THE OCCURRENCE OF ROTENONE AND RELATED COMPOUNDS IN THE ROOTS OF CRACCA VIRGINIANA     

Clark EP 《Science (New York, N.Y.)》1933,77(1995):311-312

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Ice sheet and solid Earth influences on far-field sea-level histories   总被引：1，自引：0，他引：1  

Bassett SE  Milne GA  Mitrovica JX  Clark PU 《Science (New York, N.Y.)》2005,309(5736):925-928

Previous predictions of sea-level change subsequent to the last glacial maximum show significant, systematic discrepancies between observations at Tahiti, Huon Peninsula, and Sunda Shelf during Lateglacial time (approximately 14,000 to 9000 calibrated years before the present). We demonstrate that a model of glacial isostatic adjustment characterized by both a high-viscosity lower mantle (4 x 10(22) Pa s) and a large contribution from the Antarctic ice sheet to meltwater pulse IA (approximately 15-meters eustatic equivalent) resolves these discrepancies. This result supports arguments that an early and rapid Antarctic deglaciation contributed to a sequence of climatic events that ended the most recent glacial period of the current ice age.  相似文献   

The elemental composition of asteroid 433 eros: results of the NEAR-shoemaker X-ray spectrometer     

Trombka JI  Squyres SW  Bruckner J  Boynton WV  Reedy RC  McCoy TJ  Gorenstein P  Evans LG  Arnold JR  Starr RD  Nittler LR  Murphy ME  Mikheeva I  McNutt RL  McClanahan TP  McCartney E  Goldsten JO  Gold RE  Floyd SR  Clark PE  Burbine TH  Bhangoo JS  Bailey SH  Petaev M 《Science (New York, N.Y.)》2000,289(5487):2101-2105

We report major element composition ratios for regions of the asteroid 433 Eros imaged during two solar flares and quiet sun conditions during the period of May to July 2000. Low aluminum abundances for all regions argue against global differentiation of Eros. Magnesium/silicon, aluminum/silicon, calcium/silicon, and iron/silicon ratios are best interpreted as a relatively primitive, chondritic composition. Marked depletions in sulfur and possible aluminum and calcium depletions, relative to ordinary chondrites, may represent signatures of limited partial melting or impact volatilization.  相似文献   

The formation and fragmentation of disks around primordial protostars     

Clark PC  Glover SC  Smith RJ  Greif TH  Klessen RS  Bromm V 《Science (New York, N.Y.)》2011,331(6020):1040-1042

The very first stars to form in the universe heralded an end to the cosmic dark ages and introduced new physical processes that shaped early cosmic evolution. Until now, it was thought that these stars lived short, solitary lives, with only one extremely massive star, or possibly a very wide binary system, forming in each dark-matter minihalo. Here we describe numerical simulations that show that these stars were, to the contrary, often members of tight multiple systems. Our results show that the disks that formed around the first young stars were unstable to gravitational fragmentation, possibly producing small binary and higher-order systems that had separations as small as the distance between Earth and the Sun.  相似文献   

Aptitude test bias     

Clark K  Plotkin L 《Science (New York, N.Y.)》1971,174(4016):1278-1279

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Receptor-estrogen complex in the nuclear fraction of rat uterine cells during the estrous cycle     

J H Clark  J Anderson  E J Peck 《Science (New York, N.Y.)》1972,176(34):528-530

A quantitative method was used to determine the concentration of receptor-estrogen complex in the nuclear fraction of rat uterine cells throughout the estrous cycle. The concentrations of nuclear receptor-estrogen complex were: metestrus, 0.22; diestrus, 0.75; proestrus, 1.29; and estrus, 0.31 picomoles per milligram of DNA. This cyclic fluctuation in the nuclear complex closely parallels the secretion of ovarian estrogen during the estrous cycle, an indication that the accumulation of receptor-estrogen complex by the nuclear fraction of uterine cells may be of physiological significance, and under the control of endogenous estrogen.  相似文献   

THE EFFECT OF X-RAYS ON BACTERIA     

Clark GL  Boruff CS 《Science (New York, N.Y.)》1929,70(1803):74-75

(1) X-rays act like sterilizing agents upon cultures of B.coli and Erythrobacillus prodigiosus, in that the curves are characteristic sterilization or death-rate curves showing that the total counts decrease logarithmically with time. (2) In this experiment B.coli did not show variation or mutation when it was treated with X-rays. (3) With increasing irradiation Erythrobacillus prodigiosus showed a tendency toward lack of ability to produce its characteristic red pigment. By allowing the organism to grow on the plate for a period of five days the greater portion of the colonies produced their pigment. If a transfer of a white colony is made to an agar slant the characteristic pigment is produced in twelve hours. In only one case was it necessary to make a second transfer in order to bring about the development of the pigment. The above is another example of the variation tendency of Erythrobacillus prodigiosus.  相似文献   

Deep-sea foraging behavior: its bathymetric potential in the fossil record     

Kitchell JA  Kitchell JF  Clark DL  Dangeard L 《Science (New York, N.Y.)》1978,200(4347):1289-1291

Spiral and meander foraging traces in the deep sea are not distributed in proportion to assumed food availability. Data collected by means of deep-sea photography failed to reveal a bathymetric gradient in behavioral complexity or sensitivity. The foraging paradigm developed by numerous trace fossil studies does not adequately predict the modern environment.  相似文献   

Generating solitons by phase engineering of a bose-einstein condensate     

Denschlag J  Simsarian JE  Feder DL  Clark CW  Collins LA  Cubizolles J  Deng L  Hagley EW  Helmerson K  Reinhardt WP  Rolston SL  Schneider BI  Phillips WD 《Science (New York, N.Y.)》2000,287(5450):97-101

Quantum phase engineering is demonstrated with two techniques that allow the spatial phase distribution of a Bose-Einstein condensate (BEC) to be written and read out. A quantum state was designed and produced by optically imprinting a phase pattern onto a BEC of sodium atoms, and matter-wave interferometry with spatially resolved imaging was used to analyze the resultant phase distribution. An appropriate phase imprint created solitons, the first experimental realization of this nonlinear phenomenon in a BEC. The subsequent evolution of these excitations was investigated both experimentally and theoretically.  相似文献   

Interventions to increase the participation of women in physics     

Dresselhaus MS  Franz JR  Clark BC 《Science (New York, N.Y.)》1994,263(5152):1392-1393

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