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161.
Pierre H. Ravelonandro Dominique H. Ratianarivo Claire Joannis-Cassan Arsène Isambert Marson Raherimandimby 《Food and Bioproducts Processing》2011,89(3):209-216
Arthrospira (Spirulina) platensis Toliara isolated from alkaline and salt lakes in the south-western area of Madagascar is a potential source of proteins that could efficiently fight against food deficiency in developing countries like Madagascar. Up to now, productivity in this country has been low, so a better understanding of the growth conditions of this species is needed to improve its production. Growth experiments were undertaken in bubble columns at laboratory scale. The influence of agitation of the culture, medium salinity (ranging from 13 to 35 g L−1) and CO2 addition (ranging from 0 to 2%, v/v) on growth and protein content was examined. Because Arthrospira cells are fragile, a bubble column without additional mixing gave the best growth. Arthrospira (Spirulina) platensis showed higher specific growth rate (μmax) and protein content for lower salinity. Addition of 1% of CO2 improved the productivity by near 60%. The feasability of semi-continuous culture was demonstrated and optimal culture conditions led to a mean productivity of 0.22 ± 0.03 g L−1 d−1, a mean specific growth rate of 0.015 ± 0.002 h−1 and a protein content of 53 ± 2% of total dry weight. 相似文献
162.
This study describes the effects of the addition of inorganic nanosized UV absorbers on physico-mechanical and thermal properties of an exterior commercial acrylic-based waterborne stain for wood. Electronic microscopy and water vapor (WV) permeability measurements were performed to characterize the free films of the acrylic stain and resulting nanocomposite coatings. An accelerated weathering method was used to evaluate aging behavior of the coatings on wood through appearance, Tg, abrasion resistance, adhesion strength, hardness and Young's modulus changes. In addition to improving the protection against UV, the doped TiO2 and silica-coated ZnO nanoparticles in powder form have improved the abrasion resistance and barrier effect against water vapor diffusion of the acrylic stain. For most of nanocomposite coatings, the addition of ZnO hydrophilic nanoparticles in predispersed form has resulted in a decrease in WV permeability, while the adhesion strength and abrasion resistance of those coatings were negatively affected. The addition of ZnO nanoparticles has decreased the Tg of the acrylic stain. Finally, the accelerated weathering has induced an increase in Tg, hardness, Young's modulus (stiffness) and an increase in apparent adhesion strength and abrasion resistance of the coatings. The Tg values of the aged nanocomposite coatings were lower than that of unmodified acrylic stain. 相似文献
163.
Guillermo Quijano Annabelle Couvert Abdeltif Amrane Guillaume Darracq Catherine Couriol Pierre Le Cloirec Ludovic Paquin Daniel Carrié 《Chemical engineering science》2011,66(12):2707
This work aims to evaluate the feasibility of using imidazolium ionic liquids (ILs) in the design of multiphase bioreactors for the removal of volatile organic compounds (VOCs). The IL affinity for three model VOCs (dimethyl sulfide, dimethyl disulfide and toluene) was evaluated by means of the dimensionless partition coefficient (K). It was observed that ILs showed K values comparable to typical liquid solvents used in multiphase bioreactors for VOC biodegradation (K values ranged from 0.009 to 0.011, 0.0012 to 0.0013 and 0.00061 to 0.00096 for dimethyl sulfide, dimethyl disulfide and toluene, respectively). Toxicity tests showed that both ILs at concentrations of 5% and 10% (v/v) inhibited the glucose uptake of an activated sludge during approximately 24 h. After such lag period, the microorganisms were able to recover its metabolic activity. However, VOC biodegradation experiments showed that ILs at 5% (v/v) were toxic for the activated sludge and a toxic synergistic effect of the IL–VOC combination likely occurred. After acclimation to the target VOCs, only the toluene biodegradation capacity was significantly increased in the presence of ILs. These toxic effects represent a key drawback for the potential of IL-based multiphase systems devoted to VOC biodegradation. Therefore, this study suggests that microbial acclimation only to the VOCs is not enough to get an efficient biodegradation in multiphase systems including ILs as non-aqueous phases. 相似文献
164.
