Stabilité analytique et convergence locale de translatées en dynamique homogène S-arithmétique

We present the main result of Richard and Zamojski [14] concerning, in homogeneous dynamics, the general problem of the dynamics of sequences of translates of a certain measure in a space of S-arithmetic lattices.     

Embedding Banach spaces into the space of bounded functions with countable support

We prove that a WLD subspace of the space consisting of all bounded, countably supported functions on a set Γ embeds isomorphically into if and only if it does not contain isometric copies of . Moreover, a subspace of is constructed that has an unconditional basis, does not embed into , and whose every weakly compact subset is separable (in particular, it cannot contain any isomorphic copies of ).     

Fractional electrical model for modified bismuth oxide

Modified bismuth oxide (Bi₂O₃) is of great importance to fuel cells and oxide varistors. The electrical parameters of Bi₂O₃ vary with its modifying components as well as with its aging temperature. This paper presents an analysis of impedance test results carried out to find an equivalent electric model and the relationship between the model's elements to various additives used to modify Bi₂O₃ and to changes in aging temperature. The proposed model was tested via computer simulation and the model parameters correlated to individual modifiers.     

Conformational Properties of the Phosphate Rings of Neutral Phosphoramidate Derivatives of Ribo- and 2′-Deoxyribonucleoside Cyclic 3′,5′-Monophosphates

Abstract

An investigation of the effects of changing the nature of X, nitrogen base (B), and amino substituent (R₂N) on the equilibrium 1?2 was carried out.

The influence of the above structural changes on the time-averaged coupling constants J_AP and J_BP, determined at 300 MHz, were used to follow changes in K_eq. With constant R₂N, small effects from variation of X and B were found. A large range in K_eq arose from changes in the steric size of R₂N. These results will be related to the question of the ease of chair to twist interconversion of the phosphate ring essential to the biological activities of the naturally occurring diesters, cAMP and cGMP.     

Aminophosphinic Acids in a Pyridine Series: Cleavage of Pyridine-2- and Pyridine-4-methyl(amino)phosphinic Acids in Acidic Solutions

The synthesis of a series of new pyridine aminomethylphosphinic acids is described. These compounds were obtained in the reaction of the corresponding pyridine aldehydes with primary amines and with ethyl phenylphosphinate, or methylphosphinate, in the presence of bromotrimethylsilane. In aqueous, strong acid solutions, pyridine aminophosphinic acids were split, forming the phenyl-, or methylphosphonic, acid and the corresponding secondary pyridyl-alkylamines. The kinetics of some observed cleavages were measured, and a mechanism of the cleavage has been proposed.     

Comparative studies of Pd, Ru, Ni, Cu/ZnAl2O4 catalysts for the water gas shift reaction

The activity of monometallic Pd, Ru, Ni and Cu catalysts supported on spinel ZnAl₂O₄ for water gas shift reaction (WGS) was investigated. The physicochemical properties of each catalyst was studied by XRD, TPR, BET and chemisorption methods. The highest activity was obtained for Cu/ZnAl₂O₄ among the catalysts tested. The activation process carried out in a reducing atmosphere 5%H₂-95%Ar in the case of Cu/ZnAl₂O₄ system lead to the catalytic activity improvement. In the case of copper catalysts, the water gas shift reaction proceeded by the redox surface mechanism between Cu⁰/Cu⁺. The PdZn alloy formation after reduction at 350°C was shown.      

A Simple Synthesis of 2-Phenylethynyl- and 2-Phenylthioethynyl-2-substituted Phenylacetonitriles Under Phase-Transfer Catalytic (PTC) Conditions

The efficient synthesis of 2-phenylethynyl- or 2-phenylthioethynyl-2-substituted phenylacetonitriles 4 and 5 from nitriles 3 and substituted dichloroethenes 1 or 2, respectively, in the presence of 50% aqueous sodium hydroxide and tetrabutylammonium hydrogen sulphate (TBAHS) as a catalyst (phase-transfer catalysis, PTC), has been accomplished.     

Synthesis and structure determination of 2,3-diaryl-9,9-dioxo-1H-9-thia-1,4,4a,7,10-pentaazaphenanthrene-2-ols

3-Amino-1,1-dioxopyrido[4,3-e]-1,4,2-dithiazine has been synthesized and applied to the synthesis of 3-amino-2-(4-thioxo-1,4-dihydropyridin-3-ylsulfonyl)guanidine. The reaction of the aminoguanidine with the appropriate 1,2-diarylethane-1,2-diones afforded 2,3-diaryl-9,9-dioxo-1H-9-thia-1,4,4a,7,10-pentaazaphenanthrene-2-ol derivatives. The structure of these compounds, which represent a novel heterocyclic ring system, was confirmed on the basis of elemental analysis and spectroscopic data including COSY, NOESY, ROESY, HSQC, and HMBC.     

Convenient synthesis of epimeric indolizidines by the intramolecular 1,3-dipolar cycloaddition of a sugar derived N-(3-alkenyl)nitrone

The stereoselective synthesis of two epimeric penta-hydroxylated indolizidines was accomplished from 2,3:5,6-di-O-isopropylidene-α-d-mannofuranose and N-(2-methylpent-4-en-2-yl)hydroxylamine. The transformation of these substrates into the corresponding 7-oxa-1-azabicyclo[2.2.1]heptane by the intramolecular 1,3-dipolar cycloaddition was the key step of the synthesis. The adduct was transformed into the tricyclic ammonium salt by intramolecular N-alkylation. The tricyclic ammonium salt was converted to the target compounds by: (route 1) the catalytic hydrogenation; or (route 2) the reaction with sodium azide, followed by the enantioselective reduction of the resulting indolizidinone.     

Molecular organization in two-dimensional films of liquid II. Langmuir and Langmuir-Blodgett films of a perylene-like dye mixed with liquid crystals having a terminal cyano group crystalline mixtures

Langmuir and Langmuir-Blodgett (LB) films of a perylene-like compound and its binary mixtures with 4-octyl-4'-cyanobiphenyl (8CB) and 4-pentyl-4"-cyano-p-terphenyl (5CT) have been studied. On the basis of the surface pressure-area isotherms, the molecular organization on the air-water interface has been estimated. Information about the miscibility or the phase separation of components in the binary mixtures has been obtained. The spectroscopic study of the LB films has allowed conclusions to be drawn about the arrangement of the molecules on the quartz slides. The fluorescence spectra of the LB films of the perylene-like compound have revealed the formation of self-aggregates.