Analysis of plane and axisymmetric flows of incompressible fluids with the stream tube method: Numerical simulation by trust-region optimization algorithm

New concepts for the study of incompressible plane or axisymmetric flows are analysed by the stream tube method. Flows without eddies and pure vortex flows are considered in a transformed domain where the mapped streamlines are rectilinear or circular. The transformation between the physical domain and the computational domain is an unknown of the problem. In order to solve the non-linear set of relevant equations, we present a new algorithm based on a trust region technique which is effective for non-convex optimization problems. Experimental results show that the new algorithm is more robust compared to the Newton-Raphson method.     

Structural and Magnetic Properties Control of Pr0.7Ba0.3MnO3 with Sr-Doping

Physics of the Solid State - Structural and magnetic properties of Sr-doped Pr0.7Ba0.3MnO3 polycrystallines prepared by solid state reaction are presented. Samples were in monoclinic structure...     

Mass Spectrometric (FAB) Study of Aspartic Acid Side Reactions in Peptide Synthesis

Abstract

We have been interested in the synthesis of branched peptides, by grafting an amine, eg histamine, to the carboxylic group of aspartic acid side chain of Boc-β Ala-Trp-Met-Asp-Phe-NH₂ also called Pentagastrin (or α-PG). Depending on the coupling conditions used, the main product obtained might be either the wanted derivative or a side-product identified a6 amino-succinyl-pentagastrin (or ASC-PG). Acid or base treatment of this product cleaved the amino-succinyl ring and yielded either α-PG or/and (β-Aspartyl)⁴-PC or β-PG. Amino-succinylation being a general problem in peptide synthesis of aspartyl residue containing peptides, synthesis of α-PG, β-PG, Asc-PG and their corresponding C-terminal dipeptide amides were performed to be analyzed by mass spectroscopy.

FAB mass spectra (PI in glycerol) of the free peptides, as well as of their N-Boc derivatives have been recorded and compared to the mono, di, tri and tetra peptide derivatives. The pseudo-molecular ions of Boc-peptides are usually not observed. However, the intense M+1-Boc (? 100 u) ions are present.

Several sequence ions have been identified and compared to the simulation of their spectra according to six fragmentation routes.

The identification of α, β or succinimide structures from FAB spectra has been proposed.     

Pulsed laser deposition of PZT/Pt composite thin films with high dielectric constants

PbZr_0.53Ti_0.47O₃ (PZT) thin films containing nanoparticles of Pt (3–10 nm) were produced using pulsed laser deposition (PLD). The Pt content can be tuned by varying the energy density of the laser beam. Phase and microstructure analysis of the thin films was performed using XRD, SEM, TEM and AFM. The electrical properties were investigated by C–V and I–V measurements. The effective dielectric constant of the composite films increased substantially through the Pt dispersion. These films are promising candidates, for instance, for high-density dynamic random access memory (DRAM) devices. PACS 77.22.Ch; 77.84.Lf; 81.15.Fg     

Metal-doped apatitic calcium phosphates: preparation,characterization, and reactivity in the removal of hydrogen sulfide from gas phase

With the expansion of human activities, there are more and more living areas adjacent to industrial and/or agricultural activities such as chemical processes, petroleum processes, paint finishing, food processing, livestock farming, composting plants etc. Bad odor is part of several nuisances caused by industrial and/or agricultural activities. Hydrogen sulfide (H₂S) is a typical odorous molecule which causes foul odor at very low concentration. This molecule is formed in different industrial installations, in particular in coal combustion, and petrochemical refinery. The separation and/or transformation of H₂S from gas phase to odorless products are important processes for sustainable development. In this paper, we communicate the preparation of new sorbents for the sorption of H₂S from a synthetic gas effluent. These sorbents consist in an inorganic phase (hydroxyapatite) as host particles, and well-dispersed particles of a metal oxide as guest particles which are the active phase for the removal of H₂S. At room conditions, iron, lead, and zinc doped calcium phosphates were found to be effective for the removal of H₂S. The performance of the sorbents depends on preparation method and the nature of active phases. This opens new prospects for the treatment of H₂S from gas phase.     

Flash photolysis studies of the reaction of NH2 radicals with NO

The kinetics of the reaction NH₂ + NO → N₂ + H₂O were studied, using a conventional flash photolysis system. A value of k₁ = (1.1 ± 0.2) × 10¹⁰ & mole^?1 s^?1 was obtained at room temperature and in the pressure range 2–700 torr in the presence of nitrogen. A slight negative temperature coefficient was observed between 300 and 500 K, equivalent to a negative activation energy of 1.05 ± 0.2 kcal mole^?1.     

Phenomenes de complexation entre un peroxyde et les monomeres vinyliques polaires etudies par resonance magnetique protonique

The self association of cumyl hydroperoxide and its complexing with polar monomers have been studied by proton magnetic resonance. These complexations are exothermic and strongly temperature dependent. It has been suggested that the complexation of cumyl hydroperoxide by polar monomers could be one of the causes of its efficiency in initiating the radical polymerization of vinyl monomers on an ethyl-zinc terminated polyethylene chain to form radical block copolymers. However, if this phenomenon has an effect on the initiation, it should not affect the propagation mechanisms, because the hydroperoxide is destroyed by ZnEt₂ during initiation. Moreover, the tacticity of radical polymethylmethacrylate, obtained at 60° with (ZnEt₂—cumyl hydroperoxide) in heptane does not differ from the conventional radical polymer.     

Polymerisation anionique du methacrylate de methyle par les organoalcalins—II. Polymerisation en milieu solvant protonique et influence de la temperature sur les tacticites des polymeres

Anionic polymerization of methylmethacrylate, initiated by fluorenyl-alkali metals in amine media, gives syndiotactic polymers.With amines having high dielectric constant (NH₃ and MeA) Li⁺, Na⁺ and K⁺ give approximately the same values of differential enthalpies and entropies of activation for iso- and syndiotactic placements.With primary amines having moderate dielectric constant (5 < ? < 7), influence of the nature of the counter-ion has been observed. The syndiotacticity increases with increasing alkali cation radius.For the same ion pair, the syndiotacticity of the propagation depends on the nature of the primary amine. From the absorption peak shifts detected by u.v. spectroscopy, it has been suggested that the living carbanion is solvated by amines. Because of this solvation, the coordination bond between the carboxy group of the living chain-end and the counter-ion is weakened; the syndiotactic placement is thus favoured.The strength of the solvation phenomenon depends on the steric hindrance of the amine molecule. Differences between the stereoconfiguration propagations have been observed for the bulky cyclohexylamine and the smaller and less rigid n-butylamine and ethylamine. With iso-propylamine, the behaviour of the anionic propagation is intermediate.Finally, with free ions or loose ion pairs, the anionic propagation is not affected by solvation of the living carbanion.