Single‐atom catalysts have been proposed as promising electrocatalysts for CO_(2) reduction reactions(CO_(2)RR).Co‐N_(4) active sites have attracted wide attention owing to their excellent CO selectivity and activit...Single‐atom catalysts have been proposed as promising electrocatalysts for CO_(2) reduction reactions(CO_(2)RR).Co‐N_(4) active sites have attracted wide attention owing to their excellent CO selectivity and activity.However,the effect of the local coordination environment of Co sites on CO_(2) reduction reaction pathways is still unclear.In this study,we investigated the CO_(2) reduction reaction pathways on Co‐N_(4) sites supported on conjugated N_(4)‐macrocyclic ligands with 1,10‐phenanthroline subunits(Co‐N_(4)‐CPY)by density functional theory calculations.The local coordination environment of single‐atom Co sites with N substituted by O(Co‐N_(3)O‐CPY)and C(Co‐N_(3)C‐CPY)was studied for comparison.The calculation results revealed that both C and O coordination break the symmetry of the primary CoN_(4) ligand field and induce charge redistribution of the Co atom.For Co‐N_(4)‐CPY,CO was confirmed to be the main product of CO_(2)RR.HCOOH is the primary product of Co‐N_(3)O‐CPY because of the greatly increased energy barrier of CO_(2) to*COOH.Although the energy barrier of CO_(2) to*COOH is reduced on Co‐N_(3)C‐CPY,the desorption process of*CO becomes more difficult.CH3OH(or CH_(4))are obtained by further*CO hydrogenation reduction when using Co‐N_(3)C‐CPY.This work provides new insight into the effect of the local coordination environment of single‐atom sites on CO_(2) reduction reaction pathways.展开更多
The Ontario Hydro Method （OHM） recommended by the United States Environmental Protection Agency （EPA） was used to determine mercury speciation in the combustion flue gas across wet FGD systems. Four coal-fired uni...The Ontario Hydro Method （OHM） recommended by the United States Environmental Protection Agency （EPA） was used to determine mercury speciation in the combustion flue gas across wet FGD systems. Four coal-fired units with wet FGD systems were chosen to evaluate mercury speciation and mercury removal efficiencies through these wet FGD systems. Chlorine content in coal had been suggested as a main factor that affects mercury speciation in flue gas. It is shown that the higher the chlorine concentration in coal is, the higher the percentage of oxidized mercury （Hg2＋） is removed in wet FGD systems, which can increase overall mercury removal efficiencies through wet FGD systems. The selective catalyst reduction （SCR） system has a function of oxidizing ele- mental mercury （Hg0） to oxidized mercury. A higher percentage of oxidized mercury in the total vapor mercury at the FGD inlet is observed when SCR is in service. Therefore, higher overall mercury removal efficiencies through wet FGD are attained. Because of different wet FGD operating conditions, there are different mercury removal efficiencies in different units. Elemental mercury reemission took place when a fraction of oxidized mercury absorbed in the slurry is reduced to elemental mercury, and Hg2＋ is reemitted from stack, which results in decreases in mercury removal efficiencies through wet FGD systems.展开更多
Over the past few decades, extreme changes have occurred in the characters of exploited fish populations. The majority of these changes have affected the growth traits of fish life history, which include a smaller siz...Over the past few decades, extreme changes have occurred in the characters of exploited fish populations. The majority of these changes have affected the growth traits of fish life history, which include a smaller size-at-age, an earlier age-at-maturation and among others. Currently, the causes of these life history traits changes still require systematic analyses and empirical studies. The explanations that have been cited are merely expressed in terms of fish phenotypic adaptation. It has been claimed that the original traits of fish can be recovered once the intensity of exploitation of the fish is controlled. Sustained environmental and fishing pressure will change the life history traits of most fish species, so the fish individual's traits are still in small size-at-age and at earlier age-at-maturation in exploited fish populations. In this paper, we expressed our view of points that fishing gear has imposed selectivity on fish populations and individuals as various other environmental factors have done and such changes are unrecoverable. According to the existing tend of exploited fish individual's life history traits, we suggested further researches in this field and provided better methods of fishery management and thereby fishery resources protection than those available early.展开更多
Compounds containing Cr （VI） ion are widely used for chemical industry, paints, dyes, and other applications. Because of commonly known toxicity of Cr （VI） ion, Cr （VI） is one of the important check items for qu...Compounds containing Cr （VI） ion are widely used for chemical industry, paints, dyes, and other applications. Because of commonly known toxicity of Cr （VI） ion, Cr （VI） is one of the important check items for quality of water in natural river or industrial waste water. Although the only method for selective detection for Cr （VI） ion is diphenylcarbazide, of which pretreatment spends long time according to the regulat^ons by the Ministry of Environment, Japan. Herein we develop a new and simple pretreatment for the job site and suitable for education and attempt to apply for analysis of the soil in Tama River actually.展开更多
