Bends: detection of circulating gas emboli with external sensor     

M F Gillis  M T Karagianes  P L Peterson 《Science (New York, N.Y.)》1968,161(841):579-580

Circulating gas emboli associated with rapid decompression are detectable in superficial vessels of animals by the use of an ultrasonic Doppler flowmeter transducer which is applied externally.  相似文献   

Wolves, moose, and the allometry of population cycles     

Peterson RO  Page RE  Dodge KM 《Science (New York, N.Y.)》1984,224(4655):1350-1352

After a decade of dramatic population fluctuations, protected populations of wolves and moose in Isle Royale National Park in Lake Superior returned in 1983 to the levels observed in the 1950's. Inherent lags in this predator-prey system and the strong recovery of the moose population following a wolf population crash suggest that these populations may continue to cycle with a period length of about 38 (95 percent confidence interval, +/-13) years. Such a long-term cycle is consistent with the proposal that period length of herbivore population cycles will characteristically scale according to the fourth root of body mass, a basic allometric relation linking physiological cycles to population processes.  相似文献   

Cell size and rate of protein synthesis in ventral horn neurones     

R P Peterson 《Science (New York, N.Y.)》1966,153(742):1413-1414

Autoradiographic studies show that small ventral horn neurones synthesize protein at a greater rate per unit area of cytoplasm than do large ones. It is suggested that this is related to the faster rate of firing of the smaller neurones.  相似文献   

Book reviews     

Christopher Vecsey  Lawrence Busch  Robert E. Mazur  S. 'Tunji Titilola  Joel Schor  Don F. Hadwiger  E. Wesley F. Peterson  Lorraine Garkovich  Scott R. Collard  Tony Smith 《Agriculture and Human Values》1990,7(3-4):107-131

  相似文献   

Increasing river discharge to the Arctic Ocean   总被引：10，自引：0，他引：10  

Peterson BJ  Holmes RM  McClelland JW  Vörösmarty CJ  Lammers RB  Shiklomanov AI  Shiklomanov IA  Rahmstorf S 《Science (New York, N.Y.)》2002,298(5601):2171-2173

Synthesis of river-monitoring data reveals that the average annual discharge of fresh water from the six largest Eurasian rivers to the Arctic Ocean increased by 7% from 1936 to 1999. The average annual rate of increase was 2.0 +/- 0.7 cubic kilometers per year. Consequently, average annual discharge from the six rivers is now about 128 cubic kilometers per year greater than it was when routine measurements of discharge began. Discharge was correlated with changes in both the North Atlantic Oscillation and global mean surface air temperature. The observed large-scale change in freshwater flux has potentially important implications for ocean circulation and climate.  相似文献   

Another look at MgB2 and YBCO wires     

Hawsey RA  Peterson DE 《Science (New York, N.Y.)》2002,296(5568):655

  相似文献   

Comparative genomics of trypanosomatid parasitic protozoa     

El-Sayed NM  Myler PJ  Blandin G  Berriman M  Crabtree J  Aggarwal G  Caler E  Renauld H  Worthey EA  Hertz-Fowler C  Ghedin E  Peacock C  Bartholomeu DC  Haas BJ  Tran AN  Wortman JR  Alsmark UC  Angiuoli S  Anupama A  Badger J  Bringaud F  Cadag E  Carlton JM  Cerqueira GC  Creasy T  Delcher AL  Djikeng A  Embley TM  Hauser C  Ivens AC  Kummerfeld SK  Pereira-Leal JB  Nilsson D  Peterson J  Salzberg SL  Shallom J  Silva JC  Sundaram J  Westenberger S  White O  Melville SE  Donelson JE  Andersson B  Stuart KD  Hall N 《Science (New York, N.Y.)》2005,309(5733):404-409

