Application Des Réseaux de Neurones Avec la Régularisation Bayésienne pour la Modélisation de la Synthèse de l’hydroxyapatite Élaborée à Partir du Carbonate de Calcium et de L’acide Phosphorique

We have used a new, robust model mapping technique—a Bayesian-regularized neural network—to develop a quantitative relationships model for the synthesis of the phosphocalcic hydroxyapatite by precipitation from a calcium carbonate solution and a phosphoric acid solution. This model was preformed by using a set of factors consisting on the pH of reactional medium, the Ca/P molar ratio of the reagents, reaction time, and the initial concentration of calcium. The results show that the method is robust and gives satisfied results. The Levenberg–Marquardt's algorithm implemented in the neural network Matlab's toolbox allowed a drastic improvement of the performance of the model. Very satisfactory results are then obtained by testing the validity by cross-validation technique.

We have also turned our interests to the explanatory capacities of our methodology to explore the relative contribution and/or the contribution profile of the input factors by using Garson weight portioning method.     

Synthesis and Crystal Structure of Bis (<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′,<Emphasis Type="Italic">N</Emphasis>′-tetramethylethylendiammonium) Octaiodo Pentachloroantimonate (III)

Abstract  

The synthesis and Crystal structure are given for the bis (N,N,N′,N′-tetramethylethylendiammonium) octaiodo pentachloroantimonate (III) salt. An X-ray investigation has shown that the title compound crystallizes in a monoclinic system, space group P2₁/m with the following lattice parameters a = 9.786(2) Ǻ, b = 14.024(5) Ǻ, c = 14.336(3) Ǻ, β = 91.35(2)° and Z = 2. The structure was solved from 3085 independent reflections with R ₁ = 0.0402 and wR ₂ = 0.0952 and refined with 152 parameters. The structure shows a layer arrangement perpendicular to the [(b)\vec] \vec{b} -axis: planes of [SbCl₅]²⁻, I₃ ⁻ and I₅ ⁻ anions alternate with planes of [(CH₂)₂(NH(CH₃)₂)₂]²⁺ cations. The [SbCl₅]²⁻ square pyramids present an active lone electron pair (LEP) on the Sb atoms and they are interconnected by means of N–H···Cl hydrogen bond originating from [(CH₂)₂(NH(CH₃)₂)₂]²⁺ entities. The polyiodides (I₃ ⁻ and I₅ ⁻) anions form a planer zigzag polymeric chains via I···I linking interactions. These chains are linked to the [SbCl₅]²⁻ anions by a long range contact.     

Gorenstein Analogue of Auslander's Theorem on the Global Dimension

In this paper, we prove that the Gorenstein analogue of the well-known Auslander's theorem on the global dimension holds true. Namely, we prove that the Gorenstein global dimension of a commutative ring R is equal to the supremum of the set of Gorenstein projective dimensions of all cyclic R-modules.     

Production of Xylooligosaccharides by Immobilized His-tagged Recombinant Xylanase from Penicillium occitanis on Nickel-Chelate Eupergit C

Penicillium occitanis xylanase 2 expressed with a His-tag in Pichia pastoris, termed PoXyn2, was immobilized on nickel-chelate Eupergit C by covalent coupling reaction with a high immobilization yield up to 93.49 %. Characterization of the immobilized PoXyn2 was further evaluated. The optimum pH was not affected by immobilization, but the immobilized PoXyn2 exhibited more acidic and large optimum pH range (pH 2.0–4.0) than that of the free PoXyn2 (pH 3.0). The free PoXyn2 had an optimum temperature of 50 °C, whereas that of the immobilized enzyme was shifted to 65 °C. Immobilization increased both pH stability and thermostability when compared with the free enzyme. Time courses of the xylooligosaccharides (XOS) produced from corncob xylan indicated that the immobilized enzyme tends to use shorter xylan chains and to produce more xylobiose and xylotriose initially. At the end of 24-h reaction, XOS mixture contained a total of 21.3 and 34.2 % (w/w) of xylobiose and xylotriose with immobilized xylanase and free xylanase, respectively. The resulting XOS could be used as a special nutrient for lactic bacteria.     

