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排序方式: 共有258条查询结果,搜索用时 31 毫秒
31.
Tedric D. Campbell Randy P. Washington Oliver Steinbock 《Journal of polymer science. Part A, Polymer chemistry》2007,45(13):2593-2600
We report the synthesis of poly N‐(2‐hydroxypropyl)methacrylamide ordered arrays of fluid filled channels. The polymerization and crosslinking reactions are carried out under the influence of a constant electric field (60 V/cm). A charged comonomer, immobiline (pK 3.6), and porogen, polyethylene glycol (PEG) are added to the pregel solutions. Scanning electron microscopy reveals that the channels have a typical diameter of 2–25 μm and are oriented parallel to the electric field employed during synthesis. The self‐organization of channels occurs around an optimal PEG concentration of 8.6 wt/vol %, whereas significantly higher or lower concentrations yield random, isotropic pore structures. Moreover, tensile strength measurements show that the mechanical stability increases with decreasing concentration of PEG. Rheology experiments reveal that the swelling degree of these superabsorbant hydrogels increases with increasing PEG. Possible applications of these microstructured hydrogels as bidirectional scaffolds for regenerating neurons in the injured spinal cord are discussed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2593–2600, 2007 相似文献
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Recent efforts in scientific research in the field of peripheral nerve regeneration have been directed towards the development of artificial nerve guides. We have studied various materials with the aim of obtaining a biocompatible and biodegradable two layer guide for nerve repair. The candidate materials for use as an external layer for the nerve guides were poly(caprolactone) (PCL), a biosynthetic blend between PCL and chitosan (CS) and a synthesised poly(ester-urethane) (PU). Blending PCL, which is a biocompatible synthetic polymer, with a natural polymer enhanced the system biocompatibility and biomimetics, fastened the degradation rates and reduced the production costs. Various novel block poly(ester-urethane)s are being synthesised by our group with tailored properties for specific tissue engineering applications. One of these poly(ester-urethane)s, based on a low molecular weight poly(caprolactone) as the macrodiol, cycloesandimethanol as the chain extender and hexamethylene diisocyanate as the chain linker, was investigated for the production of melt extruded nerve guides. We studied natural polymers such as gelatin (G), poly(L-lysine) (PL) and blends between chitosan and gelatin (CS/G) as internal coatings for nerve guides. In vitro and in vivo tests were performed on PCL guides internally coated either with G or PL to determine the differences in the quality of nerve regeneration associated with the type of adhesion protein. CS/G natural blends combined the good cell adhesion properties of the protein phase with the ability to promote nerve regeneration of the polysaccharide phase. Natural blends were crosslinked both by physical and chemical crosslinking methods. In vitro neuroblast adhesion tests were performed on CS/G film samples, PCL/CS and PU guides internally coated with G to evaluate the ability of such materials towards nerve repair. 相似文献
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Neshat Askarzadeh Masoumeh Haghbin Nazarpak Korosh Mansoori Mehdi Farokhi Mahdi Gholami Javad Mohammadi Fatemeh Mottaghitalab 《Macromolecular bioscience》2020,20(9)
Herein, a bilayer cylindrical conduit (P‐CA) is presented consisting of electrospun polycaprolactone (PCL) nanofibers and sodium alginate hydrogel covalently cross‐linked with N,N′‐disuccinimidyl carbonate (DSC). The bilayer P‐CA conduit is developed by combining the electrospinning and outer–inner layer methods. Using DSC, as a covalent crosslinker, increases the degradation time of the sodium alginate hydrogel up to 2 months. The swelling ratio of the hydrogel is also 503% during the first 8 h. The DSC cross‐linked sodium alginate in the inner layer of the conduit promotes the adhesion and proliferation of nerve cells, while the electrospun PCL nanofibers in the outer layer provide maximum tensile strength of the conduit during surgery. P‐CA conduit promotes the migration of Schwann cells along the axon in a rat model based on functional and histological evidences. In conclusion, P‐CA conduit will be a promising construct for repairing sciatic nerves in a rat model. 相似文献
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Distinguishing and quantification of the human visual pathways using high-spatial-resolution diffusion tensor tractography 总被引:1,自引:0,他引:1
Arash Kamali Khader M. Hasan Pavani Adapa Azadeh Razmandi Zafer Keser John Lincoln Larry A. Kramer 《Magnetic resonance imaging》2014
Quantification of the living human visual system using MRI methods has been challenging, but several applications demand a reliable and time-efficient data acquisition protocol. In this study, we demonstrate the utility of high-spatial-resolution diffusion tensor fiber tractography (DTT) in reconstructing and quantifying the human visual pathways. Five healthy males, age range 24–37 years, were studied after approval of the institutional review board (IRB) at The University of Texas Health Science Center at Houston. We acquired diffusion tensor imaging (DTI) data with 1-mm slice thickness on a 3.0-Tesla clinical MRI scanner and analyzed the data using DTT with the fiber assignment by continuous tractography (FACT) algorithm. By utilizing the high-spatial-resolution DTI protocol with FACT algorithm, we were able to reconstruct and quantify bilateral optic pathways including the optic chiasm, optic tract, optic radiations free of contamination from neighboring white matter tracts. 相似文献
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Dr. Ligang Wang Dr. Hui Su Zhuang Zhang Junjie Xin Hai Liu Dr. Xiaoge Wang Dr. Chenyu Yang Xiao Liang Dr. Shunwu Wang Dr. Huan Liu Yanfei Yin Taiyan Zhang Prof. Yang Tian Dr. Yaping Li Prof. Qinghua Liu Prof. Xiaoming Sun Prof. Junliang Sun Prof. Dingsheng Wang Prof. Yadong Li 《Angewandte Chemie (International ed. in English)》2023,62(49):e202314185
Developing cost-effective and sustainable acidic water oxidation catalysts requires significant advances in material design and in-depth mechanism understanding for proton exchange membrane water electrolysis. Herein, we developed a single atom regulatory strategy to construct Co−Co dinuclear active sites (DASs) catalysts that atomically dispersed zirconium doped Co9S8/Co3O4 heterostructure. The X-ray absorption fine structure elucidated the incorporation of Zr greatly facilitated the generation of Co−Co DASs layer with stretching of cobalt oxygen bond and S−Co−O heterogeneous grain boundaries interfaces, engineering attractive activity of significantly reduced overpotential of 75 mV at 10 mA cm−2, a breakthrough of 500 mA cm−2 high current density, and water splitting stability of 500 hours in acid, making it one of the best-performing acid-stable OER non-noble metal materials. The optimized catalyst with interatomic Co−Co distance (ca. 2.80 Å) followed oxo-oxo coupling mechanism that involved obvious oxygen bridges on dinuclear Co sites (1,090 cm−1), confirmed by in situ SR-FTIR, XAFS and theoretical simulations. Furthermore, a major breakthrough of 120,000 mA g−1 high mass current density using the first reported noble metal-free cobalt anode catalyst of Co−Co DASs/ZCC in PEM-WE at 2.14 V was recorded. 相似文献
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