Swelling Behaviour of Isotropic Poly(n-butyl acrylate) Networks in Isotropic and Anisotropic Solvents

Summary: The swelling properties of photochemically crosslinked poly(n-butyl acrylate) (PABu) networks in isotropic and anisotropic solvents were investigated experimentally. The purpose of this study was to examine the swelling kinetics of PABu networks in isotropic solvents and to compare the results obtained which those observed in the case of the low molecular weight liquid crystal 4-cyano-4′-n-pentyl-biphenyl known as 5CB. The phase diagrams were established in terms of composition and temperature for isotropic solvents, as toluene, acetone, cyclohexane, and methanol, and 5CB, using the plateau values corresponding to equilibrium states of swelling. The polymer networks were prepared via free radical polymerization/crosslinking processes by ultraviolet (UV) radiation of initial mixtures made up from a monomer, a crosslinker, and a photoinitiator. PABu networks with several crosslinking densities were formed using different quantities of difunctional monomer hexanedioldiacrylate (HDDA). Immersion of these networks in excess solvent allows measuring the solvent uptake by determination of the weight in isotropic solvents and diameter in an anisotropic solvent (5CB). Swelling data were rationalized by calculating weight and diameter ratios considering swollen to dry network states of the samples.     

Kinetics of photochemical reactions of a new biphotochromic compound upon photolysis with light of different wavelengths

Using the method of microsecond flash photolysis with UV and visible light, the spectral and kinetic characteristics of intermediate products of photolysis in toluene and methanol solutions of a new biphotochromic compound have been studied, in which two photochromic moieties, spironaphthoxazine and azomethine, are linked to each other in such a way that there is conjugation between π-electronic systems of the moieties in the ground state of the molecule. Two intermediate products have detected, whose relative efficiency of formation substantially depends on the solvent and the wavelength of excitation light.     

Improvement of Ethanol Yield from Glycerol via Conversion of Pyruvate to Ethanol in Metabolically Engineered <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

The conversion of low-priced glycerol to higher value products has been proposed as a way to improve the economic viability of the biofuels industry. In a previous study, the conversion of glycerol to ethanol in a metabolically engineered strain of Saccharomyces cerevisiae was accomplished by minimizing the synthesis of glycerol, the main by-product in ethanol fermentation processing. To further improve ethanol production, overexpression of the native genes involved in conversion of pyruvate to ethanol in S. cerevisiae was successfully accomplished. The overexpression of an alcohol dehydrogenase (adh1) and a pyruvate decarboxylase (pdc1) caused an increase in growth rate and glycerol consumption under fermentative conditions, which led to a slight increase of the final ethanol yield. The overall expression of the adh1 and pdc1 genes in the modified strains, combined with the lack of the fps1 and gpd2 genes, resulted in a 1.4-fold increase (about 5.4 g/L ethanol produced) in fps1Δgpd2Δ (pGcyaDak, pGupCas) (about 4.0 g/L ethanol produced). In summary, it is possible to improve the ethanol yield by overexpression of the genes involved in the conversion of pyruvate to ethanol in engineered S. cerevisiae using glycerol as substrate.     

On multiscale homogenization problems in boundary layer theory

This paper is concerned with the homogenization of the equations describing a magnetohydrodynamic boundary layer flow past a flat plate, the flow being subjected to velocities caused by injection and suction. The fluid is assumed incompressible, viscous and electrically conducting with a magnetic field applied transversally to the direction of the flow. The velocities of injection and suction and the applied magnetic field are represented by rapidly oscillating functions according to several scales. We derive the homogenized equations, prove convergence results and establish error estimates in a weighted Sobolev norm and in C ⁰-norm. We also examine the asymptotic behavior of the solutions of the equations governing a boundary layer flow past a rough plate with a locally periodic oscillating structure.     

