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11.
12.
One-pot polymerization of polyimide from 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (BPDA) and 4,4′-oxydianiline (ODA) was examined. The equilibrium in the polyimide with water was examined in detail in p-chlorophenol solution during the polymerization. The equilibrium constant was expressed by log K = 1.50 + 1433 (1/T). The polymerization reaction is exothermic. The molecular weight increased with decrease of temperature. © 1996 John Wiley & Sons, Inc. 相似文献
13.
The effect of chitosan feeding (for 21 days) on intestinal bile acids was studied in male rats. Serum cholesterol levels in
rats fed a commercial diet low in cholesterol were decreased by chitosan supplementation. Chitosan inhibited the transformation
of cholesterol to coprostanol without causing a qualitative change in fecal excretion of these neutral sterols. Increased
fiber consumption did not increase fecal excretion of bile acids, but caused a marked change in fecal bile acid composition.
Litcholic acid increased sigificantly, deoxycholic acid increased to a leasser extent, whereas hyodeoxycholic acid and the
6β-isomer and 5-epimeric 3α-hydroxy-6-keto-cholanoic acid(s) decreased. The pH in the cecum and colon became elevated by chitosan
feeding which affected the conversion of primary bile acids to secondary bile acids in the large intestine. In the cecum,
chitosan feeding increased the concentration of α-,β-, and ω-muricholic acids, and lithocholic acid. However, the levels of
hyodeoxycholic acid and its 6β-isomer, of monohydroxy-monoketo-cholanoic acids, and of 3α, 6ξ, 7ξ-trihydroxy-cholanoic acid
decreased. The data suggest that chitosan feeding affects the metabolism of intestinal bile acids in rats. 相似文献
14.
Single-walled carbon nanotube networks grown on SiO2 pillars were studied by means of scanning photoemission microscopy. The individual nanotubes or nanotube bundles growing from the pillar tops were observed in C 1s images. Band bending near catalytic Fe/nanotube contacts in an end-bonded configuration was studied by measuring C 1s spectra along the tube axes. Within our experimental resolution, no band bending was observed. This implies that the depletion width is less than the spatial resolution of the scanning photoemission microscope (90 nm) or that the amount of the band bending is less than 0.1 eV. 相似文献
15.
Masahiro Kato Kazuaki Nakagawa Kenji Essaki Yukishige Maezawa Shin Takeda Ryosuke Kogo Yoshikazu Hagiwara 《International Journal of Applied Ceramic Technology》2005,2(6):467-475
We have discovered a series of lithium-containing oxides that immediately react with ambient carbon dioxide (CO2 ) up to 700°C. The products react and return reversibly to the oxides at a temperatures higher than about 700°C. The absorption capacity surpasses that of other CO2 absorbents by a factor of 10. Utilizing these absorbents, the possibility of a CO2 separation system that operates at around 500°C is proposed. It is generally believed that a CO2 separation process operable at temperatures higher than 500°C has the special benefit of a small energy penalty. Moreover, the absorption also proceeds at ambient temperature in the atmospheric environment. This property offers the possibility of many other applications, such as air cleaners or cartridges. Therefore, we think these materials have the potential to make a valuable contribution to the realization of CO2 emission control. 相似文献
16.
Xiande Shen Norihiko Sugie Qian Duan Yoshikazu Kitajyo Toshifumi Satoh Toyoji Kakuchi 《Polymer Bulletin》2005,55(5):317-322
Summary The reaction of cellulose with N-carbonyl α-amino acid ester 1 leading to cellulose carbamate 2 was carried out in N,N-dimethylacetamide at 100 °C. For N-carbonyl L-leucine ethyl ester (1a), the degree of the carbamate substituent (DS) in 2a was 2.5 for [1a]/[glucose units in cellulose] = 3.0 and reached ca. 3.0 for [1a]/[glucose units in cellulose] = 4.0. Cellulose carbamate 2a was highly soluble in not only aprotic polar solvents but also other organic solvents such as ethyl ether and methyl alcohol.
The chiral discrimination ability of 2a was higher than those of the cellulose carbamates having L-phenylalanine and L-aspartic acid moieties. 相似文献
17.
