Materials Literature
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It is shown that the spectrum of the thermal surface height fluctuations on supercooled liquid close to the glass transition contains a narrow quasielastic component, which desribes slow fluctuation freezing in at the glass transition. The spectrum is obtained from a dynamic susceptibility which is calculated using th…
We performed a first-principles molecular dynamics study of liquid ${\mathrm{SiO}}_{2}$ at a temperature of 3500 K, followed by a rapid quench to 300 K obtaining a perfectly chemically ordered amorphous network. Structural and electronic properties of our amorphous sample are in good agreement with neutron diffraction…
Abstract Die Untersuchung der thermodynamischen Eigenschaften und der Reaktivität neu synthetisierter Substanzen ergibt interessante Einblicke in deren Chemie. Mit der Thermischen Analyse erhält man bei kleinen Probenmengen (oft nur wenigen Milligramm) umfangreiche Informationen. Daneben können die aus der Thermischen…
“The metallic bond still lives!” maintains the author of this highlight. In two recent papers theoreticians argue against the concept of the metallic bond as a distinct type of bond, and favor treating it as a limiting case of the covalent bond based on ab initio descriptions of bonding in solids. Still, J. C. Schön i…
The rate of intramolecular triplet energy transfer upon excitation of the RuII unit in the binuclear complex 1 decreases by roughly a third when the alkyne spacer is extended by a second ethynyl group (complex 2). The metal—metal distance increases by 2.4 Å, and correspondingly the attenuation factor for electron exch…
The cover picture shows the arrangement of two 1:1 complexes composed of a cyclic zinc porphyrin tetramer (Zn4−1) and a central meso-tetra-4-pyridyl-porphyrin unit (H2-Py4P) in the solid state (view along the c axis; purple = N, blue = C, yellow = Zn). The central porphyrin ligand, which is coordinated to each zinc ce…
Site-directed mutagenesis and Laue diffraction data to 2.5 A resolution were used to solve the structures of two sequential intermediates formed during the catalytic actions of isocitrate dehydrogenase. Both intermediates are distinct from the enzyme-substrate and enzyme-product complexes. Mutation of key catalytic re…
Locked into a tub geometry, the pentaporphyrin array illustrated has a well-defined conformation both in solution and in the crystal. Self-assembly of this light-harvesting antenna model quenches the fluorescence of both the central tetrapyridylporphyrin unit and the zinc porphyrin tetramer.
The reversible photochemical conversion between the open form 1, a strong fluorophore, and the closed form containing a central, hexyl-substituted six-membered ring, which fluoresces only weakly, makes modulation of emitted light possible. This readily adjustable system is of interest for optical data storage. R = CH,…
At low temperatures, liquid crystal-like arrays made up of inorganic-cluster and organic molecular units readily undergo reversible lyotropic transformations. Gemini surfactants, with two quaternary ammonium head groups separated by a methylene chain of variable length and with each head group attached to a hydrophobi…
We have prepared superconducting YBa/sub 2/Cu/sub 3/O/sub 7/ and ferromagnetic oxide La/sub 0.67/Ba/sub 0.33/MnO/sub 3/ hetero-epitaxial multilayer samples by pulsed laser deposition. X-ray diffraction and ion channeling results indicate that epitaxial growth of ferromagnetic La/sub 0.67/Ba/sub 0.33/MnO/sub 3/ films h…
The ferroelectricity of KDP in low temperature region is discussed quantitatively on the basis of the dipole interaction among the constituent ions. By taking account of the dipole interaction it can be shown that the spontaneous polarization Ps is mainly induced by the shift of the H-atoms perpendicular to P through…
SHOCK®: Injury, Inflammation, and Sepsis: Laboratory and Clinical Approaches includes studies of novel therapeutic approaches, such as immunomodulation, gene therapy, nutrition, and others. The mission of the Journal is to foster and promote multidisciplinary studies, both experimental and clinical in nature, that cri…
The present work describes the resonance method for measurement of a low-frequency (about 105 Hz) complex shear modulus of liquids by the use of a piezoquartz crystal. The problem of interaction of an oscillating system of the type piezoquartz-liquid interlayer-cover plate is analyzed. From the analysis of the problem…
The effect of addition of several nonnematic solute to nematic liquid crystal 5CB was studied. We found the increase of nematic-isotropic phase transition temperature in ANB/5CB mixture, contrary to the usually observed depression. The results were analyzed by a mean field treatment of mixture.
The prototypical nuclear fuel of the New Production Modular High-Temperature Gas-Cooled Reactor (NP-MHTGR) consists of spherical TRISO-coated particles suspended in graphite cylinders. The coating layers surrounding the fuel kernels consist of pyrolytic carbon layers and a silicon carbide (SiC) layer. These coating la…
A calculation model to study atomic layer deposition (ALD) in low-pressure channel-type CVD reactor with many parallel substrates is described. The calculations are based on continuity equation and kinetic equation for surface coverage. Formation of a steady-state adsorption wave propagating between the substrates dur…
A thin plastic cell containing the ferroelectric liquid crystal ZLI3654 (4 μm) was placed edge-on to a pin-hole collimated horizontal X-ray beam. In this way, the smectic layers were brought into register. Subsequently, triangular voltage waves with various peak (V p) values were applied across the cell and diffractio…
The chemical vapour deposition of SiC-based ceramics from the CH3SiCl3-H2 precursor is investigated on the basis of large scale experimental and theoretical approaches. The use of a vetirtical cylindrical hot-wall LPCVD reactor permits to get a wide isothemal reaction zone with a creeping laminar flow around the subst…
The corrosion behavior of annealed and hard-drawn copper pipes was studied in soft tap water at room temperature. The work was carried out under stagnant and flow conditions on short- and long-term bases using electrochemical techniques. As-received copper pipes did not suffer from pitting regardless of whether the wa…