Materials Literature
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The dependence of the domain structure on poling for (001)-oriented Pb(Mg1∕3Nb2∕3)O3-x%PbTiO3 crystals with x=20, 30, 35, and 40 has been investigated by scanning force microscopy in the piezoresponse mode and by polarized optical microscopy. The results demonstrate a domain hierarchy on various length scales, ranging…
Dielectric spectroscopy measurements over a broad range of temperature and pressure were carried out on poly(oxybutylene) (POB), a type A polymer (dielectrically active normal mode). There are three dynamic processes appearing at lower frequency: the normal and segmental relaxation modes and a conductivity arising fro…
Teamarbeit: Materialien aus mesoporösen Silica-Nanokugeln (MSNs), die mit einer allgemeinen Säuregruppe und einer Basengruppe in unterschiedlichen relativen Konzentrationen funktionalisiert sind, fungieren als kooperative katalytische Systeme. Die ermittelten Umsatzzahlen sprechen dafür, dass die Säuregruppen gemeinsa…
In the emerging field of spin-electronics ideal ferromagnetic electron sources would not only possess a high degree of spin polarization, but would also offer control over the magnitude of this polarization. We demonstrate here that a simple scheme can be utilized to control both the magnitude and the sign of the spin…
A simple ten-parameter interatomic potential model is described that is capable of accurately reproducing the static and dynamical properties of complex oxides. The accuracy of this model stems from the crystal-chemical bond-valence theory of ionic and covalent bonding. The development of a specific variant of this mo…
Crystalline erbium(Er)-doped zinc oxide thin films have been grown by pulsed-laser deposition and were analyzed by the complementary use of Rutherford backscattering spectroscopy, x-ray diffraction analysis, atomic force microscopy, and photoluminescence. The composition, structure, and surface morphology of films wer…
The elastic modulus of B19’ shape-memory NiTi was determined using three techniques; from the response of lattice planes measured using in situ neutron diffraction during loading, instrumented indentation using a spherical indenter and macroscopic extensometry. The macroscopic measurements resulted in a modulus of 68…
Complementarity between different techniques (magnetization, HF-HFEPR, FDMRS) and angular-overlap-model calculations allow the precise determination of the spin-Hamiltonian parameters in an isolated octahedral NiII complex (see structure), which exhibits the largest easy axis magnetic anisotropy reported to date (D=−1…
Different morphological patterns of copper sulfide crystals, e.g., flowers, distorted rods (rice, grainlike morphology), and spaghetti-like and spherical microparticles have been successfully synthesized using different organic solvents, namely, ethylenediamine, ethyleneglycol, and ethanol, by a solvothermal process.…
A neural network/trajectory approach is presented for the development of accurate potential-energy hypersurfaces that can be utilized to conduct ab initio molecular dynamics (AIMD) and Monte Carlo studies of gas-phase chemical reactions, nanometric cutting, and nanotribology, and of a variety of mechanical properties…
Abstract Infrared and Raman spectroscopic measurements were performed in order to investigate the 90%[ x B 2 O 3 (1 − x )Bi 2 O 3 ]10%MO glasses structure, where MO = Fe 2 O 3 and V 2 O 5 , with different Bi/B nominal ratios (0.07⩽ x ⩽0.625) and to obtain valuable information about the competitive role of the componen…
Although vascular bypass grafting remains the mainstay for revascularization for ischemic heart disease and peripheral vascular disease, many patients do not have healthy vessels suitable for harvest. Thus, prosthetic grafts made of synthetic polymers were developed, but their use is limited to high-flow/low-resistanc…
We report a GaAs/AlAs superlattice parametric oscillator. It was pumped by a microwave field (power few mW) and produced 3rd harmonic radiation (frequency near 300 GHz). The nonlinearity of the active superlattice was due to Bragg reflections of conduction electrons at the superlattice planes. A theory of the nonlinea…
We discuss the use of the magnetic force theorem (MFT) using different reference states upon which the perturbative approach is based. Using a disordered local moment (DLM) state one finds goo d Curie (or Neél) temperatures, and good energetics for planar spin spirals in the 3d magnets Fe, Co (fcc), Mn, Cr. On the oth…
X-ray diffraction microscopy (XDM) is a new form of x-ray imaging that is being practiced at several third-generation synchrotron-radiation x-ray facilities. Although only five years have elapsed since the technique was first introduced, it has made rapid progress in demonstrating high-resolution threedimensional imag…
We present the magnetization energy and magnetic moments of 3d monowires aligned along the step edges of Pt (533) and (322) vicinal substrates. We employ an electronic structure method which scales linearly with the size of the system. This allows us to treat with ease both ferromagnetic and antiferromagnetic solution…
If a body is resting on a flat surface, the maximal static friction force before motion sets in is reduced if an external torque is also applied. The coupling between the static friction force and static friction torque is nontrivial as our studies for a tripod lying on horizontal flat surface show. In this article we…
We report the operation of a Bloch oscillator. The active medium was a staticvoltage driven, doped GaAs/AlAs superlattice which was electromagnetically coupled to a resonator. The oscillator produced tuneable microwave radiation (frequency ~ 60 GHz; power ~ 0.5 mW; efficiency ~ 4 %). The gain (~ 10^4 /cm) was due to t…
An extremely simple biomimetic oxidation system, consisting of mixing metal complexes of amphiphilic corroles with serum albumins, utilizes hydrogen peroxide for asymmetric sulfoxidation in up to 74% ee. The albumin-conjugated manganese corroles also display catalase-like activity, and mechanistic evidence points towa…
A team effort: Mesoporous silica nanosphere (MSN) materials bifunctionalized with a general acid group and a base group in various relative concentrations are described and shown to function as cooperative catalytic systems. The turnover numbers observed indicate that the acid groups can activate substrates in coopera…