely) with fMRI LI. Conclusion The fibres that constitute the dorsal language pathway have an asymmetric distribution in the cerebral hemispheres. Only the asymmetry of the arcuate fasciculus is correlated with fMRI language lateralisation.

  3. IGR J14257-6117, a magnetic accreting white dwarf with a very strong strong X-ray orbital modulation

    Bernardini, F.; de Martino, D.; Mukai, K.; Falanga, M.

    2018-04-01

    IGR J14257-6117 is an unclassified source in the hard X-ray catalogues. Optical follow-ups suggest it could be a Cataclysmic Variable of the magnetic type. We present the first high S/N X-ray observation performed by XMM-Newton at 0.3-10 keV, complemented with 10-80 keV coverage by Swift/BAT, aimed at revealing the source nature. We detected for the first time a fast periodic variability at 509.5 s and a longer periodic variability at 4.05 h, ascribed to the white dwarf (WD) spin and binary orbital periods, respectively. These unambiguously identify IGR J14257-6117 as a magnetic CV of the Intermediate Polar (IP) type. The energy resolved light curves at both periods reveal amplitudes decreasing with increasing energy, with the orbital modulation reaching ˜100% in the softest band. The energy spectrum shows optically thin thermal emission with an excess at the iron complex, absorbed by two dense media (NH ˜ 1022 - 23 cm-2), partially covering the X-ray source. These are likely localised in the magnetically confined accretion flow above the WD surface and at the disc rim, producing the energy dependent spin and orbital variabilities, respectively. IGR J14257-6117, joins the group of strongest orbitally modulated IPs now counting four systems. Drawing similarities with low-mass X-ray binaries displaying orbital dips, these IPs should be seen at large orbital inclinations allowing azimuthally extended absorbing material fixed in the binary frame to intercept the line of sight. For IGR J14257-6117, we estimate (50o ≲ i ≲ 70o). Whether also the mass accretion rate plays a role in the large orbital modulations in IPs cannot be established with the present data.

  4. Magnetic resonance imaging in dementia: a study of brain white matter changes

    Bronge, Lena [Huddinge Univ. Hospital, Stockholm (Sweden). Dept. of Diagnostic Radiology

    2002-06-01

    Non-specific white matter changes (WMC) in the brain are common findings in the elderly population. Although they are frequently seen in non-demented persons, WMC seem to be more common in demented patients. The significance of these changes, as well as their pathophysiological background, is incompletely understood. The aim of this thesis was to study different aspects of WMC using MR imaging (MRI) and to investigate the clinical significance of such changes in subjects with mild cognitive impairment or dementia. In study I post-mortem MRI of the brain was compared to corresponding neuropathology slices. WMC were quantified and found to be more extensive on neuropathology. The areas that appeared normal on MRI but not on histopathology represented only minor changes with increased distance between the myelinated fibres but with preserved axonal network and glial cell density. Study II evaluated the blood-brain barrier (BBB) integrity to investigate if an increased permeability could be shown in WMC. A contrast-enhanced MRI technique was used to detect small degrees of enhancement. No general increase in BBB could be detected in the WMC areas. In study III the relation between WMC and apolipoprotein E (APOE) genotype was explored in patients with Alzheimer's disease (AD). Results showed that AD patients, who were homozygous for the APOE {epsilon}4 allele had more WMC than patients with other genotypes. This was most significant for changes in the deep white matter. Results also indicated that in AD patients carrying the {epsilon}4 allele, WMC are not age-related phenomena, but might be related to the aetiology of the disease. Study IV aimed to investigate if WMC in a specific brain region affect cognitive functions related to that area. Periventricular WMC in the left frontal lobe predicted a decrease in initial word fluency, a test thought to reflect left frontal lobe functioning. This indicates that WMC might have specific effects in different brain regions

  5. Magnetic resonance imaging in dementia: a study of brain white matter changes

    Bronge, Lena

    2002-01-01

    Non-specific white matter changes (WMC) in the brain are common findings in the elderly population. Although they are frequently seen in non-demented persons, WMC seem to be more common in demented patients. The significance of these changes, as well as their pathophysiological background, is incompletely understood. The aim of this thesis was to study different aspects of WMC using MR imaging (MRI) and to investigate the clinical significance of such changes in subjects with mild cognitive impairment or dementia. In study I post-mortem MRI of the brain was compared to corresponding neuropathology slices. WMC were quantified and found to be more extensive on neuropathology. The areas that appeared normal on MRI but not on histopathology represented only minor changes with increased distance between the myelinated fibres but with preserved axonal network and glial cell density. Study II evaluated the blood-brain barrier (BBB) integrity to investigate if an increased permeability could be shown in WMC. A contrast-enhanced MRI technique was used to detect small degrees of enhancement. No general increase in BBB could be detected in the WMC areas. In study III the relation between WMC and apolipoprotein E (APOE) genotype was explored in patients with Alzheimer's disease (AD). Results showed that AD patients, who were homozygous for the APOE ε4 allele had more WMC than patients with other genotypes. This was most significant for changes in the deep white matter. Results also indicated that in AD patients carrying the ε4 allele, WMC are not age-related phenomena, but might be related to the aetiology of the disease. Study IV aimed to investigate if WMC in a specific brain region affect cognitive functions related to that area. Periventricular WMC in the left frontal lobe predicted a decrease in initial word fluency, a test thought to reflect left frontal lobe functioning. This indicates that WMC might have specific effects in different brain regions. In study V we

  6. Hydrogen in hot subdwarfs formed by double helium white dwarf mergers

    Hall, Philip D.; Jeffery, C. Simon

    2016-01-01

    Isolated hot subdwarfs might be formed by the merging of two helium-core white dwarfs. Before merging, helium-core white dwarfs have hydrogen-rich envelopes and some of this hydrogen may survive the merger. We calculate the mass of hydrogen that is present at the start of such mergers and, with the assumption that hydrogen is mixed throughout the disrupted white dwarf in the merger process, estimate how much can survive. We find a hydrogen mass of up to about $2 \\times 10^{-3}\\,\\mathrm{M}_{\\o...

  7. Magnetic resonance fiber density mapping of age-related white matter changes

    Stadlbauer, Andreas; Ganslandt, Oliver; Salomonowitz, Erich; Buchfelder, Michael; Hammen, Thilo; Bachmair, Johanna; Eberhardt, Knut

    2012-01-01

    Objectives: To introduce fiber density mapping (FDM) for investigation of age-related white matter (WM) changes and to compare its capabilities with conventional diffusion tensor imaging (DTI) post-processing. Methods: DTI data with 1.9 mm 3 isotropic voxels were acquired from 44 healthy volunteers (18–88 years) at 3 T. FDM is a 3-step approach which includes diagonalization of the diffusion tensor, fiber reconstruction for the whole brain, and calculation of fiber density (FD) values. Maps of fractional anisotropy (FA) and mean diffusivity (MD) were additionally calculated. Voxel-based analyses were performed to determine volume clusters of significant correlation with age. Bivariate linear regression models and Hotelling–Williams tests were used to detect significant differences between correlations. Results: FDM detected a larger WM volume affected by age-related changes concomitant with fewer significant clusters compared to FA and MD. This indicates that WM alterations due to normal aging occur rather globally than locally. FD values showed a significant stronger correlation with age in frontal lobes (prefrontal and precentral gyrus), limbic lobes (cingulate and parahippocampal gyrus), the corpus callosum (genu) and temporal lobes. Conclusions: FDM shows higher sensitivity for detection of age-related WM changes because it includes all surrounding fiber structures into the evaluation of each DTI data voxel.

  8. Magnetic resonance fiber density mapping of age-related white matter changes

    Stadlbauer, Andreas, E-mail: andi@nmr.at [MR Physics Group, Department of Radiology, Landesklinikum St. Poelten, Propst Fuehrer Strasse 4, A-3100 St. Poelten (Austria); Department of Neurosurgery, University of Erlangen-Nuremberg, Schwabachanlage 6, 91054 Erlangen (Germany); Ganslandt, Oliver [Department of Neurosurgery, University of Erlangen-Nuremberg, Schwabachanlage 6, 91054 Erlangen (Germany); Salomonowitz, Erich [MR Physics Group, Department of Radiology, Landesklinikum St. Poelten, Propst Fuehrer Strasse 4, A-3100 St. Poelten (Austria); Buchfelder, Michael [Department of Neurosurgery, University of Erlangen-Nuremberg, Schwabachanlage 6, 91054 Erlangen (Germany); Hammen, Thilo [Department of Neurology, Epilepsy Center, University of Erlangen-Nuremberg, Schwabachanlage 6, D-90429 Erlangen (Germany); Bachmair, Johanna [MR Physics Group, Department of Radiology, Landesklinikum St. Poelten, Propst Fuehrer Strasse 4, A-3100 St. Poelten (Austria); Eberhardt, Knut [Krankenhaus Schloss Werneck, MRT-Kompetenzzentrum, Balthasar-Neumann-Platz 1, D-97440 Werneck (Germany)

    2012-12-15

    Objectives: To introduce fiber density mapping (FDM) for investigation of age-related white matter (WM) changes and to compare its capabilities with conventional diffusion tensor imaging (DTI) post-processing. Methods: DTI data with 1.9 mm{sup 3} isotropic voxels were acquired from 44 healthy volunteers (18–88 years) at 3 T. FDM is a 3-step approach which includes diagonalization of the diffusion tensor, fiber reconstruction for the whole brain, and calculation of fiber density (FD) values. Maps of fractional anisotropy (FA) and mean diffusivity (MD) were additionally calculated. Voxel-based analyses were performed to determine volume clusters of significant correlation with age. Bivariate linear regression models and Hotelling–Williams tests were used to detect significant differences between correlations. Results: FDM detected a larger WM volume affected by age-related changes concomitant with fewer significant clusters compared to FA and MD. This indicates that WM alterations due to normal aging occur rather globally than locally. FD values showed a significant stronger correlation with age in frontal lobes (prefrontal and precentral gyrus), limbic lobes (cingulate and parahippocampal gyrus), the corpus callosum (genu) and temporal lobes. Conclusions: FDM shows higher sensitivity for detection of age-related WM changes because it includes all surrounding fiber structures into the evaluation of each DTI data voxel.

  9. XUV-Exposed, Non-Hydrostatic Hydrogen-Rich Upper Atmospheres of Terrestrial Planets. Part II: Hydrogen Coronae and Ion Escape

    Lammer, Helmut; Holmström, Mats; Panchenko, Mykhaylo; Odert, Petra; Erkaev, Nikolai V.; Leitzinger, Martin; Khodachenko, Maxim L.; Kulikov, Yuri N.; Güdel, Manuel; Hanslmeier, Arnold

    2013-01-01

    Abstract We studied the interactions between the stellar wind plasma flow of a typical M star, such as GJ 436, and the hydrogen-rich upper atmosphere of an Earth-like planet and a “super-Earth” with a radius of 2 REarth and a mass of 10 MEarth, located within the habitable zone at ∼0.24 AU. We investigated the formation of extended atomic hydrogen coronae under the influences of the stellar XUV flux (soft X-rays and EUV), stellar wind density and velocity, shape of a planetary obstacle (e.g., magnetosphere, ionopause), and the loss of planetary pickup ions on the evolution of hydrogen-dominated upper atmospheres. Stellar XUV fluxes that are 1, 10, 50, and 100 times higher compared to that of the present-day Sun were considered, and the formation of high-energy neutral hydrogen clouds around the planets due to the charge-exchange reaction under various stellar conditions was modeled. Charge-exchange between stellar wind protons with planetary hydrogen atoms, and photoionization, lead to the production of initially cold ions of planetary origin. We found that the ion production rates for the studied planets can vary over a wide range, from ∼1.0×1025 s−1 to ∼5.3×1030 s−1, depending on the stellar wind conditions and the assumed XUV exposure of the upper atmosphere. Our findings indicate that most likely the majority of these planetary ions are picked up by the stellar wind and lost from the planet. Finally, we estimated the long-time nonthermal ion pickup escape for the studied planets and compared them with the thermal escape. According to our estimates, nonthermal escape of picked-up ionized hydrogen atoms over a planet's lifetime within the habitable zone of an M dwarf varies between ∼0.4 Earth ocean equivalent amounts of hydrogen (EOH) to stars—Early atmospheres—Earth-like exoplanets—Energetic neutral atoms—Ion escape—Habitability. Astrobiology 13, 1030–1048. PMID:24283926

  10. XUV-exposed, non-hydrostatic hydrogen-rich upper atmospheres of terrestrial planets. Part II: hydrogen coronae and ion escape.

    Kislyakova, Kristina G; Lammer, Helmut; Holmström, Mats; Panchenko, Mykhaylo; Odert, Petra; Erkaev, Nikolai V; Leitzinger, Martin; Khodachenko, Maxim L; Kulikov, Yuri N; Güdel, Manuel; Hanslmeier, Arnold

    2013-11-01

    We studied the interactions between the stellar wind plasma flow of a typical M star, such as GJ 436, and the hydrogen-rich upper atmosphere of an Earth-like planet and a "super-Earth" with a radius of 2 R(Earth) and a mass of 10 M(Earth), located within the habitable zone at ∼0.24 AU. We investigated the formation of extended atomic hydrogen coronae under the influences of the stellar XUV flux (soft X-rays and EUV), stellar wind density and velocity, shape of a planetary obstacle (e.g., magnetosphere, ionopause), and the loss of planetary pickup ions on the evolution of hydrogen-dominated upper atmospheres. Stellar XUV fluxes that are 1, 10, 50, and 100 times higher compared to that of the present-day Sun were considered, and the formation of high-energy neutral hydrogen clouds around the planets due to the charge-exchange reaction under various stellar conditions was modeled. Charge-exchange between stellar wind protons with planetary hydrogen atoms, and photoionization, lead to the production of initially cold ions of planetary origin. We found that the ion production rates for the studied planets can vary over a wide range, from ∼1.0×10²⁵ s⁻¹ to ∼5.3×10³⁰ s⁻¹, depending on the stellar wind conditions and the assumed XUV exposure of the upper atmosphere. Our findings indicate that most likely the majority of these planetary ions are picked up by the stellar wind and lost from the planet. Finally, we estimated the long-time nonthermal ion pickup escape for the studied planets and compared them with the thermal escape. According to our estimates, nonthermal escape of picked-up ionized hydrogen atoms over a planet's lifetime within the habitable zone of an M dwarf varies between ∼0.4 Earth ocean equivalent amounts of hydrogen (EO(H)) to <3 EO(H) and usually is several times smaller in comparison to the thermal atmospheric escape rates.

  11. Magnetic resonance spectroscopy markers of axons and astrogliosis in relation to specific features of white matter injury in preterm infants

    Wisnowski, Jessica L.; Panigrahy, Ashok; Schmithorst, Vincent J.; Rosser, Tena; Paquette, Lisa; Nelson, Marvin D.; Haynes, Robin L.; Painter, Michael J.; Blueml, Stefan

    2014-01-01

    Punctate white matter lesions (pWMLs) and diffuse excessive high signal intensity (DEHSI) are commonly observed signal abnormalities on MRI scans of high-risk preterm infants near term-equivalent age. To establish whether these features are indicative abnormalities in axonal development or astroglia, we compared pWMLs and DEHSI to markers of axons and astrogliosis, derived from magnetic resonance spectroscopy (MRS). Data from 108 preterm infants (gestational age at birth 31.0 weeks ± 4.3; age at scan 41.2 weeks ± 6.0) who underwent MR examinations under clinical indications were included in this study. Linear regression analyses were used to test the effects of pWMLs and DEHSI on N-acetyl-aspartate (NAA) and myoinositol concentrations, respectively. Across the full sample, pWMLs were associated with a reduction in NAA whereas moderate to severe DEHSI altered the normal age-dependent changes in myoinositol such that myoinositol levels were lower at younger ages with no change during the perinatal period. Subgroup analyses indicated that the above associations were driven by the subgroup of neonates with both pWMLs and moderate to severe DEHSI. Overall, these findings suggest that pWMLs in conjunction with moderate/severe DEHSI may signify a population of infants at risk for long-term adverse neurodevelopmental outcome due to white matter injury and associated axonopathy. The loss of normal age-associated changes in myoinositol further suggests disrupted astroglial function and/or osmotic dysregulation. (orig.)

  12. Magnetic resonance spectroscopy markers of axons and astrogliosis in relation to specific features of white matter injury in preterm infants

    Wisnowski, Jessica L.; Panigrahy, Ashok [Children' s Hospital Los Angeles, Department of Radiology, Los Angeles, CA (United States); University of Pittsburgh, Department of Pediatric Radiology, Children' s Hospital of Pittsburgh of UPMC, Pittsburgh, PA (United States); Schmithorst, Vincent J. [University of Pittsburgh, Department of Pediatric Radiology, Children' s Hospital of Pittsburgh of UPMC, Pittsburgh, PA (United States); Rosser, Tena [Children' s Hospital Los Angeles, Department of Pediatrics, Division of Neurology, Los Angeles, CA (United States); Paquette, Lisa [Children' s Hospital Los Angeles, Department of Pediatrics, Division of Neonatology, Los Angeles, CA (United States); Nelson, Marvin D. [Children' s Hospital Los Angeles, Department of Radiology, Los Angeles, CA (United States); Haynes, Robin L. [Boston Children' s Hospital, Department of Pathology, Boston, MA (United States); Painter, Michael J. [University of Pittsburgh, Department of Pediatrics, Division of Neurology, Children' s Hospital of Pittsburgh of UPMC, Pittsburgh, PA (United States); Blueml, Stefan [Children' s Hospital Los Angeles, Department of Radiology, Los Angeles, CA (United States); Rudi Schulte Research Institute, Santa Barbara, CA (United States)

    2014-09-15

    Punctate white matter lesions (pWMLs) and diffuse excessive high signal intensity (DEHSI) are commonly observed signal abnormalities on MRI scans of high-risk preterm infants near term-equivalent age. To establish whether these features are indicative abnormalities in axonal development or astroglia, we compared pWMLs and DEHSI to markers of axons and astrogliosis, derived from magnetic resonance spectroscopy (MRS). Data from 108 preterm infants (gestational age at birth 31.0 weeks ± 4.3; age at scan 41.2 weeks ± 6.0) who underwent MR examinations under clinical indications were included in this study. Linear regression analyses were used to test the effects of pWMLs and DEHSI on N-acetyl-aspartate (NAA) and myoinositol concentrations, respectively. Across the full sample, pWMLs were associated with a reduction in NAA whereas moderate to severe DEHSI altered the normal age-dependent changes in myoinositol such that myoinositol levels were lower at younger ages with no change during the perinatal period. Subgroup analyses indicated that the above associations were driven by the subgroup of neonates with both pWMLs and moderate to severe DEHSI. Overall, these findings suggest that pWMLs in conjunction with moderate/severe DEHSI may signify a population of infants at risk for long-term adverse neurodevelopmental outcome due to white matter injury and associated axonopathy. The loss of normal age-associated changes in myoinositol further suggests disrupted astroglial function and/or osmotic dysregulation. (orig.)

  13. Application of 3.0T magnetic resonance spectroscopy imaging in the evaluation on the development of normal brain white matter in infants and young children

    Wen-li XU

    2014-01-01

    Full Text Available Objective To calculate the radios of peak area of proton magnetic resonance spectroscopy metabolites in brain white matter of normal infants and young children, to observe the features of metabolite spectra, and to explore the relations between their ratio with age. Methods The peak areas of metabolites, including N-acetyl aspartate (NAA, choline (Cho, creatine (Cr, and their ratio of NAA/Cho, NAA/Cr, Cho/Cr, in paraventricular white matter of 180 normal infants and young children with different ages as evaluated by multi-voxel proton magnetic resonance spectroscopy. Results In paraventricular white matter, spectrum of NAA increased, and that of Cho decreased gradually, while both of them were stabilized at 2 years old. Cr was increased obviously within 3 months, and stabilized after 4 months. Significant differences were found in ratio of different metabolites in paraventricular white matter in different ages (P<0.05. The ratios of NAA/Cho and NAA/Cr in paraventricular white mater were positively correlated with age (r=0.741, r=0.625, while that of Cho/Cr was negatively correlated with age (r=–0.552, P<0.05. Conclusion The ratios of different metabolites are different in brain white matter in infants of different ages. Metabolites concentrations in brain white matter are correlated to some extent with age, which may provide a diagnostic criterion for evaluation of normal brain development and abnormal brain metabolism. DOI: 10.11855/j.issn.0577-7402.2013.12.05

  14. Longitudinal diffusion tensor magnetic resonance imaging study of radiation-induced white matter damage in a rat model.

    Wang, Silun; Wu, Ed X; Qiu, Deqiang; Leung, Lucullus H T; Lau, Ho-Fai; Khong, Pek-Lan

    2009-02-01

    Radiation-induced white matter (WM) damage is a major side effect of whole brain irradiation among childhood cancer survivors. We evaluate longitudinally the diffusion characteristics of the late radiation-induced WM damage in a rat model after 25 and 30 Gy irradiation to the hemibrain at 8 time points from 2 to 48 weeks postradiation. We hypothesize that diffusion tensor magnetic resonance imaging (DTI) indices including fractional anisotropy (FA), trace, axial diffusivity (lambda(//)), and radial diffusivity (lambda( perpendicular)) can accurately detect and monitor the histopathologic changes of radiation-induced WM damage, measured at the EC, and that these changes are dose and time dependent. Results showed a progressive reduction of FA, which was driven by reduction in lambda(//) from 4 to 40 weeks postradiation, and an increase in lambda( perpendicular) with return to baseline in lambda(//) at 48 weeks postradiation. Histologic evaluation of irradiated WM showed reactive astrogliosis from 4 weeks postradiation with reversal at 36 weeks, and demyelination, axonal degeneration, and necrosis at 48 weeks postradiation. Moreover, changes in lambda(//) correlated with reactive astrogliosis (P histopathologic changes of WM damage and our results support the use of DTI as a biomarker to noninvasively monitor radiation-induced WM damage.

  15. Application of variable threshold intensity to segmentation for white matter hyperintensities in fluid attenuated inversion recovery magnetic resonance images

    Yoo, Byung Il; Han, Ji Won; Oh, San Yeo Wool; Kim, Tae Hui [Seoul National University Bundang Hospital, Department of Neuropsychiatry, Seongnam, Gyeonggi-do (Korea, Republic of); Lee, Jung Jae; Lee, Eun Young [Kyungbook National University Chilgok Hospital, Department of Psychiatry, Buk-gu, Daegu (Korea, Republic of); MacFall, James R. [Duke University Medical Center, Neuropsychiatric Imaging Research Laboratory, Durham, NC (United States); Duke University Medical Center, Department of Radiology, Durham, NC (United States); Payne, Martha E. [Duke University Medical Center, Neuropsychiatric Imaging Research Laboratory, Durham, NC (United States); Duke University Medical Center, Department of Psychiatry and Behavioral Sciences, Durham, NC (United States); Kim, Jae Hyoung [Seoul National University Bundang Hospital, Department of Radiology, Seongnam, Gyeonggi-do (Korea, Republic of); Seoul National University College of Medicine, Department of Radiology, Jongno-gu, Seoul (Korea, Republic of); Kim, Ki Woong [Seoul National University Bundang Hospital, Department of Neuropsychiatry, Seongnam, Gyeonggi-do (Korea, Republic of); Seoul National University College of Medicine, Department of Psychiatry, Jongno-gu, Seoul (Korea, Republic of); Seoul National University College of Natural Sciences, Department of Brain and Cognitive Science, Gwanak-gu, Seoul (Korea, Republic of)

    2014-04-15

    White matter hyperintensities (WMHs) are regions of abnormally high intensity on T2-weighted or fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI). Accurate and reproducible automatic segmentation of WMHs is important since WMHs are often seen in the elderly and are associated with various geriatric and psychiatric disorders. We developed a fully automated monospectral segmentation method for WMHs using FLAIR MRIs. Through this method, we introduce an optimal threshold intensity (I{sub O}) for segmenting WMHs, which varies with WMHs volume (V{sub WMH}), and we establish the I{sub O} -V{sub WMH} relationship. Our method showed accurate validations in volumetric and spatial agreements of automatically segmented WMHs compared with manually segmented WMHs for 32 confirmatory images. Bland-Altman values of volumetric agreement were 0.96 ± 8.311 ml (bias and 95 % confidence interval), and the similarity index of spatial agreement was 0.762 ± 0.127 (mean ± standard deviation). Furthermore, similar validation accuracies were obtained in the images acquired from different scanners. The proposed segmentation method uses only FLAIR MRIs, has the potential to be accurate with images obtained from different scanners, and can be implemented with a fully automated procedure. In our study, validation results were obtained with FLAIR MRIs from only two scanner types. The design of the method may allow its use in large multicenter studies with correct efficiency. (orig.)

  16. Application of variable threshold intensity to segmentation for white matter hyperintensities in fluid attenuated inversion recovery magnetic resonance images

    Yoo, Byung Il; Han, Ji Won; Oh, San Yeo Wool; Kim, Tae Hui; Lee, Jung Jae; Lee, Eun Young; MacFall, James R.; Payne, Martha E.; Kim, Jae Hyoung; Kim, Ki Woong

    2014-01-01

    White matter hyperintensities (WMHs) are regions of abnormally high intensity on T2-weighted or fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI). Accurate and reproducible automatic segmentation of WMHs is important since WMHs are often seen in the elderly and are associated with various geriatric and psychiatric disorders. We developed a fully automated monospectral segmentation method for WMHs using FLAIR MRIs. Through this method, we introduce an optimal threshold intensity (I O ) for segmenting WMHs, which varies with WMHs volume (V WMH ), and we establish the I O -V WMH relationship. Our method showed accurate validations in volumetric and spatial agreements of automatically segmented WMHs compared with manually segmented WMHs for 32 confirmatory images. Bland-Altman values of volumetric agreement were 0.96 ± 8.311 ml (bias and 95 % confidence interval), and the similarity index of spatial agreement was 0.762 ± 0.127 (mean ± standard deviation). Furthermore, similar validation accuracies were obtained in the images acquired from different scanners. The proposed segmentation method uses only FLAIR MRIs, has the potential to be accurate with images obtained from different scanners, and can be implemented with a fully automated procedure. In our study, validation results were obtained with FLAIR MRIs from only two scanner types. The design of the method may allow its use in large multicenter studies with correct efficiency. (orig.)

  17. Magnetic monopole catalysis of proton decay

    Marciano, W.J.; Salvino, D.

    1986-09-01

    Catalysis of proton decay by GUT magnetic monopoles (the Rubakov-Callan effect) is discussed. Combining a short-distance cross section calculation by Bernreuther and Craigie with the long-distance velocity dependent distortion factors of Arafune and Fukugita, catalysis rate predictions which can be compared with experiment are obtained. At present, hydrogen rich detectors such as water (H 2 O) and methane (CH 4 ) appear to be particularly well suited for observing catalysis by very slow monopoles. 17 refs., 1 fig

  18. Study of white matter at the centrum semiovale level with magnetic resonance spectroscopy and diffusion tensor imaging in cerebral small vessel disease.

    Huang, L A; Ling, X Y; Li, C; Zhang, S J; Chi, G B; Xu, A D

    2014-04-08

    White matter lesion (WML) in magnetic resonance imaging is commonly observed in patients with cerebral small vessel disease (SVD), but the pathological mechanism of WML in SVD is still unclear. We observed the metabolism and microscopic anatomy of white matter in SVD patients. Twelve subjects clinically diagnosed with SVD and 6 normal control subjects were examined with magnetic resonance spectroscopy (MRS) and diffusion tensor imaging (DTI). The white matter at the centrum semiovale level was selected as the region of interest (ROI). The ROI metabolism parameters, including N-acetyl-l-aspartic acid (NAA), creatine (Cr), and choline (Cho) were measured by MRS. Microscopic parameters such as mean diffusion (MD) and fractional anisotropy (FA) in ROI were obtained by DTI. Compared with the normal control group, bilateral MD values in the SVD group were significantly elevated, whereas bilateral FA values in SVD were decreased, but the difference was not statistically significant. Additionally, NAA/Cho, Cho/Cr, and NAA/Cr showed no significant statistical differences. Our study suggests that the mechanisms of the SVD cognitive impairment are related to damage of the white matter structures rather than to brain metabolism.

  19. White Paper of the Society of Computed Body Tomography and Magnetic Resonance on Dual-Energy CT, Part 1: Technology and Terminology.

    Siegel, Marilyn J; Kaza, Ravi K; Bolus, David N; Boll, Daniel T; Rofsky, Neil M; De Cecco, Carlo N; Foley, W Dennis; Morgan, Desiree E; Schoepf, U Joseph; Sahani, Dushyant V; Shuman, William P; Vrtiska, Terri J; Yeh, Benjamin M; Berland, Lincoln L

    This is the first of a series of 4 white papers that represent Expert Consensus Documents developed by the Society of Computed Body Tomography and Magnetic Resonance through its task force on dual-energy computed tomography (DECT). This article, part 1, describes the fundamentals of the physical basis for DECT and the technology of DECT and proposes uniform nomenclature to account for differences in proprietary terms among manufacturers.

  20. A solution for the preparation of hexagonal M-type SrFe{sub 12}O{sub 19} ferrite using egg-white: Structural and magnetic properties

    Li, Tingting; Li, Yang; Wu, Ruonan; Zhou, Han; Fang, Xiaochen [Anhui Key Laboratory of Metal Materials and Processing, School of Materials Science and Engineering, Anhui University of Technology, Maanshan 243002 (China); Su, Shubing [School of Electronic and Information Engineering, Ningbo University of Technology, Ningbo 315016 (China); Xia, Ailin, E-mail: alxia@126.com [Anhui Key Laboratory of Metal Materials and Processing, School of Materials Science and Engineering, Anhui University of Technology, Maanshan 243002 (China); Jin, Chuangui; Liu, Xianguo [Anhui Key Laboratory of Metal Materials and Processing, School of Materials Science and Engineering, Anhui University of Technology, Maanshan 243002 (China)

    2015-11-01

    A new sol–gel route using egg-white as the binder of metal ions, is developed to prepare hexagonal M-type SrFe{sub 12}O{sub 19} ferrite in this study, and the effects of different atomic ratio of Sr and Fe (Sr/Fe), sintering temperature (T{sub s}) and usage of egg-white (M{sub ew}) on the phase formation, morphology and magnetic properties of specimens are studied. It is found that the single-phase SrFe{sub 12}O{sub 19} ferrite only can be obtained under a Sr/Fe of 1:8 and a T{sub s} between 1000 °C and 1300 °C. The magnetic properties of specimens are also obviously affected by the different Sr/Fe and T{sub s}, primarily due to the emergency of impurities. The M{sub ew} has an obvious impact on the crystallinity of specimens, which consequently affects their magnetic properties. In our study, the optimum conditions to prepare the single-phase SrFe{sub 12}O{sub 19} ferrite are Sr/Fe=1:8, M{sub ew}= 3 g and T{sub s} =1200 °C. - Highlights: • Single-phase SrM ferrite was obtained via a novel sol–gel method using egg-white. • Single-phase SrM ferrite was obtained under Sr/Fe=1:8 and T{sub s} between 1000 and 1300 °C. • The usage of egg-white affects the crystallinity and magnetic properties markedly.

  1. Binary system containing the pulsar PSR 1913 + 16 and ultra-violet and x-radiation from accreting magnetic white dwarfs

    Masters, A.R.

    1978-01-01

    Part I of the thesis deals with the binary system containing the pulsar PSR 1913 + 16. The system has been touted as a laboratory for testing relativistic theories of gravity, and is also a challenge for theories of stellar evolution. However, proposed uses of the system rely on assumptions about the nature of the pulsar's unobserved companion. Ways of determining the nature of the companion from observation of the pulsar are discussed. Geometrical constraints on the size of the pulsar's orbit and the observed slow rate of the orbit's precession require that the companion be a black hole, a neutron star, a white dwarf or a helium main-sequence star. Observable second-order relativistic effects may or may not further restrict the list of candidates. The discussion summarizes Masters and Roberts, 1975 Ap.J. (Letters), 195, L107, and Roberts, Masters and Arnett, 1976, Ap. J., 203, 196. Part II of the thesis treats ultra-violet and X-radiation from accreting magnetic white dwarfs. Matter from a companion star falling onto a white dwarf is shock-heated near the stellar surface and radiatively cooled. The post-shock region is approximated by a uniform, geometrically thin slab and determine the physical conditions behind the shock and the emitted spectrum for a range of stellar masses, magnetic fields and accretion rates. At low magnetic fields and high accretion rates, bremsstrahlung is the dominant cooling mechanism and the post-shock material is a single fluid (the electrons and ions have a common temperature). As the magnetic field increases or the accretion rate decreases, cyclotron emission becomes more important than bremsstrahlung

  2. Measurement of cerebral white matter perfusion using pseudocontinuous arterial spin labeling 3T magnetic resonance imaging--an experimental and theoretical investigation of feasibility.

    Wen-Chau Wu

    Full Text Available PURPOSE: This study was aimed to experimentally and numerically investigate the feasibility of measuring cerebral white matter perfusion using pseudocontinuous arterial spin labeling (PCASL 3T magnetic resonance imaging (MRI at a relatively fine resolution to mitigate partial volume effect from gray matter. MATERIALS AND METHODS: The Institutional Research Ethics Committee approved this study. On a clinical 3T MR system, ten healthy volunteers (5 females, 5 males, age = 28 ± 3 years were scanned after providing written informed consent. PCASL imaging was performed with varied combinations of labeling duration (τ = 1000, 1500, 2000, and 2500 ms and post-labeling delay (PLD = 1000, 1400, 1800, and 2200 ms, at a spatial resolution (1.56 x 1.56 x 5 mm(3 finer than commonly used (3.5 x 3.5 mm(2, 5-8 mm in thickness. Computer simulations were performed to calculate the achievable perfusion-weighted signal-to-noise ratio at varied τ, PLD, and transit delay. RESULTS: Based on experimental and numerical data, the optimal τ and PLD were found to be 2000 ms and 1500-1800 ms, respectively, yielding adequate SNR (~2 to support perfusion measurement in the majority (~60% of white matter. The measurement variability was about 9% in a one-week interval. The measured white matter perfusion and perfusion ratio of gray matter to white matter were 15.8-27.5 ml/100ml/min and 1.8-4.0, respectively, depending on spatial resolution as well as the amount of deep white matter included. CONCLUSION: PCASL 3T MRI is able to measure perfusion in the majority of cerebral white matter at an adequate signal-to-noise ratio by using appropriate tagging duration and post-labeling delay. Although pixel-wise comparison may not be possible, region-of-interest based flow quantification is feasible.

  3. Lower digit symbol substitution score in the oldest old is related to magnetization transfer and diffusion tensor imaging of the white matter.

    Vijay eVenkatraman

    2011-09-01

    Full Text Available Background: Slowing information processing is common among community-dwelling elderly and it predicts greater mortality and disability risk. Slowing information processing is related to brain macro-structural abnormalities. Specifically, greater global atrophy and greater small vessel disease of the white matter have been associated to slower processing speed. However, community-dwelling elderly with such macro-structural abnormalities can maintain processing speed. The roles of brain micro-structure for slow processing in very old adults living in the community is uncertain, as epidemiological studies relating these brain markers to cognition and in the context of other health characteristics are sparse. Hypothesis: Information processing is cross-sectionally associated with white matter micro-structure independent of overt macro-structural abnormalities and also independent of health related characteristics. Methods: Imaging indices of micro-structure (diffusion tensor imaging, DTI, and magnetization transfer imaging, MTI, macro-structure (white matter hyperintensities, gray matter volume, Digit Symbol Substitution Test (DSST and health characteristics were measured in 272 elderly (mean age 83 years old, 43% men, 40% Black living in the community. Results: The DTI- and MTI-indices of micro-structure from the normal appearing white matter and not from the normal appearing gray matter were associated with DSST score independent of white matter hyperintensities and gray matter volumes. Associations were also independent of age, race, gender, mini-mental score, systolic blood pressure, prevalent myocardial infarction. Interpretation: DTI and MTI indices of normal appearing white matter are indicators of information processing speed in this cohort of very old adults living in the community. Since processing slowing is a potent index of mortality and disability, these indices may serve as biomarkers in prevention or treatment trials of disability.

  4. White dwarf stars with carbon atmospheres.

    Dufour, P; Liebert, J; Fontaine, G; Behara, N

    2007-11-22

    White dwarfs represent the endpoint of stellar evolution for stars with initial masses between approximately 0.07 and 8-10, where is the mass of the Sun (more massive stars end their life as either black holes or neutron stars). The theory of stellar evolution predicts that the majority of white dwarfs have a core made of carbon and oxygen, which itself is surrounded by a helium layer and, for approximately 80 per cent of known white dwarfs, by an additional hydrogen layer. All white dwarfs therefore have been traditionally found to belong to one of two categories: those with a hydrogen-rich atmosphere (the DA spectral type) and those with a helium-rich atmosphere (the non-DAs). Here we report the discovery of several white dwarfs with atmospheres primarily composed of carbon, with little or no trace of hydrogen or helium. Our analysis shows that the atmospheric parameters found for these stars do not fit satisfactorily in any of the currently known theories of post-asymptotic giant branch evolution, although these objects might be the cooler counterpart of the unique and extensively studied PG 1159 star H1504+65 (refs 4-7). These stars, together with H1504+65, might accordingly form a new evolutionary sequence that follows the asymptotic giant branch.

  5. White Dwarf Stars

    Kepler, S. O.; Romero, Alejandra Daniela; Pelisoli, Ingrid; Ourique, Gustavo

    2017-01-01

    White dwarf stars are the final stage of most stars, born single or in multiple systems. We discuss the identification, magnetic fields, and mass distribution for white dwarfs detected from spectra obtained by the Sloan Digital Sky Survey up to Data Release 13 in 2016, which lead to the increase in the number of spectroscopically identified white dwarf stars from 5000 to 39000. This number includes only white dwarf stars with log g >= 6.5 stars, i.e., excluding the Extremely Low Mass white dw...

  6. Definition and quantification of acute inflammatory white matter injury in the immature brain by MRI/MRS at high magnetic field.

    Lodygensky, Gregory A; Kunz, Nicolas; Perroud, Elodie; Somm, Emmanuel; Mlynarik, Vladimir; Hüppi, Petra S; Gruetter, Rolf; Sizonenko, Stéphane V

    2014-03-01

    Lipopolysaccharide (LPS) injection in the corpus callosum (CC) of rat pups results in diffuse white matter injury similar to the main neuropathology of preterm infants. The aim of this study was to characterize the structural and metabolic markers of acute inflammatory injury by high-field magnetic resonance imaging (MRI) magnetic resonance spectroscopy (MRS) in vivo. Twenty-four hours after a 1-mg/kg injection of LPS in postnatal day 3 rat pups, diffusion tensor imaging and proton nuclear magnetic spectroscopy ((1)H NMR) were analyzed in conjunction to determine markers of cell death and inflammation using immunohistochemistry and gene expression. MRI and MRS in the CC revealed an increase in lactate and free lipids and a decrease of the apparent diffusion coefficient. Detailed evaluation of the CC showed a marked apoptotic response assessed by fractin expression. Interestingly, the degree of reduction in the apparent diffusion coefficient correlated strongly with the natural logarithm of fractin expression, in the same region of interest. LPS injection further resulted in increased activated microglia clustered in the cingulum, widespread astrogliosis, and increased expression of genes for interleukin (IL)-1, IL-6, and tumor necrosis factor. This model was able to reproduce the typical MRI hallmarks of acute diffuse white matter injury seen in preterm infants and allowed the evaluation of in vivo biomarkers of acute neuropathology after inflammatory challenge.

  7. Investigating the capability to resolve complex white matter structures with high b-value diffusion magnetic resonance imaging on the MGH-USC Connectom scanner.

    Fan, Qiuyun; Nummenmaa, Aapo; Witzel, Thomas; Zanzonico, Roberta; Keil, Boris; Cauley, Stephen; Polimeni, Jonathan R; Tisdall, Dylan; Van Dijk, Koene R A; Buckner, Randy L; Wedeen, Van J; Rosen, Bruce R; Wald, Lawrence L

    2014-11-01

    One of the major goals of the NIH Blueprint Human Connectome Project was to map and quantify the white matter connections in the brain using diffusion tractography. Given the prevalence of complex white matter structures, the capability of resolving local white matter geometries with multiple crossings in the diffusion magnetic resonance imaging (dMRI) data is critical. Increasing b-value has been suggested for delineation of the finer details of the orientation distribution function (ODF). Although increased gradient strength and duration increase sensitivity to highly restricted intra-axonal water, gradient strength limitations require longer echo times (TE) to accommodate the increased diffusion encoding times needed to achieve a higher b-value, exponentially lowering the signal-to-noise ratio of the acquisition. To mitigate this effect, the MGH-USC Connectom scanner was built with 300 mT/m gradients, which can significantly reduce the TE of high b-value diffusion imaging. Here we report comparisons performed across b-values based on q-ball ODF metrics to investigate whether high b-value diffusion imaging on the Connectom scanner can improve resolving complex white matter structures. The q-ball ODF features became sharper as the b-value increased, with increased power fraction in higher order spherical harmonic series of the ODF and increased peak heights relative to the overall size of the ODF. Crossing structures were detected in an increasingly larger fraction of white matter voxels and the spatial distribution of two-way and three-way crossing structures was largely consistent with known anatomy. Results indicate that dMRI with high diffusion encoding on the Connectom system is a promising tool to better characterize, and ultimately understand, the underlying structural organization and motifs in the human brain.

