Digital Commons Network^™

Impact Of Alkaline Doping And Reducing Conditions On Lafeo3, Geoffrey L. Beausoleil Ii

Geoffrey L Beausoleil II

Efficient and reliable materials for gas separation, syngas production, and hybrid nuclear power plants must be capable of reliably operating at a high-temperature range of 700-1000°C and under exposure to highly oxidizing and reducing conditions. Candidate materials for these applications include alkaline metal doped lanthanum ferrite.

In the first study, the impact of A site substitution by different alkaline metals on lanthanum ferrite (LMF, M=Ca, Sr, and Ba) was investigated. The study focused on thermal expansion near the Néel transition temperature and a magneto-elastic contribution to thermal expansion was identified for each sample. Iron oxidation, Fe3+ to Fe4+, was identified …

Titanium Oxide Nanotubes: Synthesis, Properties And Applications For Solar Energy Harvesting, Eugen Panaitescu

Eugen Panaitescu

Titanium oxide (titania) nanotubes, although relatively recently discovered (less than 15 years ago), have already shown great promise regarding solar energy harvesting applications, exhibiting very good photocatalytic and photovoltaic properties. An alternative anodization route for production of titania nanotubes at the surface of a titanium foil using chloride ions as catalyst instead of the routinely used highly toxic fluorides, is presented in this work. Moreover, the fabrication parameters are extensively studied, thus providing both an insight into the synthesis mechanism and hints towards possible process optimization routes. Although not forming uniformly over the sample surface and lacking long range ordering, …

The Unexpectedly Bright Comet C/2012 F6 (Lemmon) Unveiled At Near-Infrared Wavelengths, Lucas Paganini, Michael A. Disanti, Michael J. Mumma, Geronimo L. Villanueva, Boncho P. Bonev, Jacqueline V. Keane, Erika L. Gibb, Hermann Boehnhardt, Karen J. Meech

Erika Gibb

The Upscattering Of Ultracold Neutrons From The Polymer (C6h12)N, Eduard I. Sharapov, Christopher L. Morris, Mark Makela, Andy Saunders, Evan R. Adamek, Leah J. Broussard, Chris B. Cude-Woods, Deion E. Fellers, Peter Geltenbort, Monika Hartl, Siraj I. Hasan, Kevin P. Hickerson, Gary E. Hogan, Anthony T. Holley, C. M. Lavelle, Chen-Yu Liu, Michael P. Mendenhall, Jose Ortiz, Robert W. Pattie, David G. Phillips, John Ramsey, Daniel J. Salvat, Susan J. Seestrom, Erik Shaw, Sky Sjue, Walter E. Sondheim, Brittany Vorndick, Zhehui Wang, Tanner L. Womack, Andrew R. Young, B. A. Zeck

Robert W. Pattie Jr.

Maxwell’S Equations On Cantor Sets: A Local Fractional Approach, Yang Xiaojun

Xiao-Jun Yang

Maxwell’s equations on Cantor sets are derived from the local fractional vector calculus. It is shown that Maxwell’s equations on Cantor sets in a fractal bounded domain give efficiency and accuracy for describing the fractal electric and magnetic fields. Local fractional differential forms of Maxwell’s equations on Cantor sets in the Cantorian and Cantor-type cylindrical coordinates are obtained. Maxwell’s equations on Cantor set with local fractional operators are the first step towards a unified theory of Maxwell’s equations for the dynamics of cold dark matter.

Precise Radial Velocities Of Giant Stars. Ii. Pollux And Its Planetary Companion, Sabine Reffert, Andreas Quirrenbach, David Mitchell, Simon Albrecht, Saskia Hekker, Debra A. Fischer, Geoffrey W. Marcy, R. Paul Butler

Debra A Fischer

It has long been speculated that the observed periodic radial velocity pattern for the K giant Pollux might be explained in terms of an orbiting planetary companion. We have collected 80 high-resolution spectra for Pollux at Lick Observatory yielding precise radial velocities with a mean error of 3.8 m s-1, providing the most comprehensive and precise data set available for this star. Our data confirm the periodicity previously seen in the radial velocities. We derive a period of 589.7 ± 3.5 days and, assuming a primary mass of 1.86 M, a minimum companion mass of 2.9 ± 0.3MJup, consistent with …

