SOME PROBLEMS OF MEDICAL INVESTIGATION AND MEDICAL EDUCATION     

Christian HA 《Science (New York, N.Y.)》1925,62(1616):551-554

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Discovery of intense gamma-ray flashes of atmospheric origin   总被引：1，自引：0，他引：1  

Fishman GJ  Bhat PN  Mallozzi R  Horack JM  Koshut T  Kouveliotou C  Pendleton GN  Meegan CA  Wilson RB  Paciesas WS  Goodman SJ  Christian HJ 《Science (New York, N.Y.)》1994,264(5163):1313-1316

Detectors aboard the Compton Gamma Ray Observatory have observed an unexplained terrestrial phenomenon: brief, intense flashes of gamma rays. These flashes must originate in the atmosphere at altitudes above at least 30 kilometers in order to escape atmospheric absorption and reach the orbiting detectors. At least a dozen such events have been detected over the past 2 years. The photon spectra from the events are very hard (peaking in the high-energy portion of the spectrum) and are consistent with bremsstrahlung emission from energetic (million-electron volt) electrons. The most likely origin of these high-energy electrons, although speculative at this time, is a rare type of high-altitude electrical discharge above thunderstorm regions.  相似文献   

Comment on "Impact ejecta layer from the mid-Devonian: possible connection to global mass extinctions"     

Racki G  Koeberl C 《Science (New York, N.Y.)》2004,303(5657):471; author reply 471

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THE FRUITION OF THE CLINICIAN     

Christian HA 《Science (New York, N.Y.)》1938,87(2253):202-205

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Myxovirus antibody increases in human connective tissue disease   总被引：12，自引：0，他引：12  

P E Phillips  C L Christian 《Science (New York, N.Y.)》1970,168(934):982-984

Antibodies to measles and parainfluenza type 1 viruses were significantly increased in systemic lupus erythematosus and Reiter's syndrome. Of the individuals with highest titers of measles antibody, 75 percent had neurologic illness. Persistent virus infection may be a factor in the pathogenesis of these diseases.  相似文献   

Genetic variance in nonverbal intelligence: data from the kinships of identical twins     

R J Rose  E L Harris  J C Christian  W E Nance 《Science (New York, N.Y.)》1979,205(4411):1153-1155

The multiple relationships within kinships of adult monozygotic twins permit incisive analyses to be made of genetic and environmental effects on behavioral traits. Data from families of 65 monozygotic twin pairs yield evidence of genetic variance on the Block Design Test, a nonverbal measure of general intelligence.  相似文献   

Carbon flux and growth in mature deciduous forest trees exposed to elevated CO2   总被引：1，自引：0，他引：1  

Körner C  Asshoff R  Bignucolo O  Hättenschwiler S  Keel SG  Peláez-Riedl S  Pepin S  Siegwolf RT  Zotz G 《Science (New York, N.Y.)》2005,309(5739):1360-1362

Whether rising atmospheric carbon dioxide (CO2) concentrations will cause forests to grow faster and store more carbon is an open question. Using free air CO2 release in combination with a canopy crane, we found an immediate and sustained enhancement of carbon flux through 35-meter-tall temperate forest trees when exposed to elevated CO2. However, there was no overall stimulation in stem growth and leaf litter production after 4 years. Photosynthetic capacity was not reduced, leaf chemistry changes were minor, and tree species differed in their responses. Although growing vigorously, these trees did not accrete more biomass carbon in stems in response to elevated CO2, thus challenging projections of growth responses derived from tests with smaller trees.  相似文献   

Recycling of graphite during Himalayan erosion: a geological stabilization of carbon in the crust     

Galy V  Beyssac O  France-Lanord C  Eglinton T 《Science (New York, N.Y.)》2008,322(5903):943-945

At geological time scales, the role of continental erosion in the organic carbon (OC) cycle is determined by the balance between recent OC burial and petrogenic OC oxidation. Evaluating its net effect on the concentration of carbon dioxide and dioxygen in the atmosphere requires the fate of petrogenic OC to be assessed. Here, we report a multiscale (nanometer to micrometer) structural characterization of petrogenic OC in the Himalayan system. We show that graphitic carbon is preserved and buried in marine sediments, while the less graphitized forms are oxidized during fluvial transport. Radiocarbon dating indicates that 30 to 50% of the carbon initially present in the Himalayan rocks is conserved during the erosion cycle. Graphitization during metamorphism thus stabilizes carbon in the crust over geological time scales.  相似文献   

Neutrophil extracellular traps kill bacteria   总被引：5，自引：0，他引：5  

Brinkmann V  Reichard U  Goosmann C  Fauler B  Uhlemann Y  Weiss DS  Weinrauch Y  Zychlinsky A 《Science (New York, N.Y.)》2004,303(5663):1532-1535

Neutrophils engulf and kill bacteria when their antimicrobial granules fuse with the phagosome. Here, we describe that, upon activation, neutrophils release granule proteins and chromatin that together form extracellular fibers that bind Gram-positive and -negative bacteria. These neutrophil extracellular traps (NETs) degrade virulence factors and kill bacteria. NETs are abundant in vivo in experimental dysentery and spontaneous human appendicitis, two examples of acute inflammation. NETs appear to be a form of innate response that binds microorganisms, prevents them from spreading, and ensures a high local concentration of antimicrobial agents to degrade virulence factors and kill bacteria.  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