Laser powder bed fusion(L-PBF)of Mg alloys has provided tremendous opportunities for customized production of aeronautical and medical parts.Layer thickness(LT)is of great significance to the L-PBF process but has not...Laser powder bed fusion(L-PBF)of Mg alloys has provided tremendous opportunities for customized production of aeronautical and medical parts.Layer thickness(LT)is of great significance to the L-PBF process but has not been studied for Mg alloys.In this study,WE43 Mg alloy bulk cubes,porous scaffolds,and thin walls with layer thicknesses of 10,20,30,and 40μm were fabricated.The required laser energy input increased with increasing layer thickness and was different for the bulk cubes and porous scaffolds.Porosity tended to occur at the connection joints in porous scaffolds for LT40 and could be eliminated by reducing the laser energy input.For thin wall parts,a large overhang angle or a small wall thickness resulted in porosity when a large layer thicknesses was used,and the porosity disappeared by reducing the layer thickness or laser energy input.A deeper keyhole penetration was found in all occasions with porosity,explaining the influence of layer thickness,geometrical structure,and laser energy input on the porosity.All the samples achieved a high fusion quality with a relative density of over 99.5%using the optimized laser energy input.The increased layer thickness resulted to more precipitation phases,finer grain sizes and decreased grain texture.With the similar high fusion quality,the tensile strength and elongation of bulk samples were significantly improved from 257 MPa and 1.41%with the 10μm layer to 287 MPa and 15.12%with the 40μm layer,in accordance with the microstructural change.The effect of layer thickness on the compressive properties of porous scaffolds was limited.However,the corrosion rate of bulk samples accelerated with increasing the layer thickness,mainly attributed to the increased number of precipitation phases.展开更多
Laser powder bed fusion(L-PBF)has been employed to additively manufacture WE43 magnesium(Mg)alloy biodegradable implants,but WE43 L-PBF samples exhibit excessively rapid corrosion.In this work,dense WE43 L-PBF samples...Laser powder bed fusion(L-PBF)has been employed to additively manufacture WE43 magnesium(Mg)alloy biodegradable implants,but WE43 L-PBF samples exhibit excessively rapid corrosion.In this work,dense WE43 L-PBF samples were built with the relativity density reaching 99.9%.High temperature oxidation was performed on the L-PBF samples in circulating air via various heating temperatures and holding durations.The oxidation and diffusion at the elevated temperature generated a gradient structure composed of an oxide layer at the surface,a transition layer in the middle and the matrix.The oxide layer consisted of rare earth(RE)oxides,and became dense and thick with increasing the holding duration.The matrix was composed ofα-Mg,RE oxides and Mg_(24)RE_(5) precipitates.The precipitates almost disappeared in the transition layer.Enhanced passivation effect was observed in the samples treated by a suitable high temperature oxidation.The original L-PBF samples lost 40%weight after 3-day immersion in Hank’s solution,and broke into fragments after 7-day immersion.The casted and solution treated samples lost roughly half of the weight after 28-day immersion.The high temperature oxidation samples,which were heated at 525℃ for 8 h,kept the structural integrity,and lost only 6.88%weight after 28-day immersion.The substantially improved corrosion resistance was contributed to the gradient structure at the surface.On one hand,the outmost dense layer of RE oxides isolated the corrosive medium;on the other hand,the transition layer considerably inhibited the corrosion owing to the lack of precipitates.Overall,high temperature oxidation provides an efficient,economic and safe approach to inhibit the corrosion of WE43 L-PBF samples,and has promising prospects for future clinical applications.展开更多
The increase in release of toxic heavy metals into natural water attracts much attention due to its devastating effect on ecology and human health.The design and implementation of green electrode materials is pivotal ...The increase in release of toxic heavy metals into natural water attracts much attention due to its devastating effect on ecology and human health.The design and implementation of green electrode materials is pivotal for improving the electrochemical performance of in situ heavy metal monitoring.展开更多
