Retrieving an archive: Brook Andrew and William Blandowski's Australien in 142 Photographischen Abbildungen

Much of the critical response to Brook Andrew’s reinterpretation of images from a colonial archive in his 2008 series The Island situated the work in a tradition of post-colonial critique of documentary images. But is this an adequate account of either Andrew’s work or the archive in question, William Blandowski’s Australien in 142 Photographischen Abbildungen (1862)? This essay looks at practices involving copying and their impact on understandings of authenticity, the role of art in science, the nature of the observer and visual communication in relation to the broad scope of Blandowski’s archive, but particularly with regard to Andrew’s intervention in it. By examining the way that the past is brought into the present in the Island series, this essay seeks to facilitate a more richly nuanced understanding of these works that is cognizant of the historical issues involved

Out of the frying pan: Voyaging to Queensland in 1863 on board the Fiery Star

A picture, even a triptych such as that painted by McCubbin can only tell part of any complex story, but my research underlines the narrowness of the portrait of the pioneer emigrant propounded in Australian mythology. The pioneers in this study, the Waltons and the Hanlons did not simply cope with the adversities sent their way. Their various oceanic passages were a step towards personal transformation. In their decision to migrate, and their subsequent life choices, they reveal themselves to be canny agents of their own destiny who were resilient in the face of hardship, but also able to take advantage of opportunities that presented themselves in urban as well as rural areas

Angular momentum of a strongly focussed Gaussian beam

A circularly polarized rotationally symmetric paraxial laser beams carries hbar angular momentum per photon as spin. Focussing the beam with a rotationally symmetric lens cannot change this angular momentum flux, yet the focussed beam must have spin less than hbar per photon. The remainder of the original spin is converted to orbital angular momentum, manifesting itself as a longitudinal optical vortex at the focus. This demonstrates that optical orbital angular momentum can be generated by a rotationally symmetric optical system which preserves the total angular momentum of the beam.Comment: 4 pages, 3 figure

MIME: A Gesture-Driven Computer Interface

MIME (Mime Is Manual Expression) is a computationally efficient computer vision system for recognizing hand gestures. The system is intended to replace the mouse interface on a standard personal computer to control application in a more intuitive manner. The system is implemented in C code with no hardware-acceleration and tracks hand motion at 30 fps on a standard PC. Using a simple two-dimensional model of the human hand, MIME employs a highly-efficient, single-pass algorithm to segment the hand and extract its model parameters from each frame in the video input. The hand is tracked from one frame to the next using a constant-acceleration Kalman filter. Tracking and feature extraction is remarkably fast and robust even when the hand is placed above difficult backdrops such as a typical cluttered desktop environment. Because of the efficient coding of the gesture tracking, adequate CPU power remains to run standard applications such as web browsers and presentations

Orientation of biological cells using plane-polarized Gaussian beam optical tweezers

Optical tweezers are widely used for the manipulation of cells and their internal structures. However, the degree of manipulation possible is limited by poor control over the orientation of trapped cells. We show that it is possible to controllably align or rotate disc shaped cells - chloroplasts of Spinacia oleracea - in a plane polarised Gaussian beam trap, using optical torques resulting predominantly from circular polarisation induced in the transmitted beam by the non-spherical shape of the cells.Comment: 9 pages, 6 figure

Nanotrapping and the thermodynamics of optical tweezers

Particles that can be trapped in optical tweezers range from tens of microns down to tens of nanometres in size. Interestingly, this size range includes large macromolecules. We show experimentally, in agreement with theoretical expectations, that optical tweezers can be used to manipulate single molecules of polyethylene oxide suspended in water. The trapped molecules accumulate without aggregating, so this provides optical control of the concentration of macromolecules in solution. Apart from possible applications such as the micromanipulation of nanoparticles, nanoassembly, microchemistry, and the study of biological macromolecules, our results also provide insight into the thermodynamics of optical tweezers.Comment: 5 pages, 3 figures, presented at 17th AIP Congress, Brisbane, 200

Forces from highly focused laser beams: modeling, measurement and application to refractive index measurements

The optical forces in optical tweezers can be robustly modeled over a broad range of parameters using generalsed Lorenz-Mie theory. We describe the procedure, and show how the combination of experimental measurement of properties of the trap coupled with computational modeling, can allow unknown parameters of the particle - in this case, the refractive index - to be determined.Comment: 5 pages, 4 figures, presented at 17th AIP Congress, Brisbane, 200