Mesoporous silicates prepared using preorganized templates in supercritical fluids

Well-ordered mesoporous silicate films were prepared by infusion and selective condensation of silicon alkoxides within microphase-separated block copolymer templates dilated with supercritical carbon dioxide. Confinement of metal oxide deposition to specific subdomains of the preorganized template yields high-fidelity, three-dimensional replication of the copolymer morphology, enabling the preparation of structures with multiscale order in a process that closely resembles biomineralization. Ordered mesoporous silicate films were synthesized with dielectric constants as low as 1.8 and excellent mechanical properties. The films survive the chemical-mechanical polishing step required for device manufacturing.     

Transferable GaN layers grown on ZnO-coated graphene layers for optoelectronic devices

We fabricated transferable gallium nitride (GaN) thin films and light-emitting diodes (LEDs) using graphene-layered sheets. Heteroepitaxial nitride thin films were grown on graphene layers by using high-density, vertically aligned zinc oxide nanowalls as an intermediate layer. The nitride thin films on graphene layers show excellent optical characteristics at room temperature, such as stimulated emission. As one of the examples for device applications, LEDs that emit strong electroluminescence emission under room illumination were fabricated. Furthermore, the layered structure of a graphene substrate made it possible to easily transfer GaN thin films and GaN-based LEDs onto foreign substrates such as glass, metal, or plastic.     

Multipolymer systems

Different polymers can be combined to yield a wide variety of composite materials: layered sheets and films, homogeneous and heterogeneous blends, interpenetrating polymer networks, bicomponent fibers, and others. Some properties of a multipolymer material are roughly additive, but synergistic interactions can yield properties and performances superior to those of the individual constituents. Consequently, the use of polymers in combination is a rapidly growing component of polymer materials technology.     

连栽桉树人工林土壤硅酸盐细菌研究

以相邻的马尾松林地为对照,研究连栽桉树人工林地不同土层、不同代数非根际土壤硅酸盐细菌数量变化及根际土壤与非根际土壤硅酸盐细菌数量差异。结果表明,连栽桉树林地不同土层非根际土壤硅酸盐细菌以二代林20～60cm土层最多,其次是三代林20—60cm土层,一代林0～20cm土层最少;除了对照林0—20cm土层硅酸盐细菌数量大于20～60cm土层外,一代林、二代林、三代林和四代林均是20～60cm土层硅酸盐细菌数量大于0～20cm土层。连栽桉树林地不同代数非根际土壤硅酸盐细菌数量以二代林最多,其次是三代林,四代林最少。连栽桉树林地根际土壤硅酸盐细菌数量以二代林最多,其次是三代林,四代林最少;同代林根际土壤硅酸盐细菌数量均大于非根际土壤;连栽桉树林地硅酸盐细菌R／S的大小依次为二代林〉三代林〉一代林〉四代林。     

Synthesis of Novel Thin-Film Materials by Pulsed Laser Deposition

Pulsed laser deposition (PLD) is a conceptually and experimentally simple yet highly versatile tool for thin-film and multilayer research. Its advantages for the film growth of oxides and other chemically complex materials include stoichiometric transfer, growth from an energetic beam, reactive deposition, and inherent simplicity for the growth of multilayered structures. With the use of PLD, artificially layered materials and metastable phases have been created and their properties varied by control of the layer thicknesses. In situ monitoring techniques have provided information about the role of energetic species in the formation of ultrahard phases and in the doping of semiconductors. Cluster-assembled nanocrystalline and composite films offer opportunities to control and produce new combinations of properties with PLD.     

未知非线性动态系统神经网络模型在线识别

神经网络为未知非线性动态系统的建模提供了一条新途径。本文探讨了只用单个隐含层的前向神经网络对未知非线性动态系统的识别。只要动态系统输入输出可测量，未知非线性动态系统就能在线识别。在线识别算法依据性能函数在输出空间最优原则导出，有别于常规的BP算法。求解速度快，适合于在线识别。仿真实例进一步表明，采用神经网络建立未知非线性动态系统的在线模型具有可行性。     

塑料薄膜拉伸专用夹头的设计与制作

为解决使用新国标GB/T1040.3-2006《塑料拉伸性能测定第3部分：薄膜和薄片的试验条件》薄膜拉伸实际试验时试样100％的断在试验机夹头处的问题,对拉伸试验过程试样受力进行研究,找出原因,提出新的夹头设计原理,即对夹持力面受力方式作了改进,消除了横向剪切力,并重新设计制作了专用夹头,满足了塑料薄膜拉伸新标准方法试验要求.     

