Portrait of Science. Scientist, technologist, proto-feminist, superstar     

Macklis RM 《Science (New York, N.Y.)》2002,295(5560):1647-1648

Although Marie Curie is known primarily for her discovery of radium, her true gift to science was her realization that radioactivity is an intrinsic atomic property of matter rather than the result of chemical processes. She was one of the few Nobel laureates to win the prize twice (physics and chemistry). During her career and as one of the first prominent women scientists, she became increasingly aware of the need for funding for research and of the scientific freedom that money can bring. By nature shy and reserved, Marie's fame, as both a scientist and as an exemplar of a liberated professional woman of the roaring twenties, grew to superstar proportions.  相似文献   

Water Availability for Winter Wheat Affected by Summer Fallow Tillage Practices in Slope Dryland   总被引：2，自引：0，他引：2  

WANG Xiao-bin  CAI Dian-xiong  JIN Ke  WU Hui-jun  BAI Zhan-guo  ZHANG Can-jun  YAO Yu-qing  LU Jun-jie  WANG Yu-hong  YANG Bo  Roger Hartmann  Donald Gabriels 《中国农业科学(英文版)》2003,2(7)

The tillage experiments for winter wheat were conducted on the slope farmland in Luoyang,Henan Province in the semihumid to arid loess plateau areas of North China. Different tillage methods inclu-ding reduced tillage (RT), no-till (NT), 2 crops/year (2C), subsoiling(SS), and conventional tillage (CT)were compared to determine the effects of tillage methods on soil water conservation, water availability, andwheat yields in a search for better farming systems in the areas. The NT and SS showed good effects on waterconservation. The soil water storage increased 12 - 33 mm with NT and 9 - 24 mm with SS at the end of sum-mer fallow periods. The soil evaporation with NT and SS decreased 7 - 8 mm and 34 - 36 mm during the fallowperiods of 1999 and 2001, respectively. Evapotranspiration (ET) with NT and SS increased about 47 mm dur-ing wheat growth periods of 2000 to 2001. Treatment RT and 2C had low water storage and high water lossesduring the fallow periods. The winter wheat yields with conservation tillage practices were improved in the 2ndyear, increased by 3, 5 and 8 % with RT, NT and SS, respectively, compared with CT. The highest wheatyields were obtained with subsoiling, and the maximum economic benefits from no-till. All conservation tillagepractices provided great benefits to saving energy and labors, reducing operation inputs, and increasing eco-nomic returns. No-till and subsoiling have shown promise in increasing water storage, reducing water loss, en-hancing water availability, and saving energy, as well as increasing wheat yield.  相似文献   

Disaster management. Confronting disaster losses     

Bouwer LM  Crompton RP  Faust E  Hoppe P  Pielke RA 《Science (New York, N.Y.)》2007,318(5851):753

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Discovery of olivine in the Nili Fssae region of Mars     

Hoefen TM  Clark RN  Bandfield JL  Smith MD  Pearl JC  Christensen PR 《Science (New York, N.Y.)》2003,302(5645):627-630

We have detected a 30,000-square-kilometer area rich in olivine in the Nili Fossae region of Mars. Nili Fossae has been interpreted as a complex of grabens and fractures related to the formation of the Isidis impact basin. We propose that post-impact faulting of this area has exposed subsurface layers rich in olivine. Linear mixture analysis of Thermal Emission Spectrometer spectra shows surface exposures of 30% olivine, where the composition of the olivine ranges from Fo30 to Fo70.  相似文献   

Rise and fall of species occupancy in Cenozoic fossil mollusks     

Foote M  Crampton JS  Beu AG  Marshall BA  Cooper RA  Maxwell PA  Matcham I 《Science (New York, N.Y.)》2007,318(5853):1131-1134

In the time between speciation and extinction, a species' ecological and biogeographic footprint-its occupancy-will vary in response to macroecological drivers and historical contingencies. Despite their importance for understanding macroecological processes, general patterns of long-term species occupancy remain largely unknown. We documented the occupancy histories of Cenozoic marine mollusks from New Zealand. For both genera and species, these show a distinct pattern of increase to relatively short-lived peak occupancy at mid-duration, followed by a decline toward extinction. Thus, species at greatest risk for extinction are those that have already been in decline for a substantial period of time. This pattern of protracted rise and fall stands in contrast to that of incumbency, insofar as species show no general tendency to stay near maximal occupancy once established.  相似文献   