Microbial fuel cells(MFCs),as a sustainable and promising technology to solve both environmental pollution and energy shortage,have captured tremendous attention.The conversion efficiency of chemical energy contained ...Microbial fuel cells(MFCs),as a sustainable and promising technology to solve both environmental pollution and energy shortage,have captured tremendous attention.The conversion efficiency of chemical energy contained in organic waste or wastewater to electricity via microbial metabolism strongly depends on the performance of each functional unit,including the anode,cathode and separator/membrane used in MFCs.Therefore,significant attention has been paid toward developing advanced functional materials to enhance the performance of each unit or provide new featured functions.This review paper provides a comprehensive review on recent achievements and advances in the modification and development of functional materials for MFC systems,including 1)the development of functional anode materials for enhanced microbial compatibilities as well as electron transfer capabilities,2)the development of cost-effective separators/membranes such as ion exchange membrane,porous membrane,polymer electrolyte membrane and composite membrane,and 3)the development of functional cathode catalysts to decrease the over-potential and enhance the electrocatalytic efficiency for oxygen reduction reaction in order to substitute the common costly Pt catalyst.The challenges and outlooks of functional materials for MFC applications are also discussed.展开更多
本文汇总2014—2023年国家自然科学基金委员会医学科学部在生物医学工程/再生医学方向面上项目、青年科学基金项目与地区科学基金项目(简称“面青地项目”)的申请与资助情况,同时分析近10年相关领域的文献报道热点,为该领域的进一步高...本文汇总2014—2023年国家自然科学基金委员会医学科学部在生物医学工程/再生医学方向面上项目、青年科学基金项目与地区科学基金项目(简称“面青地项目”)的申请与资助情况,同时分析近10年相关领域的文献报道热点,为该领域的进一步高水平发展提供参考依据。回顾性收集代码H28下面青地项目的申请与资助数据资料,主要包括:资助项数与资助经费、资助项目所在依托单位与省市分布、获资助申请人的年龄与职称分布、获资助项目申请书的关键词等内容。同时,基于Web of Science数据库对近10年发表的相关方向文献关键词进行汇总,利用CiteSpace 6.2.R4软件对关键词的热点聚类及时间分布进行分析。通过分析发现:在2014—2023年中,生物医学工程/再生医学方向共资助面青地项目1279项,包括面上项目623项、青年科学基金项目599项和地区科学基金项目57项,资助经费50799万元。其中2014年的资助项目数最少,2023年的资助项目数最多。该方向的项目资助主要集中在H2808、H2809及H2810,3个代码获资助项目数与经费总和分别占全部项目的65.9%及64.6%。上海市、上海交通大学分别是获资助项目数最多的地区、依托单位,分别占比14.7%和7.0%。31~35岁的申请人获资助项目数最多,共507项,占比39.6%。近10年该方向获资助面青地项目申请书中出现频率最高的中英文关键词都与纳米相关(纳米药物和nanomedicine),而在Web of Science数据库中已发表相关方向文献的热门关键词包括biomedical engineering、tissue engineering、biomedical applications等。近年来,国家自然科学基金委员会医学科学部对生物医学工程/再生医学方向面青地项目的资助呈稳步上升趋势,资助领域广泛且重点明确,逐步建立以青年科研人员为主体的人才梯队。展开更多
The effects of pore size in additively manufactured biodegradable porous magnesium on the mechanical properties and biodegradation of the scaffolds as well as new bone formation have rarely been reported. In this work...The effects of pore size in additively manufactured biodegradable porous magnesium on the mechanical properties and biodegradation of the scaffolds as well as new bone formation have rarely been reported. In this work, we found that high temperature oxidation improves the corrosion resistance of magnesium scaffold. And the effects of pore size on the mechanical characteristics and biodegradation of scaffolds, as well as new bone formation, were investigated using magnesium scaffolds with three different pore sizes, namely, 500, 800, and 1400 μm (P500, P800, and P1400). We discovered that the mechanical characteristics of the P500 group were much better than those of the other two groups. In vitro and in vivo investigations showed that WE43 magnesium alloy scaffolds supported the survival of mesenchymal stem cells and did not cause any local toxicity. Due to their larger specific surface area, the scaffolds in the P500 group released more magnesium ions within reasonable range and improved the osteogenic differentiation of bone mesenchymal stem cells compared with the other two scaffolds. In a rabbit femoral condyle defect model, the P500 group demonstrated unique performance in promoting new bone formation, indicating its great potential for use in bone defect regeneration therapy.展开更多
Introduction Is it feasible to employ neural signals for the purpose of communication?In 1938,this thoughtprovoking query was visually embodied in a sketch received by Hans Berger,a German Professor of Psychiatry reno...Introduction Is it feasible to employ neural signals for the purpose of communication?In 1938,this thoughtprovoking query was visually embodied in a sketch received by Hans Berger,a German Professor of Psychiatry renowned for his discovery of human electroencephalography(EEG)nearly a century ago.In this fanciful sketch.展开更多
Over half of century,sanitary landfill was and is still the most economical treatment strategy for solid waste disposal,but the environmental risks associated with the leachate have brought attention of scientists for...Over half of century,sanitary landfill was and is still the most economical treatment strategy for solid waste disposal,but the environmental risks associated with the leachate have brought attention of scientists for its proper treatment to avoid surface and ground water deterioration.Most of the treatment technologies are energy-negative and cost intensive processes,which are unable to meet current environmental regulations.There are continuous demands of alternatives concomitant with positive energy and high effluent quality.Microbial fuel cells(MFCs)were launched in the last two decades as a potential treatment technology with bioelectricity generation accompanied with simultaneous carbon and nutrient removal.This study reviews capability and mechanisms of carbon,nitrogen and phosphorous removal from landfill leachate through MFC technology,as well as summarizes and discusses the recent advances of standalone and hybrid MFCs performances in landfill leachate(LFL)treatment.Recent improvements and synergetic effect of hybrid MFC technology upon the increasing of power densities,organic and nutrient removal,and future challenges were discussed in details.展开更多
