Impact of localized badger culling on tuberculosis incidence in British cattle

Pathogens that are transmitted between wildlife, livestock and humans present major challenges for the protection of human and animal health, the economic sustainability of agriculture, and the conservation of wildlife. Mycobacterium bovis, the aetiological agent of bovine tuberculosis (TB), is one such pathogen. The incidence of TB in cattle has increased substantially in parts of Great Britain in the past two decades, adversely affecting the livelihoods of cattle farmers and potentially increasing the risks of human exposure. The control of bovine TB in Great Britain is complicated by the involvement of wildlife, particularly badgers (Meles meles), which appear to sustain endemic infection and can transmit TB to cattle. Between 1975 and 1997 over 20,000 badgers were culled as part of British TB control policy, generating conflict between conservation and farming interest groups. Here we present results from a large-scale field trial that indicate that localized badger culling not only fails to control but also seems to increase TB incidence in cattle.     

基于序列模式的正负关联规则研究

序列模式可预测企业的发展方向，负关联规则可展现不良因素的根源，序列模式的正负关联规则为企业决策提供更全面的信息. 将序列模式和负关联规则的挖掘算法相结合，利用项集间的相关性，挖掘出序列模式的正负关联规则.     

幽默短信的正负偏离转化

幽默短信语言以其超越常规的偏离形式而倍受关注,也因为正、负偏离并存而良莠不齐引发争议。但正、负偏离不是绝对的、静止的,它们在一定条件下可以相互转化,这一转化需要以语境为条件,以微观语境服从宏观语境为原则。手机短信的实践者在编写和阅读手机短信时,应提倡正偏离,反对负偏离,注重短信的社会文化心理的积极需求,不能因辞害意。     

幽默短信的正负偏离转化

幽默短信语言以其超越常规的偏离形式而倍受关注,也因为正、负偏离并存而良莠不齐引发争议.但正、负偏离不是绝对的、静止的,它们在一定条件下可以相互转化,这一转化需要以语境为条件,以微观语境服从宏观语境为原则.手机短信的实践者在编写和阅读手机短信时,应提倡正偏离,反对负偏离,注重短信的社会文化心理的积极需求,不能因辞害意.     

Positive and negative selection of an antigen receptor on T cells in transgenic mice

The T-cell repertoire found in the periphery is thought to be shaped by two developmental events in the thymus that involve the antigen receptors of T lymphocytes. First, interactions between T cells and major histocompatibility complex (MHC) molecules select a T-cell repertoire skewed towards recognition of antigens in the context of self-MHC molecules. In addition, T cells that react strongly to self-MHC molecules are eliminated by a process called self-tolerance. We have recently described transgenic mice expressing the alpha beta T-cell receptor from the cytotoxic T lymphocyte 2C (ref. 11). The clone 2C was derived from a BALB.B (H-2b) anti-BALB/c (H-2d) mixed lymphocyte culture and is specific for the Ld class I MHC antigen. In transgenic H-2b mice, a large fraction of T cells in the periphery expressed the 2C T-cell receptor. These T cells were predominantly CD4-CD8+ and were able to specifically lyse target cells bearing Ld. We now report that in the periphery of transgenic mice expressing Ld, functional T cells bearing the 2C T-cell receptor were deleted. This elimination of autoreactive T cells appears to take place at or before the CD4+CD8+ stage in thymocyte development. In addition, we report that in H-2s mice, a non-autoreactive target haplotype, large numbers of CD8+ T cells bearing the 2C T-cell receptor were not found, providing strong evidence for the positive selection of the 2C T-cell receptor specificity by H-2b molecules.     

