A late Triassic impact ejecta layer in southwestern Britain

Despite the 160 or so known terrestrial impact craters of Phanerozoic age, equivalent ejecta deposits within distal sedimentary successions are rare. We report a Triassic deposit in southwestern Britain that contains spherules and shocked quartz, characteristic of an impact ejecta layer. Inter- and intragranular potassium feldspar from the deposit yields an argon-argon age of 214 +/- 2.5 million years old. This is within the age range of several known Triassic impact craters, the two closest of which, both in age and location, are Manicouagan in northeastern Canada and Rochechouart in central France. The ejecta deposit provides an important sedimentary record of an extraterrestrial impact in the Mesozoic that will help to decipher the number and effect of impact events, the source and dynamics of the event that left this distinctive sedimentary marker, and the relation of this ejecta layer to the timing of extinctions in the fossil record.     

Intercontinental spread of a new antibiotic resistance gene on an epidemic plasmid

Bacteria of different genera isolated at nine medical centers in different parts of the United States and at one center in Venezuela during the first decade of gentamicin usage carried the gentamicin resistance gene 2"-aminoglycoside nucleotidyltransferase on the same transferable plasmid. Such widespread dissemination of a newly observed resistance gene on one plasmid suggests that a new resistance gene may emerge once on a single plasmid, which then carries it to other centers and other plasmids. The resistance gene might, therefore, be contained if detected early.     

Longitudinal studies of effects of divorce on children in Great Britain and the United States

National, longitudinal surveys from Great Britain and the United States were used to investigate the effects of divorce on children. In both studies, a subsample of children who were in two-parent families during the initial interview (at age 7 in the British data and at ages 7 to 11 in the U.S. data) were followed through the next interview (at age 11 and ages 11 to 16, respectively). At both time points in the British data, parents and teachers independently rated the children's behavior problems, and the children were given reading and mathematics achievement tests. At both time points in the U.S. data, parents rated the children's behavior problems. Children whose parents divorced or separated between the two time points were compared to children whose families remained intact. For boys, the apparent effect of separation or divorce on behavior problems and achievement at the later time point was sharply reduced by considering behavior problems, achievement levels, and family difficulties that were present at the earlier time point, before any of the families had broken up. For girls, the reduction in the apparent effect of divorce occurred to a lesser but still noticeable extent once preexisting conditions were considered.     

红火蚁的入侵、扩散、生物学及其危害

2005年1月，我国广东省吴川市等地发现红火蚁入侵后，广东省率先采取了应急防治措施，启动红火蚁防治应急议案，而作为广东省红火蚁防控专家组成员的广东省农业科学院植物保护研究所，在积极参加广东省红火蚁的疫情普查及封锁控制扑灭工作的同时，承担了广东省重大科技专项、广东省社会发展攻关项目以及广东省红火蚁防控技术研究项目等课题，开展了大量有关红火蚁发生、扩散和防控技术的研究。现将该项目近期取得的部分研究进展和有关红火蚁生物学、化学防治和生物防治的综述文章在本刊2006年第5期发表，为我国红火蚁的检疫和防控提供重要的技术内容和研究参考。[编者按]     

Transmission dynamics of the etiological agent of SARS in Hong Kong: impact of public health interventions

We present an analysis of the first 10 weeks of the severe acute respiratory syndrome (SARS) epidemic in Hong Kong. The epidemic to date has been characterized by two large clusters-initiated by two separate "super-spread" events (SSEs)-and by ongoing community transmission. By fitting a stochastic model to data on 1512 cases, including these clusters, we show that the etiological agent of SARS is moderately transmissible. Excluding SSEs, we estimate that 2.7 secondary infections were generated per case on average at the start of the epidemic, with a substantial contribution from hospital transmission. Transmission rates fell during the epidemic, primarily as a result of reductions in population contact rates and improved hospital infection control, but also because of more rapid hospital attendance by symptomatic individuals. As a result, the epidemic is now in decline, although continued vigilance is necessary for this to be maintained. Restrictions on longer range population movement are shown to be a potentially useful additional control measure in some contexts. We estimate that most currently infected persons are now hospitalized, which highlights the importance of control of nosocomial transmission.     

鸡组织滴虫病的流行特点与防治

鸡组织滴虫病又称盲肠性肝炎或叫黑头病,是由单鞭毛科、组织滴虫属(Histomouas)的火鸡组织滴虫(H.meleagriidis)寄生于禽类盲肠和肝脏内而引起的一种原虫病。近年来,鸡组织滴虫病在河南各地农村及一些养鸡厂时有发生和流行,严重影响养鸡业的持续发展。根据该病流行情况及病理表现,采用中西药结合的防治办法,取得了较好的效果。1发病机理及症状鸡感染组织滴虫后的发病率和死亡率均很高。组织滴虫虫体在鸡盲肠内进行无性繁殖产生大量的组织滴虫,使盲肠细胞遭到大量破坏,溶解、脱落,鸡出现下痢,排淡黄色或深绿色粪便,严重时粪中带血及脱落的组…     

对英国工业革命时期工人工作状况的认识——马克思与雷恩的观点比较

全面比较了马克思与雷恩对英国工业革命时期工人工作状况的论述,找出了二者的差异和相通之处,并指出这段历史对我国转型期二元经济社会的人力资本配置制度变迁的启示。     

我国粮食生产格局演变下的粮地匹配

为系统把握我国粮食生产格局演变及在当前生产格局下粮地匹配特征,基于GIS地理信息系统、基尼系数和不平衡指数,通过分析2003—2019年全国31省（统计数据未含港、澳、台地区,下同）粮食生产数据,系统分析了粮食生产空间格局演变趋势和资源匹配程度,结果表明：稻谷和玉米种植逐渐向东北方向偏移,小麦种植逐渐向西北偏移;黑龙江和内蒙古等主产区在土地资源利用上不充分,导致土地生产效率低于全国平均水平,而河南和河北的粮食生产发展速度超过土地资源开发速度,耕地压力巨大。从发展趋势来看,人地矛盾、政策影响等因素将进一步加剧土地资源压力,对粮食生产和土地资源匹配形成更大挑战。因此提出相应对策建议需要统筹协调,避免粗放式发展经营,缓解高土地资源压力产区的生产压力,丰富种植结构,实现粮食生产与土地资源的匹配。     