Many studies have investigated the effects of different pretreatments on the performance of anaerobic digestion of sludge.However,the detailed changes of dissolved organic nitrogen,particularly the release behavior of...Many studies have investigated the effects of different pretreatments on the performance of anaerobic digestion of sludge.However,the detailed changes of dissolved organic nitrogen,particularly the release behavior of proteins and the byproducts of protein hydrolysis-amino acids,are rarely known during anaerobic digestion of sludge by different pretreatments.Here we quantified the changes of three types of proteins and 17 types of amino acids in sludge samples solubilized by ultrasonic,thermal,and acid/alkaline pretreatments and their transformation during anaerobic digestion of sludge.Tryptophan protein,aromatic protein I,aromatic protein II,and cysteine were identified as the key dissolved organic nitrogen responsible for methane production during anaerobic digestion of sludge,regardless of the different pretreatment methods.Different from the depletion of other amino acids,cysteine was resistant to degradation after an incubation period of 30 days in all sludge samples.Meanwhile,the“cysteine and methionine metabolism(K00270)”was absent in all sludge samples by identifying 6755 Kyoto Encyclopedia of Genes and Genomes assignments of genes hits.Cysteine contributed to the generation of methane and the degradation of acetic,propionic,and n-butyric acids through decreasing oxidation-reduction potential and enhancing biomass activity.This study provided an alternative strategy to enhance anaerobic digestion of sludge through in situ production of cysteine.展开更多
The year ahead marks the 50th anniversary of the first publication on the brain-computer interface(BCI)proposed by Vidal in 1973.Over the past decades,continuous progress has been made in designing and optimizing the ...The year ahead marks the 50th anniversary of the first publication on the brain-computer interface(BCI)proposed by Vidal in 1973.Over the past decades,continuous progress has been made in designing and optimizing the BCI system toward a high-performance,robust and ease-of-use“mind reading”.The nascent field of BCI has brought together scientists from neuroscience,computer science as well as engineers and clinicians worldwide to address the highly challenging problem.展开更多
This study compared effects of three different valent iron(Fe^(0),Fe(II)and Fe(III))on enhanced anaerobic sludge digestion,focusing on the changes of oxidation reduction potential(ORP),dissolved organic nitrogen(DON),...This study compared effects of three different valent iron(Fe^(0),Fe(II)and Fe(III))on enhanced anaerobic sludge digestion,focusing on the changes of oxidation reduction potential(ORP),dissolved organic nitrogen(DON),and microbial community.Under the same iron dose in range of 0−160 mg/L after an incubation period of 30 days(d),the maximum methane production rate of sludge samples dosed with respective Fe^(0),Fe(II)and Fe(III)at the same concentration showed indiscernible differences at each iron dose,regardless of the different iron valence.Moreover,their behavior in changes of ORP,DON and microbial community was different:(1)the addition of Fe^(0) made the ORP of sludge more negative,and the addition of Fe(II)and Fe(III)made the ORP of sludge less negative.However,whether being more or less negative,the changes of ORP may show unobservable effects on methane yield when it ranged from−278.71 to−379.80 mV;(2)the degradation of dissolved organic nitrogen,particularly proteins,was less efficient in sludge samples dosed with Fe^(0) compared with those dosed with Fe(II)and Fe(III)after an incubation period of 30 d.At the same dose of 160 mg/L iron,more cysteine was noted in sludge samples dosed with Fe(II)(30.74 mg/L)and Fe(III)(27.92 mg/L)compared with that dosed with Fe^(0)(21.75 mg/L);(3)Fe^(0) particularly promoted the enrichment of Geobacter,and it was 6 times higher than those in sludge samples dosed with Fe(II)and Fe(III)at the same dose of 160 mg/L iron.展开更多
基金funded by the National Key Research and Development Program of China(2018YFE0104200)National Natural Science Foundation of China(51875310,52175274,82172065)Tsinghua Precision Medicine Foundation.
