共查询到20条相似文献，搜索用时 647 毫秒
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为探索鸽新城疫的流行特点,在分子水平上阐明鸽新城疫病毒分离株与鸡新城疫毒株之间的相互关系,我们用RT-PCR技术获得了分离株FO裂解位点附近300bp的基因片段,将其克隆到pUC19载体上得到一重组克隆pNDV21,序列分析表明,插入片段与鸡新城疫强毒Texas相应区域的同源性为87.7%;而与弱毒株D26/76及La Sota的同源性分别是91.7%和98%.其FO裂解点的氨基酸顺序为Giy Arg-Gln-Gly-Arg.证明该分离株属于新城疫弱毒. 相似文献
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应用于植被护坡的两种野生灌木抗旱适应性研究 总被引：2，自引：0，他引：2
[目的]研究野生灌木对干旱胁迫的适应性。[方法]以木豆和山毛豆两种野生灌木为试验材料,以正常浇水为对照,探讨了盆栽条件下干旱胁迫对2种野生灌木的影响。[结果]水分胁迫下,木豆和山毛豆的平均日失水率为0.626%和0.522%。山毛豆叶片相对电导率是对照的242.86%,木豆是对照的137.07%。木豆和山毛豆的丙二醛含量相对于对照分别增加了65.10%和69.10%。木豆的可溶性糖含量增幅最大,增加了3.85倍,而山毛豆增加了1.98倍。山毛豆的叶片游离脯氨酸在35 d时出现峰值,为对照的57.85倍。而木豆在28 d达到峰值,为对照的14.34倍。[结论]木豆的抗旱性强于山毛豆。 相似文献
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鸽新城疫流行的调查研究 总被引：5，自引：0，他引：5
通过对广东省十余个鸽场的新城疫流行的调查，我们发现鸽新城疫流行期，病鸽死亡率可达５０％，其中幼鸽易感性较成鸽高。病鸽症状以下痢和神经症状为主，消化道出血少见；通过病原分离，引起鸽新城疫的病原为Ⅰ型副粘病毒的不同株；注射鸡新城Ⅱ且系、Ⅲ系弱毒疫苗或鸽新城疫油乳剂灭活苗可及时控制疫情的流行。 相似文献
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Eye movements exist to improve vision, in part by preventing excessive retinal image slip. A major threat to the stability of the retinal image comes from the observer's own movement, and there are visual and vestibular reflexes that operate to meet this challenge by generating compensatory eye movements. The ocular responses to translational disturbances of the observer and of the scene were recorded from monkeys. The associated vestibular and visual responses were both linearly dependent on the inverse of the viewing distance. Such dependence on proximity is appropriate for the vestibular reflex, which must transform signals from Cartesian to polar coordinates, but not for the visual reflex, which operates entirely in polar coordinates. However, such shared proximity effects in the visual reflex could compensate for known intrinsic limitations that would otherwise compromise performance at near viewing. 相似文献
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Keeton WT 《Science (New York, N.Y.)》1969,165(3896):922-928
Although most recent hypotheses of pigeon homing have assigned an essential role to the sun, there has been some evidence suggesting that the sun is not essential. Two series of releases were designed to examine the question more carefully. Birds whose internal clocks had been shifted 6 hours were used in the critical tests. Under sun, the vanishing bearings of the clock-shifted birds were deflected in the direction predicted by a hypothesis of use of the sun as a simple compass. By contrast, under total overcast the bearings of both the clock-shifted and the control birds were homeward oriented and there was no difference between them, even at a release site the birds could never have seen previously. Therefore it is concluded that the sun is used as a compass when it is available, but that the pigeon navigation system contains sufficient redundancy to make accurate orientation possible in the absence of both the sun and familiar landmarks; the orientational cues used under such conditions do not require time compensation. This conclusion is in complete disagreement with the Matthews sun-arc hypothesis of pigeon navigation, and it makes necessary a major reformulation (at the very least) of the other principal hypothesis, that of Kramer. 相似文献
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方光远 《金陵科技学院学报》1997,(4)
我市某新建鸽场紧靠某蛋鸡场,鸽场于1997年7月25日购进一批60日龄美国王肉种鸽700只,8月1日全群暴发新城疫,8月5日接报诊治后,8月10日鸽群停止发病,疫情得到控制。全过程死亡率达27．3％。 相似文献
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在不同繁殖时期,肉鸽嗉囊的组织学变化主要在粘膜层。随着在孵化期中产生的垂体催乳激素的增多,粘膜上皮基底层细胞增生,厚度渐增,粘膜上皮棘层的浅层细胞及扁平细胞增大,脂类物质合成并积聚,细胞逐渐变性。最后,这些聚满脂类物质的细胞脱落形成鸽乳。同时,固有膜中血管和结缔组织也逐渐增加。随着哺喂期的增加,粘膜上皮增生逐渐减弱,上皮厚度减小,细胞中脂类的合成与积聚减少,上皮的脱落细胞也日益减少。最后,粘膜层逐渐恢复至休产肉鸽的水平。 相似文献
