Retention of xenon in quartz and Earth's missing xenon     

Sanloup C  Schmidt BC  Chamorro Perez EM  Jambon A  Gregoryanz E  Mezouar M 《Science (New York, N.Y.)》2005,310(5751):1174-1177

The reactivity of xenon with terrestrial oxides was investigated by in situ synchrotron x-ray diffraction. At high temperature (T > 500 kelvin), some silicon was reduced, and the pressure stability of quartz was expanded, attesting to the substitution of some xenon for silicon. When the quartz was quenched, xenon diffused out and only a few weight percent remained trapped in samples. These results show that xenon can be covalently bonded to oxygen in quartz in the lower continental crust, providing an answer to the missing xenon problem; synthesis paths of rare gas compounds are also opened.  相似文献   

Bush cabinet. EPA's Leavitt tapped for health post     

Kaiser J  Stokstad E 《Science (New York, N.Y.)》2004,306(5704):2019

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Biomonitoring. A snapshot of the U.S. chemical burden     

Stokstad E 《Science (New York, N.Y.)》2004,304(5679):1893

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Extensive gene traffic on the mammalian X chromosome     

Emerson JJ  Kaessmann H  Betrán E  Long M 《Science (New York, N.Y.)》2004,303(5657):537-540

Mammalian sex chromosomes have undergone profound changes since evolving from ancestral autosomes. By examining retroposed genes in the human and mouse genomes, we demonstrate that, during evolution, the mammalian X chromosome has generated and recruited a disproportionately high number of functional retroposed genes, whereas the autosomes experienced lower gene turnover. Most autosomal copies originating from X-linked genes exhibited testis-biased expression. Such export is incompatible with mutational bias and is likely driven by natural selection to attain male germline function. However, the excess recruitment is consistent with a combination of both natural selection and mutational bias.  相似文献   

Traces of human migrations in Helicobacter pylori populations     

Falush D  Wirth T  Linz B  Pritchard JK  Stephens M  Kidd M  Blaser MJ  Graham DY  Vacher S  Perez-Perez GI  Yamaoka Y  Mégraud F  Otto K  Reichard U  Katzowitsch E  Wang X  Achtman M  Suerbaum S 《Science (New York, N.Y.)》2003,299(5612):1582-1585

Helicobacter pylori, a chronic gastric pathogen of human beings, can be divided into seven populations and subpopulations with distinct geographical distributions. These modern populations derive their gene pools from ancestral populations that arose in Africa, Central Asia, and East Asia. Subsequent spread can be attributed to human migratory fluxes such as the prehistoric colonization of Polynesia and the Americas, the neolithic introduction of farming to Europe, the Bantu expansion within Africa, and the slave trade.  相似文献   

The Institute for Genomic Research meeting. Gene researchers hunt bargains,fixer-uppers     

Pennisi E 《Science (New York, N.Y.)》2002,298(5594):735-736

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Outgassing behavior and composition of comet C/1999 S4 (LINEAR) during its disruption     

Bockelée-Morvan D  Biver N  Moreno R  Colom P  Crovisier J  Gérard E  Henry F  Lis DC  Matthews H  Weaver HA  Womack M  Festou MC 《Science (New York, N.Y.)》2001,292(5520):1339-1343

The gas activity of comet C/1999 S4 (LINEAR) was monitored at radio wavelengths during its disruption. A runaway fragmentation of the nucleus may have begun around 18 July 2000 and proceeded until 23 July. The mass in small icy debris (相似文献   

CD95/CD95 ligand interactions on epithelial cells in host defense to Pseudomonas aeruginosa     

Grassmé H  Kirschnek S  Riethmueller J  Riehle A  von Kürthy G  Lang F  Weller M  Gulbins E 《Science (New York, N.Y.)》2000,290(5491):527-530

Pseudomonas aeruginosa causes severe infections, particularly of the lung, that are life threatening. Here, we show that P. aeruginosa infection induces apoptosis of lung epithelial cells by activation of the endogenous CD95/CD95 ligand system. Deficiency of CD95 or CD95 ligand on epithelial cells prevented apoptosis of lung epithelial cells in vivo as well as in vitro. The importance of CD95/CD95 ligand-mediated lung epithelial cell apoptosis was demonstrated by the rapid development of sepsis in CD95- or CD95 ligand-deficient mice, but not in normal mice, after P. aeruginosa infection.  相似文献   

Translating biomolecular recognition into nanomechanics     

Fritz J  Baller MK  Lang HP  Rothuizen H  Vettiger P  Meyer E  Güntherodt H  Gerber C  Gimzewski JK 《Science (New York, N.Y.)》2000,288(5464):316-318

We report the specific transduction, via surface stress changes, of DNA hybridization and receptor-ligand binding into a direct nanomechanical response of microfabricated cantilevers. Cantilevers in an array were functionalized with a selection of biomolecules. The differential deflection of the cantilevers was found to provide a true molecular recognition signal despite large nonspecific responses of individual cantilevers. Hybridization of complementary oligonucleotides shows that a single base mismatch between two 12-mer oligonucleotides is clearly detectable. Similar experiments on protein A-immunoglobulin interactions demonstrate the wide-ranging applicability of nanomechanical transduction to detect biomolecular recognition.  相似文献   

Phosphorylation networks regulating JNK activity in diverse genetic backgrounds     

Bakal C  Linding R  Llense F  Heffern E  Martin-Blanco E  Pawson T  Perrimon N 《Science (New York, N.Y.)》2008,322(5900):453-456

Cellular signaling networks have evolved to enable swift and accurate responses, even in the face of genetic or environmental perturbation. Thus, genetic screens may not identify all the genes that regulate different biological processes. Moreover, although classical screening approaches have succeeded in providing parts lists of the essential components of signaling networks, they typically do not provide much insight into the hierarchical and functional relations that exist among these components. We describe a high-throughput screen in which we used RNA interference to systematically inhibit two genes simultaneously in 17,724 combinations to identify regulators of Drosophila JUN NH(2)-terminal kinase (JNK). Using both genetic and phosphoproteomics data, we then implemented an integrative network algorithm to construct a JNK phosphorylation network, which provides structural and mechanistic insights into the systems architecture of JNK signaling.  相似文献