The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Tai-horng Young - One of the best experts on this subject based on the ideXlab platform.
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Role of phase diagram of Membrane Formation system in controlling the crystallinity and degradation rate of PLLA Membranes
Journal of biomedical materials research. Part A, 2006Co-Authors: I-chi Lee, Liao-ping Cheng, Tai-horng YoungAbstract:In this work, the theoretical phase diagram of Membrane Formation system of ethanol, methylene chloride, and poly-L-lactide (PLLA) was studied. On the basis of the phase diagram, particulate and porous Membranes, dominated by crystallization and liquid–liquid demixing, respectively, were prepared. Furthermore, degradation of PLLA Membranes with particulate, porous, and dense morphologies was performed in phosphate buffered solution (PBS) at 37°C for 168 days and was investigated by mass loss, scanning electron microscopy (SEM), gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). Besides the Membrane morphology, a close relationship between the phase behavior of the Membrane Formation system and the Membrane crystallinity was found, which in turn influenced the degradation rate of these Membranes significantly. In the case of dense Membranes, it showed the lowest initial crystallinity and the greatest rate of mass loss and molecular weight decrease compared with particulate and porous Membranes. In contrast, the particulate Membranes had the highest crystallinity and the slowest degradation rate in this study. Therefore, the phase diagram of Membrane Formation system could not only anticipate Membrane morphology, but could also control the Membrane crystallinity and degradation rate simultaneously. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
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Polyetherimide Membrane Formation by the cononsolvent system and its biocompatibility of MG63 cell line
Journal of Membrane Science, 2005Co-Authors: Chun-te Tao, Tai-horng YoungAbstract:Abstract Polyetherimide (PEI) Membrane could be prepared by immersion–precipitation process by using the N-methyl-2-pyrrolidone (NMP)–methylene chloride (MC) cononsolvent as the coagulation medium. The Membrane, via scanning electron microscopy (SEM), showed a typically asymmetrical structure consisting of a thin and dense skin layer, sponge morphology in the cross-section and porous bottom surface. Trend expected on the basis of the phase diagram of the use of two solvents serving as a cononsolvent system for the Membrane Formation, replacing the traditional solvent–nonsolvent pair, was in reasonable agreement with the observed Membrane morphology. Therefore, the principles of Membrane Formation established for the ternary systems with polymer–solvent–nonsolvent can be applied to a polymer–cononsolvent (solvent–solvent) system. Furthermore, the biocompatibility of the PEI Membrane top (dense) and bottom (porous) surfaces was assessed in an in vitro model using the human osteoblast-like cell line MG63. Compared to cells grown on tissue culture polystyrene (TCPS), cells cultured on the PEI Membranes had lower cell growth, but every single cell on the PEI Membrane showed similar viability to control cells. SEM analysis showed comparable adhesion and confluence characteristics on all substrates. In addition, the levels of alkaline phosphotase (ALP), prostaglandin E2 (PGE2) and transforming growth factor β1 (TGF-β1) cytokines produced by MG63 cells on the prepared PEI Membranes, regardless of the top or bottom surface, were similar to those on TCPS. The results of this study suggest that the PEI Membrane prepared from a cononsolvent system is a non-toxic, biocompatible substrate for the proliferation of human bone cells in vitro.
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Phase behavior of poly(N-isopropylacrylamide) in water–methanol cononsolvent mixtures and its relevance to Membrane Formation
Polymer, 2005Co-Authors: Chun-te Tao, Tai-horng YoungAbstract:Abstract The phase behavior of poly (N-isopropylacrylamide) (PNIPAAm) in solutions composed of water and methanol was studied at 25 °C. The pair of solvents used to dissolve PNIPAAm has been selected for the purpose to perform a cononsolvent system. From the observed phase behavior, PNIPAAm was soluble in either water or methanol individually but liquid–liquid demixing was observed in water/methanol mixtures. Flory–Huggins formalism including three binary interaction parameters and one ternary interaction parameter was used to analyze the phase behavior of the cononsolvent system. The mechanism of cononsolvency and its relation with the ternary interaction parameter were discussed. In addition, the use of two solvents serving as a cononsolvent system, replacing the traditional solvent–nonsolvent pair, for the Membrane Formation was investigated. Regardless of water or methanol being used as the solvent, it showed a rapidly precipitating system and macrovoid morphology due to liquid–liquid demixing was obtained. Trend expected on the basis of the phase diagram was in reasonable agreement with the observed Membrane morphology. Therefore, the principles of Membrane Formation established for the ternary systems with nonsolvent–solvent–polymer can be extended to a cononsolvent–polymer system.