An accurate and tractable model of solubility is a pre-requisite for any careful study of precipitation. Reviewing the abundant literature on the sodium aluminate solutions and Bayer Liquor, the authors point out the need for a new model for the apparent solubility of aluminium in actual Bayer Liquors and propose such a model, based on the well established Wesolowski's expression for the infinite dilution solubility and extended Debye–Hückel expression including a large empirical b I term for the “activity coefficient effect”. They suggest a chemical interpretation for this feature. 相似文献
165.
KambalaV Subba Rao Basavaraju Srinivas Pierre Boule Machiraju Subrahmanyam 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2002,77(5):568-575
Regioselective photooxidative demethylation of methyl‐substituted N‐containing heterocyclic compounds is investigated in non‐aqueous (ethane nitrile) solutions containing semiconductor oxide (TiO2) as photocatalyst in the presence of molecular oxygen upon irradiation at room temperature conditions. A plausible electron transfer mechanism, in which an electron‐hole pair is generated on the surface of TiO2 by illumination, is proposed for the semiconductor‐mediated photocatalysis. Molecular orbital calculation by the AM 1 method has been performed for the electron densities of N‐atoms of heterocyclics in the present study. © 2002 Society of Chemical Industry 相似文献
166.
Os-catalyzed dihydroxylation will find more widespread application if truly heterogeneous catalysts are available which use O2 or H2O2 as terminal oxidants. This paper discusses and critically evaluates the concepts by which Os can be anchored on solid supports. New methods are also available for reoxidation of hexavalent to octavalent Os. 相似文献
167.
Careful combination of a metal compound,a ligand and an inorganic support material leads to supramolecular catalysts that mimic the structural, organizational and functional aspects of enzyme activity.After discussing essential features of metalloenzyme-catalyzed reactions and coordination chemistry in inorganic hosts, we present examples of supramolecular materials selected from our own work that eventually resulted in useful catalysts for organic transformations in the liquid phase. 相似文献
168.
Jacques Jupille Anne-Marie Flank Pierre Lagarde 《Journal of the American Ceramic Society》2002,85(5):1041-1046
The local structure centered on sodium after diffusion in silica (Na-SiO2 samples) has been determined by means of extended X-ray absorption fine structure (EXAFS) studies. The Na-SiO2 samples are of particular interest because (i) their sodium content can be varied over a wide range of concentration and (ii) their local structure is representative of that of soda–silica glass. EXAFS analyses reveal the existence of a well-defined local structure involving oxygen, sodium, and silicon neighbors. The Na-O, Na-Na, and Na-Si bonds lengths, which amount to 0.23, 0.30, and 0.38 nm, respectively, do not depend on sodium concentration. This environment closely resembles that found in soda–silica glass. Moreover, it is compatible with the "target site" and "the site memory effect" suggested by recent theories of the ionic conductivity in oxide glasses. 相似文献
169.
Comparative Lattice-Dynamical Study of the Raman Spectra of Monoclinic and Tetragonal Phases of Zirconia and Hafnia 总被引:1,自引:0,他引:1
Pierre E. Quintard Pierre Barbéris rei P. Mirgorodsky Thérèse Merle-Méjean 《Journal of the American Ceramic Society》2002,85(7):1745-1749
An interpretation of the Raman spectra of monoclinic ZrO2 and monoclinic HfO2 is made by analyzing the results of the zirconia–hafnia substitution jointly with a lattice dynamical treatment of both structures. The Raman spectra of tetragonal ZrO2 and tetragonal HfO2 are also interpreted. Emphasis is put on their relations to the spectrum of the parent cubic structure and on the position of the soft mode. The band assignment proposed earlier by other researchers is critically reconsidered. 相似文献
170.
Coat-hanger dies are commonly used for the extrusion of plastic sheets and films. To describe the flow of a molten polymer through a coat-hanger die, a two-dimensional approach is necessary. Moreover, the thermal effects, which play an important role in the flow distribution, have to be taken into account. In this paper, two numerical models for the simulation of coat-hanger dies are described and compared. These models differ mainly in the simplifying assumptions used and in the treatment of the thermal problem. The simulations obtained with the two models were compared with each other and with experimental data. The discrepancies between the two models can be explained by the different theoretical treatments. 相似文献