Global Weak Solutions for a Parabolic System Modeling a One-Dimensional Miscible Flow in Porous Media

We consider an initial boundary value problem for a nonlinear differential system of two equations. Such a system is formed by the equations of compressible miscible flow in a one-dimensional porous medium. No assumption about the mobility ratio is involved. Under some reasonable assumptions on the data, we prove the existence of a global weak solution. Our basic approach is the semi-Galerkin method. We use the technique of renormalized solutions for parabolic equations in the derivation ofa prioriestimates.     

New process to control hydrolysis step during sol-gel preparation of sulfated zirconia catalysts

Sulfated zirconia catalysts were prepared by sol-gel process using a new method allowing the control of the hydrolysis step of zirconium alkoxides. Prepared samples were characterized by N₂ adsorption (desorption) at 77 K, XRD, chemical analysis of total sulfur and XPS. Catalytic properties have been evaluated in n-butane and n-hexane isomerization reactions. Obtained results show that time necessary for gelation is significant and depends considerably on the nature of the zirconium precursor. Concerning the properties of the solids obtained by this method, it has been noted that the use of the zirconium propoxide led to a better retention of the sulfate species, which improves activity during isomerization reactions. It has been found also that an initial S/Zr molar ratio equal to 0.5 allowed to obtain an optimal sulfur content and a high specific surface area.     

Synthesis of fused ring heterocycles from aromatic amines with hydroximoyl chlorides

Substituted 2-arylbenzimidazoles, 2-arylbenzoxazoles and 2-arylbenzothiazoles were obtained in good yield by the reaction of hydroximoyl chlorides with ortho-substituted aromatic amines. The benzo moiety of the benzimidazoles was shown by nmr to be symmetrical, indicating that the N-H group proton of the imidazole ring is exchanging with the water protons in the DMSO-d₆ solvent.     

Study of Langmuir and Langmuir-Blodgett films of odorant-binding protein/amphiphile for odorant biosensors

To make ultrathin films for the fabrication of artificial olfactory systems, odorant biosensors, we have investigated mixed Langmuir and Langmuir-Blodgett films of odorant-binding protein/amphiphile. Under optimized experimental conditions (phosphate buffer solution, pH 7.5, OBP-1F concentration of 4 mg L(-1), target pressure 35 mN m(-1)), the mixed monolayer at the air/water interface is very stable and has been efficiently transferred onto gold supports, which were previously functionalized by self-assembled monolayers (SAMs) with 1-octadecanethiol (ODT). Atomic force microscopy and electrochemical impedance spectroscopy were used to characterize mixed Langmuir-Blodgett (LB) films before and after contact with a specific odorant molecule, isoamyl acetate. AFM phase images show a higher contrast after contact with the odorant molecule due to the new structure of the OBP-1F/ODA LB film. Non-Faradaic electrochemical spectroscopy (EIS) is used to quantify the effect of the odorant based on the electrical properties of the OBP-1F/ODA LB film, as its resistance strongly decreases from 1.18 MOmega (before contact) to 25 kOmega (after contact).     

Reactions with hydrazidoyl halides. IV. Synthesis of thiazolo[3,2-a]benzimidazoles,imidazo[2,1-6]thiazoles and pyrazolo[4,3-b]thiazines

Hydrazidoyl halides were condensed with 2-mercaptobenzimidazole yielding 4a-c and 7a,b which were cyclized to the corresponding 2-arylhydrazonothiazolo[3,2-a]benzimidazol-3-ones 5a,b and 3-substituted 2-arylazo thiazolo[3,2-a]benzimidazoles 8a,b respectively. Imidazo[2,1-b]thiazoles were obtained by the reaction of hydrazidoyl halides with 2-mercapto-4,5-dihydroimidazole. Also, hydrazidoyl halides 6a,b were reacted with 3-amino-4-mercapto-5-phenylpyrazole to give pyrazolo[4,3-b]thiazines 15a,b . The structures of the products were assigned on the basis of their elemental analysis and spectral data.     

Adsorption of Bovine Serum Albumin onto Polystyrene Latex Particles Bearing Saccharidic Moieties

The adsorption of bovine serum albumin (BSA) onto polystyrene latexes bearing various amounts of sugar moieties has been investigated as a function of pH and ionic strength and the results were compared to those for bare polystyrene latexes having negative surface charges. The functionalized latexes were produced by seeded copolymerization of (0.3 μm) liposaccharidic monomer onto polystyrene particles obtained by soap-free emulsion polymerization of styrene using potassium persulfate as initiator. At first, the electrophoretic mobility behavior of the various latexes was examined as a function of pH: a significant decrease was observed in the case of saccharide-containing latex particles compared to the bare particles. The adsorption of BSA onto these latexes exhibited a reduced amount of adsorbed BSA for those latex particles bearing saccharide groups. This adsorbed amount depends on the yield of saccharidic monomer incorporated onto the surfaces of the latex particles.     

SYNTHESIS OF MONO-AND DIALKYLPHOSPHATES BY THE REACTIONS OF HYDROXYCOMPOUNDS WITH THE PHOSPHORUS PENTAOXIDE UNDER MICROWAVE IRRADIATION

The reactions of phosphorus pentoxide with two alcohols and one phenol were performed in different conditions under microwave irradiation. The products (alkylphosphates and dialkylphosphates) were identical to those formed by classic heating and were obtained with better yields. The speed of the reaction was increased by a factor from 100 to 4000.     

Reactions of Hydrazonoyl Halides 33 1 : Synthesis of Some New 2,3-Dihydro-1,3,4-thiadiazoles Containing Pyrazol-3-yl,Indolin-2-one-2-yl and Indan-1,3-dione-2-yl Moieties

Some new 2,3-dihydro-1,3,4-thiadiazoles containing pyrazol-3-yl, indolin-2-one-2-yl and indan-1,3-dione-2-yl moieties in a good yields obtained from the reaction of hydrazonoyl halides with thiocarbamate and carbodithioate in ethanolic triethylamine respectively. In contrast, pyrazolylthiourea reacts with hydrazonoyl halides under the same condition afford corresponding hydrazonoyl sulfide derivatives.     

Mathematical Model and Numerical Simulation of Conductometric Biosensor of Urea

In this article, a mathematical model was developed to describe and optimize the configuration of the urea biosensor. The biosensor is based on interdigitated gold microelectrodes modified with a urease enzyme membrane. The model presented here focuses on the enzymatic reaction and/or diffusion phenomena that occur in the enzyme membrane and in the diffusion layer. Numerical resolution of differential equations was performed using the finite difference technique. The mathematical model was validated using experimental biosensor data. The responses of the biosensor to various conditions were simulated to guide experiments, improve analytical performance, and reduce development costs.     

Comparative study of aerogels nanostructured catalysts: Ni/ZrO2–SO4 2− and Ni/ZrO2–Al2O3–SO4 2−

Ionics - A series of Ni/ZrO2–SO4 2− and Ni/ZrO2–Al2O3–SO4 2− catalysts were prepared in one step by the sol–gel method and dried in hypercritical conditions of...