Materials Literature
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Models for predicting the shape of organic crystals use geometrical rules and intermolecular interaction energies between the building blocks of the crystal but often ignore the environment in which the crystal grows. The resulting shapes predicted by these models may differ from the actual grown shapes since shape ca…
The boron trifluoride-catalyzed Rothemund condensation of triisopropylsilyl (TIPS) propynal 1 with 3,4-diethylpyrrole in dichloromethane, followed by oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) generates a mixture of products, including [15]triphyrin(1.1.3) H3, corrole H(3)4, porphyrin H(2)2, [24]pe…
We have used several techniques, including hyper-Rayleigh scattering and Stark spectroscopy, to investigate the effects of polyene chain length on the optical properties of complexes containing ruthenium(II) electron donor groups and pyridinium electron acceptors. In marked contrast with all other known donor-acceptor…
The structures of optical spectra of a semiconducting sphere are studied over a wide range of radius. The calculation is based on a ``microscopic nonlocal theory'' and we reformulate the theory to simplify the procedure. The nonlocal theory enables us to analyze correspondences between spectral peaks and exciton state…
On a solid surface with a surface tension gradient, a liquid drop is driven toward the more wettable end. To investigate the mechanism for the movement of the drop, we first measured directly the driving force of the drop, using a flexible glass microneedle. We determined that the driving force results from an imbalan…
We study coherent strain in (001) Ge generated by an ultrafast laser-initiated high density electron-hole plasma. The resultant coherent pulse is probed by time-resolved x-ray diffraction through changes in the anomalous transmission. The acoustic pulse front is driven by ambipolar diffusion of the electron-hole plasm…
ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTPreparation of Oxide Nanocrystals with Tunable Morphologies by the Moderate Hydrothermal Method: Insights from Rutile TiO2Qinghong Zhang and Lian GaoView Author Information The State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of…
2-Anthracenecarboxylic acid (AC) makes a very stable 1:2 inclusion complex with gamma-cyclodextrin (gamma-CDx) (K(1) = 161 +/- 25 M(-1), K(2) = 38 500 +/- 3300 M(-1) at 25 degrees C). The formation of the 1:2 inclusion complex accelerated the photocyclodimerization of AC. The 1:2 inclusion could be clearly verified by…
Nanostructured carbon films produced by supersonic cluster beam deposition have been studied by in situ Raman spectroscopy. Raman spectra show the formation of a sp2 solid with a very large fraction of sp-coordinated carbyne species with a long-term stability under ultrahigh vacuum. Distinct Raman contributions from p…
Recent high-temperature studies of Raman-active modes in single-walled carbon nanotube (SWNT) bundles report a softening of the radial and tangential band frequencies with increasing sample temperature. A few speculations have been proposed in the past to explain the origin of these frequency downshifts. In the presen…
The crystal structure of highly stoichiometric magnetite $({\mathrm{Fe}}_{3}{\mathrm{O}}_{4})$ below the Verwey transition has been refined from high-resolution neutron and synchrotron x-ray powder-diffraction data. The refined model has a monoclinic $P2/c$ symmetry cell with orthorhombic Pmca pseudosymmetry constrain…
The application of magnetic hysteresisgraphs in evaluating the performance of permanent magnets and soft magnetic materials is discussed. Topics include a summary of the important magnetic properties, magnetic measurement techniques used by hysteresisgraphs and examples of typical quality control applications.
The goal of developing a highly efficient microwave power source has led us to investigate new methods of electron field emission. One method presently under consideration involves the use of oxidized porous silicon thin films. We have used this technology to fabricate the first working field emission arrays from this…
Silicone fluids appear to be well-suited to applications in higher temperature rise transformer designs; smaller, lighter-weight transformer designs; and transformers which could operate above rated capacity periodically without significant loss of insulation life. This would require a selection process to match the p…
An epoxy composite used as cast electrical insulation in outdoor applications is studied for property and structure changes caused by aging under intensified electric field. The dielectric loss and the dielectric strength of the material are found to be slightly changed over an aging time of 1500 hours. Dynamic mechan…
Stress-free micromechanical cantilever beams have been fabricated by selective etching of silicon p-n structures in HF solutions utilizing a photo-assisted electrochemical process. With this technique, n or p regions can be selectively etched at controlled rates by appropriate choice of cell bias, p-n junction bias, a…
A rather complete numerical simulation program for electrical and thermal characteristics of a two-dimensional gated field emission triode is presented. Important aspect such as space charge effect, Joule heating, Nottingham effect as well as thermally-dependent heat conductivity and electrical resistivity are include…
The thermal degradation mechanism of EI (polyester imide) film on copper and aluminum wire was investigated. The effects of the metallic conductor on the degradation behavior and diagnosis methods applied to the EI films are reviewed. The physico-chemical properties were evaluated using a thermogravimetric analyzer, a…
Abstract This article is concerned with the reflectance spectra prediction based on a neural network developed for yarn from the roving reflectance spectra. The neural network developed is a multilayer feed‐forward network. The first system is wavelength dependent, but its performance is not very satisfactory. The sca…
The application of electromagnetic field theory to the subject of partial discharges shows that discharging in a void generates large field distortions within the bulk dielectric in the proximity of the void. Such inherent over-stressing of a dielectric could be the effect which triggers the onset of electrical treein…