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31.
Patricia Amouzegh Annie Finiels Patrick Geneste Erick Ginestar Patrice Moreau 《Catalysis Letters》1995,34(3-4):389-394
The acylation reaction of 2-butylbenzofuran withp-anisoyl chloride andp-anisic acid in the presence of faujasite type zeolites, in the liquid phase, is reported. A good initial selectivity to the 3-acylated derivative is obtained, but the selectivity decreases with time. This result is explained by the involvement of a deacylation-reacylation process. 相似文献
32.
Erick Ringot 《Cement and Concrete Research》1988,18(6):933-942
Preliminary to the modeling of the fracture of concrete, it is necessary to make observations at low scale for a better understanding of the phenomena. In this paper, the author shows how to follow the development of the microcracks in a sample during a compressive loading experimentation by the mean of non-destructive takings of replicas observed under S.E.M. The quantification by the stereological method of total projection. Enables to establish a relation between the observed damages and the global behaviour of concrete. 相似文献
33.
S. John Pirt Susan M. A. Pickett Andrew M. Pickett Erick J. Vandamme Clive W. Bird 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1981,31(1):167-177
A new streptomyces strain, designated Streptomyces elizabethii, was isolated from a soil sample using a method which selected antifungal antibiotic producers. S. elizabethii produces an antifungal polyene (elizabethin) and antibacterial actinomycins. Optimal conditions were elucidated for sporulation of the streptomycete in bottle cultures and for polyene production in shake flask cultures. High sugar concentrations were found to repress actinomycin biosynthesis and increase polyene production. Excess potassium phosphate inhibited polyene production. 相似文献
34.
Herman A. M. Geeraerts Erick J. Vandamme 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1983,33(2):107-113
The cellulolytic properties of a Chaetomium crispatum strain were investigated. The cellulolytic enzyme complex i.e.: exo-1,4-β-glucosidase (EC 3.2.1.74); endo-1,4-β-glucanase (EC 3.2.1.4.) and β-glucosidase or cellobiase (EC 3.2.1.21) displayed optimal activity at pH 5.0 and 25°C. Although carboxymethyl-celluloses are the usual pseudo-substrates for this enzyme complex, those with a high degree of substitution gave rise to poor growth and low cellulase activity. Insoluble crude cellulosics such as newsprint, recycled paper, rice and flax straw were substantially solubilised at 28°C within 3–5 days of fermentation. A study of the cellulase-complex formation during the growth cycle revealed that β-glucosidase was produced mainly intracellularly in the early exponential phase, while the overall exo-1,4-β-glucosidase and endo-1,4-β-glucanase formation gradually increased during the total fermentation cycle. The mycelial protein of Chaetomium crispatum grown on crude cellulosics displayed a favourable amino acid pattern, indicating its potential value as a source of single cell protein (SCP). 相似文献
35.
Erick Scheuermann Ivette Seguel Adolfo Montenegro Rubn O Bustos Emilio Hormazbal Andrs Quiroz 《Journal of the science of food and agriculture》2008,88(3):485-492
BACKGROUND: ‘Murtilla’, ‘mutilla’ or ‘murta’ (Ugni molinae Turcz) is a native Chilean species that produces a small berry fruit with a special aroma, whose volatile compounds have not yet been identified. The fruit may be consumed raw and also as jams, juice, canned products, confections and liquor. RESULTS: At the beginning and end of the storage, 24 volatile compounds were identified in murtilla fruit aroma and the concentration of these compounds in murtilla fruit ranged from 1.2 to 250.5 µg kg?1 fresh weight. Methyl 2‐methyl butanoate, ethyl butanoate, ethyl 2‐methyl butanoate, methyl hexanoate, ethyl hexanoate, methyl benzoate and ethyl benzoate were the major components, all of which have been reported as potent odors in other aromatic fruits. Based on estimated odor activity value, the most potent compound in the murtilla fruit aroma were ethyl hexanoate and 4‐methoxy‐2,5‐dimethyl‐furan‐3‐one. The statistical analysis showed that the storage produced a distinct effect on the same volatile compounds released from the murtilla ecotypes. CONCLUSION: The volatile compounds identified in murtilla fruit aroma, which may be described as fruity, sweet and floral, have been found in other aromatic fruits. Concerning the aroma, the murtilla fruit from ecotype 19‐1 was shown to be the best in cooled storage. Copyright © 2007 Society of Chemical Industry 相似文献
36.
37.
