Chitosan, an excellent biomedical material, has received a widespread in vivo application. In contrast, its metabolism and distribution once being implanted were less documented. In this study, the pharmacokinetics an...Chitosan, an excellent biomedical material, has received a widespread in vivo application. In contrast, its metabolism and distribution once being implanted were less documented. In this study, the pharmacokinetics and biodegradation of fluorescein isothiocyanate(FITC) labeled and muscle implantation administrated chitosan in rats were investigated with fluorescence spectrophotometry, histological assay and gel chromatography. After implantation, chitosan was degraded gradually during its distribution to diverse organs. Among the tested organs, liver and kidney were found to be the first two highest in chitosan content, which was followed by heart, brain and spleen. Urinary excretion was believed to be the major pathway of chitosan elimination, yet 80% of chitosan administered to rats was not trackable in their urine. This indicated that the majority of chitosan was degraded in tissues. In average, the molecular weight of the degradation products of chitosan in diverse organs and urine was found to be <65 k Da. This further confirmed the in vivo degradation of chitosan. Our findings provided new evidences for the intensive and safe application of chitosan as a biomedical material.展开更多
A numerical study has been carried out to investigate the temperature distribution and the natural convection heat transfer in axisymmetric two-dimensional vertical saturated porous cylinder with steady state laminar ...A numerical study has been carried out to investigate the temperature distribution and the natural convection heat transfer in axisymmetric two-dimensional vertical saturated porous cylinder with steady state laminar flow. A comparison between two situations is done under the effect of MHD （magnetohydrodynamics） and radiation. In the two situations, the vertical walls of the cylinder are cooled with constant wall temperature and a constant heat generation subjected along the centerline of the cylinder. The first case for cylinder with insulated upper surface and cooled bottom surface while the second case for cylinder with cooled upper surface and insulated bottom surface. The governing equations used are continuity, momentum and energy equations which are transformed to dimensionless equations. The finite difference approach is used to obtain all the computational results using the MATLAB-7 programming. The parameters affected the system are Rayleigh number ranging within （102≤ Ra ≤104）, radiation parameter （0≤ Rd ≤ 2） and magnetohydrodynamics MHD （Mn） （0 ≤ Mn≤ 2）.The results show that the temperature of Case 1 is more than that in Case 2 at constant Ra, Mn and Rd while the value of the stream in Case 2 is greater than that in Case 1. Nu increase with the increase of Rd and increasing Mn caused the temperature to increase and the streamline dropped while Nu decreased. A correlation has been set up to give the average Nusselt number variation with Ra, Rd and Mn for which the results are found to be in good agreement with previously published researches.展开更多
The Problem of laminar natural convective heat transfer inside an eccentric semicircular enclosure of different radius ratio and eccentricity is investigated numerically. At the same time, combined effect of the radiu...The Problem of laminar natural convective heat transfer inside an eccentric semicircular enclosure of different radius ratio and eccentricity is investigated numerically. At the same time, combined effect of the radius ratio and eccentricity on fluid flow is also observed with isothermal upper and lower surface. Here laminar, steady natural convection heat transfer are predicted for radius ratio R*=1.75, 2.0, 2.25, 2.5. Simulation was carried out for a range of eccentricity, ε=0.0 to 0.6. Governing equations are solved using finite volume method with a body fitted grid with collocated variable arrangement for a range of Grashof number 101-107 based on R0.Results are presented in the form of constant stream function, isothermal lines, local Nusselt number and average Nusselt number at different angular position. Eccentricity has little dominance on heat transfer rate. But significant effect of eccentricity is observed on flow field. Radius ratio has significant effect on natural convection heat transfer as wen as on flow field. At higher eccentricity, bi-cellular now is observed with one crescent-shape vortex at narrower cross section.This crescent shaped vortex is broken down into two cells with the increase of radius ratio that means transition Grashof number for bi-cellular now to tri-cellular flow is decreased with the increase of radius ratio. Eccentricity also has the same effect on flow field. Eccentricity has little effect on heat transfer but with the increase of radius ratio, average heat transfer rate increases.展开更多
