Materials Literature
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The inclusion of anisotropic surface free energy and anisotropic linear interface kinetics in phase-field models is studied for the solidification of a pure material. The formulation is described for a two-dimensional system with a smooth crystal-melt interface and for a surface free energy that varies smoothly with o…
Abstract A simple, convenient and reliable calorimetric efficiency scale is proposed for the evaluation of nucleating additives for polymers. The scale is based on conventional differential scanning calorimetry cooling runs and makes use of a crystallization range determined in self‐nucleation experiments. It can be c…
The rare earth cryptates are used as long-lived fluorescent labels. They are formed by inclusion of a europium ion in the intramolecular cavity of a macropolycyclic ligand containing bipyridine groups as light absorbers. The use of fluoride ions in the measuring medium allows a total shielding of the label fluorescenc…
Infrared transmission spectra of molecules adsorbed on silver island films evaporated on CaF 2 have been investigated. The spectra are remarkably simple compared with those of the molecules in the solid state (KBr pellets). Only the vibrational modes which give dipole changes perpendicular to the metal surface are inf…
The dielectric behavior and structure of the Sr(Zn1/3Nb2/3)O3-Ba(Zn1/3Nb2/3)O3 solid solution have been investigated with the intention of understanding the relationship between the structural changes and the temperature coefficient of the relative permittivity τε. A correlation between the value of τε and the occurre…
J aggregate of a water-soluble porphyrin, 5,10,15,20-tetra(4-sulfophenyl)porphyrin (H2TPPS44−), formed in acidified aqueous solutions, exhibits sharp and intense absorption bands at 491 and 707 nm. These characteristic transitions, J bands, are of linear oscillators polarized in the long axis of rodlike aggregate. The…
The tissue response and in vivo molecular stability of injection-molded polyhydroxyacids--polylactides (PLA), poly(3-hydroxybutyrate) (PHB), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB/VA, 5-22% VA content)--were studied. Polymers were implanted subcutaneously in mice and extirpated at 1, 3, and 6 months in…
Abstract The crystallization behavior after partial or complete melting of the α phase of iPP is examined by combined differential scanning calorimetry (DSC) and optical microscopy: calorimetric results are directly correlated with corresponding morphologies of microtome sections of DSC samples. On partial melting at…
In kilogram quantities ; pure poly(propylene imine) dendrimers can be prepared in an extremely simple reaction sequence comprising Michael addition (primary amines to acrylonitrile) and heterogeneous hydrogenation with a Raney cobalt catalyst. Both steps proceed quantitatively and selectively and can be employed with…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTExpanding roles for templates in synthesisSally Anderson, Harry L. Anderson, and Jeremy K. M. SandersCite this: Acc. Chem. Res. 1993, 26, 9, 469–475Publication Date (Print):September 1, 1993Publication History Published online1 May 2002Published inissue 1 September 1993https…
Abstract A polyimide hybrid with montmorillonite clay mineral has been synthesized from a dimethylacetamide (DMAC) solution of poly(amic acid) and a DMAC dispersion of montmorillonite intercalated with an ammonium salt of dodecylamine. Montmorillonite consists of stacked silicate sheets about 2000 Å in length, 10 Å in…
Deviations from thermally activated and from exponential response are typical features of the vitrification phenomenon and previously have been studied using viscoelastic, dielectric, calorimetric, optical, and other techniques. Linear response data from literature on about 70 covalent glass formers, ionic melts, supe…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis and characterization of nearly monodisperse CdE (E = sulfur, selenium, tellurium) semiconductor nanocrystallitesC. B. Murray, D. J. Norris, and M. G. BawendiCite this: J. Am. Chem. Soc. 1993, 115, 19, 8706–8715Publication Date (Print):September 1, 1993Publication H…
Anodic oxidation in hydrochloric (HCl) acid and chemical dissolution in hydrofluoric (HF) acid solutions of porous silicon (PS) layers obtained from lightly doped p-type substrates have been investigated. It is shown that the wettability of PS, which is a highly hydrophobic and organophilic material, strongly affects…
The age and season of death of mammals, as well as other aspects of their life history, can be estimated from seasonal bands in dental cementum that result from variations in microstructure. Scanning electron micrographs of goats fed controlled diets demonstrate that cementum bands preserve variations in the relative…
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” opt…
The recently determined phonon dispersion curves of alpha -quartz have been analysed with various polarizable-ion, bond-charge and shell models, the shell models giving a very satisfactory account of the dispersion curves as well as of the scattering intensities. Due to the use of interatomic potentials the number of…
Anharmonic effects in crystals typically result in the symmetric broadening of the single-phonon Lorentzian line shape. However, a simple model, based on consideration of a highly anharmonic potential, shows that anharmonicity can lead not only to asymmetric line shapes but also to line shapes composed of multiple sub…
Surface modification of a P2 beam-exposed InGaAs surface and an As2 beam-exposed InP surface was studied in situ using reflection high energy electron diffraction during gas source molecular beam epitaxy. It is revealed that the InP surface remained stable under As2 beam exposure after forming an InAs surface layer a…
We report the fabrication of high aspect ratio, sub-10 nm size, structures in silicon without involving any wet chemical etching. A 50 nm thick double layer of low and high molecular weight polymethylmethacrylate resist was exposed with an 80 kV electron beam of diameter smaller than 5 nm. After exposure the resist wa…