Jilin City is a typical river valley city in Northeast China.In this paper,the authors studied the spatial and temporal expansion characteristics of the built-up areas in Jilin City from 1990 to 2020 using the analysi...Jilin City is a typical river valley city in Northeast China.In this paper,the authors studied the spatial and temporal expansion characteristics of the built-up areas in Jilin City from 1990 to 2020 using the analysis of expansion speed and strength,fractal dimension,barycenter coordinate transfer index and sector analysis.The ultimate-goal is to analyze the driving and restrictive factors that affect the spatial expansion of river valley cities.The results indicate that(1)the expansion speed of urban land in Jilin City has been re-latively slow in the past 30 years,while only slightly faster in 2010–2020;(2)in the spatial dimension,Jilin City mainly expanded to the south,then to the west,and extensive expansion has resulted in complex mor-phology with little stability and compactness;(3)the expansion is affected by multiple factors,of which the positive factor is industrial development,while the restrictive factors include natural factors,population loss,etc.This study provides a case for the formulation of land use policies and land space planning in river valley cities.展开更多
Following the trends of Chinese rural transformation development, and the sustainable development goals for resources and environment, reasonable arranging the potential development space and the ecological space, so ...Following the trends of Chinese rural transformation development, and the sustainable development goals for resources and environment, reasonable arranging the potential development space and the ecological space, so as to optimize the distributions of rural settlement would be the key challenge for rural areas in ecologically fragile regions. From the perspective of maintaining regional ecological security, this paper takes Da’an City, a typical ecological fragile region in Jilin Province, as the case area, constructing the comprehensive ecological security pattern(ESP) on basis of landscape ecology, and applying the landscape pattern indexes to quantitative analysis the spatial distribution characteristics of rural settlements. Then, different optimization directions and management strategies are put forward for rural settlements in each secure zone under the comprehensive ESP. The experimental results showed that 1) the area of the low security zone, the general security zone, the moderate security zone and the extreme security zone was 1570.18 km^2, 1463.36 km^2, 1215.80 km^2 and 629.77 km^2, representing 32.18%, 29.99%, 24.92% and 12.91% of the total area of the target area, respectively. 2) The rural settlements in Da’an City were characterized by a high degree of fragmentation with a large number of small-scale patches. 3) The area of rural settlements in the ecological relocation zone, the in situ remediation zone, the limited development zone and the key development zone was 22.80 km^2, 42.31 km^2, 36.28 km^2 and 19.40 km^2, accounting for 18.88%, 35.03%, 30.04% and 16.06% of the total area of rural settlements, respectively. Then, different measures were proposed for settlements in different optimization zones in order to scientifically plan important ecological space, production space and living space in rural areas. This paper aims to provide fundamental support for rural settlements based on redistribution from the perspective of landscape ecology and provide insights for rural planning and rural habitat environmental improvement.展开更多
Aromatic amine compounds and their derivatives are important intermediates of fine chemicals like dye and medicine. The former hydrogenation catalyst has many problems, such as environment pollution caused by old tech...Aromatic amine compounds and their derivatives are important intermediates of fine chemicals like dye and medicine. The former hydrogenation catalyst has many problems, such as environment pollution caused by old technology, strict reaction condition, complicated equipment, bad property of catalyst and so on. Holy [1] firstly reported the hydrogenation of nitrobenzene on modified polystyrene Pd catalyst. But how to improve the activity, selectivity and stability of the polymer supporter catalyst needs to studyfurther. We prepared a series of polymer supported catalysts by the methods of adsorption and mechanical mixting, selected a high active catalyst Pd-AH-1 by observing the hydrogenation of nitrobenzene.展开更多
Diethylamine, di-n-hexylamine, dicyclohexylamine and triethylamine have been used as initiators for the ring-opening polymerization of γ-benzyl-L-glutamate N-carboxyanhydride （BLG NCA） to synthesize poly（γ-benzyl...Diethylamine, di-n-hexylamine, dicyclohexylamine and triethylamine have been used as initiators for the ring-opening polymerization of γ-benzyl-L-glutamate N-carboxyanhydride （BLG NCA） to synthesize poly（γ-benzyl-L-glutamate） （PBLG）. The relationship between the molecular weight of PBLG and the molar ratio of monomer and initiator was studied. With dicy- clohexylamine as initiator, the influence of monomer concentration, and reaction temperature and time on the polymerization of BLG NCA was examined. Three reagents were used for the deprotection of benzyl groups in PBLG, including hydrobromic acid/acetic acid （33 wt.%）, NaOH aqueous solution and trimethylsilyl iodide （TMSI）. Through examining the molecular weight of PLGA obtained using different deprotection methods, it was revealed that TMSI could minimize chain cleavage in the process of deprotection and retain the degree of polymerization. The biocompatibilities of PBLG obtained using different initiators were evaluated by a live/dead assay against L929 fibroblast cells. The in vitro cytotoxicities of PLGA obtained using different deprotecting agents were evaluated by a methyl thiazolyl tetrazolium assay. The results revealed that both PBLG and PLGA exhibited good biocompatibilities.展开更多
基金Supported by Project of National Natural Science Foundation of China(No.42071255)。
文摘Jilin City is a typical river valley city in Northeast China.In this paper,the authors studied the spatial and temporal expansion characteristics of the built-up areas in Jilin City from 1990 to 2020 using the analysis of expansion speed and strength,fractal dimension,barycenter coordinate transfer index and sector analysis.The ultimate-goal is to analyze the driving and restrictive factors that affect the spatial expansion of river valley cities.The results indicate that(1)the expansion speed of urban land in Jilin City has been re-latively slow in the past 30 years,while only slightly faster in 2010–2020;(2)in the spatial dimension,Jilin City mainly expanded to the south,then to the west,and extensive expansion has resulted in complex mor-phology with little stability and compactness;(3)the expansion is affected by multiple factors,of which the positive factor is industrial development,while the restrictive factors include natural factors,population loss,etc.This study provides a case for the formulation of land use policies and land space planning in river valley cities.
