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141.
Immobilization of lipase in ordered mesoporous materials: Effect of textural and structural parameters 总被引:1,自引:0,他引:1
Elías Serra lvaro Mayoral Yasuhiro Sakamoto Rosa M. Blanco Isabel Díaz 《Microporous and mesoporous materials》2008,114(1-3):201-213
A systematic study dealing with the influence of several parameters on the immobilization of lipase in ordered mesoporous materials (OMM) is presented here. In a first step, a series of OMM have been synthesized trying to cover the most relevant structures. The aim is to get variation in the key properties susceptible of influencing their behavior as lipase supports, such as the structure (cubic or hexagonal), the nature of the pores (channel-like or cage-like), the connectivity of the porous network and the pore size. Also, by following the co-condensation technique, 5–10%-methylated analogues of the pure-silica materials have been prepared. All the samples have been fully characterized with XRD, TEM (including 3D reconstruction), SEM, TGA and N2 isotherms, and the incorporation of the organic function has been demonstrated by 29Si NMR. All of them have been tested as supports in the immobilization of Candida antarctica Lipase B (CaLB) and the leaching of the enzyme in aqueous media evaluated. With such a systematic approach, valuable information on the influence of the textural properties and the nature of the porous network on the yields of immobilization and enzyme desorption have been stated. Very interestingly, leaching of the enzyme can be diminished until it practically disappears without being covalently bonded to the wall, which places the ordered mesoporous materials at the starting point of a new scenario in enzyme immobilization on preexisting supports. 相似文献
142.
143.
Yasuhiro Tomita Mituhiro Nakamura Kimio Niwa 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1988,270(2-3):403-410
In order to study the local response of silicon strip detectors, we have developed a local charge generator using near-infrared ligh emitting diode. The edge properties of the strip detectors were studied precisely with this tool. In the case of our tested detector, the lateral extension of the depletion area was measured to be about 120 μm at a bias voltage of 40 V. 相似文献
144.
The critical behavior of excitonic fluctuations is investigated at low temperatures. The Wilson renormalization group is applied to a generalized free-energy functional of the Landau-Ginzburg-Wilson type, which is derived by coarse-graining a microscopic functional. The quantum mechanical effects give rise to an increase of the effective dimensionality at zero temperature. The values of this increase z are z = 1 for a semiconductor and z = 2 for a semimetal, depending on whether the electronic density of states is zero at the Fermi energy or not, respectively. Quantum-classical crossover phenomena appear at a finite but low temperature. As the phase transition point is approached in a semimetal the critical fluctuations in real space first grow two-dimensionally in the plane perpendicular to the magnetic field and then develop three-dimensionally. It is explicitly shown that the mean field theory breaks down in a semiconductor.Correspondence and reprint requests should be addressed to Tatsuzo Nagai. 相似文献
145.
The occurrence and determination of a herbicide, benthiocarb, 4-chlorobenzyl N,N-diethylthiolcarbamate (Saturn®) in rivers and agricultural drainages was investigated. Benthiocarb residues were detected in water samples when it has been applied to rice paddies, after rice seedling transplantation, in concentrations of between 10.00 and 0.11 μg/l. These residues entered into rivers and agricultural drainages as a result of overflows from rice paddies. However, benthiocarb residues could not be found in water samples after the termination of its application to rice paddies, suggesting that the applied benthiocarb might be degraded by microbial and physico-chemical actions such as photochemical reactions occurring on the soil surface. Benthiocarb residue levels were higher in longer rivers than in agricultural drainage. The contribution of rainfall to the benthiocarb concentrations was shown. Benthiocarb in water was extracted with n-hexane and identified by a gas chromatography using a flame photometric detector (sulphur filter 394 nm) and a combined gas chromatography-mass spectrometry-computer system. The minimum detectable amount of benthiocarb in water sample by gas chromatography was 0.56 ng and about 100 ng of benthiocarb could be identified by a gas chromatography-mass spectrometry-computer system. 相似文献
146.
