The complete family of genes encoding G proteins of Caenorhabditis elegans

Caenorhabditis elegans is the first animal whose genomic sequence has been determined. One of the new possibilities in post-sequence genetics is the analysis of complete gene families at once. We studied the family of heterotrimeric G proteins. C. elegans has 20 Galpha, 2 Gbeta and 2 Ggamma genes. There is 1 homologue of each of the 4 mammalian classes of Galpha genes, G(i)/G(o)alpha, G(s)alpha , G(q)alpha and G12alpha, and there are 16 new alpha genes. Although the conserved Galpha subunits are expressed in many neurons and muscle cells, GFP fusions indicate that 14 new Galpha genes are expressed almost exclusively in a small subset of the chemosensory neurons of C. elegans. We generated loss-of-function alleles using target-selected gene inactivation. None of the amphid-expressed genes are essential for viability, and only four show any detectable phenotype (chemotaxis defects), suggesting extensive functional redundancy. On the basis of functional analysis, the 20 genes encoding Galpha proteins can be divided into two groups: those that encode subunits affecting muscle activity (homologues of G(i)/G(o)alpha, G(s)alpha and G(q)), and those (14 new genes) that encode proteins most likely involved in perception.     

Ordering and manipulation of the magnetic moments in large-scale superconducting pi-loop arrays

The phase of the macroscopic electron-pair wavefunction in a superconductor can vary only by multiples of 2pi when going around a closed contour. This results in quantization of magnetic flux, one of the most striking demonstrations of quantum phase coherence in superconductors. By using superconductors with unconventional pairing symmetry, or by incorporating pi-Josephson junctions, a phase shift of pi can be introduced in such loops. Under appropriate conditions, this phase shift results in doubly degenerate time-reversed ground states, which are characterized by the spontaneous generation of half quanta of magnetic flux, with magnitude 1/2 Phi(0)(Phi(0) = h/2e = 2.07 x 10(-15) Wb) (ref. 7). Until now, it has only been possible to generate individual half flux quanta. Here we report the realization of large-scale coupled pi-loop arrays based on YBa2Cu3O7-Au-Nb Josephson contacts. Scanning SQUID (superconducting quantum interference device) microscopy has been used to study the ordering of half flux quanta in these structures. The possibility of manipulating the polarities of individual half flux quanta is also demonstrated. These pi-loop arrays are of interest as model systems for studying magnetic phenomena--including frustration effects--in Ising antiferromagnets. Furthermore, studies of coupled pi-loops can be useful for designing quantum computers based on flux-qubits with viable quantum error correction capabilities.     

Experimental demonstration of chaos in a microbial food web

Discovering why natural population densities change over time and vary with location is a central goal of ecological and evolutional disciplines. The recognition that even simple ecological systems can undergo chaotic behaviour has made chaos a topic of considerable interest among theoretical ecologists. However, there is still a lack of experimental evidence that chaotic behaviour occurs in the real world of coexisting populations in multi-species systems. Here we study the dynamics of a defined predator-prey system consisting of a bacterivorous ciliate and two bacterial prey species. The bacterial species preferred by the ciliate was the superior competitor. Experimental conditions were kept constant with continuous cultivation in a one-stage chemostat. We show that the dynamic behaviour of such a two-prey, one-predator system includes chaotic behaviour, as well as stable limit cycles and coexistence at equilibrium. Changes in the population dynamics were triggered by changes in the dilution rates of the chemostat. The observed dynamics were verified by estimating the corresponding Lyapunov exponents. Such a defined microbial food web offers a new possibility for the experimental study of deterministic chaos in real biological systems.     

复杂设备运行的协同服务支持

针对现有的设备服务模式存在的问题，提出支持复杂设备优化运行的协同服务模式．为了使复杂设备能充分发挥其潜在价值，指出复杂设备的运行应该与必需的技术服务关联起来，形成“产品服务捆绑体”．解释了支持复杂设备运行的协同服务内涵，并对组织结构形式、协同服务业务模式识别和过程建模关键技术进行系统论述，提出了建立嵌入式在线服务标准（embeddedo nline service，EOS）作为支持协同服务运行的设备接入技术．     

Zur Kinematik der Planetenbewegung in Copernicus' Commentariolus

Zusammenfassung Copernicus versucht, die Ptolemäischen Konstruktionen auf konzentrische Kreise und Epizykel zu reduzieren und aus ihnen ein wirklich einheitliches System zu schaffen. Bei der Umordnung, die er dazu vornimmt, bemüht er sich aber, so viel wie möglich vom Ptolemäischen System zu erhalten. Das punctum aequans ersetzt er bei den äußeren Planeten durch eine Näherungskonstruktion mit Hilfe eines Epizykels. Im Fall des Ptolemäischen Deferenten der Venus, der nach seinen Vorstellungen die Erdbahn wiedergibt, muß er einen dem punctum aequans annähernd gleichwertigen Epizykelmechanismus auf die Venusbahn verpflanzen. Vorgelegt von B. L. van der Waerden