Materials Literature
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Funktion(alis)iert: Organische Gruppen mit mehreren Alkoxysilansubstituenten werden in der Synthese mesoporöser organisch-anorganischer Hybridmaterialien verwendet (siehe Schema). Die entstehenden Systeme enthalten die organischen Bausteine als integralen Bestandteil der Porenwand. Je nach der Funktionalität der organ…
Time-resolved small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) analyses were used to study the isothermal crystallization and remelting of poly(ethylene isophthalate- co -terephthalate)s containing 0−10 mol % isophthalate unit. For each of the polymers considered, evidence of the formati…
2. Negative-index media 393 3. Wave propagation and refraction in left-handed media 394 4. Negative refraction and the causality principle 395
The structural evolution of regenerated Bombyx mori silk fibroin during shearing with a Couette cell has been studied in situ by synchrotron radiation small- and wide-angle x-ray scattering techniques. An elongation of fibroin molecules was observed with increasing shear rate, followed by an aggregation phase. The agg…
We propose an atomistic model for the nucleation of aluminum oxide on the Al(111) surface derived from first principles molecular dynamics simulations. The process begins with the dissociative adsorption of O2 molecules on the metal surface, which occurs via a "hot-atom" mechanism driven by the partial filling of the…
Nanostructures (nanotubes, nanowires, etc.) have been the object of intense theoretical and experimental investigations in recent years. Among these structures, helical nanosprings or nanocoils have attracted particular interest due to their special mechanical properties. In this work, we investigated structural prope…
The role of molecular structure, charge, and hydrophobicity in polyelectrolyte layer-by-layer assembly (LbL) of thin films has been studied using the model polypeptides poly-L-glutamatic acid (PLGA) and poly-L-lysine (PLL), quartz crystal microbalance (QCM), and circular dichroism spectroscopy (CD). The adsorption beh…
Tree-shaped molecules consisting of octa-p-phenylene as a stem segment and oligoether dendrons as a flexible head were synthesized and characterized. The molecular tree based on a small flexible head self-assembles into a lamellar structure, whereas the molecule based on a larger headgroup self-assembles into a discre…
The kinetics of exchange ofphenylethanethiolate ligands (PhC2S) of monolayer-protected clusters (MPCs, average formula Au140(PhC2S)53) by para-substituted arylthiols (p-X-ArSH) are described. 1H NMR measurements of thiol concentrations show that the exchange reaction is initially rapid and gradually slows almost to a…
Littoral diatom assemblages from different natural substrates (stones, mud, reeds) were used for estimating trophic status in seven perialpine lakes near Salzburg (Austria). Four trophic status indices were compared with the actual chemical data and the annual averages of total phosphorus concentrations. Diatom assemb…
It is shown that the shoving model expression for the average relaxation time of viscous liquids, according to which the activation energy is proportional to the instantaneous shear modulus, follows largely from a classical "landscape" estimation of barrier heights from curvature at energy minima. Although the activat…
We numerically investigate the interaction between two spherical particles in a nematic liquid crystal mediated by elastic distortions in the orientational order. We pay attention to the cases where two particles with equal radii R0 impose rigid normal anchoring on their surfaces and carry a pointlike topological defe…
A simple method for safely preparing Au nanoparticles of a few to 20 nm in diameter has been developed on the basis of chemical reduction of HAuCl 4 with glucose and fructose produced by the acidic hydrolysis of sucrose. The method includes seeding formation in the solid mixture of HAuCl 4 and sucrose via heat treatme…
The crystal structure of ${\mathrm{LiAlH}}_{4}$ and ${\mathrm{Li}}_{3}{\mathrm{AlH}}_{6}$ was determined by density-functional theory (DFT) projector augmented wave ground-state (0 K) minimizations with the generalized gradient approximation (GGA). These results were in excellent agreement with the crystal structure o…
Several recent studies have employed warm-water treatment of diatom cells to extract nominally bound extracellular polymeric substances. Where examined, the dominant neutral sugar in these extracts was glucose. In the present study, we sought to characterize the structure of the glucose-rich polymers in the water extr…
Exopolymers (EPS) are produced by unicellular and multicellular organisms. They consist largely of polysaccharides that hydrate rapidly on contact with water and link to form gels. EPS have many uses: in attachment; in locomotion on substrata; as a protection against predators, pathogens and changes in physico-chemica…
In diatoms, silica synthesis occurs by use of complex posttranslationally modified peptides, termed silaffins, and highly complex biological polyamine structures. Silaffin peptides have lysine residues that are modified to long-chain polyamine moieties of N-methyl derivatives of polypropylenimine to drive silica synth…
The spin Hall effect is a phenomenon of inducing spin current by an external electric field. We recently proposed that this effect can occur in p-type semiconductors without relying upon any disorder scattering [S. Murakami et al., Science 301, 1348 (2003)]. This intrinsic effect is due to the ``Berry phase in momentu…
Optical properties of GaAsN system with nitrogen concentrations in the range of 0.9-3.7% are studied by full-potential LAPW method in a supercell approach. The E+ transition is identified by calculating the imaginary part of the dielectric function. The evolution of the energy of this transition with nitrogen concentr…
Vanitas vanitatum et omnia vanitas: bubbles are emptiness, non-liquid, a tiny cloud shielding a mathematical singularity. Born from chance, a violent and brief life ending in the union with the (nearly) infinite. But a wealth of phenomena spring forth from this nothingness: underwater noise, sonoluminescence, boiling,…