Materials Literature
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We consider a simple model for the growth of isolated steps on a vicinal crystal surface. It incorporates diffusion and drift of adatoms on the terrace, and strong step and kink edge barriers. Using a combination of analytic methods and Monte Carlo simulations, we study the morphology of growing steps in detail. In pa…
This paper describes a method to limit the band gap widening that occurs in fully substituted conjugated polymers. This is done by constructing step growth [AB] polymers where the A-units are electron rich and the B-units are electron deficient. The thiophene-based polymers were prepared by modified Stille polymerizat…
Au colloids have been prepared by reduction of metal salt with UV irradiation in the presence of dendrimers. Poly(amidoamine) dendrimers with surface amino groups for generations 0, 1, 2, 3, 4, and 5 (G0−5) have been used. The average particle sizes decrease with an increase of concentration of surface amino group of…
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 ATP-dependent enzyme dethiobiotin synthetase from Escherichia coli catalyses the formation of dethiobiotin from CO2 and 7, 8-diaminopelargonic acid. The reaction is initiated by the formation of a carbamate and proceeds through a phosphorylated intermediate, a mixed carbamic phosphoric anhydride. Here, we report t…
Gels of a poly(oxyethylene)−poly(oxybutylene) diblock copolymer in aqueous solution forming a bcc phase have been examined using small-angle X-ray scattering (SAXS) with simultaneous rheology. Application of large amplitude oscillatory shear is observed to induce macroscopic alignment of twinned bcc crystals. Alignmen…
The emission and absorption characteristics of a conjugated poly(phenylene bithiophene), 2, and a monomeric model compound, 3, were investigated as a function of [Li + ], [Na + ], [K + ], and [Ca 2+ ]. The calix[4]arene bithiophene receptor that is present in both 2 and 3 provides selectively for Na + and the absorpti…
It has generally been assumed that the aggregation of partially folded intermediates during protein refolding results in the termination of further protein folding. We show here, however, that under some conditions the association of partially folded intermediates can induce additional structure leading to soluble agg…
Much attention has been directed to the development of sophisticated membranes that can regulate the permeability in response to environmental changes. In this study, pH-sensitive membranes were prepared by grafting of poly(acrylic acid) (PAAc) onto a porous Nuclepore membrane. The filtration rate of a membrane with a…
Crystals of an ion-channel-forming peptaibol peptide in a partial membrane environment have been obtained by cocrystallizing antiamoebin with n-octanol. The antiamoebin molecule has a bent helical conformation very similar to that established for Leu-zervamicin, despite a significantly different sequence for residues…
The synthesis of new poly(siloxysilanes) by polyhydrosilation of AB 2, AB 4, and AB 6 monomers using a solid-supported catalyst is described. Analysis of the polymers by gel permeation chromatography shows weight-average molecular weight values near 5−10 000 amu with polydispersities of ∼2. Addition of fresh monomer t…
We studied scaling in kinetic roughening and phase ordering during growth of binary systems using 1+1 dimensional single-step solid-on-solid model with two components interacting via Ising-like interaction with the strength K. We found that the model exhibits crossover from the intermediate regime, with effective scal…
Magnetic and structural studies in the series have been carried out by powder neutron diffraction for seven compositions corresponding to y = 0.0, 0.1, 0.2, 0.3, 0.5, 0.7, 1.0. At one extreme of this series is a metallic ferromagnet with rhombohedral structure while the other end member is an antiferromagnetic insulat…
The valence-band x-ray photoelectron spectroscopy (XPS) spectra of the Ge nanocrystals deposited by the cluster-beam evaporation technique were studied, and suggest the presence of the tetragonal crystal structure (ST-12) of Ge in the Ge nanocrystals. Although the ST-12 structure of Ge is known to be metastable and is…
Electron energy loss spectroscopy (EELS) has been used to observe size dependent changes in the electronic states of isolated, nanocrystalline carbon particles supported on ${\mathrm{SiO}}_{2}$ substrates. The structure and size distribution of the particles have been characterized by Raman scattering, Auger electron…
We have measured the low temperature far infrared absorption in the high and low density amorphous phases of ${\mathrm{H}}_{2}\mathrm{O}$ and ${\mathrm{D}}_{2}\mathrm{O}$ in the region $2--30{\mathrm{cm}}^{\ensuremath{-}1}$. For each isotope, resonant absorption by two level systems is observed for the high density am…
The temperature-dependent electrical resistance behaviour of and in zero field as well as in the presence of a magnetic field ( H ) is reported. The application of H up to 70 kOe does not influence the so-called metal-insulator transition in any of these compounds significantly. Interestingly, the magnitude of the mag…
The spectral characteristics of the internal (PO4 tetrahedron) modes of fast-grown KH2PO4 crystals under sub-damage threshold, 10 ns, 355 nm laser irradiation have been investigated. Pump-and-probe Raman spectroscopy indicates transient changes of the intensity of the 915 cm−1, –PO4 internal mode. This change is attri…
Crystalline thin films of SiCN have been grown by microwave plasma-enhanced chemical vapor deposition using H2, CH4, N2, and SiH4 gases. The ternary compound (C;Si)xNy exhibits a hexagonal structure and consists of a network wherein the Si and C are substitutional elements. While the N content of the compound is about…
Unidirectional liquid-crystal (LC) alignment by a linearly polarized ultraviolet light (UV) exposure was examined using two types of polyimide (PI). PI with a fluorene unit incorporated in a side chain showed LC alignment perpendicular to those of conventional PIs, i.e., perpendicular to the rubbing direction and para…