Stellar collisions in galactic centers: black hole growth and color gradients

We study the effects of stellar collisions, particularly on feeding massive black holes (BHs) and color gradients, in realistic galactic centers. We find that the mass released by stellar collisions is not sufficient to account for the present BH mass in galactic centers, especially in bright galaxies. This study, together with the study by Magorrian & Tremaine (1999) on tidal disruption of stars by massive BHs, implies that the material for BH growth (especially in galaxies brighter than ~10^9 Lsun) can only come from other sources, for example, the mass released by stellar evolution in the initial ~1 Gyr of the galaxy's lifetime, or the gas that sinks to the galactic center in a galaxy merger. We also analyze how the color of a stellar system is affected by collisions of stars. We find that collisions between main-sequence stars cannot cause observable color gradients in the visible bands at projected radius R>0.1" in M31, M32 and other nearby galactic centers. This result is consistent with the lack of an observable color gradient in M32 at R>0.1". At even smaller radii, the color differences caused by collisions between main-sequence stars are at most 0.08 mag at R=0.02". The averaged blueing due to stellar collisions in the region R<0.1" of M32 should not be larger than 0.06 mag in color index U-V and 0.02 mag in V-I. The observed blueing in the center of the galaxy M31 (in a 0.14"x0.14" box) must be caused by some mechanism other than collisions between main-sequence stars.Comment: 27 pages, including 10 figures, MNRAS in pres

Study on Actuator Line Modeling of Two NREL 5-MW Wind Turbine Wakes

The wind turbine wakes impact the efficiency and lifespan of the wind farm. Therefore, to improve the wind plant performance, research on wind plant control is essential. The actuator line model (ALM) is proposed to simulate the wind turbine efficiently. This research investigates the National Renewable Energy Laboratory 5 Million Watts (NREL 5-MW) wind turbine wakes with Open Field Operation and Manipulation (OpenFOAM) using ALM. Firstly, a single NREL 5-MW turbine is simulated. The comparison of the power and thrust with Fatigue, Aerodynamics, Structures, and Turbulence (FAST) shows a good agreement below the rated wind speed. The information relating to wind turbine wakes is given in detail. The top working status is proved at the wind speed of 8 m/s and the downstream distance of more than 5 rotor diameters (5D). Secondly, another case with two NREL 5-MW wind turbines aligned is also carried out, in which 7D is validated as the optimum distance between the two turbines. The result also shows that the upstream wind turbine has an obvious influence on the downstream one

Construction of mammary gland specific expression plasmid pIN and its expression in vitro and in vivo

The aim of this study was to construct a mammary gland specific expression plasmid pIN and validate its function in expressing goat insulin-like growth factor 1 (IGF-1). The backbone plasmid pBC1 contained goat β-casein 5′ arm and β-casein 3′ arm, to target mammary gland-specific gene expression. First, the igf-1 gene was cloned from liver tissue harvested from a Saanen dairy goat and inserted downstream of the β-casein 5' arm. Then the neo gene was amplified from plasmid pCDNA3.1 and placed downstream of the β-casein 3' arm as a positive selection marker. In order to analyze the bioactivity of plasmid pIN, it was transfected into the Bcap-37 cell line and injected into goat mammary gland. Western-blotting and quantitative polymerase chain reaction (PCR) results confirmed the expression of IGF-1 protein and mRNA in transfected Bcap-37 cells. Further studies (RIA) demonstrated that the expression of IGF-1 protein in transfected group was much higher than that in control group (p &lt; 0.05). In vivo results showed that the expression of IGF-1 in injected group was significantly higher than that in control group. All our results provide evidence that pIN is a mammary gland specific expression plasmids that can target expression of IGF-1 to mammary tissue, with the goal of increasing milk production.Key words: IGF-1, pIN, Bcap-37 cell line, goat mammary, milk production

Transmission of Water Waves under Multiple Vertical Thin Plates

The transmission of water waves under vertical thin plates, e.g., offshore floating breakwaters, oscillating water column wave energy converters, and so on, is a crucial feature that dominates the hydrodynamic performance of marine devices. In this paper, the analytical solution to the transmission of water waves under multiple 2D vertical thin plates is firstly derived based on the linear potential theory. The influences of relevant parameters on the wave transmission are discussed, which include the number of plates, the draft of plates, the distance between plates and the water depth. The analytical results suggest that the transmission of progressive waves gradually weakens with the growth of the number and draft of plates, and under the conditions of given number and draft of plates, the distribution of plates has significant influence on the transmission of progressive waves. The results of this paper contribute to the understanding of the transmission of water waves under multiple vertical thin plates, as well as the suggestion on optimal design of complex marine devices, such as a floating breakwater with multiple plates

Out of plane effect on the superconductivity of Sr2-xBaxCuO3+y with Tc up to 98K

A series of new Sr2-xBaxCuO3+y (0 x 0.6) superconductors were prepared using high-pressure and high-temperature synthesis. A Rietveld refinement based on powder x-ray diffraction confirms that the superconductors crystallize in the K2NiF4-type structure of a space group I4/mmm similar to that of La2CuO4 but with partially occupied apical oxygen sites. It is found that the superconducting transition temperature Tc of this Ba substituted Sr2CuO3+y superconductor with constant carrier doping level, i.e., constant d, is controlled not only by order/disorder of apical-O atoms but also by Ba content. Tcmax =98 K is achieved in the material with x=0.6 that reaches the record value of Tc among the single-layer copper oxide superconductors, and is higher than Tc=95K of Sr2CuO3+y with optimally ordered apical-O atoms. There is Sr-site disorder in Sr2-xBaxCuO3+y which might lead to a reduction of Tc. The result indicates that another effect surpasses the disorder effect that is related either to the increased in-plane Cu-O bond length or to elongated apical-O distance due to Ba substitution with larger cation size. The present experiment demonstrates that the optimization of local geometry out of the Cu-O plane can dramatically enhance Tc in the cuprate superconductors.Comment: 23 Pages, 1 Table, 5 Figure