Periodic mesoporous organosilicas containing interconnected [Si(CH2)]3 rings

A periodic mesoporous organosilica composed of interconnected three-ring [Si(CH2)]3 units built of three SiO2(CH2)2 tetrahedral subunits is reported. It represents the archetype of a previously unknown class of nanocomposite materials in which two bridging organic groups are bound to each silicon atom. It can be obtained with powder and oriented film morphologies. The nanocomposite is self-assembled from the cyclic three-ring silsesquioxane [(EtO)2Si(CH2)]3 precursor and a surfactant mesophase to give a well-ordered mesoporous framework. Low dielectric constants and good mechanical stability of the films were measured, making this material interesting for microelectronic applications. Methylene group reactivity of the three-ring precursor provides entry to a family of nanocomposites, exemplified by the synthesis and self-assembly of [(EtO)2Si(CHR)][(EtO)2Si(CH2)]2 (where R indicates iodine, bromine, or an ethyl group).     

Hexagonal mesoporous germanium

The blending of mesoporosity with the properties of semiconductors promises new types of multifunctional nanomaterials. It would be particularly interesting to combine the shape selectivity of a mesoporous oxide with the electronic and photonic characteristics of a useful semiconductor. We demonstrated the synthesis of a mesoporous germanium semiconductor using liquid-crystals-templated chemistry. The template removal was achieved by a two-step ion-exchange thermal procedure. This semiconductive mesoporous form of germanium possesses hexagonal pore ordering with very high surface area and exhibits strongly size-dependent optical properties as well as photoluminescence.     

具连续变量差分方程的周期解与渐近周期解

研究了具连续变量的差分方程的周期解和渐近周期解，并分别获得了周期解和渐近周期解存在性的几个充分条件，我们的结果推广了Agarwal等人的相应结果．     

核-壳介孔SiO2的合成

利用不同的三烷氧基硅在胶体介孔SiO2（CMS）的内部和外部表面烷选择性地修饰不同的官能团,这是利用了延迟共沉淀得到双功能化CMS的新方法。此种方法制得的CMS纳米粒子修饰有两种不同的官能团,它们分别位于核和壳上或同时位于核上。我们的合成方法提供了一种新颖的多步共沉淀策略,可将不同的官能团定位修饰在介孔纳米粒子的核或壳上。     

Periodic hot-spot distribution on io

The Jovian satellite Io has active volcanic hot spots. The point-to-point correlation of the hot-spot distribution indicates that the hot spots preferentially make chains. The arrangement of the chains is periodic with a typical spacing of 120 kilometers. The chains exhibit concordant trends with stresses imposed by the tidal deflection of the lithosphere, suggesting that the hot spots are formed along fissures in the lithosphere. The typical spacing may be controlled by lithosphere thickness.     

Periodic insolation variations on Mars

Previously unrecognized insolation variations on Mars are a consequence of periodic variations in eccentricity, first established by the theory of Brouwer and Van Woerkom (1950). Such annual insolation variations, characterized by both 95,000-year and 2,000,000-year periodicities, may actually be recorded in newly discovered layered deposits in the polar regions of Mars. An additional north-south variation in seasonal insolation, but not average annual insolation, exists with 51,000-year and 2,000,000-year periodicities.     

常维的p-Laplacian系统的周期解

通过临界点理论中的鞍点定理和极小化作用原理证明了具有非自治的p次线性的常维的p-Laplacian系统的周期解的存在性.

Abstract：

The existence of periodic solutions is studied for ordinary p-Laplacian systems involving non-autonomous p-sublinear by using the saddle point theorem and the least action principle in critical point theory.     

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.     

一类中立型无穷时滞脉冲微分方程的周期解

利用线性系统的指数型二分性和Krasnoselskii不动点定理,研究一类中立型无穷时滞脉冲微分方程的周期解存在性问题,给出了保证系统存在周期解的一组充分条件,推广并改进了现有文献中的相关结论.     

常维的p-Laplacian系统的周期解

通过临界点理论中的鞍点定理和极小化作用原理证明了具有非自治的p次线性的常维的p-Laplacian系统的周期解的存在性.     

