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20th Departmental Conference - Physics and Astronomy

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DEPARTMENT OF PHYSICS & ASTRONOMY20 TH DEPARTMENTAL CONFERENCEMonday 30 th August and Tuesday 31 st August 2004Maths and Computer Science 031Transit of Venus


Monday, August 30 thSession 1Chairperson: Michael Albrow9.05 – 9.10 Welcome by Michael Albrow, Conference OrganiserOpening address by Phil Butler, HOD9.10 – 9.30 Martin Kauffman The Structure of Unsupported AntimonyNanoclusters9:30 – 9.45 David Ramm Binary star research at Mt John Observatory9.45 – 10.00 Mike Lee Cellular automata10.00 – 10.15 John Hearnshaw The work of the IAU Program Group for the WorldwideDevelopment of Astornomy, and the state ofastronomy in Mongolia10.15 – 10.30 Scott Choi Laser Spectroscopy of Eu 3+ ions in theCaF 2 /Eu/CdF 2 Super-lattices10.30 – 11.00 MORNING REFRESHMENTSSession 2Chairperson: Mike Lee11.00 – 11.15 Ben Carter Brane world black holes11.15 – 11.30 Judy Mohr Astronomical Optics: Adaptive Optics at Mt John11.30 – 11.45 Steve Churchwell Overview of the RICE experiment: scientificgoals and future plans11.45 – 12.00 Musaed Alie Almalki In-vivo Gadolinium Analysis12.00 – 12.15 Pauline Harris The search for temporal coincidences betweenGamma Ray Bursts and neutrino events detectedin the RICE array.12.15 – 12.25 Paul Miller An investigation into the optical and electronicproperties of ZnO thin films12.25 – 2.00 LUNCH2


Session 3Chairperson: Bryn Currie2.00 – 2:15 Siva Sarasanandarajah Reversible changes in fluorescence of bacterialendospores found in aerosols due tohydration/drying2.15 - 2.30 Siramas Komonjinda Astronomy in Thailand: Past, Present, and Future2.30 - 2.45 Marni Sheppeard Ribbons, Knots and Chain Mail2.45 - 3.00 Andreas Baumgartner Cool winds: Climate change 80 km aboveAntarctica?3.00 – 3.30 AFTERNOON REFRESHMENTSSession 3Chairperson: Shelley Scott3.30 - 3.45 Malcolm Cropp Time-series CCD photometry3.45 - 4.00 Richard Watts Measuring Motion using Magnetic ResonanceImaging4.00 - 4.15 Chang-Kui (Jean) Duan Calculation of single-beam two-photon absorptionrate of lanthanides: effective operator method,perturbative expansion and diagrammaticrepresentation.4.15 – 4.30 Jonathan Griffin Conformal Electron Bolus: an example of MedicalPhysics in Radiation OncologyCLOSE OF DAY ONE3


Tuesday August 31 stSession 4Chairperson: Marni Sheppeard9.00 - 9.15 Adrian McDonald Mid-latitude precipitating convection observed byVHF radar9.15 - 9.30 Bryn Currie Comparison of Eye Shields in RadiotherapeuticBeams9.30 - 9.45 Derek Boyd Propagation of Radio Waves in South Polar Ice9.45 - 10.00 Veronica Miller Planet detection via the transit method10.00 -10.15 Michael Chappell Getting inside your head: warping your brain to seeit it’s normal10.15 - 10.30 William Joyce Algebra versus Geometry10.30 – 11.00 MORNING REFRESHMENTSSession 5 Chairperson: Ben Carter11.00 - 11.15 Phillip Wahrlich Measurement of the refractive index of the SouthPolar ice via Radio tomography11.15 - 11.30 Veronica Cahyadi The real-life phenomena in two classicalintroductory physics texts11.30 - 11.45 Mike Reid Excited-state dynamics of lanthanide ions11.45 - 12.00 Shelley Scott Kinetics vs. Thermodynamics: A balancing act inthe growth of nanoscale surface islands12.00 – 12.15 Allen Lim12.15 – 12.30 Phil Butler Things the Department might do12.30 – 2.00 LUNCHSession 6Chairperson: Judy Mohr2.00 – 2.15 John Campbell Assisting Undergrads to be Self-Reliant I:Dimensional Analysis4