  8. Magnetic resonance imaging and diffusion-weighted imaging of normal-appearing white matter in children and young adults with tuberous sclerosis complex

    Arulrajah, Sahayini; Ertan, Gulhan; Tekes, Aylin; Huisman, Thierry A.G.M.; Jordan, Lori; Khaykin, Elizabeth; Izbudak, Izlem

    2009-01-01

    Patients with tuberous sclerosis complex (TSC) frequently present with neurocognitive deficits which may be related to impaired white matter maturation. The purposes of our study were (a) to evaluate the white matter maturation in children and young adults with TSC by comparing the apparent diffusion coefficient (ADC) values of normal-appearing white matter (NAWM) with age-matched healthy controls and (b) to determine the association of NAWM-ADC values with the severity of neurological symptoms in TSC patients. Twenty-three TSC patients who underwent magnetic resonance imaging/diffusion-weighted imaging between January 2000 and January 2009 were studied. ADC values of NAWM were measured in the frontal, parietal, occipital lobes, and in the pons. ADC data were compared with age-matched normative data derived from healthy controls. Patients were neurologically scored by a pediatric neurologist. Two-sample t tests and linear regression were conducted using STATA software. ADC values of NAWM were higher in TSC patients compared with healthy controls; the increase, however, only reached statistical significance in the frontal white matter and pons in the age group between 96 and 144 months and in the right parietal and occipital white matter in the age group above 144 months. There was no significant change in neurological severity score per unit increase in ADC measurement. ADC values of NAWM appear increased in TSC patients. The abnormal ADC values suggest that myelination may be delayed/impaired in TSC patients, which could explain global neurocognitive deficits. Larger prospective studies, including diffusion tensor imaging, are necessary to validate our results. (orig.)

  9. Magnetic resonance imaging and diffusion-weighted imaging of normal-appearing white matter in children and young adults with tuberous sclerosis complex

    Arulrajah, Sahayini; Ertan, Gulhan; Tekes, Aylin; Huisman, Thierry A.G.M. [Johns Hopkins Hospital, Division of Pediatric Radiology, Department of Radiology and Radiological Science, Baltimore, MD (United States); Jordan, Lori [Johns Hopkins School of Public Health, Division of Pediatric Neurology, Baltimore, MD (United States); Khaykin, Elizabeth [Johns Hopkins School of Public Health, Department of Mental Health, Baltimore, MD (United States); Izbudak, Izlem [Johns Hopkins Hospital, Division of Neuroradiology, Department of Radiology and Radiological Science, Baltimore, MD (United States)

    2009-11-15

    Patients with tuberous sclerosis complex (TSC) frequently present with neurocognitive deficits which may be related to impaired white matter maturation. The purposes of our study were (a) to evaluate the white matter maturation in children and young adults with TSC by comparing the apparent diffusion coefficient (ADC) values of normal-appearing white matter (NAWM) with age-matched healthy controls and (b) to determine the association of NAWM-ADC values with the severity of neurological symptoms in TSC patients. Twenty-three TSC patients who underwent magnetic resonance imaging/diffusion-weighted imaging between January 2000 and January 2009 were studied. ADC values of NAWM were measured in the frontal, parietal, occipital lobes, and in the pons. ADC data were compared with age-matched normative data derived from healthy controls. Patients were neurologically scored by a pediatric neurologist. Two-sample t tests and linear regression were conducted using STATA software. ADC values of NAWM were higher in TSC patients compared with healthy controls; the increase, however, only reached statistical significance in the frontal white matter and pons in the age group between 96 and 144 months and in the right parietal and occipital white matter in the age group above 144 months. There was no significant change in neurological severity score per unit increase in ADC measurement. ADC values of NAWM appear increased in TSC patients. The abnormal ADC values suggest that myelination may be delayed/impaired in TSC patients, which could explain global neurocognitive deficits. Larger prospective studies, including diffusion tensor imaging, are necessary to validate our results. (orig.)

  10. Growth rate enhancement and morphology engineering of diamond films by adding CO.sub.2./sub. or N.sub.2./sub. in hydrogen rich gas chemistry

    Ižák, Tibor; Davydova, Marina; Varga, Marián; Potocký, Štěpán; Kromka, Alexander

    2014-01-01

    Roč. 6, č. 7 (2014), s. 749-755 ISSN 2164-6627 R&D Projects: GA MPO FR-TI2/736; GA ČR GAP205/12/0908; GA ČR(CZ) GP14-16549P Institutional support: RVO:68378271 Keywords : microwave plasma CVD * diamond growth * nitrogen * carbon dioxide * growth rate * SEM Subject RIV: BM - Solid Matter Physics ; Magnetism

  11. NEW COOLING SEQUENCES FOR OLD WHITE DWARFS

    Renedo, I.; Althaus, L. G.; GarcIa-Berro, E.; Miller Bertolami, M. M.; Romero, A. D.; Corsico, A. H.; Rohrmann, R. D.

    2010-01-01

    We present full evolutionary calculations appropriate for the study of hydrogen-rich DA white dwarfs. This is done by evolving white dwarf progenitors from the zero-age main sequence, through the core hydrogen-burning phase, the helium-burning phase, and the thermally pulsing asymptotic giant branch phase to the white dwarf stage. Complete evolutionary sequences are computed for a wide range of stellar masses and for two different metallicities, Z = 0.01, which is representative of the solar neighborhood, and Z = 0.001, which is appropriate for the study of old stellar systems, like globular clusters. During the white dwarf cooling stage, we self-consistently compute the phase in which nuclear reactions are still important, the diffusive evolution of the elements in the outer layers and, finally, we also take into account all the relevant energy sources in the deep interior of the white dwarf, such as the release of latent heat and the release of gravitational energy due to carbon-oxygen phase separation upon crystallization. We also provide colors and magnitudes for these sequences, based on a new set of improved non-gray white dwarf model atmospheres, which include the most up-to-date physical inputs like the Lyα quasi-molecular opacity. The calculations are extended down to an effective temperature of 2500 K. Our calculations provide a homogeneous set of evolutionary cooling tracks appropriate for mass and age determinations of old DA white dwarfs and for white dwarf cosmochronology of the different Galactic populations.

  12. The prognostic value of multivoxel magnetic resonance spectroscopy determined metabolite levels in white and grey matter brain tissue for adverse outcome in term newborns following perinatal asphyxia

    Doormaal, Pieter Jan van [University Medical Center Groningen and University of Groningen, Department of Pediatrics, Division of Neonatology, Groningen (Netherlands); Meander Medical Center Amersfoort, Department of Radiology, PO Box 1502, Amersfoort (Netherlands); Meiners, Linda C.; Sijens, Paul E. [University Medical Center Groningen and University of Groningen, Department of Radiology, Groningen (Netherlands); Horst, Hendrik J. ter; Veere, Christa N. van der [University Medical Center Groningen and University of Groningen, Department of Pediatrics, Division of Neonatology, Groningen (Netherlands)

    2012-04-15

    Magnetic resonance spectroscopy can identify brain metabolic changes in perinatal asphyxia by providing ratios of metabolites, such as choline (Cho), creatine (Cr), N-acetyl aspartate (NAA) and lactate (Lact) [Cho/Cr, Lact/NAA, etc.]. The purpose of this study was to quantify the separate white and grey matter metabolites in a slab cranial to the ventricles and relate these to the outcome. A standard 2D-chemical shift imaging protocol was used for measuring a transverse volume of interest located cranial to the ventricles allowing for direct comparison of the metabolites in white and grey matter brain tissue in 24 term asphyxiated newborns aged 3 to 16 days. Cho, NAA and Lact showed significant differences between four subgroups of asphyxiated infants with more and less favourable outcomes. High levels of Cho and Lact in the grey matter differentiated non-survivors from survivors (P = 0.003 and P = 0.017, respectively). In perinatal asphyxia the levels of Cho, NAA and Lact in both white and grey matter brain tissue are affected. The levels of Cho and Lact measured in the grey matter are the most indicative of survival. It is therefore advised to include grey matter brain tissue in the region of interest examined by multivoxel MR spectroscopy. (orig.)

  13. The prognostic value of multivoxel magnetic resonance spectroscopy determined metabolite levels in white and grey matter brain tissue for adverse outcome in term newborns following perinatal asphyxia

    Doormaal, Pieter Jan van; Meiners, Linda C.; Sijens, Paul E.; Horst, Hendrik J. ter; Veere, Christa N. van der

    2012-01-01

    Magnetic resonance spectroscopy can identify brain metabolic changes in perinatal asphyxia by providing ratios of metabolites, such as choline (Cho), creatine (Cr), N-acetyl aspartate (NAA) and lactate (Lact) [Cho/Cr, Lact/NAA, etc.]. The purpose of this study was to quantify the separate white and grey matter metabolites in a slab cranial to the ventricles and relate these to the outcome. A standard 2D-chemical shift imaging protocol was used for measuring a transverse volume of interest located cranial to the ventricles allowing for direct comparison of the metabolites in white and grey matter brain tissue in 24 term asphyxiated newborns aged 3 to 16 days. Cho, NAA and Lact showed significant differences between four subgroups of asphyxiated infants with more and less favourable outcomes. High levels of Cho and Lact in the grey matter differentiated non-survivors from survivors (P = 0.003 and P = 0.017, respectively). In perinatal asphyxia the levels of Cho, NAA and Lact in both white and grey matter brain tissue are affected. The levels of Cho and Lact measured in the grey matter are the most indicative of survival. It is therefore advised to include grey matter brain tissue in the region of interest examined by multivoxel MR spectroscopy. (orig.)

  14. Magnetic Resonance Imaging and Volumetric Analysis: Novel Tools to Study Thyroid Hormone Disruption and Its Effect on White Matter Development

    Humans and wildlife are exposed to environmental pollutants that have been shown to interfere with the thyroid hormone system and thus may affect brain development. Our goal was to expose pregnant rats to propylthiouracil (PTU) to measure the effects of a goitrogen on white matte...

  15. Coupled solar-magnetic orientation during leatherback turtle (Dermochelys coriacea), great white shark (Carcharodon carcharias), arctic tern (Sterna paradisaea), and humpback whale (Megaptera novaeangliae) long-distance migration

    Horton, T. W.; Holdaway, R. N.; Zerbini, A.; Andriolo, A.; Clapham, P. J.

    2010-12-01

    Determining how animals perform long-distance animal migration remains one of the most enduring and fundamental mysteries of behavioural ecology. It is widely accepted that navigation relative to a reference datum is a fundamental requirement of long-distance return migration between seasonal habitats, and significant experimental research has documented a variety of viable orientation and navigation cues. However, relatively few investigations have attempted to reconcile experimentally determined orientation and navigation capacities of animals with empirical remotely sensed animal track data, leaving most theories of navigation and orientation untested. Here we show, using basic hypothesis testing, that leatherback turtle (Dermochelys coriacea), great white shark (Carcharodon carcharias), arctic tern (Sterna paradisaea), and humpback whale (Megaptera novaeangliae) migration paths are non-randomly distributed in magnetic coordinate space, with local peaks in magnetic coordinate distributions equal to fractional multiples of the angular obliquity of Earth’s axis of rotation. Time series analysis of humpback whale migratory behaviours, including migration initiation, changes in course, and migratory stop-overs, further demonstrate coupling of magnetic and celestial orientation cues during long-distance migration. These unexpected and highly novel results indicate that diverse taxa integrate magnetic and celestial orientation cues during long-distance migration. These results are compatible with a 'map and compass' orientation and navigation system. Humpback whale migration track geometries further indicate a map and compass orientation system is used. Several humpback whale tracks include highly directional segments (Mercator latitude vs. longitude r2>0.99) exceeding 2000 km in length, despite exposure to variable strength (c. 0-1 km/hr) surface cross-currents. Humpback whales appear to be able to compensate for surface current drift. The remarkable directional

  16. Diseases of white matter

    Holland, B.A.

    1987-01-01

    The diagnosis of white matter abnormalities was revolutionized by the advent of computed tomography (CT), which provided a noninvasive method of detection and assessment of progression of a variety of white matter processes. However, the inadequacies of CT were recognized early, including its relative insensitivity to small foci of abnormal myelin in the brain when correlated with autopsy findings and its inability to image directly white matter diseases of the spinal cord. Magnetic resonance imaging (MRI), on the other hand, sensitive to the slight difference in tissue composition of normal gray and white matter and to subtle increase in water content associated with myelin disorders, is uniquely suited for the examination of white matter pathology. Its clinical applications include the evaluation of the normal process of myelination in childhood and the various white matter diseases, including disorders of demyelination and dysmyelination

  17. Metabolite concentrations in supraventricular white matter from teenage to early old age: A short echo time 1H magnetic resonance spectroscopy (MRS) study

    Raininko, Raili (Dept. of Radiology, Uppsala Univ., Uppsala (Sweden)), e-mail: raili.raininko@radiol.uu.se; Mattsson, Peter (Dept. of Neuroscience, Neurology, Uppsala Univ., Uppsala (Sweden))

    2010-04-15

    Background: Age- and sex-related changes of metabolites in healthy adult brains have been examined with different 1H magnetic resonance spectroscopy (MRS) methods in varying populations, and with differing results. A long repetition time and short echo time technique reduces quantification errors due to T1 and T2 relaxation effects and makes it possible to measure metabolites with short T2 relaxation times. Purpose: To examine the effect of age on the metabolite concentrations measured by 1H MRS in normal supraventricular white matter using a long repetition time (TR) and a short echo time (TE). Material and Methods: Supraventricular white matter of 57 healthy subjects (25 women, 32 men), aged 13 to 72 years, was examined with a single-voxel MRS at 1.5T using a TR of 6000 ms and a TE of 22 ms. Tissue water was used as a reference in quantification. Results: Myoinositol increased slightly and total N-acetyl aspartate (NAA) decreased slightly with increasing age. Glutamine/glutamate complex (Glx) showed U-shaped age dependence, with highest concentrations in the youngest and oldest subjects. No significant age dependence was found in total choline and total creatine. No gender differences were found. Macromolecule/ lipid (ML) fractions were reliably measurable only in 36/57 or even fewer subjects and showed very large deviations. Conclusion: The concentrations of several metabolites in cerebral supraventricular white matter are age dependent on 1H MRS, even in young and middle-aged people, and age dependency can be nonlinear. Each 1H MRS study of the brain should therefore take age into account, whereas sex does not appear to be so important. The use of macromolecule and lipid evaluations is compromised by less successful quantification and large variations in healthy people

  18. Metabolite concentrations in supraventricular white matter from teenage to early old age: A short echo time {sup 1}H magnetic resonance spectroscopy (MRS) study

    Raininko, Raili [Dept. of Radiology, Uppsala Univ., Uppsala (Sweden)], e-mail: raili.raininko@radiol.uu.se; Mattsson, Peter [Dept. of Neuroscience, Neurology, Uppsala Univ., Uppsala (Sweden)

    2010-04-15

    Background: Age- and sex-related changes of metabolites in healthy adult brains have been examined with different {sup 1}H magnetic resonance spectroscopy (MRS) methods in varying populations, and with differing results. A long repetition time and short echo time technique reduces quantification errors due to T1 and T2 relaxation effects and makes it possible to measure metabolites with short T2 relaxation times. Purpose: To examine the effect of age on the metabolite concentrations measured by 1H MRS in normal supraventricular white matter using a long repetition time (TR) and a short echo time (TE). Material and Methods: Supraventricular white matter of 57 healthy subjects (25 women, 32 men), aged 13 to 72 years, was examined with a single-voxel MRS at 1.5T using a TR of 6000 ms and a TE of 22 ms. Tissue water was used as a reference in quantification. Results: Myoinositol increased slightly and total N-acetyl aspartate (NAA) decreased slightly with increasing age. Glutamine/glutamate complex (Glx) showed U-shaped age dependence, with highest concentrations in the youngest and oldest subjects. No significant age dependence was found in total choline and total creatine. No gender differences were found. Macromolecule/ lipid (ML) fractions were reliably measurable only in 36/57 or even fewer subjects and showed very large deviations. Conclusion: The concentrations of several metabolites in cerebral supraventricular white matter are age dependent on 1H MRS, even in young and middle-aged people, and age dependency can be nonlinear. Each 1H MRS study of the brain should therefore take age into account, whereas sex does not appear to be so important. The use of macromolecule and lipid evaluations is compromised by less successful quantification and large variations in healthy people.

  19. Metabolite concentrations in supraventricular white matter from teenage to early old age: A short echo time 1H magnetic resonance spectroscopy (MRS) study

    Raininko, Raili; Mattsson, Peter

    2010-01-01

    Background: Age- and sex-related changes of metabolites in healthy adult brains have been examined with different 1 H magnetic resonance spectroscopy (MRS) methods in varying populations, and with differing results. A long repetition time and short echo time technique reduces quantification errors due to T1 and T2 relaxation effects and makes it possible to measure metabolites with short T2 relaxation times. Purpose: To examine the effect of age on the metabolite concentrations measured by 1H MRS in normal supraventricular white matter using a long repetition time (TR) and a short echo time (TE). Material and Methods: Supraventricular white matter of 57 healthy subjects (25 women, 32 men), aged 13 to 72 years, was examined with a single-voxel MRS at 1.5T using a TR of 6000 ms and a TE of 22 ms. Tissue water was used as a reference in quantification. Results: Myoinositol increased slightly and total N-acetyl aspartate (NAA) decreased slightly with increasing age. Glutamine/glutamate complex (Glx) showed U-shaped age dependence, with highest concentrations in the youngest and oldest subjects. No significant age dependence was found in total choline and total creatine. No gender differences were found. Macromolecule/ lipid (ML) fractions were reliably measurable only in 36/57 or even fewer subjects and showed very large deviations. Conclusion: The concentrations of several metabolites in cerebral supraventricular white matter are age dependent on 1H MRS, even in young and middle-aged people, and age dependency can be nonlinear. Each 1H MRS study of the brain should therefore take age into account, whereas sex does not appear to be so important. The use of macromolecule and lipid evaluations is compromised by less successful quantification and large variations in healthy people

  20. Modeling transcranial magnetic stimulation from the induced electric fields to the membrane potentials along tractography-based white matter fiber tracts

    De Geeter, Nele; Dupré, Luc; Crevecoeur, Guillaume

    2016-04-01

    Objective. Transcranial magnetic stimulation (TMS) is a promising non-invasive tool for modulating the brain activity. Despite the widespread therapeutic and diagnostic use of TMS in neurology and psychiatry, its observed response remains hard to predict, limiting its further development and applications. Although the stimulation intensity is always maximum at the cortical surface near the coil, experiments reveal that TMS can affect deeper brain regions as well. Approach. The explanation of this spread might be found in the white matter fiber tracts, connecting cortical and subcortical structures. When applying an electric field on neurons, their membrane potential is altered. If this change is significant, more likely near the TMS coil, action potentials might be initiated and propagated along the fiber tracts towards deeper regions. In order to understand and apply TMS more effectively, it is important to capture and account for this interaction as accurately as possible. Therefore, we compute, next to the induced electric fields in the brain, the spatial distribution of the membrane potentials along the fiber tracts and its temporal dynamics. Main results. This paper introduces a computational TMS model in which electromagnetism and neurophysiology are combined. Realistic geometry and tissue anisotropy are included using magnetic resonance imaging and targeted white matter fiber tracts are traced using tractography based on diffusion tensor imaging. The position and orientation of the coil can directly be retrieved from the neuronavigation system. Incorporating these features warrants both patient- and case-specific results. Significance. The presented model gives insight in the activity propagation through the brain and can therefore explain the observed clinical responses to TMS and their inter- and/or intra-subject variability. We aspire to advance towards an accurate, flexible and personalized TMS model that helps to understand stimulation in the connected

  1. Magnets

    Young, I.R.

    1984-01-01

    A magnet pole piece for an NMR imaging magnet is made of a plurality of magnetic wires with one end of each wire held in a non-magnetic spacer, the other ends of the wires being brought to a pinch, and connected to a magnetic core. The wires may be embedded in a synthetic resin and the magnetisation and uniformity thereof can be varied by adjusting the density of the wires at the spacer which forms the pole piece. (author)

  2. Chronic Use of Aspirin and Total White Matter Lesion Volume: Results from the Women's Health Initiative Memory Study of Magnetic Resonance Imaging Study.

    Holcombe, Andrea; Ammann, Eric; Espeland, Mark A; Kelley, Brendan J; Manson, JoAnn E; Wallace, Robert; Robinson, Jennifer

    2017-10-01

    To investigate the relationship between aspirin and subclinical cerebrovascular heath, we evaluated the effect of chronic aspirin use on white matter lesions (WML) volume among women. Chronic aspirin use was assessed in 1365 women who participated in the Women's Health Initiative Memory Study of Magnetic Resonance Imaging. Differences in WML volumes between aspirin users and nonusers were assessed with linear mixed models. A number of secondary analyses were performed, including lobe-specific analyses, subgroup analyses based on participants' overall risk of cerebrovascular disease, and a dose-response relationship analysis. The mean age of the women at magnetic resonance imaging examination was 77.6 years. Sixty-one percent of participants were chronic aspirin users. After adjusting for demographic variables and comorbidities, chronic aspirin use was nonsignificantly associated with 4.8% (95% CI: -6.8%, 17.9%) larger WML volumes. These null findings were confirmed in secondary and sensitivity analyses, including an active comparator evaluation where aspirin users were compared to users of nonaspirin nonsteroidal anti-inflammatory drugs or acetaminophen. There was a nonsignificant difference in WML volumes between aspirin users and nonusers. Further, our results suggest that chronic aspirin use may not have a clinically significant effect on WML volumes in women. Published by Elsevier Inc.

  3. Greigite (Fe3S4) as an indicator of drought - The 1912-1994 sediment magnetic record from White Rock Lake, Dallas, Texas, USA

    Reynolds, R.L.; Rosenbaum, J.G.; Van Metre, P.; Tuttle, M.; Callender, E.; Goldin, A.

    1999-01-01

    Combined magnetic and geochemical studies were conducted on sediments from White Rock Lake, a reservoir in suburban Dallas (USA), to investigate how land use has affected sediment and water quality since the reservoir was filled in 1912. The chronology of a 167-cm-long core is constrained by the recognition of the pre-reservoir surface and by 137Cs results. In the reservoir sediments, magnetic susceptibility (MS) and isothermal remanent magnetization (IRM) are largely carried by detrital titanomagnetite that originally formed in igneous rocks. Titanomagnetite and associated hematite are the dominant iron oxides in a sample from the surficial deposit in the watershed but are absent in the underlying Austin Chalk. Therefore, these minerals were transported by wind into the watershed. After about 1960, systematic decreases in Ti, Fe, and Al suggest diminished input of detrital Fe-Ti oxides from the surficial deposits. MS and IRM remain constant over this interval, however, implying compensation by an increase in strongly magnetic material derived from human activity. Anthropogenic magnetite in rust and ferrite spherules (from fly ash?) are more common in sediment deposited after about 1970 than before and may account for the constant magnetization despite the implied decrease in detrital Fe-Ti oxides. An unexpected finding is the presence of authigenic greigite (Fe3S4), the abundance of which is at least partly controlled by climate. Greigite is common in sediments that predate about 1975, with zones of concentration indicated by relatively high IRM/MS. High greigite contents in sediment deposited during the early to mid-1950s and during the mid-1930s correspond to several-year periods of below-average precipitation and drought from historical records. Relatively long water-residence times in the reservoir during these periods may have led to elevated levels of sulfate available for bacterial sulfate reduction. The sulfate was probably derived via the oxidation of

  4. White Ring; White ring

    Aoki, H.; Yuzawa, H. [Nikken Sekkei Ltd., Osaka (Japan)

    1998-01-05

    White Ring is a citizen`s gymnasium used for figure skating and short track speed skating games of 18th Winter Olympic Games in 1998. White Ring is composed of a main-arena and a sub-arena. For the main-arena with an area 41mtimes66m, an ice link can be made by disengaging the potable floor and by flowing brine in the bridged polystyrene pipes embedded in the concrete floor. Due to the fortunate groundwater in this site, well water is used for the outside air treatment energy in 63% during heating and in 35% during cooling. Ammonia is used as a cooling medium for refrigerating facility. For the heating of audience area in the large space, heat load from the outside is reduced by enhancing the heat insulation performance of the roof of arena. The audience seats are locally heated using heaters. For the White Ring, high quality environment is realized for games through various functions of the large-scale roof of the large space. Success of the big event was expected. 15 figs., 4 tabs.

  5. Extended magnetic resonance imaging studies on the effect of classically activated microglia transplantation on white matter regeneration following spinal cord focal injury in adult rats.

    Marcol, Wiesław; Ślusarczyk, Wojciech; Larysz-Brysz, Magdalena; Łabuzek, Krzysztof; Kapustka, Bartosz; Staszkiewicz, Rafał; Rosicka, Paulina; Kalita, Katarzyna; Węglarz, Władysław; Lewin-Kowalik, Joanna

    2017-11-01

    Spinal cord injuries are still a serious problem for regenerative medicine. Previous research has demonstrated that activated microglia accumulate in spinal lesions, influencing the injured tissues in various ways. Therefore, transplantation of activated microglia may have a beneficial role in the regeneration of the nervous system. The present study examined the influence of transplanted activated microglial cells in adult rats with injured spinal cords. Rats were randomly divided into an experimental (M) and control (C) group, and were subjected to non-laminectomy focal injury of spinal cord white matter by means of a high-pressured air stream. In group M, activated cultured microglial cells were injected twice into the site of injury. Functional outcome and morphological features of regeneration were analyzed during a 12-week follow-up. The lesions were characterized by means of magnetic resonance imaging (MRI). Neurons in the brain stem and motor cortex were labeled with FluoroGold (FG). A total of 12 weeks after surgery, spinal cords and brains were collected and subjected to histopathological and immunohistochemical examinations. Lesion sizes in the spinal cord were measured and the number of FG-positive neurons was counted. Rats in group M demonstrated significant improvement of locomotor performance when compared with group C (Pspinal cord in the group M following microglia treatment, as compared with group C. The water diffusion perpendicular to the spinal cord in group M was closer to the reference values for a healthy spinal cord than it was in group C. The sizes of lesions were also significantly smaller in group M than in the group C (Pspinal cord gives some positive effects for the regeneration of the white matter.

  6. Extended magnetic resonance imaging studies on the effect of classically activated microglia transplantation on white matter regeneration following spinal cord focal injury in adult rats

    Marcol, Wiesław; Ślusarczyk, Wojciech; Larysz-Brysz, Magdalena; Łabuzek, Krzysztof; Kapustka, Bartosz; Staszkiewicz, Rafał; Rosicka, Paulina; Kalita, Katarzyna; Węglarz, Władysław; Lewin-Kowalik, Joanna

    2017-01-01

    Spinal cord injuries are still a serious problem for regenerative medicine. Previous research has demonstrated that activated microglia accumulate in spinal lesions, influencing the injured tissues in various ways. Therefore, transplantation of activated microglia may have a beneficial role in the regeneration of the nervous system. The present study examined the influence of transplanted activated microglial cells in adult rats with injured spinal cords. Rats were randomly divided into an experimental (M) and control (C) group, and were subjected to non-laminectomy focal injury of spinal cord white matter by means of a high-pressured air stream. In group M, activated cultured microglial cells were injected twice into the site of injury. Functional outcome and morphological features of regeneration were analyzed during a 12-week follow-up. The lesions were characterized by means of magnetic resonance imaging (MRI). Neurons in the brain stem and motor cortex were labeled with FluoroGold (FG). A total of 12 weeks after surgery, spinal cords and brains were collected and subjected to histopathological and immunohistochemical examinations. Lesion sizes in the spinal cord were measured and the number of FG-positive neurons was counted. Rats in group M demonstrated significant improvement of locomotor performance when compared with group C (PMRI analysis demonstrated moderate improvement in water diffusion along the spinal cord in the group M following microglia treatment, as compared with group C. The water diffusion perpendicular to the spinal cord in group M was closer to the reference values for a healthy spinal cord than it was in group C. The sizes of lesions were also significantly smaller in group M than in the group C (P<0.05). The number of brain stem and motor cortex FG-positive neurons in group M was significantly higher than in group C. The present study demonstrated that delivery of activated microglia directly into the injured spinal cord gives some

  7. The population of single and binary white dwarfs of the Galactic bulge

    Torres, S.; García-Berro, E.; Cojocaru, R.; Calamida, A.

    2018-05-01

    Recent Hubble Space Telescope observations have unveiled the white dwarf cooling sequence of the Galactic bulge. Although the degenerate sequence can be well fitted employing the most up-to-date theoretical cooling sequences, observations show a systematic excess of red objects that cannot be explained by the theoretical models of single carbon-oxygen white dwarfs of the appropriate masses. Here, we present a population synthesis study of the white dwarf cooling sequence of the Galactic bulge that takes into account the populations of both single white dwarfs and binary systems containing at least one white dwarf. These calculations incorporate state-of-the-art cooling sequences for white dwarfs with hydrogen-rich and hydrogen-deficient atmospheres, for both white dwarfs with carbon-oxygen and helium cores, and also take into account detailed prescriptions of the evolutionary history of binary systems. Our Monte Carlo simulator also incorporates all the known observational biases. This allows us to model with a high degree of realism the white dwarf population of the Galactic bulge. We find that the observed excess of red stars can be partially attributed to white dwarf plus main sequence binaries, and to cataclysmic variables or dwarf novae. Our best fit is obtained with a higher binary fraction and an initial mass function slope steeper than standard values, as well as with the inclusion of differential reddening and blending. Our results also show that the possible contribution of double degenerate systems or young and thick-discbulge stars is negligible.

  8. USING COORDINATED OBSERVATIONS IN POLARIZED WHITE LIGHT AND FARADAY ROTATION TO PROBE THE SPATIAL POSITION AND MAGNETIC FIELD OF AN INTERPLANETARY SHEATH

    Xiong, Ming; Feng, Xueshang; Liu, Ying D. [State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing (China); Davies, Jackie A.; Harrison, Richard A. [Rutherford-Appleton Laboratory (RAL) Space, Harwell Oxford (United Kingdom); Owens, Mathew J.; Davis, Chris J., E-mail: mxiong@spacweather.ac.cn [Reading University, Reading (United Kingdom)

    2013-11-01

    Coronal mass ejections (CMEs) can be continuously tracked through a large portion of the inner heliosphere by direct imaging in visible and radio wavebands. White light (WL) signatures of solar wind transients, such as CMEs, result from Thomson scattering of sunlight by free electrons and therefore depend on both viewing geometry and electron density. The Faraday rotation (FR) of radio waves from extragalactic pulsars and quasars, which arises due to the presence of such solar wind features, depends on the line-of-sight magnetic field component B{sub ∥} and the electron density. To understand coordinated WL and FR observations of CMEs, we perform forward magnetohydrodynamic modeling of an Earth-directed shock and synthesize the signatures that would be remotely sensed at a number of widely distributed vantage points in the inner heliosphere. Removal of the background solar wind contribution reveals the shock-associated enhancements in WL and FR. While the efficiency of Thomson scattering depends on scattering angle, WL radiance I decreases with heliocentric distance r roughly according to the expression I∝r {sup –3}. The sheath region downstream of the Earth-directed shock is well viewed from the L4 and L5 Lagrangian points, demonstrating the benefits of these points in terms of space weather forecasting. The spatial position of the main scattering site r{sub sheath} and the mass of plasma at that position M{sub sheath} can be inferred from the polarization of the shock-associated enhancement in WL radiance. From the FR measurements, the local B{sub ∥sheath} at r{sub sheath} can then be estimated. Simultaneous observations in polarized WL and FR can not only be used to detect CMEs, but also to diagnose their plasma and magnetic field properties.

  9. Magnetization transfer contrast imaging detects early white matter changes in the APP/PS1 amyloidosis mouse model

    Jelle Praet

    2016-01-01

    Full Text Available While no definitive cure for Alzheimer's disease exists yet, currently available treatments would benefit greatly from an earlier diagnosis. It has previously been shown that Magnetization transfer contrast (MTC imaging is able to detect amyloid β plaques in old APP/PS1 mice. In the current study we investigated if MTC is also able to visualize early amyloid β (Aβ induced pathological changes. In a cross-sectional study, a comparison was made between the MT ratio of wild type (WT and APP/PS1 mice at 2, 4, 6, 8 and 24 months of age. We observed an increased MT-ratio in the cortex of 24 month old APP/PS1 mice as compared to WT mice. However, when comparing the MT-ratio of the cortex of WT mice with the MT-ratio of the APP/PS1 mice at 2, 4, 6 or 8 months of age, no significant changes could be observed. In contrast to the cortex, we consistently observed a decreased MT-ratio in the splenium of 4, 6 and 8 month old APP/PS1 mice as compared to age-matched WT mice. Lastly, the decreased MT-ratio in the splenium of APP/PS1 mice correlated to the Aβ plaque deposition, astrogliosis and microgliosis. This MT-ratio decrease did however not correlate to the myelin content. Combined, our results suggest that MTC is able to visualize early Aβ-induced changes in the splenium but not the cortex of APP/PS1 mice.

  10. White matter hyperintensities and cognitive reserve during a working memory task: a functional magnetic resonance imaging study in cognitively normal older adults.

    Fernández-Cabello, Sara; Valls-Pedret, Cinta; Schurz, Matthias; Vidal-Piñeiro, Dídac; Sala-Llonch, Roser; Bargallo, Nuria; Ros, Emilio; Bartrés-Faz, David

    2016-12-01

    Cognitive reserve (CR) models posit that lifestyle factors such as education modulate the relationship between brain damage and cognition. However, the functional correlates of CR in healthy aging are still under investigation. White matter hyperintensities (WMHs) are a common age-associated finding that impacts cognition. In this study, we used functional magnetic resonance imaging to characterize the patterns of brain activation during a working memory task in older participants with high and low levels of education (as a proxy of CR) and high and low WMH volumes. Ninety older volunteers (aged 63-76 years) and 16 young adults (aged 21-27) completed the study. We found that older adults with higher education had better working memory performance than their less educated peers. Among the highly educated participants, those with WMH over-recruited areas engaged by young volunteers and showed activation in additional cortical and subcortical structures. However, those with low WMH differed little with respect to their younger counterparts. Our findings demonstrate that the functional mechanisms subtending the effects of education, as a proxy of CR, are modulated according to the WMH burden. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. MAGNET

    by B. Curé

    2011-01-01

    The magnet operation was very satisfactory till the technical stop at the end of the year 2010. The field was ramped down on 5th December 2010, following the successful regeneration test of the turbine filters at full field on 3rd December 2010. This will limit in the future the quantity of magnet cycles, as it is no longer necessary to ramp down the magnet for this type of intervention. This is made possible by the use of the spare liquid Helium volume to cool the magnet while turbines 1 and 2 are stopped, leaving only the third turbine in operation. This obviously requires full availability of the operators to supervise the operation, as it is not automated. The cryogenics was stopped on 6th December 2010 and the magnet was left without cooling until 18th January 2011, when the cryoplant operation resumed. The magnet temperature reached 93 K. The maintenance of the vacuum pumping was done immediately after the magnet stop, when the magnet was still at very low temperature. Only the vacuum pumping of the ma...

  12. Hydrogen-Rich Saline Attenuates Brain Injury Induced by Cardiopulmonary Bypass and Inhibits Microvascular Endothelial Cell Apoptosis Via the PI3K/Akt/GSK3β Signaling Pathway in Rats

    Keyan Chen

    2017-10-01

    Full Text Available Background/Aims: Cardiopulmonary bypass (CPB is prone to inducing brain injury during open heart surgery. A hydrogen-rich solution (HRS can prevent oxidation and apoptosis, and inhibit inflammation. This study investigated effects of HRS on brain injury induced by CPB and regulatory mechanisms of the PI3K/Akt/GSK3β signaling pathway. Methods: A rat CPB model and an in vitro cell hypoxia model were established. After HRS treatment, Rat behavior was measured using neurological deficit score; Evans blue (EB was used to assess permeability of the blood-brain barrier (BBB; HE staining was used to observe pathological changes; Inflammatory factors and brain injury markers were detected by ELISA; the PI3K/Akt/GSK3β pathway-related proteins and apoptosis were assessed by western blot, immunohistochemistry and qRT –PCR analyses of brain tissue and neurons. Results: After CPB, brain tissue anatomy was disordered, and cell structure was abnormal. Brain tissue EB content increased. There was an increase in the number of apoptotic cells, an increase in expression of Bax and caspase-3, a decrease in expression of Bcl2, and increases in levels of Akt, GSK3β, P-Akt, and P-GSK3β in brain tissue. HRS treatment attenuated the inflammatory reaction ,brain tissue EB content was significantly reduced and significantly decreased expression levels of Bax, caspase-3, Akt, GSK3β, P-Akt, and P-GSK3β in the brain. After adding the PI3K signaling pathway inhibitor, LY294002, to rat cerebral microvascular endothelial cells (CMECs, HRS could reduce activated Akt expression and downstream regulatory gene phosphorylation of GSK3β expression, and inhibit CMEC apoptosis. Conclusion: The PI3K/Akt/GSK3β signaling pathway plays an important role in the mechanism of CPB-induced brain injury. HRS can reduce CPB-induced brain injury and inhibit CMEC apoptosis through the PI3K/Akt/GSK3β signaling pathway.

  13. MAGNET

    Benoit Curé

    2010-01-01

    Operation of the magnet has gone quite smoothly during the first half of this year. The magnet has been at 4.5K for the full period since January. There was an unplanned short stop due to the CERN-wide power outage on May 28th, which caused a slow dump of the magnet. Since this occurred just before a planned technical stop of the LHC, during which access in the experimental cavern was authorized, it was decided to leave the magnet OFF until 2nd June, when magnet was ramped up again to 3.8T. The magnet system experienced a fault also resulting in a slow dump on April 14th. This was triggered by a thermostat on a filter choke in the 20kA DC power converter. The threshold of this thermostat is 65°C. However, no variation in the water-cooling flow rate or temperature was observed. Vibration may have been the root cause of the fault. All the thermostats have been checked, together with the cables, connectors and the read out card. The tightening of the inductance fixations has also been checked. More tem...

  14. MAGNET

    B. Curé

    2012-01-01

      The magnet was energised at the beginning of March 2012 at a low current to check all the MSS safety chains. Then the magnet was ramped up to 3.8 T on 6 March 2012. Unfortunately two days later an unintentional switch OFF of the power converter caused a slow dump. This was due to a misunderstanding of the CCC (CERN Control Centre) concerning the procedure to apply for the CMS converter control according to the beam-mode status at that time. Following this event, the third one since 2009, a discussion was initiated to define possible improvement, not only on software and procedures in the CCC, but also to evaluate the possibility to upgrade the CMS hardware to prevent such discharge from occurring because of incorrect procedure implementations. The magnet operation itself was smooth, and no power cuts took place. As a result, the number of magnetic cycles was reduced to the minimum, with only two full magnetic cycles from 0 T to 3.8 T. Nevertheless the magnet suffered four stops of the cryogeni...

  15. MAGNET

    B. Curé

    2012-01-01

      Following the unexpected magnet stops last August due to sequences of unfortunate events on the services and cryogenics [see CMS internal report], a few more events and initiatives again disrupted the magnet operation. All the magnet parameters stayed at their nominal values during this period without any fault or alarm on the magnet control and safety systems. The magnet was stopped for the September technical stop to allow interventions in the experimental cavern on the detector services. On 1 October, to prepare the transfer of the liquid nitrogen tank on its new location, several control cables had to be removed. One cable was cut mistakenly, causing a digital input card to switch off, resulting in a cold-box (CB) stop. This tank is used for the pre-cooling of the magnet from room temperature down to 80 K, and for this reason it is controlled through the cryogenics control system. Since the connection of the CB was only allowed for a field below 2 T to avoid the risk of triggering a fast d...

  16. Pressure-assisted cold denaturation of hen egg white lysozyme: the influence of co-solvents probed by hydrogen exchange nuclear magnetic resonance.

    Vogtt, K; Winter, R

    2005-08-01

    COSY proton nuclear magnetic resonance was used to measure the exchange rates of amide protons of hen egg white lysozyme (HEWL) in the pressure-assisted cold-denatured state and in the heat-denatured state. After dissolving lysozyme in deuterium oxide buffer, labile protons exchange for deuterons in such a way that exposed protons are substituted rapidly, whereas "protected" protons within structured parts of the protein are substituted slowly. The exchange rates k obs were determined for HEWL under heat treatment (80 degrees C) and under high pressure conditions at low temperature (3.75 kbar, -13 degrees C). Moreover, the influence of co-solvents (sorbitol, urea) on the exchange rate was examined under pressure-assisted cold denaturation conditions, and the corresponding protection factors, P, were determined. The exchange kinetics upon heat treatment was found to be a two-step process with initial slow exchange followed by a fast one, showing residual protection in the slow-exchange state and P-factors in the random-coil-like range for the final temperature-denatured state. Addition of sorbitol (500 mM) led to an increase of P-factors for the pressure-assisted cold denatured state, but not for the heat-denatured state. The presence of 2 M urea resulted in a drastic decrease of the P-factors of the pressure-assisted cold denatured state. For both types of co-solvents, the effect they exert appears to be cooperative, i.e., no particular regions within the protein can be identified with significantly diverse changes of P-factors.

  17. Pressure-assisted cold denaturation of hen egg white lysozyme: the influence of co-solvents probed by hydrogen exchange nuclear magnetic resonance

    K. Vogtt

    2005-08-01

    Full Text Available COSY proton nuclear magnetic resonance was used to measure the exchange rates of amide protons of hen egg white lysozyme (HEWL in the pressure-assisted cold-denatured state and in the heat-denatured state. After dissolving lysozyme in deuterium oxide buffer, labile protons exchange for deuterons in such a way that exposed protons are substituted rapidly, whereas "protected" protons within structured parts of the protein are substituted slowly. The exchange rates k obs were determined for HEWL under heat treatment (80ºC and under high pressure conditions at low temperature (3.75 kbar, -13ºC. Moreover, the influence of co-solvents (sorbitol, urea on the exchange rate was examined under pressure-assisted cold denaturation conditions, and the corresponding protection factors, P, were determined. The exchange kinetics upon heat treatment was found to be a two-step process with initial slow exchange followed by a fast one, showing residual protection in the slow-exchange state and P-factors in the random-coil-like range for the final temperature-denatured state. Addition of sorbitol (500 mM led to an increase of P-factors for the pressure-assisted cold denatured state, but not for the heat-denatured state. The presence of 2 M urea resulted in a drastic decrease of the P-factors of the pressure-assisted cold denatured state. For both types of co-solvents, the effect they exert appears to be cooperative, i.e., no particular regions within the protein can be identified with significantly diverse changes of P-factors.

