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排序方式: 共有730条查询结果,搜索用时 31 毫秒
1.
Kamali Ahangar Ehsan Izanlu Morteza Dolati Khakhian Shabnam Mohamad Abdulmajeed A. Bach Quang-Vu 《Journal of Thermal Analysis and Calorimetry》2021,144(6):2525-2541
Journal of Thermal Analysis and Calorimetry - Thermal microscale gas flow was simulated into a coplanar microchannel was simulated at a broad range of Knudsen numbers. Attempts were made to improve... 相似文献
2.
Activated carbon production from almond shells using phosphoric acid activation agent was achieved by applying both conventional heating and microwave heating in succession. The morphology and surface properties of activated carbon were studied using thermogravimetric and differential gravimetric analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, and Brunauer–Emmett–Teller analysis. A surface area of 1128 m2/g was achieved by optimizing the microwave power (500?W), microwave application time (15?minutes), conventional heating time (45?minutes), conventional heating temperature (500?°C), and the phosphoric acid:sample ratio (0.7:1). An adsorption capacity of methylene blue of 148?mg/g and an iodine value of 791?mg/g was obtained for the prepared activated carbon. 相似文献
3.
In view of immense importance of silylenes and the fact that their properties undergo significant changes on substitution with halogens, here, we have used B3LYP/6-311++G** level of theory to access the effects of 1–4 halogens (X = F, Cl, Br, and I) on four unprecedented sets of cyclopentasilylene-2,4-dienes; with the following formulas: SiC4H3X ( 1 X ), SiC4H2X2 ( 2 X ), SiC4HX3 ( 3 X ), and SiC4X4 ( 4 X ). In going down from F to I, the singlet (s)-triplet (t) energy gap (ΔEs-t, a possible indication of stability), and band gap (ΔEH-L) decrease while nucleophilicity (N), chemical potential (μ), and proton affinity (PA) increase. The overall order of N, μ, and PA for each X is 2 X > 1 X > 3 X > 4 X . Precedence of 2 X over 1 X is attributed to the symmetric cross conjugation in the former. The highest and lowest N are shown by 2 I and 4 F . The trend of divalent angle () for each X is 4 X > 1 X > 3 X > 2 X . The results show that in going from electron withdrawing groups (EWGs) to electron donating groups (EDGs), the ΔEs-t and ΔEH-L decrease while N, μ, and PA increase. Also, rather high N of our scrutinized silylenes may suggest new promising ligands in organometallic chemistry. 相似文献
4.
Behavior of fine crystalline particles of W5Si3 on a beta-Si3N4 substrate at high temperatures was observed by an in situ heating experiment in a transmission electron microscope. Some of the fine particles of W5Si3 moved in a to-and-fro manner. 相似文献
5.
Yozo Miura Hiroyuki Dote Hiroyuki Kubonishi Kenichi Fukuda Tomoko Saka 《Journal of polymer science. Part A, Polymer chemistry》2007,45(6):1159-1169
A dendritic macroinitiator having 16 TEMPO‐based alkoxyamines, Star‐16 , was prepared by the reaction of a dendritic macroinitiator having eight TEMPO‐based alkoxyamines, [G‐3]‐OH , with 4,4′‐bis(chlorocarbonyl)biphenyl. The nitroxide‐mediated radical polymerization (NMRP) of styrene (St) from Star‐16 gave 16‐arm star polymers with PDI of 1.19–1.47, and NMPR of 4‐vinylpyridine from the 16‐arm star polymer gave 16‐arm star diblock copolymers with PDI of 1.30–1.43. The ring‐opening polymerization of ε‐caprolactone from [G‐3]‐OH and the subsequent NMRP of St gave AB8 9‐miktoarm star copolymers with PDI of 1.30–1.38. The benzyl ether linkages of the 16‐arm star polymers and the AB8 9‐miktoarm star copolymers were cleaved by treating with Me3SiI, and the resultant poly(St) arms were investigated by size exclusion chromatography (SEC). The SEC results showed PDIs of 1.23–1.28 and 1.18–1.22 for the star polymers and miktoarm stars copolymers, respectively, showing that they have well‐controlled poly(St) arms. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1159–1169, 2007. 相似文献
6.