2.15 - 2.30 Ahmad Ayesh Assembly of Bi clusters into nanowires usingetched V-grooves as templates.2.30 – 2.45 Stuart Barnes Progress on the design of the High ResolutionSpectrograph for the Southern African LargeTelescope2.45 – 3.00 Alex Neilsen Horizons and Skyrmion Black Holes3.00 – 3.15 Ben Wilder TBI (Total Body Irradiation) treatment utilizing amoving couch and MLC for conformal beamtreatment3.15 – 3.45 AFTERNOON REFRESHMENTSSession 7Chairperson: Michael Albrow3.45 – 4.00 Bob Hurst Recent measurements of seismic rotations usinglarge ring lasers4.00 – 4.15 Peter Smale Recent contributions of MR and PET imagingtechniques to the diagnosis and treatment ofAlzheimer’s disease4.15 – 4.30 Duncan Wright Mode identification of nonradially pulsating stars4.30 – 4.45 Petra Huck The Coupling of Dynamics and Chemistry in theAntarctic Stratosphere4.45 – 5.00 Lou Reinisch Diamonds are a surgeon’s best friendCONFERENCE CLOSESRetire to the Staff Club for end-of-conference functionand presentation of conference prizes5


Monday 30 th AugustABSTRACTSThe Structure of Unsupported Antimony NanoclustersMartin KaufmannAbstract: There are several different techniques to explore the structure of nanoclusters, however,these methods allow either only indirect measurement of the structure (e.g. mass spectroscopicanalysis of magic numbers) or they require an underlying substrate (e.g. high resolution electronmicroscopy). The substrate effects the balance of surface and volume energies which criticallyinfluences the structure of a cluster. It is therefore important to perform experiments which allow thedirect determination of the structure of unsupported clusters. An electron diffraction study onunsupported antimony (Sb) nanoclusters will be presented in this talk.* * * * *Binary star research at Mt John ObservatoryDavid Ramm* * * * *Abstract: I will describe some of my work at Mt John Observatory using the HERCULES spectrographwhich has allowed measurement of some orbital and stellar parameters of several binary stars.Cellular AutomataMike Lee* * * * *Abstract: Nucleation and percolation in stochastic cellular automata arising from geophysicalearthquake models.* * * * *The work of the IAU Program Group for the World-wide Development of Astronomy, and thestate of astronomy in MongoliaJohn HearnshawAbstract: I will discuss the work of PGWWDA, a program of the International Astronomical Union forwhich I am the chairperson. Recently I visited Mongolia on behalf of this committee and I will discuss mywork and visit there.* * * * *6


