5,805 research outputs found

    Effect of dynamic stall on the aerodynamics of vertical-axis wind turbines

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    Accurate simulations of the aerodynamic performance of vertical-axis wind turbines pose a significant challenge for computational fluid dynamics methods. The aerodynamic interaction between the blades of the rotor and the wake that is produced by the blades requires a high-fidelity representation of the convection of vorticity within the wake. In addition, the cyclic motion of the blades induces large variations in the angle of attack on the blades that can manifest as dynamic stall. The present paper describes the application of a numerical model that is based on the vorticity transport formulation of the Navier–Stokes equations, to the prediction of the aerodynamics of a verticalaxis wind turbine that consists of three curved rotor blades that are twisted helically around the rotational axis of the rotor. The predicted variation of the power coefficient with tip speed ratio compares very favorably with experimental measurements. It is demonstrated that helical blade twist reduces the oscillation of the power coefficient that is an inherent feature of turbines with non-twisted blade configurations

    Probing nuclear symmetry energy with the sub-threshold pion production

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    Within the framework of semiclassical Boltzmann-Uehling-Uhlenbeck (BUU) transport model, we investigated the effects of symmetry energy on the sub-threshold pion using the isospin MDI interaction with the stiff and soft symmetry energies in the central collision of 48^{48}Ca + 48^{48}Ca at the incident beam energies of 100, 150, 200, 250 and 300 MeV/nucleon, respectively. We find that the ratio of π/π+\pi^{-}/\pi^{+} of sub-threshold charged pion production is greatly sensitive to the symmetry energy, particularly around 100 MeV/nucleon energies. Large sensitivity of sub-threshold charged pion production to nuclear symmetry energy may reduce uncertainties of probing nuclear symmetry energy via heavy-ion collision.Comment: 5 pages, 5 figures, typo corrections, submitted to Chinese Physics Letter

    Phase transitions of hadronic to quark matter at finite T and \mu_B

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    The phase transition of hadronic to quark matter and the boundaries of the mixed hadron-quark coexistence phase are studied within the two Equation of State (EoS) model. The relativistic effective mean field approach with constant and density dependent meson-nucleon couplings is used to describe hadronic matter, and the MIT Bag model is adopted to describe quark matter. The boundaries of the mixed phase for different Bag constants are obtained solving the Gibbs equations. We notice that the dependence on the Bag parameter of the critical temperatures (at zero chemical potential) can be well reproduced by a fermion ultrarelativistic quark gas model, without contribution from the hadron part. At variance the critical chemical potentials (at zero temperature) are very sensitive to the EoS of the hadron sector. Hence the study of the hadronic EoS is much more relevant for the determination of the transition to the quark-gluon-plasma at finite baryon density and low-T. Moreover in the low temperature and finite chemical potential region no solutions of the Gibbs conditions are existing for small Bag constant values, B < (135 MeV)^4. Isospin effects in asymmetric matter appear relevant in the high chemical potential regions at lower temperatures, of interest for the inner core properties of neutron stars and for heavy ion collisions at intermediate energies.Comment: 24 pages and 16 figures (revtex4

    The cyclomodulin cycle inhibiting factor (CIF) alters cullin neddylation dynamics

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    The bacterial effector protein cycle inhibiting factor (CIF) converts glutamine 40 of NEDD8 to glutamate (Q40E), causing cytopathic effects and inhibiting cell proliferation. Although these have been attributed to blocking the functions of cullin-RING ubiquitin ligases, how CIF modulates NEDD8-dependent signaling is unclear. Here we use conditional NEDD8-dependent yeast to explore the effects of CIF on cullin neddylation. Although CIF causes cullin deneddylation and the generation of free NEDD8 Q40E, inhibiting the COP9 signalosome (CSN) allows Q40E to form only on NEDD8 attached to cullins. In the presence of the CSN, NEDD8 Q40E is removed from cullins more rapidly than NEDD8, leading to a decrease in steady-state cullin neddylation. As NEDD8 Q40E is competent for cullin conjugation in the absence of functional CSN and with overexpression of the NEDD8 ligase Dcn1, our data are consistent with NEDD8 deamidation causing enhanced deneddylation of cullins by the CSN. This leads to a dramatic change in the extent of activated cullin-RING ubiquitin ligases