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从南京某个信鸽养殖户处的1只病死鸽中，分离到两株真菌，光镜观察该菌具有假菌丝，产生芽生孢子，革兰氏染色阳性。能发酵葡萄糖、麦芽糖、甘露醇，产酸产气，不分解乳糖、棉子糖、菊糖、甘露醇等。不液化明胶。动物试验，免于腹部皮下局部脓肿。该菌对替硝唑和制霉菌素具有敏感性。病原鉴定结果和生化特性指标均符合白色念珠菌。 相似文献
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Through the use of learned symbols, a pigeon accurately communicated information about hidden colors to another pigeon. Each verbal exchange was initiated with a spontaneous request for information. The two pigeons engaged in a sustained and natural conversation without human intervention. 相似文献
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L R Young C M Oman D G Watt K E Money B K Lichtenberg 《Science (New York, N.Y.)》1984,225(4658):205-208
Unusual vestibular responses to head movements in weightlessness may produce spatial orientation illusions and symptoms of space motion sickness. An integrated set of experiments was performed during Spacelab 1, as well as before and after the flight, to evaluate responses mediated by the otolith organs and semicircular canals. A variety of measurements were used, including eye movements, postural control, perception of orientation, and susceptibility to space sickness. 相似文献
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R von Baumgarten A Benson A Berthoz T Brandt U Brand W Bruzek J Dichgans J Kass T Probst H Scherer 《Science (New York, N.Y.)》1984,225(4658):208-212
During the flight of Spacelab 1 the crew performed a number of experiments to explore changes in vestibular function and visual-vestibular interactions on exposure to microgravity. Measurements were made on the threshold for detection of linear oscillation, vestibulo-ocular reflexes elicited by angular and linear movements, oculomotor and posture responses to optokinetic stimulations, and responses to caloric stimulation. Tests were also conducted on the ground, during the 4 months before and on days 1 to 6 after flight. The most significant result was that caloric mystagmus of the same direction as on the earth could also be evoked in the weightless environment. 相似文献
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J Sturtevant 《Science (New York, N.Y.)》1970,170(955):322-324
Reproductivity of pigeons is inhibited with mestranol incorporated in a synthetic grit; continual erosion releases daily doses. Young squabs may be permanently sterilized when fed crop milk by treated birds. A theoretical model of pigeon population dynamics using laboratory-obtained data shows the advantages of chemosterilization over killing as a means of pigeon control. 相似文献
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Anti-clogging performance evaluation and parameterized design of emitters with labyrinth channels 总被引：4，自引：0，他引：4
Jun Zhang Wanhua Zhao Yiping Tang Bingheng Lu 《Computers and Electronics in Agriculture》2010,74(1):59-65
The anti-clogging performance of emitters with labyrinth channels is a key factor affecting their long-term service. Considering the limitation of evaluation on emitter's anti-clogging performance at present, a new method using passage rate of particles as the evaluation index was proposed based on stochastic trajectory model in a Lagrangian reference frame. Using orthogonal design, the passage rates of particles of 16 trapezoidal labyrinth channels with various geometries were calculated, where 4 dimensionless parameters were taken as the factors. The results obtained from analysis of range and variance showed that the influence degree on passage rate of particles ranks as follows: α > D/W > S/H > H/D. A mathematic model was established between the particle passage rate and 4 key parameters according to the multivariable regression method, which can be used to predict and compare the anti-clogging performance of trapezoidal labyrinth channels with different geometries. 相似文献