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441.
Barnes JW Brown RH Turtle EP McEwen AS Lorenz RD Janssen M Schaller EL Brown ME Buratti BJ Sotin C Griffith C Clark R Perry J Fussner S Barbara J West R Elachi C Bouchez AH Roe HG Baines KH Bellucci G Bibring JP Capaccioni F Cerroni P Combes M Coradini A Cruikshank DP Drossart P Formisano V Jaumann R Langevin Y Matson DL McCord TB Nicholson PD Sicardy B 《Science (New York, N.Y.)》2005,310(5745):92-95
Observations from the Cassini Visual and Infrared Mapping Spectrometer show an anomalously bright spot on Titan located at 80 degrees W and 20 degrees S. This area is bright in reflected light at all observed wavelengths, but is most noticeable at 5 microns. The spot is associated with a surface albedo feature identified in images taken by the Cassini Imaging Science Subsystem. We discuss various hypotheses about the source of the spot, reaching the conclusion that the spot is probably due to variation in surface composition, perhaps associated with recent geophysical phenomena. 相似文献
442.
Transmission dynamics of the etiological agent of SARS in Hong Kong: impact of public health interventions 总被引:2,自引:0,他引:2
Riley S Fraser C Donnelly CA Ghani AC Abu-Raddad LJ Hedley AJ Leung GM Ho LM Lam TH Thach TQ Chau P Chan KP Lo SV Leung PY Tsang T Ho W Lee KH Lau EM Ferguson NM Anderson RM 《Science (New York, N.Y.)》2003,300(5627):1961-1966
We present an analysis of the first 10 weeks of the severe acute respiratory syndrome (SARS) epidemic in Hong Kong. The epidemic to date has been characterized by two large clusters-initiated by two separate "super-spread" events (SSEs)-and by ongoing community transmission. By fitting a stochastic model to data on 1512 cases, including these clusters, we show that the etiological agent of SARS is moderately transmissible. Excluding SSEs, we estimate that 2.7 secondary infections were generated per case on average at the start of the epidemic, with a substantial contribution from hospital transmission. Transmission rates fell during the epidemic, primarily as a result of reductions in population contact rates and improved hospital infection control, but also because of more rapid hospital attendance by symptomatic individuals. As a result, the epidemic is now in decline, although continued vigilance is necessary for this to be maintained. Restrictions on longer range population movement are shown to be a potentially useful additional control measure in some contexts. We estimate that most currently infected persons are now hospitalized, which highlights the importance of control of nosocomial transmission. 相似文献
443.
Lange OF Lakomek NA Farès C Schröder GF Walter KF Becker S Meiler J Grubmüller H Griesinger C de Groot BL 《Science (New York, N.Y.)》2008,320(5882):1471-1475
Protein dynamics are essential for protein function, and yet it has been challenging to access the underlying atomic motions in solution on nanosecond-to-microsecond time scales. We present a structural ensemble of ubiquitin, refined against residual dipolar couplings (RDCs), comprising solution dynamics up to microseconds. The ensemble covers the complete structural heterogeneity observed in 46 ubiquitin crystal structures, most of which are complexes with other proteins. Conformational selection, rather than induced-fit motion, thus suffices to explain the molecular recognition dynamics of ubiquitin. Marked correlations are seen between the flexibility of the ensemble and contacts formed in ubiquitin complexes. A large part of the solution dynamics is concentrated in one concerted mode, which accounts for most of ubiquitin's molecular recognition heterogeneity and ensures a low entropic complex formation cost. 相似文献
444.
Perrine Geraudie Marie Gerbron Elisabeth Hill Christophe Minier 《Fish physiology and biochemistry》2010,36(3):767-777
Fish reproduction is subjected to worrying trends in many aquatic environments. In this study, we report the absence of histological
and biochemical alterations in fish sampled in a low contaminated site (characterised by the absence of detectable oestrogenic
activity and mutagenicity in sediment extracts). A total of 474 roach (Rutilus rutilus) were monthly sampled during 18 months, and no intersex fish were recorded after careful histological examination, thus indicating
that the incidence of this phenomenon may be very low under natural conditions. Furthermore, mean male plasma vitellogenin
concentration was 24 ng ml−1 and was only slightly elevated during the spawning period (up to 120 ng ml−1) indicating that these low values may be characteristic of a low contaminated site. Of the male roach, 45.3% were sampled,
a sex-ratio that did not significantly deviated from the expected 1:1 ratio between male and female. Results also showed that
natural conditions can greatly affect the reproductive cycle of roach. Gametogenesis showed a biphasic pattern with first
gonad maturation between September and December and a final maturation occurring at the end of winter/early spring. Under
decreasing temperatures, particularly below 6°C, gametogenesis was stopped or even regressed with secondary oocytes becoming
rare under histological observation. Conversely, elevated temperatures during the winter lead to an earlier gonad maturation. 相似文献