Variational Perturbation Theory for Markov Processes

We develop a convergent variational perturbation theory for conditional probability densities of Markov processes. The power of the theory is illustrated by applying it to the diffusion of a particle in an anharmonic potential.Comment: Author Information under http://www.physik.fu-berlin.de/~kleinert/institution.html Latest update of paper also at http://www.physik.fu-berlin.de/~kleinert/33

Conformational Mechanics of Polymer Adsorption Transitions at Attractive Substrates

Conformational phases of a semiflexible off-lattice homopolymer model near an attractive substrate are investigated by means of multicanonical computer simulations. In our polymer-substrate model, nonbonded pairs of monomers as well as monomers and the substrate interact via attractive van der Waals forces. To characterize conformational phases of this hybrid system, we analyze thermal fluctuations of energetic and structural quantities, as well as adequate docking parameters. Introducing a solvent parameter related to the strength of the surface attraction, we construct and discuss the solubility-temperature phase diagram. Apart from the main phases of adsorbed and desorbed conformations, we identify several other phase transitions such as the freezing transition between energy-dominated crystalline low-temperature structures and globular entropy-dominated conformations.Comment: 13 pages, 15 figure

A Transport Analysis of the BEEM Spectroscopy of Au/Si Schottky Barriers

A systematic transport study of the ballistic electron emission microscopy (BEEM) of Au/Si(100) and Au/Si(111) Schottky barriers for different thicknesses of the metal layer and different temperatures is presented. It is shown that the existing experimental data are compatible with a recently predicted bandstructure-induced non-forward electron propagation through the Au(111) layer.Comment: 5 pages, Latex-APS, 1 postscript figure, http://www.icmm.csic.es/Pandres/pedro.htm. Phys. Stat. Sol. (b) (to appear), HCIS-10 Conf, Berlin 199

Microcanonical entropy inflection points: Key to systematic understanding of transitions in finite systems

We introduce a systematic classification method for the analogs of phase transitions in finite systems. This completely general analysis, which is applicable to any physical system and extends towards the thermodynamic limit, is based on the microcanonical entropy and its energetic derivative, the inverse caloric temperature. Inflection points of this quantity signal cooperative activity and thus serve as distinct indicators of transitions. We demonstrate the power of this method through application to the long-standing problem of liquid-solid transitions in elastic, flexible homopolymers.Comment: 4 pages, 3 figure

Thickness-dependent secondary structure formation of tubelike polymers

By means of sophisticated Monte Carlo methods, we investigate the conformational phase diagram of a simple model for flexible polymers with explicit thickness. The thickness constraint, which is introduced geometrically via the global radius of curvature of a polymer conformation, accounts for the excluded volume of the polymer and induces cooperative effects supporting the formation of secondary structures. In our detailed analysis of the temperature and thickness dependence of the conformational behavior for classes of short tubelike polymers, we find that known secondary-structure segments like helices and turns, but also ringlike conformations and stiff rods are dominant intrinsic topologies governing the phase behavior of such cooperative tubelike objects. This shows that the thickness constraint is indeed a fundamental physical parameter that allows for a classification of generic polymer structures

NESTMOD: The NetMod-NEST Interface

NESTMOD is a combined analytical modeling and simulation tool, based on the existing tools NetMod and NEST. It provides both transient and steady-state response statistics from models of interconnected local area networks that can execute at any level of detail desired. This gives users the potential to model both networks of extremely large scope (hundreds of thousands of nodes), and to look at great detail for any combination of the ISO layers. This paper describes the interface implementation, and presents an example to illustrate the potential power of the tool.http://deepblue.lib.umich.edu/bitstream/2027.42/107970/1/citi-tr-91-7.pd

Produção de celulases em farelos de trigo e arroz e grão de trigo por Lentinula edodes.

Editores técnicos: Marcílio José Thomazini, Elenice Fritzsons, Patrícia Raquel Silva, Guilherme Schnell e Schuhli, Denise Jeton Cardoso, Luziane Franciscon. EVINCI. Resumos

Okuläre Pulsamplitude als biometrischer Messwert in der Glaukomdiagnostik

Zusammenfassung: Hintergrund: Die dynamische Konturtonometrie (DCT) ermöglicht direkte transkorneale Messungen des Augeninnendrucks und der okulären Pulsamplitude (OPA). Ziel dieser Studie war es, herauszufinden, ob die OPA als biometrischer Messwert Aussagen über verschiedene Glaukomformen erlaubt. Patienten und Methoden: Es wurden 441 Augen von 222Patienten in die Studie aufgenommen. Zur Druckmessung dienten die DCT und ein Applanationstonometer nach Goldmann. Ergebnisse: Die mittlere OPA betrug 3,1±1,4mmHg. Augen mit okulärer Hypertension (3,6±1,3mmHg) zeigten signifikant höhere Werte als gesunde Augen (3,1±1,4mmHg) und solche mit Niederdruckglaukom (2,9±1,4mmHg). Nach erfolgreicher Trabekulektomie wurden signifikant tiefere Werte (2,4±1,3mmHg) als bei Gesunden gemessen. Schlussfolgerung: Die OPA scheint diverse Formen des Glaukoms zu charakterisieren, könnte aber auch direkt von der Höhe des Augendrucks abhängen. Es muss weiter abgeklärt werden, ob sie einen prädiktiven Faktor in der Diagnose und der Verlaufsbeurteilung des Glaukoms darstell

A simple quantum cosmology

A simple and surprisingly realistic model of the origin of the universe can be developed using the Friedmann equation from general relativity, elementary quantum mechanics, and the experimental values of h, c, G and the proton mass. The model assumes there are N space dimensions (with N > 6) and the potential constraining the radius r of the invisible N -3 compact dimensions varies as r^4. In this model, the universe has zero total energy and is created from nothing. There is no initial singularity. If space-time is eleven dimensional, as required by M theory, the scalar field corresponding to the size of the compact dimensions inflates the universe by about 26 orders of magnitude (60 e-folds). If the Hubble constant is 65 km/sec Mpc, the energy density of the scalar field after inflation results in Omega-sub-Lambda = 0.68, in agreement with recent astrophysical observations.Comment: To be published in General Relativity and Gravitation, August 200