Topological magnetotransport and electrical switching of sputtered antiferromagnetic Ir_(20)Mn_(80)

Topological magnetotransport in non-collinear antiferromagnets has attracted extensive attention due to the exotic phenomena such as large anomalous Hall effect(AHE),magnetic spin Hall effect,and chiral anomaly.The materials exhibiting topological antiferromagnetic physics are typically limited in special Mn_3X family such as Mn_3Sn and Mn_3Ge.Exploring the topological magnetotransport in common antiferromagnetic materials widely used in spintronics will not only enrich the platforms for investigating the non-collinear antiferromagnetic physics,but also have great importance for driving the nontrivial topological properties towards practical applications.Here,we report remarkable AHE,anisotropic and negative parallel magnetoresistance in the magnetron-sputtered Ir_(20)Mn_(80)antiferromagnet,which is one of the most widely used antiferromagnetic materials in industrial spintronics.The ab initio calculations suggest that the Ir_4Mn_(16)(IrMn_4)or Mn_3Ir nanocrystals hold nontrivial electronic band structures,which may contribute to the observed intriguing magnetotransport properties in the Ir_(20)Mn_(80).Further,we demonstrate the spin–orbit torque switching of the antiferromagnetic Ir_(20)Mn_(80)by the spin Hall current of Pt.The presented results highlight a great potential of the magnetron-sputtered Ir_(20)Mn_(80)film for exploring the topological antiferromagnet-based physics and spintronics applications.

Probing the magnetization switching with in-plane magnetic anisotropy through field-modified magnetoresistance measurement

Effective probing current-induced magnetization switching is highly required in the study of emerging spin-orbit torque(SOT)effect.However,the measurement of in-plane magnetization switching typically relies on the giant/tunneling magnetoresistance measurement in a spin valve structure calling for complicated fabrication process,or the non-electric approach of Kerr imaging technique.Here,we present a reliable and convenient method to electrically probe the SOT-induced in-plane magnetization switching in a simple Hall bar device through analyzing the MR signal modified by a magnetic field.In this case,the symmetry of MR is broken,resulting in a resistance difference for opposite magnetization orientations.Moreover,the feasibility of our method is widely evidenced in heavy metal/ferromagnet(Pt/Ni_(20)Fe_(80) and W/Co_(20)Fe_(60)B_(20))and the topological insulator/ferromagnet(Bi_(2)Se_(3)/Ni_(20)Fe_(80)).Our work simplifies the characterization process of the in-plane magnetization switching,which can promote the development of SOT-based devices.

Total Synthesis of Starfish Cyclic Steroid Glycosides.Part 2,Model Synthesis via Intramolecular Etherification

Comprehensive Summary Sepositoside A(1)is a prototypical cyclic steroid glycoside bearing a hybrid 16-membered ring composed of the steroid skeleton and a 1,2-trans-linked trisaccharide.Herein,we report an expedient access toward two simplified analogues,in which the strained 16-membered ring is constructed via Au(I)-catalyzed intramolecular addition of alcohol to epoxide.A similar macroetherification in relevant steroid trisaccharides has been intensively examined,however,failed to furnish the macrocyclic skeleton of Sepositoside A.

Total Synthesis of Starfish Cyclic Steroid Glycosides.Part 3,Formal Total Synthesis of Luzonicosides A and D

Comprehensive Summary Luzonicosides A(1)and D(2)are the major saponins isolated from pacific starfish Echinaster Luzonicus,featuring a sterically congested 16-membered ring which is formed by bridging the C3 and C6 of a 3β,6β-dihydroxy-Δ7-ene steroid with a 1,2-trans-linked linear trisaccharide via glycosidic and ether bonds,respectively.Here,we describe a formal total synthesis of starfish cyclic steroid glycosides 1 and 2.The synthetic route is highly modular and versatile,involving construction of the 16-membered macrocycles via Au(I)-catalyzed intramolecular glycosylation,highly efficient installation of unsaturated sugar moieties with ortho-hexynylbenzoates,elaboration of glucuronic acid unit via post-oxidation,and a de novo synthesis of the ether-linked pyranose unit.

