Materials Literature
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The two-state valence-bond charge-transfer (VB-CT) model for π-conjugated push–pull molecules is analyzed to yield several parameter-independent relations between vibrational and electronic hyperpolarizabilities. Ab initio computational tests show that these relations are not satisfied. As a byproduct of the ab initio…
Multilayer thin films composed of a positively charged protein and cationic polymer layers can be prepared on a solid surface against their electrostatic force of repulsion, by depositing avidin and biotin-labeled polymers [poly(ethyleneimine) (PEI), poly(allylamine) (PAA), or poly(amidoamine) (PAMAM) dendrimer] alter…
The principal mechanisms of Auger recombination of nonequilibrium carriers in semiconductor heterostructures with quantum wells are investigated. It is shown for the first time that there exist three fundamentally different Auger recombination mechanisms of (i) thresholdless, (ii) quasi-threshold, and (iii) threshold…
We have studied the structure and free energy landscape of a semiflexible lattice polymer in the presence of the surface of a polymer crystal. At low temperatures coexistence of two-dimensional integer-folded crystals is observed. As the temperature is increased there is a transition from these crystalline configurati…
CdS microcrystals of various sizes embedded in a germanium dioxide glass matrix have been studied by Raman scattering and optical absorption under high pressure up to about 9 GPa. Structural phase transition of the CdS microcrystals from wurtzite to rock salt phase was observed at a pressure higher than 6 GPa, which i…
The vibrational behaviour of vacancies in bcc metals is discussed with the use of the Green function method. In particular the local densities of states of the first and second neighbours of the vacancy, the atoms most affected by the defect, in , Mo and W have been calculated. The local density of states of the first…
Blue, green and red up-conversion luminescences at around 490, 545 and 650 nm, which result from the , and transitions, respectively, were observed in co-doped -based fluoride glasses under 800 nm excitation. Among these up-conversion luminescences, the green emission was extremely strong and the blue and red emission…
Homogeneous alignment of liquid crystals can be achieved by a technique using polyimide films and in situ exposure to linearly polarized ultraviolet (LPUV) light during imidization. The alignment layers prepared by this method exhibit higher thermal stability while requiring shorter processing time than the convention…
The theory of the nonlinear dielectric response to an external dc electric field is developed in the random-field-theory framework. The equations describing the dependence of the order parameter and the dielectric susceptibility (both linear and nonlinear) on the temperature, dc electric field, frequency, parameters o…
We have investigated the magnetoresistance of graphite in fields of up to 55 T over the temperature range 1--10 K and obtained clear indications of a reentrant transition from the field-induced density-wave state to the normal state. The reentrant transition is attributed to a Landau subband crossing the Fermi level.…
Atomic-resolution $Z$-contrast images provide direct images of chemical disorder and columnar vacancies in an ideal Al-Ni-Co decagonal quasicrystal. Chemical disorder occurs in the central ring of the 2 nm clusters and involves both Al and Ni(Co) atoms. Columnar vacancies are observed in the form of closely spaced, ha…
thin films prepared by pulsed-laser ablation have been investigated by high-resolution x-ray diffraction, x-ray pole-figure, Rutherford backscattering/channelling and electrical measurements. The results show that films deposited on (0001) sapphire substrates grow with well determined orientations in the plane: and ou…
We report the activation field characteristics of (La,Sr)CoO3/Pb(Nb,Zr,Ti)O3/(La,Sr)CoO3 capacitors with areas varying from 13 to 9600 μm2. Switching properties such as maximum current and switching time depend on the capacitor area and measuring circuit elements, but the activation field is independent of capacitor a…
For the perovskites that show colossal-magnetoresistance (CMR) behaviour, we use the global instability index, R1 , as a measure of the influence of the static lattice effects on the magnetic and electrical properties. These effects arise from the size mismatch between the ions at A and Mn sites as well as the size di…
The origin of the relative stability of the cubic, tetragonal, and monoclinic phases of zirconia $(\mathrm{ZrO}{}_{2})$ is investigated. To obtain accurate energies we adopt a new all-electron bandstructure approach within the local density approximation, based on muffin tin orbitals. We also develop a self-consistent…
Single-walled carbon nanotube (SWNT) tips have been used to image nanostructures with high resolution. Studies of gold nanocrystal standards showed that SWNT tips provide a significant improvement in lateral resolution with respect to multi-walled nanotube tips and microfabricated Si tips. The nanotube tips were also…
Graphite nanofibers were synthesized and their hydrogen desorption and adsorption properties are reported for 77 and 300 K. Catalysts were made by several different methods including chemical routes, mechanical alloying, and gas condensation. The nanofibers were grown by passing ethylene and H2 gases over the catalyst…
We study the resonant transmission of light through Fibonacci dielectric multilayers (FDM). Making use of a transfer matrix renormalization technique [E. Maciá and F. Domı́nguez-Adame, Phys. Rev. Lett. 76, 2957 (1996)] we obtain closed analytical expressions for the transmission coefficient under arbitrary incidence a…
Zero-field electrical resistivity over the temperature range of 4–300 K and magnetoresistance in magnetic fields of up to 12 T have been measured in Gd5(Si1.8Ge2.2). This system undergoes a first-order magnetostructural transition at TC≅240 K, from a high-temperature paramagnetic to a low-temperature ferromagnetic pha…
The swelling and viscoelastic behaviors of samples of purified arterial elastin were investigated to develop a model for studying the viscoelastic behavior of elastin. Two osmotic stress models were used: the vapor phase model (VPM), in which the stress on the elastin sample was applied through the vapor phase by equi…