苎麻牵切原理及牵切区断裂点分布的研究

本文主要分析了苎麻单纤维在牵切区内运动及断裂的过程，通过试验考查了断裂点的分布情况。     

辐射作用下含修复DNA主链断裂随机动力学理论的研究

在辐射诱发DNA单链与双链断裂问题的研究中,迄今为止的主要理论——靶学说与击中理论,存在缺少修复机制等缺点,而Chadwick的理论仍属半经验性的.本文在Hug与Kellerer基本思想的基础上,发展了一个辐射诱发含修复DNA单、双链断裂的随机动力学理论,建立了随机动力学微分方程组数学模型.     

防火路营建火力楠防火林带的效能研究

对生土防火路营建火力楠防火林带的林木生长效果、防火性能、培肥地力与水源涵养功能以及以经济效益的研究表明,火力楠适应性强,在原防火路较差的土壤条件下,能迅速郁闭并很快成林且防火性能强,是优良的防火树种,12a生混交林带中火力楠的平均树高达9.58m,胸径达9.07cm,生物量达39.62t.hm-2,显示出较强的防火效能。同时,防火林带与生土防火路相比,不但具有较强的培肥地力、涵养水源等功能且经济效益显著,是该区较为理想的防火林带,可进一步推广营造。     

Determination of tear break-up time reference values and ocular tolerance of tetracaine hydrochloride eyedops in healthy horses

Reasons for performing study: Tetracaine hydrochloride (THCl) has been reported to cause irritation in dogs. In man, some topical anaesthetics have been shown to disrupt the tear film. Tear break‐up time (TBUT) is a useful test allowing an assessment of the quality of the precorneal tear film. Only one TBUT value has been reported in horses with no information on the technique used. Objectives: To provide a method for performing the TBUT in horses and to report any side effects of a single application of THCl in clinically normal horses, particularly on the stability of the tear film. Methods: In Study 1, one drop of 0.5 or 1% THCl was applied to one eye of 20 horses divided in 2 groups. Treated eyes were assessed for the development of side effects 2.5 and 5 min after treatment. In Study 2, the TBUT was measured in both eyes of 2 groups of 10 horses, before and 2.5 and 5 min after, instillation of one drop of either 0.5 or 1% THCl. Results: No animals developed any ocular side effect after instillation. Basal TBUT was 8.3 ± 1.3 s. TBUT decreased from baseline 5 and 2.5 min after application of one drop of 0.5% THCl and one drop of 1% THCl, respectively. Conclusions: A technique to measure the TBUT in healthy horses is described and normal range values that could be used as a reference were obtained. Potential relevance: THCl is well tolerated in horses but lowers the TBUT.     

毛梾种子萌发特性及其解除休眠技术研究

主要对毛株(Cornus wateri)种子的萌发特性和解除休眠技术进行了探讨.采用称重、测量、解剖等方法,研究种子形态结构、吸水特性,TTC法研究种子活力,内含物测定及通过白菜种子萌发实验,研究萌发抑制物的存在.低温层积,变温层积,水浸处理相比较方法,研究种子休眠打破技术.研究结果表明,毛株为综合休眠型种子,以机械处...     

Measuring the torque required to cause vertebral dislocation in cattle tails

ABSTRACT

Aim: To estimate, ex vivo, the torque required to cause vertebral dislocation of cattle tails.

Methods: Five tails from dairy cows, severed at the junction between the sacrum and the first caudal vertebra, were sourced from a slaughterhouse. Within 2 hours of slaughter, the severed end of each tail was clamped in a vice and a steel collar was placed halfway along the tail. A torque wrench was attached to the steel collar, which was then rotated to produce an audible and palpable vertebral dislocation, and the torque at the time of the break was recorded.

Results: The maximum torque required to break a tail was 20?Nm, the minimum was 9.8?Nm, and the uncertainty was 4.9?Nm.

Conclusion: The torque required to break a cow’s tail is unlikely to be applied accidentally if cattle are handled following recommended best practice. Thus if cattle on a farm can be shown to have broken tails due to manipulation by farm staff, cattle handling is not meeting the recommended best practice of the New Zealand Dairy Cattle Code of Welfare.     

人工提前破壳对中华鳖(Trionyx siensis)卵的孵化和稚鳖生长的影响研究

对恒温孵化人工统一提前破壳与自然出壳的中华鳖稚鳖的生长发育进行了实验比较,试验在记录积温28800-30000℃?h?d时人工提前统一破壳,结果表明：人工提前统一剥壳对中华鳖存活率和稚鳖的体质无不良影响,经30d养殖的稚鳖苗达到一级标准,其生长比速、生长指标指标与自然出壳的中华鳖稚鳖差异不显著（P<0.05）;而生长常数、特定生长率、生长系数指标则显著优于同期受精和孵化的自然出壳稚鳖（P>0.01）。实验证明,人工破壳的稚鳖比同时受精、同批孵化及延迟十天产出的受精卵自然出壳较迟的对照稚鳖具有明显的生长优势;2003年和2004年两年的试验比较表明,人工提前破壳稚鳖的生长系数(W末重/W始重)分别为2.932±0.094、2.808±0.074,与同批自然出壳较迟的对照差异达到21.47%--45.9%,达极显著水平（F=124.6 >F0.01）;人工提前破壳稚鳖养殖的特定生长率分别为1.5365±0.1532、1.4777±0.1325,与自然出壳较迟的对照的特定生长率差异达极显著水平（F=68.5 >F0.01）;人工提前破壳稚鳖养殖的生长常数分别为0.112±0.001、0.107±0.002,与与自然出壳较迟的对照差异达146.5%--302.7%,达极显著水平（F=1684.5>F0.01）。人工提前破壳孵化的稚鳖具备摄食强度大、抗逆性强、不易感染病虫害等优势,可为周年养殖稚鳖的生长赢取时间,是培育大规格稚鳖、缩短养殖周期,提高中华鳖养殖经济效益的有效途径。     

修正大豆期现货价格的长短期关系：一个结构突变理论的应用

本文应用z—A方法和Perron方法等结构突变检验以及Gregory—Hansen变结构协整方法,对大豆期货和现货价格之间是否存在长短期均衡关系进行重新研究。研究发现。样本期内大豆期货和现货均发生了两次结构突变。通过考虑是否发生结构突变的对比分析表明,未考虑结构突变时大豆期现货不存在协整关系,考虑结构突变时二者则存在长期均衡关系和短期动态调整关系;考虑结构突变向量的误差修正模型（EcM）的预测精度比未考虑结构突变时高出5．5％,充分证实了结构突变在处理时间序列数据时的必要性和有效性。     

皱边石杉内生真菌DNA快速有效提取的研究

为了选择一种省时省力、简单有效的皱边石杉内生真菌菌丝体总DNA提取方法,采用氯化苄法提取其总DNA,对比研究石英砂研磨与超声波振荡2种破壁方式对其DNA的提取效能。结果表明,采用石英砂研磨法提取的DNA,其点样孔附近残余杂质较多、拖尾现象严重;超声波破壁法提取的DNA质量总体较好,DNA条带在23.1 kb处集中,多糖、蛋白质等杂质污染少,拖尾现象轻微。比较而言,超声波破壁法可快捷、高效提取皱边石杉内生真菌菌丝体DNA,适于植物内生真菌DNA大规模快速提取,尤其对质地坚硬的菌落较石英砂研磨更有效。提取的DNA经琼脂糖凝胶电泳、ITS序列扩增,表明超声波破壁法提取的DNA与石英砂研磨法一样,均可获得良好的PCR扩增结果。