Laser Spectroscopy of Eu 3+ centres in CaF 2 :Eu/CdF 2 Super-latticesScott ChoiAbstract: We studied PL of Eu 3+ ions in the CaF 2 :Eu/CdF 2 super-lattices (SLs) by laser spectroscopymethod. It was shown that the Pl of cubic Eu 3+ center has been found in the SLs with fluorite layerthickness of the SL. PL intensity behaviour at different temperatures as well as with additionalillumination allowed us to suggest that the interface center is formed by located in the closest to theinterface Eu 3+ ion, which trapped an electron from the conduction band of neighbouring CdF 2 layer.Brane world black holesBen Carter* * * * *Abstract: A brief overview of braneworlds will be mentioned, along with a brief revision of black holes. Abrief summary of interesting properties of a Schwarzschild solution embedded the Susybrane model ofCarter, Nielsen and Wiltshire will be presented.* * * * *Astronomical Optics: Adaptive Optics at Mt JohnJudy MohrAbstract: Degradation in astronomical imaging because of atmospheric turbulence is an age-oldproblem and can be compensated for using techniques such as adaptive optics (AO). As part of a jointcollaboration between the Department of Physics & Astronomy and the Department of Electrical &Computer Engineering an AO instrument is being developed to the McLellan 1-m telescope at MountJohn University Observatory. Current development and progress of the AO system are discussed.* * * * *Overview of the RICE experiment: scientific goals and future plansSteve ChurchwellAbstract: The Radio Ice Cherenkov Experiment (RICE) is a neutrino detector deployed in the Antarcticice at the geographic south pole. It is designed to detect ultra high energy (10 15 eV and higher) cosmicneutrinos by utilizing the Askaryan effect. The Askaryan effect will be explained, possible origins of PeVand higher neutrinos will be discussed, and finally, future plans for data acquisition system upgrades willbe described with particular emphasis on the University of Canterbury’s planned contributions.In-vivo Gadolinium AnalysisMusaed Alie Almalki* * * * *Abstract: In recent years gadolinium received high attention in research in neutron therapy. Theelement has the highest absorption cross section for slow neutrons. The energy available from (N, γ(reaction following neutron absorption can be used for delivering dose to an organ in which the element islocalized. In this process most of the energy from the reaction is deposited into tumour and onlyinsignificant dose goes to normal tissue. Accordingly information on concentration, build-up orelimination of gadolinium from an organ can be of great significance in gadolinium neutron therapy. Inthis research, it is intended to make in-vivo measurements of gadolinium concentration in organs by x-ray fluorescence method. In this method, x-rays from x-ray machines are allowed to be incident on theorgan under investigation. Following absorption of x-rays by gadolinium atoms, characteristics x-raysare emitted and measured by detector. The intensity is proportional to Gadolinium concentration.* * * * ** * * * *7


The search for temporal coincidences between Gamma Ray Bursts and neutrino eventsdetected in the RICE array.Pauline HarrisAbstract: The Radio Ice Cherenkov Experiment (RICE) located at the South Pole, is designed to detectthe coherent broad-band radio Chernkov radiation (CR) emitted from a high energy (10 15 to 10 18 eV)electron neutrino, ν e , interacting with a nucleon in the ice. Observations have identified that ActiveGalactic Nuclei (AGN) and Gamma Ray Bursts (GRBs) are two of the most energetic sources in theUniverse and are ideal hosts for high energy neutrino production. I discuss the theory of neutrinoproduction in GRBs, how RICE can be used to validate these productions theories, and somepreliminary results from the temporal coincidence search and the limits this imposes on the models.* * * * *An investigation into the optical and electronic properties of ZnO thin filmsPaul MillerAbstract: ZnO is a wide bandgap semiconductor with many interesting optical and electrical propertiesthat make it suitable for such applications as Solar Cells, piezo electric devices, UV lasers, green andorage LED’s, and high temperature electronics. It has a wide bandgap of 3.36eV, a high exciton bindingenergy of 60 meV and when grown as a high quality film is transparent to the optical part of thespectrum. The bandgap can be tuned by introducing dopants such as cadmium and magnesium duringfilm growth which is a necessary requirement for constructing high efficiency solar cells.* * * * *Reversible effect of hydration on Bacillus globigiiSivananthan SarasanandarajahAbstract: Fluorescence is being considered as a technique for the rapid detection and identification ofpathogenic spores used in bioterrorism. Bacterial spores have a significant affinity for water. Twodimensionalfluorescence excitation/emission spectra of bacillus spores are highly specific, fingerprintlikesignatures that can also be used to discriminate between wet and dry spores. The sporefluorescence is measured with the spores on filter paper fitted at 45 degrees into a 1 cm quartz cuvette.Measurements are made for the dried, wet and redried spores using a scanning fluorometer at rommtemperature. Using the autofluorescence of bacillus spores, we confirm the result of reversible watermigration between inner spore compartments and the environment. The characteristic information isextracted from the spectral contours by applying pattern recognition methods such as principalcomponent analysis and cluster analysis. This communication is devoted to enhancing rapid decisionmakingand identification of Bacillus globigii spores in dry, wet and re-dried form using fluorescencefinger printing and statistical methods. Our results also reveal a strong effect of hydration on thefluorescence spectra of the Bacillus globigii spores. Good reproducibility was observed with the results,even for different concentrations of the spores. Current techniques of identification such as clusteringand principal component analysis are used in the analysis of spectral changes. This project is related toDepartment of the Navy Grant N62649-03-1-0009 issued by U.S. FISC YOKOSUKA.* * * * *Astronomy in Thailand: Past, Present, and FutureSiramas KomonjindaAbstract: Thai astronomy has a very long history. During the Sukothai realm, people used the lunar calendar fortheir everyday life and calculated the appearances of planets and the occurrence of eclipses which are related toreligious belief. Modern astronomy came in during the Ayuddhaya realm with the arrival of the western diplomaticcorps. The first observatory in Thailand was built in 1685. Until the Rattanakosin realm, modern astronomy was8