基金supported funancialy by Qingdao Bio-temed Biomaterial Co.,Ltd.the National ‘Twelfth Five-Year’ Support Plan for Science&Technology of Chinia(2012BAI18B06)
文摘Chitosan, an excellent biomedical material, has received a widespread in vivo application. In contrast, its metabolism and distribution once being implanted were less documented. In this study, the pharmacokinetics and biodegradation of fluorescein isothiocyanate(FITC) labeled and muscle implantation administrated chitosan in rats were investigated with fluorescence spectrophotometry, histological assay and gel chromatography. After implantation, chitosan was degraded gradually during its distribution to diverse organs. Among the tested organs, liver and kidney were found to be the first two highest in chitosan content, which was followed by heart, brain and spleen. Urinary excretion was believed to be the major pathway of chitosan elimination, yet 80% of chitosan administered to rats was not trackable in their urine. This indicated that the majority of chitosan was degraded in tissues. In average, the molecular weight of the degradation products of chitosan in diverse organs and urine was found to be <65 k Da. This further confirmed the in vivo degradation of chitosan. Our findings provided new evidences for the intensive and safe application of chitosan as a biomedical material.
文摘A numerical study has been carried out to investigate the temperature distribution and the natural convection heat transfer in axisymmetric two-dimensional vertical saturated porous cylinder with steady state laminar flow. A comparison between two situations is done under the effect of MHD （magnetohydrodynamics） and radiation. In the two situations, the vertical walls of the cylinder are cooled with constant wall temperature and a constant heat generation subjected along the centerline of the cylinder. The first case for cylinder with insulated upper surface and cooled bottom surface while the second case for cylinder with cooled upper surface and insulated bottom surface. The governing equations used are continuity, momentum and energy equations which are transformed to dimensionless equations. The finite difference approach is used to obtain all the computational results using the MATLAB-7 programming. The parameters affected the system are Rayleigh number ranging within （102≤ Ra ≤104）, radiation parameter （0≤ Rd ≤ 2） and magnetohydrodynamics MHD （Mn） （0 ≤ Mn≤ 2）.The results show that the temperature of Case 1 is more than that in Case 2 at constant Ra, Mn and Rd while the value of the stream in Case 2 is greater than that in Case 1. Nu increase with the increase of Rd and increasing Mn caused the temperature to increase and the streamline dropped while Nu decreased. A correlation has been set up to give the average Nusselt number variation with Ra, Rd and Mn for which the results are found to be in good agreement with previously published researches.
文摘The Problem of laminar natural convective heat transfer inside an eccentric semicircular enclosure of different radius ratio and eccentricity is investigated numerically. At the same time, combined effect of the radius ratio and eccentricity on fluid flow is also observed with isothermal upper and lower surface. Here laminar, steady natural convection heat transfer are predicted for radius ratio R*=1.75, 2.0, 2.25, 2.5. Simulation was carried out for a range of eccentricity, ε=0.0 to 0.6. Governing equations are solved using finite volume method with a body fitted grid with collocated variable arrangement for a range of Grashof number 101-107 based on R0.Results are presented in the form of constant stream function, isothermal lines, local Nusselt number and average Nusselt number at different angular position. Eccentricity has little dominance on heat transfer rate. But significant effect of eccentricity is observed on flow field. Radius ratio has significant effect on natural convection heat transfer as wen as on flow field. At higher eccentricity, bi-cellular now is observed with one crescent-shape vortex at narrower cross section.This crescent shaped vortex is broken down into two cells with the increase of radius ratio that means transition Grashof number for bi-cellular now to tri-cellular flow is decreased with the increase of radius ratio. Eccentricity also has the same effect on flow field. Eccentricity has little effect on heat transfer but with the increase of radius ratio, average heat transfer rate increases.