  18. MAGNET

    B. Curé

    2012-01-01

      The magnet and its sub-systems were stopped at the beginning of the winter shutdown on 8th December 2011. The magnet was left without cooling during the cryogenics maintenance until 17th January 2012, when the cryoplant operation resumed. The magnet temperature reached 93 K. The vacuum pumping was maintained during this period. During this shutdown, the yearly maintenance was performed on the cryogenics, the vacuum pumps, the magnet control and safety systems, and the power converter and discharge lines. Several preventive actions led to the replacement of the electrovalve command coils, and the 20A DC power supplies of the magnet control system. The filters were cleaned on the demineralised water circuits. The oil of the diffusion pumps was changed. On the cryogenics, warm nitrogen at 343 K was circulated in the cold box to regenerate the filters and the heat exchangers. The coalescing filters have been replaced at the inlet of both the turbines and the lubricant trapping unit. The active cha...

  19. MAGNET

    B. Curé

    2013-01-01

      The magnet was operated without any problem until the end of the LHC run in February 2013, apart from a CERN-wide power glitch on 10 January 2013 that affected the CMS refrigerator, causing a ramp down to 2 T in order to reconnect the coldbox. Another CERN-wide power glitch on 15 January 2013 didn’t affect the magnet subsystems, the cryoplant or the power converter. At the end of the magnet run, the reconnection of the coldbox at 2.5 T was tested. The process will be updated, in particular the parameters of some PID valve controllers. The helium flow of the current leads was reduced but only for a few seconds. The exercise will be repeated with the revised parameters to validate the automatic reconnection process of the coldbox. During LS1, the water-cooling services will be reduced and many interventions are planned on the electrical services. Therefore, the magnet cryogenics and subsystems will be stopped for several months, and the magnet cannot be kept cold. In order to avoid unc...

  20. MAGNET

    Benoit Curé

    2010-01-01

    The magnet was successfully operated at the end of the year 2009 despite some technical problems on the cryogenics. The magnet was ramped up to 3.8 T at the end of November until December 16th when the shutdown started. The magnet operation met a few unexpected stops. The field was reduced to 3.5 T for about 5 hours on December 3rd due to a faulty pressure sensor on the helium compressor. The following day the CERN CCC stopped unintentionally the power converters of the LHC and the experiments, triggering a ramp down that was stopped at 2.7 T. The magnet was back at 3.8 T about 6 hours after CCC sent the CERN-wide command. Three days later, a slow dump was triggered due to a stop of the pump feeding the power converter water-cooling circuit, during an intervention on the water-cooling plant done after several disturbances on the electrical distribution network. The magnet was back at 3.8 T in the evening the same day. On December 10th a break occurred in one turbine of the cold box producing the liquid ...

  1. MAGNET

    B. Curé

    2011-01-01

    The CMS magnet has been running steadily and smoothly since the summer, with no detected flaw. The magnet instrumentation is entirely operational and all the parameters are at their nominal values. Three power cuts on the electrical network affected the magnet run in the past five months, with no impact on the data-taking as the accelerator was also affected at the same time. On 22nd June, a thunderstorm caused a power glitch on the service electrical network. The primary water cooling at Point 5 was stopped. Despite a quick restart of the water cooling, the inlet temperature of the demineralised water on the busbar cooling circuit increased by 5 °C, up to 23.3 °C. It was kept below the threshold of 27 °C by switching off other cooling circuits to avoid the trigger of a slow dump of the magnet. The cold box of the cryogenics also stopped. Part of the spare liquid helium volume was used to maintain the cooling of the magnet at 4.5 K. The operators of the cryogenics quickly restarted ...

  2. Hot accreting white dwarfs in the quasi-static approximation

    Iben, I. Jr.

    1982-01-01

    Properties of white dwarfs which are accreting hydrogen-rich matter at rates in the range 1.5 x 10 -9 to 2.5 x 10 -7 M/sub sun/ yr -1 are investigated in several approximations. Steady-burning models, in which matter is processed through nuclear-burning shells as rapidly as it is accreted, provide a framework for understanding the properties of models in which thermal pulses induced by hydrogen burning and helium burning are allowed to occur. In these latter models, the underlying carbon-oxygen core is chosen to be in a cycle-averaged steady state with regard to compressional heating and neutrino losses. Several of these models are evolved in the quasi-static approximation. Combining results obtained in the steady-burning approximation with those obtained in the quasi-static approximation, expressions are obtained for estimating, as functions of accretion rate and white dwarf mass, the thermal pulse recurrence period and the duration of hydrogen-burning phases. The time spent by an accreting model burning hydrogen as a large star of giant dimensions versus time spent burning hydrogen as a hot dwarf is also estimated as a function of model mass and accretion rate. Finally, suggestions for detecting observational counterparts of the theoretical models and suggestions for further theoretical investigations are offered. Subject headings: stars: accretion: stars: interiors: stars: novae: stars: symbiotic: stars: white dwarfs

  3. MAGNET

    B. Curé

    2011-01-01

    The magnet ran smoothly in the last few months until a fast dump occurred on 9th May 2011. Fortunately, this occurred in the afternoon of the first day of the technical stop. The fast dump was due to a valve position controller that caused the sudden closure of a valve. This valve is used to regulate the helium flow on one of the two current leads, which electrically connects the coil at 4.5 K to the busbars at room temperature. With no helium flow on the lead, the voltage drop and the temperatures across the leads increase up to the defined thresholds, triggering a fast dump through the Magnet Safety System (MSS). The automatic reaction triggered by the MSS worked properly. The helium release was limited as the pressure rise was just at the limit of the safety valve opening pressure. The average temperature of the magnet reached 72 K. It took four days to recover the temperature and refill the helium volumes. The faulty valve controller was replaced by a spare one before the magnet ramp-up resumed....

  4. Supplementation of Antipsychotic Treatment with the Amino Acid Sarcosine Influences Proton Magnetic Resonance Spectroscopy Parameters in Left Frontal White Matter in Patients with Schizophrenia

    Dominik Strzelecki

    2015-10-01

    Full Text Available Dysfunction of the glutamatergic system, the main stimulating system in the brain, has a major role in pathogenesis of schizophrenia. The frontal white matter (WM is partially composed of axons from glutamatergic pyramidal neurons and glia with glutamatergic receptors. The natural amino acid sarcosine, a component of a normal diet, inhibits the glycine type 1 transporter, increasing the glycine level. Thus, it modulates glutamatergic transmission through the glutamatergic ionotropic NMDA (N-methyl-d-aspartate receptor, which requires glycine as a co-agonist. To evaluate the concentrations of brain metabolites (NAA, N-acetylaspartate; Glx, complex of glutamate, glutamine, and γ-aminobutyric acid (GABA; mI, myo-inositol; Cr, creatine; Cho, choline in the left frontal WM, Proton Nuclear Magnetic Resonance (1H-NMR spectroscopy was used. Twenty-five patients randomly chosen from a group of fifty with stable schizophrenia (DSM-IV-TR and dominant negative symptoms, who were receiving antipsychotic therapy, were administered 2 g of sarcosine daily for six months. The remaining 25 patients received placebo. Assignment was double blinded. 1H-NMR spectroscopy (1.5 T was performed twice: before and after the intervention. NAA, Glx and mI were evaluated as Cr and Cho ratios. All patients were also assessed twice with the Positive and Negative Syndrome Scale (PANSS. Results were compared between groups and in two time points in each group. The sarcosine group demonstrated a significant decrease in WM Glx/Cr and Glx/Cho ratios compared to controls after six months of therapy. In the experimental group, the final NAA/Cr ratio significantly increased and Glx/Cr ratio significantly decreased compared to baseline values. Improvement in the PANSS scores was significant only in the sarcosine group. In patients with schizophrenia, sarcosine augmentation can reverse the negative effect of glutamatergic system overstimulation, with a simultaneous beneficial increase

  5. MAGNET

    Benoit Curé

    2010-01-01

    The magnet worked very well at 3.8 T as expected, despite a technical issue that manifested twice in the cryogenics since June. All the other magnet sub-systems worked without flaw. The issue in the cryogenics was with the cold box: it could be observed that the cold box was getting progressively blocked, due to some residual humidity and air accumulating in the first thermal exchanger and in the adsorber at 65 K. This was later confirmed by the analysis during the regeneration phases. An increase in the temperature difference between the helium inlet and outlet across the heat exchanger and a pressure drop increase on the filter of the adsorber were observed. The consequence was a reduction of the helium flow, first compensated by the automatic opening of the regulation valves. But once they were fully opened, the flow and refrigeration power reduced as a consequence. In such a situation, the liquid helium level in the helium Dewar decreased, eventually causing a ramp down of the magnet current and a field...

  6. MAGNET

    B. Curé

    MAGNET During the winter shutdown, the magnet subsystems went through a full maintenance. The magnet was successfully warmed up to room temperature beginning of December 2008. The vacuum was broken later on by injecting nitrogen at a pressure just above one atmosphere inside the vacuum tank. This was necessary both to prevent any accidental humidity ingress, and to allow for a modification of the vacuum gauges on the vacuum tank and maintenance of the diffusion pumps. The vacuum gauges had to be changed, because of erratic variations on the measurements, causing spurious alarms. The new type of vacuum gauges has been used in similar conditions on the other LHC experiments and without problems. They are shielded against the stray field. The lubricants of the primary and diffusion pumps have been changed. Several minor modifications were also carried out on the equipment in the service cavern, with the aim to ease the maintenance and to allow possible intervention during operation. Spare sensors have been bough...

  7. MAGNET

    Benoit Curé.

    The magnet operation restarted end of June this year. Quick routine checks of the magnet sub-systems were performed at low current before starting the ramps up to higher field. It appeared clearly that the end of the field ramp down to zero was too long to be compatible with the detector commissioning and operations plans. It was decided to perform an upgrade to keep the ramp down from 3.8T to zero within 4 hours. On July 10th, when a field of 1.5T was reached, small movements were observed in the forward region support table and it was decided to fix this problem before going to higher field. At the end of July the ramps could be resumed. On July 28th, the field was at 3.8T and the summer CRAFT exercise could start. This run in August went smoothly until a general CERN wide power cut took place on August 3rd, due to an insulation fault on the high voltage network outside point 5. It affected the magnet powering electrical circuit, as it caused the opening of the main circuit breakers, resulting in a fast du...

  8. MAGNET

    B. Curé

    2013-01-01

    The magnet is fully stopped and at room temperature. The maintenance works and consolidation activities on the magnet sub-systems are progressing. To consolidate the cryogenic installation, two redundant helium compressors will be installed as ‘hot spares’, to avoid the risk of a magnet downtime in case of a major failure of a compressor unit during operation. The screw compressors, their motors, the mechanical couplings and the concrete blocks are already available and stored at P5. The metallic structure used to access the existing compressors in SH5 will be modified to allow the installation of the two redundant ones. The plan is to finish the installation and commissioning of the hot spare compressors before the summer 2014. In the meantime, a bypass on the high-pressure helium piping will be installed for the connection of a helium drier unit later during the Long Shutdown 1, keeping this installation out of the schedule critical path. A proposal is now being prepared for the con...

  9. In vivo magnetic resonance spectroscopy measurement of gray-matter and white-matter gamma-aminobutyric acid concentration in sensorimotor cortex using a motion-controlled MEGA point-resolved spectroscopy sequence.

    Bhattacharyya, Pallab K; Phillips, Micheal D; Stone, Lael A; Lowe, Mark J

    2011-04-01

    Gamma-aminobutyric acid (GABA) is a major inhibitory neurotransmitter in the brain. Understanding the GABA concentration, in vivo, is important to understand normal brain function. Using MEGA point-resolved spectroscopy sequence with interleaved water scans to detect subject motion, GABA level of sensorimotor cortex was measured using a voxel identified from a functional magnetic resonance imaging scan. The GABA level in a 20×20×20-mm(3) voxel consisting of 37%±7% gray matter, 52%±12% white matter and 11%±8% cerebrospinal fluid in the sensorimotor region was measured to be 1.43±0.48 mM. In addition, using linear regression analysis, GABA concentrations within gray and white matter were calculated to be 2.87±0.61 and 0.33±0.11 mM, respectively. Copyright © 2011 Elsevier Inc. All rights reserved.

  10. Dietary Docosahexaenoic Acid Improves Cognitive Function, Tissue Sparing, and Magnetic Resonance Imaging Indices of Edema and White Matter Injury in the Immature Rat after Traumatic Brain Injury

    Schober, Michelle E.; Requena, Daniela F.; Abdullah, Osama M.; Casper, T. Charles; Beachy, Joanna; Malleske, Daniel; Pauly, James R.

    2016-01-01

    Traumatic brain injury (TBI) is the leading cause of acquired neurologic disability in children. Specific therapies to treat acute TBI are lacking. Cognitive impairment from TBI may be blunted by decreasing inflammation and oxidative damage after injury. Docosahexaenoic acid (DHA) decreases cognitive impairment, oxidative stress, and white matter injury in adult rats after TBI. Effects of DHA on cognitive outcome, oxidative stress, and white matter injury in the developing rat after experimen...

  11. White House

    ... content Jump to navigation the WHITE HOUSE President Donald J. Trump Get in Touch Home Briefing Room From the ... For All Americans The Administration The Administration President Donald J. Trump Vice President Mike Pence First Lady Melania Trump ...

  12. MAGNET

    Benoit Curé

    The magnet subsystems resumed operation early this spring. The vacuum pumping was restarted mid March, and the cryogenic power plant was restarted on March 30th. Three and a half weeks later, the magnet was at 4.5 K. The vacuum pumping system is performing well. One of the newly installed vacuum gauges had to be replaced at the end of the cool-down phase, as the values indicated were not coherent with the other pressure measurements. The correction had to be implemented quickly to be sure no helium leak could be at the origin of this anomaly. The pressure measurements have been stable and coherent since the change. The cryogenics worked well, and the cool-down went quite smoothly, without any particular difficulty. The automated start of the turbines had to be fine-tuned to get a smooth transition, as it was observed that the cooling power delivered by the turbines was slightly higher than needed, causing the cold box to stop automatically. This had no consequence as the cold box safety system acts to keep ...

  13. MAGNET

    B. Curé

    During the winter shutdown, the magnet subsystems went through a full maintenance. The magnet was successfully warmed up to room temperature beginning of December 2008. The vacuum was broken later on by injecting nitrogen at a pressure just above one atmosphere inside the vacuum tank. This was necessary both to prevent any accidental humidity ingress, and to allow for a modification of the vacuum gauges on the vacuum tank and maintenance of the diffusion pumps. The vacuum gauges had to be changed, because of erratic variations on the measurements, causing spurious alarms. The new type of vacuum gauges has been used in similar conditions on the other LHC experiments and without problems. They are shielded against the stray field. The lubricants of the primary and diffusion pumps have been changed. Several minor modifications were also carried out on the equipment in the service cavern, with the aim to ease the maintenance and to allow possible intervention during operation. Spare sensors have been bought. Th...

  14. Heterogeneity in age-related white matter changes

    Schmidt, R.; Schmidt, H.; Haybaeck, J.; Loitfelder, M.; Weis, S.; Cavalieri, M.; Seiler, S.; Enzinger, C.; Ropele, S.; Erkinjuntti, T.; Pantoni, L.; Scheltens, P.; Fazekas, F.; Jellinger, K.

    2011-01-01

    White matter changes occur endemically in routine magnetic resonance imaging (MRI) scans of elderly persons. MRI appearance and histopathological correlates of white matter changes are heterogeneous. Smooth periventricular hyperintensities, including caps around the ventricular horns,

  15. Accretion onto hot white dwarfs in relation to symbiotic novae

    Livio, M.; Prialnik, D.; Regev, O.

    1989-01-01

    Numerical calculations are used to study the hydrodynamic evolution of a hot white dwarf with 1 solar mass accreting hydrogen-rich matter at rates between 10 to the -8th and 10 to the -6th solar masses/yr. It is found that for accretion at a rate of about 10 to the -8th solar masses/yr, nova-type outbursts of long duration occur at intervals of about 1500 yr. About half of the accreted envelope is ejected during these outbursts. At a rate of about 10 to the -7th solar masses/yr, the star alternates between comparable periods at a high plateau luminosity and giant dimensions and periods at a low luminosity and white dwarf dimension. At 10 to the -6th solar masses/yr, equilibrium is achieved with a typical red giant luminosity supported by steady hydrogen burning. It is concluded that symbiotic novae are more likely to occur in detached systems involving wind accretors. Thus, the contribution of symbiotic stars to the frequency of type I supernovae is severely constrained. 39 refs

  16. White Rock

    2002-01-01

    (Released 19 April 2002) The Science 'White Rock' is the unofficial name for this unusual landform which was first observed during the Mariner 9 mission in the early 1970's. As later analysis of additional data sets would show, White Rock is neither white nor dense rock. Its apparent brightness arises from the fact that the material surrounding it is so dark. Images from the Mars Global Surveyor MOC camera revealed dark sand dunes surrounding White Rock and on the floor of the troughs within it. Some of these dunes are just apparent in the THEMIS image. Although there was speculation that the material composing White Rock could be salts from an ancient dry lakebed, spectral data from the MGS TES instrument did not support this claim. Instead, the White Rock deposit may be the erosional remnant of a previously more continuous occurrence of air fall sediments, either volcanic ash or windblown dust. The THEMIS image offers new evidence for the idea that the original deposit covered a larger area. Approximately 10 kilometers to the southeast of the main deposit are some tiny knobs of similarly bright material preserved on the floor of a small crater. Given that the eolian erosion of the main White Rock deposit has produced isolated knobs at its edges, it is reasonable to suspect that the more distant outliers are the remnants of a once continuous deposit that stretched at least to this location. The fact that so little remains of the larger deposit suggests that the material is very easily eroded and simply blows away. The Story Fingers of hard, white rock seem to jut out like icy daggers across a moody Martian surface, but appearances can be deceiving. These bright, jagged features are neither white, nor icy, nor even hard and rocky! So what are they, and why are they so different from the surrounding terrain? Scientists know that you can't always trust what your eyes see alone. You have to use other kinds of science instruments to measure things that our eyes can

  17. Magnetic

    Aboud, Essam; El-Masry, Nabil; Qaddah, Atef; Alqahtani, Faisal; Moufti, Mohammed R. H.

    2015-06-01

    The Rahat volcanic field represents one of the widely distributed Cenozoic volcanic fields across the western regions of the Arabian Peninsula. Its human significance stems from the fact that its northern fringes, where the historical eruption of 1256 A.D. took place, are very close to the holy city of Al-Madinah Al-Monawarah. In the present work, we analyzed aeromagnetic data from the northern part of Rahat volcanic field as well as carried out a ground gravity survey. A joint interpretation and inversion of gravity and magnetic data were used to estimate the thickness of the lava flows, delineate the subsurface structures of the study area, and estimate the depth to basement using various geophysical methods, such as Tilt Derivative, Euler Deconvolution and 2D modeling inversion. Results indicated that the thickness of the lava flows in the study area ranges between 100 m (above Sea Level) at the eastern and western boundaries of Rahat Volcanic field and getting deeper at the middle as 300-500 m. It also showed that, major structural trend is in the NW direction (Red Sea trend) with some minor trends in EW direction.

  18. MAGNET

    Benoit Curé

    The cooling down to the nominal temperature of 4.5 K was achieved at the beginning of August, in conjunction with the completion of the installation work of the connection between the power lines and the coil current leads. The temperature gradient on the first exchanger of the cold box is now kept within the nominal range. A leak of lubricant on a gasket of the helium compressor station installed at the surface was observed and several corrective actions were necessary to bring the situation back to normal. The compressor had to be refilled with lubricant and a regeneration of the filters and adsorbers was necessary. The coil cool down was resumed successfully, and the cryogenics is running since then with all parameters being nominal. Preliminary tests of the 20kA coil power supply were done earlier at full current through the discharge lines into the dump resistors, and with the powering busbars from USC5 to UXC5 without the magnet connected. On Monday evening August 25th, at 8pm, the final commissionin...

  19. MAGNET

    B. Curé

    The first phase of the commissioning ended in August by a triggered fast dump at 3T. All parameters were nominal, and the temperature recovery down to 4.5K was carried out in two days by the cryogenics. In September, series of ramps were achieved up to 3 and finally 3.8T, while checking thoroughly the detectors in the forward region, measuring any movement of and around the HF. After the incident of the LHC accelerator on September 19th, corrective actions could be undertaken in the forward region. When all these displacements were fully characterized and repetitive, with no sign of increments in displacement at each field ramp, it was possible to start the CRAFT, Cosmic Run at Four Tesla (which was in fact at 3.8T). The magnet was ramped up to 18.16kA and the 3 week run went smoothly, with only 4 interruptions: due to the VIP visits on 21st October during the LHC inauguration day; a water leak on the cooling demineralized water circuit, about 1 l/min, that triggered a stop of the cooling pumps, and resulte...

  20. MAGNET

    Benoit Curé

    2013-01-01

    Maintenance work and consolidation activities on the magnet cryogenics and its power distribution are progressing according to the schedules. The manufacturing of the two new helium compressor frame units has started. The frame units support the valves, all the sensors and the compressors with their motors. This activity is subcontracted. The final installation and the commissioning at CERN are scheduled for March–April 2014. The overhauls of existing cryogenics equipment (compressors, motors) are in progress. The reassembly of the components shall start in early 2014. The helium drier, to be installed on the high-pressure helium piping, has been ordered and will be delivered in the first trimester of 2014. The power distribution for the helium compressors in SH5 on the 3.3kV network is progressing. The 3.3kV switches, between each compressor and its hot spare compressor, are being installed, together with the power cables for the new compressors. The 3.3kV electrical switchboards in SE5 will ...

  1. Alterations in brain white matter contributing to age-related slowing of task switching performance : The role of radial diffusivity and magnetization transfer ratio

    Serbruyns, Leen; Leunissen, Inge; van Ruitenbeek, Peter; Pauwels, Lisa; Caeyenberghs, Karen; Solesio-Jofre, Elena; Geurts, Monique; Cuypers, Koen; Meesen, Raf L.; Sunaert, Stefan; Leemans, Alexander; Swinnen, Stephan P.

    2016-01-01

    Successfully switching between tasks is critical in many daily activities. Age-related slowing of this switching behavior has been documented extensively, but the underlying neural mechanisms remain unclear. Here, we investigated the contribution of brain white matter changes associated with myelin

  2. White Paranoia

    Jørholt, Eva

    2017-01-01

    Inspired by Alain Robbe-Grillet’s novel La Jalousie (1957), the essay contends that Michael Haneke’s Caché (2005) takes its viewers inside a postcolonial white paranoia which is, arguably, the root cause of the exclusion, segregation and racist discrimination that many immigrants from the former ...

  3. European Whiteness?

    Blaagaard, Bolette

    2008-01-01

    Born out of the United States’ (U.S.) history of slavery and segregation and intertwined with gender studies and feminism, the field of critical whiteness studies does not fit easily into a European setting and the particular historical context that entails. In order for a field of European...

  4. Evaluation of white matter integrity in systemic lupus erythematosus by diffusion tensor magnetic resonance imaging: a study using tract-based spatial statistics

    Goulart Correa, Diogo; Ventura, Nina; Gasparetto, Emerson Leandro; Zimmermann, Nicolle; Paz Fonseca, Rochele; Batista Pereira, Denis; Netto, Tania Maria; Doring, Thomas M.

    2016-01-01

    The aim of this study was to evaluate the white matter integrity in brains of patients with systemic lupus erythematosus (SLE) using a voxel-based analyses of diffusion tensor imaging (DTI) data. Fifty-seven patients with SLE were compared to 36 control patients who were matched by gender, age, education, and Mini Mental State Examination score. DTI was performed along 30 noncollinear directions in a 1.5 Tesla scanner. For tract-based spatial statistics (TBSS), a white matter skeleton was created, and a permutation-based inference with 5000 permutations and a threshold of p < 0.05 was used to identify abnormalities in fractional anisotropy (FA). The mean (MD), radial (RD), and axial diffusivities (AD) were also projected onto the mean FA skeleton. We found a significant decrease of global FA in SLE patients compared to controls. The areas of reduced FA included the right superior corona radiata, the right superior longitudinal fasciculus, the body of the corpus callosum, the right inferior fronto-occipital fasciculus, the right thalamic radiation, and the right uncinate fasciculus. Patients with SLE also had increased AD and RD in several areas. Substantial overlap of areas with increased AD and RD occurred and were spatially much more extensive than the areas of reduced FA. Significant increases of AD values were concordant to those of RD and MD and more extensive than FA changes. Analyzing all diffusivity parameters, using TBSS, can detect more white matter microstructural changes in patients with SLE than analyzing FA alone. (orig.)

  5. Evaluation of white matter integrity in systemic lupus erythematosus by diffusion tensor magnetic resonance imaging: a study using tract-based spatial statistics

    Goulart Correa, Diogo; Ventura, Nina; Gasparetto, Emerson Leandro [Federal University of Rio de Janeiro, Department of Radiology, Hospital Universitario Clementino Fraga Filho, Rio de Janeiro, RJ (Brazil); Clinica de Diagnostico por Imagem (CDPI), Rio de Janeiro, RJ (Brazil); Zimmermann, Nicolle; Paz Fonseca, Rochele [Federal University of Rio de Janeiro, Department of Radiology, Hospital Universitario Clementino Fraga Filho, Rio de Janeiro, RJ (Brazil); Pontifical Catholic University of Rio Grande do Sul, Department of Psychology, Porto Alegre, RS (Brazil); Batista Pereira, Denis; Netto, Tania Maria [Federal University of Rio de Janeiro, Department of Radiology, Hospital Universitario Clementino Fraga Filho, Rio de Janeiro, RJ (Brazil); Doring, Thomas M. [Clinica de Diagnostico por Imagem (CDPI), Rio de Janeiro, RJ (Brazil)

    2016-08-15

    The aim of this study was to evaluate the white matter integrity in brains of patients with systemic lupus erythematosus (SLE) using a voxel-based analyses of diffusion tensor imaging (DTI) data. Fifty-seven patients with SLE were compared to 36 control patients who were matched by gender, age, education, and Mini Mental State Examination score. DTI was performed along 30 noncollinear directions in a 1.5 Tesla scanner. For tract-based spatial statistics (TBSS), a white matter skeleton was created, and a permutation-based inference with 5000 permutations and a threshold of p < 0.05 was used to identify abnormalities in fractional anisotropy (FA). The mean (MD), radial (RD), and axial diffusivities (AD) were also projected onto the mean FA skeleton. We found a significant decrease of global FA in SLE patients compared to controls. The areas of reduced FA included the right superior corona radiata, the right superior longitudinal fasciculus, the body of the corpus callosum, the right inferior fronto-occipital fasciculus, the right thalamic radiation, and the right uncinate fasciculus. Patients with SLE also had increased AD and RD in several areas. Substantial overlap of areas with increased AD and RD occurred and were spatially much more extensive than the areas of reduced FA. Significant increases of AD values were concordant to those of RD and MD and more extensive than FA changes. Analyzing all diffusivity parameters, using TBSS, can detect more white matter microstructural changes in patients with SLE than analyzing FA alone. (orig.)

  6. Accreting white dwarf models for type I supernovae. I. Presupernova evolution and triggering mechanisms

    Nomoto, K.

    1982-01-01

    The evolution of carbon-oxygen white dwarfs accreting helium in binary systems has been investigated from the onset of accretion up to the point at which a thermonuclear explosion occurs as a plausible explosion model for a Type I supernova. Although the accreted material has been assumed to be helium, our results should also be applicable to the more general case of accretion of hydrogen-rich material, since hydrogen shell burning leads to the development of a helium zone. Several cases with different accretion rates of helium and different initial masses of the white dwarf have been studied. The relationship between the conditions in the binary system and the triggering mechanism for the supernova explosion is discussed, especially for the cases with relatively slow accretion rate. It is found that the growth of a helium zone on the carbon-oxygen core leads to a supernova explosion which is triggered either by the off-center helium detonation for slow and intermediate accretion rates, or by the carbon deflagration for slow and rapid accretion rates. Both helium detonation and carbon deflagration are possible for the case for the slow accretion since, in this case, the initial mass of the white dwarf is an important parameter for determining the mode of ignition. Finally, various modes of building up the helium zone on the white dwarf, namely, direct transfer of helium from the companion star and the various types and strength of the hydrogen shell flashes are discussed in some detail

  7. THE CORE COMPOSITION OF A WHITE DWARF IN A CLOSE DOUBLE-DEGENERATE SYSTEM

    Vennes, S.; Kawka, A.

    2012-01-01

    We report the identification of the double-degenerate system NLTT 16249 that comprises a normal, hydrogen-rich (DA) white dwarf and a peculiar, carbon-polluted white dwarf (DQ) showing photospheric traces of nitrogen. We disentangled the observed spectra and constrained the properties of both stellar components. In the evolutionary scenario commonly applied to the sequence of DQ white dwarfs, both carbon and nitrogen would be dredged up from the core. The C/N abundance ratio (≈50) in the atmosphere of this unique DQ white dwarf suggests the presence of unprocessed material ( 14 N) in the core or in the envelope. Helium burning in the DQ progenitor may have terminated early on the red giant branch after a mass-ejection event leaving unprocessed material in the core, although current mass estimates do not favor the presence of a low-mass helium core. Alternatively, some nitrogen in the envelope may have survived an abridged helium-core burning phase prior to climbing the asymptotic giant branch. Based on available data, we estimate a relatively short orbital period (P ∼< 13 hr) and ongoing spectroscopic observations will help determine precise orbital parameters.

  8. White Dwarfs in the UKIRT Infrared Deep Sky Survey Data Release 9

    Tremblay, P.-E.; Leggett, S. K.; Lodieu, N.; Freytag, B.; Bergeron, P.; Kalirai, J. S.; Ludwig, H.-G.

    2014-06-01

    We have identified 8 to 10 new cool white dwarfs from the Large Area Survey (LAS) Data Release 9 of the United Kingdom InfraRed Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS). The data set was paired with the Sloan Digital Sky Survey to obtain proper motions and a broad ugrizYJHK wavelength coverage. Optical spectroscopic observations were secured at Gemini Observatory and confirm the degenerate status for eight of our targets. The final sample includes two additional white dwarf candidates with no spectroscopic observations. We rely on improved one-dimensional model atmospheres and new multi-dimensional simulations with CO5BOLD to review the stellar parameters of the published LAS white dwarf sample along with our additional discoveries. Most of the new objects possess very cool atmospheres with effective temperatures below 5000 K, including two pure-hydrogen remnants with a cooling age between 8.5 and 9.0 Gyr, and tangential velocities in the range 40 km s-1 3.0 and 5.0 Gyr. These white dwarfs could be disk remnants with a very high velocity or former halo G stars. We also compare the LAS sample with earlier studies of very cool degenerates and observe a similar deficit of helium-dominated atmospheres in the range 5000 < T eff (K) < 6000. We review the possible explanations for the spectral evolution from helium-dominated toward hydrogen-rich atmospheres at low temperatures.

  9. White dwarfs - the once and future suns

    Trimble, V.

    1986-01-01

    The history and properties of white dwarfs (Bessel's conclusion that Sirius and Procyon have invisible companions, Clark's discovery of Sirius B, Adams and Russell's study of white dwarf spectra, Chandrasekhar's explanation of white dwarf structure by equations incorporating quantum mechanics and relativity) are treated. Formation of white dwarfs, degeneracy, binary white dwarfs (and novae and supernovae) are explained. A mystery nearly 50 years old regarding the spectrum of the star Greenwich +70 degrees-8247 has been solved: it involves a stationary line phenomenon and a magnetic field of 300-500 million gauss. Processes being studied in white dwarfs and white dwarf models include gravitational settling, accretion, dredge-up, radiation pressure, and diffusive hydrogen burning

  10. Dietary Docosahexaenoic Acid Improves Cognitive Function, Tissue Sparing, and Magnetic Resonance Imaging Indices of Edema and White Matter Injury in the Immature Rat after Traumatic Brain Injury.

    Schober, Michelle E; Requena, Daniela F; Abdullah, Osama M; Casper, T Charles; Beachy, Joanna; Malleske, Daniel; Pauly, James R

    2016-02-15

    Traumatic brain injury (TBI) is the leading cause of acquired neurologic disability in children. Specific therapies to treat acute TBI are lacking. Cognitive impairment from TBI may be blunted by decreasing inflammation and oxidative damage after injury. Docosahexaenoic acid (DHA) decreases cognitive impairment, oxidative stress, and white matter injury in adult rats after TBI. Effects of DHA on cognitive outcome, oxidative stress, and white matter injury in the developing rat after experimental TBI are unknown. We hypothesized that DHA would decrease early inflammatory markers and oxidative stress, and improve cognitive, imaging and histologic outcomes in rat pups after controlled cortical impact (CCI). CCI or sham surgery was delivered to 17 d old male rat pups exposed to DHA or standard diet for the duration of the experiments. DHA was introduced into the dam diet the day before CCI to allow timely DHA delivery to the pre-weanling pups. Inflammatory cytokines and nitrates/nitrites were measured in the injured brains at post-injury Day (PID) 1 and PID2. Morris water maze (MWM) testing was performed at PID41-PID47. T2-weighted and diffusion tensor imaging studies were obtained at PID12 and PID28. Tissue sparing was calculated histologically at PID3 and PID50. DHA did not adversely affect rat survival or weight gain. DHA acutely decreased oxidative stress and increased anti-inflammatory interleukin 10 in CCI brains. DHA improved MWM performance and lesion volume late after injury. At PID12, DHA decreased T2-imaging measures of cerebral edema and decreased radial diffusivity, an index of white matter injury. DHA improved short- and long-term neurologic outcomes after CCI in the rat pup. Given its favorable safety profile, DHA is a promising candidate therapy for pediatric TBI. Further studies are needed to explore neuroprotective mechanisms of DHA after developmental TBI.

  11. Diffusion Tensor Magnetic Resonance Imaging Finding of Discrepant Fractional Anisotropy Between the Frontal and Parietal Lobes After Whole-Brain Irradiation in Childhood Medulloblastoma Survivors: Reflection of Regional White Matter Radiosensitivity?

    Qiu Deqiang; Kwong, Dora; Chan, Godfrey; Leung, Lucullus; Khong, P.-L.

    2007-01-01

    Purpose: To test the hypothesis that fractional anisotropy (FA) is more severely reduced in white matter of the frontal lobe compared with the parietal lobe after receiving the same whole-brain irradiation dose in a cohort of childhood medulloblastoma survivors. Methods and Materials: Twenty-two medulloblastoma survivors (15 male, mean [± SD] age = 12.1 ± 4.6 years) and the same number of control subjects (15 male, aged 12.0 ± 4.2 years) were recruited for diffusion tensor magnetic resonance imaging scans. Using an automated tissue classification method and the Talairach Daemon atlas, FA values of frontal and parietal lobes receiving the same radiation dose, and the ratio between them were quantified and denoted as FFA, PFA, and FA f/p , respectively. The Mann-Whitney U test was used to test for significant differences of FFA, PFA, and FA f/p between medulloblastoma survivors and control subjects. Results: Frontal lobe and parietal lobe white matter FA were found to be significantly less in medulloblastoma survivors compared with control subjects (frontal p = 0.001, parietal p = 0.026). Moreover, these differences were found to be discrepant, with the frontal lobe having a significantly larger difference in FA compared with the parietal lobe. The FA f/p of control and medulloblastoma survivors was 1.110 and 1.082, respectively (p = 0.029). Conclusion: Discrepant FA changes after the same irradiation dose suggest radiosensitivity of the frontal lobe white matter compared with the parietal lobe. Special efforts to address the potentially vulnerable frontal lobe after treatment with whole-brain radiation may be needed so as to balance disease control and treatment-related morbidity

  12. Terbium doped SnO2 nanoparticles as white emitters and SnO2:5Tb/Fe3O4 magnetic luminescent nanohybrids for hyperthermia application and biocompatibility with HeLa cancer cells.

    Singh, Laishram Priyobarta; Singh, Ningthoujam Premananda; Srivastava, Sri Krishna

    2015-04-14

    SnO2:5Tb (SnO2 doped with 5 at% Tb(3+)) nanoparticles were synthesised by a polyol method and their luminescence properties at different annealing temperatures were studied. Characterization of nanomaterials was done by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM). XRD studies indicate that the prepared nanoparticles were of tetragonal structures. Upon Tb(3+) ion incorporation into SnO2, Sn(4+) changes to Sn(2+) and, on annealing again at higher temperature, Sn(2+) changes to Sn(4+). The prepared nanoparticles were spherical in shape. Sn-O vibrations were found from the FTIR studies. In photoluminescence studies, the intensity of the emission peaks of Tb(3+) ions increases with the increase of annealing temperature, and emission spectra lie in the region of white emission in the CIE diagram. CCT calculations show that the SnO2:5Tb emission lies in cold white emission. Quantum yields up to 38% can be obtained for 900 °C annealed samples. SnO2:5Tb nanoparticles were well incorporated into the PVA polymer and such a material incorporated into the polymer can be used for display devices. The SnO2:5Tb/Fe3O4 nanohybrid was prepared and investigated for hyperthermia applications at different concentrations of the nanohybrid. This achieves a hyperthermia temperature (42 °C) under an AC magnetic field. The hybrid nanomaterial SnO2:5Tb/Fe3O4 was found to exhibit biocompatibility with HeLa cells (human cervical cancer cells) at concentrations up to 74% for 100 μg L(-1). Also, this nanohybrid shows green emission and thus it will be helpful in tracing magnetic nanoparticles through optical imaging in vivo and in vitro application.

  13. Visualization of white matter tracts using a non-diffusion weighted magnetic resonance imaging method: does intravenous gadolinium injection four hours prior to the examination affect the visualization of white matter tracts?

    Masahiro Yamazaki

    Full Text Available OBJECTIVES: Visualization of white matter (WM-tracts such as the corticospinal tract (CST, medial lemniscus (ML, and superior cerebellar peduncle (SCP using delayed enhanced (DE-heavily T2-weighted three-dimensional fluid-attenuated inversion-recovery (hT2w-3D-FLAIR imaging has recently been reported. In that report, all patients were clinically suspected of having Ménière's disease, because DE-hT2w-3D-FLAIR imaging of the inner ear has been reported to separately visualize perilymph and endolymph fluid and can identify the presence of endolymphatic hydrops. Therefore, the previous report could not rule out the possible effect of delayed enhancement. From this perspective, the purpose of this study was to elucidate if the use of gadolinium affects the visualization of WM-tracts on hT2w-3D-FLAIR. MATERIALS AND METHODS: The records of nine patients with suspected Ménière's disease who underwent plain (P and DE-hT2w-3D-FLAIR by 3-Tesla were retrospectively analyzed. The regions of interest were set on the CST, ML, and SCP, and on contiguous brain parenchyma: The thalamus (Th, pontine parenchyma (PP, and cerebellar parenchyma (CP, respectively. The signal intensity ratio between each WM-tract and the relevant contiguous brain parenchyma was calculated for both P- and DE-hT2w-3D-FLAIR images, and statistically compared using paired t-tests. RESULTS: The CST/Th signal intensity ratio was 3.75±0.67 on P-hT2w-3D-FLAIR and 3.62±0.50 on DE-hT2w-3D-FLAIR (p = 0.24. The ML/PP signal intensity ratio was 2.19±0.59 on P-hT2w-3D-FLAIR and 2.08±0.53 on DE-hT2w-3D-FLAIR (p = 0.25. The SCP/CP signal intensity ratio was 4.08±0.91 on P-hT2w-3D-FLAIR and 4.04±0.96 on DE-hT2w-3D-FLAIR (p = 0.43. There were no significant differences in the signal intensity ratios between P- and DE-hT2w-3D-FLAIR images. CONCLUSIONS: The use of gadolinium is not necessary for visualization of WM-tracts using hT2w-3D-FLAIR, and P-hT2w-3D-FLAIR without gadolinium may

  14. Hydrogen and helium shell burning during white dwarf accretion

    Cui, Xiao; Meng, Xiang-Cun; Han, Zhan-Wen

    2018-05-01

    Type Ia supernovae (SNe Ia) are believed to be thermonuclear explosions of carbon oxygen (CO) white dwarfs (WDs) with masses close to the Chandrasekhar mass limit. How a CO WD accretes matter and grows in mass to this limit is not well understood, hindering our understanding of SN Ia explosions and the reliability of using SNe Ia as a cosmological distance indicator. In this work, we employed the stellar evolution code MESA to simulate the accretion process of hydrogen-rich material onto a 1.0 M ⊙ CO WD at a high rate (over the Eddington limit) of 4.3 × 10‑7 M ⊙ yr‑1. The simulation demonstrates the characteristics of the double shell burning on top of the WD, with a hydrogen shell burning on top of a helium burning shell. The results show that helium shell burning is not steady (i.e. it flashes). Flashes from the helium shell are weaker than those in the case of accretion of helium-rich material onto a CO WD. The carbon to oxygen mass ratio resulting from the helium shell burning is higher than what was previously thought. Interestingly, the CO WD growing due to accretion has an outer part containing a small fraction of helium in addition to carbon and oxygen. The flashes become weaker and weaker as the accretion continues.

  15. The kinematics of the white dwarf population from the SDSS DR12

    Anguiano, B.; Rebassa-Mansergas, A.; García-Berro, E.; Torres, S.; Freeman, K.; Zwitter, T.

    2018-04-01

    We use the Sloan Digital Sky Survey Data Release 12, which is the largest available white dwarf catalog to date, to study the evolution of the kinematical properties of the population of white dwarfs in the Galactic disc. We derive masses, ages, photometric distances and radial velocities for all white dwarfs with hydrogen-rich atmospheres. For those stars for which proper motions from the USNO-B1 catalog are available the true three-dimensional components of the stellar space velocity are obtained. This subset of the original sample comprises 20,247 objects, making it the largest sample of white dwarfs with measured three-dimensional velocities. Furthermore, the volume probed by our sample is large, allowing us to obtain relevant kinematical information. In particular, our sample extends from a Galactocentric radial distance R G = 7.8 kpc to 9.3 kpc, and vertical distances from the Galactic plane ranging from Z = -0.5 kpc to 0.5 kpc. We examine the mean components of the stellar three-dimensional velocities, as well as their dispersions with respect to the Galactocentric and vertical distances. We confirm the existence of a mean Galactocentric radial velocity gradient, ∂/∂R G = -3 +/- 5 km s-1 kpc-1. We also confirm North-South differences in . Specifically, we find that white dwarfs with Z > 0 (in the North Galactic hemisphere) have reverse is true for white dwarfs with Z < 0. The age-velocity dispersion relation derived from the present sample indicates that the Galactic population of white dwarfs may have experienced an additional source of heating, which adds to the secular evolution of the Galactic disc.

