Spin dynamics for the Lebwohl-Lasher model

A spin dynamics algorithm, combining checkerboard updating and a rotation algorithm based on the local second-rank ordering field, is developed for the Lebwohl-Lasher model of liquid crystals. The method is shown to conserve energy well and to generate simulation averages that are consistent with those obtained by Monte Carlo simulation. However, care must be taken to avoid the undesirable effects of director rotation, and a method for doing this is proposed

Effects of CO2-induced pH reduction on the exoskeleton structure and biophotonic properties of the shrimp Lysmata californica.

The anticipated effects of CO2-induced ocean acidification on marine calcifiers are generally negative, and include dissolution of calcified elements and reduced calcification rates. Such negative effects are not typical of crustaceans for which comparatively little ocean acidification research has been conducted. Crustaceans, however, depend on their calcified exoskeleton for many critical functions. Here, we conducted a short-term study on a common caridean shrimp, Lysmata californica, to determine the effect of CO2-driven reduction in seawater pH on exoskeleton growth, structure, and mineralization and animal cryptic coloration. Shrimp exposed to ambient (7.99 ± 0.04) and reduced pH (7.53 ± 0.06) for 21 days showed no differences in exoskeleton growth (percent increase in carapace length), but the calcium weight percent of their cuticle increased significantly in reduced pH conditions, resulting in a greater Ca:Mg ratio. Cuticle thickness did not change, indicating an increase in the mineral to matrix ratio, which may have mechanical consequences for exoskeleton function. Furthermore, there was a 5-fold decrease in animal transparency, but no change in overall shrimp coloration (red). These results suggest that even short-term exposure to CO2-induced pH reduction can significantly affect exoskeleton mineralization and shrimp biophotonics, with potential impacts on crypsis, physical defense, and predator avoidance

Liquid crystal director fluctuations and surface anchoring by molecular simulation

We propose a simple and reliable method to measure the liquid crystal surface anchoring strength by molecular simulation. The method is based on the measurement of the long-range fluctuation modes of the director in confined geometry. As an example, molecular simulations of a liquid crystal in slab geometry between parallel walls with homeotropic anchoring have been carried out using the Monte Carlo technique. By studying different slab thicknesses, we are able to calculate separately the position of the elastic boundary condition, and the extrapolation length

A Follow-on Study of University Efforts to Provide Students with the Ability to Comprehend and Apply Total-Quality Principles in Their Fields of Study

This follow-on research investigated the educational processes employed by universities to enable their students to comprehend and apply Total Quality principles. The results of this research are intended to be used by Department of Defense institutions of higher education as a current guide to help them adopt practices which will enable their students to comprehend and apply Total Quality in their future assignments. Using a source list of schools from Quality Progress (Sept. 1995), contact individuals were interviewed at several civilian and military universities across the United States. Investigative questions were developed and asked concerning the specific educational processes of curriculum development, course construction and delivery, and the use of various feedback techniques. The results of the interviews were consolidated, compared, and contrasted to produce a guide of activities that have been attempted by universities trying to impart the principles of Total Quality to their students. By using processes similar to those of the prior research, an overview of changes in the teaching of total quality principles in the past three years was also developed

UNSWIRF: A Tunable Imaging Spectrometer for the Near-Infrared

We describe the specifications, characteristics, calibration, and analysis of data from the University of New South Wales Infrared Fabry-Perot (UNSWIRF) etalon. UNSWIRF is a near-infrared tunable imaging spectrometer, used primarily in conjunction with IRIS on the AAT, but suitable for use as a visitor instrument at other telescopes. The etalon delivers a resolving power in excess of 4000 (corresponding to a velocity resolution ~75 km/s), and allows imaging of fields up to 100" in diameter on the AAT at any wavelength between 1.5 and 2.4 microns for which suitable blocking filters are available.Comment: 16 pages, 10 figures, uses psfig.sty and html.sty (included). To appear in Publications of the Astronomical Society of Australi

Theory and simulation of the nematic zenithal anchoring coefficient

Combining molecular simulation, Onsager theory and the elastic description of nematic liquid crystals, we study the dependence of the nematic liquid crystal elastic constants and the zenithal surface anchoring coefficient on the value of the bulk order parameter

Reversible plasticity in amorphous materials

A fundamental assumption in our understanding of material rheology is that when microscopic deformations are reversible, the material responds elastically to external loads. Plasticity, i.e. dissipative and irreversible macroscopic changes in a material, is assumed to be the consequence of irreversible microscopic events. Here we show direct evidence for reversible plastic events at the microscopic scale in both experiments and simulations of two-dimensional foam. In the simulations, we demonstrate a link between reversible plastic rearrangement events and pathways in the potential energy landscape of the system. These findings represent a fundamental change in our understanding of materials--microscopic reversibility does not necessarily imply elasticity.Comment: Revised pape