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71.
Zhou O Zhu Q Fischer JE Coustel N Vaughan GB Heiney PA McCauley JP Smith AB 《Science (New York, N.Y.)》1992,255(5046):833-835
X-ray diffraction and diamond anvil techniques were used to measure the isothermal compressibility of K(3)C(60) and Rb(3)C(60), the superconducting, binary alkali-metal intercalation compounds of solid buckminsterfullerene. These results, combined with the pressure dependence of the superconducting onset temperature T(c) measured by other groups, establish a universal first-order relation between T(c) and the lattice parameter a over a broad range, between 13.9 and 14.5 angstroms. A small secondorder intercalate-specific effect was observed that appears to rule out the participation of intercalate-fullerene optic modes in the pairing interaction. 相似文献
72.
Stomatal opening: role of potassium uptake by guard cells 总被引:16,自引:0,他引:16
R A Fischer 《Science (New York, N.Y.)》1968,160(829):784-785
Stomata in isolated epidermal strips open in response to light plus air free of carbon dioxide when the strips are floated on potassium chloride solutions of low concentrations. This opening depends on the stimulation of active accumulation of potassium in quantities sufficient to account for the observed changes in solute potential of the guard cells. 相似文献
73.
Fischer MH 《Science (New York, N.Y.)》1919,49(1278):615-618
74.
Memories are thought to be due to lasting synaptic modifications in the brain. The search for memory traces has relied predominantly on determining regions that are necessary for the process. However, a more informative approach is to define the smallest sufficient set of brain structures. The rutabaga adenylyl cyclase, an enzyme that is ubiquitously expressed in the Drosophila brain and that mediates synaptic plasticity, is needed exclusively in the Kenyon cells of the mushroom bodies for a component of olfactory short-term memory. This demonstrates that synaptic plasticity in a small brain region can be sufficient for memory formation. 相似文献
75.
Air entrapped in bubbles of cold ice has essentially the same composition as that of the atmosphere at the time of bubble formation. Measurements of the methane concentration in air extracted by two different methods from ice samples from Siple Station in western Antarcitica allow the reconstruction of the history of the increase of the atmospheric methane during the past 200 years. 相似文献
76.
Terracciano A Abdel-Khalek AM Adám N Adamovová L Ahn CK Ahn HN Alansari BM Alcalay L Allik J Angleitner A Avia MD Ayearst LE Barbaranelli C Beer A Borg-Cunen MA Bratko D Brunner-Sciarra M Budzinski L Camart N Dahourou D De Fruyt F de Lima MP del Pilar GE Diener E Falzon R Fernando K Ficková E Fischer R Flores-Mendoza C Ghayur MA Gülgöz S Hagberg B Halberstadt J Halim MS Hrebícková M Humrichouse J Jensen HH Jocic DD Jónsson FH Khoury B Klinkosz W Knezević G Lauri MA Leibovich N Martin TA 《Science (New York, N.Y.)》2005,310(5745):96-100
Most people hold beliefs about personality characteristics typical of members of their own and others' cultures. These perceptions of national character may be generalizations from personal experience, stereotypes with a "kernel of truth," or inaccurate stereotypes. We obtained national character ratings of 3989 people from 49 cultures and compared them with the average personality scores of culture members assessed by observer ratings and self-reports. National character ratings were reliable but did not converge with assessed traits. Perceptions of national character thus appear to be unfounded stereotypes that may serve the function of maintaining a national identity. 相似文献
77.
Blood-brain neutral amino acid transport activity is increased after portacaval anastomosis 总被引:21,自引:0,他引:21
In rats after portacaval anastomosis (an animal model of chronic liver disease), transport of tryptophan and other members of the large neutral amino acid group from blood to brain was markedly enhanced. Increased transport activity was apparently restricted to the neutral amino acid transport system, since brain uptake of glucose, inulin, and tyramine was unaffected while blood-brain arginine transport was significantly reduced. These results strikingly confirm the hypothesis that carrier-mediated blood-brain transport is the limiting factor determining the availability of the neutral amino acids to the brain. The encephalopathy associated with cirrhosis may be the result of abnormal neurotransmitter metabolism and neurotransmission secondary to increased neutral amino acid transport activity and an increased brain content of members of the neutral amino acid group. 相似文献
78.
Effects of basal debris on glacier flow 总被引:1,自引:0,他引:1
Iverson NR Cohen D Hooyer TS Fischer UH Jackson M Moore PL Lappegard G Kohler J 《Science (New York, N.Y.)》2003,301(5629):81-84
Glacier movement is resisted partially by debris, either within glaciers or under glaciers in water-saturated layers. In experiments beneath a thick, sliding glacier, ice containing 2 to 11% debris exerted shear traction of 60 to 200 kilopascals on a smooth rock bed, comparable to the total shear traction beneath glaciers and contrary to the usual assumption that debris-bed friction is negligible. Imposed pore-water pressure that was 60 to 100% of the normal stress in a subglacial debris layer reduced shear traction on the debris sufficiently to halt its deformation and cause slip of ice over the debris. Slip resistance was thus less than debris shearing resistance. 相似文献
79.
Zhu Q Zhou O Coustel N Vaughan GB McCauley JP Romanow WJ Fischer JE Smith AB 《Science (New York, N.Y.)》1991,254(5031):545-548
Powder x-ray diffraction at 300 K on equilibrated samples of several nominal compositions chi in Rb(chi)C(60) is reported. In addition to the face-centered cubic (fcc) (chi = 3, superconducting), body-centered tetragonal (chi = 4), and body-centered cubic (bcc) (chi = 6) stoichiometric phases, direct evidence for a dilute fcc doped phase, 0 x c = 1, and for a substoichiometric bcc phase, chi approximately 5, is presented. In contrast, chi = 3 and chi = 4 appear to be line phases with nearly zero solubility of Rb vacancies and interstitials at 300 K. These results are summarized in a provisional binary phase diagram. 相似文献
80.
Fischer EA 《Science (New York, N.Y.)》1985,227(4693):1464-1465