Vertebrate digits are essential structures for movement, feeding and communication. Specialized regions of the developing limb bud including the zone of polarizing activity （ZPA）, the apical ectodermal ridge （AER）...Vertebrate digits are essential structures for movement, feeding and communication. Specialized regions of the developing limb bud including the zone of polarizing activity （ZPA）, the apical ectodermal ridge （AER）, and the non-ridge ectoderm regulate the patterning of digits. Although a series of signaling molecules have been characterized as patterning signals from the organizing centers, the delicate cellular and molecular mechanisms that interpret how these patterning signals control the detailed digit anatomy remain unclear, Recent studies from model organisms and human hand malformations provide new insights into the mechanisms regulating this process. Here, we review the current understanding of the genetic networks governing digit morphogenesis展开更多
China is the largest producer and consumer of hydrochlorofluorocarbons （HCFCs）, and the production of HCFC-22 accounts for more than 80% of all HCFCs. This paper concentrates on the residential air-conditioner indus...China is the largest producer and consumer of hydrochlorofluorocarbons （HCFCs）, and the production of HCFC-22 accounts for more than 80% of all HCFCs. This paper concentrates on the residential air-conditioner industry and analyzes the environmental benefits of accelerating the phase-out of HCFC-22 in China. According to the comparison of the baseline and phase-out scenarios of HCFC-22, the findings show that using HC-290 （propane） as a refrigerant alternative will directly reduce the greenhouse effect, and indirectly reduce the emission of greenhouse gases due to a reduction in the electricity consumption. The comparison of two scenarios of HC-290 and HFC-410A refrigerant alternatives shows that the use of HC-290 refrigerant will produce significantly higher environmental benefits than the HFC-410A refrigerant.展开更多
By studying the characteristics of the flow field around a swimming fish,useful insights can be obtained into the superior swimming capabilities developed by nature over millions of years,in comparison to what can be ...By studying the characteristics of the flow field around a swimming fish,useful insights can be obtained into the superior swimming capabilities developed by nature over millions of years,in comparison to what can be achieved using the standard engineering principles traditionally employed in naval and ocean engineering.In the present study,the flow field related to a single joint fish model is simulated in the framework of a commercial computational fluid dynamics software(ANSYS Fluent 18.0).The principle of the anti-Kármán vortex street is analyzed and the relationship between the direction of the tail vortex and the direction of the fin swing is determined according to the vortex structures and the pressure distribution.A parametric investigation is finally conducted to analyze in particular how the Strouhal number(St)can affect the fish propulsive performance and efficiency。展开更多
HFC-134a is the most important alternative to CFC-12 used in the mobile air-conditioner sector in China. The con- sumption of HFC-134a has been increasing rapidly in recent years. It becomes the most consumed HFC in t...HFC-134a is the most important alternative to CFC-12 used in the mobile air-conditioner sector in China. The con- sumption of HFC-134a has been increasing rapidly in recent years. It becomes the most consumed HFC in the sector. Selecting 2005 as the base line year, future consumption and emission amounts of HFC-134a are estimated through an analysis of a combined scenario： 1） replacement by non-HFC-134a blends, 2） good practice in servicing, 3） technology promotion, and 4） government policies on control of HFC-134a emissions. The analysis shows that HFC-134a consumption and emissions will continue to increase in the next 10 years. The projected HFC-134a consumption will approach 20,150 t and 34,875 t in 2010 and 2015 respectively, while the estimated emission amounts will reach 16,065 t and 30,186 t （i.e., 21 Mt CO2-eq and 39 Mt CO2-eq emissions） correspondingly. Compared with the business-as-usual scenario, the expected emission reductions in 2010 and 2015 will range between 6.7 Mt CO2-eq and 13.0 Mt CO2-eq.展开更多
The innovation of organizational model of tobacco production is the key to realization of sustainable development of tobacco production in China. From the perspective of sustainable development, we analyze the necessi...The innovation of organizational model of tobacco production is the key to realization of sustainable development of tobacco production in China. From the perspective of sustainable development, we analyze the necessity of innovation of organizational model of tobacco production, put forward the principles on innovation of organizational model of tobacco production, and offer corresponding recommendations for the ways of innovation of organizational model of tobacco production.展开更多
