A poly(vinyl alcohol) (PVA) fiber support incorporating various aminoacetal functional groups has been developed for immobilizing enzymes. The aminated PVA fiber seems to adsorb enzymes with electrostatic force of attraction; thus the immobilization procedure is simple. By the use of this fiber having immobilized enzymes, the reaction between enzymes and substrates is nearly independent of the size of subtstrates. This newly developed type of fiber, which is formed by a mass superfine fibers (SFF), each measuring 1 μm or less in diameter, permits much more increased surface area than the conventional enzyme immobilization supports. Our studies of the properties of the fiber for immobilization of enzymes show the following results: (1) SFF has a greater ability for the immobilization of invertase than ordinary fibers; (2) dimethyl-aminated SFF has the best performance for the immobilization of invertase. From these results, it is concluded that the dimethyl-aminated SFF is an excellent support for the immobilization of invertase. 相似文献
Enyzmatic amidation of the primary amines β-alanine ethyl ester and 3-aminopropionitrile with methyl laurate by means of immobilized
lipase (Candida antarctica lipase, CAL) resulted in the formation in good yield of N-lauroyl-β-alanine ethyl ester and 3-(N-lauroylamino)-propionitrile, respectively. When 3-amino-propionitrile was used as substrate, diisopropyl ether was a suitable
solvent. Changing the reaction temperature (12–80°C) did not affect the yields, and room temperature was a suitable temperature
for this reaction. In the investigation of reaction conditions, the use of equimolar amounts (5 mmol) of substrate and ester,
along with 0.5 g of CAL, in diisopropyl ether gave the best yield (99.3%) after 24 h of incubation at 24°C. The enzyme activity
in the amidation reaction did not decrease even after six uses. With β-alanine ethyl ester hydrochloride as substrate, diisopropyl
ether was unsuited as a solvent owing to the low solubility of the substrate in this solvent.
In this reaction, the best yield (82.0%) was attained by using dioxane as solvent. CAL achieved higher extents of amide synthesis
with long-chain than with short-chain ester substrates. The enzyme accepted only nonbulky primary amines as substrates. 相似文献
The shrinkage behavior of fine zirconia powders containing 2.9 and 7.8 mol% Y2O3 was investigated to clarify the effect of Y2O3 concentration on the initial sintering stage. The shrinkage of powder compact was measured under both conditions of constant rates of heating (CRH) and constant temperatures. CRH measurements revealed that when the Y2O3 concentration of fine zirconia powder increased, the starting temperature of shrinkage shifted to a high temperature. Isothermal shrinkage measurements revealed that the increase in Y2O3 concentration causes the shrinkage rate to decrease. The values of activation energy ( Q ) and frequency-factor term (β0) of diffusion at initial sintering were estimated by applying the sintering-rate equation to the isothermal shrinkage data. When the Y2O3 concentration increases, both Q and β0 of diffusion increase. It is, therefore, concluded that the increase in Y2O3 concentration of fine zirconia powder decreases the shrinkage rate because of increasing Q of diffusion at the initial stage of sintering. 相似文献
Anatase-type TiO2 powder containing sulfur with absorption in the visible region was directly formed as particles with crystallite in the range 15–88 nm by thermal hydrolysis of titanium(III) sulfate (Ti2(SO4)3) solution at 100°–240°C. Because of the presence of ammonium peroxodisulfate ((NH4)2S2O8), the yield of anatase-type TiO2 from Ti2(SO4)3 solution was accelerated, and anatase with fine crystallite was formed. Anatase-type TiO2 doped with ZrO2 up to 9.8 mol% was directly precipitated as nanometer-sized particles from the acidic precursor solutions of Ti2(SO4)3 and zirconium sulfate in the presence and the absence of (NH4)2S2O8 by simultaneous hydrolysis under hydrothermal conditions at 200°C. By doping ZrO2 into TiO2 and with increasing ZrO2 content, the crystallite size of anatase was decreased, and the anatase-to-rutile phase transformation was retarded as much as 200°C. The anatase-type structure of ZrO2-doped TiO2 was maintained after heating at 1000°C for 1 h. The favorable effect of doping ZrO2 to anatase-type TiO2 on the photocatalytic activity was observed. 相似文献
Summary
