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251.
Guadalupe del C. Pizarro Oscar G. Marambio Manuel Jeria-Orell Margarita R. Huerta Bernabé L. Rivas Wolf D. Habicher 《应用聚合物科学杂志》2008,108(6):3982-3989
Radical copolymerization of 1-vinyl-2-pyrrolidone with itaconic acid at different feed monomer ratios (75–25 mol %) were investigated. The copolymers were characterized by elemental analysis, Fourier transform infrared (FTIR), 1H and 13C NMR spectroscopy. The copolymer composition was determined from elemental analysis and found to be statistical copolymers. Additionally, viscosimetric measurements, molecular weight, and polydispersity have been determined. The metal complexation of poly(1-vinyl-2-pyrrolidone-co-itaconic acid) for the metal ions such as Cr(III), Co (II), Zn(II), Ni(II), Cu(II), Cd(II), and Fe(III) were investigated at pH 3, 5, and 7 in aqueous solution. The metal ion interaction with hydrophilic polymers was determined as a function of the pH and filtration factor. Poly(1-vinyl-2-pyrrolidone-co-itaconic acid) showed a high affinity for the metal ions at pH 5 and 7. The poly(NVP-co-IA), with a copolymer composition of 29 : 71 mol % (PVA-3), presented the highest metal ion retention values, particularly at higher pHs, at which the carboxylic acid groups are nonprotonated and could easily coordinate with the metal ions. According to the interaction pattern obtained, Cr(II), Zn(II), Pb(II), and Ni(II) formed the most stable complexes at pH 7. The thermal behaviors of the copolymer and polymer metal complex were characterized using differential scanning calorimetry (DSC) and thermogravimetry techniques under nitrogen atmosphere. The copolymers present high thermal stability and do not present glass transition in DSC curves between 25 and 500°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008 相似文献
252.
Effect of Thermal Stage in the Processing Avocado by Flash Vacuum Expansion: Effect on the Antioxidant Capacity and the Qualitaty of the Mash
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253.
Optimization of Ultrasonic‐Assisted Extraction of Antioxidant Compounds from Starfruit (Averroha carambola L) Leaves
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254.
Luis Arturo Bello‐Prez Francisco J. García‐Surez Guadalupe Mndez‐Montealvo Joo Roberto Oliveirado Nascimento Franco Maria Lajolo Beatriz Rosana Cordenunsi 《Starch - St?rke》2006,58(6):283-291
The pinhão seeds (Araucaria angustifolia), are composed of 34% of starch and very low fractions of protein, lipids and phenolic compounds. This composition is favorable to obtain a stable, white in color and odorless starch, useful in the food industry. The isolated starch is constituted predominantly of small‐sized round granules (10–25 μm), rather than oval ones. Compared to corn starch, pinhão starch has a lower temperature and enthalpy of gelatinization. Retrogradation occurs to a lower extent in pinhão starch, due to its lower amylose content (∼25%). The pasting profile of pinhão starch showed a higher consistency than that of corn starch, with lower temperature in the peak of maximum viscosity. The higher swelling and solubility values of pinhão starch, in conjunction with the higher storage modulus (G') suggest new different applications of this novel starch. The low protein content of the starch granule favors applications like production of glucose and fructose syrups. The simple method of extraction and the high yield of starch from pinhão seed might be attractive not only for pilot‐plant but also for commercial‐scale production. 相似文献
255.
Guadalupe C. Rodríguez-Jimenes Armando Vargas-Garcia Dolores J. Espinoza-Pérez Marco A. Salgado-Cervantes Victor J. Robles-Olvera Miguel A. García-Alvarado 《Food and Bioprocess Technology》2013,6(10):2640-2650
In this paper, experimental kinetics of vanilla pods’ solid–liquid extraction were obtained by three different methods: with agitation, without agitation, and microwave-assisted (MAE) without agitation. The extraction kinetics of aroma compounds (vanillin, p-hydroxybenzaldehyde, and p-hydroxybenzoic acid) was measured in vanilla pods (refined) and extracts by high-performance liquid chromatography. Additionally, the equilibrium distribution of aroma compounds between phases and the retained solution by refined pods were experimentally evaluated. A mechanistic model of two simultaneous algebraic equations was fitted to experimental data in order to estimate the aroma compound diffusivities inside the pods and mass transfer coefficients in the extract. The diffusivities in vanilla pods at 50 °C were 4.31?×?10?11, 2.93?×?10?11, and 3.50?×?10?11?m2?s?1 for vanillin, p-hydroxybenzaldehyde, and p-hydroxybenzoic acid, respectively. External mass transfer coefficients were in the order of 1.0?×?10?4?m?s?1 for forced convection extraction and MAE and 3.33?×?10?7?m?s?1 for natural convection extraction. 相似文献
256.