Nicolas Meyer Mohamad Nasser Eddine Christelle Delaite Guy Hurtrez Philippe Dumas 《Journal of polymer science. Part A, Polymer chemistry》2003,41(21):3329-3335
The reactions of polystyryllithium and potassium on dimethoxymethyl 1,1‐diphenylethylene derivatives were studied in different solvents. In a polar medium, A3 and A6 star types were formed according to the stoichiometry, whereas in a nonpolar medium, hyperbranched structures were synthesized. Extensions of an already proposed mechanism in polar and nonpolar media were examined. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3329–3335, 2003 相似文献
7.
Yang Ju Yo Hirosawa Masumi Saka Hiroyuki Abé 《International Journal of Infrared and Millimeter Waves》2003,24(3):391-397
We developed a compact equipment working at 94 GHz to replace the commonly used network analyzer for nondestructive testing of materials. The compact equipment was designed to measure the variations in the amplitude and phase of the reflected signal from the material relative to a reference signal. A good accuracy of the amplitude and phase measurement of the equipment was obtained in the confirmative experiments. The distribution of a drop of water in a wood plate is clearly visible in the millimeter wave images obtained by the amplitude and phase measurement. 相似文献
8.
Tomoya Kinumi Kazuo Tsujimoto Mamoru Ohashi Reiko Hara Tomiyuki Hara Koichi Ozaki Miho Saka Yuko Katsuta Akimori Wada Masayoshi Ito 《Photochemistry and photobiology》1993,58(3):409-412
Abstract— 3, 7-Dimethyl-2, 4, 6, 8, 10-dodecapentaenal was synthesized for reconstitution of the retinochrome analog. Its opsin shift was 1000 cm 1 smaller than that of native retinochrome, whose chromophore contains the same number of double bonds. The conformational change from 6-s-trans to 6-s-cis , as figured in a retinal molecule, plays an important role in the formation of the retinochrome analog, based on the estimation of opsin shifts for retinal analogs locked in the 6-s conformation. Thus the conformation of the 6–7 single bond in the native retinochrome was suggested to be 6 -cis . Analysis of the circular dichroic spectra of retinochrome analogs revealed that the 6-s conformation is independent of the appearance of the β-band. The stereoselectivity in the photoisomerization of the retinal analogs by a retinochrome template depends on the hydrophobic binding in the region of the β-ionone ring. 相似文献
9.
Kei Yoshida Junko Kusaki Katsunobu Ehara Shiro Saka 《Applied biochemistry and biotechnology》2005,123(1-3):795-806
Japanese beech (Fagus crenata Blume), its cell wall components, and model compounds were treated by supercritical water (380°C, 100 MPa) for 5 s using a batch-type reactor to investigate the production behavior of low molecular weight organic acids. It was found that cellulose and hemicellulose were decomposed to formic acid, pyruvic acid, glycolic acid, acetic acid, and lactic acid, whereas lignin was barely decomposed to such organic acids under the given conditions. However, after prolonged treatment (380°C, 100 MPa, 4 min) of lignin, some organic acids were recovered owing perhaps to the decomposition of the propyl side chain of lignin. It was additionally revealed that the predominant organic acid recovered was acetic acid, which might be derived from the acetyl group of hemicellulose in Japanese beech. 相似文献
10.
Chemical conversion of various celluloses to glucose and its derivatives in supercritical water 总被引:16,自引:0,他引:16
The supercritical water biomass conversion system was designed and developed in our laboratory. The reaction vessel with cellulose sample was treated with this system at supercritical state of water for a designated period (3–105s) under the conditions of a tin bath temperature of 500°C and pressure of 35MPa. The recovered products of hydrolysates were then analyzed by high performance liquid chromatography. The obtained results indicated that a high amount of glucose and levoglucosan can be achieved from both celluloses I and II for 5–10s supercritical treatment, while that from starch for 3–5s treatment. Although this difference could be due to a difference in the molecular structure between cellulose and starch, a difference between celluloses I and II was not significant. Instead, an accessibility of the water towards cellulose molecules seemed to be significant for their chemical conversion. With the longer treatment, amounts of these compounds observed were decreased due to decomposition. Therefore, it may be concluded that, compared with acid hydrolysis or enzymatic saccharification, cellulose may be hydrolyzed to glucose and its derivatives more or less to the same degree as in corn starch under supercritical state. This finding suggests that the supercritical treatment can overcome the difficulties in hydrolyzing cellulose to glucose, found in the acid hydrolysis or enzymatic saccharification techniques. 相似文献