The optimized bonding of glued finger joints is required for structural and nonstructural applications. The use of nonspecific adhesives, combined with the joint geometry and exposure of joints to humidity and temperature, are factors that can compromise the durability of glued joints. The main objective of this study is the development of cross-linking poly(vinyl acetate) (PVAc) hybrid adhesive to produce nonstructural finger joints of Pinus elliottii with finger lengths of 6.5 and 4.5 mm. The adhesives were produced by emulsion copolymerization of vinyl acetate with n-butyl acrylate with different amounts of N-methylol acrylamide and blended with resorcinol-formaldehyde resin (RF) and aluminum chloride (AlCl3). The rheological behavior of adhesives was investigated. We found that the joint configuration and the exposition time employed influenced joint strength. The PVAc/RF adhesive showed a thicker bond line and consequent deeper penetration into the pores of the wood as verified by microscopy analysis. Statistically differences in bond strength of the adhesive joints were found with respect to different conditioning times and finger length. The highest values were exhibited by the joints produced with a finger length of 6.5 mm and glued with the hybrid adhesive (AD-4) than that joints produced with a finger length of 4.5 mm. 相似文献
38.
Lijun Ji Mindong Gong Wei Qiao Wenqian Zhang Qingren Liu Richard Erick Dunham Jun Gu 《Journal of Polymer Research》2018,25(10):210
A polylactic acid-polyethylene glycol block copolymer (PLA-b-PEG) was used as an additive to prepare gelatin/PLA-b-PEG blend films for the first time. The PEG molecule block enhanced the compatibility of the PLA molecule block with gelatin, which greatly improved the excellent mechanical and gas barrier properties of the gelatin film. The film contained 5 wt% PLA-b-PEG possessed the highest tensile strength and the highest elastic modulus. When the PLA-b-PEG content further increased to 20 wt%, the tensile strength, elastic modulus and elongation at the break of the blend film were all higher than pure gelatin film, suggesting that the gelatin/PLA-b-PEG blend film was pliable and tough. The blend film possessed not only excellent oxygen barrier property, but also a much-improved water barrier property. The degradation rate of the blend film was elongated controllably by regulating the content of the PLA-b-PEG copolymer. The blend film showed great potential in the application of food packaging. 相似文献
39.
Irene Betancourt-Conde Claudia Avitia-Domínguez Alicia Hernndez-Campos Rafael Castillo Lilin Ypez-Mulia Jesús Oria-Hernndez Sara T. Mndez Erick Sierra-Campos Mnica Valdez-Solana Siseth Martínez-Caballero Juan A. Hermoso Antonio Romo-Mancillas Alfredo Tllez-Valencia 《International journal of molecular sciences》2021,22(24)
Leishmaniasis is a disease caused by parasites of the Leishmania genus that affects 98 countries worldwide, 2 million of new cases occur each year and more than 350 million people are at risk. The use of the actual treatments is limited due to toxicity concerns and the apparition of resistance strains. Therefore, there is an urgent necessity to find new drugs for the treatment of this disease. In this context, enzymes from the polyamine biosynthesis pathway, such as arginase, have been considered a good target. In the present work, a chemical library of benzimidazole derivatives was studied performing computational, enzyme kinetics, biological activity, and cytotoxic effect characterization, as well as in silico ADME-Tox predictions, to find new inhibitors for arginase from Leishmania mexicana (LmARG). The results show that the two most potent inhibitors (compounds 1 and 2) have an I50 values of 52 μM and 82 μM, respectively. Moreover, assays with human arginase 1 (HsARG) show that both compounds are selective for LmARG. According to molecular dynamics simulation studies these inhibitors interact with important residues for enzyme catalysis. Biological activity assays demonstrate that both compounds have activity against promastigote and amastigote, and low cytotoxic effect in murine macrophages. Finally, in silico prediction of their ADME-Tox properties suggest that these inhibitors support the characteristics to be considered drug candidates. Altogether, the results reported in our study suggest that the benzimidazole derivatives are an excellent starting point for design new drugs against leishmanisis. 相似文献
40.
A portfolio selection model which allocates a portfolio of currencies by maximizing the expected return subject to Value-at-Risk (VaR) constraint is designed and implemented. Based on an econometric implementation using intradaily data, the optimal portfolio allocation is forecasted at regular time intervals. For the estimation of the conditional variance from which the VaR is computed, univariate and multivariate GARCH models are used. Model evaluation is done using two economic criteria and two statistical tests. The result for each model is given by the best forecasted intradaily investment recommendations in terms of the optimal weights of the currencies in the risky portfolio. The results show that estimating the VaR from multivariate GARCH models improves the results of the forecasted optimal portfolio allocation, compared to using a univariate model. 相似文献