Discovery Of A Substellar Companion To The K2 Iii Giant Ɩ Draconis, Sabine Frink, David Mitchell, Andreas Quirrenbach, Debra A. Fischer, Geoffrey W. Marcy, R. Paul Butler

Debra A Fischer

We report precise radial velocity measurements of the K giant ɩ Dra (HD 137759, HR 5744, HIP 75458), carried out at Lick Observatory, which reveal the presence of a substellar companion orbiting the primary star. A Keplerian fit to the data yields an orbital period of about 536 days and an eccentricity of 0.70. Assuming a mass of 1.05 M8 for ɩ Dra, the mass function implies a minimum companion mass m₂ sin i of 8.9 M_J, making it a planet candidate. The corresponding semimajor axis is 1.3 AU. The nondetection of the orbital motion by Hipparcos …

Novel Surface State In A Class Of Incommensurate Systems, A. E. Jacobs, D. Mukamel, David W. Allender

David W Allender

We study the Landau model of the class of incommensurate systems with a scalar order parameter where the modulated phase is driven by a gradient-squared term with negative coefficient. For example, theoretical studies of cholesteric liquid crystals in a field (electric or magnetic) suggest that such an modulated phase should exist at high chirality. The bulk phase diagram in the presence of a bulk external field which couples linearly to the order parameter exhibits a modulated phase inside a loop in the temperature-field plane, and a homogeneous phase outside. On analyzing the same model for a semi-infinite system, we find …

Pseudo-Casimir Effect In Untwisted Chiral Nematic Liquid Crystals, F. Karimi Pour Haddadan, David W. Allender, S. Zumer

David W Allender

We investigate theoretically the pseudo-Casimir force between parallel plates immersed in a chiral nematic liquid crystal. We focus on small-separation limit where the director configuration between the plates inducing strong homeotropic anchoring is uniform. We find that the force is attractive at separations smaller than the crossover distance and repulsive otherwise, and that it diverges logarithmically at the critical distance where the uniform structure is replaced by a distorted structure. We also analyze modifications to the force introduced by magnetic field and comment on the possible detection of the effect.

Wide Viewing Angle, Homeotropic Nematic Liquid-Crystal Display Controlled By Effective Field, S. H. Lee, H. Y. Kim, Y. H. Lee, I. C. Park, B. G. Rho, H. G. Galabova, David W. Allender

David W Allender

The electro-opticproperties of a liquid-crystal display associated with a homeotropic to multidomainlike transition for a liquid crystal with a positive dielectricanisotropy have been investigated. The cell plates are prepared in such a way that, in the absence of an electric field, the liquid-crystal alignment is homeotropic. an electric field created by interdigitated electrodes on both substrates causes a director deformation of a multidomain type. The display shows wide viewing angle, excellent color characteristics, and a fast response time. The molecular director configuration, together with the electro-optic characteristics of the device, are discussed in this letter.

Orientation And Surface Anchoring Of Nematic Liquid Crystals On Linearly Polymerized Photopolymers, H. G. Galabova, David W. Allender, J. Chen

David W Allender

The liquid crystal orientation on a poly(vinyl cinnamate) or poly(vinyl 4-methoxy-cinnamate) coated solid substrate exposed to linearly polarized UV light has been studied. The angular distribution of the polymer side chains and the photoreaction products was derived as a function of exposure time using a simple assumption about the probability for crosslinking of two side chains. The liquid crystal was assumed to be weakly anchored to the surface but have a degree of order and orientation determined from those of the polymer side chains. The polar and the azimuthal surface coefficients were estimated as a function of exposure time using …

The Politics Media Equation:Exposing Two Faces Of Old Nexus Through Study Of General Elections,Wikileaks And Radia Tapes, Ratnesh Dwivedi Mr

Ratnesh Dwivedi

The important identity of a responsible media is playing an unbiased role in reporting a matter without giving unnecessary hype to attract the attention of the gullible public with the object of making money and money only.After reporting properly the media can educate the public to form their own opinion in the matters of public interest. Throughout the centuries, the world has never existed without information and communication, hence the inexhaustible essence of mass media. The government has the power to either make or reject whatever that will exist within its environment. It also determines how free the mass media …

