Wood is composed of mostly hollow, elongated, spindle-shaped cells that are arranged parallel to each other along the trunk of a tree. The characteristics of these fibrous cells and their arrangement affect strength p...Wood is composed of mostly hollow, elongated, spindle-shaped cells that are arranged parallel to each other along the trunk of a tree. The characteristics of these fibrous cells and their arrangement affect strength properties, appearance, resistance to penetration by water and chemical solutions, resistance to decay and many other properties. The characterisation of wood helps in identifying them. In this work, we studied the anatomical properties of three lesser utilised Ghanaian hardwood species namely Albizia ferruginea (Guill. & Perr.) Benth, Blighia sapida K. D. Koenig and Sterculia rhinopetala K. Schum using the light microscope and scanning electron microscope (SEM). Anatomical features studied were fiber length, double fiber wall thickness, fiber proportion, vessel diameter and proportion, rays and axial parenchyma proportions. We observed that the use of SEM in studying the anatomical or ultra-structural aspects of wood gave a clearer understanding of the features and structures found in wood. Anatomical features such as presence of crystals and absence of axial parenchyma in Blighia sapida and the thick wall fibers of Sterculia rhinopetala were better understood.展开更多
Background International students contribute to the academic and economic vitality of US higher education while facing exacerbated mental health challenges.Little is known about national trends in anxiety,depression,s...Background International students contribute to the academic and economic vitality of US higher education while facing exacerbated mental health challenges.Little is known about national trends in anxiety,depression,suicidal ideation and mental health service utilisation in this population.Aims This study examined national trends in the prevalence of clinically significant anxiety,depression,suicidal ideation and service utilisation among international students in US higher education from 2015 to 2024.Methods This repeated cross-sectional study analysed annual data from the Healthy Minds Study,a national survey of collegiate mental health,including 44560 international students.Weighted prevalence estimates were calculated,and multivariable logistic regression models were used to examine temporal trends,controlling for demographic characteristics.Results The weighted annual prevalence of anxiety increased by 78.25%(from 20.46%in 2015-2016 to 36.47%in 2023-2024),depression increased by 73.04%(from 20.44%to 35.37%),suicidal ideation increased by 92.52%(from 5.35%to 10.30%)and service utilisation increased by 45.82%(from 5.26%to 7.67%).In logistic models controlling for demographic characteristics,the increasing trends in anxiety(adjusted odds ratio(aOR)2.21;95%CI 2.07 to 2.36;p<0.001),depression(aOR 1.93;95%CI 1.80 to 2.06;p<0.001),suicidal ideation(aOR 1.57;95%CI 1.41 to 1.74;p<0.001)and service utilisation(aOR 2.01;95%CI 1.79 to 2.26;p<0.001)remained statistically significant over time.Conclusions The prevalence of anxiety,depression and suicidal ideation nearly doubled among international students from 2015 to 2024,while counselling service utilisation increased at a slower rate,indicating persistent gaps in mental healthcare.These findings suggest the need for proactive interventions,culturally competent services and expanded outreach efforts to bridge the mental health service gap for international students.展开更多
With the intensification of the energy crisis and the worsening greenhouse effect,the development of sustainable integrated energy systems(IES)has become a crucial direction for energy transition.In this context,this ...With the intensification of the energy crisis and the worsening greenhouse effect,the development of sustainable integrated energy systems(IES)has become a crucial direction for energy transition.In this context,this paper proposes a low-carbon economic dispatch strategy under the green hydrogen certificate trading(GHCT)and the ladder-type carbon emission trading(CET)mechanism,enabling the coordinated utilization of green and blue hydrogen.Specifically,a proton exchange membrane electrolyzer(PEME)model that accounts for dynamic efficiency characteristics,and a steam methane reforming(SMR)model incorporating waste heat recovery,are developed.Based on these models,a hydrogen production–storage–utilization framework is established to enable the coordinated deployment of green and blue hydrogen.Furthermore,the gas turbine(GT)unit are retrofitted using oxygenenriched combustion carbon capture(OCC)technology,wherein the oxygen produced by PEME is employed to create an oxygen-enriched combustion environment.This approach reduces energy waste and facilitates low-carbon power generation.In addition,the GHCT mechanism is integrated into the system alongside the ladder-type CET mechanism,and their complementary effects are investigated.A comprehensive optimization model is then formulated to simultaneously achieve carbon reduction and economic efficiency across the system.Case study results show that the proposed strategy reduces wind curtailment by 7.77%,carbon emissions by 65.98%,and total cost by 12.57%.This study offers theoretical reference for the low-carbon,economic,and efficient operation of future energy systems.展开更多
