Effects of the δ meson on the direct Urca processes in neutron stars

In the framework of the relativistic mean field theory, the effects of the δ meson on the direct Urca (DURCA) processes are investigated. In a neutron star, the DURCA processes involving nucleons, Λ and Ξ^- can take place while the process involving the Ξ⁰ can not. With the inclusion of the δ meson, the threshold densities for the DURCA processes become lower. With the δ included, the threshold neutron star mass for the DURCA process among nucleons and electrons becomes smaller while the threshold masses for the processes involving hyperons become larger. When the δ meson is included, the total neutrino emissivity remarkably increases in the density range of 0.32--0.41 fm^-3. The total neutrino luminosity increases with the neutron star mass first and then decreases. The neutrino luminosity gets larger with the inclusion of the δ meson. The cooling of the EXO0748-676 is sensitive to the isovector scalar interaction.     

宇宙演化与热寂说

在已成熟的宇宙演化理论的基础上,文章作者重新讨论了Clausius提出的热寂问题.宇宙演化指其组分和宏观面貌的变化.主要是微观结团和宏观结团.从物理原理上讲,这些结团过程是力学的,而不是热力学的.力学过程一定程度上破坏了原有的热平衡,热力学则倾向于恢复热平衡.所有已知的物理规律,包括热力学在内,都在宇宙演化中起着它应起的作用.作为后果,宇宙的熵在演化中一直是增加的.克劳修斯把热力学第二定律用于宇宙是正确的.可是他认为宇宙的熵会极大化并不正确.这是因为在演化过程中会出现组分粒子的退耦.     

水基切伦科夫μ子探测器的研究

利用高速带电粒子在透明介质中产生切伦科夫辐射的特性,以蒸馏水作为辐射介质,搭建了一个小尺寸(π×22.52cm2×45 cm)的切伦科夫探测器,对能量在GeV量级的μ子进行了相应的测量,考虑其他能量损耗、光传输和收集效率、阴极量子效率后,实验结果与理论估计值有比较高的相符度,可以初步断定仪器具备探测GeV量级μ子的能力.     

大功率白光LED恒压驱动与恒流驱动下温度特性的实时测量

采用贴片pt100设计一种快响应温度计,在恒压和恒流驱动下分别实时测量大功率白光LED温度对光电参数的影响,测量误差小、效率高.实验表明,LED在恒压驱动时电流和光强随温度的升高而增大,而在恒流驱动时光强随温度的升高而减小;发光效率在恒流和恒压驱动时均随温度的升高而降低,但前者影响较小.     

地球章动原因的分析与计算

介绍地球章动的特点,从理论上分析地球章动的主要原因,计算章动常数并给出了地球章动示意图的画法.所计算的章动常数与观测值相差仅2/10 000.     

Lower Bounds on the (Laplacian) Spectral Radius of Weighted Graphs

The weighted graphs, where the edge weights are positive numbers, are considered. The authors obtain some lower bounds on the spectral radius and the Laplacian spectral radius of weighted graphs, and characterize the graphs for which the bounds are attained. Moreover, some known lower bounds on the spectral radius and the Laplacian spectral radius of unweighted graphs can be deduced from the bounds.     

Geometric Property （T）

This paper discusses“geometric property （T）”. This is a property of metric spaces introduced in earlier works of the authors for its applications to K-theory. Geometric property （T） is a strong form of “expansion property”, in particular, for a sequence （Xn） of bounded degree finite graphs, it is strictly stronger than （Xn） being an expander in the sense that the Cheeger constants h（Xn） are bounded below. In this paper, the authors show that geometric property （T） is a coarse invariant, i.e., it depends only on the large-scale geometry of a metric space X. The authors also discuss how geometric property （T） interacts with amenability, property （T） for groups, and coarse geometric notions of a-T-menability. In particular, it is shown that property （T） for a residually finite group is characterised by geometric property （T） for its finite quotients.     

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.     

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.