Microcalorimetric Study Of Nematic-To-Neat-Soap And Nematic-To-Isotropic Phase Transitions In A Lyotropic Liquid Crystal, T. S. Shin, Satyendra Kumar

Satyendra Kumar

The results of specific-heat measurements at the nematic- (N) to-neat-soap (NS) and nematic-to-isotropic (I) phase transitions in binary mixtures of cesium-perfluoro-octanoate and water are reported. The ratio of specific-heat amplitudes above and below the N-NS transition, A+/A-, and the specific-heat exponent α remain ∼1.0 and ≤0.02, respectively, suggesting 3D XY-type behavior. At the first-order N-I transition, vanishing latent heat and coexistence range at low concentration indicate the existence of a Landau point.

Raman Scattering Study Of Phase Biaxiality In A Thermotropic Bent-Core Nematic Liquid Crystal, Min Sang Park, Beom-Kin Yoon, Jung Ok Park, Veena Prasad, Satyendra Kumar, Mohan Srinivasarao

Satyendra Kumar

Polarized Raman spectroscopy was used to investigate the development of orientational order and the degree of phase biaxiality in a bent-core mesogenic system. The values of the uniaxial order parameters ⟨P200⟩ and ⟨P400⟩, and biaxial order parameters ⟨P220⟩, ⟨P420⟩, and ⟨P440⟩, and their evolution with temperature were determined. The temperature dependence of almost all order parameters reveals a second order transition from the uniaxial to biaxial nematic phase with ⟨P220⟩ increasing to ∼0.22 before a first order transition to the smectic-C phase, upon cooling.

Morphology And Ordering In Thin Liquid-Crystal Films On Flat Glass Substrates, Yushan Shi, Brian Cull, Satyendra Kumar

Satyendra Kumar

Results of a high resolution x-ray reflectivity study of growth morphology and ordering of thin liquid-crystal films on flat glass substrate are reported. An adsorbed bilayer of crystalline order, under three dimensional clusters, was found to persist well beyond the nematic to isotropic transition. This adsorbed layer appears to be related to the surface memory effects in liquid-crystal devices. The morphology of these films can be described by the Stranski-Krastanov growth mode.

Parity-Violating Electron Scattering From 4he And The Strange Electric Form Factor Of The Nucleon, K. A. Aniol, Edgar E. Kooijman

Edgar E Kooijman

We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from 4He at an average scattering angle ⟨θ_lab⟩=5.7° and a four-momentum transfer Q2=0.091  GeV2. From these data, for the first time, the strange electric form factor of the nucleon G_Es can be isolated. The measured asymmetry of A_PV=(6.72±0.84_(stat)±0.21_(syst))×10-6 yields a value of G_Es=-0.038±0.042_(stat)±0.010_(syst), consistent with zero.

Cholesteric Liquid-Crystal Displays Illuminated By Diffuse And Partially Diffuse Light, W. D. St. John, Z. J. Lu, J. William Doane, Bahman Taheri

Bahman Taheri

We report on the photometric and colorimetric properties of surface and polymer network stabilized reflective cholesteric displays. Both diffuse and partially diffuse illumination are used, the latter being an experimental approach to emulating typical room light conditions. It is shown that addition of polymer increases the field of view while decreasing angular dependence of the color quantities: hue, chroma, and lightness. Total luminance and contrast ratio, however, are also decreased. Therefore, it is concluded that optimum polymer concentration is dependent on the viewing geometry. Luminance and contrast ratio of the surface stabilized cells exceeded that of polymer stabilized cell when …

Mechanism Of Unidirectional Liquid-Crystal Alignment On Polyimides With Linearly Polarized Ultraviolet Light Exposure, M. Nishikawa, Bahman Taheri, John L. West

Bahman Taheri

Unidirectional liquid-crystal(LC) alignment by a linearly polarized ultraviolet light(UV) exposure was examined using two types of polyimide (PI). PI with a fluorene unit incorporated in a side chain showed LC alignment perpendicular to those of conventional PIs, i.e., perpendicular to the rubbing direction and parallel to the exposure polarization of UV. The results of the dichroic ratio measurement of LCcells,UVabsorption spectra,birefringence, infrared absorption spectra, and PI conformation calculations using molecular mechanics suggest that the photodecomposition of PI by UV exposure produces anisotropic van der Waals forces, which align LC along its optical axis.

