Materials Literature
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A portable acoustic emission monitoring system has been developed and used to test both laboratory samples and practical equipment. A fibre optic cable provides electrical isolation and protection for the operator and the monitor. This has been tested on high voltage equipment up to 400 kV. In laboratory samples it ha…
Strictly alternating copolyimides containing aliphatic spiro units were prepared via diimide (with five-membered rings)−dianhydrides (with six-membered rings) derived from 2,8-dioxaspiro[4.5]decane-1,3,7,9-tetrone (TCDA) and diamines. The polymerization was conducted by the conventional two-step procedure using the di…
Micelles with unprecedented flowerlike arrangements of the poly(ferrocene) cores (shown in the TEM image) are among the supramolecular architectures generated in the self-assembly of a novel organometallic triblock copolymer from silicon-bridged [1]ferrocenophane monomers and [Me(2)SiO](3) in hexane, a solvent selecti…
A series of new anionic, cationic, and betainic methine dyes (an example is illustrated here) have been synthesized from methyl- or methylene-substituted 2,2-difluoro-1,3,2-dioxaborines and reactive formyl derivatives. These dyes have intense long-wavelength absorptions in the red or near-infrared region.
Dendrimeric polyphenylselenides are prepared in high yield using propyloxy spacers to connect the phenyseleno groups to the dendrimeric core. The selenides catalyze the oxidation of bromide with hydrogen peroxide to give positive bromine species that can be captured by cyclohexene in two-phase systems. The increase in…
Auf geordnete Weise auf Graphit adsorbieren und mit molekularer Auflösung abbilden ließen sich erstmals supramolekulare Systeme aus gitterartigen Metallkoordinationsverbindungen. Dabei zeigte sich, daß – in Abhängigkeit von den jeweiligen Liganden – die Metallgitter parallel oder senkrecht zum Substrat angeordnet sind…
Supramolecular arrays in which a free-base (or zinc) porphyrin is connected by axial coordination of its meso-pyridyl groups to one or more ruthenium porphyrin units have been studied by steady-state and time-resolved techniques. Besides their attractive structures—“open-box” or “flying saucer”—these arrays exhibit in…
The paper describes a new selective detection method for water trees developed in consideration of the electrophysical concept of the water treeing phenomenon. As most of the liquid water is not chemically bound in the water trees it can move out or in, depending on the actual physical conditions such as the solubilit…
Nature abhors a vacuum. Attempts to self-assemble nanoporous crystals (clathrates) with trimesic acid and its analogues reveal a striking variability in carboxylic acid motifs that often allow close-packing without clathrate formation. The common R22(8) carboxylic acid dimer is found in tributyl trimesic acid, which f…
In insulation materials several chemical and physical deterioration processes arise, such as thermal and electrical ageing, and moistening, due to operational and environmental stresses. As well as electrical strength, these deterioration processes influence the dielectric processes, the conduction and the polarisatio…
Wet oxidation kinetics of aqueous solutions of formic, acetic, oxalic, and glyoxalic acids was studied in a titanium autoclave at a temperature range of 150−320 °C and oxygen partial pressures between 8 and 60 bar. Oxidation reactions obeyed a first-order kinetics with respect to concentration of all substrates. On th…
Long-range ferromagnetic ordering at 3 K is observed for the title compound, which may be considered as a fully localized mixed-valence species (Mo3+ and Mo4+) as well as a mixed-spin species (low-spin and high-spin Mn2+ ions). Its two-dimensional structure consists of heart-shaped 48-membered rings, and each ring con…
Addition of aliphatic polyols to aqueous silicate solutions is shown to yield high concentrations of stable polyolate complexes containing five- or six-coordinated silicon. Coordinating polyols require at least four hydroxy groups, two of which must be in threo configuration, and coordinate to silicon via hydroxy oxyg…
We have developped a novel lift-off process for fabrication of high quality superconducting submicron niobium structures. The process makes use of a thermostable polymer with a high transition temperature T_{g}= 235 C and an excellent chemical stability. The superconducting critical temperature of 100 nm wide niobium…
In the asymptotic limit, the interlayer exchange coupling decays as $D^{-2}$, where $D$ is the spacer thickness. A systematic procedure for calculating the preasymptotic corrections, i.e., the terms of order $D^{-n}$ with $n \ge 3$, is presented. The temperature dependence of the preasymptotic corrections is calculate…
The adsorption behavior of bovine serum albumin (BSA) on high-purity austenitic low-carbon stainless steel and its effect on the state of the electrode surface have been studied over the temperature range 299−343 K under open-circuit-potential conditions, using electrochemical impedance spectroscopy (EIS). The impedan…
A drastic change in the solubility and gelation properties of 1-O-methyl-4,6-O-benzylidene derivatives of monosaccharides (see figure) results from the change in the configuration of only one carbon atom.
Reversible switching of quadratic NLO responses can be achieved in organic and metallo-organic molecular compounds by application of various external stimuli. Strategies for the molecular engineering of switchable NLO materials are outlined (an example is depicted), and practical demonstrations of the switching of NLO…
After forever changing the drug discovery process in the pharmaceutical industry, combinatorial chemistry methodologies are increasingly being applied to the discovery and optimization of more efficient catalysts and materials (see picture). With the advent of new combinatorial synthesis and screening technologies, co…
Scanning tunneling spectroscopy was used to investigate single crystals and thin films of La(1-x)Ca(x)MnO(3) (with x of about 0.3), which exhibit colossal magnetoresistance. The different spectroscopic signatures of the insulating (paramagnetic) and metallic (ferromagnetic) phases enable their spatial extent to be ima…