Well-posedness of a diffusive gyro-kinetic model

We study a finite Larmor radius model used to describe the ions distribution function in the core of a tokamak plasma, that consists in a gyro-kinetic transport equation coupled with an electro-neutrality equation. Since the last equation does not provide enough regularity on the electric potential, we introduce a simple linear collision operator adapted to the finite Larmor radius approximation. We next study the two-dimensional dynamics in the direction perpendicular to the magnetic field. Thanks to the smoothing effects of the collision and the gyro-average operators, we prove the global existence of solutions, as well as short time uniqueness and stability.     

Surfactants in Mechanical Alloying/Milling: A Catch-22 Situation

Mechanical alloying/milling technique is characterized by the repeated welding and fracturing of powder particles in a high-energy ball mill, which often results in excessive cold welding and agglomeration of ductile particles. To achieve the critical balance between cold welding and fracturing, the surface of the deforming particles is modified by introducing a suitable organic material, called surfactant or process control agent (PCA). However, the use of surfactants is self-contradictory by nature and requires further consideration of the milling variables and type/amount of surfactant. The current article provides a practical approach to the promises and challenges associated with surfactants in mechanical alloying/milling. An attempt has been made to address the most crucial aspects correlated with surfactants, including contamination, the morphology and size of powder particles, formation of alloy and microstructural evolution, and powder yield, as well as the physico-mechanical properties, such as magnetism, density, hardness, and compressive strength. An overview is also given on the adsorption mechanism of surfactants onto the surface of powder particles, with a special emphasis on type, amount, and the addition time of surfactants in the mechanical alloying process.     

An Unexpected Role of Carbon Disulfide: A New and Efficient Method for the Synthesis of 2‐Substituted Benzimidazoles

A new and efficient methodology for the synthesis of 2‐substituted benzimidazoles is described. In this procedure, CS₂ unexpectedly facilitated the cyclization reaction between benzene‐1,2‐diamine and benzenecarbaldehydes in CH₂Cl₂ at room temperature. The reactions occur under mild conditions require simpler equipment and easier workup procedures.     

Sigmatropic shifts and cycloadditions on neutral, cationic, and anionic pentadienyl+butadiene potential energy surfaces

Quantum chemical calculations were used to characterize [4,5] sigmatropic shifts in systems containing butadiene and pentadienyl substructures. Cationic, anionic, and radical systems with various tethers connecting these substructures were examined. In many cases, concerted [4,5] sigmatropic shifts with asynchronous bond making and breaking events were observed. The fundamental connections between [4,5] sigmatropic shifts and (5+4) cycloadditions are highlighted.     

Characterization of hydrocortisone biometabolites and 18S rRNA gene in Chlamydomonas reinhardtii cultures

A unicellular microalga, Chlamydomonas reinhardtii, was isolated from rice paddy-field soil and water samples and used in the biotransformation of hydrocortisone (1). This strain has not been previously tested for steroid bioconversion. Fermentation was carried out in BG-11 medium supplemented with 0.05% substrate at 25 degrees C for 14 days of incubation. The products obtained were chromatographically purified and characterized using spectroscopic methods. 11b,17 beta-Dihydroxyandrost-4-en-3-one (2), 11 beta-hydroxyandrost-4-en-3,17-dione (3), 11 beta,17 alpha,20 beta,21-tetrahydroxypregn-4-en-3-one (4) and prednisolone (5) were the main products of the bioconversion. The observed bioreaction features were the side chain degradation of the substrate to give compounds 2 and 3 and the 20-ketone reduction and 1,2-dehydrogenation affording compounds 4 and 5, respectively. A time course study showed the accumulation of product 2 from the second day of the fermentation and of compounds 3, 4 and 5 from the third day. All the metabolites reached their maximum concentration in seven days. Microalgal 18S rRNA gene was also amplified by PCR. PCR products were sequenced to confirm their authenticity as 18S rRNA gene of microalgae. The result of PCR blasted with other sequenced microalgae in NCBI showed 100% homology to the 18S small subunit rRNA of two Chlamydomonas reinhardtii spp.     

Design and synthesis of bis-amide and hydrazide-containing derivatives of malonic acid as potential HIV-1 integrase inhibitors

HIV-1 integrase (IN) is an attractive and validated target for the development of novel therapeutics against AIDS. In the search for new IN inhibitors, we designed and synthesized three series of bis-amide and hydrazide-containing derivatives of malonic acid. We performed a docking study to investigate the potential interactions of the title compounds with essential amino acids on the IN active site.     

Investigation of thermal,mechanical, and electrical properties of novel polyurethanes/high molecular weight polybenzoxazine blends

In order to prepare tough polyurethane (PU) electrical insulator with improved thermal stability and electrical insulating properties, high molecular weight polybenzoxazine precursor was mixed and co‐cured with crosslinkable urethane prepolymers. Polybenzoxazine precursor (Bmda) was synthesized from reaction of bisphenol‐A, methylenedianiline, and paraformaldehyde. Epoxy‐terminated polyurethanes (EPU1‐4) were prepared by the reaction of glycidol with NCO‐terminated urethane oligomers. The oligomers were prepared from different molecular weight versions of polycaprolactone polyol (CAPA) and hexamethylene diisocyanate. Blends were prepared through thermal treatment of equal weights of two precursors dissolved in chloroform. Optimum curing condition was determined by DSC and DMTA analysis and measurement of the gel content for cured samples. Viscoelastic, thermal, mechanical, and electrical properties of cured samples were investigated and structure–property relationship was established. Copyright © 2008 John Wiley & Sons, Ltd.     

Study on existence of solutions for some nonlinear functional–integral equations

Using the technique of measures of noncompactness in Banach algebra, we employ abstract fixed point theorems such as Darbo’s theorem to study the existence solution in Banach algebra C[0,a]$C[0,a]$ for some functional–integral equations which include many key integral and functional equations that arise in nonlinear analysis.     

Structures and biological activity of cinnamoyl derivatives of coumarins and dehydroacetic acid and their boron difluoride complexes

Computer-assisted screening for Kohonen self-organizing maps in terms of the quantitative structure??activity relationship (QSAR) model revealed the high potential activity of cinnamoyl derivatives of coumarin and dehydroacetic acid and their boron difluoride complexes against a number of biological targets, including HIV-1 integrase. The pronounced inhibitory properties of dehydroacetic acid derivatives and their boron difluoride complexes against HIV-1 integrase were experimentally confirmed by in vitro testing of their antiviral activity with respect to HIV-infected cells. The data obtained suggests a correlation between the structure of the compounds studied and their biological activity.     

Interpolation solution in generalized stochastic exponential population growth model

In this paper, first we consider model of exponential population growth, then we assume that the growth rate at time t is not completely definite and it depends on some random environment effects. For this case the stochastic exponential population growth model is introduced. Also we assume that the growth rate at time t depends on many different random environment effect, for this case the generalized stochastic exponential population growth model is introduced. The expectations and variances of solutions are obtained. For a case study, we consider the population growth of Iran and obtain the output of models for this data and predict the population individuals in each year.