Angle-resolved photoemission study of NbGeSb with non-symmorphic symmetry

We investigate the electronic structure of NbGeSb with non-symmorphic symmetry.We employ angle-resolved photoemission spectroscopy(ARPES)to observe and identify the bulk and surface states over the Brillouin zone.By utilizing high-energy photons,we identify the bulk Fermi surface and bulk nodal line along the direction X–R,while the Fermi surface of the surface state is observed by using low-energy photons.We observe the splitting of surface bands away from the high-symmetry point X.The density functional theory calculations on bulk and 1 to 5-layer slab models,as well as spin textures of NbGeSb,verify that the band splitting could be attributed to the Rashba-like spin–orbit coupling caused by space-inversion-symmetry breaking at the surface.These splitted surface bands cross with each other,forming two-dimensional Weyl-like crossings that are protected by mirror symmetry.Our findings provide insights into the two-dimensional topological and symmetry-protected band inversion of surface states.

New insight into the design of highly dispersed Pt supported CeO_(2)-TiO_(2) catalysts with superior activity for VOCs low-temperature removal

A series of CeO_(2)-TiO_(2)mixed oxides supports with various Ce/Ti molar ratio were synthesized by modified coprecipitation method. The corresponding Pt loaded(0.5 wt% Pt) catalysts were prepared by electronless deposition method and evaluated for the deep oxidation of n-hexane as a model VOCs. The results show that the CeO_(2)and TiOxnanoparticles can highly disperse into each other and form Ce_(2)Ti_(2)O_(7)solid solution with appropriate Ce/Ti molar ratio, which significantly improves their redox ability by enhancing the interaction between CeO_(2)and TiO_(x). The dispersibility of Pt species can also be adjusted by altering the Ce/Ti molar ratio, and Pt/CeTi-2/1 catalyst with Ce/Ti molar ratio of 2:1 exhibits the best Pt dispersibility that Pt species mainly exist as Pt single atoms. The high dispersion of Pt species in the Pt/CeO_(2)-TiO_(2)catalysts would promote the catalytic activity of VOCs oxidation with low T90% values(1000 ppm, GHSV = 15,000 h^(-1)), such as for n-hexane degradation with T90% of 139℃. The characterizations reveal that the superior activity is mainly related to possessing the more Pt2+species,adsorbed oxygen species and higher low-temperature reducibility owing to the strong interaction between highly dispersed Pt species and CeO_(2)-TiO_(2)as well as the promoted migration of lattice oxygen by the formation of more Ce_(2)Ti_(2)O_(7)species. Furthermore, the Pt/CeTi-2/1 catalyst also exhibits excellent stability for chlorinated and other non-chlorinated VOCs oxidation, making it very promising for real application under various operating conditions.

体重指数和血压与血管硬化的关系及护理对策

目的旨在探讨体重指数(body mass index,BMI)和血管硬化指标[包括臂踝脉搏波传导速度(brachial ankle pulse wave velocity,baPWV)和踝臂血压指数(ankle brachial index,ABI)]之间的关联,以及血压是否与之关联,并提出相关的护理对策。方法采用横断面调查研究。2019年3一12月,选取上海市张江社区医疗中心接受常规健康筛查的1894名中老年人进行调查。根据BMI将其分为3组:正常体重(n=1202)、超重(n=480)和肥胖(n=212)组。采用多变量线性回归模型和平滑曲线拟合评估BMI和血管硬化指标之间的关联。采用中介分析来检验血压是否在BMI和血管硬化指标之间起中介作用。结果多元线性回归分析显示,BMI与baPWV(m/s)[β=-0.06(-0.10,-0.03)]和ABI[β=-0.004(-0.005,-0.003)]分别显示负向关联。收缩压在BMI与baPWV关系中的交互作用检验结果有统计学意义(P=0.01)。在校正年龄和性别后,中介分析显示BMI和baPWV存在关联(β=0.090,P<0.001),收缩压(β=0.533,P<0.001)和舒张压(β=0.338,P<0.001)的中介作用有统计学意义。BMI与ABI负向关联(β=-0.135,P<0.001),收缩压(β=0.124,P<0.001)和舒张压(β=0.053,P<0.001)有部分中介作用。然而,依据血压水平进一步进行亚组分析后,多数亚组内血压中介效应无统计学意义。结论研究结果显示,BMI与不同非侵人性血管硬化测量指标之间存在矛盾的关联。在BMI和baPWV的关系中,血压可能有生物学上的交互作用。应采取针对性的健康教育和行为干预,控制血压和体质量,预防中老年人的血管硬化。

