Chicken welfare is influenced more by housing conditions than by stocking density

Intensive broiler (meat) chicken production now exceeds 800 million birds each year in the United Kingdom and 2 x 10(10) birds worldwide, but it attracts accusations of poor welfare. The European Union is currently adopting standards for broilers aimed at a chief welfare concern--namely, overcrowding--by limiting maximum 'stocking density' (bird weight per unit area). It is not clear, however, whether this will genuinely improve bird welfare because evidence is contradictory. Here we report on broiler welfare in relation to the European Union proposals through a large-scale study (2.7 million birds) with the unprecedented cooperation of ten major broiler producers in an experimental manipulation of stocking density under a range of commercial conditions. Producer companies stocked birds to five different final densities, but otherwise followed company practice, which we recorded in addition to temperature, humidity, litter and air quality. We assessed welfare through mortality, physiology, behaviour and health, with an emphasis on leg health and walking ability. Our results show that differences among producers in the environment that they provide for chickens have more impact on welfare than has stocking density itself.     

The T-cell repertoire is heavily influenced by tolerance to polymorphic self-antigens

T cells with V beta 3+ alpha beta receptors are deleted by self-tolerance in mice with particular major histocompatibility complex/self-antigen combinations. This also occurs for other V beta elements. Polymorphism in the major histocompatibility complex and/or the self-antigens that cause massive deletion of T cells using particular V beta elements may be maintained by the need to balance the advantage of a diverse T-cell repertoire against the potential involvement of those elements in autoimmune disease.     

对体育系和非体育系男生心脏功能的研究

通过对井冈山学院体育系和非体育系330名男学生进行台阶试验,客观地反映了男学生心脏功能能力,经统计学μ检验,体育系和非体育系的男生心脏F·C值,p＜0.01,具有高度显著性差别,故说明体育锻炼对人体心脏功能有良好的直接影响.     

对体育系和非体育系男生心脏功能的研究

通过对井冈山学院体育系和非体育系330名男学生进行台阶试验,客观地反映了男学生心脏功能能力,经统计学μ检验,体育系和非体育系的男生心脏F·C值,p＜0.01,具有高度显著性差别,故说明体育锻炼对人体心脏功能有良好的直接影响.     

论舍伍德·安德森短篇小说《鸡蛋》的艺术特色

舍伍德·安德森短篇小说<鸡蛋>是美国文学史上不可多得的佳作,也被视为安德森最好的作品之一,尤其是他对象征、反讽、顿悟等文学创作手法的娴熟运用和对美国梦幻灭这一主题的揭示对美国现代小说的发展产生了一定影响.     

超临界CO_2脱卵黄油及卵黄磷脂提取的研究

对超临界CO_2流体萃取卵黄磷脂及其机制进行了研究,超临界CO_2在丙酮和瓷粉作用下,在35MPa、40℃条件下萃取3h,可脱除蛋黄粉中98.6％的卵黄油。在40MPa、50℃条件下,用10wt％乙醇夹带,卵黄中磷脂的提取率最高,为27.28％。     

库存量影响需求的供应链合同

考虑由一个供应商和一个零售商构成的供应链，供应商提供零售商单一产品，而零售商的市场需求则随机地依赖于该商品的初始库存量，供应商希望通过供应链契约达到供应链协调的目的．在单一价格合同下，证明供应链不能达到协调，并讨论了供应商的最优决策．当供应商使用折价回购合同与零售商交易时，假设零售商存在线性／非线性的货架成本，分别讨论了取得供应链协调的条件，比较了零售商存货成本对于合同变量的影响，证明零售商的利润随着回购价格的上升而下降，但是其获得的利润始终大于零．     

