Unsteady Magnetohydrodynamic Free Convection Flow of a Second Grade Fluid in a Porous Medium with Ramped Wall Temperature

Magnetic field influence on unsteady free convection flow of a second grade fluid near an infinite vertical flat plate with ramped wall temperature embedded in a porous medium is studied. It has been observed that magnitude of velocity as well as skin friction in case of ramped temperature is quite less than the isothermal temperature. Some special cases namely: (i) second grade fluid in the absence of magnetic field and porous medium and (ii) Newtonian fluid in the presence of magnetic field and porous medium, performing the same motion are obtained. Finally, the influence of various parameters is graphically shown.     

Simulation of diffusion of O 2 and CO 2 in amorphous poly(ethylene terephthalate) and related alkylene and isomeric polyesters

The diffusion of small molecules through polymers is important in many areas of polymer science, such as gas barrier and separation membrane materials, polymeric foams, and in the processing and properties of polymers. Molecular simulation techniques have been applied to study the diffusion of oxygen and carbon dioxide as small molecule penetrants in models of bulk amorphous poly(ethylene terephthalate) (PET) and related alkylene and isomeric polyesters. A bulk amorphous configuration with periodic boundary conditions made into a unit cell whose dimensions were determined for each of the simulated polyesters in the cell having the experimental density. The diffusion coefficients for O 2 and CO 2 were determined via NVE molecular dynamics simulations using the Dreiding 2.21 molecular mechanics force field over a range of temperatures (300, 500 and 600 K) using up to 3 ns simulation time. We have focussed on the influence of the temperature, polymer dynamics, number of CH 2 groups, density and free volume distribution on the diffusion properties. Correlation of diffusion coefficients with free volume and number of CH 2 groups was found.     

A Theoretical Model for the Association Probabilities of Saturated Phospholipids from Two-Component Bilayer Lipid Membranes

The non-random mixing of biomembrane components, especially saturated phospholipids, exhibits important consequences in molecular biology. Particularly, the distribution of lipids within natural and model membranes is strongly determined by the selective association processes. These processes of phospholipids take place due to the cooperative modes in multiparticle systems as well as the specific lipid-lipid interactions both in the hydrophobic core and in the region of the polar headgroups. We demonstrated that the investigation of the selective association processes of saturated phospholipids might contribute to the insight of the lipid domains appearance inside the bilayer membranes. The association probabilities of like-pairs and cross-pairs from a binary mixture of saturated phospholipids were tested for both parallel and anti-parallel alignments of the polar headgroups. The present model confirms the experimental evidence for saturated phospholipids to have a high tendency for association in parallel configuration of the electric dipole moments of the polar headgroups whether the cross-sectional area of the polar headgroup is in an usual range of 25-55 2. There are three major lipid domains in a binary mixture of saturated phospholipids: (i) lipid domains in non-mixed phase of the first mixture component, in parallel alignment of the polar headgroups; (ii) lipid domains in non-mixed phase of the second mixture component, in anti-parallel alignment of the polar headgroups; (iii) lipid domains in mixed phase. We think that the selective association processes of phospholipids are neither exclusively, nor only involved in promoting the lipid domains appearance through bilayer phospholipid membranes.     

Transbilayer Pores Induced by Thickness Fluctuations

Thermally-induced fluctuations of individual phospholipids in a bilayer lipid membrane (BLM) are converted into collective motions due to the intermolecular interactions. Here, we demonstrate that transbilayer stochastic pores can be generated via collective thermal movements (CTM). Using the elastic theory of continuous media applied to smectic-A liquid crystals, we estimate the pore radius and the energetic requirements for pore appearance. Three types of thermally-induced transbilayer pores could be formed through BLMs: open and stable, open and unstable, and closed. In most of the situations, two open and stable pores with different radii could be generated. Notably, the two pores have the same generation probability. Unstable pores are possible to appear across thin bilayers that contain phospholipids with a large polar headgroup. Closed pores are present throughout the cases that we have inspected. The effects of hydrophobic thickness, polar headgroup size of phospholipids, temperature, surface tension, and elastic compression on the pore formation and pore stability have been examined as well.     

Farnesol concentrations required to block germ tube formation in Candida albicans in the presence and absence of serum

Concentrations of (E,E)-farnesol needed to inhibit germ tube formation were determined for Candida albicans strains A72 and SC5314 by using six different conditions known to trigger germination. For defined media, 1 to 2 microM farnesol was sufficient. However, with serum at 2 to 20%, up to 250 microM farnesol was required. Farnesol blocked germ tube formation but did not block elongation of existing germ tubes.     

Development and Evaluation of New Microemulsion-Based Hydrogel Formulations for Topical Delivery of Fluconazole

The aim of the present investigation was to develop and evaluate microemulsion-loaded hydrogels (MEHs) for the topical delivery of fluconazole (FZ). The solubility of FZ in oils, surfactants and cosurfactants was evaluated to identify the components of the microemulsion. The pseudo-ternary phase diagrams were constructed using the novel phase diagram by micro-plate dilution method. Carbopol EDT 2020 was used to convert FZ-loaded microemulsions into gel form without affecting their structure. The selected microemulsions were assessed for globule size, zeta potential and polidispersity index. Besides this, the microemulsion-loaded hydrogel (MEH) formulations were evaluated for drug content, pH, rheological properties and in vitro drug release through synthetic membrane and excised pig ear skin in comparison with a conventional hydrogel. The optimised MEH FZ formulations consisting of FZ 2%, Transcutol P 11.5% and 11%, respectively, as oil phase, Lansurf SML 20-propyleneglycol 52% and 50%, respectively, as surfactant–cosurfactant (2:1), Carbopol EDT 2020 1.5% as gelling agent and water 34.5% and 37%, respectively, showed highest flux values and high release rate values, and furthermore, they had low surfactant content. The in vitro FZ permeation through synthetic membrane and excised pig ear skin from the studied MEHs was best described by the zero-order and first-order models. Finally, the optimised MEH FZ formulations showed similar or slightly higher antifungal activity as compared to that of conventional hydrogel and Nizoral® cream, respectively. The results suggest the potential use of developed MEHs as vehicles for topical delivery of FZ, encouraging further in vitro and in vivo evaluation.KEY WORDS: fluconazole, in vitro skin permeation, microemulsion, microemulsion-loaded hydrogel, topical     

Heart rhythm genomic fabric in hypoxia

The molecular mechanisms by which chronic hypoxia, whether constant (CCH) or intermittent (CIH), alters the heart rhythm are still under debate. Expression level, control, maturational profile and intercoordination of 54 genes encoding heart rhythm determinants (HRDs) were analyzed in 36 mice subjected for 1, 2 or 4 weeks of their early life to normal atmospheric conditions or to CCH or CIH. Our analysis revealed a complex network of genes encoding various heart rate, inotropy and development controllers, receptors, ion channels and transporters, ankyrins, epigenetic modulators and intercalated disc components (adherens, cadherins, catenins, desmosomal, gap and tight junction proteins). The network is remodeled during maturation and substantially and differently altered by CIH and CCH. Gene Prominence Analysis that ranks the genes according to their expression stability and networking within functional gene webs, confirmed the HRD status of certain epigenetic modulators and components of the intercalated discs not yet associated with arrhythmia.