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Precise determination of d-spacings and compositional ratio of cellulose Iα and Iβ in various native cellulose samples was successfully carried out by synchrotron-radiated X-ray diffraction and time-of-flight
(TOF) neutron diffraction from quasi-powder specimens. X-ray diffraction peaks were separated by the deconvolution method
using six types of profile function: Gaussian, Lorentzian, intermediate Lorentzian, modified Lorentzian, pseudo-Voigt, and
Pearson VII. In terms of R-factors, the pseudo-Voigt function gave the best fit with the observation, and was used for determination
of d-spacings. The numerical results for Valonia cellulose were: dIα (1 0 0) = 0.613 nm; dIβ (1 1 0) = 0.603 nm; dIβ (1 1 0) = 0.535 nm; dIα (0 1 0) = 0.529 nm; Iα content = 0.65. The differences determined between dIα (1 0 0) and dIβ (1 1 0) and between dIβ (1 1 0) and dIα (0 1 0) were similar to those previously reported. Comparison between unresolved peaks for the two types of cellulose samples
revealed a small but definite difference between dIα (1 1 0) and dIβ (2 0 0). The TOF neutron diffractometry using deuterated samples confirmed this difference.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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SYNTHESIS AND CHARACTERIZATION OF POLY(ASPARTIC ACID) AND ITS DERIVATIVES AS BIODEGRADABLE MATERIALS
TAKESHI NAKATO KYOKO ODA MASAKO YOSHITAKE MASAYUKI TOMIDA TOYOJI KAKUCHI 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(7-8):949-961
ABSTRACT Three types of modified poly(aspartic acid)s, such as poly(aspartic acid-co-aminocarboxylic acid) (4), alkylamine modified poly(aspartic acid) (5) and crosslinked poly(aspartic acid) (6), were synthesized and calcium-ion chelating ability, hygroscopicity and water absorption were evaluated. The calcium-ion chelating ability of 4 depended on the kind of aminocarboxylic acids and the content of aminocarboxylic acid in the copolymer. The highest value was 3 times higher than that of poly(acrylic acid) with a Mw of 14000. The highly modified PASP, e.g., 50 mol% lauryl amine modified poly(aspartic acid), showed the highest by grogroscopicity among homopoly(aspartic acid)s and modified poly(aspartic acid)s. The maximum swelling of poly(aspartic acid) hydrogel prepared by the γ-irradiation of homopoly(as-partic acid) was 3400 g-deionized water/g-dry hydrogel. 相似文献
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YOSHIHISA FUJIWARA JUN HAMADA TAKESHI AOKI TAKASHI SHIMIZU YOSHIFUMI TANIMOTO HIROAKI YONEMURA 《Molecular physics》2013,111(9):1405-1411
High magnetic field dependence of lifetimes of methylene-chain-linked radical ion pairs (RIPs) generated by photo-induced electron transfer from zinc(II) porphyrin to viologen has been confirmed in aqueous acetonitrile using a pulse magnet-laser flash photolysis apparatus. In the case of a short methylene chain it was first revealed that the dependence was definitely different from that for a long one, and was characterized by a reversal in the dependence. In addition to a long lifetime independent of the magnetic field, RIP in fields above 7T exhibited short lifetimes that depended on the field. These results were interpreted not only by spin-lattice (longitudinal) relaxation but also by spin-spin (transverse) relaxation in RIPs. 相似文献
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Structural changes in never- dried, disintegrated bacteria l cellulose by treatment with aqueous NaOH were examined by electron microscopy, X-ray diffractometry and acid hydrolysis behaviour and compared with those of cotton cellulose. The microfibril kept its fibrillar morphology after treatment with NaOH solutions of less than 9% (w/w), but changed into irregular aggregates when treated with NaOH above 12% (w/w), corresponding to the crystal conversion to cellulose II. The crystallinity of the resulting cellulose II was very low after a brief alkali treatment, but was increased significantly by elongated treatment (up to 10 days). In contrast, cotton cellulose was converted to cellulose II of fairly high crystallinity by alkali treatment of as little as 3 min duration, and the crystallinity did not change with longer treatments. The leveling-off degree of polymerization (LODP) of bacterial cellulose was decreased from 150 to 50 by 18% (w/w) NaOH treatment, while that of cotton linter decreased from 260 to 70. These characteristic differences between cotton linter cellulose and bacterial cellulose can be ascribed to a basic difference in microfibrillar organization in these materials: the microfibrils in cotton cellulose are in close contact with neighbouring microfibrils having opposite polarity, and in bacterial cellulose are isolated from each other and require chain folding to form the antiparallel cellulose II crystal 相似文献
7.
