AIM:The generation of oxygen free radicals has been implicated in the pathogenesis of experimental pancreatitis. The aim of this study was to determine the role of oxygen free radicals in patients with acute pancreati...AIM:The generation of oxygen free radicals has been implicated in the pathogenesis of experimental pancreatitis. The aim of this study was to determine the role of oxygen free radicals in patients with acute pancreatitis. METHODS:The plasma levels of C-reactive protein(CRP), lipid peroxide(LPO),myeloperoxidase(MPO)and superoxide dismutase(SOD)were measured in 13 patients with acute pancreatitis and 14 healthy volunteers. RESULTS:Among the patients with acute pancreatitis,there were higher plasma levels of LPO and MPO and lower SOD activity in patients with severe pancreatitis than in those with mild pancreatitis.However,there was no significant difference in the serum marker of oxidative stress no matter what the etiology was.The LPO level was especially correlated with the concentration of serum CRP and CT severity index. CONCLUSION:The oxygen free radicals may be closely associated with inflammatory process and the severity of acute pancreatitis.Especially,the concentration of plasma LPO is a meaningful index for determining the severity of the disease.展开更多
A new kinetic model for commercial unit of toluene disproportionation and C9-armatiocs transalkylation is developed based on the reported reaction scheme.A time based catalyst deactivation function taking weight hourl...A new kinetic model for commercial unit of toluene disproportionation and C9-armatiocs transalkylation is developed based on the reported reaction scheme.A time based catalyst deactivation function taking weight hourly space velocity(WHSV)into account is incorporated into the model,which reasonably accounts for the loss in activity because of coke deposition on the surface of catalyst during long-term operation.The kinetic parameters are benchmarked with several sets of balanced plant data and estimated by the differential variable metric optimiza- tion method.Sets of plant data at different operating conditions are applied to make sure validation of the model and the results show a good agreement between the model predictions and plant observations.The simulation analysis of key variables such as temperature and WHSV affecting process performance is discussed in detail,giv- ing the guidance to select suitable operating conditions.展开更多
The bifurcation behavior of the CO coupling reactor was examined based on the one-dimensional pseudo homogeneous axial dispersion dynamic model. The method of finite difference was used for solving the boundary value ...The bifurcation behavior of the CO coupling reactor was examined based on the one-dimensional pseudo homogeneous axial dispersion dynamic model. The method of finite difference was used for solving the boundary value problem; the continuation technique and the direct method were applied to determine the bifurcation diagram. The effects of dimensionless adiabatic temperature rise, Damkohler number, activation energy, heat transfer coefficient and feed ratio on the bifurcation behavior were investigated. It was shown that there existed static bifurcation and the oscillations did not occur in the reactor. The result also revealed that the reactor exhibited at most 1-3-1 multiplicity patterns within the range of practical possible parameters and the measures, such as weakening the axial dispersion of reactor, enhancing heat transfer, decreasing the concentration of ethyl nitrite, were efficient for avoiding the possible risk of multiple steady states.展开更多
文摘AIM:The generation of oxygen free radicals has been implicated in the pathogenesis of experimental pancreatitis. The aim of this study was to determine the role of oxygen free radicals in patients with acute pancreatitis. METHODS:The plasma levels of C-reactive protein(CRP), lipid peroxide(LPO),myeloperoxidase(MPO)and superoxide dismutase(SOD)were measured in 13 patients with acute pancreatitis and 14 healthy volunteers. RESULTS:Among the patients with acute pancreatitis,there were higher plasma levels of LPO and MPO and lower SOD activity in patients with severe pancreatitis than in those with mild pancreatitis.However,there was no significant difference in the serum marker of oxidative stress no matter what the etiology was.The LPO level was especially correlated with the concentration of serum CRP and CT severity index. CONCLUSION:The oxygen free radicals may be closely associated with inflammatory process and the severity of acute pancreatitis.Especially,the concentration of plasma LPO is a meaningful index for determining the severity of the disease.
基金Supported by the National＇Creative Research Groups Science Foundation of China （No.60421002） and priority supported financially by ＂the New Century 151 Talent Project＂ of Zhejiang Province.
文摘A new kinetic model for commercial unit of toluene disproportionation and C9-armatiocs transalkylation is developed based on the reported reaction scheme.A time based catalyst deactivation function taking weight hourly space velocity(WHSV)into account is incorporated into the model,which reasonably accounts for the loss in activity because of coke deposition on the surface of catalyst during long-term operation.The kinetic parameters are benchmarked with several sets of balanced plant data and estimated by the differential variable metric optimiza- tion method.Sets of plant data at different operating conditions are applied to make sure validation of the model and the results show a good agreement between the model predictions and plant observations.The simulation analysis of key variables such as temperature and WHSV affecting process performance is discussed in detail,giv- ing the guidance to select suitable operating conditions.
文摘The bifurcation behavior of the CO coupling reactor was examined based on the one-dimensional pseudo homogeneous axial dispersion dynamic model. The method of finite difference was used for solving the boundary value problem; the continuation technique and the direct method were applied to determine the bifurcation diagram. The effects of dimensionless adiabatic temperature rise, Damkohler number, activation energy, heat transfer coefficient and feed ratio on the bifurcation behavior were investigated. It was shown that there existed static bifurcation and the oscillations did not occur in the reactor. The result also revealed that the reactor exhibited at most 1-3-1 multiplicity patterns within the range of practical possible parameters and the measures, such as weakening the axial dispersion of reactor, enhancing heat transfer, decreasing the concentration of ethyl nitrite, were efficient for avoiding the possible risk of multiple steady states.
