Freie Vereinigung bayerischer Vertreter der angewandten Chemie

Ohne Zusammenfassung     

Insight into the Impact of Oxidative Stress on the Barrier Properties of Lipid Bilayer Models

As a new field of oxidative stress-based therapy, cold physical plasma is a promising tool for several biomedical applications due to its potential to create a broad diversity of reactive oxygen and nitrogen species (RONS). Although proposed, the impact of plasma-derived RONS on the cell membrane lipids and properties is not fully understood. For this purpose, the changes in the lipid bilayer functionality under oxidative stress generated by an argon plasma jet (kINPen) were investigated by electrochemical techniques. In addition, liquid chromatography-tandem mass spectrometry was employed to analyze the plasma-induced modifications on the model lipids. Various asymmetric bilayers mimicking the structure and properties of the erythrocyte cell membrane were transferred onto a gold electrode surface by Langmuir-Blodgett/Langmuir-Schaefer deposition techniques. A strong impact of cholesterol on membrane permeabilization by plasma-derived species was revealed. Moreover, the maintenance of the barrier properties is influenced by the chemical composition of the head group. Mainly the head group size and its hydrogen bonding capacities are relevant, and phosphatidylcholines are significantly more susceptible than phosphatidylserines and other lipid classes, underlining the high relevance of this lipid class in membrane dynamics and cell physiology.     

Spin Electronics: From Concentrated to Diluted Magnetic Semiconductors and Beyond

This presentation will review physical properties, relevant to spintronics, of concentrated magnetic semiconductors. Examples from the open literature and current research utilizing thin film EuS will be used as illustrations. New research on potential spin injection materials and spin detection will also be described. This latter work, carried out at MARTECH, the Center for Materials Research and Technology, demonstrates that carriers from the half-metal CrO₂ may be injected across an insulator without loss of (100%) spin polarization. It also features the development of a Hall gradiometer capable of detecting as few as 10⁵ spins.     

Preface: Volume 70, Issue 3

This volume contains the Proceedings of the REFINE 2002 workshop. The Workshop was held in Copenhagen, Denmark on July 20 and 21, 2002, as a satellite event to FLoC'02 as an FME-affiliated workshop.Refinement is one of the cornerstones of a formal approach to software engineering. Refinement is the process of developing a more detailed design or implementation from an abstract specification through a sequence of mathematically-based steps that maintain correctness with respect to the original specification.The aim of this BCS FACS refinement workshop was to bring together people who are interested in the development of more concrete designs or executable programs from abstract specifications using formal notations, tool support for formal software development, and practical experience with formal refinement methodologies.The purpose of the workshop was to provide a forum for discussion of common ground and key differences. Topics of interest included:

• Simulation techniques

• Foundations and semantics

• Case studies (specification and verification)

• Compositional and modular reasoning

• Object-orientation

• Time

• Specification notations

• Programming models

• Verification and tool support

The workshop continued a long tradition of refinement workshops run under the auspices of the British Computer Society (BCS) FACS special interest group. Running since 1988, previous refinement workshops have been held at Cambridge, London, Bath etc.In 1998 the BCS refinement workshop was combined with the Australasian Refinement Workshop to form the International Refinement Workshop, hosted at alongside Formal Methods Pacific 1998 at The Australian National University.The papers in this volume were reviewed by a small program committee consisting of

•

John Derrick<

jd1@ukc.ac.uk

, University of Kent, UK.

•

Eerke Boiten<

eab2@ukc.ac.uk

, University of Kent, UK.

•

Jim Woodcock<

jcpw@ukc.ac.uk

, University of Kent, UK.

•

Joakim von Wright<

jockum.wright@abo.fi

, Åbo Akademi University, Finland

Additional information about the Workshop can be found at: http://www.cs.ukc.ac.uk/people/staff/eab2/refine/floc.htmlThis volume will be published as volume 70 issue 3 in the series Electronic Notes in Theoretical Computer Science (ENTCS). This series is published electronically through the facilities of Elsevier Science B.V. and its auspices. The volumes in the ENTCS series can be accessed at the URLhttp://www.elsevier.nl/locate/entcsA printed version of the current volume was distributed to the participants at the workshop in Denmark.We are very grateful to the following persons, whose help has been crucial for the success of REFINE 2002: Lars-Henrik Eriksson and Peter Lindsay of FME for their help with the organization of the Workshop as satellite event of FLoC'02 and an FME affiliated workshop; Mike Mislove, one of the Managing Editors of the ENTCS series, for his assistance with the use of the ENTCS style files. Thanks are also due to the Computing Laboratory of the University of Kent, which supplied financial support to cover the printing costs.July 24, 2002John Derrick     

