Materials Literature
按标题、摘要、年份、主题和来源检索公开元数据。结果保留作者、摘要、分类与原始来源链接。
Mesoporous silicas of the MSU-X type, made with nonionic polyethylenoxide-based (PEO) surfactants, were synthesized according to a two-step process that gives intermediary stable hybrid micelles. The influence of the various synthesis parameters, such as the silica concentration, the addition of a swelling agent (TMB:…
Percolation of particle arrays is of high interest in microstructural design of materials. While there have been numerous contributions to theoretical modeling of percolation in particulate systems, no analytical approximation for the generalized problem of variable aspect-ratio ellipses has been reported. In the pres…
A nonlinear thermodynamic theory is used to describe the influence of an external mechanical loading on the ferroelectric, dielectric, and piezoelectric properties of epitaxial thin films grown on dissimilar cubic substrates. The calculations are performed for single-domain perovskite films in the approximation of a h…
An algorithm is described for automated building of side chains in an electron-density map once a main-chain model is built and for alignment of the protein sequence to the map. The procedure is based on a comparison of electron density at the expected side-chain positions with electron-density templates. The template…
We show here that field emission (FE) can be used to directly observe the vibration resonances nu(R) of carbon nanotubes (CNTs) and that the tension created by the applied field allows the tuning of these resonances by up to a factor of 10. The resonances are observable by the changes they create in the FE pattern or…
The interaction of atomic hydrogen and low-energy hydrogen ions with ${\mathrm{sp}}^{2}$-bonded carbon is investigated on the surfaces of ${\mathrm{C}}_{60}$ multilayer films, single-walled carbon nanotubes, and graphite (0001). These three materials have been chosen to represent ${\mathrm{sp}}^{2}$-bonded carbon netw…
Two crystal structures of dehydrated <TEX>$Ag^+-andTl^+$</TEX>-exchanged zeolite X<TEX>$Ag_{27}Tl_{65-}X\;and\;Ag_{23}Tl_{69-}X$</TEX>have been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at 21(1) <TEX>$^{\circ}C(a=24.758(4)\AAa=24.947(4)$</TEX>, <TEX>${\AA}respectively).$</T…
A theoretical analysis of the ground state of long-chain (K@C$_{60}$)$_n$ is presented. Within mean field theory, a ferroelectric ground state is found to be stable because of the pseudo-Jahn-Teller mixing of the b$_{1u}$ and the b$_{2g}$ band with a zone-center optical phonon involving the displacement of the endohed…
The recently derived sum rules for the scattering phase shifts of the Overhauser geminals (being 2-body-wave functions which parametrize the pair density together with an appropriately chosen occupancy) are generalized to integral equations which allow in principle to calculate the momentum distribution, supposed the…
Diffusing wave spectroscopy has been used to investigate the thermally driven displacement of colloidal particles dispersed in solutions of associating polymers (APs). The effect of varying colloidal probe size on the measured particle displacements is studied in particular. Recent theories of microrheology are examin…
UV−visible spectra have been studied for a series of p-substituted tetraphenylporphyrins (TPPs) titrated with strong acid in various solvents. Substituent effects on the Soret and Q ( I ) absorption peaks and the fluorescence emission peaks have been treated by Hammett correlations. In general, there are only small ef…
Aggregates of the diacid form of tetra(p-carboxyphenyl)porphyrin (TCPP) are found to be stabilized in aqueous solution at low pH in the presence of poly(vinyl alcohol). At pH values in the range from about 1 to 4, a split Soret band is observed which is independent of counterion and tentatively assigned to a dimer spe…
Heteroepitaxial strain can be a controlling factor in the lateral dimensions of 1-D nanostructures. Bi nanolines on Si(001) have an atomic structure which involves a large sub-surface reconstruction, resulting in a strong elastic coupling to the surrounding silicon. We present variable-bias STM and first principles el…
Within a 2D model of Josephson junction arrays (created by 2D network of twin boundary dislocations with strain fields acting as insulating barrier between hole-rich domains in underdoped crystals), a few novel effects expected to occur in intrinsically granular material are predicted including: (i) Josephson chemomag…
We report a detailed study of the vibrational properties of BN single-walled nanotubes and of the BN monolayer. Our results have been obtained from a well-established tight-binding model complemented with an electrostatic model to account for the long-range interactions arising from the polar nature of the material an…
We present an intuitive physical picture for fractures in nacre-type stratified materials via scaling arguments: strain distributions around a fracture are rather different depending on directions and size of fractures. We thus observe that viscoelastic effects are important for parallel fractures. These effect are ta…
Properly functionalized dithienylethenes show promise for light-induced switching processes. To prevent cis/trans isomerization from competing with conrotatory 6π-electron ring closure, the ethene segment is usually incorporated in a (perfluorinated) cyclopentene. In the present article syntheses of perhydrocyclopente…
Epitaxial oxide trilayer junctions composed of magnetite ($\mathrm{F}{\mathrm{e}}_{\mathrm{3}}{\mathrm{O}}_{\mathrm{4}}$) and doped manganite ($\mathrm{L}{\mathrm{a}}_{\mathrm{0.7}}\mathrm{S}{\mathrm{r}}_{\mathrm{0.3}}\mathrm{M}\mathrm{n}{\mathrm{O}}_{\mathrm{3}}$) exhibit inverse magnetoresistance as large as $\ensur…
FDU-1 silicas with large cage-like pores (diameter about 10 nm) were synthesized under acidic conditions from tetraethyl orthosilicate in the presence of a poly(ethylene oxide)-poly(butylene oxide)-poly(ethylene oxide) triblock copolymer template B50-6600 (EO(39)BO(47)EO(39)). High-resolution transmission electron mic…
This paper reviews recent developments on the epoxidation of alkenes using hydrogen peroxide as an environmentally friendly oxidant. The activation of hydrogen peroxide takes place in the presence of a homogeneous metal catalyst such as tungten, manganese, iron and rhenium or through addition of stoichiometric amounts…