Physics Commons^™

Mathematical Modelling Of Nematicons And Their Interactions, Prof. Tim Marchant

Tim Marchant

The mathematical modelling of guided wave (nematicon) propagation in liquid crystals is considered. Model equations are derived based on suitable trial functions in an averaged Lagrangian. These equations are used to model nematicon interactions.

Undular Bores And The Initial-Boundary Value Problem For The Modified Korteweg-De Vries Equation, Tim Marchant

Tim Marchant

Two types of analytical undular bore solutions, of the initial value problem for the modified Korteweg-de Vries (mKdV), are found. The first, an undular bore composed of cnoidal waves, is qualitatively similar to the bore found for the KdV equation, with solitons occurring at the leading edge and small amplitude linear waves occurring at the trailing edge. The second, a newly identified type of undular bore, consists of finite amplitude sinusiodal waves, which have a rational form. At the leading edge is the mKdV algebraic soliton, while, again, small amplitude linear waves occur at the trailing edge. The initial-boundary value …

Collisionless Shock Resolution In Nematic Liquid Crystals, Tim Marchant

Tim Marchant

The diffractive resolution on a collisionless shock formed along the spatial profile of a beam in a nematic liquid crystal is considered, this material being an example of a self-focusing, nonlocal medium. It is found that the shock is resolved through the formation of an undular bore structure which persists for experimentally relevant propagation distances due to nonlocality delaying the onset of modulational instability. Both 1+1 and 2+1 dimensional bores with circular symmetry are considered (termed line and circular bores, respectively). A semianalytical solution is developed for the line undular bore, approximating it as a train of uniform solitary waves. …

Semi-Analytical Solutions For A Gray-Scott Reaction-Diffusion Cell With An Applied Electric Field, Tim Marchant

Tim Marchant

An ionic version of the Gray–Scott chemical reaction scheme is considered in a reaction–diffusion cell, with an applied electric field, which causes migration of the reactant and autocatalyst in a preferred direction. The Galerkin method is used to reduce the governing partial differential equations to an approximate model consisting of ordinary differential equations. This is accomplished by approximating the spatial structure of the reactant and autocatalyst concentrations. Bifurcation analysis of the semi-analytical model is performed by using singularity theory to analyse the static multiplicity and a stability analysis to determine the dynamic multiplicity. The application of the electric field causes …

Heavy-Fermion Superconductivity, Peter Riseborough, George Schmiedeshoff, James Smith

George Schmiedeshoff

Heavy Fermion Superconductivity: A state of the art review of superconductivity in the Heavy Fermion metals is presented. Many important results are given. Theory and experiment are compared and critically discussed

Nonlocal Validity Of An Asymptotic One-Dimensional Nematicon Solution, Tim Marchant

Tim Marchant

The propagation of coherent, polarized light in a nematic liquid crystal, governed by the nematicon equations, is considered. It is found that in the special case of 1 + 1 dimensions and the highly nonlocal limit, the nematicon equations have an asymptotic bulk solitary wave solution, termed a nematicon, which is given in terms of Bessel functions. This asymptotic solution gives both the ground state and the symmetric and antisymmetric excited states, which have multiple peaks. Numerical simulations of nematicon evolution, for parameters corresponding to experimental scenarios, are presented. It is found, for experimentally reasonable parameter choices, that the validity …

Dipole Soliton Formation In A Nematic Liquid Crystal In The Non-Local Limit, Tim Marchant

Tim Marchant

The interaction of two symmetric solitary waves, termed nematicons, in a liquid crystal is considered in the limit of nonlocal response of the liquid crystal. This nonlocal limit is the applicable limit for most experimentally available liquid crystals. In this nonlocal limit, two separate cases for the initial separation of the nematicons are considered, these being large and small separation. Both spinning and nonspinning nematicons are considered. It is found that in the case of large initial separation, the nematicons can form a spinning or nonspinning bound state with a finite steady separation, this being called a nematicon dipole, when …

Alignment Memory Of A Nematic Liquid Crystal And Thermal Isotropization Of The Surface Adsorbed Layer, A. B. Nych, D. Yu. Reznikov, O. P. Boiko, V. G. Nazarenko, V. M. Pergamenshchik, Philip Bos

Philip J. Bos

We use a digital image analysis of the schlieren textures to study the effect of memory of the surface anisotropy in a nematic-liquid-crystal cell and establish its relation to the surface adsorbed molecular layer. The anisotropy is induced on an isotropic glass surface by a flow of the nematic liquid. The proposed technique allows us to quantify the alignment and its changes under the effect of temperature. The temperature at which the memory of the alignment texture is lost is interpreted as the temperature of the full isotropization of the initial anisotropic surface layer adsorbed during the flow: the molecules …

Cavity Resonances Of Metal-Dielectric-Metal Nanoantennas, Bhuwan Joshi, Qi-Huo Wei

Qi-Huo Wei

We propose a new design of optical nanoantennas and numerically study their optical properties. The nanoantennas are composed of two cylindrical metal nanorods stacked vertically with a circular dielectric disk spacer. Simulation results show that when the dielectric disk is less than 5nm in thickness, such nanoantennas exhibit two types of resonances: one corresponding to antenna resonance, the other corresponding to cavity resonances. The antenna resonance generates a peak in scattering spectra, while the cavity resonances lead to multiple dips in the scattering spectra. The cavity resonant frequency can be tuned by varying the size of the dielectric disk. The …

Hierarchies Of Networked Phases Induced By Multiple Liquid-Liquid Critical Points, C. W. Hsu, J. Largo, F. W. Sciortino, Francis Starr

Francis Starr

No abstract provided.

