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921.
Rui P.M.F. BonifácioEduardo J.M. Filipe M. Carolina dos Ramos Felipe J. BlasLuís F.G. Martins 《Fluid Phase Equilibria》2011,303(2):193-200
The solubility of xenon in liquid cyclopentane has been studied experimentally and theoretically. Measurements of the solubility of xenon in liquid cyclopentane are reported as a function of temperature from 254.60 K to 313.66 K. The imprecision of the experimental data is less than 0.3%. The thermodynamic functions of solvation of xenon in cyclopentane, such as the standard Gibbs energy, enthalpy, entropy and heat capacity of solvation, have been calculated from the temperature dependence of Henry's law coefficients. The results provide further information about the differences between the xenon + cycloalkanes and the xenon + n-alkane interactions. In particular, interaction enthalpies between xenon and CH2 groups in n-alkanes and cycloalkanes have been estimated and compared. Using a version of the soft-SAFT approach developed to model cyclic molecules, we were able to reproduce the experimental solubility for xenon in cyclopentane using simple Lorentz-Berthelot rules to describe the unlike interaction. 相似文献
922.
Raquel Fernández Iñaki Zalakain José Angel Ramos Loli Martin Iñaki Mondragon 《European Polymer Journal》2011,(5):1176-1185
The main goal of this work was the synthesis of new azo-functionalized block copolymers (BCP) from epoxidized poly(styrene-b-butadiene-b-styrene) modified with azobenzene groups by one-step facile reaction between the epoxy groups and an azo-amine. The epoxy/amine reaction was verified by Fourier transform infrared spectroscopy. Additionally, we studied the effect of covalent attachment of the azobenzene moieties by analyzing the morphology and the optical anisotropic response of the resulting azo-containing BCP, with respect to solution mixing of the azobenzene as a guest in the BCP host without chemical bonding. Self-assembly of all modified BCP resulted in phase-separated morphologies on the nanometer scale. Nonetheless, segregation of azobenzene aggregates onto the BCP surface was observed in guest–host systems. In relation to the optical anisotropic behaviour of the resulting materials, two distinct optical responses were observed depending on the existence or not of covalent attachment of the azo-chromophores to the BCP. 相似文献
923.
Boaz Galdino de Oliveira Regiane de Cássia Maritan Ugulino de Araújo Elisa Soares Leite Mozart Neves Ramos 《International journal of quantum chemistry》2011,111(1):111-116
A theoretical analysis of linear and bifurcate halogen‐oxygen bonds is presented in this work. B3LYP/6‐311++G(d,p) and MP2/6‐311++G(d,p) calculations were used to determine the optimized geometries of intermolecular systems formed by CFCl3 and O3. Molecular properties often analyzed in hydrogen‐bonded complexes were used here to describe the interaction between chlorine (CFCl3) and oxygen (O3). The halogen‐oxygen bond in the CFCl3···O3 complex was characterized using the topological parameters derived from the quantum theory of atoms in molecules. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
924.
The molecular dimensions in dilute solution and the linear viscoelastic melt properties of a series of linear ethylene/1-hexene random copolymers with variable short chain branching content are reported. The results obtained from size exclusion chromatography and viscosimetry in dilute solution show a molecular contraction as the branching level increases. Additionally, a clear dependence of the Newtonian viscosity with the short chain branching content at T = 463 K is obtained. Both experimental observations are in agreement with previous experimental results found in ethylene/α-olefin copolymers, but more interestingly with recent full atomistic simulations made in our group in this type of macromolecular systems. The dependences observed can be related to the changes observed in the macromolecular conformational features and also in the equilibration entanglement time and the molecular weight between entanglements as the number of short chain branches increases. 相似文献
925.
926.
Ertha Janine Lacerda de Medeiros Rita de Cássia Ramos do Egypto Queiroga Antônio Gouveia de Souza Angela Maria Tribuzy de M. Cordeiro Ariosvaldo Nunes de Medeiros Darklê Luiza de Souza Marta Suely Madruga 《Journal of Thermal Analysis and Calorimetry》2013,112(3):1515-1521
Dairies add fat supplements to the diets of small ruminants to increase energy production and consequently the production and quality nutritional and sensorial of the milk. This study investigated the thermal and oxidative stability of babassu, castor, faveleira, and sesame oils by TG/DTA and PDSC. The profile of the fatty oils studied was determined by GC–MS as well as physicochemical characteristics. The thermogravimetric profile of the oils indicated that mass loss was caused by the decomposition or volatility of the triacylglycerides. Faveleira and sesame oils showed a high percentage of polyunsaturated fatty acids, especially C18:2. From a nutritional standpoint, unsaturated oils are more suitable supplements for animals because they promote biochemical changes beneficial to human health. 相似文献
927.