文摘Laser powder bed fusion(L-PBF)of Mg alloys has provided tremendous opportunities for customized production of aeronautical and medical parts.Layer thickness(LT)is of great significance to the L-PBF process but has not been studied for Mg alloys.In this study,WE43 Mg alloy bulk cubes,porous scaffolds,and thin walls with layer thicknesses of 10,20,30,and 40μm were fabricated.The required laser energy input increased with increasing layer thickness and was different for the bulk cubes and porous scaffolds.Porosity tended to occur at the connection joints in porous scaffolds for LT40 and could be eliminated by reducing the laser energy input.For thin wall parts,a large overhang angle or a small wall thickness resulted in porosity when a large layer thicknesses was used,and the porosity disappeared by reducing the layer thickness or laser energy input.A deeper keyhole penetration was found in all occasions with porosity,explaining the influence of layer thickness,geometrical structure,and laser energy input on the porosity.All the samples achieved a high fusion quality with a relative density of over 99.5%using the optimized laser energy input.The increased layer thickness resulted to more precipitation phases,finer grain sizes and decreased grain texture.With the similar high fusion quality,the tensile strength and elongation of bulk samples were significantly improved from 257 MPa and 1.41%with the 10μm layer to 287 MPa and 15.12%with the 40μm layer,in accordance with the microstructural change.The effect of layer thickness on the compressive properties of porous scaffolds was limited.However,the corrosion rate of bulk samples accelerated with increasing the layer thickness,mainly attributed to the increased number of precipitation phases.
基金funded by the National Key Research and Development Program of China (2018YFE0104200)National Natural Science Foundation of China (51875310, 52175274, 82172065)Tsinghua Precision Medicine Foundation
文摘Laser powder bed fusion(L-PBF)has been employed to additively manufacture WE43 magnesium(Mg)alloy biodegradable implants,but WE43 L-PBF samples exhibit excessively rapid corrosion.In this work,dense WE43 L-PBF samples were built with the relativity density reaching 99.9%.High temperature oxidation was performed on the L-PBF samples in circulating air via various heating temperatures and holding durations.The oxidation and diffusion at the elevated temperature generated a gradient structure composed of an oxide layer at the surface,a transition layer in the middle and the matrix.The oxide layer consisted of rare earth(RE)oxides,and became dense and thick with increasing the holding duration.The matrix was composed ofα-Mg,RE oxides and Mg_(24)RE_(5) precipitates.The precipitates almost disappeared in the transition layer.Enhanced passivation effect was observed in the samples treated by a suitable high temperature oxidation.The original L-PBF samples lost 40%weight after 3-day immersion in Hank’s solution,and broke into fragments after 7-day immersion.The casted and solution treated samples lost roughly half of the weight after 28-day immersion.The high temperature oxidation samples,which were heated at 525℃ for 8 h,kept the structural integrity,and lost only 6.88%weight after 28-day immersion.The substantially improved corrosion resistance was contributed to the gradient structure at the surface.On one hand,the outmost dense layer of RE oxides isolated the corrosive medium;on the other hand,the transition layer considerably inhibited the corrosion owing to the lack of precipitates.Overall,high temperature oxidation provides an efficient,economic and safe approach to inhibit the corrosion of WE43 L-PBF samples,and has promising prospects for future clinical applications.
基金The authors would like acknowledge the financial supports from National Pro-gram on Key Basic Research of China(973 Program,2015CB258400)the National Thousand Young Talents Program,Natural Science Foundation of China(51508213,51608217,and 21607046)+1 种基金Innovative and Interdisciplinary Team at HUST(0118261077)the Fundamental Research Funds for Central Universi-ties(2017KFYXJJ217).
文摘The increase in release of toxic heavy metals into natural water attracts much attention due to its devastating effect on ecology and human health.The design and implementation of green electrode materials is pivotal for improving the electrochemical performance of in situ heavy metal monitoring.
基金supported jointly by Natural Science Foundation of China(51878309)National Key Research and Development Program of China(2018YFC1900105).