Integrated energy systems(IES)are widely regarded as a key enabler of carbon neutrality,enabling the coordinated use of electricity,heat,and gas to support large-scale renewable integration.Yet their practical deploym...Integrated energy systems(IES)are widely regarded as a key enabler of carbon neutrality,enabling the coordinated use of electricity,heat,and gas to support large-scale renewable integration.Yet their practical deployment still faces major challenges,including rigid thermoelectric coupling,insufficient operational flexibility,and fragmented carbon and certificate market mechanisms.To address these issues,this study proposes a low-carbon economic dispatch model for integrated energy systems(IES)that reduces emissions and costs while improving renewable energy utilization.A coordinated framework integrating carbon capture,utilization,and storage,two-stage power-to-gas,combined heat and power,and ground-source heat pump technologies enhances multi-energy complementarity and overcomes the heat-led constraints of traditional combined heat and power systems.A unified carbon emission trading and green certificate trading mechanism is designed to balance economic and environmental goals through cross-market synergy.To address uncertainty,a distributionally robust chance-constrained model based on Kullback-Leibler divergence is introduced in Scenario 8.The model is solved using the GUROBI solver under multiple scenarios.Simulation results show a cost reduction from$56,166.66 to$25,840.32,carbon emission cuts from 801.38to 440.90 t,and wind/photovoltaic utilization rates reaching 98%,which fully demonstrates the effectiveness of the proposed framework in achieving cost-efficient low-carbon operation of IES.展开更多
[Objective] The purpose of this study is to determine the effects of com-bined use of boron and manganese fertilizers on the nutritional quality and physio-logical indices of Brassica campestris. [Method] In the nutri...[Objective] The purpose of this study is to determine the effects of com-bined use of boron and manganese fertilizers on the nutritional quality and physio-logical indices of Brassica campestris. [Method] In the nutrient solutions for growing B. campestris by hydroponics, boric acid and manganese sulfate were added at 0.5, 2.5, and 7.5 mg/L respectively. Another treatment without boron and manganese was prepared as the control. Quality and physiological indices of B. campestris in the 10 treatments were measured. [Result] Boron and manganese shared obvious in-teraction in improving the quality and physiological indices of B. campestris. To cul-tivate B. campestris with high quality and strong resistance, the optimum concentra-tions of boron and manganese in the nutrient solution should be 2.5 mg/L boric acid and 2.5-7.5 mg/L manganese sulfate. [Conclusion] The findings wil provide refer-ence for studying effects of trace elements on nutrient composition of vegetables.展开更多
The characteristics of the energy structure of rich coal,less oil and less gas,coupling with a high external dependence on oil and natural gas and the emphasis on the efficient and clean utilisation of coal,have broug...The characteristics of the energy structure of rich coal,less oil and less gas,coupling with a high external dependence on oil and natural gas and the emphasis on the efficient and clean utilisation of coal,have brought opportunities for coal chemical industry.However,with the large-scale popularisation of coal gasification technology,the production and resulting storage of coal gasification slag continue to increase,which not only result in serious environmental pollution and a waste of terrestrial resources,but also seriously affect the sustainable development of coal chemical enterprises.Hence,the treatment of coal gasification slag is extremely important.In this paper,the production,composition,morphology,particle size structure and water holding characteristics of coal gasification slag are introduced,and the methods of carbon ash separation of gasification slag,both domestically and abroad,are summarised.In addition,the paper also summarises the research progress on gasification slag in building materials,ecological restoration,residual carbon utilisation and other high-value utilisation,and ultimately puts forward the idea of the comprehensive utilisation of gasification slag.For large-scale consumption to solve the environmental problems of enterprises and achieve high-value utilisation to increase the economic benefits of enterprises,it is urgent to zealously design a reasonable and comprehensive utilisation technologies with simple operational processes,strong adaptability and economic benefits.展开更多
