Epidermal reconstructs: a new tool to study topical and systemic photoprotective molecules

In this study, we compared the effects of sunscreens and antioxidants on reconstructed epidermis made with or without melanocytes 24 h after UVB, UVA or UVA+B irradiation. For this purpose, we studied sunburn cells and cyclobutane pyrimidine dimer formation, protein and lipid oxidation, catalase and superoxide dismutase activities and vitamin E levels. Topical sunscreens protected against direct cell death and thymine dimer formation whereas their protective effect against protein and lipid oxidation and antioxidant depletion was less marked partly due to the difficulty of spreading the cream. Antioxidant molecules protected against direct cell death and protein oxidation but not against thymine dimer formation. Since topical sunscreens and systemic antioxidant protected the skin differently, we speculate that their association might protect more efficiently against UV-induced damage. This model is relevant to study systemic molecules but is less practical, due to the technical limitations of studying topical molecules.     

A Structural Study of the Homogeneity Domain of LaNi5

LaNi₅ is a very important intermetallic compound for hydrogen storage applications. Its homogeneity range at 1200°C has been investigated by single-crystal X-ray diffraction, electron probe microanalysis, and mass density measurements. At the nickel-rich end the hexagonal structure (CaCu₅ type) extends to the composition LaNi_5.45. The excess of nickel is accommodated by random substitutions of lanthanum atoms by nickel dumbbells and by displacements of nickel atoms which are presumably correlated with the La atom substitutions. Interatomic distances suggest that the Ni atom displacements occur in directions toward vacant La atom sites, i.e., toward the center of Ni dumbbells. At the nickel-poor end the structure extends to the composition LaNi_4.88. The excess of lanthanum is presumably accommodated by the simultaneous occurrence of lanthanum atoms and vacancies on nickel atom sites. Both models are consistent with mass density and electron probe microanalysis measurements. Hydrogenation thermodynamic properties have been measured as a function of composition.     

Combinatorial synthesis of bimetallic complexes with three halogeno bridges

Methods for the synthesis of bimetallic complexes in which two different metal fragments are connected by three chloro or bromo bridges are reported. The reactions are general, fast, and give rise to structurally defined products in quantitative yields. Therefore, they are ideally suited for generating a library of homo- and heterobimetallic complexes in a combinatorial fashion. This is of special interest for applications in homogeneous catalysis. Selected members of this library were synthesized and comprehensively characterized; single-crystal X-ray analyses were performed for 15 new bimetallic compounds.     

Europium palladium hydrides

The first fully structurally characterized ternary europium palladium hydrides (deuterides) are reported. The most Eu rich compound is Eu(2)PdD(4). Its beta-K(2)SO(4) type structure (space group Pnma, a = 749.47(1) pm, b = 543.34(1) pm, c = 947.91(1) pm, Z = 4) contains tetrahedral 18-electron [PdD(4)](4)(-) complex anions and divalent Eu cations. The compound is presumably nonmetallic and shows paramagnetic behavior (mu(eff) = 8.0(2) mu(B)) with ferromagnetic ordering at T(C) = 15.1(4) K. A metallic compound at intermediate Eu content is EuPdD(3). It crystallizes with the cubic perovskite structure (space group Pm3m, a = 380.01(2) pm, Z = 1) in which palladium is octahedrally surrounded by fully occupied deuterium sites. Metallic hydrides at low Eu content form by reversible hydrogen absorption of intermetallic EuPd(2) (Fd3m, a = 775.91(1) pm, Z = 8). Depending on the experimental conditions at least three phases with distinctly different hydrogen contents x exist: EuPd(2)H(x) ( approximately )(0.1) (a = 777.02(2) pm, Z = 8, T = 298 K, p(H(2)) = 590 kPa), EuPd(2)H(x) ( approximately )(1.5) (a = 794.47(5) pm, Z = 8, T = 298 K, p(H(2)) = 590 kPa), and EuPd(2)H(x) ( approximately )(2.1) (a = 802.1(1) pm, Z = 8, T = 350 K, p(H(2)) = 610 kPa). All crystallize with cubic Laves phase derivative structures and have presumably disordered hydrogen distributions.     