Total Synthesis of Starfish Cyclic Steroid Glycosides.Part 1,Synthesis of the Aglycone and Attempts at Installation of the Sugar Units

Comprehensive Summary Sepositoside A(1)is the major and first cyclic steroid glycoside isolated from starfishes,which features a strained 16-membered ring formed by tethering C3 and C6 of the steroid aglycone with a linear trisaccharide.We conceived a convergent synthetic plan in which sepositoside A was disconnected into a disaccharide and a steroid-glucose hybrid ether.The desired 3β,6β-dihydroxy-Δ7,8-23-one aglcyone was readily prepared from dehydroepiandrosterone in 12 steps.The etherification of the 6β-hydroxy-Δ7,8-steroid with a variety of hexopyranoside-C6-electrophiles and CO_(2)-extrusion of a steroid-pyranose hybrid carbonate were extensively studied;however,formation of the desired steroid-pyranose etherate linkage has not been successful.Model studies on theβ-selective installation of the(1→2)-linked disaccharide onto the steroidal C3β-OH with the corresponding disaccharideα-imidates were also examined,however,formation of theα-glycosides prevailed.The present results force us to explore alternative approaches to construct the steroid-pyranose etherate linkage and stepwise assembly of the glycans en route to the starfish cyclic steroid glycosides,which will be presented in two articles that follow.

秦岭南坡陕西洋县辖区哺乳动物物种多样性的空间分布格局

物种多样性的空间分布格局一直是生态学和生物地理学研究的一个热点问题。山地生态系统的生境异质性和物种多样性高,适合研究物种多样性空间分布格局及其相关机制。2016年11月至2017年11月,本研究选取秦岭南坡陕西洋县辖区作为研究区域,采用样线法、红外相机法和笼捕/夹捕法,系统分析了8目21科48种哺乳动物物种多样性的空间分布格局。研究结果发现秦岭南坡洋县辖区哺乳动物物种丰富度的空间分布格局大致是中南部低,北部和东部高;物种多样性指数大致是中南部和北部低,东部高。啮齿类动物和非啮齿类动物的空间分布格局存在差异。哺乳动物物种丰富度和多样性指数的垂直分布格局都符合中峰模式,但啮齿类动物和非啮齿类动物间存在差异。最优线性模型结果表明,研究地区哺乳动物物种多样性的空间分布格局受到多种环境因素的共同影响。其中,年均温与物种多样性的相关性最强,在6个最优线性模型中贡献都是最大。综上,秦岭南坡洋县辖区中高海拔区域的物种多样性较高,应加强对中高海拔地区的保护,以维系该区域较高的生物多样性。

基于红外相机技术调查佛坪国家级自然保护区兽类和鸟类多样性

2015年1月至2017年12月,在陕西佛坪国家级自然保护区57条巡护样线上布设130台红外相机,对兽类和鸟类多样性进行调查。累计相机工作日101,220天,共捕获独立有效事件36,100次,其中兽类独立照片30,563张,鸟类3,244张。共记录到野生兽类6目15科29种,相对多度较高的前5个物种依次是秦岭羚牛(Budorcasbedfordi,RAI=11.53)、野猪(Sus scrofa, RAI=4.80)、小麂(Muntiacus reevesi, RAI=4.35)、大熊猫(Ailuropoda melanoleuca, RAI=1.81)和中国豪猪(Hystrixhodgsoni,RAI=1.13)。共记录到鸟类8目14科54种,相对多度最高的前5个物种依次是红腹锦鸡(Chrysolophus pictus, RAI=0.97)、红腹角雉(Tragopan temminckii, RAI=0.74)、紫啸鸫(Myophonus caeruleus,RAI=0.51)、红嘴蓝鹊(Urocissa erythrorhyncha, RAI=0.13)、黑领噪鹛(Garrulax pectoralis, RAI=0.12)。保护区鸟类新记录4种,包括白眉地鸫(Geokichla sibirica)、白眉鸫(Turdus obscurus)、长尾地鸫(Zoothera dixoni)和灰脸鵟鹰(Butastur indicus);保护区兽类新记录1种,为亚洲狗獾(Meles leucurus)。本研究利用红外相机技术客观记录了佛坪国家级自然保护区兽类和鸟类的本底情况,不仅初步了解了保护区内的野生动物分布,而且更新了保护区鸟类资源数据库,为保护区未来的保护和管理工作提供了数据基础。

