Une Etude Cohomologique de la Partie 2-Primaire deK2O

Résumé On étudie par voie cohomologique les parties 2-primaires de pertains noyaux de laK-théorie associée à un corps de nombres totalement réel.

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We use cohomological methods to study the 2-primary parts of certain kernels ofK-theory associated with totally real number fields.

     

Synthesis and Crystal Structure of Bis[<Emphasis Type="Italic">N</Emphasis>-{(<Emphasis Type="Italic">S</Emphasis>)-1-Phenylethyl}-<Emphasis Type="Italic">N</Emphasis>-{1-(2-Pyridinyl)Methyl}Amine] Zinc(II) Perchlorate

Abstract  

The reaction of N-[(S)-1-phenylethyl]-N-[1-(2-pyridinyl)methyl]amine (PEPMA) with Zn(ClO₄)₂ affords (PEPMA)₂Zn(ClO₄)₂ at room temperature. The complex is characterized by elemental analysis, ¹H-MNR and X-ray crystallography. The crystal system is orthorhombic with space group of P2₁2₁2₁ and unit cell parameters: a = 8.6911(4), b = 9.7755(7), c = 37.275(2) ?, V = 3166.9(3) ?³, Z = 4, D _x  = 1.445 Mg/m³. The crystal structure reveals that zinc metal is ligated by two PEPMA ligands in a distorted tetrahedral fashion. Interestingly, both nitrogen atoms of amine at PEPMA to the central zinc metal exhibit (R)-configuration.     

Effect of drying technique on the physicochemical properties of sodium silicate-based mesoporous precipitated silica

The conventional drying (oven drying) method used for the preparation of precipitated mesoporous silica with low surface area (>300 m²/g) and small pore volume is often associated with a high production cost and a time consuming process. Therefore, the main goal of this study was to develop a cost-effective and fast drying process for the production of precipitated mesoporous silica using inexpensive industrial grade sodium silicate and spray drying of the precipitated wet-gel silica slurry. The precipitated wet-gel silica slurry was prepared from an aqueous sodium silicate solution through the drop-wise addition of sulfuric acid. Mesoporous precipitated silica powder was prepared by drying the wet-gel slurry with different drying techniques. The effects of the oven drying (OD), microwave drying (MD), and spray drying (SD) techniques on the physical (oil, water absorption, and tapping density), and textural properties (specific BET surface area, pore volume, pore size, and % porosity) of the precipitated mesoporous silica powder were studied. The dried precipitated mesoporous silica powders were characterized with field-emission scanning electron microscopy; Brunauer, Emmett and Teller and BJH nitrogen gas adsorption/desorption methods; Fourier-transform infrared spectroscopy; thermogravimetric and differential analysis; N₂ physisorption isotherm; pore size distribution and particle size analysis. There was a significant effect of drying technique on the textural properties, such as specific surface area, pore size distribution and cumulative pore volume of the mesoporous silica powder. Additionally, the effect of the microwave-drying period on the physicochemical properties of the precipitated mesoporous silica powder was investigated and discussed.     

Existence and compactness for the {\overline{\partial}} -Neumann operator on q-convex domains

The aim of this paper is to give a sufficient condition for existence and compactness of the \({\overline{\partial}}\) -Neumann operator N _q on \({L^2_{(0,q)}(\Omega)}\) in the case Ω is an arbitrary q-convex domain in \({\mathbb{C}^n}\) .     

Evaluations of initial ideals and Castelnuovo-Mumford regularity

This paper characterizes the Castelnuovo-Mumford regularity by evaluating the initial ideal with respect to the reverse lexicographic order.

     

Bistable reflectivity in bulky semiconductors due to two photon-biexciton transitions

A new mechanism has been proposed for optical bistability in a bulk system of interacting photons and biexcitons. Bistable behaviour can occur for very low pumping intensities if the input light frequency is clearly less than the two-photon resonance of the biexciton.