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231.
A solid-state NMR study of cellulose degradation 总被引:1,自引:0,他引:1
Mushtaq Ali David C. Apperley Christian D. Eley Alan M. Emsley Robin K. Harris 《Cellulose (London, England)》1996,3(1):77-90
A series of laboratory-aged transformer insulating papers were investigated using solid-state NMR spectroscopy. Carbon-13 CPMAS, and proton MAS experiments were carried out along with static proton relaxation (T1, and T1) and free induction decay (FID) measurements. Some proton CRAMPS and proton-carbon-13 correlation (WISE) experiments were also undertaken. A change in the proton T1 and FID with ageing was detected. No detectable change was found in the proton T1. Some amorphous cellulose was detected in the carbon-13 spectrum. There was, however, no evidence for a substantial change in the nature of the cellulose with ageing. The carbon-13 spectra from some aged samples showed signals not present in the spectrum from an unaged sample. This was taken to be evidence of chemical degradation. Proton MAS and the WISE exeriment gave some information about the nature of the water in the sample. 相似文献
232.
Vinay Deepak HS Joy A Suryaprakash N Ramanathan KV 《Magnetic resonance in chemistry : MRC》2004,42(4):409-413
A novel method for assigning the resonances in the 13C NMR spectrum of a static liquid crystalline sample in its nematic phase is proposed. The method is based on the fact that the carbon chemical shifts in the isotropic phase and in the oriented phase under static and off-magic angle spinning (OMAS) conditions are uniquely related by the tensorial property of the CSA tensor, requiring just one OMAS spectrum and the assignment in the isotropic phase. A computational procedure is proposed to take into account deviations arising out of non-ideal experimental conditions and the assignments are made by identifying the minimum in the differences in the frequencies between calculated and experimental line positions. Practical implementation of the method has also been demonstrated in the case of the liquid crystal N-(4-ethoxybenzylidene)-4-n-butylaniline. 相似文献
233.
Solid-state 31P NMR spectroscopy was applied to measure the isotropic chemical shifts, chemical shift anisotropies and asymmetry parameters of three phosphorylated amino acids, O-phospho-L-serine, O-phospho-L-threonine and O-phospho-L-tyrosine. The cross-polarization buildup rates and longitudinal relaxation times of 31P and 1H were-determined and compared with the values measured for a triphosphate (GppCH2p) bound to a crystalline protein (Ras). It is shown that the phosphorylated amino acids are well-suited model compounds, e.g. for the optimization of experiments on crystalline proteins. Two-dimensional exchange experiments on O-phospho-L-tyrosine indicate the existence of an exchange between the two different conformations of the molecule. 相似文献
234.
静电纺丝技术制备TiO2@SiO2亚微米同轴电缆与表征 总被引:2,自引:0,他引:2
用静电纺丝技术成功制备出大量的TiO2@SiO2亚微米同轴电缆. 用TGA-DTA, XRD, SEM, TEM, EDS, FTIR分析技术对样品结构和组成进行了系统的表征. 结果表明, 得到的产物为TiO2@SiO2亚微米级同轴电缆, 以无定型SiO2为壳层, 晶态TiO2为芯层, 电缆平均直径450 nm, 壳层厚度90 nm, 电缆长度>300 μm, 同时在样品中发现个别纤维呈现管状结构, 对其形成机理进行了讨论. 相似文献
235.
236.
介绍了天然彩色棉纤维的理化性能,分析了天然彩棉纤维纺纱、织造工艺的主要技术措施,并测试了相应产品的物理机械性能. 相似文献
237.
Chandan Singh Ratan Kumar Rai Arvind M. Kayastha Neeraj Sinha 《Magnetic resonance in chemistry : MRC》2016,54(2):132-135
Ultra fast magic angle spinning (MAS) has been a potent method to significantly average out homogeneous/inhomogeneous line broadening in solid‐state nuclear magnetic resonance (ssNMR) spectroscopy. It has given a new direction to ssNMR spectroscopy with its different applications. We present here the first and foremost application of ultra fast MAS (~60 kHz) for ssNMR spectroscopy of intact bone. This methodology helps to comprehend and elucidate the organic content in the intact bone matrix with resolution and sensitivity enhancement. At this MAS speed, amino protons from organic part of intact bone start to appear in 1H NMR spectra. The experimental protocol of ultra‐high speed MAS for intact bone has been entailed with an additional insight achieved at 60 kHz. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
238.
