1,510 research outputs found

    Behavior Problems in Toddlers With and Without Developmental Delays: Comparison of Treatment Outcomes

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    The purpose of this study is to examine the effectiveness of an in-home parent management program for toddlers with behavior problems and developmental delays by comparing outcomes for a group of toddlers with developmental delays (n = 27) and a group of toddlers without developmental delays (n = 27). The majority of children lived in single parent, low-income homes. Results suggest that the parent management program is equally effective for children with and without developmental delays. Parents from both groups reported clinically significant improvement in their children\u27s behavior and parenting practices. Clinical implications regarding the importance of these findings for improving outcomes for toddlers with behavior problems and developmental delays living in poverty were discussed

    The sloppy model universality class and the Vandermonde matrix

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    In a variety of contexts, physicists study complex, nonlinear models with many unknown or tunable parameters to explain experimental data. We explain why such systems so often are sloppy; the system behavior depends only on a few `stiff' combinations of the parameters and is unchanged as other `sloppy' parameter combinations vary by orders of magnitude. We contrast examples of sloppy models (from systems biology, variational quantum Monte Carlo, and common data fitting) with systems which are not sloppy (multidimensional linear regression, random matrix ensembles). We observe that the eigenvalue spectra for the sensitivity of sloppy models have a striking, characteristic form, with a density of logarithms of eigenvalues which is roughly constant over a large range. We suggest that the common features of sloppy models indicate that they may belong to a common universality class. In particular, we motivate focusing on a Vandermonde ensemble of multiparameter nonlinear models and show in one limit that they exhibit the universal features of sloppy models.Comment: New content adde

    CLEAR I: Ages and Metallicities of Quiescent Galaxies at 1.0<z<1.8\mathbf{1.0 < z < 1.8} Derived from Deep Hubble Space Telescope Grism Data

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    We use deep \textit{Hubble Space Telescope} spectroscopy to constrain the metallicities and (\editone{light-weighted}) ages of massive (logM/M10\log M_\ast/M_\odot\gtrsim10) galaxies selected to have quiescent stellar populations at 1.0<z<1.81.0<z<1.8. The data include 12--orbit depth coverage with the WFC3/G102 grism covering \sim 8,000<λ<11,5008,000<\lambda<11,500~\AA\, at a spectral resolution of R210R\sim 210 taken as part of the CANDELS Lyman-α\alpha Emission at Reionization (CLEAR) survey. At 1.0<z<1.81.0<z<1.8, the spectra cover important stellar population features in the rest-frame optical. We simulate a suite of stellar population models at the grism resolution, fit these to the data for each galaxy, and derive posterior likelihood distributions for metallicity and age. We stack the posteriors for subgroups of galaxies in different redshift ranges that include different combinations of stellar absorption features. Our results give \editone{light-weighted ages of tz1.1=3.2±0.7t_{z \sim 1.1}= 3.2\pm 0.7~Gyr, tz1.2=2.2±0.6t_{z \sim 1.2}= 2.2\pm 0.6~Gyr, tz1.3=3.1±0.6t_{z\sim1.3}= 3.1\pm 0.6~Gyr, and tz1.6=2.0±0.6t_{z\sim1.6}= 2.0 \pm 0.6~Gyr, \editone{for galaxies at z1.1z\sim 1.1, 1.2, 1.3, and 1.6. This} implies that most of the massive quiescent galaxies at 168168\% of their stellar mass by a redshift of z>2z>2}. The posteriors give metallicities of \editone{Zz1.1=1.16±0.29Z_{z\sim1.1}=1.16 \pm 0.29~ZZ_\odot, Zz1.2=1.05±0.34Z_{z\sim1.2}=1.05 \pm 0.34~ZZ_\odot, Zz1.3=1.00±0.31Z_{z\sim1.3}=1.00 \pm 0.31~ZZ_\odot, and Zz1.6=0.95±0.39Z_{z\sim1.6}=0.95 \pm 0.39~ZZ_\odot}. This is evidence that massive galaxies had enriched rapidly to approximately Solar metallicities as early as z3z\sim3.Comment: 32 pages, 23 figures, Resubmited to ApJ after revisions in response to referee repor

    Performance Testing of a Novel Off-plane Reflection Grating and Silicon Pore Optic Spectrograph at PANTER

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    An X-ray spectrograph consisting of radially ruled off-plane reflection gratings and silicon pore optics was tested at the Max Planck Institute for extraterrestrial Physics PANTER X-ray test facility. The silicon pore optic (SPO) stack used is a test module for the Arcus small explorer mission, which will also feature aligned off-plane reflection gratings. This test is the first time two off-plane gratings were actively aligned to each other and with a SPO to produce an overlapped spectrum. The gratings were aligned using an active alignment module which allows for the independent manipulation of subsequent gratings to a reference grating in three degrees of freedom using picomotor actuators which are controllable external to the test chamber. We report the line spread functions of the spectrograph and the actively aligned gratings, and plans for future development.Comment: Draft Version March 19, 201

    CANDELS: The Contribution of the Observed Galaxy Population to Cosmic Reionization

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    We present measurements of the specific ultraviolet luminosity density from a sample of 483 galaxies at 6<z<8. These galaxies were selected from new deep near-infrared HST imaging from the CANDELS, HUDF09 and ERS programs. In contrast to the majority of previous analyses, which assume that the distribution of galaxy ultraviolet (UV) luminosities follows a Schechter distribution, and that the distribution continues to luminosities far below our observable limit, we investigate the contribution to reionization from galaxies which we can observe, free from these assumptions. We find that the observable population of galaxies can sustain a fully reionized IGM at z=6, if the average ionizing photon escape fraction (f_esc) is ~30%. A number of previous studies have measured UV luminosity densities at these redshifts that vary by 5X, with many concluding that galaxies could not complete reionization by z=6 unless a large population of galaxies fainter than the detection limit were invoked, or extremely high values of f_esc were present. The observed UV luminosity density from our observed galaxy samples at z=7-8 is not sufficient to maintain a fully reionized IGM unless f_esc>50%. Combining our observations with constraints on the emission rate of ionizing photons from Ly-alpha forest observations at z=6, we can constrain f_esc<34% (2-sigma) if the observed galaxies are the only contributors to reionization, or <13% (2-sigma) if the luminosity function extends to M_UV = -13. These escape fractions are sufficient to complete reionization by z=6. These constraints imply that the volume ionized fraction of the IGM becomes less than unity at z>7, consistent with a number of complementary reionization probes. If faint galaxies dominate reionization, future JWST observations will probe deep enough to see them, providing an indirect constraint on the ionizing photon escape fraction [abridged].Comment: 16 pages, 7 figures, Submitted to the Astrophysical Journa

    Boomerang Litigation: How Convenient Is Forum Non Conveniens in Transnational Litigation?

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    El siguiente plan de negocios analiza la viabilidad para la puesta en marcha de una empresa dedicada a la Gestión de Redes Sociales en la ciudad de Lima, enfocada a brindar servicios de asesoría y consultoría de redes sociales al mercado latinoamericano, con el objetivo activar la marca de los clientes y generar valor para las empresas con el correcto funcionamiento y manejo de las herramientas digitales
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