Funktionspolymere-ein interdisziplinäres forschungsgebiet-

Functional polymers differ from structural polymers in various aspects. The most evident difference is their lack of visibility as they are mostly empolyed in surface applications, e.g. as crystal growth modifiers to inhibit encrustation in detergents, as hair setting agents, or as electro-conductive films. Additional important differences concerning the motivation for new developments, market aspects, and customer relationships are the subject of this paper. The development of technology and market competence in the field of functional polymers and the special problems of low-volume, high-performance chemicals are discussed in detail. The paper deals with examples of recent developments: Polyaramides for membranes, 3,4-polyethylenedioxythiophene as an electroconductive polymer, polyaspartic acid as a biodegradable polycarboxylate in detergents, highly crosslinked, insoluble vinylpyrrolidone/vinylimidazole copolymers for the removal of heavy metals from wine, and finally an insoluble, crosslinked polyvinylpyrrolidone-iodine complex for the sterile filtration of liquids. The outlook discusses the research challenges which remain before a full understanding of the structure/property relationships can be attained.     

A molecular dynamics simulation of bacteriophage T4 lysozyme

An analysis of a 400 ps molecular dynamics simulation of the164 amino acid enzyme T4 lysozyme is presented. The simulationwas carried out with all hydrogen atoms modeled explicitly,the inclusion of all 152 crystallographic waters and at a temperatureof 300 K. Temporal analysis of the trajectory versus energy,hydrogen bond stability, r.m.s. deviation from the startingcrystal structure and radius of gyration, demonstrates thatthe simulation was both stable and representative of the averageexperimental structure. Average structural properties were calculatedfrom the enzyme trajectory and compared with the crystal structure.The mean value of the C displacements of the average simulatedstructure from the X-ray structure was 1.1 ± 0.1 Å;differences of the backbone and angles between the averagesimulated structure and the crystal structure were also examined.Thermal-B factors were calculated from the simulation for heavyand backbone atoms and both were in good agreement with experimentalvalues. Relationships between protein secondary structure elementsand internal motions were studied by examining the positionalfluctuations of individual helix, sheet and turn structures.The structural integrity in the secondary structure units waspreserved throughout the simulation; however, the A helix didshow some unusually high atomic fluctuations. The largest backboneatom r.m.s. fluctuations were found in non-secondary structureregions; similar results were observed for r.m.s. fluctuationsof non-secondary structure and angles. In general, the calculatedvalues of r.m.s. fluctuations were quite small for the secondarystructure elements. In contrast, surface loops and turns exhibitedmuch larger values, being able to sample larger regions of conformationalspace. The C difference distance matrix and super-positioninganalyses comparing the X-ray structure with the average dynamicsstructure suggest that a ‘hinge-bending’ motionoccurs between the N- and C-terminal domains.     

Numerical characterization and experimental verification of an in-plane MEMS-actuator with thin-film aluminum heater

In this paper, a novel concept of a thermo-mechanical MEMS actuator using aluminum thin-film heaters on a thermal oxide for electrical insulation is presented. The actuator is part of an universal tensile testing platform for thermo-mechanical material characterization of one dimensional materials on a micro- and nano-scopic scale under different environmental conditions, as varying temperatures, pressure, moisture or even vacuum and is realised in BDRIE technology. It is shown, that the actuator concept fulfills the requirements for the use in a tensile loading stage along with heterogeneously integrated nanofunctional elements, following a specimen centered approach in line with bottom-up self-assembly processes. Simulation and experiment agree very well in the thermal and mechanical domain and allow subsequent optimisation of the actuator performance.     

Styryl Dyes for Synthetic-polymer Fibres.

The synthesis of a series of dyes derived from reaction of 2-methyl-4-(N-ethyl-N-hydroxyethyl)amino, lidicyano-styrene with acid chlorides, chloroformates, isocyanates and isothiocyanates is described. Data relevant to dye characterization by electron-impact induced fragmentation is reported. Dyeing and fastness properties of the dyes on cellulose secondary acetate, cellulose triacetate, nylon 6.6 and polyester fibres are discussed in terms of dye structure. Comparison is made between some related dyes derived from 2-methyl-4-(N-ethyl-N-β-aminoethyljamino-β,βdicyanostyrene.     

