6,737 research outputs found
On computational complexity of Siegel Julia sets
It has been previously shown by two of the authors that some polynomial Julia
sets are algorithmically impossible to draw with arbitrary magnification. On
the other hand, for a large class of examples the problem of drawing a picture
has polynomial complexity. In this paper we demonstrate the existence of
computable quadratic Julia sets whose computational complexity is arbitrarily
high.Comment: Updated version, to appear in Commun. Math. Phy
Structure of Polymer Brushes in Cylindrical Tubes: A Molecular Dynamics Simulation
Molecular Dynamics simulations of a coarse-grained bead-spring model of
flexible macromolecules tethered with one end to the surface of a cylindrical
pore are presented. Chain length and grafting density are varied
over a wide range and the crossover from ``mushroom'' to ``brush'' behavior is
studied for three pore diameters. The monomer density profile and the
distribution of the free chain ends are computed and compared to the
corresponding model of polymer brushes at flat substrates. It is found that
there exists a regime of and for large enough pore diameter where
the brush height in the pore exceeds the brush height on the flat substrate,
while for large enough and (and small enough pore diameters) the
opposite behavior occurs, i.e. the brush is compressed by confinement. These
findings are used to discuss the corresponding theories on polymer brushes at
concave substrates.Comment: 11 figure
Universality in adsorbate ordering on nanotube surfaces
Numerically efficient transfer matrix technique for studying statistics of
coherent adsorbates on small nanotubes has been developed. In the framework of
a realistic microscopic model fitted to the data of ab initio calculations
taken from literature sources, the ordering of potassium adsorbate on (6,0)
single-walled carbon nanotube has been studied. Special attention has been
payed to the phase transition-like abrupt changes seen in the adsorption
isotherms at low temperature. It has been found that the behavior during the
transitions conforms with the universality hypothesis of the theory of critical
phenomena and is qualitatively the same as in the one dimensional Ising model.
Quantitatively the critical behavior can be fully described by two parameters.
Their qualitative connection with the properties of interphase boundaries is
suggested but further research is needed to develop a quantitative theory.Comment: 11 pages, 6 figures; some typos correcte
Acne resolution rates: Results of a single-blind, randomized, controlled, parallel phase III trial with EE/CMA (Belara (R)) and EE/LNG (Microgynon (R))
Background and Objective: Acne in women can often be successfully treated by the intake of oral contraceptives containing gestagens with anti-androgenic properties. This study aimed to evaluate the efficacy of the monophasic oral contraceptive ethinylestradiol/chlormadinone acetate (EE/CMA; Belara (R)) for the treatment of mild to moderate papulopustular acne of the face and acne-related disorders in comparison to EE/levonorgestrel (LNG; Microgynon (R)). Methods: 199 female acne patients were enrolled in a single-blind, randomized, multicentre phase III study and divided into two groups who received either EE/CMA or EE/LNG. The primary end point was fulfilled if the number of papules/pustules per half of the face present on admission had decreased by at least 50% in the 12th medication cycle. Results: 59.4% of the women under EE/CMA and 45.9% under EE/LNG were responders. The relative frequency of women with complete resolution was 16.5% under EE/CMA and 4.3% under EE/LNG at cycle 12. Conclusion: EE/CMA is an efficient treatment for women with mild and moderate papulopustular acne of the face and related disorders, reflecting the well-known anti-androgenic properties of the progestogen CMA. Copyright (C) 2001 S, Karger AG, Basel
Polymer Brushes in Cylindrical Pores: Simulation versus Scaling Theory
The structure of flexible polymers endgrafted in cylindrical pores of
diameter D is studied as a function of chain length N and grafting density
\sigma, assuming good solvent conditions. A phenomenological scaling theory,
describing the variation of the linear dimensions of the chains with \sigma, is
developed and tested by Molecular Dynamics simulations of a bead-spring model.Comment: 35 pages, 38 figure
Results from a randomized, controlled trial on efficacy and tolerability of a 5% Lidocaine-Medicated Plaster vs. Pregabalin in patients with Post-Herpetic Neuralgia (PHN) and Painful Diabetic Polyneuropathy (DPN) [poster]
No abstract available
Chain length dependence of the polymer-solvent critical point parameters
We report grand canonical Monte Carlo simulations of the critical point
properties of homopolymers within the Bond Fluctuation model. By employing
Configurational Bias Monte Carlo methods, chain lengths of up to N=60 monomers
could be studied. For each chain length investigated, the critical point
parameters were determined by matching the ordering operator distribution
function to its universal fixed-point Ising form. Histogram reweighting methods
were employed to increase the efficiency of this procedure. The results
indicate that the scaling of the critical temperature with chain length is
relatively well described by Flory theory, i.e. \Theta-T_c\sim N^{-0.5}. The
critical volume fraction, on the other hand, was found to scale like \phi_c\sim
N^{-0.37}, in clear disagreement with the Flory theory prediction \phi_c\sim
N^{-0.5}, but in good agreement with experiment. Measurements of the chain
length dependence of the end-to-end distance indicate that the chains are not
collapsed at the critical point.Comment: 13 Pages Revtex, 9 epsf embedded figs. gzipped tar file. To appear in
J. Chem. Phy
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