mixed with oriental astronomy. King Rama IV, the father of Thai science, had calculated the exact time of the totalsolar eclipse of 18 August 1868. At present, there are many astronomical research groups and amateur astronomygroups in Thailand. These groups are distributed all over the country. In 2007, the National Astronomical Institute willbe established with a 2-m telescope situated on the highest peak of Thailand.Ribbons, Knots and Chain MailMarni Sheppeard* * * * *Abstract: Higher Categorical Algebra is the mathematics that unifies gravity and quantum physics. Thistalk focuses on the relation between three dimensional algebras and physical constructs such as 6jsymbols.* * * * *Cool winds: Climate change 80 km above Antarctica?Andreas BaumgartnerAbstract: Several studies have suggested that especially the polar Mesosphere may be highly sensitiveto climatic variations. In order to detect these, long-term monitoring is important. This study isconcentrating on Medium Frequency radar data from Scott Base, Antarctica, which has been measuringwind velocities in 75 to 95 km altitude since 1982. The record makes up the longest climate record ofthis type of data in the world. However, interpretation may be complicated by long-term oscillations suchas the Solar Cycle and the Quasi-Biennial Oscillation. An initial examination of inter- and intra-annualvariations in the mean wind and atmospheric tides is presented, including the analysis of the relationshipto the Quasi-Biennial-Oscillation and the Solar Cycle.Time-series CCD photometryMalcolm Cropp* * * * *Abstract: I have been observing the open clusters NGC 3096 and NGC 6451 as well as the globularcluster NGC 7099 with the CCD photometer at Mount John University Observatory. I will discuss how Ihave been making observations as well as my analysis method and what I intend to find from theseobservations. Finally I will share my latest results and how I see this study progressing into next year.* * * * *Measuring Motion using Magnetic Resonance ImagingRichard WattsAbstract: Patient motion is normally considered to be a source of artifacts in magnetic resonanceimaging. However, there are certain situations in which the motion itself is of significant interest. I willshow how motion arising from different sources can be measured and analyzed within a coherentframework. Examples of such motion include water diffusion, blood and CSF flow, cardiac-induced brainand vessel pulsations, and externally induced oscillations (MR elastography).* * * * *Calculation of single-beam two-photon absorption rate of lanthanides: effective operatormethod, perturbative expansion and diagrammatic representationChang-Kui (Jean) DuanAbstract: In order to account for contributions to single-beam two-photon transition rates due to bothhigh order perturbations and high energy intermediate states in a systematic way, the transition operatoris partitioned into two terms, one with drastically varying energy denominators which usually requires9


