First fossil lamprey: a record from the Pennsylvanian of Illinois

A fossil record of lampreys has previously been unknown. A new genus demonstrates the presence of this group in the Pennsylvanian. The body outline, parts of the head skeleton, rasping tongue mechanism, gill basket, and other internal organs are preserved. The fossils are very similar in structure to modern forms. The absence of hagfish characters in the fossil supports the view that the common ancestor of lampreys and hagfishes lived prior to the Pennsylvanian.     

Multiple gene loci for the monomeric hemoglobin of the hagfish (Eptatretus stoutii)

The fact that members of the subclass Cyclotomata possess monomeric hemoglobin molecules has been known for some time. Electrophoresis of hemolysates from 12 hagfish (Eptatretus stoutii) revealed five hemoglobin phenotypes with four to six distinct zones of hemoglobin. Each zone is believed to represent a monomer containing one heme group on a single polypeptide chain with a molecular weight of approximately 18,000. It is postulated that these monomers are controlled by genes at four loci.     

Absence or singular specificity of carotenoids in some lower fishes

No colored carotenoids were recovered from the scales or liver of the coelacanth, Latimeria chalumnae, or from skin, immature eggs, or liver of the Pacific hagfish, Eptatretus stoutii. Zeaxanthin, present as esters in the skin and largely unesterified in the liver, was the only carotenoid identified in the thornback ray, Platyrhinoidis triseriata, and in the horned shark, Heterodontus francisci, whereas the skin of the Pacific mako shark, Isurus glaucus, yielded no carotenoids.     

Threads in the hagfish slime gland thread cells: organization, biochemical features, and length

Scanning electron microscopy in conjunction with cell isolation procedures revealed details of the packing of threads in hagfish slime gland thread cells. Biochemical studies indicate that the thread is largely composed of a protein subunit with a molecular weight of 63,500. Mathematical calculations suggest that the thread may attain lengths of 60 centimeters or more.     

Genetic control of lactate dehydrogenase formation in the hagfish Eptatretus stoutii

The isozyme patterns of lactate dehydrogenases of various tissues were studied on 51 hagfish by starch-gel electrophoresis. Nine lactate dehydrogenase phenotypes were encountered, suggesting the coexistence of two alleles at each of the two separate gene loci. There apparently was no interaction between the products of these two separate loci. Even the products of two alleles at the same locus were apparently incapable of forming hybrid molecules, an indication of the possible monomeric nature of each lactate dehydrogenase molecule.     

解读影视同期书,探寻读者需求

随着影视剧的热播和影视同期书的出现,为文学界注入了新鲜的血液,同时也使图书馆拥有了一批新的读者群,文章从这一角度对读者的需求作一简单的探讨。     

新生代农民工创业SWOT分析

通过对新生代农民年龄、性别、婚姻状况等7个方面的分析,对新老两生代农民工进行了界定。针对新生代农民工这一新群体,运用SWOT分析方法对新生代农民工创业进行研究,结果表明,新生代农民工具有较高的文化教育程度、较好的社会文化成长环境以及当前国家良好的制度及政策等优势和机会,同时也存在创业竞争力薄弱、两重身份边缘化、创业融资困难等劣势和威胁;针对新生代农民工创业过程中存在的问题,提出了应对当前新生代农民工创业采取的战略,以期能为更好地促进新形势下新生代农民工创业提供指导。     

新生代农民工创业资源禀赋对创业机会的影响

新生代农民工创业带来了显著的经济、社会效益,其所具有的资源禀赋是创业行为过程中的关键要素,对创业机会的识别有着十分重要的影响。基于广东省202个新生代农民工创业的调查数据,从人力资本、社会资本以及经济资本3个维度构建了新生代农民工的资源禀赋,建立其对创业机会识别以及创新水平影响的结构方程模型,并进行实证探讨。结果表明：新生代农民工的创业素质较高,资源禀赋对创业机会整体上有着促进和提高的作用,其中人力资本和社会资本对新生代农民工识别创业机会有明显的促进作用,而经济资本对新生代农民工识别创业机会的解释能力较差,这可能与新生代农民工群体的特殊性有一定的关联性。从资源禀赋的新视角探求其对创业机会的影响机理对政府制定鼓励农民创业的政策有着重要的借鉴意义。     

为什么女孩有闺密而男孩偏好竞争?