Attempts to Rationalize the Chemical Reactivity of the 1–3 Dipolar Species Obtained when a Phosphite Reacts with Activated Ethylenic or Acetylenic Ketones or Esters

Abstract

- Addition of trivalent phosphorus compounds with α, β ethylenic ketones and esters leads to examples of prototropy or cyclisation or rearrangement with ring expansion from 5 to 7 atoms.

When trivalent phosphorus compounds react with acetylenic ketones and esters, the 1, 3 dipolar species can be trapped with an electrophilic reagent (aldehydes or the original acetylenic compound) or a protic reagent (alcohol, acid, amide, phenol, etc…) Ylides, phosphoranes, spirophos-phoranes and phospholes can be obtained.     

Hydrothermal Synthesis,Crystal Structure,and Characterization of a Two-Dimensional Open-Framework Zinc Phosphate Templated by Hexylamine: [C6H16N]·[Zn(HPO4)Cl]

The title compound has been synthesized under mild hydrothermal conditions (autogenous pressure, 368 K, 24 h). It crystallizes in the P2 ₁ /c (N°14) space group with a = 15.9323(4) Å b = 9.6203(1)Å c = 8.8024(2)Å β = 103.828(2)°; V = 1310,07(5) Å ³ ; and Z = 4. Its structure, determined from X-ray single-crystal data (1266 reflexions with I > 2σ (I), R = 7.4%, Rw = 20.6%), consists of inorganic [Zn(HPO ₄ )Cl]^? sheets lying parallel to the (100) plane between which are located the protonated organic molecules. The infrared spectroscopy and the thermogravimetric analysis are reported.     

Stabilization method for continuous approximation of transient convection problem

The aim of this work is to study a new finite element (FE) formulation for the approximation of nonsteady convection equation. Our approximation scheme is based on the Streamline Upwind Petrov Galerkin (SUPG) method for space variable, x, and a modified of the Euler implicit method for time variable, t. The most interest for this scheme lies in its application to resolve by continuous (FE) method the complex of viscoelastic fluid flow obeying an Oldroyd‐B differential model; this constituted our aim motivation and allows us to treat the constitutive law equation, which expresses the relation between the stress tensor and the velocity gradient and includes tensorial transport term. To make the analysis of the method more clear, we first study, in this article this modified method for the advection equation. We point out the stability of this new method and the error estimate of the approximation solution is discussed. © 2004 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2005     

Rings Over Which the Class of Gorenstein Flat Modules is Closed Under Extensions

A ring R is called left “GF-closed”, if the class of all Gorenstein flat left R-modules is closed under extensions. The class of left GF-closed rings includes strictly the one of right coherent rings and the one of rings of finite weak dimension.

In this article, we investigate the Gorenstein flat dimension over left GF-closed rings. Namely, we generalize the fact that the class of all Gorenstein flat left modules is projectively resolving over right coherent rings to left GF-closed rings. Also, we generalize the characterization of Gorenstein flat left modules (then of Gorenstein flat dimension of left modules) over right coherent rings to left GF-closed rings. Finally, using direct products of rings, we show how to construct a left GF-closed ring that is neither right coherent nor of finite weak dimension.     

Theory of the successive phase transitions in KNbO3

The microscopic mechanism of the successive cubic-tetragonal-orthorhombic-rhombohedral phase transitions in KNbO₃ is discussed quantitatively from the microscopic free energy based upon the mean field approximation where the Nb ions are displaced to create spontaneous deformations. From the calculation of the microscopic free energy, it is shown that the order of the phase transitions and the experimental values of the transition entropy in KNbO₃ are well explained by this model.