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121.
122.
Antioxidant survey to assess antagonism to redox stress using a prokaryotic and an eukaryotic system
H. Baker B. DeAngelis O. Frank M. Khalil S. H. Hutner E. R. Baker 《Cellular and molecular life sciences : CMLS》1996,52(6):597-599
Using a prokaryote (Escherichia coli) and a metazoa-resembling eukaryote (Ochromonas danica), we surveyed antioxidants which might overcome redox stress imposed by menadione sodium bisulphite (MD) and buthionine sulphoximine (BSO). BSO oxidant stress was evident only inO. danica; MD oxidant stress was evident in both organisms. Glutathione, its precursors, e.g. cysteine, homocysteine, and 2-oxo-4-thiazolidine carboxylic acid, and red blood cells, emerged as prime antioxidants for relieving BSO and MD oxidant stress. BSO and MD oxidant activity and antioxidant-annulling effect inO. danica were judged comparable to those found in animal cells whereas the resultsE. coli were not entirely equivalent. TheO. danica system emerged as a practical, rapid, and useful system for pinpointing oxidant stressors and antioxidants, and shows promise for studies with mammalian systems. 相似文献
123.
Associations with ants, termed myrmecophily, are widespread in the butterfly family Lycaenidae and range from mere co-existence to more or less specific mutualistic or even parasitic interactions. Secretions of specialized epidermal glands are crucial for mediating the interactions. Transfer of nutrients (carbohydrates, amino acids) from butterfly larvae to ants plays a major role, but manipulative communication with the help of odour signals is also involved. By means of myrmecophily, lycaenid butterflies largely escape ant predation, and certain species gain protection through attendant ants or achieve developmental benefits from ant-attendance. Benefits to the ants range from minimal to substantial food rewards. While most lycaenid species maintain facultative relationships with a variety of ant genera, highly specific and obligatory associations have convergently evolved in a number of butterfly lineages. As a corollary, communication systems are largely unspecific in the former, but may be highly specialized in the latter. The sophisticated communication between obligate myrmecophiles and their host ants is tightly connected with the evolutionary rise of specialized life-cycles and thus is a source of augmenting diversity within the butterflies. 相似文献
124.
上个世纪的亚洲美学家们往往依据西方美学传统的基本模式来考察各种美学问题;但实际上,亚洲各国也有自己的与西方不同的美学传统。通过对中西美学传统的比较性考察,探讨中国美学在21世纪人类美学的总体发展中所具有的世界性意义。从中国美学的视点看,美不仅在人与审美对象的关系中具有单纯审美的意义,而且更在人的存在自身中具有形而上的意义;人不仅是审美对象和艺术作品的创造者,而且首先是人自身美的存在的创造者。事实上,只有当人自身的存在首先在形而上的意义上达到了美的层面时,人才有可能一方面在外部世界中创造出审美的对象,另一方面在内心世界中形成审美的心理。中国美学的这一洞见无疑能够大大扩展21世纪人类美学的理论视界和研究内容,使其超出西方美学传统的有限观念,甚至将其提升到人的存在的形而上层面,从而使其对人类的进步发展做出更大的贡献。 相似文献
125.
太平沟大桥曲线箱梁顶推施工设计概述 总被引:1,自引:0,他引:1
闫波 《科技情报开发与经济》2004,14(6):276-277
太平沟大桥该桥全长358.8m,平面位于R=1380.965m圆曲线及L5=300m的缓和曲线上,是国内曲线连续顶推桥长最长、跨径最大的一座桥。详细介绍了太平沟大桥曲线箱梁顶推设计特点及施工设计要点。 相似文献
126.
B. Ducarme 《科学通报(英文版)》2004,49(11)
Before about 100 years, the layered structures of the Earths body and the existence of the liquid core had been found, then the solid inner core and detailed structures in the interior of the Earth are demonstrated, it proves that the satisfied achievements had been obtained in recogni-tion of the Earths interior structures. In recent years, with the increasing requirements of the basic sciences and space techniques to geodynamics of the Earths interior, the theoretical study and practical de… 相似文献
127.
目前,高分辨率遥感图象正愈来愈多地应用于土地与水资源的监测和管理,其中,IKONOS图象数据因其具有较高的空间分辨率和人机交互的解译效果.在省市土地利用信息获取及在城市研究中更具有广阔的应用前景.以南京幅的IKONOS图象数据为基础.以城乡接合部的不同试验区为对象,着重讨论了高分辨率遥感图象城市土地利用信息的提取与分类方法其主要思想是先应用常用的多光谱分类算法对试验区的土地利用现状进行初始的类别划分,然后采用Majority Filtering技术获取图象的上下信息,并给你根据地物的形状特征和空间关系对初始分类结果进行校正与调整.研究结果表明,当初始的类别划分能满足一定精度时,采用本所提出的方法能进一步改善高分辨率图象城市土地利用信息的分类效果. 相似文献
128.
Michael Ralph Fellows 《清华大学学报》2014,(4):325-328
This short paper highlights some open problems related to the work of Jianer Chen in the area of parameterized/multivariate algorithmics. 相似文献
129.
Rodney G.Downey ;Judith Egan ;Michael R.Fellows ;Frances A.Rosamond ;Peter Shaw 《清华大学学报》2014,(4):329-337
The main purpose of this paper is to exposit two very different, but very general, motivational schemes in the art of parameterization and a concrete example connecting them. We introduce a dynamic version of the DOMINATING SET problem and prove that it is fixed-parameter tractable(FPT). The problem is motivated by settings where problem instances evolve. It also arises in the quest to improve a natural greedy heuristic for the DOMINATING SET problem. 相似文献
130.
Sara B. Seidelmann Janet K. Lighthouse Daniel M. Greif 《Cellular and molecular life sciences : CMLS》2014,71(11):1977-1999
Arteries consist of an inner single layer of endothelial cells surrounded by layers of smooth muscle and an outer adventitia. The majority of vascular developmental studies focus on the construction of endothelial networks through the process of angiogenesis. Although many devastating vascular diseases involve abnormalities in components of the smooth muscle and adventitia (i.e., the vascular wall), the morphogenesis of these layers has received relatively less attention. Here, we briefly review key elements underlying endothelial layer formation and then focus on vascular wall development, specifically on smooth muscle cell origins and differentiation, patterning of the vascular wall, and the role of extracellular matrix and adventitial progenitor cells. Finally, we discuss select human diseases characterized by marked vascular wall abnormalities. We propose that continuing to apply approaches from developmental biology to the study of vascular disease will stimulate important advancements in elucidating disease mechanism and devising novel therapeutic strategies. 相似文献