Molecular structure of azopolymers and photoinduced 3D orientational order",

The combination of transmission null ellipsometry (TNE) and attenuated total reflection (ATR) methods supported by absorption measurements is shown to be an effective tool to study spontaneous and photoinduced 3D order in azopolymers. We investigated a series of azobenzene containing side-chain polyesters differing by the length of the main-chain spacer (CH 2 ) m (m ) 2, I. Introduction Presently, in the era of information technologies, there is an increasing interest in photonic processes allowing the improvement of devices for information storage, processing, displaying, and transfer. The phenomenon of photoinduced anisotropy (PIA) is one of the best candidates for this purpose. Photoinduced anisotropy (also named Weigert 1 effect) produces optical dichroism and birefringence in various materials by generating an orientational order. This order is centrosymmetric (quadrupolar) and should be more correctly named alignment, in contrast with the orientation induced by poling methods (photoassisted electrical poling (PAEP) 2 and all-optical poling (AOP) 3-5 ), which generate a noncentrosymmetric (dipolar and octupolar) orientational order, producing nonlinear effects ( (2) ). Azobenzene-containing polymers are known to be among the most effective materials for PIA generation. The microscopic explanation of PIA in azopolymers is based on two properties of azochromophores: 6,7,10 the trans-ci

Liquid crystal anchoring transitions on aligning substrates processed by plasma beam

We observe a sequence of the anchoring transitions in nematic liquid crystals (NLC) sandwiched between the hydrophobic polyimide substrates treated with the plasma beam. There is a pronounced continuous transition from homeotropic to low tilted (nearly planar) alignment with the easy axis parallel to the incidence plane of the plasma beam (the zenithal transition) that takes place as the exposure dose increases. In NLC with positive dielectric anisotropy, a further increase in the exposure dose results in in-plane reorientation of the easy axis by 90 degrees (the azimuthal transition). This transition occurs through the two-fold degenerated alignment characteristic for the second order anchoring transitions. In contrast to critical behavior of anchoring, the contact angle of NLC and water on the treated substrates monotonically declines with the exposure dose. It follows that the surface concentration of hydrophobic chains decreases continuously. The anchoring transitions under consideration are qualitatively interpreted by using a simple phenomenological model of competing easy axes which is studied by analyzing anchoring diagrams of the generalized polar and non-polar anchoring models.Comment: revtex4, 18 pages, 10 figure

Plasma-beam Alignment Technique for Ferroelectric Liquid Crystals

The plasma-beam alignment procedure earlier developed for the alignment of nematic liquid crystals is successfully extended to ferroelectric liquid crystals (FLC). The highly uniform alignment of the “chevron” structure (before electrical treatment of FLC cells) and “quasi bookshelf” structure (after the electrical treatment) are realized. The contrast of bistable switching larger than 350:1 is achieved. This makes the non-contact plasma-beam alignment procedure especially attractive for high-contrast bistable LCDs on an LCOS base, particularly used in PDA and e-books. Fast switching and realization of gray scale in the plasma-beam aligned FLC cellsmakes this technique also promising for full-color displays including color LCD TV

A unique warm–water oasis in the Siberian Arctic’s Chaun Bay sustained by hydrothermal groundwater discharge

Abstract Chaun Bay, located on the fringe of the East Siberian Sea, has been described since the mid-20th century to support a unique marine ecosystem that is atypical for the local Siberian Arctic. Here we use ship-board physical, biogeochemical and geological measurements taken in October 2020, along with hydrographic observations taken from land-fast ice in April 2023, to demonstrate that these warm-water biological communities are supported by hydrothermal submarine groundwater discharge that delivers heat, salinity, nutrients, and trace elements to the bay. We identify a cyclonic eddy that mixes the warm nutrient-rich groundwater with oxygen-rich surface water, resulting in a water mass within Chaun Bay that has similar physical and chemical properties to the highly productive waters of the North Pacific and Southern Chukchi Sea. The bay showed elevated concentrations of chlorophyll-a and zooplankton, and the abundance and species diversity of epibenthos significantly exceeded values observed elsewhere in the East Siberian Sea. The benthic communities contained a number of boreal species that are not typically found in the Arctic Ocean. We also observed Thysanoessa krill populations, a pelagic species generally considered an expatriate in Arctic waters