The mobility of relay has great influence on the performance of a cooperative relay system.This paper proposes a dynamic selection scheme under the amplify-and-forward communication mode in high mobility environment,b...The mobility of relay has great influence on the performance of a cooperative relay system.This paper proposes a dynamic selection scheme under the amplify-and-forward communication mode in high mobility environment,based on the estimation of channels and the power allocation for each relay node by comparing it with the pre-set threshold.This scheme is used to choose the cooperative relay dynamically for a multiple relay scenario.Simulation results show that this proposed relay selection scheme decreases the outage probability effectively,maintains system capacity well,and improves the performance of the relay system.展开更多
This review summarizes the utilization of supported noble metal nanoparticles (such as Au/TiO2, Au/ZrO2, Ag/AgCl) as efficient photo/sono-catalysts for the selective synthesis of chemicals and degradation of environme...This review summarizes the utilization of supported noble metal nanoparticles (such as Au/TiO2, Au/ZrO2, Ag/AgCl) as efficient photo/sono-catalysts for the selective synthesis of chemicals and degradation of environmental pollutants. Supported noble metal nanoparticles could efficiently catalyze the conversion of solar energy into chemical energy. Under UV/visible light irradiation, important chemical transformations such as the oxidation of alcohols to carbonyl compounds, the oxidation of thiol to disulfide, the oxidation of benzene to phenol, and the reduction of nitroaromatic compounds to form aromatic azo compounds, are effectively achieved by supported noble metal nanoparticles. Under ultrasound irradiation, supported noble metal nanoparticles could efficiently catalyze the production of hydrogen from water. Moreover, various pollutants, including aldehydes, alcohols, acids, phenolic compounds, and dyes, can be effectively decomposed over supported noble metal nanoparticles under UV/visible light irradiation. Under ultrasound irradiation, pollutant molecules can also be completely degraded with supported noble metal nanoparticles as catalysts.展开更多
Speciation research during the last several decades has confirmed that natural selection frequently drives the genera- tion of new species. But how does this process generally unfold in nature？ We argue that answerin...Speciation research during the last several decades has confirmed that natural selection frequently drives the genera- tion of new species. But how does this process generally unfold in nature？ We argue that answering this question requires a clearer conceptual framework for understanding selection＇s role in speciation. We present a unified framework of speciation, pro- viding mechanistic descriptions of fundamentally distinct routes to speciation, and how these may interact during lineage splitting Two major categories are recognized： reproductive isolation resulting from （1） responses to selection, ＂speciation by selection,＂ or （2） non-selective processes, ＂speciation without selection.＂ Speciation by selection can occur via three mechanisms： （1） similar selection, （2） divergent selection, and （3） reinforcement selection. Understanding ecology＇s role in speciation requires uncovering how these three mechanisms contribute to reproductive isolation, and their relative importance compared to non-selective proce- sses, because all three mechanisms can occur side-by-side during speciation. To accomplish this, we highlight examination of groups of organisms inhabiting replicated environmental gradients. This scenario is common in nature, and a large literature illus- trates that both parallel and non-parallel responses to similar environments are widespread, and each can result in speciation. This recognition reveals four general pathways of speciation by similar or divergent selection--parallel and nonparallel responses to similar and divergent selection. Altogether, we present a more precise framework for speciation research, draw attention to some under-recognized features of speciation, emphasize the multidimensionality of speciation, reveal limitations of some previous tests and descriptions of speciation mechanisms, and point to a number of directions for future investigation [Current Zoology 59 （1）： 31-52, 2013].展开更多
Aims Our objective was to quantify the contributions of the seed bank and the established vegetation to the species composition,functional composition and diversity,and discuss the implications of these differences in...Aims Our objective was to quantify the contributions of the seed bank and the established vegetation to the species composition,functional composition and diversity,and discuss the implications of these differences in regeneration and persistence of floodplain plant communities.Methods We sampled all ground cover vegetation up to 1.5 m height and seed bank in 25 plots(10 m×1 m)distributed across five sites in dry and rainy seasons in a periodically flooded savanna in the Pantanal wetland,Brazil.We evaluated the soil seed bank by seedling emergence method.Important Findings The seed bank species had traits that conferred regeneration to the communities,while persistence traits characterized the vegetation.The seed bank had higher functional richness and lower functional evenness than the vegetation.The existence of different plant traits between seed bank and vegetation allowed the coexistence of species with functionally contrasting persistence and regeneration traits,which may help maintain functional diversity.It may allow the community to be more resilient when dealing with different environmental filters such as drought,fire and flood.展开更多
