766 research outputs found

    Descriptive Analysis of Emancipated Foster Youth Seeking Mental Health Treatment

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    Current and former foster youth experience increased risk for behavioral, cognitive, and emotional problems due to maltreatment and experiences in foster care. Nonetheless, research indicates a gap between the need for mental health services and service use. The current study describes a sample of self-referring, emancipated foster youth seeking long-term psychotherapy to understand reasons youth seek psychotherapy. This study further compares a subset of youths’ data with reports collected from respective therapists to examine differences in perceptions of symptoms

    Self-similarity and long-time behavior of solutions of the diffusion equation with nonlinear absorption and a boundary source

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    This paper deals with the long-time behavior of solutions of nonlinear reaction-diffusion equations describing formation of morphogen gradients, the concentration fields of molecules acting as spatial regulators of cell differentiation in developing tissues. For the considered class of models, we establish existence of a new type of ultra-singular self-similar solutions. These solutions arise as limits of the solutions of the initial value problem with zero initial data and infinitely strong source at the boundary. We prove existence and uniqueness of such solutions in the suitable weighted energy spaces. Moreover, we prove that the obtained self-similar solutions are the long-time limits of the solutions of the initial value problem with zero initial data and a time-independent boundary source

    Partial domain wall partition functions

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    We consider six-vertex model configurations on an n-by-N lattice, n =< N, that satisfy a variation on domain wall boundary conditions that we define and call "partial domain wall boundary conditions". We obtain two expressions for the corresponding "partial domain wall partition function", as an (N-by-N)-determinant and as an (n-by-n)-determinant. The latter was first obtained by I Kostov. We show that the two determinants are equal, as expected from the fact that they are partition functions of the same object, that each is a discrete KP tau-function, and, recalling that these determinants represent tree-level structure constants in N=4 SYM, we show that introducing 1-loop corrections, as proposed by N Gromov and P Vieira, preserves the determinant structure.Comment: 30 pages, LaTeX. This version, which appeared in JHEP, has an abbreviated abstract and some minor stylistic change

    Parallel Excluded Volume Tempering for Polymer Melts

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    We have developed a technique to accelerate the acquisition of effectively uncorrelated configurations for off-lattice models of dense polymer melts which makes use of both parallel tempering and large scale Monte Carlo moves. The method is based upon simulating a set of systems in parallel, each of which has a slightly different repulsive core potential, such that a thermodynamic path from full excluded volume to an ideal gas of random walks is generated. While each system is run with standard stochastic dynamics, resulting in an NVT ensemble, we implement the parallel tempering through stochastic swaps between the configurations of adjacent potentials, and the large scale Monte Carlo moves through attempted pivot and translation moves which reach a realistic acceptance probability as the limit of the ideal gas of random walks is approached. Compared to pure stochastic dynamics, this results in an increased efficiency even for a system of chains as short as N=60N = 60 monomers, however at this chain length the large scale Monte Carlo moves were ineffective. For even longer chains the speedup becomes substantial, as observed from preliminary data for N=200N = 200

    Effective field theory and dispersion law of the phonons of a non-relativistic superfluid

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    We study the recently proposed effective field theory for the phonon of an arbitrary non-relativistic superfluid. After computing the one-loop phonon self-energy, we obtain the low temperature T contributions to the phonon dispersion law at low momentum, and see that the real part of those can be parametrized as a thermal correction to the phonon velocity. Because the phonons are the quanta of the sound waves, at low momentum their velocity should agree with the speed of sound. We find that our results match at order T^4ln(T) with those predicted by Andreev and Khalatnikov for the speed of sound, derived from the superfluid hydrodynamical equations and the phonon kinetic theory. We get also higher order corrections of order T^4, which are not reproduced pushing naively the kinetic theory computation. Finally, as an application, we consider the cold Fermi gas in the unitarity limit, and find a universal expression for the low T relative correction to the speed of sound for these systems.Comment: 14 pages, 2 figures. References adde