Bond Stiffening In Small Nanoclusters And Its Consequences For Mechanical And Thermal Properties, Pushpa Raghani, Umesh Waghmare, Shobhana Narasimhan

Pushpa Raghani

We have used density functional perturbation theory to investigate the stiffness of interatomic bonds in small clusters of Si, Sn, and Pb. As the number of atoms in a cluster is decreased, there is a marked shortening and stiffening of bonds. The competing factors of fewer but stiffer bonds in clusters result in softer elastic moduli but higher #1;average#2; frequencies as size is decreased, with clear signatures of universal scaling relationships. The stiffness of bonds is found to scale as the inverse tenth power of length. A significant role in understanding trends is played by the coordination number of the …

Improvement Of Ferroelectric Fatigue Endurance In Multiferroic (Ba(0.5)Sr(0.5))Tio(3)/(Bi(1.05)La(0.05))Feo(3)/(Ba(0.5)Sr(0.5))Tio(3) Sandwich Structures, Chew Khian Hooi, Miao J., Zhang B. P., Wang Y.

Chew Khian Hooi

We report the improved ferroelectric properties in dielectric/multiferroic/dielectric sandwich structures composed of Ba(0.5)Sr(0.5)TiO(3) (BST) and Bi(1.05)La(0.05)FeO(3) (BLF). Compared with the single BLF film, the trilayer structures exhibit a lower dielectric loss and weaker frequency dependence of dielectric properties. At room temperature, the remnant polarization and saturation polarization of the trilayer structures are 34.3 and 46.9 mu C/cm(2), respectively. More interestingly, the polarization of BST/BLF/BST trilayer exhibits a fatigue-free characteristic of up to 10(9) switching cycles. Applying Dawber's model, the concentration of oxygen vacancies and barrier energy of oxygen vacancies migration in BST/BLF/BST trilayer are calculated as 6.1x10(17) cm(-3) and 1.33 …

How Deep Is The Irrationalism In The Science?, Pal R. Molnar

Pal R. Molnar

In the last decades a strong skeptic movement started against the para-sciences or irrationalism. We welcome this endeavor and we would like to extend the target of this movement into the field of scientific irrationalism too. In this article we try to discuss some of the clear and evident contradiction in the physics. Most of these problems were published in the last 20 years [1], and here we try to collect the biggest and stunk bugs. With this paper we try to break out the wall of silence about the inner problems of scientific world view. We believe that the …

Generation Of Laser-Polarized Xenon Using Fiber-Coupled Laser-Diode Arrays Narrowed With Integrated Volume Holographic Gratings, Panayiotis Nikolaou, Nicholas Whiting, Neil A. Eschmann, Kathleen E. Chaffee, Michael J. Barlow, Boyd M. Goodson

Nicholas Whiting

Cascading Infrastructure Failures: Avoidance And Response, George H. Baker, Cheryl J. Elliott

George H Baker

No critical infrastructure is self-sufficient. The complexity inherent in the interdependent nature of infrastructure systems complicates planning and preparedness for system failures. Recent wide-scale disruption of infrastructure on the Gulf Coast due to weather, and in the Northeast due to electric power network failures, dramatically illustrate the problems associated with mitigating cascading effects and responding to cascading infrastructure failures once they have occurred.

The major challenge associated with preparedness for cascading failures is that they transcend system, corporate, and political boundaries and necessitate coordination among multiple, disparate experts and authorities. This symposium brought together concerned communities including government and industry …

Thermal Roots Of Correlation-Based Complexity, Philip Fraundorf

Phil Fraundorf

The Formation Of Sporadic E Layers By A Vortical Perturbation Excited In A Horizontal Wind Shear Flow, G. G. Didebulidze, Levan Lomidze

Levan Lomidze

The formation of the mid-latitude sporadic E layers (Es layers) by an atmospheric vortical perturbation excited in a horizontal shear flow (horizontal wind with a horizontal linear shear) is investigated. A three-dimensional atmospheric vortical perturbation (atmospheric shear waves), whose velocity vector is in the horizontal plane and has a vertical wavenumber kz≠0, can provide a vertical shear of the horizontal wind. The shear waves influence the vertical transport of heavy metallic ions and their convergence into thin and dense horizontal layers. The proposed mechanism takes into account the dynamical influence of the shear wave velocity in the horizontal wind on …

Different Long-Term Trends Of The Oxygen Red 630.0 Nm Line Nightglow Intensity As The Result Of Lowering The Ionosphere F2 Layer, N. B. Gudadze, G. G. Didebulidze, Levan Lomidze, G. Sh. Javakhishvili, M. A. Marsagishvili, M. Todua

Levan Lomidze

Long-term observations of total nightglow intensity of the atomic oxygen red 630.0 nm line at Abastumani (41.75° N, 42.82° E) in 1957–1993 and measurements of the ionosphere F2 layer parameters from the Tbilisi ionosphere station (41.65° N, 44.75° E) in 1963–1986 have been analyzed. It is shown that a decrease in the long-term trend of the mean annual red 630.0 nm line intensity from the pre-midnight value (+0.770±1.045 R/year) to its minimum negative value (−1.080±0.670 R/year) at the midnight/after midnight is a possible result of the observed lowering of the peak height of the ionosphere F2 layer electron density hmF2 …