Breeding behavior of the Plumbeous Vireo in New Mexico

The Plumbeous Vireo ( Vireo plumbeus ) is a poorly studied songbird species that breeds within the interior western United States and Mexico. We studied the breeding behavior of Plumbeous Vireos within pinyon-juniper habitats in northeastern New Mexico in 1996 and 1997. Over both years we located and monitored 40 nests and conducted behavioral observations throughout the nesting cycle. From these observations we described and compared basic behavioral traits of male and female vireos during their nest-building, egg-laying, incubation, and nestling stages, and their response to potential predators near the nest. Male vireos displayed potential nest sites to females, but the females selected the site to be used and built most of the nest. Vireos often did not initiate egg-laying until 2-3 d after nest completion. The female tended to incubate eggs and brood nestlings more than the male, but both parents contributed equally in provisioning the young. Brown-headed Cowbirds ( Molothrus ater ) parasitized 77% of nests in 1996, 63% in 1997, and parasitism was the primary cause of nest failure in this population. The conspicuousness of vireos around the nest, particularly during the nest-building stage, may contribute to high parasitism levels. Vireo aggression near the nest may also act as a cue to help cowbirds locate nests.     

Seasonal trends and colonization patterns of macroinvertebrate assemblages in two streams with contrasting flow regimes

Patterns of colonization by macroinvertebrates were examined in two streams that differ in flow regime: a snowmelt system and a mesic groundwater system. Experiments were conducted during spring runoff, summer baseflow, and winter baseflow using artificial substrata. Colonization patterns reflected seasonal changes in benthic macroinvertebrate assemblages and life histories in each stream. The density and biomass of benthic organisms were approximately 3X greater in winter than in either spring or summer for both streams. Similarly, colonization was greater in winter than in spring or summer for both streams. In spring, colonization patterns were different between streams, with colonization being imperceptible in the snowmelt stream. Macroinvertebrate abundance fluctuated during the summer colonization experiment at both sites, resulting from a complex interplay among population emergence, recruitment, and/or movement. Assemblages in the snowmelt system primarily comprised mobile or ruderal taxa, such as Beatis tricaudatus and Chironomidae, whereas relatively sessile taxa, such as Glossoma nigrior , were predominant in the mesic groundwater system. Seasonal patterns of colonization differed among stream types primarily because of the profound interplay of flow regime and temperature on benthic community structure and organism life history.     

继往开来薪火不尽——李约瑟研究所所长古克礼博士访谈录

继李约瑟、何丙郁之后,古克礼于2003年就任剑桥李约瑟研究所所长.他有什么样的家庭和学术背景?什么原因引起他对中国科技史的兴趣?怎样能在天文、数学、医学这些不同的知识领域游弋同时承担繁重的行政工作?他同李约瑟的关系如何?他对李约瑟研究所的现状与未来有何看法?他怎样看待中国科技史研究在国际学术界的地位以及相关的国际合作问题?通过访谈,古克礼博士回答了这些问题.     

Mars' volatile and climate history.

There is substantial evidence that the martian volatile inventory and climate have changed markedly throughout the planet's history. Clues come from areas as disparate as the history and properties of the deep interior, the composition of the crust and regolith, the morphology of the surface, composition of the present-day atmosphere, and the nature of the interactions between the upper atmosphere and the solar wind. We piece together the relevant observations into a coherent view of the evolution of the martian climate, focusing in particular on the observations that provide the strongest constraints.     

Three-dimensional crystal structures of Escherichia coli met repressor with and without corepressor

The three-dimensional crystal structure of met repressor, in the presence or absence of bound corepressor (S-adenosylmethionine), shows a dimer of intertwined monomers, which do not have the helix-turn-helix motif characteristic of other bacterial repressor and activator structures. We propose that the interaction of met repressor with DNA occurs through either a pair of symmetry-related alpha-helices or a pair of beta-strands, and suggest a model for binding of several dimers to met operator regions.     

龙门山茂汶─汶川变质带构造特征研究

龙门山中段茂汶─汶川韧性剪切带中可见到绿片岩相到角闪岩相的古生界。该地的巴罗型中压变质相相当于松潘—甘孜褶皱带中地壳的绿泥石带，构成了北东—南西向的茂汶—汶川变质带。雪隆包花岗岩体正位于该变质带的中心部位。三次韧性变形作用（Ｄ１～Ｄ３）造就了印支褶皱带，并在三叠纪末末形成了松潘—甘孜褶皱带。Ｄ１变形作用为北东—南西向的挤压作用和冲断作用，形成了大型的等斜褶皱，使古生界缩短和加厚。在持续的Ｄ２北京—南西向挤压作用下，松潘—甘孜褶皱带和稳定的扬子克拉通之间的差异应变由茂汶—汶川剪切带中非同轴左旋剪切作用所容纳。雪隆包花岗岩体是在Ｄ２变形作用的晚期侵入到剪切带的。产生蓝晶石的变质条件也是在Ｄ２或Ｄ２变形作用后出现的。Ｄ３变形作用为北西—南东向挤压，在局部地方形成糜棱岩状的道冲剪切带。这些特征与绿泥石退变质作用有关，揭示出在Ｄ３变形期间茂汶—汶川变质带有较大幅度的隆升。尽管雪隆包岩体在空间上与茂汶—汶川变质带有关，但作者认为其变质作用是岩层加厚引起的热作用重新达到平衡的产物，而不是由侵入作用引起的热接触变质作用。然而，与岩浆作用伴生的高温和活动性流体仍是产生Ｄ３局部变形和雪隆包岩体隆升的原因，这也是局部出现角闪告相     

Dystrophic mutation (dy2J) affecting regulation of lactate dehydrogenase (LDH) and pyruvate kinase (PK) in C57BL/6J mice

Summary The genotype difference (dystrophic vs nondystrophic) in the LDH isozymes is observed in kidney. These differences are evident only at birth and at early developmental stages (before the expression of dystrophic symptoms). The tissue specific genotype differences for PK are limited to the thigh muscle (M form) and heart (L form), after the onset of the condition. These differences may reflect the pleiotropic effect of the dy^2J locus during the temporal regulation of these and other enzymes implicated in muscular dystrophy (MD).This research was financed by a Natural Sciences and Engineering Research Council Canada grant to S.M.S.     

Immunogenicity of a highly attenuated MVA smallpox vaccine and protection against monkeypox

The potential use of smallpox as a biological weapon has led to the production and stockpiling of smallpox vaccine and the immunization of some healthcare workers. Another public health goal is the licensing of a safer vaccine that could benefit the millions of people advised not to take the current one because they or their contacts have increased susceptibility to severe vaccine side effects. As vaccines can no longer be tested for their ability to prevent smallpox, licensing will necessarily include comparative immunogenicity and protection studies in non-human primates. Here we compare the highly attenuated modified vaccinia virus Ankara (MVA) with the licensed Dryvax vaccine in a monkey model. After two doses of MVA or one dose of MVA followed by Dryvax, antibody binding and neutralizing titres and T-cell responses were equivalent or higher than those induced by Dryvax alone. After challenge with monkeypox virus, unimmunized animals developed more than 500 pustular skin lesions and became gravely ill or died, whereas vaccinated animals were healthy and asymptomatic, except for a small number of transient skin lesions in animals immunized only with MVA.