Azimuthal Dependence Of Switching Field Strength For Nematic Liquid Crystal Bistability On Patterned Alignment Layers, Jun-Ichi Niitsuma, Makoto Yoneya, Hiroshi Yokoyama

Hiroshi Yokoyama

We investigate the azimuthal dependence of the switching field strength for nematic liquid crystal bistability on patterned alignment layers to determine the validity of a switching theory proposed by Kim et al. [Appl. Phys. Lett. 78, 3055 (2001)] and to evaluate higher-order azimuthal anchoring coefficients. Director behavior during switching is described in detail for general azimuthal directions of an applied electric field and the experimental results are explained on the basis of the theory. We obtain azimuthal anchoring coefficients up to the second higher-order term in an expansion of the anchoring energy function. Detailed analysis of the director behavior reveals …

Structure And Dynamics Of Model Systems: From Ferrofluids To Brain Membranes, Matthew A. Barrett

Matthew J. Barrett

Soft condensed matter systems are a very diverse and challenging subject to study. To understand the complex macro-properties of such systems one approach is to characterize the microscopic structure and dynamics. A powerful technique for determining micro and nanoscale properties is scattering of radiation sources. Light, electron and neutron scattering techniques provide insight into the complicated molecular structures and the processes happening on these small scales. We have used neutron and x-ray scattering techniques to determine structural and dynamical information from two different types of soft condensed matter systems. The microscopic nature of a cobalt magnetic fluid was studied using …

Capillary Filling Of Nematic Liquid Crystals, Xiang-Dong Mi, Deng-Ke Yang

Deng-Ke Yang

We studied the orientation of nematic liquid crystals when they were being filled into cells by capillary action. We found that, in the flow front, the liquid crystal was always aligned along the flow direction. Far behind the flow front, the orientation of the liquid crystal depended on the anchoring direction of the alignment layers and the direction and speed of the flow. In cells with the anchoring direction parallel to the flow direction, the liquid crystal always oriented along the flow direction. In cells with the anchoring direction perpendicular to the flow direction, at low flow speed gradients, the …

Ordering And Self-Diffusion In The 1st Molecular Layer At A Liquid-Crystal Polymer Interface, G. P. Crawford, Deng-Ke Yang, S. Zumer, D. Finotello, J. William Doane

Deng-Ke Yang

H-2 NMR of a liquid crystal confined to submicron cylindrical cavities, in a 17-K interval above the nematic-isotropic transition, reveals a weakly orientationally ordered molecular layer at the cavity wall governed by local interactions. The order (S0 = 0.02) is temperature independent so that a partial wetting is realized with no prewetting transition expected. A molecular exchange rate between the surface layer and the bulk is measured to be approximately 10(3) s-1. The coherence length measuring the order penetrating further into the cavity is described by alpha = 0.4 and xi-0 = 0.6 nm.

Evolution Of Disclinations In Cholesteric Liquid Crystals, F. Zhang, Deng-Ke Yang

Deng-Ke Yang

We studied the evolution of defect lines (oily streaks) in cholesteric liquid crystals. In contrast to nematic liquid crystals, there were no interactions between the defect lines in cholesteric liquid crystals. We observed experimentally that individual open defect segments shrank with time with a linear relation, and individual defect loops shrank with time with a square root relation. We also observed that the defects in cholesteric liquid crystals were mainly interconnected loops, and the total length of the defect lines decreased with time logarithmically because of the distribution of loop size. The decay constant depended on the helical pitch of …

Pretransitional Nematic Ordering In Liquid Crystals With Dispersed Polymer Networks, Y. K. Fung, A. Borstnik, S. Zumer, Deng-Ke Yang, J. William Doane