基金the auspices of the National Natural Science Foundation of China(No.41571152,41771179)the Social Science Foundation of Jilin Province,China(No.2019B56)。
文摘Following the trends of Chinese rural transformation development, and the sustainable development goals for resources and environment, reasonable arranging the potential development space and the ecological space, so as to optimize the distributions of rural settlement would be the key challenge for rural areas in ecologically fragile regions. From the perspective of maintaining regional ecological security, this paper takes Da’an City, a typical ecological fragile region in Jilin Province, as the case area, constructing the comprehensive ecological security pattern(ESP) on basis of landscape ecology, and applying the landscape pattern indexes to quantitative analysis the spatial distribution characteristics of rural settlements. Then, different optimization directions and management strategies are put forward for rural settlements in each secure zone under the comprehensive ESP. The experimental results showed that 1) the area of the low security zone, the general security zone, the moderate security zone and the extreme security zone was 1570.18 km^2, 1463.36 km^2, 1215.80 km^2 and 629.77 km^2, representing 32.18%, 29.99%, 24.92% and 12.91% of the total area of the target area, respectively. 2) The rural settlements in Da’an City were characterized by a high degree of fragmentation with a large number of small-scale patches. 3) The area of rural settlements in the ecological relocation zone, the in situ remediation zone, the limited development zone and the key development zone was 22.80 km^2, 42.31 km^2, 36.28 km^2 and 19.40 km^2, accounting for 18.88%, 35.03%, 30.04% and 16.06% of the total area of rural settlements, respectively. Then, different measures were proposed for settlements in different optimization zones in order to scientifically plan important ecological space, production space and living space in rural areas. This paper aims to provide fundamental support for rural settlements based on redistribution from the perspective of landscape ecology and provide insights for rural planning and rural habitat environmental improvement.
文摘Aromatic amine compounds and their derivatives are important intermediates of fine chemicals like dye and medicine. The former hydrogenation catalyst has many problems, such as environment pollution caused by old technology, strict reaction condition, complicated equipment, bad property of catalyst and so on. Holy [1] firstly reported the hydrogenation of nitrobenzene on modified polystyrene Pd catalyst. But how to improve the activity, selectivity and stability of the polymer supporter catalyst needs to studyfurther. We prepared a series of polymer supported catalysts by the methods of adsorption and mechanical mixting, selected a high active catalyst Pd-AH-1 by observing the hydrogenation of nitrobenzene.
基金financially supported by the National Natural Science Foundation of China (50973060, 51173101, 51003055, 51233004, 51273196,50973108 and 51203153)the Science and Technology Commission of Shanghai Municipality (11JC1404200)the Innovation Program of Shanghai Municipal Education Commission (11YZ06)
文摘Diethylamine, di-n-hexylamine, dicyclohexylamine and triethylamine have been used as initiators for the ring-opening polymerization of γ-benzyl-L-glutamate N-carboxyanhydride （BLG NCA） to synthesize poly（γ-benzyl-L-glutamate） （PBLG）. The relationship between the molecular weight of PBLG and the molar ratio of monomer and initiator was studied. With dicy- clohexylamine as initiator, the influence of monomer concentration, and reaction temperature and time on the polymerization of BLG NCA was examined. Three reagents were used for the deprotection of benzyl groups in PBLG, including hydrobromic acid/acetic acid （33 wt.%）, NaOH aqueous solution and trimethylsilyl iodide （TMSI）. Through examining the molecular weight of PLGA obtained using different deprotection methods, it was revealed that TMSI could minimize chain cleavage in the process of deprotection and retain the degree of polymerization. The biocompatibilities of PBLG obtained using different initiators were evaluated by a live/dead assay against L929 fibroblast cells. The in vitro cytotoxicities of PLGA obtained using different deprotecting agents were evaluated by a methyl thiazolyl tetrazolium assay. The results revealed that both PBLG and PLGA exhibited good biocompatibilities.