中西合璧的老人支持体系——香港所追求的全面照顾模式

本文从老人照顾体系发展的四个阶段,回顾了香港过去五十年来家庭对传统孝亲价值的维系,政府对照顾责任的厘清,传统家庭对机构照料的忌讳;以及近年来从“在社区照顾”发展到“就地养老”的概念;并从人口结构的变化、社会经济发展的变迁以及政府角色与责任的不同作了深入的探讨剖析.并在此基础上,说明“全面照顾模式”如何结合上述价值与社会体系背景,将政府与民间的各层面力量融入成为全方位、多面向与多选项的照顾体系,同时也说明了对于政策制定者、服务提供者以及社区工作者又意味着什么样的挑战.最后,笔者提出全面护理模式是最适合东亚国家的养老照顾模式之一.

Pyrolysis-free formamide-derived N-doped carbon supporting atomically dispersed cobalt as high-performance bifunctional oxygen electrocatalyst

Non-precious metal-nitrogen-carbon(MNC)electrocatalysts have gained tremendous attention as promising electrocatalysts for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).However,the most applicable strategies for the synthesis of MNC materials heavily rely on pyrolysis treatment,which may easily lead to metal aggregation and subsequent degradation of catalytic performance.Herein,we developed a pyrolysis-free strategy for preparing MNC materials,which was demonstrated by achieving ultrathin cobalt-nitrogen-carbon(Co NC)layer with dense atomically dispersed cobalt sites depositing on graphene oxide(GO)via simple treatment of Co salt and GO in formamide.The formamide-derived Co NC layer deposited on GO(termed as f-Co NC/GO)could be controlled in 1-2 nm thick.Remarkably,the f-CoNC/GO composite without pyrolysis exhibited excellent bifunctional performance toward ORR and OER,which was attributed to the dense atomically dispersed Co-Nxsites and improved conductivity by GO substrate.Furthermore,the f-CoNC/GO-assembled rechargeable Zn-air battery showed highly efficient and stable performance,demonstrating our pyrolysis-free method to be straightforward,cost-effective,and feasible for the scalable production of MNC electrocatalysts.

Superconductivity at the Normal Metal/Dirac Semimetal Cd3As2 Interface

We investigate the interface between a three-dimensional Dirac semimetal Cd3As2 and a normal metal via softpoint contact spectroscopy measurement.The superconducting gap features were detected below 3.8 K and 7.1 K in the case of Cd3As2 single crystals sputter-coated with the Pt and Au films,respectively,in the differential conductance dI/dV-V plots of the point contacts.As the applied magnetic field increased,the drop in the zerobias contact resistance shifted toward lower temperatures.The topologically non-trivial band structure of Cd3As2 is considered to play a crucial role in inducing the superconductivity.Apart from realizing superconductivity in topological materials,our creative approach can be used to investigate possible topological superconductivity and exhibits a high application potential in electronic devices.

一种在室温附近具有高热电性能的准一维块体材料

在低维材料体系中探索高热电性能是热电材料研究领域的一个重要方向.实际上,近年来所发现的热电材料中的很大一部分,比如Bi_(2)Te_(3),SnSe,Mg_(3)Sb_(2)等,都具有准二维晶体结构.但是,到目前为止对准一维材料的热电研究还非常少见.本文报道了一种在室温附近具有高热电性能的准一维块体材料:TLCu_(3)Te_(2).在室温下,该材料沿单晶针状方向具有高达1.3的热电优值;在400 K时,其热电优值甚至可以达到1.5,一定程度超越了目前该温区的商用材料热电性能.通过详细的热电输运实验并结合第一性原理计算,作者发现TlCu_(3)Te_(2)的高热电优值主要起源于饼状费米口袋的高度各向异性准一维电子色散关系带来的大热电功率因子,以及准一维重元素复杂晶格导致的极低热导率.该研究表明准一维块体材料中的单轴性热电效应是一个值得深入探索的热电材料新领地.

