In this paper,a simple and cheap method for producing of amorphous cellulose was studied by treating the initial cellulosic material(MCC and waste paper)with a cold solvent,such as aqueous solution of 7%NaOH/12%Urea,a...In this paper,a simple and cheap method for producing of amorphous cellulose was studied by treating the initial cellulosic material(MCC and waste paper)with a cold solvent,such as aqueous solution of 7%NaOH/12%Urea,at the various ratios of the solvent to cellulose(v/w)(R).If was found that after treatment of cellulose materials with the solvent at R≥5,a completely amorphous cellulose(AC)is formed.Due to high digestibility,the AC with concentration of 50 g/L is converted to glucose almost completely for 48 h under the action of cellulolytic enzyme CTec-3 with a dose of 30 mg/g solid sample.Such sample can be used as an amorphous standard in the study of crystallinity degree and enzymatic hydrolysis of various types of cellulose and lignocellulose.It was found that enzymatic saccharification is most advantageous to carry out at elevated concentrations of AC,150 g/L.Due to high cost of MCC,it is preferable to use a cheap cellulose raw material,such as mixed waste paper(MWP),for the commercial production of AC and glucose.The resulting glucose can find application in biotechnology as a promising nutrient for various microorganisms.展开更多
In this research,the structural characteristics,specific surface area,sorption of water vapor,and wetting enthalpy of various polysaccharides(cellulose,hemicelluloses,starch,pectin,chitin,and chitosan)have been studie...In this research,the structural characteristics,specific surface area,sorption of water vapor,and wetting enthalpy of various polysaccharides(cellulose,hemicelluloses,starch,pectin,chitin,and chitosan)have been studied.It was confirmed that crystallites are inaccessible for water,and therefore water molecules can interact only with polar groups in noncrystalline(amorphous)domains of biopolymers.The isotherms of water vapor sorption for various polysaccharides had sigmoid shapes,which can be explained by the absorption of water molecules in heterogeneous amorphous domains having clusters with different packing densities.The method of contributions of polar groups to sorption of water molecules was used,which allowed to derivate a simple calculating equation to describe the shape of sorption isotherms.The wetting of biopolymers with water was accompanied by a high exothermic thermal effect,in direct proportion to the amorphicity degree.The sorption values and wetting enthalpies of amorphous domains of biopolymers were calculated,which allowed to find the hydrophilicity index and compare the hydrophilicity of the various polysaccharides.展开更多
In this article,structural characteristics of amorphous mono-,di-,and tri-substituted esters of cellulose have been studied.These esters were synthesized under homogenous conditions using anhydrides of various aliphat...In this article,structural characteristics of amorphous mono-,di-,and tri-substituted esters of cellulose have been studied.These esters were synthesized under homogenous conditions using anhydrides of various aliphatic acids.The specific gravity of the highly substituted samples was measured by a pycnometric method in the aqueous medium.To calculate the molar,Van der Waals,and free volumes,as well as the packing coefficient of amorphous esters the method of additive contributions of partial volumes of atoms and atom groups in the volumes of polymers was used.Based on the molar volume,also specific gravity of cellulose esters was calculated.The coincidence of calculated and experimental characteristics was shown.In addition,the relationship between glass transition temperature and free volume was found for the esters.The theoretical equations were derived,which provide predicting the structural characteristics of cellulose esters with different degrees of substitution.展开更多
Pedestrian well-being reflects emotional experience during walking.Analyzing which built environment factors influence pedestrian wellbeing not only helps to improve residents’physical and mental health but also enco...Pedestrian well-being reflects emotional experience during walking.Analyzing which built environment factors influence pedestrian wellbeing not only helps to improve residents’physical and mental health but also encourages more walking.Based on the data obtained via a questionnaire survey in Harbin,China,a gradient boosting decision tree(GBDT)model is developed to analyze how the perception of the built environment influences pedestrian well-being and to explain the differences across types of neighborhoods(old,new,and mixed).The results show that pedestrian well-being is most influenced by the diversity of daily service facilities,followed by the number of commercial facilities along a street,the accessibility of daily service facilities,and green spaces.Moreover,pedestrian well-being is also influenced by the type of neighborhoods.In new neighborhoods,it is dominated by the accessibility of public transport stations,while in old and mixed neighborhoods,pedestrian well-being is primarily determined by the accessibility of green spaces and the number of green spaces,respectively.Depending on the characteristics of the built environment,different intervention measures are proposed to improve pedestrian well-being and promote walking.展开更多
We analytically and numerically compute the Onsager dissociation rate(exciton dissociation)on an interface induced by a piezoelectric potential in an inorganicorganic hybrid p-n junction system(ZnO+(poly(p-phenylene v...We analytically and numerically compute the Onsager dissociation rate(exciton dissociation)on an interface induced by a piezoelectric potential in an inorganicorganic hybrid p-n junction system(ZnO+(poly(p-phenylene vinylene));PPV).When a positive piezoelectric potential is created at the interface region owing to the deformation of the system,free electrons accumulate at the interface.Hence,screening effects are observed.It is assumed that the electron layer formed at the interface then attracts free holes from the p-type PPV region,which leads to exciton formation,possibly via the Langevin recombination process.The increased exciton density can then contribute to the Onsager dissociation rate,which is maximum around the interface.This paper focuses on the role of piezoelectric effects in promoting exciton formation at the interface and its relation with the exciton dissociation rate.展开更多
文摘In this paper,a simple and cheap method for producing of amorphous cellulose was studied by treating the initial cellulosic material(MCC and waste paper)with a cold solvent,such as aqueous solution of 7%NaOH/12%Urea,at the various ratios of the solvent to cellulose(v/w)(R).If was found that after treatment of cellulose materials with the solvent at R≥5,a completely amorphous cellulose(AC)is formed.Due to high digestibility,the AC with concentration of 50 g/L is converted to glucose almost completely for 48 h under the action of cellulolytic enzyme CTec-3 with a dose of 30 mg/g solid sample.Such sample can be used as an amorphous standard in the study of crystallinity degree and enzymatic hydrolysis of various types of cellulose and lignocellulose.It was found that enzymatic saccharification is most advantageous to carry out at elevated concentrations of AC,150 g/L.Due to high cost of MCC,it is preferable to use a cheap cellulose raw material,such as mixed waste paper(MWP),for the commercial production of AC and glucose.The resulting glucose can find application in biotechnology as a promising nutrient for various microorganisms.
