553 research outputs found

    VIRIS: A Visual-Infrared Imaging System for the Lick Observatory 1-M Telescope

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    We describe a system in use at the Lick Observatory 1-m Nickel telescope for near-simultaneous imaging at optical and near-infrared wavelengths. The combined availability of a CCD and a NICMOS-3 camera makes the system well-suited for photometric monitoring from 0.5-2.2 microns of a variety of astrophysical objects. Our science program thus far has concentrated on studying variability trends in young stellar objects.Comment: 11 pages LaTex, 3 Postscript figure, Pub. Astr. Soc. Pac. 1998, in pres

    CHARACTERISTICS OF ANODIC AND CORROSION FILMS ON ZIRCONIUM

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    Zirconium anodizes similarly to tungsten in respect to the change of interference colors with applied voltage. However, the oxide layer on tungsten cannot reach as great a thickness. Hafnium does not anodize in the same way as zirconium but is similar to tantalum. By measuring the interference color and capacitative thicknesses on zirconium (Grades I and III) and a 2.5 wt.% tin ailoy, the film was found to grow less rapidly in terms of capacitance than in terms of iaterference colors. This was interpreted to mean that cracks develop in the oxide as it thickens. The effect was most pronounced on Grade III zirconium and least pronounced on the tin alloy. The reduction in capacitative thickness was especially noticeable when white oxide appeared. Comparative measurements on Grade I zirconium and 2.5 wt.% tin alloy indicated that the thickness of the oxide film on the tin alloy (after 16 hours in water) increased more rapidly with temperature than the film on zirconium. Tin is believed to act in ways to counteract the tendency of the oxide to form cracks, and to produce vacancies which promote ionic diffusion. (auth

    Jugendhilfe in der DDR im Spiegel der Zeitschrift „Jugendhilfe“

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    Welches pädagogische Leitbild war in der DDR gegenüber Kindern und Jugendlichen innerhalb der Jugendhilfe dominierend? Welche Abweichungen von diesem Leitbild standen dem gegenüber? In der Arbeit werden pädagogische Normen aus den Texten der einzigen Jugendhilfezeitschrift der DDR, bis zum Jahr 1971 eruiert. Demgegenüber standen Devianzen, die als negative Normen gekennzeichnet wurden und mit welcher Vehemenz wurden diese Normen eingefordert? Weiterhin untersucht die Arbeit die Fragestellung ob Jugendhilfe sich als Forder- oder Fördereinrichtung für Kinder und Jugendliche präsentierte. Diente Jugendhilfe in der DDR als Reparaturwerkstatt für defekte Minderjährige? Wurde die Individualität in einer subjektiven Identitätsentwicklung berücksichtigt oder standen uniforme gesellschaftliche Vorgaben im Vordergrund? Ein weiterer Schwerpunkt liegt in der Untersuchung von psychologischen Traumata generierenden Beziehungen zwischen Einzelnen, kollektiven und institutionell statuierten gesellschaftlichen Verhältnissen

    Composition Effects on Kilonova Spectra and Light Curves: I

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    The merger of neutron star binaries is believed to eject a wide range of heavy elements into the universe. By observing the emission from this ejecta, scientists can probe the ejecta properties (mass, velocity and composition distributions). The emission (a.k.a. kilonova) is powered by the radioactive decay of the heavy isotopes produced in the merger and this emission is reprocessed by atomic opacities to optical and infra-red wavelengths. Understanding the ejecta properties requires calculating the dependence of this emission on these opacities. The strong lines in the optical and infra-red in lanthanide opacities have been shown to significantly alter the light-curves and spectra in these wavelength bands, arguing that the emission in these wavelengths can probe the composition of this ejecta. Here we study variations in the kilonova emission by varying individual lanthanide (and the actinide uranium) concentrations in the ejecta. The broad forest of lanthanide lines makes it difficult to determine the exact fraction of individual lanthanides. Nd is an exception. Its opacities above 1 micron are higher than other lanthanides and observations of kilonovae can potentially probe increased abundances of Nd. Similarly, at early times when the ejecta is still hot (first day), the U opacity is strong in the 0.2-1 micron wavelength range and kilonova observations may also be able to constrain these abundances

