Magnetic microsphere carriers have received considerable attention,primarily because of their wide applications in the fields of biomedicine and bioengineering.In this paper,preparation methods,surface modification an...Magnetic microsphere carriers have received considerable attention,primarily because of their wide applications in the fields of biomedicine and bioengineering.In this paper,preparation methods,surface modification and application of magnetic carriers are reviewed.Emphasis will be placed on recent biological and biomedical developments and trends such as enzyme immobilization,cell isolation,protein purification,target drugs and DNA separation.展开更多
超深井及非常规油气藏开采常常需要压裂液耐温180℃以上,笔者以羧甲基胍胶为母体,通过引入刚性基团2-吡咯烷酮,阳离子基团(2-氯乙基)三甲基氯化铵,将改性羧甲基胍胶与非离子型聚丙烯酰胺复配形成梯形结构,提高压裂液耐温抗剪切性能.采...超深井及非常规油气藏开采常常需要压裂液耐温180℃以上,笔者以羧甲基胍胶为母体,通过引入刚性基团2-吡咯烷酮,阳离子基团(2-氯乙基)三甲基氯化铵,将改性羧甲基胍胶与非离子型聚丙烯酰胺复配形成梯形结构,提高压裂液耐温抗剪切性能.采用傅里叶红外光谱仪(FT-IR)、热重分析仪(TG)对其结构和热稳定性进行表征,并对其交联性能、高温剪切性能进行测试.其中2-吡咯烷酮+(2-氯乙基)三甲基氯化铵改性羧甲基胍胶与聚丙烯酰胺复配在200℃、170 s-1的剪切速率下剪切60 min后的表观黏度为110 m Pa·s,比未改性的羧甲基胍胶耐温抗剪切能力有明显改善.展开更多
In order to improve the dispersibility of cellulose nanocrystal(CNC)particles,three different grafted reactions of acetylation,hydroxyethylation and hydroxypropylation were introduced to modify the CNC surface.The mai...In order to improve the dispersibility of cellulose nanocrystal(CNC)particles,three different grafted reactions of acetylation,hydroxyethylation and hydroxypropylation were introduced to modify the CNC surface.The main advan-tages of these methods were the simple and easily controlled reaction conditions,and the dispersibility of the resulting products was distinctly improved.The properties of the modified CNC were characterized by means of Fourier trans-form infrared spectroscopy(FT-IR),13C nuclear magnetic resonance(NMR),transmission electron microscopy(TEM)and thermogravimetric analyses(TGA).The results indicated that after desiccation,the modification products could be dis-persed again in the proper solvents by ultrasonic treatments,and the diameter of their particles had no obvious changes.However,their thermal degradation behaviors were quite dif-ferent.The initial decomposition temperature of the modified products via hydroxyethylation or hydroxypropylation was lower than that of modified products via acetylation.展开更多
The present study describes the effect of clouds （macro-physical parameters） on global solar radia- tion （G）. Data from four years of hourly measurements of G on a horizontal surface were used. These data were col...The present study describes the effect of clouds （macro-physical parameters） on global solar radia- tion （G）. Data from four years of hourly measurements of G on a horizontal surface were used. These data were collected at the South Valley University （SVU） meteoro- logical research station （26.2~N, 32.7~E, 96 m above mean see level. In addition, the cloud modification factor for G （CMF~）was estimated in three cases： high-level, mid-level, and low-level clouds. For every level, the variation of hourly CMF~ as a function of cloud amount （CA） was illustrated. A third-order polynomial between hourly values of CMFc and CA was established. Fur- thermore, the effect of CA in the attenuation of G relative to its corresponding value in cloudless conditions is dis- cussed. For cloud cover 〉 88%, G was reduced by 54%, 34%, and 28% by low-, mid-, and high-level clouds, re- spectively.展开更多
In order to explore the influence of modification sites of functional groups on landfill gas （CO2/CH4） separation performance of metal-organic frameworks （MOFs）, six types of or- ganic linkers and three types of f...In order to explore the influence of modification sites of functional groups on landfill gas （CO2/CH4） separation performance of metal-organic frameworks （MOFs）, six types of or- ganic linkers and three types of functional groups （i.e. -F, -NH2, -CH3） were used to construct 36 MOFs of pcu topology based on copper paddlewheel. Grand canonical Monte Carlo sim- ulations were performed in this work to evaluate the separation performance of MOFs at low （vacuum swing adsorption） and high （pressure swing adsorption） pressures, respectively. Simulation results demonstrated that CO2 working capacity of the unfunctionalized MOFs generally exhibits pore-size dependence at 1 bar, which increases with the decrease in pore sizes. It was also found that -NH2 funetionalized MOFs exhibit the highest CO2 uptake due to the enhanced Coulombic interactions between the polar -NH2 groups and the quadrupole moment of CO2 molecules, which is followed by -CH3 and -F functionalized ones. Moreover, positioning the functional groups -NH2 and -CH3 at sites far from the metal node （site b） exhibits more significant enhancement on CO2/CH4 separation performance compared to that adjacent to the metal node （site a）.展开更多
文摘Magnetic microsphere carriers have received considerable attention,primarily because of their wide applications in the fields of biomedicine and bioengineering.In this paper,preparation methods,surface modification and application of magnetic carriers are reviewed.Emphasis will be placed on recent biological and biomedical developments and trends such as enzyme immobilization,cell isolation,protein purification,target drugs and DNA separation.