文摘Single‐atom catalysts have been proposed as promising electrocatalysts for CO_(2) reduction reactions(CO_(2)RR).Co‐N_(4) active sites have attracted wide attention owing to their excellent CO selectivity and activity.However,the effect of the local coordination environment of Co sites on CO_(2) reduction reaction pathways is still unclear.In this study,we investigated the CO_(2) reduction reaction pathways on Co‐N_(4) sites supported on conjugated N_(4)‐macrocyclic ligands with 1,10‐phenanthroline subunits(Co‐N_(4)‐CPY)by density functional theory calculations.The local coordination environment of single‐atom Co sites with N substituted by O(Co‐N_(3)O‐CPY)and C(Co‐N_(3)C‐CPY)was studied for comparison.The calculation results revealed that both C and O coordination break the symmetry of the primary CoN_(4) ligand field and induce charge redistribution of the Co atom.For Co‐N_(4)‐CPY,CO was confirmed to be the main product of CO_(2)RR.HCOOH is the primary product of Co‐N_(3)O‐CPY because of the greatly increased energy barrier of CO_(2) to*COOH.Although the energy barrier of CO_(2) to*COOH is reduced on Co‐N_(3)C‐CPY,the desorption process of*CO becomes more difficult.CH3OH(or CH_(4))are obtained by further*CO hydrogenation reduction when using Co‐N_(3)C‐CPY.This work provides new insight into the effect of the local coordination environment of single‐atom sites on CO_(2) reduction reaction pathways.
文摘The Ontario Hydro Method （OHM） recommended by the United States Environmental Protection Agency （EPA） was used to determine mercury speciation in the combustion flue gas across wet FGD systems. Four coal-fired units with wet FGD systems were chosen to evaluate mercury speciation and mercury removal efficiencies through these wet FGD systems. Chlorine content in coal had been suggested as a main factor that affects mercury speciation in flue gas. It is shown that the higher the chlorine concentration in coal is, the higher the percentage of oxidized mercury （Hg2＋） is removed in wet FGD systems, which can increase overall mercury removal efficiencies through wet FGD systems. The selective catalyst reduction （SCR） system has a function of oxidizing ele- mental mercury （Hg0） to oxidized mercury. A higher percentage of oxidized mercury in the total vapor mercury at the FGD inlet is observed when SCR is in service. Therefore, higher overall mercury removal efficiencies through wet FGD are attained. Because of different wet FGD operating conditions, there are different mercury removal efficiencies in different units. Elemental mercury reemission took place when a fraction of oxidized mercury absorbed in the slurry is reduced to elemental mercury, and Hg2＋ is reemitted from stack, which results in decreases in mercury removal efficiencies through wet FGD systems.
基金the financial support from Special Fund for Agro-scientific Research in the Public Interest (No. 201203018)
文摘Over the past few decades, extreme changes have occurred in the characters of exploited fish populations. The majority of these changes have affected the growth traits of fish life history, which include a smaller size-at-age, an earlier age-at-maturation and among others. Currently, the causes of these life history traits changes still require systematic analyses and empirical studies. The explanations that have been cited are merely expressed in terms of fish phenotypic adaptation. It has been claimed that the original traits of fish can be recovered once the intensity of exploitation of the fish is controlled. Sustained environmental and fishing pressure will change the life history traits of most fish species, so the fish individual's traits are still in small size-at-age and at earlier age-at-maturation in exploited fish populations. In this paper, we expressed our view of points that fishing gear has imposed selectivity on fish populations and individuals as various other environmental factors have done and such changes are unrecoverable. According to the existing tend of exploited fish individual's life history traits, we suggested further researches in this field and provided better methods of fishery management and thereby fishery resources protection than those available early.
文摘Compounds containing Cr （VI） ion are widely used for chemical industry, paints, dyes, and other applications. Because of commonly known toxicity of Cr （VI） ion, Cr （VI） is one of the important check items for quality of water in natural river or industrial waste water. Although the only method for selective detection for Cr （VI） ion is diphenylcarbazide, of which pretreatment spends long time according to the regulat^ons by the Ministry of Environment, Japan. Herein we develop a new and simple pretreatment for the job site and suitable for education and attempt to apply for analysis of the soil in Tama River actually.
