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91.
本文用通径分析方法对茶树不同种植密度与茶树骨架形成、分枝结构、蓬面结构三大要素进行对应分析,结果表明:1)随密度上升主干粗度、一、二级分枝粗度下降;2)分枝角度随密度上升而变小;3)随密度上升,小桩数随之增加,其它因子与之呈负相关。由于密度上升后,群体结构的光合面积增大,碳水化合物积累增多,而产量上升。选用合理密度与排列组合时,可用回归方程计算。 相似文献
92.
Transmission of porcine reproductive and respiratory syndrome virus from persistently infected sows to contact controls. 总被引:3,自引:0,他引:3
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M D Bierk S A Dee K D Rossow S Otake J E Collins T W Molitor 《Canadian journal of veterinary research》2001,65(4):261-266
The objective of this study was to determine if porcine reproductive and respiratory syndrome virus (PRRSV) could persist in non-pregnant sows and if persistently infected sows could transmit virus to naive contact controls. Twelve PRRSV-naive, non-pregnant sows (index sows) were infected with a field isolate of PRRSV and housed in individual isolation rooms for 42 to 56 days postinfection. Following this period, 1 naive contact sow was placed in each room divided by a gate allowing nose-to-nose contact with a single index sow. Index sows were not viremic at the time of contact sow entry. Virus nucleic acid was detected by polymerase chain reaction, and infectious virus was detected by virus isolation in sera from 3 of the 12 contact sows at 49, 56, and 86 days postinfection. All 3 infected contacts developed PRRSV antibodies. Virus nucleic acid was detected in tissues of all of the 12 index sows at 72 or 86 days postinfection. Nucleic acid sequencing indicated that representative samples from index and infected contacts were homologous (> 99%) to the PRRSV used to infect index sows at the onset of the study. This study demonstrates that PRRSV can persist in sows and that persistently infected sows can transmit virus to naive contact animals. 相似文献
93.
Wei-Na Wang An-Li Wang Yue Wang Junxia Wang Ru-Yong Sun 《Journal of the World Aquaculture Society》2005,36(1):1-7
This study examined the effects of dietary vitamin C and ammonia concentration on the cellular defense response of Macrobrachium nipponese . The response of the cellular defense was determined by monitoring changes in reactive oxygen intermediates in hemocytes, superoxide dismutase activity, catalase activity, glutathione peroxidase activity, glutathione reductase and glutathione transferase activity in muscle. The results showed that prawns fed the basal diet had a significant increase in reactive oxygen intermediates in response to exposure to ammonia-N. When dietary vitamin C was added to the feed, there was a significant decrease in reactive oxygen intermediates in response to exposure to ammonia-N. Total superoxide dismutase and glutathione peroxidase activity of prawns fed the basal diet decreased as ammonia-N increased. This decrease in activity was significantly less pronounced in prawns that were fed the dietary vitamin C supplement. In prawns that were fed the dietary vitamin C supplement there was no significant variation in catalase reductase or gluxathione reductase activity in response to variations in ammonia-N concentration. The glutathione transference activity increased at a low concentration of ammonia-N in prawns that were fed the dietary vitamin C supplement, but there was no significant variation in the prawns fed the basal diet. Overall the results indicate that dietary vitamin C supplements enhance the capacity of M. nipponese to respond to elevations in ammonia-N. This response involved several biochemical reactions known to be involved in cellular defense. 相似文献
94.
T D Butt A M Cruz J V Bailey W H Crawford 《The Canadian veterinary journal. La revue veterinaire canadienne》2001,42(12):936-939
The object of this investigation was to determine the outcome of limb amputation in wapiti. Medical records of 13 wapiti that underwent limb amputation were reviewed to determine age, weight, sex, injury preceding amputation, limb amputated, amputation location, length of hospital stay, complications, and outcome. Ages ranged from 3 months to 8 years and weights from 70 kg to 280 kg. All animals were female. Eleven animals sustained catastrophic long bone fractures prior to amputation. Five animals had front limb amputations and 8 had hind limb amputations. Of these animals, 1 with a front limb amputaiton and 5 with hind limb amputations survived. Postsurgical inability to stand is associated with hospitalization of > 1 day. Of the 13 wapiti reviewed, 5 with hind limb amputations have produced and reared offspring. Hind limb amputation can be considered a viable alternative to euthanasia when catastrophic orthopedic injuries occur in female wapiti. 相似文献
95.
当压缩机内气体的流量较低时,气体容易出现旋转脱离现象,导致压缩机不能正常工作,采取增加压缩机内部液体的流量,在出口处设置单向阀防止气体倒流等措施,可有效地防止喘振的发生,保证输气管道的正常运行. 相似文献
96.
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98.
压力实时监测法在管道泄漏检测中的应用 总被引:2,自引:0,他引:2
检测输油管道漏油的方法很多,介绍了通过压力实时监测确定输油管道漏油点方法,以及实际应用情况。实践证明,通过压力实时监视确定输油管道漏油点的方法在实际输油运行中是切实可行的。 相似文献
99.
王高银刹、仓颉双井、圣城古槐等寿光古代及现代的知名景观,全部“搬进”了第六届菜博会的土展厅,不过组成景点的不是土木砖瓦,而是清一色的蔬菜瓜果。这些普通蔬菜瓜果的独到组合,不仅组成了令人留连的“蔬菜大观园”,而且展现出“菜乡”寿光传统的民俗文化和蔬菜产业深厚的文化底蕴。寿光蔬菜种植历史悠久,北魏农学家贾思勰就诞生在这里,明清年间,“独根红”韭菜被确定为宫廷贡品。为叫响蔬菜的“文化品牌”, 相似文献
100.