Surface optical vortices

It is shown how the total internal reflection of orbital-angular-momentum-endowed light can lead to the generation of evanescent light possessing rotational properties in which the intensity distribution is firmly localized in the vicinity of the surface. The characteristics of these surface optical vortices depend on the form of the incident light and on the dielectric mismatch of the two media. The interference of surface optical vortices is shown to give rise to interesting phenomena, including pattern rotation akin to a surface optical Ferris wheel. Applications are envisaged to be in atom lithography, optical surface tweezers, and spanners

Optical Dipole Trapping beyond Rotating Wave Approximation: The case of Large Detuning

We show that the inclusion of counter-rotating terms, usually dropped in evaluations of interaction of an electric dipole of a two level atom with the electromagnetic field, leads to significant modifications of trapping potential in the case of large detuning. The results are shown to be in excellent numerical agreement with recent experimental findings, for the case of modes of Laguerre-Gauss spatial profile.Comment: 13 pages, 2 figure

Spin transport in coupled spinor Bose gases

We report direct measurements of spin transport in a trapped, partially condensed spinor Bose gas. Detailed analyses of spin flux in this out-of-equilibrium quantum gas are performed by monitoring the flow of atoms in different hyperfine spin states. The main mechanisms for motion in this system are exchange scattering and potential energy inhomogeneity, which lead to spin waves in the normal component and domain formation in the condensate. We find a large discrepancy in domain formation timescales with those predicted by potential-driven formation, indicating strong coupling of the condensate to the normal component spin wave

Learning theory and its application to female learner support in engineering

School of Engineering at Murdoch University is now in its fifth year: a new School sited on the new regional Campus. This environment enabled the staff to take an innovative approach to the School's development. One key issue addressed from the outset was that of women in a nontraditional area. Positive action was taken to attract high calibre female staff and as a consequence over 50% of the School's staff, academic and non-academic, are female. From the student perspective, issues confronting females studying in Engineering, which are reflected in international low recruitment and retention, continue to be addressed. Individuals are different and these differences affect how a student performs. In particular, gender differences in learning styles have been noted. This has directed us to administer, as part of a first year foundational unit, learning style inventories to all first year students, who then identify their self-reported learning styles. In this positive atmosphere many varied and successful initiatives, based on our learning style research, are being trialled to encourage female students into our programs and then support and retain them throughout their four years of study. This research discusses the initial learning style results and their application to our initiatives

Different Melting Behavior in Pentane and Heptane Monolayers on Graphite; Molecular Dynamics Simulations

Molecular dynamics simulations are utilized to study the melting transition in pentane (C5H12) and heptane (C7H16), physisorbed onto the basal plane of graphite at near-monolayer coverages. Through use of the newest, optimized version of the anisotropic united-atom model (AUA4) to simulate both systems at two separate coverages, this study provides evidence that the melting transition for pentane and heptane monolayers are significantly different. Specifically, this study proposes a very rapid transition from the solid crystalline rectangular-centered (RC) phase to a fluid phase in pentane monolayers, whereas heptane monolayers exhibit a slower transition that involves a more gradual loss of RC order in the solid-fluid phase transition. Through a study of the melting behavior, encompassing variations where the formation of gauche defects in the alkyl chains are eliminated, this study proposes that this gradual melting behavior for heptane monolayers is a result of less orientational mobility of the heptane molecules in the solid RC phase, as compared to the pentane molecules. This idea is supported through a study of a nonane monolayer, which gives the gradual melting signature that heptane monolayers also seem to indicate. The results of this work are compared to previous experiment over pentane and heptane monolayers, and are found to be in good agreement

Elementary Excitations of a Bose-Einstein Condensate in an Effective Magnetic Field

We calculate the low energy elementary excitations of a Bose-Einstein Condensate in an effective magnetic field. The field is created by the interplay between light beams carrying orbital angular momentum and the trapped atoms. We examine the role of the homogeneous magnetic field, familiar from studies of rotating condensates, and also investigate spectra for vector potentials with a more general radial dependence. We discuss the instabilities which arise and how these may be manifested.Comment: 8 pages, 4 figure

Polarisation rotation of slow light with orbital angular momentum in ultracold atomic gases

We consider the propagation of slow light with an orbital angular momentum (OAM) in a moving atomic medium. We have derived a general equation of motion and applied it in analysing propagation of slow light with an OAM in a rotating medium, such as a vortex lattice. We have shown that the OAM of slow light manifests itself in a rotation of the polarisation plane of linearly polarised light. To extract a pure rotational phase shift, we suggest to measure a difference in the angle of the polarisation plane rotation by two consecutive light beams with opposite OAM. The differential angle $\Delta\alpha_{\ell}$ is proportional to the rotation frequency of the medium $\omega_{\mathrm{rot}}$ and the winding number $\ell$ of light, and is inversely proportional to the group velocity of light. For slow light the angle $\Delta\alpha_{\ell}$ should be large enough to be detectable. The effect can be used as a tool for measuring the rotation frequency $\omega_{\mathrm{rot}}$ of the medium.Comment: 5 pages, 1 figur

NON-PARAMETRIC AND SEMI-PARAMETRIC TECHNIQUES FOR MODELING AND SIMULATING CORRELATED, NON-NORMAL PRICE AND YIELD DISTRIBUTIONS: APPLICATIONS TO RISK ANALYSIS IN KANSAS AGRICULTURE

Parametric, non-parametric, and semi-parametric approaches are commonly used for modeling correlated distributions. Semi-parametric and non-parametric approaches are used to examine the risk situation for Kansas agriculture. Results from the model indicate that 2000 will be another difficult year for Kansas farmers, although crop income will increase slightly from 1999. However, unless another supplemental infusion of government payments occurs, crop income is expected to be the lowest since 1992.correlated distributions, non-parametric modeling, semi-parametric modeling, Kansas agriculture, Research Methods/ Statistical Methods,

THE MULTI-PRODUCT ASYMPTOTICALLY IDEAL MODEL: AN APPLICATION TO AGRICULTURE

This paper examines the Multi-Product Asymptotically Ideal Production Model as an alternative to the translog and normalized quadratic functional forms using farm level data. Factors such as ease of estimation, imposition of regularity conditions, and quantitative differences in empirical estimates are compared.AIM, Asymptotically Ideal Model, flexible functional form, cost function, Production Economics, Research Methods/ Statistical Methods,