Materials Literature
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We consider three mechanisms of hysteresis phenomena in alternating magnetic field: the domain-wall motion in a random medium, the nucleation, and the retardation of magnetization due to slow (critical) fluctuations. We construct a quantitative theory for all these processes. The hysteresis is characterized by two dyn…
High‐temperature oxidation of monolithic boron nitride (BN) is examined at 900–1200°C. Hot‐pressed BN and both low‐ and high‐density chemically vapor‐deposited BN are studied. The oxidation product is B 2 O 3 ( l ) and the oxidation kinetics are sensitive to crystallographic orientation, porosity, and impurity levels.…
A polymer (TPD-PPV), incorporating both efficient light-emitting and hole transporting moieties has been synthesized. This polymer also possesses excellent film-forming property, good thermal stability, and high electrochemical reversibility and stability. The HOMO-LUMO energy levels were determined by cyclic voltamme…
The frequency and temperature dependence of the optical conductivity of ferromagnetic manganites is explained within the framework of the bipolaron theory. As these materials are cooled below the Curie temperature, the colossal magnetoressitance (CMR) is accompanied by a massive transfer of the spectral weight of the…
The role that Al 3 Fe intermetallic inclusions play during initiation of pitting corrosion on aluminum alloys was investigated in 0.6 M NaCl. In aerated solutions microscopic observations showed the growth of cavities in the host metal adjacent to inclusions. The rest potential of synthetic Al 3 Fe was measured in aer…
A series of high-generation (G) ethylenediamine-core polyamidoamine (PAMAM) dendrimers corresponding to G = 5, 7, 9, and 10 were conjugated with the bifunctional chelate 2-(4-isothiocyanatobenzyl)- 1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetate (p-SCN-Bz-DOTA). Gadolinium (III) ion was added to the macromolec…
Heparin is a potent anticoagulant which can be immobilized on biomaterial surfaces to increase their hemocompatability. In the present work, we have electrochemically synthesized composites comprising heparin and the electrically conducting polymer polypyrrole. The incorporation and exposure of heparin were controlled…
Low-energy metal-to-ligand charge-transfer (MLCT) excitations are associated with the very large molecular nonlinear optical (NLO) coefficients, β, of the complexes [RuII(NH3)5(N-R-4,4′-bipyridinium)]3+ (R=methyl, phenyl, or 4-acetylphenyl). Chemical oxidation to the RuIII forms causes bleaching of the MLCT absorption…
We show that polymeric materials characterized by two length scales are obtained if diblock copolymers are mixed with amphiphilic selective solvents, leading to self-organization which combines the “block copolymer length scale” with a much shorter “nanoscale”. In this work, the amphiphilic compound is 3- n -pentadecy…
Tracheary element differentiation requires strict coordination of secondary cell wall synthesis and programmed cell death (PCD) to produce a functional cell corpse. The execution of cell death involves an influx of Ca2+ into the cell and is manifested by rapid collapse of the large hydrolytic vacuole and cessation of…
Dc magnetization, ac susceptibility, and zero-field-cooled relaxation measurements are carried out for a cluster glass compound of ${\mathrm{La}}_{0.5}{\mathrm{Sr}}_{0.5}{\mathrm{CoO}}_{3}.$ The temperature dependence of the magnetic properties could be distinguished into two regimes: a high-temperature regime with th…
The Raman and infrared phonons of isostructural rhombohedral ${\mathrm{LaMnO}}_{3}$ and ${\mathrm{LaAlO}}_{3}$ are studied at room temperature. The experimental spectra are compared with the prediction of lattice-dynamical calculations and the lines observed are assigned to definite atomic vibrations. It is shown that…
Abstract Overlap integrals between HOMO’s of two non-parallel BEDT-TTF (bis(ethylenedithio)tetrathiafulvalene) molecules have been calculated. As the dihedral angle between the molecular planes decreases from 180° (parallel) to 90° (perpendicular), the overlap integral increases and attains a maximum around 90°. This…
The mechanical relaxation behavior and microstructure of a series of novel norbornyl−POSS organic−inorganic copolymers have been investigated. We have examined the influence on physical properties of both the weight fraction of POSS−norbornyl monomer and the corner group composition. POSS refers to the polyhedral olig…
Anisotropic strain broadening in X-ray line profile analysis means that the width of diffraction profiles of Bragg reflections is not a monotonous function of the diffraction angle. The lack of a physically sound model makes the interpretation of line broadening and the structure refinement procedure of Rietveld often…
Abstract The objective of this research was to show the reinforcing effects of nanofibers in an epoxy matrix and in a rubber matrix using electrospun nanofibers of PBI (polybenzimidazole). The average diameter of the electrospun fibers was around 300 nanometers, which is less than one tenth the diameter and 1/100 the…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTA Stable Neutral Hydrocarbon Radical: Synthesis, Crystal Structure, and Physical Properties of 2,5,8-Tri-tert-butyl-phenalenylKosaburo Goto, Takashi Kubo, Kagetoshi Yamamoto, Kazuhiro Nakasuji, Kazunobu Sato, Daisuke Shiomi, Takeji Takui, Mari Kubota, Tunetoshi Kobayas…
Multiwalled carbon nanotubes (MWNTs) have unique mechanical properties and are ideal candidates for high-performance composites. Elastic measurements, performed with an atomic force microscope, are described for MWNTs produced by two methods: the arc-discharge method and the thermal decomposition of hydrocarbons in th…
We have investigated the electronic structures of n - or p -type doped ZnO based on ab initio electronic band structure calculations. We find unipolarity in ZnO; n -type doping using Al, Ga or In species decreases the Madelung energy while p -type doping using N species increases the Madelung energy, in addition to ca…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTIntercalative Nanohybrids of Nucleoside Monophosphates and DNA in Layered Metal HydroxideJin-Ho Choy, Seo-Young Kwak, Jong-Sang Park, Yong-Joo Jeong, and Josik PortierView Author Information Department of Chemistry, Center of Molecular Catalysis Seoul National Universi…