An innovative in-situ stabilisation treatment followed by ex-situ sediment composting was tested for its ability to treat and dispose of heavy-metal-polluted sediments in a river near the Chinese Pearl Delta. First, p...An innovative in-situ stabilisation treatment followed by ex-situ sediment composting was tested for its ability to treat and dispose of heavy-metal-polluted sediments in a river near the Chinese Pearl Delta. First, polluted sediments were treated in-situ to stabilise the heavy metals. Then the treated sediments were dredged, dewatered and sent for high temperature aerobic composting （HTAC） treatment. Finally, the compost products were used as a fertiliser for fiver bank plants. The stabilisation efficiency of heavy metals during the process was investigated and the results are as follows： （1） using in-situ stabilisation, the extraction concentrations of Cu, Zn and Pb were reduced by 65.0%, 82.2% and 90.0%, respectively, which are much lower than the national standard given in the Identification Standard for Hazardous Waste （GB5085.3-1996）; （2） chemical fraction analysis showed that heavy metals were further stabilized during the HTAC treatment; （3） the concentrations of Cu, Zn and Pb in rainwater leachate through the river bank met the level of class V in the Environmental Quality Standards for Surface Water in China （GB3838-2002）. Therefore, using this new process, the toxicities of heavy metals in sediments were reduced markedly.展开更多
A new hemiterpenoid, （＋）-（2R,3S）-2-chloro-3-hydroxy-3-methyl-T-buty-rolactone was isolatexi from the leaves of Prinsepia utilis Royle. Its structure was clucidatexi by spectroscopic methods and X-ray crystallogra...A new hemiterpenoid, （＋）-（2R,3S）-2-chloro-3-hydroxy-3-methyl-T-buty-rolactone was isolatexi from the leaves of Prinsepia utilis Royle. Its structure was clucidatexi by spectroscopic methods and X-ray crystallographic analysis.展开更多
Using political ecology as its conceptual framework,this paper focuses on the changes in forest utilisation and management of South Kyrgyzstan’s walnut-fruit forests over the last century. The aim of this study on hu...Using political ecology as its conceptual framework,this paper focuses on the changes in forest utilisation and management of South Kyrgyzstan’s walnut-fruit forests over the last century. The aim of this study on human-environment interactions is to investigate the relationship between actors on the one side,their interests and demands,and the forests and forested lands on the other. Forest resource utilisation and management — and even the recognition of different forest products as resources — are connected with political and socio-economic conditions that change with time. The walnut-fruit forests of South Kyrgyzstan are unique,characterised by high biodiversity and a multiplicity of usable products;and they have been utilised for a long time. Centralised and formal management of the forests started with the Russian occupation and was strengthened under Soviet rule,when the region became a part of the USSR. During this era,a state forest administration that was structured from Moscow all the way down to the local level drew up detailed plans and developed procedures for utilising the different forest products. Since the collapse of the Soviet Union,the socio-political and economic frame conditions have changed significantly,which has brought not only the sweeping changes in the managing institutions,but also the access rights and interests in the forest resources. At present,the region is suffering from a high unemployment rate,which has resulted in the forests’ gaining considerable importance in the livelihood strategies of the local population. Political and economic liberalization,increased communication and trans-regional exchange relations have opened the door for international companies and agents interested in the valuable forest products. Today,walnut wood and burls,walnuts,wild apples and mushrooms are all exported to various countries in the world. Scientists and members of various international organisations stress the ecological value of the forests and are trying to establish nature conservation areas. Nevertheless,it is to fear that a multiplicity of interrelated factors — the present transformation and globalization processes,the appearance of new actors,the local population’s insecure economic situation and the erosion of managing institutions — are all leading to an intensified and unregulated exploitation of the forests,resulting in their degradation.展开更多
