Optothermal molecule trapping by opposing fluid flow with thermophoretic drift

Thermophoresis moves molecules along temperature gradients, typically from hot to cold. We superpose fluid flow with thermophoretic molecule flow under well-defined microfluidic conditions, imaged by fluorescence microscopy. DNA is trapped and accumulated 16-fold in regions where both flows oppose each other. Strong 800-fold accumulation is expected, however, with slow trapping kinetics. The experiment is equally described by a three-dimensional and one-dimensional analytical model. As an application, we show how a radially converging temperature field confines short DNA into a 10 microm small spot.     

Dynamics of long-living excitons in tunable potential landscapes

A novel method to experimentally study the dynamics of long-living excitons in coupled quantum well semiconductor heterostructures is presented. Lithographically defined top gate electrodes imprint in-plane artificial potential landscapes for excitons via the quantum confined Stark effect. Excitons are shuttled laterally in a time-dependent potential landscape defined by an interdigitated gate structure. Long-range drift exceeding a distance of at an exciton drift velocity is observed in a gradient potential formed by a resistive gate stripe.     

An improved Interior-Point Algorithm for Large-Scale Shakedown Analysis

This work focuses on the calculation of shakedown load-factors of structures by using the lower-bound theorem of shakedown analysis. The resultant optimization problem is solved by an interior-point algorithm. In general, the application of shakedown analysis to practical problems leads to large-scale problems with large numbers of unknowns and constraints. Thus the solution turns out to be computationally intensive. For this reason it is important to reduce the dimension of the considered problem. Therefore, the major improvement of the presented algorithm consists of a problem-oriented reformulation of the problem reducing the size of the system to be solved. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Fluoreszenzfarbstoffe in der Natur

In this paper we describe some fluorescent plant and mushroom dyes. This part of natural product chemistry was of little interest for most natural scientists until today. Most of these substances are published in scientific papers, but there are only rare hints for eventually fluorescence‐phenomenones. Equipped with an UV‐lamp, test tubes and some common solvents, natural products can easily be tested to show fluorescence. In the context of this publication the authors discovered a new Hypericin sensibilized Peroxyoxalate‐Chemoluminescence (strong orangered emission).     

The prescribed output pattern regulates the modular structure of flow networks

Modules are common functional and structural properties of many social, technical andbiological networks. Especially for biological systems it is important to understand howmodularity is related to function and how modularity evolves. It is known thattime-varying or spatially organized goals can lead to modularity in a simulated evolutionof signaling networks. Here, we study a minimal model of material flow in networks. Wediscuss the relation between the shared use of nodes, i.e., the cooperativity of modules,and the orthogonality of a prescribed output pattern. We study the persistence ofcooperativity through an evolution of robustness against local damages. We expect theresults to be valid for a large class of flow-based biological and technical networks.     

Ferromagnetism and Kondo insulator behavior in the disordered periodic Anderson model

The effect of binary alloy disorder on the ferromagnetic phases of f-electron materials is studied within the periodic Anderson model. We find that disorder in the conduction band can drastically enhance the Curie temperature T{c} due to an increase of the local f moment. The effect may be explained qualitatively and even quantitatively by a simple theoretical ansatz. The emergence of an alloy Kondo insulator at noninteger filling is also pointed out.     

Base doping and dopant profile control of SiGe npn and pnp HBTs

Incorporation of high doping concentrations and the creation and maintaining of steep doping profiles during processing are key enabler for high level RF performance of heterojunction bipolar transistors (HBTs). In this paper, we discuss results of base doping and dopant profile control for npn and pnp SiGe HBTs fabricated within 0.25 μm BiCMOS technologies. High level of electrically active B and P doping concentrations (up to 10²⁰ cm⁻³) have been incorporated into SiGe. By adding C to SiGe steep doping profiles have been maintained due to the prevention of dopant diffusion during device processing. It is shown that broadening of P doping profiles caused by segregation could be reduced by lowering the deposition temperature for the SiGe cap. B and P atomic layer doping is shown to be suitable for the creation of steep and narrow doping profiles. This result is demonstrating the capability of the atomic layer processing approach for future devices with critical requirements of dopant dose and location control.