On the higher-order strong isochronism of Cauchy-Riemann systems with homogeneous polynomial perturbations of a linear center

We indicate the maximum order of the general and partial (with an initial polar angle) strong higher-order isochronism of Cauchy-Riemann systems with homogeneous polynomial perturbations of a linear center.     

Structure, thermal, and infrared analyses of [NH3(CH2)3NH3]2[Ni(HP2O7)2(H2O)2] ? 4H2O

[NH₃(CH₂)₃NH₃]₂[Ni(HP₂O₇)₂(H₂O)₂] 4H₂O (NiDAP) is a new diphosphate of transition metallic and organic cations obtained from a mixture of H₄P₂O₇, 2NiCO₃ Ni(OH)₂ 4H₂O and NH₂(CH₂)₃NH₂ in a 1:1/6:1 molar ratio. This mixed organo-mineral compound crystallizes in the triclinic system, P¯, with the unit cell dimensions: a = 7.3678(3)~Å, b = 7.8018(5)Å, c = 11.1958(7)Å, = 76.914(4), = 81.052(4), = 85.46(1), V = 618.57(6)ų and Z = 1. The crystal structure of NiDAP consists of a complex anion, [Ni(HP₂O₇)₂(H₂O)₂]^4– and a diammoniumpropane cation. The complex anion is built up from two neutral water molecules (OW1) and two diphosphosphoric anions coordinated to Ni(II) in a bidentate chelating manner. (OW1) molecules link anionic complexes, [Ni(HP₂O₇)₂(H₂O)₂]^4– to create a thick bidimensional layers parallel to the (a, b) plane. These layers are interconnected in three dimensions through hydrogen bonds established between organic cations, the remaining water molecules OW2, OW3, and some external oxygen atoms of the anionic complex arrays. NiDAP was also characterized by IR spectroscopy, TG-DTA, and DSC analyses.     

An inverse gas chromatographic characterization of polypyrrole-coated poly(vinyl chloride) powder particles

Polypyrrole-coated poly(vinyl chloride) powder particles (PPy-PVC) were prepared by the in-situ chemical polymerization of pyrrole in aqueous solutions in the presence of PVC powder particles using the method of Ouyang and Chan [Polymer 39 (1998) 1857] and characterized by inverse gas chromatography (IGC). By employing n-alkane, 1-heptene, chloroform and tetrahydrofuran molecular probes, the dispersive and acid–base components of the surface energy of the composite materials were estimated at infinite dilution. The values of the dispersive contribution to the surface energy (γ_S^d), at 50 °C, range from 30.3 to 43.5 mJ/m² for the composites, which is much lower than the value of 83.2 mJ/m² obtained for para-toluene sulfonate-doped polypyrrole (PPyTS) bulk powder. This indicates that the injected molecules probe both polypyrrole and the underlying PVC, thus indicating that the conducting polymer is rather patchy at the surface of the insulating polymer substrate. This conclusion supports the previous results obtained by X-ray photoelectron spectroscopy (XPS) [19], indicating that both the coating PPyTS and the substrate PVC are detected by their elemental markers nitrogen and sulfur, and chlorine, respectively.     

New materials derivatives of tetrathiapentalene functionalized by amide groups: Synthesis,characterization, and electrical study

A new series of bis-fused tetrathiafulvalene containing functional groups was synthesized. The synthesis was carried out by using routes involving cross coupling, reduction, and oxidation reactions. The identity of these new donors is confirmed by ¹ Wudl, F.; Smith, G. M.; Hufnagel, E. J. J. Chem. Soc. Chem. Commun. 1970, 21, 1453-1454.[Crossref] , [Google Scholar] H NMR spectroscopy, mass spectrometry, and elemental analysis. We have used the cyclic voltammetry in order to determine the character π-donors of these molecules and to verify the reversibility of the redox process involved. Molecular orbital diagram has been calculated using density-functional calculations. Charge transfer complexes with tetracyanoquinodimethane (TNQ) were prepared by chemical redox reactions.     

Recovering boundary data: The Cauchy Stokes system

This paper is concerned with the severely ill-posed Cauchy–Stokes problem. We are interested in a data completion problem which is exploited to detect small leaks to control water loss Kim et al. (2008) [1]. This inverse problem is rephrased into an optimization one: An energy-like error functional is introduced. We prove that the optimality condition of the first order is equivalent to solving an interfacial equation which turns out to be a Cauchy-Steklov-Poincaré operator. Numerical trials highlight the efficiency of the method.     

Efficient Synthesis of Chiral 1,1′‐Sulfonyl Bisaziridines

An efficient three‐step synthesis of chiral 1,1′‐(sulfonyl)bisaziridines is described. Preparation of these compounds was carried out easily starting from N,N′‐sulfonyl bis‐(α‐L‐aminoester) to afford the title compounds in very good yields. These 1,1′‐(sulfonyl)bisaziridines can constitute interesting synthetic building blocks.     

Erratum to “Separation of representations with quadratic overgroups” [Bull. Sci. Math. 135 (2) (2011) 141–165]

In the paper entitled “Separation of representations with quadratic overgroups”, we defined the notion of quadratic overgroups, and announced that the 6-dimensional nilpotent Lie algebra g6,20 admits such a quadratic overgroup. There is a mistake in the proof. The present Erratum explains that the proposed overgroup is only weakly quadratic, and g6,20 does not admit any natural quadratic overgroup.     

Self‐inclusion in 5,11,17,23‐tetra‐tert‐butyl‐26,27,28‐tri­hydroxy­‐25‐(methoxy­carbonyl­methoxy)calix­[4]­arene chloro­form trisolvate

The title compound, C₄₇H₆₀O₆·3CHCl₃, is the first example of a lower‐rim mono‐ester calixarene derivative to be crystallographically characterized. The cone conformation adopted by the macrocycle is stabilized by three intramolecular hydrogen bonds. Self‐inclusion of the methyl ester chain in the cavity of an adjacent mol­ecule gives rise to infinite chains parallel to the c axis. C—H⋯π interactions involving the methyl group most imbedded in the cavity contribute to the stabilization of the system.     

Effect of current density on the microstructure and morphology of the electrodeposited nickel coatings

The aim of this research work was to study the effect of deposition current density on microstructure and surface morphology of electrodeposited nickel coatings. For this purpose, nickel deposits have been synthesized by direct current from Watts bath without additive, to limit the incorporation of pollutants resulting from surface adsorption or electro-activity of these compounds. Nickel deposits have been investigated by scanning electron microscopy and X-ray diffraction. Cyclic voltammetry was also used to gain information on the general behavior of the deposition. The optimum conditions of deposition were established and the influence of current density on the grain size, surface morphology, and crystal orientation was determined.