Materials Literature
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We study transport properties of Fibonacci semiconductor superlattices in a uniform magnetic field (B) applied along the growth direction. Complicated magnetoresistance oscillations which do not vary periodically in 1/B are found. A field-dependent metal-insulator transition is predicted, and it is shown that the magn…
Novel densely crosslinked polycarbosiloxanes were obtained by using functional branched prepolymers. Two types of soluble prepolymers were prepared from di- and trifunctional alkoxysilane monomers via cohydrolysis/condensation and for both final crosslinking occurred via hydrosilylation. The prepolymers having only vi…
We investigate the dynamics of an ideal polymer chain which is tethered with one of its ends to an impenetrable interface. Due to the geometric restrictions the relaxation of modes perpendicular to the interface differs significantly from that of modes parallel to it. A superposition of both components leads to a mark…
A simple tight-binding model is used to calculate the energy levels of CdSe quantum dots for two distinct crystal structures: the wurtzite and the zinc-blende structure. Comparison of both level schemes gives an estimate of the shift in energies due to the interior bonding geometry of the lattice structure. Our model…
The quasi-two-dimensional metal \ensuremath{\eta}-${\mathrm{Mo}}_{4}$ ${\mathrm{O}}_{11}$ undergoes two successive charge-density-wave transitions at 109 and 30 K, with corresponding changes in the electronic structure. Measurements of the magnetoresistance, Hall effect, and magnetization, in magnetic fields of up to…
BaTiO3 (BT) thin films were grown by a molecular-beam-epitaxy method using an oxygen radical source. BaO and TiO2 layers were alternately deposited on SrTiO3 (001) (ST) substrates, and the structure of the thin films obtained was evaluated by x-ray diffraction, reflection high-energy electron diffraction, transmission…
Quantum ab initio calculations and quantum semiempirical molecular-dynamics simulations were employed to study reconstructions of (100) diamond surfaces in the presence of hydrogen and oxygen. The results indicate that the energetically most favorable structures of oxygenated surfaces are those with chemisorbed hydrox…
A method for generating a full backbone protein structure from the coordinates of α-carbons, is presented. The method extracts information from known protein structures to generate statistical positions for the reconstructed atoms. Tests on a set of proteins structures show the algorithm to be of comparable accuracy t…
Experiments have shown that phase separation during the growth of solid films by molecular beam epitaxy (MBE) is a phenomenon seen in a variety of systems. We study a MBE process where two types of particles are deposited simultaneously, and where the interatomic potential energy leads to phase separation. From a micr…
The effect of microstructural disorder, such as variations in grain size and in the height of the electrostatic potential at grain boundaries, on current flow in varistors has been simulated by computing the currents in a network of grain boundaries each of which can be described by nonlinear electrical characteristic…
On the basis of an extended configuration-interaction description of the lowest singlet excited states, we investigate the third-order nonlinear optical response of the \ensuremath{\mathrm{B}}-carotene molecule by means of the sum-over-states approach. We first uncover the nature of the electronic states contributing…
We have used a density-functional-based approach to study the response of silicon clusters to applied electric fields. For the dynamical response, we have calculated the Raman activities and infrared (IR) intensities for all of the vibrational modes of several clusters (${\mathrm{Si}}_{\mathrm{N}}$ with N=3-8, 10, 13,…
Control of the internal morphology of wet-spun fibers from a fluorinated polyimide has been achieved by varying the rate of polymer coagulation through adjustments in nonsolvent/solvent miscibility and precipitation strength of the coagulation bath. Filament internal morphologies ranged from very porous or sponge-like…
To define in detail the molecular mechanism of NAD+-dependent formate dehydrogenase, the pH dependences of various kinetic and spectroscopic parameters have been studied: Vmax, Km (NAD+), Km (formate), inhibition constants for structural analogues of substrate (NO3-) and product (CNS-, CNO-, N3-), CD and fluorescence…
Photoemission from the sp band of Ag(100) is significantly affected by surface effects. The dominant surface contribution at low-photon energies is derived from a \ensuremath{\nabla}\ensuremath{\cdot}A term in the optical-transition matrix element which gives rise to a significant amplitude for indirect transitions. T…
In CuCl nanocrystals we have observed two luminescence bands associated with free and bound biexcitons in a high-density excitation at 2 K. We also observed, in subpicosecond pump-and-probe measurements, an optical gain and induced absorption at the energy position of the bound biexciton luminescence band, and another…
Raman-scattering measurements have been carried out for crystals of the ${\mathrm{RTiO}}_{3}$ (R=La,Ce,Pr,Nd,Sm,Gd) system whose members are Mott-Hubbard insulators. ${\mathrm{RTiO}}_{3}$ has an orthorhombically distorted perovskite unit cell. The distortion increases systematically from ${\mathrm{LaTiO}}_{3}$ to ${\m…
Results of surface photovoltage spectroscopy on free-standing porous silicon films fabricated from boron-doped Si wafers of various resistivities are presented. We find that all the films have bandtails, which are about 0.3 eV wide, and their optical band gap is about 2 eV. The majority carriers in the strongly lumine…
Segregation at GaAs/AlAs (001) heterointerfaces has been studied experimentally by an in situ electron diffraction technique during molecular-beam epitaxy and by ex situ transmission electron microscopy. Whereas the GaAs-on-AlAs interface is abrupt, we find Ga segregating up to 20 crystal planes when depositing AlAs o…
Sequential anionic polymerization of styrene and divinylbenzene (DVB) is known to lead to the formation of star-shaped polymers. This ‘arms-first’ method has been widely used and studied. It is known that this polymerization forms stars with anionically active cores. This article is concerned with the attempt to make…