High levels of gene flow in the California vole ( Microtus californicus ) are consistent across spatial scales

Gene flow links the genetic and demographic structures of species. Despite the fact that similar genetic and demographic patterns shape both local population structure and regional phylogeography, the 2 levels of population connectivity are rarely studied simultaneously. Here, we studied gene flow in the California vole ( Microtus californicus ), a small-bodied rodent with limited vagility but high local abundance. Within a 4.86-km 2 preserve in central California, genetic diversity in 6 microsatellites was high, and Bayesian methods indicated a single genetic cluster. However, individual-based genetic analysis detected a clear signal for isolation-by-distance (IBD) and fine-scale population structure. Mitochondrial cytochrome b sequencing revealed 11 unique haplotypes from the one local area where we sequenced 62 individuals. Phylogeographic analysis of these individuals combined with those sampled from the northern geographic range of the species (the range of the species spans western North America from southern Oregon to northern Mexico and is centered geographically within the state of California) again indicated a lack of structure but a signal for IBD. Patterns of gene flow thus are consistent across spatial scales: while dispersal of the California vole is limited across geographic distance, there is nonetheless considerable movement across the landscape. We conclude that in this species, high local population abundances overcome the potential genetic and demographic effects of limited dispersal.     

美国

美国,凭借其幅员辽阔的疆域、在研究及发展上持续不断的投入以及高质量的教育系统,自Vannevar Bush起草并发表了具有深远影响且备受推崇的讨论美国战后科学政策的报告《科学,无止境的前沿》(Science,TheEndless Frontier)[1]之时起,美国这个国家在世界科学领域就一直占据主导地位.然而进入21...     

用测量模态阻尼和振型的方法对复合材料薄平板进行无损质量检测

复合材料薄平板经热压制成后,都需要进行质量检测。本文探索用测量模态阻尼和振型的方法,对复合材料薄平板的制作质量进行无损检测,作为对其它昂贵的无损检测方法的补充。略述用振动方法进行无损检测的原理,测量薄平板阻尼的方法以及提高测量精度的措施。还讨论在测量薄平板阻尼时可能遇到的一些特殊问题(如非线性刚度、拍、模态密集等问题);以云母基复合材料薄平板作为例子,从测量其阻尼和振型的结果,对这种板的制作质量进行讨论。     

The Children's Planning Initiative: Researching Decision-Making for Children

This paper recounts the story of how a number of workers involved in the care of children decided that they needed to do more than improve their skills and began instead to question some of the assumptions on which child care planning processes are built. The paper records a growing consciousness about the value of action research in developing alternative models of decision-making. It leads us from early questioning, through model creation, and on into testing the model in a new and complex organizational setting. While other voices are quoted, the paper recounts the story from the viewpoint of two actors, practitioner/manager and consultant.     

The c-myc oncogene driven by immunoglobulin enhancers induces lymphoid malignancy in transgenic mice

Transgenic mice bearing the cellular myc oncogene coupled to the immunoglobulin mu or kappa enhancer frequently develop a fatal lymphoma within a few months of birth. Since the tumours represent represent both immature and mature B lymphocytes, constitutive c-myc expression appears to be highly leukaemogenic at several stages of B-cell maturation. These myc mice should aid study of lymphoma development, B-cell ontogeny and immunoglobulin regulation.     

Binding of myosin I to membrane lipids

The single-headed myosins called myosin-I were first isolated from the protozoan Acanthamoeba and subsequently identified in other cells. We previously reported evidence that myosin-I is responsible for the movement of membranes, extracted from Acanthamoeba, along actin filaments in vitro. Here we show for the first time that myosin-I can bind directly to NaOH-extracted membranes isolated from Acanthamoeba and to vesicles of pure lipids with an affinity sufficient for extensive binding in the cell. Membrane-bound myosin-I may provide a mechanism for many cellular movements previously thought to involve filamentous myosin-II.     

Fine structure of the tip of chemosensitive hairs in two blow flies and the stable fly

Zusammenfassung Licht- und elektronenmikroskopische Studien der chemorezeptiven Spitze von Geschmackshaaren wurden bei den FliegenPhormia regina, Calliphora vicina undStomoxys calcitrans durchgeführt. Die Geschmackshaare dieser Fliegen ähneln sich strukturell bis auf einen ausgeprägten Öffnungs- und Schliessmechanismus, der für die Geschmackshaare vonStomoxys calcitrans lichtmikroskopisch nicht nachgewiesen werden konnte. Die Resultate werden hinsichtlich der Lokalisation der chemosensiblen Membran diskutiert.     

Isolation of bacteriophages from the bovine rumen

Zusammenfassung Die Isolierung der im Pansen vorkommenden Bakteriophagen wird erstmals beschrieben. Bakteriophagen, dieStreptococcus bovis und PansenSerratiae spp. angreifen, wurden aus vielen Pansen-Proben isoliert und eingehend untersucht;Bacteroides ruminicola Phage wurde dabei nicht aufgefunden.