Russany Silva da Costa Charles Alberto Brito Negrão Sarah Regina Pereira Camelo Roseane Maria Ribeiro-Costa Wagner Luiz Ramos Barbosa Carlos Emmerson Ferreira da Costa José Otávio Carréra Silva Júnior 《Journal of Thermal Analysis and Calorimetry》2013,111(3):1959-1964
Thermogravimetric (TG) techniques and differential scanning calorimetry (DSC) used for the study of pre-formulation or drug–adjuvant compatibility have been gaining importance in Brazil. These techniques are being used for the verification of possible interactions between drugs and adjuvants. Aiming at studying the behavior of a plant extract and its mixture with adjuvants, using these thermoanalytical techniques the plant species Heliotropium indicum L. was used. This plant which is originally from India and has been well acclimatized in Brazil has healing and anti-inflammatory properties. The methodology for obtaining the extract followed the Brazilian Pharmacopoeia methodology. And the incorporation of the extract with adjuvants was through binary mixtures (1:1 w/w). The TG and DSC curves were obtained under nitrogen atmosphere (25 mL min?1) at a heating rate of 5 °C min?1; TG tests were analyzed within a temperature range from 25 to 600 °C and DSC from 25 to 300 °C. The TG curves show good thermal stability of the extract and its mixtures with adjuvants up to 150 °C, except the propylene glycol (PLG). The DSC curves revealed an incompatibility of the extract with methylparaben and PLG mixture. 相似文献
928.
Emilio Alvarez-Parrilla Pedro Ramos Cabrer Laura A. de la Rosa Wajih Al-soufi F. Meijide Jose Vázquez Tato 《Supramolecular chemistry》2013,25(3):207-211
The effect of electrostatic interactions on the complexation of ionic guests by charged β-cyclodextrin (βCD) derivatives is reviewed. Special attention is paid to the numerous studies concerning the effect of electrostatic interactions on (i) the complexation of fluorescent and UV probes; (ii) the catalytic and chiral recognition properties of βCD derivatives; and (iii) the complexation of two bile salts (sodium cholate, NaC, and sodium deoxycholate, NaDC). The formation of three-in-one complexes between NaC and alkyldiamino βCD derivatives is also presented. 相似文献
929.
A new computational approach for electrical analysis especially designed for application in biological tissues is presented. It is based on the modelling of the electrical properties of the medium by means of lumped circuit elements, such as capacitance, conductance and current sources. The cell scale model is suitable for modelling the local anisotropy around cell membranes. It permits to obtain the electric potential, ionic concentrations and current densities around cells in time steps in an iterative process. The tissue scale model utilises volume-averaged values of conductivity and permittivity and models suitably the dispersive characteristic of biological tissues. It permits to obtain potential and current distributions in large volumes of tissue in the time or frequency domain. An example of analysis of skeletal muscle is presented aiming to demonstrate the features of the method. 相似文献
930.
S. Martínez M. T. Exposito J. Ramos V. Cruz M. C. Martínez M. Lpez A. Muoz‐Escalona J. Martínez‐Salazar 《Journal of polymer science. Part A, Polymer chemistry》2005,43(4):711-725
Styrene was copolymerized with ethylene using the geometry constrained Me2Si(Me4Cp)(N‐tert‐butyl)TiCl2 Dow catalyst activated with methylaluminoxane. Increasing the styrene/ethylene ratio in the reactor feed had the effects of reducing both the activity of the catalyst and the molecular weight of the copolymers produced. However, the higher the styrene/ethylene ratio used, the greater the amount of styrene that became incorporated in the copolymer. We discuss these experimental findings within the framework of a computational analysis of ethylene/styrene copolymerization performed through hybrid density functional theory (B3LYP). In general, there was good agreement between the experimental and theoretical results. Our findings point to the suitability of combining experimental and theoretical data for clarifying the copolymerization mechanisms that take place in α‐olefin‐organometallic systems. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 711–725, 2005 相似文献