Previous work （Hussain et al. （2013）. Chemical Engineering Science, 101, 35） has pointed out that the conventional, one-dimensional population balance equation for aggregation can be expanded to accurately reprodu...Previous work （Hussain et al. （2013）. Chemical Engineering Science, 101, 35） has pointed out that the conventional, one-dimensional population balance equation for aggregation can be expanded to accurately reproduce the results of discrete simulations of spray fluidized bed agglomeration. However, some parameters had to be imported from the discrete simulation （Monte-Carlo）. The present paper shows how the expanded population balance can be run without importing parameters from the Monte-Carlo simulation. The expanded population balance still reproduces the results of Monte-Carlo simulations accurately, taking into account key micro-scale phenomena （sessile droplet drying, efficiency of collisions）, but with much lower computational cost. Required input parameters are just the drying time of sessile droplets （calculated in advance）, and the prefactor of an equation that correlates particle collision frequency with fluidized bed expansion. In this way, the expanded population balance is, apart from autonomous, also （nearly） predictive. Its performance is demonstrated by comparisons with both Monte-Carlo results and experimental data for various operating conditions （binder mass flow rate, gas temperature）. Despite formally being a one-dimensional expression, the expanded population balance captures additional properties, such as the number of wet particles and the number of droplets in the system, which are even difficult to measure in exoeriments.展开更多
Nanocrystal formulations have been explored to deliver poorly water-soluble drug molecules.Despite various studies of nanocrystal formulation and delivery,much more understanding needs to be gained into absorption mec...Nanocrystal formulations have been explored to deliver poorly water-soluble drug molecules.Despite various studies of nanocrystal formulation and delivery,much more understanding needs to be gained into absorption mechanisms and kinetics of drug nanocrystals at various levels,ranging from cells to tissues and to the whole body.In this study,nanocrystals of tetrakis(4-hydroxyphenyl)ethylene(THPE)with an aggregation-induced emission(AIE)property was used as a model to explore intracellular absorption mechanism and dissolution kinetics of nanocrystals.Cellular uptake studies were conducted with KB cells and characterized by confocal microscopy,fow cytometry,and quantitative analyses.The results suggested that THPE nanocrystals could be taken up by KB cells directly,as well as in the form of dissolved molecules.The cellular uptake was found to be concentration-and timedependent.In addition,the intracellular THPE also could be exocytosed from cells in forms of dissolved molecules and nanocrystals.Kinetic modeling was conducted to further understand the cellular mechanism of THPE nanocrystals based on frst-order ordinary differential equations(ODEs).By ftting the kinetic model against experimental measurements,it was found that the initial nanocrystal concentration had a great infuence on the dynamic process of dissolution,cellular uptake,and exocytosis of THPE nanocrystals.As the nanocrystal concentration increased in the culture media,dissolution of endocytosed nanocrystals became enhanced,subsequently driving the effux of THPE molecules from cells.展开更多
纳米塑料(NPs)与纳米活性炭(NAC)在环境中的共迁移会影响其环境行为。本研究探究了在模拟水溶液中,电解质和pH对不同表面改性的聚苯乙烯纳米颗粒(PSNPs)与NAC异型凝聚的影响。研究发现,由于静电斥力不同,在300 mM NaCl中,随着pH升高,APS...纳米塑料(NPs)与纳米活性炭(NAC)在环境中的共迁移会影响其环境行为。本研究探究了在模拟水溶液中,电解质和pH对不同表面改性的聚苯乙烯纳米颗粒(PSNPs)与NAC异型凝聚的影响。研究发现,由于静电斥力不同,在300 mM NaCl中,随着pH升高,APS(带氨基的PSNPs)与BPS(无表面修饰的PSNPs)的凝聚速率都呈大体下降趋势;在10 mM CaCl_(2)中,APS与NAC在高pH时发生凝聚,BPS与NAC在所有pH下均稳定分散。本研究有助于理解NPs与NAC在水环境中的异型凝聚行为。展开更多
The aggregation of common manganese diox- ide （MnO2） colloids has great impact on their surface reactivity and therefore on their fates as well as associated natural and synthetic contaminants in engineered （e.g. w...The aggregation of common manganese diox- ide （MnO2） colloids has great impact on their surface reactivity and therefore on their fates as well as associated natural and synthetic contaminants in engineered （e.g. water treatment） and natural aquatic environments. Nevertheless, little is known about the aggregation kinetics of MnO2 colloids and the effect of humic acid （HA） and surfactants on these. In this study, the early stage aggregation kinetics of MnO2 nanoparticles in NaNO3 and Ca（NO3）2 solutions in the presence of HA and surfactants （i.e., sodium dodecyl sulfate （SDS）, and polyvinylpyrrolidone （PVP）） were modeled through time-resolved dynamic light scattering. In the presence of HA, MnO2 colloids were significantly stabilized with a critical coagulation concentration （CCC） of-300mmol · L-1 NaNO3 and 4 mmol.L-1 Ca（NO3）2. Electrophoretic mobility （EPM） measurements confirmed that steric hindrance may be primarily responsible for increasing colloidal stability in the presence of HA. Moreover, the molecular and/or chemical properties of HA might impact its stabilizing efficiency. In the case of PVP, only a slight increase of aggregation kinetics was observed, due to steric reactions originating from adsorbed layers of PVP on the MnO2 surface. Consequently, higher CCC values were obtained in the presence of PVP. However, there was a negligible reduction in MnO2 colloidal stability in the presence of 20 mg·L-1SDS.展开更多
