Materials Literature
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The structures of the liquid crystalline chiral subphases exhibited by several materials containing either a selenium or sulphur atom have been investigated using a resonant x-ray scattering technique. This technique provides a unique structural probe for the ferroelectric, ferrielectric, antiferroelectric, and SmC(*)…
Alternating naphthyridine–pyrimidine strands self-organize into a helical conformation containing a strongly polar cavity. The binding of metal and ammonium cations promotes supramolecular self-assembly in a sort of effector-induced growth process to form polymolecular stacks (see schematic representation) and fibers…
A 3-D shape nonlinear optical chromophore encapsulated by highly-fluorinated dendrons exhibits significantly improved electro-optic properties and optical attenuation.
Orientierte Anlagerung macht's möglich: Einkristalline ZnO-Nanostäbchen von bis zu 500 nm Länge lassen sich schrittweise aus quasisphärischen Nanoteilchen herstellen. Erst nach der Bildung perlenkettenartiger Strukturen (Bild links) schließen sich die aggregierten Partikel beim Erhitzen zu Nanostäbchen zusammen (Bild…
Reaction of alpha-P(2)W(15)O(56)(12-) and Fe(III) in a saturated NaCl solution produces a trisubstituted Wells-Dawson structure with three low-valent metals, alpha-(Fe(III)Cl)(2)(Fe(III)OH(2))P(2)W(15)O(59)(11-) (1). Dissolution of this species into 1 M NaBr (Br(-) is non-coordinating) gives the triaquated species alp…
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…