Under the optimal condition of copper ions adsorption on yeast,we found some different effects among static adsorption, shaking adsorption and negative pressure cavitation adsorption, and the methods of yeast with dif...Under the optimal condition of copper ions adsorption on yeast,we found some different effects among static adsorption, shaking adsorption and negative pressure cavitation adsorption, and the methods of yeast with different pretreatments also affect adsorption of copper ions. At the same time, the change of intercellular pH before and after adsorption of copper with BCECF was studied. The copper distribution was located by using PhenGreen （dipotassium salt and diacetate）, and the surface of yeast was observed by an atomic force microscope. The results showed that negative pressure cavitation can improve bioadsorption capacity of copper ions on yeast. However, the yeasts＇ pretreatment has a higher effect on bioadsorption. It indicates that heavy metal bioadsorption on yeast has much relation with its cellular molecule basis. With the adsorping, the intercellular pH of yeast increased gradually and changed from acidity to alkalescence. These results may suggest that negative pressure cavitation can compel heavy metals to transfer from the cell surface into inside cell and make the surface of yeast coarse.展开更多
Monitoring soil microbial communities can lead to better understanding of the transformation processes of organic carbon in soil. The present study investigated the changes of soil microbial communities during straw d...Monitoring soil microbial communities can lead to better understanding of the transformation processes of organic carbon in soil. The present study investigated the changes of soil microbial communities during straw decomposition in three fields, i.e., cropland, peach orchard and vineyard. Straw decomposition was monitored for 360 d using a mesh-bag method. Soil microbial metabolic activity and functional diversity were measured using the Biolog-Eco system. In all three fields, dried straws with a smaller size decomposed faster than their fresh counterparts that had a larger size. Dried corn straw decomposed slower than dried soybean straw in the early and middle stages, while the reverse trend was found in the late stage. The cropland showed the highest increase in microbial metabolic activity during the straw decomposition, whereas the peach orchard showed the lowest. There was no significant change in the species dominance or evenness of soil microbial communities during the straw decomposition. However, the species richness fluctuated significantly, with the peach orchard showing the highest richness and the cropland the lowest. With different carbon sources, the peach orchard utilised carbon the most, followed by the cropland and the vineyard. In all three fields, carbon was utilized in following decreasing order： saccharides〉amino acids〉polymers〉polyamines〉carboxylic acids〉aromatic compounds. In terms of carbon-source utilization, soil microbial communities in the peach orchard were less stable than those in the cropland. The metabolic activity and species dominance of soil microbial communities were negatively correlated with the straw residual percentage. Refractory components were primarily accumulated in the late stages, thus slowing down the straw decomposition. The results showed that dried and crushed corn straw was better for application in long-term fields. The diversity of soil microbial communities was more stable in cropland than in orchards during the straw decomposition.展开更多
文摘Wood is composed of mostly hollow, elongated, spindle-shaped cells that are arranged parallel to each other along the trunk of a tree. The characteristics of these fibrous cells and their arrangement affect strength properties, appearance, resistance to penetration by water and chemical solutions, resistance to decay and many other properties. The characterisation of wood helps in identifying them. In this work, we studied the anatomical properties of three lesser utilised Ghanaian hardwood species namely Albizia ferruginea (Guill. & Perr.) Benth, Blighia sapida K. D. Koenig and Sterculia rhinopetala K. Schum using the light microscope and scanning electron microscope (SEM). Anatomical features studied were fiber length, double fiber wall thickness, fiber proportion, vessel diameter and proportion, rays and axial parenchyma proportions. We observed that the use of SEM in studying the anatomical or ultra-structural aspects of wood gave a clearer understanding of the features and structures found in wood. Anatomical features such as presence of crystals and absence of axial parenchyma in Blighia sapida and the thick wall fibers of Sterculia rhinopetala were better understood.
