Information Filtering in Sparse Online Systems: Recommendation via Semi-Local Diffusion

With the rapid growth of the Internet and overwhelming amount of information and choices that people are confronted with, recommender systems have been developed to effectively support users’ decision-making process in the online systems. However, many recommendation algorithms suffer from the data sparsity problem, i.e. the user-object bipartite networks are so sparse that algorithms cannot accurately recommend objects for users. This data sparsity problem makes many well-known recommendation algorithms perform poorly. To solve the problem, we propose a recommendation algorithm based on the semi-local diffusion process on the user-object bipartite network. The simulation results on two sparse datasets, Amazon and Bookcross, show that our method significantly outperforms the state-of-the-art methods especially for those small-degree users. Two personalized semi-local diffusion methods are proposed which further improve the recommendation accuracy. Finally, our work indicates that sparse online systems are essentially different from the dense online systems, so it is necessary to reexamine former algorithms and conclusions based on dense data in sparse systems.     

The Up-regulation of Carbonic Anhydrase Genes of Bacillus mucilaginosus under Soluble Ca2+ Deficiency and the Heterologously Expressed Enzyme Promotes Calcite Dissolution

Molecular mechanisms and gene regulation are of interest in the area of geomicrobiology in which the interaction between microbes and minerals is studied. This paper focuses on the regulation of the expression of carbonic anhydrase (CA) genes in Bacillus mucilaginosus and the effects of the expression product of the B. mucilaginosus CA gene in Escherichia coli on calcite weathering. Real-time fluorescent quantitative PCR (RT-qPCR) was used to explore the relationship between CA gene expression in B. mucilaginosus and promotion of calcite dissolution under condition of Ca²⁺ deficiency. The results showed that adding calcite to the medium, which lacks Ca²⁺, can up-regulate the expression of the bacterial CA genes to accelerate calcite dissolution for bacterial growth. CA genes from B. mucilaginosus were transferred into E. coli by cloning. We then employed crude enzyme extract from the resultant E. coli strain in calcite dissolution experiments. The enzyme extract promoted calcite dissolution. These findings provide direct evidence for the role of microbial CA on mineral weathering and mineral nutrition release.     

Enhancing the Thermotolerance of Isochrysis zhangjiangensis Through Co-culturing With Algoriphagus marincola

Marine Biotechnology - Isochrysis zhangjiangensis is an important microalgal species used as bait in aquaculture. However, its optimal cultivation temperature is around 25 °C,...     

我国人乳头瘤病毒（HPV16Z）基因克隆和鉴定

本文作者采用基因克隆手段,以pAt153为载体,从一份山西襄坦宫颈癌高发区宫颈癌患者的手术标本中,成功地克隆到2株与HPV16同源的基因片段。经PstI、KpnI、TaqvI、PvuII等16种限制性内切酶酶谱分析及其部分基因序列的鉴定,证明这是在国内首次克姓到一株分子量约为8．0kb完整的HPV16型全序列DNA及一株分子量为5．4kb的HPV6基因片段。经实验证明：该基因片段E6、E7及部分LI基因丢失,在750单核苷酸处发生变异,产生一新的BamHI酶切位点。该完整的HPV16基因组被命名为HPV16Z,HPV16基因片段被命名为HPV16F。用新分离到的HPV16Z作分子探针,检测襄坦337份宫颈癌及阴道活检标本的HPV16型同源序列的结果显示,慢性阴道炎阳性率为17．28％（14／81）;宫颈炎为11．89％（17／143）;宫颈癌前病变46．81％（22／47）;宫颈癌为72．73％（48／66）。证明山西宫颈癌高发区宫颈癌前病变及宫颈癌组织中主要为HPV16Z感染。     

海南产螺旋藻粉蛋白质氨基酸

采用Tecator自动定氮仪和Waters PICO-TAG氨基酸自动分析仪测定了海南螺旋藻粉中蛋白质含量和17种氨基酸含量。结果显示海南螺旋藻粉中蛋白质含量达63.3%,总氨基酸含量达60.88%,其中必需氨基酸含量超过40%,比例平衡,符合FA0标准,可与国外产品媲美。     

Porin activity of the native and recombinant outer membrane protein Oms28 of Borrelia burgdorferi.

The outer membrane-spanning (Oms) proteins of Borrelia burgdorferi have been visualized by freeze-fracture analysis but, until recently, not further characterized. We developed a method for the isolation of B. burgdorferi outer membrane vesicles and described porin activities with single-channel conductances of 0.6 and 12.6 nS in 1 M KCI. By using both nondenaturing isoelectric focusing gel electrophoresis and fast-performance liquid chromatography separation after detergent solubilization, we found that the 0.6-nS porin activity resided in a 28-kDa protein, designated Oms28. The oms28 gene was cloned, and its nucleotide sequence was determined. The deduced amino acid sequence of Oms28 predicted a 257-amino-acid precursor protein with a putative 24-amino-acid leader peptidase I signal sequence. Processed Oms28 yielded a mature protein with a predicted molecular mass of 25,363 Da. When overproduced in Escherichia coli, the Oms28 porin fractionated in part to the outer membrane. Sodium dodecyl sulfate-polyacrylamide gel-purified recombinant Oms28 from E. coli retained functional activity as demonstrated by an average single-channel conductance of 1.1 nS in the planar lipid bilayer assay. These findings confirmed that Oms28 is a B. burgdorferi porin, the first to be described. As such, it is potential relevance to the pathogenesis of Lyme borreliosis and to the physiology of the spirochete.     

菽麻（Crotalaria juncea L.）抗肿瘤化学成份的研究

我们从菽麻(Crotalaria juncea L.)种子中提取、分离出菽麻生物碱Ⅰ,对多种动物瘤谱具有较明显的抑制作用。并且对生物碱Ⅰ进行了熔点、旋光、红外光谱、核磁共振谱、质谱等理化测定,均与Trichodesmine性状一致。     

以人精子抗原消化道免疫后的体液免疫反应

The inbred Balb/c and C57 mice, and the outbred Swiss Webster mice were intragastrointestinally immunized with human sperm antigens. The lymphocytes from the spleen, mesenteric lymph node (MLN), Peyer's patch (PP) and uterus or epididymis were isolated and cultured. The lymphocyte-secreting antisperm IgG and IgA and the antisperm antibodies in the gut wash and serum were determined with enzyme-linked immunosorbent assay (ELISA). In the Balb/c and Swiss Webster mice, the immune responses to sperm have shown to be stronger than that in C57, stronger in female than in male. The antigenicity of sperm membrane extracts seems to be higher than that of whole sperm. Antisperm antibodies secreted by lymphocytes from the epididymis and uterus have demonstrated to be detectable. For stimulation of the local immune response, the intra-PP and intralumina immunizations are more effective than others.     

UPPER TRIASSIC SPORO-POLLEN ASSEMBLAGES FROM MOSUOHE RIVER VALLEY OF BAODING, SICHUAN

In 1972, after frequent investigations on lithology, sedimentology and palaeontology (especially on palaeobotany), the Upper Triassic coal series (formerly the "Lalaqing Coal Series") in the Baoding area, southwestern Sichuan was previously divided by No. 1 Regional Geological Survey Team of Yunnan Province into two formations in ascending order as the Daqiaodi Formation, and the Daqing Formation (consisting of the Lower and Upper Members).