Spatial effects in social dilemmas

Social dilemmas and the evolutionary conundrum of cooperation are traditionally studied through various kinds of game theoretical models such as the prisoner's dilemma, public goods games, snowdrift games or by-product mutualism. All of them exemplify situations which are characterized by different degrees of conflicting interests between the individuals and the community. In groups of interacting individuals, cooperators produce a common good benefitting the entire group at some cost to themselves, whereas defectors attempt to exploit the resource by avoiding the costly contributions. Based on synergistic or discounted accumulation of cooperative benefits a unifying theoretical framework was recently introduced that encompasses all games that have traditionally been studied separately (Hauert, Michor, Nowak, Doebeli, 2005. Synergy and discounting of cooperation in social dilemmas. J. Theor. Biol., in press.). Within this framework we investigate the effects of spatial structure with limited local interactions on the evolutionary fate of cooperators and defectors. The quantitative effects of space turn out to be quite sensitive to the underlying microscopic update mechanisms but, more general, we demonstrate that in prisoner's dilemma type interactions spatial structure benefits cooperation-although the parameter range is quite limited-whereas in snowdrift type interactions spatial structure may be beneficial too, but often turns out to be detrimental to cooperation.     

女性体检人群生殖道病原体的分布

目的了解体检妇女人群生殖道感染情况,为女性生殖道感染的防治提供进一步的资料。方法对1157例参加健康体检的妇女的阴道后穹窿及宫颈分泌物标本进行显微镜镜检以检测阴道清洁度、真菌、滴虫等,同时采用培养法对淋球菌、解脲支原体、人型支原体、真菌等进行检测,沙眼衣原体则采用免疫层析法;检测结果进行统计学分析。结果女性生殖道感染的感染率为54.0%,其中混合感染率为9.3%,而清洁度异常率仅为23.8%;前3位病原体依次为解脲支原体(35.3%)、衣原体(22.2%)、真菌(5.5%);年轻妇女组与年老组支原体的检出率差异有显著性(P<0.05)。结论女性生殖道感染情况严重,支原体、衣原体等感染隐匿,加强对育龄妇女的监测尤为重要。     

Making Science Accessible: A Semiotics of Scientific Communication

This article serves as a demonstration of how certain models of literary analysis, used to theorize and analyze fiction and narrative, can also be applied to scientific communication in such a manner as to promote the accessibility of science to the general public and a greater awareness of the methodology used in making scientific discovery. The approach of this article is based on the assumption that the principles of structuralism and semiotics can provide plausible explanations for the divide between the reception of science and literature. We provide a semiotic analysis of a scientific article that has had significant impact in the field of molecular biology with profound medical implications. Furthermore, we show how the structural and semiotic characteristics of literary texts are also evident in the scientific papers, and we address how these characteristics can be applied to scientific prose in order to propose a model of scientific communication that reaches the public. By applying this theoretical framework to the analysis of both scientific and literary communication, we establish parallels between primary scientific texts and literary prose.     

双低菜粕高水平替代饲料鱼粉对大黄鱼潜在风险的评估:生长、健康和营养价值

研究从生长、健康和营养价值方面评估了高水平的双低菜粕替代饲料鱼粉对大黄鱼潜在的危害。在鱼粉含量60%的基础饲料（FM）上按照质量分数用双低菜粕分别替代15%（CM15）、30%（CM30）、60%（CM60）和100%（CM100）的鱼粉,配制成5种实验饲料。每种饲料投喂5个网箱的大黄鱼[初重（135.38±1.02）g],即每个处理5个重复,进行12周的养殖实验。结果表明,当双低菜粕替代水平在15%和30%时,大黄鱼的生长及饲料系数并没有受到显著性的影响。然而,当替代水平高于30%时,大黄鱼的末重和特定生长率均显著降低,而饲料系数显著升高（P < 0.05）。当替代水平达到100%时,大黄鱼摄食率达到最高值而肥满度达到最低值（P < 0.05）。在组织形态方面,大黄鱼摄食双低菜粕替代的饲料后肠道绒毛的弯曲程度减少并且排列更加不规则,而肝细胞则呈现出圆形空泡状并伴随着细胞核的偏移。对大黄鱼骨骼进行X-射线扫描发现,摄食双低菜粕的大黄鱼椎体和头部出现了畸形。在营养价值方面,双低菜粕替代鱼粉并未显著影响大黄鱼背肌的脂肪含量、蛋白含量和氨基酸组成,然而脂肪酸组成受到了显著影响,即N-6系列脂肪酸含量显著升高,而DHA与EPA含量显著降低（P < 0.05）。根据欧洲食品安全局（EFSA）的相关标准,这些营养价值的变化并没有影响大黄鱼作为健康食品的功能。由此可见,高水平（60%和100%）的双低菜粕替代鱼粉对大黄鱼的负面影响主要表现为降低大黄鱼的生长性能、改变肠道和肝脏组织形态,以及影响大黄鱼的骨骼健康。然而,双低菜粕替代鱼粉养殖大黄鱼的肌肉仍然符合人类的膳食要求。因此,双低菜粕替代鱼粉并没有影响大黄鱼作为食用鱼的营养价值。     

Studies on methemoglobin reductase. Immunochemical similarity of soluble methemoglobin reductase and cytochrome b5 of human erythrocytes with NADH-cytochrome b5 reductase and cytochrome b5 of rat liver microsomes.

