改善管理方法控制猪的传染性疾病

20世纪90年代在英国出现新的猪病如PMWS／PDNS,迫使人们开始重新评估现有的生产系统,疫苗已经不能解决所有问题,养猪场必须采用改进管理方法来控制疾病。如PRRS,离开了综合饲养管理,疫苗仍然不起作用。本文涵盖各种控制疾病的基本饲养管理方法,每个场则须针对各自情况采用合适的方法。     

梯形明渠临界水深直接计算公式研究

【目的】寻求梯形明渠临界水深的直接计算公式。【方法】针对梯形明渠临界水深传统计算方法计算过程复杂、误差大、适用范围小的缺点,以迭代法为基础,引入无量纲参数单位水面宽度,利用数值计算方法对梯形明渠临界水深的基本计算公式进行恒等变形,得到快速收敛的迭代公式,并对合适的迭代初值进行选取。【结果】提出了新的梯形明渠临界水深的直接计算公式,对其进行的误差分析结果表明,该公式计算临界水深的最大相对误差仅为0.010%。【结论】与现有公式相比,新建立的梯形明渠临界水深直接计算公式计算精度高、适用范围广,可供工程实际参考应用。     

我国北方灌区地下水资源演变与农田生态环境问题

通过对北方灌区地下水形成机理及其演变态势的分析,认为气候变化和人类活动的负面效应是导致灌区与地下水有关的生态环境问题的主要原因,尤其是地下水资源量的衰减已经影响到了灌溉农业的可持续发展。针对以上问题,从水循环的角度提出充分利用灌区地下含水层的调蓄作用,通过地表水与地下水的联合利用控制水盐平衡、涵养地下水源是实现地下水资源永续利用、农田生态环境良性循环的有效途径。     

鸭绿沙塘鳢仔鱼、稚鱼和幼鱼的形态观察

参照国内外对硬骨鱼类胚后发育期的分期标准,描述了鸭绿沙塘鳢仔鱼、稚鱼和幼鱼的形态特征,记录了各个发育时期的全长和体重等增长情况,讨论了鸭绿沙塘鳢仔鱼、稚鱼和幼鱼发育的生态适应性。     

四川峨边县蒋沟矿渣侵蚀泥石流成因与特征

四川峨边县蒋沟是一条典型的矿渣型泥石流沟,在侵蚀作用下时常发生泥石流并造成严重危害。该文采用调查、测绘和综合研究相结合的方法,论述了蒋沟矿渣侵蚀泥石流的成因和特征。形成条件方面,矿渣侵蚀类泥石流具有物源集中和机械组成固定性特征;发生过程呈现出降雨-侵蚀-崩滑-搬运复合型和循环性,侵蚀成为泥石流形成和发生的关键环节;泥石流特征则主要表现为堆积物成分单一,堆积比降小,暴发频率高和地貌塑造作用强等方面。最后,针对成因和特征,提出了以水土分离、固床和护坡等工程措施为主,以矿山植被恢复措施为辅的防治建议。     

东北马鹿Myostatin基因单核苷酸多态性研究

Myostatin基因即肌肉生长抑制素,是一种肌肉生长的负调控因子。以物种最近的牛（Bos taurus cattle登陆号：AB076403）的Myostatin基因序列为模版,根据该基因保守序列,进行引物设计。应用pcr-sscp和测序的方法对东北马鹿Myostatin基因的第3外显子进行了多态性分析。结果表明,位于Myostatin基因DNA序列第3外显子948处发生G→A突变。该突变并没有引起氨基酸的变异,GTA、GTG密码子都编码缬氨酸（val）。     

典型冰碛补给型泥石流物源补给过程与机制研究——以泸定县干沟为例

干沟位于四川省泸定县境内,是一条典型的冰碛补给型泥石流沟,其物源补给具有复合过程的特点.在野外调查的基础上,以2005年干沟泥石流为例,对该次泥石流过程的物源补给特征及过程进行了调查和分析.结果表明,干沟泥石流的物源补给过程可分为“启动型物源”和“维持型物源”2种类型,对这2种类型的物源补给方式和过程进行了阐述,可为认识冰碛补给型泥石流的形成机理、物源补给过程及防灾减灾提供科学依据.     