Kiyoshi Okada Yu-Ichiro Shimizu Yoshikazu Kameshima Akira Nakajima 《Journal of Porous Materials》2005,12(4):281-291
Composites of carbon/zeolite with corrugated structures were prepared by carbonization, steam activation and/or hydrothermal treatment of corrugated paper. No zeolite formation resulted from conventional hydrothermal treatment of the carbonized and activated samples in NaOH solution but zeolite Na P1 was formed by addition of silica to the solution. By contrast, zeolites Na P1 and Na A were formed by the in-situ crystallization method (hydrothermal treatment of solid samples impregnated with NaOH solution). With higher impregnating NaOH concentrations, longer reaction times and higher reaction temperatures, the products changed to sodalite- and cancrinite-type compounds. Hydrothermal treatment was effective in increasing the specific surface area of the products by the formation of zeolite from amorphous calcium aluminosilicate, and also increased the mechanical strength by gluing together the carbon fibers in the samples. The resulting samples showed enhanced adsorption for polar molecules such as ammonia, water vapor and methanol due to the formation of composites of activated carbon with hydrophilic zeolites. 相似文献
18.
Jun Nakamura Yuusuke Maruyama Genichi Tajima Makiko Suwa Chikara Sato 《International journal of molecular sciences》2022,23(6)
The Ca2+-ATPase is an integral transmembrane Ca2+ pump of the sarcoplasmic reticulum (SR). Crystallization of the cytoplasmic surface ATPase molecules of isolated scallop SR vesicles was studied at various calcium concentrations by negative stain electron microscopy. In the absence of ATP, round SR vesicles displaying an assembly of small crystalline patches of ATPase molecules were observed at 18 µM [Ca2+]. These partly transformed into tightly elongated vesicles containing ATPase crystalline arrays at low [Ca2+] (≤1.3 µM). The arrays were classified as ‘’tetramer’’, “two-rail” (like a railroad) and ‘’monomer’’. Their crystallinity was low, and they were unstable. In the presence of ATP (5 mM) at a low [Ca2+] of ~0.002 µM, “two-rail” arrays of high crystallinity appeared more frequently in the tightly elongated vesicles and the distinct tetramer arrays disappeared. During prolonged (~2.5 h) incubation, ATP was consumed and tetramer arrays reappeared. A specific ATPase inhibitor, thapsigargin, prevented both crystal formation and vesicle elongation in the presence of ATP. Together with the second part of this study, these data suggest that the ATPase forms tetramer units and longer tetramer crystalline arrays to elongate SR vesicles, and that the arrays transform into more stable “two-rail” forms in the presence of ATP at low [Ca2+]. 相似文献
19.
Natural graphite particles with high crystallinity sieved to obtain a particle size range of under 63 μm were ground with a ball mill, under various well-controlled grinding atmospheres such as N2, O2, He, H2, and vacuum. The ratio, Xdif50/Xst50, i.e. between the 50 wt.% Stokes diameter and the 50 wt.% laser diffraction diameter, of the ground particles, was used as an index of the flakiness of the particles. The specific resistance of films composed of the ground graphite particles was systematically measured. The rate of reduction in the size of the particles by grinding was slow under an O2-rich atmosphere such as 100% O2 and dry air. On the other hand, it was relatively fast in vacuum, or under an N2 or He atmosphere, and a gas mixture of 99% N2 and 1% O2. The rate of size reduction by grinding under a H2 atmosphere was intermediate. In our experimental conditions, the flakiness of the ground particles increased with the decrease in the particles’ sizes. The electrical conductivity of the ground particles, however, tended to decrease with the decrease in their sizes. Under the condition that the Stokes diameter of the ground particles remains constant, the electrical conductivity of films made from the ground particles increases with the increase in the flakiness of the particles. It was finally determined from our systematic grinding experiments that small flaky particles, which had a size, Xst of ∼1 μm, with a high electrical conductivity can be produced by grinding in a gas mixture of 99% N2 and 1% O2. In this case, the flaky shape of the ground particles was visually confirmed by scanning electron microscopy. 相似文献
20.
Yukitoshi Takeshita Takuya Kamisho Seizo Sakata Takashi Sawada Yoshikazu Watanuki Ryuichi Nishio Toshinobu Ueda 《Journal of Coatings Technology and Research》2013,10(4):503-514
To improve alkaline resistance, a newly mixed powder coating film using thermoplastic polyethylene terephthalate (PET) was investigated. Two kinds of polyvinyl butyral (PVB) and two kinds of polyamide (PA) were chosen as the secondary polymer. The melting temperatures (T ms) of these materials were lower than that of primary PET polymer so the mixed powder coating was able to form a dual phase film through a fluidized bed coating process. Microscope and Fourier transform infrared spectroscopy (FTIR) observations revealed that the dual phase structure was indeed successfully formed and there was a secondary layer over the entire surface area of the film. This mixed powder coating film significantly enhanced the alkaline resistance to an environment filled with NaOH solution at 40°C in which a secondary material would be effective in protecting the film. With regard to both alkaline resistance and film formability, PET/PVB was superior to the PET/PA mixture. 相似文献