A comparison of gene content and genome architecture of Trypanosoma brucei, Trypanosoma cruzi, and Leishmania major, three related pathogens with different life cycles and disease pathology, revealed a conserved core proteome of about 6200 genes in large syntenic polycistronic gene clusters. Many species-specific genes, especially large surface antigen families, occur at nonsyntenic chromosome-internal and subtelomeric regions. Retroelements, structural RNAs, and gene family expansion are often associated with syntenic discontinuities that-along with gene divergence, acquisition and loss, and rearrangement within the syntenic regions-have shaped the genomes of each parasite. Contrary to recent reports, our analyses reveal no evidence that these species are descended from an ancestor that contained a photosynthetic endosymbiont.  相似文献   

Spatial and Temporal Variability of Sorghum Grain Yield: Influence of Soil,Water, Pests,and Diseases Relationships     

Machado  S.  Bynum  E. D.  Archer  T. L.  Bordovsky  J.  Rosenow  D. T.  Peterson  C.  Bronson  K.  Nesmith  D. M.  Lascano  R. J.  Wilson  L. T.  Segarra  E. 《Precision Agriculture》2002,3(4):389-406

This study was conducted to determine relationships between biotic and abiotic factors and to generate information needed to improve the management of site-specific farming (SSF). The effects of water (80% evapotranspiration (ET) and 50% ET), hybrid (drought-tolerant and -susceptible), elevation, soil texture, soil NO₃--N, soil pH, and greenbugs (Schizaphis graminum) (Gb) on sorghum grain yield were investigated at Halfway, TX on geo-referenced locations on a 30-m grid in 1997, 1998, and 1999. Grain yields were influenced by interrelationships among many factors. Grain yields were consistently high under 80% ET treatment and in the upper slopes where the clay and silt fractions of the soil were high. Soil NO₃--N, rainfall, hybrid, and Gb effects on grain yields were seasonally unstable. Soil NO₃--N increased grain yield when water was abundant and depressed grain yields when water was limiting. Plant density effects on grain yield were confounded with hybrid responses to drought and Gb infestation. Managing seasonally unstable factors is a major challenge for farmers and better ways to monitor crop growth and diagnose causes of poor plant growth are needed. To improve the management of SSF, effects of the relationships between biotic and abiotic factors on crop yield must be integrated and evaluated as a system. Based on our study, information on seasonally stable factors like elevation and soil texture is useful in identifying management zones for water and fertilizer application. Water and fertilizers management should be complemented by in-season management of seasonally unstable factors like soil NO₃--N, rainfall, hybrid, and Gb effects on grain yield.  相似文献   

Kinetic isotope effects for the reactions of muonic helium and muonium with H2     

Fleming DG  Arseneau DJ  Sukhorukov O  Brewer JH  Mielke SL  Schatz GC  Garrett BC  Peterson KA  Truhlar DG 《Science (New York, N.Y.)》2011,331(6016):448-450

The neutral muonic helium atom may be regarded as the heaviest isotope of the hydrogen atom, with a mass of ~4.1 atomic mass units ((4.1)H), because the negative muon almost perfectly screens one proton charge. We report the reaction rate of (4.1)H with (1)H(2) to produce (4.1)H(1)H + (1)H at 295 to 500 kelvin. The experimental rate constants are compared with the predictions of accurate quantum-mechanical dynamics calculations carried out on an accurate Born-Huang potential energy surface and with previously measured rate constants of (0.11)H (where (0.11)H is shorthand for muonium). Kinetic isotope effects can be compared for the unprecedentedly large mass ratio of 36. The agreement with accurate quantum dynamics is quantitative at 500 kelvin, and variational transition-state theory is used to interpret the extremely low (large inverse) kinetic isotope effects in the 10(-4) to 10(-2) range.  相似文献   

Structure-disrupting ions: detection of qualitative change in an enzyme   总被引：1，自引：0，他引：1  

J C Warren  D M Peterson 《Science (New York, N.Y.)》1966,152(726):1245-1246

Preparations of erythrocyte glucose-6-phosphate dehydrogenase from normal individuals show similar degrees of inhibition by neutral salts. Preparations from Caucasian subjects with different hereditary deficiency syndromes differ from each other and from normal subjects, indicating a qualitative difference in these specific "deficient" enzymes. Sensitivity to neutral salts may be a means of detecting an amino acid substitution.  相似文献