丹江口库区玉米和水稻氮合理用量研究

采用田间小区试验研究了丹江口库区玉米和水稻的氮合理用量。结果表明,在施用90kg/hm2P2O5和135.0kg/hm2K2O基础上,玉米最高产量施氮量和最佳经济施氮量分别为276.4kg/hm2和236.2kg/hm2;在施用90.0kg/hm2P2O5、75.0kg/hm2K2O和3.0kg/hm2大粒锌基础上,水稻最高产量施氮量和最佳经济施氮量分别为213.8kg/hm2和189.6kg/hm2;当玉米施氮量为225.0kg/hm2时,比不施氮增产35.8%,氮肥产投比、农学效率和表观利用率分别为4.90、11.4kg/kg和29.9%,玉米氮吸收总量为174.9kg/hm2,养分吸收量之比为N∶P2O5∶K2O=1.00∶0.51∶1.01;当水稻施氮量为180.0kg/hm2时,比不施氮增产28.5%,氮肥产投比、农学效率和表观利用率分别为5.67、12.1kg/kg和39.1%,水稻氮吸收总量为156.1kg/hm2,养分吸收量之比为N∶P2O5∶K2O=1.00∶0.34∶1.20。     

SPLENIC SEQUESTRATION SCINTIGRAPHY IN THE DOG: A COMPARISON OF DENATURING TECHNIQUES

Five mixed-breed dogs underwent splenic sequestration scintigraphy following intravenous injection of 647.5 to 740 MBq (17.5–20 mCi) of ^99mTechnetium labeled autologous red blood cells (RBCs) that had been chemically denatured using two μg of stannous chloride. Left lateral dynamic images were obtained for 20 minutes after injection. Regions of interest (ROI) were drawn around the splenic body and ventral extremity, ventral liver and caudal abdominal great vessels and time activity curves created. Count density information was obtained and uptake ratios were calculated for the spleen ROI/vessel ROI, liver ROI/vessel ROI and spleen ROI/liver ROI at 1, 2.5, 5, 10, 15 and 20 minutes after injection. Two additional studies using different RBC denaturing procedures were done in four of the five dogs. In the second study, the stannous chloride level was doubled to 4.0 μg, while in the third study, the RBCs were denatured by addition of 2.0 μg of stannous chloride and heating at 49°C for 15 minutes. Progressive splenic uptake of denatured RBCs was seen in all dogs during the first 15 to 20 minutes of each study, no matter which denaturing technique was utilized. Significant increases in the spleen ROI:/vessel ROI and spleen ROI:liver ROI ratios were obtained at 5, 10, 15 and 20 minutes when compared to the 1 minute values for each of the labeling techniques. A significant difference was not identified between the three ratios at 15 minutes between the three labeling techniques. There was a trend of increasing values for each ratio where 2.0 μg of stannous chloride technique being the lowest, 4.0 μg of stannous chloride having an intermediate value and the heated technique had the highest values. The heating technique resulted in higher liver activity and increased variability of the mean liver ROI/vessel ROI ratios at all times (1, 2.5, 5,10, and 15 minutes). Using a non-linear least squares regression analysis, a double exponential equation fit the spleen ROI/vessel ROI and spleen ROI/liver ROI ratios for all three labeling techniques. Imaging of the spleen using all three techniques was acceptable, and a persistent blood pool image would allow for vascular imaging and cardiac gated studies 30 minutes after injection of the denatured, labeled autologous red blood cells. Veterinary Radiology & Ultrasound, Vol. 36, No. I, 1995, pp 57–63.     

不同放牧强度下羊草草地三种禾草叶片再生动态研究

运用组织转化的理论与分析方法，对天然羊草草地3种禾草在不同放牧强度下的叶片再生动态进行了比较系统的研究。结果表明，3种禾草在不同再生期间的叶片伸长率、萎蔫率、发生率及枯死率都存在着显著差异（P＜0.05），放牧强度对这些参数的影响一般不显著（P＞0.05）。放牧不利于羊草叶片发生，中等强度放牧促进芦苇和碱茅叶片伸长与发生。