文摘Background International students contribute to the academic and economic vitality of US higher education while facing exacerbated mental health challenges.Little is known about national trends in anxiety,depression,suicidal ideation and mental health service utilisation in this population.Aims This study examined national trends in the prevalence of clinically significant anxiety,depression,suicidal ideation and service utilisation among international students in US higher education from 2015 to 2024.Methods This repeated cross-sectional study analysed annual data from the Healthy Minds Study,a national survey of collegiate mental health,including 44560 international students.Weighted prevalence estimates were calculated,and multivariable logistic regression models were used to examine temporal trends,controlling for demographic characteristics.Results The weighted annual prevalence of anxiety increased by 78.25%(from 20.46%in 2015-2016 to 36.47%in 2023-2024),depression increased by 73.04%(from 20.44%to 35.37%),suicidal ideation increased by 92.52%(from 5.35%to 10.30%)and service utilisation increased by 45.82%(from 5.26%to 7.67%).In logistic models controlling for demographic characteristics,the increasing trends in anxiety(adjusted odds ratio(aOR)2.21;95%CI 2.07 to 2.36;p<0.001),depression(aOR 1.93;95%CI 1.80 to 2.06;p<0.001),suicidal ideation(aOR 1.57;95%CI 1.41 to 1.74;p<0.001)and service utilisation(aOR 2.01;95%CI 1.79 to 2.26;p<0.001)remained statistically significant over time.Conclusions The prevalence of anxiety,depression and suicidal ideation nearly doubled among international students from 2015 to 2024,while counselling service utilisation increased at a slower rate,indicating persistent gaps in mental healthcare.These findings suggest the need for proactive interventions,culturally competent services and expanded outreach efforts to bridge the mental health service gap for international students.
基金supported by National Natural Science Foundation of China(52477101)Natural Science Foundation of Jiangsu Province(BK20210932).
文摘With the intensification of the energy crisis and the worsening greenhouse effect,the development of sustainable integrated energy systems(IES)has become a crucial direction for energy transition.In this context,this paper proposes a low-carbon economic dispatch strategy under the green hydrogen certificate trading(GHCT)and the ladder-type carbon emission trading(CET)mechanism,enabling the coordinated utilization of green and blue hydrogen.Specifically,a proton exchange membrane electrolyzer(PEME)model that accounts for dynamic efficiency characteristics,and a steam methane reforming(SMR)model incorporating waste heat recovery,are developed.Based on these models,a hydrogen production–storage–utilization framework is established to enable the coordinated deployment of green and blue hydrogen.Furthermore,the gas turbine(GT)unit are retrofitted using oxygenenriched combustion carbon capture(OCC)technology,wherein the oxygen produced by PEME is employed to create an oxygen-enriched combustion environment.This approach reduces energy waste and facilitates low-carbon power generation.In addition,the GHCT mechanism is integrated into the system alongside the ladder-type CET mechanism,and their complementary effects are investigated.A comprehensive optimization model is then formulated to simultaneously achieve carbon reduction and economic efficiency across the system.Case study results show that the proposed strategy reduces wind curtailment by 7.77%,carbon emissions by 65.98%,and total cost by 12.57%.This study offers theoretical reference for the low-carbon,economic,and efficient operation of future energy systems.
文摘Integrated energy systems(IES)are widely regarded as a key enabler of carbon neutrality,enabling the coordinated use of electricity,heat,and gas to support large-scale renewable integration.Yet their practical deployment still faces major challenges,including rigid thermoelectric coupling,insufficient operational flexibility,and fragmented carbon and certificate market mechanisms.To address these issues,this study proposes a low-carbon economic dispatch model for integrated energy systems(IES)that reduces emissions and costs while improving renewable energy utilization.A coordinated framework integrating carbon capture,utilization,and storage,two-stage power-to-gas,combined heat and power,and ground-source heat pump technologies enhances multi-energy complementarity and overcomes the heat-led constraints of traditional combined heat and power systems.A unified carbon emission trading and green certificate trading mechanism is designed to balance economic and environmental goals through cross-market synergy.To address uncertainty,a distributionally robust chance-constrained model based on Kullback-Leibler divergence is introduced in Scenario 8.The model is solved using the GUROBI solver under multiple scenarios.Simulation results show a cost reduction from$56,166.66 to$25,840.32,carbon emission cuts from 801.38to 440.90 t,and wind/photovoltaic utilization rates reaching 98%,which fully demonstrates the effectiveness of the proposed framework in achieving cost-efficient low-carbon operation of IES.
