178 research outputs found

    The X-ray CCD camera of the MAXI Experiment on the ISS/JEM

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    MAXI, Monitor of All-sky X-ray Image, is the X-ray observatory on the Japanese experimental module (JEM) Exposed Facility (EF) on the International Space Station (ISS). MAXI is a slit scanning camera which consists of two kinds of X-ray detectors: one is a one-dimensional position-sensitive proportional counter with a total area of ∌5000cm2\sim 5000 cm^2, the Gas Slit Camera (GSC), and the other is an X-ray CCD array with a total area ∌200cm2\sim 200 cm^2, the Solid-state Slit Camera (SSC). The GSC subtends a field of view with an angular dimension of 1∘×180∘^\circ\times 180^\circ while the SSC subtends a field of view with an angular dimension of 1∘^\circ times a little less than 180∘^\circ. In the course of one station orbit, MAXI can scan almost the entire sky with a precision of 1∘^\circ and with an X-ray energy range of 0.5-30 keV. We have developed the engineering model of CCD chips and the analogue electronics for the SSC. The energy resolution of EM CCD for Mn Kα\alpha has a full-width at half maximum of ≃\simeq 182 eV. Readout noise is ≃\simeq 11 e^- rms.Comment: 10 pages, 4 figures Accepted for Nuclear Instruments and Method in Physics Researc

    HI in the Outskirts of Nearby Galaxies

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    The HI in disk galaxies frequently extends beyond the optical image, and can trace the dark matter there. I briefly highlight the history of high spatial resolution HI imaging, the contribution it made to the dark matter problem, and the current tension between several dynamical methods to break the disk-halo degeneracy. I then turn to the flaring problem, which could in principle probe the shape of the dark halo. Instead, however, a lot of attention is now devoted to understanding the role of gas accretion via galactic fountains. The current Λ\rm \Lambda cold dark matter theory has problems on galactic scales, such as the core-cusp problem, which can be addressed with HI observations of dwarf galaxies. For a similar range in rotation velocities, galaxies of type Sd have thin disks, while those of type Im are much thicker. After a few comments on modified Newtonian dynamics and on irregular galaxies, I close with statistics on the HI extent of galaxies.Comment: 38 pages, 17 figures, invited review, book chapter in "Outskirts of Galaxies", Eds. J. H. Knapen, J. C. Lee and A. Gil de Paz, Astrophysics and Space Science Library, Springer, in pres

    Inner Polar Rings and Disks: Observed Properties

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    A list of galaxies with inner regions revealing polar (or strongly inclined to the main galactic plane) disks and rings is compiled from the literature data. The list contains 47 galaxies of all morphological types, from E to Irr. We consider the statistics of the parameters of polar structures known from observations. The radii of the majority of them do not exceed 1.5 kpc. The polar structures are equally common in barred and unbarred galaxies. At the same time, if a galaxy has a bar (or a triaxial bulge), this leads to the polar disk stabilization - its axis of rotation usually coincides with the major axis of the bar. More than two thirds of all considered galaxies reveal one or another sign of recent interaction or merging. This fact indicates a direct relation between the external environment and the presence of an inner polar structure.Comment: 12 pages, 3 figures, accepted to Astrophysical Bulletin. Minor changes and corrections are still possibl

    Time-integrated luminosity recorded by the BABAR detector at the PEP-II e+e- collider

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    This article is the Preprint version of the final published artcile which can be accessed at the link below.We describe a measurement of the time-integrated luminosity of the data collected by the BABAR experiment at the PEP-II asymmetric-energy e+e- collider at the ϒ(4S), ϒ(3S), and ϒ(2S) resonances and in a continuum region below each resonance. We measure the time-integrated luminosity by counting e+e-→e+e- and (for the ϒ(4S) only) e+e-→Ό+ÎŒ- candidate events, allowing additional photons in the final state. We use data-corrected simulation to determine the cross-sections and reconstruction efficiencies for these processes, as well as the major backgrounds. Due to the large cross-sections of e+e-→e+e- and e+e-→Ό+ÎŒ-, the statistical uncertainties of the measurement are substantially smaller than the systematic uncertainties. The dominant systematic uncertainties are due to observed differences between data and simulation, as well as uncertainties on the cross-sections. For data collected on the ϒ(3S) and ϒ(2S) resonances, an additional uncertainty arises due to ϒ→e+e-X background. For data collected off the ϒ resonances, we estimate an additional uncertainty due to time dependent efficiency variations, which can affect the short off-resonance runs. The relative uncertainties on the luminosities of the on-resonance (off-resonance) samples are 0.43% (0.43%) for the ϒ(4S), 0.58% (0.72%) for the ϒ(3S), and 0.68% (0.88%) for the ϒ(2S).This work is supported by the US Department of Energy and National Science Foundation, the Natural Sciences and Engineering Research Council (Canada), the Commissariat Ă  l’Energie Atomique and Institut National de Physique NuclĂ©aire et de Physiquedes Particules (France), the Bundesministerium fĂŒr Bildung und Forschung and Deutsche Forschungsgemeinschaft (Germany), the Istituto Nazionale di Fisica Nucleare (Italy), the Foundation for Fundamental Research on Matter (The Netherlands), the Research Council of Norway, the Ministry of Education and Science of the Russian Federation, Ministerio de Ciencia e InnovaciĂłn (Spain), and the Science and Technology Facilities Council (United Kingdom). Individuals have received support from the Marie-Curie IEF program (European Union) and the A.P. Sloan Foundation (USA)

