Direct Determination of Grain Boundary Atomic Structure in SrTiO3

An atomic structure model for a 25 degrees [001] symmetric tilt grain boundary in SrTiO(3) has been determined directly from experimental data with the use of high-resolution Z-contrast imaging coupled with electron energy loss spectroscopy. The derived model of the grain boundary was refined by bond-valence sum calculations and reveals candidate sites for dopant atoms in the boundary plane. These results show how the combined techniques can be used to deduce the atomic structure of defects and interfaces without recourse to preconceived structural models or image simulations.     

SrTiO3纳米线的溶胶-凝胶模板法制备与表征

采用二次阳极氧化法制备多孔阳极氧化铝(AAO)模板,通过溶胶-凝胶模板法在AAO模板的孔洞中制得SrTiO3纳米线,用XRD,EDS,SEM,TEM和SAED对纳米线的结构、成分和形貌进行表征. 结果表明:AAO模板孔洞相互平行,孔径大小均一,所得纳米线长约13 μm,直径约70 nm,含有Al,O,Sr,Ti 4种元素,为立方相多晶结构.     

原子荧光法测定地表水中硒的不确定度评定

[目的]解析原子荧光法在检测中的不确定度。[方法]依据测量不确定度评定与表示理论,运用国家标准方法,评定原子荧光法测定地表水中硒的不确定度。[结果]测得地表水样中硒的浓度为1.10μg/L,该法的扩展不确定度U95=0.09μg/L（k=2）。[结论]对合成标准不确定度主要贡献来自仪器分析过程。     

Colossal ionic conductivity at interfaces of epitaxial ZrO2:Y2O3/SrTiO3 heterostructures

The search for electrolyte materials with high oxygen conductivities is a key step toward reducing the operation temperature of fuel cells, which is currently above 700 degrees C. We report a high lateral ionic conductivity, showing up to eight orders of magnitude enhancement near room temperature, in yttria-stabilized zirconia (YSZ)/strontium titanate epitaxial heterostructures. The enhancement of the conductivity is observed, along with a YSZ layer thickness-independent conductance, showing that it is an interface process. We propose that the atomic reconstruction at the interface between highly dissimilar structures (such as fluorite and perovskite) provides both a large number of carriers and a high-mobility plane, yielding colossal values of the ionic conductivity.     

Crystal structure of the extracellular segment of integrin alpha Vbeta3

Integrins are alphabeta heterodimeric receptors that mediate divalent cation-dependent cell-cell and cell-matrix adhesion through tightly regulated interactions with ligands. We have solved the crystal structure of the extracellular portion of integrin alphaVbeta3 at 3.1 A resolution. Its 12 domains assemble into an ovoid "head" and two "tails." In the crystal, alphaVbeta3 is severely bent at a defined region in its tails, reflecting an unusual flexibility that may be linked to integrin regulation. The main inter-subunit interface lies within the head, between a seven-bladed beta-propeller from alphaV and an A domain from beta3, and bears a striking resemblance to the Galpha/Gbeta interface in G proteins. A metal ion-dependent adhesion site (MIDAS) in the betaA domain is positioned to participate in a ligand-binding interface formed of loops from the propeller and betaA domains. MIDAS lies adjacent to a calcium-binding site with a potential regulatory function.     

石墨炉原子吸收法测定地表水中镉的不确定度评定

为保证农作物生长环境中重金属的检测质量,科学地评定检测结果的分散性,依据国家标准方法和测量不确定度评定与表示的理论,以农业灌溉区地表水为例,评定了石墨炉原子吸收法测定地表水中镉的不确定度.测得地表水样中镉的浓度为2.15 μg/L,扩展不确定度U95=O.19 μg/L(k=2).结果表明,利用该法测定地表水中的重金属...     

Crystal Structure of the Polymer Electrolyte Poly(ethylene oxide)3:LiCF3SO3

Ionically conducting polymers (polymer electrolytes) are under intensive investigation because they form the basis of all solid-state lithium batteries, fuel cells, and electrochromic display devices, as well as being highly novel electrolytes. Little is known about the structures of the many crystalline complexes that form between poly(ethylene oxide) and a wide range of salts. The crystal structure is reported of the archetypal polymer electrolyte poly(ethylene oxide)(3):LiCF(3)SO(3), which has been determined from powder x-ray diffraction data. The poly(ethylene oxide) (PEO) chain adopts a helical conformation parallel to the crystallographic b axis. The Li(+) cation is coordinated by five oxygen atoms-three ether oxygens and one from each of two adjacent CF(3)SO(3)(-) groups. Each CF(3)SO(3)(-) in turn bridges two Li(+) ions to form chains running parallel to and intertwined with the PEO chain. There are no interchain links between PEO chains, and the electrolyte can be regarded as an infinite columnar coordination complex.     

