The variability of mechanical properties and molecular conformation among different spider dragline fibers

Spider dragline fiber is a high-performance biomaterial that has received much attention. To screen the outstanding spider dragline fibers, the mechanical properties and microstructures of dragline fibers collected from Nephia clavata, Nephia pilipes, Argiope bruennichi and Argiope amoena were investigated. It was found that the mechanical properties of spider dragline fiber were variable. Among the four different species, the larger spiders did not always extrude thicker dragline fibers and produce fibers with the maximum breaking force. The dragline fibers could sustain one to three times the body weight of the spider at a reeling speed of 20 mm/s. N. clavata dragline fiber showed a stronger breaking stress and initial modulus than that of N. pilipes, A. bruennichi and A. amoena. With an increasing reeling speed, the breaking strain decreased; the initial modulus increased in N. clavata, N. pilipes and A. bruennichi, but the breaking stress exhibited a different tendency. The results also revealed that dragline fiber of N. clavata contained the most β-sheet polypeptides and an excellent orientation of β-sheet molecular chains.     

Renal excretion of urea in the Merino and Steppe fat-tailed breeds of sheep after a short period of fasting

Urea excretion was studied in an experiment with two sheep breeds (steppe fat-tailed and merino) on the second day of fasting when the urea concentration in blood increases in fasting animals. The control group in the two breeds was given free-choice feed and water while fasting sheep were given ad libitum only water. Diuresis in both breeds was steady during the experiment. Glomerular filtration rate was not found to vary, in comparison with the control, although the plasma urea concentration rose in fat-tailed sheep (P less than 0.01) as well as in the sheep of merino breed (P less than 0.001). Fractional excretion of urea decreased in fat-tailed sheep (P less than 0.05) and also in the sheep of merino breed (P less than 0.02) while total output of urea remained steady in fat-tailed sheep but it increased in merino sheep (P less than 0.02). Tubular reabsorption of urea on the second day of fasting was observed to be higher by 65% in merino sheep (P less than 0.001), but in steppe fat-tailed sheep the increase was much higher--by up to 180% (P less than 0.001), in comparison with the control. It was demonstrated by the results that the increased tubular reabsorption of urea contributes to the rise of plasma urea concentration in sheep on the second day of fasting.     

苹果褐斑病过氧化物酶同工酶的研究

 植物受病原侵染后,病组织中的过氧化物酶同工酶往往发生变化,对于这种变化与植物病害尤其是品种抗病性的关系,近年来国内外有较多的研究。     

罗保铭省长批示:严格检测确保质量安全的豇豆出岛

2009年1月17日,新华社以<岁寒尤应念民生>为题,刊发了温家宝总理在京考察民生情况的通讯,通讯中生动记录了温总理与海南瓜菜代表黄栋的一段对话.黄栋一说起起这件事时,他就兴奋不已.     

杨氏姬花蚤发生规律与防治的初步研究

研究并明确了吉林省白城向日葵杨氏姬花蚤(Mordellistena yangi Fan)的发生危害与生物学分类,以及该虫在当地的发生规律及主要生物学特性,提出以消灭越冬寄主,改进耕作管理措施为主,适时化学防治为辅的防治方法。     

非洲猪瘟场复养成功的前提条件与关键技术措施

非洲猪瘟传入我国后,对生猪行业造成了非常不利的影响。生猪的存栏量和出栏量均出现了大幅下降,为了恢复生猪产能,保障猪肉供应,复养刻不容缓。笔者通过对猪场风险评估,对发病原因、清洗与消毒、硬件改造与升级、环境和水体检测、哨兵猪的选择与管理以及关键技术措施等进行总结与集成,并将其利用指导了3个感染过非洲猪瘟的猪场成功复养,现将这些措施的主要内容总结如下几点,供行业主管部门和养猪场(户)参考。     

