Climate Change During the Last Deglaciation in Antarctica   总被引：1，自引：0，他引：1  

PA Mayewski  MS Twickler  SI Whitlow  LD Meeker  Q Yang  J Thomas  K Kreutz  PM Grootes  DL Morse  EJ Steig  ED Waddington  ES Saltzman  P Whung  KC Taylor 《Science (New York, N.Y.)》1996,272(5268):1636-1638

Greenland ice core records provide clear evidence of rapid changes in climate in a variety of climate indicators. In this work, rapid climate change events in the Northern and Southern hemispheres are compared on the basis of an examination of changes in atmospheric circulation developed from two ice cores. High-resolution glaciochemical series, covering the period 10,000 to 16,000 years ago, from a central Greenland ice core and a new site in east Antarctica display similar variability. These findings suggest that rapid climate change events occur more frequently in Antarctica than previously demonstrated.  相似文献   

Melting in semiconductor nanocrystals     

Goldstein AN  Echer CM  Alivisatos AP 《Science (New York, N.Y.)》1992,256(5062):1425-1427

New physics occurs in semiconductors when one or more dimensions of the crystal are reduced to a size comparable to bulk electron delocalization lengths (tens to hundreds of angstroms). The properties of "quantum dots" or semiconductor nanocrystals are now being studied, as techniques to fabricate the crystallites are developed. Temperature-dependent electron diffraction studies on nanocrystals of CdS show a large depression in the melting temperature with decreasing size, as a larger fraction of the total number of atoms is on the surface. Thermal stability may play a role in determining the uses of semiconductor nanocrystals.  相似文献   

INDEPTH Wide-Angle Reflection Observation of P-Wave-to-S-Wave Conversion from Crustal Bright Spots in Tibet     

Y Makovsky  SL Klemperer  L Ratschbacher  LD Brown  M Li  W Zhao  F Meng 《Science (New York, N.Y.)》1996,274(5293):1690-1691

Three-component wide-angle seismic data acquired in southern Tibet during Project INDEPTH show strong P-to-S converted reflections from reflectors that are aligned at a depth of approximately 15 kilometers beneath the northern Yadong-Gulu rift. These converted reflections are locally higher in amplitude than the corresponding P-wave reflections. Modeling of reflection mode conversion as a function of incidence angle indicates that this condition obtains for a reflector that is a solid over fluid interface; it is not typical of a solid-solid interface. The likely candidates for a fluid trapped within the crystalline crust of southern Tibet are granitic magma and water (brine).  相似文献   

Frequency Dependence of Polarization of Pulsar CP 0328     

Goldstein SJ  Meisel DD 《Science (New York, N.Y.)》1969,163(3869):810-812

The circularly polarized emission from the pulsar CP 0328 has an approximately flat spectrum in the 1-megahertz band centered at 113.6 megahertz, whereas the linearly polarized emission varies with frequency and from pulse to pulse. A simple model for the source that has a constant Faraday rotation measure fits some of the linearly polarized spectra observed for individual pulses, but changes in the rotation measure of as much as 30 radians per square meter are required between adjacent pulses. The simple model does not fit the average spectrum of the linearly polarized emission, although the average spectrum had the same form on two nights.  相似文献   

Structure of the LDL receptor extracellular domain at endosomal pH   总被引：2，自引：0，他引：2  

Rudenko G  Henry L  Henderson K  Ichtchenko K  Brown MS  Goldstein JL  Deisenhofer J 《Science (New York, N.Y.)》2002,298(5602):2353-2358

The low-density lipoprotein receptor mediates cholesterol homeostasis through endocytosis of lipoproteins. It discharges its ligand in the endosome at pH < 6. In the crystal structure at pH = 5.3, the ligand-binding domain (modules R2 to R7) folds back as an arc over the epidermal growth factor precursor homology domain (the modules A, B, beta propeller, and C). The modules R4 and R5, which are critical for lipoprotein binding, associate with the beta propeller via their calcium-binding loop. We propose a mechanism for lipoprotein release in the endosome whereby the beta propeller functions as an alternate substrate for the ligand-binding domain, binding in a calcium-dependent way and promoting lipoprotein release.  相似文献   

Axonopathy and transport deficits early in the pathogenesis of Alzheimer's disease     

Stokin GB  Lillo C  Falzone TL  Brusch RG  Rockenstein E  Mount SL  Raman R  Davies P  Masliah E  Williams DS  Goldstein LS 《Science (New York, N.Y.)》2005,307(5713):1282-1288

We identified axonal defects in mouse models of Alzheimer's disease that preceded known disease-related pathology by more than a year; we observed similar axonal defects in the early stages of Alzheimer's disease in humans. Axonal defects consisted of swellings that accumulated abnormal amounts of microtubule-associated and molecular motor proteins, organelles, and vesicles. Impairing axonal transport by reducing the dosage of a kinesin molecular motor protein enhanced the frequency of axonal defects and increased amyloid-beta peptide levels and amyloid deposition. Reductions in microtubule-dependent transport may stimulate proteolytic processing of beta-amyloid precursor protein, resulting in the development of senile plaques and Alzheimer's disease.  相似文献   

Lesch-Nyhan syndrome: rapid detection of heterozygotes by use of hair follicles   总被引：14，自引：0，他引：14  

S M Gartler  R C Scott  J L Goldstein  B Campbell 《Science (New York, N.Y.)》1971,172(983):572-574

A method is described which permits rapid phenotypic diagnosis of the Lesch-Nyhan heterozygote by direct assay of hypoxanthine guanine phosphori-bosyltransferase activity in single hair follicles obtained from the scalp.  相似文献   

Tremor and involuntary movements in monkeys: effect of L-dopa and of a dopamine receptor stimulating agent   总被引：2，自引：0，他引：2  

M Goldstein  A F Battista  T Ohmoto  B Anagnoste  K Fuxe 《Science (New York, N.Y.)》1973,179(75):816-817

Either L-dopa, in combination with 1-alpha-methyldopa hydrazine (MK-486), or 1-(2'-pyrimidyl)-4-piperonylpiperazine, an agent that stimulates dopamine receptors, relieves surgically induced tremor in monkeys and concomitantly evokes involuntary movements. These results indicate that tremor and involuntary movements are associated with a common mechanism and that the activity of the dopamine receptors is involved in the regulation of these dysfunctions.  相似文献   

Narcotic tolerance and dependence: lack of relationship with serotonin turnover in the brain   总被引：1，自引：0，他引：1  

D L Cheney  A Goldstein  S Algeri  E Costa 《Science (New York, N.Y.)》1971,171(976):1169-1170

Serotonin turnover was measured in mouse brain by means of the conversion of radioactivity from labeled tryptophan into serotonin. Animals with a high degree of tolerance to and physical dependence on morphine did not differ from control mice.  相似文献   

Mitosis: on the mechanism for invariable sister chromatid segregation     

L Goldstein  K G Lark 《Science (New York, N.Y.)》1967,156(3778):1133-1134

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