Crystal structure of human toll-like receptor 3 (TLR3) ectodomain

Toll-like receptors (TLRs) play key roles in activating immune responses during infection. The human TLR3 ectodomain structure at 2.1 angstroms reveals a large horseshoe-shaped solenoid assembled from 23 leucine-rich repeats (LRRs). Asparagines conserved in the 24-residue LRR motif contribute extensive hydrogen-bonding networks for solenoid stabilization. TLR3 is largely masked by carbohydrate, but one face is glycosylation-free, which suggests its potential role in ligand binding and oligomerization. Highly conserved surface residues and a TLR3-specific LRR insertion form a homodimer interface in the crystal, whereas two patches of positively charged residues and a second insertion would provide an appropriate binding site for double-stranded RNA.     

Nanotribology and Nanofabrication of MoO3 Structures by Atomic Force Microscopy

Atomic force microscopy was used to characterize the sliding of molybdenum oxide (MoO3) nanocrystals on single-crystal molybdenum disulfide (MoS2) surfaces. Highly anisotropic friction was observed whereby MoO3 nanocrystals moved only along specific directions of the MoS2 surface lattice. The energy per unit area to move the MoO3 nanocrystals along their preferred sliding direction was an order of magnitude less than required to slide macroscopic MoS2-bearing contacts. This extreme friction anisotropy was exploited to fabricate multicomponent MoO3 nanostructures. These reversibly interlocking structures could serve as the basis for devices such as mechanical logic gates.     

地面气象观测数据文件质量控制方法

从记录处理和质量分析入手,介绍了地面气象观测数据文件质量控制方法,以期确保自动站数据的可用性,形成准确、连续、记录处理符合要求的地面气象观测数据文件,为国家气象气候观测网提供第一手宝贵资料。     

掺杂化合物K3C60晶体的结合能

利用点电荷模型,计算了Ｋ３Ｃ６０晶体的结合能,得出晶格常数为α＝１４．３４Ａ,并给出体积弹性模量,求得的晶格常数和实验测量值相符。     

地面数据传输及质量控制实例分析

详细阐述地面测报软件主辅通道上传数据时间设置以及数据上传不成功的处理方法。自动站采集气温、本站气压、相对湿度、风向、风速以及雨量正点数据如果判断是错误数据,应按先分钟数据替代,然后人工数据替代,最后内插的原则修改,保存形成正确上传文件;台站预审人员应正确进行月报表A文件一般性备注和历史沿革备注。     

Subatomic Features on the Silicon (111)-(7x7) Surface Observed by Atomic Force Microscopy

The atomic force microscope images surfaces by sensing the forces between a sharp tip and a sample. If the tip-sample interaction is dominated by short-range forces due to the formation of covalent bonds, the image of an individual atom should reflect the angular symmetry of the interaction. Here, we report on a distinct substructure in the images of individual adatoms on silicon (111)-(7x7), two crescents with a spherical envelope. The crescents are interpreted as images of two atomic orbitals of the front atom of the tip. Key for the observation of these subatomic features is a force-detection scheme with superior noise performance and enhanced sensitivity to short-range forces.     

不规则形体表面点三维重建方法

为实现形体的快速三维重建,在分析现有各类重建算法的基础上,针对不规则形体给出了一种三维表面点的重建方法。首先进行摄像机自定标,求取相机的内、外参数,然后对采集的图像进行处理,得到物体的轮廓,最后使用地毯式的搜索算法搜索并重建了物体的表面点。分析了不同搜索步长情况下算法的执行效率,在综合考虑逼真度和执行速度的情况下,给出了优化的步长选择,为表面的三角网格化和纹理恢复提供了依据。     

水稻田面水氮素动态径流流失特性及控制技术研究

通过测坑和大田试验,对上海市黄浦江上游水稻田面水氮素动态、径流(排水)流失规律和控制对策进行了研究。结果表明,(1)在基肥期和第1次追肥(碳铵)后,稻田水中氮素浓度下降均较快,施肥后1～2d,TN含量即可下降为施肥当天浓度的25.13%～50.25%,平均为30.17%,到第4d则下降到10%以下;(2)在第2、3次追肥(尿素)后,坑面水氮素浓度减少趋势不同于基肥期和第1次追肥,施肥后开始1～3d浓度先稍有升高,此后下降趋势同前2次施肥;(3)人工降雨试验表明,如施肥后遇暴雨,则可能导致氮素的大量流失。以基肥期为例,施肥后第2d,40mm雨量引起的TN流失量为5.54～7.95kg·hm-2,80mm雨量引起的TN流失量可达16.74～24.02kg·hm-2,氮素的径流流失以NH4+-N为主;(4)应严格控制播期排水和烤田排水,否则会引起氮素的大量流失;(5)经测产,增施有机肥而减少化肥用量对水稻产量没有影响,但可以在很大程度上减少水稻田面水氮素的径流(排水)流失。     

三维表面轮廓的测量技术

简要介绍了用于三维表面轮廓测量的接触式和非接触式两种测量方法的优缺点，重点阐述了实体光栅法、正弦波相位调制法和白先相移干涉法三种非接触式测量方法的原理。提出了用白光相移干涉法进行三维表面轮廓测量应采用的系统结构和算法。