    Efecto del contenido de aluminato de estroncio y hemihidrato sobre las propiedades de un cemento de sulfoaluminato de calcio

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    The effect of strontium aluminate (SrAl2O4) on the hydration process of a calcium sulphoaluminate (C4A3Ŝ) cement was investigated. Cement pastes were prepared by mixing C4A3Ŝ , hemihydrate (CaSO4· ½H2O, CŜH0.5) and 0, 10 or 20wt% of SrAl2O4 (SrA). The amount of CŜH0.5 was 15, 20 or 25wt% based on the C4A3Ŝ quantity. The cement pastes were hydrated using water to cement ratios (w/c) of 0.4 and 0.5. Samples were cured from 1 to 28 d. The compressive strength and setting time were evaluated and the hydration products were characterized. It was found that the setting time was delayed up to 42 min for the samples containing SrAl2O4 compared to samples without addition. The samples with 25wt% hemihydrate containing 20wt% SrAl2O4 developed the highest compressive strength (60 MPa) after 28 d of curing. The main product after hydration was ettringite (C6AŜ3H32). The morphology of this phase consisted of thin needle-shaped crystals.Se investigó el efecto de la adición de aluminato de estroncio (SrAl2O4) sobre las propiedades de un cemento de sulfoaluminato de calcio (C4A3Ŝ). Se prepararon muestras mezclando C4A3Ŝ, hemihidrato (CaSO4· ½H2O, CŜH0.5) y 0, 10 o 20% e.p de SrAl2O4 (SrA). La cantidad de CŜH0.5 fue de 15, 20 o 25% e.p. basado en la cantidad de C4A3Ŝ. Las relaciones agua/cemento utilizadas fueron 0.4 y 0.5. Las muestras fueron curadas hasta 28 d. Se evaluó el tiempo de fraguado y la resistencia a la compresión. Los productos de hidratación se caracterizaron mediante DRX y MEB. El tiempo de fraguado se retardó hasta 42 minutos con la adición del SrAl2O4 comparado con las muestras sin adiciones. Las muestras con 25% e.p. de yeso y 20% e.p. de SrAl2O4 desarrollaron la mayor resistencia a la compresión alcanzando 60 MPa a 28 d de curado. Los análisis por MEB y DRX muestran como principal producto de hidratación a la etringita (C6AŜ3H32), cuya morfología se observa como cristales aciculares

    Efecto de la adición de ácido cítrico y la cantidad de yeso sobre las propiedades del cemento de sulfoaluminato de calcio

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    The influence of citric acid on the hydration and strength development of a calcium sulphoaluminate cement was investigated. Cement pastes were prepared by mixing calcium sulphoaluminate (C4A3Ŝ) with 15, 20 and 25wt% of hemihydrate (CŜH0.5). Citric acid was added as a retarder at 0 and 0.5wt%. The samples were cured at 20 °C for periods of time from 1 to 28 days to evaluate their compressive strength and to characterize the hydration products by scanning electron microscopy and X-ray diffraction. Calorimetric curves showed that the retarding agent considerably decreases the heat release rate and the quantity of total heat released. The main product after the curing was ettringite (C6AŜ3H32). The morphology of this phase consisted of long and thin needles growing radially on the cement grains. Samples with 15wt% of hemihydrate and 0.5wt% of citric acid developed the highest compressive strength (70 MPa) at 28 days of curing.Se investigó el efecto del ácido cítrico sobre la hidratación y propiedades mecánicas de un cemento de sulfoaluminato de calcio. El C4A3Ŝ se mezcló con 15, 20 y 25% e.p. de hemihidrato (CŜH0.5). Se agregó ácido cítrico como retardante en 0 y 0.5% e.p. Las muestras fueron curadas a 20 °C por periodos de 1 a 28 días para realizar mediciones de resistencia a la compresión y caracterizar los productos de hidratación mediante microscopía electrónica de barrido y difracción de rayos X. Las curvas de calorimetría mostraron ue el ácido cítrico disminuye la velocidad de liberación de calor y la cantidad de calor liberado durante la hidratación. La resistencia a la compresión alcanzó un máximo de 70 MPa en muestras con 15% e.p. de hemihidrato y 0,5% e.p de ácido cítrico. Los resultados muestran a la etringita (C6AŜ3H32) como principal producto de hidratación. Se observa a esta fase con morfología acicular creciendo sobre las partículas de cemento