基金Supported by a grant from Ministry of Science and Technology for the Project of Science and Technology Talents Serving in Enterprise(2009GJC50042)~~
文摘[Objective] The purpose of this study is to determine the effects of com-bined use of boron and manganese fertilizers on the nutritional quality and physio-logical indices of Brassica campestris. [Method] In the nutrient solutions for growing B. campestris by hydroponics, boric acid and manganese sulfate were added at 0.5, 2.5, and 7.5 mg/L respectively. Another treatment without boron and manganese was prepared as the control. Quality and physiological indices of B. campestris in the 10 treatments were measured. [Result] Boron and manganese shared obvious in-teraction in improving the quality and physiological indices of B. campestris. To cul-tivate B. campestris with high quality and strong resistance, the optimum concentra-tions of boron and manganese in the nutrient solution should be 2.5 mg/L boric acid and 2.5-7.5 mg/L manganese sulfate. [Conclusion] The findings wil provide refer-ence for studying effects of trace elements on nutrient composition of vegetables.
基金financially supported by the National Key Research and Development Program of China(2019YFC1904302)Foundation of State Key Laboratory of High-efficiency Utilisation of Coal and Green Chemical Engineering(2021-K81)the Technology of Coal-to-liquids Research Institute of National Energy Group([2020]010)。
文摘The characteristics of the energy structure of rich coal,less oil and less gas,coupling with a high external dependence on oil and natural gas and the emphasis on the efficient and clean utilisation of coal,have brought opportunities for coal chemical industry.However,with the large-scale popularisation of coal gasification technology,the production and resulting storage of coal gasification slag continue to increase,which not only result in serious environmental pollution and a waste of terrestrial resources,but also seriously affect the sustainable development of coal chemical enterprises.Hence,the treatment of coal gasification slag is extremely important.In this paper,the production,composition,morphology,particle size structure and water holding characteristics of coal gasification slag are introduced,and the methods of carbon ash separation of gasification slag,both domestically and abroad,are summarised.In addition,the paper also summarises the research progress on gasification slag in building materials,ecological restoration,residual carbon utilisation and other high-value utilisation,and ultimately puts forward the idea of the comprehensive utilisation of gasification slag.For large-scale consumption to solve the environmental problems of enterprises and achieve high-value utilisation to increase the economic benefits of enterprises,it is urgent to zealously design a reasonable and comprehensive utilisation technologies with simple operational processes,strong adaptability and economic benefits.
基金supported by the Scientific and Tech- nological Planning Project of Guangdong Province (No. 2003A3040404)the Guangdong & Hong Kong Tech- nology Cooperation Funding (No. 2006A36702001)
文摘An innovative in-situ stabilisation treatment followed by ex-situ sediment composting was tested for its ability to treat and dispose of heavy-metal-polluted sediments in a river near the Chinese Pearl Delta. First, polluted sediments were treated in-situ to stabilise the heavy metals. Then the treated sediments were dredged, dewatered and sent for high temperature aerobic composting （HTAC） treatment. Finally, the compost products were used as a fertiliser for fiver bank plants. The stabilisation efficiency of heavy metals during the process was investigated and the results are as follows： （1） using in-situ stabilisation, the extraction concentrations of Cu, Zn and Pb were reduced by 65.0%, 82.2% and 90.0%, respectively, which are much lower than the national standard given in the Identification Standard for Hazardous Waste （GB5085.3-1996）; （2） chemical fraction analysis showed that heavy metals were further stabilized during the HTAC treatment; （3） the concentrations of Cu, Zn and Pb in rainwater leachate through the river bank met the level of class V in the Environmental Quality Standards for Surface Water in China （GB3838-2002）. Therefore, using this new process, the toxicities of heavy metals in sediments were reduced markedly.
文摘A new hemiterpenoid, （＋）-（2R,3S）-2-chloro-3-hydroxy-3-methyl-T-buty-rolactone was isolatexi from the leaves of Prinsepia utilis Royle. Its structure was clucidatexi by spectroscopic methods and X-ray crystallographic analysis.
