Luminescent zinc(II) and cadmium(II) complexes based on 2-(4,5-dimethyl-1H-imidazol-2-yl)pyridine and 2-(1-hydroxy-4,5-dimethyl-1H-imidazol-2-yl)pyridine

Complexes ZnL¹Cl₂, CdL¹Cl₂, ZnL ₂ ¹ Cl₂ ^·1.5H₂O, CdL ₂ ¹ Cl₂ ^·2H₂O, CdL ₂ ¹ Cl₂ ^·MeOH·H₂O [L¹ = 2-(4,5-dimethyl-1H-imidazol-2-yl)pyridine] and inner-complex compounds ZnL ₂ ² ·2H₂O, CdL ₂ ² [HL² = 2-(1-hydroxy-4,5-dimethyl-1H-imidazol-2-yl)pyridine] were synthesized. The complexes exhibit bright photoluminescence in the blue region of the spectrum, with the intensity exceeding this characteristic of the compounds L¹ and HL². Compound L¹ in aqueous solution is a potential chemosensor for the determination of zinc and cadmium.     

Tail ordering due to headgroup hydrogen bonding interactions in surfactant monolayers at the water-oil interface

Interactions between surfactants, and the resultant ordering of surfactant assemblies, can be tuned by the appropriate choice of head- and tailgroups. Detailed studies of the ordering of monolayers of long-chain n-alkanoic and n-alkanol monolayers at the water-vapor interface have demonstrated that rigid-rod all-trans ordering of the tailgroups is maintained upon replacing the alcohol with a carboxylic acid headgroup. In contrast, at the water-hexane liquid-liquid interface, we demonstrate that substitution of the -CH(2)OH with the -COOH headgroup produces a major conformational change of the tailgroup from disordered to ordered. This is demonstrated by the electron density profiles of triacontanol (CH(3)(CH(2))(29)OH) and triacontanoic acid (CH(3)(CH(2))(28)COOH) monolayers at the water-hexane interface, as determined by X-ray reflectivity measurements. Molecular dynamics simulations illustrate the presence of hydrogen bonding between the triacontanoic acid headgroups that is likely responsible for the tail ordering. A simple free energy illustrates the interplay between the attractive hydrogen bonding and the ordering of the tailgroup.     

Mathematical modeling of low-frequency oscillations observed in the diffusion of a substance through a membrane

In the diffusion process of a substance through a membrane under external steady-state conditions, low-frequency oscillations in its concentration are observed experimentally. A theoretical explanation for this phenomenon is given, and the results of mathematical modeling are presented. Models based on local membrane conductivity as a function of solution concentration are examined. It is shown in this case that positive feedback develops between changes in the flows and concentrations, and this determines the development of oscillations in the diffusion process of a substance.     

Oscillations of the concentration during sorption of amino acids on ion exchanger grains

Low frequency oscillations of the concentration can arise in the process of diffusion and sorption of amino acids under the stationary external conditions. This phenomenon has been observed in some experimental works. In the present paper it is studied by means of modelling. The physical factors responsible for a positive feedback between variations of solution flow and changes in the concentration are found. These factors give rise to instability of the process and oscillations of the concentration. The theoretical explanation of the phenomenon and the results of calculations are presented in this paper.     

Norm inequalities for convolution operators

We study norm convolution inequalities in Lebesgue and Lorentz spaces. First, we improve the well-known O'Neil's inequality for the convolution operators and prove corresponding estimate from below. Second, we obtain Young–O'Neil-type estimate in the Lorentz spaces for the limit value parameters, i.e., $6K1f{6}_{L(p,h_1)\to L(p,h_2)}$. Finally, similar estimates in the weighted Lorentz spaces are presented. To cite this article: E. Nursultanov et al., C. R. Acad. Sci. Paris, Ser. I 347 (2009).     

Inside Cover: Synthesis and Biological Activity of Argiotoxin 636 and Analogues: Selective Antagonists for Ionotropic Glutamate Receptors (Angew. Chem. Int. Ed. 17/2009)

Spiders of the genus Argiope , such as Argiope lobata, contain polyamine toxins that are potent but nonselective blockers of glutamate receptors. However, by very subtle modifications of the structure of native toxins, it is possible to obtain selectivity for subtypes of these receptors, as described by K. Strømgaard and co‐workers in their Communication on page 3087 ff.

     

Resonance structure of the beta-strength function

The beta-decay strength function S _β(E) is described within two approaches: numerical solution of equation of the theory of finite Fermi systems for the effective nuclear field and solution of these equations using the quasi-classical approximation. Calculations were carried out for the isotopes ⁷¹Ge and ¹²⁷Xe. A comparison with experimental data showed their good accuracy. The resonance structure of the function S _β(E) and the quenching-effect resulting from the effective charge of quasiparticles in the nucleus are discussed.     

The Role of Bile Acids in the Human Body and in the Development of Diseases

Bile acids are specific and quantitatively important organic components of bile, which are synthesized by hepatocytes from cholesterol and are involved in the osmotic process that ensures the outflow of bile. Bile acids include many varieties of amphipathic acid steroids. These are molecules that play a major role in the digestion of fats and the intestinal absorption of hydrophobic compounds and are also involved in the regulation of many functions of the liver, cholangiocytes, and extrahepatic tissues, acting essentially as hormones. The biological effects are realized through variable membrane or nuclear receptors. Hepatic synthesis, intestinal modifications, intestinal peristalsis and permeability, and receptor activity can affect the quantitative and qualitative bile acids composition significantly leading to extrahepatic pathologies. The complexity of bile acids receptors and the effects of cross-activations makes interpretation of the results of the studies rather difficult. In spite, this is a very perspective direction for pharmacology.