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A quantitative model which describes the aging of the material properties in acceptor doped ferroelectric ceramics as a result of the reorientation of defects in time is proposed. By this reorientation the domain walls are clamped by a time dependent force leading to the observed decrease of the material properties du…
We used electron-energy-loss spectrometry to measure the intensities of the white lines found at the onsets of the ${\mathit{L}}_{2}$ and ${\mathit{L}}_{3}$ absorption edges for most of the 3d and 4d transition metals. The intensities of the white lines, normalized to the trailing background, decreased nearly linearly…
A number of the d10 and s2 metal clusters are brightly luminescent, some with strongly medium dependent and temperature dependent spectral profiles. Such emissions are often from excited states assigned as having a mixed d-s/XMCT character, the key feature being enhanced electronic population in metal-metal bonding or…
The photochemical and thermal cis to trans isomerization of aromatic azo groups covalently bonded within polymers and its practical consequences as well as some other recent applications are reviewed. The kinetics and mechanism of the isomerization of azo polymers are briefly presented and then several recent developm…
Silver behenate, a possible low-angle diffraction standard, was characterized using the powder diffraction technique. Diffraction patterns obtained with 1.54 Å synchrotron and Cu Kα radiations showed thirteen regularly spaced (00l) peaks in the range 1.5–20.0°2θ. With the National Institute of Standards and Technology…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPreparation and properties of uniform size colloidsEgon MatijevicCite this: Chem. Mater. 1993, 5, 4, 412–426Publication Date (Print):April 1, 1993Publication History Published online1 May 2002Published inissue 1 April 1993https://pubs.acs.org/doi/10.1021/cm00028a004https://d…
Optical properties of liquid crystals electro-optical properties of liquid crystals nonlinear optical properties of liquid crystals nonlinear optics.
This review is concerned with quantum confinement effects in low-dimensional semiconductor systems. The emphasis is on the optical properties, including luminescence, of nanometre-sized microcrystallites, also referred to as zerodimensional systems. There is some discussion on certain of the two-dimensional systems, s…
Abstract The Rietveld method is a powerful and relatively new method for extracting detailed crystal structural information from X-ray and neutron powder diffraction data. Since such structural details dictate much of the physical and chemical attributes of materials, knowledge of them is crucial to our understanding…
A one-dimensional constitutive model for the thermomechanical behavior of shape memory alloys is developed based on previous work by Liang and Tanaka. An internal variable ap proach is used to derive a comprehensive constitutive law for shape memory alloy materials from first principles without the assumption of const…
The PROCHECK suite of programs provides a detailed check on the stereochemistry of a protein structure. Its outputs comprise a number of plots in PostScript format and a comprehensive residue-by-residue listing. These give an assessment of the overall quality of the structure as compared with well refined structures o…
Abstract A polyimide made from 4,4′‐diaminodiphenyl ether (ODA) and 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA) was synthesized in polyphosphoric acid. Although the polymerization proceeded heterogeneously, a polyimide with an inherent viscosity of 0.90 was obtained, and a tough and flexible film was made fro…
Abstract It is shown that many simple glass‐forming liquids exhibit a phenomenon known in the area of polymer science as the liquid–liquid transition. The phenomenon manifests itself as a third‐order transition in the equilibrium liquid‐specific heat data around approximately 1.2 T g and also as a bifurcation of the l…
Abstract Measurement of imidization by IR spectroscopy has frequently been reported to give results that are either insensitive to changes in the latter part of the cure or in conflict with observations by other methods. However, an analysis of imide formation using the 1370 cm −1 band (CN stretch) in conjunction wit…
Abstract Permeability measurements for oxygen and nitrogen were carried out on a series of structurally similar polyimides in order to define structure/permeability relationships. The polyimides were prepared from 5,5′‐[2,2,2‐trifluoro‐1‐(trifluoromethyl) ethylidene] bis‐1,3‐isobenzofuranedione (6FDA) and a variety of…
Abstract Poly(ether sulfone)s containing pendant sodium sulfonate groups were prepared by the aromatic nucleophilic substitution reaction of 4,4′‐dichlorodiphenylsulfone ( 1 ) and sodium 5,5′‐sulfonylbis (2‐chlorobenzenesulfonate) ( 2 ) with bisphenols ( 3 ) in the presence of potassium carbonate in N,N ‐dimethylaceta…
Abstract Ozone‐induced graft polymerization was carried out to improve polymer surfaces. The polymers were exposed to ozone and the surface density of peroxides formed was determined by three methods; iodide, DPPH, and peroxidase method. The peroxide production could be readily controlled by the ozone concentration an…
Abstract It was found that montmorillonite was intercalated with ϵ‐caprolactam. X‐ray diffraction revealed that the chain axes of the ϵ‐caprolactam were parallel to the montmorillonite plates. The intercalated montmorillonite was swollen by molten ϵ‐caprolactam at 200°C. ϵ‐Caprolactam and 6‐aminocaproic acid (accelera…
The classical in vitro denaturation-renaturation studies by Anson, Anfinsen, Neurath, Pauling and others clearly suggested that the primary structure of proteins determines all higher levels of protein structure. Protein folding in the cell is inaccessible to a detailed analysis of its kinetic mechanism. There are obv…
The valence and core level spectra of chemically prepared, ideally H-terminated Si(111) surfaces are characterized by remarkably sharp features. The valence band levels and their dispersion are well described by first-principles calculations using a quasiparticle self-energy approach within the GW approximation. From…