Electrostatic deflections and electromechanical resonances of carbon nanotubes     

Poncharal P  Wang ZL  Ugarte D  de Heer WA 《Science (New York, N.Y.)》1999,283(5407):1513-1516

Static and dynamic mechanical deflections were electrically induced in cantilevered, multiwalled carbon nanotubes in a transmission electron microscope. The nanotubes were resonantly excited at the fundamental frequency and higher harmonics as revealed by their deflected contours, which correspond closely to those determined for cantilevered elastic beams. The elastic bending modulus as a function of diameter was found to decrease sharply (from about 1 to 0.1 terapascals) with increasing diameter (from 8 to 40 nanometers), which indicates a crossover from a uniform elastic mode to an elastic mode that involves wavelike distortions in the nanotube. The quality factors of the resonances are on the order of 500. The methods developed here have been applied to a nanobalance for nanoscopic particles and also to a Kelvin probe based on nanotubes.  相似文献   

African hot spot volcanism: small-scale convection in the upper mantle beneath cratons   总被引：2，自引：0，他引：2  

King SD  Ritsema J 《Science (New York, N.Y.)》2000,290(5494):1137-1140

Numerical models demonstrate that small-scale convection develops in the upper mantle beneath the transition of thick cratonic lithosphere and thin oceanic lithosphere. These models explain the location and geochemical characteristics of intraplate volcanos on the African and South American plates. They also explain the presence of relatively high seismic shear wave velocities (cold downwellings) in the mantle transition zone beneath the western margin of African cratons and the eastern margin of South American cratons. Small-scale, edge-driven convection is an alternative to plumes for explaining intraplate African and South American hot spot volcanism, and small-scale convection is consistent with mantle downwellings beneath the African and South American lithosphere.  相似文献   

Mutations in dynein link motor neuron degeneration to defects in retrograde transport     

Hafezparast M  Klocke R  Ruhrberg C  Marquardt A  Ahmad-Annuar A  Bowen S  Lalli G  Witherden AS  Hummerich H  Nicholson S  Morgan PJ  Oozageer R  Priestley JV  Averill S  King VR  Ball S  Peters J  Toda T  Yamamoto A  Hiraoka Y  Augustin M  Korthaus D  Wattler S  Wabnitz P  Dickneite C  Lampel S  Boehme F  Peraus G  Popp A  Rudelius M  Schlegel J  Fuchs H  Hrabe de Angelis M  Schiavo G  Shima DT  Russ AP  Stumm G  Martin JE  Fisher EM 《Science (New York, N.Y.)》2003,300(5620):808-812

Degenerative disorders of motor neurons include a range of progressive fatal diseases such as amyotrophic lateral sclerosis (ALS), spinal-bulbar muscular atrophy (SBMA), and spinal muscular atrophy (SMA). Although the causative genetic alterations are known for some cases, the molecular basis of many SMA and SBMA-like syndromes and most ALS cases is unknown. Here we show that missense point mutations in the cytoplasmic dynein heavy chain result in progressive motor neuron degeneration in heterozygous mice, and in homozygotes this is accompanied by the formation of Lewy-like inclusion bodies, thus resembling key features of human pathology. These mutations exclusively perturb neuron-specific functions of dynein.  相似文献   

AN ARTIFICIAL ROOT FOR INDUCING CAPILLARY MOVEMENT OF SOIL MOISTURE     

King FH 《Science (New York, N.Y.)》1904,20(516):680-681

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Effect of Chemical Treatment Prior to Storage on Viability and Growth of Cottonseed     

Lambou MG  King GS  Condon MZ 《Science (New York, N.Y.)》1948,108(2812):563-564

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Risk factors in breast cancer     

King MC 《Science (New York, N.Y.)》1981,214(4525):1122-1123

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Science and government. Taking science out of the box--foresight recast     

King DA  Thomas SM 《Science (New York, N.Y.)》2007,316(5832):1701-1702

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Extragalactic astronomy     

King IR 《Science (New York, N.Y.)》1977,195(4277):481-482

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

King JR  Bekinschtein T  Dehaene S 《Science (New York, N.Y.)》2011,334(6060):1203; author reply 1203

Boly et al. (Reports, 13 May 2011, p. 858) investigated cortical connectivity patterns in patients suffering from a disorder of consciousness, using electroencephalography in an auditory oddball paradigm. We point to several inconsistencies in their data, including a failure to replicate the classical mismatch negativity. Data quality, source reconstruction, and statistics would need to be improved to support their conclusions.  相似文献   

Strain on the san andreas fault near palmdale, california: rapid, aseismic change     

Savage JC  Prescott WH  Lisowski M  King NE 《Science (New York, N.Y.)》1981,211(4477):56-58

Frequently repeated strain measurements near Palmdale, California, during the period from 1971 through 1980 indicate that, in addition to a uniform accumulation of right-lateral shear strain (engineering shear, 0.35 microradian per year) across the San Andreas fault, a 1-microstrain contraction perpendicular to the fault that accumulated gradually during the interval 1974 through 1978 was aseismically released between February and November 1979. Subsequently (November 1979 to March 1980), about half of the contraction was recovered. This sequence of strain changes can be explained in terms of south-southwestward migration of a slip event consisting of the south-southwestward movement of the upper crust on a horizontal detachment surface at a depth of 10 to 30 kilometers. The large strain change in 1979 corresponds to the passage of the slip event beneath the San Andreas fault.  相似文献