Tuesday 31 st AugustMid-latitude precipitating convection observed by VHF radarAdrian McDonaldAbstract: The understanding of convection at mid-latitudes has been greatly improved by the use ofweather radar data over the last several decades. New observations using VHF clear-air radar haverecently been used for the first time to examine the structure of precipitating convection. Convection canbe shown to be related to rapidly varying vertical velocities with magnitudes of the order of several m/s,these differ from the terminal velocities of hydrometeors detected by weather radar and represent trueupdrafts and downdrafts. Another signature of convection is enhanced values of signal powerassociated with the movement of moist boundary layer air into the upper troposphere.* * * * *Comparison of Eye Shields in Radiotherapeutic BeamsBryn CurrieAbstract: Both MeV electrons and kV photons are used in the treatment of superficial cancers. Theadvantages and disadvantages for each of these modalities have been widely reported in the literature.Of particular note in the literature is the use of lead and tungsten eye shields to protect ocular structuresduring radiotherapy. An investigation addressing issues raised in the literature that are relevant to theWellington Cancer Centre method of treatment of lesions near the eye shall be summarized. Varioussmall sized fields were irradiated to determine depth dose and profile curves in a water phantomshielded by various commercially available eye shields. Transmission factors relevant to critical ocularstructures and particle distribution theories are used to further elucidate the comparison between theuse of MeV electrons and kV photons in the treatment of superficial cancers.* * * * *11


Propagation of Radio Waves in South Polar IceDerek BoydAbstract: The variation with depth of the refractive index of ice at the South Pole produces a number ofeffects complicating Cherenkov cone reconstruction. These effects include regions invisible to the RICEantennas, more than one path to an antenna from a source point, and focusing of waves. All of theseeffects and others make knowledge of the refractive index profile critical to the analysis of RICE data andfor the design of expanded antenna arrays. The refractive index is inversely proportional to the speed ofthe waves in the ice so measuring the transit time of a wave from a transmitter to a receiver at knownspatial locations can be used to unravel the index profile. Transit times have been extracted for wavesfrom a transmitter at various depths within the ice, to up to sixteen receiving antennas in the ice. Untilrecently the record of the received signal in the time domain has been used in analyzing the data. In thiswork it has been used when the signal to noise ratio is high and a newly applied method using FourierTransformed data in the frequency domain has been used when the signal to noise ratio is low. Thepropagation of uncertainties through the analysis is followed.Planet detection via the transit methodVeronica Miller* * * * *Abstract: A discussion of the search for extra-solar planets via the transit method, incorporating howthe transit method works and the results gained from it. Also the preliminary results from analysis ofphotometric data collected by the PLANET collaboration at La Silla in 2002. This analysis involvedsearching several hundred thousand lightcurves for periodic reductions in the magnitude indicating aplanetary transit. The search is accomplished by using a matched filter approach and cycling throughevery possible period, phase and transit length.* * * * *Getting inside your head: warping your brain to see if it’s normalMichael ChappellAbstract: Magnetic Resonance Imaging (MRI) makes it possible to non-invasively obtain 3-dimensionalimages of the brain. Conventional MRI has been particularly successful at imaging activation areas, andstructural changes brought about by disease or injury. Eight years ago a new MRI sequence wasdeveloped that has taken brain imaging to a new level of detail. It is called Diffusion Tensor Imaging(DTI). Here the signal is sensitive to the Brownian motion of the water molecules in the brain. From thisdiffusion information it is possible to infer the trajectory of the white matter fibre tracts (“tractography”),which offers the medical fraternity a whole new range of new and exciting diagnostic and therapeuticpossibilities. In this talk I will discuss some of the assumptions and debate involved in tractography,along with some of the applications I will be investigating in my thesis.Algebra versus GeometryWilliam Joyce* * * * *Abstract: In physics, when faced with solving a problem, we take one of two approaches: a geometricor algebraic perspective. The fact that both work underlies the fundamental relationship between thetwo. In the 19 th century a battle raged over what the appropriate algebraic description of geometry shouldbe. I’ll give a flavour of the issues and personalities, what won the day and why, the aftermath and somefuture predictions.12


