Spectrophotometric determination of rhenium with 4-methylnioxime

A simple method applicable to the spectrophotometric determination of less than 0.001% to more than 1.0% of rhenium in molybdenite concentrate and in “molybdenite roaster flue dust” has been developed. Interfering elements commonly found in these materials are removed in three operations: evaporation with hydrochloric acid, precipitation of hydrous oxides with ammonia, and formation of organometallic compounds with ethyl xanthate and chloroform extraction. The method is based on the formation of a soluble, stable, yellow-green rhenium-4-methylnioxime chelate where rhenium^VII is reduced by tin^II chloride in a dilute hydrochloric acid solution in the presence of 4- methylnioxime (4-methyl-1:2-cyclohexanedionedioxime). The colour develops in less than 5 min and the chloroform extract shows a maximum absorption at 436 mμ. The calibration curve conforms to Beer's law. The molar extinction coefficient for rhenium-4-methylnioxime is about 6.89 × 10⁴ as compared to less than 4.5 × 10⁴ reported for other methods for rhenium.     

Eine Bemerkung zum Axiomensystem des Morgenstern/Thompson-Außenhandelsmodells

Zusammenfassung Es kann gezeigt werden, daß sich im Außenhandelsmodell vonMorgenstern/ Thompson gewisse Aussagen nicht unbedingt als Resultate aus dem vorgeschlagenen Axiomensystem ergeben. Werden diese Aussagen in das Axiomensystem aufgenommen, so bleibt das System unabhängig.

---

Summary In the Open Expanding Economy Model ofMorgenstern/Thompson it can be shown that some of the statements do not follow from the axioms. Adding these statements to the given system of axioms the new system is still independent.

     

Influence of coloured noise on the diffusion of a quantum particle. Part I: General results

A general stochastic model for the diffusion of a quantum particle on a fluctuating lattice is considered and several exact results useful in the calculation of transport properties are given. First, we derive a new type of integral equation for the density operator using a time-dependent projection operator and disentangling the stochastic, not the deterministic part of the motion in contrast to previous treatments. The mean square displacement is then expressed by the kernel of this equation in the case of diagonal fluctuations. We obtain an equation of motion for this kernel similar in structure to equations known from Green's function theory and containing a self-energy like quantity. Finally, two general statements concerning the exact solution of correlated models are given.     

Wavy fronts in reaction-diffusion systems with cross advection

Using a field-theoretic approach, we systematically generalize the usual semiclassical approximation for a harmonically trapped ideal Bose gas in such a way that its range of applicability is essentially extended. With this we can analytically calculate thermodynamic properties even for small particle numbers. In particular, it now becomes possible to determine the critical temperature as well as the temperature dependence of both heat capacity and condensate fraction in low-dimensional traps, where the standard semiclassical approximation is not even applicable.     

Pattern selection in biaxially stressed solids

We analyze the morphological instability of the surface of a solid which is subject to a biaxial stress. The stability calculation reveals a new favored pattern: a diamond morphology. This occurs if the stress is tensile in one direction and compressive in the orthogonal one and the ratio exceeds a certain value. A nonlinear analysis shows that the bifurcation is subcritical and hints to a nontrivial competition between tilted stripes and diamonds. This study opens a new line of inquiries in the field of stress-induced pattern selection.