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21.
Uzawa H Nishida Y Sasaki K Minoura N Kobayashi K 《Chembiochem : a European journal of chemical biology》2003,4(7):640-647
The substrate specificities of three molluscan sulfatases (E.C. 3.1.6.1; snail, abalone, and limpet origins) were investigated with assorted p-nitrophenyl (pNP) di-O-sulfonated beta-D-galactopyranosides and beta-lactosides [3,6-SO(3) Gal (1), 3',6'-SO(3) Lac (2), 4, 6SO(3) Gal (3), 2,6-SO(3) Gal (4), 3,4-SO(3) Gal (5), and 3,6-SO(3) GalNAc (6); Ac, acetyl; Gal, galactose; Lac, lactose] together with mono-O-sulfonated beta-D-galactopyranoside [pNP 3SO(3)-Gal (7)] and tri-O-sulfonated alpha-D-galactopyranoside [2,3,6-SO(3)-alpha-Gal (11)]. Some notable differences between the substrate specificity of the three sulfatases were disclosed; snail sulfatase hydrolyzed the 3O- and 2O-sulfo groups of 1 and 4, respectively, to afford 6SO(3) Gal (9) in high yields, while the abalone enzyme did not act on 4. Only the limpet enzyme could cleave the 3O-sulfo groups of 7 to give pNP beta-galactoside. In contrast, every enzyme could utilize 11 as a good substrate to afford a mixture of 6SO(3)-alpha-Gal (13) and 2,6-SO(3) alpha-Gal (12). None of the enzymes could cleave the O-sulfo groups of 5 and 6, which indicates that a primary 6O-sulfo group tends to promote the enzymatic hydrolysis of O-sulfo groups at the secondary positions. 相似文献
22.
The Mode I fracture energy of a polyurethane adhesive with low Young’s modulus was investigated. Metal adherends in standardized double cantilever beam (DCB) tests are typically too stiff for soft adhesives, making it difficult to measure the fracture energy accurately. However, soft adhesives, such as a single-component polyurethane adhesive tested in this paper, are in high demand in the automobile industry. Thus, accurate measurement techniques must be established. Flexible substrates composed of spring steel were used for the DCB tests to accommodate the deformation of the adhesive layer. First, the applicability of the flexible substrates was discussed using specimens bonded with an epoxy adhesive. For soft adhesives, however, the deformation of the adhesive layer must be considered in the calculation methods of the fracture energy. Although the deformation effect on the DCB tests has been discussed with Winkler’s elastic foundation, the crack length must be measured along with the load and displacement. To overcome the difficulty of measuring the crack length, a calculation method based on Winkler’s elastic foundation was introduced applying the compliance-based beam method (CBBM). Finally, the fracture energy of the polyurethane adhesive was discussed by comparing the calculation methods with and without measuring the crack length. 相似文献
23.
Microwave dielectric properties and crystal structures of Mg0.7Al2.2O4 and Mg0.4Al2.4O4 ceramics with defect structures 下载免费PDF全文
Susumu Takahashi Akinori Kan Hirotaka Ogawa 《Journal of the American Ceramic Society》2017,100(8):3497-3504
Mg0.7Al2.2O4 and Mg0.4Al2.4O4 ceramics with cation vacancies were synthesized using the molten salt method, and the relationships between the microwave dielectric properties and crystal structures of these materials were investigated. The 27Al NMR spectra of these ceramics indicate that the preferential occupation of tetrahedral sites by Al3+ cations was enhanced by the introduction of cation vacancies. The λ values of Mg0.7Al2.2O4 and Mg0.4Al2.4O4 ceramics fired at 1600°C, which correspond to the fraction of Al3+ cations in tetrahedral sites, were 0.37 and 0.60, respectively. Crystal structure refinements using the Rietveld method suggest that cation vacancies are preferentially located at octahedral sites in both ceramics. The εr and Q·f values of a Mg0.7Al2.2O4 ceramic fired at 1600°C were 7.7 and 201 111 GHz, respectively, while those of a Mg0.4Al2.4O4 ceramic fired at 1600°C were 7.5 and 232 301 GHz, respectively. These data demonstrate that the preferential occupation of tetrahedral sites by Al3+ cations following the introduction of cation vacancies enhances the Q·f value. 相似文献
24.
Y. Sekiguchi P. Hemthavy S. Saito K. Takahashi 《Journal of Adhesion Science and Technology》2013,27(23):2615-2626
A theory of adhesion between an elastic beam and a rigid body is proposed using linear beam theory. Normalized force between the elastic beam and the rigid body considering adhesion of the side surface of the elastic beam is investigated theoretically. Adhesion of an elastic beam is important to analyze gecko adhesion, and peeling mechanism of an adhered film. This adhesion is also important in design of grip-and-release devices. The force between an elastic beam and a rigid body is investigated by considering shear force and total energy, and is obtained as a function of the displacement of the elastic beam. The proposed theory is different from Kendall’s thin-film peeling theory in terms of the elastic energy. The proposed theory considers bending elastic energy, whereas Kendall’s theory considers extension elastic energy. Two different contacts, line contact and area contact, are taken into account to discuss the loading and unloading processes in terms of the relation between the force and the displacement. Non-dimensional parameter, which relates to the work of adhesion and the specifications of the elastic beam, is introduced to explain the normalized maximum tensile force. 相似文献
25.