Low molecular weight organic acids(LMWOAs),as active components in the rhizosphere carbon cycling,may influence the environmental behaviors of biochar colloids.This study selected the pine-wood and wheat-straw biochar...Low molecular weight organic acids(LMWOAs),as active components in the rhizosphere carbon cycling,may influence the environmental behaviors of biochar colloids.This study selected the pine-wood and wheat-straw biochars(PB and WB)as two typical biochars.The effects of typical LMWOAs(oxalic acid,citric acid,and malic acid)on aggregation kinetics of PB and WB colloids were investigated under pH 4 and 6 conditions.Critical coagulation concentrations(CCCs)of both PB and WB colloids were decreased with the LMWOAs regardless of the types of biochar and the solution pH,and the most significant effect occurred in pH 4 due to more LMWOAs sorption on the biochar colloids.The different types of LMWOAs caused various CCCs changes.For example,the CCC values of PB colloids decreased from 75 mM to 56,52,and 47 mM in the pH 4 NaCl solutions when 1 mM oxalic acid,citric acid,and malic acid were present in the suspensions,respectively.The chemical structure(functional groups)and molecular weight of LMWOAs,solution pH,and the electrophoretic mobility(EPM)of biochar co-influence the interactions between biochar colloids and LMWOAs,thus affecting the stability of biochar colloids in the presence of LMWOAs.The presence of LMWOAs accelerated the aggregation of colloidal biochar by increasing the interaction of surface bridging bonds(hydrogen bonding)and decreasing the repulsive force between colloidal biochar particles.This study showed that LMWOAs could accelerate the aggregation of biochar colloids in acidic or neutral environments and reduce the mobility of biochar colloids in soil rhizosphere.展开更多
This study of the thermal decomposition kinetics of various average diameter nano-particles of cal-cium carbonate by means of TG-DTA(thermogravimetry and differential thermal analysis) showed that the thermal decompos...This study of the thermal decomposition kinetics of various average diameter nano-particles of cal-cium carbonate by means of TG-DTA(thermogravimetry and differential thermal analysis) showed that the thermal decomposition kinetic mechanisms of the same crystal type of calcium carbonate samples do not vary with decreasing of their average diameters ; their pseudo-active energy Ea; and that the top-temperature of decom-position Tp decreases gently in the scope of micron-sized diameter, but decreases sharply when the average di-ameter decreases from micron region to nanometer region. The extraordinary properties of nano-particles were explored by comparing the varying regularity of the mechanisms and kinetic parameters of the solid-phase reac-tions as well as their structural characterization with the variation of average diameters of particles. These show that the aggregation, surface effect as well as internal aberrance and stress of the nano-particles are the main reason causing both Ea and Tp to decline sharply with the decrease of the average diameter of nano-particles.展开更多
Poly（N-isopropylacrylamide-co-N-vinylpyrrolidone） [P（NIPAM-co-NVP）] copolymers with different content of N-vinylpyrrolidone （NVP） were synthesized, and reversible aggregation kinetics of the copolymers in aqueou...Poly（N-isopropylacrylamide-co-N-vinylpyrrolidone） [P（NIPAM-co-NVP）] copolymers with different content of N-vinylpyrrolidone （NVP） were synthesized, and reversible aggregation kinetics of the copolymers in aqueous solutions was investigated with elastic light scattering （ELS） spectra. The results indicated that the apparent activation energy of aggregation process during heating and dissociation process during cooling increased with the NVP content increasing. The phase transition temperature also increased as the content of NVP increased, suggesting that the hydrophilic nature of NVP strongly affected the phase behavior of the copolymer solutions. The higher the content of NVP, the higher the temperature required to break the balance between the hydrophilic and hydrophobie interaction. Besides, during heating and cooling process, the phase transition hysteresis of P（NIPAM-co-NVP） chains decreased when the hydrophilic comonomer increased.展开更多
基金financial support provided by the German Science Foundation(DFG) within the framework of graduate school GRK-1554by the Alexander von Humboldt Foundation(research fellowship for Jitendra Kumar)