Two homologous series of regio- selectively sub stituted cellulose: 3-O-benzyl-2, 6-di-O-pivaloyl derivatives (Series 1) and 2,3,6-tri-O-acetyl derivatives (Series 2) up to an eicosamer (DP = 20), were synthesized for the first time by elongation of the carbohydrate chain from cellooctaose derivative 5 and subsequent deprotection. Some changing properties of the homologous series with increasing DP were examined. Gel permeation chromatography (GPC) analysis for series 1 and 2 indicated that plots of log M vs retention time gave a straight line. The plots of [M]n/n vs (n – 1)/n (where [M]n is the molecular rotation for an oligomer with DP = n) up to a hexadecamer 9 in series 2 gave straight lines, although the result for the eicosamer 11 deviated somewhat from the line 相似文献
8.
Application of Waste Liquids Containing Lignin from Pulp-producing Industry to CWM Preparation 总被引:1,自引:0,他引:1
IntroductionSince the first oil crisis in1 973,coal conver-sion technologies such as coal gasification,lique-faction and combustion have been studied in orderto use coal as an alternative resource of oil.In thiscontext,coal water mixtures( CWMs) are attrac-tive because they are more transportable andstorable than non- treated coal for being used as analternative resource of oil.To prepare CWMs witha higher energy density,the coal concentrationshould be high in CWMs.However,high coal con-ce… 相似文献
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TAKASHI KAWAKAMI TAKESHI TANIGUCHI YASUTAKA KITAGAWA YU TAKANO HIDEMI NAGAO KIZASHI YAMAGUCHI 《Molecular physics》2013,111(16):2641-2652
The effective exchange integrals (J ab(M)) between two cation radicals of title compounds in the Heisenberg model were calculated by ab initio molecular orbital (MO) and density functional theory (DFT) methods, together with hybrid DFT methods. The J ab(D) values between two dimer mono-cation radicals were also estimated assuming J ab(D) = J ab(M)/2. It is found that the spin lattice obtained by the ab initio method is square planar and linear in BEDT-TTF and BETS planes, respectively, although other previous calculations show that spin lattice in the BEDT-TTF plane is a triangular one. The J ab and overlap integrals (sab ) values by the ab initio methods were used to determine transfer integral (tab ) and Coulomb repulsion (Ucff ) parameters of the Hubbard model, which were compared with those of the previous results. Implications of the calculated results are discussed in relation to the spin-mediated mechanism for superconductivity. 相似文献
10.
An electron spin resonance (ESR) study on UV-photolysis of human and canine lens nuclei was carried out at room temperature. (1) At least two kinds of free radical signals, a narrow signal and a broad one, were detected at around g = 2.004. The latter is similar to that observed upon irradiation of a model solution containing both tryptophan and cysteine. (2) Two spin adducts were detected upon irradiation of canine lens in the presence of a spin trapping reagent (DMPO, 5,5-dimethyl-1-pyrroline N-oxide), i.e. a spin adduct of sulphur-centered radical (most likely glutathione thiyl radical) and the protonated adduct of solvated electron (presumably due to photo-ionization of tryptophan). (3) A tentative and simplified reaction mechanism of UV-induced damage is discussed on the basis of these observations. 相似文献