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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Tomatine and parasitic wasps: potential incompatibility of plant antibiosis with biological control     

Campbell BC  Duffey SS 《Science (New York, N.Y.)》1979,205(4407):700-702

alpha-Tomatine, an alkaloid in tomato plants, is toxic to an endoparasite of a major lepidopterous pest of tomatoes. The parasite acquires the alkaloid from its host after the host ingests the alkaloid. This form of interaction creates a potential dilemma to controlling herbivorous pests through chemical antibiosis in plants.  相似文献   

Retention of xenon in quartz and Earth's missing xenon     

Sanloup C  Schmidt BC  Chamorro Perez EM  Jambon A  Gregoryanz E  Mezouar M 《Science (New York, N.Y.)》2005,310(5751):1174-1177

The reactivity of xenon with terrestrial oxides was investigated by in situ synchrotron x-ray diffraction. At high temperature (T > 500 kelvin), some silicon was reduced, and the pressure stability of quartz was expanded, attesting to the substitution of some xenon for silicon. When the quartz was quenched, xenon diffused out and only a few weight percent remained trapped in samples. These results show that xenon can be covalently bonded to oxygen in quartz in the lower continental crust, providing an answer to the missing xenon problem; synthesis paths of rare gas compounds are also opened.  相似文献   

Adaptive phenotypic plasticity in response to climate change in a wild bird population     

Charmantier A  McCleery RH  Cole LR  Perrins C  Kruuk LE  Sheldon BC 《Science (New York, N.Y.)》2008,320(5877):800-803

Rapid climate change has been implicated as a cause of evolution in poorly adapted populations. However, phenotypic plasticity provides the potential for organisms to respond rapidly and effectively to environmental change. Using a 47-year population study of the great tit (Parus major) in the United Kingdom, we show that individual adjustment of behavior in response to the environment has enabled the population to track a rapidly changing environment very closely. Individuals were markedly invariant in their response to environmental variation, suggesting that the current response may be fixed in this population. Phenotypic plasticity can thus play a central role in tracking environmental change; understanding the limits of plasticity is an important goal for future research.  相似文献   

Factors governing tropospheric mean temperature   总被引：3，自引：0，他引：3  

Newell RE  Weare BC 《Science (New York, N.Y.)》1976,194(4272):1413-1414

Two possible factors, which in addition to Pacific sea surface temperatures might affect the mean temperatures of the tropical troposphere are Atlantic sea surface temperatures and volcanic aerosol. The Mt. Agung eruption in March 1963 produced a decrease of about 0.5 degrees C in the mean temperature of the tropical troposphere. The contribution of the Atlantic is not significant.  相似文献   

Secular variation of iron isotopes in north atlantic deep water   总被引：3，自引：0，他引：3  

Zhu XK  O'Nions RK  Guo Y  Reynolds BC 《Science (New York, N.Y.)》2000,287(5460):2000-2002

A high-precision iron isotope time series for a ferromanganese crust demonstrates that the iron isotope composition in North Atlantic Deep Water has changed substantially over the past 6 million years and that iron isotope variations in the crust are closely correlated to those of lead isotopes. The close correlation between the two isotope series indicates that the observed iron isotope variations predominantly reflect those of iron input from terrigenous sources and provides no evidence for biologically induced mass fractionation within North Atlantic Deep Water.  相似文献   

Voyager 1 explores the termination shock region and the heliosheath beyond     

Stone EC  Cummings AC  McDonald FB  Heikkila BC  Lal N  Webber WR 《Science (New York, N.Y.)》2005,309(5743):2017-2020

Voyager 1 crossed the termination shock of the supersonic flow of the solar wind on 16 December 2004 at a distance of 94.01 astronomical units from the Sun, becoming the first spacecraft to begin exploring the heliosheath, the outermost layer of the heliosphere. The shock is a steady source of low-energy protons with an energy spectrum approximately E(-1.41 +/- 0.15) from 0.5 to approximately 3.5 megaelectron volts, consistent with a weak termination shock having a solar wind velocity jump ratio r=2.6(-0.2)(+0.4). However, in contradiction to many predictions, the intensity of anomalous cosmic ray (ACR) helium did not peak at the shock, indicating that the ACR source is not in the shock region local to Voyager 1. The intensities of approximately 10-megaelectron volt electrons, ACRs, and galactic cosmic rays have steadily increased since late 2004 as the effects of solar modulation have decreased.  相似文献   

A 50,000-year record of climate oscillations from Florida and its temporal correlation with the heinrich events     

Grimm EC  Jacobson GL  Watts WA  Hansen BC  Maasch KA 《Science (New York, N.Y.)》1993,261(5118):198-200

Oscillations of Pinus (pine) pollen in a 50,000-year sequence from Lake Tulane, Florida, indicate that there were major vegetation shifts during the last glacial cycle. Episodes of abundant Pinus populations indicate a climate that was more wet than intervening phases dominated by Quercus (oak) and Ambrosia-type (ragweed and marsh-elder). The Pinus episodes seem to be temporally correlated with the North Atlantic Heinrich events, which were massive, periodic advances of ice streams from the eastern margin of the Laurentide Ice Sheet. Possible links between the Tulane Pinus and Heinrich events include hemispheric cooling, the influences of Mississippi meltwater on sea-surface temperatures in the Gulf of Mexico, and the effects of North Atlantic thermohaline circulation on currents in the Gulf.  相似文献   

Evidence of a pluripotent human embryonic stem cell line derived from a cloned blastocyst     

Hwang WS  Ryu YJ  Park JH  Park ES  Lee EG  Koo JM  Jeon HY  Lee BC  Kang SK  Kim SJ  Ahn C  Hwang JH  Park KY  Cibelli JB  Moon SY 《Science (New York, N.Y.)》2004,303(5664):1669-1674

Somatic cell nuclear transfer (SCNT) technology has recently been used to generate animals with a common genetic composition. In this study, we report the derivation of a pluripotent embryonic stem (ES) cell line (SCNT-hES-1) from a cloned human blastocyst. The SCNT-hES-1 cells displayed typical ES cell morphology and cell surface markers and were capable of differentiating into embryoid bodies in vitro and of forming teratomas in vivo containing cell derivatives from all three embryonic germ layers in severe combined immunodeficient mice. After continuous proliferation for more than 70 passages, SCNT-hES-1 cells maintained normal karyotypes and were genetically identical to the somatic nuclear donor cells. Although we cannot completely exclude the possibility that the cells had a parthenogenetic origin, imprinting analyses support a SCNT origin of the derived human ES cells.  相似文献   

Elucidation of the small RNA component of the transcriptome   总被引：3，自引：0，他引：3  

Lu C  Tej SS  Luo S  Haudenschild CD  Meyers BC  Green PJ 《Science (New York, N.Y.)》2005,309(5740):1567-1569

Small RNAs play important regulatory roles in most eukaryotes, but only a small proportion of these molecules have been identified. We sequenced more than two million small RNAs from seedlings and the inflorescence of the model plant Arabidopsis thaliana. Known and new microRNAs (miRNAs) were among the most abundant of the nonredundant set of more than 75,000 sequences, whereas more than half represented lower abundance small interfering RNAs (siRNAs) that match repetitive sequences, intergenic regions, and genes. Individual or clusters of highly regulated small RNAs were readily observed. Targets of antisense RNA or miRNA did not appear to be preferentially associated with siRNAs. Many genomic regions previously considered featureless were found to be sites of numerous small RNAs.  相似文献