The recent discoveries of superconducting oxide interfaces provide new platforms to explore the exotic superconducting properties in the two-dimensional (2D) regime. In this paper, we report the observation of quasi-2D superconductivity at the EuO/BaBiO3 (001) interface with the superconducting transition temperature of -3.5 K. The current-voltage characteristics reveal the signature of a Berezinski-Kosterlitz-Thouless transition, which indicates the existence of quasi-2D superconducting interface. Furthermore, the quasi-2D nature is also supported by the temperature- and angle-dependent upper critical fields. The realization of quasi-2D superconductivity in the BaBiO3 heterostructures could be useful for the emergent research field of superconducting oxide interfaces.

基于北京大学数字普惠金融指数和中国家庭追踪调查数据,构建双向固定效应模型,分析数字金融发展对家庭教育支出的影响及传导机制.研究发现,数字金融发展增加了家庭教育支出.机制分析表明,家庭教育支出的增长得益于数字金融发展对家庭流动性约束及预防性储蓄动机的缓解.异质性分析表明,数字金融发展更有利于家庭物质或文化资本水平较低的弱势群体,且在金融发展低水平地区作用更明显,这体现了数字金融发展的普惠性.

Focused ion beam (FIB) with keV Ga+ has been observed to be able to introduce nanoscale localized tensile stress in materials including Si3N4, SiO2, crystal-Si, poly-Si, Al, and Au. Such stress is employed as a driving force to assemble free-standing two-dimensional (2D) nano-film patterns to three-dimensional (3D) structures. Continuous bending from 0 to 90 of the 2D patterns is demonstrated. A strained-bilayer-system model is proposed to qualitatively describe the bending angle. Fabrications of a 3D cubic frame as well as helices are achieved by the FIB stress induced deformation (FIB-SID) technology with proper stress-introducing strategy. To prove the power of FIB-SID, we fabricate stereo metamaterials composed of '' standing '' 3D split ring resonators (SRR), demonstrating considerable optical absorption in IR regime. Theoretical and experimental results manifest that the metamaterial device has reflection minimum at 5.3 mu m. On this basis, we develop a programmable quasi-parallel FIB fabrication method for 3D nanostructure (taking the 3D SRRs structure as an example) which has advantages of much higher efficiency, great consistency and considerable throughput. The revealed flexibility and controllability of this technology make it promising in constructing diverse forms of 3D micro/nano-structures for micro/nano-electromechanical systems.

在教育经费投入进入"后4％时代"背景下,高校可用财力不足和大量资金沉淀的问题并存,零基预算作为一种改善预算的模式被引入高校管理中.文章基于A大学2016—2019年校级预算改革数据,运用CITS模型评估发现零基预算改革显著推进了全年预算执行进度,但预算规模扩张问题和支出习惯并未明显改善,零基预算改革面临院校两级事权财权不统一、预算工作量大、绩效预算评价不足的问题.鉴于此,为进一步健全高校预算管理,应推进院校两级预算和收入分配政策,加快财务信息化建设,打破数据孤岛,采取零基预算、全面预算与绩效预算相结合的方式,协同提升高校预算资金效率.

山地生态系统是生物多样性分布与保护的热点.山地景观遗传学(Mountain Landscape Genetics)研究在山地景观尺度上野生生物的种群遗传格局及其驱动机制和影响因素,是景观遗传学(Landscape Genetics)的重要分支.山地景观遗传学研究对于深入理解物种的空间遗传结构、形成过程、物种形成与分化机制具有重要意义与价值,同时可以为珍稀濒危物种和山地生物多样性的有效保护与管理提供科学指导.为了更好地掌握目前山地景观遗传学的发展趋势与重点研究问题,为未来生物多样性与山地生态系统的保护管理提供科学参考,基于对Web of Science核心数据库和中国知网数据库的系统检索,全面汇总分析了 1999-2020年山地景观遗传学领域发表的192篇英文文献与31篇中文文献.结果显示,该领域自2008年起迅速发展,截至2020年共有46个国家的研究机构发表了山地景观遗传相关研究,研究热点地区包括北美洲的落基山脉、内华达山脉、阿巴拉契亚山脉,欧洲的阿尔卑斯山脉、比利牛斯山脉,以及亚洲的喜马拉雅-横断山脉.研究对象类群涵盖真菌、植物、节肢动物、脊椎动物,其中脊椎动物是研究发表最多的类群,占发表文献总数的62.0％;脊椎动物中,又以对哺乳类(占脊椎动物发表文献总数的52.9％)与两栖类(23.5％)的研究最多.目前主要的研究方向包括:(1)识别山地景观中的基因流路径或阻碍;(2)量化山地景观特征对种群遗传结构时空变化的影响.中国是发表山地景观遗传学文章数量最多的亚洲国家,近十年来相关研究发展迅速,研究类群以植物(占在中国发表文献总数的62.3％)与脊椎动物(35.8％)为主,对脊椎动物的研究中以两栖动物为最多(占所有脊椎动物发文数量的52.6％),研究区域主要集中在喜马拉雅-横断山脉与秦岭.本文进一步对目前山地景观遗传学研究中存在的空缺及未来重点关注问题提出建议.