A novel N-linked oligosaccharide (N-glycan) with "beta1-4 bisecting branch (galactose beta1-4 bisecting N-acetylglucosamine)" was found in human serum IgG. Its structure was efficiently analyzed by using beta-galactosidase digestion, a MSn spectral library database, and negative-ion MS2 spectral matching. For confirmation, the novel N-glycan was synthesized by using an expected standard N-glycan (acceptor), UDP-galactose (donor), and beta1-4 galactosyltransferase. This work also demonstrates that the MSn spectral library database, in particular, negative-ion MS2 spectral matching, can efficiently reduce the number of specific, sequential exoglycosidase digestions required and is useful for rapid structural analysis of unknown glycans not in the database. 相似文献
147.
Yasuhiro Kobayashi Masaaki Ohkita Michio Inoue 《Mathematics and computers in simulation》1978,20(4):285-290
In the previous papers [1][3], fractional powers were used to approximate elementary functions and their usefulness was proved with experimental results. In the present paper, some further investigations are reported. That is, elliptic integrals in Legendre's canonical form and Bessel functions are approximated by fractional powers. As the fractional power approximation, is discussed. When all coefficients c0, c1, c2, p are properly assigned, the accuracy of this approximation becomes comparable to that of the Chebyshev approximation using polynomials up to the third degree. 相似文献
f(x) c0 + c1x + c2xp
148.
The monthly variation in HCH (1,2,3,4,5,6-hexachlorocyclohexane) residue levels in surface waters was investigated. The logarithms of monthly HCH concentrations described the wave, and the equation of the wave was calculated by the least squares method. The waves indicated maximum concentrations in summer and minimum concentrations in winter at each sampling site. The maximum concentration of HCH in each year decreased gradually. The amplitude of the wave at the reservoir was the smallest among sampling sites. The slope of the wave at the downstream sampling site was smaller than that at the upper stream. Maximum concentration of total HCH at each sampling site in 1985 is estimated from the equations; the concentrations at the upper streams will be about a thousandth or a hundredth of that at the downstreams. Also, the equations for β-and γ-HCH were calculated, and indicated that β-HCH was more persistent than γ-HCH in surface water. The ratio of β-HCH to total HCH in surface water is estimated to be about 60% in 1985. 相似文献
149.
Yasuhiro Awakura Shinya Kamei Hiroshi Majima 《Metallurgical and Materials Transactions B》1980,11(3):377-381
This paper presents the results obtained through a kinetic study of the nonoxidative dissolution of natural galena in hydrochloric
acid and perchloric acid solutions with and without the addition of sodium chloride. Under the experimental conditions employed
in this study, the dissolution rates were controlled by a chemical reaction on the surface of the galena sample. The galena
dissolution rate is of the first order with respect to hydrochloric ion activity in hydrochloric acid and perchloric acid
solutions. The addition of sodium chloride to the acid solutions greatly enhanced the dissolution rate. The effect of sodium
chloride has two possible interpretations: First, it may be the result of an increase in hydrogen ion activity. Second, the
enhancement of the dissolution rate observable at high sodium chloride concentration may be due to the specific adsorption
of chloride ions or the surface complexing of chloride ions on the galena surface. 相似文献
150.
Chul-Hoon Pai Yasuhiro Sasaki Kunihito Koumoto Hiroaki Yanagida 《Journal of the American Ceramic Society》1991,74(11):2922-2924
Porous SiC ceramics fabricated from hollow particles and polycarbosilane (PSC) are promising materials for high-temperature thermoelectric energy conversion. Reaction sintering of PCS-impregnated compacts of SiC hollow particles gave rise to porous microstructures with the hollow shape remaining. The repetition of the PCS-impregnation and sintering process resulted in only a slight increase in density but in a great improvement in thermoelectric properties. 相似文献