零维多项式组零点的1种直接表示法

给出了零维多项式组所有零点的1种直接表示算法．零点的这种表示方法可避免一般三角化方法引起的误差．此外,该方法较少地依赖符号计算,且核心算法是基于可靠的、数值的区间运算．     

Effect of pH on hydrophilicity and charge and their effect on the filtration efficiency of NF membranes at different pH

In this work the effect of pH on membrane structure, its permeability and retention was studied. In addition, we studied whether the possible changes in the membrane properties due to the pH change are reversible. This is important for understanding the performance of nanofiltration membranes at different conditions and for the selection of cleaning processes. Moreover, the results facilitate the choice of membrane for specific applications.

Several commercial NF membranes were studied at different pH values. Their retention and flux were explained by the charge and the hydrophilic characteristics of the membranes. The filtrations were made with uncharged sugar and salt solutions.

The lower the membrane contact angle (i.e., a more hydrophilic membrane) the higher was the change in apparent zeta potential when pH was increased from 4 to 7. As a result, the retention of ions with more hydrophilic membranes changed more than hydrophobic ones when the pH was increased in the feed solution. However, some membranes retained ions well at high pH although their apparent zeta potential or hydrophilicity was relatively low. These membranes had charge inside the pores and it was not detected by streaming potential measurement along the surface or by measuring the contact angle of the surface. Thus, the apparent zeta potential of the exterior membrane surface did not sufficiently describe the ionic transport through the membrane. In addition, some membranes became significantly more open at high pH (i.e., flux increased). This was explained by the chemical nature of the polymer chains in the membrane skin layer, i.e., dissociating groups in the polymer made the surface more hydrophilic and looser when charges of the polymer chains started to repel each other at elevated pH. Generally, the retention of uncharged glucose decreased more at high pH than the salt retention. The changes in permeabilities and retentions were found to be mostly reversible in the pH range studied (very slowly in some cases, however).     

Dynamic characterization of HLA-B*44 Alleles: A comparative molecular dynamics simulation study

Human Leukocyte Antigens (HLA) are highly polymorphic proteins that play a key role in the immune system. HLA molecule is present on the cell membrane of antigen-presenting cells of the immune system and presents short peptides, originating from the proteins of invading pathogens or self-proteins, to the T-cell Receptor (TCR) molecule of the T-cells. In this study, peptide-binding characteristics of HLA-B*44:02, 44:03, 44:05 alleles bound to three nonameric peptides were studied using molecular dynamics simulations. Polymorphisms among these alleles (Asp116Tyr and Asp156Leu) result in major differences in the allele characteristics. While HLA-B*44:02 (Asp116, Asp156) and HLA-B*44:03 (Asp116, Leu156) depend on tapasin for efficient peptide loading, HLA-B*44:05 (Tyr116, Asp156) is tapasin independent. On the other hand, HLA-B*44:02 and HLA-B*44:03 mismatch is closely related to transplant rejection and acute-graft-versus-host disease. In order to understand the dynamic characteristics, the simulation trajectories were analyzed by applying Root Mean Square Deviation (RMSD) and Root Mean Square Fluctuation (RMSF) calculations and hydrogen bonding analysis. Binding dynamics of the three HLA-B*44 alleles and peptide sequences are comparatively discussed. In general, peptide binding stability is found to depend on the peptide rather than the allele type for HLA-B*44 alleles.     

On a Mathematical Comparison between Hierarchy and Network with a Classification of Coordination Structures

This paper proposes a mathematical model to compare a network organization with a hierarchical organization. In order to formulate the model, we define a three-dimensional framework of the coordination structure of a network and of other typical coordination structures. In the framework, we can define a network structure by contrasting it with a hierarchy, in terms of the distribution of decision making, which is one of the main features of information processing. Based on this definition, we have developed a mathematical model for evaluating coordination structures. Using this model, we can derive two boundary conditions among the coordination structures with respect to the optimal coordination structure. The boundary conditions help us to understand why an organization changes its coordination structure from a hierarchy to a network and what factors cause this change. They enable us, for example, to find points of structural change where the optimal coordination structure shifts from a hierarchy to a hierarchy with delegation or from a hierarchy with delegation to a network, when the nature of the task changes from routine to non-routine. In conclusion, our framework and model may provide a basis for discussing the processes that occur when coordination structures change between a hierarchy and a network.     