<正>女孩子往往都有"一对一"的闺蜜,而男孩则更倾向于拉帮结派并和其他同性进行竞争。到底什么导致了这种性别上的差异?最近的一项研究通过一种新的核磁共振成像的方法,以儿童为研究对象,对此做出了解释。该研究由美国国家心理健康研究所与佐治亚州州立大学共同主导。研究结果表明,女孩儿从青春期早期到晚期的发     

Wallace h. Carothers and fundamental research at du pont

In the Depression decade, the research group headed by Wallace H. Carothers made two discoveries-neoprene and nylon-that have had an enormous impact on E. I. du Pont de Nemours and industrial research generally. At the same time, Carothers's many publications helped establish the foundations of polymer science. A theoretical organic chemist, he left Harvard University to take part in Du Pont's new fundamental research program. Although founded on the academic model, it soon began to reflect its industrial setting. Some surprising experimental results, the research philosophy of a new research director, and the economic realities of the Great Depression pushed Du Pont's pure scientists toward more practical or mission-oriented goals. Nylon and neoprene emerged from this creative tension between chemists interested in science and management committed to innovation.     

论农民工向产业工人的转化

农民工是在我国经济社会转型时期,农村人口城镇化进程中出现的新型社会群体。经过多年市场经济的磨炼,农民工从整体上已具备中国产业工人的基本特征,是当代中国工人阶级的重要组成部分。在中国这样一个农民大国,要全面建设小康社会,推动社会主义新农村建设,应大力促进农民工向产业工人的深度转化,从本质与表征上将农民工融入中国工人阶级队伍。     

国内外苜蓿种质起始密码子遗传多样性分析

为了对新引进的苜蓿种质亲缘关系进行鉴定,采用起始密码子多态性(SCo T)标记对19份国内外苜蓿种质的分子遗传多样性进行分析。结果显示,14个SCo T引物在供试苜蓿材料中共获得有效扩增条带78个,其中多态性条带72个,多态性条带百分比为92.31%;SCo T引物的有效等位基因数、Nei’s基因多样性指数、Shannon’s信息指数和多态性信息含量平均分别为1.53、0.31、0.46和0.31;供试苜蓿材料间的遗传相似系数介于0.385~0.846,平均为0.657,表明供试苜蓿材料遗传多样性较丰富;聚类分析和主成分分析均表明,供试材料可被划分为2大类,第1类群包括的苜蓿种质数达到16个,占到所有供试苜蓿种质总数的84.21%,第2类群包含的苜蓿种质数只有3个。综合分析表明,新引进的19份苜蓿种质具有较丰富的遗传多样性,其在未来苜蓿育种中具有较好的应用前景。     

丹参渣对肥育猪生产性能的影响

为开发利用新的非常规饲料资源,进行了丹参渣饲喂肥育猪试验。结果表明,饲喂含5%丹参渣日粮的肥育猪,平均日采食量与饲喂常规日粮的对照组相同,平均日增重仅比对照组降低2.15%,料重比高于对照组日粮的2.48%,说明在日粮中添加一定比例丹参渣不会明显影响肥育猪的生产性能,较适合作为肥育猪饲料使用。     

油棕新品种遗传多样性的ISSR分析(摘要)(英文)

[目的]从DNA分子水平上对油棕新品种进行遗传多样性的分析,旨在为这些新选育油棕种质的开发利用提供分子水平的理论依据。[方法]采用改良的CTAB法提取油棕叶片总DNA。从加拿大哥伦比亚大学所设计的60个引物在部分模板中进行筛选,筛选出能扩增出多态性的引物23个用于样品的进一步分析。通过一定的摸索实验,最终确定用于油棕的各个组分的ISSR最佳反应体系。优化反应体系总体积为15.00μl,各个组分的具体用量为:MgCl2(25mmol/L)+10×Buffer2.25μl、dNTP(10mmol/L)0.30μl、Taq酶(5U/μl)0.15μl、引物(0.4μmol/μl)1.00μl、模板DNA(50ng/μl)1.00μl、ddH2O(超纯水)10.30μl。PCR扩增程序为:94℃预变性4min,然后94℃变性1min,52℃退火1min,72℃延伸1min,35个循环,72℃保温10min,4℃保温。采用2%琼脂糖凝胶电泳,EB染色检测扩增产物。ISSR数据的统计分析方法:每个样品的扩增产物电泳分离谱带在某一位点上按有或无记录,存在时赋值为"1",无带的记为"0"。将每个引物对所有样品的读带记录结果形成"0-1"矩阵。用NTSYS-pcversion2.1计算Jaccard’s相似系数,在此基础上用非加权类平均聚类法(UPGMA)进行聚类分析,绘制亲缘关系树状图。[结果]用23个引物共扩增得到201条扩增条带,其中多态性条带占41.8%。根据ISSR遗传相似系数按UPGMA法聚类,以所有材料间的平均遗传相似系数0.838为阈值,可将其明显的划分为2大类:采自海南的R1～R12新种质材料与采自云南的V20新种质材料合为一类;采自云南其余的新种质材料为一类。用NTSYS-pc软件所得出的主成分分析图也能够明显的将海南和云南引进的新油棕种质材料区分开来,海南的R1～R12油棕与云南的V20油棕基本上归为一类;与聚类图不同的是,云南的新油棕种质V15、V16、V17、V19、V21、V22基本上归为一类,而品种V13、V14与V18则较远一些。[结论]海南与云南新选育的油棕种质材料可能来源于不同的国家或地区。     