文摘Previous work （Hussain et al. （2013）. Chemical Engineering Science, 101, 35） has pointed out that the conventional, one-dimensional population balance equation for aggregation can be expanded to accurately reproduce the results of discrete simulations of spray fluidized bed agglomeration. However, some parameters had to be imported from the discrete simulation （Monte-Carlo）. The present paper shows how the expanded population balance can be run without importing parameters from the Monte-Carlo simulation. The expanded population balance still reproduces the results of Monte-Carlo simulations accurately, taking into account key micro-scale phenomena （sessile droplet drying, efficiency of collisions）, but with much lower computational cost. Required input parameters are just the drying time of sessile droplets （calculated in advance）, and the prefactor of an equation that correlates particle collision frequency with fluidized bed expansion. In this way, the expanded population balance is, apart from autonomous, also （nearly） predictive. Its performance is demonstrated by comparisons with both Monte-Carlo results and experimental data for various operating conditions （binder mass flow rate, gas temperature）. Despite formally being a one-dimensional expression, the expanded population balance captures additional properties, such as the number of wet particles and the number of droplets in the system, which are even difficult to measure in exoeriments.
基金the financial support by the China Scholarship Council(No.201806995008,China)Key Projects of Chinese Medicine Research of Chongqing Municipal Health Bureau(ZY201701004,China)the Chao Endowment and Purdue Research Foundation for support(USA)。
文摘Nanocrystal formulations have been explored to deliver poorly water-soluble drug molecules.Despite various studies of nanocrystal formulation and delivery,much more understanding needs to be gained into absorption mechanisms and kinetics of drug nanocrystals at various levels,ranging from cells to tissues and to the whole body.In this study,nanocrystals of tetrakis(4-hydroxyphenyl)ethylene(THPE)with an aggregation-induced emission(AIE)property was used as a model to explore intracellular absorption mechanism and dissolution kinetics of nanocrystals.Cellular uptake studies were conducted with KB cells and characterized by confocal microscopy,fow cytometry,and quantitative analyses.The results suggested that THPE nanocrystals could be taken up by KB cells directly,as well as in the form of dissolved molecules.The cellular uptake was found to be concentration-and timedependent.In addition,the intracellular THPE also could be exocytosed from cells in forms of dissolved molecules and nanocrystals.Kinetic modeling was conducted to further understand the cellular mechanism of THPE nanocrystals based on frst-order ordinary differential equations(ODEs).By ftting the kinetic model against experimental measurements,it was found that the initial nanocrystal concentration had a great infuence on the dynamic process of dissolution,cellular uptake,and exocytosis of THPE nanocrystals.As the nanocrystal concentration increased in the culture media,dissolution of endocytosed nanocrystals became enhanced,subsequently driving the effux of THPE molecules from cells.
文摘纳米塑料(NPs)与纳米活性炭(NAC)在环境中的共迁移会影响其环境行为。本研究探究了在模拟水溶液中,电解质和pH对不同表面改性的聚苯乙烯纳米颗粒(PSNPs)与NAC异型凝聚的影响。研究发现,由于静电斥力不同,在300 mM NaCl中,随着pH升高,APS(带氨基的PSNPs)与BPS(无表面修饰的PSNPs)的凝聚速率都呈大体下降趋势;在10 mM CaCl_(2)中,APS与NAC在高pH时发生凝聚,BPS与NAC在所有pH下均稳定分散。本研究有助于理解NPs与NAC在水环境中的异型凝聚行为。
文摘The aggregation of common manganese diox- ide （MnO2） colloids has great impact on their surface reactivity and therefore on their fates as well as associated natural and synthetic contaminants in engineered （e.g. water treatment） and natural aquatic environments. Nevertheless, little is known about the aggregation kinetics of MnO2 colloids and the effect of humic acid （HA） and surfactants on these. In this study, the early stage aggregation kinetics of MnO2 nanoparticles in NaNO3 and Ca（NO3）2 solutions in the presence of HA and surfactants （i.e., sodium dodecyl sulfate （SDS）, and polyvinylpyrrolidone （PVP）） were modeled through time-resolved dynamic light scattering. In the presence of HA, MnO2 colloids were significantly stabilized with a critical coagulation concentration （CCC） of-300mmol · L-1 NaNO3 and 4 mmol.L-1 Ca（NO3）2. Electrophoretic mobility （EPM） measurements confirmed that steric hindrance may be primarily responsible for increasing colloidal stability in the presence of HA. Moreover, the molecular and/or chemical properties of HA might impact its stabilizing efficiency. In the case of PVP, only a slight increase of aggregation kinetics was observed, due to steric reactions originating from adsorbed layers of PVP on the MnO2 surface. Consequently, higher CCC values were obtained in the presence of PVP. However, there was a negligible reduction in MnO2 colloidal stability in the presence of 20 mg·L-1SDS.
