We report a systematic investigation on c-axis point-contact Andreev reflection （PCAR） in BaFe2-xNixAs2 superconducting single crystals from underdoped to overdoped regions （0.075≤ x ≤0.15）. At low temperatures,...We report a systematic investigation on c-axis point-contact Andreev reflection （PCAR） in BaFe2-xNixAs2 superconducting single crystals from underdoped to overdoped regions （0.075≤ x ≤0.15）. At low temperatures, an in-gap sharp peak at low-bias voltage is observed in PCAR for overdoped samples, in contrast to the case of underdoped junctions, in which an in-gap plateau is observed. The variety of the conductance spectra with doping can be well described by using a generalized Blonder-Tinkham-Klapwijk formalism with an angle-dependent gap. This gap shows a clear crossover from a nodeless in the underdoped side to a nodal feature in the overdoped region. This result provides evidence of the doping-induced evolution of the superconducting order parameter when the inter-pocket and intra-pocket scattering are tuned through doping, as expected in the s± scenario.展开更多
Helicobacter pylori(H.pylori)is a common human pathogen responsible for various gastric diseases.This bacterium relies on the production of urease and hydrogenase to inhabit the acidic environment of the stomach.Nicke...Helicobacter pylori(H.pylori)is a common human pathogen responsible for various gastric diseases.This bacterium relies on the production of urease and hydrogenase to inhabit the acidic environment of the stomach.Nickel is an essential cofactor for urease and hydrogenase.H.pylori has to uptake sufficient nickel ions for the maturation of urease,and on the other way,to prevent the toxic effects of excessive nickel ions.Therefore,H.pylori has to strike a delicate balance between the import of nickel ions,its efficient intracellular storage,and delivery to nickel-dependent metalloenzymes when required.The assembly and maturation of the urease enzyme is a complex and timely ordered process,requiring various regulatory,uptake,chaperone and accessory proteins.In this review,we focus on several nickel trafficking proteins involved in urease maturation:NikR,NixA,HypAB,UreEFGH,HspA,Hpn and Hpnl.The work will deepen our understanding of how this pathogenic bacterium adapts to severe habitant environments in the host.展开更多
基金Supported by the National Basic Research Program of China under Grant Nos 2011CBA00100 and 2012CB821404the Project of International Team on Superconductivity and Novel Electronic Materials of Chinese Academy of Sciences
文摘We report a systematic investigation on c-axis point-contact Andreev reflection （PCAR） in BaFe2-xNixAs2 superconducting single crystals from underdoped to overdoped regions （0.075≤ x ≤0.15）. At low temperatures, an in-gap sharp peak at low-bias voltage is observed in PCAR for overdoped samples, in contrast to the case of underdoped junctions, in which an in-gap plateau is observed. The variety of the conductance spectra with doping can be well described by using a generalized Blonder-Tinkham-Klapwijk formalism with an angle-dependent gap. This gap shows a clear crossover from a nodeless in the underdoped side to a nodal feature in the overdoped region. This result provides evidence of the doping-induced evolution of the superconducting order parameter when the inter-pocket and intra-pocket scattering are tuned through doping, as expected in the s± scenario.
基金Supported by National Natural Science Foundation of China,No.20801061,No.31000373 and No.21371182The Fundamental Research Funds for the Central Universities,No.10lgpy19 and No.21611201Pearl River Rising Star of Science and Technology of Guangzhou City,No.2011J2200079 and No.2011J2200003
文摘Helicobacter pylori(H.pylori)is a common human pathogen responsible for various gastric diseases.This bacterium relies on the production of urease and hydrogenase to inhabit the acidic environment of the stomach.Nickel is an essential cofactor for urease and hydrogenase.H.pylori has to uptake sufficient nickel ions for the maturation of urease,and on the other way,to prevent the toxic effects of excessive nickel ions.Therefore,H.pylori has to strike a delicate balance between the import of nickel ions,its efficient intracellular storage,and delivery to nickel-dependent metalloenzymes when required.The assembly and maturation of the urease enzyme is a complex and timely ordered process,requiring various regulatory,uptake,chaperone and accessory proteins.In this review,we focus on several nickel trafficking proteins involved in urease maturation:NikR,NixA,HypAB,UreEFGH,HspA,Hpn and Hpnl.The work will deepen our understanding of how this pathogenic bacterium adapts to severe habitant environments in the host.