Mating patterns in seminatural populations of mice influenced by MHC genotype

Because of the central role of major histocompatibility complex (MHC) genes in immune recognition, it is often assumed that parasite-driven selection maintains the unprecendented genetic diversity of these genes. But associations between MHC genotype and specific infectious diseases have been difficult to identify with a few exceptions such as Marek's disease and malaria. Alternatively, MHC-related reproductive mechanisms such as selective abortion and mating preferences could be responsible for the diversity. To determine both the nature and strength of selection operating on MHC genes by we have studied components of selection in seminatural populations of mice (Mus musculus domesticus). Here we assess MHC-related patterns of reproduction and early (preweaning) mortality by analysing 1,139 progeny born in nine populations, and 662 progeny from laboratory matings. Reproductive mechanisms, primarily mating preferences, result in 27% fewer MHC-homozygous offspring than expected from random mating. MHC genotype had no detectable influence on neonatal (preweaning) mortality. These mating preferences are strong enough to account for most of the MHC genetic diversity found in natural populations of Mus.     

溶剂浮选吸光光度法测定高碘蛋中总碘量

浮选法是在二氧化碳气氛中,以溴化十六烷三甲基铵（ＣＴＭＡＢ）为捕收剂,用溶剂浮选吸光光度法,对离子缔合物（ＣＴＭＡ＋Ｉ－３）的组成进行测定．实验表明,方法有较高的灵敏度,较好的准确性和重现性     

DMY is a Y-specific DM-domain gene required for male development in the medaka fish

Although the sex-determining gene Sry has been identified in mammals, no comparable genes have been found in non-mammalian vertebrates. Here, we used recombinant breakpoint analysis to restrict the sex-determining region in medaka fish (Oryzias latipes) to a 530-kilobase (kb) stretch of the Y chromosome. Deletion analysis of the Y chromosome of a congenic XY female further shortened the region to 250 kb. Shotgun sequencing of this region predicted 27 genes. Three of these genes were expressed during sexual differentiation. However, only the DM-related PG17 was Y specific; we thus named it DMY. Two naturally occurring mutations establish DMY's critical role in male development. The first heritable mutant--a single insertion in exon 3 and the subsequent truncation of DMY--resulted in all XY female offspring. Similarly, the second XY mutant female showed reduced DMY expression with a high proportion of XY female offspring. During normal development, DMY is expressed only in somatic cells of XY gonads. These findings strongly suggest that the sex-specific DMY is required for testicular development and is a prime candidate for the medaka sex-determining gene.     

证券投资分析的可拓策略研究

在分析了影响证券市场的各种因素的相互关系之后,根据证券市场变化的特点,针对证券分析问题的复杂性,运用可拓学的理论,探讨了对证券分析过程中的可拓方法以及这些可拓方法的使用策略。     

投资时机选择中的期权博弈分析

期权博弈模型很好地权衡了不确定性因素和竞争性因素,文章总结了投资竞争者相互博弈的4个阶段,对双寡头垄断期权博弈模型进行了推广;考虑在序贯均衡阶段有n个竞争者相互博弈的情况,每个投资者都能够找到自己的最优投资时机激发点,且假设每家企业所付出的成本各不相同,即不对称多寡头垄断期权博弈模型,并结合案例分析证明了其可操作性.     

运动副布置对3-SPR并联机构工作空间的影响分析

通过改变3-SPR并联机构的运动副布置,得到了10种典型的3-SPR并联机构,分析了它们的位置特性.采用CAD尺寸驱动技术求解了机构的工作空间,定义了描述工作空间及动平台姿态变化的参数,对10种机构的工作空间及姿态变化范围进行了比较,分析了运动副布置对于3-SPR并联机构工作空间及姿态变化的影响.     

