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Waite JH Combi MR Ip WH Cravens TE McNutt RL Kasprzak W Yelle R Luhmann J Niemann H Gell D Magee B Fletcher G Lunine J Tseng WL 《Science (New York, N.Y.)》2006,311(5766):1419-1422
The Cassini spacecraft passed within 168.2 kilometers of the surface above the southern hemisphere at 19:55:22 universal time coordinated on 14 July 2005 during its closest approach to Enceladus. Before and after this time, a substantial atmospheric plume and coma were observed, detectable in the Ion and Neutral Mass Spectrometer (INMS) data set out to a distance of over 4000 kilometers from Enceladus. INMS data indicate that the atmospheric plume and coma are dominated by water, with significant amounts of carbon dioxide, an unidentified species with a mass-to-charge ratio of 28 daltons (either carbon monoxide or molecular nitrogen), and methane. Trace quantities (<1%) of acetylene and propane also appear to be present. Ammonia is present at a level that does not exceed 0.5%. The radial and angular distributions of the gas density near the closest approach, as well as other independent evidence, suggest a significant contribution to the plume from a source centered near the south polar cap, as distinct from a separately measured more uniform and possibly global source observed on the outbound leg of the flyby. 相似文献
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Spin currents can apply useful torques in spintronic devices. The spin Hall effect has been proposed as a source of spin current, but its modest strength has limited its usefulness. We report a giant spin Hall effect (SHE) in β-tantalum that generates spin currents intense enough to induce efficient spin-torque switching of ferromagnets at room temperature. We quantify this SHE by three independent methods and demonstrate spin-torque switching of both out-of-plane and in-plane magnetized layers. We furthermore implement a three-terminal device that uses current passing through a tantalum-ferromagnet bilayer to switch a nanomagnet, with a magnetic tunnel junction for read-out. This simple, reliable, and efficient design may eliminate the main obstacles to the development of magnetic memory and nonvolatile spin logic technologies. 相似文献
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Genetic variation of viral protein 1 genes of field strains of waterfowl parvoviruses and their attenuated derivatives 总被引:4,自引:0,他引:4
To understand the genetic variations between the field strains of waterfowl parvoviruses and their attenuated derivatives, we analyzed the complete nucleotide sequences of the viral protein 1 (VP1) genes of nine field strains and two vaccine strains of waterfowl parvoviruses. Sequence comparison of the VP1 proteins showed that these viruses could be divided into goose parvovirus (GPV) related and Muscovy duck parvovirus (MDPV) related groups. The amino acid difference between GPV- and MDPV-related groups ranged from 13.1% to 15.8%, and the most variable region resided in the N terminus of VP2. The vaccine strains of GPV and MDPV exhibited only 1.2% and 0.3% difference in amino acid when compared with their parental field strains, and most of these differences resided in residues 497-575 of VP1, suggesting that these residues might be important for the attenuation of GPV and MDPV. When the GPV strains isolated in 1982 (the strain 82-0308) and in 2001 (the strain 01-1001) were compared, only 0.3% difference in amino acid was found, while MDPV strains isolated in 1990 (the strain 90-0219) and 1997 (the strain 97-0104) showed only 0.4% difference in amino acid. The result indicates that the genome of waterfowl parvovirus had remained highly stable in the field. 相似文献
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1. The effect of lactic acid marination at 5°C on post mortem changes in breast muscle pectoralis major of spent layer Tsaiya duck was studied.
2. Myofibrils were prepared from 0.1 M and 0.2 M lactic acid marinated muscle and control (non‐marinated samples) sampled at 0, 1, 3, 7 and 14 d post mortem.
3. Changes in myofibril fragmentation index (MFI), myofibrillar proteins and Z‐line structure were examined.
4. Marination of duck breast muscle in lactic acid at 5°C enhanced fragmentation of myofibrils and degradation of myofibrillar proteins and Z‐line structure as compared to control samples.
5. In summary, lactic acid marination at 5°C can accelerate the post mortem degradation of myofibrils in Tsaiya duck breast muscle. 相似文献
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Samples of maize grown in various districts of Taiwan were collected and analyzed for the presence of fumonisin B(1) (FB(1)) and fumonisin B(2) (FB(2)) using high-performance liquid chromatography. Forty-nine (44.5%) and 2 (1.8%) of 110 samples were found to contain FB(1) (109-1148 ng/g) and FB(2) (222-255 ng/g), respectively. The frequency of detection and also the maximum FB(1) concentration were found in samples from Penton (2/2, 262 ng/g), followed by Chiayi (18/26, 264 ng/g), Tainan (8/16, 160 ng/g), Hualinen (5/14, 1148 ng/g), Taitung (7/20, 109 ng/g), and Yunlin (9/26, 361 ng/g). Of the 110 samples examined, only 2 samples from Hualinen had been detected containing FB(2). During an analysis of the distribution pattern of FB(1), it became apparent that >79% of tested samples had FB(1) concentrations <100 ng/g, whereas 2.7% (or 3 samples) contained FB(1) >300 ng/g. These results clearly illustrated that domestically produced maize for human consumption is frequently contaminated with FB(1). 相似文献
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GIS-assisted site selection for artificial reefs 总被引:3,自引:0,他引:3