THE ROLE OF LATTICE OXYGEN IN THE DYNAMIC BEHAVIOR OF OXIDE CATALYSTS

The lattice of an oxide catalyst used for oxidation reactions can act as a reservoir for oxygen, storing and releasing it for reactions at the catalyst surface under appropriate conditions. The implication of this oxygen storage property of an oxide catalyst on its dynamic response characteristics has been investigated through an experimental study of 2-butene oxidation over vanadium oxide as a model reaction. Isothermal reaction rate measurements in a differential reactor and nonisothermal studies in a single pellet reactor have been carried out. Following a step increase in the feed butene concentration, isothermal reaction rate overshoot and pellet temperature overshoot were observed. These observations could be modelled in a qualitatively correct way by a very simple model accounting for the participation of lattice oxygen in the catalytic reactions under dynamic conditions. It is demonstrated through model simulations that the ignition characteristics of a catalyst pellet are significantly affected by the participation of the lattice oxygen, when steady state multiplicity is present.     

Visual learning and classification of human epithelial type 2 cell images through spontaneous activity patterns

Identifying the presence of anti-nuclear antibody (ANA) in human epithelial type 2 (HEp-2) cells via the indirect immunofluorescence (IIF) protocol is commonly used to diagnose various connective tissue diseases in clinical pathology tests. As it is a labour and time intensive diagnostic process, several computer aided diagnostic (CAD) systems have been proposed. However, the existing CAD systems suffer from numerous shortcomings due to the selection of features, which is commonly based on expert experience. Such a choice of features may not work well when the CAD systems are retasked to another dataset. To address this, in our previous work, we proposed a novel approach that learns a set of filters from HEp-2 cell images. It is inspired by the receptive fields in the mammalian's vision system, since the receptive fields can be thought as a set of filters for similar shapes. We obtain robust filters for HEp-2 cell classification by employing the independent component analysis (ICA) framework. Although, this approach may be held back due to one particular problem; ICA learning requires a sufficiently large volume of training data which is not always available. In this paper, we demonstrate a biologically inspired solution to address this issue via the use of spontaneous activity patterns (SAP). The spontaneous activity patterns, which are related to the spontaneous neural activities initialised by the chemical release in the brain, are found as the typical stimuli for the visual cell development of newborn animals. In the classification system for HEp-2 cells, we propose to model SAP as a set of small image patches containing randomly positioned Gaussian spots. The SAP image patches are generated and mixed with the training images in order to learn filters via the ICA framework. The obtained filters are adopted to extract the set of responses from a HEp-2 cell image. We then employ regions from this set of responses and stack them into “cubic regions”, and apply a classification based on the correlation information of the features. We show that applying the additional SAP leads to a better classification performance on HEp-2 cell images compared to using only the existing patterns for training ICA filters. The improvement on classification is particularly significant when there are not enough specimen images available in the training set, as SAP adds more variations to the existing data that makes the learned ICA model more robust. We show that the proposed approach consistently outperforms three recently proposed CAD systems on two publicly available datasets: ICPR HEp-2 contest and SNPHEp-2.     

Spin coating behavior of polyimide precursor solutions

Experimental data confirm the utility of the following simple equation in predicting the spin coating behavior of polyimide precursor solutions: in which .     

Temporal aggregation and spurious instantaneous causality in multiple time series models

Large aggregation interval asymptotics are used to investigate the relation between Granger causality in disaggregated vector autoregressions (VARs) and associated contemporaneous correlation among innovations of the aggregated system. One of our main contributions is that we outline various conditions under which the informational content of error covariance matrices yields insight into the causal structure of the VAR. Monte Carlo results suggest that our asymptotic findings are applicable even when the aggregation interval is small, as long as the time series are not characterized by high levels of persistence.     

Inhomogeneous Density in Die Compaction: Experiments and Finite-Element Calculations

X-ray density measurements and two-color powder displacement observations were used to determine the reliability of the cylindrical test cell as a source of data for a plasticity model of granular materials. Calculations with such a model agree well with the experimental density distribution, for the cylindrical test cell itself and for a cylindrical die, compacted from one side by means of a profiled plunger .     

Proline versus charge concept for protein stabilization against proteolytic attack

The virtue of the so-called ‘proline concept’ andthe ‘charge concept’ for stabilizing protease-susceptibleregions of a protein structure was compared on bovine pancreaticribonuclease A. Alanine 20 and serine 21, both of whichare located in a loop that is susceptible to the unspecificproteases subtilisin Carlsberg, subtilisin BPN', proteinaseK and elastase, were replaced with proline or lysine by site-directedmutagenesis. The rate constant of proteolysis was decreasedby up to three orders of magnitude for the proline mutants dependingon the site of the mutation and the protease used. In contrast,substitution by lysine increased the proteolytic resistanceby only one order of magnitude characterizing the ‘prolineconcept’ as superior to the ‘charge concept’.Although the four applied proteases are considered to be unspecific,the degree of stabilization of the ribonuclease molecule variedconsiderably, indicating the impact of individual differencesin their substrate specificity on the proteolytic resistanceand degradation pathway of the target protein. Received May 12, 2003; revised October 23, 2003; accepted October 30, 2003