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排序方式: 共有68条查询结果,搜索用时 16 毫秒
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The occurrence of equine arteritis virus in Australia 总被引:2,自引:0,他引:2
This paper reports the first isolation of equine arteritis virus (EAV) in Australia and serological evidence of exposure to EAV in Australian horses. Twelve Standardbred stallions imported from North America were found to shed EAV in semen. One hundred and seven stallions were tested for serum antibodies to EAV and 73% of Standardbred stallions tested were seropositive as compared to 8% of Thoroughbred stallions. Serum antibody was detected in 71% of Standardbred mares, 6% of Standardbred racehorses and 1% of Thoroughbred mares and racehorses. Examination of stored serums demonstrated that EAV had been present in Australia since at least 1975. 相似文献
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Categorical time series regression was applied to 55 fish stocks in the Potomac, Hudson, Narragansett, Delaware, and Connecticut estuaries for the period 1929–1975. Interannual variability in catch per unit effort (CPUE) was related to CPUE, hydrographic variables, and pollution variables, lagged back in time to represent the conditions contributing to the multiple ages comprising each fishery. Hydrographic variables included water temperature and flow in the estuary– and, for offshore spawning stocks, wind direction and magnitude–during the months of spawning and early life stage development. Pollution variables included measures of dissolved oxygen conditions in the estuaries, volume of material dredged, and sewage loading (or human population). Lagged CPUE, hydrographic variables, and pollution variables all played important roles in explaining historical variability in CPUE. Lagged CPUE was significant in 45 of 55 stocks generally accounting for 5–35% of the variability. Lagged hydrographic variables were significant in 53 of 55 stocks, explaining an additional 5–40% of the variability unaccounted for by lagged CPUE. Lagged pollution variables were significant in 35 of 55 stocks, generally accounting for an additional 5–30% of the variability not explained by lagged CPUE and hydrographic variables. Results did not exhibit expected patterns of consistency in the importance of lagged CPUE for a species across estuaries or consistency in the importance of pollution variables across estuaries. Results did exhibit the expected north-to-south longitudinal pattern in the importance of timing of the hydrographic variables, the months of importance being one or two months later in more northerly estuaries. Higher-order interaction effects were important in almost all stocks that were well-modeled by categorical time series regression. Of the 30 stocks with final regression models having R2 > 0.55, 26 stocks involved significant interaction effects, five had only significant interaction effects (no significant main effects), and 20 stocks had significant interactions involving variables not significant as main effects. The difficulties involved in analyzing long-term trends in fish populations and partitioning variability between natural and anthropogenic sources are discussed. 相似文献
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PM Lundquist R Wortmann C Geletneky RJ Twieg M Jurich VY Lee CR Moylan DM Burland 《Science (New York, N.Y.)》1996,274(5290):1182-1185
The performance of amorphous organic photorefractive (PR) materials in applications such as optical data storage is generally limited by the concentration of active molecules (chromophores) that can be incorporated into the host without forming a crystalline material with poor optical quality. In polymeric PR systems described previously, performance has been limited by the necessity of devoting a large fraction of the material to inert polymer and plasticizing components in order to ensure compositional stability. A new class of organic PR materials composed of multifunctional glass-forming organic chromophores is described that have long-term stability and greatly improved PR properties. 相似文献
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PC Sereno DB Dutheil M Iarochene HCE Larsson GH Lyon PM Magwene CA Sidor DJ Varricchio JA Wilson 《Science (New York, N.Y.)》1996,272(5264):986-991
Late Cretaceous (Cenomanian) fossils discovered in the Kem Kem region of Morocco include large predatory dinosaurs that inhabited Africa as it drifted into geographic isolation. One, represented by a skull approximately 1.6 meters in length, is an advanced allosauroid referable to the African genus Carcharodontosaurus. Another, represented by a partial skeleton with slender proportions, is a new basal coelurosaur closely resembling the Egyptian genus Bahariasaurus. Comparisons with Cretaceous theropods from other continents reveal a previously unrecognized global radiation of carcharodontosaurid predators. Substantial geographic differentiation of dinosaurian faunas in response to continental drift appears to have arisen abruptly at the beginning of the Late Cretaceous. 相似文献
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PHILIP JULL GEMMA L. WALMSLEY LIVIA BENIGNI NANNY WENZLOW EMMA L. RAYNER BRIAN A. SUMMERS GIUNIO B. CHERUBINI SANDRA SCHÖNIGER HOLGER A. VOLK 《Veterinary radiology & ultrasound》2011,52(6):653-657
Intramedullary masses are a dilemma due to the limited access for a nonsurgical biopsy, thus, accurate imaging characterization is crucial. Magnetic resonance imaging findings of two confirmed canine thoracic intramedullary hemangiomas are described. A capillary hemangioma was of mixed intensity but predominantly T2‐hyperintense and mildly T1‐hyperintense to spinal cord with strong contrast enhancement. A cavernous hemangioma had a target‐like appearance in both T1‐weighted (T1w) and T2‐weighted (T2w) images. In T2w images there was a small isointense center surrounded by a relatively large hyperintense area. In T1w images, there was a large isointense centre with a relatively small hyperintense periphery. Such characteristics should prioritize hemangioma as a consideration in a progressive myelopathy due to an intramedullary mass. 相似文献
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Long-term changes in the sea-age at maturity and seasonal time of return of salmon, Salmo salar L., to Scottish rivers 总被引:1,自引:0,他引:1
D.W. SUMMERS 《Fisheries Management and Ecology》1995,2(2):147-156
Abstract Using catch data, changes in salmon, Salmo salar L., sea-age and seasonal return time were compared between several Scottish east coast rivers over the last 150–200 years. Parallel long-term trends were found, suggesting common influences affecting salmon at sea. Long-term associations with marine environmental factors were investigated by literature review and comparisons with an index of Icelandic sea-ice abundance. Apparent associations were shown to exist since about 1900, although the cause was not demonstrated. However, over a longer timescale, the same associations were not apparent. Unique gradual marine changes since 1900 may have resulted in perceptible associations with salmon data which may otherwise be imperceptible when short-term marine environmental variability is greater than long-term variability. Marine factors must affect salmon, but the complexity of the marine environment and controls on age at maturity and time of return mean that a retrospective analysis cannot be expected to identify the causal factors. 相似文献
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CONGENITAL POLYCYSTIC KIDNEY AND LIVER SYNDROME IN PIGLETS 总被引:1,自引:0,他引:1