Diamond genesis,seismic structure,and evolution of the Kaapvaal-Zimbabwe craton     

Shirey SB  Harris JW  Richardson SH  Fouch MJ  James DE  Cartigny P  Deines P  Viljoen F 《Science (New York, N.Y.)》2002,297(5587):1683-1686

The lithospheric mantle beneath the Kaapvaal-Zimbabwe craton of southern Africa shows variations in seismic P-wave velocity at depths within the diamond stability field that correlate with differences in the composition of diamonds and their syngenetic inclusions. Middle Archean mantle depletion events initiated craton keel formation and early harzburgitic diamond formation. Late Archean accretionary events involving an oceanic lithosphere component stabilized the craton and contributed a younger Archean generation of eclogitic diamonds. Subsequent Proterozoic tectonic and magmatic events altered the composition of the continental lithosphere and added new lherzolitic and eclogitic diamonds to the Archean diamond suite.  相似文献   

Vasopressin and oxytocin excite distinct neuronal populations in the central amygdala     

Huber D  Veinante P  Stoop R 《Science (New York, N.Y.)》2005,308(5719):245-248

Vasopressin and oxytocin strongly modulate autonomic fear responses, through mechanisms that are still unclear. We describe how these neuropeptides excite distinct neuronal populations in the central amygdala, which provides the major output of the amygdaloid complex to the autonomic nervous system. We identified these two neuronal populations as part of an inhibitory network, through which vasopressin and oxytocin modulate the integration of excitatory information from the basolateral amygdala and cerebral cortex in opposite manners. Through this network, the expression and endogenous activation of vasopressin and oxytocin receptors may regulate the autonomic expression of fear.  相似文献   

Multi-time scale analysis of sugarcane within-field variability: improved crop diagnosis using satellite time series?     

Agnès Bégué  Pierre Todoroff  Johanna Pater 《Precision Agriculture》2008,9(3):161-171

Within-field spatial variability is related to multiple factors that can be time-independent or time-dependent. In this study, our working hypothesis is that a multi-time scale analysis of the dynamics of spatial patterns can help establish a diagnosis of crop condition. To test this hypothesis, we analyzed the within-field variability of a sugarcane crop at seasonal and annual time scales, and tried to link this variability to environmental (climate, topography, and soil depth) and cropping (harvest date) factors. The analysis was based on a sugarcane field vegetation index (NDVI) time series of fifteen SPOT images acquired in the French West Indies (Guadeloupe) in 2002 and 2003, and on an original classification method that enabled us to focus on crop spatial variability independently of crop growth stages. We showed that at the seasonal scale, the within-field growth pattern depended on the phenological stage of the crop and on cropping operations. At the annual scale, NDVI maps revealed a stable pattern for the two consecutive years at peak vegetation, despite very different rainfall amounts, but with inverse NDVI values. This inversion is linked with the topography and consequently to the plant water status. We conclude that (1) it is necessary to know the crop growing cycle to correctly interpret the spatial pattern, (2) single-date images may be insufficient for the diagnosis of crop condition or for prediction, and (3) the pattern of vigour occurrence within fields can help diagnose growth anomalies.

Pierre TodoroffEmail:

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Ecology. Quaternary refugia and persistence of biodiversity     

Taberlet P  Cheddadi R 《Science (New York, N.Y.)》2002,297(5589):2009-2010

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Physics. How soft skin wrinkles     

Brochard-Wyart F  de Gennes PG 《Science (New York, N.Y.)》2003,300(5618):441

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Infectious behavior in a parasitoid     

Varaldi J  Fouillet P  Ravallec M  López-Ferber M  Boulétreau M  Fleury F 《Science (New York, N.Y.)》2003,302(5652):1930

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Preserved feedforward but impaired top-down processes in the vegetative state     

Boly M  Garrido MI  Gosseries O  Bruno MA  Boveroux P  Schnakers C  Massimini M  Litvak V  Laureys S  Friston K 《Science (New York, N.Y.)》2011,332(6031):858-862

Frontoparietal cortex is involved in the explicit processing (awareness) of stimuli. Frontoparietal activation has also been found in studies of subliminal stimulus processing. We hypothesized that an impairment of top-down processes, involved in recurrent neuronal message-passing and the generation of long-latency electrophysiological responses, might provide a more reliable correlate of consciousness in severely brain-damaged patients, than frontoparietal responses. We measured effective connectivity during a mismatch negativity paradigm and found that the only significant difference between patients in a vegetative state and controls was an impairment of backward connectivity from frontal to temporal cortices. This result emphasizes the importance of top-down projections in recurrent processing that involve high-order associative cortices for conscious perception.  相似文献   

Agricultural land: A question of values     

Pierre Crosson 《Agriculture and Human Values》1985,2(4):6-13

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Ultrahigh-density nanowire lattices and circuits     

Melosh NA  Boukai A  Diana F  Gerardot B  Badolato A  Petroff PM  Heath JR 《Science (New York, N.Y.)》2003,300(5616):112-115

We describe a general method for producing ultrahigh-density arrays of aligned metal and semiconductor nanowires and nanowire circuits. The technique is based on translating thin film growth thickness control into planar wire arrays. Nanowires were fabricated with diameters and pitches (center-to-center distances) as small as 8 nanometers and 16 nanometers, respectively. The nanowires have high aspect ratios (up to 10(6)), and the process can be carried out multiple times to produce simple circuits of crossed nanowires with a nanowire junction density in excess of 10(11) per square centimeter. The nanowires can also be used in nanomechanical devices; a high-frequency nanomechanical resonator is demonstrated.  相似文献   

Multiple Ebola virus transmission events and rapid decline of central African wildlife     

Leroy EM  Rouquet P  Formenty P  Souquière S  Kilbourne A  Froment JM  Bermejo M  Smit S  Karesh W  Swanepoel R  Zaki SR  Rollin PE 《Science (New York, N.Y.)》2004,303(5656):387-390

Several human and animal Ebola outbreaks have occurred over the past 4 years in Gabon and the Republic of Congo. The human outbreaks consisted of multiple simultaneous epidemics caused by different viral strains, and each epidemic resulted from the handling of a distinct gorilla, chimpanzee, or duiker carcass. These animal populations declined markedly during human Ebola outbreaks, apparently as a result of Ebola infection. Recovered carcasses were infected by a variety of Ebola strains, suggesting that Ebola outbreaks in great apes result from multiple virus introductions from the natural host. Surveillance of animal mortality may help to predict and prevent human Ebola outbreaks.  相似文献