Synthesis of the Diverse Glycosides in Traditional Chinese Medicine

CT Traditional Chinese medicine （TCM） is a huge treasure trove for the discovery and development of modern pharmaceuticals. Indeed, numerous biologically and pharmacologically significant molecules have been identified from TCM; among them, a considerable portion belongs to glycosides. These glycosides are extremely diverse in structures, consisting of a large variety of aglycones, glycans, as well as glycosidic linkages. In addition, these glycosides occur frequently as a complicated mixture of congeners in the nature sources. This micro-heterogeneity leads to the isolation of a ho- mogeneous glycoside in an appreciable amount a formidable task. Therefore, development of synthetic approaches toward these nature glycosides has received great attention. In this account, we summarize our twenty-year efforts spent on this topic. Fifty five representative TCM-relevant glycosides synthesized by our group are highlighted. Based on the aglycone structure, these glycosides are categorized into three groups, i.e., steroid glycosides, triterpene glycosides, and flavonoid and phenolic glycosides. Typical synthetic approaches are discussed, showing the demanding tactics for regio- and stereo-controlled installation of glycans and overall manipulation of protecting groups. These expedient and scalable synthetic approaches have provided practical alternatives to the accessibility of these TCM components and thus opportunities for their in depth biological and pharmacological studies.

公司高层女性参与率对价格加成的影响:促进还是抑制?

劳动力市场理论中,性别分化带来的劳动力异质性不仅源于劳动力本身在物理、生理等方面的差距,还源于社会环境以及现存职场性别隔离的情况。文章基于女性参与率的不同对企业生产效率和利润水平产生的影响,构造了劳动力性别特征影响企业价格加成的理论模型,分析了其理论机制;并以2008-2019年中国沪深两市A股非金融类上市公司为样本进行实证检验。结果发现,女性高层主要通过提高生产率、降低成本两个渠道影响企业价格加成,公司高层中女性参与率对企业价格加成具有正向影响。进一步研究发现,在国有产权性质、市场化程度较高、两职分离的上市公司,女性高层的影响力更显著。回归结果支持了理论推导预测,并为相关机构制定女性就业政策提供了理论支撑和经验证据。

Vibration testing of a steel girder bridge using cabled and wireless sensors

Being able to significantly reduce system installation time and cost,wireless sensing technology has attracted much interest in the structural health monitoring(SHM)community.This paper reports the field application of a wireless sensing system on a 4-span highway bridge located in Wayne,New Jersey in the US.Bridge vibration due to traffic and ambient excitation is measured.To enhance the signal-to-noise ratio,a low-noise high-gain signal conditioning module is developed for the wireless sensing system.Nineteen wireless and nineteen cabled accelerometers are first installed along the sidewalk of two neighboring bridge spans.The performance of the wireless sensing system is compared with the high-precision cabled sensing system.In the next series of testing,16 wireless accelerometers are installed under the deck of another bridge span,forming a 4×4 array.Operating deflection analysis is successfully conducted using the wireless measurement of traffic and ambient vibrations.

Antiferromagnetic spintronics: An overview and outlook

Over the pas few decades,the diversified development of antiferomagnetic spintronics has made antiferomagnets(AFMs)interesting and very useful.After tough challenges,the applications of AFMs in electronic devices have transitioned from focusing on the interface coupling features to achieving the manipulation and detection of AFMs.As AFMs are internally magnetic,taking full use of AFMs for information storage has been the main target of research.In this paper,we provide a comprehensive description of AFM spintronics applications from the interface coupling,read-out operations,and writing manipulations perspective.We examine the early use of AFMs in magnetic recordings and conventional magnetoresistive random-access memory(MRAM),and review the latest mechanisms of the manipulation and detection of AFMs.Finally,based on exchange bias(EB)manipulation,a high-performance EB-MRAM is introduced as the next generation of AFM-based memories,which provides an effective method for read-out and writing of AFMs and opens a new era for AFM spintronics.

Microscopic insights into hydrophobicity of cerium oxide:Effects of crystal orientation and lattice constant

Cerium oxide possesses intrinsic hydrophobic properties ascribed to the unique electronic structure.However,the relationship between the crystal structure and hydrophobicity of cerium oxide has not been systematically studied.Herein,it is experimentally and theoretically demonstrated that the water contact angle(105.9°)of the(111)surface is higher than that(91.7°)of the(220)surface,associated with the lower surface free energy(28.44 mN/m)of(111)surface than that(38.48 mN/m)of(220)surface.Furthermore,cerium oxide films with(111)-terminated surface are annealed at 300℃ and 600℃ for1 h,respectively.The lattice constant increases(5.4594Å<5.4613Å<5.4670Å)with decreasing the annealing temperature(600℃>300℃>the as-deposited),leading to the increased water contact angle(96.7°<96.8°<99.0°).The First-principles calculation provides microscopic insights into the wetting mechanism,originating from the weakened adsorption capacity of the(111)surface for water molecules with the increasing lattice constant.