Dynamique des Varietes Affines

An n-affine manifold is a differentiable manifold endowed withan atlas whose transition functions are locally affine transformationsof Rⁿ. The paper studies affine dynamic, that is, affine endomorphismsof affine manifolds. The main goal is to relate the dynamicalviewpoint to the completeness problem. In particular, it isshown that the Markus conjecture is true when dim Aff(M, ) >dim M – 2.     

Comparaison de résultats théoriques et expérimentaux concernant le filtrage spatial en optique cohérente

Résumé Nous avons, à l'aide d'un montage en double diffraction, effectué la transformation de Fourier d'une fonction «fente».Un vidicon, placé à l'endroit du plan image, permet de visualiser le signal reconstruit sur un écran d'oscilloscope avec, en ordonnée, l'intensité et en abscisse, la distance.Plusieurs filtres sont introduits à l'endroit du plan de Fourier.Les résultats sont analysés sur le plan image et peuvent alors être comparés à ceux qui sont obtenus théoriquement et calculés sur IBM 1130.

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With the aid of a double diffraction mounting, we have performed the Fourier transformation of a function slit. A vidicon, placed at the image plane, allows to visualize on an oscilloscope screen the reconstructed signal with the intensity as the ordinate and the distance as the absciassa. Various filters are introduced in the Fourier plane. Results are analysed in the image plane and they may be compared to those obtained theoretically by calculation on an IBM 1130.

     

Molecular distribution of some commercial nonylphenol ethoxylates using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Nonylphenol ethoxylates (NPEs) belong to a group of nonionic surfactants that are collectively referred to as alkylphenol ethoxylates (APEs). APEs find widespread use in heavy-duty commercial and household cleaning formulations, shampoos, and industrial processing, i.e. textile manufacture. Their environmental impact depends on the molecular distribution and the extent of their biodegradation in municipal sewage systems, waterways and rivers. We have established two sample preparation methods that have enabled the determination of the molecular distributions of six commercial nonylphenol ethoxylates using matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS). In both methods, alpha-cyano-4-hydroxycinnamic acid, dissolved in acetonitrile/tetrahydrofuran, was used as the matrix. In one set of experiments, the NPEs were dissolved in an acetonitrile/tetrahydrofuran solvent system prior to mixing with the matrix solution, and the resulting MALDI-TOF mass spectra produced mostly sodiated molecules [M + Na](+). The NPEs, all having the formula 4-(C(9)H(19))-C(6)H(4)-(OCH(2)CH(2))(n)-OH, are Surfonic (R)N-95, N-100, N-102, N-120, N-150 and N-300. Surfonic N-95 and N-100 gave n values of 5-20; Surfonic N-102, N-120, N-150, and N-300 gave n values of 5-21, 5-22, 8-25 and 15-40, respectively. In order to develop a sample preparation method that could be used with less polar NPEs, we dissolved the NPEs (except N-300) in pentane prior to mixing with the matrix solution, and found that the MALDI spectral quality was unaffected by the solvent systems. Copyright 1999 John Wiley & Sons, Ltd.     

Les rotations de l'espace euclidien à quatre dimensions,leur expression au moyen des nombres de Clifford et leurs relations avec la théorie des spineurs

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Les problèmes de représentation conforme d'Helmholtz; théories des sillages et des proues

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Sur les nombres de classes de certains corps quadratiques

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Synthesis and characterization of poly(ethylene glycol)‐based thermo‐responsive polyurethane hydrogels for controlled drug release

The thermo‐responsiveness, swelling and mechanical properties of a series of novel poly(ester‐ether urethane) hydrogels have been investigated. These thermo‐sensitive hydrogels were obtained by combining hydrophobic biodegradable poly(ε‐caprolactone) diols and hydrophilic two‐, three‐ and four‐arm hydroxyl terminated poly(ethylene glycol) (PEG) of various molecular weights, using hexamethylene diisocyanate, dichloroethane as solvent and a tin‐based catalyst. The use of multifunctional PEGs leads to the formation of covalent crosslinking points allowing an additional control of the swelling capability. Thus, it was found that tuning the hydrophilic/hydrophobic balance and the crosslinking degree by changing the composition, the swelling and the thermo‐responsive behavior of these hydrogels could be modulated. The obtained hydrogels showed a volume transition at around room temperature. Therefore, and taking into account their biocompatibility, these hydrogels show promising properties for biomedical applications, such as drug delivery. Thus, the loading and release of diltiazem hydrochloride, an antihypertensive drug used as model, were investigated. These new PEG polyurethane hydrogels were able to incorporate a high amount of drug providing a sustained release after an initial burst effect. Copyright © 2013 John Wiley & Sons, Ltd.