Dynamic mechanical analysis

Using dynamic mechanical analysis (DMA) we have studied thermal degradation for a system containing a diglycidyl ether of bisphenol A (DGEBA) and 1,3-bisaminomethylcylohexane (1,3-BAC). The changes of dynamic mechanical properties during thermal degradation indicated a shift of the glass transition temperature (T _g) to higher temperatures and a decrease in the peak value of the dynamic loss factor (tan δ) with an increasing of aging time. The value of dynamic storage modulus (E′) at the rubbery state showed an increase with aging time, whiteE′ at the glassy state only underwent a moderate change with increased thermal degradation. From these results it can be argued that thermal degradation during the stage prior to the onset of the severe degradation involves structural changes in the epoxy system, as further crosslinking and loss of dangling chains in the crosslinked network.     

Use of new composite materials for the determination of Cu, Cd, Mo, As, and Sb in biological samples by radiochemical neutron activation analysis

Summary  Vezetéknév     

Local solution for the Kadomtsev-Petviashvili equation with periodic conditions

In this article we prove a local existence and uniqueness theorem for the Kadomtsev-Petviashvili Equation (u _t +u _xxx +uu _x ) _x −u _yy =0) in the Sobolev spaces of orders≥3, with initial values in the same spaces, and periodic boundary conditions. This theorem improves previous results based upon the application of singular perturbation techniques.     

Electrostatic potentials of molecules and prediction of the lewis acid-base properties of solvents,part I. General considerations

Summary Electrostatic potentials in the vicinity of isolated molecules of typical nonaqueous solvents were computed in the MNDO approximation. It was found that the calculated dipole moments are in good agreement with experimental values. However, it turned out that in many cases electrostatic interactions of ions with solvent molecules cannot be described in the frame of ion-dipole interactions. Thus, two computable parameters,UN andUP describing short-range electrostatic interactions of a solvent molecule with a cation or an anion of radiusR were proposed. The dependence ofUN andUP uponR is analyzed in the context of ion-solvent interactions.

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Elektrostatische Potentiale von Molekülen und Voraussage von Lewis-Säure-Base-Eigenschaften von Lösungsmitteln, 1. Mitt.: Allgemeine Grundlagen

Zusammenfassung Es wurden die elektrostatischen Potentiale in der Umgebung von isolierten Molekülen typischer nichtwäßriger Lösungsmittel in der MNDO-Näherung berechnet. Die berechneten Dipolmomente waren in guter Übereinstimmung mit den experimentellen Werten. Es wurde jedoch beobachtet, daß in vielen Fällen die elektrostatischen Wechselwirkungen von Ionen mit Lösungsmittelmolekülen nicht im Rahmen von Ionen-Dipol-Wechselwirkungen beschrieben werden können. Dafür wurden zwei berechenbare ParameterUN undUP zur Beschreibung von elektrostatischen Wechselwirkungen im Nahbereich eines Lösungsmittelmoleküls mit einem Kationen- oder AnionenradiusR vorgeschlagen. Die Abhängigkeit vonUN undUP vonR wurde im Zusammenhang von Ionen-Solvens-Wechselwirkungen untersucht.

     

Mössbauer spectroscopic study of Prussian Blue from different provenances

Ferric ferrocyanides synthesized from different sources of ferric cations and ferrocyanide anions and those derived from ferrous ferricyanide, ferrous ferrocyanide and ferric ferricyanide have been studied using Mössbauer and XRD techniques. Structural information of the effect of the provenance on the properties of the final compound is obtained. Significant correlations between isomer shift and quadrupole splitting of inner and outer iron cations have been observed.     

Matrix-Untersuchungen zu monomerem Kupfer(I)-chlorid und seinen Komplexen mit N2 und PN IR-spektroskopische Nachweise und ab-initio Rechnungen

Matrix-Investigations on Monomeric Copper(I) Chloride and its Complexes with N₂ and PN Ligands. IR Spectroscopic Results and ab-initio Calculation In solid argon the reaction of monomeric CuCl with N₂ yields ClCuN₂. On the basis of two absorptions in the ir-spectrum and their corresponding isotopic shifts (_14/15N) and with the help of a normal coordinate analysis, linearity of the molecule has been deduced. These results are confirmed by large scale ab-initio Calculations (CPF, MP2). Reaction of monomeric CuCl with molecular PN under matrix condition is shown to give rise to new absorptions in the IR spectrum which arev assigned to a linear molecule ClCuNP.     

TDPAC study in ZnTiF6·6H2O between room temperature and 1273 K

Using the time differential perturbed angular correlation technique, the hyperfine interactions as titanium sites in ZnTiF6·6H₂O and its decomposition products were determined between room temperature (300 K) and 1273 K. The different steps in the decomposition pattern were identified and a simple model is given for it.     

Regularity and other properties of absolutely continuous invariant measures for the quadratic family

In the current paper we study in more detail some properties of the absolutely continuous invariant measures constructed in the course of the proof of Jakobson's Theorem. In particular, we show that the density of the invariant measure is continuous at Misiurewicz points. From this we deduce that the Lyapunov exponent is also continuous at these points (our considerations apply just to the parameters constructed in the proof of Jakobson's Theorem). Other properties, like the positivity of the Lyapunov exponent, uniqueness of the absolutely continuous invariant measure and exactness of the corresponding dynamical system, are also proved.This paper was written during the author's stay at the IAS while supported by NSF grant DMS-860 1978