文摘Using political ecology as its conceptual framework,this paper focuses on the changes in forest utilisation and management of South Kyrgyzstan’s walnut-fruit forests over the last century. The aim of this study on human-environment interactions is to investigate the relationship between actors on the one side,their interests and demands,and the forests and forested lands on the other. Forest resource utilisation and management — and even the recognition of different forest products as resources — are connected with political and socio-economic conditions that change with time. The walnut-fruit forests of South Kyrgyzstan are unique,characterised by high biodiversity and a multiplicity of usable products;and they have been utilised for a long time. Centralised and formal management of the forests started with the Russian occupation and was strengthened under Soviet rule,when the region became a part of the USSR. During this era,a state forest administration that was structured from Moscow all the way down to the local level drew up detailed plans and developed procedures for utilising the different forest products. Since the collapse of the Soviet Union,the socio-political and economic frame conditions have changed significantly,which has brought not only the sweeping changes in the managing institutions,but also the access rights and interests in the forest resources. At present,the region is suffering from a high unemployment rate,which has resulted in the forests’ gaining considerable importance in the livelihood strategies of the local population. Political and economic liberalization,increased communication and trans-regional exchange relations have opened the door for international companies and agents interested in the valuable forest products. Today,walnut wood and burls,walnuts,wild apples and mushrooms are all exported to various countries in the world. Scientists and members of various international organisations stress the ecological value of the forests and are trying to establish nature conservation areas. Nevertheless,it is to fear that a multiplicity of interrelated factors — the present transformation and globalization processes,the appearance of new actors,the local population’s insecure economic situation and the erosion of managing institutions — are all leading to an intensified and unregulated exploitation of the forests,resulting in their degradation.
基金The National Basic Research Program (973) of China (No. 2004CB418505)
文摘Under the optimal condition of copper ions adsorption on yeast,we found some different effects among static adsorption, shaking adsorption and negative pressure cavitation adsorption, and the methods of yeast with different pretreatments also affect adsorption of copper ions. At the same time, the change of intercellular pH before and after adsorption of copper with BCECF was studied. The copper distribution was located by using PhenGreen （dipotassium salt and diacetate）, and the surface of yeast was observed by an atomic force microscope. The results showed that negative pressure cavitation can improve bioadsorption capacity of copper ions on yeast. However, the yeasts＇ pretreatment has a higher effect on bioadsorption. It indicates that heavy metal bioadsorption on yeast has much relation with its cellular molecule basis. With the adsorping, the intercellular pH of yeast increased gradually and changed from acidity to alkalescence. These results may suggest that negative pressure cavitation can compel heavy metals to transfer from the cell surface into inside cell and make the surface of yeast coarse.
基金supported by the Soil Erosion and Dryland Farming on Loess Plateau of the State Key Laboratory of Chinese Academy of Sciences (K318009902-1310) the Shaanxi Province Innovative Engineering Project Coordinator (2011K01-48)
文摘Monitoring soil microbial communities can lead to better understanding of the transformation processes of organic carbon in soil. The present study investigated the changes of soil microbial communities during straw decomposition in three fields, i.e., cropland, peach orchard and vineyard. Straw decomposition was monitored for 360 d using a mesh-bag method. Soil microbial metabolic activity and functional diversity were measured using the Biolog-Eco system. In all three fields, dried straws with a smaller size decomposed faster than their fresh counterparts that had a larger size. Dried corn straw decomposed slower than dried soybean straw in the early and middle stages, while the reverse trend was found in the late stage. The cropland showed the highest increase in microbial metabolic activity during the straw decomposition, whereas the peach orchard showed the lowest. There was no significant change in the species dominance or evenness of soil microbial communities during the straw decomposition. However, the species richness fluctuated significantly, with the peach orchard showing the highest richness and the cropland the lowest. With different carbon sources, the peach orchard utilised carbon the most, followed by the cropland and the vineyard. In all three fields, carbon was utilized in following decreasing order： saccharides〉amino acids〉polymers〉polyamines〉carboxylic acids〉aromatic compounds. In terms of carbon-source utilization, soil microbial communities in the peach orchard were less stable than those in the cropland. The metabolic activity and species dominance of soil microbial communities were negatively correlated with the straw residual percentage. Refractory components were primarily accumulated in the late stages, thus slowing down the straw decomposition. The results showed that dried and crushed corn straw was better for application in long-term fields. The diversity of soil microbial communities was more stable in cropland than in orchards during the straw decomposition.