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A two step mechanism of diffusion-controlled ethylene vinyl alcohol Membrane Formation
Journal of Membrane Science, 1991Co-Authors: Tai-horng Young, Leo-wang ChenAbstract:Abstract The coagulation of ethylene vinyl alcohol (EVAL) copolymer Membranes was investigated with a solvent/nonsolvent mixture. A two step mechanism model is presented which describes mass transfer processes occurring for specified Membrane Formation systems. The various morphology structures can be reasonably explained by this model by changing the solvent content of the coagulation bath. It clearly shows that the Membrane structure actually depends on the local composition at phase transition and is controlled mainly by kinetic and structural factors rather than thermodynamic equilibrium. This model also points out some aspects neglected of Membrane Formation in published research. This analysis provides better understanding and correct control of Membrane Formation techniques.
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A diffusion-controlled model for wet-casting Membrane Formation
Journal of Membrane Science, 1991Co-Authors: Tai-horng Young, Leo-wang ChenAbstract:Abstract A simplified analytical treatment of Membrane Formation mechanism, following the Paul method, is proposed using a casting solution immersed in a coagulation bath. This model assumes a discontinuous system consisting of parallel layers in the Membrane with each layer proceeding rapidly to phase inversion. It allows the measurement of local composition variation at each layer depending on the flux ratio of solvent to nonsolvent. It is difficult to test the model unless a direct method of estimating the flux ratio at each layer is developed. However, some conclusions can be drawn about the applicability of the suggested model according to the type of Membrane. For a homogeneous Membrane, the flux ratio is independent of position. For an asymmetric Membrane, the flux ratio has two values: the larger value for the skin layer and the other for the sublayer. Experimental results are compared with the values predicted by this pseudobinary mathematical model, and show fairly good agreement.
Leo-wang Chen - One of the best experts on this subject based on the ideXlab platform.
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A two step mechanism of diffusion-controlled ethylene vinyl alcohol Membrane Formation
Journal of Membrane Science, 1991Co-Authors: Tai-horng Young, Leo-wang ChenAbstract:Abstract The coagulation of ethylene vinyl alcohol (EVAL) copolymer Membranes was investigated with a solvent/nonsolvent mixture. A two step mechanism model is presented which describes mass transfer processes occurring for specified Membrane Formation systems. The various morphology structures can be reasonably explained by this model by changing the solvent content of the coagulation bath. It clearly shows that the Membrane structure actually depends on the local composition at phase transition and is controlled mainly by kinetic and structural factors rather than thermodynamic equilibrium. This model also points out some aspects neglected of Membrane Formation in published research. This analysis provides better understanding and correct control of Membrane Formation techniques.
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A diffusion-controlled model for wet-casting Membrane Formation
Journal of Membrane Science, 1991Co-Authors: Tai-horng Young, Leo-wang ChenAbstract:Abstract A simplified analytical treatment of Membrane Formation mechanism, following the Paul method, is proposed using a casting solution immersed in a coagulation bath. This model assumes a discontinuous system consisting of parallel layers in the Membrane with each layer proceeding rapidly to phase inversion. It allows the measurement of local composition variation at each layer depending on the flux ratio of solvent to nonsolvent. It is difficult to test the model unless a direct method of estimating the flux ratio at each layer is developed. However, some conclusions can be drawn about the applicability of the suggested model according to the type of Membrane. For a homogeneous Membrane, the flux ratio is independent of position. For an asymmetric Membrane, the flux ratio has two values: the larger value for the skin layer and the other for the sublayer. Experimental results are compared with the values predicted by this pseudobinary mathematical model, and show fairly good agreement.
Albert W. Biglan - One of the best experts on this subject based on the ideXlab platform.
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Risk factors for secondary Membrane Formation after removal of pediatric cataract.
Journal of cataract and refractive surgery, 2002Co-Authors: Banu M. Hoşal, Albert W. BiglanAbstract:Abstract Purpose: To evaluate the incidence of secondary Membrane Formation, factors that lead to its development, and the frequency of procedures to treat these Membranes in children after cataract surgery. Setting: Department of Pediatric Ophthalmology, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA. Methods: Clinical records of 152 patients (190 eyes) who had cataract extraction between January 1986 and 1996 were reviewed retrospectively. The mean follow-up was 6 years (range 2 to 13 years). Cataract surgery was performed through a limbal incision in all cases. Twenty-eight eyes had a primary posterior capsulectomy, and 120 eyes had posterior capsulectomy combined with an anterior vitrectomy. In 42 eyes, the posterior capsule was left intact. Nineteen eyes received a primary intraocular lens (IOL), 15 eyes received a secondary IOL, and 156 eyes were rehabilitated with spectacles or contact lenses. Results: Seventy-two eyes (37.9%) developed secondary Membrane a mean of 8.9 months postoperatively (range 3 weeks to 53 months). Membranes occurred in 78.6% of eyes with an intact posterior capsule, 42.9% with posterior capsulectomy, and 22.5% with combined posterior capsulectomy and anterior vitrectomy. Secondary Membrane Formation was associated with not performing a posterior capsulectomy with anterior vitrectomy ( P P P Conclusions: The younger the child at cataract surgery, the greater the risk of secondary Membrane. Primary posterior capsulectomy combined with an anterior vitrectomy decreased but did not eliminate the incidence of secondary Membrane.
