Encontrados 19 documentos, a visualizar página 1 de 2
Science indicators and science patterns in Europe
Almeida, J. A. S.; Pais, A. A. C. C.; Formosinho, S. J.http://www.sciencedirect.com/science/article/B83WV-4VK69B2-1/2/857bd537a0546fe2cb394c525b44341e
Structure of Microemulsion−ABA Triblock Copolymer Networks
Sarraguça, J. M. G.; Pais, A. A. C. C.; Linse, PerStructural equilibrium properties of transient networks formed by microemulsion droplets and ABA triblock copolymers in solution have been studied by Monte Carlo simulation. The droplets were represented by soft spheres, and the polymers were represented by junctions connected by harmonic bonds with an angular potential regulating the intrinsic chain stiffness. The interaction parameters were selected such that...
New insight into the discrimination between omeprazole enantiomers by cyclodext...
Figueiras, A.; Sarraguça, J. M. G.; Pais, A. A. C. C.; Veiga, J. F.; Carvalho, R. A.We report results regarding the use of 1H-NMR spectroscopy in the study of the conformational behaviour and optical activity of omeprazole. Changes in the chemical shifts of chosen atoms reveal that the conformational behaviour of omeprazole is temperature and pH sensitive. Separation and identification of omeprazole enantiomers in the presence of natural and derivative cyclodextrins, such as ß-cyclodextrin (ßC...
In vivo friction study of human skin: Influence of moisturizers on different an...
Ramalho, A.; Silva, C. L.; Pais, A. A. C. C.; Sousa, J. J. S.In order to understand the human haptic system, the mechanical characterization of skin contact is an important task. As the skin constitutes itself a surface, it is convenient to describe the problem using a contacting surface analysis, especially concerning the friction which occurs when the skin interacts with other surfaces. Several published works have shown that the analysis of the friction response of th...
Improving hierarchical cluster analysis: A new method with outlier detection an...
Almeida, J. A. S.; Barbosa, L. M. S.; Pais, A. A. C. C.; Formosinho, S. J.Techniques based on agglomerative hierarchical clustering constitute one of the most frequent approaches in unsupervised clustering. Some are based on the single linkage methodology, which has been shown to produce good results with sets of clusters of various sizes and shapes. However, the application of this type of algorithms in a wide variety of fields has posed a number of problems, such as the sensitivity...
Stratum corneum hydration: Phase transformations and mobility in stratum corneu...
Silva, C. L.; Topgaard, D.; Kocherbitov, V.; Sousa, J. J. S.; Pais, A. A. C. C.; Sparr, E.The outermost layer of skin, stratum corneum (SC), functions as the major barrier to diffusion. SC has the architecture of dead keratin filled cells embedded in a lipid matrix. This work presents a detailed study of the hydration process in extracted SC lipids, isolated corneocytes and intact SC. Using isothermal sorption microcalorimetry and relaxation and wideline 1H NMR, we study these systems at varying deg...
Aqueous solution and solid state interactions of lanthanide ions with a methacr...
Rubio, F.; García, F.; Burrows, H. D.; Pais, A. A. C. C.; Valente, A. J. M.; Tapia, M. J.; García, J. M.The interaction between trivalent lanthanide ions and poly(1,4,7,10,13-pentaoxacyclopentadecan-2-yl-methyl methacrylate), PCR5, in aqueous solution and in the solid state have been studied. In aqueous solution, evidence of a weak interaction between the lanthanides and PCR5 comes from the small red shift of the Ce(III) emission spectra and the slight broadening of the Gd(III) EPR spectra. From the Tb(III) lifet...
Polyion Adsorption onto Catanionic Surfaces. A Monte Carlo Study
Dias, R. S.; Pais, A. A. C. C.; Linse, P.; Miguel, M. G.; Lindman, B.The adsorption of a single and negatively charged polyion with varying flexibility onto a surface carrying both negative and positive charges representing a charged membrane surface has been investigated by using a simple model employing Monte Carlo simulations. The polyion was represented by a sequence of negatively charged hard spheres connected with harmonic bonds. The charged surface groups were also repres...
Simulation of polyelectrolyte solutions. The density of bound ions
Sarraguça, J. M. G.; Pais, A. A. C. C.We discuss a simple approach to describe the ion density around a polyelectrolyte chain, quantifying bound and bulk counterions, and allowing for the renormalization of the charge in the polyion. This approach is both physically motivated and readily extensible to systems containing other types of highly charged ions. The method addresses the problem in simulation experiments and allows to correlate ion condens...
Analysis of formulation effects in the dissolution of ibuprofen pellets
Costa, F. O.; Pais, A. A. C. C.; Sousa, J. J. S.In this work the effects of citric acid and of two common fillers, lactose (soluble) and tricalcium phosphate (insoluble) are examined on the release profiles from pellets, using ibuprofen as a model drug with pH-dependent solubility. Also studied is the dependence of these profiles on the specific surface area, bulk density, apparent density, porosity and porosity parameters (pore size distribution, total pore...
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