On Quantales and Spectra of C*-Algebras

We study properties of the quantale spectrum MaxA of an arbitrary unital C^*-algebra A. In particular we show that the spatialization of MaxA with respect to one of the notions of spatiality in the literature yields the locale of closed ideals of A when A is commutative. We study under general conditions functors with this property, in addition requiring that colimits be preserved, and we conclude in this case that the spectrum of A necessarily coincides with the locale of closed ideals of the commutative reflection of A. Finally, we address functorial properties of Max, namely studying (non-)preservation of limits and colimits. Although Max is not an equivalence of categories, therefore not providing a direct generalization of Gelfand duality to the noncommutative case, it is a faithful complete invariant of unital C^*-algebras.     

Comparative binding energy analysis of haloalkane dehalogenase substrates: Modelling of enzyme-substrate complexes by molecular docking and quantum mechanical calculations

We evaluate the applicability of automated molecular docking techniques and quantum mechanical calculations to the construction of a set of structures of enzyme-substrate complexes for use in Comparative binding energy (COMBINE) analysis to obtain 3D structure-activity relationships. The data set studied consists of the complexes of eighteen substrates docked within the active site of haloalkane dehalogenase (DhlA) from Xanthobacter autotrophicus GJ10. The results of the COMBINE analysis are compared with previously reported data obtained for the same dataset from modelled complexes that were based on an experimentally determined structure of the DhlA-dichloroethane complex. The quality of fit and the internal predictive power of the two COMBINE models are comparable, but better external predictions are obtained with the new approach. Both models show a similar composition of the principal components. Small differences in the relative contributions that are assigned to important residues for explaining binding affinity differences can be directly linked to structural differences in the modelled enzyme-substrate complexes: (i) rotation of all substrates in the active site about their longitudinal axis, (ii) repositioning of the ring of epihalohydrines and the halogen substituents of 1,2-dihalopropanes, and (iii) altered conformation of the long-chain molecules (halobutanes and halohexanes). For external validation, both a novel substrate not included in the training series and two different mutant proteins were used. The results obtained can be useful in the future to guide the rational engineering of substrate specificity in DhlA and other related enzymes.     

Synthetic and structural studies of cobalt-pivalate complexes

The synthesis and characterisation of a range of cobalt pivalate cage complexes are reported. The cages include: a dinuclear Co(II) complex; an oxo-centred Co(III) triangle; tetranuclear Co(II) heterocubanes and butterflies; tetranuclear heterovalent cobalt butterflies and hexanuclear edge-sharing bitetrahedra; heterovalent penta-, hexa- and hepta-nuclear cages based on [M(4)O(4)] heterocubane cores; and a tetradecanuclear cage based on heterocubanes sharing edges and vertices. Spectroscopic studies suggest that some of these cores are retained in solution, but that only in the Co(III) triangle is the structure including ligands retained. A scheme is proposed to account for the many structures observed, which may be applicable to other polymetallic cage complexes.     

Characterizations of totally ordered sets by their various endomorphisms

We characterize totally ordered sets within the class of all ordered sets containing at least three-element chains using a simple relationship between their isotone transformations and the so called 2-, 3-, 4-endomorphisms which are introduced in the paper. Another characterization of totally ordered sets within the class of ordered sets of a locally finite height with at least four-element chains in terms of the regular semigroup theory is also given.     

An estimator for parameters of a nonlinear nonnegative multidimensional AR(1) process

Let e _t=(e _t1,...e _tp) be a p-dimensional nonnegative strict white noise with finite second moments. Let h _ij(x) be nondecreasing functions from [0,) onto [0,) such that h _ij(x) x for i, j = 1,...,p. Let U = (u _ij) be a p×p matrix with nonnegative elements having all its roots inside the unit circle. Define a process X t=(X _t1,...,X _tp) by for

Influence of the concentration of Ca impurity on the magnetic threshold of the magnetoplastic effect in NaCl crystals

It is found experimentally that the threshold magnetic field B _c for the magnetoplastic effect, i.e., the field at which the depinning of dislocations from paramagnetic impurities in an external magnetic field begins to be observed, increases with increasing concentration C of Ca impurity in NaCl crystals in the range C=(0.5–100) ppm. It is shown that the dependence B _c(C) exhibits a distinct tendency toward saturation. The physical interpretation of the observed dependence rests on the notion that as the impurity concentration C increases, the average size of the impurity complexes increases and, accordingly, the local atomic configuration around the impurity atoms changes according to a definite pattern. In particular, the average number of cation vacancies among the nearest neighbors increases from 1 to 6 as the number N of Ca atoms in the complex increases, and this trend, in turn, should cause the thermal vibration amplitude of the Ca atoms to increase. In other words, the phenomenon in question appears to be physically analogous in its microscopic mechanisms to the previously observed increase of B _c with increasing temperature. The proposed interpretation is further supported by good correlation of the experimental dependence B _c(C) with the calculated function . Fiz. Tverd. Tela (St. Petersburg) 40, 81–84 (January 1998)     

Characterization of a sapphire-epoxy coating for capillary electrophoresis

A new procedure for coating capillaries for capillary electrophoresis applying a sapphire (alumina) containing epoxy resin was developed. Coated capillaries showed considerably reduced electroosmotic flow, and decreased the adsorption of proteins to the internal wall of the capillary. Coating is transparent down to 195 nm and can be used with advantage to analyze different kinds of substances, such as small cations and/or anions, and proteins.     

Natural discrete-event process forecasting: A decision support system

A decision support system for the analysis and forecasting of natural discrete-event processes is considered. The corresponding method is based on the sample path analysis using event-to-event operations. An application of the method in the computer-aided decision support system for the long-range weather forecasting is mentioned.     

Decontamination of some radioactive effluents by means of ceramic filters

The paper deals with the use of some ceramic materials for the removal of⁵⁵⁺⁵⁹Fe³⁺ and⁶⁰Co²⁺ ions from residual waters. For this purpose, chamotte powder has been used both by itself or in a mixture with aluminium oxide. The pastes obtained by wetting these materials have been shaped in the form of crucibles. The radioactive ions which exist in residual effluents, have been retained to a large extent on these filters. Separately, the leaching of radioactive ions previously retained on the filtering mass, has been studied under the influence of water and of diluted solutions of hydrochloric acid or sodium chloride.     

Determination of thallium by furnace atomic absorption spectrometry

The analytical conditions for the determination of thallium by graphite furnace atomic absorption spectrometry were studied and optimized using the peak-height mode. The charring-atomization curves for thallium from different atomization surfaces were constructed and the optimum charring and atomization conditions were established. These atomization surfaces included pyrolytic graphite-, tantalum-, zirconium- and tungsten-coated graphite tubes. The effects of different inorganic acids on the absorbance of thallium from different surfaces were studied. Using tungsten carbide-coated tubes, the interference effects due to hydrochloric and perchloric acids were eliminated. The matrix modification technique was also investigated for increasing the maximum permissible charring temperature for thallium. The matrix modifiers used included tungsten, zirconium, nickel and tantalum. The effect of adding these modifiers were studied in the presence of different acids. Tungsten increased the maximum permissible charring temperature from 400 to 1000 °C.