[en] The infiltration of uranium from the polluted River Glatt (Switzerland) into a hydraulically connected saturated aquifer was investigated during a period of almost five years. The uranium concentrations and the ²³⁴U/²³⁸U activity ratios (ARs) were analysed monthly in the water of the river and of four groundwater sampling wells. The speciation of uranium and its relation to other aqueous and solid components were investigated experimentally and in model calculations. The uranium concentration and the ARs in the river varied seasonally with a maximum and a minimum, respectively, in summer. Processes, such as photo-reductive dissolution of iron-oxyhydroxides or the enhanced decomposition of organic matter and calcite in the upstream, eutrophic Lake Greifen may have caused these variations. Laboratory experiments confirmed a possible release of uranium by photochemical reactions. The concentration maximum of uranium was also detected in the shallow groundwater, but with a delay of about six months to the maximum in the river. Under the assumption that the maxima in the river and the groundwater were related, an in situ distribution coefficient (K_D) for uranium of ∼7 mL g^-1 can be calculated for this Quaternary gravel aquifer. Uranium was present predominantly as UO₂-carbonate complexes, whereas the formation of phosphate and organic complexes (e.g., UO₂-humates/EDTA/NTA) was negligible. Particles and colloids played a minor role for the transport of uranium in this aquifer. In the course of this study, we observed an ongoing general decrease of the uranium concentrations and a disappearance of its summerly maxima in the River Glatt. We relate this unexpected effect to a better control of the phosphate concentration in surface waters, which diminished the growth of aquatic biota. This, in turn, led to changes in the redox conditions of lake and river sediments, and herewith to a reduced release of heavy metals

[en] The author considers the nucleon polarizabilities in the framework of chiral perturbation theory to one loop order. The chiral expansion of the Compton scattering amplitude in forward direction is worked out. The non-trivial information about the nucleon structure is embodied in the electric (bar α) and magnetic (bar β) polarizabilities of the proton and the neutron. The one-loop calculation sheds light on the two most prominent empirical features that (a) the sum bar α + bar β is approximately the same for the proton and the neutron and that (b) the proton and the neutron behave essentially as electric dipoles. The author also discusses the inclusion of resonances, the calculation within the framework of heavy baryon chiral perturbation theory and the hyperon polarizabilities

[en] The properties of the effective field theory relevant for the low energy structure generated by the Goldstone bosons of a spontaneously broken symmetry are reexamined. It is shown that anomaly free, Lorentz invariant theories are characterized by a gauge invariant effective Lagrangian, to all orders of the low energy expansion. The paper includes a discussion of anomalies and approximate symmetries, but does not cover nonrelativistic effective theories. 16 refs

[en] Charge exchange properties of high first ionization potential atoms passing through thin carbon foils are discussed in the context of charge transfer models. A model is presented in which the charge state equilibrium within the solid is explained by the overlap of the atomic and the solid state electron wave functions in k space. Outside the solid, near the surface, charge exchange occurs by tunneling of electrons between the carbon surface and the exiting projectile. ((orig.))

[en] Early MRI in a case of clinically established Reye's syndrome confirmed CT findings of compressed ventricles and additionally demonstrated signal alterations in the thalamus, mesencephalon and pons. On follow-up MRI the pontine lesion had vanished by 1 week later, while the thalamic lesion persisted for more than 2 months. The patient, however, recovered without neurological sequelae. (orig.). With 3 figs

[en] We calculate the finite volume effects for the pion and nucleon mass. For the pion mass we present the results of a full two-loop calculation in chiral perturbation theory. The outcome shows that the resummed version of the Luescher formula we presented in an earlier work does indeed give an excellent approximation to the two-loop result. In view of this result we apply the same resummed formula to the nucleon mass. In the nucleon sector the extension of the chiral expansion to higher quark masses appears to be more problematic and it is therefore more difficult to make reliable predictions for the size of the finite volume effects. We present some preliminary numerical estimates

[en] The chromophore 3,3'-bithiazolo[3,4-a]pyridinium 1, obtained by oxidative cyclization reactions using a tetrathiafulvalene as a leaving group, strongly absorbs at the violet end of the visible region as evidenced by its yellow color. The solution (MeCN) spectrum displays an intensive, broad absorption band around 377 nm with a ε value of 8x10³ l mol^-1 cm^-1. The chromophore also shows a strongly Stokes-shifted fluorescence emission with a lifetime τ of 2.8±0.1 ns in acetonitrile solution. Herein, we describe the photophysical properties and a theoretical investigation of the electronic structure of the chiral dicationic, bis(bicyclic) ring assembly 1

[en] We present a detailed numerical study of finite volume effects for masses and decay constants of the octet of pseudoscalar mesons. For this analysis we use chiral perturbation theory and asymptotic formulae a la Luescher and propose an extension of the latter beyond the leading exponential term. We argue that such a formula, which is exact at the one-loop level, gives the numerically dominant part at two loops and beyond. Finally, we discuss the possibility to determine low energy constants from the finite volume dependence of masses and decay constants

[en] The objective of this article is the description of imaging techniques for the evaluation of patients with acute flank pain and suspicion of urolithiasis and the impact of these techniques in the therapy management of patients with calculi. (orig.)

No abstract available