文摘Microbial fuel cells(MFCs),as a sustainable and promising technology to solve both environmental pollution and energy shortage,have captured tremendous attention.The conversion efficiency of chemical energy contained in organic waste or wastewater to electricity via microbial metabolism strongly depends on the performance of each functional unit,including the anode,cathode and separator/membrane used in MFCs.Therefore,significant attention has been paid toward developing advanced functional materials to enhance the performance of each unit or provide new featured functions.This review paper provides a comprehensive review on recent achievements and advances in the modification and development of functional materials for MFC systems,including 1)the development of functional anode materials for enhanced microbial compatibilities as well as electron transfer capabilities,2)the development of cost-effective separators/membranes such as ion exchange membrane,porous membrane,polymer electrolyte membrane and composite membrane,and 3)the development of functional cathode catalysts to decrease the over-potential and enhance the electrocatalytic efficiency for oxygen reduction reaction in order to substitute the common costly Pt catalyst.The challenges and outlooks of functional materials for MFC applications are also discussed.
文摘本文汇总2014—2023年国家自然科学基金委员会医学科学部在生物医学工程/再生医学方向面上项目、青年科学基金项目与地区科学基金项目(简称“面青地项目”)的申请与资助情况,同时分析近10年相关领域的文献报道热点,为该领域的进一步高水平发展提供参考依据。回顾性收集代码H28下面青地项目的申请与资助数据资料,主要包括:资助项数与资助经费、资助项目所在依托单位与省市分布、获资助申请人的年龄与职称分布、获资助项目申请书的关键词等内容。同时,基于Web of Science数据库对近10年发表的相关方向文献关键词进行汇总,利用CiteSpace 6.2.R4软件对关键词的热点聚类及时间分布进行分析。通过分析发现:在2014—2023年中,生物医学工程/再生医学方向共资助面青地项目1279项,包括面上项目623项、青年科学基金项目599项和地区科学基金项目57项,资助经费50799万元。其中2014年的资助项目数最少,2023年的资助项目数最多。该方向的项目资助主要集中在H2808、H2809及H2810,3个代码获资助项目数与经费总和分别占全部项目的65.9%及64.6%。上海市、上海交通大学分别是获资助项目数最多的地区、依托单位,分别占比14.7%和7.0%。31~35岁的申请人获资助项目数最多,共507项,占比39.6%。近10年该方向获资助面青地项目申请书中出现频率最高的中英文关键词都与纳米相关(纳米药物和nanomedicine),而在Web of Science数据库中已发表相关方向文献的热门关键词包括biomedical engineering、tissue engineering、biomedical applications等。近年来,国家自然科学基金委员会医学科学部对生物医学工程/再生医学方向面青地项目的资助呈稳步上升趋势,资助领域广泛且重点明确,逐步建立以青年科研人员为主体的人才梯队。
文摘The effects of pore size in additively manufactured biodegradable porous magnesium on the mechanical properties and biodegradation of the scaffolds as well as new bone formation have rarely been reported. In this work, we found that high temperature oxidation improves the corrosion resistance of magnesium scaffold. And the effects of pore size on the mechanical characteristics and biodegradation of scaffolds, as well as new bone formation, were investigated using magnesium scaffolds with three different pore sizes, namely, 500, 800, and 1400 μm (P500, P800, and P1400). We discovered that the mechanical characteristics of the P500 group were much better than those of the other two groups. In vitro and in vivo investigations showed that WE43 magnesium alloy scaffolds supported the survival of mesenchymal stem cells and did not cause any local toxicity. Due to their larger specific surface area, the scaffolds in the P500 group released more magnesium ions within reasonable range and improved the osteogenic differentiation of bone mesenchymal stem cells compared with the other two scaffolds. In a rabbit femoral condyle defect model, the P500 group demonstrated unique performance in promoting new bone formation, indicating its great potential for use in bone defect regeneration therapy.
文摘Introduction Is it feasible to employ neural signals for the purpose of communication?In 1938,this thoughtprovoking query was visually embodied in a sketch received by Hans Berger,a German Professor of Psychiatry renowned for his discovery of human electroencephalography(EEG)nearly a century ago.In this fanciful sketch.