智能时代的教育科学研究:内涵、逻辑框架与实践进路

教育科学研究是教育事业的重要组成部分,对教育改革发展具有重要的支撑、驱动和引领作用。本研究通过总结当下教育的表征形态、理论基石和研究范式,归纳出智能时代教育科学研究的内涵是以真实教育问题为导向,有效结合自然科学的研究范式,深度融合以人工智能、大数据、认知科学、神经科学为代表的科学与技术,以发现教育基础规律为重点研究内容,服务于以科学化、精准化、智能化为核心特征的高素质人才培养、多元教育评价、优质服务供给与治理的新型教育研究。基于内涵,本研究考察并参考自然科学基金"教育信息科学与技术"方向的申请主题,将智能时代的教育科学研究归为"基础规律层""技术方法层""智能服务层",构建了教育、科学、技术相融合的教育科学研究逻辑框架。最后,从教育科学研究的价值定位与实践路向、数据驱动的教育评价和教育服务体系、推动多学科交叉融合和构建教育科学研究体系四个方面明确了智能时代教育科学研究的实践进路,以期为我国教育科学研究的健康发展提供参考。

超小NiFe水滑石耦合单原子FeCo-NC纳米花用于可充电锌空气电池

单原子分散的FeCo-NC材料,具有特殊的花状结构和原子级分散Fe/Co位点,适用于可控沉积超小NiFe水滑石纳米点(NiFeND),从而制备具有优异氧还原(ORR)和氧析出(OER)性能的双功能催化材料.FeCo-NC材料本身具有三维立体花状介孔结构和丰富的N/O功能位点,可以实现对NiFe-ND尺寸的有效控制(直径约4 nm),使得制备的特殊复合材料的OER和ORR活性位暴露度达最大值.电化学测试表明在0.1 mol L-1KOH电解液中NiFe-ND/FeCo-NC的ORR半波电势为0.85 V,当电流密度为10 mA cm-2时的OER电势为1.66 V.原位拉曼结果进一步证实了NiFe-ND/FeCo-NC材料优良的OER活性来源于电化学过程中产生的丰富Ni(Fe)OOH活性相.采用NiFe-ND/FeCo-NC组装的锌空气电池具有较小的充放电电压差(0.87 V,20 mA cm-2)和持久的循环稳定性.同时,NiFe-ND/FeCo-NC也可以应用于全固态锌空气电池,即使在形变的情况下仍然具有良好的循环稳定性.本工作可为单原子金属氮碳催化剂作为特殊基底材料应用于新型多功能催化剂的研发提供指导.

Hierarchical peony-like FeCo-NC with conductive network and highly active sites as efficient electrocatalyst for rechargeable Zn-air battery

Carbon materials featuring hierarchical pores and atomically dispersed metal sites are promising catalysts for energy storage and conversion applications.Herein,we developed a facile strategy to construct functional carbon materials with a fluffy peony-like structure and dense binary FeCo-Nx active sites(termed as f-FeCo-CNT).By regulating the metal content in precursors,a three-dimensional(3D)interconnected conductive carbon nanotubes network was in-situ formed throughout the atomically dispersed FeCo-NC matrix during pyrolysis.Taking advantage of rich pore hierarchy and co-existence of highly active FeCo-Nx sites and beneficial FeCo alloy nanoparticles,the f-FeCo-CNT material exhibited excellent bifunctional performance towards oxygen reduction reaction/oxygen evolution reactions(ORR/OER)with respect to the atomically dispersed FeCo-NC(SA-f-FeCo-NC)and commercial Pt/C+Ru02 mixture,surpassing the SA-f-FeCo-NC with a 20 mV higher ORR half-wave potential and a 100 mV lower OER overpotential(at 10.0 mA/cm^2).Remarkably,the f-FeCo-CNT-assembled Zn-air battery(ZAB)possessed a maximum specific power of 195.8 mW/cm^2,excellent rate capability,and very good cycling stability at large current density of 20.0 mA/cm^2.This work provides a facile and feasible synthetic strategy of constructing low-cost cathode materials with excellent comprehensive ZAB performance.

Family Revolution： Marital Strife in Contemporary Chinese Literature and Visual Culturce

Family Revolution： Marital Strife in Contemporary Chinese Literature and Visual Culture by Hui Xiao is an excellent original study of contemporary Chinese literature and visual culture. It examines how contemporary storytelling in text and on screen represents the increasing disintegration of marriage, and stages changing attitudes toward marriage in contemporary Chinese society. The time span covered by the study is primarily the three decades starting from the 198os, but the book＇s discussion travels back to key historical moments when social change, intellectual debates, political ideologies, and government polices brought about crucial changes in the practice and perceptions of marriage.