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Search Results: 1 - 10 of 7364 matches for " Renchuan You "
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Gelation of Antheraea pernyi Silk Fibroin Accelerated by Shearing  [PDF]
Yu Liu, Siyong Xiong, Renchuan You, Mingzhong Li
Materials Sciences and Applications (MSA) , 2013, DOI: 10.4236/msa.2013.46047

The rapid manufacture of silk fibroin gels in mild conditions is an important subject in the field of silk-based biomaterials. In this study, the gelation of Antheraea pernyi silk fibroin (ASF) aqueous solution was induced by shearing, without chemical cross-linking agents. Simple shearing controlled and accomplished the steady and rapid conformational transition to β-sheets with ease. The conformational transformation and rapid gelation mechanisms of ASF induced by shearing were tracked and analyzed by circular dichroism spectrometry, Fourier transform infrared spectroscopy and X-ray diffractometry, then compared with Bombyx mori silk fibroin (BSF). ASF quickly formed hydrogels within 24 - 48 h after shearing under different shearing rates for 30 - 90 min, resulting in sol-gel transformation when the β-sheet content reached nearly 50%, which is the minimum content needed to maintain a stable hydrogel system in ASF. The gel structures remained stable once formed. The rapid gelation of ASF through shearing compared with BSF was achieved because of ASF’s alternating polyalanine-containing units, which tend to form α-helix structures spontaneously. Further, the entropic cost during the conformational transition from the α-helix to the β-sheet structure is less than the cost of the transition from the random coil

The degradation behavior of silk fibroin derived from different ionic liquid solvents  [PDF]
Renchuan You, Ying Zhang, Yu Liu, Guiyang Liu, Mingzhong Li
Natural Science (NS) , 2013, DOI: 10.4236/ns.2013.56A002

Establishing an appropriate degradation rate is critical for tissue engineering scaffolds. In this study, the degradation rate of silk fibroin three-dimensional scaffolds was regulated by changing the molecular weight (MW) of the silk fibroin. The solubility of silk fibroin depends primarily on the ionic ability of the slovent to dissolve silk fibroin, therefore, we regulated the MW of the silk fibroin using LiBr, Ca(NO3)2 and CaCl2 to dissolve the silk fibers. SDS-PAGE analysis showed that the MW of the CaCl2-derived silk fibroin was lower than the MW produced using LiBr and Ca(NO3)2. In vitro and in vivo degradation results showed that the scaffolds prepared by low-MW silk fibroin were more rapidly degraded. Furthermore, FTIR and amino acid analysis suggested that the amorphous regions were preferentially degraded by Collagenase IA, while the SDS-PAGE and amino acid analysis indicated that the scaffolds were degraded into polypeptides (mainly at 10-30 kDa) and amino acids. Because the CaCl2-derived scaffolds contained abundant low MW polypeptides, inter-intramolecular entanglement and traversing of molecular chains in the crystallites reduced, which resulted in rapid degradation. The in vivo degradation results suggested that the degradation rate of the CaCl2-derived scaffolds was better matched to dermis regeneration, indicating that the degradation rate of silk fibroin can be effectively regulated by changing the MW to achieve a suitable dermal tissue regeneration rate.

Preparation of Silk Fibroin Microspheres and Its Cytocompatibility  [PDF]
Jing Qu, Lu Wang, Yongpei Hu, Lingshuang Wang, Renchuan You, Mingzhong Li
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2013, DOI: 10.4236/jbnb.2013.41011
Abstract: The goal of this proof-of-concept study was the fabrication of porous silk fibroin (SF) microspheres which could be used as cell culture carriers under very mild processing conditions. The SF solution was differentiated into droplets which were induced by a syringe needle in the high-voltage electrostatic field. They were collected and frozen in liquid nitrogen and water in droplets formed ice crystals which sublimated during lyophilization and a great quantity of micropores shaped in SF microspheres. Finally, the microspheres were treated in ethanol so as to transfer the molecular conformation into β-sheet and then they were insoluble in water. SF particles were spherical in shape with diameters in the range of 208.4 μm to 727.3 μm, while the pore size on the surface altered from 0.3 μm to 10.7 μm. In vitro, the performances of SF microspheres were assessed by culturing L-929 fibroblasts cells. Cells were observed to be tightly adhered and fully extended; also a large number of connections were established between cells. After 5-day culture, it could be observed under a confocal laser scanning microscope that the porous microenvironment offered by SF particles accelerated proliferation of cells significantly. Furthermore, porous SF particles with smaller diameters (200 - 300 μm) might promote cell growth better. These new porous SF microspheres hold a great potential for cell culture carriers and issue engineering scaffolds.
The Cytocompatibility of Genipin-Crosslinked Silk Fibroin Films  [PDF]
Lingshuang Wang, Yiyu Wang, Jing Qu, Yongpei Hu, Renchuan You, Mingzhong Li
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2013, DOI: 10.4236/jbnb.2013.43026

