Experiments in Solving Mixed Integer Programming Problems on a Small Array of Transputers

The time-consuming process of solving large-scale Mixed Integer Programming problems using the branch-and-bound technique can be speeded up by introducing a degree of parallelism into the basic algorithm. This paper describes the development and implementation of a parallel branch-and-bound algorithm created by adapting a commercial MIP solver. Inherent in the design of this software are certain ad hoc methods, the use of which are necessary in the effective solution of real problems. The extent to which these ad hoc methods can successfully be transferred to a parallel environment, in this case an array of at most nine transputers, is discussed. Computational results on a variety of real integer programming problems are reported.     

基于三维静电势参数研究C60溶解性的构效关系

在量子化学从头算基础上,对一系列溶剂化合物分子进行了结构优化和三维静电势参数计算,运用多元线性回归分析和神经网络方法对C60在121种不同溶剂的溶解性与计算的结构参数进行了构效关系研究.用建立起来的QSPR 关系式对15种不同结构类型溶剂进行了预测,并阐述了C60溶质与不同溶剂之间的相互作用,获得了满意的结果.     

Univariate Stochastic Programming with Random Decision Variable

The problem of minimising E(X) subject to the constraints X ? 0, P(X ? b) ? a(0 < a < 1) has been considered, where b is a non-negative random variable with continuous probability distribution. A necessary and sufficient condition for randomised decisions to be superior to the non-randomised one has been derived.     

The surface catalytic mechanism: a comparative study with square-wave and staircase cyclic voltammetry

A pseudo-first-order catalytic mechanism in which both reactant and product of a redox reaction are strongly immobilized on an electrode surface is theoretically analysed under conditions of square-wave (SWV) and staircase cyclic voltammetry (SCV). A mathematical procedure is developed under diffusionless conditions. The relationships between the properties of the voltammetric response and both the kinetic parameters of the redox reaction and the parameters of the excitation signal are studied. The phenomenon of the quasi-reversible maximum is discussed. A comparative study between SWV and SCV is presented and the limitations and advantages of both techniques, from analytical and kinetic points of view, are discussed. The theoretical predictions are experimentally confirmed by the redox reaction of azobenzene in the presence of hydrogen peroxide as an oxidizing agent. Electronic Publication     

Synthesis,characterization and DNA-binding properties of zinc(II) and nickel(II) Schiff base complexes

A new ligand, 2-carboxybenzaldehyde-(4’-hydroxy)benzoylhydrazone(H₂L) and its Zn^II and Ni^II complexes have been synthesized and characterized on the basis of elemental analyses, molar conductivities, ¹H-NMR, IR spectra and thermal analyses. In addition, DNA-binding properties of these two metal complexes were investigated using spectrometric titrations, ethidium bromide displacement experiments, and viscosity measurements. The results show that the two complexes, especially the Ni^II complex, strongly bind with calf-thymus DNA, presumably via an intercalation mechanism. The intrinsic binding constants of the Zn^II and Ni^II complexes with DNA are 2.46 × 10⁵ and 7.94 × 10⁵ M ⁻¹, respectively.     

Effect of film thickness on the electro-reduction of molecular oxygen on electropolymerized cobalt tetra-aminophthalocyanine films

We studied the electrocatalytic activity of cobalt tetra-aminophthalocyanine (CoTAPc) for the reduction of molecular oxygen (O₂) on adsorbed monomeric and on electropolymerized films of different thicknesses on glassy carbon (GC) electrode. The polymeric films, denoted poly-CoTAPc, were first characterized by electrochemical impedance spectroscopy and it appears that the types of phenomena revealed to be occurring depend less on the film thickness in basic than in acid media. For O₂ reduction, the results showed that poly-CoTAPc is more active than the monomeric CoTAPc adsorbed on GC. Indeed, rotating ring-disk electrode data showed that polymeric CoTAPc promotes the four-electron reduction of O₂ to water in parallel to a two-electron reduction to give peroxide. On monomeric and thin films of poly-CoTAPc, a two-electron reduction mechanism predominates. In basic media the activity increases very slightly with thickness, whereas in acid media this increase is more pronounced. This parallels the observed behavior revealed by electrochemical impedance spectroscopy.     

