Cluster calculations of the electronic density of states in a Cu−Zr metallic glass

Summary The electronic density of states in glassy Cu−Zr has been computed by averaging the density of states of a number of clusters of atoms. The atomic positions in the clusters were chosen in such a way to reproduce the pair distribution function of the system. For each cluster the density of states was computed within the multiple-scattering theory by using Lloyd's formula. The results obtained are in fair agreement with the experimental dta. The computed density of states shows a clear split-band regime with a distance between the two main peaks comparable with the experimental results.

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Riassunto La densità di stati elettronici nel vetro Cu−Zr è stata calcolata mediando le densità di stati di piú cluster di atomi. Le posizioni degli atomi nei cluster sono state scelte in modo da riprodurre la funzione di distribuzione di coppia del sistema. La densità di stati è stata calcolata per ciascun cluster con la formula di Lloyd nella teoria dello scattering multiplo. I risultati ottenuti sono in buon accordo con i dati sperimentali e mostrano un chiaro regime di split-band, con una distanza fra i due picchi principali confrontabile con i risultati sperimentali.

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Резюме Вычисляется плотность электронных состояний в стекле Cu−Zr с помощью усреднения плотности состояний ряда кластеров атомов. Положения атомов в кластерах выбираются таким образом, чтобы воспроизвести парную функцию распределения этой системы. Для каждого кластера плотность состояний вычисляется с помощью формулы Ллойда теории многократного рассеяния. Полученные результаты довольно хорошо согласуются с экспериментальными данными. Вычисленная плотность состояний обнаруживает явный режим расщепления зоны, причем расстояние между двумя главными пиками сравнимо с экспериментальными результатами.

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Work sponsored also by Comitato Regionale CRRN/SM, Italy.     

Structure of ethyl(3-amino-5-nitrobenzo[b]thiophen)-2-carboxylate

The title compound was obtained as main product by the reaction of 3-chloro-5-nitro-1,2-benzisothiazole with diethyl malonate in sodium ethoxide. It crystallizes in the monoclinic space groupP2₁/n witha=12.143(5),b=11.172(4),c=8.567(3) Å,=95.51(2)°,Z=4. The structure was solved by direct methods and refined by full-matrix least-squares to a finalR value of 0.035 for 1217 reflections. The entire molecule is substantially planar except for the terminal methyl group. The amino group is involved in intra- and intermolecular hydrogen bonding.     

Stationary Solutions of Fokker-Planck Equations with Nonlinear Reaction Terms in Bounded Domains

Using an operator approach, we discuss stationary solutions to Fokker-Planck equations and systems with nonlinear reaction terms. The existence of solutions is obtained by using Banach, Schauder and Schaefer fixed point theorems, and for systems by means of Perov’s fixed point theorem. Using the Ekeland variational principle, it is proved that the unique solution of the problem minimizes the energy functional, and in case of a system that it is the Nash equilibrium of the energy functionals associated to the component equations.

     

Iodine monochloride in anhydrous acetic acid as an oxidizing agent

A systematic study of the redox reactions of iodine monochloride with various inorganic ions in glacial acetic acid medium is described. Sodium sulphite, mercury(I) perchlorate, antimony trichloride, arsenic trichloride and iron(II) perchlorate were examined. Potentiometric and amperometric methods were used to follow the reduction of iodine monochloride, which yields different products according to the type of reductant.     

Paramagnetic nitrosyliron adducts in pentasilic zeolites: an EPR study

The interaction of nitrogen monoxide with various types of iron-containing pentasilic zeolites has been investigated by EPR spectroscopy. The systems investigated were iron-silicalite, ion-exchanged ZSM-5 and a bare silicalite impregnated with iron ions at the external surface only. NO forms paramagnetic adducts on all these systems essentially reacting with Fe(II) species. Three distinct types of nytrosyl adducts have been identified all lacking the hyperfine structure. Two of them are in doublet (S=1/2) state while the third one, observed in ZSM-5 samples only and already reported in the literature, is a quadruplet (S=3/2). While all activated samples exhibit EPR spectra (due to Fe(III) ions) very similar one to each other, their reactivity towards NO is different in each case. This allows some advance in understanding the state of the activated samples which, due to the high importance of iron-containing pentasilic zeolites in heterogeneous catalysis, is the object of a active debate in the literature.     

Complex formation in Aerosol OT reversed micelles between sodium counterion and Kryptofix 221D macrobicyclic ligand

The interaction between 5-decyl-4,7,13,16,21-pentaoxa-1,10-diazabicyclo-[8,8,5]-tricosan (Kryptofix 221D) and reversed micelles of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in n-heptane as a function of AOT and water concentration was investigated by a calorimetric technique. The solubilization of the cryptand in the reversed AOT micelles produces an exothermic effect that increases with R (R=[water]/[AOT]) and is slightly dependent on AOT concentration. Processes due to the formation of a 1:1 complex between the cryptand and the sodium counterion of the AOT and to the transfer of Kryptofix 221D from bulk n-heptane to the micellar palisade layer have been taken into account to rationalize the experimental results. The peculiar solvation state of the sodium counterions near the water-AOT interface has also been considered.In part from the Doctor in Biology thesis of F. Pinio in the University of Palermo.     

Liquid chromatography-mass spectrometry in occupational toxicology: a novel approach to the study of biotransformation of industrial chemicals

Biological monitoring and biomarkers are used in occupational toxicology for a more accurate risk assessment of occupationally exposed people. Appropriate and validated biomarkers of internal dose, like urinary metabolites, besides to be positively correlated with external exposure, have a predictive value to the risk of adverse effects. The application of liquid chromatography-mass spectrometry (LC-MS) in occupational and environmental toxicology, although relatively recent, has been demonstrated valid in the determination of traditional biomarkers of exposure, as well as in metabolism studies aimed at investigating minor metabolic routes and new more specific biomarkers. This review presents selected applications of LC-MS to the study of the metabolism of industrial chemicals, like n-hexane, benzene and other aromatic hydrocarbons, styrene and other monomers employed in plastic industry, as well as to other chemicals used in working environments, like pesticides used by farmers, and antineoplastic agents prepared by hospital personnel. Analytical and pre-analytical factors, which affect quantitative determination of urinary metabolites, i.e. sample preparation, matrix effect, ion suppression, use of internal standards, and calibration, are emphasized.