文摘In this research,the structural characteristics,specific surface area,sorption of water vapor,and wetting enthalpy of various polysaccharides(cellulose,hemicelluloses,starch,pectin,chitin,and chitosan)have been studied.It was confirmed that crystallites are inaccessible for water,and therefore water molecules can interact only with polar groups in noncrystalline(amorphous)domains of biopolymers.The isotherms of water vapor sorption for various polysaccharides had sigmoid shapes,which can be explained by the absorption of water molecules in heterogeneous amorphous domains having clusters with different packing densities.The method of contributions of polar groups to sorption of water molecules was used,which allowed to derivate a simple calculating equation to describe the shape of sorption isotherms.The wetting of biopolymers with water was accompanied by a high exothermic thermal effect,in direct proportion to the amorphicity degree.The sorption values and wetting enthalpies of amorphous domains of biopolymers were calculated,which allowed to find the hydrophilicity index and compare the hydrophilicity of the various polysaccharides.
文摘In this article,structural characteristics of amorphous mono-,di-,and tri-substituted esters of cellulose have been studied.These esters were synthesized under homogenous conditions using anhydrides of various aliphatic acids.The specific gravity of the highly substituted samples was measured by a pycnometric method in the aqueous medium.To calculate the molar,Van der Waals,and free volumes,as well as the packing coefficient of amorphous esters the method of additive contributions of partial volumes of atoms and atom groups in the volumes of polymers was used.Based on the molar volume,also specific gravity of cellulose esters was calculated.The coincidence of calculated and experimental characteristics was shown.In addition,the relationship between glass transition temperature and free volume was found for the esters.The theoretical equations were derived,which provide predicting the structural characteristics of cellulose esters with different degrees of substitution.
基金the National Natural Science Foundation of China(Grant Nos.51878204,52278057).
文摘Pedestrian well-being reflects emotional experience during walking.Analyzing which built environment factors influence pedestrian wellbeing not only helps to improve residents’physical and mental health but also encourages more walking.Based on the data obtained via a questionnaire survey in Harbin,China,a gradient boosting decision tree(GBDT)model is developed to analyze how the perception of the built environment influences pedestrian well-being and to explain the differences across types of neighborhoods(old,new,and mixed).The results show that pedestrian well-being is most influenced by the diversity of daily service facilities,followed by the number of commercial facilities along a street,the accessibility of daily service facilities,and green spaces.Moreover,pedestrian well-being is also influenced by the type of neighborhoods.In new neighborhoods,it is dominated by the accessibility of public transport stations,while in old and mixed neighborhoods,pedestrian well-being is primarily determined by the accessibility of green spaces and the number of green spaces,respectively.Depending on the characteristics of the built environment,different intervention measures are proposed to improve pedestrian well-being and promote walking.
基金This research was supported by the Office of the Theory&Modeling Based Design of Energy Harvesting,Korea.
文摘We analytically and numerically compute the Onsager dissociation rate(exciton dissociation)on an interface induced by a piezoelectric potential in an inorganicorganic hybrid p-n junction system(ZnO+(poly(p-phenylene vinylene));PPV).When a positive piezoelectric potential is created at the interface region owing to the deformation of the system,free electrons accumulate at the interface.Hence,screening effects are observed.It is assumed that the electron layer formed at the interface then attracts free holes from the p-type PPV region,which leads to exciton formation,possibly via the Langevin recombination process.The increased exciton density can then contribute to the Onsager dissociation rate,which is maximum around the interface.This paper focuses on the role of piezoelectric effects in promoting exciton formation at the interface and its relation with the exciton dissociation rate.