Molecular positional order in langmuir-blodgett films by atomic force microscopy

Langmuir-Blodgett films of barium arachidate have been studied on both macroscopic and microscopic scales by atomic force microscopy. As prepared, the films exhibit a disordered hexagonal structure; molecularly resolved images in direct space establish a connection between the extent of the positional order and the presence of defects such as dislocations. Upon heating, the films reorganize into a more condensed state with a centered rectangular crystallographic arrangement; in this new state the films exhibit long-range positional order and unusual structural features, such as a height modulation of the arachidic acid molecules.     

Crystal structure of a complex of acridine, cytosine and water (1:1:1)

X-ray structural analysis of a crystalline complex between acridine C(13)H(9)N, cytosine C(4)H(5)N(3)O, and water (1:1:1) has been completed. The cytosine and water molecules form a sheet-like structure through a series of hydrogen bonds. The acridine molecules are bound to this layer through a hydrogen bridge from the water to the ring nitrogen. The acridine molecules stack in a parallel fashion normal to the cytosine-water sheets, with an average interplanar spacing of 3.5 angstroms.     

Cocoon surrounding desert-dwelling frogs

A cocoon formed from a single cell layer of shed stratum corneum may reduce water loss from the skin of desert-dwelling frogs while these aestivate in soil-filled burrows. In several Australian examples, the cocoon is a single layer of cells, and thus differs from the multilayered structure obtained from an American species, Scaphiopus couchi.     

Periodic interfacial precipitation in polymer films

Interfacial precipitation of silver halides in water-swollen polymer films occurred in complex, multilayered patterns if the concentrations of counterdiffusing reactants were unequal or decreased at different rates. Development of the rapidly forming Liesegang rings, which extend the phenomenon of periodic precipitation to the submicrometer range, is attributable to the combined effect of a moving reaction zone and periodic immobilization of colloidal silver halide.     

Iron-rich post-perovskite and the origin of ultralow-velocity zones

The boundary layer between the crystalline silicate lower mantle and the liquid iron core contains regions with ultralow seismic velocities. Such low compressional and shear wave velocities and high Poisson's ratio are also observed experimentally in post-perovskite silicate phase containing up to 40 mol% FeSiO3 endmember. The iron-rich post-perovskite silicate is stable at the pressure-temperature and chemical environment of the core-mantle boundary and can be formed by core-mantle reaction. Mantle dynamics may lead to further accumulation of this material into the ultralow-velocity patches that are observable by seismology.     

Viscous dissipation in three-dimensional convection with temperature-dependent viscosity

Numerical simulations of three-dimensional convection with temperature-dependent viscosity and viscous heating at realistic Rayleigh numbers for Earth's mantle reveal that, in the strongly time-dependent regime, very intense localized heating takes place along the top portion of descending cold sheets and also at locations where the ascending plume heads impinge at the surface. For a viscosity contrast of 100, these localized heat sources exceed the internal heating due to the radioactive decay of chondritic materials by more than an order of magnitude. The horizontally averaged viscous dissipation is concentrated in the top of the convecting layer and has a magnitude comparable with that of radioactive heating.     

Isolation and Structural Indentification of Herbicidal Toxin Fractions Produced by Pythium aphanidermatum

In order to understand the compsition and structure of herbicidal component of Pythium aphanidermatum,the isolation and structural indentification were researched.The culture filtrate was extracted by ethyl acetate,petroleum,and chloroform with the same volume respectively and the activity of the crude toxin was bioassayed.The toxin was separated by using the method of thin layer chromatography（TLC）,then the main fraction was separated by HPLC,and the structure was analyzed by the sepctrum of IR,13C-NMR and 1HNMR.The results showed that the ethyl acetate extracts had the strongest herbicidal activity.Using the method of TLC,the bioassay results showed that the extracts with Rf 0.19 had the strongest effect on weeds and the inhibition to Digitaria sanguinalis and Amaranthus retroflexus reached five levels,and the component was proved to be dimethyl o-phthalate from the spectrum of IR,13C-NMR and 1HNMR,which was one of the components from the toxin,and it had herbicidal activity.     

