Materials Literature
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Absorption, excitation and emission spectra and lifetime measurements in cerium-doped lanthanum fluoride single crystals were obtained using both one- and two-photon spectroscopy techniques. It is shown that two kinds of fluorescent centres are present. In weakly doped systems, a rapid fluorescence around 300 nm domin…
The critical behavior of sliding charge-density waves just above threshold is analyzed. In 4-\ensuremath{\epsilon} dimensions, the exponent \ensuremath{\zeta}, defined through ${\mathit{I}}_{\mathrm{CDW}}$\ensuremath{\sim}(V-${\mathit{V}}_{\mathit{T}}$${)}^{\mathrm{\ensuremath{\zeta}}}$, is found to be 1-\ensuremath{\…
Strain compensation is an important aspect of heterostructure engineering. In this letter, we discuss the synthesis of pseudomorphic Si1−yCy and Si1−x−yGexCy alloy layers on a silicon (100) substrate by molecular beam epitaxy using solid sources and the controlled strain compensation that results from the introduction…
The common observation of cellular substructure ((1 ÷ 10 -2 )mm) at the sea-ice-ocean interface is explained by modelling the natural solidification of seawater as that of a dilute H 2 O-NaCl solution. Linear and nonlinear perturbation theories reveal that the one-dimensional planar steady state is morphologically uns…
Raman-scattering experiments have been carried out on stage-2 silver-intercalated ${\mathrm{TiS}}_{2}$ single crystals. Below a transition temperature near 300 K, the intercalated silver atoms become ordered in a structure that produces a \ensuremath{\surd}3a\ifmmode\times\else\texttimes\fi{} \ensuremath{\surd}3a\ifmm…
Abstract The degrees of swelling of rigid aromatic polyamide networks in various solvents, nonsolvents, and solvent mixtures were used to determine their solubility parameters. This was made possible because of the amorphous nature of the rigid networks and the low levels of intersegmental H‐bonding. The solubility pa…
Abstract The effect of low dose (1–20 Mrad) γ‐irradiation on five fluoropolymers (PVF, PVDF, ETFE, FEP, PFA), differing in fluorine content and chain structure, was studied. The radiation effect, reflected by changes in thermal and mechanical properties, as well as NaOH etched surface morphology, was investigated. The…
We present the results of a study of solid–fluid phase equilibria in systems of hard dumbbells for three values of the dumbbell bond length. Monte Carlo simulations were used to calculate the equation of state and Helmholtz free energy. Four orientationally ordered solid phases have been considered—the α-N2 structure…
We demonstrate that ${\mathrm{CdS}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Se}}_{\mathit{x}}$ nanocrystals embedded in glass suffer compressive strain which increases as the crystallite radius decreases. A model based on the dependence of the cluster surface free energy on the surface-to-volume ratio explains…
The optical spectra of actinide ions in the compound AnCl3 and doped into single-crystal LaCl3 were interpreted in terms of transitions within 5fN configurations. Energy-level calculations were carried out using an effective-operator Hamiltonian, the parameters of which were determined by fitting experimental data. At…
Small unilamellar vesicles (SUVs), consisting of highly purified distearoyl phosphatidylcholine and cholesterol (2:1 mol ratio) selectively increased the delivery of entrapped daunorubicin to solid tumors in vivo. When measured against free drug, SUV-entrapped daunorubicin produced a nearly 10-fold increase in tumor u…
Electronic structure and energetics of (0001) and (11\ifmmode\bar\else\textasciimacron\fi{}02) surfaces of sapphire, \ensuremath{\alpha}-${\mathrm{Al}}_{2}$${\mathrm{O}}_{3}$, were calculated using the self-consistent-field discrete variational (DV) method in the local-density framework. Clusters of a size of 70--120…
We show that low-temperature (230--390 \ifmmode^\circ\else\textdegree\fi{}C) desorption of hydrogen from 0.1 \ensuremath{\Omega} cm p-type porous Si structures leads to a redshift and gradual disappearance of the photoliminescence (PL). Furthermore, no blueshifting of the PL peaks is apparent with pore-widening treatm…
High-porosity porous silicon, after electrochemical oxidation, is a stable and highly reproducible luminescent material with a luminescence quantum efficiency as high as 3% at room temperature. Luminescence decay rates as long as several hundreds of microseconds show that radiative and nonradiative processes both have…
We present a detailed method to construct uniform meshes for fast Fourier transforms in electronic-structure calculations. We show that a drastic reduction in the mesh size can be frequently achieved by using an unconventional set of primitive lattice vectors. The same method can be applied also to obtain optimum sets…
The optical propagation in linear tapered waveguides is studied using both the beam propagation method as a non-modal technique and for local normal mode analysis. The comparison between the results obtained by the two techniques gives a good physical understanding of the transient behaviour of the optical field in th…
The excess charge relaxation in electret structures based on Teflon-FEP films, particularly the charge behaviour in the region of polymer-metal contact, has been investigated. Measurements were made using both the standard electret techniques and a special experimental method, based on observation of the partial recov…
In an attempt to produce polymeric pyroelectric Langmuir-Blodgett films, three derivatives of a hexadec-1-ene-maleic anhydride alternating polymer and two poly-(vinyl pyridine) derivatives have been deposited as alternate-layer films using a two-compartment trough. 1-Docosylamine and 22-tricosenoic acid were also alte…
A surface having a spatial gradient in its surface free energy was capable of causing drops of water placed on it to move uphill. This motion was the result of an imbalance in the forces due to surface tension acting on the liquid-solid contact line on the two opposite sides ("uphill" or "downhill") of the drop. The r…
The crystal structures and site-populations of 12 richterites have been refined to R indices of 1-2% using single-crystal MoKα X-ray diffraction data. Potassium-fluor-richterites from lamproites are characterized by [4] (Si+Al) sums less than 8.0 apfu (atoms per formula unit), suggesting the presence of other isomorph…