Hubble Space Telescope Observations of UV Oscillations in WZ Sagittae During the Decline from Outburst

We present a time series analysis of Hubble Space Telescope observations of WZ Sge obtained in 2001 September, October, November and December as WZ Sge declined from its 2001 July superoutburst. Previous analysis of these data showed the temperature of the white dwarf decreased from ~29,000 K to ~18,000 K. In this study we binned the spectra over wavelength to yield ultraviolet light curves at each epoch that were then analyzed for the presence of the well-known 27.87 s and 28.96 s oscillations. We detect the 29 s periodicity at all four epochs, but the 28 s periodicity is absent. The origin of these oscillations has been debated since their discovery in the 1970s and competing hypotheses are based on either white dwarf non-radial g-mode pulsations or magnetically-channelled accretion onto a rotating white dwarf. By analogy with the ZZ Ceti stars, we argue that the non-radial g-mode pulsation model demands a strong dependence of pulse period on the white dwarf's temperature. However, these observations show the 29 s oscillation is independent of the white dwarf's temperature. Thus we reject the white dwarf non-radial g-mode pulsation hypothesis as the sole origin of the oscillations. It remains unclear if magnetically-funnelled accretion onto a rapidly rotating white dwarf (or belt on the white dwarf) is responsible for producing the oscillations. We also report the detection of a QPO with period ~18 s in the September light curve. The amplitudes of the 29 s oscillation and the QPO vary erratically on short timescales and are not correlated with the mean system brightness nor with each other.Comment: 20 pages, 3 figures, 1 table; accepted for publication in Ap

The Bivariate Normal Copula

We collect well known and less known facts about the bivariate normal distribution and translate them into copula language. In addition, we prove a very general formula for the bivariate normal copula, we compute Gini's gamma, and we provide improved bounds and approximations on the diagonal.Comment: 24 page

Expression of ISG15, UBE1L and MX2 in white blood cells of early pregnant and bred-nonpregnant dairy cows

Abstract only availableIdentifying pregnant and nonpregnant cows shortly after insemination can improve reproductive efficiency in dairy cows if resynchronization is practiced on nonpregnant cows. Bovine Interferon Stimulated Gene Product 15 (ISG15), Bovine Ubiquitin-Activating E1-Like (UBE1L) Enzyme and MX2 are produced in response to conceptus-dervied interferon-τ. The objective was to determine the level of these mRNA in pregnant and bred-nonpregnant Holstein cows (n=14). We hypothesized that the amount of ISG15, UBE1L and MX2 mRNA would increase between d 14 to 20 in pregnant cows but not increase in bred-nonpregnant cows. Cows were synchronized to estrus and inseminated (d 0). Blood samples were collected on d 14, 16, 18 and 20 following insemination. Pregnancy status was determined at approximately 30 and 60 d after insemination. RNA was isolated, reverse transcribed into cDNA and amplified using quantitative RTPCR. Six cows were nonpregnant (open) and eight cows were pregnant on d 30. On d 60, four of the pregnant cows remained pregnant (pregnant-pregnant) and four were found open (aborted; pregnant-open). mRNA data were expressed as fold increase above control and relative to cyclophilin. A status by day interaction was detected for ISG15 (P<.001) and MX2 (P<.02). The interaction was not significant for UBE1L. Mean ISG15 and mean MX2 remained low for open cows, but increased markedly on d 18 and 20 in pregnant-pregnant cows. Pregnant-open cows either had low levels of ISG15 and MX2 or underwent an increase in ISG15 and MX2 on d 18 and 20. We conclude that ISG15, UBE1L and MX2 are differentially regulated in dairy cows during pregnancy recognition. ISG15 and MX2 mRNA expression could be used as an indicator of early pregnancy. Cows that abort their pregnancy after d 28 (pregnant-open) have abnormal ISG15 and MX2 mRNA expression between d 14 to 20.F.B. Miller Undergraduate Research Program in Animal Science

Europium Underneath Graphene on Ir(111): Intercalation Mechanism, Magnetism, and Band Structure

The intercalation of Eu underneath Gr on Ir(111) is comprehensively investigated by microscopic, magnetic, and spectroscopic measurements, as well as by density functional theory. Depending on the coverage, the intercalated Eu atoms form either a $(2 \times 2)$ or a $(\sqrt{3} \times \sqrt{3})$R$30^{\circ}$ superstructure with respect to Gr. We investigate the mechanisms of Eu penetration through a nominally closed Gr sheet and measure the electronic structures and magnetic properties of the two intercalation systems. Their electronic structures are rather similar. Compared to Gr on Ir(111), the Gr bands in both systems are essentially rigidly shifted to larger binding energies resulting in n-doping. The hybridization of the Ir surface state $S_1$ with Gr states is lifted, and the moire superperiodic potential is strongly reduced. In contrast, the magnetic behavior of the two intercalation systems differs substantially as found by X-ray magnetic circular dichroism. The $(2 \times 2)$ Eu structure displays plain paramagnetic behavior, whereas for the $(\sqrt{3} \times \sqrt{3})$R$30^{\circ}$ structure the large zero-field susceptibility indicates ferromagnetic coupling, despite the absence of hysteresis at 10 K. For the latter structure, a considerable easy-plane magnetic anisotropy is observed and interpreted as shape anisotropy.Comment: 18 pages with 14 figures, including Supplemental Materia

Observation of a low-lying neutron-unbound state in 19C

Proton removal reactions from a secondary 22N beam were utilized to populate unbound states in neutron-rich carbon isotopes. Neutrons were measured with the Modular Neutron Array (MoNA) in coincidence with carbon fragments. A resonance with a decay energy of 76(14) keV was observed in the system 18C+n corresponding to a state in 19C at an excitation energy of 653(95)keV. This resonance could correspond to the first 5/2+ state which was recently speculated to be unbound in order to describe 1n and 2n removal cross section measurements from 20C.Comment: accepted for publication in Nucl. Phys.

