Materials Literature
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Molybdän-Monster: Die Herstellung eines gewaltigen Molybdän-Clusters wird beschrieben, wobei große Untereinheiten jeweils unterschiedliche lokale Symmetrien aufweisen (die Farben im Bild repräsentieren die kleineren Molybdat-Fragmente). Verknüpft werden diese Molybdat-Fragmente durch einen „Split-and-Link“-Prozess auf…
We present high-resolution measurements of the coefficient of thermal expansion $\ensuremath{\alpha}(T)=\ensuremath{\partial}\mathrm{ln}l(T)/\ensuremath{\partial}T$ of the quasi-two-dimensional (quasi-2D) salts $\ensuremath{\kappa}\ensuremath{-}(\mathrm{BEDT}\ensuremath{-}\mathrm{TTF}{)}_{2}X$ with $X=\mathrm{Cu}(\mat…
We discuss crack propagation along the interface between two dissimilar materials. The crack edge separates two states of the interface, ``stick'' and ``slip''. In the slip region we assume that the shear stress is proportional to the sliding velocity, i.e. the linear viscous friction law. In this picture the static f…
Ein Wasser-Kontaktwinkel von über 170° kennzeichnet die Oberfläche von unbehandelten, ausgerichteten Polyacrylnitril(PAN)-Nanofasern (das Bild zeigt einen Querschnitt durch die Nanofasern direkt nach der Synthese). Die Nanofasern wurden mittels einfachem Extrudieren einer PAN-Lösung durch ein anodisches Aluminiumoxidt…
Interaction of the homotritopic guest 1,3,5-tris[p-(benzylammoniomethyl)phenyl]benzene tris(hexafluorophosphate) (1a) with dibenzo-24-crown-8 (DB24C8) leads to the sequential self-assembly of [2]-, [3]-, and [4]-pseudorotaxanes 7a, 8a, and 9a, respectively. The self-assembly processes were studied using NMR spectrosco…
We present a continuum theory which describes the fast growth of a crack by surface diffusion. This mechanism overcomes the usual cusp singularity by a self-consistent selection of the crack tip radius. It predicts the saturation of the steady state crack velocity appreciably below the Rayleigh speed and tip blunting.…
The relationship between effective conductivity and cell structure of polyethylene/carbon composites as well as between effective conductivity and spatial distribution of carbon black are discussed. Following Yoshida's model both structures can, in a way, be said to be intermediate between the well known Maxwell-Garne…
Efficient binding of biomacromolecular surfaces by synthetic systems requires the effective presentation of complementary elements over large surface areas. We demonstrate here the use of mixed monolayer protected gold clusters (MMPCs) as scaffolds for the binding and inhibition of chymotrypsin. In these studies anion…
Suppose granular material is shaken vertically with z(t)=A_0 cos(ω_0 t). Can we expect to find convection if A_0ω_0^2 < g? By means of theoretical analysis and computer simulation we find that there is no critical Γ=|A_0|ω_0^2/g for the onset of convection. Instead we propose a modified criterion which coincides with…
Bifunctional ureido-s-triazines provided with penta(ethylene oxide) side chains are able to self assemble in water, leading to helical columns via cooperative stacking of the hydrogen-bonded pairs (DADA array). Monofunctional ureido-s-triazines do not form such helical architectures. The presence of a linker, covalent…
Introducing poly(ethylene oxide) surfactant to aluminum hydrate colloids can effectively direct the crystal growth of boehmite and the crystal morphology of final γ-alumina crystallites. Fibrous crystallites of γ-alumina about 3−4 nm thick and 30−60 nm long are obtained. They stack randomly, resulting in a structure w…
We have determined the complete 1,694,969-nt sequence of the GC-rich genome of Methanopyrus kandleri by using a whole direct genome sequencing approach. This approach is based on unlinking of genomic DNA with the ThermoFidelase version of M. kandleri topoisomerase V and cycle sequencing directed by 2'-modified oligonu…
Large-pore cubic (Im3m) mesoporous silica single crystals have been synthesized by using commercial nonionic block copolymers as templates and inorganic salts as additives. These single crystals possess exclusively uniform rhombdodecahedron shapes ( approximately 1 mum) with approximately 100% yield. The mesopore latt…
Molybdenum monsters: A huge molybdenum cluster, comprising large areas with different local symmetry (in the picture different colors represent different (smaller) Mo fragments) is prepared and characterized. Molybdate fragments, which can tolerate a change of electron density at various positions, can be linked in a…
A water contact angle exceeding 170° is exhibited by the surface of aligned polyacrylonitrile (PAN) nanofibers without any surface treatment (the picture shows a cross-sectional view of the as-synthesized nanofibers). The nanofibers were obtained by simply extruding a PAN solution through an anodic alumina template in…
Several surfactant-like peptides undergo self-assembly to form nanotubes and nanovesicles having an average diameter of 30-50 nm with a helical twist. The peptide monomer contains 7-8 residues and has a hydrophilic head composed of aspartic acid and a tail of hydrophobic amino acids such as alanine, valine, or leucine…
Twelve derivatives of peptide-amphiphile molecules, designed to self-assemble into nanofibers, are described. The scope of amino acid selection and alkyl tail modification in the peptide-amphiphile molecules are investigated, yielding nanofibers varying in morphology, surface chemistry, and potential bioactivity. The…
Oriented attachment is the key: Single crystalline ZnO nanorods with lengths up to 500 nm could be prepared in a stepwise manner from quasi-spherical nanoparticles. Only after the formation of pearl-chain-like structures (left), do the aggregated particles fuse upon heating to form nanorods (center and right).
Corrosion and dezincification of α-brass (35.9% Zn) in acid chloride solutions in the absence and presence of 8-quinolinol (C9H6NOH) (0.1 mM to 5.0 mM) were studied after 1-week immersion by mass loss and solution analysis. The severe dezincification was found to decrease substantially in the presence of 8-quinolinol,…
2-Phenylisoindole was investigated as the rigid core unit in a series of asymmetric mesogenic molecules. When the 2-phenylisoindole core was terminated with a hexyl tail, no mesophase formation could be observed. When 4-n-(tridecafluorohexyl) was used, however, both monotropic and enantiotropic phase behaviour were ob…