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81.
A simple model for complex dynamical transitions in epidemics 总被引:2,自引:0,他引:2
Dramatic changes in patterns of epidemics have been observed throughout this century. For childhood infectious diseases such as measles, the major transitions are between regular cycles and irregular, possibly chaotic epidemics, and from regionally synchronized oscillations to complex, spatially incoherent epidemics. A simple model can explain both kinds of transitions as the consequences of changes in birth and vaccination rates. Measles is a natural ecological system that exhibits different dynamical transitions at different times and places, yet all of these transitions can be predicted as bifurcations of a single nonlinear model. 相似文献
82.
83.
Terracciano A Abdel-Khalek AM Adám N Adamovová L Ahn CK Ahn HN Alansari BM Alcalay L Allik J Angleitner A Avia MD Ayearst LE Barbaranelli C Beer A Borg-Cunen MA Bratko D Brunner-Sciarra M Budzinski L Camart N Dahourou D De Fruyt F de Lima MP del Pilar GE Diener E Falzon R Fernando K Ficková E Fischer R Flores-Mendoza C Ghayur MA Gülgöz S Hagberg B Halberstadt J Halim MS Hrebícková M Humrichouse J Jensen HH Jocic DD Jónsson FH Khoury B Klinkosz W Knezević G Lauri MA Leibovich N Martin TA 《Science (New York, N.Y.)》2005,310(5745):96-100
Most people hold beliefs about personality characteristics typical of members of their own and others' cultures. These perceptions of national character may be generalizations from personal experience, stereotypes with a "kernel of truth," or inaccurate stereotypes. We obtained national character ratings of 3989 people from 49 cultures and compared them with the average personality scores of culture members assessed by observer ratings and self-reports. National character ratings were reliable but did not converge with assessed traits. Perceptions of national character thus appear to be unfounded stereotypes that may serve the function of maintaining a national identity. 相似文献
84.
Smith JD Cappa CD Wilson KR Messer BM Cohen RC Saykally RJ 《Science (New York, N.Y.)》2004,306(5697):851-853
A strong temperature dependence of oxygen K-edge x-ray absorption fine structure features was observed for supercooled and normal liquid water droplets prepared from the breakup of a liquid microjet. Analysis of the data over the temperature range 251 to 288 kelvin (-22 degrees to +15 degrees C) yields a value of 1.5 +/- 0.5 kilocalories per mole for the average thermal energy required to effect an observable rearrangement between the fully coordinated ("ice-like") and distorted ("broken-donor") local hydrogen-bonding configurations responsible for the pre-edge and post-edge features, respectively. This energy equals the latent heat of melting of ice with hexagonal symmetry (ice Ih) and is consistent with the distribution of hydrogen bond strengths obtained for the "overstructured" ST2 model of water. 相似文献
85.
We report a previously unknown process in which anoxygenic phototrophic bacteria use nitrite as an electron donor for photosynthesis. We isolated a purple sulfur bacterium 98% identical to Thiocapsa species that stoichiometrically oxidizes nitrite to nitrate in the light. Growth and nitrate production strictly depended on both light and nitrite. This is the first known microbial mechanism for the stoichiometric oxidation of nitrite to nitrate in the absence of oxygen and the only known photosynthetic oxidation in the nitrogen cycle. This work demonstrates nitrite as the highest-potential electron donor for anoxygenic photosynthesis known so far. 相似文献
86.
用曲轴箱增压改善单缸四冲程柴油机性能的研究 总被引:2,自引:1,他引:2
在X195柴油机空气滤清器,进气管和曲轴箱之间增设单向阀片,利用活塞工作反面来泵气,把进入进气管道的新鲜空气与漏入曲轴箱内的气体一齐压入气缸,以达到增压,降低油耗,减少排放污染的目的。 相似文献
87.
LEVY BM 《Science (New York, N.Y.)》1959,129(3350):720-721
Ultraviolet radiation-induced mutants of the soft rot bacterium Pseudomonas marginalis were selected for loss of pathogenicity for lettuce and witloof chicory. The avirulent mutants differed from the parent pathogen in their inability to synthesize pectolytic enzymes in culture or to ferment sodium pectate or sodium polygalacturonate as the sole carbon source in media. 相似文献
88.
A water-soluble peridinin-chlorophyll-protein complex from the dinoflagellate Gonyaulax polyedra was found to have a molecular weight of about 38,000. The complex could be disrupted by digestion with proteolytic enzymes. No electron transfer was observed when the complex was irradiated. 相似文献
89.
90.
A neutralizing antibody selected from plasma cells that binds to group 1 and group 2 influenza A hemagglutinins 总被引:2,自引:0,他引:2
Corti D Voss J Gamblin SJ Codoni G Macagno A Jarrossay D Vachieri SG Pinna D Minola A Vanzetta F Silacci C Fernandez-Rodriguez BM Agatic G Bianchi S Giacchetto-Sasselli I Calder L Sallusto F Collins P Haire LF Temperton N Langedijk JP Skehel JJ Lanzavecchia A 《Science (New York, N.Y.)》2011,333(6044):850-856
The isolation of broadly neutralizing antibodies against influenza A viruses has been a long-sought goal for therapeutic approaches and vaccine design. Using a single-cell culture method for screening large numbers of human plasma cells, we isolated a neutralizing monoclonal antibody that recognized the hemagglutinin (HA) glycoprotein of all 16 subtypes and neutralized both group 1 and group 2 influenza A viruses. Passive transfer of this antibody conferred protection to mice and ferrets. Complexes with HAs from the group 1 H1 and the group 2 H3 subtypes analyzed by x-ray crystallography showed that the antibody bound to a conserved epitope in the F subdomain. This antibody may be used for passive protection and to inform vaccine design because of its broad specificity and neutralization potency. 相似文献