Transplantations interspécifiques de gonades embryonnaires de Phasianidés

Summary When indifferent gonads from red-legged partridges, Japanese quail or pintado embryos were transplanted into the coelomic cavity of early chick embryos, they differentiated into ovaries and testes, regardless of the sex of the host. Testicular transplants brought about the retrogression of both Müllerian ducts in female hosts, and ovarian transplants the feminization of the left testis in male hosts. This demonstrates hormonal activity of the embryonic gonads in the 3 species under study. Since the embryonic sex hormones show inter-specific activity, they may be of identical chemical nature.

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Avec la collaboration technique deA. Zeis.     

新疆拳击队的现状分析

拳击运动是新疆各体育项目中的重中之重,近几年来在新疆拳击队中涌现出了许多优秀运动员,在国际,国内各级比赛中取得了可喜的成绩.文章中笔者作为一名新疆拳击队队员,根据其长期的训练与比赛经验,结合已学过的理论知识对新疆拳击队的现状进行了较全面的调查与分析,并针对上述情况提出了提高我区拳击运动训练水平的建议.     

A 160-kilobit molecular electronic memory patterned at 10(11) bits per square centimetre

The primary metric for gauging progress in the various semiconductor integrated circuit technologies is the spacing, or pitch, between the most closely spaced wires within a dynamic random access memory (DRAM) circuit. Modern DRAM circuits have 140 nm pitch wires and a memory cell size of 0.0408 mum(2). Improving integrated circuit technology will require that these dimensions decrease over time. However, at present a large fraction of the patterning and materials requirements that we expect to need for the construction of new integrated circuit technologies in 2013 have 'no known solution'. Promising ingredients for advances in integrated circuit technology are nanowires, molecular electronics and defect-tolerant architectures, as demonstrated by reports of single devices and small circuits. Methods of extending these approaches to large-scale, high-density circuitry are largely undeveloped. Here we describe a 160,000-bit molecular electronic memory circuit, fabricated at a density of 10(11) bits cm(-2) (pitch 33 nm; memory cell size 0.0011 microm2), that is, roughly analogous to the dimensions of a DRAM circuit projected to be available by 2020. A monolayer of bistable, [2]rotaxane molecules served as the data storage elements. Although the circuit has large numbers of defects, those defects could be readily identified through electronic testing and isolated using software coding. The working bits were then configured to form a fully functional random access memory circuit for storing and retrieving information.