In this study,boron–magnesium agglomerates with varying mass ratios were prepared by drying a micron-sized boron–magnesium mixed suspension,and the combustion process of these agglomerates under different oxygen-ric...In this study,boron–magnesium agglomerates with varying mass ratios were prepared by drying a micron-sized boron–magnesium mixed suspension,and the combustion process of these agglomerates under different oxygen-rich concentrations were investigated using a laser ignition system.The test results showed that when the mass fraction of magnesium powder in boron-magnesium agglomerates exceeded a certain threshold(between 2%and 5%),flame extinction and reignition occurred after a significant reduction in the agglomerate volume during combustion.This process is referred to as the transient flameout process,which is affected by the magnesium content of the agglomerate and the oxygen concentration in the ambient atmosphere.An increase in the magnesium content or oxygen concentration makes this phenomenon more pronounced.During weakening of the flame intensity,a dark film gradually covered the particle surfaces.X-ray diffraction and elemental analyses of the cross-section and outer surface of the condensed combustion product suggested that the dark film is primarily composed of Mg-B-O ternary oxides.This film prevents direct contact between boron and oxygen,thereby inhibiting surface and gas-phase reactions and leading to the occurrence of the transient flameout phenomenon.展开更多
The combustion of vinyl chloride(VC)after the train derailment accident in Ohio,USA in February,2023 has caused widespread concern around the world.This paper tried to analyze several issues concerning the accident,in...The combustion of vinyl chloride(VC)after the train derailment accident in Ohio,USA in February,2023 has caused widespread concern around the world.This paper tried to analyze several issues concerning the accident,including the appropriateness of the VC combustion in the emergency response in this accident,the meanings of so-called“controlled combustion”,the potential environmental risks caused by VC and combustion by-products,and follow-up work.In our view,this accident had surely caused environmental and health risks to some extent.Hence,a comprehensive environmental risk assessment is necessary,and then the site with risk should be comprehensively remediated,hazardous waste should be harmlessly treated as soon as possible.Finally,this accident suggests that further efforts should be taken to bridge the gap between chemical safety management and their environmental risk management.展开更多
1-Chloro-1,1-difluoroethane(HCFC-142b)was both ozone depleting substance under restriction of the Montreal Protocol on Substances that Deplete the Ozone Layer(Montreal Protocol)and potent greenhouse gas with high GWP....1-Chloro-1,1-difluoroethane(HCFC-142b)was both ozone depleting substance under restriction of the Montreal Protocol on Substances that Deplete the Ozone Layer(Montreal Protocol)and potent greenhouse gas with high GWP.Controlling its emissions in China will contribute to both mitigating climate change and protecting ozone.A national emission inventory of HCFC-142b for China during 2000–2012 was established and projected to2050 based on the 2006 IPCC Guidelines for National Greenhouse Gas Inventories and the Montreal Protocol,showing that(i)in contrast to the downward trend revealed by existing researches,HCFC-142b emissions kept increasing from 0.1 kt/y in 2000 to the peak of 14.4 kt/y in2012,making China a crucial contributor to global HCFC-142b emissions and(ii)for future emission projections,a continuous increase from 14.9 kt/y in 2013 to 97.2 kt/y in2050 was anticipated under the business-as-usual(BAU)scenarios,while a reduction of about 90%of the projected BAU emissions would be obtained by fulfilling the Montreal Protocol,namely an accumulative mitigation of 1578kt HCFC-142b from 2013 to 2050,equal to 103 kt ODP and 3504 Tg CO2emissions.Emissions from each province in 2012 were also estimated to identify key emission areas.Among the 31 mainland provinces in China(Hong Kong,Macao,and Taiwan were not included),Jiangsu,Zhejiang,Shandong,and Guangdong had the highest emission ratesin 2012(2.06,1.85,1.52,and 1.04 kt/y,respectively);Zhejiang,Jiangsu,and Shanghai exhibit the strongest emission strength(0.83,0.59,and 0.54 t/km2,respectively),much higher than the average national level of 0.33t/km2.展开更多
This paper reviews the usage and emissions of endosulfan, the newest member of the persistent organic pollutants （POPs）, in China, and its fate and behavior in Chinese environment. Endosulfan usage in China has been...This paper reviews the usage and emissions of endosulfan, the newest member of the persistent organic pollutants （POPs）, in China, and its fate and behavior in Chinese environment. Endosulfan usage in China has been estimated to be approximately 25700 t between 1994 and 2004. Concentrations of endosulfan in different environ- mental compartments in China, such as air, soil, water, and biota, but focusing at air and surface soil, have been summarized. Concentrations of total endosulfan in surface soil across China were ranged from below detection limit （BDL） to 19000 pg.g^-1 dry weight （dw）, with geometric mean of 120pg.g^-1dw. The results indicated that endo- sulfan sulfate had highest concentration in Chinese soil, followed by r- and α-endosulfan. Air concentrations of endosulfan in China were ranged 0-340 pg.m3 for a- endosulfan and 0-121 pg. m--3 for β-endosulfan, with high concentrations occurred in the cotton production areas. Gridded usage inventories of endosulfan on a fine gridded system with a 1/4° longitude by 1/6° latitude resolution were compiled, from which, emission to air and residues in soil of endosulfan were calculated in each grid by using a modified simplified gridded pesticide emission and residue model （SGPERM）, an integrated modeling system combining mathematical model, database management system, and geographic information system. Total emissions were around 10800 t from 1994 to 2004. Based on the emission and residue inventories, concentrations of α- and β- endosulfan in Chinese air and agricultural surface soil were also calculated for each grid cell, which are in general consistent with the published monitoring data.展开更多
基金the National Basic Research Program of China (973 Program) (No. 2007CB947301).
