Physics. How soft skin wrinkles     

Brochard-Wyart F  de Gennes PG 《Science (New York, N.Y.)》2003,300(5618):441

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A high-resolution paleoclimate record spanning the past 25,000 years in southern East Africa     

Johnson TC  Brown ET  McManus J  Barry S  Barker P  Gasse F 《Science (New York, N.Y.)》2002,296(5565):113-132

High-resolution profiles of the mass accumulation rate of biogenic silica and other geochemical proxies in two piston cores from northern Lake Malawi provide a climate signal for this part of tropical Africa spanning the past 25,000 years. The biogenic silica mass accumulation rate was low during the relatively dry late Pleistocene, when the river flux of silica to the lake was suppressed. Millennial-scale fluctuations, due to upwelling intensity, in the late Pleistocene climate of the Lake Malawi basin appear to have been closely linked to the Northern Hemisphere climate until 11 thousand years ago. Relatively cold conditions in the Northern Hemisphere coincided with more frequent north winds over the Malawi basin, perhaps resulting from a more southward migration of the Intertropical Convergence Zone.  相似文献   

Value of small forest fragments to amphibians     

Da Silva FR  Do Prado VH  Rossa-Feres Dde C 《Science (New York, N.Y.)》2011,332(6033):1033

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High-luminosity blue and blue-green gallium nitride light-emitting diodes     

Morkoç H  Mohammad SN 《Science (New York, N.Y.)》1995,267(5194):51-55

Compact and efficient sources of blue light for full color display applications and lighting eluded and tantalized researchers for many years. Semiconductor light sources are attractive owing to their reliability and amenability to mass manufacture. However, large band gaps are required to achieve blue color. A class of compound semiconductors formed by metal nitrides, GaN and its allied compounds AIGaN and InGaN, exhibits properties well suited for not only blue and blue-green emitters, but also for ultraviolet emitters and detectors. What thwarted engineers and scientists from fabricating useful devices from these materials in the past was the poor quality of material and lack of p-type doping. Both of these obstacles have recently been overcome to the point where highluminosity blue and blue-green light-emitting diodes are now available in the marketplace.  相似文献   

Comment on "Status and trends of amphibian declines and extinctions worldwide"     

Pimenta BV  Haddad CF  Nascimento LB  Cruz CA  Pombal JP 《Science (New York, N.Y.)》2005,309(5743):1999; author reply 1999

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The Arabidopsis circadian clock incorporates a cADPR-based feedback loop     

Dodd AN  Gardner MJ  Hotta CT  Hubbard KE  Dalchau N  Love J  Assie JM  Robertson FC  Jakobsen MK  Gonçalves J  Sanders D  Webb AA 《Science (New York, N.Y.)》2007,318(5857):1789-1792

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Electronic transitions in perovskite: possible nonconvecting layers in the lower mantle     

Badro J  Rueff JP  Vankó G  Monaco G  Fiquet G  Guyot F 《Science (New York, N.Y.)》2004,305(5682):383-386

We measured the spin state of iron in magnesium silicate perovskite (Mg(0.9),Fe(0.1))SiO(3) at high pressure and found two electronic transitions occurring at 70 gigapascals and at 120 gigapascals, corresponding to partial and full electron pairing in iron, respectively. The proportion of iron in the low spin state thus grows with depth, increasing the transparency of the mantle in the infrared region, with a maximum at pressures consistent with the D" layer above the core-mantle boundary. The resulting increase in radiative thermal conductivity suggests the existence of nonconvecting layers in the lowermost mantle.  相似文献   

In situ imaging of the endogenous CD8 T cell response to infection     

Khanna KM  McNamara JT  Lefrançois L 《Science (New York, N.Y.)》2007,318(5847):116-120

Mounting a protective immune response is critically dependent on the orchestrated movement of cells within lymphoid organs. We report here the visualization, using major histocompatability complex class I tetramers, of the CD8-positive (CD8) T cell response in the spleens of mice to Listeria monocytogenes infection. A multistage pathway was revealed that included initial activation at the borders of the B and T cell zones followed by cluster formation with antigenpresenting cells leading to CD8 T cell exit to the red pulp via bridging channels. Strikingly, many memory CD8 T cells localized to the B cell zones and, when challenged, underwent rapid migration to the T cell zones where proliferation occurred, followed by egress via bridging channels in parallel with the primary response. Thus, the ability to track endogenous immune responses has uncovered both distinct and overlapping mechanisms and anatomical locations driving primary and secondary immune responses.  相似文献   

Association of TALS developmental disorder with defect in minor splicing component U4atac snRNA     

Edery P  Marcaillou C  Sahbatou M  Labalme A  Chastang J  Touraine R  Tubacher E  Senni F  Bober MB  Nampoothiri S  Jouk PS  Steichen E  Berland S  Toutain A  Wise CA  Sanlaville D  Rousseau F  Clerget-Darpoux F  Leutenegger AL 《Science (New York, N.Y.)》2011,332(6026):240-243

The spliceosome, a ribonucleoprotein complex that includes proteins and small nuclear RNAs (snRNAs), catalyzes RNA splicing through intron excision and exon ligation to produce mature messenger RNAs, which, in turn serve as templates for protein translation. We identified four point mutations in the U4atac snRNA component of the minor spliceosome in patients with brain and bone malformations and unexplained postnatal death [microcephalic osteodysplastic primordial dwarfism type 1 (MOPD 1) or Taybi-Linder syndrome (TALS); Mendelian Inheritance in Man ID no. 210710]. Expression of a subgroup of genes, possibly linked to the disease phenotype, and minor intron splicing were affected in cell lines derived from TALS patients. Our findings demonstrate a crucial role of the minor spliceosome component U4atac snRNA in early human development and postnatal survival.  相似文献   

Edge effect and matrix influence on the nest survival of an old forest specialist,the Brown Creeper (<Emphasis Type="Italic">Certhia americana</Emphasis>)     

Jean-François Poulin  Marc-André Villard 《Landscape Ecology》2011,26(7):911-922

Conservation strategies should be based on a solid understanding of processes underlying species response to landscape change. In forests fragmented by agriculture, elevated nest predation rates have been reported in many forest bird species, especially near edges. In intensively-managed forest landscapes, timber harvesting might also be associated with negative edge effects or broader “context” effects on some species when the matrix provides additional resources to their major nest predators. In this study, we hypothesized that proximity to a forest edge and proportion of cone-producing plantations will increase nest predation risk in fragments of relatively undisturbed forest. We focused on the Brown Creeper (Certhia americana), an indicator species of late-seral forests. We compared habitat configuration and composition at four spatial scales (0.14, 0.5, 1 and 2 km) around 54 nests and related daily nest survival rate to the distance to the nearest forest edge, mean patch size of late-seral forest (r = 141 m), proportion of non-forested lands (r = 141 m), density of maintained roads (r = 1 km), proportion of cone-producing spruce plantations (r = 2 km), and year. The best model included distance to the nearest edge and proportion of cone-producing plantations. Distance of nests to the nearest edge was the best individual predictor of daily nest survival. A larger sample of nests showed a significant threshold in distance to the nearest forest edge; nests located at least 100 m away were more likely to fledge young. These results suggest that even in managed forest landscapes, matrix effects can be important and some bird species may exhibit negative edge effects.  相似文献