Materials Literature
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The solid nematic equivalent of the Fredericks transition is found to depend on a critical field rather than a critical voltage as in the classical case. This arises because director anchoring is principally to the solid rubbery matrix of the nematic gel rather than to the sample surfaces. Moreover, above the threshol…
A Fibonacci-like terrace structure along a fivefold axis of $i\ensuremath{-}{\mathrm{Al}}_{68}{\mathrm{Pd}}_{23}{\mathrm{Mn}}_{9}$ monograins has been observed by Schaub et al. with scanning tunneling microscopy. In the planes of the terraces they see patterns of dark pentagonal holes. These holes are well oriented bo…
Abstract The crystal structure of single crystals of kaolinite from Keokuk, Iowa, was refined using data measured at the microfocus X-ray beamline at the ESRF, Grenoble, France (λ = 0.6883, T = room temperature). The volume of the crystals was 8 and 0.8 μm 3 , respectively. Unit-cell parameters are: a = 5.154(9) Å, b…
High yields of nanocrystals at ambient temperaturehave been attained for several inorganic salts such as ZnS and CuO. The authors report one-step, solid-state reactions between easily obtained starting materials such as CuCl2·2H2O and NaOH to give nanoparticles with narrow size distribution. The process is carried out…
Conjugated polymers such as polypyrrole (PPy) have potential use as artificial muscles or in microsystems such as valves for microfluid handling. One of the most important parameters in such uses is the magnitude of volume change during associated redox processes; however, until now, estimates have varied greatly. Ato…
A beta isolated from neuritic plaque and vascular walls of the brains of patients with Alzheimer's disease has been shown to contain significant quantities of A beta peptides which begin at residue 3Glu or 11Glu in the form of pyroglutamyl residues (A beta 3pE and A beta 11pE). To investigate the effects of these N-te…
An explanation of the varying (ultra)drawability of semicrystalline polymers is proposed, based on NMR evidence of αc-relaxation-associated helical jumps and chain diffusion through the crystallites of polyethylene and several similarly “αc-mobile” polymers; these include isotactic polypropylene, poly(ethylene oxide),…
Nanocomposites of high density polyethylene (HDPE), linear low density polyethylene (LLDPE) and highly branched polyethylene rubbers were prepared both by means of melt compounding and ethene homo- and copolymerization in the presence of layered silicates which were rendered organophilic via ion exchange with various…
Single crystals of Ba(ZrxTi1−x)O3 were grown by templated grain growth (TGG). Millimeter size single crystals of Ba(ZrxTi1−x)O3 were produced by heating a BaTiO3 crystal in contact with a sintered polycrystalline matrix of 4.5, 5.0, or 8.5 mol % Zr-doped barium titanate for 30 h at 1350 °C. To facilitate boundary migr…
The preparation of novel biotechnological materials from chitin and chitosan, and their properties are described. Their current applications and future prospects are discussed. © 1999 Society of Chemical Industry
Recombinant non-hydroxylated gelatins based on mouse type I and rat type III collagen sequences were secreted from the methylotrophic yeast Pichia pastoris, using the Saccharomyces cerevisiae alpha-mating factor prepro signal. Proteolytic degradation could be minimized to a large extent by performing fermentations at…
Divalent manganese, magnesium, and zinc fill unique roles in biological systems, despite many apparently similar chemical properties. A comparison of the liganding properties of divalent manganese, magnesium, and zinc has been made on the basis of data on crystal structures (from the Cambridge Structural Database and…
Using a criterion given by Banerjee [Phys. Lett. 12, 16 (1964)] to distinguish first-order magnetic transitions from second-order ones, we demonstrate that not all the title perovskites exhibit a first-order transition at their Curie temperatures ${T}_{C}.$ We observe that, although ${\mathrm{La}}_{2/3}{\mathrm{Ca}}_{…
Impedance spectra obtained on high‐performance Ni/yttria stabilized zirconia (YSZ) cermet anodes at 1000°C in gas mixtures are considered. An impedance arc with a characteristic frequency of about 10 to 100 Hz is related to finite diffusion limitation by considering the dependence on water partial pressure, apparent t…
We have investigated the magnetic and structural phase diagram of iron employing the full potential linear augmented plane-wave method within the generalized gradient approximation. Therefore, total-energy calculations have been performed together with investigations with varying $c/a$ ratio to check the phase stabili…
Two ambient-temperature molecule-based magnets (Curie temperatures Tc of ∼350 K and 372 K) are presented, which are the result of research to identify factors in synthesis that control the magnetic properties of compounds. The goal is to increase Tc. The magnetic properties of the two hexacyanochromate magnets are des…
We present the results of a large scale molecular dynamics computer simulation in which we investigated the static and dynamic properties of a silica melt in the temperature range in which the viscosity of the system changes from ${O(10}^{\ensuremath{-}2})$ P to ${O(10}^{2})$ P. We show that even at temperatures as hi…
The dependence of the morphology of macropores in p‐type silicon electrodes on formation parameters such as substrate doping density, electrolyte composition, and applied current density is investigated. The results are compared with the well‐understood case of electrochemical macropore formation on n‐type silicon ele…
Organic electroluminescent devices that emit polarized light will be useful as backlights in conventional liquid-crystal displays. The necessary high polarization ratios require, in turn, highly aligned emitters. The various methods of orientation are discussed, together with the materials to which they are applicable…
The preparation of micrometer to nanometer-sized building blocks that can be selectively derivatized is reported here. Segmented multi-metal rods of controllable length (see Cover) were fabricated by electroplating in porous template membranes. Additionally it is shown how the surface chemistry of different parts with…