Chromatographische Untersuchungen zur Polydispersität von Hydroxyethylstärke

Chromatographic Studies on the Polydispersity of Hydroxyethyl Starch. A representative sample of clinically used hydroxyethyl starch was separated by semipreparative HPSEC into narrow fractions in the range of approx. 3.000 to 800.000 D. The original sample and selected fractions were characterised by gaschromatographic methylation analysis according to their substitution degrees MS and DS, which were differentiated by the substitution positions at C2, C3 and C6 of the anhydroglucoses and their kind of glycosidic bonding α-1, α-1,4 or α-1,4,6, respectively. Furthermore, polydispersity in relations to the degree of branching was determined. Mark-Houwink and molecular weight distribution parameters determined by multi-detection HPSEC are reported. The presented data demonstrate a extensive homogeneity of the original sample. The clinical relevance is discussed.     

Processing of Emulsions of Explosive Melts

In the context of the waste disposal of explosives, generally the suitability of the processing method is of importance. When processing explosives, the choice method of treatment, after having melted out the explosive, is to emulsify the aqueous solution of the melt for the purpose of disposing the emulsified explosives by subsequent emulsions the first aim is to produce a multiple phase system consisting of two components that are practically immiscible. For this purpose, emulsifying machines that work according to the rotational-stationary principle are used. Colloid millsm, for instance, employ the viscous tensions in the laminar flow field to disrupt the droplets. Gear-ring dispersing machines, on teh other hand, will cause a disruption oif the droplets by turbulent eddies. In this work the emulsifying equipment along with the mechanisms of drop deformation with subsequent disruption will be trated.     

Photoinitiierte Polymerisation mit Dialkoxythiocarbonyldisulfiden – eine Polymerisationsreaktion mit Primärradikalabbruch

Photoinitiated Polymerization with Dialkoxy Thiocarbonyl Disulfides – a Polymerization Reaction with Primary Radical Termination The photoinduced free radical polymerization of methyl methacrylate (MMA) and some other vinyl monomers using dialkoxy thiocarbonyl disulfides ( 1 – 4 ) as photoinitiators was studied. The photolysis of these initiators leads to cleavage of the S S bond, which was determined by spin trapping experiments with phenyl tert-butyl nitrone. No evidence was found for a further thermal decomposition of the primary alkoxy thiocarbonyl sulfide radicals (R·) at room temperature. In the absence of scavengers the primary radicals react back exclusively to the initial compounds, due to a strong cage effect. By means of UV spectroscopic measurements and in the presence of MMA the quantum yields of the initiator decomposition were detected to be 0.8. The polymerization of acrylic and methacrylic derivatives can be initiated by the R·, contrary to the situation with fumarates and maleates. The mechanism of MMA polymerization depends on the light intensity absorbed by the initiators. At high intensities the combination of primary and polymer radicals terminates the chain reaction. This follows from the measured monomer exponent of α = 2, the light intensity exponent of β = 0,2 and the number of thiocarbonyl end groups of 2 in the polymers isolated. Contrary to this, in the low intensity region the experimental data obey the ideal kinetic equation. Kinetic modelling gives evidence for an interaction of the monomer with the cage radicals.     

Dissolution,Transport and Reaction at a DICY/DGEBA Interface

The curing of an epoxy consisting of the solid hardener dicyandiamide (DICY) and the resin diglycidyl ether of bisphenol A (DGEBA) is studied in a system consisting of a tablet of DICY embedded in liquid DGEBA. Dissolution of DICY within the liquid DGEBA in combination with the transport of dissolved DICY from the tablet border into DGEBA and the chemical reaction of both reactants is studied by scanning Brillouin microscopy and infrared spectroscopy. Scanning Brillouin microscopy demonstrates the spatial and temporal evolution of the static and dynamic hypersonic properties in the course of curing in the vicinity of the DICY tablet. Infrared spectroscopy performed on epoxy pieces extracted from the final sample at different distances from the tablet surface give information about the spatial evolution of the curing process. The results achieved by both techniques are finally combined to yield a better understanding of the curing of DICY-based epoxies, which transform upon curing from strongly heterogeneous systems towards increasingly homogeneous systems.     

SUPRENUM: System essentials and grid applications

The SUPRENUM idea, the project, and the system has generally been described and presented in several papers. There is also a great deal of more detailed technical papers describing SUPRENUM as a whole or certain elements of it.

Here we want to give only a very general and rough survey on the essentials of the SUPRENUM system in order to enable the reader to categorize and understand the more specific SUPRENUM papers in this special issue.

Most of the supercomputer applications today are based on grid or grid-like data structures. Grid applications play also an essential role in the SUPRENUM development: in the top-down design of the architecture, in the programming environment, in the parallelization concept of algorithms, and, of course, in the application software development itself. We therefore place some emphasis on this grid orientation in our presentation.     

A mutation in the COX5 gene of the yeast Scheffersomyces stipitis alters utilization of amino acids as carbon source, ethanol formation and activity of cyanide insensitive respiration

Scheffersomyces stipitis PJH was mutagenized by random integrative mutagenesis and the integrants were screened for lacking the ability to grow with glutamate as sole carbon source. One of the two isolated mutants was damaged in the COX5 gene, which encodes a subunit of the cytochrome c oxidase. BLAST searches in the genome of Sc. stipitis revealed that only one singular COX5 gene exists in Sc. stipitis, in contrast to Saccharomyces cerevisiae, where two homologous genes are present. Mutant cells had lost the ability to grow with the amino acids glutamate, proline or aspartate and other non-fermentable carbon sources, such as acetic acid and ethanol, as sole carbon sources. Biomass formation of the mutant cells in medium containing glucose or xylose as carbon source was lower compared with the wild-type cells. However, yields and specific ethanol formation of the mutant were much higher, especially under conditions of higher aeration. The mutant cells lacked both cytochrome c oxidase activity and cyanide-sensitive respiration, whereas ADH and PDC activities were distinctly enhanced. SHAM-sensitive respiration was obviously essential for the fermentative metabolism, because SHAM completely abolished growth of the mutant cells with both glucose or xylose as carbon source.     

Impact of a thermal treatment on the emulsifying properties of egg yolk. Part 1: Effect of the heating time

The denaturation degree of egg yolk (EY) protein was determined in dilute EY suspensions containing 20% fresh EY (w/w) as a function of the heating time (0–40 min.) at 74 °C. The impact of such a thermal treatment on the emulsifying properties of the EY was studied in a fluid oil-in-water (O/W) emulsion containing 30% oil (v/v). Heating of the EY prior to emulsification appeared to slightly increase the oil droplet size and to drastically decrease of the level of flocculation. It was also shown that the concentration of proteins in the interfacial film increases with increasing degree of EY protein denaturation, which is thought to be responsible for the change in the colloidal interactions between droplets. The increased steric repulsions due to the increased interfacial protein concentration could explain the decrease of oil droplet flocculation. The impact of such modifications on the rheological properties and creaming stability of the emulsions is discussed.