Turnover of sex chromosomes induced by sexual conflict

Sex-determination genes are among the most fluid features of the genome in many groups of animals. In some taxa the master sex-determining gene moves frequently between chromosomes, whereas in other taxa different genes have been recruited to determine the sex of the zygotes. There is a well developed theory for the origin of stable and highly dimorphic sex chromosomes seen in groups such as the eutherian mammals. In contrast, the evolutionary lability of genetic sex determination in other groups remains largely unexplained. In this theoretical study, we show that an autosomal gene under sexually antagonistic selection can cause the spread of a new sex-determining gene linked to it. The mechanism can account for the origin of new sex-determining loci, the transposition of an ancestral sex-determining gene to an autosome, and the maintenance of multiple sex-determining factors in species that lack heteromorphic sex chromosomes.     

Acridines and streptomycine

Résumé La streptomycine et les acridines ont une propriété commune, en ce qu'ils forment avec les nucléoprotéides des levures de complexes électro-adsorptifs.     

The mechanism of the biochemical activity of acridines

Résumé Les acridines forment avec les nucléoprotéides des levures, des complexes électro-adsorptifs. Le pouvoir bactéricide des acridines s'exerce par une compétition entre les ion H⁺ de ce complexe et l'ion acridine. Différents enzymes activés par des ions métalliques doivent leur activité catalytique au même type de complexes. Les acridines inhibent ces enzymes parce qu'ils déplacent le cathion métallique.     

Les propriétés mécaniques du caoutchouc

Summary A survey of recent work on the theories of the peculiar mechanical behaviour of substances with rubber-like properties is given. All the theories are based on the assumption that these substances (including rubber itself) are composed of very long, flexible chainmolecules. Any segment of a chain is linked to two neighbouring segments by bonds similar to those which are present in typical solids and to all other neighbours by linkages like the bonds prevailing between the particles of liquids. The chain molecules are intermingled so as to form a kind of a felt.This state of aggregation is intermediate between the solid and the liquid; it is called the rubber-like state (état gommoïdal). Elasticity, viscosity and plastic flow as well as the influence of crystallization, vulcanization and degradation are discussed in terms of this theory.     

A mutation in SLC11A3 is associated with autosomal dominant hemochromatosis.

Hereditary hemochromatosis (HH) is a very common disorder characterized by iron overload and multi-organ damage. Several genes involved in iron metabolism have been implicated in the pathology of HH (refs. 1-4). We report that a mutation in the gene encoding Solute Carrier family 11, member A3 (SLC11A3), also known as ferroportin, is associated with autosomal dominant hemochromatosis.     

Entanglement of spin waves among four quantum memories

Quantum networks are composed of quantum nodes that interact coherently through quantum channels, and open a broad frontier of scientific opportunities. For example, a quantum network can serve as a 'web' for connecting quantum processors for computation and communication, or as a 'simulator' allowing investigations of quantum critical phenomena arising from interactions among the nodes mediated by the channels. The physical realization of quantum networks generically requires dynamical systems capable of generating and storing entangled states among multiple quantum memories, and efficiently transferring stored entanglement into quantum channels for distribution across the network. Although such capabilities have been demonstrated for diverse bipartite systems, entangled states have not been achieved for interconnects capable of 'mapping' multipartite entanglement stored in quantum memories to quantum channels. Here we demonstrate measurement-induced entanglement stored in four atomic memories; user-controlled, coherent transfer of the atomic entanglement to four photonic channels; and characterization of the full quadripartite entanglement using quantum uncertainty relations. Our work therefore constitutes an advance in the distribution of multipartite entanglement across quantum networks. We also show that our entanglement verification method is suitable for studying the entanglement order of condensed-matter systems in thermal equilibrium.     

用于数据库新兴应用程序的逻辑

逻辑与数据库及信息系统之间的关系是广泛和长期存在的。对于数据库理论家而言，逻辑是一个统一的框架。在该框架内可以理解数据模型和查询语言的语义学；允许对它们的可表达性进行比较；并且应用高度开发的数学逻辑工具给出深入的理解。随着数据库系统管理的信息类型日益丰富．数据库和信息系统的逻辑价值也就更加突出。异构和分布式数据源包括了从遗传序列到具有丰富时态的结构；从结合文本与数据的半结构文件到有关复杂组织协同进程的信息。