刍议心理契约构建与图书馆人力资源管理

从心理契约的概念入手,分析了心理契约在图书馆人力资源管理中的作用和意义,并进一步探讨了图书馆人力资源管理中心理契约的构建和维护。     

从英美硕士点和系名称院看图书馆的学科现状

本文介绍了美国和英国的图书馆学硕士点设置,描述了该学科在两国的院系归属情况,比较了图书馆学的不同英文名称,分析了名称不统一的原因和所反映出来的对学科的认识现状。     

Cloned viral protein vaccine for foot-and-mouth disease: responses in cattle and swine

A DNA sequence coding for the immunogenic capsid protein VP3 of foot-and-mouth disease virus A12, prepared from the virion RNA, was ligated to a plasmid designed to express a chimeric protein from the Escherichia coli tryptophan promoter-operator system. When Escherichia coli transformed with this plasmid was grown in tryptophan-depleted media, approximately 17 percent of the total cellular protein was found to be an insoluble and stable chimeric protein. The purified chimeric protein competed equally on a molar basis with VP3 for specific antibodies to foot-and-mouth disease virus. When inoculated into six cattle and two swine, this protein elicited high levels of neutralizing antibody and protection against challenge with foot-and-mouth disease virus.     

基督教的起源及在我国迅速传播的原因

在我们的教育里,从来没有谈到神在我们生活中的地位问题,即使有也只是批判,或者视为愚昧的表现。那么,为什么现在越来越多的人会去信仰耶酥基督呢,且还是源于西方的神?究其原因,主要有两点:一是基督教本身具有向外扩张、传播的因素;二是普通民众因文化素质偏低,导致对该教的认识肤浅。     

The impact of structural genomics: expectations and outcomes

Structural genomics (SG) projects aim to expand our structural knowledge of biological macromolecules while lowering the average costs of structure determination. We quantitatively analyzed the novelty, cost, and impact of structures solved by SG centers, and we contrast these results with traditional structural biology. The first structure identified in a protein family enables inference of the fold and of ancient relationships to other proteins; in the year ending 31 January 2005, about half of such structures were solved at a SG center rather than in a traditional laboratory. Furthermore, the cost of solving a structure at the most efficient SG center in the United States has dropped to one-quarter of the estimated cost of solving a structure by traditional methods. However, the efficiency of the top structural biology laboratories-even though they work on very challenging structures-is comparable to that of SG centers; moreover, traditional structural biology papers are cited significantly more often, suggesting greater current impact.     

海南热带雨林国家公园道路分布及其对景观完整性的影响

为揭示高速公路、国道、省道等不同类型道路对海南热带雨林国家公园生态系统完整性和景观格局的影响,选取2000、2010和2019年海南热带雨林国家公园涉及的道路分布和土地利用数据,运用缓冲区分析法获取不同等级道路两侧的景观变化趋势。结果表明:(1) 2000—2019年,海南热带雨林国家公园内道路长度增加2 134.6 km,道路密度增加了0.500 km·km?2。2010年,乡道及以下道路长度增加2 030 km;2019年,新增高速公路,省道310升级为国道361。(2) 高速公路、国道、省道两侧的斑块密度指数及景观形状指数分别在0～500 、0～300和0～250 m范围呈下降趋势,随后趋向于平缓,聚集度指数则表现相反;高速公路、国道、省道的最大影响范围分别为500 、300和250 m。(3) 2000—2019年,道路影响范围内的耕地、有林地、草地、疏林地面积减少,其中高速公路、省道附近的有林地、草地面积降幅最大,国道附近的耕地面积降幅最大;水域、灌木林、建设用地、其他林地(含果园)面积增加,高速公路、国道、省道周边的其他林地(含果园)面积增幅最大。(4) 道路影响范围内,景观形状指数、斑块密度指数和分离度指数略有增加,蔓延度指数则稍有下降;目前道路对国家公园景观的影响较小,但由于道路存在较明显的累加效应及传播作用,仍然需要注意道路对国家公园生态系统原真性和完整性的可能影响,建议加强大型道路如高速公路道路径流的汇流与净化、道路两侧生态廊道、长期环境监测等方面的研究。     

美、英两国土壤污染防治立法及其对我国的借鉴

土壤污染已成为世界环境问题。随着我国经济社会的快速发展,土壤污染问题也日趋严重。美国和英国在土壤污染防治立法方面有许多值得肯定之处,我国应借鉴美英国家立法经验,对我国土壤污染防治立法进行完善。     

发达国家创意农业发展内在机理研究——以荷兰、日本、德国、英国为例

创意农业是当今世界农业发展的新业态。发达国家率先发展创意农业且成效显著。创意产业经济学、文化经济学及体验经济学是创意农业赖以依存的重要理论基础,本文选择上述3种经济学的理论视角,深入研究发达国家创意农业发展的内在机理。在此基础上,以荷、日、德、英4国为例,分别就其创意经济环境、文化经济环境及体验经济环境进行分析,以期在实践上进一步证明创意农业与这3种经济学理论之间的紧密联系,对促进中国创意农业的快速发展具有积极的理论意义和现实价值。