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排序方式: 共有494条查询结果,搜索用时 968 毫秒
81.
Simona PotoracMarcel Popa Vasilica MaierGabriela Lisa Liliana Verestiuc 《Materials science & engineering. C, Materials for biological applications》2012,32(2):236-243
New hydrogels based on maleic anhydride (MA) modified collagen were prepared with the aim of overcoming the high degradation rate displayed by collagen that is not otherwise chemically crosslinked. Semi-interpenetrated matrices were obtained by free radical polymerization of maleilated collagen (CM) and 2-hydroxyethyl methacrylate (HEMA) in the presence of ammonium persulfate (APS) and N,N,N′,N′-tetramethylethylenediamine (TEMED) as initiating system. The resulting matrices (CMH) had a sharp decrease in degradation, when compared to pure collagen. FTIR and H1 NMR spectroscopies were used to confirm the incorporation of MA on the collagen peptide chains. The final composition of CMH was found to be strongly dependent by the concentration of maleilated collagen. The morphology of the hydrogels was studied by Scanning electron microscopy (SEM) and the macro-gel structure was confirmed. Water uptake of the synthetised hydrogels is influenced by both composition and the porosity of the matrices. 相似文献
82.
Nita LE Chiriac AP Nistor MT Tartau L 《Journal of materials science. Materials in medicine》2012,23(5):1211-1223
The study presents the possibility to use the 2-hydroxyethyl methacrylate--HEMA copolymer with a comonomer with spiroacetal moiety, 3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]-undecane)-U, as polymer network for loading the indomethacin--INN as drug model, and also, the controlled release evaluation of the prepared bioactive system. The macromolecular compounds were prepared by radical dispersion polymerization in the presence of a pair of surfactants. The use of cyclodextrin as surfactant allowed the building of the host-guest complexes by inclusion of hydrophobic molecules. Also, the cyclodextrin supplemented the hydrogen bonds and the hydrophobic interactions responsible for the stability of the achieved complexes. The copolymers composition and the INN inclusion onto the polymeric matrix were confirmed by FTIR analysis. The porous structure of the lyophilized P(HEMA-U) samples was illustrated by SEM images. The swelling studies evidenced the interdependence between P(HEMA-U) network properties and the spiroacetal moiety amount. Thus, the copolymers presented the increase of the equilibrium swelling degree with pH and temperature. Also, the polymeric matrices manifested dual sensitivity with pH and temperature. The in vitro release of the INN drug from the polymeric network as well as the in vivo experimental studies evidenced the benefit consequence of the spiroacetal compound presence. The clinical observation of the experimental groups does not show any behavioral modifications to suggest a possible toxic effect of these polymeric formulations with and without INN. 相似文献
83.
Alejandra Montenegro-Hernández Jesús Vega-Castillo Liliana Mogni Alberto Caneiro 《International Journal of Hydrogen Energy》2011,36(24):15704-15714
Thermal stability and chemical compatibility with electrolyte materials for Solid Oxide Fuel Cells (SOFC) have been studied on Ruddlesden-Popper nickelates Ln2NiO4+δ with Ln: La, Pr and Nd. Samples of each composition prepared by three different routes, were characterized by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Different microstructures were achieved by each preparation method. The thermal stability of these compounds was analyzed by annealing all the samples at 700 and 900 °C in air. Pr2NiO4+δ (PNO) decomposes after 24 h of annealing at 700 °C confirming its instability at these conditions. Evidences of chemical reaction between La2NiO4+δ (LNO) and both Ce0.9Gd0.1O1.96 (CGO) and Zr0.92Y0.08O1.96 (YSZ) were observed at 700 and 900 °C, respectively. No decomposition or chemical reaction with YSZ or CGO were found for Nd2NiO4+δ (NNO) below 900 °C. Nevertheless, reactivity with both electrolytes was found for this compound at 1000 °C. The kinetics of these reactions strongly depends on the microstructure of Ln2NiO4+δ. 相似文献
84.
