K + production inp-nucleus collisions

We present a non-perturbative dynamical study ofK ⁺ meson production in proton-nucleus collisions from 1.2 to 2.5 GeV bombarding energy. The dynamical evolution of the proton-nucleus collision is described by a transport equation of the Boltzmann-Uehling-Uhlenbeck type evolving phase-space distribution functions for nucleons, δ’s,N(1440)’s,N(1535)’s, poins and η’s with their isospin degrees of freedom. We incorporate all known sources forK ⁺ production and study their momentum and angular distributions, and the excitation function. We show that at lower energies (E _b<1.5 GeV)NΔ andNN* channels dominate the kaon yield for light systems, and the πN channel for heavy systems. At higher bombarding energies the directNN channel accounts for almost the whole cross-section.     

Steric vs. electrostatic effects in the nucleophilic addition to a hindered cyclohexanone

The relative importance of steric vs. electrostatic effects in the nucleophilic addition to (4R,6S)-4-(tert-butyldimethylsiloxy)-2,2,6-trimethylcyclohexanone (1), a well-known chiral building block, is investigated.     

The role of surface and volume defects in the fracture of glass under quasi-static and dynamic loadings

In this paper, the role of surface and volume defects on fracture in soda-lime glass is analyzed when samples are submitted to quasi-static or dynamic loadings. To investigate fracture, different experiments are carried out, namely, quasi-static compression of glass spheres and edge-on-impacts. The first test series aims at studying crack initiation. Different surface treatments are performed to study their influence on the failure load, from which it is concluded that initiation of cracks occurs in the vicinity of the contact surface. The second series is concerned with the examination of crack patterns under dynamic loadings with two different strikers (i.e., soft/flat and hard/perforating projectiles). Crack initiation under dynamic load histories is investigated near and far from the impact zone and it is concluded that it cannot take place within the volume, except in a very small zone close to the impact point. Conversely, initiation of damage from the surface, at a location far from the impact point, is possible and clearly present with a soft projectile.     

Application of radioisotope-excited X-ray fluorescence to the determination of trace elements in blood

A radioisotope-excited energy-dispersive X-ray fluorescence system has been constructed and used for the analysis of blood samples for trace elements. The possibility of determination of trace elements in blood by X-ray fluorescence based on comparison with standard reference materials has been outlined and the applicability of the method demonstrated by the analysis of blood samples. The method enables fast, non-destructive direct analyses to be carried out without lengthy sample pretreatment on a routine basis.     

Effective on-line coloring ofP 5-free graphs

An on-line algorithm is given that colors anyP ₅-free graph withf() colors, wheref is a function of the clique number of the graph.     

Microwave-assisted direct esterification of a cyclic phosphinic acid with phenols

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On linear combinatorics I. Concurrency—An algebraic approach

This article is the first one in a series of three. It contains concurrency results for sets of linear mappings of with few compositions and/or small image sets. The fine structure of such sets of mappings will be described in part II [3]. Those structure theorems can be considered as a first attempt to find Freiman-Ruzsa type results for a non-Abelian group. Part III [4] contains some geometric applications.Dedicated to the memory of P. ErdsResearch partially supported by HU-NSF grants OTKA T014302 and T019367.     

Spectroelectrochemistry of tetracyanoquinodimethane modified electrodes

Thin films of a tetracyanoquinodimethane (TCNQ) oligomer adsorbed on optically transparent platinum electrodes have been studied using spectroelectrochemical techniques. In contact with aqueous electrolytes the electron aceptor sites in these modified electrodes are reduced to mixtures of the radical aion, TCNQ^?, the dimer radical anion, TCNQ^2?₂, the dimer dianion, TCNQ₂^2?, and the dianion, TCNQ^2∮. Electrolyte effects on the reduction process and the stability of the reduced films were studied. Both monovalent and divalent ions exhibited Nernstian potential dependence, and in the presence of Ca²⁺ ions the dianion state was stabilized. Counterion effects are suggested as the origin of variations in the wave shape in multcycle voltammograms.