我国新工科建设的推进对工程科技人才的吸引、选拔和培养提出了新的要求.本研究基于具有全国代表性的学生抽样调查数据,将专业选择动机纳入分析框架,采用广义结构方程模型(GSEM),就什么样的高中生选择就读工科专业这一问题进行了实证分析.研究结果表明,家庭社会经济背景相对弱势的高中生、男生更可能选择工科;社科和工科均不受内在动机较高的学生青睐,但都能吸引外部动机较高的学生,而对数理化的较强烈学习兴趣并不能提高学生相对于社科而选择工科的概率.各类因素对专业选择的影响效果随录取院校层级的不同而不同,在不同性别之间亦存在异质性.工科专业选择的性别隔离很可能是由于女生对工科缺乏了解、存在刻板印象所致,而父辈受教育程度在一定程度上弥补了相关信息的不足和偏差.应重视对高中生进行工程前沿和新工科建设相关的宣传和普及,培养高中生对于工科学习及工程实践的兴趣,为高中毕业生专业志愿填报提供必要辅导.

合理安排支出结构、提高教学科研生产效率是高校走内涵式发展道路面临的重要议题.文章采用75所教育部部属高校2006-2018年的财务及教学科研产出数据,引入VES生产函数,从替代弹性的视角分析教学科研领域的替代弹性及产出效率,并分析替代弹性分布特征.研究发现,无论是以学生数为产出指标还是以论文数量为产出指标,人员经费的产出弹性都明显大于公用经费产出弹性;从替代弹性来看,公用经费—人员经费的替代弹性都大于1,说明公用经费和人员经费之间产生了一定的相互替代关系,且这种要素替代弹性对于产出增长起到了促进作用;从替代弹性的分类分布来看,院校类型上,理工类院校最高,综合类院校其次,文科类院校最低;区域分布上,东部院校高于西部院校,中部院校最低;从替代弹性的时间趋势来看,随着时间的推移替代弹性呈现不断扩大的趋势.研究认为,对高校经费投入应该更加重视要素替代对教学、科研生产过程的作用,在制度设置、政策制定上给予更多考量.

基于35所"双一流"建设A类高校博士学位教师样本的简历数据,对其中的学缘关系进行分析,结果发现:本校博士占每所样本高校博士学位教师总数的比例均最高.中国科学院、北京大学和清华大学在"双一流"建设A类高校教师博士学位授予单位排名中位居前列,显示出其全国性的学术声望和影响力.教师聘用呈现一定的地域和学科特征.总体上,位于同一城市或临近区域的高校具有相对密切的博士学位教师聘用关系,传统的综合性大学向"双一流"建设A类高校输送博士学位教师的学术声望影响强于科研表现,传统的理工类高校向"双一流"建设A类高校输送博士学位教师的学术声望影响则弱于科研表现.

基于某"双一流"大学本科生校园卡消费数据和学生发展情况调查数据,本文通过建立一般线性回归模型、双重差分模型和倾向性得分匹配模型,分析了贫困生资助对大学生消费行为的影响.研究发现:接受贫困生资助的学生在学校食堂就餐的次数更多、平均消费金额更低.利用倾向得分匹配和双重差分来消除选择性偏差的影响发现:贫困生资助仅对即期食堂消费水平有显著提升作用,而对学年平均食堂消费水平没有显著影响.这说明尽管受助学生与其他学生存在消费行为上的显著差异,但是贫困生资助对大学生消费水平仅产生短期效应而无中长期影响,日常餐饮消费并非贫困生资助的主要用途,若直接将补助发到餐卡未必能达到提高贫困生消费水平的目的.

