各向同性人造板材料弹性模量测量及其标准差评价

弹性模量是衡量人造板材料力学性能的重要指标,用标准差法对其进行综合评价尤为必要,对其实测及方差分析具有较好的应用价值。采用三点弯曲静力法和悬臂梁自由端振动法,测定各向同性HDF、三合板和OSB试材的静弹性模量和动弹性模量。在实测数据分析中,为反映总体弹性模量实测值数据集的离散程度及落在样本统计值某一区内的概率,还确定了其置信区间,评价了置信度。结果表明:各向同性人造板材料的静弹性模量和动弹性模量测试结果一致,其置信区间越大,置信水平越高。     

Environmental Change and the Sustainability of European Forests

Summary

It is some years now since forest decline was a major public concern in Europe and was one of the principal environmental issues around which international research programs were focused. A number of internationally coordinated activities were initiated in the 1980s and 1990s and have continued until now; these contributed significantly to our current understanding of forestry and to the way in which forestry policies have developed. In short, the concept of sustainable development has had an increasing influence and is now of immeasurable value in forest policy, with sustainable forest management well established as its guiding principle. This sequence of events is examined here. The extent to which understanding has advanced is remarkable; much has changed. Arguably this period gave the first indication of the extent to which forests and ecosystems globally are threatened by environmental change. On the basis of the last 20 years, it is tempting to conclude that we now have an effective institutional framework and have made excellent progress. However, some of the recorded ecosystem responses seem anomalous; there are surprises in system responses, e.g., the linkage between sulphur and nitrogen depositions and forest growth. Even more importantly some specific pollutant problems remain and will intensify, and climate change has become an environmental issue of overwhelming importance.     

Emerging issues in genomic selection

Genomic selection (GS) is now practiced successfully across many species. However, many questions remain, such as long-term effects, estimations of genomic parameters, robustness of genome-wide association study (GWAS) with small and large datasets, and stability of genomic predictions. This study summarizes presentations from the authors at the 2020 American Society of Animal Science (ASAS) symposium. The focus of many studies until now is on linkage disequilibrium between two loci. Ignoring higher-level equilibrium may lead to phantom dominance and epistasis. The Bulmer effect leads to a reduction of the additive variance; however, the selection for increased recombination rate can release anew genetic variance. With genomic information, estimates of genetic parameters may be biased by genomic preselection, but costs of estimation can increase drastically due to the dense form of the genomic information. To make the computation of estimates feasible, genotypes could be retained only for the most important animals, and methods of estimation should use algorithms that can recognize dense blocks in sparse matrices. GWASs using small genomic datasets frequently find many marker-trait associations, whereas studies using much bigger datasets find only a few. Most of the current tools use very simple models for GWAS, possibly causing artifacts. These models are adequate for large datasets where pseudo-phenotypes such as deregressed proofs indirectly account for important effects for traits of interest. Artifacts arising in GWAS with small datasets can be minimized by using data from all animals (whether genotyped or not), realistic models, and methods that account for population structure. Recent developments permit the computation of P-values from genomic best linear unbiased prediction (GBLUP), where models can be arbitrarily complex but restricted to genotyped animals only, and single-step GBLUP that also uses phenotypes from ungenotyped animals. Stability was an important part of nongenomic evaluations, where genetic predictions were stable in the absence of new data even with low prediction accuracies. Unfortunately, genomic evaluations for such animals change because all animals with genotypes are connected. A top-ranked animal can easily drop in the next evaluation, causing a crisis of confidence in genomic evaluations. While correlations between consecutive genomic evaluations are high, outliers can have differences as high as 1 SD. A solution to fluctuating genomic evaluations is to base selection decisions on groups of animals. Although many issues in GS have been solved, many new issues that require additional research continue to surface.     

国外生猪育种体系简析及对我国生猪育种的几点思考

选择是生猪育种的核心,而准确地选择和选种依赖于完善和成熟的育种体系。国际养猪发达国家(国际育种企业)对育种体系不断完善,长期进行生长、繁殖和肉品质等各类性状的表型测定,运用多场联合评估和基因组选择等方法不断提高遗传评估的准确性,不断挖掘新的育种性状,并进行测定、评估和选育,实现了种猪群体持续的遗传改良和综合性能的不断提升。本文对欧美发达国家(国际育种企业)的生猪育种技术体系进行了综述,以期为我国的生猪育种工作提供参考,并促进我国生猪种业的创新发展。     

Variation among stallions in sperm quality after single layer centrifugation

Although single layer centrifugation (SLC) selects robust spermatozoa from stallion semen, the effect of individual variation has not been studied in detail. The objective of this study was to determine the variation among stallions in the effects of SLC on sperm quality during cooled storage for up to 48 hr. Semen samples from seven stallions (18 ejaculates) were split, with one portion being used for SLC and the other serving as a control (CON). Sperm quality (kinematics, reactive oxygen species (ROS) production, membrane integrity (MI) and chromatin integrity) were analysed at 0, 24 and 48 hr using computer-assisted sperm analysis and flow cytometry. Sperm quality was better in SLC than in CON at all timepoints, especially chromatin integrity and MI (p < .0001 for both), and some categories of ROS production (e.g. proportion of live hydrogen peroxide negative spermatozoa, p < .0001), but the degree of improvement varied among stallions and type of ROS (p < .05–p < .0001). Total and progressive motility were also better in SLC samples than in CON at 24 and 48 hr (p < .0001), although the effect on sperm kinematics varied. The interaction of treatment, time and stallion was not significant. In conclusion, sperm quality was better in SLC samples than in CON, although there was considerable individual variation among stallions. The improvement in sperm quality, particularly in chromatin integrity, was clearly beneficial, and therefore the use of this technique would be warranted for all stallion semen samples.     

