Materials Literature
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Exciton luminescence was investigated in La-doped BaF2 crystals. Two luminescence bands at 4.26 and 3.82 eV related to excitons have been observed. The excitation spectrum of the 4.26 eV band of BaF2–LaF3 was similar to that of the exciton emission band of pure BaF2 crystals. The excitation spectrum of the 3.82 eV ban…
The title compound, C18H18N4, lies on an inversion center. The benzimidazolyl moiety is essentially planar. Intermolecular N—H⋯N hydrogen bonds give rise to an infinite helical chain structure, with the chains stacked by C—H⋯π and π⋯π interactions.
Quantum confinement effect has been the dominant approach guiding the search for light-emitting silicon. By first-principles total energy calculations of Si delta-doped with oxygen layers, however, we show that this generally accepted mechanism is ineffective. Instead, a different mechanism is proposed based on defect…
Lithium ions were electrochemically inserted into V 2 O 5 ·0.5H 2 O xerogel and studied with 7 Li magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. Two distinct lithium environments were resolved and assigned to lithium ions occupying either interfacial or intercalated sites in the V 2 O 5 ·0.5…
The site occupancy of hydrogen in Nb(74 at. %)-Mo(26 at. %) alloys is investigated at room temperature for hydrogen concentrations 0.016, 0.026, and 0.059 in the hydrogen--metal-atom ratio $([\mathrm{H}]/[M])$ by the channeling method utilizing a nuclear reaction ${}^{1}\mathrm{H}{(}^{11}\mathrm{B},\ensuremath{\alpha}…
The oxygen nonstoichiometry, transport properties, and structure stability of ZrO 2 -promoted SrCo 0.4 Fe 0.6 O 3 - δ (SCFZ) were investigated. The nonstoichiometry of SCFZ increased with increasing temperatures and decreasing oxygen partial pressures. The results of X-ray diffraction and oxygen desorption experiments…
Cubic boron nitride is synthesized from a hexagonal graphitic phase, the synthesis conditions being affected by chemical or intrinsic defects. The electronic contribution to this defect dependence is investigated using an ab initio local-density approach for the simple defects B, C, N, and O. Energy differences betwee…
Poly(γ-benzyl- l -glutamate) (PBLG) is a synthetic polypeptide with a rigid helical conformation in several solvents. Small-angle X-ray and neutron scattering measurements were used to study the reversible gelation process in semidilute isotropic solutions of PBLG in benzyl alcohol. Time-resolved measurements of the s…
Carbon nanotubes (CNTs) are an interesting class of nanostructures which can be thought of as arising from the folding of a layer of graphite (a graphene sheet) to form a hollow cylinder composed of carbon hexagons. However, practical applications are still limited by the intricate process of synthesis and the inabili…
Alanyl-alanine-derived poly(isocyanide)s possess a helical structure that persists even in aqueous media. These rigid macromolecules possess a regular distribution of carboxylic acid-terminated side chains which for the first time allows the study of the templating process involved in biomineralization using a shape-p…
The synthesis, structural characterisation and preliminary magnetic studies of a Co12 wheel are reported; the magnetic investigations reveal that the electronic ground state has a spin S = 6, which corresponds to ferromagnetic interactions between the twelve Co(II) ions.
We have investigated systematically the effects of various gas adsorbates (H2, N2, O2, and H2O) on the electronic structures and the field emission properties of open edges of single-walled carbon nanotubes by density functional calculations. All of the molecules, except N2, dissociate and chemisorb on open nanotube e…
We report here, for the first time, synthesis of anchored Pd complexes in mesoporous supports such as MCM-41 and MCM-48 as true heterogeneous catalysts for hydrocarboxylation of aryl olefins and alcohols to give excellent conversion ( approximately 100%) and regioselectivity ( approximately 99%) for 2-arylpropionic ac…
Modification induced by 110 MeV Ni ion irradiated thin film samples of C60 on Si and quartz substrates were studied at various fluences. The pristine and irradiated samples were investigated using Raman spectroscopy, electrical conductivity and optical absorption spectroscopy. The Raman data and band gap measurements…
Using an atom-vacancy exchange algorithm, we investigate the kinetics of the order-disorder transition in an fcc A_3B binary alloy model following a temperature quench from the disordered phase. We observe two clearly distinct ordering scenarios depending on whether the final temperature T_f falls above or below the o…
Codeposition of impurities during the growth of a vicinal surface leads to an impurity concentration gradient on the terraces, which induces corresponding gradients in the mobility and the chemical potential of the adatoms. Here it is shown that the two types of gradients have opposing effects on the stability of the…
Motivated by recent experiments we have carried out an Event Driven computer simulation of a diluted binary mixture of granular particles vertically vibrated in the presence of gravity. The simulations not only confirm that the kinetic energies of the two species are not equally distributed, as predicted by various th…
We present characterization data for linear poly(isoprene- b -styrene- b -ethylene oxide) (PI−PS−PEO) triblock copolymers containing equal volume fractions of PI and PS ( f PI = f PS ) and varying amounts of PEO, 0 ≤ f PEO ≤ 1 / 3 . Detailed characterization by TEM, SAXS, dynamic mechanical spectroscopy, static birefr…
Monte Carlo (MC) simulations of lattice models are a widely used way to compute thermodynamic properties of substitutional alloys. A limitation to their more widespread use is the difficulty of driving a MC simulation in order to obtain the desired quantities. To address this problem, we have devised a variety of high…
The effect of chitosan with different molecular weights as coatings for shelf-life extension of fresh fillets of Atlantic cod (Gadus morhua) and herring (Clupea harengus) was evaluated over a 12-day storage at refrigerated temperature (4 +/- 1 degrees C). Three chitosan preparations from snow crab (Chinoecetes opilio)…