  16. SDSS DR7 WHITE DWARF CATALOG

    Kleinman, S. J.; Nitta, A. [Gemini Observatory, 670 North A' ohoku Place, Hilo, HI 96720 (United States); Kepler, S. O.; Pelisoli, Ingrid; Pecanha, Viviane; Costa, J. E. S. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS (Brazil); Koester, D. [Institut fuer Theoretische Physik und Astrophysik, Universitaet Kiel, D-24098 Kiel (Germany); Krzesinski, J. [Mt. Suhora Observatory, Pedagogical University of Cracow, ul. Podchorazych 2, 30-084 Cracow (Poland); Dufour, P.; Lachapelle, F.-R.; Bergeron, P. [Departement de Physique, Universite de Montreal, C. P. 6128, Succ. Centre-Ville, Montreal, Quebec H3C 3J7 (Canada); Yip, Ching-Wa [Department of Physics and Astronomy, The Johns Hopkins University, 3701 San Martin Drive, Baltimore, MD 21218 (United States); Harris, Hugh C. [United States Naval Observatory, Flagstaff Station, 10391 West Naval Observatory Road, Flagstaff, AZ 86001-8521 (United States); Eisenstein, Daniel J. [Harvard Smithsonian Center for Astrophysics, 60 Garden Street, MS 20, Cambridge, MA 02138 (United States); Althaus, L.; Corsico, A., E-mail: hch@nofs.navy.mil [Facultad de Ciencias Astronomicas y Geofisicas, Paseo del Bosque S/N, (1900) La Plata (Argentina)

    2013-01-15

    We present a new catalog of spectroscopically confirmed white dwarf stars from the Sloan Digital Sky Survey (SDSS) Data Release 7 spectroscopic catalog. We find 20,407 white dwarf spectra, representing 19,712 stars, and provide atmospheric model fits to 14,120 DA and 1011 DB white dwarf spectra from 12,843 and 923 stars, respectively. These numbers represent more than a factor of two increase in the total number of white dwarf stars from the previous SDSS white dwarf catalogs based on DR4 data. Our distribution of subtypes varies from previous catalogs due to our more conservative, manual classifications of each star in our catalog, supplementing our automatic fits. In particular, we find a large number of magnetic white dwarf stars whose small Zeeman splittings mimic increased Stark broadening that would otherwise result in an overestimated log g if fit as a non-magnetic white dwarf. We calculate mean DA and DB masses for our clean, non-magnetic sample and find the DB mean mass is statistically larger than that for the DAs.

  17. Magnetic field and screening effects in condensed and ultradense matter

    Roussel, K.M.

    1974-01-01

    The investigations of three topics are presented: the origin of magnetic fields in white dwarfs and neutron stars, the detection of magnetic fields in white dwarfs, and screening effects due to free charged particles, particularly in semiconductors. (U.S.)

  18. White matter lesion progression

    Hofer, Edith; Cavalieri, Margherita; Bis, Joshua C

    2015-01-01

    10 cohorts. To assess the relative contribution of genetic factors to progression of WML, we compared in 7 cohorts risk models including demographics, vascular risk factors plus single-nucleotide polymorphisms that have been shown to be associated cross-sectionally with WML in the current......BACKGROUND AND PURPOSE: White matter lesion (WML) progression on magnetic resonance imaging is related to cognitive decline and stroke, but its determinants besides baseline WML burden are largely unknown. Here, we estimated heritability of WML progression, and sought common genetic variants...... associated with WML progression in elderly participants from the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) consortium. METHODS: Heritability of WML progression was calculated in the Framingham Heart Study. The genome-wide association study included 7773 elderly participants from...

  19. Narrative Constructions of Whiteness among White Undergraduates

    Foste, Zak

    2017-01-01

    This critical narrative inquiry was guided by two overarching research questions. First, this study examined how white undergraduates interpreted and gave meaning to their white racial identities. This line of inquiry sought to understand how participants made sense of their white racial selves, the self in relation to people of color, and the…

  20. Erick A. White | NREL

    Engineering, Colorado School of Mines, 2011 B.S., Chemical Engineering, University of Colorado at Boulder Research Assistant, Colorado School of Mines, Department of Chemical Engineering, 2006-2011 Field Team Erick A. White Photo of Erick A. White Erick White Chemical Reaction Engineer Erick.White@nrel.gov

  1. Superconductivity in hydrogen-rich materials at high pressures

    Drozdov, Alexander

    2016-07-01

    A room temperature superconductor is probably one of the most desired systems in solid state physics. The highest critical temperature (T{sub c}) that has been achieved so far is in the copper oxide system: 133 kelvin (K) at ambient pressure ([82]Schilling et al. 1993) and 160 K under pressure ([42]Gao et al. 1994). The nature of superconductivity in the cuprates and in the recently discovered iron-based superconductor family (T{sub c}=57 K) is still not fully understood. In contrast, there is a class of superconductors which is well-described by the Bardeen, Cooper, Schrieffer (BCS) theory - conventional superconductors. Great efforts were spent in searching for high-temperature (T{sub c} > 77 K) conventional superconductor but only T{sub c} = 39 K has been reached in MgB2 ([68]Nagamatsu et al. 2001). BCS theory puts no bounds for T{sub c} as follows from Eliashberg's formulation of BCS theory. T{sub c} can be high, if there is a favorable combination of high-frequency phonons, strong electron-phonon coupling, and a high density of states. It does not predict however in which materials all three parameters are large. At least it gives a clear indication that materials with light elements are favorable as light elements provide high frequencies in the phonon spectrum. The lightest element is hydrogen, and Ashcroft made a first prediction that metallic hydrogen will be a high-temperature superconductor ([6]Ashcroft 1968). As pressure of hydrogen metallization was too high (about 400-500 GPa) for experimental techniques then he proposed that compounds dominated by hydrogen (hydrides) also might be good high temperature superconductors ([6]Ashcroft 1968; [7]Ashcroft 2004). A lot of the followed calculations supported this idea. T{sub c} in the range of 50-235 kelvin was predicted for many hydrides. Unfortunately, only a moderate T{sub c} of 17 kelvin has been observed experimentally ([27]Eremets et al. 2008) so far. A goal of the present work is to find a hydrogen-dominant material with higher T{sub c}.

  2. Hydrogen rich gas production by thermocatalytic decomposition of kenaf biomass

    Irmak, Sibel; Oeztuerk, ilker [Department of Chemistry, Cukurova University, Arts and Sciences Faculty, Adana 01330 (Turkey)

    2010-06-15

    Kenaf (Hibiscus cannabinus L.), a well known energy crop and an annual herbaceous plant grows very fast with low lodging susceptibility was used as representative lignocellulosic biomass in the present work. Thermocatalytic conversions were performed by aqueous phase reforming (APR) of kenaf hydrolysates and direct gasification of solid biomass of kenaf using 5% Pt on activated carbon as catalyst. Hydrolysates used in APR experiments were prepared by solubilization of kenaf biomass in subcritical water under CO{sub 2} gas pressure. APR of kenaf hydrolysate with low molecular weight polysaccharides in the presence of the reforming catalyst produced more gas compared to the hydrolysate that had high molecular weight polysaccharides. APR experiments of kenaf biomass hydrolysates and glucose, which was used as a simplest biomass model compound, in the presence of catalyst produced various amounts of gas mixtures that consisted of H{sub 2}, CO, CO{sub 2}, CH{sub 4} and C{sub 2}H{sub 6}. The ratios of H{sub 2} to other gases produced were 0.98, 1.50 and 1.35 for 150 C and 250 C subcritical water-treated kenaf hydrolysates and glucose, respectively. These ratios indicated that more the degraded organic content of kenaf hydrolysate the better selectivity for hydrogen production. Although APR of 250 C-kenaf hydrolysate resulted in similar gas content and composition as glucose, the gas volume produced was three times higher in glucose feed. The use of solid kenaf biomass as starting feedstock in APR experiments resulted in less gas production since the activity of catalyst was lowered by solid biomass particles. (author)

  3. Combinatorial and conventional studies on new highly selective methanation catalysts for the removal of small amounts of CO from hydrogen-rich gas mixtures; Kombinatorische und konventionelle Untersuchungen zu neuen hochselektiven Methanisierungskatalysatoren zur Entfernung geringer Mengen an CO aus wasserstoffreichen Gasgemischen

    Kraemer, Michael

    2008-04-15

    New tailor-made catalysts for the purification of hydrogen-rich reformates by the selective methanation of CO were developed using combinatorial methods. The optimization of the catalysts was achieved within 3 or 4 generations while Ni-based oxides generally proved most promising. Conventional validations confirmed the successive enhancement of the materials. All in all, a number of catalysts providing higher CO hydrogenation activities combined with a lower reactivity towards the undesired methanation of the excess CO{sub 2} in comparison to an industrial reference was discovered. The application of numerous characterization techniques to the optimization sequence Ni{sub 100} - Zr{sub 10}Ni{sub 90} - Re{sub 2}Zr{sub 10}Ni{sub 88} - Re{sub 0,6}Zr{sub 15}Ni{sub 84,4} resulted in the following model: The catalysts are present in their as-prepared state as mixed metal oxide, which is (partly) demixed during the reductive pretreatment. The resulting (Re)Ni-particles seem to represent the actual active component while ZrO{sub 2} could stabilize the dispersion. Alloying with Ni, Re seems to modify the surface of the catalyst in such a way that it only marginally interacts with CO{sub 2}. Solo methanation tests unambiguously reveal that the increase in selectivity is not connected to a competition between CO and CO{sub 2} for adsorption sites but is based on a loss of the intrinsic reactivity of the respective samples towards the methanation of CO{sub 2}. (orig.)

  4. White dwarfs in the UKIRT infrared deep sky survey data release

    Tremblay, P.-E.; Kalirai, J. S.; Leggett, S. K.; Lodieu, N.; Freytag, B.; Bergeron, P.; Ludwig, H.-G.

    2014-01-01

    We have identified 8 to 10 new cool white dwarfs from the Large Area Survey (LAS) Data Release 9 of the United Kingdom InfraRed Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS). The data set was paired with the Sloan Digital Sky Survey to obtain proper motions and a broad ugrizYJHK wavelength coverage. Optical spectroscopic observations were secured at Gemini Observatory and confirm the degenerate status for eight of our targets. The final sample includes two additional white dwarf candidates with no spectroscopic observations. We rely on improved one-dimensional model atmospheres and new multi-dimensional simulations with CO5BOLD to review the stellar parameters of the published LAS white dwarf sample along with our additional discoveries. Most of the new objects possess very cool atmospheres with effective temperatures below 5000 K, including two pure-hydrogen remnants with a cooling age between 8.5 and 9.0 Gyr, and tangential velocities in the range 40 km s –1 ≤v tan ≤ 60 km s –1 . They are likely thick disk 10-11 Gyr old objects. In addition, we find a resolved double degenerate system with v tan ∼ 155 km s –1 and a cooling age between 3.0 and 5.0 Gyr. These white dwarfs could be disk remnants with a very high velocity or former halo G stars. We also compare the LAS sample with earlier studies of very cool degenerates and observe a similar deficit of helium-dominated atmospheres in the range 5000 < T eff (K) < 6000. We review the possible explanations for the spectral evolution from helium-dominated toward hydrogen-rich atmospheres at low temperatures.

  5. Automated measurement of local white matter lesion volume

    van der Lijn, Fedde; Verhaaren, Benjamin F. J.; Ikram, M. Arfan

    2012-01-01

    in a periventricular region close to the ventricles and a subcortical zone further away. In this work we present a novel automated method for local white matter lesion volume quantification in magnetic resonance images. The method segments and measures the white matter lesion volume in 43 regions defined...

  6. Shades of white : diffusion properties of T1- and FLAIR-defined white matter signal abnormalities differ in stages from cognitively normal to dementia

    Riphagen, Joost M.; Gronenschild, Ed HBM; Salat, David H.; Freeze, Whitney M.; Ivanov, Dimo; Clerx, Lies; Verhey, Frans R. J.; Aalten, Pauline; Jacobs, Heidi I. L.

    The underlying pathology of white matter signal abnormalities (WMSAs) is heterogeneous and may vary dependent on the magnetic resonance imaging contrast used to define them. We investigated differences in white matter diffusivity as an indicator for white matter integrity underlying WMSA based on

  7. White matter disease of the brain

    Melville, G.E.; Fernandez, R.E.; Kishore, P.R.S.; Lee, S.H.

    1987-01-01

    The white matter disorders that are discussed in this chapter are subdivided into those disorders within which there is breakdown of normal myelin, termed myelinoclastic, and those diseases involving either formation or maintenance of abnormal myeline, termed dysmyelinating. CT is a well-established technique for studying white matter disease. Magnetic resonance imaging (MRI) is a new noninvasive technique which has shown greater sensitivity to white matter abnormalities. However, because of the rarity of may white matter diseases coupled with limited availability of MR facilities, the MRI experience in evaluating these patients is not extensive yet. Some patients may not be suitable for MRI because of the longer period of patient immobility that is required to avoid motion artifacts

  8. PREFACE: 16th European White Dwarfs Workshop

    Garcia-Berro, Enrique; Hernanz, Margarita; Isern, Jordi; Torres, Santiago

    2009-07-01

    The 16th European Workshop on White Dwarfs was held in Barcelona, Spain, from 30 June to 4 July 2008 at the premises of the UPC. Almost 120 participants from Europe (France, Germany, United Kingdom, Italy, and several others), America (USA, Canada, Argentina, Brazil, and Chile), and other continents (Australia, South Africa, . . . ) attended the workshop. Among these participants were the most relevant specialists in the field. The topics covered by the conference were: White dwarf structure and evolution Progenitors and Planetary Nebulae White dwarfs in binaries: cataclysmic variables, double degenerates and other binaries White dwarfs, dust disks and planetary systems Atmospheres, chemical composition, magnetic fields Variable white dwarfs White dwarfs in stellar clusters and the halo White Dwarfs as SNIa progenitors The programme included 54 talks, and 45 posters. The oral presentations were distributed into the following sessions: Luminosity function, mass function and populations White dwarf structure and evolution White dwarf ages White dwarf catalogs and surveys Central stars of planetary nebulae Supernovae progenitors White dwarfs in novae and CVs Physical processes in white dwarfs and magnetic white dwarfs Disks, dust and planets around white dwarfs Pulsating white dwarfs Additionally we had a special open session about Spitzer and white dwarfs. The Proceedings of the 16th European Workshop on White Dwarfs are representative of the current state-of-the-art of the research field and include new and exciting results. We acknowledge the very positive attitude of the attendants to the workshop, which stimulated very fruitful discussions that took place in all the sessions and after the official schedule. Also, the meeting allowed new collaborations tp start that will undoubtedly result in significant advances in the research field. We also acknowledge the willingness of the participants to deliver their contributions before the final deadline. We sincerely

  9. Low White Blood Cell Count

    Symptoms Low white blood cell count By Mayo Clinic Staff A low white blood cell count (leukopenia) is a decrease ... of white blood cell (neutrophil). The definition of low white blood cell count varies from one medical ...

  10. AGREEMENT BETWEEN THE WHITE MATTER CONNECTIVITY BASED ON THE TENSOR-BASED MORPHOMETRY AND THE VOLUMETRIC WHITE MATTER PARCELLATIONS BASED ON DIFFUSION TENSOR IMAGING

    Kim, Seung-Goo; Lee, Hyekyoung; Chung, Moo K.; Hanson, Jamie L.; Avants, Brian B.; Gee, James C.; Davidson, Richard J.; Pollak, Seth D.

    2012-01-01

    We are interested in investigating white matter connectivity using a novel computational framework that does not use diffusion tensor imaging (DTI) but only uses T1-weighted magnetic resonance imaging. The proposed method relies on correlating Jacobian determinants across different voxels based on the tensor-based morphometry (TBM) framework. In this paper, we show agreement between the TBM-based white matter connectivity and the DTI-based white matter atlas. As an application, altered white ...

  11. Recent advances on the formation and evolution of white dwarfs

    Sion, E.M.

    1986-01-01

    Advances made in the past seven years in both the theory and observation of white dwarfs which have led to major progress in understanding white dwarf formation and evolution are reviewed. The roles of convective dredge-up, mixing and dilution, accretion, gravitational and thermal diffusion in dense plasmas, radiate forces and mass outflow, nuclear shell burning, diffusion-induced reactions, late thermonuclear shell flashes, rotation, and magnetic fields in white dwarf evolution are considered. Recent work on the properties of white dwarfs in cataclysmic variables is briefly addressed. 153 references

  12. Automatic parameterization and analysis of stellar atmospheres: a study of the DA white dwarfs

    McMahan, R.K. Jr.

    1986-01-01

    A method for automatically calculating atmospheric parameters of hydrogen-rich degenerate stars from low resolution spectra is advanced and then applied to the spectra of 53 DA white dwarfs. All data were taken using the Mark II spectrograph on the McGraw-Hill 1.3 m telescope and cover the spectral range λλ4100-7000 at a resolution of eight Angstroms. The model grid was generated at Dartmouth using the atmosphere code LUCIFER; it contained over 275 synthetic spectra extending from 6000 to 100,000 K in effective temperature and 7.4-9.3 in log g. A new value for the width of the DA mass distribution was achieved using the techniques presented here. Accuracies in the atmospheric parameters greater than twice those previously published were obtained. These results place strict constraints on the magnitude of mass loss in stars in the red giant phase, as well as in the mechanisms responsible for the loss

  13. A NEAR-INFRARED SPECTROSCOPIC SURVEY OF COOL WHITE DWARFS IN THE SLOAN DIGITAL SKY SURVEY

    Kilic, Mukremin; Kowalski, Piotr M.; Von Hippel, Ted

    2009-01-01

    We present near-infrared photometric observations of 15 and spectroscopic observations of 38 cool white dwarfs (WDs). This is the largest near-infrared spectroscopic survey of cool WDs to date. Combining the Sloan Digital Sky Survey photometry and our near-infrared data, we perform a detailed model atmosphere analysis. The spectral energy distributions of our objects are explained fairly well by model atmospheres with temperatures ranging from 6300 K down to 4200 K. Two WDs show significant absorption in the infrared, and are best explained with mixed H/He atmosphere models. Based on the up-to-date model atmosphere calculations by Kowalski and Saumon, we find that the majority of the stars in our sample have hydrogen-rich atmospheres. We do not find any pure helium atmosphere WDs below 5000 K, and we find a trend of increasing hydrogen to helium ratio with decreasing temperature. These findings present an important challenge to understanding the spectral evolution of WDs.

  14. Undergoing spherically symmetric steady-state accretion stability of white dwarfs

    Sienkiewicz, R [Polska Akademia Nauk, Warsaw. N. Copernicus Astronomical Center

    1980-01-01

    Thermal and vibrational stabilities of accreting white dwarfs with steady-state nuclear burning were considered, assuming spherically symmetric accretion of the hydrogen-rich matter and using linear stability analysis. Almost all models with masses 0.2 M(sun) - 1.39 M(sun) were found to be unstable in some way. The type of instability expected to dominate is given as a function of the accretion rate. For most accretion rates it is the thermal instability. Oscillation periods are given for the models in which the vibrational instability is the most violent one. These periods are of the order of seconds or minutes. We expect that our stability analysis may suggest the cause of the variabilities of the hot components of some symbiotic stars, for a wide range of the accretion rates. In this case our models may serve as the initial conditions for evolutionary computations. The results predict that short-period oscillations should be observed in some hot nuclei of planetary nebulae.

  15. Pulsations in white dwarfs: Selected topics

    Saio H.

    2013-03-01

    Full Text Available This paper presents a very brief overview of the observed properties of g-mode pulsations in variable white dwarfs. We then discuss a few selected topics: Excitation mechanisms (kappa- and convection- mechanisms, and briefly the effect of a strong magnetic field (∼ 1 MG on g-modes as recently found in a hot DQ (carbon-rich atmosphere white dwarf. In the discussion of excitation mechanisms, a simple interpretation for the convection mechanism is given.

  16. Strong Magnetic Field Characterisation

    2012-04-01

    an advertised surface field of approximately 0.5 T were used to supply the static magnetic field source. The disc magnet had a diameter of 50 mm and... colour bar indicates the magnetic field strength set to an arbitrary 0.25 T. The white area has a field >0.25 T. The size of the arrow is proportional...9 shows the magnetic field strength along a slice in the XZ plane. The colours represent the total UNCLASSIFIED 10 UNCLASSIFIED DSTO-TR-2699

  17. THE WHITE BLOOD ANCESTOR?

    M.Arulmani; V.R.Hema Latha

    2014-01-01

    This scientific research article focus that “Red colour blood” of human shall be considered as the 3rd generation Blood and the Human on origin shall be considered having white colour Blood. The white colour blood of human Ancestor shall be considered composed of only ions of Photon, Electron, Proton and free from Hydrogen, Carbon, Nitrogen, Ozone.

  18. Racializing white drag.

    Rhyne, Ragan

    2004-01-01

    While drag is primarily understood as a performance of gender, other performative categories such as race, class, and sexuality create drag meaning as well. Though other categories of identification are increasingly understood as essential elements of drag by performers of color, whiteness remains an unmarked category in the scholarship on drag performances by white queens. In this paper, I argue that drag by white queens must be understood as a performance of race as well as gender and that codes of gender excess are specifically constructed through the framework of these other axes of identity. This essay asks whether white performance by white queens necessarily reinscribes white supremacy through the performance of an unmarked white femininity, or might drag performance complicate (though not necessarily subvert) categories of race as well as gender? In this essay, I will suggest that camp drag performances, through the deployment of class as a crucial category of performative femininity, might indeed be a key site through which whiteness is denaturalized and its power challenged. Specifically, I will read on camp as a politicized mode of race, class and gender performance, focusing on the intersections of these categories of identity in the drag performance of Divine.

  19. Creating White Australia

    McLisky, Claire Louise; Carey, Jane

    Vedtagelsen af White Australien som regeringens politik i 1901 viser, at hvidheden var afgørende for den måde, hvorpå den nye nation i Australien blev konstitueret. Og alligevel har historikere i vid udstrækning overset hvidhed i deres studier af Australiens race fortid. 'Creating White Australia...

  20. White Dwarfs in Cataclysmic Variables: An Update

    E. M. Sion

    2015-02-01

    Full Text Available In this review, we summarize what is currently known about the surface temperatures of accreting white dwarfs in nonmagnetic and magnetic cataclysmic variables (CVs based upon synthetic spectral analyses of far ultraviolet data. We focus only on white dwarf surface temperatures, since in the area of chemical abundances, rotation rates, WD masses and accretion rates, relatively little has changed since our last review, pending the results of a large HST GO programinvolving 48 CVs of different CV types. The surface temperature of the white dwarf in SS Cygni is re-examined in the light of its revised distance. We also discuss new HST spectra of the recurrent nova T Pyxidis as it transitioned into quiescence following its April 2011 nova outburst.

  1. Magnetic and Superconducting Materials at High Pressures

    Struzhkin, Viktor V. [Carnegie Inst. of Washington, Washington, DC (United States)

    2015-03-24

    The work concentrates on few important tasks in enabling techniques for search of superconducting compressed hydrogen compounds and pure hydrogen, investigation of mechanisms of high-Tc superconductivity, and exploring new superconducting materials. Along that route we performed several challenging tasks, including discovery of new forms of polyhydrides of alkali metal Na at very high pressures. These experiments help us to establish the experimental environment that will provide important information on the high-pressure properties of hydrogen-rich compounds. Our recent progress in RIXS measurements opens a whole field of strongly correlated 3d materials. We have developed a systematic approach to measure major electronic parameters, like Hubbard energy U, and charge transfer energy Δ, as function of pressure. This technique will enable also RIXS studies of magnetic excitations in iridates and other 5d materials at the L edge, which attract a lot of interest recently. We have developed new magnetic sensing technique based on optically detected magnetic resonance from NV centers in diamond. The technique can be applied to study superconductivity in high-TC materials, to search for magnetic transitions in strongly correlated and itinerant magnetic materials under pressure. Summary of Project Activities; development of high-pressure experimentation platform for exploration of new potential superconductors, metal polyhydrides (including newly discovered alkali metal polyhydrides), and already known superconductors at the limit of static high-pressure techniques; investigation of special classes of superconducting compounds (high-Tc superconductors, new superconducting materials), that may provide new fundamental knowledge and may prove important for application as high-temperature/high-critical parameter superconductors; investigation of the pressure dependence of superconductivity and magnetic/phase transformations in 3d transition metal compounds, including

  2. The Embeddedness of White Fragility within White Pre-Service Principals' Reflections on White Privilege

    Hines, Mack T., III

    2016-01-01

    This study analyzes the prevalence of white fragility within the six white, pre-service principals' online responses to readings about white privilege. Six white, pre-service principals were asked to provide commentary to class readings on the relevance of white privilege to their preparation for future positions as principals. The findings showed…

  3. Physics of white dwarf stars

    Koester, D.; Chanmugam, G. (Louisiana State Univ., New Orleans, LA (USA))

    1990-07-01

    White dwarf stars, compact objects with extremely high interior densities, are the most common end product in the evolution of stars. In this paper we review the history of their discovery, and of the realisation that their structure is determined by the physics of the degenerate electron gas. Spectral types and surface chemical composition show a complicated pattern dominated by diffusion processes and their interaction with accretion, convection and mass loss. While this interaction is not completely understood in all its detail at present, the study may ultimately lead to important constraints on the theory of stellar evolution in general. Variability, caused by non-radial oscillations of the star, is a common phenomenon and is shown to be a powerful probe of the structure of deeper layers that are not directly accessible to observation. Very strong magnetic fields detected in a small fraction of white dwarfs offer a unique opportunity to study the behaviour of atoms under conditions that cannot be simulated in terrestrial laboratories. (author).

  4. Hypermedicalization in White Noise.

    Benson, Josef

    2015-09-01

    The Nazis hijacked Germany's medical establishment and appropriated medical language to hegemonize their ideology. In White Noise, shifting medical information stifles the public into docility. In Nazi Germany the primacy of language and medical authority magnified the importance of academic doctors. The muddling of identities caused complex insecurities and the need for psychological doubles. In White Noise, Professor Gladney is driven by professional insecurities to enact a double in Murray. Through the manipulation of language and medical overreach the U.S., exemplified in the novel White Noise, has become a hypermedicalized society where the spirit of the Hippocratic Oath has eroded.

  5. THE TRENDS HIGH-CONTRAST IMAGING SURVEY. III. A FAINT WHITE DWARF COMPANION ORBITING HD 114174

    Crepp, Justin R.; Johnson, John Asher; Howard, Andrew W.; Marcy, Geoffrey W.; Gianninas, Alexandros; Kilic, Mukremin; Wright, Jason T.

    2013-01-01

    The nearby Sun-like star HD 114174 exhibits a strong and persistent Doppler acceleration indicating the presence of an unseen distant companion. We have acquired high-contrast imaging observations of this star using NIRC2 at Keck and report the direct detection of the body responsible for causing the ''trend''. HD 114174 B has a projected separation of 692 ± 9 mas (18.1 AU) and is 10.75 ± 0.12 mag (contrast of 5 × 10 –5 ) fainter than its host in the K-band, requiring aggressive point-spread function subtraction to identify. Our astrometric time baseline of 1.4 yr demonstrates physical association through common proper motion. We find that the companion has absolute magnitude, M J = 13.97 ± 0.11, and colors, J – K = 0.12 ± 0.16 mag. These characteristics are consistent with an ≈T3 dwarf, initially leading us to believe that HD 114174 B was a substellar object. However, a dynamical analysis that combines radial velocity measurements with available imaging data indicates a minimum mass of 0.260 ± 0.010 M ☉ . We conclude that HD 114174 B must be a white dwarf. Assuming a hydrogen-rich composition, atmospheric and evolutionary model fits yield an effective temperature T eff = 8200 ± 4000 K, surface gravity log g = 8.90 ± 0.02, and cooling age of t c ≈ 3.4 Gyr, which is consistent with the 4.7 +2.3 -2.6 Gyr host star isochronal age estimate. HD 114174 B is a benchmark object located only 26.14 ± 0.37 pc from the Sun. It may be studied at a level of detail comparable to Sirius and Procyon, and used to understand the link between the mass of white dwarf remnants with that of their progenitors

  6. ESCO White Paper

    EPA developed this white paper to explore energy performance contracting with Energy Service Companies (ESCOs) and its potential to be a best practice for installing solar thermal water heating systems in the commercial and industrial sector.

  7. Northeast Atlantic blue whiting

    Heino, Mikko

    2010-01-01

    Heino, M. 2010. Northeast Atlantic blue whiting. In Life cycle spatial patterns of small pelagic fish in the Northeast Atlantic, pp. 59-64. Ed by P. Petitgas. ICES Cooperative Research Report 306. ICES, Copenhagen.

  8. White House Communications Agency

    Gimble, Thomas

    1995-01-01

    ...; and the Deputy Secretary of Defense requested the audit. The Deputy Secretary of Defense emphasized that this review should be as thorough as possible of all White House Communications Agency (WHCA...

  9. Progenitors of white dwarfs

    Drilling, J.S.; Schoenberner, D.

    1985-01-01

    Direct observational evidence is presented which indicates that the immediate progenitors of white dwarfs are the central stars of planetary nebulae (approximately 70%), other post-AGB objects (approximately 30%), and post-HB objects not massive enough to climb the AGB (approximately 0.3%). The combined birth rate for these objects is in satisfactory agreement with the death rate of main-sequence stars and the birth rate of white dwarfs

  10. Black and white holes

    Zeldovich, Ya.; Novikov, I.; Starobinskij, A.

    1978-01-01

    The theory is explained of the origination of white holes as a dual phenomenon with regard to the formation of black holes. Theoretically it is possible to derive the white hole by changing the sign of time in solving the general theory of relativity equation implying the black hole. The white hole represents the amount of particles formed in the vicinity of a singularity. For a distant observer, matter composed of these particles expands and the outer boundaries of this matter approach from the inside the gravitational radius Rsub(r). At t>>Rsub(r)/c all radiation or expulsion of matter terminates. For the outside observer the white hole exists for an unlimited length of time. In fact, however, it acquires the properties of a black hole and all processes in it cease. The qualitative difference between a white hole and a black hole is in that a white hole is formed as the result of an inner quantum explosion from the singularity to the gravitational radius and not as the result of a gravitational collapse, i.e., the shrinkage of diluted matter towards the gravitational radius. (J.B.)

  11. Black and white holes

    Zeldovich, Ya; Novikov, I; Starobinskii, A

    1978-07-01

    The theory is explained of the origination of white holes as a dual phenomenon with regard to the formation of black holes. Theoretically it is possible to derive the white hole by changing the sign of time in solving the general theory of relativity equation implying the black hole. The white hole represents the amount of particles formed in the vicinity of a singularity. For a distant observer, matter composed of these particles expands and the outer boundaries of this matter approach from the inside the gravitational radius R/sub r/. At t>>R/sub r//c all radiation or expulsion of matter terminates. For the outside observer the white hole exists for an unlimited length of time. In fact, however, it acquires the properties of a black hole and all processes in it cease. The qualitative difference between a white hole and a black hole is in that a white hole is formed as the result of an inner quantum explosion from the singularity to the gravitational radius and not as the result of a gravitational collapse, i.e., the shrinkage of diluted matter towards the gravitational radius.

  12. A DARK SPOT ON A MASSIVE WHITE DWARF

    Kilic, Mukremin; Gianninas, Alexandros; Curd, Brandon; Wisniewski, John P. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W. Brooks St., Norman, OK 73019 (United States); Bell, Keaton J.; Winget, D. E.; Winget, K. I. [Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States); Brown, Warren R. [Smithsonian Astrophysical Observatory, 60 Garden St., Cambridge, MA 02138 (United States); Hermes, J. J. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Dufour, Patrick [Institut de recherche sur les exoplanétes (iREx), Département de Physique, Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montréal, QC H3C 3J7 (Canada)

    2015-12-01

    We present the serendipitous discovery of eclipse-like events around the massive white dwarf SDSS J152934.98+292801.9 (hereafter J1529+2928). We selected J1529+2928 for time-series photometry based on its spectroscopic temperature and surface gravity, which place it near the ZZ Ceti instability strip. Instead of pulsations, we detect photometric dips from this white dwarf every 38 minutes. Follow-up optical spectroscopy observations with Gemini reveal no significant radial velocity variations, ruling out stellar and brown dwarf companions. A disintegrating planet around this white dwarf cannot explain the observed light curves in different filters. Given the short period, the source of the photometric dips must be a dark spot that comes into view every 38 minutes due to the rotation of the white dwarf. Our optical spectroscopy does not show any evidence of Zeeman splitting of the Balmer lines, limiting the magnetic field strength to B < 70 kG. Since up to 15% of white dwarfs display kG magnetic fields, such eclipse-like events should be common around white dwarfs. We discuss the potential implications of this discovery on transient surveys targeting white dwarfs, like the K2 mission and the Large Synoptic Survey Telescope.

  13. A radio-pulsing white dwarf binary star.

    Marsh, T R; Gänsicke, B T; Hümmerich, S; Hambsch, F-J; Bernhard, K; Lloyd, C; Breedt, E; Stanway, E R; Steeghs, D T; Parsons, S G; Toloza, O; Schreiber, M R; Jonker, P G; van Roestel, J; Kupfer, T; Pala, A F; Dhillon, V S; Hardy, L K; Littlefair, S P; Aungwerojwit, A; Arjyotha, S; Koester, D; Bochinski, J J; Haswell, C A; Frank, P; Wheatley, P J

    2016-09-15

    White dwarfs are compact stars, similar in size to Earth but approximately 200,000 times more massive. Isolated white dwarfs emit most of their power from ultraviolet to near-infrared wavelengths, but when in close orbits with less dense stars, white dwarfs can strip material from their companions and the resulting mass transfer can generate atomic line and X-ray emission, as well as near- and mid-infrared radiation if the white dwarf is magnetic. However, even in binaries, white dwarfs are rarely detected at far-infrared or radio frequencies. Here we report the discovery of a white dwarf/cool star binary that emits from X-ray to radio wavelengths. The star, AR Scorpii (henceforth AR Sco), was classified in the early 1970s as a δ-Scuti star, a common variety of periodic variable star. Our observations reveal instead a 3.56-hour period close binary, pulsing in brightness on a period of 1.97 minutes. The pulses are so intense that AR Sco's optical flux can increase by a factor of four within 30 seconds, and they are also detectable at radio frequencies. They reflect the spin of a magnetic white dwarf, which we find to be slowing down on a 10 7 -year timescale. The spin-down power is an order of magnitude larger than that seen in electromagnetic radiation, which, together with an absence of obvious signs of accretion, suggests that AR Sco is primarily spin-powered. Although the pulsations are driven by the white dwarf's spin, they mainly originate from the cool star. AR Sco's broadband spectrum is characteristic of synchrotron radiation, requiring relativistic electrons. These must either originate from near the white dwarf or be generated in situ at the M star through direct interaction with the white dwarf's magnetosphere.

  14. Entanglement probabilities of polymers: a white noise functional approach

    Bernido, Christopher C; Carpio-Bernido, M Victoria

    2003-01-01

    The entanglement probabilities for a highly flexible polymer to wind n times around a straight polymer are evaluated using white noise analysis. To introduce the white noise functional approach, the one-dimensional random walk problem is taken as an example. The polymer entanglement scenario, viewed as a random walk on a plane, is then treated and the entanglement probabilities are obtained for a magnetic flux confined along the straight polymer, and a case where an entangled polymer is subjected to the potential V = f-dot(s)θ. In the absence of the magnetic flux and the potential V, the entanglement probabilities reduce to a result obtained by Wiegel

  15. White matter volume changes in people who develop psychosis.

    Walterfang, Mark; McGuire, Philip K; Yung, Alison R; Phillips, Lisa J; Velakoulis, Dennis; Wood, Stephen J; Suckling, John; Bullmore, Edward T; Brewer, Warrick; Soulsby, Bridget; Desmond, Patricia; McGorry, Patrick D; Pantelis, Christos

    2008-09-01

    Grey matter changes have been described in individuals who are pre- and peri-psychotic, but it is unclear if these changes are accompanied by changes in white matter structures. To determine whether changes in white matter occur prior to and with the transition to psychosis in individuals who are pre-psychotic who had previously demonstrated grey matter reductions in frontotemporal regions. We used magnetic resonance imaging (MRI) to examine regional white matter volume in 75 people with prodromal symptoms. A subset of the original group (n=21) were rescanned at 12-18 months to determine white matter volume changes. Participants were retrospectively categorised according to whether they had or had not developed psychosis at follow-up. Comparison of the baseline MRI data from these two subgroups revealed that individuals who later developed psychosis had larger volumes of white matter in the frontal lobe, particularly in the left hemisphere. Longitudinal comparison of data in individuals who developed psychosis revealed a reduction in white matter volume in the region of the left fronto-occipital fasciculus. Participants who had not developed psychosis showed no reductions in white matter volume but increases in a region subjacent to the right inferior parietal lobule. The reduction in volume of white matter near the left fronto-occipital fasciculus may reflect a change in this tract in association with the onset of frank psychosis.

  16. White matter involvement in sporadic Creutzfeldt-Jakob disease.

    Caverzasi, Eduardo; Mandelli, Maria Luisa; DeArmond, Stephen J; Hess, Christopher P; Vitali, Paolo; Papinutto, Nico; Oehler, Abby; Miller, Bruce L; Lobach, Irina V; Bastianello, Stefano; Geschwind, Michael D; Henry, Roland G

    2014-12-01

    Sporadic Creutzfeldt-Jakob disease is considered primarily a disease of grey matter, although the extent of white matter involvement has not been well described. We used diffusion tensor imaging to study the white matter in sporadic Creutzfeldt-Jakob disease compared to healthy control subjects and to correlated magnetic resonance imaging findings with histopathology. Twenty-six patients with sporadic Creutzfeldt-Jakob disease and nine age- and gender-matched healthy control subjects underwent volumetric T1-weighted and diffusion tensor imaging. Six patients had post-mortem brain analysis available for assessment of neuropathological findings associated with prion disease. Parcellation of the subcortical white matter was performed on 3D T1-weighted volumes using Freesurfer. Diffusion tensor imaging maps were calculated and transformed to the 3D-T1 space; the average value for each diffusion metric was calculated in the total white matter and in regional volumes of interest. Tract-based spatial statistics analysis was also performed to investigate the deeper white matter tracts. There was a significant reduction of mean (P=0.002), axial (P=0.0003) and radial (P=0.0134) diffusivities in the total white matter in sporadic Creutzfeldt-Jakob disease. Mean diffusivity was significantly lower in most white matter volumes of interest (PCreutzfeldt-Jakob disease. Mean diffusivity reduction reflected concomitant decrease of both axial and radial diffusivity, without appreciable changes in white matter anisotropy. Tract-based spatial statistics analysis showed significant reductions of mean diffusivity within the white matter of patients with sporadic Creutzfeldt-Jakob disease, mainly in the left hemisphere, with a strong trend (P=0.06) towards reduced mean diffusivity in most of the white matter bilaterally. In contrast, by visual assessment there was no white matter abnormality either on T2-weighted or diffusion-weighted images. Widespread reduction in white matter mean

  17. WHITE COLLAR CRIME - Investigations

    Nyagudi, Nyagudi Musandu

    2014-01-01

    WHITE COLLAR CRIME - Investigations Presentation By  Dr. Nyagudi MusanduForensic Criminologist 2nd International Securityand Safety Conference and Exhibition, 16th April, 2010 a forum hosted by Events Management Solutions at the Sarit Centre, Nairobi, Kenya  

  18. The White Sea, Russia

    2002-01-01

    Editor's Note: The caption below, published on May 10, 2001, is incorrect. According to Masha Vorontsova, director of the International Fund for Animal Welfare in Moscow, the situation with the seal pups in the White Sea is normal. There is no disaster and there never was. For more details, refer to the article entitled 'No Danger' on the New Scientist home page. The Earth Observatory regrets the earlier errant report. Original Caption According to the Russian Polar Research Institute for Fisheries and Oceanography, between 250,000 and 300,000 Greenland seal pups face death by starvation over the next two months due to a cruel trick by mother nature. The seals, most of them less than two months old, are trapped on ice sheets that remain locked in the White Sea, located near Archangel in Northern Russia. Typically, during the spring thaw the ice sheets break up and flow with the currents northward into the Barents Sea, the seals' spring feeding grounds. The seal pups hitch a ride on the ice floes, living on their own individual stores of fat until they arrive in the Barents Sea. Their mothers departed for the Barents Sea weeks ago. In a normal year, the seal pups' trip from the White Sea out to the Barents takes about six weeks and the seals have adapted to rely upon this mechanism of mother nature. During their yearly migration, the mother seals usually stay with their pups and feed them until their pelts turn from white to grey--a sign that the pups are mature enough to swim and feed themselves. Unfortunately, this year unusually strong northerly winds created a bottleneck of ice near the mouth of the white sea, thus blocking the flow of ice and trapping the pups. These true-color images of the White Sea were acquired by the Moderate-resolution Imaging Spectroradiometer (MODIS), flying aboard NASA's Terra spacecraft. This image, taken May 2, 2000 that there is usually much less ice in the White Sea this time of year as most of it is typically en route to the

  19. White matter microstructure in transsexuals and controls investigated by diffusion tensor imaging

    Kranz, Georg S; Hahn, Andreas; Kaufmann, Ulrike; Küblböck, Martin; Hummer, Allan; Ganger, Sebastian; Seiger, Rene; Winkler, Dietmar; Swaab, Dick F; Windischberger, Christian; Kasper, Siegfried; Lanzenberger, Rupert

    2014-01-01

    Biological causes underpinning the well known gender dimorphisms in human behavior, cognition, and emotion have received increased attention in recent years. The advent of diffusion-weighted magnetic resonance imaging has permitted the investigation of the white matter microstructure in

  20. Comparative carbon-13 nuclear magnetic resonance study at 67. 9 MHz on lysozyme (human and egg-white) and. cap alpha. -lactalbumin (human and bovine) in their native and denatured state

    van Binst, G; Biesemans, M [Brussels Univ. (Belgium). Faculte des Sciences

    1975-01-01

    A first detailed comparison of the /sup 13/C spectra at high field of two lysozymes (human and egg-white) and two ..cap alpha..-lactalbumins (human and bovine milk) is presented. Assignments were made on most of the resonance peaks in the aliphatic and aromatic regions of the denatured proteins. The relative peak intensities clearly demonstrate the differences in the amino acid composition of the related proteins. The broadening and the complexity of the spectra of the native proteins reflect the non equivalence of the chemical groups in the folded conformation. The usefulness of /sup 13/C nmr spectroscopy in the study of the interaction between small molecules and proteins was tested on N-acteyl-glucosamine in the presence of lysozyme.

