ϑ-pinch in extrinsic InSb

The compression of an electron-hole plasma, caused by a ?-pinch in extrinsic InSb of 140 K, was investigated by measuring the absorption of 10·6 μm radiation and the change of the magnetic flux in the sample. A plasma density of 5 × 10¹⁵ cm^?3 was hereby found. The temporal development of the plasma density indicates that the electrons and holes resulted from impact ionization in the electric field when the magnetic field was low. Since the electric field is highest at the sample surface, the ionization was limited to the outer region of the sample and the plasma was transmitted to the inner sample volume by the ?-pinch.     

Empirical bounds for ruin probabilities

We consider the classical model for an insurance business where the claims occur according to a Poisson process and where the distribution for the cost of each claim fulfills Cramér's tail-condition. Under these conditions Lundberg's constant R is of fundamental importance for ruin calculations.We derive estimates of R, based on an observation of the insurance business and investigate the statistical properties of those estimates. We further derive bounds and confidence intervals for ruin probabilities.     

1-Aryl-6-azauracile, 7. Mitt.: Herstellung einiger funktioneller Derivate der 1-Phenyl-6-azauracil-5-carbonsäure

Zusammenfassung In der vorliegenden Arbeit wird die Herstellung des Chlorids (1), von Estern (2a, 2b), Amiden (3a-3g), des N-Hydroxyamids (3h) und Hydrazids (3i) der 1-Phenyl-6-azauracil-5-carbonsäure beschrieben.     

Gauge fields,BRS symmetry and the Casimir effect

The canonical quantization of the photon field in covariant gauge is studied in the presence of static boundaries, on which the field satisfies either “bag” or superconductor boundary conditions. The inclusion of the Fadeev-Popov ghost fields is found to be essential for agreement with Coulomb gauge calculations of the Casimir energy.     

Constitutive equations based on the transient network concept

A consitutive theory for polymetric liquids based on the transient network concept is developed, following Wiegel and Jongschaap. The Phan-Thien-Tanner equation is shown to follow from the general theory with two critical assumption, one of these is quasi-equilibrium of the internal structure, which preludes consistency of application in ”fast flows“. The Marrucci model can be made consistent with the general format with a small change in the kinetic equation that can be deduced from asymptotic behaviour and leaves the steady viscometric behavior unchanged. The simplest genaral formulation requires the linear viscoelastic spectrum and two parameters; the latter cannot be determined uniquely from steady viscometric flow data.     

Application of the flory-mandelkern equation to individual unfractionated polymer samples

A method is developed for the application of the Flory-Mandelkern equation to the determination of the weight-average molecular weights of individual, broad, unfractionated polymer samples. The method includes appropriate averaging of the sedimentation constants and of the intrinsic viscosity of an unfractionated polymer sample in a θ solution from the velocity sedimentation data. By means of the method, individual samples of polystyrene, poly(isooctyl methacrylate) and of the copolymer of styrene with 20% isooctyl methacrylate prepared under the same emulsion polymerization conditions from commercial monomers have been investigated. Appropriate θ solvents have been found by the Elias method. Equations for the dependence of the sedimentation constants and of the intrinsic viscosities in the θ solvents on the molecular weights have been established for the polymers without fractionation. Osmometric and light-scattering measurements as well as Archibald experiments have shown that by the proposed method the molecular weight cut-off effect is eliminated in the above equations and in the polydispersity parameter M _w/M _n. Molecular weight distributions have been determined for the polymer samples.     

Synthèse des pseudocyphellarines A et B,deux depsides du lichen Pseudocyphellaria endochrysea

Synthesis of Pseudocyphellarins A and B, Two Depsides from the Lichen Pseudocyphellaria endochrysea The total synthesis of the depsides pseudocyphellarin A (= 3-hydroxy-4-methoxycarbonyl-2,5,6-trimethyl-phenyl 3-formyl-2,4-dihydroxy-5,6-dimethylbenzoate; 11 ) and pseudocyphellarin B (3-hydroxy-4-methoxycarbonyl-2,5,6-trimethylphenyl 2,4-dihydroxy-3-hydroxymethyl-5,6-dimethyl benzoate; 12 ) is described.