The possible production of natural flavours by amino acid degradation

Abstract  

This work describes the degradation of phenylalanine and tryptophane catalysed by their complexes with Fe(II), Co(II), and Cu(II). The influences of the central atom and of the reaction conditions on the degradation of the amino acids were observed. The necessary condition of the degradation is the possibility of a redox reaction on the central atom between M(II) and M(III). Moreover, the coordination sphere of the central cation of the transition metal must not be sterically shielded. The necessary conditions are fulfilled only in the Fe(II) complexes. The degradation is strictly anaerobic because due to the influence of oxygen, an irreversible oxidation of Fe(II) to Fe(III) proceeds. This reaction results in 5-hydroxy-1H-indol instead of the mixture of the degradation products, such as benzaldehyde, phenylacetaldehyde, and phenylacetic acid. The influence of the temperature on the catabolism is very important because the reaction accelerates with temperature increase. The phenylalanine anion acts as a reducing agent, and Fe(II) is spontaneously reduced to Fe(0).     

Technologies and the development of the Automated Metadata Indexing and Analysis (AMIA) system

The Automated Metadata Indexing and Analysis (AMIA) project aims to provide an effective digital asset management (DAM) tool for large digital asset databases. We began with text-based indexing since it is still the most reliable approach as compared with other content-based media features. AMIA not only searches for the text of the file name, but also utilizes embedded information such as the metadata in Maya files. The AMIA system builds a linked map between all dependency files. We present an approach of preserving previously established metadata created by the old DAM tools, such as AlienBrain, and integrating them into the new system. Findings indicate that AMIA has significantly improved search performance comparing to previous DAM tools. Finally, the ongoing and future work in the AMIA project is described.     

Physico-chemical forms of radiostrontium in simulated freshwaters

A method for the analysis of the physico-chemical forms of radiostrontium in waters is described and applied to the simulated lake and groundwaters to which were later added clay minerals and humus substances. The simulated water samples were fractionated using filtration and ultrafiltration: particulates, colloids and dissolved species. The dissolved species were further separated into three fractions using ion exchange: cations, anions and non-ionic species. The physico-chemical forms of radiostrontium do not appreciable change when humus substances or clay mineral or both are added to the water samples. Only about 1–6% of added radiostrontium was found in particulate and colloid fractions. The greatest amount of⁸⁵Sr was always found in the dissolved fraction, cations (>87%). Radiostrontium was never found in the dissolved fraction, anions or non-ionic species.     

Minimal surfaces in R3 with one end¶and bounded curvature

We study complete minimal surfaces M immersed in R ³, with finite topology and one end. We give conditions which oblige M to be conformally a compact Riemann surface punctured in one point, and we show that M can be parametrized by meromorphic data on this compact Riemann surface. The goal is to prove that when M is also embedded, then the end of M is asymptotic to an end of a helicoid (or M is a plane). Received: 13 January 1997 / Revised version: 15 September 1997     

The Algebraic K-Theory of Operator Algebras

We the study the algebraic K-theory of C *-algebras, forgetting the topology. The main results include a proof that commutative C*-algebras are K-regular in all degrees (that is, all theirN ^T K _iand extensions of the Fischer-Prasolov Theorem comparing algebraic and topological K-theory with finite coefficients.     

On the probability distributions of relaxation times in glasses

The scale of relaxation times in glasses has led to generalizations of the Drude model of the dielectric function in terms of an integral, containing a Drude kernel and a probability distribution. This integral equation is solved by a Mellin or a Stieltjes transform. Beyond known results, we obtain the probability distribution of the Havriliak-Negami dielectric function. Even more general classes of dielectric models can be dealt with, using Mellin's transform. They may serve as checks for numerical procedures applied to the underlying ill-posed problem, if experimental data for the dielectric function are used. Received: 2 February 1998 / Accepted: 17 March 1998