文摘Vertebrate digits are essential structures for movement, feeding and communication. Specialized regions of the developing limb bud including the zone of polarizing activity （ZPA）, the apical ectodermal ridge （AER）, and the non-ridge ectoderm regulate the patterning of digits. Although a series of signaling molecules have been characterized as patterning signals from the organizing centers, the delicate cellular and molecular mechanisms that interpret how these patterning signals control the detailed digit anatomy remain unclear, Recent studies from model organisms and human hand malformations provide new insights into the mechanisms regulating this process. Here, we review the current understanding of the genetic networks governing digit morphogenesis
文摘China is the largest producer and consumer of hydrochlorofluorocarbons （HCFCs）, and the production of HCFC-22 accounts for more than 80% of all HCFCs. This paper concentrates on the residential air-conditioner industry and analyzes the environmental benefits of accelerating the phase-out of HCFC-22 in China. According to the comparison of the baseline and phase-out scenarios of HCFC-22, the findings show that using HC-290 （propane） as a refrigerant alternative will directly reduce the greenhouse effect, and indirectly reduce the emission of greenhouse gases due to a reduction in the electricity consumption. The comparison of two scenarios of HC-290 and HFC-410A refrigerant alternatives shows that the use of HC-290 refrigerant will produce significantly higher environmental benefits than the HFC-410A refrigerant.
基金the National Natural Science Foundation of China,Grant Nos.51906224 and 51976200.
文摘By studying the characteristics of the flow field around a swimming fish,useful insights can be obtained into the superior swimming capabilities developed by nature over millions of years,in comparison to what can be achieved using the standard engineering principles traditionally employed in naval and ocean engineering.In the present study,the flow field related to a single joint fish model is simulated in the framework of a commercial computational fluid dynamics software(ANSYS Fluent 18.0).The principle of the anti-Kármán vortex street is analyzed and the relationship between the direction of the tail vortex and the direction of the fin swing is determined according to the vortex structures and the pressure distribution.A parametric investigation is finally conducted to analyze in particular how the Strouhal number(St)can affect the fish propulsive performance and efficiency。
文摘HFC-134a is the most important alternative to CFC-12 used in the mobile air-conditioner sector in China. The con- sumption of HFC-134a has been increasing rapidly in recent years. It becomes the most consumed HFC in the sector. Selecting 2005 as the base line year, future consumption and emission amounts of HFC-134a are estimated through an analysis of a combined scenario： 1） replacement by non-HFC-134a blends, 2） good practice in servicing, 3） technology promotion, and 4） government policies on control of HFC-134a emissions. The analysis shows that HFC-134a consumption and emissions will continue to increase in the next 10 years. The projected HFC-134a consumption will approach 20,150 t and 34,875 t in 2010 and 2015 respectively, while the estimated emission amounts will reach 16,065 t and 30,186 t （i.e., 21 Mt CO2-eq and 39 Mt CO2-eq emissions） correspondingly. Compared with the business-as-usual scenario, the expected emission reductions in 2010 and 2015 will range between 6.7 Mt CO2-eq and 13.0 Mt CO2-eq.
基金Supported by Technology Project of Sichuan Tobacco Monopoly Administration(201102014)
文摘The innovation of organizational model of tobacco production is the key to realization of sustainable development of tobacco production in China. From the perspective of sustainable development, we analyze the necessity of innovation of organizational model of tobacco production, put forward the principles on innovation of organizational model of tobacco production, and offer corresponding recommendations for the ways of innovation of organizational model of tobacco production.
基金financial support provided by the National Natural Science Foundation of China(grant No.52006240)supported by Hunan Provincial Natural Science Foundation of China(grant No.2020JJ4665 and No.2021JJ30775).