There is an increasing demand for crosslinking methods of silk fibroin (SF) scaffolds in biomedical applications that could maintain the biocompatibility, bioactivity as well as improve the water resistance and mechanical properties of SF materials. In this study, SF was crosslinked effectively with genipin which is a naturally occurring iridoid glucoside and the crosslinking mechanism was investigated through FTIR and amino acid analysis. The results showed that genipin could react with the -NH2 groups on the side chains of SF macromolecules and to form inter- and intra-molecular covalent bonds, and improved the stability of SF materials significantly. In vitro, the performances of genipin-crosslinked SF films were assessed by seeding L929 cells and compared with ethanol-processed SF films, glutaraldehyde and polyethylene glycol diglycidyl ether crosslinked ones. The genipin-crosslinked SF films showed a similar affinity to cells as ethanol-processed ones, and a higher bioactivity in promoting cell growth and proliferation, inhibition of cell apoptosis, and maintenance of normal cell cycle compared with glutaraldehyde and polyethylene glycol diglycidyl ether crosslinked SF films. These features, combined with the decrease of brittleness of SF films crosslinked with chemical methods, substantiated genipin as an effective and biocompatible agent for the manufacturing of bioactive SF materials which used as tissue engineering scaffolds and drug delivery carriers.

The Relationship between Secondary Structure and Biodegradation Behavior of Silk Fibroin Scaffolds
Yongpei Hu,Qin Zhang,Renchuan You,Lingshuang Wang,Mingzhong Li
Advances in Materials Science and Engineering , 2012, DOI: 10.1155/2012/185905
Abstract: Silk fibroin has a unique and useful combination of properties, including good biocompatibility and excellent mechanical performance. These features provided early clues to the utility of regenerated silk fibroin as a scaffold/matrix for tissue engineering. The silk fibroin scaffolds used for tissue engineering should degrade at a rate that matches the tissue growth rate. The relationship between secondary structure and biodegradation behavior of silk fibroin scaffolds was investigated in this study. Scaffolds with different secondary structure were prepared by controlling the freezing temperature and by treatment with carbodiimide or ethanol. The quantitative proportions of each secondary structure were obtained by Fourier transform infrared spectroscopy (FTIR), and each sample was then degraded in vitro with collagenase IA for 18 days. The results show that a high content of β-sheet structure leads to a low degradation rate. The random coil region in the silk fibroin material is degraded, whereas the crystal region remains stable and the amount of β-sheet structure increases during incubation. The results demonstrate that it is possible to control the degradation rate of a silk fibroin scaffold by controlling the content of β-sheet structure. 1. Introduction Silk fibroin is a natural protein produced by the domestic silkworm Bombyx mori, which is composed of a heavy-chain (H-chain, 350?kDa), light-chain (L-chain, 25?kDa), and an accessory protein (30?kDa). The amino acid composition of silk fibroin from Bombyx mori consists primarily of glycine, alanine, and serine [1, 2]. The three simple amino acids form the crystalline regions of silk fibroin, while the amino acids with bulky and polar side chains form the amorphous regions [3]. The silk polymorphs include silk I, silk II, and an air/water assembled interfacial silk III [1, 4]. The molecular conformation of silk II is antiparallel β-sheet structure. Silk fibroin has been used for centuries in production of textiles and clinical sutures [5]. Silk fibroin materials can support the attachment, proliferation, and differentiation of primary cells and cell lines [6–8] and is easily prepared as films [9], porous scaffolds [10], gels [11], and mats [12]. The impressive cytocompatibility and malleability of SF materials make silk a popular starting material for tissue engineering scaffolds used in skin, bone, blood vessel, ligament, and nerve tissue regeneration [13–15]. An ideal tissue engineering scaffold is nonimmunogenic and nontoxic but is biocompatible and supports cell adhesion, proliferation, and
Reflection and transmission of water waves past a rigid vertical thin barrier in a two-layer fluid