具正负系数二阶差分方程的正解

考虑具正负系数中立型二阶差分方程:Δ(rnΔ(xn Rnxn-k)) pnxn-l-qnxn-б=0。其中{Rn}、{pn}、{qn}、{rn}为非负实数列,rn>0。pn=pn-qn-l k≥0,l≥б,k、l、б为自然数,给出了方程存在正解的若干充分条件,并给出了定理的应用。     

两类特殊三圈图的正负惯性指数和零度

讨论了Ⅰ-型三圈图和Ⅱ-型三圈图的正负惯性指数和零度问题。主要通过删除悬挂的树和压缩内部路等方法,给出了两类特殊三圈图的正负惯性指数和零度的计算方法：Ⅰ-型三圈图的正负惯性指数（零度）等于一些树和一些双圈图（或单圈图或树）的正负惯性指数（零度）之和;Ⅱ-型三圈图的正负惯性指数（零度）等于一些树和一些简单三圈图的正负惯性指数（零度）之和,对于点数较少的三圈图的正负惯性指数和零度利用软件 Matlab 计算得到。     

体育锻炼的消极心理效应及其应对措施

锻炼迷瘾和心理耗竭是锻炼者在体育锻炼中容易产生的消极心理效应.通过分析体育锻炼与消极心理效应产生原因及对心理健康带来的危害,提出5项应对措施：制定科学、合理的锻炼计划;积极参与形式多样的群体活动;养成良好的生活与饮食习惯;运用心理恢复手段和物理疗法方法消除心理疲劳;在体育锻炼中自我监督和自我评价.     

Superoxide involvement in the bactericidal effects of negative air ions on Staphylococcus albus.

The physical nature of small air ions is well established and it is recognized that they can produce a variety of biological effects. However, in only a few instances have any underlying biochemical changes been detected. Theoretically, one can consider the hydrated superoxide radical anion (O2) (H2O)n with n congruent to 4-8 as a likely candidate for a biologically active species of negative air ion. The chemical and biological reactivity of superoxide is high and includes a leading role in bacterial killing caused by radiation, in which superoxide dismutase (SOD), an enzyme that catalyses the reaction: O2 + O2 +2H leads to H2O2 +O2 protected markedly. Other studies have also demonstrated the bactericidal effect of O2 (refs 9-11). Inasmuch as the bactericidal action of small negative air ions has been repeatedly confirmed, we decided to test for the involvement of O2 in this phenomenon by evaluating the protective effect of SOD. Our results show strong O2 involvement in negative air ion bacterial kill.     

城镇居民收入分配差距问题及其正负效应研究

分析了我国城镇居民收入分配差距扩大的现象及现阶段呈现出的新特点,讨论了收入差距扩大的根源以及对社会产生的正、负效应,提出了解决收入分配差距扩大化的根本方法与途径。     

我国平原农区林带胁地效应及其控制措施研究进展

总结了近年来我国农田防护林林带尤其平原农区林带胁地的研究成果,以揭示农田防护林的胁地规律及其影响因素,并探讨克服胁地的措施.分析认为:①我国各地区由于地理位置、自然条件以及树种生物学等的差异,农田防护林的胁地范围也不同,在平原农区其胁地范围按程度大小分别为0～[0.4H,2.0H](H为林带平均高度,胁地程度大小依次为...     

攻击——高自我价值感的负效应

论述了影响自我危机与攻击的因素,指出高自我价值感攻击理论认为:攻击通常是自我危机的结果,即对自己非常有利的自我概念遭到他人质疑时的现象。认为名不副实的自我优越观念最易产生自我危机而导致攻击,其机制是愤怒外导,旨在避免降低自我概念。     

关于在欧氏空间和酉空间里的正定、半正定矩阵的对比研究

对正定、半正定矩阵在欧氏空间和酉空间里进行对比,目的是为了更好地了解正定、半正定矩阵在不同数域的性质,并且给出在复数域上的严格证明.     

自旋-轨道耦合力对核子最低负宇称态的影响

利用推广的带矢量场的手征SUM夸克模型,计算了核子最低负宇称激发态JP=1/2-,3/2-的能量,分析了各种自旋-轨道耦合势对能量劈裂的影响.结果表明,利用矢量介子场耦合可以改进计算结果,但是能级的次序和实验还是相反的.在此基础上进一步考虑其他的自旋-轨道耦合势,可以给出该激发态正确的能级次序.     

积极心理学介评

积极心理学是现代心理学研究的一个新思潮,似一股清新的空气注入传统消极心理学而迅猛发展。本文从积极心理学的背景和现状、理论研究以及应用领域予以介绍,最后对积极心理学进行简评。