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On the first-order collapse transition of a three-dimensional, flexible homopolymer chain model
2005
We present simulation results for the phase behavior of flexible lattice polymer chains using the Wang-Landau sampling idea. These chains display a two-stage collapse through a coil-globule transition followed by a crystallization at lower temperatures. Performing a finite-size scaling analysis on the two transitions, we show that they coincide in the thermodynamic limit corresponding to a direct collapse of the random coil into the crystal without intermediate coil-globule transition.
Structure of Polymers
2014
The structure and thermodynamics of polymers are discussed both with an adapted version of Flory’s regular solution theory and the concept of scaling and random walks. The salient properties of polymers like segregation and elasticity are discussed in terms of these concept. The Flory-Stockmayer theory of gelation is introduced and related to the percolation concept.
How does the pattern of grafting points influence the structure of one-component and mixed polymer brushes?
2005
Using Monte Carlo simulations of a coarse-grained bead-spring model we study the lateral structure formation of one-component polymer brushes in a bad solvent and of a mixed polymer brush upon increasing the incompatibility of the two species. We compare the morphology of the brush with a regular distribution of grafting points and with a random arrangement. Density or composition fluctuations of the grafting points enhance the formation of irregular structures but randomness prevents the formation of long-range order. Even small fluctuations of the grafting points are sufficient to pin the lateral structures of the brush.
Predicted secondary structure of hydroperoxide lyase from green bell pepper cloned in the yeast Yarrowia lipolytica
2010
International audience; Fatty acid hydroperoxide lyase (HPL) is a member of the cytochrome P450 family acting on fatty acid hydroperoxides in many organisms. The active green bell pepper HPL, cloned and expressed in the yeast Yarrowia lipolytica, was purified by immobilized metal-ion affinity chromatography (IMAC) in the presence of 2% of Triton X-100R. The secondary structure prediction by bioinformatics servers of HPL was realized by ANTHEPROT software, using the GOR, DPM and Predator methods. The theoretical results which are average values obtained from three different calculation methods showed 33% α-helix, 18% β-sheet, 7% turn and 42% coil. On the other hand, the secondary structure a…
Critical micellization density: A small-angle-scattering structural study of the monomer-aggregate transition of block copolymers in supercriticalCO2
2000
In this paper we report a small-angle neutron-scattering investigation of micelle formation by the fluorocarbon-hydrocarbon block copolymer, polyvinyl acetate-b-poly (1,1,2,2-tetrahydroperfluoro-octyl acrylate) in supercritical CO{sub 2} (scCO{sub 2}) at 313 K. At high pressure the copolymer is in a monomeric state with a random coil structure, while at low pressure the polymer forms spherical aggregates stable in a wide range of thermodynamic conditions. By profiling pressure, a sharp monomer-micelle transition is obtained due to the tuning of the solvating ability of scCO{sub 2}. We confirm the previous finding that this aggregate-monomer transition is driven by the gradual penetration of…
Cross-over study on effects of Mediterranean diet in two randomly selected population samples
2003
Abstract Two randomly selected population samples in Western Sicily, one rural (n = 40) and one urban (n = 40), were studied to evaluate the impact of dietary intervention on lipid, coagulative and fibrinolytic parameters. The two groups received the diets in a cross-over design with the following sequences: (a) baseline period; (b) 8-week dietary intervention period; (c) 8-week return to the original diet. During (a) and (c) all subjects consumed their usual diet. During the dietary intervention period (b), the rural sample consumed the urban sample's diet, while the urban sample consumed the rural sample's diet (the so-called “Mediterranean diet”). At baseline, after 8 weeks' dietary inte…
Individuell dosiertes Levothyroxin mit 150 µg Jodid versus 100 µg Levothyroxin kombiniert mit 100 µg Jodid: Eine randomisierte Doppelblindstudie
2008
BASIC PROBLEM AND OBJECTIVE Intrathyroid deficiency and the influence of thyroid stimulating hormone (TSH) are the main pathogenetic factors in the development of endemic euthyroid goitre. Goitre reduction is achieved with either administration of levothyroxine, which diminishes hypophyseal TSG production, or of iodide. Aim of this study was to compare the efficacy of treatment with a dose-fixed combination of levothyroxine plus iodide with that of an individualized dosage of levothyroxine plus iodide. PATIENTS AND METHODS After randomization 49 patients with euthyroid goitre (24 women, 25 men, aged 20-43 years) were treated for 12 weeks in a double-blind trial. Patients in group A received…
Evidence of the Gluten-Free and Casein-Free Diet in Autism Spectrum Disorders
2014
In autism spectrum disorders, many parents resort to alternative treatments and these are generally perceived as risk free. Among these, the most commonly used is the gluten-free, casein-free diet. The objective of this work was to conduct a systematic review of studies published from 1970 to date related to the gluten-free, casein-free diet in autism spectrum disorder patients. Few studies can be regarded as providing sound scientific evidence since they were blinded randomized controlled trials, and even these were based on small sample sizes, reducing their validity. We observed that the evidence on this topic is currently limited and weak. We recommend that it should be only used after…
Random quasi-phase-matched second harmonic generation in periodically poled lithium tantalate
2009
We experimentally observed and explained bulk second harmonic generation via random quasi-phase-matching, derived from a periodically poled lithium tantalate sample with a randomly patterned mark-to-space-ratio.
Isobaric Vapor−Liquid Equilibria for Binary and Ternary Mixtures with Cyclohexane, Cyclohexene, and 2-Methoxyethanol at 100 kPa
2009
Consistent vapor−liquid equilibria (VLE) data at 100 kPa have been determined for the ternary system cyclohexane + cyclohexene + 2-methoxyethanol and two constituent binary systems: cyclohexane + 2-methoxyethanol and cyclohexene + 2-methoxyethanol. Both binary systems deviate remarkably from ideal behavior presenting a minimum boiling point azeotrope. The VLE data have been correlated by the Wilson, UNIQUAC, and NRTL equations. The ternary system does not present an azeotrope and is well predicted from binary interaction parameters. Prediction with the UNIFAC method has been also obtained.