    An Improved 96-well Turbidity Assay for T4 Lysozyme Activity

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    T4 lysozyme (T4L) is an important model system for investigating the relationship between protein structure and function. Despite being extensively studied, a reliable, quantitative activity assay for T4L has not been developed. Here, we present an improved T4L turbidity assay as well as an affinity-based T4L expression and purification protocol. This assay is designed for 96-well format and utilizes conditions amenable for both T4L and other lysozymes. This protocol enables easy, efficient, and quantitative characterization of T4L variants and allows comparison between different lysozymes. Our method: •Is applicable for all lysozymes, with enhanced sensitivity for T4 lysozyme compared to other 96-well plate turbidity assays;•Utilizes standardized conditions for comparing T4 lysozyme variants and other lysozymes; and•Incorporates a simplified expression and purification protocol for T4 lysozyme

    Información molecular vs información genealógica en la gestión de poblaciones

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    Tanto en el campo de la conservación como en el de la mejora genética, se han propuesto diversos métodos para gestionar una población controlando la pérdida de diversidad genética. En poblaciones no subdivididas, el método aceptado es determinar la contribución de cada posible padre (i.e., el número de descendientes que cada individuo deja a la siguiente generación), minimizando el parentesco global de los padres ponderado por estas contribuciones (Meuwissen, 1997; Grundy et al., 1998; Fernández et al., 2003). Los coeficientes de parentesco se obtienen normalmente de la genealogía, y en dicho caso, se optimiza el parentesco global genealógico. Sin embargo, la información genealógica no está siempre disponible, en cuyo caso se pueden usar marcadores moleculares para calcular el parentesco molecular o estimar el parentesco genealógico (Toro et al., 2009). Así, cuando no se dispone de genealogías, se puede minimizar el parentesco molecular global o el parentesco global genealógico estimado con los marcadores. Fernández et al. (2005) estudiaron mediante simulaciones la capacidad de la información molecular de reemplazar a la información genealógica, y concluyeron que el uso exclusivo de información molecular era claramente insuficiente. En dicho estudio, los autores se basaron en un número limitado de marcadores microsatélites, del orden de decenas. En la actualidad, gracias a los métodos de secuenciación de última generación, disponemos de miles de marcadores de tipo SNP, lo que hace necesaria una revisión de aquellas investigaciones que concluían que la utilidad de la información molecular era limitada e inferior a la genealógica. En este estudio, reevaluamos vía simulaciones la capacidad de la información genómica de reemplazar a la información genealógica para mantener diversidad genética en programas de conservación, usando un número de SNPs en línea con los datos actualmente disponible

    A Process and Outcome Evaluation of a Shelter for Homeless Young Women

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    To evaluate the processes and outcomes of a short-term shelter, both quantitative and qualitative data were gathered via participant observation, focus group interviews with shelter staff and residents, and individual interviews with a sample of 40 young women who had been homeless prior to using the shelter. The process evaluation showed that the shelter staff strived to utilize an empowerment philosophy in their relationships with residents, but that there were many challenges to implementing this philosophy. The outcome evaluation showed that, at a 3-month follow-up, the participants reported significant improvements in housing, income, independence, and life satisfaction, but most continued to experience poverty and a number of other difficulties. The results were discussed in terms of the implications for future research and the value and limitations of shelters for dealing with homeless youth. The need for more sustained and comprehensive program interventions and supportive social policies was underscored

    Three-dimensional Simulations of Accretion to Stars with Complex Magnetic Fields

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    Disk accretion to rotating stars with complex magnetic fields is investigated using full three-dimensional magnetohydrodynamic (MHD) simulations. The studied magnetic configurations include superpositions of misaligned dipole and quadrupole fields and off-centre dipoles. The simulations show that when the quadrupole component is comparable to the dipole component, the magnetic field has a complex structure with three major magnetic poles on the surface of the star and three sets of loops of field lines connecting them. A significant amount of matter flows to the quadrupole "belt", forming a ring-like hot spot on the star. If the maximum strength of the magnetic field on the star is fixed, then we observe that the mass accretion rate, the torque on the star, and the area covered by hot spots are several times smaller in the quadrupole-dominant cases than in the pure dipole cases. The influence of the quadrupole component on the shape of the hot spots becomes noticeable when the ratio of the quadrupole and dipole field strengths Bq/Bd0.5B_q/B_d\gtrsim0.5, and becomes dominant when Bq/Bd1B_q/B_d\gtrsim1. In the case of an off-centre dipole field, most of the matter flows through a one-armed accretion stream, forming a large hot spot on the surface, with a second much smaller secondary spot. The light curves may have simple, sinusoidal shapes, thus mimicking stars with pure dipole fields. Or, they may be complex and unusual. In some cases the light curves may be indicators of a complex field, in particular if the inclination angle is known independently. We also note that in the case of complex fields, magnetospheric gaps are often not empty, and this may be important for the survival of close-in exosolar planets.Comment: 13 pages, 21 figures, accepted for publication in MNRA
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