Iron partitioning in Earth's mantle: toward a deep lower mantle discontinuity

We measured the spin state of iron in ferropericlase (Mg0.83Fe0.17)O at high pressure and found a high-spin to low-spin transition occurring in the 60- to 70-gigapascal pressure range, corresponding to depths of 2000 kilometers in Earth's lower mantle. This transition implies that the partition coefficient of iron between ferropericlase and magnesium silicate perovskite, the two main constituents of the lower mantle, may increase by several orders of magnitude, depleting the perovskite phase of its iron. The lower mantle may then be composed of two different layers. The upper layer would consist of a phase mixture with about equal partitioning of iron between magnesium silicate perovskite and ferropericlase, whereas the lower layer would consist of almost iron-free perovskite and iron-rich ferropericlase. This stratification is likely to have profound implications for the transport properties of Earth's lowermost mantle.     

Electromechanical resonators from graphene sheets

Nanoelectromechanical systems were fabricated from single- and multilayer graphene sheets by mechanically exfoliating thin sheets from graphite over trenches in silicon oxide. Vibrations with fundamental resonant frequencies in the megahertz range are actuated either optically or electrically and detected optically by interferometry. We demonstrate room-temperature charge sensitivities down to 8 x 10(-4) electrons per root hertz. The thinnest resonator consists of a single suspended layer of atoms and represents the ultimate limit of two-dimensional nanoelectromechanical systems.     

硅酸盐细菌对矿粉和土壤的解钾作用研究

以含钾矿粉和土壤为材料,用硅酸盐细菌进行解钾试验。结果表明,硅酸盐细菌对不同类型矿粉的解钾能力不同：炭渣＞石骨子＞绿豆岩＞正长石。解钾量与矿粉粒径密切相关,随矿粉粉径的减小而增加：ｙ＝９．６７５ｘ－０．７２１,ｒ＝－０．９９２＊＊。硅酸盐细菌接到土壤后长期培养,可增加土壤中的速效钾,但其增加量不稳定。土壤的营养条件对硅酸盐细菌的解钾效果有一定影响。     

Controlling molecular order in "hairy-rod" langmuir-blodgett films: a polarization-modulation microscopy study

The interplay of molecular weight, layer thickness, and thermal annealing in controlling molecular order in ultrathin Langmuir-Blodgett films is characterized with the use of polarization-modulation laser-scanning microscopy. The degree and direction of molecular alignment can be imaged rapidly and sensitively through the magnitude and orientation of linear dichroism in Langmuir-Blodgett films of rodlike poly(phthalocyaninatosiloxane) (PcPS). Images are presented for films as thin as two molecular layers ( approximately 44 angstroms). Molecular alignment along the transfer direction is much stronger for films of PcPS with approximately 25 repeat units ( approximately 10 nanometers long) than for those with approximately 50 repeat units ( approximately 20 nanometers long). Enhancement of alignment by thermal annealing is also much greater for PcPS-25 than PcPS-50. Intimate interaction with the substrate suppresses improvement in alignment by annealing, evident by an anomalously small increase in anisotropic absorption of the first two layers.     

东海磷营养盐变动影响因子分析

采用“有进有出”逐步回归等方法分析了影响东海磷营养盐变动的各环境因子的显著性及其影响权重,得到对东海磷营养盐变动起显著性影响的环境因子的相对重要性依次为:硅酸盐>硝酸盐>温度>溶解氧>亚硝酸盐>pH>盐度>碱度>氨,影响权重系数分别为18.01％、17.84％、15.17％、10.98％、8.43％、7.9％、7.63％、7.53％、6.52％;硅酸盐对磷营养盐变动显著性影响最大,表明东海磷、硅等营养盐的结构变化在浮游植物群落演变过程中起着重要作用,这与该海域近岸赤潮生物逐渐由中型(硅藻种类多)向小型和微型(甲藻种类多)发展的事实相符合。在构建东海磷营养盐动力学模型和海洋生态模型中时,必须对硅酸盐等环境因子予以充分考虑。     

东海磷营养盐变动影响因子分析(英文)

采用“有进有出”逐步回归等方法分析了影响东海磷营养盐变动的各环境因子的显著性及其影响权重,得到对东海磷营养盐变动起显著性影响的环境因子的相对重要性依次为:硅酸盐>硝酸盐>温度>溶解氧>亚硝酸盐>pH>盐度>碱度>氨,影响权重系数分别为18.01％、17.84％、15.17％、10.98％、8.43％、7.9％、7.63％、7.53％、6.52％;硅酸盐对磷营养盐变动显著性影响最大,表明东海磷、硅等营养盐的结构变化在浮游植物群落演变过程中起着重要作用,这与该海域近岸赤潮生物逐渐由中型(硅藻种类多)向小型和微型(甲藻种类多)发展的事实相符合。在构建东海磷营养盐动力学模型和海洋生态模型中时,必须对硅酸盐等环境因子予以充分考虑。