显微镜检查旋毛虫操作中的常见差错及纠正方法

旋毛虫病是一种由毛首目旋毛虫科的线虫─—旋毛虫所引起的人畜共患病,对人危害很大,能致死亡。现已查明,至少有65种哺乳动物可感染本病。在自然条件下,本病多见于猪、鼠类、狗、猫。在屠畜中主要感染猪、狗。羊,特别是山羊也可患旋毛虫病,本病在欧美各国均有流行,在我国也不少见。其成虫寄生于宿主的肠内（即肠旋毛虫）,幼虫寄生于横纹肌里且形成包囊（即肌肉旋毛虫）,当人或动物食入生的或未煮熟的肌肉旋毛虫病畜肉后,即可感染本病。猪旋毛虫病的诊断,目前采用的和正在研究的方法有：（1）显微镜检查法;（2）集样消化法;（3…     

认真贯彻落实《动物防疫法》 努力推动全市兽医工作上新台阶

《动物防疫法》是我国兽医工作的第一部大法,它的颁布,为在社会主义市场经济新形势下依法加强和规范兽医工作提供了强有力的法律武器和依据。天津市各级畜牧兽医行政管理部门和动物防疫监督机构,紧紧抓住《动物防疫法》颁布与实施这个历史性机遇,认真学习宣传和深入贯彻执行《动物防疫法》,努力强化和发展兽医法制管理,依法推动动物防疫、检疫和监督管理各项工作上新台阶。通过一年来的努力工作,全市动物防疫工作已初步呈现出一个新的发展态势。产地检疫进一步深入开展,屠宰检疫率及上市肉类持证率达到了IOO％,肉类卫生质量有了…     

水体光照强度的变化对浮游甲壳动物群落结构的影响

近年来,我国淡水湖泊富营养化现象日益严重,藻类大量生长导致水体光照强度减弱,水生植物严重衰退。为了解水体光照强度减弱对生活在沿岸带草丛中的浮游甲壳动物分布情况的影响,本研究于2015年5月至2015年11月在水族箱中通过移植苦草并覆盖不同层黑色遮阳布来建立4个光照梯度（L1- L4）,其透光率分别是40.5%、17.1%、7.1%和2.8%,来模拟自然条件下沿岸带浮游甲壳动物群落对低光压力的响应,分析了水体理化指标、苦草和浮游甲壳动物群落结构变化。结果表明：（1）从不同的光照处理来看,浮游甲壳动物生物量随光照强度减弱而减少,其平均值分别是1.27 mg/L、0.99 mg/L、0.95 mg/L和0.45 mg/L,丰度和多样性也随光照强度减弱逐渐降低;（2）与其他3个处理组相比,L4组中除了锯缘真剑水蚤相对生物量百分比从5%升高到25%,其他种类都有所下降,其中晶莹仙达溞从50%降至9%;（3）浮游甲壳动物的平均生物量在秋季（1.28 mg/L）大于夏季（0.54 mg/L）,而夏季（83.79 ind./L）平均丰度大于秋季（53.59 ind./L）。统计分析表明浮游甲壳动物群落结构变化与光照强度和苦草生长引起的水体理化的变化显著正相关,主要是溶解氧和pH值。     

Genomic Prediction of Arsenic Tolerance and Grain Yield in Rice: Contribution of Trait-Specific Markers and Multi-Environment Models

Many rice-growing areas are affected by high concentrations of arsenic(As). Rice varieties that prevent As uptake and/or accumulation can mitigate As threats to human health. Genomic selection is known to facilitate rapid selection of superior genotypes for complex traits. We explored the predictive ability(PA) of genomic prediction with single-environment models, accounting or not for trait-specific markers, multi-environment models, and multi-trait and multi-environment models, using the genotypic(1600 K SNPs) and phenotypic(grain As content, grain yield and days to flowering) data of the Bengal and Assam Aus Panel. Under the base-line single-environment model, PA of up to 0.707 and 0.654 was obtained for grain yield and grain As content, respectively; the three prediction methods(Bayesian Lasso, genomic best linear unbiased prediction and reproducing kernel Hilbert spaces) were considered to perform similarly, and marker selection based on linkage disequilibrium allowed to reduce the number of SNP to 17 K, without negative effect on PA of genomic predictions. Single-environment models giving distinct weight to trait-specific markers in the genomic relationship matrix outperformed the base-line models up to 32%. Multi-environment models, accounting for genotype × environment interactions, and multi-trait and multi-environment models outperformed the base-line models by up to 47% and 61%, respectively. Among the multi-trait and multi-environment models, the Bayesian multi-output regressor stacking function obtained the highest predictive ability(0.831 for grain As) with much higher efficiency for computing time. These findings pave the way for breeding for As-tolerance in the progenies of biparental crosses involving members of the Bengal and Assam Aus Panel. Genomic prediction can also be applied to breeding for other complex traits under multiple environments.     

