Splitting an Ordering into a Partition to Minimize Diameter

k consisting of k clusters, with k > 2. Bottom-up agglomerative approaches are also commonly used to construct partitions, and we discuss these in terms of worst-case performance for metric data sets. Our main contribution derives from a new restricted partition formulation that requires each cluster to be an interval of a given ordering of the objects being clustered. Dynamic programming can optimally split such an ordering into a partition P^k for a large class of objectives that includes min-diameter. We explore a variety of ordering heuristics and show that our algorithm, when combined with an appropriate ordering heuristic, outperforms traditional algorithms on both random and non-random data sets.     

Antioxidant survey to assess antagonism to redox stress using a prokaryotic and an eukaryotic system

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.     

Butterflies and ants: The communicative domain

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.     

太平沟大桥曲线箱梁顶推施工设计概述

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。     

Detection of the translational oscillations of the Earth''''s solid inner core based on the international superconducting gravimeter observations

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…     

IKONOS图象的城市土地利用信息提取方法研究

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．     

Cadmium is a mutagen that acts by inhibiting mismatch repair

Most errors that arise during DNA replication can be corrected by DNA polymerase proofreading or by post-replication mismatch repair (MMR). Inactivation of both mutation-avoidance systems results in extremely high mutability that can lead to error catastrophe. High mutability and the likelihood of cancer can be caused by mutations and epigenetic changes that reduce MMR. Hypermutability can also be caused by external factors that directly inhibit MMR. Identifying such factors has important implications for understanding the role of the environment in genome stability. We found that chronic exposure of yeast to environmentally relevant concentrations of cadmium, a known human carcinogen, can result in extreme hypermutability. The mutation specificity along with responses in proofreading-deficient and MMR-deficient mutants indicate that cadmium reduces the capacity for MMR of small misalignments and base-base mismatches. In extracts of human cells, cadmium inhibited at least one step leading to mismatch removal. Together, our data show that a high level of genetic instability can result from environmental impediment of a mutation-avoidance system.     

卫星低频电磁辐射在轨探测研究

利用地球空间探测双星计划探测一号卫星上的磁场波动分析仪的原始数据, 分析了探测一号卫星在轨电磁辐射的特性. 结果显示卫星的电磁辐射主要集中在30 Hz以下. 在30 Hz以上, 卫星的电磁辐射最多延伸到 190 Hz左右, 而且强度明显减弱. 在 190 Hz以下的卫星电磁辐射具有与卫星姿态相关的长周期变化. 在 190~830 Hz的范围的电磁辐射有不明显的长周期变化特征. 830~3990 Hz范围的电磁辐射没有长周期变化特征. 卫星电磁辐射的长周期变化是由卫星姿态变化造成的. 卫星姿态变化引起卫星太阳方位角变化. 卫星太阳方位角越大, 卫星电磁辐射越大. 卫星太阳方位角从90.6增加到93.6, 低于10 Hz以下的电磁辐射约增大为原来的9倍, 10~190 Hz范围的电磁辐射大约增加到原来的1.6倍. 卫星在＜10和10~190 Hz范围内的电磁辐射强度与卫星太阳方位角的相关系数分别达到0.90和0.91. 卫星在光照情况下的电磁辐射要比卫星在阴影情况下大. 卫星太阳能帆板电流产生的电磁辐射是卫星电磁辐射主要来源, 约占整个卫星电磁辐射的87％(低频段<150 Hz)和94％(高频段>150 Hz). 这些中国首次对卫星电磁辐射的在轨探测结果对于我国未来相关科学和应用卫星的设计方案的优化具有重要的参考价值.