Carolina V. Di Anibal Serena Rodríguez Liliana Albertengo M. Susana Rodríguez 《Food Analytical Methods》2016,9(11):3117-3124
A rapid, simple, and economic multivariate screening methodology based on UV-visible spectroscopy and multivariate classification is proposed to test for adulteration in sauces. Two classification strategies were evaluated to compare their ability to detect food fraud: untargeted modeling (class modeling) and targeted classification (discriminant analysis). As a case study, the possible adulteration of ketchups and barbecue sauces with the banned Sudan I dye was considered. The classification models were built with a new classification tool for class modeling (partial least squares-density modeling, PLS-DM) and with the classical discriminant partial least squares-discriminant analysis (PLS-DA). Very satisfactory classification results were obtained with both strategies: regarding untargeted modeling, only original samples (class 1) were modeled obtaining a 94.5 % of correct classification and regarding targeted classification, two classes were considered (class 1 original samples and class 2 adulterated samples) with an overall classification rate of 97.3 %. The two strategies are useful and adequate as screening tools for monitoring the quality of sauces especially in situations that require quick responses. 相似文献
85.
Stela Pruneanu A. Boughriet A. Henderson C. Malins Z. Ali Liliana Olenic 《Particulate Science and Technology》2013,31(2):136-144
Avidin-biotin has been controllable immobilized on the surface of gold electrodes using mercaptopropionic acid as self-assembled monolayer. Electrochemical impedance spectroscopy (EIS) was employed to investigate the changes that appear at the electrode surface in the presence of a redox mediator, K3[Fe(CN)6]. An electrical model more complex than that in other studies was used to interpret the EIS measurements (Randles circuit). This model is very useful because it takes into consideration both the transfer of electrons at the electrode/electrolyte interface and the diffusion of redox species through the double layer. The model allowed us to determine some important parameters like solution resistance Rsol, charge-transfer resistance Rct, double-layer capacitance Cdl, Warburg resistance RW, and the diffusion time constant τ. The EIS results proved that immobilization of avidin-biotin increased the charge-transfer resistance Rct, due to the insulating character of these molecules. 相似文献
86.
87.
DP Vargas L Giraldo JC Moreno-Piraján 《International journal of molecular sciences》2012,13(7):8388-8397
Activated carbon honeycomb-monoliths with different textural properties were prepared by chemical activation of African palm shells with H(3)PO(4), ZnCl(2) and CaCl(2) aqueous solutions of various concentrations. The adsorbents obtained were characterized by N(2) adsorption at 77 K, and their carbon dioxide adsorption capacities were measured at 273 K and 1 Bar in volumetric adsorption equipment. The experimental adsorption isotherms were fitted to Langmuir and Tóth models, and a better fit was observed to Tóth equation with a correlation coefficient of 0.999. The maximum experimental values for adsorption capacity at the highest pressure (2.627-5.756 mmol·g(-1)) are between the calculated data in the two models. 相似文献
88.
An activated carbon, Carbochem(TM)-PS230, was modified by chemical and thermal treatment in flow of H(2), in order to evaluate the influence of the activated carbon chemical characteristics in the adsorption of the catechol. The catechol adsorption in aqueous solution was studied along with the effect of the pH solution in the adsorption process of modified activated carbons and the variation of immersion enthalpy of activated carbons in the aqueous solutions of catechol. The interaction solid-solution is characterized by adsorption isotherms analysis, at 298 K and pH 7, 9 and 11 in order to evaluate the adsorption value above and below that of the catechol pK(a). The adsorption capacity of carbons increases when the solution pH decreases. The retained amount increases slightly in the reduced carbon to maximum adsorption pH and diminishes in the oxidized carbon. Similar conclusions are obtained from the immersion enthalpies, whose values increase with the solute quantity retained. In granular activated carbon (CAG), the immersion enthalpies obtained are between 21.5 and 45.7 J·g(-1) for catechol aqueous solutions in a range of 20 at 1500 mg·L(-1). 相似文献
89.
90.
Biochemical and Visual Changes in Cactus Stems (Opuntia ficus‐indica Mill.) Stored at 4, 12 and 26C 下载免费PDF全文
Lizette Liliana Rodríguez‐Verástegui Juliana Osorio‐Córdoba Fernando Díaz de León‐Sánchez Clara Pelayo‐Zaldívar David Manuel Díaz‐Pontones Elsa Bosquez‐Molina Guadalupe Judith Márquez‐Guzmán Héctor Bernardo Escalona‐Buendía José Ramón Verde‐Calvo Laura Josefina Pérez‐Flores 《Journal of Food Biochemistry》2015,39(4):449-461