Encontrados 15 documentos, a visualizar página 1 de 2
VIBRATIONAL SPECTROSCOPY (FTIR-ATR AND FT-RAMAN) - A Rapid and Useful Tool for ...
Pereira, Leonel; Amado, Ana M.; Ribeiro-Claro, Paulo J. A.; van de Velde, FredThe wide industrial application of phycocolloids (e.g. alginates, agar and carrageenans) is based on their particular properties to form gels in aqueous solution. Recently, new spectroscopic techniques have provided more accurate identification of the natural composition of the polysaccharides produced by these seaweeds. With the combination of two spectroscopic techniques (FTIR-ATR and FT-Raman) it is possible...
Identification of selected seaweed polysaccharides (phycocolloids) by vibration...
Pereira, Leonel; Amado, Ana M.; Critchley, Alan T.; Velde, Fred van de; Ribeiro-Claro, Paulo J. A.http://www.sciencedirect.com/science/article/B6VP9-4V2NKJR-7/2/a0aa172e4a0e00ab9e24983d8609f77f
Mean distance of closest approach of ions: Lithium salts in aqueous solutions
Ribeiro, Ana C. F.; Lobo, Victor M. M.; Burrows, Hugh D.; Valente, Artur J. M.; Amado, Ana M.; Sobral, Abílio J. F. N.; Teles, Ana S. N.Numerical values for the mean distance of closest approach of ions, "a", for lithium salts in aqueous solutions are presented and discussed. These values were obtained from both experimental activity and diffusion coefficients, and estimated by using different theoretical approaches. ; http://www.sciencedirect.com/science/article/B6TGR-4RR1NKM-1/1/b8d3cdac33991c5424d567940bc0c3a6
Use of Effective Core Potential Calculations for the Conformational and Vibrati...
Fiuza, Sónia M.; Amado, Ana M.; Marques, Maria P. M.; Carvalho, Luis A. E. Batista deIn the light of the recognized anticancer properties of cisplatin-type inorganic systems, the exact knowledge of their conformational preferences is of the utmost importance for understanding their biological activity. The present study reports the use of theoretical (quantum mechanical) calculations for achieving this goal. An alternative calculation method to the use of the AE basis sets, both accurate and co...
Pseudopolymorphic transitions of niclosamide monitored by Raman spectroscopy
Sardo, Mariana; Amado, Ana M.; Ribeiro-Claro, Paulo J. A.Niclosamide suffers pseudopolymorphic transformations when exposed to different ambient conditions, which can lead to changes in its bioavailability. In this study, the kinetics of the pseudopolymorphic transitions of niclosamide crystals are characterized. FT-Raman spectroscopy is used to quantify the anhydrate and hydrate forms of niclosamide crystals, mostly because of its high sensitivity to the strong inte...
Probing pseudopolymorphic transitions in pharmaceutical solids using Raman spec...
Amado, Ana M.; Nolasco, Mariela M.; Ribeiro-Claro, Paulo J. A.Theophylline is known to undergo vapor phase induced hydrate-anhydrate pseudopolymorphic transformations, which can affect its bioavailability. In this work, the kinetics of the pseudopolymorphic transitions of theophylline crystals in different storage conditions is studied using a vibrational spectroscopic technique. While the hydration is a single-step process with a half-life time of ca. 5 h, the dehydratio...
Análise comparativa dos ficocolóides produzidos por algas carragenófitas usadas...
Pereira, Leonel; Critchley, Alan T.; Amado, Ana M.; Ribeiro-Claro, Paulo J. A.As Carragenanas (E-407) constituem um dos principais aditivos usados pela indústria alimentar, como agentes gelificantes, emulsionantes, estabilizantes e espessantes. São ingredientes naturais, usados há várias décadas na área alimentar e são considerados como seguros, tendo obtido a classificação GRAS (Generally Recognised As Safe). Neste trabalho foram analisadas a percentagem de peso seco e a composição quím...
Mean distance of closest approach of ions: Sodium salts in aqueous solutions
Ribeiro, Ana C. F.; Esteso, Miguel A.; Lobo, Victor M. M.; Burrows, Hugh D.; Amado, Ana M.; Costa, António M. Amorim da; Sobral, Abílio J. F. N.The estimation of numerical values for the mean distance of closest approach of ions, a, of sodium salts in aqueous solutions, determined from activity and diffusion coefficients, and also from different theoretical approaches, is presented and discussed. ; http://www.sciencedirect.com/science/article/B6TGR-4JCCFW7-1/1/45bf32523013b068b5040514add5505a
Para-halogenated benzaldehyde molecules included in cyclodextrins: a combined s...
Ribeiro-Claro, Paulo J. A.; Costa, António M. Amorim da; Vueba, Manuel L.; Pina, M. Eugénia; Amado, Ana M.The inclusion complexes of 4-X-benzaldehyde guests (X = F, Cl, Br) in alpha-, beta-and gamma-cyclodextrins (alphaCD, betaCD and gammaCD) were prepared and characterized by means of thermogravimetry, differential scanning calorimetry (DSC) and vibrational spectroscopy. The stoichiometry of the inclusion complexes ranges from 2:1 to 1:2, depending on the cavity size of the host. Sensitive vibrational modes such a...
Computationally-Assisted Approach to the Vibrational Spectra of Molecular Cryst...
Nolasco, Mariela M.; Amado, Ana M.; Ribeiro-Claro, Paulo J. A.A new computationally-assisted methodology (PiMM), which accounts for the effects of intermolecular interactions in the crystal, is applied to the complete assignment of the Raman and infrared vibrational spectra of room temperature forms of crystalline caffeine, theobromine, and theophylline. The vibrational shifts due to crystal packing interactions are evaluated from ab initio calculations for a set of suita...
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