Existence regions of regimes with anomalously high rates of plasma generation in grid plasma switch elements

Results are presented from a systematic investigation of the conditions under which anomalously high rates of plasma generation are observed in the anode region of a low-voltage Knudsen arc in grid plasma switch elements. The phenomenon develops over a wide range of currents and switched voltages under conditions for which the plasma density in the cathode-grid region is noticeably higher than the density in the anode region. and its onset is characterized by a pronounced pressure threshold of ∼2×10⁻² Torr. The results are analyzed from the standpoint of the possible mechanisms for anomalous plasma generation — collisional nonresonance diffusion of electrons in velocity space, leading to enrichment of the distribution function in fast particles, and the collapse of Langmuir waves in the gap at the high energies of the beam produced when the wires of the grid are bridged by the quenching pulse and and the current is blocked. Zh. Tekh. Fiz. 67, 15–21 (June 1997)     

The solvable radical of Sylow factorizable groups

Let G be a finite group. A complete Sylow product of G is a product of Sylow subgroups of G, one for each prime divisor of |G|. We shall call G a Sylow factorizable group if it is equal to at least one of its complete Sylow products. We prove that if G is a Sylow factorizable group then the intersection of all complete Sylow products of G is equal to the solvable radical of G. We generalize the concepts and the result to Sylow products which involve an arbitrary subset of the prime divisors of |G|. Received: 26 January 2005     

The Chemical Potential

The definition of the fundamental quantity, the chemical potential, is badly confused in the literature: there are at least three distinct definitions in various books and papers. While they all give the same result in the thermodynamic limit, major differences between them can occur for finite systems, in anomalous cases even for finite systems as large as a cm³. We resolve the situation by arguing that the chemical potential defined as the symbol μ conventionally appearing in the grand canonical density operator is the uniquely correct definition valid for all finite systems, the grand canonical ensemble being the only one of the various ensembles usually discussed (microcanonical, canonical, Gibbs, grand canonical) that is appropriate for statistical thermodynamics, whenever the chemical potential is physically relevant. The zero–temperature limit of this μ was derived by Perdew et al. for finite systems involving electrons, generally allowing for electron–electron interactions; we extend this derivation and, for semiconductors, we also consider the zero–T limit taken after the thermodynamic limit. The enormous finite size corrections (in macroscopic samples, e.g. 1 cm³) for one rather common definition of the c.p., found recently by Shegelski within the standard effective mass model of an ideal intrinsic semiconductor, are discussed. Also, two very–small–system examples are given, including a quantum dot.     

Numerical treatment of an asset price model with non-stochastic uncertainty

In contrast to stochastic differential equation models used for the calculation of the term structure of interest rates, we develop an approach based on linear dynamical systems under non-stochastic uncertainty with perturbations. The uncertainty is described in terms of known feasible sets of varying parameters. Observations are used in order to estimate these parameters by minimizing the maximum of the absolute value of measurement errors, which leads to a linear or nonlinear semi-infinite programming problem. A regularized logarithmic barrier method for solving (ill-posed) convex semi-infinite programming problems is suggested. In this method a multi-step proximal regularization is coupled with an adaptive discretization strategy in the framework of an interior point approach. A special deleting rule permits one to use only a part of the constraints of the discretized problems. Convergence of the method and its stability with respect to data perturbations in the cone of convexC ¹-functions are studied. On the basis of the solutions of the semi-infinite programming problems a technical trading system for future contracts of the German DAX is suggested and developed. Supported by the Stiftung Rheinland/Pfalz für Innovation, No. 8312-386261/307.     

Stable hysteretic reflection of light at a nonlinear interface

We have observed a hysteretic (bistable) reflection of a Gaussian laser beam at the interface between glass and a liquid solution of polystyrene microspheres as nonlinear medium with both branches of the hysteretic curve being stable, in contrast to the results of previous experiments.     

Enzymatic polymerizations using surfactant microstructures and the preparation of polymer-ferrite composites

Applied Biochemistry and Biotechnology - Horseradish peroxidase has been used as a biocatalyst to synthesize a polymeric material from alkyl-substituted phenols. The synthesis is carried out in a...     

PHOTOREVERSION VON VIER GRUPPEN UV-INDUZIERTER MUTATIONEN ZUR GIFTRESISTENZ IM NICHTPHOTOREAKTIVIERBAREN E. COLI

Abstract— In the non-photoreaclivable bacterial strain E. coli B/phr^-/MC2 the photoreversion of four groups of u.v.-induced mutations were investigated. They lead to resistance to Chloramphenicol (2 mg/l; "C"), Penicillin (13 or 16 mg/l; "P13" and "P16") or Streptomycin (3 mg/l; "S"). The u.v.-dose curve is concave for the C-mutations (two to three hits), about linear for P13 and S, and they reach peaks and decrease at high u.v.-doses. Though no photoreactivation of killing (PR) is present there is photoreversion of all four types of mutations (PRM). At u.v.-doses below the peaks in average about 43 per cent mutations are photoreversible. At high u.v.-doses the curves with light-post treatment (L) cross the darkcurves (D). In the photoreactivable strain B/r (by the spontaneous mutation MC2 to Mitomycin-resistance strain B/phr^- was made about as u.v.-resistant as B/r is) the photoreversion of the mutation groups C, P13 and P16 (S was not investigated here) was much higher, in average about 77 per cent at low doses. It is assumed that the difference in PRM of about 34 per cent between both strains is due to a PRM-mechanism present in B/r but not in B/phr^-/MC2; this mechanism may be the photoreactivating enzyme that opens thymine-dimers. The PRM in B/phr-/MC2 must then be due to a second mechanism which is probably not the dimer opening enzyme. It may be the same mechanism as in the case of mutations of phage kappa which are induced by u.v. and reversed partially by light, both extra cellularly. The premutations giving this second type of PRM may perhaps be cytosine-hydrate in the DNA. Tn average about 23 per cent mutations of B/r are photostable. Since this ratio decreases with low u.v.-doses in the C-mutations and increases in P13 and in P16 probably two types of photostable premutations seem to exist.