基于Web of Science核心合集数据库和InCite科研绩效分析平台,运用社会网络分析法构建北京大学理工科院系科学家科研论文合著网络,并从社会资本视角采用动态面板高斯混合模型(GMM)探讨网络资本对科学家的学科认可、政府认可、市场认可等科研绩效的影响.研究发现:科学家积累更多的社会资本将更有利于提升科研绩效,但不同的社会资本维度的影响方向和影响程度不一:从结构资本来看,网络关系和活动能力对科学家学术认可有显著影响,但对政府认可、市场认可仅在部分方面有所表现;关系资本会对学术认可产生不同方面的影响,但对政府认可、市场认可不产生影响;认知资本对科学家学术认可、政府认可有部分影响,但对市场认可无影响.建议科学家和科研机构将科研合作从增量向提质转变,引入组织协调平衡和优化合作内部结构,完善科研绩效综合评价.

We propose a polarization-controlled bifunctional metasurface composed of arrayed trapezoidal nanoantennas. Under orthogonal-polarized incidence, different types of gap-surface plasmons are generated, regulating the intensity and phase, respectively. Thus, structural color printing and beam deflection functions are achieved on a miniaturized chip. The color printing function works from 400 to 800 nm, exhibiting a subwavelength-scale chromatic image with a broad gamut. The beam deflection function works from 360 to 540 nm, mapping light to the first diffraction order with the anomalous angle from 40.4° to 76.6°. The proposed bifunctional metasurface could serve as a key component in integrated optics systems and will find many other wide-ranging applications in optical and biological areas.

Due to their unique electromagnetic properties, meta-atom arrays have always been a hotspot to realize all kinds of particular functions, and the research on meta-atom structure has extended from two-dimensions (2D) to three-dimensions (3D) in recent years. With the continuous pursuit of complex 3D meta-atom arrays, the increasing demand for more efficient and more precise nanofabrication methods has encountered challenges. To explore better fabrication methods, we presented a programmable nanofabrication method for a complex 3D meta-atom array based on focused-ion-beam stress-induced deformation (FIB-SID) effect and designed a distinctive nanostructure array composed of periodic 3D meta-atoms to demonstrate the presented method. After successful fabrication of the designed 3D meta-atom arrays, measurements were conducted to investigate the electric/magnetic field properties and infrared spectral characteristics using scanning cathodoluminescence (CL) microscopic imaging and Fourier transform infrared (FTIR) spectroscopy, which revealed a certain excitation mode induced by polarized incident IR light near 8 μm. Besides the programmability for complex 3D meta-atoms and wide applicability of materials, a more significant advantage of the method is that a large-scale array composed of complex 3D meta-atoms can be processed in a quasi-parallel way, which improves the processing efficiency and the consistency of unit cells dramatically.

As chiral structures, three-dimensional (3D) nanohelixes have the circular dichroism and optical rotation under circularly polarized light. It also has a good application prospect in optical modulators with high modulation efficiency. However, it is still a challenging task to fabricate 3D nanohelixes with high precision, controllable parameters and perfect morphology. In this study, we develop FIB (focused ion beam)-SID (stress induced deformation) by using HIB (helium ion beam) instead of GIB (gallium ion beam) for nanofabrication. This general 3D nanofabrication technique allows much stronger manufacturing control, which lead to a greater programmable and accurate bidirectional folding $(-160^{\circ}-+75^{\circ})$ of various metal and dielectric thin films. Higher manufacturing accuracy of HIB makes it possible to fabricate smaller nanostructures (characteristic size is about 100 nm), which provides strong support for 3D nanostructure fabricated in visible light wave band.

义务教育均衡发展是一个系统工程,需要客观、科学的评价作为基础.以全国教育经费统计数据为基础,在地理空间技术的支持下,对全国范围内小学学校及以教育经费为代表的教育资源进行空间分析,数据显示我国小学学校主要集中于"胡焕庸线"以东地区,各地区教育资源水平不一,存在资源优势明显和劣势突出的显著差异.进一步探讨我国小学教育资源空间布局的形成机制,研究发现:学校自身条件对学校资源获得的影响作用最大,贡献率超过一半;从地理信息学的新视角看,受到经济、人口和政策等因素的影响,小学学校服务范围内人均GDP越高,其生均支出也越高;随着服务范围内人口总量的增加,小学的生均支出会增加;距离政府越近,小学生均支出越高.