An antibody preparation elicited against purified, lysosomal-solubilized NADH-cytochrome b₅ reductase from rat liver microsomes was shown to interact with methemoglobin reductase of human erythrocytes by inhibiting the rate of erythrocyte cytochrome b₅ reduction by NADH. The ferricyanide reductase activity of the enzyme was not inhibited by the antibody, suggesting that the inhibition of methemoglobin reductase activity may be due to interference with the binding of cytochrorme b₅ to the flavoprotein. Under conditions of limiting concentrations of flavoprotein, the antibody inhibited the rate of methemoglobin reduction in a reconstituted system consisting of homogeneous methemoglobin reductase and cytochrome b₅ from human erythrocytes. This inhibition was due to the decreased level of reduced cytochrome b₅ during the steady state of methemoglobin reduction while the rate of methemoglobin reduction per reduced cytochrome b₅ stayed constant, suggesting that the enzyme was not concerned with an electron transport between the reduced cytochrome b₅ and methemoglobin.An antibody to purified, trypsin-solubilized cytochrome b₅ from rat liver microsomes was shown to inhibit erythrocyte cytochrome b₅ reduction by methemoglobin reductase and NADH to a lesser extent than microsomal cytochrome b₅ preparations from rat liver (trypsin solubilized or detergent solubilized) and pig liver (trypsin solubilized). The results presented establish that soluble methemoglobin reductase and cytochrome b₅ of human erythrocytes are immunochemically similar to NADH-cytochrome b₅ reductase and cytochrome b₅ of liver microsomes, respectively.     

Inhibition of macrophage DNA synthesis by immunomodulators. II. Characterization of the suppression by muramyl dipeptide or lipopolysaccharide [3H]thymidine incorporation into macrophages

Guinea pig peritoneal exudate macrophages actively incorporated [3H]thymidine into trichloroacetic acid-insoluble fraction in vitro. The incorporation of [3H]thymidine was almost completely inhibited by aphidicolin, an inhibitor of DNA polymerase alpha and an autoradiograph showed heavy labeling in nuclei of 15% of macrophage populations. These results indicate that the observed thymidine incorporation was due to a nuclear DNA synthesis. The [3H]thymidine incorporation was markedly suppressed when macrophages were activated by immunoadjuvants such as muramyl dipeptide (MDP) or bacterial lipopolysaccharide (LPS). The suppression of [3H]thymidine incorporation by MDP was neither due to the decrease in thymidine transport through the cell membrane, nor due to dilution by newly synthesized "cold" thymidine. An autoradiograph revealed that MDP markedly decreased the number of macrophages the nuclei of which were labeled by [3H]thymidine. These results suggest that the suppression of [3H]thymidine incorporation by the immunoadjuvants reflects a true inhibition of DNA synthesis. The inhibition of DNA synthesis by MDP was also observed in vivo. Further, it was strongly suggested that the inhibition was not caused by some mediators, such as prostaglandin E2, released from macrophages stimulated by the immunoadjuvants but caused by a direct triggering of the adjuvants at least at the early stage of activation. Cyclic AMP appears to be involved in the inhibitory reaction.     

草地农业生态学研究进展与趋势

阐述了草地农业生态学的内涵,发展过程,前沿领域和发展趋势,草地农业生态系统的界面理论,结构与功能,系统耦合与系统相悖以及系统健康评价是该学科的4个前沿领域,草地农业生态系统存在3个基本界面,即草丛-地境,草地-动物以及草畜生产-经营管理界面,研究发生于各个界面的一系列生态学过程,是揭示系统行为特征的关键,草地农业生态系统有4个生产层,即前植物,植物,动物和外生物生产层,系统耦合与系统相悖是生产层之间互作的2个重要概念,不同生产层之间的系统耦合,可产生系统进化,多方面释放系统潜势,生态系统健康水平是其结构和功能的反映,健康评价是对其有序度和服务价值的度量。     

放牧草地健康管理的生理指标

依据草地对席子和牧的生理响应,用牧草生理低限（PLL）,生理上限（PUL）和再生长期（R期）长度/放牧期（G期）长度的比值（R/G）等指标。构建了放牧草地健康评价的生理阈限双因子法,并以光合作用及其相关参数分析了多年生黑麦草轮牧草地的健康指标。维持草地适宜的双因子生理阈限的R/G比值,旨在放牧后草地功能与健康的完全恢复,是放牧草地可持续经营的目标。