Materials Literature
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The first direct in situ observations of the production and microsegregation of radiolytic interstitial oxygen resulting from electron beam irradiation of crystal and amorphous oxygen deficient ${\mathrm{SiO}}_{2}$ polymorphs has been made using cathodoluminescence (CL) microanalysis (spectroscopy and microscopy). Pre…
We report conclusive high resolution small angle x-ray scattering evidence that long DNA fragments form an untwisted line hexatic phase between the cholesteric and the crystalline phases. The line hexatic phase is a liquid-crystalline phase with long-range hexagonal bond-orientational order, long-range nematic order,…
The photo- and redox-active diaza ligand 1 and its doubly alkylated derivative 2 were obtained from perylene bisimides. The suitability of 1 for obtaining supramolecular architectures was confirmed by binding studies with carboxylic acids, zinc porphyrins, and metal ions.
Using molecular-beam-epitaxy growth techniques, we have synthesized ferromagnet/insulator/ferromagnet trilayer heterostructures with the “colossal” magnetoresistance material La1−xSrxMnO3 as the ferromagnet. These trilayer films were fabricated into magnetic tunnel junctions which exhibit magnetoresistance ΔR/R(H) of…
Two Ru-porphyrin-linked β-cyclodextrin units form the supramolecular system, which as an enzyme mimic for β,β-carotene 15,15′-dioxgenase binds two substrates of the enzyme with Ka>106 M−1 and selectively catalyzes the cleavage of the central carotinoid bond in the presence of tert-butylhydroperoxide (see picture). Mec…
Synthesis and modes of self-assembly are described for the tapered monodendritic molecules 3,4,5-nGi-X of generation i = 1, 2, 3 (see structures below) that contain multiple (CH2)nH alkyl chains on their periphery (n = 12, 14, 16) and a polar group X at the apex (X = COOH, COONa, COOCs, CO(OCH2CH2)3OH). These monodend…
Small-angle X-ray scattering measurements and UV/Vis titrations have been used to characterize a new water-soluble host – guest system based on oligoethyleneoxy-modified poly(propyleneimine) dendrimers. These experiments indicate that unique interactions between the host and guests lead to a specific location of the g…
A field-effect transistor (FET) with a channel length of ∼100 nm was constructed from a small number of individual V2O5 fibers of the cross section 1.5 nm×10 nm. At low temperature, the conductance increases as the gate voltage is changed from negative to positive values, characteristic of a FET with n-type enhancemen…
Ba 0.5 Sr 0.5 TiO 3 (BST) thin films grown on Si by an in situ ultraviolet-assisted pulsed laser deposition (UVPLD) technique exhibited significantly higher dielectric constant and refractive index values and lower leakage current densities than films grown by conventional PLD under similar conditions. X-ray photoelec…
We deposited epitaxial Ba0.4Sr0.6TiO3 (BST) films via laser ablation on MgO and LaAlO3 (LAO) substrates for tunable microwave devices. Postdeposition anneals (∼1100 °C in O2) improved the morphology and overall dielectric properties of films on both substrates, but shifted the temperature of maximum dielectric constan…
We report a dynamical study on the photoinduced cooperative changes of the spin configurations in single crystals of the organometal spin-crossover complex. In the photoswitching process between low- and high-spin states, nonlinear characteristics such as thresholdlike behavior, incubation period, and phase separation…
The optical properties of clusters with metallic spherical particles embedded in an insulating matrix are studied. A theoretical approach is proposed for the calculation of the macroscopic dielectric response for a collection of spheres at random positions embedded in a homogeneous medium. While accounting for the dip…
We study the domain structure in ferroelectric thin films with a "passive" (nonferroelectric) layer at the interface between the film and electrodes. An abrupt transition from a monodomain to a polydomain state has been found with the increase of the passive layer thickness d. The domain width changes very quickly at…
The fracture of materials is a catastrophic phenomenon of considerable technological and scientific importance. Here, we analysed experiments designed for industrial applications in order to test the concept that, in heterogeneous materials such as fiber composites, rocks, concrete under compression and materials with…
Photoluminescence (PL) properties of ZnO films grown on CaF2(111) with a low-temperature buffer layer by plasma assisted molecular beam epitaxy are investigated, in which lattice misfit tensile strain is expected to be compensated by the thermal compressive strain. The low-temperature buffer layer is further introduce…
The phase diagram of ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3}$, as a function of hole doping $x$ and tetragonal distortion $c/a$, which consists of ferromagnetic (FM), A-, C-, and G-type antiferromagnetic (AF) states, is obtained by the first-principles band structure calculations. Effects…
Ball milling is an important method for the preparation of materials both for the investigation of fundamental physical properties and for a number of possible commercial applications. In the present report, the basic principles of ball milling are discussed. This includes a brief overview of experimental techniques a…
ICRP 74 and ICRU 57 recommended conversion coefficients for use in radiological protection for electrons and photons of energies up to 10 MeV and for neutrons up to 180 MeV. For various purposes (radiation protection around high energy accelerators, shielding calculations, air crew dose assessment, space activity) con…
The problem of localized superconductivity has motivated the preparation of Mg 1− x Cu x O solid solutions with NaCl structure and 0.01≤ x ≤0.20, as well as a study of the magnetization and magnetic susceptibility χ in the 2–400 K temperature range and in magnetic fields of up to 5 T. The temperature dependence of χ i…
Characteristics of complex defects in semiconductors are calculated by the method of minimizing the free energy for the actual crystal. The influence of the electron subsystem on the impurity solubility is considered. The modeling of solidus curves is carried out in terms of binary association and clustering.