3,349 research outputs found

    The Luminous Convolution Model as an alternative to dark matter in spiral galaxies

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    The Luminous Convolution Model (LCM) demonstrates that it is possible to predict the rotation curves of spiral galaxies directly from estimates of the luminous matter. We consider two frame-dependent effects on the light observed from other galaxies: relative velocity and relative curvature. With one free parameter, we predict the rotation curves of twenty-three (23) galaxies represented in forty-two (42) data sets. Relative curvature effects rely upon knowledge of both the gravitational potential from luminous mass of the emitting galaxy and the receiving galaxy, and so each emitter galaxy is compared to four (4) different Milky Way luminous mass models. On average in this sample, the LCM is more successful than either dark matter or modified gravity models in fitting the observed rotation curve data. Implications of LCM constraints on populations synthesis modeling are discussed in this paper. This paper substantially expands the results in arXiv:1309.7370.Comment: Implications of LCM constraints on populations synthesis modeling are discussed in this paper. This paper substantially expands the results in arxiv:1309.737

    Enabling Future Sustainability Transitions: An Urban Metabolism Approach to Los Angeles Pincetl et al. Enabling Future Sustainability Transitions

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    Summary: This synthesis article presents an overview of an urban metabolism (UM) approach using mixed methods and multiple sources of data for Los Angeles, California. We examine electric energy use in buildings and greenhouse gas emissions from electricity, and calculate embedded infrastructure life cycle effects, water use and solid waste streams in an attempt to better understand the urban flows and sinks in the Los Angeles region (city and county). This quantification is being conducted to help policy-makers better target energy conservation and efficiency programs, pinpoint best locations for distributed solar generation, and support the development of policies for greater environmental sustainability. It provides a framework to which many more UM flows can be added to create greater understanding of the study area's resource dependencies. Going forward, together with policy analysis, UM can help untangle the complex intertwined resource dependencies that cities must address as they attempt to increase their environmental sustainability

    A Wave Function Describing Superfluidity in a Perfect Crystal

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    We propose a many-body wave function that exhibits both diagonal and off-diagonal long-range order. Incorporating short-range correlations due to interatomic repulsion, this wave function is shown to allow condensation of zero-point lattice vibrations and phase rigidity. In the presence of an external velocity field, such a perfect crystal will develop non-classical rotational inertia, exhibiting the supersolid behavior. In a sample calculation we show that the superfluid fraction in this state can be as large as of order 0.01 in a reasonable range of microscopic parameters. The relevance to the recent experimental evidence of a supersolid state by Chan and Kim is discussed.Comment: final version to be published in Journal of Statistical Mechanics: Theory and Experimen

    Dear Wife : the Civil War letters of Chester K. Leach

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    Occasional paper (University of Vermont. Center for Research on Vermont) ; no. 20

    Swift observations of the SFXT SAX J1818.6-1703 in outburst

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    We present the Swift observations of the supergiant fast X-ray transient (SFXT) SAX J1818.6-1703 collected during the most recent outburst, which occurred on May 6 2009. In particular, we present broad-band spectroscopic and timing analysis as well as a Swift/XRT light curve that spans more than two weeks of observations. The broad-band spectral models and length of the outburst resemble those of the prototype of the SFXT class, XTE J1739-302, further confirming SAX J1818.6-1703 as a member of this class.Comment: Proceedings of 'X-Ray Astronomy 2009, Present Status, multiwavelength approach and future perspectives', September 7 - 11, 2009, Bologna, Ital

    Mutational mapping of RAS-responsive domains of the Saccharomyces cerevisiae adenylyl cyclase

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    Large deletion and small insertion mutations in the adenylyl cyclase gene of Saccharomyces cerevisiae were used to map regions required for activation by RAS protein in vitro. The amino-terminal 605 amino acids were found to be dispensable for responsiveness to RAS protein. All other deletions in adenylyl cyclase destroyed its ability to respond to RAS. Small insertion mutations within the leucine-rich repeat region also prevented RAS responsiveness, while other insertions did not

    Z=50 shell gap near 100^{100}Sn from intermediate-energy Coulomb excitations in even-mass 106112^{106--112}Sn isotopes

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    Rare isotope beams of neutron-deficient 106,108,110^{106,108,110}Sn nuclei from the fragmentation of 124^{124}Xe were employed in an intermediate-energy Coulomb excitation experiment yielding B(E2,01+21+)B(E2, 0^+_1 \to 2^+_1) transition strengths. The results indicate that these B(E2,01+21+)B(E2,0^+_1 \to 2^+_1) values are much larger than predicted by current state-of-the-art shell model calculations. This discrepancy can be explained if protons from within the Z = 50 shell are contributing to the structure of low-energy excited states in this region. Such contributions imply a breaking of the doubly-magic 100^{100}Sn core in the light Sn isotopes.Comment: 4 pages, 4 figure
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