Intramolecular construction of trifluoromethyl group by the palladium-catalyzed reaction of 2,3,3-trifluoroallylic carbonates with O-nucleophiles

The synthesis of the trifluoromethyl group containing enol ethers by the palladium-catalyzed intermolecular reaction of 2,3,3-trifluoroallylic carbonates with oxygen nucleophiles was accomplished. The reaction proceeds through the intermolecular attack of oxygen nucleophiles on the C-2 carbon atom of the allylic unit, and the intramolecular fluorine atom shift from the C-2 position to the C-3 position. The reactions with several types of alcohols and phenols proceeded smoothly, and afforded the corresponding trifluoromethyl group containing enol ethers in good to high yields.     

Comparative Study of Reversed-Phase High-Performance Liquid Chromatography and Ultraviolet–Visible Spectrophotometry to Determine Doxorubicin in pH-Sensitive Nanoparticles

Analytical methods by reversed-phase high-performance liquid chromatography (HPLC) and ultraviolet–visible spectrophotometry were developed and validated to determine doxorubicin in pH-sensitive chitosan nanoparticles. Chromatographic separation was performed on a reversed-phase C₁₈ column, with ultraviolet detection at 254?nm and a mobile phase composed by 90% (v/v) acetonitrile in water and water pH 3.0 (33:67, v/v). The spectrophotometry method had the wavelength set at 480?nm and pH 3.0 water was used as a diluent. Calibration curves were linear from 1 to 30?µg/?mL (r?>?0.9995) and the specificity was demonstrated by verifying the absence of interferences from nanoparticle components. The values of accuracy and precision were within the acceptable limits, and robustness studies were performed by a two-level full factorial design. The validated methods were further tested to assess doxorubicin content in six different batches of pH-sensitive chitosan nanoparticles. The comparative analyses showed nonsignificant differences (p?>?0.05). Likewise, the HPLC method was successfully applied to determine the drug encapsulation efficiency as well as to measure doxorubicin during in vitro release assays and degradation kinetic studies under ultraviolet light C irradiation. Both methods fulfilled all validation parameters and were shown to be suitable for the characterization of doxorubicin-loaded pH-sensitive chitosan nanoparticles, without interferences from nanoparticle matrix.     

Synthesis,characterization, and catalytic activity of FeTiO3/TiO2 for photodegradation of organic pollutants with visible light

Research on Chemical Intermediates - High-purity ilmenite, FeTiO3, was prepared by the sol–gel method and calcination under nitrogen atmosphere. Several FeTiO3/TiO2 catalysts were prepared by...     

Stability of marriage with externalities

In many matching problems, it is natural to consider that agents may have preferences not only over the set of potential partners but also over what other matches occur. Once such externalities are considered, the set of stable matchings will depend on what agents believe will happen if they deviate. In this paper, we introduce endogenously generated beliefs (which depend on the preferences). We introduce a particular notion of endogenous beliefs, called sophisticated expectations, and show that with these beliefs, stable matchings always exist. I would like to thank the editor, William Thomson, two anonymous referees, Kalyan Chatterjee, Federico Echenique, Matthew Jackson, Tarık Kara, Semih Koray, and Manabu Toda for their comments and suggestions. I am very much indebted to Vijay Krishna for his guidance and support.     

Thermodynamics of Ketone + Amine Mixtures Part V. Volumetric and Speed of Sound Data at (293.15, 298.15 and 303.15) K for Mixtures of 2-Heptanone with Aniline, <Emphasis Type="Italic">N</Emphasis>-Methylaniline or Pyridine

Densities, ρ, and speeds of sound, u, of 2-heptanone + aniline + N-methylaniline or + pyridine systems have been measured at (293.15, 298.15 and 303.15) K and atmospheric pressure using a vibrating tube densimeter and sound analyzer. The ρ and u values were used to calculate excess molar volumes, V ^E, and the excess functions at 298.15 K for the speed of sound, u ^E, the thermal expansion coefficient, a_p^E\alpha_{p}^{\mathrm{E}}, and for the isentropic compressibility, k_S^E\kappa_{\mathrm{S}}^{\mathrm{E}}. V ^E and k_S^E\kappa_{\mathrm{S}}^{\mathrm{E}} are both negative and increase in the sequence: aniline <N-methylaniline < pyridine. In contrast, u ^E is positive and changes in the opposite way. The data suggest the existence of interactions between unlike molecules, which are much weaker in the pyridine solution. Aromatic amine–alkanone interactions are stronger in mixtures with acetone. The linear dependence of Rao’s constant with concentration reveals that there is no complex formation in the investigated systems.     

