Many scientific and engineering problems need to use numerical methods and algorithms to obtain computational simulation results because analytical solutions are seldom available for them.The chemical dissolution-fron...Many scientific and engineering problems need to use numerical methods and algorithms to obtain computational simulation results because analytical solutions are seldom available for them.The chemical dissolution-front instability problem in fluid-saturated porous rocks is no exception.Since this kind of instability problem has both the conventional(i.e.trivial)and the unconventional(i.e.nontrivial)solutions,it is necessary to examine the effects of different numerical algorithms,which are used to solve chemical dissolution-front instability problems in fluid-saturated porous rocks.Toward this goal,two different numerical algorithms associated with the commonly-used finite element method are considered in this paper.In the first numerical algorithm,the porosity,pore-fluid pressure and acid/solute concentration are selected as basic variables,while in the second numerical algorithm,the porosity,velocity of pore-fluid flow and acid/solute concentration are selected as basic variables.The particular attention is paid to the effects of these two numerical algorithms on the computational simulation results of unstable chemical dissolution-front propagation in fluid-saturated porous rocks.The related computational simulation results have demonstrated that:1)the first numerical algorithm associated with the porosity-pressure-concentration approach can realistically simulate the evolution processes of unstable chemical dissolution-front propagation in chemical dissolution systems.2)The second numerical algorithm associated with the porosity-velocity-concentration approach fails to simulate the evolution processes of unstable chemical dissolution-front propagation.3)The extra differential operation is the main source to result in the failure of the second numerical algorithm.展开更多
Aim To study the effect of complexation with hydroxylpropyl-β-cyclodextrin(HP-β-CD) on the solubility, dissolution rate and chemical stability of prostaglandin E_1 (PGE_1) ,thereby providing a basis for preparing a ...Aim To study the effect of complexation with hydroxylpropyl-β-cyclodextrin(HP-β-CD) on the solubility, dissolution rate and chemical stability of prostaglandin E_1 (PGE_1) ,thereby providing a basis for preparing a stable solid or aqueous preparation of PGE_1 formulatedwith HP-β-CD. Methods The effect of HP-β-CD on the solubility of PGE_1 was studied by phasesolubility method. The formation of inclusion complexes of PGE_1 with HP-β-CD in the aqueoussolution was confirmed by UV spectra, circular dichroism spectroscopy, and that in the solid stateby IR spectra and X-ray diffractome-try. An solid inclusion complex of PGE_1 with HP-β-CD wasprepared by lyophilization. The dissolution rate and stability of the inclusion complex weredetermined and compared with those of PGE_1 alone. Meanwhile, the stability of PGE_1 aqueoussolutions in the presence of HP-β-CD was studied under different pH conditions. Results Thesolubility of PGE_1 increased linearly with increasing HP-β-CD concentration in various pH bufferedsolutions, showing typical A_L-type phase solubility diagrams. The stability and dissolution rateof the solid inclusion complex of PGE_1 were significantly increased, compared with those of purePGE_1 . The stability of PGE_1 in HP-β-CD solutions was also obviously improved under acidic andbasic conditions, but the stabilizing effect was absent under neutral conditions. Conclusions Thesolubility,dissolution rate and chemical stability of PGE_1 are markedly improved by complexationwith HP-β-CD: It is quite possible to prepare a stable PGE_1 inclusion complex-containing soliddosage forms, but almost impossible to obtain a stable aqueous preparation of PGE_1 formulated withHP-β-CD.展开更多
An antithrombus enzyme (ATE) was precipitated by (NH4)2SO4 or ethanol from supernatant of Bacillus subtilis culture broth then purified using ion exchange chromatography on CM-sepharose fast flow. The effects of ionic...An antithrombus enzyme (ATE) was precipitated by (NH4)2SO4 or ethanol from supernatant of Bacillus subtilis culture broth then purified using ion exchange chromatography on CM-sepharose fast flow. The effects of ionic strength and pH value on protein adsorption, the gradient elution at different flow rates and step elution were examined respectively. The recovery yield of the optimised process was 74.5% with a purification factor 8.1. The ATE molecular weight was estimated as 30ku by SDS-PAGE. The experimental results showed that the enzyme was stable in the range of pH 7 to pH11, and temperature 25℃ to 37℃.展开更多