Photo‐induced Charge Transfer and Relaxation of Persistent Charge Carriers in Polymer/Nanocrystal Composites for Applications in Hybrid Solar Cells

The photo‐induced charge transfer and the dynamics of persistent charge carriers in blends of semiconducting polymers and nanocrystals are investigated. Regioregular poly(3‐hexylthiophene) (P3HT) is used as the electron donor material, while the acceptor moiety is established by CdSe nanocrystals (nc‐CdSe) prepared via colloidal synthesis. As a reference system, organic blends of P3HT and [6,6]‐phenyl C₆₁‐butyric acid methyl ester (PCBM) are studied as well. The light‐induced charge transfer between P3HT and the acceptor materials is studied by photoluminescence (PL), photo‐induced absorption (PIA) and light‐induced electron spin resonance spectroscopy (LESR). Compared to neat P3HT samples, both systems show an intensified formation of polarons in the polymer upon photo‐excitation, pointing out successful separation of photogenerated charge carriers. Additionally, relaxation of the persistent charge carriers is investigated, and significant differences are found between the hybrid composite and the purely organic system. While relaxation, reflected in the transient signal decay of the polaron signal, is fast in the organic system, the hybrid blends exhibit long‐term persistence. The appearance of a second, slow recombination channel indicates the existence of deep trap states in the hybrid system, which leads to the capture of a large fraction of charge carriers. A change of polymer conformation due to the presence of nc‐CdSe is revealed by low temperature LESR measurements and microwave saturation techniques. The impact of the different recombination behavior on the photovoltaic efficiency of both systems is discussed.     

Effects of piracetam on the performance of rats in a delayed match-to-position task

The growing use of antibody-based separation methods has paralleled the expansion of immunochemical detection methods in moving beyond the clinical diagnostic field to applications in environmental monitoring. In recent years high-performance immunoaffinity chromatography, which began as a separation technique in biochemical and clinical research, has been adapted for separating and quantifying environmental pollutants. Bioaffinity offers a selective biological basis for separation that can be incorporated into a modular analytical process for more efficient environmental analysis. The use of immunoaffinity chromatography for separation complements the use of immunoassay for detection. A widely used immunochemical detection method for environmental analyses is enzyme immunoassay. The objective of this paper is to review the status of bioaffinity-based analytical procedures for environmental applications and human exposure assessment studies. Environmental methods based on bioaffinity range from mature immunoassays to emerging techniques such as immunosensors and immunoaffinity chromatography procedures for small molecules.     

Implications of sequential use of UV and ozone for drinking water quality

The formation of bromate levels exceeding the drinking water standard of 10 microg L-1 may impose the reduction of ozone doses used in the treatment of drinking water. This paper illustrates the procedure of evaluating the use of reduced ozone doses while implementing an additional UV disinfection step for an actual drinking water treatment plant. Ozonation was performed at low ozone doses in bench-scale experiments with a pretreated river water from the Paris area (France). At the low ozone dose of 0.5 mg L-1, bromate formation could be kept below 0.4 microg L-1, while inactivation of vegetative bacteria and UV-resistant viruses was calculated to exceed 5 log units, and a substantial decoloration (31% of the absorption at lambda=254 nm) was achieved. Based on the measured transient ozone and OH radical concentrations, the oxidation of micropollutants was calculated. Fast reacting micropollutants containing phenol, amine or double bond moieties, such as sulfamethoxazole, diclofenac and 17-alpha-ethinylestradiol, were completely oxidized. Slow-reacting synthetic micropollutants, e.g., atrazine, iopromide and methyl tertiary butyl ether (MTBE), were oxidized by only 20%, 20% and 10%, respectively, and the taste and odor compounds 2-methylisoborneol (MIB) and geosmin by 40% and 50%, respectively. The addition of an UV treatment step to the existing treatment train, which should guarantee disinfection of ozone-resistant pathogenic microorganisms, including Cryptosporidium parvum oocysts, has negligible effects on water matrix components but may induce significant transformation of micropollutants. Overall, the combination of ozonation at reduced doses and UV treatment leads to an improved water quality with regard to disinfection, oxidation of micropollutants and minimization of bromate.