利乐包牛奶灌装容量控制的有效方法

2008年9月份爆发的三鹿奶粉事件已经发展成为国内乳品行业发展的转折点。在这次危机中,国内乳制品企业纷纷遭受重创,并且影响的广度和深度不断扩大。对乳品企业而言,这是一个困难的时代,在乳业危机和激烈竞争的双重挤压下,整个价值链都受到了巨大的影响。如何更有效地降低成本,提升企业盈利的能力成为每一个乳品企业所关心的主题,对以薄利多销为原则的利乐包牛奶产品更是如此。针对利乐包牛奶过量灌装这一普遍现象,本文介绍了一种有效控制灌装容量的方法,对乳品企业控制成本具有一定的启示意义。     

水产饲料行业标准分析与建议——加工质量指标

<正>我国是产量位居世界第一的水产养殖大国,在我国水产养殖业的发展过程中,水产饲料工业发挥了至关重要的作用。目前,我国水产饲料的年产量已达1300万吨,是近年发展最为迅速的饲料品种。随着水产饲料业的发展,迫切需要对水产饲料的质量作出     

Comparison study of three compounds in Eucommia ulmoides on growth,flesh quality of grass carp (Ctenopharyngodon idella)

This study was conducted to compare the growth‐promoting and flesh quality ‐improving effects of three active compounds in Eucommia ulmoides (EU) on grass carp (Ctenopharyngodon idella). Four iso‐nitrogenous diets supplemented with 400 mg/kg inclusion of geniposidic acid (GA), chlorogenic acid (CGA), geniposide (GP) and their combination (GA:CGA:GP = 1:1:1, the mixture) were prepared and fed to grass carp (47.1 ± 0.6 g) for 75 days. The results indicated that weight gain was increased by 5.22%, and feed conversion ratio decreased by 0.07 by dietary CGA (p < 0.05). In flesh quality, the four supplementations significantly increased muscle fibre density, total collagen and alkaline‐insoluble collagen in skin, and reduced steaming loss of flesh. In addition, dietary CGA, GP and the active compounds mixture further increased total collagen, alkaline‐insoluble collagen and amino acid in flesh. In collagen genes expression, the expression of COL1A1 in muscle and skin was significantly promoted by the supplementation of GA, CGA, GP and their combination (p < 0.05). In conclusion, the supplementation of GA, CGA, GP and their combination improved the flesh quality of grass carp, and the growth was increased by CGA. CGA played more important roles in growth‐promoting and flesh quality‐improving effects than GP and GA.     

Immunisation against lactic acidosis in cattle.

The present study was designed to investigate the efficacy of control of lactic acidosis by immunisation against lactic acid-producing bacteria, Streptococcus bovis and Lactobacillus. Ten steers were allocated to two treatment groups. One group was immunised with a vaccine containing S. bovis (strain Sb-5) and Lactobacillus (LB-27) cells, and the other was a non-immunised control group. The vaccine, using Freund's complete adjuvant for primary immunisation and Freund's incomplete adjuvant for boosters, was administered intramuscularly. After primary immunisation, boosters were given at 2 to 4 week intervals. Both anti- S. bovis and anti- Lactobacillus IgG levels in saliva increased significantly (P < 0.01) after the 1st booster which were lower (P < 0.05) than the IgG levels after the 2nd and 3rd boosters, but were not significantly different (P > 0.05) from the IgG levels prior to a grain challenge (after the 4th booster). There were positive correlations between the anti- S.bovis and anti- Lactobacillus IgG in serum and saliva. Compared with the control group, steers in the immunised group had higher (P < 0.05) feed intakes, lower (P < 0.05) rumen concentrations of lactate and lower numbers of S. bovis and Lactobacillus. Three of the control animals were withdrawn from the grain challenge due to their rumen pH persisting below 5.2, while only one animal in the immunised group was withdrawn. These results suggest that the risk of lactic acidosis can be reduced by immunisation against S. bovis and Lactobacillus.