The effect of various concentrations of 2-hydroxypropyl-β-cyclodextrin （HP-β-CD） on the solubility of dihydroartemisinin （DHA） in aqueous solution at different pHs was investigated. The influence of different co...The effect of various concentrations of 2-hydroxypropyl-β-cyclodextrin （HP-β-CD） on the solubility of dihydroartemisinin （DHA） in aqueous solution at different pHs was investigated. The influence of different concentrations of 2-hydroxypropyl-β- eyclodextrin on the stability of dihydroartemisinin at 50, 60, 70 and 80 ℃ was also studied. Inclusion complex of dihydroartemisinin with 2-hydroxypropyl-β-cyclodextrin was prepared and characterized by X-ray diffraction and differential scanning calorimetry. The 2-hydroxypropyl-β-cyclodextrin effectively inhibited the hydrolysis of dihydroartemisinin and greatly increased its solubility. Furthermore, we showed that the higher concentrations of 2-hydroxypropyl-β-cyclodextrin, the better stability and solubility of dihydroartemisinin. When the temperature was increased, the stability of dihydroartemisinin decreased. Our results indicated that 2-hydroxypropyl-β-cyclodextrin can be used as a stabilizer and solubilizer of dihydroartemisinin.展开更多
3’,4’-Dimethoxy-flavonol-3-O-β-D-glucopyranoside monohydrate(GDH),which can significantly reduce blood lipids,atherosclerotic aortic lesions,and liver injury,has poor oral bioavailability.In the present study,we ai...3’,4’-Dimethoxy-flavonol-3-O-β-D-glucopyranoside monohydrate(GDH),which can significantly reduce blood lipids,atherosclerotic aortic lesions,and liver injury,has poor oral bioavailability.In the present study,we aimed to prepare and characterize five new polymorphs of GDH(II,III,IV,V,and VI)and the amorphous form of GDH(GDH-AM).The GDH polymorphs and GDH-AM were characterized by scanning electron microscopy(SEM),differential scanning calorimetry(DSC),thermogravimetric analysis(TGA),X-ray powder diffraction(XRPD),and Fourier transform infrared spectroscopy(FTIR).Dissolution tests,physical stability,polymorphic transformation,and permeability studies were subsequently investigated.Dissolution of GDH-II and GDH-IV reached higher concentrations compared with GDH-I.GDH-AM exhibited a significantly high dissolution rate and prolonged supersaturation during dissolution.No phase transition was found for GDH-I and GDH-AM after 3 months of storage,while GDH-II,GDH-III,GDH-IV,GDH-V,and GDH-VI were readily converted to GDH-I.In situ single-pass intestinal perfusion experiments showed that the high concentration of GDH exhibited low permeability.Sodium dodecyl sulfate and bovine bile salts were used as absorption enhancers to improve the permeability of GDH.The results showed that sodium dodecyl sulfate and taurocholate were good absorption enhancers for further formulation development of GDH.展开更多
基金Project(11272359)supported by the National Natural Science Foundation of China
文摘Many scientific and engineering problems need to use numerical methods and algorithms to obtain computational simulation results because analytical solutions are seldom available for them.The chemical dissolution-front instability problem in fluid-saturated porous rocks is no exception.Since this kind of instability problem has both the conventional(i.e.trivial)and the unconventional(i.e.nontrivial)solutions,it is necessary to examine the effects of different numerical algorithms,which are used to solve chemical dissolution-front instability problems in fluid-saturated porous rocks.Toward this goal,two different numerical algorithms associated with the commonly-used finite element method are considered in this paper.In the first numerical algorithm,the porosity,pore-fluid pressure and acid/solute concentration are selected as basic variables,while in the second numerical algorithm,the porosity,velocity of pore-fluid flow and acid/solute concentration are selected as basic variables.The particular attention is paid to the effects of these two numerical algorithms on the computational simulation results of unstable chemical dissolution-front propagation in fluid-saturated porous rocks.The related computational simulation results have demonstrated that:1)the first numerical algorithm associated with the porosity-pressure-concentration approach can realistically simulate the evolution processes of unstable chemical dissolution-front propagation in chemical dissolution systems.2)The second numerical algorithm associated with the porosity-velocity-concentration approach fails to simulate the evolution processes of unstable chemical dissolution-front propagation.3)The extra differential operation is the main source to result in the failure of the second numerical algorithm.
