The effects of the coronavirus disease 2019(COVID-19)pandemic on male fertility have received considerable attention because human testes contain high levels of angiotensin-converting enzyme-2 receptors,through which ...The effects of the coronavirus disease 2019(COVID-19)pandemic on male fertility have received considerable attention because human testes contain high levels of angiotensin-converting enzyme-2 receptors,through which severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)can enter.Early studies showed decreases in semen quality during and after recovery from COVID-19.However,no semen quality studies have examined the effects of widespread subclinical and mild disease,as well as changes in lifestyle,psychosocial behavior,intake of dietary supplements,and stress.This cross-sectional study compared semen quality parameters in male partners of infertile couples between men who underwent semen analysis before the COVID-19 pandemic(prepandemic group)and men who underwent semen analysis during the pandemic period(pandemic group);the analysis sought to clarify the overall effects of the pandemic.No participants in the pandemic group had experienced clinically overt disease.Among the 239 participants,mean body weight(P=0.001),mean body mass index(P<0.001),median sperm concentration(P=0.014),total sperm count(P=0.006),and total percentages of motile(P=0.013)and abnormal cells(P<0.001)were significantly greater in the pandemic group(n=137)than those in the prepandemic group(n=102).Among abnormal cells,the percentages of cells with excess residual cytoplasm(P<0.001),head defects(P<0.001),and tail defects(P=0.015)were significantly greater in the pandemic group than those in the prepandemic group.With the exception of morphology,the overall semenogram results were better in the pandemic group than those in the prepandemic group.展开更多
As a promising fuel candidate,ammonia has been successtully used as anode feed in alkaline fuel cells.However,current technology in catalysts for ammonia electro-oxidation reaction(AOR)with respect to both cost and pe...As a promising fuel candidate,ammonia has been successtully used as anode feed in alkaline fuel cells.However,current technology in catalysts for ammonia electro-oxidation reaction(AOR)with respect to both cost and performance is inadequate to ensure large scale commercial application of direct ammonia fuel cells.Recent studies found that alloying Pt with different transition metals and controlling the morphology of catalysts can improve the AOR activity,and thus potentially can solve the cost issue.Herein,(100)-terminated Pt-M nanocubes(M=3d-transition metals Fe,Co,Ni,Zn)are synthesized via wet-chemistry method and their catalytic activities toward AOR are evaluated.The addition of Fe,Co,Ni and Zn elements can enhance the AOR activity due to decrease in oxophilicity of platinum and bifunctional mechanism.Pt-Zn exhibits the maximum mass activity and specific ativity with values of 0.41 A/mgpt and 169 mA/cm2 that are 1.6 and 1.8 times higher than Pt nanocubes,respectively.Pt-Fe,Pt-Co and PI-Ni nanocubes also ilustrate higher mass and specific activities compared to Pt nanocubes.展开更多
Ammonia electrooxidation reaction involving multistep electron-proton transfer is a significant reaction for fuel cells,hydrogen production and understanding nitrogen cycle.Platinum has been established as the best el...Ammonia electrooxidation reaction involving multistep electron-proton transfer is a significant reaction for fuel cells,hydrogen production and understanding nitrogen cycle.Platinum has been established as the best electrocatalyst for ammonia oxidation in aqueous alkaline media.In this study,Pt/nitrogen-doped graphene(NDG)and Pt/tungsten monocarbide(WC)/NDG are synthesized by a wet chemistry method and their ammonia oxidation activities are compared to commercial Pt/C.Pt/NDG exhibits a specific activity of 0.472 mA·cm^(-2),which is 44%higher than commercial Pt/C,thus establishing NDG as a more effective support than carbon black.Moreover,it is demonstrated that WC as a support also impacts the activity with further 30%increase in comparison to NDG.Surface modification with Ir resulted in the best electro-catalytic activity with Pt-IrAVC/NDG having almost thrice the current density of commercial Pt/C.This work adds insights regarding the role of NDG and WC as efficient supports along with significant impact of Ir surface modification.展开更多
