The influence of the flexoelectric effect on the electrohydrodynamic instability in nematics

A rigorous three-dimensional linear analysis of the electrohydrodynamic instability in nematic liquid crystals including the flexoelectric effect is presented for the case of an applied d.c. voltage. The flexoelectric effect leads to an appreciable reduction of the threshold and to the appearance of oblique rolls at threshold for the standard material MBBA. We discuss the influence of a magnetic field and test several approximations against the rigorous results     

Direct potentiometric immunoelectrodes

Summary TK pencil fine mines type Faber Castell Super polymer from Staedtler are used as graphite based material for an atrazine-sensitive immunoelectrode. Eighteen procedures are tested to immobilize antibodies against atrazine but only one turned out to be useful for the preparation of a graphite based immunoelectrode. It incorporates binding of glutardialdehyde to active sites of the graphite surface and subsequent cross-linking of the antibodies with glutardialdehyde. The method has been carefully optimized with respect to selectivity and the cross-sensitivity is determined for such an electrode based on atrazine-rabbit and atrazine-sheep antibodies as well. Due to the structural difference of the used immunogens, the sign of the potential response and the cross-sensitivities are different. The application of such an electrode to a natural water sample is demonstrated and shows that the useful concentration range in a final solution is between 20 and 250 ng/l. Of course, interference from ions must be excluded in future analytical applications.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthdayPart II: Fresenius J Anal Chem     

Surface phenomena in the process of titanium hydride formation

Surface phenomena which occur in the course of titanium hydride TiH_x formation during the H₂ interaction with thin Ti films deposited in situ under UHV conditions were studied by means of surface potential and pressure measurements. The elementary steps of this process were distinguished and described.     

Photoemission Spectroscopy and Electronic Structures of LiMn2O4

We study the electronic structures of LiMn2O4 by x-ray and ultraviolet photoelectron spectroscopy （XPS, UPS） and resonant photoelectron spectroscopy （RPES）. XPS data suggest that the average oxidation state of Mn ions is 3.55, probably due to the small amount of lithium oxides on the surface. UPS and RPES data imply that Mn ions are in a high spin state, and RPES results show strong Mn3d-O2p hybridization in the LiMn2O4 valence band.