After peripheral nerve injury, the process of Wallerian degeneration is initiated in the distal stump of injured nerves. Wallerian degeneration in peripheral nerves involves axonal degeneration and degradation of the ...After peripheral nerve injury, the process of Wallerian degeneration is initiated in the distal stump of injured nerves. Wallerian degeneration in peripheral nerves involves axonal degeneration and degradation of the myelin sheath in Schwann cells. This provides the necessary conditions for axonal regeneration and remyelination. After nerve injury, macrophages are also recruited to the distal nerve stump and, together with Schwann cells, play a role in the clearance of myelin debris.展开更多
An electrocatalyst with heterogeneous nanostructure, especially the hierarchical one, generally shows a more competitive activity than that of its single-component counterparts for oxygen evolution reaction(OER), due ...An electrocatalyst with heterogeneous nanostructure, especially the hierarchical one, generally shows a more competitive activity than that of its single-component counterparts for oxygen evolution reaction(OER), due to the synergistically enhanced kinetics on enriched active sites and reconfigured electronic band structure. Here this work introduces hierarchical heterostructures into a NiMo@NiS/MoS_(2)@Ni_(2)S_(2)/MoO_(x)(NiMoS) composite by one-pot controlled moderative sulfidation. The optimal solvent composition and addition of NaOH enable NiMoS to own loose and porous structures, smaller nanoparticle sizes, optimal phase composition and chemical states of elements, improving the OER activity of NiMoS. To achieve current densities of 50 and 100 mA cm^(-1), small overpotentials of 275 and 306 mV are required respectively, together with a minor Tafel slope of 58 mV dec^(-1), which outperforms most reported sulfide catalysts and IrO_(2). The synergistic effects in the hierarchical heterostructures expose more active sites,adjust the electronic band structure, and enable the fast charge transfer kinetics, which construct an optimized local coordination environment for high OER electrocatalytic activity. Furthermore, the hierarchical heterostructures suppress the distinct lowering of electrical conductivity and collapse of pristine structures resulted from the metal oxidation and synchronous S leaching during OER, yielding competitive catalytic stability.展开更多
Biogenic hydrogen sulfide is an odorous, toxic and corrosive gas released from sewage in sewers. To control sulfide generation and emission, nitrate is extensively applied in sewer systems for decades. However, the un...Biogenic hydrogen sulfide is an odorous, toxic and corrosive gas released from sewage in sewers. To control sulfide generation and emission, nitrate is extensively applied in sewer systems for decades. However, the unexpected sulfide rebound after nitrate addition is being questioned in recent studies. Possible reasons for the sulfide rebounds have been studied,but the mechanism is still unclear, so the countermeasure is not yet proposed. In this study, a lab-scale sewer system was developed for investigating the unexpected sulfide rebounds via the traditional strategy of nitrate addition during 195-days of operation. It was observed that the sulfide pollution was even severe in a sewer receiving nitrate addition. The mechanism for the sulfide rebound can be differentiated into short-term and long-term effects based on the dominant contribution. The accumulation of intermediate elemental sulfur in biofilm resulted in a rapid sulfide rebound via the high-rate sulfur reduction after the depletion of nitrate in a short period. The presence of nitrate in sewer promoted the microorganism proliferation in biofilm, increased the biofilm thickness, re-shaped the microbial community and enhanced biological denitrification and sulfur production, which further weakened the effect of nitrate on sulfide control during the long-term operation. An optimized biofilminitiated sewer process model demonstrated that neither the intermittent nitrate addition nor the continuous nitrate addition was a sustainable strategy for the sulfide control. To minimize the negative impact from sulfide rebounds, a(bi)monthly routine maintenance(e.g., hydraulic flushing with nitrate spike) to remove the proliferative microorganism in biofilm is necessary.展开更多
An innovative treatment method by the combination of NaOH and nitrite is proposed for controlling hydrogen sulfide and methane in gravity sewers and overcome the drawbacks of the conventional single chemical treatment...An innovative treatment method by the combination of NaOH and nitrite is proposed for controlling hydrogen sulfide and methane in gravity sewers and overcome the drawbacks of the conventional single chemical treatment.Four reactors simulating gravity sewers were set up to assess the effectiveness of the proposed method.Findings demonstrated hydrogen sulfide and methane reductions of about 96.01%and 91.49%,respectively,by the combined addition of NaOH and nitrite.The consumption of NaNO_(2) decreased by 42.90%,and the consumption rate of NaOH also showed a downward trend.Compared with a single application of NaNO_(2),the C/N ratio of wastewater was increased to about 0.61 mg COD/mg N.The greenhouse effect of intermediate N2O and residual methane was about 48.80 gCO_(2)/m^(3),which is far lower than that of methane without control(260 gCO_(2)/m^(3)).Biofilm was destroyed to prevent it from entering the sewage by the chemical additives,which reduced the biomass and inhibited the recovery of biofilm activity to prolong the control time.The sulfide production rate and sulfate reduction rate were reduced by 92.32%and 85.28%,respectively.Compared with conventional control methods,the cost of this new method was only 3.92×10^(−3)$/m^(3),which is potentially a cost-effective strategy for sulfide and methane control in gravity sewers.展开更多
文摘After peripheral nerve injury, the process of Wallerian degeneration is initiated in the distal stump of injured nerves. Wallerian degeneration in peripheral nerves involves axonal degeneration and degradation of the myelin sheath in Schwann cells. This provides the necessary conditions for axonal regeneration and remyelination. After nerve injury, macrophages are also recruited to the distal nerve stump and, together with Schwann cells, play a role in the clearance of myelin debris.
