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341.
The 8000-ton water IMB nucleon decay detector has good sensitivity to the neutrino burst associated with the collapse of stars. It is particularly sensitive to the v(e) charged current interactions with protons but can also record other neutrino interactions through ve scattering. Signal, noise, physics objectives, and detector modifications that would enhance burst detection are discussed. The objectives include astrophysical questions about the pulse structure and power. It also may be possible with a distant source to study neutrino masses and neutrino oscillations.  相似文献   
342.
Geological rhythms and cometary impacts   总被引:1,自引:0,他引:1  
Time-series analysis reveals two dominant, stable long-term periodicities approximately equal to 33 +/- 3 and 260 +/- 25 million years in the known series of geological and biological upheavals during the Phanerozoic Eon. Because the cycles of these episodes agree in period and phase with the cycles of impact cratering on Earth, these results suggest that periodic comet impacts strongly influence global tectonism and biological evolution. These two periodicities could arise from interactions of the solar system with interstellar clouds as the solar system moves cyclically through the Galaxy.  相似文献   
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Polychlorinated dibenzo-p-dioxins and dibenzofurans were found in sediment from Siskiwit Lake on Isle Royale, Lake Superior, a location which can receive only atmospheric inputs. The source of these compounds is the atmospheric transport of dioxins and furans formed by combustion of domestic and chemical waste.  相似文献   
346.
Newly discovered fossils support a Wasatchian (early Eocene) age for the Punta Prieta vertebrate fauna of Baja California and reveal the utility of land mammal ages on a continental scale. Dispersal scenarios for late Paleocene and early Eocene vertebrates usually invoke heterochrony for similar, but geographically separated, faunas or taxa. Such heterochrony is not supported by independent geochronologies or adequate geographic samples.  相似文献   
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The federal government's concern about maintaining the lead of the United States over the Soviet Union and its allies in militarily critical technology has led it to attempt to control unwanted technology transfer. Its attempts have extended to control of open scientific communication as well as the transfer of physical devices and blueprints. In 1982, the Corson Panel (an independent ad hoc committee) reviewed the evidence on the costs and benefits of controls and suggested guiding principles for government policy. This article examines the major policy developments since the Corson Panel completed its work. The stringency and the reach of government restrictions, either proposed or in force, go considerably beyond the panel's recommendations.  相似文献   
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A model is proposed for the East Coast Magnetic Anomaly that, for the first time, incorporates an observed basement feature-a normal fault that consistently lies below the landward flank of the anomaly. The East Coast Magnetic Anomaly is similar to slope anomalies found over passive continental margins in many parts of the world. Thus the proposed model can be used to interpret slope anomalies in general.  相似文献   
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