Thermal study and evaluation of new menthol-based ionic liquids as polymeric additives

Thermal properties of new ionic liquids (ILs) were investigated by thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC). Chlorides, tetrafluoroborates and hexafluorophosphates of (−)mentholpyrrolidinium and (−)-mentholimidazolium cations revealed good thermal stability at air atmosphere. Morphological characteristics of poly(methyl methacrylate) (PMMA) matrices doped with 10% of these ILs were also investigated by DRX and water absorption test. Into the matrix, they exhibited a very satisfactory pattern concerning the polymer thermal stabilization. DSC results show that some of these ILs also present plasticizer features since they can lower the polymer glass transition temperature (T _g) up to 317.15 K.     

Synthesis, structures, and magnetic properties of tetranuclear CuII-LnIII complexes

The copper(II)-gadolinium(III) and copper(II)-terbium(III) complexes studied in this report derive from disymmetric trianionic ligands abbreviated H3Li (i = 4-6). These ligands are obtained through reaction of different aldehydes with "half-units" having an amide function, the latter resulting from the monocondensation of different diamines with phenyl 2-hydroxy-3-methoxybenzoate. Upon deprotonation, the Li ligands (i = 4-10) possess an inner N2O2 coordination site with one amido, one imine, and two phenoxo functions, an outer O2O2 or O2O coordination site, and an amido oxygen atom positioned out of these two sites. The trianionic character of such ligands yields original anionic complexes in the presence of copper(II) or nickel(II) ions, with a 1/1 L/M stoichiometry. The crystal and molecular structures of four complexes, two 3d (1, 5) and two 3d-4f (12, 13) complexes, have been determined. Complex 1 crystallizes in the monoclinic space group C2/c: a = 27.528(2) A, b = 7.0944(7) A, c = 22.914(2) A, beta = 92.130(6) degrees , V = 4471.9(7) A(3), Z = 8 for C(21.5)H(27)CuKN(2)O(6.5). Complex 5 crystallizes in the monoclinic space group P2(1)/n (No. 14): a = 11.0760(9) A, b = 21.454(2) A, c = 15.336(1) A, beta = 101.474(1) degrees , V = 3571.5(5) A(3), Z = 4. Complex 12 crystallizes in the triclinic space group P (No. 2): a = 8.682(2) A, b = 11.848(2) A, c = 11.928(2) A, alpha = 81.77(3) degrees , beta = 89.17(3) degrees , gamma = 85.49(3) degrees , V = 1210.6(4) A(3), Z = 2 for C20H22CuN5O11Tb. Complex 13 belongs to the monoclinic space group C2/c: a = 25.475(5)A, b = 12.934(3)A, c = 15.023(3) A, beta = 91.06(3) degrees , V = 4949.02A3, Z = 8 for C21H25CuN4O12Tb. The structural determinations confirm that the dinuclear entities involved in 12 and 13 are disposed in a head-to-tail arrangement to give tetranuclear complexes in which the copper and lanthanide ions are positioned at the vertexes of a rectangle. In the [Cu-Gd]2 species, there are two different ferromagnetic Cu-Gd interactions. The stronger one is supported by the double phenoxo bridge (CuO2Gd) while the weaker one corresponds to the single amido bridge (Cu-N-C-O-Gd). Replacement of gadolinium ions with anisotropic terbium ions yields tetranuclear entities showing slow relaxation of magnetization and magnetization hysteresis. Detailed relaxation and hysteresis loop studies establish single-molecule magnet (SMM) behavior which is influenced by weak intermolecular interactions.     

Almost periodic models in impulsive ecological systems with variable diffusion

By means of piecewise continuous functions Lyapunov’s functions we give new sufficient conditions for the global exponential stability of the unique positive almost periodic solutions of an non autonomous N-dimensional impulsive Lotka-Volterra diffusive competitive system with dispersion and fixed moments of impulsive perturbations.     

The application of 2-D dual nanoscale liquid chromatography and triple quadrupole-linear ion trap system for the identification of proteins

2-D nanoscale LC combined with a triple quadrupole-linear ion trap mass spectrometer was applied to the analysis of a complex peptide mixture. A 2-D dual nanoscale LC-MS/MS system was compared to a conventional one. Peptides were separated with a strong cation exchange (SCX) microcolumn in the first dimension and two C18 nanocolumns were used as second dimension. MS experiments were performed using information-dependent data acquisition, where two precursor ions were selected from an enhanced MS (EMS) or an enhanced multicharged ion (EMC) as survey scan. The major benefit of EMC instead of EMS was a two-fold reduction of the data file and a 15% increase of characterized proteins. The advantage of the 2-D dual nanoscale LC-MS/MS system versus the conventional 2-D nanoscale LC-MS/MS system was reflected in the significant increase of peptides which were successfully identified within the same time frame. The first factor contributing to this increase was that the mass spectrometer was collecting twice the number of relevant MS/MS data. The second factor is the use of twice the number of SCX salt fractions in the first dimension, allowing a better sample fractionation, thereby reducing the number of peptides transferred to the second chromatographic dimension per salt fraction.     

