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排序方式: 共有209条查询结果,搜索用时 15 毫秒
1.
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
2.
V Aksyuk FF Balakirev GS Boebinger PL Gammel RC Haddon DJ Bishop 《Science (New York, N.Y.)》1998,280(5364):720-722
A silicon micromechanical magnetometer was constructed and successfully used in 60-tesla pulsed magnetic fields of less than 100-millisecond duration. The device is small, inexpensive to fabricate, and easy to use. It features a fast mechanical response (up to 50,000 hertz) and extremely high sensitivity yet is relatively robust against electrical and mechanical noise. Quantum oscillations in the magnetization of a 1-microgram sample of an organic superconductor, kappa-[bis(ethylenedithio)tetrathiafulvalene]2Cu(NCS)2, have been observed with this device. 相似文献
3.
Modification of plant lipid synthesis 总被引:1,自引:0,他引:1
Genetic engineering of new storage oils and fats has produced oil crop plants with fatty acid compositions unattainable by plant breeding alone. The combination of classical breeding methods with molecular techniques provides new ways for designing oils for food and nonfood uses. Alterations in the position and number of double bonds, variation in fatty acid chain length, and the introduction of desired functional groups have already been achieved in model systems. Short-term prospects include crops such as rapeseed or soybean engineered to have greater than 70 to 80 percent medium-chain fatty acids by content, greater than 90 percent oleic acid, and high erucic acid content, and engineered to form ricinoleic acid in seed storage tissues. 相似文献
4.
5.
Uterus didelphys is a rare congenital abnormality of the reproductive tract. Although it occurs in various species, there are no published reports describing pregnancy outcome in association with this abnormality. Herein we describe a case of successful unilateral singleton pregnancy in a ewe incidentally found to have uterus didelphys during the course of a biomedical research study. The pregnancy was established using assisted reproductive techniques and interrupted in late gestation, at which point the abnormality was identified. Serial ultrasound assessment of foetal biometry revealed a normal foetal growth trajectory. Despite a 45% reduction in placentome number, total placentome weight was near normal secondary to compensatory placentome growth and development. To our knowledge, this is the first detailed report of normal foetal growth in an animal with uterus didelphys and illustrates the ability of the ovine placenta to adapt to a reduced number of placentomes and maintain foetal nutrient supply. 相似文献
6.
A diagnosis of dicoumarol toxicity in a herd of Friesian cattle was made following investigation of the deaths of three mature cows and eleven yearling heifers. Affected stock had been fed wrapped, bailed silage containing approximately 90% sweet vernal grass ( Anthoxanthum odoratum ). Sweet vernal grass contains coumarin, which can be converted to dicoumarol, a vitamin K antagonist, through the action of moulds. Most deaths were preceded by lethargy, severe anaemia and subcutaneous and internal haemorrhage. Dicoumarol toxicosis was suspected based on clinical signs, necropsy findings and prolonged prothrombin and activated partial thromboplastin times. Dicoumarol analysis of blood from affected animals and silage confirmed the diagnosis. 相似文献
7.
This study quantifies the effects of marked weight gain on glucose and insulin metabolism in 16 cats which increased their weight by an average of 44.2% over 10 months. Significantly, the development of feline obesity was accompanied by a 52% decrease in tissue sensitivity to insulin and diminished glucose effectiveness. In addition, glucose intolerance and abnormal insulin response occurred in some cats. An important finding was that normal weight cats with low insulin sensitivity and glucose effectiveness were at increased risk of developing impaired glucose tolerance with obesity. High basal insulin concentrations or low acute insulin response to glucose also independently increased the risk for developing impaired glucose tolerance. Male cats gained more weight relative to females and this, combined with their tendency to lower insulin sensitivity and higher insulin concentrations, may explain why male cats are at greater risk for diabetes. Results suggest an underlying predisposition for glucose intolerance in some cats, which is exacerbated by obesity. These cats may be more at risk of progressing to overt type 2 diabetes mellitus. 相似文献
8.