玉米赤霉烯酮吸附剂对后备母猪子宫中LC3、PCNA分布和表达的影响

【目的】已有研究证实玉米赤霉烯酮（ZEA）在动物体内可通过雌激素受体激活雌激素敏感基因,产生生殖毒性,影响子宫内膜细胞的生长、卵母细胞的成熟及卵泡颗粒细胞的增殖。探讨玉米赤霉烯酮吸附剂（沸石+蒙脱石等复合制剂）对后备母猪子宫的LC3与PCNA的分布和蛋白表达量的影响, 从组织化学角度探讨该ZEA新型吸附剂的脱毒效果。【方法】选择体重30±2.11kg左右的（杜×长×大）健康三元杂交后备母猪48头,随机分为 6 组,每组8头,对照组饲喂基础饲粮、玉米赤霉烯酮组（ZEA）饲喂含有1.008 mg·kg^-1玉米赤霉烯酮的饲粮、0.1%新型吸附剂组（ZEA0.1）饲喂含有1.0 g·kg^-1吸附剂的ZEA组日粮、0.25%新型吸附剂组（ZEA0.25）饲喂含有2.5 g·kg^-1吸附剂的ZEA组日粮、0.5%吸附剂组（ZEA0.5）饲喂含有5.0 g·kg^-1吸附剂的ZEA组日粮、蒙脱石组（ZEA-M）饲喂含有2.5 g·kg^-1蒙脱石的ZEA组日粮。预试期 7 d,正试期21 d,试验结束进行屠宰取样。【结果】ZEA引起子宫器官指数增加,添加0.25%与0.5%新型吸附剂降低子宫器官指数效果明显。免疫组化结果显示子宫中 LC3 和PCNA阳性细胞主要分布在子宫腺上皮细胞内,腔上皮细胞的LC3免疫阳性反应弱于腺上皮细胞。LC3阳性反应在对照组的子宫腺上皮细胞和腔上皮细胞胞质内呈强阳性表达;ZEA组明显弱于对照组,新型吸附剂组的LC3的免疫阳性反应及阳性细胞数量明显较ZEA组增加,且有剂量依赖趋势,但ZEA-M组效果不明显,略多于ZEA组。各组的子宫腔上皮和腺上皮中PCNA的观察结果与LC3变化趋势相反。WB和qRT-PCR结果也显示添加0.25%与0.5%新型吸附剂可促进LC3的表达,增强了自噬,降低了PCNA表达。这些结果提示ZEA抑制了LC3的表达,抑制细胞自噬,破坏子宫内膜细胞和腺上皮细胞的稳态。但新型吸附剂使LC3蛋白表达上调,PCNA表达降低,可以促进细胞自噬,并抵抗由ZEA引起的子宫内膜细胞异常增殖（PCNA表达增加）,通过双向调节对细胞起到很好的保护作用。该结果为新型吸附剂的应用提供了理论依据。【结论】本试验条件下,ZEA可引起后备母猪子宫发生增殖反应,新型吸附剂一定限度内能够对抗ZEA对子宫正常生理机能的副作用。以添加0.25%与0.5%剂量的新型吸附剂较为合适。     

