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We propose a new and efficient method of reconstructing quark mass matrices from their eigenvalues and a complete set of mixing observables. By a combination of the principle of NNI bases which are known to cover the general case, and of the polar decomposition theorem that allows us to convert arbitrary nonsingular matrices to triangular form, we achieve a parametrization where the remaining freedom is reduced to one complex parameter. While this parameter runs through the domain bounded by the circle with radius R ϭͱ(m t 2 Ϫm u 2 )/(m t 2 Ϫm c 2 ) around the origin in the complex plane one sweeps the space of all mass matrices compatible with the given set of data.

Abstract. The aim of this study was to compare structural differences in the nirS-type denitrifying microbial communities along the environmental gradients observed in the water column and coastal sediments of the Baltic Sea. To link community structure and environmental gradients, denitrifier communities were analyzed by terminal restriction fragment length polymorphism (T-RFLP) based on nirS as a functional marker gene for denitrification. nirS-type denitrifier community composition was further evaluated by phylogenetic analysis of nirS sequences from clone libraries. T-RFLP analysis indicated some overlap but also major differences between communities from the water column and the sediment. Shifts in community composition along the biogeochemical gradients were observed only in the water column while denitrifier communities were rather uniform within the upper 30 mm of the sediment. Specific terminal restriction fragments (T-RFs) indicative of the sulfidic zone suggest the presence of nitrate-reducing and sulfide-oxidizing microorganisms that were previously shown to be important at the suboxic-sulfidic interface in the water column of the Baltic Sea. Phylogenetic analysis of nirS genes from the Baltic Sea and of sequences from marine habitats all over the world indicated distinct denitrifier communities that grouped mostly according to their habitats. We suggest that these subgroups of denitrifiers had developed after selection through several factors, i.e. their habitats (water column or sediment), impact by prevalent environmental conditions and isolation by large geographic distances between habitats.

Certain Heusler phases belong to the materials which are discussed as potential half metals. Here results of tunneling experiments with the full-Heusler alloy CoCr0.6Fe0.4Al are presented. The Heusler alloy is used as an electrode of magnetic tunneling junctions. The junctions are deposited by magnetron dc sputtering using shadow mask techniques with AlOx as a barrier and cobalt as counter electrode. Measurements of the magnetoresistive differential conductivity in a temperature range between 4K and 300K are shown. An analysis of the barrier properties applying the Simmons model to the bias dependent junction conductivity is performed. VSM measurements were carried out to examine the magnetic properties of the samples.

The perturbative construction of the S-matrix in the causal spacetime approach of Epstein and Glaser may be interpreted as a method of regularization for divergent Feynman diagrams. The results of any method of regularization must be equivalent to those obtained from the Epstein-Glaser (EG) construction, within the freedom left by the latter. In particular, the conceptually welldefined approach of Bogoliubov, Parasiuk, Hepp and Zimmermann (BPHZ), though conceptually different from EG, meets this requirement. Based on this equivalence we propose a modified BPHZ procedure which provides a significant simplification of the techniques of perturbation theory, and which applies equally well to standard quantum field theory and to chiral theories. We illustrate the proposed method by a number of examples of various orders in perturbation theory. At the level of multi-loop diagrams we confirm that subdiagrams as classified by Zimmermann's forest formula in BPHZ can be restricted to subdiagrams in the sense of Epstein-Glaser, thus entailing an important reduction of actual computations. The relationship of our approach to the method of dimensional regularization (and renormalization) is particularly transparent, without having to invoke analytic continuation to unphysical spacetime dimension. It sheds new light on the role of some parameters that appear within the dimensional regularization, and thus establishes a direct link of this traditional method to the BPHZ scheme.