    How to compute the thermal quarkonium spectral function from first principles?

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    In the limit of a high temperature T and a large quark-mass M, implying a small gauge coupling g, the heavy quark contribution to the spectral function of the electromagnetic current can be computed systematically in the weak-coupling expansion. We argue that the scale hierarchy relevant for addressing the disappearance ("melting") of the resonance peak from the spectral function reads M >> T > g^2 M > gT >> g^4 M, and review how the heavy scales can be integrated out one-by-one, to construct a set of effective field theories describing the low-energy dynamics. The parametric behaviour of the melting temperature in the weak-coupling limit is specified.Comment: 8 pages; to appear in the Proceedings of SEWM08, Amsterdam, the Netherlands, August 26-29, 200

    El SIG espacio SiAR, una herramienta del mapa a disposición del regadío español para la optimización del uso del agua gracias a las imágenes satélite

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    Comunicación presentada al XXXVII Congreso Nacional de Riegos, celebrado en Don Benito del 4 al 6 de Junio de 2019 y organizada por la Asociación Española de Riegos y Drenajes y la Universidad de ExtremaduraEl Sistema de Información Agroclimática para el Regadío (SiAR), tiene como misión la optimización del uso de agua en el regadío, promoviendo su sostenibilidad económica, social y medioambiental, mediante el asesoramiento a los regantes, facilitándoles información agroclimática relevante y estimaciones de riego. La Subdirección General de Regadíos e Infraestructuras Rurales ha desarrollado el proyecto ESPACIO SiAR, una herramienta webSIG que se integra los datos procedentes de las estaciones SiAR, ubicadas en las principales zonas regables, con las secuencias temporales de los satélites Landsat 8 y Sentinel 2A y 2B. Su objetivo principal es el de realizar un seguimiento mediante teledetección de los cultivos que permita determinar con la mayor precisión posible las necesidades hídricas de los cultivos, para emplear el agua necesaria en el momento preciso. La información obtenida se pone a disposición de forma gratuita y abierta, mediante el visor ESPACIO SiAR en la página web www.espaciosiar.es, para un amplio abanico de usuarios potenciales, como son los regantes individuales, gestores de comunidades de regantes, servicios de asesoramiento y la propia administración para la planificación de los recursos hídricos a corto, medio y largo plazo

    On holographic three point functions for GKP strings from integrability

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    Adapting the powerful integrability-based formalism invented previously for the calculation of gluon scattering amplitudes at strong coupling, we develop a method for computing the holographic three point functions for the large spin limit of Gubser-Klebanov- Polyakov (GKP) strings. Although many of the ideas from the gluon scattering problem can be transplanted with minor modifications, the fact that the information of the external states is now encoded in the singularities at the vertex insertion points necessitates several new techniques. Notably, we develop a new generalized Riemann bilinear identity, which allows one to express the area integral in terms of appropriate contour integrals in the presence of such singularities. We also give some general discussions on how semiclassical vertex operators for heavy string states should be constructed systematically from the solutions of the Hamilton-Jacobi equation.Comment: 62 pages;v2 Typos and equation (3.7) corrected. Clarifying remarks added in Section 4.1. Published version;v3 Minor errors found in version 2 are corrected. For explanation of the revision, see Erratum published in http://www.springerlink.com/content/m67055235407vx67/?MUD=M
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