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151.
Journal of Thermal Analysis and Calorimetry - We report data obtained from the spinodal decomposition in samples of two compositions of intermetallic Cu–Al–Mn shape memory alloys.... 相似文献
152.
Sfarra Stefano Tejedor Blanca Perilli Stefano Almeida Ricardo M. S. F. Barreira Eva 《Journal of Thermal Analysis and Calorimetry》2021,145(6):3105-3123
Journal of Thermal Analysis and Calorimetry - The water ingress phenomenon in sandwich-structured composites used in the aerospace/aeronautical sector is a current issue. This type of defect can... 相似文献
153.
Phytochromes are ubiquitous photoreceptors found in plants, eukaryotic algae, bacteria and fungi. Particularly, when bacteriophytochrome is irradiated with light, a Z‐to‐E (photo)isomerization takes place in the biliverdin chromophore as part of the Pr‐to‐Pfr conversion. This photoisomerization is concomitant with a bathochromic shift in the Q‐band. Based on experimental evidence, we studied a possible keto–enol tautomerization of BV, as an alternative reaction channel after its photoisomerization. In this contribution, the noncatalyzed and water‐assisted reaction pathways for the lactam–lactim interconversion through consecutive keto–enol tautomerization of a model BV species were studied deeply. It was found that in the absence of water molecules, the proton transfer reaction is unable to take place at normal conditions, due to large activation energies, and the endothermic formation of lactim derivatives prevents its occurrence. However, when a water molecule assists the process by catalyzing the proton transfer reaction, the activation free energy lowers considerably. The drastic lowering in the activation energy for the keto–enol tautomerism is due to the stabilization of the water moiety through hydrogen bonds along the reaction coordinate. The absorption spectra were computed for all tautomers. It was found that the UV–visible absorption bands are in reasonable agreement with the experimental data. Our results suggest that although the keto–enol equilibrium is likely favoring the lactam tautomer, the equilibrium could eventually be shifted in favor of the lactim, as it has been reported to occur in the dark reversion mechanism of bathy phytochromes. 相似文献
154.
A Combined Experimental and Theoretical Study on the Formation of Ag Filaments on β‐Ag2MoO4 Induced by Electron Irradiation
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Juan Andrés Mateus M. Ferrer Lourdes Gracia Armando Beltran Valeria M. Longo Guilherme H. Cruvinel Ricardo L. Tranquilin Elson Longo 《Particle & Particle Systems Characterization》2015,32(6):646-651
A combined experimental and theoretical study is presented to understand the novel observed nucleation and early evolution of Ag filaments on β‐Ag2MoO4 crystals, driven by an accelerated electron beam from an electronic microscope under high vacuum. The growth process, chemical composition, and the element distribution in these filaments are analyzed in depth at the nanoscale level using field‐emission scanning electron microscopy (FE‐SEM) and transmission electron microscopy (TEM) with energy‐dispersive spectroscopy (EDS) characterization. To complement experimental results, chemical stability, structural and electronic aspects have been studied systematically using first‐principles electronic structure theory within a quantum theory of atoms in molecules (QTAIM) framework. The Ag nucleation and formation on β‐Ag2MoO4 are a result of structural and electronic changes of the AgO4 tetrahedral cluster as a constituent building block of β‐Ag2MoO4, consistent with Ag metallic formation. The formation of Ag filament transforms the β‐Ag2MoO4 semiconductor from n‐ to p‐type concomitant with the appearance of Ag defects. 相似文献
155.
156.
Beatriz B. Caravieri Pollyanna F. de Oliveira Ricardo A. Furtado Denise C. Tavares Eduardo J. Nassar Katia J. Ciuffi Eduardo F. Molina 《Journal of Sol-Gel Science and Technology》2014,72(3):627-636
Herein, we used tri-ureasil organic–inorganic hybrid material (tU5000) in order to enhance the solubility of nonsteroidal anti-inflammatory drugs and fine tuning the drug delivery profile. For the first time, we used tU5000 as a film-forming agent in order to provide an alternative vehicle for transdermal drug delivery systems which the cell viability of practically 100 % for the highest and the lowest tested concentrations of pure tU5000 indicated that the material was not cytotoxic. The physicochemical properties of the tU5000 drug carrier and drug-loaded hybrids were systematically studied using powder X-ray diffraction, differential scanning calorimetry, small-angle X-ray scattering, and Fourier-transform infrared spectroscopy. The structural changes of tU5000 as well as the relationships between the drug content and in vitro drug release behaviors were investigated. The results showed that the ibu molecules were homogeneously distributed in the tU5000 xerogels contributing to fine-tuning the drug delivery profile. Considering the ability to incorporated high drug content, simple and mild preparation procedure by one-pot sol–gel route, high stability of the materials, sustained-release property, this class of hybrid based on polymers and inorganic compounds may have potential applications in the design of pharmaceutical formulation as ophthalmic (contact lenses), transdermal (patches) and implantable (soft tissue) drug delivery systems. 相似文献
157.
