ABSTRACT
Diffraction optical elements (DOE) are important elements of systems for images displaying and processing. The DOE materials with both positive and negative birefringence enhance performances and functionality of such systems. We have calculated the diffraction of rays passing through optically anisotropic grating with surface microrelief by using our original Exedeep software. At the first time the diffraction parameters for both transmitted and reflected TE- and TM-waves are calculated for materials with both positive and negative optical anisotropy. The simulation results are to be used to create DOE for the visible, UV, IR and THz ranges.
ABSTRACT
In liquid crystal devices (LCDs) the indium tin oxide (ITO) films are traditionally used as transparent and conductive electrodes. However, today, due to the development of multichannel optical communication, the need for flexible LCDs and multilayer structures has grown. For this application ITO films cannot be used in principle. For this problem, graphene (an ultrathin material with unique properties, e.g., high optical transparency, chemical inertness, excellent conductivity) is an excellent candidate. In this work, the electro-optical and dynamic characteristics of a liquid crystal (LC) cell with graphene and ITO transparent conducting layers are investigated. To insure uniform thickness of the LC layer, as well as the same orientation boundary conditions, a hybrid LC cell containing graphene and ITO conductive layers has been prepared. The characteristics of LC cells with both types of conducting layers were found to be similar, indicating that graphene can be successfully used as a transparent conductive layer in LC devices.
ABSTRACT
Conformation changes of calf thymus DNA induced by nanomole concentrations of Co(+2) and TOEPyP4 and influence of this ion on porphyrin binding mode with DNA duplex were studied at two NaCl concentrations (10 and 100 mM) using circular dichroism spectroscopy and absorption data. It was shown that addition of 85 nM Co(+2) into TOEPyP4/DNAb.p. = .015 solution caused an immediate change of the intercalative binding mode of porphyrin to external binding modes at low ionic strengths (10 mM NaCl). Increase of Co(+2) concentration from 165 to 650 nM caused a cooperative transition of DNA from B form to C-like conformation. Similar changes in binding mode and DNA conformation were observed at 100 mM NaCl, but they took place at higher concentrations of Co(+2) ions. Incubation of TOEPyP4/DNAb.p. = .015 in the presence of nanomole concentrations of Co(+2) ions at 36.6 °C showed a transition of DNA-B form into Z-like conformation. Maximal percent of Z-like DNA was observed when the incubation time was from 6 to 8 h. Longer incubation times of [DNA-TOEPyP4]+Co(+2) complexes caused a considerable recovery of CD spectra in UV region and a strong decrease in absorption at 260 nm. Here, we discuss some mechanisms of transition from B-DNA to C- and Z-like conformations.