文摘超深井及非常规油气藏开采常常需要压裂液耐温180℃以上,笔者以羧甲基胍胶为母体,通过引入刚性基团2-吡咯烷酮,阳离子基团(2-氯乙基)三甲基氯化铵,将改性羧甲基胍胶与非离子型聚丙烯酰胺复配形成梯形结构,提高压裂液耐温抗剪切性能.采用傅里叶红外光谱仪(FT-IR)、热重分析仪(TG)对其结构和热稳定性进行表征,并对其交联性能、高温剪切性能进行测试.其中2-吡咯烷酮+(2-氯乙基)三甲基氯化铵改性羧甲基胍胶与聚丙烯酰胺复配在200℃、170 s-1的剪切速率下剪切60 min后的表观黏度为110 m Pa·s,比未改性的羧甲基胍胶耐温抗剪切能力有明显改善.
文摘In order to improve the dispersibility of cellulose nanocrystal(CNC)particles,three different grafted reactions of acetylation,hydroxyethylation and hydroxypropylation were introduced to modify the CNC surface.The main advan-tages of these methods were the simple and easily controlled reaction conditions,and the dispersibility of the resulting products was distinctly improved.The properties of the modified CNC were characterized by means of Fourier trans-form infrared spectroscopy(FT-IR),13C nuclear magnetic resonance(NMR),transmission electron microscopy(TEM)and thermogravimetric analyses(TGA).The results indicated that after desiccation,the modification products could be dis-persed again in the proper solvents by ultrasonic treatments,and the diameter of their particles had no obvious changes.However,their thermal degradation behaviors were quite dif-ferent.The initial decomposition temperature of the modified products via hydroxyethylation or hydroxypropylation was lower than that of modified products via acetylation.
基金supported by the Deanship of Scientific Research-King Saud University
文摘The present study describes the effect of clouds （macro-physical parameters） on global solar radia- tion （G）. Data from four years of hourly measurements of G on a horizontal surface were used. These data were collected at the South Valley University （SVU） meteoro- logical research station （26.2~N, 32.7~E, 96 m above mean see level. In addition, the cloud modification factor for G （CMF~）was estimated in three cases： high-level, mid-level, and low-level clouds. For every level, the variation of hourly CMF~ as a function of cloud amount （CA） was illustrated. A third-order polynomial between hourly values of CMFc and CA was established. Fur- thermore, the effect of CA in the attenuation of G relative to its corresponding value in cloudless conditions is dis- cussed. For cloud cover 〉 88%, G was reduced by 54%, 34%, and 28% by low-, mid-, and high-level clouds, re- spectively.
基金supported by the National Natural Science Foundation of China(No.51606081)the Basic Research Foundation of Shenzhen(No.JCYJ20160506170043770)
文摘In order to explore the influence of modification sites of functional groups on landfill gas （CO2/CH4） separation performance of metal-organic frameworks （MOFs）, six types of or- ganic linkers and three types of functional groups （i.e. -F, -NH2, -CH3） were used to construct 36 MOFs of pcu topology based on copper paddlewheel. Grand canonical Monte Carlo sim- ulations were performed in this work to evaluate the separation performance of MOFs at low （vacuum swing adsorption） and high （pressure swing adsorption） pressures, respectively. Simulation results demonstrated that CO2 working capacity of the unfunctionalized MOFs generally exhibits pore-size dependence at 1 bar, which increases with the decrease in pore sizes. It was also found that -NH2 funetionalized MOFs exhibit the highest CO2 uptake due to the enhanced Coulombic interactions between the polar -NH2 groups and the quadrupole moment of CO2 molecules, which is followed by -CH3 and -F functionalized ones. Moreover, positioning the functional groups -NH2 and -CH3 at sites far from the metal node （site b） exhibits more significant enhancement on CO2/CH4 separation performance compared to that adjacent to the metal node （site a）.
