Self-similar chain conformations in polymer gels

We use molecular dynamics simulations to study the swelling of randomly end-cross-linked polymer networks in good solvent conditions. We find that the equilibrium degree of swelling saturates at Q_eq = N_e**(3/5) for mean strand lengths N_s exceeding the melt entanglement length N_e. The internal structure of the network strands in the swollen state is characterized by a new exponent nu=0.72. Our findings are in contradiction to de Gennes' c*-theorem, which predicts Q_eq proportional N_s**(4/5) and nu=0.588. We present a simple Flory argument for a self-similar structure of mutually interpenetrating network strands, which yields nu=7/10 and otherwise recovers the classical Flory-Rehner theory. In particular, Q_eq = N_e**(3/5), if N_e is used as effective strand length.Comment: 4 pages, RevTex, 3 Figure

How to use the development of individual Drosophila larvae as a metabolic sensor.

Metabolic research is a challenge because of the variety of data within experimental series and the difficulty of replicating results among scientific groups. The fruit fly, Drosophila melanogaster, is a cost-effective and reliable pioneer model to screen dietary variables for metabolic research. One of the main reasons for problems in this field are differences in food recipes, diet-associated microbial environments and the pharmacokinetic behavior of nutrients across the gut-blood barrier. To prevent such experimental shortcomings, a common strategy is to pool scores of subjects into one sample to create an average statement. However, this approach lacks information about the biological spread and may provoke misleading interpretations. We propose to use the developmental rate of individual Drosophila larvae as a metabolic sensor. To do so, we introduce here a 96-well plate-based assay, which allows screening for multiple variables including food quality, microbial load, and genetic differences. We demonstrate that on a diet that is rich in calories, pupation is sensitive to the variation of dietary lipid compounds and that genotypes considered as wild-types/controls produce different developmental profiles. Our platform is suited for later automation and represents a potent high-throughput screening tool for the pharmacology and food industry. If used systematically, our assay could become a powerful reference tool to compare the quality of used dietary configurations with published benchmark recipes

Selective phosphorylation of Akt/Protein-kinase B isoforms in response to dietary cues.

A calorie-rich diet is one reason for the continuous spread of metabolic syndromes in western societies. Smart food design is one powerful tool to prevent metabolic stress, and the search for suitable bioactive additives is a continuous task. The nutrient-sensing insulin pathway is an evolutionary conserved mechanism that plays an important role in metabolism, growth and development. Recently, lipid cues capable to stimulate insulin signaling were identified. However, the mechanistic base of their activity remains obscure to date. We show that specific Akt/Protein-kinase B isoforms are responsive to different calorie-rich diets, and potentiate the activity of the cellular insulin cascade. Our data add a new dimension to existing models and position Drosophila as a powerful tool to study the relation between dietary lipid cues and the insulin-induced cellular signal pathway

UCTR - Mammascanner. UCTR = Ultraschall-Reflexions-Computertomographie Abschlussbericht

TIB Hannover: FR 1483 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

SATNAB - Voruntersuchung fuer ein satellitennavigationsgestuetztes Bodenexperiment Technischer Bericht

Within the phase 1 of the project SATNAB the theoretical basis for a satellite navigation based ground experiment was developed and analysed. The procedure of measurement offers the possibility to determine the exact position of a mobile, trackborne user by means of a single Navigation satellite of a future European navigation Satellite System (ENSS/ GNSS 2). In this study the requirements of the experiment for different satellite orbits were investigated. Two scenarios for the experiment have to be distinguished. The first scenario is the verification of the accuracy of positioning of the future satellite navigation system, named reference measuring system. The second one implies the application of positioning in track bound traffic, named the location scenario. As the reference measuring system is a standard of comparison for the quality of the satellite navigation, an error budget was built in. Based on that estimation the concept for the scenarios was defined. A realisation concept for the test configuration was also developed. The predictable errors in the control segment and in the space segment were estimated. This investigation focused on the alignment of the antenna and the clock synchronisation between the oscillator of the space segment and the one placed in the moving vehicle. The procedure of the experiment was summarised in an schedule for the next phases. (orig.)SIGLEAvailable from TIB Hannover: F99B692 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany); DLR Deutsches Zentrum fuer Luft- und Raumfahrt e.V., Bonn (Germany)DEGerman

Numerical methods in vehicle system dynamics: state of the art and current developments

Robust and efficient numerical methods are an essential prerequisite for the computer based dynamical analysis of engineering systems. In vehicle system dynamics, the methods and software tools from multibody system dynamics provide the integration platform for the analysis, simulation and optimization of the complex dynamical behaviour of vehicles and vehicle components and their interaction with hydraulic components, electronical devices and control structures. Based on the principles of classical mechanics, the modelling of vehicles and their components results in nonlinear systems of ordinary differential equations (ODEs) or differential-algebraic equations (DAEs) of moderate dimension that describe the dynamical behaviour in the frequency range required and with a level of detail being characteristic of vehicle system dynamics. Most practical problems in this field may be transformed to generic problems of numerical mathematics like systems of nonlinear equations in the (quasi-)static analysis and explicit ODEs or DAEs with a typical semi-explicit structure in the dynamical analysis. This transformation to mathematical standard problems allows to use sophisticated, freely available numerical software that is based on well approved numerical methods like the Newton-Raphson iteration for nonlinear equations or Runge-Kutta and linear multistep methods for ODE/DAE time integration. Substantial speed-ups of these numerical standard methods may be achieved exploiting some specific structure of the mathematical models in vehicle system dynamics. In the present paper, we follow this framework and start with some modelling aspects being relevant from the numerical viewpoint. The focus of the paper is on numerical methods for static and dynamic problems including software issues and a discussion which method fits best for which class of problems. Adaptive components in state-of-the-art numerical software like stepsize and order control in time integration are introduced and illustrated by a well known benchmark problem from rail vehicle simulation. Over the last few decades, the complexity of high-end applications in vehicle system dynamics has frequently given a fresh impetus for substantial improvements of numerical methods and for the development of novel methods for new problem classes. In the present paper, we address three of these challenging problems of current interest that are today still beyond the mainstream of numerical mathematics: (i) Modelling and simulation of contact problems in multibody dynamics, (ii) Real-time capable numerical simulation techniques in vehicle system dynamics and iii) Modelling and time integration of multidisciplinary problems in system dynamics including co-simulation techniques