Pseudoscalar quarkonium exclusive decays to vector meson pair

The pseudoscalar quarkonia exclusive decays to light mesons still poses a challenge to the theoretical understanding of quarkonium properties in decay. In this work, we evaluate the processes of pseudoscalar heavy quarkonium decays into vector meson pairs, especially the helicity suppressed processes of ηb→J/ψJ/ψ and ηc→VV. In the framework of NRQCD, the branching fraction of Br[ηb→J/ψJ/ψ] are evaluated at the next-to-leading order of perturbative QCD; and within the light-cone distribution formalism, we calculate also the higher twist effects in these processes. Numerical results show that the higher twist terms contribute more than what from the NLO QCD corrections in the process of ηb→J/ψJ/ψ. It is found that the experimental results on ηc→VV are hard to be understood by merely the quark model and perturbative QCD calculation.     

Pluricanonical maps of varieties of Albanese fiber dimension two

In this paper we prove that for any smooth projective variety of Albanese fiber dimension two and of general type, the \(6\) -canonical map is birational. And we also show that the \(5\) -canonical map is birational for any such variety with some geometric restrictions.     

齐性空间SU(2n)/Sp(n)的H-同伦指数

令p为大于3的素数.在一定维数限制下,通过把齐性空间SU(2n)/Sp(n)分解为若干个同伦可结合,同伦可交换的H-空间的乘积,进而得到了SU(2n)/Sp(n)的p素H-同伦指数的一个上界.     

基于分数维Vasicek利率模型的CDS定价

本文研究CDS的定价问题, 其中涉及到利率风险和传染风险. 文中用分数维Vasicek利率模型刻画利率风险, 对公司的违约强度进行建模, 给出了违约与利率相关时风险债券的价格, 并在此基础上得到CDS的价格.     

改性松香键合二氧化硅高效液相色谱固定相的制备及其对三七总皂苷的分离

三七中发挥药效的主要成分为三七皂苷R1、人参皂苷Rg1、人参皂苷Re、人参皂苷Rb1和人参皂苷Rd,用于贫血、冠心病、高血压、脑卒中后遗症等疾病的治疗,但其化学成分多且难分离.将氢化松香丙烯酸羟乙酯(HRHA)通过巯基-烯点击化学反应键合到烷基化硅胶表面,制备出一种新型的改性松香键合二氧化硅高效液相色谱固定相(SiO2...     

新型镁合金螺钉体外腐蚀降解及细胞活性研究

研究了基于NZ30K合金开发的新型Mg-3Nd-0.2Zn-0.4Zr-0.2Mn镁合金耐腐蚀性、体外降解行为特性及浸提液细胞生物毒性. 采用金相显微镜得到新型镁合金金相显微图, 采用扫描电镜(Scanning Electron Microscope, SEM)获取SEM图; 采用武汉科思特电化学工作站进行电化学测试, 并绘制动电位极化曲线, 以磷酸盐缓冲液(Phosphate Buffer Solution, PBS)模拟体液环境, 记录氢气析出体积并计算腐蚀速率; 利用细胞完全培养基测定pH值、重量变化曲线; 获取大鼠骨髓间充质干细胞(Bone Mesenchymal Stem Cells, BMSCs), 并利用完全细胞培养基制作新型镁合金浸提液, 检测细胞生物活性, 以ZA75镁合金为基础添加0.3%Mn元素制成合金作为对照组, 比较腐蚀电位、体外降解情况以及细胞活性. 结果表明: 新型Mg-3Nd-0.2Zn-0.4Zr-0.2Mn镁合金横截面等轴晶体组织细小均匀性较好, 纵截面呈长条状组织均匀性稍差; 自腐蚀电位较高, 为-1.3912V; 自腐蚀电流密度较低, 为7.37×10-7 A?cm-2; 体外析氢量低, 失重量、pH值变化幅度相对较小; 降解速率下降后呈现小范围上升后趋于平缓; 具有良好的细胞相容性, 可以促进BMSCs细胞增殖分化.     

Polar dependence of impurity incorporation and yellow luminescence in GaN films grown by metal-organic chemical vapor deposition

We have investigated the unintentional impurities, oxygen and carbon, in GaN films grown on c-plane, r-plane as well as m-plane sapphire by metal-organic chemical vapor deposition. The GaN layer was analyzed by secondary ion mass spectroscopy. The different trend of the incorporation of oxygen and carbon has been explained in the polar (0 0 0 1), nonpolar (1 1 2¯ 0) and semipolar (1 1 2¯ 2) GaN by a combination of the atom bonding structure and the origin direction of the impurities. Furthermore, it has been found that there is a stronger yellow luminescence (YL) in GaN with higher concentration of carbon, suggesting that C-involved defects are originally responsible for the YL.     

Measurement of the Binding of Adenosylcobalamin to Glutamate Mutase by Fluorescence Spectroscopy

Fluorescence spectroscopy is a fast, highly sensitive technique for investigating protein‐ligand interactions. Intrinsic protein fluorescence is usually occurred by exciting the proteins with 280‐295 nm ultraviolet light, and the light emission is observed approximately between 330‐350 nm. No emission light between 330‐350 nm can be observed when adenosylcobalamin (AdoCbl) is excited at 282 nm. The binding of AdoCbl to glutamate mutase was therefore investigated by fluorescence spectroscopy in this study. Our results show that direct measurement for determining the K_d of AdoCbl by fluorescence spectroscopy leads to significant errors. Here we report the source of error and a corrected method for measuring the binding of coenzyme B₁₂ to glutamate mutase using fluorescence spectroscopy.