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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
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...
Comparison of dissolution profiles of Ibuprofen pellets
Costa, F. O.; Sousa, J. J. S.; Pais, A. A. C. C.; Formosinho, S. J.In this work we use both model dependent and independent techniques to assess the difference between dissolution profiles in which ibuprofen, in the form of uncoated pellets, is used as a model drug. The choice of a proper regression function, the relevance of the estimated parameters and the influence of the choice of dissolution points in the assessment of differences is discussed. The results obtained via me...
Room temperature and low-temperature absorption and emission spectra of some po...
Silva, M. I.; Burrows, H. D.; Formosinho, S. J.; Miguel, M. da G.Electronic absorption and luminescence spectra are reported for a series of complexes of type [Ru(tpy)(L-L)(py)]2+, where tpy and py are 2,2',2''-terpyridine and pyridine, and L-L represents the bidentate ligands bipyridyl, 4,4'-dimethylbipyridyl, 4-nitrobipyridyl, oxalate and acetylacetonate. The effect of solvent polarity and temperature on their spectral and light emission properties is studied. Energies are...
The intersecting-state model: a link between molecular spectroscopy and chemica...
Arnaut, L. G.; Pais, A. A. C. C.; Formosinho, S. J.The intersecting-state model is applied to calculate the energy barriers and rates of atom transfers, SN2 reactions, proton transfers and electron transfers, including electron transfer at the metal-electrolyte interface. The calculated rates are usually within one order of magnitude of the experimental ones. These applications of the model reveal the main factors that influence the rates of these chemical reac...
The characterisation by luminescence spectroscopy of uranium(VI) incorporated i...
Azenha, M. E. D. G.; Miguel, Maria da Graça; Formosinho, S. J.; Burrows, H. D.Luminescence spectroscopy of solids at 77 K has been used to characterise the uranium(VI) species incorporated into [alpha]-alumina, [gamma]-alumina and zeolites Y and ZSM-20 by adsorption from solution and into ZSM-5 by chemical synthesis. With uranyl adsorbed from nitrate solutions onto [alpha]- and [gamma]-aluminas, the luminescence measurements show the dominant uranium species is schoepite, UO3·xH2O, in ag...
Effective distances of exothermic charge-transfer reactions in the excited state
Costa, Sílvia M. B.; Maçanita, A. L.; Formosinho, S. J.A study of intermolecular, exothermic charge-transfer interactions is described. A distance dependence on the unimolecular charge-transfer rate constant k,,(R) is observed in viscous solvents where transfer at longer distances than the collisional one can compete with dissociation of an encounter complex. A comparative study of the quenching phenomena, occurring in a family of redox partners of aromatic esters ...
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