Superconductivity in chromium nitrides Pr3Cr10-xN11 with strong electron correlations

Exploration of superconductivity in Cr-based compounds has attracted considerable interest because only a few Cr-based superconductors (CrAs, A₂Cr₃As₃ and ACr₃As₃ (A = K, Rb, Cs, Na)) have been discovered so far and they show an unconventional pairing mechanism. We report the discovery of bulk superconductivity at 5.25 K in chromium nitride in Pr₃Cr_10-xN₁₁ with a cubic lattice structure. A relatively large upper critical field of H_c2(0) ∼ 12.6 T is determined, which is larger than the estimated Pauli-paramagnetic pair-breaking magnetic field. The material has a large electronic specific-heat coefficient of 170 mJ K⁻² mol⁻¹—about 10 times larger than that estimated by the electronic structure calculation, which suggests that correlations between 3d electrons are very strong in Pr₃Cr_10-xN₁₁, and thus quantum fluctuations might be involved. Electronic structure calculations show that the density of states at the Fermi energy are contributed predominantly by Cr 3d electrons, implying that the superconductivity results mainly from the condensation of Cr 3d electrons. Pr₃Cr_10-xN₁₁ represents a rare example of possible unconventional superconductivity emerging in a 3D system with strong electron correlations. Nevertheless, clarification of the specific pairing symmetry needs more investigation.     

Evolution and distribution of medullary bone: evidence from a new Early Cretaceous enantiornithine bird

Living birds are unique among vertebrates in the formation of a female-specific bone tissue called medullary bone (MB) that is strictly associated with reproductive activity. MB is a rapidly mobilized source of calcium and phosphorus for the production of eggshell. Among living taxa, its skeletal distribution can be highly extensive such that it even exists in the ribs of some species. Due to its ephemeral nature, MB is rarely fossilized and so little is understood with regard to the origin of MB and its skeletal distribution in early taxa. Here we describe a new Early Cretaceous enantiornithine bird, Mirusavis parvus, gen. et. sp. nov., indicating that skeleton-wide distribution of MB appeared early in avian evolution. We suggest that this represents the plesiomorphic condition for the Aves and that the distribution of MB observed among extant neornithines is a product of increased pneumatization in this lineage and natural selection for more efficient distribution of MB.     

敦煌莫高窟唐代前期菩萨璎珞

璎珞是菩萨装饰中不容忽视的主要部分,唐代前期菩萨璎珞继承了敦煌前期的璎珞形式,但是其形式、色彩、艺术制作以及材质表现却相当精致、丰富多彩,富于创造性.复杂、丰富、多元化的装饰元素体现了唐代菩萨的装饰风格已经完全确立并日益臻于成熟.璎珞作为菩萨佩饰重要的一部分,对它的研究尚为缺乏.本文从概念、种类、来源、造型特征以及意义等方面对璎珞做出一定的诠释.     

2001-2004年《人大复印资料》转载的民族问题研究文章的统计分析

文章以《人大复印资料》2001-2004年间全文转载民族问题研究方面的文章为资料源,从栏目设置、作者所在省市、收录的期刊及引文中被引用的期刊等进行统计分析,为民族问题研究者提供一定的信息和有益的帮助.     

高职院校图书馆服务质量危机及对策探析

作者结合实际工作经验,具体分析了高职院校图书馆服务质量危机的表现及成因,初步提出了优化服务质量的几点对策.     

图书专供商网站建设探析

图书专供商网站建设的水平影响着高校图书馆采访工作的效率.通过网上书店与图书专供商网站功能差异的比较,分析和探讨了图书专供商网站建设存在的不足及其原因,并从满足高校图书馆采访业务需要的角度,对图书专供商网站的建设提出了一些改进建议.     

武德融入学校传统美德教育的研究

本研究运用文献资料、专家访谈、逻辑分析等研究方法,基于武术的武德融入学校传统美德问题,针对性地进行探讨分析。目的在于适应当今的传统文化教育,引起人们对武术道德的关注,有利于中国软实力的提高。研究建议:大力发展武德文化体系;通过社会实践重新认识武德与传统美德;明确教育目标,将“德育”放在教学的第一位等。     

数字化图书馆建设中面临的知识产权问题及对策

本文分析了我国数字图书馆建设中所面临的一系列知识产权保护问题 ,提出了加强我国数字化图书馆知识产权保护工作的相关对策.参考文献3.     

Success Begins with Exploration--Zhou Changxin＇s heavy-color oil painting

With years of practice in mural and oil painting, Zhou Changxin has developed an innovative slyle of heavy-color oil painting by integratingtraditional freehand brushworks with use of thick and bright colors in Western painting.     

当代大学生感恩教育探析

感恩作为中华民族的传统美德,是大学生最基本的道德品质之一。然而,随着当前社会物质文明的高速发展．再加上长期以来对感恩教育的忽视,导致许多大学生感恩意识淡薄,甚至出现感恩缺失的现象,如今已引起社会各界的重视。在改革开放深入发展、全面建设小康社会的今天,对大学生进行感恩教育已刻不容缓。分析当代大学生感恩教育的现状及其原因,在此基础上,提出加强大学生感恩教育的具体措施。