Etude du mecanisme de l'hydrolyse alcaline des N-methyl acetanilides au moyen des effets de milieu

N-methyl acetanilides alkaline hydrolysis mechanism has been studied by means of solvent effect (DMSO and ²H₂O) and of structure-reactivity correlation (log k_obs = f(pK_{B aniline})). Our results are consistent with HO^? rate determining attack only for p-nitro anilide and with a rate determining water assisted decomposition of the tetrahedral intermediate for X  p-CH₃O, H, p-Cl, m-Cl.     

Babassu Nanoemulsions Have Physical and Chemical Stability

Babassu is considered one of the greatest native resources in the world and its oil is used in body and hair formulations. The aim of this study was to evaluate the short-term stability in oil-in-water (O/W) nanoemulsions containing babassu oil prepared by emulsification phase inversion submitted to the centrifugation, thermal stress, and heating/cooling cycle tests. The formulations showed no change compared to the droplet size, polydispersity index, pH, and electrical conductivity values after thermal stress and heating/cooling cycle tests. Based on these results, the nanoemulsions obtained can be considered as promising disperse systems for pharmaceutical and cosmetic applications.     

Lyapunov–Razumikhin method for impulsive functional differential equations and applications to the population dynamics

The present paper deals with the investigation of the stability of the zero solution of impulsive functional differential equations. By means of piecewise continuous functions coupled with the Razumikhin technique sufficient conditions for stability, uniform stability and asymptotic stability of the zero solution of such equations are found.     

Radiative quantum efficiency of CdSe/ZnS quantum dots suspended in different solvents

The radiative quantum efficiencies η of the CdSe/ZnS core-shell nanoparticles embedded into polymethyl methacrylate (PMMA) and suspended in three different solvents: chloroform (CHCl₃), toluene (C₆H₅CH₃) and tetrahydrofuran (C₄H₈O) were measured using thermal lens (TL) technique. The mode-mismatched pump-probe TL measurements were accomplished in function of the CdSe/ZnS quantum-dot concentration (12-60 mg/ml) at λ_e = 594 nm (pump) and λ_p = 632.8 nm (probe). The values obtained for η were higher for CdSe/ZnS nanoparticles suspended in tetrahydrofuran and chloroform, as compared to the values for toluene. Thermal diffusivity (D) and the absolute nonradiative quantum efficiency (φ) were determined.     

Determination of composition of ethylene–propylene copolymers by intrinsic viscosity

Intrinsic viscosities have been measured at 25° on five ethylene–propylene copolymer samples ranging in composition from 33 to 75 mole-% ethylene. The solvents used were n-C₈ and n-C₁₆ linear alkanes and two branched alkanes, 2,2,4-trimethylpentane and 2,2,4,4,6,8,8-heptamethylnonane (br-C₁₆). This choice was based on the supposition that the branched solvent would prefer the propylene segments and the linear solvent the ethylene segments, due to similarity in shape and possibly in orientational order. It was found that [η]_n ? [η]_br ≡ Δ[η] is indeed negative for propylene-rich copolymers, zero for a 56% ethylene copolymer, and positive for ethylene-rich copolymers. The Stockmayer–Fixman relation was used to obtain from Δ[η] a molecular-weight independent function of composition. The quantities (Δ[η]/[η])(1 + aM^?1/2) and Δ[η]/M are linear with the mole percent ethylene in the range investigated with 200 ≤ a ≤ 2000. The possibility of using these results for composition determination in ethylene–propylene copolymers is discussed. Intrinsic viscosities in the same solvents are reported for two samples of a terpolymer with ethylidene norbornene.     

Existence of almost periodic solutions for strong stable impulsive differential equations

Conditions for strong stability and the existence of almostperiodic solutions of systems of impulsive differential equationswith impulsive effect at fixed moments are obtained. The investigationsare carried out by means of piecewise continuous functions whichare analogues of Lyapunov functions.