Preparation and characterization of polyvinyl alcohol—chitosan biocompatible magnetic microparticles

This work addresses the obtaining of biocompatible magnetic polyvinyl alcohol—chitosan microspheres, specifically tailored/functionalised to bind directly blood toxins using an emulsion crosslinking preparation method. The following synthesis parameters were studied: water to oil phase ratio, polyvinyl alcohol molecular weight, chitosan to polyvinyl alcohol weight ratio, surfactant composition and concentration of the crosslinking agent. These parameters were optimized for producing a high yield of colloidally stable and uniformly sized particles with significant magnetization of saturation, bearing surface amino groups that can be further used to bind blood toxins directly. The particles were characterized regarding their size distribution and surface charge (laser diffraction analysis), morphology (transmission electron microscopy), magnetic properties, chemical composition (Fourier transform infrared spectroscopy) and concentration of the surface amino groups (conductometric titration).     

Periodic Homogenization for Inner Boundary Conditions with Equi-valued Surfaces: the Unfolding Approach

Making use of the periodic unfolding method, the authors give an elementary proof for the periodic homogenization of the elastic torsion problem of an infinite — dimensional rod with a multiply-connected cross section as well as for the general electroconductivity problem in the presence of many perfect conductors (arising in resistivity well-logging). Both problems fall into the general setting of equi-valued surfaces with corresponding assigned total fluxes. The unfolding method also gives a general corrector result for these problems.     

Spectroscopic study of laser irradiated chromatin

Antiprotonic helium is a metastable three-body neutral atom consisting of an antiproton, a helium nucleus and an electron, which we serendipitously discovered some 20 years ago. The antiproton, which normally annihilates within a few picoseconds when injected into matter, can be “stored” in this system for up to several microseconds, and laser spectroscopy is possible within this time window. From the laser transition frequency, the antiproton-to-electron mass ratio can be deduced to high precision. Recent progress at CERN’s antiproton decelerator (AD) will be discussed.     

Micellar behavior of some amphiphilic block polyurethanes in aqueous/nonaqueous media

Amphiphilic polyether block polyurethanes based on Pluronic type macrodiol and polyethylene glycol as co-segment have been prepared. Their micellar behavior in N,N-dimethylformamide solution, aqueous solvent mixtures and with added inorganic salts or urea was investigated by employing fluorescence spectroscopy and tensiometry techniques. Increased values of the critical micelle concentration were found for the more soluble block copolyurethane. The structural components have a strong influence on micellar characteristics of the studied systems.     

Laboratory analyses of 60Co2+, 65Zn2+ and (55+59)Fe3+ radiocations uptake by Lemna minor

The living Lemna minor vascular plant and two different sorbents obtained by chemical treatment of this plant were tested to study the removal process of 60Co2+, 65Zn2+ and (55+59)Fe3+ from low radioactive wastewaters. The most effective sorbent was the protonated biomass, indicating the decisive contribution of the complexation process in the assembly of the uptake mechanisms. The uptake performance of the biosorbent obtained from the L. minor can be increased with approximately 20% by treatment with 0.1 N HNO3. Concerning the metabolically active mechanism, it can be notice the slow elimination of 65Zn2+ and the continuously increase of (55+59)Fe3+ uptake degree. The Na2CO3 generated in situ in systems participates to a double exchange reaction with the metallic cations during the uptake. 60Co2+, 65Zn2+ and (55+59)Fe3+ radiocations prefer for coordination N-donor ligands at the expense O-donors ones.     

Structural investigations of ITO-ZnO films grown by the combinatorial pulsed laser deposition technique

Mixtures of transparent and conductive oxides such as ITO-ZnO have been grown by a combinatorial pulsed laser deposition technique from two targets that were located 15 mm apart. The films were deposited on (1 0 0)Si and quartz substrates that were heated at temperatures from 300 to 500 °C. Measurements of the In to Zn ratios along the transversal axis of the substrates, which passes through the maximum thickness points corresponding to each target position were performed using energy dispersive X-ray spectroscopy and spectroscopic ellipsometry. From simulations of the X-ray reflectivity spectra, collected with a 2 mm mask on different locations along the transversal axis of the samples, the density and thickness of the deposited films were calculated and then the In to Zn ratios. The crystalline structure and electrical properties of the deposited films were also investigated along the same axis. Changes in the ratio of In/Zn along this axis resulted in changes of the film lattice constant and texture.     

Characterization of magnetic nano-fluids via Mössbauer spectroscopy

The laser pyrolysis became a useful tool, providing various ways, in production of nano materials. The iron Mössbauer spectroscopy is one very accurate method in evidencing the physical properties and related processes in the nano scale compounds. The effect of pressure, laser spot area and induced combustion, of gas mixture and laser power on the phase composition and inside particle distribution, grain size as well as the related phenomena were investigated by temperature dependent Mössbauer spectroscopy. A selection of most relevant properties is presented and discussed in details.     

Periodic unfolding and homogenizationÉclatement périodique et homogénéisation

A novel approach to periodic homogenization is proposed, based on an unfolding method, which leads to a fixed domain problem (without singularly oscillating coefficients). This method is elementary in nature and applies to cases of periodic multi-scale problems in domains with or without holes (including truss-like structures). To cite this article: D. Cioranescu et al., C. R. Acad. Sci. Paris, Ser. I 335 (2002) 99–104.     

Sorption and Separation of Al(III), Ga(III), In(III), and Tl(III) from hydrochloric acid—water—methanol and hydrochloric acid—water—ethanol mixtures onP-cellulose ion-exchanger

Microchimica Acta - A study of sorption and separation of Al(III), Ga(III), In(III), and Tl(III) on P-cellulose cation-exchanger in hydrochloric acid-water-methanol and hydrochloric...