Measurement of the refractive index of the South Polar ice via Radio tomographyPhilip WahrlichAbstract: High energy particle interactions in the south polar ice can result in the production ofbroadband Cherenkov radiation which could be detected by the RICE neutrino detector. To accuratelyreconstruct the trajectories though which this radiation has propagated requires knowledge of how therefractive index of the ice varies inside the volume through which the radiation propagates. We use theRICE detector to probe the variation of the south polar ice sheet refractive index with depth through radiotopography. Geometric ray tracing is used to calculate the trajectory of radiofrequency radiation throughthe ice sheet. We model the variation in the refractive index of the ice sheet with a selection of simplefunctions of 203 adjustable parameters which best fit the tomographic observations. The effectivenessof the fitting criteria is examined.* * * * *The real-life phenomena in two classical introductory physics textsVeronica CahyadiAbstract: There has been a concern among physics education researchers that students exposed totraditional instructions have conceptual difficulty in their understanding despite their skill in solvingnumerical problems. Moreover, the physics they study is believed to have little or no relevance to theireveryday experiences. The students’ perception that physics is a collection of unrelated formulas doesnot agree with the “meaning” of physics conveyed by dictionaries, encyclopaedia, and experts. Anincreasing amount of effect has been initiated to remedy the problem, including the inclusion of moreexamples of real-life phenomena in the development of two classical introductory physics texts. Mypresentation will explore the endeavour of the textbooks’ writers to incorporate more real-life phenomenain the attempt to reinstate the students’ perception of physics and to improve their understanding.Excited-state dynamics of lanthanide ionsMike Reid* * * * *Abstract: In collaboration with various people in our Department and overseas I have been working onthe modeling of excited states of lanthanide ions in various host crystals. We have a good understandingof the energy levels, and a lot of our effort is now focused on understanding the mechanisms forradiative and non-radiative decay.* * * * *Kinetics vs. Thermodynamics: A balancing act in the growth of nanoscale surface islands.Shelley ScottAbstract: The nucleation and growth of thin films from the vapour phase generally occurs in an nonequilibriumenvironment. Particles deposited on atomically flat and weakly interacting substrates candiffuse over substantial distances. Their migration comes to an end when they collide with anotheradatom (or defect trap) to nucleate an island. There exists a thermodynamic tendency to minimize thefree energy of these surface islands, leading to compact structures. However the continuous diffusion ofparticles to the island boundaries often leads to dendritic and irregular morphologies, where the kineticsof diffusion is the driving force. An understanding of this delicate interplay between kinetics andthermodynamics can allow the self-assembly of nanoscale surface features with tailored properties.Results for Bi 2 deposited on graphite surfaces will be discussed.13


