Two‐Step Synthesis of Multifunctional γ‐Lactams from γ‐Lactone

We present herein an efficient and rapid method for the synthesis of N,1‐dialkyl‐4‐(2‐hydroxyethyl)‐5‐oxopyrrolidine‐3‐carboxamides based on the conversion of γ‐lactone to γ‐lactam via the conjugate addition of primary amines to an ethyl α‐functionalized acrylate followed by intramolecular cyclization.     

Convergence and decay estimates for a class of second order dissipative equations involving a non-negative potential energy

We estimate the rate of decay of the difference between a solution and its limiting equilibrium for the following abstract second order problem

     

On a Ginzburg-Landau Type Energy with Discontinuous Constraint for High Values of Applied Field

In the presence of applied magnetic fields H such that |lnε| 《H 《1/ε2,the author evaluates the minimal Ginzburg-Landau energy with discontinuous constraint.Its expression is analogous to the work of Sandier and Serfaty.     

Anisotropic self-assembling micelles prepared by the direct dissolution of PLA/PEG block copolymers with a high PEG fraction

A series of polylactide-poly(ethylene glycol) (PLA-PEG) block copolymers with a high PEG fraction were synthesized by the ring-opening polymerization of L- or D-lactide in the presence of mono- or dihydroxyl PEG using nontoxic zinc lactate as a catalyst. Micelles were then prepared by direct dissolution of the obtained water-soluble copolymers in an aqueous medium without heating or using any organic solvents. Large anisotropic micelles instead of conventional spherical ones were observed from a transmission electron microscopy examination. Various parameters influencing the structure of the novel micelles were considered, such as the copolymer chain structure, molar mass, PEG fraction, copolymer concentration, and stereocomplexation between L- and D-PLA blocks. Anisotropic micelles were obtained for both diblock and triblock copolymers but vanished with increasing molar mass of the copolymers. The morphology of micelles strongly depends on the PEG fraction. Anisotropic micelles were found only in an intermediate EO/LA ratio range in which a higher PEG fraction leads to a higher length/width ratio of micelles. Stereocomplexation between L- and D-PLA or a lower concentration disfavors the formation of anisotropic micelles. Under appropriate concentrations, spherical and anisotropic micelles coexist in the same micellar solution. Moreover, it was found that anisotropic micelles are susceptible to further self-assemble into more organized complex aggregates. Similar results were obtained from light scattering and aqueous gel permeation chromatography measurements. A novel model is proposed to explain the formation of anisotropic micelles and the effects of various parameters on the structure of micelles in an aqueous medium.     

Dielectric measurements,X-ray diffraction and raman studies of mixed caesium-ammonium mercury chloride: Cs0.7(NH4)0.3HgCl3

Measurements of the dielectric constants have revealed a transition at T=449K in Cs_0.7(NH₄)_0.3HgCl₃. This transition was confirmed by X-ray diffraction and Raman scattering on polycrystalline samples. The room-temperature phase is ordered and exhibits trigonal symmetry (space group P3₂ with the unit cell dimensions a = 13.295(11) Å; c = 9.419(8) Å). Transport properties in this material appear to be due to the high mobility of NH⁺ ₄ andCs⁺.     

Development and validation of a turbidimetry method for hydrogen sulphide evaluation in effluents of phosphoric acid production unit

The aim of this study was to develop and validate a simple, new and efficient method for the analysis of hydrogen sulphide (H₂S) released from the effluents of phosphoric acid production units. H₂S sampling was performed by absorption of the industrial gas into a cadmium acetate absorbing solution. The formed cadmium sulphide (CdS), as a result of a chemical reaction, was analysed by turbidimetry. A methodical validation study of the proposed method was performed according to the requirements of ISO 17025 standards. The proposed method was demonstrated to be precise, linear and accurate over a concentration range of 6.91–92.16 mg/l. Detection and quantification limits were equal to 5.09 mg/l and 6.91 mg/l, respectively. Sample analysis had to be performed within 48 h of the sampling step. The turbidimetry method was applied successfully to the industrial gaseous effluents and can be considered as an economical alternative to the iodometric method.     

Dynamical analysis and anti-oscillation-based adaptive control of the FO arch MEMS with optimality

Nonlinear Dynamics - This paper mainly investigates dynamical analysis and anti-oscillation-based adaptive control issues of the fractional-order (FO) arch microelectromechanical system (MEMS) with...     

Synthesis,characterization and in-vitro antitumour activity of dibutyltin carboxylates involving the perfluorophenyl moiety: Crystal structure of the dimeric bis[(4-fluoro- and pentafluoro-benzoato)di-n-butyltin] oxides

Crystal structure determinations of {[(F₅C₆COO)Bu₂Sn]₂O}₂ and {[(4-F-C₆H₄COO)-Bu₂Sn]₂O}₂ show that the structures are similar and feature central Bu₄Sn₂O₂ units with two Bu₂Sn groups connected by bridging oxygen atoms. Each pair of exo- and endo-cyclic tin atoms is linked by an almost symmetrically bridging carboxylate group, with the two remaining groups attached to the exocyclic tin atom only. Crystals of {[(F₅C₆COO)Bu₂Sn]₂O}₂ are triclinic, space group P1, with unit cell dimensions a = 12.425(3) Å, b = 13.090(5) Å, c = 11.697(3) Å, α = 95.31(3)°, β = 93.28(2)°, γ = 113.01(2)°, V = 1734(1) ų, Z = 1. Crystals of {[(4-F-C₆H₄COO)Bu₂Sn]₂O}₂, are also triclinic, space group PI, a = 12.599(6) Å, b= 25.359(4) Å, c = 11.480(4) Å, α = 91.44(3)°, β = 114.77(3)°, γ=97.43(3)°, V=3289(2) ų, Z=2. The structures were refined to final R= 0.046, R_w = 0.046 for 4312 reflections with I≥ 3.0 σ(l) for {[(F₅C₆COO)Bu₂Sn]₂O}₂ and R=0.061, R_w=0.068 for 4112 reflections with l≥3.0 σ(l for {[(4-F-C₆H₄COO)Bu₂Sn]₂O}₂.