Sorption of uranium by non-living water hyacinth roots

Summary Many studies have shown that water hyacinth (Eichhornia crassipes) roots can be used to accumulate high concentrations of organic as well as inorganic pollutants. They are currently used to remediate aquatic environments and aqueous solutions. In the present study, sorption of uranium from aqueous solutions by using dried roots of water hyacinth has been investigated. The sorption of uranium was examined as a function of initial concentration, pH, weight of roots and contact time. Five different concentrations 20, 40, 60, 80, and 100 μg ^. ml^-1 were used. Sorption proves to be very rapid and depend on pH, weight of roots and concentration of uranium. Maximum sorption capacity of water hyacinth roots was 64,000 U⁶⁺ μg/g. The sorption of uranium by water hyacinth roots follows a Langmuir isotherm.     

Addition of benzylic and allylic organozinc and Grignard reagents to resin-bound imines to provide alpha-branched secondary amines bearing a wide variety of functional groups. Utility in the synthesis of beta-3 adrenergic receptor agonists

Benzylic and allylic organozinc and Grignard reagents have been added to resin-bound imines to provide alpha-branched secondary amines. Many functional groups, including electrophilic groups, were compatible with this methodology. Three modules--a resin-bound primary amine, an aromatic aldehyde, and the organometallic--were independently varied to produce a combinatorial library of alpha-branched secondary amines designed as beta-3 adrenergic receptor agonists.     

Anti-oxidant and pro-oxidant reactivities of copper(II), manganese(II) and iron(III) 3,5-di-<Emphasis Type="Italic">i</Emphasis>-propylsalicylate chelates during peroxidation of alkylbenzenes

Bioactive copper(II), iron(III), and manganese(II) 3,5-di-i-propylsalicylate (3,5-DIPS) chelates were investigated in order to determine their ability to inhibit the free radical initiated chain reactions leading to the peroxidation of isopropylbenzene (i-PrPh) and ethylbenzene (EtPh). Quantitative kinetic studies of these chelates established the following order of anti-oxidant reactivities: manganese(II)-(3,5-DIPS)₂>iron(III)(3,5-DIPS)₃>copper(II)₂(3,5-DIPS)₄> > 3,5-DIPS acid. The mechanism of anti-oxidant reactivity of these three chelates is established as being due, in part, to their chain-breaking capacity resulting from the chemical reduction of the generated peroxyl radical to yield alkybenzenelhydroperoxides via reaction of the 3,5-DIPS ligand with the peroxyl radical. In the case of manganese(II)3,5-di-i-propylsalicylate, the central metalloelement also interacts with the peroxyl radical. The manganese(II)-(3,5-DIPS)₂ and copper(II)₂(3,5-DIPS)₄ chelates were also found to exhibit alkylhydroperoxide pro-oxidative reactivity leading to the formation of the alkylbenzeneperoxyl radical. In addition, the manganese(II) atom underwent oxidation to manganese(III) with the formation of the alkylbenzenehydroperoxide or superoxide with air oxygen oxidation. Amyl acetate and dipropylamine (n-Pr₂NH) were added to the reaction mixture to model the biochemical presence of ester or amine cellular components. Addition of amyl acetate to the reaction mixture increased the anti-oxidant reactivity of manganese(II)-(3,5-DIPS)₂ while decreasing its pro-oxidant reactivity. The weaker anti-oxidant reactivites of iron(III)(3,5-DIPS)₃ and copper(II)₂(3,5-DIPS)₄ were less affected by the addition of amyl acetate and the pro-oxidant reactivity of copper(II)₂(3,5-DIPS)₄ was not changed by the addition of amyl acetate, while the pro-oxidant property of iron(III)(3,5-DIPS)₃ was eliminated. In contrast to 2,6-di-t-butyl-4-methylphenol, butylated hydroxy toluene (BHT), anti-oxidant reactivities of copper(II), iron(III), and manganese(II) 3,5-DIPS chelates were dramatically enhanced by the addition of n-Pr₂NH to the reaction mixture. It is concluded that all three metalloelement chelates react with and remove alkylbenzeneperoxyl radicals and the hydroperoxyl radical. The manganese(II)-(3,5-DIPS)₂ and copper(II)₂(3,5-DIPS)₄ chelates may also be useful in removing hydroperoxides in vivo. These reactivities, in addition to their established superoxide dismutase (SOD)-mimetic and catalase-mimetic reactivities, are suggested to possibly permit anti-oxidant and pro-oxidant reactivities in aqueous and organic cellular compartments.