Short-season cotton (Gossypium hirsutum) may be a suitable response to late planting in sub-Saharan regions

In Cameroon, seed cotton yields have not increased over the last 20 years because of the shortening of the rainy season and the worsening socioeconomic context. Farmers consequently often delay planting their crops. The main objective of this study was to investigate whether local indeterminate long-season cottons, grown at the recommended density, were more consistent with the farmers’ current constraints than determinate short-season cultivars from Latin America that could be sown more densely. We carried out a 3-year three-location survey in northern Cameroon, which included two planting dates (recommended and delayed) and two planting densities (recommended and high). We show that these three factors acted independently. Late planting had a highly negative impact on most traits at both plant and plot scale by delaying flowering, reducing seed cotton yield and fibre quality. Dense sowing mainly had an impact on individual plant traits by reducing boll retention and elongating main-stem internodes. Local cultivars have already evolved favourably (enhanced earliness, yield performance, harvest index, ginning out-turn, and fibre maturity) and could be improved further by crossing with highly determinate cottons. However, such a strategy requires further investigation to ensure that a more determinate growth pattern would not have a negative impact on the adaptive response of the traditional cotton plant to other adverse conditions.     

Numerical simulation of contact problems in high pressure reciprocating pump systems

The cylinder bodies of reciprocating pumps easily fail from cracks due to complex external loads. Based on the working principle of reciprocating pumps, hydrodynamics, and a numerical method for surface to surface contact problems, a contact model involving a cylinder body, a valve base, and a valve pocket is established. Considering pressure fluctuation, flow pulsation, alternate loads, and the impact of the inlet and outlet valves, a finite element model for the complete system is established. Using this model, the contact state of the complete system is analyzed, and the stress distribution, contact state, contact stress distribution of the interface, and position of the weak part are obtained.     

经营规模、农业技术培训与家庭农场收入——基于江苏省的调查

农地规模经营绩效的实现与生产者的经营能力息息相关,而农业技术培训是提高经营能力的重要政策工具。因此,将技术培训纳入到经营规模与收入关系的探讨中统一考察,有助于更好把握规模经营主体的收入增长规律。利用江苏省360个粮食类家庭农场调研数据,采用多元回归方法,从单位面积纯收益的维度分析了经营规模、农业技术培训对农场收入的影响,并检验了技术培训所发挥的调节效应。结果表明:经营规模与收益之间呈倒"U"型关系,在6.67～13.33 hm~2区间内纯收益最高,并计算得出样本农场最优规模为8.5 hm~2,在未达到最优规模之前,经营规模每增加1 hm~2将使得收益增加1.7%,超过该规模后收益随着规模的增加而减少;技术培训对农场收益具有显著的正向影响,影响系数为0.031。另外,农业技术培训能够改善农场生产者经营能力与规模的匹配度,对经营规模与收益之间的关系具有正向调节作用。因此,提出加强农地流转市场建设,发挥适度规模效应;培育家庭农场等规模主体要与主体农业技术培训,经营能力提升相结合的政策建议。     

极小种群川柿野外资源现状

为了掌握极小种群川柿(Diospyros sutchuensis Yang)的种质资源现状并评估其濒危等级,对川柿资源历史发现地及现发地——华蓉山、缙云山、江津四面山保护区进行了系统野外调查。结果表明：(1)当前历史发生地华蓉山已无川柿野生植株,缙云山有疑是川柿1株,而在江津四面山保护区发现少量植物。(2)江津保护区有3个分布点,共计6株,均为成年植株。(3)依据IUCN全球物种濒危等级评估标准,川柿应当被评为(EN,B2a)。     

大气氮沉降对黄土高原土壤氮特征的影响

为了解氮沉降对土壤氮特征的影响,通过人工氮肥添加模拟试验,分析在不同氮添加梯度下黄土高原典型草原土壤全氮（TN）和轻组有机氮（LFON）含量的变化特征。结果显示,氮添加对黄土高原典型草原土壤0～40 cm土层TN含量没有显著影响(P>0.05);但是显著增加了土壤表层（0～10 cm）的LFON含量和LFON/TN(P<0.05)。氮添加对10～20和20～40 cm的LFON含量和LFON/TN没有显著影响(P>0.05)。本研究表明,在黄土高原典型草原实施氮添加的初期,LFON含量和LFON/TN比TN含量能更早地显示出土壤氮特征的变化。     

猪传染性胃肠炎的诊断和防制

经临床观察、病理剖检。人工感染试验和血清学检验确诊武汉市郊区某猪场于1998年初春爆发猪传染性胃肠炎,并以病猪肠组织制备了组织灭活革,取得了初步的效果,据此制定了相应的防制措施。1发病情况及临床症状1998年1月武汉市郊区某猪场少数肥猪栏内的肥猪发生严重腹泻,第2d迅速蔓延至全栋并进而波及全场,发病率达100％。猪群主要表现为水样腹泻,排泻物呈灰或褐色,略带腥臭味,少数猪有呕吐现象。病猪食欲下降,精神很差,被毛蓬松,少数脱水现象明显。病猪很少死亡,病程1周～2周。2病理变化创检2头断奶拉稀刚死亡仔猪。一头脱水明显…