A quantitative ionicity scale for liquid chloride salts

Knowledge of ionicity is requisite for successful identification of those salt qualities required to design and couple the most appropriate fluid for performance of an intended chemical function. We report on utilisation of (35)Cl(-) quadrupolar coupling constants (C(Q)) to quantitatively assess the ionicities of given chloride salts, by exploiting the electronic response of the quadrupolar chlorine atom as a function of its immediate chemical environment. We find that protic salts in particular, like their aprotic analogues, are highly ionised, while at the same time being highly associated, in stark contrast to literature reports claiming in general that they are of sub-ionic origin.     

Effect of sorbitan-based surfactants on glass transition temperature of cellulose esters

Thermal behavior of mixtures composed of cellulose acetate butyrate (CAB), carboxymethylcellulose acetate butyrate (CMCAB), or cellulose acetate phthalate (CAPh), and sorbitan-based surfactants was investigated as a function of mixture composition by means of differential scanning calorimetry (DSC). Surfactants with three different alkyl chain lengths, namely, polyoxyethylenesorbitan monolaurate (Tween 20), polyoxyethylenesorbitan monopalmitate (Tween 40), and polyoxyethylene sorbitan monostearate (Tween 60) were chosen. DSC measurements revealed that Tween 20, 40, and 60 act as plasticizers for CAB, CMCAB, and CAPh (except for Tween 60), leading to a dramatic reduction of glass transition temperature (T _g). The dependence of experimental T _g values on the mixture composition was compared with theoretical predictions using the Fox equation. Plasticization was strongly dependent on mixture composition, surfactant hydrophobic chain length, and type of cellulose ester functional group.     

Standardization of NAA Using the Activation Equation and Isotope-Related Constants

A standardization method for NAA has been developed based on the activation equation and on isotope-related k _i -values that are composite nuclear constants. This approach combines the simplicity of the absolute methods with nearly the same accuracy as that obtained by the relative ones. The k _i -constants are calculated from the well measured k ₀-factors and the neutron flux is determined as with the k ₀-method. A computer program was developed for the determination of the neutron flux parameters and the concentration of the trace element. These calculations start with the measured activity of the radionuclides.     

Growth of strain-compensated GaInNAs/GaAsP quantum wells for 1.3 μm lasers

Strain-compensated GaInNAs/GaAsP quantum well structures and lasers were grown by gas source molecular beam epitaxy using a RF-plasma nitrogen radical beam source. The optimal growth condition for the quantum well structure was determined based on room-temperature photoluminescence measurements. Effects of rapid thermal annealing (RTA) on the optical properties of GaInNAs/GaAsP quantum well structures as well as laser diodes are examined. It was found to significantly increase the photoluminescence from the quantum wells and reduce the threshold current density of the lasers, due to a removal of N induced nonradiative centers from GaInNAs wells.     

Bose-Einstein correlations in neutrino and antineutrino interactions in deuterium

Bose-Einstein correlations between pions of equal charge have been observed in Charged Current and Neutral Current (anti)neutrino-deuterium interactions in the BEBC bubble chamber exposed to the SPS wide band beam. The pion emission region is found to be essentially spherical with a mean radius of (0.48±0.07) fm; the chaoticity parameter is 0.36±0.04.     

Corner bifurcations in non-smoothly forced impact oscillators

We consider an impacting mechanical system in which a particle at position u(t) impacts with a periodically moving obstacle at position z(t), the motion of which is non-smooth. In particular we look at corner events when u impacts with z very close to a point where z loses smoothness. We show that this leads, through a corner bifurcation, to complex dynamics in u which can include periodic orbits of arbitrary period and period-adding cascades. By analysing associated maps close to the corner event, we show that this dynamics can be understood in terms of the iterations of a two-dimensional, piecewise linear, discontinuous map. We also show some links between this analysis and the difficult problem of understanding the motion of three objects which may have simultaneous impacts.     

Application of a low-level anti-coincidence gamma-spectrometer for environmental radioactivity measurement

Sensitive environmental radioactivity measurement using direct γ-spectroscopy needs to be carried out under particular low-level conditions as the quantity to be determined generally is very close to the natural background. Passive shielding of the detectors in addition to electronic suppression of Compton background resulting from scattering of high energy γ-rays in the gemanium detector seems to be the most promising approach to obtain statistically well defined peaks within reasonable measurement time. Results obtained with a heavily shielded anti-coincidence spectrometer installed at the Research Center Jülich, ideally suited for the measurement of low-level environmental radioactivity in various materials are described.     

Mellin operators and pseudodifferential operators on graphs

We demonstrate how Mellin operator calculus can be used to study the mapping properties of the Dirichlet to Neumann map on graphs. These operators naturally arise in photonic crystal theory. The calculus adds rigour to some previously given heuristic arguments.