不同养殖模式翘嘴鲌肌肉营养品质比较

为评价池塘与大湖不同养殖模式翘嘴鲌(Culter alburnus)肌肉营养品质差异,试验分析了商品翘嘴鲌肌肉常规营养成分、氨基酸、脂肪酸、矿物元素含量等营养指标。结果表明:大湖翘嘴鲌肌肉水分含量显著低于池塘翘嘴鲌(P<0.05),粗蛋白质含量高于池塘翘嘴鲌,差异不显著(P>0.05)。池塘与大湖翘嘴鲌肌肉,除了赖氨酸和组氨酸以外(P<0.05),绝大部分氨基酸含量均无显著性差异(P>0.05)。大湖翘嘴鲌肌肉的总氨基酸、必需氨基酸和鲜味氨基酸含量分别较池塘翘嘴鲌高出2.72%、2.87%和2.50%。根据氨基酸评分(AAS)和化学评分(CS)结果,池塘与大湖翘嘴鲌肌肉中第一限制性氨基酸均为蛋氨酸+胱氨酸,赖氨酸相对含量最高,必需氨基酸指数(EAAI)分别为68.81和69.62。池塘翘嘴鲌的棕榈油酸(C16:1)含量显著高于大湖翘嘴鲌(P<0.05),而大湖翘嘴鲌肌肉的单不饱和脂肪酸(MUFAs)、高不饱和脂肪酸(HUFAs)、必需脂肪酸(EFA)、EPA+DHA含量则高于池塘翘嘴鲌(P>0.05)。试验检测了池塘与大湖翘嘴鲌肌肉11种矿物元素,其中镁有显著差异(P<0.05),重金属元素(铬、镉、铅)含量均在限量范围以内。综上所述,大湖养殖翘嘴鲌营养品质优于池塘养殖。     

饲料加工企业内控评价指标体系的构建及其应用研究

面对日益复杂的竞争形势,饲料加工企业需要加强内控管理。为了评价内控体系的有效性,通常寻找一些评价指标形成体系对内控进行评价。本文提出构建内控评价指标体系需要一些前提,包括对关键环节的识别、评价原则的确定等,在指标选取中,至少应涵盖公司层面、业务层面、财务层面和合法合规层面的指标。内控评价体系构建后,需要有组织保障和制度保障,并且需要不断改进完善。 [关键词] 饲料加工企业|内部控制|评价指标体系|风险管理     

补播羊草和黄花苜蓿对退化草甸植物群落特征的影响

呼伦贝尔草原区是我国北方重要的生态屏障,近年来不合理的利用方式导致该地区退化草地面积不断扩大,为了探究牧草补播时间及补播比例对呼伦贝尔退化草甸草原植物群落特征的影响,为该地区退化草地修复提供依据。本研究以羊草（Leymus chinensis（Trin.） Tzvel.）和黄花苜蓿（Medicago falcata L.）为试验材料,采用双因素随机区组试验设计,通过测定幼苗数、高度、生物量等群落指标,并综合评价补播效果,结果表明：夏播羊草和黄花苜蓿幼苗数量显著高于春播和秋播（P<0.05）,夏播和秋播植物群落总生物量呈增加趋势,春播则呈减少趋势;补播措施提高了退化草地植物群落Shannon-Weiner指数、Simpson指数和Pielou指数,豆科和禾本科植物重要值呈增加趋势,其他科植物呈下降趋势。呼伦贝尔地区夏季补播羊草和黄花苜蓿以1∶3补播效果较好,而春播由于恢复时间短,需进一步观察。     

青海扁茎早熟禾混播草地生产性能与种间关系的研究

为了探究早熟禾混播草地种间关系与生产特征,使用‘青海’中华羊茅（Festuca sinensis ‘Qinghai’）、'青牧1号’老芒麦（Elymus sibiricus ‘Qingmu No.1’）、‘同德’小花碱茅（Puccinellia tenuiflora ‘Tongde’）分别与‘青海’扁茎早熟禾（Poa pratensis var. anceps Gaund.‘Qinghai’）混播,在海北州西海镇开展了植株形态特征、生物量积累和分配、混播草地养分特征等研究。结果表明：使用老芒麦与早熟禾混播具有较高的生产性能。该处理相较于老芒麦单播草地的粗蛋白与总磷含量,分别提高7.51%与14.50%。相对饲用价值较早熟禾单播草地提高34.12%。因此,为解决青海扁茎早熟禾单播草地生产力不足的问题可以选用老芒麦与早熟禾进行混播。使用碱茅与早熟禾混播具有较高的种间相容性,因此碱茅与早熟禾混播具有较高的群落稳定性与产量稳定性。选用碱茅与早熟禾进行混播可以用于建植以生态治理为目的的混播草地。     

基于灰色关联法的小型农田水利工程建设项目绩效评价研究

运用灰色关联法原理,采用均方差法计算指标权重,根据近年来湖北省进行小型农田水利工程建设项目绩效评价的实际情况,建立了小型农田水利工程建设项目评价定性定量混合指标体系和模型,应用该模型和方法对湖北省2012年第二批20个小农水重点县工程建设项目进行了评价(作为研究,各县、市名以汉语拼音字头代替)。结果表明:LHK、SSS、ZJS、DJK、XTS等14个县为优秀,XCX、TMS、JSX等5个县为良好,CYX为一般,无及格等级的重点县。评价结果与实际基本相符。证明本文所提出的模型和方法可应用于实际,是一种快速便捷的评价工具。