Morphology and thermomechanical properties of latex films

Latex films involve polymers, copolymers and (or) polymer blends, with more or less complex morphologies. First of all, the mechanical behavior of their amorphous polymeric component is considered. A theoretical approach, which relates macroscopic behavior to molecular processes, is used to model its dynamic mechanical properties and also plastic behavior. Then, in the case of heterogeneous films, we propose that information about the morphology of samples can be deduced from a comparison of their measured viscoelastic properties with the corresponding properties calculated for a suitable model. After a brief review of the theoretical approaches for the mechanical behavior of multiphase systems, we show the validity of the procedure in the case of latex films obtained from different copolymerization pathways. Thus, it is possible (a) to get information about the morphology of binary systems, (b) to determine the stability of the morphology, and (c) to characterize a third phase as an interphase between nodules and matrix. High stress–strain behavior is discussed in the case of latex films reinforced with nanoparticles of silica or with cellulose whiskers.     

Sulfobetaine zwitterionomers based on n‐butyl acrylate and 2‐ethoxyethyl acrylate: Monomer synthesis and copolymerization behavior

New materials with potential applications for adhesives and coatings, based on copolymers containing zwitterionic pendent groups, were investigated. n‐Butyl acrylate and 2‐ethoxyethyl acrylate were copolymerized with a series of five zwitterionic sulfobetaine monomers. The structure of the monomers was varied in terms of the zwitterion intercharge spacing and the bulkiness of the alkyl substituents at the quaternary ammonium unit. Four of the five zwitterionic sulfobetaine methacrylate (SBM) monomers used in the study were synthesized. An evaluation of the reactivity ratios for the copolymer systems was performed with programs based on statistically sound techniques such as the error‐in‐variables model and the nonlinear‐least‐squares method. Reactivity ratio estimates for all 10 comonomer pairs were obtained, and they showed clear variations in reactivity with the structure of the SBM. In general, the more hydrophobic the SBM was, the lower its reactivity was with respect to the acrylate monomers. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 511–523, 2002; DOI 10.1002/pola.10138     

Comportement thermique des benzènesulfonates de lithium,sodium et potassium

Résumé Le comportement thermique des benzènesulfonates de lithium, sodium et potassium a été étudié par TG et ATD à l'air et sous atmosphère d'azote.Dans la zone de stabilité des sels anhydres, nous avons mis en évidence des transformations réversibles (changements de phase cristalline) dont certaines ont fait l'objet de mesures calorimétriques.L'étude des résidus solides de la décomposition a montré une proportion importante de sulfates dans les produits obtenus dans l'air, alors que sous azote, il s'agissait surtout de sulfures. Les sulfites ne se présentent qu'en très faible quantité dans les deux cas.

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The thermal behaviour of benzènesulphonates of lithium, sodium and potassium has been investigated by TG and DTA in air and in an atmosphere of nitrogen.We have shown in the stability interval of the anhydrous salts reversible transformations (phase transitions), some of which were quantitatively studied by calorimetry.The radiocristallographic study of the solid residues has shown an important proportion of sulphates in the residues in air and of sulphides in an inert atmosphere. The sulphites were found in very small quantity in both cases.

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Zusammenfassung Das thermische Verhalten der Benzolsulfonate von Lithium, Natrium und Kalium wurde durch TG und DTA in Luft und in Stickstoff untersucht.Im Stabilitätsbereich der wasserfreien Salze wurden reversible Umwandlungen (Phasenübergänge) nachgewiesen, von denen einige quantitativ durch Kalorimetrie untersucht wurden.Das radiokristallographische Studium der festen Rückstände zeigte, daß in Luft ein bedeutender Anteil der Rückstände aus Sulfaten und in inerter Atmosphäre aus Sulfiden besteht. Sulfite wurden in beiden Fällen in sehr geringen Mengen gefunden.

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