  1. Plato: White and Non-white Love

    Amo Sulaiman

    2009-06-01

    Full Text Available Plato’s dialogues, the Symposium, and Phaedrus, provide a reasonableexplanation of love. G. Vlastos and M. Nussbaum do not share such anopinion. The former contends that Plato’s view of love is about lovingonly a person’s beauty, but not the entire person; thus, it falls short of anappropriate explanation of love. The latter holds that a theory of love should be complete, and that Plato’s one is incomplete on the grounds that it does not account for personal love. These criticisms will be re-evaluated in light of the duality of love (the white and non-white horses—in Phaedrus as well as participants’ views in the Symposium; a re-assessment will weaken the mentioned objections. This paper contends that from the Symposium and Phaedrus, one can have a fruitful understanding of being in love, being out of love, falling inlove, loving for its own sake and being erotically in love. In order to account for these related issues of love it is important to consider Plato’s works in terms of his “official” and “unofficial” views. The former is construed as the doctrine of the lover or loving for its own sake: this is associates with Diotima’s views which are repeated by Socrates. With reference to the latter, it is possible to explain what personal love or being in love, being out of love, falling in love, and being erotically in love involve. Erotic love will be interpreted as an extension of our philosophical conception of love, related to views of love that are mentioned in the Symposium other than Socrates’ report of Diotima’s conceptions. This paper is divided into two parts: the first one will show views of love in the Symposium. That is, being in love, being out of love, falling in love and loving for its own sake will be discussed. In addition, the forementioned criticisms will be re-evaluated. In the second section, we will show that Aristophanes’ speech expresses erotic love, and then Kant’s objections will be

  2. A Voxel-Based Diffusion Tensor Imaging Study of White Matter in Bipolar Disorder

    Mahon, Katie; Wu, Jinghui; Malhotra, Anil K.; Burdick, Katherine E.; DeRosse, Pamela; Ardekani, Babak A.; Szeszko, Philip R.

    2009-01-01

    There is evidence from post-mortem and magnetic resonance imaging studies that hyperintensities, oligodendrioglial abnormalities and gross white matter volumetric alterations play a role in the pathophysiology of bipolar disorder. There is also functional imaging evidence for a defect in frontal cortico-subcortical pathways in bipolar disorder, but the white matter comprising these pathways has not been well-investigated. Few studies have investigated white matter integrity in patients with b...

  3. Visualizing White Matter Structure of the Brain using Dijkstra's Algorithm

    Everts, Maarten H.; Bekker, Henk; Roerdink, Jos B. T. M.; Zinterhof, P; Loncaric, S; Uhl, A; Carini, A

    2009-01-01

    An undirected weighted graph may be constructed from diffusion weighted magnetic resonance imaging data. Every node represents a voxel and the edge weights between nodes represent the white matter connectivity between neighboring voxels. In this paper we propose and test a new method for calculating

  4. AGREEMENT BETWEEN THE WHITE MATTER CONNECTIVITY BASED ON THE TENSOR-BASED MORPHOMETRY AND THE VOLUMETRIC WHITE MATTER PARCELLATIONS BASED ON DIFFUSION TENSOR IMAGING.

    Kim, Seung-Goo; Lee, Hyekyoung; Chung, Moo K; Hanson, Jamie L; Avants, Brian B; Gee, James C; Davidson, Richard J; Pollak, Seth D

    2012-01-01

    We are interested in investigating white matter connectivity using a novel computational framework that does not use diffusion tensor imaging (DTI) but only uses T1-weighted magnetic resonance imaging. The proposed method relies on correlating Jacobian determinants across different voxels based on the tensor-based morphometry (TBM) framework. In this paper, we show agreement between the TBM-based white matter connectivity and the DTI-based white matter atlas. As an application, altered white matter connectivity in a clinical population is determined.

  5. Diffusion tensor imaging, white matter lesions, the corpus callosum, and gait in the elderly

    Gait impairment is common in the elderly, especially affected by stroke and white matter hyper intensities found in conventional brain magnetic resonance imaging (MRI). Diffusion tensor imaging (DTI) is more sensitive to white matter damage than conventional MRI. The relationship between DTI measure...

  6. Microstructural Abnormalities of Short-Distance White Matter Tracts in Autism Spectrum Disorder

    Shukla, Dinesh K.; Keehn, Brandon; Smylie, Daren M.; Muller, Ralph-Axel

    2011-01-01

    Recent functional connectivity magnetic resonance imaging and diffusion tensor imaging (DTI) studies have suggested atypical functional connectivity and reduced integrity of long-distance white matter fibers in autism spectrum disorder (ASD). However, evidence for short-distance white matter fibers is still limited, despite some speculation of…

  7. White Matter Lesion Progression in LADIS

    Schmidt, Reinhold; Berghold, Andrea; Jokinen, Hanna

    2012-01-01

    BACKGROUND AND PURPOSE: White matter lesion (WML) progression has been advocated as a surrogate marker in intervention trials on cerebral small vessel disease. We assessed the rate of visually rated WML progression, studied correlations between lesion progression and cognition, and estimated sample...... sizes for clinical trials with pure WML progression vs combined WML progression-cognitive outcomes. METHODS: Those 394 participants of the Leukoaraiosis and Disability Study (LADIS) study with magnetic resonance imaging scanning at baseline and 3-year follow-up were analyzed. WML progression rating...

  8. Asteroseismology of White Dwarf Stars

    Hansen, Carl J.

    1997-01-01

    The primary purpose of this investigation has been to study various aspects of multimode pulsations in variable white dwarfs. In particular, nonlinear interactions among pulsation modes in white dwarfs (and, to some extent, in other variable stars), analysis of recent observations where such interactions are important, and preliminary work on the effects of crystallization in cool white dwarfs are reported.

  9. Cerebral white matter hypoplasia

    Dietrich, R.B.; Shields, W.D.; Sankar, R.

    1990-01-01

    This paper demonstrates the MR imaging findings in children with cerebral white matter hypoplasia (CWMH). The MR studies of four children, aged 3-7 y (mean age, 2.3 y) with a diagnosis of CWMH were reviewed. In all cases multiplanar T1-weighted and T2-weighted spin-echo images were obtained. All children had similar histories of severe developmental delay and nonprogressive neurologic deficits despite normal gestational and birth histories. In two cases there was a history of maternal cocaine abuse. Autopsy correlation was available in one child. The MR images of all four children demonstrated diffuse lack of white matter and enlarged ventricles but normal-appearing gray matter. The corpus callosum, although completely formed, was severely thinned. There was no evidence of gliosis or porencephaly, and the distribution of myelin deposition was normal for age in all cases. Autopsy finding in one child correlated exactly with the MR finding

  10. White noise on bialgebras

    Schürmann, Michael

    1993-01-01

    Stochastic processes with independent increments on a group are generalized to the concept of "white noise" on a Hopf algebra or bialgebra. The main purpose of the book is the characterization of these processes as solutions of quantum stochastic differential equations in the sense of R.L. Hudsonand K.R. Parthasarathy. The notes are a contribution to quantum probability but they are also related to classical probability, quantum groups, and operator algebras. The Az ma martingales appear as examples of white noise on a Hopf algebra which is a deformation of the Heisenberg group. The book will be of interest to probabilists and quantum probabilists. Specialists in algebraic structures who are curious about the role of their concepts in probablility theory as well as quantum theory may find the book interesting. The reader should havesome knowledge of functional analysis, operator algebras, and probability theory.

  11. White Dwarfs in the HET Dark Energy Experiment

    Castanheira, B. G.; Winget, D. E.; Williams, K.; Montgomery, M. H.; Falcon, R. E.; Hermes, J. J.

    2010-11-01

    In the past decades, large scale surveys have discovered a large number of white dwarfs. For example, the Sloan Digital Sky Survey (SDSS) Data Release 7 [5] lists about 20 000 spectroscopically confirmed new white dwarfs. More than just a number, the new discoveries revealed different flavors of white dwarfs, including a new class of pulsators [7] and a larger percentage of stars with a magnetic field [4]. The HET Dark Energy Experiment (HETDEX) will use the 9.2 m Hobby-Eberly Telescope at McDonald Observatory and a set of 150 spectrographs to map the three-dimensional positions of one million galaxies. The main goal of the survey is to probe dark energy by observing the recent universe (2products. We expect to obtain spectra for about 10 000 white dwarfs in the next 3 to 4 years.

  12. White matter hyperintensities and normal-appearing white matter integrity in the aging brain.

    Maniega, Susana Muñoz; Valdés Hernández, Maria C; Clayden, Jonathan D; Royle, Natalie A; Murray, Catherine; Morris, Zoe; Aribisala, Benjamin S; Gow, Alan J; Starr, John M; Bastin, Mark E; Deary, Ian J; Wardlaw, Joanna M

    2015-02-01

    White matter hyperintensities (WMH) of presumed vascular origin are a common finding in brain magnetic resonance imaging of older individuals and contribute to cognitive and functional decline. It is unknown how WMH form, although white matter degeneration is characterized pathologically by demyelination, axonal loss, and rarefaction, often attributed to ischemia. Changes within normal-appearing white matter (NAWM) in subjects with WMH have also been reported but have not yet been fully characterized. Here, we describe the in vivo imaging signatures of both NAWM and WMH in a large group of community-dwelling older people of similar age using biomarkers derived from magnetic resonance imaging that collectively reflect white matter integrity, myelination, and brain water content. Fractional anisotropy (FA) and magnetization transfer ratio (MTR) were significantly lower, whereas mean diffusivity (MD) and longitudinal relaxation time (T1) were significantly higher, in WMH than NAWM (p curve, 0.982; 95% CI, 0.975-0.989). Furthermore, the level of deterioration of NAWM was strongly associated with the severity of WMH, with MD and T1 increasing and FA and MTR decreasing in NAWM with increasing WMH score, a relationship that was sustained regardless of distance from the WMH. These multimodal imaging data indicate that WMH have reduced structural integrity compared with surrounding NAWM, and MD provides the best discriminator between the 2 tissue classes even within the mild range of WMH severity, whereas FA, MTR, and T1 only start reflecting significant changes in tissue microstructure as WMH become more severe. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  13. Defence White Paper 2013

    2013-01-01

    nurtured, particularly in Australia’s highly competitive labour market. The Government recognises that Defence’s approach to its people must be... satisfaction , increase attraction and retention, improve cost-effectiveness and support the contemporary Total Force employment model. Defence White...improve job satisfaction and thereby increase attraction and retention in areas of critical skill. Recruiting 10.13 To ensure that we have the high

  14. White in architecture

    Hašič, Sabina

    2014-01-01

    Throughout life, human beings are continuously in contact with colours and shapes. Some people are well aware of and understand their influence, while others are not aware or do not pay attention. Our feelings are often associated with certain colours. We tend to paint our living environment in mood-enhancing shades and cover ourselves with our favourite colours and materials. The colour that attracts my emotions is white, therefore I set out to dedicate my research to its nature and to find ...

  15. Decoding white coat hypertension

    Bloomfield, Dennis A; Park, Alex

    2017-01-01

    There is arguably no less understood or more intriguing problem in hypertension that the “white coat” condition, the standard concept of which is significantly blood pressure reading obtained by medical personnel of authoritative standing than that obtained by more junior and less authoritative personnel and by the patients themselves. Using hospital-initiated ambulatory blood pressure monitoring, the while effect manifests as initial and ending pressure elevations, and, in treated patients, a low daytime profile. The effect is essentially systolic. Pure diastolic white coat hypertension appears to be exceedingly rare. On the basis of the studies, we believe that the white coat phenomenon is a common, periodic, neuro-endocrine reflex conditioned by anticipation of having the blood pressure taken and the fear of what this measurement may indicate concerning future illness. It does not change with time, or with prolonged association with the physician, particularly with advancing years, it may be superimposed upon essential hypertension, and in patients receiving hypertensive medication, blunting of the nighttime dip, which occurs in about half the patients, may be a compensatory mechanisms, rather than an indication of cardiovascular risk. Rather than the blunted dip, the morning surge or the widened pulse pressure, cardiovascular risk appears to be related to elevation of the average night time pressure. PMID:28352632

  16. White dwarf planets

    Bonsor Amy

    2013-04-01

    Full Text Available The recognition that planets may survive the late stages of stellar evolution, and the prospects for finding them around White Dwarfs, are growing. We discuss two aspects governing planetary survival through stellar evolution to the White Dwarf stage. First we discuss the case of a single planet, and its survival under the effects of stellar mass loss, radius expansion, and tidal orbital decay as the star evolves along the Asymptotic Giant Branch. We show that, for stars initially of 1 − 5 M⊙, any planets within about 1 − 5 AU will be engulfed, this distance depending on the stellar and planet masses and the planet's eccentricity. Planets engulfed by the star's envelope are unlikely to survive. Hence, planets surviving the Asymptotic Giant Branch phase will probably be found beyond ∼ 2 AU for a 1  M⊙ progenitor and ∼ 10 AU for a 5 M⊙ progenitor. We then discuss the evolution of two-planet systems around evolving stars. As stars lose mass, planet–planet interactions become stronger, and many systems stable on the Main Sequence become destabilised following evolution of the primary. The outcome of such instabilities is typically the ejection of one planet, with the survivor being left on an eccentric orbit. These eccentric planets could in turn be responsible for feeding planetesimals into the neighbourhood of White Dwarfs, causing observed pollution and circumstellar discs.

  17. White matter cysts in patients with tuberous sclerosis

    Marti-Bonmati, L.; Dosda, R.; Menor, F.; Arana, E.; Poyatos, C.

    1999-01-01

    The presence of cysts in the white matter of the central nervous system of patients with tuberous sclerosis (TS) is an uncommon finding that has been reported only recently in neuroimaging studies. This article assesses the prevalence of these lesions in a large series of patients studied by magnetic resonance imaging (MRI) and their relationship to other epidemiological and imaging findings. MRI studies were performed in 46 patients (23 males and 23 females) with a mean age of 12.7 years, and the results were examined retrospectively in the search for cortical tubers, subependymal nodules and white matter nodules, lines and cysts. Nine patients (19.6%) presented cysts in white matter. Seven had only one cyst and the remaining two patients each had two. Multiple regression analysis relating the presence of the cysts with other neuroimaging findings in these patients revealed a statistically significant relationship only with white matter nodules (odds ratio: 7.5; p=0.006). White matter cysts are small, supratentorial lesions of deep location. There is a statistically relationship between the presence of these cysts and that of nodular lesions in the white matter. This finding supports the theory that the cyst originate from white matter nodules. (Author) 17 refs

  18. The role of annealing temperature and bio template (egg white) on the structural, morphological and magnetic properties of manganese substituted MFe2O4 (M=Zn, Cu, Ni, Co) nanoparticles

    Ranjith Kumar, E.; Jayaprakash, R.; Kumar, Sanjay

    2014-02-01

    Manganese substituted ferrites (ZnFe2O4, CuFe2O4, NiFe2O4 and CoFe2O4) have been prepared in the bio template medium by using a simple evaporation method. The annealing temperature plays an important position on changing particle size and morphology of the mixed ferrite nanoparticles were found out by X-ray diffraction, transmission electron microscopy and scanning electron microscopy methods. The role of manganese substitution in the mixed ferrite nanoparticles were also analyzed for different annealing temperature. The substitution of Mn also creates a vital change in magnetic properties which is studied by using vibrating sample magnetometer (VSM). These spinel ferrites are decomposed to α-Fe2O3 after annealing above 550 °C in air. However, α-Fe2O3 phase was slowly vanished after ferrites annealing above 900 °C. The effect of this secondary phase on the structural change and magnetic properties of the mixed ferrite nanoparticles is discussed.

  19. Stark Broadening and White Dwarfs

    Dimitrijević Milan S.

    2011-12-01

    Full Text Available White dwarf and pre-white dwarfs are the best types of stars for the application of Stark broadening research results in astrophysics, since in the atmospheres of these stars physical conditions are very favorable for this line broadening mechanism - in hot hydrogen-deficient white dwarfs and pre-white dwarfs Teff = 75 000–180 000 K and log g = 5.5–8 [cgs]. Even for much cooler DA and DB white dwarfs with the typical effective temperatures 10 000-20 000 K, Stark broadening is usually the dominant broadening mechanism. In this review, Stark broadening in white dwarf spectra is considered, and the attention is drawn to the STARK-B database (http://stark-b.obspm.fr/, containing the parameters needed for analysis and synthesis of white dwarf spectra, as well as for the collective efforts to develop the Virtual Atomic and Molecular Data Center.

  20. Magnets and magnetic materials

    Meuris, Ch.; Rifflet, J.M.

    2007-01-01

    The Large Hadron Collider (LHC), the world's largest highest-energy particle collider that the CERN plans to commission in 2008, gets a double boost from superconducting magnet technology. Superconducting magnets are first used to guide the particles scheduled for collision through the accelerator, and then to observe the events triggered by the collision inside giant detectors in a known magnetic field. Despite the installation's massive dimensions, all this is done with minimal expenditure of energy. (author)

  1. Magnetic novae

    Zemko, Polina; Orio, Marina

    2016-07-01

    We present the results of optical and X-ray observations of two quiescent novae, V2491 Cyg and V4743 Sgr. Our observations suggest the intriguing possibility of localization of hydrogen burning in magnetic novae, in which accretion is streamed to the polar caps. V2491 Cyg was observed with Suzaku more than 2 years after the outburst and V4743 Sgr was observed with XMM Newton 2 and 3.5 years after maximum. In the framework of a monitoring program of novae previously observed as super soft X-ray sources we also obtained optical spectra of V4743 Sgr with the SALT telescope 11.5 years after the eruption and of V2491 Cyg with the 6m Big Azimutal Telescope 4 and 7 years post-outburst. In order to confirm the possible white dwarf spin period of V2491 Cyg measured in the Suzaku observations we obtained photometric data using the 90cm WIYN telescope at Kitt Peak and the 1.2 m telescope in Crimea. We found that V4743 Sgr is an intermediate polar (IP) and V2491 Cyg is a strong IP candidate. Both novae show modulation of their X-ray light curves and have X-ray spectra typical of IPs. The Suzaku and XMM Newton exposures revealed that the spectra of both novae have a very soft blackbody-like component with a temperature close to that of the hydrogen burning white dwarfs in their SSS phases, but with flux by at least two orders of magnitude lower, implying a possible shrinking of emitting regions in the thin atmosphere that is heated by nuclear burning underneath it. In quiescent IPs, independently of the burning, an ultrasoft X-ray flux component originates at times in the polar regions irradiated by the accretion column, but the soft component of V4743 Sgr disappeared in 2006, indicating that the origin may be different from accretion. We suggest it may have been due to an atmospheric temperature gradient on the white dwarf surface, or to continuing localized thermonuclear burning at the bottom of the envelope, before complete turn-off. The optical spectra of V2491 Cyg and V

  2. Pulsations in carbon-atmosphere white dwarfs: A new chapter in white dwarf asteroseismology

    Fontaine, G; Brassard, P; Dufour, P; Green, E M; Liebert, J

    2009-01-01

    We present some of the results of a survey aimed at exploring the asteroseismological potential of the newly-discovered carbon-atmosphere white dwarfs. We show that, in certains regions of parameter space, carbon-atmosphere white dwarfs may drive low-order gravity modes. We demonstrate that our theoretical results are consistent with the recent exciting discovery of luminosity variations in SDSS J1426+5752 and some null results obtained by a team of scientists at McDonald Observatory. We also present follow-up photometric observations carried out by ourselves at the Mount Bigelow 1.6-m telescope using the new Mont4K camera. The results of follow-up spectroscopic observations at the MMT are also briefly reported, including the surprising discovery that SDSS J1426+5752 is not only a pulsating star but that it is also a magnetic white dwarf with a surface field near 1.2 MG. The discovery of g-mode pulsations in SDSS J1426+5752 is quite significant in itself as it opens a fourth asteroseismological 'window', after the GW Vir, V777 Her, and ZZ Ceti families, through which one may study white dwarfs.

  3. The White Rabbit project

    Serrano, J; Gousiou, E; van der Bij, E; Wlostowski, T; Daniluk, G; Lipinski, M

    2013-01-01

    White Rabbit (WR) is a multi-laboratory, multi- company collaboration for the development of a new Ethernet-based technology which ensures sub-nanosecond synchronisation and deterministic data transfer. The project uses an open source paradigm for the development of its hardware, gateware and software components. This article provides an introduction to the technical choices and an explanation of the basic principles underlying WR. It then describes some possible applications and the current status of the project. Finally, it provides insight on current developments and future plans.

  4. Magnetism and magnetic materials

    1990-01-01

    It describes the actual status of physics in Brazil concerning the study of magnetism and magnetic materials. It gives an overview of different research groups in Brazil, their needs, as well as the investments needed to improve the area. (A.C.A.S.)

  5. Top emitting white OLEDs

    Freitag, Patricia; Luessem, Bjoern; Leo, Karl [Technische Universitaet Dresden, Institut fuer Angewandte Photophysik, George-Baehr-Strasse 1, 01069 Dresden (Germany)

    2009-07-01

    Top emitting organic light emitting diodes (TOLEDs) provide a number of interesting opportunities for new applications, such as the opportunity to fabricate ITO-free devices by using opaque substrates. This makes it possible to manufacture low cost OLEDs for signage and lighting applications. A general top emitting device consists of highly reflecting metal contacts as anode and semitransparent cathode, the latter one for better outcouling reasons. In between several organic materials are deposited as charge transporting, blocking, and emission layers. Here, we show a top emitting white organic light emitting diode with silver electrodes arranged in a p-i-n structure with p- and n-doped charge transport layers. The centrical emission layer consists of two phosphorescent (red and green) and one fluorescent (blue) emitter systems separated by an ambipolar interlayer to avoid mutual exciton quenching. By adding an additional dielectric capping layer on top of the device stack, we achieve a reduction of the strong microcavity effects which appear due to the high reflection of both metal electrodes. Therefore, the outcoupled light shows broad and nearly angle-independent emission spectra, which is essential for white light emitting diodes.

  6. The White House saga

    Daković Nevena

    2015-01-01

    Full Text Available Frank Capra expressed his gratitude to the immigrant dream come true by creating a brilliant cinematic myth about the American political system, presenting it as an 'inherently good' when in the hands of honest and good people. His 'morality fairytales', 'fantasies of good will' imbued with belief in restoration of old-new principles, offer complex reflections on an idealised Americanism of the 1930s which have become the foundation of representations of the American political system. The Capraesque narrative - 'a blend of optimism, humor, patriotism, and, to those who really understand his work, (and darkness, despair, and the need to fight for things you care about...' (Bassinger 1982: 48 - as a combination of all-American values, ordinary people and historical figures, a democracy myth - has been extended by an endless network of intertextual echoes in film and TV production. Following the developmental lines - through political melodrama, melodramatic politics and political soap opera - one will be led from Capra to the series The West Wing (1996 - 2006, House of Cards (2013 - 2015 and Madame Secretary (2014 - ; from the comprehensive Washington Postcard (Mr. Smith Goes to Washington, 1939 to the focal points at the White House; from Capra's comedy to the saga of the fight against terrorism led by the president and both ordinary and trained American citizens (White House Down, 2013, Roland Emmerich.

  7. White dwarfs and revelations

    Saltas, Ippocratis D.; Sawicki, Ignacy; Lopes, Ilidio

    2018-05-01

    We use the most recent, complete and independent measurements of masses and radii of white dwarfs in binaries to bound the class of non-trivial modified gravity theories, viable after GW170817/GRB170817, using its effect on the mass-radius relation of the stars. We show that the uncertainty in the latest data is sufficiently small that residual evolutionary effects, most notably the effect of core composition, finite temperature and envelope structure, must now accounted for if correct conclusions about the nature of gravity are to be made. We model corrections resulting from finite temperature and envelopes to a base Hamada-Salpeter cold equation of state and derive consistent bounds on the possible modifications of gravity in the stars' interiors, finding that the parameter quantifying the strength of the modification Y< 0.14 at 95% confidence, an improvement of a factor of three with respect to previous bounds. Finally, our analysis reveals some fundamental degeneracies between the theory of gravity and the precise chemical makeup of white dwarfs.

  8. White piedra in children.

    Kiken, David A; Sekaran, Anand; Antaya, Richard J; Davis, Amy; Imaeda, Suguru; Silverberg, Nanette B

    2006-12-01

    White piedra is a fungal infection of the hair shaft caused by species of Trichosporon. Rarely has this infection been reported in the United States. Historically, infected individuals required shaving of their hair to achieve clearance of the infection. We sought to describe 8 cases of Trichosporon scalp infections seen in the northeastern United States. We conducted chart review and prospective evaluation of 7 girls and 1 boy seen in two dermatology practices in New Haven, Conn, and New York, NY. Seven girls, ages 4 to 16 years old, and one 4-year-old boy were determined to have Trichosporon scalp infection, all through culture. Of the 8 children who were available for follow-up, 7 had clearance of their infection with a combination of oral azole antifungal medication and azole antifungal shampoo, without shaving the scalp hair. This was a sample of patients from a localized region of the United States. White piedra is emerging as a commonly seen hair and scalp infection in the northeastern United States. Contrary to prior publications, scalp and hair infection may be successfully treated with a combination of oral azole antifungals and shampoos without shaving the scalp.

  9. Pulsations in white dwarf stars

    Van Grootel, Valérie; Fontaine, Gilles; Brassard, Pierre; Dupret, Marc-Antoine

    2017-01-01

    I will present a description of the six distinct families of pulsating white dwarfs that are currently known. Pulsations are present at various stages of the evolution (from hot, pre-white dwarfs to cool white dwarfs), at various stellar masses, and for various atmospheric compositions. In all of them, a mechanism linked to opacity changes along the evolution drives the oscillations. The existence of these oscillations offers the opportunity to apply asteroseismology for constraining physics ...

  10. WHITE DWARF/M DWARF BINARIES AS SINGLE DEGENERATE PROGENITORS OF TYPE Ia SUPERNOVAE

    Wheeler, J. Craig

    2012-01-01

    Limits on the companions of white dwarfs in the single-degenerate scenario for the origin of Type Ia supernovae (SNe Ia) have gotten increasingly tight, yet igniting a nearly Chandrasekhar mass C/O white dwarf from a condition of near hydrostatic equilibrium provides compelling agreement with observed spectral evolution. The only type of non-degenerate stars that survive the tight limits, M V ∼> 8.4 on the SN Ia in SNR 0509-67.5 and M V ∼> 9.5 in the remnant of SN 1572, are M dwarfs. While M dwarfs are observed in cataclysmic variables, they have special properties that have not been considered in most work on the progenitors of SNe Ia: they have small but finite magnetic fields and they flare frequently. These properties are explored in the context of SN Ia progenitors. White dwarf/M dwarf pairs may be sufficiently plentiful to provide, in principle, an adequate rate of explosions even with slow orbital evolution due to magnetic braking or gravitational radiation. Even modest magnetic fields on the white dwarf and M dwarf will yield adequate torques to lock the two stars together, resulting in a slowly rotating white dwarf, with the magnetic poles pointing at one another in the orbital plane. The mass loss will be channeled by a 'magnetic bottle' connecting the two stars, landing on a concentrated polar area on the white dwarf. This enhances the effective rate of accretion compared to spherical accretion. Luminosity from accretion and hydrogen burning on the surface of the white dwarf may induce self-excited mass transfer. The combined effects of self-excited mass loss, polar accretion, and magnetic inhibition of mixing of accretion layers give possible means to beat the 'nova limit' and grow the white dwarf to the Chandrasekhar mass even at rather moderate mass accretion rates.

  11. White Faculty Transforming Whiteness in the Classroom through Pedagogical Practice

    Charbeneau, Jessica

    2015-01-01

    The primary objective of this qualitative study is to present a conceptual framework of pedagogical practices reported by white faculty that serve to challenge the hegemony of whiteness in the university classroom. These transformative teaching practices surfaced through a review of racialized pedagogies discussed in the literature and in…

  12. Silvicultural guide for northern white-cedar (eastern white cedar)

    Emmanuelle Boulfroy; Eric Forget; Philip V. Hofmeyer; Laura S. Kenefic; Catherine Larouche; Guy Lessard; Jean-Martin Lussier; Fred Pinto; Jean-Claude Ruel; Aaron. Weiskittel

    2012-01-01

    Northern white-cedar (eastern white cedar; Thuja occidentalis L.) is an important tree species in the northeastern United States and adjacent Canada, occurring both in pure stands and as a minor species in mixed stands of hardwoods or other softwoods. Yet practitioners have little and often contradictory information about cedar ecology and...

  13. White Dwarf Stars

    1999-01-01

    Peering deep inside a cluster of several hundred thousand stars, NASA's Hubble Space Telescope has uncovered the oldest burned-out stars in our Milky Way Galaxy, giving astronomers a fresh reading on the age of the universe. Located in the globular cluster M4, these small, burned-out stars -- called white dwarfs -- are about 12 to 13 billion years old. By adding the one billion years it took the cluster to form after the Big Bang, astronomers found that the age of the white dwarfs agrees with previous estimates that the universe is 13 to 14 billion years old. The images, including some taken by Hubble's Wide Field and Planetary Camera 2, are available online at http://oposite.stsci.edu/pubinfo/pr/2002/10/ or http://www.jpl.nasa.gov/images/wfpc . The camera was designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif. In the top panel, a ground-based observatory snapped a panoramic view of the entire cluster, which contains several hundred thousand stars within a volume of 10 to 30 light-years across. The Kitt Peak National Observatory's .9-meter telescope took this picture in March 1995. The box at left indicates the region observed by the Hubble telescope. The Hubble telescope studied a small region of the cluster. A section of that region is seen in the picture at bottom left. A sampling of an even smaller region is shown at bottom right. This region is only about one light-year across. In this smaller region, Hubble pinpointed a number of faint white dwarfs. The blue circles indicate the dwarfs. It took nearly eight days of exposure time over a 67-day period to find these extremely faint stars. Globular clusters are among the oldest clusters of stars in the universe. The faintest and coolest white dwarfs within globular clusters can yield a globular cluster's age. Earlier Hubble observations showed that the first stars formed less than 1 billion years after the universe's birth in the big bang. So, finding the oldest stars puts astronomers within

  14. ILC Higgs White Paper

    Asner, D.M.; Calancha, C.; Fujii, K.; Graf, N.; Haber, H.E.; Ishikawa, A.; Kanemura, S.; Kawada, S.; Kurata, M.; Miyamoto, A.; Neal, H.; Ono, H.; Potter, C.; Strube, J.; Suehara, T.; Tanabe, T.; Tian, J.; Tsumura, J.; Watanuki, S.; Weiglein, G.; Yagyu, K.; Yokoya, H.

    2013-01-01

    The ILC Higgs White Paper is a review of Higgs Boson theory and experiment at the International Linear Collider (ILC). Theory topics include the Standard Model Higgs, the two-Higgs doublet model, alternative approaches to electroweak symmetry breaking, and precision goals for Higgs boson experiments. Experimental topics include the measurement of the Higgs cross section times branching ratio for various Higgs decay modes at ILC center of mass energies of 250, 500, and 1000 GeV, and the extraction of Higgs couplings and the total Higgs width from these measurements. Luminosity scenarios based on the ILC TDR machine design are used throughout. The gamma-gamma collider option at the ILC is also discussed.

  15. THE TRENDS HIGH-CONTRAST IMAGING SURVEY. III. A FAINT WHITE DWARF COMPANION ORBITING HD 114174

    Crepp, Justin R. [Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Johnson, John Asher [Department of Planetary Science, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Howard, Andrew W. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Marcy, Geoffrey W. [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Gianninas, Alexandros; Kilic, Mukremin [Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019 (United States); Wright, Jason T., E-mail: jcrepp@nd.edu [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States)

    2013-09-01

    The nearby Sun-like star HD 114174 exhibits a strong and persistent Doppler acceleration indicating the presence of an unseen distant companion. We have acquired high-contrast imaging observations of this star using NIRC2 at Keck and report the direct detection of the body responsible for causing the ''trend''. HD 114174 B has a projected separation of 692 {+-} 9 mas (18.1 AU) and is 10.75 {+-} 0.12 mag (contrast of 5 Multiplication-Sign 10{sup -5}) fainter than its host in the K-band, requiring aggressive point-spread function subtraction to identify. Our astrometric time baseline of 1.4 yr demonstrates physical association through common proper motion. We find that the companion has absolute magnitude, M{sub J} = 13.97 {+-} 0.11, and colors, J - K = 0.12 {+-} 0.16 mag. These characteristics are consistent with an Almost-Equal-To T3 dwarf, initially leading us to believe that HD 114174 B was a substellar object. However, a dynamical analysis that combines radial velocity measurements with available imaging data indicates a minimum mass of 0.260 {+-} 0.010 M{sub Sun }. We conclude that HD 114174 B must be a white dwarf. Assuming a hydrogen-rich composition, atmospheric and evolutionary model fits yield an effective temperature T{sub eff} = 8200 {+-} 4000 K, surface gravity log g = 8.90 {+-} 0.02, and cooling age of t{sub c} Almost-Equal-To 3.4 Gyr, which is consistent with the 4.7{sup +2.3}{sub -2.6} Gyr host star isochronal age estimate. HD 114174 B is a benchmark object located only 26.14 {+-} 0.37 pc from the Sun. It may be studied at a level of detail comparable to Sirius and Procyon, and used to understand the link between the mass of white dwarf remnants with that of their progenitors.

  16. Specialty magnets

    Halbach, K.

    1986-07-01

    A number of basic conceptual designs are explained for magnet systems that use permanent magnet materials. Included are iron free multipoles and hybrid magnets. Also appended is a discussion of the manufacturing process and magnetic properties of some permanent magnet materials

  17. Magnetic resonance imaging: effects of magnetic field strength

    Crooks, L.E.; Arakawa, M.; Hoenninger, J.; McCarten, B.; Watts, J.; Kaufman, L.

    1984-01-01

    Magnetic resonance images of the head, abdomen, and pelvis of normal adult men were obtained using varying magnetic field strength, and measurements of T1 and T2 relaxations and of signal-to-noise (SN) ratios were determined. For any one spin echo sequence, gray/white matter contrast decreases and muscle/fat contrast increases with field. SN levels rise rapidly up to 3.0 kgauss and then change more slowly, actually dropping for muscle. The optimum field for magnetic resonance imaging depends on tissue type, body part, and imaging sequence, so that it does not have a unique value. Magnetic resonance systems that operate in the 3.0-5.0 kgauss range achieve most or all of the gains that can be achieved by higher magnetic fields

  18. White coat hypertension in pediatrics.

    Jurko, Alexander; Minarik, Milan; Jurko, Tomas; Tonhajzerova, Ingrid

    2016-01-15

    The article summarizes current information on blood pressure changes in children during clinic visit. White coat as a general dressing of physicians and health care personnel has been widely accepted at the end of the 19th century. Two problems can be associated with the use of white coat: white coat phenomenon and white coat hypertension. Children often attribute pain and other unpleasant experience to the white coat and refuse afterwards cooperation with examinations. Definition of white coat hypertension in the literature is not uniform. It has been defined as elevated blood pressure in the hospital or clinic with normal blood pressure at home measured during the day by ambulatory blood pressure monitoring system. White coat effect is defined as temporary increase in blood pressure before and during visit in the clinic, regardless what the average daily ambulatory blood pressure values are. Clinical importance of white coat hypertension is mainly because of higher risk for cardiovascular accidents that are dependent on end organ damage (heart, vessels, kidney). Current data do not allow any clear recommendations for the treatment. Pharmacological therapy is usually started in the presence of hypertrophic left ventricle, changes in intimal/medial wall thickness of carotic arteries, microalbuminuria and other cardiovascular risk factors. Nonpharmacological therapy is less controversial and certainly more appropriate. Patients have to change their life style, need to eliminate as much cardiovascular risk factors as possible and sustain a regular blood pressure monitoring.

  19. Axion cooling of white dwarfs

    Isern, J.; Catalan, S.; Garcia--Berro, E.; Salaris, M.; Torres, S.

    2013-01-01

    The evolution of white dwarfs is a simple gravothermal process. This process can be tested in two ways, through the luminosity function of these stars and through the secular variation of the period of pulsation of those stars that are variable. Here we show how the mass of the axion can be constrained using the white dwarf luminosity function.

  20. Optical appearance of white holes

    Lake, K.; Roeder, R.C.

    1978-01-01

    The detailed optical properties of white holes are examined within the framework of geometrical optics. It is shown that the appearance of the objects most likely to be observed at late times is in fact determined by their early histories. These ccalculations indicate that one cannot invoke the simple concept of a stable white hole as a ''natural'' explanation of highly energetic astrophysical phenomena

  1. Recurrent novae as a consequence of the accretion of solar material onto a 1.38 M/sub sun/ white dwarf

    Starrfield, S.; Sparks, W.M.; Truran, J.W.; and Theoretical Division,Los Alamos National Laboratory)

    1985-01-01

    We have computed three evolutionary sequences which treat the accretion of hydrogen-rich material onto 1.38 M/sub sun/ white dwarfs. In each of these sequences the accreting matter had only a solar composition of the CNO nuclei (Z = 0.015). In the first sequence we utilized an accretion rate of 1.7 x 10/sup hyphen8/ M/sub sun/ yr/sup hyphen1/ onto a white dwarf with an initial luminosity of 0.1 L/sub sun/ . It took this sequence '33 yr to reach the peak of the thermonuclear runaway which resulted in an outburst that ejected 3x10/sup hyphen8/ M/sub sun/ . of material moving at speeds up to 2900 kn s/sup hyphen1/. The light curve, the time to outburst, and the amount of mass ejected during the evolution are in excellent agreement with the observed outburst of Nova U Sco 1979. However, only 6% of the accreted envelope was ejected during the outburst. The remaining material quickly burned to helium ('2 yr) and settled back onto the white dwarf. The second study involved an accretion rate of 1.7x10/sup hyphen9/ M/sub sun/ yr/sup hyphen1/ onto a white dwarf with an initial luminosity of 10/sup hyphen2/ L/sub sun/ . It took nearly 1600 yr to reach the burst phase of the evolution, and by this time the dwarf had accreted '3x10/sup hyphen6/ M/sub sun/ . Peak temperature in the shell source reached 3.5x10 8 K, about 1.3x10 8 K higher than was found for model 1. This sequence ejected 3x10/sup hyphen7/ M/sub sun/, only 13% of the accreted envelope, moving at low velocities. For both of these evolutionary sequences, we find that as a result of the accretion of matter onto a massive white dwarf, the mass of the white dwarf grows toward the Chandrasekhar limit. If our study is a realistic representation of the evolution of U Sco, then this star is well on its way to becoming an SN I

  2. The White Rabbit Project

    Serrano, J; Cattin, M; Garcia Cota, E; Lewis, J; Moreira, P; Wlostowski, T; Gaderer, G; Loschmidt, P; Dedic, J; Bär, R; Fleck, T; Kreider, M; Prados, C; Rauch, S

    2009-01-01

    Reliable, fast and deterministic transmission of control information in a network is a need formany distributed systems. One example is timing systems, where a reference frequency is used to accurately schedule time-critical messages. TheWhite Rabbit (WR) project is a multi-laboratory and multi-company effort to bring together the best of the data transfer and timing worlds in a completely open design. It takes advantage of the latest developments for improving timing over Ethernet, such as IEEE 1588 (Precision Time Protocol) and Synchronous Ethernet. The presented approach aims for a general purpose, fieldbus-like transmission system, which provides deterministic data and timing (sub-ns accuracy and ps jitter) to around 1000 stations. It automatically compensates for fiber lengths in the order of 10 km. This paper describes the WR design goals and the specification used for the project. It goes on to describe the central component of the WR system structure - the WR switch - with theoretical considerations a...

  3. Whiting in Lake Michigan

    2002-01-01

    Satellites provide a view from space of changes on the Earth's surface. This series of images from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) aboard the Orbview-2 satellite shows the dramatic change in the color of Lake Michigan during the summer. The bright color that appears in late summer is probably caused by calcium carbonate-chalk-in the water. Lake Michigan always has a lot of calcium carbonate in it because the floor of the lake is limestone. During most of the year the calcium carbonate remains dissolved in the cold water, but at the end of summer the lake warms up, lowering the solubility of calcium carbonate. As a result, the calcium carbonate precipitates out of the water, forming clouds of very small solid particles that appear as bright swirls from above. The phenomenon is appropriately called a whiting event. A similar event occured in 1999, but appears to have started later and subsided earlier. It is also possible that a bloom of the algae Microcystis is responsible for the color change, but unlikely because of Lake Michigan's depth and size. Microcystis blooms have occured in other lakes in the region, however. On the shore of the lake it is possible to see the cities of Chicago, Illinois, and Milwaukee, Wisconsin. Both appear as clusters of gray-brown pixels. Image courtesy the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  4. Physical sample structure as predictive factor in growth modeling of Listeria innocua in a white cheese model system

    Møller, Sandie M.; Bertram, Hanne C.; Andersen, Ulf

    2013-01-01

    Growth of Listeria innocua at 9 °C was investigated in white cheeses manufactured from ultra-filtrate milk concentrate added varying amounts of skimmed milk powder, NaCl and glucono-delta-lactone. Characterization of the white cheese structures was performed using nuclear magnetic resonance (NMR) T...