Mechanism of stratospheric decadal abrupt cooling in the Early 1990s as influenced by the Pinatubo eruption

Studies have suggested that one volcanic eruption can influence seasonal to inter-annual climate variations.This study indicates that the Pinatubo eruption in 1991 may have actually induced the stratospheric decadal cooling recorded in the early 1990s.Using the NCEP/NCAR reanalysis and TOMS/SBUV satellite data,a decadal abrupt cooling of stratospheric tropical air temperature was found to have occurred in the early 1990s during a long-term descending trend.We generated the spatio-temporal structures of the decadal abrupt changes(DACs) for the stratosphere,and explored the relationship between the Pinatubo volcano eruption in 1991 and stratospheric DACs in the early 1990s.Our results suggest that the eruption of Pinatubo prompted a decadal decrease of ozone by the activation of nitrate and sulfate volcanic aerosols on ClO free radicals.The stratospheric heat absorbed by ozone decreased over a decadal time scale.As a result,decadal abrupt cooling of stratospheric tropical air temperatures occurred in the early 1990s,and may be attributed to the Pinatubo eruption.The results therefore indicate that one strong volcanic eruption can induce stratospheric decadal climate variation.     

The histone H3.3 chaperone HIRA is essential for chromatin assembly in the male pronucleus

In sexually reproducing animals, a crucial step in zygote formation is the decondensation of the fertilizing sperm nucleus into a DNA replication-competent male pronucleus. Genome-wide nucleosome assembly on paternal DNA implies the replacement of sperm chromosomal proteins, such as protamines, by maternally provided histones. This fundamental process is specifically impaired in sésame (ssm), a unique Drosophila maternal effect mutant that prevents male pronucleus formation. Here we show that ssm is a point mutation in the Hira gene, thus demonstrating that the histone chaperone protein HIRA is required for nucleosome assembly during sperm nucleus decondensation. In vertebrates, HIRA has recently been shown to be critical for a nucleosome assembly pathway independent of DNA synthesis that specifically involves the H3.3 histone variant. We also show that nucleosomes containing H3.3, and not H3, are specifically assembled in paternal Drosophila chromatin before the first round of DNA replication. The exclusive marking of paternal chromosomes with H3.3 represents a primary epigenetic distinction between parental genomes in the zygote, and underlines an important consequence of the critical and highly specialized function of HIRA at fertilization.     

互联网影响下的消费者行为特征及企业营销策略

对消费者行为的研究是企业制定市场营销策略的基础.在网络经济时代,消费者行为呈现出崭新的特征.因此,企业有必要认真分析影响消费者行为的因素,并制定合理、有效的营销策略,以满足消费者的需求,实现企业的目标.     

桥面铺装对简支空心板桥受力行为的影响研究

为了研究桥面铺装层对简支空心板桥受力性能的影响,将有限元计算结果与实桥静载试验结果进行了对比,分析了考虑及不考虑铺装层两种情况下的空心板桥在受力行为上的差异,研究了设有不同设计参数或状态铺装层的空心板桥受力特性的差异及其变化规律;研究结果表明铺装层可以有效地削减简支空心板桥的反应;通过加厚铺装层、增强连续性可以改善空心板桥的受力,其中采用桥面连续结构方法效果更为明显.研究结果对同类桥梁设计有一定的借鉴意义.     

价格和初始库存水平影响需求的二级供应链协调模型

文章针对由单一供应商和单一零售商构成的二级供应链系统,在考虑产品的市场需求依赖于初始库存水平和零售价格的情形下,研究了作为Stackelberg博弈主导方的供应商如何利用数量折扣机制来激励零售商合作,从而促进供应链协调性问题;理论结果表明,该策略能使供应商、零售商和供应链利润增加,却不能实现供应链系统完美协调,最后进行了数值验证。     

荧光定量PCR监测抑制剂对低温SBR微生物的影响

为研究氯酸盐抑制剂对SBR活性污泥中微生物的影响,采用序批式活性污泥反应器(SBR),在低温(15℃)条件下通过向反应器定时投加氯酸盐抑制剂,成功抑制系统中亚硝酸盐氧化菌(NOB)的活性,氨氮去除率和亚硝酸盐积累率均达到90%以上,实现了城市污水短程硝化的快速启动.采用实时荧光定量PCR对氨氧化菌(AOB)、亚硝酸盐氧化菌(NOB)和总细菌进行菌群定量分析,分析结果表明,氯酸盐抑制剂对NOB具有选择抑制性,对AOB的活性没有明显影响,而对NOB的活性抑制在短时间内是不可恢复的.