2012 RESEARCH SEMINARS
Seminars are usually over 40 minutes plus questions on Fridays at 12.40 in Room P25 on the ground floor of PEMS South, Building 26, unless otherwise advertised. Light refreshments (coffee and biscuits) served 10 minutes before presentation.
A link to the 2011 and 2010 programs of Maths and Physics Seminars is placed here for those interested in previous year's activities.
Date and Venue: Friday 20 April, P25, Building 26, UNSW Canberra
Time: 12:40 pm
Topic: Spectroscopy of a Sm(III) Activated X-ray Storage Phosphor
Presented by: Zhiqiang Liu, PEMS PhD student
X-ray storage phosphors are materials capable of recording images produced by the absorption of X-rays. They have many applications in medical imaging and personal radiation monitoring (dosimetry). Recently, Professor Hans Riesen and his team have discovered that nanocrystalline BaFCl:Sm3+, as prepared by co-precipitation from aqueous solutions, is an efficient photoluminescent storage phosphor for ionising radiation. The storage mechanism is based on the reduction of Sm3+ to Sm2+ ions upon exposure to X-irradiation; subsequently, the Sm2+ ions can be efficiently read out by the photoexcitation of the intraconfigurational f-f luminescence lines, such as the 5D0-7F0 transition at 687.8 nm, via excitation into the very intense and parity-allowed 4f6-4f65d transition in the blue-violet region of the spectrum.
My PhD project focuses on investigations of the detailed storage mechanism of nanocrystalline BaFCl:Sm3+ by the application of a variety of spectroscopic techniques, with individual measurements providing both unique and complementary information. These techniques include synchrotron X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, photoluminescence spectroscopy, cathodoluminescence microanalysis, synchrotron-based X-ray absorption spectroscopy, high-resolution laser spectroscopy (e.g. spectral hole-burning) and electron spin resonance. In this talk, the results obtained by different optical spectroscopic techniques for nanocrystalline BaFCl:Sm3+ are discussed and further compared with those obtained for microcrystalline BaFCl:Sm3+ prepared by high-temperature sintering. The storage mechanism of nanocrystalline BaFCl:Sm3+ X-ray storage phosphor is also summarized.
Date and Venue: Friday 30 March, P25, Building 26, UNSW Canberra
Time: 12:40 pm
Topic: Polarised cases: ferroelectricity of SrTiO3 and LuFe2O4
Presented by: Maciej Bartkowiak, PEMS PhD student
As a part of our research on multiferroics we decided to study two systems showing unusual mechanisms of ferroelectric polarisation. The ferroelectricity of SrTiO3 is isotope-induced, and in LuFe2O4 it originates from charge order on Fe atoms. Our approach combined neutron and x-ray scattering techniques with density-functional theory calculations. We determined the structure of the ferroelectric phase of SrTiO3 and the extent of charge disproportionation on Fe atoms in LuFe2O4.
Date and Venue: Friday 9 March, P25, Building 26, UNSW Canberra
Time: 12:40 pm
Topic: The physical oceanography of the Great Barrier Reef and hydrodynamic modeling of estuaries in Brazil
Presented by: Fernando P. Andutta, James Cook University
Using data from twenty current meter sites and tide gauges and the 2D SLIM finite element unstructured numerical model, I modeled the water circulation in the Great Barrier Reef with a horizontal resolution that can capture variability of currents at a spatial scale relevant to coral reefs and the small bays in the Great Barrier Reef (GBR). The model uses grid cells in the range of 150 m near reefs to nearly 20 km in open waters far from reefs. I focus on modeling three processes, namely (1) the general circulation in order to estimate the age of waters and the flushing time of the GBR, (2) the sticky water effect that leads to decreased flushing and a high exposure time in high reef density areas in the southern and central regions of the GBR matrix, and (3) the dynamics of the hypersaline coastal boundary layer in the dry season.
I will also summarise my field studies and 3D modeling of two estuaries in Brazil, one in the tropics and one in a temperate climate. In both estuaries diffusion reduces the residence time. Using that experience of contrasting estuaries, I have also re-evaluated the application of simple analytical solutions to estimate these time scales for a range of estuaries worldwide. The analytical results were compared with residence time results from numerical models including the LOICZ model and the Constituent-oriented Age and Residence time Theory (CART), and a synthesis is presented.
Date and Venue: Friday 2 March, P25, Building 26, UNSW Canberra
Time: 11.10 am
Topic: Roving the Red Planet: Spirit, Opportunity and the Exploration of Mars
Presented by: Dr Paulo de Souza, Research Director, CSIRO Sensors and Sensor Networks; Professor of Sensor Informatics with University of Tasmania
ABSTRACT:
The purpose of the Mars mission is to look for geological evidence concerning whether the red planet had conditions on its surface that would have been suitable for life as we know it. In other words, we set out to look for sedimentary rocks: a sure sign that there was once water on Mars.
After six years of intense exploration and key discoveries on Mars, Spirit
showed signs of age and did not resist the last Martian winter. The
rover Opportunity is learning from the difficulties encountered by her sister and is continuing the exploration of Mars over the last eight years.
You will be introduced to these rovers' curriculum vitae. You will see how they were born, constructed, tested, packaged, sent to Mars and changed our knowledge about the history of Mars and of our Solar System.
SPEAKER PROFILE:
Paulo de Souza is a Physicist with a PhD in Natural Sciences (Johannes Gutemberg Universitaet, Mainz, Germany). He is Science Leader in Sensor Networks and Research Director of the across-disciplinary platform on sensors and sensor networks from CSIRO. He was Research Director of the Tasmanian ICT Centre at CSIRO, and is a collaborator scientist on NASA’s Mars Exploration Rovers Project. Paulo has been appointed Professor of Sensor Informatics with UTAS. He has worked in industrial research centres in Brazil and Europe, and received many international awards as a result of his research in industry. Paulo has written over 200 scientific papers, and co-authored a series of papers identified as ‘Breakthrough on the
Year: 2004’ by the prestigious magazine Science.
Date and Venue: Friday 17 February, P25, Building 26, UNSW Canberra
Time: 11.10 am
Topic: Superconductivity: 101 Years of its Discovery
Presented by: Professor Mukunda P. Das, Department of Theoretical Physics, RSPE, ANU Canberra
Superconductivity is an unanticipated phenomenon and its 101 years history is a fascinating subject in physical science. The fact that certain materials below a critical temperature lose their electrical resistance and at the same time repel a magnet remained a miracle until a microscopic explanation became available in 1957. In this pedagogic talk I shall present a brief overview of the important landmarks and major advances in this exciting and difficult area of research. I shall also present a variety of novel superconductors discovered in the past three decades and highlight several associated anomalies in their properties, which demand new microscopic mechanisms. Surprisingly over one hundred years of accumulated knowledge is still inadequate for understanding the novel unconventional superconductors.
About the Speaker:
Professor Mukunda Das is in the Research School of Physics and Engineering at the Australian National University, Canberra. He is Fellow of American Physical Society, Institute of Physics (UK) and Australian Institute of Physics. He is a senior member of Editorial Board of J. Physics: Condensed Matter.
His research interest concerns the fundamental aspects of condensed matter, which include Superconductivity, Bose-Einstein Condensation, Mesoscopic Systems, Strongly Correlated Electrons, Density Functional Theory and Theory of Disordered States.