基金Supported by the National Natural Science Foundation of China(No.61172073)the State Key Laboratory of Rail Traffic Control and Safety,Beijing Jiaotong University(No.RCS2011ZT003)+2 种基金the Open Research Fund of National Mobile Communications Research Laboratory,Southeast University(No.2012D19)the Fundamental Research Funds for the Central Universities of Ministry of Education of China(No.2013JBZ001)the Program for New Century Excellent Talents in University of Ministry of Education of China(No.NCET-12-0766)
文摘The mobility of relay has great influence on the performance of a cooperative relay system.This paper proposes a dynamic selection scheme under the amplify-and-forward communication mode in high mobility environment,based on the estimation of channels and the power allocation for each relay node by comparing it with the pre-set threshold.This scheme is used to choose the cooperative relay dynamically for a multiple relay scenario.Simulation results show that this proposed relay selection scheme decreases the outage probability effectively,maintains system capacity well,and improves the performance of the relay system.
文摘This review summarizes the utilization of supported noble metal nanoparticles (such as Au/TiO2, Au/ZrO2, Ag/AgCl) as efficient photo/sono-catalysts for the selective synthesis of chemicals and degradation of environmental pollutants. Supported noble metal nanoparticles could efficiently catalyze the conversion of solar energy into chemical energy. Under UV/visible light irradiation, important chemical transformations such as the oxidation of alcohols to carbonyl compounds, the oxidation of thiol to disulfide, the oxidation of benzene to phenol, and the reduction of nitroaromatic compounds to form aromatic azo compounds, are effectively achieved by supported noble metal nanoparticles. Under ultrasound irradiation, supported noble metal nanoparticles could efficiently catalyze the production of hydrogen from water. Moreover, various pollutants, including aldehydes, alcohols, acids, phenolic compounds, and dyes, can be effectively decomposed over supported noble metal nanoparticles under UV/visible light irradiation. Under ultrasound irradiation, pollutant molecules can also be completely degraded with supported noble metal nanoparticles as catalysts.
文摘Speciation research during the last several decades has confirmed that natural selection frequently drives the genera- tion of new species. But how does this process generally unfold in nature？ We argue that answering this question requires a clearer conceptual framework for understanding selection＇s role in speciation. We present a unified framework of speciation, pro- viding mechanistic descriptions of fundamentally distinct routes to speciation, and how these may interact during lineage splitting Two major categories are recognized： reproductive isolation resulting from （1） responses to selection, ＂speciation by selection,＂ or （2） non-selective processes, ＂speciation without selection.＂ Speciation by selection can occur via three mechanisms： （1） similar selection, （2） divergent selection, and （3） reinforcement selection. Understanding ecology＇s role in speciation requires uncovering how these three mechanisms contribute to reproductive isolation, and their relative importance compared to non-selective proce- sses, because all three mechanisms can occur side-by-side during speciation. To accomplish this, we highlight examination of groups of organisms inhabiting replicated environmental gradients. This scenario is common in nature, and a large literature illus- trates that both parallel and non-parallel responses to similar environments are widespread, and each can result in speciation. This recognition reveals four general pathways of speciation by similar or divergent selection--parallel and nonparallel responses to similar and divergent selection. Altogether, we present a more precise framework for speciation research, draw attention to some under-recognized features of speciation, emphasize the multidimensionality of speciation, reveal limitations of some previous tests and descriptions of speciation mechanisms, and point to a number of directions for future investigation [Current Zoology 59 （1）： 31-52, 2013].
基金This work was supported by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior(CAPES)under grant PNADB-17/2009.
文摘Aims Our objective was to quantify the contributions of the seed bank and the established vegetation to the species composition,functional composition and diversity,and discuss the implications of these differences in regeneration and persistence of floodplain plant communities.Methods We sampled all ground cover vegetation up to 1.5 m height and seed bank in 25 plots(10 m×1 m)distributed across five sites in dry and rainy seasons in a periodically flooded savanna in the Pantanal wetland,Brazil.We evaluated the soil seed bank by seedling emergence method.Important Findings The seed bank species had traits that conferred regeneration to the communities,while persistence traits characterized the vegetation.The seed bank had higher functional richness and lower functional evenness than the vegetation.The existence of different plant traits between seed bank and vegetation allowed the coexistence of species with functionally contrasting persistence and regeneration traits,which may help maintain functional diversity.It may allow the community to be more resilient when dealing with different environmental filters such as drought,fire and flood.
