Materials Literature
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Glacial phase clustering and growth in triphenyl phosphite is observed in the temperature interval of 210 K to 214 K by small angle neutron scattering performed at the NIST Center for Neutron Research. Presented are the radius, volume fraction, and polydispersity of clusters of glacial phase surrounded by a supercoole…
Assuming the sample to consist of ferromagnetic metallic (FMM) particles with a volume fraction (f ) randomly distributed over the paramagnetic insulating background, Monte Carlo simulations of electrical conductivity show excellent fits to the data measured in (La1−xYx)2/3Ca1/3MnO3 (x=0, 0.1 and 0.2). We find that th…
A universal expression of localization lengths for all metallic carbon nanotubes has been found. Our results indicate that all types of metallic nanotubes behave as molecular quantum wires, which can be explained by a new microscopic mechanism for it. We have shown that the micron-sized localization lengths in them st…
Gleich zwei Synthesewege zu den ersten Tetrathiafulvalen-anellierten Porphyrinen wurden entwickelt. Diese neuartigen Verbindungen (siehe Bild; Pe=Pentyl) wurden durch verschiedenste Methoden charakterisiert, darunter EPR-Spektroskopie, Cyclovoltammetrie und Massenspektrometrie. Weitere Untersuchungen durch Röntgenbeug…
Hydrogenated amorphous carbon films were deposited with and without hydrogen gas dilution in a small dc bias-assisted plasma chemical vapor deposition system. The field emission characteristics were investigated and compared. It was found that the vacuum electron emission with a very low turn-on electric field (∼0.5 V…
Abstract The frequency‐dependent conductivity of interpenetrating polymer network composites of polypyrrole (PPy) and poly(vinyl acetate) (PVAc) synthesized by FeCl 3 ‐impregnated PVAc films being dipped into solutions of pyrrole in water was investigated over a frequency range of 100 Hz to 2 MHz and a temperature ran…
Two moieties of mono- and trimethincyanines as well as those of styryl dyes were connected by a saturated alkyl tether made from compounds 3a-c, 5, 7, and 9a,b. In most cases, cyclic voltammetry and spectroelectrochemistry for these dyes together with the data for their monomeric models 4, 6, 8, and 10 reveal electroc…
The effects of the hydrodynamic interactions on the short-time dynamics of colloidal, hard-sphere-like particles confined between two parallel walls are measured by digital videomicroscopy. We find that such effects can be described in terms of an effective two-dimensional hydrodynamic function H(k), defined as a stra…
Abstract The effect of crystallization from the glassy state (cold crystallization) on the oxygen‐barrier properties of copolyesters based on ethylene terephthalate with up to 10 mol % isophthalate, phthalate, or naphthalate was examined. Generally, crystallization affected diffusivity D more than solubility S; thus,…
Two efficient synthetic routes to the first tetrathiafulvaleno-annelated porphyrins are reported. These novel porphyrin systems (see picture; Pe=pentyl) have been characterized by using a variety of techniques including EPR spectroscopy, cyclic voltammetry, and mass spectrometry. Langmuir-Blodgett films obtained from…
Four tetramers of MoV centers and four tetramers of CoII centers, linked by phosphate groups around a central isolated [Co(H2O)6]2+ octahedron form the key structural unit (see picture) in the molybdenum(V) cobaltophosphates 1 and 2, which were prepared by hydrothermal synthesis. These units are connected to produce t…
We report a holographic polymer-dispersed liquid crystal cell whose reflection peak can be tuned as a function of applied voltage. Electro-optic results are presented which are in excellent agreement with our model based on coupled wave theory.
Strong up-conversion luminescence of ${\mathrm{Mn}}^{2+}$ is observed in ${\mathrm{Z}\mathrm{n}\mathrm{S}:\mathrm{M}\mathrm{n}}^{2+}$ bulk and nanoparticles. The up-conversion emission band excited at 767 nm is redshifted from the photoluminescence emission excited at 300 nm with the bulk and the particles encapsulate…
Calculations are presented for thermoelectric transport in quantum well and quantum wire superlattices, using (i), the full superlattice electronic band structure in (ii) a multisubband inelastic Boltzmann equation for carrier-phonon scattering. The transport direction is taken to be in the quantum well planes and alo…
Der Halogenidligand entscheidet über den Grundzustand bei den Komplexen 1. Der Chloridkomplex hat einen reinen St=3/2-Zustand, der Iodidkomplex einen reinen St=1/2-Zustand, und im Bromidkomplex liegen Moleküle mit St=3/2- und St=1/2-Zustand im Verhältnis 1:1 nebeneinander vor. Eine starke intramolekulare, antiferromag…
Anziehende Wechselwirkungen mit dem Kation überwinden die elektrostatische Abstoßung zwischen zwei Tetracyanoethylen-Radikalanionen [TCNE].− und führen zur Bildung eines diamagnetischen Dimers, [TCNE]22− (siehe Bild), beispielsweise in [K(glyme)]2[TCNE]2. Die Bindung wird als Zwei-Elektronen-vier-Zentren-Bindung inter…
Transported to the other side: Cyclic D,L-α-peptides self-assemble in lipid bilayers into transmembrane ion channels that may allow efficient transport of glutamic acid. The molecular transport is size/shape selective, as evidenced by the high transport rates observed with cyclodecapeptide-based transmembrane pores bu…
A hexadecamer, first-generation, octasilsesquioxane liquid-crystalline dendrimer was synthesized by a platinum-catalyzed hydrosilylation reaction of the parent first-generation vinyl octasilsesquioxane dendrimer with a modified, laterally substituted mesogen. The structure and purity of the octasilsesquioxane substrat…
Molecular strands composed of alternating 2,6-diaminopyridine and 2,6-pyridinedicarbonyl units have been designed to self-organize into single stranded helical structures upon forming intramolecular hydrogen bonds. Pentameric strands 11, 12, and 14, heptameric strands 1 and 20, and undecameric strand 15 have been synt…
A model is proposed here to explain how the chemical features of metal oxide varistors can alter their nonohmic physical behavior, based on nonohmic similarities in the electrical properties of ZnO- and SnO2-based varistors. The proposed model explains the electrical properties of ZnO- and SnO2-based varistors before…