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TH Jones LJ Thompson JH Lawton TM Bezemer RD Bardgett TM Blackburn KD Bruce PF Cannon GS Hall SE Hartley G Howson CG Jones C Kampichler E Kandeler DA Ritchie 《Science (New York, N.Y.)》1998,280(5362):441-443
In model terrestrial ecosystems maintained for three plant generations at elevated concentrations of atmospheric carbon dioxide, increases in photosynthetically fixed carbon were allocated below ground, raising concentrations of dissolved organic carbon in soil. These effects were then transmitted up the decomposer food chain. Soil microbial biomass was unaffected, but the composition of soil fungal species changed, with increases in rates of cellulose decomposition. There were also changes in the abundance and species composition of Collembola, fungal-feeding arthropods. These results have implications for long-term feedback processes in soil ecosystems that are subject to rising global atmospheric carbon dioxide concentrations. 相似文献
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M Liley D Gourdon D Stamou U Meseth TM Fischer C Lautz H Stahlberg H Vogel NA Burnham C Duschl 《Science (New York, N.Y.)》1998,280(5361):273-275
Lateral force microscopy in the wearless regime was used to study the friction behavior of a lipid monolayer on mica. In the monolayer, condensed domains with long-range orientational order of the lipid molecules were present. The domains revealed unexpectedly strong friction anisotropies and non-negligible friction asymmetries. The angular dependency of these effects correlated well with the tilt direction of the alkyl chains of the monolayer, as determined by electron diffraction and Brewster angle microscopy. The molecular tilt causing these frictional effects was less than 15 degrees, demonstrating that even small molecular tilts can make a major contribution to friction. 相似文献
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The tidal rhythmites in the Proterozoic Big Cottonwood Formation (Utah, United States), the Neoproterozoic Elatina Formation of the Flinders Range (southern Australia), and the Lower Pennsylvanian Pottsville Formation (Alabama, United States) and Mansfield Formation (Indiana, United States) indicate that the rate of retreat of the lunar orbit is dxi/dt approximately k2 sin(2delta) (where xi is the Earth-moon radius vector, k2 is the tidal Love number, and delta is the tidal lag angle) and that this rate has been approximately constant since the late Precambrian. When the contribution to tidal friction from the sun is taken into account, these data imply that the length of the terrestrial day 900 million years ago was approximately18 hours. 相似文献
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A 19-year-old Thoroughbred gelding presented with sudden onset, non-weight bearing lameness in the right hindlimb. Radiography confirmed distal luxation of the patella, which was replaced into its normal anatomical location under general anaesthesia. There were no pathological sequelae noted on follow-up examination 9 months after the initial injury. To our knowledge, this is a rare manifestation of patellar luxation, only reported once previously in the equine literature. 相似文献
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R.A. SAMS D.F. GERKEN T.M. DYKE S.M. REED & S.M. ASHCRAFT 《Journal of veterinary pharmacology and therapeutics》1997,20(5):355-361
Cimetidine was administered intravenously and by the intragastric route to six mares at a dose of 4.0 mg/kg of body weight (bw). Specific and sensitive high performance liquid chromatographic methods for the determination of cimetidine in horse plasma and urine and cimetidine sulfoxide in urine are described. Plasma cimetidine concentration vs. time data were analysed by non-linear least squares regression analysis to determine pharmacokinetic parameter estimates. The median (range) plasma clearance (Cl) was 8.20 (4.96–10.2) mL/min.kg of body weight, that of the steady-state volume of distribution (Vdss ) was 0.771 (0.521–1.15) L/kg bw, and that of the terminal elimination half-life ( t ½β ) was 92.4 (70.6–125) minutes. The median (range) renal clearance of cimetidine was 4.08 (2.19–6.23) mL/min.kg bw or 55.4 (36.3–81.8)% of the corresponding plasma clearance. Cimetidine sulfoxide was excreted in urine and its urinary excretion through 8 h accounted for 12.0 (9.8–16.6)% of the plasma clearance of cimetidine. The median (range) extent of intragastric bioavailability was 14.4 (6.82–21.8)% and the maximum plasma concentration after intragastric administration was 0.31 (0.24–0.50) μg/mL.
Intravenous cimetidine had no effect on the disposition of intravenous phenylbutazone or its metabolites except that the maximum plasma concentration of γ-hydroxyphenylbutazone was less after cimetidine treatment. 相似文献
Intravenous cimetidine had no effect on the disposition of intravenous phenylbutazone or its metabolites except that the maximum plasma concentration of γ-hydroxyphenylbutazone was less after cimetidine treatment. 相似文献
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D. JORDAN JW PLANT† HI NICOL‡ TM JESSEP CJ SCRIVENER 《Australian veterinary journal》1996,73(6):211-215
Factors associated with the proportion of sheep cured of virulent footrot after antibiotic treatment were studied in a field trial under dry environmental conditions. From 2 similar flocks, 1091 Merino sheep weighing about 50 kg and infected with virulent footrot received an intramuscular injection of either 12 mL of a mixture of penicillin (250 mg/mL) and streptomycin (250 mg/mL), 6 mL of long acting oxytetracycline (200 mg/mL) or 6 mL of a mixture of lincomycin (50 mg/mL) and spectinomycin (100 mg/mL). Variables that were significantly associated with the proportion of sheep cured were: the type of antibiotic used, the number of feet infected and the flock from which the sheep came. There was an interaction between antibiotic type and number of feet infected and between antibiotic type and flock in association with the proportion of sheep cured. The extent of paring and the occurrence of blowfly strike in footrot lesions treated with diazinon had no significant association with the proportion of sheep cured. 相似文献
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New detrital-zircon geochronologic data reveal that a through-going paleoriver connected Texas with Nevada in Late Triassic time. Sandstone from the Upper Triassic Santa Rosa Sandstone (Dockum Group) from northwestern Texas contains a detrital zircon suite nearly identical to that found in western Nevada in the Upper Triassic Osobb Formation (Auld Lang Syne Group, correlative with the Chinle Formation). The Santa Rosa Sandstone was derived in large part from the eroded Cambrian core of the Amarillo-Wichita uplift, as evidenced by abundant zircons with ages of 515 to 525 million years. Other zircon grains in the sandstone are Permian, Devonian, Proterozoic, and Archean in age and, with the exception of the Archean grain, are also matched by the population in the Nevada strata. 相似文献