Determination of arsenic at a gold-plated carbon paste electrode using constant current stripping analysis

A new stripping method for the determination of arsenic in water samples with a gold film-plated carbon paste electrode has been developed for the use in constant current stripping analysis (CCSA). In the novelized procedure, differentiation between As(III) and chemically pre-reduced As(V), the effect of Cu(II) on the response of arsenic, and the stability of sample solutions were studied in detail. Compared to the voltammetric approach, the method utilizing CCSA offers a more rapid procedure with improved analytical characteristics such as reproducibility, selectivity over the Cu(II) ions, or lower detection limit (3 ppb for As(III) and 0.5 ppb for As(V), respectively). The possibilities of the optimized method are demonstrated by determinations of As(III), As(V), and total arsenic in samples of polluted river water.     

Expression patterns of antioxidant proteins in brains of patients with sporadic Creutzfeldt-Jacob disease

Using two-dimensional gel electrophoresis (2-DE) and Western blot analysis, we were able to identify and quantify six antioxidant proteins, peroxiredoxin (Prx) I, Prx II, Prx III, 1-Cys Prx, putative peroxisomal antioxidant enzyme (PLP), and mitochondrial Mn superoxide dismutase (Mn-SOD) in two individual brain regions, cerebellum and frontal cortex of patients with sporadic Creutzfeldt-Jacob (sCJD). Among six antioxidant proteins, 1-Cys Prx showed significant increase (P > 0.05) in sCJD frontal cortex whereas Prx I was decreased (P > 0.01). In cerebellum, levels of all antioxidant proteins studied were comparable to those of controls. Our findings provide evidence for the link between aberrant expression of antioxidant proteins, 1-Cys Prx and Prx I and CJD neuropathogenesis and we discuss the neuropathological meaning of these dysregulated antioxidant proteins in sCJD brain.     

On the distribution of the length of the longest increasing subsequence of random permutations

The authors consider the length, , of the longest increasing subsequence of a random permutation of numbers. The main result in this paper is a proof that the distribution function for , suitably centered and scaled, converges to the Tracy-Widom distribution of the largest eigenvalue of a random GUE matrix. The authors also prove convergence of moments. The proof is based on the steepest descent method for Riemann-Hilbert problems, introduced by Deift and Zhou in 1993 in the context of integrable systems. The applicability of the Riemann-Hilbert technique depends, in turn, on the determinantal formula of Gessel for the Poissonization of the distribution function of .

     

A Projection Method for the Integer Quadratic Knapsack Problem

In this paper we present a new branch and bound algorithm for solving a class of integer quadratic knapsack problems. A previously published algorithm solves the continuous variable subproblems in the branch and bound tree by performing a binary search over the breakpoints of a piecewise linear equation resulting from the Kuhn-Tucker conditions. Here, we first present modifications to a projection method for solving the continuous subproblems. Then we implement the modified projection method in a branch and bound framework and report computational results indicating that the new branch and bound algorithm is superior to the earlier method.     

ARC study of the oxygen Schumann-Runge system

Other investigations have shown that the Schumann-Runge system of oxygen is excited by an inverse predissociation mechanism, O + O→ O^*₂. Under the condition where this excitation mechanism dominates, there is some question as to whether the radiation yielded a true rotational/vibrational electronic band spectrum, as opposed to a recombination continuum. Furthermore, there is controversy as to whether the spectral intensity is that given by equilibrium theory. The present work utilized a 1 atm arc jet facility to heat air and O₂-noble gas mixtures to temperatures between 3000 and 3500°K. Both photographic and photoelectric spectra were recorded. In the latter case, wavelength scans from 2000 to 6000 Å were carried out with 5 Å resolution to obtain absolute intensity data. The spectra were found to have true rotational/vibrational electronic band structure, and were identified as the O₂ Schumann-Runge ssytem. Comparison with an equilibrium radiation model showed excellent agreement. A slight adjustment was made in the electronic transition moment for the NO(β) system as demanded by the air runs.     

Identitäten und das Radikal in Jordan-Tripelsystemen

Ohne Zusammenfassung     

KonvexitÄtsaussagen zum linearen stochastischen Optimierungsproblem

Ohne Zusammenfassung     

Interpretation of Einstein's theory of gravitation including the cosmological term as a de Sitter-invariant field theory on the de Sitter space

In order to remove the singular nature of Einstein's theory of gravitation including theΛ term, within the domain of field theories, it is shown that this theory can be consistently interpreted as a field theory on the fixed de Sitter space, invariant with respect to the de Sitter groupO(4,1). The corresponding field equations as well as the equations of motion are derived, their structural properties are discussed, and they are integrated for a spherical mass source of the field.