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Comparison of declassified satellite photography taken in 1963 with more recent satellite imagery reveals that large changes have occurred in the region where an active ice stream enters the Ross Ice Shelf. Ice stream B has widened by 4 kilometers, at a rate much faster than suggested by models, and has decreased in speed by 50 percent. The ice ridge between ice streams B and C has eroded 14 kilometers. These changes, along with changes in the crevassing around Crary Ice Rise, imply that this region's velocity field shifted during this century.  相似文献   

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For 10 months the Infrared Astronomical Satellite (IRAS) provided astronomers with what might be termed their first view of the infrared sky on a clear, dark night. Without IRAS, atmospheric absorption and the thermal emission from both the atmosphere and Earthbound telescopes make the task of the infrared astronomer comparable to what an optical astronomer would face if required to work only on cloudy afternoons. IRAS observations are serving astronomers in the same manner as the photographic plates of the Palomar Observatory Sky Survey; just as the optical survey has been used by all astronomers for over three decades, as a source of quantitative information about the sky and as a "roadmap" for future observations, the results of IRAS will be studied for years to come. IRAS has demonstrated the power of infrared astronomy from space. Already, from a brief look at a miniscule fraction of the data available, we have learned much about the solar system, about nearby stars, about the Galaxy as a whole and about distant extragalactic systems. Comets are much dustier than previously thought. Solid particles, presumably the remnants of the star-formation process, orbit around Vega and other stars and may provide the raw material for planetary systems. Emission from cool interstellar material has been traced throughout the Galaxy all the way to the galactic poles. Both the clumpiness and breadth of the distribution of this material were previously unsuspected. The far-infrared sky away from the galactic plane has been found to be dominated by spiral galaxies, some of which emit more than 50 percent and as much as 98 percent of their energy in the infrared-an exciting and surprising revelation. The IRAS mission is clearly the pathfinder for future missions that, to a large extent, will be devoted to the discoveries revealed by IRAS.  相似文献   

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Legeckis R 《Science (New York, N.Y.)》1977,197(4309):1179-1181
During 1975, westward-moving long waves with a period of about 25 days and a wavelength of 1000 kilometers were observed at a sea surface temperature front in the equatorial Pacific on infrared images obtained by a geostationary environmental satellite system. The absence of these waves during 1976, and the above-average equatorial sea surface temperatures during 1976, may be related to a decrease in the southeasterly trade winds during that year.  相似文献   

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对一株分离自萝卜(Raphanussativus)的黄瓜花叶病毒(CMV)卫星RNA(Rs)进行了cDNA克隆与序列确定,并与12个已知的卫星RNA序列进行了比较。结果表明:卫星RNARs的大小为368nt;该卫星RNA所比较的13个卫星RNA的大小分布为334~405nt,可分为3个组和4个亚组;CMV卫星RNA的序列同源性和分组与卫星RNA的大小并无直接联系。卫星RNA序列之间的连续缺失和插入均集中在90~255nt间几个邻近的区域。在卫星RNA二级结构中的非配对区序列、卫星RNA的5'端近80个碱基和3'端近45个碱基相当保守。由此推测CMV卫星RNA的理论长度可达446nt。序列结构的比较显示,CMV卫星RNA具有作为外源基因载体的潜力。  相似文献   

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During detailed analysis of Voyager 2 pictures of the Jupiter ring, a starlike object was identified in the plane of the ring. The same object was subsequently found on a higher-resolution frame and proved to be a satellite of Jupiter. This satellite has a circular orbit whose radius is 1.8 Jupiter radii, a period of 7 hours and 8 minutes, and a diameter of less than 40 kilometers. It is located at the outer edge of the Jupiter ring.  相似文献   

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Mills  Linda  Flemmer  Rory  Flemmer  Claire  Bakker  Huub 《Precision Agriculture》2019,20(5):911-925
Precision Agriculture - The dry matter content of New Zealand kiwifruit is currently measured using destructive testing of a 90-fruit sample. Dry matter content varies from 14 to 20% with a...  相似文献   

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Magnetization of selected nonmare areas, principally on the moon's far side, is inferred from positive disturbances in the magnitude of the magnetic field exterior to the magnetic signature of the lunar cavity observed in magnetometer data from the lunar orbiter Explorer 35. A less favored model for the field perturbations involves variations in the thickness of the low-conductivity crustal layer of the moon.  相似文献   

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Many Landsat images of Antarctica show distinctive flow and crevasse features in the floating part of ice streams and outlet glaciers immediately below their grounding zones. Some of the features, which move with the glacier or ice stream, remain visible over many years and thus allow time-lapse measurements of ice velocities. Measurements taken from Landsat images of features on Byrd Glacier agree well with detailed ground and aerial observations. The satellite-image technique thus offers a rapid and cost-effective method of obtaining average velocities, to a first order of accuracy, of many ice streams and outlet glaciers near their termini.  相似文献   

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A method is described for photographing bats or other rapidly moving objects as they intercept in space a particular area which is covered by a camera system. Photographs taken at Carlsbad Caverns show that the tail membrane of the Mexican freetail bat is extended when the animal is in flight.  相似文献   

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