  5. Genetics Home Reference: white sponge nevus

    ... Twitter Home Health Conditions White sponge nevus White sponge nevus Printable PDF Open All Close All Enable ... to view the expand/collapse boxes. Description White sponge nevus is a condition characterized by the formation ...

  6. White matter connectivity and Internet gaming disorder

    Jeong, Bum Seok; Han, Doug Hyun; Kim, Sun Mi; Lee, Sang Won; Renshaw, Perry F.

    2017-01-01

    Internet use and on-line game play stimulate corticostriatal-limbic circuitry in both healthy subjects and subjects with Internet gaming disorder (IGD). We hypothesized that increased fractional anisotropy (FA) with decreased radial diffusivity (RD) would be observed in IGD subjects, compared with healthy control subjects, and that these white matter indices would be associated with clinical variables including duration of illness and executive function. We screened 181 male patients in order to recruit a large number (n = 58) of IGD subjects without psychiatric co-morbidity as well as 26 male healthy comparison subjects. Multiple diffusion-weighted images were acquired using a 3.0 Tesla magnetic resonance imaging scanner. Tract-based spatial statistics was applied to compare group differences in diffusion tensor imaging (DTI) metrics between IGD and healthy comparison subjects. IGD subjects had increased FA values within forceps minor, right anterior thalamic radiation, right corticospinal tract, right inferior longitudinal fasciculus, right cingulum to hippocampus and right inferior fronto-occipital fasciculus (IFOF) as well as parallel decreases in RD value within forceps minor, right anterior thalamic radiation and IFOF relative to healthy control subjects. In addition, the duration of illness in IGD subjects was positively correlated with the FA values (integrity of white matter fibers) and negatively correlated with RD scores (diffusivity of axonal density) of whole brain white matter. In IGD subjects without psychiatric co-morbidity, our DTI results suggest that increased myelination (increased FA and decreased RD values) in right-sided frontal fiber tracts may be the result of extended game play. PMID:25899390

  7. Y WHITE CHITWOOD

    Raquel Cervantes-Moreno

    2014-01-01

    Full Text Available Se determinó la tolerancia de 26 colectas de tomates nativos de México a Meloidogyne incongnita (Kofoid y White Chit- wood, con el fin de identificar aquellas con potencial para su empleo en el mejoramiento genético o como portainjertos. Para ello, plantas de 30 días de edad fueron establecidas en hidroponia bajo invernadero. Diez días después del trasplante (ddt fue aplicada al sustrato una solución con 100,000 huevecillos-larva por planta. Se registraron caracteres de la parte aérea de plantas y a los 210 ddt se cuantificó el desarrollo de poblaciones de nematodos en raíces. M. incognita disminuyó el diámetro de frutos y el porte de planta (altura al primer racimo, peso seco de tallo y número de nudos, e incrementó el número de frutos y flores. Además, redujo la longitud de raíces y aumentó el volumen de éstas por la formación de nó- dulos. Mediante análisis multivariados (agrupamiento y discriminante se definieron cinco grupos de colectas en función de la cantidad de agallas pequeñas y grandes, así como el total de éstas (82 % de variación y por la cantidad de larvas en raíz y huevecillos en sustrato (13 % de variación. Se identificaron tres colectas tolerantes con bajos índices de agallas y menor presencia de huevecillos-larva en raíz y en sustrato. Ocho colectas fueron moderadamente tolerantes; nueve, moderadamente susceptibles, y seis, susceptibles. No se detectaron asociaciones entre orígenes de colectas o forma de fruto con respecto a la tolerancia al nematodo.

  8. Structure and Evolution of Magnetic Cataclysmic Variables

    Andronov, I. L.

    2007-06-01

    Theoretical models and observational results are reviewed. The general picture of the structure and evolution of cataclysmic variables (CV) is presented, together with a brief discussion of additional mechanisms of intrinsic variability of the components and magnetic activity of secondaries. Special attention is paid to the accretion structures - flow, disk, column - which are affected by the magnetic field of the white dwarf. The mass and angular momentum transfer in asynchronous MCVs leads to a "propeller" stage of rapid synchronization, after which the "idlings" of the white dwarf are altered to "swingings" with a characteristic time of century(ies). The disk- magnetic field interaction leads to precession of the white dwarf, which causes quasi-periodic changes of the equilibrium rotational period. "Shot noise" in cataclysmic variables is discussed based on one-bandpass and multi-color observations.

  9. Magnetic Spinner

    Ouseph, P. J.

    2006-01-01

    A science toy sometimes called the "magnetic spinner" is an interesting class demonstration to illustrate the principles of magnetic levitation. It can also be used to demonstrate Faraday's law and a horizontally suspended physical pendulum. The levitated part contains two circular magnets encased in a plastic housing. Each magnet stays…

  10. White mold of Jerusalem artichoke

    Jerusalem artichoke (Helianthus tuberosus) is a Native American food plant closely related to the common sunflower (Helianthus annuus). Tubers of Jerusalem artichoke are increasingly available in retail grocery outlets. White mold (Sclerotinia stem rot), caused by the fungus, Sclerotinia sclerotioru...

  11. The White Adolescent's Drug Odyssey.

    Lipton, Douglas S.; Marel, Rozanne

    1980-01-01

    Presents a "typical" case history of a White middle-class teenager who becomes involved with marihuana and subsequently begins to abuse other drugs. Sociological findings from other research are interspersed in the anecdotal account. (GC)

  12. The odour of white bread

    Mulders, E.J.

    1973-01-01

    Volatile constituents of white bread were investigated. Different methods were used for isolating and concentrating components to avoid artefacts as far as possible. Especially good was enlarged vapour analysis. Ninety-four components were identified, including hydrocarbons, alcohols,

  13. Are hills like white elephants?

    Sunil Sharma

    2016-11-01

    Full Text Available 'Are Hills Like White Elephants?' is, of course, inspired by Hemingway; the tribute reflects on the abiding relevance of serious art in a changed world and extends the boundaries of his message to other human situations.

  14. Magnetic transients in flares

    Zirin, H.; Tanaka, K.

    1981-01-01

    We present data on magnetic transients (mgtr's) observed in flares on 1980 July 1 and 5 with Big Bear videomagnetograph (VMG). The 1980 July 1 event was a white light flare in which a strong bipolar mgtr was observed, and a definite change in the sunspots occurred at the time of the flare. In the 1980 July 5 flare, a mgtr was observed in only one polarity, and, although no sunspot changes occurred simultaneous with the flare, major spot changes occurred in a period of hours

  15. Does functional MRI detect activation in white matter? A review of emerging evidence, issues, and future directions

    Gawryluk, Jodie R.; Mazerolle, Erin L.; D'Arcy, Ryan C. N.

    2014-01-01

    Functional magnetic resonance imaging (fMRI) is a non-invasive technique that allows for visualization of activated brain regions. Until recently, fMRI studies have focused on gray matter. There are two main reasons white matter fMRI remains controversial: (1) the blood oxygen level dependent (BOLD) fMRI signal depends on cerebral blood flow and volume, which are lower in white matter than gray matter and (2) fMRI signal has been associated with post-synaptic potentials (mainly localized in gray matter) as opposed to action potentials (the primary type of neural activity in white matter). Despite these observations, there is no direct evidence against measuring fMRI activation in white matter and reports of fMRI activation in white matter continue to increase. The questions underlying white matter fMRI activation are important. White matter fMRI activation has the potential to greatly expand the breadth of brain connectivity research, as well as improve the assessment and diagnosis of white matter and connectivity disorders. The current review provides an overview of the motivation to investigate white matter fMRI activation, as well as the published evidence of this phenomenon. We speculate on possible neurophysiologic bases of white matter fMRI signals, and discuss potential explanations for why reports of white matter fMRI activation are relatively scarce. We end with a discussion of future basic and clinical research directions in the study of white matter fMRI. PMID:25152709

  16. White dwarfs in cataclysmic variables

    Sion, E.M.

    1987-01-01

    The physical properties and evolutionary state of the underlying white dwarfs in CVs are explored. Observations of 25 white dwarfs with effective temperature upper limits of 9000-75,000 K are discussed. Correlations between effective temperature, orbital period, accretion rate, and CV type with respect to the CV period gap are considered. Quasi-static and hydrodynamic evolutionary models are used to explain the surface temperature/luminosity distribution ratios. 42 references

  17. Evolution of White Dwarf Stars

    L. G. Althaus

    2001-01-01

    This paper is aimed at presenting the main results we have obtained for the study of the evoution of white dwarf stars. The calculations are carried out by means of a detailed evolutionary code based on an updated physical description. In particular, we briefly discuss the results for the evolution of white dwarfs of different stellar masses and chemical composition, and the evolution of whit e dwarfs in the framework of a varying gravitational constant G scenario as well.

  18. Economists and White House Decisions

    Stuart E. Eizenstat

    1992-01-01

    While I served in the White House, [as Assistant to the President for Domestic Affairs and Policy and Executive Director of the White House Domestic Policy Staff from 1977-81], Ph.D. economists occupied the positions of Secretary of Labor, Secretary of Commerce, Secretary of Treasury, Director of the Council on Wage and Price Stability, the President's anti-inflation adviser, Chairman and Council Members of the Council of Economic Advisers, and many other senior positions throughout the gover...

  19. The mouthfeel of white wine.

    Gawel, Richard; Smith, Paul A; Cicerale, Sara; Keast, Russell

    2017-07-05

    White wine mouthfeel which encompasses the tactile, chemosensory and taste attributes of perceived viscosity, astringency, hotness and bitterness is increasingly being recognized as an important component of overall white wine quality. This review summarizes the physiological basis for the perception of white wine mouthfeel and the direct and interactive effects of white wine composition, specifically those of low molecular weight phenolic compounds, polysaccharides, pH, ethanol, glycerol, dissolved carbon dioxide, and peptides. Ethyl alcohol concentration and pH play a direct role in determining most aspects of mouthfeel perception, and provide an overall framework on which the other minor wine components can interact to influence white wine mouthfeel. Phenolic compounds broadly impact on the mouthfeel by contributing to its viscosity, astringency, hotness and bitterness. Their breadth of influence likely results from their structural diversity which would allow them to activate multiple sensory mechanisms involved in mouthfeel perception. Conversely, polysaccharides have a small modulating effect on astringency and hotness perception, and glycerol does not affect perceived viscosity within the narrow concentration range found in white wine. Many of the major sensory attributes that contribute to the overall impression of mouthfeel are elicited by more than one class compound suggesting that different physiological mechanisms may be involved in the construct of mouthfeel percepts.

  20. Magnetic skyrmions

    2018-06-01

    Welcome to the special issue of Journal of Magnetism and Magnetic Materials on magnetic skyrmions. We are proud to present, with great pleasure, a timely collection of 9 original research articles on the recent hot topic "magnetic skyrmions" which studies the static and dynamic properties of skyrmions and the methods to control them in a variety of ways, including magnetic field, electric current and applied strain.

  1. Let's Talk about Race, Baby: How a White Professor Teaches White Students about White Privilege and Racism

    Heinze, Peter

    2008-01-01

    There are a variety of methods by which the themes of White privilege and racism can be presented to White students. By using the concept of racial identity a continuum of racism can be considered. Furthermore, addressing White privilege and racism in the context of a multicultural psychology course allows White students to have a greater…

  2. Sorting white blood cells in microfabricated arrays

    Castelino, Judith Andrea Rose

    Fractionating white cells in microfabricated arrays presents the potential for detecting cells with abnormal adhesive or deformation properties. A possible application is separating nucleated fetal red blood cells from maternal blood. Since fetal cells are nucleated, it is possible to extract genetic information about the fetus from them. Separating fetal cells from maternal blood would provide a low cost noninvasive prenatal diagnosis for genetic defects, which is not currently available. We present results showing that fetal cells penetrate further into our microfabricated arrays than adult cells, and that it is possible to enrich the fetal cell fraction using the arrays. We discuss modifications to the array which would result in further enrichment. Fetal cells are less adhesive and more deformable than adult white cells. To determine which properties limit penetration, we compared the penetration of granulocytes and lymphocytes in arrays with different etch depths, constriction size, constriction frequency, and with different amounts of metabolic activity. The penetration of lymphocytes and granulocytes into constrained and unconstrained arrays differed qualitatively. In constrained arrays, the cells were activated by repeated shearing, and the number of cells stuck as a function of distance fell superexponentially. In unconstrained arrays the number of cells stuck fell slower than an exponential. We attribute this result to different subpopulations of cells with different sticking parameters. We determined that penetration in unconstrained arrays was limited by metabolic processes, and that when metabolic activity was reduced penetration was limited by deformability. Fetal cells also contain a different form of hemoglobin with a higher oxygen affinity than adult hemoglobin. Deoxygenated cells are paramagnetic and are attracted to high magnetic field gradients. We describe a device which can separate cells using 10 μm magnetic wires to deflect the paramagnetic

  3. Radio and white-light observations of coronal transients

    Dulk, G. A.

    1980-01-01

    Optical, radio and X-ray evidence of violent mass motions in the corona has existed for some years but only recently have the form, nature, frequency and implication of the transients become obvious. In this paper the observed properties of coronal transients are reviewed, with concentration on the white-light and radio manifestations. The classification according to speeds seems to be meaningful, with the slow transients having thermal emissions at radio wavelengths and the fast ones nonthermal. The possible mechanisms involved in the radio bursts are then discussed and estimates of various forms of energy are reviewed. It appears that the magnetic energy transported from the sun by the transient exceeds that of any other form, and that magnetic forces dominate in the dynamics of the motions. The conversion of magnetic energy into mechanical energy, by expansion of the field, provides a possible driving force for the coronal and interplanetary shock waves.

  4. Radio and white-light observations of coronal transients

    Dulk, G.A.

    1980-01-01

    Optical, radio and X-ray evidence of violent mass motions in the corona has existed for some years but only recently have the form, nature, frequency and implication of the transients become obvious. The author reviews the observed properties of coronal transients, concentrating on the white-light and radio manifestations. The classification according to speeds seems to be meaningful, with the slow transients having thermal emissions at radio wavelengths and the fast ones non-thermal. The possible mechanisms involved in the radio bursts are discussed and the estimates of various forms of energy are reviewed. It appears that the magnetic energy transported from the Sun by the transient exceeds that of any other form, and that magnetic forces dominate in the dynamics of the motions. The conversion of magnetic energy into mechanical energy, by expansion of the fields, provides a possible driving force for the coronal and interplanetary shock waves. (Auth.)

  5. Digging of 'Snow White' Begins

    2008-01-01

    NASA's Phoenix Mars Lander began excavating a new trench, dubbed 'Snow White,' in a patch of Martian soil located near the center of a polygonal surface feature, nicknamed 'Cheshire Cat.' The trench is about 2 centimeters (.8 inches) deep and 30 centimeters (about 12 inches) long. The 'dump pile' is located at the top of the trench, the side farthest away from the lander, and has been dubbed 'Croquet Ground.' The digging site has been named 'Wonderland.' At this early stage of digging, the Phoenix team did not expect to find any of the white material seen in the first trench, now called 'Dodo-Goldilocks.' That trench showed white material at a depth of about 5 centimeters (2 inches). More digging of Snow White is planned for coming sols, or Martian days. The dark portion of this image is the shadow of the lander's solar panel; the bright areas within this region are not in shadow. Snow White was dug on Sol 22 (June 17, 2008) with Phoenix's Robotic Arm. This picture was acquired on the same day by the lander's Surface Stereo Imager. This image has been enhanced to brighten shaded areas. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  6. Medial frontal white and gray matter contributions to general intelligence.

    Toshiyuki Ohtani

    Full Text Available The medial orbitofrontal cortex (mOFC and rostral anterior cingulate cortex (rACC are part of a wider neural network that plays an important role in general intelligence and executive function. We used structural brain imaging to quantify magnetic resonance gray matter volume and diffusion tensor white matter integrity of the mOFC-rACC network in 26 healthy participants who also completed neuropsychological tests of intellectual abilities and executive function. Stochastic tractography, the most effective Diffusion Tensor Imaging method for examining white matter connections between adjacent gray matter regions, was employed to assess the integrity of mOFC-rACC pathways. Fractional anisotropy (FA, which reflects the integrity of white matter connections, was calculated. Results indicated that higher intelligence correlated with greater gray matter volumes for both mOFC and rACC, as well as with increased FA for left posterior mOFC-rACC connectivity. Hierarchical regression analyses revealed that DTI-derived FA of left posterior mOFC-rACC uniquely accounted for 29%-34% of the variance in IQ, in comparison to 11%-16% uniquely explained by gray matter volume of the left rACC. Together, left rACC gray matter volume and white matter connectivity between left posterior mOFC and rACC accounted for up to 50% of the variance in general intelligence. This study is to our knowledge the first to examine white matter connectivity between OFC and ACC, two gray matter regions of interests that are very close in physical proximity, and underscores the important independent contributions of variations in rACC gray matter volume and mOFC-rACC white matter connectivity to individual differences in general intelligence.

  7. Superconducting Magnets

    CERN. Geneva

    2008-01-01

    Starting from the beam requirements for accelerator magnets, we will outline the main issues and the physical limitations for producing strong and pure magnetic fields with superconductors. The seminar will mainly focus on the magnets for the accelerator, and give some hints on the magnets for the experiments. Prerequisite knowledge: Basic knowledge of Maxwell equations, and linear optics for particle accelerators (FODO cell, beta functions).

  8. Magnetic strings

    Chaves, Max

    2006-01-01

    The conception of the magnetic string is presented as an infinitely thin bundle of magnetic flux lines. The magnetic strings are surrounded by a film of current that rotates around them, and are a solution of Maxwell's equations. The magnetic potential contains a line singularity, and its stability can be established topologically. A few comments are added on the possibility that they may exist at a cosmological scale as relics of the Big Bang. (author) [es

  9. Magnetic Materials

    Spaldin, Nicola A.

    2003-04-01

    Magnetic materials are the foundation of multi-billion dollar industries and the focus of intensive research across many disciplines. This book covers the fundamentals, basic theories and applications of magnetism and conventional magnetic materials. Based on a lecture course given by Nicola Spaldin in the Materials Department at University of California, Santa Barbara, the book is ideal for a one- semester course in magnetic materials. It contains numerous homework problems and solutions.

  10. Theory of Disk Accretion onto Magnetic Stars

    Lai Dong

    2014-01-01

    Full Text Available Disk accretion onto magnetic stars occurs in a variety of systems, including accreting neutron stars (with both high and low magnetic fields, white dwarfs, and protostars. We review some of the key physical processes in magnetosphere-disk interaction, highlighting the theoretical uncertainties. We also discuss some applications to the observations of accreting neutron star and protostellar systems, as well as possible connections to protoplanetary disks and exoplanets.

  11. Social imaginaries, sperm and whiteness

    Andreassen, Rikke

    2017-01-01

    media coverage of these new families, this article explores contemporary constructions of race, especially whiteness, and gender, and shows how imaginaries of Vikings, genes and white superiority circulate in British media and among British mothers. The article illustrates how a racial discourse, which......This article analyses narratives about so-called Viking babies and Viking sperm. Over the last few years an increasing number of British single women and lesbian couples have been creating families by becoming pregnant with Danish donor sperm, termed ‘Viking sperm’. Through analyses of British...

  12. Blanco White and Walter Scott Blanco white y Walter Scott

    Fernando DURÁN LÓPEZ

    2011-01-01

    Full Text Available The first edition of Ivanhoe; a romance. By the author of Waverley was published in Edinburgh in 1820. From the beginning of year 1823, José María Blanco White translated several excerpts from Ivanhoe in the numbers 1-3 of the magazine Variedades, owned by the publisher Rudolph Ackermann. in these articles and other later writings, the translator praised Scott as a model for a new way of painting history in a narrative. This paper studies his ideas on Scott’s historical novel, as well as his translation technique, compared with that of José Joaquín de Mora. En 1820 se publicó en Edimburgo la primera edición de Ivanhoe; a romance. By the author of Waverley. Desde comienzos de 1823, en los tres primeros números de su revista Variedades, promovida por el editor Rudolph Ackermann, José María Blanco White tradujo varios fragmentos de Ivanhoe entre grandes elogios. Asimismo, Blanco White tomó a Scott como modelo de referencia de una nueva manera de pintar la historia por medio de la novela en otros varios escritos críticos de años posteriores. El artículo estudia las ideas de Blanco White acerca de la novela histórica de Scott y su técnica como traductor, comparada con la de José Joaquín Mora.

  13. Working through Whiteness: White, Male College Students Challenging Racism

    Cabrera, Nolan L.

    2012-01-01

    This qualitative study relies on Freire's conception of liberatory praxis to examine White male college students' becoming aware of racism and translating awareness into action. The participants developed racial cognizance via cross-racial contact and course content. They also tended to be open to interrogating racism and racial privilege due to…

  14. Superconducting magnets

    1994-08-01

    This report discusses the following topics on superconducting magnets: D19B and -C: The next steps for a record-setting magnet; D20: The push beyond 10 T: Beyond D20: Speculations on the 16-T regime; other advanced magnets for accelerators; spinoff applications; APC materials development; cable and cabling-machine development; and high-T c superconductor at low temperature

  15. Superconducting magnets

    Willen, E.

    1996-01-01

    Superconducting dipole magnets for high energy colliders are discussed. As an example, the magnets recently built for the Relativistic Heavy Ion Collider at Brookhaven are reviewed. Their technical performance and the cost for the industry-built production dipoles are given. The cost data is generalized in order to extrapolate the cost of magnets for a new machine

  16. A Dark Spot on a Massive White Dwarf

    Kilic, Mukremin; Gianninas, Alexandros; Bell, Keaton J.; Curd, Brandon; Brown, Warren R.; Hermes, J. J.; Dufour, Patrick; Wisniewski, John P.; Winget, D. E.; Winget, K. I.

    2015-12-01

    We present the serendipitous discovery of eclipse-like events around the massive white dwarf SDSS J152934.98+292801.9 (hereafter J1529+2928). We selected J1529+2928 for time-series photometry based on its spectroscopic temperature and surface gravity, which place it near the ZZ Ceti instability strip. Instead of pulsations, we detect photometric dips from this white dwarf every 38 minutes. Follow-up optical spectroscopy observations with Gemini reveal no significant radial velocity variations, ruling out stellar and brown dwarf companions. A disintegrating planet around this white dwarf cannot explain the observed light curves in different filters. Given the short period, the source of the photometric dips must be a dark spot that comes into view every 38 minutes due to the rotation of the white dwarf. Our optical spectroscopy does not show any evidence of Zeeman splitting of the Balmer lines, limiting the magnetic field strength to B Tecnologia e Inovação (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).

  17. White Matter Volume Predicts Language Development in Congenital Heart Disease.

    Rollins, Caitlin K; Asaro, Lisa A; Akhondi-Asl, Alireza; Kussman, Barry D; Rivkin, Michael J; Bellinger, David C; Warfield, Simon K; Wypij, David; Newburger, Jane W; Soul, Janet S

    2017-02-01

    To determine whether brain volume is reduced at 1 year of age and whether these volumes are associated with neurodevelopment in biventricular congenital heart disease (CHD) repaired in infancy. Infants with biventricular CHD (n = 48) underwent brain magnetic resonance imaging (MRI) and neurodevelopmental testing with the Bayley Scales of Infant Development-II and the MacArthur-Bates Communicative Development Inventories at 1 year of age. A multitemplate based probabilistic segmentation algorithm was applied to volumetric MRI data. We compared volumes with those of 13 healthy control infants of comparable ages. In the group with CHD, we measured Spearman correlations between neurodevelopmental outcomes and the residuals from linear regression of the volumes on corrected chronological age at MRI and sex. Compared with controls, infants with CHD had reductions of 54 mL in total brain (P = .009), 40 mL in cerebral white matter (P Development-II scores but did correlate positively with MacArthur-Bates Communicative Development Inventory language development. Infants with biventricular CHD show total brain volume reductions at 1 year of age, driven by differences in cerebral white matter. White matter volume correlates with language development, but not broader developmental indices. These findings suggest that abnormalities in white matter development detected months after corrective heart surgery may contribute to language impairment. ClinicalTrials.gov: NCT00006183. Copyright © 2016 Elsevier Inc. All rights reserved.

  18. Rotation of White Dwarf Stars

    Kawaler, Steven D.

    2014-01-01

    I discuss and consider the status of observational determinations of the rotation velocities of white dwarf stars via asteroseismology and spectroscopy. While these observations have important implications on our understanding of the angular momentum evolution of stars in their late stages of evolution, more direct methods are sorely needed to disentangle ambiguities.

  19. White LED motorcycle headlamp design

    Sun, Wen-Shing

    2015-09-01

    The motorcycle headlamp is composed of a white LED module, an elliptical reflector, a parabolic reflector and a toric lens. We use non-sequential ray to improve the optical efficiency of the compound reflectors. Using the toric lens can meet ECE_113 regulation and obtain a good uniformity.

  20. The Next White (NEW) Detector

    Monrabal, F.; et al.

    2018-04-06

    Conceived to host 5 kg of xenon at a pressure of 15 bar in the fiducial volume, the NEXT- White (NEW) apparatus is currently the largest high pressure xenon gas TPC using electroluminescent amplification in the world. It is also a 1:2 scale model of the NEXT-100 detector scheduled to start searching for $\\beta\\beta 0\

  1. One-Dimensionality and Whiteness

    Calderon, Dolores

    2006-01-01

    This article is a theoretical discussion that links Marcuse's concept of one-dimensional society and the Great Refusal with critical race theory in order to achieve a more robust interrogation of whiteness. The author argues that in the context of the United States, the one-dimensionality that Marcuse condemns in "One-Dimensional Man" is best…

  2. White adipose tissue: Getting nervous

    Fliers, E.; Kreier, F.; Voshol, P. J.; Havekes, L. M.; Sauerwein, H. P.; Kalsbeek, A.; Buijs, R. M.; Romijn, J. A.

    2003-01-01

    Neuroendocrine research has altered the traditional perspective of white adipose tissue (WAT) as a passive store of triglycerides. In addition to fatty acids, WAT produces many hormones and can therefore be designated as a traditional endocrine gland actively participating in the integrative

  3. The Whiteness of Climate Change

    Jensen, Lars

    2011-01-01

    This article examines two major debates in contemporary Australian discourses on the nation: climate change and whiteness studies. It is primarily concerned with establishing a framework for connecting the two discourses, and in that process it raises pivotal questions about how narratives about...

  4. Shale Gas Technology. White Paper

    NONE

    2011-09-15

    Shale gas is extracted using horizontal drilling and hydraulic fracturing or 'fracking'. None of which are particularly new technologies or shale gas specific. In this white paper attention is paid to Horizontal drilling; Hydraulic fracturing or 'frackin'; Other 'unconventionals'; and Costs.

  5. Shale Gas Technology. White Paper

    NONE

    2011-09-15

    Shale gas is extracted using horizontal drilling and hydraulic fracturing or 'fracking'. None of which are particularly new technologies or shale gas specific. In this white paper attention is paid to Horizontal drilling; Hydraulic fracturing or 'frackin'; Other 'unconventionals'; and Costs.

  6. Arithmetic crystal classes of magnetic symmetries

    Angelova, M.N.; Boyle, L.L.

    1993-01-01

    The symmetries and properties of a broad class of magnetic crystals are described by magnetic space groups which contain both (unitary) spatial symmetry operations and their combinations with the (anti-unitary operation of) time inversion, 0. The spatial symmetry operations form a halving, non-magnetic, space group H of the magnetic group M such that M=H+aH. As an abstract group the magnetic group M is isomorphic to a non-magnetic group G. The anti-unitary operator a is simply the time inversion 0 when M is a grey group but a product of time inversion with some spatial operation belonging to the coset G-H when M is a black-and-white group. (Author)

  7. Occipital deep white matter hyperintensity as seen by MRI, 1

    Miyazaki, Masahito; Hashimoto, Toshiaki; Tayama, Masanobu; Kuroda, Yasuhiro

    1992-01-01

    Magnetic resonance imaging was performed in 270 patients with various neurologic complaints (1-15Y) with a 0.5 tesla superconducting imaging system using a field echo T1-weighted sequence and spin echo T2-weighted and PD-weighted sequences. Twenty-seven of them had deep white matter hyperintensity (DWMH) in the occipital lobe on T2-weighted images. The frequency of mild DWMH differed in different age groups, suggesting that mild DWMH may result from delayed myelination in the central nervous system. However, the frequency of severe DWMH, which was revealed as isointense relative to cerebrospinal fluid, did not differ in different age groups and it was significantly more common in severely retarded patients. Classification of DWMH based on the signal intensity is valuable to distinguish white matter abnormalities in the occipital lobe from delayed myelination in the same site. (author)

  8. ABCD1 dysfunction alters white matter microvascular perfusion

    Lauer, Arne; Da, Xiao; Hansen, Mikkel Bo

    2017-01-01

    Cerebral X-linked adrenoleukodystrophy is a devastating neurodegenerative disorder caused by mutations in the ABCD1 gene, which lead to a rapidly progressive cerebral inflammatory demyelination in up to 60% of affected males. Selective brain endothelial dysfunction and increased permeability...... of the blood–brain barrier suggest that white matter microvascular dysfunction contributes to the conversion to cerebral disease. Applying a vascular model to conventional dynamic susceptibility contrast magnetic reson- ance perfusion imaging, we demonstrate that lack of ABCD1 function causes increased...... capillary flow heterogeneity in asymptom- atic hemizygotes predominantly in the white matter regions and developmental stages with the highest probability for conversion to cerebral disease. In subjects with ongoing inflammatory demyelination we observed a sequence of increased capillary flow hetero...

  9. Hydrogen-Rich, Multifunctional Polymeric Nanocomposites for Radiation Shielding, Phase II

    National Aeronautics and Space Administration — NASA has identified the need for development of technologies to support Lunar Lander and Lunar Habitats programs and for transfer of relevant technology to Crew...

  10. Hydrogen-Rich, Multifunctional Polymeric Nanocomposites for Radiation Shielding, Phase I

    National Aeronautics and Space Administration — NASA has identified the need for the development of lightweight structures technologies to support Lunar Lander and Lunar Habitats programs and for the transfer of...

  11. A massive hydrogen-rich Martian greenhouse recorded in D/H

    Pahlevan, K.; Schaefer, L. K.; Desch, S. J.; Elkins-Tanton, L. T.

    2017-12-01

    The deuterium-to-hydrogen (D/H) ratio in Martian atmospheric water ( 6x standard mean ocean water, SMOW) [1,2] is higher than that of known sources [3,4] alluding to a planetary enrichment process. A recent measurement by the Curiosity rover of Hesperian clays yields a D/H value 3x higher than SMOW [5], demonstrating that most enrichment occurred early in planetary history, buttressing the conclusions of Martian meteorite studies [6,7]. Extant models of the isotopic evolution of the Martian hydrosphere have not incorporated primordial H2, despite its likely abundance on early Mars. Here, we report the first 1D climate calculations with an atmospheric composition determined via degassing from a reducing magma ocean to study Martian climate during an early water ocean stage. A reducing Martian magma ocean is expected based on experimental petrology [8], the degassing of which gives rise to an H2-rich steam atmosphere [9] with strong attendant greenhouse warming [10,11] even after the removal of steam via condensation. At the pressures and temperatures prevailing in such a degassed greenhouse, we find that isotopic exchange in the fluid envelope is rapid, strongly concentrating deuterium in water molecules over molecular hydrogen [12]. The subsequent loss of the isotopically light H2-rich atmosphere results in a 2x D/H enrichment in the oceans via isotopic equilibration alone. These calculations suggest that most of the D/H enrichment observed in the first billion years of Martian history is produced by the evolution of a massive ( 100 bar) H2-rich greenhouse in the aftermath of magma ocean crystallization. The proposed link between early planetary process and modern isotopic observable opens a new window into the earliest history of Mars. [1] Owen, T. et al. Science 240, 1767-1770 (1988). [2] Webster, C. R. et al. Science 341, 260-263 (2013). [3] Lunine, J. I. et al. Icarus 165, 1-8, (2003). [4] Marty, B. et al. EPSL 441, 91-102, (2016). [5] Mahaffy, P. et al. Science 347, 412-414 (2015). [6] Greenwood, J. P. et al. GRL 35 (2008). [7] Boctor, N. et al. GCA 67, 3971-3989 (2003). [8] Zhang, H. L. et al. GCA 204, 83-103, (2017). [9] Hirschmann, M. M. EPSL 341-344, 48-57, (2012). [10] Wordsworth, R. Icarus 219, 267-273, (2012). [11] Pierrehumbert, R. & Gaidos, E. ApJL 734, L13 (2011). [12] Richet, P. et al. AREPS 5, 65-110, (1977).

  12. Formation of vacancy clusters in tungsten crystals under hydrogen-rich condition

    Kato, Daiji; Iwakiri, Hirotomo; Morishita, Kazunori

    2011-01-01

    Di-vacancy formation assisted by hydrogen trapping is studied in terms of nucleation free-energies evaluated with density functional theory. Calculations give binding energies for single hydrogen atom as first- and second-nearest-neighbor of di-vacancies of 1.80 and 2.15 eV, respectively, which are significantly larger than that for mono-vacancies. At elevated atomic concentrations of interstitial hydrogen atoms, evaluated nucleation free-energies indicate that the hydrogen assisted di-vacancy formation becomes more favorable. It is suggested that the formation would be preceded by VH cluster formation.

  13. First principle investigations of the physical properties of hydrogen-rich MgH2

    Zarshenas, Mohammed

    2013-11-28

    Hydrogen being a cleaner energy carrier has increased the importance of hydrogen-containing light metal hydrides, in particular those with large gravimetric hydrogen density like magnesium hydride (MgH2). In this study, density functional and density functional perturbation theories are combined to investigate the structural, elastic, thermodynamic, electronic and optical properties of MgH2. Our structural parameters calculated with those proposed by Perdew, Burke and Ernzerof generalized gradient approximation (PBE-GGA) and Wu-Cohen GGA (WC-GGA) are in agreement with experimental measurements, however the underestimated band gap values calculated using PBE-GGA and WC-GGA were greatly improved with the GGA suggested by Engle and Vosko and the modified Becke-Johnson exchange correlation potential by Trans and Blaha. As for the thermodynamic properties the specific heat values at low temperatures were found to obey the T3 rule and at higher temperatures Dulong and Petit\\'s law. Our analysis of the optical properties of MgH2 also points to its potential application in optoelectronics. © 2013 The Royal Swedish Academy of Sciences.

  14. Desulfurization and denitrogenation in copyrolysis of coal with hydrogen-rich gases

    Liao, H.; Li, B.; Zhang, B. [Chinese Academy of Sciences, Taiyuan (China). Institute of Coal Chemistry

    1999-06-01

    Desulfurization and denitrogenation were systematically investigated by analyzing the chars and tars from copyrolysis of Yanzhou high sulfur bituminous coal with coke-oven gas (COG), synthesis gas (SG) and hydrogen. The results indicated that under the conditions of 3MPa, up to 650{degree}C with a heating rate of 10{degree}C/min, the desulfurization of coal pyrolysis with COG, SG and hydrogen were almost equal (about 80%, w%, ad), the order of denitrogenation were: hydrogen (41%) {gt} SG(35%) {gt} COG(30%). The distributions of sulfur in char, oil and gas was very similar under the three reactive gases, i.e., about 205 in char, 105 in tar and 70% (diff.) in gas, respectively. Compared with hydropyrolysis at the same hydrogen partial pressure, the desulfurization of coal pyrolysis with coke oven gas was increased by about 4.5%, while the denitrogenation was decreased by about 3.5%. There is an important desulfurization advantage for hydropyrolysis using COG and SG instead of pure hydrogen. Compared with the copyrolysis of coal with COG, Yanzhou coal pyrolysis under SG can achieve the same level of desufurization but higher denitrogenation. 11 refs., 3 figs., 4 tabs.

  15. Characterizing the V-band light-curves of hydrogen-rich type II supernovae

    Anderson, Joseph P.; González-Gaitán, Santiago; Hamuy, Mario

    2014-01-01

    a dispersion of 0.56 mag, offering the prospect of using type II supernovae as purely photometric distance indicators. Our analysis suggests that the type II population spans a continuum from low-luminosity events which have flat light-curves during the "plateau" stage, through to the brightest events which...

  16. Formation of vacancy clusters in tungsten crystals under hydrogen-rich condition

    Kato, Daiji, E-mail: kato.daiji@nifs.ac.jp [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, Gifu 509-5292 (Japan); Iwakiri, Hirotomo, E-mail: iwakiri@edu.u-ryukyu.ac.jp [University of the Ryukyus, Okinawa 903-0213 (Japan); Morishita, Kazunori, E-mail: morishita@iae.kyoto-u.ac.jp [Institute of Advanced Energy, Kyoto University, Kyoto 611-0011 (Japan)

    2011-10-01

    Di-vacancy formation assisted by hydrogen trapping is studied in terms of nucleation free-energies evaluated with density functional theory. Calculations give binding energies for single hydrogen atom as first- and second-nearest-neighbor of di-vacancies of 1.80 and 2.15 eV, respectively, which are significantly larger than that for mono-vacancies. At elevated atomic concentrations of interstitial hydrogen atoms, evaluated nucleation free-energies indicate that the hydrogen assisted di-vacancy formation becomes more favorable. It is suggested that the formation would be preceded by VH cluster formation.

  17. First principle investigations of the physical properties of hydrogen-rich MgH2

    Zarshenas, Mohammed; Ahmed, Rashid; Kanoun, Mohammed; Ul Haq, Bakhtiar; Isa, Ahmad Radzi Mat; Goumri-Said, Souraya

    2013-01-01

    Hydrogen being a cleaner energy carrier has increased the importance of hydrogen-containing light metal hydrides, in particular those with large gravimetric hydrogen density like magnesium hydride (MgH2). In this study, density functional and density functional perturbation theories are combined to investigate the structural, elastic, thermodynamic, electronic and optical properties of MgH2. Our structural parameters calculated with those proposed by Perdew, Burke and Ernzerof generalized gradient approximation (PBE-GGA) and Wu-Cohen GGA (WC-GGA) are in agreement with experimental measurements, however the underestimated band gap values calculated using PBE-GGA and WC-GGA were greatly improved with the GGA suggested by Engle and Vosko and the modified Becke-Johnson exchange correlation potential by Trans and Blaha. As for the thermodynamic properties the specific heat values at low temperatures were found to obey the T3 rule and at higher temperatures Dulong and Petit's law. Our analysis of the optical properties of MgH2 also points to its potential application in optoelectronics. © 2013 The Royal Swedish Academy of Sciences.

  18. Mechanical test of E110 cladding material oxidized in hydrogen rich steam atmosphere

    Windberg, P.; Perez-Fero, E.

    2005-01-01

    The behavior of the fuel cladding under accidental conditions has been studied at the AEKI for more than a decade. Earlier, the effect of oxygen and hydrogen content on the mechanical properties was studied separately. The present experiments can help to understand what kind of processes took place in the cleaning tank at Paks NPP (2003). The purpose of our experiments was to investigate high temperature oxidation of E110 cladding in steam + hydrogen mixture. A high temperature tube furnace was used for oxidation of the samples. The oxidation was carried out at three different temperatures (900 0 C, 1000 0 C, 1100 0 C). The hydrogen content in the steam was varied between 19-36 vol%. The oxygen content of the sample was defined as oxidation ratio. Two sizes (length: 2 and 8 mm) of cladding rings and 100 mm long E110 cladding tubes were oxidized. After the oxidation we made compression and tensile tests for rings, and ballooning experiments for 100 mm long tube. The most important conclusions were the following. Oxidation in H-rich steam atmosphere need longer time to get the same oxidation ratio compared to the steam oxidation without hydrogen. The shorter oxidation time results in a more compact oxide layer. The longer oxidation time leads to a cracked oxide layer. (author)

  19. Catalytic Steam Reforming of Bio-Oil to Hydrogen Rich Gas

    Trane-Restrup, Rasmus

    heating value and high content of oxygen, which makes it unsuited for direct utilization in engines. One prospective technology for upgrading of bio-oil is steam reforming (SR), which can be used to produce H2 for upgrading of bio-oil through hydrodeoxygenation or synthesis gas for processes like......-oil. There are two main pathways to minimize carbon deposition in steam reforming; either through optimization of catalyst formulation or through changes to the process parameters, like changes in temperature, steam to carbon ratio (S/C), or adding O2 or H2 to the feed. In this thesis both pathways have been...

  20. A WHITE DWARF MERGER AS PROGENITOR OF THE ANOMALOUS X-RAY PULSAR 4U 0142+61?

    Rueda, J. A.; Boshkayev, K.; Izzo, L.; Ruffini, R.; Lorén-Aguilar, P.; Külebi, B.; Aznar-Siguán, G.; García-Berro, E.

    2013-01-01

    It has been recently proposed that massive, fast-rotating, highly magnetized white dwarfs could describe the observational properties of some of soft gamma-ray repeaters and anomalous X-ray pulsars (AXPs). Moreover, it has also been shown that high-field magnetic white dwarfs can be the outcome of white dwarf binary mergers. The products of these mergers consist of a hot central white dwarf surrounded by a rapidly rotating disk. Here we show that the merger of a double degenerate system can explain the characteristics of the peculiar AXP 4U 0142+61. This scenario accounts for the observed infrared excess. We also show that the observed properties of 4U 0142+6 are consistent with an approximately 1.2 M ☉ white dwarf, remnant of the coalescence of an original system made of two white dwarfs of masses 0.6 M ☉ and 1.0 M ☉ . Finally, we infer a post-merging age τ WD ≈ 64 kyr and a magnetic field B ≈ 2 × 10 8 G. Evidence for such a magnetic field may come from the possible detection of the electron cyclotron absorption feature observed between the B and V bands at ≈10 15 Hz in the spectrum of 4U 0142+61

  1. White matter injury in newborns with congenital heart disease: a diffusion tensor imaging study.

    Mulkey, Sarah B; Ou, Xiawei; Ramakrishnaiah, Raghu H; Glasier, Charles M; Swearingen, Christopher J; Melguizo, Maria S; Yap, Vivien L; Schmitz, Michael L; Bhutta, Adnan T

    2014-09-01

    Brain injury is observed on cranial magnetic resonance imaging preoperatively in up to 50% of newborns with congenital heart disease. Newer imaging techniques such as diffusion tensor imaging provide sensitive measures of the white matter integrity. The objective of this study was to evaluate the diffusion tensor imaging analysis technique of tract-based spatial statistics in newborns with congenital heart disease. Term newborns with congenital heart disease who would require surgery at less than 1 month of age were prospectively enrolled (n = 19). Infants underwent preoperative and postoperative brain magnetic resonance imaging with diffusion tensor imaging. Tract-based spatial statistics, an objective whole-brain diffusion tensor imaging analysis technique, was used to determine differences in white matter fractional anisotropy between infant groups. Term control infants were also compared with congenital heart disease infants. Postmenstrual age was equivalent between congenital heart disease infant groups and between congenital heart disease and control infants. Ten infants had preoperative brain injury, either infarct or white matter injury, by conventional brain magnetic resonance imaging. The technique of tract-based spatial statistics showed significantly lower fractional anisotropy (P tensor imaging analysis technique that may have better sensitivity in detecting white matter injury compared with conventional brain magnetic resonance imaging in term newborns with congenital heart disease. Copyright © 2014 Elsevier Inc. All rights reserved.

