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21.
Tolbutamide (TBM) was found to form an inclusion complex with beta cyclodextrin (beta-CD) in solution and in solid state. Inclusion complex formation between tolbutamide and beta-cyclodextrin in aqueous solution was studied by phase solubility and spectral shift methods. The apparent stability constant Ks calculated by these techniques, in water, were estimated as 195.7 and 236.5 M(-1), respectively. The phase solubility studies revealed a B(S)-type diagram with an inclusion complex of 1:2 molar ratio. The solid inclusion complexes of TBM and beta-CD were prepared at a molar ratio of 1:2 by kneading, coprecipitation, freeze-drying, and spray-drying methods. In addition, the physical mixture was prepared. Characterization of TBM: beta-CD inclusion was performed using differential scanning calorimetry (DSC), Raman spectroscopy, and X-ray diffractometry and by application of a so-called ether wash method. All the inclusion systems investigated led to a significant improvement in the dissolution over free TBM, and the dissolution rate of the active material was observed to be independent of the preparation method. 相似文献
22.
An appropriately designed controlled-release drug delivery system can be a major advance towarb solving problems concerning the targeting of a drug to a specific organ or tissue and controlling the rate of drug delivery to the target tissue. Hydrophilic matrices are an interesting option when developing an oral controlled-release formulation. The present study focuses on oral controlled-release dosage forms and the application of cellulose ether polymers in hydrophilic matrices. Key Words. Controlled-release matrices; Hydrophilic matrices; Cellulose ether polymers; Hydroxypropylmethylcellulose; HPMC 相似文献
23.
Daniela de Oliveira Ribeiro Bianca Waruar Lobo Nádia Maria Volpato Venício Féo da Veiga Mendes Lúcio Cabral Valeria Pereira de Sousa 《Nutrition journal》2009,8(1):51-13
Background
Preterm infants need high amounts of calcium and phosphorus for bone mineralization, which is difficult to obtain with parenteral feeding due to the low solubility of these salts. The objective of this study was to evaluate the physicochemical compatibility of high concentrations of calcium associated with organic phosphate and its influence on the stability of AIO admixtures for neonatal use. 相似文献24.
Martina Rudnicki Marcos Roberto de Oliveira Tiago da Veiga Pereira Flávio Henrique Reginatto Felipe Dal-Pizzol José Cláudio Fonseca Moreira 《Food chemistry》2007,100(2):719-724
The leaves of Passiflora alata Dryander and Passiflora edulis Sims, traditionally used in American countries to treat both anxiety and nervousness by folk medicine, are rich in polyphenols, which have been reported as natural antioxidants. In this study, the antioxidant activities of P. edulis and P. alata hydroalcoholic leaf extracts were verified in in vitro and ex vivo assays. P. alata showed a higher total reactive antioxidant potential than did P. edulis. The antioxidant activities of both extracts were significantly correlated with polyphenol contents. In addition, both extracts attenuated ex vivo iron-induced cell death, quantified by lactate dehydrogenase leakage, and effectively protected against protein damage induced by iron and glucose. These findings demonstrate that the P. alata and P. edulis leaf extracts have potent in vitro and ex vivo antioxidant properties and might be considered as possible new sources of natural antioxidants. 相似文献
25.
Examined the relationship between job control and job strain. Three models of that relationship provide a framework for the study hypotheses: (H1) Control is inversely related to job strain, (H2) job demands interact with job control such that job strain will be highest when job demands are high and job control is low, and (H3) strain increases as the discrepancy between actual and desired levels of job control increases. Study participants (N?=?316) were health care workers in 2 hospitals in the northeastern US. Objective measures of job control and job demands were obtained through supervisor evaluations of incumbents' job characteristics, and perceptual measures were obtained through incumbents' self-reports. Results provide support for Hypotheses 1 and 3; little support was found for an interaction between job control and job demands. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
26.
Although the teleworking literature continues to raise concerns regarding the adverse consequences of professional isolation, researchers have not examined its impact on work outcomes. Consequently, the authors first examine professional isolation's direct impact on job performance and turnover intentions among teleworkers and then investigate the contingent role of 3 salient work-mode-related factors. Survey data from a matched sample of 261 professional-level teleworkers and their managers revealed that professional isolation negatively impacts job performance and, contrary to expectations, reduces turnover intentions. Moreover, professional isolation's impact on these work outcomes is increased by the amount of time spent teleworking, whereas more face-to-face interactions and access to communication-enhancing technology tend to decrease its impact. On the basis of these findings, an agenda for future research on professional isolation is offered that takes into account telework's growing popularity as a work modality. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
27.
JM Quintela C Peinador C Veiga L González LM Botana A Alfonso R Riguera 《Canadian Metallurgical Quarterly》1998,6(10):1911-1925
The synthesis of a series of pyridothienopyrimidines and their evaluation as inhibitors or inducers of the release of histamine from rat mast cells is reported. The activity was measured after immunological stimulation with ovoalbumin and chemical stimulation with polymer 48/80 and the drugs adryamicin and vinorelbine. The experiments were carried out with and without preincubation of the stimulus with the cells before addition of the drug. Several pyridothienopyrimidines show inhibitory IC50 values in the range 2-25 microM, indicating they are up to 100 times more potent than cromoglycate (DSCG) and 10 times greater than Ketotifen. Compound 9l is a potent inhibitor in all the conditions tested and shows IC50 = 9-25 microM. Pyridothienopyrimidines 4l and 9e are very strong inducers of histamine release in the immunological (4l, 170-230%) and chemical (9e, 100-150%) assays, respectively. Compounds 4l and 9i are cytotoxic in vitro (IC50 = 0.1-0.2 microgram/mL) against P-388, A-549, HT-29, and MEL-28 tumor cell lines. 相似文献
28.
29.
Fernando L.G. Silva Amanda G. Veiga Nakédia M.F. Carvalho 《International Journal of Hydrogen Energy》2021,46(21):11677-11687
Manganese oxides of different crystalline structures: α-MnO2, δ-MnO2, α,γ-MnO2 and Mn2O3; were treated with the organic compounds picolinic acid, ethylenediamine and pyridine; and were applied as catalysts in the chemical water oxidation reaction using Ce(IV) ammonium nitrate as sacrificial oxidant. The treatment led to modifications in the oxides properties, such as reduction of the particle size, increase of surface area and partial reduction of Mn4+ to Mn3+ for the Mn(IV) oxides, or of Mn3+ to Mn2+ for Mn2O3, because of favored interactions of the organic molecules with the lattice planes with higher d spacing. Oxygen evolution reaction (OER) tests showed the superior catalytic activity of the treated Mn(IV) oxides, for instance α,γ-MnO2-en presented TOF five times higher than pure α,γ-MnO2. The increase in surface area as well as the higher Mn3+ content caused by the treatment of the Mn(IV) oxides were correlated with the improvement in the OER catalytic activity. 相似文献
30.
Water Resources Management - It is a challenge to develop models that can represent the stochastic behaviour of rivers and basins. Currently used streamflow models were constructed under rigid... 相似文献