基金International Science&Technology Innovation Program of Chinese Academy of Agricultural Sciences(Grant No.CAAS-ZDRW202110)the National Natural Science Foundation of China(Grant No.41771255).
文摘Low molecular weight organic acids(LMWOAs),as active components in the rhizosphere carbon cycling,may influence the environmental behaviors of biochar colloids.This study selected the pine-wood and wheat-straw biochars(PB and WB)as two typical biochars.The effects of typical LMWOAs(oxalic acid,citric acid,and malic acid)on aggregation kinetics of PB and WB colloids were investigated under pH 4 and 6 conditions.Critical coagulation concentrations(CCCs)of both PB and WB colloids were decreased with the LMWOAs regardless of the types of biochar and the solution pH,and the most significant effect occurred in pH 4 due to more LMWOAs sorption on the biochar colloids.The different types of LMWOAs caused various CCCs changes.For example,the CCC values of PB colloids decreased from 75 mM to 56,52,and 47 mM in the pH 4 NaCl solutions when 1 mM oxalic acid,citric acid,and malic acid were present in the suspensions,respectively.The chemical structure(functional groups)and molecular weight of LMWOAs,solution pH,and the electrophoretic mobility(EPM)of biochar co-influence the interactions between biochar colloids and LMWOAs,thus affecting the stability of biochar colloids in the presence of LMWOAs.The presence of LMWOAs accelerated the aggregation of colloidal biochar by increasing the interaction of surface bridging bonds(hydrogen bonding)and decreasing the repulsive force between colloidal biochar particles.This study showed that LMWOAs could accelerate the aggregation of biochar colloids in acidic or neutral environments and reduce the mobility of biochar colloids in soil rhizosphere.
文摘This study of the thermal decomposition kinetics of various average diameter nano-particles of cal-cium carbonate by means of TG-DTA(thermogravimetry and differential thermal analysis) showed that the thermal decomposition kinetic mechanisms of the same crystal type of calcium carbonate samples do not vary with decreasing of their average diameters ; their pseudo-active energy Ea; and that the top-temperature of decom-position Tp decreases gently in the scope of micron-sized diameter, but decreases sharply when the average di-ameter decreases from micron region to nanometer region. The extraordinary properties of nano-particles were explored by comparing the varying regularity of the mechanisms and kinetic parameters of the solid-phase reac-tions as well as their structural characterization with the variation of average diameters of particles. These show that the aggregation, surface effect as well as internal aberrance and stress of the nano-particles are the main reason causing both Ea and Tp to decline sharply with the decrease of the average diameter of nano-particles.
基金Funded by the National Natural Science Foundation of China(50973129,51273048)the National Natural Science Foundation of Guangdong Province(S2012010009743)
文摘Poly（N-isopropylacrylamide-co-N-vinylpyrrolidone） [P（NIPAM-co-NVP）] copolymers with different content of N-vinylpyrrolidone （NVP） were synthesized, and reversible aggregation kinetics of the copolymers in aqueous solutions was investigated with elastic light scattering （ELS） spectra. The results indicated that the apparent activation energy of aggregation process during heating and dissociation process during cooling increased with the NVP content increasing. The phase transition temperature also increased as the content of NVP increased, suggesting that the hydrophilic nature of NVP strongly affected the phase behavior of the copolymer solutions. The higher the content of NVP, the higher the temperature required to break the balance between the hydrophilic and hydrophobie interaction. Besides, during heating and cooling process, the phase transition hysteresis of P（NIPAM-co-NVP） chains decreased when the hydrophilic comonomer increased.