    <<Die>> Ehe zwischen Juden und Christen

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    The Beta Problem: A Study of Abell 262

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    We present an investigation of the dynamical state of the cluster A262. Existing optical line of sight velocities for select cluster galaxies have been augmented by new data obtained with the Automated Multi-Object Spectrograph at Lick Observatory. We find evidence for a virialized early-type population distinct from a late-type population infalling from the Pisces-Perseus supercluster ridge. We also report on a tertiary population of low luminosity galaxies whose velocity dispersion distinguishes them from both the early and late-type galaxies. We supplement our investigation with an analysis of archival X-ray data. A temperature is determined using ASCA GIS data and a gas profile is derived from ROSAT HRI data. The increased statistics of our sample results in a picture of A262 with significant differences from earlier work. A previously proposed solution to the "beta-problem" in A262 in which the gas temperature is significantly higher than the galaxy temperature is shown to result from using too low a velocity dispersion for the early-type galaxies. Our data present a consistent picture of A262 in which there is no "beta-problem", and the gas and galaxy temperature are roughly comparable. There is no longer any requirement for extensive galaxy-gas feedback to drastically overheat the gas with respect to the galaxies. We also demonstrate that entropy-floor models can explain the recent discovery that the beta values determined by cluster gas and the cluster core radii are correlated.Comment: 31 pages, 14 figures, AAS LaTeX v5.0, Encapsulated Postscript figures, to be published in The Astrophysical Journa

    Human TLR1 Deficiency Is Associated with Impaired Mycobacterial Signaling and Protection from Leprosy Reversal Reaction

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    Toll-like receptors (TLRs) are important regulators of the innate immune response to pathogens, including Mycobacterium leprae, which is recognized by TLR1/2 heterodimers. We previously identified a transmembrane domain polymorphism, TLR1_T1805G, that encodes an isoleucine to serine substitution and is associated with impaired signaling. We hypothesized that this TLR1 SNP regulates the innate immune response and susceptibility to leprosy. In HEK293 cells transfected with the 1805T or 1805G variant and stimulated with extracts of M. leprae, NF-κB activity was impaired in cells with the 1805G polymorphism. We next stimulated PBMCs from individuals with different genotypes for this SNP and found that 1805GG individuals had significantly reduced cytokine responses to both whole irradiated M. leprae and cell wall extracts. To investigate whether TLR1 variation is associated with clinical presentations of leprosy or leprosy immune reactions, we examined 933 Nepalese leprosy patients, including 238 with reversal reaction (RR), an immune reaction characterized by a Th1 T cell cytokine response. We found that the 1805G allele was associated with protection from RR with an odds ratio (OR) of 0.51 (95% CI 0.29–0.87, p = 0.01). Individuals with 1805 genotypes GG or TG also had a reduced risk of RR in comparison to genotype TT with an OR of 0.55 (95% CI 0.31–0.97, p = 0.04). To our knowledge, this is the first association of TLR1 with a Th1-mediated immune response. Our findings suggest that TLR1 deficiency influences adaptive immunity during leprosy infection to affect clinical manifestations such as nerve damage and disability

    The felon, the faithful and the fighter: the Ppotean face of the chivalric man (javanmard) in the medieval Persianate and modern Iranian worlds

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    Javanmardi is one of the most significant components in the identity of Persians and those who have lived and live in areas where Persianate culture has been and remains strong. This essay argues that the ethic of javanmardi demonstrates a high level of cultural continuity. The difficulty of defining this concept is partly resolved by relying on seminal texts from the medieval period and referring to important historical figures from early Iranian history. A taxonomy of types, the felon, the faithful and the fighter, are utilised in this article to provide a bricolage of characters who demonstrate that javanmardi is just as important in modern Iran as it was in medieval Persia
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