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排序方式: 共有74条查询结果,搜索用时 907 毫秒
1.
Graft copolymerization of acrylonitrile onto a soluble wool keratin derivative was studied with the reduced and carboxymethylated low-sulfur protein fraction from wool. Copolymerization was carried out under a variety of conditions with a redox system of (NH4)2S2O8–Na2SO3 in 60% (w/w) aqueous ZnCl2 solution at 10°C. Monomer conversions higher than 90% were obtained by the stepwise addition of initiator. The graft products were successfully separated into grafted copolymer and homopolyacrylonitrile (PAN) by fractional precipitation or solvent extraction with DMF. Grafted PAN were isolated by acid hydrolysis of the keratin backbone. Characterization of grafted and homo-PAN was carried out by IR spectroscopy, amino acid endgroup analysis, and viscometry. On the basis of the results, effects of polymerization conditions on grafting parameters were discussed. Membranes were prepared from 60% aqueous ZnCl2 solution by using ice-cold water as the regenerating medium. All the membranes formed from the graft products were transparent. Observation by scanning electron microscopy showed that the surface consisted of rather spherical keratin domains regularly distributed in the PAN matrix. Selective hydrolysis of the keratin domains allowed a new type of porous PAN membrane to be obtained, with the inner walls of the pores being charged with amino acid residues attached to PAN chains as the endgroup. 相似文献
2.
Summary
A series of cellulose esters bearing olig(oxyethylene)s with different degree of substitution (DS) and different length of
the oxyethylene chain were synthesized by a homogeneous reaction of cellulose with corresponding monofunctional acid chloride
in a 10% LiCl-dimethyl acetoamide (DMAc) solution. The effect of total DS value on the solubility of the derivatives in aqueous
solution was investigated. It was found that the lower limit DS value for both water-soluble and amphiphilic derivatives decreases
with increasing length of oxyethylene chains. The amphiphilic derivatives, which are soluble in both water and chloroform,
precipitate out of aqueous solution on heating without gel forming, such a phase transition behavior was studied in terms
of DS value, length of oxyethylene and concentration. The precipitation temperature (Tp) of the amphiphilic derivatives is range from 54°C to 96°C. It decreases with increasing the total DS value, and increases
with an increase in the length of oxyethylene chains. The Tp value of the derivatives was found to be almost independent in the concentration range of 1–15 wt %, however the Tp value increases sharply with decreasing polymer concentration when the concentration is lower than 1 wt%.
Received: 29 August 2000/Revised version: 16 October 2000/Accepted: 31 October 2000 相似文献
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Hitoshi Tonomura Masateru Nagae Ryota Takatori Hidenobu Ishibashi Tomonori Itsuji Kenji Takahashi 《International journal of molecular sciences》2020,21(22)
This paper aims to provide a comprehensive review of the changing role of hepatocyte growth factor (HGF) signaling in the healthy and diseased synovial joint and spine. HGF is a multifunctional growth factor that, like its specific receptor c-Met, is widely expressed in several bone and joint tissues. HGF has profound effects on cell survival and proliferation, matrix metabolism, inflammatory response, and neurotrophic action. HGF plays an important role in normal bone and cartilage turnover. Changes in HGF/c-Met have also been linked to pathophysiological changes in degenerative joint diseases, such as osteoarthritis (OA) and intervertebral disc degeneration (IDD). A therapeutic role of HGF has been proposed in the regeneration of osteoarticular tissues. HGF also influences bone remodeling and peripheral nerve activity. Studies aimed at elucidating the changing role of HGF/c-Met signaling in OA and IDD at different pathophysiological stages, and their specific molecular mechanisms are needed. Such studies will contribute to safe and effective HGF/c-Met signaling-based treatments for OA and IDD. 相似文献
7.
Summary
In this work, a series of 2,3-O-methylcellulose (MC) with different DS value were prepared. Its phase transition behavior in aqueous solution was studied
in terms of DS value, concentration and molecular weight. The the following conclusions were obtained. (1) All the 2,3-O-MC samples show no sol-gel transition in aqueous solution despite the molecular weight. (2) No phase separation was observed
for the 2,3-O-MCs with a DS value lower than 1.0, even when the temperature was raised to 95°C. (3) The precipitation temperature is surprisingly
different between 2,3-O-MCs. and other MCs possessing comparable total DS value. (4) The precipitation temperature of 2,3-O-MCs depends on the molecular weight rather than on the concentration.
Received: 3 February 1998/Revised version: 30 March 1998/Accepted: 11 April 1998 相似文献
8.
A three-dimensional (3D) digital holographic display system with image processing is presented. By use of phase-shifting digital holography, we obtain the complex amplitude of a 3D object at a recording plane. Image processing techniques are introduced to improve the quality of the reconstructed 3D object or manipulate 3D objects for elimination and addition of information by modifying the complex amplitude. The results show that the information processing is effective in such manipulations of 3D objects. We also show a fast recording system of 3D objects based on phase-shifting digital holography for display with image processing. The acquisition of 3D object information at 500 Hz is demonstrated experimentally. 相似文献
9.
Ohya Y Miyoshi N Hashizume M Tamaki T Uehara T Shingubara S Kuzuya A 《Small (Weinheim an der Bergstrasse, Germany)》2012,8(15):2335-2340
Divalent DNA-AuNP (gold nanoparticle) conjugates comprising two DNA strands at diametrically opposed positions are prepared. Highly linear 1D and tetragonal lattice-like 2D AuNP arrays are constructed using the conjugates and DNA assemblies based on T- and double-crossover motifs and the Holliday junction. 相似文献
10.
Takahiro Itoh Mutsuo Matsumoto Takeaki Miyamoto Hidematsu Suzuki 《Polymer International》1993,30(3):345-349
Amphiphilic polymers of amylose tri(n-decanoate) (C10AS) and amylose tri(n-octadecanoate) (C18AS) were prepared and examined with respect to their ability to form monolayers at the air-water interface. The surface pressure-area isotherm of C10AS was found to have a plateau region, indicating a monolayer-to-bilayer transition, while the isotherm for C18AS had no such plateau. Transmission electron microscopic observations of the transferred films revealed that C10AS formed a homogeneous monolayer film at a particular point of the π-A isotherm, while C18AS gave no homogeneous film at any point of the isotherm. These results are different from those derived from the corresponding cellulose esters. The differences in the isotherms and fine structures of the transferred films are discussed in terms of the difference in chemical structure between amylose and cellulose. 相似文献