40 research outputs found
Microscopic Model of Charge Carrier Transfer in Complex Media
We present a microscopic model of a charge carrier transfer under an action
of a constant electric field in a complex medium. Generalizing previous
theoretical approaches, we model the dynamical environment hindering the
carrier motion by dynamic percolation, i.e., as a medium comprising particles
which move randomly on a simple cubic lattice, constrained by hard-core
exclusion, and may spontaneously annihilate and re-appear at some prescribed
rates. We determine analytically the density profiles of the "environment"
particles, as seen from the stationary moving charge carrier, and calculate its
terminal velocity as the function of the applied field and other system
parameters. We realize that for sufficiently small external fields the force
exerted on the carrier by the "environment" particles shows a viscous-like
behavior and define an analog of the Stokes formula for such dynamic
percolative environments. The corresponding friction coefficient is also
derived.Comment: appearing in Chem. Phys. Special Issue on Molecular Charge Transfer
in Condensed Media - from Physics and Chemistry to Biology and
Nano-Engineering, edited by A.Kornyshev (Imperial College London), M.Newton
(Brookhaven Natl Lab) and J.Ulstrup (Technical University of Denmark
The representation of heart development in the gene ontology
AbstractAn understanding of heart development is critical in any systems biology approach to cardiovascular disease. The interpretation of data generated from high-throughput technologies (such as microarray and proteomics) is also essential to this approach. However, characterizing the role of genes in the processes underlying heart development and cardiovascular disease involves the non-trivial task of data analysis and integration of previous knowledge. The Gene Ontology (GO) Consortium provides structured controlled biological vocabularies that are used to summarize previous functional knowledge for gene products across all species. One aspect of GO describes biological processes, such as development and signaling.In order to support high-throughput cardiovascular research, we have initiated an effort to fully describe heart development in GO; expanding the number of GO terms describing heart development from 12 to over 280. This new ontology describes heart morphogenesis, the differentiation of specific cardiac cell types, and the involvement of signaling pathways in heart development. This work also aligns GO with the current views of the heart development research community and its representation in the literature. This extension of GO allows gene product annotators to comprehensively capture the genetic program leading to the developmental progression of the heart. This will enable users to integrate heart development data across species, resulting in the comprehensive retrieval of information about this subject.The revised GO structure, combined with gene product annotations, should improve the interpretation of data from high-throughput methods in a variety of cardiovascular research areas, including heart development, congenital cardiac disease, and cardiac stem cell research. Additionally, we invite the heart development community to contribute to the expansion of this important dataset for the benefit of future research in this area
Magnetic Modulation in Mechanical Alloyed Cr1.4fe0.6o3 Oxide
We have synthesized Cr1.4Fe0.6O3 compound through mechanical alloying of
Cr2O3 and Fe2O3 powders and subsequent thermal annealing. The XRD spectrum, SEM
picture and microanalysis of EDAX spectrum have been used to understand the
structural evolution in the alloyed compound. The alloyed samples are matching
to rhombohedral structure with R3C space group. The observation of a modulated
magnetic order confirmed a systematic diffusion of Fe atoms into the Cr sites
of lattice structure. A field induced magnetic behaviour is seen in the field
dependence of magnetization data of the annealed samples. The behaviour is
significantly different from the mechanical alloyed samples. The experimental
results provided the indications of considering the present material as a
potential candidate for opto-electronic applications.Comment: 8 figure
Determination of diffusion coefficients of glycerol and glucose from starch based thermoplastic compounds on simulated physiological solution
Blends of corn starch with poly(ethylene-vinylalcohol) copolymer (SEVA-C) have been
studied and reported as biodegradable. These materials are known to be sensitive to
enzymatic action, evidencing a degradation of the starch phase in α-amylase assays.
However, from the physical-chemical point of view the degradation of the blend is mainly
associated with the leaching of glycerol, since other compounds are not released and no
carbohydrates were found in the degradation solution. Based on these results, the present
work attempts to determinate the respective diffusion coefficients. Four different
experiments were performed, using samples with different thicknesses that were
immersed in a simulated physiological solution. High performance liquid chromatography
(HPLC) was used to separate the sugar derivatives and glycerol from the degradation
solutions. The obtained data were fitted to an empirical model to allow the estimation of
the diffusion coefficient for glycerol and glucose, based on the analytical solution for Fick’s
law of diffusion, and a good agreement was found (R² ≈ 1). The glycerol leaches quickly
out during the first few days of immersion, stabilizing thereafter, presenting greater
diffusion coefficients for thicker samples. As the quantity of saccharides in the solution
remains almost invariable along the experiments, this work also confirms that the
degradation process is difficult without the action of enzymes
A survey of the timing and approach to the surgical management of cholelithiasis in patients with acute biliary pancreatitis and acute cholecystitis in the UK
Indium/TFA-Catalyzed Synthesis of Tetracyclic [6,5,5,6] Indole Ring, via a Tandem Cycloannulation of β‑Oxodithioester with Tryptamine
The cycloannulation of β-oxodithioesters and tryptamine in dichloromethane in the presence of a catalytic amount of InCl<sub>3</sub> and TFA gave the novel 5-aryl/heteroaryl 2a<sup>1</sup>,9b-dihydro-1<i>H</i>-2a,5a-diaza-cyclopenta[<i>jk</i>]fluorene-3(2<i>H</i>)-thiones in moderate to good yields. The reaction was proposed to involve a tandem transformation of thioamide, protonation, and dehydrative cyclization. KMnO<sub>4</sub>-oxidation of these newly prepared compounds yielded oxidative desulfurization products in good yields
Remote atmospheric pressure DC glow discharge treatment for adhesion improvement of PDMS
In this paper, a remote DC glow discharge at atmospheric pressure is employed for surface modification of PDMS aimed at improvement of its adhesive properties. The effects of the discharge on the surface properties of PDMS are probed using contact angle measurements, XPS and T-peel tests. Results show that the DC glow discharge transforms the initially hydrophobic PDMS surface into a hydrophilic one due to the incorporation of silanol groups at the expense of methyl groups. Moreover, T-peel tests confirm that the remote DC glow plasma is able to remarkably enhance the adhesion between two PDMS layers, but only when both layers are plasma-treated