    A search for the decay B+→K+ΜΜˉB^+ \to K^+ \nu \bar{\nu}

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    We search for the rare flavor-changing neutral-current decay B+→K+ΜΜˉB^+ \to K^+ \nu \bar{\nu} in a data sample of 82 fb−1^{-1} collected with the {\sl BABAR} detector at the PEP-II B-factory. Signal events are selected by examining the properties of the system recoiling against either a reconstructed hadronic or semileptonic charged-B decay. Using these two independent samples we obtain a combined limit of B(B+→K+ΜΜˉ)<5.2×10−5{\mathcal B}(B^+ \to K^+ \nu \bar{\nu})<5.2 \times 10^{-5} at the 90% confidence level. In addition, by selecting for pions rather than kaons, we obtain a limit of B(B+→π+ΜΜˉ)<1.0×10−4{\mathcal B}(B^+ \to \pi^+ \nu \bar{\nu})<1.0 \times 10^{-4} using only the hadronic B reconstruction method.Comment: 7 pages, 8 postscript figures, submitted to Phys. Rev. Let

    High-reflectivity broadband distributed Bragg reflector lattice matched to ZnTe

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    We report on the realization of a high quality distributed Bragg reflector with both high and low refractive index layers lattice matched to ZnTe. Our structure is grown by molecular beam epitaxy and is based on binary compounds only. The high refractive index layer is made of ZnTe, while the low index material is made of a short period triple superlattice containing MgSe, MgTe, and ZnTe. The high refractive index step of Delta_n=0.5 in the structure results in a broad stopband and the reflectivity coefficient exceeding 99% for only 15 Bragg pairs.Comment: 4 pages, 3 figure

    EuFe2_2As2_2 under high pressure: an antiferromagnetic bulk superconductor

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    We report the ac magnetic susceptibility χac\chi_{ac} and resistivity ρ\rho measurements of EuFe2_2As2_2 under high pressure PP. By observing nearly 100% superconducting shielding and zero resistivity at PP = 28 kbar, we establish that PP-induced superconductivity occurs at Tc∌T_c \sim~30 K in EuFe2_2As2_2. ρ\rho shows an anomalous nearly linear temperature dependence from room temperature down to TcT_c at the same PP. χac\chi_{ac} indicates that an antiferromagnetic order of Eu2+^{2+} moments with TN∌T_N \sim~20 K persists in the superconducting phase. The temperature dependence of the upper critical field is also determined.Comment: To appear in J. Phys. Soc. Jpn., Vol. 78 No.

    Improved measurement of CP asymmetries in B-0 ->(c(c)over-bar)K0((*)) decays

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    We present results on time-dependent CP asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 227x10(6) Upsilon(4S)-> B (B) over bar decays collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. The amplitude of the CPasymmetry, sin2 beta in the standard model, is derived from decay-time distributions from events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the other B meson is determined to be either a B-0 or (0) from its decay products. We measure sin2 beta=0.722 +/- 0.040(stat)+/- 0.023(syst) in agreement with the standard model expectation

    The Physics of the B Factories

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    Inflammation and treatment response to sertraline in patients with coronary heart disease and comorbid major depression

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    OBJECTIVE: Treatment-resistant depression has recently emerged as a marker of increased risk for morbidity and mortality in patients with coronary heart disease (CHD). Studies in depressed patients without CHD suggest that elevated markers of inflammation predict poor response to treatment. This may help to explain the increased risk of cardiac events associated with depression. We therefore studied the relationship between pre-treatment markers of inflammation and treatment response in patients with CHD and major depression. METHODS: This was a planned, secondary analysis of a clinical trial in which 122 patients with CHD and comorbid major depression were randomly assigned to 50mg of sertraline plus 2g/day omega-3 fatty acids or to 50mg of sertraline plus 2g/day corn oil placebo capsules for ten weeks. Depressive symptoms were assessed with the Beck Depression Inventory-II (BDI-II). Blood samples were collected at baseline to determine levels of high-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α). The primary outcome was the post-treatment BDI-II depression score. RESULTS: Baseline levels of hs-CRP, IL-6, and TNF-α were not associated with the 10-week post-treatment depression score (p=0.89, p=0.88, and p=0.31, respectively). Treatment responders (>50% reduction from baseline BDI-II score) did not differ from non-responders in either baseline hs-CRP, IL-6, or TNF-α (p=0.83, p=0.93, and p=0.24, respectively). Similarly, depression remitters (BDI-II ≀8 at post-treatment) did not differ from non-remitters on the three baseline inflammation markers. CONCLUSION: These findings do not support the hypothesis that elevated baseline inflammatory markers predict poor response to sertraline in patients with CHD and major depression. The explanation for the increased risk of cardiac events associated with poor response to depression treatment remains unclear
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