Conducting polyaniline filaments in a mesoporous channel host

Conducting filaments of polyaniline have been prepared in the 3-nanometer-wide hexagonal channel system of the aluminosilicate MCM-41. Adsorption of aniline vapor into the dehydrated host, followed by reaction with peroxydisulfate, leads to encapsulated polyaniline filaments. Spectroscopic data show that the filaments are in the protonated emeraldine salt form, and chromatography indicates chain lengths of several hundred aniline rings. The filaments have significant conductivity while encapsulated in the channels, as measured by microwave absorption at 2.6 gigahertz. This demonstration of conjugated polymers with mobile charge carriers in nanometer channels represents a step toward the design of nanometer electronic devices.     

Ordering of ruthenium cluster carbonyls in mesoporous silica

The anionic ruthenium cluster carbonylates [Ru6C(CO)16]2- or [H2Ru10(CO)25]2- interspersed with bis(triphenylphosphino)iminium counterions (PPN+) are incorporated from solution into the pores of MCM-41 mesoporous silica (3 nanometers in diameter), where they form tightly packed arrays. These arrays were shown by high-resolution transmission electron microscopy, Fourier transform optical diffraction, and computer simulations to be well ordered both along and perpendicular to the axis of the cylindrical pores. In their denuded state produced by gentle thermolysis, the cluster carbonylates yield nanoparticles of ruthenium that are less well ordered than their assimilated precursors but show good activity as hydrogenation catalysts for hexene and cyclooctene. In both their as-prepared and denuded states, these encapsulated clusters are likely to exhibit interesting electronic and other properties.     

A neutral templating route to mesoporous molecular sieves

A neutral templating route for preparing mesoporous molecular sieves is demonstrated based on hydrogen-bonding interactions and self-assembly between neutral primary amine micelles (S degrees ) and neutral inorganic precursors (l degrees ). The S degrees l degrees templating pathway produces ordered mesoporous materials with thicker framework walls, smaller x-ray scattering domain sizes, and substantially improved textural mesoporosities in comparison with M41S materials templated by quaternary ammonium cations of equivalent chain length. This synthetic strategy also allows for the facile, environmentally benign recovery of the cost-intensive template by simple solvent extraction methods. The S degrees 1 degrees templating route provides for the synthesis of other oxide mesostructures (such as aluminas) that may be less readily accessible by electrostatic templating pathways.     

Ordered mesoporous materials from metal nanoparticle-block copolymer self-assembly

The synthesis of ordered mesoporous metal composites and ordered mesoporous metals is a challenge because metals have high surface energies that favor low surface areas. We present results from the self-assembly of block copolymers with ligand-stabilized platinum nanoparticles, leading to lamellar CCM-Pt-4 and inverse hexagonal (CCM-Pt-6) hybrid mesostructures with high nanoparticle loadings. Pyrolysis of the CCM-Pt-6 hybrid produces an ordered mesoporous platinum-carbon nanocomposite with open and large pores (>/=10 nanometers). Removal of the carbon leads to ordered porous platinum mesostructures. The platinum-carbon nanocomposite has very high electrical conductivity (400 siemens per centimeter) for an ordered mesoporous material fabricated from block copolymer self-assembly.     

Yoshizawa周期解定理的拓广

证明了有限时滞泛函数分方程解的一致最终有界性蕴含周期的存在性，从而推广了著名的Ｙｏｓｈｉｚａｗａ周期解定理。     

分式线性递归关系的周期解研究

递归关系不仅在数学中有广泛应用,而且在计算机算法设计与分析中也有广泛应用。对一阶分式线性递归关系具有周期解的条件进行了详细讨论,得到若干有用的结论;对二、三阶分式线性递归关系,分别列举了一个具有周期解的例子,并对解的周期性进行了验证。     

一类p-哈密顿系统无穷多个周期解的存在性

通过临界点理论中的极小极大方法,得到了一类p-哈密顿系统无穷多个周期解的存在性结果.     

分式线性递归关系的周期解研究

递归关系不仅在数学中有广泛应用,而且在计算机算法设计与分析中也有广泛应用。对一阶分式线性递归关系具有周期解的条件进行了详细讨论,得到若干有用的结论;对二、三阶分式线性递归关系,分别列举了一个具有周期解的例子,并对解的周期性进行了验证。