文摘In this study,boron–magnesium agglomerates with varying mass ratios were prepared by drying a micron-sized boron–magnesium mixed suspension,and the combustion process of these agglomerates under different oxygen-rich concentrations were investigated using a laser ignition system.The test results showed that when the mass fraction of magnesium powder in boron-magnesium agglomerates exceeded a certain threshold(between 2%and 5%),flame extinction and reignition occurred after a significant reduction in the agglomerate volume during combustion.This process is referred to as the transient flameout process,which is affected by the magnesium content of the agglomerate and the oxygen concentration in the ambient atmosphere.An increase in the magnesium content or oxygen concentration makes this phenomenon more pronounced.During weakening of the flame intensity,a dark film gradually covered the particle surfaces.X-ray diffraction and elemental analyses of the cross-section and outer surface of the condensed combustion product suggested that the dark film is primarily composed of Mg-B-O ternary oxides.This film prevents direct contact between boron and oxygen,thereby inhibiting surface and gas-phase reactions and leading to the occurrence of the transient flameout phenomenon.
文摘The combustion of vinyl chloride(VC)after the train derailment accident in Ohio,USA in February,2023 has caused widespread concern around the world.This paper tried to analyze several issues concerning the accident,including the appropriateness of the VC combustion in the emergency response in this accident,the meanings of so-called“controlled combustion”,the potential environmental risks caused by VC and combustion by-products,and follow-up work.In our view,this accident had surely caused environmental and health risks to some extent.Hence,a comprehensive environmental risk assessment is necessary,and then the site with risk should be comprehensively remediated,hazardous waste should be harmlessly treated as soon as possible.Finally,this accident suggests that further efforts should be taken to bridge the gap between chemical safety management and their environmental risk management.
基金supported by the State KeyLaboratory Program of China(09Z02ESPCP)
文摘1-Chloro-1,1-difluoroethane(HCFC-142b)was both ozone depleting substance under restriction of the Montreal Protocol on Substances that Deplete the Ozone Layer(Montreal Protocol)and potent greenhouse gas with high GWP.Controlling its emissions in China will contribute to both mitigating climate change and protecting ozone.A national emission inventory of HCFC-142b for China during 2000–2012 was established and projected to2050 based on the 2006 IPCC Guidelines for National Greenhouse Gas Inventories and the Montreal Protocol,showing that(i)in contrast to the downward trend revealed by existing researches,HCFC-142b emissions kept increasing from 0.1 kt/y in 2000 to the peak of 14.4 kt/y in2012,making China a crucial contributor to global HCFC-142b emissions and(ii)for future emission projections,a continuous increase from 14.9 kt/y in 2013 to 97.2 kt/y in2050 was anticipated under the business-as-usual(BAU)scenarios,while a reduction of about 90%of the projected BAU emissions would be obtained by fulfilling the Montreal Protocol,namely an accumulative mitigation of 1578kt HCFC-142b from 2013 to 2050,equal to 103 kt ODP and 3504 Tg CO2emissions.Emissions from each province in 2012 were also estimated to identify key emission areas.Among the 31 mainland provinces in China(Hong Kong,Macao,and Taiwan were not included),Jiangsu,Zhejiang,Shandong,and Guangdong had the highest emission ratesin 2012(2.06,1.85,1.52,and 1.04 kt/y,respectively);Zhejiang,Jiangsu,and Shanghai exhibit the strongest emission strength(0.83,0.59,and 0.54 t/km2,respectively),much higher than the average national level of 0.33t/km2.
文摘This paper reviews the usage and emissions of endosulfan, the newest member of the persistent organic pollutants （POPs）, in China, and its fate and behavior in Chinese environment. Endosulfan usage in China has been estimated to be approximately 25700 t between 1994 and 2004. Concentrations of endosulfan in different environ- mental compartments in China, such as air, soil, water, and biota, but focusing at air and surface soil, have been summarized. Concentrations of total endosulfan in surface soil across China were ranged from below detection limit （BDL） to 19000 pg.g^-1 dry weight （dw）, with geometric mean of 120pg.g^-1dw. The results indicated that endo- sulfan sulfate had highest concentration in Chinese soil, followed by r- and α-endosulfan. Air concentrations of endosulfan in China were ranged 0-340 pg.m3 for a- endosulfan and 0-121 pg. m--3 for β-endosulfan, with high concentrations occurred in the cotton production areas. Gridded usage inventories of endosulfan on a fine gridded system with a 1/4° longitude by 1/6° latitude resolution were compiled, from which, emission to air and residues in soil of endosulfan were calculated in each grid by using a modified simplified gridded pesticide emission and residue model （SGPERM）, an integrated modeling system combining mathematical model, database management system, and geographic information system. Total emissions were around 10800 t from 1994 to 2004. Based on the emission and residue inventories, concentrations of α- and β- endosulfan in Chinese air and agricultural surface soil were also calculated for each grid cell, which are in general consistent with the published monitoring data.