Ya-nan Yang - One of the best experts on this subject based on the ideXlab platform.
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The research of rheology and thermodynamics of organic-inorganic hybrid Membrane during the Membrane Formation
Journal of Membrane Science, 2008Co-Authors: Ya-nan Yang, Chen Xuesi, Zheng Yi-qing, Zhang XuanAbstract:To clarify the mechanism of organic-inorganic hybrid Membrane Formation by phase-inversion method, the thermodynamical and theological properties of PSF/TiO2 casting solution were investigated by the viscosity measurement and the triangle phase diagram, respectively. TiO2 introduction decreased the non-solvent tolerance of casting solution with non-solvent 20% ethanol aqueous solution, which caused thermodynamic enhancement of phase separation, and also resulted in the change of theological properties from Newtonian fluid to non-Newtonian fluid and the viscosity increase of casting solution, which induced rheological hindrance in demixing process
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The research of rheology and thermodynamics of organic–inorganic hybrid Membrane during the Membrane Formation
Journal of Membrane Science, 2007Co-Authors: Ya-nan Yang, Chen Xuesi, Wu Jun, Zheng Qing-zhu, Zhang Hui-xuanAbstract:To clarify the mechanism of organic-inorganic hybrid Membrane Formation by phase-inversion method, the thermodynamical and theological properties of PSF/TiO2 casting solution were investigated by the viscosity measurement and the triangle phase diagram, respectively. TiO2 introduction decreased the non-solvent tolerance of casting solution with non-solvent 20% ethanol aqueous solution, which caused thermodynamic enhancement of phase separation, and also resulted in the change of theological properties from Newtonian fluid to non-Newtonian fluid and the viscosity increase of casting solution, which induced rheological hindrance in demixing process
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The relationship between porosity and kinetics parameter of Membrane Formation in PSF ultrafiltration Membrane
Journal of Membrane Science, 2006Co-Authors: Qing-zhu Zheng, Ya-nan Yang, Peng Wang, De-jie CuiAbstract:In order to clarify the relationship between the porosity of Membrane and the kinetics parameter of Membrane Formation (Da) in polysulfone (PSF) ultrafiltration Membrane, phase-inversion process was used in PSF Membrane preparation from PSF casting solution with poly(ethylene glycol) (PEG) or poly(vinyl pyrrolidone) (PVP) introduction. A new method used to calculate Da was founded and an equation of Da = d2/t was established on the basis of the relationship between wet Membrane thickness and coagulation time. It was found that there was substantial relationship between Da and porosity in PSF ultrafiltration Membrane, and that the linear relationship between Da and porosity in PSF ultrafiltration Membrane could be described as P(%) = a + bDa.
Banu M. Hoşal - One of the best experts on this subject based on the ideXlab platform.
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Risk factors for secondary Membrane Formation after removal of pediatric cataract.
Journal of cataract and refractive surgery, 2002Co-Authors: Banu M. Hoşal, Albert W. BiglanAbstract:Abstract Purpose: To evaluate the incidence of secondary Membrane Formation, factors that lead to its development, and the frequency of procedures to treat these Membranes in children after cataract surgery. Setting: Department of Pediatric Ophthalmology, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA. Methods: Clinical records of 152 patients (190 eyes) who had cataract extraction between January 1986 and 1996 were reviewed retrospectively. The mean follow-up was 6 years (range 2 to 13 years). Cataract surgery was performed through a limbal incision in all cases. Twenty-eight eyes had a primary posterior capsulectomy, and 120 eyes had posterior capsulectomy combined with an anterior vitrectomy. In 42 eyes, the posterior capsule was left intact. Nineteen eyes received a primary intraocular lens (IOL), 15 eyes received a secondary IOL, and 156 eyes were rehabilitated with spectacles or contact lenses. Results: Seventy-two eyes (37.9%) developed secondary Membrane a mean of 8.9 months postoperatively (range 3 weeks to 53 months). Membranes occurred in 78.6% of eyes with an intact posterior capsule, 42.9% with posterior capsulectomy, and 22.5% with combined posterior capsulectomy and anterior vitrectomy. Secondary Membrane Formation was associated with not performing a posterior capsulectomy with anterior vitrectomy ( P P P Conclusions: The younger the child at cataract surgery, the greater the risk of secondary Membrane. Primary posterior capsulectomy combined with an anterior vitrectomy decreased but did not eliminate the incidence of secondary Membrane.