24,725 research outputs found

    The bounds of adult language acquisition: Blocking and learned attention.

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    Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/139848/1/EllisandSagarraSSLA2010offprint.pd

    Learned attention in adult language acquisition: A replication and generalization study and meta-analysis.

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    Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/139849/1/EllisandSagarra_SSLA_2011_Offprint.pd

    A Solution to the Graceful Exit Problem in Pre-Big Bang Cosmology

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    We examine the string cosmology equations with a dilaton potential in the context of the Pre-Big Bang Scenario with the desired scale factor duality, and give a generic algorithm for obtaining solutions with appropriate evolutionary properties. This enables us to find pre-big bang type solutions with suitable dilaton behaviour that are regular at t=0t=0, thereby solving the graceful exit problem. However to avoid fine tuning of initial data, an `exotic' equation of state is needed that relates the fluid properties to the dilaton field. We discuss why such an equation of state should be required for reliable dilaton behaviour at late times.Comment: 16 pages LaTeX, 5 figures. To appear in Physical Review

    The Star Formation History of the Hubble Sequence: Spatially Resolved Colour Distributions of Intermediate Redshift Galaxies in the Hubble Deep Field

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    We analyse the spatially resolved colours of distant galaxies of known redshift in the Hubble Deep Field, using a new technique based on matching resolved four-band internal colour data to the predictions of evolutionary synthesis models. We quantify the relative age, dispersion in age, ongoing star-formation rate, star-formation history, and dust content of these galaxies. To demonstrate the potential of the method, we study the near-complete sample of 32 I ~ 0.5 studied by Bouwens et al (1997). The dispersion of the internal colours of a sample of 0.4<z<1 early-type field galaxies in the HDF indicates that ~40% [4/11] show evidence of star formation which must have occurred within the past third of their ages at the epoch of observation. For a sample of well-defined spirals, we similarly exploit the dispersion in colour to analyse the relative histories of bulge and disc stars, in order to resolve the current controversy regarding the ages of galactic bulges. Dust and metallicity gradients are ruled out as major contributors to the colour dispersions we observe in these systems. The median ages of bulge stars are found to be signicantly older than those in galactic discs, and exhibit markedly different star-formation histories. This result is inconsistent with a secular growth of bulges from disc instabilities, but consistent with gradual disc formation by accretion of gas onto bulges, as predicted by hierarchical theories. We extend our technique in order to discuss the star formation history of the entire Bouwens et al sample in the context of earlier studies concerned with global star formation histories.Comment: 8 colour postscript figures plus LaTeX source; submitted to MNRAS. Uses the mnras.sty LaTeX style fil

    Alefacept therapy produces remission for patients with chronic plaque psoriasis

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    Background  Alefacept, human LFA-3/IgG 1 fusion protein, is a novel biological agent currently being developed for the treatment of chronic plaque psoriasis. Alefacept selectively reduces the memory-effector T cells that have been implicated in the pathogenesis of the disease; as a result, alefacept is classified as a therapy that induces remission (so-called ‘remittive’ therapy). In a previously published randomized, placebo-controlled phase II study of intravenous alefacept in 229 patients with chronic plaque psoriasis, clinical improvement was observed during dosing as well as in the postdosing follow-up period. Objectives  To assess the remission period following alefacept therapy. Methods  The time before re-treatment was required was measured in patients who were ‘clear’ or ‘almost clear’ of disease according to a physician global assessment at the end of the follow-up phase. Results  In these patients, responses were sustained for a median of 10 months, and for up to 18 months. No patient reported disease rebound after cessation of alefacept. Conclusions  Alefacept is a biological agent for the treatment of chronic plaque psoriasis that provides disease-free intervals and time off drug therapy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75170/1/j.1365-2133.2003.05239.x.pd

    Shrinking II -- The Distortion of the Area Distance-Redshift Relation in Inhomogeneous Isotropic Universes

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    This paper and the others in the series challenge the standard model of the effects of gravitational lensing on observations at large distances. We show that due to the cumulative effect of lensing, areas corresponding to an observed solid angle can be quite different than would be estimated from the corresponding Friedmann-Lema\^{\i}tre model, even when averaged over large angular scales. This paper concentrates on the specific example of spherically symmetric but spatially inhomogeneous dust universes, the Lema\^{\i}tre-Tolman-Bondi models, and shows that radial lensing significantly distorts the area distance-redshift and density-redshift relations in these exact solutions compared with the standard ones for Friedmann-Lema\^{\i}tre models. Thus inhomogeneity may introduce significant errors into distance estimates based on the standard FL relations, even after all-sky averaging. In addition a useful new gauge choice is presented for these models, solving the problem of locating the past null cone exactly.Comment: Minor technical refinement, 16 pages, RevTex, 8 eps figure

    Brany Liouville Inflation

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    We present a specific model for cosmological inflation driven by the Liouville field in a non-critical supersymmetric string framework, in which the departure from criticality is due to open strings stretched between the two moving Type-II 5-branes. We use WMAP and other data on fluctuations in the cosmic microwave background to fix parameters of the model, such as the relative separation and velocity of the 5-branes, respecting also the constraints imposed by data on light propagation from distant gamma-ray bursters. The model also suggests a small, relaxing component in the present vacuum energy that may accommodate the breaking of supersymmetry.Comment: 23 pages LATEX, two eps figures incorporated; version accepted for publication in NJ
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