Model structures of thermoplastic polyesters having regularly alternated aromatic and fluorinated segments

Linear segmented polyesters containing soft perfluoropolyether (PFPE) and hard aromatic segments are obtained by an interfacial polycondensation reaction of an acyl chloride-ended fluorinated prepolymer with various aromatic diphenols in the presence of phase transfer catalysts (PTC) as accelerators. Experimental conditions for reaching high molecular weights are discussed. The calorimetric analysis (DSC) of all the polyesters synthesized shows a typical biphasic morphology, where a very low T_g (< −110°C) corresponding to the segregated PFPE moiety, is always accompanied by another T_g or a higher melting temperature, depending on the nature of the hard phase. Dynamic-mechanical analysis (DMA) has been carried out confirming the DSC results and suggesting diversified mechanical behaviors at the various temperatures in line with the amorphous or semicrystalline nature of the polymer. Chemical resistance was finally tested by dipping in several solvents and chemicals. The new polyesters show high contact angles, a moderate swelling in many organic solvents and excellent stability in aggressive hydrolytic environments. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 939–947, 1998     

Development and validation of a sensitive and selective method using GC/MS-MS for quantification of 5-fluorouracil in hospital wastewater

Pollution of the environment by pharmaceuticals is a subject of growing scientific and societal concern. However, few quantitative data have been reported concerning hospital wastewater contamination. Among the different molecules used at hospital, antineoplastic drugs appear to be of special interest, and 5-fluorouracil (5-FU) can be considered as a key compound of this therapeutic class. To monitor this pharmaceutical in hospital wastewater, a highly specific and selective method was developed using gas chromatography tandem mass spectrometry after solid-phase extraction. This sensitive method (limit of quantification = 40 ng L⁻¹) was then applied to assess sewage contamination of a middle-size hospital with oncology service located in Paris, France. Native 5-FU was detectable in 12 of the 14 analysed samples. In positive samples, concentration range was measured from 0.09 to 4.0 μg L⁻¹. Finally, a predicting model for the hospital wastewater concentrations is presented, and results of this model are discussed.     

Classification of discrete equations linearizable by point transformation on a square lattice

We provide a complete set of linearizability conditions for nonlinear partial difference equations defined on four points and, using them, we classify all linearizable multilinear partial difference equations defined on four points up to a Möbious transformation.     

Lie symmetries of difference equations

The discrete heat equation is worked out to illustrate the search of symmetries of difference equations. Special attention it is paid to the Lie structure of these symmetries, as well as to their dependence on the derivative’s discretization. The case ofq-symmetries for discrete equations in aq-lattice is briefly considered at the end. Talk delivered by J. Negro at the DI-CRM Workshop held in Prague, 18–21 June 2000. This work has been partially supported by DGES of the Ministerio de Educación y Cultura of Spain under Projects PB98-0360 and the Junta de Castilla y León (Spain).     

Segregation of Aluminium at Nickel-Sapphire Interfaces

Sessile drop experiments of pure liquid Ni on the basal surface of pure sapphire were conducted under controlled atmosphere and temperature. This system has been traditionally considered as non-reactive, based on thermodynamic assessments. However, the results of this study demonstrate that a capillary driven interaction exists between the pure liquid Ni and the sapphire, which causes the dissolution of the sapphire substrate mainly at the triple junction. Oxygen and Al resulting from the dissolution process diffuse into Ni and segregate at its interfaces with the atmosphere and the sapphire (probably as Al _x O _y clusters), which reduces the interface energy. It is considered that this reduction is beneficial for the adhesion of both liquid and solid Ni on sapphire. The amount of Al introduced into the drop, and hence the segregation of Al that affects the interface energy (and adhesion), are related to the size of the sessile drop.     

Symmetries of the Discrete Nonlinear Schrödinger Equation

The Lie algebra L(h) of point symmetries of a discrete analogue of the nonlinear Schrödinger equation (NLS) is described. In the continuous limit, the discrete equation is transformed into the NLS, while the structure of the Lie algebra changes: a contraction occurs with the lattice spacing h as the contraction parameter. A five-dimensional subspace of L(h), generated by both point and generalized symmetries, transforms into the five-dimensional point symmetry algebra of the NLS.     

Effects of Citicoline,Homotaurine, and Vitamin E on Contrast Sensitivity and Visual-Related Quality of Life in Patients with Primary Open-Angle Glaucoma: A Preliminary Study

The aim of the present study was to evaluate the effects of supplementation with a fixed combination of citicoline 500 mg, homotaurine 50 mg, and vitamin E 12 mg (CIT/HOMO/VITE) on contrast sensitivity and visual-related quality of life in patients with primary open-angle glaucoma (POAG) in mild stage. This was a multicenter, observational, cross-over, short-term, pilot study on POAG patients with stable controlled intraocular pressure (IOP). Patients were randomly assigned to Group 1 (current topical therapy for 4 months and then current topical therapy plus CIT/HOMO/VITE for 4 months) or Group 2 (CIT/HOMO/VITE in addition to current topical therapy for 4 months and then topical therapy alone for 4 months). Best-corrected visual acuity, IOP, visual field, and the Spaeth/Richman contrast sensitivity (SPARCS) test score were recorded at baseline and after 4 and 8 months. The Glaucoma Quality of Life-15 (GQL-15) questionnaire was administered at each check time. Forty-four patients were assigned to Group 1 and 65 to Group 2. Over the follow-up period, there were no significant changes in IOP or visual field findings, whereas SPARCS and GQL-15 findings significantly varied from baseline, both being improved in subjects treated with CIT/HOMO/VITE fixed combination. These results demonstrate that a daily intake of a fixed combination of citicoline, homotaurine, and vitamin E in addition to the topical medical treatment significantly increased the total score of the contrast sensitivity test and the quality of life in patients with POAG.     

On the generation of internal solitary marine waves

Summary A nonlinear model of generation of internal ?solitary? marine waves is discussed: when a large surface wave—for instance a superficial wave or a bore of tidal origin—passes over a submarine mountain or crosses a strait, packets of internal waves may often be detected. We study this phenomenon taking into account the effect of the air-sea surface; we show that the phenomenon can be schematized, in an approximate but realistic way, by using the solutions of an inhomogeneous KdV equation. The forcing term depends on the air-sea surface elevation and on the bottom topography. We then apply our model to the marine currents, of tidal origin, flowing through the straits of Gibraltar.

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Riassunto Si studia un modello non lineare della generazione di onde interne marine. Quando una grande onda superficiale passa sopra una montagna sottomarina o attraversa uno stretto si osservano pacchetti di onde interne. Si studia questo fenomeno tenendo conto della interfaccia aria-mare, si mostra che il fenomeno può essere rappresentato in maniera approssimata dalle soluzioni di un'equazione di KdV non omogenea. Il termine forzante dipende dalla superficie aria-mare e dalla topografia del fondo. Infine il modello proposto è applicato alle correnti di marea dello stretto di Gibilterra.

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Резюме Обсуждается нелинейная модель образования внутренних ?одиночных? морских волн: когда большая поверхностная волна проходит над подводной горой или приливная волна пересекает пролив, часто могут детектироваться пакеты внутренних волн. Мы исследуем зто явление, учитывая влияние границы раздела воздух-море. Мы показываем, что это явление может быть схематизировано приближенным, но реалистическим способом, используя решения неоднородного уравнения Кортевега-де Вриса. Силовой член зависит от возвышения границы раздела воздух-море и от топографии дна. Затем мы применяем нашу модель для морских течений (приливного происхождения), проходязих через Гибралтарский пролив.