In vivo multi-spectral lifetime spectroscopy and imaging of human melanomaAllen LimAbstract: Pigmented lesions usually have high concentration of melanin. In order to extract theinformation to determine if the lesion is cancerous, relevant fluorescence information from the lesion hasto be extracted. This we hope can be done by measuring the pigmented lesions with lifetime (timeresolved) fluorescence and/or multispectral fluorescence.Things the Department might doPhil Butler* * * * *Abstract: One of the delights of being Head of Department is to gain an overview of much of whathappens within the department, and to have the opportunity to relate this to how other departments in theuniversity and elsewhere operate. One of the frustrations is that there are always too many opportunitiesto follow up, with the corresponding recognition that one spends too much of ones time on matters thatseem pointless. This talk will cover a selection of the matters that I consider important for theDepartment’s future in the medium term.* * * * *Assisting Undergrads to be Self-Reliant I: Dimensional AnalysisJohn CampbellAbstract: It is my recommendation that we teach one lecture of Dimensional Analysis during the firstlectures of the year to first year classes. This is a powerful technique which not only allows students tocheck their own work, thus helping them to become self-reliant, but is also most helpful to them duringexams.I teach this to PHYS114 (electricity). A testimonial to this approach was from a student this yearwho said “what a shame we weren’t taught this before mechanics”.* * * * *Assembly of Bi clusters into nanowires using etched V-grooves as templatesAhmad AyeshAbstract: The cluster assembly method reported here employs V-grooves as a template for nanowirefabrication. This templated cluster assembly technique allows the formation of contacted electricallyconducting nanowires using simple lithography techniques and without painstaking manipulation of theclusters. The clusters were directed as a beam from a source into the deposition chamber and havedeposited on to the V-grooves. Contacted V-grooves were mounted on a cryostat cold finger allowingin situ temperature dependent measurements. I (V) and temperature dependent resistancemeasurements of nanowires allow detailed investigation of the conduction mechanism in the wires.* * * * *14


Progress of the design of the High Resolution Spectrograph for the Southern African LargeTelescopeStuart BarnesAbstract: We have recently been given the go ahead to fully develop our design for the SouthernAfrican Large Telescope High Resolution Spectrograph (SALT HRS). The design has evolvedconsiderably since the original R2 echelle design which, like HERCULES (for the MJUO 1 metretelescope), used large prisms for cross-dispersion and a very large catadioptric camera. The currentdesign uses a monolithic R4 echelle grating, volume phase holographic (VPH) gratings for crossdispersion,and a novel form of the dual beam white pupil relay with very fast dioptric cameras. The useof VPH gratings coupled with a significant advance in the cameral design will allow this design to be verycompetitive with our previous concepts while also allowing a considerably smaller instrument.Horizons and Skyrmion Black HolesAlex Nielsen* * * * *Abstract: Black Holes are of interest both astronomically and theoretically. One of their most interestingaspects for theorists is the existence of horizons – casual boundaries of spacetime. The understandingof the nature of these horizons has grown considerably since pioneering work by Stephen Hawking andothers in the 1970’s. The talk will present some of these developments, in particular the work byAshtekar and colleagues on Isolated Horizons, and discuss some current work on relating these ideasto Skyrmion Black Holes.* * * * *TBI (Total Body Irradiation) treatment utilizing a moving couch and MLC for conformal beamtreatmentBen WilderAbstract: This project idea is an extension on a thesis done by a colleague. His thesis was about Arc-TBI. Patient-phantom is stationary on couch while the gantry rotates through an arc at varying speeds togive a uniform dose to the patient/phantom, this is one method of doing a TBI treatment. My idea isinvestigating an alternate technique and adding the idea of using an MLC (multi-leaf collimator) toconfirm the radiation beam to the patient/phantom. Patient/phantom lies on a couch, the couch moveslongitudinally either while the beam is on or the treatment is done in a step and shoot technique: couchmoves then beam is turned on. The MLC leaves move in and out to compensate for the thinner/thickerareas of the patient/phantom which get higher/lower doses. This achieves a more uniform dose to thepatient/phantom.* * * * *Recent measurements of seismic rotations using large ring lasersBob HurstAbstract: The large ring laser tyros at the Cashmere cavern and in the departmental RutherfordBuilding readily detect the rotational components of seismic disturbances. A search has been made forresidual permanent rotations that are expected to occur as part of post-earthquake elastic rebound. Atleast one probably candidate event has been found, form a small local earthquake. The PR-1 laser canmeasure the responses of the Rutherford Building at its normal modes. The mode of lowest frequency(~2.6 Hz) is almost continuously excited by background seismic noise. Nearby earthquakes havesufficient spectral power at this frequency to cause a transient increase in this excitation, and theconsequent swaying of the building can reach amplitudes of 1 microradian.15


