Pd/silica cluster catalysts: synthesis and reactivity with H2 and C2H4

Silica-supported Pd clusters were characterized by in situ EXAFS spectroscopy. Clusters with an average nuclearity of six atoms were derived from either an inorganic or an organometallic precursor by reduction at 100–150C. Despite the small size of the clusters, EXAFS contributions from the metal-support interface were not detected. These clusters and larger ones formed by reduction at 320C absorb hydrogen on cooling in H₂ to 30C; the resultant interstitial hydride species decompose in vacuo at 30C. Vacuum treatment at 300C removes chemisorbed H₂ yielding bare Pd clusters. In contrast to larger crystallites, the Pd clusters do not react with C₂H₄ at 150 to form interstitial carbide species.     

Genome Evolutionary Dynamics Meets Functional Genomics: A Case Story on the Identification of SLC25A44

Gene clusters are becoming promising tools for gene identification. The study reveals the purposive genomic distribution of genes toward higher inheritance rates of intact metabolic pathways/phenotypes and, thereby, higher fitness. The co-localization of co-expressed, co-interacting, and functionally related genes was found as genome-wide trends in humans, mouse, golden eagle, rice fish, Drosophila, peanut, and Arabidopsis. As anticipated, the analyses verified the co-segregation of co-localized events. A negative correlation was notable between the likelihood of co-localization events and the inter-loci distances. The evolution of genomic blocks was also found convergent and uniform along the chromosomal arms. Calling a genomic block responsible for adjacent metabolic reactions is therefore recommended for identification of candidate genes and interpretation of cellular functions. As a case story, a function in the metabolism of energy and secondary metabolites was proposed for Slc25A44, based on its genomic local information. Slc25A44 was further characterized as an essential housekeeping gene which has been under evolutionary purifying pressure and belongs to the phylogenetic ETC-clade of SLC25s. Pathway enrichment mapped the Slc25A44s to the energy metabolism. The expression of peanut and human Slc25A44s in oocytes and Saccharomyces cerevisiae strains confirmed the transport of common precursors for secondary metabolites and ubiquinone. These results suggest that SLC25A44 is a mitochondrion-ER-nucleus zone transporter with biotechnological applications. Finally, a conserved three-amino acid signature on the cytosolic face of transport cavity was found important for rational engineering of SLC25s.     

The graphite arc-discharge in the presence of CCl4: Chlorinated carbon clusters in relation with fullerenes formation

The graphite arc-discharge in the atmosphere consisting of CCl₄ 40 Torr and increasing partial pressure of He from 0 to 300 Torr produced, in addition to carbon species such as graphite and fullerenes C₆₀ and C₇₀, numerous chlorinated carbon clusters (CCCs). The yields of some CCCs, including C₆Cl₆ (perchlorobenzene), C₁₀Cl₈ (perchloronaphthalene), C₁₂Cl₈ (perchloroacenaphthylene) and C₁₂Cl₈ (isomer II), C₁₄Cl₈ (isomer I), C₁₆Cl₁₀ (perchlorofluoranthene), C₁₈Cl₁₀ (isomer I and II), and C₂₀Cl₁₀ (isomer I), correspond well with C₆₀ yields, which may imply these CCCs share the same growth mechanism with fullerenes. Such a yield correlation can be used to distinguish the fullerene precursors from the irrelevant by-products, thus contributes to the mechanistic study of fullerene formation.     

一个自动确定聚类数目的微粒群算法

提出了一个微粒群优化算法（autoPSO）自动聚类高维数据。autoPSO优化了Davies-Bouldin（DB）有效性函数,并将聚类问题转化为一个界约束的连续函数的优化问题。用一个实数矩阵和一个二进制向量来表示微粒,使得同一迭代中能够表示具有不同聚类数目的划分;并且,在二进制向量的控制下指导相关联的实数矩阵交叉操作,保持算法良好的种群多样性,避免算法早熟收敛。通过高维模拟数据集的实验结果表明,本文算法不需要预设聚类数目k,能够自动正确识别高维数据的聚类。     

集群系统下的动态网络负载平衡

对集群系统的基本特性和负载平衡的工作原理作了必要的概述。就负载平衡器功能的实现,在前人工作的基础上提出了负载平衡作业调度算法,并论述了该算法的策略、节点与通信域的基本概念,提出由更新因子将通信域节点进行分类,最后建立了通信域中作业调度算法模型。     

延边区域竞争优势的源泉--全球化背景下的企业集群

企业出现以来，企业组织形式随着技术进步和市场需求的变化不断演进．21世纪，中小企业和企业集群逐渐成为主流，并成为全球化背景下延边区域竞争优势的源泉．本文立足延边现状，分析了延边企业集群的类型选择和发展问题，并提出了对策．     

湖北省承接东部地区加工贸易产业转移的思考

我国加工贸易由东部向中西部地区转移的趋势已经形成.面对广大中西部省份的激烈竞争,湖北省要立足自身优势,大力承接东部地区的加工贸易产业转移,积极投入基础设施建设,加大招商引资力度,创造良好的投资环境,引导当地劳务人员就业观念,完善产业配套体系,推动加工贸易产业集群.     

高新技术产业集群发展下的湖北创新驿站构建

构建湖北创新驿站的建设框架,分析了湖北创新驿站的运作模式和技术服务功能,即通过建立创新驿站提高湖北省各市州高新区（园）的技术创新能力,带动各地区特色高新技术产业集群的发展.     

带电小银团簇几何结构的研究

采用密度泛函的广义梯度近似(GGA)下的BLYP方法,对带电Agn(n=2 ～6)团簇的几何结构进行了优化,结果表明Ag2 ～ Ag5团簇为平面结构,从Ag6团簇开始出现三维立体结构.     

基于最小树切割的自适应聚类方法

为了简单有效地对数据集进行结构分析,提出了一种基于最小树进行聚类的算法(MSTCA).其基本思想是在最小树中切割所有大于一定阈值的边,对数据集进行子类划分,同时对较小的子类进行合并.MSTCA产生的聚类结果在不考虑子类次序时是唯一的。对它的递归调用还可在若干不同粒度层次上形成数据集的聚类结构.计算实验表明,MSTCA不仅能为具有各种不同聚类形状的数据集自适应地选择较好的聚类个数,而且只需简单的参数选择就能准确地分析出数据中存在的合理聚类和例外样本.