Random-Walk Aggregation Phenomena in Solid Bimodal Liquid Dispersions: Transition to Nondeterminism from Si3N4to Si3N4+ Al2O3Aqueous Systems

This paper, which is based on another recent work, (Mezzasalma, S. A.,Phys. Rev. E55(4), (1997)) deals with experiments and theory concerning an aqueous dispersed system formed from silicon nitride (Si₃N₄), alumina (Al₂O₃), and mixed silicon nitride + alumina (Si₃N₄+ Al₂O₃) solid agglomerates. From titration data applied to a thermodynamic equilibrium condition, the minimum number of each agglomerate species and their maximal average dimensions have been derived as functions of the aqueous solution pH. These parameters are of the order of, respectively, (1–2) μm for Si₃N₄and Al₂O₃agglomerates and (20–50) μm for the mixed agglomerates. The numbers of solid particles of all species are poorly correlated with changes in pH of the liquid phase. This behavior has been interpreted as intrinsically related to the complexity of the system which, due to the many interactions among the different species, probably becomes nondeterministic. In order to describe such behavior a probabilistic approach has been developed. The probability of finding a given solid agglomerate number within a scatter band varies with the suspension pH. Furthermore, the scatter band amplitude becomes negligible near the isoelectric point. Accordingly, only the numbers of aggregates derived in the neighborhood of the isoelectric point are predictable.     

Domination number of catacondensed hexagonal systems

Journal of Mathematical Chemistry - In this paper we answer all the conjectures about the domination number of a catacondensed hexagonal system given in Automated Conjecturing VI: Domination Number...     

The local structure of gadolinium vanadate–tellurate glasses and glass ceramics: Te2V2O9 crystalline phase

Glasses in the system xGd₂O₃ · (100 − x)[0.7TeO₂ · 0.3V₂O₅] with 0 ≤ x ≤20 mol% have been prepared from melt quenching method. Influence of gadolinium ions on structural behavior in vanadate–tellurate glasses has been investigated using FTIR spectroscopy, X-ray diffraction (XRD), and magnetic susceptibility measurements. The structural changes have been analyzed with increasing rare earth concentration. The structural changes, as recognized by analyzing band shapes of XRD and FTIR spectra, revealed that Gd₂O₃ causes a higher extent of network polymerization as far as 20 mol%. The structure of the heat-treated glasses was found to consist mainly of the Te₂V₂O₉ crystalline phase. These vitreous systems were investigated by magnetic susceptibility measurements. From the paramagnetic susceptibility χ was calculated at different temperature and from the 1/χ(T) graph, the Curie temperature of the glass has been evaluated. Magnetic susceptibility data show the presence of small antiferromagnetic interactions between the Gd⁺³ ions.     

Memetic algorithms, domain knowledge, and financial investing

How might domain knowledge constrain a genetic algorithm and systematically impact the algorithm’s traversal of the search space? In particular, in this paper the hypothesis is advanced that a semantic tree of financial knowledge can be used to influence the results of a genetic algorithm for financial investing problems. An algorithm is described, called the “Memetic Algorithm for Domain Knowledge”, and is instantiated in a software system. In mutation experiments, this system chooses financial ratios to use as inputs to a neural logic network which classifies stocks as likely to increase or decrease in value. The mutation is guided by a semantic tree of financial ratios. In crossover experiments, this system solves a portfolio optimization problem in which components of an individual represent weights on stocks; knowledge in the form of a semantic tree of industries determines the order in which components are sorted in individuals. Both synthetic data and real-world data are used. The experimental results show that knowledge can be used to reach higher fitness individuals more quickly. More interestingly, the results show how conceptual distance in the human knowledge can correspond to distance between evolutionary individuals and their fitness. In other words, knowledge might be dynamically used to at times increase the step size in a search algorithm or at times to decrease the step size. These results shed light on the role of knowledge in evolutionary computation and are part of the larger body of work to delineate how domain knowledge might usefully constrain the genetic algorithm.     