A novel three-dimensional (3D) nanoantenna array, consisting of double-claw shape unit cell, is fabricated by focused ion beam stress-introduced deformation (FIB-SID) technique [1]-[3], and is employed as an ultrabroadband infrared (IR) optical modulator. The measured reflection spectra of the device show that an ultrabroadband infrared optical modulation can be achieved with tiny change of the double claw's distance. The relative modulation value calculated from reflection spectra for the nanoantenna with lager unit size indicates that a broad IR modulation range of 3.39 μm (2.93 μm - 6.32 μm) and a maximum modulation value of 17.5% at 5.8 μm is realized as the double claw's distance changes. Furthermore, the scaled down nanoantennas were also fabricated and measured, which covers a surprisingly ultrabroadband IR modulation range, from long-wave (9.93 μm) to short-wave (2.04 μm), and realizes a maximum modulation value of 71.7% at 3.29 μm as the double claw's distance changes about 180nm.

落实高等学校办学自主权是激发高等学校办学活力,提高高等教育竞争力的关键,财务自主权是高校自主权的核心内容,反映了政府和社会对学校活动的支持和干预.文章采集了75所教育部直属高校8年财务数据,通过分解高等学校可分配经费和不可分配经费,度量高校的财务弹性水平,测算我国高校财务自主性水平和变化特征,分析不同院校之间存在的差异,以窥见我国高等学校自主权状况.研究发现,教育部直属高校的财务弹性约为50％,学校可分配经费主要来自于政府,且受制力进一步加强;高等学校财政实力逐年的增长,学校可分配经费规模增大,但学校财务弹性不断减小,高等学校的财务自主权略显下降,不同院校的财务弹性差异呈现扩大趋势.

Visual and real-time plasmonic metamaterial biosensors, relying on surface plasmon resonance (SPR) on metallic subwavelength structures, have significant potential for colorimetric biochemical sensing by simple instrumentation or even naked eye. In this paper, we present a visual and real-time sensing strategy for the detection of the biotin-avidin-system (BAS), which is a powerful tool in biological sciences. The metamaterial, consisting of an array of three-dimensional all-metal nano-cavities, can confine the light into the near field and enable strong light-matter interactions there. Therefore, The metamaterial shows significant color shifts with small refraction index changes. When a monomolecular layer of thiolated biotin and streptavidin bonding to the surface of the nanostructure successively, the color of the metamaterials changes from red to violet and then loden. This sensing strategy offers new opportunities for convenient detection of proteins, nucleic acids and lipids.

Colorimetric and label-free plasmonic biosensors, relying on localized surface plasmon resonance (LSPR) on metallic subwavelength structures, have significant potential for many application areas such as clinical diagnosis and environmental monitoring detection by simple instrumentation or even naked eye. In this paper, we present a high-performance colorimetric and label-free plasmonic biosensors, consisting of an array of three-dimensional all -metal nano-cavities. The nanostructures, composed of a top array of gold disk, aluminum pillar and bottom gold reflection film, are similar to metal-insulator-metal and the insulating layer is air cavities that are easy to be filled with other gaseous or liquid dielectric. Therefore, the analytes could permeate into the nano-scale cavities and enable strong light-matter interactions there. The sensor shows significant color difference with small refraction index changes and the sensitivity reaches 683.5 nm/RIU. Moreover, when a monomolecular layer of Dithiobis(succinimidyl propionate) (DSP) was bonded to the surface of the nanostructure, the color of the metamaterials change from blue to green back. The metamaterials will offer great potential for detection and studies of binding events between the target analyte and its corresponding receptor.

We report a new arrayed three-dimensional (3D) air-gap nanocavities with multiple tunable geometrical parameters. Light is tightly confined into the nanocavities and strong surface-plasmon coupling is introduced, realizing narrow band resonance. Vivid plasmonic colors are generated, and can be tuned by multiple geometrical parameters of the 3D nanocavities, including shapes, separations, and heights. What's more, the surface-plasmon coupling resonance has different dependence on different variable geometrical parameters. So, multi-dimensional color tuning with different spectral sensitivities is realized by proper and precise structural design, leading to both broad gamut and sophisticated plasmonic color printing at the optical diffraction limit.

中国的教育经济学是在改革开放后产生发展的交叉学科领域.虽然起步较晚,但开端良好,发展迅速.在40年的发展历程中,以国家财政性教育经费占GDP比例达4％的研究为代表,中国教育经济学在以学术研究支持和推动国家教育改革和政策制定方面做出了巨大的贡献,呈现了重要的应用价值和实践意义,同时也引领推动了整个教育学术领域的科学化,为教育学和经济学科的发展做出了丰富的知识贡献.展望未来,中国的教育经济学一方面要更紧密地结合教育实践,另一方面需要继续提高研究质量,为理论创新和实践应用做出更多重要贡献.