Local and global approaches of affinity propagation clustering for large scale data

Recently a new clustering algorithm called ＇affinity propagation＇ （AP） has been proposed, which efficiently clustered sparsely related data by passing messages between data points. However, we want to cluster large scale data where the similarities are not sparse in many cases. This paper presents two variants of AP for grouping large scale data with a dense similarity matrix. The local approach is partition affinity propagation （PAP） and the global method is landmark affinity propagation （LAP）. PAP passes messages in the subsets of data first and then merges them as the number of initial step of iterations; it can effectively reduce the number of iterations of clustering. LAP passes messages between the landmark data points first and then clusters non-landmark data points; it is a large global approximation method to speed up clustering. Experiments are conducted on many datasets, such as random data points, manifold subspaces, images of faces and Chinese calligraphy, and the results demonstrate that the two approaches are feasible and practicable.     

川西北某县城新建供水工程的必要性和可行性

以川西北某县城为例,分析了县城供水现状,提出新建供水工程构想,根据供水需求初步分析了取水、净水、输配水各构筑物的设置与设计,并对工程投资进行了初步估算,结果表明该供水工程的兴建是切实必要并可行的。     

老年人血小板谷胱甘肽过氧化物酶的纯化和分子特性研究

报道老年人血小板谷胱甘肽过氧化物酶由ＳｅｐｈａｒｏｓｅＱ柱层析、ＭｏｎｏＱＨＲ５／５ＦＰＬＣ和亲和层析后，经ＳＤＳ／ＰＡＧＥ鉴定为一条区带，其分子量为２３ｋＤａ．等电聚焦测定ＰＩ为５．１．用Ｓｕｐｅｒ－ｏｓｅＨＲ１０／３０柱经ＦＰＬＣ测定的分子量为９２ｋＤａ，这表明在自然状态下血小板谷胱甘肽过氧化物酶由四个相同的亚单位组成。这些结果与人红细胞谷胱甘肽过氧化物酶的特性相一致．     

纳米技术与环境工程

纳米技术和纳米材料是当前材料领域的研究热点,这为解决人类生存环境所面临的日益严重的环境问题提供了新型的手段和方法,简要综述了纳米技术和纳米材料,着重介绍了纳米材料及纳米科技在有机、无机污水处理以及空气净化等环境保护领域的应用进展情况。     

Efficient Expression of Bioactive Human Leptin in <Emphasis Type="Italic">Escherichia coli</Emphasis> in Soluble Fusion Form

Leptin, a 16 kDa nonglycosylated hormone, is produced by mature adipocytes and functions primarily in the hypothalamus to reduce food intake and body weight. To explore a new approach for high-level expression of human Leptin in Escherichia coli, the human Leptin gene, synthesized according to the published sequence, was cloned into the vector pET32a to construct a fusion expression plasmid: Trx–Leptin/pET32a. Our data showed that more than 40% of the fusion protein Trx–Leptin was expressed in soluble form. After purified by Ni-IDA affinity chromatography, cleaved by enterokinase and applied Ni-IDA affinity chromatography again, purified Leptin with homogeneity over 96% was achieved. The bio-functional experiments of purified Leptin showed a significant reduction in food intake and body weight of female mice treated with Leptin by comparing with control mice, and it indicated that the purified Leptin has full biological activity. In addition, our expression system was a very low-cost and efficient prokaryotic expression system. So taken together, our results demonstrated that our expression system of bio-active Leptin provided a new method for producing Leptin in big scale and would be widely applied in commercial Leptin producing industries.     

南极假丝酵母(Candida antarctica)脂肪酶A在毕赤酵母中的表达、纯化及性质

将编码南极假丝酵母脂肪酶A的基因进行克隆,与pPIC9K连接构建成重组载体,并将其电转化入毕赤酵母GS115中。通过MD和MM平板及PCR扩增,筛选和鉴定重组子。重组细胞经过120 h培养后,发酵液上清酶活达到13 U/mL。聚丙烯酰胺凝胶电泳显示,重组脂肪酶分子量约为50 kD,比原始脂肪酶略大。粗酶液经中空纤维素膜超滤浓缩、硫酸铵分级沉淀和离子柱交换层析后,得到在SDS-PAGE上显示为单一条带的重组脂肪酶。该酶最适反应温度为75℃,在70℃保持30 min后,仍具90%以上的活性,最适反应pH值为7.0,在pH6.0～8.0的范围内,具有一定的稳定性。     

虫生真菌毒素的性质与分离研究进展

虫生真菌是一类重要的生防真菌,生产中广泛应用.现对虫生真菌的界定、侵染机制以及对已发现的虫生真菌毒素的性质、结构和分离纯化方法进行了综述.     

重组肠激酶在大肠杆菌中的发酵与纯化

对重组肠激酶在大肠杆菌中的高密度发酵表达条件、纯化方法及其生物活性测定进行了研究。结果表明:在E.coli表达系统中,控制温度为37℃,培养基pH 7.4,当A600为8.0时,加入0.3mmol/LIPTG进行诱导,温度降低至30℃,连续诱导3 h,蛋白表达量达25%。经SDS-PAGE测定,纯化的重组肠激酶纯度达80%以上,并能高效切开融合蛋白。     

小麦可溶性和不溶性PGIP分离纯化的初步研究

以小麦黄化苗为材料,采用不同离子强度的缓冲液抽提,通过硫酸铵分级沉淀、离子交换层析和分子筛层等步骤分离出两种不同分布的PGIP.经SDS-PAGE分析:不溶性PGIP出现两条谱带,分子量为41KD和39KD,而可溶性PGIP出现一条谱带,分子量为41KD.     

《圣经》“乐园”神话:作为文学原型的流变

《圣经》中的"乐园"神话是西方文学的一个宝藏,它蕴涵有丰富的人生寓意,是文学家创作出传世佳作的温床,由"乐园"神话构筑了一个个文学原型。这一切在基督教文化中又被以原罪与救赎、迷惘与净朗、善与恶等思想形式保存下来。