文摘Aim To study the effect of complexation with hydroxylpropyl-β-cyclodextrin(HP-β-CD) on the solubility, dissolution rate and chemical stability of prostaglandin E_1 (PGE_1) ,thereby providing a basis for preparing a stable solid or aqueous preparation of PGE_1 formulatedwith HP-β-CD. Methods The effect of HP-β-CD on the solubility of PGE_1 was studied by phasesolubility method. The formation of inclusion complexes of PGE_1 with HP-β-CD in the aqueoussolution was confirmed by UV spectra, circular dichroism spectroscopy, and that in the solid stateby IR spectra and X-ray diffractome-try. An solid inclusion complex of PGE_1 with HP-β-CD wasprepared by lyophilization. The dissolution rate and stability of the inclusion complex weredetermined and compared with those of PGE_1 alone. Meanwhile, the stability of PGE_1 aqueoussolutions in the presence of HP-β-CD was studied under different pH conditions. Results Thesolubility of PGE_1 increased linearly with increasing HP-β-CD concentration in various pH bufferedsolutions, showing typical A_L-type phase solubility diagrams. The stability and dissolution rateof the solid inclusion complex of PGE_1 were significantly increased, compared with those of purePGE_1 . The stability of PGE_1 in HP-β-CD solutions was also obviously improved under acidic andbasic conditions, but the stabilizing effect was absent under neutral conditions. Conclusions Thesolubility,dissolution rate and chemical stability of PGE_1 are markedly improved by complexationwith HP-β-CD: It is quite possible to prepare a stable PGE_1 inclusion complex-containing soliddosage forms, but almost impossible to obtain a stable aqueous preparation of PGE_1 formulated withHP-β-CD.
文摘An antithrombus enzyme (ATE) was precipitated by (NH4)2SO4 or ethanol from supernatant of Bacillus subtilis culture broth then purified using ion exchange chromatography on CM-sepharose fast flow. The effects of ionic strength and pH value on protein adsorption, the gradient elution at different flow rates and step elution were examined respectively. The recovery yield of the optimised process was 74.5% with a purification factor 8.1. The ATE molecular weight was estimated as 30ku by SDS-PAGE. The experimental results showed that the enzyme was stable in the range of pH 7 to pH11, and temperature 25℃ to 37℃.
文摘The effect of various concentrations of 2-hydroxypropyl-β-cyclodextrin （HP-β-CD） on the solubility of dihydroartemisinin （DHA） in aqueous solution at different pHs was investigated. The influence of different concentrations of 2-hydroxypropyl-β- eyclodextrin on the stability of dihydroartemisinin at 50, 60, 70 and 80 ℃ was also studied. Inclusion complex of dihydroartemisinin with 2-hydroxypropyl-β-cyclodextrin was prepared and characterized by X-ray diffraction and differential scanning calorimetry. The 2-hydroxypropyl-β-cyclodextrin effectively inhibited the hydrolysis of dihydroartemisinin and greatly increased its solubility. Furthermore, we showed that the higher concentrations of 2-hydroxypropyl-β-cyclodextrin, the better stability and solubility of dihydroartemisinin. When the temperature was increased, the stability of dihydroartemisinin decreased. Our results indicated that 2-hydroxypropyl-β-cyclodextrin can be used as a stabilizer and solubilizer of dihydroartemisinin.
文摘3’,4’-Dimethoxy-flavonol-3-O-β-D-glucopyranoside monohydrate(GDH),which can significantly reduce blood lipids,atherosclerotic aortic lesions,and liver injury,has poor oral bioavailability.In the present study,we aimed to prepare and characterize five new polymorphs of GDH(II,III,IV,V,and VI)and the amorphous form of GDH(GDH-AM).The GDH polymorphs and GDH-AM were characterized by scanning electron microscopy(SEM),differential scanning calorimetry(DSC),thermogravimetric analysis(TGA),X-ray powder diffraction(XRPD),and Fourier transform infrared spectroscopy(FTIR).Dissolution tests,physical stability,polymorphic transformation,and permeability studies were subsequently investigated.Dissolution of GDH-II and GDH-IV reached higher concentrations compared with GDH-I.GDH-AM exhibited a significantly high dissolution rate and prolonged supersaturation during dissolution.No phase transition was found for GDH-I and GDH-AM after 3 months of storage,while GDH-II,GDH-III,GDH-IV,GDH-V,and GDH-VI were readily converted to GDH-I.In situ single-pass intestinal perfusion experiments showed that the high concentration of GDH exhibited low permeability.Sodium dodecyl sulfate and bovine bile salts were used as absorption enhancers to improve the permeability of GDH.The results showed that sodium dodecyl sulfate and taurocholate were good absorption enhancers for further formulation development of GDH.