  2. White Matter Lesion Progression: Genome-Wide Search for Genetic Influences

    E. Hofer (Edith); M. Cavalieri (Margherita); J.C. Bis (Joshua); C. DeCarli (Charles); M. Fornage (Myriam); S. Sigurdsson (Sigurdur); V. Srikanth (Velandai); S. Trompet (Stella); B.F.J. Verhaaren (Benjamin); C. Wolf (Christiane); Q. Yang (Qiong Fang); H.H.H. Adams (Hieab); P. Amouyel (Philippe); A. Beiser (Alexa); B.M. Buckley (Brendan M.); M. Callisaya (Michele); G. Chauhan (Ganesh); A.J.M. De Craen (Anton J. M.); C. Dufouil (Carole); C.M. van Duijn (Cornelia); I. Ford; P. Freudenberger (Paul); R.F. Gottesman (Rebecca); V. Gudnason (Vilmundur); G. Heiss (Gerardo); A. Hofman (Albert); T. Lumley (Thomas); O. Martinez (Oliver); B. Mazoyer (Bernard); C. Moran (Chris); W.J. Niessen (Wiro); T.G. Phan (Thanh); B.M. Psaty (Bruce); C.L. Satizabal (Claudia L.); N. Sattar (Naveed); S. Schilling (Sabrina); D.K. Shibata (Dean); P.E. Slagboom (Eline); G.D. Smith; D.J. Stott (David. J.); K.D. Taylor (Kent); R. Thomson (Russell); A.M. Töglhofer (Anna Maria); C. Tzourio (Christophe); M.A. van Buchem (Mark); J. Wang (Jing); R.G.J. Westendorp (Rudi); B. Gwen Windham; M.W. Vernooij (Meike); A.P. Zijdenbos; R.J. Beare (Richard); S. Debette (Stéphanie); M.A. Ikram (Arfan); J.W. Jukema (Jan Wouter); L.J. Launer (Lenore); W.T. Longstreth Jr; T.H. Mosley (Thomas H.); S. Seshadri (Sudha); R. Schmidt (Reinhold); R. Schmidt (Reinhold)

    2015-01-01

    textabstractBackground and Purpose-White matter lesion (WML) progression on magnetic resonance imaging is related to cognitive decline and stroke, but its determinants besides baseline WML burden are largely unknown. Here, we estimated heritability of WML progression, and sought common genetic

  3. Determinants of cerebral white matter lesions: A longitudinal population based MRI study

    H.F. de Leeuw (Frank)

    1999-01-01

    textabstractW hite matter lesions are frequently found on cerebral magnetic resonance imaging scans of elderly non-demented and demented people. l-4 The pathogenesis of white matter lesions is largely unknown. However age and high diastolic and systolic blood pressure levels and indicators of

  4. Integrated analysis of gray and white matter alterations in attention-deficit/hyperactivity disorder

    Francx, W.C.; Llera, A.; Mennes, M.; Zwiers, M.P.; Faraone, S.V; Oosterlaan, J.; Heslenfeld, D.; Hoekstra, P.J.; Hartman, C.A.; Franke, B.; Buitelaar, J.K.; Beckmann, C.F.

    2016-01-01

    BACKGROUND: Magnetic resonance imaging (MRI) is able to provide detailed insights into the structural organization of the brain, e.g., by means of mapping brain anatomy and white matter microstructure. Understanding interrelations between MRI modalities, rather than mapping modalities in isolation,

  5. Integrated analysis of gray and white matter alterations in attention-deficit/hyperactivity disorder

    Francx, Winke; Llera, Alberto; Mennes, Maarten; Zwiers, Marcel P.; Faraone, Stephen V.; Oosterlaan, Jaap; Heslenfeld, Dirk; Hoekstra, Pieter J.; Hartman, Catharina A.; Franke, Barbara; Buitelaar, Jan K.; Beckmann, Christian F.

    2016-01-01

    Background: Magnetic resonance imaging (MRI) is able to provide detailed insights into the structural organization of the brain, e.g., by means of mapping brain anatomy and white matter microstructure. Understanding interrelations between MRI modalities, rather than mapping modalities in isolation,

  6. Risk factor analysis of cerebral white matter hyperintensities in children with sickle cell disease

    van der Land, Veronica; Mutsaerts, Henri J. M. M.; Engelen, Marc; Heijboer, Harriët; Roest, Mark; Hollestelle, Martine J.; Kuijpers, Taco W.; Nederkoorn, Paul J.; Cnossen, Marjon H.; Majoie, Charles B. L. M.; Nederveen, Aart J.; Fijnvandraat, Karin

    2016-01-01

    Sickle cell disease (SCD) is complicated by silent cerebral infarcts, visible as white matter hyperintensities (WMHs) on magnetic resonance imaging (MRI). Both local vaso-occlusion, elicited by endothelial dysfunction, and insufficiency of cerebral blood flow (CBF) have been proposed to be involved

  7. Black holes, white dwarfs and neutron stars: The physics of compact objects

    Shapiro, S.L.; Teukolsky, S.A.

    1983-01-01

    The contents include: Star deaths and the formation of compact objects; White dwarfs; Rotation and magnetic fields; Cold equation of state above neutron drip; Pulsars; Accretion onto black holes; Supermassive stars and black holes; Appendices; and Indexes. This book discusses one aspect, compact objects, of astronomy and provides information of astrophysics or general relativity

  8. Serum carotenoids and cerebral white matter lesions : The Rotterdam Scan Study

    den Heijer, T; Launer, LJ; de Groot, JG; de Leeuw, FE; Oudkerk, M; van Gijn, J; Hofman, A; Breteler, MMB

    OBJECTIVES: To study the relation between serum levels of carotenoids and white matter lesions (WMLs) on magnetic resonance imaging (MRI). DESIGN: Evaluation of cross-sectional data from a cohort study. SETTING: The Rotterdam Scan Study. PARTICIPANTS: Two hundred and three nondemented older persons,

  9. Central Nervous System Brucellosis Granuloma and White Matter Disease in Immunocompromised Patient.

    Alqwaifly, Mohammed; Al-Ajlan, Fahad S; Al-Hindi, Hindi; Al Semari, Abdulaziz

    2017-06-01

    Brucellosis is a multisystem zoonotic disease. We report an unusual case of neurobrucellosis with seizures in an immunocompromised patient in Saudi Arabia who underwent renal transplantation. Magnetic resonance imaging of the brain showed diffuse white matter lesions. Serum and cerebrospinal fluid were positive for Brucella sp. Granuloma was detected in a brain biopsy specimen.

  10. White Sturgeon Bibliography, 1985 Final Report.

    Fickeisen, Duane H. (Pacific Northwest National Laboratory, Richland, WA)

    1986-03-01

    This bibliography presents citations to the majority of published materials on white sturgeon (Acipenser transmontanus). The purpose was to assist in planning and implementing research on white sturgeon in the Columbia River system. (ACR)

  11. White Mango Scale, Aulacaspis tubercularis , Distribution and ...

    White Mango Scale, Aulacaspis tubercularis , Distribution and Severity Status in East and West Wollega Zones, ... Among the insect pests attacking mango plant, white mango scale is the most devastating insect pest. ... HOW TO USE AJOL.

  12. Low white blood cell count and cancer

    ... gov/ency/patientinstructions/000675.htm Low white blood cell count and cancer To use the sharing features on this page, please enable JavaScript. White blood cells (WBCs) fight infections from bacteria, viruses, fungi, and ...

  13. Magnetic Hysteresis

    Della Torre, Edward

    2000-01-01

    Understanding magnetic hysteresis is vitally important to the development of the science of magnetism as a whole and to the advancement of practical magnetic device applications. Magnetic Hysteresis, by acclaimed expert Edward Della Torre, presents a clear explanation of the connection between physical principles and phenomenological hysteresis. This comprehensive book offers a lucid analysis that enables the reader to save valuable time by reducing trial-and-error design. Dr. Della Torre uses physical principles to modify Preisach modeling and to describe the complex behavior of magnetic media. While Pretsach modeling is a useful mathematical tool, its congruency and deletion properties present limitations to accurate descriptions of magnetic materials. Step-by-step, this book describes the modifications that can overcome these limitations. Special attention is given to the use of feedback around a Preisach transducer to remove the congruency restriction, and to the use of accommodation and aftereffect model...

  14. Planetary Magnetism

    Connerney, J. E. P.

    2007-01-01

    The chapter on Planetary Magnetism by Connerney describes the magnetic fields of the planets, from Mercury to Neptune, including the large satellites (Moon, Ganymede) that have or once had active dynamos. The chapter describes the spacecraft missions and observations that, along with select remote observations, form the basis of our knowledge of planetary magnetic fields. Connerney describes the methods of analysis used to characterize planetary magnetic fields, and the models used to represent the main field (due to dynamo action in the planet's interior) and/or remnant magnetic fields locked in the planet's crust, where appropriate. These observations provide valuable insights into dynamo generation of magnetic fields, the structure and composition of planetary interiors, and the evolution of planets.

  15. Magnetic levitation

    Štěpánek,B.; Paleček,M.

    2015-01-01

    The paper deals with magnetism and its influence on superconducting materials. We describe the discovery and development of superconductivity, superconducting levitation and its use in future technology - called. MAGLEV speed trains. We show the interaction of the magnetic field of a strong neodymium magnet and high-temperature superconductor, cooled with liquid nitrogen at about -200 ° C. Of superconductors at this temperature becomes perfect diamagnetic material. That is ejected from the ma...

  16. Magnet Systems

    Federal Laboratory Consortium — Over the decades, Fermilab has been responsible for the design, construction, test and analysis of hundreds of conventional and superconducting accelerator magnets...

  17. Planetary Magnetism

    Russell, C.T.

    1980-01-01

    Planetary spacecraft have now probed the magnetic fields of all the terrestrial planets, the moon, Jupiter, and Saturn. These measurements reveal that dynamos are active in at least four of the planets, Mercury, the earth, Jupiter, and Saturn but that Venus and Mars appear to have at most only very weak planetary magnetic fields. The moon may have once possessed an internal dynamo, for the surface rocks are magnetized. The large satellites of the outer solar system are candidates for dynamo action in addition to the large planets themselves. Of these satellites the one most likely to generate its own internal magnetic field is Io

  18. Magnetics Processing

    Federal Laboratory Consortium — The Magnetics Processing Lab equipped to perform testing of magnetometers, integrate them into aircraft systems, and perform data analysis, including noise reduction...

  19. Explosive helium burning in white dwarf stars

    Khokhlov, A.M. (AN SSSR, Moscow. Astronomicheskij Sovet)

    1984-04-01

    Helium burning kinetics in white dwarfs has been considered at constant temperatures T >= 10/sup 9/ K and densities rho >10/sup 5/ g/cm/sup 3/. It is found, that helium detonation in white dwarfs does not lead to formation of light (A < 56) elements. Thus, helium white dwarf model for supernova 1 is inconsistent with observations.

  20. 21 CFR 163.124 - White chocolate.

    2010-04-01

    ... 21 Food and Drugs 2 2010-04-01 2010-04-01 false White chocolate. 163.124 Section 163.124 Food and... CONSUMPTION CACAO PRODUCTS Requirements for Specific Standardized Cacao Products § 163.124 White chocolate. (a) Description. (1) White chocolate is the solid or semiplastic food prepared by intimately mixing and grinding...

  1. Multiculturalism, Teaching Slavery, and White Supremacy

    Bery, Sadhana

    2014-01-01

    This article argues that multiculturalism, especially when it is led and controlled by Whites, and in the absence of collective anti-racist struggles, can reproduce the ontologies, epistemologies, and practices of white supremacy. I use a case study of a reenactment of Atlantic black slavery, produced by white teachers to investigate whether…

  2. White noise excitation in a hot plasma

    Ito, Masataka

    1977-01-01

    In a low frequency range, a property of white noise in a hot plasma is studied experimentally. A frequency component of white noise is observed to propagate with a phase velocity which is equal to the ion accoustic wave velocity. The white noise, which is launched in a plasma, is considered as the sum of ion acoustic waves. (auth.)

  3. Static speckle experiments using white synchrotron radiation

    Sant, Tushar; Panzner, Tobias; Pietsch, Ullrich [Solid State Physics Group, University of Siegen (Germany)

    2008-07-01

    Static speckle experiments were performed using coherent white X-ray radiation from a bending magnet at BESSYII. Semiconductor and polymer surfaces were investigated under incidence condition smaller than the critical angle of total external reflection. The scattering pattern of the sample results from the illumination function modified by the surface undulations. The periodic oscillations are caused by the illumination function whereas other irregular features are associated with sample surface. The speckle map of reflection from a laterally periodic structure like GaAs grating is studied. Under coherent illumination the grating peaks split into speckles because of fluctuations on the sample surface. It is important to understand which length scales on the sample surface are responsible for the oscillations in reflectivity map. To investigate this experiments are done with a triangular shaped sample. Different parts of the sample are illuminated with the footprint on the sample larger or smaller than the actual sample length. This gives prior information about total illuminated area on the sample. Using this additional information a detailed surface profile of the sample is reconstructed.

  4. Branes constrictions with White Dwarfs

    Garcia-Aspeitia, Miguel A. [Consejo Nacional de Ciencia y Tecnologia, Mexico (Mexico); Unidad Academica de Fisica, Universidad Autonoma de Zacatecas (Mexico)

    2015-11-15

    We consider here a robust study of stellar dynamics for white dwarf stars with polytropic matter in the weak-field approximation using the Lane-Emden equation from the brane-world scenario. We also derive an analytical solution to the nonlocal energy density and show the behavior and sensitivity of these stars to the presence of extra dimensions. Similarly, we analyze stability and compactness, in order to show whether it is possible to agree with the conventional wisdom of white dwarfs dynamics. Our results predict an average value of the brane tension of left angle λ right angle >or similar 84.818 MeV{sup 4}, with a standard deviation σ ≅ 82.021 MeV{sup 4}, which comes from a sample of dwarf stars, being weaker than other astrophysical observations but remaining higher than cosmological results provided by nucleosynthesis among others. (orig.)

  5. Branes constrictions with White Dwarfs

    García-Aspeitia, Miguel A., E-mail: aspeitia@fisica.uaz.edu.mx [Consejo Nacional de Ciencia y Tecnología, Av, Insurgentes Sur 1582, Colonia Crédito Constructor, Del. Benito Juárez, C.P. 03940, Mexico, D.F. (Mexico); Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad esquina con Paseo a la Bufa S/N, C.P. 98060, Zacatecas (Mexico)

    2015-11-06

    We consider here a robust study of stellar dynamics for white dwarf stars with polytropic matter in the weak-field approximation using the Lane–Emden equation from the brane-world scenario. We also derive an analytical solution to the nonlocal energy density and show the behavior and sensitivity of these stars to the presence of extra dimensions. Similarly, we analyze stability and compactness, in order to show whether it is possible to agree with the conventional wisdom of white dwarfs dynamics. Our results predict an average value of the brane tension of <λ>≳84.818 MeV{sup 4}, with a standard deviation σ≃82.021 MeV{sup 4}, which comes from a sample of dwarf stars, being weaker than other astrophysical observations but remaining higher than cosmological results provided by nucleosynthesis among others.

  6. Branes constrictions with White Dwarfs

    García-Aspeitia, Miguel A.

    2015-01-01

    We consider here a robust study of stellar dynamics for white dwarf stars with polytropic matter in the weak-field approximation using the Lane–Emden equation from the brane-world scenario. We also derive an analytical solution to the nonlocal energy density and show the behavior and sensitivity of these stars to the presence of extra dimensions. Similarly, we analyze stability and compactness, in order to show whether it is possible to agree with the conventional wisdom of white dwarfs dynamics. Our results predict an average value of the brane tension of <λ>≳84.818 MeV 4 , with a standard deviation σ≃82.021 MeV 4 , which comes from a sample of dwarf stars, being weaker than other astrophysical observations but remaining higher than cosmological results provided by nucleosynthesis among others

  7. Raman spectroscopy of white wines.

    Martin, Coralie; Bruneel, Jean-Luc; Guyon, François; Médina, Bernard; Jourdes, Michael; Teissedre, Pierre-Louis; Guillaume, François

    2015-08-15

    The feasibility of exploiting Raman scattering to analyze white wines has been investigated using 3 different wavelengths of the incoming laser radiation in the near-UV (325 nm), visible (532 nm) and near infrared (785 nm). To help in the interpretation of the Raman spectra, the absorption properties in the UV-visible range of two wine samples as well as their laser induced fluorescence have also been investigated. Thanks to the strong intensity enhancement of the Raman scattered light due to electronic resonance with 325 nm laser excitation, hydroxycinnamic acids may be detected and analyzed selectively. Fructose and glucose may also be easily detected below ca. 1000 cm(-1). This feasibility study demonstrates the potential of the Raman spectroscopic technique for the analysis of white wines. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. White Nights rebuts Pravda claims

    Anon.

    1992-01-01

    This paper reports that another Russo-foreign joint venture under attack in the Moscow press has denied charges of impropriety and mismanagement in its operations. The White Nights joint venture last month came under scathing attack from Moscow newspaper Pravda, which alleged the venture has reneged on its promises, is virtually bankrupt, and mistreats Russian employees. White Nights is a joint venture owned 50% by Varyeganneftegaz (VNG), a Russian oil and gas enterprise, and 50% by Salomon Inc. unit Phibro Energy Inc., Greenwich, Conn., and Anglo-Suisse (U.S.S.R.) Ltd., a subsidiary of Anglo-Suisse Inc., Houston. The venture started operations Apr. 1, 1991, with a program of workovers, redevelopment, and horizontal wells in West Varyegan and Tagrinsk oil fields in western Siberia

  9. Broad spectrum of neuropsychiatric phenotypes associated with white matter disease in PTEN hamartoma tumor syndrome.

    Balci, Tugce B; Davila, Jorge; Lewis, Denice; Boafo, Addo; Sell, Erick; Richer, Julie; Nikkel, Sarah M; Armour, Christine M; Tomiak, Eva; Lines, Matthew A; Sawyer, Sarah L

    2018-01-01

    White matter lesions have been described in patients with PTEN hamartoma tumor syndrome (PHTS). How these lesions correlate with the neurocognitive features associated with PTEN mutations, such as autism spectrum disorder (ASD) or developmental delay, has not been well established. We report nine patients with PTEN mutations and white matter changes on brain magnetic resonance imaging (MRI), eight of whom were referred for reasons other than developmental delay or ASD. Their clinical presentations ranged from asymptomatic macrocephaly with normal development/intellect, to obsessive compulsive disorder, and debilitating neurological disease. To our knowledge, this report constitutes the first detailed description of PTEN-related white matter changes in adult patients and in children with normal development and intelligence. We present a detailed assessment of the neuropsychological phenotype of our patients and discuss the relationship between the wide array of neuropsychiatric features and observed white matter findings in the context of these individuals. © 2017 Wiley Periodicals, Inc.

  10. White matter damage is related to ataxia severity in SCA3.

    Kang, J-S; Klein, J C; Baudrexel, S; Deichmann, R; Nolte, D; Hilker, R

    2014-02-01

    Spinocerebellar ataxia type 3 (SCA3) is the most frequent inherited cerebellar ataxia in Europe, the US and Japan, leading to disability and death through motor complications. Although the affected protein ataxin-3 is found ubiquitously in the brain, grey matter atrophy is predominant in the cerebellum and the brainstem. White matter pathology is generally less severe and thought to occur in the brainstem, spinal cord, and cerebellar white matter. Here, we investigated both grey and white matter pathology in a group of 12 SCA3 patients and matched controls. We used voxel-based morphometry for analysis of tissue loss, and tract-based spatial statistics (TBSS) on diffusion magnetic resonance imaging to investigate microstructural pathology. We analysed correlations between microstructural properties of the brain and ataxia severity, as measured by the Scale for the Assessment and Rating of Ataxia (SARA) score. SCA3 patients exhibited significant loss of both grey and white matter in the cerebellar hemispheres, brainstem including pons and in lateral thalamus. On between-group analysis, TBSS detected widespread microstructural white matter pathology in the cerebellum, brainstem, and bilaterally in thalamus and the cerebral hemispheres. Furthermore, fractional anisotropy in a white matter network comprising frontal, thalamic, brainstem and left cerebellar white matter strongly and negatively correlated with SARA ataxia scores. Tractography identified the thalamic white matter thus implicated as belonging to ventrolateral thalamus. Disruption of white matter integrity in patients suffering from SCA3 is more widespread than previously thought. Moreover, our data provide evidence that microstructural white matter changes in SCA3 are strongly related to the clinical severity of ataxia symptoms.

  11. Asteroseismology of white dwarf stars

    Córsico, A. H.

    2014-01-01

    Most of low- and intermediate-mass stars that populate the Universe will end their lives as white dwarf stars. These ancient stellar remnants have encrypted inside a precious record of the evolutionary history of the progenitor stars, providing a wealth of information about the evolution of stars, star formation, and the age of a variety of stellar populations, such as our Galaxy and open and globular clusters. While some information like surface chemical composition, temperature and gravity ...

  12. The Blue Box White Paper

    Tippett, Benjamin K; Tsang, David

    2013-01-01

    This white paper is an explanation of Ben and Dave's TARDIS time machine, written for laypeople who are interested in time travel, but have no technical knowledge of Einstein's Theory of General Relativity. The first part of this paper is an introduction to the pertinent ideas from Einstein's theory of curved spacetime, followed by a review of other popular time machine spacetimes. We begin with an introduction to curvature and lightcones. We then explain the Alcubierre Warp Drive, the Morris...

  13. Black and White Women's Leadership

    Showunmi, Victoria; Atewologun, Doyin

    2013-01-01

    This paper contributes to literature on ethnic identity and experiences in the workplace leadership and identity by examining how race, gender and class may confer disadvantage or bestow privilege in accessing leadership positions and enacting the role of leader. We interviewed 130 white and BME women leaders in public and private sector organisations in the UK to gather their reflections on how they defined leadership, how their identities as leaders had developed and their experiences of en...

  14. WHITE CEMENT IN SUSTAINABLE DEVELOPMENT

    Y.C.P RAMANA BABU; B.SAI DOONDI; N. M .V .VAMSI KRISHNA; K.PRASANTHI

    2013-01-01

    India is one among the fast developing countries in the world in the areas of Infrastructure. Now a day, Carbon monoxide (CO) and carbon dioxide (CO2) are the temporary atmospheric pollutants in the environment chiefly emitted from the fuel burning vehicles and street lights which lead to global warming and pose a major threat tothe survival and sustainable development. This paper deals with the principal purpose of use of white cement in pavement design which will take care of the Green hous...

  15. Making Whites from the Dark Side: Teaching Whiteness Studies at San Francisco State University

    Sueyoshi, Amy

    2013-01-01

    While whiteness studies at most institutions aims to expose the persistence of white supremacy to a disbelieving audience, whiteness studies within the College of Ethnic Studies (COES) at San Francisco State University (SFSU) begins with the assumption that racism still exists. The course then traces how whiteness is constructed and fortified to…

  16. Complexity in White Noise Analysis

    Hida, Takeyuki

    We restrict our attention to random complex systems and discuss degree their degree of complexity based on a white noise. The white noise is realized as the time derivative of a Brownian motion B(t), and denoted by Ḃ(t). The collection {Ḃ(t)}, is a system of idealized elementary variables and at the same time the system is a stochastic representation of the time t, in other words it is time-oriented. Having expressed the given evolutional random phenomena in question in terms of the Ḃ(t), we introduce the notion of spectral multiplicity, which describes how much the phenomena are complex. The multiplicity is the number of cyclic subspaces that are spanned by the given random phenomena. Each cyclic subspace has further structure. Typical property is multiple Markov property, although this property appears only particular cases. As a related property, in fact as a characteristic of a complex system, one can speak of the time reversibility and irreversibility of certain random phenomena in terms of the white noise. We expect an irreversible random complex system may be decomposed into reversible systems.

  17. White Dwarfs in Cataclysmic Variable Stars: Surface Temperatures and Evolution

    Edward M. Sion

    2012-06-01

    Full Text Available A summary is presented of what is currently known about the surface temperatures of accreting white dwarfs (WDs detected in non-magnetic and magnetic cataclysmic variables (CVs based upon synthetic spectral analyses of far ultraviolet data. A special focus is placed on WD temperatures above and below the CV period gap as a function of the orbital period, Porb. The principal uncertainty of the temperatures for the CV WDs in the Teff - Porb distribution, besides the distance to the CV, is the mass of the WD. Only in eclipsing CV systems, an area of eclipsing binary studies, which was so central to Robert H. Koch’s career, is it possible to know CV WD masses with high precision.

  18. White public regard: associations among eating disorder symptomatology, guilt, and White guilt in young adult women.

    Lydecker, Janet A; Hubbard, Rebecca R; Tully, Carrie B; Utsey, Shawn O; Mazzeo, Suzanne E

    2014-01-01

    As a novel investigation of the role of White racial identity, the current study explored the link between White guilt and disordered eating. Young adult women (N=375), 200 of whom self-identified as White. Measures assessed disordered eating, trait guilt, White guilt, and affect. White guilt is interrelated with disordered eating, particularly bulimic symptomatology. Distress tolerance and tendency to experience negative affect moderated the relation between White guilt and several disordered eating variables. Exploration of White guilt in clinical and research settings can inform understanding and treatment of disordered eating. © 2013.

  19. Normal Axillary Lymph Node Variability Between White and Black Women on Breast MRI.

    Grimm, Lars J; Viradia, Neal K; Johnson, Karen S

    2018-03-01

    This study aimed to determine if there were differences in the imaging features of normal lymph nodes between white and black women using magnetic resonance imaging. Following institutional review board approval, we identified white and black women who underwent breast magnetic resonance imaging from November 1, 2008 to December 31, 2013 at our institution. To identify normal lymph nodes for measurement, patients with any benign or malignant causes for lymph node enlargement and patients with any subsequent breast cancer in the following 2 years were excluded. Black and white women were age matched at a 1:2 ratio. The largest lymph node in each axilla was measured for the long-axis length and maximal cortical thickness. Comparisons were made between white and black women using a conditional logistic regression to control for matching. There were 55 black women and 110 white women for analysis. The mean lymph node long-axis length was 14.7 ± 5.3 mm for black women and 14.4 ± 6.4 mm for white women (P = .678). The mean maximum cortical thickness was 3.3 ± 1.6 mm for black women and 2.6 ± 1.4 mm for Caucasian women (P < .001). A significantly higher percentage of black than white women had cortical thicknesses greater than threshold values of 3, 4, 5, 6, and 7 mm (P < .01 for all). The normal lymph node cortical thickness in black women is significantly greater than in white women, which should be considered when deciding to recommend a lymph node biopsy. Copyright © 2018 The Association of University Radiologists. Published by Elsevier Inc. All rights reserved.

  20. A voxel-based diffusion tensor imaging study of white matter in bipolar disorder.

    Mahon, Katie; Wu, Jinghui; Malhotra, Anil K; Burdick, Katherine E; DeRosse, Pamela; Ardekani, Babak A; Szeszko, Philip R

    2009-05-01

    There is evidence from post-mortem and magnetic resonance imaging studies that hyperintensities, oligodendroglial abnormalities, and gross white matter volumetric alterations are involved in the pathophysiology of bipolar disorder. There is also functional imaging evidence for a defect in frontal cortico-subcortical pathways in bipolar disorder, but the white matter comprising these pathways has not been well investigated. Few studies have investigated white matter integrity in patients with bipolar disorder compared to healthy volunteers and the majority of studies have used manual region-of-interest approaches. In this study, we compared fractional anisotropy (FA) values between 30 patients with bipolar disorder and 38 healthy volunteers in the brain white matter using a voxelwise analysis following intersubject registration to Talairach space. Compared to healthy volunteers, patients demonstrated significantly (p or =50) higher FA within the right and left frontal white matter and lower FA within the left cerebellar white matter. Examination of individual eigenvalues indicated that group differences in both axial diffusivity and radial diffusivity contributed to abnormal FA within these regions. Tractography was performed in template space on averaged diffusion tensor imaging data from all individuals. Extraction of bundles passing through the clusters that differed significantly between groups suggested that white matter abnormalities along the pontine crossing tract, corticospinal/corticopontine tracts, and thalamic radiation fibers may be involved in the pathogenesis of bipolar disorder. Our findings are consistent with models of bipolar disorder that implicate dysregulation of cortico-subcortical and cerebellar regions in the disorder and may have relevance for phenomenology.

  1. Magnetic starspots

    Jahn, K.; Stepien, K.

    1984-01-01

    Models of large magnetic starspots with an axisymmetric untwisted magnetic field on late type stars are discussed. It is assumed that the magnetic field reduces the efficiency of convection inside the spot. A unique relation between the stellar mass and the difference of effective temperatures of the spot and the surrounding photosphere is adopted from observations. It is equivalent to the reduction of a s (the mixing length theory parameter) inside the spot to the value 0.15 independently of the stellar mass. The surface magnetic field of large spots covering a considerable part of the stellar surface is a decreasing function of the magnetic flux. Hence a coverage of a star by magnetic regions rapidly increases as a function of the magnetic flux in a narrow range of fluxes. This behaviour can explain the Vaughan-Preston gap. Recent observations of magnetic fields on G and K type stars are in a good agreement with our predictions. 35 refs., 3 figs., 4 tabs. (author)

  2. Magnetic superlattices

    Kwo, J.; Hong, M.; McWhan, D.B.; Yafet, Y.; Fleming, R.M.; DiSalvo, F.J.; Waszczak, J.V.; Majkrzak, C.F.; Gibbs, D.; Goldmann, A.I.; Boni, P.; Bohr, J.; Grimm, H.; Bohr, J.; Chien, C.L.; Grimm, H.; Cable, J.W.

    1988-01-01

    Single crystal magnetic rare earth superlattices were synthesized by molecular beam epitaxy. The studies include four rare earth systems: Gd-Y, Dy-Y, Ho-Y, and Gd-Dy. The magnetic properties and the long-range spin order are reviewed in terms of the interfacial behavior, and the interlayer exchange coupling across Y medium

  3. Magnetic resonance in neuroborreliosis

    Ustymowicz, A.; Zajkowska, J.

    2003-01-01

    Magnetic resonance (MR) is commonly used in diagnosing infections of the central nervous system. The aim of the study is to evaluate central nervous system changes in neuroborreliosis patients. MR examinations were performed in 44 patients with clinical symptoms, epidemiology and laboratory tests results of neuroborreliosis. Abnormalities were detected in 22 patients. Most of them presented cortico-subcortical atrophy (86%). In 9 cases foci of increased signal in T2-weighted and FLAIR images were observed in white matter. They were single or multiple, located subcorticaly and paraventriculary. In 2 subjects areas of increased signal were found in the brain stem. Central nervous system abnormalities detected with MR are not specific for Lyme disease. They can suggest demyelinating lesions and/or gliosis observed in many nervous system disorders (SM, ADEM, lacunar infarcts). (author)

  4. Magnetic Field

    Olsen, Nils

    2015-01-01

    he Earth has a large and complicated magnetic field, the major part of which is produced by a self-sustaining dynamo operating in the fluid outer core. Magnetic field observations provide one of the few tools for remote sensing the Earth’s deep interior, especially regarding the dynamics...... of the fluid flow at the top of the core. However, what is measured at or near the surface of the Earth is the superposition of the core field and fields caused by magnetized rocks in the Earth’s crust, by electric currents flowing in the ionosphere, magnetosphere, and oceans, and by currents induced...... in the Earth by time-varying external fields. These sources have their specific characteristics in terms of spatial and temporal variations, and their proper separation, based on magnetic measurements, is a major challenge. Such a separation is a prerequisite for remote sensing by means of magnetic field...

  5. White constancy method for mobile displays

    Yum, Ji Young; Park, Hyun Hee; Jang, Seul Ki; Lee, Jae Hyang; Kim, Jong Ho; Yi, Ji Young; Lee, Min Woo

    2014-03-01

    In these days, consumer's needs for image quality of mobile devices are increasing as smartphone is widely used. For example, colors may be perceived differently when displayed contents under different illuminants. Displayed white in incandescent lamp is perceived as bluish, while same content in LED light is perceived as yellowish. When changed in perceived white under illuminant environment, image quality would be degraded. Objective of the proposed white constancy method is restricted to maintain consistent output colors regardless of the illuminants utilized. Human visual experiments are performed to analyze viewers'perceptual constancy. Participants are asked to choose the displayed white in a variety of illuminants. Relationship between the illuminants and the selected colors with white are modeled by mapping function based on the results of human visual experiments. White constancy values for image control are determined on the predesigned functions. Experimental results indicate that propsed method yields better image quality by keeping the display white.

  6. The strongest magnetic fields in the universe

    Balogh, A; Falanga, M; Lyutikov, M; Mereghetti, S; Piran, T; Treumann, RA

    2016-01-01

    This volume extends the ISSI series on magnetic fields in the Universe into the domain of what are by far the strongest fields in the Universe, and stronger than any field that could be produced on Earth. The chapters describe the magnetic fields in non-degenerate strongly magnetized stars, degenerate stars (such as white dwarfs and neutron stars), exotic members called magnetars, and in their environments, as well as magnetic fields in the environments of black holes. These strong fields have a profound effect on the behavior of matter, visible in particular in highly variable processes like radiation in all known wavelengths, including Gamma-Ray bursts. The generation and structure of such strong magnetic fields and effects on the environment are also described.

  7. Magnetic and optical bistability in tetrairon(III) single molecule magnets functionalized with azobenzene groups.

    Prasad, Thazhe Kootteri; Poneti, Giordano; Sorace, Lorenzo; Rodriguez-Douton, Maria Jesus; Barra, Anne-Laure; Neugebauer, Petr; Costantino, Luca; Sessoli, Roberta; Cornia, Andrea

    2012-07-21

    Tetrairon(III) complexes known as "ferric stars" have been functionalized with azobenzene groups to investigate the effect of light-induced trans-cis isomerization on single-molecule magnet (SMM) behaviour. According to DC magnetic data and EPR spectroscopy, clusters dispersed in polystyrene (4% w/w) exhibit the same spin (S = 5) and magnetic anisotropy as bulk samples. Ligand photoisomerization, achieved by irradiation at 365 nm, has no detectable influence on static magnetic properties. However, it induces a small but significant acceleration of magnetic relaxation as probed by AC susceptometry. The pristine behaviour can be almost quantitatively recovered by irradiation with white light. Our studies demonstrate that magnetic and optical bistability can be made to coexist in SMM materials, which are of current interest in molecular spintronics.

  8. White Paper on Nuclear Astrophysics

    Arcones, Almudena; Bardayan, Dan W.; Beers, Timothy C.; Berstein, Lee A.; Blackmon, Jeffrey C.; Messer, Bronson; Brown, B. Alex; Brown, Edward F.; Brune, Carl R.; Champagne, Art E.; Chieffi, Alessandro; Couture, Aaron J.; Danielewicz, Pawel; Diehl, Roland; El-Eid, Mounib

    2016-01-01

    This white paper informs the nuclear astrophysics community and funding agencies about the scientific directions and priorities of the field and provides input from this community for the 2015 Nuclear Science Long Range Plan. It summarizes the outcome of the nuclear astrophysics town meeting that was held on August 21-23, 2014 in College Station at the campus of Texas A&M University in preparation of the NSAC Nuclear Science Long Range Plan. It also reflects the outcome of an earlier town mee...

  9. Delayed demagnetization jumps in (NdDy)(FeCo)B magnets in a steady-state magnetic field

    L'vova, G. L.; Kirman, M. V.; Koplak, O. V.; Kucheryaev, V. V.; Valeev, R. A.; Piskorskii, V. P.; Morgunov, R. B.

    2017-11-01

    Spontaneous demagnetization jumps are observed in sintered magnets (Nd0.6Dy0.4)16(Fe0.77Co0.23)78B6 in a constant magnetic field after a sharp decrease in an external magnetic field from the value corresponding to the saturation to a value close to the coercive force. It is shown that the number of the magnetization jumps is proportional to their amplitudes. A low value of the autocorrelation coefficient between the jump amplitude and the time of its appearance ( R white magnetic noise is observed. The distribution of the magnetic field gradient has been obtained near the sample surface that makes it possible to distinguish domains and the grain magnetization in the dependence on the direction of the texturing of the sintered magnet.

  10. Lunar magnetism

    Hood, L. L.; Sonett, C. P.; Srnka, L. J.

    1984-01-01

    Aspects of lunar paleomagnetic and electromagnetic sounding results which appear inconsistent with the hypothesis that an ancient core dynamo was the dominant source of the observed crustal magnetism are discussed. Evidence is summarized involving a correlation between observed magnetic anomalies and ejecta blankets from impact events which indicates the possible importance of local mechanisms involving meteoroid impact processes in generating strong magnetic fields at the lunar surface. A reply is given to the latter argument which also presents recent evidence of a lunar iron core.

  11. Keeping Minorities Happy: Hierarchy Maintenance and Whites' Decreased Support for Highly Identified White Politicians.

    Jun, Sora; Lowery, Brian S; Guillory, Lucia

    2017-12-01

    We test the hypothesis that, to avoid provoking minorities, Whites will withhold their support for White political candidates who are highly identified with their race. In Study 1, we found that White Republicans were less supportive of White candidates the higher the perceived White identity of the candidate due to beliefs that such candidates would provoke racial minorities. In Study 2, we replicated this effect with a manipulation of candidates' White identity. Study 3 found that Whites reported less support for high-identity candidates when they were led to believe that the hierarchy was unstable rather than stable. Consistent with our hypothesis that those who have the most to lose are most likely to avoid provoking minorities, in Study 4, we found that Whites with high subjective socioeconomic status (SES) varied their support for provocative White candidates as a function of hierarchy stability, whereas those with low subjective SES did not.

  12. Executive dysfunctions in migraine with and without aura: what is the role of white matter lesions?

    Le Pira, Francesco; Reggio, Ester; Quattrocchi, Graziella; Sanfilippo, Cristina; Maci, Tiziana; Cavallaro, Tiziana; Zappia, Mario

    2014-01-01

    Executive dysfunctions and white matter lesions on magnetic resonance imaging have been reported in migraine. The aim of this study was to determine whether any correlation between these 2 variables exists. Forty-four subjects affected by migraine with or without aura were compared with 16 healthy subjects. A battery of neuropsychological tests assessing executive functions was administered to all subjects. Number and total volume of white matter lesions were assessed in the whole brain and in the frontal lobe. The performances of both groups of migraineurs, with and without aura, were significantly worse when compared with controls on Boston Scanning Test. Moreover, we found lower performances compared with controls respectively on Frontal Assessment Battery in patients with migraine with aura and on Controlled Oral Word Association Test in patients with migraine without aura. Nineteen patients (43.2%) and one control subject (6.2%) had white matter lesions. We did not find any significant correlation between white matter lesions load and neuropsychological performances. On the basis of our results, white matter lesions load on magnetic resonance imaging do not seem to contribute to neuropsychological performances deficit in migraineurs. © 2013 American Headache Society.

  13. Polarimetric Evidence of the First White Dwarf Pulsar: The Binary System AR Scorpii

    David A.H. Buckley

    2018-01-01

    Full Text Available The binary star AR Scorpii was recently discovered to exhibit high amplitude coherent variability across the electromagnetic spectrum (ultraviolet to radio at two closely spaced ∼2 min periods, attributed to the spin period of a white dwarf and the beat period. There is strong evidence (low X-ray luminosity, lack of flickering and absense of broad emission lines that AR Sco is a detached non-accreting system whose luminosity is dominated by the spin-down power of a white dwarf, due to magnetohydrodynamical (MHD interactions with its M5 companion. Optical polarimetry has revealed highly pulsed linear polarization on the same periods, reaching a maximum of 40%, consistent with a pulsar-like dipole, with the Stokes Q and U variations reminiscent of the Crab pulsar. These observations, coupled with the spectral energy distribution (SED which is dominated by non-thermal emission, characteristic of synchrotron emission, support the notion that a strongly magnetic (∼200 MG white dwarf is behaving like a pulsar, whose magnetic field interacts with the secondary star’s photosphere and magnetosphere. Radio synchrotron emission is produced from the pumping action of the white dwarf’s magnetic field on coronal loops from the M-star companion, while emission at high frequencies (UV/optical/X-ray comes from the particle wind, driven by large electric potential, again reminiscent of processes seen in neutron star pulsars.

  14. Rare earth permanent magnet with easy magnetization

    Kim, A.S.; Camp, F.E.