Deng-Ke Yang

The birefringence induced by partially ordered polymer networks dispersed in an isotropic phase of liquid crystals is studied. Polymer networks were formed by the polymerization of 1-4 % mixtures of prepolymer in the nematic phase of liquid crystals. The partial nematic (paranematic) ordering is analyzed in terms of the Landau-de Gennes approach using a simple model of an array of thin fibrils, which can, on a large scale, form bundles of polymer-rich material. The comparison of the theory and birefringence data clearly shows that the main building bloc of the network is a few nanometers thick fibril. The average thickness …

Effect Of Chiral Dopant On The Performance Of Polymer Dispersed Liquid Crystal Light Valve, Z. J. Lu, Deng-Ke Yang

Deng-Ke Yang

We have experimentally studied the effect of chiraldopant on the electro‐optical performance of a polymer‐dispersed liquid crystal(PDLC) light valve. Adding a small amount of chiraldopant decreases the turn‐OFF time significantly but increases the drive voltage only slightly. A phenomenological theory is presented to explain the experimental results.

Light-Scattering From Polymer-Dispersed Liquid-Crystal Films - Droplet Size Effects, G, Paul Montgomery Jr, John L. West, W Tamuralis

John L West

The effects of droplet size on light scattering by polymer-dispersed liquid crystal (PDLC) films have been studied theoretically and experimentally. Rayleigh-Gans calculations predict that, provided the droplets scatter independently, backscattering will be maximum at wavelength lambda when the droplet radius is about lambda/7. noticeable for droplet volume fractions eta above about 0.2 and shift the radius for maximum backscattering to about lambda/5 as eta increases to 0.5. These calculations are consistent with hemispherical transmittance and reflectance measurements on PDLC films in which multiple scattering is known to be important. These measurements indicate that solar attenuation by PDLC films will probably …

Drag On Particles In A Nematic Suspension By A Moving Nematic-Isotropic Interface, John L. West, A Glushchenko, Gx Liao, Y Reznikov, D Andrienko, Mp Allen

John L West

We report a clear demonstration of drag on colloidal particles by a moving nematic-isotropic interface. The balance of forces explains our observation of periodic, striplike structures that are produced by the movement of these particles.

Field-Induced Polymer Wall Formation In A Bistable Smectic-A Liquid Crystal Display, Ebru A. Buyuktanir, Nadina Gheorghiu, John L. West, Maxim Mitrokhin, Borre Holter, Anatoliy Glushchenko

John L West

We developed a composite system to produce robust bistable smectic-A (SmA) liquid crystal based flexible displays by encapsulating the liquid crystal material in a polymer wall structure. While keeping all the intrinsic bistable properties of the SmA material, the field-induced polymer walls bridge the two display substrates and bring significant advantages over the polymer dispersed liquid crystal structure. Here we analyze the performance of an encapsulated pixel and demonstrate superior electro-optical characteristics, high contrast ratio, and excellent sunlight readability. (c) 2006 American Institute of Physics.

One Order Parameter Tensor Mean Field Theory For Biaxial Liquid Crystals, Xiaoyu Zheng, Peter Palffy-Muhoray

Xiaoyu Zheng

In this paper, we present a simple one tensor mean field model of biaxial nematic liquid crystals. The salient feature of our approach is that material parameters appear explicitly in the order parameter tensor. We construct the free energy from a mean field potential based on anisotropic dispersion interactions, identify the order parameter tensor and its elements, and obtain self-consistent equations, which are then solved numerically. The results are illustrated in a 3D ternary phase diagram. The phase behavior can be simply related to molecular parameters. The results may be useful for designing molecules that show a thermotropic biaxial phase.

Modeling Elastic Instabilities In Nematic Elastomers, Badel L. Mbanga, Fangfu Ye, Jonathan Selinger, Robin Selinger

Robin Selinger

Liquid crystal elastomers are cross-linked polymer networks covalently bonded with liquid crystal mesogens. In the nematic phase, due to strong coupling between mechanical strain and orientational order, these materials display strain-induced instabilities associated with formation and evolution of orientational domains. Using a three-dimensional finite element elastodynamics simulation, we investigate one such instability, the onset of stripe formation in a monodomain film stretched along an axis perpendicular to the nematic director. In our simulation, we observe the formation of striped domains with alternating director rotation. This model allows us to explore the fundamental physics governing dynamic mechanical response of nematic elastomers …