基金financial supports from the National Natural Science Foundation of China (52004155,51690164, and 51805321)the China Postdoctoral Science Foundation (2020M681261)the Science and Technology Commission of Shanghai Municipality (19XD1401600 and 19010500300)。
文摘An electrocatalyst with heterogeneous nanostructure, especially the hierarchical one, generally shows a more competitive activity than that of its single-component counterparts for oxygen evolution reaction(OER), due to the synergistically enhanced kinetics on enriched active sites and reconfigured electronic band structure. Here this work introduces hierarchical heterostructures into a NiMo@NiS/MoS_(2)@Ni_(2)S_(2)/MoO_(x)(NiMoS) composite by one-pot controlled moderative sulfidation. The optimal solvent composition and addition of NaOH enable NiMoS to own loose and porous structures, smaller nanoparticle sizes, optimal phase composition and chemical states of elements, improving the OER activity of NiMoS. To achieve current densities of 50 and 100 mA cm^(-1), small overpotentials of 275 and 306 mV are required respectively, together with a minor Tafel slope of 58 mV dec^(-1), which outperforms most reported sulfide catalysts and IrO_(2). The synergistic effects in the hierarchical heterostructures expose more active sites,adjust the electronic band structure, and enable the fast charge transfer kinetics, which construct an optimized local coordination environment for high OER electrocatalytic activity. Furthermore, the hierarchical heterostructures suppress the distinct lowering of electrical conductivity and collapse of pristine structures resulted from the metal oxidation and synchronous S leaching during OER, yielding competitive catalytic stability.
基金supported by the National Natural Science Foundation of China (No. 51638005)the Fundamental Research Funds for the Central Universities (No. 20lgzd24)+1 种基金the Guangdong Basic and Applied Basic Research of the Joint Regional Fund (No. 2019A1515110569)Guangdong Provincial International Joint Research Center on Urban Water Management and Treatment (No. 2021A0505020010)。
文摘Biogenic hydrogen sulfide is an odorous, toxic and corrosive gas released from sewage in sewers. To control sulfide generation and emission, nitrate is extensively applied in sewer systems for decades. However, the unexpected sulfide rebound after nitrate addition is being questioned in recent studies. Possible reasons for the sulfide rebounds have been studied,but the mechanism is still unclear, so the countermeasure is not yet proposed. In this study, a lab-scale sewer system was developed for investigating the unexpected sulfide rebounds via the traditional strategy of nitrate addition during 195-days of operation. It was observed that the sulfide pollution was even severe in a sewer receiving nitrate addition. The mechanism for the sulfide rebound can be differentiated into short-term and long-term effects based on the dominant contribution. The accumulation of intermediate elemental sulfur in biofilm resulted in a rapid sulfide rebound via the high-rate sulfur reduction after the depletion of nitrate in a short period. The presence of nitrate in sewer promoted the microorganism proliferation in biofilm, increased the biofilm thickness, re-shaped the microbial community and enhanced biological denitrification and sulfur production, which further weakened the effect of nitrate on sulfide control during the long-term operation. An optimized biofilminitiated sewer process model demonstrated that neither the intermittent nitrate addition nor the continuous nitrate addition was a sustainable strategy for the sulfide control. To minimize the negative impact from sulfide rebounds, a(bi)monthly routine maintenance(e.g., hydraulic flushing with nitrate spike) to remove the proliferative microorganism in biofilm is necessary.
基金grateful for the financial support from the National Natural Science Foundation of China(Grant Nos.51778523,52000146)the China Postdoctoral Science Foundation(Grant No.2020M673351)the Key Research and Development Program of Shaanxi Province(grant no.2019ZDLSF06-04).
文摘An innovative treatment method by the combination of NaOH and nitrite is proposed for controlling hydrogen sulfide and methane in gravity sewers and overcome the drawbacks of the conventional single chemical treatment.Four reactors simulating gravity sewers were set up to assess the effectiveness of the proposed method.Findings demonstrated hydrogen sulfide and methane reductions of about 96.01%and 91.49%,respectively,by the combined addition of NaOH and nitrite.The consumption of NaNO_(2) decreased by 42.90%,and the consumption rate of NaOH also showed a downward trend.Compared with a single application of NaNO_(2),the C/N ratio of wastewater was increased to about 0.61 mg COD/mg N.The greenhouse effect of intermediate N2O and residual methane was about 48.80 gCO_(2)/m^(3),which is far lower than that of methane without control(260 gCO_(2)/m^(3)).Biofilm was destroyed to prevent it from entering the sewage by the chemical additives,which reduced the biomass and inhibited the recovery of biofilm activity to prolong the control time.The sulfide production rate and sulfate reduction rate were reduced by 92.32%and 85.28%,respectively.Compared with conventional control methods,the cost of this new method was only 3.92×10^(−3)$/m^(3),which is potentially a cost-effective strategy for sulfide and methane control in gravity sewers.
