A Main‐Chain de Vries Smectic Liquid Crystal Polymer Prepared by Hoveyda–Grubbs Catalyst Initiated Acyclic Diene Metathesis Polymerization

A main‐chain liquid crystalline polymer has been obtained by applying a Hoveyda–Grubbs 2nd generation catalyst in acyclic diene metathesis polymerization (ADMET) of a monomer containing on one end a terminal dimethylvinylsilyl group and at the other end a terminal C C double bond. This material showed an interesting Iso‐de Vries SmA* – SmC* – Glass phase transition with a very small layer shrinkage on progressing from the SmA* phase into the SmC* phase. Will this material present a helical structure along the fiber axis in the SmC* temperature range? Several physical characterization methods including XRD, optical observation, and microtome technique have been used to investigate the internal structural organization in this liquid crystalline fiber.

     

Growth of the magnetic semiconductor Fe2? x Ti x O3± δ thin films by pulsed laser deposition

The understanding and control of the ilmenite–hematite solid solutions (Fe_2−x Ti _x O_3±δ or IH) thin film structure and properties are crucial for spintronics applications. Good quality films of Fe_2−x Ti _x O_3±δ on Al₂O₃(0001) substrates were obtained by pulsed laser deposition. For the studied compositions (x=1, 0.7, 0.5) in a wide oxygen pressure range all the films were epitaxial, with flat interfaces, and without secondary phases. Unconventional lattice strain relaxation with the increase of in-plane lattice parameter above its relaxed bulk value was observed for different film compositions, oxygen pressures, substrate temperatures, and film growth rates. This phenomenon is most likely explained by the buckling of a few first film monolayers because of a significant compressive stress induced on the film by the sapphire substrate. The IH thin films with x=0.7 and 0.5 exhibited the properties of a room temperature magnetic semiconductor. The resistivity changed over three orders of magnitude in the studied pressure range, thus clearly demonstrating the important role of oxygen stoichiometry in the creation of carriers.     

Cryopreservation for plant genebanks - a matter between high expectations and cautious reservation

Cryopreservation is the best method of storing germplasm efficiently and safely, particularly for the maintenance of vegetatively propagated material. In IPK cryopreservation is used for potato, garlic, mint and yam. IPK collaborates with other cryobanks and research groups (ECPGR, COST, EURALLIVEG) and finds considerable differences in the adoption of cryopreservation between crops and their host institutes, depending on crop, local and historical circumstances. A better understanding of the long-term benefits of cryopreservation and its further integration into general genebank management is therefore needed. Recommended approaches include: comparative validation of methods between different laboratories, detailed comparisons of crop-based methods, economical analyses, efficient integration strategies of cryobanks by genebanks; including safe duplication of cryopreserved resources for the limitation of risk of loss Importantly, there has been recent progress in the development of quality management systems. Cryopreservation is, however, characterized by high expectations. Therefore, to ensure its sustainable and practicable use, basic knowledge of storage protocols must be combined with increased awareness of the rationales required to validate, implement and apply cryobanking technologies in working genebanks.     

Asymptotic analysis of a viscous cochlear model

A model of cochlear macromechanics, involving a viscous cochlear fluid, is analyzed asymptotically for slowly varying membranes. The results exhibit the effect of viscosity on the amplitude, wavelength, and damping rate, and confirm the conclusion that viscosity is not important. However the method can be used on other models, such as those of cochlear micromechanics, where viscosity is more important.     

Darstellung und Kristallstruktur von Blei(II)-monoglycerat

Preparation and Crystal Structure of Lead(II) Monoglycerolate Crystals of lead(II) monoglycerolate, of a quality suitable for diffraction studies, have been prepared from an alkaline plumbate solution and an excess of glycerol. The compound crystallizes in the monoclinic space group P2₁/c with a = 5.617(6) Å, b = 9.471(8) Å, c = 9.726(7) Å, β = 102.65(11)°. The structure was refined by full matrix least-squares techniques to an R value (1026 F₀) of 0.078. The compound to which the formula Pb(C₃H₆O₃) could be assigned, is polymeric in one direction. The lead and a part of the oxygen atoms built up a zig-zag chain parallel to the aaxis. The oxygen form a distorted tetragonal pyramid with lead at the apex. A decomposition temperature of 235°C has been determined.     

Spectral reflectance of the one-dimensional organic metals (perylene)2(PF6)1.1 × 0.8CH2Cl2 and (perylene)2(AsF6)1.1 × 0.7CH2Cl2

We report on the optical reflectance of (perylene)₂(PF₆)_1.1 × 0.8CH₂Cl₂ and (perylene)₂(AsF₆)_1.1 × 0.7CH₂Cl₂ single crystals in the energy range from 0.25 to 4 eV. For light polarized perpendicular to the molecular stacks the crystals exhibit the optical behaviour of an insulating molecular crystals, whereas for light polarized parallel to the stacks a pronounced plasma edge at $\text{h}\text{?}\text{ω = 0.9}\text{eV}$ is observed. The experimental data were analyzed by a Lorentz-Drude model in order to determine the electrical conductivity, the carrier concentration, the effective mass, the collision time, the band width, and the Fermi vector of the crystals.