Electrically induced lipid migration in non-lamellar phase

Inverted hexagonal blocks of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) lipid adsorbed on a polyethyleneimine (PEI)-coated surface in deionized water transformed its shape upon the application of an electric field, forming lipid objects in a variety of shapes (e.g. lines with a width of 10-50μm). The phenomenon was driven by the electrophoresis, because the zwitterionic lipid, DOPE turned out to be highly negatively charged in deionized water. The interaction between DOPE and the PEI surface stabilized the system, assuring a lifetime over several weeks for the formed structures after the electric field was switched off. The free-drawing of microscopic objects (lines, crosses, and jelly fish) was also achieved by controlling the direction of the lipid movement with the field direction.     

Remarks on hierarchic control for the wave equation in moving domains

We study a Stackelberg strategy subject to the evolutionary linearized Kirchhoff equation for small vibrations of a stretched elastic string when the ends are variables. We assume that we can act in the dynamic of the system by a hierarchy of controls. According to the formulation given by H. von Stackelberg (see [3]), there are local controls, called followers, and global controls, called leaders. In fact, one considers situations where there are two cost (objective) functions. One possible way is to cut the control into two parts, one being thought of as “the leader” and the other one as “the follower”. This situation is studied in the paper, with one of the cost functions being of the controllability type. Existence and uniqueness is proven. The optimality system is given in the paper.     

Convergence theorems for common fixed points of asymptotically quasi-nonexpansive mappings in convex metric spaces

In this paper, we consider an implicit iteration process to approximate the common fixed points of two finite families of asymptotically quasi-nonexpansive mappings in convex metric spaces. As a consequence of our result, we obtain some related convergence theorems. Our results generalize some recent results of Khan and Ahmed [4], Khan et al. [6], Sun [12], Wittmann [14] and Xu and Ori [15].     

Effect of introducing thioether linkages on the molecular organization of chiral twin liquid crystals

Novel symmetric and non-symmetric chiral twin compounds possessing one or two thioether groups in a central spacer were prepared, and the effect of substituting oxygen for sulphur on the liquid crystalline properties investigated. Chiral twin compounds possessing an alkylsulphanyl spacer showed an antiferroelectric phase exclusively. However, replacing the alkyloxy chain of the analogous monomer by the alkylsulphanyl chain has no significant effect on the phase transition behaviour, i.e. both of the monomers showed the ferro- and ferri-electric phases as well as the antiferroelectric phase. Thus, different effects of introducing the thioether linkage were for the first time observed between twin and monomeric systems. The introduction of oxygen or sulphur atoms into the central alkyl spacer of the chiral twin was also investigated, and these modifications were found to stabilize the SmA phase. Furthermore, the twin compound possessing a thiaalkyl spacer showed two different molecular assemblies in the smectic A phase.     

Kinetics and Equilibria of Synthesized Anionic Surfactant onto Berea Sandstone

We present static adsorption studies of anionic surfactants on crushed Berea sandstone. The maximum adsorption density was 0.9604 mg/g. The kinetics of adsorption process was modeled using pseudo-first-order and pseudo-second-order rate equations at 25°C and 70°C. The equilibrium adsorption process was validated using Langmuir and Freundlich adsorption models. In addition, the effects of different parameters that govern the effectiveness of these surfactants such as pH and temperature were also investigated. The kinetic study results show that the surfactant adsorption is a time dependent process. The apparent rate constant of adsorption process determined by the first-order kinetic model at 25°C and 70°C were 0.11768 and ?0.04513, respectively. The rate constant for pseudo-second-order kinetic model was 0.0086 at 25°C and 0.0101 at 70°C. The adsorption of anionic surfactant followed pseudo-second-order kinetic model. The Freundlich and Langmuir model constant were 1.6509 × 10^?4 and ?9.775 × 10^?5, respectively. The equilibrium results showed that the adsorption of anionic surfactant onto Berea sandstone was well described by Langmuir adsorption model. It was concluded that anionic surfactants performed better at higher pH and temperature.