Ricardo Molina Miguel Gómez Chi-Wai Kan Enric Bertran 《Cellulose (London, England)》2014,21(1):729-739
Materials with hydrophilic–oleophobic properties are of relevance due to their application to different fields such as self-cleaning coatings, liquid–liquid separation membranes and functional textiles for different technical applications. In this work, hydrophilic–oleophobic coatings have been deposited on cellulosic materials (filter paper and bleached cotton) by means of plasma assisted polymerization of acrylic acid solutions in water followed by cationic fluorosurfactant complexation. Chemical composition of the coatings on cellulosic materials was characterized by means of FTIR–ATR and XPS whereas their morphology was studied by SEM. Hydrophilic–oleophobic behavior was characterized by means of contact angle and wetting time. Additionally wetting properties of cationic, anionic and non-ionic surfactant solutions on the hydrophilic–oleophobic coatings were used to characterize the polyelectrolyte electrostatic forces upon the functionalized layer. 相似文献
158.
159.
Chien-Tai Tsai Ricardo Morales-Rodriguez Gürkan Sin Anne S. Meyer 《Applied biochemistry and biotechnology》2014,172(6):2815-2837
The objective of this study is to perform a comprehensive enzyme kinetics analysis in view of validating and consolidating a semimechanistic kinetic model consisting of homogeneous and heterogeneous reactions for enzymatic hydrolysis of lignocellulosic biomass proposed by the U.S. National Renewable Energy Laboratory (Kadam et al., Biotechnol Prog 20(3):698–705, 2004) and its variations proposed in this work. A number of dedicated experiments were carried out under a range of initial conditions (Avicel® versus pretreated barley straw as substrate, different enzyme loadings and different product inhibitors such as glucose, cellobiose and xylose) to test the hydrolysis and product inhibition mechanisms of the model. A nonlinear least squares method was used to identify the model and estimate kinetic parameters based on the experimental data. The suitable mathematical model for industrial application was selected among the proposed models based on statistical information (weighted sum of square errors). The analysis showed that transglycosylation plays a key role at high glucose levels. It also showed that the values of parameters depend on the selected experimental data used for parameter estimation. Therefore, the parameter values are not universal and should be used with caution. The model proposed by Kadam et al. (Biotechnol Prog 20(3):698–705, 2004) failed to predict the hydrolysis phenomena at high glucose levels, but when combined with transglycosylation reaction(s), the prediction of cellulose hydrolysis behaviour over a broad range of substrate concentrations (50–150 g/L) and enzyme loadings (15.8–31.6 and 1–5.9 mg protein/g cellulose for Celluclast and Novozyme 188, respectively) was possible. This is the first study introducing transglycosylation into the semimechanistic model. As long as these type of models are used within the boundary of their validity (substrate type, enzyme source and substrate concentration), they can support process design and technology improvement efforts at pilot and full-scale studies. 相似文献
160.
Renato D’Angelo Cristy Leonor Azanza Ricardo Alberto Mittiga Paolo Scardi Matteo Leoni 《Journal of Sol-Gel Science and Technology》2014,72(3):490-495
Zinc-rich/copper-poor Cu2-xZn1+xSnS4 (x = 0.2, CZTS) has been successfully produced in film and powder form using two non-aqueous solutions (of metal salts and thiourea) without the need for sulfurization during the annealing phase. A reaction route is proposed and the choices of the solvents (water, ethyleneglycol, ethanol, methanol) and of the tin source (tin chloride pentahydrate or anhydrous) discussed and justified. A pure and coarse-grained material is obtained with a mix of metal salts in methanol and thiourea in ethylene glycol. The tin pentahydrate salt seems a better alternative to the commonly used anhydrous chloride. 相似文献