You Yunxiang,Miao Guoping,Cheng Jiansheng,Zhu Renchuan,

力学学报 , 2005,
Abstract: The interaction of water waves for both surface- and internal-wave modes with a rigid vertical thin barrier in a two-layer fluid was examined. The theoretical solutions were obtained by an eigenfunction expansion method for the reflected and transmitted energies for waves of both modes. It is shown that for the incident wave of each mode, the energies of the reflected and transmitted waves of the other mode are equal. The reflected and transmitted energies, as well as the hydrodynamic force on the barrier due to incident waves of both surface- and internal-wave modes were computed for two types of structures which are a bottom-touched barrier and a surface-piercing barrier respectively. The results indicate that density stratification can have a relative large effect on the reflection, transmission and hydrodynamic characteristics of the barrier over a wide range of frequencies. In particular, when an end of the barrier is located on the interface of the two-layer fluid, such an effect is very strong.
Velocity Decomposition Method for Ship Advancing in Calm Water Simulation  [PDF]
Ji Zhao, Renchuan Zhu, Guoping Miao
World Journal of Engineering and Technology (WJET) , 2017, DOI: 10.4236/wjet.2017.54B005
In this study, a viscous-inviscid method based on velocity decomposition is presented. The velocity of the flow field is decomposed into viscous velocity and inviscid velocity, the inviscid velocity is applied for the whole domain, which includes the damping area, and the remaining viscous velocity is just acting on a small domain around the ship hull according to the boundary layer theory. The remaining viscous velocity is computed by a modified N-S equation which coupled the inviscid part, after the inviscid velocity is obtained by solving Euler equation. The simulation of Wigley hull advancing in calm water is accomplished with present method also the decomposed velocity has been studied. The result shows the present method is robust and can be a practical method for partial viscous correction.
Study on Settlement of Xuefuzhuyukoufuye by Method of Membrane Separation

Chai Guoyong,Ma Renchuan,Yu Jiangbo,

世界科学技术-中医药现代化 , 2005,
Abstract: “血府逐瘀口服液”是由桃仁、红花、川芎、赤芍、柴胡等11种中药材并添加蜂蜜配制而成。蜂蜜的加入对复方成份起了絮凝和结团作用,使产品出现沉淀。作者采用平均孔径为 0.45μm、2μm和5μm的微滤膜以及截留分子量为10000和30000道尔顿的超滤膜进行了终端膜分离试验。结果表明膜分离可以使产品得到澄清,分离除去杂质后的口服液产品经高效液相色谱分析,发现其芍药甙浓度提高了2-6%。在试验条件下,求取了膜分离过程的膜通量与污染速度数据,并推断可能的单程膜分离处理量,为放大试验或生产装置选择设计参数提供了参考。本文系攀登计划支持性课题——“膜组件污染与再生过程的实时监测与分析”的应用研究。
Analysis of the Focusing Characteristics of Double Negative Binary Diffractive Lens  [PDF]
Zongxin Wang, Lizhi You
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2010, DOI: 10.4236/jemaa.2010.29072
Abstract: For a compact millimeter wave imaging system it is very important to design every component into small size, for the components in a millimeter wave system are usually much larger than those in an optical imaging system due to rela-tively long wave lengths. In this paper, we suggest a kind of binary diffractive lens (BDL) designed using double nega-tive materials (DNG) as the objective lens for a millimeter wave imaging system. The DNG-BDL has not only the ad-vantage of low profile but also small f number, which will be benefit for constructing a compact millimeter wave imaging system. Several DNG-BDL are designed and analyzed using the FDTD method. The numerical results of the focal plane field of the DNG-BDL are presented, which show that the DNG-BDL with small f number has relatively better focusing characteristic than that of a double positive BDL with same f number.
Prospect of Natural Gas Utilization in China  [PDF]
Wei Huang, Hongjun You
Advances in Chemical Engineering and Science (ACES) , 2011, DOI: 10.4236/aces.2011.12010
Abstract: This paper introduces the source and utility circumstance of natural gas in China. The utility cir-cumstance of natural gas is discussed in detail, such as, natural gas as feedstock is produced to acetylene; natural gas is used to cut metal; natural gas is applied to generate ethylene; natural gas instead of heavy oil is fired to produce chromium trioxide. In so doing, the energy demand of China will be better met with least damage to the environment. According to the full utility of natural gas sources, their good economic and social benefits are obtained.
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