BTB proteins are substrate-specific adaptors in an SCF-like modular ubiquitin ligase containing CUL-3

Programmed destruction of regulatory proteins through the ubiquitin-proteasome system is a widely used mechanism for controlling signalling pathways. Cullins are proteins that function as scaffolds for modular ubiquitin ligases typified by the SCF (Skp1-Cul1-F-box) complex. The substrate selectivity of these E3 ligases is dictated by a specificity module that binds cullins. In the SCF complex, this module is composed of Skp1, which binds directly to Cul1, and a member of the F-box family of proteins. F-box proteins bind Skp1 through the F-box motif, and substrates by means of carboxy-terminal protein interaction domains. Similarly, Cul2 and Cul5 interact with BC-box-containing specificity factors through the Skp1-like protein elongin C. Cul3 is required for embryonic development in mammals and Caenorhabditis elegans but its specificity module is unknown. Here we report the identification of a large family of BTB-domain proteins as substrate-specific adaptors for C. elegans CUL-3. Biochemical studies using the BTB protein MEL-26 and its genetic target MEI-1 (refs 12, 13) indicate that BTB proteins merge the functional properties of Skp1 and F-box proteins into a single polypeptide.     

Gigantic jets between a thundercloud and the ionosphere

Transient luminous events in the atmosphere, such as lighting-induced sprites and upwardly discharging blue jets, were discovered recently in the region between thunderclouds and the ionosphere. In the conventional picture, the main components of Earth's global electric circuit include thunderstorms, the conducting ionosphere, the downward fair-weather currents and the conducting Earth. Thunderstorms serve as one of the generators that drive current upward from cloud tops to the ionosphere, where the electric potential is hundreds of kilovolts higher than Earth's surface. It has not been clear, however, whether all the important components of the global circuit have even been identified. Here we report observations of five gigantic jets that establish a direct link between a thundercloud (altitude approximately 16 km) and the ionosphere at 90 km elevation. Extremely-low-frequency radio waves in four events were detected, while no cloud-to-ground lightning was observed to trigger these events. Our result indicates that the extremely-low-frequency waves were generated by negative cloud-to-ionosphere discharges, which would reduce the electrical potential between ionosphere and ground. Therefore, the conventional picture of the global electric circuit needs to be modified to include the contributions of gigantic jets and possibly sprites.     

加强大学生网络道德教育的认识与思考

随着人类进入信息社会，网络以其独特的方式影响着社会的各个领域。大学生作为一个特殊群体，网络给他们带来了诸多影响。重视与加强网络时代大学生网络道德教育是当前高校德育与思想政治工作的一项重要任务。文章分析了加强大学生网络道德教育的必要性，并提出加强大学生网络道德教育的途径。     

福州发展乡村旅游的思考

近年来,乡村旅游以其特有的风格与魅力吸引了大批城市游客,成为旅游业中新的亮点,乡村旅游开发也继农业产业化之后成为农村经济发展新的增长点。如今,福州的乡村旅游得到了较快的发展,而在迅速发展的同时,也存在一些不足之处。本文从乡村旅游的概念入手,在分析福州发展乡村旅游的有利条件、现状及存在的问题的基础上,提出发展福州乡村旅游的建议。     

支持向量机在电力变压器故障诊断中的应用

利用支持向量机的学习方法，构建了电力变压器故障诊断模型．该模型将变压器故障分为放电性和过热性两大类，通过统计分析寻求特征量区分类间的故障类型，采用支持向量机识别类内的故障类型，利用基于交叉验证的网格搜索法来确定支持向量机的参数．考虑到变压器油中溶解气体特征空间的紧致性原理，利用模糊C均值聚类算法对所获取的样本进行预选取，有效地解决了确定模型参数时耗时巨大的问题，并一定程度提高了模型的推广能力．实例验证表明，该模型在有限样本情况下，能达到较高的变压器故障判断率，放电性故障样本正确判断率为90．5％，过热性故障样本正确判断率为85．9％，说明该模型具有很好的分类效果和推广能力．     

The equilibrium between diagenetic calcites and dolomites and its impact on reservoir quality in the sandstone reservoir of Kela 2 gas field

Based on the equilibrium theory of chemical reactions between water and rocks,this paper establishes a thermodynamic phase relationship diagram among calcites,dolomites and water solution under the condition of diagenesis based on the thermodynamic database of related minerals and fluids and dolomite's degree of order parameters.It has been discovered that the equilibrium between calcites and dolomites in the diagenetic environment is strongly impacted by temperature and the Ca/Mg ratios in groundwater,and that the dolomite's degree of order in the diagenetic environment is a function of crystallization temperature and time,not controlled by water solution.Hereby,the authors make a further analysis of the close relationship of chemical reaction between carbonate cements and pore water in the sandstone reservoirs of Kala 2 gas field in Kuche sag.It can be seen that there are different impacts on sandstone reservoir quality among the equilibrium system of calcites,dolomites and pore water at different depths of reservoirs.     

马尾松愈伤组织诱导条件的研究

采用马尾松(Pinus massoniana Lamb.)成熟合子胚为起始材料,经过0.1%升汞溶液7~9min消毒后,接种于WPM培养基上,在温度26℃,光照强度2 000~3 000 lx,光照时间16 h/d的条件下培养得到无菌苗.采用无菌苗的各器官作为外植体在光照条件下进行愈伤组织的诱导条件的研究,结果显示,以幼茎为外植体,在含GD 6-BA 4.0 mg.L-1 NAA 0.10 mg.L-1 0.3%~0.4%活性碳(CA) 500 mg.L-1水解酪蛋白的培养基上,愈伤组织诱导率可达到93%.     

变速地貌单位线

本文提出了一种较为有效地考虑流域汇流非线性的方法——变速地貌单位线V~2GUH,对其特殊情况h_p=θV和i_p=K/V进行了理论证明,其动力因子流速意义得到了初步验证,坡地汇流在V~2GUH中得到了客观地考虑,应用结果证明V~2GUH方法的精度较高,同时,对本法在无资料和设计流域的应用问题进行了研究。     

凸多面体的干扰算法

检测物体之间的干扰问题,对许多工业设计来说是个重要课题,应用计算机图形学方法,快速而有效,一改过去手工作图慢而差的状态,本文着重阐述凸多面体的边面关系算法,并在此基础上,提出一种点面关系的算法。     

浅谈提高马克思主义理论课教学效果的途径

针对当前高校马克思主义理论课教学中存在着一系列的问题,分析了提高马克思义理论课教学效果的途径.