In order to obtain materials with nanopores which will be applicable for many fields, the structures of the cured blends of phenolic resin (PhN), poly(methyl methacrylate) (PMMA) and curing agent were studied. After PMMA was extracted from cured blends, the structures of cured phenolic resins were observed with SEM. As a results, it was found that nanosized continuous pore structures were formed in extremely wide composition region if curing temperature was high. 相似文献
In recent years, a lot of attentions have been paid for a development of water-free polymer electrolyte membranes fuel cells (PEMFC) at intermediate temperatures (above 100 °C) because of many technological advantages of higher temperature operation. However, the proton conductivity of conventional polymer membranes under water-free condition is usually very low and the polymeric membranes are not stable at higher temperatures. So, the development of non-hydrous proton conducting membrane under water-free condition has been a state of the art issue in the advanced PEMFC technology. In this study, non-hydrous protonic conducting material was prepared by the mixing of acidic surfactant of mono-dodecylphosphate (MDP) and organic base of benzimidazole (BnIm). The proton conductivity and thermal stability of MDP-BnIm mixed material increased with the mixing ratio of BnIm. Maximum proton conductivity of MDP-BnIm mixed material (BnIm mixing ratio of 200 wt.%. vs. MDP) was found to be 1×10−3 S cm−1 at 150 °C under water-free condition. 相似文献
Using Bogoliubov-de Gennes equation, we study quasiparticle excitations in layered superconductors in the presence of a straight vortex line which is parallel to the layers. The lowest bound state is shown to have energy eigenvalue of the order of magnitude , the energy gap, in contrast to the corresponding value 2/EF when the line is perpendicular to the layers. 相似文献
Single-atom (SA) catalysts exhibit high activity in various reactions because there are no inactive internal atoms. Accordingly, SA cocatalysts are also an active research fields regarding photocatalytic hydrogen (H2) evolution which can be generated by abundant water and sunlight. Herein, it is investigated whether 10 transition metal elements can work as an SA on graphitic carbon nitride (g-C3N4; i.e., gCN), a promising visible-light-driven photocatalyst. A method is established to prepare SA-loaded gCN at high loadings (weight of ≈3 wt.% for Cu, Ni, Pd, Pt, Rh, and Ru) by modulating the photoreduction power. Regarding Au and Ag, SAs are formed with difficulty without aggregation because of the low binding energy between gCN and the SA. An evaluation of the photocatalytic H2-evolution activity of the prepared metal SA-loaded gCN reveals that Pd, Pt, and Rh SA-loaded gCN exhibits relatively high H2-evolution efficiency per SA. Transient absorption spectroscopy and electrochemical measurements reveal the following: i) Pd SA-loaded gCN exhibits a particularly suitable electronic structure for proton adsorption and ii) therefore they exhibit the highest H2-evolution efficiency per SA than other metal SA-loaded gCN. Finally, the 8.6 times higher H2-evolution rate per active site of Pd SA is achieved than that of Pd-nanoparticles cocatalyst. 相似文献
Epilepsy is a neurological disorder that may affect the autonomic nervous system (ANS) from 15 to 20 min before seizure onset, and disturbances of ANS affect R–R intervals (RRI) on an electrocardiogram (ECG). This study aims to develop a machine learning algorithm for predicting focal epileptic seizures by monitoring R–R interval (RRI) data in real time. The developed algorithm adopts a self-attentive autoencoder (SA-AE), which is a neural network for time-series data.
The results of applying the developed seizure prediction algorithm to clinical data demonstrated that it functioned well in most patients; however, false positives (FPs) occurred in specific participants. In a future work, we will investigate the causes of FPs and optimize the developing seizure prediction algorithm to further improve performance using newly added clinical data.
In this article, we review the growth of AROB conferences, and assess the various contributions, which have covered digital
life, the artificial brain, artificial society, and evolutionary robots, etc. We analyze the relations between artificial
life, complexity, and intelligent robots, and finally give our view of the expected future of AROB.
This work was presented in part at the 5th International Symposium on Artificial Life and Robotics, Oita, Japan, January 26–28,
2000 相似文献