Elia Hoz Zavala and Guadalupe de la Lanza Espino 《Lakes & Reservoirs: Research and Management》2000,5(4):249-260
The environmental characteristics and degree of pollution of a jagüey (a small, shallow tropical water‐body) in Mexico were identified by means of an environmental impact matrix. Jagüeys are important as their main sources of water are the subsurface water‐table and rainfall, however, they have not been studied because of their small size. A flow diagram was designed to incorporate the main climatic, geological and hydrological environmental factors, as well as physico‐chemical data on sediment and water qualities, and biological, technostructural and socioeconomic aspects. The resulting index of –90 in the environmental impact matrix indicates a severe negative impact on jagüeys from the input of allochtonous nutrients because of their small depth, limited circulation and the high rate of evaporation. The jagüeys studied appear in a state of hypertrophy and senility, despite geological youth. 相似文献
257.
Carlos Eduardo da Silva Pinto Gregorio Guadalupe Carbajal Arizaga Fernando Wypych Luiz Pereira Ramos Kestur Gundappa Satyanarayana 《Composites Part A》2009,40(5):573-582
Poly (hydroxy butyrate) (PHB) is a biodegradable polymer that can be obtained from both renewable and synthetic resources. There have been many attempts to improve its structure and properties by different methods. This paper, while mentioning briefly PHB and sugarcane bagasse fibers, focuses on the effect of compressive/molding pressure on its structure and thermal properties with incorporation of sugarcane bagasse fibers, with and without steam explosion treatment. Thermal behavior (thermogravimetry and dynamic mechanical analysis), X-ray diffraction, Fourier transform infrared spectroscopy, optical microscopy methods were used to understand the changes in PHB resulting from the pressure and incorporation of fibers while scanning electron microscopy is used to understand the morphology of both the fiber and PHB. 相似文献
258.
Montserrat Trilla Guadalupe Borja Roser Pleixats Michel Wong Chi Man Catherine Bied Joël J.E. Moreau 《Advanced Synthesis \u0026amp; Catalysis》2008,350(16):2566-2574
The systems formed by palladium acetate [Pd(OAc)2] and hybrid silica materials prepared by sol‐gel from monosilylated imidazolium and disilylated dihydroimidazolium salts show catalytic activity in Suzuki–Miyaura cross‐couplings with challenging aryl bromides and chlorides. They are very efficient as recoverable catalysts with aryl bromides. Recycling is also possible with aryl chlorides, although with lower conversions. In situ formation of palladium nanoparticles has been observed in recycling experiments. 相似文献
259.
Alginate films containing dissimilar amounts of guluronate (G) and mannuronate (M): M/G∼0.45 and M/G∼1.5, soaked in a calcium chloride solution up to 20 min were evaluated for water vapor permeability (WVP). M/G∼0.45 films proved to be better moisture barriers at all calcium immersion times compared to M/G∼1.5. WVP of M/G∼0.45 and M/G∼1.5 films decreased as time of immersion in calcium increased; after 3 min, a decrease in WVP was observed. M/G∼0.45 films soaked for 1 min in calcium were further analyzed to determine the effect of plasticizer and relative humidity (RH) on their mechanical properties and WVP, using fructose, glycerol, sorbitol, and polyethylene glycol (PEG-8000). Films without plasticizer showed a lower capacity to adsorb water compared to those with plasticizer. As RH increased, tensile strength (TS) decreased and elongation (E) increased for all films. This effect was more pronounced on films containing plasticizer, which had lower TS at all RHs. Plasticizer did not increase E at 58% RH. At 78% and 98% RH, glycerol, sorbitol and fructose showed a significant increase in E compared to PEG-8000 and no-plasticizer. PEG-8000 provided lower TS and E, while glycerol showed the highest among all plasticizers. There was no difference on WVP between no-plasticizer and glycerol. Fructose and sorbitol showed the lowest WVP while PEG-8000 showed the highest. 相似文献
260.
Optimization of Thermoultrasound Conditions for the Processing of A Prickly Pear Juice Blend (Opuntia Ficus Indica) Using Response Surface Methodology
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