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排序方式: 共有358条查询结果,搜索用时 265 毫秒
351.
Simmons G Glynn SA Komaroff AL Mikovits JA Tobler LH Hackett J Tang N Switzer WM Heneine W Hewlett IK Zhao J Lo SC Alter HJ Linnen JM Gao K Coffin JM Kearney MF Ruscetti FW Pfost MA Bethel J Kleinman S Holmberg JA Busch MP;Blood XMRV Scientific Research Working Group 《Science (New York, N.Y.)》2011,334(6057):814-817
Murine leukemia viruses (MLVs), including xenotropic-MLV-related virus (XMRV), have been controversially linked to chronic fatigue syndrome (CFS). To explore this issue in greater depth, we compiled coded replicate samples of blood from 15 subjects previously reported to be XMRV/MLV-positive (14 with CFS) and from 15 healthy donors previously determined to be negative for the viruses. These samples were distributed in a blinded fashion to nine laboratories, which performed assays designed to detect XMRV/MLV nucleic acid, virus replication, and antibody. Only two laboratories reported evidence of XMRV/MLVs; however, replicate sample results showed disagreement, and reactivity was similar among CFS subjects and negative controls. These results indicate that current assays do not reproducibly detect XMRV/MLV in blood samples and that blood donor screening is not warranted. 相似文献
352.
Ludwig KR Simmons KR Winograd IJ Szabo BJ Riggs AC 《Science (New York, N.Y.)》1993,259(5101):1629-1627
353.
354.
Ludwig KR Simmons KR Szabo BJ Winograd IJ Landwehr JM Riggs AC Hoffman RJ 《Science (New York, N.Y.)》1992,258(5080):284-287
The Devils Hole calcite vein contains a long-term climatic record, but requires accurate chronologic control for its interpretation. Mass-spectrometric U-series ages for samples from core DH-11 yielded (230)Th ages with precisions ranging from less than 1,000 years (2sigma) for samples younger than approximately 140 ka (thousands of years ago) to less than 50,000 years for the oldest samples ( approximately 566 ka). The (234)U/(238)U ages could be determined to a precision of approximately 20,000 years for all ages. Calcite accumulated continuously from 566 ka until approximately 60 ka at an average rate of 0.7 millimeter per 10(3) years. The precise agreement between replicte analyses and the concordance of the (230)Th/(238)U (234)U/(238)U ages for the oldest samples indicate that the DH-11 samples were closed systems and validate the dating technique in general. 相似文献
355.
Lane AL West RA Hord CW Nelson RM Simmons KE Pryor WR Eposito LW Horn LJ Wallis BD Buratti BJ Brophy TG Yanamandra-Fisher P Colwell JE Bliss DA Mayo MJ Smythe WD 《Science (New York, N.Y.)》1989,246(4936):1450-1454
The Voyager photopolarimeter successfully accomplished its objectives for the Neptune encounter, performing measurements on the planet, several of its satellites, and its ring system. A photometric map of Neptune at 0.26 micrometer (microm) shows the planet to be bland, with no obvious contrast features. No polar haze was observed. At 0.75 microm, contrast features are observed, with the Great Dark Spot appearing as a low-albedo region and the bright companion as being substantially brighter than its surroundings, implying it to be at a higher altitude than the Great Dark Spot. Triton's linear phase coefficients of 0.011 magnitudes per degree at 0.26 microm and 0.013 magnitudes per degree at 0.75 microm are consistent with a solid-surface object possessing high reflectivity. Preliminary geometric albedos for Triton, Nereid, and 1989N2 were obtained at 0.26 and 0.75 microm. Triton's rotational phase curve shows evidence of two major compositional units on its surface. A single stellar occultation of the Neptune ring system elucidated an internal structure in 1989N1R, in the approximately 50-kilometer region of modest optical depth. 1989N2R may have been detected. The deficiency of material in the Neptune ring system, when compared to Uranus', may imply the lack of a "recent" moon-shattering event. 相似文献
356.
Simmons AH Köhler-Rollefson I Rollefson GO Mandel R Kafafi Z 《Science (New York, N.Y.)》1988,240(4848):35-39
'Ain Ghazal, an archeological site located on the outskirts of Amman, Jordan, is one of the largest early villages known in the Near East. The site dates to the Neolithic period, during which mankind made one of its most significant advances, the adoption of domestic plants and animals as primary subsistence sources. Recent excavations at 'Ain Ghazal have augmented considerably current knowledge of several aspects of the Neolithic. Of particular interest has been the documentation of a continuous, or near continuous, occupation from early through late Neolithic components, and a concomitant dramatic economic shift. This shift was from a broad subsistence base relying on a variety of both wild and domestic plants and animals, to an economic strategy reflecting an apparent emphasis on pastoralism. 相似文献
357.
Hord CW West RA Simmons KE Coffeen DL Sato M Lane AL Bergstralh JT 《Science (New York, N.Y.)》1979,206(4421):956-959
The photopolarimeter instrument on Voyager 2 was used to obtain a map of Jupiter at an effective wavelength of 2400 angstroms. Analysis of a typical north-south swath used to make this map shows strong absorption at high latitudes by a molecular or particulate constituent in the Jovian atmosphere. At 65 degrees north latitude, the absorbing constituent extends to altitudes above the 50-millibar pressure level. 相似文献
358.
S Chen RS Ingram MJ Hostetler JJ Pietron RW Murray TG Schaaff JT Khoury MM Alvarez RL Whetten 《Science (New York, N.Y.)》1998,280(5372):2098-2101
A transition from metal-like double-layer capacitive charging to redox-like charging was observed in electrochemical ensemble Coulomb staircase experiments on solutions of gold nanoparticles of varied core size. The monodisperse gold nanoparticles are stabilized by short-chain alkanethiolate monolayers and have 8 to 38 kilodaltons core mass (1.1 to 1.9 nanometers in diameter). Larger cores display Coulomb staircase responses consistent with double-layer charging of metal-electrolyte interfaces, whereas smaller core nanoparticles exhibit redox chemical character, including a large central gap. The change in behavior is consistent with new near-infrared spectroscopic data showing an emerging gap between the highest occupied and lowest unoccupied orbitals of 0.4 to 0.9 electron volt. 相似文献