房地产板块与金融板块指数相关性研究——基于Copula-Kermel模型的分析

近年来,房地产市场与金融市场的关联关系越来越紧密.选取2001年7月3日至2011年9月30日房地产板块与金融板块指数日收益率数据,利用非参数核密度估计单指数收益率的边缘分布,采用Copula方法定量刻画两者的相关结构及尾部相关性.实证结果表明:T-Student-Copula是描述房地产和金融板块指数日收益率的最佳Copula函数形式,且两者具有较强的上尾和下尾相关关系,因此投资者不能通过投资这两类股票降低投资组合风险.另外,政府在制定宏观经济政策时,一方面需注意在采取措施促进金融行业发展时,要防范房地产泡沫的加剧,另一方面还需注意在对房地产业进行调控时,要防止金融业的衰退.     

Energy density analysis of cluster size dependence of surface-molecule interactions (II): formate adsorption onto a Cu(111) surface

Adsorption of formate (HCOO) onto a Cu(111) surface has been treated theoretically using 18 kinds of Cu(n) (6 < or = n < or = 56) clusters. The energy density analysis (EDA) proposed by Nakai has been adopted to examine surface-molecule interactions for different cluster sizes. EDA results for the largest model cluster Cu(56) have shown that the adsorption-induced energy density variation in Cu atoms decays with distance from the adsorption site. Analysis of this decay, which can be carried out using the EDA technique, is important because it enables verification of the reliability of the model cluster used. In the case of formate adsorption onto the Cu(111) surface, it is found that at least a four-layer model cluster is necessary to treat the surface-molecule interaction with chemical accuracy.     

Validating state-dependent queueing models for uninterrupted traffic flows using simulation

In this paper, the effectiveness of state-dependent queueing models for analyzing traffic flows is tested by comparing the speeds generated by the queueing models with the ones obtained by simulation. Simulation is thus used to evaluate speeds generated by the different queueing models. Different state-dependency functions are described and their performance is assessed. An M/G/1 queueing model with Gaussian state-dependency outperforms all other state-dependent queueing models. Different test results and insights are provided. Received: July 2004, Revised: September 2005 AMS classification: 60K25, 60K30     

Zinc(II) complexes of 1,3-bis(2-pyridylmethylthio)propane: Anion dependency, crystal structure and DNA binding study

Zinc(II) complexes of the formula [Zn(L)(X)₂] (where X = Cl⁻, N₃⁻, NCO⁻ and SCN⁻ (1a-d, respectively)) and {[Zn(L)(ClO₄)(H₂O)](ClO₄)}_n (2), were isolated in the pure form on the reaction of 1,3-bis(2-pyridylmethylthio)propane (L) with different zinc(II) salts. All the complexes were characterized by physicochemical and spectroscopic tools. The X-ray crystallographic analyses of the complexes 1d and 2 showed that the former is mononuclear while complex 2 is a 1D coordination polymer, {[Zn(L)(ClO₄)(H₂O)](ClO₄)}_n, due to a different coordination mode of the tetradentate ligand L. The zinc(II) ions present an octahedral coordination geometry in both compounds, which is more distorted in the mononuclear complex 1d. The study indicates that the counter anion of the zinc(II) salt used as reactant leads to a different type of complex when isolated as a crystalline material. A spectroscopic study of the interaction of complex, 2 with calf thymus-DNA (CT-DNA) in Tris-HCl buffer showed a significant non-intercalative interaction with a binding constant (K_b) of 4.7 × 10⁴ M⁻¹, and the linear Stern-Volmer quenching constant (K_sv) and the binding sites (n) were found to be 1.3 × 10³ and 0.92 respectively, calculated from ethidium bromide (EB) fluorescence displacement experiments.