Abstract:Here we report a new quaternary iron-arsenide superconductor Nd[O 1-x F x ]FeAs, with the onset resistivity transition at 51.9 K and Meissner transition at 51 K. This compound has the same crystal structure as LaOFeAs, and becomes the second superconductor after Pr[O 1-x F x ]FeAs that superconducts above 50 K.
Here we report a new class of superconductors prepared by high pressure synthesis in the quaternary family ReFeAsO 1-d (Re = Sm, Nd, Pr, Ce, La) without fluorine doping. The onset superconducting critical temperature (T c ) in these compounds increases with the reduction of Re atom size, and the highest T c obtained so far is 55 K in SmFeAsO 1-d . For the NdFeAsO 1-d compound with different oxygen concentration a dome-shaped phase diagram was found.
Ren Zhi-An (任治安)*, Lu Wei (陆伟), Yang Jie (杨杰), Yi Wei (衣玮), Shen Xiao-Li (慎晓丽), Li Zheng-Cai (李 正才), Che Guang-Can (车广灿), Dong Xiao-Li (董晓莉), Sun Li-Ling (孙立玲), Zhou Fang (周放), Zhao Zhong-Xian (赵忠贤)*
Here we report the fabrication and superconductivity of the iron-based arsenic-oxide GdFeAsO 1-δ compound with oxygen-deficiency, which has an onset resistivity transition temperature at 53.5 K. This material has a same crystal structure as the newly discovered high-T c ReFeAsO 1-d family (Re = rare earth metal) and a further reduced crystal lattice, while the T c starts to decrease compared with the SmFeAsO 1-δ system.
T he Convention on Biological Diversity (CBD) sets the policy framework for biodiversity conservation and sustainable use through the commitments of 195 countries and the European Union. The Strategic Plan for Biodiversity 2011-2020 included Aichi Biodiversity Target 12, which set the goal for 2020 of preventing the extinction of known threatened species and improving and sustaining their conservation status. Despite government commitments and successful efforts for certain species 1 , the overall extinction risk continues to increase, and widespread implementation shortfalls will prevent Target 12 from being met 2 . A new global framework with revised goals and targets is currently being negotiated, which places the stabilization and restoration of species' populations as an outcome goal for 2030, as a stepping stone towards the CBD's 2050 Vision 3,4 .
Recent studies have shown that heterogeneous reactions of hydrogen peroxide (H(2)O(2)) on aerosol surfaces may play an important role in tropospheric chemistry. The data concerning the kinetics and mechanisms of these reactions, however, are quite scarce so far. Here, we investigated, for the first time, the heterogeneous reactions of gaseous H(2)O(2) on SiO(2) and α-Al(2)O(3) particles, two major components of mineral dust aerosol, using transmission-Fourier Transform Infrared (T-FTIR) spectroscopy, and high-performance liquid chromatography (HPLC). It is found that H(2)O(2) molecularly adsorbs on SiO(2), and a small amount of molecularly adsorbed H(2)O(2) decomposes due to its thermal instability. For α-Al(2)O(3), catalytic decomposition of H(2)O(2) evidently occurs, but there is also a small amount of H(2)O(2) molecularly adsorbed on the particle surface. The BET uptake coefficients of H(2)O(2) on both particles appear to be independent of gaseous H(2)O(2) concentration (1.27-13.8 ppmv) and particle sample mass (2.8-6.5 mg for SiO(2) and 8.6-18.9 mg for α-Al(2)O(3)), but are strongly dependent on relative humidity with the values ranging from (1.55 ± 0.14) × 10(-8) and (1.21 ± 0.04) × 10(-7) at 2% RH to (0.61 ± 0.06) × 10(-8) and (0.76 ± 0.09) × 10(-7) at 76% RH for SiO(2) and α-Al(2)O(3), respectively. On the basis of the experimental results and literature data, the potential mechanisms for heterogeneous decomposition of H(2)O(2) were proposed, and the atmospheric implications of these reactions were discussed. It is found that heterogeneous reaction of H(2)O(2) on both mineral oxides plays a significant role in processing mineral aerosols, although its role as a sink for ambient H(2)O(2) is probably limited.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.