基金supported by the National Key Research and Development Program of China (No. 2018YFD1100604)the China Scholarship Council grant (CSC No. 2018GBJ008465)。
文摘Over half of century,sanitary landfill was and is still the most economical treatment strategy for solid waste disposal,but the environmental risks associated with the leachate have brought attention of scientists for its proper treatment to avoid surface and ground water deterioration.Most of the treatment technologies are energy-negative and cost intensive processes,which are unable to meet current environmental regulations.There are continuous demands of alternatives concomitant with positive energy and high effluent quality.Microbial fuel cells(MFCs)were launched in the last two decades as a potential treatment technology with bioelectricity generation accompanied with simultaneous carbon and nutrient removal.This study reviews capability and mechanisms of carbon,nitrogen and phosphorous removal from landfill leachate through MFC technology,as well as summarizes and discusses the recent advances of standalone and hybrid MFCs performances in landfill leachate(LFL)treatment.Recent improvements and synergetic effect of hybrid MFC technology upon the increasing of power densities,organic and nutrient removal,and future challenges were discussed in details.
基金The research was supported by the National Natural Science Foundation of China(Grant Nos.51708239 and U1901216)Natural Science Foundation of Hubei Province(No.2020CFA042)+1 种基金Applied Basic Research Program of Wuhan(No.2020020601012277)Additionally,we would also like to thank the Analytical and Testing Center of Huazhong University of Science and Technology for providing experimental measurements.
文摘Many studies have investigated the effects of different pretreatments on the performance of anaerobic digestion of sludge.However,the detailed changes of dissolved organic nitrogen,particularly the release behavior of proteins and the byproducts of protein hydrolysis-amino acids,are rarely known during anaerobic digestion of sludge by different pretreatments.Here we quantified the changes of three types of proteins and 17 types of amino acids in sludge samples solubilized by ultrasonic,thermal,and acid/alkaline pretreatments and their transformation during anaerobic digestion of sludge.Tryptophan protein,aromatic protein I,aromatic protein II,and cysteine were identified as the key dissolved organic nitrogen responsible for methane production during anaerobic digestion of sludge,regardless of the different pretreatment methods.Different from the depletion of other amino acids,cysteine was resistant to degradation after an incubation period of 30 days in all sludge samples.Meanwhile,the“cysteine and methionine metabolism(K00270)”was absent in all sludge samples by identifying 6755 Kyoto Encyclopedia of Genes and Genomes assignments of genes hits.Cysteine contributed to the generation of methane and the degradation of acetic,propionic,and n-butyric acids through decreasing oxidation-reduction potential and enhancing biomass activity.This study provided an alternative strategy to enhance anaerobic digestion of sludge through in situ production of cysteine.
基金The authors would like to thank H.Wu for his coordination in organizing the research topic.
文摘The year ahead marks the 50th anniversary of the first publication on the brain-computer interface(BCI)proposed by Vidal in 1973.Over the past decades,continuous progress has been made in designing and optimizing the BCI system toward a high-performance,robust and ease-of-use“mind reading”.The nascent field of BCI has brought together scientists from neuroscience,computer science as well as engineers and clinicians worldwide to address the highly challenging problem.
基金funded by the National Natural Science Foundation of China(Grant Nos.52170133,U1901216,51708239)the Natural Science Foundation of Hubei Province(No.2020CFA042)Applied Basic Research Program of Wuhan(No.2020020601012277),and Program for HUST Academic Frontier Youth Team.
文摘This study compared effects of three different valent iron(Fe^(0),Fe(II)and Fe(III))on enhanced anaerobic sludge digestion,focusing on the changes of oxidation reduction potential(ORP),dissolved organic nitrogen(DON),and microbial community.Under the same iron dose in range of 0−160 mg/L after an incubation period of 30 days(d),the maximum methane production rate of sludge samples dosed with respective Fe^(0),Fe(II)and Fe(III)at the same concentration showed indiscernible differences at each iron dose,regardless of the different iron valence.Moreover,their behavior in changes of ORP,DON and microbial community was different:(1)the addition of Fe^(0) made the ORP of sludge more negative,and the addition of Fe(II)and Fe(III)made the ORP of sludge less negative.However,whether being more or less negative,the changes of ORP may show unobservable effects on methane yield when it ranged from−278.71 to−379.80 mV;(2)the degradation of dissolved organic nitrogen,particularly proteins,was less efficient in sludge samples dosed with Fe^(0) compared with those dosed with Fe(II)and Fe(III)after an incubation period of 30 d.At the same dose of 160 mg/L iron,more cysteine was noted in sludge samples dosed with Fe(II)(30.74 mg/L)and Fe(III)(27.92 mg/L)compared with that dosed with Fe^(0)(21.75 mg/L);(3)Fe^(0) particularly promoted the enrichment of Geobacter,and it was 6 times higher than those in sludge samples dosed with Fe(II)and Fe(III)at the same dose of 160 mg/L iron.