农业高校图书馆与新农人合作共赢运行模式研究

新农人群体作为我国农村发展中的一支新的生力军,正迅速出现在人们的视野中。新农人自身具备的较高文化素质,以互联网为工具,营销创新思维都是农村发展形式中前所未有的。农业高校图书馆作为传播农业科技文化信息的重要场所,必然与新农人群体产生一定的联系。本文通过对新农人群体及其特征的分析,提出农业高校图书馆服务新农人的合作共赢模式,即由新农人参与的"冠名一捐赠"、"跨界合作营销"运行新模式。     

Information functions of an international meeting

In spite of a number of difficulties and shortcomings, this international meeting was relatively effective for this group of respondents. They benefitted from the informal interaction of participants, from information that pertained to current and planned work, and from the prospects of continued exchange with colleagues in other countries. That the meeting could have been even more valuable was also the consensus. Additional data on another such meeting reinforce these findings and suggest that the results obtained are probably not peculiar to one social science or to this specific meeting. Reports of a small group of sociologists, who received grants from the National Institute of Mental Health to attend the Sixth World Congress of Sociology at Evian in September 1966, showed marked concurrence with those of the psychologists who attended the Moscow congress. For both groups there was the same preponderence of United States and Russian presentations on the program, informal interaction was more productive of useful information than were formally scheduled events, and the main type of information obtained was a broader knowledge of research activity and effort in various countries. The sociologists emphasized even more than did the psychologists the importance of acquiring new points of view and perspectives. More than half the sociologists planned to use information obtained in their current or future work, and a fourth planned international collaborative research efforts; in both these respects they surpassed the percentages found in the data on the psychologists. Finally, all the criticisms voiced by Moscow respondents appeared also among the Evian group, though not in sufficient numbers to constitute a trend. These data suggest that international meetings can and do fill certain information needs in spite of organizational difficulties and the problems attendant upon any large gathering in an environment unfamiliar to most of those who participate.     

基于用户分群的数字社区消费者多模态特征分析与服务效能提升研究

[目的/意义]对数字社区消费者进行多模态特征分析与服务效能提升，有助于为数智赋能在线社区建设提供新视野、为相关部门部署数字决策提供新动能。[方法/过程]结合社区特性构建用于消费者分群的数据维度，将维度下的24个指标数据进行二次聚合后实现分群，并构造参数、决策变量及函数表，从而分析消费者多模态特征，基于这些特征实现数字消费服务效能的提升。[结果/结论]实证分析结果表明，本文模型能够生成合理有效的分群结果，进而实现类群特征区分以及群间渗透与漂移现象分析；分群结果呈现出6类消费者群体：重点、中心、特殊、沉睡、流失和一般类群，绝大多数类群都会产生用户渗透现象，仅有一般用户类群会发生群间漂移现象；服务效能提升模型表明最受关注价值的群体为中心和重点类群。     

中国大陆淡水真菌研究

对淡水生真菌类群在中国大陆的分类学和生态学研究进行了回顾，同时对该类群应用方面的研究进行阐述。自从20世纪80年代初期该研究在我国大陆开展以来，许多淡水生卵菌、壶菌、子囊菌和半知菌类等的新种和新记录相继被报道于北京、安徽、四川和云南等地。在生态学方面，围绕着温度、季节、地理、污染和着生基质与淡水生真菌关系的研究也逐步展开。目前对于淡水生真菌的应用研究集中于胞外酶对木质素类的分解的研究和真菌毒素对线虫毒杀作用的探索。作为对于淡水环境中分解者的重要一员，淡水生真菌是一类与人类生活息息相关的珍贵生物资源，在环境指、污染处理、新功能结构化合物以及生物防治等方面的研究前景广阔。     

基于近红外光谱与DPLS的潲水油快速鉴别方法

潲水油回流餐桌等食品安全问题越来越受到社会关注,探寻准确、快速、简便、高效且成本低廉的潲水油鉴别新方法成为食用油安全性能检测的新要求.对收集的82份潲水油和合格食用油样品进行了理化检测,鉴别出潲水油样品37份,合格油样品45份.从82份样品中随机选出24份样品作为第一组,余下58份样品作为第二组,以第一组24份样品作为校正集,建立判别偏最小二乘法(DPLS)模型,鉴别第二组58份样品,总体鉴别正确率为86.21%;再以第二组58份样品作为校正集,建立DPLS模型,鉴别第一组24份样品,总体鉴别正确率为95.83%.研究表明,基于近红外光谱与DPLS的潲水油快速鉴别方法可行,具有较好的鉴别效果.