Recent contributions of MR and PET imaging techniques to the diagnosis and Treatment ofAlzheimer’s diseasePeter SmaleAbstract: Neuroimaging can assist in the earlier diagnosis and differentiation of dementias, and theevaluation of treatment progress. Recent work in Positron Emission Tomography (PET) has madepossible the imaging of the amyloid plaques diagnostic of Alzheimer’s disease, while MagneticResonance Imaging (MRI) studies have shown that certain patterns of brain atrophy correlate withclinical memory decline. This talk – based on a report for the MDPH406 Medical Imaging paper –reviews these advances.* * * * * *Mode identification of nonradially pulsating starsDuncan WrightAbstract: Correct identification of the modes of oscillation in a nonradially pulsating star is vital to theprocedure of asteroseismology – placing limits on a star’s parameters by matching observed pulsationmodes in models of the stellar atmosphere. Over the last ten years new methods of mode identificationhave been developed. I will outline the properties of nonradial pulsators and how they are observed. I willthen look at the difficulties of mode identification and then briefly at a few methods used to determinemodes today.* * * * *The Coupling of Dynamics and Chemistry in the Antarctic StratospherePetra HuckAbstract: Trends and variability in global ozone have important consequences for life on earth. Withoutthe protection of stratospheric ozone, life-threatening surface ultraviolet irradiation would increase. Thishas important consequences for the biosphere, human health and economic sustainability.Since the discovery of the Antarctic ozone hole in 1985 the severity and the size of the ozone holehave increased steadily. The increase has not been monotonic however, and there are significant interannualdifferences which are suggested to be strongly linked to mid-latitude planetary wave activity.This project aims to further examine the effects of planetary wave activity on Antarctic ozonedepletion. Furthermore, models suggest that there is a delay between anomalies in planetary activity andanomalous Antarctic ozone depletion so that mid-winter planetary wave activity could be used toforecast Antarctic ozone hole severity.Diamonds are a surgeon’s best friendLou Reinisch* * * * *Abstract: Background and Objectives: We investigated the reduction in lateral thermal damageform laser incisions while using thermally conducting templates. We previously showed metal templateswith slits approximately the same width as the laser beam diameter reduced the lateral thermal damagefrom laser incisions. In this study, we investigated transparent thermal conducting templates, whichallow tissue visualization during the procedure. Materials and Methods: We compared no template tocopper, sapphire, and diamond at room temperature and at 4°C with water cooling, using speciallydesigned template hand pieces. The pulsed free-electron laser was used at 6.45 microns, thewavelength noted for minimal thermal damage. In vitro human skin was incised and examined16


histologically using computer morphometrics. Results: The following amount of thermal damage wasfound:No template Sapphire Copper DiamondLateral thermal 67.4 ± 9.3 39.8 ± 3.0 37.7 ± 2.1 33.3 ± 5.0Damage (microns)The reduction in thermal damage from no template to any of the templates was statistically significant(p


NOTES FOR SPEAKERS1. Please keep your presentation to the allocated time of 10 minutes.5 minutes is allowed for discussion after your talk.2. Speakers with slides,It is your responsibility to load them into the projector.3. A computer and data projector will be available. Please load your presentations onto it before thestart of your session.RESEARCH STUDENT TALKSThe B.G. Wybourne prize will be awarded for the best research student talk while the Departmentawards a prize for the second best research student talk.Last year the B G Wybourne Prize went to Liz Wylie. The Department prize was shared between BenCarter and Judy Mohr.LUNCHParticipants who are not members of the Staff Club are welcome to be the (paying) guests of those whoare going for lunch at the Staff Club.AFTER CONFERENCE GATHERINGYou are all welcome to attend the end-of-conference gathering and prize-giving to be held in the NorthLounge of the Staff Club between 5.00-6.00 p.m. on Tuesday evening, 31 st August. Buy your owndrinks, nibbles will be provided.18

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