Identification of novel Cyclooxygenase-2-dependent genes in Helicobacter pylori infection in vivo

<p>Abstract</p> <p>Background</p> <p><it>Helicobacter pylori </it>is a crucial determining factor in the pathogenesis of benign and neoplastic gastric diseases. Cyclooxygenase-2 (Cox-2) is the inducible key enzyme of arachidonic acid metabolism and is a central mediator in inflammation and cancer. Expression of the <it>Cox-2 </it>gene is up-regulated in the gastric mucosa during <it>H. pylori </it>infection but the pathobiological consequences of this enhanced Cox-2 expression are not yet characterized. The aim of this study was to identify novel genes down-stream of Cox-2 in an <it>in vivo </it>model, thereby identifying potential targets for the study of the role of Cox- 2 in <it>H. pylori </it>pathogenesis and the initiation of pre- cancerous changes.</p> <p>Results</p> <p>Gene expression profiles in the gastric mucosa of mice treated with a specific Cox-2 inhibitor (NS398) or vehicle were analysed at different time points (6, 13 and 19 wk) after <it>H. pylori </it>infection. <it>H. pylori </it>infection affected the expression of 385 genes over the experimental period, including regulators of gastric physiology, proliferation, apoptosis and mucosal defence. Under conditions of Cox-2 inhibition, 160 target genes were regulated as a result of <it>H. pylori </it>infection. The Cox-2 dependent subset included those influencing gastric physiology (<it>Gastrin, Galr1</it>), epithelial barrier function (<it>Tjp1, connexin45, Aqp5</it>), inflammation (<it>Icam1</it>), apoptosis (<it>Clu</it>) and proliferation (<it>Gdf3, Igf2</it>). Treatment with NS398 alone caused differential expression of 140 genes, 97 of which were unique, indicating that these genes are regulated under conditions of basal Cox-2 expression.</p> <p>Conclusion</p> <p>This study has identified a panel of novel Cox-2 dependent genes influenced under both normal and the inflammatory conditions induced by <it>H. pylori </it>infection. These data provide important new links between Cox-2 and inflammatory processes, epithelial repair and integrity.</p

Coherent Bayesian analysis of inspiral signals

We present in this paper a Bayesian parameter estimation method for the analysis of interferometric gravitational wave observations of an inspiral of binary compact objects using data recorded simultaneously by a network of several interferometers at different sites. We consider neutron star or black hole inspirals that are modeled to 3.5 post-Newtonian (PN) order in phase and 2.5 PN in amplitude. Inference is facilitated using Markov chain Monte Carlo methods that are adapted in order to efficiently explore the particular parameter space. Examples are shown to illustrate how and what information about the different parameters can be derived from the data. This study uses simulated signals and data with noise characteristics that are assumed to be defined by the LIGO and Virgo detectors operating at their design sensitivities. Nine parameters are estimated, including those associated with the binary system, plus its location on the sky. We explain how this technique will be part of a detection pipeline for binary systems of compact objects with masses up to 20 \sunmass, including cases where the ratio of the individual masses can be extreme.Comment: Accepted for publication in Classical and Quantum Gravity, Special issue for GWDAW-1

HST/FOS Eclipse Observations of the Nova-like Cataclysmic Variable UX Ursae Majoris

[abridged abstract] We present and analyze Hubble Space Telescope observations of the eclipsing nova-like cataclysmic variable UX UMa obtained with the Faint Object Spectrograph. Two eclipses each were observed with the G160L grating (covering the ultraviolet waveband) in August of 1994 and with the PRISM (covering the near-ultraviolet to near-infrared) in November of the same year. The system was 50% brighter in November than in August, which, if due to a change in the accretion rate, indicates a fairly substantial increase in Mdot_acc by >~ 50%. Model disk spectra constructed as ensembles of stellar atmospheres provide poor descriptions of the observed post-eclipse spectra, despite the fact that UX UMa's light should be dominated by the disk at this time. Suitably scaled single temperature model stellar atmospheres with T_eff = 12,500-14,500 K actually provide a better match to both the ultraviolet and optical post-eclipse spectra. Evidently, great care must be taken in attempts to derive accretion rates from comparisons of disk models to observations. One way to reconcile disk models with the observed post-eclipse spectra is to postulate the presence of a significant amount of optically thin material in the system. Such an optically thin component might be associated with the transition region (``chromosphere'') between the disk photosphere and the fast wind from the system, whose presence has been suggested by Knigge & Drew (1997).Comment: 35 pages, including 12 figures; to appear in the ApJ (Vol. 499