29,767 research outputs found

    Color-Magnitude Diagram Constraints on the Metallicities, Ages, and Star Formation History of the Stellar Populations in the Carina Dwarf Spheroidal Galaxy

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    Victoria-Regina isochrones for 0.4-0.4 \le [alpha/Fe] +0.4\le +0.4 and a wide range in [Fe/H], along with complementary zero-age horizontal branch (ZAHB) loci, have been applied to the color-magnitude diagram (CMD) of Carina. The color transformations that we have used have been "calibrated" so that isochrones provide excellent fits to the [(BV)0,MV][(B-V)_0,\,M_V]-diagrams of M3 and M92, when well supported estimates of the globular cluster (GC) reddenings and metallicities are assumed. The adopted distance moduli, for both the GCs and Carina, are based on our ZAHB models, which are able to reproduce the old HB component (as well as the luminosity of the HB clump) of the dwarf spheroidal galaxy quite well --- even if it spans a range in [Fe/H] of ~ 1.5 dex, provided that [alpha/Fe] varies with [Fe/H] in approximately the way that has been derived spectroscopically. Ages derived here agree reasonably well with those found previously for the old and intermediate-age turnoff stars, as well as for the period of negligible star formation (SF) activity (~ 6-10 Gyr ago). CMD simulations have been carried out for the faintest turnoff and subgiant stars. They indicate a clear preference for SF that lasted several Gyr instead of a short burst, with some indication that ages decrease with increasing [Fe/H]. In general, stellar models that assume spectroscopic metallicities provide satisfactory fits to the observations, including the thin giant branch of Carina, though higher oxygen abundances than those implied by the adopted values of [alpha/Fe] would have favorable consequences.Comment: 15 pages, including 12 figures; accepted for publication in the Astrophysical Journa

    Annuities and Individual Welfare

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    This paper advances the theory of annuity demand. First, we derive sufficient conditions under which complete annuitization is optimal, showing that this well-known result holds true in a more general setting than in Yaari (1965). Specifically, when markets are complete, sufficient conditions need not impose exponential discounting, intertemporal separability or the expected utility axioms; nor need annuities be actuarially fair, nor longevity risk be the only source of consumption uncertainty. All that is required is that consumers have no bequest motive and that annuities pay a rate of return for survivors greater than those of otherwise matching conventional assets, net of administrative costs. Second, we show that full annuitization may not be optimal when markets are incomplete. Some annuitization is optimal as long as conventional asset markets are complete. The incompleteness of markets can lead to zero annuitization but the conditions on both annuity and bond markets are stringent. Third, we extend the simulation literature that calculates the utility gains from annuitization by considering consumers whose utility depends both on present consumption and a which they have become accustomed. The value of annuitization hinges critically on the size of the initial standard-of-living relative to wealth.

    Democratizing the American Dream: The Role of a Regional Housing Legislature in the Production of Affordable Housing

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    Economic, ethnic and racial residential segregation are ubiquitous across United States metropolitan regions. As a result, the majority of affordable housing is located in central cities or inner-ring suburbs, generally in areas of highly concentrated poverty. Outer suburbs are often exempt from providing significant housing for the economically disadvantaged regional citizens. This should not be. If housing policy in metropolitan regions were established in a democratic fashion, the give-and-take of the political process would create strong incentives for regional cooperation in the creation of affordable housing. Drawing together scholarship in the fields of local government law, administrative law, and housing policy, this Note proposes the creation of a Regional Housing Legislature (RHL), a democratically elected body composed of representatives from each of the region\u27s localities, charged with establishing a coherent regional affordable housing policy. The existence of the RHL will diminish the contentiousness of existing affordable housing solutions by providing democratic legitimacy and by giving each locality a meaningful voice in the development of regional affordable housing policy

    Simultaneous measurement of multiple parameters of a subwavelength structure based on the weak value formalism

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    A mathematical extension of the weak value formalism to the simultaneous measurement of multiple parameters is presented in the context of an optical focused vector beam scatterometry experiment. In this example, preselection and postselection are achieved via spatially-varying polarization control, which can be tailored to optimize the sensitivity to parameter variations. Initial experiments for the two-parameter case demonstrate that this method can be used to measure physical parameters with resolutions at least 1000 times smaller than the wavelength of illumination

    Trumpet slices of the Schwarzschild-Tangherlini spacetime

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    We study families of time-independent maximal and 1+log foliations of the Schwarzschild-Tangherlini spacetime, the spherically-symmetric vacuum black hole solution in D spacetime dimensions, for D >= 4. We identify special members of these families for which the spatial slices display a trumpet geometry. Using a generalization of the 1+log slicing condition that is parametrized by a constant n we recover the results of Nakao, Abe, Yoshino and Shibata in the limit of maximal slicing. We also construct a numerical code that evolves the BSSN equations for D=5 in spherical symmetry using moving-puncture coordinates, and demonstrate that these simulations settle down to the trumpet solutions.Comment: 11 pages, 6 figures, submitted to PR

    Near Infrared Surface Properties of the Two Intrinsically Brightest Minor Planets (90377) Sedna and (90482) Orcus

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    We present low resolution K band spectra taken at the Gemini 8 meter telescope of (90377) Sedna and (90482) Orcus (provisional designations 2003 VB12 and 2004 DW, respectively), currently the two minor planets with the greatest absolute magnitudes (i.e. the two most reflective minor planets). We place crude limits on the surface composition of these two bodies using a Hapke model for a wide variety of assumed albedos. The unusual minor planet (90377) Sedna was discovered on November 14, 2003 UT at roughly 90 AU with 1.6 times the heliocentric distance and perihelion distance of any other bound minor planet. It is the first solar system object discovered between the Kuiper Belt and the Oort Cloud, and may represent a transition population between the two. The reflectance spectrum of (90377) Sedna appears largely featureless at the current signal-to-noise ratio, suggesting a surface likely to be highly processed by cosmic rays. For large grain models (100 micron to 1 cm) we find that (90377) Sedna must have less than 70% surface fraction of water ice and less than 60% surface fraction of methane ice to 3 sigma confidence. Minor planet (90482) Orcus shows strong water ice absorption corresponding to less than 50% surface fraction for grain models 25 micron and larger. Orcus cannot have more than 30% of its surface covered by large (100 mm to 1 cm) methane grains to 3 sigma confidence.Comment: Accepted for publication in the Astrophysical Journa

    Forced Abortions and Involuntary Sterlization in China: Are the Victims of Coercive Population Control Measures Eligible for Asylum in the United States

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    This article discusses the propriety of granting political control policy. It argues that China is persecuting some of its citizens through its population control policy and that the United States should grant asylum to those who have been persecuted or who have a genuine fear of future persecution

    Alien Registration- Brown, Thomas S A. (Portland, Cumberland County)

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    https://digitalmaine.com/alien_docs/23889/thumbnail.jp
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