Solution blow spinning, SBS, a quite novel processing method, was used to obtain poly (ethylene-co-vinyl acetate), EVA, films with controlled surface properties. The influence of the surface characteristics of EVA films on the adhesion of DH5α Escherichia coli was studied. In particular, the initial concentration of the EVA solution to be blow spun was varied in order to get different surface topographies. Considering the potential use of EVA based materials in applications such as food packaging or scaffolds for tissue engineering all factors affecting proliferation of microorganisms on their surfaces should be studied and understood. Structural, morphological and surface characterizations based on the use of infrared spectroscopy, FTIR, scanning electron microscopy, SEM, and contact angle measurements were performed to ascertain the main factor influencing the E. coli adhesion on the EVA films. Roughness data were determined at different scales from 3D surfaces obtained using a stereoscopic reconstruction of SEM images. It was concluded that, depending on the conditions of the SBS process, only variations of topography were found on the EVA films, being therefore the unique cause of different adhesion capacity of E. coli cells. A correlation between roughness and the number of attached E. coli cells showed that the higher the roughness at microscale level the higher the biofilm development, demonstrating that, apart from specific interactions at nanoscale surface, heterogeneity at microscale can greatly modify the antibacterial action. 相似文献
239.
Nanofibrous polysulfone/TiO2 nanocomposites: Surface properties and their relation with E. coli adhesion
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Jorge Teno Gustavo González‐Gaitano Javier González‐Benito 《Journal of Polymer Science.Polymer Physics》2017,55(21):1575-1584
Solution blow spinning, SBS, was used to prepare fibrous films of thermoplastic nanocomposites with potential antibacterial properties based on polysulfone, PSF, filled with well dispersed TiO2 nanoparticles. The PSF/TiO2 nanocomposites were produced with different nanoparticles content up to 10% by weight. A wide characterization was carried out focusing on the morphology at the nanoscale, roughness, contact angles, and surface free energy. Cell adhesion was studied by inspection by scanning electron microscopy (SEM). A uniform dispersion of the nanofiller was achieved, with the nanoparticles evenly embedded in the polymer along the fibers when they were created during the blow spinning process. TiO2 content influenced the topography of the films, most likely due to a direct effect on the solvent evaporation rate. The results obtained pointed out that an increase of the surface hydrophobicity as a result of the increased roughness induced by the presence of TiO2 nanoparticles was the main contribution to the reduction of DH5α Escherichia coli cells adhesion. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1575–1584 相似文献
240.
Yutaka Kawahara Wataru Takarada Masaki Yamamoto Yasuhito Kondo Kohji Tashiro Takeshi Kikutani 《Journal of Macromolecular Science: Physics》2020,59(7):440-456
AbstractVarious types of bicomponent fibers composed of polylactide (PLA) and poly(butylene terephthalate) (PBT) with different molecular weights, arranging the polymers separately in the skin or core, were produced by high-speed melt-spinning. The bicomponent spinning, arranging the PLA with high molecular weight (melt flow rate =1.9?g/10?min, L-lactide content = 98.7%) in the skin and the PBT with low molecular weight (IV = 0.835–0.865 dL/g) in the core, resulted in orientation-induced crystallization in the PLA component at the spinning speed of 2?km/min. This crystallization effect was ascribed to a chain-extending treatment applied to the original PLA (MFR = 4.0?g/10?min) to increase its molecular weight. By the treatment the PLA could crystallize when spun even at 1?km/min in its single-component spinning. On the other hand, the bicomponent spinning system interfered with the orientation-induced crystallization of PBT in the core. As a result, the critical spinning speed needed to generate the orientation-induced crystallization in the core PBT was elevated to 4?km/min. The inferior tensile behavior of the bicomponent fibers, as compared to the single-component PLA or PBT fibers, suggested poor compatibility between PLA and PBT. Transesterification reactions rarely occurred at the interface of the two polymers. The bicomponent fibers prepared from high molecular weight PLA and low molecular weight PBT, however, showed sufficient antibacterial activity and physical properties to be suitable for designing medical clothing materials. 相似文献