Abelian groups which have trivial absolute coGalois group

In this article we characterize those abelian groups for which the coGalois group (associated to a torsion free cover) is equal to the identity.     

Range sets for weak efficiency in multiobjective linear programming and a parametric polytopes intersection problem

ABSTRACT

The aim of this paper is to obtain the range set for a given multiobjective linear programming problem and a weakly efficient solution. The range set is the set of all values of a parameter such that a given weakly efficient solution remains efficient when the objective coefficients vary in a given direction. The problem was originally formulated by Benson in 1985 and left to be solved. We formulate an algorithm for determining the range set, based on some hard optimization problems. Due to toughness of these optimization problems, we propose also lower and upper bound approximation techniques. In the second part, we focus on topological properties of the range set. In particular, we prove that a range set is formed by a finite union of intervals and we propose upper bounds on the number of intervals. Our approach to tackle the range set problem is via the intersection problem of parametric polytopes. Thus, our results have much wider area of applicability since the intersection (and separability) problem of convex polyhedra is important in many fields of optimization.     

Surface tension and density of liquid Bi–Pb,Bi–Sn and Bi–Pb–Sn eutectic alloys

Surface tension and density measurement of liquid Bi₅₆Pb₄₄, Bi₄₃Sn₅₇ and Bi₄₆Pb₂₉Sn₂₅ eutectic alloys was carried out by using the large drop method over the temperature range of 380–750 K. The regular solution model has been used in conjunction with Butler's equation to calculate the surface tension of binary and ternary alloys of the Bi–Pb–Sn system, while the surface tension of ternary alloys has also been predicted by using geometric models. The new experimental results were compared with the calculated values of the surface tension as well as with the data available in the literature.     

Coprinus comatus filtrate extract,a novel neuroprotective agent of natural origin

Abstract

In vitro acetylholinesterase (AChE) inhibitory activity of an autochthonous sample of the mushroom Coprinus comatus (encompassing fruiting body FB, mycelia M and filtrate F from the submerged cultivation) was the subject of this study. C. comatus F extract exhibited rather potent anti-AChE activity (73.0?±?1.5%) at in liquid conditions, comparable to those of the conventional drug donepezil (80.6?±?1.4%). Also, the same extract exhibited high anti-AChE activity (1?µg) in solid. While its FTIR spectrum indicated the presence of phenolic compounds, quercetin (28.1?µg g^?1 d.w.) was found to affect the observed bioactivity (59.8?±?0.9%). This is the first report of profound anti-AChE activity of any C. comatus extract, a medicinal mushroom that has been successfully cultivated in P.R. China, due to the demanding needs of food industry.     

Solitary wave solutions to the Tzitzeica type equations obtained by a new efficient approach

The properties of Tzitzeica equations in nonlinear optics have received a great attention of many recent studies. In this work, the so-called generalized exponential rational function method (GERFM) has been applied for finding the analytical solution of two nonlinear partial differential equations type of equations, namely Tzitzeica-Dodd-Bullough and Tzitzeica equation. The proposed method provides a wide range of closed-form travelling solutions leading to a very effective and simply-applied method by means of a symbolic computation system. The method not only provides a general form of solutions with some free parameters but also shows potential application to other types of nonlinear partial differential equations.     

Spectroscopic Characterization of Dental Ceramics Composed of Yttrium-Stabilized Zirconium

Yttria–zirconia ceramics in various compositions of Y₂O₃ and SiO₂ were synthesized by a high temperature solid state reaction process in alumina crucibles at 1400°C for 2?h. The obtained samples were characterized by X-ray diffraction, infrared spectroscopy and X-ray absorption near edge structure analysis. Combining all of the structural characterizations, we conclude that the addition of lower Y₂O₃ and SiO₂ contents induces structural changes in the host matrix without partially or/and fully stabilizing the lattice of the zirconia crystalline phase.