    1998-01-01

    Rare earth permanent magnets have high energy products and coercivities, and thus the volume miniaturization of magnetic devices has been possible with improved magnetic performance. Although the high energy products of these rare earth permanent magnets provide substantial advantages for magnetic design and application, the strong magnetic force of the magnetized magnets makes assembly difficult. Therefore, a special device is needed to assemble the magnetized magnets. On the other hand, unmagnetized magnets are assembled and then they are magnetized. The assembled magnets are generally more difficult to magnetize than unassembled magnets because a much less effective magnetic field may be applied to them. This is particularly true for the rare earth permanent magnets because they usually need a much higher magnetic field to be fully magnetized than alnico or ferrite magnets. To obtain optimum magnetic properties, the required minimum magnetizing fields for SmCo 5 , Sm 2 TM 17 and Nd 2 Fe 14 B magnets were reported as 25-30 kOe, 45-60 kOe and 25-30 kOe, respectively. If the required magnetizing field for full saturation could be lowered, the effective utilization of magnetic properties would be maximized and the magnetic design option could be expanded with reduced restrictions. To meet this demand, we have sought to lower the field required for full magnetic saturation, and found that an increase in Dy content in R-(Fe,Co,Cu)-B type magnets lowers the field required for full saturation as well as improves the temperature stability. By increasing the H ci with Dy addition from 14 kOe to 24 and 34 kOe, the field required for full magnetic saturation decreases from about 20 to 15 and 10 kOe, respectively. This dual benefit will open up new application areas with more freedom for magnet design options. The mechanism for the lower magnetizing fields will be discussed. (orig.)

  15. Magnetic monopoles

    Fryberger, D.

    1984-12-01

    In this talk on magnetic monopoles, first the author briefly reviews some historical background; then, the author describes what several different types of monopoles might look like; and finally the author discusses the experimental situation. 81 references

  16. Quantum magnetism

    Richter, Johannes; Farnell, Damian; Bishop, Raymod

    2004-01-01

    The investigation of magnetic systems where quantum effects play a dominant role has become a very active branch of solid-state-physics research in its own right. The first three chapters of the "Quantum Magnetism" survey conceptual problems and provide insights into the classes of systems considered, namely one-dimensional, two-dimensional and molecular magnets. The following chapters introduce the methods used in the field of quantum magnetism, including spin wave analysis, exact diagonalization, quantum field theory, coupled cluster methods and the Bethe ansatz. The book closes with a chapter on quantum phase transitions and a contribution that puts the wealth of phenomena into the context of experimental solid-state physics. Closing a gap in the literature, this volume is intended both as an introductory text at postgraduate level and as a modern, comprehensive reference for researchers in the field.

  17. Magnetic monopoles

    Preskill, J

    1984-01-01

    This article offers a review of the physics of the magnetic monopole, which, although as yet unseen, offers sound theoretical reasons to believe that it must exist. Several theories are presented and equations are given. The idea that magnetic monopoles, stable particles carrying magnetic charges, ought to exist has, according to the authors, proved to be very durable. One theory presented demonstrates the consistency of magnetic monopoles with quantum electrodynamics. Another theory demonstrates the necessity of monopoles in grand unified gauge theories. The authors believe it is reasonable to expect the monopole to be an extremely heavy stable elementary particle. The stability of the classical monopole solution given is ensured by a topological principle explained

  18. Magnetic Bacteria.

    Nelson, Jane Bray; Nelson, Jim

    1992-01-01

    Describes the history of Richard Blakemore's discovery of magnetotaxic organisms. Discusses possible reasons why the magnetic response in bacteria developed. Proposes research experiments integrating biology and physics in which students investigate problems using cultures of magnetotaxic organisms. (MDH)

  19. Biological effect of the magnetic resonance on fruit flies, drosophila melanogaster

    Restrepo, Ana; Angel Karen; Lopez P, Monica; Sanabria, Ana I; Lopez, Maria I

    1992-01-01

    This article describes an investigation in which fruit flies, D. Melanogaster of the white and vestigial strains, were exposed to a magnetic resonance field for 171 hours, to determine possible genetic alterations

  20. Leucoencephalopathy with brainstem and spinal cord involvement and high lactate: quantitative magnetic resonance imaging

    Steenweg, M.E.; Pouwels, P.J.W.; Wolf, N.I.; van Wieringen, W.N.; Barkhof, F.; van der Knaap, M.S.

    2011-01-01

    Leucoencephalopathy with brainstem and spinal cord involvement and elevated lactate is a white matter disorder caused by DARS2 mutations. The pathology is unknown. We observed striking discrepancies between improvement on longitudinal conventional magnetic resonance images and clinical deterioration

  1. LHC magnets

    Anon.

    1992-01-01

    Preparations for the LHC proton collider to be built in CERN's LEP tunnel continue to make good progress. In particular development work for the high field superconducting magnets to guide the almost 8 TeVproton beams through the 'tight' curve of the 27-kilometre ring are proceeding well, while the magnet designs and lattice configuration are evolving in the light of ongoing experience. At the Evian LHC Experiments meeting, this progress was covered by Giorgio Brianti

  2. Magnetic resonance imaging in diffuse brain injury

    Yokota, Hiroyuki; Yasuda, Kazuhiro; Mashiko, Kunihiro; Henmi, Hiroshi; Otsuka, Toshibumi; Kobayashi, Shiro; Nakazawa, Shozo

    1992-01-01

    Forty cases diagnosed as diffuse brain injury (DBI) were studied by magnetic resonance imaging (MRI) performed within 3 days after injury. These cases were divided into two groups, which were the concussion group and diffuse axonal injury (DAI) group established by Gennarelli. There were no findings on computerized tomography (CT) in the concussion group except for two cases which had a brain edema or subarachnoid hemorrhage. But on MRI, high intensity areas on T2 weighted imaging were demonstrated in the cerebral white matter in this group. Many lesions in this group were thought to be edemas of the cerebral white matter, because of the fact that on serial MRI, they were isointense. In mild types of DAI, the lesions on MRI were located only in the cerebral white matter, whereas, in the severe types of DAI, lesions were located in the basal ganglia, the corpus callosum, the dorsal part of the brain stem as well as in the cerebral white matter. As for CT findings, parenchymal lesions were not visualized especially in mild DAI. Our results suggested that the lesions in cerebral concussion were edemas in cerebral white matter. In mild DAI they were non-hemorrhagic contusion; and in severe DAI they were hemorrhagic contusions in the cerebral white matter, the basal ganglia, the corpus callosum or the dorsal part of the brain stem. (author)

  3. Superconducting magnet

    1985-01-01

    Extensive computer based engineering design effort resulted in optimization of a superconducting magnet design with an average bulk current density of approximately 12KA/cm(2). Twisted, stranded 0.0045 inch diameter NbTi superconductor in a copper matrix was selected. Winding the coil from this bundle facilitated uniform winding of the small diameter wire. Test coils were wound using a first lot of the wire. The actual packing density was measured from these. Interwinding voltage break down tests on the test coils indicated the need for adjustment of the wire insulation on the lot of wire subsequently ordered for construction of the delivered superconducting magnet. Using the actual packing densities from the test coils, a final magnet design, with the required enhancement and field profile, was generated. All mechanical and thermal design parameters were then also fixed. The superconducting magnet was then fabricated and tested. The first test was made with the magnet immersed in liquid helium at 4.2K. The second test was conducted at 2K in vacuum. In the latter test, the magnet was conduction cooled from the mounting flange end.

  4. Magnetic resonance imaging in psychiatry

    Mann, K.

    1993-01-01

    Diagnosis and research in psychiatry are increasingly availing themselves of magnetic resonance imaging (MRI). In comparison to computed tomography (CT), this offers the combined benefits of no exposure to radiation, high resolution, artefact-free display of structures near bone, and a sharp contrast between the grey and white brain matter, with freedom to select the section. With the exception of very anxious patients, MRI will gradually replace CT scans for a wide range of differential diagnostic investigations. Its superiority in systematic studies of psychiatric patients with discrete cerebral parenchyma lesions is already considered proven. This is illustrated on the basis of research into schizophrenia and alcoholism. (orig.) [de

  5. Biomarkers in white-coat hypertension

    Martin, Catherine Ann

    2017-01-01

    The introduction of ambulatory blood pressure monitoring in the 1960s provided new insights into the nature of high blood pressure disorders. Blood pressure is now categorised into four quadrants:normotension, masked hypertension, hypertension and white-coat hypertension. In white-coat hypertension blood pressure is elevated when taken at the doctor’s office but normal if taken outside the doctor’s office. Several controversies are associated with white-coat hypertension, which are discuss...

  6. BIOMODIFICATION OF KENAF USING WHITE ROT FUNGI

    Rasmina Halis,; Hui Rus Tan,; Zaidon Ashaari,; Rozi Mohamed

    2012-01-01

    White rot fungi can be used as a pretreatment of biomass to degrade lignin. It also alters the structure of the lignocellulosic matter, thus increasing its accessibility to enzymes able to convert polysaccharides into simple sugars. This study compares the ability of two species of white rot fungi, Pycnoporous sanguineus and Oxyporus latemarginatus FRIM 31, to degrade lignin in kenaf chips. The white rot fungi were originally isolated from the tropical forest in Malaysia. Kenaf chips were fir...

  7. Merging White Dwarfs and Thermonuclear Supernovae

    van Kerkwijk, Marten H.

    2012-01-01

    Thermonuclear supernovae result when interaction with a companion reignites nuclear fusion in a carbon-oxygen white dwarf, causing a thermonuclear runaway, a catastrophic gain in pressure, and the disintegration of the whole white dwarf. It is usually thought that fusion is reignited in near-pycnonuclear conditions when the white dwarf approaches the Chandrasekhar mass. I briefly describe two long-standing problems faced by this scenario, and our suggestion that these supernovae instead resul...

  8. Menopausal Hot Flashes and White Matter Hyperintensities

    Thurston, Rebecca C.; Aizenstein, Howard J.; Derby, Carol A.; Sejdić, Ervin; Maki, Pauline M.

    2015-01-01

    Objective Hot flashes are the classic menopausal symptom. Emerging data links hot flashes to cardiovascular disease (CVD) risk, yet how hot flashes are related to brain health is poorly understood. We examined the relationship between hot flashes - measured via physiologic monitor and self-report - and white matter hyperintensities (WMH) among midlife women. Methods Twenty midlife women ages 40-60 without clinical CVD, with their uterus and both ovaries, and not taking hormone therapy were recruited. Women underwent 24 hours of ambulatory physiologic and diary hot flash monitoring to quantify hot flashes; magnetic resonance imaging to assess WMH burden; 72 hours of actigraphy and questionnaires to quantify sleep; and a blood draw, questionnaires, and physical measures to quantify demographics and CVD risk factors. Test of a priori hypotheses regarding relations between physiologically-monitored and self-reported wake and sleep hot flashes and WMH were conducted in linear regression models. Results More physiologically-monitored hot flashes during sleep were associated with greater WMH, controlling for age, race, and body mass index [beta(standard error)=.0002 (.0001), p=.03]. Findings persisted controlling for sleep characteristics and additional CVD risk factors. No relations were observed for self-reported hot flashes. Conclusions More physiologically-monitored hot flashes during sleep were associated with greater WMH burden among midlife women free of clinical CVD. Results suggest that relations between hot flashes and CVD risk observed in the periphery may extend to the brain. Future work should consider the unique role of sleep hot flashes in brain health. PMID:26057822

  9. Rare White dwarf stars with carbon atmospheres

    Dufour, P.; Liebert, James; Fontaine, G.; Behara, N.

    2007-01-01

    White dwarfs represent the endpoint of stellar evolution for stars with initial masses between approximately 0.07 msun and 8-10 msun, where msun is the mass of the Sun (more massive stars end their life as either black holes or neutron stars). The theory of stellar evolution predicts that the majority of white dwarfs have a core made of carbon and oxygen, which itself is surrounded by a helium layer and, for ~80 per cent of known white dwarfs, by an additional hydrogen layer. All white dwarfs...

  10. The galactic population of white dwarfs

    Napiwotzki, Ralf

    2009-01-01

    The contribution of white dwarfs of the different Galactic populations to the stellar content of our Galaxy is only poorly known. Some authors claim a vast population of halo white dwarfs, which would be in accordance with some investigations of the early phases of Galaxy formation claiming a top-heavy initial- mass- function. Here, I present a model of the population of white dwarfs in the Milky Way based on observations of the local white dwarf sample and a standard model of Galactic structure. This model will be used to estimate the space densities of thin disc, thick disc and halo white dwarfs and their contribution to the baryonic mass budget of the Milky Way. One result of this investigation is that white dwarfs of the halo population contribute a large fraction of the Galactic white dwarf number count, but they are not responsible for the lion's share of stellar mass in the Milky Way. Another important result is the substantial contribution of the - often neglected - population of thick disc white dwarfs. Misclassification of thick disc white dwarfs is responsible for overestimates of the halo population in previous investigations.

  11. White dwarfs in the WTS: Eclipsing binaries

    Burleigh M.R.

    2013-04-01

    Full Text Available We have identified photometric white dwarf candidates in the WFCAM transit survey through a reduced proper motion versus colour approach. Box-fitting with parameters adjusted to detect the unique signature of a white dwarf + planet/brown dwarf transit/eclipse event was performed, as well as looking for variability due to the irradiation of the companions atmosphere by the white dwarf's high UV flux. We have also performed a simple sensitivity analysis in order to assess the ability of the survey to detect companions to white dwarfs via the transit method.

  12. THE HYADES CLUSTER: IDENTIFICATION OF A PLANETARY SYSTEM AND ESCAPING WHITE DWARFS

    Zuckerman, B.; Xu, S.; Klein, B.; Jura, M.

    2013-01-01

    Recently, some hot DA-type white dwarfs have been proposed to plausibly be escaping members of the Hyades. We used hydrogen Balmer lines to measure the radial velocities of seven such stars and confirm that three, and perhaps two others, are/were indeed cluster members and one is not. The other candidate Hyad is strongly magnetic and its membership status remains uncertain. The photospheres of at least one quarter of field white dwarf stars are ''polluted'' by elements heavier than helium that have been accreted. These stars are orbited by extended planetary systems that contain both debris belts and major planets. We surveyed the seven classical single Hyades white dwarfs and the newly identified (escaping) Hyades white dwarfs and found calcium in the photosphere of LP 475-242 of type DBA (now DBAZ), thus implying the presence of an orbiting planetary system. The spectrum of white dwarf GD 31, which may be, but probably is not, an escaping member of the Hyades, displays calcium absorption lines; these originate either from the interstellar medium or, less likely, from a gaseous circumstellar disk. If GD 31 was once a Hyades member, then it would be the first identified white dwarf Hyad with a cooling age >340 Myr.

  13. CORRELATION OF HARD X-RAY AND WHITE LIGHT EMISSION IN SOLAR FLARES

    Kuhar, Matej; Krucker, Säm; Battaglia, Marina; Kleint, Lucia; Casadei, Diego [University of Applied Sciences and Arts Northwestern Switzerland, Bahnhofstrasse 6, 5210 Windisch (Switzerland); Oliveros, Juan Carlos Martinez; Hudson, Hugh S. [Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450 (United States)

    2016-01-01

    A statistical study of the correlation between hard X-ray and white light emission in solar flares is performed in order to search for a link between flare-accelerated electrons and white light formation. We analyze 43 flares spanning GOES classes M and X using observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager and Helioseismic and Magnetic Imager. We calculate X-ray fluxes at 30 keV and white light fluxes at 6173 Å summed over the hard X-ray flare ribbons with an integration time of 45 s around the peak hard-X ray time. We find a good correlation between hard X-ray fluxes and excess white light fluxes, with a highest correlation coefficient of 0.68 for photons with energy of 30 keV. Assuming the thick target model, a similar correlation is found between the deposited power by flare-accelerated electrons and the white light fluxes. The correlation coefficient is found to be largest for energy deposition by electrons above ∼50 keV. At higher electron energies the correlation decreases gradually while a rapid decrease is seen if the energy provided by low-energy electrons is added. This suggests that flare-accelerated electrons of energy ∼50 keV are the main source for white light production.

  14. Probing white-matter microstructure with higher-order diffusion tensors and susceptibility tensor MRI

    Liu, Chunlei; Murphy, Nicole E.; Li, Wei

    2012-01-01

    Diffusion MRI has become an invaluable tool for studying white matter microstructure and brain connectivity. The emergence of quantitative susceptibility mapping and susceptibility tensor imaging (STI) has provided another unique tool for assessing the structure of white matter. In the highly ordered white matter structure, diffusion MRI measures hindered water mobility induced by various tissue and cell membranes, while susceptibility sensitizes to the molecular composition and axonal arrangement. Integrating these two methods may produce new insights into the complex physiology of white matter. In this study, we investigated the relationship between diffusion and magnetic susceptibility in the white matter. Experiments were conducted on phantoms and human brains in vivo. Diffusion properties were quantified with the diffusion tensor model and also with the higher order tensor model based on the cumulant expansion. Frequency shift and susceptibility tensor were measured with quantitative susceptibility mapping and susceptibility tensor imaging. These diffusion and susceptibility quantities were compared and correlated in regions of single fiber bundles and regions of multiple fiber orientations. Relationships were established with similarities and differences identified. It is believed that diffusion MRI and susceptibility MRI provide complementary information of the microstructure of white matter. Together, they allow a more complete assessment of healthy and diseased brains. PMID:23507987

  15. THE HABITABILITY AND DETECTION OF EARTH-LIKE PLANETS ORBITING COOL WHITE DWARFS

    Fossati, L.; Haswell, C. A.; Patel, M. R.; Busuttil, R. [Department of Physical Sciences, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Bagnulo, S. [Armagh Observatory, College Hill, Armagh BT61 9DG (United Kingdom); Kowalski, P. M. [GFZ German Research Centre for Geosciences, Telegrafenberg, D-14473 Potsdam (Germany); Shulyak, D. V. [Institute of Astrophysics, Georg-August-University, Friedrich-Hund-Platz 1, D-37077 Goettingen (Germany); Sterzik, M. F., E-mail: l.fossati@open.ac.uk, E-mail: C.A.Haswell@open.ac.uk, E-mail: M.R.Patel@open.ac.uk, E-mail: r.busuttil@open.ac.uk, E-mail: sba@arm.ac.uk, E-mail: kowalski@gfz-potsdam.de, E-mail: denis.shulyak@gmail.com, E-mail: msterzik@eso.org [European Southern Observatory, Casilla 19001, Santiago 19 (Chile)

    2012-09-20

    Since there are several ways planets can survive the giant phase of the host star, we examine the habitability and detection of planets orbiting white dwarfs. As a white dwarf cools from 6000 K to 4000 K, a planet orbiting at 0.01 AU would remain in the continuous habitable zone (CHZ) for {approx}8 Gyr. We show that photosynthetic processes can be sustained on such planets. The DNA-weighted UV radiation dose for an Earth-like planet in the CHZ is less than the maxima encountered on Earth, and hence non-magnetic white dwarfs are compatible with the persistence of complex life. Polarization due to a terrestrial planet in the CHZ of a cool white dwarf (CWD) is 10{sup 2} (10{sup 4}) times larger than it would be in the habitable zone of a typical M-dwarf (Sun-like star). Polarimetry is thus a viable way to detect close-in rocky planets around white dwarfs. Multi-band polarimetry would also allow us to reveal the presence of a planet atmosphere, providing a first characterization. Planets in the CHZ of a 0.6 M{sub Sun} white dwarf will be distorted by Roche geometry, and a Kepler-11d analog would overfill its Roche lobe. With current facilities a super-Earth-sized atmosphereless planet is detectable with polarimetry around the brightest known CWD. Planned future facilities render smaller planets detectable, in particular by increasing the instrumental sensitivity in the blue.

  16. Reduced thalamic volume in preterm infants is associated with abnormal white matter metabolism independent of injury

    Wisnowski, Jessica L.; Ceschin, Rafael C.; Choi, So Young; Schmithorst, Vincent J.; Painter, Michael J.; Nelson, Marvin D.; Blueml, Stefan; Panigrahy, Ashok

    2015-01-01

    Altered thalamocortical development is hypothesized to be a key substrate underlying neurodevelopmental disabilities in preterm infants. However, the pathogenesis of this abnormality is not well-understood. We combined magnetic resonance spectroscopy of the parietal white matter and morphometric analyses of the thalamus to investigate the association between white matter metabolism and thalamic volume and tested the hypothesis that thalamic volume would be associated with diminished N-acetyl-aspartate (NAA), a measure of neuronal/axonal maturation, independent of white matter injury. Data from 106 preterm infants (mean gestational age at birth: 31.0 weeks ± 4.3; range 23-36 weeks) who underwent MR examinations under clinical indications were included in this study. Linear regression analyses demonstrated a significant association between parietal white matter NAA concentration and thalamic volume. This effect was above and beyond the effect of white matter injury and age at MRI and remained significant even when preterm infants with punctate white matter lesions (pWMLs) were excluded from the analysis. Furthermore, choline, and among the preterm infants without pWMLs, lactate concentrations were also associated with thalamic volume. Of note, the associations between NAA and choline concentration and thalamic volume remained significant even when the sample was restricted to neonates who were term-equivalent age or older. These observations provide convergent evidence of a neuroimaging phenotype characterized by widespread abnormal thalamocortical development and suggest that the pathogenesis may involve impaired axonal maturation. (orig.)

  17. Reduced thalamic volume in preterm infants is associated with abnormal white matter metabolism independent of injury

    Wisnowski, Jessica L. [Children' s Hospital Los Angeles, Department of Radiology, Los Angeles, CA (United States); University of Pittsburgh, Department of Pediatric Radiology, Children' s Hospital of Pittsburgh of UPMC, Pittsburgh, PA (United States); University of Southern California, Brain and Creativity Institute, Los Angeles, CA (United States); Ceschin, Rafael C. [University of Pittsburgh, Department of Pediatric Radiology, Children' s Hospital of Pittsburgh of UPMC, Pittsburgh, PA (United States); University of Pittsburgh, Department of Biomedical Informatics, Pittsburgh, PA (United States); Choi, So Young [University of Southern California, Brain and Creativity Institute, Los Angeles, CA (United States); Schmithorst, Vincent J. [University of Pittsburgh, Department of Pediatric Radiology, Children' s Hospital of Pittsburgh of UPMC, Pittsburgh, PA (United States); Painter, Michael J. [University of Pittsburgh, Department of Pediatrics, Division of Neurology, Childrens Hospital of Pittsburgh of UPMC, Pittsburgh, PA (United States); Nelson, Marvin D. [Children' s Hospital Los Angeles, Department of Radiology, Los Angeles, CA (United States); Blueml, Stefan [Children' s Hospital Los Angeles, Department of Radiology, Los Angeles, CA (United States); Rudi Schulte Research Institute, Santa Barbara, CA (United States); Panigrahy, Ashok [Children' s Hospital Los Angeles, Department of Radiology, Los Angeles, CA (United States); University of Pittsburgh, Department of Pediatric Radiology, Children' s Hospital of Pittsburgh of UPMC, Pittsburgh, PA (United States)

    2015-05-01

    Altered thalamocortical development is hypothesized to be a key substrate underlying neurodevelopmental disabilities in preterm infants. However, the pathogenesis of this abnormality is not well-understood. We combined magnetic resonance spectroscopy of the parietal white matter and morphometric analyses of the thalamus to investigate the association between white matter metabolism and thalamic volume and tested the hypothesis that thalamic volume would be associated with diminished N-acetyl-aspartate (NAA), a measure of neuronal/axonal maturation, independent of white matter injury. Data from 106 preterm infants (mean gestational age at birth: 31.0 weeks ± 4.3; range 23-36 weeks) who underwent MR examinations under clinical indications were included in this study. Linear regression analyses demonstrated a significant association between parietal white matter NAA concentration and thalamic volume. This effect was above and beyond the effect of white matter injury and age at MRI and remained significant even when preterm infants with punctate white matter lesions (pWMLs) were excluded from the analysis. Furthermore, choline, and among the preterm infants without pWMLs, lactate concentrations were also associated with thalamic volume. Of note, the associations between NAA and choline concentration and thalamic volume remained significant even when the sample was restricted to neonates who were term-equivalent age or older. These observations provide convergent evidence of a neuroimaging phenotype characterized by widespread abnormal thalamocortical development and suggest that the pathogenesis may involve impaired axonal maturation. (orig.)

  18. THE HABITABILITY AND DETECTION OF EARTH-LIKE PLANETS ORBITING COOL WHITE DWARFS

    Fossati, L.; Haswell, C. A.; Patel, M. R.; Busuttil, R.; Bagnulo, S.; Kowalski, P. M.; Shulyak, D. V.; Sterzik, M. F.

    2012-01-01

    Since there are several ways planets can survive the giant phase of the host star, we examine the habitability and detection of planets orbiting white dwarfs. As a white dwarf cools from 6000 K to 4000 K, a planet orbiting at 0.01 AU would remain in the continuous habitable zone (CHZ) for ∼8 Gyr. We show that photosynthetic processes can be sustained on such planets. The DNA-weighted UV radiation dose for an Earth-like planet in the CHZ is less than the maxima encountered on Earth, and hence non-magnetic white dwarfs are compatible with the persistence of complex life. Polarization due to a terrestrial planet in the CHZ of a cool white dwarf (CWD) is 10 2 (10 4 ) times larger than it would be in the habitable zone of a typical M-dwarf (Sun-like star). Polarimetry is thus a viable way to detect close-in rocky planets around white dwarfs. Multi-band polarimetry would also allow us to reveal the presence of a planet atmosphere, providing a first characterization. Planets in the CHZ of a 0.6 M ☉ white dwarf will be distorted by Roche geometry, and a Kepler-11d analog would overfill its Roche lobe. With current facilities a super-Earth-sized atmosphereless planet is detectable with polarimetry around the brightest known CWD. Planned future facilities render smaller planets detectable, in particular by increasing the instrumental sensitivity in the blue.

  19. Topics in white dwarf astrophysics

    Hintzen, P.M.N.

    1975-01-01

    This study was designed to investigate the apparent deficiency, compared to theoretical predictions, of cool degenerate stars. Two approaches to the problem were employed: a spectroscopic survey designed to identify red degenerates, and a model atmospheres study of the spectroscopic and photometric differences between red dwarfs and red degenerate stars. On computed atmospheric models for white dwarfs at the temperatures under investigation. Line profiles obtained from these models indicate that degenerate stars with T/sub e/ approximately 6000 0 K and depleted surface metals would be extremely difficult to identify spectroscopically. Their hydrogen and calcium line profiles would strongly resemble those of classical sub-dwarfs. Three apparently degenerate stars whose spectral features match our predictions have been identified. These results indicate that the existence of the previously postulated deficiency of red degenerate stars is uncertain

  20. Object technology: A white paper

    Jordan, S.R.; Arrowood, L.F.; Cain, W.D.; Stephens, W.M.; Vickers, B.D.

    1992-05-11

    Object-Oriented Technology (OOT), although not a new paradigm, has recently been prominently featured in the trade press and even general business publications. Indeed, the promises of object technology are alluring: the ability to handle complex design and engineering information through the full manufacturing production life cycle or to manipulate multimedia information, and the ability to improve programmer productivity in creating and maintaining high quality software. Groups at a number of the DOE facilities have been exploring the use of object technology for engineering, business, and other applications. In this white paper, the technology is explored thoroughly and compared with previous means of developing software and storing databases of information. Several specific projects within the DOE Complex are described, and the state of the commercial marketplace is indicated.

  1. White House nominates nuclear commissioner

    Showstack, Randy

    2012-06-01

    Just 3 days after U.S. Nuclear Regulatory Commission chairman Gregory Jaczko announced his intention to resign (Eos, 93(22), 211, doi:10.1029/2012EO220005, 2012), President Barack Obama nominated Allison Macfarlane to serve out the remainder of Jaczko's term, through June 2013. The White House announced that upon her appointment, Macfarlane would be designated as chair of the commission. Macfarlane is an associate professor of environmental science and policy at George Mason University. A member of the Blue Ribbon Commission on America's Nuclear Future from March 2010 to January 2012, she is also the author of the 2006 book Uncertainty Underground: Yucca Mountain and the Nation's High-Level Nuclear Waste and is an AGU member.

  2. Magnetizing of permanent magnet using HTS bulk magnet

    Oka, Tetsuo; Muraya, Tomoki; Kawasaki, Nobutaka; Fukui, Satoshi; Ogawa, Jun; Sato, Takao; Terasawa, Toshihisa

    2011-01-01

    A demagnetized Nd-Fe-B permanent magnet was scanned just above the magnetic pole containing the HTS bulk magnet, generating a magnetic field of 3.27 T. The magnet sample was subsequently found to be fully magnetized in the open space of the static magnetic fields. We examined the magnetic field distributions when the magnetic poles were scanned twice to activate the magnetic plates inversely with various overlap distances between the tracks of the HTS bulk magnet. The magnetic field of the 'rewritten' magnet reached the values of the magnetically saturated region of the material, showing steep gradients at the border of each magnetic pole. As a replacement for conventional pulse field magnetizing methods, this technique is proposed to expand the degree of freedom in the design of electromagnetic devices, and is proposed as a novel practical method for magnetizing rare-earth magnets, which have excellent magnetic performance and require intense fields of more than 3 T to be activated. (author)

  3. Magnetic spring based on two permanent magnets

    Tsivilitsin, V.Yu.; Mil'man, Yu.V.; Goncharuk, V.A.; Bondar, I.B.

    2011-01-01

    A new type of the magnetic spring construction 'two permanent magnets' has been considered. A mathematical expression for the estimation of a pulling-in force has been offered. This expression is verified experimentally on the produced operating magnetic spring. The theoretical and experimental data are in good accordance. A number of advantages of the magnetic spring over the construction 'permanent magnet - magnetic circuit' such as an insignificant friction force between two magnets and a higher pulling force are discussed.

  4. Cigarette smoking is associated with reduced microstructural integrity of cerebral white matter.

    Gons, Rob A R; van Norden, Anouk G W; de Laat, Karlijn F; van Oudheusden, Lucas J B; van Uden, Inge W M; Zwiers, Marcel P; Norris, David G; de Leeuw, Frank-Erik

    2011-07-01

    Cigarette smoking doubles the risk of dementia and Alzheimer's disease. Various pathophysiological pathways have been proposed to cause such a cognitive decline, but the exact mechanisms remain unclear. Smoking may affect the microstructural integrity of cerebral white matter. Diffusion tensor imaging is known to be sensitive for microstructural changes in cerebral white matter. We therefore cross-sectionally studied the relation between smoking behaviour (never, former, current) and diffusion tensor imaging parameters in both normal-appearing white matter and white matter lesions as well as the relation between smoking behaviour and cognitive performance. A structured questionnaire was used to ascertain the amount and duration of smoking in 503 subjects with small-vessel disease, aged between 50 and 85 years. Cognitive function was assessed with a neuropsychological test battery. All subjects underwent 1.5 Tesla magnetic resonance imaging. Using diffusion tensor imaging, fractional anisotropy and mean diffusivity were calculated in both normal-appearing white matter and white matter lesions. A history of smoking was associated with significant higher values of mean diffusivity in normal-appearing white matter and white matter lesions (P-trend for smoking status = 0.02) and with poorer cognitive functioning compared with those who never smoked. Associations with smoking and loss of structural integrity appeared to be strongest in normal-appearing white matter. Furthermore, the duration of smoking cessation was positively related to lower values of mean diffusivity and higher values of fractional anisotropy in normal-appearing white matter [β = -0.004 (95% confidence interval -0.007 to 0.000; P = 0.03) and β = 0.019 (95% confidence interval 0.001-0.038; P = 0.04)]. Fractional anisotropy and mean diffusivity values in normal-appearing white matter of subjects who had quit smoking for >20 years were comparable with subjects who had never smoked. These data suggest

  5. The effects of whiteness on the health of whites in the USA.

    Malat, Jennifer; Mayorga-Gallo, Sarah; Williams, David R

    2018-02-01

    Whites in the USA are the dominant racial group, with greater than average access to most material and social rewards. Yet, while whites have better outcomes than other racial groups on some health indicators, whites paradoxically compare poorly on other measures. Further, whites in the USA also rank poorly in international health comparisons. In this paper, we present a framework that combines the concept of whiteness-a system that socially, economically, and ideologically benefits European descendants and disadvantages people in other groups-with research from a variety of fields in order to comprehensively model the social factors that influence whites' health. The framework we present describes how whiteness and capitalism in the USA shape societal conditions, individual social characteristics and experiences, and psychosocial responses to circumstances to influence health outcomes. We detail specific examples of how social policies supported by whiteness, the narratives of whiteness, and the privileges of whiteness may positively and negatively affect whites' health. In doing so, we suggest several areas for future research that can expand our understanding of how social factors affect health and can contribute to the patterns and paradoxes of whites' health. By expanding research to include theoretically-grounded analyses of the dominant group's health, we can achieve a more complete picture of how systems of racial inequity affect health. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Beyond Black and White: How White, Male, College Students See Their Asian American Peers

    Cabrera, Nolan L.

    2014-01-01

    This research is a cross-site analysis of how white, male, college students see their Asian American peers. Semi-structured interviews with 43 white males were conducted at two universities that differed substantially in their representation of Asian American students. The interviews were theoretically framed by Critical Whiteness Studies and Bobo…

  7. Subliminal exposure to faces and racial attitudes : Exposure to whites makes whites like blacks less

    Smith, P.K.; Dijksterhuis, A.; Chaiken, S.

    Despite recent social and political advances, most interracial contact is still superficial in nature, and White individuals interact mainly with other Whites. Based on recent mere exposure research, we propose that repeated exposure to Whites may actually increase prejudice. In a series of

  8. Memory binding and white matter integrity in familial Alzheimer's disease.

    Parra, Mario A; Saarimäki, Heini; Bastin, Mark E; Londoño, Ana C; Pettit, Lewis; Lopera, Francisco; Della Sala, Sergio; Abrahams, Sharon

    2015-05-01

    Binding information in short-term and long-term memory are functions sensitive to Alzheimer's disease. They have been found to be affected in patients who meet criteria for familial Alzheimer's disease due to the mutation E280A of the PSEN1 gene. However, only short-term memory binding has been found to be affected in asymptomatic carriers of this mutation. The neural correlates of this dissociation are poorly understood. The present study used diffusion tensor magnetic resonance imaging to investigate whether the integrity of white matter structures could offer an account. A sample of 19 patients with familial Alzheimer's disease, 18 asymptomatic carriers and 21 non-carrier controls underwent diffusion tensor magnetic resonance imaging, neuropsychological and memory binding assessment. The short-term memory binding task required participants to detect changes across two consecutive screens displaying arrays of shapes, colours, or shape-colour bindings. The long-term memory binding task was a Paired Associates Learning Test. Performance on these tasks were entered into regression models. Relative to controls, patients with familial Alzheimer's disease performed poorly on both memory binding tasks. Asymptomatic carriers differed from controls only in the short-term memory binding task. White matter integrity explained poor memory binding performance only in patients with familial Alzheimer's disease. White matter water diffusion metrics from the frontal lobe accounted for poor performance on both memory binding tasks. Dissociations were found in the genu of corpus callosum which accounted for short-term memory binding impairments and in the hippocampal part of cingulum bundle which accounted for long-term memory binding deficits. The results indicate that white matter structures in the frontal and temporal lobes are vulnerable to the early stages of familial Alzheimer's disease and their damage is associated with impairments in two memory binding functions known to

  9. Magnetic reheating

    Saga, Shohei; Tashiro, Hiroyuki; Yokoyama, Shuichiro

    2018-02-01

    We provide a new bound on the amplitude of primordial magnetic fields (PMFs) by using a novel mechanism, magnetic reheating. The damping of the magnetohydrodynamics fluid motions in a primordial plasma brings the dissipation of the PMFs. In the early Universe with z ≳ 2 × 106, cosmic microwave background (CMB) photons are quickly thermalized with the dissipated energy and shift to a different Planck distribution with a new temperature. In other words, the PMF dissipation changes the baryon-to-photon number ratio, and we name such a process magnetic reheating. From the current baryon-to-photon number ratio obtained from the big bang nucleosynthesis and CMB observations, we put the strongest constraint on the PMFs on small scales which CMB observations cannot access, B0 ≲ 1.0 μG at the scales 104 generation mechanisms of PMFs in the early Universe.

  10. Magnetic monopoles and dipoles

    Dominguez, Daniel

    2016-01-01

    Conventional bar magnets are also called ‘magnetic dipoles’ because they have two magnetic poles (a “North” and a “South” magnetic pole, like the Earth). In theory, “magnetic monopoles” could exist that act like an isolated “magnetic charge”, i.e. either a “North” or a “South” magnetic pole.

  11. Study of relativistic effects in magnetoemission from white dwarfs

    Markes, C.T.H.

    1978-01-01

    Some white dwarfs have been observed to emit circularly polarized light, which is believed to be due to magnetoemission because of the existence of high magnetic fields. To explain this, an approximate relativistic Hamiltonian is developed describing the motion of a spinning charged oscillator in a uniform magnetic field. The exact solutions and energy eigenvalues of this Hamiltonian are determined. The fractional circular polarization is calculated using this model in time-dependent peturbation theory. Calculations taking into account low-lying states (low temperatures) as well as higher excited levels (all temperatures). Spin and relativity effects become increasingly important as more and more excited levels are included in the possible transitions. In fact, there appears to be a tendency for one of the polarization components to be quenched in the limit of very large excitations. Thus, the reason for the discrepancy in the infrared and other regions has to be sought elsewhere than in the assembly of charged oscillators in interaction with a high magnetic field, as this model, with relativization, is reasonably complete

  12. Designing a magnet for magnetic refrigeration

    Bjoerk, R

    2010-03-15

    This thesis investigates the design and optimization of a permanent magnet assembly for use in a magnetic refrigeration device. The heart of magnetic refrigeration is the adiabatic temperature change in the magnetocaloric material which is caused by the magnetic field. In order to design an ideal magnet assembly the magnetocaloric materials and the refrigeration process itself and their properties and performance as a function of magnetic field are investigated. For the magnetocaloric materials it is the magnetization, specific heat capacity and adiabatic temperature that are investigated as functions of the magnetic field. Following this the process utilized by a magnetic refrigerator to provide cooling is investigated using a publicly available one dimensional numerical model. This process is called active magnetic regeneration (AMR). The aim is to determine the performance of the AMR as a function of the magnetic field in order to learn the properties of the optimal magnet assembly. The performance of the AMR as a function of the synchronization and width of the magnetic field with respect to the AMR cycle, the ramp rate and maximum value of the magnetic field are investigated. Other published magnet designs used in magnetic refrigeration devices are also evaluated, using a figure of merit based on the properties of the investigated magnetocaloric materials, to learn the properties of the best magnet designs to date. Following this investigation the Halbach cylinder, which is a hollow permanent magnet cylinder with a rotating remanent flux density, is investigated in detail as it forms the basis of many magnet designs used in magnetic refrigeration. Here the optimal dimensions of a Halbach cylinder, as well as analytical calculations of the magnetic field for a Halbach cylinder of infinite length, are presented. Once it has been determined which properties are desirable for a magnet used in magnetic refrigeration the design of a new magnet is described. This is

  13. On the symbolism of the white coat.

    Nash, David A

    2014-12-01

    The white coat ceremony has become an academic ritual in the health professions: a ceremony that signals a transformation of status from ordinary student to that of one studying to become a health professional. While donning the white coat is a sign of a changed role, the white coat is also a powerful symbol of transformation. White is a symbol of purity, and the white coat symbolizes the purity of purpose being affirmed in becoming a health professional. Dentistry is afforded the status of a learned profession as a result of the power dentists possess over patients seeking care; this power is based in sophisticated knowledge. Patients must trust that the dentist's knowledge and skills will be used in their best interest-always to benefit, never to exploit. The white coat symbolizes an affirmation on the part of aspiring dentists that their purpose will be pure and that they can be trusted to honor the tradition of the learned professions in placing the interest of patients above self. Absent an emphasis on the symbolic nature of the white coat ceremony, it can simply become an opportunity to publicly congratulate individuals for their success in gaining entrance to the study of dentistry. By understanding its significance, however, the white coat ceremony can serve as a powerful, meaningful ritual emphasizing the transformation occurring within an individual who is entering the profession of dentistry.

  14. Understanding Colombian Amazonian white sand forests

    Peñuela-Mora, M.C.

    2014-01-01

    Although progress has been made in studies on white sand forests in the Amazon, there is still a considerable gap in our knowledge of the unique species composition of white sand forests and their structure and dynamics, especially in Western Amazon. This thesis aims to fill this gap by addressing

  15. Black and white human skin differences

    Andersen, Klaus Ejner; Maibach, H I

    1979-01-01

    This review of black and white human skin differences emphasizes the alleged importance of factors other than the obvious, i.e., skin color. Physicochemical differences and differences in susceptibility to irritants and allergens suggest a more resistant black than white skin. Differences appear...

  16. PROXIMATE AND ELEMENTAL COMPOSITION OF WHITE GRUBS

    DR. AMINU

    This study determined the proximate and mineral element composition of whole white grubs using standard methods of analysis. ... and 12.75 ± 3.65% respectively. Mineral contents of white grub in terms of relative concentration .... of intracellular Ca, bone mineralization, blood coagulation, and plasma membrane potential ...

  17. White holes and eternal black holes

    Hsu, Stephen D H

    2012-01-01

    We investigate isolated white holes surrounded by vacuum, which correspond to the time reversal of eternal black holes that do not evaporate. We show that isolated white holes produce quasi-thermal Hawking radiation. The time reversal of this radiation, incident on a black hole precursor, constitutes a special preparation that will cause the black hole to become eternal. (paper)

  18. Facilitation of Retention by White Noise

    Baumeister, Alfred A.; Kistler, Doris

    1975-01-01

    This study attempted to determine if white noise (an arousing stimulus), when presented at the time of recall, facilitates performance of second and fifth grade students, and if this effect generalizes across different kinds of learning tasks. Findings indicate that white noise produces improvements in performance in both age groups. (GO)

  19. Opportunities in white-box cryptography

    Michiels, W.

    White-box cryptography is the discipline of implementing a cryptographic algorithm in software such that an adversary will have difficulty extracting the cryptographic key. This approach assumes that the adversary has full access to and full control over the implementation's execution. White-box

  20. White piedra in a mother and daughter.

    Roshan, Anupama S; Janaki, C; Parveen, B

    2009-07-01

    White Piedra is a superficial fungal infection of the hair caused by Trichosporon asahii. It is also known as trichomycosis nodosa or trichomycosis nodularis. We report two cases of White Piedra in a mother and her daughter for the rarity of such occurrence.