Ryo Kubota Mark A. Schell Gabriel D. Peckham Joanne Rue Anne M. Alvarez Caitilyn Allen Daniel M. Jenkins 《Journal of General Plant Pathology》2011,77(3):182-193
New rapid diagnostic methods are urgently needed to discriminate the quarantine pathogen Ralstonia solanacearum (Rs) race 3 biovar 2 (R3B2) from other populations of Rs that lack the adaptation to cause bacterial wilt disease in temperate
regions. We used an in silico bioinformatic approach to identify several genome sequences potentially specific to R3B2 strains. Primer sets were designed
to PCR-amplify sequences in these regions, and four sets were ultimately shown to be >99% accurate for detection of R3B2 strains.
On the basis of these results, several primers were designed to enable development of a loop-mediated isothermal amplification
assay that was rapid, technologically simple, and essentially 100% accurate for identification of R3B2 when applied to a comprehensive
collection of geographically diverse Rs strains. We fortuitously found that a sequence in one of the “R3B2-specific” regions
has ~90% identity to a sequence present in strains of the blood disease bacterium (BDB), a member of the Rs species complex
that infects banana. Alignments of these sequences allowed design of a second PCR primer set that proved 100% accurate for
identification of BDB strains when tested on the 22 BDB strains available to us. These results demonstrate the power of in silico genomic subtraction for rapid identification of population-specific DNA sequences and for the development of simple, reliable
detection methods for Rs subpopulations. 相似文献
9.
A. HüTtermann Marie-Therese Oelbe E. Fritz G. Schlechte A. Bytom A. D. Jungk Y. Okon E. Fallik Rivka Hadas S. Sarig E. Yahalom Sara Tal A. Hartmann B. Kishinevsky Debora Gurfel Rina Lobel Y. Kapulnik D. A. Phillips Y. Hadar Y. Chen E. Jurkevitch J. Katan A. Gamliel H. Ziegler I. Chet A. Ordentlich Hadar Kless A. Oppenheim Avia Zilberstein D. Holland J. Berman A. Zamir R. Kaufman N. Bawnik C. Koncz J. Schell 《Phytoparasitica》1987,15(2):141-147
10.
Acute cortisol responses of calves to scoop dehorning using local anaesthesia and/or cautery of the wound 总被引:1,自引:0,他引:1
SP SYLVESTER DJ MELLOR KJ STAFFORD RA BRUCE RN WARD 《Australian veterinary journal》1998,76(2):118-122
Objective To measure plasma cortisol responses in calves dehorned using a scoop after administration of local anaesthesia and/or cautery of the wounds.
Design A physiological study with controls.
Procedure There were six treatments: control handling with and without local anaesthesia, dehorning, dehorning after local anaesthesia, dehorning followed by wound cautery, and dehorning after local anaesthesia followed by wound cautery. Blood samples were taken before and after dehorning.
Results Dehorning caused an increase in plasma cortisol concentrations, which decreased a little to plateau values and then declined to pretreatment values 3 to 4 h after dehorning. The peak was smaller after local anaesthesia was administered but when its effects wore off, cortisol concentrations increased and thereafter were similar to those in the dehorned animals. The combination of local anaesthesia and cautery resulted in a plasma cortisol response similar to those in control calves with or without local anaesthesia.
Conclusions If plasma cortisol concentrations reflect the distress being experienced by the calves, then local anaesthesia reduces the acute distress for about 3 h after dehorning but not during the subsequent 3 to 4 h. Combining local anaesthetic and cautery prevented the significant increase in plasma cortisol following dehorning and may eliminate the acute distress caused by scoop dehorning. 相似文献
Design A physiological study with controls.
Procedure There were six treatments: control handling with and without local anaesthesia, dehorning, dehorning after local anaesthesia, dehorning followed by wound cautery, and dehorning after local anaesthesia followed by wound cautery. Blood samples were taken before and after dehorning.
Results Dehorning caused an increase in plasma cortisol concentrations, which decreased a little to plateau values and then declined to pretreatment values 3 to 4 h after dehorning. The peak was smaller after local anaesthesia was administered but when its effects wore off, cortisol concentrations increased and thereafter were similar to those in the dehorned animals. The combination of local anaesthesia and cautery resulted in a plasma cortisol response similar to those in control calves with or without local anaesthesia.
Conclusions If plasma cortisol concentrations reflect the distress being experienced by the calves, then local anaesthesia reduces the acute distress for about 3 h after dehorning but not during the subsequent 3 to 4 h. Combining local anaesthetic and cautery prevented the significant increase in plasma cortisol following dehorning and may eliminate the acute distress caused by scoop dehorning. 相似文献