Materials Literature
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The morphology of melt-crystallized polyethylene is reported. The samples were crystallized for different times at high temperature to produce early stages of spherulitic growth. Morphology studies using transmission electron microscopy showed that the largest proportion of the early objects was monolayers associated…
Continuum concepts are used to evaluate the competition between crack advance and dislocation nucleation at the tip of a crack having a finite tip curvature. The analysis reveals that the favorability of crack propagation versus dislocation emission depends upon the bluntness of the crack tip. One implication is that…
The layered charge-density-wave (CDW) material $2H\ensuremath{-}{\mathrm{NbSe}}_{2}$ was studied by angle-resolved photoelectron spectroscopy. We present the first experimental mapping of the Fermi surface (FS) portions involved in the CDW transition. From this and additional data on the conduction band dispersion nea…
A peculiar bonding feature of $\ensuremath{\alpha}$-rhombohedral boron is found in the electron density distribution of the icosahedral ${\mathrm{B}}_{12}$ cluster. The electron density distribution is obtained by using the maximum entropy method with synchrotron radiation powder data. It clearly shows the characteris…
We have studied lattice dynamic properties of ${\mathrm{SrTiO}}_{3}$ thin films from 5 to 300 K using metal-oxide bilayer Raman scattering. First-order zone-center optical phonons, symmetry forbidden in single crystals, have been observed in the thin films, indicating strain-induced lowering of symmetry. The asymmetri…
The intergrain magnetoresistance (IMR) observed in polycrystalline half-metallic ferromagnets at temperatures below the Curie temperature ${T}_{C}$ was investigated. The systematics of the IMR, as a function of field and temperature for ferromagnetic manganites with varying ${T}_{C}$, shows that the high field magneto…
The symmetry-induced magnetic anisotropy due to monoatomic steps at strained Ni films is determined using results of first - principles relativistic full-potential linearized augmented plane wave (FLAPW) calculations and an analogy with the Néel model. We show that there is a magnetoelastic anisotropy contribution to…
Composites of uniaxially oriented multiwalled carbon nanotubes embedded in polymer matrices were fabricated and investigated by transmission electron microscopy. In strained composite films, buckling was ubiquitously observed in bent nanotubes with large curvatures. By analyses of a large number of bent nanotubes, the…
Abstract: Carbohydrate researchers may think it is reasonable to believe that the synthesis and structure of a crystalline b-1,4 glucan would be quite straightforward; however, this is not the case. The pitfalls and detours of research have been counterbalanced by exciting new discoveries in cellulose structure, biosy…
DFT calculations have been carried out on the titanium carbide clusters Ti 3 C 8, Ti 4 C 8, Ti 6 C 13, and Ti 7 C 13 and their anions, in relation with the recent experimental and theoretical report by L.-S. Wang and his group on those clusters (Wang, L.-S.; Wang, X.-B.; Wu, H.; Cheng, H. J. Am. Chem. Soc . 1998, 120,…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTElectrochemical Reduction of Pyrrole in the Presence of Trinitrofluorenone: Isolation of a Meisenheimer ComplexKatsuyoshi Hoshino, Nobuo Ozawa, Hiroshi Kokado, Hiroko Seki, Tatsuhiro Tokunaga, and Tsutomu IshikawaView Author Information Faculty of Engineering, Chemical…
PE−EP and PE−EP−EPDM block polymers have been made in yields exceeding 70% with Ziegler−Natta catalysts by matching the polymerization time for each block to chain growth time and catalyst decay rates. A short residence time tubular flow reactor with multiple side stream feeds was used to accomplish this result. The a…
Density functional calculations were performed on 1,1‘,5,5‘-tetramethyl-6,6‘-dioxo-3,3‘-biverdazyl diradical (BVD) and BVD[CuI(PL 3 )] 2 complexes (L = H, Me, OH, OMe, F) in order to investigate how Cu chelation affects the singlet−triplet splitting of the verdazyl system. It was found that donating ligands on Cu dest…
Square-planar rhodium or iridium “ n -decyloxy-β-diketonate” complexes of the general formula [M(β-diketonate)(CO) 2 ] (M = Rh ( 1 − 3 ) or Ir ( 4 − 6 )) and pyrazole−rhodium derivatives of the type [RhCl(CO) 2 (pyrazole)] ( 7 − 9 ) have been prepared and their liquid-crystalline properties studied. Compounds 1 and 4…
While ongoing efforts continue to explore the high-pressure phase equilibria of polymer blends, few studies have attempted to address the impact of a supercritical (sc) fluid on such equilibria. In this work, we report on the phase behavior of an upper critical solution temperature (UCST) polymer blend in the presence…
The 1 H NMR spectra of iron(III) complexes of dimeric 5,5‘-bis(10,15,20-triphenylporphyrin) [(TrPPH 2 ) 2 ], 5,5‘-bis(10,15,20-tris( p -methoxyphenyl)porphyrin) [(Tr( p -MeOP)PH 2 ) 2 ], and hybrid (TrPPH 2 )(Tr( p -MeOP)PH 2 ) and the respective monomeric 5,10,15-triphenylporphyrin (TrPPH 2 ) and 5,10,15-tris( p -met…
Continuous crystallization of calcium lactate pentahydrate was investigated in a mixed-suspension-mixed-product removal crystallizer. Wide ranges of the mean residence time, relative supersaturation, and magma density were covered (40−215 min, 0.01−1.12, and 2−65 kg/m 3, respectively). Crystal growth was found to be d…
Unique temperature-dependent syn-anti conformational switching in bis- and monozinc ethane-bridged porphyrin dimers takes place in nonpolar solvents containing a small amount of alcohol (1−5%). These dimers adopt a syn conformation at any studied temperatures in the absence of alcohol added, while, in the presence of…
The formation of a molecular assembly composed of a naturally occurring peptide with a helical structure was investigated. Gramicidin A, a 15-mer peptide antibiotic, was conjugated with poly(ethylene glycol) (PEG, average molecular weight 600). This peptide conjugate formed vesicles with an unilamellar membrane in wat…
The nature of the structural ordering within semicrystalline poly(3-dodecylthiophene) films has been analyzed using a Warren−Averbach line-shape analysis which includes up to five orders of the ( h 00) lattice reflections. This analysis yields a semiquantitative measure of the volume averaged crystallite sizes, the la…