Biomedical research publication system     

Wang YL  Burridge K  Dembo M  Gabbiani G  Hanks SK  Hosoya H  Janmey P  Karlsson R  Lindberg U  Mabuchi I  Otey C  Rottner K  Small JV  Wang CL  Zigmond S 《Science (New York, N.Y.)》2004,303(5666):1974-1976

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Legionella effectors that promote nonlytic release from protozoa     

Chen J  de Felipe KS  Clarke M  Lu H  Anderson OR  Segal G  Shuman HA 《Science (New York, N.Y.)》2004,303(5662):1358-1361

Legionella pneumophila, the bacterial agent of legionnaires' disease, replicates intracellularly within a specialized vacuole of mammalian and protozoan host cells. Little is known about the specialized vacuole except that the Icm/Dot type IV secretion system is essential for its formation and maintenance. The Legionella genome database contains two open reading frames encoding polypeptides (LepA and LepB) with predicted coiled-coil regions and weak homology to SNAREs; these are delivered to host cells by an Icm/Dot-dependent mechanism. Analysis of mutant strains suggests that the Lep proteins may enable the Legionella to commandeer a protozoan exocytic pathway for dissemination of the pathogen.  相似文献   

Regulation of blood glucose by hypothalamic pyruvate metabolism     

Lam TK  Gutierrez-Juarez R  Pocai A  Rossetti L 《Science (New York, N.Y.)》2005,309(5736):943-947

The brain keenly depends on glucose for energy, and mammalians have redundant systems to control glucose production. An increase in circulating glucose inhibits glucose production in the liver, but this negative feedback is impaired in type 2 diabetes. Here we report that a primary increase in hypothalamic glucose levels lowers blood glucose through inhibition of glucose production in rats. The effect of glucose requires its conversion to lactate followed by stimulation of pyruvate metabolism, which leads to activation of adenosine triphosphate (ATP)-sensitive potassium channels. Thus, interventions designed to enhance the hypothalamic sensing of glucose may improve glucose homeostasis in diabetes.  相似文献   

Structure of a thiol monolayer-protected gold nanoparticle at 1.1 A resolution     

Jadzinsky PD  Calero G  Ackerson CJ  Bushnell DA  Kornberg RD 《Science (New York, N.Y.)》2007,318(5849):430-433

Structural information on nanometer-sized gold particles has been limited, due in part to the problem of preparing homogeneous material. Here we report the crystallization and x-ray structure determination of a p-mercaptobenzoic acid (p-MBA)-protected gold nanoparticle, which comprises 102 gold atoms and 44 p-MBAs. The central gold atoms are packed in a Marks decahedron, surrounded by additional layers of gold atoms in unanticipated geometries. The p-MBAs interact not only with the gold but also with one another, forming a rigid surface layer. The particles are chiral, with the two enantiomers alternating in the crystal lattice. The discrete nature of the particle may be explained by the closing of a 58-electron shell.  相似文献   

Constraints on neon and argon isotopic fractionation in solar wind     

Meshik A  Mabry J  Hohenberg C  Marrocchi Y  Pravdivtseva O  Burnett D  Olinger C  Wiens R  Reisenfeld D  Allton J  McNamara K  Stansbery E  Jurewicz AJ 《Science (New York, N.Y.)》2007,318(5849):433-435

To evaluate the isotopic composition of the solar nebula from which the planets formed, the relation between isotopes measured in the solar wind and on the Sun's surface needs to be known. The Genesis Discovery mission returned independent samples of three types of solar wind produced by different solar processes that provide a check on possible isotopic variations, or fractionation, between the solar-wind and solar-surface material. At a high level of precision, we observed no significant inter-regime differences in 20Ne/22Ne or 36Ar/38Ar values. For 20Ne/22Ne, the difference between low- and high-speed wind components is 0.24 +/- 0.37%; for 36Ar/38Ar, it is 0.11 +/- 0.26%. Our measured 36Ar/38Ar ratio in the solar wind of 5.501 +/- 0.005 is 3.42 +/- 0.09% higher than that of the terrestrial atmosphere, which may reflect atmospheric losses early in Earth's history.  相似文献