Materials Literature
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The diketonate Schiff-base complexes shown below were investigated, and the square planar derivatives (M=Ni, Cu, Pd) were found to display discotic hexagonal disordered phases (Dhd). The M=VO analogs are not liquid crystalline. None of the complexes can exhibit a disc-shape independently, and in the mesophase they mus…
Abstract The photo‐ and thermooxidative degradation of different grades of high‐impact polystyrene (HIPS) has been studied by FT‐IR spectroscopy. The oxidized films were treated with NH 3 and SF 4 for the rapid identification and resolution of the various carbonyl species, alcohols, and hydroperoxides. All the sample…
Abstract Hydration behavior of Na-smectite crystals synthesized at a pressure of 5.5 GPa and temperatures of 1400°–1500°C was examined by X-ray powder diffraction at various relative humidities (RH) in the range of 0–100%. The basal spacing of the Na-smectite crystal increased stepwise with increase in RH. The reflect…
Readily available chiral aldehydes and pyrrole provide porphyrins like 1 in a single step. Mn-Cl derivatives of such compounds are effective catalysts for the enantioselective epoxidation of nonfunctionalized olefins. The design of chiral porphyrin ligands should receive new impetus, since in the synthesis of 1, the D…
Two new protein kinase C inhibitory glycosides, vanicosides A [1] and B [2] were isolated from Polygonum pensylvanicum (Polygonaceae) by chromatographic techniques guided by bioassays for PKC inhibition. The structures of these glycosides were established primarily by analysis of 1H- and homonuclear correlated nmr and…
Abstract The synthesis and spectroscopic characterization of several benzoanellated [5.5.5]‐, [5.5.5.6]‐, and [5.5.5.5]fenestranes, including the parent difuso ‐centrotriindan 7 , the parent tetrafuso ‐centrotetraindan 8 (“fenestrindan”) as well as the tribenzo[5.5.5.6]‐ and tribenzo[5.5.5.5]fenestranes 27 and 35 , ar…
The gamma-aminobutyric acid (GABA) receptor is an abundant neuronal receptor in the mammalian and invertebrate nervous systems and is associated with an inhibitory chloride ion channel. GABA is the endogenous neurotransmitter for the receptor and can trigger both fast activation and a reversible desensitization of the…
Electrical properties of different compositions of lead vanadate glasses are reported in the temperature range 80--500 K. The experimental results are analyzed with reference to theoretical models existing in the literature. It has been observed that at high temperatures, Mott's model of phonon-assisted small polaron…
ADVERTISEMENT RETURN TO ISSUEPREVArticleIn Situ Synthesis of Ferrites in CellulosicsLouise Raymond, J.-F. Revol, D. H. Ryan, and R. H. MarchessaultCite this: Chem. Mater. 1994, 6, 2, 249–255Publication Date (Print):February 1, 1994Publication History Published online1 May 2002Published inissue 1 February 1994https://p…
Lattice defects in five wurtzite crystals, ZnO, BeO AlN GaN and InN, have been studied by high-resolution electron microscopy for samples pulverized at room temperature. High-density stacking faults were produced in BeO and GaN. With the weak-beam technique, dissociation of basal dislocations was observed in BeO. By h…
Molecular dynamics simulations have been carried out for sinple point charge (SPC) water, in normal, compressed, and stretched states. A detailed analysis of local structures using both pair correlation and Voronoi polyhedra distribution, which describes the information about the multiparticle distribution, was report…
Abstract The occurrences of sepiolite beds and nodules in alkaline and saline Miocene Eskisehir lake deposits provide unique examples of ancient lacustrine environments. Stockwork-type magnesite deposits, which were formed very close to the Miocene lake, served as parent rocks for sepiolite nodules (meerschaum). The M…
A comprehensive theory is presented which successfully explains the polarization, isothermal, and isochronal behavior of the optical absorption bands responsible for the color in blue and blue‐green sapphire (Fe,Ti: α‐Al 2 O 3 ). The experimental study on which this theory is based has conclusively shown that (Fe,Ti)…
In this work, we have analysed the effects of alpha-hederin, a monodesmosidic triterpenoid saponin isolated from Hedera helix, on mouse B16 melanoma cells and non-cancer mouse 3T3 fibroblasts cultured in vitro. Our results indicate that, in a serum-free medium, alpha-hederin is cytotoxic and inhibits proliferation in…
We report results of a large-scale Monte Carlo study of a grafted-polymer "brush" composed of two types of chains of length N = 100 segments under near-melt conditions, with respulsive interactions of strength χ acting between segments of the two species. Following a quench from χ = 0 to χ = 1, we observe the formatio…
The current-voltage relationship I(V) for several different ferroelectric thin films often exhibits an apparent negative differential resistivity. In the present paper we show that in lead zirconate-titanate (PZT) this is a spurious artifact arising from rapid (parametric) measurement techniques and that it disappears…
Pyriporphyrins like the isolable porphyrin analogue 1 react unexpectedly upon oxidation. Depending on the reaction conditions either a ketone (C = O instead of CH2) or a dimer is formed. A conjugated [18]annulene derivative is, however, not obtained.
The multiphonon relaxation (MR) rates for a large number of 3- to 5-phonon transitions of ${\mathrm{Er}}^{3+}$ ions in ${\mathrm{LiYF}}_{4}$ and ${\mathrm{LaF}}_{3}$ crystals were measured at 77 K. The MR rates of ${\mathrm{Nd}}^{3+}$ and ${\mathrm{Er}}^{3+}$ ions in these crystals have been analyzed with a point-char…
Abstract The influence of thermal annealing on molecular weight, microphase mixing, and multiple melting behavior of a segmented block copolyurethane is reported. The material studied contained 55% of hard segment consisting of 4,4'‐diphenylmethane diisocyanate and butanediol, and a poly (propylene oxide) diol of mole…
Abstract Metal phthalocyanines (M = Cu, Ni, Co, SnCl 2 ) 3–6 containing four 14‐membered tetraaza macrocycles have been prepared. Detosylation of the aza functions has provided donor sites for binding four Ni 2+ ions giving a pentanuclear complex which is extremely soluble in polar solvents. The mass spectrum of the […