Polycarbonates were synthesized by transesterification polymerization of isosorbide, bisphenol A, and diphenyl carbonate in the presence of n‐BuSn(?O)OH as the catalyst. The polymers were prepared by varying the ratio of the two monomers. The polymers exhibited good thermal stability, rigidity, and strength. The storage moduli for the polymers were 2.6 to 3.2 GPa at 25°C and increased with increasing isosorbide content. The dynamic mechanical analysis indicated that the storage moduli (E′) of the polymers are constant to higher temperatures than that of bisphenol A polycarbonate. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
26.
Fabrication process for picoliter volume SiO2 glass tube array partially embedded in Si wafer was developed. As a template for the glass tubes, macropore array was formed at the surface of n-Si(1 0 0) wafer by photo-assisted electrochemical etching process. The area-selective formation of the array was achieved by applying Au/Cr micropatterns formed at the back-side surface of the substrate as the shade mask, which controls the illumination condition to optimize the etching reaction conditions. Subsequently, surface of the macropores was wet-thermally oxidized to form glass layer, and the bulk Si region was removed by alkaline etching, remaining the “glass tubes”. As a result of complete removal of the bulk Si, released glass tubes were obtained. By partial removal of the bulk Si part, the glass tubes were exposed, fixed in the remaining Si substrate in the form of well-ordered array. It was confirmed that the depth, the exposed region and the wall thickness of each glass tube were controllable by adjusting the parameters such as the duration of the Si electrochemical etching, the alkaline etching and the wet-thermal oxidation, respectively. In order to demonstrate microreaction in the glass tube, aqueous rhodamine B solution was injected into the tubes and excitation light was irradiated to them. As a result, the fluorescence of rhodamine B was clearly detected, confirming the applicability of the glass tubes for various kinds of devices and systems such as microreactors. 相似文献
27.
This article proposes a new method to measure the creep strength of adhesively bonded joints using a hydro-pneumatic testing machine and a specimen holder, on which multi-specimens can be mounted in one testing machine. Creep tests were conducted on stainless steel butt joints bonded with epoxy adhesives. A hydro-pneumatic loading system was introduced to avoid successive failures of multi-specimens as well as to achieve a stable and constant loading through the experiments. Even after a failure occurs in one of the joints and thus generates an impact, the loading system is capable of absorbing the shock so that the other remaining joints do not fail simultaneously. It was experimentally verified that choke valves, which were introduced in the hydraulic circuit of the system, worked as a damper when failure occurred. Additionally, it was established that automatic reloading to the remaining specimens after the failure was short enough compared with the creep rupture time. As this new method relates to the efficiency of creep testing, the utility of the proposed approach with the multi-specimen setup has been verified. 相似文献
28.
Kazuyuki Chihara Caroline F. Mellot Anthony K. Cheetham Shani Harms Hirotaka Mangyo Masaki Omote Ryuichi Kamiyama 《Korean Journal of Chemical Engineering》2000,17(6):649-651
Equilibrium and isosteric heat of adsorption for the system of chloroform and USY-type zeolite were studied. The USY-type zeolite (PQ Co., SiO2/Al2O3=70) was used both as a pure crystalline powder and as granulated particles with binder. Chloroform was reagent grade. The adsorption equilibria were measured using a gravimetric method and were expressed as isotherms. A chromatographic method (i.e. pulse response of chloroform through the USY column with helium carrier) was used to get the initial slope of the isotherms. In the simulation, the GCMC method was used to calculate amounts adsorbed for various conditions. FF parameters were confidently applied. And modified structure model was effective for simulation. This paper was presented at The 5th International Symposium on Separation Technology-Korea and Japan held at Seoul between August 19 and 21, 1999. 相似文献
29.
Water Vapor Adsorption and Desorption on Materials Hydrothermally Solidified from Clay Minerals 总被引:1,自引:0,他引:1
Water vapor isotherms were examined and 1 H-magic-angle spinning nuclear magnetic resonance (1 H-MAS NMR) analysis was conducted to determine the amount of water vapor adsorbed and desorbed on hydrothermally solidified materials derived from clay minerals. The amount of water vapor adsorbed and desorbed decreased with increasing mesopore volume of the materials, which disagreed with the estimation obtained using the Kelvin equation. Water vapor was physisorbed on alumina-like sites in the materials. An increase in the binding energy between water vapor and the materials led to an improvement in the water vapor adsorption–desorption properties of materials. 相似文献
30.
J. Chen T. Sekiguchi R. Xie P. Ahmet T. Chikyo D. Yang S. Ito F. Yin 《Scripta materialia》2005,52(12):1412-1215
Recombination activity of small-angle grain boundaries (SA GBs) in multicrystalline silicon (mc-Si) was studied by means of electron-beam-induced current (EBIC) technique. In the as-grown mc-Si, the EBIC contrasts of special Σ and random GBs were weak at both 300 and 100 K, whereas those of SA GBs were weak (<3%) at 300 K and strong (30–40%) at 100 K. In the contaminated mc-Si, SA GBs showed stronger EBIC contrast than Σ and R GBs at 300 K. It is indicated that SA GBs possess high density of shallow levels and are easily contaminated with Fe compared to other GBs. 相似文献