文摘The effects of the coronavirus disease 2019(COVID-19)pandemic on male fertility have received considerable attention because human testes contain high levels of angiotensin-converting enzyme-2 receptors,through which severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)can enter.Early studies showed decreases in semen quality during and after recovery from COVID-19.However,no semen quality studies have examined the effects of widespread subclinical and mild disease,as well as changes in lifestyle,psychosocial behavior,intake of dietary supplements,and stress.This cross-sectional study compared semen quality parameters in male partners of infertile couples between men who underwent semen analysis before the COVID-19 pandemic(prepandemic group)and men who underwent semen analysis during the pandemic period(pandemic group);the analysis sought to clarify the overall effects of the pandemic.No participants in the pandemic group had experienced clinically overt disease.Among the 239 participants,mean body weight(P=0.001),mean body mass index(P<0.001),median sperm concentration(P=0.014),total sperm count(P=0.006),and total percentages of motile(P=0.013)and abnormal cells(P<0.001)were significantly greater in the pandemic group(n=137)than those in the prepandemic group(n=102).Among abnormal cells,the percentages of cells with excess residual cytoplasm(P<0.001),head defects(P<0.001),and tail defects(P=0.015)were significantly greater in the pandemic group than those in the prepandemic group.With the exception of morphology,the overall semenogram results were better in the pandemic group than those in the prepandemic group.
基金Research Grant Council(Nos.26206115 and 16304117)of the Hong Kong Special Administrative Region.
文摘As a promising fuel candidate,ammonia has been successtully used as anode feed in alkaline fuel cells.However,current technology in catalysts for ammonia electro-oxidation reaction(AOR)with respect to both cost and performance is inadequate to ensure large scale commercial application of direct ammonia fuel cells.Recent studies found that alloying Pt with different transition metals and controlling the morphology of catalysts can improve the AOR activity,and thus potentially can solve the cost issue.Herein,(100)-terminated Pt-M nanocubes(M=3d-transition metals Fe,Co,Ni,Zn)are synthesized via wet-chemistry method and their catalytic activities toward AOR are evaluated.The addition of Fe,Co,Ni and Zn elements can enhance the AOR activity due to decrease in oxophilicity of platinum and bifunctional mechanism.Pt-Zn exhibits the maximum mass activity and specific ativity with values of 0.41 A/mgpt and 169 mA/cm2 that are 1.6 and 1.8 times higher than Pt nanocubes,respectively.Pt-Fe,Pt-Co and PI-Ni nanocubes also ilustrate higher mass and specific activities compared to Pt nanocubes.
基金the Southern Marine Sciencc and Engineering Guangdong Laboratory(Guangzhou)(Grant No.SMSEGL20SC01)Innovation and Technology Commission(Grant No.ITC-CNERC14EG03)of the Hong Kong Special Administrative Regionstartup funding of Hong Kong University of Science and Technology.
文摘Ammonia electrooxidation reaction involving multistep electron-proton transfer is a significant reaction for fuel cells,hydrogen production and understanding nitrogen cycle.Platinum has been established as the best electrocatalyst for ammonia oxidation in aqueous alkaline media.In this study,Pt/nitrogen-doped graphene(NDG)and Pt/tungsten monocarbide(WC)/NDG are synthesized by a wet chemistry method and their ammonia oxidation activities are compared to commercial Pt/C.Pt/NDG exhibits a specific activity of 0.472 mA·cm^(-2),which is 44%higher than commercial Pt/C,thus establishing NDG as a more effective support than carbon black.Moreover,it is demonstrated that WC as a support also impacts the activity with further 30%increase in comparison to NDG.Surface modification with Ir resulted in the best electro-catalytic activity with Pt-IrAVC/NDG having almost thrice the current density of commercial Pt/C.This work adds insights regarding the role of NDG and WC as efficient supports along with significant impact of Ir surface modification.
