Being subject-centred: A philosophy of teaching and implications for higher education

Being subject-centred as a higher education teacher offers a rich and illuminating philosophical and practical understanding of learning. Building upon previous research on subject-centred learning, we draw on reflection, literature review and a phenomenological approach to show how our ways of being infuse the teaching and learning environment. Philosophically, it is our way of being with our subject as teachers that influences the learning within our students. We show how posing the question: 'What is the best way to teach this subject?' helps a teacher find the best way to enhance the learning experience. It entails moving away from reliance solely on approaches that simply 're-present' content, such as lectures and online learning management systems, to interactive classrooms where space is created for the students to enter into their own engagement with the subject in a shared pursuit with the teacher, resulting in more effective teaching and learning. We illustrate this with personal accounts of our own journeys as teachers. We acknowledge that it takes courage to teach and to fully be subject-centred in the face of prevailing trends and pressures for other ways of teaching currently prominent in the higher education sector. But, ultimately, it is who we are as teachers that matters most, and being subject-centred provides the most effective way for us to most meaningfully reach our students

Dynamic holographic interferometry using a Bi12SiO20 photorefractive crystal and monomode optical fibres

Dynamic holographic interferometry using polarization preserving opticai fibres as light guides and incorporating a photorefractive Bi12SiO20 (BSO) crystal as the recording medium is described. An experimental investigation of the recording of time average holograms through the diffusion process (employing anisotropic self-diffraction) and the drift process (application of d.c. and a.c. electric fields across the crystal) is also described. The holographic interferometer was optimised to produce holograms with a high diffraction efficiency and a high signal-to-noise ratio. Results are presented on optimising parameters such as the writing beam angle and writing beam intensity ratio. The advantages that can be gained by deploying this holographic interferometer in an industrial environment, where the laser light is guided to the location of the object by means of monomode fibres and images are stored within a photorefractive crystal is described. The holographic interferometer is capable of producing time average and double exposure interferograms of vibrating and deformed objects which can be displayed in real time

Challenges in using GPUs for the real-time reconstruction of digital hologram images

This is the pre-print version of the final published paper that is available from the link below.In-line holography has recently made the transition from silver-halide based recording media, with laser reconstruction, to recording with large-area pixel detectors and computer-based reconstruction. This form of holographic imaging is an established technique for the study of fine particulates, such as cloud or fuel droplets, marine plankton and alluvial sediments, and enables a true 3D object field to be recorded at high resolution over a considerable depth. The move to digital holography promises rapid, if not instantaneous, feedback as it avoids the need for the time-consuming chemical development of plates or film film and a dedicated replay system, but with the growing use of video-rate holographic recording, and the desire to reconstruct fully every frame, the computational challenge becomes considerable. To replay a digital hologram a 2D FFT must be calculated for every depth slice desired in the replayed image volume. A typical hologram of ~100 μm particles over a depth of a few hundred millimetres will require O(10^3) 2D FFT operations to be performed on a hologram of typically a few million pixels. In this paper we discuss the technical challenges in converting our existing reconstruction code to make efficient use of NVIDIA CUDA-based GPU cards and show how near real-time video slice reconstruction can be obtained with holograms as large as 4096 by 4096 pixels. Our performance to date for a number of different NVIDIA GPU running under both Linux and Microsoft Windows is presented. The recent availability of GPU on portable computers is discussed and a new code for interactive replay of digital holograms is presented

Mosaicking with cosmic microwave background interferometers

Measurements of cosmic microwave background (CMB) anisotropies by interferometers offer several advantages over single-dish observations. The formalism for analyzing interferometer CMB data is well developed in the flat-sky approximation, valid for small fields of view. As the area of sky is increased to obtain finer spectral resolution, this approximation needs to be relaxed. We extend the formalism for CMB interferometry, including both temperature and polarization, to mosaics of observations covering arbitrarily large areas of the sky, with each individual pointing lying within the flat-sky approximation. We present a method for computing the correlation between visibilities with arbitrary pointing centers and baselines and illustrate the effects of sky curvature on the l-space resolution that can be obtained from a mosaic.Comment: 9 pages; submitted to Ap

Systematic Errors in Cosmic Microwave Background Interferometry

Cosmic microwave background (CMB) polarization observations will require superb control of systematic errors in order to achieve their full scientific potential, particularly in the case of attempts to detect the B modes that may provide a window on inflation. Interferometry may be a promising way to achieve these goals. This paper presents a formalism for characterizing the effects of a variety of systematic errors on interferometric CMB polarization observations, with particular emphasis on estimates of the B-mode power spectrum. The most severe errors are those that couple the temperature anisotropy signal to polarization; such errors include cross-talk within detectors, misalignment of polarizers, and cross-polarization. In a B mode experiment, the next most serious category of errors are those that mix E and B modes, such as gain fluctuations, pointing errors, and beam shape errors. The paper also indicates which sources of error may cause circular polarization (e.g., from foregrounds) to contaminate the cosmologically interesting linear polarization channels, and conversely whether monitoring of the circular polarization channels may yield useful information about the errors themselves. For all the sources of error considered, estimates of the level of control that will be required for both E and B mode experiments are provided. Both experiments that interfere linear polarizations and those that interfere circular polarizations are considered. The fact that circular experiments simultaneously measure both linear polarization Stokes parameters in each baseline mitigates some sources of error.Comment: 19 pages, 9 figures, submitted to Phys. Rev.

Off-axis transmission holographic system for recording aquatic particles

We describe a holographic system for recording particles suspended in water. The hologram plate is located in air, separated from the test tank by an air/glass/water boundary. The holographic emulsion is therefore unaffected by adverse aquatic conditions within the tank (i.e. surface contamination, non-uniform swelling). The design geometry is intended to minimise the aberrations that arise from recording subjects located in water and replaying their hologram image in air. Third order aberrations, most crucially spherical aberration and astigmatism, are suppressed to give an experimental resolution of 7 lp/mm using USAF 1951 target in water 600mm from the boundary. Particles (plankton species) in the sub-millimeter to several millimeters size range are observed at planar sections within the recording volume by visual inspection of the hologram replayed in real image mode