On the Weak Limiting Behavior of Almost Surely Convergent Row Sums from Infinite Arrays of Rowwise Independent Random Elements in Banach Spaces

For an array {V _nk ,kge8805.gif" alt="ge" align="MIDDLE" BORDER="0">1,nge8805.gif" alt="ge" align="MIDDLE" BORDER="0">1} of rowwise independent random elements in a real separable Banach space with almost surely convergent row sums geqslant 1} $$ " align="middle" border="0"> , we provide criteria for S _n –A _n to be stochastically bounded or for the weak law of large numbers to hold where {A _n ,nge8805.gif" alt="ge" align="MIDDLE" BORDER="0">1} is a (nonrandom) sequence in .     

A Note on Some (3, 2<Emphasis Type="Italic">K</Emphasis> + 1)-Associative Rings

In this paper we consider the associativity of a (3, 2k + 1)-associative ring R in the following cases: (1) R is simple 2-divisible; (2) R is p-divisible trivial right ideal ring; (3) R is prime p-divisible.AMS Subject Classification: 17A30     

多孔活性硅胶的制备及吸附性能的研究

以硅酸钠和氯化铵为原料,通过添加表面活性剂制备高吸附活性的多孔硅胶.采用SEM,IR和XRI)等手段对硅胶样品的结构和形貌进行表征,并利用紫外分光光度法研究硅胶样品对垃圾渗滤液中有机污染物的吸附性能.结果表明,合成的硅胶样品是由纳米量级的无定形二氧化硅颗粒组成的多孔性、疏松状物质,对垃圾渗滤液中的有机物分子具有较强的吸...     

高斯光束通过有硬边光阑ABCD光学系统的近似解析传输公式

 对高斯光束通过有硬边光阑近轴ABCD光学系统的传输进行了研究,采用将矩形函数展开为复高斯函数的技巧,推导出了近似的解析传输公式。以高斯光束在有光阑情况下自由空间的传输为例进行了数值计算,对所用方法能节约大量机时的优点和计算误差作了讨论,并进一步推广用于平面波和平顶高斯光束,证实了这一方法具有广泛的应用意义。     

How does geographical distance translate into genetic distance?

Geographic structure can affect patterns of genetic differentiation and speciation rates. In this article, we investigate the dynamics of genetic distances in a geographically structured metapopulation. We model the metapopulation as a weighted directed graph, with $d$ vertices corresponding to $d$ subpopulations that evolve according to an individual based model. The dynamics of the genetic distances is then controlled by two types of transitions — mutation and migration events. We show that, under a rare mutation–rare migration regime, intra subpopulation diversity can be neglected and our model can be approximated by a population based model. We show that under a large population-large number of loci limit, the genetic distance between two subpopulations converges to a deterministic quantity that can asymptotically be expressed in terms of the hitting time between two random walks in the metapopulation graph. Our result shows that the genetic distance between two subpopulations does not only depend on the direct migration rates between them but on the whole metapopulation structure.     

Nuclear clocks based on resonant excitation of γ-transitions

We review the ideas and concepts for a clock that is based on a radiative transition in the nucleus rather than in the electron shell. This type of clock offers advantages like an insensitivity against field-induced systematic frequency shifts and the opportunity to obtain high stability from interrogating many nuclei in the solid state. Experimental work concentrates on the low-energy (about 8 eV) isomeric transition in ²²⁹Th. We review the status of the experiments that aim at a direct optical observation of this transition and outline the plans for high-resolution laser spectroscopy experiments.