Synthesis, identification, and acute toxicity of alpha-benzylphenethylamine and alpha-benzyl-N-methylphenethylamine. Contaminants in clandestine preparation of amphetamine and methamphetamine     

F T Noggle  C R Clark  T W Davenport  S T Coker 《Journal of the Association of Official Analytical Chemists》1985,68(6):1213-1222

Amphetamine samples obtained from clandestine laboratories often contain other by-product amines. The most common of these are the alpha-benzylphenethylamine derivatives. This article reports the independent synthesis of reference samples of these amines, spectrophotometric and chromatographic methods for their identification, as well as acute toxicological studies. The utility of the analytical methods is demonstrated by the analysis of several amphetamine samples containing these alpha-benzylphenethylamines.  相似文献   

Adverse effects of simulated harvesting of short-rotation willow and poplar coppice on vertical pressures and rut depths     

C.W. Watts  L.J. Clark  W.C.T. Chamen  A.P. Whitmore 《Soil & Tillage Research》2005,84(2):192-199

Little is known of the effects of mechanized harvesting on ground conditions during the harvesting of short-rotation coppice. An investigation was therefore carried out in which different vehicles were used to simulate the effects of wheeling from heavy and light harvesters and crop removal equipment. The experiments were carried out on sites containing Bowles hybrid willow (Salix viminalis) and poplars (Populas rap) and on clay and sandy loam soils. The effect of different vehicles was assessed in terms of rut damage and direct measurements of soil stress using buried sensors. Maximum stresses measured 0.3 m below tractor wheels ranged from 50 to 200 kPa, but the greatest stresses, 350 kPa, were recorded under laden trailer wheels. Maximum stresses measured beneath crawler tracks were only 25 kPa. Similarly, substantial ruts were caused by vehicles simulating wheeled harvesters, the deepest ruts were caused by laden trailers but crawler tracks created least disturbance. Wheeling was carried out at soil water contents above the plastic limit and the deepest ruts were created on clay rather than sandy loam soil. The effects of the stresses generated in the soil could impede future root growth, and the deeper ruts formed could damage existing root systems of coppice.  相似文献   

Effect of Flavonoids (Vitamin P) on Mortality From Total Body Roentgen Irradiation     

Clark WG  Uncapher RP  Jordan ML 《Science (New York, N.Y.)》1948,108(2814):629-630

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The economics of overexploitation     

Clark CW 《Science (New York, N.Y.)》1973,181(4100):630-634

The general economic analysis of a biological resource presented in this article suggests that overexploitation in the physical sense of reduced productivity may result from not one, but two social conditions: common-property competitive exploitation on the one hand, and private-property maximization of profits on the other. For populations that are economically valuable but possess low reproductive capacities, either condition may lead even to the extinction of the population. In view of the likelihood of private firms adopting high rates of discount, the conservation of renewable resources would appear to require continual public surveillance and control of the physical yield and the condition of the stocks.  相似文献   

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