Proteomics of cypress pollen allergens using double and triple one-dimensional electrophoresis

Italian cypress (Cupressus sempervirens, Cups) pollen causes allergic diseases in inhabitants of many of the cities surrounding the Mediterranean basin. However, allergens of Cups pollen are still poorly known. We introduce here a novel proteomic approach based on double one‐dimensional gel electrophoresis (D1‐DE) as an alternative to the 2‐DE immunoblot, for the specific IgE screening of allergenic proteins from pollen extracts. The sequential one‐dimensional combination of IEF and SDS‐PAGE associated with IgE immunoblotting allows a versatile multiplexed immunochemical analysis of selected groups of allergens by converting a single protein spot into an extended protein band. Moreover, the method appears to be valuable for MS/MS identification, without protein purification, of a new Cups pollen allergen at 43 kDa. D1‐DE immunoblotting revealed that the prevalence of IgE sensitization to this allergen belonging to the polygalacturonase (PG) family was 70% in tested French allergic patients. In subsequent triple one‐dimensional gel electrophoresis, the Cups pollen PG was shown to promote lectin‐based protein‐protein interactions. Therefore, D1‐DE could be used in routine work as a convenient alternative to 2‐DE immunoblotting for the simultaneous screening of allergenic components under identical experimental conditions, thereby saving considerable amounts of sera and allergen extracts.     

Suivi de fissuration de matériaux par thermographie

The purpose of this work is to present a novel strategy for real-time monitoring crack growth of materials. The process is based on the use of thermal data extracted along the horizontal axis of symmetry of single edge notch tension (SENT) specimens, during fatigue tests. These data are exploited using an implemented program to detect in situ the growth of fatigue crack, with the critical size and propagation speed of the crack. This technique has the advantage to be applicable to a wide range of materials regardless of their electrical conductivity and their surface texture. To cite this article: D. Ait Aouit, A. Ouahabi, C. R. Mecanique 336 (2008).     

Equilibres Liquide-vapeur Isothermes De Melanges Binaires, Amine+amine

The authors have measured the vapour pressure of the binary systems, piperidine+n -butylamine, piperidine+dipropylamine, piperidine+N-methyl piperidine, piperidine+N,N-dimethyl amino butane and N-methyl piperidine+n -butylamine. The measurements were carried out using an isoteniscope built by Jose [1]. The vapour pressure, excess Gibbs free energies at 298,15, 303,15, 313,15, 323,15, 333,15, and 325,15 K, are reported for these mixtures. The excess Gibbs free energies have been fitted to Redlich-Kister equation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synergistic Effect of Bioactive Monoterpenes against the Mosquito,Culex pipiens (Diptera: Culicidae)

Mosquitoes represent one of the most important vectors and are responsible for the transmission of many arboviruses that affect human and animal health. The chemical method using synthetic insecticides disturbs the environmental system and promotes the appearance of resistant insect species. Therefore, this study investigated the insecticidal effect of some binary monoterpene combinations (1,8 cineole + α-pinene and carvone + R (+)-pulegone) using a mixture design approach. The fumigant toxicity was evaluated against Culex pipiens female adults using glass jars. The results show that the toxicity varies according to the proportions of each compound. Indeed, Mixture 1 (1,8-cineole + α-pinene) displayed a strong toxic effect (51.00 ± 0.86% after 24 h and 100.00 ± 0.70% after 48 h) when the pure compounds were tested at 0.25/0.75 proportions of 1,8-cineole and α-pinene, respectively. Nevertheless, the equal proportion (0.5/0.5) of carvone and R (+)-pulegone in Mixture 2 exhibited a toxic effect of 54.35 ± 0.75% after 24 h and 89.96 ± 0.14% after 48 h, respectively. For Mixture 1, the maximum area of mortality that the proposed model indicated was obtained between 0/1 and 0.25/0.75, while the maximum area of mortality in the case of Mixture 2 was obtained between 0.25/0.75 and 0.75/0.25. Moreover, the maximum possible values of mortality that could be achieved by the validated model were found to be 51.44% (after 24 h) and 100.24% (after 48 h) for Mixture 1 and 54.67% (after 24 h) and 89.99% (after 48 h) for Mixture 2. It can be said that all purev molecules tested through the binary mixtures acted together, which enhanced the insecticide’s effectiveness. These findings are very promising, as the chemical insecticide (deltamethrin) killed only 19.29 ± 0.01% and 34.05 ± 1.01% of the female adults after 24 h and 48 h, respectively. Thus, the findings of our research could help with the development of botanical insecticides that might contribute to management programs for controlling vectors of important diseases.